3 90 15 OO378 438 University of Michigan - BU HR ∞• #！!！！！!！!!!!!！！!!！!!!！!！!！!!!!!!!!！!!!!!!!!!{{#############EEEEEEEEEEĽ№ ĒģŠĶĒģſſſſſſſſſſ|IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIĘ －---§§§ |||||||||||| |||| Wy ## º t U - & US （…№ ſiiſiſſiſſiſſiſſiſſiſſiſiſſiſſiſſiliſiſſiiiiiiiiſſiſſiſſiſi fºußE. • * * ºù № \，^ • • •º ： + 3 \\£$%！ | -§§§);§§ ，r，，） ： NS kſ § J. Jºliº Gºjºſº UAE U20 Nº UCLºſ Gyº, U.J.C., V J C, Cy. 2：2，2：2Zſ.æ：ĶU L-A، ĒáſáRË№mſĪĪĪĪĪĪĪĪĪĪĪĪĪĪĪĪĪĪ ºilitiºninºff ºr-º-º-º-º-º-º-º-º-º-º-º-º-º-º-º-º-º-º-º-º-º-º-º-º-a -ºr-º-º-º-º-º-º-º-º-º-º-º-º-º-º-º-º-º-º-º-º-º-º-º-º-º-º- Tulilºtillmºttºnmºutnummºn Eº- Rı | DATE DUE TO REM FAA'ſ pi- (DN: Form 7 O79g. :...º.º. *::::::::::::: ºr . . . . * * ***. -- " " . " * - A . . - * * * * *\,...º.º.º.º.” * 3.3','º', * .” ºr, ...º. ****, . 3. | : łº A * * r - ---, - HistoRY OF INFUSORIA, INCLUDING THE DESMIDIACEE AND DIATOMACEF, BRITISH AND FOREIGN. BY ANDREW PRITCHARD, ESQ., M.R.I., AUTHOR of THE ‘MICROSCOPIC CABINET,” ETC. FOURTH EDITION, ENILARGED AND REWISED BY J. T. AIRLIDGE, M.B., B.A. LOND.; W. ARCHER, Esq.; J. RALFS, M.R.C.S.L.; W. C. WILLIAMSON, Esq., F.R.S.; - AND THE AUTHOR. ILLUSTRATED BY FORTY PLATES. - L O N T) O N : WHIT TAKER AND Co., Av E MARIA LAN E. • * * 1861, * ºf: [The right of translation is reserved.] PRINTED BY TAYLOR AND FRANCIS, RED LION COURT, FLEET STREET. s P. R. E. F. A. C. E. SPECIAL interest has always been taken by man in the structure and development of the minute forms of life, whether animal or vegetable: in this volume I propose to lay before the reader a résumé of the present state of our knowledge of the multitude of living beings called Infusoria. This term, as employed by Professor EHRENBERG of Berlin, includes a wide range both of animal and vegetable life; while it is now restricted by other naturalists to the Protozoa, and, in the works recently commenced by Dr. STEIN and MM. CLAPAREDE and LACHMANN, to the ciliated members of that group. The former editions of this work having included a History of the Bacillaria, Phytozoa, Protozoa (under the name Polygastrica), and of the Rotatoria, it is incumbent on me to retain these groups, though the researches of late years have so extended our acquaintance with them that much difficulty has been felt in the attempt to comprise the whole in a single volume, so necessary for a practical manual. The successful investigation of this department of Natural History arose mainly from the improvement of the microscope consequent upon the discoveries of “Test Objects” and “penetrating power,” the latter depending upon “angular aperture,”—discoveries which my colleague the late Dr. GoRING and myself had the pleasure of presenting to the public. The microscope, having become thereby a reliable instrument, has revealed to us the true forms and structure of these beings. Part I. is devoted to a General History of the several more or less natural groups of Infusoria: it contains also the observations and opinions of British and Continental naturalists on their nature, structure, functions, and classification. The foreign writings on these subjects are so voluminous that even an abstract of them has increased this part of the work much beyond what it occupied in iV PREFACE, former editions, while the introduction of the Tables from Part II. has further extended it ; but, as I have been anxious to give an impartial account of the researches on this subject, a briefer summary might have impaired its usefulness and value. To Dr. ARLIDGE is due the rearrangement and preparation of this part. Part II. contains descriptions of the Families, Genera, and Species of the groups whose general history forms the subject of the preceding part of this volume. The systematic arrangement of Ehrenberg has been retained for the Phytozoa, Protozoa, and Rotatoria, the new genera and species of other naturalists being collated and engrafted thereon. The descriptions of those curious and highly-organized creatures the Rotatoria have been extended and revised by Professor WILLIAMSON of Manchester, whose original researches and observa- tions on this group are greatly appreciated, both in this country and abroad. - In consequence of the long illness of Mr. RALFs, who had under- taken the revision of the Bacillaria, the publication of this edition has been delayed, and that group has been printed last—a deviation from the original design which it is hoped will not inconvenience the reader, while it has allowed opportunity for the insertion of the latest researches. Owing to the circumstance stated above, the revision of the Systematic History of the Family or Subgroup Desmidiaceae has been kindly carried out by Mr. WILLIAM ARCHER of Dublin, who has added some original views, expressing by symbols the characters of certain genera; moreover, M. DE BRáBIsson of Falaise has given this edition the benefit of his valuable co-operation, by furnishing descrip- tions of the newly-discovered foreign species. • The elegance and variety of the forms, the beauty and elaborate sculpturing of the silicious shells of the Diatomaceae, and the general interest now taken in their study, renderedit desirable to bring together in this volume all the known genera and species, British and foreign. This I have been able to effect by the research of Mr. RALFs, whose name is so intimately identified with the knowledge of these organisms, and whose present arrangement of their families and genera will no doubt tend to facilitate our better acquaintance with them. Owing to the great dimensions which this treatise has acquired, and the limited space consequently at command, I was under the necessity of con- densing the manuscript of Mr. RALFs, and of introducing abbrevi- PREFACE. e V ations. Still I have, in accordance with my original design, given every known specific name, whether synonym or variety, whereby observers may avoid confusion in the momenclature by not employing the same names for newly-discovered forms. The references now introduced are to works published subsequently to the early editions of this book: for their verification I am indebted to Mr. KITTON of Norwich. - Twenty-one new Plates have been added to this edition, of which six are engraved by Mr. TUFFEN WEST. In the case of the Diatoms, all the new figures are drawn to one scale, representing a magnifying power of 300 diameters; many of them likewise are drawn from specimens, whilst others are engraved from Original drawings kindly lent by Mr. GeoRGE Norm AN of Hull, Mr. RoPER of Clapton, and Mr. BRIGHTwº LL of Norwich. - It now becomes my pleasing duty to acknowledge the kind assist- ance received from the late Professors GREGORY of Edinburgh and BAILEY of New York; also to tender to Drs. DoNKIN, GREvil LE, FRANCIS, WALLICH, STRETHILL WRIGHT, and Mr. GossE, along with the gentlemen before named, my best thanks for their aid and advice during the progress of this laborious undertaking. In conclusion, should the object proposed in the reissue of this Work be attained, viz. to produce in a single volume a compendium of the present state of knowledge, calculated to promote and facilitate the study of the very interesting branch of Natural History which forms its subject, and which has occupied much of my leisure time for more than forty years, I shall be fully content. ANDREW PRITCHARD. Canonbury, London, N. November 15, 1860. C O N T E N T S. PREFACE ............................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page iii List of works quoted and abbreviations used herein ............................................. IX PART I.-A GENERAL HISTORY OF INFUsor[A, ETC. BACILLARIA: Desmidieæ, their figure, page l; colour, consistence, envelopes, openings in lorica, 4; movements and external cilia, 5; contents of fronds, 6; circulation of con- tents, 7; reproduction, 11; habitats, distribution, appearance in masses and vital endowments, vegetable mature and affinities, mode of collection, 20--Pediastree, their figure, composition, and contents of cells, 24; number and disposition of the cells in the fronds, 25; development and growth, 29; systematic position, 30.—Diatomaceæ, their general and external characters, 31; figure, 32; the silicious shell or lorica, its divisions and structural composition, markings, striae, camaliculi, puncta, &c., 37; contents of frustules, supposed digestive sacs, reproductive vesicles, &c., 47; move- ments, their character and causes, cilia, circulation of contents, respiration, 50; nutritive functions, supposed stomachs, 56; multiplication, reproduction, and develop- ment, 58; conjugation, 61; habitats, appearance in masses, abundance, 75; geogra- phical distribution, 79; geological importance and fossil accumulations, 82; ačrolitic Diatomeae, 85; uses of Diatomaceous deposits, 86; of the nature of Diatomeae, whether animals or plants, various hypotheses, 87; determination of species and genera, varieties, classification of Kützing, Smith, and others, 96; on the mode of obtaining, preparing, and preserving specimens, 102. PIIYTozoA: the beings included under this name, their general character, division into groups or tribes, their figure, coverings, 111; cell-contents, 113; movements, 117; process of nutrition, 1.19; multiplication and reproduction, fission, macrogonidia, microgonidia, 120; encysting process, condition of rest, 123; phases of being and alternation of generation, 124; on their nature, animal and vegetable characters, 128; habitats, occurrence in masses, colour caused by their accumulation, 129.-Families: Monadāna, 130; Cryptomonadina, 140; Volvocina, 144; Vibrionia, 184; Astasiaea or Euglenſea, 188; nature of Astasiaea, 196. PROTOZOA, 199—Rhizopoda, 201; movements of contained particles, 210; nucleus, 211; reproduction, 213; of the testaceous shells of Monothalamia, 218; shells of Polytha- lamia or Foraminifera, 222; dimensions and conditions of life, 227; habitats and distribution, 229; of their cell-mature and characters as individuals or as colonies of animals, 232; on their affinities, 234; classification, 237. Actinophryina, 243; movements, 246; prehension and entrance of food, 247; contractile vesicle, 250; mucleus, 252; encysting, fission, gemmation, embryos, 253; conjugation, 256; loca. lities, affinities, 257. Acinetina, 258; origin and development, 261. Gregarinida, 262. Psorospermia, 265. Ciliata, 266. Subgroup A. Astoma: Opalinea, their general characters and functions, 267; nucleus, self-division, supposed embryos, 269; habitats, vital endowments, mature, affinities, classification, 270. Peridiniea, 27 1; ºtents, 274; reproduction, 275. Subgroup B. Stomatoda: dimensions, 277; figure, 2783, Consistence, 279; integument, markings on surface, spines, lorica, 280; externai sheaths or, cases, 282; cilia and ciliary action, 285; locomotive and fixed forms, Yºieties of locomotion, transitory power of locomotion among the attached genera, 288; structure of pedicles, 292; compound special organs of locomotion and pre- hension, the peristom and rotary or ciliated disc, the spirally-coiled head of Spiro- Choº, 294-0%aº Protozoa, internal organization: subtegumentary layer, chloro- phyll, thread cells, 297; muscles, 300; organs of digestion, nutrition, and secretion, 301; the polygastric hypothesis, 303; dental a paratus or teeth, 311; contractile Vesicle, 312; mucleus, nucleolus, 326; ovules, 334; spermatozoids, 337; accessory Contents, granules, molecules, spherical cells, supposed glands, 338; circulation of contents, 839. The encysting process, 341; reproduction, fission, gemmation, internal viii CONTENTS. ova producing germs or embryos, impregnation, production of mew beings with and without metamorphosis, transformation into Acimetas, 345; nature of Ciliated Pro- tozoa, their existenco as independent organisms, cell-theory applied to them, 368; conditions of life, 370; succession of specics, 371; duration of life, influence of external agents, heat and cold, 373; necessity of air, chemical agents, electricity and galvanism, 374; affinities with other animals, geographical distribution, 375; classi- fication, 376. Subgroups of Ciliated Protozoa: Ichthydina, 380; Noctilucida, 382; Dysteria, 387. RotATORIA or ROTIFERA: general characters, 392; appendages, 397; the muscular system, 406; movements, 409; the digestive system, 410; reception of food, its deglutition, 420; the secreting system, 422; the vascular and respiratory systems, 426; the nervous system, organs of sense, psychical endowments, 434; reproductive organs, 441; formation of ova, 442; development of embryo, 445; the embryo-metamor- phosis, 447; winter ova, 450; male Rotatoria, 453; duration and conditions of life, habitats and distribution, 463; affinities and classification, 468; Ehrenberg's classifi- cation, 478; Dujardin and Leydig's classifications, 480. TARDIGRADA: their structure, habitats, and affinitics, 482. PART II.-A SysIEMATIC HISTORY OF INFUsorLA, WITII DESCRIPTIONs of TIIE FAMILIES, GENERA, AND SPECIES. Group PIIYTozoA. Families: Momadina, 485; Hydromorina, 503; Cryptomomadina, 505; Wolvocina, 514; Wibrionia, 529; Astasiaea or Euglenaea, 538; Dinobryina, 547. Group PROTozo A–Subgroup Rhizopoda, 547: Amoebaca, 548; Arcellina, 551; Actino- phryina, 558; Acimetina, 564. —Subgroup Ciliata, 568. Astoma: Opalimaca, 569; Cyclidima, 571; Peridiniaea, 574. Stomatoda: Vorticellina, 579; Ophrydima, Waginifera, 598; Enchelia, 605; Colepima, 616: Trachelina, 616; Ophryocercina, 630; Aspidis- cina, 631; Kolpodea or Colpodea, 631; Oxytrichima, 639; Euplotina, 645. Group ROTATORIA. Families: Ichthydima, 660; CEcistina, 663; Megalotrochaca, 664; Floscularia, 665; Hydatinaea, 677; Albertina, 693; Euchlanidota, 693; Philodinaea, 700; Brachiona’a, 706. Group TARDIGRADA, 713. Group BACILLARIA: Desmidiaceae, 715; Diatomaceæ, 756. Index to the Illustrations of the Diatomaceæ, 941. Description of the Plates, 949. Index to the Families and Genera, 965. A. LIST OF A B B R E V IATION S OF WORKS AND AUTHORS’ NAMES REFERRED TO IN THE PRESENT EDITION, Abhandlungen der Berliner Academie der Wissenschaftem. Abhandlungen der Senckenbergischen Gesellschaft in Frankfurt am Main, Ag CD, or AD. Agardh's Conspectus Diatomorum. ANH. Annals and Magazine of Natural History. Anat, d, wirbellos. Thiere. Siebold, C. Th. von. Lehrbuch der vergleichenden Anatomie der wirbellosen Thiere. Berlin, 1848. Ar, or Arn. Professor G. Walker-Arnott, LL.D. ASA, or AA. Agardh's Systema Algarum, ASN. or Ann, d. SN. Annales des Sciences Naturelles, Paris. B. or Bai. Professor Bailey of New York. BAJ. Professor Bailey, in American Journal of Science. BC. or BSC. Professor Bailey's Contributions to Knowledge, Smithsonian Insti- tution. BMO. Professor Bailey's Microscopic Organisms Boston Journal of Natural History. 1853. Braun, A., Prof. Algarum Unicellularum Genera nova aut minus cognita, 1855. Bréb. M. de Brébisson of Falaise. B.D. M. de Brébisson's Diatomaceae of Cherbourg. Bri, T. Brightwell, Esq., Norwich. *º Transactions of the British Association for the Advancement of C1011C0. British Desmidieæ. By John Ralfs. 1848. Érik and Foreign Med. Rev. British and Foreign Medico-Chirurgical Review. Bulletin de L'Académie de St. Pétersbourg, xiii. 1855. Carpenter, Dr. W. B. The Microscope. Carus, Icones Zootomicae, 1858. 90hn, R. S. Professor Cohn on the Structure of Protococcus pluvialis. Ray { Society, 1853. London. Qºm * Rendus de l'Académie Impériale des Sciences. PQrbigny, Alcide, Foraminiferes Fossiles, is 46. Pujº. Dujardin, F., Histoire Naturelle des Zoophytes.—Infusoires. Paris, #: Eh., or Ehr. Professor Ehrenberg, Berlin. E.A. §rofºº Ehrenberg's Mºhº Lebens in Amerika. Edin. New Phil J oùn, Edinburgh New Philosophical Journal. Einzell. Alg, Nägeli, Prof, Gattungen einzelliger Algem. Zurich, 1849. EI. or Inf, . Professor Ehrenberg's Die Infusionsthierchen. EK. Professor Ehrenberg's Kreidethierchen. {M}, . Professor Ehrenberg's Mikrogeologie. ERBA, or EB, or ER. Frofessor £hreiberg in Reports of Berlin Academy. Ehrenberg, Prof. Passatstanbund Blutregen. X LIST OF ABBREVIATIONS, ETC. Entw. Cohn, Prof. F. Entwickelungs-geschichte der mikroskopischen Algem und Pilze. 1854. Fauna Infusoria, Norfolk, T. Brightwell, Norwich. Gr. Dr. R. K. Greville. GB.F. Dr. R. K. Greville's British Flora. GCF. Dr. R. K. Greville's British Cryptogamic Flora. Greg. Dr. Gregory of Edinburgh. GDC or GC, Dr. Gregory's Diatomaceae of the Clyde. HBA. Hassall's British Algae. Jones, T. Rymer, Prof. A General Outline of the Animal Kingdom, London, 1841 R. or Kütz. Professor Kützing. KA, or KSA, Professor Kiitzing's Species Algarum, IB, , Professor Kitzing's Bacillarien. Kützing. Phycologia Germanica. 1845. K.L. Die kleinsten Lebensformen. KSD. Professor Kützing's Synopsis Diatomeorum. Linnaea, xiv. 1840. Lyngb., Professor Lyngbye's Tentamen Hydrophytologiae Danicæ. Medical Times. London, 1856. Professor Huxley's Lectures. Me, or Men, Professor Meneghini. Meneghini, R. S. Professor Meneghini on the AnimalNature of Diatomeae. Ray Society. London, 1853. Mém, de l'Acad, Roy. Belgique. Mémoires de l'Académie Royale de Belgique. Micrographic Dictionary, The. By Dr. Griffith and Prof. Henfrey. Microscopic Illustrations. By C. R. Goring, M.D., and Andrew Pritchard. Mittheilungen der Naturforschenden Gesellschaften in Bern, 1849. Mjor JMS, journal of Microscopical Science. Momatsb. Berlin. Acad. Monatsbericht der Berliner Academie, MT, or TMI. or TMS. Transactions of Microscopical Society. Müller's Archiv. , Archiv für Anatomie und Physiologie. Von Dr. J. Müller, Müller, O. F. Prof. Animalcula Infusoria, Nā, or Nāg. Professor Nägeli. Nat. Hist. Review. Natural IIistory Review, Dublin, Nov. Act. Acad. Curios. Nova Acta Academiae Naturae Curiosorum. Owen, Richard. Lectures on the Invertebrate Animals, London, 1843. Owen, Richard. On Parthenogenesis. London, 1849. Ph. Professor John Phillips, F.R.S. Phil. Trans. Philosophical Transactions of the Royal Society of London. Perty, Max., Dr. Zur Kenntniss kleinster Lebensformen. 1852. Proceedings of the American Association for the Advancement of Science, Proceedings of the Boston Society of Natural History. Proc. Roy. Soc. Proceedings of the Royal Society of London. Proc, Roy. Soc. Edin. Proceedings of the Royal Society of Edinburgh. IProceedings of the Academy of Natural Sciences of Philadelphia. 1853, Rab D. or R.D. Dr. Rabenhorst, Die Süsswasser Diatomaceen. Ra, or R. Mr. Ralfs. R.S. Ray Society's publications. R.S. Reports. Ray Society Reports. Rejuv, R.S. Braun, A., Professor, On the Phenomena of Tejuvenescence in Nature. Ray Society. London, 1853. Ro. F. C. S. Roper, Esq. Schleiden, J. M., Prof. Principles of Scientific Botany: translated by Dr. Lam- kester. 1859. Schultze, Dr. Max S. Ueber den Organismus der Polythalamien, Leipzig, 1854. Schneider, Ant. Symbolae ad Infusoriorum. Historiam Naturalem Disseriatio In- auguralis. Berlin, 1854. Sh, or Shadb. G. Shadbolt, Esq. Sill. Journ. Silliman's American Journal of Science and Arts. S. or Sm. Professor Smith. SBD, or SD. Professor Smith's Synopsis of British Diatomaceae. Stein, F., Prof. Die Infusionsthiere, auf ibre Entwickelungsgeschichte, ERRATA, ETC. xi Transactions of the Philosophical Society of Manchester, Transactions of the Medical and Physical Society of Bombay. Untersuchungen über die Familien der Conjugaten. By Professor de Bory. Van der Hoeven. Lehrbuch der Zootomie, 1850 & 1856. Wagner, Zootomie. Wiegmann's Archiv. Archiv für Naturgeschichte. Von A. F. A. Wiegmann. Williamson, Prof. On the Recent Foraminifera of Great Britain, Ray Society, London, 1857. Zeitschr, or Siebold's Zeitschr. Zeitschrift für wissenschaftliche Zoologie. Von Carl T. von Siebold und Albert Kölliker, 1848–59, NoTE.—The names of Ehrenberg, Dujardin, Perty, and Siebold are frequently mentioned without particular notice of the work quoted; but the treatises intended are those in which each of those several authors has given a general history of Infusoria, and which are named in the above list. So, in the account of the Rhizopoda, Schultze is often quoted, his special work on their organization being referred to ; and lastly, in the History of the Rotatoria, the opinions of Leydig are all derived from his essays in Siebold’s ‘Zeitschrift.” For abbreviations employed in Systematic History of Desmidiaceae, see p. 721. NOTE. —The references to the engravings in this work are printed thus: (XII, 20.) for Plate XII, fig. 20. ER R A TA, ETC. Page 10, line 8 from bottom, dele See Appendix at end. – 218, line 7 from top, for Foraminifera read Foraminifera. 243, line 7 from bottom, for peuliarity read peculiarity. 253, line 3 from top, for Actinophrgs read Actinophrys. 259, line 4 from bottom, for XVIII, read XXIII. 316, line 6 from bottom, for Leuckhart read Leuckart. 324, line 14 from bottom, for Wagener read Wagner. 470, line 7 from top, for 1855 read 1858. * 535, line 5 from bottom, after figured, insert subsequently. 726, Col. 2, line 20 from bottom, insert segment 3-lobed, before lateral lobes. 726, col. 2, line 11 from bottom, for side read sides. 729, Col. 2, line 25 from bottom, dele comma after surface, and insert after middle. 732, Col. 2, line 22 from bottom, for finely read finally. 735, . “C. aciculare (West)—Elongated, very slender, straight, except at extre- mities.” 74], Col. 2, transpose reference to figure from S. globulatum to S. bacillaro. 744, Col. 2, line 34, for paradocum read tetraceriſm. 75% line 18 from top, for Pediastrium read Pediastrum. T; line 5 from bottom, dele Synedrete. (See p. 940.) 760, col. 1, line 28, after capitate, insert striae. 73), Coll, line 4 from bottom, for 159 read 156, and insert xi. 1–8. 764, for E. Terra read E. Serra. 7% col. 2, line 2 from bottom, for Argus read Arcus. 768, «ſe. Genus Oncosphenia, insert Genus Podosphenia from p. 769. 771, Col. 1, line 14, for broadly read loosely. 77% col. 2, line 5 from bottom, for pear-like read pearl-like. 773, Col. 1, line 10 from bottom, for III. read xiii. 774, col. 1, line 5, insert (Iv. 32.) 775, transpose Odontidium mesodon to end O. hyemale as Sym. 775, for “O, pinnatum” read pinnulatum, xii ERRATA, ETC. Page 777, end of F. virescens, insert (Ix. 176.) — 778, line 6, after Ralfs, insert.— — 779, before Genus Nitzschia, insert Fam, characters of Surirelleae from p. 783; and see Note, p. 940. 781, col. 1, line 2 from bottom, for 20 read 21. 783, col. 1, line 12, for 22 read 23. 784, col. 1, line 5 from bottom, for 2, 3; read 24. 784, col. 2, line 22 from bottom, for 19 read 20. 786, S. pulchella, insert (IV. 28.) 789, S. fulgens, insert (XIII. 20.) 791, Col. 1, line 2, for xvii.I. read VIII. 796, S. striatula, insert (Ix. 137, 138.) 798, col. 1. line 24, for dividuate read dimidiate. 799, col. 1, line 21 from bottom, for magnificent read marginal. 802, col. 2, line 14, for xv. read xII.; line 29, for xv. read XII. ; last figure, for 56 7'ead 50. 806, Gomphogramma rupestre, insert (IV, 46.) 806, Tetracyclus lacustris, inserá (VIII. 10.) 809, Gephyria incurvata, inserá (v. 50.) 809, Gephyria media, insert (v. 49.) 809, Eupleuria pulchella, insert (VIII. 2.) 812, for C. undulata read C. undata. 821, col. 2, line 6, after ochracea, insert (Ralfs) from next line; and after ferruginea insert (Ehr.). 836, col. 2, line 8 from bottom, for x. read xI. 844, A. Kittoni, insert (VIII. 24.) 851, col. 1, line 17 from bottom, for nervosa read emervis. 863, Dicladia Capreolus, inserá (VI. 28.) 875, Cymbella Arcus, insert (VII, 78.) 891, col. 1, lime 2 from bottom, for XII. read XI. 893, for “N. dissimilis (Rab.)” read “N. clepsydra (Ralfs).” 903, for “N. producta” read “N. eatensa.” 911, S. Fulmen (Breb.), read “S. Fulmen (Bri.),” and insert that species after S. con- stricta. 923, col. 1, last line, for (VIII. 43.) read (VIII.48.) 929, col. 1, top line, for octocarpoides read ectocarpoides. 938, col. 1, line 9, for “C. radiała” read “C. Stylorum.” 941, Actinoptychus Jupiter, now Actinocyclus Ehrenbergii. 952, in description of PLATE WII., insert “78. Cymbella Arcus, to right of fig. 42. 79. Amphora momilifera, to right of fig. 49.” [Note. The engraver has omitted the numbers to these two figures in that Plate.] WORKS BY THE SAME AUTHOR, MICROSCOPIC ILLUSTRATIONS, with Descriptions of the New Microscopes, Rules for constructing them, and Directions for their management. MICROSCOPIC CABINET, with Descriptions of the Jewel and Doublet Micro- scopes, Test Objects, &c. MICROGRAPHIA, with practical Essays on Eye-pieces, Solar and Gas Micro- Scopes, &c. NOTES ON NATURAL HISTORY, selected from the ‘Microscopic Cabinet, with 10 coloured Plates from original Drawings by C. R. GoRING, M.D. MICROSCOPIC OBJECTS : Animal, Vegetable, and Mineral. A. H. OF ENGLISH PATENTS for the first Forty-five Years of the present entury, PART I. A GENERAL HISTORY OF INFUSORIA. SECT. I.-OF THE BACILLARIA. UNDER this designation, contrived by Ehrenberg, two families of microscopic unicellular Algae are comprehended, viz. the DESMIDIEE and the DIATOMEE. The Diatomeae differ from the Desmidicae chiefly by their dense silicious envelope, composed of two opposite portions or valves and of an interposed segment, and by the general absence of the usual green colouring matter of plants—chlorophyll or chromule. The Desmidieæ, on the contrary, have a non-silicious envelope, separable into two segments, and filled with bright grass-green chromule. In various vital phenomena the two tribes accord; but whilst the Desmidieæ are all but universally admitted to be plants, the Diatomeae are still regarded by many to be of an animal nature. With respect to this question, the arguments pro and con. will be best understood when the organization and vital endowments of these beings have been discussed. I.—OF THE FAMILY I) ESMIDIEAE OR DESMIDIACEAE. (Plates I. II. III. and XVI.) The Desmidieæ are (pseudo-)llnicellular Algae of a herbaceous green colour, of freshwater habit, and have a membranous lorica composed of two symme- trical segments or valves. In Kützing’s arrangement (Sp. Alg.), the Desmidieæ, constitute a family of the Chamaephyceae, a suborder of the class Isocarpeae. Ehrenberg treated the genus Closterium as a distinct family, which he placed- between the Vibrionia and Astasiaea, with the name Closterina. That the Desmidieæ are actually unicellular (in the sense of forming a single enclosed cavity), Mr. Ralfs has, in his most valuable monograph on the family (1848), taken much pains to demonstrate. Owing to the very deep constriction of the fronds of many genera, e.g. of Euastrum and Micrasterias, the appearance of the little organism is that of two cells united by a narrow band (I. 1, 2, 24, 26, 27; II. 18, 28), forming, in Ehrenberg's opinion, a binary cell or frustule. However, between such deeply partite forms, and others in which no constriction is perceptible, for instance in Closterium, every intermediate gradation is met with. Other evidence of the unicellular structure is afforded by the phenomena of conjugation and of the formation of sporangia, by the newly-formed segments resulting from self-fission being , interposed between the old valves, and by the fact that the entire contents will escape through an opening made in either valve. Moreover, in several genera the circulation of portions of the contents throughout the frond, from one segment to the other, clearly demonstrates the continuity of their interior. , FIGURE.—There is great variety in the figure of Desmidieæ, and much •ºf B 2 GENERAL EIISTORY OF TEIT, INFUSORTA, beauty. This will be best illustrated by reference to the Plates I. and II. ; for description alone would fail to convey even a tolerably accurate conception. In Micrasterias (I, 18, 20, 21) the frustule has a general circular outline, but is bipartite and variously cut. In Euastrum (I. 23, 24, 26; II. 10) it is bipartite, and each valve deeply sinuated. In many species of Cosmarium (I. 1, 2; II. 33) the constriction is much shallower, the valves hemispherical, and their margin entire. In Stawrastrum (I. 31–34; II. 3, 7) each segment is more or less irregularly produced at the extremities into horn-like pro- cesses. In Penium, Docidºwm, and Closterium (II. 1, 2, 9, 14) the frond is elongated and wand-like, without constriction, or with only a very faint one, and in many species is, moreover, curved or crescentic. Not a few genera present numerous fronds united together; the outline of the compound being will consequently vary, both according to the figure of each individual frond, and especially to the mode in which the several fronds are united. Thus in Hyalotheca, Desmidium, and other genera (II. 35, 37, 39), the quadrate fronds are united side by side in single series, so as to form a chain or filament, in other words are concatenated. The lateral view or cross-section of the fronds furnishes valuable characters, and is largely made use of by Mr. Ralfs with that object, especially to distin- guish between the several filamentary species. His figures show that the fronds may be more or less compressed, and consequently offer on a transverse section (end view) an oval and more or less acuminate form (I. 25; II. 23, 29), further modified by the elevations and depressions which the surfaces possess (I. 25; II. 23). In other cases the section is circular, e.g. in Hya- lotheca and Didymoprium (II. 32, 38), whilst in others, again, three or four sides exist which are commonly concave, as in Desmidium (II. 40). The end view exhibits the arrangement of the mass of chlorophyll, which in some instances would appear to be peculiar and determinate of species. The appearance of the Desmidieæ is much modified by the sinuosities, eminences, depressions, and processes, as well of the surface as of the margin of the fronds, and also by the depth and width of the central constriction. The surface may be dotted over irregularly, or more often regularly : the dots themselves are in most cases elevated points, and in fewerinstances depressions. An irregular distribution of minute dots produces a granular-looking surface (I. 24; II. 23, 30). Where the spots are larger their elevated character becomes evident on the margin, to which they give a finely-toothed or dentate appearance, e.g. in Cosmarium (I. 1, 2, 3). In some elongated forms, such as Tetmemorus and Penium (II. 15), the puncta are disposed in lines parallel to the length ; in Docidiwm, however, the disposition, so far as regular, is transverse. In several examples the surface is marked by elevated lines or by furrows (II. 6). Such markings seem peculiar to the elongated genera, particularly to Closterium. - Many apparent lines are resolvable by higher magnifying powers into rows of puncta. Where the lines are fine, they are said to produce a striation of the surface, as in Closteriwm attenuatum and C. acérosum ; where they are more distinct they are termed costae, and the surface they cover is costate or ribbed, as in Closterium costatum and C. angwstatum. In general, in order to disgover the striation of the surface, the fronds must be viewed when empty; sometimes indeed the lines can be made out at the extremities which are unoccupied by chlorophyll. - The striae and costae of Closterium and Penium referred to are disposed longitudinally, but frequently they are intersected at one or more points by a transverse line. In these spindle-shaped genera, where no constriction is found, one such transverse line, usually central, is constant, and indicates OF TEIE DESMIDIEAE. 3 the point of separation into two valves (II. 1, 2, 9). Each valve again is occasionally subdivided by another line (II. 6, 15). These lines may be single or double, and in the case of the middle suture their number may be more multiplied, as in Closterium lineatum and C. Ralfsii. The median sutural line is evident in other genera, e.g. in Hyalotheca, Cosmarium, and Ehtastrum (II. 35). In several it takes on a further development, and becomes an elevated ridge or band, appearing, in a front view, as a double line, terminating on each margin in a dentation. Instances occur in Docidium and in Didymoprium (II. 9, 39). Such double lines are also sometimes met with on each side the median suture, and at others, among the concatenate forms, at the junction-surfaces of connected fronds. That the dots or puncta on the surface of the frustules are commonly small elevations has already been stated; a further dovelopment of such into papillae or minute spines Crowned by a globular apex is seen in Micrasterias papillifera; whilst in many Cosmaria and Staurastra, the edge or the entire surface is bedecked by fine hair-like spines or by obtuse ones, looking on the margin like crenations (I. 1, 2, 3). When short and stout, many elevated processes of the surface are called tubercles (II. 16, 17); when long and tapering, they constitute spines, and in this form may be either straight or curved: such are especially produced from the angles of the fronds, as in Arthrodesmus (II. 18, 28). Among the Staurastra, illustrations of forked spines (II. 3, 7) are found; whilst among sporangia of many species, spinous processes, besides tubercles and other appendages, are highly developed (II. 22, 25, 34) and attain their most complex conditions. The modification of surface in several genera seems due, not to mere simple appendages, but to positive expansions of the limiting membrane itself into thick processes, which in their turn usually end in spines; instances occur in Xanthidium and Stawrastrum (I. 27, 28; II. 3, 7, 20, 25). Generally these large productions from the surface occupy constant and definite positions, such as the extremities, the rounded angles of the fronds, or a margin, and are rarely indifferently placed. A general distribution over the surface is rather characteristic of Xanthidium (I. 27, 28). In Euastrum the surface is thrown into very broad round swellings, hence called inflations; such may be presumed to be constant in number and position (I. 24, II. 30, the empty divided fronds). The margin of the more flattened, and the extremities of the elongated, spe- cies furnish important specific and generic characters. Micrasterias has its margin deeply incised into lobes (I.18, 20, 21, 22), which, with reference to the centre of the frond, have a radiating arrangement, and are themselves incised or inciso-dentate. The fronds of Euastrum are more or less deeply sinuated (I. 23, 24, 26; II. 10), and the intermediate lobes produced vary both in dimensions and outline. Where the lobes on the margin of fronds are small and little prominent, they constitute crenations and dentations which may occur singly or in pairs; in the latter case, the margin so modified is said to be bidentate or bicrenate (I. 1, 2, 3; II. 31, 26, 37). For example, some fronds of Euastrum binatum are bicrenate on the sides, and those of Didy- moprium at the angles of the filaments (II. 39), whilst bidentate frustules are seen in Desmidium (II. 37), and in Hyalotheca mucosa. It has been before remarked that when the Surface is covered by tubercular eminences or conical granules, a dentate outline is produced; instances of this occur in Euastrum verrucosum and in several Cosmaria. Another variety of margin exists, known by the term undulated or wavy, where its elevations and de- pressions are comparatively shallow. Lastly, the general concavity or the convexity of the margin furnishes other specific characteristics. B 2 4 GENERAL IIISTORY OF THE INFUSORIA. Among the variations in the ends of the fusiform or elongated genera may be noticed the notched or emarginate apices of Tetmemorus (II. 12); the truncate extremities of Docidium (II. 9, 10), sometimes also, as in D. Ehrenbergii, tuberculate; and the more or less acutely conical apices of Closterium, prolonged in some species, as in C. attenuatum, by an abrupt contraction of the frond into a conical process—in others, as in C. Setaceum and C. rostratum, by the gradual tapering of the whole frond—into long rostrate or Setaceous beaks. CoLour.—This is due to the endochrome or internal substance, which is usually of a herbaceous green colour, and often diffused pretty uniformly throughout the fronds, sometimes however leaving intervals at which the enclosing membrane (lorica, Ehr.) becomes visible. This lorica is itself mostly colourless; yet in several species of Closterium and Penium it has a reddish-brown tint (II.5, 6, 15). The green colouring matter of the interior is identical with that of plants, i. e. it is chlorophyll or chromule, and con- sequently undergoes a change of colour in autumn, becoming, like the leaves of plants at that season, a reddish-brown. When this change occurs, it is equally indicative of the termination of life. CoNSISTENCE.-ENVELOPES.—The limiting membrane of Desmidiaceae is firm, though flexible; it exhibits some elasticity and considerable resistance to pressure, is not brittle, and not readily decomposable. Traces of silica are found in a few species, but not, says Mr. Ralfs, “in sufficient quantity to interfere with their flexibility.” It is lined by a softer flexible membrane; and besides this, the Desmidieæ generally have an eacternal mucows or gela- tinous covering, mostly so transparent and homogeneous as to be overlooked. To bring it into view, it is a common plan to add some colouring matter to the water in which the organism is viewed; but good manipulation with a high power will frequently succeed without recourse to this expedient to demonstrate it. The particles of colour diffused about the frond, and indeed any external bodies, such as Small vegetable cells, are seen, not in contact with the fronds, as they would often be if these were naked, but kept at a distance corresponding with the width of the hyaline envelope (I. 15; II. 35). In Didymoprium Grevillii and Stawrastrum tumidum the mucous sheath is distinct and well defined; “in others (to quote Mr. Ralfs) it is more atte- nuated . . . . , and, in general, its quantity is merely sufficient to hold the fronds together in a kind of filmy cloud which is dispersed by the slightest touch. When they are left exposed by the evaporation of the water, this mucus becomes denser, and is apparently Secreted in larger quantities to protect them from the effects of drought.” The liming or the primordial membrane of the firm lorica is thin, colourless, and highly elastic, and alters its contour with the varying movements of the endochrome which it immediately invests. It is in contact with the outer case only at some points, mostly about the centre, and being elsewhere free, an interval exists between the two envelopes. This elastic lining is acted on by various chemical reagents; for instance, it is contracted or corrugated by iodine and by acids. OPENINGS IN LORICA.—Openings have been represented by several writers in the firm envelopes of Desmidieæ, and more particularly in those of Clos- terium. Ehrenberg, for instance, stated that apertures existed at the extre- mities, through which soft, very short, and conical transparent papillae slightly protruded to serve as locomotive organs. Both Mr. Varley and Mr. Dalrymple also described terminal orifices, closcă within, however, by a mem– bramous envelope; but neither they nor any other observers have detected the papilla-like locomotive organs Ehrenberg represented. “In no instance OF TELE DESMIDIE ZE. - 5 (Mr. Ralfs says) can any portion of the contents of the cell be forced out from the extremities.” More recently the belief in terminal apertures has been revived by the published researches of the Rev. Mr. Osborne and others (J. M. S.), who affirm, that not only the outer hard case, but also the mem- branous lining is penetrated by foramina, through which water enters from without into the cavity of the frond. Another writer in the Mic. Journ., Dr. Wright, describes, in a specimen of Closterium didymoticum, certain circular markings, consisting of two concentric rings, as apertures penetrating “both layers of the investing membrane at irregular intervals:” yet neither the character of these circular bodies, as represented by their observer, nor their irregular distribution, countenances such a notion, and the appeal he makes to Mr. Ralfs's figures, instead of aiding his argument, is totally subversive of it; for although, in the fronds of Closterium didymoticum and of C. Ralfsii, Some large globules are distinguishable, these are in single linear series in a definite and constant position, except when disturbed from it by the death of the plant, or by its exhaustion by parasitic growths upon it, and clearly are not apertures. Besides, any such globules are sought in vain when the frond is empty, as Mr. Ralfs distinctly shows by his figures; whereas if they were openings, they would then be more evident than when the frustule is filled with its endochrome. Mr. Wenham (J. M. S. 1856, p. 159) has been un- able to confirm the presence of apertures, and writes—“It may be assumed that if such an opening existed it would have something like a structural margin of such a size as to allow its position at least to be visible under the microscope, but not the slightest break can be observed in the laminated structure that the thickened ends display.” MoVEMENTS AND EXTERNAL CILIA.—By continued observation the Desmidieæ are seen to move very slowly onwards, or with an oscillating movement backwards and forwards. This phenomenon is most notable in the long spindle-shaped fronds of the genus Closterium; in others it is scarcely, in many not at all, cognizable. Ehrenberg having persuaded himself of the existence of pedal organs or papillae at the extremities of the fronds of Clos- térium, found no difficulty in explaining their locomotion; but other observers, who deny the presence of such organs, have been compelled to seek some other explanation of the subject. Some have referred the locomotion to the influence of the vital acts taking place within the organism, to the extri- cation of gas, &c.; others again, particularly of late, have attributed it to the presence of cilia covering the surface. This latter hypothesis is sup- ported chiefly by the Rev. Mr. Osborne and Mr. Jabez Hogg, who represent these organs as covering the fronds of Closterium, of Staurastrum, and of other Desmidieæ (see page. 7, on the Circulation). Mr. Wenham has sought cilia in vain, and attributes the supposition of their existence to an optical illusion. Powerful oblique sunlight, which is found necessary to display the apparent ciliary movement, this observer remarks, “causes a refractive atom to appear elongated as a ray or line . . . ., and this line also to appear to extend over the boundary of a cell-wall or other adjoining body: another cause of deception arises from a large angle of aperture.” The pos- sibility of such errors he illustrates by reference to the circulation as seen in Anacharis. In those fronds invested with a mucous sheath, cilia on the Surface of the lorica could perform no locomotive function, and therefore can scarcely be supposed present. Likewise in the concatenated species they cannot be looked for, since any movements they possess are of that general Sort seen in other filiform Algæ, springing from vital action under the influence of light. Apart from this inconsiderable movement, seen under the microscope, the 6 GENERAL EIISTORY OF TEIE INFUSORIA. Desmidieæ are known to move through considerable spaces. They travel towards the light; appear on the side of the vessel on which the light falls, or rise to the surface and form a pellicle upon it. These, and the analogous fact of their penetrating to the surface of mud in which they have been imbedded, when exposed to light, are phenomena common to the Desmidieæ with other Algae. “Another proof (writes Mr. Ralfs) of their power of locomotion is afforded by their retiring in some instances beneath the surface when the pools dry up,” a phenomenon witnessed also in the case of other plants. Braun (R. S. p. 203) casually refers to this kind of motion, dependent on the resumption of vital action. The Penium cwrtum (Cosmarium curtum, Ralfs), which grows “in rain-pools which are alternately quickly filled and dried up in the changes of the weather, ascends from the muddy bottom, when the pools fill, in the form of beautiful bright green clouds, produced by the social growth and the very fluid, widely-extended gelatinous invest- ment of the cells.” The movement of this plant, it is added, is more active and more regular than that of other Desmidieæ, and “it is a remarkable sight to behold all the individuals in a dish of water in a short time turn their long axes towards the light, and thus arrange themselves in beautiful streaks in the gelatinous mass. Observation likewise shows that it is the younger half of the cell, distinguishable as such for a long time after division, which here turns towards the light.” CoNTENTS OF FRONDs.-The contents of the fronds or frustules of Desmidieæ are designated generally by the name of Endochrome. This endochrome, we have already remarked, is of a grass-green colour, and contained in a proper sac lining the denser lorica. It is not homogeneous, but presents numerous globules, Small vesicles, and many refracting corpuscles; it is commonly not uniformly diffused, but collected in a definite manner, and it either com— pletely fills its sac or leaves it unoccupied at parts, which not seldom are constant in position and aspect. The appearance of the endochrome is modified by age, by external physical circumstances, and by the process of development. Nägeli and Braun describe it as constituting two layers within the primordial utricle, viz. an outer and an inner mucilaginous layer, the latter the thicker of the two. Ehrenberg, influenced by his belief of the animal nature of the Desmidiaceae, and by his peculiar hypothesis of their polygastric organization, represented the larger vesicles or globules to be digestive sacs or stomachs, and the Smaller green corpuscles, ova. He even exerted his imagination still further, by announcing that in Micrasterias, Arthrodesmus, and one or two other genera, male reproductive structures are visible. These suppositions it is not necessary to discuss, seeing that they are unsupported by any facts in the structure and Oeconomy of this family. The globules and corpuscles of the endochrome of Desmidieæ seem to differ in no respect from those in other Algae, consisting of chlorophyll, starch, and of oily materials floating in a watery medium. In most species of Clostérium and of Tetmemorus, Some large diaphanous vesicles are con- spicuous, either disposed irregularly, or more frequently in a single longi- tudinal Series (II. 1, 12, 13). These have the appearance of being distinct cells; and Mrs. Thomas has indeed described two such, of large size, in Cosmarium margaritiferum, as “vesicles filled with moving granules.” No doubt many of the apparent vesicles are nothing more than vacuoles which, as in other protoplasmic substances, tend to arise in the cell-contents, and may assume a fixity in size and in position. The several species of Closterium and of Docidium, and some of Penium, present also, at each extremity of the endochrome (II. 2, 9, 14), “a large OF TELE DESMIDIE ZE. 7 hyaline or straw-coloured globule which contains minute granules in con- stant motion.” It is seen even in the earliest stage of the frustules, but disappears in dried specimens. In addition to these structures, distinguishable in certain genera only, Nägeli and others state that a central nucleus exists in all the Desmidieæ, mostly containing within itself a nucleolus. “In Closterium (Braun writes) the nucleus with its colourless mucilaginous envelope is maintained in the centre of the spindle-shaped cell by the green lamellae of contents, arranged radiantly around the long axis of the cell, which lamellae are interrupted by it in the middle of the cell. In many cases it seemed to be surrounded as by a band, or by a cavity containing water.” Nägeli affirms that “Arthrodesmus possesses a small colourless corpuscle on the wall of the cell, which looks like a nucleolus. Euastrum also exhibits frequently among the green contents two obscure bodies resembling nuclei, always one in each half, when the division through the middle takes place. These are not attached to the cell-membrane, but lie free in the midst of the cavity: they appear to possess a dark centre (nucleolus) and a clear peri- phery (enveloping layer?). . . . In Clostérium a nucleus lies in the centre which possesses a thick whitish nucleolus within a clear enveloping layer. It is coloured brown by iodine, and wholly resembles the nucleus in Spi- rogyra.” Probably the vesicles mentioned and figured by Mrs. Thomas are really nuclei (I. 2, 5). There is something special in the disposition of the endochrome in very many of the Desmidieæ. On a front view of Desmidium, the endochrome is divided into linear portions by a pale transverse line between the angles; and on a transverse view it is seen to send out as many thick rays as the cell has angles. Again, in Cosmarium Ralfsii the endochrome is somewhat radiate ; but it is in the elongated genera, in Penium and Closterium, that its disposition is most characteristic. In both these genera the green matter of the endochrome seems condensed, so as to produce broad longitudinal bands (II. 2, 14), technically called fillets, which have their continuity always interrupted at the median transverse suture, and in several examples of the genus Penium by three cross bands. These fillets are more or less strongly marked in different cases, and, it may be, are constant in number in the same Species. Mr. Ralfs (p. 159) tells us that Meneghini considers them of too much importance to be omitted in the specific definition. They may occa- sionally be useful in discriminating nearly allied forms; but as they are fre- quently indistinct, or from various causes not readily counted with certainty, he is unwilling to introduce them into the specific characters, except in the absence of more permanent marks of distinction. CIRCULATION OF CONTENTS.–A circulation or rotation of much of the liquid contents may frequently be seen in the Desmidieæ. The Closteria afford the best subjects for witnessing this phenomenon, but careful focusing and other microscopical adjustments are always needed to display it. Even Mr. Ralfs had failed to observe it until he watched it in conjunction with Mr. Bower- bank, in Closterium, Lunula and in Penium Digitus. Since Mr. Ralfs's account was written, much more attention has been bestowed on this phenomenon; and it has been observed by every micro- scopist who has sought for it. The Rev. Mr. Osborne has particularly studied it, and has come to the conclusion that it is due to ciliary action. “If (he writes, J. M. S. ii. 235) I put a specimen on the stage, cover the stage So as to exclude the light, use the parabolic illuminator with the direct light of the sun, in certain focal positions I see what appear to be cilia working evenly and continuously along the whole external margin of the plant. I 8 GENERAL HISTORY OF THE INFUSORfA. am inclined to believe that this is not so, that this is some ocular deception, and that these cilia, so seen, are within the outer case. It may be that these cilia are on the external surface of the membranous sac, as well as over the endochrome; more practised observers with higher powers may yet determine that. Of the existence of the cilia throughout the plant there can be no doubt, and no object I have ever seem will bear comparison with this when beheld under sunlight. . . . . It is seldom that I can trace a current up one margin, and round the point down the other; these currents seem to me as the rule to pass from the point, when they reach it, down to the centre of the spot where the cilia are seen terminating the endochrome.” In a second part of this communication the writer adds: “I have scarcely failed in one attempt to see the circulation and ciliary motion in the Clos- terium Lunula. I tried today heating a little water, by putting a small bottle in a cup of warm water; the effect seemed to retard the circulation, but to make the globules larger. I have traced it over the whole extent of the en- dochrome, but it is best seen at the convex side a short way from the edge. I am more than ever convinced the cyclosis is the waving of attached tongues of cilia. The specimens are capricious in the results they afford; they show best when the sun has been on the jar for a time. I have watched the move- ments of the globules in Vallisneria, Nitella, &c., and they are to me altogether of a different nature to that in the Closterium, &c. To my eye there is no real analogy between this circulation and that in the above plants; but there is much more with the branchial action in the mussel.” Mr. Jabez Hogg's supplementary notes to Mr. Osborne's paper represent the whole frond as “brilliantly glittering with the moving and active cilia; whilst in the cyclosis numerous zoospores were most actively moving about by the same agency. When the sunlight falling on these little bodies warmed them into life and motion, the rapid undulations produced by the action of the cilia illuminated the whole frond with a series of most charming and delicately- coloured prismatic fringes or Newton’s rings. The motion and distribution of the cilia must be seen by the aid of the direct sun-rays and parabola ; for although I tried every other mode of illumination, and with Mr. Brooke used Gillett's condenser, yet neither of us noted satisfactorily their situation and distribution until we resorted to the parabola. At the same time the cir- culation may be most accurately observed to take place over the entire surface of the frond. The stream is best seen to be running up the external margin, just internal to a row of cilia, with another taking a contrary direc- tion next to the serrated ciliary edge of the endochrome; the whole being restricted to the space between the mass of endochrome and hyaline integument passing above and around the cyclosis, but not entering into it.” Another writer (J. M. S. 1855, p. 84), Mr. Western, adduces an observa– tion which he believes to confirm the presence of cilia in Closterium, and even goes So far as to advance the motion that the circulation in the cells of Chara, and, by analogical reasoning, in those also of other water-plants, originates in ciliary movements. In Chara, as in Closterium, he tells us, he observed “precisely the same appearances, the same rapid undulations, to- gether with the same brilliant coruscations.” Dr. Wright, whose contribu- tion in the same Journal (1855, p. 171) we have previously quoted, admits the presence of cilia, and starts the extraordinary supposition that the circu- lation of the contents of Closterium is carried on through canals or vessels, which he describes as marginal, and that it is independent “ of a frequent irregular movement of granules of endochrome more resembling imperfect cyclosis.” If our doctrines concerning the physiology of animal and vegetable cells be OF THE DESMIDIEAE, 9 at all correct, the statements above quoted respecting the ciliary origin of cyclosis, and more particularly the hypothesis of a vascular system, are scarcely or not in any way admissible. We are disposed to attribute the appearances so interpreted to misconception. Dr. Wright's notion of canals or vessels is equally extravagant with that once advanced by Schultze, of the network of sap-vessels in and about the cells of plants, and requires no dis- cussion. The opinion of Mr. Osborne that the currents in Closteria and other Desmidieæ are due to cilia, and are not analogous with the in all respects similar currents in the cells of various aquatic plants, is simply an assump- tion, and one indeed in opposition both to what an unbiassed observation of the phenomenon in the two sets of plants would suggest, and to what com- parative physiology would teach. Again, the analogy he suggests between his supposed ciliary cyclosis and the ciliary action of the branchiae of the mussel will be inconceivable to any one who understands the structure of the branchial apparatus of Mollusca, the distribution of the cilia on the external surface of a mucous membrane, and their office there in providing for the active performance of the respiratory function. Analogy would, indeed, in- duce us to believe, that if cilia are the motory organs of the cyclosis of Desmidieæ, they are equally so of that in other unicellular Algae, as well as of that in the cells composing the tissue of compound forms. If so, we might adopt Mr. Western’s belief in the existence of cilia wherever a circulation of the contents of cells is visible, did not our opinion of the nature of cells and of the histological relations of their parts deter us from accepting the doc- trine at all of the presence of internal cilia within unicellular organisms. Then, again, we cannot see the necessity of a ciliary apparatus to secure the fluctuating, oscillating or irregular and mostly incomplete movements of the corpuscles within the cells of Desmidieæ. To us such movements are expli- cable by reference to the changes ensuing in the nutritive processes of the living organism, and to the currents caused by the ever-acting endosmose and exosmose. Moreover, it should be borne in mind how exceedingly minute these molecular movements are; how very inconsiderable the space passed through is; how sluggish, compared with those due to undoubted ciliary ac- tivity, the movements themselves are. But in addition to arguments deducible from analogy and general morphology, those put forward by Mr. Wenham, resting on direct observation and experiment, seem to us strongly adverse to Mr. Osborne's hypothesis, and indicate it to be a consequence of optical de- ception. At a preceding page (p. 5) we have quoted Mr. Wenham’s remarks on the deceptive effects produced in viewing objects by oblique sunlight, or by any powerful source of illumination, and by the use of a large angle of aperture; we will here add his comparative observation of the circulation of Anacharis. In viewing this, he tells us (op. cit. p. 159), “with a large aper- ture, the chlorophyll-granules traversing along a straight and thin septum (if the position is favourable) appear to project into the neighbouring cell, seem- ing to pass directly under the line of the cell-wall. Smaller particles will apparently travel within the substance of the cell-wall; and in case of a boundary or single cell, or in unicellular plants, if the surrounding water has nearly dried up, the rim or prism remaining round the exterior (by the way, just the conditions under which Mr. Western made his observation) causes irregular refracted images of the particles of protoplasm to appear outside the cell, bearing such a remarkable similarity to external cilia, that the passing shadows may even be mistaken for currents in the water.” Besides the incomplete rotation or circulation of the contents just con- sidered, there is an active bustling sort of movement of minute granules within an apparent globular vesicle situated at each end of the elongated 10 GENERAL EIISTORY, OF TELE INFUSORIA. fronds of some Desmidieæ, e.g. of Docidium and of Closterium. The vesicles in question are known as the “terminal globules,” or chambers, and would appear to be actually invested with a membrane, and therefore distinct en- closed sacs. In Closterium rostratum and C. Setaceum, the collection of moving granules is at a distance from the extremities, and apparently not contained within a vesicle. In all species exhibiting terminal globules these structures appear in their earliest stage, but disappear when they are dried. Ehrenberg imagined the supposed retractile locomotive organs to be fixed to these globules, and that the granular movement within them was no other than that of the bases of these organs. Mr. Warley described the chambers as having contractile walls, and the molecules as transparent spheroids mea- suring from 1-20,000th to 1–40,000th of an inch, sometimes escaping from their chamber and circulating vaguely and irregularly between the periphery of the gelatinous body and the shell. Mr. Ralfs regarded the terminal glo- bules to be peculiar to the Closterina; yet their contained granules seemed to him “to differ in no respect, except in position and uninterrupted motion, from other granules in the same frond.” He once saw the motion continue after their escape from the cell. Mr. Osborne (op. cit. p. 235) believes the granules to be ciliary bodies. He writes: “At the extremities of the green matter there are certain bodies acting with a ciliary movement within what has been called a chamber, lying towards the point of the membranous Sac ; certain bodies, apparently of the same kind, separate from the endochrome in a small mass, appearing at the extreme end of this so-called chamber, or at the side close to the end; these also impart a ciliary movement to the water within the sac around them.” He adds (p. 239): “When the endochrome is of a rich dark green, I find the chamber at the extremity very plain and defined, with its cilia very active. . . . As the endochrome gets of a lighter colour. . . . the chamber becomes smaller and the cilia are barely seen.” At p. 236, Mr. Osborne further states, “The loose bodies secn in the chamber of Closterium Lumula have very generally cilia, and are, I believe, Zoospores; loose pieces of endochrome are sometimes brought round in the current, but these are easily distinguished. I have never seen anything like true cyclosis, i. e. molecules in circular movement, within the so-called chamber.” Of the purpose of the moving granules within the terminal globules, the prevailing notion is that they are zoospores. Meyen likened them to the “spermatic animalcules of plants;” and, as above noted, Mr. Ralfs saw them move about as do the zoospores of other Algæ when freed from the enclosing capsule and frond. So far as we can gather from his remarks, Mr. Osborne also inclines to this opinion, which is likewise supported by Mrs. Thomas (T. M. S. 1853, p. 37). We are sorry that we can present no more definite views concerning the nature, characters, and purpose of the terminal globules than those comprised in the foregoing extracts. We find no similar globules in other Algae, and therefore obtain no guide from analogy; indeed such structures seem to be peculiar to the elongated Desmidieæ—to the genera Closterium, Penium, and Docidium ; we must consequently look to Subsequent research to elucidate the question. (See Appendix at end.) Another sort of internal movement, more prevalent among the Desmidieæ than that last considered, is “the swarming motion,” so called, seen either at one or two parts of the frond when mature, or otherwise throughout its con- tents. Having Once commencod, it mover ceases, but extends itself, and induces changes in the nature, appearance, and colour of the endochrome; for this loses its grass-green colour, acquires the autumnal yellowish or reddish-brown tint, and a finely granular aspect. When the granules burst OF THE DESMIDIE ZE. 11 through the openings of the suture between the valves, they escape to a distance and still keep up their active movement. In the genus Cosmarium this phenomenon is frequently and readily ob- served. Mrs. Thomas, in her interesting observations on Cosmarium mar- garitiferum (T. M. S. 1855, p. 33), has detailed the following appearances:— “In each half (she writes) the centre was occupied by a vesicle (as it appeared) filled with moving granules, while Smaller vesicles were at the four sides (I.2). The granules did not appear to circulate through the plant, but kept to their own place, which was either a bag or cavity—I could not decide which.” In another example “ the granules were swarming over the whole plant.” These peculiar movements of the granules are not restricted to this tribe, but are known to occur in many genera of Algae. Their purpose seems con- nected with the reproductive process. Mrs. Thomas (loc. cit.) refers to it as in some way related with the formation of sporangia; whilst Mr. Ralfs, who speaks of the Swarming particles as “Zoospores,” confesses himself perfectly unacquainted with their subsequent history, although he coincides with Pro- fessor Parvey in regarding the phenomenon of Swarming as a “strictly vege- table peculiarity.” IREPRODUCTION OF DESMIDI.EXE.—This function presents itself under two phases, the end of one of which is to multiply or perpetuate the individual plant, whilst that of the other is to reproduce the species. The former pur- pose is attained by the process of fission, the latter by that of the development of sporangia, and, it may be, by the Swarming of Zoospores. The act of self-division is frequently observed, and is in all respects the same process as in the cells of other Algæ, or indeed of any plant. Analogy, and not, indeed, direct observation, suggests as necessary the initiative action of a nucleus to precede the constriction of the soft lining sac of the lorica, ?. e. of the primordial membrane, which is next followed by that of the harder external coat. The proceeding is varied, in some non-essential particulars, by the figure of the fronds, and also by the circumstance of its own completeness or incompleteness. Mr. Ralfs has well described the fission of Euastrum (op. cit. p. 4). The narrow connecting band between the two segments of the frond lengthens and is “converted into two roundish hyaline lobules;” these, though at first very minute, increase rapidly in size, and exhibit from their origin the deep constriction characteristic of the mature fronds. The advancing growth of the interposed new formations necessarily pushes further asunder the original segments, which finally become disconnected, “each taking with it a new segment to supply the place of that from which it has separated. . . . At first the new portions are devoid of colour, and have much the appearance of condensed gelatine; but as they increase in size the internal fluid acquires a green tint, which is at first very faint, but soon becomes darker; at length it assumes a granular state. At the same time the new segments increase in size and obtain their normal figure; the covering in some species shows the presence of puncta or granules, and, as in Xanthidium and Stawrastrum, the spines and processes lastly make their appearance, beginning as mere tubercles, and then lengthening until they attain their perfect form and size. Complete separation, however, often occurs before all these details of develop- ment are complete (II. 11, 24, 26). This singular process is repeated again and again, so that the older segments are united successively, as it were, with many generations.” Illustrations of this act are furnished, in the case of two species of Cosmarium, in the appended plates (I. 4; II. 26), to which the above account will be found equally well to apply. “In Sphaerozosma the same changes take place (I. 11), and are just as 12 GENERAL HISTORY OF TEEE INFUSORIA. evident; but the cells continue linked together, and a filament is formed, which elongates more and more rapidly as the joints increase in number. This continued multiplication by division has its limits; the segments gradually enlarge whilst they divide, and at length the plant ceases to grow; the division of the cells is no longer repeated; the internal matter changes its appearance, increases in density and acquires starch-granules, which soon become nume- rous; the reproductive granules are perfected, and the individual perishes. In a filament the two oldest segments are found at its opposite extremities; for so long as the joints divide, they are necessarily separated further and further from each other. Whilst this process is in progress, the filament in Sphaerozosma consists of segments of all sizes (I.11); but after it has reached maturity there is little inequality between them, except in some of the last— formed segments, which are permanently smaller. The case is the same with those genera in which the separation of the cells is complete. . . . It is obvious that the new portions must arise from the whole of the junction-margin of the original valves; consequently when the junction occupies only a part of . the breadth, the new portion will be narrower than the old; but when the junction of the valves is as broad as the cell, the new portion will from the beginning be of the same breadth,” and will remain undistinguishable by its size when fission is complete. Mr. Ralfs goes on to say that, “when the cell is oblong, or only rounded at the extremities, the process, though similar, is less evident; the cell at first seems merely to elongate (II. 11), until it attains nearly twice its ori- ginal length, when the division commences, and the rounding of the new ends becomes apparent. The tapering cells present but little difference, for the separation takes place before the extremities are fully developed; sometimes these cells separate obliquely, as in Spirotaenia.” The mode of self-division in Closterium has been illustrated by the Rev. Mr. Osborne (J. M. S. 1854, p. 57), from whose account we abstract the fol- lowing particulars:–“I have (he says) watched for hours the process of complete self-division; one-half of the frond has remained passive, the other has had a motion from side to side, as if moving on an axis at the point of juncture; the separation has become more and more ardent, the motion more active, until at last, with a jerk, one segment leaves the other,” each having one extremity—the one newly formed along the line of junction of the two segments—much more obtuse than the other. “The circulation of the con– tained globules for some hours previous to Subdivision, and for some few hours afterwards, runs quite round the obtuse end of the endochrome.” Previously to complete separation each segment begins to show a central constriction of its endochrome, which in due time extends across the new frond, and constitutes the median clear space or band. A true reproductive act is presented by the act of conjugation, or coupling of two fronds, and by the resultant development of a sporangium (II. 6, 8; XVI. 11, 12, 13, 14). This process consists in the apposition and subsequent intercommunication of the cavities and contents of two cells, which may be free, or otherwise, members of a chain or filament. It is an act not peculiar to the Desmidieæ, but common to them along with the Diatomeae and Con- jugatae. “In the family Conjugatae (says Mr. Ralfs) the cells conjugate whilst still forming parts of a filament; but in the Desmidieæ the filamentous species almost invariably separate into single joints before their conjugation, and in most of the species the valves of the cells become detached after they are emptied of their contents.” To bring about the necessary apposition, it is usual for the conjugating cells to expand or bulge out on those sides which are to come into union; and whilst this is proceeding, the vesicles or globules OF THE DESMIDIEE. 13 increase much in number, and, together with the granular contents, become aggregated about the conjugating part. When contact is complete, an absorp- tion of the opposed walls of the two cells takes place, or the suture of each opens, the endochrome from both is discharged and intermingled, and an orbicular green granular mass, enveloped in a mucous sheath thrown out around it by the conjugating cells, is produced. When the process has pro- ceeded thus far, the original valves are more or less completely emptied of their contents, lose their vitality, and are sooner or later detached, and float away from the sporangium developed. The formation of a sporangium by conjugation occupies no great time. Indeed, in the case of Closterium Ehrenbergii, the Rev. W. Smith tells us that “the discharge of the endochrome and the formation of the sporangia are accomplished with much rapidity, and may often be seen taking place in the field of the microscope; the whole operation not occupying more than a few minutes. . . . During the formation of the sporangia there appears to be a second development of mucus in the form of rings around the reproduc- tive bodies; this is probably only the effect of the pressure produced by the growth of the sporangia on the mass of investing mucus.” This act of conjugation admits of slight variations in character, determined by the form of the conjugating cells, and by other circumstances peculiar to the tribe, family, or genus in which in it occurs. In the filamentous species of Desmidieæ, the joints, as before noted, usually become separated before their conjugation; and in most instances the old valves left empty after the act of conjugation are almost immediately detached from the sporangium; but in a few species they persist some time afterwards, e. g. in several of Penium. In Didymopriwm the separated joints, on conjugating, unite by means of a narrow process pushed out from each, and often of considerable length; through this the endochrome of one cell is transferred into the other, and thus the sporangium is produced within one of the two cells, just as in the Conjugatae. In Stawrastrum and Micrasterias the contents of both fronds are discharged into a delicate intermediate Sac or bag, which gradually thickens, produces eminences, and at last forked spines (II. 25). Again, in Tetmemorus, “the process of forming the sporangium (says Mr. Ralfs) is interesting, as it exhibits a striking similarity to the change during the formation of similar bodies in Stawrocarpus among the Conjugatae. In Staurocarpus, after conjugation, a subquadrate cell is formed, within which the endochrome is collected. The latter is at first of the same figure as the cell, but in at least one species is at length condensed into a compact globular body, and in every species the cell with the contained sporangium finally separates from the filaments with which it is connected. In this separate state I can discover no character by which to distinguish the sporangium of Tetmemorus from one belonging to a species of Staurocarpus.” To quote the same authority,+*In Penium Jenner the conjugating fronds do not open and gape at the suture, as is usual in the Desmidieæ, but couple by small and distinct cylindrical tubes like many of the Conjugatae. . . . . . In Closterium two fronds unite by means of projections arising at the junction of the two segments, and then the newly-formed portion continues to enlarge until the original segments are separated by a cell of an irregular figure (II. 5, 6). The contents of the fronds being collected in this cell become a dense seed-like mass, which is sometimes globular, resembling the sporangium of Mougeotia, and sometimes square, like that of Staurospermum. The newly- formed cell is thinner and generally paler than the segments of the fronds; in some species it looks like a prolongation of the segments, and in others these are so loosely attached that their connexion is scarcely perceptible. 14 GENERAI, EIISTORY OF TEIE INFUSORIA. The coupling of the fronds generally takes place from the convex margin, but may occur on the concave, or even the convex margin of one frond may couple with the concave of the other.” The Rev. W. Smith (A. N. H. 1850) represents the conjugation of Closterium Ehrenbergii to be peculiar (XVI. 11, 12, 13, 14). The first phenomenon (he tells us) is an alteration in the granular condition of the endochrome. This, from a light yellowish green, passes to a much darker shade, and the larger granules, or “ diaphanous vesicles” of Ralfs, which were originally few in number, and arranged in a somewhat irregular longi- tudinal series (XVI. 10), become exceedingly numerous and pervade the entire frond. While this change is about taking place, the fronds approach in pairs, approximating by their concave surfaces, and finally coming into such close neighbourhood that their inflated centres are in contact and their extremities slightly overlapped (XVI. 11). In a short time, probably in the course of twenty-four hours, a remarkable change takes place, both in the appearance and condition of the fronds; a mass of delicate mucus is secreted around the approximated fronds; these remove to a little distance from each other, undergo “self-division,” and present altogether an irregular oval figure, the outline of which is formed by the periphery of the mucus, the four divi- sions of the fronds being placed in the middle in a somewhat quadrilateral manner (XVI. 12). During the progress of cell-division, the internal mem- brane of the cell-wall becomes enlarged at the suture or line of separation, and projects in the form of an irregular cone, with a blunt or rounded apex forming a beak, whose side view presents a triangular outline. This beak becomes filled with endochrome, either by the dilatation or increase of the contents of the half-frond, and the divided frond assumes the appearance of one with two unequal segments (12), being what M. Morren calls “a Clos- teriwm of two unequal cones.” On these membranous expansions, at the con– cave surfaces of the fronds, and close to the original sutures, there appear, almost simultaneously with the formation of the beaks, two circular projec- tions, which, rupturing at their apices, give egress to the delicate sacs which enclose the endochrome, and which, drawing with them their contents, and meeting with the endochrome sacs emitted through similar projections from the other half-fronds, form, by their connexion, irregular masses, which quickly consolidate and assume the appearance of perfectly circular, smooth, dark-coloured balls, the sporangia of Ralfs and seminules of Morren, Lastly, we may add, that Siebold (J. M. S. 1853, pp. 118, 119) remarks that the conjugation in Closterium Dianae, C. lineatum, C. striolatum, C. setaceum, &c., differs from that in C. Lumula, C. rostratum, and other members of the family, by dehiscence at the central transverse suture, and the consequent coalescence of the contents of the two cells into a rounded or angular mass, an observation which tallies with the account presented us by Mr. Ralfs. Braun (On Rejuvenescence, R. S. p. 286 et seq.), speaking of conjugation generally in simple cells, gives an elaborate view of the variations the phe- momenon exhibits, and arranges them under several heads. Thus among the Desmidieæ “the conjugating cells unite with participation of the external membrane, [and] the reproductive cell is formed [either] through contraction of the contents clothed by the internal cell-membrane, [or] out of the mere contents as a new cell inside the mother-cell.” But in the majority of the Desmidieæ, “the conjugating cells, after dehiscence of the outer membrane, unite through the inner; the reproductive cell is formed out of the mere contents as a new cell inside the conjugation-cell.” By the first-named mode, “the formation of the reproductive cell is . . . . not a direct result of the conjugation, but it is formed subsequently in the interior of the con. OF TEIE DESMIDIE ZE, -> 15 jugation-cell, in the strongly expanded isthmus of this. The delicate internal membrane, with the contents enclosed by it, drawing itself out of the extre- mities of the double cell, forms a seed-cell, at first cruciate, four-lobed, then bluntly quadrangular, and finally globular, clothed by a many-layered thickened membrane within the persistent four-horned conjugation-cell. From Ralfs's representation, this is most probably the way in which the pro- cess is to be understood in Cylindrocystis (Penium) Brebissonii.” The second mode, when the union of the isolated cells is also lateral and parallel, is exemplified in Closterium Lumula, in which, according to Morren’s express statement, three different membranes take part in the formation of the canal of union,--an inner and an outer cell-membrane, and a membrane (the primordial utricle) immediately enclosing the green mass. The glo- bular reproductive cell formed in the connecting canal is an active gonidium, which begins to revolve even while in the canal, and soon breaks through the gelatinously-swollen membrane of the latter. Very often two approximated individuals divide again and conjugate before they have completely separated, whence result conjugated double pairs. - The third scheme of conjugation, the most widely extended, is itself reduced by Braun to two principal secondary varieties, and to several sub- sidiary ones. Thus conjugation takes place either in a parallel position or in a crossed (decussate) manner. The former is peculiar to the Closterina; the latter is met with in Euastrum and allied forms, and also in many genera formerly united with Desmidium. The modifications, in various species, of these plans are well explained in Braun's work, to which we would refer for particulars, as well as for an elucidation of the production of a “really double spore (not two-lobed, as Ralfs terms it)" in Closterium lineatum. The next question which presents itself is, whether the product of con- jugation is to be esteemed a spore or a spore-case, i. e. a sporangium. That the latter is its nature appears pretty clear, and is assumed as a fact by Mr. Ralfs. This authority observes: “The sporangia I consider capsules, and this view seems to be confirmed by the experience of Mr. Jenner, who states that the covering of the sporangium Swells, and a mucus is secreted, in which minute fronds appear, and by their increase at length rupture the attenuated covering.” In this opinion Siebold coincides; and the Rev. W. Smith (A. N. H. 1850, p. 4) represents, on the authority of Mr. Jenner, the bursting of a sporangium of Clostérium acérosum, and the development of young fronds from its contents. Braun, in his philosophical treatise (op. cit. R. S. p. 133), remarks of the products of conjugation in the Desmidieæ, that “they do not pass, like the Swarming-cells of the Palmellaceae and the reproductive cells of the Dia- tomaceæ, directly and by uninterrupted growth into the primary generation of the new vegetative series, but persist for a long time in a condition of rest, during which, excepting as regards imperceptible internal processes, they remain wholly unchanged. To distinguish these from the direct germ-cells (gonidia), I shall call them seed-cells (spores). The development of these spores has not yet been observed; but it may be assumed as certain, that they do not pass as such into the primary generation, but produce this at the period of germination, by an internal transformation of their contents, and bring these to light as a new generation with a dehiscence of the old en- velope. Certain early conditions observed in Closterium and Euastrum, namely families of unusually Small individuals, enclosed in transparent colourless vesicles, render it even probable that in certain genera of Desmidieæ, a number of individuals are produced from one spore, by a formation of transi– ...tory generations occurring already within the spore. The enclosing yesicle 16 GENERAL BIISTORY OF TELE INIFUSORIA. is probably the dissolved and swollen-up internal cell-coat of the spore, which holds the young individuals combined for some time after the outer coat of the spore has been thrown off.” Although Braun has, in the preceding account, made use of the term “spore” to express the conjugation-product, yet, in the very admission that, in those Desmidieæ in which only we have any clue to the subsequent history, it produces, not a single individual, as does a spore commonly so called, but a multitude, he essentially agrees with Mr. Ralfs, who prefers to call the body a capsule. We may quote Mrs. Thomas in support of the same view; for she considers the sporangium a capsule, or (T. M. S. 1855, pp. 36, 37) “the winter casing of a large number of young plants which escape from it by rapidly knocking against its walls, when these have been loosened by Spring warmth, or which grow up as the walls gradually decay in the midst of slimy gelatinous masses.” In proof of this opinion this lady appeals to the immense increase in the number of plants seen in the spring beyond what can be ex- plained as the result of self-fission. In her opinion the sporangium is a capsule (I. 8, 9) filled with Zoospores similar to those moving granules, supposed to be such, seen within the full- grown plant, capable, when their fitting time comes, of filling the waters with their countless progeny. In these accounts there is a pervading harmony; and the truth seems to be that, by the formation of a sporangium, provision is made for the per- petuation of the species through the winter, when the large majority, at least of adult plants, have ceased to exist. The phenomenon is clearly analogous to that of the formation of seeds by herbaceous plants, or of ova. by insects and other animals, when the cycle of existence of the parent being is complete, or is put an end to by unfavourable external circumstances. Braun has expressed the sequence in the phases of existence in the follow- ing technical language (R.S. p. 133): “In the Desmidiaceae, the Zygnemaceae, and in Palmogloea, the transitional generation is divided into a double one, since the last generation does not pass directly into the first, but the first generation of the succeeding cycle is produced as a new structure in the ger- mination; so that we have here to distinguish three kinds of generation of cells, the commencing generation, the concluding generation, and the intermediate vegetative generations.” The last-named is represented by the process of self-fission, which takes place in the perfect plant, and is con- tinued through a long series of individuals. Between its first appearance and its ultimate development, the sporangium of Desmidieæ undergoes a progressive series of changes; at first it is pale and homogeneous, but soon gets granular, acquires a gradually deepening green colour, and presents vesicles and globules in large number. The enve- lope, at first very delicate, augments in thickness, and becomes lined by others, whilst its surface either remains smooth or becomes granular, tuber- culated, or Spinous, and the spines themselves in many instances forked or branched (II. 15, 22, 25, 30, 34). Simultaneously with these changes the integument increases in density, and together with its processes acquires considerable firmness and toughness. Moreover, as it advances in age it usually assumes a reddish-brown colour; when this has happened, the sporangium and contents may be presumed to have reached maturity. Mrs. Thomas (op. cit. p. 35) thinks she encountered a mature sporangium of Cosmarium margaritiferum in the shape of a many-coated ball filled with granules in the same rapid motion as observed in the full-grown Cosmarium (I. 10, 11). “The similarity of the movement (she says) attracted my attention; and I also saw that in one part the enclosing membrane appeared OF TITIE DESMIDIE ZE. 17 thinner, as if giving way at that spot. On the third morning the membrane had broken and the granules escaped, leaving the nearly emptied case ’’ (I. 12). Inasmuch as a sporangium may pass successively from a Smooth to a spinous condition, it follows that the transitional stages of One species may be mistaken for the final stage of another; hence a difficulty in determining to what plant detached scattered sporangia may belong. It is only, indeed, when these secd- capsules occur in company with the fronds producing them that we are enabled to pronounce decisively by what species they are generated. As the foregoing account of conjugation and sporangia passed through the press, we met with the valuable paper of Dr. Hofmeister on the propagation of the Desmidieæ and Diatomeae, translated by Prof. Henfrey from the Report of the Natural History Society of Savony for 1857. This commu- nication tends to clear up the questions of the nature of the sporangia and of the relation of their contents to the propagative process. The conciseness of the description renders abridgment undesirable; and we accordingly present it (so far as it relates to the points in question) as it stands in the Annals of Natural History (1858, i. p. 2):— “The conjugated individuals of Cosmarium tetraophthalmum displayed exactly the behaviour which Ralfs has represented and Braun described of those of Cosmarium margaritiferum. The Cosmaria which had commenced the conjugation process appeared cracked apart at the constricted place in the middle. Into each of the halves of the tuberculated cell-coat of the two mother-individuals oxtended a continuation of the membrane of the conju- gation-cell. This smooth membrane completely lined the interior of the tuberculated half-shells. The contents of the conjugation-cell revealed no definite arrangement; they were mostly accumulated in the middle into an irregularly-shaped ball; in other cases separated into several such balls, part of which extended even into the split half-shells of the mother-cell. With these conjugated individuals, in the same fluid, occurred (very sparingly) par- ticular specimens which bore, in the middle space between the two separated half-shells, a broad, delicate-walled utricle, the circumference of which about equalled that of the two half-cells taken together. The arrangement of the cell-contents in the primary portions of the cell did not appear essentially altered; the contents of the intermediate expansion consisted of a thick coat upon the wall of granular protoplasm with sparingly-scattered chlorophyll. This condition is probably that which immediately precedes conjugation, originating by excretion of new cellulose at the deepest part of the constric- tion, after the cracking of the membrane and separation of the primary halves of the cell, exactly as in normal cell-division, from which this process can only be distinguished by the omission of the formation of a septum at the narrowest part of the isthmus. Similar phenomena have been observed by Nägeli in Cosmarium crenulatum, and by Mrs. Herbert Thomas in Cosmarium margaritiferum (scarcely specifically distinct from C. tetraophthalmum), only that here the intermediate piece of the Alga did not conjugate with the similar piece of another individual, but, producing tubercles on its outer surface, continued the vegetative life. “In other conjugation-cells there lay, in the middle part of the conjugation- cell, a globular cell enveloped in a rather thick membrane, of gelatinous aspect, and smooth on the outside (the spore). No intermediate stages could be found between this and the previously-described condition. Experiments, in which an attempt was made to obtain a completion of the less-advanced conjugation under the microscope, all failed. Apparently the conjugation- coll is exceedingly sensitive to any external injury, especially to contact with C 18 GENERAL IIISTORY OF THE INFUSORIA. foreign bodies. Very probably the contents, in the above-described cases, were already abnormally altered, and incapable of further development. “In other conjugation-cells the young spore displayed a still thicker mem- brane, covered on the outside with truncate-conical elevations, in which membrane could be detected a composition of two colourless layers. The outer of these layers remained clear and transparent even in the advance to maturity. Its elevations became developed into rather long spines, which forked at the apices into two or four branches. The deeper-seated layer of the spore-membrane meanwhile assumed a dark-brown colour. By rolling under the covering-glass, the tough, colourless, Outer layer may be readily stripped from the inner, more brittle, brown layer; then the latter appears covered on its outer surface with slight elevations, similar to those which first appeared upon the young spore. The brown layer of the spore-coat encloses a third, delicate, colourless layer (perhaps the primary membrane of the spore) which immediately envelopes the cell-contents. “At the beginning of July, the green contents of all the spores appeared conglobated into a spherical mass with sharp outlines, which, lying frce in the middle part of the cell, nowhere touched its internal wall. Three weeks later, in many of the spores these contents appeared separated into two flattened ellipsoidal masses; when I cracked the cell by careful pressure, I was sometimes successful in driving out one or both of the masses of contents in an uninjured condition. They could then be recognized beyond all doubt as primordial cells; bodies destitute of a solid cell-membrane, having a thin coat of protoplasm which ‘bubbled' out in water, to which adhered a thick investment, coloured bright green by numerous imbedded chlorophyll-granules, surrounding a central cavity filled with transparent fluid. The fluid contained in the spore in which the two primordial cells were immersed, was not colourless, but rendered turbid by numerous im– measurably small granules exhibiting molecular motion. In August each of the ellipsoidal primordial cells had divided into two globular cells, of similar character to the mother-cell. Towards the end of September, some of the spores exhibited another such division, so that they then contained cight, not globular, but strongly flattened primordial cells. Most, however, passed through the winter-rest unchanged, during which the majority died. At the beginning of April of the next year, the Spinous, transparent, outermost layer of the coat was more or less completely decayed on all the spores, even on those which were still to be recognized as living by the vivid green colour of the contents. All the spores still alive contained at least eight, many six- teen daughter-cells, all very strongly flattened, almost discoid. In several spores the outline of the daughter-cells was no longer circular, but displayed two shallow lateral notches. The still-existing, brownish, inner layer of the spore-coat was now seen to be softened; it no longer oxhibited its former brittleness, and it was difficult to crack it by pressure. Daughter-cells whose lateral constrictions were most strongly marked, were about half as large again as the circular, whose diameter about equalled that of the isthmus of the former, and they almost cntirely filled up the cavity of the spore. When these were pressed out from the crushcd spore, their form and size agreed almost exactly with that of Cosmarium Meneghinii. “I saw similar phenomena in the spores of Cosmarium whdulatum (Corda), in which the investigation is rendered very difficult by the minute size, and which, cultivated for some months in my room, entered abundantly into con- jugation. In this, again, I observed the contraction of the green contents of the cell into a globule occupying the central part; the division of this ball into two, four, eight, and sixtcon spherical masses; finally, the transition of OF TIII DESMIDIE ZE, 19 these daughter-cells of the last generation from the form of circular lenticular bodies into two-lobed ones like the mother-plant. Here the young Cosmaria, whose diameter amounted to scarcely #th or +th of that of the mother-plant, woj e set free by the very gradual solution of the membrane of the spore. A similar process very probably occurred in Cosmarium tetraophthalmum, but could not be observed there, from the circumstance that all the materials had been used up in the investigation. “These facts place it beyond doubt that the contents of the spores produced by the conjugation of two individuals of Cosmarium, are transformed by repeated binary division into eight or sixteen daughter-cells, which assume the form of the mother-cell, and finally become free by the solution of the wall of the spore. Such behaviour of the spores had indeed been rendered pro- bable before, by the discovery of the vesicular structure observed by Focke and Ralfs, which enclosed a number of small Closteria, for the most part beginning to divide. But the certainty which can only be given by direct observation of the development was altogether wanting. “The development of four daughter-cells in the interior of spores produced by the conjugation of two individuals (with participation of the whole of the cell-membrane), has been demonstrated by Alex. Braun for the Palmellacean Palmogloea macrococca, Kütz. (?).” Sporangia are the only portions of Desmidieæ of past eras which have been preserved to us in a truly fossil condition. Ehrenberg discovered certain orbicular and spinous bodies in flint, some of which he referred to the genus Manthidium among the Desmidieæ, and others to Pyazidicula among the Dia- tomeae. However, as Mr. Ralfs remarks (p. 13), this association is, no doubt, erroneous, since in true Xanthidia the cell is compressed, bipartite and bi- valved, whilst in these fossils it is globosc and entire, and there can be no doubt that they are fossil sporangia (XVII. 506 to 515). To quote Mr. Ralfs's account (p. 13)—“The fossil forms vary like recent sporangia, in being. Smooth, bristly, or furnished with spines, which in some are simple, and in others branched at the extremity. Sometimes, too, a membrane may be traced even more distinctly than in recent specimens, either covering the spines or entangled with them. Some writers describe the fossil forms as having becn silicious in their living state; but Mr. Williamson in- forms me that he possesses specimens which exhibit bent spines and torn margins, and thus wholly contradict the idea that they were silicious before they were imbedded in the flint.” Another mode of propagation is presumed to take place by means of the active molecules seen within the fronds of Desmidieæ—in other words, by zoospores, as happens in many families of Algae. M. Morren advanced this notion, and imagined the minute particles which he denominated “propa- gules,” to be at once transformed into small fronds. Mr. Ralfs countenances the opinion so far as to say that the escape of the granular contents of the mature frond is probably one mode of reproduction. He, however, likewise regards (as Prof. W. Smith observes) the swarming of the granules as identical with the movement of the zoospores, and confessos to his ignorance of the history of the motile granules after their escape. But we perfectly coincide with Prof. Smith that the Swarming of the granules within a mature frond is in most cases “a disturbance attendant upon the decay of the granular mass,” and not a phonomenon connected with reproduction. Still our acquaintance with the Swarming granules, particularly after their escape from the frond, is so imperfect that it is useless to speculate on their func- tional purpose. Ehrenberg, to carry out his hypothesis of the animal nature of Desmidieæ, C 2 20 GENERAL HISTORY OF THE INFUSORIA. and to assimilate their organization with that he attributed to other Poly- gastrica, represented the larger oil-vesicles and starch-grains to be either stomach-sacs or ova, at one time the one, at another the other, in a purely arbitrary fashion. Some again of the more transparent or refracting vesicles were, with no shadow of reason, called fecundating or spermatic glands. An attempt to show the error of such an hypothesis of internal Organization would be futile and uncalled for at the present day. BABITATs, DISTRIBUTION, APPEARANCE IN MASSES, AND WITAL ENDOWMENTS of DESMIDIEE. VEGETABLE NATURE AND AFFINITIES. MoDE OF COLLECTION.— . The Desmidieæ live in fresh water, in ditches and ponds, and rarely in streams, except when these are very sluggish. They will often rapidly appear in a recent collection of water, and are not destroyed when the pool is dried up, as their reappearance immediately after a shower proves; nevertheless, ponds which do not dry up during the summer, and pools in boggy ground, are richer in these organisms, provided the water remains Sweet. To quote Mr. Ralfs's experience—“The Desmidieæ prefer an open country. They abound on moors and in exposed places, but are rarely found in shady Woods or in deep ditches. To search for them in turbid water is useless; such situations are the haunts of animals, not the habitats of the Desmidieæ, and the waters in which the latter are present are always clear to the very bottom.” They no doubt inhabit the fresh waters in all parts of the globe, for they have been found wherever sought in each hemisphere. Still the several genera and species are not universal, for, as in the case of higher plants, some species are peculiar to one country, others to another; and in the same country the presence and prevalence of any one species will be determined by the physical features of localities, by the nature of the soil, and the like. The distribution, however, of the Desmidieæ has not been inquired into so fully as to justify any attempt to lay down special laws. Oftentimes in small collections of water, Desmidieæ of the same or of various species and genera multiply to such an extent as to colour the water, and in the case of the filamentous species, to appear in filmy masses on the surface or at the bottom of the pool; still this enormous multiplication, and the coloration of the water they inhabit, are far less frequent in the case of the family in question than with others—for instance, the Eugleneae, or even the Diatomeae. Mrs. Thomas (op. cit. p. 36) has described the green masses formed by Cosmarium, which during summer and autumn “would float to the surface, rapidly disengaging oxygen as the Sun shone on them, and sinking again to the bottom with the coolness of the evening. Later in the year, masses would adhere to the inner surface of the bottle in the form of a thin pellicle, or collect in .slimy masses, which appeared to dissolve with the warmth of the coming spring. The green colour changed to that of a reddish yellow; and it might have been thought that all was dead, did not the microscope show the same beautiful green, bothin young and full-grown plants, together with much bright red and brown, apparently the casings of the sporangia. . . . . . Large Cosmaria still in active motion (the remains of the mature growth of the pre- ceding Summer) layimbedded in the mass, when a small portion was separated for microscopic observation, as well as clusters of young ones (I. 13, 14) When the bottle had remained more than a year untouched, except for chang, of water, these masses increased in leathery hardness; green life was not extinct, but became feeble in colour, and too much changed to warrant further observations, while a small portion placed in another bottle, and more freely exposed to the light, multiplied with great rapidity.” Many of the vital endowments of the Desmidieæ have already been de- of THE DESMIDIEE. 21 scribed: we have noted their process of reproduction and of growth, the molecular and circulatory movements within them, their slight locomotive power; but besides these, there are others requiring to be mentioned: for instance, their powers of secretion are highly pronounced;—the production of firm envelopes to fronds and sporangia; the formation of starch-grains, of colouring matter, and of oil-globules within; the exhalation of oxygen from the surface,—a respiratory act; and lastly, their ability to resist decomposition. The Desmidieæ serve as food to many sorts of Small aquatic animals, to the Rotifera, to various Annelida and small Crustacea, and to the freshwater Mollusca. They are supposed also to preserve the freshness of the water, " and by the oxygen they exhale, to furnish the vital air necessary to the respiration of the aquatic animals found with them. They are subject to destruction not only in the way of Supplying food to animals, but also by disease. For instance, Cohn has shown (Entw. d, mikr. Alg.) that the Closteria are attacked by a microscopic unicellular fungus, called Chytridium, the spores of which affix themselves on the integument, and on germinating, penetrate the cavity of the frond by their delicate fibres, and induce a pro- gressive breaking-up and absorption of the contents, until nothing but the empty hull of the plant remains. Mr. Ralfs has the following remarks (p. 13):—“In all the Desmidieæ, but especially in Clostérium and Micrasterias, Small, compact, seed-like bodies of a blackish colour are at times met with. Their situation is uncertain; and their number varies from one to four. In their immediate neighbourhood the endochrome is wanting, as if it had been required to form them, but in the rest of the frond it retains its usual character and appearance. I cannot satisfy myself respecting the nature of these bodies; but I believe them to arise from an unhealthy condition of the plant, or else to be parasitic.” With respect to the views expressed in this extract, we are disposed to think Mr. Balfs right in his conclusion that the black bodies he met with were parasitic; and on comparing his account with the figures and description of the parasitic Chytridium in Cohn's memoir (Entw.), it seems to us highly probable that the globules referred to were no other than the spores of that microscopic fungus. IFor a long time discussion was rife respecting the animal or the vegetable nature of the Desmidieæ. That it was the former was the prevailing notion until within the last few years, when the improvements in the microscope, and the more extended and accurate knowledge of the features of vegetable life in its simplest manifestations, rendered this opinion no longer tenable, and at the present day it may be considered exploded. It is un- necessary, therefore, to go minutely into this question; for it will suffice to indicate the most striking distinctive characters, especially those which rest upon the affinities of the family under consideration. Those readers who would see the point fully discussed will do well to refer to Mr. Ralfs's admi- rable monograph, to which we, and others also, resort as to a mine, for the materials to build up a history of the Desmidieæ. An old argument advanced by Ehrenberg for the animality of the Des– midieæ, was, that they had a power of voluntary movement like animals. Without staying to consider the loose and unphilosophic use of this term -oluntary, as applied to the motion, whether in the Desmidieæ or in the Mplest animal existences, its occurrence can be no proof of animal life, seeing that it is exhibited by acknowledged plants, and in a still more marked manner by their spores. Moreover, such movements are doubtless effected by cilia, both in the animal and vegetable world alike, and are likewise determined by the vital processes going on within and also without these simple organisms, in relation with external media and with surrounding 22 GENERAL HISTORY OF THE INFUSORIA, physical conditions. Siebold, quoting Nägeli’s opinions, says (J. M. S. i. p. 120)—“The slow turning, and at the same time rare movements of the Closteria (the genus in which motion is more -evident), present no character of spontaneity; these motions are merely the consequence of an active endosmosis and exosmosis, by which the water immediately surrounding the Closteria, and consequently themselves, are put into motion.” Again, as Mr. Ralfs remarks, the motive power is less in degree than in the Diatomeae. Cell-multiplication by fission or transverse division, enumerated by Ehren- berg as an animal peculiarity, is now so completely established as a vegetable “ phenomenon, that it can claim no consideration when the question of the actual affinities of a disputed organism is to be solved. And equally unde- serving of critical examination at the present day is the complex animal organization attributed by the Berlin microscopist to the fronds of Desmidieæ. Concerning the apparent sac containing the moving particles in the Closteria and in other genera, regarded by Mr. Dalrymple as a vegetable peculiarity, Mr. Ralfs observes, “I confess I am unable to refer to any example in other Algae of terminal globules like those present in the Closteria, but neither can one be found amongst animals; and if in Some respects they have an analogy with organs belonging to the latter, in others they agree better with vegetable life.” On another argument raised, the same author remarks, “The con- traction of the internal membrane of the Closteria, or the expulsion of their contents on the application of iodine or other reagents, cannot be relied upon as a satisfactory test for determining their nature; for the blandest fluids will in some cases (both among recognized Algae and the Closteria themselves) occasion violent action.” On the other side of the question, the act of swarm- ing, the emission of actively motile germs (presumed in this family), the presence of starch and of chlorophyll, the chemical relations between these substances, and also with the oily matters formed in the fronds, the exhala- tion of oxygen in sunlight, and the absence of azotized material in their chemical constitution furnish reasons for arranging the Desmidieæ with plants. Besides these reasons, others are found in the general form and in the modes of propagation being precisely analogous with those in admitted unicellular Algae. Their intimate affinities with Algae are shown by the fact that Meneghini and Kützing placed Merismopaedia among the Desmidieæ, and that Braun refers the two genera Scenedesmus and Pediastrum, included by Ehrenberg himself in the family in question, to the Palmellaceae. The process of conjugation, which has been often appealed to as a characteristic of plant-life, would appear, however, to be, in exceptional cases and under peculiar modifications, also an animal phenomenon, and therefore inapplicable as a test. Meneghini, who contends for the animality of the Diatomeae, has pro- nounced (R. S. p. 497, 1853) the opinion that—“The Closteria and Des- midieæ in general are plants, and not animals. In the actual state of science we are compelled to admit this proposition. The organic structure, the phy- Siological phenomena, the history of their development, the chemical materials they contain, manifest in these beings a perfect correspondence with others, which in every point of view correspond with the abstract idea of a plant. But what they present in common with other beings evidently animal, is merely an appearance, or at the most, a resemblance in external form. Ehrenberg was misled by this appearance, and, guided by this fallacious similitude, thought that he discovered in the Desmidieæ the same organic peculiarities which proved the animality of other beings.” Respecting the affinities of the Desmidieæ, Mr. Ralfs states that, “on one side, they are allied to the Conjugatae (Zygnemea) by similarity of reproduc- OF TELE DESMIDIE ZE. 23 tion, and on the other to the Palmellea, by the usually complete transverse division, and by the presence of a gelatinous investment. Indeed the relation to the latter is so intimate, that it is difficult to say to which family some genera belong. . . . Some species of Scenedesmus may be allowed to have an almost equal claim to rank with either.” Again, they are related to the Diatomeae by similarity in the reproductive process. In Ehrenberg's system of Polygastria, the Closteria were placed together as a distinct family, under the name of Closterina, whilst all the other genera of Desmidieæ were ranged as a section of the Bacillaria. This separation, based as it was upon presumed structural peculiarities, is no longer accepted by microscopists, who cojoin Closterium with the several genera included in Ehrenberg’s section Desmidiacea in one group—the Desmidieæ. . The division of this family proposed by Mr. Ralfs is made according as– 1. The plant forms an elongated jointed filament (by incomplete division of its cells); or—2. The frond is simple, from complete transverse division, and distinctly constricted at the junction of the segments, which are seldom longer than broad; sporangia spinous or tuberculated—rarely, if ever, smooth ; or— 3. The frond is simple, as above, generally much elongated, never spinous, frequently not constricted at the centre; sporangia Smooth; or—4. Cells . elongated, entire, fasciculated; or—5. The frond composed of few cells, de- finite in number, and not forming a filament. This last section is so exceptional in general characters, and especially in the mode of reproduction, that Braun detaches it from the Desmidieæ and associates it with the Palmelleae. In this plan we coincide, and have there- fore treated separately this last section of Mr. Ralfs, comprehending Pedias- trum and ScénédéSmws. Kützing (Species Algarum) includes the Desmidieæ in his subclass MALA- COPHYCEE, suborder Chamaephyceae. Mr. Ralfs enumerated 20 genera; viz.-In Sect. 1, Hyalotheca, Didymo- privn, Desmidium, Aptogonium, Sphaerozosma. Sect. 2, Micrasterias, Euas- trum, Cosmarium, Xanthidium, Arthrodesmus, Stawrastrum, Didymocladon. Sect. 3, Tetmemorus, Penium, Docidium, Clostérium, Spirotania. Sect. 4, Ankistrodesmus (Rhaphidium). Sect. 5, Pediastrum, Scenedesmus. When compiling his systematic work, Kützing appears not to have seen Mr. Ralfs's monograph, but only his detached papers in the Magazines, and consequently was unable to compare the genera established by the English author with those described by himself. The consequence is that Kützing describes several genera not admitted by Mr. Ralfs, who has otherwise dis- posed their representative species, disallowing the Supposed distinctive generic character. Nevertheless it seems desirable to enumerate the additional genera of Kützing, since several are new (unnoticed by our English authority), and derived from the papers of Ehrenberg or of other observers, or from his own researches. Those instituted by Ehrenberg were introduced in our last edition. The additional genera are:—Trochiscia (K.), Tetraedron (K.), Pithiscus (K.), Stawroceros (K.), Polysolenia (E.), Microtheca (E.), Polyedrum (Nägeli), Zygoalanthium (E.), Phycastrum (K.), Asteroa'anthium (K.), Stephanoaan- thium . (K.), Grammatonema (Agardh), Bambusina (K.), Isthmosira (K.), Spondylosum (Brébisson), Eucampia (E.), Geminella (Turpin), Monactinus (Corda), Staurogonia (K.), Sphaerastrum (Meyen), Sorastrum (K.), Coelas- trum (Nägeli), Rhaphidium (K.), Oocardium (Nägeli). • The value of the several genera instituted and their characteristics form the subject of the systematic history of the Desmidieæ by Mr. Ralfs in the subsequent portion of this treatise. • * 24. GENERAL HISTORY OF THE INFUSORIA. SUBEAMILY PEDIASTREAE. (Plate I. 37 to 69. Plate II. 19, 36, 37.) This includes the genera Micrasterias and Arthrodesmus of Ehrenberg, the Pediastrum and Scenedesmus of Ralfs, Kützing, and others; and, in addition to these two, to follow Nägeli’s classification, Sorastrum, Coelastrum, and probably also Sphaerodesmus. At the time Mr. Ralfs wrote, much uncertainty prevailed respecting what should be considered characteristics of species, and what were the modes of propagation ; and it is much to be regretted that, although some of the diffi- culties and doubts are removed, our knowledge of these microscopic Algæ is far from complete. Ehrenberg, in harmony with the general views of organization he had adopted, placed Micrasterias and Arthrodesmus among the Desmidieæ, in the class of Polygastric Infusoria, and described the existence in them of ova, stomach-vesicles, and Seminal glands. Yet he was unable to point out one single feature really indicative of their animal nature, even locomotion being unrecognized. Indeed, among those who might be inclined to follow the distinguished Berlin maturalist in attributing an animal nature to most of his Polygastria, the generality would hesitate, in face of the many intimate ho- mologies, structural and physiological, between the Pediastreas and admitted Algae, to predicate it of that group of Organisms. -- FIGURE, COMPOSITION, AND CONTENTS OF CELLS.–The individual cells among the Pediastreat do not exist isolated and independent, but are united together in a frond, in determinate Inumber and in a definite arrangement for each genus. In all the species they agree in having a membranous wall like the Desmidieæ and Palmelleae. We confine ourselves, it should be understood, in noting the figure of the cells, to the mature phase or stage, which, although but one of several known phases, is that most marked, best understood, and most perfect. The cells of Scenedesmus (Arthrodesmus, Ehr.) (I. 37 to 43) are entire, oval, oblong, or fusiform, with their ends either rounded or pointed. Their length is from two to four times their width or thickness, and they are spherical on a transverse section. They exhibit no constriction or suture at the middle, neither in their wall nor in their endochrome, and in these particulars con- sequently differ from the cells of true Desmidieæ. The membrane is fre- quently drawn out in the form of straight or curved spines; this happens usually only with the cell at each end of the chain (I. 40, 41); but in a few cases, other cells nearest to the outer ones become also armed with spines (I. 42). When this extension to the other cells occurs, Nägeli remarks that the spines do not appear on both the Superior and inferior extremities of each cell, but only on the upper of the One, two, or three next within the one terminal cell, and on the lower extremity of the same number within the other terminal cell (I. 42). It is rare that the central cells of the chain are armed, and even when this occurs it is only with short spines. In addition to a spine, or, as may happen, a pair of spines from the upper and lower ex- tremity, the end cells at times have a third spine standing at right angles from their sides (I. 41). The cells of Pediastrum are considerably compressed, so that when aggre- gated they form a flattened tabular structure (I. 44 to 48, 59 to 69). In figure, as seen from above, they vary according as they occupy the margin of the collection, i. e. are peripheral, or are central. The latter are polygonal, frequently hexagonal, and no doubt owe this shape to mutual lateral pressure during growth : the marginal cells have fewer sides, and are frequently irre- OF THE PEDIASTREAE. 25 gularly quadrilateral, but their free margin is more or less deeply notched, and therefore bilobed (I. 44, 45, 53, 62). The lobes are usually tapering, and form a tubular process either truncate or acute at the extremity (I. 62). In a few cases the notch is not angular, but curved and crescentic (I. 62); in others again it is deep, angular, and gaping (I. 52, II. 27), and gives the cell an irregular figure ; this latter condition is more seen where only a few cells are united together, and where the lobes are not prolonged as pro- cesses. In some species, moreover, the lobes are terminated by short hair- like spines. The notch on one side is not confined to the peripheral cells, but extends, in several species, also to the contained cells of the frond (T. 52, 66); their lobes, however, are not tapering, but sharply truncate. Nägeli instituted a Subgenus of Pediastrum under the name of Anomopedium, the chief charac- teristic of which is the absence of bilobed peripheral cells (I. 46, 47, 48). The cells of Coelastrum are hexangular (T. 49, 50, 51), the central ones very regularly so, whilst the peripheral are rounded off on their free aspect in one species, and in another notched and bilobed (I. 54, 55). Those, lastly, of Sorastrum (I. 56, 57) are wedge-shaped or triangular, with rounded angles; they cohere by their apices, whilst the base is peripheral, often rather concave or emarginate, and, as a rule, armed at each angle by a pair of short spines. On a lateral view the cells are oblong (I. 58). There is a pervading uniformity in the contents of the cells of the different genera of Pediastreas, which consist of the usual vegetable protoplasm, and are spoken of collectively as the endochrome. At first the colour is very pale green, but it becomes deeper with advancing age, and in fully mature or decaying cells is seen to change to red or brownish red, just as the leaves of trees change colour on the approach of autumn. At first, the protoplasm is clear and homogeneous, but in course of time granules appear, enlarge in bulk, and multiply in number. Moreover, each cell presents a single chlo- rophyll-vesicle, which is least discernible in very young and in very old cells (I. 53 to 58). It is ordinarily seen in or about the centre of the cell, but may occur on one side, as in Pediastrum Rotula. Around this vesicle are seen in several species clear circular spaces or globules, recalling those of Closterium, varying in number in different cases from two to six (I. 44, 45, 53). In Pediastrum Rotula, Nägeli observed two such ; in P. Boryanum and P. Selenaea (I. 44, 45), from two to six ; in the species of Scenedesmus and of Sorastrum (I. 57), one hyaline space. This author likewise represents the relative position of the chlorophyll-vesicle and of the translucent space to be constant in similar fronds. In those made up of two cells only, the chloro- phyll-vesicle is placed outside, whilst the clear cavity lies against the parti- tion-wall. In chains of four to eight cells the chlorophyll-vesicle is external relatively to the central cell, and the clear space internal (I. 40, 41), the position being regulated, not by the partition-wall, as in the Palmelleae in general, but by the centre of the entire frond. Oil-globules are also con– tained in the cells; their presence is readily demonstrated by the addition of tincture of iodine, for they continue colourless when the surrounding mass is coloured brown ; their position often exhibits much regularity. Unless the chlorophyll-vesicle be esteemed nuclear, no nucleus has been discerned in the cells of Pediastrea. On one occasion Nägelisaw, in Pediastrum Boryanum, the endochrome disposed in a radiating manner around the chlorophyll-vesicle, an arrangement which often obtains in Algæ, and in many vegetable cells where there is a central nucleus. - g NUMBER AND DISPOSITION OF THE CELLS IN THE FRONDS.–The cells of Pe- diastreas are always united together in compound fronds. The number so 26 - GENERAL HISTORY OF THE INFUSORIA. united, and their mode of combination, differ in the different genera añd species. In Scenedesmus the cells are arranged (I. 37 to 43) in single linear series, side by side, united by a mucous hyaline matrix, which is less abundant than in Pediastrum. Two, mostly four, and less frequently eight cells are concatenated; and, as a rule, the line of union extends the entire length. Ex- ceptions occur, owing to the junction-surfaces being less extensive, in the form of chains of cells having a zigzag border, every alternate cell being depressed below the normal plane, or in that of an oblique chain, having each member in succession depressed beneath the preceding. Sometimes two rows of eight cells each lie side by side (I. 38), so that the one dovetails into the other by the alternate elevation and depression of their component cells: this may happen in the whole extent of the two coherent chains, or in a portion only of their length at one or other extremity; or one chain may be broken into two segments, each dovetailed to the other chain at opposite ends so as to leave an unoccupied central space. The alternation of the cells in fronds composed of two rows, is the result, according to Mr. Ralfs, of the oblique manner of division. In the genus Pediastrum the fronds are generally com- posed of a larger number of cells than in Scenedesmus, disposed in the same plane according to a definite and usually concentric arrangement, and forming compound stellate fronds (I. 52, 53, 62, 66, 67), whence the term Micras- terias (little star-like beings) invented by Ehrenberg, and also the second half of the generally adopted term (Pedi)-astrum. e - To distinguish species, Ehrenberg chiefly employed the number of the cells in a frond—both the entire number and that of each concentric circle, together with the number of circles. Succeeding naturalists, however, have pointed out that the number of cells in the same species is subject to con- siderable variation. Turpin detected the true law determining their number, and Nägeli further illustrated and enforced it. The latter writes that (Einzell. Alg. p. 92) “the cells are united 2, 4, 8, 16, 32, or 64 together in a frond. These numbers are always constant in young fronds without exception. In older specimens one or more cells may be lost, and the frond become therefore apparently irregular. These cells do not spontaneously detach themselves from the rest, but die, and are partially or entirely dissipated, as a consequence of injury from Some external cause, probably in most cases by small aquatic animals. They occur in all stages of destruc- tion, and when entirely vanished, the vacant space indicates their former position. The cells are aggregated together in a single plane, which possesses mostly a circular or somewhat rounded outline; but in the disposition of the cells there is considerable variety. In the case of 4 cells they are either all in opposition (II. 27), or only 2 in the centre; with 8 cells, one usually lies in the middle, and the other 7 surround it in a circular manner (I. 52); less commonly, 2 are central and 6 peripheral (I. 62); rarely, one occupies the centre with 6 around it in a circle, whilst the remaining or eighth cell is placed on the periphery; and still rarer, the disposition is quite irregular. Where 16 cells are combined, the rule is that there is one in the centre surrounded by an inner circle of 5 and an outer circle of 10. At times, 4, 5, or 6 internal cells are encircled by 12, 11, or 10 outer ones (I. 53, 66, 67), whereby a double ring is produced: more rarely the arrangement is completely irregular. Again, 32 cells are mostly so placed that one central cell has around it 3 circles, the innermost of 5, the middle of 10, and the outer of 16 cells; less frequently, the 3 circles are respectively composed of 5, 11, and 15, or of 6, 10, and 16; occasionally 5 internal cells have 2 outcr series, one of 11, the other of 16 OF TEIE PEDIASTREZE, 27 cells; or 6 cells are enclosed by 11 and 15, or by 10 and 16; or, lastly, the distribution is partly or completely irregular. In the case of 64 cells, no regular aggregation frequently is observable: sometimes 2 or 3 external con- centric series are perceptible, where the position of the inner cells follows mo rule; less frequently, the concentric arrangement can be followed to the centre; when this is the case, one central cell may be enclosed by four series respectively of 6, 13, 19, 25, or of 7, 13, 19, 24 cells; or again, 2 middle cells have around them 8, 13, 18, 23, or 7, 12, 19, 24, or 7, 13, 19, 23 cells in four rows; or further, 3 central cells have 8, 13, 18, 22 cells around, and so forth. “The form of the genus Pediastrum has in general a decided tendency to a concentric disposition of the cells. Thus 4 cells combine in 1, 8 in 2, 16 in 3, 32 in 4, and 64 in 5 circles. When this concentric arrangement is disturbed, it occurs more frequently in larger than in small fronds, and more frequently among the central than the peripheral cells.” Braun (Gen. Nov. p. 71) has entered much in detail respecting the number and disposition of the cells, and arrived at the same general results as Nägeli. He observes that “the same numerical law is common to all the species [of Pediastrum], but the number may vary more or less within the legitimate series, even indeed in one and the same species: the disposition also is liable to variation where there is the like number of cells in the same multifarious species; and this so much the more the greater the number of cells....The legitimate (normal) series, viz. 1, 2, 4, 8, 16, 32, 64, 128, is explained by the binary division which takes place in the formation of gonidia, and which is quickly arrested or continued for a longer period. “I have no direct observations to show whether specimens consisting of a single cell are generated singly from the parent cell, or, after being developed in company with others, they have become dispersed by some accident, which is very probable. Such specimens, belonging pretty clearly to Pediastrum Ehrenbergii, occur everywhere in company with the multicellular fronds of this species. Unicellular examples of other species are, it would seem, very rare. I have seen one such of P. Rotwia ; of some which I think should be assigned to P. Boryanum. Bi-cellular specimens I have only observed in the case of P. Ehrenbergii: instances of 128 cells have frequently occurred to me with P. valgum, and twice with P. Boryanum. The other numbers are common, and occur in very many or in all species, or in the majority; certain of them indeed much more frequently than others. “Numbers divergent from the normal series, whether incomplete or more than complete (supra-complete), are rare, whilst very divergent ones are very rare. The former have their origin in the process of fission and the formation of gonidia, when one or other segment in the penultimate division remains undivided, or divides once too often. Thus in P. Boryanwm, specimens are occasionally found having 15 instead of 16, 31 for 32, 63 for 64 cells, or on the contrary, 17 for 16. Examples of 65 in lieu of 64 cells have occurred to me in P. asperum. The latter, i. e. those numbers widely divergent, may originate, if in the earlier division of the cytioplasm [protoplasm] some seg- ment is, as it were, passed by, and subsequently enters again in the series of segmentation. In this way the numbers entering into the series 3, 6, 12, 24, 48, examples of which are at hand, may be explained. Three cells have been met with by me in P. Ehrenbergii, and more frequently 6, both in this species and in P. Rotula; . . . .24 cells, once, in P. asperum.” Braun adds that, if any person should doubt that the number of cells differs in the same species, he has only to inspect collections made in the same place and living under like conditions, and to note the unequal forms produced 28 GENERAL HISTORY OF TELE INFUSORIA. from the same parent individual, and lastly, to remark the analogy presented in other allied genera, e. g. Scenedesmus, Sorastrum, and Coelastrum, to con- vince himself of the fact. - Moreover, as shown by Nägeli, when the number of cells is the same in a frond (coenobium, Braun), their arrangement varies considerably, tending more and more to irregularity as the cells are more multiplied. “The normal and most frequent disposition is orbicular, the cells being arranged, according to their number, in one or several concentric circles, around either a single central cell or none at all. Where two cells are placed in the centre, the circles around incline to an elliptic figure; from this a transition to an elongated form still more aberrant from the orbicular type is indicated, in which the elongate-elliptic circles surround several intermediate cells placed in single or double longitudinal series. By the less regular concentric or the entirely confused disposition of the cells, the elliptic form passes at length into others still more abnormal, such as reniform, panduriform, cuneiform, &c., all which agree in håving 64 or 128 cells. The regular concentric arrangement is moreover deranged by the occasional intercalation of cells referable to no one of the circles; and lastly, owing to an incompleteness of the circles of cells, they become so connected one with another, that a spiral disposition is the result, which, although abnormal in every species, is in some specimens constructed with wonderful regularity. All these various arrangements arise from the manner in which the motile gonidia are disposed and marshalled in their first stage; for these are distributed within the parent depressed orbicular cell, according to the laws of juxtaposition, in a lane.” D Another peculiarity in the disposition of the cells in the fronds of Pedias- trum is, that sometimes, instead of being all in juxtaposition, so as to form an unbroken congeries of cells, or, in the language of Nägeli (op. cit. p. 94), instead of being parenchymatic, apertures or interspaces are left between them (I. 53). This is most seen where the inner cells are more or less bi- lobed, so that an opening subsists between the lobes of each cell; but similar apertures may likewise occur at the angles where the cells come into contact. When the position of the cells in the table is regular, that of the foramina is so also. Pediastrum Selenaea with 16 cells has, as a rule, 6 large and 8 small openings; the large are bounded by 3 cells, the Small by 2; the small spaces are sometimes absent, when the large become very evident. Fronds of the same species, having 32 cells, display usually 11 larger interspaces lying betwixt 3 cells, and 18 smaller enclosed between 2 cells. Anomopedium, a subgenus of Pediastrum, differs not only in its peripheral cells not being bilobed, but also in having its cells partially disposed in a double plane (I. 46, 47, 48). The cells which are in the numerical series of 4, 8, 16, 32, and 64, are subject to manifold arrangements, and frequently aggre- gated quite irregularly. They are mostly so placed, that in one, two, or even three directions, they can be clearly discerned to be in parallel straight rows. A concentric disposition is quite exceptional; not unfrequently, instead of all the cells occupying the same plane, Some form a partial second layer upon the other about the middle. In Coelastrum (T. 50, 51, 52) the hexangular cells are so arranged that they form a hollow, globular, areolar frond. Coel. sphaericum consists of 25 to 40 cells, which compose a lamina perforated by 3, 4, 5, 6, 8 angular meshes (areolae) somewhat larger than the cells themselves, and from 13 to 22 in . number. Coel. Cwbicum consists of 8 cells united in a cubical form, hollow inside : on each side are 4 cells enclosing a quadrangular aperture. Lastly, in Sorastrum the wedge-shaped or cordate cells (I. 56, 57) are all OF TEIE PEDIASTREAE. 29 in close apposition and form a globular frond. The cells in the typical species, S. echinatum, are 8 or 16 in number, and so arranged that all their apices converge towards and meet in the centre of the frond. Sphaerodesmus, which probably is rightly accounted one of the Pediastreas, is named, but not described, by Nägeli; we are, however, informed by Braun (Gen. Nova, p. 70, in foot-note) that its fronds are composed of 4 spherical cells closely aggregated in a rhomboidal form. - - DEVELOPMENT AND GROWTH.—Scenedesmus multiplies by fission, as Ralfs believed, in an oblique direction, but according to Nägeli, parallel to the long diameter of the cells. The former adopted his opinion from the features of biserial chains; but the latter interprets those appearances by the simulta- neous occurrence of longitudinal and of transverse fission (I. 37, 39). The process of Self-division commences generally at the same period in each cell of the frond (family, Nägeli), and proceeds with so great rapidity that its intermediate stages are unobserved. One of the two terminal cells (I. 39), or, in an eight-celled, probably the two, sometimes remain for awhile undivided. The cell separates into two, then each of these again into two others, and at times this act of subdivision is repeated a third time. By a more prolonged act of segmentation of the cell-contents, the result is a number of minute cells which arrange themselves in rows of two, four, or eight, and thus form miniature fronds which ultimately escape the parent-cell by rup- ture. Occasionally, adds Nägeli, the young fronds are connected together by mucus, formed by dissolution of the parent cell-wall. Development takes place in parallel planes, although by their increase they become mutually compressed and irregular, and the chains curved prior to their discharge. This production of macrogonidia and their cohesion into fronds has not been seen by Braun, and is, in his experience, an exceptional phenomenon (Gen. Nova, p. 67). When Mr. Ralfs wrote his work on the Desmidieæ (in 1848), he had to confess himself altogether ignorant of the modes of reproduction both of Pediastrum and Scenedesmus. He, however, described self-division of the cells in both genera, but rightly regarded this process as one not of develop- ment, but of vegetative increase and repetition. On this subject he remarked (op. cit. p. 182), “I have not seen the cells during the process of division, but I am informed by M. de Brébisson that it takes place at the notch, in the same manner as in other DeSmidieæ : hence the cells in each circle are connected at their ends, like those of the filamentous genera. I do not, however, understand in what manner the additional circles are formed, nor why the numbers in each circle are so constant.” Nägeli, likewise, was equally ignorant of the propagation of Pediastrum, but thought it highly probable it resembled that of Scenedesmus. The num- ber of cells in a table or frond, indicated to his mind its production by a series of fissions in the power of two; and he presumed that a new frond was gene- rated within a parent cell by division of its protoplasm, just as in Scenedesmus, —a Supposition supported by the fact that the entire young fronds are not larger than the single cells of mature specimens, that like these they are composed of the same number of individual cells similarly disposed, and undergo no Subsequent segmentation into a larger number. The more recent researches of Braun are confirmatory of the views of Nā- geli (Gen. Nova, p. 68). Amid a large number of specimens of Pediastrum Boryanum he detected the escape of, in most instances 32, more seldom of 16, and rarely of 8 gonidia, from a parent cell,—the number gene- rally, but not invariably, corresponding with that of the cells composing the mature frond or coenobium. The collection of gonidia was enclosed by a 30 GENERAL EIISTORY OF TEIE INFUSORIA. common envelope, within which they moved actively about for a quarter of an hour before coming to a state of rest, and arranging themselves regularly in a frond (I. 64). This sac is described in the author's work on Rejuvenes– cence (Ray Soc. p. 184) as the vesicular inner layer of the mother-cell. He witnessed this production of gonidia from many, but not from all the cells of the fronds, for it seems to take place in them in succession, and pro- bably in some definite manner, according to their position in the frond. He further describes the development of microgonidia to follow the same plan as that of macrogonidia, but to differ from the latter in number, size and form, and in duration and cessation of motion. Macrogonidia have a subglobose figure, a diameter of Tłºth of a millimetre ; one side hyaline, and scarcely elongated, the other turned towards the periphery of the frond, green, and by-and-by extended and emarginate: no vibratile cilia discoverable on them. They never leave the sac in which they are produced; and the young frond is seen, until the close of the second day, loosely enveloped by a gelatinous layer, which ultimately disappears by deliquescence (I. 64). - On the other hand, microgonidia are at first densely aggregated and closely invested by the Sac in which they are generated; like macrogonidia they are subglobose (I. 60, 61, 68, 69). After a while the sac is gradually dilated, and, growing more and more in length, forms an acute hyaline beak (rostrum) as long as the green portion, which constitutes the rest, or the body, of the gonidium. This rostrum, moreover, is furnished either with a pair of cilia, longer than the body, or with a single cilium. The length of these developed microgonidia is nearly Tººth millimetre; the thickness #gth (I. 61, 68, 69). The movement within the sac is at first slow; but when this is fully expanded, it is very active, and continued for an hour and upwards, until the Sac is ruptured, and the whole heap of microgonidia escape. The number of microgonidia cannot, by reason of their aggregation and their swarming movement, be easily determined; at least 64 occur in a sac, and most commonly many more, for instance, 128. Of their subsequent history, Braun can give no satisfactory account. . A reference to the same able writer's book on Rejuvenescence (R.S.) informs us, at p. 200, that before the formation of the gonidia of Pediastrum, the single starch-grain, the nuclear character of which has been above re- marked, disappears. From the same source we also obtain a series of illus- trations of the development of macrogonidia, of their arrangement in the characteristic stellate frondose form, and of the varieties in the number and arrangement of the component cells, which may be seen in examples of the same species of Pediastrum. The development both of Coelastrum and Sorastrum is unknown. The Pediastrea are of freshwater habit, living in ponds, on which they frequently form, in conjunction with other small plants, a coloured film or scum. They are also common in turfy pools on moors, and invest the surface of various aquatic plants. SYSTEMATIC PosLTION OF PEDIASTREAE.—Mr. Ralfs followed Ehrenberg, Meneghini, and others in placing the Pediastrea” among Desmidieæ ; but Corda, Nägeli, and Braun have separated the two as distinct tribes. Indeed, Mr. Ralfs has modified his views since the publication of his monograph, and would treat the Pediastreac as a subfamily of Desmidieæ. Nägeli (Einzell. Alg) arranges them with the Palmelleae as a distinct group, and in this has the support of Braun (Gen. Nova, p. 69). These naturalists point out that the distinctive features between the Pediastrea” and the Desmidieæ, are that the former neither conjugate nor multiply by continued transverse division of their cells in the same direction, each newly-formed segment acquiring all the OF TEIE DIATOMEAE, 31 characters of a complete cell; that, unlike the Desmidieæ, they propagate by gonidia; have but one instead of two or more equally-sized starch-grains and a central nucleus; and that their fronds are not distinguishable into two symmetrical halves. “The Desmidieæ are evidently multicellular, or pseudo- . unicellular, from separation of their cells, whilst (Says Braun) Pediastrum is a true unicellular Alga rendered pseudo-multicellular by the cohesion of the cells. The aggregation of cells in Desmidieæ is always uniserial, filiform or concatenate; the fronds of Pediastrum are grouped on a plane of a disc-form or frondose character.” Braun next traces the affinities of Pediastrum, and remarks that, although it resembles Hydrodictyon in the construction of its fronds (coenobia) by the connexion of motile gonidia, yet since in Hydrodictyon the gonidia are simultaneous, and in Pediastrum successional, it is rather an analogy than an affinity which exists between these two genera. However, he admits the correctness of the association of Pediastrum with the genera Nägeli indicated, viz, with Sorastrum, Coelastrum, Scenedesmus, and probably Sphaerodesmus, and would add to their number the genus Stavrogonia (Kütz.), the Crucigenia of Morren (Ann. des Sciences Nat. 1830, p. 404). All these genera agree with Pediastrum in the successional formation of gonidia, yet differ from it in other particulars except in the construction of the frond from motionless gonidia. Among other genera, Polyédrum may be likened to Pediastrum in the form of its cells, but its propagation is unknown; lastly, Characiwm and Cystococcus agree with Pediastrum in the successional genesis and activity of their gonidia. To this elucidation of the affinities of Pediastrum we have to add the observation of Cohn (Entwick. d. mikr. Alg.), of the analogy or affinity in general structure between this genus and Gonium. The division of Pediastrum into tribes or subgenera, as proposed by Braun, and the distinction of species of the Pediastrea in general, will receive due consideration in our systematic account of the family. II.—OF THE FAMILY I)IATOMEAE OR DIATOMACEAE. (Plates IV. to XVII.) GENERAL AND EXTERNAL CHARACTERS OF DIATOMEE.-Testules or Frus- tules.—Figure: free, concatenated, and fived Forms.-Varieties of Filaments and of Pedicels.-Aggregated Frustwles.—The Diatomeae, Diatomaceæ, or Cymbelleae, are unicellular organisms composed of two opposite plates or valves, generally convex, and of an interposed connecting third segment, forming together a miniature box of a silicious nature, enclosing a soft organic matter, rarely green, but usually yellowish or orange-brown in colour. They inhabit either fresh, salt, or brackish water. They were reckoned by Ehrenberg among the Bacillaria, and have in con- sequence been sometimes described as silicious Bacillaria. Each individual Diatom enclosed in its silicious envelope is spoken of as a frustule, testule, frond, or bacillum, and in general phraseology as a cell. The first term is that now most in use, whilst “testule * and “bacillum ” are words rarely employed, except in the works of Ehrenberg and of his im– mediate disciples. - A rectangular or prismatic figure most widely obtains in this family; and the angles of junction of the valves are as a rule acute. Deeply notched fronds, like those in Desmidieæ, e.g. Micrasterias and Euastrum, do not occur; and the production of spines and tubercles on the valves, so common in that family, is rare among the Diatomeae. 32 * GENERAL HISTORY OF THE INFUSORTA, FIGURE.—There is an immense diversity of figure among the frustules, determined chiefly by that of the opposed valves, but in some degree also by the amount of development of the interposed third segment or cingulum (XVI. 23, 24.) This last Mr. Ralfs considers an essential part of every frustule; but Prof. Smith states it to be a secondary, non-essential element consequent on the growth of the organism, and specially developed in rela- tion to the process of self-division. When this cingulum or “connecting membrane'' is much enlarged prior to fission, the figure as viewed on this side is considerably changed, and the appearance of a double frustule often occasioned. Not a few of the Diatomeae are much elongated and narrow, and from pre- senting a wand-like figure (IX. 148, 166, 174; X. 184, 185), suggested to Ehrenberg the term Bacillaria to designate the family. However, some species are trapezoid, or square, or nearly so (X. 47, 21, 22), others round like pill-boxes (IX. 131, 181; X. 200, 204), whilst others again are almost globular or spheroid, owing to the great convexity of the valves. Several genera are boat-shaped, Scaphoid, or navicular in figure (IX. 139, 135; XII. 5, 6, 8, 48, 43); some are rather oval, egg-shaped, or ovoid; many resemble thin flattened discs—are discoid (XI. 33, 35, 36, 39); many are wedge-shaped—cuneiform, or cuneate ; a few are triangular (XI. 43, 45); lastly, some are curved or twisted on themselves, and others assume in certain directions a sigmoid or an undulated figure (IX. 144, 145; XV. 11, 22, 59, 60). Evenly-curved valves are said to be arcuate, such as those of Eunotia (DX. 165; XVI. 10, 18), and of some species of Cymbella and Nitzschia, whilst the peculiarly-twisted valves of Campylodiscus (XVII. 517) are saddle-shaped. In Cymatopleura, again, the surface of the valves is undulated, and when bent rather sharply at an angle on themselves, the valves become geniculate, as in Achmanthidium. As a rule the frustules of Diatomeae are symmetrical, and consist of two equal and similar halves; but exceptions to this are found in the Achnantheat, Cocconeidae, and one or two other families (DX. 159). - Another variety of frustules is described as winged or alate, the ala being a smooth expansion in the form of a margin (XIII. 5, 6, 7). The alae may arise from the margin, and are then Said to be marginal, as in Surirella, or otherwise from the disc, as in Trybliomella, in which they are called submar- ginal. A further modification of the valves affecting the figure is exemplified in Nitzschia and Amphiprora, which have a longitudinal elevated ridge extending from one extremity to the other; such ridges are called keels, and the valves keeled or carinated. In the discoid forms two portions are commonly distin- guishable, viz. the disc and margin or rim (XI. 31, 35, 38), the one at times separated by a distinct line, and often presenting different sculpturing from the other. The disc moreover exhibits occasionally at its centre a promi- mence or elevated thickness called an umbo or boss. In Eupodiscus (XI. 41, 42) tubular horns come off from the surface of the valves, and in Tricerativiſm from the angles. - The extremities of some species, e. g. in Nitzschia and Pleurosigma, are extremely elongated, forming long, filiform, tubular processes; and in Den- ticella, Biddulphia (II. 46, 48, 50), and Rhizoselenia (Ehr.), short tubular processes and spines are produced from the surfaces and margins. These processes are commonly simple, but according to Ehrenberg are branched (ramose) in the genus last cited, and in Dicladia and Symdendrium. More- over, very singular hispid and sometimes bifid processes or styles have been noted on the valves of some species of Goniothecium (Ehr.), recalling by their figure that of the spines on the sporangia of many Desmidieæ. Other OF THE DIATOMEAE. - 33 Diatoms, referred by Mr. Brightwell (J. M. S. 1856, p. 106) to the genus Chae- toceros, have highly developed spines on the valves, besides the two pairs of very long filiform smooth or spinous horns springing from the frustules themselves, or from the interposed cingulum. Ceratawlus is another genus provided with a pair of long horn-like processes. Great variety of outline may prevail in a genus, so considerable indeed that an accurate definition is with difficulty laid down, the characteristics shading off through several species, until at length the similarity to an as- sumed typical form is much diminished, whilst on the other hand an ap- proach is made towards the features of another genus. The like latitude of form prevails also with species, and gives rise to very numerous and fre- quently perplexing varieties. On this topic Prof. Smith remarks—“While a typical outline of its frustule is the general characteristic of a species, this outline may be modified by the accidental circumstances which surround the embryo during its growth and the development of its silicious epiderm; then, any such aberration of form becomes stereotyped by the process of self-divi- sion of the frustule, generating multitudes of others slightly deviating from the normal form.” It must not be forgotten that the figure is greatly modified or entirely changed by the position of the valves, whether seen in face or on one side; for each frustule generally presents four planes or sides, and, unless regard be paid to this circumstance, one genus may be mistaken for another, or even each view be presumed a distinct genus. Thus in the genera Navicula, Pinnularia (XII. 5, 6, 15, 18), and in many others, the frustules are on one aspect boat-shaped, but on the other oblong with truncated ends, or prismatic. In the genus Tricerativm (XI. 43,44), the difference of figure is very re- markable according to the side viewed (as presently illustrated). It is there- fore necessary to examine a specimen on every aspect it presents: this can generally be effected by the accidental rolling over of frustules under inspec- tion, or can otherwise be brought about by a very slight sliding movement of the thin glass cover upon the slide under the microscope. Mr. Brightwell thus describes and explains the transitions of form produced by a change in position of the frustules of the genus Triceratiºn (J. M. S. i. 248):—“The normal view of the frustule may be represented by a vertical section of a triangular prism. If the frustule be placed upon One of its flat sides, we look down upon its ridge and obtain a front view of its two other sloping sides. If it be placed upon one of its ridges, we have a front view of one of its flat sides, generally broader than long, and of its smooth or transparent suture or connecting membrane. If the frustule be progressing towards self-division, it is then often considerably longer than broad, and when nearly matured for separation presents the appearance of a double frustule.” It would be in vain to attempt to describe all the numerous forms assumed by the members of this extensive family; the representations in the plates of this volume will convey the clearest notions of their diverse outline and markings (see Plates 4 to 17). Great difference unfortunately has existed re- specting the sides which should be esteemed primary and afford specific cha- racteristics, and those which should be held as only secondary; and the nomenclature of the surfaces has been equally a matter of dispute and uncer- tainty. Ehrenberg employed the terms dorsum, venter, and lateral surfaces or sides, but so loosely that they do not always indicate homologous portions. Thus he has often called a convex surface the dorsum, simply from its convexity, and a concave one the venter, on account of its concavity. Kützing attempted a more certain and Scientific phraseology by calling those sides which have no central opening (wmbilicus), but through which self-division occurs, the primary sides, and the other two the secondary sides, further distinguishing D 34 - GENERAL ELISTORY OF TELE INFUSOTIA. the latter into a right and a left with reference to the frustule when lying on a primary side. The left side is often concave, and the right convex; mostly, however, the two are alike. As a general rule the primary sides correspond with the lateral surfaces, and the secondary with the dorsum and venter in the terminology of Ehrenberg. Mr. Ralfs, in his papers in the Ann. Wat. Hist., used the simple terms “front view’ and ‘side view,’ corresponding respectively with Kützing’s names primary and secondary sides. The Rev. W. Smith adopts this nomenclature as the most convenient for the English student, and uses the term ‘front view’ to denote the aspect of the frustule when the valvular suture (connecting membrane), or the line along which self-division takes place, is turned towards the observer, and the term ‘side view' when the centre of one valve is directed to the eye. He adds— “Bven these terms will require modification when applied to some of the more complex and irregular forms; but in general their meaning will be sufficiently obvious.” . • - It must happen, therefore, from this terminology, that at times a front view cannot be said to exist, viz. When the connecting membrane is obsolete and the opposed valves are closely applied to each other, a suture alone in- dicating the line of junction. In size the Diatomeae vary very greatly; some individual frustules are cognizable by the naked eye, whilst others require the highest powers of the microscope to display them. Even among specimens of the same species great diversity of size prevails, a peculiarity much determined by the cir- cumstances surrounding a frustule at the period of its development, and afterwards perpetuated through a long series of individuals multiplied by self-fission. - The Diatomeae exist under three chief forms, as-1. Single isolated free frustules. 2. Frustules attached by a stalk, stipes, or pedicle. 3. Frustules coherent in chains, or aggregated together in ramose tufts by an interposed gelatinous substance. The third form is the consequence of incomplete fission, or of imperfect separation after fission. Incomplete fission and consequent concatenation are observed in Bacillaria, Meridion, Himantidium, Melosira, . Odontidium, Striatella, Fragilaria, &c. (IX. 131, 167, 171, 175, 176, 177); and the form of the chain or filament produced will be determined by the figure of the individual frustules composing it. For instance, if these be rectangular, then the resulting chain (IX. 171, 172, 176; XIV. 2, 4, 6, 13) is straight, but if wedge-shaped, it is curved or spiral (IX. 177, 179; XII. 21). The extent and degree of attachment of the adjoining frustules differ in different genera; thus, in Bacillaria it is very slight, and readily yields, allowing one segment to glide on another, or to separate from it, except at one point, yet at the same time possessing the power of recovering itself. In Odontidium, Himantidium, Denticula, and Meridiom (IX. 177), the mutual adhesion of the Several segments is stronger; and after the opposed surfaces have been separated, future adhesion is not effected. In Fragilaria, the ad– herence is more tenacious. In Diatoma, Tabellaria, Grammatophora, Am- phitetras, &c. (II. 46; XI. 22, 52; XIV. 23), the frustules hang together by a sort of hinge inserted between adjoining angles in a zigzag fashion. In Isthmia, this hinge or connecting link attains a greater magnitude, and, in fact, is double. In Podosira (II. 45) and in some species of Melosira a junction-process is developed from the centre of each frustule in the chain. In other Melosira, and in Orthosira, the junction-surfaces are toothed (den- tate), and thus hold the adjoining frustules in firm union. In the instance of Biddulphia (II. 46, 48), the surfaces in union are curiously elongated at the angles into rounded or horn-like processes, whilst their convexity is OF TELE DIATOME ZE. 35 crowned by several bristles or setae. Lastly, in Eucampia (II. 43) the junction-surfaces are so excavated, that when the frustules are concatenated a filament is formed, perforated by oval foramina. - In not a few genera, as above mentioned, the attachment is at opposed angles, and a zigzag chain produced; but in Isthmia (X. 183) it is peculiar in being indiscriminately made at any part of the adjacent frustule, and thereby produces an irregularly branched filament. - - The above examples will suffice to illustrate the characters and varieties of concatenation in the form of filaments, whether straight or spiral; but it is necessary to add that the width of a filament “equals the length of the frustule or valve measured along the suture or junction-line, and that the breadth of the valve denotes the thickness of the filament” (Smith, Synops. ii. 6). In those instances in which frustules are connected together by a process or Small isthmus acting as a sort of hinge, the concatenation cannot be ascribed to incomplete division only, for the existence of such a process is the result of a special formation which essentially corresponds with the pedicle or stipes of fixed species. - Numerous Diatomeae grow attached to foreign bodies by a stalk of variable length, and which, although generally simple, is sometimes compound by dividing and subdividing in a ramose manner. Even among the recognized free Diatomeae, such as Navicula, Pinºvularia, Nitzschia, &c., specimens are not unfrequently seen adherent by one extremity, about which they turn or bend themselves as on a hinge; however, in these instances such union is but temporary, and no connecting medium exists. In Synedra (X. 184), on the other hand, a bond of union occurs in the form of a little gelatinous conical nodule, resembling very nearly the hinge-like isthmus which binds to- gether the frustules of many genera in a sort of ZigZag chain. By the process of self-division it also comes to pass that groups of Symédraº occur attached together by the same point, in a fan-like or a stellate form, as in S. radians, S. affinis, &c. In other species detachment after fission is too speedy to allow of this sort of combination, except of Some two or four individuals. The fan-like collection of frustules is said to be flabellate, fan-like, or radiating; and when the component members are curved, they and the bun- dles they form are described as arcuate. The nodule of attachment occurs in various degrees of development, and attains in this same genus Symedra to the dimensions of a pedicle—ex. in Symédra Superba, and even to branch, as in Synedra fulgens and Synedra pulchella. When a stipe branches, it does so normally in a dichotomous manner by the very circumstance of the process of self-division, each new individual produced by that act developing its own secondary pedicle, or pedicel. This regular dichotomy is instanced in the genera Doryphora (XIV. 21), Cocconema (XIII. 10), and Gomphonema (XIII. 11). In Licnophora (XIII. 20), and in one species of Rhipidophora, viz. Rh. Dalmatica, an irregular branching—essentially dichotomous, however—is met with, and is thus ex- plained by Prof. Smith:—“In Rhipidophora paradova and Rh. elongata, self-division is immediately followed by the separation of the half-new frus- tules and a dichotomy in the filamentous stipes, while in the present genus the frustules remain for a time coherent, and continue dividing and mul- tiplying on the summit of the pedicel, which becomes elongated and incras- sated at each successive repetition of the process. . . . A branching, or rather longitudinal rupture, of the pedicle takes place at irregular intervals; and the entire organism presents us with more or less complete flabella (fan-like clusters) on the summit of the branches, and imperfect flabella or single frustules irregularly scattered throughout the entire length of the pedicel.” - - - D 2 36 GENERAL HISTORY OF TEIE INFUSORTA, The same authority has the following remark on the process of ramification: he says (i. 75), “When self-division (i.e. of the frustules) is completed, the extension of the filament below the frustules is suspended, a joint or arti- culation is formed at the base of the dividing frustule, and each of the half- new frustules begins anew, in its progress towards special self-division, the secretion of a new joint or internode; and a dichotomy is the result.” The occurrence of the double condition of union of frustules in a con- catenate manner and of attachment by a pedicle is illustrated in the genera Achnanthes (X. 201, 202), Striatella (X. 203,204), Rhabdomema (XIII. 27), and Podosira (II. 45). In Melosira also, attached species occur; and Prof. Smith inclines to the opinion that all filamentous Diatomeae are stipitate on their first production. In the second stalked genus cited, viz. Striatella, the stalk attains the highest development, but remains slender and unbranched. between this most developed form and the mere nodules of attachment in the genera Achnanthes and Melosira, every intermediate phase is encountered. In any one species, however, there is no positive determinate length of the stipes, for this varies according to the idiosyncrasy, vigour, and external con- ditions affecting the organism; consequently characters derived from the dimensions of the stems can have no specific value. There is a large section of Diatomeae in which the frustules are diffused throughout a mucous or muco-gelatinous mass, rarely confusedly, but mostly in a definite manner, usually in thread- or tube-like branches, which nor- mally ramify in a dichotomous fashion, and resemble on a minute scale the tufts formed by many large sea-weeds. This peculiar aggregation is the consequence of the large production and subsequent persistence of the mucus which is thrown out when the system of reproduction, whether by sporangia or by fission, takes place. Histologically, therefore, it is homologous with the pedicles and connecting nodules or isthmi thrown out during the act of self-division, as also with the mucous stratum, which still very often persists when that act is complete, around specimens of Cocconeis, Chaetoceros, Melo- sira, Fragilaria, Striatella, &c. - The tissue thus composed of mucus and enclosed frustules constitutes what is called (from analogy with the large Algae and other Cryptogamic plants) the frond, and affects various shapes, in some measure characteristic of the genera. Thus, in one of those so-called frondose Diatomeae, viz. Dickieia (XV. 30, 31), it is membranous and leaf-like, and resembles a species of Ulva; in Mastogloia, filiform with nipple-like expansions; in Encyonema (XIV. 22), Homoeocladia (XIV. 37, 38, 47, 49), and Schizomema, filamentous and more or less branched; in Colletonema subcohaerens, globose. Again, when filamentous, the ramifications differ much in thickness and in expansion, and in the extent of adhesion between the branches; where these are long and slender they are called ‘ capillary,’ and where contiguous branches coalesce, they give rise to a submembranous condition. The degree and mode of division, the collection of the branches into bundles (i. e. fasciculi), or, on the contrary, their loose or diffuse arrangement, supply useful characters in the distinction of species. Again, the fronds differ in consistence, being in some genera or species more rigid, Setaceous, or robust, in others softer, flaccid, and more delicate; these opposite conditions furnish Prof. Smith with grounds for the division of the genus Schizonema into two tribes. The disposition of the frustules within the mucous investment supplies other important distinctions. Thus in Dickieia it is irregular; in Mastogloia each little frustule occupies “the summit of a little nipple-like cushion of gelatine;” in Berkeleya (XIV. 34, 35) the frustules are densely packed in the filaments; in Encyonema they occur mostly “in single file, except OF TEIE DIATOME ZE. 37 towards the extremities, where they are somewhat crowded ” within the distinctly tubular filaments, and enjoy a certain latitude of movement; and, lastly, in Colletonema and Schizomema (X. 207, 208) they are arranged in one or more files according to the stage of growth, within less per- fect tubes than in the genus last mentioned, and retained in situ by the mucus around. Ehrenberg recognized this tribe of compound Diatomeae, and introduced it as one of the sections of his great family Bacillaria, under the name of Lacernata, or Naviculae with a double lorica. His acquaintance with the group was, how- ever, very imperfect, and he appears to have comprehended in it organisms quite foreign to it, and to have failed to give that precision to his classifi- cation of the included beings which could alone confer a high scientific value and permanence upon it. OF THE ENVELOPES OF THE FRUSTULES OF DIATOMEE.-The Silicious Shell or Lorica : its Divisions and Structural Composition, Markings, Stride, Canali- culi, Puncta, &c. —Sufficient has been said of the mucous coat which at certain times, and always in certain genera, Surrounds the frustules of Diatomeae. The frustules themselves remain to be described: they are hollow variously-shaped cells having but one cavity—unicellular, and a silicious outer wall, unaffected by a red heat and by strong acids, which would corrode and dissolve every other substance belonging to a living being except silex. This silex is stated not to polarize light, as does the mineral silex not in combination with organic beings; and the erroneous statement made by some authors, of the polarizing effect of some Diatomaceous shells is due to the circumstance, that they did not take care to thoroughly remove the organic carbonaceous matter with which the silex is in union in the frustules in question. The silex, besides being united with organic matter, deposited it may be within a cellular tissue, is contaminated by iron, which Professor Frankland of Manchester states (Smith, Synops. p. xxi) “exists in the state of a silicate or protoxide . . . . “and he attributes to its presence” the brown colour which is assumed upon exposing the Diatoms to the influence of a moderate heat; the protoxide of iron, by the gradual absorption of oxygen, being converted into brown peroxide of iron, which assumes a redder tinge upon being more strongly heated.” The relative proportion of silica varies within considerable limits in different genera of Diatomeae. In several genera, perhaps in marine ones exclusively, it is very deficient, and the wall of the frustule is little more than horny, or it may be even flaccid, as for example in Dickieia and Schizomema. The frustules of Fragilaria, Striatella, and Podosira are less firmly silicious than those of many others of the filamentous Diatomeae. In some genera (those, viz., which produce tubular processes) silex is deficient or absent from the pro- duced wall; in Podosira this deficiency occurs at the apex of the valves, and in Prof. Smith's opinion is probably intended “to allow a free secretion of the mucus which unites the frustules and provides a pedicle for their attach- ment to the plant on which they grow, as it does not occur on the non- attached valve of the first-formed frustule. In the living state the absence of silex is not perceived; but when the frustules have been macerated in acid, these portions of the valves appear as perforations, owing to the dis- appearance of the cell-membrane.” The frustules of the Diatomeae are composed, as before stated, of two usually more or less convex valves, enclosing a single cavity, which becomes augmented by the growth of a third segment interposed between them, pro- duced preparatory to the process of self-division. Meneghini asserts that 38 GENERAL EIISTORY OF THE INFUSORIA. the silicious shield or lorica is four-sided, and composed of four pieces or valves. Although this appears to be the true structure of some species, owing to the ready separation of the connecting membrane into two portions, yet the majority offer no countenance to the notion, the connecting membrane forming a continuous oval or circular ring. In Tricerativm, however, is an example of an even more pseudo-multiple composition; for its prismatic tri- angular frustule breaks up into “two triangular plates or walls of silex forming the ends, and into three oblong rectangular pieces or bands forming the three sides, the latter usually dividing themselves into several elongated paralleliform pieces” (Brightwell, J. M. S. i. 248). - Again, in several genera, doubtfully arranged by Ehrenberg among the silicious Bacillaria, e.g. Dictyocha (XII. 62,63) and Mesocena (XII. 71), the individuals are represented as composed of several segments united together. Each valve consists of a silicious lamina Superposed on an organic soft lining (or primordial) membrane which immediately encloses the contents of the cell. Nägeli speaks of a mucilaginous pellicle on the inside of the organic layer as a sort of third tunic; and Kützing likewise discovers a thin stratum brought into view when recent frustules are dried, and particularly after heating them to redness, in the shape of an opake brownish stain, or of brown lines or points, extending not unfrequently over a considerable portion. To this supposed independent material its observer applied the name ‘cement,’ imagining it to be the connecting matter of the valves and of frustules when in union, and attributed its brown colour to the presence of iron. This presumed layer of cement we can regard as nothing more than the stain produced by the oxidation of the salts of iron in chemical union with the silica, as Prof. Frankland has shown (p. 37). However, Meneghini adopts the notion of this third envelope or cement, inasmuch as he observes it to be constant, without employing the means used by Kützing to display it, not merely in the species enumerated by its discoverer, but in many others, and possibly in all (R. S. 1853, p. 361):—“For to me (continues the same author) it appears to, correspond with that fine membrane of the Ach- manthidia, which, according to Kützing’s own observation, is always visible whenever the two new individuals (into which every Diatom is resolved in its multiplication by deduplication) begin to separate. The lines and points supposed to belong to the subjacent shield belong very frequently to this kind of covering.” The analogy expressed in the quotation just given, between the delicate stratum—the “cement’ of Kützing, and the secretion poured out when self-division is proceeding, we cannot regard as correct ; for this latter is a special and usually not persistent coating, in all probability exuded through the fissures or pores uncovered by the silicious lamina, by the sub- jacent organic mémbrane, and is withal destroyed by the heat generally required to bring the “cement’ into view, whereas the presumed coat is represented to be constant and also permanent both under the operation of fire and of acids. However, the belief in the existence of a vegetable mem- brane outside the silicious epiderm gains ground; for Mr. Shadbolt, in his presidential address before the Microscopical Society, 1858 (T. M. S. 1858, p. 72), states it as the result of his researches, that the frustule of Arach– noidiscus and of other forms consists of a silicious framework, over which is stretched a species of membrane, whether silicious or not he does not presume to decide, but certainly pliant to a considerable extent, capable of being par- tially rolled up by mechanical agency without breaking, and elastic enough to return to its original position when the extraneous force is removed. “The structure noticed by Mr. Roper in Coscinodiscus labyrinthus, and by myself in the more common species C. radiatus and Triceratium favus, I OF TELE DIATOMEAE. 39 believe to be of precisely the same mature, and I am much mistaken if we do not find it in many other species of the Diatomacea.” In the accompanying part of the Journal (J. M. S. 1858, p. 162), Prof. Walker-Arnott refers with approval to this opinion of Mr. Shadbolt, and appends some most important remarks bearing on the presence or absence of this membrane in the determination of species. He observes that “ There can be no doubt that these discs (i.e. of Arachnoidiscus) have a horny vegetable outer covering, in addition to the silicious one, and that by too long boiling in acid, as is necessary for guano, the marks are much obli- terated or entirely removed. This, however, is not peculiar to the present genus, but may be observed, more or less, in all Diatoms, although sometimes the vegetable pellicle is very thin and may be removed by a few seconds' immersion in boiling nitric acid. It is this circumstance which gives a quite different appearance to the same species, according as the preparation is made. Thus, in Actinocyclus the vegetable epidermis is cellular, while the silicious part is striated like a Pleurosigma; and when the vegetable part is removed, we often find nodules or knobs along the margin (forming, then, the genus Omphalopelta), not previously visible. Those who describe Diatoms from slides are thus liable to commit great errors, and indeed no certainty can be obtained, except by getting the recent or growing Diatom and examining it, 1st, after being immersed for a short time in cold acid, or simply washed in boiling water; 2ndly, after being boiled in acid for about half a minute, or a whole minute at most ; and 3rdly, after being boiled for a considerable time: we shall then see that many of the Supposed distinct species of authors are the same, prepared in a different way. Of course, deposits or guanos can yield little or no information, although, when Once a species has been determined by the way I have indicated, we may be able to refer forms occurring in guano or deposits to it with tolerable certainty.” Mr. Brightwell, speaking of the lorica or silicious epiderm of Triceratium, states that the valves are resolvable into “several distinct layers of silex, dividing like the thin divisions of talc, and frequently found of such exquisite delicacy as to be difficult of detection” (J. M. S. i. 248). The silicious lamina is generally looked upon as a production or Secretion from the Subjacent organic membrane, the true cell-wall. Nägeli (R. S. Reports, 1846, p. 220) says, “it lies outside the membrane, and must be regarded, from analogy with all other similar structures, as an extra-cellular substance excreted from the cell;” and, as Meneghini (op. cit. p. 360) adds, “in fact, an Organic mem- brane ought to exist, for the silica could not become solid except by crystal- lizing or depositing itself on some pre-existing substance.” Prof. Smith moreover states (A. N. H. 1851) that, apart from analogy, he has direct evi- dence of the independence of the silicious coat, having in his possession numerous specimens of a Stauroneis (probably S. aspéra, Kütz.), in which the valves, after slight maceration of the frustules in acid, have, in part or wholly, become detached from the cell-membrane, leaving a scar on its Walls bearing the distinct impression of the numerous and prominent Valvular markings of this beautiful species. The same observer adds that he has in Some cases noticed this organic membrane to contract around the cell-contents, upon the death of the cell. Again, the application of hydrofluoric acid, proposed by Prof. Bailey, to recent, and sometimes even to fossil shells, proves the same fact, by leaving a distinct internal flexible cell-membrane retaining the general form, after the dissolution of the silica by the acid. Further support, if needed, is furnished by the phenomena of cell-division, in which the lining membrane takes the initiative, and is followed by the doubling-in of the external coat upon it. 40 GENERAL HISTORY OF THE INFUSORIA. Nevertheless, although a silicious layer be artificially separable from the underlying organic coat, the relation and union of the two are indeed very intimate : and in the case of the apparently inorganic external lamina, the silex must be presumed to be deposited in some form of connective tissue, or, in other words, to permeate it. This opinion is advocated by Meneghini, who adduces in its support the circumstance of the silicious shield of Ach- manthidia being covered with “a very delicate dilatable membrane, itself containing silica, as is proved by its sustaining unchanged the action of fire and acids.” This author goes on to suggest that “this permeation may occur either in the wall of a simple cell, as is seen in the epidermal cells of many plants, or within minute cells, as in various plants and animals.” The surface of Diatomaceous frustules is generally very beautifully sculp- tured, and the markings assume the appearance of dots (puncta), stripes (striae), ribs (costae), pinnules (pinnae); of furrows and fine limes; of longi- tudinal, transverse and radiating bands; of canals (canaliculi), and of cells or areolae, whilst each and all these varieties present striking modifications in number, relative distribution, and in degree of development. Again, two or more sorts of markings may occur together in the same individual; and lastly, the entire frustule may be covered, or certain spots may be left unoccupied by them, in the form of bands, circular spaces, and the like. The preceding account of the coverings of a Diatomaceous frustule make it clear that the apparent superficial markings, although chiefly due to the sculpturing of the silicious epiderm and to its internal involutions, are still in some instances and in a certain degree dependent on the overlying firm vegetable membrane which Mr. Shadbolt and others have shown to exist. But, apart from this, modern research shows that puncta, lines, costae and other markings are not the same in nature in all examples presenting them ; that in One case a circular point is a depression, in another an elevation, and in a third a mere thickening or condensation of silicious material. So of lines or costae: some are markings of the surface, and either furrows, ridges or thickenings, or actual canals, whilst others are the result of invo- lutions or foldings of the internal coat or incomplete septa. Again, the fine lines or striae of many frustules are resolvable into rows of minute dots, as in Navicula and Pleurosigma. When the striae are more distinctly composed of rows of dots or puncta, they are described as monili- form; examples occur in Gomphonema and Podosphenia. - Speaking of striae, lines, and puncta generally, Prof. Smith (op. cit. i. p. xvii) confesses his belief that they are all “modifications in the arrangement of the silex of the valve, arising from the mode of development peculiar in each case to the membrane with which the silex is combined;” and, referring to the areolar or cellular-looking valves of Tricerativºn and of Isthmia especially, and to the recognized growth of Organized beings by cells, he arrives at the conviction that “the valvular markings in every case arise from modifications of cellular tissue,” which forms, so to speak, the matrix of the silicious epiderm. “No difficulty (he adds) presents itself to the supposition that the moniliform striae of Epithemia, Navicula, and others, the circular markings of Coscinodiscus eccentricus, and the irregular star-like structure of Eupodiscus Argus, are all modifications of cellular tissue; and even in the costae of Pin- ovularia, and the unresolvable striae of Eupodiscus sculptus and others, it is not difficult to conceive we have confluent cells whose union gives rise to the appearance of lines or bands.” - Great difference has existed, and even yet exists, in the interpretation of the exact nature of many superficial markings. Some circular dots or puncta are held by certain observers to be pits, by others holes, and by others to be OF TEIE DIATOMEAE. 41 elevations. So of stripes, costae, and pinnules: to some, such markings in special instances are ridges; to others, furrows or fissures; to others, ele- vations; and to others again, canals. The ardent microscopical research of this period is daily diminishing the number of these enigmas, and intro- ducing certainty in place of doubt and vague conjecture. To Ehrenberg’s apprehension, many puncta were real pores, and many striae or costae real fissures; the former of these were supposed to give exit to a few or to multi- tudinous imaginary “pedal organs’ for locomotion, the latter to serve for the passage of ova, and generally to bring the presumed internal animal organiza- tion into immediate relation with the external medium around it. Perhaps the discussion respecting the nature of apparent pores has been most animated in the case of the genera Navicula and Pinnularia, which present a large rounded spot at each extremity of the frustule and a central space known as the umbilicus, with a tubular or canal-like band connecting them together (XII. 15, 21, 46; XVI. 1). From the umbilicus, Ehrenberg believed a single locomotive organ to proceed—an undivided sole-like foot, similar to the locomotive organ of snails, whilst he represented the terminal points to be orifices for the purposes of nutrition (IX. 134). Although denying the offices assigned them by the Berlin micrographer, Kützing coin- cided with him in the belief of their being actual pores, and supposed that they give exit to a gelatinous Substance, such as is actually found Sur- rounding some Navicula, and becomes a prominent character in the tribe of Diatomeae represented by Schizomema. Schleiden (Principles of Botany, by Lamkester, p. 594) speaks of the longitudinal band as a cleft, and of the median and terminal spots as circular enlargements or thickened spots of silicious matter. He moreover appends an enlarged lateral view of a Pin- ovularia (XVI. 2, 3, 4, 5), to prove that the seeming central orifice is simply a depression. This explanation of their nature coincides in the main with that given by Prof. Smith, who asserts that these markings are due to a lon- gitudinal band of condensed and more solid silex, widened into Small expan- sions at the centre and extremities, or at the extremities only, and probably designed to give firmness to the valve. “That these expansions (he adds) are not perforations in the valve, as alleged by Ehrenberg, and acquiesced in by Kützing, might be shown in various ways. The internal contents of the frustule never escape at such points when the frustule is subjected to pressure, but invariably at the suture or the extremities . . . . nor does the valve when fractured show any disposition to break at the expansions of the central line, as would necessarily be the case were such points perforations, and not nodules. Moreover, the central band of silex is itself frequently traversed by a narrow line which arises from the confluence of a series of cells, which thus form a minute tube; but this tube invariably ends in a rounded extre- mity at the central and terminal nodules, and does not pass into an opening or aperture in the valve . . . . . . The bending down of this tube and the thickening downwards of the silex at the modules give the semblance of depressions to the surface of the valve at such places. But I am disposed to think that this is merely an optical appearance, and at all events assured that no perforation exists at such points, and that the terms applied to these nodules by different authors, implying that they are openings or ostiola, are altogether inadmissible.” Lxamples of nodules at the centre and extremities are found in the genera Amphiprora, Pinnularia, Navicula (XII. 5, 6), and Gomphonema (XII. 15, 21, 46). In Stauroneis the central nodule is developed transversely, so as to form a smooth transverse band or “stauros” free from markings (XII. 7, 8, 18). A median longitudinal ridge or band exists in Navicula, 42 GENERAL, ELISTORY OF TEIE INFUSORIA. Stauroneis, &c., whilst in Amphipleura (XIII. 1, 2) two ridges are noticeable, but whether these are of the same nature structurally is uncertain. In Doryphora, again, there is a median band, but no nodules distinguishable; and in Eurotia and Himantidium the terminal nodules would seem exceptional in character, being due, as Prof. Smith supposes, “to an inflection of the valves at the point of junction.” The rounded space in the centre of the discoid valves of Actinocyclus (XI. 132) and Arachnoidiscus (XV. 18-21), which is devoid of areola, is designated by him a pseudo-module, in order, we presume, to contrast a mere bare space with the like Smooth but condensed and thick- ened spots described as nodules. In this record of opinions, those of Siebold and Nägeli (J. M. S. i. 196) should not be omitted:—“Precisely at the spots (says the former writer) at which Ehrenberg and others suppose they have seen six openings (i. e. three on each valve) in Navicula, the silicious cell-membrane is thickened, and con- sequently forms so many rounded eminences which project internally.” These views thus far tally with those of Prof. Smith and others; however, a few lines further on in his essay, Siebold expresses the belief that the lines running along the middle of the surfaces from one thickening to another “are to be referred to a suture, fissure, or rather gap, in which no silicious matter is deposited, so that in these places the delicate primordial membrane which lines the silicious shield can be brought into close relation with the external world. I come to this conclusion from the circumstance that it is exactly at these four sutures or fissures that the water surrounding the Navicula is set in motion.” (See p. 50.) Upon the whole question of the actual nature of the markings on the surface of the silicious frustules, we are happy to add a paper published by Prof. Bailey (Sill. Journ. ii. 349), which appears to afford a satisfactory elucidation. We present it entire, with the practical notes on manipulation, so that our readers may undertake a critical examination for themselves:– “I now offer proof which removes all doubt, and shows that these markings are neither apertures nor depressions, but are in reality the thickest parts of the shell. If the shells are placed in dilute hydrofluoric acid and watched by the aid of the microscope as they gradually dissolve, the thinnest parts of course dissolve first, and apertures, if any exist, should become enlarged. Now the very parts which have been called orifices by some, and depressions by others, are the last of all to disappear as the shell is dissolved. This mode of observation, besides establishing the fact that these are the thickest parts of the shell, reveal many interesting particulars of structure. Thus, in the large Pinnularia, it may be seen, with even a low power, that the two parallel bands (separated by a canal) which reach from the central knob to the terminal Ones, and which appear Smooth before the application of acid, become distinctly striated after their surface is dissolved off, as does also the central spot itself, showing that striae which existed in the young shell are covered up and nearly obliterated by Subsequent deposits. In Staurosira the cross-band and the two longitudinal bands are the last to dissolve, and these last bands, as in most Diatomacea, appear separated by what is either a canal or thin portions of the shell. In Grammatophora the undulating lines are internal plates, which are the last to dissolve. In Heliopelta, Actinoptychus, &c., the polygonal central spotis the last to disappear. In Isthmia, the spots on the surface, which at first appear like granular projections, are in reality thin portions of the shell, and under the action of the acid they soon become holes. The acid also proves that the larger spots at the transverse bands are a series of large arcuate holes in the silicious shell, and the piers of this series of arches remain some time after the rest of the shell has vanished. OF THE DIATOMEAE. 43 A few directions on the mode of manipulation may be useful. As the fumes of the hydrofluoric acid, if they reach the lenses, would greatly injure them, it is advisable to protect the front face of the objectives by temporarily con- necting to them a thin plate of mica by Canada balsam, as mica resists the action of hydrofluoric acid much better than glass. I prepare the cell in which the solution is to take place by cementing a plate of mica to a glass slide, and then cover all its surface, except a central small disc, with wax. On this disc, which forms a cell, the shells are put with a dish of water, and after adding a drop or two of acid by means of a dropping-rod of silver or platinum, the cell is covered with another plate of mica, and the slide is then placed under the microscope.” Some markings of the surface, apparent only as striae under inferior magni- fying powers, are in several genera resolvable, as before noticed (p. 40), into rows of rounded dots, e.g. in Pleurosigma; and in consequence such specimens have been employed to try the relative powers of microscopes, and are spoken of as “test objects.” But the powers of microscopes have been more severely tested of late years, by the endeavour to ascertain whether such dots are eleva– tions or depressions of the surface, and, as might be expected, the dissension on this matter has equalled that respecting the central band and umbilicus. Dr. J. W. Griffith is in favour of their being depressions (Proc. Roy. Soc. 1855). He argues that, as the markings “are evidently depressions in the genera and species with coarsely marked valves (Isthmia, &c.), we should expect from analogy that the same would apply to those with finer markings (those viz. in dispute, Gyrosigma, Pleurosigma, and others). And this view receives further support from the fact that under varied methods of illumina– tion corresponding appearances are presented by the markings when viewed by the microscope—from those which are very large, as in Isthmia, through those of moderate and small size, as in the species of Coscinodiscus, down to those in which they are extremely minute, for instance in Gyrosigma, &c. The angular (triangular or quadrangular) appearance assumed by the markings arises from the light transmitted through the valves being un- equally oblique; this may be readily shown in the more coarsely marked valves (Isthmia, Coscinodiscus), which present the true structural appearance when the light is reflected by the mirror in its Ordinary position, and the spurious angular appearance when the light is rendered oblique by moving the mirror to one side.” Another statement is put forward by the same author in the Micrographic Dictionary (Introduction, p. xxxiii) in support of his opinion, viz. “that the line of fracture of the broken valves passes through the rows of dots on the dark lines corresponding to them, showing that they are thinner and weaker than the rest of the substance. Had these dots represented elevations, the valves would have been stronger at these points.” The more prevalent opinion, however, is, that these delicate dots in rows are elevations of the surface. Mr. G. Hunt (J. M. S. 1855, pp. 174–175) adduces an observation to demonstrate this fact. He found that on a speci- men of Pleurosigma being moistened, the markings were almost entirely obscured, but that on the application of a gentle heat “the moisture slowly retreated, leaving patches of the shell dry, and with the markings as dis– tinct as before.” On observing these dry parts of the shell, they were seen to be uniformly bounded by straight lines, parallel to the two directions of least distance of the dots. “Now (continues Mr. Hunt), on the supposition of these little dots being elevations, the phenomenon appears to me easily ex- plicable on the principle of capillary attraction. We can readily conceive the moisture clinging from One dot to another; and it would always have a tendency to arrange itsclf in lines parallel to the directions of least distance. 44 GENERAL ITISTORY OF TELE DNFUSORIA. I am, however, quite at a loss to imagine how the same principle would apply on the hypothesis that the dots are depressions, nor do I see upon what principle the phenomenon is explicable.” A direct demonstration that the markings in general of the Diatomeae are elevations is attempted by Mr. Wenham, whose knowledge of optics and prac- tical skill in mechanical manipulation are not exceeded by any microscopist of the present day (J. M. S. 1855, pp. 244-245). To quote his words—“A careful study of the coarser varieties will distinctly prove that the markings are raised ribs or prominences on the surfaces, in some instances on one side of the shell only, as seen in the Campylodiscus spiralis and others. Though the microscope proves this fact satisfactorily in the large species, it fails to do so in the most difficult specimens, chiefly on account of the above-named deceptive appearances, arising from the irregular refraction and reflection of light. It occurred to me that it might be possible to obtain a perfect cast or impression of the structure; and by viewing this as an opake object, the error, if arising from refraction, would be avoided, and a discovery might be the reward of the experiment. I have succeeded in effecting this by means of the electrotype process, which for many reasons is to be preferred, as it does not distort the object, and is so minutely faithful that even the mere trace of organic matter, left by a slight finger-mark, is perfectly copied. The method I have adopted is this:—Procure a small plate of metal highly polished (a piece of daguerreo- . type plate answers extremely well), and, after gently heating it, rub a piece of bees-wax over the surface; while this is still melted wipe it nearly all off again with a piece of rag, so as to allow a very thin film to remain; when the plate is cold, arrange the Diatomacea or other objects, previously moist- ened, upon the waxed surface, heat the plate again to at least 212°, in order to cement the objects on it. The wax serves a twofold purpose: first, its interposition prevents the possibility of a chemical union of the metallic deposit with the plate; and secondly, the object is securely held thereto by its agency. The objects are now ready to receive a coating of copper. If the battery is in good working order, three or four hours will give a film sufficiently strong to bear removal; when this is stripped off, if the process has been properly managed, the objects will be seen imbedded in its surface; whether they are silicious or organic, they may be entirely dissolved out by boiling the cast in a test tube with a strong solution of caustic potash, and afterwards washing with distilled water; the copper film may then be mounted in Canada balsam. By these means I have obtained distinct impressions of the markings of some of the more difficult Diatomacea, such as N. (Pleuro- sigma) Balticum, P. Hippocampus, &c., leaving no doubt of their prominent nature.” (See Microscopic Cabinet, ed. 1832, chap. xvi. and xviii.) Besides the Superficial markings explicable on the Supposition of an invest- ing areolar membrane, and the sculpturing of the silicious epiderm, there are others, dependent on structural modifications of the silicious laminae of the valves, and on inflections of these internally. Among the former are many of the stronger-marked costae and pinnules of Ehrenberg; and among the latter are to be reckoned the imperfect partitions (‘septa”) seen in several genera, and those peculiar processes of the internal surface which Kützing called ‘vittae.’ Schleiden described ‘pinnules’ to be clefts or fissures. “In these spots (Says he), the shield consists of two leaves lying one over the other; these leaves are penetrated by the small clefts, which, when both the lamellae touch cach other, are somewhat broader, which explains the varying breadth of the clefts according to the alteration of the foci. Frag- ments in which this structure is clearly represented may be frequently obtained by crushing the shield.” (XVI. 5, 6.) OF TEIE DIATOMIE ZE. 45 Prof. Smith likewise describes inter-lamellar channels, under the name of ‘ canaliculi,” “hollowed out between the silicious epiderm and internal cell- membrane, and apparently formed by waved flexures of the epidermal enve- lope. . . . . . They are very conspicuous in Epithemia longicornis, and form distinctive characters in the genera Surirella and Campylodiscus.” This observer also regards them “as minute canals which convey the nutri- mental fluid to the surface of the internal membrane,” this fluid entering them from without through pores or fissures existing along the line of suture of the valves (p. 50). That these canals are not modifications of the cellular structure of the silicious epiderm is shown by the circumstance of the striae passing uninterruptedly over the entire surface of the valves in some Epithemice. The costae of Campylodiscus equally appear to be canaliculi, and are dis- posed in a radiate manner. In Surirella and Trybliomella these canals are usually parallel, whilst in Mastogloia they take the form of loculi. Rützing assigned a special structure and purpose to the markings he called ‘ vittae,’ and used them in forming a SubSection of Diatomeae he called Vittatae. The Rev. Prof. Smith remarks that to him these markings do not seem special organs, but modifications in the outline of the valve, which is inflected. In Grammatophora (XI. 48, 49, 52, 53) these inflections con- stitute a leading feature of the genus, and, from their resemblance to written characters, have suggested its name. In this instance they form incomplete septa. * *. terms striae and costae or pinnules are not synonymous. Striae are the finer lines of slight breadth, which may look like narrow grooves or ridges, whilst costae or pinnules are the wider markings, having an evident double contour, and the appearance of fissures or canals. The fineness of some striae is such that, as before noted, they may be readily overlooked; however, their presence, when not positively demonstrable, may be assumed by the colours displayed on focusing dried specimens. An analogous fact presents itself in the case of mother-of-pearl, which owes its varying and beautiful colours to the existence of fine lines covering its surface. The colour varies in different species, and is due to the refraction of the rays of light passing through the silicious epiderm; its shades depend on the direction of the striae and on their distance from each other; its aid may therefore be advantageously evoked in the determination of species. Striae generally seem to be produced by the confluence of minute rounded points or beads—in other words, are commonly moniliform, and often extend, as products of an investing areolar tissue, over the entire surface of the valves, unlike those costae which originate in structural peculiarities of the silicious plates. Rows of puncta occur in Nitzschia, and moniliform striae in Navicula, Pleurosigma, Gomphonema, and Podosphemia. To the confluence of the superficial cells, Mr. Smith attributes the production of the costae of Pinnu- laria, whilst those of Achnanthes he looks upon as thickenings on the under surface of the silicious valves, and generally similar to those of Isthmia, which line the valves and anastomose on their under surface; lastly, the striae of Rhabdomema are constituted of series of oblong cells. The value of the external markings of Diatomeae, in a systematic point of view, has been much discussed. Ehrenberg assumed the number of striae or of costae or pinnules to be constant in the same space in each species, and accordingly gives the number of striae counted within a given fraction of a line. A great multitude of species was the consequence of this plan; never- theless the mere fact of number of striae within a given space cannot be esteemed a valid specific character by itself; for it seems quite clear that the relative closeness of striae, their number within the ‘001 of an inch, varies according 46 GENERAL EIISTORY OF TEIE INFUSORIA. to the age and to the size of the valves, and both size and figure are consi– derably affected by circumstances of growth, of locality, and the like. A writer in the Microscopical Journal (1855, p. 307) suggests that the number of striae on the entire valve may supply a more stable character; yet even on this point we are wanting in direct observation to show that this number may not be affected by accidental circumstances. * Although “the relative distance of the striae and their greater or less dis– tinctness” be accounted by Prof. Smith of specific importance, yet he is obliged to admit (J. M. S. 1853, p. 133) that it is by no means certain that these features may not to a slight extent be modified by localities and age, and is disposed to believe that they are certain guides only when we have made allowance for these conditions, and that while they are constant in frustules originally from the same embryo, they may slightly vary in those which owe their birth to different embryonic cells. It is also worthy of note that, in certain instances, e.g. in Odontidium hyemalis, Epithemia Arcus, &c., the costae are frequently more numerous on One valve than on the other. Other illustrations of the variation in the number and in the distinctness of striae in the same species are to be found in the late lamented Dr. Gregory’s valuable papers (T. M. S. 1855, p. 10). The relative position of striae—if parallel or radiate, their moniliform or confluent character, their equal and general diffusion over the entire surface, or their absence at parts, are other circumstances available for the purposes of classification. Besides striation, the other descriptions of superficial markings are resorted to for specific and generic characters. Such are the presence or absence of a median band, with central and terminal nodules, the existence of a trans- verse band, the figure, relative position and aggregation of the areolae or cells of the surface. The median and transverse bands have been employed by all systematists, and would seem well suited to furnish characteristics by their constancy. The same may be said of the pore-like spots or nodules. Kützing went so far as to make the presence or absence of a central nodule or um- bilicus the turning-point in his grand division of the Diatomeae into um- bilicated and non-umbilicated. - Lastly, speaking generally, the precaution intimated by Prof. Walker-Arnott (p.39), of having specimens, intended to be compared together for the determi- nation of specific forms, similarly prepared, must ever be borne in mind where the Superficial markings are referred to for characters; otherwise an excessive and erroneous multiplication of species, and a deplorable confusion will result. We have already seen that the connecting membrane is not an essential segment of a Diatomaceous frustule, but an after-development in connexion with the process of self-division; yet, notwithstanding, it is so frequently present, and in many examples its dimensions and characters are so marked, that it supplies an important element in Specific and generic descriptions. In the circular and discoid Diatomeae, it assumes the form of a continuous ring (XI. 40, 42), but in many oblong and navicular frustules it is itself oblong or navicular, having a figure the reverse of the valves it is placed between (XII. 17, 24, 31; XIII. 5, 6, 7). In these latter and in other instances it is frequently separable into two portions, at the opposite extre- mities of the frustules where the silex is absent; and hence it is that the shells of the Diatomeae have been described by Meneghini and other writers as composed of four segments. In general, the proportion of silex in its constitution is less than that in the valves; and the existence of markings—of areolae, striae, and the like— is also much rarer. Where they do occur, they furnish useful particulars in defining species and genera. The small development of the connecting OF TEIE DIATOMIE ZE. 47 membrane in Pleurosigma is a remarkable feature of that genus, whilst in Gomphonema (XII. 28, 53), and other genera with cuneate (wedge-shaped) frustules, the figure is due to the greater development of this segment at one end than at the other. In Amphiprora (XIII. 5, 6), Achmanthes, Himanti- dium (XII. 50, 52), and Melosira, the connecting membrane is striated, and in Biddulphia (II. 48), Isthmia (X. 183), and Amphitetras (XI. 21, 22) is cellulate or areolate. In certain genera the connecting membrane takes on an extraordinary development, which greatly modifies the figure of the frustules. Instead of being limited to the interspace between the opposed valves, it extends on either side beyond the sutures (XII. 9), presents itself as a band of greater or less width, and acquires an unusual persistence. Under this form it con- stitutes the ‘cingulum' of descriptive writers, and is seen in Amphitetras, Biddulphia, Podosira, and Melosira. In the last two genera, Prof. Smith tells us, the persistence of this circular band is “eminently conspicuous, retaining the frustules after Self-division in a geminate union until the self- dividing process is renewed.” CoNTENTS OF FRUSTULES.–Nucleus, supposed Digestive Sacs, Reproductive Vesicles, &c.—The organic membrane of the frustules of Diatomeae, strength- ened externally by the silicious plates, encloses within its cell-like cavity a soft mucilaginous substance filled with numerous granules and globules, and usually of a yellow-brown or orange-brown colour, but at times of a green hue, and technically known as the ‘endochrome,” or in Kützing’s phraseology, the ‘gonimic substance.’ The granular matter is particu- larly aggregated about the Organic wall, leaving the central portion more clear. In this clear central space is a transparent vesicle, representing the nucleus of the cell, having the granules frequently collected around it in an annular form. Nägeli states that the nucleus, enclosing a nucleolus, lies sometimes free in the centre of the frustular cavity, but at other times is affixed at one spot to the wall, and therefore ‘parietal.’ He also describes two sorts of nuclei, viz. primary and Secondary, attributing to the former the active part. Schleiden represents the nucleus to be primarily concerned in the original formation of the cell, as well as in its subsequent multiplication by self-division. Among other elements of the endochrome are more or fewer rather translucent globules, which Prof. Smith believes, like Kützing, to be secre- tions of the cell, of a fatty or oily composition, and to be the source of the peculiar odour emitted on burning the Diatomeae. In support of this view Kützing states that he has occasionally seen two coalesce, proving the absence of proper walls, and expresses his conviction that these corpuscles are akin to the amylaceous Secretions of the Desmidieæ and Confervae and the starch-granules of the higher vegetables. These globules are Smaller than the nuclear space, and occupy a pretty constant and definite position. “The number of these globules is frequently four, often placed near the extremities, or more rarely clustered round the central vesicle.” Meneghini (op. cit. R. S. p. 364), alluding to these vesicles, states them to vary in number, size, and disposition at different stages, and according to various conditions, even under the eye of the observer. These apparent oil-globules were called by Ehrenberg male sexual glands or testes, whilst those other vesicles distributed within the mucilaginous matter, often about the nucleus, were named stomachs. The latter idea he based especially on a series of experiments to introduce colouring matter into the interior of the frustules, in which he believed he succeeded. The species mentioned are Navicula gracilis, N. Amphisboena, N. viridula, N. fulva, 48 GENERAL EIISTORY OF TELE INFUSORIA. N. Nitzschii, N. lanceolata, and N. capitata ; also Gomphonema truncatum, Cocconema cistula, Arthrodesmus quadricaudatus, and Closterium acerosum. The two last, however, are Desmidieæ. In the seven species of Navicula enumerated, from 4 to 20 little stomach-sacs are said to have become filled with the indigo employed as the colouring matter. - “This effect (as Meneghini remarks) could only be produced by keeping the Diatomeae a long time in water laden with particles of indigo, and often re- newed.” Kützing deduced an opposite conclusion from these experiments, viz. that they were solid corpuscles which, being seated near an opening, exerted an especial attraction upon the colouring matter. Meyen argued, so long since as 1839 (Jahresbéricht d. Akad. Berlin), against the supposed stomach-sacs and the entrance of colouring matter within them. His objections are thus expressed:—“On the one hand, I can see no stomach-sacs in the Naviculae, and never observed in the living and moving Bacillaria the colouring matter received at one extremity and carried towards the centre, where these stomach-sacs should lie, whilst among the ciliated Infusoria such observations are easy; on the other hand, it is not uncommon, especially in the larger species, to see the molecules of the colouring matter employed, lie upon the middle of the broad ventral surface, looking as if actually within the Organism; but if a glass plate be placed upon the specimen and then carefully removed, the particles of colouring matter are taken away with it.” Even Ehrenberg admitted that the presumed stomach-sacs varied in number, were quite irregular in their disposition in the interior, and not unfrequently wanting altogether. This last circumstance, Kützing remarks, is opposed to the belief in their digestive functions, since such important organs as stomachs can never be supposed absent. - Although the existence of this fanciful polygastric apparatus in the Diatomeae is scarcely worth controverting, yet we may add to the above objections to it the fact that, in the hands of other experimenters, the attempt to introduce colouring matter by any definite apertures into the frustules of this family has been unsuccessful. - The arrangement of the mucilaginous endochrome, or rather of its pro- minent globules, vesicles, and granules, is sufficiently definite and constant in the same species to afford useful characteristics. At one time these molecules are diffused rather irregularly; at another they are collected in a rounded heap towards the centre, whilst at another they are disposed in lines radiating from the nucleus, or formed in a layer upon the cell-wall,— “at all times * (adds Prof. Smith) “having one or several oily globules, which occupy in different species different positions, but are constant in number and position in the same species. The minute granules” (he con- tinues, i. p. 20) “are generally accumulated in thin layers towards the internal cell-walls: when the frustule is so turned that this layer of endochrome is presented edgeways to the eye, the granules appear to be chiefly aggregated into two plates applied to the opposite sides of the frustule; and when self- division is in progress and the cell-contents are divided into two portions, such a separation or temporary aggregation must necessarily ensue; but in the simplest condition of the frustule the contents are diffused over the entire surface of the cell-walls, precisely as may be seen in the cells of many of the larger Algæ, or of some water-plants of a higher order, as in the leaves of Hydrocharis Morsus-range and others.” Schultze has recently represented (Müll. Archiv, 1858) a definite peculiar disposition of the endochrome—of its mucilaginous and granular portions and its coloured corpuscles. In the more or less quadrate frustules of Denticella, and in the circular ones of Coscinodiscus, he describes the existence of a central OF TEIE DIATOMEAE, 49 clear vesicle, from which thin, finely granular lines or threads extend and intersect and branch in a reticulate manner, with a more or less distinct radiation, the more fluid contents flowing between them. In the long cylin- drical frustules of Rhizosolemia, on the contrary, these granular mucilaginous threads run longitudinally. Within these threads the colouring, yellowish- brown corpuscles, not circular, but, as Schultze says, irregularly multangular, are disposed and retained in their position. Although these researches extend to so few forms, yet we are disposed to believe that this disposition of the elements of the endochrome will be found to be the rule. A regular arrange- ment is figured in many drawings of the Diatomeae by various observers; and where it does not appear it is most probably due to the want of attention to its presence,—or to the excessive multiplication of the colouring corpuscles, causing them to appear spread beneath the envelopes as a pretty uniform layer. A definite disposition of the chlorophyll-granules is common in plants, particularly among the lower Algae, and owes its constancy to the presence of the mucous and less fluid contents, which are condensed from the sur- rounding fluid in the form of filmy threads, and serve as a nidus to the colour- ing particles. In this disposition, therefore, of the endochrome and its cor- puscles we perceive a vegetable character, as contrasted with what is seen in animal cells, and find in it an additional argument for the vegetable nature of the Diatomeae. ~ Notwithstanding that the endochrome is, by pretty general consent, ho- mologous with that of recognized vegetable Algæ, still it would seem to be of a different chemical composition as well as of another colour. Kützing, indeed, insisted on the fact of the similarity of the endochrome to the gonimic substance of Algae, from the circumstance that, by means of alcohol, he was able to extract a colouring matter similar to chlorophyll; yet Raben- horst and others have remarked a difference in chemical nature. Prof. Smith again, whilst admitting the imperfection of our knowledge on this point, goes on to say that “the tincture of iodine causes the internal membrane to contract upon the cell-contents, and converts these from the golden yellow which they exhibit in some species, into bright green, and that a weak solution of sulphuric acid, while it effects the same contraction in the cell– wall, gives to the contents, which have been previously treated with iodine, a dark-brown hue: alcohol, on the other hand, as in the case of vegetable cells in general, dissolves the utricle and its contained endochrome, or at all events entirely removes their colour, and leaves their silicious epiderm in a state of perfect transparency. It does not, however, dissolve the envelope in which the frustules of the frondose forms are imbedded, nor the filamentous stipes or gelatinous cushions to which other species are attached.” Meneghini (op. cit. R. S. p. 365) contends that the identity in nature of the endochrome of Diatomeae and of Algae is not proved. “Its colour is dif- ferent; and it is differently coloured by chemical reagents. The resemblance to it in some instances, as in Melosira, in regard to conformation and suc- cessive alterations, is only in appearance. In the endochrome of Algae the monogonimic substance begins by presenting a granular appearance; then it becomes distinctly granulated and changes into the polygonimic substance, so minutely described by Kützing. But these changes do not occur in the coloured substance of Diatomeae. If we insist on a parallel, we can only compare it to the cryptogonimic substance of Byssoidia, Callithamnia, Griffithsia, and Polysiphonia. It divides into two parts which successively undergo ulterior division; and in regard to these changes we may observe that there is an essential distinction between those that occur during life and those that take place after death, the greater number happening in the latter E 50 GENERAL, HISTORY OF THE INFUSORIA. condition. . . . . The identity of this substance with endochrome is contradicted by Kützing’s own experiments, . . . . . . which prove it to be very rich in nitrogen: it emits ammonia copiously when decomposed by heat; and this can only proceed from a substance abounding with it, which such a decom- position compels it to yield up. Nor, on the contrary, do I believe that there is any weight in the argument from the solubility of its colouring principle in alcohol; for this is not aproperty peculiar to chlorophyll, or to any sub- stance of vegetable origin.” - The contents of the frustules are brought into relation with the surround- ing medium through certain pores or fissures, which have been referred to as existing here and there along the sutures between the opposed valves, or otherwise between the valves and the interposed connecting membrane. The existence of such openings in the silicious envelope, and the consequent exposure of the Organic internal or primordial membrane in the situations mentioned, have been demonstrated chiefly by the researches of Prof. Smith, who applies to them the name of “foramina.” They are thus described (op. cit. i. p. 15):-‘‘Along the line of suture in disciform or circular frustules, but more generally at the extremities of the valves only, when the Diatom is of an oblong, linear, or elongated form, there exist perforations in the silex which permit the surrounding water to have access to the surface of the internal cell-membrane. The formation of silex seems occasionally to be arrested in the neighbourhood of these spots; and the connecting membrane is in consequence either wholly or partially interrupted at such places. Thus, after the internal cell-membrane has been removed by acid, when it often happens that the valves fall away from the gonnecting membrane, the latter Separates into two parts; and the frustule has in consequence been described as consisting of four plates. The interruptions in the silicious epiderm are usually apparent as slight depressions at the extremities of the frustule; and the appearances they present have been denominated “puncta” by Mr. Ralfs. In some species these interruptions are more numerous, being found along the entire line of suture, and are often connected with minute canals hollowed out between the silicious epiderm and the internal cell-membrane, and ap- parently formed by waved flexures of the epidermal envelope.” The latter constitute the canaliculi heretofore spoken of (p. 45). . Siebold regarded the longitudinal bands having a double outline, and ex- tending from the apparent dots or pores at either end of Naviculae to near the centre, to be fissures; but the account previously given proves this able man to have been mistaken on this point. Like Prof. Smith, however, he con- cluded that the internal membrane was imperforate, and that it served as the medium for the exoSmosis and endosmosis attending the function of nutrition. -- MoVEMENTS OF THE DIATOMEAE;—THEIR CHARACTER AND CAUSES;—CILIA ;- CIRCULATION OF CONTENTs;—RESPIRATION.—The peculiar movements noticed in many Diatomeae have attracted the observation of all microscopists, and have induced many, especially among the older observers, to receive it as evidence of their animal nature; but even those who agree on this point are in no better accord among themselves respecting its cause than are those who refer these beings to the vegetable kingdom. - The power of movement is not confined to those only which are free, bu also to concatenate and to some fixed forms, e.g. Symedra, which move on their fixed extremity. There is considerable diversity bothin the manner and extent of movement of different species; but in none is it exhibited in an equal degree to that seen in the spores of Algae. “The motion,” says Prof. Smith, “is of a peculiar kind, being generally a series of jerks producing a rectilinear OF THE DIATOMEAE. 51 movement in one direction, and a return upon nearly the same path, after a few moments’ pause, by another series of isochronal impulsions. The move— ment is evidently of a mechanical nature, produced by the operation of a force not depending upon the volition of the living organisms: an obstacle in the path is not avoided, but pushed aside; or, if it be sufficient to avert the onward course of the frustule, the latter is detained for a time equal to that which it would have occupied in its forward progression, and then retires from the impediment as if it had accomplished its full course. There is cer- tainly no character of animality in the movement; and the observer, familiar with the phenomena of life in the earlier stages of vegetable existence, is constrained to see a counterpart in the involuntary motions of the filaments of the Oscillatorieae, or of the gemmiparous spores of the Fuci and Con- fervae.” - - - - This same view was taken by Morren in 1839 (op. cit.), who says—“The movement of the Bacillaria, however free it may be, is by no means so free and active as that of the spores of Algæ, which are plants, or, at least, parts of plants; and the motion is no positive ground for the belief in their ani- mality.” • * The cause of the motion of the Diatomeae has hitherto not been satisfacto- rily determined. To the hypothesis of a snail-like expanding foot projecting from the central pore or umbilicus, advanced by Ehrenberg, we have already alluded (p. 41); and since no one original observer, in spite of the best-directed efforts, has been able to detect the remotest evidence of such an organ, and as all evidence goes to show that no actual perforations exist at the point indicated for its extrusion, it would be useless to raise any argument upon it. This distinguished naturalist subsequently Satisfied himself of the presence of other locomotive organs in a Navicula (Surirella gemma, XII. 3, 4), which he has thus described:—“Instead of a Snail-like expanding foot, long delicate threads projected, where the ribs or transverse markings of the shell joined the ribless lateral portions, and which the creature voluntarily drew in or extended. An animalcule Tººth of a line long had 24 for every two plates, or ninety-six in all; and anteriorly, at its broad frontal portion, four were visible. Whether these organs were Supernumerary, and existed along with cirrhi, &c., and with the flat snail-like foot which the rest of the Naviculae possess, could not be determined. Longitudinal clefts at the broad side of the shell were not present; but as many as 96 lateral openings for the exit of the cirrhi were perfectly distinct.” These ciliary processes were further stated to be actively vibratile, and to be retracted or extended at short periods. Prof. Smith has remarked on this appearance, that the presence of hairs apparently on all parts of the frustule may often be detected, and that he has noticed them on nearly every occasion on which he has gathered this species, but in no case has he been able to perceive any motion in such hairs; and he therefore concludes that they are merely a parasitic growth, such as the mycelium of some Algae. He has also seen similar appendages to other Dia- tomeae, but in every case devoid of motion. The notion of exsertile and retractile feet has been renewed by M. Focke (Comptes Rendus, 1855, p. 167), who attributes the movements of Navicula to such organs of a temporary kind, which he says pass through openings he has detected on the sides of the lorica. - Nägeli offered the following, and, to Siebold’s mind, Satisfactory, explana- tion of the forward and backward movement, as well of many Desmidieæ as of Diatomeae (J. M. S. 1853, p. 195). “The cells,” he writes, “ have no special organs for these movements. But as in consequence of their nutri- tive processes they both take in and give out fluid matters, the cells neces- . E 2 52 GENERAI, EIISTORY OF THE INFUSORTA, sarily move when the attraction and the emission of the fluids is unequally distributed on parts of the surface, and is so active as to overcome the resistance of the water. This motion, consequently, is observed more particu- larly in those cells which, in consequence of their taper form, easily pass through the water; these cells, moreover, move only in the direction of their long axis. If one half of a spindle-shaped or ellipsoidal cell chiefly or en- tirely admits material, the other half, on the contrary, giving it out, the cell moves towards the side where the admission takes place. But as in these cells both halves are physiologically and morphologically exactly alike, so it is that it is first the one and then the other half which admits or emits, and consequently the cell moves sometimes in one, at other times in the opposite direction.” In our apprehension, this mechanical interpretation of the phenomenon is not sufficient; the alternate reception and discharge of fluid matters by each opposite half requires an effort of imagination, to conceive, unwarranted by analogy. We shall, however, presently see that Prof. Smith gives the pre- ference to this supposition, amid the many conflicting fancies of authors and the obscurity of the question. -- Encouraged by apparent success in discovering cilia on the fronds of Des- midieæ, Mr. Jabez Hogg searched for them on Diatomeae, and tells us (J. M. S. 1855, p. 235) that he has repeatedly satisfied himself that their motive power is derived from cilia arranged around openings at either end,-in some also around the central openings, which, with those cilia at the ends, act as paddles or propellers. He, moreover, states his impression that the frustules have a degree of volition sufficient “to move along and to steer their course; for intervals of rest and motion are most clearly to be distinguished.” To this belief in cilia on the frustules of Diatoms, Mr. Wenham is as determined an opponent as he is to the like hypothesis respecting the Desmidieæ (J. M. S. 1856, p. 159), and he offers the following speculations on the cause of the movements:—“If caused by the action of cilia, such extremely rapid impulses would be required to propel the comparatively large body through the water, that surrounding particles would be jerked away far and wide; a similar effect would be observed if the propulsion were caused by the reaction of a jet of water, which, according to known laws of hydrodynamics, must neces- sarily be ejected with a rapidity sufficient to indicate the existence of the current a long distance astern. I consider that there is no ground for assuming the motions of the Diatomaceae to be due to either of these causes. They are urged forward through a mass of sediment without displacing any other particles than those they immediately come in contact with, and quietly thrust aside heavy obstacles directly in their way, with a slow but decided mechanical power, apparently only to be obtained from an abutment against a solid body. In studying the motions of the Diatomeae, I have frequently seen one get into a position such as to become either supported or jammed endways between two obstacles. In this case, particles in contact with the sides are carried up and down from the extreme ends with a jerking move— ment and a strange tendency to adherence, the Diatom seeming unwilling to part with the captured particle. Under these circumstances I have dis– tinctly perceived the undulating movement of an exterior membrane; whether this envelopes the whole surface of the silicious valves I am not able to determine, nor do I know if the existence of such a membrane has yet been recognized. The movement that I refer to occupied the place at the junction of the two valves, and is caused by the undulation of what is known as the ‘connecting membrane.” This will account for the progressive motion of the Diatomeae, which is performed in a manner analogous to that of the OF THE DIATOMEAE. O 53 Gasteropoda. The primary cause, however, is different, and not due to any property of animal vitality, but arises, in my opinion, merely from the effects of vegetable circulation. I have observed several corpuscles of uniform size travel to and fro apparently within the membrane, which is thus raised in waves by their passage.” Mr. Wenham follows up this explanation by a conjecture with respect to the rarer movements of the Desmidieæ. “As there are in these,” he writes, “no indications of either external orifices or cilia, may not their locomotion be effected by the currents of protoplasm forcing their way between the primordial utricle and outer tunic, which will thus be raised in progressive waves if the investment happens to be in a suitably elastic condition.” (See p. 5.) The undulating movement of an exterior membrane thus indicated by Mr. Wenham, over the surface of Diatomaceous frustules, is doubtless identical with the current demonstrated by Siebold by means of indigo (J. M. S. i. pp. 196, 197). The latter states that the particles of this colouring matter which come in contact with the living Naviculae are set into a quivering motion, although previously quite motionless; but this happens only along the lines of the four sutures, the particles adherent to other parts of the shield remaining motionless. “The indigo particles, which are propelled from the terminal towards the two central eminences, are never observed to pass beyond the latter : at this point there is always a quiet space, from which the particles of indigo are again repelled in an inverse direction towards the extremities. This proves that the linear sutures, as may in fact be seen, do not extend over the central eminences of the shield. The current at these clefts is occasionally so strong, that proportionally large bodies are set in motion by it.” The sutures and clefts alluded to by Siebold, it should be understood, are not the sutures between the valves and connecting membrane, but the evident lines extending between the apparent pores on the valves, and which, to his apprehension, are actual fissures in the silicious envelope, by which “the delicate primordial membrane which lines the silicious shield can be brought into close relation with the external world.” This belief in the presence of such fissures on the valves we have previously examined and shown to be unfounded. (See p. 41.) Prof. Smith has the following remarks on this debateable point of the cause of the motions of Diatomeae (op. cit. vol. i. p. xxiii):—“Of the cause of these movements, I fear I can give but a very imperfect account. It appears certain that they do not arise from any external organs of motion. The more accurate instruments now in the hands of the observer have enabled him confidently to affirm that all statements resting upon the revelations of more imperfect object-glasses, which have assigned motile cilia, or feet, to the Diatomaceous frustule, have been founded upon illusion and mistake. Among the hundreds of species which I have examined in every stage of growth and phase of movement, aided by glasses which have never been Surpassed for clearness and definition, I have never been able to detect any semblance of a motile organ ; nor have I, by colouring the fluid with carmine or indigo, been able to detect, in the coloured particles Surrounding the Diatom, those rotatory movements which indicate, in the various species of true infusorial animalcules, the presence of cilia. I am constrained to believe that the movements of the Diatomaceae are owing to forces operating: within the frustule, and are probably connected with the endosmotic and exosmotic action of the cell. The fluids which are concerned in these actions must enter and be emitted through the minute foramina at the extremities of the silicious valves; and it may easily be conceived that an exceedingly small quantity of water expelled through these minute aper- 54. © GENERAL HISTORY OF TELE INFUSORIA. tures would be sufficient to produce movements in bodies of so little specific QTaylt, W. - s eſ. #a. motion be produced by the exosmose taking place alternately at one and the other extremity, while endosmose is proceeding at the other, an alternating movement would be the result in frustules of a linear form, while in others of an elliptical or orbicular outline, in which foramina exist along the entire line of suture, the movements, if any, must be irregular, or slowly lateral. - “Such is precisely the case. The backward and forward movements of the Naviculeſe have been already described ; in Swrirella and Campylodiscus the motion never proceeds farther than a languid roll from one side to the other; and in Gomphonema, in which a foramen, fulfilling the nutritive office, is found at the larger extremity only, the movement is a hardly perceptible advance in intermitted jerks in the direction of the narrow end. The subject is, however, one involved in much obscurity, and is probably destined to remain, for some time to come, among the mysteries of Nature, which baffle while they excite inquiry.” - The last clause of this quotation expresses the unsatisfactory state of the question; yet the foregoing examination will, we think, leave only three hypotheses deserving further inquiry: viz., 1, the existence of cilia, or, 2. of an undulating membrane; and 3. the operation of endosmose and exoSmose, as a mechanical cause. To our apprehension, the presence of cilia, perhaps ranged only along the sutural lines, has not been completely disproved; and, on the other hand, considered as locomotive organs, cilia have the great advantage of analogy over the presumed undulatory membrane. Do not, indeed, the experiments with indigo, recounted by Siebold, suggest cilia to be the active agents of the movements recorded ? The rate of motion of the Diatomeae is exceedingly languid and slow; Sometimes it amounts to no more than an oscillating movement, with little or no change of place ; and at another, the backward and forward movements are so nearly equal, that the frustule makes no appreciable advance. Prof. Smith has measured the rate of motion of some species, and remarks that, however vivacious and rapid they may at first sight seem, yet, when con- sidered with reference to the high magnifying powers employed, and the consequent amplification of their movements, they are very slow. “I have noted the movements of several species with the aid of an eye-piece micro- meter and a seconds watch, and found that one of the most rapid, viz. Bacil- laria paradoara, moved over gºrgth of an inch in a second; Pinnularia radiosa, one of the slowest, over ºrgth of an inch in the same time; and that the same period was occupied by Pinnularia oblonga in traversing grºwth of an inch, Nitzschia linearis gºrgth of an inch, and Pleurosigma strigosum gºrgth of an inch. Or, expressing the spaces and times by other units, we find that the most active required somewhat more than three minutes to accomplish movements whose sum would make one inch, and the slowest nearly an hour to perform the same feat.” Before quitting the subject of the movements of the Diatomeae, we would briefly advert to the peculiar motion of some species, especially of Bacillaria paradova. The movements of this organism, as the specific name implies, are paradoxical, or very strange in character. Mr. Thwaites essayed to describe what indeed can be rightly apprehended only by personal ob- servation, in the following words (Proc. of Linn. Soc. i. p. 311):—“When the filaments have been detached from the plants to which they adhere, a remarkable motion is seen to commence in them. The first indication of this consists in a slight movement of a terminal frustule, which begins to slide OF THE DIATOMIEAE. - 55 lengthwisé over its contiguous frustule ; the Second acts simultaneously in a similar manner with regard to the third, and so on throughout the whole filament, the same action having been going on at the same time at both ends of the filament, but in opposite directions. The central frustule thus appears to remain stationary, or nearly so, while each of the others has moved with a rapidity increasing with its distance from the centre, its own rate of movement having been increased by the addition of that of the inde- pendent movement of each frustule between it and the central one. This lateral elongation of the filament continues until the point of contact between the contiguous frustules is reduced to a very small portion of their length, when the filament is again contracted by the frustules sliding back again as it were over each other; and this changed direction of movement proceeding, the filament is again drawn out until the frustules are again only slightly in contact. The direction of the movement is then again reversed, and con- tinues to alternate in opposite directions, the time occupied in passing from the elongation in one direction to the opposite being generally about 45 seconds. If a filament while in motion be forcibly divided, the uninjured frustules of each portion continue to move as before, proving that the filament is a compound structure, notwithstanding that its frustules move in unison. When the filament is elongated to its utmost extent, it is extremely rigid, and requires some comparatively considerable force to bend it, the whole filament moving out of the way of any obstacle rather than bending or separating at the joints. A higher temperature increases the rapidity of the movement.” To this account Prof. Smith appends these observations:—“The motion here so accurately described is not essentially different from that noticeable in many of the free species of Diatomeae, the peculiarity being that it is here exhibited in numerous united frustules; when observed in a band of one hundred or more frustules, the singular appearances assumed by the filament under the action of so many individuals moving at one time in apparent concert, and another in opposition, never fail to excite, astonish- ment.” - Mr. Thwaites’s account conveys the impression that the movements are always regular: but this is not the case; for Mr. Ralfs tells us, by letter, that both Dr. Bailey and himself have convinced themselves that they are at many times irregular. Dr. Donkin, in his description of a new species of Bacillaria he names B. cursoria (J. M. S. 1858, p. 27), has the following account of its singular move- ments:—“When the filament is in a quiescent state, the frustules are all drawn up side by side, their extremities being all in a line, thus forming a group. When a filament previously at rest resumes its activity, the movement is commenced by the second or immer frustule at one end of the filament gliding forward along the contiguous surface of the first or outer frustule until their opposite extremities overlap each other. This is soon followed by a similar movement of the third, fourth, and fifth, &c., all moving forward in the same direction, and each frustule gliding along the surface of the one preceding it, until they have extended themselves into a lengthened filament or chain. In the course of two or three seconds after this has been accomplished, a retrograde movement, exactly of the same character, begins to take place, and continues until the filament has retraced its course, and stretched itself out in a direction exactly opposite to the position it had previously occupied. This phenomenon is repeated again and again; and in this manner the whole group is kept in a state of activity for an indefinite period of time; and all the while, if no impediment produces irregularity, the outer or terminal frustule, next to which the movement commenced, maintains a stationary and fived position, 56 GENERAL ELISTORY OF THE INFUSORIA. “The rapidity with which each individual frustule moves is in direct ratio to its distance from the terminal stationary frustule, being most rapid at the opposite or moving extremity of the filament. On this account, most of the frustules, while the filament is moving to and fro, cross a line drawn at right angles to the middle of the long axis of the stationary frustule, at the same instant of time, afterwards shooting past each other like horses on a race- COULTS62. & “The force with which the filament moves is very great, so much so that I have observed it upset and shove aside a large frustule of A. arenaria, n. sp., at least six times its own bulk, obstructing its path. This force is, in a great measure, due to the rapidity with which the frustules move, the time which a filament, even of considerable length, occupies in Crossing the field of the microscope being only a few seconds. “Light appears to be a necessary stimulus for the maintenance of this motion. When a filament in active motion is placed in the dark for a short period, and then examined, the movement is seen to have ceased, but again commences when the filament is exposed to the light for a short time. Is not this singular movement, with which the present species is endowed, a vital phenomenon, and independent of physical causes for its existence 2 “When the moving extremity becomes entangled in any kind of substance intercepting its course, the opposite or stationary extremity commences to move, and continues to do so until the entangled extremity is set free ; sometimes, in such instances, a frustule in the centre remains fixed, a move- ment of éach half of the filament in opposite directions, on either side of it, taking place. But all these irregularities cease as soon as the impediment has been got rid of. * • “These facts lead to the conclusion that the present species is a true Bacil- laria, although apparently somewhat anomalous in the structure of its frustule. The gliding movement of one frustule over the contiguous one is the same as is observed in B. paradoaca; but it differs from this latter species in this essential particular, that the whole of its filament moves on one side of a terminal frustule which is stationary, while, in B. paradoara, each half of the filament moves in opposite directions on either side of a central stationary frustule.” . . The movement of one segment upon another is witnessed in other con- catenate species, but in a less degree, where the medium of attachment is limited to a small space, as in those several genera having the alternate or opposite angles of their frustules connected by a link-like isthmus, e. g. Diatoma, Fragilaria, Grammatophora, &c. NUTRITIVE FUNCTIONs;—SUPPOSED STOMACHs;–CIRCULATION OF CONTENTS;- RESPIRATION.—The nutrition of Diatomeae is provided for primarily by the endosmotic and exoSmotic action going on through the “foramina’ in the silicious epiderm, whereby fluid material laden with the matters necessary to build up the various elements of the endochrome is introduced into the organisms. * On the first appearance of a frustule, the endochrome is homogeneous and granular; but as time advances, granules are seen to congregate in certain parts, and globules or vesicles of various size speedily develope themselves, and either take up definite positions or are irregularly diffused. During these changes in the contents—during, indeed, the entire life of the cell, under the influence of light, oxygen is given off, and the gases with which it was united in various chemical compounds are appropriated to the purposes of the economy. ; : . The very fact of the existence of the silicious epiderm, thrown off, it would OF THE DIATOMEAE. 57 seem, as an excretion from the organic membrane of the frustules, indicates the activity and energy of the nutritive functions,—a fact further demonstrated by the production of the ‘connecting membrane,’ and, in short, by the whole process of reproduction, whether by self-division or by sporangia. The silica present in the lorica must be taken up by the Organism in a state of solu- tion; and although the quantity of silica dissolved in water is inconceivably small, it is nevertheless sufficient to supply the material for the construction of millions of Diatomaceous shells, even in a short time, as the phenomena of reproduction and the rapid appearance of these structures as an appre- ciable powder, or as a colouring matter in water, prove. “It is probable,” says Dr. Gregory (J. M. S. 1855, p. 2), “that as fast as the silex is extracted from the water by them, it is dissolved from the rocks or earths in contact with the water, so that the supply never fails;” and we may add, so that the quantity never accumulates beyond the very minute fractional portion chemists can detect. - Ehrenberg’s untenable hypothesis of the presence of stomach-sacs and of an alimentary canal opening externally has received sufficient attention in the history already given (pp. 47,48), of the nature of the contents of the Diatomeae and of their investing lorica. Were other considerations needed, the absence at times of any such vesicles as Ehrenberg conceived to be gastric cells, their occasional coalescence, and the phenomenon of cyclosis or the circulation of the contents, each and all subjects of direct observation, might be appealed to as proofs of the errors that great naturalist fell into respecting the internal organization of the Diatomeae. \ The phenomenon of cyclosis has been observed by Nägeli in a species of Navicula, and in One of Gallionella (Melosira) (XW. 27), and by Prof. Smith in other Diatoms. This writer says (op. cit. i. p. xxi)—“In Swrirella biseriata this motion has been more especially apparent; but I have also observed it take place in Nitzschia scalaris and Campylodiscus scalaris. This circulation has not, however, the regularity of movement so conspicuous iſ the Des– midieæ, and is of too ambiguous a character to furnish data for any very certain conclusions, save one, viz. that the Diatom must be a single cell, and cannot contain a number of separate organs, such as have been alleged to occupy its interior, since the endochrome moves freely from One portion of the frustule to the other, approaching and receding from the central, nucleus unimpeded by any intervening obstacle.” - Schultze, in his contribution on the movements within the frustules of Diatomeae (Müll. Archiv, 1858), represents them to occur in and along the finely granular threads into which the less fluid mucilaginous portion of the endochrome is drawn out. He compares the movements in character to those of the ‘variable processes’ or pseudopoda of Rhizopodes, and thereby assimilates the mucilaginous films of Diatomaceous frustules with the soft sarcode of those simplest animalcules, a similarity countenanced by the now well-known fact of an Amoebiform phase in the cycle of development of some of the lower Algae (vide section on Phytozoa). The cyclosis in plant-cells is no doubt rightly attributed to the operation of the vital processes of nutrition and of the so-called respiration, and primarily to the chemico-vital action proceeding by the medium of the chlorophyll-globules; and it seems most con- sonant with the teachings of Science to assign the less active and less complete and regular internal movements of the Diatomeae also to the similar vital forces, the coloured corpuscles, it may be, acting here likewise as the prime mover. We are aware that the nucleus has been represented to be the first source of the movements in plant-cells, since the current seems to flow from and to return to it in many cases; but this phenomenon is explicable in 58 . GENERAL, HISTORY OF THE INFUSORIA. another way, by admitting the disposition of the mucous threads as displayed by Schultze, extending as they do from the nucleus on all sides, and serving at the same time to limit and to direct the movements taking place within and by them. We have not adverted to ciliary action as the cause, for; so far as we can gather, Mr. Osborne and Mr. Jabez Hogg have failed to impress many naturalists with the fact of its existence and operation in Diatoms. Lastly, Schultze remarks that, to see the mucilaginous threads and the internal movements, living and fresh specimens are needed; for they are soon arrested when the frustules are removed from their natural habitats, and are quite lost to vision when they become dry. Hence it is, no doubt, that no previous observer has detected and rightly apprehended the facts enunciated by Schultze. The so-called function of respiration is evinced in the fixing of the carbon of the carbonic acid and in the disengagement of oxygen gas; but this is rather an act of nutrition, and resembles that Silent and invisible disengage- ment of certain particles, and the rearrangement of others, which proceed in the formation and in the removal of worn-out tissues in higher animals. MULTIPLICATION, REPRODUCTION, AND DEVELOPMENT OF DIATOMEE-Among the modes of reproduction of the Diatomeae, self-division has usually been accounted one, but erroneously so, since this process is no more than a mul— tiplication of an individual cell, and completely homologous with the process of cell-fission exhibited in the construction of animal and vegetable tissues in general. The peculiarity in the self-division of the Diatomeae, i. e. among the free simple beings, is, that the division is followed by separation; for each cell, instead of uniting with its neighbours in the formation of a tissue, commences an independent existence. Self-division in. One direction, not followed by separation, produces the filamentary or concatenated Diatomeae, whilst the abundant excretion of a mucus around the dividing frustules, and its persistence, give rise to the frondose genera, which make an approach towards the character of vegetable cellular tissue, each cell, however, retain- ing an independent vitality greatly more pronounced than in the latter. The process of self-fission or deduplication in this family resembles in all essential particulars that in other vegetable cells (XV. 28, a, b, c). Preparatory to its visible occurrence, or rather simultaneously with certain changes in the interior, the valves separate by the progressive growth of the connecting membrane. The nucleus within is observed to divide into two portions, each of which eventually becomes detached from the other, and, in Prof. Owen’s language, serves as a centre of Spermatic force, and induces an aggregation of the granules of the endochrome about it. Whilst this separation of the nucleus and of the general contents is going forward, the lining or primordial membrane of the cell becomes doubled inwards in the entire circumference along the line of division, and advances gradually until it at length forms a complete septum, cutting the original single cell into two. This septum is actually double; and in each lamina a deposit of silicious material speedily proceeds, so as to produce two new valves, each opposed to, and immediately continuous around its circumference with, one of the two original valves. Thus, on the completion of this process of deduplication, two frustules result, awaiting only the final act of separation to enter on an independent exist- ence and to repeat the like Series of phenomena, and so on through a seemingly almost endless chain, to perpetuate the existence of the particular species or individual. (See Meneghini’s account of the process and peculiari- ties of Self-division in this class, in the examination of the arguments for the animality of the Diatomaceae, in a Subsequent page.) The true nature, there- fore, of this process of self-division being an extension, not a renewal, of OF TEIE DIATOMLE_E. 59 individual life, has been justly represented by Mr. Thwaites as an act of gemmation, not of reproduction. In the course of self-division, in some instances at least, a mucous or muco-gelatinous matter is thrown out around the frustules engaged. This . circumstance did not escape the notice of Nägeli; and Prof. Smith (Synopsis, i. p. 62) has, after noting it in previous pages as a common phenomenon in the family, thus referred to it in the genus Pleurosigma:—“While self-division is actively going forward, the mucus generated by the dividing frustules is often so considerable as to produce the appearance and effect of a distinct frond, which assumes the form of a thin pellicle of some little tenacity. At other times, when the mucous secretion does not assume the continuity of a pellicle, it invests the individual frustule with a transparent envelope, which has the appearance of an exterior membrane, and has been sometimes mis- taken for such. On one occasion I also met with the frustules of P. Hippo- campus enclosed in mucous or gelatinous tubes, precisely like those of a Colletonema ; but these conditions must be regarded, for the present at least, as temporary or accidental, and cannot be admitted into the specific or generic descriptions.” The process of self-division is affected in some unimportant particulars by the figure and habits of certain genera. Thus in one section of the Melosiredº, the frustules of which have convex ends, Mr. Ralfs points out (A. W. H. xii. p. 347) that the central line is more strongly marked, and seems to divide the frustule into two equal portions. It becomes broader, and at length double, and ultimately an intermediate growth separates the two halves of the frustule, which, during this process, do not increase in size ; but when the intermediate space is equal to the diameter of the original frustule, two new frustules are formed, by the addition of two hemispheres on the inner sides of the separated portions. The outer silicious covering still remaining, the frustules are connected in pairs, and appear like two globules within a joint, as they are characterized by Harvey in Melosira nummuloides, and by Carmichael in M. globifera. The above description belongs more particularly to M. nummuloides; but the process in the other species of this section is the same : a series of changes, nearly similar, occurs in Isthmia. “In this genus,” the author quoted says, “the mode of growth is very curious. As in most of the Diatomeae, the plant increases by a division of the frustules; but in this genus, as also in Biddulphia and Amphitetras (and in the Achmantheſe), two new frustules are formed within the old one, and as they enlarge, rupture it, when it falls off. In these the front portion is at first very narrow, and merely a broad line, but it increases greatly in breadth until the new frustules are fully formed.” In this description and explanation the widening band or front portion mentioned is in fact the * connecting membrane' of Prof. Smith, which, in the genera named, has an extra development, “an Cxtension beyond the sutures of the valves,” and also an unusual porsistence, retaining the two frustules together after self- division, in such a manner that they seem to be enclosed within an original single frustule, just as Mr. Ralfs describes. .This longer persistence of the connecting membrane has been noted by Prof. Smith (A. N. H. 1851, p. 4), who writes—“In some cases, by the new, or rather semi-now frustules proceeding immediately to repeat the process [of self-division], the connecting membrane is thrown off and disap- pears; in others it remains for some time, linking the frustules in pairs, as in Melosira and Odontella.” Another peculiarity, again, not unfrequently obtains in this process of sclf- fission, viz. a departure from the prevailing law of similarity which exists 60 GENERAL HISTORY OF TEDE INFUSORIA, between the new valve and the parent one with which it is united in the newly-created frustule. The newly-developed segment occasionally acquires slightly greater dimensions,—a fact best exhibited in the filamentous genera, since in them it gives rise to an evident irregularity in the chain, affecting its width. Yet, as Prof. Smith remarks (i. p. xxvi), “This increase is so small, that in a filament of many hundred frustules, the enlargement is scarcely appreciable. The rapid attenuation represented by some authors in the filaments of the Fragilariae must therefore be attributed to the deceptive appearance presented by a compressed band when slightly twisted, the sem- blance of attenuation being thus given to the portions which are presented in an oblique direction to the eye of the observer. . . . Starting from a single frustule, it will be at Once apparent, that if its valves remain unaltered in size, while the cell-membrane experiences repeated self-division, we shall have two frustules constantly retaining their original dimensions, four slightly increased, eight somewhat larger, and so on in a geometrical ratio, which will soon present us with an innumerable multitude containing individuals in every stage, but in which the larger sizes preponderate over the smaller; and such are the circumstances ordinarily found to attend the presence of large numbers of these organisms.” Mr. Ralfs has favoured us with the following remarks on this subject in letters. He writes (March 1856)—“In a recent number of the Ann. Nat. Hist., Mr. Carter expresses his belief that the frustules of Diatomaceae gra- dually become smaller by division, and that it requires the sporangial frustule from time to time to keep them the proper size. This I cannot admit; for any person who will take the trouble to watch a species of Gomphonema from its first appearance in Spring, as a scarcely visible fringe to aquatic plants, will observe not only increase of mass, but also enlargement of the frustules. If Mr. Carter is right, the filament in Fragilaria would be very unequal: for instance, as the first-formed frustule could not decrease, and as its segments after division would always form the two ends of the filament, they should be the largest, then the adjacent valves of the two central frustules of the filament the next largest, and so on.” In a subsequent letter the same distinguished authority Writes:—“I see that Prof. Smith, in his Synopsis, p. xxvi, takes the contrary view to Mr. Carter, and considers that the frustules do not grow after they are fully formed, but that, in dividing, the new frustules may slightly increase in size. It is thus that he accounts “for the varying breadth of the bands in the filamentous species, and the diversity of size in the frustules of the free forms.” If he is correct, his opinion is still more adverse to Mr. Carter's views respecting the frustules formed after self-division. But I doubt also the correctness of Mr. Smith’s views. He himself states that “the enlargement is scarcely appreciable;” and yet we find a vast difference of size in the frustules of the same gather- ing. The filaments are so fragile in Fragilaria, and even in Himantidium, that it is very difficult to determine whether the frustules in the same fila- ment do differ much in size, and whether, if they do, the variations are alter- nating or irregular, as would be the case if either Prof. Smith or Mr. Carter be correct. The rate of production of specimens of Diatomeae, even by this one pro- cess of simple self-division, is something really extraordinary. So soon as a frustule is divided into two, each of the latter at once proceeds with the act of self-division; so that, to use Prof. Smith’s approximative cal- culation of the possible rapidity of multiplication, supposing the process to occupy, in any single instance, twenty-four hours, “we should have, as the progeny of a single frustule, the amazing number of one thousand OF TEIE DIATOMEAE. 61 millions in a single month, a circumstance which will in Some degree explain the sudden, or at least rapid appearance of vast numbers of these organisms in localities where they were, but a short time previously, either unrecognized or only sparingly diffused.” - This multiplication by self-division now described, is generally supposed, after a time, so to speak, to exhaust itself, and thereby to render necessary other plans of propagating species. That some other modes do really exist is suggested by the fact of the considerable variations of size of frustules of the same species obtained at one time from the same locality, and moreover by diversities in the relative distance and in the delicacy of the striae of the surface. One such mode of propagation Mr. Thwaites has demonstrated to consist in the production of sporangial frustules by a process of conjugation analogous to that in the Desmidieæ and many other Algae. CONJUGATION.—The method of conjugation, although essentially alike in all cases, exhibits several important modifications in the genera of this family. These were more or less clearly perceived by Mr. Thwaites, who spoke of them as exceptional varieties; but to Mr. Smith belongs the credit of reducing all of them under four principal forms: viz., 1. That in which two parent frustules produce two sporangia by conjugation, as in Epithemia, Cocconema, Gomphonema, Encyonema, and Colletonema. 2. Two parent frustules generate a single spo- rangium, e.g. in Himantidium. 3. “The valves (vol. ii. p. xii) of a single frustule separate, the contents set free rapidly increase in bulk, and finally become condensed into a single sporangium. This may be seen in Coccomeis, Cyclotella, Melosira, Orthosira, and Schizomema. “In Melosira nummuloides, M. Borrerii, and M. Subfleavilis, the second valve of the conjugating frustule is rarely found united to the mucus surrounding the sporangium, the conjugation taking place only in the last frustule of the filament; but in Melosira varians and Orthosira orichalcea, conjugation taking place throughout the entire filament, both valves are usually found adherent to the sporangium or its surrounding mucus. “From a single frustule, as in the last method, two sporangia are produced in the process of conjugation: this takes place in Achmanthes and Rhabdomema.” In describing the process as generally as possible, we cannot do better than follow Mr. Thwaites's account, although it is illustrated by an example taken from the first category of variations. “For the most part,” he tells us, “conjugation in the Diatomeae, as in the DeSmidieæ, consists in the union of the endochrome of two approximated fronds,-this mixed endochrome developing around itself a proper membrane, and thus becoming converted into the sporangium. In a very early stage of the process, the conjugated frustules, as in Eumotia turgida, have their concave surfaces in nearly close apposition (XI. 1), and from each of these surfaces two protuberances arise, which meet two similar ones in the opposite frustule (XI.3); these protu- berances indicate the future channels of communication by which the endo- chrome of the two frustules becomes united, as well as the spot where is Subsequently developed the double sporangium, or rather the two sporangia. A front view of two frustules at the same period shows each of them to have divided longitudinally into two halves (XI. 4), which, though some distance apart, are still held together by a very delicate membrane: this, however, Soon disappears. “The mixed endochrome occurs, at first, as two irregular masses between the connected frustules; but these masses shortly become covered, each with a smooth cylindrical membrane,—the young sporangia, which gradually increase in length (XI. 5, 6), retaining nearly a cylindrical form (XI. 7), until they far exceed in dimension the parent frustules, and at length, when 62 GENERAL HISTORY OF TEIIL INFUSORIA. mature, become, like them, transversely striated upon the surface (XI. 8). Around the whole structure a considerable quantity of mucus has, during this time, been developed, by which the empty frustules are held attached to the sporangia (XI. 5-8).” - - - The variations in the process are alluded to in the following extracts from the same eminent observer’s papers:–“In different genera, slight variations are met with in the method of conjugation: thus, in some species of Gom- phonema the sporangia lie in a direction parallel to the empty frustules, instead of across them, as described in Eurotia twrgida. Again, there are examples (in Gomphonema minutissimum and Fragilaria pectinalis) where, instead of the conjugated frustules separating into two halves, only a slit appears at one end, to serve for the escape of the endochrome. Instead also of the pair of conjugated frustules producing between them two sporangia, they may develope but a single one, as happens in Fragilaria pectinalis. In this species, too, the sporangium, at first cylindrical, soon assumes a flattened, somewhat quadrangular form, and in many cases undergoes fissiparous divi- sion before it has put on the exact appearance of the frustule of a Fragilaria. “The Melosiredº (Gallionellae, Ehr.) and the Biddulphiae,” Mr. Thwaites remarks, “would seem, in their development of sporangia, to offer an excep- tion to most Diatomeae ; for in those genera no evident conjugation has been seen. However, something analogous to it must take place ; for, excepting the mixture of endochromes of two cells, the phenomena are of precisely similar character. Thus, instead of the conjugation of two frustules (XV. 29, a, b, c, d, 32, 33), a change takes place in the endochrome of a single frustule,_that is, a disturbance of its previous arrangement, a moving towards the centre of the frustule, and a rapid increase in its quantity: subsequently to this it becomes a sporangium; and out of this are developed sporangial frustules, as in the other Diatomeae. In a single cell, therefore, a process physiologically precisely similar to that occurring between two conjugating cells takes place; and it is not difficult to believe, taking into view the secondary character of cell-membrane, that the two kinds of endo- chrome may be developed at the opposite ends of one frustule, as easily as in two contiguous frustules, and give rise to the same phenomena as ordinary conjugation.” - - . Further, in his notes on Schizomema subcohaerens, Mr. Thwaites writes, “The sporangia of this species are produced by the conjugation of a pair of frustules outside the filaments; but sporangial frustules are frequently found in a filament intermixed with ordinary frustules, from which they differ only in size.” Dr. Griffith and Mr. Carter, moreover, have portrayed peculiarities in the conjugating process, which Prof. Smith can neither explain nor confirm, and is equally unable to reduce under either of the leading variations he has defined. The first-named naturalist stated that in the conjugation of a species of Navicula (amphirhynchus?) a silicious sheath enveloped the spo- rangial frustule, indestructible by heat and nitric acid. “It is,” he writes, “colourless, elongate, rounded at the ends, and furnished with coarse trans- verse striae or depressions, through which the line of fracture runs when the object is crushed.” This account seems to Prof. Smith erroneous; and he suggests that this sheath “may probably have been an appearance resulting from the condensation and corrugation of the mucus developed around the reproductive body.” This conclusion Dr. Griffiths declares untenable, since no kind of mucus will resist the action of a red heat and nitric acid. The specimen examined was, besides, not an isolated one, but hundreds such were present” (A. W. H. xvi. 92). - - OF TEIE DIATOME ZE, 63 Prof. Smith thus alludes to Mr. Carter’s views :-" The circumstance dwelt upon by Mr. Carter as having an important bearing upon the rationale of the process, viz. that one of the conjugating frustules is invariably smaller than the other, is altogether at variance with my experience, and is totally irreconcilable with the process as it occurs in the genera mentioned under the third and fourth classes. I am therefore disposed to believe that the difference in size noticed by Mr. Carter was a mere accidental diversity, and of no essential signification.” The four typical modes of conjugation established by Prof. Smith have their occurrence thus explained (Synops. ii. p. xiii):—“The functions of life and growth are not suspended during the act of conjugation; and in consequence self-division may take place at any stage of the process which accompanies the formation of the reproductive body, or the latter process may intrude upon, or arrest any step in the progress of self-divi- SIOIl. “In the first mode of conjugation, as occurring in Epithemia, &c., self- division may be regarded as in the earliest stage of its progress, which merely involves the separation of the endochrome of the parent frustules into two portions, but does not include such a differentiation of these portions as renders them capable of the conjugative act: the endochrome capable of conjugating with these segregated portions must be sought for in other frustules; hence the process in these genera involves the presence of two parent frustules, and results in the production of two sporangia. “In the second mode, met with in Himantidium, the progress of separa- tion is arrested at a still earlier stage; no differentiation has taken place, and conjugation intervening, necessitates the union of the entire contents of two parent frustules to form a single sporangium. “In the third mode, the progress of the separation of the endochrome in the parent frustule must be considered as so far advanced that complete differentiation has taken place. In every respect but the formation of new valves, self-division has been completed; the incomplete frustules are there- fore prepared for conjugation, which, intervening at this stage, leads the observer to believe that but one frustule has been concerned in the produc– tion of the single sporangium. This we see in Melosira and the other genera mentioned under this class. “And lastly, self-division occurring during the progress of conjugation, the endochrome becomes segregated in the very act of intermingling, and a single frustule, whose contents have been already differentiated, gives rise to two sporangia, as in Achmanthes and Rhabdomema. sº “Nor is the self-dividing disposition in all cases permanently arrested by the complete formation of the sporangium. Having assumed the form of the parent frustules, with a great increase in size (the enlargement in dimen- sions being in some cases due to the accumulation of the contents of the two conjugating frustules, and in others to a rapid assimilation of nutritive material from the surrounding medium), the sporangial frustule immediately submits to self-division, and by the repetition of this act developes a series of frustules cqual in size to the original product of the conjugating process. This is notably the case in the filamentous species, as may be easily seen in Melosira, in Orthosira, and in Himantidium. How far this self-division may be carried in the sporangial frustules is at present unknown; it is pro- bably of short duration, as we rarely meet with any considerable number of frustules characterized by the enlarged size of the sporangial form. In most cases an arrest of growth, and consequently of Self-division, seems imme- diately to follow the complete formation of the sporangia, and the reproduc- 64 GENERAL EIISTORY OF TELE INFUSORIA. tive body assumes the quiescent character which belongs to the seed of the higher plant, its vital function remaining dormant until circumstances favour its further development and the production of the young frustules of which it is the destined parent. “In the gathering of Cocconema Cistula made in April 1852, which con- tained numerous instances of the conjugating process, I observed the frequent occurrence of cysts enclosing minute bodies, variable in their number and size, and many of which had the outline and markings of the surrounding forms, and were obviously young frustules of the Cocconema. It would appear from the figures [appended to this account], that the production of the young frustules is preceded by the separation and throwing off of the silicious valves of the sporangium, and the constriction or enlargement of its primordial utricle, according to the number of young frustules originating in its pro- toplasmic contents. In this gathering, forms of every size intermediate between the minutest frustule in the cyst and the ordinary frustules engaged in the conjugating process were easily to be detected; and the conclusion was inevitable, that the cysts and their contents were sporangia of the species with which they were associated, and indicated the soveral stages of the re- productive process.” Since the preceding account of conjugation was written, a valuable, although not a very lucid, contribution on the subject has appeared by Dr. Hofmeister, in the Reports of the Saxony Natural History Society for 1857, and has been translated by Prof. Henfrey in the A. N. H. for January 1858. From this we extract the following as supplementary to the previously-written history of the conjugation-process and of Self-fission, as well of the Desmidieæ (p.11) as of the Diatomeae:— “Conjugation is far more rarely met with in the Diatomeae than in the Desmidieæ. It appears that this process occurs here only at particular epochs, differing according to the seasons, happening simultaneously in all individuals, and quickly completed. Frequently as indications of conjugation having taken place have been met with (the occurrence of individuals of the same species, of remarkable diversity of size, side by side, in free Diatomeae, e.g. Pinnularia viridis, Surirella bifrons, Stawrosigma lacustre, all the year round, besides the occurrence of shorter or longer rows of cells of about double the diameter, in the bands, of the forms remaining connected by the lateral surfaces, e. g. Melosira, Podosira), yet it has seldom happened that they have been met with in the moment of conjugation. “Since the classic researches of Thwaites upon this subject, the knowledge of it has on the whole been but little advanced by the observations of Focke (conjugation of Surirella), Griffith (conjugation of Navicula), W. Smith and Carter (conjugation of Cocconeis, Cymbella, Amphora). The following cases have been observed:—“Formation of a single conjugation-cell, dividing very soon after its origin: in Himantidium ſpectorale, Cymbella Kützingiana, Cocco- neis Pediculus, Coccone's Placentula, Gomphonema lanceolatum, Schizomema Grévillii, Orthosira Orichalcea, O. Dickiei, remarkable from the repeated throw- ing-off of the coats of the conjugation-cell, the cracked halves of which clothed the conical ends of the conjugation-cell in shape of funnels; Orthosira va– rians, Surirella bifrons, and a Navicula not specifically determined. Here belongs also the only conjugation of a Diatomacean that I have seen, that of Cyclotella operculata, conjugation-cells of which, with adherent empty coats of the mother-cells, I found abundantly in ditches of a marshy meadow not far from Leipsic, in October 1852. They were not distinguishable in any essential respect from the Cyclotella Kützingiana figured by Thwaites. “Next to these cases of the formation in the first place of only one conju- OF TEIE DIATOMEAE. 65 gation-cell, come a series of observations in which two new cells were seen between the empty conjugated mother-cells, without any convincing evidence being offered of a division of the mother-cells having occurred just before conjugation, as in the cases hereafter to be mentioned,—where, rather, the position of the empty cells in relation to the conjugation-cells, and the affinity of the forms in question to some in which the entire development has been observed, render it probable that the unicellular condition of the conjugation- cell has hitherto escaped observation. In this group are to be counted Coc- conema lanceolatum, C. Cistula, Gomphonema dichotomum, G. lanceolatum, G. marinwm, Achmanthes longipes, Rhabdomema arcuatum, Colletonema swbcohaerems. “In a smaller number of Diatomeae, species of the genera so nearly allied together, Epithemia, Cymbella, and Amphora, the conjugation is immediately preceded by a division of the mother-cells into two, analogous to the division of the cells of Closterium rostratum when about to conjugate. This division is longitudinal, taking place exactly as in the vegetative division in Cymbella Pediculus, Amphora ovalis, and Epithemia Sorea, but transverse and in a direction crossing that of the vegetative division in Epithemia turgida, E. gibba, and E. verrucosa. “Recent observations show distinctly that the conjugation of the Diatomeae agrees in all essential points with that of the Desmidieæ. When a cell is about to conjugate, there is produced in it a coat round the entire contents, accurately liming the old membrane, but not adhering to it. The growth of this coat cracks the old cell-membrane exactly in the same way as occurs in vegetative division. From the fissure the young, smooth coat emerges, in the form of a vesicle, and unites with the similar structure produced by a neigh- bouring cell. Al. Braun thought it must be assumed, from Thwaites’s obser- vations, that the primordial utricles of the two conjugating Diatomean cells united; but that this is not the case, and that a soft and flexible cell-mem- brane, protruded from the Cracked, rigid, old shell, encloses the contents destined to be blended with those of the neighbouring cell, is distinctly shown by Smith's figure of Rhabdomema arcuatum, and Carter’s of Coccomeis Pedi- culus and Amphora ovalis. The introductory part of the conjugation is dis- tinguished in no respect from the vegetative cell-division in Epithemia Sorea, Amphora ovalis and Cymbella Pediculus, and, further, in Closterium rostratum; in Epithemia turgida, gibba, and verrucosa, only by a different position of the wall dividing the mother-cell; in the rest of the Diatomeae and Desmidieæ, by Omission of the formation of Septa, frequently, also, by one-sided dehiscence of the cracked mother-cell, whose shells remain still commected at one side. “Thwaites's observations established that the cell produced from the conju- gation of two cells of a Diatomacean, very soon after its origin, assumed the form of the mother-cell, becoming distinguishable from it almost solely by being twice as large. Smith has endeavoured to render it probable that the colonies of young individuals, enclosed in a cyst, of Cocconeis Cistula, Gom- phonema dichotomum, and Synedra radians, some of which he found associated with conjugated, full-grown individuals, must have originated from the divi- sion of the spores (sporanges of English authors). This hypothesis has much in its favour, but, in the present condition of our knowledge, it is inexplicable where the silicious shells of the spore-cells remain. However this may be, there is no doubt of the occurrence of cysts of this kind. In the same pools of a marshy meadow which repeatedly furnished me with conjugated indivi- duals of Cyclotella late in autumn, I found, in early spring of two successive years, globular cells, each of which enclosed a great number (32 to 40) of small individuals of the same species. The walls of these cells appeared sharply defined internally and externally; the contents of a thin, fluid nature, F 66 GENERAL IIISTORY OF THE INFUSORIA. Structures similar to those represented by Smith, of Synedra radians, occurred in extreme abundance in the crld of the autumn of 1854, in company with Synedra Ulna. Here the cells, which, like those observed by Smith in the allied species, had a diseased aspect and an abnormal arrangement of the coloured contents, were imbedded in a granular jelly, of a reddish colour by transmitted light. I very much doubt whether these last were in a condition capable of further development; while in reference to the cysts of Cyclotella operculata, I share Smith's opinion. “The establishment of the assertion that the commencement of conjugation in the Desmidieæ and Diatomeae is but little distinguished from the com- mencement of vegetative cell-division, renders some discussion of the latter requisite. Pringsheim has already directed attention to the resemblance of this process in the Desmidieæ to the vegetative cell-multiplication of the joints of GEdogonium. In fact, it is an absolutely general phenomenon in the true Desmidieæ, so far as observation reaches, that the older parts of the membrane of a cell about to divide, do not, as in other cases (for example, in Zygnemeae), regularly increase in size with the parent-cell by growth in all directions; but the older, outer layers of the integument split open with an annular crack at the equator of the cell, shortly after (or during?) the division. They still remain sticking on, covering the ends of the cell with a thick envelope, but become removed gradually further apart by the interpo- sition of new cellulose between their fractured edges. The interposed new coat is the direct continuation of that which lines the internal surface of the cracked halves of the old shell. It is the margins of the half-shells which constitute the rings, parallel to the end-surfaces, upon the cylindrical lateral surfaces of the cells of Hyalotheca dissiliens and H. mucosa, the wrinkled pro- jections of the membrane in the middle of the deep constriction of the cell of Micrasterias and the large Euastra, of the flat constriction of the cell of Docidium, as also the ring at the equator of the external surface of Closte- a'iwm : in Clostérium and in Docidium, frequently as many as six may be counted,—a phenomenon which, in Docidium truncatum and the large Clos- teria, may be recognized at first sight as dependent upon a number of halves of cracked cells regularly encasing their successors. “The dehiscence of the coat of the dividing cell is, in all observed cases, preceded by the formation of the septum dividing the cell into two halves (Cosmarium margaritiferum). The gradual development of this from the margin of the cell-wall inwards, as a gradually-widoning annular fold of the immermost layer of the integument, has not yet been observed, and, from analogy with the processes in GEdogonium, is scarcely probable. But, as in CEdogomium, the contents of the cell may be contracted, before the formation of the Septum, into two masses, in contact, but separated by a sharp line of demarcation (two contracted daughter-cells imperfectly cut off from one another, still adhering together at the place of constriction). “From the half-shells of cells of the same Docidium which dehisced under the eye of the observer, emerged, within half-an-hour, to the extent of ºth or 4th of the length of the half-shells, the daughter-cells, still intimately con- nected at the point of contact. They could henceforth be perceived to be enclosed by a cellulose coat, firm although delicate. Treated with reagents strongly extracting water, such as glycerine, one or both of the extruded pieces frequently drew back into the halves of the shells of the mother-cell, the projecting pieces of membrane becoming doubled inwards. The just– emerged coats of the daughter-cells of Docidium did not take a blue colour when treated with iodized chloride of zinc, while the old halves of the mom- brane of the divided cell assumed the blue colour immediately. OF TIII, DIATOMEAE. 67 s “In Cosmarium margaritiferum and Staurastrum dejectum, it may be easily observed that a slight elongation of the isthmus, and the formation of a septum passing across the middle of this, precede the appearance of new half-cells in the deep constriction. It is after the appearance of the septum that the old wall of the mother-cell breaks by an annular fissure exactly at the place where that septum is formed. The two halves of the old cell-coat are then separated by the bulging-out of the younger, inner layers of membrane, not firmly adherent to the old portions. The new halves are at first lined only by protruded portions of the pellicle of their contents (outermost layer of the parietal coats of protoplasm) belonging to the older half-cells; from the moment only of the dehiscence of the old cell-coat, does a portion of the granular contents of the older cell-halves make its way into the new emerging halves. “In like manner, doubtless, occurs the cell-division of Micrasterias, of the large forms of Euastrum, Cosmarium, Stawrastrum, and other Desmidieæ, only that they have not been observed completely, because these larger Des— midieæ very seldom multiply by division out of their natural stations. The cell-division of the Diatomeae that have hitherto been observed in vegetative multiplication, differs in essential points from that just described. “When a cell of Navicula (Pinnularia) viridis is about to divide, there appears upon one of the secondary sides (front view of English authors), parallel to the primary sides (the furrowed faces of the cell having an elon- gated elliptical outline), an annular rim, which, growing gradually inwards, constricts the contents of the cell by an annular furrow, in a manner exactly similar to that of the commencement of cross-division in a cell of Cladophora. When a cell in this state is treated with substances producing slight endos- mosis (for instance, a weak solution of carbonate of ammonia), the contents retract on both sides from the annular rim, and constitute two completely separate cell-like structures (halves of a primordial utricle), each of a very long ellipsoidal form, and each lying close against One of the primary sides (faces of halves) of the cell. When the annular rim has grown inwards to about the sixth part of the shortest diameter of the cell, its development is arrested. In natural conditions, this stage is succeeded by the retraction of the primordial utricle from it. Each of these halves of the cell-contents becomes clothed, on the side turned away from the primary side of the cell, with a new membrane, which soon exhibits the first indications of the pecu- liar thickening ribs and modules of one of the primary sides of our Pinºvularia. The cell has now completed its division. Seen from one of the secondary sides, it contains two new individuals, equal to the mother-cell in length and breadth, but only possessing one-third of its thickness. The externally- situated primary side of each of them is the old primary side of the mother- cell, to which we must imagine the newly-formed membrane of the daughter- cell closely adherent at all points. Perhaps the narrow secondary sides of the new cells may be in the same condition. But the contiguous primary sides of the daughter-cells are totally new structures, which, developed rapidly, in a short time become similar to the old primary sides in every part. The two daughter-cells are at first held together by the broad middle piece of the secondary sides of the mother-cell, bearing the above-mentioned annular rim inside. The contents of the intermediate space consist of a transparent fluid destitute of any solid structures, doubtless pure water. The two daughter- cells are finally set free by the gradual ‘weathering' of the Zone-membrane which holds them together. The division of Surirella bifrons takes place exactly in the same way. An essentially similar kind of vegetative multipli- cation is widely diffused, if not general, in the Diatomeae. The wº-ºwn F 68 GENERAL Illſ STOIRY OF THE INFUSORIA, phenomenon of the formation of a tubular membrane, often impregnated with silex, and elegantly dotted or areolated, connecting the two segments of Isthmia, Melosira, &c., depends upon the same process. “An amalogous case is met with in the formation of the spores of Pellia epiphylla. The mother-cell here produces six ridges of cellulose projecting inward from the internal wall, intersecting at an angle of 60°; these ridges grow in toward the middle point of the cell, like the annular ridge of Cla- dophora at the commencement of cell-division. When these projecting ridges have attained the breadth of a fourth part of the transverse diameter of the mother-cell, the cell-contents divide into four parts, which, retracting from one another and from those ridges, occupy the four chambers of the cell, each of which is vaulted externally and bounded laterally by three of the ridges, here becoming coated with a membrane and developed into a spore, while the tetrahedral space in the middle of the cell, bounded by the six ridges, remains filled only with watery fluid. The spores become free by the solution of the enveloping part of the membrane of the mother-cell. The resemblance of this process to the vegetative multiplication of Navicula consists in the inter- ruption of the division of the cell by the formation of septa, and the subse- quent completion of the daughter-cells by Secretion of membrane on the external surface of contracted portions of the contents of the mother-cell. A deviation occurs in the circumstance that in Pellia the segment of the coat of the mother-cell which is in contact with the external surface of the daughter- cell becomes dissolved, while in Navicula it persists and remains most inti- mately connected with the daughter-cell. * “The newly-formed parts of the cell-coat facing together in the division are, in the Diatomeae, and still more clearly in the Desmidieæ, perfectly smooth and even for some time after their production; it is subsequently that they obtain the often very considerable tubercles and spines, consisting principally of cellulose. The same applies to the processes upon the outerintegument of the spores of Euastra, Cosmaria and Stawrastra produced in the conjugation. These phenomena, as also the autumnal secretion of jelly by many of the Desmidieæ, deserve more notice than they have hitherto attracted in connexion with the theory of the life of the vegetable cell. Still more remarkable behaviour is displayed by the cell-coat of an organism which I refer only doubtfully to the Desmidieæ. In many pools about Leipsic, in which Desmidieæ abounded, occurred large, accurately spherical, thick-walled cells, some as much as '05 millim. in diameter, rich in chlorophyll, which not only lined the internal wall as a connected granular layer, but—as in many Desmidieæ—formed groups, distributed, in the interior of the cell, in a system of radially-arranged plates, which presented a stellate appearance when seen from the side. It would be no great stretch of imagination to regard these cells as the conjugation- spores of a large Desmidiean. But these spores are all spiny, with the single exception of those of Xanthidium armatum. This very striking form occurs but rarely with us, having hitherto been found only in a single locality, while these globules are as common as they are abundant, and are often found in great numbers in forest pools, which harbour, in addition to them, only very small Desmidieæ. But such a supposition is still more decidedly negatived by the circumstance that the cells in question are sometimes found dividing into two. This renders it in the highest degree probable that they are inde– pendent organisms—Dosmidieæ without a central constriction, which may form the commencement of a series of forms terminating in Micrasterias. “These cells frequently appear surrounded by a wider coat, inside which the cell then floats freely, enclosed by its own closely-investing coat. Several Such empty coats are often met with, even as many as six sticking one inside OF TIII, DIATOMIE ZE. 69 \ another. Close investigation shows that the broader empty coats have an orifice, towards the border of which the membrane grows gradually thinner. These holes have not the aspect of perforations of the outer walls through external injury; they rather resemble the orifices of the walls of Cladophora, through which the Swarming-spores escape. It might be conjectured that the plant multiplied by Swarming-spores, and that Solitary ones becoming developed inside the empty coat of the mother-cell gave rise to that appear- ance; but this is contradicted by the great frequency of their occurrence, as also by the circumstance that we never find a number of green cells inside one cell-coat. It is more probable that the contents of the cell contract, and become coated with a new membrane, when the old one is perforated,—by unknown causes, which perhaps lic in the course of development of the species. . “If we seek to bring the phenomena introductory to vegetative cell-mul- tiplication under one point of view with the preparations for conjugation, we find that, in the Desmidieæ, in both cases a new membrane is formed around the total contents of the cell, which indeed lies close upon the old coat at all points, but by no means adheres to it, as we are accustomed to conceive of the so-called layers of thickening of the cell-wall. The growth of the young membrane cracks the stronger old onc—in vegetative cell-multiplication always in an annular form, in conjugation, mostly in a one-sided manner, with a valve-like slit (Hyalotheca dissiliens; Closterium). At this stage first occurs a distinction between the two processes of development, the formation of a septum taking place in cell-division, while in conjugation the protruding part of the young membrane continues to enlarge outwards, without, in many cases, any separation of the contents into two halves taking place. The younger, innermost layer of membrane remains with that portion lining the old cell-coat, sticking wholly in this in Hyalotheca, Bambusina, Cosmarium. But even in individuals of species of the last genus it sometimes occurs, in Tetmemorus and Closteriwm (e. g. C. acutum) as a rule (although by no means without exception), that the ends of the connected inner coats of the conjugating cells draw themselves out of the cast-off shells of the mother- cells, in extreme cases entirely; so that the cell originating by the blending of the internal coats of two individuals (inside which the spore is formed) becomes capable of being rounded off into a sphere. “Both the cell-division and the preparation for conjugation of Zygnemea are distinguished from the processes in Desmidieæ by the circumstance that in the former the wall of the oldest cells grows in its entire mass, and does not allow the younger layers of membrane to protrude through fissures or slits. “In the Diatomeae, lastly, the division into two, like the conjugation, takes place, seemingly, in all cases, through and after a preparatory contraction of the contents or separate portions of the contents of the cells; and in not a few cases the conjugation takes place during, and is accompanied by, division of the contracted contents into two portions. What import for the life of the species has the conjugation of the Zygnemea, Desmidieæ, Palmellege (Pal- mogloea), and Desmidieæ 2 Our knowledge of the race of Algæ, so import- antly advanced by the labours of Pringsheim and Cohn, should allow a more positive answer to this question than that inquirer, to whom the study owes most brilliant acquisitions, is inclined to give. The idea of sexuality of the lower Algae depends principally upon the perfectly justifiable, but still only analogical conclusions which, starting from the observations made during a century on the Phanerogamia, have advanced, through the intermediation of those, less numerous, on the Vascular Cryptogamia and Muscineae, and the 70 GENERAL EIISTORY OF TIII), INFUSORIA. facts established in Fucus by experiment of artificial separation or union of the sexes, to the GEdogonia, Vaucheria, Sphaeroplea and Volvoaz. Pringsheim’s declaration, that physiological questions of such a kind as the necessity of the action of the fecundating matter in generation can only be certainly decided by the observation of morphological processes, will not be adopted. Expe- riment has long ago proved the existence of sexes in the Phancrogamia, before the penetration of the pollen-tube into the ovule, and its relation to the germinal vesicle, had been made out, observations which that theory really no longer required for the establishment of its main question. And if, among so many confirmatory experiments, a few negative results present themselves, in what branch of human knowledge do we not meet with similar phenomena 2 The general rules of evidence hold good in such cases. “The same analogies, then, which lead us to recognize a fecundation in the penetration of the spermatic body of GEdogonium into the mother-cell of the spore, in the mixture of that body with the contracted contents of the mother-cell of the spore (with Pringsheim’s ‘fecundation–globule'), must necessarily lead us to regard conjugation as a fecundation. It is distinguished from the process in CEdogonium only by the fact that the portions of cell- contents which become blended into one cell are of equal size, and that there is not one of them provided with apparatus by means of which, like the spermatic body of GEdogonium by its cilia, it is moved onward until it reaches the cell to be fecundated,—both points, evidently, of no essential importance. “The sporangial frustules differ in general from the parent forms not mercly in size, but also in the number of striae or of other markings, and to some slight degree in outline. Such variation, M. Thuret contends, proves the phe- nomenon of conjugation to be, not a true mode of reproduction, but only ‘a socond mode of multiplication of frustules, very curious and very abnormal.” “In the immature condition, we are informed by Mr. Thwaites, it happens that the sporangia in many species resemble in general characters the mature frustules of another species or even of an allied genus. Thus the sporangia of Gomphonema minutissimum (XI. 17) and of G. dichotomum have a close resemblance to the frustules of Cocconema. On the other hand, in some genera, as in Cocconema, the sporangia take on at once the exact characters of the ordinary frustules, from which they differ only in their exceeding that of the majority of the latter in dimensions. “When a sporangium in a transitional condition is like the frustule of another genus, we are assisted in distinguishing its true nature and affinity, oftentimes, by the persistence of the mucus diffused around it; or by continued observa- tion we may witness its assumption ultimately of its true specific characters, including the development of its pedicle or stalk, where the possession of such an organ is a characteristic (as in Gomphonema).” The above fact suggests it as very probable that transitional forms have been described as particular species, or located in wrong genera. Thus Mr. Thwaites thinks that Kützing’s Epithemia vertagus is no other than the sporangium of Eumotia turgida, and also that the enlarged frustules of the Melosirede, which that same writer had conjecturally regarded as reproductive bodies, are in fact the sporangial product of conjugation, and give rise to a chain of frustules larger than those from which they had themselves originated., The subsequent history of the sporangial frustules on being matured is not satisfactorily made out. Prof. Smith has the following on the question (J. M. S. 1855, p. 131):-‘‘The ordinary Diatomaceous frustule seems to owe its production to the protoplasmic contents of the sporangial frustule formed by the process of conjugation. These sporangia, like the seeds of higher OF THE DIATOMIE ZE. 71 `plants, often remain for a long period dormant, and are borne about by cur- rents or become imbedded in the mud of the waters in which they have been produced, until the circumstances necessary to their development concur to Call them into activity. At such times their silicious epiderms open to per- mit the escape of the contained endochrome, which is resolved into a myriad of cmbryonic frustules; these either remain free or surround themselves with mucus, forming a pellicle or stratum, and in a definite but unascertained period reach the mature form of the ordinary frustule,” when their further growth appears almost entirely arrested by the production of the silicious coat, and when multiplication by self-division provides for the continuation of individual life. To continue the quotation, “The size of the mature frustule before Self-division commences is, however, dependent upon the idiosyncrasy of the embryo, or upon the circumstances in which its embryonic growth takes place; consequently a very conspicuous diversity in their relative magnitudes may be usually noticed in any large aggregation of individuals, or in the same Species collected in different localitics.” The belief that the contents of the sporangial frustules resolve themselves into a ‘brood’ of Diatoms, having the same form and specific characters as the original parent-cells, Prof. Smith establishes by the following observations made by himself (Synopsis, vol. ii. p. xv):—“In the gathering of Cocconema Cistula made in April 1852, which contained numerous instances of the con- jugating process, I observed the frequent occurrence of cysts enclosing minute bodies variable in their number and size, and many of which had the outline and markings of the surrounding forms and were obviously young frustules of the Cocconema. It would appear that the production of the young frustules is preceded by the separation and throwing off of the silicious valves of the sporangium and the constriction or enlargement of its primordial utricle, according to the number of young frustules originating in its protoplasmic contents. In this gathering, forms of every size, intermediate between the minutest frustule in the cyst and the ordinary frustules engaged in the conjugating process, were easily to be detected; and the conclusion was inevitable, that the cysts and their contents were sporangia of the species with which they were associated, and indicated the several stages of the reproductive process.” Again, in a gathering of Symedra radians, although not found at the time in a congregating state, yet the appearance of the cysts and of their contents was equally characteristic of the reproductive process. That such a “cystoid condition is one stage in the normal development of its reproduc- tion,” a subsequent examination in a distant locality satisfied him. The prosecution of this inquiry into the final changes of the sporangial frustules is seriously impeded by the dissolution of the investing mucus and the consequent dispersion of the reproductive bodies. Thirty-two species of the Diatomeae have been observed in the act of con- jugation, belonging to the genera Epithemia, Cocconeis, Cocconema, Cymbella, Cyclotella, Gomphonema, Himantidium, Achnanthes, Rhabdomema, Melosira, Navicula, Surirella, Amphora, Orthosira, Encyonema, Colletonema, and Schizo- mema. On this paucity compared with the number of known genera, Prof. Smith has the following explanatory remarks (Synops. ii. p. xi):-"One reason for the paucity of observations on this process in the Diatomeae is no doubt to be found in the changes which usually take place in the condition of these organisms at this period of their existence. Turing conjugation the progress of self-division is arrested, the general mucous envelope or stratum produced during self-division is dissolved, and the conjugating pairs of frustules become detached from the original mass; they are thus more readily borne away and 72 GENERAL HISTORY OF THE INFUSORIA. dispersed by the surrounding currents or the movements of worms and in- sects, and their detection becomes in consequence more casual and difficult. By far the greater number of the species I have mentioned belong to those genera whose frustules are adherent, or attached by stipes to foreigni bodies, or which form continuous filaments or aggregated frondose expansions. Not more than four, viz. Cyclotella Kitzingiana, Navicula firma, Amphora ovalis, and Cymbella Pediculus, are to be regarded as free forms: the reason I have just given will account for this circumstance; and the larger proportion of adherent or frondose species detected in conjugation may doubtless be ascribed to the firmer position conferred upon such forms by the presence of these accessory methods of attachment and adhesion, while the filamentous species, being usually aggregated in considerable masses or entangled amidst the branches of the larger Algae, are also less liable to dispersion.” Another mode of development, first pointed out by Mr. Ralfs in his early contributions to the history of the Diatomeae (A. W. H. 1843), by an internal gemmation or production of cells approaching in physiological features to self-division, appears to prevail in at least some instances. It is alluded to by Prof. Smith, when speaking of the Meridion circulare (op. cit. 7). He met with a variety of frustules, which upon a close examination, especially in a living state, led him to the conviction “that the appearance of a double wall of silex is owing to the formation within the original frustule of a second perfect cell, instead of the usual mode of division by which the original frustule is divided into two half-new cells. . . . In the present case, the central vescicle or cyto- blast becomes enlarged without division, and secretes on its extension two new valves, which are pushed outwards until they lie in close approximation with the original valves. This process is not always repeated; the usual mode of self-division again recurs, and two valves are formed in the interior of this new cell according to the normal method. . . .This unusual method of development is not, however, sufficiently constant to warrant the separation of such frustules from the species in which it occurs, perhaps hardly sufficient to constitute a variety, as frustules in both the ordinary and abnormal states may be met with in the same gathering and even in the same filament.” Himantidium Soleirolii is another species producing internal cells, which Prof. Smith quoted, remarking that he had no doubt it is merely an accidental modification of cell-growth, since, in the same filament, cells thus formed may be frequently found along with others following the normal mode of self-divi- sion. In Odontidium anomalum, this variety is in fact the usual condition of the frustules, and the ordinary mode of self-division is but rarely to be met with. A remarkable instance of this abnormal development presented itself to Prof. Smith in Achmanthes subsessilis, in which “the formation of a cell interior to the original one had proceeded through several successive stages, and the result is a compound frustule, consisting of the mother-cell and a number of included cells, each successive development being embraced by the others previously formed.” Mr. Ralfs has recently (J. M. S. 1857, p. 14) recurred to the subject of this plan of reproduction, and has found himself obliged to differ from Prof. Smith in some particulars. He writes: “Although it is true that “we frequently find in the same filament cells thus formed, and others following the normal mode of growth,’ as I formerly showed, yet I cannot agree to Prof. Smith's statement under Himantidium Soleirolii, that ‘ there is no doubt of its being merely an accidental modification of cell-growth.” On the contrary, I believe it to be a reproductive state of the species, and consequently to have a definite and important part in their economy. “For several years I have attentively watched the circumstances connected OF THE DIATOMDEAE. 73 N with the formation of these inner cells in Himantidium wrºdulatum, by gathering specimens at short intervals. During great part of the winter, the filaments increase in bulk, by repeated division of the frustules, until they form large masses, filling the ditches; at length the inner cells make their appearance, at first sparingly; but as spring advances, it is difficult, in many situations, to obtain a filament without them. I have found that when these become abundant, the filaments cease to grow, and the entire mass soon breaks up and disappears. The same thing happens in the other species of Himan- tidium, and in Meridiom. “I do not find that the inner cell commences in the centre and pushes its valves outwards, as stated by Prof. Smith. Were this the case, the internal matter also would necessarily be pushed outwards by the advancing valves, and thus condensed between them and the walls of the frustule. On the contrary, in the Himantidium the internal matter, before nearly fluid, collects within the new cell, becomes dense and more granular, and the new walls are formed round it in the situation they are to occupy, leaving an empty space between them and the walls of the frustule. “The alteration and condensation of the colouring matter, and the ap- pearance, or at least great increase of vesicles, have a strong resemblance to what takes place previous to the formation of sporangia, the completion of which, as in this case, usually preludes the death and disappearance of the DOl8lSS. “As in most acknowledged sporangia, the cell thus formed always tends to assume an oval or orbicular form. It, however, is very frequently, and perhaps generally, divided in halves, as in the fission of the frustules, so that the oval seems made up of two neighbouring frustules; but this is not the case, as may readily be ascertained by noticing the marginal puncta of the original frustule. * - - “Do these newly-constituted cells ever continue to divide, as Prof. Smith supposes? I believe not ; at least I have never seen a specimen in which the semi-elliptic portions were separated by the interposition of other valves resembling either themselves or those of the ordinary frustule. For my own part, I have been unable to trace the species after the formation of these cells, owing to the quickly succeeding disappearance of the mass. If, indeed, this renewed division does occur, the resemblance to what takes place in the sporangia of some species of Melosira would be increased. “Prof. Smith, in his most interesting and valuable account of the ‘Repro- duction in the Diatomaceæ,’ enumerates four modes in which sporangia are formed. The third is thus defined:— - “‘The valves of a single frustule separate; the contents, set free, rapidly increase in bulk, and finally become condensed into a single sporangium.’ “As far as regards the Melosira varians, the only one in this group which I have had an opportunity of noticing, I believe the process is essentially the . same as in the examples already described. The only difference is, that the new-formed cell being inflated, and much larger than the original frustule, . the valves of the frustule must necessarily be either ruptured or pushed apart by the increasing growth of the sporangium, and the latter alternative happens. “I have seen no specimen of Mr. Brightwell's Chaetoceros Wighamii, but from his figures I believe the goniothecia-like bodies constitute another example of the formation of internal cells. “I have said that I consider these internal cells sporangia, and essentially of the same nature as the inflated ones of Melosira varians. At the same time we should not forget that Mr. Thwaites discovered the Himantidium pectinale in a truly conjugated state, and that it is contrary to our experience 74. GENERAL IIISTORY OF THE INFUSORIA. of the economy of nature that the same result should be obtained in the same species in two different ways.” M. Focke has satisfied himself of the reproduction of Some species of Navi- culae (A. N. H. 1855, 237) by a strange complication of the phenomena of “alternation of generation” and conjugation. Navicula bifrons, for example, forms, he says, by the spontaneous fission of its internal substance, spherical bodies which, like gemmules, give rise to Surirella microcora. These by conjugation produce N. splendida, which gives rise to N. bifrons by the same process. This last act of gemmation has been observed by the author in all its phases. He saw two specimens of N. splendida, enveloped in a sort of mucosity, open and evacuate the whole of their contents, which served to form a N. bifrons. The production of the reproductive bodies by the latter was also observed; but their development into Swrirella microcora, and the pro- duction of N. splendida by conjugation, rest solely on the inductions of the author. These facts require revision and confirmation, but they are, nevertheless, worthy of the attention of observers, and appear to point to phenomena quite as singular as those which have been revealed to us within the last few years by the study of the reproduction of so many of the lower animals. They, in fact, present in a manner the converse of the phenomena exhibited in the ordinary alternation of generation, as several germs or eggs are necessary for the production of the last individual of the cycle. Rützing has surmised the existence of another mode of development, viz. by germs or spores prepared from the gonimic contents of the frustules. This method of propagation was indeed comprehended in Ehrenberg's doctrine that much of the granular contents were ova; an hypothesis started rather to bring the structure of the Diatomeae in accordance with the generally assumed poly- gastric organization, than to explain any observed phenomena, complicated as it also was with other suppositions of fecundating male glands or seminal vesicles and a sexual discharging orifice. Rabenhorst (Süsswasser-Diatom. p. 3) has followed up Kützing's suggestion, and affirms that the frustules of Diatomeae swell up in a vesicular manner and become filled with a greater or less number of cells, which at first have an irregular figure, but subsequently assume a regular oval shape. This having happened, the cells move in a current from right to left within the cavity of the parent-cell, which by-and-by splits open and cmits its progeny, each of which has, at an anterior clear space, two long projecting cilia. For a very short time these germs enjoy a swarming movement, and afterwards, on becoming stationary, attain with extreme rapidity, or even surpass, the size of the parent-cell, which is itself destroyed in the act. This plan of reproduc- tion by the development of a brood of young organisms within a parent-cell, or, in more technical terms, this formation of active gonidia (microgonidia), prevails in many of the lower Algae, and consequently has no à-priori argu- ment against it. However, as Prof. Smith remarks, “Its occurrence in the Diatomeae cannot be received as established without further observation and a more carcful record of the phenomena attending its progress” (op. cit. vol. ii. p. xvii). Rabenhorst has illustrated this mode of development in only one species of Melosira, although he puts it forward in a gencral manner as if true of all the Diatomeae. Indeed it occurs to us that it is not a special and otherwise unobserved process of reproduction, but merely that variety of the act of con– jugation described by Mr. Thwaites in the genus Melosira, in which a change in the endochrome of a single frustule, attended by an increase of contents and a consequent enlargement—such as is intimated in Rabenhorst’s account— OF TELE DIATOME ZE. 75 N converts it into a sporangium. Beyond this stage, Mr. Thwaites does not appear to have followed the sporangial frustule so generated; but, assuming the correctness of Prof. Smith's hypothesis of the generation and Subsequent evolution of numerous minute frustules within it, do we not find a precisely analogous phenomenon with that which Rabenhorst represents as an addi- tional mode of propagation, or with what Focke (see preceding page) describes as the formation of gemmules out of the internal substance, and their sub- sequent discharge? The supplementary phenomenon of alternation with change of specific form, included in the statement of the latter observer, even if confirmed, will not affect the general analogy presumed. HABITATS.—Appearance in masses, abundance, geographical distribution. —Fossil Diatomede.—Eaºistence in the atmosphere.—Practical wses and appli- cations of the Diatomede.—The habitats and the distribution of the Diatomeae, both in time and space, are the most extensive, various, and wide, of all organic beings. In fresh, in salt, and in brackish waters they are alike found; they exist abundantly in a living state about the roots of plants and diffused in moist earth; they are also to be mot with in the dust of the atmosphere and in meteoric products. They are, in fine, inhabitants of earth, air, and water. When no longer alive, their silicious skeletons preserve their form and constant characters, uninjured by most of the causes which obliterate the remains of other living beings. They are so preserved in most of the rocks above the oldest primary—in all, indeed, in which intense heat has not operated to fuse silica into a molten mass. At the present day they are ejected from the bowels of the earth in the lava, cinders, and ashes of Vol- canos, and are borne about by the winds from one continent to another in showers of dust. In respect of habitat, the Diatomeae are divisible into marine and fresh- water species; some indeed are common to both fresh and Salt water, or cxist in brackish water. The following account of the habitats of Diatomeae, illustrated by reference to particular cramples, is from the experienced pen of Mr. Ralfs, who has supplied us with it:— “The Diatomeae may be obtained at all seasons of the year, but are most plentiful in spring and summer, many of them indeed being limited to that period; thus the species of Micromega and Schizomema are, with few excep- tions, in perfection only in May and June, when they are met with in shel– tered situations, forming wide patches on the ground and on the flat surfaces of rocks exposed at ebb-tide. About the end of May the Enteromorpha compressa, so common on our shores, often seems as if faded at the end; this appearance is frequently accompanied by the presence of Grammonéma Jur- gensii, which is easily recognized by its slippery feel, when from its pale colour it would otherwise escape detection. “At all seasons of the year, the smaller and more slender Algae, marine and freshwater, as soon as they attain maturity, become almost invariably covered with parasitic Diatomeae, which impart to them a brownish colour. In this way we obtain species of Cocconeis, Achmanthes, Striatella, Tabellaria, Grammatophora, Isthmia, Gomphonema, Podosphemia, Rhipidophora, and Synedra. On the contrary, Amphitetras and Biddulphia prefer the muddy crevices in the sheltered sides of perpendicular rocks. “In salt marshes we may expect to find the Achmanthes subsessilis on the slender filaments of Enteromorpha, but so sparingly as hardly to discolour them. The species of Epithemia are parasitic on Cladophora, both in brackish and in freshwater pools. The Melosirae are common in marshes, especially at the mouths of large rivers, where they form Conferva-like brownish masses. “Many of the unattached Diatomeae are produced in dark brown patches 76 GENERAL FIISTORY OF THE INFUSORIA. at the bottom of pools, or on the surface of mud; the freshwater species often by the road-side ; the marine forms usually near high-water mark. Am- phipleura inflea'a and A. Scalaris congregate, in large brown stains or spots, on the muddy sides of rocks, whilst other species, for instance Campylodiscus, and Coscinodiscus concinnus, form similar collections, but prefer more shady situations. “The sides of ditches in brackish marshes are very prolific, especially after spring-tides, and in situations not again covered until the next high-tides. We may expect to gather in such places species of Surirella, Navicula, Plew- rosigma, Ceratoneis, Amphiprora, Amphora, &c. The soil about the roots of rushes and of other plants inhabiting salt marshes often afford interesting forms, but seldom in abundance. We find there species of Coscinodiscus and of Zygoceros; but such are obtained more abundantly from the mud or from the washings of bivalve shells brought up from deep water or collected at the mouths of rivers. Oyster-beds are in general productive. The Bacillaria paradova inhabits ditches in which the water is nearly fresh, and is frequently obtainable from the scum driven from the surface to the banks. “Few Diatomca are peculiarly autumnal; we have, however, gathered Homoeocladia Martiana, Berkeleya fragilis, Dickieia pinnata, and Striatella wnipunctata, chiefly at that season. “On warm Summer days, Diatomeae, with various microscopic Algae and Fungi, rise to the surface of water by the disengaged oxygen gas still ad- hering to them and buoying them up, and there form a delicate film or a scum, and at times even a layer of considerable thickness. Such collections are rich in species of Navicula, Cymbella, Surirella, and Synedra. When an entangled larger mass is formed, there is usually one prevailing species. Specimens of Fragilaria are gencrally found on decaying wood or leaves, or amongst Confervae diffused in the water. From the drainings of Sphagnum may often be obtained Synedra biceps and various species of Himantidium. Boggy soil, especially when situated on a slope, affords various species of Epi- themia and Navicula; so likewise does the soft matter on rocks on which water constantly trickles. Washings from oysters and the refuse raised by trawlers are usually rich in spheres of Coscinodiscus, Actinoptychus, Pleurosigma, Di- plomeis, Navicula, Dictyocha, &c. The same kind of Washings from sheltered harbours give Surirella fastwosa, Awliscus sculptus, together with species of Campylodiscus, Tricérativm, &c. Washings of corallines are likewise some- times productive.” Mr. Norman supplies us with the following hints:—“The most interesting forms occur in Salt water, especially in shallow lagoons, saltwater marshes, estuaries of rivers, pools left by the tide, &c. Their presence in any abun- dance is shown by the colour they impart to the aquatic plants they are attached to ; or when found on mud, by the yellowish-brown film they form on the surface, and which, if removed with a spoon without disturbing the mud, will be found a very pure deposit. “Such collections are best put at once in bottles, or even partially dried and wrapped in pieces of paper or tin-foil. When placed in bottles, a few drops of spirit are advantageously added. In all cases it is essential that the locality whence obtained should be plainly written on each package. Capital gatherings are obtainable by carefully scraping the brownish-coloured layer from mooring-posts, or the piles of wharfs or jetties. “In clear running ditches, the plants and stones have often long streamers of yellowish-brown slimy matters adhering to them, generally composed almost wholly of filamentary species. The layers of Diatomaceous fronds on the surface of mud are often covered with bead-like bubbles of oxygen, which OF THE DIATOMIEAE. 77 N from time to time rises to the surface of the water and carries up with it Some of the deposit in the form of a scum, which gets blown to leeward, and may be readily collected from the edge of the pond quite free from particles of mud and other impurities. - “Good and rare specimens have been obtained from the stomachs of Ho- lothuridae and other Mollusca which inhabit deep water, and are often thrown on shore after severe gales of wind. These animals may be merely dried and preserved just as found, and the contents of the stomach obtained afterwards by dissection. Shells and stones, covered with seaweed, &c., from deep water, also afford most interesting and little-known forms. The rougher these are, the better (they ought by no means to be cleaned). Deep-sea soundings (especially those from great depths) should be preserved; for they are often exclusively Diatomaceous. “Very rare species have often been formed in immense quantities in the arctic and antarctic regions by melting the “pancake ice,’ rendered brownish by these microscopic shells. The sea is also often observed discoloured with brownish patches, which should be collected, and the water filtered through blotting-paper or cotton wool: the residuum will frequently turn out to be composed of Diatomeae. It is also highly interesting to collect and examine the impalpable dust which occasionally falls into the folds of the sails of ships at Sea.” Scallops and other Mollusca often contain rich and rare collections in their stomachs. In Ascidia (e.g. Phallusia sulcata, Ascidia mentula) Mr. Norman and the Rev. R. Cresswell found an abundant source. Mr. Norman adds, in a further note kindly sent us—“The Ascidians, whose stomachs are almost always so loaded with Diatomaceous frustules, are to be found abundantly on the shells of oysters dredged in deep water, and readily procurable from the trawlers. “The Salpae (found so abundantly floating on the surface of the sea in warm latitudes) afford very pure gatherings. The roots of the various species of mangrove, growing in the dense swamps of rivers and estuaries in the tropical regions of Africa, Australia, and the Eastern Archipelago, are said to be fre- quently covered with a brownish mucous slime very rich in Diatomeae. I have also obtained very pure gatherings from the roots of the Dutch rushes, as imported, and from the Zostera marina from the Baltic, used for stuffing beds, &c., by upholsterers. Stones, moreover, brought as ballast from abroad, will amply pay the diligent collector by yielding foreign and perhaps rare species. The roots of aquatic plants from tropical countries, stored in her- baria, would, if properly examined, yield many interesting forms of Diatoms.” Indeed we may add, generally, that the roots of land plants, particularly of mosses, lichens, &c., growing around trees on the ground, or upon them, are fruitful in Diatomeae, and, in fact, of some of the rarer forms. In the Number of the Microscopical Transactions just published (July 1858, p. 79), Col. Baddeley notes the occurrence of Diatoms in considerable numbers in the Noctiluca miliaris. They are the chief constituents of a mass of dark matter near the nucleus, and lie in the so-called vacuoles, into which they enter from the mouth. This occurrence suggests an easy method of obtaining different marine species of Diatomeae in their natural state, often alive, and with their endochrome perfect. The Colonel discovered in this way several rarer species, and gives a list of nearly 50 which he identified, besides not a few forms of whose true name he was uncertain. To extract the Diatoma- ceous mass from the interior of the Noctilwege, Col. Baddeley recommends that the seawater and its living freight be poured, on arriving home, in a white hand-basin, and be let stand for an hour or two. “This rough treat- 78 GENERAL EIISTORY OF TITE INFUSORIA. ment causes these creatures to disgorge their food; and if, after an interval, the water be carefully poured off, a sediment will be found at the bottom, which will consist of Diatoms mixed with some refuse.” Dr. Donkin lately (T. M. S. 1858, p. 11) called attention to the occurrence of that rare form, Symdendrium diadema, in the stomach of the lobster, and in a subsequent paper (op. cit. p. 14) alludes to the abundant deposit of living Diatoms upon the sands at the sea-side, in the following paragraph :- “Professor Smith states that ‘ the shallow pools left by the retiring tide at the mouths of our larger rivers’ are the favourite habitat of marine species. But such localities I have found not to be half so prolific in species as the sands of still bays, on the shore, where they are earposed by the reflua, of the tide, at a distance corresponding with the half-tide margin. In these places, where the sands are sloping towards the sea, and grooved out into Small furrows, filled with salt water oozing out from behind, the abundance of Diatoms aggregated into a living mass imparts to the surface of the sand different hues of chestnut and olive, the difference of colour being due to the nature of the species present. These coloured patches, it is interesting to observe, are, during the sunshine, studded with numerous minute air- bubbles, undoubtedly given off by the Diatoms themselves. “To separate the Diatoms thus detected, from the surface of the sand, I found to be impossible. I therefore seized hold of the nearest bivalve shell which happened to lie in the way, and with this I carefully scooped up the surface of the coloured sand. This I emptied into a wide-mouthed, stoppered bottle, capable of holding eight ounces, until half full; the other half of the bottle I filled up with salt water. I then shook the whole briskly and allowed the bottle to stand for a short period. The sand, being composed entirely of fine round grains of quartz and the minute fragments of shells, settled at the bottom in a few seconds, leaving the Diatoms all suspended in the water above, and forming by their abundance a chestnut-coloured cloud, but not more than 1 part in 1000 of the whole sand collected. The coloured water was then poured into another bottle, and formed the gathering, while the sand was thrown away. The Diatoms, in their turn, were separated from the superfluous water by subsidence, and brought home in 13–0Z. bottles. In this manner I soon found that any quantity could be collected in a pure and un- mixed condition, affording an excellent opportunity of examining their living forms, and one of which I availed myself on every occasion. “After carefully examining materials collected in this way from various parts of the beach, I detected not less than about 100 species, all these strictly marine, and, with a few exceptions, each species in considerable abundance.” * The fact of Diatomeae rendering themselves perceptible to common vision by their excessive accumulation and the colour they impart to water, is illus- trated by the phenomenon of coloration of the sea recorded by Dr. Hooker, also by the Melosira ochracea, which occurs in many, perhaps in all, cha- lybeate waters, and also in peat water containing a small proportion of iron. It is of the colour of iron rust, and in mineral springs, in which it abounds, is often taken for precipitated oxide of iron. It covers everything under water, but forms so delicate and floccose a mass that the least motion dissi- pates it. In the spring of the year this mass is composed of very delicate, pale-yellow globules, which can be easily separated from each other. They unite together in rows like short chains, and produce an irregular gelatinous felt or floccose substance. About summer, or in autumn, they become de- veloped into more evidently articulated and stiff threads of a somewhat larger diameter, but still form a complicated mass or web, and, either from adhering OF TITE I) IATOME ZE, 79 to each other or to delicate Confervae, appear branched. In the young con- dition, when examined under shallow magnifiers, they resemble gelatine; but with a power of 300 diameters the flexible granules are discoverable, and, with dextrous management, the little chains forming the felt or floccose Web can be made out. In summer, on the other hand, its structure can be observed much more easily and distinctly. Early in spring the colour is that of a pale yellow ochre, but in summer that of an intense rusty red. Other examples occur where a single species becomes tangible to the unaided senses; such are met with in the brown specks mentioned in the preceding account of habitats formed by particular species upon the larger Algae and Confervae. So the Gomphonema geminatum forms on rocks tufts of a spongy texture and brownish colour when young, but white afterwards. The Synedra Ulna often produces a white incrustation on stones in rivers in summer; and Fragilaria and Odontidium are seen outstretched as delicate brown filaments, several feet in length, like many filiform Algae, from which, however, they differ by breaking up so very readily, on the least disturbing force, into their separate joints. “Large numbers of Rhizoselenia’’ (writes Mr. Brightwell, J. M. S. 1858, p. 95) “have been detected in the stomachs of Salpas, and they have also been observed floating free in the ocean in warm latitudes, their appearance being that of little confervoid flakes of exquisite delicacy, but of a sufficient aggregation of filaments to be seen by the naked eye. The mass appeared (probably from the endochrome) of a faint, evanescent, ochraceous colour.” Moreover, the frondose species generally attain an appreciable magnitude. Thus Encyonema prostratum forms a tuft-like stratum, when recent, dark brown, but when dried, of a dull green colour. Schizomema. Subcohaerens grows into tufts from a quarter to half an inch or more high; and S. vulgare con- stitutes a dark brown gelatinous stratum on stones in shallow water, fila- ments simple or nearly so in deep still water, and much branched filaments in deep rapid streams. Mr. Norman, of Hull, has most kindly furnished us with the following original observation on the growth of one species, the Campylodiscus cos- tatus:—“In the early part of the spring of 1856,” he writes, “I made a gathering of freshwater Diatomeae from the ‘Spring Ditch,’ Hull. Although I met with a few odd frustules of the species named, I did not consider it of sufficient interest to boil in acid for mounting, and the phial containing them was left in the window of my laboratory during the ensuing summer. Some time in the autumn I had occasion to make use of this bottle, and was on the point of throwing away the contents, when I noticed the surface of the do- posit and the sides of the bottle to be covered with a dense brown growth of Diatoms. On further examination I found an immense colony of Campylo- discus, which gave by preparation some boautifully pure slides of this species. In removing the upper layer I purposely loft a few of the frustules in the bottle, which was again placed in the window. These have again increased to a great extent, and now (December 1857) they appear to thrive in perfect health. Does not this occurrence suggest an easy plan of procuring in a pure state such forms as are rarely found together in any abundance 2 ° GEOGRAPITICAL DISTRIBUTION.—Species of Diatomeae are for the most part distributed over a very wide geographical area. Some, indeed, would seem cosmopolitan, whilst others are limited to certain regions. For instance, the Terpsinoë has not been discovered in Europe; and Synedra Entomon is reckoned by Ehrenberg as peculiarly a South American production. This author has given full force to this sceming fact, and employed it in the en- deavour to discover the origin and course of meteoric dust, and also to arrive at certain geological deductions. For example, he says (Momatsb. Berlin. 80 GENERAL, ELISTORY OF THIS INFUSORIA. Akad. 1849), “The chain of rocky mountains traversing the continent of North America, forms, with reference to the distribution of Infusoria, a stronger barrier between California and Oregon, and the rest of the continent, than does the Pacific Ocean, with China, between the western plains of North America and the region of Siberia. Thus, the United States, with Mexico, never present any of the forms characteristic of Oregon and Cali- fornia, whilst, on the other hand, the peculiar forms of these latter countries are met with in Siberia. All this is remarkably confirmed in this, that the gold region of the Sacramento, in the extent and abundance of its Infusorial products, finds its parallel only in Siberia.” This presumed fact of limited geographical distribution is thus applied by Ehrenberg in another paper (Momatsb. 1846):-‘‘The atmospheric dust which, since 1830, has fallen in the Atlantic Ocean as far as 800 miles west from Africa, on the Cape de Verde Islands, and even in Malta and Genoa, has been all of an ochre-yellow colour, never grey like the dust seen in the north of Africa, and consists of from #th to ºrd of organic particles referable to 90 species, the greater number of which are of froshwater habit, and found equally in the most widely separated regions named. This dust, even in Genoa, whence it is carried by the Sirocco wind, contains no characteristic African forms, but, on the contrary, presents the Symedra Entomon, a deci- dedly characteristic species of South America.” From his observations on this meteoric dust, Ehrenberg concludes that there is a current of air uniting Africa and America in the region of the trado winds, and occasionally directed towards Europe. On the other hand, their wide diffusion is exemplified in Dr. Hooker's Report on the Diatomaceous vegetation of the Antarctic sea (Brit. Assoc. 1847):-‘‘The genera and species of Diatomaceae collected within the Antarctic sea are not at all peculiar to those latitudes; on the contrary, some occur in every country between Spitzbergen and Victoria Land. Others, and even some of these, have been recognized by Ehrenberg as occurring fossil in both Americas, in the south of Europe and north of Africa, in Tripoli stone and in volcanic ashes ejected both from active and extinct volcanos, whilst others again exist in the atmosphere overhanging the tropical At- lantic.” Prof. Smith has the following remarks on cosmopolitan or very widely- diffused species (Synops. ii. p. xxvii):— “Of freshwater species frequent in the British Islands, the following seem almost cosmopolitan, viz. Synedra radians, Pinnularia viridis, Pinnularia borealis, and Cocconema lanceolatwm. Gatherings from many localities in Europe, from Smyrna and Ceylon, from the Sandwich Islands, New Zealand, and New York, from the loftiest accessible points of the Himalaya in Asia, and the Andes in America, have supplied specimens of these forms. “Navicula serians abound in all our mountain bogs, and is equally common in the marshes of Lapland and America. “Epithemia gibba is an inhabitant of the Geysers of Iceland and the lakes of Switzerland. “The South Sea Islands supply Stauroneis acuta, and Ceylon Synedra Ulna, while Stauroneis Phoenicenteron is equally abundant in Britain, Sicily, and Nova Scotia. “These notes of localities will give some idea of the wide distribution of our fluviatile Diatomaceae: more numerous gatherings would, no doubt, greatly extend the list; and the following circumstance will show how gene- rally our commoner British forms are diffused throughout European localities that have been carefully examined. During a tour in Languedoc and the Auvergne in the spring of 1854, I made upwards of forty gatherings from ÖF THE DIATOMIEAE, SI the rivers, streams, and lakes of the district I traversed. In these I detected 130 species, and but one form not yet determined as indigenous to Britain. If this be the case with a district much of whose Phanerogamous flora is so different from our own, it bears out the view I have taken, that these or— ganisms enjoy a range of distribution far more general than the higher orders of plant-life. “Nor is the distribution of marine species less notable for its extent and uniformity. Coscinodiscus eccentricus and C. radiatus range from the shores of Britain to those of South Africa. Grammatophora marina and G. macilenta are found in almost every marine gathering from the Arctic Ocean to the Mauri- tius. Stauroneis pulchella, Cocconeis Scutellum, and Biddulphia pulchella are equally abundant on the European, the American, and the African coasts, While Rhabdomema Adriaticwm belies its name by its occurrence in the Indian, Atlantic, and Pacific Oceans. During the researches already mentioned, in the South of France, I made several prolific gatherings on the shores of the Gulf of Lyons; but, of 33 forms occurring in these, Hyalosira delicatula, Kütz., was the Only one not familiar to me as a British species.” The Supposition that many species of Diatomeae occupy a very limited geo- graphical area, and that considerable numbers have, in course of ages, disap- peared or become extinct, as many animal and vegetable organisms have done, was thus ably examined by the lamented Dr. Gregory in a communication to the Royal Society of Edinburgh, made in 1856 (Proc. Roy. Soc. Edin. 1856– 57, p. 442). The subject of discussion is introduced in his notice of Na- vicula praeteata, a form previously considered only fossil. “I have,” he says, “Selected this form because the bed in which it occurs fossil is the oldest in which Ehrenberg has found any Diatoms. He has indecd found microscopic Organisms in the chalk, and even in older rocks, among which he mentions the mountain limestone and the Silurian greensand. But the forms in the two latter rocks are not numerous, and, as well as thosc which abound in the chalk, belong to the Foraminifera or to the Polycystina, not to the Diato- macea. . . . In short, I have no hesitation in saying, that I believe all the forms in the AEgina clay-marl, which is the oldest Diatomaccous deposit yot de- scribed, will be found living on our coast.” The stratum at AEgina belongs either to the chalk formation, or to the oldest tertiary or Eocene beds. Dr. Gregory continues, “It may also be observed that, of all the forms figured by Ehrenberg from more recent strata, whether miocene, like the bed on which the town of Richmond (Virginia) is built, and several kinds of Berg- mehl–or pliocene, like other Berg-mehls or polishing-slates, &c.—or still more recent, the groat majority aro perfectly identical with existing Diatoms. Indeed, although many forms are stated in Ehrenborg's earliest writings to be fossil only, and have been supposed to be extinct, the progress of obser- vation is continually adding to the number of species which are found also in the recent state. Thus, for oxample, the whole group of dentate Eunotice, which abound in the Lapland and Finland Borg-mohls, were long thought to be only fossil ; but they have been nearly all found in America, and I have myself seen several of them recent in this country. Eunotia triodon, long supposed to be extinct, occurred scattered in many of the Scottish freshwater gatherings. “Taking these facts into consideration, I am led to believe that we have no ovidence that any species of Diatom has become extinct, as so many species, and even genera and tribes, of more highly organized beings have done. I observe that Mr. Brightwell expresses a similar opinion in his valuable paper on Chaetoceros (J. M. S. iv. p. 105).” Wherefore Dr. Gregory comes to the conclusion, that “the whole of the G. 82 GENERAL IIISTORY OF THE INFUSOIRIA, species which occur fossil will, ere long, be detected in the recent state. It is at all events certain that a very large proportion of the Diatoms found in the fossil state also occur in the living state, and that every day adds to their number. There is at present no good evidence of the existence of Diatoms earlier than the chalk, if so early. But we must not forget that the shells of Diatoms appear to be altered by long contact with carbonate of lime, so that they may have existed at one time in the chalk. We find them, how- ever, in spite of the action of calcareous matter, in the recent chalk-marls of Moudon and of Caltanisetta, which are rather more recent than the chalk, and probably of about the age of the clay-marl of Ægina. If, as I believe, no Diatoms have become extinct, this may perhaps depend on their minute size and extreme simplicity of structure, which probably render them more indifferent to climatic changes than more highly organized and larger beings. We have evidence, to a certain extent, that this is the case; for by Ehron- berg's figures it appears that, in gatherings of recent Diatoms from all parts of the world, in every possible variety of climate, the majority of species are identical with our own. “Diatoms, therefore, are not materially affected by existing differences of climate, and have probably been as little affected by the geological changes which have occurred, at all events, since the period of the Eocene deposits.” GEOLOGICAL IMPORTANCE OF DLATOMEE.-FOSSIL ACCUMULATIONS.—Although so exceedingly minute and apparently insignificant in comparison with the animals and plants usually claiming our notice, yet, by their excessive multi- plication and accumulation, they assume even a greater importance, in the physical history of the earth, than the largest trees or animals with which we are acquainted. This lesson is taught us by living examples of these microscopic beings constituting appreciable masses, and by innumerable in- stances where only the silicious skclotons remain, in a fossil or somi-fossil condition. Ehrenberg thus illustrates their rapidity of production and accumulation. “Silicious Infusoria,” he says, “form, in stagnant waters during hot weather, a porous layor of the thickness of the hand. Although more than 100,000,000 weigh hardly a grain, one may in the course of half-an-hour collect a pound weight of them ; hence it will no longer seem impossible that they may build up rocks. However, one of the most striking examples of the operation of Diatomeae as a physical agency on a large scale, is afforded by Dr. Hooker's observations addressed to the British Association (Report, 1847). He says— “The waters, and especially the newly-formed ice of the whole Antarctic Ocean, between the parallels of 60° and 80° south, abound in Diatomacca, so numerous as to stain the Sea everywhere of a pale ochroous brown, the surface having that colour as far as the eye can reach from the ship. Though pecu- liarly abundant in the Icy Sea, these plants are probably uniformly dispersed over the whole ocean, but, being invisible from their minutemoss, can only bo recognized when washed together in masses, and contrasted with some opake substance. They were invariably found in the stomachs of Salpac and of other sea animals, in all latitudes between that of the tropic and the highest parallel attained in the Antarctic expedition. Their death and decomposition produce a submarine deposit or bank of vast dimensions, consisting mainly of their silicious shields, intermixed with Infusoria and inorganic matter. Its position is from the 76th to the 78th degree of South latitude, and occupies an area 400 miles long by 120 wide. The lead sometimes sank two feet in this pasty deposit, and on examination showed the bottom made up in great measure of the species now living on the surface. This deposit may be considered as resting upon the shores of Victoria Land and of the Barriors, and hence on the OF TTITS 1) [ATOME.E. 8:3 c Submarine flanks of Mount Erebus, an active volcano 12,000 feet high. From the fact that Diatomeae and other organisms cnter into the formation of pumice and ashes of other volcanos, it is perhaps not unreasonable to con- jecture that the subterranean and subaqueous forces, which keep Mount Brebus in activity, may open a direct communication between this Diato- maceous deposit and its volcanic fires. Moreover, this bank flanks the whole length of Victoria Barrier, a glacier of ice 400 miles long, whose seaward edge floats in the ocean, whilst its landward CXtends in one continuous sweep from the crater of Mount Erebus and other mountains of Victoria Land to the Sea. The progressive motion of such a glacier, and accumulation of snow on its surface, must result in its interference with the deposit in question, which, if over raised above the surface of the ocean, would present a stratified bod of rock which had been subjected to the most violent disturbances.” But instances of the abundance of silicious Organisms in sea- or river- bottoms are to be met with nearer home. Mr. Roper has explored the mud of the Thames (J. M. S. 1854, p. 68); and he tells us that, excluding the coarse sand, nearly one-fourth of the finer part of the residuum is entirely composed of the silicious valves of different species of Diatomeae, “marine forms prevailing.” This writer also quotes the experience of Ehrenberg, who, with respect to the mud of the Elbe, has established the remarkable fact that at Gluckstadt, a distance of 40 miles, and even above Hamburg, upwards of 80 miles above the mouth of the river, marine silicious-shelled Infusoria were found alive, and their skeletons deposited in it in such abun- dance, that at the former locality they form from one-quarter to one-third of the entire mass, and that the proportion is still about one-half that amount at Hamburg, as far as the flood-tide extends. All his observations gave a great predominance of marine over freshwatcr Species, even when the salt taste of the water was no longer perceptible. His examination of the mud of the Scheldt and Ems furnished similar results, as did that of the marino deposit in various littoral regions of the North Sca and Baltic, Reverting to the Thames deposit, Mr. Roper expresses his belief that the silicious shells “have a perceptible influence in the formation of shoals and mud-banks in the bed of the river. . . . And the great abundance and general distribution of species serve to illustrate the occurrence of similar deposits in a fossil state at localitics now far removed, by alterations in the earth’s surface, from the streams or harbours in which they were originally do- posited. “Another point worthy of attention is the influence of these organisms in the formation of deltas at the mouths of large and slowly-flowing rivers—such, for instance, as the Mississippi, in which the mean velocity of the current at New Orleans is only about one mile and a half per hour for the whole body of water. Sir Charles Lyell, from Cxperiments on the pro- portion of sediment carried down by the river, has calculated that, taking the area of the delta at 13,600 square miles, and the quantity of solid matter brought down annually at 3,702,758,400 cubic feet, it must have taken 67,000 years for the whole delta. Now, as the silicious frustules of the Diatomeae are secreted from the water alone, and would most probably be extremely abundant in so sluggish a stream (especially as Prof. Bailey has found both marine and freshwater species abundant in the rico-grounds), thore can be little doubt that, without taking the larger proportion noticed by Ehrenberg in the Elbe, even if it were considerably less, it would reduce the above period by several thousand years; and the same cause would probably apply with equal force to the Ganges and Nile. Ehrenberg considered that, at Pillau, there are annually deposited from the water from 7200 to 14,000 G 2 84 GENERAL IIISTORY OF TITE INFUSORIA. cubic metres of fine microscopic organisms, which, in the course of a century, would give a deposit of from 720,000 to 1,400,000 cubic metres of infusory rock or Tripoli stone.” * Another fact excmplifying the widely pervading presence of silicious In- fusoria was revealed by the experiments of Ehrenborg, viz. their existence in a living state in moist earth beneath the surface, the only vital condition necessary being a small quantity of moisture. The presence of their remains at considerable depths in mud also is well exemplified by the experimental borings made by Mr. Okeden (J. M. S. 1854, p. 26) at Neyland, a creek of Milford Haven, where deposits rich in Diatomaceous remains of marine or brackish and freshwater character occurred at the depth of 20, 30, and 40 feet. The preceding illustrations will suffice to show the active share taken by the Diatomeae at the present day in the ever-occurring changes of the earth’s surface; othors must now be adduced to excmplify their influence in the past physical changes of the globe. These examples are so numerous, and, relative to other phenomena, so important, that it is embarrassing to make a selection. Ehrenberg is the most assiduous cultivator of this department of knowledge. He has personally examined deposits collected from almost every country of the world, and described, with illustrative plates, the genera and species he has encountered in them, in his recent large work the Mikrogeologie, 1855. One of the most striking and, to his mind, unique instances of a Diatoma- ceous deposit, formed at a remote or geological poriod, he has shown to cxist in North America, on the banks of the Columbia River. The river of Columbia, in its course at Place-du-Camp, runs between two precipicos 700 to 800 feet high, composed of porcelain-clay 500 feet thick, covered over by a layer of compact basalt 100 feet thick, on which, again, some volcanic deposits exist. The clay strata are of very fine grain, and vary in colour; some are as white as chalk. Dr. Bailey has shown, from Some por- tions submitted to him by Col. Fremont, that this apparently argillaceous layer is entirely composed of freshwater Infusoria. Its perfect purity from sand shows that it is not a drift, but has been formed on the spot. By its immense thickness of 500 feet, this layer of biolithic Tripoli far surpasses any similar layers elsewhere, which attain ordinarily only one or two feet thickness, although those of Lunchurg and Bilin have a depth of 40 feet. Some beds we also know elsewhere having 70 feet; yet such are not pure, but inter- sected by strata of tufa or of other material. A very pure Diatomaceous deposit has becm met with by Dr. Gregory in the island of Mull, which when dry is almost white, and much Tosombles chalk, being light, pliable, and adherent to the fingers (T. M. S. 1853, p. 93), and in composition hardly contains anything besides silicious organic remains “for the most part entire, but with some fragments; other portions which are donsor contain also many fragments of quartz of various sizes, and vast numbers of comminuted fragments of loricae.” Prof. Smith (Synops. vol. i. p. xii) says—“Districts recovered from the sea, in the present or other periods of the earth’s history, frequently contain myriads of such exuviae forming strata of considerable thickness.” Examples of this nature in our own country are met with in “the ancient site of a mountain lake in the neighbourhood of Dolgelly, localitics of a similar kind near Lough Island- Reavey in Down, and Lough Mourne in Antrim.” Mr. Okoden concludes, from facts collected by borings in the mud of some creeks and rivers of South Wales, “that not the surface merely, but the whole mass of these tidal deposits is penetrated by these minute and wondrous organisms, while, from the fact of their being found at Neyland at a depth of 40 feet below the OF TEIE DIATO MEAE. 85 present surface, and close upon the rock which forms the original bed of this estuary, the mind is irresistibly led to the conclusion that they have existed there from the time when the waters first rolled over the spot.” Berg-mehl, Tripoli, and other polishing-powders, the stratified deposits at Bilin in Bohemia and in AEgina, and numerous others examined and reported on by various microscopists might likewise be adduced to demonstrate the important part played by these individually invisible beings, when accumu- lated in countless myriads, in the construction of the carth’s crust. The Oolitic, and cven Some earlier metamorphic rocks, porphyritic rocks, &c., are not wanting, according to Ehrenberg, in species of Diatomeae ; but in the Pliocene, Miocene, Eocene, and in chalk and flint, and still more in the tertiary deposits, the abundance and varicty of forms are greater. Diato- maceous shells are curiously prescrved to us in large abundance and perſee- tion in guano, in which they have doubtless entered as a component in the way of mixture with food taken by the birds which have deposited that Iſlå Ill II’G. The foregoing facts teach us that probably, in the present condition of our planet, no portion of its surface is destitute of Infusorial life; and now, from the prosecution of microscopic research in connexion with geological facts, it would appear that, under this simplest and primary form, organic life made its first appearance on the globe, and has, during the many epochs of this world’s history, and notwithstanding the mightiest changes its surface has undergone, becn Sustained until the present moment; and, what is more, so extraordinary is the capability of the silicious Dialomeae to preserve life, and so astonishing their powers of multiplication, that species which are now found living have their generic and even their specific types at the very dawn of creation. Prof. Ehrenberg has advanced this same statement in his recent work (Mikrogeologie), saying that the oldest silicious Infusoria, who- ther Carboniferous or Silurian, belong to the same genera, and often to the Same species. AïROLITIC DIATOMETS.–Ehrenborg was the first to demonstrate the fro- quent Cxistence of Diatomca along with other microscopic beings and or- ganic particles in the atmosphere, principally in those showers of dust which fall from time to time in various parts of the world, and in those other mote- oric products known by the name of ‘meteoric paper’ and ‘blood-rain.” In Such atmospheric productions, the Berlin naturalist has detected above a hun- dred species; these, accompanied by descriptions and figures, and prefaced by an account of all such atmospheric phenomena on record, were published by Ehrenberg in a large brochure entitled “Passatstaub whd Blutregen,” consisting of 192 folio pages. An extract from this book will convey the best attainable notion of the physical importanco of these aërial dust-showers. The quantity of actual Solid matter that has fallen from the atmosphere by showers is far more considerable than supposed; for, though it falls in a diffused dust-like form, the extent of surface covered at any one time is very considerable. Comparing it with meteorolites, Ehrenberg observes that the total quantity of these stones which fell between 1790 and 1819 weighed 600 cwt., whilo in a single dust-shower at Lyons, in 1846, the solid matter weighed fully 7200 cwt. Other dust-storms in Italy, at Cape de Verd, and in other localitics have exceeded even that at Lyons, in the quantity of matter precipitated to the earth; and Ehronberg suggests to the imagination the millions of tons that must have fallen since the time of Homer. Lastly, he entertains the curious opinion, that this meteoric dust does not necessarily derive its existence from the carth’s Surface, and from the force of atmosphoric currents, but from some general law of the atmosphere, according to which S6 GENERAL HISTORY OF THE INFUSORIA, the living organisms mainly composing it may have the power of self- development in the air. - USEs of DIATOMACEOUS DEPOSITS.–The utility and possible and probable purposes of these minute organisms to mankind have not yet met with due consideration. Their relation to the soil, in which they are so abundant, and their influence on its fruitfulness are matters Ónly incidentally reflected on by authors. “Sufficient attention,” remarks Prof. Gregory (J. M. S. 1855, p. 2), “has not yet been paid to the fact of the invariable presence of Diatomeae in all earths in which plants are found. Ehrenberg, in his Mi- krogeologie, has established the fact as a universal one, and pointed out the important bearing it has on the growth of the soil. Indeed, it is difficult to imagine a more effectual agent in the transference of silica from the waters to the solid earth than the growth of Diatomeae, the shells of which are as indestructible as their multiplication is rapid. Ehrenberg is of opinion that they live in the soil as well as in water; and the constant presence of moisture in the soil Tenders this conceivable. Although the proportion of silicious matter dissolved in ordinary water is but small, it is evidently sufficient to supply the shells of millions of Diatoms in a very short time ; and it is therefore probable that, as fast as it is extracted from the water by them, it is dissolved from the rocks or earths in contact with the water, so that the supply Inever fails.” Mr. Roper has also suggested, from the consideration that the best Samples of guano contain the greatest number of these silicious skeletons, which doubtless serve to replace the large amount of silica abstracted from the soil by the cereal crops, that it is probable that the deposits of many of Our rivers would have a beneficial effect if applied to the land; and it’rests with the microscopist to point out the most favourable localities for obtaining them. Ehrenberg notices an instance where this has been done in Jutland, where a blue sand abounding in calcareous and silicious shells is collected, and greatly increases the fertility of the arable soil to which it is applied ; and Prof. Bailey also states that the mud of Newhaven harbour is used as a fertilizer, and is found to contain 58.63 per cent. of silica. The author last-named has moreover adduced instances to prove that the great fertility of the rice-fields of South Carolina is mainly due to their richness in Diato- maceous remains. This notion is strengthened by the examinations of Ehrenberg, and by the commonly observed fact of the occurrence of Diatomeae about the roots of plants, especially of the cereals, which demand a large supply of silicious material to construct their stems. * Dr. Hooker (op. cit.) contends that the abundant Diatomaceous deposits of the South Pole supply ultimately the means of existence to many of the smaller denizens of the ocean, and that they keep up that balance between the animal and the vegetable kingdom which prevails through all other lati- tudes. He adds that they probably purify the vitiated atmosphere, just as plants do in a more temperate region. In the arts, the remains of Diatomaceous shells, as the chief ingredients in certain deposits, are brought into use as polishing-powder under the name of Tripoli, and also, as an extremely fine and pure silicious sand, in the manu- facture of porcclaim. The powder called Tripoli has various origins, and differs in the microscopic organisms it contains. Species of Melosira especially abound—for instance, of Melosira varians. Ehrenberg informs us that the Tripoli of Jastraba in Hungary and that from Cassel resemble each other in their component species. A very remarkable application of a deposit of Diatomeae is its use as an article of food, under the pressure of want, by the wretched inhabitants of OF TDIE DIATOMEAE. 87 some inhospitable and barren districts of Europe—for instance, in some localities of Lapland and of Hungary, and in other parts of the world. Ehrenberg mentions a sort of earth under the name of “Tanah,” eaten in Samarang and Java, which overlays Some mountains of Java at several places at a height of 4000 feet. It is generally Solid, plastic, and sticky; it is rolled and dried in the shape of Small sticks over a charcoal fire, and is eaten as a delicacy. An examination of this earth disclosed 3 or 4 species of Polygastrica and 13 of Phytolitharia. It has been attempted to make the specific characters of Diatomaceous de- posits of critical value in deciding on the date and superposition of rocks. However, the geographical distribution of these beings is as yet insufficiently known; and every day reveals the fact that species decned peculiar to some one locality are to be found in others, and to have at least a very wide range. We have already quoted Some examples of apparent limited diffusion in our remarks on geographical distribution; it is therefore not necessary to illustrate the subject further in this place. The circumstance that some one or two species seem at times peculiar to a neighbourhood, has encouraged antiquarians to Scize on it with the hope of determining the locality whence the clay was procured from which anciont specimens of pottery or porcelain Were manufactured. Another practical purpose to which the shells of Diatomeae have been put is as test-objects for microscopes, the penetrating and defining powers of which are measured by their ability to detect and demonstrate the Cxistence and nature of certain markings on the surface of the silicious epiderm—such, for example, as the striae of Pleurosigma. ON THE NATURE OF DIATOMIEZE, WITETTIER ANIMALS OR PLANTs — VARIOUS IIYPOTHESES.–The mature of the Diatomcae is still a much-vexed question, although the opinion of those naturalists who hold them to be plants—mem- bers of the great family of Algae—proponderates. Ehrenberg assumed their animal nature, and persuaded himself of the existence of a complicated organi- zation, such as neither the researches of others can confirm nor analogy Sup- port. In his latest papers on Organization, he has insisted most strongly on the apparent successful feeding of these organisms with particles of colour which entered within their interior. These experiments are not satisfactory, and have failed in the hands of others; it is besides quite clear, that the umbilicus, at which he represented the colour-granules to enter, is no real opening in the lorica, but a thickening of its epiderm. Prof. Meneghini, now many years ago, penned a learned treatise to prove the animality of the Diatomeae; but although he offered many ingenious argu- ments to support his opinion, he did not succeed in establishing it. Many de- tails of structure and organization and micro-chemical characters, urged by him in favour of their animal nature, have been considerably modified or entirely set aside by subsequent researches; and the general argument, that the varia- tion from recognized plants is in many particulars very marked, has only a comparative or relative force, according to the Oxtent of differential structure of animals which may, on the other hypothesis, be Sct forth and proved. The distinguished Italian naturalist indeed limits his design in the treatise before us (On the Animal nature of the Diatomeae, R. S. 1853) to disputing Kützing’s arguments for their vegetable nature, saying (p. 365), “Whilst unable to confirm or refute the opinions of Ehrenberg, We SCCm to have observed facts sufficient to disprove those of Kützing.” On this same side are ranged Focke, Eckhardt (a pupil of Ehrenberg), and Prof. Bailey, who express their inability to reconcile some of the structural details and physiological phenomena with vegetable organization. Schleidon 88 GENERAL IIISTORY OF THE INFUSORIA. perhaps should also bo reckoned of the number, since he remarks, in his de- scription of the shield of a Navicula, that “such an artificial and complicated structure amongst plants has no explanation, and is cntirely without signifi- eation. In all actual plants we find the silica present in quite a different form, as little separate scales or drops, and distributed through the substance of the cell-wall.” In favour of the vegetable nature of the Diatomeae, on the other hand, the majority of the original observers in this country unite with many of the most distinguished naturalists of the Continent, such as Kützing, Siebold, Nägeli, Rabenhorst, Braun, Cohn, Meyen, &c. The last inquirer, so long ago as 1839, urged various objections against the presumed animality of the DCSmidieæ and Diatomeae, and more particularly against Ehrenberg’s views. Respecting the animality of the Diatomeae (Naviculacea), he remarks gencrally—“The reasons adduced for such belief are so weak, that the conclusions deduced from them are yet for the most part very doubtful.” A small number of naturalists have expressed the motion that the Diatomca, belong equally to the animal and to the vegetable kingdom. M. Thuret may bo named as One of these, since he has stated that thero is no more roason in favour of the onc affinity than of the other. Such an idea is certainly unphilo- sophical; for it would cut the knot instead of loosening it, by the assumption of an order of organic beings intermediate between the animal and the vege- table kingdom, and undeterminable to which they belong. Wo will now proceed to state the leading arguments for the animality of the Diatomeae, indicating the name of the writer suggesting each, so far as practicable:– 1. The Diatomea –many species at least—Oxhibit a peculiar spontaneous movement, which is produced by certain locomotive organs.—Ehrenberg. 2. The greater part have in the middle of the lateral surface an opening, about which certain round corpuscles are situate, which become coloured blue when placed in water containing indigo, like the ‘stomach–cells’ of many In- fusoria, and consequently may equally be regarded as stomachs.-Ehrenberg. 3. The shells of many Diatomaceæ resemble in structuro and conformation the calcareous shells of Gastoropoda and similar Mollusca.--Ehrenberg. 4. The method of multiplication by self-division.—Ehrenberg and Meneghini. 5. The complicated structure of the wall of the frustules, and the characters of the silicious deposit.—Schleiden, Bailey, and Meneghini. 6. The greater affinity in chemical composition of the contents (the endo- chrome) with animal than with vegetable products.-Meneghini. Each of these arguments requires examination in detail, and its value tested. To begin therefore with the first—the occurronce of locomotion and the organs by which it is effected, as evidences of animal constitution. Morren, in the paper quoted (Jahresbericht Akad. Berlin, 1839), pointed out that motion is not confined to animals, but exhibited also by the spores of Algae and by sporm- atic particles. To these examples may be added the Oscillatoriae, Proto- coccus in its various phases, Vaucheria clavata, Ulothria zomata, and othor Algæ, among which are the now admitted gonera of Volvocincap. In many of these, the movements are much more active and lively, and present more seeming spontaneity than those of any of the Diatoms. The employment of tho word Spontaneous to signify the sort of movement of these organisms is certainly unjustifiable, if understood at all in its usual signification, of an act originating in the moving body directéd to a special purpose ; for no more spontancity is manifested in the motions of these silicious organisms than in those of the leaves of the Dioncea muscipula when any particle impinges on their sensitive hairs. Meneghini, in examining this point, is compelled to Ol' TIII, DIATOMIELE. 89 admit that no absolute proof is deducible from the movements of the frustules, in support of their animal nature; and the only difficulty to him against admitting that they may be vegetable in character, is, that they are so dif- ferent from those of Oscillatoriae, Desmidieæ, and Protococcoideae, a worth- less objection, to be sufficiently answered by asking whether that motion docs not differ as widely from that of any animals, and whether the movements of the Desmidieæ are not equally unlike those of the Oscillatoriae as those of the Protococcus. The locomotive Organs insisted on—consisting, according to Ehrenberg, of a retractile foot and of retractile ciliary processes—have not been sufficiently demonstrated to use as an argument. Ehrenberg, Corda, and more lately Focke, are the only observers who pretend to have seen such organs, although the organisms said to possess them are subjects of daily minute research by hundreds of wonder-finding microscopists. The mucous film which invests many Diatomaccous frustules may, indeed, have been seen and misinterpreted. Meneghini calls attention to a kind of sparkling or agitation—actually a rapid and indeterminate change in the refraction of light at their extremities, which he seems disposed to believe shadows forth the presence there of some sort of ciliary locomotive organs. Granting, however, that cilia were ascertainctl to be the cause of the movements perceived, the doctrine of animality would in no way be advantaged, since cilia are not peculiarly animal structures. According to Nägeli, one sort of vegetable movements originates in the act of growth. Of such a kind are probably the vibrations of the Oscillatoriae; and possibly the motions of the Diatoms are in some degree reducible to the same category. And it is to be remarked that these motions are not equally apparent and active under all circumstances, oven among specimens of the same species, but are most so when the vital phenomena of the organisms are most aroused— when the most rapid interchange of material is going on between the external medium and the internal cavity. 2. The second argument rests entirely upon hypothetical grounds, derived from Ehrenberg's observations, and is valueless so long as those observations are unconfirmed. It seems quite clear that the central opening or umbilicus spoken of has no real existence; and if this be so, then the apparent entrance of colouring matter within a set of corpuscles situated around it must be an crror of obscrvation, unless the unproved and improbable assumption be made that the colour-particles enter at foramina placed clsewhere (as at the extro- mities), and become transmitted to these contrally placed sacs or so-called stomachs. Kützing declares that the seeming entrance of colour-granules is the result of mechanical causes, and adds the more important statement that the central collection of vesicles is often wanting. 3. The third argument, that a resemblance obtains between the shells of Bacillaria and those of some Molluscous animals, is, to say the least, fanciful, and in a scientific inquiry can be admitted to prove nothing. If external similarity proved anything, it might as well be adduced to demonstrate the affinity of a lead-tree with the higher plants, whilst, again, the error to which this sort of proof will lead is well exemplified in the case of the Foraminifera, which from more outward resomblance were for years accounted members of the Cephalopodous family. In the latter instance, indecd, the similarity in external form was very striking—far excociling that of any Diatom with any testaceous animal. Kützing, in his review of this assigned reason for their animality, mects it in another way, by observing that, among the cells of higher plants, examples are to be found which in configuration and other particulars agroc with Dia- toms—for instance, the numerous forms of pollen with their angles, spines, 90 GENERAL IIISTORY OF THE INFUSORIA. &c. But, as Meneghini remarks, “he might have added the more appropriate instance of the Desmidieæ, which would be very closely allied to the Diatomeae, if the latter, like the former, could be referred to the vegetable kingdom. If not equal in constancy and regularity, the Desmidieæ display a greater degree of complication: and we must remember the different nature of their substance; for in the vegetable cell, when lime or silica predominates, the wall becomes uniform and regular.” 4. Multiplication by self-division was at one time cited by Ehrenberg as peculiarly an animal phenomenon, a motion at variance with the observations of every naturalist, and now requiring no refutation. However, Meneghini has more recently advanced the statement that an essential difference in the process of fission prevails between the Diatomeae on the one hand and the Desmidieæ and Algæ in general on the other, applying to the former modifi- cation (in accordance with Brébisson’s views) the term deduplication, to the latter reduplication. To cxtract his remarks (op. cit. 368)—“ Division is always longitudinal, and takes place underneath a fine external silicious membrane, by the formation of contiguous diaphragm walls which divide the internal cavity. Thus the contents are longitudinally divided; and this divi– sion is complete if the two new individuals detach themselves and so acquire individual liberty. It is imperfect if the fine silicious persistent membrane and the secreted gelatinous substance retain them connected together. This mode of reproduction (which Brébisson distinguished by the name of dupli- cation and deduplication, from the reduplication of Desmidieæ) deserves the most attentive observation. The foregoing exposition presents the fact in its most rude and Superficial goneral appearance, and makes us feel acutely the want of a more circumstantial description peculiar to various forms. It is only after having established facts relative at least to the principal generic types, that we can establish, on a scientific basis, the general idea of multi- plication by duplication. A few observations suffice, however, to prove that this does not occur in so simple a manner as we are taught to believe, by comparing it with that in vegetable cells. In the Achnanthidia, for example, it is described and figured that the principal surfaces, which occupy the inter- mediate space between the two superior and the inferior valves, commonco by presenting fine transverse lines, and noxt a strong longitudinal line along the middle; then there appear two new intermediate valves contiguous to each other—the superior valve (?) of the new inferior individual, and the inferior one of the Superior. My observations convince mc that the affair does not procced with so much simplicity. I have often seen the two lateral valves scparated, and the intermediate space thus largely amplified. In other cases there appeared only a new inferior valve complementary to the Superior, the inferior individual thus romaining incomplete. Finally, in others, botween the complete Superior individual and the incomplete inferior valve, thero appeared a new individual with both its valves, but nearer together, Smaller, finor, with lines much less distinct.” In short, “in this phenomenon there is more complication than that of a simple cellular deduplication.” 5. In a previous page (p. 88) we have quoted Schleidon's notice of a dif- ficulty in the way of recognizing Diatoms to be plants. It is one likewise which has presented itself to others, for instance, to Prof. Bailey and Meno- ghini. “If we suppose them to be plants,” says the lattor writer, “we must admit overy frustule, every Navicula, to be a cell. We must suppose this coll with walls penetrated by silica developed within another cell of a different nature, at least in overy case where there is a distinct podiclo or investing tube. In this silicious wall we must recognize a complication certainly un- equalled in the vegetable kingdom.” (op. cit, p. 372.) OF THE DIATOMEAE. 91 This critique of Meneghini loses much of its force when it is noticed that the Qxistenco of a pedicle, or isthmus, or of a muco-gelatinous sheath envelop- ing the frustules, is assumed by him, quite hypothetically, to indicate their formation within a cell-wall represented by the Soft investment, an idea originated by him because he could not admit of an Oxtra-cellular formation. The present state of knowledge, however, clearly recognizes the not infrequent formation of extra-cellular matters about cells, and consequently this portion of the difficulty in question will cease to have importance. On the other hand, no animals can be pointed out having a similar complex silicious structure, whilst an analogy may be, to a certain extent, found with the Desmidieæ, some of which have a small deposit of silica in their envelopes, which again in some 1)iatomaccous frustules is very deficient (see p. 37). Indeed, the affinity between the Desmidieæ and the Diatomca is manifested by the differential characters which naturalists feel themselves called upon to indicate (see p. 95). The composite structure of the frustules is principally the result of the per- meation of the external tunic with silex. The little box or capsule, when first produced, represents a simplo cnclosed cell, imbued with more silica than a Desmidiaceous frond, but otherwise not histologically unlike. When the little being preparcs for Self-division, the opposite valves separate, much as the opposed halves of a frond of one of the Desmidicae, and the intermediate production, according to the habit of the class, becomes penetrated by silica (to a less extent, however, than the Original valves), and assumes so much of a permanent character that it is very frequently considered an independent third segment. So again, the cellular, or arcolate, or otherwise figured and involuted surface of the frustules, cited by Monoghini as dissimilar to any plant-structure, would also appear to be a consequence of this permeation of the Organic membrane with silica, and of various modifications consequent thcroon. To show that analogies are not wanting in the vegetable kingdom of curiously modified and figured cell-walls, we may mention as examples, besides pollon-grains, in- stanced by Kützing, the sporangia of Desmidieæ and of various Algae. More- over, tho capability of the simplest enclosing membrane to develope a very complex superficial structure is illustrated in the case of the Rhizopodes, among which are many examples of striated, areolated, and otherwise modified shells, which, in the eyes of many, range with unicellular Organisms. We must not forgot to state that Meneghini himself seems to have appreciated the offect of the permeation of silica upon the charactors of the cell-wall; for he says, in his supplementary annotations (op. cit. p. 511), “the part which silox takes in the formation of the cell-wall is undeniable,” as in the opi- dermis of Gramincac, Palms, and Equiseta. “The stomatic cells of Equiseta mcrit particular attention, both from the silex they contain, and the transverse striae they present on the intornal surface. This resomblance to the shield of Diatomeae might lead us to believe that we ought to regard it as an argument for maintaining the vegetability of the latter: but I do not think that I ought to dwell upon such an objection ; I Only notice it because I Would not appear to be, or pretend to be, unacquainted with it. Yet it Scems to me important in another point of view—the apparent complication that the simple cell may assumo when penetrated by silica.” We cannot do better than close this part of the argument by Prof. Smith’s review of the subject (Synops. ii. p. xix):—“In overy case this mombrane [of the frustule] is more or less penetrated or imbued with silex; and the presence of this substance appears to have modificd the intimate structuro of the membrane, and induced great variety in the mode and charactor of its 92 GENERAL IIISTORY OF THE INFUSOR.I.A. formation in different genera, accompanied by great regularity in the indi- vidual species. “These variations exhibit themselves in the different modifications of structure which constitute the markings of the valves, appearing under the form of ribs and nodules, costae, striae, or cellules of an elliptical, circular, or hexagonal outline. A wide comparison of specimens seems to me to prove that these various markings originate in the tendency impressed upon all organized structure to develope itself upon the type of the cell, and that the presence of the silicious constituent in the cell-membrane of the Diatom gives a fixedness to this tendency, which, in ordinary cases, is either not discern- ible in the structure of the membrane, or whose effect is obliterated by the coalescence of the softer matorial which constitutes its substance. However this may be, it appears to me certain that the structure of the silicious valve in the Diatomaceae is invariably cellulate, the cellules being more or less modified according to the peculiar requirements of each species, and that no other explanation of their characteristic markings seems consistent with the facts which are established by a careful oxamination and comprehensive know- ledge of Diatomaceous structure. That this oxplanation does not involve con- siderations at variance with the conditions of unicellular vegetable life, will be obvious to any one familiar with the structure of the silicious epiderm in the Equisetaceae and Graminacca, and the distinctly cellulate structure of many pollen-grains, while this very presence of silex as a constituent of the cell-wall in the Diatomaceæ appears to be wholly unaccountable except on the supposition of the vegetable nature of these organisms. In no instance do we find a parallel condition in the animal kingdom (for the secretion of silicious spicula, as an internal skeleton, in Some of the Spongideae, cannot be regarded as an analogous phenomenon), whereas the vegetable kingdom furnishes us with cases, not merely of the Secretion of silex as a vegetable product in the Bamboo, but with frequent instances of its intimate union with cellulose in the membrane which forms the epiderm of the cell, as in the Natural Orders already mentioned, in the Palmaceae and others.” On the nature and mode of deposition of the silex, Dr. Bailey has ad- vanced the statement that the silica in Phytolitharia, as well as in Diatomeae, Polycystineae, and Spongilithes, is not doubly refractive and polarizing, as Ehrenberg described, and that even the admitted exception of Arachnoi- discus is not such. The error in supposing it so has originated from the im– perfect removal of the dense carbonaceous tissues which are deposited beneath the silica. 6. The final argument we have to consider for the animality of the Diatomeae is, that the greater affinity in the chemical composition of the contents, i.e. of the endochrome or gonimic substance, is with plants, and not with animals. This argument is certainly based on a nice and very difficult- to-be-determined fact. Meneghini insists on it as important. His romarks have already been given in our notice of the contents of the frustulos, to which we must refer (p. 47), adding here only some supplementary obser- vations to fully convey his opinions. “Finally,” he writes (op. cit. p. 366), for this is not a property peculiar to chlorophyll, “I may add that, if a portion of chlorophyll could be demonstrated in the interior of Diatomeae, this would by no means invalidate their animal nature; we might still suppose they had swallowed it for food. As to the oil-globulos' which Kützing represents, Meneghini considers they may be no more than particles of sarcode, which have an oily appearance ; and he would observe “that the number and volume of these globules increase considerably after death, and that during life they are situated upon a longitudinal line CXtcnding from one extremity to the N OF TELE DIATOMEAE. 93 other. And,” he continues, “I rely upon the observation that thore is some motion and successive alteration in them, as if these minute globules mixed with larger ones, and separated again from them.” For, to the mind of the Italian naturalist, the hypothesis of stomachs is admissible, although the fact that a polygastric structure (affirmed by Ehrenberg) has not been shown in the ciliated Protozoa is in itself an à priori argument that such an organization is not to be found in the Diatomeae, among which animal cha- racteristics are so much more deficient and indoterminate. Although, to our apprehension, this argument, based on the differential chemical composition, to the extent it is developed by Meneghini, is incom— plete and inconclusive, yet it was a duty to present it, in order that some of the many ardont English microscopists may be induced to attempt the solution of this micro-chemical question. Rabenhorst, we should not omit to state, describes the colouring mattor of Diatomeae as quite different from the chlorophyll of plants. For instance, he statos that the chlorophyll of plants is taken up by alcohol, dissolves with a yellowish-green colourin alkalies, and with muriatic acid acquires an emerald- green colour, whereas the colouring material of Diatomeae is insoluble in alcohol (although after a time its colour fades), remains unchanged by alkalies, and acquires a pale-green colour with muriatic acid. It still remains to point out the facts which speak in favour of the vegetable nature of the Diatomaceae. The following summary was offered by Kützing:— “1. The great resemblance of compound forms to Algæ, and their develop- ment by fission. There are, indeed, compound Infusoria, as Monad—masses and Polypes: but the former are very questionable animals; and the latter have this essential distinction, that the individual animal lives without (external to) its habitation, and moves freely, whereas such Naviculae as Encyonema, Schizonema, and Micromega, and similar genera, grow within the enclosing substance, building themselves up like the cells in the stem of a plant—so vegetating here only as cells. In like manner, the individuals of Fragilaria, Melosira, Himantidium, &c., are steadily fixed, and unable to exhibit animal motion. “2. The innor soft organic parts, which I have designated gonimic sub- stance, possess, as well in their chemical nature as in their development, peculiarities akin to those met with in the cell-contents of confervoid Algae. “This relation is most clearly seen in the genus Melosira and its allied forms, which, not only in form, but also in the chemical components of their con- tained matter (since the presence of chlorophyll is common to all Diatomeae), are closely allied to the confervoid Algae. “3. The development of seeds, or young [as Kützing represents it], occurs here as in undoubted Algae, but Inever as in true animals. “4. The Diatomeae, and ospecially the free moving Naviculae, develope, in the sun’s rays, an appreciable quantity of oxygen, like all admitted plants. “The evolution of oxygon, indeed, occurs in green Monads and Euglence; but this affords no argument for the animality of the Diatomoge, but renders the animal nature of those Infusoria thomsolves very doubtful, and the more so as recent observations confirm the idea of the origin of the lower plants themselves from Monads and Euglence. Wherefore all these comparisons serve to favour the belief in the vegetable nature of Diatomcae.” To these arguments has been added another, resting on the assumption of conjugation being peculiar to plants; and Mr. Blackwell discovers further evidence of plant-life in the variations of form of the frustulcs of the same species (J. M. S. 1853, i. p. 247). It is necessary to inquire, seriatim, into the real value of the arguments 94 w” GENER.A.L. IIISTORY OF THITE INIFUSORT.A. on this, as has been done with those on the other side of the question, Meneghini enters the lists with Kützing, and disputes the conclusions arrived at by him, rather than the facts on which they rest. The first argument, founded on external resemblance, has little value, and offers no certain indications of affinities. However, taking Kützing’s state- ments in his own words, modern research has added to its weight, ; for it has proved, what was before only a probability, that the so-called Monad- masses are only of a vegetable nature. The second reason advanced has boom already discussed, whilst the third rests as yet on incomplete observations, and in Meneghini’s opinion has an equally strong analogy in animals, for example, “in the ovaries of Polypes and other inferior animals, as in many Ovipara of Superior classes. And, in fact, the bag of a spider, with the thousands of Small eggs that it contains, seems to me quite as like, as the spore of an Alga, to the organ of propaga- tion of a Schizomema or a Micromega.” These analogics cannot be allowed much weight, whilst it is, on the contrary, pretty clearly ascertained that tho sporangia of Diatomcae produce a brood of young forms within them,--a phenomenon according in all particulars with the mode of reproduction in numerous Algae and Fungi. The fourth argument for their vegetable nature must be admitted to possess great importance. Since Kützing enunciated it, the apparent objections against the vital phenomena in question being restricted to plants, have becn removed by subsequent inquiry. The green Monads and Euglence, cited by Rützing, are now recognized to be vegetable, and can no longer cast doubt, by reason of an assumed animal nature, on the fact of the evolution of oxygen being a characteristic of vegetable life. The evolution of oxygen, as Prof. Smith, like every other careful observer, tells us, “may be noticed in any mass of Diatomaceae during the warmer months of the year, or in gatherings frecly exposed to the Sun, in the clevated temperature of a confined apartment, during the wintor or spring. Undor those conditions the water in the vessel becomes covercd with minute bubbles of oxygen, and portions of the Diato- maceous stratum are floated up by the buoyancy of the globules of this gas adhering to their frustules. Such phenomena can only be accounted for by supposing that the Diatomaceae are plants, and that they cxhale, like all plants in a state of active vegetation, oxygen from their tissues; but this pro- cess is irreconcilable with the hypothosis of their animal nature.” (Synops. vol. ii. p. XX.) - Prof. Carpenter insists (Microscope, p. 469), that the most positive and easily defined distinction between Protophyta and Protozoa “lies in the nature of the alimont, and in the method of its introduction,” in oach case. “For whilst the Protophyto obtains the materials of its nutrition from the air and moisture that surround it, and possesses the power of detaching oxygen, hydrogen, carbon, and nitrogen from their previous binary combina- tions, and of uniting them into ternary and quaternary organic compounds (chlorophyll, starch, album.cn, &c.), the simplest Protozoon, in common with the highest members of the animal kingdom, seems utterly destitute of any such power, and is dependent for its support upon organic substancos pre- viously elaborated by other beings. But further, the Protophyte obtains its nutriment by mere absorption of liquid and gaseous molecules, which penc- trate by simple imbibition, whilst the Protozoon, though destitute of any proper stomach, makes (so to speak) a stomach for itsclf in the substance of its body, into which it ingests the solid particles that constitute its food, and within which it subjects them to a regular process of digestion. Hence tho simplest members of the two kingdoms, which can scarcely be distinguished OF TITE DIATOMIEAE. 95 \ from each other by any structural characters, scom to be physiologically sepa- rable by the mode in which they perform those actions wherein their life most cssontially consists.” The process of conjugation has becm used as an argument for the vegetable nature of Diatomeae by Mr. Thwaites and others. This subscquently seemed to be set aside by the obscrvation of apparent conjugation in Actinophrys and Gregarina observed by Kölliker and Cohn. However, this phenomenon appears again in the ascendant as a vegetable characteristic ; for the observa– tions of Mr. Weston (J. M. S. 1856, 122), of Leuckart, Lieberkuhn, and others, go to show that the act believed to be one of conjugation in the Actinophrys, is not really a process of reproduction, but merely a temporary cohesion: morcover Lieberkuhm (Mém. de l'Acad. Roy. Belgique, vol. xvi.) proves that the production of the Navicellae is not necessarily a conscquence of the act of conjugation in the Gregarince. If future research substantiate the fact that conjugation is ossentially a vegetable process, then the naturo of the Diatomeae will no longor be doubtful. On a rovicw of the arguments urged on each side, and on consideration of the whole structural and vital peculiarities of the Diatomeae, we are disposed to consider them of a vegetable nature—members of the great family of Algae, and, together with many other unicellular plants, to constitute a group known by the name of Protophyta. Nägeli, in 1849, took this view, and reckoned the Diatomcºe as one of his eight orders of unicellular Algæ, of which the Desmidiacca and Palmellacca were other two. How close must be the affinity of the Diatomcae with the Desmidieæ is shown by the fact of the two families having so long been treated of together under the common head and name of Bacillaria. And although sufficiently decisive characters separate the one set of beings from the other, yet, in the grand phenomena of life and organization, a true homology exists. The difference between some Desmidicae and Palmellcae is as much pronounced as it is betwcom the former and some Diatomeae ; and between these several orders, together with the Zygnematae, various intermediate forms are to be found, which serve as con- necting links. Although Mr. Ralfs would not now insist upon the distinc- tions between the Desmidicae and Diatomcae, formerly laid down by him as decisive, yet they may be here reproduced with advantage. 1. In Diatomeae (op. cit. p. 19) “each frustule consists of three pieces, one contral, ring-like and continuous all round, and the others lateral.” In opposition, Prof. Smith asserts that the central third segment is no essential part of the frustulos, but a portion produced, just like that between the opposed valves of Desmidieæ, preparatory to the process of sclf-fission. 2. “The division is completed by the formation of new portions within the onlarged contral piece, which then falls off, or else by a new septum arising at the contre;” but Mr. Ralfs believes that in overy case the separation commences internally before it oxtonds to the covering. So far as we can understand the matter, no essential variation in this process provails in the two families. 3. “Their coverings, with vory few exceptions, are silicious, withstand the action of fire and acids, and may be broken, but not bent; the frustules are ofton rectangular in form, are novor warted, and scarcely ever spinous.” To these statements it may be replied, that in a few Diatoms the silex is in Small quantities in the valves, and that, on the contrary, examples of partially silicious Desmidicae are known. The action of fire and acids, the capability of being bent or not, are qualitics dependent on the relative proportion of silex in the frustules, and are but secondary distinctions. The same may be said of the remaining points mentioned—the rectangular form, and the presence of warts and spinos. The form indeed is, at best, of little value in 96 GENERAL ELISTORY OF THE INFUSORTA, the argument. The rectangular form of the Diatomeae is doubtless a conse- quence mainly of the silicious composition: yet it is far from universal among them; for some species are rather orbicular, others sections of cylinders, others capsular, and others again not unlike square sacs with bulging sides and rounded corners. Even where a rectangular outline exists, it is most frequently only in one view ; and the most that can be said is, that the lines of junction are in many instances acute. On the other hand, examples of a rectangular outline are to be found among the Desmidieæ and their allies: the junction-surfaces of Hyalotheca and Didymoprium are at right angles to the sides of the frond; the end view of Staurastrum tumidum is as angular as the front view of a Triceratium ; and the front view of Euastrum cuneatum presents decidedly rectangular truncate extremities. So too in the gonus Pediastrum, formerly enumerated among the Desmidicae, although now detached as a subfamily and placed between them and the Palmelleae, examples of an angular outline occur, as in the Pediastrum Tetras and other species. As to the production of spines, sufficiently numerous examples exist among the Diatomca to provo it no distinctive peculiarity of the Desmidieæ ; and although warty expan- sions or elevations of the surface precisely like those of some Desmidieæ, may not be noticed in Diatomeae, yet certain exaggerated inflations of the surface are secn in some Diatomeae, e. g. in Biddulphia pulchella and B. regima. The two next distinctions indicated by Mr. Ralfs are of more consequence, but nevertheless cannot be admitted as demonstrative of an entire difference in nature. They are thus stated:—“Their internal matter is usually brown when recent; and although some species are greenish, or become green after they have been gathered, none are of a truly herbaceous character. Their vesicles bear some resemblance to those in the Desmidicae; but they are of a yellower colour, and no starch has been detected in them.” The last section of this statement must be held as still sub judice; the chomistry of the cIldochrome is too imporſect to afford a safe argument, and the chemical relations of starch and isomeric compounds too little understood. The con- cluding distinction, “that the Diatomcas do not conjugate,” the researches of Mr. Thwaites have negatived. To employ the summary of the affinities of the Diatomeae presented by Prof. Smith (Synops. Vol. ii. p. xxi):-‘‘The Diatomaceæ, with specialities of their own, have also intimate alliances with the other orders of the Proto- phyta, resembling the Zygnemaceae and Desmidiaceae in the reproductive pro- cess, the Nostochaceae in the tendency shown by several genera to surround their frustules with frondoso masses of mucus, within which linear series of cells arc Subsequently developed,—the Oscillatorieae in their movements, the Palmellaccae and all the orders I have named, in the self-dividing act by which the individuals of the species are multiplied, or the aggregate of spe- cific life maintained and increased.” DETERMINATION OF SPECIES AND GENERA ; VARIETIES ; CLASSIFICATION.— The question has been very much discussed of late, what characters of the frustules and of their contents are to be employed in the construction of species? Ehrenberg generally proccoded on the principle of notifying evory departure from any one form, assumed to be specific, as representing another Species ; but this loosc plan has been found productive of error and of ex- cessive multiplication of species, inasmuch as shape, or outline, or markings of the surface are not nearly so permanent and distinctive as formerly imagined. Although in some species the size and figure seem pretty constant, yet in many they are subject to endless variations. Prof. Gregory cites as examples of changeableness of form the three species, Eunotia gibba, Pinnularia divergens, and Himantidium bidens; and he would comprehend several pre- OF THE DIATOMEAE, 97 sumed species of Naviculae under the name of N. varians. So again Dr. Greville, speaking (A. N. H. 1855, p. 258) of the Grammatophora (?) Bal- fowriana (Smith), which he erects into a new genus Diatomella, observes, “There is greater variation in the relative length and breadth of the frustules than would be likely to occur in other Diatomaceous groups. In some the length is more than cqual to twice the breadth, while others are exactly Square; and between these two extremes every gradation may be observed; resembling in this inequality Fragilaria, Odontidium, Grammatophora, and other filamentous genera having plano-compressed frustulos.” But in this very case a difference arises between Dr. Greville and Mr. Smith respecting the value of internal markings as a characteristic distinction ; for the latter author remarks, “The absence of a curve in its septa, relied upon by Dr. Greville, I cannot regard as of sufficient importance to constitute a generic distinction, as this feature is scarcely noticeable in some states of Gramma- tophora macilenta, and is uniformly absent in G. Stricta.” (Synopsis, vol. ii. p. 44.) “The size of the mature frustule” (says Prof. Smith, J. M. S. 1855, p. 132) “before self-division commences, is, however, dependent upon the idiosyncrasy of the embryo, or upon the circumstances in which its embryonic growth takes place; consequently a very conspicuous diversity in their relative magnitudes may be usually noticed in any large aggregation of individuals, or in the same species collected in different localities. “It may also be easily conceived that, while a typical outline of its cell must be the characteristic of a certain species, such outline may to some extent be modified by the accidental circumstances which surround the em– bryo during its earlier growth and development. A lanceolate form may become linear, elliptical, or even somewhat oval, by the pressure of surround- ing cells; and acute onds may be transformed into obtuse or rounded ex- tromities. “Those who understand the process of self-division will see here a suffi- cient reason for the occurrence of multitudes of frustules deviating from the normal form, or even for the existence of myriads at One spot, all having a form different from the type, the single embryo from which they have all sprung by self-division (which process stereotypes the shape with which it commences) having from some accidental circumstances become modified in its outline. “It follows, then, from these considerations, that neither size nor outline is sufficient to enable the observer to determine the species of a Diatoma— ceous frustule. If he has the means of comparing specimens in sufficient numbers and from various localities, he may fix with tolerable certainty upon the magnitude and form which may be regarded as the average and type of the species; but, without such opportunitics, a reliance upon such characters will inevitably lead to the undue multiplication of species and to a confused and erroneous momenclature.” In the construction of genera, similar difficulties present themselves. Thus, Mr. Brightwell complains (J. M. S. i. 252)—“It appears as if we could carry our real knowledge little beyond that of species; and when we attempt to define kinds and groups, we are met on every side by forms which set at nought our definitions. With reference to the species of the present genus (Tricerativm), looking upon T. favus or T. megastomum as what we con- ceive to be the most perfect plan (if any) on which this group is constructed, we find all the species diverging from it, and carrying us to analogous forms in other groups, or lost in them. Placing the perfect triangular form of TH 98 GENERAL EIISTORY OF TIII, INFUSORIA. T. favus in the centre, we may diverge in limes to a circumference ending in one line, in the long-armed T. Solennoceros, itself nearly resembling DeSmi- divºm tridens or D. heavaceros; in another line ending in a form resembling Desmidium apiculosum ; in another like Zygoceros rhombus, especially in the front view; in another analogous to Amphitetras antediluviana; and in another to Campylodiscus cribrosus.” Next after size and form, markings existing on the surface or within the frustules have been employed as specific and generic characteristics; but with these, as with the former conditions, great uncertainty prevails in their ap- plication, as we have already seen in the difference of opinion, regarding some internal markings of Grammatophora, between Dr. Greville and Prof. Smith. In like manner the character, the breadth, the relative position and distribu- tion, the distinctness and the number of striae on the valves, although tolerably constant in some species, are, in the majority, Subject to great variation. Then again some naturalists count the number of striae in a given space, as, for example, in the Tºrpth of an inch, whilst others advo- cate counting the entire number in the length of the valve. The latter plan, to all appearance, must afford more certainty, although the trouble of it is much greater; for in the growth of frustules there would seem an expansion of their walls, inducing consequently a displacement of the striae further apart; and observation does not confirm the opinion, that in the imperfectly developed frustules a smaller number exists, which are added to in course of rowth, £ However, just as in the case of the form and size, so, in this matter of the superficial markings, there will be variations according as the frustules result from self-division and are stereotyped impressions of an already existing form, or according as they originate from sporangial frustules and may have an individual idiosyncrasy, or be modified in their development by the locality, and by surrounding circumstances, season and the like. A writer in the Mic. Journ. (1855, p. 309) invites notice to another cir- cumstance –“Sufficient attention has not yet been paid to the sporangial state of the Diatoms. From the observations recorded by Thwaites, Smith, and others, different genera seem to follow different laws on the subject. In Navicula this state appears to be always accompanied by a great dilatation of the frustule, and the formation of a strong line or band between the median line and the margin; sometimes the new line is nearly straight and parallel to the median line, except near the nodule, with which it seems connected ; sometimes it is curved ; but whether both structures occur in the same species, or are indicative of different species, no evidence has hitherto been adduced. . . . . . The striae appear, however, to preserve nearly the same in- clination, to the new or intermediate lines which they did in the non- sporangial state to the median line ; and hence the direction of the striae is not sufficient of itself to distinguish species, however good a character it may afford, unless regard be had to the peculiar state of the frustule.” Prof. Smith has endeavoured to frame some general rules for the guidance of naturalists in instituting generic and specific characters, which we cannot do better than subjoin in an abridged form (J. M. S. 1855, pp. 132-134; and Synops. Vol. ii. p. xxii). In determining specific character, three circumstances are of essential importance: 1. the structure of the valve; 2. the habitat ; 3. the arrangement of endochome in the living frustule. The first can be applied to both living and dead or fossil specimens, and affords the most constant and obvious characters. “These varieties of struc- ture arise from the modes in which the silex combines with the cellulose of OF TEIE DIATOMEAE. 99 the epiderm; and this combination seems to follow certain and invariable laws, which are subject to no derangement from the external circumstances in which the growth of the embryo may take place. The structure of the valve reveals itself in the character of the striation, which may therefore be found a good specific distinction.” Thus the striae may be costate or monili- form, parallel or radiate, reach the median line or be absent from a greater or lesser portion of the surface, &c. The relative distances and the distinct- ncSs of the striae are also other features to be recorded, allowance being made for the influence of localities and of age, and for the fact of their having Originated from the same or from different sporangia. Next to striation in importance is locality, which will often aid to discri- minate between closely allied forms, since fresh- and salt-water species cannot exchange habitats. Locality also seems even more restricted by other external conditions of a more limited nature. Lastly, the arrangement of the endochrome confers a specific character more certain than habitat. Examples of various arrangement of gonimic Substance, and of the large, constant, oil-like globules, have been already given. It follows, therefore, that the difficulty of defining species is much en- hanced where examples occur only in a fossil state. Even in the living state, shape and size cannot be implicitly relied on, but gatherings are re- quired from different localities, and every condition of growth observed, before an average size or a typical outline can be decided on. And although stria- tion is an important guide, it often happens that this feature is so nearly alike in allied species of the simple forms, such as Cocconema, Cymbella, and Navicula, that our determination must be influenced by less important con- siderations, and the habitat, outline, and arrangement of cell-contents all require to be brought under review before we should feel justified in consti- tuting a species. In the construction of genera, the Several conditions (viz. form, size, stria- tion, habitat, and disposition of endochrome) employed in the determination of species are also resorted to. Other peculiarities, however, are noted, such as the transverse or longitudinal lines or bands, indicating thickenings of the valves, the presence of a central spot (umbilicus) or of terminal Ones, and (as Prof. Smith mentions) “the obvious varieties of form or combination to which the cellules submit in the progress of their formation, exhibiting themselves as hexagonal, circular, or irregular in outline, as distinct from each other, or as more or less confluent.” (Synops. Vol. ii. p. xxiv.) Yützing has extensively used the circumstance of the presence or absence, the number and the position of apparent pores, not only in constituting genera, but also the higher divisions, families and orders. The figure of frustules on a transverse scetion, or an end view, is another point he has resorted to in framing his classification. He would, indeed, appear to assign a yet higher importance to the central spot or umbilicus than Ehrenberg him- self, since he has distinguished his tribes Striatae and Vittatºe, respectively, into two orders, Stomaticce and Astomaticº, according as this structural pecu- liarity is present or absent. So, again, in the case of the Navicular frustules, he has constituted Suriyella with some other genera into a family Surirellede, separated from Navicula, Pinnularia, and other genera, and placed in a dis- tinct order of Striatae, because the former group is destitute of an umbilicus (hence Astomatica), which the latter possesses (the Stomaticae). Moreover, as the family Naviculeae, along with others, presented an umbilicus on each valve of their frustule, the term Distomatica, was applied to distinguish them II 2 100 GENERAL IIISTORY OF THE INFUSORIA. from other families having an umbilicus only on One valve—Monostomatica. In this plan, therefore, Kützing assigned to the circumstance of striation an altogether secondary place to that of the existence of a central umbilicus, asserting that the presence or absence of transverse striae was inconstant, and therefore not to be used in gencric distinctions. Meneghini critically reviews Kützing’s system of classification, and points out many anomalies and errors in it. “In the three proposed tribes,” re- marks this author, “We have unnatural dismemberments and associations. The same conclusion prevails also in respect to the six orders, as well as to the ulterior divisions in the first two, taken from the continuity or inter- ruption of the striae and the presence of one or two stomatic apertures” (op. cit. p. 492). For instance, he asserts that the character of the median aperture, given as distinctive of Tabellariece from Striatellect, is absolutely false; and he doubts generally of the presence, constancy, and value of a median aperture in framing such distinctions as Kützing has done. The Actiniscede he would separate from the Diatomeae. Again, proceeding on the principle that no one character can be allowed an absolute value, he divides the Diatomeae into two sections, the Actinisceae and Loricatae. Of the latter he would create 8 families:–1. Eunotiece ; 2. Fragilariede (uniting with them the Meridieae, Striatelleae, and Tabellariede); 3. Melosired, comprising the Coscinodisceae, Tripodisceae, Anguliferae, Bid- dulphieſe, and Angulatae; 4. Cocconeideae; 5. Achnamthede; 6. Cymbelledº; 7. Naviculedº (with all the Surirellede); 8. Gomphonemece (with all the Licmophorea, except the genus Licinophora).” To the presence or absence of an external muc0-gelatinous investment around the silicious frustules, this naturalist gave little weight in framing a classification, reckoning it, together with the existence or not of a pedicle or of concatenation, as scarcely admissible in the identification of species. On the other hand, Prof. Smith has employed these circumstances, con- sidered in relation to the process of Self-division, as the basis of his system of classification. He would look to the phenomena of reproduction as the most sure basis; but in the absence of precisc information, except in a few instances, these are at present inapplicable, and self-division seems to him “ to come next in order, as a most important function connected with in- crease and growth, and to supply the necessary variety of phenomena on which to ground our sectional divisions.” And he thus proceeds to explain his plan (Synops. i. p. xxviii):— “I have therefore separated those forms where self-division is accom- panied by the Secretion of a permanent gelatinous or membranaceous envelope, in which the frustules are subsequently imbedded, from those in which such secretion is altogether absent, or is represented merely by a cushion or stipes, to which the frustules are attached by a small portion of their sur- face; and I have placed the latter, as of simpler organization, in my first tribe, arranging the genera belonging to it into subtribes, depending upon the permanency or otherwise of the connecting-membrane, another product of the self-dividing process. This enables me to place apart those genera whose species present us with frustules in which the union of the cells is dissolved almost immediately upon the completion of self-division, as well as those where a cushion or stipes still maintains a kind of indirect individuality in the divided frustules, from the genera in which the cells cohere after gemmiparous increase, and by such coherence form filaments of various lengths and forms, allotting the latter to subtribes which respectively pro- sent a compressed filament, a zigzag chain, or a cylindrical thread. In the OF THE DIATOMEAE. 101 second tribe, including those genera which have frondose forms, I find cha- racters for my subtribes in the nature of the frond and the arrangement of the frustules. “I do not propose this arrangement as frce from exceptions or even serious defects; but I have adopted it in preference to those hitherto given, as bring- ing more frequently together forms allied in structure and mode of growth, and as being at the same time more strictly in accordance with the external physiognomics of these organisms, and therefore more likely to be appre- hended by the inquirer entering upon the study of this department of nature. A wider study of Diatomaceous forms will doubtless lead to more accurate and more natural generalizations.” We subjoin the systems of classification proposed by Kützing and by Smith. The former is presented in a tabular form— DIATOMEAE. ( * Transverse striae unbroken, Order I. Tamily 1. Eumotieae. ASTOMATICE. 2. Meridieæ, Without a central 3 — 3. Fragilarieae. opening on the * Striæ broken (interrupted) in the median line. Secondary side. Family 4. Melosirca). 5. Surirellea). Tribe I. ſ Having a median aperture on only sia. a. MonoSTOMATICE. { one of the two secondary surfaces. Order II. Family g ‘. STOMATICE. . Achmantheas. With di t } wº ºnal i b. Distomatics. { : CC o:dº ...” ll I'0 OIT ©8,CIl pening. Family 8. Cymbelleae. 9. Gomphonemea, \ ( — 10. Naviculea). ſ Order I. ASTOMATICE. * wº e — 11. Licmophoreae, Withºut median — is sºji. Tribe II. aperture on se- Wittat 3 condary side. lüſºlº, Order II. STOMATICAE. •: With a large dis- || T 13. Tabellarieae. V tinct one. / Order I. — 14. Coscinodisceae, DISCIFORME. — 15. Anguliferae. Tribe III. Order II. — 16. Tripodisceae. Areolatae. APPENDICULATE. — 17. Biddulphiege. Appended doubt-] — 18. Angulatae. V ful forms. — 19. Actiniscego. Smith contains only those genera then The Synoptical Table of Prof. known in Britain ; but since the date of its publication not a few others have been added to the list. CLASS CRYPTOGAMIA. SUBCLASS ALGAE. NATURAL ORDER DIATOMACEAE. Plant a FRUSTULE ; consisting of a unilocular or imperfectly septate cell invested with a bivalve silicious epidermis. GEMMIPAROUS INCREASE, by 102 GENERAL HISTORY OF THE INFUSORIA. SELF-Division; during which process the cell secretes a more or less sili- cious CoNNECTING MEMBRANE, REPRODUCTION, by CONJUGATION and the formation of Sporangia. TRIBE I. Frustules maked ; not imbedded in gelatine nor enclosed in mêm- branaceous twbés. SUBTRIBE 1. Connecting membrane deciduous ; frustules solitary or dw- ring self-division in pairs, rarely in greater numbers, adherent or free, dispersed, or aggregated into a mucows Stratºv. 22 GENERA. Epithemia, Eunotia, Cymbella, Amphora, Cocconeis, Coscinodiscus, Eupodiscus, Actinocyclus, Arachnoi- discus, Triceratium, Cyclotella, Campylodiscus, Surirella, Tryblionella, Cymatopleura, Nitzschia, Amphiprora, Amphipleura, Navicula, Pinnularia, Stauroneis, Pleurosigma. SUBTRIBE 2. Connecting membrane subpersistent; frustw!es after self- division attached by a gelatinous cushion, or dichoto- mous stipes. 7 GENERA. Synedra, Doryphora, Cocconema, Gomphonema, Po- dosphenia, Rhipidophora, Licmophora. SUBTRIBE 3. Connecting membrane evanescent, or obsolete ; frustwles after self-division writed into a compressed filament. 12 GENERA. Meridion, Bacillaria, Himantidium, Odontidium, Den- ticula, Fragilaria, Eucampia, Achnanthes, Achman- thidium, Rhabdonema, Striatella, Tetracyclus. *. SUBTRIBE 4. Connecting membrane subpersistent; frustules after self- division writed into a zigzag chain. 6 GENERA. Diatoma, Grammatophora, Tabellaria, Amphitetras, Biddulphia, Isthmia. SUBTRIBE 5. Connecting membrane subpersistent as a silicious annulus; frustwles after self-division writed into a cylindrical filament. 3 GENERA. Podosira, Melosira, Orthosira. TRIBE II. Frustules invested with a gelatinous or membranaceous envelope. SUBTRIBE 6. Frond indefinite, mammillate ; frustules scattered. 1 GENUs. Mastogloia. SUBTRIBE 7. Frond definite, compressed or globular ; frustules scattered. 2 GENERA. Dickieia, Berkeleyia. SUBTRIBE 8. Frond definite, filamentous ; frustules in rows. 3 GENERA. Encyonema, Colletonema, Schizomema. SUBTRIBE 9. Frond definite, filamentous; frustules fasciculated. 1 GENUS. Homoeocladia. ON THE MODE OF OBTAINING DIATOMEA. PREPARATION or DIATOMAGEous DEPOSITs MIXED WITH MUD OR IN THE FossIL STATE. PRESERVATION or Spp- CIMENS.–Many hints on the obtaining of specimens of Diatomoa are scat- OF TELE DIATOMEAE. 103 tered in previous sections of this history of the Order, particularly in that on their habitats (p. 75); yet, to make the directions complete, additional details are necessary. Where Diatomeae in the living state exist in any considerable number, they usually form a brilliant cinnamon, or sometimes an olive-brown film or patch, and thereby become visible to the naked eye or to an ordinary lens, adherent to various water-weeds, to decayed portions of wood, leaves, or other floating Substances, or as a patch on the mud at the bottom, or other- Wise floating on the surface of the pond as a scum or film. Besides such positions and such collections, Diatomeae exist diffused more or less abun- dantly through the water or in the mud itself (see p. 75 et seq.). When secn adherent to an aquatic plant, the process of collection is very simple—by carefully gathering or removing the plant from the water and Washing it to detach the Diatomaceous frustules, if these cannot be more advantageously viewed whilst still adherent to its stem or leaves. So, too, where, mostly in conjunction with other organisms, the Diatomeae float in mass, like a scum on the surface, nothing is easier than to lightly skim the collection from the surface. But when the layer of frustules reposes on the Surface, or is more or less intermixed with the mud, some additional pre- cautions are required in their collection, unless indeed the film has sufficient tenacity, by cohesion of its component frustules, as in the case of Schizonemea, to allow of its being raised en masse upon Some thin flat instrument, a spoon Or spatula, insinuated beneath it. The general methods of collection applicable to the DCSmidieæ and other minute Algae are equally so to the Diatomeae, whilst various modifications will suggest themselves to the mind of every practical naturalist to meet the varying circumstances under which he makes the collection. Mr. Ralfs has kindly furnished us with notes on this point. He writes—“It is often difficult to procure clear specimens of those species which form strata on mud; most of thom, however, can be obtained, tolerably free from the mud on which they congregate, by the following method, which is applicable both to those found in marine situations and to those gathered from the Wayside. When the water is somewhat dried up, if the finger be pressed upon the stratum with a gentle force, the Diatomaceæ will adhere to the finger, and may then be removed by scraping them off upon a piece of linen folded over the edge of a tin box or of a knife; by repeating this process, a sufficient quantity can easily be collected. At first, probably, a portion of mud, espe- cially if very wet, will also be taken up; but a little practice will soon show the force requisite for places where the water is plentiful, and for those where it is nearly dried up. Specimens thus collected can be prepared for mounting with much less trouble than if gathered mixed with a large quan- tity of dirt.” When it is wished to capture frustules diffused in water, a piece of muslim may be used as a filter, just as for Desmidieæ, and the residue left upon it examined as it is, or, if required, washed, to detach foreign matters mixed with it. Whore some admixture of mud is unavoidable, frequent Washing of the collected substance will often suffice to separate sufficiently the silicious frustules from the other particles—the heavier grains of Sand sinking to the bottom of the vessel, while the Diatoms are still suppended in the fluid ; and on the other hand, the decayed organic and other matters, lighter than the frustules, will remain in the supernatant liquid after the latter are precipi- tated. Repeated careful decanting and washing may be all, therefore, that is required. Another method applicable to recent living specimens, dependent on the 104 GENERAL HISTORY OF THE INFUSORIA, tendency towards the light, at least, of many species, may be adopted by placing the half-liquid mud in shallow pans or plates in the Sunshine, when many species may be found to rise as a film on the surface, or to congregate near the edge or sides of the vessel. When the frustules are much intermixed with mud, which is, under Cer- tain circumstances, inevitable, various plans have been adopted for separating them for examination. Mr. Okeden details the following plan, which, with certain modifications to be mentioned, has been described also by Dr. H. Munro :— “The plan” (J. M. S. 1855, pp. 158, 159) “ consists in making the deposits fall through a constant depth of water, in various periods of time; thus dividing the Diatoms, according to their sizes, into portions of several dif- ferent gravities.” It is thus carried out: “Take about a cubic inch of the clay to be examined, digest it for about four hours in strong nitric acid at a moderate temperature; now add gradually an equal quantity of hydrochloric acid, effervescence takes place, a further action on the clay ensues; keep boiling for about three hours more, occasionally stirring, and then allow the mixture to cool and settle down, which it will do in about an hour; pour off the Superfluous acid and wash the residuo repeatedly with water, so as to get rid of the remaining acid. “The next operation is to divide the sediment into portions of various specific gravities: for this purpose it is necessary to have several beakers, about 3 or 4 inches in height, and about 1% to 2 inches in diameter; also One very large beaker, about 6 to 9 inches in diameter: we will call the large beaker A. Now transfer the sediment into one of the small beakers, and pour in water till there is just 2 inches depth of water in the glass. Stir, and let stand half a minute by the watch, and then pour off carefully into the large beaker A ; repeat this about half a dozen times, each time pouring off into A all that does not fall through the 2 inches of water in the half- minute, and at last the small beaker will contain only what falls through 2 inches of water in half a minute. Now let A stand about half an hour, pour off carefully, and transfer the sediment in A to another small beaker; put 2 inches of water with it, stir and let stand for 2% minutes, then pour off into A. Repeat this about six times, and there will now be another small beaker containing all that falls through 2 inches of water in 24 minutes, while in A is all that does not fall through that distance in that period. Let A stand half an hour, pour off and transfer the sediment to another small beaker, stir and let it stand five minutes, pour off into A as before, and repeat this as before about six times. There is now another beaker, containing all that falls through 2 inches of water in 5 minutes. After this I do not divide them any further, but call the last remainder, or what remains in A after it has stood its half-hour, ‘Not in five minutes.” Thus we have four different glasses, containing Diatoms and clay mixed, of four different densi- ties: thus, 0 to #; } to 2% ; 2% to 5; not in 5. There is now a method of concentrating the coarsest of these sediments, namely the 0 to #, the , to 2}, and sometimes the 2% to 5. It consists in taking the beaker containing the sediment and pouring about an inch of water on it. Let it settle about 5 minutes, and then place the glass on a table, and impart a whirling motion to the whole by moving it round and round, when the greatest portion of the Tiatoms will rise up in a sort of eddy, while the particles of mud or sand Will remain at the bottom, even though they are of the same specific gravity as the Diatoms, and have fallen through the same distance of water in the same time. This is because the Diatoms are mostly flat and thin, while the particles of sand and mud are round; in the same way, if we take a round OF THE DIATOME ZE. 105 pebble and an oyster-shell both of the same weight, and throw both hori- Zontally into the water, the pebble will reach the bottom sooner than the oyster-shell. So, when the whirling motion is imparted to the glass, the thin flat shells of the Diatoms will rise up in a cloud, while the round particles of mud and sand will remain behind; when the cloud rises up, pour it off quickly and dextrously into another glass, and, if necessary, repeat the process; and a little practice will enable the operator to separate all the Diatoms most effectually. I have said before that this process will only apply to the 0 to #, # to 24, and sometimes the 2# to 5 sediment, but not to any finer one; practice will soon teach this. The ‘not in 5' cannot be concentrated—it is too fine, and the whole rises together on imparting the whirling motion to it. “It is not necessary to abide invariably by the divisions of time which I have given here. “These must be varied, of course, according to the nature of the clay to be examined. For instance, in a clay I have recently tried from 34 feet below the bed of the river at Cardiff, nearly the whole of what was left after the 0 to # fell in the # to 2%. I therefore divided it thus: 0 to #, # to 1%, and 1} to 24; a little practice will soon teach this. “The advantages of the plan are, I think, obvious. In the first or coarsest sediments we get all the larger and finer Diatoms by themselves, unmixed with, and consequently unobscured by, the innumerable smaller ones and the fine particles of mud and sand, while, if any of them, such as the Eupo- disci or Campylodisci, are rare, they are sure to be found in either the first or second division of densities, and by their being concentrated and brought as it were into a small compass, the detection of them is easy and certain. “In the next division, or the 2% to 5, we shall find the moderate-sized Diatoms; and lastly, in the ‘not in 5,’ we get a mass of the remaining and smaller Diatoms, all of which small ones are themselves the more readily seen and identified when separated from their larger brethren. “I would venture to add, moreover, that I think the examination of these deposits for the various species is much facilitated, as the slides containing the 0 to 1% sediment may be czamined with the inch objective, the #-inch will do to examine the 1% to 2% and 2% to 5, while the #-inch need not be used till we come to the ‘not in 5;’ whereas, were they all mixed, the +-inch would be required to examine the whole. “I should add, that what is poured off the large beaker A, after it has stood the half-hour each time, may be flung away and the sediment only transferred to the small beakers, as from the large size of it there will rarely be more than 2 inches depth of water in it, and half-an-hour is ample time to ensure every diatomaceous particle falling to the bottom and being pre- served and detected in one or the other of the divisions.” Dr. Munro's plan is a variation of the above procceding, and is thus de- tailed (J. M. S. 1855, p. 242): “I first boil the deposit in strong hydrochloric acid for five or ten minutes, then allow it to subside, pour off all the acid, and by a few washings get as much of it away as possible ; then treat the deposit in the same way with strong nitric acid, Washing the deposit by repeated washings to get rid of the remaining acid. When this is done, I then sepa- rate the Diatoms according to their different gravities by allowing them to pass through a column of water in the following manner:— “I take a long glass tube about four feet long and half an inch in bore. At the bottom of this tube is fixed a stop-cock to enable me to let out any of the Diatoms during any stage of the process. Having nearly filled this tube with distilled water, I pour in my deposit washed free from the acids. I watch the deposit as it falls slowly and gradually down the tube, and with a 106 GENERAL DIISTORY OF TILE INFUSORIA. Coddington lens can easily detect the larger Diatoms as they are precipitated. In about a quarter of an hour, many of the larger forms will have doscended to the bottom of the tube. By turning the tap at the bottom of the tube, I let out a drop of the mixture on a slide, and examine it with a low power (#-inch); and if it be tolerably clear, and the Diatoms of one character, Ithon let off five or six inches of the mixture into a tost-tube, and sot it asido for re-examination after the Diatoms have subsided. In a quarter of an hour more, I again let off into another test-tube six or cight inches more of the mixture, and place it aside to settle. In half an hour more I lot off into another test-tubo six or eight inches of the mixture, which will contain the finer Diatoms by themselves, generally free from all mud and sand. I then pass each of these Washings again through the long tube of distilled watcr; and by CXamining the mixture during the process of its subsidence, I am enabled to let out the heavier particles of sand or mud, and to obtain pretty clean all those Diatoms which are alike in size, or at all events in specific gravity. Some Diatoms tako a longor timo than others in settling to the bottom of the tube, and separating themselves from Cztrancous matter, such as the Nitzschia, Clostérium, &c.; but, by a little patience, and an extra washing through the tube, those difficultics may, in a great measure, bo overcome. By this method, I have found the Pleurosigmata, Pinnulariae, Surirellae, and Symedraº very well separated, those of a like character being found together. I have becn stimulated to send these fow remarks on tho washing of Diatomaccae, on account of the great difficulty I have hitherto experienced in procuring slides frce from mud, sand, and other cztraneous mattors.” Mr. Okoden offers the following plan for obtaining specimens imbedded in mud at considerable depths, in making borings for engineering purposes. . He prefaces the description of his apparatus by that of the usual boring ap- paratus, which “consists cssentially of any number of iron rods” (J. M. S. 1854, p. 26), “which screw onc into the other; to one of these is scrowed an auger or a chiscl-point, as the case may require. This is inserted into the ground to be tested, and worked round by manual force and downward pres– Sure, length after length of rod being added as the ground is penetrated. In addition, them, to this apparatus, I obtained, first, several lengths of wrought- iron gas-pipe, about an inch in diameter, and each screwing into the other; and also a similar number of iron rods, cach a ſow inchcs longer than the lengths of gas-piping, and each also screwing into the other : to the end of one of these lengths of rod is attached a cork of the eacact diameter of the gas-pipe, or a trific larger. This cork is fixed by a washer and nut. The gas-piping should be in lengths of about 8 feet cach, as this is the most con- venient in work : one of these lengths should also be again divided into two parts, which must, however, screw and unscrew; and this length is to be the one first put into the ground or mud, for reasons which I will presently explain. “The mode of proceeding is as follows: First, a hole is bored to the required depth—say 20 feet—with the usual boring apparatus; this done, the appa- ratus is drawn out, the jointed length of gas-pipe is now introduced,—the end of it, with the rod to which the cork is attached, having been previously stopped, the rod passing up the centre of the gas-pipe; this is let down the hole, another length of pipe being attached, and another length of rod, and so on, length after length of pipe and rod, until the bottom of the hole is reached. We shall thus have a continuous length of gas-piping, which will be penetrated by a continuous length of iron rod attached to the cork at the end of the pipe. It is obvious that this cork will entirely prevent any foreign OF THE DIATOMIE ZE. 107 matter from entering the gas-pipe. Having thus reached the bottom of the hole, now pull up the cork into the gas-pipe about 4 feet, by means of the rod attached to it, and then press the whole apparatus into the soft mud. The pressure will now drive the mud up into the pipe as far as the cork is drawn up. Now remove the whole apparatus, and by means of the rod push the cork back again to the end of the last longth of pipe, when the charge of mud will be driven out in the form of a sausage; and by rejecting the two ends of it, and taking only the middle piece, we may be perfectly sure that the mud at that depth, and that only, has been obtained. “Having secured the prize, the short length of piping which contained it is now to be unscrewed, and carefully washed with a common gun-cleaning rod and some tow, when it is ready for another experiment. “With this apparatus, then, I have penetrated Neyland mud in various places to depths of 20, 30, and 40 feet.” The Diatomca existing often so abundantly in Guano may be separated on a simpler plan to that pursued in the case of sedimentary deposits and col- lections of fossil specimens. The proceeding is always preceded by several washings in clear water, and by pouring it off carefully, after allowing a sufficient time ſor the insoluble and more weighty particles to subside. The subsided matter is then treated with hydrochloric (muriatic) acid several times, a due interval being allowed for the cessation of offervescence and for the solid particles to settle before the decanting of the liquid and the ap- plication of a fresh quantity. When the muriatic acid ceases to produce any chemical action, as ovidenced by effervescence, nitric acid should be substi- tuted and used in a similar way two or throo times, and the mixture raised to nearly or quite a boiling heat, after which the powder collected at the bottom of the vessel—a comical one should, by the way, be preferred, such as chemists know by the name of “precipitate glasses *—is to be washcd re- peatedly in pure water. The resultant substance will be ſound to be com- posed of silicious particles, which are cither Diatomaccous frustules or the silicious spicules of Spongcs. Prof. Bailey, in a recent number of Silliman's Journal, 1856 (p. 145), re- commends the following method of cleaning Diatomaccous deposits, as more speedy and efficacious than any other he has tried, whether mixed with soundings, guano, or with mud, &c.:—“I)issolve out the lime compounds, if present, by means of nitric or hydrochloric acid, wash, and filter. Then put the moist contents of the filter into a porcelain capsule with enough strong sulphuric acid to make the whole a fluid mass. Heat the capsule over a spirit- lamp until the organic matters are all charred, and continue the heat until strong acid fumes are evolved. Kocp the capsule hot, and add, in minute portions at a time, finely powdered chlorate of potassa. If the acid is hot enough to give oſſ ſumos, the chlorate will be immediately decomposed with- out the accumulation of cxplosive gases, and it will excrt so powerful an oxidizing action, that in a few moments a carbonacoous matorial as black as ink will become perfoctly clean and colourless. Nothing now Will romain to be done but to wash off the acid, which is best dono by the addition of water and repeated decantations. I would also advise that the materials thus cleaned should not be dried, but should be kept in bottles with a little alcohol, which provents their felting togethor, and does not allow the growth of the byssoid plants which often develope in wator. “It is necessary to caution those not familiar with chemistry against using the chlorate of potassa with Sulphuric acid in any othor way than above di- rected, as violent and dangerous Cxplosions might result. The process as above given is porfectly safe and very offective.” Another plan of separation of the shells of Diatomcø or of Foraminiſera 108 GENERAL IIISTORY OF THE INFUSORIA. is successfully adopted by Prof. Bailey and D’Orbigny, and is thus described by the former (Proceedings of American Assoc. for the Advancement of Science, 1849, p.409):—“Where the mixture of inorganic matteris in large propor- tion to the Infusoria and other microscopic Organisms, and corresponds nearly in specific gravity,” the deposit is to be thoroughly dried, whereby the minute unbroken shells will become filled with air, and consequently when rapidly stirred up with water they will be buoyed up, and continue suspended after the intermixed sand has settled at the bottom. They may then be easily re- moved from the surface and transferred by alternately touching the surface of the water with the finger, and the glass slide on which they are to be placed. The sediment, if dried again, will often yield another abundant supply of the minute shells. “By the above means,” adds Dr. Bailey, “I have obtained exquisite specimens from the bottom of dried-up ponds, from the sands of harbours, and from the mud attached to floating ice in the Hudson River, materials presenting the two extremes of very coarse gravel and the finest sediment, neither of which would have given good results by any other process.” In the case of some deposits the shells of the Diatomaceae are so far the chief constituents, that no preparation is needed before subjecting them to microscopic investigation. The cohesion of Diatomaceous deposits is at times so great that a difficulty is encountered in separating them. A method of dealing with such is de- tailed by Prof. Bailey (Sill. Journ. 1856, p. 356):—“Many masses of fossil Diatomaceae are so strongly coherent, that they cannot be diffused in water (for the purpose of mounting in balsam) without a degree of mechanical vio- lence which reduces to fragments many of the most beautiful and interesting forms. This is particularly the case with some specimens from the ‘infusorial deposits' of California. Some of these I endeavoured to break up by boiling in water and in acids, and also by repeated freezing and thawing when moist- ened, but without good results in either case. At last it occurred to me that the adherence might be due to a slight portion of a silicious cement, which the cautious use of an alkaline solution might remove without destroying any but the most minute shells of the Diatoms. As the case appeared a desperate one, a “heroic remedy’ was applied, which was, to boil small lumps of the Diatomaceous mass in a strong solution of caustic potassa or soda. This proved to be perfectly efficacious, as the masses under this treatment rapidly split up along the planes of lamination and then crumbled to mud, which, being im– mediately poured into a large quantity of water, ceased to be acted upon by the alkali, and gave, when thoroughly washed, not only all the large shells of the Diatoms in a state of unhoped-for perfection, but also furnished abum- dance of the minute forms. Having obtained by this method highly satis- factory results from specimens from many localities, I can confidently recom- mend it as an addition to our modes of research. “The following directions will enable any one to apply the process:—Put small lumps of the mass to be examined into a test tube, with enough of a solution of caustic potassa or soda to cover them; then boil over a spirit-lamp for a few seconds, or a few minutes, as the case may require. If the solution is sufficiently strong, the masses will rapidly crumble to mud, which must be poured at once into a large quantity of watcr, which, after subsidence, is re- moved by decantation. If the mass resists the action of the alkaline liquor, a still stronger solution should be tried, as, while some specimens break up instantly in a weak solution of alkali, others require that it should be of tho consistence of a dense syrup. The mud also should be poured off as fast as it forms, so as to remain as short a time as possible in the caustic loy. “The only specimens which I have found not to give good results by the OF TELE DIATOME ZE, 109 method above described, are those from Tampa Bay, Florida, and the infu— sorial marls from Barbadoes. In the masses from Tampa, the lapidification is so complete that the alkali destroys the shells before the lumps break up; and in the case of the Barbadoes marls the cementing material is calcareous, and requires a dilute acid for its removal. In applying the above process, one caution 1s necessary, which is to thoroughly wash the shells with water, and not with acids, as the latter will cause the deposit of a portion of the dissolved silica, and materially injure the beauty of the specimens. When the washings are no longer alkaline, the specimens may be thoroughly cleansed by acids, or by the chlorate process described above.” * * A very ingenious plan of getting transverse and oblique Sections of Dia- tomaceous shells is mentioned by Schleiden (Principles of Botany, translated by Lankester, p. 594), which is precisely similar to that for obtaining trans- verse sections of hair, as first given in Pritchard’s Microscopic Objects. It consists in mixing any very pure deposit with mucilage, and, before the mixture is completely hardened, cutting off delicate slices with a razor or sharp knife. The preservation of Diatomeae for examination is, on account of their silicious composition, easy; and it is only in the case of the stalked, fila- mentous, and frondose species that any special arrangements are necessary— except, indeed, those demanded in order to mount them as permanent micro- scopic preparations. - Before the structure of the silicious epiderm can be made out, the endo- chrome of living specimens must be destroyed, which can be effected by heat- ing the frustules on a piece of talc or platinum-foil. But where it is wished to preserve them in a fresh state, so that their natural living appearance may as far as possible be retained, immersion in creosote and water is recom- mended by Mr. Shadbolt. Prof. Smith, however, finds distilled water supe- rior to any mixture, which is not merely unnecessary, but injurious. “If,” says the author last mentioned, “the filamentous and stipitate forms are not mounted in a fresh state, the frustules separate from each other, part from their stipes, and lose their characteristic appearance. To remedy these in- conveniences, I immerse such specimens as cannot be placed in cells when freshly gathered, in spirits of wine and water, one part of the former to six of the latter; and their attachment to their stipes remains afterwards undis- turbed, unless violence be employed to separate them.” Eossil, and chemically-prepared and dried specimens are usually preserved in Canada balsam, which is heated and rendered fluid, so that it enters within the cavity of the frustules. The fluidity of the balsam is increased by the addition of a little turpentine or rectified spirit. The presence of balsam, however, obscures the markings of the silicious epiderm; and it has been found better, where the resolution or determination of the superficial sculp- turing is very difficult, to mount the frustules, in a dry state, on a thin object-glass, and under cover of a very thin piece. “To prevent the admis- sion of moisture, which would ultimately make its way to the object and de- stroy its value, it is indispensable that the cover should be cemented to the thin glass below.” (Synops. i. p. xxxii.) In a collection of Diatomeae, we may, by a magnifier, such as a Coddington lens, select certain specimens from the rest to be mounted. This can be effected, when the size permits, by the projecting terminal hairs of a fine camel-hair pencil, or by the moistened tip of a needle ; but if the shell be too minute for this, a single stout hair or bristle will frequently suffice, and more satisfactorily and readily if the hair be split at the end. Prof. Redfern, of Aberdeen, pointed out the advantage of split hairs for the purpose, in a brief communication to the J. M. S. 1853, p. 235. He recommends a hair, split 110 GENERAL EIISTORY OF THE INFUSORIA. into three to five or six parts at one extremity, to be fixed by the other in a piece of cork, and held in a common needle-holder. Such split hairs are com- mon enough in an old shaving-brush ; but the divergence of the split portions should be so slight that, until pressed upon, the hair should appear single and unbroken. He has also found entire hairs very useful when set in needle- holders in a similar manner. The split hairs act like forceps, expanding by pressure so as to embrace the object, and closing upon it by their elasticity when the pressure is withdrawn. To select certain portions of a collection of Diatomeae from others, Dr. Carpenter gives these directions (The Microscope, p. 340):-‘‘ Either of the two following modes may be put in practice. A small portion of the sedi- ment being taken up in the dipping-tube, and allowed to escape upon the slide, so as to form a long narrow line upon it, this is to be examined with the lowest power with which the object we are in search of can be distin- guished; and when one of the specimens has been found, it may be taken up, if possible, on the point of the hair, and transferred to a new slide, to which it may be made to adhere by first breathing on its surface. But if it be found impracticable thus to remove the specimens, on account of their mi- nuteness, they may be pushed to one side of the slide on which they are lying; all the remainder of the sediment which it is not desired to preserve may be washed off; and the objects may then be pushed back into the middle of the slide, and mounted in any way that may be desired.” See GoRING and PRITCIIARD’s Microscopic Illustrations, Microscopic Cabinet, and Micrographia for much original information on these matters. OF TITE PITYTOZOA. 111 SECT. II.—OF THE PHYTOZOA. (Plates XVIII. XIX. XX, and XXVI.) THE BEINGS INCLUDED UNDER THIS NAME: THEIR GENERAL CIIARACTER,- DIVISION INTO GROUPS OR TRIBES.–TIIE collection of microscopic beings we would comprehend under the term PHYTozo A comprises most of the Amentera of Ehrenberg, with the exception of Amoebaea, Arcellina, Dinobryina, Bacil- laria, Closterina, Peridiniata, and Cyclidina. After excluding these families, there remain Monadina, Cryptomomadina, Hydromorina, Volvocina, Vibri- onia, and Astasiaea, which, although they exhibit great diversity among themselves, nevertheless have certain characters in common, whilst their mutual differences in essential particulars of organization and vital endow- ments are less than those separating them from the ciliated animalcules. On the other hand, they—at least the majority—exhibit very marked genuine affinities with the DIATOMEE and DESMIDIEE as plants. In point of fact, these organisms stand on the confines between the animal and vegetable kingdoms, some genera distinctly belonging to the latter, others doubtfully to the former, whilst many pass through such phases of existence that at one time they assume the characters of animals, at another those of plants. This apparently mixed animal and vegetable nature is expressed by the term Phytozoa, derived from two Greek words, signifying plant–animals. Another term, used by Perty, viz. Phytozoida, is a simple expansion of the word Phytozoa, signifying literally animal-like plants. Cohn employs in its stead the term Flagellata, derived from the locomotive organ or flagellum which most species possess, whilst others prefer the word Flabellifera. In the opinion of the majority of modern writers, the Phytozoa are in general undistinguishable from unicellular Algae, among the different families of which they consequently seek to distribute them ; and doubtless the creation of such a group is purely artificial, and cannot be admitted in any attempted philosophical or natural classification of microscopic organisms. However, since so much uncertainty and dispute still prevail on the question of the animal or vegetable nature of very many, and since our knowledge of the phases of existence of a large number is so imperfect, it is really impos- sible to establish any satisfactory classification. On this account, and also to bring together for convenience’ sake a mass of information rospecting several collections of beings enumerated among the Amenderous Polygastrica of Ehrenberg, difficult or impossible to arrange under any other heading, we resort to this artificial division, and in so doing have the example of Perty and other writers. After describing what can be predicated of the Phytozoa in general, we shall find it necessary to consider them under soveral sections or tribes, by reason of the differences which prevail among them in form, mode of growth, and other particulars; and in Speaking of each tribe shall point out its general affinities to the others, and to any families of Infusoria or of Algæ. EIGURE. CovCRINGS OF PHYTozo A.—The Phytozoa are of more simple organization and of less varied outline than the ciliated Protozoa. In figure they are commonly round, or oval, or elliptical, and either present no processes, 112 GENERAL EIISTORY OF TELE INFUSORIA. or only an elongated neck bearing one or more cilia (flabella) to serve as locomotive organs. & Bow greatly their figure and size are dependent on the external influence of light, is well shown by some recent researches of Cohn on Stephanosphaera (Nov. Act. Acad. Curios. xxvi. 1857). On placing specimens of this organism, some in transparent glass vessels, others in Semitransparent and green ones, others in porcelain, and others again in perfoctly opaque cups, the modifica- tions in size and figure, according to the intonsity of light they received, were altogether incredible. In the opaque vessels, where they got little light, the green cells remained delicate, small, and widely dispersed, whilst in the transparent glasses, under Sunlight, they became many times larger and crowded together, and their figure fusiform, irregular, and produced into numerous protoplasmic processes. Indeed, on placing two portions of the same collection of Stephanosphaera-globes, the one in a transparent, the other in an opaque vessel, the Swarming individuals in the two will be found so unlike that they might be readily conceived to be different species. The outline is fixed where the organism has a firm envelope; and most of the Phytozoa have such in one phase of their existence, viz. when they undergo the encysting-process. We are not acquainted with the entire history of many genera; but from what we know of some, we may argue by analogy of all, that in the earliest stages of existence these cellular organisms have no distinctly organized wall, although they may have a pellicle derived from the contact of the protoplasm, of which they consist, with Surrounding media, a mere superficial induration, but no separable membrane. Such is true of the individual cells of Volvoa (XX), of Euglena (XVIII. 45, 46), and of Monads (XVIII. 1 to 28) in general. Subsequently a cell-wall, the primordial mem- brane or sac, may be produced, distinct and separable from the contained Substance. Furthermore, many examples do not stop here, but proceed to throw out a second wall exterior to the last-named, separated frequently from it by a small interspace, and having a much denser and firmer consist- ence. The cell, or, as Prof. Henfrey calls it in the case of Pandorina, the gonidium (XIX. 61), encloses itself, in fact, within a cyst (XIX. 69), and in so doing mostly alters its form materially, loses its previous animal characters, becomes ‘still,’ and at the same time qualified to sustain life under various adverse external influences, and to continue the species by an ulterior act of development. In all this we trace an exact parallel with the history of the spores of the lower Algae; and there is no question that many of the Phytozoa are no other than spores, sporozoids, or zoospores. Moreover, it is equally clear that many Momadina and Cryptomonadina described by Ehrenberg are but two phases of one and the same organism. Not a few Phytozoa present an additional covering in the shape of a muci- laginous layer. This is found in isolated species, as Protococcus pluvialis, and generally in all the aggregated forms; indeed, it is the principal agent in the construction of the latter. It has generally been assumed that this mucilaginous investment is an extracellular product, without a definite bound- ary ; but Cohn (on Protoccocus, R. S. 1853) has a long argument to prove that the true cell is represented by it, conjointly with the included, coloured, apparent cell. Thus, he writes (p. 531)—“Neither of these bodies are true, perfect cells, inasmuch as the first wants the primordial utricle, and the second is without the true cell-membrane. The two together would represent the perfect cell.” Again, it is stated in the same page, “that the internal globular body is not surrounded by any special cellulose-membrane, but only by one readily destroyed by chemical or physical agency—probably nothing more than a dense layer of protoplasm. On the other hand, the external membrane OF THE PIIYTOZO.A. 113 represents a true cell-membrane, enclosing between itsclf and the coloured substance a colourless aqueous fluid, probably pure or nearly pure water.” And in the subsequent considerations of this structure, Cohn appears to arrive at the conviction that the internal coloured body generally spoken of as the cell, the actual unicellular organism, represents the nucleus of a cell, of which the periphery of the mucous envelope is the boundary. In this interpretation of the nature of the mucilaginous envelope, Prof. Williamson concurs. Indeed this accurate observer proceeds, further, to show that there is in the case of Volvoa, a true cnclosing delicate membrane to Cach cell, and that the hexa- gonal form is owing to the mutual pressure of the aggregated cells (Pl. XX. 38). In aggregate forms, such as Volvoay, Goniwm, Pandorina, &c., an additional common Cxternal membrane would seem to be thrown out, to unite together into one symmetrical whole the various members of the colony. Perhaps it should be rather called a pellicle than a membranc, seeing that its independent existence as a separable structure cannot be demonstrated: yet it has a power of resistance; for when external force is applied to a globe of Volvoas, the surface, though at first depressed, presently recovers itself by an innate elasticity; and in the case of Pandorina it seems so resistant and firm that it does not indent on pressure (XIX. 61). CELL-CONTENTS.—The fluid distending the mucilaginous envelope around most Phytozoa, in One or other stage of being, is, according to Cohn, as above noticed, probably pure water. This opinion Prof. Williamson does not enter- tain; for he says (J. M. S. 1853, p. 55) “it is apparently mucilage. In a preparation in which a number of these objects [of Volvoaz) are mounted in dilute alcohol, this gummy matter has changed to a brown colour, and refused to mingle with the alcohol, as would be the case Supposing it to be mucila- ginous. This proves that it is a true Secretion from the organism, and not merely water absorbed by endosmosis. . . . . The Secretion itselfis, perhaps, little more than a diluted condition of the Same gum as that which is more or less completely converted into cellulose in the various investing membrancs.” The central globule, or the whole recognized Organism where a mucilaginous envelope is not present, consists of a mass of protoplasm. At first it is homo- geneous and without colour; Subsequently it becomes generally coloured and granular ; but very shortly the included matters gather together into a sort of layer subjacent to the surface, and leave the central part clear, sometimes so completely so that it assumes the appearance of a vacuole. This substance moreover has the property of contractility inherent in it, and would seem, in all essential circumstances, homologous with the simple contractile matter— the sarcode of animalcules. Like the lattor, it may hollow itself out into vacuoles at any part; and such, says Cohn (R. S. p. 535), “are present in all young cells, and play a considerable part in cell-division and the Sap-currents.” The property of contractility is singularly displayed in the case of the actively moving zoospores or sporozoids of the Algae, and in the motile form of Proto- coccus, i. e. in every instance where, from the absence of more or less inelastic membranes, it can exhibit itself. The vacuoles of the protoplasm occur in varying numbers, and change or disappear from time to time: within they contain an aqueous fluid. The contractile protoplasm is itself colourless; yet, except in the carliest stages of dovelopment, it partakes of a groom or a rod colour, Jr of both theso colours together, save in one spot, which in oblong forms is situated at one end, and in the projection or beak (proboscis, Ehr., or rostellum) extending from the anterior extremity. “It appears,” says Cohn (R. S. p. 536), “as a delicate, almost imperceptible layor constituting the outer boundary of the coloured primordial cell, the periphery of which then becomes sharply de- I 114 GENERAL EIISTORY OF TDIE INFUSORIA. fined, and, as it were, surrounded by a delicate transparent membrane.” The green colour is due to chlorophyll vesicles and granules, either diffused or collected in a layer just beneath the surface. Among other contents are also starch-granules without colour, and very frequently globules of oil. Green or red may exist alone : but more frequently green prevails; and the red pigment, sometimes termed erythrin or erythrophyll, is seen only at one spot, occasionally at the centre, but usually on one side of it, or at one ex- tremity: when occupying the position last-named, it was looked upon by Ehrenberg as an eye-speck or organ of vision. Although, as Cohn (op. cit. R. S. p. 528) tells us, the green and red colour- ing matters differ in chemical and physical conditions, yet the one passes into the other. The red or brownish-red colour is formed when the cells become drier; but neither deficiency of water nor the influence of light appears to be the exclusive cause of the transition. It is especially in the transition to red that vesicles of an oily aspect make their appearance. Indeed, that oil is really formed, is supported both by analogy with the spores of many Algæ which clearly Secrete that substance, and by the vesicles in question having a similar refraction to oil, and behaving like it with alcohol and ether. “The forma- tion of fixed oil,” says Braun (Rejuv., R. S. p. 200), “is intimately connected with that of starch in the economy of cell-life; its appearance, in like manner, announces the repose of age in coll-life; its disappearance, the beginning of rejuvenescence. We meet with fixed oil in the cells, either mixed with starch, substituted for it, or gradually displacing it; its occurrence is porhaps still more general than that of starch. . . . Like the latter, it is met with in greatest abundance in those parts in which vegetation is destined to rest and to await a future re-awakening;” and such are the resting-cells of Phytozoa, in which a red colour predominates or exists alone. Braun furnishes an illustration of this in his remarks on Chlamydomonas during its sleeping or resting state (op. cit. p. 214). The opinion, moreover, that the so-called red eye-specks of Phytozoa are no other than drops of oil, is shared by Perty (p.117) and by Nägeli (Einzell. Alg. p. 9). Speaking of Protococcus, Cohn remarks (op. cit. p. 526), “The red and the green portions of the contents appear to be of equal physiological importance . . . . When still or motile cells are brought into contact with a very weak watery solution of iodine, they become internally, in most parts, of an intense violet or blue colour.” Yet he does not believe this colour to depond, in all instances, upon starch; for the red contents are equally coloured blue, and he therefore surmises there may be some other substance besides starch ex- hibiting the same reaction with iodine. Besides diffused chlorophyll-particles, to which the green colour is due, one, two, three, or more large nuclear-like vesicles exist in Phytozoa-indeed, in unicellular plants generally—described by Nägeli under the name of ‘chloro- phyll wtricles or vesicles.’ The number of such in any genus seems commonly to be constant : thus, in Stéphanosphaera there are two ; in Gonium only one. However, they are occasionally absent, chiefly so in more minute examples. In Protococcus (Chlamydococcus), Cohn says they occur principally in the green cells, to the number of one, two, three or more, having the appearance of minute green rings, about 0.002” in diameter—the interior being sometimes darker, at others more clear, and frequently almost opake. Nägeli regarded them as minute membranous vesicles, containing a mucus coloured by chloro- phyll. Cohn imagined that in Protococcus they stood in connexion with the division of the cell, but could not determine with certainty that their number corresponded with that of the secondary cells. Kützing looked upon them as gonidia or cell-nuclei, concerned in the propagation of the individual. . OF THE PIIYTOZOA. 115 Ehrenborg entertained a similar notion, and called them the testes. “Caustic potash,” says Cohn (A. N. H. 1852, x. p. 340), “which destroys thorest of the contents of the primordial cells, makes the chlorophyll-utricles of Stéphano- sphaera show themselves more distinctly as hollow rings surrounded by a rather granular membrane ; iodine colours them deep violet, which leads to the con- clusion of the presence of starch.” Iodine sometimes, however, produces a deep brown tint (Cohn, R. S. p. 529), due, we may suppose, to an ulterior meta- morphosis of the starch, as it is itself a transitional condition of chlorophyll. Another structure met with among the contents of Some of the Phytozoa is the contractile vesicle or sac. This sac has been noticed in Volvoay, Gonium, Pandorina, Chilomonas, Cryptomonas, and in Chlamydomonas, and its rhyth- mical contractions observed (XIX. 16, 33; XX.40, 41). In Stephanosphaera a similar vesicle was seen by Cohn, but its contractility not detected: so in Astasia, Euglena (XVIII.), and Polytoma (XX. 1, 2), a clear sac-like space presents itself at the anterior extremity, immediately beneath the surface ; but its alternate expansion and contraction have not been witnessed. A nucleus is detected in Euglena, Astasia, Polytoma (XX. 1, 2, 3), and others in which an animal nature predominates. Even among the vegetablo genera Volvoas, Pandorina, and Gonium (XIX. 32, 34, 61), most writers, as already scen, secm disposed to view the constant chlorophyll-vesicles as of a nuclear character. In Gonium, indeed, Cohn (Entw. p. 178) describes only one such vesicle, which seems to demonstrato its nuclear nature by breaking up, during the process of fission, into as many parts as the primordial cell itself. Braun (op. cit. p. 174, in note) mentions his observation of a central vesicle or nucleus in Chlamydococcus (XIX. 22, 24, 26), and remarks, “ in most of the true Palmellacca thore is a chlorophyll-vesiclo in the contro of the cell.” The appearance of the cells of Phytozoa is much modified by variations in the relative quantity or in the arrangement and colour of the contents, so much so indeed that such varietios have been described as different species or even as different genera. Thus the accidental presence of a red spot, called an eye- speck, or the occurrence of a rod central space, have had a specific importanco wrongly attached to them. The inutility of characters deduced from the disposition and appearance of the cell-contents, or from the figure, is further shown when the offects of external agents—of temperature, of the abundance or deficiency of nutritivo matters, of light, &c.—aro taken into account; and it becomes even still more evident when the changes of form one and the same being may undergo are duly considered. In a previous page it has been stated that in the earliest phase of existence, when the future cell is but Ono of several macrogonidia within its mother-cell, the protoplasm of which it consists is unenclosed by a membrane—has no cell- wall. But it would scom that a cell-membrane is wanting even at maturity in some genera, for example, in Stephanosphaera ; for Cohn writes (A. N. H. 1852, x. p. 326), “This is not only mado evident by the multifold changes of form which they undergo in the course of vegetation, and by the filiform prolongations and ramifications which are produced directly from their sub- stance (XIX. 38, 39–53), but is cloarly shown by the transformations which the primordial cells pass through in conscquence of external influences. Under certain circumstances namely, the filiform processes may be retracted, being torn away from the onvclopc-cell and taken up into the substanco of the primordial cells; the produced ends of the primordial colls also disappear, the latter becoming rounded off into their original spherical or short cylindrical form. Such a change would be impossible if the primordial cells woro sur- rounded by a rigid membrane, such as that of the envelope-cell for example.” I 2 116 GENERAL IIISTORY OF TEIE INFUSORIA. According to Prof. Henfrey, the primordial cells or gonidia of Pandorina (XIX. 59–63), and also, in the opinion of many, the Euglence (XVIII. 45–48), are similarly undefended. The internal globular coloured body of the motile form of Protococcus is in the same state. Thus Cohn (R. S. p. 531) points out that although this body has a sharply defined outline, yet, “either by mechanical means, or by chemical reagents, the internal globular mass may suddenly be made to lose its contour, and to spread so as entirely to fill the cavity of the colourless onvelope. From which it would appear that the internal globular body is not surrounded by any special cellulose membrane, but only by one readily destroyed by chemical or physical agency—probably nothing more than a dense layer of protoplasm.” gº In the case of Volvoa, the cells originate without an onclosing membrane; but after the appearance of the red spot, a delicate one shows itself, and extends at different points into the connecting thread-like processes (XX. 37, 39, 41). So in Gonium we may presume the primordial cells to be originally naked, although Cohn has not remarked this fact, but confined himself to describing the mature cells (XIX. 32, 34), which have an enclosing wall of cellulose (Entw. pp.175,176). Lastly, in the ‘still’ form of Protococcus a special membrane invests the protoplasmic gonidium. In Gonium (XIX. 34), and in Volvoa (XX. 37, 39, 40), filiform prolongations extend between the several cells in the compound organism ; in Stephanosphaera similar processes are given off at the opposite poles of the cells, and are consequently not inter- current (XIX. 39). Prof. Williamson has in the case of Volvoa offered the best explanation of these threads, which have by some been supposed inter- communicating canals. He first makes good his opinion that the green cell- like organism represents the nucleus of a cell, the wall of which is separated from it by a greater or less space; and then he compares the processes in question with the filiform extensions from the nucleus which are met with in many vegetable cells, suspending that organ in the centre. In the early stage of the cell, the protoplasmic substance fills up more or less completely the cell-wall (XX. 42,44): by-and-by the latter becomes outstretched from it by a sort of dropsical effusion within it (XX. 37); but as the protoplasmic nucleus has contracted adhesions at different parts, it becomes drawn out from the adherent points into thread-like processes (XX. 39, 40, 45), which grow more and more filiform in proportion as the cell-wall expands. This expla– nation (agreeing in every particular with the observed phenomena of cell- growth) being accepted, it follows that these elongations are bounded by the particular cell-wall to which they belong, and are not continuous with those of adjoining cells. The processes of Volvoa are therefore off-shoots of tho protoplasm of which each cell or gonidium consists; they are given off before any enclosing wall or pellicle appears, and whilst that substance is still duc- tile, and they disappear on the commencement of the process of development, whether of macrogonidia or of microgonidia, and whether with or without the process of encysting. In the case of Gonium, Cohn gives (Entw. p. 176) a different account of the connecting bands. It will be remembered that in this genus that ob- server indicates an enclosing cellulose membrane to each cell or gonidium. Now this cell docs not closely invest the protoplasmic substance at all points, but is so separated as to produce a hexagonal cell-wall around it, from each angle of which the membrane is produced in a tubular form, and joins with a similar process coming from the angle of an adjoining coll (XIX. 32, 34). Pſence each process of the membranc has a double outline, and is in fact a tube, only that its interior must be presumed to be shut-off from that with OF TELE PDIYTOZOA. 117 which it joins, by a septum representing the divisional membrane of each of the contiguous cells. The state of things here is therefore quite different from that in Volvoa: ; for in the latter the cell-membrane is widely detached from the protoplasmic nucleus, but the adjoining cells are adherent at all points; the intercurrent threads are therefore within the cells, and uphold an attachment between the nucleus and the cell-wall,—whilst in Goniwm the contrary obtains: the cells themselves are not in apposition, but held together by a tubular extension from each angle; and the nuclear protoplasm within nearly fills the cell-cavity, and has no bands uniting it with the wall—in fine, the intercurrent processes of Gonium and of Volvoa are not homologous. Besides the Wall and processes just described, calculated to give strength and resistance to the organisms, there are also the long cilia or filiform ap- pendages known as filaments, flabella, or flagella, seen at One extremity of most Phytozoa, derived from the protoplasmic mass. To those are entirely or chiefly due the locomotive powers of these beings; they also act the part of rudders in turning them on themselves, and in directing them hither and thither. They do not belong to the class of vibratile cilia, but are larger, filiform or whip-like, and have an undulating lashing movement. In some cases they are many times longer than the Organism to which they are attached (XVIII. 15, 21, 22); and when two, as more frequently happens, are pre- sent, they will often cross and intertwine. At times, in clongated forms, they appear to be the more terminations of the tapering-like extremity or neck; but the rule is, they do not proceed from the apex itself, but from one side of it. Where the species is encased in a firm integument, separated by an interval from the central protoplasm, the filaments actually extend from the latter and perforate the enclosed case; in which, particularly when these processes are fallen away, their points of issue are occasionally to be detected by depressions or by pores. During frequent rapid movements these fila- ments are not to be seem ; but when the motion is more gentle, or they are at rest, or otherwise when colouring matter is mixed with the water, they generally become visible. Even when their existence has not been noticed during life, it may be sometimes domonstrated after the drying up of the being, by the streak left upon the glass where it rested. Where more than one or two filaments are present, their whirling, and the conscquent agitation of the fluid about them, makes their existence apparent. The number of filamonts in Phytozoa varies. Two is the prevailing number, which may or may not be of cquallength; but in not a few genera only one is found, e.g. in Euglena, Monas, and Chilomonas, whilst in others more than two may be counted, situated together anteriorly, or some in front and others behind. Whore two are present anteriorly, it is not an uncommon arrange- ment for one to extend in the direction of the long axis of the body, whilst the other trails behind (XVIII. 12, 22, 23). Movi,MENTS OF PHYTozo A.—The motion of many Phytozoa is but slow, and rarely intermitted; in others it is more rapid and varied. It will be modified by the figure of the organism and by the degree of firmness of its walls, with which it stands in inverse proportion. In Eugléna the move— monts aro extremely varied and lively: the being is unrestricted in its movements by an integument, and the contractile protoplasm has full scope; it is, in fact, in the condition of swarming gonidia, unenclosed by a wall of cellulose. In many species of Monas and Bodo (Cercomonas), the motion is irregular and pcculiar; it may be oscillating or rolling, at times leaping, at others backward. Among the Vibriomia (XVIII. 57–69), an oscillating spiral movement is a common characteristic, and either Cnd may be advanced. The revolving rolling motion of Volvocineſe has for many years attracted 118 GENERAL ELISTORY OF THE INFUSORIA. attention, and for a long time was decned sufficient proof of the animality of the beings exhibiting it. It is the consequence of the play of the ciliary filaments of cach of the component cells of the aggregate organism, which project beyond the common envelope: it consists in a revolution on the axis, and a simultaneous onward movement—not, however, in a straight course, but in an irregular one, representing a spiral or series of curves. “The collective idea of such motions,” says Cohn (A. W. H. 1852, x. p. 328), “is best represented by the course described by a top, which runs through the most varied curves, while at the same time constantly revolving on its axis.” Nägeli (as quoted in J. M. S. i. p. 198) remarks of swarm-cells (zoospores), which many Monads undoubtedly are, that “under the microscope the motion appears very rapid, somewhat of an infusorial character, consisting in a con- tinual progression, in which the hyaline narrower extremity is usually in front, and the cell is continually turning on its long axis. Although the swarming bears a resemblance to the motion of Infusoria (i.e. of Ciliated Protozoa), it clearly wants the spontaneity of the lattor. The Infusoria advance, spring back, turn round, return, all spontaneously; the Swarm- spores pursue a uniform and, for the most part, pretty straight course, de- viating from it, or turning round only upon meeting an obstacle, impinging upon which they are diverted into another direction.” To this account Siebold (loc. cit. p. 201) adds that the spores do not retreat, as if frightcmed, like the Infusoria, when they strike against an object, but “remain close to it, and continue their motions according to the number and arrangement of their ciliary apparatus, in a rotatory or vibratory way for a little time longer, as if they aimed at overcoming the obstacle by force, until at last, probably in consequence of the death of the cilia, they become still, and germination goes On. . . . . The movements of the Swarm-spores in general have only a short duration. After the spores have come to a state of rest, they usually become attached by the hyaline ciliated oxtremity, and the locomotive faculty is for ever lost.” In the aggregated families the process of reproduction is ever going on in some members of the colony, and the movements are kept up much longer. Braun (Réjuv., R. S. p. 212) represents Chlamydococcus as enjoying a longer duration of motion than is usual with the Swarming gonidia of Algæ, whilst Protococcus viridis forms an intermediate link in this respect between it and the Volvocimede. The kind of movement, he adds, is essentially the same in these Organisms as in all active gonidia, namely an uninterrupted revolution round the long axis, combined with an advance towards the side of the ciliated point. It is, indeed, in the swarming movement of gonidia and spormatozoida that the phonomena of motion are most striking, “that is, in cells which are either yet without their cellulose coating, or which never acquire one.” Cohn (R. S. p. 558) states generally that, “ leaving out of the question the more highly organized Infusoria furnished with a manifest mouth and osophagus, the motion of a large part of the Amentera (Ehr.), the Astoma (Sie- bold), is not essentially different from that of the zoospores of certain Algae.” Likewise, in his description of Gonium (Entw. p. 180), he observes that the movements of this organism resemble in every particular those of Stephano- sphaera, Chlamydococcus, and other Swarming-cells, “which cortainly do not bear at all the character of purposing, conscious volition, but appear as an activity determined not by any external causes, but by internal causes in the organization and vital processes.” (A. N. H. 1852, x. p. 328.) The charactor of the locomotion of Phytozoa may be doscribed in brief as ‘automatic ;’ accepting that term as physiologists now agree to do, to distin- guish such motion from the voluntary movements of animals. It cannot be OF THE PEIYTOZOA. 119 voluntary, or the result of volition, any more than the marvellous motion of the leaves of Dioncea muscipwla. PROCESS OF NUTRITION.—The process of nutrition of Phytozoa is of the most simple kind; and no valid evidence can be adduced in proof of the com- plex polygastric organization represented by Ehrenberg. In fact, an apparatus of stomach-sacs could not, by any analogy, be presumed in a set of beings destitute of mouths; and Ehrenberg was unable to demonstrate, even to his own satisfaction, an oral aperture, except in a very doubtful manner and in a very few instances. What he took to be gastric cells are no other than vacuoles and clear vesicles—sometimes the chlorophyll-cells; the last, how- ever, were more commonly assumed to be “testes.” To support his belief in the presence of stomachs, and also of a mouth at the anterior clear space, particularly where there is a projection of the protoplasmic mass, the Berlin naturalist appealed with most confidence to his experiments in feeding with coloured substances. By this means he believed he demonstrated such organs in some Monadina, but so rarely, amid a large number submitted to experiment, and moreover in so few species, that much weight could not be attached to the result, especially when it is considered how many difficulties and doubts must arise where such very minute beings are concerned. Allow- ing that particles of colour actually entered within the interior, and were not merely adherent (a question which the magnifying powers of the instrument Ehrenberg used could scarcely determine), it is even then much more rational to suppose that their entrance was by mere mechanical causes (by pressure or the like), than by the medium of a mouth. This interpretation is adopted both by Perty and Leuckart, who describe the introduction of such particles as possible, although, indeed, exceedingly rare in the more clearly vegetable structures, the Diatomeae. The former mentions (op. cit. p. 61) three in- stances in which he encountered foreign particles within the substance of Phytozoa ; but these would, instead of supporting, be really opposed to the polygastric hypothesis. For instance, he discovered in a Peronema a species of Bacillaria as large as itself, and consequently not containable within one of the supposed gastric cells. In the case of the soft, illoricated minute Monadina, into which fine particles have found their way, it is to be remembered that they are mere masses of yielding protoplasm unprotected by a cuticle; and further, we may, along with Perty, reasonably presume that, in some examples of the entrance of external matters, it has been effected much in the same way as with the Amoebae, by the soft substance overlying and then surrounding them. If a mouth and stomachs have no oxistence, it follows that nutrition must be effected by imbibition—by endosmotic and exosmotic action—just as in any simple vegetable or animal cells. Perty (op. cit. p. 62) adduces an experiment showing that, to Some Phytozoa at least, water rich in nutritive organic material is necessary to their complete and healthy development; for when taken from such water and placed in other quite pure, they dwindled in size, although, curiously enough, they at the same time became more active. To complete what we have to say of their vital endowments (irrespective, that is, of the reproductive functions), the Phytozoa seck the light; and all their nutritive acts are carried on more actively under its influence. The only oxception is whom, in the process of propagation, they are about to pass into the ‘still’ condition and to become encysted; then they eschew the light, sink out of sight, and recede to the bottom, or under cover of aquatic plants or of their debris. Under the influence of light they exhalo oxygen gas, and the green colour is especially developed,—whilst when kept in the dark they lose colour, become pale, and present few chlorophyll-particles. The 120 GISNERAL IIISTORY OF THE INFUSOTRIA. intensity of light may be too great, and destroy life; and a great elevation of temperature is less favourable to vital activity than a moderate one. Cold retards vital action, and if considerable, arrests it, except in the case of the encysted beings, which are so modificd by nature as to resist its injurious influence; these conscquently persist through the winter when the motile forms are cut off, and in the coming spring burst forth into life. The same provision which imparts to the encysted organisms a tolerance of cold, enables them also to withstand the effects of evaporation, which to the unprotected motile varietics is speedily destructive, unless, indeed, so gradual as to allow them time to pass into the ‘still’ form. Starch or cellulose may be detected chemically in the great majority of the Phytozoa ; and even where iodine fails to produce the characteristic blue colour during life, it will at times act strongly when a breaking-up of the contents follows evaporation or some other injurious influence. The efficiency of nutrition is manifested by the decided changes, chemical and vital, which are scom in constant operation within the beings—such as, among others, the transformation of chlorophyll into starch, and of one or both those into an oily matter. When in the ‘still’ encysted condition (XIX. 44-69), all nutritive changes are at a standstill, and the organism may crist Wecks, months, and even years unchanged, until external conditions are supplied to awaken its latent energies and to renew the cycle of life. In this torpid form the spores are carried about with the dust, or remain buried in the carth, or are elsewhere hidden or stored up against the day of revival. The passage into the ‘still’ condition by the throwing-out of an external denser envelope and by the loss of cilia, is governed, it would Secn, in some measure by external circumstances. Motile forms are replaced by the ‘still” in whole or in part, and with greater or less rapidity, by pouring the water containing them into a larger and shallower vessel, and by gradual evaporation. The protoplasm of Phytozoa being homologous in all perceptible particulars with the ‘sarcode’ of Protozoa, suffers, like it, the destructive process of ‘ diffluence’ or ‘dcliquescence’ when evaporation reduces the quantity of water around the unprotected motile forms below the quantity necessary to vital action. The first noticeable result of evaporation is, according to Cohn, at least in the instance of Protococcus (op. cit. p. 538), a more rapid change of figure and appearance, followed, if the evaporation continue, by diffluence, in which he distinguishes two stages or phasos : —“In the first, the outlines appear less sharply defined, because the coloured substance is somewhat retracted from the border of the primordial cell; the cells become flattened, and at the same time wider: the contents are also now altered; previously more homogeneous and transparent, they now become throughout granular, and the rod substance runs together in large drops. At this time the forma- tion of vacuoles commences; and their number continues to increase. In this way the intorior of the primordial cell again becomes colourless, clear as water, and the granular coloured contents pressed against the walls. . . .The figure of the cell in the warm time is so much cxpanded, that it comes to be applied upon the wall of the enveloping cell, alternately filling it altogether, so that the entire Zoospore appears to consist of only a single coloured gra- nular vesicular disc, corresponding in size with the original enveloping cell.” MULTIPLICATION AND REPRODUCTION OF PIIYTozo A. FISSION: MACROGONIDIA ; MICROGONIDIA : ENCYSTING PROCESS : PIASEs of EXISTENCE.-The multiplica- tion of the individuals of the species of Phytozoa is provided for by the process of self-division, deduplication, or fission. This takes place according to the plan obtaining in vegetable and animal cells in general. OF THIS PIIYTOZOA. 121 The coll-contents divide into two or more Scgments, each of which can further develope around itself a gelatinous investment, and enter on an inde- pendent existence. In Euglena, self-division occurs longitudinally into two portions; and the newly-developing half is of Smaller size than the other, but becomes complete in all its parts before its severance is effected. The motile cells of Chlamydococcus undergo fission into two or four seg- ments (XIX. 23–26); this takes place in the protoplasmic or primordial cell contained within the hyaline spherical envelope-cell; when division is com- plete, the latter is ruptured, the sections escape as independent beings, each throws out around itself its envelope-cell, and in all points goes through the same cycle of development as the parent-cell. Many Monads also divide into two beings, whilst others separate into four. In the above-cited ex- amples the fission is complete, and cach segment, on detaching itself from the other, becomes an independent, free being. But this same act of fission may proceed under different circumstancCs; and instead of a single organism, a colony may be formed, consisting of several individual cells united together, either permanently or only for a time, within a common envelope. These aggregate Phytozoa are especially represented in the family Volvocineſe. In this socond mode of fission the process is ropcated a greater number of times—for instance, some 3, 4, or 5 times—the result being a higher multiple of 2, the product of the first act of scission. Each repetition of the process of fission, from the commencement until its completion, constitutes, in Nägeli’s language, a transitional generation, whilst the final repetition produces the permanent generation. For example, in Stephanosphaera two segments are produccd by the act of fission, which re- present the first generation (XIX. 45); then cach of these subdivides, and so developes four portions (XIX. 40, 46)—the second generation ; and, lastly, each of the four scparates into two, and in that way produces cight segments —the third, and in this organism the final or permanent generation (XIX. 41, 42, 56). Unlike the Scgments resulting from a single act of division, or, as may happen, from this act once repeated, cach newly-formed primordial cell docs not commonly surround itself with an envelope and enter on an isolated existence, but the whole eight or more continue to live within a common tunic, which presently expands by endosmotic action and acquires a more or less spherical figure (XIX. 56, 57, 58). Simultaneously with this cypansion, the previously contiguous particles are drawn away more and more from cach other, and disposcd within the common envelope, after a more or less regular fashion, characteristic of the species to which they belong (XIX. 42, 58). In general, the separation of the primordial cells is not complete; bonds of union betwcCn them in their early state, when closely approximatcd, become drawn out, and ultimately prosent themselves as intorcurrent threads. When this Scrics of changes is terminated, we have before us a reproduction of the aggregate organism of which the dividing primordial coll was but an individual member. Braun has styled this variety of reproduction by fission, development by ‘macrogonidia.’ It is well illustrated in Stephanosphaera, above cited, in Volvoa (XX.), in Gonium and Pandorina (XIX. 35, 36, 37, and 62–66), and also in undoubted Algæ, the Hydrodictyon or Water-net for example. But the segmentation of the cells of Phytozoa occurs in yet another form ; i.e. the fission, instead of stopping at the third or fourth generation, pro- cccds still further, until 32 or 64, a hundred, a thousand and upwards of minuto Coll-structures are produced, technically called “microgonidia,” in- 122 GENERAL EIISTORY OF THE INFUSORIA, tended to perpetuate the species by their ulterior development. Although, like the “macrogonidia,” they are formed within a common envelope, yet each cell among them does not, as in those products, enclose itself with its own tunic, and fix itself permanently within the general investment—in other words, assume at once the ‘still’ condition; but the whole, after entire separation from one another, become endued with vital activity, and are sub- sequently set free, by the dissolution or rupture of the surrounding parent-cell, as so many moving Zoospores (XIX. 51). The motion of these little bodies within the original coll is of a hurrying to-and-fro or up-and-down cha- racter, and has been styled “swarming.” On emerging from the ruptured cell, each little body is seen to have a spindle-shaped figure, terminated at its anterior clear and usually elongated extremity by two or four cilia (XIX. 52). In every essCntial particular these microgonidia are homologous with the motile gonidia, Swarming-cells, or spores of the common Algae, such as Bry- opsis, Codium, Achlya, Chaetophora, Ulothria, Hydrodictyon, &c. Cohn's re- marks on the formation of microgonidia in Stephanosphaera (A. N. H. 1852, x. p. 346) may elucidate this subject still further. He says, “While, in the formation of macrogonidia, the secondary cells become surrounded by a common envelope and are not free (as an entire connected family of cells arranged according to a definite law), in the mode of propagation of micro- gonidia the little Secondary cells finally become totally separated from one another without Secreting an envelope-cell; and in this way each of the eight primordial cells of the perfect Stephanosphaera is broken up into 32 to 64 independent, green, elliptical or spindle-shaped corpuscles, which then separate from one another, commence an independent and active motion, and fill up, in great numbers (as many as 256–512), the common parent envelope- cell (XIX. 51). . . . The crowding-in among each other of the microgonidia of Stephanosphaera presents a picture fixing the attention in the highest degree: sometimes the cellules are scattered in a few large masses—then they unite again into a knot in the middle—every moment the general aspect varies. At length the common envelope is ruptured,” and they escape in masses into the water. “Their true form may then be detected readily by killing them with iodine ; they are spindle-shaped and acuminated at both ends, bright green in the middle, and run out into a colourless beak at each Cnd— on the whole not unlike young Euglence, without trace of an envelope-cell (XIX. 52).” On reaching the water their movements are most active, and then rapidly disperse out of sight. These bodies are true primordial cells, “ that is, primordial utricles resembling cells, organized exclusively of co- loured protoplasm, without any cell-membrane.” Upon a general Survey of development by gonidia, Cohn remarks (A. N. H. 1852, x. p. 403)—“Abstracting the differences which may always be shown between two genera, we detect the same law of development in Hy- drodictyon as in Stéphanosphaera : the biciliated, less numerous macrogo- midia arrange themselves into a family of cells already within the parent-cell, according to the character of the given conditions of the two genera,_the cell-family being active in the Volvocineae and immoveable in the Proto- coccaceae; while the more numerous, more actively-moving microgonidia with four cilia leave the parent-cell and enter upon a metamorphosis, the re- trogradation from which to the normal type of the genus has not boon ob- scrwcd yet here, or indccd in the microgonidia of any of the Algae.” It may be conjectured that these latter pass into a resting state, prior to any further dovelopment; for both Cohn and Braun have witnessed this change in Chlamydococcus pluvialis. The formation and cscape of microgonidia have becn obscrved by many OF THE PITYTOZOA. 123 naturalists—for instance, by Weisse in Chlorogonium, and by Perty in each family of Phytozoa. The production of such bodics is frequently treated of as development by germs, and, no doubt, is the same phenomenon Ehrenberg represents as viviparous reproduction. Microgonidia are not so commonly developed as macrogonidia; and indeed their formation would seem determined, at times at least, by external cir- cumstances affecting their functions and vital activity unfavourably. Thus, Cohn (Entw. p. 168) narrates the circumstance of the peculiar and pretty general development of microgonidia, in Chlamydococcus, after a thunder- storm. PROCESS OF ENCYSTING: CONDITION OF REST.-The perpetuation of Phytozoa is provided for, as before intimated, by another process, which both secures to the cells undergoing it a power of successfully resisting influences that to unprotected gonidia are destructive, and is connected with an ulterior act of development. This faculty of sclf-protection is called “the encysting pro- cess,” since by it the cell encloses itself within an additional firm tunic, which surrounds it like a case or cyst, and transforms it into a “still’ or ‘winter 'spore. The process takes place in all the Phytozoa after the same fashion: the protoplasmic covering of the gonidium or cell secretes around it a dense, firm cnvelope, which in general becomes raised from it all round, so as to leave a clear intervening space. On the assumption of this extra covering, cells previously motile and active enter on the ‘still’ condition and lose their cilia; at the same time, the character of the contCnts is altered, and a red colour frequently acquired. The transformation in their physical structure is accompanicd by a physiological change; for in place of Secking the light, oxhaling oxygen, and carrying on all the vital procCSSCs with a corresponding activity, they sink to the bottom and conceal themselves from the light. It appears, from Cohn’s researches on Protococcus, Gonium, and other Phytozoa, that they become released from their imprisonment, undor the influence of favourable Cxternal conditions, by the deliquescence of the rigid external sac, and sometimes by its transformation into an external mucilaginous invest– ment, and by the breaking-up of the internal protoplasmic cell into a number of motile zoospores. The act of encysting may proceed with macrogonidia in their ‘still' con- dition; or it may overtake motile primordial cells, as in the case of Euglena and of some phases of Protococcus, and in such, just as in the zoospores of Algæ, prove antecodent to further acts of development by fission. Cohn im- plies, in his history of Protococcus, that microgonidia may themselves be emi- cystod; and the same eminent observer describes the primordial cells of that plant as in some instances surrounding themselves with a firm external envclope, pushing out two cilia, and moving about for a time in a “swarming” manner cre assuming the ‘still’ condition, when the cilia disappear. But, further, he shows that gonidia, furnished with a rigid external wall, proceed to develope others like themselves by sclf-division of their substance (XIX. 25), and that these secondary cells, cach included within its own sac, go on to divide into other sporos, which, however, prove not to be ‘still” like their parents, nor like them emcysted, but motile zoospores. In the aggregated family Volvocineae, some or all the primordial cells be- come encysted. When this takes place, their contents grow thicker, less transparent, darkor, and change from green to brown and brownish, or to a yellowish red. At the same time, the intercurrent filaments disappear, the cells themselves acquire a more spherical figure, and gradually looscn them- Selves from the common Cnvelope, and move slowly about within it by means of two cilia, until they at length cscape by a rupturo at some point (XIX. 44, 124 GENERAL HISTORY OF TELE INIFUSORIA. 50). These encysted spores resemble Chlamydomonads, and are called ‘ Pro- toccocoid’ cells or globules, from their homology with the encysted cells of Protococcus. Occasionally, instead of one or several of the individual gonidia of a com- pound organism being encysted, the process ensucs with a gonidium deve- loped by fission into macrogonidia, and the whole mulberry or Uvella-like mass becomes surröunded by a rigid envelope, either pretty closely applied, or separated by an interspace. & Examples of the encysted condition will occur in the following account of the soveral groups of Phytozoa ; it suffices at present to say that Prof. Wil- liamson and others have pretty clearly shown that Volvoa aureus is only the encysted or ‘still’ form of V. globator, that Cohn has discovered the cysts of Stephanosphaera, Gonium, and Eudorina, and Henfrey those of Pandorina. The after-history of the encysted spores of Phytozoa has not yet been elucidated: wo have above referred to Cohn's researches upon it; but they are too indefinite to supply any positive information. The act of conjugation is common with many of the lower Algae, but has not been witnessed among the Phytozoa. PIIASES OF BEING AND ALTERNATION OF GENERATION IN PHYTOZOA.—From the proceding account of Phytozoa, it is evident that those best known exist under a considerable variety of form—in other words, prosent soveral phases of existence, or, viewed in relation with a prevailing hypothesis, exhibit an alternation of generation. The whole history of any Phytozoon is com— prehended in the cycle of changes which the Organism passes through ; yet, under any transformation, it is the sclf-same being, and its Cxistence may be said to cxtend from its most perfect through all intermediate phases until the like degree of perfection is again attained. As happens in alternation of gencrations among other Organized beings, the transition may not be direct and simple, but intermediate phases may reproduce themselves, and these again develope into other forms of Cxistence, as accessory or collateral and usually imporſect cycles. Perhaps the metamorphoscs in question are most striking in Euglence; for the contrast between the actively-moving, contractile, ever-changing being in one phase of existence, and the encysted, ‘Protococcoid,” spore-like and motionless condition with a rigid unvarying outline, is so remarkable as to give colour to the hypothesis of the convertibility of animal into vegetable life, or of the transformation of animals into plants. It is not our intention at present to give illustrations of the varying phases in the life of Phytozoa involved in the process of fission, or of a duplicative multiplication under its various forms. However, other more extended instances of transformation require to be noted, as obscrved by various microscopists, although, it may be, some orrors have crept im, from the difficulty of tracing the relation and succession of the different phases of being. As a very good example of the wide and varied range of existence enjoyed by most Phytozoa, we may adduce the Protococcus pluvialis (XIX. 20–31), of which the industry and perseverance of Prof. Cohn have obtained for us so complete an account. According to the researches of this eminent natu- !alist, the simple plant in question, in its motile and still conditions, assumes the form and characters of many microscopic organisms presumed to be, and described by Ehrenberg and others as, distinct CKistences. To quote from Cohn's memoir (R. S. p. 559), “We see that a single species, owing to its numerous modes of propagation, can pass through a number of very various forms of dovelopment, which have becm either crpOncously arranged as distinct genera, or, at least, as remaining stationary in those genera, although, in OF TEII, PEIYTOZOA. 125 fact, only transitional stages. Thus, the ‘still” Protococcus-cell corresponds to the common Protococcus coccoma (Kütz.). When the border becomes gela- tinous, it resembles P. pulcher, and the small cells P. minor. The encysted motile zoospore is the genus Gyges granulum among the Infusoria, resembling also, on the other side, P. turgidus (Kütz.), and perhaps P. versatilis (Braun). The zoospores divided into two must be regarded as a form of Gyges bipar- titus, or of P. dimidiatus. In the quadripartite zoospores, with the Secondary cells arranged in one plane, we have a Gonium. That with eight segments corresponds to Pandorina Morum, and that with sixteen to Botryocystis Volvoag. When the zoospore is divided into thirty-two segments, it is a Uvella or Syncrypta. When this form enters into the ‘still’ stage, it may be re- garded as a form analogous to Microhaloa protogenita : this Algal genus is probably, speaking generally, only the product of the Uvella-division in the Euglence or other green forms. The naked zoospores, finally, would represent the form of a Monad, or of an Astasia ; the caudate variety approaches that of Bodo. A critical and comparative consideration of the foregoing facts would therefore appear to render untenable almost all the principles which modern systematists have hitherto adopted as the basis for construction of their natural kingdoms, families, genera, and species.” - Cohn (op. cit. pp. 541, 542) makes the following general deductions:— “1. The Protococcus pluvialis is a plant, subject to an alternation of genera- tions; that is to say, the complete idea of the species is not exhibited in it until after a series of generations. The forms of development which can be possibly comprehended in the idea of the species do not in reality make themselves apparent until a series of independent successive generations has been gone through. 2. The individuals of each generation are capable of propagating themselves in new generations. The individuals of the second generation are among themselves, speaking generally, of equal value: as re- spects the individuals of the parent generation, they are sometimes of equal value with them, sometimes not. 3. If the secondary cells are not of equal value with the parent-cells, a Series of Successive generations must precede the last generation, the individuals of which are again equivalent to the first mother-cell. The number of these generations does not seem to be deter- minate.” By equivalent, the author means such individuals or generations as correspond with each other in their essential, physiological, and organo- logical relations, although they may differ in unessential properties, such as colour, size, internal consistence, &c. Non-equivalent are those generations which in their structure and vital relations exhibit essential differences, such as ‘still' and ‘motile ’ cells, and among these, again, their various forms, and particularly those which are derived from a different mode of propa- gation. - Major von Flotow (Nova. Acta Acad. Nat. Curios. 1844, p. 413), it is right to state, remarked on the similarity of various forms of development of Haematococcus (Protococcus, Cohn) pluvialis with Infusoria, signalizing the genera Chilomonas, Cryptomonas, Gyges, Chlamydomonas, Pandorina, Chae- toglena, and Chaºtotyphla of Ehrenberg’s system. Phytozoa, or structures undistinguishable from them, constitute links in the chain of still more marvellous transformations. Thus, Itzigsohn repre- sents several in the history of the development of the Oscillatorieae. For ex- ample (J. M. S. 1854, p. 189)—“The filaments of Oscillatoria tenuis break up into perfectly distinct joints, which, at first urceolate, soon become spherical. The minute yellowish-green gonidia thus arising gradually increase in size, become motile, and present in all respects the aspect of Chlamydomonas.” These bodies “gradually enlarge ; a red eye-point becomes visible in them; 126 GENERAL EIISTORY OF THE INFUSORIA. and, presenting a thousand intermediate forms, they grow into perfect Euglence.” After awhile these Euglence become encysted, and terminate in the quiescent or ‘ Protococcus-condition,’ and subsequently, by self-division of the contents, are resolved into motile microgonidia which escape free into the water. “If a number of these remain conjoined, and move about with a rowing kind of movement, their locomotion being governed by a common spontaneity, they represent a Volvoag-like Colony, which, perhaps, may even have been described as Volvoa by authors. The microgonidia of the Euglena, like those of all the Algae hitherto examined by me, are the motile parent- cells of extraordinarily minute spiral filaments. They are at first green, gradually becoming pellucid—exactly like the spermatospheres of Spirogyra, presenting a Monadiform aspect. A peculiar appearance arises when many microgonidia in such groups remain green whilst the others have already become clear as water; the mass then presents, in fact, the aspect of being composed of two kinds of animalcules. Such or similar conditions would re- present several species of the Supposed genus Uvella (atomws, glaucoma, Bodo, &c.). Each ultimately colourless microgonidium, then, by the dissolution of its minute gelatinous envelope, discharges a small motile spiral filament.” . . . “These spiral filaments do not appear to be destined for the purposes of im– pregnation; for they gradually increase in length and thickness, soon exhi- biting numerous spiral turns,” and then exchange the Spirilla-like for a Spirulina-form. “Finally, when their motile faculty has become weakened, they affix themselves by one extremity to any larger object near (for instance, Conferva-filaments, &c.), whilst the other extremity continues to move about with a creeping motion—the peculiar Oscillatorian movement, in performing which a young filament frequently returns to the spiral. The last-described condition constitutes the Leptothria of authors. The filaments now gradually become thicker; and though at first of the lightest emerald-green, they gra- dually assume a deeper and deeper tint. The first indications of articulation are perceptible in them, until at last a young Oscillatoria is again perfected.” But the remarkable metamorphoses of this Oscillatoria are surpassed by those of the Phytozoa of antheridia, as recounted by Prof. Hartig (J. M. S. 1855, p. 51) : the antheridia of Marchantia form the subject of observation. Their Phytozoa first assume the form of Ehrenberg’s genera Spirillum and Vibrio, of which the most frequent varieties met with are Vibrio rugula and V. prolifera; “after twenty-four hours most of these Vibrios and Spirilla—after forty-eight, all of them—have become disarticu- lated.” The whole drop of water in which they float is now rendered milky and turbid by numberless globules, similar to Monas crepusculum, in a state of active motion; and it is an important circumstance that Spirillum does not originate from Monas, but always Monas from Spirillum. After forty-eight hours, “groups of Several hundreds may frequently be seen, in which the primary active motion has ceased. Shortly afterwards a sharply- defined hyaline skin is formed round these groups, and, as it would seem, by the amalgamation or conjunction of the exterior molecules; by this means the young Amoeba (Proteus) is formed. This transformation takes place pretty regularly towards the end of the third day. The original size of the Amoeba is 1-300” in diameter. In the course of three or four days, it grows to about the size of 1-100". This species differs from the Amoebae hitherto described, in the fact that the inner portion of the body which bears the granules is much smaller than a certain hyaline covering, which covering is closely attached to the hinder part of such inner portion, but extends far away from the anterior part; and, in addition to this, the progressive motion in this species originates in an alternate enlargement of the longitudinal and OF TELE PEIYTOZOA. 127 transverse diameters, and is so slow as to amount at the utmost to no more than 1–40" per minute. The form of the body resembles that of Amoeba. princeps (Ehrenberg). The vesicle in the hinder part of the body, which was first described by Ehrenberg as a mouth, and afterwards as an ovarium, is also present. “After four or five days the Amoeba assumes a spherical shape and becomes motionless, the vesicular body expanding and contracting rapidly as before, in a manner similar to what takes place in many Vorticellaº. These spherical motionless Amoebae are then for the most part united by a mucilage into groups of from ten to twenty. The mucilage appears to be produced by the decomposition of a cast-off external skin. “In about a fortnight after the commencement of the experiment, a green point appears in the interior of the spherical colourless body of the Amoeba ; this point gradually increases in size until it fills up the entire hollow of the Amoeba, and after becoming covered with a cuticle it escapes in the form of an elliptical bright green cell, 1-300” in diameter, resembling a Protococcus. It exhibits a round transparent cavity, devoid of chlorophyll, corresponding in size and position to the vesicular body of the Amoeba, and resembling at its colourless apex the motile gonidia of Cladophora. A few days later the elliptic or roundish cell lengthens, a formation of transverse septa commences, and the umicellular Alga becomes an articulated one. - “All these transformations of Phytozoa into Spirilla, Vibriones, Monads, Amoebae, unicellular and articulated Algae, may be observed not only in the detached Phytozoa, but in those which remain in the interior of the sections of the antheridia. In those antheridia of which the Phytozoa are not fully ripe, the Amoebae are seen to originate in the middle of the internal mass of phytozoary cells: some of them make their way out through the softened mass of cellular tissue; but others remain in the interior of the antheridium until their development into an articulated Alga. “Contemporaneously with Amoeba, and often earlier, there may be seen, amidst the mass of Monads, bodies very similar in form and motion to the genus Bodo (socialis), and which increase by transverse division; they have the front end furnished with a long whip-shaped antenna or cilium similar to that of Euglena. At their first appearance, their motion, their change of form, and their whole exterior differ so little from the earliest states of Amoeba, that at this period they cannot be distinguished. In these early stages they both resemble Chlamydomonas destruens of Ehrenberg. “The above forms uniformly make their appearance, and always in the succession above described. It is true that other forms, such as Uvellae and even Leptomita, and Periconice, are sometimes met with, the germs of which may have been imported by the atmosphere during the observation; but these organisms, which always appear singly and after the commencement of the observation, do not interfere with the above results when we consider the immense number of the Phytozoa and their uniform and contemporaneous transformations. If about a dozen preparations are made, and if they are carefully covered with a bell-glass after each observation, and if care be taken not to extend the observations for too long a time at once, at least half of the preparations will be free from all admixture of foreign organisms.” Mr. Carter has advanced some remarkable statements respecting the de- velopment of Amoebiform and other Infusoria from the so-called ‘gonidial cells’ of the mucous contents of various Algae—as Chara, Nitella, Clado- phora, Spirogyra, and Hydrodictyon, and also of some Desmidieæ and Ew- glenece (A. N. H. 1856, xvii. p. 101). Again, he finds (p. 114) the cells of Spirogyra particularly infested, during conjugation, with Euglence, which are 128 GENERAL. EIISTORY OF TELE INFUSORIA. produced with such rapidity as would lead to the conclusion that the germs from which they originate must have pre-existed in the cells in which they appear (as in the Characeae), without interfering with their functions. “Young Astasiae are also developed within the cells of Spirogyra to a great extent; and although they at first have almost as much polymorphism as an Amoeba, still they retain their cilium, and after awhile assume the form and move— ments peculiar to Astasia. On one occasion I saw a large Amoeba with a long cilium at one time assuming the form of an Astasia, and at another that of an Amoeba, which thus gives the link between these two Infusoria, The cilium, however, had not the power of the filament of Astasia, though it occasionally became terminal.” - Developments of a similar Rhizopodous character are, he goes on to say, frequent in Euglema:-‘‘I was led to notice this development by an apparent metamorphosis of the cell-contents of some fixed and capsuled Euglence into granuliferous Amoebae, of a pinkish colour, within the old cell of Euglena itself; and the presence of several such Amaºboe creeping about the watch- glass, while many of the cells of the Euglence (viridis?) were empty, or only contained a little effete matter, left no doubt in my mind as to the origin of both colour and infusorium. It was also observed in some instances, where the contents of the Bugléna had passed into an Amoebous mass, that the latter underwent a kind of segmentation, so that several (perhaps eight) small Amoebae were developed instead of one large one.” OF THE NATURE OF PHYTOZOA. ANIMAL AND VEGETABLE CHARACTERS.— The collection of organisms we have grouped together for convenience' sake, and from want of a better arrangement, under the name of Phytozoa, is actually so heterogeneous that no general discussion respecting the nature of them as a class is practicable, whilst, at the same time, a separation between vegetable and animal forms is equally impracticable. The remarkable phases of existence through which any one species may pass upsets all our notions based on presumed constant characters: for, as we have seen, one and the same being may at one period of its existence exhibit in a preponderating degree the vital phenomena of an animal, at another those of a plant, whence has arisen the hypothesis of the metamorphosis of plants into animals, and vice versé, -an idea that has found little favour, being opposed to the prevailing belief of the fixity of nature imposed on all beings. The real fact of the case is, that we have no certain criterion between the two divi– sions of organic nature which can be relied on and practically resorted to in cases of difficulty, such as many of the Phytozoa present. Some naturalists have broached the notion that the phases of existence of a presumed animal or plant, which resemble in outward aspect supposed independent species or genera, are not identical with them ; so that, for instance, the animal-looking Amaºba Hartig met with in the developmental series of Phytozoa of antheridia should not be considered really an animal Amoeba, but merely a vegetable mass simulating one. So, again, in Proto- coccus they would deny anything but external general characters to exist in common between its forms of development and the several genera Cohn would assimilate them with. There may be some truth in this supposition—there may be real animal organisms and true vegetable coinciding in form, yet distinct in nature; but the onus probandi rests with those who will make this distinction. - However this may be, the advance of science has rendered it certain that some families and genera which Ehrenberg, and most observers before his era, reckoned among animals, are rightly to be numbered among plants, whilst of others, again, it must still be said their position is doubtful. Deferring OF TEIE PEIYTOZOA, 129 at present a detailed review, we will confine ourselves to a few general obser- vations on the nature of the several families brought together under the head of Phytozoa. The Momadina (XVIII.) of Ehrenberg comprise a multitude of beings differing widely among themselves, and, for the most part, not placeable with certainty either among plants or animals. Of the genus Monas, especially, it may be said that its species are, with few or no exceptions, mere phases of being of other organisms. Of other genera the like may be presumed, although the organisms in whose cycle of life they enter as one of the links have not been determined. Not a few are doubtless zoospores of Algae or of micro- scopical Fungi. Uvella (XVIII. 5) is, in the opinion of most authorities, a vegetable struc- ture (see p. 134); but Cohn (Entw. p. 115) still seems disposed to consider it an animalcule, and represents Anthophysa (see p. 135), which has likewise been extensively believed to be a parasitic Alga or Fungus, to be an animal Uvella surmounting a branching stem. Polytoma is another disputed posses— Sion between zoologists and botanists: among the most recent advocates of its animal character is Schneider (see pp. 136–139). The Cryptomonadina would, in the language of naturalists generally, be called “encysted' Monadina, and, like this family, are divisible into true vegetable and into doubtful animal organisms, the former certainly prepon- derating. The next two families, Volvocina and Vibrionia, and more especially the former, may without hesitation be counted with plants, whilst the remain- ing one, Astasicea, the majority of naturalists reckon among animalcules. PIABITATs. OCCURRENCE IN MASSES. Colour CAUSED BY THEIR ACCUMULA- TION.—By far the majority of known Phytozoa are of a freshwater habit ; yet it may be that, were the search as diligent, marine species might be found in nearly equal abundance, particularly in inland and shallow seas, gulfs, or lakes affording appropriate habitats for the larger Algae. Monads and Vibrios, Bodos, and the Cyclidia of Dujardin, are probably the most abundant and widely diffused of all created organisms, a fact not remark- able when it is considered that those genera represent the primary or ger- minal stage of so many Organized beings, both animals and plants. They make their appearance, in collections of water and in infusions, before all others, and, unlike most microscopical creatures, find a fitting habitat in foul or decomposing fluids as well as in Sweet water. They also propagate them- selves with such astonishing rapidity, that the fluid or other medium in which they occur becomes coloured by them. However, this very rapid de- velopment, and this capability of colouring the surrounding medium, are not restricted to the genera named, but are partaken by others among the Phy- tozoa, for example, Uvella, Astasia, Euglema, and the genera of Volvocineae, all of them denizens of pure water, incapable of existence in impure, stagnant, and decomposing liquids. The colour presented by their accumulation in large numbers, varies according to the species. Thus, the Astasia hammatodes and Buglena san- guinea give a blood-red colour to water. The Monas (Vibrio) prodigiosa is stated by Ehrenberg to be the cause of the blood-like spots which have made their appearance at times in bread and meal, much to the consternation and dismay of the ignorant and Superstitious; and, again, the Haematococcus or the red-coloured stage of the Hysginum of Perty is the cause of the phenomenon of red snow. A green colour is much more frequent, and due to a larger variety of Infusorial organisms; such are Monas bicolor, Uvella Bodo, Cryp- tomonas glauca, Gonium, Chlorogonium, Euglena viridis, Chlamydomonas, Pandorina, Volvoas, Stephanosphaera, and others. Besides becoming thus obvious to common observation by their colour, IC 130 GENERAL HISTORY OF TEIE INFUSORIA. many Phytozoa render themselves so by the evident masses or accumulations they form. The dust-like stratum frequently noticeable on the surface of water, or at the sheltered margins of ponds, is often composed of various. genera, such as Euglena, Chlorogonium, Pandorina, and Gonium, more or less intermingled with other Infusorial beings, such as ciliated Protozoa, Desmidieæ, and Diatomeae. The stratum at times assumes the appearance of a slimy film, at others of a frothy scum. - Moreover, the variable affinity of different genera for light will cause a film at one part of a pond to differ in its composition from that at another, when the degree of exposure of the two is different. Further, there may be a transition of colour, by the changing phase and attendant change of hue of these organisms, or by the effects of the sun's heat and light at noonday, and of the darkness of night. Hence a pond which may be coloured green in the warmth of the day, when the sun’s influence brings the Phytozoa to the surface and causes their rapid development, may in the morning and evening become quite clear, owing to their settlement at the bottom. Of the modes of obtaining the Phytozoa for examination there is nothing special to record, except it be a plan mentioned by Cohn in his account of Stéphanosphaera (A. N. H. 1852, x. p. 405):-‘‘At their stations,” writes this observer, “the Stephanosphaera-spheres occur mingled with Chlamydococcus, but by no means in the abundance requisite for the investigation; and although green clouds do collect at certain points in the water wholly composed of our Volvocineae, it is difficult to extract sufficient of them for examination, since they immediately start apart when touched. I succeeded in overcoming this inconvenience by a simple means, so as to bring thousands of these elegant organisms on to the object-holder at any moment. I took, namely, a flat bottle with a short narrow neck, and nearly filled it with the water contain- ing Stéphanosphaerae, stopped it with a cork, and then laid it horizontally, so that the cork partly dipped in the water. In a few hours almost all the Stephanosphaerae in the water collected on the cork, which was covered with a green coat, composed exclusively of the revolving spheres, while the rest of the water in the bottle contained only Chlamydococcus, and scarcely any Stephanosphaera ; so that when I wished to examine them I had only to take out the cork, and a drop of the water adhering to it furnished me with all the stages of development of our organism simultaneously in very large numbers. After a short time the Stephanosphaerae had again assembled on the cork.” For a more satisfactory elucidation of the Phytozoa, of their structure and physiological action, it is necessary to enter into more detail; and since there is so much structural diversity among the several groups or tribes, this more lengthened account must be given of each tribe separately. And first— FAMILY I.—OF THE MONATDINA. (Plate XVIII. 1–28.) In the systematic portion of his great work, in 1838, Ehrenberg instituted the following genera of Momadina, viz. Monas, Uvella, Polytoma, Microglena, Phacelomonas, Glenomorum, Dowococcus, Chilomonas, and Bodo. Subsequent researches led him to add the genus Chloraster, and to remove Polytoma in order to unite it with a newly discovered genus, named by him Spondylomorum, in a distinct family, the Hydromorina. This family, however, deserves no special consideration, but will fall within the compass of our general remarks on the Monadina, as will also the genus Anthophysa, in accordance with the results of Cohn's researches. (See Part II., Systematic History of Monadina.) OF TEIE PEIYTOZOA. 13] Very little observation and reflection will soon convince the student that the members of this group of beings can be distinguished by no such constant definite characters as suffice to establish genera and species with any pre- cision; their history is too imperfectly known, and their individuality is un- proved. If they make their appearance in a fluid, it is only transitory; for they are soon replaced by a different series of existences, and direct observa- tion has shown many of them to be no other than transitional phases of life of other organisms. Thus, Dujardin advances as an apology for his attempted classification of Monadina, that the generic distinctions he has essayed to make “are entirely artificial, and simply intended to facilitate the naming of Infusoria which may have been met with in any particular infusion, but which, when better known, may prove in some instances mere varieties of one and the same species” (Hist. Infus. p. 273). Siebold entirely rejects this family of Monadina from the Infusoria, believing them only embryonic forms, and chiefly zoospores of Confervae, &c. (Amat, d. wirbellos. Thiere, 1848, p. 8). In so doing he has had many approvers, among them the eminent naturalist M. Agassiz, who thus writes:—“Recent investigations upon the so-called Amentera have Satisfactorily shown, in my opinion and in that of most competent observers, that this type of Ehrenberg’s Polygastrica, without gastric cavities and without alimentary tube, are really plants belonging to the order of Algae in the widest extension of this group, while most of the Monas tribe are merely moveable germs of various kinds of other Algae'' (A. N. H. 1850, vi. p. 156). Nevertheless the character of this treatise renders it necessary for us to present Ehrenberg’s views of organization. According to these, “the Monadina are illoricated, with a homogeneous body, and no external appendages except cilia, having many separate gastric sacs or vesicles, but no alimentary canal connecting them, and a bisexual or hermaphrodite pro- pagative system. They multiply by simple and complete Self-division of the body into two, four, or more individuals. The uniformity or unvarying external form may be considered one of the principal characteristics of the family; for no one of the Monadina can voluntarily alter the shape of its body, nor can it extend any portion of it and then contract it again. Pro- pagation by ova is assumed of all the Momadina, and by living young, or viviparous reproduction, in Monas vivipara. Some of them have an eye- speck, but no vascular or respiratory system is discernible.” Although the general characters of the Monads are rightly delineated in this account, yet the peculiar hypothesis implied will not at the present day find supporters. Dujardin denied the presence of an enveloping skin or integument; and if a separable distinct tunic is intended, that naturalist is in the right; yet it would be an error to ignore the existence of a layer of different consistence to the contained matter, i.e. of a pellicle. Besides such a pellicle, some Monads, at least, have the power of secreting around them- selves a second oxternal envelope or cyst, or of ‘encysting themselves. When thus transformed, Ehrenberg would not recognize them as Momadina, but as Cryptomonadina, or loricated Monadina. , Hence one source of error in his distribution of these minute microscopical forms. The invariability of form and incapability of extending and retracting the body, so prominently advanced as special features of Monadina, Dujardin does not admit as facts, but, on the contrary, states them to be without integument, and susceptible of adhesion to one another or to foreign par- ticles, and to be capable of stretching themselves out so as to alter their form, even so far as to produce an expansion which may at times be mistaken for another filament. Some Monadina, he adds, can, while freely swimming about, change their form, and by so doing approach the character of Amoebae. K 2 132 GENERAL HISTORY OF THE INFUSORIA. This power of the Momadina to become polymorphic is likewise alluded to by Mr. Carter (A. N. H. 1856, vol. xviii. p. 122). - According to modern phraseology, we might describe these beings as com- posed of protoplasm enveloped by a pellicle, and as having an extension of the protoplasmic mass developed in the form of a flagelliform filament, to serve as a locomotive organ. The presumed gastric cells are the vacuoles in the protoplasm hollowed out spontaneously within it, and ever changing in posi- tion and magnitude. Dujardin affirms that they at times form near the surface, open externally, and on again closing up include foreign particles which have found their way within them, and that they thus act in some measure as instruments of nutrition in aid of the general process carried on by endosmose or absorption. . That the Monadima had a mouth communicating with the ‘gastric Sacs,’ Iºhrenberg believed to be demonstrated by the introduction of particles of colour within those cavities from without. “The nutritive apparatus,” he tells us, “may be readily seen in some species in their ordinary state (for instance, in Monas guttula and M. vivipara), whilst in others it is proved by using coloured food (for example, in Monas Termo and M. socialis). It consists of several distinct or separate cells (from 8 to 20), not all filled at the same time, but one after the other. These are always invisible when empty, but when filled with limpid fluid appear like so many lucid vesicles.” Cohn states that he can confirm the accuracy of Ehrenberg’s observation of the entrance of colouring particles into some Monads, and therefore inclines to the belief that such examples must have an oral aperture, and be of an animal mature (Entw. p. 162). To this he adds that many of the Monads of Ehrenberg may really be swarm-spores of microscopic Fungi; still he holds it to be improbable that true plant-cells should take up within them indigo-particles. So, at p. 148, when remarking on the precise similarity in all visible features of the swarm-spores of Achlya prolifera with Trichodina grandinella and Bodo Saltans, he says Ehrenberg’s Bodo eats indigo-particles, which is not the case with the form in question. - What weight should be attached to these observations of the reception of molecules of colour within Momadina, as proving a mouth and stomach–cells, must be decided by further experiments. Sometimes, possibly enough, when the minuteness of the objects concerned is remembered, the colour-grains have not actually been within, but above or below them, on the surface; and, again, other experimenters damage the force of the argument by affirming that they have succeeded in getting colour taken up by Diatomeae, and by undoubted vegetable-cells. This statement has been made, among others, by Braun. After the consideration given in a previous page to the nature of the supposed eye-specks, further reference to them here is uncalled for. Concerning the modes of multiplication, the great Berlin micrographer is correct in his account of the process of fission; yet few will join with him in describing ova and viviparous reproduction among Monadina, or in imagining distinct male and female generative organs—in other words, an hermaphrodite (monoecious) structure. Certainly the phenomenon Weisse witnessed in Chlorogonium euchlorum, of the development and subsequent discharge of a host of young germs, might be termed viviparous reproduction; but it is no other than the usual plan of development of microgonidia among Algae. In fact, no one has witnessed the development and extrusion of germinal ova, although the breaking up of the substance of Monadina into minute particles, by the process of diffluence or by often-repeated fission, and the reproduction of gonidia may be constantly noticed. Perty so far countenances Ehrenberg’s views as to affirm the development of Monas vivipara and of M. Lens by OF TEIE PELY TOZOA. 133 germs which, whilst still within the parent-cell, exhibit an oscillating move- ment. He would even extend the phenomenon to all Monads; yet we regard it as no other than that of gonidial development. Another circumstance this same writer points out is, that in Monas Lens and allied forms, the anterior individual produced by transverse self-division is 3 to 4 times Smaller than the posterior, and that in Tetramitus rostratus, where longi- tudinal fission prevails, the right segment is much less than the left. It is this unequal segmentation of Monads which induced Dujardin to represent their multiplication to occur by the detachment of a lobe or of an expansion, and not by actual self-division: but in our opinion such a distinction is too refined; for the term self-division has a meaning wide enough to embrace the phenomenon of fission whether by equal or unequal segments; indeed the latter variety is sufficiently common where no difficulty is felt in reckoning it a mode of self-fission. In further elucidation of this act of segmentation in Monadina, we may add the following remarks from Schneider (A. N. H. 1854, xiv. p. 327–328). Speaking of Chilomonas Paramecium, this author writes—“Whatever number of these animals may be observed, no trace of division will ever be remarked in them. Very rarely we may see two individuals adhering by their middle, evidently produced by a longitudinal division. We shall endeavour to ex- plaim this. On close examination, one or two reddish lines may be seen running backwards from the bottom of the indentation, which might readily be taken for organs lying in the interior of the body. I have convinced myself, however, especially by the comparison of the process of division in a species of Bodo, that these lines indicate furrows, which gradually divide the whole by cutting deeper and deeper on each side. As during this process the animal undergoes no change of form, except in becoming a little broader, and the division takes place along its whole length, the process must readily escape observation. The anterior end is always a little thicker; the furrows consequently are deeper and more distinctly recognizable in that part. With a suitable arrangement of the microscope, it is evident that, the two furrows being looked at simultaneously, two reddish lines are seen. It is only in rare cases, when the division has taken place more slowly in Some particular spot, that the two specimens must endeavour to tear themselves free, and thus, by twisting in contrary directions, draw our attention to them. That the process of division is effected in a similar manner in other Momadina, appears from an observation of Ehrenberg's upon Cryptomonas cylindrica (p. 42):—‘I saw no instance of constriction or fissation; but two individuals were swimming whilst adhering together, which might lead one to Suppose that a longitudinal division from behind forwards had taken place.’ And it is not improbable that the specimen represented by him on tab. II. fig. xix. 2, with two seminal glands (nuclei?) and two longitudinal lines, was in the act of division.” That Monads are only the first and simplest stage of existence of numerous animal and vegetable organisms, is an undoubted fact ; but, if we may credit some observers, their transformations are, in certain cases, Very extraordi- mary. Thus, Stein represents the nucleus of encysted Vorticella, to break up into Monads (the Monas colpoda or M. Scintillans), which by various in- termediate stages become reconverted into Vorticellae. So, again, Hartig (J. M. S. 1855, p. 52) and Carter (A. N. H. 1856, xviii. p. 122) represent the conversion of Monads into Amoebae, the former by a coalescence of a group, the latter by the simple assumption by individual Monads, on losing their cilia, of polymorphism. Lastly, the resemblance of the zoospores of Achlya to Bodo saltans hås already been mentioned to be complete in every respect, save in the non-imbibition of colouring particles. - 134 GENERAL HISTORY OF THE INFUSORIA. Few details, excepting those comprehended in attempted generic and specific characters, have been published by observers on the genera of Monadina in general. Uvella, Anthophysa, and Polytoma have, however, received more attention than the rest ; and the results arrived at we will here abstract. Uvella is, in the system of Ehrenberg, characterized by the aggregation of numerous Monads (XVIII.3), severally undistinguishable from simple isolated species (XVIII.4), into spherical or mulberry-like masses, freely moveable in the surrounding liquid. The individuals, like those of the genus Monas, have a locomotive organ, consisting perhaps of two cilia, situated close to the mouth at the anterior extremity, but neither tail nor eye-speck. They pro- gress in the direction of the longer axis of the body, and are capable of com- plete self-division. In the best-examined species, U. glaucoma, Ehrenberg represented large internal vesicles, a double filiform proboscis, and a great number of small colourless granules, conceived to be ova, lying between the nutritive sacs. He supposed it to propagate both by transverse and longitu- dinal self-fission, and stated that, on feeding it with indigo, as many as twelve stomachs were filled, and that sometimes little blue particles like undigested matter might be seen voided from its mouth, and, lastly, that he had dis- cerned several green Monads within its body, which it had eaten, and which proved it to subsist on prey directly transmitted into its interior. Individual Monads, he added, can detach themselves from the mass, live apart for a time, and again become members of the colony. This account was rejected by Dujardin, who denied the existence of a mouth, of gastric cells, and of ova, and doubted the occurrence of true self- division. He likewise never witnessed the re-attachment into masses of the Monadiform individuals after being once separated, but believed that the re- union of certain Monads, occasionally observed in infusions rich in these beings, is a fortuitous result of the glutinous nature of their surface. These strictures of Dujardin are, without doubt, in general very just. The supposed mouth is the clear space seen at the anterior extremity of most unicellular organisms, whilst the supposed stomach-sacs are no other than chlorophyll-vesicles Or, otherwise, vacuoles. The green Monad-like cells seen by the Berlin micrographer were probably starch- or chlorophyll-cells, or, it may be, gonidia; and it was a mere assumption to represent them as swal- lowed particles. ItzigSohn, Cohn, and Mr. Busk make Uvella, or at least an organism like it in all essential external features, a phase of existence of vegetable struc- tures,--the first-named of Oscillatoria (J. M. S. 1854, p. 190), the second of Protococcus, the last of Volvoaz. Itzigsohn describes the Euglena-phase of Oscillatoria as breaking up into microgonidia which collect themselves in colo– nies, resembling, according to the presence or absence of coloured contents, Uvella atomus, U. glauca, Bodo, &c. Cohn's views are sufficiently represented in our remarks on Protococcus (see p. 124), and need not be here repeated. Busk represents the ciliated zoospores of Volvoa (T. M. S. i. p. 39) as sub- dividing into minute ciliated cells (i. e. microgonidia), which “form by their aggregation a discoid body, in which the separate fusiform cells are connected together at One end, and at the other are free, and furnished each with a single cilium. In this stage these compound masses become free and swim about in the water, constituting in fact a species of the genus Uvella, or of Syncrypta of Ehrenberg.” If these representations be correct, Uvella is but a phase of existence of Volvocina and of Oscillatoria, and probably of other plants. If this be not allowed, then the alternative remains, of supposing both a vegetable and an animal organism partaking like characters and qualities. OF THE PE(YTOZOA. 135 The genus Anthophysa (XXVI. 2) has been more particularly studied by Dujardin and Cohn, Ehrenberg provisionally placed it among the Vorticel- lina as a doubtful species of Epistylis, as he was unable to determine whether it possessed a wreath of cilia at its head or only a single filament: if the latter, he remarked, it would belong to the Monads. Müller, its discoverer, had indeed more rightly seized on its true position by associating it with Volvoag. Dujardin subsequently made out its affinity with Uvella, and adopted M. Bory de St. Vincent’s generic appellation for it. In this determination of its position Dujardin has the weighty support of Cohn, who has recently sub- mitted it to careful examination. Dujardin’s description is very accurate, and will serve our purpose. “It is very difficult,” he writes, “to distinguish a Uvella from a free Anthophysa ; but no difficulty will exist if some of the branching supports of the latter are seen in the surrounding fluid. These Supports have an arborescent figure irregularly branched, are brownish at the base, but clearer and even diaphanous at the extremities of the branches, which are themselves modular or rugged; they are secreted by the animals, and are found affixed to the sides of the vessel in which water containing these Infusoria has been but recently placed. Each group of animalcules is at first fixed on the diaphanous extremity of the branch which it has secreted (XXVI. 2); but any agitation of the liquid, or sudden shock, easily detaches it, and it then moves in a revolving manner in the liquid. This movement is the result of the simultaneous action of the flagelliform filaments with which each individual of the colony is provided. When, moreover, a group has been detached, whether accidentally or spontaneously, isolated individuals may be seen moving about precisely like Monads with a single filament. The branch- ing support is at first soft and glutinous, but gradually acquires consistency and a brownish and horny aspect, when it seems no longer to participate in the life of the animalcules, and recalls to the mind the construction of the fibrous skeleton of certain sponges. It is conceivable either that the branches themselves bifurcate, or that the division is the consequence of the multipli- cation by fission of the groups of animalcules.” Cohn has little to add to this account. He describes the probably chitinous stem to be invested externally by a brownish mucilaginous layer; and also finds that from 2 to 8 and from that to 20 Monads may be aggregated at the extremity of the branches. Frequently a branch is bare at its point, having lost its animal colony; and it would seem that the whole of the groups are in succession thrown off and dispersed as free Monads and as Uvella-like groups. Cohn, indeed, intimates his belief that Uvella and Anthophysa are not actually distinct genera, but mere representatives of two conditions of the same animalcule. Unlike Ehrenberg, he failed to get indigo-particles taken up by the Uvella-like beings. Before arriving at the conclusion that Anthophysa is no other than Uvella Uva seated on a branching stem, and of animal nature, he canvasses the question if this organism be not rather the mycelium of a Fungus bearing its spores at the extremities of its branches, and decides against the supposition chiefly from the irregular and indefinite multiplication of the monadiform members of the groups, from the detachment of these en masse instead of by separate spores, and from the want of evidence to show that, when these Uvella-like groups are detached, they assume the quiescent or ‘still’ condition, and germinate into an arborescent mycelium like the parent, to develope in its turn terminal masses of spores. * The branching stem has been described by Kützing and others as a micro- scopical Fungus (Conferva), under the name of Stereomema, and several species instituted; but Cohn points out its analogy with the pedicle of Gomphonema 136 GENERAL ITISTORY OF TILE INFUSOIRIA. and other Diatomcas, in which both the branched stem and the beings it supports are alike part and parcel of the same organic structure. He has met with fibres supporting but one or two Uvella-bundles, and others like little trees bearing ten such. The consistence of the stem is such that it resists the action both of sulphuric acid and of solution of potash. One other genus of Monadina, viz. Polytoma (XVIII. 5), has received special attention from Schneider, Cohn, and Perty; it nevertheless still remains in that neutral ground claimed both by Zoologists and botanists. Ehrenberg at first placed it in the family Monadina; but having subsequently met with a similar form, Spondylomorum, he instituted a new family, Hydromorina, to include the two genera, and set forth as its chief differential characters the aggregate or compound nature of its members, dependent on imperfect fission. He asserted also that individuals set free from the groups enter on the same cycle of fission and compound development, and form similar groups. Poly- toma was described to be destitute of an eye-speck, to have a truncated mouth and a delicate double flagelliform proboscis, and, from repeated incom- plete self-division, to form a mulberry-like mass, which eventually breaks up into isolated Monads. “The ova,” he adds, “from their minuteness and the want of transparency, have hitherto eluded observation (XVIII. 5): but the alimentary organization is, on the contrary, clearly demonstrable ; for al- though for a long time the entrance of coloured food could not be displayed, yet at length, by using a magnifying power of 600 to 800 diameters, the entrance of indigo-particles into their bodies was rendered evident.” In addition to these structures, he mentions a large contractile vesicle as a male sexual organ, and a white spot at the anterior part of the body as a seminal gland. In all essential particulars the associated genus Spondylomorwm was stated to agree with it, except in having a dorsal eye-speck. Dujardin confesses his inability to distinguish by any definite characters between Uvella and Polytoma; he would seem, however, not to have per- sonally investigated the latter. Cohn, after examining both, declares them to be identical in all particulars except that in Polytoma chlorophyllis absent, and that it inhabits decomposing fluids along with Chlamydomonas pulviscw- lus. However, it is to Schneider that we are indebted for the most complete history of this organism (Inaugural Dissertation, “Symbolae ad Infusorium historiam naturalem,” Berlin, 1853, translated in A. N. H. 1854, xiv. p. 321). We extract the following copious details from the translation:-‘‘ Polytoma Uvella is of an oval form ; it is from gºth to ºth of an inch long, and about half that width. At one end, which, with Ehrenberg, we will call the an– terior extremity, it bears two filaments as long or longer than the body. When the living animal is examined under a magnifying power of 300 dia– meters, the body appears to be bounded by a simple outline. But in many instances, and especially when a large specimen can be found at rest, it may be seen that the internal substance of the body is surrounded by a thin and perfectly clear membrane, from which it is separated by a distinct space. When the investing membrane is more closcly attached, its existence may always be demonstrated by the employment of reagents to produce the con- traction of the substance of the body : chromic acid and solution of iodine in chloride of zinc are the best substances to employ, the latter especially, as it at the same time communicates a brown colour to the internal sac (Pl. XX. fig. 2). Under certain circumstances, the investing membrane divides into minute granules, assuming when viewed from the side a regular necklace- like appearance (fig. 8). A reproduction of the membrane then takes place. The substance of the body is perfectly clear, with the same refractive proper- ties as that of Amoeba. About the middle lies a clear globular nucleus, sur- OF TEIE PEIYTOZOA. - 137 rounded by a narrow reddish halo (figs. 1, 2, 3, 8). Dilute acids render this more distinct. At the anterior extremity, close to the margin, there are two reddish vesicles, the contractions of which may easily be recognized in individuals in a state of repose. The hinder extremity always contains a mass of granules with dark outlines, which are not altered by acetic acid. A weak solution of iodine in iodide of potassium gives them a deep blue colour, gene- rally verging upon black, as it is difficult to hit the right quantity of the reagent to be added. The fine blue colour is better attained by the addition of dilute solution of iodine in chloride of zinc, as with this the granules become slightly liquefied, and when left standing for some time even form a blue paste. Muriatic and sulphuric acids also dissolve them, so that the subsequent addition of iodine gives the whole body a blue colour. When the putrefaction of the infusion is going on very rapidly, the granules fill the entire body. They are not arranged in balls like the nutritive matter in the bodies of other Infusoria; and it is by no means probable that they are taken in from the exterior. Besides the two contractile vesicles, single, non-contractile, reddish vacuoles are seen scattered through the substance of the body. - . “The starch-like granules are often converted into an indigo-blue pig- ment, which is then partially dissolved, and colours the whole parenchyma. Such specimens as these still retain the power of division, so that there can be no doubt as to their identity with Polytoma Uvella. Individuals were also frequently met with of which the substance of the body was of a uniform green colour, but which in other respects agreed exactly with Polytoma. . - “Deviations from this normal form never occur singly in the same vessel, but always make their appearance simultaneously in a great number of indi- viduals. Certain peculiarities of their abode appear therefore to have an influence upon the form. Very compressed forms are rare. However, it not unfrequently happens that, whilst the investing membrane retains its normal form, the substance of the body is not equally distributed in its interior. Sometimes it lies to one side, so as to fill only half the interior of the sac ; sometimes it is entirely collected in the anterior, and sometimes in the pos– terior extremity; in the latter case it is connected with the anterior extre- mity by a slender filament (fig. 14). In infusions in which fermentation has long ceased, and which contain a large quantity of brown humus-like matter but very small portions of nitrogenous substances in solution, the two last modifications of the parenchyma are most frequently met with. At the same time the starch-like granules disappear, the substance of the body acquires a darker fatty outline, and finally disappears with formation of the well-known large vacuoles. “The movements of Polytoma are the same as those usually ascribed to organisms furnished with two filaments. Whilst in motion the filaments are always in front, the animal rotates upon its axis, and this again describes circular vibrations upon a central point. If a movement in the opposite direction is taking place, the animal is endeavouring to turn the anterior extremity; and until this is effected it swims backwards. When a drop of the infusion has been left for a few minutes upon a glass plate covered over with a piece of thin glass, a considerable number of the animals will be found attached to both glasses by their anterior extremity; the filaments are free, and it is probably by their vibration that the hinder extremity is made to oscillate in the direction of the plane of the two filaments. They collect in the same manner in crowds upon aquatic plants, as well as upon the sides of the vessel containing them. Their mode of attachment is still unintelligible to me. In any case, some contrivance for this purpose, however simple, must 138 GENERAL EIISTORY OF TELE INFUSORTA. exist, either between the two filaments, or at the side of their points of issue from the membrane. “During the swarming-state, a division of the substance of the body goes on uninterruptedly at all hours of the day. The different stages of this process follow one another with greater or less rapidity in proportion as the conditions of nutrition are more or less favourable. Soon after the commencement of fer- mentation in an infusion, the rate of increase attains its maximum ; it then diminishes as the fermentation ceases, the Offspring at the same time undergo— ing a diminution of size. “The commencement of the process of division is indicated by the uniform distribution of the granular substance. A constriction of the substance then takes place, usually commencing on One side ; by this the body is divided into two parts, which are still enclosed in the uninjured investing membrane. Simultaneously with, or perhaps before the completion of this bisection, the nucleus also divides (fig. 3). Although no constriction of the nucleus was ever noticed, nothing certainly was observed to contradict the supposition that the second nucleus was produced in this manner. The two halves then become constricted from their surfaces of contact, in such a manner that the constriction of one half crosses that of the other at right angles (fig. 4). To every depression thus produced on the one side there is a corresponding ele- vation of the other. The quadrisection (figs. 9, 12) then takes place suddenly as if by cutting, and without any appearance of a circular constriction, each por- tion containing its proper nucleus. The divisions now acquire an oval form, and arrange themselves in such a manner that the ends of the posterior pair, which are turned towards the middle, alternate with those of the anterior pair in the same place (fig. 12). In very favourable circumstances (as for in- stance at the commencement of fermentation), a third division into eight parts takes place, each division being still furnished with a nucleus. As a general rule, however, the young individuals acquire filaments soon after the quadrisection, and move about in various directions within the investing mem- brane, until this bursts and the young, which are exactly like the mother except in their smaller size, are set free. In favourable circumstances the empty membrane remains with the two filaments. After the division of the substance into four or eight parts, the investing membrane is always visible without the employment of any reagents. This has not escaped Ehrenberg (loc. cit. and tab. I. xxxii.); he explains the appearance as a consequence of a superficial constriction. The filaments of the parent always appear to be con- nected only with one of the young individuals, although this is less distin- guishable in the present mode of division than in that about to be described. “In this the quadrisection takes place in another manner. After bisection, the two portions shift their position in such a manner that the surfaces of contact form a distinct angle with their original position. If this change of position be but trifling, the quadrisection goes forward nearly in the manner just described, and the arrangement of the developed young only differs as far as is rendered necessary by this change of position (figs. 9, 12). But if it be more considerable, the new surfaces of division run parallel to each other and nearly perpendicular to the surfaces of contact of the two halves. The posi- tion of the young individuals is then completely different from that seen in the preceding case; all four lie parallel to each other, with their longitudinal axis oblique as regards the axis of the whole (fig. 10). “This difference may perhaps be explained as follows:—Each portion has a tendency to acquire an oval form, so that Soon after the bisection the ante- rior portion extends itself posteriorly, and the posterior towards the front. When sufficient time has not elapsed for the one dimension to predominate over OF THE PEIYTOZOA. 139 the other, the quadrisection takes place as in the former case; but when, on the other hand, one dimension has become predominant, the division into four takes place in accordance with the same law as the original division into two. “The method of division first described is always met with in the early periods of an infusion, which are most favourable to the development of the creatures. Towards the end the latter mode alone occurs. This phenomenon was so remarkable that, on the first occasion of my examining an infusion towards the close of its action, I imagined that I had at first misunderstood the mode of division. “ Under certain circumstances the individuals pass to a state of rest. They are then completely filled with the starch-like granules, so that the nucleus only appears as a reddish spot. The substance of the body becomes spherical, and invests itself with a membrane which is frequently of considerable thick- mess (fig. 7). In this state I have never observed them to undergo any divi- sion or any other change; and when dried the cysts still retain their contents. When clear water is poured over them they do not return to life, but would probably do so in a fermenting infusion. “The mode in which the swarming individuals arrive at this state of repose appears to be as follows:—The filaments are gradually shortened, their sub- stance collecting at the free extremity in the form of a small knob, until at last the filiform portion entirely disappears, and, in place of the filaments, two vesicles are seen at the anterior extremity of the investing membrane. I have observed a similar contractibility of the substance of the filaments in a Bodo which is most nearly allied to Bodo grandis, Ehrbg. As this possesses not three filaments only, as seen by Focke (Ehr. p. 34), but often as many as five, the vesicles produced in this manner cannot easily be overlooked. I cannot, however, state with certainty whether all the individuals which undergo this change invest themselves with cysts. When infusions containing Polytoma are dried slowly, individuals with the vesicles just described are found in the deposit, but no cysts; and it is not impossible that such individuals may assist in the continuation of the species in some other way.” After some valuable notes on other Infusoria, Schneider concludes his history of Polytoma by the following arguments for its animal nature:— “That Polytoma is an animal may be maintained upon two grounds. “1. The constitution of the investing membrane.—As soon as the starch-like granules have been destroyed by the long action of concentrated sulphuric acid, no part of the creature is coloured blue by iodine. Now we have no more reason for believing that the vegetable cell-membrane must necessarily consist of cellulose, than that the animal cell-membrane should not consist of that substance, so that we are still compelled to seek for other characters for their distinction. These would be— “2. The contractile spaces.—A statement of Cohn has certainly rendered it doubtful whether the occurrence of these is henceforward to be regarded as an essential indication of an animal nature. He says, “On the other hand, certain genera of Algae exhibit a stage of development in which, in external form, in the absence of a cellulose membrane, in the distinct existence of ciliary organs of motion, red eye-like spots, vacuoles, and, according to a very recent discovery, of internal pulsating spaces, they undoubtedly appear very similar to the Astomatous Infusoria.” If these pulsating spaces occur only in unicellular Algæ provided with cilia, these perhaps should properly be re- stored to their place amongst animals, notwithstanding the subsequent ap- pearance of cellulose-membrane upon thcm. But if they occur in the swarm- cells of the Confervae, they certainly cease to be a characteristic of animal nature. Thus; if we are not yet in a position to refer Polytoma with perfect 140 GENERAL IIISTORY OF TEIE INFUSORIA, certainty to its proper place, there is decidedly no reason for excluding it from the animal kingdom. We will not, however, venture to consider the Infusoria furnished with a mouth (Stomatoda, Von Siebold) as formed, like Polytoma, upon the type of a simple cell: for, high as we may rate the ad- vantage accruing to science from the comparison of the Protozoa with simple cells, difficulties stand in the way of its complete application in the case of animals of such complicated structure as the Vorticella for example ; and these cannot be considered as entirely done away with until the history of their development has furnished proof that at no period does a fusion of several cells take place. - “In conclusion, we bring together the results of the investigation as shortly as possible. “1. Polytoma is an animal. - “2. It is characterized by a clear investing membrane, which does not consist of cellulose; two contractile spaces in the substance of the body; a nucleus with a nucleolus; two filaments; and by the deposition of layers of starch-like granules. - - “3. The starch-granules may become converted into a blue or green co- louring matter. “4. Polytoma divides within the investing membrane into two, four, or eight parts, and propagates itself in this manner. - “5. It passes into a state of repose.” These arguments will, we fear, not be deemed Satisfactory to most natu- ralists. That the investing membrane should not be coloured blue by iodine is an unimportant fact in determining its nature; for the same thing happens with many undoubted vegetable tissues, and we are, besides, not sufficiently acquainted with the chemical history of starch, cellulose, and allied isomeric substances, to appeal to their presence or absence as decisive of an animal or vegetable nature. Then, again, as to the contractile spaces, these cannot be considered peculiar to animal life, seeing that they are present in such gene- rally recognized vegetable forms as Chlamydomonas, Gonium, and Volvoa2. Moreover, Schneider himself describes starch-granules and chlorophyll- vesicles within Polytoma, which, if these substances had any decisive bearing on the question, would quite settle its affinity with plants, irrespective of the constitution of the enveloping membrane. Besides, the whole history of the organism accords so closely with the known phenomena of life and develop- ment of the simplest plants, that this alone must carry much weight in fixing its position in the scale of beings. - FAMILY II.—CRYPTOMONADINA. (Plates XVIII. 29–34.) The CRYPTOMONADINA, which follow the Momadina in the arrangement of Ehrenberg, claim but a brief consideration, inasmuch as so little precise infor- mation is obtainable with respect to them, and as the existence of possibly all of them as independent organisms is a matter of much uncertainty. The genera enumerated were—Cryptomonas, Ophidomonas, Urocentrum, Lagenella, Cryptoglena, and Trachelomonas. To characterize the Cryptomonadina in two words, they are encysted Monadina or Eugleneae. Ehrenberg puts forward the following account –“They exhibit all the characteristics of the Monadina, but have, in addition, an external diaphanous membrano, or lorica, which either encloses them entirely—i. e. forms an wrceolus, or leaves one side exposed, and so constitutes merely a shield—scwtellum. Locomotive organs, in the shape of two delicate filiform and generally retractile filaments or pro- OF TITE PEIYTOZOA. 14] boscides, extend from the margin of themouth in all the genera except Lagemella, in which also, by the way, Werneck thinks he has discerned them. Coloured food has not been known to be received; and hence the nutritive organization has not been demonstrated; however, in six or soven species (nearly one-half the family) internal gastric cells have been discovered. In two genera sensation is exhibited by the presence of a coloured spot or ocellus at the fore part of the body. Multiplication by complete division has been secn in some specimens.” Such is Ehrenberg's account of Cryptomomadina. Dujardin has a parallel family with it he names TheCamomadina, and details the following particu- lars (op. cit. p. 323):—“The Infusoria of this family having in some mea- sure merely one negative character in common, viz. the non-contractility of their integument, can be divided into several families according to the nature of the enclosing membrane and the number and disposition of their locomo- tive filaments. Thus, Some arc globular and others leaf-like ; some have a hard, as it were stony shell, whilst others are covered only by a thin flexible membrane; some, again, have but one filament, others two similar ones or two of different size, and others, again, more than two. Until new observa– tions have augmented the number and the knowledge of species, the differ- cnces just pointed out will merely serve to characterize genera which are indeed much more really distinct in this family than in Monadima. The Thecamonadina aro in fact more advanced in organization than the Momadina ; they are not, like the latter, produced in artificial infusions, nor do they change figure and characters according to the medium in which they exist. They stand in the same relation to the Monadina that the Rhizopoda (Arcellina, or Monothalamia) do to the Amaebac: their organs are no more distinct; but their individuality is more pronounced.” “The Thecamonadina are all very small, although they may be rendered visible to the naked eye by their accumulation in great numbers, and by the colourthcy then give rise to ; their colour is usually green, . . . . but sometimes red. They are mostly cognizable by the stiffness of their body and the uniformity of their movement.” Dujardin ignores the stomach-sacs, the con– tractile scninal vesicle, the testis, and the grocn ova which Ehrenberg attri- buted to this family: he likewise can assign no value to the eye-specks as generic features, and is compellcd to deny the occurrence of shells in the form of a shield, open on One side; for those appearing so are merely flattened on that aspect. He adds, the integument in all these cases is much more roomy than the contents, from which it is separated by a clear space having the appearance of a ring. Perty adopts both the terms, Cryptomonadina and Thecamonadina, to ex- press the two families under which he arranges the several genera enumerated by Ehrenberg and Dujardin, together with some instituted by himself. This is not the place to point out the distinctions he has drawn between the two families so constructed; but the original observations Perty has made on some specimens will be of interest. For instance, he says that (op. cit. p. 81), “When the green animalcule of Trypemonas volvocina (Trachelomonas vol- vocina, Ehr.) is about to self-divide, it contracts itself within its glass-like globular shell, oscillates to and fro, whilst the motor-fibres become lost, or remain without further connexion with the animal, fixed in the circular opening of the outer shell. Fission now proceeds in the usual mode into two and four individuals, which on their completion czhibit the red stigma, previously undistinguishable among the green molecules: the breaking up of the shell, scarcely rºtºth of a line in thickness, is offected either by the movements of the contained beings or by dissolution.” The shells of Thºſpermonas, Chonemonas, and Cryptomonas, which contain no silox in their 142 GlöNERAL EIISTORY OF THE INFUSORIA. composition, seem to be particularly prone to decomposition, so that their empty shells or their fragments are extremely seldom to be met with in water abounding in loricated Monads. “In Cryptomonas polymorpha I have repeatedly witnessed this rapid breaking up of the shell; the margin is resolved into numerous drops which separate from one another, and in the course of ten or twelve minutes the lorica spreads itself out as an inconspicuous mem- branous structure. Moreover, in Chonemonas hispida, a constant movement is observed in the shell when the animal is about to divide, and when, as almost always happens, the filaments are lost, or remain attached to the shell without any connexion with the animal. Until the period of self-division the connexion between the animal and shell persists, for the latter is, at its origin, simply the hardened periphery of the former; but when fission hap- pens this bond is ruptured and cannot be re-established, and the contained animalcule, being thus set free, no longer moves with the shell, but in it, and this in an uneasy, irregular manner.” At p. 83 he goes on to say that in Cryptomonas polymorpha internal germs (Blastien) are almost constantly cognizable ; in Smaller and young specimens in less abundance. In a pool containing Utricularia in July 1848, he met with the dark green variety in immense numbers, along with clear green germs from gº" to Tºp", col- lected in masses held together by a very delicate pellicle, and either motion- less or in active movement among the old individuals. In other varieties he has seen similar gorms. Thus, on pressing the large brown variety the germs escaped as independent isolated beings. In the hyaline variety (Chilomonas Paramecium, Ehr.) he not seldom witnessed astonishingly rapid development by longitudinal fission ; in one specimen the two halves remained for a con- siderable time tied together by a band, which became stretched thinner and thinner by the long-continued movements of the two beings until it at length gave way. After moving about for some time, vital energy is lost, and probably one-half of the specimens sink to the bottom of the drop of fluid under obser- vation. The germs in this hyaline variety are moreover very evident and numerous. Amid the many specimens of nearly equal and minute size, others much larger are not uncommon, furnished with a red eye-speck. Schneider gives (A. N. H. 1854, xiv. p. 327) an account of Chilomonas Paramecium, differing much from the foregoing. He describes it as having a clear nucleus with a reddish halo around it, and, although he could distin- guish no contractile space, observed a reddish vesicle always in the anterior extremity, and, in direct opposition to Perty’s observations, states that what- ever number of these animals he examined, he never observed multiplication by fission (p. 133). In March 1848, Perty noticed Anisonema acinus (Duj.) in different stages of development; the smallest forms were evidently derived from the germs, about #" in length, and circular; by further growth they became elliptic, and presented a larger number of internal germs; at the same time the fibres, which are so easily seen in the full-grown beings, were perceived with the greatest difficulty in the Smallest. Among his Thecamonadina are enumerated two genera, named Chonemonas and Trypemonas: the latter is equivalent to Ehrenberg’s genus Trachelo- monas; but the former includes, besides Lagemella, two genera which the Berlin systematist placed in families far removed from his Cryptomonadina, viz. Chaetoglena, placed among the Peridiniata, and Pantotrichum, classed with the Cyclidina. Concerning the reproduction of these two genera, Perty has some original observations. In some decomposing water he met with Chonemonas and Trypermonas in great abundance—the greater part of a green colour with red eye-specks, OF TEIE PEIYTOZOA. 143 without lorica, and of various dimensions. In both, the lorica first made its appearance as a Smooth hyaline envelope, which grew stronger, then red, and at length brown or blackish brown—becoming also in Chonemonas still firmer, and covered with asperities. During this transition from a soft periphery into a shell, two sets of intersecting lines were at times visible, which by-and-by vanished. Moreover, examples of Chonemonas occurred which continued Smooth, and constituted the variety Ch. glabra. By using very high mag- nifying powers to fully developed specimens of Trypermonas volvocina, the lorica appeared to be everywhere perforated, or more probably beset with a series of depressions or thinner spots. On the shell becoming very dark, the green contents and the red stigma ceased nearly or quite to be visible. Naked Chonemonads and Trypermonads are easily distinguishable from Euglence, because their contractility is so much less, and consequently their actual round form so much the more permanent. All these minute naked examples are doubtless produced from germs: fission was witnessed in no instance. Ordi- marily the animal-like Chonemonas, furnished with a red eye-speck, had an elliptical form prior to the construction of the shell, just like loricated forms; yet ovate and obovate examples are also to be seen. Minute specimens are poorer in endochrome, this material occurring only in one or two specks. The locomotive filaments are absent at first, and after their appearance only gra- dually attain the normal length. The construction of the lorica frequently proceeds to completion in very small specimens, whilst large Ones remain naked, notwithstanding the formation of germs goes on in those where the chromule is in a certain quantity. Many dead Chonemonads were encountered having their contents either shrivelled up or even so completely removed as to leave only an empty yellowish-brown shell. At a subsequent page (p. 131) Perty mentions certain abnormal forms, among others Cryptomonas polymorpha, having but one instead of two fila- ments, and at other times elongated into a tail-like process. From all the preceding accounts of Cryptomonadina there seems sufficient to show that these beings are but a certain phase, the encysted state, of a set of organisms which have a general resemblance to Zoospores, or to simple unicellular Algae. The germs mentioned by Perty accord, to all appearance, with the microgonidia of other authors, and behave themselves in a similar manner. Cohn observes (A. N. H. 1852, x. p. 335)—“Trachelomonas and the analogous forms do not belong to the vegetable kingdom at all, but are nearest allied to the Astasiaea, and appear to be loricated Eugleneas, not loricated Monads, as Ehrenberg assumed.” We shall hereafter see that this indefatigable naturalist leans to the belief that Eugleneae are animals; hence the idea he puts forward respecting the Trachelomonads. As these sheets were passing through the press, Mr. Carter's valuable paper on Eudorina and Cryptoglema made its appearance (A. N. H. 1858, ii. p. 237). The Cryptoglena described is supposed to be a new species, and is named O. lenticularis, on account of its lenticular shape. It is compressed and emarginate, and furnished with a pair of cilia. In this little being Mr. Carter supposes an act of fecundation to take place, the microgonidia being supposed to represent the male, the macrogonidia the female element. Among the numerous specimens met with, there was a number of deciduous lorica, “ some of which were split into halves which were separated, while others only adhered together anteriorly, and presented a pair of cilia attached to their point of union.” In several instances, the internal cell, or the con- tents enclosed in their protoplasmic sac, often distended by imbibition of water to three or four times the dimensions of the germ lorica, were seen escaping from the separated segments of the latter, and in their globular shape and 144 GENERAL EIISTORY OF TEIE INFUSORIA. general features undistinguishable from Chlamydococcus under similar forms, These escaping internal cells were divided into two, four, eight, and sixteen parts; and it was noticed that the variety which came forth with only two gonidia was surrounded by a swarm of from ten to twenty much smaller gonidia, which were identical in all appearance with those resulting from division into sixty-four parts. But the cells divided into two segments were not the only ones so surrounded by microgonidia; for in two or three instances a few were found around and adhering to the inner cell of those divided into four gonidia. “It was also observed that the two-division did not always come forth in one cell, but that sometimes this was also divided, so that each gonidium had its proper cell. The form of the macrogonidia or female cells did not differ from the internal cell of the parent, except in being a little Smaller,-while the microgonidium, which was not more than 1-7th of the diameter of the macrogonidium, and therefore very Small, appeared, though equally green, and provided with an eye-spot, to have only one cilium. I cannot help thinking, however, that, with a higher power, I might have seen two.” The purpose fulfilled by the contact of the microgonidia with the macro- gonidia, Mr. Carter concludos to be that of impregnation; for he observed one of the former, as a spermatozoid, fix itself to one of the latter (the spores or female cells), and gradually become incorporated with it. The microgo- midium, after having so attached itself, assumed a conical or peg-top shape, and thus appeared to gradually Squeeze itself into the macrogonidium. This mode of impregnation, thus directly observed by Mr. Carter, is the copy of that the same observer witnessed in Eudorina (Pandorina), and of that first noted by Cohn in Volvoaz. He, moreover, believes that it obtains in the case of Trachelomonas, for he “has often seen the largest Trachelo- monad of a pool divided up into a group of apparently sixteen cells within the lorica; and this may account for the myriads of three to four smaller sizes that are frequently found together in this way. The latter certainly appear in a green form first ; that is, without the lorica, which gradually becomes supplied afterwards. Thus, impregnation also in the Trachelomo- nads may take place like that seen in Eudorina, after the parent-cell has undergone division within the lorica.” (See Part II., Systematic History of Cryptomonadina.) FAMILY III.—WOLWOCINEAE OR WOLWOCINA. (Plates XIX. XX.) This is the most important and most interesting family of the Phytozoa. The genera enumerated in it by Ehrenberg were Gyges, Pandorina, Go- mium, Syncrypta, Symura, Uroglema, Eudorina, Chlamydomonas, Sphaerosira, and Volvoaz. The name is derived from the rolling (volvere, to turn) motion of the genus Volvoaz, which is typical of the family. Ehrenberg was the first rightly to appreciate the true nature and compound structure of the principal genera as the aggregation of numerous monadiform beings in a common polypary-like mass. He correctly described the several individuals as resembling Monads in most particulars of their organization, but was so carried away beyond this simple natural statement by his peculiar views of structure, as to describe them as having an unvarying body, without other external appendages than a pair of cilia or filaments, and internally several digestive Sacs but no true alimentary canal, green ova, two rounded seminal glands, a contractile (spermatic) vesicle, and eye-specks indicating the exist- ence of Sensation. The substance connecting the several beings, and in OF TIII, PTIYTOZOA. * 145 which they are imbedded, he called the lorica, and stated that propagation occurred by self-division within the envelope, and probably also by ova. The genera Chlamydomonas and Gyges, or Chlamydococcus (XIX. 9–31), offer an exception to the other members of the family in not producing aggregate forms or colonics, at least not in their assumed typical phase. Whilst denying in toto the elaborate animal organization presumed by Ehrenberg, M. Dujardin nevertheless continued to recognize the Volvocima as animal structures, and contented himself with merely proposing a dif- ferent distribution of the gonora. However, since this distinguished French naturalist wrote, the opinion has been powerfully advocated, and everywhere gaining ground, that the Volvocineſe belong to the vegetable kingdom; con- sequently their structure and vital phenomena receive quite a different inter- pretation from that given by the writers above named. The Volvocineſe are now, in the language of algologists, “ Tetraspora,’ of the family Palmellea, or Palmellacece. The monadiform beings are ‘primor- dial cells,’ and, in more general language, ‘corpuscles,” whilst the common pellicle or nidus connecting them is called by Cohn and others the ‘envelope- cell.’ The author just named says (Entw. p. 165), that, from his observa- tions on Chlamydococcus, Chlamydomonas, and Stéphanosphaera, the Volvo- cinece in general consist essentially of two parts:–1. of a colourless, hyaline, completely closed, and usually spherical envelope-cell composed of cellulose; and 2. of green primordial cells, single in the two first-named genera, but eight in number in Stephanosphaera, enclosed within the envelope-cell. In each case these cells are simply primordial sacs, unenclosed by any special firm cellulose membrane, and consist of a fine granular protoplasm, coloured green or red by chlorophyll, or by a peculiar oil (XIX. 48, 49). The proto- plasm forms only the outer layor of the cells, and is often prolonged on the inner surface of the ‘envelope-cell’ in the form of delicate mucous fibres (XIX. 53). The primordial cells are moreover themselves elongated from before backwards, forming a colourless apex from which two vibratile fila- ments take their rise, and passing through two foramina in the envelope- cell, stretch themselves outwards in the surrounding water, and by their vibration serve to move the ontine compound organism. The only difference between Chlamydococcus and Stephanosphaera is one affecting the mode of development, in which only the primordial cells (not in any way the common envelope) take part. These colls divide first into two, then into four, then into eight or more daughter-cells (macrogonidia) (XIX. 40, 41, 42); but after the third or the Second, and often, indeed, after the first act of division, a permanent generation results. Thus, in Chlamydomonas and Chlamydo- coccus, each of the daughter-cells becomes free and independent, encloses itself within an envelope-cell of its own, and after developing two fibres, breaks through, with their aid, the common envelope of the parent-coll (XIX. 23–26 and 30). In Stephanosphaera, on the contrary, the eight primordial cells produced by the third act of fission secrete around themselves a common envelope (XIX. 56), which invests them like an integument, first lying close upon them, but afterwards, through the imbibition of water, raised from them all round, assuming a globular form; but so that the primordial cells occupy the periphery at the equator of the globe like a ring or zone (XIX. 57, 58), having their eight pairs of filaments protruded through the openings in the common envelope (XIX. 38). Chlamydococcus and Chlamydomonas stand in the same relation to Stéphanosphaera that Pleurococcus does to Pal- mella, Phycastrum to Desmidium, Navicula to Schizomema, Vorticella to Epi- stylis, or as Hydra to Campanularia. But, further, a second mode of development, viz. by microgonidia, prevails L 146 GENERAL IIISTORY OF THE INFUSORIA. alike in the three genera in question, the bisection of the contents of the cell proceeding so far that they are eventually resolved into numberless small, mostly spindle-shaped corpuscles (XIX. 51), which at first oscillate by the aid of two or four vibratile filaments within the common envelope-cell, but subsequently escape singly from it, (XIX. 52), and, after enjoying for a con- siderable time very energetic infusorial movements, finally pass into a state of rest, preparatory to some future development. “The larger undivided macrogonidia, after swarming ofton the whole day, are also seen to enter (as witnessed in Chlamydococcus and Stephanosphaera) into the condition of rest, when each primordial cell contained within the delicate envelope-cell secretes about itself a second more compact cellulose membrane which closely invests it, and is not perforated by the ciliary fila- ments (XIX. 20, 21). It is, in fact, the counterpart of the membrane which, in common plant-cells, overlies the primordial layer. In this distinctly plant-like or protococcoid condition the cells remain without motion, and may endure, even when dried, for a whole year, and then, on the addition of water, undergo Segmentation into two, four, or eight gonidia, which, imme- diately after developing their filaments and envelope-cells, break through the walls of the parent-cell and crowd the surrounding fluid.” The facts relating to the structure and functions of the genera above adduced, apply in the main to all the Volvocinece; for the differences between the several genera, although demanding special consideration, are not essen- tial. Thus, for example, in Gonium (XIX. 32) the figure is a flattened sphe- roid, and the green primordial cells, viewed collectively from above, resemble a four-sided disc or plate, having each angle truncated. Moreover, the trans- parent colourless envelope does not acquire the character and appearance of a firm membrane, but presents itself as a mucous or gelatinous, not cellulose, sheath. CHLAMYDOMONAS.—The first of the genera included by Ehrenberg in his family Volvocina, of which we shall attempt a description, is Chlamidomonas or Chlamydomonas (XIX. 16). It recommends itself to our attention because of its simplicity and its existence in an isolated state. This last fact seemed to Dujardin a sufficient reason for removing it from the Volvocina to the ThecamOnadina, and for renaming it Diselmis, on account of its having two filaments; for he would admit into the former family only aggregate organ- isms “ enclosed within a common envelope, or having special envelopes mutually adherent.” On this same ground he also advocated the transposi- tion of Gyges from the Volvoa family to that of the Thécamonadina, a genus which we shall presently have to note under the name of Chlamydococcus or Protococcus pluvialis. To this arrangement Cohn objects (A. N. H. 1852, x. p. 334); for, says he, “a more profound investigation, not only of the structure, but also of the history of development, teaches us that Chlamydo- 'monas (Diselmis, Duj.) possesses only external analogies with Trachelomonas, while this form, as Ehrenberg already discovered, exhibits the closest alliance to Gonium and Pandorina. The relation of the colourless envelope to the enclosed green globes, the position of the two cilia, which arise from the latter and pass out through the former, and lastly, the laws of division of the green cells inside the envelope, in powers of two, display themselves in exactly the same way in Chlamydococcus as in the rest of the Volvocineae; and the only distinction between them consists in the circumstance that in Chlamydomonas (and Chlamydococcus) the individuals produced by the division of the green globes separate after the absorption of the parent envelope, and live on as individuals, while in the other Volvocineſe the daughter-cells produced by the division of one green primordial cell remain connected by the persistent OF TDIE PIIYTOZOA. 147 }-y parent-cell as by a common envelope, and move about as a well-defined body composed of many cells.” The best accounts of the structure of Chlamydomonas we have at hand are those by Perty (op. cit. p. 85), by Braun (Réjuv., R. S. p. 214), and by Thuret (Sur les Zoospores, Ann. Sc. Nat. xiv. 1850). Unfortunately, each of these writers describes a different species, which rendors our attempt at a general history the more difficult. The figure varics between ovoid and globular; and the cell is not prolonged at the point from which the pair of vibratile filaments proceed, although a colourless space exists there. The organism consists of a green mass—the primordial cell—Surrounded by a dia- phanous delicate envelope, which, unlike that of Chlamydococcus, is closely applied to it, so that it leaves no clear intorspace between the two. The contents are green globules and larger vesicles, with a single large chlorophyll- utricle in the centre—the nucleus (XIX. 16)—very like in appearance to the starch-globule so frequent in the cells of green Algae. In addition, there is a red stigma, and in Some rare instances two such ; in other examples, again, it is altogether wanting. Motion is effected by the ciliary filaments, which penetrate the external cnvelope from the enclosed globule; the envelope resembles that of Zoospores in general; and, like those structures, these uni- cellular beings seek the light and exhale oxygen. Perty describes colourless germs from which new specimens originate, a statement no doubt equivalent to saying that these beings reproduce them- selves by microgonidia, as Cohn represents. Fission into macrogonidia is binary or quaternary, as in Tetraspora, and gives rise to two, four, eight, and even, at times, sixteen or thirty-two individuals. Generally whilst this act proceeds the cells are quiescent, ceasing from their usual movements. This process of multiplication is not influenced by the size of the Chlamydomonads, for it occurs in specimens varying between gºt to fºr". Amid the film-like collections of Chlamydomonas, groups of individuals may be encountered in various stages of change and of breaking up : Some have entirely or partially lost their green contents; others have acquired a yel- lowish-brown, or, more seldom, a red colour; others are much contracted as Small globules within the clear gelatinous cases, whilst others, lastly, acquire a proboscis-like process, or, by pressure, an angular outline. The variety and transition of colour just remarked depend upon the phase of existence and the entrance on the resting or quiescent condition. The cells of Chlamydomonas obtusa, Braun tells us, when swarming are of a dark green colour, truncate at both ends, and, after multiplying for some time, produce here and there very minute paler and more brownish-yellow micro- gonidia. “In the course of a few weeks no more active cells could be found in the water, the full-grown swarms having all gradually come to rest and sunk to the bottom. The original longish shape of the cells had changed into a perfect sphere with the transition to rest; the colour of these resting- cells, originally green, gradually passed into a light yellowish brown; at the same time a number of small, sharply-defined, brilliant globules were formed in the interior, having quite the appearance of drops of oil. In this altered condition the Chlamydomonads remained, exhibiting neither growth nor increase.” It is added, in a note, that these resting (seed) cells are about #" in diameter, have a tough, colourless, and transparent membrane, and finally assume a flesh-red colour. On awakening from this ‘resting’-stage, segmentation of the contents revives, with the disappearance of the red and oil-like elements. The resting-stage of the microgonidia has not been suffi- ciently investigated. Chlamydomonas Pulviscwlus, in the opinion of Cohn and most others, is L 2 148 GENERAL EIISTORY OF TEIE INFUSOIRIA. undistinguishable from Polytoma Uvella in every material point, the absence of colour, and its habitat in decomposing infusion alone offering themselves as distinctive of the latter. Nay, what is more, he discovers the intimate resemblance of Chlamydomonas to the resting-stage of a Volvow which he discovered in decomposing infusions, and named V. hyalina. From these considerations he concludes that Chlamydomonas and Polytoma must be ranked with Volvoa in the vegetable kingdom. - - But Chlamydomonas is made to appear a metamorphic condition of yet other organisms. For instance, Itzigsohn states that, after the joints of the filaments of Oscillaria tenuis are separated, they produce motile gonidia “which present in all respects the aspect of Chlamydomonads, but which, after passing through many intermediate forms, grow into perfect Euglence” (J. M. S. 1854, p. 189). Likewise Hartig, in his account of the transforma- tions of the Phytozoa of Antheridia (J. M. S. 1855, p. 54), makes one phase to resemble Chlamydomonas destruens of Ehrenberg. Lastly, Cohn confesses (On Protococcus, R. S. p. 555) that the motile or swarming form of Protococcus is scarcely distinguishable from Chlamydomonas, except that the latter has not been observed by him in the ‘still’ condition. But this presumed point of divergence itself vanishes since Braun's observations have made us ac- quainted with the quiescent phase of that organism (p. 147). The relation of Chlamydomonas to Stephanosphaera, and, in general, its alliance with the Volvocina as a plant, have been reviewed in the preceding remarks on the family (p. 145). Chlamydococcus (XIX. 20–31), another unicellular, isolated organism of the family Volvocina, has arrested much attention, and been described at large by Flotow, Braun, Cohn, Perty, and others under the additional names of Protococcus, Haºmatococcus, and Hysginum. Ehrenberg has no genus similarly named; but modern researches show that Gyges is in part its equivalent, although but one phase of its existence. Ehrenberg's account of Gyges is very meagre. He characterizes it as wanting both filaments, eye, and tail, and as completely encased within its lorica (an urceolus). He could discern no traces of a nutritive system, and, except a very slight movement rendered evident by colouring the fluid, could detect no indication of animality. On the other hand, Mr. Shuttle- worth examined G. sanguineus, and stated it to have a lively motion (Edinb. Phil. Jowrm. v. p. 29). In our preliminary notes on the Volvocineſe in general, a vegetable nature is assigned to the Chlamydococcus; and its relation to other Volvocineae is thus laid down by Cohn (A. N. H. 1852, x. p. 335):— “ Chlamydococcus is a unicellular Alga in the strictest sense of the word, never composed of more than one cell at any period of its growth, and each division forms the commencement of a new individual, whilst the remainder of the Volvocineae [i.e. excepting Chlamydomonas] present themselves as families of cells, in which a definite number of equivalent cells are combined, in some measure, into an individual of a higher order. “The researches of Alex. Braun, like my own,” he continues, “ have proved most distinctly that Chlamydococcus can only be placed with pro- priety among the Algae. It is distinguished, indeed, from the moving germ- cells by which far the greater part of the species of Algae are propagated, both by a somewhat more complex structure and by the circumstance that the motion lasts for a very long time, and, finally, by the power of the moving cells to propagate as such without entering into the state of rest (germina- tion) otherwise than as quite a temporary condition. But these objections touch only, to some extent, the specific character of Chlamydococcus and the OF THE PITYTOZOA. 149 Volvocineſe generally as unicellular plants; and they do not stand there among the Algae altogether without intermediate conditions, as Alex. Braun has proved, especially from the long movement of the Volvocineae. “On the other hand, the external form, like the chemical and morphological organization of the contents, the laws of motion, and the general physiological phenomena, especially however the behaviour in the transition into the con- dition of rest, in Chlamydococcus, agree so perfectly with the moving spores, the transformation of which into undoubted plants has been demonstrated with scientific clearness, that no unprejudiced observer can discover an essential distinction. I have mentioned in my essay that Ehrenberg himself, although he claims the moving condition of the forms allied to Chlamydo- coccus as Infusoria, has declared the resting-stage of this, or a most closely allied genus, to be an undoubted Alga; and yet the moving Infusoria are only a propagative form of the motionless Alga. Finally, I have succeeded in demonstrating the membrane of the cells of Chlamydococcus, both in the resting and particularly in the moving stage, to consist of cellulose, and thus in establishing the most important criterion of a vegetable cell we are at present acquainted with—the termary composition of the cell-membrane— in the Infusorioid condition of Chlamydococcus. In fact, all the more recent observers of Chlamydococcus, the number of whom is not inconsiderable, have, almost without exception, agreed in recognizing in all conditions of the development of this form, only a plant and nothing but a plant.” Besides the valuable sketch referred to, of the relations of Chlamydococcus, Cohn has presented an elaborate memoir on this organism under the name of Protococcus, in a paper translated for the Ray Society (Botanical and Physio- logical Memoirs, 1853), and has subsequently extended his views of it and its affinities in his essay on the development of microscopical Algae (Entwick. d. mikr. Algen, 1854). Of these most important papers we shall make free use in sketching the history of this genus. - “The moving cell of Chlamydococcus is composed of two principal parts, a hyaline spherical envelope, which is formed of a delicate structureless mem- brane consisting of cellulose, and immediately surrounds colourless contents, perhaps consisting of pure water. In the centre of the envelope occurs a coloured globule, composed of the universal nitrogenous protoplasm or mucus of vegetable cells, coloured red or green by chlorophyll or a carmine-red oil, and containing imbedded in it numerous granules of protoplasm, as well as One or more large chlorophyll-vesicles. This coloured globule is attenuated at the upper end into a colourless point; from this go out two cilia, which protrude into the water through two orifices in the membrane of the enve- lope, and produce the movements of the whole. The inner coloured globule is not bounded by any rigid membrane, but merely by a thickened layer of protoplasm ; hence its contour is very changeable and passes through mani- fold transformations in the course of its development. In particular it fre- quently becomes elongated in all directions into colourless radiating filaments, which keep the internal coloured globule suspended freely in the envelope, and are afterwards retracted in the course of the development. “The motionless cells of Chlamydococcus are of much simpler structure, and, like all forms of Protococcus, consist simply of a tough spherical cellulose membrane and green or red contents organized as primordial utricle. The history of development shows that under certain conditions the contents of the motionless cells become divided into a number of portions, which always correspond to two, or a power of two, in their number, that these portions become organized into special primordial utricles, and as such break through the parent-cell, each developing two cilia, amd by the aid of these rotating 150 GENERAL EIISTORY OF TEIE INFUSORIA. . actively in the water. During their motion they excrete a delicate cellular membrane over their entire surface, which is gradually removed farther and farther from the primordial utricle by endosmose of water, until at length it becomes the wide envelope of the moving form described above. From this it follows that the latter forms do indeed possess on the whole the character of simple cells, but display some peculiarities in their structure and develop- ment, since the internal coloured globule corresponds originally to the pri- mordial utricle of other vegetable cells, yet is not surrounded by a membrane, as usual, but suspended free in it like a cell-nucleus, while watery, unazotized contents appear between the membrane and the primordial utricle. For this reason I have called the enclosed coloured globule, which is formed first, and originally moves about without a special membrane in the manner of a cell, and corresponds to the primordial utricle of vegetable cells in general, the primordial cell, and the enclosing membrane with its watery contents the envelope-cell. The moving Chlamydococcus-condition is capable of propagating as such, by the enclosed primordial cell dividing anew, the individual portions slipping out of their envelope-cell and running through the cycle of develop- ment of their parent-cells. In passing into the state of rest, the enclosed primordial cell secretes over its surface, inside its envelope, like every pri- mordial utricle, a new tough cellulose membrane, and through this metamor- phosis assumes the form of an ordinary Protococcus-cell, while the envelope- cell is dissolved. But only such primordial cells behave in this way as are produced by the division of a Chlamydococcus-globule in a lower power of two : the primordial cells originating from a 16–64-fold division move far more actively and do not secrete an envelope-cell; they are incapable of any propagation, and pass immediately into the condition of rest. Alex. Braun has called these forms of Chlamydococcus, which develope an envelope-cell, macrogonidia, and distinguished the smaller ones originating from multifold division, as microgonidia.” The division of the spore- or red resting-cells of Chlamydococcus into two, and then into four segments, each producing a new generation of resting- cells, has of late been questioned by Cohn and Wichura ; but Mr. Currey. believes he can confirm this occurrence, since he has “ distinctly observed the process of self-division in some red resting-cells, which were probably those of Chlamydococcus. I say,” he writes, “probably, because the red resting-cells of Chlamydococcus are quite undistinguishable from those of another of the Volvocinece, viz. Stephanosphaera pluvialis, so that without following out the development it is impossible to predicate whether such red cells belong to one or the other.” (J. M. S. 1858, p. 209.) A further refer- ence to this topic will be found in the account of Stephanosphaera. On reviewing his history of Chlamydococcus (Protococcus) pluvialis, Cohn attributes to this plant an “alternation of generations,’ and points out the periodicity observed in the appearance in a collection of water of the several phases, the one replacing the other (Om Protococcus, R. S. 1853, pp. 549, 550). Subsequently he details the number of very various and changing forms of development it passes through, “which have been either erroneously arranged as distinct genera or at least as remaining stationary in those genera, although in fact only transitional stages” (p. 559). “Thus,” he continues, “the ‘still” Protococcus-cell (XIX. 20) corresponds to the common Protococcus coccoma (Kg.); when the border becomes gelatinous it resembles P. pulcher, and the small cells P. minor. The encysted motile zoospores are the genus Gyges granulum among the Infusoria, resembling also on the other side P. turgidus (Kg.), and perhaps P. versatilis (Braun). The zoospores divided into two must be regarded as a form of Gyges bipartitus, or of P. dimidiatus. In the quadri- OF TELE PEIYTOZOA, 151 partite zoospores with the secondary cells arranged in one plane, we have a Gonium. That with eight segments corresponds to Pandorina Morwm, and that with sixteen to Botryocystis Volvoa. When the Zoospore is divided into . thirty-two segments, it is a Uvella or Syncrypta (XIX. 27). When this form enters the ‘still’ stage, it may be regarded as a form analogous to Microhaloa protogenita ; this Algal genus is probably, speaking generally, only the product of the Uvella-division in the Euglena or other green forms. The naked zoospores (XIX. 28), finally, would represent the form of a Monad or of an Astasia (XIX. 29); the caudate variety approaches that of a Bodo.” Perty has devoted several pages to recount his own observations and ex- periments on the genus Chlamydococcus, or, as he prefers to call it, Hysgi- num. He institutes two species, which he states to be equivalent to Proto– . coccus pluvialis and P. nivalis of other authors, and insists on their specific distinctness. Probably, he adds, other varieties of Protococcus coloured red are also referable to this genus, at least such of them as present an animal phase of existence. To his mind, the vital phenomena of such organisms are best explicable on the Supposition of an animal nature ; for, says he, cells which move altogether like Infusoria, and exhibit sensation in their young condition, so long as they present such phenomena, are not vegetable cells. Moreover, he thinks it established concerning the Phytozoa in general, that in certain stages of their life they sometimes belong to one, and in others to another kingdom of nature, or are so Inearly allied to both that a separation is impossible. After the space already devoted to the structure of Chlamydomonas and Chlamydococcus, an abstract of Perty’s long contribution on the subject can- not be introduced; and indeed, apart from his different interpretation of their vital phenomena, little could be produced not included in Cohn’s com- plete examination. There is, however, a paragraph in Mr. Carter's just published valuable contribution on Eudorina, referring to Chlamydococcus, which must not be omitted. He writes (A. N. H. 1858, ii. 244): “Chlamy- dococcus undergoes the same kind of changes in development as Eudorina, from which it only differs in structure in being smaller and globular instead of ovoid, in the absence of an external envelope, and in the cilia of the daughter-cells being included within the parent-cell; hence it also differs in being motionless, though the compartments of the daughter-cells are suffi- ciently large for them to turn round and move their cilia freely therein, which they are continually doing. The primary cell of Chlamydococcus, like that of Eudorina, divides up into two, four, eight, or sixteen cells, and those of the eight- and sixteen-divisions again into groups of sixteen or thirty-two each, so as to resemble the third stage of Eudorina. Hence we may perhaps infer that its fecundating process is similar to that of Eudorina; but this remains to be discovered. Chlamydococcus has also a great tendency to stop at the two- and four-division, from which it may pass into the ‘still’ or Protococcus-form, and, floating on the water in a kind of crust, present cells of all kinds of sizes undergoing ‘still’ division. In all its multiplications, partial and entire, however, it generally maintains its primary or spherical form, and does not become ovoid or oblong like the groups of Eudorina, the only exceptions being in the two- and four-division, where the green cells are sometimes ovate (probably from want of room in the parent capsule), as represented by Ehrenberg in C. Pulvisculus, to which I should refer it, had he not also given an ovate form to the type-cell of this species: nor can I refer it to C. pluvialis; for in all the changes I have yet seen it undergo, the red colour has not increased beyond the minute eye-spot, while this also dis- 152 GENERAL EIISTORY OF TELE INFUSOIRIA. appears, and the cilia too, when this species passes into the ‘still” form. Bere it undergoes the same kind of division that it does in the active state ; but the parent-cell, instead of becoming distended by imbibition, remains closely attached to the daughter-cells, so as to give the group a mulberry. shape. How long it remains in the ‘still form I am ignorant; but having only seen it in the active state during the months of May, June, and August, and throughout the rest of the year in the ‘still’ one, I am in- clinied to think that it only comes into the active state during the summer months, and then for the purpose of fecundation. - “In several instances, also, where I have found this Chlamydococcus with Eudorina, they have been accompanied by long Closteriform cells. It was the case in that above mentioned, where the latter was undergoing impreg- nation. Some of these have an eye-spot, which, with the nature, arrange- ment, and general aspect of their internal contents, shows that they belong to the class of organisms with which they are associated. Their cell-wall also is more or less plastic, or was so when they were assuming this spicular form; for many have one or more diverticula extending from them, some are bifid, and a few irregularly stellate. What they are, I know not; but Dr. Cohn has figured the same kind of cells, in company with Sphaeropled ammu- lima, under impregnation.” Mr. Currey (op. cit. p. 216) has noticed and figured what he conceives to be a generative variety of Chlamydococcus (XX. 24). “This,” he says, “I take to be a state of Chlamydococcus. The outer membrane was colourless, and the two internal globular cells of a clear, bright ruby crimson. The pecu- liarity of the plant consisted in the fact of the cell being filled with minute staff-like subcylindrical bodies in active motion, precisely similar to the spermatozoa of Vaucheria. I watched these bodies at intervals for about twenty-four hours; and the motion was incessant. At the end of that time the cell slipped amongst some other Algae on the same slide and was lost. Whether these little active organisms were really spermatozoa, or whether they belonged to the mysterious bodies which, in some way or another, are supposed to find their way from without into the cells of Algæ, it is im– possible to say.” The next figure (XX. 25) is also copied from Mr. Currey, and, as he re- marks, evidently “represents the final stage of some Volvocimede in which the gonidia have become encysted.” We allude to it here, although it does not belong to Chlamydococcus. Mr. Currey observes further, “I notice it be- cause the encysted cells were of a pale yellowish-brown colour, and covered with minute pits or depressions, and were altogether different from those of any other Alga with which I am acquainted. In Pandorina and Stephano- Sphaera the resting-spores are red, in Volvoa bright orange; and in neither case are there any such markings as those in the membrane of the cells shown in the figure referred to.” GONIUM (XIX. 32–37).-This genus received considerable attention from Müller and Ehrenberg. The latter described it as composed of sixteen Monads, resembling Chlamydomonas in all points except in the absence of an eye-speck, collected together in a quadrangular tablet, with from three to six intercommunicating tubes or cords. Each Monad was said to be enclosed in a hyaline lorica, called here a mantle (lacerna), which it could at times quit ; also to have two filaments (proboscides) extended from the mouth, re- presented by a clear spot at their base; several clear stomach-sacs, a con- tractile vesicle, two round sexual glands, and numerous green ova. Detached individuals, he added, swam like Monads, in the direction of the longitu- dinal axis of their bodies, with the mouth in advance; but when in tablet- OF THE PEIYTOZOA. 153 like colonies sometimes moved horizontally, at others vertically, or rolled on their edges like wheels by the aid of the pair of vibratile filaments of each member projecting from the surface. The animal organization here represented is now-a-days generally ignored, and Gonium takes up its position among plants. Prof. Cohn (to whom we are so much indebted for our knowledge both of Protozoa and Protophyta) has contributed a valuable paper (Ehtw. d, mikr. Algén w. Pilze) on this in- teresting being, of which we shall present an abstract. The entire organism is invested by a colourless transparent muco-gela- tinous envelope without any cellulose limit-membrane, whence it is that this common envelope has frequently passed unobserved unless some colouring matter, such as Indian ink, has been added to the water. The figure varies according as the plant is viewed from above (on its polar aspect) or from its side (on its equatorial aspect), being in the former point of view a quadrilateral tablet with truncated angles and rounded cor- ners (XIX. 32), and in the latter a flattened spheroid. The simple or primordial cells (XIX. 33) enclosed in this mucous sheath are sixteen in number, disposed in a uniform manner, so that four cells, leaving a square interval in the centre, are bounded externally by twelve others, three of which form one of the four sides of the organism (XIX. 32). The central cell of the three is, moreover, not in a line with the other two on the same side, but set nearer to the centre ; hence each side of the tablet is hollowed out in the middle. Closer research also shows that each of the cells is not spherical, but polygonal, the four internal being six-sided (hex- agonal), the twelve peripheral five-sided (pentagonal); the consequence is, angular intercellular spaces are left, the central of all being quadrangular, and all the rest triangular. This arrangement of the primordial cells is normally so regular, that Cohn represents it by a geometrical diagram ; still, in all tablets of Goniwm this is not the case, and particularly in very young specimens. The regular polygonal contour of the cells indicates that they are not mere masses of soft variable protoplasm, like those of Stéphanosphaera, but, on the contrary, are each of them surrounded by a colourless, hyaline, deli- cate but firm membrane, imposing on them their fixed form (XIX. 34). This structure indeed is not generally discernible, unless by some abnormal conditions, or by the occurrence of self-division (XIX. 35), in which, as . only the green contents are concerned, it comes to stand apart from the latter as a distinct, separable Sac. It can, moreover, be demonstrated by crushing the cells, when the chlorophyll escapes through the rent, and leaves the colourless and fractured case. Cohn is convinced that this membrane is composed of cellulose, although, from the inability to isolate them, he has been unable to prove it by chemical reagents. Without any preparation this investing membrane can, further, be detected at the angles of the cells, from each of which it is prolonged in the form of a short tubular process, empty and colourless, the contents being restricted to the general cavity of the cell (XIX. 34). Each cell sends out such a pro- cess from its several angles to unite with a similar one from each contiguous cell: in this way are formed the intercurrent cords or canals alluded to by Ehrenberg. It follows also from this structure that the link connecting the angles of conjoined cells, belongs one half to One and the other to its com- panion-cell. The nature of the Gonium-cells and their connecting tubes is clearly dis- played by observing the changes consequent on the gradual evaporation of the water about them. For instance, on adding salt by degrees, a portion of 154 GENERAL ELISTORY OF THE INFUSORIA. the water included in the cells is withdrawn, whereupon their contents con- tract themselves into a globular form, revealing the investing membrane in its entire periphery. Again, when the mucous envelope breaks up by difflu- ence, the cells show a tendency to separate : the link-like canals are first drawn out, and subsequently give way at the point of junction of the two processes which form them—and this with such a degree of elasticity, that the cells appear to burst from one another with a spring; and thus at length the entire organism is resolved into an irregular collection of cells. In the immature period (XIX. 33–36) the outline of the cell-membrane is spherical; for the angular figure and the development of the junction-pro- cesses are subsequent phenomena. Further, the extension of the processes at times goes on so far that the Gonium-cells at first sight appear detached from each other and free, which is never the case naturally. In other points of organization the cells of Gonium correspond with other loricated swarm-cells, particularly with those of Chlamydomonas. Their con- tents consist of protoplasm coloured by chlorophyll, among which, in older specimens, are numerous corpuscles (the ova of Ehrenberg) that impart a deeper colouring ; of a central circumscribed darker corpuscle, which, as par- ticipating in every act of fission of the cell, must be esteemed a nucleus; of several vacuoles, often numerous but occasionally wanting, and of two or three sharply-defined vesicular spaces, constant in position at the base of the filaments (XIX. 33). The last-named are the locomotive organs of the organism, are two in number, and proceed from the protoplasm, passing through foramina in the special cell-wall, and afterwards through the com— mon mucilaginous envelope, so as to appear, in the polar aspect, like out- stretched fibres from the tabular organism. The movements of Gonium resemble in all respects those of Stephanosphaera and Chlamydococcus and other swarm-cells. The plant revolves on its short axis, so that in its polar aspect it appears like a rotating Surface, whilst in its equatorial it has on the contrary a linear outline. In the course of its development by Sclf-division, neither the general mu- cilaginous coat nor the cell-membrane is concerned, but only the contents. The fission into 16 segments to form a new colony has not that simultaneous character which Ehrenberg implies, but takes place by four stages or genera- tions, in every one of which a bisection of each cell already developed ensues . (XIX. 35). It is only in fully developed Gonium-tablets that self-division is effected—for example, in Such as have cells gºt," in diameter, and sepa- rated from One another by the elongated intercommunicating processes, and where those cells have the disposition described as characteristic. On the completion of the act of Self-division by the construction of 16 Small cells, these are found occupying just the same relative position within the membrane of their parent-cell as do the members of a perfect Gonium (XIX. 36). Amid numerous examples of the plant, specimens may be met with abnormal in the number of constituent cells; for instance, colonies of only 8 cells occur, which are explicable on the supposition that the last stage of fission, i. e. the last act of generation, has been arrested, and only three such acts completed. The like irregularities are often noticed in other Wolvocineae. * The primordial cells of the newly generated colonies appear unconnected with each other, whilst the mother-cell wall, which still includes them, is considerably distended and elongated in one direction (XIX. 30). The move— ment of the colony as a whole continues until the last stage of fission is com— pleted, whereupon it ceases, and the newly formed groups commence a move— ment within their enclosing cell, Sometimes presenting themselves in one OF THIE PHYTOZOA. 155 plane as a disc formed by a collection of green globules, at others, on their cdge, looking little more than a green line. At length the mother-cell ruptures, and, the mucous envelope having dis- appeared at a previous stage (XIX. 37), the young colony escapes into the surrounding water, moves freely about, and commences an independent ex- istence. These young forms.have usually a diameter of Tºp". Supposing, which is very probable, that a young Gonium after 24 hours is capable of development by fission, it follows that under favourable conditions a single colony may on the second day develope 16, on the third 256, on the fourth 4096, and at the end of a week 268,435,456 other organisms like itself. This calculation sufficiently explains the extremely rapid multiplication of these organisms, colouring a collection of water, floating on its surface as a scum, or settled in bad weather as a filmy stratum at the bottom. The cells which break away from the group, and so leave vacuitics in its conformation, resemble in their isolated condition the cells of Chlamydomonas. Such detached cells were deemed by Ehrenberg equally capable of fission as the persistent members of a colony; Cohn, however, has never observed the phenomenon, and believes, on the other hand, that, after Swarming for a time, they enter into a state of rest, and by shedding their locomotive filaments assume the Protococcoid state. This ‘still’ form of the Gonium-cells is in all likelihood also entered upon when the water in which they live is dried up and the functions of life suspended; and it may be that on the addition of fresh water such cells give issue to motile forms, and thus a parallel series of changes occur in this organism to that observed in Stephanosphaera. Never- theless a resting-stage of Gonium is not positively demonstrated; for although analogy is in favour of it, and the occurrence of Protococcoid cells in com- pany with the ordinary tabular groups suggests the probability that these are ‘still' cells, yet the absence of characters to distinguish them from the swarm-spores of other Algae renders their determination at best a matter of doubt. Development by fission as described is, therefore, the only mode proved to exist; it resembles that in Chlamydococcus and Stephansophaera, by which macrogonidia are formed. The production of microgonidia, as seen in both the genera just named, as well as in Eudorina (Pandorina) and Volvoas, is as yet unknown in Goniwm. Respecting its relation to other Volvocinece, it is to be observed that, although there are striking differences, there are, on the other hand, decided natural affinitics betwixt them and Gonium. Thus, although the envelopc- cell is so imperſectly developed that it cannot be represented as a special shut Sac, as in the case of Stephanosphaera, Chlamydococcus, &c., yet it is analogous to the Cnvelope-cell of those genera in its relation to the cell-con- teats; and, besides, in the case of the intimately allied Eudorina elegans, the common envelope, which resembles that of Stephanosphaera, is found first as a simple, and later as a double fine cell-membrane. (In Pandorina, indeed, Professor Henfrey asserts the mucous envelope to be devoid of a limiting membrane.) Again, the primordial cells of Gonium are enclosed in a special membrane, and not more globules of protoplasm unprotected save by a pellicular layor of the same substance; thus the disposition in Gonium (the primordial cells enclosed by a membrane, the envelope-cell not invested) is just the reverse of that in Chlamydococcus, Chlamydomonas, and Stéphanosphaera. However, the existence of a membrane around the primordial cells is not an anomalous cir- cumstance among the Volvocineae, since, in certain stages of development, a firm closely applicd membranc is produced around the cells of the other 156 GENERAL, ELISTORY OF TELE INFUSOIR.I.A., genera—as, for example, around the microgonidia of Chlamydococcus when they enter on their resting-stage, and about the cells of Stephanosphaera when preparing to leave the common envelope. But, further, in these in- stances, when this special closely applied membrane appears, the envelope-cell breaks up into a mucilaginous layer, and then presents the normal condition of that of Gonium. In other structural matters, in the number of vibratile filaments, and in the history of development, Goniwm entirely accords with the other genera. After this review of the affinity of Gonium with the other Volvocineae, it follows that, like them, it must be of a vegetable nature, although collulose has not been detected in it. Still more, the evident relation of Gonium with Pediastrum (II.44), the plant-nature of which no one at the present day will gainsay, points to the same natural position. It agrees with that plant in general structure, in the union of several cells in one plane, in the number of those cells and in their self-fission in the power of two, in the development of new tablets and in obedience to the same laws. The only difference between these two genera is, that in Pediastrum the Swarming of the cells, although surrounded by a common envelope-cell, ceases when they are asso- ciated together in a tabular form, whilst in Goniwm the reverse is seen, the power of motion becoming manifest when the several cells are in combination. To state this generally: in Pediastrum the individual cells swarm, and the colony is quicScent; in Gonium the colony Swarms, and the quiescent state of the several cells follows upon their separation. However, there are organs in Gonium which, did they admit of proof as essentially animal structures, would be fatal to all these arguments for its vegetable nature. These are the two, or more rarely three, permanent vacuoles visible near the origin of the vibratile filaments, which are seen to contract and expand alternately within a brief interval. These contractile vesicles have a sharp outline, are colourless, and look like clear rings in the midst of the green cells. To detect them and their movements, the most translucent and large cells must be chosen ; they must also be perfectly still, and lie flat upon the glass slide,--an object attainable by a partial evaporation of the drop of water. The two vacuoles (XIX. 33) are but little apart, equally clear and large, and apparently unconnected. Their action is alternate, each vacuole under- going a systole and diastole in Succession, whilst the time occupied by the systole, by the diastole, and by the interval is equal. The same equality in time obtains also between the two vacuoles of the same cell. Likewise a uniformity prevails among the different cells of the same Gonium, but not among the cells of different specimens; and Cohn holds the occurrence of rhythmical contractions of these vacuoles as a well-established fact. These, therefore, are pulsating spaces, filling up with water, and after a time expelling it, and agree in all points with the so-called ‘seminal vesicle’ of Ehrenberg (the contractile Sac or vesicle of other authors) met with in ciliated Infusoria. Cohn next proceeds to discuss the question if these pul— sating sacs are to be considered exclusively animal organs, and arrives at the conclusion that they cannot be so considered, and cannot be appealed to in the decision of the question of the animal or vegetable nature of any doubtful organism. To conclude this complete history of Gonium, as abstracted from Cohn's elaborate essay, we must add that the description applies only to Gonium pectorale (Ehr.), which, in the author's opinion, is the only species referable to the Volvocimede, the remainder cnumerated by Ehrenberg being members of the genus Merismospédia of the Palmellaceae. OF TIII; PIIYTOZOA. 157 }~ PANDoRINA (XIX, 59–69; XX. 22, 23).-This genus has recently been very carefully and thoroughly examined by Prof. Henfrey (J. M. S. 1856, p. 49) in an able memoir, of which we shall make free use to supply our readers with a satisfactory description of this interesting and beautiful or— ganism. The specimens examined were of the species Pandorina Morum, of which, as Prof. Henfrey justly remarks, the description “given by Ehren- borg is so incorrect, that no one would be able to determine the organism by its aid; but the figures in the Infusionsthierchen, although rude, are sufficient for identification.” Dujardin contributed nothing to our knowledge of this genus, which he treated as one with Eudorina, objecting, very justly, to the worthlessness of the red speck as a distinctive gencric character between them. Prof. Henfrey’s account is so succinct that it admits of no abridgement, we are therefore induced to present it entire. “The forms,” he writes (p. 50, op. cit.), “presented by this organism are exceedingly varied; and nothing can be more boautiful than a number of them revolving slowly on their long axes in a drop of water, as seen under a power of about 100 diameters. In the first place, the perfect form exhibits two patterns (shown in XIX. figs. 59 and 60); and there are minute counterparts to these, remaining in that state, while, in the water where the species is actively multiplying, all sizes between fig. 64, just emerged from the parent frond, and the full-grown form, figs. 59 and 60, &c., occur. The form with 32 gonidia results from the cell- division going on one stage further than in the form with 16; but this dif- forence is fixed during the earliest stages of development, as the form with 16 nover changes into that with 32 after it has become frce from the parent. In the perfect forms the gonidia are arranged near the periphery of the frond, in circles, like the equator and parallels of latitude on a globe, so that Pan- dorina resembles Cohn’s Stephanosphaera more closely than any of the other Volvocinece, that having a single equatorial ring of gonidia in its globular frond. Among the forms with the isolated gonidia occur others almost equally numerous with the gonidia collected together into berry-like heaps (figs. 65– 68): these are smaller than the others, but equally varied in dimensions; their gonidia resemble those of the other form ; they appear destined to form the resting-spores. “The gonidia are almost globular ; they have no proper membrane, but consist of a gelatinous granular substance which contains a thinner fluid in the centre, as it contracts strongly by exoSmosis when strong Saline solutions are applicd. There is a large nucleus-like body (the chlorophyll-vesicle of A. Braun) at the posterior end of the gonidium (fig. 61); and at the opposite side is a short beak-like process, with a colourless space behind it : the pair of cilia arise here; and a little to one side and below these is the reddish- brown granule called the ‘eye-spot.” We have nover boon able to observe a pulsating vacuole, as described by Busk and Cohn in Volvoa and Gonium. “The gelatinous frond appears to be perfectly homogeneous, without any boundary membrane. Iodine and sulphuric acid do not colour it blue. It is tolerably resistent, and appears solid, as it docs not give way or become indented by external pressure, as is the case with the hollow frond of Volvoa. “The fronds are multiplied by the conversion of the gonidia into now families. If they are viewed at night, many of the fronds may be found at rest at the bottom of the vessel (in the daytime they assemble at the side next the light), motionless, and with the gonidia rounded and deprived of their nucleus. By covering up the bottle from the light, the development of the new fronds, which naturally takes place very early in the morning, may be retarded, so as to be followed during the morning until noon. Some of the fronds may be found with the gonidia converted into borry-like heaps (fig. 62), 158 GENERAL IIISTORY OF THE INFUSORIA. others with the gonidia already distinct (fig. 63), while many parent fronds present the young fronds more or less regularly arranged in the softened and expanded parent mass, which ultimately dissolves and sets them free (figs. 64, 65). They then increase in size in proportion to the favourable conditions in which they are placed. I have never seen anything like what are described by Cohn in Stéphanosphaera as “microgonidia.’ In a letter re- ceived from Professor A. Braun since the above was written, he speaks of the forms with small gonidia (fig. 64) as the ‘microgonidial’ form. “When kept for some weeks, an increasing quantity of fronds became accumulated at the bottom of the water, and these chicfly of the character shown in fig. 66, but devoid of cilia; and while many of them decayed, in others the gonidia became cncysted so as to form globular cellules. Left for a fortnight, the wator was found without a trace of green colour, with merely a brownish sediment at the bottom, upon examining which, it was found to contain a large number of berry-like forms with the gonidia not only en- cysted, but with their contents converted into a red, oily, granular substance (figs. 67, 68), as in the resting-spores of many Confervoids. The gelatinous frond was here almost dissolved away; and a slight pressure was sufficient to detach and scparate the cellules, which are doubtless resting-spores (fig. 69) and destined to become subsequently developed into new fronds. This remains to be decided. “The organism thus described is a well-marked and distinct species, very different from Volvoa and Gonium, but approaching near to Stephanosphaera. The form which produces the resting-spores, after losing its cilia, is Kützing's Botryocystis Morum. I have met with a form like this not unfrequently, but never before with the perfect Pandorina. Mr. Pollock tolls me that he has collected from the same pond for some years past, but never found Pamdorina before, and yet it colours the water green this season. Volvox, seems, in like manner, to come and go at intervals of years, its revivification from the rest– ing-spores depending much on external conditions.” Mr. Currey's valuable contribution to our knowledge of the British freshwater Algae (J. M. S. 1858, p. 213) furnishes the following memoranda on Pan- dorina. He writes—“In speaking of the reproduction of Pandorina, Mr. Henfrey mentions two processes: 1. the conversion of each gonidium into a new frond within the parent mass; and 2. the conversion of the gonidia into encysted resting-spores, which are set free, and Subsequently germinate to produce new fronds. Upon this I may remark, that the process of becoming encysted does not invariably take place within the parent frond, for I have seen the gonidia of Pandorina escape from the parent frond in the form of membraneless active Zoospores; and although I was not fortunate enough to trace the subsequent fate of these Zoospores, the probability is that, like those of Chlamydococcus and Gonium, they would become encysted at a subsequent period, as, without undergoing this process, it is difficult to see how they could produce new fronds. This mode of escape of the zoospores seems to throw some doubt upon the suggestion of Mr. Henfrey with regard to the nature of the frond of Pandorina, which he considers to be solid, inasmuch as it does not give way or become indented by pressure, as is the case with the hollow frond of Volvoaz. If, however, the frond were solid, the zoospores could not well escape, except by its gradual dissolution ; but, in the instance I have men- tioned, the escape certainly took place by a rupture (as may often be seen with Volvov), and not by a gradual process of dissolution. In a paper on some Volvocineae by Dr. Fresenius, in the Second volume of the Transactions of the Senckenberg Natural History Society, he speaks of the easy escape of the cells of Gonium pectorale as being evidence against the existence in that OF THE PITYTOZOA. 159 Alga of any firm covering, and he draws a distinction in this respect between Gonium and Pandorina. My observation, however, leads me to think that Pandorina, as far as relates to its coat, does not substantially differ from Volvoa and Goniwm, Besides the nature of its coat, there are some other points of structure in Pandorina requiring further examination and elucida- tion. Ehrenberg stated that the gonidia of Pandorina have one cilium, and no eye-spot, a view adopted by Frescrius in the paper I have alluded to. Focke and Dr. Braun considered Ehrenberg’s observations inaccurate, and Mr. Henfrey agrees with them. As far as my observations go, I should say that the gonidia have usually two cilia, but that they frequently have no cye- spot. Mr. Honfrey has never been able to observe a pulsating vacuole, nor was any such vacuole visible in my specimens. Dr. Fresenius, on the other hand, has observed one, sometimes two, such vacuoles; and he remarks that cilia and rod spots are subject to considerable variation, and suggests that Stephanosphaera and Volvoa are probably the only distinct forms to be met with in the Volvocineſe. I should protest against including Gonium pectorale in the same genus as Stephanosphaera ; but, with this exception, Dr. Fresenius's suggestion is probably correct. If, however, Stephanosphaera and Pandorina are only forms of the same plant, the generic name ‘Stéphanosphaera' must give place to ‘Pandorina,” the latter being of much earlier date.” According to Braun (Réjuv., R. S. p. 21, note), the colonies of Pandorina revolve always to the right; but Prof. Henfrey corrects this statement, assert- ing that they change the direction constantly. Another circumstance re- marked by Braun is, that both the birth of the first generation of gonidia, and the production of the succeeding generations by the division of the earlier, occur in the morning after nocturnal preparation (p. 224), a circumstance, indeed, which prevails in all the Volvocimede. We must also note that among the many phases of development of Chlamydococcus pluvialis, Cohn discovers two comparable in form to Pandorina Morum and to the Botryocystis Volvoa: of Kützing (op. cit. R. S. p. 559). The late valuable contribution of Mr. Carter on Eudorina (Pandorina) (A. N. H. 1858, ii. p. 237) claims our especial attention as confirmatory of Cohn's discovery of the sexuality of Volvoas, a parallel fact to that he had pre- viously made out in the case of certain indubitablo Algae. Mr. Carter identi- fies the Organism he has studied with the Eudorina elegans, Ehr., a species which naturalists at the present day refuse to consider actually distinct from Pandorina morum, inasmuch as the solitary character upon which the sepa- ration was made by Ehrenberg, viz. the presence of a red speck in Eudorina, is well known to have no pretensions to a specific, and still less therefore to a generic character. Indeed, Mr. Carter himself treats the ‘eye-spot,” if not as a mere accidental feature, yet as only an adjunct of a particular phase of plant-life; for in the very paper under notice he puts forward the query, “Does not the disappearance of the eye-spot in the ‘still” form thus seem to point out its analogy with the bright colours, especially the red, presented by plants in their flowers during the season of fecundation, rather than with the eye of animals?” We may consequently regard this excellent paper by Mr. Carter as an im- portant supplement to Prof. Henfrey’s admirable and lucid memoir on Pan- dorina, especially its developmental history. At the risk of some repetition, we shall allow the author to explain his researches and opinions in his own words, and the more so as his plan of proceeding and manner of description do not tally very precisely with those observed in the preceding account of Pandorina. “Before going,” Mr. Carter writes, “to the fecundation, it is desirable that we should trace the development of Eudorina up to this point; but not having 160 GENERAL IIISTORY OF THE INFUSORIA. been able to recognize this organism in its simplest form (that is, as a solitary single cell), nor any stage of its segmentation prior to the third degree of du- plicative subdivision (that is, into 16 cells, when the mother-coverings have dropped off), I must begin from this period. “At this time, which we will call the first stage, the Eudorina consists of an ovoid green body, partially divided into the number of cells just mentioned, each of which is provided with a pair of cilia which project through a thin gelatinous envelope that surrounds the whole mass. It is now in its Smallest size, about 5–5400ths of an inch long, that is, not more than the diameter of the Chlamydococcus-cell, and swims by means of its cilia, with the Small end foremost, and with a rotatory motion on its longitudinal axis, as often from right to left as from left to right. An eye-spot is also present in each of the four anterior cells, but seldom visible in the rest at this period. “As the development progresses and the Eudorina increases in size, the di- vision becomes complete, and cach coll, in addition to the granular mucus and chlorophyll which line its interior, may now be seen to be provided internally with a spherical translucent ºutricle (which is the nucleus), an eye-spot situ- ated peripherically and midway between the cilia and the opposite end of the cell, a contracting vesicle at the base of the cilia, and the pair of cilia them- selves. Each pair of cilia passes out through a single channel in the gelati- mous cell or envelope, which has now become much thickened—and thus their movements are limited up to this point, while a defined line internally marks the boundary of the original cell-wall, through which, of course, the cilia also paSS. “During the second stage, each of the cells again undergoes duplicative division (the nuclei having been doubled previously); and the whole organism becoming larger, they are separated from each other, and being no longer Sub- ject to the compression which, with the lines of fissiparation tending towards the centre of the ellipse, and their confined position, induced a more or less conical and polygonal shape, now become spherical and enclosed respectively within distinct transparent capsules. The Eudorina is now 30–5400ths of an inch long, and contains thirty-two green cells, which are evidently situated between two large, ovoid, colourless, transparent cells, one of which bounds a similarly-shaped cavity in the centre of the Eudorima, and the other is the original cell-wall, round which again is the newly secreted envelope, while the green cells are further fixed in their respective positions by the passage of their cilia through the two latter, both original cell-wall and envelope. Thus we see that the Eudorina is derived from a simple (daughter-) cell, and that its green cells have resulted from a duplicative subdivision of the green matter which lined the cavity of this cell. Arrived at this state, which we shall pro- sently see is that of maturity, we also observe that the posterior part of the envelope becomes crenulated, apparently from flaccidity. “After this, however, it again presents another phase, which may be called the third or last stage of development. Here each cell again undergoes a rapid duplicative subdivision into sixteen or thirty-two cells, which, in the group, assume a more or less oblong figure respectively; and thus the Eudorina's length is increased to 50–5400ths of an inch. The internal structure now gradually breaks down before the external envelope, when for a short time the groups may be seen swimming about the cavity thus formed, till at last the envelope bursts and they become liberated. What becomes of them after- wards, I cannot state from observation; but the green cells having been greatly reduced in size by the latter subdivisions, it is probable that many of the groups, if they do not form new individuals, sooner or later become disinte- grated, and the Eudorina thus eventually perishes. OF THE PEIYTOZOA, 161 “When, however, the process of impregnation takes place, the division stops at the second stage, that is, when the Eudorina consists of thirty-two cells of the largest kind, each of which is about 1-1866th of an inch in diameter within its capsule, which is therefore a little larger. The process is as follows:— “At a certain period after the second stage has become fully developed, the contents of the four anterior cells respectively present lines of duplicative sub- division which radiate from a point in the posterior part of the cell (and this distinguishes this subdivision from that which took place in the original cell from which the Eudorina was derived, and that which takes place in the third or last stage of development just described, where the lines of fissiparation tend towards the centre of the ellipse or ovoid cell). These lines, which ulti- mately divide the green contents of the cell into sixty-four portions, where the division stops, necessarily entail (from their radiating from a point and terminating a little beyond the centre of the cell) a pyriform shape on the segments, from whose extremities a mass of cilia may be observed waving in the anterior part of the cell of the parent, while yet her own pair of cilia are in active motion, and her eye-spot still exists in situ. On one side of her pro- geny, thus showing that the latter may be almost fully formed before the parent perishes. At length, however, this takes place, and the progeny, which we shall henceforth call “spermatozoids,’ separate from each other, and finding an exit, probably by rupture, through the effete parent-cell and her capsule, soon become dispersed throughout the space between the two large ovoid cells mentioned, where they thus freely come into contact with the capsules of the twenty-eight remaining or female colls. “The form of the spermatozoid now varies at every instant, from the activity of its movements and the almost semifluid state of its plasma ; and therefore, if we had not seen it in the parent-cell, it would be very difficult to define what this form really is. Its changes in shape, however, are confined to elongation and contraction, like those of Euglena viridis, and not polymorphic like those of Amoeba ; hence it is sometimes linear-fusiform or lunular, at others pyriform, short, or elongate. The centre of the body is tinged green by the presence of a little chlorophyll, while the extremities are colourless; the anterior one bears a pair of cilia, and there is an eye-spot a little in front of the middle of the body, also probably a nucleus. Thus we have a product widely different from the common cell of Eudorina. It is about 1–2700th of an inch long, and 1–10,800th of an inch broad. “Once in the space mentioned, the spermatozoids soon find their way among the female cells, to the capsules of which they apply themselves most vigor- ously and pertinaciously, flattening, elongating, and changing themselves into various forms as they glide over their surfaces, until they find a point of in- gress, when they appear to slip in, and, coming in contact with the female cell, to sink into her substance as by amalgamation. I say ‘appear,’ because, the female cells as well as the spermatozoids being so small, so numerous, and so nearly grouped together, and there being no point like a micropyle that I could discover, and the Eudorina continually undergoing more or less rotation, I do not feel so certain of having seen the act of union take place as if there had been only a female cell present with a fixed point for the entrance of the spermatozoids, as in the resting-spore of CEdogonium. But the act itself does not require to be seen; for the constancy of this form of Eudorina, the way in which these little bodies are produced, their plastic nature, and their be- haviour towards the female cells are quite sufficient to convince those who have given their attention practically to such subjects that they are spermato- Zoids, and that there can be no other object in their congregating about the female cells than impregnation. If this be not sufficient, their number may IM 162 GENERAL EIISTORY OF THE INFUSORIA. frequently be seen to diminish as they pass backward among the female cells, when their disappearance can only be accounted for by their having become incorporated with the green cells. Eudorina in this stage also may frequently be seen with all the four anterior cells absent, and only a few spermatozoids left, most of which are motionless and adherent to the capsules, indicating that the rest have disappeared in the way mentioned. Lastly, many Eudorinae in this stage may be observed with not only the four anterior cells absent, but with hardly a single spermatozoid left, indicating that the whole had passed into the female cells, or had become expended in the process of impregnation. I have never seen any spermatozoids in the central or axial cavity, nor do I think that there is a means of their escaping externally without rupture ; so that their being confined to the space between the two ovoid cells of the Eu- dorina, where the green cells are situated, is another reason, if any more be needed, for considering them fecundating agents. “What changes take place in the Eudorina after this, I have not been able to discover. At the time, the female cells appear to become more opake by the incorporation of the spermatozoids; and the crenulated state of the poste- rior part of the envelope in this stage seems also to indicate an approach to disintegration. I have also observed that those Eudorinae which are under- going, or apparently have undergone impregnation, are less active than the rest,--that is, those in which the spermatozoids are scattered throughout the interspace mentioned and applying themselves to the capsules of the green cells, and those in which there are only a few spermatozoids left. But even if they did become disintegrated, the latter, when free, would so closely re- semble those of Chlamydococcus, which was also abundantly present, that un- less the Eudorina could be found undergoing impregnation by itself, or apart from this organism, there appears to me no chance of distinguishing the two, and therefore no other means of completing this part of its history. It is true that the impregnated cells may undergo some change in form similar to those of Volvoa globator after impregnation; but I think I should have seen this among the numbers which came under my observation, if it had been the case. “While undergoing impregnation, the female cells always contain from two to four nuclei, as if preparatory to the third stage of development, into which they are sometimes actually seen passing, with the spermatozoids pre- sent and scattered among them ; but the effect of imprognation generally seems to arrest this stage, and thus Save the species from that minute divi- sion which leads to the destructive termination of Eudorina already noticed. “Sometimes all the cells together undergo the spermatoid fissuration, when the Eudorina passes into Pandorina Morwm, Ehr. ; but in this case the de- velopment does not stop at the pyriform spermatozoids, but goes on to the development of thirty-two larger globular cells in each group, similar to those produced in the third stage of Eudorina above described, when they assume respectively a dome-shaped form, held together by a membrane which is fixed to the point in the postcrior oxtremity of the cell from which the lines of fissiparation first radiated. As the groups, however, progress in de- velopment, this dome appears to become flatter, and, the Eudorina breaking up, as in the third stage, these groups, when liberated, finally appear to pass into the form of Gonium, when I think they perish like the corresponding groups of the third stage. I did not observe this development (in which may be included some abnormal states, where only one or two of the spermatic cells fail, and one or more of the female cells take on this mode of fissiparation irregularly) until the normal one of impregnation ceased to appear. Ehren- berg was Wrong in giving the cells of Pandorina and Eudorina single cilia, as has before been stated, and partly wrong in leaving out the cye-spot, both OF TEIE PEIYTOZOA. 163 of which, though disappearing ultimately, indicate the continued life of the parent-cell, as in the development of the spermatozoids, long after the forma- tion of her progeny. “Thus the process of impregnation in Eudorina agrees closely with that described by Dr. F. Cohn in Volvoa globator, in which organism I had seen Some of the cells of the interior undergoing a spermatoid development exactly like that above described, and also that previously figured by Mr. Busk, and alluded to by him as one of ‘microgonidia;' and therefore the moment I perceived it in Eudorina, in connexion with Dr. Cohn’s announcement, I felt convinced that the latter was right, and that I had before me Eudorina also undergoing a similar process of fecundation. “So much for the spermatoid development; let us now return to that of the Eudorina in totality, concerning which there is still an interesting ques- tion for our consideration, bearing on the early development of this organism, which I have already stated my inability to supply, viz. how does the sixteen- division of the cell in the third stage of development take place, so as to allow the cilia to become extermal? It will be remembered that this cell in the Second stage, before it passes into the sixteen-division of the third stage, con- sists of its capsule or cell-wall and the green contents; and it should also be remembered that, although these contents have now no other covering distinct from the protoplasm but the capsule, yet in all algal cells, whenever the green contents take on a new form, such as that of a spore or group of cells, a second more delicate covering is separated from them, for which I have heretofore used the term ‘protoplasmic sac ; ' these two coverings, then, are the parental division of the mass, and become caducous as the rest takes on its new form and developes on its surface a cell-wall. Thus we get the sixteen cells sepa- rated from their capsule, &c., and surrounded by their proper cell-wall and the external envelope, which may be a still further thickening of the former, or a new secretion; but, be this as it may, the cilia are seen outside it. And at first it might be thought that they were formed before either the cell-wall or envelope, so as never to have been enclosed by either ; but if this were the case, the cilia of the sixteen cells, which are added by duplicative division to the first stage of Eudorina to form the second stage, should be inside these coverings, or protrude through the original sixteen channels with the other sixteen pairs of cilia. However, neither is the case; for these sixteen cells have their channels respectively as well as the other sixteen cells, in which case they must have been made by the sixteen new cells themselves, unless the thirty-two-division is formed before the pellicle which subsequently forms the cell-wall is supplied, and our first stage does not pass into the second stage, but both forms are produced at once and separately from the beginning, —a point which can only be determined by following the development of the Eudorina from the spore itself, and that, too, alone, since it is impossible to say whether the sixteen-division groups, when previously mixed up with all the other forms of Eudorina, are or are not derived direct from the spore, or from the third stage of development of this organism. That the sixteen-divi- sion or second stage may pass direct into a similar form to the third—that is, into a form of Eudorina consisting of sixteen groups of sixteen cells each—I have occasionally seen ; but then this form has been globular (only ####ths of an inch in diameter), and not ovoid, although the groups have possessed the latter form : perhaps this is the spore, and the sixteen groups the young Eudorinae, if not a different species. Again, the robust individuals of the sixteen-division one would think to be direct from the spore, and to pass into the robust individuals of the second stage or thirty-two-division,--while the puny, meagre individuals one would think to come from the third stage, and, M 2 164 GENERAL EIISTORY OF THE INFUSORIA. as before conjectured, end in disintegration and death. But all this, as I have just stated, can only be determined by following the development of the spore from the commencement. One fact I might add, however, viz. that the robust forms of good size have the power of withdrawing their cilia and protruding them again; this happens when they are transferred, from the vessel in which they may be contained, to the slide for examination: many may just at this time be seen to be motionless, with the channels for the cilia empty; but gradually the cilia are protruded through them, and as gradually the Eudo- rina evinces increasing power of motion, until they are fully protruded, and it swims away. “Chlamydococcus undergoes the same kind of changes in development as Eudorina, from which it only differs in structure in being smaller, and glo- bular instead of ovoid, in the absence of an external envelope, and in the cilia of the daughter-cells being included within the parent-cell; hence it also differs in being motionless, though the compartments of the daughter-cells are sufficiently large for them to turn round and move their cilia freely therein, which they are continually doing. The primary cell of Chlamydo- coccus, like that of Eudorina, divides up into 2, 4, 8, or 16 cells, and those of the eight- and sixteen-divisions again into groups of 16 or 32 each, so as to resemble the third stage of Eudorina. Hence we may perhaps infer that its fecundating process is similar to that of Eudorina ; but this remains to be discovered. Chlamydococcus has also a great tendency to stop at the two- and four-division, from which it may pass into the ‘still’ or Protococcus-form, and, floating on the water in a kind of crust, present cells of all kinds of sizes undergoing ‘still” division. In all its multiplications, partial and entire, however, it generally maintains its primary or spherical form, and does not become ovoid or oblong, like the groups of Eudorina, the only exceptions being in the two- and four-division, where the green cells are sometimes ovate (probably from want of room in the parent capsule), as represented by Ehrenberg in C. Pulviscwlus, to which I should refer it, had he not also given an ovate form to the type-cell of this species; nor can I refer it to C. pluvialis, for in all the changes I have yet seen it undergo, the red colour has not increased beyond the minute eye-spot, while this also disappears, and the cilia too, when this species passes into the ‘still' form. Here it undergoes the same kind of division that it does in the active state; but the parent- cell, instead of becoming distended by imbibition, remains closely attached to the daughter-cells, so as to give the group a mulberry shape. How long it remains in the ‘still” form I am ignorant; but having only seen it in the active state during the months of May, June, and August, and throughout the rest of the year in the ‘still' one, I am inclined to think that it only comes into the active state during the summer months, and then for the purpose of fecundation. “In several instances, also, where I have found this Chlamydococcus with Eudorina, they have been accompanied by long Closteriform cells. It was the case in that above mentioned, where the latter was undergoing impreg– nation. Some of these have an eye-spot, which, with the nature, arrange- ment, and general aspect of their internal contents, show that they belong to the class of organisms with which they are associated. Their cell-wall also is more or less plastic, or was so when they were assuming this spicular form; for many have one or more diverticula extending from them, some are bifid, and a few irregularly stellate. What they are I know not ; but Dr. Cohn has figured the same kind of cells, in company with Sphaeroplea annulina, under impregnation.” Stephanosphaera.--To Dr. Ferdinand Cohn, to whom science is so deeply OF THE PEIYTOZOA. 165 indebted for his researches among the simplest organisms of creation, additional thanks are due for the elaborate essay on a new genus of Volvocineae, in which he has most philosophically displayed the structure and relations of that family at large. The new genus is named by him Stephanosphaera, the structural and physiological characters of which have been presented to the English reader by an excellent translation of Cohn’s original paper, in the A. N. H. 1852, x. p. 321 et seq. Besides this account of Stephanosphaera by its discoverer, none other exists; we must accordingly make extensive use of it in attempting an abridged description,--a difficult task on account of the importance of almost every paragraph it contains. The organisms to be described “exhibit an extraordinary variety of size and shape,” writes Cohn ; “but they are all essentially of similar structure, and consist of eight green spherical corpuscles having their central points situated at the circumference of a circle (XIX. 38), and of a large common envelope, en- closing the former as a colourless vesicle, at the equator of which are ranged the said eight green globules (XIX. 40–58). “The common envelope is bounded by a membrane wholly devoid of struc- ture and transparent, so that it may be overlooked if the illumination be not properly modified, under which circumstances the 8 green globules appear destitute of any common bond of union. But the membrane of the envelope always exists; and although very delicate and thin while young (XIX. 57–58), it becomes thickened with age, and then possesses an evident breadth, albeit no compound structure can be detected. The membrane of the envelope is ab– solutely rigid, and mover changes its shape, excepting through the ordinary expansion of growth ; therefore it is not only totally devoid of contractility, but is even elastic only in a slight degree. “In whatever direction the total organism may lie during its movements, the envelope always appears as a perfect, absolutely regular circle (XIX. 38, 39); thence it results most decidedly that the membrane of the envelope forms a sphere which may perhaps deviate but very little from the mathematical ideal. The diameter of the envelope varies between tolerably wide limits: while some younger forms possess an envelope ºth of a line (0.028 mm.) in diameter, most attain one of ºth (0.044 mm.), and the largest are as much as Tºth of a line (0.055 mm.) in diameter. “The phaenomena in dissolution and during propagation prove that the membrane of the envelope immediately surrounds a colourless watery fluid, the refractive power of which does not differ from that of water. The enve- lope may therefore be regarded as a broad spherical cell with a delicate struc- tureless membrane, colourless and transparent like glass, containing a thin, water-like, colourless fluid; consequently I shall denominate it the envelope- cell (Hüll-zelle). “While the envelope-cell varies, generally speaking, only in size, and no difference whatever of shape and structure can be detected in the different individuals, the variations in the development of the eight green globes in its interior are very great. In fact it is difficult to represent the multiplicity of forms which here display themselves, so as to give a full and clear idea of them; and our figures even can afford but a very insufficient picture, since scarcely a single individual exactly resembles another in this respect. The cight green bodies in the interior of each envelope-cell, which, for reasons to be given hereafter, I shall call primordial cells, are in their simplest condition globular, and stand at equal distances in a circle at the largest circumference of the envelope-cell, so that the whole structure looks like a hollow glass globe with a ring formed of eight green globules in its interior (XIX. 38). If the circular line in which the centres of the eight primordial 166 GENERAL IIISTORY OF TELE INFUSORLA. cells stand, is regarded as the equator of the envelope-cell, we ordinarily find their position such that the equatorial zone lies parallel with the planc of the object-glass, and the observer consequently looks down upon the pole of the envelope-cell. In this, the polar view, the eight primordial cells stand in a perfect circle and are placed very close to the circumference of the envelope-cell. The distances between the primordial cells are more or less considerable according as they are proportionately larger or Smaller; some- times they constitute an elegant wreath composed of eight large green rosettes, almost without any intervals between them, or resemble an interrupted eight- angled star; sometimes the green globules are so far apart as to look like the eight spokes of a wheel. The diameter of a primordial cell in the polar view amounts in the former case to +}t;th of a line (0.012 mm.), in the latter to ###th (0.0065),=on an average to #6th of a line (0-0087 mm.). “When, however, the whole revolves, so that the axis passing through the two poles of the envelope-cell lies parallel with the stage of the microscope, and the equatorial zone marked by the eight green primordial cells stands perpendicular to the latter, consequently in the optic axis of the microscope, the envelope-cell still looks like a circle, because it is a sphere ; but the eight primordial cells, lying in one plane, are then projected in a line which corre- sponds to the diameter of this circle, so that the whole resembles, under the microscope, a colourless disk cut in half by a green zone (XIX. 40–58). And in this, the equatorial view, according to the position, the four primordial cells in the anterior hemisphere sometimes completely cover the four behind, so that only four are seen altogether; sometimes the latter appear through the interspaces between the former, and all eight are scen in one line. This view also, of course, gives very different pictures according to the size of the primordial cells and the distance between them. “Between the polar and cquatorial views lie countless intermediate posi- tions in which the ring of primordial cells, more or less contracted, appears as an ellipse, with its longest axis constantly in the diameter of the envelope- cell, while the shorter axis appears longer or shorter, and the separate pri- mordial cells are approached more or less towards each other, according to the laws of projection. “Besides this difference of the aspect which one and the same individual affords merely in consequence of the different positions resulting from its movements, a still greater variation is displayed in the shape of the green primordial cells themselves. I have called them globes above; properly they are always acuminated to Some extent, in the form of a pear, toward the periphery of the envelope-cell; and they are imperceptibly attenuated to a point here, from which two cilia pass out (XIX. 38). These cilia therefore arise from the primordial cells inside the envelope-cell, and they emerge freely into the water through minute orifices in the latter: from the analogy with Chlamydococcus, I conjecture that there is a separate passage for each cilium, so that the Orifices corresponding in each case to the primordial cells are placed in pairs, and all sixteen orifices occur in the equator of the envelope- cell. Hence in the polar view the eight pairs of cilia go out from the circum- ference of the envelope-cell like elongated rays. “The primordial cells moreover expand principally in the direction of the aſcis perpendicular to the equatorial plane, so that in the equatorial view they appear not spherical, but rather elliptical, or even sometimes stretched so considerably in this direction, that they become cylindrical or almost spindle- shaped, without undergoing any remarkable enlargement on the other axis. If in this case, the primordial cells are large and near together, they form in the equatorial view a broad green zone inside the colourless envelope- OF TIIIE PEIYTOZOA. 167 cell, filling up a more or less considerable portion of this (XIX. 39), while in the polar view they form only a circular wreath. In some instances the proper green body of the primordial cells is only shortly cylindrical; but it becomes elongated at both ends into long beaks which reach almost to the poles, and give each primordial cell something of the shape of the Closterium setaceum figured by Ehrenberg. In this case the whole resembles a sphere surrounded by eight green bands placed in meridians and swollen only in the equatorial region. But even in this very frequently occurring preponderating development of the one dimension, the cilia of each primordial cell are sent out from the middle of its shorter axis; and when the primordial cells appear projected in a Zone, in the equatorial view, the motile cilia are visible only at four points of the diameter. “The primordial cells are very frequently developed unequally in the two hemispheres of the envelope-cell; they are not then divided into two equal halves by the equator of the envelope-cell, but show themselves crowded principally into one hemisphere, which they almost fill; and they reach almost to the pole there, while they occupy but a far smaller portion of the other, which consequently appears in greater part colourless. In such a case the primordial cells almost touch with one end, while they diverge widely at the other, and thus they look like a kind of basket composed of eight pieces, like the gaping dental apparatus of a Chilodon. “Besides the two cilia which pass out from each primordial cell, through the orifices of the envelope-cell into the water, the former very frequently send out other prolongations, which however do not perforate the envelope- cell. These are colourless mucilaginous filaments, going out from each pri- mordial cell, especially from the ends of their longer aaris, and which hence present themselves especially clearly in the equatorial view. The ends of the primordial cells are mostly not green but colourless, and elongated into numer- ous, likewise colourless, broader or thinner bristle-like processes, which run out like rays in all directions, are often Tamified, and are attached to the inside of the envelope-cell, without however perforating it (XIX. 39). If these fila- ments are much developed, they form a proper network, which maintains each primordial cell floating in the common envelope. The extremities of the pri- mordial cells are also frequently divided dichotomously into colourless muci- laginous bands, which again branch into radiating filaments and thus produce the most wonderful forms. These colourless filiform prolongations of the primordial cells may also be scen in the polar view, stretching in all direc- tions, and giving the total structure a most strange aspect, almost similar to that of a Xanthidium. “In the internal organization of the primordial cells, all that can be made out is a green-coloured Softish Substance, of which they are composed, and in which numerous delicate granules or points are imbedded. When the pri- mordial cells are actively vegetating, they are of a transparent vivid green; but the colour exhibits various tints: in the youngest conditions it is purer, more yellowish green, less obscured by dark points; in the largest forms, on the contrary, the contents appear brownish green and opake, with the dark granules multiplied to such an extent, that the whole almost loses its transpa- rency. In the middle of the primordial cells are found two larger, nucleus-like vesicles, mostly symmetrically placed; and these examined separately appear annular, so that they possess an internal cavity; iodine colours them remarkably dark, with a violet tinge (XIX. 39). The centre of each primordial cell is frequently occupied by a lighter circular space, which however does not vanish periodically, and therefore cannot be regarded as a contractile vesicle (XIX.38). “The primordial cells are not surrounded by any special rigid membrane; 168 GENERAL HISTORY OF THE INFUSORIA. and this is not only made evident by the multifold changes of form which they undergo in the course of vegetation, and by the filiform prolongations and ramifications which are produced directly from their substance, but is clearly shown by the transformations which the primordial cells pass through in con- sequence of oxternal influences. Under certain circumstances, namely, the filiform processes may be retracted, being torn away from the envelope-cell and taken up into the substance of the primordial cells; the produced ends of the primordial cells also disappear, the latter becoming rounded off into their original spherical or short-cylindrical form. Such a change would be impossible if the primordial cells were surrounded by a rigid membrane, such as that of the envelope-cell for example. Still more rapid and decided are the metamorphoses which the primordial cells undergo in the interior of the envelope-cell, through influences destructive to the life of the organism. These phaenomena, usually called dissolution, do not change the rigid enve- lope-cell at all; but they totally decompose the primordial cells, depriving them of their form and dissolving them into a single structureless green mass, which lies upon the inside of the envelope-cell, frequently destroying all evi- dence of the origin from eight spheres, while not a trace of special enveloping membranes comes to light. These phaenomena of dissolution moreoverindicate that the envelope-cell, as I have already mentioned, is composed of a delicate membrane enclosing a clear watery fluid, which cannot be dense, gelatinous, or mucilaginous, since it is readily displaced by the radiating filaments and the dissolved substance, and which therefore is very similar to pure water, if not exactly the same. “Motion.—The cilia which are protruded from the equator of the envelope- cell are but short inside this; but the portion projecting into the water is much longer and vibrates actively, thereby causing all the movements. During their vibration the cilia are difficult to detect; but when dried on glass, and still better by wetting them with iodine, they may readily be traced in their whole length, especially if sulphuric acid is added, this rendering them more distinct and giving them a darker colour. The motion of the entire Organism, depending on the eight pairs of cilia, exactly resembles that well known in the Algae and many Infusoria. First there is a rapid revolution round that axis of the onvclopc-cell which passes through its poles and stands perpen- dicular to the ring of primordial cells, so that the envelope-cell rotates like a wheel upon its axle. In the polar view (XIX. 38), our form gives exactly the impression of a revolving wheel, while in the equatorial vicw (XIX. 39), where the primordial cells are mostly elongated, it has more the aspect of a globe turning upon its axis. Besides this revolution on its axis, which endures throughout the whole life, there is an advancing movement, which produces a very irregular course; in this way these organisms screw themselves, as it were, onwards in the water. Sometimes they swim straight out with uniform rapidity, the pole going first, the rotating ring of primordial cells standing at right angles to the course and appearing only in one line; sometimes they turn round, so that the equatorial plane presents itself as a circle again (in the polar view): they rotate thus round their centre without moving from the spot; then they set one pole forward and Swim on in another direction, bend to the right or to the left, or turn quite round, mostly without any per- ceptible obstruction, move in curves of the most varied kinds, run round any point in spiral lines, come into different planes, sometimes ascending, some- times descending; in short, they exhibit all those most complex and wonderful dhaenomena of locomotion which we are acquainted within the moving propaga- tive cells of the Algæ, and, as I have demonstrated clicwhere, in eacactly the same way in the Astomous and Amenterous Infusoria (Momadina, Astasiaea, OF TECE PITYTOZOA, -- 169 Cryptomonadina, &c.), and which certainly do not bear at all the character of purposing, conscious volition, but appear as an activity determined not indeed by purely external causes, but by internal causes in the organization and vital process. The collective idea of such motions is best represcrited by the course described by a top which runs through the most varied curves while at the same time constantly revolving on its axis. “Although Alex. Braun describes a constant revolution to the left in the in many respects analogous Swarming-cells of Chlamydococcus and the Swarm- ing-spores of GEdogonium, and to the right in the moving gonidia of Vaucheria and the families of Pandorina, I must assert that no such constant law of re- volution easists in the structure here described. “As to its systematic position.—It is evident that the organism we have described belongs to the family of the Volvocineae. For not only do we find in it the two principal characters which are characteristic of this interesting family—the presence of a number of green globes which, enclosed in a common colourless envelope, represent a family of cells (polypidom), together with the constant rolling motion which the Volvocineſe possess through almost the whole of their life, but our form also displays, as we shall see hereafter, the third character of the Volvocimede, that the separate globes propa- gate within the envelope. In fact, there exist the greatest analogies between the known genera of Volvocimede, especially Gonium and Pandorina, and the organism here described; and these genera are only essentially distinguished by the arrangement of the green globes or primordial cells, which in Pando– rina are placed on a spherical surface, in Gonium on a flat plane, while in our form they stand at the circumference of a circle. Since, however, this very law of arrangement is, in the family of the Volvocineae, the most im– portant criterion on which the establishment of the genera depends, it follows that we here have a peculiar genus which I do not find described cither in Ehrenberg’s great work or in any later publication. “If we now compare the conditions of organization of Stephanosphaera with those of Chlamydococcus, we find the most essential agreement. In the first place the envelope-cell of Stephanosphaera corresponds exactly to that of the moving macrogonidia of Chlamydococcus; it is composed of a delicate colourless membrane and contents resembling water. Chemical actions to which I subjected the envelope-cell of Stephanosphaera, bear witness of this agreement in the most minute particulars. The envelope-cell is indifferent to acids and alkalics and is not dissolved in them; but it suffers a peculiar thickening by Sulphuric acid, which causes it to apply itself more closely to the primordial cell, and present itself very distinctly and clearly defined. In general the application of dilute sulphuric acid is often the best means of making clear delicate vegetable membranes which would otherwise be readily overlooked, especially when iodine is added, which then ordinarily colours the membrane yellow. The cilia also are rendered more distinct by sulphuric acid. The envelope-cells of Pandorina, Chlamydococcus, and Volvoa behave in exactly the same Way. “With regard to the chemical composition of the envelope-cell of Stepha- mosphºra, I have succeeded in demonstrating the characteristic reaction of vegetable cellulose, the blue colouring by iodine and sulphuric acid, in the enve- lope-cell of Stephanosphºra. . For this purpose it is requisite to allow a drop of pretty concentrated sulphuric acid to act upon the Swarming Stéphanosphaera- globes until the green primordial cells in the interior are decomposed,—by which time the proper transformation of the envelope-membrane has taken place, and a drop of solution of iodine (iodine in iodide of potassium), suffi- ciently diluted to prevent the Sulphuric acid precipitating it in crystals, then 170 GENERAL IIISTORY OF THE INFUSORIA, produces a coloration of the envelope, which appears at first violet, gradually becoming more intense, and at last beautiful indigo-blue. Thus the chemical behaviour of the envelope-cell in Stéphanosphaera, as in Chlamydococcus, is the most evident proof that the organisms to which they belong cannot be regarded as Infusoria, but are simply Algae. Moreover this behaviour of the envelope-cell of Stephanosphaera shows that the latter is bounded by a true cellulose membrane, and not, as is assumed almost universally of the Volvo- cineae, and by Nägeli oven of all Algæ, of Secreted mucus or jelly. The direct observation of the envelope-cell of Stéphanosphaera likewise shows that this is completely closed in its normal condition, and only perforated by orifices in the spots where the cilia of each primordial cell pass out. Not until a later stage, when the primordial cells singly leave the envelope or have begun to propagate, does the membrane of the envelope tear, gradually collapse, and become dissolved, so that the included globos can make their exit freely. “It is obvious that the eight green globes of Stéphanosphaera correspond exactly to the primordial cell of Chlamydococcus. The primordial cells of Stephanosphaera consist in like manner of nitrogenous protoplasm, in itself colourless, which is coloured brown by iodine and almost wholly dissolved by caustic potash and ammonia. The protoplasm is coloured by the universal colouring matter of vegetables, chlorophyll; for alcohol and aether bleach the green globules, and concentrated Sulphuric acid changes the green colour into a verdigris-green or blue, a reaction which, from my observations, is cha- racteristic of chlorophyll. “The chemical nature of the fine granules in the primordial cells, which with age multiply so that the primordial cells at length lose their transparent green colour and appear dull, opake, and olive-brown, is difficult to deter- mine on account of their small size; they are either protoplasm-granules, or, as a bluish colour given by iodine might leave One to conclude, perhaps starch-granules. On the other hand, the two darker nuclei in each pri- mordial cell are undoubtedly the same structures which occur in Chlamy- dococcus and, in like manner, not only in all the Volvocineae, but also in most of the Algae of the orders of Palmellece, Desmidece, Confervede, &c. Nägeli has called these chlorophyll-wtricles, and demonstrated their universal occur- rence in the vegetable kingdom by comparative descriptions (Gattung. einzell. Alg. ii.). Ordinarily there exist only two in Stephanosphaera, which may be distinguished in the earliest stages, while, among other Volvocimede, for instance, Gonium contains only one chlorophyll-wtricle. It is difficult to settle anything definite concerning their structure and function; they must not be regarded as cell-nuclei, although they resemble them very much, especially when only one is present. Caustic potash, which destroys the rest of the contents of the primordial-cells, makes the chlorophyll utricles of Stepha- mosphaera show themselves more distinctly as hollow rings, surrounded by a membrane which is rather granular; iodine colours them deep violet, which leads to the conclusion of the presence of starch. Ehrenberg thought the chlorophyll-utricles were to be recognized as the testes of the Volvocineae; it is certain, however, that these structures may be seen in greater or less number, in exactly the same way, in undeniable plants, such as Hydrodic- tyon, CEdogonium, Mougeotia, and others. “I have already shown that the primordial cells of Stephanosphaera as well as those of Chlamydococcus are destitute of a special rigid membrane; con- sequently they do not correspond to perfect cells, but on the whole only to primordial utricles. In like manner the curious colourless mucous filaments which extend out from the extremities of the primordial cells of Stepha- mosphaera arc evidently analogous to the rays which make one condition of OF TEIE PEIYTOZOA. 171 the Chlamydococcus-cells look hairy (var. setiger, W. Flotow). They are merely prolongations of the colourless protoplasm forming the substance of the primordial cells, and correspond pretty well morphologically to the reticu- lated branching filaments of protoplasm, the sap-currents as they are termed, which maintain the nucleus suspended freely in the interior of the cells of the articulations of Spirogyra or of the hairs of the anthers of Tradescantia. Alcohol and acids cause these prolongations to be retracted into the substance of the primordial cells; the same thing takes place during the course of the development. Ehrenberg has called these peculiar mucous rays, which also occur in some other Volvocineae, in some cases a tail (Synura, Uroglena), in others connecting canals or indications of a vascular system (in Volvoa and ‘Gonium). These protoplasm-filaments naturally present a different aspect according to the shape and arrangement of the primordial cells: while they appear as a Wreath of cilia in the globular Chlamydococcus-cell, in the more spindle-shaped Stéphanosphaera they rather resemble bundles of rays passing out from each end; in Volvoas, if seen only from above, they give the indi- vidual primordial cells a polygonal, radiating aspect, and form threads of communication between them: Focke has wrongly considered them as inter- cellular passages between the individual animalcules. The connecting threads in Goniwm, on the other hand, are something quite different, and do not belong at all to the domain of the protoplasm-filaments, as I shall explain more fully at another opportunity. - “Thus the microscopic analysis, like the chemical investigation, of Stepha- mosphaera, in exact analogy with Chlamydococcus and the swarming-cells of the other Algae, has enabled us to distinguish all the characters of a plant, but not one mark of a true animal organization, in particular not a trace of a mouth, stomach, and sexual organs. But the genus Stephanosphaera is thereby pre-eminently important for the decision of the question of the limit between the animal and vegetable kingdom, because the history of its development affords the most convincing proof of the vegetable nature of this genus, and thus of all the other Wolvocineae. “Development of Stéphanosphaera.-Both the very delicate envelope-cell and the widely distant, transparent, green, globular, primordial cells of the young Stephanosphaera are of a relatively small size. Both grow so much as to double their dimensions during their vegetation: the former acquires a tough membrane; the latter fill up the greater part of the envelope-cell, advance towards each other so as to touch, develope thicker, denser contents, and assume most curious forms through the ramification of the protoplasm- filaments. Finally the process of propagation shows itself in the primordial cells. The radiating ends retract all their prolongations, and become rounded into a perfect sphere; the primordial cells are now merely attached to the envelope-cell by their cilia, and thus are readily moved from their normal corresponding positions, and then appear devoid of any definite arrangement in the envelope-cell. “These changes take place in the course of the afternoon ; towards evening more influential metamorphOSes make their appearance. The primordial cell, namely, extends itself predominantly in one direction in the axis perpendicular to the equatorial plane, consequently in the position which represents from above downwards. The two chlorophyll-utricles respectively repair to the two ends; the green contents likewise flow chiefly to the two sides, and leave a broad colourless Zone visible in the middle, such as we observe somewhat in the same position in Clostérium. Finally the primordial cell becomes con- stricted, gradually from the periphery to the centre, in the middle line, and is thus divided into two secondary cells, the septum of which, in the position 172 GENERAL EIISTORY OF THE INFUSORIA. above assumed, runs from right to left. Each of the halves cut off by the division then expands somewhat in the direction from left to right; a new constriction soon presents itsclf in the direction from above downwards; when this is complete, the originally globular primordial cell is divided into four quarters (XIX. 40). “This process of constriction and cutting off is repeated once more, each secondary cell becoming divided by a new Septum into two equal halves (XIX. 41–56). “This process of division, by which each primordial cell produces in the first generation two, in the second four, and in the third eight secondary cells, is completed in the course of the night, so that early in the morning, in the long summer days even by 3 o'clock, we perceive each of the eight primordial cells divided into eight in the manner described (XIX. 41, 42). The gene- rations produced in each case by this triple subdivision vary in the duration of their lives and in their capacity of development; the first two rapidly divide again, and therefore are, according to Nägeli’s expression, mere ‘transitional generations; the third alone arrive at complete development and persist a long time as such ; these form the ‘permanent generation.’ “The process of division does not always take place simultaneously in all the eight primordial cells of Stephanosphaera ; we not unfrequently find inside the same envelope-cell some primordial cells still wholly unaltered, while others are already preparing to divide into two, a third perhaps already into four, and a fourth has already resolved itself into its eight secondary cells. Very often most of the primordial cells are found already completely sepa- rated into eight, while one or other of them is still wholly unaltored. “When the act of division has gone on favourably up to the point to which we have followed it above, some hours elapse before the young families of cells escape completely from the envelope. The process which precedes their birth consists principally in the more complete isolation, in a centrifugal direction around their common centre, of the secondary cells produced by each pri- mordial cell. Since the parting off of the secondary cells advances gradually from the periphery towards the centre, they are already completely indivi- dualized and separated by intercellular spaces at the periphery, while all eight remain still connected in the centre into a common colourless mucous mass filled with protoplasm-granules (XIX. 42). But the flow of the contents from the centre to the borders, which continues up to this time, at length causes the constriction of the central mass of protoplasm also into eight parts; the eight secondary cells then appear of a deep yellowish green externally, passing internally into colourless green towards finely granular beaks which are all connected in the centre, but become gradually attenuated, torn away, and retracted. Then the young primordial cells become rounded into short cylinders and stand in a circle, without organic connexion, but placed closely beside one another: seen from above (in the polar view), under the micro- scope, they resemble a wheel with eight notches; from the side, examined in the equatorial view, we see four or eight short cylinders lying side by side,- so that the whole is not unlike a small Scenedesmus obtusus (XIX. 57–58). “The primordial cell undergoing division behaves as a whole towards external things, until the parting off into eight is quite completed; that is to say, its two cilia move uninterruptedly, and consequently the entire Ste- phanosphaera-globe still rolls through the water according to the known laws, even when most of its primordial cells have already become more or less com- pletely divided into four or eight secondary cells. Only shortly before the completion of the division do the cilia of the parent-cell lose their motion and disappear, it may be by being retracted or by being thrown off; but the OF TTIE PIIYTOZOA. 173 orifices through which the cilia previously passed out into the water may now be observed in the common envelope-cell, as minute points surrounded by a thickened border. “Immediately after that, it is soon that the newly-formed secondary cells have developed their own cilia; for the young generations formed in the interior of the parent-envelope now begin to move and to roll over like a wheel, so far as the confined space allows of this. In consequence of this movement of the eight Small wheels rotating in the interior of the common envelope-cell, which constitutes a very pretty object, the parent-cell soon becomes enlarged and attenuated at certain points; the cellulose of which it is composed appears to be transformed into soluble jelly, and soon afterwards one after the other breaks through out of the common envelope and revolves freely and independently in the water, according to the same laws as the old spheres, but more actively and emergetically. The young Stephanosphaera exactly resembles a green wreath composed of eight small cylinders, upon which by itself no envelope and cilia can be detected (XIX. 42, 48, 49); but if killed with iodine, the eight primordial cells are scen to be surrounded by a common envelope-cell in the form of an exceedingly delicate membrane,—only this lies in all parts almost immediately upon the green globes, so that it follows the waved outline they produce, and in its total form resembles a flat spheroid with eight notches on its border; it is perforated by the cilia, which go off in pairs from each of the primordial cells; and two chlorophyll-utricles are already distinguishable in the latter. By degrees the envelope-cell is lifted up by the endosmotic absorption of water; its surface becomes smoothed out, and it appears circular in the polar view ; on the other hand, it retains for a longer time the form of an almost tabular spheroid, and hence presents an ellipse in the equatorial view (XIX. 58); finally it expands uniformly in all directions and thus acquires its normal spherical form, while at the same time it becomes considerably thickened. This whole process of propagation is completed during the night; and on bright days Stéphanosphaerae are rarely seen in course of division at Sunrise; on dull days they may be observed in this condition in the first part of the morning. “The primordial cells, however, not unfrequently come to a standstill in the stage of division of the second generation, so that they only separate into four secondary cells; these at once develope cilia and an envelope-cell, with- out dividing a third time, and make their exit from the parent-envelope in this condition. Here therefore only the first generation of each primordial cell is a transitional génération, the second already a permanent generation. Hence arises the circumstance that we often find, among other eightfold Ste- phanosphaera-globes, some in which the envelope-cell encloses only four pri- mordial cells standing at equal distances, which in other respects behave in the ordinary manner. “It is still more frequently observed, when the primordial cells have already become constricted into four secondary cells and are beginning to divide again into eight, that this process of division is not perfectly completed in all four portions, but that the young Stéphanosphaera already becomes free and developes the envelope-cell, although one or other of the four quadratic segments of the sphere has become constricted but not parted off. Hence origi- nate monstrous forms, since the general envelope-cell then encloses only seven primordial cells; but in these cases it is always observed that one of them is distinguished by most curious prolongations or mucous filaments, that it appears twice as large as the rest, that it contains four chlorophyll-utricles instead of two as is usual, and that it is also more or less constricted in the middle. All this furnishes proof that here one secondary cell of the Second 174 GENERAL EIISTORY OF THE INFUSORIA. generation has not been divided the third time like the rest, but occupies by itself the space which is ordinarily filled by two. Very often only six, or even no more than five primordial cells are found in one envelope-cell; but then two or three of these are twice as large as elsewhere. In like manner Alex. Braun figures a Pediastrum composed of fifteen instead of sixteen cells, wherein one, however, is twice as large as the rest. “On the whole, it is obvious that the mode of propagation of Stephanosphaera already examined corresponds completely to that we are already acquainted with as formation of macrogonidia in Chlamydococcus. It both cases it de- pends upon the envelope-cell remaining unaltored, while the primordial cells become divided, first into two secondary cells, and then so on in a lower power of two, each of the secondary cells immediately developing two cilia, and Secreting over its whole surface, as do all primordial utricles of vegetable cells, a delicate cellulose membrane, which, however, becomes gradually re- moved further from the secreting primordial cell through absorption of water. The only distinction between Chlamydococcus and Stephanosphaera arises from the formation of a special cnvelope-cell to cach individual secondary cell in Chlamydococcus, while in Stephanosphaera all the generations produced by division form one primordial cell, become enclosed by a common envelope, and move away as families of cells. On the contrary, the developmental history of Gonium, Pandorina, and Volvoag agrees in all ossential particulars with the laws of propagation which I have just described in Stephanosphaera, as will be shown elsewhere. We may call the mode of multiplication of the Volvocineſe by the general name of propagation by macrogonidia. “Another process is met with in Stephanosphaera, besides the above, and which I have observed more rarely, viz. propagation by microgonidia. In this mode of multiplication the introductory processes are oxactly like those of the formation of macrogonidia; in particular each primordial coll is at first divided into two, then into four, and lastly into eight secondary cells. But instead of this third generation being permanent and becoming free, as is usual, it not unfrequently happens that the process of division is not arrested with the separation into eight—that the original primordial cell becomes parted off a fourth, fifth, and even a sixth time, in the same manner, and at length is broken up into a large number of cells (16, 32, 64), which naturally are so much the Smaller the greater number of times the subdivision into two has taken place (XIX. 43, 51). These little secondary cells finally become totally separated from one another, without socroting an envelope-cell. These little cellules—I shall follow the example of Alex. Braun and call them microgonidia—exhibit a very active and energetic motion inside the envelope- cell, hurrying very rapidly up and down in all directions in its cavity, pro- ducing by their great number that curious swarming which Alex. Braun has very aptly compared with the intermingling of a crowd of people in a confined area, where every one is constantly changing his place, while the whole together constantly occupy the same space. Sometimes the cellules are Scattered in a few large masses; then they unite again into a knot in the middle; every moment the general aspect varics. At length the common envelope is ruptured where the microgonidia omerge one after another or in large masses, but free and singly, into the water. Their true form may be then readily detected by killing them with iodine; they are spindle-shaped and acuminated at both ends, bright green in the middle, and run out into a colourless beak at each end, on the whole not unlike young Euglence, without a trace of an envelope-cell; the extremity which goes first in their swimming bears delicate cilia; the number of the cilia is four (XIX. 52). When the microgonidia reach the water they move most actively in all directions, and OF THE PEIYTOZOA, 175 in a short time all the corpuscles emitted from an envelope-cell are scattered and disappear in the wide surface of the drop of water. “I have not been able to make out what becomes of the microgonidia Subsequently, since they are ordinarily decomposed on the object-holder after a brief swarming; but it may be conjectured that they also serve for propa- gation, and probably pass into a condition of rest. At least the latter has been observed in the microgonidia of Chlamydococcus pluvialis by Alex, Braun and myself: the history of the development of the latter agrees wholly with those of the Stephanosphaera ; they originate also by the division of the pri- mordial cell in a higher power, are distinguished by their minute size and more active, peculiarly Infusorioid movement, and never develope an envelope- cell during their movement. The microgonidia of both therefore are true primordial cells; that is, primordial utricles resembling cells, organized ex- clusively of coloured protoplasm, without any cellular membrane. The only distinction between them is, that the microgonidia of Chlamydococcus, like their macrogonidia, possess two cilia, while in those of Stéphanosphaera I observed four. That the microgonidia of Stephanosphaera correspond per- fectly in morphological respects to the macrogonidia, and only depend upon a higher power of division, is proved by a case in which seven out of the eight primordial cells in one envelope-cell were broken up into microgonidia, while one divided merely into eight secondary cells; the latter were developed as macrogonidia, and formed a connected wreath surrounded by an envelope-cell, which rolled slowly about in the parent-envelope, surrounded by the Swarm of free, rapidly moving microgonidia. “Abstracting the differences which may be shown always between two genera, we detect the same law of development in Hydrodictyon as in Stépha- mosphaera,_viz. the biciliated less numerous macrogonidia arrange them- selves into a family of cells already within the parent-cell, according to the character of the given conditions of the two genera, the cell-family being active in the Volvocineae and immoveable in the Protococcaceae, while the more numerous more actively moving microgonidia with four cilia leave the parent-cell and enter upon a metamorphosis, the retrogradation from which to the normal type of the genus has not been observed yet here, or indeed in the microgonidia of any of the Algae. Such an undemiable agreement of the law of development of Stephanosphaera with an undoubted plant like Hydro- dictyon, which testifies to a near relationship, would be inconceivable if the former were to be regarded as of essentially different organization—as belong- ing to quite another kingdom of nature. Thus the developmental history of Stephanosphaera also furnishes the most convincing proof of the vegetable nature of this genus, and consequently of the Volvocineae generally. “That the formation of macro- and microgonidia does not exhaust the whole series of forms which Stéphanosphaera may pass through, is proved by the following observation, which unfortunately I have not yet been able to complete. Having cultivated some Stéphanosphaerae for a long time in a little glass cup, in the way described in my essay on Loa:0&es bursaria (l.c.), all the primordial cells at length oxhibited dark, thick, greenish brown contents, so densely filled with numerous granules that the two chlorophyll-vesicles could no longer be detected; their form was more or less globular, and the mucous radiating processes were entirely absent; their outlines were remark- ably sharply defined, as if they had become surrounded by a rigid membrane. At the same time I remarked that the primordial cells were no longer fixed immoveably at the periphery of the envelope cell, never changing their relative positions, but jerked backwards and forwards, finally tore themselves away from the envelope-cell, and then began to rotate slowly and lazily in the interior. 176 GENERAL EIISTORY OF TELE INFUSORIA, Soon after, I saw the envelope-cell also burst at some spot and collapse ; and the eight primordial cells gradually emerged, one after another, as inde- pendent globes: they were now seen to be enclosed in a pretty closely applied envelope, through which penetrated two cilia; and hence they presented the utmost resemblance to Chlamydomonas Pulvisculus. They moved about for some time in the water and at length came to rest, losing their cilia and accw- mulating like little green Protococcus-globules at the bottom of the glass. We therefore have here a motionless, perfectly plant-like stage of Stephanosphaera, such as we are acquainted with in Chlamydococcus and Chlamydomonas; the remainder of the Volvocineſe undoubtedly pass into a similar condition of rest, which is the means of their preservation whom the water of ditches is dried up in summer. The emergence of single globes from the common enve- lope, in a form rescnbling Chlamydomonas, may also be readily observed in Gonium. “I conjecture that the motionless Protococcoid cells of Stephanosphaera are the means of the preservation of the species when the water, as is always the case in the shallow hollows in stones, their natural station, is dricd up for a long time and all the living inhabitants are precipitated on the stone. The observations of Major von Flotow have already demonstrated that the dried-up muddy sediment always reproduces Stephanosphaerae when water is again poured on to it. This capability of reviving from the dried condition is shared by Stephanosphaera with Chlamydococcus pluvialis, in which likewise the motionless cells remain living after being dried up for years, and are capa- ble of giving birth to moving forms, while the swarming-cells themselves are destroyed for ever by rapid desiccation. Herr von Flotow has sent earth with dried Stephanosphaerae to Dr. Rabenhorst in Dresden, who, in like manner, succeeded in reviving them by moistening. “Since the moving Stephanosphaerae are destroyed, just like the swarming- cells of Chlamydococcus, by rapid desiccation, I believe that the motionless Protococcoid globes, the development of which I have just described, are the forms which do not lose their vitality by drying, but are capable, when wetted again with water, of going through a cycle of development, by which they return to the normal moving form of Stéphanosphaera. Yet I must remark that I have not hitherto obtained sufficient material to observe the resting Stephanosphaera, and to trace the processes which occur in the revivification. “Respecting their vital manifestations, repeated experiments showed that the moving spheres of Stephanosphaera seek the darker part of the vessel, avoid- ing however a total absence of light, and assembling in preference in a moderated light or half-shadow. Since other Algae and Infusoria exhibit a different behaviour towards the light, we thus possess a means of sorting, to a cer- tain extent, the microscopic inhabitants of a specimen of water, as I did the shade-loving Stéphanosphaerae from Chlamydococcus, which ordinarily seek the brightest light.” An important appendix to this history of Stephanosphaera has quite recently appeared from the joint labours of Professor Cohn and Wichura (Nov. Act. Acad. Curios. Naturae, 1857, Part I.), and has been translated into English by Mr. Currey (J.M.S. 1858, p. 131). The resting-stage above spoken of is again referred to concisely and clearly in this paragraph:—“Under certain circumstances each of the eight cells secretes a cellular covering, and swims about in the interior of the globe in the form of free Chlamydomonas-like cells (XIX.44); eventually they escape, either by fissure of the globe, or by its gradual dissolution, lose their cilia, form a thicker membrane, become motionless, and accumulate at the bottom of the vessel. If the vessel be then permitted to become thoroughly dry, and OF THE PEIYTOZOA. 177 p-r afterwards be again filled with water, motile Stéphanosphaerae reappear, from which it seems probable that the green globes are the resting-spores of the plant.” These, it may be added, are with difficulty, if at all, distinguishable from those of Chlamydococcus pluvialis : they vary very much in size, and apparently grow after entering on the state of rest. Their colour is deep green (occasionally yellowish or olive); and they have a nucleus, and fre- quently a nucleolus. We cannot do better than copy Mr. Currey’s abridged translation, in endeavouring to convey the results arrived at by Cohn and Wichura :- “When the water is permitted to evaporate gradually, the resting-cells become yellow, and afterwards orange or red, and their contents have a more oily appearance. The authors found that if the water was not permitted to evaporate, the resting-spores, although continuing to live, did not become developed into Stéphanosphoerce; but when fresh water was poured upon de- siccated resting-spores, twenty-four hours sufficed for the production of motile Stephanosphaerae. “The following is the process of transformation from the state of rest into the motile form. “The dried resting-spores take up the water, and their contents (hitherto Somewhat misshapen) gradually fill up the cavity of the containing mem- brane, and become cloudy and granular; the border becomes yellowish, and the red colouring matter is concentrated in the centre. The cells them begin to divide; and the successive forms assumed in this process will be better understood by reference to XIX. 44–47, than by description. In pass- ing from the state shown in fig. 45 to that shown in fig. 46, the outer mem- brane has gradually become invisible. Up to fig. 47 the process has occupied about two hours. The four daughter-cells (fig. 47) begin to quiver, and to endeavour to separate from one another. Two cilia are now perceptible at the pointed extremity of each of the four cells, by the action of which the group begins to move as a whole, and in a laboured manner, in the Water ; ultimately, however, all trace of the enveloping membrane and of the gluti- mous connecting Substance disappears, and one by one the daughter-cells escape and become frce. Figs. 48 and 49 exhibit different forms of these free daughter-cells, which contain two, three, or several granules (amylon 2) and sometimes also vacuoles. The sharp end is often prolonged into a colour- less beak. At this period there is no proper cellulose membrane. At the moment of escaping, their diameter nover exceeds 0.010 mm. ; but they soon onlarge and attain a diameter of 0.013 to 0.015 mm. “Their form and the longth of the beak are variable, the latter being some- times altogether wanting. In form and motion they resemble exactly the naked primordial-cells, which are produced by division from the resting-cells of Chlamydococcus pluvialis. The authors have never seen the resting-cells of Stéphanosphaerae divide into more than four parts, but think it not improbable that division into a greater number (eight or possibly sixteen) sometimes OCCULES. “The length of time which elapsed between the immersion of the dried resting-spores and the first appearance of the motile cells varied from nine to twenty-four hours. It was noticed that those resting-spores which did not produce zoospores within six days never did so afterwards, although they continued to live and were perfectly healthy. “Zoospores, produced in the month of November, did not advance beyond the first stage (fig. 49). Others, however, produced in March, remained only a few hours in that condition, after which time a delicate membrane was formed round the body of the primordial cell (XIX. 50); this membrane was N 178 GENERAL HISTORY OF THE INFUSORIA. at first closely attached to the primordial-cell, but became gradually enlarged by absorption of water into a colourless enveloping vesicle (figs. 50, 54), usually globular but sometimes oval, having two openings, through which the cilia penetrate. In this condition they attain a diameter of 0.017–0.022", and are not distinguishable from encysted forms of Chlamydococcus plw- vialis. Other zoospores, produced on the 1st of April, 1857, attained a larger size; and the protoplasm of the primordial cell, instead of retaining its con- tinuous outline, became elongated here and there into simple or forked muci- laginous rays, which were either colourless or green from the presence of chlorophyll (fig. 53). These rays are probably produced by the protoplasm adhering at certain points to the Surrounding membrane, and being carried outwards by its growth. The Chlamydococcus-like form only lasted a few hours: towards the even- ing the zoospores mostly began to divide. In the first place, the protoplasmic rays are drawn in, and the primordial cell becomes round; it then elongates itself in the direction of an axis passing through the point of origin of the cilia, and by the process of division assumes the forms shown in figs. 54 and 55. This state is usually attained by about nine o’clock in the evening ; and about eleven o’clock a constriction commences in a plane at right angles to the former plane of division; and eventually the primordial cell is divided into quadrants, cach containing a nucleus and a portion of the red substance. The two cilia, which have retained their activity, originate in the interspace be- tween two quadrants. About midnight usually, but sometimes earlier, con- striction recommences, and the form in fig. 56 is attained. This constriction proceeds towards the middle point of the spheroid, by which the quadrants are bisected, and ultimately divided into eight wedge-shaped portions, whose con- tour-lines, like the spokes of a wheel, meet in the middle. “And now commences a further process of development, which forms the ground of the generic distinction between Stéphanosphaera and Chlamydo- coccus. For, whilst in Chlamydococcus the individual portions of a primor- dial cellseparate entirely from one another, each developing its own enveloping membrane, and ultimately escaping as a unicellular individual, in Stéphano- sphaera, on the other hand, the eight portions remain united as a family. The coloured contents of the individual portions become drawn back towards the periphery in a centrifugal direction, a colourless plasma remaining about the central point ; this disappears at first in the centre; a cavity is formed in the middle of the disk; and as this enlarges, the eight portions assume the form of a wreath, consisting of eight globular or ellipsoidal bodies in close contact (fig. 57), and usually not exactly in one plane, owing to the outer membrane not having expanded in proportion to the enlargement of the plasma. The original cilia continue active, causing the motion of the whole organism, until the eight portions are completely individualized; and then their motion ceases: but at this period each of the cight parts may be seen to be provided with two cilia, which are in motion so far as their limited space allows. The separate parts of the plasma now form eight independent but closely- packed membraneless primordial cells. Shortly afterwards it is seen that a delicate membrane, common to them all, has been secreted beneath the mo– ther-cell mombrane, round the disk formed by the primordial cells; this membrane at first lies in close contact with the latter cells, following the constrictions of the disk, but afterwards becomes further and further re- moved as it swells and tends to assume a globular form (fig. 58). By the motion of the cilia the mother-cell membrane is gradually thrown off, and the young family escapes into the water. Its eight green primordial cells still enclose the last traces of the rod substance, which gradually disappears, and OF THIE PITYTOZOA. 179 instead of which are seen two granules; the primordial cells are in im- mediate contact at the sides, and are of an oval or globular shape; their common enveloping membrane is at first constricted at the border following the outline of the primordial cells; it eventually becomes globular, although continuing for a long time much flattened at the poles, in the form of a disk- shaped spheroid. When the Chlamydococcus-like unicellular Stéphanosphaera has commenced its division early in the evening, the division into eight is perfected during the night, and early in the morning the young family quits its cast-off mother-cell membrane. “In the course of the day the individual primordial cells, and their common enveloping membrane, grow until the latter attains a diameter of 0-040– 0.048". During this growth the shape of the primordial cells is changed by the formation of various prolongations in the manner above described: but in the course of the afternoon the primordial cells again become round; and during the evening, division commences in them precisely similar to the process in the unicellular Stephanosphaera : on the following morning we find eight young families, with the common enveloping membrane, which Soon escape and go through the same process. It is calculated that in eight days, under favourable circumstances, 16,777,216 families may be formed from one resting-cell of Stephanosphaera. It is remarkable that the division of the primordial cells in Stephanosphaera is confined to a certain time of day: it begins towards evening, and is completed the following morning. In the obscrwations made in Lapland, at a time when the daylight there lasted during the whole night, the beginning and end of the division were observed to take place at almost the same hours as in the observations made at Breslau in the spring, when the day and night were almost of equal length. Sometimes the division ceases after the formation of only four primordial cells. On one occasion the authors observed a family with only three cells, one only of the two halves first formed having undergone a second division. In Lap- land a family with sixteen cells was once observed. “The authors then proceed to discuss the nature of the resting-cells in Stéphanosphaera and Chlamydococcus, and come to the conclusion that they are not spores; i. e. that they are not of the same nature as the red cells of GEdogonium, Bulbochaete, Draparmaldia, Chaetophora, Sphaeroplea, Volvoas, &c. “They come to this conclusion upon two grounds: 1st, that the resting- cells in question continue to grow after becoming quiescent; and secondly, that it is probable (although not yet proved) that the resting-cells increase by self-division, thus producing new generations of resting-cells. These two characteristics the authors consider inconsistent with the idea of a spore. “In conclusion, the authors notice the formation of microgonidia in Stepha- mosphaera, which takes place by the division of the primordial cells into num- berless small portions. Fig. 5 shows a Stephanosphaera, in which seven of the eight primordial cells have formed microgonidia; the individual microgonidia (fig. 52 a, b, c) become free by the disintegration of these eight groups into their constituent portions. The authors think it not improbable that the microgonidia exercise an impregnative influence in spore-formation, but admit that there is no evidence to prove it.” Mr. Currey (J. M. S. 1858, p. 209) reopens the question concerning the nature of the red resting-cells of Stéphanosphaera, and argues against the conclusion drawn by Cohn and Wichura. He says those observers have noticed “that these cells in Stephanosphaera pluvialis, which are at first of a green colour, and furnished with cilia, increase in growth after the green colour and the cilia have disappeared, i. e. after they have assumed a state of rest, a fact which they consider to militate against their character as spores. N 2 180 GENERAL IIISTORY OF THE INFUSORIA. “‘We have seen,” they say, ‘ that these resting-colls, after they have been formed by the metamorphosis of a motile primordial cell, increase in growth considerably, that they go through a further vegetative development, and have, therefore, not reached the termination of their vital process.’ And they then add—‘It is contrary to the idea of a spore, that it should continue to grow after having assumed the character of a resting-cell; and the fact has never yet been observed in any single case.’ It would seem that those remarks are intended to be limited to the Algae; but it is Worthy of observa– tion, that the spores of the ascigerous Fungi frequently increase in growth after escaping from the asci; and if this circumstance is not to be looked upon as affecting their character as spores, it is difficult to see why a different rule should be applied to the Algae. “Cohn and Wichura moreover consider that the increase by self-division is irreconcileable with the idea of a spore. In speaking of the red cells of Chla– mydococcus pluvialis, they express a doubt whether in those cells increase by self-division takes place, but assert that, if such should prove to be the case, it would be conclusive against their being spores, considering self-division (if I understand them right) to be a process of vegetative development distinct from germination. These observations are worthy of the careful attention of microscopists; and without venturing an opinion as to their correctness, I would only remark, that if the resting-cells of Chlamydococcus and Stepha- mosphaera are not to be considered spores, that character must also be denied to the resting-cells of GEdogonium, Bulbochaete, Draparmaldia, Sphaeroplea, and Volvoas, if, as is more than probable, there should be detected in these latter cells, 1st, an increase in growth after becoming quiescent ; or, 2dly, increase by self-division.” Volvox (XX. 32–49).-This genus has always becn an especial favour- ite with microscopical students. Its colonies of numerous monadiform green bodies distributed over the surface of miniature globes, endowed with active motion, revolving hither and thither, form one of the most pleasing objects that the microscope can display. Moreover, the more minutely the globes of the Volvoa are examined, the more interest do they awaken, by reason of the regularity and beauty of their intimate structure, and of the results of their vital processes. The consequence of this has been a host of observers and writers on the amatomy and physiology of Volvoaſ, and a formidable array of conflicting views on those topics, the conscquence of careless and insufficient research, of indifferent instruments, and of the influence of fanciful hypotheses. We shall, however, attempt no analysis of the many accounts of Volvoa in existence, but restrict ourselves to an abstract of the more recent important observations and conclusions of Professors Williamson and Busk, particularly of the former and earlier observer on that organism, premising it by a brief notice of Ehrenberg’s views. Formerly the whole globular mass was regarded as a single warty and ciliated animalcule ; and the act of bursting, whereby the smaller globes de- veloped within it which had reached maturity were liberated, was considered to be the birth of young animals. This theory Ehrenberg clearly proved to be erroneous, and showed that, to use his language, the supposed spherical animalcule was in reality a colony of monad-like beings distributed over the inner surface of a common lorica, and connected together by filiform cords or tubes; in other words, he proved each sphere or globe to be, if we may so term it, a hollow cluster of many hundreds or even thousands of living occu- pants, and to frequently contain within it other smaller hollow spheres, similar in mature to itself, and in fact developed from it by a process of self- OF THE PIIYTOZOA, 181 division. The result of these considerations led Ehrenberg to perceive the true homology between the spheres of Volvoa and the four-sided tablets of Gonium. Each member of the colony, he added, has an individuality of its own, and to all appearance resembles an ordinary simple monad, enclosed within a lorica (a lacerma), having a red eye-speck, a double filiform proboscis or filament protruding from the surface of the common spherical lorica and giving the hairy or ciliated appearance to it, and at the base of these filaments a mouth, indicated by a bright, clear spot. Internally Ehrenberg believed he discerned clear digestive cells, a contractile seminal vesicle, one or two round sexual glands, and numerous green ova. The following history of Volvoa conveys the present state of information and opinion on this interest- Ing Organism. The globes of Volvoa are bounded externally by a hyaline structureless membrane or pellicle, which corresponds to the “envelope-cell” as understood by Cohn (XX. 34, 45). Distributed on the inner wall or surface of this mem– brane, is (in Cohn’s words J. M. S. 1857, p. 140) “an infinitude of very minute hexagonal cells, attached to each other in the same way as are the elements of an epidermic tissue” (XX. 38). The protoplasmic matter or the endochrome of each cell constitutes the presumed monad of Ehrenberg, which is flask-shaped, and protrudes its tapering extremity or neck outwards, bearing at its apex two ciliary filaments which penetrate the common envelope and vibrate freely in the surrounding water. The green substance composing each monadiform individual or “primordial cell,” is the usual vegetable protoplasm, and contains chlorophyll-vesicles, a clear globule or nucleus, one or rarely two contractile vesicles, and usually a brownish-red speck, regarded by Ehrenberg as a visual organ (XX. 35); the filaments are, as usual, productions from the protoplasm. Further, each green globule is enveloped in one or more partially organized special membranes, which are in more or less close apposition with it according to the age and the conditions of life under which the Volvoa is placed (XX.35,37), and give it the essential characters of a cell with a cell-wall. In the early stage of development the several protoplasmic masses in a colony are closely aggre- gated; but as age advances, a clear interval surrounds and separates them, traversed by several prolongations of the protoplasmic matter connecting together adjoining cells (XX. 37). These processes extend outwards like so many rays from each primordial cell, and as a rule encounter those from Sur- rounding cells at a determinate distance, where they meet with an external, delicate, transparent membrane—the wall of the cell of which the contral green globule represents the nucleus. This thin membrane forms the bound- ary of each clear space surrounding the contained green globule; and from the mutual pressure of the assemblage of cells composing the Volvoay, it acquires, as seen from above, a hexagonal figure (XX. 38, 39–41, 45). We have observed already that, as age advances, the space or areola around each primordial cell increases; that is, the external coll-wall becomes further detached from the contained protoplasmic mass, and hence the processes con- necting the two—at first, and even for some considerable time during active nutrition, thick, clumsy, and irregular (XX. 42, 43)—become gradually stretched, until they are eventually converted into attenuated threads or almost imperceptible lines. In fact, by over-distension of the cells from any cause, whether, as commonly happens, from advancing age, or from the breaking up of the globe, these cords get ruptured, and then, by retracting themselves from the outer delicate cell-wall, coalesco with the protoplasmic central mass. On comparing this structure with that of Gonium as recorded 182 GENERAL HISTORY OF THE INFUSORIA. by Cohn, a close homology is perceptible. In this plant the membrane sur- rounding the hexagonal primordial cells gives off from each angle a tubular process, which comes into intimate apposition at its extremity with that from an adjoining cell. However, between these processes of Gonium and those of Volvoas, there is this difference, that in the former it is only the primordial membrane which is drawn out to form a canal or tubule, whilst in the latter the protoplasm itself is at first extended with its membrane, and subsequently collapses into a delicate band. The circular contractile vesicle noticed by Ehrenberg has had its existence confirmed by Mr. Busk in mature cells (T. M. S. 1852, p. 35):-‘‘It may be situated in any part of the zoospore (XX. 35), not unfrequently in the base, or even in the midst of one or other of the bands of protoplasm connecting it with its neighbours; it is pretty uniform in size, and about 1-9000th of an inch in diameter.” Its most curious property is its rhythmical contractility, its pulsations occurring very regularly at intervals of about 38" to 41". The contraction is rapid, whilst the dilatation is gradual.” The vesicle “would seem to exist, or at all events to present a contractile property only for a limited period, and to disappear soon after the formation of the brown spot,” i. e. the eye-speck. The coloured cye-speck or stigma lies close against the primordial-cell wall, it is not invariably present, and consequently cannot be estcomed of essential importance as a characteristic. The wall of a Volvoa has an appreciable thickness, represented by a vertical section—in fact by the depth of the cells, which are placed side by side, the lines of junction being straight and perpendicular to the external surface of the globe (XX. 36). The inner sides of the cells, bounding the internal cavity of the globe, are somewhat convex, the result of mutual lateral pressure, and the absence of centrifugal pressure. Prof. Williamson has well displayed this by sectional diagrams taken from his preparations. These sectional views also demonstrate the position of the rounded masses of green protoplasm— the primordial sacs—to be immediately on the inside of the peripheral mem- branc or envelope-cell of the Volvoa (XX. 37, 38). Development of Volvoag.—Self-division of the primordial cells, or zoospores (Busk), of Volvoa is regulated by tho Same laws that prevail in other Volvo- cineCe and in other unicellular Algae in general. Among the younger speci- mens of Volvoaſ, one or more larger globules are observable (XX. 42–44), which, if watched, will be found to undergo segmentation, first into two (XX.42), then into four portions (XX. 43), and so on (XX. 46), always keeping to the power of two and its multiples, until some hundreds of minute corpuscles are developed (XX. 47), which, according to the nature of the genus, so dispose themselves in a lamina as to enclose a hollow spherical space, and to assume the characteristic globular form. Thus a new Volvoa is generated, but differ- ing from mature forms in the contiguity of its component individuals, a differ- ence, however, which progressively vanishes with advancing age. The young globe lies immediately within the parent being, to which for a time it adheres, as it would seem, by means of a delicate capsular membrane, within which its dovelopment has proceeded. This indeed forms its sole bond of union with the common envelope of the parent Volvoz (XX. 33). When first formed, the cilia of the primordial cells do not penetrate through the Cxternal envelope of the young globe: however, this condition is of short duration; for no sooner is the detachment from the wall of the parent about to Supervcne, than the cilia protrude externally, and, commencing their vibratile movements, soon set the newly-developed colony in motion within the cavity of its parent. The detachment is consequent on the rupture of the investing capsule, caused, no doubt, by the constantly enlarging bulk of the young QF THE PHYTOZOA. 183 organisms. Constantly several young colonics are developed from the parent at the same time, or nearly so, by the self-fission of various primordial cells; hence, as a rule, a brood of young globes is to be seen revolving within the parent sphere (XX. 33), from which ere long it is released by its rupture. The condition of the individual cells of a young Volvoa has already been mentioned,—viz. their close apposition at first, their gradual separation by an interval, the appearance of radiating processes from the protoplasm, and their progressive attenuation. To this account we may add that contiguous inter- current processes, in their earlier stages, appear to coalcSce,—a circumstance which indicates that the protoplasm is then unenclosed by a pellicle or envelope. Again, the protoplasm gradually contracts itself into its flask-shape, the retrac- tion and coalescence of its processes being a simultaneous phenomenon; indeed contraction of the protoplasmic globules advances continuously until, as in old specimens, only a small rounded mass appears in the centre of a large clear space. Lastly, the coloured stigma is an after-production; and its advent would seem to indicate the maturity of the cell. Analogy with other Volvocinea, would lead us to look for a quiescent or “still” stage of the cells of Volvoag, and the formation of microgonidia, in addition to the process described, viz. multiplication by Self-division with the production of macrogonidia. That a “still" form actually occurs is pretty clearly shown by Mr. Busk’s observations of Volvoaſ awrews, from which this presumed species appears to be nothing more than Volvoa glo- bator, having a varying number of its cells encysted to form the winter or “resting ” spores. The primordial cells which are to undergo this change are at first indistinguishable from the Ordinary ones, except in having a deeper green colour (Busk, op. cit. p. 38). Afterwards, however, they ac- quire a thick wall, change to a yellow colour (hence the appellation awrews, golden or yellow), without material alteration of size, and produce a second equally firm and distinct envelope; or rather, it may be, the Original cells contract somewhat, and then form a second coat around themselves. Even- tually a considerable space exists between these two coats, occupied by a clear and apparently aqueous fluid; but upon the addition of a solution of iodine, a granular cloudiness is produced in it. The contents of the inner cell consist chiefly of amylaceous grains, mixed with a greenish material in the one case, and with a bright yellow, apparently oily fluid in the other. The amylaceous particles are of an irregular botryoidal form, and far from uniform in size. Mr. Currey, in a recent interesting communication on fresh-water Algae (J. M. S. 1858, p. 208), states that he has seen “one of the large, orange- coloured spores of the so-called V. aureus, which is only the resting form of V. globator, where the contents divided into five globular colourless cells, which floated in a mass of reddish plasma, being apparently the remains of so much of the original contents of the cell as had not been absorbed in the formation of the secondary cells.” Of the Volvoa stellatus, Mr. Busk adds that it seems to him merely a modi- fication of V. awrews, and appears to follow the same course of change, and doubtless of future development. With these conclusions Prof. Williamson coincides, and remarks (op. cit. p. 56) that “the Ordinary power of gemma- tion in V. stellatus appears to have worn itself out, since, though the gemmae often exist with the spores (?), they are small, colourless, and abortive.” It must also be mentioned that Perty Suggests an analogous interpretation of the nature of Volvoas awrews, and doubts likewise the specific importance of V. Stellatus. Since the above remarks were penned, Cohn’s researches on Volvoa globator 184 GENERAL HISTORY OF THE INFUSOIRIA. have determined the reality of another mode of reproduction besides fission, as surmised (Ann. Sc. Nat. and Comptes Rendus, 1856). The abstract of this most interesting paper is translated in the J. M. S. 1857, p. 149 :-“The second mode of reproduction of Volvoa requires a Sexual conjunction, and is not observed indifferently in all individuals. The spherules endowed with the sexual function are distinguished by their volume and the more consi– derable number of their component utricles: they are generally monoecious; that is to say, they enclose at the same time male and female cells, although the majority of their contents are neuter. The female cells soon exceed their neighbours in size, assume a deeper green colour, and become elongated like a matrass towards the centre of the Volvoaz. The endochrome of these cells does not undergo fission. In other cells, on the contrary, which acquire the size and form of the female cells, the green plasma may be seen to divide symmetrically into an infinity of very minute particles, or linear corpuscles, associated into discoid bundles. These are furnished with vibratile cilia, and oscillate at first slowly in their prism; but the movement soon becomes more active, and the bundles speedily break up into their constituent elements. The free corpuscles are very agile, and it is impossible to regard them as any- thing but true spermatozoids; they are linear and thickened at the posterior extremity; two long cilia are placed behind their middle, and the rostrum, which is curved like the neck of a Swan, possesses sufficient contractility to execute the most varied movements. These spermatozoids, so soon as they are they are able to disperse themselves in the cavity of the Volvow, quickly crowd around the female cells, into which they eventually penetrate; arrived there, they attach themselves by the beak to the plastic globule, destined in each cell to form a spore, and with which they are gradually incorporated. Fecundation having been thus effected, the reproductive globule becomes enve- loped successively by an integument exhibiting conical pointed eminences, and by an interior smooth membrane; the chlorophyll which it contained is now replaced by starch grains, and a red or Orange-coloured oil. This is the con- dition of the spore at maturity; and occasionally forty of these bodies may be counted in a single globe of Volvoa. The germination of these reproductive bodies has not yet been observed, so that their history cannot be regarded as complete; but from analogy it may in the meanwhile be assumed that they germinate in the same way as do the spores of CEdogonium, Sphaeroplea, and other Algae belonging to the same Order. It may be maintained, moreover, as certain that the Sphaerosira volvoa, Ehr., is nothing else than a monoecious Volvoa globator; that his Volvoa stellatus is also V. globator, observed at the time when it is filled with stellate spores; and lastly, that his V. awrews differs from the other forms of the same species, simply in the smooth [and coloured] condition of the spores.” . . FAMILY IV.- WIBRIONIA. (Plate XVIII. 57 to 69.) This family follows, in Ehrenberg's system, the Volvocineſe; yet, by reason of the extreme simplicity of structure of the beings composing it, it should, in any attempted natural system, be placed even below the Momadina. The distinguished author of the Infusionsthierchen attributed an animal nature to the Vibrionia, and although obliged to confess his inability to detect any internal organization, nevertheless argued, from analogy, that a polygas- tric structure was to be presumed, and that their movements were voluntary, and of themselves sufficient proof of animality. In Bacterium triloculare, indeed, Ehrenberg believed he saw an internal granular ova-mass, a vibratile OF TEUTE PEIYTOZOA. 185 filament, and spontaneous fission. Of the Vibrionia generally, he stated that they were unable to change the form of their body, although without lorica, and that by imperfect self-division they formed chains or concatenated fila- ments, which in Spirillum, from the obliquity of the junction-surfaces of the component Vibrios, assume a spiral form. Various later writers, among whom are Leuckhart, Cohn, and Burnett, would transfer the Vibrionia to the vegetable kingdom. The last-named author contributed a valuable paper to the American Association in 1850; but the most recent examination of the nature and structure of the beings in question is from the able pen of Dr. Cohn (Entw.). We must also mention that Perty has given considerable attention to the Vibrionia, and contributed Some original observations. It is to Cohn’s account, however, that we shall chiefly resort in our attempt to describe the minute and curious members of this family, which, if not rich in genera, is unsurpassed by any in the abun dance and diffusion of its members. - Some naturalists have considered the Vibrionia to be the active agents in producing putrefaction, since they are invariably found in decomposing fluids, just as the yeast-plant (Torula) always occurs in fermenting Saccharine mat- ters and appears to excite the process of fermentation. The Vibrionia are for the most part colourless; under certain conditions, however, they assume a yellow, red, or a blue tint, but never a green colour. Their movements, says Perty, are rapid and energetic, so much so that the corpuscles of Hysginum nivale, although at least one thousand times larger, are thrust aside by Bacterium Termo when in motion. They can advance. with either end forward with equal facility, and mostly seem, after proceed- ing a certain distance, to retrace their course to the point they started from. The extreme minuteness of some Vibrionia may be conceived from the statement of Perty, that, according to his calculation, four thousand millions occupy no more space than one cubic line. Dujardin, who retains the Vibrionia among animalcules, makes the follow- ing remarks:–“The Vibrionia are the first Infusoria which present them- selves in all infusions, and which from their extreme smallness, and the im– perfection of our means of observation, must be considered the most simple; $ tº tº dº º º for it is only their more or less active movements which lead to their being regarded as animals at all. I have been sometimes induced to believe that there is a flagelliform filament, analogous to that of monads, or rather perhaps a spiral undulating one, which produces the peculiar mode of loco- motion. Is the Bacterium triloculare, described by Ehrenberg as having a proboscis, a true Vibrio 2 “All that can be with certainty predicated respecting their organization is that they are contractile, and propagate by spontaneous fission, often imper- fect in character, and hence give rise to chains of greater or less length.” Cohn modestly premises (Entw. p. 118) that his researches have been di- rected chiefly to One species; yet, from scattered observations, and from pre- sumptive evidence, he would assign a vegetable nature to all the species. In decomposing infusions, often after a few hours, extremely minute corpuscles may be seen in countless number, having the figure of a dot or comma, or of very delicate lines with the ends somewhat thickened. Their motion is tolerably active, darting hither and thither, contorting themselves at the same time by a rotating movement upon their long axis, and, when in masses, produce the appearance of a ceaseless Swarming, in which the indi- vidual specks are easily overlooked on account of their smallness. They, however, differ in size among themselves, varying from 1–2000 to 1-700" in length. Ehrenberg attributed to this world-wide form the name of Vibrio 186 GENERAL BIISTORY OF THE INFUSORIA, lineola, whilst Dujardin more correctly separated it from the Vibrios under the name of Bacterium Termo. Under this latter appellation Perty has also described it. Now when we come to examine an infusion rich in these organisms, nu- merous jelly-like colourless masses of different size and figure (XVIII. 69) may be met with on the walls of the vessel, and on the surface of the fluid. These when young resemble small balls, from 1-100" and less in diameter; but as they continue constantly to enlarge, they acquire a clustered outline, and exhibit themselves as colourless masses and films of very considerable superficial dimensions and thickness, resembling soft Palmellae in consistence. Like these they are composed of a transparent mucus, in which numberless punctate or linear corpuscles are imbedded. These last are identical with the isolated particles known as Bacterium Termo. That these corpuscles are held together by the common mucus, is evident to the eye; even the largest films are also composed of globular clusters agglomerated together, the out- line of the gelatinous mass appearing sharply defined in the water. More- over, the linear corpuscles appear more thickly congregated at the periphery than in the centre of the spherical collections; but this is an optical delusion. Again, when colouring matter is added to the water, the Bacterium—mucus is not tinged by it ; and when any passing Infusorium impinges against it, its surface is pressed in ; and lastly, the absence of an independent and inherent molecular motion among the particles show them to be enclosed within a re- sistant medium. Frequently, whilst under observation, single corpuscles may be seen to detach themselves and Swim away in the characteristic manner. The definite outline and figure of the mucilaginous globules, and of their clusters, refute the notion that such are merely collections of dead Bacterium- corpuscles. The indication is rather that the Palmella-like masses represent the young condition of Bacterium; indeed, the same cycle of development proceeds as in Palmella, Tetraspora, and allied forms. . . . The only differenge betwixt the Bacterium-heaps and Palmella- or Tetraspora-masses is, that in the first the individual corpuscles are so minute that the characters of simple cells cannot confidently be assigned them, and that, instead of being yellow or light green, they are quite colourless. Nevertheless, in Kützing’s Palmella Brebissonii and P. hyalina, the cells are only 1–3000 to 1-1000" in length, whilst their figure and distribution are indistinguishable from Bacterium. The absence of colour is a feature of the Fungi connected with their occurrence in decomposing infusions; yet Palmella hyalina has only a pale ochreous hue, and Cohn seems to Satisfactorily establish that the mere presence or absence of colour cannot constitute that decisive character which the separation of the microscopic Fungi from the Algae implies. Prom the above it appears evident that the corpuscles known as Bacterium Termo are the Swarm-cells (zoospores) of a plant allied to Palmella and Te– traspora, but referable, by reason of the want of colour, to the microscopical aquatic Fungi. When these Vibrios pass into a state of rest, they accumu- late on the surface of the water in the form of films, &c., as do the resting- spores of Tetraspora, Stigeoclinium, Conferva, and other Algae, but, unlike these, are connected together by an intercellular substance, within which their growth proceeds, and leads frequently, as Perty has illustrated, to their disposal in linear branching series. From the analogy with Tetraspora and the other swarm-cells of Algae and Fungi, it must be assumed that the Bacterium-corpuscles move by means of a vibratile fibre ; indeed Ehrenberg intimates having seen a filament in Bacterium triloculare, and Dujardin considered some such mechanism pro- bable. OF TEIE PEIYTOZOA, 187 The growth of the mucous balls is the consequence of the constantly re- peated transverse fission of the Bacteriuſh-bodies, and is exceedingly rapid. Von Flotow seems to have detected the compound masses, and named one such Microhaloa teres; but Cohn finds it necessary to create a new genus, which he has named Zoogloea. - Of the remaining Vibrios, Cohn has not as yet complete researches; yet he finds sufficient support from analogy to warrant him in assuming a like history for them as for Zoogloea. The larger forms of Vibrio have (he says) a striking affinity with the Oscillarice, whilst the longer, slowly-moving species have a very great likeness to the shorter fibres of Hygrocrocis, from which, some have stated, Vibrios derived their origin. The affinity of Vibrio with the colour- less Oscillarice—with the genus Beggiatoa, in which also very delicate forms occur—may be especially pointed out; but this affinity is yet more striking with Spirillum and Spirochaºta, the other two genera of Vibrionia. Further, in Oscillarieae we meet with straight species, e. g. Oscillaria, and spirally convoluted forms, e. g. Spirulina, just as we have straight forms in Vibrio, and spirally-twisted ones in Spirillum and Spirochoeta. Likewise, on com— paring the movements of Spirochaeta with those of Spirulina, we find no dis- tinction between them except in energy and liveliness. The results of his examination of Vibrionia are thus summarily stated by Cohn (p. 130):— “1. The Vibrionia apparently all belong to the vegetable kingdom; for they exhibit an intimate affinity with undoubted Algæ. “2. By reason of their want of colour, and their occurrence in decomposing infusions, the Vibrionia belong to the group of aquatic fungi (Mycophyceae).” Cohn, however, shows good reason for not admitting this as a natural group distinct from Algae. * “3. Bacterium Termo is the motile Swarming-phase of a genus, Zoogloea, allied with Palmella and Tetraspora. “4. Spirochaeta plicatilis belongs to the genus Spirulina, of which it must be at once admitted as a species (Spirulina plicatilis). “5. The long Vibrios which do not coil (Vibrio Bacillus) arrange them- selves with the more delicate forms of Beggiatoa (Oscillaria). “6. The shorter Vibrios and Spirillae resemble indeed, in form and charac- ter of motion, the Oscillarice and Spirulinae; nevertheless I cannot positively decide on their true nature.” To this abstract of Cohn’s paper on Vibrionia we must add a notice of Dr. Burnett's essay, which is equally in favour of their plant-like nature. The chief observations and opinions of Dr. Burnett are—that a branching of the chains, similar to that of the Ordinary forms of Algæ, is observable in Vibrionia, particularly in Spirillum; that, on watching their gradual growth, the Smaller seem no other than the younger forms of larger species (for in- stance, that Vibrio is the first condition under which Bacterium and Spi- rillum appear); that besides self-division, propagation is effected by budding, a fact further exemplified by the occurrence of ramifications; and that in young forms a nucleus is absent, although one becomes apparent in advanced stages. Again, as to the movements of Vibrionia, Dr. Burnett can see no further indication of movement in them than in spermatozoa and in vegetable cells, like which they are unaffected by electrical shocks, which are fatal to the lower forms of animal life. “Their cell-structure and their vital (not voluntary) motion would then lead us to infer that the Vibrionia are Algous plants, and not animals. This throws light on several common phenomena. One in particular is, that the Vibrionia should almost invariably be found in infusions and liquids that I88 GENERAL HISTORY OF THE INFUSORIA. contain other Algæ, and especially the common Torula; for I do not re- member to have seen the Torula without Vibrionia.” - - Perty moreover testifies to Vibrio Bacillus assuming a still condition, and, by its branching concatemation, a plant-like form, out of which are constructed masses and films in the infusion and upon its surface, resembling Hygro- crocis and other Algae and aquatic Fungi. Dr. Ayres (J. M. S. i. p. 301) contributes the following observations on the self-division of the Vibrionia –“ While,” he writes, “the shortest of the Vibriones were in active motion, the longer ones were comparatively quies- cent; and these exhibited, according to their length, from one to six trans- verse lines, indicating the points of separation in the reproductive process. Those of moderate length, presenting only One or two transverse lines, were rather active, and often bent at an angle at the transverse lines, which pre- sented the appearance of separation into two distinct individuals; and the character of the movements appeared such as to favour the separation. Those with from three to six transverse lines were, for the most part, quiescent. I imagined, although from their excessive minuteness and transparency this was not plainly and unequivocally discernible, that there were indentations of the extremities of the transverse lines, by which constrictions were pro- duced, which, by their increase, would finally effect a complete transverse division of the animals.” - The occurrence of Vibrios, or at least of Vibrio-like forms, as one of the metamorphic phases of the Phytozoa of the antheridia of Characeae, e.g. Marchantia, has been mentioned in a foregoing page (126), to which we must refer our readers. FAMILY W.—ASTASLAEA OR EUGLENAEA. (Plate XVIII. 36—50, 52, 53, 55, 56.) Dujardin very properly prefers to call this group Euglenaea (Eugléniens), on account of the resemblance in Sound of the first name with that of Astacicea (Astaciens) used to designate a family of the higher Crustacea. . In Ehrenberg's system it constituted a family of the Polygastrica, and was characterized by wanting a true alimentary canal, a lorica and appendages, and by having a mouth surmounted by one or two proboscides, and in most species by a changeable form. Internally, digestive sacs, ova, a seminal gland, and contractile vesicle, and in most genera one or more red specks or eyes, were represented as present. The genera included were-Astasia, Ambly- ophis, Eugléna, Chlorogonium, Colacium, and Distigma. The value of these genera has been called in question by various Writers. Dujardin makes the variability of form—in other words, a contractile integument—a leading fea- ture, and rejects the eye-speck as neither distinctive nor constant ; conse- quently he excludes from the family the Euglence with rigid integument, and transplants them to the Thecamonadina, and rearranges the remaining species according to the number, disposition, and character of their locomo- tive filaments. . Likewise Schneider (A. N. H. 1854, xiv. p. 327) separates Chlorogonium from the Astasiaea because of its unchangeable figure; and Mr. Carter (A. N. H. 1856, xviii. p. 116) would also detach Astasia from Ew- glena, from the conviction that the former has an animal organization, and that the latter is referable to plants. In the following general history of the Astasiaea, our description will chiefly apply to the two genera Astasia and Euglena, respecting which we have very copious details in the papers by Mr. Carter, (A. N. H. 1856, xviii.). OF THIS PEIYTOZOA. 189 Of the remaining genera, some comparative observations will be made in pass- ing, and particular researches respecting them added from Perty and other inquirers. - - Euglence and Astasiae are mostly spindle-shaped (fusiform), and give off from their anterior extremity one or two delicate filaments, and posteriorly a usually short blunt tail. Excluding the doubtful Euglenece, which, on account of their rigid integument, we think, with Dujardin, should be transferred to another family, the remaining species of the two genera in question are, from their inherent contractility, capable of varying their form to a remarkable extent; i.e., to use a technical word, they are “meta- bolic.” This property is, nevertheless, much more restricted than in the Amoebae ; for the Astasiaea can send off no offshoots or variable processes like those animalcules, but in all their manifold contortions, elongations, and contractions do not completely lose their primitive figure. In general, the recurrence of the changes of figure is quite arbitrary and without regu- larity. In Eutreptia viridis and Astasia margaritifera, however, Perty represents an alternate or peristaltic expansion and contraction of the or— ganism, so that first the anterior and then the posterior extremity expands. Pſe adds, besides, that in this Astasia the contained clear globules are not transferred backwards and forwards, but only a fluid matter which runs in channels between them. The Astasiaea are covered by a distinct flexible and elastic envelope, which Mr. Carter calls the “pellicle,” and states that it resembles the cover- ing of Amoebae, is structureless, and hardens after Secretion. Stein also affirms that in Euglena it is similar to the enclosing membrane of Gregarina, and, like it, a shut sac without mouth or other aperture. On the contrary, the translator of Kölliker’s paper on Actinophrys (J. M. S. i. p. 100, note) denies the existence of a distinct envelope to this genus. Beneath the pellicle, adds Mr. Carter, is a transparent moving substance, with an inhe- rent property of contractility and polymorphism, which proves itself inde- pendent of the Superposed pellicle when, in the process of encysting, the two become separated: this substance is the “ diaphane.” Enclosed within these laminae are the contents, consisting of a proto- plasmic matter with suspended particles and certain definite structures, viz. a nucleus and contractile vesicle (XVIII. 46 a, c). The protoplasm is the same matter Dujardin names the “Sarcode,” and is occupied with a varying quantity of corpuscles, differing among themselves in size, and imparting the colour peculiar to the species. “In Euglena,” writes Mr. Carter (op. cit. p. 119), “the sarcode is separated from the diaphane by a layer of pointed sigmoid fibres, arranged parallel to each other, so as to form in Crumenula teata (Duj.) a conical cell, which, so soon as the ovules have become developed, and the diaphane and other con– tents of the sarcode have died off, becomes transparent, although it still retains its conical form until the resiliency of the fibres, now unrestrained by the diaphane and other soft parts, causes dehiscence, and sets the ovules at liberty.” - These fibres are therefore the cause of the spiral markings of several Euglence, as well as of Phacus and Chonemonas; they are strongly marked in Euglena spirogyra. “In another specimen of Euglena,” says Perty (p. 57), “ of fully a sixth of a line in length, and of a grass-green colour, some thirty delicate longitudinal lines were perceptible, which, when the body turned on itself, looked as if spirally disposed. Moreover, on examining Lepocinclis- globules when partially dried, the spiral lines appear composed of rows of closely arranged dots”—a phenomenon probably explicable on the supposi- 190 GENERAL BIISTORY OF TEIE INFUSORIA. tion that the fibres, as a consequence of evaporation, have been broken up into particles by the act of diffluence. Mr. Carter distinguishes certain minute colourlèss granules diffused in the general protoplasm of the interior, which he specially designates “mole- cules.” These, says this observer, are the first to appear in the homogeneous sarcode, but afterwards become intermixed with larger corpuscles—“gra- nules”— and with “ovules;” and by the time the ovules have become fully formed, the sarcode and its molecules have dried off or disappeared. “More- over, in Astasia, digestive globules also appear; but here the food is taken in through a distinct mouth, while in Euglena the absence of such vesicles would appear to indicate that its support is of a different kind, if not intro- duced in a different way.” Bhrenberg noted the existence of a contractile vesicle at the anterior ex- tremity of Euglema; the like is also seen in Astasia; but in neither instance have its pulsations been directly observed. A nucleus is also present of a discoid shape, and surrounded, according to Mr. Carter, by a transparent capsule, which appears like a narrow pellucid ring around it, owing to its greater size. In Chlorogonium and Amblyophis, Ehrenberg encountered what he called a seminal gland, i.e. a nucleus, and, in the latter genus, men- tions the presence of two wand-like bodies in front and three behind it. Thirteen such peculiar structures were also seen by Perty in a large specimen of Euglena spirogyra, which he concluded had originated from a peculiar disposition of the internal substance. The same ambiguous structures are doubtless referred to in the following paragraph by Mr. Carter, although, indeed, structural peculiarities are detailed which would render Perty’s ex- planation inadmissible unless qualified in some measure (A. W. H. 1856, xviii. p. 241):-‘‘With reference to the single, glairy, capsuled body which exists in the centre of Phacus and in the large lip of Crumenula teacta, also dually in Euglena geniculata, Duj. (Spirogyra, Ehr.), on each side the nu- cleus, I can state nothing further than that in the two first it consists of . a discoid transparent capsule, which at an early stage appears to be filled with a refractive, oily-looking matter; that it is fixed in a particular posi- tion, and remains there apparently unaltered, with the exception of becoming nucleated, until every part of the animalcule has perished, and nothing is left but the spiral-fibre coat, and perhaps a few ovules. In Euglena geniculata it is bacilliform, and contains a correspondingly-shaped nucleus; and al- though I can state nothing respecting its uses, I cannot fail to see that it has an interesting analogy, particularly in the latter instance, with two similar organs which are commonly seen in the Navicula, and which in N. fulva, e.g., are situated in a variable position between the nucleus and the extremities on either side.” The numerous globules diffused throughout the body, which, in addition to the foregoing, make up the contents of the Astasiaea, and according to Ehrenberg are to be considered ova, have, after being denied that nature by Dujardin and others, been again brought to notice under the name of ovules or germ-cells by Perty and Carter. They are, in the words of the latter observer (p. 223), nucleated cells, which, at an early stage, “ consist of a transparent capsule lined with a faint yellow film of semi-transparent matter, which subsequently becoming more opaque and yellowish, also be- comes more marginated and distinct, and assumes a nucleolar form.” . . . . “In the discoid cells of Astasia I have seldom been able to distinguish the capsule from the internal contents, on account of their smallness and the incessant motion of the animalcule. In Euglena, however, they are very evident ; and it is worthy of remark, that each partakes of the form of the OF THE PIIYTOZOA. 191 Euglena to which it belongs. Thus, in E. acus it is long and cylindrical; in E. viridis, oblong and compressed; and in Crwmenwla teacta and Phacus, cir- cular and compressed. There is yet another set of structures pointed out by Mr. Carter, deve- loped from the nucleus, to which he assigns the nature of Spermatozoids, or male reproductive particles. “In Astasia,” he writes (p. 227), “irregular botryoidal masses, dividing up into spherical cells, colourless and translu- cent, or of a faint opaque yellow tint, present themselves so frequently (and generally inversely developed with the ovules, as in the Rhizopoda), that I cannot help thinking that they are also developments from the nucleus; but, from not having seen them present that evident granular aspect which characterizes this development in the Rhizopoda, I have not been able to determine satisfactorily whether they are parts of the latter, or that kind of division of the sarcode into green spherical cells which sometimes takes place in Euglena. “In Euglena, also, I have described a development of the nucleus partly under the idea that it might be a parasitic Rhizopodous development; but now it appears to me a simple enlargement, granulation, and segmental de- velopment of this body into polymorphic, reptant, mucous cells filled with spermatozoid granules, as in Rhizopods. . . . . I have never been able to see the nucleus and its capsule in their original form when the spermatozoid mass has been present, though I have occasionally in Amoeba, and almost always in Euglypha, seen the empty globular capsule in connexion with the latter.” The contents of Astasiaea, even of the same individual, are subject to great variations in colour, distribution, and other characters, induced by age, the action of the reproductive processes, and the influence of external conditions. Thus, Perty tells us (p. 57) Phacus pleuronectes is at times filled with a homogeneous green mass, at others has a large, round, central spot (vacuole or nucleus 2), at others a large, clear space in the middle, having a central dark nucleus; and at others, again, the contained endochrome forms three or four segments, each exhibiting many dark green nuclei. In Euglena viridis and E. Acus the contents become resolved into a formless mass, or into a heap of nearly equal-sized germ-cells, and froquently the colour is changed from green to red, or the whole organism is rendered hyaline by the escape of the colouring matter. The coloured speck in Eugléna, Amblyophis, and other Astasiaea, reckoned as an eye by Ehrenberg, has in fact no pretensions to that character. We have pointed out that similar specks occur in Volvoa and other generally recognized plants, in all probability precisely similar to and structurally the same as those of Astasiaea. Sometimes in Euglena the red is diffused over the entire body, as Cohn represents to occur in Sphaeroplea annulina (A.N.H. 1856, xviii. p. 83), in small globules, which have the physical and chemical relations of oil. In other instances, and occasionally in very young forms, the red stigma is altogether absent. In Phacus plewronectes, Perty states, one speck is placed close behind another with an intermediate band uniting them. Often in Euglence, instead of one stigma, two or more red granules occur, whilst in Euglena deses the pigment-mass is quite irregular. In Cru- menula the red spot is comparatively very large, and rests in the form of a small obtuse cone upon the contractile vesicle. “The eye-speck of Euglena viridis,” says Perty (p. 117), “is round or oval, and exhibits an elliptic or spherical vesicle, within which the colouring matter is contained, surrounded by a more or less complete brownish-black ring : at a subsequent period the colouring matter is diffused in a most irregular manner 192 GENERAL ELISTORY OF THIE INITUSORIA, beyond the ring.” In Amblyophis viridis the red pigment may either cntirely or only partially fill the dark areola. Perty very sensibly remarks, “All these red stigmata are deficient of all the requisites of an eye—they have no refracting medium ; and the presence of an eye is inconceivable among beings which have neither nervous centres nor communicating nerves. They are probably nothing more than drops of red-oil, like those which are produced among the chlorophyll in unicellular Algae’’ (p. 118). Another fact, bearing on the character of a red pigment-speck in Euglence, is the change of colour these beings at times undergo from green to red, just as Chlamydococcus and various unicellular Algae do when they enter on the “resting” stage. Reproduction of Astasiaea.—In Ehrenberg's opinion, the members of this family are reproduced both by self-division and by ova: he speaks of having witnessed the former process in the genus Eugléma, but only as a rare occurrence. In other genera he failed to discover it. When fission takes place it does so in the usual manner, longitudinally, and produces two equal and similar organisms; rarely, the new beings are of unequal size. More- over, in the encysted condition, which was mistaken by Ehrenberg for the death of the Euglena, or confounded with other structures, fission is a con- stant phenomenon. When the motile Euglena becomes “still,” or enters into a state of rest, it contracts itsclf into a ball, and, while retaining its red stigma, loses its fila- ment. A gelatinous layer is thrown out around it, which gradually hardens into a rigid colourless cyst; this at first lics close upon the mass of the Euglena, but ultimately is removed from it all round by an interval; and when quite mature, it frequently acquires a brownish colour and opacity. In the encysted condition, Euglena closely resembles the “still” cells of Protococcus; hence the term “Protococcoid,” to express this condition. When Euglence have undergone this transformation, they cohere together by a mucilaginous ex- cretion, so as to form expansions or films resembling in appearance those produced by many Palmellege. This close resemblance subsisting between encysted Euglence and the rest- ing-spores of numerous Algæ, e.g. of GEdogonium, explains many of the wonderful transformations recounted, such as the germinating of encysted Euglena-cells into branching filiform Algae. Again, the filmy masses pro- duced by Euglence have been described as independent genera and species of Algae, as, for instance, those formed by E. viridis, as Microcystis olivacea, and those by E. Sangwinea, as Microcystis Noltii. That the contained green Euglena is not dead within its case, is proved by its sometimes being seen to revolve within it, and also by the circumstance that, in the early period of encysting, on rupturing the cyst, the contained being escapes and resumes the appearance and movements of its free brethren. It would seem, indeed, that Euglence are in the habit of temporarily encysting themselves as a means of protection against injurious external causes, such as evaporation, and that, when a normal condition is restored, they throw off their protecting envelope and reassume their active contractile character and movoºr" . The empty cases are often to be met with floating on the sur- face ol water, united with others and with encysted Euglence in a common membranous mass. The vitality of the enclosed being is further displayed by the process of fission, which advances in the power of two until very small segments are produced, which soon develope severally a red speck and fila- ment, and, on the dissolution orrupture of the common cell-wall of the parent, escape as Small free-moving corpuscles rather resembling Monads than Ew- glence by their minuteness. The encysting act may transpire in very small as well as in large Euglence, OF TELE PEIYTOZOA. - 193 and the subsequent fission may be arrested at any point, so that either a few sections which, in the phraseology of botanists, may be called macrogonidia, or otherwise very numerous small ones, or microgonidia, may be developed. As the simply encysted Euglence have been represented as independent genera of plants, so the same thing has occurred when their contents have been seen in the process of self-division; thus, for instance, Perty thinks it probable that Protococcus twrgidus and P. chalybews (Kütz) are no other than two such transitional conditions. Another circumstance attending encysted Euglence, is the forming an attach- ment to other bodies by a sort of pedicle, which extrudes from what has been the anterior extremity of the being. When viewing large collections of Eu- glence, specimens may occur of two or several united together by the head or tail, sometimes with the tail of one to the head of another. Examples of two partially united have been explained by Supposing the act of fission of a parent–animal to be nearly accomplished; but other observers have seen in such united beings an instance of conjugation, i.e. of an act, to some degree, of impregnation. The union, however, of several by the tail, sometimes seen, is an argument against this supposition, and is rather suggestive that such combinations are the remnants of primitive adhesions between gonidia within the parent-cell or between germs before a pellicle has formed around them, or, again, that a mucoid matter thrown out from the surface, as happens in many Phytozoa, may constitute the band of union, when incomplete fission or persistent primitive adhesions cannot be considered its origin. There is cer– tainly no & priori argument against the occurrence of conjugation in this family, and some naturalists would, from analogy with related beings, look for it; but at present it has not, we think, been proved. Ovules or germs.--That Euglence reproduce by internal germs is an opinion now advocated by several naturalists. To our minds this mode of propagation is really homologous with the formation of gonidia in admitted plants. Köl- liker writes (J. M. S. i. p. 34)—“Multiplication by means of germs generated in the interior indubitably occurs in certain Infusoria : in Euglena four to six embryos are seen in one individual, entirely filling it, which at length, fur- nished with their red speck and filament, break through their parent, leaving it as an empty case.” Mr. Carter (op. cit.) has entered very largely into an account of the ovules of Infusoria and of their development. “In Euglena viridis,” he writes, “the ovules are of an oblong shape: they are found, like those of Spongilla, scattered over the sides of the vessel, and evidently have in like manner the power of locomotion in addition to that of turning upon their long axis when otherwise stationary. . . . The pellucid central area in them corresponds with the oblong shape of the capsule; but beyond this and the central granule I have not been able to follow their development out of the parent, though, from the number of young E. viridis present, it may be reasonably inferred that they came from the ovules. The young Euglence, however, being so rapid in their movements when once the cilium is formed, it can hardly be expected that, except under a state of incarceration, their development can b cd so Satisfactorily as that of the slow-moving Riizopod. Instances do occur, how- ever, where the ovules gain the cilium within the cell, and there bound about when fully developed like the zoospores of Algæ within their spore-capsules. In this way I have seen them moving rapidly within the effete transparent capsuled body of E. viridis and in Crumenula teata, where the spiral-fibre layer is so strongly developed as to retain the form of the Euglena for a long time after all the soft parts have perished. On these occasions the embryos are perfectly colourless, with the exception of a central point which reflects a O 194 GENERAL EIISTORY OF TEIE INFUSORIA, red tint; and on one occasion, while watching a litter in rapid motion within the encysted body of E. viridis, the capsule gave way, and they came out one after another just as zoospores escape from the spore-capsule; but, from their incessant and vigorous movement, I was unable to follow them long enough to make out anything more about them.” This same observer, moreover, refers to a rhizopodous development of the nucleus of Euglena, whereby the form of an “actinophorous Rhizopod’” is assumed, from which, in his opinion, young Euglence are probably developed. Perty, again, records some original observations on the development of Euglence from ovules or, as he terms them, germs (Keime). At p. 79 he states that, among numerous very minute rosting germs, intermingled with larger individuals, some were seen to acquire the faculty of motion, to stretch themselves out, and to assume the form of Cercomomas. Between such and completely–formed Euglence every intermediate size occurred. The motionless spheroidal germs set free by the dissolution of the parent-cell soon develope a tapering extremity, terminated by a locomotive filament, at the base of which is a hyaline space, and in and near to this a dark speck which subse- quently changes to red. The differentiation of the homogeneous contents of the granules, out of which the germs are to be developed, takes place at a very carly period, but not in the same way or time in all specimens; neither do all the young of a brood attain the same dimensions and figure ; indecd but few attain a considerable size, and many acquire an abnormal figure. For example, Perty regards Amblyophis viridis as only an accidental variety of Euglena, of large size and truncate at one end; for he has remarked numerous Small individuals, derived from a Euglena, also with a truncated extremity. Fulther, he reports the multiplicd varieties in form, in colour, and in arrange- ment of contents, &c., which occur in collections of the same species of Euglena, and adds that the great differences exhibited by E. viridis, when in a dying condition, are most varied and inexplicable. In illustration of this opinion, he remarks that the utmost varicty of form occurs; or all the vesicles and granules change to a red colour or become transparent ; or the vesicles vanish and the green mass contracts itself into a small ball, or otherwise dis- appears, leaving only an empty shell. In the last-named state the stigma often retains a black colour. The empty envelopes frequently accumulate so as to form masses resembling a vegetable cellular tissue, and in one instance approached, by mutual pressure, a regular hexagonal figure. Some such acci- dental groupings of withered Euglema-cells have been, as Perty believes, described under the name of Palmella botryoides by Kützing; and Cercomonas viridis, and also probably Bodo viridis, are mercly phases of development of Euglena viridis. There is a distinct concordance between Carter's and Porty’s account of the development of the contents of Euglence into minute germinal bodies, or, as we may legitimately call them, microgonidia; and, on the other hand, the formation of two- and four-fission products (in other words, the formation of macrogonidia from these beings in their still-condition) has been a matter of direct observation. Consequently the developmental history of Euglena is so far complete; and it only remains for naturalists to witness the actual relation, the contact and incorporation of the micro- with the macrogonidia, to bring this genus within the same pale as Volvoas, in reference to its sexuality. Mr. Carter has reverted to his notes on the ovules or germs of Euglena, in his just-published paper on Eudorina (A. N. H. 1858, ii. p. 245), in the following remarks:—“There is no doubt that E. viridis becomes distended with the cells which I have heretofore described, and thought to be ovules OF THE PEIYTOZOA. 195 or embryonic cells, and that during this time the chlorophyll passes into red grains, and subsequently disappears, while the Organism is Secreting a capsule around itself, and its original cell-wall passes into a tough spherical ovisac, so to speak. But what becomes of this, if it be the result of impregnation, or what the process of impregnation is like, or when it takes place, is for future discovery to determine.” Chlorogonium euchlorum (Pl. XX. 15–21) was the subject of an interest- ing observation by Weisse (Wiegmann’s Archiv, 1848), who thought he had demonstrated in this species propagation by ova or germs, and, in fact, elu- cidated in it the development of microgonidia, by repeated acts of self-fission of the contents, just as in the spores of Algae. For instance, he described the contained green matter of the fusiform being first to contract in some mea- sure upon itself (XX. 16), then to exhibit a constriction followed by a line of division into two portions, which, by subsequent redivisions, resolved the whole into a nodular mass resembling a bunch of grapes (XX. 17–18). This grapebunch-like mass possessed a certain mobility within the enclosing integument; and as the process of development proceeded further, its se- veral particles or segments displayed a movement among themselves, which in- creased in extent and vigour until the external envelope gave way before it, and permitted their escape in the form of so many distinct particles or beings (gonidia) endowed with ciliary filaments, whereby they kept up an active movement in the surrounding water (XX. 21). The young forms produced exhibited active movements within the parent-cell, and at One stage prior to their discharge, when connected together in heaps, resembled Uvella Bodo. On the rupture of the cyst they escaped freely into the water with the figure of Chlorogonium. Schneider has also some remarks on this genus (A. N. H. xiv. p. 326). He could discover no decided red speck, although as many as twelve reddish spots were distributed over the surface of the green mass; a contractile vesi- cle, moreover, eluded his search. Of the mode of propagation he reports that “ division takes place in the interior of the investing membrane, in exactly the same manner as in Polytoma. The number of individuals produced is never less than four, but often as many as thirty-two; in the latter case they are very small, but always resemble the parent in other respects. A spheri- cal state of rest also occurs. It appears that, when the requisite conditions are present, the young proceeding from the division of the parent pass into this state immediately after they are set free,_their soft investing mem– brane probably rendering them fitter for this purpose. The contractions which then take place are probably the same that were observed by Ehren- berg. In other respects I have found the form unchangeable; and Chlo- rogonium must consequently be separated from the Astasiaea, amongst which it has hitherto been arranged. On the addition of iodine, only a few blue granules are to be seen in the fusiform individuals; the green spheres, on the contrary, which are completely filled with green granules, acquire a deep blue colour with this reagent: if the colouring-matter be destroyed by means of concentrated sulphuric acid, the granules are dissolved, and on the addition of iodine, a beautiful blue colour is produced. By long keeping, the green of the cyst passes to red. The cysts are not to be roused from their torpid condi- tion by the production of fermentation. I have, however, observed their re- vivification under other circumstances; but my materials are insufficient to enable me to describe the mode of reproduction of the investing membrane and filaments, which would certainly be interesting. The conditions required for the existence of Chlorogonium are apparently quite different from those of Polytoma: the former did not multiply abundantly in infusions until the O 2 196 GENERAL HISTORY OF THE INFUSORIA. latter had passed to the state of repose.” This view of the affinity of Chlo- rogonium accords with that which Weisse indicates in the statement that this genus and Glenomorum tingens (species of Ehrenberg’s family Momadina) are but two phases of the same being. Weisse has appended some remarks to the preceding account by Schneider Müll. Archiv, 1856, p. 160). He says that he witnessed the revivification of encysted Chlorogonia (a phaenomenon unnoticed by Schneider) on placing some cysts, collected the preceding year, in water. The reddish and pre- viously spherical cysts were seem to gradually lose their regular outline by the elongation of one end, and thereby to acquire an ovate form. After a short time the narrower end of the cyst ruptured, and a very thin-walled vesicle protruded through the rent: whilst this took place, a movement of the contents of the cyst became evident; and after a while several constric- tions appeared, which extended deeper until they divided the whole into four portions. For a time the protruding sac elongated itself more and more, but ultimately, owing to the pressure within it of the moving particles, gave way and allowed their exit. The escaped sections were, as a rule, of pretty uniform sizes, but had not the remotest resemblance to the mature Chlorogonium, and indeed might have readily been assigned to another group of beings. Their figure was elongated, irregular, and often triangular, on first escaping from the cyst; they were also flexible in every direction, and of a dusky brown colour. After dispersion, on reaching the margin of the drop of water, they re- sumed a globular shape, changed to a rusty red colour, and after a few hours assumed the appearance of clear-green spindle or bodo-shaped organisms. Between their evolution from the cysts and their development into the form of Chlorogonium, two hours, less or more, intervened. This division into four segments, represcnting four new beings of Chlorogonium progressively evolved, apparently without actual metamorphosis, may be rightly esteemed an act of reproduction by macrogonidia, whilst the breaking up of the organism into a multitude of Zoospores, as previously described by Weisse, is a process of re- production by microgonidia. NATURE OF ASTASLEA.—It is with certain members of this family that Thuret pointed out (Ann. Sc. Nat. 1850, xiv.) the close resemblance to the zoospores of Algae, amounting, as far as outward appearances indicate, to actual identity. “This affinity,” he says, “is oxhibited in the colour, form, in the number and character of the ciliary filaments, in the contents, not excepting the coloured eye-speck, in the mode of self-fission, and also in the power of locomotion. What is still more, both zoospores and Astasiaea tend to the light, disengage a gas, most probably oxygen, and emit a peculiar spermatic odour. However, by continued watching the zoospores are seen to affix themselves to some body, surrender their seeming animal life, and proceed to germinate, developing a tissue similar to that of the plant which gave them birth. On the other hand, the true Astasiaea, if they attach themselves, it is but for a time, and no ap- pearance of germination ensues. The closest similarity exists in the case of the Chlamydomonas pulvisculus (Diselmis viridis, Duj.), and in a less degree in the Euglenae. . . . In the form of the body, in that of the flabelliform cilia, and in the disposition of those cilia, as also in the contents of the body, the resemblance is complete. The movements of Dise/mis are like those of zoospores; and, like them, they tend to the light. In one distinct species, or rather, in a particular state of the same species, a very clear red spot is dis- cernible, and a central globule, very like in appearance to the amylaceous granules so frequent in the cells of green Algae. These Infusoria appear to act on the atmospheric air like Algae and the green parts of other plants, dis- OF THE PELY TOZOA. 197 engaging a gas (oxygen 2) under the influence of light. They exhale an evi- dent spermatic odour. Their reproduction occurs by spontaneous division, 2–4 young ones being formed within the common integument. I have ob- served the same mode of reproduction in the Euglence, which act on the air and turn to the light like Diselmis, but have an extremely contractile body changing its figure every moment, which will not admit of their being con- founded with zoospores, and leaves no doubt of their animality. This binary or quaternary division is met with also in the various species of Tetrasporae, Which, though arranged with the Algae, appear to me of very doubtful vege- table nature. In Tetraspora gelatinosa I have recognized green globules, dis- posed in fours, and each furnished with two cilia of extreme length, which are lost in the gelatinous mucus of which the frond of this supposed plant is constituted. All these productions, as well as Gonium, Pandorina, Volvov, Protococcus nivalis, &c., present, in my opinion, characters of animality too decided and too permanent for it to be possible to refer them to the vegetable kingdom ; and I think it would prove more convenient to unite them, with all the other Infusoria (Polygastrica) coloured green, in One and the same group, which might be called Chlorozoideae. We have before noticed the sweeping statement of M. Agassiz, that all the mouth- less Infusoria are nothing but various forms and phases of development of Algae.” - - - Although many naturalists stoutly claim the Astasiaea, and the genus Eu- glena especially, as plants, yet others, and among them some of the most able, particularly in Germany, still pronounce them animals. But, as we have before noticed, there are undoubted Euglema-forms which are actually phases of existence of known plants, and which, if watched, may be followed in their development until by germination they assume all the special fea- tures of those plants; and, on the other hand, there are Euglence which at no period of their existence can be seem to germinate, although they may exhibit a plant-like condition when encysted and motionless, like Protococcus resting- cells. As an example of the former set of transitional beings, we may appeal to the observations of Itzigsohn already recorded (p. 125), showing that, in the development of Oscillatorice, minute Chlamydomonads are transformed into Buglenae, that these in their turn generate microgonidia, which, after some in- termediate transformations, eventually produce the ‘Leptothria,’ and lastly the perfect Oscillatoria. Another illustration might be adduced from Cohn's essay on Protococcus pluvialis, in which he points out both an Astasia- and a Puglena-like phase of that unicellular plant. Let it, however, be noted that Whilst Cohn records a Euglema-phase in Protococcus, he nevertheless admits the existence of animal Euglence, distinguished by their extraordinary con- tractility (Entw. p. 208). Withal, this distinguished observer's discovery of the mutual sexual relation of micro- and of macrogonidia constitutes (sup- posing these reproductive products, as seems to be actually the case, to be generated in Euglence) an additional argument for their vegetable nature, by bringing them within the same category of organized beings as Volvoa and Pandorina. - If Mr. Carter be correct in his account of Astasia, this genus can no longer remain in the category of doubtful organisms, but must forthwith be trans- ferred to the animal kingdom ; for he asserts the existence of a mouth with a complicated buccal apparatus for biting off and taking in food, of a strong prehensile organ, and stomach-sacs. Besides, he speaks of its near affinity with Amaeba, and refers it to the Rhizopoda. In Euglema, on the contrary, no mouth- or stomach-vesicles are discoverable, and the filament is comparatively 198 GENERAL HIStory of THE INFUsonia. imperfectly developed; hence Mr. Carter allies this genus rather with the zoospores or gonidia of Algae, and assumes that it must, like other mouthless organisms, derive its nutrition through endosmosis. Cohn, on the other hand, although cognizant of many plant-like features in Eugléna, cannot ac- quiesce in detaching it from animalcules, because of its great contractility and of the fact that there are undoubted animals, such as Opalina, Rhizopoda, Gregarina, Trématoda, &c., which want the special animal characteristic of a mouth. Mr. Carter would, it seems, recognize both Euglena and Astasia as close allies with Amoeba, an affinity remarked by Ehrenberg, who placed the family As- tasiaea between Closterina and Amoebaea, treating the variability of the form of the body as a leading characteristic. Indeed, the first—named observer alludes to an actual transition of Astasiae into Amoebae, in the following paragraph (A. N. H. xvii. 1856, p. 115):-‘‘Young Astasiae are developed within the cells of Spirogyra to a great extent; and although they at first have almost as much polymorphism as an Amoeba, still they retain their cilium, and after a while assume the form and movements peculiar to Astasia. I might here mention that on one occasion I saw a large Amoeba with a long cilium at one time assuming the form of Astasia, and at another that of Amoeba, which thus gives us the link between these two Infusoria. The cilium, however, had not the power of the filament of Astasia, though it occasionally became terminal.” At a previous page, a rhizopodous development of the contents of Euglence into granuliferous Amoebae of a pinkish colour has been adduced as a fact noticed by the same observer. We necd not stay to examine the vital endowments and habitats of the Astasice ; for, except the facts occurring in the preceding history of the family, and in the general account of Phytozoa, there is nothing important to adduce. Ol' TELE PROTOZOA. 199 SECT. III.—OF THE PROTOZOA. (Plates XXI-XXXI.) THE term Protozoa, borrowed from two Greck words, protos, first or primi- tive, and zoom, an animal, has of late been very generally adopted to signify the simplest forms of animal life. Upon a review of these rudimentary animals, it is at once perceived that they differ among themselves in organiza- tion—that whilst some are amorphous and almost homogeneous, others exhibit a degree of differentiation of parts, and the first vestiges of internal organs to carry on the processes of life; again, it is seen that some have a distinct orifice for the admission of food, or a mouth, which in others is absent, and, lastly, that some with a definite figure are moved by vibratile cilia, whilst others slowly progress by the alternate protrusion and retraction of ever-changing and changeable processes derived from the general mass of their body. From a consideration of these structural differences, one division of the Protozoa is suggested into those moved by cilia, and those moved by variable processes or ‘pseudopodes’; and a second, into those furnished with a mouth, and those which are mouthless. We have accordingly constituted two pri- mary divisions, viz., 1. Ciliata, Protozoa moved by cilia; and 2. Rhizopoda, moved by variable processes. The Rhizopoda (XXI.) aro all mouthless, or “astomatous,” whilst the Ciliata (XXIV.-XXX.) have a mouth, and are styled by Siebold “Stomatoda,” with the exception of a small family, the Opalinaea (XXII. 46, 47), and perhaps also of that of the Peridiniaea (XXXI. 16–23). However, besides the beings usually included among the Ciliata and Rhizo- poda, there are several subordinate Protozoic groups, some of which either stand as it were midway between them, or represent a development of the amorphous and mouthless Rhizopoda in a different direction; such are the Gregarinida (XXII. 28–36), with the associated Psorospermia (XXII. 37– 41), the Spongiada, Thalassicollida, and Polycystina, all which must rightly also be numbered with the Protozoa. Of the CILIATA themselves, there is a further and higher development of their type in the subordinate groups of Ichthydina (XXII. 46–47) and Noc- tilucida (XXXI.), and, on the other hand, a degradation of it, as already noted, in the case of the Opalinaea and Peridiniaea. Here we would remark that the term ‘Infusoria” has been employed by several writers, in lieu of that of Ciliata, which we adopt ; still it is, to our mind, both less appropriate, and also open to objection, not only on account of its meaning being quite indefinite, but also by its having everywhere acquired a very much wider signification, in consequence of which it will always be open to misconception when applied to a comparatively very small class instead of, as heretofore, to a very various and wide collection of microscopic organisms. Another word invented is ‘Stomatoda,” which is precisely equivalent in the extent of its signification with the term Ciliata, the mouthless families only being excluded. Excepting their subordinate groups, the organisms comprehended among the Ciliata and Rhizopoda formed, in conjunction with the Desmidieae, Dia- tomede, and the families we have brought together under the appellation Phytozoa, the great class Polygastrica in the system of Ehrenberg. Little reflection is necessary to convince ourselves of the very heterogeneous nature 200 GENERAL HISTORY OF THE INFUSORIA. of the collection of living objects assembled in that class; and even Ehrenberg himself would never have suggested such a grouping, had he not imbibed the hypothesis of a pervading uniformity of organization possessed by the simplest animated beings in common with animals considerably advanced in the scale, and under its influence, aided by his imagination, found in all these various organisms, a polygastric structure, viz. an apparatus of numerous stomach- sacs, communicating directly or indirectly with the mouth. Notwithstanding the many prominent errors in Ehrenberg’s classification, he rightly recognized in framing it the value of the external means of locomotion, and distinguished a group of Polygastrica under the name of Pseudopoda. Siebold, who proposed the term Protozoa, limited it to two classes, distin- guished as the ‘Infusoria’ and the ‘Rhizopoda ', omitting the supplementary groups above mentioned. The Infusoria he divided into two orders, the “Astoma' and “Stomatoda,” the latter of which, together with two of the three families of Astoma, is equivalent to our class Ciliata, its remaining family Astasiaea being a member of our group of Phytozoa. The Protozoa, as understood by us, may be thus exhibited at one view. CILIATA. RIIIzopop.A. a. Astoma Opalinaea a. Amoebaea § C. Peridinia’a (?) b. Monothalamia or Momosomatia b. Stomatoda Sº ºil-` c. Polythalamia, Polysomatia, or Foraminifera. Gregarinida Psorospermia •ln{livrii Polycystima ſhºydiº ! ... ..Supplementary groups...... ſ Thalassicollida Noctilucida l Spongiada In treating of these sovoral classes and groups we shall commence with the Rhizopoda, omitting, however, lest our subject-matter be too much ex- tended, the Polycystina, Thalassicollida, and Spongiada; we shall next pro- ceed with a brief description of the Gregarinida, and its subordinate family Psorospermia, and then after considering the Opalinaea and Peridiniaca as intermediate groups, proceed to detail the history of the perfect Ciliata— the Stomatoda, finishing our account with the Ichthydina and Noctilucida as the highest developments of Protozoic life. As a result of our inquiry, we shall See, on the one hand, in the true Ciliata, simple animal organized matter, with a very slight amount of differ- entiation, attain its acme of development in the Vorticellina, and in these animalcules exhibit a Superiority in Organization above the lowest links of groups relatively higher in the chain of animal life; and, on the other hand, in the Rhizopoda, of still simpler organization, the same organic living material developed in a totally different direction to a maximum in the most beautiful and complex-shelled Foraminifera, which in outward form, although in no real homology, emulate the highest class of Invertebrata, viz. the Cephalopoda - Another lesson may also be derived from the objects of our present study, viz. the fact of the marvellous variations which can be made out of one or, it may be, two elementary structures. Thus the simple contractile substance which can live independently in the Amoeba condition (XXI. 1–4; XXII. 1–23) encases itself in a one-chambered shell in the Monothalamia (XXI. 6–19), and into a many-chambered one in the Polythalamia (XXI. 20–36), and again lives partly within and partly without the curious silicious skeleton of Poly- OF THE PROTOZOA.—REIIZOPODA. 201 cystina, and in singular relation with a spicula skeleton in Spongiada and Thalassicollida. So, if we look to the Ciliata, we find that the hardening of the Superficial lamina of their substance into a sort of integument gives rise to numerous modifications in external form and functions, according to the degree of induration, and the processes sent out. The flexible-skinned Colpodea. (XXIX. 25–50) depend for their movements upon their garniture of vibratile cilia, and are merely swimmers, whilst the hard-coated Euplota (XXV. 350– 353) produce short moveable processes which act as legs, upon which they can rapidly creep. Lastly, the selfsame primitive contractile substance is formed into a stem in the Vorticella, which supports the animalcule at its apex, and exhibits helicoid contractions, astonishing both by their rapidity and completeness. SUBSECTION I.- RHIZOPODA. (Plates XXI. XXII.) The true Rhizopoda constitute a large class of microscopic animated beings of the most simple character. They may be defined as non-ciliated Protozoa moving by variable expansions. Their organic animal substance presents no distinction of tissues or of organs, but is homogeneous, contractile, and trans- lucent, resembling a tenacious mucus or soft tremulous jelly, and is perpetually changing its form by expanding itself at one or several points into processes of ever-varying dimensions, arrangement, and number, and called in conse- quence “variable processes.” Inasmuch, moreover, as these shifting offshoots are their only means of locomotion, they have frequently been called “feet,” and, as they are also characteristic of the class, have given origin to the terms “Pseudopoda" (with false feet) and “Rhizopoda" (root-like feet) to desig- nate it. Again, the living mass is, in numerous instances, capable of enclos- ing itself by a shell of various figure, consistence, and complexity; and such variations serve to Scparate the Rhizopoda into families and genera. In the simplest shell-less beings (XXI. 3, 4), vitality is exhibited by the slow protrusion and retraction of the variable processes, by the change of form, their onward movement, and the introduction of nutritive substances, and by the gradual changes of the introduccd matters indicating a digestive act. They therefore manifest vital contractility, a power of locomotion, a degree of Sensibility, and a digestive process. Repeated observation likewise reveals the fact of progressive growth, and the faculty of reproduction. The testaceous forms exhibit their vitality after the same manner, and Surpass the naked Rhizopoda only in the mar- wellous power of secretion displayed in the production of their shells (XXI. 6–36). Although in organization the Rhizopoda stand even below the ciliated Protozoa, yet an animal nature must be allowed them; indcod the simplest forms are the rudest specimens of animal oxistence. Under the term Rhizo- poda are comprised three well-marked families, viz. the Amoebina or Amoebaea, which are without, and the Monothalamia and the Foraminifera, with shells. The Monothalamia have one large opening to their monolocular (one-celled) shells (XXI, 6–17)—hence the name, whilst the Foraminifera owe their de- signation to the existence of numberless small orifices, generally distributed over a multilocular (many-colled or chambered) testa (XXI. 20–36). We have frequently, in the following pages, used the term Arcellina as synonymous with Monothalamia: for although the family known to Ehrenberg under that name comprehended only a portion of the genera that Schultze 202 GENERAL BIISTORY OF THE INFUSORIA. arranges in his group of single-chambered or monolocular shells, yet its meaning may be equally extended. It would probably have been correct to have placed the Acinetina (XXIII.) among the Rhizopoda, as another family closely allied to the Amoebina ; but the detail of their peculiarities would have too much embarrassed the general description of structure which we have endeavoured to give of all the usually acknowledged or true Rhizopoda; we have therefore preferred to describe them as a subclass in the following chapter. The examination of the Rhizopoda requires to be conducted with great care and skill,—a requirement sufficiently illustrated by reference to the erroneous notions and descriptions of the older observers. They must be viewed in all positions under different degrees and modes of illumination, by reflected as well as by transmitted light, and, especially in the case of the testaceous varieties, after submitting them to pressure and to the action of various chemical agents, or, when sufficiently large, after making Sections of them in different directions. The organic living mass of all Rhizopoda is alike, and corresponds with the “Sarcode * of ciliated Protozoa and with the amorphous contractile substance of Hydra and of other low organisms. It appears in the present class a con- tractile, highly elastic, colourless, almost fluid mucus, hyaline or diaphanous, homogeneous, and in refracting power differing little from water. No di- stinction into an enclosing firmer membrane or integument and contents is discoverable; and cilia are never found. These characters exist in entirety only in very young animals; for at a very early period molecules, granules, and globules or vesicles, and various foreign particles, make their appear- ance, diminish the transparency, and often impart colour. A new species of Amoeba, figured by Schultze, the A. globularis, is repre- sented as having a thin, transparent, Colourlesslamina of contractile Substance, from which the processes are given off, and which surrounds a globular, co- loured, and granular chief or nuclear mass (XXI. 1, 2). A similar distribution of the substance of an Amoeba into a hyaline colourless cortical, and a granu- lar coloured medullary portion, is represented by the same author in another species; and it is moreover a structure homologous with that in the allied genus Actinophrys (XXIII. 28, 29). As to the assigned character, of the animal sarcode being destitute of a distinct investing membrane or integu- ment, the shell produced by the testaceous forms might be considered equiva- lent to one; and if some observations hereafter alluded to be correct, a re- sistant integument among the Rhizopoda must be admitted as an established fact. It is possible that in some instances the organic substance has a colour of its own; for instance, Ehrenberg describes Amoeba princeps as having a yellow colour. However, in general the occurrence of colour is consequent on that of granules, and on the introduction of food; and observation proves that the depth of colour augments with age, and is otherwise in direct relation with the abundance of food. The colour is usually pretty uniformly diffused. Schultze shows this, and also its relation with the thickly-distributed minute granules, in many Miliolidae, Rotalidae, and Gromiſe. In larger species (he adds), such as Polystomella strigilata and Gromia oviformis (XXI. 16), the colour occurs in scattered and much larger particles or vesicles; yet under what form soever found, it is, in the case of the many-celled or chambered Foraminifera, deepest in the oldest cells, and progressively fades on approach- ing those most recently formed, the last being commonly quite colourless (XXI. 28, 33, 36). Experiment also showed that, by depriving the animals of food which could convey colour, other chambers than the last lost their OF THE PROTOZOA.—REIIZOPODA. 203 tint, and, vice versä, that by feeding them abundantly with such food, even the animal substance of the ultimate cell acquired colour. Irregular accu- mulations of colouring particles in the ultimate chamber are of rare occur- rence. Ehrenberg has figured such in Nonionina germanica. The colourless, or almost colourless Rhizopods, principally Amoebae, are, owing to their transparency, visible with difficulty, and require nice adjust- ment of the microscope and of the light to demonstrate their vitality and movements. Concerning the chemical relations of the organic Substance, it is stained yellow or yellowish-brown by solution of iodine, like other proteine matters, and, according to Schultze, is unaltered by diluted acetic acid, is slightly hardened by a dilute solution of the alkalics, and more so by one of the car- bonates. Moreover, its resistance to chemical action would seem to differ in different species; for the Gromia Dujardinii was the least affected of se– veral animals experimented on. “The colouring-material,” to quote the same writer, “assumes by the action of sulphuric and of hydrochloric acids an intense verdigris green, and by that of nitric acid, first a green and then a yellow tint. Concentrated Sul- phuric acid destroys the coloured substance, but when combined with sugar, renders it green. By concentrated solutions of potash and soda, the coloured granules are dissipated without change; and in ether and alcohol they are readily and completely dissolved. In these reactions the colouring-matter agrees with Diatomede, from which, no doubt, it is derived in the form of food.” No definite figure can be said to belong to the animal portion of the Rhi- zopoda, owing to its capability of throwing out processes in every direction, of various dimensions and in different numbers, changing them almost every moment. Auerbach, however, asserts of the Amoebae that they have normally a spherical figure. Dr. Bailey has pointed out the influence of pressure from within, due to the various articles Swallowed, in modifying the figure. The Amoebae, being untrammelled by a shell, exhibit the Protean changes of form in the highest degree, whilst the completely enclosed Foraminifera present them in the lowest. In the latter the organic mass must follow the windings of the cavity of the shell (XXI. 24), and can escape only from the foramina (holes) as thread-like filaments, in the form, extension, and subdivisions of which great latitude prevails. We have said that the sarcode of Polythala- mia follows the windings or adapts itself to the figure of cach segment of the shell, and has actually no figure of its own. However, when separated from its calcareous investment by means of an acid, it retains the outline originally imposed on it. Thus (XXI. 24) Schultze exhibits the sarcode substance of a Miliola so separated, which shows a constriction at each half turn of the spiral and the delicate membrane which invests it or lines the shell. So, again, Dr. Carpenter, in his description of Orbitolites, states that the soft sarcode body is made up of a number of segments equal and similar to each other, and arranged in concentric Zones around a central nucleus. Among the Amoebae the varia- ble processes may either be protruded at one time from every portion of the little mucous mass, so that, as Ehrenberg remarks of the Amoeba radiosa, it may, when fully outspread, be likened to a miniature porcupine; or, otherwise, they may be produced chiefly or entirely from one side; or, as when the ani- mal is moving, they are thrown forward in the direction it is progressing, and retracted on the opposite side. Among many Monothalamia the bulk of the living mass issues through the one large orifice, and can spread out in a similar manner to the free Amoebina, the shell, according to the direction of the pseudopodes, resting in the centre of the mesh or on one side. The Forami- nifera have a like capacity of extruding their processes in one direction rathor 204 GENERAL HISTORY OF THE INFUSORTA, than in another, or in all directions together; and accumulations of their mucous substance, or fusions, may take place on any one side. In this family the filiform fibres are, as a rule, not seen protruded at any one time through all the pores perforating the shells. . Many genera have, besides the generally-distributed Small foramina, a larger orifice in the ultimate chamber; such is seen in Rotalia and Teactilaria. In these, says Schultze, it may be remarked that the processes first thrown out come principally from the large openings, and frequently a considerable time elapses before the numerous fine pores give exit to fibres. Often, again, the filaments are extended only from the two or three last-formed cells. Yet after long lying undisturbed, fibres may be seen proceeding from every part of the surface of the finely porous shells. Still the question requires further examination, to decide whether the processes can be extruded through all the foramina or only through some of them in certain places. However, as Schultze remarks, the universal porosity would seem without a purpose if it does not give vent to the contained substance at all points. - The processes of Polythalamia attain the greatest length and fineness, an often constitute a network of several lines in diameter, the shell of the ani- mal occupying the centre, like a spider lodged in the middle of its web. The length of such fibres not uncommonly exceeds twelve times the diameter of the shell. The processes of most Monothalamia are not so numerous, and do not equal on an average those of the Polythalamia, whilst those of the Amoebae are mostly shorter and broader. The length, number, and fineness of the processes, together with their mode of termination, supply, under considera– ble limitations, characters for distinguishing species chiefly of the Amoebiña, and, in a less degree, of the single-chambered testaceous Rhizopoda. The ever-fluctuating form of the animal mass and of its processes is ex- pressed by the term “polymorphism.” It is, as before noticed, a well-marked, character of Rhizopoda, although not restricted to them ; for the like is exhi- bited by the yolk-cells of Planaria, and by detached fragments of the substance of Hydra ; in fact, illustrations are not wanting in the vegetable kingdom. The phaenomenon of polymorphism would seem to discountenance the hy- pothesis of the presence of a limiting membrane or skin. Ehrenberg described a resistant, very elastic, and contractile integument, and, to explain the vari- ability of figure and the extension of the pseudopodes, supposed a relaxation or suspension of the natural contractility of the integument at the extending point, and a consequent passive yielding before a pressure from within exerted by the contained substance. This explanation he endeavoured to illustrate by comparing the process with the formation of a hermia or rupture, a com— parison, by the way, involving an effort of imagination to discover any simi- larity between the two occurrences. Thus he remarks of Amoeba princeps that “its normal shape, if such it can be said to possess, is globular; but it can relax any portion of its body, and contract the rest, so as to force the in- termal substance down into this relaxed portion, which thus becomes, as it were, a hermial tumour.” This notion is opposed by the results of observa– tion. The very characters of the processes, their great length and frequent tenuity, their branching, adhesion, and coalescence contradict the assump- tion ; and the fact of their not uncommon extensoin from all sides of an ami- mal involves, as a consequence of Ehrenberg’s hypothesis, a belief in the exertion of internal pressure in opposite directions at the same time. Other evidence of the error of this hypothesis is found in the following facts, viz. the adhesion and entrance of foreign bodies at any part of the sarcode sub- stance, the cohesion of two individuals, and that, as pointed out by Dujardin, when the gelatinous mass of an Amoeba is torn or cut across, no escape OF THE PROTOZOA.—REIIZOPODA. 205 of a contained softer matter or of granules takes place, but each segment con- tracts on itself and continues to live, and, again, that when a Rhizopod is shaken about, its proccsses become flexuous, and float loosely instead of being withdrawn within the general mass, as should happen if a general contractile integument enveloped it. Among the Amoebae generally, a distinct hyaline cortical substance is found enveloping the interior more fluid matters, and restraining their escape. (See afterwards, on shells of Monothalamia, excep- tional forms noticed by Dujardin and Bailey, and the researches of Auerbach.) Although an integument be, therefore, no part of the structure of Rhizopoda, yet their soft substance is capable, as is shown best in the Amoebina, of resist- ing internal pressure, such as that from silicious shells of Diatomede and other hard substances, which oftentimes cause irregular and sharp projections during the movements of the animals, but yet very rarely perforate them. On the other hand, Rhizopoda become sometimes impaled upon the rigid fibres of plants or other substances, and, though thus transfixed, will move from one extremity to the other, without any apparent inconvenience or injury. This circumstance has been long noticed in the case of the Amoebae ; and Schultze has figured a specimen of a testaceous Rhizopod—the Gromia Dujardinii —penetrated by a large curved hair. Dr. Auerbach, in a recent Essay on the Amoebaea (Zeitschr. 1855, pp. 365– 430), has advanced the statement, from observation, that all the Amaebae are enclosed by an adhesive, elastic and structureless membrane or integument. This fact has, he says, been so universally overlooked by reason of the diffi- culty in determining it, and, where caught sight of, has been misinter- preted, as, for instance, by Schneider (Müller's Archiv, 1854, p. 201), who represents Amoeba enclosed by a membrane as being in a state of “rest,” or encysted. Auerbach makes particular reference to two new species discovered by him, as illustrative of the presence of an integument, viz. A. bilimbosa (XXII. 7– 11), and A. actinophora (XXII. 13), in both of which he detected a double peripheral line. But besides this evidence he appeals to the effects of reagents, of acetic or of diluted Sulphuric acid and alkaline solutions, both on the species just cited and on others well known—for instance, A. princeps—in demon- strating the membranous investment. And what seems at least very strange, we might say quite inexplicable, he asserts that upon all the processes, how- ever branched, anastomotic, or fine, this membrane is extended to their very extremitics; for on adding a dilute alkaline solution to Amoeba radiosa, the granular and molecular contained mass became shrunken, and retreated to- wards the centre, leaving the figure of the animalcule with all its processes as before the addition, the latter appearing as tubules with closed ends, which ruptured by over-extension. This same author accounts for the entrance of solid particles from without by imagining the integument to rupture to receive them, and then to close on them so as to leave no trace of the proceeding. Further, the membrane is not soluble, at the Ordinary temperature, in acetic nor in mineral acids, nor in dilute alkaline solutions, and therein agrees with the tissue noticed by Cohn in Paramecium and othel Ciliata (vide chap. on CILIATA), and with the cell-membranc of animal cells. These observations of Dr. Auerbach are well deserving attention, although we are indisposed to accept them in their entirety. The wonderful poly- morphism, the coalescence of processes, and the particulars alluded to above (p. 204) as inconsistent with the presence of an integument need not be again adduced in argument. What is desirable is, that observations should be multiplied on this subject, which is one that strongly commends itself to 206 GENERAL EIISTORY OF TELE INFUSORIA. the notice of microscopists on account of its bearing on the question of cell- constitution. The variable processes serve the Rhizopoda for locomotive organs. An ex- pansion is thrown out in advance, into which a constant influx of the sarcode Substance sets, whilst in the opposite direction a counter-current occurs, effecting the retraction of the posterior processes. This onward flow of the substance of the body proceeds until at length the whole is transferred into the advanced process, moving from its base to its termination. In this manner the animal progresses, the space passed over equalling the length of the ex- pansion it protrudes. This method of locomotion may be designated creep- ing or crawling, and is the only one with which this class of animals is en- dowed. The consequence is that they are, as a rule, to be only found adherent to Solid bodies, and cannot move by swimming. However, they can move as passive particles of matter, be rolled along by currents upon any substance they are in contact with, or, from being (as in the case of Amoeba) of almost the same specific gravity with the water in which they live, may float, or be suspended in it for a long time. Their motion by creeping is exceedingly slow, and oftentimes is appreciable only by attentive watching. The graphic description of Schultze, of the expansion of processes in a naked Amoeba and in a testaceous species, viz. the Gromia oviformis, will make the phaenomenon more distinct. The former is a new species discovered and named by himself the Amoeba porrecta (XXI. 3). It is distinguished from other species in the genus by the great extension it is capable of, and by the lively motile energy of its contractile substance. “It sends out from its colourless body, on all sides, numerous fibrous processes, short and broad on their first extrusion, but which gradually elongate until they exceed the diameter of the body eight or ten times, and taper to such fine extremities that a mag- nifying power of 400 diameters is needed to distinguish them. The figure and extension of the body change every moment, according to the side in which the ramifications are extended. If two or more of the filiform pro- cesses touch, a coalescence takes place, and broader plates or net-like inter- lacements are produced, which, in the continual changes of figure, are either. taken up again into the general mass, or otherwise are further increased by a fresh influx of matter, until finally the entire body is transposed to their place.” In the testaceous Gromia oviformis (XXI. 16), after a state of rest of some duration, fine fibrous processes are seen to be extended from the single large opening of the shell, which, on their first extrusion, move about in a groping manner until they lay hold of some solid body (such as the surface of the glass slide) on which they may stretch themselves out, receiving in the meanwhile new matter from within the shell. The first fibres are extremely fine; but pre- sently they grow wider, and proceed to elongate themselves, pursuing a straight course, ramifying in their own way and coalescing with adjoining processes, until, becoming progressively finer and finer, they attain a length exceeding that of the body six or eight times. The fibres having now outstretched themselves in every direction, and absorbed the greater part of the finely- granular contractile substance, their further extension in length ceases. However, the reticulations go on multiplying; numerous bridges (inoscula- tions) are established between them; and by the continued changes of position a constantly shifting protean web is produced, where a greater number of fibres come together at the periphery of the sarcode-net as we may term it, broader plates (laminae) of the perpetually-flowing substance are formed, from which again now filaments are pushed out in new directions, as if it were a separate Amoeba. In the Polystomella, the long fibres are seen to converge to form a pyramidal bundle, and to coalesce into wide laminae at its apex. OF TEIB PROTOZOA.—RBIZOPODA. 207 Dujardin made some precise observations respecting the characters of the locomotive variable processes and the rate of movement. In Gromia oviformis, he describes a filament to begin as a very fine simple and uniform offshoot, which elongates and directs itself in different directions, in order to seek a point of attachment; sometimes it oscillates, at others it czhibits a tolerably rapid undulatory movement, or, otherwise, it rolls itself up in a spiral manner, when the several coils coalesce, and a mass is formed capable of throwing out afresh other processes. Proportionately to the extension of the filament, its substance is added to by an afflux of new substance from the chief mass, evi- denced by the movement of irregular granules, which give the fibres an un- equal and nodose appearance. Moreover, the fibre gives off branches here and there at a more or less acute angle, which, in their turn, ramify after the same fashion, and establish communications or anastomoses with one another. Often also films or laminae of the gelatinous Substance form at the extremities of contiguous fibres, which extend themselves variously. The filaments retreat by an inverse movement; and this is occasionally so sudden that the end as- sumes a button-like termination from the fusion of the mass of matter engaged in its formation. The expansions of Miliola, he further tells us, are six times finer than those of Gromia, and the movement of the animal more rapid ; for during summer it moves from about Tºth to #th of an inch in an hour. Cristellaria moves ºth of an inch, and Vorticialis from #th to #rd of an inch in a like period. The variable processes also constitute the prehensile organs of the Rhizo- poda. Any small objects serviceable for nutrition, with which they come into contact, are laid hold of by them apparently by means of their viscid surface; and, except they are animalcules of considerable size and power, they are un- able to escape. When a filament or, as we may call it with reference to this function, a tentacle has so seized its prey, adjoining fibres aggregate about it and coalesce, a current of the viscous substance sets in towards the spot, and very soon envelopes the object by a film. The prey being thus secured, the processes shorten themselves and draw it towards the chief mass or body of the animal, or, otherwise, the object seized continues in the same place, and the Whole organic Substance moves towards it, the result being in either case that it is engulfed. In the Amoebina this prehensile act proceeds as just stated; in the Monothalamia and in those Foraminifera having a large opening in the last chamber, the body seized is directed to the large orifice of the shell; but in those having no other than fine pores or minute fissures, it would not seem to reach the general mass, but to be used up for the pur- poses of nutrition externally to the shell, by a digestive action inherent in the fibres themselves. The mode of entrance, therefore, of food within the viscid organic matter, is not so simple and mechanical an act as Dujardin re- presented it, but has much more of a vital character. This observer’s state- ment was, that the more pressure of the body of the animal on the surface it moved over caused the penetration of foreign matters, which, by subsequent extensions and contractions of different parts of the substance, became at length completely involved in it. It would seem that animalcules may swim about unharmed within the meshes of the sarcode-web, but that so soon as they touch one of its fibres, they are as it were paralysed and incapable of further motion, and are consequently drawn deeper into the net without any opposition. Schultze, who has noticed this circumstance, believes it to be quite explicable as a simple mechanical act, and no proof of a special be- numbing property resident in the soft Substance as Ehrenberg was inclined to suppose. Food, or indeed any extraneous matters, may enter the soft bodies of Rhizopoda at any point of their surface; i. e. in other words, those 208 GENERAL EIISTORY OF THE INFUSORIA, animals have no definite aperture for food—no mouth. This absence of a mouth, on anatomical grounds alone, involves that of an alimentary canal, or of a polygastric structure such as Ehrenberg imagined. The digestive cells, so called, of Arcellina are nothing more than hollow spaces or vacuoles (XXII. 7, 8, 9), which spontaneously and irregularly develope themselves in the mu- cous sarcode substance. They especially make their appearance after the in- troduction of food, the particles of which generally appear enclosed within them, and to be surrounded by a fluid. In the allied organisms represented by Actinophrys, M. Claparède states that the particle of food always lies in a cavity filled with fluid—a vacuole,_and that the fluid is of a pale reddish colour, with different refractive powers to those of water, and is in all proba- bility a solvent or digestive fluid. This pale-red or reddish-yellow tint of the vacuoles is remarked also in Amoebae ; and the observed dissolution and eventual disappearance of organic matters absorbed is a sufficient proof of the presence of a digestive secretion. In an Arcella vulgaris, Perty witnessed the successive appearance of four vacuoles, each in its turn enlarging from a small round to a large reniform space, and thereby expanding the dimensions of the animal itself. He believed them to be filled with air, and, like the air-bladders of fish, to serve to float and turn the animals in the water, when free and without solid objects to crawl upon. w Ehrenberg states that in some Arcellina, where “digestive sacs” were otherwise invisible, they were brought into view by feeding the animals with coloured substances. He thus presumed on the prior existence of these cells, supposing the colouring particles to be merely the means of bringing them into view. The true explanation, however, is, no doubt, that the con- struction of vacuoles is consequent on the introduction of food, and de- pendent on the manner in which the animal substance enfolds the solid par- ticles which it has seized. Observation, indeed, proves that the vacuoles have no constant and definite existence and position; for they collapse and disappear when the contents are removed or are reduced to a few fine granules dispersable in the common mass. They also constantly shift their position, and not unfrequently make their way to the surface, at which they burst and disappear. As Dujardin also remarks, they sometimes form at or near the surface, and may even serve as a medium for introducing foreign matters into the body. Dr. Bailey, in his description of a new species which he names pamphagus, represents it as having (although a shell-less Rhizopod) a mouth from which alone pseudopodes protrude, and a single stomach ; hence, he adds, it cannot be considered polygastric. However, no evidence is adduced to support this motion of a gastric cavity; on the contrary, indeed, the details given stand opposed to such an hypothesis, for instance, to quote only one, that of their being frequently seen transfixed by delicate fibres of foreign matters, and moving unharmed up and down them. Schultze states that in Foraminifera very clear vesicles are uniformly diffused throughout the body, some entirely homogeneous, others finely granular, or filled with corpuscles. However, nuclear corpuscles, which can be regarded as cells in the ordinary signification, are never found. This naturalist, moreover, indicates the existence of a larger species of vesicles in Gromia oviformis (XXI. 16), containing other clear corpuscles, sometimes to the number of eighteen, but never strumg together ; he believes likewise that similar vesicles exist among other Foraminifera, and seems disposed to attri- bute to them a nuclear character. - Ehrenberg professed to discover in the Polythalamia, in each chamber, saving the last, an alimentary tube, having a greyish-green colour and very of THE PROTOZOA.—RHIZOPODA. 209 thick. This intestimal cavity, he affirmed, communicated with the cell in front, and the one next behind it by a narrower canal—the siphon, and that in this manner a sort of continuous moniliform intestine was produced, extending from the primary to the penultimate-cell. He adds that, after the solution of the shell of Nomionina Germanica by dilute acid, various silicious Infusorial shells could be seen within this digestive tube, as far back in the animal as the first chamber. Moreover, he was fortunate enough to be able, after the dissolution of the shell of Rotalia by acid, and by proceeding very gradually, to set free an internal, spiral, jointed body, the Segments of which were strung together in Nomionina by one, and in Geoponus by from 18 to 20 tubes (siphons); strong acids destroyed the shell so rapidly that the con- tained delicate body became broken up into many insignificant fragments. In nome did he succeed in introducing coloured food. This digestive apparatus others have sought in vain in the Foraminifera. The spiral articulate body extracted by the Berlin naturalist from the shell, was undoubtedly nothing more than the soft animal contents, somewhat acted on by the acid, such as Schultze has pictured from the cavity of a Miliola (XXI. 24). Respecting the penetration of food to the primordial chamber, which Ehren- berg imagined he had seen in Nomionina, Schultze observes that, among the many beings he has examined, he has not detected nutritive matters further back than the second or third cell. The substances received from without, after having served their purpose within the gelatinous body of Rhizopoda, make their way outwards and escape from any part of the surface,—an anus being, like the mouth, pro- duced temporarily, at any point whatever, where matters present themselves for discharge. The materials taken within the body of Rhizopods are most heterogeneous; no selecting power being displayed by the animals, various Ciliated Protozoa, fragments of the filaments and spores of Algae, frustules of Diatomea, and Desmidieæ, even Rotatoria, fall a prey: but along with these, from which nutriment may be extracted, are other substances which can be supposed to serve no useful purpose; such are particles of Sand, morsels of woollen and of Cotton tissues, and the like. The introduction of particles indiscriminately is explicable from the mode in which they are captured by the filamentary arms, which seem to act in a prehensile manner, on feeling the contact of any foreign object, be that what it may. Dujardin threw doubts upon the nutritive purpose of the solid objects swallowed, and supposed the act of nutrition consisted in the simple imbibition or endosmosis of fluid from without. “It is,” he writes, “ difficult of belief that these included particles, by reason of their consistence and the unalter- ability of many of them, can serve to nourish the Amoebae ; yet, whilst admit- ting that they are nourished by absorption, I would not deny that they may find means of still more readily appropriating nutritive materials, by swallow- ing various foreign bodies, and by so increasing their absorbent surface.” The evidence of direct observation, however, is in favour of the conclusion that the substances received within the simple animal mass actually afford ma– terials for its nutrition. The contents are ever changing and making their exit from it; and an act of digestion or of solution is perceptible—slow, indeed, even when soft Ciliated Protozoa are the subjects. Thus animalcules, when within the Sarcode mass, are first compressed into small balls; the distinct- mess of their parts then fades, and they are presently converted into small gelatinous globules, which in due course disappear, from amalgamation with the enclosing substance. Where the included body consists partially of . insoluble material, this remains behind in the form of fine granules, or, in 210 GENERAL ELISTORY OF THE INFUSORIA. the case of the silicious–enveloped Diatomede, the dense skeleton, emptied of its organic contents, continues visible for a longer or shorter time. The robbing of the frustules of Bacillaria, and the appropriation of their coloured endochrome, has been referred to in the foregoing remarks on the colouring of Rhizopoda (p. 203) by the green colouring-matter of plants. - The Rhizopods Bailey describes were met with in a vivarium, into which “bits of boiled beans and potatoes had occasionally been introduced as food for other animalcules; . . . . on the application of tincture of iodine to these animals, a distinct blue colour was often seen diffused over the whole surface of many of the grains of Sand in their stomach.” The above facts—to which we may add another, viz. that the abundance of granules in the interior is in direct proportion with that of food—furnish sufficient proof of the occurrence of a digestive faculty, and of a power of assimilation among the Rhizopods. This implies the existence both of a digestive fluid, and of a secretory function; the latter, too, is further ex- emplified by the production of shells in the majority of the class. - Auerbach (op. cit. p. 422) distinguishes two leading varieties of granules in Amoebae :—one of a pale colour and finely divided, and either soluble in alkalies and acids, and turned brown by iodine, or, more rarely, insoluble in alkalies; the other, dark in hue, strongly refracting, and usually corre- spondent in number and relative size with the animalcules to which they appertain. These latter have the aspect of fat-molecules; are spherical or elliptic, or at times crystallized in a rhombic form; and they are easily soluble in cold alkaline Solutions, and more slowly so in concentrated acetic and sul- phuric acids. In one species, A. bilimbosa, he met with starch globules; but these were probably of extraneous origin. MoVEMENTS OF CONTAINED PARTICLES.—Every movement of the mucous sub- stance of Rhizopoda is accompanied by one of the granules, and of the small vesicles or globules contained within it. This motion of the contents follows a certain course, and is especially observable in the outstretched variable pro- cesses. Schultze thus describes it in the large Amoeba porrecta :—“A continued current of the granules, imbedded in the contractile substance, accompanies all these phenomena (viz. of polymorphism); and, in the processes, this current follows two directions; thus the globules may be seen advancing on one side, towards the end of the process, when they turn round to the other, and are carried with a comparatively more rapid motion back towards the base of the filament, where they are lost in the substance of the body, unless they happen to meet another stronger stream by which they are reconveyed through the same circuit.” A precisely similar phenomenon is witnessed in the testaceous Rhizopods. Thus in Gromia oviformis, Schultze says, the granules are seen to depart from the substance within the shell to the end of the filaments, and thence to return again to the point from which they set out. This circula- tion goes on in every process; but it is in the broader filaments, containing numerous granules, that the double stream is chiefly visible : for in the finer ones, whose diameter is often less than that of some of the corpuscles, it is more rarely seen; in fact, in the latter the granules seem not to be included within the substance, but to be transported on the surface. Oftentimes a corpuscle, on arriving at a point where a fibre bifurcatcs, is arrested for a time, until drawn into one or other current, whilst at the bridge-like con- nexions between adjoining filaments, where the granules pass across from one to the other, it not unfrequently happens that they are transferred from a centrifugal to a centripetal stream, and are consequently turned back again towards the body. Moreover, in the broader processes, granules are observed to come to a stand, to oscillate for a time, and at length to take a retrograde OF TELE PROTOZOA.—RHIZOPODA. . 211 course. Since there is no appreciable distinction of tissues, not even of integument and contents, the existence of vessels to account for these cur- rents cannot be presumed. A curious exception appears to exist in Gromia Dujardinii, the filaments of which exhibit no granules, but are perfectly hyaline, and moreover show no circulation. In their transparency, Schultze remarks, they resemble the processes of Arcella and Difflugia, and so also in the matter of breadth, but differ by their greater length, their finely-pointed extremities, and by their frequent ramifications. This species has also in its principal mass peculiar corpuscles, round, Oval, or irregular in figure, with a sharp outline, and of a brown colour, differing from all other known elementary particles in chemical reaction, in resistance to alkaline solutions, and to mineral acids, even to sulphuric. Amid the many shifting corpuscles and Small globules is a large vesicle, constant in position, alternately collapsing and dilating, and hence called the contractile vesicle (XXII. 4, 5, 6). This organ, which is homologous with the pulsating sacs of Ciliated Protozoa, has not been remarked by every observer, nor in many of the Rhizopoda; nevertheless we presume it to be an essential organ, and its existence general in the class. In Arcella a con- tractile vesicle has been seen by many; in Actinophrys Sol, Claparède has satisfactorily proved it a true Sac, having a resistant membranous wall, and has counted as many as ten such vesicles in Arcella vulgaris; Auerbach treats of the vesicle as general among Amoebaea ; on the other hand, Schultze was unable to discover such an organ among the many Foraminifera he examined. NUCLEUS.—Another definite body is mostly discoverable in Rhizopods, viz. a nucleus in the form of a more or less rounded or oval body, more opaque than the rest of the contents, and consequently more solid in appearance (XXII. 4, 5, 9, 16, 20). In Amoeba and Arcella, Ehrenberg and Siebold admitted the existence of a nucleus; Schneider says that Amoeba diffluens and A. radiosa possess one, that a round reddish nucleus having a white nucleolus is present in Difflugia at its hinder end (XXI. 19 a, b, f), and that probably all the Rhizopoda have such an organ. Rölliker, to whose hypothesis of the cell–nature of Rhizopods the recognition of a nucleus was of much importance, remarks, “with respect to the nucleus, it really appears to be present in some of them (see Ehrenberg’s figures); and where it is want- ing, as in Actinophrys, a true nucleus may have existed at an early period, and be absent only in the full-grown animal, or, again, it may be entirely Wanting, and still the animal be regarded as a cell.” Claparède, on the contrary, denies a nucleus to the naked Rhizopoda, at least to Amoeba diffluens; and likewise to the testaceous species, such as Arcella. However, he admits that the usual opacity of the shell is an obstacle to an accurate determination of the question, and remarks, concern- ing the foregoing supposition of Kölliker, that there is no evidence of its truth, and no foundation in fact. Schultze has encountered an undoubted nucleus in nine different species of Amoeba, in Difflugia proteiformis, D. acuminata, and D. Helia, in Arcella vulgaris and several species of Euglypha. In Gromia oviformis a round, clear, delicate body filled with very transparent small vesicles may always be found. In old full-grown individuals not one but several such bodies are Seen at the posterior part of the animal, all of equal size and of similar struc- ture (XXI. 12, 13, 14). In one specimen as many as eighteen of these nuclei were counted. In young small Gromice only one nucleus is seen; in a solitary instance two were found. - P 2 212 GENERAL HISTORY OF TEIE INFUSORIA. In Difflugia proteiformis usually several (8 to 12) nuclei are perceptible, as in Gromia oviformis, in the posterior portion of the shell. The nuclei of freshwater Rhizopods either appear to be homogeneous deli– cate elastic globules, here and there finely granular, or they resemble the nuclear body of Gromia oviformis, and consist of a group of Small vesicles or globules enclosed by a common membrane (XXI. 14). The single nucleus of young beings, Schultze supposes to be derived from the parent animal; and he further presumes that, in the course of age and growth, this organ is capable of multiplying itself, and may, moreover, serve as a centre around which the fine granules of the living contents aggregate, and that, after the formation of an enclosing membrane, an embryo is generated from it. On the other hand, this careful observer was not able to discover a nucleus in Foraminifera, and admits that the above suppositions are highly doubtful. - In a large specimen of Gromia Dujardinii, Schultze met with certain en- closed bodies, having a firm shell and granular contents, and only wanting a mouth to complete their resemblance to the parent animal (XXI. 18 a, b). IHe also cites, as still more questionable examples of a nucleus, a clear spot in the first chamber of Rotalia veneta, and in Teactilaria picta, a finely-granular, solid, and nucleariform body in each of the two last cells (XXI. 32). - On this point, the presence of a nucleus in Foraminifera, we have the state- ment of Ehrenberg, that in each cell, except the last, there is a coarsely granular yellowish brown mass, which represents an ovary in structure and function. Unfortunately, however, the Berlin microscopist stands alone, both in this observation and in its pendent corollary. Dr. Carpenter uses the word nucleus to signify the primordial mass of Sarcode seen in the first cell, of which all the subsequent chambers and their contents may be deemed the offshoots. t Scattered among the amorphous granules of the sarcode are, for the most part, numerous refracting corpuscles of less size than vacuoles, which are soluble in ether, and therefore concluded to be fat-globules (XXI. 14–16). There are also other molecules dissolved by caustic potash. It is these various globules and granules that some observers have esteemed to be ova, without, however, any countenance from facts for the supposition. To recur to the naked Rhizopoda, Auerbach, in the essay before quoted, attributes a nucleus to the Amoebaea in general. He remarks that the Solid-looking organ, of a dull aspect and commonly spherical figure, noted by certain authors in some Amoebae, is rather the nucleolus than the nucleus, and that the latter is perceptible in the form of a hollow space, oftentimes having a glistening rosy hue, which surrounds the other like a sac (XXII. 4, 5, 9, 10, 11). This sac is sometimes visible as a dark areola, but at others requires the operation of chemical reagents to reveal it, or will manifest itself in dead specimens when all the ordinary vacuoles have disappeared. At times, both it and its nucleolus have a dumb-bell figure, and thereby indicate the occurrence of the process of Self-division. A similar nuclear sac is men- tioned by Schneider. - As to its chemical relations, Auerbach found that both nucleus and nucleolus were readily soluble in alkalies, and that they became darker in dilute acetic or sulphuric acid, which also caused the precipitation of a finely-granular matter in the vesicular or Saccular nucleus. In concentrated acids they first expanded, and were subsequently dissolved. The generally-assigned character of the nucleus, viz. that it becomes darker on the addition of acetic acid, is true only when dilute acid is used. Auerbach discovers a nucleus and nucleolus in Arcella, similar to those OF TEIE PROTOZOA.—REIIZOPODA. 213 of Amoebae, often displayed when, by a fracture of the shell, the animal con- tents escape. The nucleus has the form of a thick-walled Sãc, and encloses a large nucleolus. But it is remarkable that, whilst one or at most two nuclei only are discoverable in Amoebae, several such organs are frequently present in Arcellae, their number being in direct proportion with the magnitude of the animals. In large specimens, of #" in diameter, above 40 such nuclei have been encountered. REPRODUCTION OF RHIZOPODA.—This function is not satisfactorily made out, especially in the case of the Foraminifera; what is known will best be de- tailed of each family separately. Among the Amoebina self-division has been noticed by Ehrenberg to occur in the Amoeba princeps; and Dujardin remarks that “they may doubtless multiply by spontaneous fission, or by the throwing off a lobe which imme- diately commences an independent existence.” This separation of a portion of their substance is not unusual, as, when a large variable process has been shot out far from the chief mass and become enlarged at the extremity, the expanded end retains its position, whilst the portion connecting it with the body becomes finer and finer by being withdrawn into the parent mass, until it at last breaks across, leaving a detached piece, which immediately on its own account shoots out processes, and manifests an independent existence. This phenomenon is therefore one of simple detachment, and cannot rightly be called a process of fission. Schneider terms it “propagation by gemma- tion,” and supposes it attended by a division of the nucleus, of which every such offset, in his opinion, includes a portion. This same observer further states that Amoeba has actually a “state of rest” (i. e. an encysted condition). He observed it first to become round, and them to form a firm membrane on one side, whilst the other portion continued its peculiar character and move- ments. By degrees the membrane extended itself over the whole body, the moveable portion constantly becoming smaller, until at last a completely- closed cyst was produced, in the clear interior of which a round nucleus, with a reddish halo, exactly like that of Polytoma and other Monadina, might be distinctly observed. He adds—“In the nucleus of Amoeba I have often noticed on the Outer Surface of the reddish halo, granulations which united to form a closed membrane, whilst at other times the nucleus exactly resembled that of Polytoma’’ (i. e. was without an enclosing membrane). What is the next phase of development following this encysted stage, Schneider has nothing to show. - If Lieberkuhn's observation be correct, a most extraordinary relation sub- sists between Amoebae and Gregarince, involving the existence of the former as a distinct class of animated beings. This observer saw the production of Amoebae from Navicellae, the origin of which from Gregarince is as good as proved; and also met with such Amoebae in every transition to perfect Gre- garinae. This fact is alluded to in a paper by Kölliker (J. M. S. i. p. 212), who believes the Anguillula-like animal noticed by Henle, and termed by Bruet Filaria, to be an Infusorium allied to Opalina Protews, and goes on to say that the transition of this presumed Filaria into a Gregarina– and finally into a Navicella-receptacle is nothing extraordinary. Auerbach asserts the encysting process to be shared in by the Amoebaea along with other Infusoria; but he looks upon Schneider’s recorded instance as an erroneous conception of a specimen clearly enveloped by an integument. Monathalamia would seem capable of multiplying themselves like the Amoebina, by detaching portions of their substance, i.e. by a species of gem- º Peltier has described this occurrence, although Ehrenberg failed to detect it. - • 214 GENERAL HISTORY OF THE INFUSORIA. Reproduction by positive complete fission is opposed by the existence of the shell, which is a product from the surface of the animals adapted to their outline, and increasing only in proportion with the augmentation of the animal Substance. The cohesion of two or even more Arcellina by means of their gelatinous substance, and often with the near approximation of the orifices or mouths of their shells, has been remarked by many observers, who for the most part have pronounced it a sort of “ conjugation,” a true reproductive act. Cohn has indeed designated it “copulation,” and states it to be a general phe- momenon among Rhizopods. He affirms that he has many times seen two Difflugia, with the mouths of their shells so firmly connected, that strong shaking of the water about them failed to detach them ; and that likewise one shell was often empty, and the contents of the two aggregated into a globular mass in the other. Leclerc, the first describer of Difflugiae, in 1815, noticed a like cohesion between two individuals of Difflugia Helia: ; and Cohn, moreover, is able to confirm the fact represented by Perty of the cohesion of a brown and of a pale shell together. - Schneider has likewise noticed this adhesion of two animals, and thus speaks of it —“True double animals of Difflugia Enchelys are frequently met with (XXI. 19 f), two bodies with membranous cases and nuclei being attached to a common foot. The foot very often consists only of a thin thread, but in other cases it exhibits all the forms which have been described as belonging to the foot of the simple animal. Both bodies are well filled with food. Three, four, or five bodies are frequently seen hanging together in the same manner; these, however, are by no means in the same plane, but stand out from the foot in various directions. If these animals are ob- tained in considerable numbers, the formation of these colonies by gemmation may easily be observed. The foot is seen gradually to increase in size, and acquire an oval form. A new investing membrane and nucleus are then formed. The offset is always equal to the parent-animal in size. Eike the foot of a single animal, the common foot of two or more is, as might be supposed, still in a condition to form offsets.” This adhesion Schneider prefers to consider an act of gemmation rather than of copulation, and Sup- poses its occurrence among other Rhizopoda. He adds, “with Perty and Cohn I have also seen a pair of the Arcella vulgaris attached to one another by their openings, of which one (as was observed by those naturalists) was provided with a white, the other with a yellow shell. The white shell is probably newly formed, and therefore indicates the young specimen produced by gemmation from its companion.” An aggregation of the animal contents of a Monothalamous shell, such as Cohn noticed in one of the two coherent Difflugia, and attributed to an act of conjugation, Schultze has seen in Rhizopods, quite independently of that phenomenon. In Lagynis Baltica, he states he has frequently seen the con- tents collected into a ball, having a clear speck in the centre, and situated at the posterior end of the shell, without trace of extended fibres; and he adds, “the origin of this globular mass may be followed in a great number of individuals. The posterior portion of the transparent body of the actively- moving animal gradually becomes darker, owing to the advancing develop- ment of numerous molecular and strongly refracting particles. In the midst of this dark portion a clearer spot is always visible, although it cannot be isolated or more intimately examined. By degrees the dark portion en- croaches upon the entire substance of the body, and at last fills up the whole posterior portion of the shell, the body of the animal thus seeming to shrivel up into the ball-like mass described.” This process, observed in numerous OF TEIE PROTOZOA.-REIIZOPODA. 215 individuals in different stages, Schultze never saw accompanied by a con- mexion between two animals; and he was not able to discover what Subsequent changes awaited the spherical body produced. . The phenomenon just considered appears to us to be analogous to the encysting process recounted by Schneider in the case of Amoeba, and by Stein in so many Ciliated Protozoa. Two other probable modes of reproduction are briefly noticed by Schneider, but require to have their existence confirmed by further observations. “I have observed,” he says, “another mode of propagation in our Difflugice; and although my observations have certainly not been frequent, they have been sufficiently Satisfactory. After I had kept a great number of these creatures for some weeks in a clayey sediment, the substance of the body in all the individuals contracted into a ball. All foreign substances had previously disappeared. The ball, which had a fatty outline, then divided into two and four parts; but the nucleus could not be traced during this pro- cess (XXI. 19 d, e). This investing membrane fell to pieces, and the little spheres which may perhaps be regarded as four quiescent spores, were no more to be seen. “Whether another circumstance observed by me has any connexion with the reproduction of Difflugia must be ascertained hereafter. In all the individuals of Difflugia contained in one vessel, the substance of the body became converted into granules closely packed together, the form and the investing membrane being retained (XXI. 19 c). I often saw these granules in quick molecular movement in the interior of a sac, which appeared to be formed from the outermost layer of the body, but I watched in vain for any issue to this; after moving about for about half an hour, the granules always became quiescent again.” - A note by Perty must not be omitted, although no considerable importance can be assigned to a solitary and ambiguous observation. That naturalist tells us he “Once Saw two round motionless animals within an Arcella vul— garis, each having a much greater diameter than the mouth of the shell con- taining them. Were these,” he asks, “young beings to be set free on the death of the parent and the breaking up of the shell?” A somewhat similar fact is recounted by Schultze of Gromia Dujardinii, in one large specimen of which he found several oval bodies enclosed possessing a firm envelope and granular contents, and representing in every respect young Gromia, except in having no evident opening in their shell, which, however, may possibly be formed when set free from the parent (XXI. 18). * That the purpose of the nuclear bodies in Gromia oviformis (see p. 211) is not connected with the function, Schultze feels compelled to assume, princi- pally from the absence of such nuclei in Rhizopoda generally, and from his having failed to observe their undergoing those changes known to occur in true nuclei when the generation of new individuals is in progress. Young Arcellina, when first recognizable as such, have the general form of older individuals; but their shells and tissues are much more transparent, and at first colourless and without granules. But it is very probable that the young of many Arcellina, when first thrown off from the parent, are naked— destitute of shell,—a view supported by an observation of Cohn, who records having seen, amid the slimy matter about living Difflugiae, a large number of peculiar animalcules consisting of a contractile greyish or brown finely- granular substance, about ºth of a line in diameter and upwards, of a round, ovoid, or angular outline, and having a muco-gelatinous envelope, through, but chiefly at one end of which several fibres were extended. At a still earlier period these young beings may therefore be presumed to have been mere 216 GENERAL EIISTORY OF TEIE INFUSORIA. sarcode-like particles or minute Amoebae. If this be so, some ground may be said to exist for the hypothesis of certain naturalists, who esteem the Arcellina, and even the Foraminifera, to be a more advanced stage of existence of the simple naked Amoebina. Schneider hints at the possibility of a still greater transformation in the case of his Difflugia Enchelys. He writes—“A Rhizopod occurred in com- pany with Polytoma (see p. 136), the description of which will show how very readily it might be supposed to be produced by a metamorphosis of the latter animal. Unfortunately I cannot confirm this supposition, and must confine myself to recording the fact.” Foraminifera.-It is very questionable whether the Many-chambered Rhi- zopods can reproduce themselves by offshoots after the manner of Amaebina, and Monothalamia; and, in short, nothing certain is known as yet of the modes of propagation of this family. A group of figures occurs in Schultze’s illustrations of Polystomella (XXI. 39) which bear on this point of the possible production of new beings by de- tachment of sarcode matter. The description of the figures informs us that some of the sarcode-globules, separated from the chief mass by pressure, have the tendency and power to throw out from themselves contractile variable processes. They exhibit a finely-granular delicate semifluid tissue, contain- ing many flat globules and large coloured vesicles. Other portions, pressed from the general mass, are almost exclusively composed of colouring-particles, derived from the inmost part of the shell; such become entirely free, or otherwise continue attached by a sort of pedicle. In the following examination into the modes of development of Polythalamia we are greatly indebted to Schultze’s valuable monograph. Dujardin men- tions seeing in some Truncatulinae the grouping of the contents of the cham- bers into spherical masses, comparable to the green bodies in Zygnema. Schultze, moreover, encountered, in a deposit of living Foraminifera, along with numerous empty shells of Rotalidae, several wholly or partly filled with black globules, the appearance of which suggested their connexion with the reproductive process. Repeated observation showed that these globules differed in size, but mostly had the diameter of the siphon intervening be- tween the several chambers, or of that of the opening of the last cell. They occupied either every segment of the shell, when those of the innermost were smaller than those of the outer compartments, or otherwise they occurred in only one or two of the ultimate chambers. Every intermediate condition was met.with between these two extremes. The globules were composed of a collection of dark molecular corpuscles not enclosed by a membrane, but proved by pressure to be an aggregation, held together by some sort of delicate tissue. They were unacted on by Sulphuric, nitric, and by hydro- chloric acid, and by boiling alkalies. The ordinary animal Substance coexisted in some of the chambers of an animal when others were occupied by these black balls; but in such instances no outstretched fibres were seen. These structures must be derived either from without as foreign matters, or otherwise be the result of a metamorphosis of the sarcode matter. The former supposition is discountenanced by their appearance, by their resistance to reagents, and their presence even in the immost chambers. On the latter Supposition they are either the result of decomposition of the substance, or they are physiological products, probably of the transformation of the entire body into germinal masses. The former origin is opposed by the direct observation that such bodies have never been en- countered among Foraminifera in course of breaking up or of decomposition, As to the second mode of origin, they bear an analogy to the germinal OF THE PROTOZOA.—REIIZOPODA. 217 elements of Gregarinae, viz. to the Navicellae developed from the contents of those animals, and to the brood of germs déveloped out of the contents of an encysted Vorticella : and it may so happeñ with the Foraminifera, that their entire substance is resolved into germs; indeed, a progressive formation of such germs is intimated by the circumstance of the ultimate chamber being the last to become completely emptied. Although, therefore, the figure and size, the peculiar and successive empty- ing and distribution, the evident periodical appearance in the spring, and the analogy of other Protozoa speak for the hypothesis of these globules being reproductive germs, it must, on the other hand, not be concealed that their peculiar composition out of granules imperfectly bound together and enclosed by a membrane, and their remarkable resistance to the strongest acids and alkalies, are facts opposed to this supposition. Hoping to elucidate their purpose, Schultze, in some few cases, isolated those shells filled with these black balls, but, after keeping them several weeks, could discover no change in them. Ehrenberg surmised that the Polythalamia propagated by ova, and thought he perceived in them a sexual apparatus. On the surface of the shells of some samples of Geoponus (Polystomella) and Nomionina, from Cuxhaven and Christiania, he discovered stalked, yellow, membranous sacs, which he repre- sented to be ova-sacs. When first thrown out they were soft and small, but soon swelled up and hardened in the water. Schultze also met with many specimens of Geoponus, at Cuxhaven, having Cothurmiae affixed to their shells, and of a yellow colour, which he believes Ehrenberg mistook for ova-cases. Being so unsuccessful by direct observation in his attempts to detect the method of reproduction among Foraminifera, Schultze endeavoured by an ex- amination of these beings in their earliest recognized form to gather some knowledge of it. The smallest and youngest beings he met with belonged to the families Rotalidae and Miliolidae. Those of the latter family have a non- porous shell, and a spherical figure exhibiting the commencement of the spiral winding which eventually extends to several turns (XXI. 20 a, b). The shell- contents are quite colourless, and present few granules. As the spiral winding advances, the contents of the first-formed orbicular cell acquire a darker colour from the appearance of fat-drops and sharply-defined proteine corpuscles; and the shell simultaneously assumes the characteristic yellow colour. The differ- ence in size of the primary cell in different species is remarkable. Still younger forms of Rotalidae occurred to him, 0:01 of a line in diameter, spherical, and colourless, with a delicate glass-like Calcareous shell, through the fine open- ings of which fibres protruded. Others also, entirely colourless, had a second chamber Superposed on the first, or even three or four ; but in the latter instances the characteristic yellow hue made its appearance, and rapidly in- creased on further growth (XXI. 31). A striking variety was, moreover, remarked in the size of the first chamber, even in the same species; the dimensions of the second and third cells were determined by those of the first. This great variation in size considerably lessens the possibility of the certain specific determination of young Specimens. From these researches it follows, that in Miliolidae and Rotalidae, and pro- bably in all other Polythalamia, the first appearance of the animal is in the form of a colourless spherical mass, invested by a delicate calcareous wall,— the mass consisting of a homogeneous, sparingly-granular Amoeba-body. This first-formed cell has the faculty of producing others like itself from those portions of its sarcode substance. Of the manner in which successive chambers are formed, we learn from Dr. Carpenter that the addition of new zones (in the Polythalamia) probably 218 GENERAL EIISTORY OF THE INFUSORIA. takes place by the extrusion of the sarcode through the marginal pores, so as to form a complete annulus, thickened at intervals into Segments, and nar- rowed between these into connecting stolons, the shell being probably pro- duced by the calcification of their outer portions. Since the above account was written, Schultze has produced a supple- mentary sheet detailing further observations on the development of Forami- miſfera (Bericht der Naturforschenden Gesellschaft in Halle, 11th August, 1855). Baving met with some large specimens of Triloculina #" in diameter and without a tooth in the oral aperture, he kept them for a length of time under observation. Those which remained adherent to the sides of the glass vessel for eight to fourteen days mostly became invested with a brownish slimy matter, which more or less completely obscured the view of the external characters of the shell. After some more days had elapsed, the lens brought into view a num- ber of small, round, sharply-defined corpuscles, which loosened themselves from the soft enveloping mass, and gradually diverged from one another until some forty were visible. On removing these, and placing them under the microscope, they proved to be young Miliolidae, with their process outstretched. Inter- nally, neither vacuoles, cells, nor contractile vesicle, nor a nucleus could be detected. The brief abstract of Dr. Carpenter's elaborate essay (read before the Royal Society, 1855) furnishes us also with the following memorandum of his views regarding the reproduction of Foraminifera, with especial reference to Orbi- tolites. “He is only able to suggest that certain minute spherical masses of sarcode with which some of the cells are filled may be gemmules, and that other bodies enclosed in firm envelopes which he has more rarely met with, but which seem to break their way out of the superficial cells, may be ova.” Mr. Jeffrey's views (Proceedings of Royal Society, 1855) do not quite coincide. Dr. Carpenter’s “idea of their reproduction by gemmation,” he says, “is also probably correct, although I cannot agree with him in considering the granules which are occasionally found in the cells as ova. These bodies I have fre- quently noticed, especially in the Lagence; but they appeared to constitute the entire mass, and not merely a part, of the animal. I am inclined to think they are only desiccated portions of the animal separated from each other in consequence of the absence of any muscular or nervous structure. It may also be questionable if the term ‘ova' is rightly applicable to any animal which has no distinct organs of any kind. Possibly the fry may pass through a metamorphosis, as in the case of the Medusae.” Of the many Amoebae seen in company with Foraminifera, the A. porrecta is particularly remarkable, and might easily pass for one of the latter when young and destitute of its shell; for its processes resemble those of Miliolidae and Rotalidae in delicacy and extensibility and in the current of granules which passes through them. This circumstance suggests the possible deriva- tion of testaceous Rhizopoda from the naked forms; and if we recall to mind the black globules surmised to be germs, their primary transformation into Amoebae is imaginable, and the whole cycle of development of Foraminifera becomes thereupon explicable. “However, I must,” says Schultze, “ confess that this change of the black spheres into Amoebae is a further argument against their nature as germs, since between these granular bodies, so unaffected by che- mical agents, and Amoebae no intermediate link is discoverable. OF THE SHELLS OF TESTACEOUS RHIZOPODA. a. SHELLS OF MONOTHALAMIA.— The family Arcellina (Ehr.) corresponds in most points with the section Mono- thalamia of Schultze. The Berlin Professor, however, believed that his family Arcellina and the Polythalamia belonged to entirely different classes of ani- OF TEIE PROTOZOA.——REIIZO.PODA. 219 mals, because, as he supposed, the Polythalamia are aggregated animals with calcareous shells, and the Arcellina Solitary animals with a silicious testa. Subsequent researches prove, on the contrary, that all these differential cha- racters are wanting. Each foraminiferous shell contains a solitary inmate; and although, as a rule, of a calcareous composition, yet a genus, Polymor- phina, is pointed out by Schultze, which, as in the instance of Difflugia, has its testa made up of coherent silicious particles (XXI. 38). Besides all this, the shells of Arcellina are not silicious, but of a chitinous nature, and the basement membrane in which the earthy matter is deposited in Foraminifera is the same. These circumstances, together with the homology in the animal contents both of Monothalamia and of Polythalamia, the absence of the hypo- thetical polygastric organization in the former, and of the imaginary internal . structures in the latter, render Ehrenberg's distinction of the two families as separate classes untenable. The Arcellina of Ehrenberg, and the Monothalamia of Schultze, do not en- tirely accord in respect to the genera grouped under them. Ehrenberg in- cluded in his family the genera Difflugia, Arcella, Cyphidium, and Spirillina. The last-named genus departed much from the others by having a marine habitat and a convoluted, spiral, porous shell,—its only real relationship, it would seem, being comprehended in the One assigned feature, its silicious lorica. On the other hand, Schultze (see tabular view of his system, p. 241), by not employing the chemical constitution of the shells as a distinctive cha- racter, includes among his Monothalamia calcareous, membranous (chitinous), and such silicious shells as are exemplified by Difflugia. The essential cha- racter employed is that of the unilocular chamber; for the other nearly general feature, viz. the presence of one considerable orifice, is departed from in the instance of the porous shell of Orbulina. - The shells of Monothalamia are of a more or less spherical figure; some- times they are ovoid (XXI. 11, 12, 16) or pyriform (17), at others compressed in one or other direction (XXI. 8), and even at times in opposite directions, so that several faces are produced. Thus in the genus Difflugia the spherical out- line prevails (XXI. 10): the shells are globose, or subglobose, or elongated in a pear-shape (XXI. 17), or in a club-like (clavate) manner; in Arcella they are frequently compressed, and assume a more or less discoid figure, mostly convex above and flat beneath (7, 8, 9). In Gromia, again, the ovoid or glo- bular shape is diversified by the elongation of the portion about the mouth of the shell into a sort of neck (16). In Lagynis (Schultze) this tapering of the oral end developes a retort-shaped shell. In Squamulina (Schultze), again, the testa resembles a plano-convex lens. An exceptional form is described by Ehrenberg, under the name of Arcella disphaera, as oblong, almost divided into two by a central constriction. The first impression would be that the supposed species was no other than two animals coherent by the mouth of the shell; that such, however, is not the case is indicated by the next clause of the description—that one segment is nearly occupied by the large foramen. Another example of a remarkably-formed shell is afforded by Cyphidium (XXII, 24–27), which Ehrenberg states to be cubical, with large protuber- ances, giving it in some positions a four-sided or an irregular figure. Again, in the genus Spirillina (Ehr.) (XI. 37) and Cornuspira (Schultze) (XXI. 25), we have examples of spirally-rolled equilateral shells, like those of Planorbis. In consistence the shells of most Arcellina are firm, with a degree of flexibility and elasticity, and are composed of a dense membrane proved by its chemical properties to be of a chitinous nature. This shell not only resists the action of boiling solutions of the caustic alkalies and of vinegar, but also concen– trated nitric and chloric acids, and a mixture of the two, also chromic acid, 220 GENERAL EIISTORY OF THE INFUSORIA. in the solution of which chitine itself is dissolved. Further the shell is dis– solved in sulphuric acid, and, unlike cellulose, is not coloured blue by this acid. Such are the chemical relations of the testa of Gromia according to Schultze; and such we may presume with him are those of the freshwater genera Arcella, Euglypha, and Trinema. The shells of Difflugia are peculiar by being composed in many species of a softer substance, to which various foreign particles, shells of Diatomede, grains of sand and the like, adhere and thereby furnish an accidental or supple- mentary shield to the animals (XXI. 17). The substance on which those accidental matters are affixed we may presume to be chitinous, but not con- densed or hardened as in the true testaceous forms. Schultze is disposed to think that, besides merely agglutinated silicious particles accidentally, as it were, appropriated, the investing tunic has actually the power of Secreting silicious molecules, represented by the smallest and most intimately adherent granules of the testa. He would also extend this hypothesis to the silicious polythalamous shells, illustrated by Polymorphina silicea (XXI. 38) and another newly-discovered species. .* Cohn apparently saw young Difflugiae in the act of building their shells. These young beings consisted of a mass of sarcode surrounded by a muco- gelatinous envelope, through which fibres were protruded in different direc- tions. These processes, by retraction, brought to the surface of the animal various foreign particles, which had become affixed to them, and were then imbedded in the mucous involucre. At length all other pseudopodes, save those from one extremity, were permanently withdrawn, and the exterior of the animal was clothed with a layer of silicious particles, grains of sand, shells of Cyclotella, and of other Diatomede, many of them of a blackish or brown colour. Dr. Bailey indicates an exceptional tunic in a Rhizopod, having much of an Amoeba-like character, which he names Pamphagus. It would seem to be enveloped by an integument, which, although resistant, admits of an immense modification of figure, both from external and internal pressure, and offers no impediment to the animal transfixing itself, just as if it were a completely homogeneous jelly. “These creatures,” says their discoverer, “ connect the genus Amoeba with Difflugia, agreeing with the first in the soft body without shell, but differing in having true feelers or rhizopods confined to the interior part of the body.” Just as in Difflugia, they are limited to the region of the mouth. From this last-named genus, “ and from the whole family of Arcellina, these forms are distinguishable by having no lorica or shell.” A very similar tunicated amoebiform animal is described by Dujardin under the name Corycia (A. S. N. 1852), which, although clothed by a membranous envelope, can be twisted and folded in every direction by the movements and contractions of the animal, and permits the extrusion of processes from any part of its surface. In this respect it differs from the Pamphagus of Bailey, and certainly exemplifies a peculiar phenomenon, which, in the case of the usual variable processes with circulating contents, would not be conceivable, but become so upon the explanation of Dujardin, that they do not contract on adhesion to the surface on which the animal moves, nor glide along it in the ordinary manner, but remain free, and, as we are told, seem only to serve to change the centre of gravity of the animal. “It must, therefore,” says its describer, “form a new genus of Amaebina,” intermediate between the naked Amoebae and the Arcellina ; and in another direction indicating an alliance with the Noctilucida. With reference to these peculiar beings, it is worth while to bear in mind , the account given by Cohn of the development of young Difflugia, and the OF TETE PROTOZOA.-REIIZOPODA, * * 221. progressive formation of the shell. To recall the particular points of interest, in the primary stage the Difflugia was seem covered by an integument, but having processes extruded from various parts of its surface, so far resembling the Corycia of Dujardin,_whilst in a later stage all processes were withdrawn, except those at the one end where the single large orifice or mouth is placed, and thus came to resemble the Pamphagus of Bailey. Calcareous-shelled Monothalamia are represented by the genera Squamw- lina, Orbulina, and Cornuspira. Such shells are brittle, and in all essential features resemble those of the next-considered family, the Foraminifera. The shells of Monothalamia are generally coloured. When seen, as they often may be, empty, they have an orange-yellow, a brown, or brownish-black tint. This colour is acquired by age; the younger the being the less is it, casteris paribus, coloured. In the youngest, as before noticed, the whole sub- stance and its commencing envelope are quite colourless. Most shells are also translucent or diaphanous when empty; but in others the colour is so deep, that, when filled, scarcely anything of the contained substance is dis- cernible through them. The testae of Difflugiae are mostly opaque. The sur- face of the shells is subject to numerous modifications. Occasionally it is uniformly smooth; but many, which so seem when occupied by the animal, are found when empty to be really finely sculptured (XXI. 11–15). Arcella hyalina is represented by Ehrenberg to have a smooth and colour- less testa; A. vulgaris and A. dentata, one superficially divided into facettes; A. aculeata, A. spinosa, and A. Cawdicola, a delicately hispid shell. Where the intersecting lines or ridges are not sufficiently developed to produce fa– cettes, they give rise to areolae and an areolated or reticulated surface. The surface is beset with rounded tubercles or eminences in Euglypha tuberculata, and by spirally-disposed polygonal depressions (alveola) in Euglypha alveo- lata (XXI. 11). In Difflugia acanthophora (Ehr.) (XII. 64), the surface looks as if covered by Scales laid on in an imbricated manner and in a spiral direction. The same species and Euglypha alveolata (XXI. 11) afford instances of testae armed with large and strong spines. This same Difflugia presents likewise an example of the mouth of the shellbeing strongly serrated. Several Arcellina have Small depressions or pits on their surface, which at first sight resemble pores, e.g. Arcella Okenii; and both this species and A. vulgaris, according to Perty, present very numerous striae diverging from the centre of the closed end, and concentric circles, the outermost of which in Arcella Okemi are dentated, and follow the stellate expansions of the shell (XXI. 15). Among Difflugia, the shell is more often rough from the adhesion of parti- cles of sand and of other extraneous substances (e.g. in D. proteiformis, D. gigantea, D. acuminata), but in others consists of a Smooth membrane, as in D. Enchelys, D. oblonga, and D. globulosa. Moreover, Ehrenberg enumerated D. ciliata, D. acanthophora, and other species as having an areolated surface, D. ampulla as punctated, D. dryas and D. reticulata as cellular, D. Bructerii as rugose, and D. striolata as striated. He further states that D. ciliata has a bristle or cirrus in the centre of each posterior areola. . - Where spines or other elevations of the surface—or, in fact, markings in general, exist—they may not be uniformly disposed, but be produced in larger number or of larger dimensions in some parts than in others. Thus Ehrenberg signalizes an irregular disposition of the spines in Arcella aculeata ; and not uncommonly such processes are produced only from the vicinity of the mouth. These examples will sufficiently illustrate the -diversity of surface preva- lent among monolocular shells; but these shells moreover differ as remark- ably among themselves in size, figure, and character of the margin, and likewise in the relative position of their mouth, foramen, or orifice. These 222 GENERAL EIISTORY OF THE INFUSORIA. differences supply specific and generic characters of much value by reason of their constancy. Where the mouth has an even uninterrupted margin, it is said to be “entire.” Its normal figure may be considered circular (XXI. 9). However, in many instances it is irregular (XXI. 15), or a projecting portion encroaches on it (XXI. 6). In Difflugia depressa and D. gigantea it is uneven ; in Arcella lunata, semilunar ; in Difflugia ampwlla, ovate; in Sphenoderia, so contracted as to be linear. Still more frequently the margin of the aperture is dentated or spinous : examples occur in Difflugia denticulata, D. laevigata, D. oligodon, D. acanthophora (XII. 64), and D. ciliata, in Arcella dentata and in Euglypha. The symmetrical position of the mouth is wanting in several species; and Schlumberger elevated this variation to the importance of a ge- meric distinction. The obliquity of the aperture—its position out of the median line—is noticed in Arcella Américana, A. constricta, A. ecormis, and in A. lu- nata, also in the genus Trinema (Duj.) and in Cyphoderia (Schlumberger). When the mouth appears formed by the mere incompleteness of the outline of the shell, and is without a neck or deep margin, it is often said to be truncate —in fact, the oral end of the shell is truncated or abruptly cut off by the orifice. The shells of Arcellina may be fractured by pressure when the contained sarcode matter escapes through the fissures, extending itself in lobe-like pro- longations, which take on the characters of ordinary expansions (XXI. 7). Since the opacity of the shell is generally an impediment to the observation of the contained matter, its rupture by pressure, or its partial solution by some reagent, as Sulphuric acid, which acts upon the chitinous basis, must be resorted to in order to discover the nature of the animal mass within. With or without such preparation, it is not unfrequently seen that the living mass is not uniformly adherent to the inner surface of the shell, but is, on the contrary, detached at different parts, leaving interspaces between it and the testa, varying in size and number. These vacuities may possibly arise from the detachment of the soft matter by reason of the quantity poured out. from the mouth of the shell, or otherwise from the formation of vacuoles at those points, just as often happens on the surface of an Amoeba. b. SHELLS OF POLYTHALAMIA OR FORAMINIFERA.—These have a great diver- sity in figure and size, and are often very beautifully coloured and sculptured. From the resemblance of many to the shells of Cephalopoda, especially to those of Nautili (XXI. 28), they were for a long time ranged along with those highly-developed Mollusca. The shells of Polythalamia consist of a greater or less number, according to age and species, of communicating chambers or cells, aggregated together or superposed on one another in different ways, the mode of disposition, however, varying within certain limits even in the same species. Thus Dr. Carpenter, speaking of Orbitolites, says (Proceedings Royal Society, 1855),="Starting from the central nucleus, which consists of a pear-shaped mass of Sarcode nearly surrounded by a larger mass connected with it by a peduncle, the development may take place either on a simple or upon a complex type. In the former (which is indicated by the circular or oval forms of the cells, which show themselves at the surface of the disk, and by the singleness of the row of marginal pores), each zone consists of but a single layer of Segments, connected together by a single annular stolon of sarcode, and the nucleus is connected with the first zone, and each with that which surrounds it, by radiating peduncles proceeding from this annulus, which, when issuing from the peripheral Zone, will pass outwards through the marginal pores, probably in the form of pseudopodes. In the complex type, on the other hand (which is indicated by the narrow and straight-sided form of the Superficial cells and by the multiplication of the horizontal rows of OF THE PROTOZOA.—RIIIZOPODA. 223 marginal pores), the segments of the concentric Zones are elongated into vertical columns, with imperfect constrictions at intervals; instead of a single annular stolon, there are two, one at either end of these columns, between which, moreover, there are usually other lateral communications, whilst the radiating peduncles, which connect one zone with another, are also multiplied, so as to lie in several planes. Moreover, between each annular stolon and the neighbouring surface of the disk, there is a layer of Superficial segments distinct from the vertical columns, but connected with the annular stolons; these occupy the narrow elongated cells just mentioned, which constitute two superficial layers in the disks of this type, between which is the inter- mediate layer occupied by the columnar segments. “These two types seem to be so completely dissimilar, that they could scarcely have been supposed to belong to the same species; but the examina– tion of a large number of specimens shows that, although one is often developed to a considerable size upon the simple type, whilst another com- mences even from the centre upon the complex type yet many individuals, which begin life and form an indefinite number of annuliupon the simple type, then take on the more complex mode of development.” Each cell is occupied by the animal Sarcode Substance—sometimes not completely, so that intervals exist at points between the contained matter and the enclosing calcareous wall, just as in Monothalamia. The first cell pro- duced, about which all others are arranged and may be considered offshoots or dependencies, is called the primary or primordial cell; and in it is con- tained the mass of condensed sarcode which Dr. Carpenter calls the nucleus. The link-like portions connecting one chamber with another are called by Schultze bridges (Brücken) or isthmi, by Ehrenberg siphons, and by Car- penter ‘stolons.” In chemical composition the shells of Polythalamia are calcareous, with the exception of those of Polymorphina silicea, which, like those of many Diffiugia, are composed of Small granules and tablets of silex. Schultze observes that, in addition to this species, Spirulina agglutinams and Bignerina agglutinams have their surface covered by adherent grains of Sand, to give it the firmness and resistance provided for in other forms by their shells. The consequence of their calcareous composition is, that the shells are hard, brittle, and opaque, and their contents only visible so far as protruded in the form of processes. To examine, therefore, the animal matter, it is necessary to crush the shells, or, better, to carefully remove some portions and so expose the subjacent tissue to view; or they may be acted on by dilute acid, which dissolves out the earthy matter, leaving the transparent organic basis of the testa. Dujardin employed dilute acid mixed with alcohol, which contracted and rendered the sarcode substance harder, and gave it. the appearance, in the many- chambered cells, of laminated or lobulated masses connected together by thinner portions. When the calcareous earthy matter is dissolved out of the shells of Forami- nifera, the organic matrix or basis is left as a transparent membrane, retaining the precise form and markings of the complete shell, and perforated by the characteristic pores. Its chemical relations are those of the membranous testa of Gromia. In thin shells the organic matter is in relatively greater abund- ance than in the thick ones. Acids produce an active effervescence, and so prove the presence of carbonate of lime as the principal mineral constituent. Schultze has also detected the presence of phosphate of lime, at least in some shells, viz. in those of Orbiculina adwmca and Polystomella strigilata. The shells of Polythalamia are commonly white, when viewed by reflected light, and when emptied of their organic contents. When the latter remain, 224 GENERAL DIISTORY OF TITE INFUSORIA. a reddish- or yellow-brown colour is produced. Sufficiently transparent specimens and opaque fragments, viewed by transmitted light, exhibit either a glass-like (vitreous) colourless appearance, or have a brown hue. Examples of the latter condition are afforded by all solid and not finely porous shells, by Miliolidae, Ovulinae, and others. Moreover, the youngest, thinnest, and most transparent shells are rendered visible by their apparent intense brown colour. Amongst porous species are some, such as Orbiculina and Sorites, which have the brown colour only in stripes. Lastly, Schultze has never met with the peculiar yellow, red, and violet tints mentioned by D’Orbigny in some Rotalinae, Rosalinde, and Planorbulinae. The figure assumed by various Polythalamia is extremely varied, but is nevertheless reducible to cortain types. We will restrict ourselves to a brief description of the primary forms established by Schultzo ; those are three in number:-1. In which the chambers or cells are Superposed on one another in a straight series. 2. In which they are disposed in a spiral manner; and, 3. in an irregular fashion. The Nodosaridae, which have their cells placed one on another in a simple row, are examples of the first type; the Spiroculinge of the second; and the Acervulinae of the third (XXI. 34). In spiral shells the chambers may be rolled in One plane, so as to form a symmetrical shell with opposite sides alike, e.g. in Cristellaria, or, otherwise, in an asymmetrical mode, so as to produce a shell like that of the common snail (Helia), e.g. Rotalia and Rosalina (XXI. 25–28). This latter variety may be so modified by the great elongation of the spiral, as to produce an elongated conical outline, as in Uvigerina and Bulimina, when the chambers above and below each other may present an alternate arrangement. Other varietics of the spiral are exemplified in Orbiculina, Alveolina, and Womionina. In many instances a simple or regular spiral disposition is commenced in young animals, which is departed from variously as they attain the adult condition and characters. Thus in Planorbulina the regular spiral is transformed eventually into a completely irregular form. Lastly, the Acervulinae con- sist of spherical or spheroidal cells aggregated into formless colonies. With reference to the minute structure of the shell, Prof. Williamson (Report of British Association, 1855, p. 105) recognizes three principal types: viz. –“ 1. The hyaline, generally consisting of a transparent vitreous carbonate of lime, with, usually, numerous foramina. 2. Porcellanous, white, opaque, and rarely foraminated. 3. The arenaccous, mainly consisting of agglomerated grains of Sand.” Schultze makes two types: in the one, the shell is perforatod by numerous fine pores or canals; in the other, it is homogeneous and solid. . The contents of the second series are brought into relation with the external world, by means of one large opening, or by many Smaller ones collected in One group. This division corresponds, in tho main, with that of Prof. Williamson, oxcept that the German naturalist has omitted to notice, as a third series, those shells constituted of a membrane covered by extraneous particles of Sand and the like. The size and distribution of the foramina, along with other structural pecu. liarities, afford the best specific characters. To oxamine these dotails the shells must be vic wed by transmitted light, and by high powers. The thick- walled opaque Foraminifera are best explored, as Ehrenberg first pointed out, after being Soaked in Some strongly refracting varnish, either entire or when cut into thin sections. The dimensions of the canals vary in different species from .0003 of a line (a scarcely measurable size) to .005 of a line. They are of extraordinary fineness in Polystomella strigilata, in P. gibba, and P. venusta, whilst in Orbulina OF TIII; PIROTOZOA.—RITIZOPODA. 225 wniversa and in Acervulina globosa (XXI. 35–37) they obtain their greatest diameter. In the latter, and in Globigerina, the canals dilate towards the surface, and are consequently funnel-shaped (infundibuliform). In a few instances two different sorts of pores exist, as in Oröwlina wniversa and Ičosalina varians, the finer kind being more abundant. A peculiar sort of slits is characteristic of the genus Polystomella ; that they completely perforate the shell is shown by sections. They are largest in P. strigălata, and in P. gibba appear to be only shallow oxcavations. Besides the openings named, the surface of the shells often presents regularly- disposed eminences or elevated lines. In Polystomella strigălata and P. venusta (XXI.28–30) there are hemispherical or conical eminences, perforated severally by a fine opening. In Teactilaria picta elevated lines are arranged around the widely-separated pores, so as to produce an elegant design (XXI. 25). Lastly, many shells have a spinous or stellate appearance, from the prolongation of some canals into long and fine projecting tubes, or from that of the whole of them into thick processes. Illustrations aro afforded by Rosalina Imperatoria, Cal- carina, and particularly by Siderolina calcitrapoides. Carter has described a greenish, perishable, organic membrane as investing the entire surface of the shells with all their irregularities; and d’Archiac has assumed this to be the secreting membrane of the calcareous matter. Schultze, however, has failed to detect such a structure in every specimen he has examined, whether in a living or in a dried condition; and he observes that, even if this membrane does oxist in certain cases, there are abundant facts to prove that it is not the secreting organ of the shell. The foramina are, as a rule, uniformly distributed over the shells, those parts only being free which are placed immediately above the partitions between adjoining cells. Exceptions, however, occur. Thus, in the inequi- lateral Rotalidae (XXI. 33) and their allies, the under or umbilical side has fewer porcs than the upper. Also, in some of the thick-shelled species tho position of the subjacent septa are not indicated by the absence of pores. The long winding canals pass in different directions, unite, and appear on the surface in groups, producing a complex Wavy pattern On the surface, as in many Calcarinae. The partitions between the several cells are perforated by orifices, which differ in size, number, and distribution in the several species. They occur in the septa as fine pores similar to those of the surface, but in less number. Again, in species having a single large opening in their terminal chamber, there is a similar one in each partition, as in Nodosarida, Miliolida (XXI. 21, 22), Teactilaria (XXI. 36), Rotalida, and in Nonionina, Rotulina, Cristellaria, &c. Among this group the Corvulina form an exception, in having numerous foramina in the last cell and in the septa between the others. In Acervulina, again, the Several cells communicate by a single opening. In Penéroplis, Coscinospira, and in Polystomella the Septa have numerous pores; and the foramina proportionally increase in number with the increasing size of the septa, i. e. from the first- to the last-formed chamber (XXI. 28–30). In Orbiculina the thick septa are penetrated by canals. Ehrenberg pointed out the presence, in several species, of numerous per- pendicular calcareous columns interposed between the septa, which he sup- posed to be hollow tubes, opening up a communication between the whole series of chambers and the exterior. Both their function and their tubular nature Schultze disbelieved, and asserted that Lwnwlites (Etw.) is not one of the Polythalamia, but actually a colony of Bryozoa. Mr. Carter (A. N. H. 1852, x. p. 170), on the contrary, asserts the ex- istence of such tubes in the septa, in the following passage:— Q. 226 GENERAL HISTORY OF THE INFUSORIA, “The septa occupy (in Operculina Arabica), transversely, about ºth of the breadth of the chambers; and each septum encloses within its walls two calcareous tubes or vessels, one on each side, some little distance below the contiguous surface of the shell (fig. 7 a, a); these we shall call interseptal vessels. They are irregular both in their size and course, though generally about Túrgth of an inch in diameter, in the last-formed septa of a shell having the dimensions of the one described, and diminish in calibre back- wards or towards the first-formed whorls. Each vessel commences in the centre of an intricate network of smaller ones, spread over its own side of the margin of the preceding whorl, and under the layers of the shell; these networks, which are joined together, we shall call the marginal pleaſus. In its course each interseptal vessel gives off two sets of ramwsculi, and the marginal plexus one set. Of those coming from the interseptal vessel, One set terminates on the surface of the shell, particularly about the borders of the septum ; the othcr goes into the walls of the shell, and through the septum, to open probably on the inner surface of the chamber, while the set from the marginal plexus opens on the margin. As this vascular system appears to extend throughout every part of the shell, and must be for the circulation of some fluid, we will call it the interseptal circulation.” Prof. Williamson has likewise described a scries of intraseptal canals in Faujasima, and illustrated their arrangement by engravings. We have not space to give the details, but can quote only the general results:—“The intra- septal spaces are vertical, and give off true divergent cylindrical canals from their external margins, penetrating the thick parictes of the shell. These spaces extend from the top to the bottom of each septum, and only assume the form of canals when they approach the peripheral shell-walls. The con- necting branches which unite the spaces of different convolutions are also tubular. In no instance do these spaces or their divergent canals communi- cate with the interior of the segments (chambers); for the only direct com- munications between the two parts of the organism are through the pseudo- podian foramina, many of which open into the tubular portions of these passages; but never, so far as I have observed, into the intraseptal spaces.” Again, “the cavities in the translucent shell are thickly lined with a dark olive-brown substance, which, if it be the desiccated soft animal, proves that in this species the gelatinous tissue has not only filled the true chambers, but has also occupied the intrascptal canals and passages. If this be so, it is curious that the only medium of communication between the soft tissues in- habiting the spiral segments of the shell and those occupying the intraseptal and central passages, should be the minute pseudopodian foramina. . . . It is, however, obvious that this organism supports the conclusion at which I arrived in a previous memoir, viz. that the soft animal had the power of extending itself externally far beyond the limits of any individual segment, and would thus be able to Secreto calcareous matter in other situations than the mere parietes of its own segment. It is only in this way that we can explain the production of the dome-like covering which cncloses the central umbilical cavities and their ramifying canals. But if it should be ultimately proved that the soft tissues have occupied all these irregular cavities, we shall then have a form of organization which, from its great variability of contour, will º much more closely to the calcareous sponges than any hitherto de- scribed.” Schultze says that the species referred to by the two observers just quoted have not come in his way, but that in none of the genera he has examined has he met with a similar structure. He has been equally unsuccessful in finding the interseptal spaces noticed by Carpentor in Nummulites; and in OF THE PROTOZOA.—REIIZOPODA. 227 no genus he has examined, has he been able to discover its shell to be com- posed of calcareous spicula, such as Carter represents in Opérculina Arabica, and refers to as indicative of the intimate affinity between Foraminifera and sponges, in the ensuing paragraph (A. N. H. X. 1852, p. 173):-"It must be now generally allowed that the Rhizopodous nature of Foraminifera is identical with that of the Amoeba or Proteus, and through the latter with the Sponge-cell; and in addition to this, we have the former, at least the genus Operculina, still more nearly allying Foraminifera to the Sponges, by possess- ing a spicula structure, if not a circulating system also, like that of Sponges.” Pºiº calcareous shell of Rhizopoda is lined (XXI. 16) within by a delicate organic homogeneous membranc, with a sharp outline, and of a more or less deep-brown colour. It is in immediate contact with the animal, and closely applied to the shell, and has the same perforations (XXI. 24). It penetrates from one chamber to the next through the intermediate pores and canals, During life it is, in the last-formed chambers, colourless. It is not equally visible in all species. By the addition of dilute acid to Rotalia, Rosalina, and Teactilapia, it is readily brought into view ; but in Miliolida this is difficult, owing to its delicacy and want of colour. In the first-formed (primordial) chamber, occupied by colourless substance, it would secn to be absent. In its chemical relations it resembles the chitimous shell of Gromia, and is so very slowly destroyed by decomposition, that it may be demonstrated in empty shells found amidst the sand at the sea-side, and, according to d’Archiac and Jules Haime, even in fossil specimens. DIMENSIONS AND CONDITIONS OF LIFE OF RHIZOPODA.—The size of the Rhi- zopoda is very varied, even among members of the same genus. Ehrenberg describes Amoebae from gºrgth and ###th to #5th of an inch ; Difflugia, from & 9 ºth, and ºth toºth, and ſºilº fººth toºth of an inch. Between individuals even of the same species, hº represents a diversity of size of nearly equal extent. Schultze states the diameter of the shells of Gromia oviformis, and of G. Dujardinii, to be ºrth of an inch, whilst that of Lagynis is only gºth in length. Dujardin remarks that the largest fresh- water Rhizopoda attain a diameter of sºnd, whilst the marine Foraminifera are for the most part visible to the naked eye, and have a length of from ºth to #th of an inch. The Nautiloid shells of Polystomella have a diameter of #th to ºrth of an inch, and the irregularly-chambered Acervulinae a length of from Tººth to 4th of an inch. Among fossil Foraminifera larger sizes prevail: thus, Sir E. Belcher brought one species from Borneo measuring more than 2 inches in diameter; and many Nummulites are found an inch and upwards in diameter. Mr. Jeffreys gives the following account of the habits of Foraminifera (Proc. Royal Soc. 1855):-‘‘Most are free, or only adhere by their pseudo- podos to foreign substances. Such are the Lagena of Walker, Nodosaria, Vor- ticialis, and Teaſtwlaria, and the Miliola of Lamarc. The last genus has some, although a very limited, power of locomotion, which is effected by exserting its pseudopodes to their full length, attaching itself by them to a piece of seaweed, and then contracting them like india-rubber, so as to draw the shell along with them. Some of the acephalous mollusks do the same by means of their byssus. This mode of progression is, however, exceedingly slow ; and I have never seen, in the course of 24 hours, a longer journey than a quarter of an inch accomplished by a Miliola. . . . Some are fixed or sessile, but not cemented at their base like the testaceous Annelids. The only mode of attachment appears to be a thin film of Sarcode. The Lobatula of Fleming, and the Rosalia, and Planorbulina (D'Orb.) belong to this division. Dr. Carpenter considers the Q 2 228 GENERAL DIISTORY OF THE INFUSORIA. Foraminifera to be phytophagous, in consequence of his having detected in some specimens fragments of Diatomaceæ, and other simple forms of vegetable life. But as I have dredged them alive at a depth of 108 fathoms (which is far beyond the Laminarian zone), and they are extremely abundant at from 40 to 70 fathoms, ten miles from land and beyond the range of any seaweed, it may be assumed, without much difficulty, that many, if not most of them, are zoophagous, and prey on microscopic animals perhaps of even simpler form and structure than themselves. They are in their turn the food of Mollusca, and appear to be especially relished by Dentaliwm entale.” The assumption that, because the Laminarian Zone ceases at a much less depth than that at which Foraminifera occur, therefore no Diatomeae are found, is quite gra- tuitous, and opposed to observation. The notion also that animal life fur- nishes nutriment to Foraminifera at depths where vegetable existence, and where the doubtful Diatomeae cannot be sustained, is opposed to all proba- bility. Of the rate of growth and of the duration of Rhizopoda we have few re- corded observations: we must, however, suppose them regulated by external circumstances, such as abundance of food, moderate temperature, and the like. Schultze observed of Foraminifera living in a small quantity of sea-water, so to speak, in captivity, that they grew exceedingly slowly. In only one Po- lystomella out of many, kept under observation for several months, did he ob- serve the production of a new chamber. Rotalia, however, were more fre- quently seen in process of growth, the walls of the new-formed segments being extremely delicate and deficient of calcareous matter. Some very young specimens of Miliola obesa were found to produce two new chambers, after the completion of the primary one, in the course of four weeks. From this fact of their very gradual growth, says Schultze, we may con- clude that a year or more may elapse before the construction of a many- chambered shell is completed. This naturalist has, indeed, kept the same specimens of Polystomella and of Rotalida in captivity for nine months; and their persistence for a much longer period is highly probable. If, he adds, the production of germs put a termination to life, then this phenomenon entails a fixed limit to its duration. Dujardin, again, found Arcellae alive after two years, in a vessel in which he had preserved them. The testaceous Rhizopoda possess the power of repairing the effects of me- chanical injuries to their shells. This has been proved by Schultze in the case of the Polythalamia; and we may conclude the same faculty is possessed by the Monothalamia. He has seen almost one-half of the shell of Polysto- mella strigilata, which had been broken away, repaired by a new calcareous wall resembling the normal one both in its pores, eminences, and markings. He also frequently noticed in this same species irregularities in the conforma- tion of the shell, which he attributed to damages previously inflicted; and experiment showed him that, even on the same day that a considerable portion was removed, the animal set vigorously to work to replace the lost shell, and protruded its processes just as before. Occasionally the destruction of a portion of the shell gives rise to monstrous (abnormal) forms. Thus Schultze noticed a double Polystomella strigilata, and Reuss a monstrous Nodosaria annulata, which he called N. dichotoma ; and Dr. Carpenter has found several “monstrosities of Orbitolites resulting from an unusual outgrowth of the contral nucleus.” The Rhizopoda can, doubtless, maintain life under very prejudicial condi- tions. The power possessed by the sarcode substance, of sustaining existence when even the greater part is torn away, and the capability of repair mani- fested by the testaceous species, are facts indicative of their tenacity of life. . OF TEIE PROTOZOA.—RELIZOPODA. 229 Another proof is found in the capacity of Foraminifera to exist for weeks and months in the same water. Schultze states that he has found them lying motionless, with retracted processes, at the bottom of a vessel of putrid water, in which they had been kept a long time, and that when this water has been changed, or its foul odour removed by an acid, they have recommenced to move about, and to thrust out their fibres. In a Small glass containing mud from the lagoons of Venice, and in which life appeared extinct, he found Ro- talidae and Miliolidae creeping on the sides, and in great numbers in the sedi- ment at the bottom. Some still more recent experiments have convinced this eminent naturalist that fresh water is not very detrimental to them, but that, on the contrary, they may be kept alive in it for a considerable time. He found at the same time that some dried Polythalamia from mud obtained at Muggia, and let dry for five weeks, continued motionless after six weeks’ immersion in sea-water. - HABITATS AND DISTRIBUTION OF RHIZOPODA.—FOSSIL FORMS.—The Amoebae are met with particularly in water containing much organic débris, provided that decomposition is not proceeding. They are common inhabitants of infu— sions, and of stagnant water, and are found adherent to foreign bodies, to plants, Confervaº, and the like. Although unable to swim, they are frequently floated to the surface on the matters to which they stick, such as dead leaves, Algae, or stalks of plants. They occur both in fresh- and in Sea-water, but are much more commonly seen in the former. The Monothalamia, with reference to their habitats, form two groups, one marine, the other freshwater. Arcella, Difflugia, and Euglypha are essential freshwater genera, whilst Spirillina (Ehr.), Gromia, Lagynis (Sch.), and Squamella (Sch.) are marine. They are not met with in infusions arti- ficially prepared although common in stagnant water holding organic matters in Suspension, and found crawling on these or on the sides of the vessel containing the water. Polythalamia are all marine. Their abundance and extent of distribution are surprising; this is true of them both in the living and in the dead or fossil condition. Schultze states that on the northern level shore of the har- bour of Ancona, the shells of the Foraminifera cover the surface here and there like a fine Sand, and are discovered in many places in smaller numbers at a depth of 20 feet. When this sand was placed in water in a glass jar, no Specimens were found to crawl up the sides; and observation showed that few among them retained any organic contents. From a small rocky islet in the harbour he scraped into a fine net the slimy mud, and then separated the lighter suspended particles from the mixture of animal and vegetable matter, and placed them in another glass. On examining, a few hours later, the fine Sand so separated, he found it almost entirely composed of Polythalamia, filled with their organic substance and alive, many of them having crawled up the sides of the vessel. His experiments at Venice were entirely correspondent; no living beings were found in the sand from the shore, but countless specimens in the débris about the Algae in the lagoons. Once, however, at Cuxhaven, on the Elbe, he met with living Foraminifera in the sand. Dujardin also says of the Polythalamia, that, from being unable to swim, they are only to be found attached to the surface of bodies on which they crawl, such as aquatic plants, or, otherwise, lying amidst the débris covering the base of such plants, or in the hollows between the asperities of the shells of marine Mollusca. Sponges, again, form a convenient habitat for living Polythalamia, having their pores at times pretty well filled with them; in the same way Corals and Corallines are frequently beset with them. This necessity of attachment cannot universally prevail, since the Foraminifera are 230 GENERAL ELISTORY OF THE INFUSOIRIA. so often found scattered over the bed of the ocean, as well in the living as in the dead state, without any Algae near, whereto they can adhere. The extraordinary abundance of Foraminiferous shells in the Sand of some sea-shores has been long observed. Plancus, in 1739, counted, with the aid of a low magnifying power, 6000 individuals in an ounce of Sand from Rimini, on the Adriatic; and D’Orbigny states that 3,840,000 exist in an equal quantity of sand from the Antilles. Schultze also counted 500 shells of Rhi- zopoda in ºth of a grain of sand collected from the Mole of Gaëta, which had previously been passed through a sieve and separated from all particles above Hºgth of an inch in size. Ehrenberg describes finding Polythalamia both on the surface of the sea and also at the bottom, even at a depth of 12,000 feet. From these great depths they are procured by soundings; the lead, after being coated with grease at the bottom, brings up attached to it the Small particles of Sand and other matters with which it comes into contact at the sea-bottom. Numerous such soundings were taken by Sir J. Ross in his Antarctic expedition, and have been practised by others in different regions. Dr. Bailey records the results of a series of deep soundings made in the Atlantic, over a considerable geographical area, from latitude 42° 4 to lat. 54° 17', and depths varying from 1080 to 2000 fathoms. “None of the soundings,” he states, “ contain a particle of gravel, sand, or other recognized unorganized mineral matter. They all agree in being almost entirely made up of the shells of Foraminifera. . . . . But neither the surface-water nor that of any depth. . . collected close to the places where the soundings were made, contained a trace of any hard- shelled animalcules.” Schultze is unable to receive Ehrenberg’s statement of finding shells floating on the Surface of the sea, seeing that they naturally sink in water. Still he admits that in shallow water they may be suspended by the tossing of the waves, and that they may float on the surface attached to Sea-weed torn from the bottom, or to other floating substances. He likewise, and, we think (judging from the laws of distribution of organic life at different depths as pointed out by the late Prof. Edward Forbes), very justly, demurs to Ehrenberg's conclusion, that the Polythalamian shells fished up from the great depths cited, and others approaching them, lived at those depths, and had become empty by speedy decomposition of their animal contents. At depths far less considerable, we believe all organic life ceases, and should consider the Foraminiferous shells there found to have been drifted from other less profound places by currents in the ocean. Prof. Bailey also started the question, whether the Foraminifera found at the bottom of the sea actually lived there, or were borne there by submarine currents, but admitted that these and other like questions could not be at present decided. What, however, is very remarkable, is that the Species “whose shells now compose the bottom of the Atlantic Ocean have not been found living in the surface waters, nor in shallow waters along the shore. It is but fair, also, to state that Mr. Jeffreys has dredged living Polythalamia from a depth of 108 fathoms (648 feet). So far as Schultze’s researches go, they prove a very limited geographical distribution of some species of Polythalamia. Thus, he has never found the Rotalia Veneta elsewhere than at Venice and Muggia, near Trieste, whilst the Polystomella strigilata, of Ancona, is altogether absent at Venice and Trieste. Nodosaridae, which are common enough at Rimini, are sought in vain at Ancóna, close by, whilst Rotalia. Beccarii occurs at both those places. So Penéroplis planata is found in the sand on the Istrian coast, from Città Nuova to Pola, but is absent at Trieste, Venice, and Ancona. Similar illus- trations might, says Schultze, be multiplied, to show the considerable diversity of local fauna. OF TELE PROTOZOA.—RITIZOPODA. 231 A limited distribution, both in reference to place and to the conditions of existence, has been determined by Ehrenborg and other observers of the Poly- thalamia, and also employed by geologists in fixing the period of the deposi- tion of certain strata, and the circumstances under which it has occurred. Thus Bailey records of the Atlantic soundings, that they “contain no species belonging to the group Agathistegia (D’Orbigny), a group which appears to be confined to shallow waters, and which in the fossil state first appears in the tertiary, where it abounds.” Again, they “agree with the deep Soundings off the coast of the United States, in the presence and predominance of Species of the genus Globigerina, and in the presence of the cosmopolite species Orbw- lina universa (D’Orb.); but they contain no traces of the Marginulina Bachii, Teactilaria Atlantica, and other species characteristic of the sonndings of the Western Atlantic. In the vast amount of pelagic Foraminifera, and in the entire absence of Sand, these Soundings strikingly resemble the chalk of England, as well as the calcareous marls of the Upper Missouri; and this would seem to indicate that these also were decp-sea deposits. The Cretaceous deposits of New Jersey present no resemblance to these soundings, and are doubtless littoral, as stated by Prof. H. D. Rogers.” A fixed geographical distribution is also implied by the division made by D’Orbigny of the species he observed,—viz, into 575 peculiar to the torrid zone, 350 to the temperate, and 75 species to the frigid zone. Moreover, Dr. Carpenter stated (in the Annual Address at the Microscop. Soc. 1855) that he and Prof. Williamson find “ that there are certain species whose range of distribution is limited, and whose form is remarkably constant, but that, in by far the greater number of cases, the species of Foraminifera are distributed over very wide geographical areas, and have also an extensive geological range.” Mr. Jeffreys remarks that, in his opinion, “the geographical range, or distribution of species, is regulated by the same laws as in the Mollusks and other marine animals. I have found in the gulf of Genoa species identical with those of our Hebridean coast, and vice versä.” * Fossil Foraminifera.-In a fossil form the Polythalamia are very common, and enter largely into the formation of several rocks, chiefly calcareous or of the tertiary Series, in every part of the world. Ehrenberg, in his microscopic examination of the chalk formation, represents these shells as the most im– portant constituent; and Tr. Bailey speaks of them as largely concerned in the formation of the tertiary rocks of South Carolina, and adds, they “are still at Work in countless thousands on her coast, filling up harbours, forming shoals, and depositing their shells to record the present state of the sea- Shore, as their predecessors, now entombed beneath Charleston, have done with regard to ancient oceans. For the city just named is built on a marl 236 feet thick. The marls from the depth of 110 to 193 feet are tertiary, as also, in all likelihood, are those beneath, extending from 193 to 309 fect, and also of the Eocene opoch. The lithological characters of the marls from 236 to 309 feet differ from those above them, although many of the same species are still to be detected” (A. W. H. 1845, vol. xv.). The most abundant Foraminifera of the chalk belong to Rotalia, Spirulina, and Teºtilaria: the fossil genus Nummulina abounds in tertiary strata; and their shells constitute the chief ingredient in the composition of many lime- stone rocks used in building, such as those in Egypt, from which the huge stones of the Pyramids are quarried. In America this genus is largely re- placed, as a component of limestone, by the genus Orbitoides. Species of Teºtilaria are the most abundant in Oolitic formations. In the cretaceous earths, says D'Orbigny, genera and species augment in rapid progression from the lower to the higher formations. On arriving at the fertiary rocks, Fora- 232 GENERAL EDISTORY OF TEUE INFUSORIA. minifera become still more multiplied, and many previously unobserved genera make their appearance. In the Silurian and Devonian rocks of the palaeozoic series, Foraminifera appear to be absent. In the carboniferous deposits D’Orbigny found one species, but detected none in the Permian, Triassic, or Jurassic strata. Mr. King has, however, discovered shells in the Permian rocks. Many genera have hitherto been found only in the fossil state : some such we may suppose to have become extinct; but others will probably be discovered when the search after living specimens is further prosecuted. It may be generally stated that the relative number of identical fossil and recent species is much greater in this family of Foraminifera than in any other known; and specific forms have continued from the Mesozoic era until the present day, so connecting, as by an unbroken chain, the fauna of our own time and that of almost countless ages past. QUESTION OF THE CELL-NATURE OF RHIZOPODA, AND OF THE CHARACTER OF FoEAMINIFERA AS INDIVIDUALS, OR AS COLONIES OF ANIMALS.—The prevailing theory of the cellular composition of all animal and vegetable tissues induced several distinguished naturalists to represent the Rhizopoda as cells. Kölliker ingeniously argued (J. M. S. 1853, i. p. 101) in favour of this view, and for a time succeeded in persuading most scientific men of its truth. It had the character of a grand generalization, and recommended itself by its simplicity. Various structural peculiarities and general considerations are, however, opposed to this theory: these we will adduce after Kölliker’s arguments have been stated. He first assumes that the Rhizopoda and Ciliated Pro- tozoa are comprehended in a single class of simple animals, which, like the Gregarinae, are unicellular; and he further groups the Actinophryina with Rhizopoda. The absence of an integument to represent the cell-wall, and in most of them of a recognized nucleus, are difficulties he would explain away. First, he supposes that, where a nucleus is not seen, it “may have existed at an earlier period, and be absent only in the full-grown animal, or, again, that it may be entirely wanting, and still the animal be regarded as a cell.” Secondly, “with respect to the membrane, it may be regarded as certain that there are cells with a membrane of such extreme tenuity as to be hardly distinguishable from the contents,” and others in which at a later period all difference between the membrane and contents disappears, for instance, the elements of the smooth muscles of the higher animals.” Which of these two possible conditions obtains in the Rhizopods, he cannot undertake to say, but would remark “that their other relations are not opposed to the notion that they may be simple cells, such as their structureless homogeneous contents, their contractility, and the vacuoles which occur in them, resembling in all respects the contents of the body of unicellular Infusoria. So, likewise, the simplicity of their form and mode of taking food, so closely resembling the way in which Infusoria introduce a morsel into their parenchyma. Certainly the presence of a cell-membranc is scarcely reconcilcable with the circumstance that the body is capable of admitting a morsel of food at any part of the sur- face; but in one point of view it is not indispensably necessary to assume that such exists in the fully-developed Actinophrys, and in another it is by no means wonderful that a membrane, in consistence almost the same as the rest of the parenchyma, should be capable of being torn and of reuniting.” It is therefore, he concludes, best to consider the Rhizopoda simple, although modified, cells, especially since there is little else to be made of them. “It cannot be admitted that they consist of a whole aggregation of cells; and as little is it to be supposed that they are simply a mass of animal matter with- out further distinction—as it were, independent living coll-contents. And the loss can this opinion be entertained, because “cells are the elementary OF TEIE PROTOZOA.—RELIZOPODA. 233 parts of the higher animals and plants, and the unicellular condition the simplest form in the animal kingdom.” The existence of an investing mem- brane in the Rhizopoda he finally considers probable. The arguments here quoted from Kölliker’s paper on Actinophrys, have been examined by several later writers, and have had their defects pointed out. Perty declares himself opposed to the cell-theory since Rhizopoda are want- ing the essentials of the cell-nucleus and cell-wall; and the hypothesis cannot be applied to animals composed not of cells, but of an amorphous primitive substance. M. Claparède attacks Kölliker's arguments in detail. The question raised, whether the nucleus and membrane may not disappear in the course of growth, he answers by another query—“We may conceive the possibility of this; but where do we find any proof of it?”—and proceeds to remark his own failure, and that of Ehrenberg and of most others, to discover a nucleus, even in very small animals, and after treating them with dilute acetic acid. “The supposition, that Actinophrys and other Rhizopoda pass through a previous cellular condition, has consequently no foundation in fact.” He cannot agree with Kölliker, that of the three parts of a cell—the nucleus, membrane, and contents—two “may be deficient, that for example, we may attribute the signification of a cell to the contents remaining alone and contained in nothing. . . . If, therefore, with Kölliker, we regard the Rhizopoda as a class of unicellular animals, the organisms which it includes will be principally distinguished by their having nothing to do with cells, as they consist of a shapeless mass of a structureless homogeneous substance.” M. Claparède next subjects to examination the argument for the cell–nature of Rhizopoda deduced from analogy with Ciliated Protozoa, which Kölliker takes for granted to be unicellular organisms. This assumption, and conse- quently the analogy dependent on it, are shown to be erroneous; and then the writer goes on to say that, “even if we admitted that Actinophrys was the equivalent of a cell, it would still not be unicellular, inasmuch as an endogenous cell-production has taken place in it. The contractile vesicle is nothing but a cell” invested by a membrane ; and this being the case, the existence of such a membrane in other Ciliated Protozoa becomes all the more probable. “Kölliker himself supposes that the contractile vesicle, when pre- sent, is the equivalent of a cell-membrane; and with the proof of the exist- ence of such (an endogenous) formation in Actinophrys, his hypothesis of the unicellular constitution of the animal consequently falls to the ground.” Leuckart has also briefly argued against the cell-theory of Rhizopoda; but as no novel views are taken of the question, we shall not quote his remarks. Our own opinion is, that to insist upon the unicellular nature of Rhizopoda and of other Infusoria is to limit the operations of nature, in the manifesta- tion of animal life, to one sort of mechanism, as though life could not be exhibited except by an organic substance enveloped by a membrane and enclosing a nucleus. Reasoning by analogy should teach us differently; for everywhere in the animal series do we see types or grades of organization progressively developed from their simplest to a more or less complicated degree, as if nature would show us by how many different plans she can attain similar and equally beneficial results. And are not the Rhizopoda an illustration of this fact, an example of the establishment of independent animality in primordial animal matter, and, as in the case of the multilocular Polythalamia, of the possible extent of development this simple type may undergo without the separation or addition of any other definite structural element 2 If Schneider's researches be confirmed, we must admit several Rhizopoda 234 GENERAL EDISTORY OF TELE INIFUSORIA. to be possessed of a nucleus. On the other hand, a large number of species are able to produce new individuals by the mere detachment of a portion of their sarcode substance,—an act in which no nucleus is concerned, whereas in cell-propagation by fission a preparatory section of the nucleus appears a necessary process. In the Rhizopoda, therefore, we may conclude that, in the language of Professor Owen, “the spermatic force’ is diffused through- out their entire substance, and not, as it were, concentrated in a particular organ or nucleus. The question respecting the nature of the many-chambered Foraminifera, whether they are to be considered single individuals or colonies of animals, is elaborately examined by Schultze, who comes to the conclusion that the inhabitant of each shell is a single animal. Ehrenberg is the supporter of the opposite view; but Schultze shows that several structural details given by him, upon which the colony-theory is partly established, are erroneous, and that it is one common connected substance which occupies each and every chamber. Prof. Williamson (T. M. S. 1851) has the following pertinent observation on this colony-theory. Speaking of the Orbiculina adwmca, he says—“The attempt to isolate the various portions, and to raise each portion to the rank of an individual animal, even in the limited sense in which we should admit such a distinction in the polypes of a Sertularia or of a Gorgonia, appears to me wholly inadmissible.” Moreover, the soft-structures being devoid of visible organization, “the whole animal will be very little raised above the Polypifera, only possessing a symmetrical calcareous skeleton, which is at once both external and internal” (i. e. the Porifera). OF THE AFFINITIES OF RBIZOPODA.—That the Rhizopoda constitute a class of animalcules distinct from every other is evidenced by their characteristic vital structure and phenomena, their power of producing their like, their growth, their faculty of digesting and appropriating nutrient matters, and by the ascending stages of development seen among them, advancing from the simple Amoeba to the compound testaceous Cristellaria and Polystomella. In the nature of their animal portion they resemble Ciliated Protozoa ; it con- tains similar vacuolae and granules, and also a contractile vesicle. On the other hand, they differ from them in having no definite outline to the animal tissue bounded by a limiting membrane or integument, and particularly in possess- ing no cilia, which, as locomotive organs, are replaced by the peculiar and characteristic pseudopodes. In variability of outline an approach is made to Thizopoda by some genera of the heterogeneous family, Enchelia of Ehrenberg; but they never exhibit any such changeable character as the surface of the former, never protrude similar variable processes, nor present a circulation of granules. The Dinobryina might perhaps be cited as affording an example of a considerable variability of form; but our knowledge of this family is too incomplete to render analogies based on it of value. The affinity between Rhizopoda and Phytozoa is no closer. Some of the latter can greatly modify their form in moving ; but in none does this partake of the character and extent of the variability exhibited by Rhizopods. More- over in none are variable processes found, but in general one or more elon- gated cilia or filaments, which, by their undulation, serve as the principal organs of locomotion. - Between the Testaceous Rhizopoda and Ciliated Protozoa the alliance is even less evident; for in none of the latter do we meet with shells like those of the former, and in none is the relation between a lorica and its contents corre- spondent to that of the shell and sarcode substance of Rhizopoda. It has already been noted that the distinction between the two classes of Protozoa founded on the silicious character of the shells or loricae of the Ciliated, and OF TELE PROTOZOA.—REDIZOPODA. 235 the calcareous nature of those of the Pseudopodous class, is not in accordance with fact; for although all, or almost all, Polythalamia have calcareous shells, yet the flexible lorica of many Monothalamia are chitinous, just as those of loricated Ciliata. In the presumed fact of the shells of Arcellina being silicious, Ehrenberg discovered a relation between that family and the Bacillaria. This affinity he traced still further; for, when describing the genus Cyphidium, he remarked —“It forms a connecting group between Arcella and Bacillaria, by reason of the simple locomotive organ (like a snail’s foot), and approaches very closely to the group Desmidieæ.” However, even if he be right as to the single un- divided process of Cyphidium, the presence of any extended foot or pedal organ from the silicious fronds of Bacillaria, whether Diatomede or Desmidieæ, is not now admitted by any naturalist. If Stein’s observations and opinions be correct, an indirect relationship actually exists between Ciliated Protozoa and Rhizopoda; for that pains- taking observer has convinced himself that the Vorticellina, by ulterior de- velopment, become transformed into Acimeta-like or Actinophryean organisms, of the intimate affinity of which no doubt can be raised. The questions raised by this apparent transformation do not require discussion here, since they are fully entered upon in the history of the Ciliata, and in that of the Acimetina, considered as a subclass of Rhizopoda. Another alliance was formerly assigned to the Multilocular Rhizopoda, viz. with the Cephalapoda, of which they were treated as a subdivision. This association was suggested, by the Nautilus-like form of some genera, to the earliest observers of the Foraminifera—Beccarius in 1731, and Plancus in 1739; and the error was perpetuated by D’Orbigny in 1826. Dujardin has the great merit of first combating this mistaken opinion, and of pointing out. the extremely simple nature of their contents, and their true affinity with the simple Amoebae. Several naturalists, and among them M. de Quatrefages, have classed the comparatively large Noctiluca, with the Rhizopoda. But direct observation seems to show that, although in a few particulars a likeness obtains, yet the sum of the differences greatly surpasses that of the resemblances. The Noctiluca show a more complex organization; they have an integument com- posed of two layers, an evident mouth and gastric cavity with appendages, and motile filaments, but no variable processes. A striking general resemblance subsists between the Naked Rhizopoda– Amoebae—and the like isolated individuals and the germs of freshwater Sponges or Spongillae, which Mr. Carter has named Proteans (XXI. 5 a, b, c). The resemblances are well conveyed in the following quotation from Mr. Carter's paper:—“A ragged portion torn off with a needle, will be seen gradually to assume a spheroidal form; and if there be a spiculum, it will embrace it within its substance, it may even be seen to approach it, and it may bear away the spiculum, having, as it were, Spit itself upon it. On its circumference will be observed little papillae, which gradually vary their form, extending and retract- ing themselves, until one of them may be seen to detach itself from the parent mass and go off to another object. This little animal, one of the group which it has left, may remain stationary On the Second object, or descend to the watch-glass, assuming in its progress all forms that can be imagined, sphe- roidal or polygonal, whilst every point of its body appears capable of ex- tending itself into a tubular attenuated prolongation . . . . These transparent little sacs (the gemmules of Grant and Hogg) are sometimes filled with green matter. They appear to be able to adapt themselves to any form that may be convenient for them to assume; and when forcibly separated from each 236 GENERAL HISTORY OF TELE INFUSORIA, other (by tearing to pieces a minute portion of the sponge under water in a watch-glass), the isolated individuals may be seen to approach each other, and apply themselves together in twos and threes, &c. and so on, until, from a particle only discernible by the microscope, they assume the form of an aggregate mass visible to the naked eye; and such a portion, growing and multiplying, might ultimately reach the size of the largest masses adhering to the sides of the tanks at Bombay. They appear to belong to the genus Amoeba of Ehrenberg.” These changeable globules Mr. Carter, in the subsequent part of his paper, designates Proteans, and states that they commonly resemble the Pro- teus diffluens (Müller). (“Notes of the species, &c. of the Fresh-water Sponges of Bombay,” Trans. Med. and Phys. Society, Bombay, 1847. Appendix.) In his more recent contribution on the freshwater Sponges, Mr. Carter describes cells, capable of greatly and rapidly changing their form, endowed with considerable motile powers, and furnished each with an undulating locomotive filament (XXI. 5). These organisms he considers to be zoosperms, or the spermatozoa of Spongilla. Speaking of one, he says—“When its power of progression and motion (of a serpentine creeping character) begins to fail, and if separated from other fragments, it soon becomes stationary, and, after a little polymorphism, assumes its natural passive form, which is that of a spherical cell. During this time the motions of the tail become more and more languid, and at length cease altogether.” On the other hand, it may attach itself to some fragment, or to another cell, and “become indistinguish- able from the common mass; and the tail, floating and undulating outwards, is all that remains visible.” In these structures there is, therefore, polymor- phism as in Rhizopoda, but no actual extrusion of pseudopodes; and the points of agreement, after all, are really accidental, and not demonstrative of a structural affinity. In them we have reproductive germs, which coalesce and disappear as independent existences, whilst in the case of Amoeba each speci- men is an independent individual, and is never seen to coalesce with others into a common or Sponge-like mass. Dujardin devoted a couple of pages to speak of this affinity between Amoebae and Sponges; and Perty even goes so far as to make the latter a third class of the Rhizopoda, intermediate between Arcellina and Amoebina, on account of the calcareous, silicious, or horny spicula which occur in their compound mass, and constitute a sort of skeleton. The affinity with Sponges is traceable even in the case of the testaceous Polythalamia, as Prof. Williamson pointed out in 1848, and in a subsequent memoir in 1851 (Trans. Mic. Soc.) thus enters on the question:—“Looking at the structure of the shell of the Orbiculina adunca, and especially at the large orifices which communicate between its various cavities, we cannot fail to observe that it is a reticulated calcareous skeleton, whose proportionate rela- tion to the size of the Soft animal has differed but little from that of the siliceo-keratose network of many Sponges to the slimy substance with which they are invested.” So Dr. Carpenter (Proc. Roy. Soc. 1855), in his critical examination of Orbito- lites, “places that genus among the lowest forms of Foraminifera, and con- siders that it approximates closely to Sponges, some of which have skeletons not very unlike the calcareous network which intervenes between its fleshy segments.” With respect to this idea of Dr. Carpenter, that they are allied to Sponges, Mr. Jeffreys (same journal) would remark “that Polystomella crispa has its periphery set round at each segment with silicious spicula, like the rowels of a spur. But as there is only one terminal cell, which is con- nected with all the others in the interior by one or more openings for the OF THE PROTOZOA.—RETIZOPODA, 237 pseudopodes, the analogy is not complete, this being a solitary, and the Sponge a compound or aggregate, animal.” In a previous page the theory of Ehren- berg, that the Foraminifera are compound or aggregate animals, has been referred to. It was on this hypothesis that he assumed their affinity with Polypes—with Flustrae and Bryozoa, at the head of which he arranged them. This association, like the hypothesis it rests upon, is untenable. In his work on the Foraminifera of the Vienna basin, M. D’Orbigny assigned a position to these animals as an independent class between Echinoderms and Polypes, which, from the present knowledge of the structure and reproduc- tion of those classes, we cannot suppose he would seek to maintain. CLASSIFICATION OF RHIZoPopA.—The first division of Rhizopoda that suggests itself is into naked and testaceous forms, or, as Ehrenberg would say, into illoricated and loricated. The naked forms constitute the family Amoebina, represented by the single genus Amoeba. - The determination of specific characters in this family is attended by almost insurmountable difficulties, and can only be unsatisfactory, by reason of the absence of any definite figure, and of determinate organs or parts. More- over the semifluid body of any one presumed species must be much influenced by external causes, and in some measure by the matters which may have entered into its substance; and the like causes will doubtless operate by modifying the outline, dimensions, and number of the processes. Among such causes the density of the liquid in which they live, and the quantity of organic matter contained in it, may be particularly mentioned. Claparède remarks—“It appears almost absurd to attempt the distinction of species amongst the Amoebae until we know something more of their intimate organization. Thus Ehrenberg's A. radiosa is characterized by the regularity of its processes, and its generally stellate form when at rest; but when the creature creeps, it slowly expands and the peculiar outline disappears; it flows along like a cloudy veilor drop of oil, and A. radiosa has become converted into A. diffluens.” Yet, this author afterwards goes on to say—“even the changeable Amoebae have their typical forms, such as the stellate and globu- lar.” Other grounds of specific distinction (of no very certain value, indeed) are found in the shape, length, and mode of termination of the variable pro- cesses, and in the size, colour, transparency, activity, and habitats of these beings. The Testaceous Rhizopoda naturally fall into two groups, one distinguished by having a unilocular, the other a multilocular, shell—the former called, by Schultze, Monothalamia, the latter, Polythalamia or Foraminifera. These grand divisions have been recognized by every naturalist; but some have been led, from giving importance to other particulars, to arrange differently cer- tain genera, or, otherwise, to detach some as additional families. Thus Ehrenberg, swayed by his polygastric hypothesis, and satisfied in his own mind that the Arcellae, Difflugia, and one or two other monolocular genera possessed a series of stomachs and other organs like other Polygastria, united those genera into a family which he called Arcellina. This detachment of one group of pseudopodous beings from the rest, he further justified, as heretofore stated, by representing it to have silicious instead of calcareous shells. In this dislocation of evidently-allied forms he finds no imitators, and is unsup- ported by facts. D'Orbigny distinguished the one-chambered, sac-like, shelled Rhizopoda as one of the six orders into which he separated the Foraminifera, and named it Monostegia. This order is nearly equivalent to that framed by Ehrenberg, under the title of Monosomatia, to comprehend the genera Gromia, Orbulina, and Ovulina, a term subsequently borrowed by Siebold, but extended by him 238 GENERAL, ELISTORY OF TELE INFUSORIA. so as to include not only the particular genera enumerated, but also the families Amoebae and Arcellina of that naturalist. The term Monothalamia contrasts well with that of Polythalamia, expresses the fact, and involves no hypothesis as do Ehrenberg’s words Momosomatia and Polysomatia, which are founded on his belief in the colony-like aggrega- tion of several individuals within a Foraminiferous shell. The Monothalamia of Schultze (as before remarked) do not precisely cor- respond with the one-celled group of either of the other authors named; for, besides the Monostegia of D’Orbigny, it comprehends the Arcellina of Ehren- berg and a few other new genera. The groupings and relations of the Several species are represented in the appended table exhibiting Schultze’s system. In the classification of the Monothalamia certain and constant characters are deducible from the shells, whilst those drawn from the soft parts, from the length or tenuity or mode of termination of the pseudopodes, are of compara- tively secondary importance, and not to be relied on alone. Definite charac- ters are derivable from the figure, size, composition, Sculpturing or appendages, and colour of the entire shell, from the presence of a single large aperture or of many small pores, and from the form of the aperture and of its margin ; consequently it is in the shells of the Polythalamia that we must seek generic and specific distinctions. As animals, they have all alike the same sarcode sub- stance, which extrudes similar variable fibres; hence any diversities observed in its colour or transparency, in its contents, or in the manner in which the processes are extruded or otherwise comport themselves, serve but a sub- ordinate purpose in the scheme of classification. On the contrary, the cha- racters of the shells are, within certain limits, determinate and fixed. They are derivable from the figure, size, colour, and consistence of the shell; from the markings, processes, pores, and slits occupying its surface; from the relative position and figure of the several chambers; from the mode and degree of their connexion ; and from the presence or absence of large apertures in company with the usual foramina; and last, not least, from the intimate structure of the shell. Dujardin recognized the value of the shells to supply the basis of a classification of the Rhizopoda ; but he had recourse to the form of the variable expansions to make his primary division, “although,” as he remarks, “it has no absolute value.” He arranged all the Rhizopoda, with the exception of the Amoebae (which he treats as a distinct family), into two sections,—One having a single unilocular shell with a single large aperture; the other a foraminiferous compound shell, or one having several aggregated chambers, each with a simple orifice, as represented by the tribe Miliola. It is in the Subdivision of these Sections that he employs characters derived from the variable processes. Thus he separates the first into—1. those animals pro- vided with short and thick processes rounded at the extremities, viz. Difflugia and Arcella; and 2, into those having filiform expansions, acutely drawn out at the ends. The latter division is more largely represented; and he separates its numerous species into three tribes, viz. Trinema, with a lateral orifice; Euglypha, with a tuberculated or areolated shell and few simple expansions; and Gromia, with a membranous spheroidal shell and expansions, thick at the base, but very long and branching. He has not attempted the classifica- tion of the whole of the Foraminifera, but restricted his account to some few genera which he has found in a living condition. D'Orbigny instituted five orders of the Polythalamia, viz. –1. Stichostegia, having the cells arranged one above another in a straight or slightly-curved line ; 2. Helicostegia, with cells disposed spirally around an axis; 3. Ento- ºnostegia, having the chambers alternating and coiled spirally; 4. Enallo- stegia, with alternating but not spirally-disposed chambers; 5. Agathistegia, OF TETE PROTOZOA.—REIIZOPODA. 239 having the cells spirally arranged, but each one occupying only one-half the circuit. The three sections proposed by Schultze are—1. Shells disposed in recti- linear series or in a slightly-curved line, Rhabdoidea ; 2. those goiled in a spiral, Helicoidea ; 3. those irregularly aggregated, Soroidea. The first of these corresponds to the Stichostegia of D’Orbigny; the second includes all the remaining orders of that writer; whilst the third section is represented by a small number of species, previously unmentioned, which Schultze unites in the genus Acervulina. What structural peculiarities should be employed to determine species, is a question now much mooted with respect to the Foraminifera. In reference to this subject, Dr. Carpenter (in the annual address at the Microscopic So- ciety, Feb. 1855) observed “ that a large proportion of the species, and even of the genera, which have been distinguished by systematists, and especially by M. D’Orbigny, have no real existence, being mothing else than individual varieties.” This error is at once accounted for by M. D’Orbigny’s mode of proceeding (as stated): “for that, in examining any new collection, he set an assistant to pick out the most divergent forms, and then described all that might prove new to him as distinct species, without troubling himself in the least about those connecting links, the existence of which should have at once convinced him that he was following an altogether wrong method. Through- out the whole of his labours on the group, in fact, I find the influence of the erroneous ideas which he originally entertained with regard to the mature of the animal of the Foraminifera; for in the formation of his orders, as well as of his genera and species, he has proceeded as if the characters of the tes- taceous skeleton were of the same distinctive value when its construction is due merely to the solidification of the surface of a minute fragment of animal jelly, which is subject to an almost indefinite variation both in size and in shape, as when it belongs to a mollusk of high organization, the plan of whose conformation is definitely fixed. . . . When a collection is brought to— gether containing large numbers of individuals of one generic type, which appear, however, to belong to several distinct species, it very commonly hap- pens that, although it would be easy to make 6, 8, 12, or 20 species by Selecting the most divergent forms, yet, when the attempt is made to sort the entire collection under these types, only a part of it can be unhesitatingly arranged around them as centres, the remainder being transitional or inter- mediate forms, for which another set of species must be made, if the principle of separation be once adopted. In fact, to such an extent does individual Variation often go, that (as in the case of the human race) no two specimens are precisely alike, and there is no satisfactory medium between grouping them all as varieties of one species, and making every individual a species, which is manifestly absurd.” The error of D’Orbigny has not escaped Schultze’s notice; for in his chapter On classification he has repeatedly pointed out the insufficiency of the charac- ters on which that observer relied in framing his species, genera, and families. For instance (p. 52), he points out the erroneous separation of the Stichostegia (D’Orb.) into two families, according to the equilateral or inequilateral con- dition of the shell. And further on, he remarks that the variations elevated by D’Orbigny to the rank of specific distinctions are merely accidental diver- sities in growth, connected together by every intermediate variety. Hence, for example, he combines the genera Triloculina and Quinqueloculina (D’Orb.) into one genus Miliola, and the Orbitoides and Orbitulina (D’Orb.) into a single genus Orbitolites. Various other illustrations might be adduced, for instance, the family Nautiloidae; but it is unnecessary to multiply them. It 240 GENERAL EIISTORY OF TELE INFUSORIA. is only fair, however, to state that D’Orbigny is not alone guilty of unduly manufacturing species, but that Ehrenberg, Reuss, and others are equally involved in the fault, which, by the way, is one almost inseparable, and therefore very excusable, in the case of the first observers and systematists of any newly-discovered group of organic beings. Mr. Jeffreys (Proc. Roy. Soc. 1855) deplores the multiplication of species and genera in the present day, and observes that “the Foraminifera exhibit a great tendency to variation of form, some of the combinations (especially in the case of Marginulina) being as complicated and various as a Chinese puzzle. It is, I believe, undeniable, that the variability of form is in an inverse ratio to the development of animals in the scale of Nature. . . . . . I am induced to Suggest the following arrangement:— “1. Lagena and Entosolenia. “2. Nodosaria and Marginulina, &c. “3. Vorticialis, Rotalia, Lobatula, and Globigerina, &c. “4. Teatularia, Uvigerina, &c. “5. Miliola, Biloculina, &c. “This division must, however, be modified by a more extended and cosmo- politan view of the subject, as I only profess to treat of British species. To illustrate McLeay's theory of a quinary and circular arrangement, the case may be put thus:— - “The first family is connected by the typical genus Lagena with the second, and by the Entosolemia with the fifth ; the second is united with the third through Marginulina; the third with the fourth through Globigerina; and the fourth with the last through Uvigerina.” We append a tabular view of the groupings into families and genera, as proposed by Prof. Schultze, since it presents the most complete system yet pro- duced, and advances much nearer a true arrangement of the Foraminifera than that made by M. D’Orbigny. of THE PROTOzoA.—RHIZOPODA. 241 RHIZOPODA. A. NUDA. Gen. Amoeba (Noctiluca?). IB. TESTACEA. I. MonoTHALAMIA. Testa or shell one-chambered; animal undivided, having the same conformation as the shell. Fam. 1. LAGYNIDA.—A sacciform, calcareous or membranous, non-porous testa, with a large opening. Gen. Arcella, Difflugia, Trinema, Euglypha, Gromia, Lagynis, Ovulina, Fis- surina, Squamulina. Fam. 2, ORBULINIDA—A globose, calcareous testa, finely porous throughout, without a large opening. Gen. Orbulina. Faºn. 3. CornusPIRIDA.—A calcareous shell, convoluted like that of a Planorbis, with a large opening. Gen. Cornuspira. II. Polyth ALAMIA. Shell polythalamous; the animal composed of segments, connected by commissural bands. 1. Group HELICOIDEA. The chambers disposed in a spiral. Fam. 4. MILIOLIDA—Each chamber occupies a half-spiral, which is developed either in one plane or in various planes. The shell has only one large opening at the extremity of the last spiral, and no pores. Gen. Uniloculina, Biloculina, Miliola, Spiroloculina, Articulina, Sphae- roidina, Adelosina, Fabularia. Fam. 5. TURBINo1pA.—The chambers so disposed spirally as to resemble the shell of Helix or Turbo. The spiral is only visible on one side of the shell. Some are so much elongated that the chambers are, as it were, disposed alternately in two contiguous rows. The shell has a large opening in the last chamber, and its surface is almost always finely perforated. Subfam. 1. Ročalida.-Shell flattened or comical; chambers do not encircle each other; shell glass-like, transparent ; finely perforated. º Gen. Rotalia, Rosalina, Truncatulina, Anomalina, Planorbulina, Asterigerina, Calcarina, Siphonina, Planulina, Colpopleura, Porospira, Aspidospira. Subfam. 2. Uvellida.-Shell in the form of a longer or shorter cluster like a bunch of grapes. The chambers frequently appear to almost completely º: one another. Shell usually thick and coarsely perforate, or solid. Gen. Globigerina, Bulimina, Uvigerina, Guttulina, Candeina, Globulina, Chrysalidina, Pyrulina, Clavulina, Polymorphina, Dimorphina, Wer- neuillina, Chilostomella, Allomorphina, Rhynchospira, Strophoconus, Grammobotrys. - Subfam. 3. Teactilarida-Spire so much produced that the chambers form a double row and alternate. s Gen. Gaudryma, Textilaria, Virgulina, Vulvulina, Sagrina, Bigenerina, Bo- livina, Gemmulina, Cuneolina, Clidostomum, Proroporus. Subfam. 4. Cassidulinida.-Textilaridae curved once in a direction perpendicular to the original spiral. Gen. Ehrenbergina, Cassidulina. Fam. 6. NAUTILoIDA.—The chambers so disposed spirally that the shell has a general resemblance to that of an Ammonite or Nautilus. The spire is either visible or, otherwise, concealed on both sides of the shell. The anterior wall of the last chamber is furnished with one larger or several smaller openings; the other portion of the shell is usually finely perforated. Subfam. 1. Crisiellarida.-Shell thick, finely perforate, colourless, transparent; chambers encircling, with a large opening at the upper angle of the anterior wall of the last chamber, which corresponds in position with the communicating openings between the several chambers. *...* Gen. Cristellaria, Robulina, Marginulina, Flabellina. Subfam. 2. Nomionida.—Shell thick or thin, colourless, transparent, finely perforate; chambers either encircling (imbricate) or not. The opening is in the R 242 GENERAL ELISTORY OF TELE INFUSORIA. anterior wall of the first chamber on the under side looking towards the penultimate spiral; the communicating openings of the several chambers have a similar position. Gen. Nomionina, Hauerina, Orbignyna, Fusulina, Nummulina, Assilina, Siderolina, Amphistegina. Operculina and Heterostegima should pro- bably be formed into a special subfamily of Nonionida. Subfam. 3. Peneroplida-Shells usually thin, always brown, and transparent with or without fine pores; the chambers very narrow, either imbricate or not. Numerous openings, scattered over the whole of the anterior wall of the last chamber; or, instead of these, a large opening produced by the coalescence of numerous smaller ones. Gen. Peneroplis, Dendritima, Wertebralina, Coscinospira, Spirolina, Lituola. Appended genus, Orbiculina. Subfam. 4. Polystomellida-Shell tolerably thick, colourless, transparent, finely por- ous; chambers imbricated; the anterior wall of the last chamber has, besides the fine pores, either no larger opening at all, or a few very small irregular scattered fissures, on the contrary side to the penultimate whorl. The same applies to the septa. On the surface of all the chambers, rows of fissure-like, often perforating, depressions are placed at right angles to the direction of the septum. Gen. Polystomella. Fam. 7. ALVEoLINIDA—Globose, ovoid, or barley-shaped shells, composed of spiral tubes, each resembling a cornuspira, and furnished with a special opening at the end of the turn or spiral. The tubes all communicate by con- necting openings, and, besides this, are all subdivided by incomplete dissepiments (partitions), in the same manner as species of Nomionina. The situation of these septa, which are but few in number, and of the connecting openings, is indicated by lines, which traverse the shell in the direction of meridional lines. Gen. Alveolina. Fam. 8. SoFITIDA.—Discoid, multicellular shells, exhibiting an indication of a helicoid spiral only in the centre; elsewhere cycloid, that is, growing uniformly at the whole border of the disk. The brown, transparent, finely porous shell is formed of minute chambers, connected together in the direc- tion of straight or curved radii, and each presenting a large opening at the border of the disk. Gen. Sorites, Amphisorus, Orbitulites. Appended genus, Cyclolina (cham- bers * annular, with numerous openings on the border of the disk). 2. Group RHABDoIDEA. The chambers piled one on another, in a straight or slightly curved line, in a single row. Fam. 9. NoDOSARIDA.—Rod-shaped shells, whose chambers are superimposed one upon another in a row, and communicate with each other by a large opening; a similar opening in the last chamber (except in the genus Conwlina, which has numerous openings instead of the single one). The shell usually thick, probably always perforated by fine pore-canals. Gen. Glamdulina, Nodosaria, Orthocerina, Dentalina, Frondicularia, Lin- gulina, Rimulina, Waginulina, Webbina, Conulina. 3. Group SoroDEA. Chambers grouped in irregular masses. Fam. 10. ACERVULINIDA—Chambers usually globose, disposed very irregularly, and of pretty uniform dimensions; shell finely perforate, with a few larger openings at indeterminate places. Gen. Acervulina. The preceding account of the Rhizopoda we believe to be ample to lead the student forward in the study of that peculiar class of animals. Yet, with re- spect to the division Foraminifera it may be considered less complete : for, from the close attention given of late to those beings, every monthly and quarterly periodical of natural science teems with fresh facts and opinions concerning them ; and, above all, we have had placed in our hands, since the foregoing history was written, the very elaborate and critical researches of OF TEIE PROTOZOA.—ACTINOPEIRYINA, 243 Prof. Williamson and Dr. Carpenter, to which we would particularly refer the inquirer intent on following out his knowledge of the Foraminifera, but which both the dimensions and the character of the present work forbid the attempt to condense or analyse in its pages. Prof. Williamson’s work, ‘On the Recent Foraminifera of Great Britain,” forms the volume for 1857, published by the Ray Society. Dr. Carpenter’s learned essays on the structure of shells, on the value of form and other external characters in generic and spe- cific groupings, and on the structural and physiological relations of several genera, are to be found in the ‘Transactions’ and in the ‘ Proceedings' of the Royal Society. Additional facts concerning both the structure and relations of the several groups of Rhizopoda will be found in our Systematic History of them in Part II. SUBFAMILY OF RHIZOPODA, ACTINOPHRYINA. (Plate XXIII. 24–37.) This is a remarkable group of Protozoa, which can take its place neither with Ciliata nor strictly with Rhizopoda, although its affinities with the latter are very close. Ehrenberg attached the several forms of this family with which he was acquainted to his heterogeneous collection—the family Enchelia, and referred them to five genera, viz. Actinophrys, Trichodiscus, Podophrya, Dendrosoma, and Acimeta. Moreover, according to his fundamental hypothesis, he represented them to have a mouth and an anus, an alimentary canal with offshoots in the shape of stomach-vesicles, a sexual gland, and ova. Since the Berlin professor's investigation of these animalcules was made, several distinguished naturalists have most carefully studied them, and particularly the Actinophrys Sol. In our last edition we named a genus Alderia, in honour of Prof. Alder, to distinguish certain organisms described by him in the Annals of Natural His- tory (1851, vii. p. 427). Subsequently, however, that eminent naturalist wrote us to state that the name proposed had been already applied to a genus in an- other class of animals; and on further consideration and reference to Stein’s researches, we were inclined to renounce their claim to a generic independ- ence, and to consider them three forms of Podophrya. Dr. S. Wright has, however, apparently observed the same beings very lately, and instituted a new genus, Ephelota, to receive them (Edinb. New Phil. Journ. 1858, p. 6). Notwithstanding the very close affinities of Actinophryina and Acinetina, there are sufficient differences between the two, and so many peculiar forms of the latter that they deserve a particular consideration. - The history of the first family is very fairly represented by that of Actino- phrys Sol, or of Act. Eichornii, both of which have been very completely studied by Siebold, Kölliker, Claparède, Stein, and Weston. Some diversity prevails among these several observers respecting a few points in their organ- ization, which it will be incumbent on us to notice in the proper place. The species of Actinophrys have a circular figure, and are either spherical or so compressed as to have a discoid form (XXIII. 28, 29). The distinctive peuliarity of their figure is, however, due to the filaments or tentacles, which radiate from all parts of their surface and give the beings (to employ a familiar and not inapt illustration) the appearance of a ball of cotton stuck thickly over with pins; for the filaments have nodular extremities, or, in technical phrase, are capitate. The figure is determinate, and in this respect contrasts with the proteam changes of form exhibited by Rhizopoda. Not that the figure is completely unalterable; for slight variations are possible, - R 2 244 GENERAL EIISTORY OF TEIE INFUSORTA, although slower than even those of Amoeba. Stein represents the usual orbi- cular figure to be frequently exchanged for a pear-shaped, an oblong, or a partially angular and lobed one,—varieties dependent, according to his state- ments, upon inherent changes taking place in connexion with progressive de- velopmental phenomena. The aspect of the entire organism is, moreover, modified from time to time, by the altered length, direction, and disappear- ance of a portion of the filaments, chiefly consequent on the act of prehension in which they are engaged. Stein, indeed, represents still more considerable modifications, involving the complete disappearance of tentacles from various portions of the surface, and the aggregation of the rest upon angular emi- nences in a penicillate manner, an occurrence which would assimilate still more closely the Actinophryina and the Acimetina. Lastly, the figure is varied during the acts of self-division and of conjugation, as will be presently noticed at large. - In colour the Actinophryima are commonly of a milky-yellow or greyish hue, the intensity of which is determined by the number of contained granules, or, in other words, by the supply of nutriment. Acetic acid and cold solution of potash remove colour; the latter fluid, when heated rapidly, dissolves the entire mass, and indicates its nitrogenous nature. Observers are not agreed on the point of the existence of an integment. Dujardin, Kölliker, and Cla- parède deny it, whilst Stein, Perty, and Mr. Weston (J. M. S. 1856) affirm its presence. Among the latter, one speaks of it as a hyaloid membrane; another declares it to be double, consisting of a delicate elastic membrane immediately investing the contractile Substance of the animalcules, covered by an outer firmer tunic. This statement is especially made by Stein of Podophrya, which is, in his opinion, a merely stalked variety of Actinophrys, and indistinguishable from it even as a species (XXIII. 1, 3, 4, 5). On the contrary, Cienkowsky (J. M. S. 1857, p. 98) remarks that he could discover no membrane surround- ing the body of that animalcule. To account for this diversity in descriptive details, we must suppose that the different authors have not had the same animalcule under observation ; indeed Stein asserts that Kölliker did not examine Actinophrys Sol, as he supposed, but Act. Eichormii. Lieberkuhn likewise suggests that Claparède and Kölliker have written upon different species under the same name; and Stein must, we believe, have committed a similar mistake; for the Actinophrys and Podophrya described by him differ in so many important particulars from beings bearing the same name in the writings of others, that it seems impossible they can be identical with them. The fact seems to be that certain Acimetae have in external characters so close resemblance to Actinophryina, that they may be mistaken for them. Be this how it may, if we take into consideration the peculiar relation of the tentacles with the body, their movements, and especially the mode of introducing food into the interior, it seems quite improbable that there should be a firm investing membrane. These remarks, indeed, apply only to the usual forms or phases of these beings; for when an encysting process proceeds, then, certainly, an external envelope will manifest itself, yet not without the sacrifice of the tentacula and of the ordinary phenomena of vital activity, the ingestion of food and the like. “It is impossible,” to quote Claparède (A. W. H. 1855, xv. p.286), “to admit the existence of a general integument, as Actinophrys can push out the mucous or gelatinous matter of which its body is composed, take in nourishment, or evacuate the residue of digestion, from any point of its surface at pleasure.” In this same observer's opinion, Perty’s notice and figures of a capsule are evidently erroneous, the consequence of optical illu- sion. Mr. Carter adopts an intermediate opinion, by admitting the existence of an enveloping pellicula, like that in Amoeba, which, although not a separable of THE PROTOZOA.—ACTINOPEIRYINA. 245 layer or skin, is a somewhat firmer or more condensed tissue than that sub- iacent. J The Actinophryina are composed of a homogeneous elastic sarcode, occupied by granules in varying number, and by vacuolae. The granules are especially accumulated in the centre, to which they consequently impart a greater opacity and deeper colour. Hence several authors have spoken of a central medullary mass surrounded by a clearer cortical lamina (XXIII. 28, 29). Still there is no natural separability into two such portions; for their relative size varies according to the supply of food received. Dr. Strethill Wright (in a letter) proposes to apply the unexceptionable terms “ endosarc’’ and “ectosarc * to the medullary and cortical portions respectively. The contained granules are rounded, opaque, and, for the most part, of a fatty character. The granules are less abundant in the ectosarc ; but those of a finer Sort are seen in Smaller numbers even in the lower end of the filaments, and Lachmann (A. N. H. 1857, xix. p. 223) asserts that he has seen their motion there, as well as in the general substance of the body. Mr. Weston also remarks (op. cit. p. 122), “With a 4th objective I can distinctly see granules in constant motion in the body of the Actinophrys, similar to those always found in the points of Clos- terium Lunula.” The vacuoles occur both in the cortical and medullary portions, but are smaller in the latter, and they never penetrate into the substance of the filaments. - At first sight, as Kölliker notices, the tissue appears delicately cellular: a closer inspection, however, shows that this is not the case ; for on pressure being made, a coalescence into larger, or, otherwise, a subdivision into Smaller, areolae is the consequence (XXIII. 28, 29, 30). - The tentacles or filaments give to the Actinophrying their most distinctive features. They are usually pretty regularly and uniformly distributed over the entire surface, and in figure taper from the base to the apex, which is surmounted by a rounded knob. Unlike other observers, Cienkowsky (J. M. S. 1857, p. 101) represents the capitate form to be exceptional, and that the rule is for the filaments to taper like setae. Dujardin, by the way, appears to have thought the capitate extremities accidental; for he describes the filaments as often becoming globular in the act of contraction. In smaller specimens the filaments exceed the diameter of the body in the length, but in larger ones are not more than equal to, or are even less than, it. In the same species their number and position are tolerably constant. In composition, the tentacula are processes given off from the sarcode mass, and are destitute of an integument, as proved by their power of coalescence when approximated. They are retractile, and can be withdrawn into the common mass ; they can also be directed towards different sides, and curved upon themselves. Perty states that they can assume so rigid a condition that other animalcules some- times impale themselves upon them ; this statement is nevertheless uncon- firmed, and, indeed, seems scarcely probable. Kölliker (op. cit, p. 31) speaks of the filaments as undergoing various changes of form, “Such as elongation, shortening, local swelling, bending, &c. . . . . It is especially interesting to observe that the filaments, singly or together, frequently disappear entirely, entering at last, as it were, by continued retraction, into the Substance of the body, leaving no trace of their former existence. . . . whether the filaments which disappear are always reproduced in the same spot is not determined; in some instances this did not appear to be the case, although in every instance the number and position of the filaments is pretty constant ’’—unlike the variable processes of Amaeba. Ehrenberg assigned to the tentacles, among other purposes, that of organs of progression ; direct observations are, however, wanting to prove this purpose, and both Kölliker and Stein are 246 GENERAL ELISTORY OF TEIE INFUSORIA. quite unable to admit it as even probable. They have been supposed by several authors to have a benumbing effect upon the prey they may seize ; but this view is merely hypothetical. “It is nevertheless,” says Claparède (op. cit. p. 287), “quite certain that small animalcules and plants remain adherent to them ; for these rays are true tentacles. Indeed, their contact must have something very unpleasant about it ; for larger Infusoria, even such as Paramecium Aurelia, on coming accidentally within their reach, start back with the greatest rapidity, sometimes even dragging the Actinophrys a considerable distance with them.” So, again, Weston states—“ on the instant of contact with these tentacles, the victim appears paralysed.” Yet, withal, it seems clear that, unless actual contact ensue, no harm attends proximity to the formidable prehensile organs; for animalcules may frequently be seen swimming about unharmed among them. ICölliker rejected the supposition of an intrinsic fatal influence existing in the filaments, which appeared to him to serve only for retaining the prey by their adhesive surface, and pro- bably to involve it with their extremely fine extremities, until they drew it by their progressive contraction to the surface. Even after being seized upon, an animalcule may escape, both by great exertions in tearing itself away, and sometimes, as Mr. Weston remarks, by the act of the Actinophrys, when, as it would seem, its appetite was “Sated, or the prisoner was not approved; for after remaining stunned sometimes for a few seconds, four or five, some- times much longer, ciliary motion (of a Vorticella, for instance) is feebly com- menced, not with sufficient energy to produce motion, but as if a return to vitality were being effected by struggles; shortly it is seen to glide off the tentacle (as if this appendage possessed the power both of appropriation and rejection), and, frequently with but little sign of recovered life, it slowly floats out of the field.” One function distinctly possessed by these tentacula is that of sensibility. Kölliker has thus well conveyed this fact (op. cit. p. 33): —“Actinophrys perceives mechanical influences, and reacts upon them by movements. This is proved by what takes place when animalcules, &c. remain affixed to its tentacles, and moreover by the circumstance that, when the water in which it is contained is carelessly agitated, every Actinophrys contracts its tentacles and even makes them disappear altogether (and, indeed, with greater speed than is otherwise perceived in these creatures), and when all is quiet they are again protruded. These filaments, conse- quently, may just as well be called tactile as prehensile; or it may more generally be said, that the substance of the body is both contractile and sensitive.” Movemſ ENTS.—There is not much to be said respecting the movements of the Actinophryina; for these beings are even more sluggish than the Amoebaea, and appear to change place rather as mere passive particles of matter than as living animals. They may float hither and thither in the fluid surrounding them, or rise to the surface; but how this latter movement is effected we have no data to show. On this subject Kölliker has the following paragraph:— “Its power of moving from place to place is indubitable; for it was found, for instance, that when a vessel, with several individuals of Actinophrys, was emptied into a flat glass capsule, they were all at first scattered about at the bottom, but subsequently, after from 12 to 24 hours, were all floating at the surface, and, indeed, at the side of the capsule. Ehrenberg and Eichhorn assert that the ascension of Actinophrys in the water is effected by the taking im, and the descent by the giving out, of air. But this is certainly not the case; for whence could they obtain this air 2 Can it be said they secrete it within themselves like fishes? In that case it must be visible. It appears to the author more natural that the rising and sinking should be effected by OF THE PROTOZOA.—ACTINOPEIRYINA. 247 alternate contractions and expansions of the whole body. Other motions can affect both the filaments and the body, but in any case only through the slowest possible contractions.” Besides these ill-understood translations from place to place, and those movements chiefly affecting the tentacles in the act of taking in food, to be presently noticed, there also occur, according to Kölliker, “faint indications of contraction, such as slight undulations of the border, and inconsiderable quivering motions here and there. The creature also seems to be capable of altering its entire form to a certain extent, and to be able to expand and to contract itself in toto.” Stein contradicts these statements, affirming that he could neither observe any movement in the organic mass, nor any change of position, whilst Claparède, on the other hand, writes, “nevertheless the animal, in its ordinary Sun-like form, is able to move slowly in a given direction; but during this movement no contraction of the body or bending of the tentacles is to be observed.” A singular obser- vation is recorded by Mr. Boswell (T. M. S. 1854, p. 25), which needs con- firmation before it can be accepted, viz. that the Actinophryima can suddenly change their place by a leap. This phenomenon, he tells us, he witnessed twice among a number of the animalcules found floating on the Surface of the water. Usually the Actinophrys is found attached to some object, and that so firmly that large animalcules may strike against it, or strong succussions of the water take place without loosening it from its hold. Podophrya and Dendrosoma are exceptional Actinophryina, by possessing a pedicle. In the former this stem is commonly short and always simple, whilst in the latter and hitherto little-known genus it is branched. As elsewhere noticed, Stein will not admit the pedicle of Podophrya to be a generic, indeed not even a specific, distinction, and therefore treats Actinophrys and Podophrya as identical. In connexion with his belief in the presence of an enclosing integument, he describes the wall of the hollow pedicle of Podophrya to be continuous upwards with the external envelope of the body (XXIII. 3, 4). It is proper, however, to remember that Stein wanted both to establish his hypothesis of the conversion of Vorticella into an Actinophrys and Podophrya, as a consequence of the act of encysting, and preparatory to embryonic repro- duction, and, further, to assimilate those genera with various Acimetas, which, in his opinion, were derivable from other members of Vorticellina. This detracts from the value of his details of the structure and functions of Actino- phrys; and, as expressed above, a great doubt suggests itself whether he has always examined the selfsame animalcules, and whether what he has de- scribed applies to the Actinophrys investigated by Kölliker and Claparède. Cienkowsky, who has latterly tested Stein’s hypothesis, asserts, respecting the question of the structure of the stem of Podophrya, that the pedicle is an appendage to the body, which has no integument. “I am unable ’ (op. cit, p. 100), he writes, “to adopt Stein’s view that the Podophrya are enclosed in a membrane, of which the slender pedicle is simply a tubular protrusion. This is true only with respect to the short peduncle of the encysted Podophrya.'” (XXIII. 36, 37). PREHENSION AND ENTRANCE OF FooD.—The movements of the tentacula of Actinophryina are chiefly directed to the prehension of prey for food. This they effect primarily by seizing it by means of their apparently sticky surface, and then, by shortening themselves, drag it to the surface of the animalcule. If the prey has been caught by one tentacle, the neighbouring ones conspire to clutch it more firmly, and (to use Kölliker’s words) “apply themselves upon it, bending their points together, so that the captive becomes gradually en- closed on all sides.” This concurrence and crossing of the tentacles is men- tioned also by Stein ; but Mr. Weston states that he has never witnessed it. 248 GENERAL ELISTORY OF TEIE INFUSORIA. Concerning the mode of entrance of the nutritive matter when drawn to the surface, some difference of opinion prevails among the several writers who have treated of it. Ehrenberg, true to his hypothesis, attributed to Actino- phryina a mouth surmounted by a proboscis, and an amus at the opposite side with an intercommunicating intestine and numerous stomach-sacs opening into it. In short, they were, according to his scheme of Organization, Enantiotreta, of the class Enterodela. Dujardin rejected this account, and supposed them to be nourished by absorption, carried on by the general surface, or by means of thick expansions from it. At the present time all observers unite in denying a mouth, anus, and alimentary canal to Actino- phryina, and in admitting that food may be introduced, and its débris dis- charged, at any part of the surface,—a fact patent to direct observation, which shows the seizing and the entrance of prey going on, occasionally, at more than one point at a time (XXIII. 29–32). We have followed the captured morsel until it approaches the surface, and when the force of the tentacles behind it still tends to press it onwards into the body. The following pro- ceeding, according to Kölliker (op. cit. p. 28), now takes place:–“The spot of the surface, upon which the captured animalcule is lying, slowly retracts and forms at first a shallow depression, gradually becoming deeper and deeper, in which the prey, apparently adherent to the surface and following it in its retraction, is finally lodged (XXIII. 29 m). The depression, by the continued retraction of the substance, now becomes deeper; the imprisoned animalcule, which up to this time had projected from the surface of the Actinophrys, disappears entirely within it; and at the same time the tentacles, which had remained with their extremities applied to each other, again erect themselves and stretch out as before. Finally, the depression acquires a flask-like form, by the drawing in of its margin, the edges of which coalesce; and thus a cavity closed on all sides is formed, in which the prey is lodged. In this situation it remains for a longer or shorter time, gradually, however, ap- proaching the central or nuclear portion, and at last passing entirely into it in order to await its final destination. In the meanwhile the external por– tion of the Actinophrys regains in all respects its pristine condition. The engulfed portion is gradually digested and dissolved.” Whilst admitting the general correctness of this account by Kölliker of the act of inglutition, Stein asserts that, prior to the appearance of the prey in a depression of the body, a large vacuole, rising above the surface, comes into contact with it, and then, by its collapse, drags it downwards into the substance of the animalcule. This stage he supposed Kölliker to have overlooked. However, Claparède denies that the reception of food is ever effected by means of the expansion and contraction of a vesicle, or that, as Kölliker believed, the food penetrates the substance of the body by the force exercised upon it behind by the tentacula: it is rather, he says, the Substance of the body which approaches and embraces the food; for before the latter has touched the surface of the body, it is seen to be enveloped in a kind of mucus. “This mucus is com— pletely undistinguishable from the parenchyma of the Actinophrys; it appears as though the substance of which it is composed had suddenly drawn itself over the captured object. The elevation thus produced then slowly flattens; and by this means the food is gradually drawn into the body. Astasiae, which I frequently saw Sucked in by Actinophrys in this way, continued to move for a little time, endeavouring to break through the substance that enveloped them ; their movements, however, soon ceased; they became converted into a globular mass, which circulated very slowly through the parenchyma with the so-called vacuola.” . . . . “At first I thought the substance, which so suddenly enveloped the object to be swallowed, was produced by the mere OF TELE PROTOZOA.—ACTINOPEURYINA. 249 bending, expansion, and fission of the tentacles. I could not, however, retain this opinion: an extension of a mucous substance, apparently the parenchyma, really takes place from the side of the Actinophrys; and this is afterwards drawn in with the prey. This expansion sometimes takes place very slowly; a thick, regularly lobed mass is seen to embrace the object; and I have once observed this extension without the presence of any prey. I can only compare this process with what takes place in Amoeba.” Dr. Strethill Wright (in lit.) expresses the same fact in a condensed form, thus:—“In Actinophrys the tentacles bring the food to the surface of the ectosarc, which closes over it and carries it to the endosarc.” Mr. Weston’s observations tend to a similar interpretation of the mode of introduction of food. “Rrom the margin of the body of the Actinophrys,” says this gentle- man, “a thin pellucid membrane is projected up the side of the creature destined for food (XXIII. 24–32), which proceeds rapidly, but almost imperceptibly, to surround one side of it; a similar membrane springs sometimes also from the Actinophrys, but more frequently from the tentacle on its other side; these amalgamate on the Outer surface of the prisoner, which is thus enclosed in a sac composed of what I take to be the extended outer vesicle of the Actinophrys. This vesicle gradually contracts, or, rather, seems to return by elasticity to its original position; and the food thus be- comes pressed within the body, there to become digested.” The conclusion to be drawn is, that, after the act of prehension by the tentacles is complete, the retraction of those processes is succeeded by the protrusion of a sort of variable process, similar to those of Amaºba in character, and also in its mode of enveloping and engulfing the morsel. After its admission into the Soft Substance of the interior, the nutrient matter undergoes a process of digestion, by which, if soft, it suffers complete dissolution and absorption; but if it contain insoluble matter, this remains behind, after the disappearance of the rest, as a residue to be sooner or later cast out through an aperture temporarily formed at the point of the surface it comes into contact with, and of which all trace is lost so soon as the act of extrusion is accomplished. The molecular and granular matters derived from food collect especially in the central or nuclear portion of the body, the depth of colour, opacity, and strength of which are directly proportionate to the supply of food. The particle of food (the animalcule or other substance), when in the interior, is surrounded by or suspended in a drop of fluid, or, in Dujardin’s phraseology, occupies a vacuole. This fluid is either drawn in by the act of inglutition, or is a secretion poured out around the food for the purpose of digestion. Claparède takes the latter view, and states that the fluid always exhibits the same pale-reddish colour as the contents of the contractile vesicle, and indicates different refractive powers from those of water. This observation accords with one made by Schneider, of the digestive vacuoles of Amoeba. The process of digestion is slow. Claparède observed the changes of a Chlamydomonas, and states that three hours scarcely sufficed for its conver- Sion into an unrecognizable gelatinous mass. Kölliker represents the time to vary from two to six hours; but this must differ perpetually according to the mature of the food, the vitality of the animal, &c. “The number, as well as the size,” writes Kölliker, “of the morsels taken at One time by the Actinophrys is very various. Very frequently there may be 2, 4, or 6 at the same time, frequently also more than 10 or 12. Ehrenberg Counted as many as 16 stomachs, i. e. in other words, so many separate morsels. He also noticed the ingestion of indigo, which could not have gained admission in any other way than that by which the Infusoria and other aliments enter. The largest morsels 250 GENERAL, ELISTORY OF THE INFUSORIA, noticed consisted of a Lynceus and a young Cyclops. Eichhorn, indeed, mentions a water-flea (Daphnia 2), about the size of which, however, no re- mark is made.” Indeed, the Actinophryina are rapacious animals, and will appropriate to themselves any organisms, vegetable or animal, which fall in their way. Thus, besides those beings alluded to already, Rotifera, various minute Crustacea, Ciliated Protozoa, Phytozoa of all sorts, DeSmidieæ, Dia- toméae, minute Algae, and their spores alike fall a prey to these remarkable animalcules. The excrementitious particles of food, as already stated, pass out at any spot where circumstances may direct them; and no definite anal aperture, such as Ehrenberg imagined, has an existence. The expulsion of re- sidual matters, Mr. Weston (J. M. S. 1856, p. 121) states he has “frequently seen,_in one specimen twice in less than half an hour, at different spots. In watching the digestion of a Rotifer, it occurred to me to see a dark body, composed apparently of the case, remain for Some hours in the same spot, and then gradually approach the side, as if for expulsion; but while waiting for this to take place, an opening in another part occurred, and excrement was voided in quantity: this voided matter lies amongst the bases of the tentacles, while the opening through which it has passed closes; and then, with the same stealthy motion I have before described, it is apparently driven along the tentacles (as if by repulsion) beyond their extremities, finally dis- appearing in the surrounding medium.” CoNTRACTILE VESICLE.—The rule is, that only one contractile vesicle belongs to each animalcule (XXIII. 36, 37). If more appear, it usually indicates either the approach of fission, or the conjugation of two or more individuals (XXIII. 33–35). Kölliker failed to recognize this organ in Actinophrys, and concluded that Siebold had described as such the mere changeable vacuola. Bowever, Stein, Claparède, Cienkowsky, and others concur in representing a contractile vesicle as normally present ; the first-named writer, indeed, de- scribes in a few instances two such, as Siebold has done before him. Stein exhibits, in Actinophrys Sol, the vesicle as central (XXIII. 1); but other maturalists concur in representing it as Superficial,—so much so, according to Siebold, that it will frequently during its expansion project above the general surface, and thereby prove itself to have a distinct wall (XXIII. 29 m); for if composed of only the gelatinous parenchyma of the body, it would burst at the moment of greatest expansion. It is, therefore, a closed sac or cell. Claparède has never found more than one vesicle, and thinks both Siebold and Stein in error in describing two. “Several vesicular elevations,” he writes, “often occur on the margin; but only one of these is contractile. I have, however, observed two contractile vesicles in several individuals; but in these cases the form always gives rise to a suspicion of fission, or of an amalgamation of two individuals (Act, difformis, Ehr.). The presence of a single contractile vesicle does not, however, appear to be universal among the Rhizopoda; I have observed two in Arcella vulgaris. . . . It is surprising that Kölliker, who was acquainted with Siebold’s observations, should have cha- racterized them as inexact, and as arising from an illusion. According to him, Siebold had mistaken accidental expansions and contractions of the sub- stance enclosing the vacuoles, in which the latter were persistent, for phe- momena indicating the existence of contractile reservoirs. This, however, is not the case; the size, the unchanging position, and the regular expansion and contraction of this organ will prevent its being confounded with a vacuole. That Kölliker should have overlooked it is particularly unintelligi- ble, as the phenomenon is immediately presented by nine out of ten specimens of Actinophrys.” Carter (A. N. H. xviii. p. 129) makes the curious assertion, that the “Actino- OF TELE PROTOZOA.—ACTINOPEIRYINA. 251 phrys Sol, Ehr., is surrounded by a peripheral layer of vesicles” (he is speaking of contractile vesicles), “which, when fully dilated, appear to be all of the same size, to have the power of communicating with each other, and each, individually, to contract and discharge its contents externally, as occasion may require, though generally only one appears, and disappears, in the same place.” Stein describes and figures a row of vesicles immediately beneath the surface of a new species he calls Actinophrys oculata (XXIII. 24, 25), but does not, like Carter, treat them as so many contractile Sacs, an interpre- tation which cannot be received without much more extended inquiry and confirmation. Notwithstanding this assertion, Mr. Carter, in his outline of facts relevant to contractile vesicles in general, has the following clause, ap- plying specially to the animalcules under consideration, and giving a most apt illustration of the phenomena witnessed:—“In Actinophrys Sol, and other Amoebae, during the act of dilatation, the vesicula projects far above the level of the pellicula, even so much so as occasionally to form an elongated, transparent, mammilliform eminence, which, at the moment of contraction, subsides precisely like a blister of some soft tenacious substance that has just been pricked with a pin.” At another part, this same author says, generally (op. cit. p. 128), and in some measure contradictorily to the first statement quoted from him, that “in Amoeba and Actinophrys the vesicula is generally single ; sometimes there are two, and not unfrequently in larger Amoebaea a greater nnmber.” It should be mentioned that Stein found in the animal- cule, which he took to be Act. Eichornii, a Superficial group of vacuola, ren- dering the outline irregular, a phenomenon no doubt the same as that intended by Carter. Stein, moreover, described in the same animalcule two contractile spaces, one at each pole, immediately beneath the surface, but capable of alternately elevating themselves above, and depressing themselves within it, and of thereby aiding to introduce food. Podophrya has, according to Stein and Cienkowsky (XXIII. 34, 35, 36, 37), a single circular contractile vesicle. Stein, indeed, figures two in one specimen. So far as appears, the vesicle is not placed so close to the surface as in Actinophrys. Among other structures mentioned by Ehrenberg, was a contractile proboscis, by means of which the animalcule was supposed to re- ceive food; but other observers have looked in vain for any process to which such an appellation could with justice be applied. The structure intended by Ehrenberg is, in Claparède's opinion, no other than the contractile vesicle, —an opinion in which Mr. Weston seems to agree (see below), although he attributes to it a structure and action without parallel in other Infusoria. A glance at the quotation above made from Mr. Carter's paper will show also that the contractile Sac was intended. The following are the observations of Claparède, referring to the matter in question:—“From time to time a globular prominence rises slowly and gradually from a particular point on the surface of the animal; this increases more or less in different cases, sometimes, espe- cially in Small individuals, attaining nearly a third of the size of the entire body, but generally reaching only ºth or Tºth of that size. The margin of this projection is always well defined, much more so than the other parts of the body, especially when it has attained its greatest evolution. At this moment it contracts suddenly and disappears entirely, so that a flattening of the outline is often to be observed at the point previously occupied by this remarkable elevation: the margin soon becomes rounded again; the globular projection gradually rises, attains its previous highest development, and then suddenly disappears again.” The following paragraph from Mr. Weston's paper (J. M. S. 1856, p. 116) refers, doubtless, to the selfsame expanding and contracting process distinguished by Claparède ; but the function of respiration 252 GENERAL IIISTORY OF TEIE INFUSORIA. and a valvular structure of a very extraordinary nature are attributed to it. We suspect, indeed, that Mr. Weston has been led into error by appearances, —a supposition he will pardon us for making, since, as he himself tells us, his microscopic experience is less than two years old. His account runs thus:— “There appears to be no doubt about the existence of a valvular opening: I have had some thousands of these animalcules under my observation, and have never met with a specimen where the valve was absent. It is best distinguished when about the edge of the seeming disc, and, so far as my observations go, is never still night nor day, being slowly, but without cessa- . tion, as it were, protruded, occupying from 10 to 70 or 80 seconds in its development, and then, like the bursting of a vesicle, rapidly and totally subsiding ; for an instant it has utterly disappeared, only to be again as gradually and as certainly reproduced. Should that side of the creature, where the valve is placed, be turned from the observer, the effects of the contraction are distinctly seen, although the valve itself is not ; for at the instant of its bursting and closure, some half-a-dozen or more of the tenta- cles, situated on or about it, which have been gradually thrust from their normal position by the act of its protrusion, now rapidly approach each other with a jerk-like motion, caused by the sudden bringing together of their bases. • - “With ºth of an inch objective, I have been led to imagine the valve to be formed of a double layer of the external hyaloid membrane, the edges of which appear to adhere to each other tenaciously, notwithstanding the growing distension from within, until the force becomes so great that the lips, as they may be called, Suddenly separate, apparently to give vent to some gaseous product; and at this moment there is, as I have stated, enough seen to induce the belief in the existence of a double lip-like valve, perhaps the organ of respiration.” He afterwards adds (p. 118)—“In many instances I have seen half-a- dozen or more prisoners attracted to the tentacles of an individual; each gra- dually absorbed; and although thus busily occupied, no cessation of the action of the valve takes place.” Stein imagined the movements of the contractile sac to be subservient to the reception of food; but this supposition, as men- tioned already (p. 248), is opposed to analogy, and is wanting in direct obser- vation to establish it. Among the general contents of the body of Actinophrys, Kölliker (op. cit. p. 27) mentions some separable nuclear cells as detached by crushing from the innermost portions of the animal. When isolated by pressure, they be— have themselves as cells, with nucleus and nucleolus, sometimes as free nuclei. “The author is, in fact, inclined to regard them as cells and nuclei, lying in Some of the interior vacuoles; for such, and such only, are the vesi- cular spaces in which they are enclosed.” (XXIII. 29.) NUCLEUS.—Kölliker applied the term nucleus, very improperly, to the more granular and darker central or medullary portion of the body (XXIII. 29 h), and overlooked the presence of the real nucleus. However, Stein, Carter, Cienkowsky, and others have determined the existence of this organ in the genera Actinophrys and Podophrya. Unfortunately, some difference prevails in the descriptions of this organ by the several observers, which it is most desirable to have removed. Carter (A. N. H. 1856, xviii. p. 221) represents it to be a cloudy body, “discoid in shape, of a faint yellow colour, and fixed to one side of a transparent capsule, which, being generally more or less larger than the nucleus itself, causes the latter to appear as if surrounded by a narrow pel- lucid ring.” Stein describes it in Actinophrys Sol as finely granular, band- shaped, and curved, or reniform, or rounded oblong (XXIII. 1 b). Cien- OF TEIE PROTOZOA.—ACTINOPEIRYINA, 253 kowsky says that the nucleus of Podophrya is “transverse and frequently curved,” and thereby implies that it is an elongated body. The nucleus of Actinophrgs oculata (says Stein, p. 159) may be brought into view either by crushing the animalcule, or, much more satisfactorily, by adding dilute acetic acid (XXIII. 24 b, 25 g). On viewing it from above, it appears like a round hyaline cell, containing a granular nuclear mass in its centre, and Surrounded by a rather condensed layer of the medullary matter. On its entire detachment, by means of the acid, it is seen to possess a distinct wall, having a double out- line; its nucleolus, on the contrary, seems undefined and irregular in shape, composed of a mere heap of fine granules. The relative size of the nucleus to the whole animal is very considerable. Thus, whilst the majority of spe- cimens had a diameter of 1–38 to 1–35", the nucleus measured 1–1.25", and its nucleolus 1-250". From his account of Act. Eichornii, Stein would appear to have seen a similar nucleus in that species; for he states that the round nucleus appeared like a nucleus—holding cell, having a double contour and clearly-defined wall, and containing a large, finely-granular nucleolus. ENCYSTING AND REPRODUCTIVE PROCESSES OF ACTINOPHRYINA :—ENCYSTING— FISSION.—GEMMATION.—EMIBRYOS—CONJUGATION.—Stein represents his Acti- nophrys Sol and Podophrya fiva as having a double integument (XXIII. 1, 3), through which the tentacles penetrate, whilst, as we have seen, other ob- servers insist upon the naked state of the muco-gelatinous body of those as well as of the other species of Actinophryina. The questions therefore arise, whether the being so named and described by Stein is identical with that in- tended by other naturalists, and, if so, whether it is not, in the so-called encysted condition, at least in its earlier stage. For Stein subsequently describes and figures truly encysted examples, in which the cyst appears like a plicated loose sac around the contracted body, and the tentacles in part or wholly gone (XVIII. 3). Cienkowski affirms (op. cit. p. 101) that the being described as Actinophrys by Ehrenberg is really a non-pedunculate Acineta ; and he further remarks that, although numerous points of relation exist between certain Acineta-forms and Podophrya fiva, he is unable to determine whether they should be regarded as identical, or as the extreme links in the morphological cycle of one and the same species. The same critical observer details the process of encysting of Podophrya, a process, by the way, which he has not met with in Acimeta-form organisms having a general resemblance with it. To quote his account (op. cit. p. 99), “If Podophrya are allowed to remain several days upon the object-glass, and care is taken not to let the Water dry up, every stage towards the quiescent condition—that is to say, towards the ‘encysting '—may be followed (XXIII. 34, 36, 37). “In Podophrya this process takes place in the following manner:—On the surface of the body a gelatinous mucous layer appears to be secreted, through which the tentacles pass. The tentacles disappear in the neighbourhood of the peduncle; and the gelatinous layer in this situation hardens into a loose transversely-plicated membrane, whilst at the upper end it is still soft, and the tentacles clearly visible. Ultimately these also are retracted, and the entire body of the Podophrya is enveloped in a wide loose membrane; the plications are caused by parallel annular constrictions, placed at equal di- stances apart, and separated by circular, angular, or rounded ridges; these pli- cations are in a plane perpendicular to the peduncle. At the summit of the Podophrya, and often also at the base, the membrane presents deep depres– sions; the inclosed body of the Podophrya acquires on its surface a sharply- defined smooth membrane, whilst the contents of the body become somewhat opaque, enclosing a round clear space. The Podophrya-cyst thus formed is supported by a peduncle, which is widened at the base. In many instances 254 GENERAL EIISTORY OF THE INFUSORIA. in which the membrane was not plicated, but loosely enclosed the Podophrya like a sac, I noticed that the peduncle of the cyst was continued uninterrupt— edly into the membrane, of which consequently it must be regarded as a pro- trusion, and that it had no connexion whatever with the original slender pe— duncle of the Podophrya itself. In fact, I noticed cysts in which this original slender peduncle was appended to the Saccular envelope. I am unable, there- fore, to adopt Stein’s view that the Podophrya are enclosed in a membrane, of which the slender peduncle is simply a tubular protrusion. This is true only with respect to the short peduncle of the encysted Podophryae. “What afterwards becomes of the cysts I have been unable, in spite of ob- servations continued for months, to determine.” Multiplication by Spontaneous Division seems now to be sufficiently de- monstrated. Ehrenberg and other earlier writers, indeed, mentioned the occurrence of self-fission; but their accounts were too uncertain and inde- finite, and strong doubts prevailed whether they had actually witnessed that process, or the act of conjugation, to be presently noticed. Mr. Brightwell appears (Fawna Infusoria of Norfolk) to have confounded the two processes; for he says—“They multiply by division, so that two and sometimes three individuals are seen adhering together by their outer edge—the middle one, the parent, being the largest,”—an explanation inconsistent with the process of fission as generally understood. Claparède states distinctly that he has seen the act of fission; Weston describes it in Actinophrys, and Cienkowsky in Podophrya. “With regard to the reproduction of Actinophrys Sol,” writes Mr. Watson (op. cit. p. 119), “I can positively affirm that self-division is one mode; for I may say I have witnessed it a hundred times and shown it to others. . . . First was noticed a deep depression above and below, riot far from the centre of the body; this, as it increased, threw the tentacles across each other, in a manner similar to that described by Kölliker, when in the act of inclosing an object of prey. This crossing, however, in the act of self- division would appear to be only the necessary consequence of the depressions alluded to, and the position into which the outer membrane (in which the tentacles are inserted) is drawn. As division proceeded (XXIII. 31), the two animalcules steadily, but rather quickly, increased the distance between them, until the connecting medium was apparently a long membranous neck, which, to my unpractised eye, appeared composed first of four, then of three, then two irregular lines of cells (possessing no nuclei), which ultimately di- minished into a single cord composed of three simple cells elongated like the links of a chain, this becoming gradually more attenuated, until the exact moment of its division could not be seen. All this latter portion of the pro- cess was rather rapidly performed,—that is, from the first formation of the rows of cells to the time of what I supposed to be the final separation, occupied only about a quarter of an hour. . . . During the whole of the process, the valve (i. e. the expanding and contracting Superficial vacuole) of each segment, situ- ated at nearly opposite extremes, was in constant action, and each creature was busily employed seizing its food.” On following one segment after its separation, “a floating faint line, the broken thread” (of connexion), extended from it; and two of the cells,formerly contained within this bond, were attached to its side, but were in a few minutes drawn into the body of the Actinophrys, which there assumed a perfectly normal character. In Podophrya the process of fission is similar (XXIII. 34); at first an annular constriction displays it- self, and so rapidly deepens, that in an about half-an-hour complete trans- verse fission is effected. The history of the segments is thus portrayed by Cienkowsky (op. cit, p. 98), about ten minutes after the commencement of the act of division:—“The upper segment had assumed an elongated form, was more OF TEIE PROTOZOA.—ACTINOPHRYINA. 255 cylindrical, a little indented in the middle, and rounded at each end; and at the extremities, slight oscillations to the right and left could be perceived. A transverse, and frequently curved, nucleus was visible in the fluid contents; and a lateral contractile space could be clearly distinguished in the upper parts. The vibrations increased in frequency and force until the segment became wholly detached and escaped. During the process of division both segments were furnished with tentacles; but when the oscillations of the cylindrical portion commenced, very fine and short cilia might be seen, though with difficulty, vibrating on the free end,-the tentacles at the same time being retracted, and remaining visible only on the posterior segment. Inow followed uninterruptedly the movements of the liberated segments. They moved for the most part in curved lines, in the course of which the motile segment appeared to seek the illuminated side of the drop of water. Cilia could not be perceived over the whole surface. The contractile space during the movements was al- ways in front. The motions were rapid, but still such as to allow of their being followed with a magnifying power of 370 diam. After waiting patiently for twenty minutes, I saw the motion cease; and at the same time short tentacles made their appearance, which were protruded more and more ; and in a few minutes afterwards the segment regained the spherical form ; thus, after moving about freely for a time, it was again transformed into a Podophrya. “This process of division was witnessed by other observers. It takes place more especially when sufficient nutriment is supplied by numerous Stylomy- chice to the Podophrya. The Podophrya does not always divide into two equal halves; the segments are more frequently unequal. After repeated division, the specimens always become more transparent.” This temporary production of vibratile cilia from the surface of one of the Actinophryina, in connexion with the process of fission, is a phenomenon so opposed to received motions, that it will necessarily be admitted with great reserve until confirmed by repeated observation. The process of Gemmation is recorded by Lachmann to occur in Dendrosoma 'radians, a being of which we know too little to pronounce with certainty if it be one of the Actinophryina or of the Acinetina. He says (op. cit. p. 231)— “In Dendrosoma radians, Ehr., a branch of the nucleus grows into the bud whilst it still remains united to the parent animal.” Reproduction by Embryos or Germs has been presumed by several autho- rities. Stein, in pursuing the history of the organisms he identified with Actinophrys Sol and Podophrya fiva, satisfied himself of the successive development in their interior of a ciliated germ, which he compared to the gemma of a Vorticella, into which, indeed, he supposed it subsequently to fully unfold itself (XXIII. 2, 4, 5). However, as before noted, Cienkowsky rejects the beings observed by Stein from Actinophryina, and treats them as Acimetina; yet he, at the same time, confirms the production of ciliated motile embryos within Acineta, but declares them reconverted into similar Podophrya to those that give birth to them. Apart from the researches of Stein, which have invoked so much attention to the development of Protozoa generally, and particularly to that of Actinophryina and Acinetina, the idea that the members of the former family probably reproduce themselves by germs has been suggested by the occurrence of very minute individuals, either alone or in clusters. Thus Kölliker remarks (op. cit. p. 34) that the smallest individuals of Actinophrys Sol measured only 0:01" to 0.02", and presented very inconspicuous and few granules, and that the granular and vesicular corpuscles within the nuclear portion of the body may be germs just beginning to be evolved. Mr. Weston is also led to believe in the internal generation of minute germs; but the observation he records, as 256 GENERAL EIISTORY OF TEIE INFUSORIA. possibly an instance of such a process, entirely fails, in our opinion, to sus- tain the supposition. The occurrence alluded to was that of a thin, pellicular, irregularly-shaped Sac—sometimes of two or three such,--which elevated itself above the surface of the Actinophrys, and presently burst, emitting some fluid and fine granular matter, and then contracted. “Does this emitted fluid,” he asks, “ contain the germ of future generations?” We think not ; for, to our mind, the phenomenon witnessed was nothing more than the bursting of Superficial vacuola, probably acting as excrementory media; and if this view be not correct, Mr. Weston’s is improbable, inasmuch as such a discharge of germs from Superficial sacs is without parallel in the history of Protozoa. CoNJUGATION.—The remarkable act of conjugation, also known as Zygosis, has attracted very much attention in the class of animalcules under consi– deration, among which it is of very frequent occurrence. Much discussion has taken place concerning the purpose of this process. Most of its early observers considered it a reproductive act, a sort of copulation between two individuals; but the tendency of opinion at the present day is to deny it this nature, and to treat it as little more than an accidental phenomenon, without apparent object or aim. Nevertheless its occurrence is so frequent, and the process of so complete a character, that it is hard to believe it to be in vain and to no purpose in the economy of the Actinophryina. A difference of opinion likewise prevails as to the nature of the process, one set of authors maintaining that there is an actual fusion and intermingling of substance between the conjugating animals, whilst another party asserts that there is no fusion, but merely a temporary adhesion or accretion between their bodies. The determination of this question is very necessary before we can speculate fairly respecting the purpose of the act. Kölliker, who was among the first to carefully explore this phenomenon, described it as a process of complete fusion, and surmised it to be of a reproductive character. Stein speaks at one place of conjugation (op. cit. p. 148) in Actinophrys and Podophrya as consisting in a fusion (Verschmelzung) of the animalcule. At another (p. 160) he describes it as an organic union of two or more individuals into a group, involving no fusion of their contents, but only a cohesion by their surfaces; and goes on to say (p. 161) that the coming together of two Actinophrides is due to external forces, and that the first thing observed is an entangling together of their tentacles, which act precisely in the same manner as when a foreign body is seized upon, and by their contraction bring the bodies into apposition. At the same time they fuse together and form a sort of commis- Sure, which is sometimes areolated, owing to interruptions to its continuity by the incomplete confluence of the tentacles. In the case of Act. oculata, several—as many as Seven—individuals were seen by Stein connected toge- ther, in a line, by this intermediate commissural matter, which he calls a common mantle, but all of them preserving their individuality, just as in the instance of other species. This mode of connexion, by means of an interposed matter derived from the tentacula of the conjoined surfaces, explains what Stein means by conjugation being a fusion of the animalcules concerned—not a fusion or commingling of their substance in general, as Some have thought it. ſohn, in his account of the conjugation of Actinophrys (Zeitschr. Band iii. p. 66), noticed the connecting band or commissure to sometimes contain, besides granules, particles of food, and vacuola, a vesicular body which he presumed to be nuclear, or a germ, developed as a consequence of the zygosis in operation. Stein encountered once or oftener a similar body, but concluded that it was accidental, probably of vegetable origin, and not in any degree embryonic ; and (p. 164) he expresses himself satisfied that this act of con- OF THE PROTOZOA.— ACTINOPEIRYINA. 257 jugation is not associated with the reproductive faculty. In fact, he has never met with the development of an embryo in conjugated individuals of his (Acinetiform) Actinophrys and Podophrya. Claparède questions (op. cit. p. 286) whether the compound forms noted by Stein and Perty were, as they supposed, all derived from conjugation; and he proceeds to say that, if it be proved that more than two individuals may thus be fused together, the connexion of conjugation with reproduction will become exceedingly doubtful, and that the term had better be dropped, and either Stein’s phrase “process of fusion,” or Ehrenberg’s word “zygosis,” adopted in its room. Whatever value attaches to Claparède’s deduction from the circumstance of more than two being fused together, there can be no doubt that this may, and indeed does frequently, happen. Lieberkühn, one of the most recent investigators of this group of beings (Zeitschr. 1856, 308), recognizes the occurrence, and observes that the number united may be estimated by that of the contractile vesicles. The process, he further asserts, is not one of genuine conjugation, but merely a temporary cohesion ; for, after watching a group for six hours, he saw the separation of the several component individuals, preceded by a narrowing of the connecting bands or commissures. Such is an outline of the opinions and statements of some leading naturalists respecting the nature and design of this so-called act of conjugation. The balance of authority and evidence is against the supposition of its reproductive purpose; but when this view is rejected, we have no other to replace it, and are sensible of the want of sufficient data from direct observation before a hopeful attempt can be made. Ehrenberg, it should not be omitted to state (Momatsb. Berl. Akad. April 1854), started the notion that conjugation is intended as a means of invigo– rating the species: “a curious idea,” says Claparède (op. cit. p. 286), “and not very reconcileable with the ordinary laws of nature.” Kölliker (op. cit, p. 100) canvassed the question, if Actinophryina, along with Rhizopoda, are to be considered cells, and, after an elaborate examina– tion of the point, concluded that they must be regarded as peculiarly modified simple cells. Claparède, after weighing Kölliker’s arguments and reviewing the structural peculiarities of these animalcules, comes to the opposite conclu- sion, viz. that, “as regards Actinophrys Sol in particular, we must either drop the class of unicellular animals altogether, or refer this animal to some other place.” We do not deem it at all necessary here to enter upon this con- troversy; it has already engaged our attention in other places, and has of late lost much of its interest by the extended modifications introduced latterly in that particular hypothesis of cell–nature, which, at the date of Kölliker’s paper in 1849, exerted so powerful an influence over the histological specu- lations of all the writers of that period. LOCALITIES.—Actinophryina are inhabitants both of fresh and salt water. They occur often as parasites upon the larger Protozoa, such as Stylonychia, and on various Small animals of other classes, and seem to draw nourishment from them. They are also common among the filaments of Conferva and the stalks of Lemma, where other animalcules congregate. Another locality is amid the vegetable débris and minute animals which often float together, as a dust-like film, on the surface of ponds. ! AFFINITIES OF ACTINOPERYINA.—All recent writers refer this group of beings to the Rhizopoda, except Siebold, who curiously enough retains Actinophrys in the family Enchelia, along with Leucophrys and Prorodon, two genera of Ciliata of quite a different type of organization. Although the preceding sketch of the history of Actinophryina will afford ample evidence of many homologies with the Rhizopoda, yet it will equally display not a few differ- ential characters, sufficient, we believe, to separate them at least as a subclass. S 258 GENERAL EIISTORY OF TEIE INFUSORIA. The most striking points of divergence are the more definite and constant figure of Actinophryina, their peculiarly formed tentacula in lieu of ordinary variable processes, and, of minor moment, their greater immobility, and the operation of the tentacles in the introduction of food. Acineta was placed by Ehrenberg with Actinophrys in a family or order Acinetina; and most writers treat them as if the relation between these two families were actually so near. A closer attention will, however, prove that something more than a generic difference subsists, and that Acineta had better stand as the representative of another group, well named Acimetina, although more limited in its significa- tion than that so termed by Ehrenberg. The most tangible differences between Actinophryina and Acimetima are, that no food enters the substance of the body in the latter group, and that the body is covered with an integu- ment. The history of this division, as far as at present known, reveals yet other distinctions; for self-division has never been observed, whilst the pro- duction of motile ciliated embryos from the interior has been seen over and over again, without, as far as is known, an antecedent act of conjugation. It must likewise not be forgotton, that it is the Acinetina which, according to Stein’s hypothesis, constitute an intermediate phase of existence in the de- velopment of many Vorticellina. Indeed, could this naturalist’s supposition be proved, the existence of Acimetina as a class of independent beings would at once be sacrificed. Another affinity is discoverable with the Polycystina, both in the nature of the soft, muco-gelatinous mass, in the long, tentacular filaments, and in the currents of granules detected in the processes. This relation is best seen with some Acanthometra (vide Müller's paper, Monats- bericht, Berlin, April 1855). The Actinophryina are related to the Ciliata also by their sarcode, by the structure and action of the contractile vesicle, by the formation of alimentary vacuoles, and by the nature and composition of their granules. But, over and above these general resemblances, a more special affinity is manifested if Cienkowsky’s statement, that the fission produced is clothed with vibratile cilia, be correct. This degree of affinity must be ad- mitted in the case of the Acinetina which appear, as a rule, to generate ciliated embryos. Since the above history was written, Dr. Strethill Wright, of Edinburgh, has most kindly furnished us with notes on several Infusoria, among others of two new forms of Actinophryina, presenting great peculiarities in struc- ture. The account of these novel genera will be found in the second part of this work, in the Systematic History of the Actinophryina. SUBEAMILY ACINETINA. (Plates XXIII. 1–23; XXVI. 3, 4; XXX. 3, 4, 7, 8, 21–26.) The reasons for separating Acinetina from Actinophryina, with which they have generally been united, have been stated in the last chapter, where likewise the differential characters of the two groups, and the supposed part they play in the cycle of development of Vorticellina, have been examined. There remains therefore, to fill up the history of the Acimetina, nothing more than some further remarks on the various forms they assume, and on certain peculiarities in their structure. The form of Acinetae is subject to great variety. Pyriform and ovoid shapes are the most prevalent; but some are almost spherical, and others, again, nearly triangular (XXIII. 6, 7, 8, 15, 17, 22, 23). A lobulated anterior end is common; and then the tentacles are usually restricted to the lobules (6, 17, 18). These lobed forms have no such firm integument or capsule at all as OF THE PROTOZOA.—ACINETINA. 259 that seen in others; or the anterior lobed part is undefended by Such a cover- ing, except of a very delicate and yielding structure. Cienkowsky speaks of the Acineta he examined as naked without limitary membrane (XXIII. 40). Very frequently, on the other hand, the Acineta is entirely enclosed within a stout capsule. This capsule is readily discerned when, as frequently happens, the internal animal mass of the Acineta does not fill it ; or it may be brought into view by the application of diluted acetic acid or alcohol, either of which causes the shrinking of the contained body. In general the capsule appears to be a very thin, colourless, hyaline membrane; but after the action of acetic acid, Stein represents it to be, in the supposed Acineta of Opércularia Lichtensteinii, of considerable thickness (XXIII. 22, 23). This thickening is doubtless due to the action of the acid in causing the membrane to Swell out. With the exception of the so-called Actinophrys Sol of Stein, and the Dendrocometes, the Acimetina are attached by a stalk of varying length, more commonly very short, to the body on which they live (XXIII. 17, 18, 22; XXVI. 3, 4). This stalk or pedicle is a tubular prolongation backwards of the capsule itself, like which, it is hyaline and transparent. It is not articulated with the body of the Acineta, but expands more or less abruptly into the capsule, and has a proportionately greater or less infundibuliform figure. Occasionally the stem at the upper part has trans- verse rugae, and in a few instances exhibits a sort of longitudinal striae, par- ticularly near its junction with the body (XXIII.3, 4). Stein describes the stem of the supposed Acineta of Epistylis, to be solid like that of an Epistylis itself. Frequently the capsule is thrown into transverse folds, at times, of considerable depth. There is no aperture in it; but it is penetrated by the tentacles which rise from the contained organic being. The capsule, if in Some specimens of considerable firmness, would seem to be in others, even when thick, very yielding, so much so as to allow great variety in figure by the contractions of the contained body, as instanced by Stein in the Acimeta attributed to Opercularia Lichtensteinii. The tentacles of Acinetina have not the uniformity of structure seen in those of Actinophryina. In some Acinetoe they closely resemble those of Actinophrys, are long, gently tapering, and capitate; in others they form parallel tubular processes, dilated a little, or not at all, at the extremity, and either straight or slightly curved or undu- lated; in others, again, they rather resemble bristles, appear stiff, and taper to a sharp point. In the remarkable Acineta called Dendrocometes, the tentacular character is entirely lost, and a few most bizarre branched tubular processes spring from one to six points of the surface (XXX. 22, 23). Per- haps these processes are homologous with tentacles; yet, unlike them, they seem to be formed from the capsule of the animal, into which the granular Contents of the interior penetrate, as into hollow tubules prolonged from the surface of the organism. In certain Acinetina that approach Actinophrys in external characters, the tentacles are equally diffused over the body. In the large pyriform Acineta, assigned by Stein to Opercularia articulata, the short slender tubular pro- cesses appear chiefly marginal (XXX. 3, 4). The digitate Acineta is covered by long tapering and thick processes on its dorsal convex surface (XXIII. 21); and the Diademiform Acimeta has its long Setiform tentacles in twos and threes at considerable intervals, chiefly on the margin (XXIII. 15, 16). The Actinophryean Acineta of Epistylis plicatilis bears a bundle of long finely capitate tentacula on each of its four lobes (XVIII. 2); that of Vorticella nebulifera has two such bundles, whilst the triangular Acineta, with its tongue-like process (XXIII. 17, 18, 19), carries a large expanding pencil of shorter-obtuse tentacles upon each angle at its base. s 2 260 GENERAL EIISTORY OF THE INFUSORIA. The tentacula are moveable and retractile, the divergent bundles may be collected into parallel groups, and drawn inwards, with the protruding Sup- porting lobes, to a greater or less extent. Stein affirms that, in the first stage of development, Acimetae have no tentacula. - º - The body of an Acineta, within the capsule or external integument, con- sists of soft colourless sarcode, rich in granules, fat-corpuscles, and minute globules. It is enveloped by an elastic yielding membrane, which becomes most distinct when the body shrivels within the capacious cavity of the capsule (XXIII. 3, 6, 8). The body appears in some Acimetae capable of extending itself above the capsule, which must therefore be fissured in front, in the form of a tongue-like process (XXIII. 17, 18, 19). A finely granular and opaque nucleus is always distinguishable in the interior, usually near the centre. Its shape is very varied, and may be oval, ovoid, clavate, reniform, band-like, vermiform, or horse-shoe shaped (XXIII. 1, 6, 17, 22). In a few examples, e.g. of the supposed Acimeta of Opercularia, it is much and irregularly branched (XXX. 3, 4). The addition of dilute acetic acid is a ready and effectual means of bringing the nucleus to light, and of demon- strating its enclosing Sac ; and as it is more solid and compact than the contents around it, it may now and then be separated by crushing the Acineta. The nucleus is enveloped by its peculiar membrane; a fact which becomes evident in several cases by the apparent double line surrounding its gra- nular mass (XXIII. 6–22). In a few instances, moreover, Stein has de- scribed a contractile space within the nucleus, e.g. in that of Opercularia berberina. Not unfrequently the nucleus looks as if double, or as sending off a process from itself; a critical examination of such specimens has convinced Stein that the offshoot is the commencing development of the germ or embryo of the Acineta (XXIII. 7, 8, 19). This he has proved by watching the nucleus through all its intermediate stages, from a simple ovoid or elongated figure until the embryo has grown and separated itself from it prior to its escape from the Acimeta. The nuclear appendix, when separated, is found to have an enclosing membrane, which ultimately surrounds the embryo like a sac, and admits of a certain degree of movement within it (XXIII. 4, 5). Another distinct organ of Acinetina is the contractile vesicle. Usually one only is present; but in some instances two, and more rarely three or more, make their appearance (XXIII. 1, 5, 21). Near the external margin a series of clear vesicular or vacuolar spaces presents itself, as in the Diademiform Acineta (XXIII. 15, 16); such, however, present no rhythmical contractions, and cannot be regarded as true contractile sacs. The embryos developed from Acineta are likewise furnished with one, and occasionally with two, of those organs (XXIII. 2, 4, 5, 15, 27). Excepting the embryos or germs, no other special structures are seen amid the granular contents of Acimetina. Alimentary vacuoles and particles of food or other matters derived from with- out never make their appearance; for the body, even if not entirely enclosed within the shut Sac or capsule, is covered with an integument, and has no sign of a mouth for the admission of food. Yet Acineta generally have the power of nourishing themselves, by the medium of their tentacula, which appear to act as Suckers, drawing in by endosmosis the nutrient juices from the animalcules which get entangled by them. If Stein’s details be correct, some Acinetiform beings would appear to have no power of self-nutrition ; for their substance is described as gradually used up in the formation of germs, and this decrease to be followed by a shrinking or collapse of the capsule, but at a comparatively slower rate. This phe- momenon is illustrated by Stein in the Acineta ascribed to Vaginicola OF TEIE PROTOZOA.—ACINETINA, 261 crystallina, and in the so-called Acineta with the tongue-like process (XXIII. 17, 20). If this account be admitted, that certain Acineta display no power of Self- nutrition, and seem destined only to subserve, as mere media, the purposes of reproduction, an independent nature could scarcely be attributed to such beings, and their history would be entirely comprehended in that of the beings in whose cycle of development they might enter as one link. Lach- mann (A. N. H. 1857, xix. p. 222) has the following account of the mode in which Acinetina nourish themselves:—“Each ray” (tentacle) “is a sucking proboscis, and we soon see that a current of chyme-particles runs from the alimentary cavity of the captured Infusorium into the body of the Acineta, through the axis of the rays, which, after seizing the prey, have become shortened and thickened. In the body of the Acineta the chyme-particles still run at first in a slender row, but afterwards they collect in a drop, which although drops are also formed in the chyme of the Acineta by other suckers, Soon becomes amalgamated with these. When a considerable quantity of the chyme of the captured animal has passed over into the body of the Acineta, a remarkable change gradually takes place in its appearance: if it was previously pale, nearly transparent, and only very finely granulated, larger dark globules, resembling fat-drops, now make their appearance here and there ; and these Soon increase so that the body (which at the same time, of course, increases in thickness) acquires a coarsely-granular aspect, and becomes opaque. The globules or drops which make their appearance can only be formed in the body of the Acineta, as they are far larger than the chyme-particles which are seen flowing through the sucker. The animal whose contents are thus Sucked out, gradually collapses and dies; many become liquefied when only a little of the chyme is extracted from them, others still live for a long time; in large animals, such as Stylomychia Mytilus, Paramecium Aurelia, &c., the Sucking often continues for several hours.” ORIGIN AND DEVELOPMENT OF ACINETINA.—In our history of the development of Vorticellina, Stein’s hypothesis of the transformation of those highly-de- Veloped Ciliata into Acimetiform beings as a stage of existence necessary to their development by embryos, and of the reconversion of the embryos into Ciliata of the primitive type, is sufficiently enlarged upon. In the same chapter, moreover, Cienkowsky’s contradictory statement and observation are detailed, viz. that, though Acineta develope ciliated embryos, yet these embryos give origin to beings like those they issue from, and are not trans- formed into Vorticellina. According to this opinion, the Acinetina take a position as independent beings in the animal series. Stein determined, to his own Satisfaction, an Acinetiform phase in the following Vorticellina and Ophrydina:— Cothwºnia maritima. Spirochona gemmipara. Epistylis branchiophila. Vaginicola crystallina. Opércularia articulata. Vorticella microstoma. Opercularia berberina. Vorticella nebulifera. Opércularia Lichtensteinii. Zoothamnium affine. Ophrydium versatile. Carchestwm pygmaewm ? The description of the Acimetiform beings assigned to the species enume- rated is given in the Systematic History of the Acimetina, which will likewise afford a more complete idea of the structure and forms of this peculiar class of beings than the above general history itself. g 262 - GENERAL HISTORY OF TEUTE INFUSORIA. SUPPLEMENTARY FAMILIES OF PROTOZOA. A.—GREGARINIDA. THEIR GENERAL CHARACTERS, STRUCTURE, AND AFFINI- TIES.—The Gregarinida constitute one of the three groups into which several eminent naturalists subdivide the Protozoa ; they therefore claim from us a brief description. They are of the most simple structure; indeed, some writers place them below the Rhizopods in the animal series, because, unlike these, their simple type undergoes no further elaboration or developmental complication. They are parasites, living in the visceral cavities of other animals, and in their simple structure are comparable to a cell, or to the ovum of higher animals. Thus they consist of a homogeneous albuminous-like matter, with numerous granules of coarser and finer character and fat-like globules, enclosed within a membrane of more or less perfect structure, which in all essential points represents a cell-wall; besides, they have always one distinct central vesicular body or space containing one or more granules, and evidently of the nature of a nucleus. Of these parts, the general mass may be taken to resemble the yelk-matter, and the nucleus the germinal vesicle of an ovum. The enclosing membrane is very yielding, and admits of great and constantly fluctuating alterations of figure by the varying contractions and extensions of the internal contractile mass; but there is no such thing as the formation of pseudopodes, as happens among Rhizopoda. It is entire, without Orifice either in the shape of a mouth or anus; consequently no foreign particles are ever seen in the interior. Moreover, the Gregarinida contain no contractile vesicle, and have never been found to undergo either fission or gemmation. Their vital endowments are so slight, that their animality is at first sight doubtful; but, unlike vegetable organisms, their envelope contains no cellulose. The above brief account comprehends all that can be stated generally of the organization of these simple creatures, which, if above the Amoebaea in the possession of a more or less definite membrane, yet sink beneath them in not possessing a contractile vesicle. - Notwithstanding their simplicity of structure, they yet are truly animal organisms, enjoying an independent existence, manifesting the phenomena of motion, growth, nutrition, and reproduction, in the last of which they exhibit a peculiar cycle of changes. Moreover, there are various notable differences between the various Grega- rinida known, with respect to size, figure, to the activity of their functions, and to some minuter points of structure. Hence their division into genera and species. In size they vary from four or five lines (as in the genus Didymophrys) to a few thousandths of an inch. Of their figure, some are simply rounded or oval sacs, as in Monocystis; others constricted around the middle, e.g. Grega- rinida. Again, the majority have a Smooth, naked membrane, whilst others are armed with a ring of uncini at one extremity, like many Helminthidae. When two nuclei occur in a single animal, it probably betokens an act of reproduction. The encysting process is exhibited among the Gregarinida, in connexion, however, only with their reproductive processes, and has this pe— culiarity, that it does not occur to a single individual, but to two together, which become enclosed within the common cyst or capsule. In their progress to this union the two Gregarinae are seen first to approach, and then by mu- tual pressure to flatten, the opposed surfaces, so that the binate being acquires a globular form. The substance to form the cyst is in the meantime thrown out, of a soft gelatinous consistence, but gradually becomes condensed and contracted into a membranous-looking capsule. OF THE PROTOZOA.—GREGARINIDA, 263 . Stein stated that, on the completion of the act of apposition, an actual fusion of the contents of the two animals transpired, the opposed walls being previously removed by absorption. Other observers state, however, that there is no such removal of the external membranes, and that the reproductive processes in the interior of each being proceed without any real commingling of their contents, which is a subsequent and probably not a necessary event. This act, which, from its general resemblance to the zygosis of plants, is spoken of as one of conjugation, appears immediately concerned in the de- velopment of a multitude of germs within each Gregarina, by the general breaking up of the granular contents. Still, if Lieberkühn’s account be ad- mitted, this process of conjugation is not a necessary prelude to the develop- ment of the internal germs; for, according to it, this result may accrue in individuals which have never conjugated. The germs assume a rod- or spindle-shaped figure, which, from its re- semblance to the prevailing form of the Naviculae, has suggested for them the name of “Navicellae'' or “pseudo-Navicellae.” They consist of an external comparatively firm wall, enclosing a finely-granular gelatinous substance. When the “Navicellae º are sufficiently mature, the cyst of the Gregarinae bursts and sets them at large. Their future history, according to Lieberkühn’s researches, is, that the case of each pseudo-Navicella ruptures and gives exit to the soft contained matter, which at first much resembles a minute Amoeba, but gradually assumes, by progressive growth and the formation of a pellicle around it, the characters of a Gregarina. Between this mode of development of Gregarinida and that of the Ciliated Protozoa, Leuckart draws this distinction, that in the former it consists in the production of granular germs, in the latter of living embryos. But it may be questioned whether there is a positive difference in kind between these two results of the reproductive process, and whether, on the contrary, the Navicellae of the Gregarinida may not be considered as merely encysted em- bryos, homologous with those of Colpoda Cucullus among the Ciliata. The act of conjugation in the Gregarinida is not precisely like that occur- ring among the lower Algae, the leading difference being that in the former there is no commixture of the two approximated beings. In all essentials, indeed, conjugation in this family resembles that believed to happen in the Actinophryima. - There has been much dispute whether the Gregarinida are to be held in- dependent animals, or merely embryonic phases of others; the balance of authority is in favour of the former view. Kölliker and Leydig advocated the opinion that they are metamorphic stages of Angwillulae or Filarice, or a link in the series of development of the Helminthidae. The arguments adduced by Leydig are thus briefly stated (J. M. S. i. p. 208, and Müller's Archiv, 1851):—“In the intestine of a large species of Terebella he was enabled to observe the most distinct transition between Filaria-like Nematoid worms and Gregarinae. The forms of the latter, which he observed not once only, but many times, were—1. A Gregarina of from 0.02" to 0.04" long, which had the form of an elongated sac, rounded at one extremity, and sharp at the other. The contents were those usual in the Gregarince—a consistent fluid with a corpuscular substance, which did not occupy the pointed end, and im– bedded in this a clear vesicle with a nucleus. 2. A Gregariniform creature, of a spindle-shaped figure, closely resembling Gregarina Terebellae, Köhl. 3. A Gregarina, generally resembling the preceding, differing only in two particulars: the internal substance is arranged in longitudinal streaks; and the body, instead of being straight, is more or less curved at each end. 264 GENERAI, EIISTORY OF TEIF INFUSORIA. 4. The same form, but with the body more elongated, vermiform, and for the first time exhibiting motion. 5. A very pretty Nematoid worm, about 0:10" long, blunt at one end, sharp at the other; the contents in longitudinal streaks, as in the two preceding forms, but with the spaces between them wider. Its motions are very active.” This view of a metamorphosis being admitted, the question arises, do the Gregarinae become changed into Filariae 2 or is it that the Filaria-like worms are transformed into Gregarince 2 Although at first inclined to consider the former as the true state of the case, Leydig is now disposed to follow Heule and Bruch, and adopt the latter view ; otherwise it would seem impossible to account for the formation of the pseudo-Navicellae and “Psorospermia * within the “Gregarinae.” Rölliker has the following remarks on this subject (J. M. S. i. p. 212):— “Although the change of a Filaria into a Gregarina is not an impossible cir- cumstance, before we admit such a thing it is first necessary to inquire whe-. ther the facts stated may not be otherwise explained. It is by no means proved that the Angwillula-like animal noticed by Henle, and termed by Bruch Filaria, is really a Nematoid worm.” Kölliker is more inclined to regard it as an Infusorium allied to Opalina, Proteus, &c. If this be the case, there is nothing extraordinary in its transformation into a Gregarina, and finally into a Navicella-receptacle. “For many reasons,” says Stein (Zeitschr. iii. 1852), “the endeavour to show the Gregarinae to be larvae of higher animals, and especially to connect them with encysted Nematoid worms, appears to be a vain attempt. Thus, I am acquainted with Gregarince of such peculiar forms that one requires a very strong imagination to deduce them from Nematoidea, or to suppose they can pass into these. The encysted Nematoidea are always found in the cavity of the body of insects, never in their intestinal canal, where alone encysted Gregarinae are to be found.” Again, the cysts of the Nematoidea of insects are made up of nucleated cells, and are plainly a product of the vital activity of the insects, not the exudation of the enclosed worm, while the cysts of Gre- garinae are produced as an amorphous secretion from the animals themselves. “If, therefore, encysted Nematoidea change into Gregarinae, or vice versä, their cyst must undergo a metamorphosis which, perhaps, no one will assume, and of which no observer has seen anything.” - - Lieberkühn’s observations have gone far in showing that, under usual con– ditions at least, the Gregarinida are not converted into Filarice or any other form of Vermes, but that their germs, after a short-lived Amoebiform period, not amounting, however, to a true metamorphic stage, assume the characters of their parent. Thus the cycle of development of these beings appears com- plete ; the Saccular animal constructs, by a process of segmentation of its in- ternal Substance, a host of germs, which, after breaking loose from their parent and involving its destruction, emerge from their cases in a soft Amoe- biform condition, and soon acquire the mature Gregariniform condition. The Gregarinida exhibit a marked affinity with other Entozoa, particularly with the Trématoda and Opalinaea ; and, as before remarked, they are allied with the Amoebaea in the extreme simplicity of their structure. By the possession of a limiting membrane (not independent or separable, indeed), they stand between the mucilaginous fluctuating Amaebaea and the Ciliated Protozoa. Unlike the Amoebaea, they do not receive into their substance solid particles, —a circumstance explicable by their being covered by a somewhat resistant, hardened lamina or tegument, which necessarily impedes that peculiar intus- susception of solid matters witnessed in that family. As to habitat, the Gregarinida are parasites in the intestines of various In- OF TEIE PROTOZOA.—PSOROSPERMIA. 265 vertebrate animals—worms, mollusks, and insects, but have not been found in Wertebrata. - B.—PsorosPERMIA (Plate XXII. 37–41).-This is a small group of para- sitic animals, first observed by John Müller in 1841, closely related to the Gregarinida, of which, indeed, they might be included as members. Unlike the Gregarina, they live upon vertebrate animals, viz. upon many species of fish, about their skin, gills, and internal organs, several together enclosed within sacs. Leydig has more recently applied himself to the study of these minute parasites, and has given the results of his observations in Müller’s Archiv for 1851, of which an abstract appeared in the Journ. of Mic. Science, i. p. 206, which we shall here take the liberty of using, as sufficient for our pur- OSG :— pos: The Psorospermia are microscopical corpuscles of a peculiar kind, which may be generally characterized, in the full-grown condition, as rounded organisms, having a sharply-defined outline, with or without a tail-like ap- pendage. They are flattened and lenticular in figure, and one pole is usually acuminate ; and towards this pole several internal vesicles converge in a symmetrical manner. These creatures were discovered by John Müller in 1841 (Müll. Archiv, 1841, p. 477). He found in a young pike minute round cysts in the cellular tissue of the muscles of the eye, in the substance of the sclerotica, and between this and the chloroid coat. The contents of the cysts was a whitish substance, which, when examined microscopically, was found to consist of peculiar elements—the ‘ Psorospermia.’ [A detailed notice of these observations is given in the Microscop. Journal, vol. ii. p. 123, and in the Brit, and Foreign Med. Rev., January, 1842.] In the following year the same observer (Müller's Archiv, 1842, p. 193) discovered parasitic corpuscles in the swimming-bladder of a Gadus Callarias, which, although specifically distinct from the Psorospermia, approached very near to the latter in their organization. They resembled in general a Smooth ventricose Navicula, and consisted of two elongated cases applied to each other at the cavity, and with an elliptical outline and convex outer surface. They were in part free, in part enclosed in masses within a tunic. Similar cysts, containing Psorosper- mia, have been found by Leydig in several species of fish, and in all parts nearly of their bodies, and even in the blood contained in the heart and in the peritoneal cavity. “Some facts, however, observed by him, connected with this subject, which came under his notice in 1850, during some researches on the cartilaginous fishes, served to throw a more general light upon these mysterious forms. “In the gall-bladder of a Squatina Angelus there occurred in the bile, and in large quantity, peculiar forms of various organization, but which were manifestly developmental forms:–1. Rounded vesicles, consisting of a delicate membrane and a consistent fluid; the latter was of a yellow colour, and con- tained a multitude of also yellow granules. 2. Other vesicles presented, be- sides these, other elements of a new kind: in the middle of the granular contents were several perfectly transparent cellules; small vesicles had only One of these cellules, larger ones as many as six. 3. Other parent vesicles, again, exhibited, besides their membrane, a granular contents and secondary vesicles, containing Psorospermia, always one in each secondary vesicle. 4. In the latter form, finally, the secondary vesicle had attained a large size, and the Psorosperm floated in a spacious clear chamber, which occupied nearly the whole of the parent cyst. Besides these motionless cysts, there were nu- merous free Psorospermia in the bile. “He found, upon examination, very similar things in other fishes of the 266 ** GENERAL HISTORY OF THE INFUSORIA. same class, as in Spinaa, vulgaris, Scyllium Canicula, Torpedo Narke, and Raja Batis, in which the Psorospermia differed from the more usual form, in being grooved or ribbed. - “It was very remarkable that the above-described organisms were never met with in any other part or tissue of the body than the gall-bladder or biliary duct. “With respect to the nature of these bodies, Leydig is inclined to think that the cyst should be regarded as belonging to the family of the Gregarince, and that the Psorospermia must be looked upon as generically analogous to the pseudo-Navicellae which have been observed to be generated within the Gre- Cºº"???.C82. ga, The question next arises, as to the existence of similar Gregariniform or- ganisms producing Psorospermia in fresh-water fishes. Leydig thinks there is reason to suppose that the animalcule discovered by Valentin in the blood of Salmo Fario is a Gregarina. Moreover, John Müller and Leydig have ob- served two or three ecaudate Psorospermia in Leuciscus Dobwlst enclosed in a cyst,--whence it might be supposed that secondary cells may be developed within one of Walentin’s Haematozoa after it has been conveyed in the course of the circulation to one organ or another, in which cells Psorospermia may originate. With the growth of the latter, the granular contents of the Gre- garinae gradually disappear, which are thus transformed into cysts filled with Psorospermia. Such a cyst would then be equivalent to a Navicella-recep- tacle.” Prof. Huxley, in his Lectures on Natural History (Medical Times, 1856, xxxiii. p. 508) has the following account — “The Psorospermia are pyriform sacs, frequently provided with an elon- gated, filiform, motionless appendage, and containing two or four clear rounded bodies, attached side by side, within their smaller ends, and besides these, as Lieberkühn has lately pointed out, a rounded mass of plasma. Under fitting conditions, the Psorospermia burst, and the plasmatic mass emerges as an Amoebiform creature. The sacs in which the Psorospermiae are developed, on the other hand, can be traced back to Amoebiform masses full of granules; and it seems a legitimate conclusion, that the Psorospermia are the pseudo- Navicellae of an Amoebiform Gregarina or Gregarinoid Amoeba.” SUBSECTION II.—CILIATA. (Plates XXIV-XXXI.) According to the arrangement we have adopted (p. 200), the Ciliata, as a subsection of Protozoa, are divisible into two groups:–1. Of such as are mouthless; 2. Of those possessing a mouth. The former group constitute the Astoma, the latter the Stomatoda. In Ehrenberg’s system the Astoma were not recognized; for where he did not find a mouth in any ciliated Polygastrica, he nevertheless assumed its existence, Smpposing that from its minuteness, or some other cause, it merely escaped observation. This procedure was, indeed, rendered necessary by the hypothesis with which he set out, of their polygastric organization. It must be admitted, to Ehrenberg’s credit, that recent researches have proved him right in assigning a mouth, in by very far the largest number of Ciliated Protozoa, contrary to the assertions and opinions broached by many of the most eminent microscopists a few years since. Yet there is a limited number of mouthless Ciliata, independently of the peculiar family repre- sented by the genus Actinophrys, placed very erroneously in the family OF THE PROTOzoA.—CILIATA. 267 Enchelia by Ehrenberg, which must be separated not only from Stomatoda, but also from the Ciliata. This separation we have carried out, in consti- tuting the two groups Actinophryina and Acinetina, intermediate between Rhizopoda and Ciliata. Excluding these very remarkable creatures, the Ehrenbergian families comprehended in our history of Ciliata are the Peri- diniaca, Dinobryina, Vorticellina, Ophrydina, Enchelia, Colepina, Trachelina, Ophryocercina, Aspidiscina, Kolpodea, Oaytrichina, and Euplota. Among the Trachelina were enumerated those very simple parasitic beings which late observations have proved to be mouthless, and are referred chiefly to a genus Opalina. These we therefore abstract, and, treating Opalina as the type, have constituted a new family, Opalinaea, a member of the group Astoma. In connexion with this we have placed the very imperfectly known Peridiniaea, although some recent writers seem disposed to attribute to them the posses— sion of a mouth and digestive apparatus. The organization of the Dinobryina is, if possible, still less understood; and since we have no other descriptions of it than those supplied by Ehrenberg, we shall allow it to be mustered with the other ciliated families named in the large group of Stomatoda. GROUP A.—ASTOMA, ASTOMATOUS OR MoUTHLESS CILIATA. FAMILY I.–OPALINAEA. (Plate XXII, 46, 47.) GENERAL CHARACTERS AND FUNCTIONS.—This family, represented by the genus Opalina, consists of minute miscroscopical animalcules, moved by vibra- tile cilia distributed generally over the body, without mouth, of an oval or oblong compressed figure, living parasitic in the interior of larger animals, upon whose juices they nourish themselves. Their contents consist of a finely-granular substance, hollowed out into a small number of vesicular spaces, with no contractile power; extending through the centre is an elon- gated band—like (ligulate) nucleus, enclosed by a definite but delicate mem– brane, and composed of a homogeneous finely-granular substance. In two species, O. Planariarwm and O. ww.cinata (XXII. 46, 47), a large pulsating vascular canal is found; the latter species is also furnished with strong hooks, whereby it effects its attachment to the intestinal surface, from which it draws its nutriment. Propagation takes place by transverse self-division, and also, in the opinion of a few observers, by germs or embryos. The Opalinae are com— posed of sarcode enveloped by an integument, and rapidly undergo diffluence. In Several species the existence of a mouth has been surmised,—for instance, by Ehrenberg in Bursaria (Opalina) Ranarwm, and by Dujardin in Opalina Lumbrici. All doubt on this point may be always removed, Stein tells us (op. cit. p. 181), by using chemical reagents, such as alcohol, acetic acid, or weak solution of iodine, which destroy the fold, and prove no real opening to exist. If further proof were wanted, the constant absence of foreign particles in the interior might be adduced. This absence of a mouth affords evidence of the merely transitional nature of Opalinaea; for the same feature prevails in the case of embryos produced from the Acimetina, &c. The vesicles or, as Dujardin calls them, “vacuoles,” seen in greater or less number in all the Opalinaea, are irregularly disposed in the interior, and, according to this author and Stein, have no limiting membrane. However this may be, they remain clear and transparent when the rest of the contents are coloured by the bile of the animals the Opalinde inhabit. This fact, moreover, attests another, viz. that they cannot owe their formation to fluids received from without, but that it must depend on the peculiar properties of the contents themselves. The formation of vacuoles in Opalinae was adduced 268 GENERAL EIISTORY OF TEIE INFUSORIA. to disprove the origin of the alimentary globules in the Ciliata generally by the introduction of liquid from without; but it is to be remembered that in these two groups of organisms we have very different structural conditions, and that in the Ciliata the entrance of water mostly holding solid particles in suspension, through the oesophagus, and the moulding of it into a more or less spherical outline, are matters sufficiently proved by direct observation. We have stated above, that the vesicles are not contractile; Dujardin has, however, described those of Leucophrys striata as irregularly so. The cilia are disposed in longitudinal lines, and in some instances, where there are ridges or margins, present a greater length and thickness, as, for instance, upon the edges of the curved surface by which the O. Planariarwm adheres. The surface can throw itself into plaits or folds,--an occurrence, however, probably limited to animals in a diseased or dying state, as Perty remarks in speaking of Opalina Ranarum (op. cit. p. 156). The Opalinaea are not very active; they swim onwards, moving at the same time in an oscillating manner. The above account comprises all that can be stated of the Opalinaea gene- rally, since the differences in internal structure among the several reputed species are so great, that it constitutes, as Stein points out (op. cit. p. 182), a strong argument against the existence of the family as a group of inde- pendent beings. However, from the study of the peculiarities of the several members of the admitted genus Opalina, this author reduces them to three types, viz.:-1. The most common form of Opalina, represented by the Leucophrys striata of Dujardin, has an oblong body, marked by some 35 longi- tudinal granular striae, and contains a number of vacuoles varying according to external conditions, and a central band—like nucleus. This animalcule occurs in the interior of the common earth-worm (Lumbricus). Stein found them of different lengths from 1–60" to 1-14", and in all stages of the process of transverse fission. When placed in water, they become more active. . 2. The second form differs from the preceding by the irregular distension of the body when placed in water: a strong endosmotic currents sets in through the enclosing wall and raises it from its contents, so that these at length pro- duce the appearance of a smaller Opalina enclosed within a large one. Du- jardin has described this variety under the name of Leucophrys modulata. This Stein would unite with the first named, under the term of Opalina Lum- brici, which, indeed, Schultze applied to the same animalcule. 3. The third modification of Opalina might be treated as an independent species; for, notwithstanding a general resemblance, it has a striking peculiarity of its own, visible under a strong magnifying power (such as 100 diameters), in the shape of a single, strong, horny apparatus, placed near the anterior end on the flat abdominal surface of the animal (XXII. 47). From a short common base situated to the right of the median line, slightly curved, uncinate, pointed processes are given off, of which one is much longer and stronger than the other. To the left of this organ a fold or furrow occurs in the surface, which might be mistaken for the entrance to a mouth. The deve- lopment of this organ may be readily followed during self-division. It appears first as a horny protuberance close to the line of section (XXII. 47), which extends backwards into the base of the process, and forwards or up- wards into the two hooks. It is also worthy of notice, that generally a greater or less number of Solid oval nucleoli and short rod-like bodies make their appearance within the homogeneous substance of the nucleus. The Opalina Lumbrici of Dujardin is no other than the animalcule described, although its characters are incorrectly represented by that author, who, from his figure, OF TEII PROTOZOA.—OPALINAEA. 269 has evidently seen a specimen which has very recently completed the act of self-fission and not yet reacquired its rounded posterior extremity. The dark stripe shown at the fore part, and supposed to indicate a mouth, repre- sents the uncinate apparatus above described. Stein would call this form of Opalina the O. armata, and regard it as a further stage of development of his so-called O. Lumbrici. - This view is supported by the fact that he has never met with young individuals of O. armata; for all the specimens he encountered were of a nearly equal size, and larger than the largest of O. Lumbrici, in company with which young beings are very common. Thus O. armata attains a length of 1–12" to 1-9", and O. Lumbrici of not more than 1–14"; even the products of fission of the former are from 1-16" to 1-14". “If now it be considered that, excepting the horny process, not the least difference in structure exists between O. Lumbrici and O. armata, it is rem- dered very probable that the latter is merely a further stage of development of the former. If this be the case, a subsequent more considerable meta- morphosis of O. armata may be presumed, when it becomes transferred to a more favourable habitat, as happens when the worm it inhabits becomes the food of some other animal. I have not actually seen Opalina armata adhering to the surface of the intestine, for I have always found it amidst the undi- gested mineral and organic fragments which fill the alimentary canal of the earth-worm. Hence it is more likely that the adhesive organ is destined to subsequently fix the Opalind in a more permanent manner.” The long pulsating vessel seen in Opalina Planariarwm and in O. wheinata deserves particular notice, by reason of its peculiarity. Stein has described it in the first-named species, where it extends the entire length of the ani- malcule, as bounded by a definite, delicate, structureless membrane, and to be without the outlets Schultze imagined. It contains a clear liquid like water, which, by its rhythmical movements, it forces to and fro within it. On killing the animal with alcohol, the walls of the vessel are rendered very evident. It becomes divided through the centre in the act of self-fission, and is, in Stein’s opinion, not homologous with the contractile vesicles of the Ciliata. NUCLEUS. SELF-DIVISION. SUPPOSED EMIBRYo.—The nucleusis a very evident organ in all the Opalinaea, with the single exception of O. Ramarum, in which Stein has sought for it in vain among multitudes of specimens and by the aid of various reagents. In this same exceptional species it is also to be noted that he never witnessed the act of fission, yet Siebold (“Ueber Monostomum,” Wiegmann's Archiv, 1835) described, in an Opalina living as a parasite in the intestines of a frog, the existence of a number of small embryos within a cavity of the posterior extremity of the body: whether this animalcule, however, was the Opalina Ranarum does not appear; for the peculiar habitat does not by any means prove such to be the case. A contrast occurs in the Opalina Branchiarum, where the nucleus which lies in the axis of the body has the same figure as the entire being, and one- half its dimensions. Even among examples of the same species the position of the nucleus varies exceedingly. Simultaneously with the appearance of a constriction in the general figure, the nucleus shows signs of approaching fission; but ere this is manifested it assumes a central position (whatever may have been its previous one), so that each of the two future segments may acquire an equal section of it. Moreover, it would appear, in some cases at least, that the constriction and scission of the body advance more rapidly on one side than on the other of the animal. - According to Stein, the production recorded by Schultze (Beiträge zur Natur- 270 GENERAI, EIISTORY OF TEIE INFUSORIA. geschichte der Turbellarien, 1851, p. 67), of a granular germ-mass in Opalina Planariarwºn, at the posterior extremity of the animalcule, Was nothing more than the act of fission misconceived. The granular contents of the nucleus (says Stein) are finer or coarser in the animals irrespective of their size; and the supposed germinal masses, as the figure given shows, were merely the segments of the nucleus in process of division, and not illustrations of the ulterior development of that organ into other beings. Schultze witnessed this process but once, in a specimen he named Opalina polymorpha, but which was the same as the O. Planariarwm of Siebold and Stein. HABITATs, VITAL ENDOWMENTs, &c.—As stated before, the Opalinaea are pa- rasites of various animals, the most common of which are frogs, newts, and other Batrachia, earth-worms (Lumbrici), some shell-fish, as the Anodon and the common muscle (Mytilus edulis), and of Planarice and several Entozoa. They are found in the intestines in the earth-worm, in the rectum and bladder in the frog, among the cilia of the tongue of that reptile, or among those of the gills in the shell-fish, &c. As a memorandum touching the vital properties of Opalinaea, we may quote here an experiment made by Kölliker on the vitality and development of the spermatic filaments (J. M. S. 1855, p. 298):-‘‘The Opalinae move in a solu- tion of common salt of 1 per cent., and of phosphate of soda of the strength of from 5 to 10 per cent. In a solution of salt of 5 per cent., and of sugar of from 10 to 15 per cent., they shrink up and become quiescent, though reviving upon the addition of water. I have even succeeded in reviving the Opalinae after they had been treated with a solution of common salt in the proportion of one-tenth.” NATURE OF OPALINAEA.—The observations of microscopists in general concur to prove that these simple beings are not independent, but the mere embry- onic or transitional phases of other animals. This opinion was put forward by Schultze, and has been seconded by Agassiz, Stein, and others. Agassiz asserts (Silliman’s American Journal, 1853) that the deficient link in Steenstrup's history of the succession of alternate generations of Cercaria, and its metamorphosis into Distoma, is supplied by his discovery that a ge- nuine Opalina is hatched from the eggs of Distoma. Stein coincides also in considering them metamorphosed into Vermes, and states that Steenstrup has watched the transformation of Leucophrys anodonta (Ehr.) into an intestinal worm. He saw first that the cilia vanished, that they fixed themselves, and became by-and-by changed into oval motionless bodies, which continued to grow, and formed an internal space, within which a germinal mass was de- veloped, out of which Cercaria originated. AFFINITIES AND CLASSIFICATION OF OPALINAEA.—Upon this head the first point is to settle what genera and species are to be numbered with the Opali- maea. For our part we are disposed to place in this family all Ciliata which are mouthless, and which lead a parasitic life. As already noted, the absence of a mouth is indicative of an embryonic character, an indication strengthened, if not confirmed, by observation; consequently this group of beings is at best but provisional, Serving only the purposes of definition and nomenclature, until science shall be enabled to indicate the particular animals into whose cycle of life they severally enter. - Furthermore, we have seen that some reputed species are, in all probability, only different stages of existence of the same Opalina, for instance, the O. armata a more adult state of O. Lumbrici. And, again, the structural differ- ences between O. wheinata and O. Planariarwm (consisting in the possession of a singular pulsating vessel) and the rest of the group are so striking, that they can scarcely be rightly included in one genus. OF THE PROTOZOA.—OPALINAEA. 271 On turning to the systematic descriptions of various writers, we find much discrepancy in detail, and much difference in opinion, respecting both the species to be counted among Opalinaea and their generic distribution. The family Leucophryens' of Dujardin, and the Cobalina of Perty, severally include most of the species which we would reckon as Opalinaea. These, in Jºhrenberg’s system, were scattered through several genera, the majority, however, being comprised in his genus Bwrsaria. Stein points out three prin- cipal modifications of form, but is not prepared to constitute them into genera. In the classification adopted by the three first-named writers, the Opalinaea were accounted ordinary Ciliated Protozoa. Perty and Dujardin so far re- cognized their peculiarities as to erect them into a distinct family. Siebold went further, and, on account of the absence of a mouth, placed them, with Astasiaea and Peridiniaea, among the Astoma. We coincide with Siebold in thus more completely separating them from the stomatodous Ciliata than the other authors named, but at the same time look upon them as more nearly allied with Ciliata than with either Peridiniata or Astasiaea, and consequently prefer to treat the Opalinaea as a subgroup of those Protozoa. Neither the intimate structure, nor the developmental history of the Opa- linaea, is sufficiently well understood for them to be arranged in well-defined genera; nevertheless, as both Dujardin and Perty have each essayed a sy- stematic distribution, it behoves us to set their schemes before the reader. Dujardin divides the Lewcophryens into three genera, viz. Spathidium, Leucophrys, and Opalina. Besides these, he has other mouthless genera in his family Ploesconiens, viz. Diophrys and Coccudina, marine but not parasitic animalcules; also a genus Trochilia without distinct mouth, also marine in habit, located in the family Erviliens; and last, the genus Plagiotoma, among the Bursariens, parasitic in habit, and supposed to have a mouth situated at the bottom of a fossa, but which contained no foreign matters, and could not be fed artificially with colouring matter. Of these genera Coccudina, Dio- phrys, and Trochilia are imperfectly known, particularly the two last, and the absence of a mouth cannot be predicated of them with any certainty,+ whilst of the last named (Plagiotoma) the balance of evidence is against the existence of a mouth, and, as we shall see, this genus is a member of Perty's family Cobalina, and has, moreover, in Stein’s opinion, no claim to rank as a distinct genus. The parasitic family Cobalina, Perty, comprises the genera Alastor, Plagio- toma, Leucophrys, and Opalina. The characters of these several genera, placed by observers among the Opalinaea, or some parallel group, together with their mutual relations and differences, will be fully treated of in the systematic section of this work. FAMILY II.—PERIDINIAEA. (Plate X. 224–226; XXXI. 16–23.) This family, in Ehrenberg's classification, comprehended four genera, viz. Chaetotyphla, Chaetoglena, Peridinium, and Glenodinium; but, as Dujardin rightly judged, the two first genera belong rather to the Cryptomonadina, by being destitute of the ciliary furrow, the leading characteristic of the Peri- diniaca. Our description will therefore particularly apply to the two other genera, Peridinium and Glenodinium. The beings under consideration have received little attention from natu- ralists, and are still imperfectly understood. Indeed, we feel that no sufficient data are at hand whereon to ground an opinion relative to their true position, nature, and affinities. We place them here as a supplementary group of 272 GENERAL EIISTORY OF THE INFUSORIA. Ciliated Protozoa, first, because of their wreath or general clothing of cilia—a phenomenon seen among none of the Phytozoa or Flagellata, which have never more than one or two, or, rarely, four filaments or flabella ; and secondly, be- cause every author who has described them treats them as animalcules. Perty, although recognizing them as animals, nevertheless groups them with his Phytozoidia, probably owing to their bizarre form and to the characteristic internal organization of Ciliata not being perceptible. Siebold, on the con- trary, places them, together with Euglenaea and Opalinaea, among the asto- matous or mouthless Protozoa. Ehrenberg's description of the Peridinicea is as follows:—The animalcules of this family are polygastric, but have no alimentary canal; the mouth is usually found in a depression near the middle, and from its vicinity a delicate filament (proboscis) is given off in three of the genera. They are clothed with a shell or lorica, having a transverse furrow or Zone occupied with a row of vibratile cilia; and besides this Wreath, several species have also fine setae or cilia scattered over them. In Peridinium acuminatum, P. fulvum, and P. (Ceratium) cornutum the digestive sacs are visible without recourse to artificial means; but in P. Pulviscwlus and P. cinctum, those organs can be demonstrated only by the use of coloured food, chiefly because they are hidden by the clusters of ova, to which the colour of the animalcules is due. This is com— monly red, yellow, or brown, and rarely green. In Peridinium Tripos and P. Fusus a seminal gland (nucleus) is visible, and in Chaetoglena and Glenodinium a red eye-speck. Longitudinal Self-division has been observed in P. Pulvisculus and P. Fusus. Dujardin, unable to accept these views of their organization, described the * Peridiniens’ as “animals without known internal organs, enveloped by a definite resistant membranous lorica, which sends off a flagelliform filament, and has, in addition, one or more furrows beset with vibratile cilia. The lorica would appear to have no orifice, since foreign particles and colouring matters cannot enter it. . . . The members of this family are distinguished from Thecamomadina by the ciliated furrow or furrows.” Further, Dujardin ignored the red stigma as a generic distinction, and in this is followed by Perty. Ehrenberg created a subgenus of Peridinium for those species which have the lorica prolonged into horn-like processes, under the name of Cerativim. Both Dujardin and Perty retain this appellation, but would elevate the group comprehended under it to the rank of a genus. Let us now proceed with a résumé of the facts at present received respect- ing the organization and habits of the Peridiniaea. The lorica is double, consisting of an outer, more or less firm, non-contrac- tile layer, and an inner, homogeneous, hyaline membrane: usually a space occurs between the two coats; but in Glenodinium they are in close apposi- tion—a double contour, however, being perceptible. The inner layer may be taken to represent the primordial utricle; it immediately cnvelopes the contents, which consist of a homogeneous protoplasm, enclosing within itself numerous globules, granules, and vesicles. In the case of the smallest Peri- diniaca, such as P. Pulvisculus, P. momadicum, and P. Corpusculum, the di- stinctness of envelope from contents ceases, and when in a dying condition the whole figure undergoes a great variety of changes—a fact indicating a less perfect development of the lorica—and there is a rapid breaking up of the contents. In the larger species the outer tunic is more elaborated, and either displays a minute cellular or reticulate structure, or appears quite smooth and structureless, although firm and resistant (as in Glenodinium cinctum). A cellular lorica occurs in Cerativim, and also in various Peridinia, which Perty separates from the rest, under the name of Glenodinium, by reason of this OF TEIE PROTOZOA.—PERIDINIAEA. 273 structure. This external tunic is decomposable, although it resists destruc- tion much longer than the contained matters; and it is especially after a certain amount of change has proceeded, that its delicate retiform structure is more distinctly exhibited. The figure of Peridiniata is very various and bizarre : the simplest is that of a spheroid divided into two segments, equal or unequal in size, by a trans- verse ciliated furrow or Zone. In some instances one side is flatter and concave, and, according to Perty, presents a wide opening, or elongated fissure (XXXI. 16), from which the filament may sometimes be seen to proceed. Moreover, besides the transverse furrow, a secondis seen in some species to proceed from it at right angles, as far as the vertex of the anterior half-as, for example, in Dr. Allman's species Peridinium wberrimum (XXXI. 16, 18), and in P. fuscum and P. oculatum (Glenodinium cinctum, Ehr.). Indeed, in Glenodinium apæw- latum. Ehrenberg describes several subsidiary, shallower,hispid furrows branch- ing over the surface (X. 224–226), and in G. tabulatum a series of non-hispid lines or ridges. These last two forms recall in general features the pollen-cells or grains of the higher plants, and may, indeed, from the deficiency of a loco- motive filament, and from other exceptional characters, be considered doubtful members of the family Peridiniaca. An inequality of the two segments, as separated by the ciliary zone, is seen in Peridinium Corpusculum and P. mo– madicum, and in a less degree in P. oculatum (Glenodinium cinctum). The figure, however, is very curiously and materially altered by the production of tapering or horn-like processes, of a large diameter and great length relatively to the principal portion or body of the organism. These processes differ in number in different species, and give rise to very bizarre forms, departing widely from those of any Phytozoa or from any other ciliated Protozoa. The number of horns in Cerativm Fusus is two, and, being in the same line, produce the spindle-shaped figure of the entire being (X. 222, 223). In C. furca two occur in front and one of larger dimensions behind; the same is seen in P. Tripos (X. 219, 220), in which, however, the two anterior processes are curved,—whilst P. cornutum (Ceratium Hirundinella) has from two to three posteriorly, and one, usually curved, anteriorly. In Cerativm Michaelis (X. 221), again, we see three short processes project from the posterior half; and, lastly, in C. macroceras (Perty) three are represented behind, of which the central is much the longest and straightest, and in front one still longer but rather curved. The length of the horns compared with the body of the Ce– ratia affords, however, no specific character, inasmuch as it varies according to age and probably also other conditions. The vibratile cilia are usually con- fined to the groove surrounding the lorica, and to the direct continuations from it. Nevertheless Dr. Allman discovers in P. wberrimwm the whole sur- face sparsely covered with them; and Ehrenberg mentions the supplementary furrows of Glenodinium apiculatum as occupied with hispid hairs (X. 224– 226). The locomotive filament, which Ehrenberg failed in seeing in all even of his genus Peridinium, is usually of great length and tenuity, and, accord- ing to the great Berlin micrographer, proceeds from the neighbourhood of the mouth which he believed he detected in Peridinium Fusus in a hollow near the middle of the animalcule. Allman more definitely points out its situation as being near the junction of the transverse and vertical furrows in the species he has described (XXXL 16). Lastly, Perty states that Cerativm Hirundinella (C. cornutum, Ehr.), when swimming, stretches out the filament as if stiff, and that, although 24 times longer than the body, it may be easily overlooked, on account of its active swinging movement. It is apparently a production of the protoplasm, protruded externally through an aperture in the investing tunics. Opinion is divided respecting the existence of a mouth. Ehrenberg repre- T 274 GENERAL BIISTORY OF THE INFU SOI&IA. sented one, and also the possible admission of coloured food, but was contra- dicted by Dujardin, who denied both. Siebold reckons Peridiniata among mouthless Infusoria (Astoma). Perty mentions the fossa in the shell, but no aperture; and Allman remains silent on the matter. On the other hand, Lach- mann admits its presence, and thus discusses the mode of reception of food (A. N. H.1857, vol. xix. p. 220):—“From the point of insertion of the flagel- lum, on one side the large notch, in the upper part of the row of cilia, a clear canal passes into the body of the animal, and dilates at the extremity to form a cavity of variable diameter. The flagellum is often seen to contract rapidly into a spiral form, and apparently disappear; and not unfrequently we may then succeed in perceiving that it is jerked back into the above-mentioned cavity, from which it soon returns into its previous position. Now it cer- tainly appears worth while to see whether small particles of food are not carried into the cavity by this jerking in of the flagellum.” CoNTENTs.-These may be divided, as in the Euglence, into minute shapeless molecules, and globular corpuscles and vesicles with red stigma and nucleus. Sometimes the corpuscles are green, and resemble chlorophyll, but more fre- qnently they are red, yellow, or brown, or intermixtures of those colours. In the earliest stages, indeed, colour is absent, and, just as in Eugléndea, only minute moleculae are found interspersed in the colourless protoplasm. More- over, when a colour appears, it may not simply become more intense or darker by age, but chango to another tint belonging to the same series of colours. In younger specimens again, the contents more completely occupy the entire being, whilst frequently in old, and more especially in specimens withering or dying, they become contracted into a ball, placed either in the centre or more or less to one side (excentric). A swelling out of the external tunic, the disappearance of the red stigma, the vibratile cilia, and the filament accompany this shrinking of the cell-contents. The retrograde change in the contents is further manifested by the appearance of a large vesicle about the centre, or of several dispersed smaller ones at that or in other parts. Some at least of these vesicles are merely oil-drops, which, as Braun shows in his essay on Rejuvenescence, are the usual concomitants of a process of destructive assimilation. After the destruction of the cell-contents, the firm lorica remains like an empty shell, boldly displaying its sculpturing, and in many instances also a curved, apparently internal, stripe about the middle or to the right of it, which Perty presumes to be either the line of attachment of the contents or a fold. Among more constant structures, Dr. Allman describes a central nucleus— the organ probably alluded to by Ehrenberg under the name of an oval semi- nal gland, in Peridinium Thripos and P. Fusus. Allman describes the nucleus to be of an irregular oval form, quite colourless, and marked on the surface with curved striae (XXXI. 20); under pressure the envelope gives way, and the nucleus escapes with the other contents. A contractile vesicle has not hitherto been discovered. One or more large clear vacuoles may originate in the internal substance ; but such have not the pulsating power of definite vesicles. The red speck or stigma (XXXI. 16, 17) has no pretensions to the nature of a visual organ. It is not always present even in examples of the same species; or it is multiplied; and it is known also to disappear with advancing age. Again, Perty recounts the fact of the diffusion of the red colour of the speck throughout the whole contents, at times leaving a narrow ex- ternal ring which retains its green colour. This phenomenon was witnessed in a specimen of Glenodinium cinctum. In young individuals of Peridinium tabulatum, which are of a light-green colour and translucent, there is no trace of a red speck; yet Perty met with a collection of these beings of apparently OF TEIE PROTOZOA.—PERIDINIAEA. 275 smaller size than usual, yellow in colour, and not, like older animalcules, greenish-brown or brown, which had from 10 to 12 red vesicles or globules about the middle of the anterior segment, Still the general rule is that in very young individuals no stigma is present. The inconstancy of the presence of the red speck, even in mature specimens, its absence in very young, its dis- appearance in old ones, and the many irregularities, not only in its occurrence but also in size and number, are facts which sufficiently prove its worthless- ness as a generic or even as a specific distinction, and which declare against its assumed function of a visual organ in this as in other families of Protozoa. REPRODUCTION.—Longitudinal fission has been seen to take place in several species. Self-division, says Perty, presents many peculiarities among the Peridiniaea. In Ceratium Hirundinella, fission is longitudinal; it commences anteriorly close to and on the left side of the great horn (as the animalcule is viewed from above), and advances towards the posterior extremity. The pro- cess is not confined to the large specimens, but is equally enjoyed by the small. During the act of fission in Peridinium Pulvisculus, Perty noticed that before its completion the newly-formed segment continued to augment in size until it surpassed the original being, which underwent no enlargement. Dr. Allman noticed, in the species he examined (J. M. S. 1854, p. 25), that spontaneous division took place “parallel to the annular furrow ’’ (XXXI. 18), i. e. therefore transversely, “and in the unfurrowed hemisphere.” He also remarked the important fact, that this process appears to be invariably preceded by a division of the nucleus; and he had succeeded in isolating nuclei presenting almost every stage of transverse fission. But besides their reproduc- tion by fission, Perty adopts Ehrenberg's views and insists on their development from ova or ovules, which present themselves in the form of brown or green corpuscles in the interior. Peridinium tabulatum is often seen to be full of such, elliptic in figure, and as much as 1-150" in length, and which can be expelled by pressure from the animalcule. In P. Pulvisculus Perty met with specimens from 1-400" which were aggregated together in masses, and moved together. In P. Corpusculum, he asserts, development from ovules may be directly observed; and he gives figures of ovules set free, and of the young generated from them, which would seem the same structures with the addition of a cell-wall. The ovules, too, are large and very evident in Cerativrn corrºwtwm; and he regards the Small brown organisms which may be found in company with mature individuals at various times of the year, as the primitive stage of ge– neration of those ova before acquiring the perfect figure of Cerativm. In some specimens, indeed, he remarked the long filament peculiar to the species, and a red stigma in the posterior segment. The Smallest examples measured 1–200", and were at first elliptic; from this they changed to reniform, and became distinguished into an anterior and a posterior half. Their movement was ro– tatory or spiral, and quicker than in old individuals. On one occasion he saw small examples of Cerativm Hirwmdinella only 1–25", of the same figure as the large specimens, but completely colourless; at another time he encountered pale brownish-green individuals, with a beautiful red stigma, and the poste- rior lateral horns scarcely developed,—whilst in One instance the anterior cornu was completely formed, and the posterior extremity rounded. These examples, he observes, appear to be different structural phases through which the products generated from the ovules have to pass. The reproduction by ovules or internal germs has its parallel in Euglenaea; and, like as in this group, so in the family Peridinidea a quiescent, resting, or “still” stage appears to occur. Dr. Allman has put forward this fact most clearly. He writes (J.M. S. 1854, p. 24)—“Before death, and also when passing from a motile to a quiescent state, most likely preparatory to under- * T 2 276 GENERAL EIISTORY OF TELE INFUSORIA. going some important developmental change, the contents contract towards the centre; and then an external transparent and perfectly colourless vesicle becomes visible, while the flagellum and cilia disappear. The contracted contents present a very definite and general spherical boundary, and are evi- dently included in a distinct cell”—the primordial utricle. On a subsequent examination of the pond in which the species examined occurred in prodi- gious quantity, he found “immense masses” of the Peridinium “towards the bottom, where they appeared quite healthy, though presenting the condi- tion described above as characterizing the quiescent state of the animalcule.” Our imperfect information respecting the organization of the Peridiniata renders any arguments concerning their nature unsatisfactory and inconclu- sive. Perty, to whom we owe most of our knowledge respecting these crea- tures, agrees with Ehrenberg in assigning them an animal nature ; and we gather from the few remarks Dr. Allman has made, that this opinion has also the advantage of his support. Dujardin, we may add, treated the Peridinidea as animalcules. Of the opposite opinion, viz. that they are members of the vegetable kingdom, we know of no advocates, although some facts, such as the apparent absence of the known internal structure of the Ciliated Protozoa, the non-contractility of their bodies, the character, colour, and changes of their contents, might be adduced in its favour. However, the force of those presumed facts will be much lessened by the consideration that the internal organization of the Ciliata may yet be discovered in these organisms when they receive their due share of attention from microscopists, that even the ab- sence of a mouth and rudimentary digestive tube would not absolutely exclude them from the animal kingdom; and that in the form and character of their ciliary armature they present an animal much more than a vegetable type. Of their WITAL ENDOWMENTS, we may state that some swim with consi– derable activity by means of their flagellum, aided, no doubt, by their ciliary wreath, which probably gives the oscillating and rolling character to their movements. They are inhabitants both of Salt and of still fresh water, among aquatic plants, but not of infusions; and they disappear from water when long kept. Most of the genus Peridinium are marine. They may occur in such enormous multitudes as to colour the pond or other collection of water in which they have accumulated. Of this phenomenon Dr. Allman mentions an example in which his Peridinium wberrimum was so abundant in the ponds of Phoenix Park, Dublin, as to colour the water brown :—“This colour was sometimes uniformly diffused through the water; at other times it appeared as dense clouds varying from a few square yards to upwards of a hundred in extent.” This was in June ; in July “the coloration of the ponds had much increased in intensity. . . . The colour in some parts was of so deep a brown, that a white disk half an inch in diameter became invisible when plunged to a depth of 3 to 6 inches, while a copious exit stream, which constantly flowed away from one of the ponds, presented the same deep-brown tint.” The most remarkable vital phenomenon presented by the Peridiniaca, and which is particularly common in them as a family, is that of phosphorescence, which is possessed in a high degree by several of the marine species, having a yellow or yellow-brown colour. In nine phosphorescent drops of sea-water from near Kiel, taken up one after another by Ehrenberg, nothing save a single individual of Peridinium (Cerativm) Tripos was discoverable. Besides this species, the following other Ceratia are phosphorescent, viz. Ceratium Fusus, C. acuminatum, C. Michaelis, and C. Furca. Ehrenberg has reported the occurrence of fossil Peridiniata ; but the or— ganisms so considered are peculiar in having a silicious shell, which renders OF THE PROTOZOA.—CILIATA. 277 their alliance to this family somewhat doubtful. They are met with in chalk, the only secondary stratum, and here in the substance of flints; but they also occur in strata of later formation. Their presence in flints renders it, indeed, supposable that their silicious constitution is an ulterior result of the infiltration of silex in a state of solution into the texture of their previously membranous envelope. They are found in company with fossil Pyazidicula and Xanthidia. Ehrenberg described two fossil species under the name of Ceratium pyrophorum and C. Delitiense. CILIATA. GROUP B.—STOMATODA. (Illustrated by Plates XXIV.-XXXI.) The animalcules whose general history we have now to write are, as before mentioned, comprehended for the most part in the families Dinobryina, Vorticellina, Ophrydina, Enchelia, Colepina, Trachelina, Ophryocercina, Aspi- discina, Kolpodea, Oaytrichina, and Euplota, as instituted by Ehrenberg, with the removal of the Opalinaea from the Trachelina, and of the Acinetina and Actinophryina from the Enchelia. - The descriptions of the beings composing these several families, as furnished by Ehrenberg, are so tinged by his peculiar views of Organization as to mar their utility; and therefore, for precision and accuracy of detail, we have to rely in great measure on the observations made within the last few years, chiefly by German naturalists. Notwithstanding the persevering industry with which these scientific men have pursued their inquiries, many genera yet remain almost unknown, or little understood, in respect to their structure, whether internal or external. The Ciliated Stomatoda, or as we shall more briefly style them the Ciliata, are microscopical animals having a definite limiting membrane or external tunic covered more or less completely with vibratile cilia, by which they swim ; and when it is indurated, as not unfrequently happens, it is further furnished with bristles or other tegumentary appendages, by which they are capable of crawling or leaping. They all possess a more or less di- stinct mouth, which opens into an Oesophagus or gullet, continued to a vari- able extent into the interior as a digestive or alimentary tube, but ending abruptly by an open extremity. In many genera a discharging orifice or anus is perceptible; and in all there are a nucleus and one or more contractile vesicles. They propagate by self-division, by gemmation, and by internal germs or embryos, with a greater or less degree of metamorphosis, and they undergo the encysting process: the act of gemmation appears limited to a few genera; but self-fission and embryonic development may be predicated as general phenomena. DIMENSIONS.—In dimensions all the Ciliata are microscopical; for if some, such as Spirostomum, Stentor, Opercularia, Zoothamnium, Vaginicola, and other genera of Volvocina and Ophrydina are visible to the naked eye as minute specks or globules, they are far beyond its ken for any purposes of investigation, and are therefore essentially objects for the microscope. Yet amid these hosts of equally microscopic beings, the range in point of size is actually as great as that between the dog and the elephant among animals cog- nizant to our ordinary observation. Even among members of the same genus, and, indeed, of the same species, their dimensions may vary within limits extremely wide. To quote a few examples: Spirostomum ambiguum (Ehr.) has a length of Tºth of an inch; the branching polyparies in Epistylis and Opercularia reach #th in height, those of Zoothamnium 4th, whilst many 278 GENERAL BIISTORY OF THE INFUSORTA, stalked Vorticellae extend themselves to Tºth in length. Paramecia are men- tioned by Ehrenberg from ºth to rºtºthin length; and specimens of the same species of Vorticella, viz. V. microstoma, are described to vary in size between gºrith and #pth. Stein has also noticed examples of Chilodon Cucullulus from #gth to rºoth. A most surprising magnitudeis attained by the polypoid masses of Ophrydium versatile, which range between mere microscopic globules and aggregated masses the size of the fist or even of the head of a man. FIGURE.-In figure the Ciliata exhibit an immense variety, but have a rounded outline in all instances. The prevailing figure is oval or oblong ; but some taper much at one or both ends, and acquire a spindle-, or a flask-, or a club-shaped aspect, whilst others, as the Vorticellina (XXVII. 1, 2, 4, 16; XXX. 1, 9, 11), present a bell-shaped or campanulate outline, and others again, as Spirostomum (XXIV. 298), an elongate ribbon- or band-like one. However, the best idea of the manifold forms can be gathered by inspecting the subjoined plates of the Ciliated Protozoa, which render verbal description unnecessary. The figure is determinate and constant under like phases of existence for each species, although liable in the majority to very great changes by the contraction and movements of the animalcules, by their contact with more solid bodies, and by the introduction of food. These changes are proportionate to the elasticity of the integument and to the contractile power of the contents; and hence, in several with firm integument, they are very limited, or not possible. The figure is also much modified by the processes of multiplication and of reproduction. The act of fission materially modifies it ; gemmation does so to a less extent; but the most remarkable change is caused by the encysting- process, which is generally a prelude to the peculiar set of phenomena attend- ing the reproduction by germs or embryos, and, according to Stein’s views, would seem to terminate in actual metamorphosis or transformation of the beings concerned. Indeed the Ciliata in general appear to pass through a cycle of changes, each of these entailing a distinct figure; in other words, in the history of each ciliated Infusorium, there are several phases of ex- istence, differing from one another in form and other particulars. The history of an animalcule, therefore, is comprehended in that of no one form or phase, but in that of every one it normally assumes; nevertheless it is necessary to fix upon one phase, either as the most important or the most perfect, and to characterize and name it, just as is done in the case of insects, which are described in their most developed or “imago” condition. - Another point to be remembered is, that the figure of a specimen appears different in most cases, according to the aspect in which it is viewed; and, again, there is often much diversity in shape between young beings and those arrived at maturity. Perty has applied the term ‘metabolia’ to express the changes of figure animalcules may assume. The figure is extremely varied in Lacrymaria by its movements, and chiefly by the lengthening or shorten– ing of its elongated anterior portion or neck. This variability of form struck Baker and other old observers so forcibly, that they applied the term Proteus to designate the animalcule (XXIV. 274, 275). Trachelocerca (XXIV. 317– 319) and Phialina have a similar power of varying their outline; and all three genera are further remarkable by the manner in which their surface can be thrown into transverse or even intersecting folds or plaits. The influence of food when swallowed in modifying the figure, Ehrenberg particularly illustrated in his Enchelys Farcimen (XXVIII. group 64). This animalcule devours others nearly as large as itself, and, to effect this, widely dilates its mouth, and so becomes shorter and broader; and as during the OF THE PROTOZOA.-CILIATA, 279 operation it continues to Swim about, its appearance with the half-Swallowed being is very curious. Again, when engulfed the anterior portion contracts, whilst the posterior becomes dilated, giving the Enchelys a flask-shaped outline. In descriptions of the Ciliata, authors have used various terms, applied to the segments or members of higher animals, to designate varieties in the form and in the mutual relation and position of their parts. The application of many of these terms to the Protozoa is indeed very arbitrary and fanciful; and it is only from the absence of better that we continue to employ them. The end of the body which advances foremost in swimming, and at which or near to which the mouth is ordinarily placed, is called the head, and often has an additional claim to the appellation by its construction as a segment distin- guished by some points of structure from the rest of the body. The opposite portion of the animal constitutes, when tapering or provided with some sort of process, the tail, but is more generally spoken of, especially when not distinguishable as a segment, as the posterior or caudal extremity. A ‘dorsum' or back, and a ‘venter’ or abdominal surface, are usually de- scribed, but are not readily determinable in all genera, as, for instance, in the Vorticellina and Ophrydina. To distinguish the one surface from the other, regard must be had to the position of the mouth (which indicates the abdo- minal Surface), to that of the locomotive cilia and other processes, and to the mode of progression. But, after all, the distinction will oftentimes be arbi- trary, and in consequence the description of a right and a left side frequently so too. It is a general character of the Ciliata, that they are asymmetrical, i. e. not formed of two equal and similar halves. An exception to this rule exists in Coleps (XXIV. 284) and in the Ichthydina (XXXI. 28–30), which in Ehrenberg's system were included with the Rotatoria. Where, although symmetry is not visible, a right and a left side are distinguishable, such Infu- soria are called ‘bilateral,”—e.g. the Oaytrichina (XXVIII. 10), Paramecium (XXIX. 25–30), Chilodon (XXIX. 48). Of minuter modifications in the figure of Protozoa, a large number have found names which will be best understood in the special structural details of particular animalcules. However, to mention some here used by Ehrenberg, we may cite the frontal region or forehead—the obtuse or truncate part of the head above the mouth ; the lips—projections above and below the mouth, when this aperture is situated in a fissure; the tongue or palate, usually a process in the oral fissure; the rotary or ciliary disk, seen as a ciliated pro- jectile process above the margin of the anterior extremity of the Vorticellina (XXX. 1, 2, 9, 11, 14). In several genera the anterior portion of the body is much produced, and looks like a long tubular neck or a trunk, and hence is called frequently by Ehrenberg proboscis, e.g. in the genera Lacrymaria (XXIV. 274, 275), Trachelius (XXIV. 287–289), Amphileptus, and Trache- locerca (XXIV. 317–320). This term proboscis we have already seen used to designate the long locomotive filaments or flabella of Phytozoa, totally different processes from those called by the same name in the Ciliata just enumerated. Its use for one or the other should be set aside; and although at the best it conveys a very erroneous impression—for no such thing as a proboscis or trunk, in the proper meaning of the word, has an existence in any of the Protozoa-its application to these is less objectionable than to the Phytozoa. In Uroleptus (XXV. 333) the posterior extremity is abruptly elongated, and forms, according to the description of the same distinguished naturalist, a tail. CONSISTENCE.-The Ciliata are composed principally of a very soft, almost mucilaginous matter, which has been well named ‘Sarcode,” since, like the flesh or muscular tissue of higher animals, it seems to present an inherent 280 GENERAL EIISTORY OF THE INIFUSORIA. contractility and elasticity, and is the active agent in the movements of their bodies. It is hyaline, transparent, and colourless; but its refractive power is not much greater than water, which is essential to the exhibition and continuance of its properties, for when this fails the homogeneous mass of sarcode breaks up into minute globular portions, which disperse themselves on every side. This disruptive process has received the appropriate name, from Dujardin, of diffluence.” Ecker states this self-same sarcode to be the common contractile element of all the lowest forms of animal life—for instance, of the Polypes. The par- ticles set free by diffluence,’ he also represents to be contractile, and to assume Amoeba-like movements; but this, according to Cohn and Stein, is an error, inasmuch as they are simply elastic. Cohn also adds that the variable movements of the sarcode-particles of Hydra are merely a physical phenomenon due to endosmosis. The process of diffluence, whether from external injurious conditions or damage, or from noxious matters received within, varies so much in rapidity, that Cohn (Zeitschr. 1851, iii. p. 267) con- cludes that it must indicate some variations in its composition and structure in different animalcules. For instance, he says, Stentor carwlews bursts; and its contents break down by diffluence as rapidly as Sugar in Water, streaming out from the rest until the funnel-like pharynx only is left behind. On the contrary, in other animalcules, e.g. Paramecium Awrelia, the Sarcode exudes through the surface at all points, and Swims away, leaving a vacuolated or areolated interior. Again, Loacodes breaks up into fragments of a considerable size, which escape through lacerations of the surface. INTEGUMENT. MARKINGS ON THE SURFACE. CoNDENSED INTEGUMENT OR LORICA. APPENDAGES OF INTEGUMENT. CILIA. SPINEs. EXTERNAL SHEATHs. —Ehrenberg described his Polygastrica as in all cases defended, and their figure defined, by an integument or skin, a statement as generally contra- dicted by Dujardin, though now confirmed (in the case of all the true Ciliated Protozoa) by the researches of numerous later naturalists. The means resorted to for its demonstration, where not otherwise evident, consistin the application of chemical agents—for example, of acetic acid, of tincture of iodine, and of diluted alcohol, all which operate in a different manner upon the integument and on the contents of the body, most frequently causing a separation of the two by corrugating the latter, and, it may be, colouring it at the same time. Perty could not convince himself of the existence of an epidermis, although he believed the external surface to be modified so far as to render it more resistant, or in fact to form what Mr. Carter calls a pellicle; at the same time he attributed marks or lines visible on the surface to fat- or other corpuscles subjacent to it. “The pellicula,” Mr. Carter says, “is a structureless pro- duct, which hardens after secretion; and the inference is that there is a layer below specially organized for its formation,” and that it is not secreted by the lamina known as the “cortical layer” or the “ diaphane.” On the other hand Meyen, Siebold, Kölliker, Frey, and Leuckart concur in describing a distinct enveloping delicate membrane, which Frey thought evidenced both by the manner in which an animalcule ruptures under pressure and gives vent to the soft contents, and by the appearance of little shreds he noticed on the torn edges of a Stentor. A more direct demonstration was afforded by Cohn, who resorted to chemical reagents for the purpose. This excellent observer experimented with several of the larger Ciliata, but for illustration referred chiefly to Loacodes (Paramecium) Bursaria. Stein argues that the animalcule so described by Cohn was not a Lowodes, but a Paramecium, since all its cilia were of equal length, a feature peculiar to this genus (Stein, op. cit. p. 239). On adding a little alcohol to a drop of water containing Ol' THE PROTOZOA.—CILIATA. 281 specimens of this animalcule, death ensued; but before this happened, a deli- cate membrane was seen to elevate itself at parts of the surface, producing a vesicular appearance, and accompanied by a shrinking of the contained matters; while these changes proceeded, several contiguous vesicles would run into one, and thus strip more or less completely the subjacent tissue, until, by the pro- longed action of the alcohol, a central shrunken mass appeared, Surrounded by a loose membrane, adherent to it only at the spot where the mouth was con- tinued inwards as a pharynx. This membrane, so demonstrated, is homoge- neous and transparent, but not entirely structureless; for close observation reveals, over its entire surface, two series of spirally-disposed, delicate, and closely-approximated lines, which so intersect one another as to produce a miniature diamond pattern (XXIX. 26). Further, the notched or serrated appearance of the periphéry (XXIX. 28, 29, 30) shows that these lines are actually folds or furrows, and that each little diamond may be represented as a minute four-sided pyramid bearing a cilium at its summit. By pursuing a similar plan of investigation, a separable integument has been demonstrated in many Ciliata. For instance, Stein described such a covering in the several genera he subjected to observation, and proves its ex- istence also after the process of encysting has taken place. On adding dilute acetic acid to the Vorticellina—for example, to specimens of Epistylis or Oper- cularia—the contents shrink into a denser mass, and in so doing detach them- selves from the integument, which is then rendered evident as a transparent, structureless, homogeneous, and smooth membrane, having a clear, sharp out- line. When tincture of iodine is applied, the integument remains uncoloured, whilst the contents acquire a golden-yellow tint. A solution of Sugar, and afterwards a drop of concentrated sulphuric acid, being used, causes the con- tents to swell up and to assume a rose-red colour, the extermal wall continuing uncoloured. - Respecting the chemical constitution of the membrane of Loa:0des, Cohn informs us it is soluble neither in sulphuric acid nor in potassa, whilst the con- tents are dissolved and dispersed by the latter. From this reaction he con- cludes that the cuticle is not a proteine compound, like animal membrane in general, but the substance called chitime, and therefore in this respect similar to the cuticle of plants. In Paramecium, he adds, an integument having the same sort of markings and a similar chemical reaction exists, and that, with- out doubt, all the species described by Dujardin as having a reticulated envelope, in his families • Bursariens’ and ‘Parameciens,’ have a like structure. Moreover, this skin has its special characters in different genera, as is illus- trated in the above account of Paramecium Bursaria, and may be exemplified in other cases. Thus in Coleps and Stentor polymorphus, the cuticle is so intersected by lines as to leave intermediate four-sided prisms, each of which bears a cilium at its apex, whilst at the intersection of the lines, single long hairs are also seen, similar, says Lachmann (A. W. H. 1857, xix. p. 125, in foot- note), to the hairs of many Turbellaria. Again, Ophrydium versatile has its integument thrown into fine, closely-aggregated, annular folds, and into three longitudinal rugae on one side (XXX. 5), which disappear when the animal shortens itself by contraction (XXX. 6). Spirochona (XXX. 17), says Stein (p. 208), has a hyaline, firm, inflexible parchment-like skin, with a distinct double outline, but without any inherent contractility. It is most like the integument of Euplotes, but differs apparently in not being capable of falling into folds around the body. It resists the action of acetic acid, which dis- solves out the whole of the living contents, and leaves it in an isolated state. Whilst representing all animalcules to be covered with an integument, Ehrenberg distinguished those enclosed by a firm, more or less unyielding, 282 GENERAL EIISTORY OF THE INFUSORIA. envelope or sheath, as ‘loricated,” in opposition to the rest, which he called ‘illoricated.’ These terms he has, however, employed in so loose a manner, that they really possess no definite and constant meaning. For example, the sheaths of encased animalcules represented by the Ophrydina are designated lorica”, the enclosed animal, although possessing a distinct integument, being considered naked,—while, again, the indurated closely-fitting integument of Euplotes and Coleps is equally styled a lorica, although so different in cha- racter and relations. The term lorica could only, indeed, be legitimately. employed either to designate the sheaths of such animalcules as the Ophry- dina, or the indurated integument of others, as Coleps, to one or the other, but not to both ; to the former it is unnecessary, to the latter it is admissible. The integument of the Ciliata has generally been regarded to be in itself contractile ; but it seems that this is an error, and that, in fact, it is simply elastic. As such, its action must be counter to that of the subjacent con- tractile layer, and be therefore the chief agent in restoring the figure when the contractile force is relaxed ; at the same time its elasticity will allow of considerable alterations in form, from contact and pressure of external more rigid objects. To this an exception occurs in the case of those Ciliated Pro- tozoa in which the integument is much hardened, and forms a lorica or shield. This induration may be more or less extensive, so as either to cover the dorsum with a shield-like plate (scutellum), as in Chlamidodon, or to entirely sur- round the animalcule, as in Coleps, when it constitutes an “urceolus,” open at the ends. The external envelope, when thus hardened, has developed from it various processes, of a more or less rigid character, which look like spines (setae) (XXIV. 284, 285), or hooks (uncini) (XXV, 344, 347), or are elongated as styles (XXXVIII. 10; XXV. 350, 351), all which are oftentimes made sub- servient to the act of locomotion, and less frequently to that of prehension also. It must, however, be admitted that such processes are not confined to genera in which the integument is very appreciably indurated, but occur where it is of softer consistency—for instance, in Stylonychia (XXV. 343, 344). The integument is combustible and also diffluent, even when indurated, just as are the softer contents, although more slowly. ExTERNAL SHEATHS OR CASES.–Before quitting the account of the common integument or cuticle immediately investing the body of the Ciliated Protozoa, a description of an homologous membrane, in fact, of a prolongation, dedu- plication, or process of it, in the form of an external sheath or case about certain fixed species, becomes necessary. The species so encased are either sessile or have only a short stalk attach- ing them to the bottom of the case; thus Vaginicola (XXVII. 10, 11) is stalkless or nearly So, whilst Tintinºvus has a more appreciable pedicle: on the other hand the case itself may be stalked, as in Cothurnia (XXX.12–16); where this happens, the stem does not equal the length of the sheath, but is short, solid, and thick, expanding upwards to its attachment with the base of the latter, and frequently thrown into transverse folds and curved (XXX. 12, 15). It is homologous with the rigid stem of Epistylis, which it resem- bles also in chemical characters. 4. A very remarkable exception to the general rule of the attachment of tunicated Vorticellina to the bottom of their case, occurs in the new genus Lagenophrys, in which the animalcule is suspended from the narrow aperture of the sheath, so as to leave a more or less considerable space around it (XXX. 29–34). The margin of the head of the animal, i. e. the peristom, is beneath the opening of the sheath, which has the further peculiarity of being very narrow and two-lipped (XXX. 29, 32, 34). In one species (L. massa) a OF THE PROTOZOA.—CDLIATA, 283 cylindrical short tube, with a serrate edge and longitudinally striated, is re- presented by Stein to project from the opening of the sheath. It is, he adds, separable above into two lips, which close when the animal retracts itself. It is not very unusual to meet with sheaths occupied by two animalcules, —a circumstance due to the act of self-division (XXVII. 10; XXVIII. 19). In a few instances also, one, two, or more small young individuals lie free within the sheath of the parent, e.g. Lagenophrys (XXX. 29, 34). The sheath is always a product secreted from the animalcule, and first makes its appearance around its base as a soft, homogeneous, colourless, jelly-like matter. During the process of its formation, the animal preserves a contracted State, which diminishes, however, as the excreted layer advances, and ceases on its completion ; and since each genus has a characteristic outline, as well in the contracted as in the expanded condition, the sheath acquires also its special character only. More or less of the posterior extremity is concerned in ex- creting the formative matter; but this having adhered to the anterior part whilst in a contracted state, becomes drawn forward by the progressive elongation of the entire body, until at length, on full expansion taking place, the connexion is broken and the sheath acquires a free edge. So soon as excreted, the gelatinous layer proceeds to Solidify, and simultaneously to contract itself in thickness, so as to form a membrane, which, on its subse- quent detachment from the fore part of the animal, forms a loosely-investing case around it. This description of the construction of the sheath applies to all those genera where the animal is fixed at the bottom ; but in the instance of Lagenophrys, where it is suspended from the constricted orifice of the case by its peristom, some other plan of formation must be presumed, concerning which, however, we have as yet, unfortunately, no direct observation to teach us. In several species, as Cothwrnia imberbis, the sheath not merely acquires a parchment-like firmness, but also a decided colour—mostly yellow at first, afterwards a rusty red. Dr. Strethill Wright, of Edinburgh, has kindly sent us some notes on the intimate structure of the sheath of Lagotia; and doubtless they hold good to a greater or less extent, so far as they represent general facts, in the case of sheaths of other Ophrydina. He writes—“The tube consists of yellowish chitine, lined with a layer of dark-green sarcode of varying thickness (which, I believe, secretes the chitine), and covered externally by a much thinner layer of matter, which appears to be equivalent to the ‘colletoderm ' of the Hydroidae.” This structure is illustrated by figs. 12 and 13, Pl. XXXI. The following account applies specially to the sheath of Lagotia (XXXI. 7, 8, 12, 13), which presents a series of rings, apparently spiral, but, in our opinion, not so. “The lines,” says Dr. Wright, “are seen to consist of the remains of the trumpet-shaped mouth, which is partially absorbed as the tube increases its length, but still remains as a slightly-overlapping ridge over the new part of the tube growing within it. The groove thus formed is filled up with the ‘ colletoderm.” The spiral character seems to be in some way connected with this mode of growth; but I have not satisfied myself in what way.” In a subsequent letter he writes—“The chitinous matter of each successive ring is not continuous with that of the rings above and below it; it is only at- tached to it by the inner lining of sarcode and by its outer covering (XXXI. 12, 13). We have by this condition a provision for the growth of the tube, both in width, length, and thickness, similar to that which occurs in the shell of Echinus. Growth in length may be effected by deposition of chitine on the upper and lower edge of each ring, growth in breadth by the gradual unrolling of the spiral, while a continuous deposition of hard matter from the inner lining of sarcode thickens and strengthens the whole tube.” 284 GENERAL HISTORY OF THIE IN FUSOTTA. In speaking of the attachment of the sheath, we have mentioned only that by the base, with or without a stalk. But there are a few forms which affix themselves to foreign bodies by one side of their sheath, e. g. Vaginicola decumbens (Ehr.) and the genus Lagenophrys. In such cases the attached side is flattened, so as to increase the surface in contact. But, apart from the mode of attachment, the sheaths of different genera vary in figure; and as to size, there is no constant relation between that of the case and that of the enclosed being. The figure of the sheath, even in one and the same species, is subject to modification from age and from surrounding circumstances. Thus, in Vaginicola crystallina it is usually cylindrical and truncate (XXVII. 11), but at times it may be bellied posteriorly (XXVII. 10), or, otherwise, have its anterior border expanded and curved outwards, or be narrowed in front, or compressed in one direction. Nevertheless there is usually a general resemblance in figure among individuals of the same species or genus, sufficient to furnish descriptive characters. For example, Cothurnia imberbis has commonly a cylindrical sheath, bellied posteriorly and slightly contracted anteriorly (XXX. 15), whilst C. Sieboldii is campanulate, and has its anterior half compressed in one direction, and its angles in front prolonged and tapering (XXX. 13, 14). In the genus Lagenophrys, when adherent by its flattened side, the sheath appears ovoid or shaped like a bellied oil-jar, with a contracted truncate mouth (XXX. 29, 30). A peculiar form of sheath is presented to us in the genus Lagotia (XXVIII. 21, 23), which may be de- scribed as retort-shaped, the relative diameter and longth of the body and neck differing in different specimens or species. In one species, at least, the neck has the further peculiarity of being thrown into spiral or, otherwise, annular folds or rings (XXXI. 7, 8), the presumed form and origin of which have just been described. We are further indebted to the discoverer of Lagotia for the recognition of a remarkable valvular structure within the tubular sheath of a species of Va- ginicola, which he in consequence names Vag. valvata (XXVIII. 18, 19). Dr. Wright states (Edin. New Phil. Journ. April, 1858)—“On examining the valve in sità, I found it to consist of a rigid plate imbedded in a thick layer of transparent sarcode (XXVIII. 18 b), which latter was continuous at the lower end of the valve with a thin layer of the same substance, lining the whole of the interior, and coating the upper part of the exterior of the tube. The valve was closed by a contractile process passing from its under- surface to the wall of the tube. . . . I am disposed to consider the whole ap- paratus to consist of an oval plate of soft Sarcode, supported by an included bar or narrow plate of horn or chitine. . . . In some specimens the tube was marked with close transverse or circular striae.” In Stentor Mülleri (XXVIII. 16, 17), we have the curious instance of an animal living indifferently with or without a sheath, and enjoying freedom of movement. Amidst numerous specimens of this species, not a few (says Cohn) may be secn Swimming freely about, or, otherwise, attached, enclosed within a roomy ovate sheath, composed of a softgelatinous substance, and open at one end (XXVIII. 17). The animalculo is fixed by its posterior extremity (apparently converted for the time into a suctorial disk) to the closed end of the sheath; but it is still able to evert its spiral ciliary wreath, and to extend itself beyond the open mouth, or to retract itself in a contracted condition within its interior. Ehrenberg remarked the exudation of a mucous sheath around this animal- cule when kept confined for some time for observation within small glass tubes, but mistook it for a sort of morbid act preparatory to death. Cohn, on the contrary, has shown (Zeitschr. 1853, iv. p. 263) that it is in no way con- mected with disease or with approaching death, but happens with individuals OF TDIE PROTOZOA.—CILIATA, 285 in full vital activity and surrounded by favourable external conditions, and adds that gemmation frequently proceeds in these encased beings, and that, when from evaporation of the surrounding fluid or other prejudicial cause the animals are threatened with injury, they quit their sheaths and swim away, the previously suctorial extremity resolving itself into a pencil of bristles. The result of these observations of Cohn is to disassociate this phenomenon of sheath-formation in Stentor from that of the encysting process, to which Phrenberg's account of it would have led it to be referred. Dr. Strethill Wright coincides with Cohn in denying the relation between the presence of the sheath of Stentor Mülleri and the diseased or dying state of the animalcule. Indeed he speaks of the presence of a gelatinous case as the rule, and adds that “as the zooids (animalcules) divide they form a gelatinous mass, which is attached to weeds and often to the surface of the water, from which I have seen some 10 or 15 combined Stentors hanging with their heads downwards.” CILIA AND CILIARY ACTION.—The most common, and at the same time the characteristic external appendages of the Ciliated Protozoa are the cilia, which constitute their most active and powerful locomotive organs. Cilia are, moreover, not wanting internally, but are there comparatively few, since they are appendages only of free surfaces. They are met with lining the osophagus, where they, no doubt, serve to facilitate the ingestion of food and of the water taken in for the purposes of ačration. The nature and cause of ciliary movement have becn much debated. To account for the emergetic and peculiar movements of cilia, Ehrenberg imagined the existence of a muscular apparatus at their globular roots, consisting of four muscles, cach pulling in an opposite direction, but, by acting in succession, causing the apparent rotation of the axis around the fixed base. This bold idea has met with no favour among physiologists, who condemn it as purely imaginary and as opposed to the simplicity of nature, to all analogy, and to all the admitted facts and principles of histology. Most inquirers despair of attaining a satisfactory cxplanation, of ciliary action, and treat it as an ulti- mate fact. However, Cohn, looking to the peculiar structure of the integu- ment of Paramecium (Loa:0des) Bursaria (XXIX. 26), fancied that ciliary motion admitted of explanation, since, on the supposition of an inherent contractility in that membrane, each little pyramid might be imagined to contract its sides in turn, and make the cilium surrounding it revolve in the figure of an inverted cone. But granting the possibility of this explanation in the case of the animalcule cited, it could in no wise be applied generally to ciliary motion; for a similar structure is found in comparatively few other examples, and the innate contractility of the supporting membrane, assumed in the instance in question, has certainly no existence in many ciliated sur- faces, and involves nearly an equal stretch of imagination to conceive as JEhrenberg’s muscles. Returning from this digression on the nature and cause of ciliary action, let us briefly review the mode of distribution of cilia in the Protozoa. In many genera they are distributed universally over the surface (XXIX. 20, 28, 48; XXVIII. 1, 8, 31), not at random, however, but in definite parallel lines, more or less approximated, usually traversing the length of the body. A distribution in parallel lines is also not unfrequently observed across or around the body. Even where generally diffused over the body, they are commonly more developed at certain parts, as about the mouth, the head, and tail, as well as on any processes or in any depressions of the body, e. g. in Chilodon (XXIX. 48), Bursaria, Leucophrys, Stentor, &c. Stein represents it as a generic character, that in Paramecium (XXIX. 28) all the cilia are 286 GENERAL EIISTORY OF TEIE INFUSORIA. of uniform length. In Coleps (XXIV. 284), the lorica is divided into a mul— titude of minute facettes by intercurrent lines or sulci, and the cilia are placed at the points of their intersection. In Colpoda Cucullwlus (XXIX. 35, 36, 37), the cilia are much longer at the anterior prolonged extremity, the lip, just as in Chilodon. ; but there is besides, in the deep sulcus where the mouth is found, a dense pencil of long and strong cilia (XXIX. 37), which Ehrenberg mistook for a solid process of the body, and called the “tongue.” From this fasciculus or bundle, a row of long cilia is, moreover, seen to extend backwards to the posterior extremity (XXIX. 37). Other groups of Ciliated Protozoa have the cilia confined, more or less strictly, to one part or organ of the body, a circumstance exemplified in the Vorti- cellina and Ophrydina (XXX. 1, 2, 5, 9; XXIX.1, 3, 4, 5). This limita- tion, as contrasted with the general diffusion of cilia, implies an advance in the scheme of organization, and is attended by the construction of a special apparatus about the head of the animalcules. Thus, in the families named, the rule is that the anterior extremity is bounded by an evident, mostly thick- ened margin, either curved or straight—the “peristom *—Crowned with vibra– tile cilia and complicated by an internal, usually extensile, ciliated disk or rotary organ (XXX. 1, 2, 9 a., 29 a), the whole apparatus recalling the struc- ture of the rotary organ of the Rotatoria. The cilia appertaining to the pe— ristom and disk are highly developed and strong, although, instead of serving for locomotion, they only subserve the processes of nutrition and ačration or respiration, by reason of the fixed condition of the animalcules possessing them. Another peculiarity of the ciliary apparatus of the Vorticellina and Ophry- dina is that it is retractile (XXX. 6a), or can be involuted and withdrawn into the interior of the animal (XXX. 13), and the peristom closed completely, and contracted sometimes so far as to draw in a part of the wall around it, and not leave a single cilium visible externally (XXX. 11B, 31, 33). When thus retracted, the ciliated organ appears like an internal, irregular-sigmoid, contracted cavity or fissure, with the cilia closely packed together and scarcely distinguishable (XXVII. 5 a, b : XXX. 11 B). The retraction of the ciliary wreaths, which takes place very rapidly, is caused by the presence of sur- rounding objects in the immediate vicinity of the animal, by their contact with it, by any shocks it may feel, and by the presence of noxious matters in the water. On the removal of Such and similar causes of annoyance, the ex- tension of the delicate apparatus follows; this act, however, is less rapid than that of retraction, and may be arrested at any point. A more permanent withdrawal of the rotary apparatus, in the families named, occurs when the process of self-division is about to proceed (XXVII.3; XXVIII. 18), and also when the animalcule prepares to enter into the en- cysted condition (XXVII. 5, 7). The disappearance of cilia is witnessed not only in Vorticellina and Ophry- dina when the process of encysting takes place, but is a general phenomenon among ciliated organisms under the same circumstances; yet it would appear that in some cases, even when an animalcule has surrounded itself with a cyst, its cilia are not actually lost, but only withdrawn from view, a fact adverted to by Stein in his account of Chilodon Cucullulus, which at times, after encysting itself and developing one or more living germs within the cyst, has been seen to renew its original appearance, to regain its cilia upon its surface, and, after rotating for a while within the sac, to burst at length through it and escape (XXIX. 55, 58). Moreover many observers have asserted the fact that an animalcule may, soon after encysting itself, be set free by rupturing the cyst by pressure, and then reassume its previous ciliated and active condition. Nevertheless the act of encysting, when advanced to OF THE PROTOZOA.—CILIATA. 287 a certain point, or when the reproductive process consequent upon it differs from that seen in Chilodon, appears to involve the final disappearance both of generally diffused cilia and of specially organized ciliary wreaths. The arrest of the motion, and the ultimate disappearance of cilia, are phe- momena attendant also on the death, or on the approaching diffluence, of ani- malcules—when the surrounding water dries up, or when their vitality is injured by chemical agents or by physical forces, such as electricity and heat. Stein, however, states that, although the animalcule, e.g. a Paramecium, is killed by the addition of very dilute acetic acid, yet its cilia continue visible and of their normal length. Cohn believed the cilia to be very much longer than Ehrenberg represented; but, as Stein affirms, this notion originated from an unnatural appearance consequent on the dying state of the animalcule, from evaporation of the surrounding water; and he adds that a similar elongation of cilia appears immediately at the point where strong acetic acid comes into contact with the surface. But this explanation has since been set aside by Prof. Allman’s discovery of the existence of trichocysts, or thread-cells, within the subtegumentary layer of the body (XXXI. 1–4), to which he at- tributes the phenomena observed and discussed by Cohn and Stein. An instance of a temporary formation of cilia is seen in the Vorticellina and Ophrydina when the offspring, formed by fission or by gemmation, is pre- pared to detach itself from the parent being. Under such circumstances, and prior to the development of the interior retractile ciliary organ, a wreath of cilia makes its appearance (XXVII. 4, 11) near the posterior extremity—but which, indeed, for the time, advances first in Swimming, and continues to do so until the animalcule has attached itself and proceeds to unfold the ciliated apparatus at its head. In the above account, reference has been chiefly made to vibratile cilia, but, as before noticed, there are tegumentary processes of larger size, coarser and stiffer, and withal not vibratile, although moveable. Such serve frequently as special organs of locomotion, or of prehension, or of both, and may also be occasionally considered weapons of offence and defence. According to their form they are named setae, or bristles; wincini, or hooks; cirri, styles and filaments. Some of these terms are both loosely defined and used. Thus the bristles so called of one author, are spoken of by another as cirri, or styles or fila- ments, the structures thus variously called being long bristles, mostly taper- ing, and either straight or but slightly curved. The term “cirri” (in English, tendrils) should be disused, both as being unnecessary and also as conveying an erroneous conception; for no organs like tendrils exist among Protozoa. Un- cini (hooks) are verythick at the base, strong, curved, and comparatively short processes (XXIX. 15, 17); styles are stout setiform bristles, articulated at their base to the cuticle, and of considerable length (XXVIII. 10; XXV. 350, 351). These last-named processes, Lachmann tells us, are sometimes split up at the apex into two, or cven as many eight, parts, as happens in various Euplotes (for instance, E. Patella, in which species, moreover, one style bears a number of small lateral setiform branches). The divided styles occur at the posterior extremity, and are trailed along in the movements of the animals, and only occasionally employed in pushing them forwards, whilst the uncini in advance serve for actual Creeping and climbing. As examples of these tegumentary appendages, may be adduced the setae of Urostyla and Korona; the uncini, setae, and styles of Oaytrichina (XXVIII. 10), Euplotes (XXV. 350-353), and of Ploesconia. Intermediate grades, between the highly- developed Sctose processes cited and ordinary vibratile cilia, may be seen in the larger and more rigid ciliary structures alluded to above as often found 288 GENERAL HISTORY OF THE INFUSORIA. along the margin of animalcules, on eminences and in depressions and other particular parts; such Lachmann would name “ciliary bristles.” In Tricho- dina Pediculus (XXIX. 17), Stein describes a circle of uncini supported on a cartilaginous or corneous ring, and external to this a yellowish membrane of corneous consistence and extraordinary flexibility, with closely-placed striae across it. On a lateral view of the animalcule, this membrane is seen to rise round the circlet of uncini like a raised rim (XXIX, 17 f). LoCOMOTIVE AND FIXED FORMS OF THE CILIATA. VARIETIES OF LOCOMOTION. TRANSITORY PoWER OF LOCOMOTION AMONG THE ATTACHED GENERA. PEDICLE SINGLE AND BRANCHED. WARIED OUTLINE OF RAMIFIED STEMs. STRUCTURE OF STEM. CoNTRACTILE STEMs. RIGID STEMS.—The Ciliata, with respect to the function of locomotion, present themselves under two groups, one compre- hending those genera which at all periods of their existence can move from place to place at will, the other embracing all those which under ordinary conditions are attached by means of a stem or pedicle, of greater or less length. The former—the locomotive group—includes the larger number of genera, in all of which the cilia are more or less generally distributed over the entire body. Their swimming movements are especially due to the cilia, but may be aided by other tegumentary processes, by setae, styles, or uncini, and in several instances by the general figure of the body. It is rare that swimming is a simple onward movement; on the contrary, it is usually attended with a rotary motion about the long—seldom the short—axis of the body; and when the animalcule is considerably elongated, it becomes undulating, as in an eel. In the case of Spirostomum (XXIV. 297, 298), the elongated ribbon-like figure is particularly favourable to rapid writhing motion. In short, as before intimated, the developement of the body to a greater extent in one or more parts, so as to form processes, or the constriction of a portion, reducing it to the dimensions of a member, or the lengthening of the entire animal into a band—like or ligulate figure is made Subservient to the purpose of locomo- tion, and imparts to it a more or less special character. Moreover, the loco- motive Ciliata have the power of altering the direction of their movements, and will often retrace their course, and this frequently without turning them- selves round in order to advance the same extremity foremost. . The simple movement of Swimming is common to all the Ciliata; but in the case of those furnished with setae and uncini, a creeping or crawling motion is superadded, as, for example, in Stylonychia (XXVIII.10), Himan- tophorus, Euplotes, and Kerona (XXV. 322, 328, 347, 353). In several of these examples we find one side of the body covered with a more resistant integument or shield, whilst the locomotive uncini or setae are disposed along the other, just as in the case of a myriapodous insect, and supply a locomotive apparatus whereby the animalcules can run, with much activity, over the surface of an Alga or other solid body, or climb it without difficulty. The movements of the setae, in Creeping, are not independent like those of vibratile cilia, but are produced by the contraction of the substance into which their bases are fixed. Every microscopist has observed Ciliata suddenly arrest their course and as quickly reverse it. This phenomenon Perty calls ‘diastrophy,” and asserts (op. cit. p. 122) that this change in movement is accompanied by such a transition, that not only does the posterior extremity become, for the time, the anterior, but it also acquires the size and appearance of the latter. There is, in his language, an actual polar reversion of the organism. This peculiarity is observed among the Swimming, but not among the creeping Protozoa, which always advance with the anterior end first. When Paramecium versutum or P. leucas becomes diastrophied, its figure elongates and changes to cylindrical OF THE PROTOZOA.-CILIATA. 289 ——the present anterior portion (formerly the posterior) grows thicker, whilst the opposite end becomes somewhat more pointed. For a few seconds the animal Swims about, revolving at the same time upon its long axis, and after Sud- denly making a turn, reassumes its regular form and its usual movements. It is singular that the cilia of the reversed anterior extremity acquire a greater length and strength, and act with increased vigour, whilst those at the oppo- site end become inconspicuous and passive. During diastrophy, moreover, rotation upon its long axis is particularly rapid. Perty illustrates this pecu- liar act of diastrophy in many other species, of which we may mention Para- mecium Colpoda, Colpoda Ren, Coleps hirtus, Oxytricha Pellionella, &c. A very indifferent conception can be formed of the emergetic ever-varying movements of the Ciliata by any attempted descriptions of their manner and direction. One method is combined with or rapidly exchanged for an– other; and we see the little beings not simply swimming, but revolving and curving on themselves in a marvellous and beautiful manner, to be appre- ciated only by observation. tº: Could we imagine the existence of a will, or of a power of control, in such tiny creatures, we should say that ciliary motion is at its bidding; we see it incessantly varying in the same individual, both in activity and power, at one moment urging on the moving atom at full force, at another merely revolving it rapidly, at another slackened and presently stopped. These va– riations, too, appear not fortuitous, but directed to certain ends—to the pro- curing of food, to the avoiding of an obstacle, or to the escape from an enemy. Yet, on the one hand, the belief in the need of a special organization for the manifestation of volition, and, on the other, the observation of very similar movements in the ciliated cells of higher animals when detached and free in water, in the Phytozoa and in the spores and filiform cells of plants—are circumstances which make us hesitate in attributing such phenomena to any other than purely physical forces. - - “There is no sufficient reason,” says Dr. Carpenter (‘The Microscope,” p. 476), “to regard such actions as indicative of a wonderful adaptation, on the part of these simple ciliated cells, to a kind of life which enables them to go in quest of their own nutriment, and to introduce it, when obtained, into the interior of their bodies.” Prof. Owen remarks, in his lectures on the Comparative Anatomy and Phy- siology of the Invertebrated Animals (1843), p. 19,-‘‘If you watch the motions of the Polygastric Infusoria, you will perceive they avoid obstacles to their progress, rarely jostle one another; yet it is difficult to detect any definite cause or object of their movements.” Further on, he writes—“The motions of the Polygastrica have appeared to me, long watching them for indi- cations of volition, to be in general of the nature of respiratory acts, rather than attempts to obtain food or avoid danger. Very seldom can they be construed as voluntary, but seem rather to be automatic—governed by the influence of sti- muli within or without the body, not felt, but reflected upon the contractile fibre—and therefore are motions which never tire. We may thus explain the fact which Ehrenberg relates (not without an expression of surprise), namely, that at whatever period of the night he examined the living Infu- soria, he invariably found them moving as actively as in the day-time; in short, it seemed to him that these little beings never slept.” Turning now to the fixed Ciliata, we perceive that the true Vorticellina, not invested by an external sheath, arrange themselves under two sections, according as the stem is flexible and contractile, or non-contractile and almost or completely inflexible. The genus Vorticella is the type of the contractile group, and Epistylis that of the non-contractile and inflexible. The stem IJ 290 GENERAL EIISTORY OF TITE INFUSORIA. of the genus first named is always simple or unbranched (XXVII. 1, 2, 3, 4); but in that of the other genera of Vorticellina—viz. Carchesium (XXX. 9) and Zoothamnium (XV. 69) of the contractile-stalked group, and Epistylis and Opercularia of those having rigid stems (XXX. 1, 11)—the young beings produced by fission continue adherent to the parent stem, and then proceed to develope secondary branching pedicles of their own, and in this manner give rise to compound ramified collections of polyparies. Since this ramification is consequent on the division of a parent-being into two, it has necessarily a more or less regular dichotomous (forked) character, and will be more com— pound the oftener the process of fission has been repeated. The stem produced by each half continues to acquire length and strength until the being which surmounts it begins in its turn to undego self-division, when its growth at once ceases; and it undergoes no further change whilst it exists, except in acquiring increased consistence. “The individuals on the same stem have,” says Stein (p. 75), “as a rule, similar dimensions, those undergoing fission, and therefore wider, excepted. At times, indeed, one may be found smaller than its neighbours; but this will be traceable to some accidental circumstance, such as a less Supply of nu- triment to it, and is never very considerable. The size of the members of the same colony agrees in general with that of the individual from which the whole have sprung. When the newly-developed fission-segment, after detach- ing itself from its parent, forthwith proceeds to fix itself and Secrete its stalk, the newly-developed colony will coincide in dimensions with that from which this animalcule has proceeded. On the contrary, if the detached member enjoys its freedom a longer time, appropriates nourishment, and attains a larger growth, the new arborescent polypary developed from it will be larger in all respects than the parent colony. Hence it is, that in the same species we have great variety in the dimensions of individual members as well as of colonies; and therefore the height of the pedicle, the thickness of its branches, and the size of its individuals are useless as specific characteristics.” The style of ramification is equally devoid of constancy in the same species: for (to continue our extracts from Stein) “the several branches may attain an equal elevation, and so produce a corymb or cyme; or the inner may out- grow the outer branches, and the whole polypary resemble a bunch of grapes or a panicle; or, as occasionally happens, the branches may be all incompletely developed, but at the same time bear numerous individuals on short stems, arranged in close Series on One side, when there will be a resemblance to an ear of corn.” In the case of Ophrydium there is a considerable departure from the ordi- nary structure and arrangement of the polyparies of Vorticellina and the rest of the Ophrydina. Ehrenberg considered the globular masses of Ophrydium to be constituted by the cohesion of their gelatinous sheaths, and to be the consequence of their incomplete Self-division. This, however, seems to be incorrect ; for Stein (p. 246) confirms the statement of Frantzius, that the gelatinous ball is not made up of coherent sheaths, but that the bodies of the Ophrydia are merely attached by their tapering posterior extremities to its surface, and not imbedded within it. The animal sends, indeed, a prolonga- tion of its tapering base Some short way within the homogeneous matrix, like a root; and when it forcibly contracts itself, a slight depression of the Surface occurs; but in no strict sense can the gelatinous excretion be called a sheath or lorica. Although, in their usual phase of being, the attached Ciliata have no power of locomotion, they are nevertheless capable of considerable relative move- ment. The highest degree of this is seen in the actively contractile stems of OF THE PROTOZOA.—CILIATA, 291 Vorticella, Carchesium, and Zoothamnium, and the lowest in the nearly sessile Vaginicola, and in the rigid-stalked Epistylis. The movements of the stems of Vorticella are most astonishing by their activity and energy. In their contraction, which is much quicker than extension, the pedicle is twisted into a close spiral comparable to a coiled spring; and besides this action, by which the animal is instantaneously drawn down to the point of attachment, the body itself shortens, and the ciliated head and appendages are retracted under cover of the general integument. The branched pedicle of Zoothamnium is less actively contractile, although still capable of considerable movement, whilst that of Opercularia and Epistylis is quite rigid, or very slightly flexible, and this in most species only in younger stems, before they are in- durated by age. In Opércularia berberina we have the most marked example of flexibility of the stem among rigid-stalked genera. Apart from the movements of the animacules dependent on their pedicles, others are due to the contraction and elongation of their bodies, and to the retraction and oxtension of their rotary apparatus. In the instance of Vagi- nicola (XXVII. 11), of Cothwrnia (XXX. 12, 13, 14, 15), and of Tintinºvus, these, indeed, are the only movements of which those genera are capable,_the external sheath constituting of itself a safe house of defence when the ani- malcule retreats within it, and thus offering a compensatory provision in lieu of the locomotive power of the freely-swimming Ciliata, or of the actively- coiling spiral of Vorticella. On the other hand, when not in retreat, the ani- malcule outstretches itself, and, advancing its ciliated delicate head beyond the limit of the case (XXVII. 10, 11), expands its ciliary apparatus. The animalcules fixed on rigid stems appear exposed to every passing danger without defence; nature, however, has furnished them with a firm resistant integument within the anterior margin or peristom, of which they can completely retract the delicate rotary disc and ciliated head. However, they are not positively motionless; for a certain latitude of motion is allowed them by their mode of articulation, and by the annular segmentation of the posterior extremity (XXVII. 16), in addition to the possible contraction into an ovoid or more or less globular figure. In Opercularia berberiformis the contraction of the body is facilitated by the transverse rugae which normally exist,--whilst in Ophrydium it is carried so far that the elongated figure be- comes oval, and, the head being retracted, the animal presents itself as an inconsiderable prominence above the surface of the gelatinous mass it rests upon. The absence of a protecting sheath in this genus is partly compen- sated for, further, by the aggregation of the Ophrydia, since the globose mass produced is of itself a security, and is rendered still more so by its revolving movements, the result of accidental external forces, and, we may suppose, also by the activity of the animals projecting from its surface. The Vorticellina and Ophrydina live as free beings for a certain time after their production, whether by fission or by gemmation, or by internal germs or embryos. In the case of the products by gemmation and fission, this locomotive power is due to the temporary formation of a wreath of cilia be- hind the posterior third of the body, as mentioned in a preceding page; and it is curious that it is not then the head which moves in advance, but the hinder extremity, by which attachment is to be presently made. There seems to be an object in this backward progression; for by it the animal is brought directly into contact with any object to which it can affix itself, and its attachment made more firm. The part to be attached is the first to come into contact with the supporting medium ; and whether it proceeds to Secrete about itself a sheath, or to develope a peduncle, it finds itself rightly placed without any revolution of the body. U 2 292 GENERAL IIISTORY OF TEIT, INFUSOIRIA. STRUCTURE OF PEDICLES.—The intimate structure of the stem of the Vor- ticellina is different in the contractile and in the rigid forms. The highly- sensitive, contractile, simple pedicle of the genus Vorticella has challenged especial study. It is evidently a compound structure, consisting of a hollow tube containing a cylindrical band. The tube is a portion of the general integument, and continuous with it ; in diameter it is uniform throughout, except at its point of junction with the body, where it undergoes a very slight expansion. Owing to the excessive rapidity of its spiral contraction, this act can with difficulty be observed, except after the addition of a weak solution of corrosive sublimate, which renders it so much slower that its progress may be watched. Ultimately, indeed, the solution kills the animal. The contained band, or, to borrow a term from generalamatomy, the “ axis- cylinder,” does not fill the cavity of the tube, but is disposed within it in a loose spiral manner. Opinion has been much divided as to the nature of this structure. Ehrenberg, judging from its active contractility, pronounced it a muscle, and went So far as to represent it as striated, i.e. as belonging to the highest-developed condition of muscular tissue, which, however, com- parative anatomy teaches us is absent in the lowest classes of animals. Many other writers have united with Ehrenberg in considering the band muscular, and some few also striated, whilst others, again, have regarded it as a simple primitive contractile substance, less elevated than muscle proper in the range of tissues. Indeed, when we contemplate the contractility exhibited by certain plants, and can find nothing more than spiral vessels which can be conceived the seat of this property, we are forced to admit that muscular tissue is not the only actively contractile element in organized bodies. Stein, after remarking that the histology of the stem in Vorticella, Carchestwm, and Zoothamniwm is essentially similar, proceeds to describe the axis-cylinder as an opaque, Solid, finely-granular mass, presenting delicate longitudinal lines or stripes. In Vorticella nebulifera, V. convallaria, V. Campanula, and in Carchesivm polypinum (XXX. 9), it extends into the body as a single tapering band or streak, and in other Vorticellina in two such diverging from one another, as remarked by Ehrenberg, who concluded them to be two muscular cords. When the stem contracts spirally, transverse lines or stripes appear in the axis-matter, which are no other than cross folds, not parallel, and most strongly marked on the concave side (XXX. 10); they have therefore no homology with the transverse striae of muscle. That the contractile power is dependent on the contained axis-cylinder is shown by the facts, that where this is deficient at any part, as not unfrequently hap- pens in Zoothamnium, that portion is rigid, as in Epistylis or Opercularia ; that when destroyed by maceration, or by chemical agents, the stem is out- stretched and remains immoveable ; and that, as is not seldom seen both in Carchesium and Zoothamnium, this axis-matter may be torm across, at one or more parts, without the external sheath being injured: the contractility is destroyed, except in that Segment which is still in continuous union with the body of the animal; and generally the pedicle is only so far and so long con- tractile as its axis-cylinder continues its unbroken connexion with the body. “Although,” observes Stein (p. 80), “these phenomena are in favour of the axis-matter being a muscle, yet there are others sufficiently conclu- sive against the notion. For instance, were the axis a muscle, its move— ments should cease when it loosens its hold from the object it is affixed to ; but this, although asserted by Eckhard, does not happen ; for when Vorticelloe and Carchesia relax their hold and swim freely about with their stems, these last are seen to actively contract in their usual spiral manner, and presently again to extend themselves. In like manner Vorticellae, when Ol' TEDE PROTOZOA.—CILIATA, 293 détached from their stems, alternately contract and extend their bodies; and yet no one pretends to see any distinct lines or bands in their interior to be termed muscles.” Stein’s conclusion therefore is, that the contained substance of the stalk of the contractile Vorticellina is not muscular, although it is the organ through which the will of the animal is exercised over the pedicle. Further, as the action of chemical reagents upon the enclosing tube or sheath of the pedicle corresponds with their action upon the cuticle of the body, so also is there a similar correspondence, in chemical relations, between the axis-cylinder and the internal tissue of the body. Czermak, in his essay on the stem of Vorticellae (Zeitschr. iv. p. 442), describes in that of Carchesium three distinguishable structures:–1, the hyaline colourless sheath; 2, a yellowish contained fibre or band; and 3, a finely- granular fibre lying parallel to the last (XXX: 10). These three pºtions he terms three isotropous helicoids, with reference to their spiral mode of con- traction. Eckhard supposed the effective cause of the contractility to consist in the constant intimate connexion between the motions of the stem and those of the body: but there is no such constant connexion ; for the ciliary wreath may be retracted frequently without any contraction of the pedicle. According to Czermak, the explanation of the movements is to be found in the external hyaline fibre or tube being elastic, and tending naturally to keep the stem outstretched, whilst the yellow contained filament is contractile, serving to throw the stem into folds,-the one consequently antagonistic to the other. To the third or granular element, he is disposed to attribute only a vegetative function. The elastic force of the stem is constant, whilst the contractile is momentary in operation ; the result of this, coupled with its tubular structure, affords an explanation of the particular spiral mode of contraction. This, Czermak has taken much pains to elucidate by reference to physical laws, and an appeal to arguments which we deem unnecessary to reproduce here. . More recently, the idea of the muscular nature of the axis-cylinder of Vorticellae has been revived by Lachmann (op. cit. p 229), who does not hesitate to call it a stem-muscle, and “cannot allow any value to Stein's objection, that it still contracts even when the stem is not attached to another object; for the muscle does not thus loose its insertion, as it is attached to the sheath of the stem itself by its hinder extremity, and not to the foreign object.” This reply to the objection seems perfectly admissible, although for our part we do not at all perceive the necessity of regarding the axis-matter as muscle in the exact sense of the term, even if it is in function homologous with that compound tissue of higher animals. A further statement made by Lachmann is, that the muscular tissue of the stem extends upwards into the body, where it joins with the Supposed muscular lamina liming the cortical layer. The manner in which the axis-cylinder is produced and disposed, is shown by Stein to afford a distinction between the allied genera Carchesium and Zoothamniwm. In the former, each branch developes its own canal and its own central Substance, so that neither of them is directly continuous with the canal or the contractile matter of those portions previously formed (XXX. 9); in Zoothamnium, on the contrary, both the sheath and the axis-cylinder of the stalk are continuous throughout the ramified polypidom (XII. 69). It is in this genus, particularly, that the oldest portion of the stem is often solid; indeed imperfectly-developed stems occur, in which after one or more divisions this same solid and rigid condition is seen. Such varieties, as Stein points out (op. cit. p. 218), are to a certain extent difficult to distinguish from specios of Epistylis; nevertheless they are never So rigid as the latter, but admit of 294 GENERAL HISTORY OF THE INFUSORIA. being curved and are more elastic, and, besides all this, they exhibit trans- verse folds or constrictions, of different depths, which are rendered still more evident when the animals contract and shorten themselves upon their stems. The rigid stems of Opercularia (XXX.1) and Epistylis (XXX. 11) are solid, without internal canal and contractile matter; frequently they appear finely striated longitudinally, and in several species (e. g. Opercularia articu- lata) present transverselines (XXX.1), along which they more readily fracture. These last are commonly described as articulations or joints; but they occur at irregular distances, and are, even in the same species, neither constant in num- ber, in distinctness, nor in distribution, and are consequently worthless in specific descriptions. - The substance of these rigid stems is, however, not uniform, but divisible into a cortical layer and an inner or medullary substance. This is manifest by the fact ºthe transverse lines, which become more evident during the limited undulating movements of the stem, penetrating only through its cuticle or covering. “On the addition of concentrated sulphuric acid,” says Stein (p. 112), “the pedicle swells up, and both longitudinal striae and transverse lines or folds vanish, the whole mass appearing homogeneous and hyaline. Tincture of iodine colours it yellow ; but sulphuric acid being added, it is again rendered colourless.” CoMPOUND SPECIAL ORGANs of LocoMOTION AND PREHENSION. THE PERISTOM AND ROTARY OR CILLATED DISK. THE SPIRALLY-COILED HEAD OF SPIROCEIONA. —Before entering on the description of the internal organization of the Ciliated Protozoa, there is one set of organs, belonging to the important genera Vorti- cellina and Ophrydina (Ehr.), which demands our attention. The organs in question are appurtenances of the head, and consist of a ciliary wreath and a retractile ciliated disk. Ehrenberg appears not to have recognized the existence of the ciliated disk as a special structure; for in his several generic descriptions of Vorticellina and Ophrydina, he speaks of the head as simply crowned by a wreath of cilia, more prominent at one part, which he called the forehead, and inter- rupted at one spot by a sort of gap where the oral aperture is placed. Stein’s researches, however, show clearly that the armature of the head, in most of the genera of those families, is much more complex. The excepted genera are Stentor, Trichodina, Urocentrum, and Tintinnus, which are, in fact, not true members of the family. Stentor furnishes an example of the structure of ciliary wreath, presumed by Ehrenberg to belong to all Vorticellina, being in fact a single line of cilia fringing the periphery of the head, and bending down spirally to the mouth (XXVIII. 16; XXIX. 7, 8). Trichodina is very curiously fringed with an anterior and posterior wreath of cilia, and has besides a firm collar-like ring, within which is a circlet of stiff uncini (XXIX. 15, 16, 17). In the genus Vorticella the apparatus is most simple; it is slightly more developed in Ophrydium and in Vaginicola, still more so in Epistylis, and most of allin Opércularia and Lagenophrys; lastly, in Spirochona, Chaetospira, and Lagotia, totally exceptional forms occur. When examined closely, Lachmann says (A. N. H. 1857, xix. p. 118), we find the wreath is a spiral, and not a complete circle (XXIX. 1, 2, 3, 4, 7). It begins in the vicinity of the orifice of the vestibule, runs above it towards the left, and round the margin of the ciliary disk; but before it again reaches its starting-point, it descends, upon the stem of the rotary organ, into the commencement of the digestive apparatus (i. e. the vestibulum). . . . The portion of the ciliary spiral, which is outside the vestibulum, is not of equal length in all Vorticel- lina; in many—Vorticella, Carchesium, Zoothamnium, Scyphidia (XXIX. 3), OF TEDE PROTOZOA.—CILIATA. 295 Trichodina (XXIX. 15, 17), some species of Epistylis, &c.—it scarcely de- scribes more than one circuit round the disk, whilst in Opercularia articulata and Epistylis flavicans it runs round the disk three times, and in other forms the length lies between these two extremes. This portion consists of a double row of cilia; those of the outer row are usually somewhat shorter than those of the inner, and inserted upon the ciliary disk nearly in the same line, but at a different angle, as they appear to be far more strongly bent outwards. In the vestibulum and Oesophagus the cilia appear to stand in a single row. The peristom bears no cilia; those represented upon it by Stein belong to the outer series of cilia of the disk, or to that portion of the spiral which descends, on the stem of the rotatory organ, into the vestibulum. The latter also, perhaps in conjunction with the bristle above mentioned, appear to have been what induced Ehrenberg to suppose the existence of a frilled lower lip in Epistylis mutans, and Stein in all the Opércularice. “To see the particulars above described, it is peculiarly advantageous to observe animals which have died during expansion.” In Vorticella (XXVII. 1, 2, 4; XXIX. 1) we have a truncate anterior ex- tremity, the margin of which, i. e. the peristom, is ciliated, expanded, and often rather rolled outwards, and has within and rising slightly above it the rotary or ciliated disk. This is separated by a fissure from the peristom (XXVII. 1, 2), except at one part, where the two are continuous, and on examination the disk, with its supporting stem narrowing downwards and outwards obliquely into the body, appears to be a fold reflected from the inner margin and surface of the peristom. The mouth opens at the bottom of the fissure or cavity (the vestibulum), and is furnished with several cilia. The ciliated disk when outstretched is elevated a little above the peristom, but can be retracted and covered in by it completely. The peristom, like- wise, can so curve itself inwards as to include its own cilia within the ring of integument which closes over, like a sphincter, the whole ciliary ap- paratus of the head. The rotary disk has some general resemblance to a cork or plug, which can be drawn inwards by the animalcule itself, or pushed outwards, so as to serve, by its ciliated margin, to produce a vortex in the fluid, and thereby fulfil the purpose of a prehensile or purveying organ, in addition to its locomotive power when the Vorticella is free. The tapering basis of the disk ends below in the general cavity of the body, and is held in sità by its retractor fibres, which proceed to it from the sides of the animal- cule posteriorly. Its interior is continuous with the general cavity of the body. The unfolding of the ciliary apparatus of the head is more gradual than the retraction ; and, so to speak, the animal seems to feel its way by first everting a portion of its delicate peristom (according to our own observation, in a sinuous manner) along with a few of its stronger cilia, before expanding the rest. In Ophrydium (XXX. 5), the disk is rather more convex on its surface, and advances somewhat higher above the peristom, but in all essential parti- culars resembles that of Vorticella. On the retraction of the disk, the peri- stom contracts above it into a short cylinder, and the head swells out in a globose manner (XXX. 6). Between Ophrydium and Vaginicola (XXVII. 11) there is a close resemblance in the conformation of the ciliated organs, except that, in the latter, the act of retraction agrees rather with that of Vorticella than with Ophrydium. A truncated, thickened, somewhat everted peristom, fringed with cilia (this Lachmann denies, see above), belongs to Epistylis (XXX. 11) as well as to the above-named genera, and to Carchesium (XXX. 9) and Zoothamnium. It has also a similar rotary disk, only rather more developed, and its stem short and thick, 296 GENERAL HISTORY OF THE INFUSORIA. In Opércularia, on the contrary, the peristom is neither ciliated, expanded, nor everted in a campanulate manner, but, by the tapering of the anterior third of the body, is narrow (XXX.1, 37), and frequently thrown into longi- tudinal rugae, and withal simply truncate. Further, the disk has a flat surface, and is supported on a long stem which tapers internally to a fine extremity; and the whole organ assumes a trumpet-like figure (XXX. 1 a, 2 a., d). Moreover, instead of an infundibuliform fissure conducting to an oral aperture or entrance to the alimentary canal, there is a wide throat or pharynx, occupying almost the whole diameter of the peristom, having its border extended upwards in the form of a free edge (XXX. 2, 3), which Stein calls an under lip, in contradistinction to the rotary disk, which Ehren- berg represented to be a forehead and upper lip. The tapering stem of the disk bounds one side (the upper) of the pharynx, and by its narrow extremity communicates with the general cavity of the body. The flat disk itself is surrounded by two or three concentric rows of long cilia, and when drawn inwards suffices, with little aid from the constric- tion of the peristom, to close that opening. When, however, contraction is more forcible and complete, this process is entirely retracted, and the peristom closed above it (XXX. 37). When in this condition—and this is true also of the other allied genera,_the only indication, as before mentioned, of the ciliary apparatus of the head is an irregularly-shaped streak or space, in which cilia may still be discerned. This irregular space is nothing more than the remnant of the pharyngeal cavity not occupied by the retracted Organs. On the retraction of the rotary disk a portion of its contents is transferred from the expanded free extremity into its stem, the quantity so removed being in direct ratio with the degree of contraction ; when this is considerable the trumpet-like process appears like a mere internal lobe (XXX. 37 B, h). In Lagenophrys the peristom is peculiar in being adherent to the narrow two-lipped aperture of the sheath ; the diameter of the two orifices is consequently equal. From the peristom a long trumpet-shaped rotary organ projects, similar to that of Opercularia (XXX. 29, 32, 33, 34). The most singular conformation of the head occurs in a new member of the Vorticellina, described and figured in Stein's admirable monograph (p. 205) under the name of Spirochona (XXX: 17, 27, 28). In this the ordinary struc- ture of the head is entirely departed from ; and we have in its place a con- voluted spiral membrane or lamella, rolled inwards around a solid central axis, forming a sort of exaggeration of the single spiral wreath of Stentor. In full-grown specimens of Spir, gemmipara, two complete circuits (XXX. 17) are made by the lamella, each of which is morphologically the same as the ciliated peristom expanded and flattened out. The surface is clothed with cilia; and at its termination in the body, near the axis of the spiral, is placed the mouth, into which foreign substances are rapidly transmitted by the action of the cilia. Among the several members of the families passed in review, we have seen a considerable range in the complexity of the ciliary wreath; and on extending our examination to other genera, intermediate gradations in structure may be discovered. Thus, through the simple spirally-curved wreath of Stem for (XXIX. 7), we have a connecting link between Vorticella, on the one hand, and several genera, of which, in respect of the ciliary armature of the head, Th’ichodina may be taken as the representative. Chatospira, a new genus instituted by Lachmann (A. N. H. 1857, xix.), has a ciliary apparatus so abnormal and peculiar, that it would seem rather a representative of another family than one of the Vorticellina. The anterior OF THE PROTOZOA.—Clſ.IATA. 297 portion of the body is much elongated, and supports a ciliated process, when fully extended, straight and of a sword-shaped figure, fringed along one side and at the end with cilia (XXIX. 5); but when in active vibration and twirl- ing the animalcule onward in a spiral manner, the greater part of this ciliated process becomes curved like a sickle (XXIX. 6). Another bizarre form of ciliary apparatus is exhibited by the genus Lagotia, described by Dr. Strethill Wright as a member of the family Ophrydina. The head of this animal protrudes a pair of horn-like divergent processes, fringed around with cilia, flat or folded longitudinally, and straight or recurved at the extremities. These ciliated appendages, together with the elongated body they surmount, enjoy a very great latitude of motion by alternate con- traction and extension, and by curving and twisting in different directions. The mouth lies in the angle between the processes. The whole being may be said to stand in a position, with regard to the rest of the Vorticellina and Ophrydina, similar to that of Stephanoceros to the other Rotatoria. INTERNAL ORGANIZATION OF THE CILIATED PROTOZOA. SUBTEGUMENTARY LAYER ; CHLOROPHYLL; THREAD-CELLs; MUSCLEs.—Sub- jacent to the cuticle is a layer of granules and small globules, which is often spoken of as a second lamina, just as the cutis vera in higher animals is of the cuticle. Its thickness is considerable ; it is hyaline, and more con- sistent than the contents, and, although homogeneous itself, contains a multi- tude of granules, and, at least in several genera (e.g. Paramecium, Ophrydium, Nasswla), numerous chlorophyll-vesicles, often so thickly disposed as to impart a lighter or deeper green colour to the animal (XXIX. 28). In young, and also in very old, specimens this colouring-matter is wanting, and only colour- less granules with a dark outline, resembling Small fat-particles, present. In Mr. Carter’s phraseology this cortical lamina bears the name of the “ diaphane,” and is said to lie beneath the “pellicula,” but not to be secreted from it. The property of contractility resides in it, whence it becomes so far analogous to the muscle or flesh of animals, that to it the term ‘sarcode * may most appropriately be applied. Dujardin, however, who first employed this term, did so to designate the entire component Organic mass of Protozoa ; but as later observers seem to make out the presence of a somewhat dis- similar substance, of a much looser and more mucilaginous consistence, sur- rounded by the contractile layer in question—in other words, within the so-called abdominal cavity—we feel quite justified in limiting its signification as we have done. - That the cortical layer alone is contractile, Lachmann considers (A. N. H. 1857, xix. p. 126) to be shown by the fact, that “in torn Infusoria fragments of it not unfrequently contract, whilst the internal mass, the ‘chyme,” which flows out, never does so.” Its contractions effect the various alterations in the figure of animalcules, whilst by its greater consistence compared with the abdominal contents, and its fixity as a layer subjacent to the cuticle, it affords a surface, and even a nidus, for the attachment of the nucleus and contractile vesicle, which it therefore serves to retain in sitti, notwithstanding the opposing forces of the circulatory current and of particles of food propelled against them (see section on Circulation). To demonstrate this quiescent cortical lamina and the inner moving stratum also, chromic acid affords the most effective means. The cavity enclosed by the cuticle and Subjacent cortical lamina is occupied by an almost fluid matter, for which the term “abdominal mucus’’ is suggested by Carter, and that of “chyme” by Lachmann, the former we esteem the better, although it imperfectly represents the actual state of things; for in 298 GENERAL IIISTORY OF TICE INFUSORIA. these central almost fluid contents, two portions are distinguishable—one occurring as a stream moving around the animalcule, within and upon the cortical lamina, the other as a thinner central medium, apparently quiescent, and in direct communication with the surrounding water through the channel of the alimentary tube and mouth. To the first only of these two portions Lachmann’s term ‘chyme' is rightly applicable, since it no doubt represents the nutritive material drawn from the alimentary matters swallowed, and to the elaboration of which the watery fluid of the centre most likely contributes. Both portions contain food-vesicles, granules, and molecules; but the former possesses them in much greater abundance. When an animalcule dies, the central contents are the first to cscape, streaming forth from the mouth as a diffluent film with granules and moleculesimbedded in it; a similar discharge and “diffluence ’’ also ensue when the protecting envelopes are torn through, and the more so when some pressure is at the same time exerted. The following quotation from Lachmann elucidates very well several points concerning the contents of the body in general. “When,” he writes (op. cit. p. 126), “an Infusorium is sucked out by an Acineta, the cortical layer or parenchyma of the body may often contract for a long time, and the con- tractile vesicle placed in it may also continue its contractions for hours; nay, I have observed a Stylonychia, which, although a considerable part of its chyme had been sucked out of it by an Acineta, still underwent division, so that one of the gemmules of division swam away from it briskly, and only the other half of the old animal was destroyed. This appears also, to a cer- tain extent, to prove that the mass sucked out does not represent the true parenchyma of the body; and as it only fills the large cavity of the body in the form of a tenacious fluid mass, and becomes mixed with the nutritive matters, especially when no small masses are formed, it is certainly the most natural course to regard it as chyme. It cannot be urged against this view, that in those Infusoria which contain chlorophyll-corpuscles in the substance of their bodies, we sometimes meet with single corpuscles in the rotating mass, as they may certainly be easily loosened from the parenchyma, and thus get into the chyme-mass. The nucleus, indeed, projects into the chyme- mass; but as a general rule it appears to be affixed to the parenchyma of the body, as we do not sce it rotate with the chymc-mass: in Opercularia berberina, Stein sometimes saw the nucleus moved a little out of its previous position by a mass of food striking against it; but as it soon returned again to its position, this rathor speaks for than against its attachment.” Imbedded within the cortical layer a collection of remarkable structures is discoverable in many species—for instance, in Paramecium, Ophryoglena, and Bursaria—known under the name of thread-cells or trichocysts (XXXI. 1–4). We are indebted to Prof. Allman for the minute and complete examination of these bodies (J. M. S. 1855, iii. p. 177). He believes it was these structures which Cohn represented (as mentioned in a previous page) to be oxceedingly long cilia, and which Stein, in criticising Cohn’s account, affirms to be cilia of ordinary length, but appearing abnormally lengthened under external circum- stances, such as the addition of strong acetic acid. Prof. Allman's description is the best we have :— “When Bursaria leucas is examined under a sufficiently high power, minute fusiform bodies may be detected thickly imbedded in its walls. Those bodies are perfectly colourless and transparent; they are about the gºrgth of an inch long, and may easily, even without any manipulation, bo witnessed at the margin, where they arc Scon to be arranged perpendicularly to the outline of the animalculc, while on the surface turned towards thc obscrver the cxtreme transparency and want of colour rendor them invisible OF THE PROTOZOA.—CILIATA. 299 against the opaque background, and it becomes necessary to crush the animalcule beneath the covering glass, so as to press out the green globules which it contains, in order to bring the fusiform bodies into view. To these bodies I propose to give the name of trichocysts. “As long as the animalcule continues frce from annoyance, the trichocysts undergo no change ; but when subjected to external irritation, as occurs during the drying away of the Surrounding water, or the application of acetic acid or other chemical irritant, or the too forcible action of the compressor, they become suddenly transformed into long filaments, which are projected from all parts of the surface of the animalcule; and it is these filaments which, being mistaken for cilia by Cohn and Stein, gave rise to the erroneous views just mentioned. “The rapidity with which this remarkable change is effected, joined with the great minuteness and transparency of the object, renders it extremely difficult to follow it; and for a long time I could only satisfy myself of the fact that the fusiform bodies were suddenly replaced by the projected fila- ments. After continued observation, however, I at last succeeded in wit– messing the principal steps in the evolution of the filament. “It is not difficult, by rapidly crushing the animalcule, to force out some of the trichocysts in an unchanged state. If the eye be now fixed on one of the isolated trichocysts, it will most probably be seen after the lapse of a few seconds to become all at once changed with a peculiar jerk, as if by the sudden release of some previous state of tension, into a little spherical body. In this condition it will probably remain for two or three seconds longer, and then a spiral filament will become rapidly evolved from the sphere, apparently by the rupture of a membrane which had previously confined it, the filament unrolling itsclf so quickly that the eye can scarcely follow it, until it ulti- mately lies straight and rigid on the field of the microscope, looking like a very fine and long acicular crystal. “This remarkable body, when completely evolved, consists of two portions —a rigid spiculum-like portion acutely pointed at One end, and continuous at the opposite end with the second portion, which is in the form of an ex- cessively fine filiform appendage less than half the length of the spiculum : this second portion is generally scen to be bent at an angle on the first, and is frequently more or less curved at the free end. The form of the evolved trichocysts is best observed in such as have floated away towards the margin of the drop of water, and are there left dry by the evaporated fluid. In many of them the filiform appendage was not visible; and they then merely presented the appearance of a simple, long, fusiform spiculum. “The resemblance of the organs now described, to the well-known thread- cells of the Polypes and of certain other lower members of the animal king- dom, is obvious. That they are entirely homologous, however, with these bodies we can scarcely yet assert. Their origin, at least, appears to be different ; for, if we admit the unicellular structure of the Infusoria, we have the trichocysts apparently developed in the substance of the cell-wall, instead of being produccd in special cells, as we know to be the case with the thread- cells of the Polypes.” These structures have also arrested the attention of Oscar Schmidt, Leuckart, and Lachmann. The Second-named observer Surmised them to be “poison organs; ” and very probably they have a defensive purpose, for this is suggested both by Allman’s history of them, and by Lachmann’s observa- tions (op. cit. p. 126, in foot-note) “ of similar, but much thickor corpuscles, which presented a deceptive resemblance to the urticating organs of the Campanwlarice, in an animal living as a parasite ” upon individuals of that 300 e GENERAL HISTORY OF TELE DNFUSORIA. family of Polypes, and “which is probably to be referred to the Acinetina. . . . In the oval embryos, ciliated on One side, which were squeezed out of the body of the mother, we were enabled to convince ourselves that these corpuscles were enclosed, from two to nine together, in a roundish proper vesicle’ (cell). MUSCLES.—Ehrenberg presumed the existence of internal muscles, to ex- plain the varied and active movements of the Ciliata, a presumption required by his hypothesis of the repetition of the organization of higher animals in all lower forms, but entirely unwarranted by analogy. Dujardin considered the whole bulk of the body to be composed of ‘Sarcode,’ having an inherent con- tractility, and the source of all the movements. Little doubt can exist that the cortical lamina is the seat of contractility,+not that it is muscular on this account, but that, as animal tissue in its simplest condition, it possesses the property of contractility as one of the characteristics of such tissue, along with others, such as sensibility, all which, in highly-organized animals, have severally their special structure elaborated for their more complete operation and independent action. In short, in the language of physiologists, the tissues in more perfect animals are differentiated, in the lowest are not so. This physiological fact being admitted, the existence of nerve-fibres and of nervous centres, or ganglions, can be no more than imaginary. The same follows of the supposed organ of sense, the so-called eye of Glenodinium, which many have concluded to be homologous with the coloured specks of Protozoa, of Euglena, and the like. Lieberkühn’s observations would lead, however, to the conclusion that the eye-speck of Ophryoglena rightly deserved that epithet, and is something more than a pigment-spot. His account of it runs thus (A. N. H. 1856, xviii. p. 321):-‘‘Close by the oral slit, on its concave side, lies the pigment-spot. Its form is extremely irregular, some- times globular, sometimes ellipsoidal, in many cases toothed. Ordinarily it is so distinct as to be at Once perceived; sometimes, however, it is so small that it can only be detected by close examination. In animalcules filled with strongly-refracting substances alone, it is always difficult to discover it. The pigment-spot of Ophryoglena atra has, on the whole, more uniformity of form and magnitude. If we squeeze down an Ophryoglena flavicans between the covering glass and the slider, we find that the pigment-spot is composed of a heap of minute, Scarcely measurable granules, strongly refracting light. I never could discover a lens in the pigment. All the specimens examined by me possessed but a single pigment-spot. Beside this lies always a hitherto unobserved structure, the form of which is perfectly described when we call it a watch-glass on a Small scale. This watch-glass-like organ is transparent and colourless, and shows no trace of fibrous or any other structure. The circular base has a diameter of about Tărth of a millimetre ; its depth amounts to about a third part of this diameter; the convexity is very con- siderable. The watch-glass-shaped organ usually turns its convex side towards the pigment-spot; its concave side is directed towards the point of the head; it does not seem to be moveable by the animalcule. When isolated, it withstands the action of water for a longer time than is usually the case with the other parts of the body of this Infusorium. After lying some time in water, it swells up in Some degree, and frequently becomes perforated by a hole in the middle. The presence of the watch-glass-shaped organ is not dependent on the presence of a pigment-spot ; for Ophryoglema atra possesses a pigment-spot, but no watch-glass-shaped organ, while Bursaria flava has a watch-glass-shaped organ, but no pigment-spot. In other Infusoria with eye-spots, as in the Euglence and Peridiniaea, I have sought in vain for this organ. I have not met with any facts throwing light on its function.” Notwithstanding, in the interior of the Ciliated Protozoa there is not an OF TIII. PROTOZOA.-CILIATA, 301 actual homogeneity of tissue. The act of differentiation is carried so far that certain distinct organs and parts become distinguishable. Thus there is a mouth or oral orifice for the entrance of food, succeeded by a dilated cavity— an Oesophagus or pharynx, which is contracted posteriorly into a tubular prolongation of various length, homologous with a digestive or alimentary tube. Apart from this rudimentary alimentary apparatus, numerous globular or vesicular spaces containing granular particles or objects evidently swallowed, are met with in the general loose contents of the body; these were the di- gestive Sacs, or stomach-vesicles, so much insisted upon by Ehrenberg; other included organs are the contractile vesicle, a certain striated cylindrical organ in one or two genera described by Ehrenberg as a dental cylinder or teeth, the nucleus with usually its nucleolus, the red speck (eye) in Ophryoglena, and in one genus a pair of organs imagined by Stein to be glandular. To these contents Carter adds spermatozoida, and Perty internal germs or ovules. We have already mentioned chlorophyll-corpuscles in some genera, and the general prevalence of fat-vesicles and granules interspersed within the substance of the body, or collected into a layer as in several of the Vorti- cellina; the collection of fat-corpuscles is remarkable in the contracted portion or base above the point of attachment, whether this be by a pedicle or not. “Perhaps,” he adds, “the transverse annulations which are exhibited by the bodies of some Vorticellina are to be attributed to muscular fibres; at all events they do not belong to the skin, but to the parenchyma (i. e. the cor- tical lamina) of the body.” Lately, Lachmann has broached the hypothesis that an actual muscular stra- tum lies within the cortical layer. He writes (A. N. H. 1857, xix. p. 228)—“I was so fortunate, in common with my friend Claparède, as to observe an indu- bitable separate contractile layer, in which longitudinal striae were generally to be detected in various Vorticellina, in which Ehrenberg states that he saw muscular striae at the posterior extremity. It forms a hollow cone, the apex of which is situated in the hinder extremity of the animal, and, in the contrac- tile-stemmed species, is produced into the muscle of the stem : in its apparent section it of course appears like two small fibres separating from each other like a fork—as which, indeed, it has hitherto been always regarded, except by Ehrenberg. This layer is very beautifully seen in Epistylis plicatilis, in which we may most completely convince ourselves that it is a special stratum, which possesses contractility. In Epistylis plicatilis, namely, during the con– traction of this stratum, the non-contractile part of the parenchyma which surrounds it, with the skin covering it, separates from the contractile layer, and forms the well-known folds, whilst the contractile or muscular layer be- comes shortened and thickened without folding.” ORGANs OF DIGESTION, NUTRITION, AND SECRETION.—To take the several parts or organs in succession, we will first consider those concerned in the processes of digestion and nutrition, beginning with the oral orifice or mouth. This is variously situated in different Ciliata, its position having reference to the figure and the mode of life, and being generally indicated by the particular provi- sion made to secure a proper current of water into it, such as a tuft, a curved row, or a circlet of larger cilia, a process or a depression of the body, the axis of a convolution of the surface, and the like. Thus in Lacrymaria, Enchelys, Prorodon, Coleps, &c., it is at the anterior narrower extremity; in Trachelius and Amphileptus it has a similar position, but is besides under cover of a process of the body. In Chilodon a still larger segment surmounts it; in Nassula, Paramecium (XXIX. 28), and in Pleuronema (Duj.) it is lateral; and lastly, among the Vorticellina it is within an involution of the integu- ment of the head, called the ‘ vestibulum,” on one side of the ciliated disk 302 GENERAL EDISTORY OF TEDE INFUSORIA. (XXX. 1, 2). The opening of this vestibule or ante-room to the entrance of the digestive tube, i. e. the mouth, should not be confounded with the latter, as often has been done. A funnel-like hollow having the true Oral aperture at its bottom, is met with in Paramecium, and may have the same appellation extended to it. Among the processes about the mouth facilitating the inglu- tition of food, we have just alluded to the wreaths, rows, and tufts of cilia, mostly large and strong like bristles, and to special developments of the Sur- face of the body. Several species possess a tuft of cilia almost indistinguish- able from a plaited membrane; for instance, Colpoda Cucullus (XXIX. 37) and Chilodon Cucullwlus have what Ehrenberg called a tongue, but which, as we have seen, Stein has resolved into a thick pencil of ciliary bristles. A similar structure prevails in Pleuronema and Alyscum (Duj.), in Cyclidium and Aphthonia (Perty). In Glaucoma (XXVIII. 4) and Cyclidium marga- *itacewm, “the margins of the buccal orifice appear,” says Lachmann (op. cit. p. 216), “to be produced into two valves which are in constant motion.” A special curved or spirally-turned row of cilia directs a current into the mouth in Stentor, Spirostomum, Bursaria, Chaºtospira (XXIX. 5, 6), Oaytrichina, Euplotes, and Aspidiscina, and a nearly straight row in Chilodon and Colpoda. In Coleps, Trachelius, Enchelys, and Trachelocerca, the mouth opens imme- diately upon the Surface without any conducting ciliary channel, and is Sur- rounded by a simple circle of cilia. The mouth is protrusible in Prorodon and Nassula (XXVIII. 8, 65), and not distinguished by any special external array of cilia. In the true Vorticellina and in the Ophrydina, as above mentioned, the complex ciliary apparatus directs the current into a cavity, the vestibu- lum common to both the mouth and anus; and lastly, in Paramecium the cilia are uniform at all parts, and the course of food to the mouth provided for by a wide and deep tapering channel. In size the mouth varies both in different genera and in relation to the dimensions of the animals; but in all it is more or less extensile, so that foreign particles or other animalcules are engulfed within it even when their diameter equals that of the body itself. The oral aperture opens below into a rudimentary digestive tube (XXVII. 1, 10, 11 ; XXIX. 4; XXX. 1, 11, 29), formed by an involution of the ex- ternal integument. It is commonly a funnel-shaped space, which, for the sake of a name, may be called the pharynx or digestive tube; within this, and especially near its entrance, a few vibratile cilia are mostly seen, serving by their action to accelerate the onward transmission of the particles of food. The walls of this cavity are formed by a special very extensile membrane, which, as supporting the internal cilia, may be called a ‘basement mem– brane.” The pharynx extends (as a gently tapering, mostly curved, tube) obliquely inwards towards the centre of the general cavity of the body, where it abruptly ends. Its length is subject to considerable variation in different genera. In Paramecium and allied genera, and in Owytrichina, it is short and of greater relative width ; in Chilodon, Nassula, Prorodon, and others it is continued, from the posterior extremity of the so-called cylinder of teeth, far into the interior. It is also of very considerable length in the Vorticellina generally, as illustrated by Epistylis and Opercularia (XXX.1). - “In Ehrenberg's families,” Lachmann tells us (op. cit. p. 217), “Oxytri- china, Euplotes, and Aspidiscina (as also in Stentor, Bursaria, and Spirosto- mum), we meet with an internally ciliated Oesophagus, and a curved line open towards the right, composed of strong cilia leading to the mouth.” This Oesophagus always forms “an open tube, and is often collapsed at its inner extremity, and thus forms a transition to the oesophagus of the following groups. - “Many Infusoria,” he continues, “ have a completely collapsed obsophagus, OF THE PROTOZOA.-CILIATA. 303 which, as forming a tube distinct from the parenchyma of the body, and hanging freely in the alimentary cavity, is perhaps entirely wanting in some species; at least, I have hitherto been unable to detect it in Amphileptus, most species of Trachelius, Enchelys, Coleps, and Trachelocerca, in which it only appeared to be a canal through the parenchyma of the body: and these are generally incapable of forming roundish morsels like the species hitherto under consideration; but they usually swallow larger particles, which then pass separately into the cavity of the body, often even without being accom- panied by water. It is very difficult to determine whether the oesophagus of these animals is furnished internally with cilia. In some, such as Coleps, this almost appears to be the case: these swim to any slimy mass, such as a deliquescent Infusorium, press the anterior extremity of the body against it, and open the mouth and Oesophagus, which are usually closed, so as to form a wide canal; the mass lying before the Coleps then passes through this canal into the interior of its body, apparently without any swallowing movements on its part, so that it can hardly be driven in except by ciliary action. In others, on the contrary, the cilia of the Oesophagus appear to be wanting, as in Amphileptus, Enchelys, Trachelius; these perform regular movements of deglutition, in order to overcome their prey, which usually consists of Infu- Soria of tolerable size: they push themselves, as it were, with swallowing motions, like the Snakes, over their prey (so that they can very rarely be fed with colour); and this never forms stomach-like morsels, except when it is contained in this form in the Infusoria devoured.” STOMACH-SACS. THE POLYGASTRIC HYPOTHESIS.—The next organs, con- cerned with digestion, to be considered, are the stomach-sacs or vesicles of Ehrenberg—the “digestive globules” of Mr. Carter (XXVIII. 8 f). The former has described these to be disposed after certain definite types, which form the basis of his system of classification of the Polygastrica. To describe these types, we must premise that the families comprised in our group of Ciliated Protozoa represent the Enterodela of the Berlin naturalist, or those Polygastrica having a true alimentary canal uniting the stomach-sacs together, and continuous throughout from the mouth to the assumed discharging orifice. The Enterodela were subdivided into sections according to the relative posi- tions of the mouth and anus. The first of these was named Anopisthia, in which the intestine was so curved upon itself that its two extremities were conterminous in one aperture, which therefore served the double office of a receiving- and a discharging-orifice. This curvature of the intestime further suggested the term Cyclocoela to express it. The families in this section were Vorticellina and Ophrydina. The next section, called Emantiotreta, included animalcules in which the oral and the anal apertures were at opposite ends of the body. When this was the case, the intestine might either pass straight between the openings, or be more or less twisted in its course: in the former case, the Polygastrica were called Orthocoela ; in the latter, Campylocoela. The Enchelia and Colepina were the two families of Enantiotreta. The third section was the Allotreta, having one orifice terminal, and the other lateral, and the fourth the Catotreta, having the two orifices on the same side, not terminal but abdominal. The members of these two last sections, lastly, had either a straight or, more commonly, a contorted intestine, Or, in other words, were either Orthocoela or Campylocoela. Such is an outline of Ehrenberg’s views of the alimentary apparatus of the Ciliated Protozoa, as advanced in his great work of 1838, and never since re- called. They rested chiefly on some imperfect observations and experiments made with coloured food, and have failed to be confirmed in the hands of other microscopists. Although diligently sought after, no one has been able 304 GENERAL ETISTORY OF TEII) INFUSORIA. & to demonstrate the intestine connecting together the several gastric cavities; and what is of more weight than the absence of direct evidence, are certain facts subversive of the notion that any such tube exists, viz. the irregularity in the course taken by the bolus of food when transmitted into the interior; the intermingling of the first- and last-swallowed morsels; the movements hither and thither, and the actual rotation within the interior of the globules called stomach-sacs; the occasional coalescence of these sacs, and the not infrequent occurrence internally of frustules of Diatomede and joints of various micro- scopic Algae of great relative length to the animalcule (XXVIII. 31)—some- times, indeed, so long as to stretch the soft body itself (XXVIII.1). On the strength of these facts, coupled with the absence of demonstrative evidence of its truth, the polygastric theory, and the system of classification founded upon it, have together been all but universally rejected. Meyen was one of the first seriously to examine the statements of Ehren- berg: his conclusions were quoted at large in our last edition. He rejected the polygastric hypothesis because he failed to discover the connecting intes- tinal tube represented by Ehrenberg, and, on the other hand, detected the rotation and coalescence of the assumed stomachs. His views of internal organization closely tally with those now generally admitted. He recognized the digestive tube, the formation of the globule of food at its apparently open termination, and its onward course into the interior of the animalcule, where it constituted one of the Supposed stomach-sacs. He seems, indeed, to have imagined a sort of stomach-like dilatation at the end of the alimentary canal, which served to limit the dimensions of the food-globule there formed. The circulation of the globules he attributed to the force of deglutition and to the pressure of others subsequently swallowed: the residue left after diges– tion he described as escaping by an anus. An extract from Mr. Carter's valuable paper (A. N. H. 1856, xviii. p. 123) may with propriety be introduced here. “I cannot,” he says, “with some others, think that there is any intestinal canal in the abdominal cavity, be- cause the digestive globules and other particles of food are constantly under- going circulation round the whole of its interior. In Vorticella, particles of food may occasionally be seen to circulate throughout, and accumulate in every corner of its interior, particularly those which do not happen to be en- closed in globules. Moreover, the intimate resemblance which exists between the alimentary organs of higher Infusoria (viz. Nassula, Otostoma, &c.) and those of the binocular and so-called blind Planariae—in the distance of the mouth from the anterior extremity, the presence of a buccal apparatus, and a simple sac-like stomach in the latter, lined with a layer of mucous substance (sarcode?), charged with the ‘spherical cells' about to be described—is so great, that, with Such a simple gastric organ in an animal so closely allied to these Infusoria as Planaria, I do not see what reason we have, in descending the scale, to expect a more complicated digestive apparatus, but, on the con- trary, one still more simple, in which there would be no stomach at all,—a condition which appears to me to be common to all the Infusoria that have come under my notice.” The results of actual observation show that food is drawn into the mouth by the action of its surrounding cilia, and is thence transmitted rapidly through the pharynx and its continuation, the digestive tube, into the loose tissue of the interior, assuming at first an elongated oval shape, but which soon changes to globular in its passage. The food so introduced appears mostly like a minute drop of Water holding some solid particles in suspension, and presents. a clear areola around a darker centre. Its course in the interior seems toº.” depend on the varying force of projection exerted by the contractility of the OF THE PROTOZOA.—CILIATA. 305 tube behind it and by the primary impetus given it by the action of the cilia; thus, the more rapidly it is propelled, the greater is the circuit it describes. Stein represents it to make a wide spiral curve of one or two gyrations in Opercularia, and in O. berberina to escape finally by a determinate discharg— ing orifice situated at the bottom of the vestibule. In this latter species, he moreover describes the impetus of the swallowed portion to be so strong as to drive the nucleus from its usual position. Although a discharging orifice in a particular site is thus referred to by Stein in the Opercularia berberina, yet at another page (p. 17) he says, generally, that he has been unable to de- tect such a fixed vent in any animalcule, but that where the excreted matters do not, as in Chilodon and other species, escape by the mouth, they make their way to one particular region of the body, through which they escape, not by an opening with a visible margin, but through a rupture of the in- tegument, which closes up and disappears immediately after their exit. This production of a fortuitous opening for the escape of the excreta, had. been previously described by Dujardin as general in the Ciliata. Siebold, on the contrary, upheld the opposite opinion of the existence of a defined anal aperture among them. In most Stomatoda, the anus (he writes) is generally situated at the opposite extremity of the body to the mouth, and on the under surface; but where it is absent, the mouth serves both as inlet and outlet, as among the Polypes. Cohn admits, at least in certain cases, the presence of a definite anus; for in his recent figures of Nassula elegans (Zeitschr., 1858) he indicates such an aperture (XXVIII. 11 g). Lachmann is very positive on this question. He states (op. cit. p. 127) that “a long and careful ob- servation of an individual will always show that the faeces are invariably thrown out at the same part of the body; and in many Infusoria we may frequently recognize the anus in the form of a small pit on the surface of the animal, even for a considerable time before and after excretion (this is often the case in Paramecium Aurelia, P. Bursaria, and Stentor). That the faeces are not forced through the parenchyma at any point on the surface of the body, is proved especially by the careful observation of Spirostomum ambi- guum, and some new animals which are to be united with the Stentors in one family. In the former, the anus is situated at the hinder end of the animal; and close in front of it is the very large contractile vesicle. When fully ex- panded, this vesicle appears to be surrounded only by a thin membrane; but nevertheless we see balls of excrement, often several at the same time, on different sides of the vesicle, separating the laminae of its apparently simple covering, and forming projections which are often nearly hemispherical both towards the vesicle and the outer surface of the body. If masses of excre- ment do usually penetrate through the parenchyma of the body, we should expect it to be the case here when the tension of this is so great; we should also expect to see the masses of excrement pass into the contractile space, if it were not a vesicle but only a space in the parenchyma without proper walls. Neither of these things occurs, however; the faecal masses are not deposited from the body until they have reached the anus at the hinder ex- tremity of the body. A similar strong expansion of a thin part of the body by faecal masses, without any rupture, is seen, as already mentioned, in some new Stentorina, which are distinguished from the genus Stentor by their having that part of the parenchyma of the body which bears the ciliary spiral and the anus (which in all the Stentorina lies on the dorsal surface of the body close under the ciliary spiral, and not in a common pit with a mouth) drawn out into a thin process. In one genus, of which I observed two species (one is the Vorticellina ampulla of O. F. Müller) in company with E. Clapa- rède on the Norwegian coast, and which I will describe elsewhere, this pro- X 306 GENERAL HISTORY OF THE INFUSORIA. cess is broad and foliaceous, and bears the rows of cilia on the margin, whilst the anus is placed far up on the dorsal Surface of a thin plate. In the other genus, Chaetospira (Lachmann), observed by me in fresh-water near Berlin, the process is narrow and bacillar; the series of cilia commences at its free extremity, and only forms a spiral when in action by the rolling up of the lamina ; in this genus also the process bears the anus. In both, faecal masses which are thicker than the process in its extension, pass through it to the anus, without breaking through it, notwithstanding the great expansion of its walls. “Not unfrequently several balls of excrement unite into a large mass before the amus, in order to be passed out together. When an excretion takes place, the anus is seen to open (but often closes once more and opens again before the expulsion of the masses is effected), and then the faecal masses are often expelled slowly.” He further describes the situation of the amus in Ehrenberg's Ovytrichina and Euplota, in Colpodea with the exception of the species of Amphileptus and Uroleptus, in the Cyclidina, and in Glaucoma, Trachelius, Chilodon, and Nasswla, to be on the ventral surface near the posterior extremity, or at the posterior extremity itself. In Bursaria and Spirostomum it is placed at the posterior extremity, as also more commonly in Coleps, Enchelys, and Trache- locerca. In the Stentorina it occurs on the back close beneath the series of cilia, and in Chilodon Cucullulus it is nearly on the right margin of the body near the hinder end. Among the true Vorticellina and Ophrydina the anus opens into the vestibule very close to the oral aperture, a stout curved bristle being placed between the two (XXIX. 2 e, i.). Excepting on this point of a preformed, constant, and definite discharging orifice, there is among microscopists an almost universal accord in the pre- ceding account of the phenomena connected with the reception and digestion of food. It would be a useless expenditure of space to insert even an epitome of the observations and arguments of only the most eminent of modern naturalists who coincide with it; it will be sufficient to cite their names and their contributions on the subject:-Meyen, in Edinb. Phil. Journ. vol. xxviii.; Dujardin, Histoire des Infusoires, 1841; Siebold, Anatomie der TVärbellosen. Thiere, 1848; Boek, Oken’s Isis, 1848; Wagner, Zootomie, sect. Infusoria, 1848; Van der Hoeven, Lehrbuch der Zootomie, 1850; Leuckart, in Van der Hoeven's new edition, 1856; Stein, Die Infusionsthiere, 1854; Lachmann, “On the Organization of the Infusoria,” A. W. H. 1857, Xix.; Carter, Huxley, and Carpenter; indeed, all British authorities, with whose works we are acquainted, who have written on the subject. This is certainly a long array of authorities against Ehrenberg’s theory of polygastric organization ; and almost the only advocate he has found on his side is Eckhard, once a pupil of his own. This gentleman has published some observations which seemed confirmatory, but are undoubtedly erroneous in several particulars. The following remarks, bearing specially on the subject at present under con- sideration, may be quoted:— Be writes—“In such forms as are not too minute, we can distinctly see how the nutriment, artificially supplied, constantly takes a definite course in the body : in some instances the first portion of the alimentary tube can, when not in action, be observed, as in Epistylis grandis; it is then frequently seem to be covered on the inner surface with cilia, which, in the Opércularia, may even be counted. But that this alimentary canal does not, after a short course, terminate abruptly in the body, can also be proved in the Epistylis grandis. “In this animalcule a portion of colouring-matter swallowed is seen to OF TEIE PROTOZOA.—CILIATA. - 307 course along an intestine and enter a cell. I also once attentively observed what appeared to be the extremity of the intestinal canal, to ascertain what the further course of the coloured particles would be. At this time the animal had not filled any of the cells in its inside; suddenly two lateral cells became filled, although I did not perceive any nutriment pass along the common tube. This clearly points out that the two cells must be in connexion with the com- mon cavity from which they had become filled; and when, after the animal has fed for a considerable time, we see that similar filled cells are diffused throughout the body, this phenomenon affords a ground for the supposition that the intestinal cavity is of greater length than we should at first sight imagine.” (Wiegmann’s Archiv, 1846, translated in A. W. H. 1847, xviii. p. 433.) M. Pouchet, of Rouen (Comptes Rendus, xxviii. pp. 82–516), has also adopted Ehrenberg's motion of definite gastric cells, but has been unable to convince himself of the connecting intestine. Mr. Samuelson also (J. M. S. 1856, p. 165; 1857, p. 104) seems to coincide with this view; but in his se- veral papers on Glaucoma, cited, there occur variations in description, which very much detract from their weight in deciding on any disputed point. Lachmann gives the following details (A. N. H. xix. p. 118):-‘‘The vesti- bulum continues the spiral line formed by the row of cilia, constituting a bent tube, which contains a portion of this spire of cilia. In accordance with the direction of this spiral, the concavity of the tube is turned towards the right, and its convexity towards the left: on the convex side the lumen of the tube is still more enlarged, especially in the parts placed furthest inwards, where the anus opens. Between the amus and the mouth which leads further in- wards into the Oesophagus springs a bent bristle, which is generally long enough to project outwards beyond the peristome. This bristle is stiff, and is only displaced a little to one side occasionally, when balls of excrement, which are too thick to pass between it and the wall of the vestibulum, are thrown out from the anus; but it immediately returns again to its old position. “From the mouth a short tube, the oesophagus, with a far Smaller lumen than the vestibulum, leads to a rather wider fusiform portion, which we will call the pharyma.” This selection of terms we consider unfortunate, because it is opposed to their customary usage in comparative anatomy, the pharynx being always said to..be prolonged into the Oesophagus, and not the latter into the former. In all the Ciliata, except the Vorticellina, the canal continuing from the oral aperture is not distinguishable into two portions or segments; and one term would suffice to designate it throughout. In that class, where a division may possibly be remarked, it would be better to call the upper segment the pharynx or Oesophagus, and the lower the alimentary tube; by So doing, no false con- ceptions could well arise. However, in quoting from Lachmann’s description we must let the words abide with the meaning he has assigned them. To continue our extract—“In most Vorticellina (those with a contractile stem, and the species of Epistylis and Trichodina) the longitudinal axis of the vestibulum and oesophagus runs tolerably parallel to the plane of the ciliary disk, whilst that of the pharynx has rather the direction of the axis of the body. In these, therefore, the axis of the ciliary spiral, which is continued as far as the pharynx, changes its direction at the commencement of the vestibulum : whilst it coincided with the axis of the body outside the vestibulum, it stands almost perpendicular to it within the vestibulum and in the Oesophagus. In the very elongated forms of the Ophrydina (Ehr.), which inhabit sheaths (Ophrydium, Vaginicola, Cothurnia), the longitudinal axis of the vestibulum and oesophagus coincides more with that of the body, as also in the genera * x 2 308 GENERAL HISTORY OF TEIE INFUSORIA, Opercularia (as circumscribed by Stein) and Lagenophrys, Stein; in the two latter the vestibulum is very wide, whilst in the elongated species it is narrow, but generally possesses a deep excavation for the anus.” “Besides the cilia of the spiral (ciliary wreath), some stronger cilia also stand in the vestibulum, in front of the mouth ; these do not take part in the regular activity of the others, but only strike forcibly sometimes, appa- rently to remove from the vestibulum coarse substances which may have got into it, and also the masses of excrement.” “The morsel passed from the pharynx into the interior of the body runs nearly to the posterior extremity of the Vorticella, and then, turning upwards, rises on the side of the body opposite to the pharynx. During this portion of its course, it usually still retains the spindle-shape communicated to it by the pharynx, and only here changes to the globular form, often rather Sud- denly ; this induced me at first to think that the morsel was still enclosed in a tube during this part of its course; and this opinion seemed to be supported by the circumstance that, before and behind the morsel, two lines are not un- frequently seen, which unite at a short distance from it, like the outlines of - a tube which it has dilated. Subsequent observations, however, have again shown me that this opinion is an improbable one ; for the circumstances de- scribed must also occur when a fusiform morsel is passed with some force and rapidity through a quiescent or slow-moving tenacious fluid mass: the above- mentioned lines, before and behind the morsel, must be produced by the se– paration and reunion of the gelatinous mass, even if the morsel is not Sur- rounded by a tube. But the existence of a tube depending from the pharynx appears also to be directly contradicted by the fact, on the one hand, that the curves described by the morsel are sometimes larger and sometimes Smaller, and on the other, that the morsel acquires the globular form sometimes sooner and sometimes later, according as it is pushed out of the pharynx with greater or less force and rapidity. The masses whirled into the pharynx are not always aggregated into a morsel; but sometimes, under conditions which have not yet been satisfactorily ascertained, all the masses which reach the pharynx are seen to pass quickly through it without staying in it; they then stream through the mass Surrounding them in a clear streak which, like the morsels, describes a curve at the bottom of the bell, and only mix with the mass when their rapidity of motion has diminished. A roundish morsel, which might be regarded as a full stomach, is then never formed. We might easily be inclined to regard the clear bent streak with the particles flowing in it as an intestine; and this has probably been done by Ehrenberg, who states that he distinctly saw the bent intestine in some Vorticellina, especially in Epi- stylis plicatilis, in which I have also been able to study the phenomenon very closely. But in this case also there are the same reasons against the Sup- position of an intestinal tube, as in that of the lines appearing before and behind a fusiform mass: here likewise, not only the form, but also the length, of the curvo varies: whilst at One time it is but short, and soon terminates by the intermixture of the particles contained in it with the surrounding mass, it may immediately afterwards be twice as long or longer—it may even make a complete circuit and return nearly to its point of commencement be- neath the pharynx—a variation which appears only to depend upon the force with which the cilia of the rotatory organ act; so that we cannot explain the whole phenomenon otherwise than that the water with the particles contained in it, streaming with some rapidity into the mass with which the body is filled, cannot mix with the latter immediately but only when its rapidity of motion is diminished by friction,-just as we see a rapid stream which falls into a sluggish or stagnant pool, or into the sea, still retaining its independ- OF THE PROTOZOA.—CILIATA. 309 ence for a certain space, so that, if it differs in its colour or turbidity from the water of the sea or pool, we may distinguish it from the latter (with which it does not mix for a long time) in the form of a streak, which is often of great length. “When the nutritive particles in the body of the Vorticellae have attained the end of the clear streak under a constant diminution of their rapidity—and in the other case, when the morsel has lost its spindle-shape and become glo- bular—they have no longer any separate movement, but now only take part in a circulatory motion, in which all the parts in the interior of the body, with the exception of the nucleus and contractile vesicle, are engaged.” This account applies in general to the alimentary mechanism of all other Ciliata besides the Vorticellina, oxcept so far as concerns the dilated lower half of the Oesophagus (i. e. pharynx of Lachmann), which is never seen. The ciliated oesophagus ends by an obliquely truncate extremity, through which the drop of water introduced by the mouth enters the tenacious fluid mass of the interior, where it expands into a rounded vacuole or stomach-sac, which continues its onward curvilinear course until, by absorption or by ex- pulsion through the anal outlet, it disappears. Yet it may happen, just as in the Vorticellina, that the water and food, instead of, as usual, being united into drops and morsels, may be mixed at once with the contents of the abdo- men, and no semblance of a full vacuole be produced. A remarkable fact is recorded by Lachmann, of the digestive organization of Trachelius Ovum, in which, by the way, Ehrenberg declared the alimentary canal was more easily seen than in any other animalcule. “In Trachelius Ovum,” writes the author we quote (p. 127), “alone we see a proper stomach– wall separated from the rest of the parenchyma by spaces filled with fluid, and thus form an arborescent ramified canal, which, however, must not be confounded with the nucleus.” To this statement he adds, in a foot-note, —“The animalcules devoured (Trachelius Ovum is one of the most voracious robbers) arc always scen lying in the ramifications of the stomach, in the clear spaces between them, except in crushed animals. The clear round spaces in the parenchyma (cortical lamina) of the body, are certainly no stomachs, but contractile spaces.” This structure was affirmed to the writer by Lieberkühn, and was, no doubt, seen by Ehrenberg, but misunderstood by him in most points. Its gastric charactor, however, has not past unchallenged, for both Cohn and Leuckhart (Wiegmann’s Archiv, Bericht, 1855) assert that it is no- thing more than a fibrous band extending inwards from the integument in different directions through the soft contents of the interior. In this expla– nation Gegenbauer secms to agree—the granular bands described by this observor under the name of “trabeculae º appearing identical with the fibres of the two last-named writers. Those traboculae are stated to be contractile and to have a definite arrangement, the principal One oxtending backwards from the long, ciliated, oral fissure along the same side of the body, and having secondary trabeculae branching from it and proceeding to the cortical lamina, where they are lost. And although Gegenbauer speaks of an intestine-like structure prolonged backwards from the mouth, in which numerous food- globules could be secn, yet he says that there was no perceptible difference in structure to distinguish this so-called intestine from the rest of the body. Morcover he notes that the nutritive globulos may be often seen passing through the smaller trabeculae. Besides the oral fissure, he remarked another opening situated further forward than it, beneath the motile proboscis, where the tegumentary wall is thick, and connected with a trabecula Oxtending inwards to unite with others. This opening he found to be constant in size and position, to be prolonged inwards to the chief trabecula as a wide 310 GENERAL BUISTORY OF TEIE INFUSORIA. funnel-shaped tube, often delicately plaited longitudinally, and surrounded with cilia. Artificial feeding was tried; but no colouring particles were swal- lowed. The existence of a digestive power is shown by the disappearance of organic matters which have been swallowed, leaving little or no residue un- absorbed. Thus other smaller animal organisms are often the prey of Ciliata ; and their gradual absorption into the general mass may be occasionally watched; the same, too, is true of vegetable matters such as Diatomede, Dés- midiedº, portions of Oscillatorice, and of various minute Algae, although here a certain amount of unassimilated matter in the hard lorica or valves remains over and above, to be subsequently got rid of. The changes ensuing in food during the act of digestion are illustrated by Ehrenberg in his account of Bursaria vernalis. This animalcule feeds very much on Oscillatorice; and on watching the fibres, they are seen, when first Swallowed, to be elastic, rigid, and of a beautiful bluish-green colour, but presently they become lax and of a bright green hue, which afterwards changes to a yellowish green, and ultimately to a yellow, the filaments at the same time breaking up into de- tached joints. An assimilative function is evidenced both by the foregoing facts of the absorption of foreign organized matters, and also by the circumstances, that the magnitude acquired and the activity of other functions are regulated by: the quantity of nutriment received, and that after certain substances have been taken as food they may be detected in certain parts, or throughout the tissue of the animalcule. Of the latter, the introduction of chlorophyll into the subtegumentary tissue, by the medium of food containing this vegetable constituent, is an example; and in gencral the colour of an animalcule depends directly on the food taken, or is indirectly influenced by its quality and quantity; for an animal well nourished always exhibits its peculiar colour in the highest degree, whilst ill-nourished sickly examples present little or Il OI).0. This topic suggests another closely allied to it, viz. the artificial feeding with coloured substances, so much resorted to by Ehrenberg in his researches. It consists in the introduction of a very small quantity of some insoluble colour, not a poison, capable of minute division, into the water in which the animal floats whilst under observation. The colours generally cmployed are indigo and carmine, a little of one or other of which is rubbed on the wet margin of the slide, surrounding the thin glass cover, whence it gradually steals under the cover, and disperses its fine particles through the little drop in which the animalcule floats. -- Another substance has been proposed as preferable, by Mr. Thomas White (J. M. S. 1854, p. 282), viz. the red eyes of the common fly, reduced to fine powder by pressure. By feeding animalcules with this in lieu of carmine, the disadvantage arising from the dark particles of the latter crowding the field of view and obscuring the objects is obviated; and, on the other hand, it has the actual advantage of being more readily imbibed, and therefore of appearing more speedily in the apparent stomach-sacs. Ehrenberg imagined that the Ciliata enjoy the sense of taste, leading them to choose or refuse at will among articles of nourishment within their reach. Thus he says that, amidst a number of individuals of Paramecium Aurelia, some took one sort of food, and others another, no doubt a correct observa– tion, but insufficient to prove the existence of taste. Nevertheless it must be allowed that Some animalcules are especially found in company either with certain other small animal organisms, or with particular plants, or in watcr holding certain matters in solution,--a fact upon which our knowledge con- cerning their habitats and modes of life rests, but in itself no proof of the of THE PROTOZOA.—CILIATA. 311 existence of a sense of taste. Indeed, in the case of minute plants we per- ceive a similar apparent Selection of localities abounding in appropriate nutritive matters. Another assumed vital characteristic was, that Ciliated Infusoria have a feeling of company (a fondness for Society), inducing them to con- gregate together, an idea requiring considerable effort of imagination to conceive, but which, we fear, will scarcely find acceptance as a fact by any person who will look abroad for parallel instances of the congregating together of the same organisms; and plenty such are at hand, even among the lowest plants. DENTAL APPARATUS, OR TEETH.-Before quitting the subject of digestion and of the digestive organs, some notice must be taken of the peculiar formations considered by Ehrenberg to represent a dental apparatus concerned in the preparation of the food for digestion. This apparatus occurs in the form of a cylinder of apparent bristles (XXIV. 282, 283, 308, 309; XXIX. 48)— the supposed teeth—placed behind the mouth, as seen in Chilodon (XXIX. 48), Nassula, Chlamidodon, and Prorodon (XXVIII. 8, 65). The cylinder of teeth was further stated to be wider in front, to be able to expand itself to receive, and afterwards to contract on the engulfed particle of food, so as to crush it and drive it inwards. To these notions of the nature and action of the organ in question, Stein cannot assent. He states (p. 128) that he has frequently tried in vain to isolate it. On killing an animalcule with solution of iodine, or with dilute acetic acid, the funnel-like tube, at times straight, at others curved, is di- stinctly displayed, as well in the smallest as in the larger specimens. It tapers posteriorly, and ends abruptly by an open extremity in the cavity, and is composed of the same resistant elastic membrane as the cuticle. Stein gives it the name of the “oesophageal funnel.” Its wider and thicker end is truncate and dentate or serrate, having from 8 to 16 dentations: between these the membrane appears to be plaited or groved for a considerable distance downwards; and it is these plaits or folds which Ehrenberg took to be long bristle-like teeth arranged side by side. This cylinder, therefore, is nothing more than an involution of the integument. It can be retracted and appear like a tapering Oesophageal tube, or be protruded like a trumpet-shaped pro- cess beyond the general Surface. It has not, however, that independent motile power in itself represented by Ehrenberg; but all its movements depend upon those of the integument; for Stein has never seen it either con- tract or dilate, except simultaneously with the contractions of the general surface. It bends, and is doubled up under pressure, and is neither denser nor a more brittle tissue than the Cuticle; nor can it be resolved into rod-like segments. - - The plaited upper portion is not apparent in all species which have a homologous organ: thus in Nassula ambigua (Stein, p. 249) the infundibulum is smooth, although the double outline its membrane exhibits indicates its very considerable thickness. SECRETION.—Sufficient evidence of the operation of this function is found in the Ciliated Protozoa, although no special organs or tissues can be pointed out for its exercise, unless, indeed, the pair of peculiar Solid-looking organs in the head of Opercularia berberiformis, hereafter mentioned among accessory undetermined structures, be considered glandular (XXX. 2 c). The production of cilia may be considered an act of Secretion, exercised so soon as an animalcule assumes a definite outline, and, under certain circum- stances in connexion with the encysting-process, repeated a second time within the life-time of an individual. Again, the excretion thrown out around Protozoa when about to encyst themselves is another example of the 312 GENERAL HISTORY OF THE INFUSORIA. same process; so is also the special production of cuticular matter in the con- struction of the dense resisting shields and urceoli of loricated species, e. g. Coleps, or that of the substance used in the formation of stems and of external sheaths. Another instance of a secretion may be seen in the solvent fluid poured out for the solution of solid particles of food in the interior, a fluid certainly not demonstrable apart, but presumable from the phenomena of digestion. Having observed the particles of food in the abdominal cavity to be fre- quently surrounded by a clear space filled mostly with colourless, but some- times with a coloured liquid, Ehrenberg at once attributed to it a digestive faculty, and termed it the bile. He speaks of this in the history of the genus Bursaria, where it is stated to be either colourless or reddish. In Nasswla, again, he figures biliary glands in the shape of vesicles forming a wide circlet around the mouth, filled with a violet-coloured juice, which is discharged with the excrementitious particles, and which at first appears like drops of oil, but soon mixes with and becomes diffused through the water. The following species are enumerated as possessing one such vesicular gland: viz. Chilodon ornatus, Bursaria vernalis, Trachelius Meleagris, Amphileptus mar- garitifer, A. Meleagris, and A. longicollis. The bodies thus represented by Ehrenberg as vesicular glands have not escaped the notice of Stein, who pronounces distinctly against their glandular nature, and insists upon their being nothing but sections or joints of the fibres of the Oscillatoriae and other plants that the animalcules feed upon, and which, in the course of their digestion, change from green to a dusky blue, afterwards to a reddish-brown colour, and at length, when broken up, become diffused throughout the interior, and impart to the entire animalcule a reddish- yellow hue. - Cohn (Zeitschr. 1857, p. 143) has remarked in Nassula elegans numerous granules of a yellowish-brown and violet colour, either collected into heaps or scattered through the interior. On the under surface, near the amus, is usually a large violet mass, and at the opposite extremity a similar Smaller one, which have been described by Ehrenberg as biliary glands (XXVIII. 11, 12). If they are not particles of vegetable-coloured food altered in hue by the process of digestion or solution, they may, says Cohn, be considered analogous to the chlorophyll-corpuscles of Paramecium (Loacodes) Bursaria, of Spirostomum, or of Vorticella viridis, and a special form of colouring matter. The collection of the coloured mass about the amus, and its dis– charge in the shape of bluish particles—facts noticed by Ehrenberg—indicate its nature to be effete and excrementitious. Yet it is not the mere crude joints of Oscillatoria, as Stein supposed, but matter which has been digested. The heap about the neck is by no means constant. CONTRACTILE WESICLE.—Passing now to the other contents of the Ciliata, the contractile vesicle or space first arrests our attention. Mr. Carter would callit simply the ‘ vesicula; ” but this word, without the adjunct “contractile” to particularize it, seems insufficient, especially when the Latin language is used in description. This organis of universal occurrence among the Ciliata; it is mostly single; but in a few instances two and even three such, mostly of unequal magnitude, occur. It did not escape the notice of Ehrenberg, who has figured it in all his plates of these beings. It occurs as a clear, hollow, mostly rounded space in the interior, its precise position differing in different species. It is always placed in, or closely connected with, the cortical or contractile lamina, and is not affected by the circulatory current. In the great majority of species it is situated nearer the anterior extremity, and in very close relation with the OF THE PROTOZOA.-CILIATA. 313 mouth or alimentary tube : thus in Ophryoglena, Bursaria, Opercularia, Epistylis, and Zoothamnium it lies close upon the vestibulum within, or almost within, the region of the ciliary wreath (XXVII. 16; XXX. 9–11); in Vorticella and Vaginicola it is placed against the upper part of the ali- mentary tube, and in Trichodina, Nassula, and many others, near it at its termination (XXX. 5, 6, 17; XXIX. 4). Exceptions to this position are met with in Coleps and Colpoda (XXIX. 35–37), where it occupies the posterior extremity, placed very close to the external surface. When two vesicles exist, they are often placed on opposite sides of the body, the one more or less anterior to the other, as seen in Paramecium (XXIX. 29, 30). In Chilodon Cucullulus a third is sometimes seen near the posterior extremity (XXIX. 48). On watching these clear spaces, they are observed to disappear for a few moments and again to reappear—in other words, to exhibit rhythmical con- tractions, a feature which distinguishes them from any other vesicular spaces. The contraction is known as the ‘systole,” the re-expansion as the ‘diastole;’ these movements may be either regular or irregular, and they differ in dura- tion in different species. Perty states that the pulsations in Stylonychia pustulata occupy from six to seven seconds: in Spirochona and Colpoda they are more prolonged; indeed, as Stein affirms, they are slower in the former genus than in any other animalcule he has examined. When more than one vesicle is present, no uniformity in the Order of their movements has hitherto been proved, although Siebold believes they must follow some rule. As evi- dence of the independence of the vesicle of the general contents of the body, Lachmann records (A. N. H. 1857, xix. p. 126) the fact that, even after the contents of an animalcule have been Sucked out by an Acineta, the vesicle lodged in the still present and contractile layer may continue to pulsate for several hours. With regard to the number of these vesicles in particular species, much discrepancy has existed among observers. Siebold affirms that Ehrenberg has proceeded in a purely arbitrary manner in calling one a contractile or sper- matic sac, and others, indistinguishable from it, gastric cells, and quotes in illustration the Berlin Professor's description of the vesicles of Amphileptus meleagris and of A. longicollis. To this objection Eckhard rejoined by assert- ing that Ehrenberg was guided in determining the nature of vesicles by cer- tain appreciable differences in the character and contractions of different sacs, and that Siebold had erroneously represented lateral abdominal vesicles in Stentor, and an elongated one in Spirostomum ambiguum. In this, however, he was wrong, for the description of Siebold has been confirmed by Lachmann and others (XXIX. 7); and on the other hand, Ehrenberg is not so much in error respecting the numbers of these vesicular spaces as Siebold was led to Suppose. It is, indeed, only by careful and repeated observations that such variations can be reconciled. In pronouncing a space Contractile, a sufficient criterion seems to be found in the circumstance of a like organ being found, in all specimens of the same animalcule, constant in position, and rhythmical in its movements. Gastric cavities or alimentary vacuoles may collapse and disappear; but this movement is not followed by renewed acts of disappear- ance and reappearance in regular succession, and in the same spot; for if one such vacuole do replace another, a general movement onwards in the course of the internal cyclosis may be discovered. Another test to distinguish a stomach-vesicle from a true contractile Sac may be found in the use of coloured food. Now that the special contractile sac is admitted generally to be merely the central organ of a system of contractile vessels disposed at various parts 314 GENERAL EIISTORY OF THE INFUSORIA. of the body, the appearance at times of additional vesicles, and consequently also the discrepancies of authors as to the numbers present, are explicable by supposing the accidental dilatation of a tube here and there—as a vari- cose vessel,-the dilatations representing for the time additional contractile SIO8,CGS. I This explanation occurred, among others, to Mr. Carter. Thus he remarks (A. N. H. 1856, xviii. p. 128) that in Chilodon, where the vesicle is normally single and near one extremity, it is not uncommon to meet, amid a group of these animalcules, various individuals presenting a variable number of Con- tractile vesicles irregularly dispersed through the body, without one being in the true position of the ‘ vesicula.” “That,” he writes, “the ‘ vesicula' does make its appearance now and then, may be inferred, as it perhaps may also be inferred that from over-irritability, or some such cause, it does not remain under dilatation long enough to receive the contents of the sinuses; and hence their accidental dilatation, and the appearance of a plurality of vesiculae.” To this accidental dilatation of vascular channels at particular points may be referred the 50 to 60 regularly placed vesicles described by Gegenbauer in Trachelius, the 12 to 16 mentioned by Siebold and Perty in Amphileptus, and also the row of them seen along the side of Stentor. In this last-named genus there is a circular canal surrounding the head or ciliary Wreath, which sends off a branch at right angles along the side to nearly its posterior end XXIX. 7). In Spirostomum, again, a long contractile channel occupies the length of the body. The existence of a second vesicle in an animalcule normally possessing but one, Ehrenberg explained by supposing an act of fission to have occurred prior to division of the entire being, an explanation in which Mr. Carter concurs. But if Stein be right, the contractile vesicle does not undergo fission, but makes its appearance in the newly-formed half by an act of development de novo. In this statement Wiegmann concurs (Perty, p. 63). Ehrenberg concluded the contractile spaces to be true Sacs, limited by a definite membrane,—a conclusion sanctioned also by Siebold, forasmuch as, during successive contractions and dilatations, the vesicles retain the same place, figure, and number. Mr. Carter supplies direct evidence of the fact (A. N. H. 1856, xviii. p. 130), having observed on one occasion a vesicle re- main pendent in a globular form to the buccal cavity of a Vorticella, “when, by the decomposition of the sarcode and the evolution of a Swarm of rapidly- moving momadic particles, these two organs, with the cylindrical nucleus or gland, though still slightly adhering to each other, were so dissected out as to be nearly separate; and thus yielding in position from time to time, as they were struck by the little particles, their forms and relative positions respect- ively became particularly evident.” Moreover, Lachmann (A. N. H. 1857, xix. p. 226) argues at length in favour of the true vesicular character of contractile spaces. Thus he remarks—“The mode of contraction, which differs from the other contractile phenomena of the parenchyma of the body, appears to speak decidedly in favour of the vesicular nature of the contractile space. The circumstance that, before its complete expansion, it frequently appears to be divided into two or three, is not opposed to this, as a vesicle may very well be constricted into two or more parts by the partial contrac- tion of annular portions, or by strictures. Some other facts appear to be in favour of the vesicular nature of the contractile space, such as the phaenomenon presented by Spirostomum ambiguum, already referred to, in which balls of excrement pass to the anus between the contractile space and the outer skin of the animal, and, although often arching the wall of the contractile space into a semiglobular form, yet never break through into it. In Actinophrys, the OF TEIE PROTOZOA.-CILIATA. 315 supposition that there is a membranous boundary, at least on the outside of the contractile vesicle, can hardly be rejected, as its wall, which is situated on the outermost surface of the body, must burst at the moment of greatest expansion, if it were only composed of the gelatinous parenchyma of the body.” Still the contrary opinion, viz. that the contractile spaces are mere vacuoles in the Substance of the interior, without a limiting membrane, has found able supporters in Meyen, Dujardin, Stein, and Perty. The first-named writer compares them to the changing vacuoles which spontaneously generate in the vegetable protoplasm of plant-cells, by an inherent property or process known as that of vacuolation, and which is equally a phenomenon of simple animal protoplasm or contractile tissue. Indeed, there is no doubt that clear hollow spaces or vacuoles may appear and disappear within the substance of Protozoa, and that some of those remarked by Dujardin, Siebold, and others immediately beneath the integument were of this number; yet such vacuoles want the constancy in position, figure, and pulsating power belonging to true contractile sacs. Besides, as we shall presently see, the evident ramifications or canaliculi of many contractile vesicles among the Ciliata afford further grounds for distinguishing between these and mere vacuoles, which, as far as we are aware, never have such offshoots. Another questionable point among observers is, whether any communica- tion exists between the cavity of the contractile vesicle and the free surface near to which it is placed. The majority concur in the negative; but several, among whom are Oscar Schmidt (Froriep's Notiz., 1849, vol. ix. ; Lehrbuch der Vergleichend. Anatomie, 1853), Mr. Gray (Silliman's Journ. 1853), Mr. Rood (Silliman's Journ. 1853, p. 70), and Mr. Carter, are of opinion that a direct communication, between the fluid contents of the vesicle and the watery medium bathing the external surface, is established by means of foramina in the walls. On this question Lachmann remarks (op. cit. p. 227)—“In many Infusoria we see one or more pale spots upon the contractile vesicle, which may easily be mistaken for orifices, but on closer examination prove to be only thin spots in the parenchyma of the body and the skin, by which the action of the external water upon the contents of the vascular system is certainly facilitated, so that they probably serve for respiratory purposes. These round clear spots are particularly numerous upon the contractile space of Spirostomum ambiguum.” The admission or the denial of such a commu- nication will very much affect the opinion held concerning the nature of the office performed by the vesicle, to which we shall immediately advert. The superficial vesicles or vacuoles before alluded to, considered by Dujardin of the same nature as the contractile vesicle itself, have not been sufficiently examined and defined of late to warrant a conclusion as to their real cha- racter: yet probably some of those spaces are no more than mere vacuolae, whilst others are dilatations of the channels of the ramified vascular system. Mr. Carter would in general assign to them the latter character. However, we believe that many of those which have attracted attention have been isolated vesicles, developed from time time, and to be concerned in securing a more perfect ačration of the contained fluid. Siebold, indeed, went so far as to presume they opened upon the external surface, and brought their con- tents into relation with the surrounding water. In figure, contractile spaces are, for the most part, round or somewhat oval, and as to size stand in no direct relation with that of the animalcules they appertain to. Examples of the prevailing figure are seen in Ophrydium, Zoothamnium, Chilodon, Colpoda, Trichodina, &c. Even in some of these appa- rently simple globular sacs, Mr. Carter discovered a series of spherical sinuses 316 GENERAL EIISTORY OF TEIE INFUSORIA. surrounding and communicating directly with them. These accessory vesicles, he tells us (op. cit. p. 130), are, “under exhaustion of the animalcule from various causes, so distended, and thus so approximated, as to assume the appearance of an areolar structure immediately in contact with the vesicula. Each globular sinus would, however, appear to be the proximal or largest of a concatenation of smaller ones, which diminish in size with their distance from the vesicula.” This account tallies with that recorded by Mr. Samuelson (J. M. S. 1857, p. 104), respecting the single globular vesicle of Glaucoma scintillans, which “when it contracts forces the fluid into others which appear temporarily formed around it; ” and these, by contracting in their turn, refill the central vesicle. besides the seemingly simple spherical vesicles, there are others that pre- sent evident branches and a different figure. Such, for instance, are the elongated vascular canal of Spirostomwm, and the annular canal with its row of vesicles down the side,-which seem capable of coalescing into a continuous channel, seen in Stentor (XXIX. 7). In Paramecium Awrelia (XXV. 329), each contractile vesicle assumes a stellate form, owing to the radiating pro- cesses it sends off on all sides, and which Eckhard represented as prolonged through the body by interrupted channels. It is from the study of this Paramecium especially, that observers have generally arrived at the belief in the existence of vascular canals in the Ciliata, connected with the contractile vesicle as a central Organ. That there exists a vascular system more or less distributed through the body, most recent microscopists are in accord: we may mention Lieberkühn, Lachmann, Mr. Carter, Professor Busk, and Mr. Samuelson. As this apparatus will be best considered in connexion with its assigned functions, we shall speak of them together, premising our account with the history of Ehrenberg's conjectures on the nature and function of the con- tractile vesicle. This distinguished naturalist was led by his hypothesis of organization to seek for each of the organs of higher animals a parallel or analogue in the Infusoria; and one of the most curious analogies he hit upon was that of the contractile sac with the spermatic vesicle. In this office he represented the vesicle as receiving from the testis (nucleus) a reproductive fluid, which it again ejected among the ova (granules, alimentary vesicles, &c.) occupying the interior of the animalcule. In this peculiar notion Ehrenberg has met with few disciples: for, as Siebold has justly objected, it is a perfectly gratuitous hypothesis, without analogy in the animal kingdom ; for in no animal is such a thing seen as an incessant projection of seminal fluid into the interior ; and further, both the nature of the nucleus as a testis or secretory organ of spermatic fluid, and the existence of recipient ova, are at best very doubtful hypotheses. The opinions now in vogue concerning the function of the contractile vesicle and of its prolongations or processes are that it is either (1) a water- vascular and respiratory system, homologous with that of the Rotatoria, or (2) homologous with a blood-vascular system, or (3) an excretory appa- ratus. The first conjecture presupposes a direct communication between the fluid in this vascular system and the surrounding aqueous medium ; by the second, no such direct communication need be presumed ; the third view is especially supported by Mr. Carter, Bergmann, and Leuckhart. In his motions concerning the Organization and function of the contractile vesicle, Stein differs from most other recent investigators. As we have already seen, he denies a limiting membrane to the vesicle; he, moreover, can neither acquiesce in the belief of the existence of outlets, nor in the respiratory purpose attributed to it by Siebold and O. Schmidt. He is even OF THE PROTOZOA.—CILIATA. 317 doubtful of the stellate structure, as an actual fact, in the Paramecia ; for in P. Bursaria, in Nassula, and other animalcules this apparent structure may be, he believes, produced at will by the exercise of slight pressure, as by that of the thin glass-cover upon the object, when the diastole of the vesicle is incomplete. Again, he objects against the supposed water-vascular system and its respiratory office, that, in comparison to the large ciliated pharynx, Within which a fresh supply of water is perpetually introduced, and through Whose delicate walls a respiratory act may be readily conceived to take place, the Small contractile space commonly appended to it appears of inconsider- able importance as an ačrating organ. Further, he cannot conceive the necessity of a respiratory apparatus in any animalcule which lives surrounded on all sides by water, besides receiving it incessantly within its interior, and which can therefore so readily absorb its oxygen through its delicate tissues. Another fact adverse to this assigned function is, that the vesicles of embryos, Whilst still within the parent, are seen in full activity, although in that posi- tion no renewed supply of fresh water is afforded them. These objections of Stein lessen upon consideration: thus his opinion that the vesicle is a mere vacuole, that its radiating canals are probably accidental appearances, and his ignoring the existence of a set of vascular channels through the interior, are set aside by the direct observations of several naturalists to the contrary. So, although his arguments, generally, against the presence of a special respiratory apparatus are not without force, yet the remark that he can conceive no need of such an apparatus in animalcules so circumstanced as the Ciliata is worthless as an argument ; for in all such inquiries into the phenomena of life we are not to suppose an organization and then to find it, but, on the contrary, to discover facts, and then, if possi- ble, to determine on their nature. That the contractile vesicle and its connected channels do not constitute a water-vascular and respiratory system, is also the opinion of Lachmann and Carter. The former able observer has confirmed and extended our previous knowledge of the vascular apparatus, and thus conveys his researches and opinions (op. cit. p. 224):—“When the contractile space (of Paramecium Aurelia) is full and wide open, the rays can only be observed as fine lines, or, when the light is not good, are entirely imperceptible; by the Sudden con- traction of the space, however, they instantly swell into a pyriform com- mencement close to the position of the contractile vesicle which has disap- peared. With favourable illumination, when the animals possess the proper degree of transparency, the rays may be traced in Paramecium Awrelia across the half of the animal, and we may sometimes perceive a bifurcation of one or other of them. During the slow reappearance of the contractile space, the rays gradually decrease; and they have almost entirely disappeared, or become reduced to fine lines, when the vesicle has attained its full extension. These rays, as well as the contractile spaces, lie, as in all Infusoria, close under the skin (“cuticula’ of Cohn), in the parenchyma of the body (‘ corti- cal layer’ or ‘cell-membrane' of Cohn). “In many Vorticellae we also find processes going off from the contractile vesicle (Ehrenberg even states that he has frequently seen the contractile vesicle of Carchesium polypinum lobate or almost radiate); of these I have been able to trace one particularly, in V. nebulifera, V. Campanula, and Carché- sium polypinum, up to close beneath the skin of the ciliary disk; this, when seen from above, exhibited a longish section. From this a fine branch appears to run, on the upper wall of the vestibulum, transversely across this to the other side ; at least, I have seen a thin process hanging down like a short curtain into the vestibulum from the side turned towards the ciliary disk, 318 GENERAL BUISTORY OF THE INFUSORIA. which swelled up when the above-mentioned process became enlarged in con- sequence of the contraction of the vesicle. “In Dendrosoma radians (Ehr.), a fine vessel runs through the whole length of the body, and sends branches into its ramifications: it is furnished with a number of contractile spaces, partly in the stem and partly in the branches. - “The processes of the contractile space are seen with remarkable distinct- ness in the large Stentor polymorphus (including S. Roeselii and S. Mülleri), in which a very considerable portion of a vascular system may be recognized. The large contractile space lies a little to the left of the Oesophagus, near the plane of the ciliary disk. From it a longitudinal vessel runs to the posterior extremity of the animal, and an annular vessel round the ciliary disk (Stirn) close under its series of cilia. Both these are visible even during the expan- sion of the contractile vesicle, but Swell up suddenly like the vessels of the above-mentioned Infusoria during its contraction : at this time the longitu- dinal vessel usually exhibits considerable dilatations, which, when Superfi- cially examined, may easily be taken for independent, disunited cavities (vacuoles). The annular vessel exhibits a more uniform lumen; only two roundish dilatations make their appearance in it—one close to the anus on the dorsal side of the animal, and the other close to the Oesophagus on the ventral surface. Both vessels gradually decrease during the reappearance of the con- tractile vesicle, apparently without any contraction of their own, in the same way as the vessels of the Paramecia. The longitudinal vessel of the Stentors, and a similar one in Spirostomum ambiguum, were first described by Won Sie- bold, whilst their existence has been erroneously denied by Eckhard. “As we thus find a vascular system in the Stentors, and in other Infusoria recognize the parts lying nearest to the centre (the contractile space) some- times easily and sometimes with difficulty, we may certainly conclude that such a system exists in all Infusoria which possess a contractile space, even when no branches have been detected running out from this. That this system does not merely consist of accidental chasms in the parenchyma of the body (vacuoles of Dujardin), is apparent from its regularity. When it is as- serted, in proof of the inconstancy of these vacuoles, that exactly similar ones frequently make their appearance in other parts of the body, this appears to me to arise from very different things being confounded together. The swell- ing dilatations of existing vessels are certainly often regarded as such vacu- oles, without its being remembered that these dilatations always gradually decrease again, whilst the true vascular centres, the contractile spaces, always diminish Suddenly in healthy animals. Moreover, in diseased Infusoria, an exudation of a fluid, with which the parenchyma is normally imbued, appears to take place from it even into the cavity of the body, and perhaps into chasms of the parenchyma, as we often see it take place in Infusoria and many other low invertebrate animals, on the surface of the body. These sarcode-drops appear to be incapable of ever being again absorbed; but their formation always appears to lead, although slowly, to the death of the animal.” After the above details, Lachmann inquires the nature of the function this vascular apparatus performs; and having Satisfied himself of the nonexistence of a communication between the interior of the vesicle and the external sur- face, he rejects the idea of its being a water-vascular system, as “we do not possess the certain proof of one of the most essential requirements of a water- vascular system—the existence of an external orifice,—and some things appear directly opposed to it.” --- Mr. Carter coincides with Lachmann in many particulars respecting the structure of the vascular system of Ciliata; but in others he materially differs: OF TEIE PROTOZOA.—CILIATA. 319 for instance, he thinks he has made out the existence of apertures opening on the free surface whether of the alimentary tube or of the general integu- ment, close to one or other of which he always finds the vesicle; and, with this view of the structure, he connects the function of an excretory organ with the sac in question. To support this view respecting the office of the contractile vesicle, he ad- vances the following observations (op. cit, p. 126):—“1st. It is always seen either close to the pellicula or close to the buccal cavity, and always sta- tionary. Thus, in Paramecium Awrelia it is close to the surface, and although it, of course, passes out of view as the animalcule turns on its long axis, yet it always reappears, after contraction, in the same place,—while in Vorticella it is attached to the buccal cavity, and, being centrically situated, seldom passes out of view, except when it disappears under contraction, after which it also reappears in the same place. “2nd. In Actinophrys Sol and other Amoebae, during the act of dilatation, the vesicula projects far above the level of the pellicula, even so much so as occasionally to form an elongated, transparent, mammilliform eminence, which, at the moment of contraction, subsides precisely like a blister of some soft tenacious substance that has just been pricked with a pin. “3rd. Lastly, when we watch the contraction of the vesicula in a recently encysted Vorticella, we observe that at the same moment that it contracts the buccal cavity becomes filled with fluid, and, further, that this fluid dis- appears from the buccal cavity, and all trace of the latter with it, long before the vesicula reappears, thus proving at Once that the fluid comes from the vesicula, and does not return to it, whatever may become of it afterwards. “The position of this organ, then, its manner of contracting, and the buccal cavity of encysted Vorticella becoming filled with fluid the moment it disap- pears (where we know it to be attached to the buccal cavity, and not to the pellicula), are almost conclusive of its excretory office.” Adopting Spallanzani's observation (which, however, wants confirmation to establish it as the rule) that the fusiform sinuses of Paramecium Awrelia be- come empty as the vesicle fills, and do not reappear until some time after it has contracted, he infers “that the fluid with which the vesicula is distended comes through the sinuses, but is not returned by them to the body of the Paramecium.” “Now in some cases,” he continues, “faint hyaline or transparent lines may be seen to extend outwards from each of these sinuses, which lines, Eckhard has stated, ‘traverse the body in a stellate manner.” Hence, when we add Eckhard’s evidence (which I have been able to confirm in a way that will be presently described) to the observation of Spallanzani, and connect this with the facts already adduced in favour of the excretory office of the vesicula, it does not seem unreasonable to conclude that the whole together forms an excretory vascular system, in which the vesicula is the chief recep- tacle and organ of expulsion. “While watching Paramecium Aurelia, I on several occasions not only ob- served that the vesiculae were respectively surrounded by from Seven to twelve pyriform sinuses of different sizes, and that lines extended outwards from them in the manner described by Eckhard, but I further observed that these lines were composed of a series of pyriform or fusiform sinuses, which diminished in size outwards; and frequently I could trace as many as three in succession, including the one next the vesicula. Hence I am inclined to infer that this vascular system throughout is more or less composed of chains of such sinuses, and that all have more or less contractile power like that of the vesicula. Just preceding death, when Paramecium Awrelia is compressed, 320 GENERAL HISTORY OF THE INFUSORIA. and under other favourable circumstances, these sinuses run into continuous hyaline lines, and may not only be seen extending in a radiated vascular form across the animalcule, but even branching out round the position of the vesicula, which, having now become permanently contracted, has thus poured back the contents which render them visible. They enter the lower or inner part of the organ, and at this point, therefore, are pushed inward as the vesi- cula becomes distended. Under the same circumstances, also, when the vesi- cula is slowly dilating and contracting, it may be seen to be attached to a small papilla on the surface, about twice the diameter of those which sur- mount the trichocysts, and through which it probably empties itself (XXVIII. 25). In Otostomathere appears to be a similar arrangement of vesicles round each vesicula; and here also they seemed to me to be branched—at least such was my impression after having watched this animalcule for a long time in order to determine the point.” “Of the use of the vesicula and its vascular system,” Mr. Carter concludes, “we are at present ignorant, further than that its functions are excretory; and when we observe the quantity of Water that is taken into the sarcode with the food, and try to account for its disappearance, it does not seem improbable that the vesicula and its vessels should be chiefly concerned in this office. Another service, however, which it performs, is to burst the spherical membranes of Vorticellae and Plasconice when they want to return to active life after having become encysted: this it effects by repeated dis– tension, until the lacerated cyst gives way sufficiently for the animalcule to slip out.” P. Should it have any other uses, they are probably similar to those of the ‘water-vascular system of Rotifera.” In answer to the question, if all vacuolar spaces, excepting those produced by the deglutition of food, belong to this excretory system of contractile si- nuses, he replies—“Certainly, where there is a plurality of actively-con- tracting vesicles without the appearance of the vesicula, as in Chilodon Cucul- lulus, we may, as before stated, attribute this to a kind of over-irritability or constrictive spasm of the vesicula, and therefore consider that these vesicles are accidental dilatations of the sinuses in connexion with it, as we may set down the dropsical state of Himantophorus Charon (Ehr.), and other animal- cules of the kind, to an opposite condition of this organ, viz. that in which it is unable to relieve itself of its contents: this I have often seen occur under my own eyes.” Many thanks are due to Mr. Carter for his painstaking investigation on this subject. We are nevertheless very doubtful of several of his details of structure. For example, he describes globular sinuses to appear around the vesicle when an animalcule is exhausted, and those of Paramecium to run into radiating hyaline (moniliform) lines just before death and under a certain amount of compression. Now, such conditions are ill-adapted to accurate research ; and knowing how readily the integrity of the soft filmy substance of the Protozoa is disturbed, and diffluence induced, by unfavourable external circumstances, the observation in question must be received “cum grano salis.” Moreover, looking to most of his figures (which, we regret, are rather diagrams than exact delineations after nature), the impression forces itself upon the mind, that he has many times mistaken the commence- ment of diffluence, and, in Some instances, vacuolation resulting from the entrance of water into the tissues, for the manifestation of sinuses about the contractile vesicle or scattered over the body in connexion with it. Thus we should rather attribute the Several vesicles this naturalist saw in different numbers, and variously and irregularly dispersed, in different spe- OF TELE PROTOZOA,-CILIATA. 321 cimens of Chilodon Cucullulus, to one or other or to both of the conditions we have mentioned, than to the purely hypothetical notion of the presence of a state of “over-irritability” in a presumed vascular network. It is here worth calling to mind Stein’s belief that gentle pressure may give rise to a stellate or branched appearance of the vesicle, and that the conflicting ac- counts between Ehrenberg and Focke are reconcileable on the Supposition of this occurrence (Stein, p. 240). With reference to the hypothesis that the vascular apparatus is only ex- Cretory in function, we may remark that the exercise of such an office is no bar to that of a respiratory function, since the latter is in itself in part an excretory process, and among the lower Invertebrata many examples might be cited where one and the same mechanism is equally respiratory and ex- Cretory in purpose. - We may add that Mr. Samuelson (J. M. S. 1857, p. 105) agrees with Lachmann in attributing to the contractile vesicle a cardiac nature, and Sup- plies the following particulars:–“ In Paramecium caudatum a species of Amphileptus, a freed Vorticella, &c., I have frequently and clearly traced the canals that empty themselves into the contractile vesicle. In the second- named species these canals were very perceptible; they proceeded along the edge of the body where the cilia were the most active (also probably because there the current of fresh water would be constantly renewed), and, at the embouchure into the central vesicle, swelled into a bulb-shape. In the Vor- ticella, the contractile vesicle had a canal which either communicated with the eaſternal surface through the oral aperture, or passed round the oral wreath. I was inclined to believe the latter to be the case (perhaps my bias may have influenced the observation). “In certain Infusoria there appears to be a more active vital power than in others. Thus in Glaucoma. . . . . . (especially such as are probably larval forms), the contractile vesicle appears to have the power only to form a row of auxiliary vesicles around it, whilst in Amphileptus (which approaches the Planarians in its character), the Setifera or bristle-bearers, and other types it is more powerful, and the fluid is ejected with sufficient force to work its way into the body, and form canals or arteries, however primitive they may be. The progressive vitality I have often noticed in the same form at dif- ferent stages of its growth.” On a survey of the facts and opinions now passed in review, it seems to us that the contractile vesicle is a closed sac representing a central circulatory organ or heart in its most rudimentary condition; that this cardiac Sac pro- pels its contents through a more or less complex system of channels, probably walled, extended through the cortical lamina of the body; that the contents represent a chyle or blood, formed by the process of digestion, and absorbed by the vessels; that this chyle is exposed in the cardiac pulsating vesicle especially, and in the ramified channels less, to the indirect action of the water incessantly introduced within the body, or constantly surrounding it exter- nally, and thereby becomes aérated, and consequently in all probability fur- ther elaborated; lastly, that the perfected chyle is circulated through its channels, and brought by them into the immediate vicinity of the tissue in which the most active vital changes are going on, and which, On account of its higher differentiation, especially when in the form of cilia, integument, &c., demands the greatest supply of nutritive matters to repair its waste and to provide for the processes of growth and development perpetually proceed- ing in it or in its appended organs. Since the foregoing review of the structure and functions of the contractile vesicle was written, Lieberkühn's valuable contribution, founded on original Y 322 GENERAL EIISTORY OF TEIE INFUSORIA. researches chiefly concerning Bursaria and Ophryoglena, have come into our hands (A. W. H. 1856, xviii. p. 323). Since the introduction of it piecemeal in our history of the organ would both have sacrificed its merits as an original essay and have disturbed the continuity of our own account, we have deter- mined to reproduce it here as a supplement. . After describing the existence of two vesicles in Ophryoglena and Bursaria, one near the mouth, the other situated posteriorly, he goes on to say that if we examine a Bursaria flava containing only the smallest forms of the strongly refractive granules, “with a power of 300 diameters, we perceive near the surface a quantity of light streaks, which run together towards the contractile vesicle from the anterior and posterior parts of the body, in more or less considerable curves. In each streak we detect an extremely delicate but perfectly distinct canal, terminating ultimately in the contractile vesicle; its walls and its contents are readily distinguished by their different refrac- tive power. When one of these canals is traced backwards from its orifice, we may often perceive, after it has run a short distance, a ramification : this may frequently be traced to one of the extremities of the body, and some- times it gives off another branch ; ultimately the canals become so excessively fine that they are invisible. Their opening into the vesicle and their course in running from it are seen very distinctly when the contractile vesicle is turned directly upwards; we may then recognize how the canals run between the contractile reservoirs, which lie very close to the surface of the body, and between the surfaces of the body inside the cortical substance; and the ori- fices may likewise be seen. Another remarkable position is when the nucleus is turned next the observer at the surface of the body; the canals are then seen remarkably clearly on its bright background. A few canals always run over directly, with a slight curvature, towards the posterior part of the mouth. When the animalcule lies so that the contractile vesicle appears at the margin of the body, there is sometimes an appearance as if one or more of the canals opened externally at this point; but close examination shows that they curve round and run towards other parts of the body. “The number of vessels opening into the contractile vesicle in Bursaria flava is about thirty; this number, or a few more or less, existed in all the specimens which I examined in reference to this point. They are apparently uniformly distributed over the whole surface. “The specimens of Bursaria flava with two contractile vesicles have the system of canals double, each system grouped independently around its re- servoir. The canals of the posterior reservoir stretch into the district of the anterior; but I have never been able to detect any communication between the two. In the Ophryoglenae from the Spree very little could be detected of the canals, even when the interior of the body contained only slightly re- fractive substances. When a suitable specimen is somewhat compressed be- tween the glasses, so that it cannot move about, the vessels are especially seen when they have the nucleus for a background, and when they end in the contractile vesicle. “I have never been able to trace any vessels into the interior of the body —for instance, towards the nucleus. I am also ignorant at present whether that part of the contractile vesicle which is turned toward the centre of the body of the animalcule receives any vessels. “Both Bursaria flava and Ophryoglena flavicans belong to those Infusoria in which the contractile reservoirs may assume the well-known stellate form. Von Siebold describes this phenomenon in Paramecium in the following words:—‘These pulsating spaces have a very striking shape; they consist of two central round cavities, around which stand from five to seven smaller OF TEIE PROTOZOA.--—CILIATA. 323 pear-shaped reservoirs, with points directed outwards in the shape of a star. In the pulsation of these strange star-shaped reservoirs sometimes the stars disappear entirely, sometimes only the central round spaces, and Sometimes only the rays.” The opaque Bursariae exhibit this phenomenon just in the same way as it is described by Von Siebold; and those speci- mens in which the vascular system can be detected, offer the explanation of it. The Small pear-shaped spaces are really the commencements of the vessels, which expand with the accumulated fluid; and the rays are the further prolongations of the same, which may be traced to the ends of the body. “At the moment when the contractile vesicle has attained the greatest ex- pansion (that is, when the diastole is terminated), it appears in the form of a globe filled with colourless fluid, from which the vessels run out on all sides in the cortical substance as canals, apparently of equal diameter; they have at this time the smallest diameter they can assume at their embouchure into the reservoir. In opaque specimens, this is the moment when the opened contractile vesicle is observed. A little before we observe the commencement of the systole, the vessels begin to expand slowly, at points distant about one diameter of the contractile vesicle from the surface of the latter, to many times their original size. The more the systole progresses, the wider and longer become the swollen’ places, and they approach gradually to the contractile vesicle. If we make an observation at the moment when the diameter of the contractile vesicle is diminished to about one-fourth of its original size, the shape of the apparatus agrees in all essential points with the well-known stellate figure represented by Dujardin in Paramecium Aurelia, with the single exception that the embouchures of the rays are distinctly visible, and their peripheral prolongations run out widely in the form of canals over the entire animalcule. Opaque specimens of the Bursaria display the phenome- non only in such a degree that the rays terminate in delicate attenuated points, at a distance of about one diameter of the reservoir from the latter. When the contractile vesicle has closed completely, the fusiformly-expanded vessels only are seen, as they run together with their apices to one point. This completes the systole. The diastole then recommences. If we examine the animal at the moment when the reservoir has again attained half its greatest diameter, we find a totally different appearance from that at the cor- responding epoch of the systole. The vessels are not expanded now in the form of a spindle, but of a funnel, with the base of the funnel in the contrac- tile vesicle, and the point prolonged out into the vessel. This is the form which Ehrenberg has figured in Paramecium Aurelia, only omitting the fur- ther prolongations of the vessels. Von Siebold rejects Ehrenberg's figure and recognizes Dujardin’s; but both are really correct, only representing different instants; Dujardin gives a stage of the systole, Ehrenberg of the diastole. “The more the contractile vesicle now expands, the more is the depth of the funnel decreased, and its diameter proportionately increased ; or, in other words, the vessel expands only at its embouchure, and the depth of the ex- panded part decreases in proportion with the advance of the diastole. In opaque Bursaria, we see at this time only the contractile vesicle produced out in various directions into short funnel-shaped processes. By degrees these processes entirely disappear, the contractile vesicle having expanded to its original volume. We now see again how, from the fully-expanded contrac- tile vesicle, the whole of the vessels run out in the cortical layer, in all di- rections, as slender streaks; in opaque specimens only the contractile reser- voir is visible. - Y 2 324 GENERAL ELISTORY OF THE INFUSORIA. “The processes above described are those usually observed when a suitable specimen is placed so that it cannot moye, or only move very little, upon the slider. If, however, a Bursaria is compressed somewhat more with the co- vering-glass, or if the water on the slider is almost all evaporated, some other peculiar phenomena present themselves, not only in the contractile vesicle, but in the vessels. The last diastole coming perfectly to rest, and nothing unusual being observed, except that the reservoir is more elongated, with the systole appear suddenly two contractile vesicles instead of one ; that is, a portion of the surrounding substance makes its way across the middle of the contractile vesicle while it is contracting, and thus divides it into two parts. Bach of these two new reservoirs has its own systole and diastole. In most cases their contractions do not occur at the same moment. Each is in con- nexion with those vessels which opened into it before the separation. The vessels exhibit the same play as if there were but one uninjured contractile vesicle. Sometimes the two reservoirs reunite into a single one. I saw this happen during a diastole which occurred exactly simultaneously in both : they advanced near together, projected out points toward each each other, which came in contact and formed a dumb-bell-shaped reservoir; and this was ra– pidly converted into a globular vesicle, which contracted and expanded as at the origin. “Won Siebold has already observed in Phialina vermicularis, Bursaria cordiformis, &c., ‘ that in strong contractions of the whole body, a largish round pulsating space was drawn out longitudinally, constricted in the mid- dle, and at length was separated into two smaller round spaces—exactly as occurs when a drop of oil is separated into two portions.” During the above- described alterations in the contractile vesicles, alterations ordinarily take place in the vessels also. Thus expansions appear in them at points lying very distant from the contractile reservoirs. These enlargements are not, however, subject to rhythmical disappearance and reappearance, but are per- manent; they are filled with the same colourless fluid as the contractile vesi- cles, and are mostly globular or ellipsoidal. If such enlargements of the vessels are seen in specimens which, from unfavourable optical conditions, do not display the vessels themselves, they may be taken for vacuoles (in Dujardin’s sense). Their connexion with the vessels, and their mode of origin, which is readily accessible to observation, prove that they are totally distinct from the vacuoles in the interior of the body, part of which contain nutrient sub- stance, while part do not. - “I have not succeeded in any case in isolating a membrane of the contrac- tile reservoir or of the vessels. I find no trace of cilia in the interior of the vascular system. This alone suffices to distinguish essentially those Infusoria furnished with vessels from the Distoma-embryo in which G. R. Wagener has discovered ciliated vessels. “Different hypotheses have been put forth in explanation of the function of the contractile vesicles. There is a detailed account of these in Claparède's paper on Actinophrys. Claparède rightly explains the contractile vesicles as organs of the circulation. As to the direction in which the fluid flows in the vessels, nothing can be directly observed in most cases, since we cannot per- ceive in the fluid any solid corpuscles at all similar to the blood-corpuscles of other animals. Is it a perfect circulation ? or does the fluid flow back again in the same vessel in which it has been propelled forward by the contractile vesicle? or are the contents of the contractile vesicles constantly expelled externally? The last view has been set up by Oscar Schmidt. He states that he has seen the place of exit in the genera Bursaria and Paramecium. Claparède is opposed to this, since, in the most minute examination, he was OF TEIE PROTOZOA.—CILIATA, 325 unable to discover that the contents of the contractile vesicle were expelled externally in the systole. Actinophrys is better suited to the settlement of this question than a ciliated Infusorium. I have many times sought for currents in the fluid surrounding Actinophrys Sol and A. Eichhornii, when the fluid contained masses of fine globules immediately in front of the projection of the contractile reservoir; but I have never seen, any more than Claparède, any corresponding displacement when the vesicle contracted. In Bursaria !ewcas, B. Vorticella, Paramecium Aurelia, and P. Chrysalis, I obtained the following results:—The contraction takes place exactly in the manner de- scribed by Schmidt; the vesicle contracts from the interior of the animalcule towards a point lying near the surface, and it expands on the entrance of the fluid in such a manner that it increases in diameter gradually from the surface of the animacule inwards toward the centre. But does this teach us what Schmidt concludes from it, that the reservoir expels its contents outwardly everytime when it contracts toward the outside, and becomes filled from without When it expands toward the interior 2 If the contractile reservoir is attached by that part turned toward the surface of the animalcule to the internal surface of the cortical substance, while the portion projecting into the interior of the body is free in the soft medullary mass, will not the contraction take place from within outwardly, and the expansion from without inward, whether the fluid flow inwards or outwards? In Actinophrys, sometimes in Arcella vul- garis, and in Urostyla grandis, a totally different import must be attributed to the contractile reservoir, if Schmidt’s criterion be valid; for here the re- Servoir does not contract toward the surface, but toward the interior of the body, and forms an elevation on the surface when it becomes filled, as de- scribed minutely in Actinophrys by both Von Siebold and Claparède. But it is not on this alone that Schmidt rests his opinion : he asserts that he has observed also an actual external orifice of the contractile vesicle. I must admit that Bursaria Vorticella has a distinct orifice at the hinder part of the body, and this exactly at the place to which the contractile vesicle contracts until it vanishes. But regarding this orifice which I saw, only so much is established—that it is the anal orifice which Ehrenberg has already described. I have Seen the emergence of remains of devoured substances, of lorica of Bacillaria, of fine undeterminable granules, &c., from this very hole, so fre- quently, that there can be no doubt on this point; and it is even not rare for a corpuscle to slip out from the anal Orifice during the diastole,_that is to say, at the very time when, according to Schmidt, the fluid should flow in from the outside. I found the Bursaria just named during spring and sum- mer in standing water near Tempelhof; it agrees in the main with Ehren- berg’s Bursaria Vorticella. The buccal orifice is situated as in Bursaria truncatella, in which, however, I did not observe any contractile vesicle at the posterior end of the body. The specimens of B. truncatella I observed were all about ; of a line or more long, those of B. Vorticella at most # of a line. The latter is in any case not a Leucophrys; therefore, in case Ehrenberg considers his Bursaria Vorticella a Leucophrys, it is a different animalcule from the latter. I was equally unable to satisfy myself of the correctness of Schmidt’s view in the Paramecia. When a specimen of Para- mecium Aurelia lies so that the contractile vesicle, either the anterior or pos- terior, is seen at the margin, it appears, under certain circumstances, as though a short canal ran directly out through the integument of the animalcule; but in reality it only runs into the integument, and turns round toward the side of the body directed away from the eye : I found the same in Parame- cium Chrysalis also: it was always one of the rays of the contractile vesicle. which presented to Schmidt the appearance of an external orifice. The same 326 * GENERAL IIISTORY OF TEITE INFUSORIA. is the case in Bursaria flava, where I could always trace the curvature of the vessel toward the opposite side of the body most distinctly. F. Stein strongly questions the external opening of the contractile vesicle in the Vorticellae. Hence it is clear that the explanation of the contractile vesicles as part of a water-vascular system is unproven. - “Is it, however, established, on the other hand, that the contractile reser– voirs pour back their contents again into the parenchyma whence they re- ceive it, as Won Siebold says? And if this is the case, how does it happen? Everything indicates most strongly that the contractile vesicles are filled out of the vessels during the diastole. We see how, during this process, the Swollen part of the vessels near their embouchure gradually or suddenly re- turns to its smallest diameter as the stellate figure vanishes; and I have observed a part of a vessel inflated with the fluid, originating at the extreme end of the animalcule, traverse the whole distance up to the contractile vesi- cle during a single diastole. This phenomenon may be supposed to show that the absorbed fluid which had inflated the vessel into a globule, flowed during the said period into the contractile reservoir. “But if there is a fair presumption that the contractile vesicles are filled out of the vessels, the above observations teach us nothing whatever on the question as to where the fluid flows during the systole. “I have hitherto only become acquainted with one fact relating to this point. In Bursaria Vorticella we may detect the following fact : as soon as the con– tractile vesicle which lies at the posterior end of the body has contracted, we may observe at the margins of the animalcule, in its usual position of swim- ming, that two long narrow cavities originate, filled with transparent colour- less fluid ; and these stretch from opposite the mouth as far as the region of the contractile vesicle. They both gradually enlarge, and thus approach near to the anal point ; here they meet, lose their often very irregular form, and change into the globular : the remaining contents of the body are displaced upwards by this; and then these globular reservoirs contract until they vanish, without it being perceptible where the fluid has been driven to ; after Some time the narrow light streaks reappear, and the process is repeated in the way above described. The afferent canals, therefore, are not filled at the commencement of the systole; but must this not be so much the more expected if the fluid flowed back in the same path as it came in, the vanishing of the contractile vesicle taking place much more rapidly than its production ? “I have never yet found in any Infusorium special canals in which the fluid is seen to flow back into the body during the systole, and which would give the means of a perfect circulation.” NUCLEUS. NUCLEOLUS.—A most important internal organ remains for description, viz. the nucleus. This name, if not accurate, is convenient to de- signate the structure in question: it took its rise in the hypothesis of the unicellular nature of the Ciliata, and has ever since replaced the name “testis,” or male spermatic gland, assigned it by Ehrenberg on the sup- position of its being the male reproductive organ in these presumed herma- phrodite beings. Indeed, when viewed as the centre of reproductive activity, or, in Prof. Owen’s phraseology, the seat of the ‘spermatic force,” the Berlin naturalist’s name for it does not appear so inappropriate; nevertheless no real homology can be said to exist between the testis of higher animals and this body, which, on the contrary, has several points of analogy, at least, with the nucleus of plant-cells; nor can a hermaphrodite nature be rightly ascribed to the Ciliata. The nucleus is present in all the Ciliata, and is mostly very readily seen, OF TEIE PROTOZOA.—CILIATA. 327 unless the body is much occupied by food and opaque particles of any kind. If not at once apparent, it is demonstrable by the disruption of the body by pressure ; by the process of diffluence, which disperses the surrounding tissues; or by the addition of acetic acid, which dissolves the rest of the animal, leaving the nucleus more or less completely isolated. It occurs as a well-defined, finely-granular, more or less opaque body, having a more Solid look than the surrounding parts, and frequently also a tawny or slight yellow blush (XXIX. 28 c, 30 c, 48 c : XXX. 1, 11 d, 12 b, 27 f). It varies both in position and shape in different species, and either presents one or more internal spots or small bodies of a circular outline which represent the nucleolus or nucleoli, or this organ may appear as a distinct appendage to it (XXVIII. 9–15; XXIX. 28). The nucleus is im- bedded in or closely united with the cortical lamina; and although it may be thrust aside by the impetus of passing particles of food, it retains its hold. Under the usual point of view of an animalcule, its position will look more central than it really is ; for it is either in advance or in rear of the real centre, or to one side or other of it, and often lies across the alimentary tube when elongated or band-like. But what is curious about this organ is, that it is not at all firmly fixed in its position, but is pushed forward or backward to one side and to the other by the movements of the animal, particularly by those of the retractile ciliary wreath, and also by the ingestion of food. This may be witnessed in Opércularia and Epistylis. Lastly, even in examples of the same species its position is not constant. The usual figure of the nucleusis circular or oblong, but it may be clavate or reniform, or sinuous and band-like. The first type of outline prevails in Para- mecium (XXIX. 28), Colpoda (XXIX. 37), Nassula (XXVIII. 1), Chilodon (XXIX. 48), Spirochona (XXX. 17), and Stylonychia (XXVIII. 10 d). A reniform or kidney-shaped one is seen in Epistylis plicatilis, in Opercularia articulata (XXX.1), and in O. berberina ; a horse-shoe figure in Vorticella and Zoothamniwm; whilst in Epistylis branchiophila, in Ophrydium (XXX. 5, 6), Carchesium, Trichodina (XXIX. 16, 17), Lagenophrys (XXX. 29, 30), &c. it is still more elongated and band-like and much curved, or actually sinuous. Cohn represents it as having a thick clavate figure in Nasswla elegans. The figure, moreover, is very much modified during the reproductive processes, and in the metamorphoses which befall some at least of the Ciliated Protozoa ; these modifications, however, we shall not here consider, but reserve them to the details on development. Again, even among examples of the same species, slight variations occur in length and width, and in curvature or sinuosity, where no reproductive act is discernibly in progress. Lastly, not a few of the nuclei, which are at first sight simply oblong, are, on closer examination, seen to have a depression or sulcus on One side, and consequently to be, strictly speaking, bean- or kidney-shaped. This is exemplified in the nuclei of Para- mecium, certain Nasswlae, and in Prorodom. Where the nucleus is elongated, it is a common event to see it bent par- tially round the pharynx or the Oesophagus, at some little distance from it. The nucleus being the last of the soft contents to break up after death, is presumably of a more solid texture. Its tissue may be described as normally homogeneous; but various changes are ever occurring in it, render- ing it at one time more transparent, at another more granular and opaque. It must owe a certain degree of resistance to external injuries to the fact that it is enclosed by a tough elastic membrane or sac, which sometimes is separated from it by a clear interspace or areola, but at other times is closely adherent, and only demonstrable by artificial means, such as the application of chemical reagents, or of a solution of potash, or of acetic acid: this 328 GENERAL HISTORY OF THE INFUSORIA. happens in Vaginicola. When loose, this membrane not unfrequently falls into plaits or folds. It is represented in Cohn’s figure of the nucleus of Nassula elegans as a very distinct and stout tunic. The rule is, that the nucleus is single, and it has been assumed as a fact that the appearance of a double nucleus or of two nuclei is a general indica- tion of the approaching or progressive act of fission. However, Stein in a recent figure of Stylonychia mytilus (XVIII. 10), delineated in Carus's Icomes Zootomica, represents two ovoid nuclei as present without the accompanying process of self-division. In Chilodon Cucullulus, he also represents the nucleus (XXX. 48 e) to be composed of a moderately thick external or cor- tical portion surrounding a clear cavity, in the centre of which the opaque solid nucleolus is placed. The cortical lamina, he affirms, consists of the usual homogeneous granular substance which makes up the mass of most nuclei, but rather firmer ; and its internal free surface towards the cavity is, he says, undulated or dentated. The interspace between the nuclear lamina and the nucleolus is not always clear, but occasionally occupied by a cloudy, finely-granular matter, whence the nucleus acquires rather the characters of a homogeneous tissue, having a central, well-defined nucleolus. Although the last-named structure is probably never absent, it has nevertheless escaped Stein’s notice in very young specimens. The nucleus of Spirochona in young specimens is either solid and homogeneous, or transversely divided into two by a crescentic space (XXX. 28.f); the nucleolus occupies the middle of the nuclear cavity, and has around it a finely-dotted areola (XXX. 17). In the case of Paramecium both Cohn and Stein describe the nucleolus to be included in a depression or hilum on One side the nucleus. Like the nucleus it is formed of a membranous coat and homogeneous contents (XXIX. 28 d.); the connexion between the two appears to be only by the adhesion of their membranes, an adhesion readily broken through by pressure or by the action of acetic acid. Further, in the long band-like nuclei, the nucleoli seem to be multiplied in number. On the subject of its chemical nature, Stein concludes from the reaction of tincture of iodine, and of acetic acid with a solution of sugar, that the nucleus is a proteine compound, like the other contents, except the fat-corpuscles. Although its office in Secreting a spermatic fluid may be justly called in question (direct observation being contrary to it), yet this so-called testis, or, perhaps more correctly, this nucleus, certainly plays a most important part in the well-observed mode of propagation by spontaneous fission; for whenever fission, whether longitudinal or transverse, is about to occur in an animalcule, the first change observed is a progressive constriction of the nucleus, suc– ceeded by that of the body generally. This constriction goes on till division is complete, each segment of the body being consequently provided with a nucleus. The division of the nucleus, as an essential element in the process of spontaneous fission, may be well observed in the transverse division of Paramecium, Bursaria, or Chilodon. Professor Owen, in his learned and able Essay on Parthenogenesis, refers to the initiative, assumed by the nucleus of Infusoria, in their reproduction by spontaneous fission, between which and the essential contact of the sper- matozoon with the germ-cell, as a preliminary to the primary process of self-division of the latter, in the course of the development of more perfect animals, he indicates an analogy; and, after having completed the comparison of the results in the two cases, goes on to say, “This is certain, that the analogy between these phenomena in the multiplication of the parts of the germ-mass, and those of the nucleus in the multiplication of monads, is so close, that one cannot reasonably suppose that the nature and properties OF THE PROTOZOA.—CILIATA. 329 of the nucleus of the impregnated germ-cell, and that of the monad can be different. - “Therefore, I infer, that the nucleus of the Polygastric animalcules is the seat of the spermatic force ; it can only be called testis, figuratively, it is the essence of the testis. It is the force which governs the act of propagation by spontaneous fission: and, if Ehrenberg be correct, in viewing the interstitial corpuscles as germ-cells (to which opinion Professor Owen inclines), these essential parts of ova may receive the essential matter of the sperm from the nucleus, which is discharged along with them in the breaking up of the monad, which Ehrenberg regards as equivalent to an act of oviposition; and impregnated germ-cells may thus be prepared to diffuse through space, and carry the species of Polygastric animalcules to a distance from the scene of life of the parent’’ (p. 67, Ed. 1849.) Lieberkühn (A. N. H. xviii. 1856, p. 321) makes the nucleolus of import- ance in founding specific characters. He says, that, excepting the eye-point, the nucleolus is properly the only part which distinguishes Ophryoglena flavicans from Bursaria flava.-‘‘This body,” he proceeds to say, “is shaped like a grain of barley, and is marked at each end with a few sharply-defined streaks or furrows; its length is somewhat more than Târ of a millimetre, its thickness in the middle about Tºg of a millimetre. Its substance has a stronger refractive power than that of the rest of the body, but far less than the fat-like globules. Under the highest magnifying power, no structure could be distinguished, and it withstands for a considerable time the action of water. The nucleolus is situated on the middle of the nucleus, which is about one-fifth of the entire length of the animalcule, and its breadth in the middle about one-third of its length. . . . It is of ovate form ; its substance displays no recognizable structure. “The nucleolus has very different characters in all the specimens of Bur- saria flava I have hitherto observed. It was always so small that it was difficult to find it, and never became visible until the Infusorium was com- pressed, while in Ophryogléna flava it may usually be seen through the integuments. Its form is globular, and it presents no structure. It gene- rally adheres firmly to the surface of the ovate nucleus.” The same lesson concerning the utility of the nucleus and nucleolus in distinguishing genera and species, might be gathered from the descriptions of Stein and others, which show clearly enough that these organs have a determinate figure and relation in several genera, as, for example, in Spiro- chona and Paramecium. The figure of the nucleus and the relation of the nucleolus to it, in Pro- rodon teres and in Nassula elegans, are deserving attention. In the former species the nucleus is represented as globular, with a nucleolus surmounting it (XXVIII. 9); in the latter, the nucleus is stoutly clavate, and terminated by a small oblong nucleolus at its narrower extremity. These well-marked peculiarities in the two examples named, coupled with the views of Lieber- kühn just cited, and the conclusions of Stein and Balbiani concerning the physiological relations of the two organs in question, will challenge for them much more attention than they have hitherto received. M. Balbiani has lately contributed to the French Academy two most im– portant papers, in which he has endeavoured to demonstrate a sexual repro- duction of the Ciliata, the nucleus representing the female, and the nucleolus the male, element. In his first essay he illustrates his hypothesis by reference to Paramecium Bursaria (A. N. H. 1858, i. p. 435), and thus writes:— “For several generations the Paramecia multiply by spontaneous Scission, each of the two new individuals obtaining half the primitive nucleus. . . . 330 GENERAL EIISTORY OF THE INFUSORIA. But under the influence of conditions of which we are still ignorant, the species propagates itself in a very different manner, and in the midst of phe- nomena far more complex than those which preside over the multiplication by fissiparity. In this new mode we shall see the actual anatomical signifi- cation of the nucleus and nucleolus, the function of which, if we except the division of the former of these two organs in the act of spontaneous division, has hitherto been perfectly passive. It is, in fact, at their expense that the male and female reproductive elements which characterize this mode of propagation are formed. . “When the period arrives at which the Paramecia are to propagate with concourse of the sexes, they are seen assembling upon certain parts of the vessel, either towards the bottom, or on the walls. The copulation is always preceded by certain preliminaries which are very curious to observe, but upon which we cannot dwell here. Soon they are found coupled in pairs, adherent laterally and as it were locked together, with the similar extremities turned in the same direction, and the two mouths closely applied to each other. In this state the two conjugated individuals continue moving with agility in the liquid, and turning constantly round their axis. There is nothing, before the copulation, to announce the considerable changes which are about to take place in the nucleus, and the nucleolus which accompanies it. It is during the copulation itself, of which the duration is prolonged for five or six days or more, that their transformation into Sexual reproductive apparatus takes place. “The nucleolus has undergome a considerable increase in size, and has become converted into a sort of capsule of an oval form, of which the surface presents longitudinal and parallel lines or streaks. Nearly always, it soon divides in the direction of its greater axis, into two, or more frequently into four, parts, which continue increasing independently of each other, and in a very irregular manner, and form so many Secondary sacs or capsules. At a period which is still near that of division, these latter appear to be composed of an extremely fine membrane, enveloping a bundle of Small, curved bacilla, extending from one extremity of the Sac to the other, inflated towards the middle, narrowed towards the extremities. It is these which, when seen through the enveloping membrane, give the capsule the striated appearance which is characteristic of it, and which even exists in the nucleolus at almost all the other periods of the life of the Infusorium. It also contains a perfectly colourless and homogeneous fluid. “At the same time the nucleus has also changed its form and aspect; it has become rounded and widened; its substance has become softer and lost its refractive power, and towards its margins it presents notches, which, penetrating more and more deeply into its mass, isolate one or more frag- ments, in which a sufficient magnifying power enables us to see a certain number of small transparent spheres with an obscure central point. In other cases the nucleus, whilst still almost entire, presents this aspect, and then appears as if stuffed with these little rounded bodies, the analogy of which to ovules cannot be doubted in the least. The evolution of the nucleus and nucleolus being identical and progressing at the same rate in the two coupled individuals, it follows, if from this moment we regard the former as an ovary, and the second as a testicle or Seminal capsule, not only that each of them possesses the attributes of both sexes, but that they fecundate each other, and serve at the same time as male and female. As regards this fecundation itself, everything seems to prove that it takes place by means of an exchange, made by the two coupled individuals, of one or more of their seminal capsules, which pass, through the apertures of the mouths closely applied against each other, from the body of one Paramecium into that of the other; for, very OF THE PROTOZOA.—CILIATA. 331 often, although we may not be able to perceive this passage itself, we may at least detect the moment when one of the capsules already engaged in one of the mouths, is on the point of clearing this aperture. Does the exchange which causes fecundation take place with all the capsules in a single copula- tion, or in so many successive copulations with different individuals? This is a question the Solution of which is not easy, and which, to keep within the field of our observations, we shall not attempt to solve at present. “However this may be, each capsule, after its transmission, still continues to increase in size in the body of the individual which has received it; for we have never found any which had attained the limit of their development in individuals which were still coupled. They then frequently attain a volume greater than that of the nucleus itself; but there is never more than one that arrives at maturity at the same time. When, having arrived at this state, it is examined after being pressed out of the body of the animalcule to free it from the granulations which mask it more or less while there, it appears under the form of a large ovoid body, the surface of which presents a multi- tude of parallel striae directed longitudinally, and due to the arrangement in series of the corpuscles contained in the interior. Compression, carried so far as to cause its rupture, distinctly shows it to be formed by a membrane of extreme tenuity, and contents, enclosing an innumerable quantity of small fusiform corpuscles, of which the extremities are completely lost to sight in consequence of their extreme fineness. As soon as they are free, these little bodies show themselves to be animated by a vacillatory and translatory move- ment, which Soon causes their dispersion in the circumambient fluid. These are the spermatozoids of P. Bursaria. Iodine, alcohol, and acetic acid instantly stop their movements; they are insoluble in the last-mentioned reagent when concentrated, although this dissolves all the other elements of the body, with the exception of the green granules. “It is usually from the fifth to the sixth day following the copulation, that the first germs are seen to make their appearance, in the form of small rounded bodies, formed of a membrane which is rendered very evident by acetic acid, and greyish, pale, homogeneous, or almost imperceptibly granular contents, in which neither nucleus nor contractile vesicle is yet to be distinguished. These organs do not appear until afterwards. The observations of Stein and F. Cohn have shown how these embryos quit the body of the mother in the form of Acinetoe furnished with knobbed tentacles—true suckers, by means of which they remain for some time still adherent to the mother, deriving their nourishment from her substance; but their investigations did not reveal to them the ultimate fate of these young animalcules. I have been able to follow them for a considerable time after they detached them- selves from the body of the mother, and have convinced myself that, after losing their suckers, becoming Surrounded with vibratile cilia, and obtaining a mouth which first shows itself in the form of a longitudinal furrow, they definitely acquired the form of the mother, becoming penetrated in the same way by the green granulations characteristic of this Paramecium, without undergoing any more important metamorphOSes.” At the time this first record of his observations was read, M. Balbiani stated that he had collected them from the investigation of six or seven species, but since that period he has pursued his observations in several other species, and completed some old ones previously interrupted from want of materials (A. N. H. 1858, ii. p. 439). In his latest paper, he enunciates the remark– able statement that he has been led to regard, in a great number of cases, what nearly all authors have considered to be a spontaneous division in a longitudinal direction, as a sexual union of two individuals. “Wery often, 332 GENERAL EIISTORY OF TEIE INFUSORIA. in fact, I have been able to ascertain that this state coincided with cer– tain remarkable changes which took place in the internal organs of these animals.” * - The following is the general summary of the results M. Balbiani has arrived at:—“I. The corpuscle which, in the Infusoria, has been described under the name of nucleolus, and which I have shown to be the male genital gland, has hitherto only been indicated in a few rare species. In connexion with this, I have examined a great number of individuals belonging to numer- ous and varied forms, and I have convinced myself that, far from constituting an exception, the presence of one or even several nucleoles, was a nearly con- stant fact in the different types of this class; but frequently the simple or multiple nucleole which they contain is so intimately confounded with the substance of the nucleus, that it only becomes apparent when it is separated therefrom accidentally by the action of reagents, or spontaneously at certain determinate periods in the life of these creatures, principally at the time of their sexual propagation. I have counted fourteen species in which this organ was very evident to me, and in which I have also been able to follow its evolution, to a greater or less extent, at the breeding-season, at the same time that I was an eye-witness of the other actions which concur in assuring the reproduction of these animalcules by fecundated germs. “As regards the number and situation of the testicular organ of the Infu- soria, I have met with the following varieties. It is simple, rounded, and lodged in more or less deep depressions of the nucleus in Paramecium Aurelia and P. caudatum, and also in a third species, nearly allied to P. Bursaria, but smaller and destitute of green granules. The genus Bursaria (B. leucas, flava, and vernalis) also presents a simple nucleole situated in the vicinity of the nucleus. The same thing occurs in Chilodon Cucullulus. But with regard to the latter, I must remark that I do not regard as the analogue of the nucleole of the preceding species the corpuscle to which M. von Siebold has given this name, and which is placed in the interior of the granular mass of the nucleus, in the centre of a broad transparent Zone. The true nucleole or testicle of Chilodon appears in the form of a Small, rounded, brilliant grain, provided with a proper membrane, and situated quite to one side and towards the middle of the nucleus. It is very easily perceived in large specimens by employing the action of reagents. As regards the nucleus and its internal parts, I make no difficulty in regarding them as representing all the elements of an ovum, of which the nucleole of the celebrated German naturalist would be nothing but the germinal spot. The disappearance of the clear zone and of its central corpuscle in the animals which have just copulated, especially appears to me to militate in favour of this view. “II. I have met with a multiple testicle in many species belonging to the groups of the Oaytrichince and of the Euplotes or Ploesconice, including the highest types of this class. In the genus Oaytricha the two nuclei, which are elongated in the direction of the greater axis of the body, are each accom- panied by a small, rounded, testicular body, very distinct from the correspond- ing nucleus. There are also two, placed one to the right and the other to the left of the long nucleus, which is curved into the form of a horse-shoe, in Euplotes Charon and E. viridis. In the genera Stylonychia (S. Mytilus, pustulata, and lanceolata) and Urostyla (U. grandis) the nucleoles, to the number of four or five, are distributed in two groups in the vicinity of the nuclei, of which the anterior is accompanied by two, and the posterior also by two or sometimes three, of these little organs. They are remarkable from their distinctly-rounded outline, their great refractive power, and their homogeneous structure. In Spirostomwm ambiguum, each of the grains of OF TEIE PROTOZOA.--CILIATA. 333 the long moniliform cord which here replaces the oval nucleus of the other species, gives lodgment, in a deep depression of its surface, to a small rounded corpuscle, which corresponds with the nucleole of the preceding species; this brings the number of testicles in this animal to forty-five or fifty. I have only been able to perceive them in individuals which have been copulating for a certain time, and by employing dilute acetic acid. It is very probable that an analogous arrangement will be found in the other types, in which the nucleus is formed of grains placed in a single row, like a necklace, such as Stentor, Kondylostomum, Trachelius moniliger, &c. “III. The evolution of the male genital apparatus of the Infusoria, as just characterized, in the other species of the genus Paramecium does not differ from that presented to us by P. Bursaria. In the Oxytrichina each of these organs remains entire, becomes enlarged, and exhibits in its interior, applied against its wall, a thick granular body, furnished with a tubular appendage, which projects into the cavity of the capsule, and appears to be open at its free extremity. This tube, which seems to be an excretory duct, often appeared to be filled with capillary filaments of extreme fineness, arranged parallel to the axis of the duct in question, in which they were fixed by a portion of their length, whilst the remainder, escaping by the orifice of the tube, radiated in all directions in the interior of the capsule. Subsequently the granular body and its duct disappear, and the filaments, becoming free, collect into a bundle, which fills the whole of the formative sac. Although I have never seen them execute any movements, I do not hesitate in consi– dering them as the spermatic filaments of these animals. “IV. It is with equal certainty that we may call the nucleus the female genital organ of the Infusoria, in opposition to the perfectly hypothetical assertion of Ehrenberg, who regards it as the testicle. Its evolution likewise only commences at the time of reproduction, and often during the sexual union itself. In P. Aurelia and P. caudatum, towards the end of the copulation, its surface is traversed in all directions by numerous furrows, which, penetrat- ing deeper and deeper into its mass, finally divide it into a great number of unequal and irregularly-rounded fragments, having a clear centre more or less surrounded by granules. I should compare these with the first rudi- ment of a vitellus, and the transparent central portion to a more or less developed germinal vesicle. The fragments thus formed are soon dis– persed in the surrounding parenchyma. Here a very small number of them, almost always four, never more and very rarely less, complete their evolution, and soon acquire the appearance of complete and well-developed ova. In this state they present themselves in the form of small brilliant bodies, per- fectly equal in volume, slightly oval, and of a bluish-grey appearance. We may very clearly distinguish in them a finely-granular vitellus, surrounded by its proper membrane, which separates from it more or less. after a few moments’ exposure to water. The germinal vesicle and spot are also visible with a distinctness truly surprising, considering that we have to do here with the smallest of living organisms. I have met with these ova still enclosed in the body of the animal on the seventh day after the copulation: they no longer exhibited either germinal vesicle or spot; and their volume had slightly increased. In the allied species, P. Bursaria, the reniform nucleus becomes unrolled before breaking up, and in this state resembles the ribbon-shaped nucleus of the Vorticellae. About twenty or twenty-five of the fragments produced from it continue their development and become so many perfect ova. In the nucleus of Chilodon Cucullulus, also, we observe, after the copu- lation, the disappearance of the transparent Zone with its central obscure spot. In the genera Stylonychia and Urostyla the ova are four in number, 334 GENERAL BIISTORY OF TELE INFUSORIA. as in Paramecium caudatum, but they are produced by a different mechanism. Each of the two nuclei divides into two halves, as in the act of spontaneous division; and the four fragments thus produced form an equal number of perfect ova. Lastly, in Spirostomum ambiguum, we have seen, in individuals which have been copulating for some time, the forty or fifty grains of the long flexuous cord which traverses the body become rounded and detached from each other. But we have been unable to discover in these all the characters of an ovum with the same distinctness as in the preceding species, no doubt because they had not yet arrived at their complete development. “W. I have not witnessed the deposition of the ova in these animals. It is very probable that they escaped by the anus, or by some neighbouring aperture. Thus, in the Stylonychiae, I have seen them collect in the posterior part of the body, which bears the anal orifice, and diminish gradually in num- ber from the first or second day after the copulation. It is a singular thing, that about this period a round pale body begins to make its appearance in the centre of the animal; this becomes Constricted about the middle, and recon- stitutes the double nucleus of Stylomychia. “WI. The Infusoria are destitute of copulatory organs. In most cases the copulation is effected by simple juxtaposition, the two mouths establishing the sexual communication (Paramecium, Bursaria, Euplotes, Chilodon, Spiro– stomum). In the Oaytrichina the union is more intimate, and goes so far as to constitute a true soldering of the two individuals for more than two-thirds of their anterior part. Any one who had not witnessed all the phases of this singular copulation, would be unable to avoid regarding this state as a longi- tudinal division, proceeding from behind forwards, in a single animal. But, even if direct observation were wanting, the concomitant changes of the internal organs, which are so characteristic, cannot leave the least doubt as to the actual signification of this act.” Ovu IES.–In Ehrenberg’s organology of Infusoria, ovules or ova assumed a high importance. The structures he so designated had no distinctive features assigned them, whereby they could be distinguished from other corpuscles and granules in the interior; and, in consequence, their existence could not be confirmed by other microscopists, who for the most part declared that the supposed ova were indifferently alimentary vacuoles, particles of food, fat globules, or the ordinary granules of the interior. The general opinion became pronounced against the very existence of ovules and of development by their means, whilst the deposition of ova, which Ehrenberg believed he witnessed in several instances, was explained to be an act of diffluence misconceived. This explanation, for instance, has been given to his recorded observation and his figures of the act of oviposition in Colpoda Cucullulus, which represented this animalcule as bursting and giving vent to strings of Ova, which first ran together in a reticulate manner, and then, after a time, became individually developed into young Colpoda. According to the opposite view, the bursting and extrusion of contents are no other than the phenomena of diffluence and the dispersion of particles of sarcode, whilst the young supposed to originate from those particles are merely minute Monads or monadiform corpuscles found in company with the Colpoda. One objection brought against the assumption of ova being ejected from Protozoa in the exercise of a generative function is certainly frivolous—viz. that the empty or broken shells of the ova ought to be met with ; for the shell of an egg, however useful in larger animals as a defence against injury, is no essential part of an ovum from which a new being can be developed. Although the existence of ova among the Ciliata has been denied by the great authorities on Infusoria—by Kölliker, Siebold, Leuckart, Cohn, Stein, OF THE PROTOZOA.—CILIATA. 335 Van der Hoeven and others, yet it has latterly found two advocates in Prof. Perty and Mr. Carter. The latter writer (A. N. H. 1856, xviii. p. 225) can adduce little direct evidence to support his views, and seems to rest more weight upon argument from analogy with Amoebaea, Arcellina, Astasiae, and Euglence, in all which he has satisfied his own mind of the presence of ovules, and of their development in the two latter genera. “The same kind of develop- ment,” he writes, “ of the ovule probably takes place in all the Rhizopoda as in Spongilla and in Astasia and Euglena:” but this is not proving that Rhi- zopoda are developed by ova; and the entire value of the presumed analogy with Astasice depends on our admitting a natural affinity and close similarity in organization between that family and Ciliated Protozoa, on the one hand, and Rhizopodous Protozoa on the other. Indeed, we imagine the prevailing’ opinion to be, that the history of development of Astasiaea corresponds rather with that of vegetable organisms than with that of the Protozoa ; for this so- called ovular reproduction of the Astasiaea certainly seems analogous with the development of Zoospores in many unicellular Algæ. To recur to Mr. Carter’s statements, he tells us he applies the term “ovules” to “a number of discoid or globular nucleated cells, which appear together in the sarcode of some of the Infusoria; ” and he subsequently pro- ceeds to uphold his views by his own personal observations, and by inferences drawn from others. “In many of Ehrenberg’s enterodelous Infusoria it is not uncommon to see a number of defined globular bodies, of nearly equal size and of a faint opaque yellow colour, which closely resemble ovules— e.g. Amphileptus fasciola (Ehr.), Himantophorus Charon (Ehr.), &c.; nor is it improbable that many of his Trachelina, which come near Planaria, possess ovules similar to those which are found in the latter; but, from being so much mixed up with the spherical cells, pass equally unnoticed while in, as well as when out of, the body, under such circumstances. M. J. Haime, however, has distinctly seen instances in which these bodies have been ejected from Infusoria, and have passed into locomotive animalcules under his eye. Thus he states that in Ploesconia they form a group of from forty to fifty in the middle of the body, are round, issue one by One, remain tranquil Some time, then deve- lop two filaments, one in front, the other behind, and move about rapidly. In an ‘undescribed 'species of Dileptus they are whitish, and form a wreath extending almost throughout the whole length of the body, become yellow towards the anal extremity, where they pass out with the remains of the food, soon develope two opposite filaments, and move about rapidly. In Paramecium Aurelia, M. Haime states that an ovary appears some hours before death, about the middle of the body, which becomes filled with about sixty little nuclei: these increase in size, burst the ovisac, and thus pass into the body of the parent, from which they finally escape by an opening in the tegumentary covering, formed by the diffluence of the latter; and the ovisac follows them.” Perty has used great diligence in Searching for the presence of ovules or, more accurately, of germs (Blastien), and has adduced various arguments for their existence. He states (op. cit, p. 66) that their aspect is distinctive, although their colour varies in different species, that, unlike food, they re- tain their form, increasing only in size, and that, on the dissolution or breaking up of the animalcules, they display themselves as free individualized struc- tures. It is only, he adds, in incomplete forms, in young and imperfect beings, that any doubt can exist respecting the character of these corpuscles. Ovular development does not take place as Dujardin Surmised, by detached morsels of the sarcode, nor by ova. Such as Ehrenberg Supposed, but by a peculiar set of bodies, originating in the interior of the animals, and progressively 336 GENERAL HISTORY OF TELE INFUSORIA. multiplied. Their minuteness is a bar to observation; and it is only by the concurrence of favourable circumstances—by the presence of the ovules in their first, intermediate, and finished stages—that they can be satisfactorily made out, as in Nassula aurea, Euglena viridis, Chonemonas bicolor, &c. Fission may be several times repeated; but the formation of germs takes place at the expense of the contents of the parent. The unusually small size of many animalcules is another argument advanced in favour of propagation by germs or ova, since the act of fission is limited to a certain size, and the natural characters of the species are to be preserved. Thus Perty met with examples of Kerona pustulata as small as 1-70", which could scarcely originate from fission. They were exactly like the original animalcule except in being more round. Specimens of Pleuronema crassum occur no larger than 1–90", devoid of molecules, more transparent and slender than old ones, with a more pointed apex, but otherwise their counterpart. Again, Nassula awrea varies from 1–150” to 1-12"; and in those of 1–50” the rudiments of the “dental” apparatus are distinguishable. An Amphileptus mo– miliger, 1–6", having a very short neck, was distended by 100–150 germs or ovules surrounded by some thousands of fine molecules; that these were neither vacuoles nor stomach-sacs was seen at places where they displayed themselves as individualized corpuscles. Moreover there were no other animalcules or par- ticles of food in the glass containing the Amphileptus, and all the germs were uniform in size, in hue, and in refractibility, and readily distinguishable from some swallowed Infusoria present in some spots. The green spheroidal cor- puscles in Paramecium versutum, having a medium size of 1–450", are true ovules: they do not change colour, like the green nutritive matters of Infusoria, to yellow, red, or brown; and when the animalcule is left dry by evaporation, they become isolated. Although no germinal speck is discoverable in these bodies as in ordinary ovules, yet it is remarkable that a fold, streak, or darker space is visible. Small specimens of this Infusorium also occur in which the ovules are colourless or pale green; and on One occasion Perty saw, amid the fully-developed individuals, oval greenish animalcules of about 1-60", which seemed no other than the escaped germs of the Paramecium. Such are some of the principal observations Perty appeals to in order to substantiate his hypothesis of internal germs and of development from them. He has given, in illustration, a number of figures; but they are too rudely drawn to efficiently answer their object; and we must confess our inability to receive the fact of the existence of ova or germs as at all demonstrated in the Ciliata either by the researches of Mr. Carter or of Perty. The discoid or globular nucleated cells which the first-named writer makes out so clearly in the Astasiaea, are merely supposed to be represented by certain “defined glo- bular bodies of nearly equal size and of a faint opaque yellow colour, which closely resemble ovules” (why?), not uncommon in many ciliated Protozoa, e.g. “Amphileptus fasciola, Himantophorus Charon, &c.” Such evidence is purely presumptive, and is little aided by M. Jules Haime's anomalous obser- vations. Respecting Perty’s arguments and reported phenomena, it may be objected that he does not establish his attempted rigorous description of germs —does not show their distinctive peculiarities as stated, and seems to have confounded together various internal bodies in his description of germs. Thus in the Paramecium versutum (which he presumes to be the same animalcule described by Cohn as Loacodes Bursaria) the green spheroidal corpuscles look to be nothing more than the chlorophyll globules pointed out by Cohn and Stein. Again, of the ambiguous corpuscles in other Protozoa cited as ovules or germs, it is simply from their doubtful character that this can be presumed; for our knowledge of the contents of the Ciliata, of the OF THE PROTOZOA.—CILIATA. . 337 changes they may visibly undergo from the action of external agents, from age, and other conditions, is at present too imperfect to signalize certain par- ticles, definable by no sufficient characteristics, as special structures, such as ova, unless, indeed, we can watch their origin, growth, extrusion, and de- velopment into animalcules assuming the particular form and organization of the parent animal at an earlier or later date. Perty, indeed, has imagined—not proved—certain minute organisms floating in the vicinity of an animalcule, having about the same size as the Supposed internal ovules, to be the young resulting from those germs; and although it cannot be denied that he is in the right, yet it is for him to show that he is so, by elucidating the phases of development; and we must always keep in view the very erroneous fancies which result from these supposed relations between contiguous organisms, very probably only accidentally brought together, of which we have an illustration in the visionary hypotheses of spontaneous development and ascendant embryogeny put forth by Gros and others. We have stated the preceding objections against the particular statements of Carter and Perty, and not against the hypothesis of the production of in- ternal germs ; for sufficient examples are on record of the production of such germs and of living embryos within animalcules, after preparatory develop- mental changes, from the fission and breaking up of the nucleus. Before leaving this hypothesis of the existence and development of internal germs, it is but right to mention that it has been received, among others, by Eckhard and by Oscar Schmidt, both of them supporters, in almost all their details, of Ehren- berg’s views, and who are believed by most authorities to have too much the character of advocates of a particular theory, to discuss or to observe in ge– neral without prejudice. To allude briefly to their observations, Eckhard (A. N. H. 1847, xviii. Suppl. p. 446) in the first place remarks, as others have done, on the very different sizes of animalcules of the same species, as a proof of ovular development, arguing that the very smallest cannot result from fission or gemmation. To this he appends an observation made on Stentor coºruleus (XXIX. 8), which, from its completeness and apparent truthfulness, deserves quotation when we come to speak of the development of ova. Schmidt corroborates Eckhard’s statement of the production of living germs from Stentor carwlews, and affirms, in addition, that germs are frequently extruded and developed outside the parent, and that their subse- quent development from minute globular and conical transparent and almost colourless organisms, with long cilia, may be watched through all the inter- mediate stages until the complete animalcule, with its spiral ciliary wreath and mouth, is perfected. The preceding speculations on the development of ovules and germs have their importance materially modified by M. Balbiani’s recent researches and hypotheses respecting the prevalence of a sexual mode of reproduction among the Ciliata, as detailed above (pp. 329–334). SPERMATOZOIDS (?).—This term is provisionally applied by Mr. Carter to granules originally developed from the nucleus in Amoeba, Euglypha, and Spongilla, and supposed by him to impregnate the ovules. “With reference to the organs of generation,” he writes (A. W. H. 1856, xviii. p. 228), “in the other Infusoria, I can state no more than that, although there is a fusiform nucleus in Otostoma (XXVIII. 25, 26), I have also constantly seen a bunch of string-like filaments floating about its interior, which appeared to be at- tached near the buccal cavity; and although I could make out nothing more, I could at the same time only liken these to the generative apparatus in the Planaria mentioned, which floats round the buccal cavity and upper part of the membranous stomach in a similar manner.” & Z 338 GENERAL HISTORY OF THE INFUSORIA. The notice of Mr. Carter, of the peculiar structures he would designate spermatozoids, is as yet unconfirmed by other writers; and we must therefore consider their nature and purpose still sub judice. Since the above was written, M. Balbiani's researches (A. W. H. 1858, vol. i. p. 435) confirm Mr. Carter's opinion so far as relates to the development of spermatozoids or male reproductive elements, but refers their origin to the nu- cleolus instead of the nucleus. In our history of these last-named organs, we have presented M. Balbiani’s views, and must here refer back to them (p. 329). ACCESSORY CONTENTS:—GRANULES; MOLECULES; SPHERICAL CELLs; SUP- PoSED GLANDS.—Among the remaining contents of the Ciliata are numerous granules, molecules and fat-cells. Mr. Carter (A. N. H. 1856, xviii. p. 121) makes a distinction between granules and molecules—two terms which by others are very loosely used and not specially defined. This writer, however, would restrict the term molecules (moleculae) to colourless granules more minute than those he understands by the latter appellation. “They differ in size, and are the first bodies that appear in it (i. e. the Sarcode). . . . By the time the ovules have become fully formed, the sarcode and its moleculae have died off or disappeared.” The granules “make their appearance among the moleculae, and are cir- culated round the abdominal cavity in the manner of the digestive globules and particles of food. They are of different sizes, but chiefly characterized by being much larger than the moleculae, few in number, of a circular, ellip- tical, elongated, subround, or irregular shape, with thick dark edges, appa- rently produced by obstruction to the passage of light, colourless, or of a yellowish-green tint. When large, and with no other granular matters pre- sent but the moleculae, they form a striking feature in the interior of Amoeba, Vorticella, Oaytricha, Paramecium Awrelia, &c.; but at times they are so in- significant in size as to be undistinguishable from the moleculae, even if present at all. That they are not ovules may be satisfactorily seen when both are together, the dark, thick, and frequently irregular edges and colour- less state of the former contrasting strongly with the thin circular margin and faint yellow tint of the latter. They appear to increase in size and number with the age of the Infusorium, and, when fully developed, to remain unaltered in size, though apparently somewhat shrivelled in form, until their dissolution. On one occasion, while watching the metamorphosis of an Oay- tricha (similar to, but not the same as, that described by M. Jules Haime, and of which I hope to give a detailed account hereafter), these granules, during the formation of the globular cell within the body, which enclosed the materials from which the Ploesconia was ultimately developed, became con- gregated together at the posterior extremity of the Oaytricha, and remained there in a roundish mass, shut out from the cell, until the latter burst for the liberation of the Ploesconia, when, with the deciduous coverings, they passed into dissolution. Of the nature of their office I am ignorant; but they are sufficiently remarkable and constant to demand particular notice.” Perty speaks of molecules and granules together, and expresses his opinion that some are simple fat-corpuscles, and others the first rudiments of internal germs or ovules. Stein also carefully distinguishes fat-granules from others not fatty. In Opercularia, Epistylis, and allied genera of Vorticellina, this observer points out that no particles of food penetrate to the posterior extre- mity, where its diameter is narrowed to unite with the stem, but that this region is occupied with a heap of large fat-corpuscles and of minute granules of probably the same nature. Isolated corpuscles resemble precisely the fat- particles scattered through the body. He cannot assent to Ehrenberg's pro- position, that this heap of granules represents a sort of loose ovary, but would OF THE PROTOZOA.—CILIATA. 339 consider it to be a store of nutritive matter specially intended to furnish the material required in the construction of the stem. Under the name of “spherical cells” Mr. Carter (op. cit. p. 124) describes Some special structures, which, so far as we know, are not mentioned by any other observer. “They abound,” he writes, “ in the sarcode of Otostoma (XXVIII. 25, 26), and apparently in many of Ehrenberg’s “Allotreta.” In Otostoma they are of different sizes, because they are in all stages of develop- ment; and to keep up their numbers without distending the animalcule, they must be continually undergoing rapid decay as well as reproduction. The most remarkable feature in them is, that the largest contain, besides other granular bodies, several small cells filled with a yellowish-brown fluid ; and these cells are also found free among the general group; but of what their ultimate destination is, as they do not appear to grow larger, or to become re- productive, we know nothing.” On comparing these cells with those seen in the stomachs of Planaria, and Rotifera, Mr. Carter concludes that they are homologous with them, and represent a biliary secreting organ. “Although,” he adds, “ ovules may occasionally issue together with these cells from Oto- stoma, &c. as well as from the Plamarice, yet the two can hardly be con- founded.” On the correctness of this description we have no means of deciding: the genus Otostoma has not fallen under our observation; and the figures to illus- trate these spherical cells convey no clear conception of their characters. We might hazard the conjecture that these supposed definite cells are only glo- bules of food; for we are scarcely prepared to admit the existence of hepatic cells in the simple tissue of Protozoa, between which and the complex organ- ization of Rotifera, with their true membranous stomach, so wide a difference Subsists that no true homology can obtain. Perhaps the coloured “spherical cells" of Mr. Carter are identical with the yellowish and brown vesicles Perty (op. cit. p. 53) separated from Nas- sula aurea by crushing it between the glass slide and cover, from stºry" to Tºrp" in size, and which he concluded to be fat-globules, and only another stage of development of numerous smaller white corpuscles he met with in the same being. - Stein has established the existence of a pair of oblong or reniform solid glandular-looking organs a little beneath the peristom of Opércularia arti- culata (XXX. 20), the purpose of which cannot be surmised. Lachmann has hinted at the possibility of their being nervous ganglions, but neverthe- less feels quite unable to express an opinion. & The chlorophyll-corpuscles, chiefly confined to the soft subtegumentary lamina, have already been spoken of (p. 297), and need no further notice, except it be to recall an opinion of Cohn, that the coloured masses, called by Ehrenberg ciliary glands, seen in a few species of Nasswla, are probably of the same nature as those corpuscles. CIRCULATION OF CONTENTs (XXIX. 25).--—The remarkable phenomenon of the circulation or rotation of a portion of the contents, similar to the cy- closis in the cells of many plants, is witnessed in most of the Ciliated Protozoa. It had attracted the notice of several observers before Ehrenberg published his great work in 1838, and was very speedily urged in argument against his views of polygastric organization, to which, indeed, it seemed fatal, inasmuch as such a rotation is clearly incompatible with the existence of stomachs at- tached to, and connected together by, a fixed intestine. To meet the objec- tion thus raised, the Berlin professor suggested that the apparent circulation was abnormal, or a diseased condition, the consequence of an over-distension of one stomach-sac at the sacrifice of others, an explanation quite inadmissi- * - z 2 340 - GENERAL HISTORY OF THE INFUSORIA. ble, since the phenomenon is one to be very frequently observed in animal- cules evidently in full functional activity and uninjured, and because the particles of food entering the interior assume their usual globular form (i. e. acquire the characters given by Ehrenberg to his so-called stomach-sacs), take their usual course, and do not accumulate in a confused manner within a large sac, such as the supposition in question implies. 4. - Microscopists are now agreed in representing this rotation to be confined to a layer or stratum of the contents within the subtegumentary or cortical lamina, and not to extend to the central portion, as Cohn represented (Zeitschr. 1851, p. 265). The current is from left to right, as we look down upon the animalcule (XXIX. 25) under the microscope, and therefore is actually the reverse, or from right to left, with regard to the animal itself. It never changes its direction or course; but its rapidity varies in different species, and even in the same species under different circumstances affecting its vitality: such are, among external conditions, light, air, warmth, and food; others, age, the encysting and reproductive acts. Cohn observed that some particles in a Paramecium Bursaria occupied 1% to 2 minutes in making the circuit. In Vorticella the current is slower. The stream is composed of a thin mu- cilaginous matter, bearing in it numerous granules and molecules, fat-cor- puscles, globules of food (the stomach-sacs of Ehrenberg), and the remnants of alimentary matters in their passage to the discharging outlet. The chlo- rophyll-corpuscles of the cortical layer, the nucleus, and the contractile wesi- cles are not involved in the current, unless, indeed, a few of the first named when accidentally detached from their matrix. The nucleus lies more or less within the stream ; and although moveable to a considerable extent at times by the onward pressure of a bolus of food, it yet seems to maintain a con- nexion with the subtegumentary lamina, and to escape being drawn into the rotating current. Further, in the large Vorticellina, such as Epistylis and Opercularia, the mass of fat-corpuscles at the base of the body does not join in the current; and it must be noted that the food-globules do not circulate until they have lost the independent motion received by them on their pro- pulsion from the extremity of the oesophagus. . The most correct view, in our opinion, of the nature of the rotating stream, is that of Lachmann, who conceives it to be the nutritive fluid elaborated from the food, in a word, “chyme.” Such a fluid, analogy suggests to be needed by the cortical and sarcode laminae over which it spreads itself, to supply ma– terial for their renovation and rebuilding, and to compensate for the constant waste consequent on the perpetual movements of the animal. And may we not further presume that this current also serves to bear away from the lamina effete particles prior to their elimination, just as the blood of higher animals serves both as a pabulum to the tissues and a channel for the removal of their worn-out material? Moreover, this circulation of a nu- tritive fluid around the inner layer of the animalcule has its analogy in the rotation of a similar fluid around the general abdominal cavity of the Coelen- terata, such as the Hydrozoa and Actinozoa. - - Respecting the cause of this rotation of the contents, several explanations have been broached. Some seeing in it a close similarity to the cyclosis of plants, have attributed it to a like cause ; but what this is in vegetable cells is anything but certain. According to some, the nucleus of the plant-cell is the exciting force, since the stream seems to set out from and to return to the nucleus; but this is not universally the case. Others, again, imagine cilia to cover the interior of the cell-wall—but this is only an hypothesis, whilst others find in the functional activity of growth and nutrition, coupled with the co-ordinate actions of light, heat, and chemical affinity, a sufficient cause OF THE PROTOZ.O.A.—CILIATA. 341 for the phenomenon. This last view comprehends the interpretation Stein puts upon the movement in question in the Protozoa, which is, that the chlo- rophyll-globules by their action on light, by the exhalation of carbonic acid gas, and the resultant chemical forces developed, produce the revolving move— ‘ment; for, as he remarks, the movements of the animals have nothing to do with the rotation, as some have suggested, seeing that it goes on when they are in perfect repose; and moreover is seen only in those rich in chlo- rophyll, and not in colourless individuals. In elucidation of chemico-vital action as a motor force, we may allude to vegetable physiology, which teaches us its power in the circulation of the Sap through the appointed channels in the leaves and thence downwards through the inner bark. But, apart from the influence of chemico-vitalforces, we cannot exclude the idea that the propulsive force of the oesophagus, in impelling food or water into the general cavity, must aid the current, even if its axis do not precisely correspond with the course at the point where it is first operative, since, from the difference in the arcs described by the course of the stream and by the Oesophageal current, the two must eventually become coincident and concurrent. - In a recent letter to us, Dr. Strethill Wright remarks that “in Carche– sium polypinum active molecular movements may be detected throughout every part of the zooid (animalcule), even in the thickened rim upon which the cilia are placed. This movement seems to be distinct from the rotatory motion of the whole contents of the body, so readily seen in Epistylis grandis, and which only occasionally occurs in Carchesivm. The zooids of the class of Protozoa seem to be composed of sarcode in its most fluid state, enclosed in a delicate contractile coat. In this Sarcode a desultory circulation occurs, either as molecular motion or as steady rotation, or as a backward and for- ward flowing occasioned by change of shape in the body, as in Ophrydium versatile.” - THE ENCYSTING-PROCESS IN THE CILLATED PROTOzoA (XXVIII. 6, 7, 66, 67, 74–76; XXIX. 18, 19, 21–23, 39–46, 52–58).-Although the encysting- process is very frequently associated with the act of reproduction, yet it is also concerned with the preservation of individual life, and, so far, deserves consideration apart from the former. Were it not for some provision against such a contingency, animalcular life would be exposed to wide-spread destruc- tion by the change of seasons, by the drying up of the pools and ditches they inhabit, and by other injurious external influences. Such a provision is made by the act of encysting, which enables these minute animal organisms at all ages to resist those destructive agencies, and also provides for their almost unlimited diffusion. The construction of sheaths around animalcules is an– other protective act (see p. 282), but differs from encysting in not completely enclosing them. - - When an animalcule is about to encyst itself, its movements become less active, and presently cease; at the same time it withdraws and folds up its rotary or other prominent process, closes its oral aperture and contracts itself in a more or less spherical shape, and its cilia disappear. Having proceeded thus far, an excretion is thrown out around, which gradually hardens, assumes a membranous-form, and invests the animalcule as a cyst or case. It may happen that the construction of the cyst commences before the animal is quiescent, while it still moves slowly about or revolves on itself by the out- pouring of the soft gelatinous matter out of which it is to be elaborated, as is seen in Amphileptus (XXIX. 19), Colpoda (XXIX. 35–43), and Chilodon (XXIX. 48–58). Moreover, after the animalcule is enclosed within its case, it may for a time vary its figure, and also turn on itself with more or less & 342 GENERAL EIISTORY OF THE INFUSORIA. activity, by means of its cilia, which yet remain apparent. Stein mentions. this phenomenon in Stylonychia pustulata (XXIX. 18), and in the encysted embryos or gemmae of Colpoda; and we know that similar movements precede its revival from its quiescent condition in all cases. The cyst-wall is, at least in some examples, double, consisting of an outer, finely-granular, softer layer and an inner, consistent, elastic, homogeneous membrane (XXIX. 21, 22, 41, 43). It may be that two such laminae always exist; for the outer one crumbles away So soon as the enclosed animal prepares to reassume its activity, and it is after the Onset of internal changes that most observations have been made upon cysts. The two coats were remarked by Auerbach (Zeitschr. 1854, p. 431) in Oaytricha Pellionella (XXIX. 21–23); by Stein in Chilodon Cucullulus (XXIX. 53, 54), in Stylonychia pustulata XXIX. 18), and in Nassula ambigua ; and by Cienkowsky in Nassula viridis (XXVIII. 67), &c. In Chilodon, indeed, Stein represents several concentric layers to the cysts (XXIX. 55, 56), and states that in this instance the walls acquire no firmness, but remain soft and gelatinous. Another peculiarity attaching to cysts in some species, is, that they: produce folds or plaits on their surface, and therewith acquire an apparent angular outline, as Stein exhibits in his figures of encysted Epistylis plicatilis and E. branchiophila, where the lines are longitudinal, and in encysted Oper- cularia berberiformis, where they are transverse or annular. Again, the cyst-walls are not always smooth: thus, in Nassula ambigua Stein represents them as punctate in longitudinal lines; in Stylonychia pus- tulata (Müller's Archiv, 1856, iv.; A. N. H. 1857, xix. p. 228) they have stellate markings, and in a small undescribed species of Epistylis a finely- shagreened surface. The changes which the encysting animal itself undergoes have been men- tioned generally; but a few more details, aided by reference to particular examples, are required for a more complete elucidation of them. So soon as the animalcule becomes quiescent within the Sac Secreted around it, the cilia which covered the surface, including any of larger dimensions disposed along certain tracts, or upon particular processes, disappear, and have generally been presumed to be destroyed; however, various observations are on record which seem to show that this is not universally the case, but that not unfrequently they are merely concealed from view; and this being so, it becomes ques- tionable whether—especially in the ordinary process of encysting, where only the conservation of the individual is intended—their destruction or absorption is the rule. An observation of Stein may be quoted on this ques- tion:-An encysted Chilodon Cucullulus, after developing several embryos, ceased this process of propagation, redisplayed its cilia as if by simple evolu- tion, and commenced moving within its cyst along with one of its embryos (XXIX. 58). The inference deducible from this particular observation in the case of the encysting-process, even when exercised for the distinct purpose of generation, is greatly strengthened by the oft-repeated observations of the release of the imprisoned beings, by pressure causing the rupture of the newly- formed cyst, in the possession of their complete figure and their ciliary arma- ture. We may add that no proof exists of an actual new formation of cilia upon beings when emerging from their cyst; all that can be predicated is, that cilia reappear in their normal positions and arrangement. To sketch now the history of the encysting-process by a reference to some of the many examples recorded by various microscopists; for the act has been witnessed in so many species and genera, that it is assumed to be common to all. The description given by Cohn (Zeitschr. 1853, iv. p. 267) of the encyst- ing of Trachelius Ovum may be given as an example (XXIX. 19, 20):—The sº OF TELE PROTOZOA.—CILIATA. 343 movements of the animalcule become slower, and before ceasing altogether, consist in a simple rotation without change of position. The cilia are next Seen to become indistinct and to disappear; and a delicate line, removed some little distance from the periphery of the enclosed animal, makes its appear- ance, indicating the limit of a soft gelatinous envelope. Whilst this proceeds, the animal assumes a more globular and contracted figure, chiefly by folding down its lip- or trunk-like process upon its general surface. The secreted covering in the meanwhile gains in firmness, but loses in thickness, and thus acquires the character of a membrane, which closely invests the Trachelius, except at places where the two surfaces are separate and distinct. This may be termed the first degree of encysting, and affects the creature so slightly that it can shake off its coating of its own accord, and, by rupturing its sac, reassume its pristine appearance and activity. This phenomenon was Witnessed four times in the same individual by Cohn, and supposed by him to have been induced by the abnormal conditions (the action of light, &c.) in which the animalcule was placed under the microscope. Stein (op. cit. p. 133) in a similar manner recounts the formation of a cyst around Chilodon Cucullulus, and the possibility of setting it free by breaking down the cyst by pressure. In Trachelius the development of the cyst, to the stage described, occupied, according to Cohn, only ten minutes. Where the process advances beyond this degree, the cyst commonly acquires a denser and firmer con- sistence; the animalcule can no longer deliver itself at once of its own accord from its prison, but undergoes a further change from its normal form, and requires those vivifying influences of external warmth, light, and moisture, such as spring-time brings with it, to arouse it from its torpid state, and to cause the reappearance of its hitherto obliterated organs. * Stein has very copious details of the whole process of encysting in various Ciliated Protozoa ; but in none is that process more interesting to follow than in the Vorticellina. In members of this family the state of extreme contrac- tion, induced by some external cause obnoxious to them, becomes fixed, and only the irregularly-curved space covered over by the completely-closed peristom indicates the complicated ciliary apparatus of the head; and even this decreases to a streak, and at length vanishes altogether. Whilst this goes forward, a membrane forms around the being which is now detached from its stem, and a globular or ovoid cyst, containing a nucleus and a con- tractile vesicle, is the representative of the once active and elaborately- organized Vorticella. To what degree the encysting process may advance without depriving the animal of its ability to recover its freedom and original character, is well ex- emplified by Auerbach’s observation on the cysts of Oxytricha Pellionella (XXIX. 21, 24) (Zeitschr. 1854, v. p. 430). This able microscopist found a number of globular cysts, with two coats, enclosing a homogeneous, finely- granular, brown substance, within which was a darker, rounded body (XXIX. 21), or at times two, and more rarely three such, seemingly derived from it, indicating the nucleus. The contents naturally filled the capsule; the addi- tion, however, of a little muriatic acid caused them to shrink into a roundish body, somewhat more extended on one side, and traversed by a few deep folds or fissures (XXIX. 22). Such were the bodies met with during the continuance of winter; but when early spring arrived, these began to exhibit signs of vital activity within. The first change remarked was the appearance of a vesicle, which by degrees acquired increased contractility; then the body retracted itself from the cyst-wall and commenced to revolve in a vacillating manner, whilst the outer granular lamina of the cyst broke away. Cilia now could be seen dis- 344 GENERAL EIISTORY OF THE INFUSORIA, tributed over the surface of the animal, and a close row of much stronger ones along a fold recalling the characteristics of Stylonychia or of Oaytricha, although the animal still wanted the general conformation of the body peculiar to either of these genera (XXIX. 23). All this time the darker nuclear body or bodies had retained their existence and position, whilst the contractile vesicle, on the other hand, grew smaller, apparently by the ex- pulsion of part of its fluid contents to occupy the space left between the animal and its capsule by the contraction of the former. The enclosed body, when freed from the wall of the cyst, commenced moving, not in a regular rotation, but in a jerking manner, from side to side as it turned, until at length it ruptured the walls of its prison and made its escape. The animal thus set at large presented the characters of Oaytricha (XXIX. 24) di- stinctly enough to recognize it as belonging to the genus ; and at the same time the numerous escaping germs and the rapid appearance of a multitude of Oaytricha Pellionella of all sizes confirmed this view of their nature. Nevertheless a slight difference existed between the newly-emerged indi- viduals and mature specimens,—the former being more oval, and their contents less hyaline, more granular, and of a yellowish colour by transmitted light: still, specimens occurred of every intermediate shade. - This observation by Auerbach demonstrates to us how completely modified and actually lost the characters of an animalcule may be when it becomes encysted even temporarily, during what has been termed the winter-sleep; for; as that writer shows, the Oxytricha-cysts he discovered could not have been ova, or a mere transitional phase to a higher form of existence. Similar instances of cyst-evolution are recorded by other observers; but generally the whole history of the cyst is not given, but only that portion in which an actual animalcular form, in movement by means of cilia, has revealed itself; such is the instance of Amphileptus Fasciola mentioned by Cohn (Zeitschr. V. 1854, p. 434). Furthermore, variations in the internal appearance and per- ceptible contents of cysts vary in different species, just as do their walls; thus, for example, in Oxytricha-cysts the contractile vesicle had vanished and appeared de novo only when its vital activity was resumed,—while in other cases this sac or space never disappears, but is even more prominent than the nucleus before the action of reagents, which is true of most, or of all, Vorticellina. The particulars recounted by Mr. Brightwell, respecting Zoothamnium Arbuscula (“Fauna Infusoria of Norfolk,’ 1848), which he thought indicative of a mode of development by alternate generation, appear to us to represent probably the act of encysting, or that degree of it assumed by gemmae prior to detachment from their parent stem, and retained by them until they have taken up a fixed position and proceed to develop a peduncle (see section on Fission and Gemmation). We extract Mr. Brightwell’s account, so that our readers may form their own opinion of the nature of the phenomena detailed :— “Sept. 16th, 1846. Early in the morning of this day, we observed one of the Zoothamnium arbuscula, a large old specimen, which had lost all its small bell-shaped animals, but had several medlar-shaped buds or ova re- maining upon it. It was seen to detach from its stalks nearly all these ova, which went off as free animals. One of them soon after settled at the side of the water-trough, and after agitating its anterior cilia it suddenly, and with a kind of violent effort, opened into a cup-shaped form, and darted about with great rapidity, occasionally settling, and darting off again. “ At nine in the morning, one of these buds, or ova, was observed fixed to the glass by a sheathed pedicle; a ciliary motion became perceptible at the OF TEIE PROTOZOA.—CILIATA. . - 345 top of the bulb ; and at ten it had divided longitudinally into two buds, each supported by a short stalk. The ciliary motion continued in the centre of each of these two buds, which by degrees expanded longitudinally, and at twelve had become four buds. By four in the afternoon, these four buds had divided in like manner and increased to nine, with an elongated foot-stalk, and interior contractile muscle. - “During the development of another specimen, the stalk appeared to have transverse ribs or joints, and, whilst a drawing was making, gradually bent downwards, and all the buds severally detached themselves from it, and went off as free animals, leaving only the bent stalk. In this interesting process we see something analogous to what Steenstrup describes as “a mode of development by means of nurses or intermediate generations.” “This mode is described as that in which an animal produces a progeny permanently dissimilar to itself, but which progeny produces a new generation, in itself or its offspring, returning to the form of the parent animal. It will be seen that this development differs from that of metamorphosis, in the circumstance of the intermediate animal (the nurse) being itself a perma- ment and producing form. “To show this to be the case with Zoothamnium, it would be necessary to prove that the medlar-shaped animals were a permanent form, producing a race which, in themselves or in what they produced, returned to the form of the parent animal. “We have not been able to carry the development of these buds or ova further than Pl. 12. f. 67, 68, 69, and wood cut” (see Part II.), “And it is remarkable that in all these the buds have produced, not the little bell-shaped animalcules like the parent animal, but other buds like themselves. May it not be the case, that these medlar-shaped bodies are propagated at the close of the year, and that, when the plant to which the Zoothamnia bearing these bodies are attached dies away, they remain in the mud, protected from the cold of the winter, and in the spring burst forth, and settle upon the new-growing plants, and produce animals of the parent-form. They would thus form an intermediate nursing race answering to Steenstrup's description.” Prof. Cienkowsky has witnessed (Zeitschr. 1855, vi. p. 301) cyst-construc- tion in Nassula viridis (Duj.) (XXVIII. 65–71), Stylonychia pustulata (XXVIII, 74–76), S. lanceolata, in various Vorticellae, in Bursaria trunca– tella, B. lateritia, Podophrya fia’a, Loa:06es Cucullwlus (Duj.), Leucophrys Spathula, Amphileptus margaritifer, Holophrya brunnea, andless completely in Amphileptus Anas, Stylonychia Mytilus, Paramecium chrysalis, Spirostomum ambiguum, Stentor polymorphus, St. Mülleri, Paramecium Aurelia, and Loacodes Bursaria. - In Lowodes Cucullwlus (Duj.) and Stylonychia pustulata, he saw the dis- charge of the whole of the contents of the cyst in the form of encysted Infu- soria. The embryo born from the cysts of Stylonychia pustulata resembles closely the Trichoda Lynceus, and can multiply itself by self-fission just in the same manner as mature and independent beings. In cyst-development, he observes, the whole of the contents are, as Jules Haime stated, not metamorphosed into the resultant embryo, but one or more portions escape in the form of globules, apparently ciliated, and move off with a rotating motion. REPRODUCTION OF THE CILLATED PROTOZOA:—FISSION, MODES OF; GEMMATION; rNTERNAL OVA PRODUCING GERMS OR EMIBRYOS ; IMPREGNATION ; PRODUCTION of Nºw BEINGs witH AND WITHOUT METAMORPHOSIS ; TRANSFORMATION INTo AcINETE, AND DEVELOPMENT OF EMBRYOS-Until lately, naturalists in general did not acknowledge other methods of reproduction than by fission, or, as 346 - GENERAL, ELISTORY OF THE INFUSORIA. some would call it, fissation, and by gemmation or budding, which, from not being true generative acts, have been called ‘ vegetative’ modes of propagation or multiplication. Recently, however, the Ciliata have had attributed to them true generative processes, resulting in the development of embryos either with or without intercurrent metamorphoses. The simpler processes of fission and gemmation are, in Stein’s opinion, modes of propagation peculiar to immature beings, and are replaced in mature animalcules by the agency of germs or embryos. FISSION.—This duplicative subdivision may be longitudinal, transverse, or oblique; and whilst some species divide in only one direction, others are capable of so doing in two, for instance, in the longitudinal and transverse, but not simultaneously. Among the Vorticellina longitudinal fission alone occurs; Paramecium (XXIX. 27), Chilodon, and others divide both longi- tudinally and transversely; Lagenophrys obliquely only. Fission has not been witnessed in Spirochona nor in Trichodina, nor in Colpoda when in a free state and not encysted. Ehrenberg came to the conclusion that multiplication by spontaneous divi- sion is the character which separates animals from plants. It is true (he argued) that gemmation in plants, especially in very simple cells, is at times very similar to the division in animals; but this relates to the form, not the formation. A vegetable cell, apparently capable of self-division, produces one, or contemporaneously many exterior buds (gemmae), without any change in its interior. An animal which is capable of division, first doubles the inner organs, and subsequently decreases exteriorly in size. Self-division proceeds from the interior towards the exterior, from the centre to the periphery; gemmation, which also occurs in animals, proceeds from the exterior towards the interior, and forms first a wart, which then gradually becomes organized. This supposed distinction between fission in vegetable cells and that in simple animals like Infusoria is set aside by modern researches, which show that, when a plant-cell is about to divide, the mucilaginous layer of the wall (i. e. the primordial utricle) manifests a constriction, which presently involves the wall itself, and, gradually deepening, at length cuts the cell into two. The observations on this subject in the chapters on DESMIDIEZE and DIATOMEE will more completely elucidate it. Considered with respect to the condition of the animalcule, fission occurs in the active and unchanged state, as in Paramecium ; or in a contracted state, as in Vorticellina; or only when encysted, as in the case of Colpoda. Hence it follows, that it presents several slight modifications in its course. One general fact is, that whilst fission proceeds, the rotation of the contents of the animalcule is at a stand-still. In its simplest variety, the dividing being first presents a constriction at each pole or side of the body, which gradually ex- tends until it completely cuts it into two equal or unequal parts. Simulta- neously with the first indication of an act of fission, and in some cases before a sign of it is to be detected in the periphery of the animal, it has been generally taught that the nucleus, after elongating and usually disposing itself across the direction of the line of scission, takes the initiative in the act, by commencing a fission of its own substance (XXIX. 27), which ‘sub- sequently proceeds step by step with that of the entire body, until complete. This statement is, according to Lachmann (A. N. H. 1857, xix. p. 230), a mistake when made respecting the Protozoa generally; for in some cases the division of the nucleus is consecutive to that of the body, and “in others, again, the actual fissation of the nucleus does not lead to that of the body, but embryos are developed in it; ” on the other hand, “fissation is generally commenced rather by a new formation of contractile vesicles.” OF TELE PROTOZOA.—CILIATA. 347 In some species where fission proceeds on its simple type, food may con- tinue to be received for a short period by the dividing animal. The small share the abdominal contents within the cortical lamina have in the vital processes, is shown by Lachmann’s observation of a Stylonychia, “which, although a considerable part of its chyme had been sucked out of it by an Acineta, still underwent division, so that one of the gemmules of division swam away from it briskly, and only the other half of the old animal was destroyed.” The direction of the line of section is perhaps, when longitudinal, usually from before backwards, the constriction appearing first and advancing more rapidly at the head; but the contrary, according to Stein, prevails in Chilodom Cucullulus, where the constriction makes its way solely from the posterior pole. When fission is transverse or oblique it necessarily involves the reproduc- tion, in the posterior half, of the organs existing in the anterior, viz. the ciliary apparatus of the head, the oral aperture, the tube prolonged from it, and the contractile vesicle. So far, therefore, it approaches nearer the act of gemma- tion than does longitudinal fission, wherein segments of the already existing organs are separated for the purposes of the new individual, and are not actually reproduced or created anew. “In those Infusoria,” says Lachmann (A. N. H. loc. cit.), “in which a peculiar series of stronger cilia leads to the mouth (such as Oxytrichince and Euploteae), the furrow in which this series of cilia is situated is seen, Subsequently to or simultaneously with the division of the contractile vesicle, to become produced backwards over the mouth; in this prolongation cilia are produced, and its posterior extremity becomes deepened into a mouth and Oesophagus, which then opens towards the ali- mentary cavity of the animal; then, simultaneously with the external con- striction of the body, the new furrow is separated from the old one. (In Stentor the new frontal series of cilia first makes its appearance on the old animal as a lateral straight series—the crista lateralis of Ehrenberg). In animals which also possess peculiar processes of the body as organs of motion (hooks, styles, &c.), the fissation usually takes place in such a manner, that each of the newly-formed animals acquires a portion of these from the old animal, whilst the other part is of new formation.” The manner in which self-division proceeds in Protozoa with a firm, and seemingly almost brittle integument, is exemplified in Coleps (XXIV. 284, 285). Along the line of section a new secretion of chitinous substance takes place, soft in consistence and transparent, which by its increasing width separates the two portions of the original lorica; in this interposed new tissue a constriction presently manifests itself, and advancing in depth, the two segments are finally Sundered. It thus comes to pass that each product of fission is one half covered with a dense shield, and the other half with a soft, yielding integument. After a while, more molecules make their appear- ance in the latter, which gradually assumes a firmness equal to that of the old lorica. The Vorticellina, including the Ophrydina, do not divide until they have assumed a sort of semiquiescent condition, by the complete withdrawal of their ciliary apparatus and the contraction of the body generally into a more or less rounded or oval shape, in short, until they have advanced one step towards encysting themselves. Ehrenberg portrayed their fission as a simple constriction advancing from before backwards to separation of the body; but Stein pointed out the actual antecedents of the process. According to the latter writer, the head-portion and its appendages withdraw ; the rotary organ is absorbed, and also the oºsophagus; at the same time the contractile space vanishes; the body ex- pands in width, the nucleus outstretches itself across it, a constriction appears 348 GENERAL HISTORY OF THE INFUSORIA, on its anterior border, and, extending constantly in depth, at length effects its complete division. When the section has reached the third of the body, a conical space displays itself towards the anterior portion of each half (XXVII. 3), lined by a special membrane, covered by cilia on its posterior side or base, which are seen to vibrate within the cavity. This formation is the rudiment of the future rotary organ. The apex of the conical hollow is prolonged by a canal which eventually opens on the surface, and thus establishes a con- tinuity between the lining membrane and the external integument. At the same time the internal angle at the base of the cone is produced inwards so as to form the alimentary tube. When these changes are accomplished, the body is half cut through, and the appearance is rather that of two individual animalcules united posteriorly, having their ciliary apparatus retracted, and the peristom contracted in a splinter-like manner over it. Lastly, the advancing act of scission divides the nucleus; and the whole body becomes resolved into two individuals seated upon the same stalk. From this account it follows, that, of the original organs of the animalcule, the nucleus is the only one divided between the two resultant beings by the process of fission; all the rest are formed anew out of the homogeneous substance of the body, viz. the peristom, the rotary organ, the alimentary tube, and the contractile vesicle. This absorption and renewal of parts during fissation is denied by Lachmann, who affirms that the movement of the cilia upon the ciliary apparatus, and in the vestibulum and Oesophagus, which are closed up by the peristom, may be observed during the whole process. We have no means of deciding which of these two statements is correct: yet we rather incline to Stein’s account ; for when we admit that in fission there is a separation of all the organs and appendages of the body into two portions, one to each resultant being, an act of structural development becomes necessary to reproduce the remaining por- tion, so as to perfect each new animal and to assimilate it in characters to the parent. This being the case, the method of development stated by Stein is more consonant with our views of histogeny than that of Lachmann. The oblique fission of Lagenophrys vaginicola (XXX. 32, 35, 36) presents several peculiarities. The line of Section commences below the peristom on one side, and proceeds diagonally across to the opposite, and thus gives rise to an anterior lateral Segment retaining all the Special organs, and a posterior lateral possessing nothing Save its half of the elongated divided nucleus. During the process, the anterior half continues in the enjoyment of all its functions and activity (XXX. 32), whirls its ciliary organ, and takes in food by the mouth : the food, however, does not reach to the segment behind; and whatever alimentary particles might be present in this vanish, and its whole contained substance becomes homogeneous and granular, the half of the curved band-like nucleus extending into it. When the line of section is fully formed, Stein remarks that the posterior lateral segment rather resembles a gemma than the result of Self-division, and proves how closely united are the two processes of gemmation and of fission. - When the Scission is nearly complete, a contractile space appears, and, either before or behind this, a curved elongated cavity, ciliated on one side and produced upwards as a tube from one angle, is formed (XXX. 35), out of which the rotary organ and peristom are developed. As there is no room for movement, the new being lies motionless close against the old one : how- ever, its contractile space acts energetically; and the alimentary tube, filled with fluid, moves upwards and downwards, and from side to side within it. At length a row of cilia appear around the circumference of the body; and now two beings occupy One case, the anterior adhering by its peristom to the narrow OF TEIE PROTOZOA.—CILIATA, - 349 orifice of the sheath, whilst the posterior lies immediately behind it, fixed from want of space, and unable to free itself (XXX. 36). The question that now presents itself is, how is the newly-formed animal to escape its prison and to exercise its vital endowments 2 This, Stein has been able to solve by ob- servation of another species of Lagenophrys, viz. L. Ampulla. The upper seg- ment ceases to put forth its ciliary organs and to take in food, and shortly contracts itself and detaches its hold from the opening of the external sheath, developing simultaneously a row of cilia around its margin (XXX. 35). It also not unfrequently happens that the body is divided from the peristom, leaving this portion adherent in its natural position to the orifice of the sheath, and possessed of Such remarkable vitality, that it continues to con- tract and dilate, and to implicate the orifice of the sheath itself in its move— ments (XXX. 35). When the peristom, with a portion of contractile sarcode (35 b) enclosing at times a contractile space within it, thus plugs the only outlet from the cyst, the two products of fission cannot gain their liberty, and only enjoy the limited degree of locomotion allowed within their narrow prison-house. But where, as is more common, the orifice is opened, they sooner or later make their way out, experiencing, nevertheless, some difficulty in passing through the narrow outlet. - A curious circumstance pertains to these fission-products of Lagenophrys, and indeed to those of all the Ophrydina and Vorticellina, viz. they are not precisely like the parent. Thus, the young of Lagenophrys, produced as above described, exhibit the rotary organ and peristom in a contracted con– dition, whilst a row of cilia surrounds the body in a ring-like groove on the abdominal surface, and serves the purpose of a locomotive organ (XXX. 35, 36). On the ventral aspect, adds Stein, the figure of the animalcule recalls that of Stylonychia, between which and the normal form of Vorticellina it may be considered a transitional type. - Turning now to the other members of the Vorticellina and Ophrydina, we see that the history of the fission-products differs according to their habits and structural peculiarities. In the branching forms many of the newly- formed beings proceed each to Secrete from its base a pedicle, and so continue the dichotomy of the little arborescent colony they belong to. Others, on the contrary, detach themselves from the parent-stem and enter on a free and independent existence. In this case one of the two segments consequent on self-division, in order to enter on its new mode of life, undergoes certain modifications in structure, viz. it continues in a completely contracted state, and a furrow appears about the posterior third of the body, within which a ciliary circlet develops as the locomotive organ of the animal (XXVII. I.1). This occurrence is general among Vorticellae and Ophrydina; for among the former the pedicle never ramifies, and in the latter one fission-product must quit the capsule, which Serves as the nidus of only one being at a time. The after-history of these locomotive segments is widely different in dif- ferent specimens. Some, after Swimming about for a time, come to a state of rest, affix themselves by their posterior extremity, and produce, according to their natural habit, either a stalk or a sheath, and resume all the charac- teristics of the parent-stock. Others, again, become quiescent, but instead of se– creting a pedicle or sheath, proceed to encyst themselves, either for their own preservation or preparatory to the fulfilment of an act of reproduction. In- deed, the process of encysting may overtake the animals whilst still seated on their stalk or within their case, and thus anticipate the formation of the posterior ciliary wreath. Lastly, in a few genera, fission seems only, or at least mostly, to occur after the animalcules are encysted. Stein represents this to be the case ge- 350 GENERAL HISTORY OF TEDE INFUSORIA, nerally in Colpoda Cucullulus, which he never found in process of fission (XXIX. 38–47). Indeed, Ehrenberg himself never saw self-division of this animalcule, although he has, on the authority and ambiguous observa- tions of some of the old observers, described its occurrence. According to Stein’s researches, encysting would not appear absolutely necessary; for he witnessed self-division in some specimens only contracted in a spherical form : . however, in others, the more numerous, a cyst was thrown around the body before that process ensued. According to the general plan, the Ciliated Protozoa divide into two ; yet there are some—and Colpoda is one of such— in which the act of fission is repeated, and 4, 8, and even 16 segments and upwards result. The products of fission have a certain latitude of motion within their cysts, and ultimately escape by rupture. Another peculiarity about Colpoda is, that the segments resulting from fission secrete individually a capsule around themselves, and thus we have encysted beings enclosed within a general cyst. Lastly, each young cyst has its own nucleus and contractile vesicle (XXIX. 43). The fission of the animal when encysted appears to be the rule in Glaw- coma, ; for example, in G. scintillans; and Stein surmises that it is this occurrence which Cohn witnessed in Chilodon whcinatus, and thought to be two animalcules enclosed within a common cyst, as happens with Gregarinae. The importance of fission as a means of multiplying individuals among the Ciliata admits of numerous striking illustrations. We may quote one given by Ehrenberg, by no means an extraordinary instance. He made out that a single individual of Stylonychia Mytilus lived nine days: during the first 24 hours it divided into 3; and during the next space of 24 hours each of these three had subdivided into two beings; so that by self-division alone this animalcule can multiply itself three or fourfold in four and twenty hours, and in the space of ten days be represented by a million derived beings or offshoots. Another instance may be adduced from the same distinguished micrographer. On the 14th of November, he divided a Paramecium Awrelia, Tººth of a line in length, into four parts, each of which he placed in a sepa- rate glass. On the 17th, the glasses numbered 1 and 4 each contained an iso- lated Paramecium swimming actively about. The pieces in Nos. 3 and 2 had disappeared. On the 18th, there was no change. On the 19th, each animal- cule presented a constriction across the middle of the body. On the 20th, No. 1 had propagated 5 individuals by transverse fission, and No. 4 eight such. On the 21st, no change had taken place. On the 22nd, No. 1 contained 6, and No. 4, 18 specimens. On the 23rd, the beings produced were too nu- merous to be counted. From these notes Ehrenberg calculated, if this process continued in activity for a month, 268 millions might be produced. Apart, however, from these, which we may term speculative considerations, we have in Ophrydium the clearest and most direct evidence of the extent to which fission is carried out. On the completion of self-division in this animal, the products remain together, connected by a common gelatinous mass at their base exerted by themselves. By the repetition of the process again and again, through a long series, the Ophrydia accumulate in large greenish masses, or polyparies, at times of the size of the fist or even of the head of a man. Now, by comparing the size of the individual Ophrydia (about fºrth of an inch in length) with that of the masses they form, “some estimate,” says Dr. Car- penter (The Microscope, p. 487), “may beformed of the number included in the latter; for a cubicinch would contain nearly eight millions of them, if they were closely packed; and many times that number must exist in the larger masses, even making allowance for the fact that the bodies of the animalcules are separated from each other by their gelatinous cushion, and that the masses OF TEIE PROTOZOA.—CILIATA. 351 have their central portions occupied only by water. Hence we have in such clusters a distinct proof of the extraordinary extent to which multiplication by duplicative subdivision may proceed without the interposition of any other process. These animalcules, however, free themselves at times from their gelatinous bed, and have been observed to undergo an ‘encysting process corresponding with that of the Vorticellina. It is much to be desired that mi- croscopic observers should devote themselves systematically to the continuous study of even the commonest and best-known forms of these animalcules, since there is not a single one whose entire life-history, from one generative act to another, is known to us; and since it cannot be even guessed at, with- out such knowledge, what, among the many dissimilar forms that have been described by Prof. Ehrenberg and others, are to be accounted as truly di- stinct species, and what are mere phases in the existence of others that are perhaps very dissimilar to them in aspect, it is obvious that no credit is really to be gained by the discovery of any number of apparently new species, which shall be at all comparable with that to be acquired by the complete and satisfactory elucidation of the life-history of any one.” GEMMATION (illustrated by XXVII. 1–4; XXX. 17, 27, 29, 31, 33, 34).- This is the next process of multiplication to be considered. It has much analogy with fission, but is not nearly so widely diffused, being restricted apparently to the families Vorticellina and Ophrydina, that is, to attached species of Ciliata; yet even among these it would seem not to be general; for Stein has failed to observe it in the genus Opércularia. In it a promi- nence forms upon the surface, mostly near the posterior extremity, and of the same granular homogeneous substance as the rest of the animal: a line of constriction soon displays itself, and gradually deepens, whilst the budding process increases in size and developes internal organs and external ap- pendages, until, being sufficiently perfected for an isolated existence, it severs itself from the parent stock. The gemmae or buds thus produced are much smaller than the parent, and, even when they have acquired their largest di- mensions before separation, are less than the new beings originating from self-division. In every instance of fission the nucleus becomes divided be— tween the two segments; and some authors, as we have seen, hold the opi- nion that these share between them a portion of other pre-existent organs of the dividing animal; on the other hand, in gemmation the bud is a mere offshoot of the general substance, containing no portion of any pre-existing organ—not even, so far as can be seen, of the nucleus; and consequently all the specially-organized parts are developed in it de novo. If the doctrine of internal germs be admitted, then it may be imagined that each gemma origi- nates from one of these, which takes on this external direction of development. On the completion of the gemma, we find that it resembles (except in Spi- rochona and Lagenophrys) a completely-contracted specimen of the parent animalcule, and possesses, in lieu of the usual ciliated whorl on the head, a posterior ciliary wreath, whereby, when detached, it swims freely away, with the posterior extremity, however, in advance. It resembles, therefore, in all respects the product of fission when separated from its fellow, and, like it, may either presently attach itself, losing its posterior circlet of cilia, and acquire all the characters of its parent—as well as, in process of time, its dimensions,—or advance to a completely encysted state, prepara- tory to a process of development, or simply for the object of preservation from untoward external conditions. The act of gemmation goes on alike in small and in large specimens. Stein notes its occurrence in Vorticellae of only #" in length. - A few illustrations may render the above account of gemmation more clear. 352 GENERAL EIISTORY OF TEIE INFUSORIA. Speaking of this process in Vorticellae, Stein (op. cit. p. 28) says, the interior of the knob-like process is quite homogeneous at first (XXVII. 1); but when it has attained a hemispherical shape, a crescentic cavity forms at its anterior part, from which the peristom, rotary organ, and alimentary tube are even- tually developed (XXX. 17, 27), just as happens in the result of fission. Whilst this proceeds, the Swelling acquires an oval or globose figure, and the width of its attached base dwindles to a constricted neck or isthmus. The addition of acetic acid proves that no portion of the nucleus extends into it, but that this organ retains its normal curved reniform figure. Stein here adds the remark, that no sharp line of distinction exists between self-fission and gemmation—that the latter may be looked upon as an act of unequal division, in which the whole organization has to be created, and not, as in fission, simply perpetuated ; or fission may be described as a variety of gemmation, one segment being regarded as a bud; at least this view holds good in the case of transverse fission. Longitudinal fission consists in the formation of two gemmae, which subsequently involve the entire being. So also in one sense gemmation does not always end in the production of a single bud; for Vorticella, with two are common, and occasionally with three, one of which is ready for detachment, whilst the other or others are very incomplete. In Spirochona (XXX. 17, 27), which does not multiply by fission, gem- mation is very frequent; and often two buds are produced, one immediately behind the other, the hindmost being first in development. Where two exist, the first-formed usually appears on the side of the body at its widest part ; and the second forms subsequently in front of it, nearer the neck. Re- latively to the size of the parent, the bud is usually of greater dimensions than in Vorticella, and may, by thrusting aside the head of the Spirochona, place itself in the longitudinal axis of the body. When the gemma com— mences to contract its base and to acquire the form of an independent being, an opaque, sharply-defined, homogeneous speck makes its appearance about its middle, or, rather, in front of it, which, by further development, becomes the nucleus (XXX. 17), whilst a shallow groove displays itself at its anterior truncate end, and Somewhat later is transformed into a curved and rather angular ciliated fissure extending some way down one side of the body. In this so-formed gemma of Spirochona there is, therefore, a wide depar- ture from the rule observed in any of the Vorticellina and Ophrydima. No posterior ciliary wreath is formed; and the anterior ciliary apparatus, together with the head itself, is at first developed in a temporary and rudimentary manner. After moving about for some time by means of the ciliary antero- lateral channel, the free gemma fixes itself by its posterior extremity, by an adhesive substance, or occasionally by a short stem ; and then the opposite sides of the ciliated furrow approximate, and coalesce behind, whilst in front one edge rises above the other (XXX. 19), and soon forms a spirally-con- voluted membrane, which becomes clothed with cilia replacing those of the old furrow, which are absorbed and disappear (XXX. 20). This growth into perfect Spirochonde does not happen with all gemmae; for some assume a quiescent condition, become encysted, and, if Stein be right, are ultimately converted into very peculiar Acinetiform beings—the Dendrocometes para- doacus (XXX. 23). Before encysting, the cilia cease to play, and disappear; and very soon the furrow itself closes up. When enclosed within the trans- parent but firm capsule, nothing but a finely-granular homogeneous substance appears, containing the peculiar nucleus, which, however, requires the action of acetic acid to display it (XXX. 21). - The process of gemmation presents several peculiarities in the genus La- genophrys, due mostly to the peculiar connexion between the enclosed ani- OF THE PIROTOZOA.— CILIATA. 353 malcule and its sheath. The rule seems to be that two or four gemmae are produced within the sheath at the same time (XXX. 29, 34); but since Stein had never encountered four, and very rarely three, gemmae upon any animalcule, the idea crossed his mind that these Small buds of Lagenophrys might perhaps be embryos developed within the interior, and subsequently discharged. Another explanation was possible, viz. that they were animal- cules which had found their way into the sheath, and were quite foreign to it. However, both these hypotheses are set aside by the history of deve- lopment and by the characters of the beings produced. The process consists in the enlargement of the posterior extremity (XXX. 33), or of a part of the side of the Lagenophrys, and the progressive detachment of the enlargement as a segment or bud, and simultaneously the production of a band-like nu- cleus and contractile vesicle within it. This stage being so far complete, the gemma does not proceed to develope into the form of the parent animal, but self-fission takes place, and two similar ovoid bodies, each with its contractile vesicle, is the result (XXX. 29). When the constriction of the single gemma announces approaching fission, a circlet of cilia appears on each side of it (XXX. 34); and on the completion of the process, each segment has a conical head surrounded with a wreath of cilia. From this mode of production in pairs, the number of gemmae within the sheath of Lagenophrys should always be two or a multiple of two ; hence, when three are seen, it is to be presumed that one has previously made its escape. From the peculiar way in which the body of the Lagenophrys is sus- pended by its attached peristom to the orifice of the sheath, it is clearly im- possible that anything can directly either make its entrance into or its escape from the animal, without rupture, of which we have no indication. The way in which this impediment is surmounted is, on Stein's authority, by the sudden contraction of the body of the Lagenophrys rupturing the adhesion of the peristom to the orifice of the sheath, and by its subsequent retraction within it (XXX. 31). In this manner a free exit is afforded to any contained gemmae; and after a certain time allowed for their passage, the anterior part of the body again enlarges itself, and reassumes its adhesion to the sheath. After their exit, Stein has no observations to show what becomes of them; but his idea seems to be that they do not produce a sheath until nearly arrived at maturity, since they are so much smaller than the least of the sheathed examples to be met with. If this account be correct, the gemmation of Lagenophrys is actually a compound process of budding and fission, whilst the resultant beings differ widely from those of other Vorticellina in all details, and are so very aberrant in form from the parent, that they require to undergo a metamorphosis before they gain it. DEVELOPMENT FROM OVA. INTERNAL GERMS AND EMBRYos.—Although the reproduction of the Ciliated Protozoa is so largely provided for by the two processes of fission and gemmation as just described, it is even more marvellously so by their possession of true generative functions—a fact clearly established by the latest observers, although denied by Siebold, Rölliker, and others Some years since, when the unicellular hypothesis of Protozoic life militated against the notion of the existence of internal ova or germs. Even now, indeed, when we look to the researches disclosing to us the development and discharge of germs and of living embryos, we find diverse and contradictory statements concerning both the antecedent or pre- paratory acts, and the final results. We cannot attempt to reconcile these discrepancies, but will record the principal opinions of naturalists and the observations on which they are based. 2 A 354 GENERAL EIISTORY OF TEIE INFUSORIA. In a previous page we have stated the views of Carter and Perty, relative to the existence of ova or germs in the interior of Ciliated Protozoa, and have rejected them as unsatisfactory. Further, when we come to inquire the process of development of the presumed ovules, their mode of exclusion, and other particulars necessary to complete their history and even their identification, we find that those naturalists have no direct observations to adduce, but can appeal only to analogy and to some casual and unconfirmed observations of others. For instance, Mr. Carter, when treating of the develop- ment of ovules, appeals to the process in Spongilla and Euglypha, and endea— vours to make out that, with Some modifications, the ovules of Euglence, and pro- bably those of all the Rhizopods and Astasiae, have a similar mode of generation. Perty, likewise, unable to advance any direct proof of the existence of ovules and of their discharge, appeals to Eckhard’s observations on Stentor coºrwlews, which Oscar Schmidt repeated and generally confirmed. In the recorded observation of Eckhard (A. N. H. xviii. 1846), three or four globules, in different stages of development occurred in the interior of the Stentor in a row (XXIX. 8–13):—“In the first stage, the contents of the globules, consisting of minute granules, exist most imperfectly developed; but few granules at present occur, and the globule, when it lies in the body, is not very distinct, on account of the granular parenchyma of the lat- ter. In the second stage of development (fig. 9) the granules appear more numerous, the contents are therefore more concentrated, and the globules can then be very distinctly observed in the body. Fig. 11 shows the third stage; granules commence arranging themselves in a row. . . . . Or, as some- times happens, they appear grouped in the same manner at two spots. The granules thus arranged and closely pressed together, blend into a glandular but clear organ (fig. 12), in which the granular structure cannot be any longer detected; frequently it is also divided in two parts. Lastly, in the situation of the transparent glandular Organ a row of cilia appears, evidently the mouth (fig. 13). Whether this organ is formed immediately from the former, I have not been able to ascertain with certainty; yet that it is so, is extremely probable, since on the one hand the row of cilia occurs in the situation of the bright gland, whilst, on the other hand, in all the germs which exhibit this, the former organ is absent. Simultaneously with the development of the mouth there appear one or two clear vesicles (fig. 13). On the 18th of May I observed in the interior of St. caeruleus a germ as in fig. 12; I saw the cilia very distinctly in motion; the vesicles were, however, still absent, and they did not escape on this occasion. On the 21st, I saw the perfect form (fig. 13), which issued out, whilst the parent animal swam away. I now attentively observed the young one to follow up its further changes, perhaps the bursting of the carapace; but I was obliged to leave off watching it in half an hour, as I could not vouch for the accuracy of further observa– tion on account of the strain upon my eyes. On the 4th of June I saw a germ escape, as in fig. 13: it differed from that observed on the 21st of May; for, being at first round, it at once exhibited an incurvation at its lower extremity—an appearance frequently observed in young Stentors, sometimes in old ones, when they contract from the elongated form to one more or less rounded. I have subsequently once seen the escape of a similar germ ; and it appears to me that the true point of maturity is that at which vesicles begin to be visible. In Stentor polymorphus I have observed two such globules, but I have not succeeded in seeing any perfectly formed escape. In autumn I have often sought for the recurrence of this phenomenon, but have never been able to observe it so perfectly as in the spring, although similar globules are not rare in the later parts of the year.” OF THIE PROTOZOA.—CILIATA. 355 From the perusal of this account, the thought arises, whether, instead of proving the existence and progressive development of internal ovules or germs in the sense Perty adopts, it is not another illustration of embryo-de- velopment by a sort of gemmation or breaking up of the nucleus, such as the researches of Cohn, Stein, Lachmann and others have made known to us, and concerning which we have now to speak (see Balbiani’s researches, p. 329). The development of the nucleus into embryos takes place under different circumstances and in a varied manner in different genera of Ciliated Protozoa. It may occur either without the previous encysting of the animalcule, or after this process is completed. Again, in the latter condition, and without ulterior change or metamorphosis, either a few active embryos, or some encysted germs, may be the result, or the whole nucleus may resolve itself into a brood of monadiform beings, or, lastly, according to the views of Stein, the encysted animal may be metamorphosed into an Acinetiform being, out of which embryos are developed diverging in character more or less com- pletely from the original ciliated Protozoon, to which, however, they eventually recur. The development of embryos without the previous encysting of the animalcule has been followed out by Focke, Cohn, and Stein in Nasswla and in Paramecium (Loacodes, Cohn) Bursaria (XXVIII. 10–14, XXIX. 28 to 34). A portion of the nucleus is separated by fission or by an act of gemmation, and constitutes a more or less orbicular body, in which a nucleus (XXIX. 34), and then a contractile vesicle, shortly declare themselves (XXIX. 29). Focke surmised that the so-called nucleolus originated this germ, which then found, as it were, a lodgment and nutrition in the Inucleus as in a uterus (see Balbiani, p. 329); but Stein affirms that this body has nothing to do with the origin of the germ, and is frequently to be seen separated and removed to some distance from the nucleus (XXIX. 29). In appearance the disk-like germ is finely granular, paler than the nucleus, and not surrounded, like the latter, with a special membrane. Cohn represents it as existing in a distinctly limited cavity, prolonged to the external surface as a tube or Oviduct, and terminated by a two-lipped orifice, through which the embryo makes its exit (XXVIII. 11, 12). According to Stein, however, no such duct and external orifice have an existence, except temporarily, during the passage of the germ, or germs when two or more follow in succession. This assertion of Stein is supported by Cohn's own observation, that the point of extrusion varied in different individuals in its position, being at one time at the middle, at another above it, at a third below it, and, as the rule, on the left side, although as an exception on the right side or even towards the anterior margin. The act of birth occupies about twenty minutes; and when the embryo is about to escape, it exhibits a vibration on its surface, which causes a motion in the surrounding water and hastensits detachment. This motion, after continuing a short time, ceases, and the little being attaches itself to the exterior of the parent (XXIX. 30). The chasm produced in the parent during the extrusion soon closes up, and leaves no trace, except, it may be, a slight hollow in the surface. The embryo has an elongated fissure, is rounded at each end (XXIX. 30), and frequently rather contracted at its middle ; internally it is finely granular and colourless—not greenish, as Focke asserted— and contains, besides a darker nucleus, one or two contractile spaces (XXVIII. 14). Cohn could discover no mouth; but Stein displays in his figure an oblique fold or groove (XXIX. 30), which may possibly represent the oblique funnel-like vestibule of the mature Paramecium. The vibratile movement visible about the surface indicates ciliary action; and if the embryo be killed with iodine, the presence of long cilia is demonstrated. Still the most peculiar feature in the new-born animalcule is the possession of several soft 2 A 2 356 GENERAL EIISTORY OF THE INFUSORIA, tentacular processes at each end, Surrounded by Small knobs, recalling in figure the knobbed tentacles of some Acinetina (XXVIII. 14, XXIX. 30); by means of these the embryo secures its hold to its parent. Such pro- cesses are not present in all specimens, and are therefore non-essential; or it may be they have disappeared by withdrawal into the general substance of the body. The embryo once freed from its parent, commences an independent existence, moving freely about in the water—much more similar in figure and structure, however, to some of Ehrenberg's Cyclidina or to Dujardin’s Enchélyens than to Paramecium. Cohn notes its affinity with the Cyclidium margaritacewm, or to the Pantotrichum Enchelys (Ehr.), and also with several species of Dujardin’s genus Enchelys (Cyclidium. Ehr.). Cohn adds that, in his opinion, several embryos are developed simultaneously, and that, where only one or two are found, others have already escaped. In some instances he has noticed as many as six or eight in process of develop- ment, and, it would seem, in almost precisely the same stage, although their birth is successive. Further, besides these normal embryos, he has fre- quently witnessed the escape of others having a globular figure, clothed with cilia and furnished with tentacular processes and a contractile vesicle. During the act of birth, the pulsations of the contractile space of the parent are uninterrupted, and the rotation of the contents is arrested until every germ has escaped. Another curious fact is, that the birth of embryos may proceed as usual even whilst the act of fission is taking place in the parent animal. The further history of the free embryo is not known; yet, in all pro- bability, it is ultimately transformed into a perfect Paramecium, an event which, from its figure and structure, ensues readily and perhaps without more than one intermediate phase. Judging from the above details, it is probable, as before remarked, that the development of embryos in Stentor coeruleus (XXIX. 8) recorded by Eckhard (suprá, p. 354) was a precisely similar phenomenon to that just described in Paramecium ; and it is clear that the like obtains in Stentor polymorphus, in an Opalina or Bursaria noticed by Siebold (probably the Bursaria Entozoon Ehr., parasitic in a frog), in Urostyla grandis, as mentioned by Cohn, and in the animalcule which we conceived to be Trichodina pediculus (A. N. H. 1849, iii. p. 269). sº this was written, the indefatigable labours of Cohn have added another instance of this endogenous mode of development, in Nassula elegans (Zeitschr. 1857, p. 143; XXVIII. 11–14). This animalcule possesses an elliptic nucleus, having its nucleolus lodged in a fossa near one end, and surrounded by a vesicle, just as in the Paramecium Bursaria. Among many specimens, Cohn found several having a large, elliptic, hollow space, evidently limited by a membranous wall. Where this space approached nearest the external surface of the animalcule, this was depressed in a cup- like form, and from its centre a canal or fissure (XXVIII. 11 f) penetrated the interior of the space, where were two, never more, large globules, Thy" in diameter (XXVIII. 11 d). After a longer or shorter delay, these globules escaped and appeared motionless, without colour, but granular, and having a central nucleus and an excentric contractile vesicle. As in the instance of the germs of Paramecium Bursaria, no cilia, but a few short, knobbed, radiating, tentacular-looking processes (XXVIII.14), were visible on the surface. Lastly, Cohn noticed the formation of these germs in animalcules recently produced by self-fission, and which had attained only one-half their normal dimensions. The development of an embryo within an encysted animalcule is illustrated OF TETE PROTOZOA.—CILIATA. 357 in Stein's history of Chilodon Cucullwlus (op. cit. p. 134). At a preceding page (p.342) we have given an abstract of the mode of encysting of this animal, and have stated that the capsule remains gelatinous and soft. Inside the cyst, Stein discovered an actively-moving embryo contained within a special cavity (XXIX. 54–56), occupying precisely the spot where in other encysted Chilo- dons the nucleus is found, viz. in the diagonal line connecting the two oppo- site contractile spaces. The embryo had an oval or ovate compressed figure, with one side straight or gently curved, and the anterior extremity notched. Its entire surface was covered with longitudinal, widely-separated rows of unusually long cilia, in incessant motion, which turned it in a spiral or vermi- cular manner. Pressure on the cyst caused its expulsion (XXIX. 59), either alone or together with the substance of the parent-cyst, to which it always remained adherent. This embryo, Stein concludes, is derived from the nucleus. Many cysts may be met with in which the nucleus is replaced by a much larger body, having a different consistence, opaque and motionless, and possessing in all respects the outline of a germ. On pressing it out of its place, its surface is seen to be not quite naked, but to have short, stiff, and imperfectly-developed cilia at one end or entirely around its margin. Since the embryo occupies the site of the nucleus, it might at first sight be supposed that the latter was wholly transformed into it; but analogy leads us to the contrary inference, that the nucleus, although obscured from view by the internal germ, is nevertheless present ; and this conclusion is further supported by the fact, that a successive development of embryos goes on until the entire contents of the cyst are used up in their formation, an event that does not occur without the influence of a nucleus. Stein declares the embryo (XXIX. 59) to be precisely similar to Cyclidium Glaucoma, both in figure and movements. Its size varies with that of the animalcule producing it; and individuals of all sizes may undergo the encysting process. The smallest cysts met with were #" in length, and their embryo not more than gºp"; the largest gº", and their embryo from T}s" to #" (XXIX. 56). A remarkable circumstance happens in the case of some encysted Chilodons, even after they have given birth to one or more embryos, viz. that they seem to emerge from their quiescent state and resume their active form. For instance, Stein met with cysts containing a freely-moving Chilodon, together with an active embryo, both which ultimately escaped by an aperture in their walls (XXIX. 58). This revivification of the ciliated Chilodon as above referred to, is urged by Stein as an argument to prove that the cilia are not lost or destroyed when encysting takes place, but probably merely closely compressed against the Surface. Another variety of development of germs within an encysted animalcule is seen in Colpoda Cucullus (XXIX. 35–47), which we have described under the head of “Fission,” since the formation of the germs is the consequence of self-divison of the whole animal either into two or, as a rule, into four segments, which themselves become individually encysted, and present their own nucleus and contractile space. This plan of development explains the occurrence of very small encysted Colpoda. It was in this genus that Ehrenberg conceived he had made out very clearly the hermaphroditism and cyclical development of “Polygastrica.” A third way in which the encysting of an animalcule is made to serve the process of development is by the resolution of the nucleus into a multitude of minute segments, each eventually assuming an independent animal ex- istence. This formation of what may be called brood-cysts, occurs, as shown by Stein’s later researches, in Vorticella microstoma (XXIII. 10–14). 358 GENERAL HISTORY OF THE INFUSOIRIA. Among cysts of the usual form and dimensions, are some in which a sac, not uniformly adherent to the inner surface of the capsule, contains from two to eight, or, more generally, from four to six, oval or reniform secondary sacs, irregular both in position and size (XXIII. 10, 11), and containing a dull and fine or coarse granular matter, within which, again, is a clear (contractile?) space, but no nucleus is discoverable even when acetic acid is added. Pre- sently these vesicles elongate, and, becoming flask-shaped, protrude their necks through the enclosing sac and the cyst-wall (XXIII. 12, 13), and proceed to discharge their contents (XXIII. 14) through their open extremi– ties; after which, they corrugate and wither. The discharged matter is composed of a mass of monadiform corpuscles united together in a globose gelatinous mass, the whole of the organic matter filling the cyst being used up. A precisely similar act of propagation Stein also witnessed in an encysted Vorticella nebulifera. Cienkowsky (Zeitschr. Band vi. p. 381) also reports its occurrence in Nassula viridis, Duj. (XXVIII. 65-71); according to this author’s researches, the contents of the cysts of Nasswla viridis break up into a number of globular cells (XXVIII. 68–70), which soon partake of a certain degree of rotating movement among themselves, develope in their interior a multitude of what he terms swarm-spores, and at a certain period, when mature, severally produce, in turn, a tapering neck-like tubular process (XXVIII. 68, 69), which perforates the softened cyst-wall and gives exit to the spores or germs (XXVIII. 71). This account tallies with that given by Stein of certain Vorticella-cysts. Lachmann has the following remarks on this topic (A. W. H. 1857, xix. p. 238):-‘‘ It was only in his most recent observations on Vorticella microstoma, that Stein saw the production of larger globules, daughter-vesicles’ (Tochterblasen), in the interior of the mother- vesicle; but previously he had seen nothing of the kind: it must remain uncertain whether he had overlooked them, whether, instead of several globules, only one very large one, entirely filling the mother-vesicle, had been produced, or whether two different modes of development actually occur in this case. This is the only mode of reproduction of the Infusoria which has hitherto been observed in encysted animals alone; but some ob- servations made by E. Claparède and myself upon an undescribed vagini- colous Infusorium, indicate that encystation is not a necessary condition even for this mode of propagation.” The last plan of generative development to be considered is that wherein, according to Stein’s hypothesis, the encysted animalcule undergoes an actual metamorphosis, and Subsequently, as a rule, produces an embryo which, although very dissimilar to the original ciliated animalcule, is nevertheless presumed to be convertible into it after passing through one or more trans- itory phases of existence. - This cycle of life, or, according to Steenstrup's hypothesis, this “alterna- tion of generation,” in the generative acts of ciliated Protozoa, Stein has most diligently sought to establish as a fact, but, in the opinion of most of the best naturalists, has failed so to do. Still the hypothesis is too curious and interesting to be omitted from our description, and, what is more, has been adopted as true by several observers. It will therefore be best, first to set forth Stein's own account, and then to add the remarks and objections of others. On some of the branching stems of Epistylis plicatilis, and of E. mutans, Stein encountered not only the ordinary animalcule in full activity and in a contracted state, but also some pear-shaped bodies, presenting merely the ordinary nucleus and a contractile space, without mouth or any remnants of the alimentary tube or of food. On other branches, again, were other OF TELE PROTOZOA..—CILIATA. \ 359 bodies having the figure of Acimetae, furnished with tentacles slightly move— able and more or less retractile (XXVII. 17, 18, 19, 20). These Acineti- form beings were noticed and figured by our countryman Baker a century ago; they, moreover, did not escape the observation of Ehrenberg, in the allied genus Opercularia, but were regarded by him as parasitic animalcules. On another occasion, Stein met with a stem of Epistylis plicatilis bearing some thirty Acineta, differing among themselves very much, both in size and in their stage of development. Each was supported on a branch presenting the characteristics of this species, but smaller in dimensions, and tapering from the base of the Acinetiform body (where it had the usual thickness of an Epistylis-Stalk) to its junction with the stem below. The length of the branches also varied greatly, being in Some instances not quite so much as that of the body they supported, in others twice as long; however, there was no proportion between the length of the stem and the size of the body. Most of the Acinetoe had a smooth surface and no tentacula; they were of a pyri- form compressed figure, and contained a coarsely granular and homogeneous substance, two or three irregularly-placed contractile spaces, and a central nucleus having either the normal horse-shoe- or an elongated oval shape. Where the Acinetco had tentacles, these processes were few and small, and the surface of the body thrown into irregularities by its contractions; their nuclei were either round or oval. These Acinetae exhibited no movements, except some slight ones affecting the tentacula. Were their anterior extremity un- folded and their tentacles outspread, they would assume the figure presented by those described in the first observations on this species, whilst the closed pyriform bodies were precisely alike. The further developmental history of this particular Epistylis could not be followed out, and to arrive at the purpose of its Acimeta-metamorphosis, the research was extended to other Species. A particular form of Acimeta occurs in company with Epistylis digitalis, which Stein concluded to be derived from it by a similar process to that presumed in E. plicatilis, although the Acinetae were isolated and seated on short pedicles. At the anterior part of each Acineta, amid the large granules crowding the homogeneous contents, were a contractile space and, in many specimens, a moving embryo having a cylin- drical figure, rounded at each end and narrower in the middle, where several zones of long cilia, in apparent folds of the surface, Surrounded it. In ge- neral characters it would, as an independent organism, be referable to the genus Trichodina, and is probably no other than the T. voraa, or T. gran- dinella, Ehrenberg. The embryo escaped through a temporary opening, which closed very speedily afterwards, leaving the animal apparently unin- jured; moreover the tentacles, which are retracted during the birth, were again outstretched. The conclusion arrived at is, that the Acimeta-condition is specially provided to carry out embryonic development, and that in so doing the Acineta gradually exhausts itself. . Stein’s first impression was, that the embryo resulted from the develop- ment of the entire nucleus, and that this organ was formed anew from the general contents of the Acineta ; however, later researches lead him to be- lieve that only a portion of the nucleus is concerned in building up the em- bryo. No particular season seems devoted to this Acimeta-formation, since Stein has observed it from the middle of March through the whole sum- mer, and in fewer instances until December ; moreover, embryonic gene- ration is not restricted to any particular size of Acineta, but occurs in all except the very smallest; nevertheless the embryo is Smaller proportionably to the decreasing size. Active embryos were seen in Acineta of only fºr", 1 / 1 / the germ itself being only gºo". 360 GENERAL HISTORY OF THE DNFUSORLA. Besides the cysts and Acinetoe supported on branching Epistylis-stems, Stein found others attached separately by very short stalks, or nearly sessile; these, his observations go to show, are probably derivable from the beings produced by fission or gemmation, which have detached themselves from the parent-stem in the strongly-contracted or partially-encysted condition, and, on afterwards fixing themselves, proceeded either to complete their encysted state or to assume the Acinetiform condition. Another set of beings Stein is disposed to introduce in the developmental history of Epistylis digitalis, in the shape of miniature branching Vorticellina. The branches are dichotomously disposed, very slender, short, and rigid. Seated at the extremity of each is a small campanulate being, with a stiff bristle proceeding from each angle of the base (XXVII. 22, 23). Internally they are finely granular. They exhibit slight changes of outline and jerking movements upon their stalks; they, moreover, can detach themselves and swim freely away like a detached Epistylis digitalis, and may sometimes be seen to affix themselves again by their base and produce a pedicle. These beings, whether derived from E. digitalis or from Carchesium pygmaeum— for they occur in company with both these animalcules, their discoverer would regard as their earliest phase of development, and believes that not improbably similar miniature beings belong to all the pedicellate Vorticellina. This notion involves no great stretch of the imagination; for there is no extra- ordinary metamorphosis necessary, and we may throw out the suggestion that such minute Vorticellina are developed from the monadiform contents of the brood-cysts. To take another illustration of Stein’s hypothesis from the allied genus Oper- cularia—the O. berberina. Direct observation is wanting to identify the Aci- meta as belonging to this Opércularia, except so far as contiguity on the same filament of a plant or on the same member of a marine animal, and their frequent occurrence, be allowed to have weight. Stein argues that the conversion of an encysted Opercularia into an Acimeta is readily conceivable, by reason of their congruity of form and the existence of intermediate phases, whilst, on the con- trary, the transformation of the ciliated embryo into an Acineta, without first passing through the intervening stage of an Opercularia (a change easily imagined), is a circumstance scarcely probable: on similar grounds he would associate the pear-shaped Acineta, having a ramified nucleus (XXX. 3, 4), with Opercularia articulata (XXX. 1), as a phase of existence interposed between it and its embryonic stage of a free ciliated animalcule; but his developmental history of Vorticella microstoma is by far the most elaborate, although much too long to present here except in abstract. His first step in the investigation of this species was the illustration of the act of encysting (XXVII. 5 a-d) in its widest range, and the next, to identify certain globular cysts, found in company with the Vorticellae, with the cysts of those animals. These cysts were about ºn" in diameter; they had a clear double outline, and contained a homogeneous, transparent, colour- less and granular substance. In most, the characteristic band-like nucleus and contractile space were visible, together with, in many specimens, the in- voluted ciliary apparatus and oral cavity, looking, as a whole, like a fissure at the anterior part of the cyst (XXVII. 7, 9). In other cysts, again, nought could be discerned Save the nucleus and the contractile space, sometimes di- vided (XXVII. 1, 8); and lastly, in others, all distinction of organs was lost, the nucleus being the last to disappear (XXVII. 9). Stein considered, at first, those peculiar capsules to be connected with the process of reproduction, and, from meeting with torn empty sacs, supposed that the interior was broken up into germs which made their escape through OF TEIE PROTOZOA.—CILIATA, 361 the walls. With this interpretation, however, he was not satisfied; and at the same time his attention was aroused to the circumstance of Vorticelloe occurring so frequently in company with Actinophrys and Podophrya, and to that of the increase in the number of the one as that of the other decreased. He therefore applied himself to watch the changes going on in the cysts de- scribed, and at length satisfied himself of the intermediate changes in their transition into Actinophrys or Podophrya—two varieties of the same animal- cule, in his opinion, and not two genera, as usually represented. Stein was brought to the conclusion that this transition takes place, by comparing Podo- phryce at an early stage of development with metamorphosed Vorticella-cysts. Among Podophryde of the common form, examples occurred having their usually wide roundedcapsule produced into a hollow funnel-shaped pedicle, and thrown into annular folds, alternating with acute, parallel, angular ridges (XXIII. 3). Most of these individuals were unarmed; but some had numerous capi- tate tentacles. On the other hand, old Vorticella-cysts were found in which the enclosed animal had detached itself from the cyst-wall, and become thrown into sinuosities and elevations, the latter of which pressed against the wall, threat- ening to rupture it. These and the above-described Podophryae Stein supposed to merge into one another. The leading changes noticed in the encysted Vorticellae consisted in the disappearance of the nucleus, in the multiplication of the contractile spaces, and in the detachment of the contents from the walls of the cyst (which they no longer completely filled), and their disposi- tion into irregular and changing lobes. Thus far, in detecting such Vorticella- cysts, Stein proceeds by direct observation; but his next step is simply hypo- thesis, viz. supposing their contents to shoot out tentacula through the dense capsule, and assume the figure of Actinophrys or of Podophrya (XXIII. 1, 2, 4, 18, 19). That the metamorphosis should at one time be into the one ge- neric form, at another into the other, he endeavours to explain by assuming that where no resistance is offered on any side to the developing Actino- phryan, it assumes the form of an Actinophrys, but where resistance occurs at one point, it there developes a stem and becomes a Podophrya. To coun- tenance his hypothesis further, he appeals to the great similarity between the Acinetae met with in company with Vorticella nebulifera on duck-weed, and Podophryae—so great, he says, that when the former are detached, it is difficult to know them from Podophrya. Granting that the history of metamorphosis is thus far complete and satisfactory, it remains to show what becomes of the Actinophryans thus transformed from the cysts of Vorticella, and to reply to the question whe- ther they originate a generative act. At the outset of this inquiry Stein finds himself at variance with Kölliker and others respecting the structure and vital endowments of Actinophrys. The writers referred to state Acti nophrys to receive food within its interior, to excrete undigested matters, and to exhibit certain powers of locomotion; these peculiarities Stein ignores, and insists on identifying the Acinetiform beings he has encountered with Actino- phrys Sol and Podophrya fiva, which, he affirms, give birth to a ciliated embryo. This embryo, he asserts, is produced within a defined cavity, so far larger than itself that it can move within it (XXIII. 2, 4, 5). Its figure is pear- shaped with a central constriction, and several folds occupied by cilia; and it appears composed of a finely-punctate Sarcode, containing, in the axis of its posterior and larger segment, an oval or band-like nucleus, and near to this a circular actively-pulsating space, and occasionally, on the other side of the nucleus, a second smaller one. No mouth could be detected. The being, as a whole, very closely resembles a detached gemma of Vorticella microstoma, into which it can be very easily conceived to be changed, on fix= 362 GENERAL HISTORY OF TELE INFUSORIA, ing itself by its anterior end and then developing, in its larger and hitherto posterior segment, a mouth and ciliary Wreath. After lively rotary movements within what might be called its uterine cavity, the embryo escapes with a sudden bound, and gains a free, active existence. The passage by which it has made its way through the substance of the parent Actinophrys continues for some time open, but is gradually closed up from behind. The size of the embryo is proportioned to that of the parent, and varies between Tºtº" and tº ". The diameter of the smallest parent being in which a mature germ presented itself, scarcely exceeded ##". One other instance will suffice to illustrate Stein’s hypothesis of Acineti- form transformation. The one we select is the Vaginicola crystallina, which that author attempts to show becomes, by a metamorphosis, Acimeta mystacina (XXVII. 10–15). Out of a large number of specimens contained in a vessel of water, few could be found at the end of fourteen days, the place of the great majority having been assumed by Acimetina. This occurred even when great pains were taken to isolate a certain number of Conferva- filaments richly covered with Vaginicolae, and to place them in pure spring- water, so as to avoid the introduction of other colonists. That the Acimetae were derived from the Vaginicolae, a comparison of the structure of the two will indicate. The contracted body of the Vaginicola may be recognized in the Acineta detached from the bottom of its sheath and raised to the upper part, which it completely fills, the mouth of the sheath having previously been bent inwards over it as a cover, and a layer of gelatinous matter poured out to bind the two together. The outermost parts of the roof-like cover project freely above this layer, and are traversed by several radiating folds or fissures. The clearest notion of the transformation effected is obtained when we can look down upon the top surface of the capsule, by getting the axis perpendicular to the eye. - The contained body is closed in on all sides; and its contents are substan- tially the same as those of the body of the Vaginicola (XXVII. 12), with numberless fine granules, and sometimes with a preponderating number of large granules scattered through them, rendering the body opaque and of a greyish-yellow colour. There is likewise a similar round contractile space; but instead of a band—like nucleus, there is a rounded one. This difference in respect of the nucleus is not important, inasmuch as its length varies greatly in Vaginicola according as the animal is extended or in a contracted state,_being in the latter much shortened or merely elongated-oval, whilst in the former its length exceeds two or three times its width. Hence it is in no way remarkable that, in the very contracted condition of the encysted and Acinetiform state, the nucleus should be very much shortened and rounded,— a change which analogy, indeed, with various encysted animals would lead us to anticipate. Trom the upper surface of the encysted body very many bristle-like tentacles with knobbed ends are given off, which penetrate the gelatinous layer through the fissures in the cover of the sheath, and outspread them- selves in a radiating manner. These tentacles are for the most part straight, and slowly extend and retract themselves in length. Pressure causes their contraction, and huddles them together; but they are not entirely withdrawn. Some smooth Acinetiform specimens are met with, which may be considered to be in an earlier stage, and similar to the incomplete Acineta of Epistylis plicatilis. The origin of the Acinetoe from Vaginicola is further substantiated by the relative dimensions of the two. Thus Vaginicolae were found on Confervo OF TELE PROTOZOA.—CILIATA. 363 having sheaths betwixt tº" and #" in length; those most common were from #" to ºn" in length and #" in width. The height of the cap- sule of the Acineta was from #3" to #3", and its width not much less. Moreover, intermediate phases between Vaginicola and Acimetina were met with, as, for instance, capsules occupied anteriorly by the contracted body, which still exhibited, upon being moved up from the bottom of the case, the posterior annular furrow and traces of the ciliary wreath previously existing, and had its anterior half enveloped in a gelatinous lamina, uniting it to the inner surface of the sheath, which was at one time more, at another less, incurved upon the animal, but had as yet not been converted into the peculiar pent-house-like cover. The metamorphosis, therefore, of a Vaginicola into an Acineta may be thus explained. The animacule is in the first place contracted in the ordi- nary manner; it then developes its posterior furrow and ciliary wreath (XXVII. 11), and, detaching itself from the bottom of its sheath, rises to the upper part, which it entirely fills and closes up. From this time the rotary apparatus and digestive tube disappear by absorption ; the excretion of the gelatinous matter from the fore part ensues, and fixes the animal in its posi- tion, while its tendency to fall to the bottom of the case, and to contract, draws inwards the mouth of the case, and completes its enclosure within a shut sac or capsule (XXVII. 12). The contractile tendency of the body still continuing to operate, brings about a narrowing of the anterior part, and with this a consequent elongation of the sheath; in this way an ex- planation may be given of the very long specimens frequently encountered. The extrusion of the tentacles is an after-occurrence (XXVII. 13). The complete Acineta can entangle Small Infusoria with its tentacula, which, by their crossing and retraction, draw the captured particles to the surface, where probably their nutritive matters are absorbed through it; at all events, no food or foreign particles are seen in the interior. Stein next attempts the identification of this Acineta of Vaginicola crystal- lina with the Acineta mystacina of Ehrenberg, and in a subsequent paper proceeds to show that it developes within itself a ciliated embryo. Amid many Acinetae, he discovered some bearing a clear oval or rounded cyst, or, less commonly, several such, upon the surface of the enclosing lid; where there was a plurality, they were evidently in different stages of development. The cyst contained a sharply-defined Infusorial being, of a homogeneous finely- granular substance, and having an actively-pulsating sac. At first Stein imagined these might be animalcules casually affixed to the Acimetae; but fur- ther observation proved their organic connexion with, and derivation from it. The cyst-walls were internally soft and gelatinous, and their substance continuous, through the fissures of the cover, with the gelatinous layer of the Acineta, of which they might be more correctly represented pouches or diverticula. The appended animalcule is not a bud produced from the Acimeta-body; for it is never found in organic connexion with it, but un- doubtedly has its origin as a germ within it, and makes its way outwards. In fact, it is developed from the rounded nucleus by its elongation and sub- sequent transverse fission. The youngest cysts are round or shortly oval, and have no other indication of life and movement than that exhibited by the contractile space. In the next stage they are slightly emarginate at one end and still motionless, whilst in the oldest the fissure or emargination extends deeply into the interior in a curved manner, and very clearly exhibits a number of vibratile cilia. In this mature state they enjoy considerable locomotive powers within their capsule, and recall in their form that of con- tracted Vorticellina. Thus, at their fore part they present a rounded ciliated 364 GENERAL HISTORY OF THE INFUSORIA. lobe, resembling somewhat a retracted rotary organ, whilst the fissure ex- tending inwards indicates the alimentary tube. - There is yet another apparent mode of embryonic development in the Acineta of Vorticellina described by Stein, which occurred in some.specimens not provided with tentacles. In place of these, one or two short closed tubular processes extended from the fore part of the animalcule; of the usual granular contents scarcely a trace remained; and the nucleus and contractile space had entirely vanished. The membrane of the enclosed body, thus deprived of its ordinary constituents, contained, in their room, six elongated- oval cell-like bodies, ºr," long, which seemed to have been developed at the cost of the contents of the original Acineta. These structures had a sharp outline, and contained a coarse granular substance and a contractile sac. They seem to develope into embryos ; for in one case a ciliated furrow was observed, assimilating the being to the more usual embryos of the Acineta. Probably the Acimeta-condition of the Vaginicola is terminated in this manner, after developing for a period embryos according to the plan above mentioned, by the final breaking up of the nucleus into several large germs. In addition to the species described, Stein believed he made out the Acineta-state of several other species of Vorticella, of Epistylis, and Opercu- laria (XXX. 1–4), as well as of Zoothamniwm, Ophrydium (XXX. 5–8), and Spirochona (XXX. 18–26). However, sufficient details have been given to illustrate the presumed fact in the developmental history of the Ciliated Pro- tozoa ; and we must refer those of our readers desirous of more fully testing the views of that most excellent observer, to his often-cited work, ‘T)ie Infusionsthiere auf ibre Entwickelungsgeschicte,” Leipzig, 1854. More- over, the several new forms of Acinetina he has pointed out will be found referred to in the general history as well as in the systematic views of that group. - It is now incumbent on us to review the opinions of other naturalists upon this remarkable and interesting hypothesis. A few have accepted it, among whom are Mr. Busk (as we gathered from his lectures at the College of Surgeons in 1857) and Mr. Carter. The latter has the following remarks on the subject (A. N. H. 1856, xviii. p. 237):—“I could not discover an elongated nucleus, as Stein has figured, in the Amoebae and Acinetce, which I saw developing young Vorticellae, the former in plurality (one to three) and the latter singly : if present in the Amoebous form, it was circular, and if in the Acimetae, undistinguishable from the general “granulation.” Again,” he goes on to Say, “where are these transformations to end ? Into what kind of Rhizopods do the sheathed Vorticellae pass 2 How many of the fresh- water Rhizopoda are alternating forms of Vorticellae 2° At the time of his writing the above, Mr. Carter had not seen Stein’s latest work, which would have resolved some of the doubts and queries expressed. Thus, the German maturalist finds the nucleus, if elongated and band-like in the encysted being, to become orbicular or oval when in an Acimeta-state, and points out that acetic acid will reveal this organ when obscured by the granules of the interior. Moreover, his later researches have been extended to sheathed Vorticellina or Ophrydina—for instance, to Vaginicola, of which we have given the par- ticulars. However, it is very important to obtain Mr. Carter’s statement that he has seen young Vorticellae developed from Acinetoe and Amoebae, in- tending by the latter, we apprehend, Acinetae without tentacles and capsule, and not the simple Amoebae commonly understood by that term. The objectors to the hypothesis are by far the more numerous. The emi- ment physiologist Johannes Müller, to whom Stein showed Actinophrys and OF THE PROTOZOA.-CILIATA, 365 Podophrya developing embryos, could not agree with the conclusion the latter arrived at (viz. that they became Vorticellae), but was more disposed to believe that they relapsed into Acinet@. Ehrenberg (Ueber die Formbeständigkeit wnd den Entwickelungskreis der organischen Formen, Berlin, 1852, at pp. 23, 24, and 34) attributes the theory to erroneous and hasty observation. The supposed embryo of Acineta is, to his apprehension, simply a Trichodina which has been swallowed. To these strictures Stein replies that the Acimeta- bodies have no mouth, that they never contain any foreign matters taken as food, and that no more than one Trichodina appears in them at a time, al- though many may live around them, and several would, no doubt, if taken as food, be often found together in the interior. It is, moreover, to be noted, that Acineta collected from the most different localities contained the self- same Trichodina-form, and that such forms occurred in sparing number. Again, it must not be forgotten that the embryo may be watched in active movement within the Acineta for the space of an hour, whereas Infusoria swal- lowed by other animalcules are speedily reduced to a state of rest and de- stroyed. Lachmann rejects the hypothesis, and gives, in much detail, his reasons for so doing. At the same time he confirms the fact of “the forma- tion of embryos, not only in many Acinetina, but also in numerous other In- fusoria " (A. N. H. 1857, xix. p. 232), and attests the fact of the nucleus being primarily concerned in this act of development, adding some particulars which require to be recorded. “The nucleus,” he writes (loc. cit.), “is usually seen, first of all, to divide into two or more parts, when the same processes take place in One or several of these parts, which in other cases occur in the undivided nucleus. Upon or in the wall of the nucleus, or of one of its products of division, we now sometimes perceive small round glo- bules, which increase in size, finally acquire a contractile vesicle, and become converted into embryos; these at last become furnished with cilia, escape out of the parent animal, and Swim about freely, generally in a form more or less differing from that of the mother. Very different numbers of embryos may be formed in one section of the nucleus; in the same species we sometimes find many, and sometimes only one embryo formed in it; and an embryo which has been developed alone in a fragment of the nucleus is usually as large as all the embryos formed in a similar fragment which has developed many of them taken together. - “The true import of the nucleus, of course, is not decided by this state- ment ; [we cannot say] whether it is to be regarded as a germ-stock, in which germs are formed asexually, as an ovary, in which the ova are de- veloped at the same time, or, in accordance with Focke's views, as a uterus, in which the ova or germs formed in another place (perhaps in the nucle- olus?) are further developed. “The fate of the embryos which are unlike their parents after their birth is still unknown in most cases.” Perty displays distinct opposition to Stein's views, but has not thoroughly examined them, contenting himself with an occasional critique in passing. For instance, he states that those miniature beings regarded as the brood of Vorticella, both by Stein and Ehrenberg (see p. 357), are in his opinion no more than specimens of Cercomonas truncata (Duj.). Again, he remarks, Epistylis anastatica is very rare at Berne; and the Trichodina grandinella, which Stein represents to be its embryo, is very common in every collection of water; also Vorticella microstoma is most abundantly distributed, but its supposed metamorphic condition, viz. Podophrya, very uncommon. Respecting the latter animalcule, and likewise Actinophrys, he adds an observation of his own, which convinced him of the reproduction of these animals by minute 366 GENERAL EIISTORY OF THE INFUSORIA. internal germs, which, when set free, immediately assumed the special characters of their parents (Kleinste Lebenform. p. 74). To Dr. H. Cienkowsky we owe the latest examination of this subject (J. M. S. 1857, p. 96). He rejects Stein's theory because, instead of finding Podophrya fiva in company with Vorticella microstoma, he met with it in great abundance along with multitudes of Stylonychia mytilus and St. pustu- lata. Having watched its process of encysting, he felt “unable to adopt Stein’s view, that the Podophryde are enclosed in a membrane of which the slender peduncle is simply a tubular process.” In fact, he noticed cysts in which the original slender peduncle was appended to the Sacculate envelope. He also traced, step by step, from Podophryae, the derivation of the supposed transitional stages between Vorticella-cysts and Podophryae, and asserts “ that they are most certainly not metamorphosed Vorticella-cysts, but the commencement of the encysting of Podophrya. Podophryae are not formed out of them ; but, on the contrary, from the latter arise the forms above described, which Stein looks upon as Podophryae remaining at an early stage of development. The metamorphosed contents of older Vorticella-cysts, re- garded by Stein as the first commencement of the formation of a Podo- phrya, indicate, according to what I have seen in other infusorial cysts, and to what Stein himself states with regard to Vorticella microstoma, the commencement of the breaking up of the entire contents into numerous smaller “swarm *-cells.” Dr. Cienkowsky’s next proceeding was to show the relations of the motile embryo developed from the Podophryean animalcule Stein met with. He encountered numerous Acimetae precisely like those figured by Stein. “Most of these Acimetap were without peduncles, and had no limitary membrane, although numerous specimens might be seen with a short peduncle and imbedded in a mucoid thick envelope; and this was especially observed when the Acineta, had lived for about a week on the object-glass (XXIII. 33–39). Although numerous points of relation exist between these Acimeta-forms and Podophrya fiva (Ehr.), I am nevertheless unable to determine whether they should be regarded as identical, or, with Stein, whether Podophrya and Actinophrys should be considered as the extreme links in the morphological cycle of one and the same species (Stein, loc. cit. p. 143). The peduncle of an Acimeta is a tubular elongation of the enveloping membrane, whilst in the membraneless Podophrya it is an independent formation. When the Podophryae are left in water for a few days upon the object-glass, they form the very characteristic pedunculate cysts; but, under the same conditions, I have never been able to follow the Acimeta-forms now in question to the formation of cysts; the former multiply by division, whilst in the Acimetae I have never noticed the occurrence of that process. What Stein describes as Actinophrys is really a non-pedunculate Acineta ; the Actinophryde have no tentacles, but Setae, though perhaps occasionally some of these setae are capitate. In almost every specimen of the Acinetce in question might be seen rotating a round or oval embryo, of various size and position, with one or two contractile spaces. This embryo slowly approached the wall of the Acineta, caused it to protrude a little outwards; and after remaining for a short time quiescent, it slowly made its way through the wall (XXIII. 41), and quitted the parent site with the rapidity of lightning when it had freed about half of itself. This rapidity was so great, that the course could not be traced with a magnifying power of 170 diameters. About five minutes elapsed from the commencement of perceptible motion to the complete libe- ration of the embryo ; and on many occasions I saw two rotating embryos liberated in succession. When the embryo is half out of the parent-cyst, OF THE PROTOZOA.—CILIATA. 367 a transverse ring of very fine vibratile cilia may be perceived at a short distance from its summit.” This rapidly-moving embryo was followed in its course, under “the mi- croscope, and was seen to traverse ’’ the drop of water from one side to the other, in divers straight and undulating lines, as quick as lightning. Upon meeting a mass of mucus on the edge of the drop, it bounced back again, re- peating the manoeuvre on each occasion of the same kind; sometimes, though more rarely, the movement was circular, around the margin of the drop. “Judging from what I had noticed in the division of the Podophryas, I expected that the movement would not be of long duration. But after a continuous observation, for fully five hours, of the active motions of the tiny brilliant point, a determination of blood to the head obliged me to desist. “A fresh drop of the infusion, in which two embryos were in active mo– tion, was observed at intervals of a quarter of an hour. At the end of five hours, the rapidity of the movement was notably diminished—it became tre- mulous, and then, perhaps, for a time, as rapid and emergetic as before. I now placed the object under the compound microscope, and continued my observation of the indefatigable embryo for another quarter of an hour; the embryo became stationary. I waited with drawn breath what would come next ; its form from oval became spherical; at the border appeared short, thick, equidistant rays, which, after a while, were developed into elongated, capitate tentacles; the contractile space was visible; and I could no longer doubt as to the Acimeta-nature of the creature (XXIII. 42, 43). This obser- vation was twice repeated. “It can, therefore, no longer be doubted that from the Acimeta-embryo, after a prolonged motile stage, another Acineta is formed. My observations do not, of course, show that it is impossible that the motile Acimeta-embryo should be transformed into a Vorticella, and a Vorticella-cystinto an Acimeta; but the field of possibilities is very wide; everything is possible if it only be founded on facts. I believe, therefore, that it may justly be concluded that Stein’s Acineta doctrine, as concerns Vorticella microstoma (Ehr.), must be regarded as hypothetical, and not based upon facts.” - Lachmann and Claparède have jointly examined into the facts and appear- ances upon which Stein's hypothesis is based, and have presented an abstract of their views, which are entirely adverse to it, in the Annales des Sciences Naturelles, 1858, in anticipation of the publication of their essay, to which the French Academy awarded the first prize for original researches into the development of Infusoria. They state that they have witnessed the development of embryos in many other Acinetina besides those recognized by Stein; that the embryos of different species vary; that the tentacles of Acimetima are suctorial and active in seizing food, which is absorbed with avidity into the interior; and that the internal organization of those animalcules is in all probability more elaborate than Stein supposed. The appearance of the joint essay on the development of the Infusoria, by the gentlemen mentioned, as well as of that by Lieberkühn, which shared in the prize offered, will be anticipated with much eagerness and pleasure by all naturalists who feel how obscure and confused is the present state of in- formation on the subject. At the present time, we may say that Stein’s hypothesis of the transform- ation of Ciliated Protozoa (or, more strictly, of the Vorticellina and Ophry- dina, to which alone it has been sought to refer it by observation) remains unproven ; yet doubtless it is a step in the right direction to arrive at a know- ledge of the true generative process of these animalcules, and has already proved the development of ciliated embryos in Acinetina and in various Ciliata. 368 GENERAL EIISTORY OF THE INFUSORIA. The history of the metamorphoses of Trichoda Lymcews recounted by M. Jules Haime (Ann. d. S. N. 3 Sér. xix. p. 109) calls for notice in this place, although we are not disposed to assign it much value, inasmuch as some of the phenomena stated are very extraordinary, are unsupported by any parallel facts, and are in actual opposition to those best ascertained respect- ing the organization and functions of the Ciliata. We would especially direct attention to the statement of the exudation of sarcode, and the consequent reduction of size, as a necessary step in the developmental phases, an occur- rence, in our belief, without analogy and quite anomalous. He first asserts that “Oaytricha (Ehr.) is a larval phase of Trichoda Lyn- cews, and next that, on its fissiparous division, generally one of the two seg- ments produced assumes a globular form, losing almost all its appendages, both cilia and setae, and, at the same time, gives exit to successive portions of its sarcode, so that vacuoles multiply in its interior. At this stage a ge- latinous cyst is excreted around it which ultimately hardens into a mem- branous envelope. In a short time the contents of the cyst shrink from the cyst-walls and leave a space around them, when ciliary movement appears at One part, and, a further escape of granular sarcode having taken place through the cyst-wall, the figure becomes more or less modified. Two por- tions are now distinguishable within the cyst—a ciliated embryo and a mass of effete granular matter; and, as time elapses, the former seems to grow at the expense of the latter, and eventually makes its escape from the nearly- emptied cyst. The freed animalcule is not at first very different in appearance from the parent Oaytricha, although only about two-thirds its diameter; but ere long it developes itself into a very different being. In so doing, it first exudes some more of its substance, then produces numerous short stiff setae to serve it as feet, acquires a hard integument in the form of a shield, or carapace, and forms a mouth, in the form of a slit on one side, and, in front of this, a gyrating filament to produce a current for the introduction of food. In this transformed being the Aspidisca (Ehr.) is recognizable, having a very much smaller size than the original Oaytricha. The reversed course of development, viz. that of Aspidisca into Oxytricha has not been fol- lowed; but it may be conjectured that a sexual process is interposed, pro- bably in connexion with other metamorphoses.” Before taking leave of the subject of reproduction among the Ciliata, it is important to add a statement made by Lachmann in his excellent and oft-quoted essay (p. 239). He writes—“With regard to the peculiar pro- cess of copulation or zygosis of the Infusoria, as its object is still entirely unknown, I shall only state that, except in the Diatomaceae and Desmidiaceae, the position of which is still doubtful, it has hitherto been observed par- ticularly in Actinophrys and Acinetina. According to an oral statement, E. Claparède has also seen Vorticellina (especially V. microstoma) in zygosis; and I have twice met with double animals of Carchesium, still sitting upon a double stalk and constantly becoming more amalgamated, so that the cavities of both the fused animals communicated, and the morsel which was passed from the pharynx of one animal usually ascended in the cavity of the other, up to the lower surface of its ciliary disk. The rotatory organs remained separate ; and after the lapse of Some time, the double animal cast itself loose from the stems, and swam about for more than twenty-four hours by means of a circlet of cilia, which was produced around the rounded hinder extremity formed by the coalescence of the two posterior extremities of the individual animals.” NATURE OF THE CILIATED PROTOZOA. THEIR ExISTENCE As INDEPENDENT ORGANISMs. CELL THEORY APPLIED TO THEM.–That the beings we have com- OF TELE PROTOZOA.—CILIATA. 369 prehended under the appellation Ciliated Protozoa are indubitably animals, has never been called in question; nevertheless their claim to be considered independent organisms has been challenged by a few naturalists, who insist on their being generally nothing more than phases of development of animals more or less elevated in the scale. These objectors have, however, hitherto failed to produce sufficiently direct and exact observations in proof of this general assertion, which rests mainly upon presumed external resemblances, and on analogy with many of the inferior animals, among which the so-called “alternation of generations ° is the rule. In the foregoing pages there is certainly sufficient evidence that some Infusorial forms are merely stages of development of others; and nothing is more probable than that some may similarly be phases of animals belonging to other classes than the Ciliata ; yet, on the other hand, the independent character of several families (for example, of Vorticellina, Ophrydina, and Colepina) has not been at all shaken by the researches of naturalists. There is, we believe, a true typical organization appertaining to the Ciliata, of a distinct character from that of other animal organisms, and inconverti- ble. It may be more or less perfected, or more or less degraded, and may, in the process of development, be put in abeyance for a time, though not replaced by another; and under this impression, Stein's views of Acineti- form metamorphosis have, to our mind, an air of improbability. The very distinguished naturalist M. Agassiz stands among the foremost in advancing the sweeping conclusion, that the Ciliated Protozoa have no existence as a class. Most of the Enterodela of Ehrenberg, he says (A. N. H. 1850, vi. p. 156), “far from being perfect animals, are only germs in an early stage of development. The family of Vorticellae exhibits so close a relation with the Bryozoa, and especially with the genus Pedicellina, that I have no doubt that wherever Bryozoa should be placed, Vorticella should follow, and be ranked in the same division with them. The last group of In- fusoria—Bursaria, Paramecium, and the like—are, as I have Satisfied myself by direct investigation, germs of fresh-water worms, some of which I have seen hatched from eggs of Planaria laid under my eyes.” In these statements Mr. Girard (Proceedings of American Association, 1848, p. 402) coincides, and adds that Colpoda Cucullulus is one of the embryonic stages of fresh-water Planaria. - To these statements it may very fairly be objected, that the embryonic animalcules presumed to be identical with certain Ciliata may possess merely a deceptive outward resemblance, and, again, that in the case of the assigned affinity of the Vorticellina, an exact comparative examination of the organi- zation of this family with that of Bryozoa will show that there is no true homology, but simply some general points of similarity, between them. When Schleiden and others unfolded the cell-theory as a general fact in organic beings, attempts were at once made to apply it to the simplest animal structures, among which the Ciliated Protozoa are numbered. The Protozoa were called unicellular animals; a cell-wall, more or less modified, was everywhere discovered or supposed; and the more solid body, the testis of Ehrenberg, was at Once assumed as the “nucleus.” This name we have for convenience' Sake retained, although its special relation with cell-structure and the cell-theory cannot, in our opinion, be sustained. The cell-theory, in its application to Protozoa, found a very able advocate in Kölliker (J. M. S. 1853, i.), and was upheld by many others; its simpli- city, and the generalization as to structure and function it suggested, recom- mending it to philosophic minds. Latterly, however, a more exact apprecia- tion of the true organization and functional history of animalcules has caused - 2 B 370 GENERAL EIISTORY OF TEIE INFUSORIA. the abandonment of the hypothesis, the greatest names in microscopic Science having pronounced against it. - To sum up the leading circumstances opposed to the theory in question. The processes of the surface, both in variety of character and of movements, are not paralleled in any known simple cell; the same may be said of the pedicles and branched stems of Vorticellina, and of the sheaths of Ophrydina: the presence of a mouth, and, according to the descriptions of many excellent observers, of a discharging aperture or anus, and the involution of the external surface in the form of an alimentary tube, are facts irreconcileable with the idea of a cell. So, likewise, the beautiful and complicated ciliary apparatus of the Vorticellina and Ophrydina—the existence of cells, or at least of vesicles, in the interior—the reception of external matters into the general cavity, where they are either entirely digested or partially or wholly extruded again—and, lastly, the activity, persistence, and apparently voluntary cha- racter of their movements, are circumstances without parallel in the economy of simple cells. In the face of all these discrepancies in structure and func- tion between the bodies of Ciliated Protozoa and simple cells—closed sacs, containing a nucleus amid their protoplasmic substance—it appears to us it would be a mere visionary notion to insist upon a homology betwixt the two. To conceive such a thing, the accepted idea of a cell must be set aside, and replaced by So loose and general a definition as would be worthless. Without quoting their remarks, which is uncalled for here, the following observers may, among others, be cited in opposition to the hypothesis of the unicellular nature of the Ciliata: viz. Leuckart, Lachmann, Claparède, Perty, and Schneider. Our countryman, Mr. Busk, is, as we gathered from his lec- tures, to be reckoned in the number. - CONDITIONS OF LIFE.-Under this head we have to consider the habitats of the Ciliata, the usual conditions under which they live, their successive appearance in liquids, the influence of heat and cold, and of chemical agents upon them, and their probable duration of life. The majority of the Ciliated Protozoa are inhabitants of fresh water; few are marine ; or perhaps it would be more correct to state that few marine species are known. Cohn affirms that fresh water acts as a poison and kills the marine forms (Entw. pp. 132, 133); that the several genera of Entero- dela (Ehr.)—Cyclidium, Paramecium, Euplota, Oaytricha, and Vorticella— occur in water holding organic matter in solution or decomposition; and that Stentor, Ophrydium, and Loacodes are found only where the water is pure and uncontaminated with dead matter. This statement must not be taken arbi- trarily ; for among the former series, specimens are constantly seen in water free from appreciable organic impurities. Moreover, in all cases, the aqueous medium in which the Ciliata live must contain a certain proportion of organic materials (either living in the tissues of minuter organisms, or in a state of transition, commencing decomposition or breaking up into mineral or dead matter), from which they can derive the elements of their nutrition. Animalcules indeed, if we may so say, stand between the living and the dead, rescuing the atomic fragments of organic matter which are ready to perish and to lapse into the domain of dead matter. Thus we find them constantly in infusions, either artificially made by steeping animal or, more particularly, vegetable substances in water, or naturally occurring in ponds and ditches containing growing aquatic plants or their detached portions, or in the turfy hollows of commons and bogs. At times, indeed, the water in which they occur appears to the eye almost pure, and free from extraneous matters; but a closer examination will prove it to be inhabited by multitudes of monadiform existences, of minute plants, Desmidieſe, Diatomeae, Nostochineſe, OF THE PROTOZOA,-CILIATA. 371 Conferva, and Algae, which are diffused throughout, or float upon the surface, or form a stratum at the bottom. The attached forms find appropriate habitats upon the stems of aquatic plants, and very commonly upon the surface of various animals living in Water; for instance, on the shells of Mollusca, such as the water-snails, and on the surface of the Entomostraca. A few species find a suitable locality within the interior of larger animals, of which, therefore, they are esteemed the parasites, a fact illustrated in the genus Bursaria. This subject of the habitats of the Several genera needs not here to be enlarged upon, since it recurs again and again in the generic and specific descriptions of the systematic division of our work. The Ciliata do not so frequently constitute the colouring ingredients in water as do the Phytozoa. Nevertheless there are several species which make their presence known by their colour, either when collected in a stratum upon the surface of plants or of the water, or when generally diffused in a Small pool. Thus Stentor polymorphus and Vorticella chlorostigma coat the stems of aquatic plants green, whilst several spécies of Vorticellina cover them as with a bluish-milky film, and Stentor awrews with an orange-coloured in- duvium. Bursaria vernalis, Trachelocerca viridis, Coleps viridis, Glaucoma viridis, and Paramecium Chrysalis are found dispersed through the water—the four first imparting to it a green, the last a milky tint. The greenish masses of Ophrydium versatile at times float on the surface, driven about by the wind, and at others are attached to the tendrils of roots and to the stalks of aquatic plants. The distinct colours, such as green, yellowish-red, and Orange-brown, are in all cases, we believe, not essential to the animalcules exhibiting them, but due to the food they swallow, and to its changes in course of digestion. These changes, as affecting the colour, have been illustrated in a preceding page (p. 310) in the instance of Bursaria vernalis, for which the Chilodon ornatus might have been substituted. Moreover, in Nassula the reddish-blue or violet spots, conceived to be glands by Ehrenberg, are apparently the product of di- gested Oscillatorice (p. 312). SUCCESSION OF SPECIES.—If a fluid containing Infusoria be examined from time to time over a considerable period, it will be found that certain species disappear, and are replaced by others not before found in it. This succession of forms in the same liquid has been remarked from the earliest period of microscopic research, and has been the fruitful source of the wildest theories of the metamorphoses of Infusoria. Succeeding animals have been forth- with concluded to be the transformed states of previous ones, however wide the dissimilarity between them : no intermediate phases or transitional changes have been watched; but the conclusion that the one is derived from the other, has been jumped at without reserve. Some theorists have even pro- ceeded further, and, like Unger, believed in the transformation of vegetable into animal life, or, like Laurent and Gros, have imagined the conversion of mineral matter into organized animalcules, and these last into beings of still higher position in the animal scale, such as Annelida and Crustacea. A partial explanation of the succession of animal forms in a collection of water is to be found in the following facts:— First, no vessel of water of ordinary dimensions can be so thoroughly ex- amined but that some animalcules may be overlooked; the same accident will happen still more frequently with their minuter germs or embryonic condi- tions, or with their encysted state. The earliest phases, again, may, in their transient form, very nearly resemble certain known independent species, and be readily mistaken for them, or even for encysted simple plants. So, also, por- * 2 B 2 372 GENERAL HISTORY OF TELE INFUSORIA. tions of plants, small aquatic animals, organic débris, and other substances in the water may conceal in their cavities orinterstices either mature animalcules or their immature or encysted forms. Further, we know the air to be per- meated by animalcular life; that every wind wafts organized beings, for the most part in an encysted state, together with germs and spores, animal and vegetable, to and fro; and every exposed collection of water, unless protected by the most careful and complex contrivances, must perpetually receive fresh colonists. Now, among all these mature, encysted, immature, and embryonic inhabitants of a portion of water, existing in it when first submitted to obser- vation, or subsequently introduced into it from without, there must neces- sarily be a constant change in their relative abundance, and even in their con- tinued existence in it. Mature individuals may die out, be devoured by other animals, or be otherwise destroyed before multiplying themselves, or may, by encysting and reproduction, develope beings of a different general character, i.e. undergo a real transformation ; encysted beings may merge into life, immature and embryonic forms take on their perfect conformation ; hidden organisms may come out from their concealment; or the new ones borne by the air may manifest themselves; and in these and other conceivable ways new series of inhabitants may make their appearance on the scene. Lastly, the succession of species is greatly influenced by the changing con- ditions of the water and its contents, by atmospheric conditions—cold, heat, and electricity, and the moisture or dryness of the air. All the facts collected under the head of Habitats indicate the mutual relations between the appear- ance of certain animalcules and the presence of particular plants or even of certain animals, or the existence or absence of decomposing organic matter. We have, moreover, so to speak, carnivorous and herbivorous Ciliata, each and all severally requiring their special nutritive elements in the water. From these circumstances it is evident that particular species will disappear when the conditions favourable to them fail, to be in all probability replaced by others to which the change is favourable and necessary; for instance, the vegetable feeders will decrease and disappear when the minute plants on which they feed are consumed ; so those animals requiring pure water will die out when decomposing organic matters multiply, and will be replaced by the forms which delight in their presence, but have remained undeveloped until the conditions favourable to their existence are brought about. The little Coleps (to give a particular illustration) delights in the eggs and contained substance of Entomostraca, and makes its appearance in company with those animals, without which it is only occasionally seen. And it remains to be noted, that unless an animalcule is duly supplied with appropriate nourish- ment, its reproductive powers remain in abeyance, and consequently its whole race may vanish from this cause. º A particular example of the succession of species may be quoted from Cohn’s essay on Reproduction of Infusoria (Zeitschr. 1851, p. 258). In a vessel containing decomposing Spirogyra, at first appeared countless speci- mens of Paramecium Aurelia; these were replaced by the Protews of Baker, either the Lacrymaria Proteus or the Trachelocerca Olor (Ehr.); these in their turn were followed by Chilodon Cucullulus, and after a few days by a Colpoda; afterwards large Euplotes with prominent green globules, probably a new species, and lastly, colourless specimens of Euplotes Charon exhibited themselves, all these species following each other in Succession in the course of three weeks, a new form appearing on the decline of a preceding, attaining its maximum in number, and then decreasing in its turn to make room for the next in the Series. Moreover, this excellent observer remarks that a similar succession is observed in the case of microscopic plants, such as Oscillatoria. OF TEIE PROTOZOA.—CILIATA. 373 DURATION OF LIFE.-What this may be among the Ciliata is little known to us. “The Infusoria have a comparatively long life” was one of the general facts enunciated by Ehrenberg. Under favourable conditions certain species have been known to live four or five weeks. This applies to them only in one phase of existence, viz. that which we regard as the normal and mature one. But when we take into consideration the encysting-process as an act of conserva– tion, we are compelled to assign them a duration of life of a very much longer range; for by its means the Ciliated Protozoa are preserved in a quiescent, torpid, or hybernating state, not only over periods of drought when the ponds containing them may be dried up, but also during the entire winter. Further, by the medium of fission and gemmation, the existence of the animalcule is prolonged or perpetuated through all the multiplied series of divisions and subdivisions and of gemmation, primary, secondary, and multi- fold, until the chain is broken by a sexual act of generation, and the being perishes in the production of its offspring. The resuscitation of Infusoria, after apparent death, forms a chapter in Ehrenberg’s great work; but the facts discussed have little or no bearing on this group of Ciliata; and the marvel formerly attaching to the subjectis much diminished by our knowledge of the phenomena of encysting, whether for the purpose simply of self-preservation or the carrying out of the process of de- velopment. INFLUENCE OF EXTERNAL AGENTS, HEAT AND COLD.—The Ciliata can Sup- port very considerable variations of temperature. Even in winter, beneath the ice, various species may be found still living. Ehrenberg tells us that Vorticella microstoma will live after being exposed to a temperature of 8° Fahr., and the ice gradually thawed; in fact, however, not more than one in a hundred will survive this process. Below this temperature none can live. The same is true of Paramecium Aurelia, Cyclidium Glavcoma, Glaucoma scintillans, and Colpoda Cucullus. When death is caused by cold, no rupture or injury of the body is perceptible, except in the case of Chilodon Cucullulus and some few other species, which are frequently quite disintegrated and dis– persed. Stentor polymorphus and S. Mülleri will not live many hours at a temperature of 9° Fahr. ; and arborescent Vorticella, Subjected to the same . degree of cold, fall from their stems and die. Perty gives a list of about 40 species of Ciliata which he found in Switzer- land during the cold of winter, beneath the ice ; we name a few as a guide to investigators:—Coleps hirtus (often without a shell), C. inermis ; Oaytricha pellionella, O. caudata, O. prisca, O. gibba ; Pleuronema crassa; Euplotes striatus; Vorticella patellina; Stentor Röselli: ; Paramecium Colpoda, P. versutum, P. leucas; Trachelius Anas, T. Lamella, T. Meleagris ; Trachelocerca Olor ; Glaucoma scintillans ; Lacrymaria rugosa ; Enchelys Farcimen ; Chilo- don, Cucullwlus ; Spirostomwm ambigww.m. ; Amphileptus Fasciola, &c. Ehrenberg affirms that when animalcules are frozen in ice, they are as it were lodged in a little cavity, and surrounded by water. This circumstance he imagined to be due to their animal heat, an explänation too improbable to be admissible; and, if the observation be correct, it must give place to some other. - - Respecting the effects of cold, it is a general law of the Ciliata, that their numbers rapidly diminish when winter sets in, and that, on the Contrary, they rapidly augment so soon as the warmth of the Sun in Spring manifests itself, and continue to increase in number and variety until the height of Summer is passed. - - Their endurance of heat is almost equally extraordinary as that of cold. Some are found in hot springs: thus Perty found specimens in the hot springs 374 GENERAL HISTORY OF TEIE INFUSORIA. of Leuk, at a temperature of about 80°; and Ehrenberg heated water gradu- ally to 120°Fahr., when Colpoda Cucullus and Chilodon Cucullwlus survived. NECESSITY OF AIR.—The water which Ciliata inhabit must be duly ačrated to support their existence, as is shown by the experiment of pouring a layer of oil on the top of a vessel of water containing them, and by their disap- pearance from a bottle which has been kept too long corked. They decrease in number and variety after water has been kept for some time in the house, even though it remains sweet ; this is probably due in part to the more stagnant atmosphere and the consequent diminished admixture of air with the water. CHEMICAL AGENTs. ELECTRICITY AND GALVANISM.–For chemical substances to act, they must be soluble in the water. Sea-water is generally more or less speedily fatal to fresh-water species; and, on the other hand, fresh water is destructive to marine species, especially when the change of medium is sudden. However, some species are common both in sea- and in Spring- water; and there are others living in brackish water which can readily ac- commodate themselves to a change of habitation. There are also substances, such as sugar, which, although not in them- selves poisonous, are damaging to animalcules, probably by causing an in- jurious alteration in the density of the water. Other substances, having active properties as poisons to animal life at large, such as corrosive Subli- mate, Strychnine, arsenic, and the like, are also poisonous to animalcules. Reference has been made to several chemical compounds which, by reacting variously on the tissues of animalcules, are employed for the purpose of demonstrating points in their organization: such are acetic acid, alcohol, tincture of iodine, solution of potassa, &c. The last acts as a solvent, caus- ing diffluence, as Mr. Addison pointed out some years since (A. N. H. 1843, xii. p. 101). * Of the effects of electricity, galvanism, and magnetism, we know little: ex- periments with these forces are few and imperfect. Ehrenberg collected the accounts of several, among which are the following:—A shock from a Leyden- jar charged with twenty sparks from an electrophorus having a resinous plate 7% inches square, and a collector 5% inches, suddenly killed Stentor niger, St. aureus, and Amphileptus moniliger. The bodies of Ophryoglena atra and Stentor polymorphus were entirely dissipated by it, as were also those of Epistylis flavicans, after having first been thrown from their stalks. It generally required two such shocks to kill the Paramecium Aurelia. When the electrical current passed near and not through them, their movements ap- peared unsteady. Electricity slowly produced has a more powerful effect than in the form of rapid shocks; and when either it or the magnetic current de- composes the water in which the animalcules are, then death is a necessary consequence. Mr. Rood (Sill. Journ. 1853, xv. p. 71) has experimented more recently, and states that, when a feeble galvanic current is passed through water con- taining Paramecia, the animals are brought to a stand-still, particularly in the neighbourhood of the negative pole, and after revolving for a time on their own centres, entirely cease to move ; ciliary action is also arrested, and diffluence quickly ensues. On the subject of the operation of chemical reagents on Protozoa, or, strictly speaking, on Paramecia, with which he chiefly experimented, Mr. Rood has the following remarks:—Alcohol stopped their motion, coagulated their con- tents so that they shrunk within their integument, and caused speedy death. Phosphate of Soda killed in a few minutes; and Epsom salts, the ammonio- chloride of mercury, acetate of lead, and perchloride of mercury destroyed OF THE PROTOZOA.—CILIATA. 375 life instantly. Cyanide of potassium did the same, producing at the same moment rupture of the integument and the discharge of the contents. On adding a quantity of oxalate of ammonia to the water, a stupefying effect at once follows, but after a few minutes the animalcules revive, and death does not result—at least, not for Some hours. Likewise, neither ferrocyanide of potassium nor neutral chromate of potash kills—at least, not under several hours. This last-named fact suggests the possibility of chemically injecting or impregnating animalcules, whilst still living, with a mixture of suitable reagents to produce coloured precipitates which might serve in demonstrating their internal structure. GEOGRAPHICAL DISTRIBUTION.—We know as yet of no special laws of geo- graphical distribution of the Ciliated Protozoa ; and a long time must, we fear, elapse ere the waters of the earth are sufficiently explored to warrant even an approximative sketch of Such laws. Wherever on this globe we may seek for these animalcules, they are, it seems, to be found—even the same families, genera, and species ; and if our present knowledge leads us to define particular localities for particular species, it amounts to little more than stating that they have there arrested the attention of some observer or observers, and have been overlooked or searched for at the wrong season, or under unfavourable circumstances, in other places. For, as our remarks on the succession of species imply, the animalcules present in any collection of water one week, may be in vain Searched for the next ; and the inhabitants of a pool or stream of One season, or of one year, may be exchanged for others the next. Although, therefore, laws of geographical distribution are wanting, yet we may be very much guided in our search for particular genera and species by a knowledge of their habitats and of the conditions which prove most favourable to their existence. Since the whole framework of Ciliata is sooner or later destructible by diffluence, their occurrence in a fossil condition is not to be looked for. AFFINITIES OF THE CILLATED PROTOZOA WITH OTHER ANIMALS.–Regarding as we do the organization of Ciliated Protozoa as belonging to a type sui generis, their affinities with other animals partake rather of a general than of a particular character. They possess an affinity with Rhizopoda, Gre- garinida, and Spongilla, with Opalinaea, Polypes, and with many Phytozoa, such as Euglence, in the nature of their contractile substances or Sarcode; also with the first and last-named, in the presence of one or more contractile vesicles. Multiplication by fission is also common to those several tribes, and that by gemmation to Vorticellina, Ophrydina, and Polypes; lastly, they agree with the Rhizopoda and Polycystina in the process of dissolution by diffluence. In the process of encysting, also, they are related with the Opa- linaea and Phytozoa, with some, at least, of the Rhizopoda, and, in general characters, with the Gregarinida. Of the mutual relations between the Ciliata (Opalinaea, Gregarinida) and Rhizopoda, we shall have further occasion to speak. But the Ciliata are also allied to the Rotifera by the chitinous constitution of their integument, by being moved chiefly by cilia, and more closely so through certain families, e.g. the Vorticellina and Ophrydina, which have a frontal ciliary mechanism approaching in structure that of the rotary apparatus. So, again, in some general features, the sheathed Ophrydina (e. g. Vaginicola) may be assimi- lated with the encased Rotatoria, such as OEcistes and Conochilus. Lastly, by means of the Ichthydina an additional link is established between these two classes, and also between them and the Twrbellaria ; for some, as Schultze (Müller's Archiv, 1853, p. 241), seem disposed to range the Ichthydina with the last-named family. A homology may be perceived between the hardened 376 GENERAL EIISTORY OF TEDE INFUSORIA. integument, with its uncini, styles, and setae, in such forms as Coleps and Euplotes, and the covering and appendages of Entomostraca and of some in- ferior Annelida; and some would note the similarity in movements between Coleps and Daphnia. . Through the Vorticellina a relation is established with the Bryozoa or cilio-brachiate Polypes—one, indeed, which some naturalists (Agassiz, for instance) affirm to be so intimate, that the two families should be placed to- gether in the same group. Lastly, there is, in the case of many Ciliata, a very close apparent affinity, almost amounting to identity (at least, so far as form is concerned) be- tween them and certain embryonic stages of other animals, for example, of Plamariae and of several of the lowest among the Vermes. It is possible, indeed, that some of the presumed independent Ciliata are nought else but larval conditions; but unless this can be shown by direct observation of their development and transformation, they must be still retained in their present place. The group represented by Bursaria and Paramecium are, as Agassiz (A. N. H. 1850, vol. vi. p. 156) asserts he has satisfied himself by direct in- vestigation, no other than germs of fresh-water worms, “ some of which,” he writes, “I have seen hatched from eggs of Planaria laid under my eyes.” To this assertion Mr. Girard assents (Proceedings of American Association, 1848, p. 402). However, there is one caution to be borne in mind in seeking to establish the unity of certain supposed specific forms and known embryonic phases of any animals—viz, not to confound general resemblance with specific identity. For, notwithstanding the former may be very distinct and close, this is not enough (as the history of development of the higher animals teaches us) while there is aught wanting in the image, to render it an exact counterpart of the original, identical in kind with it. The above offers a general sketch of the most evident affinities of the Ciliata. By the exercise of the imagination directed simply to external form, these might be greatly multiplied: this, however, would, instead of advancing our knowledge, lead only to misconceptions. CLASSIFICATION OF THE CILIATED PROTOZOA.—Among the many heteroge- neous groups of beings which have at a previous period been assembled under the name of Infusoria, or other terms tantamount to it, that of the ciliated animalcules has been more or less clearly distinguished from the rest, and has received much attention from the several propounders of schemes of clas- sification. However, as our knowledge of the Ciliata, both with respect to the number of known species and to their minute organization, on which alone any correct classification can be based, has been so greatly extended during the last few years, it would be useless to describe the various systems which were suggested when, as we may say, this branch of natural history was in its infancy. - We shall therefore omit all notice of any systematic arrangement of the Ciliata prior to that proposed by Ehrenberg. Now, although this arrange- ment is very imperfect and incorrect, and founded, moreover, upon certain views of their organization now generally rejected, yet, as it was the system adopted in previous editions of this work, and will be generally followed in the present one; and as, moreover, no other classification can lay claim to such completeness and accuracy as to command its adoption instead, it behoves us to detail its principal features. Besides this distribution of Ciliata, suggested by the great micrographer of Berlin, there are three others it will be necessary to describe in this place, severally proposed by Dujardin, Siebold, and Perty. Of these, however, it will only be necessary to present the outline as given by their respective authors, since the examination of the OF TEIE PROTOZOA,-Cl].TATA, 377 characters, limits, and mutual relations of the families described will form the subject of the Systematic portion of this work. The Ciliata, in our meaning, are very nearly the same beings that Ehren- berg called Enterodela, or Polygastrica furnished with an intestine connecting together their stomach-sacs. A division of the Enterodela was made, accord- ing to the mutual relation in position between the two orifices of the body— the mouth, and anus or discharging vent—into, 1st, Anopisthia, in which the intestine is so curved on itself that its two ends unite together in a common aperture; 2, Ehuantiotréta, having an oral opening at one extremity, and the anal at the other, i. e. opposite to each other; 3, Allotreta, with the two orifices placed obliquely with reference to one another; and 4, Catotreta, with both situated on one surface—the abdominal. The subjoined tabular view will display these divisions, and also their subdivision into families. We have departed from this arrangement of Ehrenberg chiefly by omitting a few genera and species, viz. Actinophrys, Trichodiscus, and Podophrya among the Enchelia, and some species of Bursaria from the Trachelina, and also by adding several new genera and families. Concerning the necessity of detaching the Actinophrys and its two congeners from the Enchelia, no doubt can be entertained when their structure comes to be considered ; we have thrown them together into one family under the name of Actinophryina (p. 243), and have brought them and the peculiar beings known as Acimetina (p. 258) together as two subdivisions of Rhizopoda. The peculiar parasitic Bursarice without mouth constitute, with some similar ciliated mouthless beings, a subdivision of the Ciliata, standing in near relation with Gregari- mida, and, in some measure, intermediate between the Ciliata and Rhizopoda. Lastly, we have removed the Ichthydima from the Rotatoria, and treated them as a subclass of Ciliata. The additional families and genera we shall not here specify, but must direct the reader forinformation tothe systematic descriptions. The following tabular view represents Ehrenberg’s classification. SECTIONS. - FAMILII.S. ( One receiving - and discharging illoricated ............................................. Worticellina. orifice only for * nutrition. loricated ................................................ Ophrydina. # Anopisthia. # tº:º lilloricated .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Enchelia, g each extremity, sº . # jº. ) loricated ................................................ Colepina. cº < & e - mouth furnished with pro-l ºr, tº # Orifi ituated | illoricated boscis, tail absent ............ Trachelina. jº rinces situa ILIOl’IC850 mouth anterior, tail present ...... Ophryocercina. B. obliquely. § Allodreča. loricated ................................................ Aspidiscina. 's - SYY - § locomotive organs, cilia............ Rolpodea. Orifices illoricated abdominal. various......... Oxytrichima. Catočreta. loricated ................................................ Euplota. \ | Dujardin's distribution next claims attention. Having, as we have seen, entirely rejected Ehrenberg's polygastric hypothesis, and at the same time failed to recognize many important points of internal organization now well established, he had, to construct his system, recourse to external 378 GENERAL ELISTORY OF THE INFUSOIRIA. characters only—to the presence or absence of locomotive organs, to the characters of those organs, to the nature of the external Surface, whether protected by an integument or not, or defended by a lorica, to the general conditions of attachment of fixed forms to other objects, and to the cha- racter of their movements when free. Moreover, his Ciliated Infusoria com- prised not only our group of Ciliated Protozoa, but also the Phytozoa, the Vibrionia only excepted; for he made no distinction between organisms moved by a single or few filaments, and those moved by vibratile cilia generally dis- tributed, or associated together in the construction of special locomotive organs. In his tabular view, the beings we have brought together under the appel- lation of Ciliata are all comprehended in the fourth and fifth orders of Infu- soria, with the exception of Coleps and the Ichthydina, which, in his opinion, belong to a type of structure differing from all others reckoned by him as Infusoria, in being symmetrical. The accompanying outline of this system of Dujardin will sufficiently illus- trate it at present, without further remarks on the value either of the prin- ciples he has adopted, or of the families and genera he has instituted. DUJARDIN'S CDASSIFICATION OF CILIATA. ord; IV.-Ciliated animalcules without a contractile integument. All swimmers. . NARED. Fam. 11. Enchélyens, without mouth; cilia disposed without order. 12. Trichodiens, with the mouth either visible or indicated by a fringe of cilia, with- out cirrhi. 13. Kéroniens, with a mouth and a fringe of cilia, together with some cirrhi or strong cilia in the form of styles or uncini. IB. LORICATED. Fam. 14. Ploesconiens. Lorica or shield diffluent or decomposable like the rest of the body. 15. Erviliens. Lorica genuine and persistent. A short pedicle. Order V-Ciliated animalcules provided with a lax, reticulated, and contractile integu- ment; or having their cilia so arranged in regular linear series as to denote the presence of an integument. A. ALWAYS FREE. Fam. 16. Leucophryens, without a mouth. 17. Paraméciens, with a mouth but no prominent row of cilia. 18. Bursariens, with a mouth and a prominent row of cilia. B.—EITHER VOLUNTARILY ATTACHED OR FIXED BY THE MEDIUM of ORGANs. Fam. 19. Urcéolariens, voluntarily attached. - 20. Vorticelliens, attached, at least temporarily either by their organs or by some part of their body. - SYMMETRICAL INFUSORIA.—Of several types without mutual relations. Planariola. Coleps. Chaetonotus. Ichthydium. With the exception of the family Leucophryens, which is nearly equivalent to our subgroup Opalinaea, and of the genera Planariola, Chaetonotus, and Ichthydium (the two last constitute our family Ichthydina), all the other families and genera are members of our class of Ciliata, and are described in the Systematic portion of this work. Prof. Siebold (Anatomie der Wirbellosen. Thiere) agreed with Dujardin in rejecting the Polygastrica of Ehrenberg as a class, and at the same time em- ployed the term Infusoria, applied after Ehrenberg's example to a multitude of various organisms both animal and vegetable, to designate a comparatively limited group. To this restricted use of the term we have already objected (p.199); we will now, therefore, proceed with the classification in question. Siebold's Infusoria included all those microscopic organisms, exclusive of the Rhizopoda, of supposed animal nature, whether possessing a mouth or not. Of these he made two classes: one named Astoma, the other Stomatoda, the latter equivalent to our Ciliata. The following tabular outline is presented OF THE PROTOZOA.—CILIATA. 379 by Siebold, without any comments on the characters and distinctions of the several families, which, however, agree in general with those instituted by Ehrenberg, the most striking departure being the exclusion of Ophryocercina and Aspidiscina. SIEBOLD'S CLASSIFICATION OF CILIATA, CLASS I.-INFUSORIA, Animals moving by cilia. Order 1.—ASTOMA, Infusoria without a mouth. Fam. 1. ASTASLEA.—Gen. Amblyophis, Euglena, Chlorogonium. Fam. 2. PERIDINIAEA.—Gen. Peridinium, Glenodinium. Famº. 3. OPALINEA.—Gen. Opalina. Order 2.—STOMATODA, Infusoria with a mouth. Fam. 1. WoRTICELLINA.—Gen. Stentor, Trichodina, Vorticella, Epistylis, Carchesium. Fam. 2. OPHRYDINA.—Gen. Waginicola, Cothurnia. I 2 Fam. 3. ENCHELIA.—Gen. Actinophrys, Leucophrys, Prorodon. Famº. 4. TRACHELINA.-Gen. Glaucoma, Spirostomum, Trachelius, Loxodes, Chilodon, Phialina, Bursaria, Nassula. Fam. 5. KolPODEA.—Gen. Kolpoda, Paramecium, Amphileptus. Fam. 6. OxyTRICHINA.—Gen. Oxytricha, Stylonychia. Fam. 7. EUPLOTA.—Gen. Euplotes, Himantophorus, Chlamidodon. Perty is the latest writer, as far as we can discover, who has attempted a classification of Infusoria, among which he distinguishes, as we do, a class under the name of Ciliata, having also in almost all respects similar limits, except in the retention of the Actinophryina as one of the two sections he makes, viz., 1, animalcules with vibratile cilia; and 2, with non-vibrating but slightly contractile cilia, or filaments. Leaving this second section out of view, the other is divided into three subsections, with the titles Spastica, Monima, and Metabolica, according to the varying character of their move— ments, which in the first are sudden and jerking, in the second, unvarying and constant, and in the third, associated with striking changes in the figure of the body. Under these three subsections he distributes all the Ciliata into families, to many of which, in departing from Ehrenberg's groupings, he has given new names. He moreover describes many new genera and species. Besides the Actinophryina, we exclude also the family Cobalina, which is equal to our family Opalinaea, and to Dujardin’s Leucophryens. We shall attempt to represent this system of classification by a tabular outline:– PERTY'S CLASSIFICATION OF CILIATA. A. SPASTICA.—Animalcules capable of contracting their bodies and their stems, when such exist, in a sudden Spasmodic manner, so that their more or less elongated figure is rendered oval or globular, and the stem coiled spirally. They are the only Ciliata which live associated, and are related to Bryozoa, and many to Rotatoria. Fam. 1. WAGINIFERA.—Enclosed in a sheath, into which they can withdraw themselves. Mouth with a ciliary wreath. Fam. 2. WoRTICELLINA-Without a sheath; living isolately, or in arborescent polyparies; with a contractile body and evident mouth, but no intestine. Deve- loped by fission, by germs, and gemmation, and by means of transi- - tional phases. Fam, 3. OPHRYDINA-Numerous animalcules associated together in a solid gelatinous mass, but without contractile fibres. Fam. 4. URCEOLARINA.—The Urcéolariens of Dujardin, Ophrydium being excluded, and Spirostomºſºm added. - B. MoniMA.—Animalcules which, although very contractile, neither undergo change of form nor eachibit jerking movements. A. General covering Soft.—1. Free forms, with a mouth, nutriment received solid. Fam. 5. BURSARINA. Fam. 6. PARAMECINA.—Body covered by longitudinal rows of cilia. Mouth lateral, often situated in a furrow. - Fam. 7. Holophry INA.—Mouth anterior; amus posterior. Cilia in longitudinal rows. 380 GENERAL EIISTORY OF THE INFUSORIA. Famº. 8. APHTHONIA.—Surface ciliated, and furnished besides with filaments. Fam. 9. DECTERIA.—Mouth provided with a circlet of bristles; in three genera lateral, in two anterior in position. Famº. 10. CINETocIIILINA.—Mouth on the upper surface, furnished with a vibrating flap. Cilia in longitudinal lines. Fam. 11. APIONIDINA (in part the Enchelia, Ehr., and the Paraméciens, Duff.).-Bodies small, soft, thicker at one end than the other; cilia in longitudinal rows. Mouth, where perceptible, at the anterior extremity. Fam. 12. TAPINIA.—Cilia scattered, or collected in particular spots, but never in rows. Body usually very small. Mouth only proved to exist by means of artificial feeding. Fam. 13. TRACHELINA.—Body elongated into a neck-like anterior process, or a laterally curved trunk. . Fam. 14. OxyTRICHINA.—Equal the Kéroniens of Dujardin. - 2. Parasitical forms, with or without a mouth, mostly receiving only the juices of other animals. - Fam. 15. CoBALINA.—Body mostly flattened, oval, elliptic or reniform, covered by numer- ous rows of fine cilia, and oftentimes with jointed cilia on the under surface. A raised margin or hollow fold occupied by cilia often indicates the mouth, of which, however, in several cases, no trace is evident. The animalcules commonly live internally, upon the juices of other beings, and occasionally on their outer surface, in which case the food they take is solid. They present among themselves numerous peculiarities and points of agreement, and at the same time many anomalies, and are lower in the scale than free living forms similar to them, e.g. Oxytrichina; their movements are rather automatic. The genera included are, Alastor (Kerona, Ehr.), Plagiotoma, Leucophrys, and Opalina. B. General covering firm by £nduration of the integument, or by excretion of hard Tanules. • & Faon. 16. Eurrorisºn the Ploesconiens of Dujardin. Fam. 17. Col.EPINA.—Represented by the genus Coleps (Ehr.). C. METABOLICA.—Very contractile ; undergoing protean alterations of their figure through a contraction and eatension of the body. Cilia scarcely observable on the body at large, but collected on the neck-like process. Fam. 18. OPHRYoCERCINA (Ehr.), including also Trachelocerca and Phialina. FAMILY I.—ICHTHYDINA. (Plates XXV. 357, 358. Plate XXXI. 28, 29, 31.) This family, which in our arrangement forms a subgroup of Ciliata, con- stituted in Ehrenberg's system a section of Rotatoria, an association which cannot be maintained now that their more intimate and essential organiza– tion is known. Indeed, these beings seem to have received but little atten– tion from that great naturalist, who had only an imperfect account of them to offer. They were described as Rotatoria with a single continuous rotary Organ, not cut or lobed at the margin, and without lorica or shell. Four genera were enumerated—viz. Ptygwra, Ichthydium, Chaºtonotus, and Gleno- phora. Their relative peculiarities were thus stated:—Ptygwra and Gleno- phora had a simple rotary locomotive organ; Ichthydium and Chautonotus, only a long ciliary band upon the ventral surface. Again, the two former had a simple foot-like process, and evident Oºsophageal teeth; the two latter a forked tail and no visible teeth. Dujardin, who has given a very good account of Chaºtonotus, rejected that genus, together with Ichthydium, from among the Rotatoria, and placed the two in a sort of subfamily of Ciliated Protozoa, under the name of ‘Symmetrical Infusoria.” Of the other two genera, Glenophora and Ptygura, he ignored altogether the former, and transposed the latter to his family of ‘Melice, tiens.’ Since the date of his systematic treatise (Hist, des Infus. 1841), he has sketched the history of a genus under the name of Ellimoderia, which is evidently allied to Chaetonotus (A. S. N. xv. p. 158). . OF TEIE PROTOZOA.—TCFITEIYDINA, 381 The latest researches, we have seen, on the Ichthydina are contained in a paper by Dr. Max. Schultze (Müll. Archiv, 1853, p. 241), on Chaetomotus and , Ichthydium, and on a new allied genus, Turbanella. In this communication Schultze clearly shows that Chaetomotus and Ichthydium are not Rotatoria, whilst he admits Ptygwra and Glenophora to be so. The leading and suffi- cient reasons for separating Ichthydium and Chaetomotus from Rotatoria are, that they want the peculiar ciliary apparatus of that class have no retractile rotary disk, no jointed tail-like process, no water-vascular system with vibratile tags, and no perceptible muscular and nervous system. The best account of the organization we have of any of the Ichthydina is furnished by Schultze’s contribution above quoted, wherein he details that of Turbanella. Of this we will present an abstract, but, before so doing, will preface a few notes from Dujardin on Chaetomotus. This genus has a symmetrical elongated- oblong body slightly contracted at its anterior third, and having its posterior half expanded; covered on its upper or posterior surface by cilia or by ciliated scales; terminated anteriorly by a rounded edge, near to which is a distinct circular oral aperture; and posteriorly ending by a bifurcate process. Some long vibratile cilia are visible on the anterior half of the ventral surface; and Dujardin thought he discovered four or five minute papillae around the mouth. This aperture he represents to lead into a long narrow Cesophagus, which abruptly ends in a wide intestine, that continues a straight course to the posterior extremity, where an anal opening is probably placed. The Turba- mella hyalina, of Schultze, has an elongated, rather compressed, colourless body, from ºth to #5th of an inch long, and Tłoth to #5th broad. The head is separated from the body by a constriction (XXXI. 28). Along the body, at apparently regular distances, numerous bristle-like processes stand out at right angles on each side. The posterior extremity is slightly contracted, and divided into two comb-like flattened processes or lamellae, having an inter- vening fossa, into which the anal aperture opens. A dorsal and ventral surface are distinguishable, the latter ciliated throughout, the former bare. The head is entirely covered on its upper surface by fine cilia, besides which, it has a circlet of larger ones around its middle. The ciliated condition of the under surface is displayed by a side or a transverse view of the animal. The bristle-like processes on each side are growths from the integument, and neither articulated nor separable (XXXI. 28, 30). The row is double on either side ; the under setae from 20 to 25 in number; the upper, only from 6 to 8 on a side. The latter are rather appendages of the dorsal surface, and are, moreover, not at right angles like the others, but bent backward. Each cutaneous process is terminated by a motionless cilium, equal to or ex- ceeding it in length. The cuticle and its processes are soluble in a warm solution of potash, and are not chitinous. - The alimentary canal passes straight through the middle of the body (XXX. 28, 29). The mouth, situated at the anterior extremity, is circular, and sur- rounded by a finely plicate or dentate margin; it opens into a muscular Oesophagus, which very much resembles that of Anguillula, and terminates below in the straight intestine. The oesophagus extends for the first fourth of the length of the body; and its muscular coat is so developed, that its canal looks like a mere central line. Its muscles are annular. The tubular intes- time has, on the contrary, thin walls, in which numerous molecules and fat- corpuscles are distinguishable, except, indeed, at its posterior conical termina- tion. The intestine lies in a soft, finely-granular parenchyma. No water- vascular apparatus with vibratile tags exists. At the posterior third of the body, on the dorsal surface of the intestime, a large ovary is placed, and in front of it a very much smaller testis. Both glands present a mulberry- 382. GENERAL ELISTORY OF TEII, INFUSORTA, like aggregation of rounded cells. The posterior portion of the ovary exhibits ova, having a germinal vesicle and spot surrounded by a fine granular yelk- mass; and one or two ova are frequently seen separated, having a delicate colourless shell developed around them. The diameter of the largest ova. equals +}uth. The mature eggs lie close to the testes. Besides this distinct male organ, two groups of Spermatozoid-cells seem present, lying apparently free in the loose parenchyma, and apparently without any investing membrane or envelope. As to their affinity, Schultze makes no doubt that they are Wermes, and belong to the group of Turbellaria, considered as a division of the Cestoidea. Among Turbellaria they are best placed with the Arhynchia; including Microstomum and Dinophilus. They resemble Nematoidea and Anguillulae in the form of the intestinal canal, but are unlike these in their figure, their ciliated integument, and their hermaphrodite structure. The Ichthydina are inhabitants of fresh water, living among aquatic plants. They have a sluggish, creeping gliding movement, resembling that of most Turbellaria. * - - FAMILY II.—NOCTILUCIDA. (Plate XXXI. 32–39). This small but remarkable SubSection is represented by only one animal, the Noctiluca miliaris, which has attracted much attention as one of the sources of the phosphorescence of the Sea. By several recent authors it has been treated as a near ally of the Ciliata, although it must be confessed to have few outward indications of such a relationship, and, in our estima- tion, is a representative of quite a different and independent group of animals. At first sight, a Noctiluca appears a round gelatinous corpuscle having a depression or groove at one part, surmounted by a filamentary pro- cess or tentacle. Compared with the Ciliated Protozoa, it is of gigantie pro- portions, attaining #5th of an inch in diameter. On closer examination it is found to have an integument of two layers: the Outer Smooth and reticular, structureless, and of considerable density; the inner a delicate, granular, gelatinous membrane, which Dr. Webb (J. M. S. 1855, p. 103) describes to be in union at all points with the whole system of reticulations spreading from the central organs,—a fact rendered evident by the action of indigo and the primary changes consequent on death. “The internal fibrous reticulations . gradually contracted, drawing the ‘vacuoles’ together, and with them the inner membrane. This was detached without rupture, but after a time fell into folds, which so included the other structures as to have the look of a wrinkled tube with a series of pouches ending in a larger membranous sac. The external layer distended by degrees till it suddenly burst. I should mention that a new supply of water had been given before most of these changes happened. I have also been successful in separating the two layers mechanically, by means of pressure, slowly and steadily applied to the animal under the screw compressor.” The external membrane is extended at one point into a tapering process, which acts as a locomotive organ. It springs from the edge of the infundibulum, which is extended backwards into a pha- rynx or gullet. This process or tentacle appears transversely striped, and breaks short; of the nature of those stripes we know nothing. Dr. Webb believes this process to be tubular, with an orifice on the inner side at its base. “At any rate,” he writes, “I have seen the colour, when iodine has been used, proceed towards the distal extremity; and under the influence of indigo poisoning, the granular matter of which the striation consists has been disarranged, scattered up and down the interior of the organ, and in the end has aggregated together in Small globules, without much impairing the OF TEIE PROTOZOA.—NOCTILUCIDA. 383 power of motion.” These appearances do not at all convince us of the tubular character of the tentacle; for they are attributable to the difference of action of the chemical reagents upon the contained matter and upon its investment. Dr. Webb adds—“I have never perceived any tendency to restoration of the lost part, nor any independent movement in the detached fragment. The stump continues active, and readily comes off at the base. The point is a little flattened. When the animal is killed in such a manner that this organ has free play, it always shows a disposition to coil up spirally.” Prof. Huxley’s comparison of the Noctiluca, in figure, to a peach is very good, and conveys a clear idea of the relative position of the external groove and its appendages (J. M. S. 1854, p. 50). “One surface,” he writes, “is a little excavated ; and a groove or depression runs from one side of the excava- tion, halfway to the other pole. Where the stalk of the peach might be, a filiform tentacle, equal in length to about the diameter of the body, depends from it, and exhibits slow wavy motions when the creature is in full activity. I have even seen a Noctiluca appear to push repeatedly against obstacles with this tentacle.” Behind the tentacle is a rounded or oval mouth, having a harder margin extending from the base of the tentacle, along its right side, in the form of an elevated ridge. This ridge has a horny appearance (although Dr. Webb declares it to be of fibrous consistence), and is usually described as sigmoid in outline. About its middle is a triple (tricuspid) tooth-like eleva- tion, composed of a middle, bifid, large portion, and a smaller one on each side. Dr. Webb says that when this tooth is “seen in profile, it has the appear- ance of a conical papilla, or, with a slight change in the point of view, of a hooked process terminating in a sharp. nib. It readily yields to pressure ; and I have seen it become shrivelled up from the use of astringents, before motion ceased in the cilium and tentacle. . . . The ridge may be sometimes observed in regular contractile action. Corresponding with these contrac- tions, I have witnessed a to-and-fro motion of the tooth, as though working on an axis in a direction towards the base of the tentacle. A good illustra- tion of this performance is given by bending the fore and middle fingers, and flexing them on the palm of the hand.” On the other hand, Prof. Huxley states that he never observed any movement in this tooth-like body. The oral aperture opens into a funnel-like cavity or pharynx, from the bottom of which a ciliary process extends, having a rapid undulatory move- ment, and retractile. Mr. Huxley only now and then detected this cilium, and states that it is difficult of observation; but Dr. Webb says—“The cilium may be found in every instance in which it is looked for with a quarter-inch glass, or even with the half-inch, provided the creature is left at perfect liberty, and is made to move if not in the right position. It often remains at rest for Some time, and then from above looks like a small bright spot at the base of the ‘tooth; * or it may occasionally be seen extended over the S-shaped ridge, or even the base of the tentacle. I have many times detected it in motion from behind, through the intervening substance of the body, and have noticed it vibrating vigorously long after rupture of the integument and partial discharge of the contents. A Chara-trough, or shallow concave cell, is most convenient for observations on this part, as the animal swims close to the under surface of the thin glass, and may be made to turn in any direction.” A minute oval aperture is represented both by Huxley and Webb as open- ing into the funnel-shaped oral cavity. This last expands into an alimentary space “ of Very various form and dimensions, capable of great dilatation, and presenting no distinct walls, but rather excavated in the central substance of the body, which is connected with the parietes by numerous granular radi- 384 GENERAL EIISTORY OF TELE INFUSORIA. ating filaments” (Huayley’s Lectures, Medical Times, 1856, vol. xxxiii. p. 511). These granular filaments radiate, from a central portion which seems to serve as a bond of union and a basis of Support for all the organs about the oral cavity, to the integument in every direction; and probably the apparent reticulation of the external membrane is due to the crossing of the very fine terminations of those filaments as they proceed to attach themselves to it. Lying amid the meshes of this fibrous network, chiefly towards the centre of the Noctiluca, are more or fewer vacuolar bodies. “The whole internal network of fibrous tissue,” writes Dr. Webb (op. cit. p. 104), “with the manner in which it invests the so-called vacuoles, is most beautifully demonstrated by the effect of iodine. The creature dies suddenly, without collapsing. The progress of the fluid can be traced along the fibres into the minutest meshes; and there remains for a long time a transparent ball, traversed in every direction by the brown fibres, headed with the vacuoles and granules, and having every reticulation on the surface sharply defined.” The “vacuoles " referred to are not homologous with those of Protozoa, and, to avoid confusion, another name should be found for them. They are actual sacs or cells, with a definite membranous wall, and thus appear to resemble in structure the contractile sacs of Protozoa. Dr. Webb asserts them to be alimentary sacs; and we gather from him the following account of them (op. cit. p. 105):—“When empty, they are usually contracted and grouped near the membranous tube which leads from the oral aperture— a few only being scattered among the internal reticulations. Their situa- tion is constantly changing, sometimes with a steady advance, at others by jerks, while the fibrous meshes with which they are connected undergo a relative alteration in shape. Gentle pressure will occasionally expel them through the oral or anal aperture ; but I have seen them spontaneously ejected without rupture, and float away from the body. In one instance where this occurred, and where the contents consisted of granular matter, fragments of Diatomaceae, and particles of Sand, the Sac remained entire for some time. When it burst, the membrane doubled up, the contents escaped, and the bits of silica were characteristically shown with the polariscope. I have never known these gastric pouches, or alimentary substances to be voided by any other outlet than those connected with the central depression.” At the bottom of the infundibulum is a large-sized oval, or ovoid, brownish body, of granular consistence, and strongly refracting light, which is the nucleus. It lies in front of and above the gastric cavity, and, Prof. Huxley states (op. cit. p. 54), assumes the appearance of a hollow vesicle when acted upon by acetic acid. Dr. Webb writes (op. cit. p. 106)—“The nucleus may be demonstrated as a nucleated vesicle, sometimes solitary, more frequently with several similar but smaller nucleated vesicles grouped around it. By careful manipulation it may be removed from the other structures; and as it floats about, its true form is displayed. Seen in One position, you have a view of a raund vesicle with a smaller vesicle attached to it by a sort of hour-glass contraction; in another, of a round vesicle with a central spot, a nucleated cell. I have found the nucleus enclosed in a second membranous envelope with a granular yelk-like fluid, which could be seen pouring out when the membrane gave way.” The reproduction of the Noctilucida is as yet not understood. Quatrefages and Krohn, Prof. Huxley informs us (op. cit. p. 54), “ consider that a process of fissiparous multiplication takes place, and that both of these observers have found double individuals, though very rarely. According to the latter writer, division of the body is preceded by that of the nucleus. I have not had the good fortune to meet with any of these forms; and the only indication of a OF TEIE PROTOZOA.—NOCTILUCIDA, 385 possible reproductive apparatus, which I have seen, consisted of a number of granular vesicular bodies of about grºwth of an inchin diameter, scattered over the surface of the anterior and inferior part of the body.” Dr. Webb (op. cit. p. 105) has the following observations on this subject:-‘‘I have never met with a double individual, but on one occasion witnessed the process of division, without, however, noting any proof of its connexion with that of fissiparous multiplication. Contractions of the integument took place in such a way as to cut off a globular mass from the body, about one-fourth of the whole. The two portions afterwards retained their form, with a puckered mark at the point of separation. The nucleus was not involved in this ope- ration, which occupied about two hours. “It is also a matter of every-day observation, that when the body has been torn and nearly all the contents have been lost, the animal continues to live in a deformed state, if the nucleus and central parts are left together. They acquire a new investment; or a portion of the original integument gathers up round them, while the ragged shreds are cast off. . “When several of these creatures have been kept for some time in still water, it is not unusual to find two of them in apposition; but I have never discovered any indications of conjunction, and look upon the condition as one of mere adhesion. It may, however, have given rise to the mention of double individuals, as the adhesion is tolerably firm. It may easily be broken up without injury to either animal.” In the Journ. of Micr. Science for 1855, p. 99, is the translation of a paper by Dr. Busch on the structure and function of Noctiluca, in which several original observations are given which appear to bear on this question of de- velopment. There is, however, such uncertainty about them, and the want of confirmatory evidence, that we deem it unnecessary to quote them, and must therefore refer our readers to the Journal cited. The fourth volume of the same excellent periodical (p. 74) contains a translation of a paper by Prof. Müller, from which it appears that this distinguished naturalist had discovered Noct- luca in an encysted condition. The account he gives stands thus:–“ These encysted bodies constituted the principal luminous animalcules observed at Messina in the autumn of 1853. Free Noctilucce at that season were not seen there; and in 1849 the same kind of encysted bodies were very common at Nice. The cyst is a perfectly transparent, spherical capsule, with a light- bluish brilliancy at the edge, and appearing like the egg-membrane of some Crustacea. Within this cyst is lodged a body in all respects resembling the Noctiluca miliaris, except that at this time no vibratile filament can be per- ceived. The Noctiluca-like creature fills the cyst more or less entirely, though occasionally it is much Smaller. In this condition the animalcules are lumi- nous without being agitated. When the cysts are examined under the microscope in a small quantity of sea-water, in such a way that during the observation the Saline contents are notably increased in consequence of the evaporation, a moment speedily arrives when the Noctiluca-like body Sud- denly contracts itself within its case into a little nodule; that is to say, it contracts upon the yellowish granular nucleus from which the filamentary strings of the interior proceed. I have noticed this vital phenomenon, not on one occasion only, but in many of the encysted animalcules. “The size of the case is usually from 4" to 4". But many are far smaller, even down to Tºy". Occasionally also, instead of a Noctiluca, cysts may be observed, containing a yellow nucleus #" in diameter; and once I noticed a cyst ı”,” in size, containing, besides this rounded yellow nucleus, quite isolated, an extremely minute Noctilwca-like body. Of the free Noctiluceae taken near Heligoland in the autumn, the smallest were ºn", and the larger 2 C 386 GENERAL HISTORY OF THE INFUSORIA. #" to gº" in diameter. The common variety of form, with a constriction of the circumference, which is noticed in free Noctiluca, and the radiating filamentary branching striae beset with extremely minute granules in the interior, were also characteristic of the encysted bodies, which I should be more indisposed to separate from the Noctilucas, from their possessing the most remarkable luminous power. At present we want the key to these re- remarkable phenomena, as well as all knowledge of the development and course of life of the Noctilucas.” We have, in our prefatory observations on this family, alluded to the opinion of the affinity of Noctilucida with Ciliated Protozoa. Prof. Huxley (op. cit. p. 54) has the following notes on this subject:-"If the preceding account be correct, it is obvious that the animal is no Rhizopod, but must be promoted from the lowest rank of the Protozoa to the highest. The exist- ence of a dental armature and of a distinct anal aperture, are structural peculiarities which greatly increase the affinity to such forms as Colpoda and Paramecium, indicated by Krohn. Noctiluca might be regarded as a gigantic Infusorium with the grooved body of Colpoda, the long process of Trachelius, and the dental armature of Nassula united in one animal. “On the other hand, the general absence of cilia over the body, and the wide differences in detail, would require the constitution of at least a distinct family for this singular creature.” . To our apprehension there is no homology between the dental armature of Noctiluca and of Wassula. In the latter, the so-called teeth appear to be nothing more than hardened folds of the membranous tube of the oesophagus, which may disappear by distension,--whilst in Noctiluca it is the condensed uncinate margin of the oral cavity on one side which constitutes the dental apparatus. Again, as to the presence of a distinct anal aperture, this cer– tainly establishes no other affinity with the higher Ciliata than it does with any other microscopic animalcules which possess such an outlet. On the contrary, there is force in the particulars mentioned as opposed to their re- lation with the Ciliata, viz. “the general absence of cilia, and the wide differ- ences in detail;” for cilia either diffused over the body, or collected into groups to form a special ciliary organ, are, when taken in connexion with the peculiar internal organization, so very characteristic that no microscopist, unbiassed by imagination, would reckon Noctiluca among Ciliata. In further opposition to the notion of such an affinity, it may be urged that Noctiluca is destitute of a ciliated contractile Oesophagus, and of a contractile vesicle, that it does not produce vacuoles in the introduction and transmission of food, and that its so-called vacuoles appear to be actual closed Sacs, separable from the body. Other distinctive peculiarities between the two might be ad- duced; but we think that, on reflection and a comparison between them, ob- servers will agree with us that Noctiluca is not a member of the Ciliated Protozoa, that it cannot be included among them as a new family, but must be placed in some other class of animalcules, or of itself form the representa- tive of a new class. The Noctilucida are inhabitants of the ocean, of the luminosity of which they seem to be the most potent cause, of the many which have been found in operation. They occur in the British seas, as well as elsewhere, floating on the surface of the water. Mr. Byerly, of Liverpool, noticed their prevalence in such numbers that the water acquired a rose-colour; and Dr. Webb (op. cit. p. 102) intimates that their luminosity must depend on some peculiar condition of their organs, or the media acting upon them. This supposition is analogous to that made by Ehrenberg respecting the phosphorescence of the Peridiniaea, which he believed to be due to what he OF TELE PROTOZOA.—DYSTERIA. 387 termed the “ ovaries,” or the masses of brownish-red matter which sometimes nearly fill the interior. Perhaps the brown granular matter which at times accumulates in and about the nucleus of Noctiluca, and which is probably related to the reproductive function, is the luminous material in this ani- mal; and there is nothing contrary to analogy in supposing the development of phosphorescence to be associated with a particular period of vital activity, but rather everything in its favour. The following valuable note on the collection of specimens occurs in Dr. Webb's excellent paper (op. cit. p. 102): —“As a caution to those who may undertake the further examination, I may state that the buoyancy of the Noctiluca is such as to bring it to the surface of tranquil water without any apparent effort, and that the best way to effect its capture is, not as is most frequently done, to use the muslin net, by which means the greater number of the creatures are lost or destroyed, but to skim the top, and especially those parts near the sides of the vessel in which the water has been standing. If removed in this way, and kept by themselves in a test-tube, they may be preserved for two or three weeks without a fresh supply of water. Even at the end of that time, if they die, it does not appear to be from having reached the natural term of their ex- istence, but as the result of some accidental cause ; they will not, however, bear carriage to any great distance in closed vessels.” We gather the following hints for the capture of Noctilucida from a paper by Col. Baddeley (T. M. S. 1858, p. 79):-‘‘Attach,” he says, “a fine muslin net to the end of a light pole, and proceed to some spot where the Noctilu- cida are likely to be driven. A breakwater which causes an eddy to collect. Medusae, &c. generally yields a good harvest. Skim the surface, and wash the net repeatedly in a can of salt water. At night these creatures are easily seen by their luminosity; by day, if plentiful, they cover the surface of the sea in brownish streaks. . . . The best winds in which to capture these crea- tures appear to be those from south to west ; during their prevalence, I have taken Noctiluca, every month of the year on the east coast of England; but it is during the summer months they are most abundant, and during calm weather. Abroad, they are constantly to be met with in warm lati- tudes; and I feel confident some interesting results might be obtained by securing these creatures in various parts of the world.” In conclusion he refers to the Diatomede which are so commonly found in considerable quantities in their interior. - FAMILY III. DYSTERIA. (Plate XXXI. Figs. 24–27.) Dysteria, which is clearly the type of a new family of animalcules, was so named by Prof. Huxley in honour of its discoverer, Mr. Dyster. Although its exact systematic position and affinity are not agreed upon, it certainly occupies a position in the Zoological scale above the Ciliata, if it does not rightly take its place, as Mr. Gosse contends, among the Rotatoria. As we have unfortunately no knowledge, personally, of this interesting being; we must avail ourselves of the excellent description afforded by Prof. Huxley (J. M. S. 1857, p. 78), and of the critical examination of its affinities furnished by Mr. Gosse (ibid. p. 138). - “Dysteria armata has an oval body, gºth to gºth of an inch long, by ++gth to #5th broad, which is not altogether symmetrical—the one side presenting a considerable evenly-rounded convexity, while the other, less prominent, is divided by an angulated longitudinal ridge into a smaller, dorsal, and a larger, Ventral area. The edges of both lateral surfaces are 2 C 2 388 GENERAL ELISTORY OF THE INFUSORIA. sharp and thin; dorsally they are separated by a shallow groove; but along. the ventral line of the body the groove is deep and narrow, and the produced: edges of the lateral parietes resemble the valves of a bivalve shell. “The ventral and dorsal grooves pass into one another in front; but pos- teriorly the lateral edges are united for a short space. The edge of the left, less convex, side of the body ends anteriorly in an obtuse point, which cor- responds with the anterior termination of the angulated ridge, and does not extend by any means so far forward as the edge of the right side, which re- mains thin, and forms the anterior extremity of the body. • * ~ * “At the anterior extremity, the large oral aperture is seen, just below the angulated ridge, and occupying the bottom of a deep fossa, which here takes the place of the dorsal and ventral grooves. The left wall of this fossa is thickened, and projects inwards so as to form a cushion-like lobe, clothed with remarkably long cilia; and these cilia are continued into the oral aper- ture itself-the posterior ones being large, usually directed transversely to the axis of the body, and having at times much the appearance of vibratile membranes. - - “The bottom of the oral fossa is strengthened by a curious curved rod, which terminates superiorly in a bifid tooth, while inferiorly it appears to become lost in the wall of the fossa. “But there is a much more prominent and easily distinguishable apparatus of hard parts situated on the opposite or ventral side of the mouth, and ex- tending thence through two-thirds of the length of the body. It consists of two portions—an anterior, somewhat rounded mass, in apposition with a much elongated, styliform, posterior portion. “It is very difficult to assure oneself of the precise structure of the ante- rior portion; but it would seem to be a deep ring, composed of three pieces— two supero-lateral and mutually-corresponding, united with a third, inferior, azygos portion. The latter is somewhat triangular, with a broad base and rounded obtuse apex,−the latter being directed forwards, and immediately underlying the oral aperture, while the former is turned backwards, and unites with the two supero-lateral pieces. Each of these is concave inter- nally, and convex externally, so as to form a segment of a circle, and presents a clear median space, the optical expression either of a perforation or of a much-thinned spot. “The anterior edge of each supero-lateral piece is nearly straight; but the posterior is convex, and it is by this edge that it articulates with, or is ap- posed to, the anterior extremity of the posterior division of the apparatus. Viewed laterally, this posterior portion appears to consist of two styles, which are somewhat like nails in shape, their anterior extremities being truncated, so as to present a sort of nail-head, while the posterior ex- tremity seems to taper to a fine point. Rather in front of the middle of its inferior edge each style seems to give off a short process downwards; and this process is, in botanical language, decurrent upon the style. Careful examination of the dorsal or ventral aspect of these parts shows that the decurrent process is, in fact, only the expression of a delicate membrane, which is bent so as to have a ventral convexity, and connects together the two styles. It might be said, therefore, that the posterior part of the apparatus is a triangular membrane, deeply excavated in front, bent so as to be convex downwards, and having its margins thickened and produced into styliform enlargements. This curious piece of mechanism is directed upwards and backwards, and terminates in the substance of the body without any apparent connexion with other parts. - - “The whole apparatus is moveable. The posterior portion is pushed against OF TELE PROTOZOA.—DYSTERIA. - 389 the anterior; and the heads of the styles come into contact with the posterior convex edges of the supero-lateral pieces, and push them forwards; the posterior portion is then retracted, and the whole apparatus returns to its previous arrangement. - - “In one Dysteria, which had swallowed a filament of Oscillatoria so long that the one extremity projected from the mouth when the other was as far back in the body as it could go, these movements took place as many as tWenty times in a minute. + “Mr. Dyster further informs me that in one of these animals which he saw feed, the frond of Oscillatoria was rather “swum upon’ than seized— ingestion being accomplished by a smooth gliding motion, apparently without displacement of the styles, but that, when the act was completed, the styles ‘gave a kind of Snap and moved slightly forwards.’ “Mr. Dyster is inclined to think that the Oscillatoria passed through the anterior ring-like portion of the apparatus. I have not seen the animal feed, but, on structural grounds, I should rather have been inclined to place the oral aperture at, and to suppose that the food would pass above, the anterior ring. The apparatus is destroyed by caustic potash, but remains unaltered on the addition of acetic acid; it is therefore probably entirely composed of animal matter. - “Immediately above the annular portion of the apparatus, there is inva- riably present a remarkable amethyst-coloured globule, apparently composed of a homogeneous fluid. It has on an average a diameter of stºry in., and it is entirely lodged in the more convex portion of the body. In many spe- cimens no other colouring matter than this can be detected; but in Some, minute granules (+gºrºd in.) of a similar colour are scattered through the body. What connexion these have with the large constant globule is not clear, since, although the dimensions of the latter vary from the size given above to one-fourth or less, no relation could be observed between this diminution and the presence of the granules in other parts of the body. “Behind the amethystine globule, the substance of the body has the ap- pearance, common to the Infusoria generally, of a mass of ‘Sarcode,” in which the ingested matters are imbedded, and no clear evidence could be obtained of the existence of any digestive cavity with distinct walls. “A little behind the middle of the body, and towards its ventral edge, there is a clear spheroidal ‘contractile space,’ which varies a good deal in size. One measured Tºrºth of an inch in diameter, and became entirely obliterated in the contracted state. “The contractions are not rhythmical, but take place irregularly. On the approach of death, the space becomes irregularly and enormously enlarged, until it occupies perhaps a third of the whole contents of the body. “Immediately beyond the contractile space there is a curious oval body, having its long axis (stºry in.) directed upwards, and containing a compara- tively small central cavity, so that it appears like a thick-walled Sac. “Indications strongly suggestive of an inferior opening were sometimes observed in this body; but no demonstrative evidence of the existence of any such aperture could be obtained. “The walls of the ventral groove are provided with long and powerful cilia—a remarkably strong one being attached behind the base of the ‘ appendage; ' and by their means the animal, when free, is propelled at no very rapid rate through the water. Its more usual habit, however, is to remain fixed by means of the peculiar appendage; and then the cilia act merely in creating currents, by which nutritive matters are brought towards the mouth. - 390 * GENERAL EIISTORY OF THE INFUSORIA. “The appendage referred to is attached to the surface of the body, rather . towards the convex side, at the bottom of the ventral groove, and is distant about one-fifth of the whole length from the posterior extremity. It is sºuth to rºoth of an inch in length, and is not altogether unlike a boot with a very pointed toe in shape; and the toe appears to be viscid at its extremity, so as readily to adhere to any foreign object. The appendage then forms a pivot on which the whole body turns about ; and this appears to be the habitual and favourite position of the Dysteria. “Internally, the appendage contains a canal, wider above than below, and apparently blind at each extremity. “No nucleus’ could be found, though carefully sought for with the aid of acetic acid. : - “The occurrence of transverse fission was noticed very distinctly in one case ; but it is remarkable that, notwithstanding the great number of speci- mens which were observed, no other instance of this mode of multiplication came under the notice of Mr. Dyster or myself. It would appear that the * apparatus’ disappears, and is reproduced during fission; for, in the single case observed, mere rudiments of it were sto be seen in each half of the strongly-constricted mass. . “Dysteria has not hitherto been observed to become encysted, although this condition has been carefully sought for. “The creature was found in Swarms among the Algae, coating the shells of a Patella and a Littorina which had long inhabited a marine vivarium. “There can * (p. 82) “be little doubt as to the true systematic position of Dysteria. The absence, in an animal which takes solid nutriment, of an alimentary canal with distinct walls, united with the presence of a contrac- tile vesicle, with the power of transverse fission, and with cilia as locomotive organs, is a combination of characters found only in the Infusoria. In this class, again, the existence of a sort of shell or lorica, constituted by the structureless outer layer of the body; the presence of a submarginal ciliated groove around a large part of the margins of the body; and the inequality of the two lateral halves, leave no alternative save that of arranging Dysteria near or in the Euplota of Ehrenberg. “Indeed, there is one species figured by Ehrenberg (Infusionsthierchen, p. 480, pl. 42, fig. 14), Euplotes macrostylus, found at Wismar, on the Baltic, which, in general aspect, and in the possession of a foot-like appendage, so closely resembles the present form, that, were it not for the absence of any allusion to the amethystine globule, or to the “apparatus,” I should be strongly inclined to think it identical with Dysteria. That an internal armature is not inconsistent with the general plan of the Euplota, is shown by Chlamidodon, whose apparatus of styles would probably repay re-exami- nation. “ Notwithstanding certain analogies which might be shown to exist be- tween the manducatory apparatus of Some Rotifera (see, e.g., that of Furcw- laria marina, figured by Mr. Gosse, in his excellent memoir, Phil. Thrams. 1846) and the “apparatus’ of Dysteria, I see no grounds for regarding the latter as in any way an annectant form between these groups.” Mr. Gosse dissents from this conclusion of Prof. Huxley relative to its connexion with Euplota, and considers it a member of the family Monocer- cadede among the Rotifera. - “Presuming,” he says (J.M. S. 1857, p. 138), “Dysteria to be an In- fusorium, it must be a species Sui generis, with no close affinity with the Euplotidae. An animal whose soft parts are enclosed between two deeply- compressed valves, and which crawls by the aid of a hinged shelly foot, is OF TEIE PROTOZOA.—DYSTERIA. 39]. widely different from one greatly depressed, covered with a dorsal plate, and whose organs of locomotion are short flexible setae scattered over the soft Ventral surface. - - “But I am by no means sure that it should be placed among the Infusoria at all. Mr. Huxley observes that ‘ the absence, in an animal which takes Solid nutriment, of an alimentary canal with distinct walls, united with the presence of a contractile vesicle, with the power of transverse fission, and with cilia as locomotive organs, is a combination of characters found only in the Infusoria. “Now the presence of a contractile vesicle, and of locomotive cilia, are quite as characteristic of the Rotifera as of the Infusoria. The absence of an alimentary canal is, I think, not proved: it seemed to me that the animal possessed a defined digestive cavity, though very ample. In Sacculus—an indubitable Rotiferon, which carries its large eggs in the manner of a Bra- chiomws—the alimentary canal, without apparent distinction of stomach and intestine, is so large that it occupies fully five-sixths of the whole volume of the lorica ; and though it is invariably found filled with a green Alga, on which the animal feeds, the walls of the digestive cavity are not better defined than in Dysteria. There remains, then, only the fact of increase by trans- verse fission. This, I confess, is a strong point, if well established. But it does not seem certain, from Mr. Huxley’s words, whether he witnessed the progress of constriction from an early stage until two perfect animals were formed out of one, or only saw an individual so strongly constricted that the result seemed legitimately inferable. If the latter was the case, is it not just possible that it was an example, not of spontaneous fission, but of malforma— tion, instances of which are frequent among the highest animals 2 It is highly worthy of note that the nucleus, so characteristic of the Infusoria, was not found, even under careful search with acetic acid. “The presence, position, and movements of the foot, hinged as it is upon a tubercle, and the form of the principal organs of manducation, seem to me to determine the place of Dysteria within the class Rotifera; while, at the same time, the lack of internal motion, the apparent want of distinct muscle- bands, the great extent of the vibratory cilia, and the absence of a rotatory arrangement, show that it occupies one of the vanishing points of the class.” Mr. Gosse next proceeds to examine to which group of Rotatoria it ap- proaches most nearly, and concludes, as above intimated, that it ought to have a place in the family Monocercadea, represented by the genera Mono- cerca and Mastigocerca, although, at the same time, a very aberrant genus. He adds “that it has also remote relations with the Salpinada, and especially with the Coluridae (through Monwra); and that it is an annectant form be- tween the Rotifera and the Infusoria (i. e. the Ciliata), with a preponderance of the characters of the former class.” * 392 GENERAL HISTORY OF TELE INFUSORIA. SECT. IV.-OF THE ROTATORIA OR ROTIFERA. (Plates XXXII.-XL). GENERAL CHARACTERS.—Symmetrical animals, having a distinct head and body; the former surmounted by a wreath of cilia, the latter presenting transverse folds or joints, with a simple alimentary canal and internal maxil- lary apparatus; a muscular and a water-vascular system; nerves and nervous ganglia, but not arranged in a symmetrical chain; reproductive organs sepa- rate in opposite sexes; and propagation without undergoing actual metamor- phosis, by ova of two forms. The Rotatoria, moreover, are destitute of limbs in pairs, but have mostly the posterior extremity of the body produced as a powerful, although a symmetrical, organ of locomotion, in which a transverse articulation is particularly evident. This is a very natural group of animals, its characters being definite, and readily recognized by reason of the comparatively large size and transparency of the organisms. The name Rotatoria, sometimes exchanged for Rotifera, is derived from the apparent whirling or wheel (rota)-like motion of the ciliary wreath around the head, seen in most species. Since this rotary movement is not universal, and at best but an ocular deception, some ob- servers have been discontent with the appellations derived therefrom ; and Dujardin, for one, has suggested as preferable the term ‘Systolides,’ as indicative of the remarkable contractile and flexible nature of their bodies. They are also still spoken of under the old name of ‘wheel-animalcules; ” indeed, the early observers of the class actually believed the animals to be furnished with wheels, by the rotation of which they moved. ExTERNAL FORM, INTEGUMENT, AND APPENDAGES.—The Rotifera are symme- trical, and in this respect contrast with the asymmetrical Protozoa. They present a determinable dorsal and abdominal surface, and consequently a right and a left side. They have an oblong, ovoid, or much-elongated figure, and are mostly separable, by the presence of a constriction more or less developed, into an anterior segment or head, and a larger posterior one or trunk. The extension of the latter in a tail-like fashion may be regarded as a third seg- ment. The constriction or narrower portion behind the head is frequently called the neck; this is wanting in many cases, and then the head is undistin- guishable from the trunk as a distinct section, e.g. in Notommata Myrmeleo. On the contrary, the separation of the head from the trunk is well seen in Brachionus (XXXIX. 15–18; XL. 11), Stéphanops (XL. 8–10), Euchlanis (XXXIX. 4), Noteus (XXXVIII. 25), and Melicerta (XXXVII. 17). The articulation of the tail-like segment is always evident. In a certain number this prolongation is wanting; and the animal is then tailless, e. g. Anuraea (XXXV. 495–498) and Sacculus (XXXIX. 18). To facilitate the recognition of the general divisions of the body of Rotatoria, ..considered as bilateral symmetrical animals, Mr. Gosse furnishes the following remarks (Phil. Trans. 1855, p. 424):—The bilateral organization is, he ob- serves, in most cases “obvious, the motions of the animal, like those of the footed larvae of insects, being performed on the belly, with the head foremost. Where this is not the case (as with those genera which, either with or with- OF THE ROTATORIA. 393 out an enveloping tube, adhere to foreign substances by the tip of the foot, and elevate the body in an erect position), the dorsal aspect is always deter- minable by the eye or eyes being towards that surface, by the stomach and intestine passing down it, and by the cloaca being on that side of the foot. The ventral aspect has the manducatory apparatus and the ovary.” But, besides these great divisions, all the Rotifera exhibit transverse lines, folds, or joints, analogous to those seen in the Articulata, especially among the Crustacea, such as the lobster and shrimp. Mostly, such are but folds or Wrinkles, and not true articulations, in the Rotatoria (though perhaps as much So as the like in the larvae of many insects), and consequently disappear on the extension of the animals. However, in not a few instances, veritable articulations occur, e.g. Hydatina, Rotifer, Eosphora, Philodina (XXXVIII. 1, 2). In Euchlamis dilatata, writes Ehrenberg, the abdominal surface pre- sents four decided articulations. The minimum development of the articulate condition occurs in those genera the most removed from the Rotatorial type, viz. in Stephanoceros (XXXVII. 1), Lacinwlaria (XXXVII. 19), and some anomalous Notommata (XXXVIII. 28), which only present fine lines under the surface, looking like annular threads. The construction of the joints is peculiar, one portion or segment sliding within another after the manner of the tubes of a telescope. This telescopic action is best illustrated in the genus Philodina, where the entire body is fusiform and articulated; but it is oftentimes to be seen also in the tail-process, when absent or imperfect in the rest of the body, e.g. Brachionus, Notews (XXXVIII. 25), Stephanops (XL. 8–10), Scaridium (XXXVIII. 22). An incomplete articulation, or mere wrinkling, is seen in the pedicle of Megalotrocha, Melicerta, and Lacinw- laria (XXXVII. 17–19). All the Rotatoria are invested by a firm, usually smooth and elastic, integument or skin, which follows the contained parenchyma in all its con- tractions, accommodating itself to the various movements of the body. It is more delicate on the head, where the cilia are inserted, and there becomes continuous with the membrane of the interior. It is composed of two layers —an external, the cuticle, and an inner, immediately subjacent, the dermis (XXXVIII. 26). Where the structure is not evident, it may be rendered so by the use of chromic acid. The cwticle is homogeneous, structureless, and firmer than the dermis, which is soft, granular, and contains in its thickness numerous fat-globules and nucleated particles (XXXVII. 29). The latter tissue acts as a lining to the general cavity of the body, and gives attachment to the muscular cords of the interior. It is much developed about the head, beneath the vibratile ciliary apparatus, and there sends inwards numerous projections or lobes (XL. 2), which Ehrenberg assumed to be of a muscular nature, and to be permeated by vessels and nerves. At other parts also, delicate fibres or threads are seen to pass inwards from the dermis to the viscera, Sustaining and connecting them together. These fibres have some- times been described as muscles, at other times as nerves. The former is apparently their true nature, although, as Cohn believes, nerve-fibres may be mixed among them. The integument is histologically, i. e. in its anatomical nature, a connective tissue derived from the coalescence of branching cells, and still presents in its inner layer the scattered nuclei of the original cells, in the form of the nucleated particles described. Where the dermis is much developed, its soft tissue becomes here and there hollowed out into clear spaces or vacuoles, which have been mistaken for nerve-ganglions, especially when situated in the head (XXXVII. 29). So, again, at the posterior part of the body, behind the viscera, and in its prolongation or foot-process, where the dermic 394 GENERAL EIISTORY OF TETE INFUSORIA. tissue abounds, the vacuolar thickenings have been conceived to represent ganglions or, otherwise, glands. The cuticle, or external limiting membrane of the integument, is hardened by the deposition in it of the peculiar chemical principle chitine, the same which imparts firmness to the covering of Entomostraca, Insects, and other Articulata ; or if not actually chitine, it is a substance closely allied thereto. This is Leydig’s opinion, and it seems sufficiently confirmed by the reaction of chemical agents. Thus, he shows that caustic alkali (potash) does not dis- Solve the cuticle when it possesses, as it usually does, moderate firmness, in other words, when an infusion of chitine exists in its substance. But when the animal lives within an external case, and does not need the protection of an immediately investing skeleton, the chitine is absent, and the integument dissolves in the alkali. The analogue of this may be found among the Articulata. - The prevalent opinion has been, that the dense cuticle or external skeleton of Rotifera differed from that of the Crustacea and other Articulata in not being of a chitinous nature ; and this hypothesis was used in arguments relative to the affinities of the Rotatoria. Thus Kaufmann advances it as a decided distinction between this class and the Tardigrada; but, as Leydig remarks, the skin of the latter animals is even more affected by potash than that of the Rotifera (see section on the Affinities of Rotatoria). The cuticle, as just intimated, differs much in firmness and thickness in different species. It is softest in those which live in an external case—e.g. Stephanoceros, Melicerta, Tubicolaria, and in such as are invested by a gelatinous sheath—e.g. Notommata centrura. In Diglena, Notommata awrita (XXXVI. 3, 4), Asplanchma, and others, it is firmer, but still flexible; whilst in such genera as Brachionus (XXXIX. 16, 17, 21), Noteus, Salpina, and Euchlanis (XXXIX. 4) it attains a rigid, horny consistence, resembling that of the shells of Entomostraca. Even where the skin is of considerable firmness, it is yet capable of distension, as Perty observed in the Scaridium longicaudum when its stomach was stretched with food. The form of the body is much modified by the degree of firmness of the integument. When this is soft and yielding, or flexible, the figure is rounded, and more or less elongated, and may taper towards one or both extremities; but when the cuticle is much hardened, the rounded configuration is often lost, and various irregularities in form result. For example, in Metopidia and in Euchlamis dilatata (XXXVIII. 5) the body is ovate and compressed, or depressed; in Euchlamis triquetra it is triangular (XXXIV. 443); in E. hipposideros and in Lepadella (XXXIV. 430–432) the dorsum is convex, the abdominal surface flat; in Noteus quadricornis (XXXVIII. 25–27), suborbicular and com- pressed; in Mastigocerca carinata and Ratulus carinatus (XXXIV. 438–440) it is prismatic, with one angular ridge or crest; in Colurus, compressed laterally. There is, besides, a direct relation between the segmentation of the integu- ment, the perfection of its articulate condition, and the degree of firmness of the integument. The soft-skinned Rotatoria only throw their bodies into folds during contraction, whilst those with firmer cuticle, such as Philodinaea, develope the sliding joints, and, lastly, those (e.g. Lepadella and Euchlanis) which have a dense horny covering present two or three decided segments, recalling in form and disposition the divisions of the external skeleton of the monocular Entomostraca, or even of the higher Crustacea. Where the cuticle is condensed into a rigid, horny lamina, defending the animal like the shell of a Crustacean or the carapace of a tortoise, it may well be termed a testa, testula, or lorica. This last name was very loosely OF TELE IROTATORIA. - 395 used by Ehrenberg, being alike applied to the soft, pliant skin, to the hard shell-like cuticle, and to the loose and large external cases in which some Rotatoria live, as do the Coralline Polypes, in a cell or chamber. If limited, however, in its signification, as above suggested, the term may still be use- fully retained, and is preferable to the word ‘shell,’ which peculiarly belongs to the habitation of the Mollusca. By some authors the term carapace is employed; but to this there occurs a similar objection. . The lorica received from Ehrenberg various names, according to its form. Where a firm cuticle entirely enveloped the trunk, leaving the head and tail free, it constituted a testwla, as in Pterodina ; where it covered only the upper surface and sides, it formed a scwtellum or shield, as in Monwra (XXXIV. 457–459). The term “carapace,” employed by some authors, is equivalent to Scwtellum. The anterior and posterior openings of a testule vary much in different species; and an equal diversity occurs in the space left uncovered by a scutellum. This space is small and very narrow in Euchlanis Lynceus, in E. pyriformis, and in E. déflewa. In the last, moreover, the free edges are bent outwards at right angles. In Several genera, again, the lorica appears composed of an upper and an under plate, or is, in other words, bivalved. This is seen in Dinocharis (XXXIV. 454, 455), Salpina, and Colurus, and resembles the envelope in some of the lower Crustacea, as Cypris. In a few Rotifera, e.g. Euchlanis (XXXVIII. 5), the lorica appears much too large, the contained viscera only partially filling it. An increased firmness of the lorica enables it to resist decomposition longer than its soft contents; hence the occurrence of empty ones. Where the integument is of sufficient firmness to present an anterior and posterior margin, it is subject to many variations in form. Thus it may be truncate in front, as in Hydatina, Diglena (XXXIII. 403–405), and Polyarthra (XXXVIII. 30); or behind, as in Notommata Felis. It is crescentic in Metopidia; deeply and widely notched in Depadella patella ; has several spines, in front only, in Anwraea ; and both anteriorly and posteriorly in Noteus, Salpina (XXXIV. 447–453), and Bra- chiomus (XXXIV. 499–501). Sometimes the spines are so short and wide, that the border appears simply dentated or undulated; in other cases, spines may be long and strong, and themselves dentated, as in Noteus quadricornis (XXXVIII. 25). Not only do the anterior and posterior margins differ, but even those of the upper and under surface of the lorica, for example, in Salpina spinigera and in S. mucronata. Animals with spines projecting from the anterior margin, Ehrenberg speaks of as ‘ horned.’ - The surface of the integument is variously modified. Ths slightest change from the normal Smooth condition consists in a shagreened, dotted, or stippled surface, or in the presence of fine lines, e.g. in Anuraea inermis, Dinocharis and Diglena lacustris. In Notommata centrura, fine silky prominences clothe the surface. In Notews quadricornis and Brachiomus militaris, the points are elevated, and give the surface a rough (scabrous) aspect. Lines crossing each other, producing a tessellated or reticulated condition, are seen in Anwraea curvicornis and in Brachionws Baker; ; whilst in Anuraea testwdo, Brachionus militaris (XXXIX. 21, 22), and Noteus quadricornis (XXXVIII. 25) the lines assume the character of ridges, and divide the surface into squares or facettes. Radiating or curved striae are seen in Anuraea striata and A. foliacea, which in Euchlanis Lynceus are replaced by flutings. The elevated points may assume a further development, and project from the surface in the form of curved spines or hooks (aculei), as in Philodina acwleata ; or they may be so extended in length as to form long spines or rigid styles or setae having particular functions, as in Triarthra (XXXVIII. 30, 31, 32), and Polyarthra, where they are important organs of locomotion. o 396 GENERAL ELISTORY OF THE INFUSORIA. In the last-named genus they attain a still more complex nature, and assume a plumose (feather-like) structure (XXXVIII. 30). The opposite condition is seen in depressions or pits, few and scattered, on the surface of the integument, often apparently surrounded by a margin. Illustrations are found on the dorsum of Polyarthra, of Notommata Myrmeleo, and of N. Sieboldii (XXXVII. 32). All the markings and processes of the integument of Rotatoria are produc- tions of the chitinous cuticle, just as hairs, feathers, horns, and claws in the Vertebrata originate from the epidermis. They are similarly affected by chemical reagents, and decompose with the same facility as the integument which supports them. They are, moreover, of much value in supplying generic and specific characters. Several genera possess, in addition to the integument immediately investing them, an external sheath or case, to the bottom of which they are attached by a prolongation of the body in the form of a contractile pedicle. This external sheath received from Ehrenberg the particular designation of ‘wrceolus; ' and consequently the beings inhabiting it were said to be urceo- lated, or, as many prefer to say, are “encased.’ The composition of the case varies greatly ; for, although it originates always as a secretion from the animal itself, the substance differs in different genera, both in its characters and modes of formation: moreover, in some species, particles of foreign matters are superadded, to give it strength and solidity. . . The cases of Floscularia (woodcut, Part II.) and Stephanoceros (XXXVII. 1) are colourless, and apparently structureless, and, though roomy, are visible with difficulty on account of their tenuity and transparency. They are best demonstrated by the addition of some colouring matter, such as indigo, to the water in which they are examined. An exception to the usually trans- parent homogeneous case of Floscularia occurs, according to Dr. Dobie, in F. campanulata. Dujardin, again, asserts that the urceolus of Floscularia may vanish during the lifetime of the animal, and that in many French species it is always absent ; he therefore denies its value in generic distinctions. His statements, however, require confirmation, being opposed to the observa- tions of other maturalists. Again, the tubes of CEcistes, Conochilus, and Lacinularia are hyaline, with a more gelatinous consistence, and, in the two last genera, adhere together. In Comochilus the individuals are aggregated around a central globule of gelatine, from which they project like so many rays; whilst in CEcistes each urceolus is free, but has its surface encrusted with foreign particles. Twbi- colaria (XXXII. 379) has a thick gelatinous case, of a milky hue, which, from its effervescing on the addition of an acid, is attributed to a deposit of carbonate of lime within it. In young animals the case is quite transparent. This is also true of the urceolus of Limnias (XXXVI. 2), which, as it grows older, changes to a brown and brownish-black colour; and, as it is viscid, various extraneous bodies affix themselves to it. In one newly-discovered species, the usually smooth surface is departed from, and the case becomes annulated, and is also semitransparent. Dr. Bailey found in North America a species of Melicerta with a brown annulated urceolus. But the most re- markable tubular sheath is that of Melicerta ringens (XXXII. 386; XXXVI. 1), which is composed of equal-sized lenticular pellets, of a brownish-red colour, and of a substance secreted by the animal itself and deposited in a regular oblique or spiral series. This wonderful phenomenon will be consi– dered hereafter, in the section on Secretion. The cohesion of particles of foreign substances to the enclosing tubes is seen also in some Annelida, and in the aquatic larvae of certain Insects. C. OF TEIE ROTATORIA, - 397 - The urceolus serves as a place of shelter and defence for the adult animal, and also for the ova it deposits. The latter often remain within the case until they are hatched. The necessity for shelter is entailed by the fixed condition of these Rotatoria, because, unlike the free animals, they cannot escape their pursuers by flight. By means, therefore, of their highly con- tractile pedicles they can entirely withdraw themselves within their tubular dwelling, until the threatening danger is overpast. Ehrenberg, however, states that the animal may detach itself from its case and swim away free : if this be true, we must suppose it will again affix itself and proceed to con- struct another urceolus. The possibility of this acquisition of freedom is favoured by the analogous detachment of Vorticellae, and the formation by them of a new pedicle on reattaching themselves. Empty urceoli are indeed not uncommon ; but, unless the process be witnessed, it is impossible to say whether the inhabitant has quitted its abode at will, or disappeared by de- composition after death or by becoming a prey to other animals. Mr. Gosse noticed that a Melicerta, which had its case slit up for some distance, pro- truded itself through the opening ; and during several days’ observation, though it made pellets, they were never deposited in order to repair the breach, but were allowed to float away: this observation does not support Ehrenberg’s above-cited opinion. Each member of a colony of adherent Rotatoria is generated free, and swims at large until it chooses to join its fellows in becoming fixed. The encased Rotatoria attach themselves to any convenient substance in the water, especially the stems and leaves of water— plants. The single individuals are many of them just visible to the naked eye ; and where they unite in compound masses, they can be detached in the form of jelly-like globules, having a milky hue, often ºth of an inch and upwards in diameter. Tubes of Melicerta and Tubicolaria occur from ºth to #rth of an inch in length. An external envelope is found in a few free Rotatoria in the form of a soft gelatinous coating, for example, in Notommata Copews and N. centrura (XXXVIII. 26). In the latter species, moreover, this coat exhibits a regular arrangement of fine molecules within it, and a consequent apparent striation. Ehrenberg describes the confervoid fibres of Hygrocrocis as sometimes para- sitic on this gelatinous involucre ; but this account Leydig doubts. It is certainly, however, not improbable, since urceoli of every variety furnish a favourable nidus to parasites, both vegetable and animal; and this writer himself speaks of Vibrios adherent to the hyaline case of Stephanoceros, on the surface of which, as he imagines, they sometimes give rise to an ap- parent striation. - APPENDAGES OF ROTATORIA.—Each great division of the body is furnished with certain prominent parts or appendages, adapted to supply various re- quirements of the economy. The appendages of the head and neck exceed all others, both in number and importance,—the rotary organ, the peculiar characteristic of the class, being one of them. This latter organ is essentially a ciliated wreath or circlet, mostly sup- ported on an expanded margin or disk, and subject to considerable variations, which are employed in the classification of these animals; the rotary is also called the rotatory organ or disk, the trochal disk, at times, less definitely, the ciliated disk or wreath, or the wheel organ. Ehrenberg employed the rotary organ in its different modifications as the basis of his classification of the Rotatoria, making two chief types, in one of which the ciliated ring was single and complete, in the other Subdivided into several independent portions or secondary wheels. A subordinate type pre- sented two equal symmetrical circlets of cilia, forming a pair of wheels. To 398 GENERAL EIISTORY OF TEIE INFUSORIA, the first of these groups he gave the name of Sorotrocha, to the second Poly- trocha, and to the last Zygotrocha. The further subdivisions which he formed, and the names he applied to the varieties of the rotary organ, will be ex- plained in the section on Classification. The belief in actually compound trochal disks has been shared by nearly all observers, and both Perty and Siebold adopt it along with Ehrenberg’s classification. On the other hand, it is denied by Leydig, who affirms that the disk is never divided into such secondary wreaths or lobes, but always constitutes one continuous margin, variously extended and folded, and, it may be, furnished with inde- pendent accessory ciliated disks. This able writer remarks—“It is only to the exceptional genera Stephanocéros and Floscularia, that Ehrenberg's term Polytrocha can be rightly applied. In truth, an observation recorded by the great micrographer himself negatives his hypothesis of polytrochous division, that, viz., where he applied strychnia to the rotary organ of Hydatina, which became thereby reduced to a simple whorl of cilia.” The various degrees of complication assumed by the trochal disk are thus detailed by Leydig :—“It forms a simple ciliated margin around the mouth of Notommata tardigrada; in Stéphanops (XL. 8, 10) it is wider, more pro- minent, and triangular; in Euchlanidota, Polyarthra (XXXVIII. 30), Di- glena, Distemma, Hydatina (XL. 1), Pleurotrocha, and others, it occupies the entire periphery of the head, and is not at all, or but very slightly, elevated as a distinct disk above it; in Notommata Copews, N. aurita (XXXVI. 4), and in Symchaeta, it is enlarged and elevated as a distinct disk on each side of the head, forming the “ears ” so called by Ehrenberg; in other instances it is enlarged, and projects on the ventral surface of the animal like a ciliated trunk or proboscis. A higher development is seen in Brachionus (XXXIX. 15–18) and Philodina, where the ciliated border is involuted and extended upwards laterally (XXXVIII. 2); and lastly, in Megalotrocha, Lacinularia, Melicerta (XXXVI. 1; XXXVII. 17), and Limnias (XXXVI. 2), the high- est complexity is reached, and the trochal disk appears to be an appendage surmounting the head, expanded in the form of a sinuous or lobed ciliated margin.” In the variety last mentioned, Mr. Gosse speaks of the expanded lobes under the name of “petals.” The row of cilia fringing the rotary organ is often single, but in several species is double, and even treble. Mr. Huxley has noticed its double con- dition in Lacinularia socialis. To quote his description—“The edge of the disk has a considerable thickness, and presents two always distinct margins, an upper and a lower, of which the former is the thicker, and extends beyond the latter. The large cilia are entirely confined to the upper margin, and form a continuous horse-shoe-shaped band, which, upon the oral side, passes entirely above the mouth. The lower margin is smaller and less defined than the upper ; its cilia are fine and Small, not more than one-fourth the size of those of the upper margin. On the oral side this lower band of cilia forms a W-shaped loop, which constitutes the lower and lateral margins of the oral aperture. About the middle of this margin, on each side, there is a small prominence, from which a lateral ciliated arch runs upwards into the buccal cavity, and, below, becomes lost in the cilia of the pharynx. The aperture of the mouth, therefore, lies between the upper and lower ciliated bands (XXXVIII. 21).” Prof. Williamson has signalized a like arrangement in Melicerta (XXXVII. 17), and Leydigin Brachionus, Pterodina (XXXVIII. 29), and Megalotrochaea. The latter writes—“On the free surface of the head of Brachionus (XXXVIII. 14, 15), two lateral and and a median lobe elevate themselves, which Huxley compares to the two ciliated borders of Lacinularia, an interpretation that OF TEIE ROTATORIA. 399 has very many arguments in its favour, and in support of which I may adduce the structure of the rotary organ of Pterodina. This species, belong- ing to the family of Brachiomata, has its free projecting lobes furnished with a double row of cilia, analogous to what occurs in Megalotrocha. That the wheel organ of Philodinaea also is referrible to the same type, is evident from the account Huxley gives of it.” Cohn (Zeitschr. 1855, vii. p. 437) describes two complete rows of cilia, besides five or six special ciliary bundles, on the head of Hydatina senta (XL. 1). On the outer margin is an unbroken row of long and fine cilia, extending thence into the oral fissure, and still further, into the oesophagus. Within this circle is an interrupted one formed by 6 or 7 (Ehrenberg counted 11) bundles, having few or many broader and longer cilia, nearly resembling the setae on Stylonychia, and supported on as many cushion-like eminences. Lastly, the third series is unbroken like the first, and composed of finer cilia, disposed in a quincuncial manner in two lines. All the parts of this ciliary apparatus work harmoniously together in effecting the movements of the animal or in securing the capture of food. The figure of the trochal disk (XXXVIII. 14, 15, 20, 21) varies exceed- ingly, as the quotation from Leydig indicates, and is especially influenced by the addition of supplementary ciliated eminences. In Megalotrocha (XXXII. 374–378) the disk is horse-shoe-shaped; in Melicerta it is petaloid, or, as Prof. Williamson called it, flabelliform ; in Rotifer it is seen under two forms, according to its degree of expansion, either as a single conical eminence, or, when completely unfolded, as two cylinder-like processes, one on each side of the head, apparently whorling like two wheels. In the family Brachio- maea (Ehr.) accessory disks or processes give rise to much complication (XXXIX. 15–22). Ehrenberg described this family as having two ciliated organs—a central one of three parts, and a lateral one of two, the latter being the true wheel organ, and the former, frontal processes which are stiffly extended whilst the rotary organ is in action. An appendage such as that last named, in Notews, he designates a three-lobed ciliated brow. Exceptional or aberrant forms of the ciliated disk are seen in Floscularia, in Stephanoceros, and in Lindia (XXXIX.1, 3). In the first, the head (XXXVII. 1) is surmounted by five ciliated flattened lobes, ending in knob- like processes which bear very long, divergent, non-vibratile hairs or cilia of uniform thickriess (see woodcut, Part II.). “These exceptional cilia,” says Dr. Dobie, “are slowly moved and spread out by the contractile substance of the lobes of the rotary organ.” In Stéphanocéros, the departure from the normal structure is still greater (XXXVII. 1), so much so, that the ciliated appendages have no claim to the title of a rotary organ. Five long arms extend from the head, like five tentacles, covered by cilia in rings (ver- ticellate cilia). These arms not only act like a common trochal disk by pro- ducing a vortex directing all particles within its range to the mouth, but also as organs of prehension, closing themselves on any larger object which may come within their grasp. This ciliated armature around the head bears a close resemblance to that of the cilio-brachiate Polypes or Bryozoa, to which class of animals, indeed, several distinguished naturalists have referred the genus Stephanoceros, not merely on account of this one affinity named, but also from several other coincident characters. A third peculiar form of rotary organ has been recently pointed out by Cohn in Lindia (Zeitschr. 1858, p. 284). It takes the form of a club-shaped process on either side of the head (XXXIX. 1, 3), having its extremity somewhat expanded and spherical. Čilia exist only on the round summits of these processes; there is no whorl around the margin of the head, none elsewhere on the body; and this ex- 400 GENERAL HISTORY OF THE INFUSORIA, ample may be adduced as that of the least complicated rotary organ among Rotifera. It is in these aberrant forms alone that the ciliated apparatus can be strictly called “polytrochows;” in them, also, the wheel-like motion is completely absent. This peculiar motion, on the contrary, is most evident where the wreath is a simple circle, as in Conochilus and Actinwrus, or where, as in Rotifer and Philodina, it is peculiarly involuted, although continuous. Where, on the contrary, it is interrupted by a notch at any point, or is sinuated, or complicated by supplementary processes, as in Hydatina (XL. 1), Digléna, many Notommata (XXXVII. 29, 32), Synchceta, &c., the illusion of com- plete revolutions vanishes. Formerly, the belief existed that an actual whirling of the ciliated cephalic appendages took place, and that the little animals moved along, by the aid of these wheels, after the manner of a steamer with its paddle-wheels. Such an opinion is no longer entertained; and various explanations of the apparent rotary motion are now offered in its stead. Dutrochet attributed it to the undulation of a delicate membrane fringing the head of the Rotatoria. Faraday explains it by supposing the distinct cilia to become visible by slowly returning to an erect state, after having previously been suddenly bent. Ehrenberg assumed the existence of four muscles at the base of each cilium, each muscle acting in its own direction, and so producing a revolution around the fixed point of attachment or base of the cilium. In this way, each cilium would be alternately nearer to or more remote from the eye, and more or less visible. Another explanation has been offered by Dujardin. He says—“The vibra– tile cilia being arranged parallel and at equal distances, will equally refract or intercept the light, and none will be more visible than the rest; but if, by a movement propagated along the row of cilia, some, momentarily inclined, are brought into juxtaposition with adjoining cilia, the light will be more inter- cepted, and a band more or less dark will be the result. It can be imagined, therefore, that if the cilia come to be inclined one after another, a series of juxtapositions, or of apparent intersections will be produced in the direction of the general movement. Further, if each of the intersections preserve the same form, as if produced by a number of equal lines, and are equally in- clined to each other, an appearance of a Solid body of a definite form, like the teeth of a saw or the spokes of a wheel, moving uniformly, presents itself to the eye.” The action of the trochal disk is under the control of the animal. The ciliary movement can be arrested at will or exercised with varying rapidity; or the whole organ may be retracted, partially or entirely, within the body. When completely withdrawn, the ciliary wreath can frequently be detected at the fore part of the animal, oftentimes deep within the trunk, and gene- rally in the form of a striated cylinder at the bottom of a funnel-like canal. In complete retraction the anterior extremity of the body is involuted, or doubled inwards, and supports, as it were, the ciliated wreath within, whilst the contractility of the integument at the margin closes the entrance pretty accurately, giving a more or less conical outline to the fore part of the ani- mal (XXXVII. 19; XXXIX. 17). In complete retraction of the trochal disk, the antenna-like processes which may be seated on it are also with- drawn; but at other times, when the inversion is incomplete, these processes continue to project from the head, and in the process of evolution are always the first to appear, as if intended to test the safety of unfolding the delicate ciliary wreath. - The inversion of the ciliary apparatus and appendages is effected by strong OF TEIE ROTATORIA. 401 muscles arising within the abdomen, which draw downwards, and therefore inwards, the disk to which they are attached. At the commencement of their traction, they draw together the sides of the ciliary whorl, then pull inwards the cilia, which are previously collected in a cylindrical manner, and at last cause the inversion of the integument immediately beneath the disk, when the now anterior extremity of the body contracts itself upon the in- cluded parts. This process of involution may be arrested by the animal at any stage ; thus, sometimes it is stayed when the cilia are grouped together in a cylinder-like heap, and still project from the head like a pencil; or, as above mentioned, the cilia may be withdrawn, and some process or an– tenna be left protruding. The collection of the cilia into a brush-like group during the process of retraction is well exemplified in the long cilia of Flos- cularia; and in Rotifer and Philodina we have a special example of the pro- trusion of a ciliated process during the involution of the major part of the trochal disk (XXXVIII. 1). In the genera last cited, this median process serves as the anterior organ of progression when the animals advance in a leech-like manner, and disappears when the pair of trochal organs are evolved and the crawling movement is changed to Swimming. The retraction of the trochal disk we may suppose to be controlled by the will of the animal to arrest its motion or to avoid danger. Another motive is conceivable, especially in the case of the attached species: for the cilia, when in active operation, attract every sort of particle within their vortex— as well those appropriate to nutrition as others noxious or which have been lately discharged and still float about the animal; hence it may be ne– cessary to arrest their action, withdraw the disk, and close all access to the interior, until these unfit substances are floated away and have been replaced by others. The ciliated mechanism of the head is, as just hinted, the active agent in procuring food, by dragging within its vortex the nutritive particles in reach, and transferring them to the mouth, which is so situated that the current produced sets directly into it. Where the ciliary wreath is double, as in Melicerta, “the food” (to use Prof. Williamson’s description) “that reaches the mouth is whirled around the wheel-organs along the groove that sepa- rates the two circlets of cilia; and since these circlets diverge near the ‘chin’ (or fifth ciliary lobe), the mouth being located between them, the food is necessarily conveyed directly to the latter organ. The two sets of marginal cilia, by bending towards each other whilst in motion, almost con- vert this groove into a simus, especially in the two large segments.” But besides locomotion and nutrition, the rotary apparatus must be admitted to subserve the function of respiration, both by its own delicate structure, and by its action in constantly renewing the water around the animal; also, by forcing fluid within the alimentary canal, it may serve to ačrate and renew, by endosmosis, the fluid in the general cavity surrounding the viscera. In the fixed species of Rotatoria the rotary organ can have no locomotive use, merely subserving the functions of nutrition and respiration. In addi- tion to the rotary organ, the head is often beset with various appendages in the shape of styliform and tubular processes, lobes, disks, uncini, and spines. These are situated either within the circle of the ciliary wreath on its margin, or immediately external to it. Examples of tapering, styliform, and bristle-like processes are found in Notommata Myrmeleo, Monocerca bi- cornis, in Synchaeta, Monostyla, Brachionus, and others. On the head of Cono- chilus are four stout wart-like elevations. In Polyarthra platyptera two long bristles project from near the mouth, each bent on itself midway at a right angle (geniculate). Dujardin describes, in his genus oranº uncinate - 2 D 402 GENERAL EIISTORY OF TEIE INFUSORIA. retractile appendage surmounting the trochal disk. In Brachionws wrceolaris (XXXIX. 15, 16), straight non-vibratile cilia occur between the ciliated lobes of the rotary organ; and in Polyarthra there are fleshy tentacular appendages, which Siebold suggests are antennae or feelers. The 2–4 styliform processes of Symchaeta, Ehrenberg supposed to possess prehensile powers. In Como- chilus, four processes, terminated by bristles, project from the ciliary disk; in Melicerta are two curved hooks. To some of these appendages, and to others about the head, various fanciful names have been given, borrowed mostly from remote resemblance in appearance, situation, or function to parts existing in the higher animals. For instance, on each side of the head of Notommata aurita, N. Copews, and Diglena awrita, a lobe of the trochal disk is more elevated or elongated than the rest, and has received the appellation of “ear” or “auricular ; ” the 2–4 supplementary processes of the head of Polyarthra (XXXVIII. 30 a, b) have been called “horns,”—a name applied to a similar projection in other Rotatoria. In Stephanops a prominent scale-like process of the head is known as the “hood’” (XL. 8–10). Mr. Gosse speaks of a projecting spoon-shaped lobe in Melicerta, covered with cilia, as the chin, which Williamson recognizes as a “fifth lobe” of the wheel organ (XXXVII. 17 c). The latter writer, again, adopts from Schäffer the appellation of “lips” for two hook-like appendages of the head of Melicerta, and further describes, on each side the oral aperture, two projecting “flattened lobes, with ciliated margins continuous with those of the ‘chin,” which obviously assist in directing the food into the oesophagus.” Lastly, Ehrenberg frequently employs the term “frontal region ” or forehead, to signify the anterior surface of the head. - Certain tubular-looking processes, frequently furnished with a pencil of fine non-vibratile cilia or bristles at the extremity, have gained particular consideration owing to the functions assigned them by Ehrenberg and others. They protrude from the head near the trochal disk, and more commonly from the neck, as is seen in Rotifer, Philodina (XXXVIII. 20), Brachionus (XXXVIII. 15; XL. 11), Actinurus, in Euchlamis Lynceus, in Melicerta (XXXVII. 17), in Salpina mucronata, in Notommata clavulata, N. Myrmeleo, N. Sieboldii, and other species. In all the above the appendage is single, but in Tubicolaria and Melicerta (XXXVII. 17 d) it is double. In Calli- dina Ehrenberg mentions a thickly-ciliated proboscis, apparently retractile,and attached to the trochal disk; occasionally, instead of terminating by a bunch of setae, these processes have a horn-like prolongation, as in Notommata centrura and W. Copews. The short conical elevations of Symchaeta and Polyarthra belong to the same category with the tubular variety. A long flabelliform process occurs in connexion with one of the ciliary lobes of Floscularia, which is often called a proboscis, and supposed to be tubular. Ehrenberg has as- signed two different appellations to these tube-like appendages. At one time he calls such a process a spur (“calcar’’), and imagines that it subserves the generative process as an intromittent organ ; at another he represents it as a respiratory tube (siphon), through which water may enter to act on the vibratile tags (gills) seen within the abdomen. The former view has found no supporters, and is entirely set aside by our present knowledge of the reproductive act of the Rotatoria; the latter has been admitted by several, among others, by Siebold, although recent researches now render it untena- ble, and demonstrate the analogy of these appendages with the feelers (an- tennae and palpi) of Entomostraca and other Crustaceans. Dujardin seems to have been the first to suggest the analogy mentioned. Referring to these processes and to others less considerable, terminated by a bundle of stiff cilia, he observes that they recall, to some extent, the palpi and antennae of OIF TEIB. ROTATORIA. 403 Entomostraca and Cypris, and that no trace of the entrance or exit of water is perceptible, even when particles of colouring matter are diffused through the liquid, calculated to indicate the slightest current.” $ Since this was written, Perty, Gosse, Williamson, Huxley, and Leydig in particular, have minutely studied the point in dispute, and coincide with the French naturalist as to the non-perforated character of the organ, and its ho- mology with antennae. Mr. Gosse writes—“The tubes or spurs on each side of the head (of Melicerta) below the chin (XXXVII. 17 d d) are evidently consimilar with the antennae of Rotifer, &c. There is a slender piston in each, capable of being retracted, and bearing at its extremity a tuft of very fine, divergent, motionless hairs.” Mr. Williamson’s account is more detailed; he calls them “tentacles,” and states that, when fully protruded, they are seen “to be terminated by a brush of fine divergent setae implanted on the convex side of a small deltoid body (the piston, Gosse) (XXXVII. 12); from the flat side of this latter appendage there proceeds, along the interior of the tube, towards the body of the animal, a delicate muscular band (XXXVII. 13, 14), which, by its contractions, draws the deltoid body backwards, thus inverting the extremity of the tube, and forming a double sheath protecting the setae (XXXVII. 14). This inversion of the tube was, we believe, first noticed by Dutrochet. The whole apparatusis, as suggested by Schäffer, very similar to that seen in the tentacles of the Snail, and appears to constitute a tactile rather than a respiratory organ. This is rendered more probable by the fact that, when the animal first emerges from its tessellated case, the ex- tremities of these two tentacles are the first parts that make their appear- ance (XXXVII. 17 d d), the two curved hooks being the next (XXXVII. 17 b). The setae are usually half drawn into the inverted tentacle; but they project sufficiently forward to constitute delicate organs of touch, supposing the deltoid body, into which they are inserted, to be endowed with sensi- bility. The animal cautiously protrudes these tentacles before it ventures to unfold its rotary organs, but it does not direct them in an exploratory manner from side to side, as an insect does its antennae.” But there are many strictly homologous processes with a terminal tuft of setae which are tubular and not retractile, or otherwise neither tubular nor re- tractile, but horn-like in figure, or merely conical. Examples occur in Notom- mata Myrmeleo (XXXVIII. 26 b) and N. Sieboldii (XXXVIII. 32 g), and in the shorter conical elevations on the disk of Symchaeta and Polyarthra, and in the horns of the last-named genus. * - - - - A further departure from the highly-developed antennae of some Rotatoria is exemplified in the fossae, pits, or apparent apertures (XXXVIII. 28–30), oftentimes with elevated edges, containing a tuft of bristles, which are met with usually on the necks of the animals. These fossae, as well as the retractile and non-retractile antennae of all forms, Leydig believes to be in immediate and special relation with nerves which extend to the base of the brush of rigid cilia. The number of such fossae varies in different species. In accordance with his hypothesis of respiration, Ehrenberg called them “ciliated respiratory openings.” In Enteroplea (XL. 2), Hydatina (XL. 1), Diglena, Otoglena, in Euchlamis triquetra, and in several Notommatae, an apparent aperture exists on the neck. More than two are seen in Poly- arthra, Notommata Myrmeleo, and in N. Sieboldić (XXXVIII. 29), arranged along the back; and in Asplanchna Brightwellii (Gosse), Dalrymple met with two on the back, which he supposed to be and described as lateral apertures, but which, Leydig affirms, have the unbroken cuticle lining them (XXXVI. 9). - Interesting variations are found in Noteus, in which Ehrenberg describes 2 D 2 404 GENERAL ELISTORY OF TEI.E INFUSORIA, a short, stout, respiratory tube, or, as it actually is, a depression surmounted by a very elevated margin. In Notommata centrura (XXXVIII. 26 b), and in N. Copews, a long seta projects from a small elevation of the cuticle, on each side of the back, having its extremity divided like a brush. The doubtful ciliated depression conceived by Prof. Huxley to be the nervous centre, belongs, in Leydig's opinion, to the category of tactile fossae. APPENDAGES OF THE TRUNK.—The account already given of the cuticle and lorica and their processes, leaves no special appendages of the trunk to be described. Thus we have spoken of the spines from the anterior and posterior margins of the lorica, of those which, in a few examples, are produced from its surface, and of the setae or cirrhi which extend from it in Anuraea biremis, in Notommata Copews, and, on a larger Scale, in Triarthra and Polyarthra (XXXVIII. 30 c). The pseudopodium, or false foot, may either be accounted a production or appendage of the trunk, or a distinct segment of the body. Its dimensions and figure vary much in different species; and in several it is entirely ab– sent. It attains the highest development in Philodinaea (XXXVIII. 1, 2), where it consists of several progressively diminishing segments united by sliding joints, like the tubes of a telescope, and is analogous to the tails of many Entomostraca, e.g. the Cyclopidae. In this family, Philodinaea, the body tapers into the pseudopodium by a gradual lessening of the articulated seg- ments; so that the termination of the trunk proper and the commencement of the process have no external indication, except what is supplied by the anal orifice of the alimentary canal, which usually opens at the base of the tail. In other families the termination of the trunk is more abrupt, and the distinct— ness of the pseudopodium as a Subordinate Segment or member strongly pro- nounced (XXXVIII. 25, 26). The high development of the organ gradually diminishes, until the telescopic-jointed foot-process is degraded to the condi- tion of one or two stiff styles, supported on an enlarged base (XXXVIII. 22), the intermediate stages being represented in various species (XXXVIII. 23, 24, 25, 31). In Brachionus, Colurus, Stephanops, and Dinocharis the foot- process, although of three or more telescopic joints, is of much smaller diameter, and depends like an appendage from the trunk, and is a transition between this form and the usually tapering figure of the Philodinaea, as seen in Rotifer macrurus, the trunk of which is abruptly attenuated into a long foot. A further reduction of the many-jointed telescopic pseudopodium to one or two joints, terminated by a single, double, or triple styliform or pincer process, is exemplified in many Notommatae (XXXVIII. 26), in Cycloglena, Lepadella, Metopidia, Salpina, Difflena, Eosphora, Hydatina (XL. 1), Ratulus, &c., where the articulate structure is reduced to the condition of an appendage of the trunk, its terminations assuming the chief importance. Indeed, in Some cases, one or two styliform processes seem to be produced immediately from the trunk without the intervention of an articulated segment at the base (XXXIX. 1–3). At the same time a styli- form foot-process is, as a rule, a very short pseudopodium supporting one or more long styles. In the case of the less-developed or perfect tail-processes, the section of the body is frequently attached obliquely to the trunk. In a very few examples the posterior dorsal surface of the body is pro- longed as a true tail, having the pseudopodium fixed in front of it, the anal orifice being between them. This is witnessed in Notommata Copews (XXXVIII. 26). - The pseudopodium has in some genera styliform processes attached to it throughout its length, as seen in the highly-developed telescopic pro- longation of the Philodinaea (XXXVIII. 1), in Callidina, Rotifer, Actinurus, OF TELE IROTATORIA. 405 and Philodina, and also on the shorter foot-process of Dinocharis. These styles are moveable and flexible, and occur in a single pair or in two or three pairs; Ehrenberg gave to such, when short and not rigid, the name of ‘toes,’ and distinguished the prolongation on each side of the posterior border of the sliding-joints, seen in Rotifer, Actinwrus, and Callidina, as ‘horn-like pro- cesses.” In Scaridium (XXXVIII. 22) and Dinocharis, the foot, though jointed, seems not to be retractile. The pseudopodium differs much in its length and mode of termination. Where the articulated segments are few and small, the foot, if terminated by styles, oftentimes acquires a great length. In some species the terminal styles are three in number—e.g. Actinurus, Philodina Neptunius, Dinocharis, and in some Stéphanopes ; and more frequently the central style is shortest. Two terminal styles are more common. Illustrations are found in Furcularia, Scaridium, Distemma, &c. A foot ending in a pair of styles is said by Ehren- berg to be ‘forked’ (furcate). - In numerous species the styles have much rigidity, and are greatly elon- gated; in such instances they are known as styliform setae, or simply “setae.’ Two such terminate the trunk in Notommata longiseta, N. aequalis, and in N. Felis—in the last-named they are also curved backwards,--whilst but one is produced from the body in Monocerca (XXXVIII. 399), Mastigocerca (XXXIV. 438–440), and in Ratulus; in the last, moreover, the base of the setae is surrounded by stiff hairs. Another very common termination of the foot is by a pair of short thick flaps, moveable on their base, and named ‘pincers,” or ‘pincer-like processes.’ Such are seen in Brachiomws, Hydatina (XL. 1), Enteroplea (XL. 2), Diglema, Eosphora, Noteus (XXXVIII. 25), and in several Notommatae (XXXVIII. 5, 25, 26). All i. preceding varieties of the pseudopodium are modifications of the articulated telescopic type, and associated with a tolerably firm cuticle. But there is yet another type, in which no articulated segments occur, and which, from the softness of its tissues, is thrown into wrinkles or folds during con- traction. Illustrations of this are found in all the urceolate genera of the Rotatoria, viz. in Conochilus, Lacinularia, Melicerta, Tubicolaria, Stephanoceros (XXXVIII. 1, 17, 19), &c., and, besides these, in the free Megalotrochaea (XXXII. 374–378) and in Pterodina (XXXV. 502–504). In the attached genera especially, this form of pseudopodium rather merits the name of ‘pedicle’ or footstalk. In Pterodina the cylindrical foot-process is trumpet- shaped, and discoid at its free extremity, which is supposed to act like a sucker. A Suctorial end to the pedicle is likewise presumed to exist in some or all of the fixed genera. Cilia have been discovered on the extremity of the pseudopodium of Ptero- dina and Tubicolaria, and on that of Megalotrocha, Lacinularia (XXXVII. 10), and Brachionws in the young or immature state. Lastly, a pseudopodium is absent in Anuraea, Asplanchna (XXXVI. 9; XXXVII. 29–32), Polyarthra, Triarthra (XXXVIII. 30), and Ascomorpha. The observations of these and other particulars concerning the pseudopo- dium, its presence or absence, its structure, its length relatively to the body, and to its own processes, supplies valuable characters in the systematic distri- bution of the Rotatoria; and the details so derived furnish the fundamental divisions of the classification proposed by Leydig (see Classification). The foot-like process is essentially a muscular organ; it contains no viscera, but in highly-developed forms some Small bodies supposed to be glands, and in some examples certain vesicular spaces supposed by some to be ganglia, by others, vacuolar thickenings of the connective tissue (XXXVII. 17 m). The 406 GENERAL EIISTORY OF TEIE INFUSORIA. amus always opens at the base of this segment, and on its posterior aspect ; hence it is that, though often called a tail, it is really not homologous with that appendage of higher animals; and consequently most writers prefer to name it pseudopodium, foot-process, or foot. It certainly has no evident re- semblance to a foot, although anatomically it is a limb or member, and is functionally an organ of locomotion and of Support. It is much less con- cerned with motion than the rotary Organ, and, from its occasional absence, is evidently a non-essential organ. A principal purpose which it seems to answer is that of a rudder, steering the animal in its course like the tail of a fish. However, occasionally, when developed in a styliform manner, as in Scaridium (XXXIII. 423), it is a powerful and peculiar locomotive append- age, enabling the animal to leap. The pincer-like termination seems to enable the animals to hold fast to or grasp objects, or to push themselves forward. The short flexible toes developed on the pseudopodium, and the supposed discoid extremities, serve to attach the animal whilst the head may be moved freely about, or whilst it advances in a leech-like manner by the alternate forward movement of the head and foot. OF THE MUSCULAR SYSTEM AND MOVEMENTS OF THE ROTATORIA. MUSCULAR SYSTEMI.—In this class a muscular system, Subservient to the functions of locomotion, nutrition, &c., is well developed ; and, the integument being transparent, its structure and arrangement are distinctly visible. The muscles (XXXVI. 5; XXXVIII. 28 a) resemble fine lines, cords, or bands passing from one part to the other, and may generally be distinguished by being thickened during contraction, and attenuated by extension. All those attached to the walls of the body arise from the inner layer of the integu- ment, which is thickened at the spot. They may be considered, with refer- ence to their functions, to be of two kinds—the One concerned in the general movements of the body, the other in acting upon special Organs or viscera. The first constitute two sets—the one annular, encompassing the body, the other longitudinal. The annular or transverse muscles (XXXIII. 5, 6 t; XXXVIII. 26 v) are separated from each other by considerable intervals; and to them is due, in many species, the apparent segmentation of the trunk. They are, so to speak, imbedded in the inner epidermic layer. Ehrenberg mistook them for vessels. The longitudinal muscles are more numerous and definite (XXXVI. 5 l, 9 l; XXXVIII. 28 a ; XL. 1n). Mr. Williamson believes that delicate fibres occur in the thickness of the skin of the trunk, designed to shorten the animals by corrugating the surface. The long muscles extending from the posterior ex- tremity of the body to the rotary organ and the maxillary bulb, and serving to retract those parts, are the most highly developed. Dr. Dobie describes muscular bands in Floscularia, passing up between the lobes of the ciliated head, and more delicate fibres along the centre of each lobe towards its ex- tremity. The muscles of the tail (foot-process) are also numerous, large, and strong, and traceable to its terminal segments (XXXVI. 5b ; XXXVIII. 26 m) on the one side, and on the other as far forward as the anterior part of the body and the maxillary bulb. Williamson states that the fibres reaching the extremity of the foot-process are inserted into a little concavo- convex body found there. By its muscular apparatus the tail can be curved, moved from side to side, and shortened, and in a few examples, e.g. Scaridium, doubled beneath the belly. The counterforce, whereby the pseudopodium recovers its straight figure and position relative to the body, is the elasticity of the integument. Where the sliding joints exist, this elasticity must chiefly reside at the lines of junction, since the segments themselves have great rigidity, and do not admit of corrugation. However, the extension of this OF TEIE ROTATORIA. 407 process much depends on the influx of fluid forced into it by a general trans- verse contraction of the body which is seen to precede it. The extension of the body, after having been shortened by the contraction of its longitudinal muscles, is chiefly due to the elasticity of its integument, which has an in- herent tendency to constrict itself or to lessen its diameter. Prof. Williamson dissents from this explanation, believing the extension to be due to the cir- cular muscular bands, as in the pseudopodia of the Echinus and starfish, or in the trunk of an earthworm. The shortening of the body is provided for by the sliding structure of its segments, and by the wrinkling (XL. 1) of its sur- face (XXXIX. 1–3), sometimes by both these modes together, at others by one alone. Even where its length is diminished by the formation of mere folds of the skin, those folds are constant in position and arrangement. Longitudinal folds pretty regularly disposed occur in the softer-skinned varieties—for instance, in various species of Notommata and Hydatina. Muscles Supplying special organs are seen in connection with the trochal disk, the maxillary head and jaws, the alimentary canal, and the reproduc- tive apparatus (XXXIX. 7). Excepting the muscles moving the rotary organ, these will be best described in the account of the organs with which they are connected. The trochal disk, and, indeed, the whole head supporting it, is constricted, corrugated, contracted, and moved from side to side by considerable muscles, extending from it to the maxillae, and to the sides and posterior boundary of the abdominal cavity (XXXVIII. 28 a); special muscular threads act upon particular lobes, prominences, or processes which may extend from the head or its ciliated disk. In the trochal disk of Melicerta, Prof. Williamson de- tected interlacing threads which he supposed to be muscular ; and Mr. Gosse has remarked in the same animal “a series of five or six annular threads set in the inner skin, which are probably muscular, and aid in the complex movements of the head.” Some of the interlacing threads, which Ehrenberg described in several Rotatoria (as, for instance, in Lacilunaria), and which at one time he regarded as vascular, at another as a nervous or muscular network, probably were muscular, although most of them were merely fibres of connective tissue. The extrusion of the head and trochal disk, after retraction, is principally effected, as in the case of the pseudopodium, by the elasticity of the integu- ment, consentaneous with the relaxation of the muscular contraction,-this elasticity serving to unroll the involuted head and trochal disk, and to expand their parts, and, by its general operation on the body, to elongate the whole figure, and thereby press the contained fluid forward and backward against the retracted organs, so as to push them out. Prof. Williamson would also attribute the protrusion of the head to the action of the circular muscles, as he does not think there is sufficient proof of such elasticity independently of muscular fibres. The retracted head and appendages of the Bryozoa are thrust outward in a similar manner. The cilia of the trochal disk have generally been assumed to be seated on a muscular mass, forming the cushion-like contractile thickenings on the head of the Rotatoria (XXXVI. 93). These structures display, according to Dujardin, no distinct muscular fibres; but in the opinion of others, such are present. Ehrenberg, as before stated, went so far as to imagine, not merely a network of muscular fibrils moving the entire apparatus, but also a series of four muscles at the base of each cilium moving it in every direction. Such an array of definite muscles to move an almost imperceptible organ, is not only entirely hypothetical, but most improbable. Leydig, on the other hand, opposes the idea of the muscular nature of the trochal disk, and regards 408 GENERAL HISTORY OF TEIE INFUSORLA. it as consisting solely of the soft epidermic tissue, or, which is nearly the same thing, of connective tissue. Much discussion has arisen concern- ing the structural composition (i. e., in a word, the histology) of the muscles of Rotatoria. Dujardin and Ecker questioned the existence of actual mus- cular fibres, but recognized a soft contractile substance, often drawn out into threads. The former, however, inclined to the belief in the existence of determinate muscles, although observation, when he wrote, had not made it certain. Thus, at p. 611, when describing a new species of Floscularia, he remarks that, “by gentle compression of the animal, five independent cords were brought into view, contractile and tolerably regular in outline, which perhaps ought to be called muscles; they extended through the pedicle and to the extremities of the lobes of the rotary organ.” Ehrenberg noted the presence of muscles in most Rotatoria, and in a few specimens believed he had detected transverse striation,--a fact which would establish an analogy between them and those of the highest animals. This highly-developed organization was denied by Siebold, who described the muscles to be of the non-striated variety so largely distributed among other Invertebrata as well as Vertebrata. But the belief now prevails, that the possession of transversely-striated muscles is one of the characteristics of the Rotatoria, although non-striated fibrils may likewise occur. Leydig thus treats this subject:-" The element of muscle is the primitive cylinder, which is of two sorts—fine and thick,--the former in clear homo- geneous threads, which, when traceable, are perceived to be branches of cells; such occurs principally in muscular networks; the latter—the thick primitive cylinder—originates from cells coalesced in rows, and it, therefore, presents internally, at considerable intervals, the still-remaining cell-nuclei. These cylinders exhibit a gradual advance in their further histological phases. They may remain homogeneous like the finest primitive cylinders, or resolve themselves into a homogeneous sheath, and an axial substance in the form of molecules. Lastly, the contents of the cylinder may break up into mus– cular (sarcous) particles, and therein approximate to the so-called trans- versely-striped muscles, to which at length it may attain a complete resem- blance.” Thus the cell-wall comes to form an investing sheath or sarcolemma of each fibre, and the cell-contents the vital contractile substance, or the sar- cous particles. Leydig adds—“Both varieties of muscle, simple and striated, occur in the same species, so that the gradual transition of one into the other is unmistakeable.” The existence of striated muscle has been noted by Ehren- berg in Euchlamis triquetra; by Oscar Schmidt in Pterodina Patina; by Perty in the foot of Scaridium longicaudum, in Polyarthra (XXXVIII. 30 m), in the marginal muscle of Diglena lacustris, and of Brachionus tripos ; by Leydig in Notommata Sieboldii (XXXVII. 32 a) and Noteus; by Dalrymple, in No- tommata Anglica ; by Williamson and Gosse in Melicerta; and, without doubt, it may be discovered in most other genera (XXXIX. 7). Perty has noticed in the foot of Floscularia rows of granules, and fine longitudinal striae, an intermediate condition referred to in the description of Leydig, given above. Bergmann and Leuckart mention in a note (p. 377) in their work, that in Some animals transversely-striated muscles are visible. Prof. Williamson’s observations support some of Leydig's views. “When one of these muscular fasciculi,” writes the English naturalist, “is drawn out at full stretch, its surface is seen to be marked, at very regular intervals, by dark transverse bars (XXXVII. 18). Each fasciculus has a diameter of about gåröth of an inch ; and the transverse striae recur at distances of about . frºm oth. These intervals are rather larger than those seen in the fasciculi of human voluntary muscle. . . . On rupturing the fasciculi transversely, we OF THE ROTATORIA. 409 perceive that each one is invested by a delicate sarcolemma. This is well seen at the upper part of the tail, where, on the contraction of the muscle, the non-elastic sarcolemma becomes corrugated, and Only recovers its Smooth aspect when the muscle becomes relaxed. These rugae of the sarcolemma must not be confounded with the transverse striae of the muscular fibre.” MoVEMENTS OF ROTATORIA.—These are very various ; at the same time Some varieties are so constant in several genera and species, as to furnish characters of much utility in the systematic distribution of the class. There are two principal modes of locomotion,--one by simple motion onwards, or Swimming, with or without rotation of the body on its long axis (e. g. in Brachionus), the other, confined to the family Philodinaea, by crawling after the manner of leeches, each extremity of the body being alternately fixed. The latter mode of locomotion is partaken with the first, and the one or the other resorted to at the will of the animal. The rotary organ is almost exclusively concerned in producing the uniform Swimming movement and in turning the animal on itself, whilst the muscular tail acts as a rudder in directing the course. The trochal disk is worked with various degrees of energy and completeness; when in full action, the velocity attained is very great. Usually the Rotatoria swim on the abdomen; but exceptions occur, as in Eosphora Najas, which, like the Phyllopoda, swims on its back. Notews and a few others turn on their short axis, or, in common parlance, head over heels. Other exceptional modes of locomotion are met with in Scaridiwm, in Triarthra, and Polyarthra (XXXVIII. 30, 32), which have, besides the or— dinary Swimming movement, the power of leaping or skipping, in the first, by means of the elongated styliform tail, which can be doubled under the body, and then suddenly relaxed like a spring; in the two last, by the aid of Some rigid bristles, or cirrhi, attached to the body, and acting like the long legs of a flea. A skipping movement is likewise attributed by Ehrenberg to Notommata longiseta, due to its double, long, caudal styles, and an act of rowing, by means of a long lateral spine on each side, to Anuraea biremis. The preceding remarks apply to the locomotive Rotatoria; but the encased species, although unable to change place, have, nevertheless, a considerable power of movement within and about their urceoli. They can extrude the greater part of their body, and bend themselves over the edge of their case, or withdraw themselves entirely within it. They owe this latitude of motion chiefly to their long pseudopodium or pedicle, which contracts by throwing itself into very numerous and deep wrinkles; for in none of the attached species is this organ articulated. In comparison with that of the pedicle, the capacity of the trunk of the animal to shorten or contract itself is but Small, and its transverse folds few, distant, and collected, mostly towards the posterior extremity. The movements, in fine, of the urceolated Rotatoria are limited to those of extension, retraction, and flexion; and the extent to which they may be exercised is in direct proportion to the length of the pedicle. Ne- vertheless, when forcibly expelled from its case, which can easily be done without injury to the soft animal, the mature Melicerta Swims about with considerable velocity by means of its ciliated rotary disk, the peduncle being partially drawn up towards the body. Although incapable of movement as individuals, a cluster of Such as live in compound masses, Comochilus for instance, may float about freely, remind- ing us of the spheres of Volvoaz. The locomotive Rotifera also enjoy, in a considerable measure, the power of moving their own bodies, thus frequently altering the relative positions of the various parts, and modifying their general form. Their rotary organ, as already seen, may be extruded or retracted 410 GENERAL HISTORY OF TEIIL INFUSORLA. within the body; the body itself may be extended at full length, or very much contracted on itself. So much may the whole animal be contracted, that, except by the detection of the characteristic Rotatorial organization, its nature would certainly be mistaken. An illustration of this is furnished in the figures of Dujardin and Perty (XXVIII. 4). The mode of termination of the pseudopodium permits many of the Rota- toria to attach themselves at will to any object, some (Pterodina, for in- stance) assuming a fixed position for a long time together. When thus at rest, the rotary organ may be retracted or extended; in the latter case, al- though suspending its function as an organ of locomotion, it is in full operation as a respiratory organ, as well as Serving to procure food. The body, more- over, is often in active motion when fixed by the extremity of the foot-process —oscillating from side to side, bending itself, and even turning as on a pivot. THE DIGESTIVE SYSTEM.–The Rotatoria possess a distinct and undoubted alimentary canal, evident as a tube, traversing the interior, from a mouth to a posterior outlet or anus, composed of distinguishable parts with accessory organs. One group of the family is deficient of the anal outlet; and in male animals the digestive apparatus is atrophied or wanting. The digestive tube is mostly straight throughout its course (XXXIX. 1; XL. 1); the exceptions to the rule occur with the encased genera, in which the intestine is curved on itself, and the amus advanced forwards to some spot beneath the head (XXXVII. 17 i). The parts to be distinguished in the alimentary canal are—1st, the mouth or oral cavity; 2nd, the pharynx or vestibule (XXXVII. 19 a) between the 1st and 3rd, the Oesophageal head (XXXVII. 19 b); 4, the stomach, with appendages (XXXVII. c, d); 5, the intestine with its outlet; and 6, the cloaca (XXXVII. 6, f). Each and all of these parts present great diversity in figure, size, and accessory Organs; but yet in nearly all forms the peculiar type of the digestive canal of Rotatoria is well marked. The mowth is situated, as a rule, on the margin of the trochal disk, at the centre of its ventral aspect. Where the circlet of cilia is double, as in Lacinularia and Melicerta (XXXVIII. 21), the mouth, as we have already seen, is placed between the two rows; and in Floscularia and Stephanoceros it occupies the centre of the area formed by the ciliated apparatus of the head. The mouth is, moreover, subject to variations from the presence of appendages about it. Thus, in Melicerta, Prof. Williamson describes two small, projecting, “flattened lobes with ciliated margins, continuous with those of the ‘chin,” which obviously assist in directing the food into the oesophagus.” Leydig notices, in Notommata Sieboldii, a sort of upper lip, not ciliated; and Huxley, in Lacinularia, states that the mouth is vertically elongated, and its cavity expanded into “two lateral pouches, which give it an obcordate form; these lateral pouches contain the lateral ciliated arches that become lost below in the cilia of the pharynx.” In Floscularia the cavity of the mouth is funnel-shaped (infundibuliform) (woodcut), and is termed by Dr. Dobie the “infundibulum,” who describes the edge to be “frequently divided into lobes.” - The mouth opens posteriorly into a canal, through which the food passes to reach the “Oesophageal bulb.” This canal has unfortunately received various names, viz. oesophagus, pharyna, vestibule, infundibulum, and “buccal funnel.” The first term has likewise been applied to another tube intervening between the “oºsophageal head’ and the stomach; hence a looseness of no- menclature, tending to confusion and error in description. If, as is usually dome, the name “Gesophageal bulb '' be given to the jaws and their muscular envelope, then that of Oesophagus rightly belongs to the canal leading thence OF THE ROTATORIA. 411 to the stomach. If, on the other hand, the “oesophageal bulb '' be regarded as an accessory stomach containing a dental apparatus, as in the lobster, then the term oesophagus belongs to the tube extending between the mouth and the bulb. The following physiological distinction is, however, noted by Prof. Williamson, who says—“The stomach of the lobster, with its dental append- ages, is that in which the digestive process is carried on. Such is never the case with the pharyngeal bulb of the Rotifera. The digestive sac is situate lower down. The pharyngeal bulb bears closer affinity to a gizzard, resem- bling that of Bowerbankia and other Bryozoa, differing, however, from that of a bird, which is located below the “proventriculus’’ or true stomach. However, some confusion will be removed by avoiding the term “oesophagus,” and, without troubling ourselves with the precise homologies of the parts, by naming the tube between the mouth and jaws the “pharyna, ’’ or “vestibule,” the jaws themselves with their surrounding mass the “maavillary bulb '' or mastaw (Gosse), and the Canal between the last and the stomach the pro- ventricular or gastric canal. The name “buccal funnel” has been imposed on the tube leading from the mouth to the maxillary apparatus by Mr. Gosse, and might advantageously have been adopted. To proceed. The pharynx (XXXVII. 19 a ; XL. 23 m) varies much in its dimensions: sometimes it is a narrow tapering tube, and, when contracted, visible only as a double line ; at other times it is wide and short, and then especially deserves the name of “vestibule,” since it ceases to be a canal. Several peculiarities in its structure occur in different genera,_the most re- markable in Floscularia and Stéphanocéros. In the former genus, the oral cavity (infundibilum, Dobie) is separated from the pharynx by a rim armed by non-vibratile cilia; the pharynx itself is again subdivided by a fissured partition or diaphragm, into an upper space (vestibule), and a lower large and very dilatable cavity, called the “proventriculus’’ or “crop.” The crop ends below in, or in some measure embraces, the maxillary bulb (see woodcuts, Part II.). A similar structure obtains in Stéphanoceros. In Melicerta Prof. Williamson observed, within the pharynx near its junction with the maxillary bulb, the ciliated lining membrane “to hang in several loose, vibratile, longitudinal folds; ” and Prof. Huxley, in his account of Lacinularia, gives the subjoined summary of these folds and valvular par- titions:—“A narrow pharynx leads horizontally backwards from the lower part of the buccal cavity, and becomes suddenly widened to enclose the pha- ryngeal bulb in which the teeth are set (XXXVII. 19 a). Where the buccal cavity meets the pharynx, a sharp line of demarcation exists. In Melicerta two curved lines are seen in a corresponding position, and evidently indicate two folds projecting upwards into the Oesophagus (pharynx). In Brachionus these folds are stronger (XL. 1 b), while in Stephanoceros and Floscularia (XXXVII. 1 & 19) this partition between the pharynx and what may be called the crop is still more marked. From the inner margin of the aperture in the partition, two delicate membranes hang down into the cavity of the crop, which have a wavy motion; and it is to them, I think, that what Mr. Gosse describes as an appearance of “Water constantly percolating into the aliment- ary canal’ is due. Dujardin had already noticed these ‘vibrating membranes’ in Floscularia.” Observers coincide in describing the cilia of the oral cavity to extend into and line the pharynx (XL. 23 m). The walls of this tube are sovery dilata- ble, that bodies of very considerable size can traverse it to the maxillary apparatus. In the genera Lacinularia, Mélicerta, Brachiomus, Noteus, and Tubicolaria, close to the wall, or actually within its substance, as Leydig represents in Notews, are two conspicuous structures, described by that author 412 GENERAI, EIISTORY OF TEIE INFUSORIA. to be vesicular, and not improbably salivary glands (XXXVIII. 27 l). Mr. IHuxley alludes to these structures in the ensuing account:-‘‘ On each side the pharynx is a yellowish horny-looking mass, which sometimes appears cordate, at others, more or less completely composed of two lobes. I believe its function is to give strength to the delicate walls of the pharynx, and that it is, therefore, to be considered a part of the horny skeleton.” The pharynx ends mostly below, and partially embraces the “maa'illary bulb" or “mastaa,” which contains the maxillae or jaws supporting the “teeth,” and has its mass made up of nuclear cells and muscular fibres (XXXVIII. 26 m). In the living animal the bulb is almost constantly in motion, con- tracting and expanding itself in what some have called a “peristaltic ’’ manner. This alternate and constant movement, visible even in the embryo before escap- ing from the egg, was mistaken by Bory St. Vincent, and other of the older microscopists, for the pulsating action of a heart. The apparatus, however, is rather comparable to the gizzard of birds, or to the tooth-crushing mechanism in the stomach of lobsters and other Crustacea, though not, indeed, homologous with it. The “maxillary bulb '' is bulky, more or less globose, with a prevailing tendency to a triangular figure with rounded angles (XL. 20, 23, 24). Sometimes it is oval or ovoid, and still more com- monly heart-shaped, from being notched or furrowed on One side, indicating a bilobed structure. In Melicerta. Mr. Gosse figures and describes a third lobe, below the usual “two globose bodies (or rather the bilobed single mass), equally hyaline and probably muscular, which seems united to the two others, and alters in form as they and the jaws work, lengthening down- ward as they approach, and dilating and shortening as they recede ’’ (XXXVII. 23). The mass of the “maxillary bulb '' surrounding the maxillae has been generally assumed to be muscular, and, as such, actively concerned in work- ing the contained jaws. Gosse calls it a “muscular sac,” and has even attempted the description of its component muscular bands. Leydig has re- presented the jaws to be acted on by exquisitely striated muscles (XXVII. 31). Prof. Williamson admits the existence of muscles affixed to the pro- cesses of the jaws, but states that the conglobate organ in which these are imbedded “is transparent, and composed of numerous large cells, each of which contains a beautiful nucleus with its nucleolus. The cells are only seen when the organ is ruptured between two plates of glass, when they readily separate from one other; but the nuclei, with their contained nucleoli, are distinctly visible in the living animal. Delicate muscular threads most probably penetrate this organ to reach the dental apparatus, though I have not yet detected them.” Here a great discrepancy of opinion appears, between Mr. Williamson and Leydig and most other writers, respecting the constitution of the globose mass of the maxillary bulb, and such as only reiterated examination can remove. Dr. Leydig asserts that the bulb is covered externally by a chitinous membrane, of the same nature as the cuticle, and that the existence of a like membrane in its interior, developed for a special end, constitutes the maxillae and appendages, just as bristles and horny plates and processes are developed out of the external cuticle. The maxillary apparatus, contained within the soft mass of the bulb, is visible without any preparation, but may, from its hardness, be detached by strongly compressing or crushing the animal. Although much denser than the soft tissues of the body, yet like them the dental apparatus disappears by decomposition. Ehrenberg having an enormous number of Brachioni in a vessel of water, evaporated the fluid, and having burnt the desiccated OF THE ROTATORIA. 413 animals, examined their ashes chemically, convinced himself they contained much phosphate of lime, derived, as he supposed, from the maxillae. Mr. Gosse likewise concludes that, from their great solidity and density, and from the action of menstrua upon them, they are of calcareous nature. The construction of the jaws, and the number and position of the transverse bars or ‘teeth,’ afforded Ehrenberg characters of primary importance in the construction of his system ; and he indicated three leading types, under which all the Rotatoria could be classed, viz.:-‘‘ 1. Agomphia, toothless; 2. Gym- nogomphia, free-toothed (unconnected); 3. Desmogomphia, connected or attached teeth. In Gymnogomphia the teeth are free in front, and, like the fingers, united behind by a common band—the jaw; in Desmogomphia they are attached transversely across the jaw-piece, like an arrow lies across the bow. In the former, again, the teeth in each jaw are single or several in number; in the latter, either two or many. Hence there are 5 groups:– 1. Agomphia—e.g. Ichthydium, Chaetomotus, Enteroplea ; 2. Monogomphia (one-toothed)—Pleurotrocha, Furcularia, Cycloglema, Monostyla, Lepadella; 3. Polygomphia (many-toothed)—Hydatina, several Notommatoe, Euchlamis, Stephanoceros, Brachionus, &c.; 4. Zygogomphia (twin-toothed)—Callidina, Rotifer, Activurus, Philodina, Monolabis, and Pterodina ; 5. Lochogomphia (teeth set in rows)—Ptygura, Megalotrocha, Melicerta.” This classification of the Rotatoria, however, Ehrenberg confessed to be imperfect, as wanting repeated researches to fix on the truly generic and specific resemblances and differences of the dental apparatus. In fact, although the conditions may be constant in the same species, yet they are so minute, that they frequently can be made out very imperfectly and with un- certainty; and, besides this, the variations in the positions of the animal when moving its body appear So materially to alter the form of the mechanism in question, that careful students often differ respecting it in the case of the self-same animal. To illustrate these remarks, we may appeal to the descrip- tion of Melicerta ringens, as separately and independently detailed by Prof. Williamson and by Mr. Gosse. The latter represents three or four transverse bars or teeth to each lateral jaw (XXXVII. 23), the former above a dozen (XXXVII. 26); the one detects a trilobed bulb, the other speaks of a single conglobate organ, but which, from his figures, might be called bilobed. Addi- tional illustrations of such doubt and uncertainty are to be found on compar- ing the descriptions of the maxillary Organs recounted by any two observers. Ehrenberg’s representations are now set aside by all, improvements in the microscope, and repeated examinations, having demonstrated their erroneous- mess. The whole tribe of Agomphia or toothless Rotatoria must be set aside; for it seems a well-established rule, that no female of the class is de- ficient of dental organs, and the genera Ichthydium and Chaetonotus cannot, as before shown, be retained in the class. Enteroplea, again, is in all proba- bility a male animal, and Cyphonautes wants, according to Ehrenberg's plates, the characteristic organization of Rotatoria in all its details. But it would be useless to continue an analysis of the other types established by the Berlin Professor, the existence of any one of which, having the particulars of struc- ture assigned to it, is not to be demonstrated. What is worse, we must con- fess to the absence of any one detailed account of the dental apparatus which can be received with implicit confidence in its accuracy; so greatly have the leading writers on the Rotatoria differed among themselves in describing the mechanism in question. Dujardin distinguished the following parts in the maxillary apparatus:– the “fulcrum” or support, a single central piece with two articulated branches; the “scapus” or lateral branch ending in an articulated point, “acies,” and 414 GENERAL HISTORY OF TELE INFUSORIA. itself single or multiple, which is the jaw properly so called. In most cases, says Siebold, the horny jaws consist of two bent, geniculate processes, an anterior and a posterior; the latter gives attachment to the muscles moving the apparatus, whilst one or several teeth are developed on the former. In some many-toothed Rotatoria, each jaw is provided with three horny arches (e.g. in Philodina, Lacinularia, and Melicerta). Two of these arches (arcus superior et inferior) are turned inwards, whilst the third (arcus eacterior) is directed outwards. To the under arch the muscles of the jaw are attached, which move the other two arches, with their transverse teeth, against each other. Williamson gives the following particular account of the grinding apparatus of Melicerta —“The gastric teeth consist of two essential portions, a pair of strong crushing plates, which bruise the food, and various appendages afford- ing leverage and facilitating the action of the muscles upon them. The crushers are two broad elongated plates (XXXVII. 26), each being about sºuth of an inch long, and separated from each other at the mesial line, near which they become much thickened. From each of these plates there proceed laterally numerous parallel bars, all of which are somewhat thickened at their inner extremities where they are attached to the plates, whilst at their oppo- site ends they are united with the others of the same side by a curved con- necting bar (fig. 26), from the outer sides of which are given off various loops and processes. The three uppermost of these bars are the largest, the rest gradually diminishing in size and strength as we descend, the inferior ones being almost invisible. From the upper extremities of the two crushers there project upwards and backwards two slender prolongations united by a kind of double hinge-joint near their apex, where they not only play upon each other, but also on a third Small central fixed point, lodged in a little conglobate cellular mass. Ehrenberg only describes three transverse bars on each side, which he regards as teeth. It is obvious that he has only noticed the three upper and larger pairs. It is equally evident that these transverse teeth, as he terms them, do not move upon the strong longitudinal plates, as he imagines, but are firmly united with them. Muscles are either attached to the divergent peripheral processes, or to the cellular mass in which these processes are imbedded, causing the entire apparatus to separate into two parts along the mesial line by means of the hinge joint, the so- called teeth merely transmitting the motor force to the two longitudinal plates. These latter appendages are thus made to play upon each other with great power, and act as efficient crushers, bruising the food before it passes into the stomach, as is the case with the gastric teeth of the Crustacea. From the above remarks it will be seen that, though in its construction the dental apparatus is more complex than is represented by Ehrenberg, in its mode of working it is less so.” - Prof. Huxley, to quote another accurate English observer, has seen in Jacinularia socialis, as also in Stéphanoceros, the “pharyngeal armature com- posed of four separate pieces (XXXVII. 30): two of these (which form the ‘ incus' of Mr. Gosse) are elongated triangular prisms, applied together by their flat inner faces; the upper faces are rather concave, while the other faces are convex, and upon these the two other pieces (the mallei of Mr. Gosse) are articulated. These last are elongated, concave internally, convex externally, and present two clear spaces in their interior ; from their inner surface a thin curved plate projects inwards. At its anterior extremity this plate is brownish, and divided into five or six hard teeth with slightly en- larged extremities. Posteriorly the divisions become less and less distinct, and the plate takes quite the appearance of the rest of the piece.” This is OF TEIE ROTATORIA, 415 essentially the same structure as that of the teeth of Notommata described by Mr. Dalrymple (Phil. Trans. 1849), and by Mr. Gosse (XXXVI. 6) (T. M. S. 1851), and very different from the stirrup-shaped “armature * represented by Ehrenberg and Dujardin in Lacinularia. Prof. Huxley notes, moreover, the omission of the two pieces constituting the “incus,” in the description given of the apparatus by Leydig. The last-named author has attempted no general description of the dental organs, and has, in the specific details, so briefly adverted to their structure, that he would seem to attach to them little importance. He has, however, figured the maxillae of Notommata Sieboldii (XXXVII. 31), wishing especially to represent the transversely-striated muscles acting upon them. He men- tions the maxillae, which occupy the spacious angular maxillary bulb, as ex- hibiting a bifid or forked portion, hooked at the ends, with a spine projecting from the inner side, and a margin on the outer side: to the latter the strong muscles for opening and shutting the maxillae are affixed. The transverse striation of the muscles is particularly brought into view by pressure on the apparatus. Cohn (Zeitschr. 1855) has some very precise details respecting the structure of the dental mechanism of Hydatina senta, and of two or three other Rotatoria; but it would lead us beyond Our Scope, to transfer them to Our pages. The most elaborate attempt to unfold the true structure of the maxillae, and to reduce all the varied forms to a common type the essentials of which are always detectable notwithstanding any degree of general modifi- cation, has been made by Mr. Gosse. The diversity of descriptions met with among writers on the Rotatoria, respecting the maxillae, is materially due to the limited examination, undertaken by any one of them, of those organs,— each observer having studied some one, or at most but a few species, and then describing the peculiar maxillary organs met with as pervading the whole class: such as is essential to the discovery of their true relations, a comparison of their structure among all the genera, has been neglected. The right mode of study seems to have been undertaken by Mr. Gosse ; but his conclusions require to be tested by repeated observation (Phil. Trams. 1855). His method of manipulation, for the purpose of examination, is well worth noting. He says (op. cit. p. 424), “In the course of experiments with various chemical reagents on these animals, I found that a solution of potash had the effect of instantly dissolving the flesh and most of the viscera, leaving the general integument, the walls of the pharyngeal bulb, and all the solid parts of the manducatory apparatus uninjured. In most cases, also, the last- named organs are expelled from the visceral cavity by the contraction of the integuments, so that they float at large in brilliant clearness, undimmed by intervening tissues, and as patent to observation as when crushed between plates of glass, with the advantage of all the parts being unbroken and re- taining their relative positions. Now, by turning the screw of the compres– sorium, flattening or deepening the drop of water, waves were communicated to it, by means of which the floating bulb, being nearly globular, was made to revolve irregularly, and thus to present, in Succession, various aspects to the eve.” - ºnly his researches ever So briefly, we must first introduce his no- menclature. The gizzard or enclosing maxillary bulb, he calls the mastaa: (XL. 20); and declares it to be a muscular trilobate sac. The maxillae con- sist of two geniculate bodies (mallei) (XL. 20 b), and a third on which they work (incus) (XL. 20 f). Each malleus is of two parts—1, the manubrium (c), and 2, the wheus (e), united by a hinge joint. The manubrium is a piece of irregular form, consisting of carince of solid matter, enclosing three 416 GENERAL ELISTORY OF TEIE INFUSORIA. areas, which are filled with a more membranous substance. The wrºcus consists of several slender pieces, more or less parallel, arranged like the teeth of a comb, or like the fingers of a hand. The incus consists of two rami (g) articulated by a common base to the extremity of a thin rod (fulcrum) (h) in such a way that they can open and close by proper muscles. The fingers of each “uncus * rest upon the corresponding ramws, to which they are attached by an elastic ligament. The “mallei” are moved to and fro by distinct muscles; and by the action of these they approach and recede alternately, the “rami” opening and shutting simultaneously, with a movement derived partly from the action of the “mallei’’ and partly from their own proper muscles. Under all the variations in form and disposition of the parts presented in Euchlamis, Anuraea, Symchaeta, Diglena (XL. 24), Polyarthra, Asplanchma, Monocerca, &c., the same type prevails as in Brachionus (XL. 20–23) (which is the genus Mr. Gosse uses as his standard of comparison). The modifica- tions in those genera may in general “be considered as successive degenera- tions of the ‘mallei,’ and augmentations of the incus. In another collection of genera (the fixed or urceolate), the organs, although essentially the same as in the former type, are somewhat disguised by the excessive dilatation of the ‘mallei,’ and by the soldering of the unci and rami together into two masses, each of which approaches in figure the quadrant of a sphere. The ascribed ‘stirrup-shaped armature of the Philodinaea arises from misappre- hension; for it has no essential diversity from the common type, their analogy with the genera last mentioned being abundantly manifest, though they are still further disguised by the obsolescence of the ‘manubria.” In Floscularia (XL. 25, 26) and Stephanoceros (XL. 27, 28) the most aberrant Rotatoria, the “mastaa: ' is wanting ; and in the former genus the incus and manubria are reduced to extreme evanescence, though the two-fingered unci show, in their structure, relative position, and action, the true analogy of these organs.” * As to their homology, he argues they have no true affinity with the gastric teeth of the Crustacea, though he states his conviction that the Rotifera belong to the great Arthropodous division of animals. • “The action of the horny jaws,” Mr. Gosse remarks in his account of Melicerta, “is not exactly that of two flat-surface mullers, working on each other in a grinding manner, but a complex motion impossible to be explained by words.” Since the nature of our work has compelled us to limit ourselves to a mere outline of Mr. Gosse's most elaborate and important researches on the manducatory organs of the Rotifera, we cannot too strongly recommend the student to refer to that gentleman’s essay in the Transactions of the Royal Society, both for a more complete acquaintance with his views and discoveries relative to those particular organs, and for a host of valuable details on other parts of the anatomy of this class of animals. Some Rotatoria, the so-called single-toothed species, have the faculty of protruding their maxillae beyond the mouth, and of using them, in this curious position, as prehensile organs. Thus the animal is enabled to seize upon prey without awaiting its being casually engulfed within the vortex of its ciliated head. Examples are found in Symchaeta mordaac, in Distemma Forficula, and in Diglena (XL. 24). The maxillary bulb communicates immediately, or by the medium of a mem- branous canal, with the stomach—the next division of the alimentary tube. This canal is very commonly termed the oesophagus; but we prefer to call it the proventricular canal, to avoid confusion and doubtful analogies. It com- mences at the posterior inferior part of the bulb. OF TELE ROTATOEIA, 417 p=y Leydig represents this tube to be lined by a continuation of the chitinous inner layer of the maxillary bulb, and uses this view to explain the distinct- mess of outline frequently remarkable in the walls when of considerable thickness, e.g. in Notommata centrura (XXXVIII. 26 g) and N. tardigrada. This sharp contour is especially manifest during contraction of the canal, whereby it is thrown into transverse folds or wrinkles, noticed by Ehrenberg under the title of “hard oesophageal folds,” and elsewhere of a “rather firm framework at the commencement of the Oesophagus.” Leydig adds—“The organs described by Ehrenberg in Notommata saccigera, as ‘large vibrating gills,” must, I think, be considered transverse folds of the chitin membrane in question.” The existence of so dense a lining to the gastric tube implies the absence of cilia on its surface ; and, in fact, Leydig declares he has never seen the least sign of such organs, although both Perty and Williamson affirm their existence. The folds into which this tube is thrown when contracted are occasionally (e. g. in Notommata Sieboldii) (XXXVII. 22) longitudinal instead of transverse. Mr. Gosse says of it that it is “composed of longitu- dinal and annular contractile tissue,” and that, at least in Asplanchma prio- donta (XXXVI. 9 t), “it is capable of immense dilatation, but commonly takes the form of a slender tube with the lower extremity swollen, where an oval pancreatic gland is attached on each side. The passage of a small morsel, such as a Chilomonas, shows that the walls of this organ are thick, leaving only a slender tube when corrugated.” However, in different species the width and the thickness of its walls vary much. The proventricular canal has a considerable length in Diglena and Symchaeta ; it is rather long in Triarthra, Lacinularia, and Hydatina, and very short in Euchlanidota, Bra- chiomata, and Melicerta. In not a few genera it is altogether wanting, the maxillary bulb being Superposed immediately upon the stomach : such are Ascomorpha and the genera of the family Philodinaea. The stomach succeeds to the gastric canal as a distinct segment separated from the alimentary tube below by a constriction, and is remarkable also in general by its greater capacity (XL. 1 e). Leydig affirms that a portion of the digestive canal separated from the rest by a constriction, and essentially representing a stomach, exists in all true Rotatoria; but other writers describe, as in Philodina (XXXVIII. 1, 2), and in Lindia (XL. 1, 3), the existence of a straight, slender, funnel-like alimentary canal extending from the mouth to the cloaca without any constriction or any stomach dilatation. In Hy- datina and Symchaeta, Perty says the canal is uniform in calibre, without any stomach-like expansion ; yet Cohn distinguishes the narrower lower end of the alimentary tube of Hydatina as an intestine, because it is less constantly occupied with food, is colourless, and, unlike the stomach, has no such cells on its wall. Moreover, as an irregularity, he twice met with a sphincter- like constriction (pylorus) separating the two. In Euchlamis and Brachionws, on the other hand, the division is clearly indicated (XXXIX. 16). The opposing statements of authors on this question may probably be re- conciled on the supposition that, of different observers, some have viewed the canal when it has been full and distended, others when empty and contracted, and that the constriction indicating a definite stomach has appeared only during repletion, just as happens with the human stomach, which, when full and engaged in digestion, is deeply constricted, and for the time appears almost like a double organ. Ehrenberg distinguished four types of Rotatoria, according to the cha- racters of the alimentary tube, which he respectively named—1. Thrachelo- gastrica; 2. Coelogastrica; 3. Gasterodela; 4. Trachelocystica. 1. The Trachelogastrica comprehended animals having a long filiform gullet, 2 E 418 GENERAL HISTORY OF TEIE INFUSORIA. rapidly transmitting and not retaining the food, and terminating in a compa- ratively short conical intestine, without a stomach dilatation, e.g. Ichthydium, Chaetomotus. - 2. Coelogastrica, Rotatoria with a very short gullet, a long conical in- testine, and no stomach, e. g. Hydatina, Synchceta. 3. Gasterodela, those Rotifers having an evidently developed stomach, or a dilatation of the alimentary canal limited by a definite constriction, e.g. Euchlamis, Brachiomus, Lepadella, Diglena, &c. 4. Trachelocystica, with an indistinct gullet, but having a very long, fili- form, Small intestine, in which the food is detained, and also a large globular intestine (rectum or cloaca) placed close to the discharging orifice, e.g. Rotifer, Actinºrus, Philodèma. - Subsequent independent observers have been able neither to recognize all these distinct types of structure nor to admit their value. Leydig, in fact, insists that the so-called “gasterodelous” type is the only one seen in Rota- toria; but, as just now stated, several authors admit the existence of a simple conical or tapering alimentary tube, without dilatation or stomach, in Several of the class. - . - The Trachelogastrica are represented only by beings which are now, by gene- ral consent, excluded from the Rotifera. The termination of the intestine in a dilated sac-like expansion, in which also the generative canals end, whence its name, “cloaca,” is the rule; or, to use Ehrenberg’s term, the majority of the Rotatoria are Trachelocystica. - The stomach dilatation, like the rest of the alimentary canal, is capable of great expansion, by which its figure is considerably altered. Usually but one gastric cavity has been described ; but in some species there is a second, and Huxley, in his history of Lacinularia (XXXVII. 19), describes three portions or divisions between the gastric canal and the rectum, the first with two pyriform sacs opening into it, the middle one frequently with several short cellular caeca, and the lowest with several cellular casca projecting ex- ternally, and clothed within with very long cilia. According to Prof. Wil– liamson, the stomach of Melicerta (XXXVII. 17) consists of an upper and lower segment, separated the one from the other by a marked though vary- ing constriction,-the upper stomach elongated, the lower almost spherical. Mr. Gosse describes this same organization in Melicerta, but calls the upper segment “a wide cylindrical stomach,” and goes on to say that the food passes from this into a globose intestine which ends in a slender but dila- table rectum. A similar double organ is found in Floscularia, Stephanoceros (XXXVII. 1 f), and Tubicolaria. Moreover Ehrenberg noted a sac attached to the stomach of Megalotrocha, which he called a caecum. The configuration of the stomach is otherwise altered by tubular and Saccular appendages, and in a few instances is lobular, as stated by Mr. Gosse in Asplanchna (XXXVI. 9s). Ehrenberg states, at p. 399 of his great work, that the stomach of Lacinularia is complicated by two blind tubes (intestines), and yet, at p. 403, reverses this statement by saying that it is “without blind intestine-like ap- pendices.” Leydig admits the latter as the truth; but, as already seen, Huxley remarked two pyriform sacs attached to the first, and caeca to each of the other two segments. Ehrenberg further describes caecal appendages to the stomach of Notommata clavulata, and of Diglena lacustris, but such were probably the turgid stomach–cells presently noticed. The tissues or histological elements entering into the formation of the stomach are—1, a limiting external membrane, and, 2, an internal layer of epithelium (XL. 4). The former is the same tissue with that constituting OF THIE ROTATORIA. 419 the walls of other portions of the alimentary canal, and is supposed by many to contain muscular fibrillae, although so very thin, pellucid, and apparently structureless. Leydig, however, calls it a homogeneous connective tissue. The lining of epithelium is made up of large turgid cells, rendering the wall thick and of a pulpy appearance (XXXVIII. 26 f). In young animals the epithelial cells are colourless; but in adult beings their granular contents are coloured and interspersed with fat-globules, whence it is that the walls of the stomachs assume a yellowish hue often intermingled with green and brown tints. The cells, moreover, commonly possess a nucleus and a nucle- olus, and their free surface is constantly ciliated. They are readily detached from the subjacent membrane and from each other, and are then seen to have a spherical or ovoid figure. “The great thickness of the epithelial layer,” writes Mr. Williamson, “as compared with the entire diameter of the organ, is curious: whilst the latter averages about gºth of an inch, the former is often not less than ++gth, or ºth of its entire diameter. The cells, when detached, vary in size, from a diameter of Tºrnth to riºrith of an inch; one of these was fringed with * * s 1 00 0. 6 () () () e cilia Tºrºth of an inch long, and had a nucleus Tºrith of an inch. After being detached, some of the ciliated cells floated slowly away, like so many animalcules.” Although this description and the measurements refer specially to the Melicerta ringens, yet the relatively large size of the cells is a feature com- mon to all the Rotatoria, and has been pointed out and figured by Leydig, Siebold, and others. - The secondstomach, noticed by Williamson in Melicerta, also had a layer of epithelial cells bearing cilia “even longer than those of the upper viscus, —although the parietes were very much thinner and more transparent, the cells being less easily traced.” In the third or lowest dilatation, seen by Huxley in Lacinularia, the interior was clothed with very long cilia (XL. 4). Ehrenberg remarked the existence of large stomach–cells in Diglena la- custris, and of less distinct ones in Notommata Myrmeleo and N. Copeus. The pouches he speaks of around the alimentary tube of Hydatina senta, and which imparted the appearance, to his eye, of a bunch of grapes, are no other than epithelial cells. In Philodinced the intestinal canal is stated to be fili- form, and enveloped in a granular cellular mass; that is to Say, the calibre is very much reduced by the turgid cells lining the walls. The compact mass of blind tubules, so described in Rotifer, admits a like interpretation. In Notommata tardigrada Leydig failed to detect cilia either in the stomach or intestine. In the great majority of the Rotatoria a definite “intestine’’ follows the stomach, and ends below in the cloaca. This intestine is generally known as the “rectum,” and is supposed to represent the large intestine of higher ani- mals. It varies much in its dimensions in different species, especially in its length and course. It is long, straight, and capacious in Notommata centrural (XXXVIII. 26), and in Euchlamis triquetra (XXXVIII. 5), short in Lacinw- laria, and extremely short in Notommata tardigrada. Among the encased Rotatoria it is of considerable length, owing to its curving forwards from the second stomach, so as to reach its outlet near the margin of the enclosing urceolus, or in other words the neck of the animal, and thereby provide for the immediate removal of the excrementitious matter from contiguity with it (XXXVII. 17). In Stephanoceros and Floscularia, as exceptions to this rule, this intestine is short. Looking at the so-called second stomach, placed at the head of the rectum in these fixed Rotifers, we might rather assimilate it to the ca-cum, which in some of the higher classes forms 2 E 2 º 420 GENERAL EIISTORY OF TEIE INFUSORIA. a sort of subsidiary stomach, where the digestive process is finally completed. Still it is not possible to establish all the minute homological relations be- tween these animals and those of the vertebrate class. The intestine, like the stomach, has a limiting membrane, possibly muscular, and is lined by a ciliated epithelium which, unlike that of the stomach, is not coloured, and its cells less easily detected. It is capable of very great distension. The rectum commonly ends in, Or, it may be said, expands into, a globular sac, which, from its likewise receiving the eggs from the Oviducts opening into it, is analogous to the cloaca of birds (XXXVIII. 26 i). This cloaca has a fine, transparent wall, and opens, posteriorly or dorsally, at the base of the pseudopodium, or, where this segment is absent, near the extremity of the body, by an outlet usually called the anus. The cloaca is particularly dilatable; for sometimes it is much loaded with accumulated faecal matter, and at others is distended by one or more of the enormous eggs the Rotatoria habitually produce. In discharging an egg, or in emptying itself of other matters, the cloaca is everted and thrust out through its external Orifice. From the mode in which the walls are drawn into longitudinal and circular folds, as exemplified in Notommata centratra (XXXVIII. 26), Leydig is in- duced to admit the presence of muscular fibrils regularly disposed in the two corresponding directions. Moreover the manner in which the cloacal orifice is closed, after the extrusion of any mass, indicates, in this author's opinion, a sphincter power, and consequently the presence of muscular fibres around it. The contraction of the entire canal on itself is sometimes so great that it is only manifest by a streak. - A most remarkable structural exception is met with among certain female Rotatoria, viz. the entire absence of an intestine and amus. It prevails in the genus Asplanchma (Gosse), in the Notommata Sieboldii (Leydig) (probably in N. Syrina), in Ascomorpha Helvetica (Perty), and in A. Germanica (Perty) (XXXVI. 9; XXXVII. 32; XXXVIII. 28). This want of a discharging posterior outlet necessitates the rejection of excrementitious matters from the stomach through the mouth. This structure is so very exceptional and peculiar, that Prof. Williamson is not prepared, without further evidence than has yet been advanced, to admit it as true of any Rotifera. It is, he writes (in lit.) contrary to pro- bability, and, if established, would induce him to exclude the animals so organized from that class. - RECEPTION OF FooD—ITS DEGLUTITION, &c.—The food of the Rotatoria, as before noticed, is attracted towards the mouth by the vortex caused by the rotation of the cilia crowning the head. An exceptional means of prehension is seen in those Rotatoria which protrude their jaws beyond the mouth, using them as pincers or forceps to seize any larger prey. “In general,” writes Mr. Gosse (Phil. Thans. 1856, p. 429), “the ciliary vortices are sufficient to bring the prey within the buccal funnel (pharynx); but in several genera of the family Euchlanidota, as Metopidia, Colurus, Monura, and Stephanops, there is a curious accessory organ, which aids in the capture of the prey; at least I am sure it is so employed in several species of Metopidia. Thus in M. acuminata the frontal region is formed by an arched fleshy process occi- pitally, which is approached by a small one on the ‘mental” side; and be- tween these is the wide entrance of the buccal funnel. The occipital process is protected by a horny crystalline plate, forming a segment of a sphere, and, when viewed laterally, taking the appearance of a curved horn. It can be partially protruded and retracted, and also bent down to meet the mental lobe. This apparatus, when the animal is taking food, is kept in vigorous © OF THE ROTATORLA. 421 action. A strong vortex is produced by the ciliary wheels; and as the floating atoms whirl by, the moveable plate is thrown forward with a grasp- ing motion, the fleshy head being at the same time protruded, and, when the lobes are in contact, retracted. This is repeated almost every instant with manifest eagerness and discrimination, the manducatory apparatus working vigorously all the while. r “The same curious organ is frequently employed in another way. It is bent considerably downward; and as the animal crawls deliberately up and down the stems of aquatic plants, it is used to rake and grub, among the floccose deposits, the minute Diatomaceae, &c., that adhere to them.” Having entered the mouth, it is usually rapidly conveyed along the pharynx to the jaws. In those species which have the pharynx expanded into a “crop,” such as Floscularia and Asplancha, this transmission of the food is less speedy. Mr. Gosse imagines the “crop ’’ to possess a suctorial power. He says— “I think that when the animal (Asplanchma priodonta) is cognizant of food brought to the mouth by the ciliary vortices, it suddenly expands the crop by the action of the muscles that go from it to the skin, when the water rushing into the vacuum carries in the prey. Then the network of fibres contracts again, and the prey is secured.” - Having reached the “maxillary head,” the food is “ lodged” (to quote Mr. Gosse's paper) “upon the ‘rami” between the two ‘unci.” These con- jointly work upon the food, which passes on towards the tips of the ‘rami,’ and enters the oesophagus (the proventricular tube), which opens immediately beneath them.” - Baving escaped the mandibular apparatus, the food is subjected to the action of some digestive fluids which are poured into the portion of the ali- mentary tube below, whether that portion be dilated into a distinct stomach, or retain a nearly uniform calibre. How long this process of digestion need be continued, we have no data to determine ; but we may conclude that the time will vary according to the nature of the food, the condition of the animal, its species, and other circumstances. In Melicerta ringens, which has a double stomach, Prof. Williamson remarks that the upper one “appears to be chiefly a receptacle for the food. From time to time, especially when the viscus is distended, a portion of its contents pass down into the lower stomach.” In this the mass of food usually distending it “is constantly revolving, the motion being due to ciliary action. This process goes on for Some minutes, after which the creature contracts its body, and forces the entire exuviae out of the viscus into a long narrow cloaca (rectum), which terminates externally by an anal outlet. As it does this, it everts a considerable portion of the cloaca, thus almost bringing the cloacal outlet of the stomach to the exterior, and causing, at the same time, a large transparent protuberance to be deve- loped on the corresponding side of its body. At other times the creature can draw in these appendages, so that Scarcely any trace of a cloacal canal is visi- ble.” Mr. Gosse suggests that this protrusion, at the moment of discharge, is designed “to shoot the faecal mass out of the case” (urceolus); for the outlet is then projected above the rim. “The faces,” he adds, “are slightly coherent and jelly-like, not at all like the coloured pellets of which the urce- olus is built up.” - The food of the Rotatoria consists of the lower Algæ, of Protozoa, Ento- mostraca, other Rotifers, and even the weaker members of the same species. “The stomach,” remarks Mr. Gosse, “ of the Asplanchna is frequently occu- pied with animals; the smaller Anuraece, as A. aculeata, A. curvicornis (?), and A. stipitata (?), seem to constitute its chief food, I have taken one with the species last-named in its stomach, which, after about an hour, was ejected 422 GENERAL HISTORY OF THE INFUSORIA. and swam about as lively and apparently uninjured as ever. In one I saw several specimens of a long slender Fragilaria loose in the cavity of the body, and in the stomach of another the long cell of a Conferva.” From the manner in which the food is obtained, apparently without any selection on the part of the animals, the vortex driving into the mouth what- ever particles may come within its reach, we might conclude that the con- tents of the stomach must be of a very miscellaneous character. This is true to a great extent; yet the Rotifers can eject what is unsuitable, and they have the power of moving from place to place in search of suitable nutri- ment, or at least, as in the fixed forms, of arresting and withdrawing the ciliary apparatus until noxious materials are floated past, or appropriate ones have come within reach. That they are passive recipients of the current setting into their mouths, is indicated by their swallowing carmine or other colouring matters mixed with the Water, which, as Mr. Gosse observes, are deleterious to them. - The-feeding of Rotatoria with colouring matter serves a practical purpose in the examination of their structure; for it helps to reveal, by the contrast of coloured with uncoloured parts, details of structure not apparent amid the uniform and delicate hue of the entire organism in its natural state. For example, Mr. Gosse writes—“The process of Swallowing carmine enabled me to see (in Melicerta), very distinctly, that the Oesophagus enters the giz- zard between the larger ends of the jaw-mullers, and that the stomach—duct leads off from their smaller ends through the semiglobular lobe beneath.” The same observer employed this means to demonstrate the manner in which the case of the Melicerta is deposited, and with very satisfactory results (see p. 425). THE SECRETING SYSTEM.—Special organs of secretion exhibit themselves in the Rotatoria under the simplest form of cells, and of involutions of the lining membrane of the alimentary tube, as sacs and tubules. Frequently their contents are coloured; and these always differ in density and physical ap- pearance from the general fluids of the body. The glandular organs situated about the walls of the digestive canal, are supposed to have discharging ducts through which their contents percolate into that tube. The testes or spermatic glands in the male, and the ovary in the female— both of them secreting organs,—together with Some accessory secerning vesi- cles, will be described under the section on the Reproductive Organs. Some– thing has already been said of some other glands in the last section, on the Digestive Organs: a more precise account is, however, necessary. The most constant glands are the two situated on the upper surface of the stomach near the entrance of the gastric or proventricular tube, and some- times on that tube itself (XXXVIII. 26 h, 27 l). They are usually hemi- spherical or Oval, but assume other shapes, as pyriform, conical, cylindrical, reniform, Crescentic, and forked. In a few, e.g. Noteus and some Brachiomata, they are stalked, or, more properly speaking, have an elongated, tapering ex- tremity. Cylindrical or club-shaped glands are seen in Notommata clavulata, and forked ones in Diglema lacustris. In these two species, and also in Me- galotrocha there are likewise four long filiform tubes, equalling the glands in length, and of the like colour, but opening at the centre instead of the fore- part of the stomach. In Polyarthra, Leydig noticed two elongated secreting- sacs attached to the posterior surface, and in Lacinularia, a pair of glands, instead of a single. One, at the fore part of the stomach. Not being able to detect the ducts of the “2–3 pyriform glandular (?)-looking bodies often attached to the base of the upper stomach (of Melicerta) near the constriction which separates it from the lower one, Prof. Williamson hesitates to call OF TEIE ROTATORIA. 423 them glands, and doubts likewise the Secrétory character of the similar but larger bodies seen in the neighbourhood of the Oesophagus.” . The glands are usually transparent, or have only a slight milky opacity; they contain fine nucleated granules and molecules, and in some examples, e.g. Polyarthra (XXXVIII. 39) and Pterodina, a few small oil vesicles. Externally they are invested by a transparent homogeneous membrane, to which, in Albertia, Dujardin assigned an active contractility; but this is very doubtful. “They are,” says the French naturalist, “stalked sacs, placed at the commencement of the intestine, susceptible of contraction, pouring out their secretion into the intestine, from which they again fill themselves, and undergo dilatation : in this example at least, these appendages must be con- sidered caeca rather than glands.” “Sometimes,” Leydig observes, “the elements of the contained granular mass have an elongated figure, as in No- teus; and then the contents of the glands assume a striated appearance.” This account recalls that given by Mr. Williamson of a glandular structure he supposes may possibly represent a spermatic gland; but of this hereafter. Cohn believes he detected the exudation of a blackish granular fluid from these glands in Hydatina senta, and its entrance within the stomach by a definite aperture. The granular vesicles of the glands were termed “vacuoles” by Dujardin, and have been represented by Ehrenberg in many figures, e.g. of Euchlamis macrura, E. dilatata, Megalotrocha, and Lacinularia ; they have also been spoken of by him as “glands, vesicular within.” Moreover the sharply- defined clear vesicles he has represented in Theorus (XXXIV. 427–429) and Pterodina, and termed “eyes,” Leydig believes to be nothing else than fat- vesicles of the gastric glands. Mr. Dalrymple has accurately figured these glands in his so-called Notommata (Asplanchma) Anglica (XXXVI. 9 g). The function and homologies of these gastric glands are doubtful. Ehren- berg's first notion of them was that they were spermatic ; but he subsequently changed his views, and called them “pancreatic.” “For what reason,” says Prof. Rymer Jones, “Ehrenberg has given the name of pancreas to these se– creting caeca, it is difficult to conjecture, since the first rudiments of a pan- creas are only met with in animals far higher in the Scale of animal existence; every analogy, indeed, would lead us to denominate these caeca the first ru- diments of a liver, by far the most important and universal of the glandular organs subservient to digestion, and in a variety of creatures presenting an equal simplicity of structure.” . Bowever unsupported the notion of the pancreatic or Salivary nature of these glands may be, it has met with several advocates, who have in all pro- bability assigned to them this function rather from the want on their part of any definite opinion of their character than for any other reason. Thus Dal- rymple alludes to them as salivary glands; and Perty affirms of two filiform vessel-like appendices of the stomach (?) in Enteroplea, that they are repre- sentatives of the pancreas or of salivary glands. Siebold adopted a similar hypothesis; but Leydig, on the contrary, regards them, in a morphological point of view, not as pancreatic glands, but as the analogues of those pro- cesses often seen on the stomach of Arthropoda ; he would therefore desig- nate them generally gastric glands,--a view with which we are disposed to coincide. The small glandular appendages on the dorsal Surface of the sto- machs of starfish, suggest themselves as of the same nature as the appendages under consideration. A yellowish clear body is situated on each side of the pharynx, imme- diately in front of the maxillary bulb, in Lacinularia, Tubicolaria, Melicerta, and Brachionus (XXXIX. 16), and rather within the substance of the bulb 424 GENERAL EIISTORY OF TETE INFUSORIA, in Noteus. This is possibly the structure alluded to by Mr. Gosse as “several yellow glandular (?) spots” seated on the top of the cushion of the dental organs of Asplanchna (XXXVIII. 28), and the same with the yellowish, clear, horny-looking masses mentioned by Huxley in Lacinularia (XXXVII. 19 g) and Brachionus. The last-named naturalist refers these bodies to the “ horny skeleton’’ (see p. 412). Leydig considered they might possibly be “salivary glands.” The epithelium of the alimentary canal has probably a glandular purpose: its large cells are filled with a granular matter, and many oil-vesicles, besides a nucleus. The number and large size of these gastric cells have been already illustrated (see p. 419); they are mostly coloured—yellow or yellowish brown, with sometimes green spots interspersed. Ehrenberg remarked these cellular accumulations, and advanced the hypothesis of their homology with the liver of higher animals, The colouring matter was consequently esteemed to be the bile. We have seen that Rymer Jones has assigned the functions of a liver to the so-called “pancreatic ’’ sacs, or “gastric glands.” However, most naturalists favour Ehrenberg's view ; among them are Dujardin, Sie- bold, Leydig, and Dalrymple. The belief, indeed, of the great Berlin natu- ralist was, that the cells grew from the exterior of the wall of the alimentary canal, and were so many Saccular appendages; this view modern research does not countenance, but affirms the presence of the cells within the canal. The examples of Secerning cells given by Ehrenberg deserve to be mentioned. He remarked that in Enteroplea the biliary cells and ducts were most pro- nounced, and that there was great accumulation of cellular or glandular ele- ments about the intestine of Rotifer, Callidina, and Philodina ; in the last two he also asserted that the mass becomes coloured by colouring particles swallowed by the animals. - Mr. Gosse puts the question whether the little granular body near the tip of the pedicle of Melicerta is a secerning gland for the Secretion of an adhesive glue, by which the foot adheres, as in Monocerca. This faculty of Secreting an adhesive matter from the end of the pseudopodium is sur- mised by Perty to be possessed by several Rotatoria, viz. by Conochilus, La- cinularia, CEcistes, Floscularia, Limnias, Tubicolaria, and Stephanoceros. This idea is countenanced by Cohn (Zeitschr. 1855, p. 439), who inclines to the belief that the Solid-looking elongated-oval bodies situated at the poste- rior extremity of the abdomen of Brachionus and other species, and usually considered muscular (moving the tail-process), are rather of a glandular na- ture, and possibly secrete an adhesive glue to fix the animal. More recently (Müller's Archiv, 1857, and A. W. H. 1857, xx. p. 292) Leydig has accepted this view, and thus treats of these structures in Hydatina senta —“The clavate bodies in the tail consist of a delicate envelope and pale molecular contents, in which beautiful nuclei, each with a nucleolus, may be distin- guished; in many individuals, Small fatty points are also present in variable amount. I regard the organs in question as glands, which in their position and function correspond with the caudal glands of Enoplus for example; they open at the apex of the caudal appendages (Fusszangen); and as the worm just mentioned ‘ can attach itself firmly to the object-bearer by the posterior extremity of the body, in order to carry the body round this point with a waving motion,” So also can the Hydatina fix itself by the tips of the caudal append- ages, probably by means of the sticky substance excreted here. It seems to me also, that in a certain upright position of the caudal appendages, I have detected the opening at their tip.” • * * Other large vesicles, which some think may be glandular, occur in different parts of the body, and in the foot-process of several genera. Such are noticed OF TEIE ROTATORIA, 425 by Dobie in the pseudopodium of Floscularia; and Leydig mentions a clear gland or space at the root of the tail of Lacinularia, from which he supposes a duct to extend to the extremity; such a structure Huxley cannot discover, but states that the extremity of the tail always seemed to him “to present a ciliated hemispherical cavity, closed above;” the supposed gland at the base he called a “vascular mass.” e An active secreting power is displayed by those Rotatoria which invest themselves in cases or urceoli; for such cases are always produced from the animal, and are the result of excretion. The formation of its case by the Meli– certa ringens has often been most thoroughly examined; and Mr. Gosse was enabled to watch the deposition of pellet by pellet of the excreted matter. This direct observation has entirely overthrown the prevalent notion first ad- vanced by Ehrenberg, that the case was built up of excrementitious particles discharged from the alimentary canal. The organ actively engaged in the building of the case is seated immediately above the long tubular process extending from the neck of the animal (XXXVI. 1 c); it is cup-shaped, and its concave surface so ciliated, that when in full activity it seems to revolve. In this, which Mr. Gosse calls the “pellet-cup,” the building- material seems to be prepared and fashioned into an oval or hexagonal figure, and then the pellets so moulded are regularly laid down in rows, “straight and uninterrupted perpendicularly,” but zigzag transversely, so that a dia- gonal disposition is the result. “Each pellet, examined separately, is of a yellowish or olive colour, composed of granules; the whole tube is of a red- dish-brown (XXXVI. 1 d). After a certain number were deposited in one part, the animal would suddenly turn itself round in its case, and deposit some in another part.” It seems that the action of the pellet-cup is volum- tary, and not always coexistent with the passing of the ciliary current over the chin. The animal frequently makes abortive efforts to deposit a pellet, and sometimes bends forcibly forward to the edge of the case before the pellet is half formed. Coloured particles in the water are hurled round the margin of the ciliated disk until they pass off in front through the great sinus be- tween the large petals; and the atoms, if few, glide along the facial surface, following the irregularities of the outline with great precision, and, dashing round the projecting chin, lodge themselves one after another in the little cup-like receptacle beneath, in which they are whorled round with great rapidity, and prepared into pellets for the construction of the case. On mix- ing carmine with the water, the torrent that poured off in front and the ap- pearance of a rich crimson pellet in the cup were instantaneous. A large animal which had its case accidentally slit for some distance, watched for several days, was seen to make pellets frequently; yet it never deposited them nor attempted to construct a new case, but let the pellets float away.” Such is a résumé of Mr. Gosse’s interesting observations. Prof. Williamson adds that, when the animal is not engaged in its architectural occupations, the sac (pellet-Cup) becomes so contracted as to be almost invisible. In connection with this subject of secretion, must be mentioned the views of Leydig respecting the accumulation of granules or crystalline particles seen in many embryonic and young Rotatoria, enclosed in a sac contiguous to the cloaca (XXXVII. 4; XXXVIII. 7, 8). Ehrenberg remarked these granular heaps in Microcodon, Lacinularia, Stéphanocéros, Floscularia ornata, Enteroplea, and in Notommata granularis, and called them at one time “a dark glandular body or speck,” at another “a single glandular organ ” having no evident function. Weisse represented them to be unconsumed and still-remaining yelk-Substance, and supposed the animals presenting such granular masses “premature * or “aborted.” Williamson noticed similar 426 GENERAL IIISTORY OF TIIE INIFUSORIA. masses in Melicerta, and found that they disappeared soon after the young animal escaped from the ovum. Leydig's conclusion, from optical and chemical qualities of the granules, is that they are urinary or uric concretions, and that the clear space containing them is formed by the end of the intestinal canal, or by the cloaca. To elucidate this view, an analogy is pointed out in the case of those insects which undergo complete metamorphosis, in which solid urinary concretions accumulate in the rectum during the pupa-State, but are evacuated when the insect emerges from that torpid condition. • - The actual secreting organ of these urinary concretions, or in other words the kidney, must, says Leydig, be sought for in the cells of the intestinal wall, which stand out in a knob-like matter. Ehrenberg's account of the “dark bodies’ about the rectum of Enteroplea, and of Notommata granularis, favours this opinion ; and the granular heap near the termination of the intestine of the larva of Cyclops may be adduced as another allied fact in illustration of the nature of the bodies in question. Vogt, however, is opposed to this presumed analogy, and states that this peculiar collection in the cloaca. of embryo Cyclopes is originally produced of a green colour, within a sac on each side of the intestime, and when subsequently discharged into the cloaca, is of a yellow hue. These sacs therefore have, in his estimation, rather the signification of a liver than a kidney. The like structures are common enough in Vermes. Excepting therefore, Leydig contends, male Rotifers, urinary concretions occur only in the embryo and in the first period after birth, and the existence of a primordial kidney must be admitted as a fact. Cohn has come forward to oppose these views of Leydig, and says that this whole hy- pothesis falls with the proof that in Enteroplea the vesicle with the dark granules stands in no sort of connexion with the intestine, nor, indeed, can do so, as no intestine exists, and it is rather firmly adherent to the Outer wall of the testis. To this adverse opinion Leydig rejoins (Müller's Archiv, 1857, p. 404, and A. W. H. 1857, xx. p. 295) that Cohn’s “undoubted proof” is itself an error; “for the clear space containing the dark granules is not ad- herent to the true wall of the testis, but to that outer envelope which repre- sents the rudimentary stomach and intestine; or, more properly speaking, the clear space enclosing the concretion belongs to the abortive alimentary canal itself, which extends from the notch of the rotary organ to the cloacal open- ing, so that Enteroplea displays the same characters as the other Rotatoria, although this is in complete opposition to the description given by Cohn. My opinion, that the granules in question are uric concretions, is, of course, no more strongly supported by the position of matters detected in Enteroplea than before ; but the objection raised by Cohn appears to be removed. The opinion first put forward by Weisse, which is also favoured by Cohn, that the granules are the remains of unused yelk-masses, I must reject, without taking other reasons into account, if only because the vitelline elements and the granules in question have no resemblance to each other, but are perfectly different things.” Several authors have suggested that the vascular apparatus to be described as a respiratory organ in the following chapter has also in part, or even principally, the function of a kidney or excretory organ. These views can be best propounded after the apparatus in question has been described. THE WASCULAR AND RESPIRATORY SYSTEMs (XXXVIII. 26 e, i, l; XL. 1 i, 5). —The existence of vessels subservient to the circulation of a fluid analogous to blood was surmised by Ehrenberg. Among such assumed structures were the transverse cords to which the semblance of articulation is often due, as well as other similar bands now proved to be muscular fibres of con- OF TEIE ROTATOERTA, 427 nective tissue. For instance, the intercurrent fibres about the head and neck of the Rotatoria, and the interlacing cords passing forward to the lobes of the rotary organ, and backward to the maxillary head, were reckoned parts of the vascular system. The purpose of a circulatory system is to convey the blood (the nutritive, reparative fluid) within the reach of every tissue and organ, so that all its parts may be renovated, and their effete, worn-out particles removed. The necessity for such a contrivance is at once intelligible in large animals, where the parts have considerable size and thickness, and are pretty closely packed within the limits of the body; but in the case of the Rotifers, the proto- plasmic fluid fills up all the large space within the body unoccupied by the viscera, and is in immediate contact with them, whilst none of them have such a density or thickness as to preclude their being readily permeated by it. The result of digestion within the alimentary canal is the production of a nutritive juice or chyle, which apparently passes by exosmosis through the walls of the canal into the general cavity of the body, mixing there with that already existing, and is the representative of the blood of higher animals. But, in addition to this, a constant renovation of the chyliferous liquid of the body, by water taken in from without, appears to be necessary. Ehrenberg witnessed a periodical transparency in the body, with an alter- nating distension and collapse occurring regularly in almost all Rotatoria. During distension, the outline of all the viscera seemed clearer, whilst, upon the collapse, the organs approximated their limits, became less defined and somewhat confused, and the integument crumpled. These movements he attri- buted to the alternate entrance and exit of water from without, through the medium of the Supposed siphon tube on the head, or of openings upon other parts of the body. It has, however, been shown that the siphon and apparent openings have no external communication; we must consequently believe, with Leydig, that the imbibition and exudation must be, in great measure, the result of endosmotic action,--not forgetting, however, the influence which is necessarily exerted on the alternate movements in question by the action of the respiratory apparatus to be presently described. Leydig remarks that “the mingling of the sanguineous fluid with water from without seems, at first sight, extraordinary ; it is, however, a fact in physiology, founded on direct observation, Van Beneden having detected it in marine Mollusca, myself in Paludina vivipara, and, more recently, Gegen- baur in Heteropoda and Pteropoda.” The nutritive or sanguineous fluid of the Rotatoria is, as a rule, clear and colourless, but in some species it has a red or yellowish hue, e.g. in Notommata centrura, Symchaeta, and Polyarthra; it is, moreover, usually destitute of distinct floating particles or elements: exceptions occur in Eosphora Najas, Euchlamis, and a few others, in which small clear corpuscles move about in it just as in the blood of Annelida. “Such genuine elements,” continues Leydig, “ of the circulating fluid must, however, not be confounded with the minute particles which at times detach themselves from the tissues within the body and float about in the liquid. Such false corpuscles are not uncommon in animals which have been partially crushed or left dry by evaporation; those noticed by Ehrenberg in Hydatina senta were, in all probability, of this accidental kind.” Dr. Dobie has recorded an observation of seemingly genuine moving cor- puscles, which deserves a place here. He found, “immediately below the integument of Floscularia cormwia, groups and limes of very small granules continually in a state of rapid molecular motion, in appearance exactly resem- bling the molecules in the cusps of Closterium. Besides the molecular, they are subject to another motion; for occasionally they move from One part of 428 GENERAL EIISTORY OF TEIE INFUSORIA. the surface to another, in currents not very distinct or persistent, and in no definite direction. He has seen them running in lines down the tail, and collecting in groups. This flowing movement occurs chiefly during the con- tractions and relaxations of the entire animal. He thinks it probable that these granules are connected with the nutrition of the animal, and analogous to the free floating corpuscles of the Tardigrada, described by M. Doyère.” In his recent paper (Müller's Archiv, 1857, p. 404), Leydig notes that when individuals of Hydatina senta have been plentifully fed with Eugléma viridis, the fluid (blood) which fills their abdominal cavity, contains numerous clear globules, or blood-corpuscles, of a roundish form and unequal size. We would rather compare these corpuscles to those seen in chyle during the process of digestion, as more strictly homologous with them than with blood- disks. Although no true vascular system is discoverable in the Rotatoria, there is, nevertheless, a tubular apparatus readily seen in most animals of the class (XXXVI. 6 a. a, 9 m ; XXXVII. 29 d, 32 ef; XXXVIII. 5 did, 25 ef, 26 e i l, 27 g). It has the form of an apparent band, extends upwards from the cloaca, or near to it, on each side of the body; and within this a cord or vessel is visible, more or less coiled or convoluted in its course, from which small vibrating organs, often pear-shaped, and likened by Ehrenberg to written notes of music, project towards the cavity of the body. These vessels may possibly communicate by one or more transverse vessels running across the neck of the animal; whilst below, they end either in a vesicle endowed with an active power of contractility or immediately in the cloaca itself. Now it happens that the mechanism of this organization, as well as its functions and relations to the other parts of the body, have been so variously described by different writers, that it is difficult to draw up any satisfactory general account of it; we shall therefore be compelled chiefly to confine ourselves to the reproduction of the several statements as presented by their authors respecting the side bands and the contractile vesicle. Ehrenberg adopted the curious motion that they were parts of the Sexual organization. The side bands with their coiled canal he represented to be the testes, and the contractile vesicle a sperm-sac (seminal vesicle). The inconsistency of this notion with all our knowledge of animal structure and functions, has struck every observer. To adduce but one counterargument:—the constant discharge of spermatic fluid in a profuse quantity, and in no relation with the number of eggs contained within the ovary, is an idea which is per se at vari- ance with all analogy, and directly opposed by the fact that the apparatus is in full activity even when the embryo is still unhatched within the body of its parent, and entirely negatived, at least in several instances, by the disco- very of distinct male beings. Again, Ehrenberg called the tremulous tags (XXXVIII. 26 e) gills or gill- like organs, and therein recognizes them as parts of a respiratory system. He thus refers to them:—“Oval, tremulous bodies are in some species observed attached to a free filament-like tube generally placed longitudinally within the body; in some instances they are attached to the two sexual glands (i. e. the side bands), as in Hydatina. Their function is respiratory, and they are analogous to gills; the tremulous motion observable is that of the laminae composing them. The reception of water within the body for these gills to act upon, is provided for by one or more openings at the anterior part of the body, or in Some species by spur-like processes or tubes (siphons).” The erroneous belief that the siphon-like antennae (XXXVII. 17 d: XXXVIII. 27 e) and the cuticular fossae were channels for the admission of water into the body was countenanced by Siebold, who explained the respi- ratory act to consist in the entrance of water, by the supposed apertures, from OF TEIE ROTATORIA, 429 without into the general cavity of the body, its percolation through “short lateral vessels '' (the oscillatory tags) into the winding canal of the lateral band of each side, and its passage thence into the contractile vesicle, by which it is pumped out through the cloaca. This process Siebold designated a water- circulating system. Mr. Dalrymple, in his excellent description of a supposed new Notommata (the Asplanchna Brightwellii of Gosse), differs from Siebold in the account of the respiratory apparatus in several particulars. He says—“This pecu- liar organ consists in a double series of transparent filaments (for there is no proof of their being tubes or vessels), arranged, from above downwards, in curved or semicircular form, symmetrical when viewed in front (XXXVI. 6 a a). These filaments, above and below, are interlaced, loop-like, while another fine filament passes in a straight line like the chord of an arc, uniting the two looped extremities. To this delicate filament are attached little tags or appendices, whose free extremities are directed towards the interior of the animal, and are effected by a tremulous, apparently spiral motion, like the threads of a screw. This is undoubtedly due to cilia arranged round these minute appendices. The tags are from eight to twelve, or even twenty, in number, varying in different specimens (XXXVI. 6). “I believe the organ in question to be a peculiar circulatory system. The body of the animal is filled with fluid, most probably analogous to blood, while the ciliated tags, in perpetual motion, must produce currents in this fluid, and probably in a uniform and determinate direction. In this way the nutrient plasma will be brought regularly in contact with all parts of the body, and the process of nutrition go on as in insects, without the interven- tion of tubular vessels, the dorsal heart in them serving only to give direc- tion and circulation to the blood. I am the more impressed with this belief, since these filamentous Organs are in close approximation with the large con- tractile sac, which probably performs a respiratory function.” Moreover Mr. Dalrymple does not believe in any communication between the sac and the apparatus furnished with the ciliated tags, as Siebold supposes; on the contrary, he represents the sac to communicate directly with the ex- terior. He writes—“This sac, spherical when distended, is placed just above the ovisac, and communicates with the vaginal canal. It is ex- ceedingly delicate, and may be seen to contract, by the action of muscular fibres, with great rapidity, in which act it is thrown into numerous regular folds or pouches, and in that condition appears not very dissimilar to the large cellular lungs of Batrachia. . . . The explanation which I venture to give is, that this Sac draws in Water and expels it again by the vaginal orifice; and it is by bringing the blood, by means of the ciliary movements of the tags, into immediate contact (the delicate membranous wall of the sac in- tervening) with the air of the water, that ačration or respiration is per- formed. An analogous contractile sac may be seen in Rotifer vulgaris.” Lastly, the author adds that he is convinced, from repeated observation, that the contractile sac has no relation with the generative function, and that “the supposed vascular ramifications upon it are neither more nor less than the muscular fibrillae by which the contractions are effected.” Perty coincides with the explanation offered by Dalrymple, and reproduces it in his work. Mr. Gosse presents, in his notice of Asplanchma priodonta, the following description of the mechanism in question :-‘‘ On the upper side of the oviduct sits a contractile bladder, which, when full, is perfectly globular and small, being scarcely, if at all, larger than the two pancreatic glands put together. Round this, attached at or near its base, passes on each side a tortuous thread, apparently glandular, which goes up along each side 430 GENERAL ITISTORY OF THE INTUSORIA. of the ventral region, and is attached to the head-mass behind the jaw- cushion. The middle part of each thread is wrinkled into a large plexus of four or five pairs of doublings, laid with some regularity; on this plexus are placed four tremulous tags, directed inwards, making eight in all. None are visible on any other part of the threads. The presence of these organs, as well as of the contractile bladder, in the female, shows that these are not con- nected with impregnation. From the above extract it appears that Mr. Gosse believes that the “ tortuous threads '' of the apparatus have a glandular office; and though he so far countenances the hypothesis of Ehrenberg, nevertheless pronounces against their sexual nature. Dujardin expresses an opinion that the contractile vesicle is a respiratory organ, and that the water freely penetrates into the interior of the body to bathe the vibratile organs, as the variability of volume of the animals proves. Leydig has very elaborately described the structures in question, and their several modifications. We feel justified in submitting an analysis of his researches, even at the risk of Some repetition:- “The canal of the respiratory apparatus extends along each side of the body. Generally there is a single canal on each side, much contorted in its course, and forming actual coils or plexuses, e.g. in Stephanocéros, Brachiomaea, Lacinularia, Euchlamidota, and many Notommatae. Two canals, which coalesce at either end, are seen in Notommata Myrmeleo, W. Sieboldii, N. Syrina, N. clavulata, and N. Anglica. The canals have a thick cellular wall, and their cavity is clear and well defined. They are not solid cords, as Perty and others affirm. The cellular walls may be much thickened, and contain, besides the usual fine granular contents, many fat-particles, as seen in Sté- phanoceros, Notommata centrura, and in Lacinularia. In the first-named, indeed, the deposit of fat is so great that the coils of the respiratory canal near the head rather resemble a collection of fat-vesicles (XXXVII. 1 t). I have not been able to discover any anastomoses between the canals of opposite sides, as Huxley represents in Lacinularia.” In many Rotatoria, particularly in Small species, such details of structure escape our powers of observation, and the canals described are invisible, as, for example, in Floscularia, Polyarthra, and Ascomorpha; a more close and search- ing inquiry may, however, reveal them, particularly where the contractile sac shows itself. Indeed, Perty has detected the tubes in Ascomorpha Helvetica. “The vibratile or ciliated tags are processes of the respiratory canal (XL. 5). They are constructed after two types, which do not concur in the same animal, but are found as peculiarities of different genera. In one type the process is of equal width and cylindrical throughout, as in Notommata Myrmeleo (XXXVII. 29 e, 32 k); in the other, the extremities are dilated and a trumpet-shaped figure assumed, as in Notommata centrura (XXXVIII. 26 e), Euchlamis triquetra, and in Eosphora Najas. “In Lacinularia I have been unable to satisfy myself if these processes of the respiratory canal discharge themselves freely into the abdominal cavity. Huxley states that they have blind extremities; but I regard it as still an open question, for in other species, for example in Notommata Sieboldi; and N. centrura, it can be most satisfactorily made out that they open freely into the cavity of the body. “Vibratile hairs (cilia) project from their free end and in the trumpet- shaped processes; the direction of the ciliary motion is evidently inward. “The number of the vibratile organs varies much in different species: usually there are but from 4 to 8 or 10, distributed at unequal distances along the respiratory tube; but in some animals, e.g. in Notommata Copews, W. OT THE ROTATORIA, 431 Syrina, N. Sieboldii, N. Anglica, N. clavulata, and in N. Myrmeleo, the number is greatly augmented, and from 30 to 50 tags may be counted. When thus multiplied, they are for the most part appended to a clear canal of little width and thickness, rather than to one with thick cellular walls. (The tags are mostly more numerous on one side than on the other.) “The posterior extremities of the respiratory canals either open at once into the cloaca, as in Tubicolaria, or more commonly expand to form the contractile sac, the respiratory vesicle (XXXVIII. 26 i). “At the first appearance of the respiratory vesicle, it is of insignificant size, and clearly a dilated state of the united ends of the two respiratory canals. It is then little or not at all contractile. This condition is illustrated in Lacinularia, and Stéphanoceros. “It generally, however, exists as a consider- able and actively contractile Sac opening into the cloaca. Its walls are very thin, and covered with a fine muscular network, discoverable in most species, and imagined by Ehrenberg to be vascular. The openings of the respiratory canals into this sac are readily perceived by a proper adjustment of the focus of the microscope.” - From this organization, Leydig concludes that a portion of the water sur- rounding the animal enters by endosmosis, or possibly by minute orifices hitherto unperceived, within the cavity of the body, and there mixes with the nutritive juices, the analogue of the blood of higher beings. The simple act of respiration is consequently limited to the imbibition and the intermix- ture of fresh water with the blood. Further, it would appear that the waste material is discharged through the vibratile processes, which by their ciliated appendages direct the fluid into the respiratory canals, from which it escapes either first into the contractile sac, and thence into the cloaca, or at once into the latter. Here the question of a glandular, a renal function performed by the re- spiratory tubes meets us; but it will be more convenient to defer its consi– deration until we have set forth the researches of Mr. Huxley, who differs in not a few details from Leydig :—we must premise that they apply specially to the Lacinularia socialis, to which, among other peculiarities, he assigns the absence of a contractile Sac, although Leydig affirms a very Small one to exist. - Prof. Huxley acquaints us that the opinion of Oscar Schmidt is, “ that the ends of the water-vessels are closed, and that the vibrating body is within them.” And he goes on to say—“There is no contractile Sac opening into the cloaca as in other genera; but two very delicate vessels about Tărth of an inch in diameter, clear and colourless, arise by a common origin upon the dorsal side of the intestine. Whether they open into this, or have a distinct external duct, I cannot say. “The vessels separate; and one runs up on each side of the body towards its oral side. Arrived at the level of the pharyngeal bulb, each vessel divides into three branches: one passes over the pharynx and in front of the pha- ryngeal bulb, and unites with its fellow of the opposite side, while the other two pass, one inwards and the other outwards, in the space between the two layers of the trochal disk, and there terminate as caeca. Besides these, there sometimes seemed to be another branch just below the pancreatic sacs. “A vibratile body was contained in each of the caecal branches; and there was one on each side in the transverse connecting branch. Two or more were contained in each lateral main trunk, one opposite the pancreatic Sacs, and one lower down, making in all five on each side. Each of these bodies was a long cilium (TThrºth of an inch) attached by One extremity to the side of the vessel, and by the other vibrating with a quick undulatory motion in 432 GENERAL HISTORY OF THE INFUSORIA. its cavity. As Siebold remarks, it gives rise to an appearance singularly like that of a flickering flame. * “I particularly endeavoured to find any appearance of an opening near the vibratile cilium, but never succeeded, and several times I thought I could distinctly observe that no such aperture existed. Animals that have been kept for some days in a limited amount of water are especially fit for these researches. They seem to become in a manner dropsical ; and the water- vessels partake in the general dilatation. “The band which accompanies the vessel appeared to me to consist merely of contractile substance (connecting-tissue), and to serve as a mechanical support to the vessel. It terminates above in a mass of similar substance containing vacuola attached to the upper plate of the trochal disk.” This account differs from that of Leydig chiefly in the denial of the patent condition of the free ends of the vibratile tags, and consequently of the en- trance of the fluid from the cavity of the body through them into the lateral vessel. It also casts doubt upon coils of the water-vessel in the neck, and upon the presence of a small non-contractile sac at the inferior termination. of the lateral vessels, whilst, on the other hand, it répresents anastomosing branches between the vessels of opposite sides in the neck. Mr. Huxley’s description therefore appears rather to favour Mr. Dalrymple's hypothesis as to the contractile vesicle, whilst, with respect to the lateral canals, it is suggestive of a glandular excretory function. Dr. Carpenter adopts Prof. Huxley’s description of the tags, and of the inosculating vessels in the neck. - Cohn, in his account of Hydatina senta (Zeitschr. f. Zool. 1855, p. 444), describes two tubes as springing from the thick-walled, muscular contractile sac, lying on the abdominal surface of the animal, immediately subjacent to the skin, and communicating with the cloaca. These tubes are “respiratory canals; ” they have a finely granular wall, and advance with more or fewer curvatures and coils towards the head, where they appear to end in straight, blind, pointed ends or in loops, which attach themselves to the skin of the rotary organ. The “tags,” four on either side, affixed to the canal are triangular in One aspect, and shortly cylindrical in another, and supported on short pedicles, through which their cavity becomes continuous with the interior of the canals. The different figure of the tags from different points of view has given rise to the error of their being of two sorts—cylindrical and triangular. In Brachionws militaris the contractile vesicle is remarkable on account of its very large dimensions. It occupies as much as two-thirds of the abdominal cavity, and is composed of two chambers, of which the posterior is the larger. The diastole and systole of the two chambers are alternate ; the posterior opens into the cloaca, through a small duct. That there is a direct communication between the contractile sac and the cloaca, Cohn decisively proved by mingling colouring matter in the water, and wit– nessing a current inwards during each dilatation, and one outwards on each act of contraction, alternately—an experiment sufficiently conclusive of the respiratory mature of the Sac. The mechanism under consideration appears, as Leydig also remarks, to be occasionally absent—or perhaps only imperceptible. Dr. Dobie states that in Floscularia “no trace of a vascular system can be observed. The tremulous gill-like organs found in some Rotifers are here absent.” After his complete examination of Melicerta ringens, Prof. Williamson says—“I have found no special organs of circulation or respiration. . . . I detect no vessels or pulsating organs.” Nevertheless a structure at least resembling the vibratile tags was noticed in this animal by Mr. Gosse, who states that between the gizzard OF TEII. ROTATORIA. - 433 “ and the base of the stomach there was one little tremulous tag, of the same structure as in Notommata awrita. From the same spot also project, into a space of peculiar clearness, two trumpet-shaped bodies of the greatest delicacy, and without motion.” Prof. Williamson reminds us, in a note, that he has described two tubes springing from a pyriform organ, apparently hollow, and located immediately below the stomach. Though he saw no pulsation in this organ, it appeared to be the homologue of the contractilevesicle in other species. He believes the two filamentous organs to be tubular, and suggests the possi- bility of their supplying a spermatic Secretion, though he is not able to affirm it as a fact. He moreover observed the vibratile spermatozoon-like corpuscles “in various parts of the body, where they are apparently enclosed within hollow canals. I have never seen them occupying the two main trunks of the water-vascular system, as Caeca, nor can I succeed in tracing any con- nexion between them ; ” but it is probable that they were really located in some of the branches of that system, as observed by Mr. Huxley in Lacinw- laria. The glandular renal function of the lateral tubes and appendages has the support of analogy among other lowly-organized forms allied to the Rotatoria; but such an hypothesis falls to the ground, if, as Leydig thinks, the urinary concretions noticed and So named by him in embryo and young animals are deposited within the cavity of the intestine, and not in the contractile sac. Bowever, naturalists generally will certainly not accept the doubtful disco- very of the position and the interpretation of the nature of the particles offered by Leydig as conclusive evidence of the nature of those structures, but will, in the absence of direct and exact observation, be rather guided by analogy. We will therefore append some extracts, showing the comparative physiology of the supposed respiratory mechanism. Leydig writes—“There is the greatest similarity between it and the organs in Lumbricinae and Hirudince, which are conceived to have a respira– tory office. In these are similar contorted and coiled tubes, with a clear canal opening either without an intermediate contractile sac, as in Clepsine, or with one, as in Nephelis. Moreover, the canal opens by a wide ciliated aperture into the cavity of the body; and in this termination of the tubes I recognize the homologue of the vibratile tags of the Rotatoria. Moreover, the direction of the ciliary motion in the Annelida is inwards to the main canal. In the Lwmbricinae, Gegenbauer has attributed a renal function to the otherwise-called respiratory canal.” - Dr. Carpenter describes a “water-vascular system ’’ among all the vermi- form members of the Articulata, and as represented in its simplest type in the Rotifers. “Similar lateral vessels, often ramifying more minutely (especially in the head and anterior part of the body), are found in many of that group of vermiform animals clothed over the whole surface of their bodies with cilia, to which the designation Turbellaria has been given.” This writer surmises that the water-vascular system may contain some other fluid than pure water, and, as Van Beneden has suggested, may serve as a urinary apparatus. Prof. Huxley presented the following philosophical summary of the com- parative relations of the respiratory mechanism of the Rotifer; before the British Association:-‘‘In certain Distomata, such as Aspidogaster, there is a system of vessels of essentially similar character with that in Rotifer; but the principal canals, those lateral trunks which come directly from the con- tractile vesicle, present regular rhythmical contractions. The smaller branches are all richly ciliated. In other Distomata the lateral trunks appear to be converted into excretory organs, as they are full of minute granules: they remain eminently contractile; but their connexion with the system of smaller 2 F 434 GENERAL EIISTORY OF TEIT, INFUSORIA, ramified vessels ceases to be easy of demonstration. They still form one system; but the cilia are no longer to be found in the smaller ramified vessels. In certain Nematoidea the vascular system is reduced to a couple of lateral contractile vessels altogether devoid of cilia, but communicating with the exterior by a small aperture. Now in all these cases there is no doubt the vascular system is, physiologically, a respiratory and perhaps a urinary system, while the common cavity of the body represents the blood-vascular system of the Mollusca and Articulata. If this system, then, be not at all homologous with the blood-vascular system of the higher Annulosa, it is so with the tracheae of Insecta.” We may repeat here that the delicate and ciliated rotary organ must in some measure subserve the purpose of respiration, after the manner of the gills of a reptile or of a fish, by providing for the aération of the liquids contained within it through the agency of the constantly renewed contact of fresh water flowing over its actively-vibratile surface. OF THE NERVOUS SYSTEM AND THE ORGANS OF SENSE ; PSYCHICAL IENDOWMENTS. a. Of the Nervous System. — The existence of a rudimentary nervous system is now universally admitted; but at the period when Dujardin wrote, that talented observer felt that the state of knowledge respecting the Rota- toria was not sufficiently precise to establish the existence of nerves and of inervous ganglions. His scepticism was, no doubt, increased by observing the unphilosophical facility with which Ehrenberg described and represented nerve-cords and ganglions according to preconceived notions and loose ana- logies. Illustrations of Ehrenberg’s supposed nervous apparatus, and of its modifications of form in different animals, are to be found in his descriptions of every family and genus. Thus in giving the characters of Lacinularia, he says that “Ihear the Oesophagus is situated a nervous mass, the analogue of a brain divided into four or six lobes; also, as in Megalotrocha (XXXII. 374), two ring-like and radiating masses with a row of ganglions lying beneath the muscles of the ciliary wreath.” In Melicerta, he speaks of a curved gland- like band of nerve-matter; in Enteroplea, which has no eyes, of a brain-like knot, sending off a thick tortuous nerve-cord along the dorsal surface to the second transverse vessel, where the respiratory opening probably exists; of a ganglion placed beneath the eye in twenty-six species of Notommata, which in N. Copeus and N. centrura is three-lobed and seated above the maxillary bulb, whilst in the remainder it consists of one or more nervous ganglia seated amidst the muscles of the ciliary apparatus; and in Otoglena, of an oval cerebral ganglion with two dark appendages, a red eye, a long nerve- loop in the neck, with a prolongation backward, a forked ventral nerve, and two ear-shaped frontal protuberances bearing two visual points. - It would be useless to multiply these references; the general deduction from the many descriptions of Ehrenberg is, that there exists a cerebral or brain ganglion, which Supports the eyes, and by its extension encircles the Gesophagus like a loop, sending off nerve-cords in every direction, and often complicated by the presence of other nerve-ganglions about the head, neck, and body. Moreover, the apparent reticulations frequently visible below the ciliary wreath, which he sometimes viewed as a vascular network, he at others spoke of as a nervous plexus. The present prevailing opinion is similar to the above, viz. that there exists a brain or central nerve-ganglion above the Cesophagus, with outgoing nerve- fibres, and sometimes accompanied by supplementary ganglia in other regions. Nevertheless the special descriptions of Ehrenberg are not accepted ; the • OF THE ROTATORIA. 43 5 portions of tissue fixed on by him as nervous masses, receive in general an entirely different interpretation. Thus in the case. Of Lacinularia the Sup- posed 4–6–lobed brain, with extending nerve-fibres, is set down as mere col- lections of “vacuðlar thickenings,” with intercurrent fibres of connective tissue. The same interpretation is extended to the “nine pairs of ganglia, with fine interlacing nerve fibres,” in Notommata clavulata, and to the four or five such in Diglena lacustris; yet in both these species, the central or brain ganglion represented by Ehrenberg is allowed to retain this character by Leydig, who sets aside all the rest as mythical. The following critique on Ehrenberg’s views is from Prof. Williamson:— “The Small organs so common amongst the Rotifera, and which Ehrenberg regards as nervous ganglia, are abundant in the Melicerta, but they afford no countenance to the hypothesis of the great Prussian Professor (XXXVII. 17 k). They appear to be nothing more than small cells, or vesicles, formed of granular viscid protoplasm, very similar to those into which the yelk of the egg becomes divided. Sometimes they float freely in the fluid which distends the integument and bathes the viscera ; at others, thin ductile threads pass from One vesicle to another. . . . There is no uniformity in their arrangement in different individuals. They differ as widely as possible in their size, number, and distribution. So far from being nervous vesicles, they appear rather to be cells modified into a rudimentary form of areolar (connective) tissue. That they are hollow vesicles or cells, very viscous, readily cohering, and, owing to this coherence, readily drawn out by the movements of the various organs to which they are attached, are facts capable of easy demon- stration.” . A central nervous mass or brain, immediately subjacent to the eye-specks, and above the oesophagus or pharynx, which sends off nerve-fibres in different directions, is, as already intimated, generally admitted to exist. It is men- tioned by Siebold, Perty, Gosse, Dalrymple, Leydig, Cohn, and others. The two first-named authors allude to it as a group of ganglions; but Leydig affirms that, although it may be lobed, it is always a single and undivided organ. Some, again, have treated of it as forming a loop or ring around the gullet; but such a condition is denied by Leydig, who states that it only extends itself in the form of diverging nerves, which end by enlarged extre- mities, and never form loops, such as Ehrenberg represented, around the tubular process or respiratory siphon. This nervous centre or brain, supporting the eyes, is seen in the families Hydatinaea, Euchlanidota, and Brachionaba. Leydig, however, cannot admit the masses supposed to represent the cerebrum in the families CEcistina, Mega- lotrochaea, and Floscularia, nor the pairs of nerve-like ganglions at the base of the trochal disk of Stephanoceros, to have a cerebral character; he supposes them rather to be “coils of the respiratory canal, or heaps of granules or nuclei, such as are met with beneath the cuticle.” . Prof. Huxley discovers the nervous centre under a peculiar and unusual usual form in Lacinularia socialis. To quote his words—“On the oral side of the neck of the animal, or rather, upon the under Surface of the trochal disk, just where it joins the neck, and therefore behind and below the mouth, there is a small hemispherical cavity (about Tºrgth of an inch in diameter), which seems to have a thickened wall, and is richly ciliated within. Below this sac, but in contact with it by its upper edge, is a bilobed homogeneous mass (about sºuth of an inch in diameter), resembling in appearance the ganglion of Brachionus, and running into two prolongations below ; but whether these were continued into cords, or not, I could not make out. 2 F 2 436 GENERAI, EIISTORY OF TELE INFUSORIA. “I believe that this is, in fact, the true nervous centre, and that the sac in connexion with it is analogous to the ciliated pits on the sides of the head of Nemertidae, to the ‘ciliated sac of the Ascidians, which is similarly con- nected with their nervous centre, and to the ciliated sac which forms the olfactory organ of Amphioarus. “Mr. Gosse has described a similar organ in Melicerta ringens ; and I have had an opportunity of verifying his observations, with the exception of one point. According to this observer, the cilia are continuous from the trochal disk into the cup; so far as I have observed, however—and I paid particular attention to the point, the cilia of the cup are wholly distinct from those of the disk. The interesting observations of the same careful observer, upon the architectural habits of Melicerta, would seem to throw a doubt upon the pro- priety of ascribing to the organ in question any sensorial function. But however remarkable it may seem that an animal should build its house with its nose, we must remember that a similar combination of functions is ob- vious enough in the elephant.” - This last analogy is assuredly very far-fetched, and can serve nothing in the argument; and to us it seems a much more reasonable supposition that the homogeneous bilobed body below the ciliated cup is a gland, than that it is a brain ; were it a brain, Surely some nerve-fibres would be traceable from it into the interior of the animal. Of this body Prof. Williamson says—“I see no sufficient reason for assigning to the small organ nervous functions;” and he further remarks that “the ciliated sac or cup becomes so contracted when the animal is not busy in constructing its case, as to be almost invisible,” which is another circumstance discountenancing Prof. Huxley’s notion of its pur- pose. Cohn has no doubt of the cerebral nature of the large semiglobular mass, noticed also by Ehrenberg, in the head of Hydatina senta; and he records having frequently observed in its interior a large, transparent, circu- lar vesicle or vacuole. A large number of nerves are given off from its an- terior portion; but from its posterior, two thick fibres proceed backwards and outwards to the apparent ciliated opening on the surface of the back, and constitute a cervical loop. There is, however, no actual opening, but merely a ciliated fossa, which is probably a sentient organ. About the large cerebral ganglion are other lobules, also probably nervous, from which fibres are given off and possibly form a plexus between the alimentary tube and ovary, be- sides supplying the muscles. Above the ciliated fossa named, is another de- pression supplied with nerves; and, according to Ehrenberg, a similar one is present on the opposite side of the body. Various accessory ganglions or nerve-centres have been represented by authors at different parts of the body, mostly in relation with some of the principal organs, this arrangement being suggested by the known nervous system of other Invertebrata—for instance, the Mollusca, which have usually a special ganglion for the nervous supply of each principal organ of the body. Such a multiplication and disposition of ganglia, Oscar Schmidt endeavoured to demonstrate in Brachionus wrceolaris and in Hydatina senta. His inter- pretation has, however, not been accepted by others, and, generally, the characteristics of ganglions are so ill-defined, that the bodies considered to be such by the observer are pronounced to be no other than vacuolar thick- enings of connective or other dissimilar tissue by others. Perty makes the statement that in Hydatina, Synchaeta, and Diglena there is a series of ganglions along the anterior surface of the abdomen, with con- necting nerve-fibres between them and the brain. A nervous system of this sort belongs to the higher Crustacea; but although many have sought it in the Rotatoria, Perty is the only observer who has affirmed its existence in any. OF THE ROTATORIA. 437 Mr. Dalrymple mentions the presence, in his Notommata anglica, of a small ganglion sending off nerves to the stomach, salivary glands, and ovary; but Leydig looks upon this structure as no more than the cells and fibres of con- nective tissue, and states that “similar clear cells, of various size, having delicate elongated branches, are seen in Notommata centrura, N. Myrmeleo, N. clavulata, and in Diglena lacustris. The delicate branches, or threads, extend between the epidermis and the viscera of the body, and were described by Ehrenberg to be nerves, but are actually the means of retaining the vis- cera in situ,”—a conclusion supporting that of Prof. Williamson. There is, however, one set of nerves recognized by most observers, which proced from the cerebral ganglion to the surface of the body, ending at the bottom of the epidermic pits described above (p. 403), from which stiff cilia or bristles project, or, otherwise, running to the extremity of the protuberances and antenna-like processes, which are also armed with bristles. Dalrymple noticed nerves so distributed in Notommata anglica ; and Leydig has indicated the like in many species. The supply of a nerve to the so-called siphon or respiratory tube imparts to it the character of an antenna, tactile organ, or feeler. The evident delicate band or cord seen within the tubular process of Melicerta is indeed called by Mr. Williamson a muscular band; yet at least some portion of it must be esteemed a nerve-cord, if the organ in question really possesses tactile powers. - A similar distribution of nerves is witnessed in the Turbellaria, and, as Leydig says, among the Phyllopoda and Arthropoda. . . Nervous substance has its origin in simple cells, which in ganglia retain their cellular character, but in nerves appear to be elongated as tubes, the cell-wall constituting the nerve-sheath or the neurilemma−the cell-contents (the contained nerve-tissue) existing as a fine molecular matter. In nerve- masses or ganglions the original nuclei remain, and the several constituent cells are aggregated and held together by diffused connective tissue. Some peculiar structures, supposed to stand in especial relation to the nervous system, are described by Leydig. We cannot do better than follow his account in an abstract. Immediately above or about the brain-ganglion, in many genera, a sac is observable filled with a whitish substance, called by Ehrenberg the “chalk- sac '' (Kalkbeutel). Leydig confesses that he has hitherto been unable to determine whether this sac is in immediate connexion with the brain, or in- dependent of it. In Notommata centrura (XXXVIII. 26 t) it appears as a process or lobe of the brain; but in another species, N. aurita, the sać is so elongated as to form a thin stem filled with the chalk-like matter, which it seems to discharge by an opening on the head. This organ would therefore seem to partake of the nature of a gland. Beside the genera named, this sac is seen in Notommata tripws, in N. collaris, and in N. tardigrada ; also, if the black speck noticed by Perty be the same structure, in N. roseola. Ehrenberg refers to its existence in Diglena, Megalotrocha, and Brachionus; but in the last-named genus Leydig has failed to discover it. - The vesicular space or sac is, in several instances, not single; but two, three, or four are noticeable. Thus in Megalotrocha Ehrenberg mentions four opaque, white, spherical bodies at the base of the rotary organ. Another sac, distinct from the foregoing, is seen in Euchlamis and Notom- mata centrura, lying in the median line close above the brain, and discharging itself by a duct passing forwards to the cuticle. It contains no chalky matter, but is translucent and composed of clear cells. The peculiar and considerable organ which Leydig met with in Stephanocéros, placed in advance of the sto- mach, and consisting of a group of hyaline vesicles with a discharging orifice 438 GENERAL HISTORY OF THE INFUSORIA. on the neck, its observer is inclined to refer to the same category with the problematical structures of Euchlanis and Notommata centrura. He more- over seeks to establish an affinity between these organs and the Small clear space surmounted by a ring on the cuticle, situated in the middle line of the body, behind the frontal speck in Phyllopoda, such as Branchipus ; but even if this affinity be admitted, no light is thrown upon the functions of these questionable structures. & b. Organs of Sense.—The existence of some of the senses is to be in- ferred from that of a nervous system. The sense of touch is one concerning which there can be no question; that of taste, in its nature allied to the tactile sensibility, is very doubtful, whilst those of smelling and hearing may be pretty safely stated to be entirely absent. Lastly, the sense of sight is generally admitted to exist, and to have special organs, or eyes, for its exercise. Touch may be supposed to be diffused as common sensibility over the entire surface of the body, and especially developed in the soft tissue of the rotary organ, in its processes and antennae, and in the Soft processes arid termination of the pseudopodium. Something approaching a sense of taste has been imagined present, particularly in the antennae or feelers. If the faculty of hearing seems occasionally exercised, we must attribute the cir- cumstance in part to the perception of the disturbing cause by vision, and in part to the vibrations produced in the liquid. The visual organs (XXXVIII. 16–19, 33) have claimed particular atten- tion, and now have their existence in the majority of Rotatoria, at Some pe- riod of their life, satisfactorily proved. Dujardin, dissatisfied with Ehrenberg's hasty generalizations, and compelled to deny the visual character of the co- loured specks in various Protozoa and Phytozoa, looked, no doubt, with greater scepticism upon the Berlin Professor's representations of eyes in Rotatoria than he otherwise would have done, and started some objections against them. He says—“I will not deny a certain analogy between the red specks and the coloured points observed in Cyclopidae, and which may be called eyes; but I cannot assign to such specks a very high importance, seeing that they con- stantly disappear in the adult condition of many Rotifera, and otherwise show themselves more distinctly, according to the degree of development as deter- mined by the season and the place of development.” It should be noted, however, in reply to this objection, that a similar disappearance, on the at- tainment of the adult state, occurs in the parasitic Crustacea, the visual cha- racter of whose eye-specks or ocelli is not questioned. Moreover, although some coloured specks in the Rotifera are undoubtedly mere heaps of granules, yet others have assuredly a definite optical organization and function. These possess a refracting medium, the essential part of an eye; and their organ- ization, though simple and imperfect, yet elevates them to the rank of eyes, eyelets, or ocelli. - Ehrenberg gave much attention to the position, number, and other pecu- liarities of the eye-specks of Rotatoria, as he employed them largely in framing his classification. Unfortunately, however, he did not acquaint him- self sufficiently with their minute structure, but was content to call all the coloured specks he met with eyes, and insisted on unimportant and inconstant particulars as generic and specific characteristics. These errors have conse- quently much vitiated his classification (see chapter on Classification); and the tendency at the present day is to assign to the coloured eye-spots an al- together secondary rank among the characteristics of Rotatoria. Ehrenberg described the eye-specks as variously situated, on the fore part of the head (forehead) or on the neck, as mostly sessile (i.e. situated imme- To F TELE ROTATORIA, 439. diately on the part), and rarely pedunculate (i. e. Supported on a pedicle or stem), as in Otoglena. In some species, as in Rotifer, the eyes are placed on a protrusile part of the head, and consequently appear at one time in ad- vance of the head, and at another far backward within the body. In Monura, Ehrenberg states they are moveable. The number of eye-spots varies con- siderably : in several genera there is but one, e.g. Furcularia, Monocerca, Notommata, and Brachiomws; but two eyes are more common, as in Melicerta (XXXVII. 15), Lacinularia, Megalotrocha (XXXII. 376), Rotifer (XXXV. 476–478), and Diglena ; three eye-specks occur in Asplanchma, Triophthal- mus (XXXIII. 412–414), Eosphora, and Otoglena; four in Squamella ; and from six to twelve coloured spots and upwards are met with in Cycloglena and Theorus (XXXIV. 425–429), but their visual character is more than doubt- ful. These last “conglomerate eyes,” as Ehrenberg calls them, appear to be no other than collections of coloured (it may be oil) particles, and are akin to the large coloured spaces seen on Notommata forcipata and Symchaeta Baltica, having neither a definite nor a regular outline (see p. 440). Subse- quent research has proved Ehrenberg in error respecting the number of eyes in several species, an error which seriously affects his classification. * The ordinary colour of the eye-specks is red, but sometimes it is reddish- brown, and rarely violet or black. The colour may change in the lifetime of the individual, as from red in the young to black in the adult state. In a few instances no eye-specks are visible. Except some of the doubtful collections of coloured specks, the eye-spots are placed immediately above the great ganglion of the head, the homologue of the brain, or, as Siebold affirms, are united with it by intermediate nerve-fibres. The intimate structure of the eyes was ill-understood by the great Prussian Professor. He was unable to convince himself of the existence of a cry- stalline lens and of a cornea. Thus, in his account of Rotifer vulgaris, he states that the eyes consist of Several cells filled with a granular pigment, and sometimes they separate abnormally into several portions. He thinks there is no crystalline lens, although they are probably compound, like the eyes of insects. Siebold insisted on the coloured specks of Rotatoria being sharply defined, and in many cases, at least, furnished with a capsule, in contradistinction to the ill-defined vanishing pigment-masses imagined to be eyes in the Protozoa. Wagner also speaks of a lens in the eyes of Lacinularia. Perty is adverse to the notion of a lens or cornea, or of a capsule ; yet in Pterodina Patina he notes that the elliptical eye-speck, viewed on the side and from below, is seen to consist of an upper red and an under white half. That the latter represents a refracting medium is highly probable. A compound structure is further indicated by Perty in Scaridium longicaudum, in which he perceived “a mass of small granules resembling a gland, in the midst of the red pig- ment-corpuscles, which are outspread irregularly, and paler at the circum- ference. Moreover, in Euchlanis triquetra there is an irregular brown scale with reddish-brown contents, whilst in E. Luna the unusually large eye-spot appears to be made up of ten to twelve distinct red granules. . Leydig arranges the single eye-specks under three types:–1. an ordinary pigment-spot, of a rounded or irregular outline, a reddish-brown, black, or violet colour, not sharply defined, e. g. in Notommata Symchaeta ; 2. a de- fined, sharply-bounded speck, actually composed of two coalesced hemi- spherical portions, such is seen in Brachiomus; 3. a speck having a clear refracting body projecting from the mass of pigment—a structure discovered by Leydig in Euchlamis wrisetata (XXXVIII. 19). The first type is the most prevalent. 440. GENERAL ELISTORY OF THE INFUSORIA, Leydig next proceeds to show that the single eye-specks, appearing only as an accumulation of pigment-granules, are precisely homologous structures with the reputed eyes of Cyclops and Daphnia among the Entomostraca, and of Argulus, Artemia, and Branchipus among the Phyllopoda. In neither the one nor the other does a lens, cornea, or capsule exist, although in a few (for instance, in Notommata Myrmeleo) a glistening white substance is intermixed. The single eye-spot of Brachionus, with its coalesced central segments, has its counterpart in the eye of the larva of Cyclops, and an evident analogy with that of Cyclopsina, as also with that of Caligus, in both which a refract- ing lens makes its appearance, it is likewise similar in general conformation. Who then, asks Leydig, can advance any direct arguments against the hypothesis that, by the medium of the pigment-granules in immediate con- tiguity with the nerve-cells of the brain, without a refracting body, a percep- tion of light is possible 2 That the Rotatoria, on the contrary, may possess, equally with the Crustacea, a refracting medium, is illustrated by the example of Euchlanis wrisetata. With reference to those species having two eyes, Leydig has convinced himself of the presence of a lens in both in Pterodina, Ste- phanops, Metopidia, Rotifer citrinus, and in R. macrurus; and he thinks he has seen one in the eyes of the young of Tubicolaria, Melicerta, and Stephanoceros, although the soft state of the parts and their indistinct outline render the observation less certain. In the last-cited animals, when any trace of the eye-pigment remains, none whatever of the crystalline lens is visible. Of the other binocular Rotatoria, not mentioned, Leydig's opinion is, that ana- logy intimates the existence of a refracting medium, and their nature as true eyes. The presence of a special horny skin or a particular capsule sur- rounding the pigmentis doubtful; for the cuticle probably performs the office of a cornea. . Of the many-eyed Rotatoria, Leydig has particularly examined Eosphora and Theorus. He finds Ehrenberg in error respecting Eosphora, which, in fact, possesses a single eye-speck above the brain; and what that naturalist took to be two clear eye-points on the frontal margin are merely intensely orange- or yellow-coloured spaces, which are at once seen to be without any affinity with the other eye-specks. The eyes of Theorws are nothing more than oil- drops within the stomach-glands. Ehrenberg, moreover, describes colourless eyes, the visual nature of which may well be doubted. Although he has no direct observation, Leydig believes that in Squamella the pigment is composed of numerous portions disposed around a crystalline lens, and that the animal may consequently be called many-eyed. The conclusions arrived at by Leydig are, “that the single-eyed species of Rotatoria have, many of them, a refracting body in their eye-specks, which are therefore true simple eyes, but that in most cases a lens is wanting, and the specks are merely rudimentary eyes; whilst in those with two eye spots, each of them is, by the presence of a lens, an actual simple eye.” Ehrenberg stated that eye-specks were entirely absent in several genera: such were the doubtful Rotatoria Ptygwra and Ichthydium, also Chaºtonotus, Cyphonautes, Tubicolaria, Enteroplea, Hydatina, Pleurotrocha, Lepadella, Hydrias, Typhlina, and Noteus. With reference to Tubicolaria, Leydig shows that in the young state this genus has two eye-specks; of the other exceptional forms, several have been insufficiently examined to found any cer- tain statements upon. The curious fact of the disappearance of the eye-spots in several Rotatoria has been already referred to. Examples occur in the genera Melicerta, Laci- nularia, Floscularia, Tubicolaria, and Megalotrocha. c. The Psychical Endowments of Rotatoria are probably of the nature of in- OF THE ROTATORIA, g 441 stinct; some so supposed are simply acts dictated by external circumstances. Perty intimates that the apparent sinking after one another, the gamboling among themselves, and the fact of their depositing their eggs in chosen and ap- propriate localities, to which, after an absence, they will return, are pheno- mena evidencing perception, design, and a sense of company. This last imagined sense was one suggested by Ehrenberg, who affirmed that he had observed it in the case of Philodina roseola, which, when kept in glasses, deposited its eggs in heaps, the parent remaining a long time with the young ones pro- duced from them, and so constituting a sort of family or colony, an act dictated, as he surmised, by a sense of company or family. The occasionally-observed rejection, and ejection, of what may be deemed disagreeable or unsuitable nutriment, are acts which some might interpret to be indicative of volition, and, in some degree, of pain or unpleasant impression; but they are quite explicable without reference to a sentient nerve-centre, or to high psychical endowments. The same thing may be said of other reputed evidences of the existence of psychical or mental faculties. - - OF THE REPRODUCTIVE ORGANs AND DEVELOPMENT OF ROTATORIA.—The Rotatoria were for a long time assumed to be hermaphrodite or monoecious, i. e. that each individual possessed a perfect male and female reproductive apparatus, by which ova are formed, and fructified without the presence or contact of any other individual. There has never been any difficulty in determining the female generative organs, which are very clear and well defined; but the greatest diversity of opinion has subsisted respecting the coexistence of male and female organs in the same individual. Dujardin attempted no explanation of this matter, whilst Siebold candidly affirmed that in the absence of any precise knowledge as to the male organs, it is impossible to say whether the Rotatoria are monoecious, or have the sexes separate—are dioecious. The clearing up of this questio vealata, in several at least of the Rotatoria, is due to our countryman Mr. Brightwell of Norwich, who demonstrated the existence of distinct male animals, and figured them (XII. 65, 66) in his ‘Fauna Infusoria.’ This discovery was further carried out by Mr. Dal- rymple, and has subsequently been extended by Mr. Gosse, Leydig, and others. Inasmuch, however, as the monoecious or hermaphrodite condition is very prevalent among the lower Invertebrata; as the males of the majority of the Rotatoria have as yet escaped detection ; and as there are parts dis- cernible in several of them presenting some similarity with recognized male organs in other animals, not a few eminent observers still incline to the belief that, at least in a portion of this class, the sexual organization is of the monoecious type. These doubtful organs will be discussed after the well- determined female apparatus, and the male animals, have been described. FEMALE REPRODUCTIVE ORGANs.-These were pretty accurately determined by Ehrenberg, who noticed a single or double ovary, an oviduct, an ovisac, and a vaginal sheath or outlet leading to the cloaca or the rectum. The ovary, in which the ova or eggs are generated, lies immediately beneath or behind the alimentary canal, between it and the contractile Sac (XXXVIII. 26 o, p: XXXVII. 1 e, 19 h, 32 c); its anterior border often advances as far forward as the maxillary (oesophageal) head. Oftentimes its position is rather transverse, and it lies across the intestine, or is curved to some extent around it. It varies in size, but is always a very large organ, and occupies a consider- able space in the interior of the body. It also presents much diversity of figure, being sometimes round, oblong, or oval, at others flattened, elongated, reniform, bilobed, horned, or curved like a horse-shoe. It is enveloped by à delicate membrane, rendered very obvious by the action of acetic acid 4:42 GENERAL EIISTORY OF TELE IN FUSORIA. (XXXVII. 220), which contracts the substance of the ovary, and throws the membrane into sharp folds. This membrane may likewise be detected With- out the assistance of chemical reagents, where it is contracted below into an outlet or duct opening in the cloaca. It forms a pellucid membranous bag, which may be ruptured by pressure, giving exit to its viscid contents; and Leydig asserts that the wall of the ovary is contractile, as the addition of alcohol demonstrates. - The substance of the ovary is called the ‘stroma' or protoplasm ; it has a finely-granular appearance and a viscid consistence. It is usually of a milky or a light-grey colour, and has interspersed in it, besides granules, numerous clear bodies of a vesicular appearance (XXXVII. 1 e ; XXXVII. 7), but which, Leydig says, are really homogeneous. Williamson counted between 20 and 30 in the ovary of Melicerta, varying in diameter from Tºrgth to Tºrpth of an inch (XXXVII. 22). These, by development, constitute the ova or eggs, and may be termed rudimentary ova. Within each a finely-molecular, more or less opaque, and rounded body is perceptible (the nucleus), Surrounded by a clear, transparent ring, apparently filled with fluid (the germinal vesicle) (XXVII. 6, 7). “These are,” writes Huxley, “the germinal vesicles and spots of the future ova. Acetic acid, in contracting the pale Substance, groups it round these vesicles, without, however, breaking it up into separate masses. It renders the nuclei more evident.” This author further remarks, “the pale clear space is sometimes seen to be limited by a distinct membrane.” The measurements of the nuclei in Melicerta are, according to Williamson, from gºrgth to Tºrgth of an inch in diameter. Within each nucleus are usually from one to three clear spots—the nucleoli. The nucleolus, as understood by Williamson, corresponds with the nucleus in the preceding description, whilst this last term is applied by Huxley to the entire germinal body or rudi- mentary Ovum. - FoEMATION OF OVA, THEIR ExTRUSION, AND DEVELOPMENT.—After fructifi- cation, and preparatory to their transition into ova, the germinal spaces undergo various changes in constitution and appearance. The germinal vesicle en- larges, its nucleus disappears, and the ovum is indicated only by an ill-defined transparent spot, which may, by pressure, be isolated as “a small spherical cell about Túrgth of an inch in diameter, having very thin pellucid walls, and scarcely any visible cell-contents” (Williamson). Consentaneously with these movements in the germinal space, the construction of the ovum pro- ceeds by the attraction and separation of a portion of the surrounding proto- plasm forming a yelk. The portion so appropriated is particularly rich in granules which have previously congregated in the ovary, and now attracted, - it may be supposed, by the active vital action set up in the rudimentary ovum. This abundance of granules produces a deeper colour and an increased opacity in this portion of the ovary; so that when, as Prof. Williamson re- marks in the instance of Melicerta, this process of development proceeds in the centre of the ovary, the latter organ appears divided by the incipient ovum into an upper and a lower half. The consequence of these several changes is that the resultant ovum is of considerable size (XXXVII. 170) and stands prominently outward from the general Surface of the ovary, acquiring at the same time an independent character by the production of a limiting membrane about the vitellus or yelk, called the Vitelline or vitellary membrane. Huxley, indeed, does not regard this as a distinct and specially produced covering, but as derived from a portion of the enclosing membrane of the ovary, pinched off from the rest. Prof. Williamson enters into a comparison of the development of the ova of Melicerta with that of the higher Mammalia, to show the close relationship OF TEIE ROTATORIA. . 443 that subsists between them during this process. We have not space to follow out this piece of comparative physiology in the words of the author, but can Qnly state his conclusions: viz. that the elements which are contained in and solely occupy the ovisac of the Melicerta, are those which, in the ovaries of the higher Mammalia, are restricted to the interiors of the Graafian vesicles; that, whilst in the former the protoplasmic stock forms one undivided mass from which portions are successively pinched off to form the ova, in the latter (the Mammalia) it is divided into Small portions, each being contained within a special receptacle or Graafian vesicle, the interspaces being occupied by the stroma or tissue of the Ovary. It is in the yellº-matter, derived from the protoplasm, that the red tint noticed by Ehrenberg and others occurs ; the colour depends on red element- ary granules, and on highly refractive oil-like particles. Mr. Gosse suggests that “possibly the colouring matter of these reservoirs may be resolved into the red pigment of the eyes, and the yellow of the jaw-cushion and other parts; ” such a destiny we deem scarcely probable. Moreover the appear- ance of oil-molecules often refracting a red colour, about parts in which active development is proceeding, is a fact very generally observed. A red hue of the ova is seen in Philodina roseola, Brachionus rubens, Mastigocerca carinata and Polyarthra; in Notommata Sieboldii, Asplancha, Anuraea curvicornis, Symchaeta pectinata, and in Lacinularia socialis. Leydig believes that in many forms, e. g. Brachionus, Notews, and Euchlamis, one portion of the ovary produces almost exclusively the yelk, and has in consequence a darker colour than the other part, which developes the germinal spaces. This phenomenon has, he remarks, its analogue in various Crustaceans—the Hearapoda and Asellina. It may be here stated, however, that the darker portion of the ovary has assigned to it, by other naturalists, the office of preparing the winter ova, presently described, rather than the yelk, as supposed by Leydig. The preceding account, indeed, applies particularly to the production of the ordinary ova; the early history of the winter ova referred to will be given in the account of development. . THE OVA.—The Rotatoria develope two varieties of eggs, called re- spectively “summer” and “winter” ova, besides male eggs. Much difference obtains between them, especially in their developments, contents, and later history. The summer eggs have thin, Smooth, firm, and elastic shells, so transparent that the course of the changes proceeding within may be watched throughout. In figure they are ellipsoid, oval, or ovoid (XXXVII. 5, 6, 8, 9). They are laid by the animals during the whole course of the summer, and are forthwith hatched. The winter ova, on the contrary, are chiefly produced in the autumn, and are destined to remain in an inactive or torpid state during the winter. They are generally of larger dimensions, often irregular in form, from inequality of the two sides, or from prominences or depressions of the surfaces (XXXIX. 20), and opaque on account of their dark granular con- tents and of their double shell (XXXVII. 21, 22, 24). Caustic potash renders the shells clearer and more transparent, and causes some of the inequalities of their surface to decrease. Huxley says that the tough elastic membrane or shell is soluble in both hot nitric acid and caustic potassa. Between the two shells is an interspace, more roomy, at the opposite ends of the egg. The inner shell is thin and delicate, and immediately envelopes the yelk enclosed in its vitelline membrane. The external one is thicker, firmer, and usually of a brownish-yellow colour. Its surface is mostly roughened, or tuberculated, striated, or thrown into ridges, areolated, cellular, or divided into facets, beset with longer or shorter hairs and bristles, and occa- sionally with spines. Examples of such modifications of the surface occur in 444 GENERAL HISTORY OF TELE INFUSOR.I.A. Anwroea Testwdo, A. serrulata, Notommata Sieboldii, N. Myrmeleo, Melicerta ringens, Ascomorpha Germanica, Lacinularia socialis, Scaridium longicawdum, Hydatina senta, Anuraea valga, &c. Ehrenberg was not prepared to admit the existence on ova of actual hairy processes, but supposed them to be the hair-like filaments of Hygrocrocis, or of other Algae. This supposition may in some cases be correct ; for ova, like other bodies in the water, may become the nidus for the growth of various microscopic plants and animals. That some ova, however, are actually hairy is evidenced by their visible occurrence in that state even whilst still within the abdomen of the parent; as may be seen in the ova of Hydatina senta, of Notommata Parasitus, &c. Both winter and summer ova may often be met with in the same animal (XXXIX. 16)— the one kind perhaps still in the ovary, the other on the point of expulsion ; or, it may be, both sorts may be carried about attached to the posterior part of the parent animal. This last occurrence is noticed by Leydig in Brachionus Baker. These two varieties of ova were recognized by Ehrenberg, who assigned them the names applied to them, Mr. Huxley suggests, instead of the term “winter ova, the appellation, ‘ephippial' ova, to indicate their analogy with the similar eggs of Daphnia and other Entomostraca. When recounting the propagation of Notommata Sieboldii, Leydig remarks that male and female ova are not developed together in the same animal. This fact has been extended by Cohn to apply to the whole family of Rota- toria. According to him the ephippial are always distinguishable by their external characters from the common summer ova, particularly by their much smaller dimensions. They have thin, transparent shells, and are chiefly pro- duced at those seasons when “ephippial' ova are generated. Their develop- ment follows the same course as that of the ‘summer’ ova; but they are pro- duced in very much smaller numbers, a circumstance that affords another reason for the paucity of males compared with females, whenever a collection of Rotatoria is examined. When the development of Summer ova in the ovary has proceeded to the point we have mentioned, and the egg is already become a distinct body from the general substance of the ovary (XXXVII. 2 d), it is slowly moved down- wards towards the passage or oviduct (XXXVII. 2.f), which ends in the cloaca (XXXVII. 32 d); and it is in this part of its course that the shell becomes perfected. In the majority of the Rotatoria the ova are at this stage extruded, the further phases of development proceeding externally to the animal; in others they are detained in their passage until the embryo is more fully elaborated, or even until it is perfect and released from its shell. The size of the ova prior to expulsion XXXVII. 32d; XXXVIII. 26 p) is very extraordinary, so much so that a single ovum will sometimes occupy the larger portion of the interior of the animal. The completed egg of Me- licerta has an average length, says Williamson, of ++gth of an inch, and a diameter of gº-gth. The eggs of some Hydatinae are gºth, of Lacinularia +}oth of an inch and upwards in diameter. In several Rotatoria, two or more ova become agglutinated together near the termination of the Oviduct, or in the cloaca, and are expelled together en masse, and still remain adherent to the parent, close to the cloacal outlet at the base of the tail. This is exemplified in Triarthra (XXXVIII. 30 d), Po- lyarthra (XXXIII. 400, 401), Anuraea (XXXV. 496; XXXIX. 16), and Notews. - The Oviduct, or passage from the ovary to the cloaca, is a membranous tube formed by a prolongation of the tunic of the ovary. It is always extremely dilatable; and sometimes an egg is so long detained in its lower part, that it OF TELE ROTATOR1A. 445 seems to serve the purpose of a uterus, and has received the name of ovisac. The orifice of this oviduct or ovisac into the cloaca is called the “vaginal orifice; ” the vaginal sheath, spoken of by Ehrenberg, would appear to be either the termination of the Oviduct or sometimes the cloaca itself. The oviduct may occasionally be deficient. Prof. Huxley states that he could discover no such passage in Lacinularia. - The egg, having descended into the cloaca, is expelled thence by means of a strong contraction of the whole body, and, in the act of escaping, involves the eversion of the cloaca. The time occupied in the formation of the sum- mer egg, from its first appearance as a vesicular space in the ovary to its completion and extrusion, is very brief, generally only a few hours. We have noted the discharge of several eggs adherent together, and their subsequent attachment at the anal outlet. In other Rotatoria, likewise, ova expelled singly attach themselves at the posterior extremity of the body, singly or united together by a gelatinous matter, and not uncommonly at- tached by evident cords or pedicles to the parent. This is seen in Megalo- trocha, in Brachiomws rubens, and in B. Pala. In the species last named, as many as ten may often be seen in a group near the cloacal orifice. In Ascomorpha, Some six may be found adherent. In Polyarthra (XXXVIII. 30), not more than one egg is found attached at the same time. Thus the eggs are carried about by the parent one after another, arriving at maturity and escaping from its shell. The like phenomenon is seen in various Entomostraca, and in Polymoé, Ea'ogona, and other Wermes, which likewise produce both summer and winter ova. Among the urceolate Ro- tifers, the eggs escape into the case or gelatinous investment, and there pro- ceed to their ultimate development, Safe from many obnoxious influences and from destruction by other animals. DEVELOPMENT OF THE EMBRYo. —The following changes transpire pre- paratory to the construction of the embryo. The nucleus is seen to elongate, and then to present a constriction about its middle (XXXVII. 5); the yelk at the same time shows a similar constriction, which continues to deepen in correspondence with that of the nucleus, until at length there are two seg- ments, each with its contained nucleus—the result of the fission of the primary one. Leydig states that this division is not into two equal portions, but that a segment is cut off from one end or pole (XXXVII. 2 b), and that in the continued segmentation which ensues, this same unequal fission is again and again repeated. However this may be, the act of division goes on (XXXVII. 8) until at length the whole yelk is broken up into a mass of minute cells, and its opacity increased by the number of molecules they con- tain (XXXVII. 2 c, g). Out of this mass, the tissues and organs of the em- bryo are developed, appearing in their characteristic forms without any, or otherwise very slight, transitional phases (XXXVII. 2 e, d; XXXVIII. 9). It is characteristic also of Rotatoria, in common with all the Vermes, that the embryo is generated from the entire yellº, and not, as in Crustacea and still higher animals, from an accessory body Superposed upon the yelk, into which the yelk is gradually taken up. Dr. Carpenter remarks that the mode of development is in all essential respects the same as that of the Nematoid Entozoa, each group of cells evolving some one principal organ. The order of succession of the parts of the embryo in the egg is thus de- scribed by Ehrenberg in the instance of the Megalotrocha albo-flavicans:– “A turbid central spot appears, which becomes the oesophageal bulb and teeth; a blackish granular oval body is also seen posteriorly; the eyes gra- dually become red, and a motion of the cilia of the head is visible; after some hours the whole foetus, which is folded up, turns itself round, the shell bursts, 446 GENERAI, EIISTORY OF TETE IN FUSOTRIA. and the young animal creeps out.” In a specimen of Brachionus Baker: the first thing Mr. Brightwell detected was a motion like that of the muscular Oesophagus of the parent. * - The best account we have of the subject is that given by Prof. Williamson of the Melicerta ringens —“The first trace,” he says, “ of future organiza- tion which presents itself, appears in the form of a few freely moving cilia . . . . at two points, one of which corresponds with the future head, the other near the centre of the ovum. . . . with the cavity of the stomach; shortly after. . . . traces of the central parts of the dental apparatus present them- selves, this, again, being soon succeeded by the union of the entire mass of yolk-cells, and the formation from them of the various organs of the animal. The cilianow play very freely, especially at the head. The creature twists itself about in its shell; two red spots appear near the head, which Ehrenberg re- gards as organs of vision, and along with them a very dark-brown and some- what larger spot is developed in the integument near the lower stomach, The young animal now bursts its shell; . . ... and although its external ap- pendages (XXXVII. 15), and especially the rotatory organs are imperfectly developed or unexpanded, yet the whole of its internal organization, though but obscurely seen, is nevertheless that of the perfect animal, and not that of the larval state.” - In the embryo animal, whilst within the egg (XXXVII. 2 k), as well as for a short time after its escape (XXXVII. 3, 4 b), Leydig finds in most Ro- tatoria the collection of black or dark-brown particles close upon the cloaca (XXXVIII. 7, 8, 9), which has been described in the section on Secretion, as a supposed mass of urinary concretions. - The period occupied in the development of the embryo differs in different species. Ehrenberg stated that in Hydatina senta, eleven hours after the deposition of a complete ovum, vibration of the anterior cilia was visible, and in 24 hours the young being escaped from its shell. Mr. Brightwell, in his notice of Brachionws Bakeri, states that “about 2 o’clock the animal was ob- served with one egg placed externally between the two posterior spines of the shell, and another Small egg in the left side of the animal, which increased much in size in the course of the day; at 9 in the evening a motion was per- ceived in the exterior egg like that of the muscular obsophagus of the parent; and about this time the internal egg was protruded and placed by the side of the other, being longer than it. At 11 the young Brachionws burst with a bound from the egg in which the motion was perceived, and affixed itself by its tail.” - The egg-shell splits open, longitudinally or transversely, to give exit to the young animal. This seems brought about by the active movements of the embryo itself, which sometimes bursts (as Brightwell says) with a bound or spring from its prison. Where the eggs have been attached, the empty fissured shell continues still adherent for a time, until by the movements of the parent, or by some accident, it is detached. The variation among different Rotatoria in the stage of development in which the ovum is found when it quits the ovary, or when it is expelled from the body, has been already remarked; but additional illustrations are desira– ble. In the greater number, the egg is laid just before or very soon after the process of segmentation of the yelk commences; for example, in Meli- certa, Lacinularia, and Brachionus. In many genera the ovum continues in the oviduct, the ovisac, or the cloaca, or otherwise remains within the ovary itself until the embryo is complete and even free. Examples of this are found in Stephanoceros, Actinuºus, in Rotifer, and in Notommata Syrino, N. Sie- boldii, and in Asplanchma. In Rotifer, Ehrenberg remarks that, in the ova- OF TEIIE ROTATORIA. - 447 rium, four or five ova sometimes so completely develope themselves, that the young Creep out of their envelopes, in which they were coiled up in a spiral manner, extend themselves, and put their wheels into motion while within it ; and they sometimes occupy two-thirds of the bulk of the parent. So Mr. Gosse tells us that in Asplanchna “the ovum produces the living young in the ovisac, which, when matured, occupies the whole lower part of the parent.” The occurrence of embryos free within the saccular ovary of Ste- phanoceros (and still more, if as some have thought, they detected them loose - in the general cavity of the body) forms another bond of affinity between this aberrant genus of Rotatoria and the Bryozoa. Where the young in general quit the parent in a free, and so far perfect form as to be able to lead at Once an independent existence, the animals may be said to be viviparous (producers of living young). This viviparousness (viviparity) is still more pronounced in some Philodinaea and in Albertia, in which the formation of an actual egg-shell seems to be omitted, and the developed embryo to be at once liberated within the Sac of the ovary, where it may be seen in active movement. - THE EMBRYO METAMORPHOSIS.—It has already been remarked, generally, that the embryo on emerging from the egg has all the characters of its class, and is complete in its internal organization ; that any dissimilarity between the new-born and the adult animal is due, not to the absence of parts or organs, but to their lesser growth and their imperfect expansion or evolution. In other words, the Rotatoria undergo no positive metamorphosis; they pass through no intermediate phases of existence, no larval form resembling that of any Protozoa, in advancing from the embryonic to the complete and per- fect condition. - Leydig does not partake this opinion, but thinks that a metamorphosis is exhibited in the course of development of most or all Rotatoria, certainly not complete, but still sufficient to advance it as a phenomenon of the class. He specially adduces the instance of the embryo of Stephanoceros, as the most striking proof (XXXVII.3, 4), and he adds that, if the representation by Ehrenberg of the young of Triarthra longiseta be correct, the fact of a meta- morphosis must be recognized also in that genus. Again, he notes the great difference between the newly-born and the adult animals in several genera, e.g. in Tubicolaria and Melicerta, where the ciliary wreath is still very simple, and the absence of the tentacles (antennae) sufficiently notable (XXXVII. 15) to render the subsequent modifications an act of metamor- phosis. Moreover, the disappearance of the bunch of cilia in the young state at the end of the pseudopodium, and likewise that of the coloured eye-specks in many genera, when the adult condition is attained, are also indications of the same phenomenon. - The advocacy of this opinion was especially incumbent upon Leydig, in order to furnish an additional argument in favour of the affinity of the Rota- toria with the Crustacea. But even were the evidences of metamorphosis among the Rotifera as complete as he represents, they would serve his pur- pose, of demonstrating the affinity he advocates, but little, seeing that the immature Rotatoria have no real resemblance to the larval Crustaceans with their three pairs of jointed feet. Cohn (Siebold’s Zeitschr. 1855, p. 481) has discussed this question, and Surmises that the peculiar embryo of Stephano- ceros, which Leydig cites as the strongest instance of an act of metamor- phosis, is a male being (XXXVII. 3). As to the other supposed instances, Cohn disproves its occurrence in Brachionws, and considers the disappearance of the eye-speck in Tubicolaria and Melicerta too trivial a circumstance to urge in its Support. - - e 448 GENERAL ELISTORY OF THE INFUSORIA. Perty seems struck by the considerable variations in form between many embryo and adult Rotatoria, and enunciates the opinion that many supposed perfect forms are no other than embryonic conditions,—for example, Glen0- phora Trochus, Monocerca valga, Notommata Felis, and Cycloglena elegans. We do not understand whether he believes in a metamorphosis, or if he would simply state that Ehrenberg unnecessarily multiplied genera and spe- cies by describing immature beings as distinct forms. If the latter be all that Perty intends, we entirely concur with him. It is necessary to detail the form and structure of some embryo Rotifera,' to illustrate the preceding statements. The embryo of Stephanocéros (XXXVII.3, 4) is thus described by Leydig —“It has in general a vermi- cular figure. The head, which supports the eyes, is separated from the trunk by a well-marked constriction, and is furnished with long cilia. The head and cilia are retractile. The red specks (two in number) appear actually to be of the nature of eyes; they have a sharp outline and are slightly concave in front, as if a refracting body was there seated. Within the abdominal cavity behind the head, a peculiar striation is observable, the purpose of which I cannot imagine; further backward is a clear space in which long cilia are seen in activity, and which indicates the cavity of the alimentary canal. Moreover, the maxillary apparatus, and the special vesicle containing the inorganic particles (urinary concretions) are perceptible. The termina- tion of the body bears some delicate vibratile cilia.” Beyond this phase of development, the embryo does not advance in the egg, but after being hatched, it would seem to assume another intermediate form before arriving at the adult state. Leydig found, in water containing Stephanoceros, a young animal still possessing in some measure the previous vermiform figure and apparent articulation of the trunk and foot, and a proboscis-like head with four projecting arms. The eye-specks were still present. From the trunk- like process of the head, two considerable tubular appendages were out- stretched, ciliated at the extremities: the cilia on the end of the foot-process had disappeared, but were very evident in the abdomen, near to the sac con- taining the inorganic particles. The mandibular apparatus had the regular structure. He frequently encountered also another variety, which, together with the figure of the perfect animal, had five arms, but was without any apparent Sexual organs, while the foot-process and the whole body were strewn with numerous fat-globules. We will now continue the description (see p. 446), by Prof. Williamson, of the embryo of Melicerta after escaping the egg-shell. He writes—“The young Melicerta stretches itself out, and, everting the anterior part of its body, unfolds several small projecting mammillae covered with large cilia, by means of which it floats freely away (XXXVII. 15, 16). These mammillae are in this stage not unlike those of Notommata clavulata, but they soon en- large and become developed into the flabelliform wheel organs of the mature animals. The dental apparatus is now fully developed; the alimentary canal and muscular fasciculi are all present, only the epithelial cells of the former have not as yet obtained their yellow granular contents; consequently the viscera exhibit the same hyaline aspect as the rest of the organism. The two red specks are imbedded in two of the mammillae. After swimming about for Some time like other free Rotifera, the animal undergoes further changes. The dark-brown spot is the first to disappear; and soon after, the two pink ones cease to be visible. The animal attaches itsclf by the tail to some fixed support, and developes from the skin of the posterior portion of its body a thin hyaline cylinder, the dilated extremity of which is attached to the sup- porting object. The formation of the case is now begun ; the first-formed OF THIE IROTATORIA. 449 spheroidal or tentacular particles are arranged in a ring round the middle of the body, and appear to have some internal connexion with the thin mem- bramous cylinder. At first, new additions are made to both extremities of the enlarging ring; but the jerking contractions of the animal at length force the caudal end of the cylinder down upon the leaf, to which it becomes se– curely cemented by the same viscous secretion as causes the little spheres to cohere. All the new additions are now made to the free extremity, which, as Ehrenberg remarks, never extends beyond the level of the cloacal aper- ture of the outstretched animal. In the new-born being, therefore, the parts, as in the adult, are all present; they only require to be expanded by the ordinary process of growth.” - - Mr. Gosse's account of a newly-hatched Melicerta implies a greater aber- ration of form than that narrated by Prof. Williamson. He states that “ its form is trumpet-shaped like that of Stentor, with a wreath of cilia around the head, interrupted at two opposite points. The central portion of the head rises into a low cone.” After various movements and gyrations for an hour, the young animal Settled itself, and the form of the adult became manifest: “the four petals of the disk were well made out, though the sinu- osities were yet shallow ; the antennae at first were only small square nipples, but soon shot out into the usual form ; the ciliated chin was distinct, as was also the whirling of the pellet-Cup immediately beneath it.” We are indebted to Mr. Huxley for an elaborate description of the young of Lacinularia socialis (XXXVII. 10, 11). “The youngest foetuses,” he writes, “are about ºth of an inch in length. The head is abruptly trun- cated, and separated by a constriction from the body; a sudden narrowing separates the other extremity of the body from the peduncle, which is ex- ceedingly short and provided with a ciliated cavity, a sort of sucker, at its extremity. The head is nearly circular seen from above, and presents a central protuberance, in which the two eye-spots are situated. The margins of this protuberance are provided with long cilia; it will become the upper circlet of cilia in the adult. The margin of the head projects beyond this, and is fringed with a circlet of shorter cilia in the adult. The internal organs are perceived with difficulty; but the three divisions of the alimentary canal, which is as yet straight and terminates in a transparent cloaca, may be readily made out. The water-vascular canals cannot be seen; but their pre- sence is indicated by the movement of their contained cilia here and there. “In young Lacinularia, ºth of an inch in length, the head has become triangular ; the peduncle is much elongated, and it gradually takes on the perfect form. The young had previously crept about in the gelatinous in- vestment of the parents; they now begin to “swarm,” uniting together by their caudal extremities, and are readily pressed out as united, free, swim- ming colonies, resembling in this state the genus Conochilus.” Mr. Brightwell gives the appended brief account of the Brachiomus Baker. on its escape from the egg —“At first it had the appearance of an oblong ball; by degrees the anterior part spread, and the wheel processes were de- veloped. Soon after, the posterior shell (lorica) processes were visible in a semilunar shape, with the points nearly touching each other, which gradually expanded.” - These examples are sufficient to illustrate the general character of embryo Rotatoria and their progressive assumption of the adult form ; they more- over furnish evidence of the doctrine that there is no metamorphosis, or transformation, in the proper sense of the word—no change but what is expli- cable by the Ordinary laws of growth, or progressive expansion or evolution. Ehrenberg has announced it as a fact (Monatsb. d. Berl. Akad. 1853, p. 532), 2 G 450 GENTERAL ELISTORY OF TEIE INFUSORIA. that Rotifera found at great altitudes among snow do not attain a complete development, but retain, as he expresses it, an ovate contracted figure within an egg-like envelope or capsule, through which food reaches them by a funnel-shaped canal. All the functions of life he represents to go on as usual under these peculiar conditions of existence, including the deposition and hatching of eggs. This account reads like a description of an encysting- process in the first degree—that, viz., for self-defence and preservation— such as is illustrated in the formation of an open sheath around Stentor, as stated by Cohn (see p. 284). - CoNTENTS AND DEVELOPMENT OF WINTER OVA.—The contents of “winter ’’ widely differ from those of “summer’’ ova. Mr. Gosse gives the following account of those of Melicerta ringens. He writes—“Opening one or two cases (urceoli), I find one and another very curious egg-like bodies, not sym- metrical in shape, being much more gibbous on one side than the opposite, and measuring Tºgth by gºth of an inch. Each was encircled by five or six raised ribs running parallel to each other longitudinally, somewhat like . the varices of a wentle-trap : viewed perpendicularly to the ribs, the form is symmetrical—a long narrow oval. The whole surface between the ribs appeared punctured or granulate, and the colour was a dull-brownish yellow. Under pressure it was ruptured, and discharged an infinity of atoms, of an excessive minuteness, but every one of which for a few seconds displayed spontaneous motion. Their whole appearance, and the manner in which they presently turned to motionless disks, were exactly the same as the spermatozoa which the male eggs of other Rotifera contain, except that these were so minute.” Mr. Dalrymple describes similar peculiar ova in Notommata (Asplanchna) to consist of an aggregation of cells and of pigment-granules, without a dis- tinguishable germinal vesicle. The most complete and satisfactory account of the structure and develop- ment of the winter ova is supplied by Prof. Huxley in his History of Laci- nularia (T. M. S. 1852, vol. i.); we will, however, preface it by Leydig's description. We learn from this writer that in winter ova, a space filled with fluid usually intervenes between the yelk at each pole or end of the egg, and the inner shell, as in Tubicolaria, and that, according to Weisse's observation of Brachionus wrceolaris, the outer shell, when the embryo is ready to come forth, springs open in a valvular or a lid-like manner. The central portion of the yelk has a darker and more granular appearance, and is surrounded by a clearer peripheral or cortical lamina, as in Brachiomºus Bakeri, Notommata Myrmeleo, and N. centrura. Intermingled with the yelk- molecules are numerous clear vesicles, and oftentimes fat-particles; moreover, the yelk of Notommata Sieboldii has a yellowish-red colour (XXXVII. 27, 28). These “lasting ova,” as Ehrenberg has otherwise named them, are always developed externally to the animal. Like the summer eggs, they are fre- quently carried about by the parent ; it would not seem, however, that they ever accumulate in groups about the cloaca, but that mostly the egg is solitary, and that two or three are of rare occurrence. Thus in Brachiomºus Bakeri and in Ascomorpha never more than one is present, in Brachiomus owbens a couple are occasionally noticed, and in Notommata Sieboldii the highest number seen was three. Concerning the changes ensuing on development, Leydig states that, “ on the formation of a membrane around the commencing ovum in the ovary, the peripheral portion of the yelk exhibits numerous clear spots, which recall the appearance of the small cells originating from repeated fission of the yelk of the summer ova. From this we may conclude, either that the germi- Ol' TEIE ROTATORIA. 451. mal vesicle may, by repeated fission, resolve itself into numerous clear vesicles, without any further change, except that of an attendant grouping of the yelk- particles about the products from the germinal vesicle, or that perhaps the winter eggs, at their origin in the ovary, enclose a number of nuclei (germinal vesicles) unlike other ova, which never commence with more than one nucleus (germinal vesicle). If,” continues Leydig, “I rightly understand Huxley, this is the manner of development of the winter eggs of Lacinularia socialis ; and the bisection into two equal halves, which I formerly referred to fission, has, according to this writer, no relation to it.” Respecting this description, Prof. Huxley remarks that he thinks Leydig “has not observed the genesis of the ephippial ova with sufficient care, and he thence interprets their structure by supposing that they are ordinarily fecundated ova, which have undergone a peculiar method of cleavage;” and having quoted the opinion of other naturalists, he goes on to say—“it will be observed that all these authors consider the winter or ephippial ova and the ordinary ova to be essentially identical, only that the former have an outer case. The truth is, that they are essentially different structures. The true ova are single cells which have undergone a special development; the ephip- pial ova are aggregations of cells (in fact, larger or Smaller portions—some- times the whole of the ovary) which become enveloped in a shell and simulate true ova. “In a fully-grown Lacinularia which has produced ova, the ovary or a large portion of it begins to assume a blackish tint (XXXVII. 22): the cells, with their nuclei, undergo no change; but a deposit of strongly-refracting elementary granules takes place in the pale connecting substance. Every transition may be traced, from deep-black portions to unaltered spots of the ovarium ; and pressure always renders the cells, with their nuclei, visible among the granules. The investing membrane of the ovary becomes sepa- rated from the dark mass, so as to leave a space (XXXVII. 24); and the outer surface of the mass invests itself with a thick reddish membrane, which is tough, elastic, and reticulated from the presence of many minute apertures. This membrane is soluble in both hot nitric acid and caustic potassa. “The nuclei and cells, or rather the clear spaces indicating them, are still visible upon pressure, and may be readily seen by bursting the outer coat. “By degrees the ephippial ovum becomes lighter, until at last its colour is reddish-brown, like that of the ordinary ova; but its contents are now seen to be divided into two masses, hemispherical from mutual contact (XXXVII. 21). If this body be now crushed, it will be found that an inner, structure- less membrane exists within the fenestrated membrane, and sends a partition inwards, at the line of demarcation of the two masses. The contents are precisely the same as before, viz. nuclei and elementary granules. This, indeed, may be seen through the shell without crushing the case. “I was unable to trace the development of these ephippial ova any further. Those of Notommata, it appears, lasted for some months without change (Dal- rvmple). yº º remarkable that in Lacinularia these bodies eventually, like the ephippium of Daphnia, contain two ovum-like masses; and there can, I think, be little doubt that the former, like the latter, are subservient to reproduction. “There are two kinds of reproductive bodies in Lacinularia —1. Bodies which resemble true ova in their origin and Subsequent development, and which possess only a single vitellary membrane. 2. Bodies half as large again as the foregoing, which resemble the ephippium of Daphnia, like it having altogether three investments, and which do not resemble true ova, either in their origin or subsequent development; which, therefore, probably do not & 2 G 2 452 GENERAL EIISTORY OF TEIE INFUSORIA, require fecundation, and are thence to be considered as a mode of asexual reproduction.” The multicellular character of the contents of these ‘ephippial' ova, Cohn is unable to confirm. In his very valuable essay on the “Development of Rotatoria” (Zeitschr. 1855), this able observer has promulgated the hypothesis of the occurrence of the phenomenon of “alternation of generations,” of par- thenogenesis or virgin-development. A résumé of the reasons for this view may stand thus:—Female Rotifera lay eggs of only one sex; and winter eggs are produced only by certain females and at certain periods—contemporane- ously, that is, with the generation of males: again, the males are too few to impregnate the whole of the apparent female beings, which are so largely found, and always replete with ova in course of development, at all seasons. The conclusion, therefore, forces itself upon us that the common “summer" ova are produced within the parent animal without any antecedent genera- tive act or impregnation ; that is, in other words, they are asexual products or germs. If this be true, it follows that the beings producing them are not true females, but merely asexual nurses (Ammen), furnished with a germinal mass, but destitute of a real ovary, and not demanding the action of the male for the development of its germinal elements. On the other hand, the “winter” must be considered the true ova, and the beings producing them the only true females, furnished with an ovary, to which the energy of the spermatozoa of the male is necessary. But, notwithstanding these phy- siological differences, the mere nurses and the actual female Rotifera are in- distinguishable in structure. In illustration of this hypothesis, its analogy with what occurs in Aphis, Daphnia, and Artemia, may be quoted. Of the rate of development of these winter eggs, we know little. Huxley’s account would render it a final act, involving the sacrifice of a large, or even of the largest, part of the ovary, and consequently one which we cannot sup- pose capable of frequent repetition. Leydig has, indeed, an observation which, if accurate, proves a rapid reproduction of such ova by the ovary. He informs us he observed an isolated individual of Notommata Myrmeleo lay the solitary bristle-shelled winter ovum which its oviduct contained about 12 o'clock in the day; and on renewing his researches at 3 in the afternoon, discovered another such egg completely formed in the ovary. This author recounts also, in his history of Notommata Sieboldii, the following particulars, which, if confirmed, would prove the formation, whether of winter or of summer ova, to be determinable by accidental external circumstances : —“When I kept the Notommata for some days in clear water containing no nutriment, the ovary shrivelled, the granular mass (yelk) altogether vanished, the germinal vesicles became simple bodies, and all such individuals produced only winter eggs.” sº That the Rotatoria, on the approach of winter, are likely to be placed under conditions in which food is scarce, and which are unfavourable to vigorous life, is at Once admissible, and, if Leydig’s observation be correct, furnishes an explanation of the generally apparent limitation of the production of winter ova to that season. Be this as it may, the winter ova must be re- garded as indicating the conservative tendency of nature in providing for the continuance of the species by organisms so constructed as to endure the severity of the winter season, and to retain a dormant vitality through it, until the genial influence of spring awakens them into activity and life. FECUNDITY OF ROTATORIA.—Although the Rotatoria are not endowed with the various faculties of reproduction possessed by the Protozoa, yet their vast increase by eggs only is astonishing. Ehrenberg wrote that he insulated a single specimen of Hydatina senta, and kept it in a separate vessel for OF THE ROTATORIA, 453 eighteen days, that during this interval it laid four eggs per day, and that the young of these, at two days old, lay a like number. From these data he made an erroneous calculation, that one million individuals may be obtained from one specimen in ten days, that on the eleventh day this brood would amount to four millions, and on the twelfth day to sixteen millions. This is the only direct observation we have met with intended to prove the remarkable fertility of the class, yet, throughout the history of the Rotifera now detailed, numerous incidental illustrations of the fact occur, for example, the presence of several ova in different parts of the sexual apparatus, in various stages of development, and the observed rapidity of the phases of development, at least of summer ova. - The latter continue to be formed and deposited throughout the whole of the warm part of the year; and when this draws to its close, the production. of the winter ova provides for the continuous propagation of the species. Ehrenberg, in his specific descriptions, notes the number of ova he met with at the time of observation, intimating that some animals bring forward but one egg at a time, others two or several. - There is, very probably, a difference in the productiveness of various species; but differences in this respect will also occur from accidental and external circumstances, such as abundange of food, and changes of temperature. MALE ROTATORIA AND MALE REPRODUCTIVE ORGANS. QUESTION OF MALE AND FEMALE ORGANS IN TEDE SAME INDIVIDUALS. Male Rotatoria.-Few male Rotatoria have as yet been determined. Those decisively made out are those of Asplanchna Brightwellii (Notommata anglica, Dalrymple), Asplanchma priodonta and A. Bowesii (Gosse), and the Notommata Sieboldii (Leydig). This able German observer argues also that Enteropled Hydatina is the male of Hydatina senta, Notommata granularis that of N. Brachionws, and Diglena granularis that of Diglena catellina. Since this was written, Cohn has pursued the inquiry, and confirmed Leydig's conjecture, that Enteroplea Hydatina (Ehr.) is the male of Hydatina senta. He has moreover discovered the males of two other species, viz. of Brachiomws wrceo- laris and Br. militaris. Still more recently, Leydig has been able to confirm his belief of Enteroplea Hydatina being the male of Hydatina senta (Müller's Archiv, 1857, p. 404); and Cohn has discovered the males of Euchlanis dilatata and Notommata Parasitus (Zeitschr. 1858, p. 284). Meanwhile Mr. Gosse had discovered the male animals and their eggs in the undermentioned genera and species:–Brachiomus Pala, B. rubens, B. amphiceros, B. Bakeri, B. angw- laris, B. Dorcas, B. Mülleri, Sacculus viridis, Polyarthra platyptera, Symchaeta tremula (?), and in all probability Melicerta ringens, besides the three species of Asplanchna previously determined (Phil. Trans. 1856). The first male discovered was that of Asplanchna Brightwellii, then sup- posed to be a species of Notommata, and is thus described by Mr. Brightwell (A. N. H. 1848, ii. p. 155):-It is “about half the size of the female, and differs from it in form, being much shorter and of a rude triangular shape. It is more difficult to detect than the female, being exceedingly transparent, and, from the emptiness of the body, appearing little more than a transparent ciliated bubble. It is very active, and occasionally puffs out the sides of its body, so as entirely to alter its form, and remains thus distended some time.” There was no indication of any digestive apparatus, or of matters in course of digestion. “At the bottom of the body, on one side, is a conspicuous round sperm- vessel or testis, in which, under a high power, spermatozoa in active vibra– tile motion may be seen, and at its external side a duct, closed by distinct 454 GENERAL HISTORY OF THE INFUSORIA. lateral muscles. Connected with the testis is a well-defined intromittent organ, and a conspicuous passage or opening for its extension from the body of the animal. In the opposite lower angle are three small, irregularly- formed, kidney-shaped bodies, connected with an angular lobe or muscle lying beneath them. The male is also furnished with the delicate mem- bramous plicated bag, and rudiments of the curled tubular structure, found in the female.” Besides determining the dioecious character of this Rotifer, Mr. Brightwell was also enabled to repeatedly verify the occurrence of an actual coitus occur- ring between the sexes, and enduring the greater part of a minute. The male of the allied species Asplanchma priodonta was described by Mr. Gosse. As the description supplies additional particulars concerning the organization, we extract it entire. IHaving isolated an adult female, in which the developing young seemed different from the ordinary embryos, he at length had the Satisfaction of seeing two males born. “Another was produced the same evening from another parent, likewise under my eye.” “The length of these specimens (XXXVI. 7, 8) (male) was THuth of an inch (that of the females was #th to #nd of an inch). They had a general agreement in outline with the female. But...the outlet corresponding to the vagina was at the very bottom of the ventral side (XXXVI. 7, 8 b), which ran down to a point, while the dorsal side was rounded off. At the base of this tube was a globular sperm-sac, with a short thick penis in front, the whole nearly surrounded by a delicate glandular mass. The place of the stomach was occupied by a long Sac, having a slender neck originating from the fore part of the head mass, and at the bottom broadly attached to the sperm-bag. This whole organ was filled with minute granular matter, except three or four clear globular bladders; the sperm-bag showed a structure very similar. “The principal muscles agreed with those of the female. The tortuous threads, and their plexuses, were represented by two thickened glandular bodies, extending from the head mass to the foliaceous substance surrounding the sperm bag. . . . The three eyes were present, situated as in the female, but no trace of jaws was discernible, even on pressure, nor any crop, nor true stomach. These animals were very active, Swimming rapidly about, and scarcely still an instant. On one or two occasions, I observed one of the males with a slender process protruded to a considerable length from the sexual orifice, and adhering to the glass by its tip, moving round on it as on a pivot.” * - - Leydig admits the bisexual or dioecious nature of the Rotatoria as a general fact; and although, he says, his studies have been diverted from special re- searches on this matter, yet, from the descriptions and representations of others, he believes he can detect several male forms arranged in the class as distinct species. Of the male of a new species, which he calls Notommata Sieboldii, but which is equally a member of the genus Asplanchna with “the supposed new Notommata” of Brightwell, he has given an elaborate description and draw- ings. He remarks that in all details of organization it agrees with Mr. Dalrymple's account, but, unlike the English species, differs considerably in figure from the female, especially by the presence of four pointed arms (XXXVII. 29). He remarks that “the so-called ” sperm-bag of Dalrymple is the testicle, and what that author terms the “penis '' is its duct. The figures he gives of the seminal corpuscles are not altogether distinct, although the resemblance between them and those of Notommata Sieboldii are unmis- takeable. However, I must point out an error into which Dalrymple has OF THE ROTATORIA. 455 fallen, in describing the linear seminal corpuscles that lie parallel to one another about the outlet of the seminal vesicle to be bundles of muscular fibres attached to the base of the penis, and acting as “ ejaculatores seminis.” The Enteroplea Hydatina (Ehr.) is, in Leydig's opinion, the male of Hydatina senta : the reasons for this belief briefly are, that, according to Ehrenberg's de- scription and figures, the Enteroplea has neither jaws nor teeth; that its ovary is homogeneous and granular; that the animal is always smaller than Hydatina senta; and that among the eggs of this last-named species, those developing into embryo Enteroplea were intermixed. Now each and all these differential, and some of them very exceptional characters, are at once inter- preted by assuming Enteroplea to be a male animal. Indeed, in no female perfect Rotifer are the jaws wanting, and even in very young specimens the ovary is not homogeneous, but contains many germinal vesicles or spaces. A reference to Dujardin’s description and engravings adds additional weight to this opinion. This supposition has been confirmed, both by Leydig himself Müller's Archiv, 1857, p. 404, and A. N. H. 1857), and by Cohn (Zeitschr. 1855, p. 451), and we would refer the reader to their memoirs for an ex- tended description of this male being. By these researches, the testicle and its contained spermatozoa, together with a male projectile organ, the absence of a digestive apparatus, and other sexual peculiarities, have been satisfactorily made out. In the case of Notommata gramwlaris, the arguments for its male character are, the absence of the maxillae, and probably of the ovary also—for neither Ehrenberg nor Weisse could satisfactorily make out the existence of the latter, —and, further, the presence, as the Berlin Professor points out, of two sorts of eggs upon Notommata Brachionws, the Smaller of which bring forth individuals of the supposed different species, Notommata granularis. The evidence for the male mature of Diglena granularis (Weisse) is its constant occurrence in company with D. Catellina, and the production of two sorts of eggs by the latter, the smaller of which give birth to embryos wanting the dental apparatus. Such imperfect beings as the Diglena gramw- laris and the Notommata granularis were explained by Weisse to be immature or premature embryos. “It is truly interesting,” says Leydig, “that Weisse, at the time he wrote perfectly ignorant of male Rotifera, should arrive at the conclusion that Notommata granularis, Diglena granularis, and Enteroplea Hydatina were not distinct species, but the incomplete and toothless young of the several species, Notommata Brachiomus, Diglena Catellina, and Hydatina senta.” It is added in a note—“ Under the name Notommata granularis may well be associated together the very similar males as well of Notommata Bra- chiomws, as also of B. Marceolaris and B. Pala.” A few notes in illustration may be added from Cohn’s account of the male of Brachionus wrceolaris (Zeitschr. 1855, p. 471). This is much smaller and more active than the females. Its rotary apparatus forms a wide ciliated rim; but its cilia are not turned inwards and downwards, as in the females, to enter the mouth, for no . such orifice exists: hence there is no maxillary head, no intestine, and no gastric glands. In the place of those organs lies a large pyriform saccular testicle, as much as Tºrgth of an inchin length, incompletely filled with fine dark corpuscles, which, when mature, acquire the characteristic figure and swarming movements of spermatozoa. The wall of the testicle is excessively thick, perhaps muscular, and is extended upwards into a thick cylindrical band, which appears to serve as a medium of attachment to fix the gland above to the region of the cephalic disk. At its posterior end, the testis presents a close longitudinal striation, and is perforated by an aperture which opens into a wide canal ending in the penis. This last-named organ has the aspect of a 456 GENERAL ELISTORY OF TEIE INIFUSORIA. short tube, which, as a rule, lies free upon the foot, and extends nearly to its extremity. Its inner canal, and its external border, exhibit vibratile action. The foot is transversely wrinkled, and ends in two small toes. About the origin of the penis from the testicle are two club-shaped glands which pour their secretion into the canal; and near them is the contractile vesicle, giving off its respiratory canal on each side, with the usual tag-like appendages. Several spherical cell-looking bodies occur about the head, with the largest of which the eye-specks are in connexion, and which may therefore be con- sidered the cerebral ganglion. Upon the testis, near its lower end, two or three vesicles are placed, filled with dark granules, resembling those seen in Enteroplea Hydatina, and of which we cannot predicate further than that they are not of the nature of urinary concretions (as Leydig imagined), but in some way belong to the sexual apparatus, or else are unconsumed cells of the yelk-mass. +. The tubular or band-like prolongation from the upper extremity of the testicle, noticed by Cohn, and considered by him a “suspensor testis,” repre- sents, in Leydig's opinion, rather the rudiment of the undeveloped alimentary tube. This author likewise denies Cohn's statement that the walls of the testis are thick and muscular, asserting that they consist of a thin membrane. The Spermatozoa, i. e. the fecundating male particles, have been described by Mr. Dalrymple, Gosse, and Leydig. We borrow the description of the latter as the more recent:-‘‘The testicle (XXXVII. 29 c) of Notommata Sieboldii is at once seen to be more or less completely filled with spermatozoa, arranged about the excretory duct in a radiating manner; when not too much compressed, they move about within the testis. On isolating by slight pres– sure the contents of the Organ, may be noticed, 1, large round vesicles, in which, by a stronger magnifying power, two, or probably more, hyaline nuclei with nucleoli, entirely occupying the space, may be distinguished (XXXVII. 30 e); 2, somewhat larger cell-formed elements, disposed in a radiating manner about a centre, and larger towards one side (XXXVII. 30 c)—at the rounded extremity a clear nucleus, with a nuclear corpuscle, is always placed; 3, elongated, mostly falcate or curved structures, which have the before-mentioned nuclei in their interior, and on One margin are expanded into an evidently undulating membrane (XXXVII. 30 a, b, d). They move about, and Swim hither and thither, in Such a manner that they remind one not a little of many Infusoria, having a clear sharply-defined contour and a rod-like figure, with a slight enlargement at the middle. It is these bodies which lie around the commencement of the excretory duct, and give rise to the apparent striation above alluded to.” In Hydatina senta the spermatozoa are likewise of two forms, and are noticed sometimes to have a swarming movement even within the testis. Leydig has been unable to satisfy himself whether the stave- or rod-like variety (XXXVII. 30 f) is to be considered the ripest of the spermatozoa, and derived from one of the other forms, or whether there are two sorts of spermatozoa in Notommata Sieboldii, as there are in Paludina vivipara, one of the Mollusca. . & Perty states briefly and generally, of the spermatozoa of Rotatoria, that they have a broad-oval refracting body, and a tail-like appendage. The spermatozoa have been seen within the abdominal cavity of not a few female Rotifera, freely moving about within it. For instance, it has been witnessed in Brachionus, Conochilus, Lacinularia, Megalotrocha, and Hyda- tima. It is not known how they reach this cavity, since the cloaca into which they are normally received is a closed sac. Cohn imagines they may enter through some aperture in the integument as yet unnoticed ; it is, how- OF TEII. ROTATORIA . 457 ever, more conceivable that they may pass from the cloaca into the respiratory tubes, and escape into the general cavity through the vibratile tags—supposing these last to terminate by open mouths. On the other hand, it is just possi- ble that some supposed examples of the presence of spermatozoa within the abdominal cavity, have rather been instances of parasitic beings (Entozoa) in the interior. Thus, in Hydatina senta, Leydig describes the interior occupied by many numerous active animalcules, which he refers to the genus Astasia. The minute male beings just considered are brought into existence for the sole purpose of fertilizing the ova of the larger and highly-organized female animals. In relation to the females, they may be looked upon as little other than parasites; they are even deficient in organs necessary to carry on their own existence: the one purpose of impregnating the opposite sex being fulfilled, their career is ended; and this career is so brief, that the complicated apparatus otherwise required to nourish and Sustain the beings can be dis- pensed with. - The early history of the male Rotifer is that of the female. The evolution of the ovum from the ovary, and the changes transpiring in the contents of the egg until the several organs become distinguishable, are identical in the two. The following particulars from Cohn’s paper (Zeitschr. 1855, p. 471) will serve for illustration. The males of Brachionus urceolaris are developed from smaller eggs than the females, and which are adherent in large number at the same time to the parent-animal. These eggs are very spherical, and reach fºrth of an inch in length and sºrth in diameter. Their shell is more delicate, the contents clearer and much more transparent, from containing fewer granules, and of a pale-yellow hue, whilst the usual Summer eggs are dusky grey. Even when mature, this greater transparency and absence of colour persist. Fission proceeds in the same way as in the female ova; and after it has been many times repeated, the different organs of the embryo begin to make their appearance,—the red eye-specks being among the first. However, unlike what happens in the female ova, no signs of the maxillary apparatus come into view, but two or three dark heaps of granules which are not seen in those. When mature, the embryo springs from the shell through a trans- verse rupture, and is then seen to have a totally different figure from the female beings, and at least three times smaller. When completely extended, it measures only between ºrth and girth of an inch in length, and ++gth to ºuth in width, and is observed at the first glance to be destitute of the firm integument or shield of the female animals, and to have a short-cylin- drical figure, prolonged anteriorly in the form of a short head separated by a constriction from the body. The foot is short and tubular, the head crowned by a flattened disk expanded into a wide margin, which is clothed with long vibratile cilia and a few non-vibratile bristles. Their movements are extra- ordinarily emergetic. - The same female may lay in succession several male ova. According to Leydig, both male and female ova are not generated at the same time. The small size and relatively incomplete organization of the male Rotifera is a circumstance not peculiar to the class; the like is seen in the imperfect “imago” of many Insects, destined only to a sexual purpose, in the para- site-like males of Lernaea, in the miniature and incomplete males of Daph- niadae, and in the equally inferior male representatives of Polynoë, Evogome, and of the Nematoda generally, among Vermes. Leydig, moreover, finds an analogous fact in the Siphonophora, in which he assumes the so-called genital capsules, distributed everywhere in the aggregate mass of animals, to have a male character, and shows this opinion is in harmony with the views put forward by Leuckart respecting them. 458 GENERAL, HISTORY OF TELE INFUSOIRIA. Mr. Gosse's conclusion (Phil. Trans. 1857, p. 322) is, that “a distinction of sex is the normal condition of the class, or at least of that group which is most typical, viz. Such as have articulated mallei working upon a separate articulated incus. Whether the same rule prevails so generally in those which have the mallei and incus fused together into quadrantic masses, and in those in which the organs exist in a rudimentary condition, is a question yet to be determined. As these are certainly the lowest forms of their class, it is pos- sible that hermaphroditism may be found in them—in the Philodinadoe, for instance.” The summary of the facts as yet ascertained, concerning male Rotatoria, will form a valuable addendum to our account :— “The most prominent thing that strikes us is the absolute and universal atrophy (so to speak) of the digestive system in male Rotifera. Another curious peculiarity is the dissimilarity that always exists between the sexes. In Asplanchna and Hydatina the resemblance is at its highest point; in every other instance observed, the sexes are so unlike, that they would be taken for widely-remote genera. The male is always inferior in size, and also in organization, to the female. - “Whether certain individuals produce only male, and others only female young, or whether separate impregnations are required for the production of the separate sexes, I do not know ; but from all my observations I gather that the development of the one sex never takes place coetaneously with that of the other ; for male and female eggs are never seen attached to the same parent, and the immature eggs in the ovary invariably develope themselves into the same sex as those which are already extruded. “The duration of life in the male is always very brief. I have never been able to preserve one alive for twenty-four hours. Their one business is to impregnate the females, which is the work of a few minutes, probably, in a state of freedom ; and for this momentary occupation no supply of loss, by assimilation of food, is wanted ; and hence we can understand the lack of the nutritive organism. “Some organs are found, with greater or less distinctness, in all. The (presumed) male of Hydatina senta received its names of Enteroplea and Organ-fisch from Ehrenberg on account of the copiousness of its internal organization. A muscular system is well developed there, and in the males of Asplanchna and of Brachionus Mülleri ; and, from the varied movements of all, its existence may be inferred where it is not detected. The frontal cilia are, in almost all cases, much more developed than in the females; the result of which endowment is seen in the excessive rapidity with which the male shoots in all directions through the water. The great head-mass of granular substance is generally distinct; and in several cases (as in the As- planchnae and in Brachionus Dorcas and Br. Mülleri) the great occipital gan- glion is well-defined, with the red eye seated on it as in the other sex. Even where the ganglion is not apparent, the eye is conspicuous, with the exception of Sacculus and Polyarthra; and in this last instance the small size of the animal must be borne in mind, and the density of the anterior parts. “In the (presumed) male of Hydatina, in those of all the Asplanchnae, and of Brachionus Dorcas, there are organs answering to the lateral convoluted threads of the female ; and, in Asplanchna Brightwellii at least, these are accompanied by tremulous tags, and by a contractile bladder. “A large mass of Substance which, being perfectly opaque, appears black by transmitted light, but is white when the rays are reflected, is so generally found in male Rotifera as to be characteristic, though it is not universally present. I do not find it in the Asplanchnae, nor in Sacculus. On the other OF TELE ROTATORIA, 459 hand, I have observed it in the young of Stéphanoceros, Floscularia compla– mata, and F. cornuta ; and Ehrenberg mentions it in F. ornata and Lacinw- laria. In Stephanoceros, it was certainly associated with well-developed jaws; and hence I presume it is not exclusively an indication of the male sex. The mass is sometimes broken up into fragments, of irregular size and shape, and sometimes apparently pulverulent. In general, it appears to lie loosely in the midst of the granular amorphous matter that occupies the pos- terior region of the body-cavity; but in Brachiomus Pala, and especially in Br. amphiceros, I have fancied that I discerned traces of a vesicle, within which the white substance seems to be contained. “On the nature of this substance I have no light from personal research. Dr. Leydig, however, considers it to be a urinary concretion (Harnconcre- mente), analogous to the chalky fluid which is discharged by many insects immediately after their evolution from pupae. “In the male of Asplanchna Brightwellii, there is, as its discoverer observes, “a conspicuous round sperm-vessel, or testis, in which . . . . spermatozoa in active vibratile motion may be seen.” Mr. Dalrymple, and subsequently myself, also saw these, both within the Sac and discharged by pressure. Each spermatozoon, according to my own observation, consists of an oblong body, Tºrnth of an inch long, and an abrupt, slender, vibratile tail of equal length. In the sperm-sac of A. Sieboldii, Dr. Leydig finds various seminal elements, viz. round cells; pyriform cells, drawn out to a fine point, and ad- hering to each other by their rounded ends in a stellate manner; oblong bodies, with one side dilated into a free, undulating, membranous border; and slender, stiff, rod-like bodies, with a central swelling; all containing nucleated nuclei. On the male of A. priodonta, my observations were too limited to determine more than the existence of the globular sperm-sac. “In Brachiomus rubens and Br. Mülleri I found spermatozoa, which I have above described. In the latter, the sperm-bag is of great size, and contains, besides the spermatozoa of unusual development, slender spiculiform bodies, which may be the equivalents of the little rods described by Dr. Leydig in Aspl. Sieboldii. The sperm-bag (in Br. Mülleri) is closed posteriorly, as it is also in Asp. Brightwellii, by what appears to be a true sphincter; and such I conjecture to be the explanation of those diverging lines which M. Dujardin saw in Enteroplea (so-called), which he considered to be pedi- cles of his touffes de granules,” while the touffes” themselves I take to have been the masses of urinary concrement. Dr. Leydig, however, con- siders the whole to have been masses of spermatozoids. “The outlet of the sperm-bag is, in all cases, by a thick protrusile and retractile penis. Wherever a foot exists, this intromittent organ is continu- ously united to its dorsal side, and is often so greatly developed that the foot itself appears as an appendage. The protrusion of the organ, at least in most of the examples that I have noticed, is by the eversion of the integuments. When these are evolved to the utmost, the organ is seen to be a thick column, conical or nearly cylindrical, with the extremity truncate, and sur- rounded by a wreath of vibratile cilia. It was doubtless the extremity of the penis that M. Dujardin saw, as ‘wn organe cilié entre les muscles de la queue,” in the (so-called) Enteroplea. The male of Sacculus viridis, a species which is footless in both the sexes, is the only example in which I have not seen the penis; but the organ is probably wholly retractile within the body, and my observations, on the only individual of this sex that I saw, were in- sufficient to determine anything concerning it.” That male Rotatoria have been recognized in comparatively few species, admits of several explanations. The smaller size and comparative rarity of 460 GIENERAL ELISTORY OF TEIE [NI"USORIA. the males; their dissimilarity of figure to that of the females, which, coupled with imperfect examinations or misconception of their interior organization, would readily lead to their institution as new species or genera; the influ- ence of the prevalent hypothesis of a hermaphrodite nature, and the conse- quent exclusive search for male organs in the perfect female forms, in which, too, the uncertainty appertaining to the purpose of several appreciable tissues or organs would tend still further to lead astray; the short existence of the males, and even that brief life limited, it would seem, to a particular period of the year, the early spring, when such creatures are less sought after ; each and all these are circumstances which have caused the male Rotatoria to be overlooked, and continue to do so. However, the non-recognition of the male animals occurs not only in the case of the Rotatoria, but also of other classes of animals, even more highly organized and so large as to be capable of examination without the aid of the microscope. Among minuter organisms in which an uncertainty prevails, may be mentioned the Daph- niadae and other Entomostraca, among the majority of genera of which the males are still undetected, nevertheless the bisexual character of the class is admitted. - The comparative rarity of male Rotatoria admits of an interpretation de- rived from analogy. It is a well-recognized fact, that in several classes of Invertebrata (for example, in Daphniadae and, among Insecta, in the genus Aphis) several generations succeed one another without the concurrence of a male animal in their production,-a phenomenon well named by Prof. Owen, Parthenogenesis or Virgin-generation. Now it clearly appears that one contact with a male Rotifer may suffice for the fertilization of all the germinal cells in any female ovary, and be followed by their successive de- velopment. To use the language of Prof. Owen, the spermatic force once applied suffices for the impregnation of a multitude of ova, or, in fact, of the whole ovary; and the fact quoted, of Aphides developed by the immediate action of the spermatic force being in their turns capable of reproducing others by gemmation without a renewal of that force, warrants the supposi- tion that an analogous phenomenon may exist in the Rotatoria. This analogy is strengthened by Mr. Huxley’s interpretation of the nature and purpose of “winter’ ova, which he believes to be the instruments of an asexual repro- duction. A portion of the ovary seems to be modified and extruded, and sub- sequently to generate a couple of embryos. On the other hand, in the Aphides an internal germinal mass remains within the body, and a portion of it ap- pears to be abstracted by each successive individual produced, until at length the spermatic force is exhausted. This internal germinal or reproductive body, the instrument of an aseaſual generation in the Aphides, is then surely homo- logous with the extruded external generative bodies, or “ephippialova,” of Ro- tatoria. Such an asexual reproduction implies a fewness of male beings com— pared with the multitude of young which must be developed by the generative processes. Again, the male Rotatoria are not only developed in smaller numbers than the female, but their whole term of existence is very brief, only long enough to fulfil their generative purpose ; and, lastly, they are to be found only at particular seasons, mostly in the spring. Another obvious reason for the scarcity of male Rotifera suggests itself, viz. that the Social institutions of the class may not be on the monogamous model, but that one little active male may divide his favours among a whole harem of females before he completes his brief career. However this may be, to discover the male of any one species, continuous observation is needed, particularly at certain times of the year; and it must be confessed that but few Rotatoria have hitherto had their history fully investigated. In most OF TEIE ROTATORIA. 461 cases, the examination of a species has been casually undertaken; the attention has been directed to it only by some accidental circumstances, and this only on Some one occasion. We cannot,therefore, wonder that therarely-occurring males . have not often been encountered. But the most satisfactory means of deter- mining the existence and characters of the males of any species of Rotatoria have latterly been furnished by the careful descriptions of the special cha- racteristics of male ova, whereby they can be distinguished even before leaving the Oviduct, and their developmental history traced forwards until their ma– turity. - We may mention that Mr. Hallett, formerly demonstrator of anatomy in the University of Edinburgh, and subsequently a student in anatomy at the College of Surgeons, London, directed his special attention for many years to the Rotatoria, and especially to the detection of the male individuals ; and although his early death has deprived naturalists of the published results of his researches, yet, from repeated verbal communication, we can state that he had arrived at the discovery of the male beings of the majority of the Rotatoria. Doubtful Male Organs.—Many naturalists are unprepared to admit bi- sexuality to be the universal rule in Rotatoria; and several eminent observers are disposed to consider certain organs in female animals to be of a male sexual character. Prof. Williamson, in his history of Melicerta, says—“I have sought in vain for any organ to which the functions of a spermatic gland can be indis- putably assigned. Immediately beneath the lower stomach and the conti- guous oviduct, there is an elongated pyramidal organ, apparently hollow, the thick extremity of which is directed towards the ovary, and its opposite at- tenuated portion passes upwards towards the cloaca, between the oviduct and the general integument. Into the thick inferior extremity of this organ, there are inserted, exactly opposite to each other, two long-cylindrical ap- pendages, which diverge, and, passing on each side of the alimentary canal, proceed towards the upper part of the body, where their extremities are not easily traced. In but one instance I observed them to terminate in a series of irregular convolutions near the base of the two tentacles. Though not yet capable of demonstration, it appears probable that this curious appendage may be a filamentous spermatic tube resembling those found in many Arti- culata. That they are tubes, and not muscular bands, appears unquestionable; and as they have obviously a direct connexion with the cloaca, they might easily discharge a fertilizing secretion into that common excretory canal, from which it would find its way to the ovary through the oviduct” (p. 432). Now it is to be remarked that Mr. Williamson states he could discover “no special organs of circulation or respiration, no vessels or pulsating organs,” and that the two tubes he has referred to as being possibly sper- matic ducts are the homologues of similar ones in other Rotifera, to which Ehrenberg has assigned fertilizing functions. Further on he observes— “The singular bodies resembling spermatozoa exist in various parts of the organism, where they are apparently enclosed within hollow canals. I have never seen them occupying the two main trunks of the ‘water-vascular system ’ or caeca ; nor can I succeed in tracing any connexion between them. In several cases I have seen one or two of these curious bodies opposite the centre of the upper stomach, very near to, but independent of, the main caecal canal, and at some distance below the point where the latter probably sub- divides into branches. Near the neck there are usually from two to three pairs. Their vibratile motion ceases the moment the animal is killed by pressure. This fact does not countenance the idea that they are spermatozoa.” 462 GENERAL HISTORY OF TEIE INFUSORIA. From the above remarks and statements, it seems to us quite clear that the pyramidal sac opening into the cloaca, and its upwardly-prolonged canals referred to, are nothing more than the “water-vascular system ’’ of the Me- licerta, and that more or fewer of the observed vibratile bodies are, in fact, the ciliated tremulous tags. Had the pyramidal sac represented a testicle, spermatozoa ought to have been seen within it; for these particles are readily cognizable by their size, figure, and movements. - - Prof. Huxley having failed to find a male among some scores of female Lacinwlariae, or a single ordinary spermatozoon, is disposed to recognize the male sexual element in some singular bodies met with in many individuals he examined. These bodies “answered precisely to Kölliker's description of the spermatozoa “ of Megalotrocha. They had a pyramidal head about Túrûth of an inch in diameter, by which they were attached to the parietes of the body, and an appendage four times as long, which underwent the most ex- traordinary contortions,—resembling, however, a vibrating membrane much more than the tail of a spermatozoon, as the undulating motion appeared to take place on Only one side of the appendage, which was zigzagged, while the other remained Smooth. “According to Kölliker, again, these bodies are found only in those animals which possess ova undergoing the process of yelk-division, while I found them as frequently in those young forms which had not yet developed ova, but only possessed an ovary. “Are these bodies spermatozoa 2 Against this view we have the unques- tionable separation of the sexes in Notommata, and the very great difference between them and the spermatozoa of Notommata. Neither the mode of de- velopment, nor the changes undergone by the ovum, afford any certain test that it requires or has suffered fecundation, inasmuch as the process closely resembles the original development of the Aphides. “In the view that Kölliker's bodies are true spermatozoa, it might be said, 1. That the sexes are united in most Distomata, for instance, and separated in species closely allied (e. g. D. Okenii). 2. That the differences between these bodies and the Spermatozoa of Notommata, is not greater than the dif- ference between those of Tritons and those of Rana. 3. That their develop- ment from nucleated cells within the body of Megalotrocha (according to Rölliker) is strong evidence as to their having some function to perform; and it is difficult to imagine what that can be if it be not that of spermatozoa. However, it seems to me impossible to come to any definite conclusion upon the subject at present.” In Melicerta, Prof. Huxley notes having met with “an oval sac lying below the ovary, and containing a number of strongly-refracting particles, closely resembling in size and form the heads of the spermatozoa of Lacinwlaria.” These views of Mr. Huxley are of no value in deciding the question; they rest on a supposed similarity between the bodies discovered and those which Kölliker believed to be spermatozoa in Megalatrocha,_an opinion not incon- trovertible. On the other hand, their spermatozoid nature is discountenanced by their similarity (which, indeed, Huxley remarks) to undoubted sperma- tozoa of Rotifera. In a new species of Melicerta discovered by Prof. Bailey in America, that accurate observer found that pressure between two plates of glass liberated vast numbers of spermatozoa ; but he was unable to ascertain from what organ in the animal they were set free. The observation, however, is im– portant as indicating the existence of true male organs in Melicerta of a very different character from those suggested by various observers as having pos. sibly fecundating functions. Respecting these questionable male elements, Leydig has the following OF TEIE ROTATORIA. 463 remarks, premising that the detection of spermatic particles in one species furnishes a criterion in pronouncing upon the signification of some other bodies:–“I have heretofore mentioned my idea that the hairy corpuscles of Lacinularia (occupying the general cavity of the body, and impelled hither and thither by its movements) are seminal particles: although this is still questionable, yet these presumed parasites of Lacinwlaria must, I believe, be still rather looked upon as unequivocal spermatozoids. The form and struc- ture, moreover, of the bodies figured by Huxley, and doubtfully called by him spermatozoa, have an evident affinity with the seminal elements of No- tommata Sieboldii. It also seems to me probable that the spermatozoids portrayed by Kölliker in Megalotrocha are really such, and that the animals in which they are found should be esteemed as previously impregnated females. I moreover consider that the illustrations furnished by Ehrenberg of Conochilus volvoa, show an individual with two spermatozoa ; and the account referring to it, in which he says “I lately saw oscillating, very pe- culiar, gill-like organs, in the form of two spirally-twisted bands, at the pos- terior extremity of the body,” also speaks in favour of this signification. The entire delineation of these “spiral gills' might replace very well that of the peculiar seminal elements with undulating membranes.” Afterwards, when speaking of the parasites of Rotatoria, Leydig observes that having formerly erroneously described the seminal corpuscles of Lacinu- laria as parasites, he must now, on the other hand, class the once-presumed spermatic particles with parasitic Organisms. In the course of subsequent researches on Hydatina senta (Müller’s Archiv, 1857, p. 104), Leydig has discovered the same sort of structures in that ani- mal. He writes—“They are globular bodies with sharp outlines; and their margin looks as if clothed with fine hairs. Towards the end of March, the entire abdominal cavity was in many specimens so filled with them that the animals presented a white appearance by reflected light; yet the animals so affected swarm about just as briskly as the others.” This repletion with such particles appears to us to intimate that they cannot be spermatozoa, either generated within the beings themselves or received from without from male animals. Indeed their occurrence within the abdomen of Hydatina senta is of itself an argument against their being spermatozoa derived from a male gland within, inasmuch as this species is proved to be impregnated by its own male partner, formerly known as the Enteroplea Hydatina. The ques- tion presents itself, whether they can be derivable from the food, as products of digestion or chyle-globules. - The search for male Rotatoria has led the occasional connexion of two in- dividuals to be noticed, and to be explained as of a sexual character. Perty noticed two individuals of Colurus wrºcinatus, and two of Lepadella ovalis, in union. But such connexions may rather be considered accidental; for Perty re- marked a Colurus so attached to Lepadella, and a Chaetonotus Larus to Lepadella ovalis. Cohn has had his attention directed to the same circumstance, and remarks that two Rotatoria of the same or even of a different species are very often to be seen attached together, sometimes by the back, at others by the abdomen, at others by the pseudopodium, and to swim about together for a length of time. This he has seen in Diglena, Colurus, and Lepadella; it has, however, no connexion with the reproductive function. OF THE DURATION AND CONDITIONS OF LIFE OF THE ROTATORIA, AND OF THEIR |HABITATS AND DISTRIBUTION.—It is next to impossible to determine, by direct observation, the duration of life among the Rotatoria when placed under natural and favourable conditions. Many may well be supposed to survive from their birth in the spring until the winter, and not a few even through 464 GENERAL HISTORY OF THE INFUSORIA. this season until some future period, since observations prove their power of assuming a torpid condition when existing circumstances are unfavourable to the full exercise of life. It has been noticed by Ehrenberg, of some Rota- toria living, so to speak, in confinement, or in a limited quantity of water under examination, that when the weather was warm and nourishment abundant, life was prolonged to 18 or 20 days and more ; and Mr. Gosse also speaks of a Melicerta which lived in confinement for 14 days. The conditions of life, or the causes affecting the vitality of Rotifera favourably or unfavourably, are in some respects very remarkable, as an ap- peal to their habitats alone would abundantly illustrate. It is during the height of summer that the Rotifera are multiplied most abundantly; but when the cold frosty nights of autumn supervene, their numbers undergo a rapid reduction. However, often during the most beauti- ful parts of the year, as Perty remarks, a sudden decrease will occur. “Two kinds of disease,” writes Ehrenberg, “ destroy the Hydatina and most of the Rotatoria : 1, the formation of vesicles, which give rise to the appearance of Small rings all over the creature; and, 2, the formation of granules which so penetrate the internal organs that these seem composed of them, and have a shagreen appearance.” The first condition has been noted by Weisse, who regards the apparent vesicles as parasitic organisms. The Rotatoria also suffer from the overgrowth upon their surface of Algae and of parasitic animals, Protozoa and the like, and are at length destroyed thereby. Foul or decomposing water is incompatible with their existence, as are some chemical mixtures, whilst to others they seem indifferent. Thus Hydatinae have been fed with rhubarb and indigo in powder without sensible effect, and neither calomel nor corrosive sublimate kills them; at least, they live for some time after these substances have been mixed with the water. Strychnia causes instant death. The deprival or the want of renewal of air in water inhabited by Rotifera causes their destruction, for example, when collected in abottle for examination, the cork being allowed to remain too long. In like manner the exclusion of air by a pellicle of oil on the surface of the water, or the withdrawal of air by means of an air pump, speedily destroys the Rotatorial inhabitants. Ehren- berg affirms that they exist much longer in an atmosphere of nitrogen than in one of carbonic acid or of hydrogen, and that the vapour of sulphur speedily puts an end to their existence. - Still a very imperfect renewal of air seems, at least in some instances, t suffice—as in the case of the Rotifer vulgaris and R. parasita, which have been seen within the spheres of Volvoa and in the cells of aquatic plants (the Vaucheria clavata.) Perty likewise mentions the Notommata Werneckii as inhabiting the Vaucheria caespitosa ; and Albertia vermicularis is parasitic within the intestine of earth-worms and slugs. In all these instances life is compatible with a very slight renewal of atmospheric air, or, in fact, is sup- ported amid the gases generated within these organic beings and mixed with their fluids. e The evaporation of the water from around Rotifera, as when under exami- nation by the microscope, is a frequent cause of their destruction, by the breaking up of their soft parts. But there is a happy provision against such evil consequences; for, so soon as the animal experiences the deficiency of water around it, it withdraws its tender wheel apparatus, and limits its ex- posed parts as much as possible, by retracting its pseudopodium and contract- ing itself into a ball-like form, so that only the denser integument is exposed to the injurious influences, and the evaporation of water from the contained organs reduced to its minimum. - - - OF TEIE ROTATORIA. 465 Indeed the Rotatoria, in part at least, have a remarkable power of preserv- ing their vitality, not only when left dry by Ordinary evaporation, but also when thoroughly desiccated by the assistance of heat. Leuwenhoek and Spallanzani experimented on them, and announced the fact of their revivifi- cation on the addition of moisture, months and even years after their com— plete desiccation. Schrank, Bory St. Vincent, and Ehrenberg questioned the truth of this statement, at least in its full acceptation; and the writer last- named affirmed “ that wherever these creatures are completely desiccated, life can never again be restored. In this respect the Rotifera exactly correspond with animals of a larger kind: like them, for a time they may continue in a lethargic and motionless condition; but, as is well known, there will be going on within them a consumption or wasting away of the body, equivalent to so much mourishment from without as would be needed for the sustentation of life.” Neither the last statement nor those preceding it are correct; M.M. Schultze and Doyère have repeated and confirmed, the experiments of the old observers; and the latter authority concludes that Rotifera may be completely dried in pure Sand in the open air, and in a vacuum, without losing the capability of being revived by moisture. Many indeed are sacrificed in the process; but enough recover to demonstrate the possibility of the fact. - This extraordinary power of resuscitation after drying explains the re- appearance of Rotatoria on the collection of water in shallow pools which have been entirely dried up by the hot sum of summer, and their con- stant presence in the dry debris of the roofs, and even of the interiors of houses. In their relation to temperature, also, the Rotatoria exhibit great tolerance. M. Doyère proved that when placed in water at from 113° to 118°, they could afterwards be revived, but that when thrown suddenly into boiling water (at 212°) they were at once killed. In the latter case, the sudden heating is supposed to coagulate the albuminoid contents of the animals, and in that way to cause death, because individuals previously dried by a gradually raised heat of 216°, 25.2°, and even of 261°, were many of them still capable of being revived. On the other hand, Rotatoria can live in water at the freezing-point. They are to be found under ice, and also within the hollow cavities of ice; and Perty mentions a score of species which he met with in such localities. He also recounts meeting with individuals contracted in a more or less globular figure, preparatory, as he surmises, to a winter sleep or torpor. He figures a Philodina erythrophthalma (XXXVIII. 4) in this condition, which is pre- cisely the same as that assumed when the animal is left dry; and he adds that when Scaridium longicaudum assumes this state, it withdraws its head within its envelope and doubles its tail under the abdomen, just in the same way as a Podwra. Ehrenberg doubtless refers to this same contracted con- dition in the account before quoted from him (p. 449–50) respecting the Rotifera found at great altitudes among snow, which he described as having an ovate figure and enclosed in an egg-shaped envelope. Conochilus and Lacinwlaria are examples of Rotifera living in aggregated masses. The former recalls, by its compound revolving spheres, the appear- ance of Volvoa, Globator, whilst the latter occurs in small transparent jelly- like balls adherent to the leaves of aquatic plants. - At times the Rotatoria multiply so rapidly in small stagnant pools as to colour the water. Hydatina senta, Diglena catellina, Triarthra, and Lepa- della are adduced by Ehrenberg as producing a milky turbidity in water, and the Typhlima viridis as imparting a green colour. - 2 H 466 GENERAI, HISTORY OF THE INFUSORIA. The Symchaeta Baltica has been presumed to be phosphorescent; and Anwraea biremis was discovered in phosphorescent sea-water. The Rotatoria are distributed everywhere over the surface of the earth, in- habiting its waters, both fresh and salt. Of the known species, by far the greater number are dwellers in fresh water, abounding in pools, ditches, and gently-flowing streams, especially where aquatic plants grow in sufficient quantity to afford shelter and indirectly supply food by the hosts of animal- cules which congregate on and about them. A too much overgrown or shaded piece of water is less favourable; for they require a complete intermixture of air with the water, and the vivifying influence of the sun, for their healthy existence. Some species especially delight in the little turfy pools on moors or in boggy ground; others have been especially found in green-coloured ponds—the colour being due to Protozoa and minute Algæ, which furnish them with suitable food. - Some of the early observers sought these animalcules especially in infusions, very generally made with sage-leaves and chopped hay; but the Rotifera are comparatively rare in infusions: a few common species only appear; and unless the infusion be comparatively fresh, none will be found; for they occur in no fluid in which decomposition is going forward. When they do exist in these infusions, they appear at a later period than do the Monadina and less highly organized infusorial forms. The known salt-water species are comparatively few ; this is very possibly owing to their being much less sought after than the freshwater animals. The principal marine forms recognized are Brachiomus Mülleri, B. heptatomus, and Symchaeta Baltica. Distemma marina and Furcularia marina, Colurus wncinatus, O. caudatus, and Amurded striata are encountered in both fresh and salt water : several are found in brackish water. Immersion in water is, however, not necessary to their existence: thus they are to be found in the damp earthy deposit from rain-water spouts, and in the detritus of the walls and roofs of houses; in the moist humus or decaying vegetable matter about trees, and especially upon the moist roots and leaves of mosses and lichens—for example, among the tufts of Bryum and of Hyp- mum, from which they may be separated by washing with a little water. We have mentioned the peculiar habitat of Albertia, within the intestine of the earth-worm, of which animal it may be accounted an entozoon ; the Notommata Parasitus also leads a parasitic existence within the hollow spheres of Volvoa, Globator; and M. Morren, many years since, gave the following interesting history of the habitat of Rotifer vulgaris in the cells of Vaucheria clavata (A. N. H. vi. p. 344):— - “The labours of Roeper show that the cells of Sphagnum are sometimes furnished with openings, which place their interior cavity in communication with the air or water in which they are immersed. This skilful observer satisfied himself that, when circumstances are favourable, the Rotifer vulgaris, one of the Infusoria whose organization has been explained by the researches of Ehrenberg, exists in the cells of the Sphagnum obtusifolium. This grew in the air, in the middle of a turf-pit: but Roepér observed its leavesin water; he does not mention whether the infusorial animal came from thence, or whether it was previously contained in the cavities of the cells. The general purport of the paper seems to imply that these Rotifers exist in the cells of that part of the plant which was exposed to the air; and in this case, the presence of an animal so complicated, living as a parasite in the cells of a utricular ačrial tissue, is a phaenomenon of the most curious kind in the phy- Siology of plants, and the more so as this animal is an aquatic One. “I recollected that, the last year of my residence in Flanders, I found at OF THE ROTATORIA. 467 Everghem, near Ghent, the Vaucheria clavata, in which I observed something similar. M. Unger had already published the following details respecting this plant in 1828: ‘Beneath the emptied tubercles and at several points of the principal stalk, at different angles, rather narrower branches are produced; these branches are generally very long, and greatly exceed the principal stalk in length. At the end of ten or twelve days after their development, there are seen, towards one or other of their extremities, here and there, at different distances from the Summit, protuberances of a clavate form, more or less regular, straight or slightly bent back; and others on the sides of the stalk, which have the form of a capsule or vesicle. These vesicles are at first of a uniform bright-green colour; and without increase of size, which exceeds several times that of the branches, they always become of a blackish-green colour, darker towards the base ; and then one or two globules of a reddish- brown may be clearly distinguished there, often surrounded by smaller gra- nules, evidently destitute of motion, whilst the great ones move spontaneously and slowly here and there in the interior of the capsule, by unequal contrac- tions and dilatations, whence arise remarkable changes of form. I saw these globules, at the end of eight or ten days after their appearance, still enclosed in the capsule, moving more and more slowly, receiving no very decided in- crease, whilst the base of the capsule became more transparent ; at last I observed that, instead of their expulsion, which I was watching for, the extremity of the capsule at the end of some days took an angular form, and subsequently gave birth to two expansions in the form of horns; it remained in this state and became more and more pale, whilst the animalcule became darker and died; and afterwards it ended by perishing at the same time as the other parts of the Conferva.” . “Subsequent researches have not succeeded in informing us what this animal might be, of which Unger spoke. As this author drew so much atten- tion to the spontaneous movements of the propagula of the Vaucheride, and as he admitted the passage from vegetable life—characterized, according to him, by immobility—to animal life, the principal criterion of which was motion, his animalcule was confounded with the propagula; and Ino one, so far as I know, has returned to this very interesting subject. “When, therefore, I found the Vaucheria clavata at Everghem, I was as much surprised as pleased to see the mobile body noticed by Unger better than he did. With the aid of a higher magnifying power, I found it easy to ascertain the true nature of the animal; for it was not a propagulum, but a real animal, the Rotifer vulgaris, with its cilia imitating the wheel, its tail, &c. - “The first protuberances or vesicles which I saw containing this anim enclosed but one of them ; afterwards they laid eggs and multiplied; but it seems that then they descend the tubes of the Vauchéria and lodge themselves in new protuberances, whose development they may possibly stimulate, as the galls and oak-apples, or organic transformations attributable to the influence of parasitic beings. “The Rotifer vulgaris travels quite at his ease in these protuberances; he traverses the partitions, displaces the chromule and pushes it to the two ex- tremities of the vesicle, so that this appears darker at these parts. One day I opened a protuberance gently: I waited to see the Rotifer Spring out and enjoy the liberty so dear to all creatures, even to infusorial animals; but no —he preferred to bury himself in his prison, descending into the tubes of the plant, and to nestle himself in the middle of a mass of green matter, rather than swim about freely in the neighbourhood of his dwelling. “Some of these protuberances had greenish threads appended to their free 2 H 2 468 GENERAL HISTORY OF THE INFUSORIA. end, and others had none: I thought at first that these threads were some mucus from within, escaped through some opening which might have served the Rotifer as an entrance; but an attentive and lengthened observation con- vinced me that in this there was no solution of continuity, and that the arrival of the Rotifers in the Vaucheride was not at all to be explained in this way. How are these parasitic animalcules generated within them? This is what further research has some day to show. Meanwhile I have thought that it should be made known that the animalcule found in the Vaucheride by Unger was the Rotifer vulgaris of zoologists.” Several of the Philodinaea, and particularly the Callidinae, have been met with in Snow, along with the so-called red snow, in very cold regions, and at considerable elevations, such as above the perpetual snow-line of the Alps. Perty informs us that mosses and lichens collected in the Swiss mountains, at a height of 9000 feet, have yielded, on washing with distilled water, numerous Infusoria, including several Rotatoria, viz. Callidina ele- gans, Rotifer vulgaris, Philodina roseola, Diglena catellina, and Ratulus lwmaris. We have no data whereon to construct laws of geographical distribution for the Rotatoria. Observation has proved no definite regional limitation of species; wherever searched for, the same species seem discoverable. Owing to the perishable nature of their tissues, the Rotifera do not occur in a fossil state ; they are, moreover, rare Components of the showers of In- fusorial dust. OF THE AFFINITIES AND CLASSIFICATION OF THE ROTATORIA.—That the Rotatoria, by their high degree of organization, should be elevated in the animal scale far above Protozoa, is now universally admitted. Indeed they cannot be rightly comprehended among Infusoria if this term be accepted to indicate a definite class of beings; for although there are slight general re- semblances between some Rotatoria and Protozoa, no true near affinities of structure exist between them. While naturalists generally are in accord on this necessary separation of Rotatoria from Protozoa, they are much at variance respecting the relative position of the Rotatoria in a classification of the Invertebrata, or, in other words, concerning the true affinities of the class. Thus Burmeister, Owen, Leydig, Dana, and Gosse would range them among Crustacea as a particular order; whilst Wiegmann, Milne-Edwards, Wagner, Siebold, Cohn, Perty, Williamson, Huxley, and others would class them with Vermes—a section comprehending Helminthae, Turbellaria, and Annelida. We shall first state the arguments used to demonstrate the Crustacean alliance, which are most fully and powerfully brought forward by Leydig ; they are, that “The external figure is rather that of Crustacea than that of Vermes. . None of the latter have a jointed organ of motion, such as most Rotifera possess in their annulated or jointed pseudopodium devoid of all viscera. “The shield-like hardened integument or lorica of some species, such as Euchlamis and Salpina, has its analogue among the Crustacea, whilst in none of the Vermes is a similar indurated cuticle to be found. “Vermes are destitute of striated muscles; but Rotifera, equally with Crustacea, possess them. The movements of many species recall in a striking manner those of Crustaceans. The nervous system supplies further evidence; for although the Rotatoria have no pharyngeal ganglionic ring and no chain of abdominal ganglia proceeding from it, yet a similar deficiency prevails with the Lophyropoda and the Daphniae, recognized Crustaceans, which have only a cerebral ganglion and radiating nerves like the Rotifera; consequently it OF THE ROTATORIA. 469 cannot be adduced as a law, that the highly developed nervous system of the higher forms is an essential character of the Crustacea. “The mode of termination of the sensitive nerves is that seen in Crustacea and Insecta; but the like is not known among Vermes. Ehrenberg pointed out the similarity of the eye-specks to those of Crustacea. The several seg- ments and texture of the alimentary canal afford no decisive evidence, since many Vermes have horny jaws, as have the Rotifera. The masticatory apparatus of the young Daphnia, presents a pretty close resemblance with that of Rotatoria—the two opposed jaws expanding into a plate toothed with numerous transverse ridges, like those of Lacinularia. The stomach-glands probably have their analogues in the lobed glandular appendages—the so- called “ salivary glands’ of Cirripedia. - “Similar organs, however, exist in many dorsibranchiate Vermes; and like- wise in many Vermes and lower Crustacea the liver is represented by large cells with peculiar contents, situated in the Walls of the stomach and intes- time. The absence of an intestine in a few Rotifera may appear opposed to their Arthropodous type; yet in the Neuropterous larva of Myrmeleo the faeces are discharged by the mouth, and the rectum itself is transformed into a spinning organ. Moreover, the intestinal canal of many Rotifera, e.g. Euchlanis and Stephanoceros, recalls, in its peculiar bell-like movement, the exactly similar character of the intestine of certain parasitic Crustacea (Achtheres, Tracheliastes, &c.). “The substance regarded as urinary concretions is evidently closely re- lated to that formed in the larva of Cyclops; but no such point of resemblance is found among Wermes. “Lastly, the anatomical and physiological phenomena of sexual life greatly favour the Crustacean relationship. Several minor particulars may be alluded to—such as the production of two kinds of ova (indeed the winter ova of Triarthra have a great likeness in the construction of the shell with the ephippial ova of Daphnia), the fact that many species carry their eggs about with them (although it is true the same is seen among Wermes, for instance Clepsine), and the occurrence of coloured oil-corpuscles in the yelk of not a few Rotatoria—all indicating a Crustacean type. The striking analogy be- tween the male (in some sense aborted) Rotatoria and the males of many Crustacea is one of far higher import. It is only necessary to call to mind the diminutive parasitic males Nordmann discovered in the females of Achtheres, Brachiella, Chondracanthus, and Anchorella, and such as Kröyer found in other Lernatopoda and Lermaece. “Moreover, the embryonic history of Rotifera is in favour of the alliance, —viz. the imperfect development of the young of several species, on their emergence from the egg, and the necessary metamorphosis they undergo before attaining the adult condition. Lastly, the diminution or even com- plete disappearance of the eyes after birth further indicates an analogy with certain Crustacean forms. - “Whilst the foregoing considerations approximate the Rotifers to the Crustacea, the nature of the respiratory apparatus and the presence of the vibratile cilia separate the two, and assimilate the Rotatoria to Vermes; yet in both these particulars they make an equal approach to Echinodermata, inasmuch as the peculiar vibratile organs of Synapta digitata appear to be similar structures with the vibrating organs (tags or gills).” Now, argues Leydig, it seems but just to allow the sum of the resem- blances to any class, if greater than that of the differences, to determine the systematic position. If this be granted, as the sum of resemblances. of the Rotifera with the Crustaceans seems assuredly greater than that of their 470 GENERAL HISTORY OF THE INIFUSORIA. differences from them, their alliance with them must be admitted. Making due allowance, therefore, for the vibratile cilia and the peculiar respiratory apparatus of Rotatoria, Leydig would constitute them a “special class of Crustacea, under the name of Ciliated Crustacea. The foregoing arguments of Leydig for the Crustacean nature of Rotatoria have been severally met and replied to by C. Vogt, in a recent paper “On the Systematic Position of the Rotifera " (Zeitschr. 1855, p. 193). The ob- jections advanced are these :— That Leydig assigns an undue importance to external resemblances; and that, as to movements, there is as much similarity between those of Philodina and a leech, as between those of any other of the Rotifera and the skipping motions of Entomostraca. The figure is no actual evidence of affinity: no perceptible likeness exists between fixed Rotifera, or a sac-like Notommata and a Crustacean, whilst, on the contrary, an undoubted similarity prevails between a Stephanoceros and a Bryozoon; and between Notommata tardigrada and many of the Wermes the resemblance is more pronounced than that be- tween any of the Rotatoria and a water-flea. Besides, there are Vermes of a smooth, oval, discoid, and expanded figure, and others with bodies not less clearly divided into regions than the Rotifera. An annulate articulation, like that of the pseudopodium of Rotifera, is also a feature seen among Annelida; and the telescopic joints and movement are witnessed in Eunice. It is the possession of limbs, each consisting of several segments, which is characteristic of Articulata, both in the full-grown and in the larva condition, and not an asymmetrical process actually forming but a single segment. Further, spines and hooks, in some degree moveable like the pincer-processes on the pseudopodium of Rotatoria, occur in many Vermes, especially among the parasitic species. Lastly, a pair of jointed locomotive organs is never found among Rotatoria at any period of their existence. The assertion that the thickening of the integument as a lorica is not seen in any Vermes is correct, if the constitution of the lorica of one piece be a necessary feature, although the thick cartilaginous tube of Gordiaceae and the firm in- tegument of many other Annelids may be adduced as analogous conditions. But if a lorica may be composed of several pieces, the whole family of marine Annelida, in which the skin is hardened into a firm shield, may be cited as homologous. To Leydig's remark that he knows of no Vermes with a lorica, the rejoinder may be made, that no Crustacean is found enveloped in a gela- tinous sheath, like Notommata centrura, whilst, on the contrary, such an investment is common among Vermes, and especially exemplified in Siphono- St07???!???. Striated muscles are not unknown in Annelida; they have been seen in Salpa; and in Some Radiata the particles of muscles separate as so many disks. Moreover, such muscles occur in other Invertebrata besides Crustacea, and they therefore furnish no real argument for allying Rotifera with the latter. The nervous system lends no support to Leydig's views, as he professes it does. A coalesced cerebral ganglion sending off nerves to depressions in the cuticle armed with bristles, finds no analogy among the lower Crustacea, but exhibits, on the other hand, an actual identity of structure with the nervous system of the Turbellaria. The same resemblance is apparent among all the Cestoidea, the Nemerta, Planarice, and Trematoda. Again, the like degrees of development of eye-specks, from a simple heap of pigment to a definite organ with a refracting medium, is illustrated by all those sections of the class Vermes, as Quatrefages shows in his figures of the Nemertae. The mode of termination of the nerves described by Leydig in Rotatoria and Crustacea OF TELE ROTATORIA. 471 is also seen in Vermes; and in general the organization of the nervous sy- stem is much more in accordance with that of Cestoidea than with that of the lowest Crustacea. Leydig remarks the great similarity of the maxillary apparatus of young Daphnia, with that of some Rotatoria, but forgets that a similar structure occurs in many Vermes. On the other hand, there are no Crustacea which can, like several Notommatoe, protrude the maxillary organs as prehensile instruments; yet it is a common phenomenon with many Vermes. Further, in no Articulata are the anus and rectum wanting, as happens with Some Rotatoria; for although in the larva of Myrmeleo, as Leydig states, the rectum is transformed into a spinning organ, still the viscus is present, though modified for a different functional purpose: however, among Vermes such an imperfect intestinal canal is common enough. From the preceding con- siderations, the structure of the alimentary tube must be admitted to accord rather with that of Wermes than with that of Crustacea. The secreted solid matter in the cloaca of embryo Cyclops, compared by Leydig to the “urinary concretions ° of Rotifera, is, however (unlike them), produced originally of a green colour, within a sac on each side of the intestine, but subsequently becomes yellow, and is discharged through the cloaca. Such sacs or cells have rather the signification of a liver, and are common among Wermes. Leydig relies most on the phenomena of the sexual system and the occur- rence of distinct male animals. But Polynoë, Ea'ogone, and the Cystoneidae produce both summer and winter ova, and carry them about. And with re- ference to the existence of Small distinct males, Krohn has proved it in Aw- tolytus prolifer, whilst among Nematoid worms generally a marked difference obtains between the males and females; and what, indeed, can be more striking than the difference between Distoma Okemii and D. haematobium ? The variation in form and structure between the two sexes can therefore furnish no differential character, seeing that it occurs alike in some Crustacea and in most bisexual Vermes. The occurrence of a metamorphosis, and the shrivelling or obliteration of the eyes, are phenomena common to Wermes and Crustacea. The larval Ste- phanoceros is equally comparable and similar to the occasional type of Annelid larva, having a frontal ciliary wreath in advance of the eyes, or otherwise to the larvae of Nemertidae, such as Alardus caudatus, as to the embryos of any Crustacea. Wherefore all Leydig's characters, even where they indicate some affinity with the Crustacea, exhibit, at least, an equally close one with Vermes. The presence of vibratile cilia and the peculiar respiratory organs are, as Leydig admits, circumstances approximating Rotifera to Annelida. A tor- tuous canal with ciliated tags occurs in none of the Articulata, and is incon- sistent with the type of their water-breathing apparatus. At best there is only a remote analogy, whilst a close similarity, and even an identity, is seen between such structures and those of most Cestoidea. The history of development is in favour of the Annelid alliance, and op- posed to Leydig's hypothesis; for in all Crustacea the embryo originates from a primitive part Superposed upon the yelk, whilst in Rotifera, in com- mon with all Vermes, such a supplementary part is wanting, and the embryo is generated from the entire yelk. The appeal to metamorphosis lends its Support to the present argument: for no trace of resemblance is perceptible between the larvae of such Crusta- ceans as undergo transformation, having three pairs of jointed legs or feet, and the embryo stages of Rotatoria—for instance, of Stéphanoceros, with ciliary wreath, posterior bunch of cilia, lateral eyes, and vermiform trunk; yet in 472 GENERAL HISTORY OF THE INFUSORIA. all these particulars it, on the contrary, assimilates to the larvae of Vermes, between which and the adult state the diversity is equally great. The accompanying tabular statement given by Vogt briefly presents the chief points of the discussion. SYSTEMATIC POSITION OF THE ROTATORIA. Characters inconsistent Characters common| Characters incon- Characters not ex- Characters peculiar stem and or- gams of sense. with Crustacea but in to Crustacea and sistent with to Crustacea. clusive but common accordance with Vermes. Vermes. Vermes. to other classes. 1. Ciliary motion. Ammulation of ......... ......... Formation of a the bodies lorica. with telesco- pic segments. ... Wessels with cili-|Structure of the ......... . ......... Structure of the ated tags. nervous sy- muscles. . Development of Maxillary ap-| ......... . ......... Structure of in- embryos from the paratus. testimal canal. entire yelk with- - out primitive part. . Typical structure |Formation of ......... ......... Urimary secre- of the larvae and eggs and tion (?). young, without their carry- jointed locomo- ing about by tive organs. parent. . Total absence of |Dissimilarity articulated limbs in pairs during their entire exist- €11C0. and imper- fect organiza- tion of the males. Cohn's name may now be added to the list of opponents to the Crustacean alliance. We have already seen (p. 447) that he denies the occurrence of any metamorphosis in the course of development of the Rotatoria, and by so doing sets aside one indication Leydig brought forward in favour of their alliance with Crustacea. The following is a summary of his arguments against that relationship:—“The ciliated condition of the Rotifera, their respiratory apparatus, their nervous system, the position of the intestine, and even their general form, are all of them circumstances in favour of their affinity with Vermes.” Cohn can find no true articulations, but merely shallow folds of the skin in the principal portion of the body; and even the pseudopodium and toes are not articulated motory Organs (or limbs), but prolongations from the common cavity of the body. The circumstance of his having united the Tardigrada with the Systolides (Rotatoria) indicates Dujardin’s recognition of the affinity of the latter with Crustacea; for in structure the Tardigrada make an unmistakeable approach to Arthropoda by the pairs of limbs and chain of ganglions on the abdominal surface, and to Arachnida also by the structure and disposition of their digestive organs, by their suctorial mouth, and by other details of organization. Their association with Rotatoria, how- ever, is not recognized by any other naturalist besides Dujardin; and they are generally placed amongst the lowest Arachnida, near the Pycnogonidae and Acarinae (the lowest families of Arachnida) (see Section W., OF THE TAR- DIGRADA). A still higher affinity has been recently claimed for the Rotatoria by Mr. OF THE ROTATORIA. 473 j-y Gosse, viz. with Arthropoda and Insects. He supports this notion by an appeal to the structure of the maxillary apparatus and to supposed analogies of its several parts with the mandibles, jaws, &c., of insects. The “mastax." (see chapter on Digestive Apparatus) he identifies with a true mouth; the “mallei’’ with mandibles; the “manubria * possibly with the cheeks, into which the “mallei’’ are articulated; the “rami” of the “incus ” with maxillae; and the “fulcrum ” he imagines to represent the “cardines” sol- dered together. While maintaining this connexion with Insecta through the maxillary organs in their highest development, he suggests their affinity with Polyzoa by the same organs at the opposite extremity of the scale, since the oval muscular bulbs in Bowerbankia approach and recede in their action on food, and seem to represent the quadriglobular masses of Limnias and Rotifer further degenerated. If this affinity be correctly indicated, the in- teresting fact is apparent that the Polyzoa present the point where the two great parallel divisions Mollusca and Articulata unite in their course towards the true Polypi (see Mr. Gosse's valuable paper in the Philosophical Trans- actions, 1855). In a memoir since read before the Royal Society (Phil. Trans. 1857) by this same distinguished naturalist, the Crustacean alliance is further insisted on upon the ground of the sexual peculiarities of the Ro- tatoria. In this paper the author remarks that we must look, for a parallel to the curious facts established concerning the dioecious character of Rotifera and their peculiar males (see p. 455), to the Crustacea. “The economy of the Hectocotylus of certain Cephalopod Mollusca, though perhaps even still more abnormal, is only remotely analogous. Nor is the parallelism very close of those Entozoa in which the males are organically united to the females, as the genera Heterowra and Syngamus, described by Professor Owen. “In the class Crustacea, however, many examples occur of a sexual differ- ence, which may instructively be compared with the one before us. Thus, among the Isopoda, we find the parasitic genera Bopyrus, Phryavus, and Ione, in which the males are notably smaller than the females, very diverse in form, and in some respects inferior in structure. In the Siphonostoma the males are extremely small, and do not in the least resemble the females,” though those of different genera bear a strong resemblance inter se, even when the females are very dissimilar. So low is their grade of organization, that Burmeister has attempted to prove these minute creatures to be embry- onic or larval forms. And, finally, in the Cirripedia, Mr. Darwin has proved the existence of males in the genera Ibla and Scalpellum, which are very minute as compared with their females, excessively abnormal in form, and in some respects in an embryonic condition, though unquestionably mature, as shown by the spermatozoa. And, what is still more interesting, the same accurate zoologist observes—‘After the most careful dissection of very many specimens, . . . . I can venture positively to assert that there is no vestige of a mouth or masticatory organs, or stomach.” Again, he describes the internal structure as ‘a pulpy mass with numerous oil-globules,’ and the sperm- vesicle as “a pear-shaped bag at the very bottom of the sack-formed animal, containing either pulpy matter, or a great mass of spermatozoa,’—terms which might have been employed in describing some of the male Brachiomi. “In all these analogies I conceive we may find additional reasons, to those that have been before adduced, for assigning to the Rotifera a zoological po- sition among the Articulata.” - The attempt of Mr. Gosse to identify parts of the maxillary mechanism of Rotatoria with that of Insects, although praiseworthy, is in our opinion un- successful, and involves a considerable stretch of imagination. Moreover, if the identifications, or more correctly speaking the homologies, be correct, we 474 GENERAL HISTORY OF THE INFUSO.R.I.A. do not see that this circumstance is per Sé adequate to establish an alliance with the Insecta, particularly when, in most other respects, the differences between the two groups of beings are so very considerable. Referring only to the particulars mentioned in Vogt's critique, we may observe that if the aberrations of organization of Rotatoria from the lowest Crustacea render their alliance with the latter more than doubtful, still less possible is their connexion with the highest Articulata, in which every differential character becomes more developed. The arguments and illustrations of Vogt in favour of the close affinity of Rotatoria with Wermes will to most minds appear convincing; but should any demand further evidence, it is supplied by the opinions of the majority of naturalists and by the reasons adduced in their support. At present we will confine ourselves to the views and arguments of Perty, Siebold, William- son, and Huxley. * Perty enters into no discussion, but merely states generally that the posi- tion of Rotifera with Vermes is indicated by their want of jointed feet in pairs, and of a ganglionic abdominal chain such as Crustacea have, whilst, on the contrary, they are provided with external voluntary and internal invo- luntary cilia, after the type of Vermes. The class to which he would refer them is that of the Thoracozoa (Arthrozoa). - Siebold affirmed that the affinity of Rotifera with the Crustacea is but remote, since they are, he conceives, deficient of a distinct abdominal mem- brane, of limbs in pairs, and of striped muscular fibre, undergo no meta- morphosis like Crustacea, have organs of respiration (cilia) both externally and internally, and an epithelium lining the alimentary tube, such as no Ar- thropoda or Crustacea possess. Subsequent research has invalidated a few of the reasons put forward by Siebold, such as that of the absence of striated muscles; but the majority retain their force. Prof. Williamson argues, from the particular instance of Melicerta, against a Crustacean relationship. His words are—“In the possession of so highly- organized a form of voluntary muscle, in the investment of the fasciculi by a sarcolemma, and in the existence of a well-defined, ciliated, cellular epithe- lium lining the alimentary canal, we have indications of an organization ap- proaching that of the lower Articulata. The dental apparatus appears to constitute a splanchno-skeleton, like that of the Crustacea; but, on the other hand, the absence of a visible nervous system removes the Melicerta far below the Homogangliate animals. That they should possess a nervous system of some kind appears almost a matter of necessity if the presence of a striated muscular fibre indicates volition; but its actual existence has yet to be de- monstrated. I have found no special Organs of circulation or respiration. On watching the movements of the small free cells which float in the visceral cavity, as well as in the tail, it becomes obvious that the fluid contained within the integument moves freely with every contraction of the body. I detect no vessels or pulsating organs. These facts also tend to associate the animal with the Acrita rather than with the Homogangliate Crustacea. At the same time its organization is of a higher type than that of the Bryozoa. . . . . Again, many Vermes possess horny jaws not wholly unlike those of Rotatoria, together with similar stomach-glands, equally resembling those of some lower Crustaceans; and, moreover, many Vermes, e.g. Clepsime, carry their eggs about with them.” Prof. Huxley has very ably examined the question of the affinities of the Rotatoria. Containing, as his opinions and illustrations do, many additional facts, we shall, at the risk of some repetition, add them to the preceding dis- cussions and details. In the first place, he adopts, as a group of the lower OF TELE ROTATORIA, 475 Annulosa, under the name of Annuloida, the several families Annelida, Echi- modermata, Trematoda, Turbellaria, and Nematoidea, and in company with these he would place the Rotifera. “The terms of resemblance (to the An- muloida) are these :—1. Bands of cilia, resembling and performing the func- tions of the wheel organs, are found in Annelid, Echinoderm, and Trematode larvae. 2. A water-vascular system, essentially similar to that of Rotifera, is found in Monoecious Annelids, in Trematoda, in Turbellaria, in Echino- derms, and perhaps in the Nematoidea, the Cestoidea, and the Nemertidae. 3. A similar condition of the nervous system is found in Turbellaria. 4. A somewhat similarly armed gizzard is found in the Nemertidae; and the pha- ryngeal armature of a Nereid larva may well be compared with that of Albertia. 5. The intestine undergoes corresponding flexures in the Echino- derm larvae. There are therefore no points of their organization in which the Rotifera differ from the Annuloida; and there is one very characteristic circumstance, the presence of the water-vascular system, in which they agree With them.” - - Prof. Huxley next proceeds to inquire to which of the Annuloida the Roti- fera are most closely allied, and in so doing seeks for the fundamental types of their organization by an ingenious mode of demonstration, adducing the genera Stephanoceros, Philodina, Notommata, Brachionus, and Lacinularia as “the types of the great division of the Rotifera, and of which whatever is true will probably be found to be true of all the Rotifera.” The result he arrives at is, “that the Rotifera are organized upon the plan of an Annelid larva, which loses its original symmetry by the unequal development of various regions, and especially by that of the principal ciliated circlet or trochal band.” After some further remarks, Prof. Huxley adds—“I do not hesitate to draw the conclusion ” (which at first sounds somewhat startling) “that the Rotifera are the permanent forms of Echinoderm larvae, and hold the same relation to the Echinoderms that the Hydraform Polypi hold to the Medusae, or that Appendicularice hold to the Ascidians. “The larva of Sipºwnculus might be taken for one of the Rotifera; that of Ophiura is essentially similar to Stephanoceros; that of Asterias resembles Lacinwlaria or Melicerta.” - Again, this talented naturalist believes that the Rotifera furnish the link between the lower Echinoderms (which otherwise seem to lead nowhere) and the Nemertidae and Nematoid worms, the Rotifera themselves forming the lowest step of the Echinoderm division of the Annuloida, the proposed subkingdom of Cuvier's Radiata. To elucidate his views, Prof. Huxley has appended to his essay a series of diagrams showing the essential correspondence between Rotifera and Annelid or Echinoderm larvae. When Leydig wrote his memoir on the Rotatoria, he had the advantage of seeing this contribution to their history by Prof. Huxley, and has remarked in general terms, of the above views and their illustrations, that although the ingenuity of the attempt to prove Rotatoria permanent larvae of Echinoderms must be admitted, he is nevertheless unable to adopt the hypothesis of the English observer, and must hold to his own idea of their Crustacean cha- racter. The conclusion which it seems to us must be adopted is, that the Rotatoria belong to the great group of the Radiata known as Vermes, and stand in more particular relation with those families which make up the proposed di- vision “Annuloida.” We must now add a few observations concerning the affinity exhibited by the Rotatoria with the Ciliobrachiate Polypes or Bryozoa (a family of Polyzoa). 476 GENERAL HISTORY OF THE INFUSORIA. This affinity is particularly marked in the genus Stéphanoceros on the part of the Rotifera, and in that of Bowerbankia on the side of the Bryozoa. The members of the latter genus live in an elongated tubular case, and have themselves an elongated, rather club-shaped figure. The case is transparent; its upper portion is soft, so that it can close over the animal when retracted. The head of the Bryozoon is armed with several long processes or tentacles similar to those of Stéphanoceros, which are clothed with cilia and spines; and the margin of the head itself is also ciliated. This whole armature is retractile. Muscles are distinguishable, moving the several parts. The di- gestive system comprehends a mouth, Oesophagus, gizzard, stomach, a gastric tube or pylorus, and an intestine, lined with cilia, returning upwards, so that the anus opens near the mouth. The lining membrane of the gizzard is moreover furnished with many horny teeth, seated on oval muscular bulbs, which, according to Mr. Gosse (see p.473), “approach and recede in their action on food, and seem to represent the quadriglobular masses of Limnias and Ro- tifer further degenerated.” The Bryozoa as a class are reproduced by three modes: 1. by ova; 2. by ciliated gemmules; and 3. by budding (gemma- tion) from the common stem or polypidom where they grow. The second mode is not met with in Bowerbankia, but only in species having fleshy or gelatinous polyparies (e. g. Halodactylus), where the ciliated gemmules occur in sacs, which appear as whitish points imbedded in the general mass. Is there, we may ask, any analogy between these and the winter ova of Rotifera, which are in some cases ciliated or hairy 2 The ovary producing the ordinary ova is placed close above the stomach; and contiguous to it is the testis, filled with spermatozoa. The ova when ripe escape into the general cavity of the body, where they are surrounded and impregnated by the spermatozoa ; and after several have accumulated about the base of the tentacles, they are at length discharged through the anus. The ova are remarkable from their irregularity of shape. The embryo escapes as a free being, not unlike some ciliated Pro- tozoon, but by-and-by it fixes itself, produces its pedicle, and assumes the form of its parent. On comparing this description of Bowerbankia with that of Stéphanoceros, the points of similarity between the two are very many and striking. The points in which Bowerbankia chiefly differ are—1. its character as a member of a compound mass or polypary from which it may itself have grown as a bud, whilst reproduction by gemmation is unknown among Rotifera; 2. the position of the ovary above the stomach, in close proximity, with an evident testis ; 3. the apparent absence of an Oviduct, and the consequent escape of the ovum, followed by its fertilization, within the general cavity of the body; 4. the imperfect development of a maxillary apparatus; 5. the absence of a water-vascular system; 6. the greater length and stiffness and more slender figure of the tentacles or arm-like processes of the head; and 7. the different disposition of the cilia upon them—for these in Stéphanoceros are arranged in little bunches or whorls at short distances from each other. But several of these distinctive particulars lose much of their force from other comparisons and considerations. Thus the absence of an oviduct is admitted as an occasional event in Rotifera; and the escape of the embryos into the general cavity of the body has been stated by many observers to occur in Stephanoceros; Leydig, however, denies this ; yet the birth of the young in Philodina and their active life within the body of the parent may present the analogy in request. It cannot be affirmed with certainty that Bowerbankia is unlike Stephanoceros in having a testis in company with the ovary; for no male Stéphanoceros has yet been found, and some doubtful structures have been by some assumed to represent the testicle. To cite yet OF THE ROTATORIA. º 477 another circumstance, a water-vascular system is indistinct in Stéphanoceros, and would be overlooked, as Leydig remarks, did not the knowledge of its form and of its existence in other Rotatoria direct in the search for it ; and, on the other hand, such a structure has not been sought after in Bowerbankia. These and other considerations, which might easily be added to, lessen the differential characters, and, together with the many undoubted points of re- semblance between Bowerbankia and Stéphanoceros, incline us to the very prevalent opinion that there is a real affinity between Rotifera and Bryozoa, although we would not go so far as some naturalists and place the genus Stephanoceros among the latter. IHuxley entertains an adverse opinion, and believes that “there is a funda– mental error in approximating the Polyzoa and the Rotifera at all, that the resemblance between Stephanocéros and a Polyzoon is very superficial, and that the relations between the Polyzoa and the Rotifera are at the best mere analogies.” The resemblances between the Rotatoria and the Ciliated Protozoa are merely superficial. Vaginicola is enclosed in a transparent sheath, like a Floscularia or a Tubicolaria; the urceolated individuals of Ophrydium are grouped into gelatinous balls, like those of Conochilus; the ciliary wreath about the head of Vorticella, Stentor, and Vaginicola makes an approxima- tion to that of Rotatoria; and the contractile muscular pedicle of Vorticella and Zoothamnium recalls, in some respects, the retractile pedicles of the fixed Rotatoria. . A connecting link is, however, supplied between the Ciliated Protozoa and the Rotatoria by most genera of the family Ichthydina, which Ehrenberg indeed numbered among the latter class. This great microscopist had but an imperfect acquaintance with their organization ; and at the present time our knowledge of it is far from complete. The genera referred to are Ichthydium and Chaetonotus; and perhaps Mr. Gosse's genus Sacculus should be united with them. The genus Glenophora of Ehrenberg is not recognized by most naturalists. - They differ from Rotatoria in having no transverse joints or folds to the body, no water-vascular system, no appreciable muscles or nerves, whilst the ciliary wreath is on the model of Ciliated Protozoa, and the alimentary canal after the type of that of Nematoda and of Anguillula. The vibratile cilia extend also over the abdominal surface of Ichthydium, and over both the ventral and dorsal of Chaetonotus. Lastly, according to M. Schultze they are hermaphrodite, and have pin-shaped spermatozoa. These peculiarities of organization have induced observers generally to exclude these genera from Rotatoria. Dujardin has found a place for them along with Coleps; and a doubtful subgenus he named Planariola, as a subclass of Ciliated Protozoa, unlike the rest of this class in being symmetrical. Another link between Rotifera and the Ciliata is to be found in the peculiar genus Dysteria, which Prof. Huxley referred to the Euplota, and Mr. Gosse to the Monocercaded, among the Rotatoria (see p. 387). CLASSIFICATION.—Since no observers, prior to Ehrenberg, duly recognized the Rotatoria as a class distinct from the Protozoa, We may at Once commence with an analysis of the classification he has proposed. This was based on the apparent structure of the rotary organ, of which he distinguished two types: 1. in which the circlet of cilia is complete—Mono- trocha ; 2. in which it is divided into two or more segments—Sorotrocha. Each typical form was subdivided; the first into Holotrocha, in which the ciliated ring is entire, and Schizotrocha, in which the wreath is notched. The second (Sorotrocha) into Polytrocha, with a compound wreath of several lobes 478 GENERAL EIISTORY OF TEIF INFUSORIA. ſº ! i | | } Illoricated: Ich- \ Loricated: GEcistina ..................... (IIloricated: Mega- or secondary circlets, and into Zygotrocha, where the organ consists of two (a pair of) symmetrical Wreaths. - The further division of these sections into families was founded on the circumstance of the animals being either loricated or not loricated; and the distribution into genera was made, primarily, according to the number and disposition of the red eye-specks, and in a secondary degree, according to the characters of the jaws and teeth, or of those of the foot-process, or other- wise, more rarely, of the lorica. This classification we present in a tabulated form for convenience of reference. CLASS ROTATORLA, ACCORDING TO EHRENBERG'S SYSTEM. SECTION I. MONOTROCHA. FAMILIES. b h df P GENERA. eyes absent ...... ins with trumcated foot....... • * *8. y hair absent {:}; forked foot............ #ium. hair present ................................. Chaetonotus. eyes present ......................................................... Glenophora. lorica distinct................................. CEcistes. { lorica: agglomerated ........................ Conochilus. thydima ......... One eye . . . . . . . . . . . . . . . . . . . . . • * * * * * * * * * * * * * * * * * Microcodon. ''' U two eyes ...................... * * * * * * * * * * * * * * * * * Megalotrocha. eyes absent ............................................................ Cyphonautes. lotrochaea ...... . eyes present eyes absent ............................................................ Tubicolaria. one eye (when Stephanoceros. we t - | young) .........................................::::::::::::::::::: Loricated: Floscu urceoli distinct Limnias. two eyes (when rotary organ bifid { urceoli agglomerate Lacinularia. young) ...... rotary organ 4-fid ........................... Melicerta. rotary organ 5–6-fid ........................ Floscularia. SECTION II. SOROTROCHA. DIVISION I. PoEYTROCHA. ſ no teeth .................... • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Enteroplea. eyes absent teeth { jaw many-toothed ........................ Hydatina. , ºvº ºf º- i. e. g. e º ſº tº jaw one-toothed ................ * * * * * * * * * * * Pleurotrocha. frontal...................................................... Furcularia. * foot styliform .............................. Monocerca. y frontal cilia alone ...... Notommata. ' ' ) cervical 4 foot furcate do. with styles Symchaeta. do. with umcini Scaridium. foot absent; body with lateral cirrhi... Polyarthra. frontal... foot **ś & e º is tº $ tº e tº #. $4'an. Cll'l’Ill Oll 110CK. . . . . . . . . l’I3]"UEll’8. two eyes ... foot styliform {; wanting......... Batulus. - cervical ...foot furcate ................................. Distemma. ............................................................... Triophthalmus. three eyes { ............................................................... Eosphora. \ , s • * * * * * * * * ... • * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Otoglema. eyes numer- { e e º a s e g g g g g s is g g g g g g g º e º & & is e s tº a tº º e º gº tº * * * * * * * * * * * * * * * * * * * * * * *.... Cycloglema. tº a e g º e º e º e º e º s º & a tº t e s tº € e º & e º 'º e º º e º 8 & 9 & 8 & 6 º' & 8 & 9 & ................ Theorus. ( Lepadella. Monostyla. Mastigocerca. Euchlamis. Euchlamidota... eyes absent ............................................................... < †. Momura. Colurus. Metopidia. Stephanops. Squamella. lariasa ............ one eye \ OF TEIF ROTATORIA. 479 DIVISION II. ZygoTRocIIA. FAMILIES. GENERA, / with a proboscis and foot-processes ........... . . . . . . . . . . Callidina. without proboscis ; no e -> e eyes absent horn-li 2 rotary organ pedicled ... Hydrias. rg orn-like processes - - $3 on the foot ............ do. not pedicled Typhlina. .# Philodinaea 4 foot with horn- ſº toes two ... Rotifer. 3 like processes do. three Actinurus. H eyes present two frontal foji processes; terminal toes two ................................. Monolabis. two cervical ................................................ Philodina. re; eyes absent........................... foot furcate ........................... Noteus. $2 3 & Brachiomaea º foot absent .............................. Anuraea. § eyes present one (cervical) {: furcate.............................. Brachiomus. \ two (frontal), foot styliform .............................. Pterodina. Many serious objections attach even to the fundamental principles which Ehrenberg has adopted in his systematic distribution of Rotifera. Leydig has well argued against the existence of an actually compound trochal disk (p. 398); and to designate the peculiar ciliated organs of Floscularia and Stephanoceros simple notched wreaths is certainly a misnomer, and conveys an erroneous Impression. The employment of the “loricated ” and “illoricated” condition, as un- derstood by Ehrenberg, in the construction of families, is even more faulty; for, as before observed (p. 394–5), he uses the term “lorica” so loosely, that it designates no one special structure. The existence and position of eye- specks, as characteristic of genera, are very uncertain and insufficient. These coloured specks, especially when numerous, are not constant either in number or position; they disappear with age in numerous instances, in some even before the adult condition is attained; they may be deficient from various external circumstances of development; and, in general, they have not that importance in the organization and life of the Rotatoria which can warrant their employment as generic distinctions. The formation of the jaws and the number of the apparent teeth might afford valuable characteristics; but they are facts difficult of determination on account of the minuteness of their parts. From the above considerations it is evident that the descriptions of the Berlin Professor are open to much question, and the generic characters based on them uncertain. - That this artificial system of Ehrenberg is erroneous, is also evidenced by the separation of undoubtedly allied forms which it often entails. This evil involves another, that of the unnecessary multiplication of genera and of di- stinctive names. Thus Dujardin rightly insists on the erroneous distribution of a naturally single genus, from the really unimportant variation in the number of coloured specks, into the several genera Lepadella, Metopidia, Stephanops, and Squamella ; and also indicates the division of the families Philodinaea and Hydatinaea as carried too far. On the other hand, the ex- tensive genus Notommata comprehends many very dissimilar animals, including, for instance, not only such as possess the typical alimentary canal of the Rotifera, but also those recently discovered forms that diverge from that type in wanting a separate anal outlet. Such a genus requires revision. The same may be said of the genus Digléna. In the opinion of many naturalists, the Berlin Professor falls into an additional error in admitting the family Ichthydina among the Rotatoria. In fine, the result of modern research is to call equally in question several of the Subdivisions and genera which he has instituted. Although the defects and errors of Ehrenberg's system be generally ad- 480 GENERAL HISTORY OF THE INFUSORIA. mitted, yet several writers, such as Siebold, Perty, and Gosse, have been con- tent to employ it in the absence of a better. Indeed, before a correct natural classification of the Rotatoria can be made, the organization of each inde- pendent form must be investigated, and the signification and relative import- ance of its parts determined. & Various temporary arrangements have been suggested. Ehrenberg himself indicated a division of the class according to the form and disposition of the alimentary canal, and another according to the structure of the dental appa- ratus. Both these are unsatisfactory and artificial; and even their author was compelled to admit that genera and species were thereby associated in alliances quite different from those they occupied in his accepted system. Dujardin considers that, “in the present state of science, we do not possess the elements of a definite classification; ” and therefore proposes, as a merely provisional scheme, four grand divisions of the Rotatoria, including the Tardi- grada: viz., 1. those which live fixed by their posterior extremity; 2. those which have but one mode of locomotion, and are always swimmers; 3. those which enjoy two modes of progression—by crawling, after the manner of leeches, and by swimming ; 4. those which creep by moveable uncini on their lower sur- face, and are destitute of cilia. It is the Tardigrada which constitute this fourth division; and they so far differ from Rotatoria, particularly in the ab- sence of a ciliary apparatus and the presence of rudimentary feet, that their alliance with the latter is generally objected to ; even Dujardin himself views it as of doubtful propriety. . The classification of Dujardin, omitting the Tardigrada, is as follows:– Families. * FLOSCULARIENS 1. Fixed forms ...................................................... * F MELICERTIENs. BRACHIONIENS. 2. Having one mode of locomotion, viz. by swimming...... FURCULARIENs. ALBERTIENs. 3. Having two modes of locomotion : 1. by swimming : b y ê ' | ROTIFERES. - 2. by crawling ................................................ For the further division into genera we must refer to Dujardin's work. The system, as Leydig remarks of it, is founded on a correct principle, and recommends itself by its simplicity. The groups of individuals it brings together generally consort by natural affinities; still some are exceptional and aberrant, and occur as disjecta membra. Leydig makes the attempt to form a division, primarily according to the form of the body, and secondarily, to the nature and the presence or the absence of the foot-process. There are three primary forms:–1. in which the figure is club-shaped or cylindrical; 2. in which it is saccular; 3. in which it is compressed. The accompanying plan represents in full the system in ques- tion. The Ichthydina are omitted. LEYDIG'S CLASSIFICATION, A. Figure club-shaped or cylindrical. I. With a long, Čransversely wrinkled, attached foot. In this section are comprised the families (Ecistina, Megalotrochaea, and Fosculariza of Ehrenberg, excepting the genera Pºgura, Glenophora, Cyphonautes, and Microcodon. The last belongs to another section; and the other three are incomplete forms. II. With a long, jointed, telescopic, and retractile foot. Is represented by the family Philodinaea (Ehr.). III. With a long, jointed, not retracáile foot. Includes the genera Scaridium and Dinocharis (Ehr.). IV. With a short foot and long foot-processes. Includes the genera Monocerca, Furcularia, and Microcodon (Ehr.), and the OF TEIB ROTATORIA, 481 species Noćommata Tigris and N. longiseta (Ehr.). Leydig surmises that Microcodon is a male animal. W. With a short foot; the foot-processes equal to the foot in length, or but slightly shorter or longer. Comprises the genera Hydatina, Pleurotrocha, Diglena, Ratulus, Distemma, Triophthalmus, Eosphora, Cycloglena, Theorus, Synchſeta (Ehr.), and Lindia (Duj.); together with the species Noćommata Thaba, N. petro- myeon, N. saccigera, N. Copeus, N. centrura, N. brachyota, N. collaris, N. Najas, N. aurita, N. gibba, N. ansata, N. decipiens, N. Felis, N. para- Sitica, N. tripºs (Ehr.), N. tardigrada (Leydig), N. vermicularis (Duj.), N. roseola and N. onisciformis (Perty), and the Furcularia Rheinhardtii (Ehr.), which is, however, actually a Nočommata. The genus Ländia § is doubtful; and that of Enteroplea (Ehr.) is the male of Hyda- tºna Senta. WI. Without a foot. Is represented by the genus Albertia (Duj.). B. Figure saccular. I. With a short foot. Such are the species Noćommata clavulata?, N. Myrmeleo, N. Syrina, and Diglena lacustris. II. Wężhow? #: Includes Noćommata anglica (Dalrymple), N. Sieboldii (Leydig), Polyarthra platyptera (Ehr.), and the genera Triarthra (Ehr.) and Ascomorpha (Perty). C. Figure compressed. I. With a foot, Represented by the genera Euchlamis, Lepadella, Monostyla, Metopidia, Stephanops, Squamella, Noteus, Brachionus, Pterodina (Ehr.), and Notogonia (Perty). II. Without a foot. The genus Anuraa (Ehr.). a. Compressed horizontally. b. Compressed laterally. Includes the genera Salpina, Mastigocerca, Monura, and Colurus (Ehr.). This arrangement of the Rotatoria the author confesses to be defective. In our opinion, it has no advantage over the scheme of Dujardin, and, on the other hand, wants its simplicity. Its basis is not such as will combine the species according to their natural affinities; for there is no necessary or direct relation between external form and internal organization, and it is on the latter alone than any classification can Securely repose. 482 GENERAL EIISTORY OF TELE INTUSORIA. SECT. W.-OF THE TARDIGRAT) A. THEIR STRUCTURE, HABITATs, AND AFFINITIES.—The Tardigrada or Tardi- grades (in German, Wasserbären, lit. water-bears) constitute a small group of animals, first noticed by Eichhorn, and latterly more fully investigated by Doyère, Dujardin, and Kaufmann. • Their size is so considerable (from ºth to ºth of an inch in length) that they are visible to the naked eye. They have oblong, symmetrical, non- ciliated, and very contractile bodies, admitting of their rolling themselves into a ball, and of otherwise varying their figure. The head is somewhat pro- duced, assuming a comical or pyramidal figure ; but they have no pseudopo- dium or other posterior process. They are invested by a resistant, firm, and Sometimes horny integument, composed of two layers. The firmness is due to the chitinous composition of the external lamina or cuticle, which is not affected by caustic alkali. In Emydium, M. Doyère describes the integument to consist of four horny plates. During contraction, the integument is thrown into transverse folds, and the anterior and posterior segments retracted. Its surface is generally smooth; but in Emydium there are a few pretty regularly disposed bristles (setae) on the back and sides; and in the neighbourhood of the mouth there are, as a rule, several soft flexible processes, palpi or antennae. Numerous and definite muscles extend between the inner skin or epidermis and the various organs and members. The under or abdominal surface is clearly distinguished from the dorsal by the presence of four pairs of rudimentary feet without joints, each consisting of a nipple-like (mammilliform) process supporting on its extremity from two to four well-developed curved and acute umcini or hooks. These are the locomotive members by which the animals crawl upon and adhere to solid substances. The head is without a trochal disk or ciliary wreath, vibratile cilia being entirely wanting. The mouth, opening at its extremity, in the median line, is modified so as to form a sucking-tube; it is narrow, and drawn out to a more or less fine extremity; it is bounded on each side by a lateral, rigid, horny, narrow or linear process—the maxilla, which is moveable upon a single or double central piece or fulcrum. The whole organ constitutes a tube-like sucker, and is protrusile at will beyond the head, like the suctorial mouths of Acari and Insecta. On each side of the mouth are the small re- tractile palpi already noticed. The mouth opens posteriorly in a pharyngeal muscular bulb, furnished internally with a horny articulated dental apparatus, Serving to crush food, but less highly organized than in Rotifera. Under the polarizing microscope the manducatory organs exhibit the same appearance as horn. From them the food passes into an elongated tubular stomach or intestine, continued straight through the body, and terminating in an anus at the posterior extremity. In its course it presents numerous lateral offshoots or diverticula. • No form of respiratory or circulatory apparatus has been detected; but a multitude of granules and corpuscles are seen to float freely in the general cavity between the integument and the alimentary canal, which Doyère sup- posed to be concerned in the processes of nutrition, and to be analogous to blood-corpuscles. M. Quatrefages states that the fluid within the body is in perpetual irregular motion. OF TEIE TARDIG RAIDA. 483 The nervous system is well developed. It consists of a chain of ganglia, with intercommunicating (anastomosing) nerve-fibres, besides a central or cerebral ganglion. The eyes are variable and fugacious. The sense of touch may be presumed to reside specially about the suctorial mouth and its contiguous palpi. All the Tardigrada are hermaphrodite. The ovary is of large size; but the ova, according to Kölliker and Frey, do not in the course of development exhibit a germinal disk: in this they differ from Arthropoda. Few eggs are pro- duced at a time, and are of large size. They are, curiously enough, found in the exuviae or moultings of the animals; for from time to time the outer skin is cast off. M. Doyère convinced himself of the existence of a testis and spermatozoa. Dujardin Says the embryo emerges from the ovum perfect in form ; but Kaufmann, on the contrary, affirms that they undergo some de- . gree of metamorphosis ere they attain the adult structure. The Tardigrada have received their name from their slow movements. They are parasitic animals, and live by sucking the juices from other beings. They are common upon water-plants and vegetable debris in ponds; yet immersion in water is not necessary, since they are found, like Rotifers, in the dust and rubbish on the roofs of houses (a locality in which they were first encountered by Spallanzani), and especially amid the Small lichens, mosses, &c., which spring up in such situations. The Bryum is a favourite moss for these crea- tures. On shaking portions of this or of other mosses or aquatic plants in a basin of water, the Tardigrada will fall to the bottom, and may be easily collected. In most vital phenomena they very closely accord with Rotatoria ; thus, like these, they can be revived after being put into hot water at 113° to 118°, but are destroyed by immersion in boiling water. They may be gra- dually heated to 216°, 25.2°, and even 261°. It is also by their capability of resuscitation after being dried that they are able to sustain their vitality in such localities as the roofs of houses, where at one time they are subjected to great heat and excessive drought, and at another are immersed in water. O. Müller (in 1785) seems, from the name (Acarus Ursellus) which he imposed on the species he then knew of, to have rightly conceived their natural affinity. Ehrenberg and Schultze (1834) placed them among the Lernece. Dujardin (in 1841) advocated their alliance with the Rotatoria, and constituted them one of the divisions of that class, under the name of “Sy- stolides Marcheurs,” or creeping Rotatoria ; for he considered them to form a link between the Rotatoria and the Helminthidae on one side, and the Anne- lida and Arachnida on the other. M. Doyère at first coincided in this opinion; but his subsequent researches led him to give it up and to constitute the Tar- digrades a distinct group. Dujardin himself has, moreover, modified his first opinion, as appears by his memoir in the Annales des Sc. Nat. for 1851; for he there remarks that the Tardigrada are equally allied to the Rotifera and to the Nematoid Helminthidae, and that it is uncertain whether they ought to be referred to Articulata or Vermes. Our countryman Mr. White (in a paper read before the Linnean Society in 1851) stated his belief “that the so-called Acarus folliculorum, and probably also Tardigrada, are parasitic Rotatoria, with legs or leg-like appendages adapted to their peculiar habits, and that their retractile, antenna-like, Subtelescopic appendages may have eyes passing through them, as in snails, and may also be the equivalents of the rota (rotary lobes), but, from the limited, or rather the absolutely re- stricted, power of motion of these animals, have neither the ciliary processes nor the movements and economical uses of the appendages so characteristic of most of the Rotatoria.” Perty tells us that in 1848 he constructed a family Xenomorphidae, which 2 I 2 484 GENERAL EIISTORY OF TEIE INIFUSORIA, was accepted by Ehrenberg, to comprehend the Tardigrada, the best-known of which were included in a genus Aretiscom, so named by Schrank. His opinion now is, that “perhaps they should rather be associated with the class Arachnida, as a lower type, near the Acarinae,” and not be numbered with the Crustacea, as he formerly proposed. “Doyère’s figures of Emydium indicate their alliance with the Acarinae, like many of which the Xenomorphidae (Tar- digrada) suck the juices of other animals. Their development differs from that of Rotifera; and their skin is composed of chitin.” This last distinction, also insisted upon by Kaufmann, Vanishes if Leydig be correct in his state- ment that Rotatoria likewise have a chitinous cuticle. The most recent writer on Tardigrada we have met with is Kaufmann (Zeitschr. 1851, p. 220), who has presented an able memoir on those beings. He indicates the following distinctive features between them and Rotatoria: —The history of their development accords with that of Arthropoda, and disagrees with that of Rotifera: the epidermis is composed of chitin, a sub- stance only found in Arthropoda (this we have already stated is probably an error); the pairs of indistinctly-jointed limbs and the abdominal chain of ganglia no Rotifer possesses, whilst, on the other hand, the Tardigrada have no trochal disk and no vibratile cilia, but possess a suctorial mouth; lastly, they are deficient of a water-vascular system, and are all hermaphrodite. Cohn, in a recent paper (Siebold's Zeitschrift, 1855, p. 481), throws some doubt on this presumed monoecious nature of the Tardigrada. Thus, he says, Doyère, whilst maintaining their hermaphrodite character, has noticed seminal corpuscles (spermatozoa) in only two individuals. On the other hand, he men- tions certain examples in which the oral organs were aborted, and both sucto- rial disk and maxillary head were wanting ; this happened most frequently in Macrobiotus Hufelandii, and more rarely in other species. Another notable fact is, that in the two closely-allied species, Macrobiotus Hufelandii and Mag,'. Oberhawserii, the ova of one are thick-shelled and tuberculated, and those of the other thin-shelled and Smooth. In these circumstances Cohn is disposed to find a parallel between Tardigrada and Rotatoria in what relates to their sexual peculiarities, inferring by this, that, as in the latter family the sexes are separated, and ova of three sorts—male, “summer” (asexual), and “winter’—are produced, so, from the facts indicated, the Tardigrada may also be bisexual (dioecious) and may deposit eggs of each several kind. The relation of Tardigrada to Arachnida through the lowest divisions of the latter, Kaufmann proceeds to demonstrate by the following particulars:— They have suctorial mouths, like most Acari ; in the structure and disposition of the digestive organs they agree with Arachnida; by the absence of circu- latory and respiratory Organs they are allied to the Acarina in part, and to the Pycnogonidae entirely ; like many mites (Acarina), they lay few and large eggs. But, again, the occurrence of a metamorphosis to some extent detaches them from the Pycnogonidae and from most Acarina; and they differ from all Arachnida by being hermaphrodite; however, the circumstance of the separation of the Sexes, or their union in the same individual, in no class of animals can supply the basis for constituting family distinctions. Even among Arthropoda a family of hermaphrodite animals occurs, viz. the Cirripedia. In this respect the Crustacea and Arachnida, by their lowest members, through which they are linked to other classes of animals, accord; in the former the Cirripedia, which ally them with the Mollusca,—in the latter the Tardigrada, which approximate the Arachnida to the Amnelida, bring the two into connexion. The conclusion therefore is, that the Tardigrada constitute the lowest section of the Arachnida, by the side of the Pycnogonidae and the Acarina, PART II. A SYSTEMATIC HISTORY OF INFUSORIA. [Note—The several groups whose general history is treated of in the first part of this work, viz. Bacillaria (p. 1), Phytozoa (p. 111), Protozoa (p. 199), and Rotatoria (p. 392), being independent of each other, their respective families, genera, and species will not, for the reason stated in the Preface, be described in the same order in this second part, but those of the Bacillaria will be printed last. For an explanation of abbreviations, see end of Contents.] OF THE GROUP PHYTOZOA (p. 111). Families:—1. Monadina; 2. Hydromorina ; 3. Cryptomomadina ; 4. Wolvocina; 5. Vibrionia; 6. Astasiaea. FAMILY 1.—MONADINA. (Plate XVIII. figs. 1 to 28.) THE Monadima are among the most minute living creatures which have been discovered by man. They are (according to Ehrenberg) destitute of an ali- mentary canal, are illoricated or shell-less, and have a uniform body without. any appendages issuing from it, cilia not being considered as such. They increase by simple and complete self-division into two, four, or more indi- viduals. The uniformity or unvarying appearance in their external form (he says) may be considered as one of the principal characteristics of this family; for no one of the Monadina can voluntarily alter the shape of its body, whether into a filiform, knotty, or globular figure, nor can it extend any portion of it, and then contract it again. All possess organs of locomotion, nutrition, and propagation, the last of the hermaphrodite character. Some of them have a rudimentary eye; but it has never been discerned that they are furnished with a vascular or circulating system, which, however, is not surprising when we reflect that, should they possess it (a supposition by no means to be rejected), the diameters of the tubes of this system would necessarily be of such extreme minuteness as to defy investigation. None but microscopes of high magnify— ing powers can display their structure; indeed they cannot be observed accurately with a less amplification than 500 diameters, by glasses of consi- derable penetration and good definition. The apparent eye of some Monadina is used as a generic character for Microglena (XVIII. 6), Phacelomonas, &c.; but its possession does not prove the existence of sensibility, although, as Ehrenberg thinks, this faculty is pre- sumable from the alternate vibration and quiescence exhibited by the pro- boscis when one of these beings is in a place abundantly supplied with food. The details given in the first part of this work (p.130), of the nature and struc- ture of the animalcules comprised by Ehrenberg in this family, render it unne- 486 SYSTEMATIC EIISTORY OF TELE INFUSORIA. cessary here to state more than that the beings so grouped together are hete- rogeneous both in nature and character, and partake Scarcely any other features in common than those of minuteness and the possession of one or of few elon- gated cilia or filaments as locomotive organs. The deficiency of characteristics necessary to constitute a natural family, and the absence of any proof of the animality of the several genera, were perceived by Siebold, who rejected the Monadina from his group of Infusoria. Agassiz says of them that they are mostly moveable germs of various kinds of Algae; and in this statement, we believe, as far as relates to the majority, he is correct. Dr. Burnett (Boston Journ. Nat. Hist. 1853, vi. p.319) has the following remarks on these topics:– “As the family Monadina now stands, it undoubtedly includes very hetero- geneous elements, particles being grouped together from their general aspects rather than from their physiological characteristics. I cannot pretend to take them up in that systematic way in which they have been arranged by Ehren- berg; for I have found but little system about them, and for the most part have been unable to follow his descriptions. If we are to judge of them by mere form and size alone, I should say that the varieties they present under the microscope are numberless. Indeed, in watching the same particle for a long time, I have seen it change its form and size four or five times, and each as distinct from the other as many of Ehrenberg's species. Those which con- tain chlorophyll must, it appears to me, in virtue of that fact, be regarded as of a vegetable nature. As to the others this point would be doubtful.” Again, Dujardin, whilst admitting generally the animal nature of the ge- nera in question, differed widely from the Berlin naturalist both as to their organization and distribution. Since, however, in the present state of our knowledge, it is impossible to fix on the Organisms of which they are but de- velopmental phases, it is well, for the purpose of future identification and future researches, to attempt definitions and descriptions of these simple beings, although, as an artificial and temporary proceeding, the whole be doomed to ultimate neglect and destruction. Consequently, we shall retain all Ehrenberg’s genera and species, which, however ill-defined and unsatis- factory, give the best representation we possess of these varied and variable microscopic organisms. The views of Ehrenberg on the special organization of the Monadina have been widely criticised and condemned. The possession of an integument, the fixed invariable outline, and the ocular nature of the red speck, are statements which have encountered the opposition of Dujardin and of very many subse- quent naturalists. The existence of a mouth and the reception of coloured food have likewise been widely denied, in accordance with the prevalent hypothesis of their vegetable nature as early phases of Algae and Fungi ; but latterly Cohn has witnessed the entry of coloured particles into their interior, a circumstance confirmed by Lachmann, who moreover adds that he has twice observed Monadina which contained a small Diatom, the excretion of which, in the vicinity of the posterior extremity, taking place soon afterwards, also made him consider the existence of an anus probable. Schneider remarked in Chilomonas Paramecium one or two reddish lines running from the inden– tation into which the filaments were fixed, to the opposite end, and, from a comparison of these with the process of fission as seen in Bodo, concluded that they were furrows which gradually deepen until the animalcule is bisected. As during this process the being undergoes no change of form, except in be— coming a little broader, and the division takes place along its whole length, the process must readily escape observation. The anterior end is always a little thicker; the furrows consequently are deeper and more distinctly recog- mizable in that part. It is only in rare cases, when the division has taken place ÖF THE MONADINA. 487 more slowly in some particular spot, that the two segments must endeavour to tear themselves free, and thus, by twisting in contrary directions, draw our attention to them. It was without doubt a specimen of Cryptomonas cylindrica in this condition which Ehrenberg conceived to be two individuals adhering together and not in the act of fissation. Dujardin failed in seeing spontaneous fission among the Monadina, and thinks it more probable that their multi- plication takes place by the separation of a lobe or of the termination of an expansion, which his notion that they are without any sort of integument presupposes they may, after the manner of Amoebae, push out from their mass. The family is distributed into nine genera, as follows:— Single ................................. Monas. Eye wanting Aggregate........................... ...Uvella. ſ (Swimming Pºiº * o: } Microglena. # # g Single Proboscides not Chloraster ſ: : l Eye present 916 . . . . . . more than four & c; # * & * -: #, Proboscides Phacelomonas. "3 • rº V many ......... E- H VAggregate.............................. Glenomorum. \Rolling........................................................................ Doxococcus. Lips present........................................................................ Chilomonas. Tail present ................................................................................. Bodo. Dujardin was unable to recognize all the genera of Ehrenberg, and believed that Microglena, Phacelomonas, Glenomorum and Doacococcus appertain to another family, and that the distinction between the genera Polytoma and Uvella is erroneously deduced from the supposed fission of Polytoma in two opposite directions and the periodical grouping of Uvella. He thus reduced the genera of Ehrenberg to four in number, viz. Monas, Uvella, Chilomonas and Bodo, the last comprehending in part his Hea'amita, Amphimonas and Cercomonas. The Subjoined table represents the distribution he proposed:— MONADINA, / / Moveable in its en- tire length ...... Monas. e Proceeding from the ante-J Thickened, and rt #. < rior extremity. moveable only #.ent towards the ex- o \ tremity ......... Cyclidium. Proceeding obliquely from behind an anterior \ prolongation ....................................... Chilomonas. (A second filament or lateral appendage ......... Amphimonas. Isolated 3 A second filament or posterior appendage ...... Cercomonas. Two equal filaments, terminating the rounded Several angles of the anterior extremity ............... Trepomonas. |Filaments. * Four equal filaments in front, two thicker be- ind ................................................ Hexamita. A second filament proceeding from the same point as the flagelliform filament, but thicker, trailing and retractile ........................... Heteromita. \A filament and vibratile cilia.......................................... Trichomonas. Groups always free and whirling .................................... Uvella. w ſ Aggregate l Groups fixed to the extremity of a branching polypidom ...... Anthophysa. 488 - SYSTEMIATIC HISTORY OF TEIE INFUSORLA. “These generic distinctions are, however,” Dujardin very justly adds, “en- tirely artificial, and simply intended to facilitate the naming of Infusoria one may have met with in such and such an infusion, and which, when better known, may prove in some instances only varieties of a single species.” Perty appends to his history of Monadina the following observations:— “Ehrenberg's Monadina are very difficult to determine; many, like Monas bicolor, M. Colpoda, M. Enchelys, M. Umbra, M. hyalina, M. ovalis, M. Mica, M. cylindrica, M. deses, M. flavicans, M. simplew, M. inamis, and M. Scintillans, appear to be only the earlier stages of other Monadina, or the young stages of Ciliata. M. Crépusculum forms my genus Acariceum ; M. Termo is a Cercomonas ; M. Guttula and M. vivipara are most likely varieties of the multiform M. Lens ; M. grandis and Microglena monadina are Sporozoids; Monas ochracea, M. erubescens, M. vinosa, and probably M. gliscens belong to the genus Chromatium (XIX. 1); M. Punctum is no other than the one fila- mentary variety of Polytoma ; M. socialis goes along with Cercomonas; M. tingens is the young condition of Chlorogonium euchlorum ; Uvella virescens possesses one filament and no cilia; U. Uva may be a colourless variety of it; U. Glaucoma scarcely belongs to the genus Uvella, as it has always two filaments U. Bodo appears a developmental phase of Euglena viridis; Polytoma Uvella is equivalent to my P. Uva ; Microglena punctifera is un- known to me. The genus Doacococcus I consider untenable; D. ruber and D. Pulvisculus are merely resting forms of Astasia; Chilomonas Volvoa and C. destruens are in all probability embryos of Ciliata, and Ch. Paramecium is the hyaline variety of my Cryptomonas polymorpha; and Bodo is divisible into Anisonema (XIX. 8) and Cercomonas (XVIII. 11, 12, 20).” The new genera instituted by the Swiss naturalist are Tetramitus (XIX. 3), Mallomonas (XIX. 4), Pleuromonas (XVIII. 25), Spiromonas (XVIII. 24), Menoidium (XIX. 2), Chromativm (XIX.1), and Acariaeum. Fresenius accepts two of these new genera, viz. Mallomonas and Tetramitus, and creates in addition two others, Rhabdomonas and Grymaea, the former not identical with the Rhabdomonads (staff-like monads) mentioned by Ehrenberg as a group of his genus Monas. Respecting the large contribution by Perty to the number of Momadina catalogued by Ehrenberg and Dujardin, the question arises, whether the forms named are really different and distinguishable. We fear, indeed, that the increased number will rather perplex and encumber the observer than advance his real knowledge of microscopic forms. Still, to make our résumé. complete, they must be enumerated. In effecting this, the plan pursued will be to describe the several genera admitted by Ehrenberg first, adding the species noted by others, and after these to give the characters of genera and species constituted by Dujardin, Perty, or any other naturalist: where the same being has had a second name given it, it will be added as a synonym. In the systematic details we shall preserve the descriptions and remarks in general which appeared in the last edition, and are largely borrowed from Ehrenberg's most valuable works. These, indeed, are everywhere tinged with the peculiar hypothesis of that writer, the value and bearing of which, however, have been sufficiently examined in the first part of this work to render explanations and corrections here unnecessary. The description, therefore, of mouths, eyes, stomach sacs, glands, vessels, hermaphrodite deve- lopment, ova, and of all other structures or organs of higher animal organiza- tion, will have no other value as applicable to such special organs than that accorded to it in the mind of every individual reader of the chapter on the structure and functions of the Monadina, who can draw for himself his own inferences from the facts and opinions therein recorded. OF TEIE MONADINA, 489 Genus MONAS (XVIII. 1, 2, 15, 17, 19, 21).-The animalcules of this genus—the true Monads—are described (see table) by Ehrenberg as destitute of an eye, with projecting lip and tail, and as always Swimming in the direction of the longitudinal axis of the body, their mouth being situated at the anterior end. It is another distinguishing character of the true Monad, that it is never seen to cluster, like others of its family, so as to form a berry-like mass; and hence it is designated single, in contradistinction. Amongst the several species distinguished, some few are green, yellowish, or of a reddish tint; but the majority are colourless; colour, moreover, is not a characteristic to be relied upon. Monads may often be present in water, under inspection, with- out being seen, owing to the magnifying power employed being insufficient. They will be sought for in vain with a power of less than 300 diameters; and even this, in some cases, will be found insufficient. They are, besides, as a genus, difficult to be accurately determined, not only on account of their ex- ceeding minuteness, but because the young of other genera are so likely to be mistaken for them,-for instance, the young of the Bacterium, Vibrio, Uvella, Polytoma, Pandorina, Gonium, &c., when separated from their clusters. And this difficulty in discriminating them will be more likely to happen when they are not observed whilst undergoing the process of self-division, or when seen in water containing but a small number of them; under which circumstances, however anxious we may be to ascertain their name, we must often rest con- tented with probable surmise. When the water swarms with the creatures, the decision will be far easier, and more trustworthy, since the characters are then more easily discoverable, and their possible variations appreciable. The observer may, however, be guided to a certain extent by the following rule:— Suppose that in a drop of water containing species of the genus Vibrio, Bac- terium, Uvella, or Polytoma (easily distinguished by their clustering forms), separate Monad-like bodies were to be observed; the probability is that they would be either single forms, or the young of the clustering animalcules; and if there were no great difference in the size of the separate individuals and those forming the clusters, this conclusion would be generally correct : and this rule applies equally to those green Monad-like creatures found amongst Pandorina and Gonium. Chlamidomonas Pulvisculus, when young, is very deceptive, and may often be mistaken for an illoricated and eyeless green Monad. - The only locomotive organ which has been discovered in the genus is the single filiform proboscis (filament) issuing from near the mouth. The numer- ous cilia sometimes apparent thereabouts are nothing more than this filament in a state of vibratory or rotatory motion. This organ, Ehrenberg observes, has a twofold office, one being locomotive, and the other to provide the creature with food, and hence may be called a purveying Organ. . Vacuoles are readily seen in some of the species (e.g. M. Guttula and M. vivipara) without the aid of coloured food; in others (M. Termo, M. Guttula, and M. socialis), its aid is required. The propagative apparatus Ehrenberg represented in M. Guttula and M. vivipara to consist of a vast number of granules formed into a net-like mass, dispersed generally throughout the creature, having a comparatively large spherical body (the nucleus) which divides in the process of self-fission. Monads multiply rapidly by self-division, either transversely, as in Monas Guttula, M. hyalina, M. gliscens, M. Okenii, and M. socialis; or longitudi- nally, as in M. Punctum (XVIII. 2) : both methods have been observed in M. vivipara. As the members of this genus are chiefly curious on account of their extreme minuteness, only the leading characters and size of the several species are 490 SYSTEMATIC HISTORY OF THE INFUSORIA. given. Most of them are inhabitants of water in which organic matter is un- dergoing decomposition. The Monads of Ehrenberg are arranged under two divisions, according to their external form. The first division contains all those of a globular or oval shape (globular Monads); the second those of a lengthened form, the length being more than twice the breadth (elongated Monads). A.—GLOBULAR MONADS. MoMAS Crépusculum (XVIII. 1).-The smallest of all living creatures; of a spheroidal form, and hyaline, although, when seen in masses, with the naked eye, of a whitish hue. They are active, and feed on animal as well as on vegeta- ble substances, and are found in water holding animal matter in solution; but as decomposition proceeds, they die, and their bodies rise to the surface of the water, and form a thick and colourless gº stratum. Rarely 1-1200" in iameter; never larger. M. Termo (M.), so named from its having been supposed to be the limit of animal organization; globular, active, herbivorous; found in stagnant water; increases rapidly where there is an abundance of vegetable matter under- going decomposition. 1–6000" to 1–12000", and less. M. Guttula (M.).-Round, inactive; may be preserved by drying; 12 di- #. vacuoles seen by the aid of in- igo or carmine; surface appears granu- lated. In vessels of water containing plants or flowers, 1-2300" or less. M. vivipara.--Spherical, inactive. In stagnant water; coloured. 1-620" or less. M. grandis.-Spherical; colour green- ish, except near the mouth; filament short, 1-3rd or 1-4th the length of the body; motion sluggish. In marsh water, very rare. 1-430". M. bicolor.—Globular; colourless, ex- cepting one or two green spots within it; attenuated anteriorly; motion vacil- lating. 1–1440". M. ochracea.—Globular; of a yellow- ochre colour. In water-courses. 1-6000" at most. - M. erubescens. – Circular; rose-co- loured; motion slow but continued. In salt water. 1–1728". M. vinosa,—Globular, colour of red wine; motion tremulous; rejects, co- loured food. In vegetable infusions. 1–12000" to 1-6000". M. Kolpoda.-Colourless, oval or egg- shaped ; motion vacillating. In water in the silver mines of Siberia. 1-7200". M. Enchelys, Colourless; continuous slow motion. In marsh water. 1-1200" to 1-960". M. Umbra.-Ovate, colourless; motion rapid. Among fresh Confervae. 1-2400" T. hyalina.-Ovate, colourless; ac- tive, and seems to leap or jump. In stale wateringlass vessels. 1-6000"to 1-2880". M. gliscens.—Ovate, colourless; mo– tion gliding. In infusions of the sting— ing-nettle. 1-4500". M. ovalis.-Oval, colourless; motion tremulous. In water from the Anodonta Mollusca. 1-9600". M. Mica. —Oval, colourless; rotary and vacillating motion. In clear fresh- water. 1–1440" to 1-1200". M. Punctum.—Egg-shaped; revolves on its longitudinal axis (xVIII. 2); the lower figure exhibits one undergoing longitudinal division. In water with tannin. 1-1150". M. Semen.—Large, green, rather obo- vate, subcompressed; anterior end di- lated, rounded; posterior attenuated; oral aperture (!) triquetral beneath the frontal portion; vibrates by numerous cilia (!). Length 1-48"; motion vacil- lating, slow; a central, hyaline, Subglo- bose gland; ovules large, green, ovate, It readily shows by diffluence the ova, gland, and bacillary spicula. Frontal end exhibits rugae extending from the mouth. With decaying Sphagnum from marshes, Berlin. §. y this organism is not a Monad. B.—ELONGATED MONADS. M. cylindrica. — Solitary, elongated, colourless; motion revolving. In salt water. 1-1150". M. Okemi.-Elongated, red; motion revolving, vibratory, social. In running Water. 1-2300". M. deses.—Conical, green, solitary. In water from hills. 1-1200". M. socialis. – Conical, colourless, so- cial. In water-butts. 1-700". M. flavicans. --Top-shaped; social; motion gliding. Inditch-water. 1-1720". M. Simplex,−Spindle-shaped; colour- less; motion gliding and rotary. In water of the Nile, and at Berlin. 1-1720". M. indnis.--Fusiform, colourless; mo- OF THE MONADINA. 491 tion vacillating. water, i-3606. M. Scintillans.—Fusiform, very active; motion vacillating. Amongst fresh- water Confervae, &c. 1-6000" to 1-4600". M. Dumalii.—Of a deep red colour; in vast numbers in the Saltmarsh-water of the Mediterranean, to which they give a deep blood-colour. Discovered Éy M. Joly. In stagnant and foul M. prodigiosa,—A very minute red Monad, so named by Ehrenberg from its surprisingly rapid development. It is this animalcule which has produced the blood-like º occasionally appear- ing mysteriously on bread and other farinaceous substances, and which have ever been a cause of terror to the super- stitious. Cohn asserts this organism to be a Vibrio, and not a Monas. Being desirous of making this manual as complete as possible, the following species, described by M. Dujardin, are inserted; but it may be that some of them refer to Monads already characterized, but differently named. M. Lens (xvii.I. 10, 21).--Rounded or discoid; surface in appearance tuber- cular. 1-5200" to 3-5200". This spe- cies, one of the most frequent in animal or vegetable infusions, has been recog- nized by most of the ancient microgra- phers. It sends out obliquely a flagel- liform filament, three, four, or even five times as long as the body, andmobile in all its length. Probably=M. Guttula (Ehr.). M. concava.--Circular, concave on One side, thin in the centre, margin tumid; filament long, moveable throughout. In marsh water, Toulouse. 1-2080". M. globulosa (XVIII. 17). —Globular; form mostly constant; compressed at origin of filament; more globular than M. Lens, and its surface Smooth. In sea- water at Cette, France. 1-2000". M. elongata. — Elongate; modular, flexible, of variable form. 1-1200". In marsh-water. M. attenuata (XVIII. 19).-Ovoid, ta- pering at each extremity, modular, va- cuolae large and distinct, as is also its filament. 1-1660". M. oblonga.-Ovoid, oblong, unequal, tubercular, hollowed by , vacuolae. 1-3600". In vegetable infusions. M. nodosa–Oblong, irregular, nodose, tapering behind, truncate in front, fila- ment arising from centre of truncate ex- tremity. 1-2170". In sea-water at Cette, France. - M. gibbosa,—Oblong, angular, irregu- larly distended and gibbose; filament springing mostly from an anterior con- striction. Length 1-2000". In infu- Sions of gelatine. M. varians.—Oblong, narrower in front, very soft, and variable in form. 1–650" to 1-700'". M. intestinalis.-Very elongated, form constantly changing, or one end rounded, the other tapering to terminate in a long filament; motion undulatory. 1-1600". Found in the excrement of a newt (Triton palmipes). “I think this is one of the species of Bodo, described by Ehrenberg as met with in the intestines of frogs” (Duj.). M. fluida.--—Soft, semifluid; form variable, irregularly ovoid, sometimes constricted posteriorly, hollowed by large vacuoles. 1–2600'". M. constricta.-Elongated, four or five times longer than broad; constricted, often much so at the centre. 1-1300". Perty has distinguished the following Monadiform beings by specific names:– MoMAs curvata. —A variety of M. Lens; tapering posteriorly. M. astasioides.—Of variable form, often with one or two longitudinal lines, and a central vacuole. 1-1340". M. irregularis.--more or less globular, sometimes with capillary or angular pro- cesses; numerous dark internal mole- cules. 1-2000" to 1-1250". In ponds, Berne. , M. pileatorum. – Irregularly oval ; pointed anteriorly; colourless; motor fila- ment short, scarcely 14 times the length of the body; movement sluggish; nearly resembles M. socialis. 1-1400". M. succisa.--Oval; usually truncafe, rarely pointed behind; colourless, trans- parent, with large vacuoles; filament twice the length of body; movement active and revolving. In water contain- ing decomposing Anodonta, and foul pond-water. 1-1800". M. cordata. — Cordate seen on one side, on another oval and truncate; rounded anteriorly; hyaline or greyish from internal granules; swims tolerably fast with an oscillating motion, and sel- dom revolves; occurs singly and not often; filament extremely difficult to see, more than double the length of the body. 1140" to 1080". In freshwater ponds. 492 SYSTEMATIC HISTORY OF TEIE INFUSORIA. M. urceolaris.-Very small, urceolate, obliquely emarginate in front; colour- less, transparent, with scarcely an ap- reciable #ºn of substance; ilament indicated by the movement produced in the water at the anterior extremity; motion slow. 1-2640". In brooks with Hysginum pluvialis. M. eaccavata.-Round or oval, with a conspicuous speck in the anterior half; colourless, or occupied with amorphous brownish or greenish matter; filaments very fine, from 2 to 24 times longer than the body. Motion active, in a straight line, and rarely revolving. 1-2100" to 1-1200". among Chara. M. Rotulus. -Elongated, cylindrical, of a homogeneous pale-green colour; At Berne, in ponds filament apparently short ; onward movement slow, although it revolves rapidly upon its long axis. 1-3000" to 1-600'". - M. Farcimen. —Cylindrical, greenish, with red spots; flexible; onward move- ment and rotation rapid. 1-1800" to 1-1080". M. Hilla.-Globular, or slightly elon- gate; of a dusky-green or brown colour. Larger specimens at times present a clear areola around coloured contents, with vacuoles in the latter; progression tolerably fast, turning more rapidly on the long axis. Length from 1-6000" to 1-600". The three species last named º very closely to sporozoids of plants. Fresenius has added the following species of Monas to the number already distinguished 2– -- MoNAS truncata.-Hyaline, colour- less; figure oval and rounded, truncate anteriorly, compressed; one larger and many Smaller vacuoles often seem, the former near the middle. The truncate end supports two filaments, mostly on one side, equal to or rather longer than the body. Close beneath the anterior margin a Small transverse corpuscle is mostly visible, of a faint green †: and, Some way beneath this, a small contractile vesicle. A side view shows a slight hollow on the under surface. Swims without revolving, and mostly in a straight course. 1-150 to 1-100 millim. in diam. M. consociata.--Ovate, with one end tapering and trunk-like, and terminated by a filament more than double the length of the body. The proximal half of this filament often seems rigid, and only the distal or terminal hałf, which is difficult to detect without the use of iodine, motile. Body and its corpuscles colourless; among the latter is one pro- minent vacuole, not contractile. A mul- titude of these Monads occupied a trans- parent mucoid matter, which was not seen in motion. In still spring-water at Walldorf in June and July. It bears the nearest resemblance to Cercomonas vorti- cellaris (Perty). 1-100 to 1-75 millim. M. Oberhauseri...—A carmine-coloured Monad found in the sulphureous spring at Frankfort, allied to Monas Okemi, (Ehr.), and possibly the same as Chro- matium Weissi (Perty). Cylindrical, rounded at each end, hyaline; faintly carmine-coloured, with a variable num- ber of intensely crimson globules inter- mally. Some specimens, however, have only a homogeneous red colour. Trans- verse fission frequently seen. It rotates rapidly, and advances with a tumbling sort of movement, no doubt by means of a filament; but this eludes observation. 1–83 to 1-46 millimètre. M. bipunctata. — A much smaller species was found in the same glass with the preceding, having a red colour, an elongated oval figure, and a red point at each end. Longer specimens were noticed with four such red points, which might be in the act of fission. This form may be the same as the Monas 7'osea of Morren. Genus UVELLA (XVIII. 3, 4).-Well characterized by the aggregating together occasionally of the individual Monads, so as to form a grape- or mulberry-like mass, and by their generally possessing two (?) hair-like fila- ments at the mouth. Like the Monads, says Ehrenberg, they are deficient of the projecting lips, visual organ, and tail, and have the mouth situated at the anterior extremity. They progress also in the direction of the longer axis of their body, and are capable of complete self-division. three are green, and the remainder colourless. Of the several species, This genus belongs to the Aggregate Momadina of Dujardin, and is thus O]? TTITE MONATDINA, 493 defined by him :—“animals globular or ovoid, having a single flagelliform fila- ment, and living aggregated in spherical masses, freely moving about in the liquid.” He further observes that isolated individuals are not at all distinguish- able from simple Monads, that there is no good reason to suppose them to live alternately isolated and in masses—a circumstance therefore which cannot, according to Ehrenberg's statement, be employed to distinguish them from Polytoma. - - Busk describes an early stage of development of Volvoa, Sphaerosira as constituting “a species of the genus Uvella, or of Syncrypta, Ehrenberg” (M. T. vol. i. p. 40). Again, Cohn (on Protococcus, Ray Soc. 1853, p. 559) makes one of the multiform phases of development of Protococcus pluvialis, “when the zoospore is divided into thirty-two segments,” equivalent to a Uvella or Syncrypta. Perty, in his account of Uvella virescens, denies the existence of a common envelope, stating that when the water evaporates from around a specimen, the coverings of each individual corpuscle coalesce, and give rise to the appear- ance of a general investment around them. He adds, moreover, that at times the corpuscles are green, with a clear central stripe; at others, hyaline with a distinct green border, and Some scattered specks; and at others, again, hyaline throughout. Dujardin describes only two species, viz. U. virescens, and U. rosacea = U. Glaucoma (Ehr.). UVELLA virescens (Volvoa. Ulva, M.). —Ovate, colour green, occurs in dense clusters amongst Conférvae and Lemmae. 1-2000"; diam, of cluster I-280." U. Chamaemorum.—Smaller than the breceding . One, In water-butts. 1-2880"; diam. of cluster 1-570". U. Uva.—Has indistinct vesicles, and is very Small. In stagnant water. 1-4800"; diam, of cluster 1-960". U. atomus (Monas atomus, M. Lens et Volvoa socialis, M.).-Voracious, with large vesicles. 1-6900" to 1-3406"; diam. of cluster 1-1150". U. Glaucoma (Volvoa socialis, M.).- Oval, inclining to conical; as it advances in age the posterior extremity is attenu- ated, and an elongated outline is assumed. Hyaline, with large vesicles, and two evident filaments: individuals loosely aggregated. ... In 1831, Ehrenberg first observed a vibration at its anterior part, and its reception of coloured food. In 1835, he discovered within the body of this minute creature some green Monads Perty contributes to the list U. Stigmalica. which it had swallowed. When fed on indigo, as many as twelve vesicles were filled, and it was sometimes seen to void little blue particles, like undigested matter, from its mouth. With a power of 800 diameters, a great number of small colourless granules, which he called ova, were discerned lying between the nutri- tive sacs. Fission both transverse and longitudinal (XVIII. 3, 4: figures mag- mified about 350 diameters). In water- butts. 1-2300" to 1-2350"; diam, of cluster 1-430". U. Bodo, Rounded in front, attenu- ated posteriorly; colour a beautiful green. In stagnant water. 1-4030" to 1–3450"; diam, of cluster 1-2350". U. Stigmalica (Perty).-Corpuscles of a uniform sea-green colour; each with a very fine red stigma. They are also somewhat broader than those of U. virescens, and have a more decidedly hyaline and apparently crenulated enve- lope. At Berne much rarer than U. vèrescens. - - Genus MICROGLENA (XVIII. 6).-Characterized by the presence of a minute red eye-like speck at the anterior part of the body. In other respects the species resemble true Monads, having a very delicate filament, no pro- jecting lips and tail, and swim in the direction of the long axis of the body. They multiply by complete self-division. Two species only are known—the one yellow, and the other green. - MICROGLENA punctifera (Enchelys Eye-speck red with a blackish central punctifera, M.).-Yellowish, oval, or al- spot. Among slimy-water plants, 1-620". most comical; posterior extremity acute. M. monadina, Of a beautiful green; 494 SYSTEMATIC ELISTORY OF THE INFUSORIA. form ovate, rounded equally at both ex- tremities; red Stigma; filament distinct, nearly as long as its body; motion vibrat- ing, rotary on its long axis, (XVIII, 6. Three animalcules magnified, the first 800 diameters, exhibiting the internal organization as represented by Ehren- berg.) Among slimy-water plants (Hampstead and Finchley). 1-2300" to 1-720". Genus CHLORASTER.—Solitary, without tail; mouth terminal; with a frontal ocellus or eye-speck; central portion of body with radiating rows of raised points (verrucae). It is allied to the genera Glenomorum and Phacelo- monas, but differs from the former by being solitary (not clustering), and by the greater number of filaments, and from Phacelomonas by having fewer filaments. - CHLORASTER gyrams.-Green; central acute; central rays of puncta four. part of body fusiform; extremities | Filaments from 4 to 5". 1-632". Genus PHACELOMONAS.—Filaments numerous (8–10)around the mouth. In other respects it resembles Microglena: it has the small red eye, the trun- cated mouth at the anterior extremity, but is without a tail. It swims in the direction of the longitudinal axis; and its self-division is simple and complete, but not constant in occurrence. Many vacuoles are seen within the body, but they have not been noticed to admit coloured food. This genus has not been figured by Ehrenberg. PHACELOMONAS Pulvisculus (Monas pulvisculus, M.). — Figure oblong or slightly comical, attenuated posteriorly; when dying it changes to a globular shape. In Swimming, it turns quickly upon its longitudinal axis, without any vibration, ſm green puddles. 1-1152". Ph. Bodo (Stein) = Uvella Bodo (E.). of a beautiful green colour. Just pre- vious to self-division, its body becomes cylindrical, then contracts at the centre; Genus GLENOMORUM (XVIII. 7).-Characterized by having a single red eye-speck, a truncated mouth, and two filaments; tail absent. Self- division simple and complete; their clustering is voluntary as occasion may require, and gives them the resemblance to a bunch of grapes. They swim in the direction of their long axis. In this enumeration of the characters belonging to this genus, we are pre- sented with an excellent illustration of the table (and one that exceedingly well explains its use), under which all the genera of the family Momadina are so arranged as to exemplifyin what respects they are alike, and in what they differ from each other. For example (see Table, p. 487), Glenomorum closely resembles Uvella, but differs from it by the superaddition of the red stigma; it differs from Monas and Microglema in occasionally aggregating; from Chilomonas, in being deficient of the projecting lips; from Bodo, in not having the tail; from Phacelomonas, by the double proboscis; from Doacococcus, by swimming instead of rolling over or revolving in the water; and from Polytoma, by never appearing in clusters whilst undergoing self-division. GLENOMORUM tangens (XVIII. 7). — Fusiform, three or four times longer than broad, of a beautiful green colour, with double, exceedingly delicate proboscis about half the length of its body. Inter- nally are some small whitish vesicles, and the minute granules which give rise to the green colour. About the centre of the body is a large transparent colour- less organ, the nucleus. The beautiful red eye-speck is placed about one-third from the anterior extremity of the body. These animalcules constitute a great portion of the green matter commonly seen on stagnant water, and discovered by Priestley. They appear to be nearly allied to Cercaria viridis, from which they differ only in magnitude and in the unalterable form of their bodies. Plentiful at Hampstead. Size 1-3600" to 1-1700". OF TEITE MONATOINA. 495 Genus DOXOCOCCUS.—The Monads forming this genus differ from all others of the family Monadina by the singularity of their motion, which may be defined to be neither that of swimming nor of rotation, but a sort of roll- ing over and over. In other particulars they are like other Monads: they have the same unvarying form, and are destitute of the eye-speck, project- ing lips, and tail; and self-division is simple and complete. Four species are known. DoxococCUS Globulus. – Subglobose or ovate; transparent as water; easily known by its tedious rolling motion; mouth not discerned. In salt water, 1-860". D. ruber (XVIII. 8).-Brick-red, glo- bular, and opaque, Ehrenberg º to doubt whether this animalcule be- longs here (though its motion is very peculiar) or to the genus Trachelomo- Genus CHILOMONAS (XVIII. 14, ºnas; and he has not been able to satisfy himself of the existence of a lorica. Amongst Confervae, &c. 1-1720". D. Pulvisculus-Green, perfectly (?) globular, and opaque. Amongst Con- ervae. Not exceeding 1–1280". D. inequalis. – Irregularly globular, transparent, and covered with green spots. Amongst Confervae. 1-2400". 18).-Characterized by the obliquity of the mouth with respect to the longitudinal axis of the body, which occasions a projection above the mouth of a lip-like appearance. Motion in the direction of the long axis of the body; form invariable; devoid both of eye-speck and tail. Whether the projecting lip is furnished with cilia, or with a double filament, Ehrenberg has not satisfactorily determined, except in the case of C. Paramecium, in which he states two filaments are to be clearly seen. On C. destruens there are a number of indistinct cilia. Self-division is simple and complete. Dujardin’s characters of this genus are, “Animals with an ovoid, oblong body, obliquely notched in front, with a very slender filament proceeding from the bottom of the notch. Movement from before backwards, on its centre. It is with doubt that I refer the Infusoria. I thus name to the genus Chilo- monas of Ehrenberg. The mode of insertion of the filament behind a pro- jecting lip-like portion, approaches the animals to the Euglence and to certain Thecamomadina ; but I cannot discover any trace of an integument, either contractile or resistant.” CHILOMONAS Volvoac.—Ovate, attenu- ated and truncated anteriorly, trans- parent and colourless ; projecting lip long; will feed on indigo. In stagnant water. 1–1440". C. Paramecium (XVIII. 14).-Oblong or ovate, wider at one end than at the other, keeled longitudinally; colour like that of dirty water. The contained gra- nules have the reaction of starch. At the osterior end a clear nucleus with a red- ; halo may be observed; and at the anterior is areddish vesicle, probably con- tractile. It refuses coloured food. This animalcule is easily distinguished by its shape and P. lip-like process. With a power of about 240, numerous vesicles are visible, and with 380 the two fila- ments, which are half the length of the body, and proceed from a sinus in the wider end. It moves in the direction of its long axis, in a fluctuating or waver- ing manner. It sometimes clusters. In water wherein wheaten bread has been steeped, 1-1020". The colourless va- riety of this species is enumerated by Perty as one of the many forms of his Cryptomonas polymorpha. C. destruens.—Oblong, but variable in form, on account of its softness, nearly colourless or faint yellow. In salt and fresh water, and in the bodies of dead Rotatoria, e. g. Anuraea, foliacea and Monocerca Rattus. 1-860". C. granulosa (Duj.) (XVIII. 18).-Co- lourless, oblong, larger anteriorly, al- most invariable in form, although of ge- latinous consistence; filled with granules which seem to project from its surface; filament very fine, arising from an ob- lique notch. 1-940" to 1-850". C. obliqua-Ovoid or pyriform, no- dular, of variable form; the filament la- teral. 1–2600", 496. SYSTEMATIC [[ISTORY OF TEIE INFUSORIA. Genus BODO (XVIII. 9).-The caudal appendage at the posterior extremity of the animalcules is a decisive character of the genus; mouth terminal, fur- nished with a (single 2) filament; self-division simple and complete ; eye- speck absent. They never constitute true or perfect clusters like some of the family Monadina, although, like Uvella, they occasionally aggregate. In B. grandis, several vacuoles have been observed, and (as also in B. intestinalis) a simple (perhaps double 2) filament. B. didymus has been known to divide transversely. This genus Bodo partly comprehends the genera Hea'amita, Amphimonas, and Cercomonas of Dujardin, which are, with others, introduced as addenda to this family Monadina. Dr. Burnett has made the following very correct and just remarks on this genus Bodo and its division into species:— “The tailed Monads or Bodos are found in the intestines of the common house- fly or in those of the frog. Those from the fly, when first seen, resemble in shape a kernel of rye, and are about 1-6000th of an inch in breadth, and 1–2000th in length. Attached to the body is a delicate hair-like tail, four or five times its length. By the addition of water, the body enlarges by endosmosis, as- suming a perfectly spherical shape after passing through all the intermediate ones, so that, when magnified by the highest power of Spenser’s microscope, it is nearly one inch in diameter, permitting the most thorough and satisfac- tory study of their structure, which I find, after repeated observations, has no peculiarities except those belonging to cells. It is a closed cell sac, with a filiform caudate process, and capable of the actions of cell-membranes, viz. endosmosis and exosmosis. In the interior of this sac are found sometimes a few granules and sometimes a nucleus. - “In the Bodos of the frog, which are larger, I have seen distinctly, in some, a nucleus with a nucleolus, in others two nuclei, and in others still, four nuclei of equal size, thus showing that here the multiplication of cells takes place, as elsewhere, by segmentation of the nucleus. “Apart from these characteristics, which are insufficient, the fact that I have sometimes met with them in the interior of epithelial cells, would be strongly presumptive of their cell origin from minute granules that pass through the cell-walls. The representatives of the genus Bodo therefore appear to be simple cells, each with a filiform appendage for locomotion, and which locomotion, therefore, can have no adaptive character. “There are differences in them as they may be taken from different locali- ties; but, because these particles are cells capable of much change by dilata- tion and contraction, these differences can never serve as the basis of species, which would also be true from the fact that, having no individuality of their own, there is necessarily no absence of type characteristics.” BoDo intestinalis (xvii.I.9).-Almost conical, transparent, and colourless; tail of equal length with the body. in several living animals, such as frogs and toads. Amongst the watery mucus of the alimentary canal Ehrenberg has observed great numbers of these crea- tures, and remarks that the Cercaria Gyrinus of Müller (a different animal- cule) might pass as a representation of this species, and that it was confounded by its discoverer with Spermatozoa. 1-1720". B. ranarum (= Cercomonas Ranarum, Perty).-Body turgid, ventricles indi- stinct. In live frogs, with the preceding Found | species, and with the Bursaria ranarum. 1–1440". B. viridis.-Green, nearly globular; tail very short. Amongst Confervae. 1-2400". Perty believes this species to be merely the young of Euglena viridis. B. socialis (Monas Lens, M.), Ovate or subglobose; tail often longer than the body; transparent and colourless. Clus- ters in a mulberry shape. Single forms are sometimes observed hopping. Com- mon in stagnant water. 1-2970". B. vorticellaris (= Cercomonas, Perty). — Body three times as long as it is broad; tail very short. In fresh water, |-11200", OF TEIE MON ADINA. 497 B. didymus, -Generally constricted about midway, tail short. 1-9600". B. Saltans.—Very small; body with ample ventricles; tail short. This creature, most probably from its small size, has been mistaken for Müller's Monas Termo; but its brisk leaping move- ment will sufficiently distinguish it. 1–1200". B. grandis.-Oblong; vesicles ample; tail rigid, Setaceous, affixed to the abdo- men. In stagnant water, 1-864". Lachmann states that an animal which was probably Bodo grandis, but might have been an Astasia, devoured Vibrio of two to four times its own length, and in this way acquired the most extraordinary forms; the mouth was close to the insertion of the flagellum. B. ostrea (Pritchard).-Globular; the anterior three-fourths occupied with ve- sicles, the rest hyaline; length of tail four times the diameter of body. This active creature was discovered in the liquor of an oyster, Swimming freely among the ova (Sept. 1834). Diam. 1–2000". B. P. Mastia (Ehr.).-Obovate, turgid, Smooth; terminal seta flexuose, acute, exceeding some two or three times the length of the body. Length 1:48" to 1–30", with the filament 1–20". The filament trails behind; motion slow, not leaping. This is the largest form of Bodo observed by Ehrenberg. Found about Sphagnum, The following genera, named and described by Dujardin, are introduced into his family Monadina — Genus CYCLIDIUM (D.) (XXVI. 14, 15).-Body discoid, compressed, or lamelliform, scarcely variable ; the filament thicker and more rigid near the base than that of Monas, the frce extremity only being moved. This genus is as yet but artificial, and indeed provisional; for true Monads perfectly developed may possess a filament with a thicker base, and, again, the constant outline of the body may be the consequence of the presence of an integument—in which case the animalcules in question would be referable to the family Thecamonadina. Movement slow and uniform. It is to be regretted that Dujardin uses this generic name, as Ehrenberg previously employed it to designate certain ciliated animalcules which cor- respond but partially with those of Dujardin. Indeed this naturalist ob- serves that “the genus Cyclidium (Ehr.) contains Monads also, and very probably some of those to which I have applied the same ‘generic' name.” CYCLIDIUM modulosum (Duj.). — Flattened, discoid, with rows of nodules and vacuoles; movement extremely slow. Length 1-5200". In water from nodular, irregularly bent, with a tumid border. 1-1800" to 1-800". “This species is perhaps only one phase of development of Monas Lens; it was the Seine. C. abscissum (Duj.) (XXVI. 15).-- Membranous, lamelliform, truncated posteriorly; filament rigid ; movement slow, regular, 1–1040", C. crassum (Duj.).—Oval, thick, and rounded; filament thickened at its base and rather sinuous; movements more active, zigzag, 1-1090". Length of fila- ment 1-600". C. distortum (Duj.) (xxvi. 14) * Spiromonas volubilis, Perty).-Oval, flat, found in Seine water kept during three months. When young it has the form of a disk, with a tumid and modular margin; when, however, it has grown larger, it becomes twisted upon itself, and its movements irregular. Some in- dividuals offered a certain affinity with the Trepomonads, which favours the opinion already advanced, that the ma- jority of the Monadina are but modifica- tions of one or of several types.” Genus CERCOMONAS (D.) (XVIII. 11, 12, 20, 22, 23).-Body rounded or discoid, tubercular, with a posterior variable process in the form of a tail, of greater or less longth and fineness. The Cercomonads differ from the Monads by the posterior prolongation, which serves, by the adhesion of its extremity, as a point of support: it occurs either as a very fine thread or contracted into a small tubercle; it is some- times nearly as fine as the anterior filament, and susceptible of an undulatory 2 R. 498 SYSTEMATIC HISTORY OF TITE INFUSORIA. motion. condition of Cercomonads. I have not unfrequently witnessed the transition of Monads to the We may conclude that many of the animalcules described in the genus Bodo (Ehr.) are examples of this genus (Cercomonas, Duj.), although suffi- ciently marked characters are wanting in order to discover specific identity. CERCOMONAS detracta. — Discoid or oblong, granular, with a thick tail. I-7000" to 1–2300". C. crassicauda. – Elongated, nodular, flexible, or variable in form, more or less contracted posteriorly into a tail, 1-3400" to 1–2600'". C. viridis.-Ovoid, oblong, tubercular, green, prolonged posteriorly into a tail of varying tenuity, or into a rounded lobe or spathulate expansion. 1-1500". Perty believes this to be no other than an early stage of development of Euglena viridis. C. lacryma.-Globular, unequal, elon- gated posteriorly as a long flexuose tail. Length of body 1–5200" to 1-3000"; of tail 1–2600"; of filament 1-750". C. acuminata (XVIII. 20).-Globular or ovoid, contracted posteriorly into a short tail, terminated by a very fine filament. 1–2600" to 1-1900". C. Globulus (XVIII. 23). —Globular, with a filament at each extremity double its length, the anterior one more actively moved. In marsh- water. C. longicauda (XVIII. 22).--—Fusiform, flexible, terminated posteriorly by a long and very slender flexuose filament. 1–1800”. C. fusiformis.--Dilated at centre, con- stricted in front, and prolonged behind into a long delicate tail. Length of body 1–1900". C. cylindrica. —Elongated, cylindri- cal, constricted posteriorly, terminated by a long, straight, and very thin tail. Length of body 1–2600"; of tail the same. C. truncata (XVIII. 12 a, b). — Con- tracted posteriorly; truncate in front, with a filament springing from each of the truncated angles; the posterior angle extended more or less into a lobe, 1–3000" to 1-1900". C. lobata (XVIII, 11 a, b)-Variable in form, tubercular, sending out a flagelli- form filament from the end of an ante- rior lobe, and emitting also one or two other lobes. 1–3250” to 2–3250". Length 1-2600". It is right to mention that Dujardin has noted the occurrence of several of the above Cercomonads in organic infusions, in conjunction particularly with Monas Lens, and that he inclines to the idea that these differently-named In- fusoria are morely different conditions of the same animalcule. Perty adds the following species:– C. intestinalis.-Has a posterior vi- brating filament, and probably an ante- rior one also. Internal molecules very fine; body transparent; posterior fila- ment about three times the length of the body. Is common in the intestine of the frog, and is in part equivalent to Bodo intestinalis (E.). 1-3000". C. curvata.--Cylindrical, curved, with an anterior and a posterior filament. In some specimens apparently two fila- ments occurred in front, 1-2400". Very active : occurs among the ova of the frog (Rana temporaria). C. vorticellaris = Bodo socialis and B. vorticellaris (E.). C. Ranarum= Bodo ranarum P (E.).- Colourless, soft, more or less conical; tapering or rounded behind, but without osterior filament. In water with Mol- usca, and in the intestine of frogs. C. clavata. — Colourless or greyish, thickened anteriorly, tapering poste- riorly, club-shaped ; motion rather quick; periphery clearer than the centre. 1-570". C. Falcula.—Colourless, transparent, compressed and curved (?), much widened in front, truncate and emar- ginate; posterior portion tapering to a blunt apex ; movements sluggish. 1–720". Genus AMPHIMONAS (Duj.) (XVIII. 13).-Animals of variable, irre- gular form, having at least two filaments, of which one is either in front, and the other on one side, owing to a constriction of the body, or both are lateral, and accompanied or not with a caudiform prolongation. The leaping move- ments of A. caudata are remarkable, and the variability in form is charac- teristic of each species. OF THE MONADINA, 499 AMPHIMONAS dispar . 13a, b)- Oblong, of very variable form, one or other end constricted, or prolonged laterally into two filaments. 1-3500" to 1-2900". Movement active, jerking. A. caudata.-Of very variable form, mostly depressed, tubercular, convex on one side, angular on the other, with a filament proceeding from the summit of each angle. 1-2180" to 1-1300". “This species seems to me,” says Du- jardin, “to be allied to the Bodo Saltans of Ehrenberg. In every example, I saw two flagelliform filaments, one from the anterior, the other from the lateral angle; A. brachiata.-Under this name is in- dicated an animalcule of the family Mo- madina, which Dujardin only once met with, of an ovoid or pyriform shape, filled with granules, and giving off from its narrower anterior end a simple flexu- ose filament, together with a variable dilated lobe emitting two other fila- ments having an undulatory motion. The animal progressed by leaps, revolv- ing at the same time. A. exilis (Perty).-Colour soft grey; figure wedge-shaped, oftentimes emar- ginate anteriorly; filaments two, twice the length of the body, colourless; mo- a caudiform prolongation, obtuseordrawn |tion oscillating, 1-2000". out as a third filament, often adhered to the slide,” Genus TREPOMONAS (D.) (XVIII. 16 & 27).—Body compressed, thicker and more rounded posteriorly; its anterior extremity presents two thin lobes, bent to one side and each terminated by a flagelliform filament, which pro- duce an active whirling and jerking movement. “The examples of this genus are very common in all collections of marsh- water containing decomposing plants, but are most difficult to determine, owing to the irregularity of their form and the rapidity of their movements. I have rather glimpsed than certainly detected their flagelliform filaments, and have in vain attempted accurately to delineate them.” TREPOMONAS agilis (XVIII, 16, 27).-Body granular, unequal. 1-1300". Genus HEXAMITA (D.) (XXVI. 1)-Animals with an oblong body rounded in front, constricted and bifid or notched behind. Two to four fila- ments extend from the anterior border; and the two posterior lobes are pro- longed as two flexuose filaments. This genus, characterized by the number of its motor filaments, appears sufficiently distinct from the preceding. Its species occur in decomposing marsh-water and in the intestine of Batrachians, but not in artificial infu- S10IlS. HEXAMITA nodulosa (XXVI. 1).-Ob- long, with three or four longitudinal rows of nodules, the two lateral of which are extended into tapering slender lobes, each terminated by a filament; move- ment vacillating, 1-1300" to 1-1500". H. inflata. — Oval oblong, rendered which give origin to the filaments. 1–600" to I-1300". - H. intestinalis.--Fusiform, prolonged into a bifid tail. Very common in the abdominal cavity of the Batrachia (frogs and newts). It moves in a straight line, oscillating from side to side, almost quadrangular by the processes Genus HETEROMITA (D.) (XXVI. 5; XVIII. 26).—Body globular, ovoid, or oblong, with two filaments extending from the same point in front —one slender, undulating, and producing an onward movement, the other thicker, stretching posteriorly, and free, or contracting adhesion with the glass slide along which it moves, so as to cause a sudden movement backwards. “The several sections of the Monadina, together with the Thecamonadina and the Euglenæ, contain Infusoria possessing two filaments, by one of which they progress, by the other adhere for Support to any solid body, and produce a sudden movement backwards by its contraction. To prevent confounding Specimens of these several families, the same distinctions which mark the 2 K 2 500 SYSTEMATIC IIISTORY OF TETE INFUSORIA. Monadina generally, must be found in order to constitute the Heteromita members of that family,–such as the absence of integument, the gelatinous appearance of the entire mass admitting of agglutination to other objects, and the drawing out of its substance into filamentous processes, together with the existence of certain corpuscles, which can only have penetrated the inte- rior as a consequence of the formation of vacuoles at the surface” (Duj.). HETEROMITA ovata (XXVI. 5). — Ovate, narrower anteriorly, containing vacuoles, granules, and Naviculae. 1-1050” to I-1150". This is probably the Bodo grandis of Ehrenberg. His other Bodos are not Bieteromiţa, but imperfectly-observed Cercomonads or Amphimonads. H. Granulum.—Globular, surface gra- nular, 1–2600". In rather putrid sea- water. H. angusta. — Narrow, lanceolate, slightly bent, tapering at each end, with a flagelliform and a second filament from the same point anteriorly, erect at the base, but floating freely the rest of its length. 1-1050". his is a doubtful species; it is of the shape of a lanceolate leaf, with a mid- rib or longitudinal fold. The following species are from Perty’s work:- H. pusilla.-Colourless, very delicate, cylindrical or Euglena-like in figure, constricted at the centre, often emargi– mate posteriorly; filaments 2 to 24 times longer than the body; movements in- active, oscillating; few fine granules in- ternally. 1-3000" to 1-2160". Allied to, but Smaller than, H. angusta, and like Amphimonas dispar, in which, how- ever, both filaments are equal. In ponds at Thun. H. eacigua,—Oval or spheroidal, co- lourless; filaments about three times the length of the body; movements in- active. 1-7000" to I-4800". In turf- hollows on the Bernese Alps. Genus TRICHOMONAS (D.) (XVIII.28).-Body ovoid or globular, capable of being drawn out when adherent, and in this way presenting sometimes a caudal prolongation. a group of vibratile cilia. TRICHOMONAs vaginalis.—Gelatinous, nodular, unequal, hollowed by vacuoles, often adhering to other bodies; move- ment oscillating, 1-2600". T. Limacis.-Ovoid, Smooth, *... at each end, and terminating in front by a flagelliform filament, from the base of which a row of vibratile cilia is directed backwards; progressive movement act- ive, the animalcule at the same time The anterior flagelliform filament is accompanied with turning on its axis. I-1730". Found in the intestine of Limaa: agrestis. T. Batrachiorum (Perty) (XVIII, 28a, b, c, d). — Widely oval, at times slightly emarginate in front, mostly with a keel along the back, colourless, and 8 to 10 cilia on the left side; resembles T. Limacis, but is more finely granular. 1–2400" to 1-1800”. Genus ANTHOPHYSA (D.) (XXVI. 2). — Animals ovoid or pyriform, furnished with a single flagelliform filament, and collected in clusters at the extremities of a branching stem, or polypidom, Secreted by themselves; clusters when detached resembling those of Uvella. The tree-like polypary is brown at the base, but clearer and even dia- phanous at the termination of the branches, which appear nodular. The groups of animalcules are easily detached from the stem, and then commence a rotatory movement by the action of the filaments of each individual in the group. Detached solitary animalcules move like the common monads with a single filament. The branching support, at first Soft and gelatinous, becomes by degrees more consistent, brown, and of a horny character, appearing to partake no longer of the vitality of the animalcules. A. Mülleri was erroneously placed by Ehrenberg in the genus Epistylis, among the Vorticellina, and called E. vegetans. • The delicate branched fibre or stem has been considered a microscopic. OF THE MONADINA. 501 fungus, and been named by Kützing Stereomema. Upon this view, the monadiform beings crowning the summits of the branches have been con- ceived to represent the spores. This opinion has been carefully investigated and rejected by Cohn (Entwick. d. mikroskop, Algen w. Pilze, pp. 114–115), who confirms Dujardin’s description, and regards it as a stalked Uvella. ANTHOPHYSA Müller. — With the characters described. A. solitaria (Bory).-A species was described under this name by Bory de St. Vincent, and is again brought to notice by Fresenius, who met with it in some standing water with Salvinia. The stem is simple (not branched), and has a clear outline to its extremity. Its length is from 1-25 to 1-8 millim.; and in water it has a clear brownish-green colour. Its apex is surmounted by the monadiform beings, looking like so many short hyaline fibres. Each monad con- tains a comparatively large non-con- tractile vacuole having a red refraction, and is furnished with a filament at its free extremity. Length of monads 1–100 to 1-75 millima. The fixed stem can bend itself from side to side. In one specimen a contractile vesicle was Seenin one of the monads. This organism appears to be precisely the same as the Epistylis Botrytis (Ehr.). Genus PERONIUM (Cohn), represented by one species. PERONIUM aciculare has been newly described by Cohn (Entwick, &c. p. 158) as a form allied to Anthophysa. It is parasitic on the spores of Pilularia, and consists of a delicate colourless fibre sur- mounted by a globular head, which re- Solves itself into numerous swarm-cells of a monadiform character. The two next genera are named by Werneck (Momatsbericht der Berlin. Akad. 1841, p. 377), and thus briefly described:— Genus ANCYRIUM = Enterodelous Bodos (i.e., according to the nomen- clature of Ehrenberg, Bodos furnished with an intestinal tube) with a moveable setaceous foot. The existence of an alimentary tube (so supposed) removes the Bodo grandis and the six allied species (i. e. the genus Ancyrium) far above the Monadina of Ehrenberg, whilst the possession of the setaceous foot also indi- cates a higher organization. •º. Genus E.R.ETES = Loricated Phacelomonads. The following are the new genera of Monadina instituted by Perty :- Genus TETRAMITUS (Perty) (XIX. 3).-Figure conical, tapering pos- teriorly, and having four vibratory filaments in front. Beaſamita differs in having in addition two posterior filaments. TETRAMITUS descissus (XIX. 3). — Wedge-shaped, curved, truncate ante- riorly, and colourless or pale grey. Sur- face marked by cross-lines. Movements tolerably active and oscillating. Fila- ments nearly twice the length of the body. 1-1860". T. rostratus.-Colourless, with an an- terior border; one side elongated as a prominent angle or beak. Smallest specimens 1-7000", the largest 1-1080" in length. Bern. In stale pond-water. Fresenius describes it as rather pyriform, truncate anteriorly, with a short trunk- like process from one side; elongated and pointed behind. A vesicle (contractile P) at the anterior extremity. Genus MALLOMONAS (Perty) (XIX.4–6).-Body oval, elliptic, or discoid, with brown or greenish contents. hairs. MALLOMONAS Plösslii (XIX, 4–6) (formerly described as M. acaroides).-- Mostly oval; the smaller end anterior; rarely elliptic or discoid; the periphery apparently crenulated—an appearance probably due to the points of insertion Surface covered with long motionless A single filament anteriorly, double the length of the body. of the hairs; these are commonly longer on the posterior half. Contents sometimes seen longitudinally or trans- versely divided. Movements rather rapid, but rarely attended by a rotation of the body. In one example the hairs 502 SYSTEMATIC HISTORY OF TEDE INFUSORIA, seemed terminated by a knob. It is not improbable that Pantotrichum Enchelys (E.) is also a member of this genus. 1–1440" to 1-960". Bern. In ponds. — A variety (M. epilis) occurs, hav- ing the hairs short or actually absent, although covered with little nodules which serve as bases for hairs. Frese– nius has noticed this organism. He adds, the ends are often pointed. The hairs or bristles are long, and tolerably numerous—as many as 30 have been counted, placed at all parts of the peri- phery. The anterior setiform hairs are most concerned in locomotion; those placed laterally either lie along the sides pretty closely, or stand out at a greater or less distance, and appear concerned chiefly in changing the position. The two most in advance seem to have the character of feelers. A clear vacuole was sometimes seen in the middle of the dusky-green contents. A few Small, contractile, optically red specks have also been observed. 1-720" to 1-444". Fresenius considers it ought to be re- moved from the Monadina; and Perty is himself unable to decide whether this genus is referable to the Ciliata or to the Phytozoa. Genus PLEUROMONAS (Perty) (XVIII. 25).-Body reniform, extremely delicate, Small, colourless; filament extended from the concave side of the body, and three times its length. PLEUROMONAS jaculans = Chilomonas obliqua (?) (Duj.) (XVIII. 25).-Colour- less, transparent, with a few small mole- cules. M. eccentric, hither and thither in a jerking and leaping manner, followed by intervals of rest. Very young specimens are round. 1–6000" to 1-3160". Bern. In stale water and infusions of Lycopodium Seeds. Genus SPIROMONAS (Perty) (XVIII. 24).-Body leaf-like, compressed, rounded at both ends, and rolled spirally on itself longitudinally. SPIROMONAs volubilis = Cyclidium dis- tortum (Duj.).—Colourless, transparent, smooth, very delicate. Revolves rapidly on its long axis. Not modular on the margin, lice the Cyclidium distortum of Dujardin, but is probably (as Dujar- din believes the latter to be) merely a phase of Monas Lens. 1-1800" to 1–1300". Bern. In foul water. Genus MENOIDIUM (Perty) (XIX. 2).-Body small, crescentic, thicker on the outer or convex margin; containing internally small molecules and vesicles; colourless, or occupied with a little chlorophyll. MENOIDIUM pellucidum (XIX. 2), — sickle. Movement tolerably rapid, jerk- Recalls by its figure a little Closterium ing and revolving. 1-670" to 1-430". lunula; not rounded, but flattened like a Genus CHROMATIUM (Perty) (XIX.1)—Body extremely small, red, brown, violet, or green in colour, containing in the mature condition some internal vesicles. cation by transverse fission. A motor filament at the anterior extremity (?). Multipli- To this genus Perty would refer the greater part of the Monads described by Ehrenberg which possess a brilliant colour; and he is in doubt whether they are not all rather referable to the genus Bacterium, as well as the next genus named, i. e. Acariaeum. However, he at present retains Chromativm and Acaricewm among the Monadina, and establishes two species of the former. - a straight course. The vesicles are not present in very young specimens: they first show themselves as dark points, and afterwards assume the vesicular form. Perty cannot discover the filament de- scribed by Ehrenberg in Monas Okenii. Eichwaldsays of this species that it swims CHROMATIUM. Weissi; (xIx. 1). — Of a violet or brownish colour, rounded and truncate both before and behind; vesicles within sharply defined. The Monas Okenii of Weisse is very closely allied, but still more minute. It pro- gresses and revolves rather rapidly, º OF THE HYDROMORINA. 503 backwards or forwards indifferently,– a circumstance adverse to the existence of a filament at all. I-4800" to 1-2400". Occurs among Characeae. - C. violescens.—Globular or elliptical, transparent, and of a very pale violet colour. It appears closely related to, al- though not ...i with, Monas vinosa (E.). A filament could not be detected, nor any internal Organs. At Bern, with Chara. 1-14,000" to 1-3000". These coloured organisms form a colouring layer on the mud at the bottom of ponds, &c. The several species men- tioned by authors referable to the genus Chromatium are—Monas rosea, Morren; Monas Okenii, Weisse; Monas vinosa, M. erubescens, M. ochracea, and probably M. prodigiosa and M. gliscens of Ehren- berg's category. Genus ACARLAEUM.—Extremely minute, globular or elliptical; perfectly transparent, without a trace of either external or internal organs. ACARIAEUM Crepusculum = Monas Cre- movements in common with those of the pusculum (E.).-They swim rapidly past || Monads, but much rather with those of each other, yet have nothing in their the Bacterium Termo. Genus RHABDOMONAS (Fresenius). RHABDOMONAS incurva. —Stout, elongated and cylindrical, slightly fal- cate; anterior extremity rather the thicker; three prominent longitudinal ridges; green vesicles or granules occupy the anterior half of the body; progresses Genus GRYMAEA (Fresenius). GRYMAEA vacillans.—Colourless, hya- line, compressed; when seen on itsflat side its outline is circular, but on the narrow side, pyriform, the posterior compressed portion gradually thickening towards the in a straight line, with a rotary or semi- rotary motion on its long axis; filament 14 the length of the i. 1–60 to 1–50 millim. In stagnant water with Confervae, &c. thick end foremost, slowly revolving on its long axis, with an oscillating motion. Filament revealed by iodine. in stand. ing water with Wallisneria in the Botanic Gardens. It is, not unlikely, the same thicker front part. Advances with the being as Monas urceolaris (Perty). FAMILY II.-HYDROMORINA. Characters.-Amenterous Polygastrica without appendages; body uniform, like that of the Monads, but, by reason of the spontaneous fission being im– perfect, developed into a moniliform mass or polypary; lorica absent. Indi- viduals are at periods set free, which commence the same cycle of compound development as the parent beings to which they originally belonged (Ehr.). The genera belonging to this family are Polytoma and Spondylomorum. Polytoma was described by Ehrenberg in the family Momadina; but the sub- sequent discovery of the genus Spondylomorum, having the same general characters, and differing like it from the other monads, led him to create this new family Hydromorina to embrace the two. Perty has also recognized the propriety of detaching those Monadina which, by the act of self-fission continuing incomplete, live together in compound masses, and to designate them has invented the term “Momadina Familiaria,” equivalent in English to “gregarious or aggregated Momadina.” Under this group, however, he has placed two other genera, which Ehrenberg has let remain, somewhat unaccountably, among those Monadina living in an isolated or free state. These other members of the Hydromorina or Aggregated Monads are, Uvella and Anthophysa. Schneider (A. N. H. 1854, xiv. 326) observes on the near alliance of Polytoma to Chlorogonium euchlorum. It would seem that Cohn fails to find any truly distinctive characters between 504 SYSTEMIATIC EIISTORY OF THE INFUSORIA. Polytoma and Chlamydomonas; for he proposes (Entwick. p. 140) to apply to P. Uvella the name of Chl. hyalina. te Genus POLYTOMA (XVIII. 5; XX, 1–14).-Mouth terminal, truncate, surmounted by a double flagelliform filament situated as in Monas and Uvella; eye and tail wanting. It will not imbibe colouring matter. A large con- tractile vesicle and the trace of a nucleus are sometimes observable. Self- division occurs both transversely and longitudinally, and produces a berry-like cluster of many individuals. As the young increase in size, the parent body assumes a decussated or wrinkled appearance, like a mulberry, and in this manner indicates its approaching self-division into many sections (as the name Polytoma denotes), or numerous individuals. In Swimming, the filaments are extended in advance. In putting forward the self-division of Polytoma as a peculiar feature, Cohn says that Ehrenberg has mistaken a transitional for a permanent condition. PolytomA Uvella (Monas Uva, M.). —Colourless, of an oval or oblong form; extremities equally obtuse. It is often abundant in water where animal matters are in solution, upon which it appears to be nourished; generally in company with species of Vibrio and Spirillum, and some- times with Uvella Uva and U. Atomus. Group 5 shows two isolated indi- viduals; another about to divide longi- tudinally; a cluster of eight united within a common envelope; another cluster, of which the common envelope has disappeared prior to the separation of the individual Monads, and in the two isolated beings the double filament is very distinct. 1-200" to 1-90”; diam. of clusters 1-380". Schneider (Part I, p. 136) has closely examined this species (xx. 1–14). The hyaline investing membrane, he says, can be distinctly displayed by using chromic acid, or solution of iodine in chloride of zinc. A globular nucleus lies near the centre, with a narrow red- dish halo around it: dilute acids render It was known to Müller and Wrisberg. this more distinct (xx. 2). At the anterior extremity are two reddish vesi- cles, which are contractile; and other non-contractile reddish ones are scattered in the interior. The creature “rotates upon its axis; and this, again, describes circular vibrations upon a central point.” Self-division takes place at first into two (xx. 3), then into four (xx. 9), and, under favourable conditions, into eight seg- ments, each of which acquires its fila- ments, and moves about within the en- velope of the parent with the rest until set free by its rupture. Under certain circumstances the individuals pass to a state of rest (xx. 7), and then do not undergo fission or any other change, but remain in a torpid condition. In assum- ing this state the filaments contract gradually, and at length seem to be withdrawn completely within the con- tained substance of the encysted being. The internal granules of Polytoma are, according to Schneider, composed of starch, and are convertible into a blue or a green colouring matter. Perty has distinguished three additional species, viz. – POLYTOMA Uva. —Divides into as many as ten segments. The mode of fission much resembles that of Chlamy- domonas, but differs in exhihiting active movements during the process, instead of the state of rest seen in the latter. The corpuscles are usually oval, and hya- line; rarely yellow or brown; filled with larger or smaller vesicles, and in old specimens with black molecules. Self- division proceeds rapidly. Movements darting and revolving. An enveloping cyst has been noticed in Some examples. Uncommon in fresh, but frequent in water holding animal decomposing mat- ters in solution. Two varieties are distinguishable: viz. –Var, a unifilis, having only one filament, resembling Trachelius globulifer (E.), and very pro- bably identical with Monas punctum; War. b. rostrata Seu hysginoides, of a feeble yellow colour, with a prominent cyst-wall, within which it is contracted and deprived of its filaments. It does not break up on drying, but can continue several weeks without change. . [This is evidently not even a variety in the proper sense, but simply an encysted Polytoma.] P. ocellata. —Oval; filled with vesi- cles, like P. Uva, except that it has a clear-red stigma at the centre. Motion languid, Self-fission produces few new OF THE CRYPTOMONADINA, 505 * beings; and these lie parallel to each other. Has the dimensions of P. Uva. Found in decomposing infusions. Schneider describes a peculiar mode of fission seen at times in P. Uvella, in which the segments lie parallel to each other : very probably this supposed spe- cies, P. ocellatum, is nothing more than that phase of P. Uvella. The reddish P. P virens,—Greenish or actually green, surrounded by a hyaline cyst. Seen only in process of fission, when each segment i. its own filament. These organisms were for some seconds at rest, and soon afterwards moved here and there with activity. Very probably this being is only a sporule, and seems nearly akin to Chlamydomonas. vesicle is worthless as a specific character. Genus SPONDYLOMORUM.—Individuals furnished with a dorsal ocellus, are destitute of a tail, and, in consequence of their imperfect self-division, deve- lope a compound body (polypary) resembling a whorl or cluster of berries. SPONDYLoMoRUM quaternarium. — A' | slender; colour green; filaments four to group of four alternating corpuscles, five. Length of polypary 1-576", of each of which the terminal one is the most individual 1-1728". - FAMILY III.—CRYPTOMONADINA. (XVIII. 29–34; XIX. 7–16 and 20–31; XXVI. 6, 8, 9, 10.) THE Cryptomonadina (vide General History, p. 140) are Monadina enve- loped within a distinct gelatinous, membranous, or hard induvium, forming a shell-like covering or lorica. According to Ehrenberg, the lorica sometimes resembles an open shield (scutellum), at others a closed box or pitcher (urce- olus). The construction of the lorica, however, as a scutellum, open on one side, is denied by every recent writer; and in all cases it would appear to completely enclose the contents. Two delicate, filiform, and generally re- tractile filaments, capable of being put into very powerful whirling and lash- ing motion, are clearly perceptible in all the genera, excepting, perhaps, the genus Lagenella; and even in this, Dr. Werneck believed he had discerned them. Six or seven species exhibit internal vesicles; and in two genera a coloured spot is present at the fore part of the body. From the position of this speck the dorsal line may be readily conceived, and a right and left side described. Self-division, when it occurs, is simple and complete. “It is possible,” says Ehrenberg, “that the fossil animalcules discovered in the flint of chalk and porphyritic formations, and named by me Pyazidicula (see Plate XVII. upper figures), belong to the genus Trachelomonas.” Lachmann (op. cit. p. 219) asserts that in all transparent Monadina and Cryptomonadina a contractile vesicle exists, and that even in the more opake Chilomonas Paramecium and Cryptomonas ovata he was able to observe its contractions. Mr. Carter confirms this statement. The genera were thus tabulated by Ehrenberg:— ſ Form short ; self-division Lorica obtuse and Smooth longitudinal or :} Cryptomonas. Eye-speck -: ' ' ' || Form long and tortuous; Ophidomon absent. self-division transverse f *P Oll&S. Lorica pointed anteriorly .......................................... Prorocentrum. (Lorica with a neck and narrow orifice..….......... Lagemella. Eye-speck ſ Lorica an open shield * present. | Lorica with orifice, but no º Cryptoglema. neck. Lorica, a closed box i. - - \ (urceolus). } Trachelomonas. 506 SYSTEMATIC HISTORY OF THE INFUSORIA. The members of this family are readily recognized by the stiffness or in- flexibility they display while swimming or when brought into contact with other bodies. The lorica of Prorocēntrum and Lagemella is at once perceived to be a distinct covering. When any doubt, however, exists upon this point, a slight degree of pressure upon the specimens placed in an aquatic live-box, or between two slips of polished glass, will easily determine it. The lorica of Trachelomonas Ehrenberg affirmed to be silicious, and indestructible by fire. Dujardin has a parallel family he names Thecamonadina, consisting of eight genera. These, however, are not the same as the genera of Cryptomo- madina of Ehrenberg, of which only two are retained, viz. Trachelomonas and Cryptomonas. In the last-named genus are included Cryptoglena and Lagenella, which Dujardin considers have no claim to generic distinction. Prorodon may, he thinks, be the same as his genus Oxyrrhis ; and under the head of Trachelomonas he unites Chaetotyphla and Chaetoglena, numbered among the Peridiniaea in the classification of Ehrenberg. A new genus, Phacus, is constructed by the same author, to receive those green organisms having a rigid inflexible tunic, which Ehrenberg placed with the flexible and protean Euglence. Another group, styled Diselmis, includes many of the Chlamidomonads of Ehrenberg. Besides these, three other new genera, viz. Crwmenula, Ploeotia, and Anisonema, enter into this family Thecamonadina, and are described as addenda to the Cryptomonadina of Ehrenberg. The accompanying tabular view represents at a glance the distribution adopted by Dujardin — THECAMONADINA. e s Integument hard and brittle... 1. Trachelomonas. Body ovoid or globular......... {#: membranous... ... 2. Cryptomonas. Body flattened or leaf-like, ſ With a caudal prolongation ... 3. Phacus. with a single filament......... Without such ..................... 4. Crumenula. The two filaments equal ................................................ 5. Diselmis. ilin #. prismatic or mavicular ... 6. Ploeotia. One flagelliform, one trailing 3 Body ovoid, in form of a grape- e - 3. Seed, with two filaments } 7. Anisonema. # * * g e & With several filaments ......... ſº º * intº } 8. Oxyrrhis. Perty borrows from both Ehrenberg and Dujardin, by instituting two families, Cryptomonadina and TheCamonadina, and distributes the several species in another fashion, under new generic names, The distinctive cha- racters of the two families are thus set forth :— Cryptom0nadina.-The surface of the body more or less hardened, but in- separable from the contained substance as a distinct testa. Thecamonadina-Possess a distinct red stigma, and, though naked at first, acquire an apparently separable, brittle, silicious shell or testa, having an opening at its fore part for the protrusion of the filaments. In the act of fission the beings (which may or may not entirely occupy the shell) divide into two or four new individuals. - The Cryptomonadina comprise the genera Cryptomonas, Phacotus, Anisonema, Phacus, and Lepocinclis; and the Thecamonadina include Chaetotyphla, Try- pemonas, and Chonemonas. - Cohn (Siebold’s Zeitschr, 1853, Band iv. pp. 275-277) sanctions this sub- division of the Cryptomomadina into two families; for he remarks that Crypto- OF THE CRYPTOMONADINA. 507 monas and Cryptoglena, and other forms, have a hard integument or lorica (Panzer) inseparable from the subjacent mass, whilst Trachelomonas, Lagenella, and Chaetoglena possess a distinct separable capsule or cyst, within which, at a certain period, the contained Euglena-like being can contort itself and revolve at pleasure. Moreover, Cohn's opinion is that these capsuled forms should be detached from the Monadina or Cryptomonadina, and placed with the Buglenae. In this opinion we entirely coincide, and would regard the cap- Suled monadiform beings as simply encysted Euglence. Indeed, the present state of knowledge, especially respecting the process of encysting, irresistibly leads to the conclusion that this entire family Cryptomonadina of Ehrenberg must be broken up, and its several forms distributed among various groups of animalcules and plants, as representing their encysted phase or condition. Fresenius adds a new genus to the Cryptomonadina, which he calls Dre- panomonas. Genus CRYPTOMONAS (XVIII. 29)—Coloured stigma absent; lorica obtuse, or not attenuated anteriorly; body short, but not filiform; self-divi- sion, if any, longitudinal; flagelliform filament very fine. Dujardin writes, “In this genus Cryptomonas I comprise all Thecamo- nadina with a single filament, and with a lorica neither hard nor brittle, and whose body is not depressed (compressed) like that of Phacus or of Crumenwla; and I moreover do not doubt that when these Infusoria are better known, other genera may be distinguished by their more or less globular form, by the consistence of their envelope, and especially by their mode of existence. I already indicate as Subgenera, Lagemella with an elongated lorica, and Tetrabaena, the species of which are united in groups of four, not enclosed, however, within a common envelope. As to the character supplied by the presence of a red speck in Some individuals, assumed by Ehrenberg to be an eye, I cannot discover in it a generic distinction; nor am I able to admit the existence of a lorica open on One side (below) like a shield (carapace). On the contrary, I have always observed the lorica to be closed and entire, though sometimes compressed on One side, adapting itself to the living mass enclosed. The covering in every case is evidently larger than the contained mass, a diaphanous space intervening between the two visible in the form of a clear ring.” Of the species enumerated by Ehrenberg, Dujardin re- marks that “ C. curvata is so compressed that it is properly referable to our genus Crumenula.” C. glauca and C. fusca he regards as doubtful species. . Perty briefly characterizes his genus Cryptomonas thus:– “Body an elon- gated urceolus, from the anterior and mostly-rounded extremity of which two filaments are protruded, somewhat exceeding the length of the body; within are usually one or more dark nuclei, from which the vesicular germs seem to be developed.” - CRYPTOMONAs curvata.-Green, com- pressed, slightly bent like the letter S, and twice as long as broad. Amongst Confervae. 1-570". C. ovata (Enchelys viridis, M.) (XVIII. 29).-Green, depressed oval, and twice as long as broad; motion slow, vacil- lating, and rotating on the longitudinal axis, but when obstructed (says Ehren- berg) is seen to leap ; lorica paper-like, not hard; numerous internal transparent vacuoles and green granules. In the middle of the creature there are two or three egg-shaped nuclear bodies, and at the posterior part a single vesicle; self- division not observed. Found amongst Confervae. 1-570". - C. erosa,—Green, hyaline anteriorly, depressed, oval. In clean water among Confervae. 1-960". C. cylindrica (Enchelys viridis, M.).-- Elongated, subcylindrical, three times as 508 SYSTEMATIC EIISTORY OF THE INFUSORIA. long as broad. Amongst Conferve. Almost 1-1000". C. (?) glauca.-Oval, twice as long as broad; anteriorly truncated with a double flagelliform proboscis; body tur- gid, and of a bluish-green colour, found with Chlamydomonas Pulvisculus, 1-864". C. (?) fusca.-Oval, turgid, and of a brown colour. Amongst Confervas. 1-1500". C. lenticularis.-Orbicular, resembling a lens; colour green; lorica thick. 1–1729", The following are described and named by Dujardin:- C. Globulus.—Globular, green, often with folds (stripes), the diaphanous en- velope nearly filled. 1-2600" to 1-2250". This species, in Perty's opinion, is a sporule of a yºut or a ‘sporozoid.’ C. indequalis. --Ovoid, green, of less thickness than breadth, with a longitu- dinal depression, and one or two unequal notches in the coloured portion, which is always smaller than the envelope. 1–2600". In stagnant sea-water, impart- ing to it a green colour. C. (LAGENELLA) inflata.—Ovoid, en- larged posteriorly, contracted anteriorly; envelope º thicker about the anterior neck-like portion, filled with a green substance, having a central red speck; motion zigzag, 1-1180". In a vessel of marsh-water with Lemma. C. (LAGENELLA) euchlora (XVIII, 31).- Ehrenberg has described under this name an Infusorium of the same size, differing from the last by its more elongated form, and especially by the green contents more completely occupying the anterior neck- like portion, whereas in ours but a nar- row streak is visible. C. (TETRABANA) socialis.-Regularly ovoid, green, with a central red point, enveloped by a thick diaphanous lorica; commencing self-division frequently seen; occurs in regular groups of four individuals, simply agglutinated, and having their filaments directed all to the same side. 1-1700" to 1-1300", In a water-butt in the King's garden, Paris. “I should have taken,” says Dujardin, “the specimens of Tetrabaena socialis at first for Gonia, if a trace of a common enclosing envelope had been found; yet I cannot doubt that they have the closest analogy with the true Gonia, and with what łº, has called Syncryptain his family Volvocina. One may suppose that the commencing self- fission observed in some individuals would give rise to such groups upon the destruction of the lorica (integument) in these different genera. This mode of propagation occurs undoubtedly in most of those having a soft gelatinous integu- ment; but in animals like Trachelomonas, whose lorica is hard and brittle, we can- not understand how multiplication does take place.” In the addenda to his treatise, Dujar- din has this remark: “I am convinced that my Cryptomonas (Tetrabaena) be- longs rightly to Gonium.” The generic characters of Cryptomonas, as understood by Perty, have been detailed; the following are the species he describes:— C. polymorpha.—Is so very variable in form that no single description can be applied to it. . It ranges between 1-840" to 1-300" in length, and may be green or colourless, brown or golden yellow, and contain at one time red specks, at another not. The Smallest are usually yellow or of a verdigris-green; many small ones are hyaline; the largest Sea- green and brown. These changes of colour are doubtless due to the choro- phyll developed within these minute organisms, and to the modifications this matter undergoes in different stages and conditions of life—a subject well exa- mined and illustrated in Braun's work on Rejuvenescence in Nature. In figure, individual specimens are oval or globu- lar, compressed, and emarginate. Small ones move rapidly, frequently in circles; larger examples more slowly, and at times backwards. The species is com- mon among Confervae the whole year, and under the ice in winter. Perty assumes it to represent the following Species of Cryptomonas named by Ehren- berg, viz. C. curvata, C. ovata, C. erosa, C. cylindrica, C. glauca, and C. fusca, and also Chilomonas Paramecium. OF THE CRYPTOMONADINA, ſº 509 C. dubia.-Quite flattened, elliptical, allied to Cryptoglena pigra, C. carrulescens, not rounded anteriorly; of a clear green and, in a less degree, to C. comica of colour, with a hyaline central band, Ehrenberg. and, in most instances, a red stigma. C. urceolaris (Smarda)—Belongs, by Movement rather quick; the filament reason of its firm testa, to the Theca- not seen. 1-1900" to 1-1400". It is monadina. Genus OPHIDOMONAS.—Body filiform; eye-speck absent; lorica smooth, obtuse, and tubular with a single filament; self-division transverse and com- plete; internal vacuoles numerous. Its extremely small transverse diameter is the great impediment to a better acquaintance with this being. (It has not been figured.) OPHIDOMONAS Jenensis, -Very thin, O. Sanguinea, Very slender, the in- curved spirally, and equally obtuse at | terspaces between the vacuoles filled both extremities; colour olive-brown; with a red colour. 1-576". In brackish motion brisk. In well-water. 1-570". water. Genus PROROCENTRUM (XVIII. 30).-Lorica resembling a little box (wrceolus), Smooth, pointed at the anterior extremity; eye-speck absent ; pro- boscis filiform ; vacuoles numerous. Self-division has not been observed. “It is worthy of remark,” says Ehrenberg, “ that the only species of this genus with which we are acquainted [i. e. in 1838] belong to the luminous crea- tures of the Sea, which, perhaps from Some peculiar organic relation or con– dition, yet unknown to us, are instrumental in producing that curious and certainly vital phenomenon usually termed phosphorescence.” It may be further noticed, that all the luminous Infusoria of the sea, hitherto discovered, are characterized as being of the same yellowish waxy colour as the best- known species of this genus—P. micans; and it is probable that this condition is immediately connected with the interesting phenomenon in question. PROROCENTRUM micans. – Oval and cates the position of the supposed compressed, attenuated posteriorly, but mouth. 1-430". dilated and pointed anteriorly; colour of P. viridis–Ovate, suborbicular, tur- yellow wax. In sea-water. (XVIII. 30). gid; posterior end rounded; anterior Two figures, magnified 300 diameters; shortly pointed; colour green. 1-1100". the first is a side view, the latter a back | In the Baltic. view; the filament in the former indi- - Genus LAGENELLA (XVIII. 31).-Distinguished from other loricated monads by the lorica being extended anteriorly, or flask-shaped. The lorica is perfectly distinct, and crystalline. Within are the bright-red speck and green granules. (Wide Cryptomonas Lagemella, p. 508, and Chonemonas, Perty, p. 513.) LAGENELLA. euchlora (XVIII, 31). — crystalline; colour green. Amongst. Oval, neck short and truncated; lorica | Confervae. 1-1200". Genus CRYPTOGLENA (XVIII. 32).-Lorica open, in the form of a shield (scutellum), folded or rolled inwardly at the sides, and without a projecting neck. Eye-speck distinct ; granules green in all the species. In C. comica two oval greyish masses are seen in the centre, and also two filaments. Self- division not observed. These characters, given by Ehrenberg, are valueless to distinguish Cryptoglena from other Cryptomonadina, or from Chlamydococcus. The scutellar form of the lorica is an error; for it forms a complete investment, interrupted only at the point where it gives exit to the filaments. The red eye-speck is no distinction, as so often remarked; and the absence of a neck- like extension of the lorica is seen in Cryptomonas, Chlamydococcus, and other genera. Carter describes one species with four filaments. We unite with Dujardin in rejecting this as an independent genus, 510 SYSTEMATIC HISTORY OF THE INFUSORIA CRYPTogLENA conica (xVIII, 32). — Comical, anteriorly dilated and trun- cated; filaments two, half the length of the body; posterior end acutely attenu- ated. Colour bluish-green, Abundant in river water, in company with Crypto- monas glauca, from which they are readily distinguished by their form, larger size, and red eye. . They move briskly in the direction of the longitudi- mal axis of their bodies, but when ob- structed spring or leap out of their direct course, 1-1100". * - C. pigra.-Oval, approaching to glo- bular, and emarginate anteriorly; colour a beautiful green; movement slow. In water when covered with ice. 1-3000". C. caerulescens.—Depressed, elliptical and emarginate anteriorly; colour bluish #. motion quick. Amongst Con- ervae, 1–6000". Mr. Carter has added and figured some new species, viz.-- C. lenticularis (A. N. H. 1858, p. 253). —Spherical, compressed ; lorica distinct and stout; endochrome separated from it by a distinct clear zone; contrac- tile vesicle seated at the point of in- sertion of the two filaments, where there also seems to be an interruption in the continuity of the lorica (emar- ginate); eye-speck on one side, nucleus visible. The horizontal view is ovate, and acuminate at both ends. Fission takes place in the power of two, just as in Chlamydococcus, from which in- deed no satisfactory distinctive fea- tures are perceptible in the engravings furnished. . C. cordiformis.--Distinguished by its cordiform lorica. The contents are orbi- cular, and do not nearly fill the lorica; filaments four; a resting-stage perceived, wherein the contents are covered by a thick envelope, and are divided into numerous cells (microgonidia. C. angulosa (A. N. H. 1859, iii. 18).- Lorica compressed, oblong, angular, shield-shaped, transparent, round poste- riorly, square anteriorly, where it pre- sents a short neck in the median line for the passage of the cilia; border thin, curled up posteriorly and anteriorly on opposite sides. Internal or green cell at Some distance from the lorica, angular, lined with chlorophyll, provided with two cilia, which issue through the neck of the lorica; two contractile vesicles at their base; an eye-spot median and peripheral, and one to four starch-cells of a circular form. Swimming with its cilia forwards in an extremely irregular line. Length of lorica. 1-1080", and breadth 1-1800". Freshwater tanks in the island of Bombay. Genus TRACHELOMONAS (XVIII.33, 34; XIX. 9–11).-Have a single long filament, an eye-speck, and a closed elongated or spherical lorica, with- out a projecting neck. Very minute transparent vesicles have been discerned in T. nigricans and T. volvocina. It is probable that some of the highly inter- esting animalcules which enter so abundantly into the silicified substances in certain chalk formations belong to this genus. The genus Trypemonas (Perty) is equivalent to this, the characters of which are hereafter given at large in Perty’s words (p. 513). TRACHELOMONAS migricans. – Oval, approaching to globular; colour, rarely green, mostly of a reddish or blackish brown, Eye-speck brown. 1-1700". T. volvocina (XVIII. 33, 34; XIx. 9, 10). —Spherical, with a delicate, filament; colour mostly green, sometimes of a brownish hue, with a distinctive red ring around the body: between the in- ternal vesicles is a very fine granulated substance, to which the colour of the body is due. The red circle, so re- markable a feature in this species, always appears in the same horizontal position, how quickly soever the creature may be revolving on its long axis. The uppermost figure represents the flabellum extended; in the next it is retracted; the lowest of the three is a very young spe- cimen; and 34, a full-grown one that has been forcibly pressed and the lorica broken. Amongst Confervae. 1-860". T. cylindrica (XIX. 11)-Oblong, ap- proaching to cylindrical; filament almost as long as the body. Colour a beautiful green; eye-speck red; ring purple. 1-1000". Perty points out the fact that T. nigricans is nothing more than an old specimen of this species, brown and opake by age. T. areolata.-Globose, surface areo- lated. T. aspera.-Similar to preceding, but its surface covered with rough points. OF THE CRYPTOMONADINA, 511 T. granulata.-Similar, but its surface tween the surface of this and the two pre- very minutely granulated, ceding are too trivial to be characteristic. T. laevis—Globose, with its surface | T. pyrum. —Oblong or pear-shaped smooth. The assigned differences be- | (pyriform), Smooth. Dujardin, in his family Thecamonadina, includes some genera of animalcules not described by Ehrenberg, or described by him under different names and according to a different arrangement. They are appended here as best agree- ing with the Cryptomonadina. Genus PHACUS (D.).-Body flattened, leaf-like, and mostly green. It displays a red speck in front, together with a flagelliform filament; and the resistant membranous integument is prolonged posteriorly in the form of a tail. “Three out of the four species are referred by Ehrenberg to his genus Euglena, on account of similarity in colour. The difference between the two genera is, however, considerable ; for in Euglema the integument is contractile, and permits of a frequent change of form, whilst in Phacus, on the contrary, the integument appears quite wanting in contractility, and the animal inva- riable in form. “The enclosing integument of Phacus persists after the death of the animal and the destruction of the contained green mass, and also after the action of various chemical agents, becoming, in the latter cases, quite transparent. The motor filament disappears with the living contents; globules of the latter remain after death.” Mr. Carter (A. N. H. 1856, xviii. p. 241) describes a single, glairy, discoid, capsuled body in the centre of Phacus, as well as in the large lip of Crume- mwla teacta. 1. Phacus pleuronectes= Eugléna pleuronectes; 2. P. longicauda = E. longi- cauda; and 3. P. triquetra = E. triquetra. (See EUGLENA.) The new species, of which the characters are given, is PHACUS tripteris. – Oblong, with with a red speck in front and a dia- three longitudinal plaits meeting along phanous caudiform prolongation behind. the axis, rather twisted on the midrib, 1-420" to 1-312". Genus CRUMENULA (D.) (XXVI. 6).-Oval, compressed, covered by a resistant integument (testa) apparently reticulated, sending out a long flagelli- form filament obliquely from a notch in the anterior border. Motion slow. There is no tail-like prolongation, as in Phacus. A contractile vesicle present. CRUMENULA teacta, – Envelope re- pointed sigmoid fibres arranged parallel ticular, filled with a green matter, toge- to each other, so as to form a conical ther with vacuoles or hyaline globules, cell, which remains behind when the and having a largered globule anteriorly. softer contents have dispersed. 1–520". †. persistent after death. The anterior notch is produced by a In this species Mr. Carter (op. cit. sort of overhanging lip. The filament p. 119) describes an immer layer of is three times longer than the body. Genus DISELMIS (D.)-Ovoid or globular, covered by an integument, not contractile, of almost gelatinous consistence; two equal locomotive filaments proceed from the anterior extremity. “This genus nearly corresponds to the Chlamydomonas of Ehrenberg, placed by him in the family Volvocina by reason of its apparent-self-division into two or four segments within the testa. Dujardin, on the other hand, admits none as Volvocina which do not exhibit an aggregation of perfect individuals within a common envelope.” The removal, by Dujardin, of the Chlamydomonads described under this name of Diselmis, from Volvocina to Cryptomonadina, is generally held to be an error, dependent on an imperfect conception of their characters and true affinities. (See genus CHLAMYDOMONAS.) 512 SYSTEMATIC HISTORY OF THE INFUSORIA, The integument of Diselmis is non-resistant, diaphanous, breaks up after death by diffluence, and is sometimes filled with a green substance. Like plants, these beings are sensitive to light, fix themselves to the lightest part of the containing vessel, and disengage oxygen when exposed to the Sun’s rays. In the green substance are seen granular masses, a disk with an expanded border, and a red speck. The motor filaments proceed from the same opening of the integument, and often form a diaphanous lobe projecting from the opening. The red colour oftentimes seen in the water of the Mediterranean appears due to Infusoria of this genus. DISELMIS viridis = Chlamydomonas inside, sometimes with an indistinct red pulvisculus (Ehr.) (XIX, 16). D. marina. —Nearly globular, obtuse and rounded in front, granular within. 1-1050". This species is larger than D. viridis, more globular, and apparently deficient of the red speck. In stagnant sea-water of a green colour. D. angusta.-Pyriform, oblong, ap- pearing to be plaited and tubercular speck. 1-2600" to 1-1850", D. Dunalii – Oval or oblong, often constricted about the middle; colourless when very young, then green, afterwards red; with 2 flagelliform filaments longer than the body, seated on a projecting and retractile anterior lobe. Interior occupied by coloured globules. Discovered by M. Joly to be the chief cause of the red colour of the water of the Mediterranean, Genus ANISONEMA (D.) (XIX. 8; XXVI. 8).-Colourless, oblong, more or less compressed, having a resistant envelope giving exit by an opening to two filaments, one directed forwards and flagelliform, the other trailing back- wards and retractile; movement slow. “In other genera, as in Heteromita, two similar filaments exist; but the present genus is known by its non-contractile resistant integument, which is often met with empty and transparent. It may be that the Bodo grandis (Ehr.) is allied to this genus as well as to Heteromita.” ANISONEMA Acinus (XIX, 8).-Oblong, depressed, rounded posteriorly, and mar- rower in front, like the seed of an apple, with an opening close to the apex; colourless and transparent, except a few vesicles, mostly green, but occasionally red; movement in a straight line for- wards. 1-1300" to 1-850". In pond- water. This species = Bodo grandis (P) (Ehr.). Perty gives a figure of an º: ism he identifies with this species, hav- ing four filaments anteriorly and none trailing: he supposes it in the act of fission; but his figure does not show it. A, sulcata (XXVI. 8).--Oval, depressed, with 4 to 5 longitudinal furrows, and an oblique notch in front, from which the two filaments proceed; movement vacil- lating, circular, Perty has seen it divide longitudinally. 1-1300". The projecting filament is three times, and the floating one about twice as long as the body; in this, however, says Perty, there is no constancy. Genus PLCEOTIA (D.) (XXVI. 10, a, b).-Diaphanous, having several ribs or longitudinal ridges along the middle, and a circular translucent margin, giving the whole a navicular form; two locomotive filaments proceed from one end. This distinct form might be mistaken for one of the Bacillaria, were not the filaments clearly visible. The characters of the filaments are similar to those of Anisonema—one extending forwards with an undulatory movement, the other trailing and capable of suddenly arresting the movement of the body by its adhesion and power of retraction. PLCEOTIA vitrea (XXVI, 10a, b).-Hy- 1-130"; movement slow. In sea-water aline, with 3 to 4 longitudinal salient kept for two months. lines at the centre, and some granules. Genus OXYRRHIS (D.) (XXVI. 9 a, b). — Ovoid, oblong, obliquely notched in front, and prolonged into a point ; several flagelliform filaments proceed laterally from the bottom of the fissure, OF THI]. CRYPTOMON ADINA, 513 * The name is indicative of the elongated apex. These Infusoria being but imperfectly known, one species only is described:— OXYRRHIS marina (XXVI, 9 a, b.)—Colourless; Subcylindrical rugose, rounded posteriorly. 1-520". the Mediterranean. The next three genera are taken from Perty, the first being one of his Cryptomonadina, the others Thecamomadina:— Genus PHACOTUS (XIX. 7, a, b, c).-Body round, biconvex, with two (possibly four) filaments. PHACOTUS viridis. –Green, usually divided through the middle by a clear or a dark line. Margin acute; the central part more or less convex, sometimes elevated into a sharp angular ridge, ren- vidual. Medium size 1–1440". Among Confervae. Bern. It = Cryptomonas lenticularis (E.). Like Dujardin, Perty removes Chatotyphla and Chatoglena from the Peridiniaea to the Thecamo- dering the figure four-sided. The shell shows a double contour, and persists Some days after the death of the indi- Genus TRYPEMONAS– generally TRACHELOMONAS (Ehr.) (XIX. 9, 10, 11).-Shell globular or elliptic, with a small round aperture (the elevated margin of which frequently produces a funnel-like appearance), from which the filament protrudes; colour green, with a red stigma; lorica at first hyaline, then purplish, and lastly brown, thick and opake; not armed, but apparently porous from the presence of numerous puncta indicating the absence of deposit, as elsewhere. Perty justly objects to the term Trachelomonas, as prone to cause confusion of ideas from its etymology signifying beings with nadina. The former genus he retains, but merges the latter in his group Chonemonas. % necks, which none of those it includes possess. TRYPEMONAS volvocina (XIX. 9, 10) = Trachelomonas volvocina; and T. cylindrica (XIX, 11) = Trachelomonas cylindrica and T. nigricans (Ehr.). - Genus CHONEMONAS (XVIII. 35 a, b, c, d).—Green with a red stigma; testa hard, ellipsoidal, with a funnel-shaped opening at the anterior end—from which two filaments proceed. It represents in part the genera Chaetoglena, Pantotrichum, and Lagemella (E.). CHONEMONAS Schrankić (XVIII. 35 a, b, c, d), formerly named C. hispida- Lorica clear or dark brown, more or less spinous. Filaments double the length, and hyaline. Portions of the lorica ex- hibit apparent pores, and empty speci- mens often decussating lines. The green contents escape unhurt, on fracturing their enclosing case, which they gene- rally do not fill. When fission proceeds, the contents alter their form, and the filaments disappear. Onward movement not rapid, seldom oscillating, but actively revolving. 1-900" to 1-540". At Bern, in pools of snow-water, and beneath the ice. Two varieties occur:—a, glabra, with a Smooth lorica, which is no other than the Lagenella euchlora (E.); b. unftlis, with a single filament, equiva- lent to Chatoglena volvocina (E.). The very hispid examples of this Chonemonas are = Pantotrichum Lagenula, placed by Ehrenberg among his Cyclidima. C. acuminata. — Shell oval, strongly pointed posteriorly; bristles Scarcely ob- servable. Funnel at front distinct. 1-500". Hyaline and quite smooth speci- mens also occurred. ð. the St. Gothard. Genus DREPANOMONAS (Fresenius). DREPANOMONAS dentata.-Colourless; falciform, compressed; pointed at each end, with five outspreading furrows, of which two are on either fiat side, and one on the convex edge. In the centre of the concave surface is a ventricose swelling with a small tooth-like process; a similar process is remarked beneath the apex. From near the last, several lines extend upwards and outwards. In one aspect an undulating line is percep- tible º the convex margin; this is also visible in the loricae of dead speci- mens. Internally are only colourless granules, imparting a pearly hue. On one occasion a vacuole was seen having 2 L 514 SYSTEMIATIC IIISTORY OF THIE INFUSOIRIA, a reddish glimmer; possibly a contrac- than those on the posterior extremity; tile vesicle; movements slow; no con- but still seen with difficulty. In Swim- tractions of figure observed. Both ends | ming it lies on the flat surface; it also furnished with delicately motile fila- revolves on its long axis, 1-15" to 1-14". . ments, those on the anterior longer | In water from Walldorf. FAMILY IV.-VOLVOCINA. (See p. 144.) (XIX. 32–69; XX. 22–47). THIS family derives its name from the genus Volvoa, and from the rolling motion with which the beautiful creatures belonging to it make their way through the water. They resemble the Monads in most particulars relating to their organization; have an unvarying form, and, except a filament, no appendages; vacuoles present. Whilst propagation by self-division is pro- ceeding, and the young are increasing in size, the Surrounding envelope or lorica is observed to expand in a corresponding degree, but continues entire until its numerous occupants have come to maturity, when it bursts and sets them at liberty. All the genera are provided with organs of locomotion, which consist, as with the Monads and Cryptomonads, of a single or double very delicate fila- ment ; and hence it is that when they are clustered, the entire group appears to be ciliated, or beset with hairs. Besides granules, one or two round nuclei and a contractile sac are present. This family Ehrenberg disposed into ten genera—five furnished with a red stigma, situated at the anterior part of the body, and five without it. In the former, a sensitive system was presumed on the Supposition of the red speck being an eye. The following is an analysis of the family:- ſ ſ vibrating - filament absent Gyges. ſ Lorica box-like is Tail Lorica single { vibrating Pandorina # absent (filament present l’IIl8l. 3 3 * Clusters tabulated or in plates ...... Gonium. G) e à Lorica double ................................................ Syncrypta. \ Tail present ............. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Synura. / (Tail present .............................. Uroglena. Self-division both # equal and perfect filament single ... Eudorina. § (mo internal globes) || Tail absent ... #. 4 filament double ... Chlamydomonas. § Filament single ........................ Sphaerosira. Self-division unequal (forming internal \ globes) e e º 'º e s is º ºs e º 'º g g e Filament double ........................ Volvox. The above account, derived from Ehrenberg's work, affords a very imperfect conception of the Volvocina, especially of their structural characteristics as a family,–a defect we have endeavoured to supply in the chapter on their general history (p. 144). Moreover, as there noticed, these beings are numbered by the majority of naturalists, at the present day, among plants, although a respectable minority, among whom are Thuret and Lachmann, incline to the opinion that they are for the most part animals, as Ehrenberg represented. Thuret expressed this opinion now several years since, when the physiology of the simplest vegetable organisms was imperfectly under- OF THE WOLVOCINA, 515 stood, and supported it on the fact that an act of germination, similar to that seen among the spores of the lower Algae, was never witnessed among the Wolvocina. This absence of a supposed vegetable characteristic, more recent researches appear clearly to set aside as an argument against the vegetable nature of a doubtful organism; for in the whole cycle of life of many of the simplest, or so-called unicellular plants, an act of germination, as understood by Thuret, never occurs. Dujardin, when he published his work on Infusoria in 1841, admitted the Volvocina among animalcules, but proposed a different distribution of their genera to that put forward by Ehrenberg. Thus, he transferred Gyges and Chlamydomonas, owing to their not being aggregated within a common envelope, to the Thecamomadina, and united Eudorina with Pandorina (XIX. 59–69), and Synura with Uroglena, because he could not regard the presence or absence of a red speck to be a generic characteristic. Further, he considered Syncrypta a doubtful genus, and combined Sphaerosira with Pandorina. Although the present state of science proves that the appearance of a red Speck or specks in a monadiform being is mostly a transitory phenomenon, associated with a certain condition or phase of existence, and that therefore the union of Eudorina with Pandorina, and of Symura with Uroglena, is a correct proceeding, yet Dujardin erred both in detaching Gyges and Chlamy- domonas (XIX. 16) from the Volvocina, and in considering Sphaerosira and Pandorina modifications of a common form. The relation of Chlamydomonas to the Volvocina has been well shown by Cohn, Braun, and others; and Gyges itself might probably be dispensed with as a distinct genus, since there is good evidence to show that its species are simply stages of development of Chlamydococcus or Protococcus (XIX. 20–31), and of Chlamydomonas. Again, Sphaerosira, instead of being a varied phase of Pandorina, is a member of the genus Volvoa: ; indeed Prof. Busk inclines to the notion that it is merely a developmental stage of the common Volvoa, Globator (T. M. S. i. p. 39). Perty, however, advances as an argument for its independent nature, that it is com— mon about Bern, whilst Volvoa, Globator is not met with. This fact speaks at least for the specific independence of Sphaerosira, although its generic must be given up. Moreover, a genus Botryocystis was instituted by Kützing, of the independence of which, however, there is no good evidence. The con- dition of Protococcus pluvialis (Cohn, Ray Soc. 1853, p. 559), when divided into sixteen segments, corresponds to the Botryocystis Morwm. Further, the last- cited author in another treatise (Entwick. d. Mikroskop. Alg. und Pilze, p. 209) treats Botryocystis as synonymous with Pandorina, and in this agrees with Prof. Henfrey, who remarks (M. T. 1856, p. 51) that the form of Pandorina which produces the resting-spores, after losing its cilia, is Kützing’s Botryo- cystis Morwm. Perty coins two new genera, called Synaphia and Hirmidium (XIX. 15). Cohn points out a natural division of the Volvocina into two sections, in the first of which, represented by Chlamydomonas and Chlamy- dococcus, the fission of each primordial cell is complete, and the products single and unicellular, whilst in the second section, including all the rest of the Volvocina, the cells formed by the fission of the parent primordial cell con- tinue united in groups or clusters. The difference between the several genera obtains from the disposition of the produced cells; and this, again, depends on the direction of the line of fission. Thus, in Stephanosphaera (XIX. 38–52) the plane of fission is the meridian of the sphere ; in Gonium it occurs in two planes at right angles to each other, and in Volvoa and its allies in three planes. If the Volvocina are referable to the vegetable kingdom, they consti- tute a family of the order Palmellaceae (Chamaephyceae, K.), among the Algae. The separation of Syncrypta from Gyges, and its independent generic ex- - 2 L 2 516 SYSTEMLATIC IIISTORY OF TEIE INIMUSORTA. istence, are very questionable; for the possession of a double lorica, attributed to Syncrypta by Ehrenberg, cannot serve as a generic distinction from Gyges, with a single lorica, since Cohn has shown in Chlamydococcus that the pro- duction of a distinct, loosely investing, and apparently second covering, is one of the series of developmental phenomena in the selfsame being. The same statement is true of the so-called tail which is used to separate Synwra from other allied forms; for caudate beings make their appearance in the cycle of existence of non-caudate: thus a caudate variety of naked “Zoospore ” re- sembling a Bodo is represented by Cohn in his illustrations of the multiform phases of Protococcus. The presence of a mouth, and the construction of the envelope with one side or end open, through which the animal can protrude itself at will, are statements now generally ignored. After excluding the inadmissible and the very doubtful genera of this family of Ehrenberg, there remain only Pandorina, Gonium, Chlamydomo- mas, and Volvoaz. To these, other naturalists add Chlamydococcus (Braun), Gloeococcus (Braun), Stephanosphaera (Cohn), and Stephonoma (Werneck). Ehrenberg himself has added a new genus he names Trochogonium; but, from the imperfect description given, it is not possible to decide accurately whether it is distinct from some of the genera instituted by other naturalists. Genus GYGES.—Lorica of a simple box-like form (wrceolus); eye-speck and “tail’ absent; filament doubtfully present ; the internal organization is little known. Two species are mentioned by Ehrenberg, both of a green colour and enclosed in a transparent lorica. GYGES Granulum (Volvoa Granulum, M.). —Oval, or nearly globular; con- tained granules of a darkish green colour. Amongst Lemmae and Confervae. 1-1150". According to Cohn (on Protococcus, p. 559), the encysted motile zoospore (XIX.31) of Protococcus (Chlamydococcus) pluvialis is the same as this species Gyges Granulum; whilst the same zoospores di- vided into two must be regarded as the next species, Gyges bipartitus, G. bipartitus.--Crystalline, gelatinous, and nearly spherical; the superficies co- lourless, but its granular contents yel- lowish green; it is sometimes seen di- vided into two, at others as a simple sphere. Amongst Confervae. 1-480". G. sanguineus.—Oval, red, inclining to crimson, surrounded by a broad colour- less ring representing the enveloping lorica. ºri. species was discovered by Mr. Shuttleworth in the red snow which fell at the Grimsel in August 1839. Its motion is lively. Group 527 (XVII.) shows several highly magnified. Found with Astasia nivalis and Monas gliscens, among the globules of Protococcus nivalis (Ed. Phil. Journ. V., xxix.). 1-1200" to T-300". This is probably only the ‘still’ phase of Chlamydococcus pluvialis. M. Vogt gives a very singular account of the mode of reproduction of this being. He says, “It gives off from se– veral parts of its body small transparent buds, apparently vesicular, and for the most part filled with granular matter. As they enlarge they become gradually detached; sometimes two of equal size, of which one is red and loricated, the other colourless, adhere by a very narrow point of attachment, which subsequently gives way, and the bud appears as an Infusory animal, like what Mr. Shuttle- worth has represented in his 7th and 8th figures, and which approaches Pandorina hyalina (Ehr.).” This account of the reproduction of this species of Gyges is so peculiar and exceptional, that the questions arise whether it really is a member of this genus and family, and, if it be, whether the description is a correctinterpretation of the facts observed. M. Vogt adds that Gyges sanguineus ought not only to be looked upon as the type of a new genus, but even of a new family, on account of its very peculiar mode of reproduction. He further de- scribes a new species:– . . G. Vogti-Globular, containing in its interior from two to five individuals, enveloped by an apparently silicious lorica; colour dark red; frequently found adherent and arranged in the form of a cross, also often separate. “The small individuals, probably the young, were of a clear yellow hue. I could not ob- serve the slightest motion in them.” —On the Animalcules of the Red Snow, Bibliothèque Univ. de Genève, May 1841. OF TEIE WOLVOCINA. 517 Genus PANDORINA (XIX. 59–69) (Part I. p. 157).-Destitute of eye- speck and tail, but provided with a globular lorica and a slender filament. During self-division the creature acquires the appearance of a mulberry. Transparent vesicles occur in one species: two exhibit green, and a third colourless granules. Dujardin esteems the presence of the red speck to be insufficient to distin- guish Eudorina as a genus distinct from Pandorina ; and most recent observers agree with him. It has been shown by Braun (Rejuvenescence, Ray Soc. 1853, pp. 169—209), as well as by others, that Ehrenberg was in error in assigning a single fila- ment only to Pandorina, and no eye-speck—since two flabella extend from the more pointed extremity of the being, and close to their base is a brownish- red speck. Prof. Henfrey details (M. T. 1856, p.49) the characteristics of Pandorina much more fully, and corrects the errors into which Ehrenberg fell. He assumes it to be a plant, and thus describes it :—“ Pandorina.-Frond a mi- croscopic, ellipsoidal, gelatinous mass, containing, imbedded near the peri- phery, sixteen or more biciliated, permanently active gonidia, arranged in several circles perpendicular to the long axis of the frond. The gonidia, al- most globose, with a short beak-like process, a red spot, and a pair of cilia which project through the substance of the frond to form locomotive organs upon its surface. Reproduction: 1. By the conversion of each gonidium into a new frond within the parent mass. 2. By the conversion of the go- midia into encysted resting spores, which are set free, and (?) subsequently germinate to produce new fronds.” The genus more closely resembles Ste- phanosphaera than any other of the family. PANDoRINA Morum (Volvox. Morum, M.) (XIX. 59–69).-Body simple or mul- tipartite, enclosed within a simple lorica. Colour green; filament twice as long as the body. In water with Lemnae and Confervae. Size of individual 1-1150", cluster 1–120". Some individuals broken from the cluster by Ehrenberg have not been above one-third the former mea- surement. P. Morum is much more satisfactorily and correctly described by Mr. Henfrey, thus:– “Fronds hyaline, from about and then in 5 circles—2 at the poles, of 4, and the intermediate 3 of 8 gonidia; which, in the perfect form, stand near the º and wide apart. In the forms which produce the resting-spores, the gonidia are crowded together in the centre. The gonidia are green; but the contents of the resting-spores, after they have become encysted, are converted into oily and granular matter of a bright red colour.” P. hyalina-Form globular. In the Nile with Confervae, and is a doubtful 1-80" downwards. Gonidia either 16, species. 1-5760". and then arranged into circles of 4; or 32, Genus GONIUM (XIX. 32–37; Part I. p. 152).-Deficient both of eye- speck and tail; lorica simple; in the process of self-division, form regular four- cornered tablets or plates. The lorica (a lacerna) of each individual (as is seen after its separation) is nearly round; and the organism can cast it off and form it anew. In one of the species (G. Pectorale), two vibratory filaments are placed at the mouth as organs of locomotion, &c.; in the other species these have not been observed. Vacuoles are seen within G. Pectorale ; and a red speck (produced probably by refracted light) at the base of the filaments has been conceived by Ehrenberg to indicate the mouth. Cohn's elaborate account furnishes the following additional notes on Go- mium (Entwick. p. 179; and Part I. p. 152.):-The quadrate tablets consist of sixteen polygonal (mostly hexagonal) cells, united together by tubular prolon- gations from their angles, the whole being Surrounded by a common gelatinous 518 sysTEMATIC HISTORY OF THE INFUSORLA. investment (the envelope-cell). Each cell or gonidium has its own hyaline membrane, is somewhat elongated into a neck-like form on one side, and con- tains a homogeneous protoplasm, chlorophyll, and dark granules (except in the neck-like portion), and in the centre a single chlorophyll vesicle; besides these, several vesicular spaces, and One, two, or rarely three contractile vesicles. From the pointed end two filaments proceed, and pierce the common envelope, to vibrate freely on the outside of the tablet. Reproduction by fission is not a simultaneous act, as represented by Ehrenberg, but is effected by repeated divisions through four generations or series, in each of which the “daughter cells’ severally resolve themselves into two others, as happens in all the Wol- vocina and Palmelleae. The result of this act of reproduction, when uninterfered with and complete, is the formation of sixteen tablets similar to the parent, but without any organic connexion, each young tablet, however, being enclosed within the wall of the parent cell, out of which it has been produced, for this cell-wall takes no part in the process of fission. Sometimes a tablet breaks up, setting its component gonidia free, when, their angular processes becoming absorbed, and their membrane further removed from the contents, they as- Sume the general aspect of a Chlamydococcus or Chlamydomonas, and probably enter on a resting-stage like the gonidia of Stephanosphaera. Ehrenberg be- lieved the isolated cells to be reproduced by fission like those united in the tablets; but Cohn never observed this take place. If this resting-stage actually occurs, then Goniwm is propagated by ‘macrogonida'; but of ‘microgonidia’ no evidence has been discovered. The tablets revolve on their shorter axis, and hence, on a polar aspect, appear like a disk, on an equatorial like a line of cells. A peculiar structural relation obtains between Gonium and Pedias- trum. Lastly, Cohn asserts that Gonium Pectorale is the only true species of this genus; that the others enumerated by Ehrenberg are motionless, and belong to the genus Merismopedia among the Palmellaceae. GONIUM Pectorale (M.) (see p. 152). pencil will be required to see the whorls —Consists of sixteen spherical bodies and currents set in motion around it. enclosed within a transparent lorica, and disposed regularly in a quadrangular form, and in the same plane, like the jewels in the breast-plate of the Jewish High Priest, whence the specific name. The four central ones are generally larger than those which surround them; and the combined diameters of the three smaller balls are about equal to the two larger centre ones to which they are attached; the external corners are consequently vacant. As these animalcules swim and revolve in the water, they occasionally present a side view to the observer, when the circumference of the larger central globules may be seen projecting beyond the others. Sometimes the clusters ap- pear irregular. They are of a beautiful transparent green colour; and in Swim- ming, the globules often appear of an ellipsoidal figure. In order to observe the structure of this highly curious and beautiful crea- ture, considerable adroitness is necessary in the management of the microscope; while a little indigo conveyed into the water with the point of a camel's-hair The single animalcules (XIX. 33) swim like the Monads, in the direction of the longitudinal axis of their bodies; but the tablets have a variety of movements: Sometimes they move quite horizontally, at others vertically, at others again on their edge, revolving like a wheel. A magnifying power of 200 diameters is sufficient for general examination; but to exhibit all the structures shown in the engravings, four times that power will be required. In clear water, salt and fresh, near the surface. Discovered by Müller in clear water at Copenha- gen, 1773. Size of animalcule from 1–460" to 1-1150", of tablet not exceed- ing 1-280". - G. punctatum. – Corpuscles green, spotted with black, and enclosed within a crystalline lorica. Amongst Confervae. 1–4600"; a tablet of 16, 1-570" in breadth. G., tranquillum. — Corpuscles green, within a crystalline lorica, each 1-2880"; a tablet of 16 corpuscles, from 1-140" to 1-220" in breadth. Tablet sometimes twice as broad as long. G. hyalinum.-Corpuscles transparent, OF THE WOLVOCIN.A. 519 within a crystalline envelope. In stag- nant water. Corpuscles 1-3000"; tablet of 20 to 25, 1-600" in breadth. G. glaucum. — Corpuscles bluish- green, within a crystalline envelope. The number of animalculos in the tablets varios from four to sixty-four. In sea- water. Size 1-5000"; tablet 1–500" in diameter. Gonium tranquillum and G. glaucum, says Perty, are Algae (i. e. he would Say, are not members of this genus). G. helveticum. —The green, spherical corpuscles combined in a tabular, gela- tinous envelope, without any intercom- municating bands, each furnished with a fine red stigma and two ciliary loco- motive filaments. On a polar view, one large round vesicle is visible; on the lateral aspect, two such are apparent, one larger than the other. On drying IHe adds as a new species, the specimen, the stigma itself assumes the form of a vesicle. It is readily dis- tinguished from G. guadrangulatum by the absence of the connecting bands or tubules between the several corpuscles in the tablet. Diameter of tablet T-360", of corpuscles 1-1300". Filaments 24 times longer than the gonidia. In ponds about Bern, Genus SYNCRYPTA (XX. 26–28).-This genus is mainly characterized by secreting or hiding itself (as the name implies) within a second envelope. Each individual is provided with a special lorica of the form of a little shield (scwtellum), and is united with others in a common gelatinous envelope (la- cerma) into which it can retreat ; neither eye-speck nor tail is present, but there is a large filament; self-division longitudinal. The filaments of the several corpuscles give the cluster an appearance of being Surrounded with hairs. With this genus Dujardin would identify his Cryptomonas (Tetrabaena). The very doubtful position and independence of this genus as a member of the Volvocina have been remarked on in the general notes. On this family (p. 144). Mr. Carter, in a paper lately published (A. N. H., 1859, iii. p. 1 et seq.), represents Syncrypta to be the “spermatic form * of Volvoa or of Sphae- rosira (Ehr.). (See notes on SPHEROSIRA.) SYNCRYPTA volvoz (xx. , 26–28). — Form oval; colour green, with whitish rays in the centre. Generally in water drained from Confervae. 1-2880"; a clus- tered globule in its crystalline tunic, hardly exceeding 1-570". Fresenius states that he has seen a red stigma in each corpuscle, which was overlooked by This berry-like cluster of animalcules, when rolling through the water, is a beautiful object for the microscope; and with the . of a little indigo, the nu- merous currents it creates are readily perceived: XX. 27. magnified 260 dia- meters; fig. 26.400; and fig. 28 a cluster about to sever into four. Ehrenberg. Genus SYNURA (XX. 29, 30).-Eye-speck absent; tail filiform, attached either to the base of its own lorica or to the centre of the cluster to which it belongs. The general envelope is spherical, gelatinous, and is hollowed out by as many compartments or cells as there are individuals in the little com- munity. From out of these colls they can stretch themselves a considerable distance, whilst they continue attached by the extremely delicate and exten- sible tail. This so-called tail or pedicle is homologous with the connecting rays or threads of the several corpuscles in the globe of Volvoay, and is, like them, a production of the protoplasm of the interior. As before remarked, this genus is doubtfully retained; for the chief distinctive feature Ehrenberg insists on, viz. the presence of a double lorica, loses its significance now that modern researches have shown that the formation of a second or common en- velope is an ordinary phenomenon at a certain stage of existence of most or of all Wolvocina. Morcover, the description given of this genus is too loose and faulty, and its accompanying illustrations too rude, to rendor it possible SYSTEMATIC HISTORY OF TITE INFUSORIA. to rightly appreciate its characters and to assign it its proper place, even if it is admitted to be an independent organism. Mr. Carter has lately pub- lished (A. N. H. 1859, iii. p. 10) the opinion that Synura is the “spermatic form * of Volvoa or of Sphaerosira. (See notes on SPHAEROSIRA). SYNURA uvella.-Corpuscles oblong, yellow, capable of extending themselves to three times their usual length, by a cluster, and the manner in which the tails are inserted in the common enve- lope. This species, along with Syncrypta and Uroglena Volvoa, may have often been confounded with Uvella virescens. means of the extensile tail. The cluster has the form of a mulberry, and its mo- tion is rolling like that of Volvoz Globa- | Length, exclusive of tail, 1-700"; dia- tor. xx. 29, xx. 30, show a portion of meter of cluster from I-190" to 1-280". Genus UROGLENA (XX. 31).-The members of this genus, unlike other Volvocina, possess both an eye-speck and tail; they live in clusters under a common envelope (lacerma), which is subdivided into cells for the accommo- dation of the several individuals. Self-division takes place simply and equally in these individuals, whilst in their clustering condition. They are placed at uniform distances from each other, attached by their tails, which radiate from the centre. Each monad is furnished with a filament, which projects ex- ternally and gives to the entire group the appearance of being covered with hairs. When the creatures divide, the mantle or lacerna enlarges only, and does not itself undergo fission. The red speck is in the fore part of the body; the tail is filiform, resembling that of Vorticella and Bodo. The tail mentioned in the above description is the same as that of Synura: the use of the term is very inappropriate in both cases. It may be that Uroglena should be united with Symura as Dujardin proposed, since the presence of an eye-speck in the former and its absence in the latter is not distinctive; still wo know too little of the being which Ehrenberg would call a Uroglena, to come to a decision respecting its affinities and generic independence. This genus is another which Mr. Carter would set aside, as he considers it (A. N. H. 1859, iii. p. 10) the same with Sphaerosira, or the “spermatic form * of Volvoa. (See notes on SPHLEROSIRA.) DROGLENA Volvoz (xx, 31). —Cor- family. Ehrenberg states that he has puscles yellow, oblong; tail extensible, observed individuals with two or three from three to six times the length of the coloured specks, which he conceives to body, and even more; cluster mulberry- have been a symptom of approaching shaped. There is little doubt that single | Self-division. In turf water. "I)iam, of corpuscles of this genus have often cluster 1-90". been taken for creatures of a different Genus EUIDORINA.—Has no tail, but possesses a distinct eye-speck, and a simple vibratory filament anteriorly. Self-division proceeds simply and equally, whilst the corpuscles retain their clustered condition. They are periodically able to cast off their globular envelope (lacerna), and to exude a new one, like certain Annelida. To observe the eye-speck, a power of 300 diameters must be skilfully employed. Dujardin’s proposition to combine Eudorina with Pandorina has been already mentioned (p. 515), and appears to be a correct one. The assigned characteristic difference between those two genera is worthless; for Pandorina, like Eudorina, has a coloured speck (see p. 157 et seq.). EUDORINA elegans.—Corpuscles green, globular, never protruding from their cells beyond the common envelope. Stigma sparkling red. The clusters, which are of an oval or globular form, contain generally from 30 to 50 individuals, and never less than 15. Motion revolving. Fig. 47 exhibits the filaments extended, and the bodies of the animalcules within the lacerna (i. e. the “common enve- OF THIE VOLVOCINA. 521 lope”). Clusters of these beautiful ani- malcules are often seen in such amazing numbers, along with the Volvoz Globator and Chlamydomonas Pulvisculus, as to render the water (otherwise colourless) of a decided green colour, especially towards its edges. They are exceed- ingly delicate—so much so that it is difficult to preserve them alive for more than a day or two : whenever it is at- tempted to retain them in large quanti- ties, the second day will º 6×- hibit a thick mass of dead ones at the bottom of the vessel. When a few only remain alive, if the stale water be poured away, and they are removed into a vessel of clear water, they will live for weeks. At Hackney and Hamp- stead; most abundant in the spring of the year. Diam, of cluster 1-180". Genus CHLAMYDOMONAS (XVIII. 40, 51–54; XIX. 16) (Part I. p. 146).--Tail absent, eye-speck distinct red, filament double; multiplication takes place by self-division within the common envelope, which is ruptured to give the products liberty. The lorica indistinct in young beings. Braun (On Rejuvenescence, Ray Soc. 1853, p. 158) appears to elevate this genus, in union with Chlamydococcus and Gloeococcus, to the rank of a family parallel with the Volvocina, under the name of Chlamydomonada. Indeed, although, as Cohn has well shown, these genera agree in all essential particu- lars and relations with the Wolvocina, yet the existence of each gonidium as an independent being contrasts so strongly with the aggregate condition of the rest of the Volvocina, that there seems sufficient ground to group them as a sub-family. In order, therefore, to retain the Chlamydomonada toge– ther, we shall depart from our usual custom, by inserting the new genera Chlamydococcus and Gloeococcus after Chlamydomonas. Chlamydomonas was erroneously transferred, as before noticed, by Dujardin to the Thecamonadina, and renamed Diselmis. Its characters are thus discussed by Braun (op. cit. pp. 214, 215):-‘‘ Chlamydomonas is distinguished from the genus Chlamydo- coccus by the closely applied membrane of the old Swarming-cells, also by the absence of the little starch-vesicles in the interior, while, however, as is usual in most of the Palmellaceae, a single large chlorophyll utricle exists in the interior. There is no central red nucleus, as in the gonidia of Chlamy- dococcus; but some species have a parietal red spot. Motion is effected by two cilia, as in Chlamydococcus. As in that genus, there is a growth of the gonidia during swarming, which lasts over the day and night. There is also a formation of microgonidia,” and a resting-stage in which the colour changes from green to yellowish red, or to red. CHLAMYDOMIONAS Pulvisculus (Monas Pulvisculus, M.)(XIX.16).-Colour green; lorica oval; eye-speck brilliant red; fila- ment double. (See Diselmis viridis, p.512.) Cohn identifies it with Polytoma Uvella. These creatures form a large portion of the green matter which colours the water contained in water-butts, ponds and puddles in the summer and autumn, and especially after a storm. . They will rarely fail to be observed when any of this green water is examined under the microscope. Whenever these creatures exist in large quantities, multitudes of them and of their envelopes rise to the surface of the water, and form a green stratum upon it. Although this film Somewhat resembles one of ifivaceae, yet it is easily distinguishable by its com- position of living corpuscles with red Specks, connected together by a loose mucous tissue, formed of dead speci- mens and empty lorica. 1-550". Rützing affirmed that this species was merely a phase of Stygeoclinium, into the filaments of which it became transformed by an act of germination. This opinion has not been accepted, as it is supposed that Kützing confounded the spores of that Alga with the gonidia of Chlamydomonas Pulvisculus. Among the additional species of Chlamydomonas, those forms described by Dujardin as members of Diselmis (p. 512) should probably take their place 522 SYSTEMIATIC IIISTORY OF TEIE INFUSORIA. here. Braun describes the following new species, premising the remark that “ the species are doubtless very numerous, but the distinction of them from one another, as well as from the swarming cells of many other Algæ, is very difficult without a complete acquaintance with the history of their existence.” C. obtusa (Braun).-Colour dark green; truncate at both ends, and oblong, chang- ing to spherical and a yellowish brown, and at length a red colour on assuming the resting-stage. “The macrogonidia grow during swarming, from 1–60th to almost 1-30th of a millimetre long; they are longish, of equal diameter on both sides, and very obtuse, almost truncated, having a colourless space at the ciliated extremity, presenting the form of a notch. The contents are dark green, finely granular, with a large vesicle at the pos- terior extremity, a roundish lighter space in front of this, and no red point. They multiply by simple, or double halving in several successive genera- tions. Sometimes a further continua- tion of the division of the full-grown macrogonidia occurs, forming 16 or 32 macrogonidia from 1-200th to 1-120th millimëtre long, of ovate shape and lighter colour, tending towards brownish- yellow. The resting (seed-) cells are globular, about 1-40th millimètre in dia- meter, at first green, subsequently light yellowish-brown, finally flesh-red; they have a tough, colourless, and transpa- rent membrane. In the Rhine valley, near Freiburg, in pools in Sand-pits, which are occasionally almost completely dried up in summer.” C. tingens (Braun).-Gonidia Smaller than in the preceding species, 1-120 to 1–60 millim. long, ovate, lighter green, likewise destitute of a red spot; the membrane is more distinct in old age. Increase by double, rarely by single halving; in the former case, by decussat- ing sections. Contents granular, punctate in appearance, green, with one large vesicle. In the resting-stage they ac- quire a pale reddish colour; the vesicle becomes indistinct, and the contents coarsely granular in aspect from the formation of oil. Microgonidia also are formed. “The resting- but still green condition seemed to me to correspond to Protococcus Felisi (K.), that which turned red through desiccation, to Pr. Orsini.” In pools near Freiburg. Cohn (Entwick. pp. 202, 203) detected two vesicles in Chlamydomonas, below the point of insertion of the filaments, very slowly but rhythmically contractile, and mentions a species under the name of Chlamydomonas hyalina, which he makes synonymous with Polytoma Uvella (E.), and states to differ from Ch. Pulvisculus only by the want of chlorophyll and of a red speck (op. cit. pp. 140 & 169). He moreover notes a new form, probably generically distinct by having not a globular but a winged prismatic figure, quadrangular on a transverse section, with the two wings like two outstretched points, although in other respects agree- ing with Chlamydomonas Pulvisculus. Perty (p. 85) objects to making Chla- ºmydomonas a genus of Volvocina, and refers it instead to the so-called “Spo- rozoidia.” He further tells us that Chl. Pulvisculus (E.) is rare about Bern, but there is a smaller form very common, which he proposes to call C. communis (Perty).-He finds also, but less frequently, a more globular variety, which appears to be the Tra- chelomonas emarginata (Eichwald), but is in, fact a Chlamydomonas, which he Il{LITOleS C. globulosa (Perty). — His species Elysginum pluviale and H. nivale (i. e. Chlamydococcºs) he suggests uniting, with the species of Chlamydomonas, into a group (of Sporozoidia) under the name of Schizomema. C. multfilis (Fresenius).-Round or oval; a distinct nucleus in the centre; granular contents green; filaments four, longer than the cell; at their base a rose- coloured contractile vesicle, and posto- riorly to this a red stigma. Lorica thin, closely investing contents. As many as six filaments seen in some larger speci- mens. 1-92" to 1-63". In fresh water. C. hyalina (Cohn, Fresenius).-Elon- #. elliptical; rounded at both ends; ilaments two, longer than the body; posterior half of cavity occupied by gra- nules; a clear non-contractile space in the centre; a Small contractile sac at the base of the filaments, 1–66" to 1-46". In * coloured by Euglenae. t is doubtfully separable from Chl. Pulvåsculus. Genus CHLAMYDOCOCCUS (Part I, p. 148) (XIX, 20–31)—Gonidia OF TELE WOLWOCINA. 523 spherical; colour green or red, enclosed by a hyaline structureless mem- brane, removed some distance from the coloured contents by a clear interspace or areola. The central protoplasm, coloured by chlorophyll or a red oil, and having one or more chlorophyll utricles at the centre, has its spherical figure destroyed by an elongation at one part into a tapering process, from which two filaments proceed, and, after perforating the external “envelope cell,” protrude as motile vibratile organs. The inner, coloured globule has no special membrane, and in consequence undergoes multiform transformations of its outline in the course of development. In the resting-stage the enclosed coloured mass, the “primordial cell,” secretes over its surface, inside its enve- lope cell, a new, tough, cellulose membrane, whilst the envelope cellis dissolved into a mucous layer. In such still cells macrogonidia are produced by fission of the contents, in the power of two, and after a time burst through the parent cell, develope their two ciliary filaments, and proceed to develope a cellulose mem– brane over their entire surface, which becomes further and further removed until they acquire the characters of the ordinary moving cells. When divi- sion is more frequently repeated, microgonidia are formed, which move much more actively, and do not secrete an envelope cell; they are incapable of propagation, and passimmediately into the condition of rest. The motionless cells of Chlamydococcus are of much simpler structure than the motile, and consist simply of a tough, Spherical, cellulose membrane, and green or red contents, organized as a primordial utricle. Vacuoles are found among the contents of Chlamydococcus-cells; but a contractile vesicle has escaped observ- ation. Chlamydococcus and the two allied genera, Gloeococcus and Chlamydo- monas, differ from the true Volvocineae in this respect: viz. they separate from each other after complete fission, as primordial utricles, and then severally pro- ceed to form an independent envelope cell; whilst the rest of the Volvocineae continue, on their production by fission, to live in groups and produce around their aggregated mass an envelope cell in common. It bears the same rela- tion, therefore, to the rest of the Wolvocineae that Plewrococcus does to Palmella, Cyclotella to Meloseira, or Vorticella to Epistylis. Chlamydococcus is distin- guished from the moving germs (sporozoids) by which the greater number of Algæ propagate, both by a somewhat more complex structure, and by the circumstance that the motion lasts for a very long time, and, finally, by the power of the moving cells to propagate as such, without entering into the state of rest otherwise than as quite a temporary condition. Perty, who has studied this genus very minutely, employs the term Hysginum to designate it, although it had previously received other names from other observers, besides that we have employed. Indeed, owing to the various appellations given, and especially the specific names invented for the multiform varieties of the same organism, the synonyms became very perplexing and a positive impediment to the progress of our knowledge of this genus. Among the multitude of proposed species, two only are now accepted, viz. Chlamydococcus pluvialis and Chl. nivalis; but their distinctive characters are nowhere detailed in a definite and available form for our purpose. The red snow of Alpine regions is the red variety of both these species. The other varieties of Chlamydococcus have been more widely described under the title of Proto- coccus, and those of a red colour under that of Haematococcus. Cohn cites two principal synonyms for Chl. pluvialis, viz. Haematococcus pluvialis and Chlamydococcus versatilis, and in his Monograph on this organism employs the term Protococcus plwvialis, although in a subsequent contribution he adopts Braun's designation as employed by us. The many modifications of form of this one species under different circumstances of development and habitat have received as many different names, from the motion of their 524 SYSTEMATIC EIISTORY OF THE INFUSORIA. being specifically distinct. These Cohn has pointed out in his essay; but only that portion of them is worth citing which has attracted notice in various works. “Thus the still Protococcus-cell corresponds to the P. Coccoma (Kütz.): when the border becomes gelatinous, it resembles P. pulcher, and the small cells P. minor. The encysted motile zoospore, on the other hand, is the Gyges Granulum, and resembles also P. turgidus (K.) and perhaps P. versatilis (Braun). The zoospores divided into two must be regarded as a form of Gyges bipartitus, or of P. dimidiatus.” A red variety of the cell was de- scribed by Girod Chantrans as a Volvoas, under the name of Volvoa lacustris; but Perty refers it to Haematococcus. CHLAMYDococcus pluvialis.-Sufficiently characterized in the above history. CHL. nivalis.-Unsatisfactorily distinguished. Genus GLOEOCOCCUS.—This is a new genus suggested by Braun (On Rejuvenescence, p. 159), who thus describes it:-‘‘ Ovate, green cells, with a colourless point, from which a funnel-shaped, lighter space extends inwards; a rather large vesicle also is formed at the posterior extremity. Multiplica- tion by simple or double, in the latter case decussating fission, after which the cells remain loosely connected together by the secretion of soft, gela- tinous, confluent coats, forming globular and finally amorphous families (clusters). The cells of all the generations succeeding each other during the formation of these families (excepting the transitory cells in the case of double halving) are provided with two very long persistent cilia, which dis- appear only when division commences. The cells exhibit a feeble motion inside the enveloping and connecting jelly, the anterior end jerking in and out, or suddenly retracting a little. The last generation of the family leave the gelatinous mass, and Swarm out, to settle down quickly in some other place. It is probable that the formation of a new family is preceded by a rather long state of rest—perhaps there are several resting generations; but we have no observation on this point.” A red speck is not perceptible. Two species are named:— GLOEococcus mucosus. – The full- grown cells are 1-60 to 1-50 millim. long: the clusters, forming at the bottom of little ponds, attain the size of an apple, and are of compressed globular, often lobed-shaped form; but at length they break up, and come to the surface of the water in irregular fragments. The gelatinous mass has a peculiar greenish spotted aspect, which depends upon sub- ordinate groups of generations being more closely packed together. G. minor. — Perhaps specifically di- stinct. Appears in the springs at Frei- burg early in the year, in the form of light-yellowish-green, often pear-shaped “stocks” (masses), almost as large as a hazel nut, attached to the sides of the utters of the springs, finally becoming etached, swimming, and shapeless. The cells are somewhat small, 1-100 to 1-75 millim. long. Genus SPHAEROSIRA.—Tail-like process absent; eye-speck and fila- ment single. Self-division, unlike that in the preceding genera, occurs un- equally within the envelope, and forms young clusters at once from the parent OlléS. This genus differs from Pandorina in having the eye-speck, from Eudorina by its unequal mode of self-division, and from Volvoa by its simple filament. Self-division in these creatures takes place in the longi- tudinal direction, in parallel planes; so that laminae are produced, as in the case of Gonium. Sphaerosira, as heretofore remarked, is regarded by Prof. Busk as a doubtful independent organism; he is, however, unable to speak positively on this point, and therefore, whilst still keeping it distinct from Volvoa, Globator, of OF TEIE WOTVOCINA. 525 which he had some reason to suppose it a peculiar mode of development, ranks it as only a species of Volvoas, instead of elevating it to the rank of a genus, and calls it Volvoa, Sphaerosira. Dujardin also denied the distinction drawn by Ehrenberg between Sphaerosira and Volvoas, but did so from mis- taken views; for he represented Volvoa to have only a single filament, whereas both this and Sphaerosira have two. “It presents the appearance,” says Mr. Busk (M. T. 1852, p. 33), “of a transparent globe, set with green spots, but it differs from the ordinary varieties of Volvoa, Globator in two important respects: 1, in the absence of any internal globules or embryos ; 2, in the irregular size of the green granules lining the wall which, instead of being of uniform size, are of various dimensions. The different-sized granules are irregularly disposed, although, in relation to the sphere itself, they, or rather the centres of them, are as regularly distributed as in the three just-described forms (of Volvoa). What is rather remarkable with respect to this form is the circumstance that the larger granules are not disposed over the whole periphery of the sphere, rarely occupying more than two-thirds of it towards one side.” Again, he adds—“The Smaller ones appear to resemble in all respects those of Volvoa, Globator, and each to possess two cilia, which is im– portant, if true, because the only distinction between Volvoa and Sphaerosira in Ehrenberg's classification depends upon the circumstance that in Sphae- Tosira there is only one cilium to each zoospore, whilst there are two in Volvoaz. “My supposition that S. Volvoa and V. Globator are allied is founded, it must be owned, not upon any direct observation, but chiefly on the fact that in the water in which the specimens of Volvoa were contained there were at first none of Sphaerosira, any more than of V. aureus, and that after some days both were very numerous. The difference I am about to describe in the after-development of the ciliated Zoospores is not by any means a sufficient ground upon which they should be deemed distinct species, because much greater differences are known to exist in other of the lower Algae during their various forms of development, without it being thence allowable to suppose that they are of different species. In Volvoa, Sphaerosira, then, as at all events it may be termed, the larger green granules are in fact the ciliated zoospores in a state of further progressive development. In the same specimen they will be seen in all states of division or segmentation,-first into two, then into four, and so on, till, as in the case of the embryo Volvoas, the ultimate result of the segmentation constitutes numerous minute ciliated cells or bodies, not, how- ever, as in that case, lining the inner surface of the wall of a spherical case, but forming by their aggregation a discoid body in which the separate fusi- form cells are connected together at One end, and at the other are free, and furnished each with a single cilium. In this stage their compound masses become free and Swim about in the water, constituting, in fact, a species of the genus Uvella, or of Syncrypta of Ehrenberg.” Mr. Carter affirms (A. N. H. 1859, iii. p. 4) that Sphaerosira is not a distinct genus, but the “spermatic form * of Volvoa, Globator, which he describes as one phase of development of this species, wherein upwards of a hundred of the gonidia, scattered over the periphery of the primary gemmae of the parent. globe, divide repeatedly until they are broken up “into 128 (?) linear ciliated segments, which are ultimately arranged vertically upon the same plane, in a circular tabular group, with their cilia upwards; and when the latter are sufficiently developed, the group oscillates and rotates by their aid both upon its long and short axis. These segments are, in fact, the spermatozoids, each of which, when they separate, is observed to be linear, horn-shaped, and colourless anteriorly (where it is attenuated), and greenish posteriorly, 526 SYSTEMIATIC EIISTORY OF THIE INFUSORIA. provided with a pair of cilia which are attached to the anterior extremity, and some distance behind them with an eye-spot ; their progression is vermicular from their extreme plasticity, and they keep up an incessant flagellating movement with their cilia. As yet, I have never seen any of these free in the daughter bearing the spermatic cells when the former has been outside the parent ; nor have I ever seen them free under any cir- cumstances, except once, in the old Volvoaſ, when the daughter containing the spermatic cells from which they had been developed had been partly eaten up by Rotatoria. - “This is the form of Volvoa, Globator which has been called Sphaerosira Volvoa by Ehrenberg; and, like the daughters bearing the spore-cells, it becomes liberated from the parent before the spermatic cells attain their ultimate development, that is, before the groups of Spermatozoids become separated, not before they are formed. It is worthy of remark, too, that the daughter bearing spermatic cells is never more than half the size of the spore- bearing daughter, at least as far as my observations extend. - “Thus we have the spore-cells and the spermatic cells in different daughters; and as I have never seen them together in the same daughter, nor the daughters respectively bearing them in the same parent Volvoas, out of Some scores of instances, I can come to no other conclusion than that the two daughters meet after they have left their respective parents, when, both the spores and the spermatozoids having become ripe for fecundation, individuals forming the groups of the latter separate, burst from their capsules into the cavity of the daughter, and from thence find their way out into the water, and then into the cavity of the daughter bearing the spore-cells, where they become incorporated with the latter. “Hence Volvoa, Globator would appear to be dioecious, and not monoecious as stated by Cohn ; and Sphaerosira Volvoa not, strictly speaking, another form of Volvoa, Globator, but the spermatic form. Cohn, considering Volvoa, Globator and Volvoa stellatus the same species, has taken his fecundating character from the spermatic form of the latter.” The spermatic groups above described, Carter Subsequently remarks, con- stitute in all probability Ehrenberg’s genera Syncrypta, Symura, and Uro- gléna. SPHEROSIRA Volvox. — Corpuscles compressed clusters within it. Found in pale green, of nearly a globular shape, considerable numbers in company with enveloped in a common mantle. Eye | Volvoa Globator, and often attains its bright red. The cluster resembles a size. Sometimes found by itself. great ball of corpuscles, containing Small Genus WOLVOX (XX. 32–47) (Part I. p. 180).-The genus Volvoas, which is the type of the family Volvocina, was instituted by Linnaeus, and promul- gated to the world in 1758, in the tenth edition of his ‘Systema Naturae.” As . first described by him, the two species V. Globator and V. Chaos comprehended all known Infusoria, excepting eleven of the tribe Vorticella, which were separated from them, under the denomination of Hydra. In his twelfth edi- tion (1766) of the same work, he distributed the Infusoria into four genera, viz. Vorticella, Volvoa, Hydra, and Chaos. Volvoa is characterized by the aggregation of its cells or gonidia over the internal surface of a transparent lorica or common envelope cell, of the form of a hollow globe. Each corpuscle or gonidium possesses a red speck and two filaments, which protrude beyond the surface of the lorica. So as to give the whole globe the appearance of being covered with cilia. The mode of increasing by a sort of internal gemmation is characteristic of the genus. * OF TEIE WOLVOCTNA. 527 Dujardin was unable to detect more than one filament; but Ehrenberg’s description of two is now amply corroborated. The structure of Volvoa has received the careful study of many eminent microscopists, who have been compelled to differ largely from Ehrenberg in their accounts of it. The résumé given in the general history of Phytozoa renders it perfectly unnecessary to repeat in this place the particulars of the organization of the members of this genus or to enter into the discussion respecting their true natüre as organic beings. Volvox Globator (M.) (xx. 32–47) (p. 180 et seq.). —So called from the globular figure of the aggregate mass or colony constituted by the individual monadiform beings or gonidia. When blue or red colouring matter is mixed with the water, strong currents may be observed under the microscope around each globe, which, when in motion, always proceeds with the same part foremost. XX. 32 represents a large globe with eight Smaller ones (termed by Ehrenberg, sisters) within it. xx. 34 is a section of a globe, more magnified. XX, 35 represents three gonidia in Situ within the common envelope. In shallow pools of clear water, in spring and summer. The largest globes mea- sure 1–30" in diameter ; the smallest free swimming ones 1-360" to 1-240". Size of a single corpuscle 1-3500". Ehrenberg notified the peculiar occur- rence of living Rotatoria within the globes of the Volvoa Globator. Mr. John Williams has communicated (T. M. S. 1851, iii.) an interesting observation, confirming Ehrenberg's account. Within the cavity of a large specimen of this species, evidencing its usual vitality, and the ciliary movements on its surface, he noticed a very active Rotifer, which he believes to have been the Notommata parasitica, and which was subsequently accompanied by another of the same species, but smaller. He adds, “By the most careful examina- tion, no opening could be perceived by which they could have been introduced; neither did there appear to have been any viscera by which their motions might be impeded, as they swam about as freely as fish in a glass globe, to which, indeed, they bore no faint resem- blance.” The two following species, named V. aureus and V. Stellatus, are, in the opinion of Profs. Busk, Williamson, and Perty, merely developmental phases of V. Glo- bator—V. Stellatus being the later stage. “V. aureus” says the writer first named (op.cit. p.32), “exhibits precisely the same structure as V. Globator, the only appa- rent difference between them consisting in the deeper green colour of the internal globes. These, however, soon exhibit a more important distinctive character, in the formation of a distinct cell-well of considerable thickness around the dark- green globular mass. This wall becomes more and more distinct; and after a time the contents change from darkgreen into a deep orange-yellow, and simultaneously with this change of colour the wall of the globule acquires increased thickness, and appears double. “The third form, or V. stellatus, differs in no respect from the two former, except in the form of the internal globules, which exhibit a stellate aspect, caused by the projection on their surface of numerous conical eminences formed of the hyaline substance of the outer wall. The deep colour of the contents of their embryos, and their change into an orange colour, at once point out their close analogy with those of V. aureus. I have no doubt of their being mere modifica- tions of the latter, and I have observed smooth and stellate globules in the in- terior of one and the same parent globe.” Mr. Carter, however, does not share this opinion with reference to V. Stellatus, which he treats (A. W. H. 1859, iii. p. 5) as a distinct species. - These extracts from recent and well- known authorities are further valuable as supplying an explanation of Laurent's statements that two sorts of reproduc- tive bodies appear in the globes of Vol- vow. Little weight is attached to this gentleman's microscopical researches, which are mostly ideal. - V. aureus. – Green, nearly globular. The Small secondary globes within them are of a golden colour, and smooth sur- face. In rain-water standing on turf. Diam. of globe 1–30". V. Stellatus.--Small, subglobose, somé- times oblong, or of an angular form, and green colour. The contained globes within them are of a green colour, and have their surfaces tuberculated or stel- lated. Diam, of globe 1-30". Carter, who accepts this species, de- 528 SYSTEMATIC HISTORY OF THE INFUSORIA. scribes it in the following words, using the quaint terms “daughters” and “grand-daughters” for the “primary" and “secondary” generations or gemmae of the parent globe of the Volvoz :— “Adult form.—Globular, slightly ovoid, consisting of three generations or families within one another; containing generally eight daughters, in each of which there are generally eight grand-daughters in- distinctly visible. Daughters confined to the posterior three-fourths of the sphe- roid, the anterior fourth being empty. Progressing with the empty end for- wards. Daughters rotating (this marks the adult form here also) in their cap- sules respectively, which are fixed to the internal periphery of the parent. Grand- daughters Small and indistinct, motion- less, and fixed to the internal periphery of the daughters respectively. Peripheral cells conical and biciliated, not uniciliated as figured by Ehrenberg. 59-1880" long and 54-1880" broad.” In his subsequent remarks, he makes it the specific point of difference between the primary gemmae of this W. Stellatus and V. Globator, that those of the former begin to undergo duplicative subdivision almost immediately after they appear, or “at the time when they do not exceed three times the diameter of the peri- pheral cells,” or 1–2700", instead of “not passing (as in V. Globator) into Small cells until they have arrived at more than the 1–300" in diameter.” He also alludes to differences between these two species in the form of the spermatozoids and the mode of fecundation. We ven- ture to remark that if these latter par- ticulars are sufficient to indicate specific differences, it is not so with the size of vegetable cells at , which fission may commence. The history of all the sim- plest cellular organisms we know of shows that the period of cell-life, and therefore the dimensions of the cells at which it occurs, stands in no constant relation with the act of fission. The size of a cell and the proclivity to fission depend much on external conditions affecting its vital activity. The following genera are distinguished by Perty:- Genus SYNAPHIA (Perty).-Corpuscles from 10 to 12, aggregated together within a spherical gelatinous envelope, in mutual contact, so as to form a compact mass. The corpuscles, each furnished with a single filament, are not spherical but angular and wedge- or pear-shaped, with the wide end turned towards the pheriphery. In very exceptional specimens the gonidia are somewhat separated from each other. Length of filament equal to, or 1, the diameter of the corpuscle, and very fine. The relation between Gonium and Pediastrum has been noted by Cohn and other observers; but that between this newly-constituted genus of Perty and the second-named group is much more striking, whether the description given or the illustrative figures be considered; indeed the impression forces itself upon us, that Synaphia is simply a form of Pediastrum. This impression is moreover strengthened by the fact mentioned by Perty, that the movement of the organism, and the fine filament, disappear as the organism advances in age and dimensions. SYNAPHIA Dujardini; (Perty).-Cor- puscles clear green to dark or blackish green, measuring within the enclosing envelope 1-1300" to 1-360", more com- monly from 1–720" to 1-480". Move- ments torpid or tolerably quick, around one or other axis, always oscillating. The filaments are only visible when the spherical colony is at rest. The radi- ating grouping of the individual gonidia is not completely symmetrical; some- times the spherical figure is exchanged for an ellipsoid. The gelatinous envelope varies in breadth, is clear and trans- lucent, rarely having a red blush under the microscope, and, in large specimens, frequently divided by fine lines into two or three halos. When dying, the several corpuscles detach themselves, and after j, do not undergo diffluence, but turn yellow and ultimately dissolve away. Frequently a green granule is visible internally, and a scarcely-dis- cernible red point. Genus HIRMIDIUM (XIX. 15) (Perty).-A chain of from 4 to 8, very Small rounded corpuscles of a pale green colour, surrounded by a gelatinous OF THE WIBRION LA, 529 envelope. This genus appears to us very erroneously referred to the Volvocina ; but the figures given are not sufficient to determine to what family they more rightly belong. HIRMIDIUM inane (XIX, 15). — Cor- common envelope inconspicuous. Length puscles irregularly spherical, almost cup- of chain 1-360"; size of individual cor- shaped, and probably furnished each with puscles 1-1900". From its smallness, this two filaments. Some very fine molecules, organism is difficult of observation, and one generally of a hark hue, perceptible requires further investigation. Only in internally. The chain advances quickly small numbers, in some ponds in the by revolving on its long axis; gelatinous; cantom of Bern, Werneck characterized several new genera, which he referred to the Poly- gastrica of Ehrenberg (Momatsb. der Berl. Akad. 1841, p. 377), two of which are to be inserted in this family, as allies of Pandorina, and are very briefly characterized under the names of Calia and Stephanoma :— CALIA.—Monads imbedded in a gelatinous mass, affixed to plants, and not swimming freely about. Two species are known; the characters not given. This genus is very probably nothing more than one of the simple Algae. STEPHANOMA = Pandorina with a single zone of corpuscles, which divide like the cells of Gonium. One species observed exhibiting a circlet of sphe- rules united to form a wreath or Zone. This genus is probably the same as Stephanosphaera (Cohn, A. N. H. 1852, p. 407). Genus STEPHANOSPHAERA (Cohn) (XIX. 38–58).-A family of cells, rotating and moving throughout life ; composed of eight green primordial cells, each bearing two active cilia; arranged at equal distances in a circle, enclosed in a common hyaline globose vesicle, or common envelope; pro- pagated both by macrogonidia (originating from eightfold division of each of the green cells), which bear two cilia, and are congregated into eight octomary families, and by very numerous smaller microgonidia (produced by multifold division), revolving at first within the common vesicle by the action of four cilia, and then escaping singly, STEPHANOSPHAERA pluvialis.-Green, 1-40th of a line (0.028 to 0.055 mm.). cells globose, elliptical, or fusiform, often | Revives after desiccation. Inhabits running out into mucous rays at both hollow stones filled with rain-water, in ends. Diameter of the cells = 1-330th to company with Chlamydococcits pluvialis: 1-180th of a line (0.0065 to 0:012 mm.); Salzburg, Werneck P; Zamora, A. von diameter of common vesicle = 1-80th to Frantzius; Hirschberg, Von Flotow, Dr. Strethill Wright has met with Stephanosphaera in Scotland. FAMILY W.—WIBRIONIA (see p. 184). (XVIII, 57–69.) ACCORDING to Ehrenberg, the members of this family are distinctly or ap- parently polygastric, but without a true alimentary canal; have neither appendages nor lorica, and are incapable of changing the form of their body. They are linked together in thread-like chains, formed by their imperfect transverse self-division. Information respecting the Vibrionia is very im- perfect; this is attributable to the exceeding minuteness of the individual ani- malcules which compose the chains. These last have never any determinate length, or number of component corpuscles, and they are sometimes so short as to be made up of not more than two or three individuals, which are only distinguishable from Monas Termo and M. Crépusculum by their union in chains, and by their peculiar, though not easily characterized movements. The motion of the chains is generally of a writhing character. In one genus 2 M 530 SYSTEMIATIC EIISTORY OF TELE INIFUSORIA, (Bacterium), a single vibratory filament is present. In this same genus the individuals are strung more tightly together, so that the filiform cluster, not being able to exert the writhing movement seen in the true Wibrionia, moves rigidly in a direct course. In Spirillum the articulations or lines of imperfect fission are oblique; hence increase in length by division engenders a spiral chain. The animals of this family, says Dujardin, “are the first Infusoria which present themselves in all infusions, and those which from their extreme Small- ness and the imperfection of our means of observation must be considered the most simple; . . . . and it is only their more or less active movements which lead to their being regarded as animals. I have been sometimes induced to believe that a flagelliform filament, analogous to that of Monads, or rather a spiral undulating one, exists, and that this is the cause of the peculiar mode of locomotion, Is the Bacteriwin triloculare, described by Ehrenberg as having a proboscis, a true Vibrio 2 “All that can be with certainty predicted respecting their organization is that they are contractile, and propagate by spontaneous fission, often imperfect, and hence giving rise to chains of greater or less length.” As stated in our general history of the family (p. 184), the present tendency among naturalists is to refer Vibrionia to the vegetable kingdom. Cohn assigns them a place in the family Mycophyceae among the microscopic aquatic Fungi. Perty retains them in his group Phytozoida, expressing at the same time his conviction that they are of a vegetable nature. Indeed the only reasons advanced by Ehrenberg in support of the animality of Vibrionia are, that they are actively, and, to his apprehension, voluntarily moving beings, and multiply by self-division,-reasons which, in the present state of know- ledge, must be held worthless. A re-examination of all the enumerated species, as Cohn remarks, is imperatively necessary before we can come to any safe conclusions relative to the true structure and affinities of the Vibrionia; and this same able observer has himself set the example by con- ducting such an examination of one species as to clearly indicate its physio- logical characters and its relation to Palmella and Tetrašpora among the Algæ, and more particularly to Sphaerotilus among Mycophyceae. The Vibrionia are developed with extreme rapidity in all liquids containing changed or decomposed organic substances, in animal fluids—the Saliva, Serum, urine, &c. When colouring matter has been mingled with the water, its imbibition by the corpuscles has never been observed. This family is distributed by Ehrenberg as follows:— Articulated threads (clusters) ſ Inflexible.................................... Bacterium. straight, the transverse divisions being rectangular .................. | Flexible, like a Snake..................... Vibrio. Aiº, º spirally twisted Flexible .................................... Spirochaeta. ike a bell-spring or cork-screw), : 1. in ºlwº º tº: #. º ..º.º....} * Spirillum. oblique .............................. \Inflexible... with a compressed spiral form ......... On this subdivision of the family Vibrionia, Cohn (Entw. p. 117) has ex- pressed himself very strongly. He says, “An inextricable confusion prevails when specific characteristics are attempted: we have the observations, good and bad, of various authors, weak and strong amplification of the objects, young and old conditions commingled without any critical endeavour to distinguish between them.” Feeling that there is no sufficient basis for it, Cohn does not attempt a classification of the Vibrionia. The Monas Lineola } Spirodiscus. OF TEIE WIBRIONIA, 531. (E.) or Bacterium Termo (Duj.) is, according to his well-conducted investiga- tions, no other than the Swarming stage of a microscopic aquatic fungus belonging to the Mycophyceae, of which he makes a new genus, named Zoogloea: again, Spirochaeta plicatilis is, in his opinion, an Alga of the genus Spirulina, and the stiff Wibrios allies at least of the Oscillariaea, of the genus Beggiatoa ; the shorter Wibrios and Spirilla likewise resemble Oscillariaea and Spirulina. Should Cohn's opinions be confirmed, the Wibrionia, as a distinct family, would be well nigh broken up. In fact, his views are generally acceded to ; for Perty, Burnett, and others all point out their peculiar affinities with the Oscillariae, and discover similar forms among the transitional phases of various Algae, and, indeed, among the antheridial spores of higher plants. The value of Spirodiscus as a genus is little insisted upon by Ehrenberg, who instituted it; and in all probability it should be set aside, and Spirochaeta also be sacrificed with it. The only species of Spirodiscus named, Perty surmises, might have been nothing more than the spore of a fungus. Dr. Burnett has expressed himself as follows to the same effect; for he observes, “When we come to organisms as minute as these, the distinguishing characteristics of genera and species become too obscure and equivocal to have much value; and the best microscopists have arrived at the conclusion that such distinctions are too refined and will not bear the test of experience. “The genus Vibrio—the simplest—I regard as the first appearance of the young Alga, existing then as the Smallest cells, arranged in linear series. The genera Spirillum and Bacterium, composed of larger forms, and of a finer and more solid structure, represent the more advanced forms; and as all Algae, as they advance in size, tend to consolidate into mycodermous forms, losing much of their primitive cell-structure, so these two genera appear to have lost their old beaded type. As for the two remaining genera, Spirochaeta and Spirodiscus, but little is positively known. They scarcely appear to belong to the other forms of this family; and as Ehrenberg himself has expressed a doubt upon the subject, one may as well omit a further notice. Therefore, in a structural point of view, the species of this family seem to be only Algae at different stages of growth.” Dujardin instituted only three genera of Wibrionia, viz.: 1. Bacterium— straight, slightly flexible threads, more or less distinctly jointed, and slow in their movements; 2. Vibrio—either straight or flexuose, with a more or less vivacious writhing movement; 3. Spirillum—having the form of a corkscrew, revolving on their long axis, oftentimes with great rapidity, but never straight. Perty has made a more ambitious attempt to classify these minute organisms; of its utility, however, little can be said, for our acquaintance with them is too imperfect to establish satisfactorily any distribution of them. To resume : Perty makes a section of his heterogeneous group Phytozoida, which he calls Lampozoidia, represented by the one family “Vibrionida.” The “Lampo- zoidia " are defined as “colourless, or rarely blue, yellow, or red, never green, organisms, without special organs, and with scarcely a trace of differentiation of substance. Their motions, though seemingly voluntary, are in fact only automatic. They multiply by transverse fission, and in so doing produce chains and fibres.” Of the family Vibrionida, two varieties are distinguishable:— A. Spirillina, in which the chain or fibre is spirally coiled; B. Bacterina, in which it is contorted or straight. Spirillina contains two genera, Spirochaeta and Spirillum; whilst Bacterina is made up of four, viz. Vibrio, Bacterium, Metallacter, and Sporonema. The new genera named will follow after our account of those recognized by Ehrenberg, and the notes on the others in their proper places. 2 M 2 532 SYSTEMATIC EIISTORY OF TETE INFUSORTA, Genus BACTERIUM.–Vibrionia distinguished by the corpuscles being connected together in a thread-like more or less rigid or inflexible chain, and by multiplying by transverse self-division at right angles to the chain. The three species known are colourless, and extremely minute. Ehrenberg remarks “that only one of the species has been Satisfactorily determined, and that their organic relations are altogether so obscure, that our judgment respecting them must unavoidably be left in a fluctuating state.” In B. triloculare a vibratory proboscis, a granular mass within the body of the crea- ture, and spontaneous division are discoverable. All the species enjoy an active power of locomotion. Perty says that he is unacquainted with the species of Bacterium enumerated by Ehrenberg. A magnifying power below 500 diameters will not exhibit the divisions or transverse lines between the individuals or links of the wand or chain. Bacterium occurs around decomposed vegetable matter, on the surface of water containing Chara, &c. BACTERIUM triloculare. — Chain in the form of short cylinders of from two to five oval corpuscles, and generally about three times as long as their dia- meter; transverse junction-lines distinct. Ehrenberg has observed not more than five links together, nor less than two, “By throwing,” he adds, “a little colour- ing matter into the water, an evident j may be perceived near the an- terior portion of the corpuscle or of the chain; and upon a very close inspection a simple filiform, though short, proboscis may be seen, which, in the larger speci- mens, is one-third the length of the body, and in the smaller, one-half.” The motion of this creature is tremulous, or slowly revolving upon its longitudinal axis. In the water of bogs. Length of chain 1-4800" to 1-2304"; single corpuscle 1-11520" (XVIII, 57). Group 57 repre- Sents several of them; two towards the right are magnified 1000, the others 290 diameters. B. Enchelys.-Chain composed of somewhat indistinct, colourſess, oval corpuscles united in smaller cylinders than the preceding; transverse lines faintly marked. In river water. Length of chain 1–2880". B. Punctum,_-Chain cylindrical, com- posed of indistinct, colourless, globose corpuscles; much smaller than the pre- ceding species; transverse lines faintly marked. In water wherein bread has been steeped. Length of chain 1-4032". B. Catenula (D.)-Filiform, cylindri- cal. Length of individuals 1-8600" to 1-6500"; 3, 4, or 5 are united together, forming a chain 1-1300" in length. Genus VIBRIO,-Characterized by the corpuscles being connected together, through incomplete self-division, in filiform flexible chains resembling in miniature the figure and movements of a snake. angles to chain. VIBRIo Lineola (Bacterium Termo, Duj.), (xviii. 69). —Forms a minute cylindrical and slightly flexible wand, rounded at both ends; separate cor- puscles somewhat indistinct, of nearly globular form, and colourless. Common in vegetable infusions, especially around the stalks of flowers in glasses, and in foul ponds. , Length of wand, from 1-3600” to 1-200". Thickness 1-3600". Both Cohn and Perty join in the use of Dujardin's name for this species, and in representing Ehrenberg as in error in identifying and fixing its characters (see genus Zoo GECEA). W. tremulans.—Wand short; stouter, yet more flexible, than the preceding; articulations of an oblong form, not distinct. In water emitting a disa- Junction-lines at right greeable odour. Length of wand 1-3600". V. Subtilis.-Wand slender and elon- gated; colourless; articulations distinct; motion slightly vibrating, without vary- ing the direct position of the articula- tions. Length 1-450"; thickness 1-24000". Perty says this species is only a variety of V. (Metallacter) Bacillus. § V. Rugula (Vibrio Rugula, M.) (xviii. 64).-Wand elongated; stouter than the preceding; articulations distinct; and colourless; motion brisk and serpentine; Common in infusions and foul water. Length 1-580"; thickness 1-12000". V, prolifer.—Wand short, stout, and colourless; articulations distinct. Mo- tion slow and tortuous. In infusions where mildew is present, 1-1100". V. Bacillus (M.)= Metallacter Bacillus OF TDIE WIBRIONIA, 533 (Terty).-Wand stout, elongated, and transparent; articulations distinct, or be- come so when dried; motion serpentime; form straight when quiescent (xvii.I. 62). In vegetable infusions and fetid water. Length 1-200"; thickness I-17200". V. Synaxanthus.--Wands (bacilli) very fine and short, rather flexuose, rarely, of more than five segments (individuals), yellow and minute. Corpuscles 1-70000" to 1-52000". In decomposing cow's- milk, in which it produces a yellow tint. V. syncyanus.--Wands very slender and short, somewhat flexuose, of seldom more than five segments, very small, and of a blue colour, 1–78000" to 1-52000", Also found in cow's-milk, in which it produces a decided blue shade. The following species are from Dujardin’s work:- V. serpens (M.).-Body very long, fili- form, undulating, generally pursuing a rectilinear course, with from ten to fifteen bends in its length. 1-1050". V. ambiguus.-Under this name, Du- jardin describes a Vibrio with stiff fili- form joints like those of V. Bacillus, but much larger (XVIII. 60). Four or five, or even more, were articulated together; owing to the large dimensions, each joint could be seen composed of a resistant tube, in which a glutinous substance was more or less closely packed. Moreover, a bifurcation at the extremity of a joint was sometimes seen to occur, giving rise to two rows of branching chains, of more or less length. Such observations tend to rendor the animality doubtful, not only of this Vibrio, but also of the similar but smaller V. Bacillus, Genus SPIROCHAETA.—Chains spiral, filiform and flexible, lengthening by the imperfect or incomplete mode of self-division. The details of orga- nization are at present unknown. Dujardin does not admit this as a genus distinguishable from Spirillum ; and Cohn is unable to discover any suf- ficiently distinctive characters between this and the acknowledged vegetable genus Spirulina. Spirochaeta moves with an immense activity, surpassing what is observed in the recognized species of Spirulina; but this difference is not sufficient to separate the two generically. Spirulina plicatilis is figured (XVIII. 67,68). Cohn moreover inclines to the opinion that Spirulina, Spirochaeta, and Spirillum are members of one common group of organisms of a vegetable nature. The distinctive feature between Spirillum and Spirulina is the small number of corpuscles found united in the chains of the former compared with the latter. numerous and closely-arranged coils; colourless. At Tilbury Fort. Length cate, nearly globular, connected together of chain 1-170" to 1-440"; thickness in a long, filiform, spiral chain, having 1-12000." Gonus SPIRILLUM.—Developes in the form of tortuous chains, or of inflexible and cylindrical spirals. The incomplete sclf-division, which is oblique in direction, produces the characteristic coiling of the chain. Motion brisk and encrgetic. SPIRocILETA plicatilis (Vibrio serpens, M.) (xviii. 63).--Corpuscles very deli- 1-20000". This species, Perty remarks, frequently grows so as to form clusters or masses which are motionless, and, like all the rest of the Vibrionia, never SPIRILLUM tenue.—Spiral of three or four coils, constituted of very slender, slightly bent colourless fibres; articu- lations distinct. In vegetable infusions. Length about 1-900"; thickness 1-1200". S. Undula (Vibrio Undula, M.) (XVIII. 59–61).-Spiral of one turn and a-half; corpuscles short, stout, and much bent; articulations distinct; colourless; when dry, the articulations are more distinct. In stagnant water having a mildew scent, Length about 1-1500"; thickness produces true vegetable fibres. S. volutans (Vibrio Spirillum, M.).-Of three, four, or more coils; fibres very tortuous, long, and stout; articulations distinct; colourless. In vegetable inſu- sions. Length of spiral 1-2200" to 1–500"; thickness 1-14400", 534 SYSTEMIATIC ELISTORY OF THE INFUSORIA. Porty adds the following species:— S. rufum.—Has the figure and size of S. Undula, but is of a red colour. No articulation discoverable. In pond-water about Bern, which had been kept several weeks. The claim of this to be considered a distinct species is highly doubtful; for its only assumed charac- teristic, viz. its red colour, is of no weight, being in the Phytozoa generally a variable condition, due to chemico- vital changes in the organisms, and ephemeral in duration. S. (?) Bryozoon (Unger) (XVII. 520– 531).-Coils consist of a thick body, with a delicate, wavy, hair-like proboscis. These creatures, found in the reproduc- tive organs of plants, were called by their discoverer, Dr. Unger of Gratz, spermatic animalcules, and are described in detail in the Regensburger Botan. Flora, 1834; and also in the 18th vol. of the Nova Acta Nat. Cur., Bonn, 1838. A con- densed view of this subject is given by Dr. Meyen in the Jahresbericht for 1838, from which the appended translation is made. The accompanying illustrations (xvii. 520–531) were kindly supplied by Dr. Unger for this work, “The spermatic animalcules in Sphagnum consist, according to the earlier observations of Unger, of a thick body, and a thin filiform tail; when in motion, this tail being anterior, he considers it analogous to the proboscis (filament) of many of the Infusoria. No true active motion of the body itself has been observed by Unger; but he distinguishes between the mere locomotive and the rotary movements of the whole animalcule. The simplest motion takes place in a spiral direction ; and if the proboscis is contracted, the movement is simply rotary. During the locomotion of the creature, which proceeds in a spiral manner, Unger saw from one to three revolutions of the body in a second; and during rotation he noticed the point of the proboscis to be in a continual state of tremor. Unger endeavoured to show that the spermatic animalcules of the mosses are analogous to the Spermatic animalcules of animal organisms, although we find certain features in the former not soon in the latter, and which may somewhat embarrass their classification, the chief of which are the steadiness of the spiral direction of the proboscis, and their manner of movement. Lately, Unger has found spermatic corpuscles in the antheridia of Polytrichwm juniperinum, P. commune, P. wrmigerum, and P. alpestre, as well as in Funaria hygrometrica, Bryum cuspidatum, B. punctatum, &c. In Polytrichum commune, the corpuscles are found in very small hexahedral cells with rounded corners. Generally, whilst in the cells they are motion- less; in Some, however, a tremulous motion of the thin proboscis was seen, and in others, again, a rotatory motion, interrupted at intervals. The dia- meter of the delicate proboscis is 0.004 of an inch. In a few corpuscles, isolated from their cells, a trembling oscillating motion of the proboscis was perceptible.” To these particulars may be added a remark of Dr. Unger, quoted in the Ann, des Sciences Nat, which led to the introduction of the subject in this work. “The doubts,” Unger says, “which remain concerning some of the organs of the animalcules of mosses, further increase the uncertainty as to their situation in the Scale of beings. From all circumstances, I am inclined to place them in the genus Spirillum of Ehrenberg, and to describe them undor the name of Spirillum Bryozoon.” Mr. Varley, in his article on Chara, in the 50th vol. of Trans. Soc. Arts, has the following observations on the same structures:– “From these cells” [in the globule of the axil of the Chara] “grow out numerous clusters of long vessels, possessing the most extraordinary ſcatures yet observed. . When these are first protruded from the globule, if not quito mature cnough, their appearance is like dense or strongly-marked ringed OF TEIE WIBRIONIA, 535 vessels, the divisions of which, or their contents, soon begin to appear irre- gular. . . . After a while, these curls within the divisions become agitated: Some shake or vibrate; others revolve in their confined places; and many come out, thus showing that they are spirals of two or three curls; these, With an agitated motion, swim about. . . . Now the field of view appears filled With life: great numbers of these spirals are seen agitated and moving in all directions; they all have a directile force, one end going foremost, and never the other; many stray a great way out of the field: these, by getting clear of each other, are the best to observe; they do not quite keep their form as a stiff spiral, but their foremost end seems to lash about, and to many are Seen attached almost invisible but very long fibres. These fibres were in quick undulations, which ran in waves from the spiral to their farthest end. It appears that these fibres cause many of the spirals to entangle together, and thus bring them sooner to a state of rest; therefore the separate ones were best to observe.” Among the more recent observations on these motile fibres (from the anthers of Chara vulgaris and Ch. hispida), are those of M. Thuretin the Annales des Sciences Naturelles, a translation of which will be found in the Annals of Natural History, vol. vii., from which we extract the following paragraphs:— “The portion of their body most apparent appeared like a spirally-rolled thread, of three to five curves. They were slightly tinged with green, similar to the nuclei; and, like them, turned brown with iodine, their two extremities becoming more or less coloured (according to the quantity of iodine employed) than the rest of the body, thus indicating a difference of nature in these portions. At a little distance behind one extremity proceed two bristles, or tentacula, of excessive tenuity, which the animalcule incessantly agitates with great rapidity. These are probably organs of locomotion, similar to the filiform prolongation found in the Infusoria without cilia. Indeed, the part thus furnished with tentacula moves foremost, drawing after it the rest of the body, which turns about in the water, but always preserves its corkscrew form. The incessant agitation of these tentacula, and their extreme tenuity, rendered it impossible to observe them in the living animal; recourse was therefore had to the evaporation of the water, or to the application of a slight tincture of iodine, when the animalcules ceased their motions, became con- tracted, and their spiral unrolled, when the tentacula were rendered very distinct, from their brown colour. These tentacula were frequently observed to be soldered together from one-half to one-third of their length upwards; but others were also noticed to be entirely separated down to their bases. A swelling similar to that in the flexure of the body was perceived in their Cllr WOS. “Ammonia arrested their motions, and contracted the body gradually into a small oval mass, but did not produce the phenomenon of decomposition by solution (diffluence), so remarkable in the Infusoria. A very weak solution of hydrochloric acid in water violently contracted them into a shapeless mass.” In Plate XVII., figs. 520–522 represent the spermatozoa found in Poly- trichnum commune, the first figure exhibiting them enclosed in the cellules, and the others, swimming freely. Figures 522–524 are taken from Marchantia polymorpha. Figure 525 is from Sphagnum capillifolium. All the above are magnified 1000 diameters. Figures 526–528 are from the Chara vulgaris, and figures 529–531 from Jungermannia pinguis, as figured in Meyen's work (Newes System der Pflanzen). * * * * On this subject of vegetable spermatozoa, Schleiden, in his recent work on the “Principles of Botany,” remarks—“The doctrine of vegetable spermatozoa is now, I hope, gradually dying away. The granules (generally starch), taken 536 ſº a SYSTEMIATIC EIISTORY OF TEIE INFUSORIA. from spermatozoa, have indeed lost their life in Fritzsche's tincture of iodine, since their evidently purely physical molecular movement remained un- destroyed. “. . . . Fritzsche has completely settled the matter; and every unprejudiced observer may convince himself with ease of the completely untenable nature of the wonders formerly spun out, especially by Meyen. The confirmatory observations of Nägeli on this point are also of great value.” Again, he says—“As to the mechanism of the motion, we know just as little as we do of that of the moving cilia; of the cause of motion, of the motive power, just as much as of that of the contraction of the primitive muscular fibre, of the motion of animal spermatic filaments, and of the vibratile cilia on animal and vegetable cells; that is to Say, absolutely nothing.” Further, in reference to the motion of the so-called spermatozoa, Schleiden observes—“There can be no question as to its not being a vital phenomenon, because the motions continue even in the alcoholic tincture of iodine (an absolute poison for all vegetable and animal life), of which one may readily convince himself, and which Fritzsche has, with his well-known accuracy, shown to be the case in a great number of plants.” (Dr. Lankester’s trans- lation, pp. 99 and 359.) This assertion of Schleiden, that tincture of iodine is an absolute poison to all animal and vegetable life, must be received with reserve, since animalcular life has been known to exist in agents, such as strong acids and mineral poisons, which, & priori, Would appear quite as inimical to it as tincture of iodine ; and even minute animals—the Acari, of far higher organization than the Polygastrica, have been stated to preserve life in strong acetic acid. . Before dismissing this subject, it may be useful to append Some observa- tions made by Wagner and Leuckart, in their elaborate and original article before-quoted. * Having stated that, up to the most recent period, the so-named spermatozoa of animals have been considered independent animal organisms, or parasitical animals, and classed among the Infusoria, the authors proceed to say that such assumption is perfectly irreconcileable with our present knowledge of these bodies, derived principally from the discoveries of R. Wagner, Won Siebold, and Kölliker:—“With our existing means of scientific diagnosis it can be proved that the formations in question are mere elementary consti- tuents of the animal organization, like the Ova—constituents equally as neces- sary for the spermatic fluid as the blood-globules are for the blood. The re- markable phenomena of the life of Spermatozoa are quite analogous to those phenomena of motion observable not only in animal formations, but also in vegetable structures—as, for instance, in the spores of Algae and of the lower species of Fungi, and in the so-termed Vibriones which grow out into the fibres of the Conferva called Hygrocrocis. Moreover, an unprejudiced observation will prove that the spermatozoa are everywhere void of a special organization, and consist of an uniform homogeneous substance, which exhibits, when examined by the microscope, a yellow amber-like glitter. The opinion of an internal organization of the developed animal elements was not a little supported by the various remarkable phenomena of motion which were frequently perceived in them. In former times, when people had no idea of the existence and extent of the so-called automatic phenomena of motions which take place without the intervention or influence of the nervous system—when nothing was known of the motion very similar to a voluntary one which exists even in plants—this movement was certainly calculated to place the independent animal nature of the spermatozoa beyond a doubt. But it is different now. We know that motion is not an exclusive attribute of animals, and that an OF THE WIBRIONIA. 537 inference respecting the animal nature of the formations in question, however similar the motion observed in them may be to that of animal organizations, is a very unsafe and venturesome one. “We know that certain elementary constituents, animal as well as vegeta- ble, possess a power of movement, and that they retain it for some time after . having been separated from the organisms to which they belonged. We only need here remind our readers of the so-called ciliated epithelium, the several cells of which swim about in the fluid surrounding them, and have not un- frequently, and that even quite recently, been considered independent animals; or, again, of the spores of the Algae, which actively move by the aid of a ciliated investment, or of a single or manifold long whip-like fibre, until they eventually become fixed and develope themselves into a new plant. Such spores as these may be found described and illustrated in the well-known magnificent work of Ehrenberg, classified as Infusoria, under the groups of Monadina, Wolvo- cina, &c. - “Under such circumstances we may consider ourselves perfectly justified in declaring every attempt to prove the parasitic nature of the spermatozoa by the charactoristic of their peculiar motion, as futile and inadmissible.” Genus SPIRODISCUS (XVIII. 63).-Self-division imperfect and oblique, producing elongated chains, or inflexible spirals, of a disc-like figure. Its organization is so little known that Ehrenberg considers the genus as by no means satisfactorily determined; indeed there is little doubt that it is not a member of the Vibrionia. SPIRODISCUS fulvus, – A lenticular sents three spirals, magnified 200 dia- spiral, of a yellowish brown colour. meters. Amongst Confervae. Breadth Articulation indistinct. XVIII, 63 repre- of spiral 1-1200". Genus ZOOGLCEA (Cohn)—Cells (corpuscles) very minute, bacilliform, hyaline, aggregated together in a hyaline muco-gelatinous, globose grape- like, and subsequently membranaceous mass, from which they may detach themselves, and swim away with a vacillating movement. ZoogDQEA Termo. — Free, moveable described forms of Cryptococcus, and to cells, straight, from 1-2000" to 1-700". Bacterium Termo (Duj.), the Vibrio It is equivalent to Palmella infusionum | Lineola (E.) (XVIII, 69). (See Part I. (E.), Micraloa teres (von Flotow), to some p. 187 et seq.) Genus METALLACTER (Perty).-Bacterium-like corpuscles, growing by repeated imperfect division into stiff or slightly flexible fibres (chains), which, under certain determinate conditions, eventually lose their power of movement and grow into Hygrocrocis-like, tangled, fibrous masses, colourless or of a greyish hue. METALLACTER Bacillus = Pºbrão Ba- cillus. – Articulation unobservable, or seen with much difficulty, Vibrio Sub- of this same organism. In Switzerland, tilis (E.) and Bacterium Catentila (Duj.) in foul pond-water, at all seasons. Genus SPORONEMA (Perty) (XVIII. 65)—Very minute, cylindrical, unarticulated, hollow fibres, closed at one end (rarely at both), frequently enclosing two elliptical corpuscles (probably spores). are, in Perty's judgment, nothing more than delicate and transparent varieties SPORONEMA gracile (XVIII, 65). — Fibres from 1-700" to 1-80" long, and 1-1000", and under, broad, of extremely pale-greenish tint. Often occurs with Mediacier Bacillus, which it much re- sembles; yet is always non-articulate, Movements tolerably quick, either end forward. Specimens occur where the spores distend the fibre; others contain none. In the sediment of pond-water containing Chara, and Lemma, from various Swiss localities, 538 SYSTEMIATIC EIISTORY OF TEIE INFUSORIA, In Ehrenberg's system the family Closterina follows here, but in this edi- tion it is transferred to the Desmidieæ, of which it constitutes an important genus. (See Part I. p. 1 et seq.) FAMILY WI-ASTASLAEA on EUGLENAEA (see p. 188). (XVIII. 35–56; XX. 15–21). THE members of this family are, according to Ehrenberg, characterized by being deficient of a true alimentary canal and lorica, and by having a single aperture and the power of changing their form at pleasure. Their organs of locomotion consist of a tail in most cases, a single filament in three genera, and a double one in a fourth. It is probable that filaments exist also in the other two genera, Colacium and Distigma. The internal vesicles were pre- sumed to be gastric Sacs, although the usual test of their being so, viz. the application of coloured food, failed in Ehrenberg's hands; yet, he says, he noticed some manifestations of a digestive power in the green and red cells of Euglona viridis. In Euglena there are, besides green ova (granules), a gland (nucleus) and a contractile vesicle ; but Astasia, Distigma, and Colacium ex- hibit only ova. Large red points are found in five genera. In Eugléna longicauda and E. amblyophis, adds Ehrenberg, “the first indication of the presence of nervous matter to be found in the polygastric Infusoria " is met with in the form of a white glandular knot, situated below the eye. The following table illustrates the characters of the genera of this family as instituted by Ehrenberg:— - Eye wanting.” e tº $ tº a tº s g º g tº $ tº t e s e g º a tº $ tº e º e º e s tº e s 4 & © tº $ tº $ tº º Astasia. With one ſ Tail wanting............ Amblyophis. Free proboscis l Tail present ............ Euglena. With one eye With two proboscides .................. Chlorogonium, Eye present VAttached by a pedicle ........................... Colacium. With two eyes ......................................................... Distigma. The family Euglenaea (Eugléniens) of Dujardin in a great measure corre- sponds with that of Astasiaea of Ehrenberg; but Dujardin prefers the term Buglenaea, on account of the resemblance of the other name to that of a family of Crustaceans, viz. the Astacia‘a. Dujardin looks upon the so-called eyes as insufficient to afford generic characters, which he would derive from the nature or apparent structure of the integument, and the number and mode of insertion of the filaments. On these principles he establishes a genus Polyselmis, characterized by its many filaments; two genera, Zygoselmis and Heteronema, by a pair of filaments, in the former of equal, in the latter of unequal size. The remaining Euglenaea, which have but a single filament, can be but uncertainly defined: such are the Euglence, mostly coloured, and having a red eye-speck and a tail; the Astasiae without colour and tail, but with a filament flexible throughout, and springing abruptly from a notch in the anterior extremity; and the Peranema, only differing from the Astaside in having a filament rigid at the base, and apparently a continuation of the tapering anterior extremity of the animalcule. The two last genera are, however, but provisional. Astasiaea is one of the families in the group of Phytozoidia of Perty, who ignores the genera Amblyophis and Distigma of Ehrenberg, adopts the Pera- nema and ZygoSelmis of Dujardin, and adds, as now genera, Eutréptia and OF TELE ASTASIZEA OR EUGIENAEA. 539 Dinéma. Again, Schneider (A. N. H. 1854, xiv. p. 327) would separate Chlorogonium from the Astasiaea on account of its unchangeable form, and Mr. Carter (A. N. H. 1856, xviii. p. 116, and 1859, iii. p. 15) would refer Euglence to the vegetable, and Astasiae to the animal kingdom. The differences pre- Vailing among naturalists relative to the beings to be admitted into the family Astasiaea indicate either that its characters are not laid down with sufficient precision, or that it is not a natural group. The power to vary the figure can be no adequate character; for this is partaken by the gonidia of various Algae in certain amoebiform stages of existence, and, on the other hand, is absent in some species enumerated by Ehrenberg in the genus Euglena, as well as in Chlorogonium. The tapering or tail-like prolongation of one ex- tremity, the existence of One, two, or more ciliary filaments, as also of a red Speck, are likewise features common to numerous zoospores. Even when appeal is made to their internal Organization and functions, nothing appears whereon the definite characters of a natural family can be built. For, on the one hand, the organization assigned them by Ehrenberg is now held to be untenable, and, on the other, no harmony prevails respecting the internal structure as recorded by different observers of the various genera. Mr. Carter, in the paper just quoted, states unhesitatingly that most of the Astasiae enumerated by Ehrenberg are animal forms, whilst the Euglence are vegetable. He remarks that, “although no two Infusoria can be more alike than Astasia limpida and Euglena when casually observed. . . . yet the absence of chlorophyll and the presence of a stomachal cavity, &c. for the digestion of crude food in the former, and the presence of chlorophyll and absence of a stomachal cavity, as well as of all means of taking in crude food for digestion, in the latter, are distinguishing characters which at once place Astasia limpida on the animal, and Eugléna on the vegetable side, respectively, of the great organic kingdom; yet both Ehrenberg and Dujardin have classed Astasia and Eugléna together.” If the organic difference between Astasiae and Euglence be what Mr. Carter asserts, his proposition to divide the Astasiaea of Ehrenberg into two families, viz. Astasiaea and Euglenaea, must be accepted. The Astasiaea inhabit ponds, mostly occurring on the surface, and frequently tinge the water with their own colour when their multiplication has been very rapid. When swimming, they present an elongated form, but when fixed, often appear as round globules. From their beautiful colour, their ever varying changes of form, and the rapidity of some of their vital acts, they are most interesting and pretty objects under the microscope, and from their common occurrence are almost always at hand for the student. Many are capable of progressing by alternately fixing and advancing the head and tail after the manner of a leech, as well as by the usual process of swimming. Genus ASTASIA (XVIII. 36, 48,49, 50).-Individuals free (not attached by a pedicle), and furnished with a long or short tail, but no eye-specks. A. pusilla is the only species in which vacuoles have been clearly seen. Ova (granules) are perceptible in A. haematodes, and probably exist in the three other species; a locomotive organ in the form of a thread-like proboscis exists in A. pusilla. Perty unites this genus with Distigma. The immense mum- bers in which these Infusoria are sometimes developed in a few days, and the blood-red colour they impart, have not unfrequently been the cause of con- siderable alarm and anxiety to persons residing in the vicinity of ponds or Small lakes which have become blood-coloured by their swarming. - Dujardin’s genus Astasia is defined as colourless, obtuse or rounded poste- riorly; whilst those described by Ehrenberg are mostly green or red, and provided with a longer or shortor caudal prolongation. 540 SYSTEMATIC EIISTORY OF TEIE INFUSORIA. AsTASIA haematodes (XVIII, 86, two figs.).-Body fusiform or spindle-shaped i. extended; tail very short; body green at first, afterwards of a blood-red colour. The illustrations represent one creature extended, and another con- tracted, Hampstead, 1-380". This spe- cies is referred by Dujardin and Carter to the genus Euglena. A. flavicans. – Extensible, cone- shaped, approaching cylindrical, and rounded at the foremost extremity. Tail very short and blunt; granules of a yellowish colour. In yellow ditch- water. Length about 1-430". A. pusilla. Extensible, cone-shaped, swelling out and rounded at the fore extremity, tail very short and pointed; colourless. Motor filaments above twice the length of the body. Movements slow; but rotation on the longitudinal axis rapid. Several phases of Euglena viridis resemble this species in form, molecular arrangement of contents, size, and motion, and are peculiar only on account of their green colour and red stigma. Ehrenberg remarks that they are often so abundant that thousands, perhaps millions, of these creatures are sometimes contained in the hollow of a watch-glass, and form a stratum on the surface of the water. They might be mistaken for the young of the A. fla- vicans, but that the vesicles within them are larger than those in that species, which is, moreover, without proboscis. As soon as a little colouring matter was thrown into the water, an evident cur- rent was observed near the fore part of the creature; and by this means, in 1833, the thread-like filament, which is about half the length of the body, was first perceived. Sometimes the entire crea- ture appears to glisten. Should this species, upon closer inspection, be found to be ciliated, it would be rightly placed among Peridiniaea. 1-1440" to 1-500", The size of the vesicles remarked by Ehrenberg is no distinctive character; and Mr. Carter believes that both this species and A. flavicans are either j with or very nearly allied to A. limpida, and therefore animal organisms, unlike the Euglema, to which they have a general resemblance. A. (?) viridis. – Extensible; of an ovate-oblong form, distended a little at the middle; tail yey short and pointed; green. Amongst Confervae. 1-1200" to 1-900". This species and A. haema- todes are, in Dujardin's opinion, members of the genus Buglenſt, the only appre- ciable difference between them being the Fº of a red stigma in this genus. this opinion Mr. Carter coincides. A. nivalis (Vogt) (XVII, 532–533).- Oval, extremities rounded, rarely pear- shaped, colour deep reddish-brown, mo- tion rapid. Found with Protococcus ºne- bulosus in snow (Switzerland). 1-1500". M. Vogt, in his account of the Astasia nivalis, describes it as invested with a carapace (lorica), open only at the an- terior extremity. This opening is fur- nished with numerous small cilia; and here, doubtless, the mouth is situated, the indication of which is given by an orange-coloured tint, which is clearer than that of the rest of the animal. “The presence of a lorica and cilia affords a character which does not allow this animalcule to be placed with Astasia, as Shuttleworth has done; on the contrary, it ought to be placed in the family Peridiniaea (Ehr.), or else be regarded as the type of a new genus, distinguished by the absence of a groove in the lorica, and by the stiff hairs of Peridinium being replaced by soft cilia.” (On the Animalcules of the Red Snow, Bibl. Univ. de Genève, 1841.) This pre- sumed species is, in all probability, nothing more than an encysted cor- puscle, probably a species of Chlamy- dococcus. A. Acus. –Hyaline, figure long-fusi- form, acute at each end; filament the length of the body, 1–650". Berlin. Under the head Astasia, Perty enume- rates the following species; but, as he makes no distinction between Astasia and Distigma, the generic appellation is not quite equivalent to that used by Ehrenberg. A. margaritifera (Smarda),—Remark- able by its variability of form, or meta- bolia, the contents appearing to be driven from one part to another, filling and dis- tending one portion, whilst the other is left empty and contracted. Hyaline granules (germs?) very distinct. At periods it loses its filaments, and with them its powers of swimming, when it adopts a crawling movement. Two clear spots occur near the base of the filament, which is once and a half to twice the length of the body: these spots were called eyes by Ehrenberg, who made them the distinctive feature of a genus Distigma. In pond-water, and cven under ice, but not common. A variety, much elongated and slender, has been called Astasia Serpentulus. OF TEIE ASTASIAEA OR EUGIENAEA. 541 The following species are described by Dujardin — A. contorta (XVIII, 49, 50). —Colour- less, semi-transparent, containing pale- yellow granules; cylindroid, enlarged in the middle, obtuse at each end, and marked with oblique striae, giving rise to a twisted appearance. 1-450". In sea-water. A. inflata. — * dia- §. contractile, ovoid, obliquely ut regularly plaited or striated. 1-560". In sea-water. A. limpida (XVIII, 48 a, b, c). —Dia- phanous, smooth, very variable, fusiform, more or less obtuse at each end, cleft anteriorly, and often obliquely doubled on itself or twisted. 1-650" to 1-530". In ditch-water, Perty remarks that pusilla and A. flavicans with this species. Mr. Carter (A. N. H. 1859, iii. p. 15) treats this organism as an undoubtedly animal form, and describes it as having a stomach or digestive cavity, into which it receives food from without. Unlike JEuglena, which it outwardly resembles, it contains no chlorophyll. He also con- siders that it is the same being which Ehrenberg has described and figured as Thrachelius trichophorus. A. longjilis (Perty).-Hyaline, with pale-green internal granules; filament at least three times longer than the body : a lateral plait or figure is seen in the anterior half. Form unchangeable. Motion tolerably fast. 1-1000". Dujardin is wrong in identifying Astasia Genus AMBLYOPHIS (XVIII. 45).-Free, with a single eye-speck and flabellum, but no tail. The flabellum or filament serves as an organ of locomotion, and is situated at the fore extremity, which, says Ehrenberg, is cleft, so as to represent a two-lipped mouth, the filament being very readily distinguished on the upper lip. The colour of the animalcule is derived from the closely compressed mass of green granules, which nearly fills the body. Near the middle of the creature is a large, bright, globular, together with five wand-like bodies, two of which are situated before, and three behind the former; these structures together were supposed to be male generative organs. No contractile vesicle has been observed. Self-division is unknown. The coloured speck is very highly developed. Towards the anterior part of the body, and just behind the filament where the mass of granules commences, there is a bright-red and somewhat lengthened spot (resembling, as to situ- ation and colour, the eye of the Rotatoria and Entomostraca), in the glear space beneath which is a mass of matter of a very peculiar description, of a globular form, having, to Ehrenberg's apprehension, the appearance of a nervous ganglion, and being most probably connected with the organ of vision. This genus is not distinct from Euglena; for the absence of the so- called tail is insufficient to distinguish it, and, what is more, Perty has seen Amblyophis viridis proceed from Eugléma viridis in the process of reproduction, AMBLYOPHIS viridis (XVIII. 45). — Large, elongated, cylindrical, distended or compressed, and abruptly rounded at the posterior extremity; green, head colourless; eye-speck large, bright red. The motion of this creature is sluggish and serpentine, and by its evolutions might easily be mistaken for the Euglena Spirogyra, were that creature, like this, tailless. Found with Euglenae, chiefly in the spring, 1-210" to 1-140" (vide p. 194). Genus EUGLENA (XVIII. 37–44, 46, 51, 52, 54).-This beautiful genus of the family Astasiaea is characterized by being furnished with an eye, a single thread-like filament, and a tail, and by being free. The locomotive filament is seen in nine species out of the eleven, and has a double appearance, in E. sanguinea ascribed to the condition of the animalcule preparatory to self-division. In Euglema hyalina, E. pleuronectes, and E. longicauda, vacuoles are generally visible; but in the other species they are obscured by the masses of green granules which colour their bodies. Certain internal appearances have been recognized, which Ehrenberg supposed to be of a male generative 542 SYSTEMATIC HISTORY OF TEIE INFUSORIA. nature, i. e. a nucleus. Longitudinal self-division has been observed in E. Acus, and the commencement of it in E. sanguinea (XVIII. 37–39). Close to the red point a supposed nervous ganglion or eye-speck is visible in E. longi- cawda (XVIII. 44), such as is seen in Amblyophis. The genus Euglena of . Ehrenberg, says Dujardin, contains some species of a compressed leaf-like form, and quite deficient of contractility, which require to be placed in the genus Phacus of the family Thecamonadina. EUGLENA sanguinea (Cercaria viridis, M.) (XVIII, 37–39).-Extensible, of an oblong-cylindrical or spindle-shaped form, with head greatly rounded; tail short, conical, and somewhat pointed. Flabellum longer than the body in its extended condition. When young, they are green, but when full-grown, of a blood-red colour; and specimens are frequently found variegated red and green. The motion of this multiform animalcule is generally slow; and it sometimes revolves upon its longitudinal axis in swimming. The thread-like fila- ment, which is a prolongation of the §. lip, and rather longer than the body, is so delicate as to require consi- derable care in investigating it, and, being retractile, will often elude obser- vation. A little colouring matter in the water will exhibit this organ in active operation; and it may be distinctly seen in a single animalcule in a dried state, upon a plate of clear glass. The double appearance of the organ in this species has been before noticed. Ehrenberg conjectured that the miracle in Egypt, recorded by the great lawgiver of the Jews, of turning the water into blood, might have been effected by the agency of these creatures, or by the Astasia hamatodes. In stagnant water, often in great abundance on the surface. 1-800" to 1-210". This is in all probability a mere variety of E. viridis; the red colour is not a specific distinction, but only a sign of maturity. - E. hyalina.-Extensible in a spindle- shaped manner; head attenuated, blunted at the extremity, and two-lipped; tail short, and somewhat pointed; colour transparent and whitish ; rare. 1-280". Perty asserts that it is only a variety of JE. viridis. E. deses (Enchelys deses, M.), Extensi- ble, cylindrical, abruptly rounded at the head, and slightly bi-lipped. Tail very short and pointed; colour green; motion a winding and sluggish creeping, never swimming. Filament very long and fine. Amongst Lemmae. 1-240" to 1-760". E. viridis (Cercaria viridis, M.) (xvii.I. 46). — Extensible in a spindle-shaped manner; head attenuated and short. Tail short, and cone-shaped, not cleft; colour green, excepting the two ex- tremities, which are colourless. The double-pointed tail represented by Leeu- wenhoek and others does not exist. When the creature is young, its eye- speck is imperceptible or very pale, and it may readily be mistaken for Astasia viridis or Monas deses. When dried on glass, the speck seldom retains its colour more than a week; but the filament may be well examined and pre- served when so treated. Filament twice the length of the body, which differs very much—between 1-600" and 1-140". Perty affirms that E. hyalina is a mere variety of this species, and that Am- blyophis viridis (xVIII. 45) is the same, for he has witnessed the same individual Euglena produce both Euglena and Am- blyophis. This observer has found E. viridis at an elevation of 9000 feet, on the Alps. On the surface of ponds at Hampstead and elsewhere, common. E. Spirogyra (XVIII. º and cylindrical; very finely striated and granulated. The head is a little trun- cated, and the hinder part attenuated into a short pointed tail; colour a brownish green; motion like E. deses. Its colour varies from a beautiful green to yellow or brown. It always occurs singly. E. Oaſyuris &º is not specifically distinct. Amongst Confervae and Bacillaria. 1-240" to 1-120". E. Pyrum (XVIII, 41, 42).--Obliquely fluted; when distended, oval or pear- shaped. The tail generally about the length of the body, and pointed; colour green. Found with many other species at Hampstead, but not so frequently as the other species. 1-1152" to 1-864". E. pleuronectes º pleuronectes, M.). — Compressed, ovate-orbicular, or in the form of an obovate leaf; striated longitudinally; colour green; tail pointed, one-third or one-fourth part the length of the body, and colourless. In stagnant water, 1–1152" to 1-480". E. longicauda (XVIII.44)—Mostly stiff, compressed, elliptical, and leaf-like; co- lour green; tail the length of the body, OF TEIE ASTASIZEA OR EUGIENZEA, 543 awl-shaped and colourless. Within this creature may often be seen a yellowish- green mass of granules. The very deli- cate vibrating thread-like filament has its origin from the more projecting side of an indentation on the anterior edge of the body, and is about two-thirds its length. This creature has the power of twisting its body into a spiral form, but not of contracting it. It swims freely, and mostly with a vibratory motion, occasioned by the action of the filament. In fresh-water amongst Confervae and Bacillaria, 1–480" to 1-120". E. triquetra. — Leaf-shaped, three- sided, oval-keeled; colour green; tail shorter than the body, and colourless. Amongst Lemnae. 1-580". E. Acus (Vibrio Acus, M.). —Slender, spindle-shaped, and straight; head atte- nuated, and a little truncated; tail very pointed; body green in the middle, and colourless at the extremities. This is one of the most beautiful animalcules seen under the microscope; its graceful form when swimming, its bright-red eye, the curious forms it assumes when stationary, and its remarkable appearance when un- dergoing self-division, all combine to remieri worthy of observation. Fresh and brackish water. 1-570" to 1-110". IE. rostrata.—Elongated and conical, with the hinder part gradually attenu- ated into a very short tail, Head slightly bent, like a beak; colour green. Amongst Oscillatoriae and Bacillaria, Length about 1–500", E. Ovum.–Ovate, green, with a very short hyaline caudal prolongation, and a large, double, circular nucleus, 1-1560". Berlin. E. geniculata (D.).-Green, elongated, cylindrical, flexible but not very con- tractile; movement slow; tail tapering, clear, and at an angle with the body— hence the name, 1-208" to 170". This large Euglena is remarkable by its elong- ated form, by its diameter being nearly equal to its length, without the bulging of E. viridis, and by its articulated tail. E. obscura (D.). —Thick, oblong; dis- tended and obtuse posteriorly; but the form very variable; clearer and of a red tint anteriorly, eye-speck reddish-black; filament half as long again as the body. 1-870". This form Perty surmises to be only a deeper-coloured specimen of E. sanguinea, which he often found of a brown or blackish-red colour. E. mucronata (Perty).-Of a beautiful green colour, the anterior segment or head frequently hyaline, with a clear-red stigma; tail pointed and transparent. Body oval, often longitudinally and finely striped. Filament overlooked. Differs from E. geniculata by the absence of the angularly-set filament, 1-108" to 1-84". Mr. Carter describes the following new species from the freshwater tanks of Bombay :— E. fusiformis.-Short, thick, fusiform, obtuse, of a rich green colour, provided with along, delicate, single cilium, which projects from a slightly bilabiate anterior extremity; a little behind which is the eye-spot, attached to the contracting vesicle. Nucleus central, situated be- tween the ends of two elongated, refrac- tive, nucleated cells, which extend round the body equatorially. Tailless. Motion during progression oscillatory, and rotat- ing on the longitudinal axis. Length about 1–700", breadth about 1-1100". Freshwater tanks in the island of Bombay. E. zonalis.-Short, thick, ovoid cylin- drical, slightly narrowed anteriorly, of a rich green colour; provided with a long delicate cilium, which projects from the notch of a slightly bilabiate anterior ex- tremity; a little behind which is the eye- spot, attached to the contracting vesicle. Nucleus central, between the ends of two wide, refractive, nucleated cells, which extend round the body equatorially. Tail adhesive or suctorial (?), short, about one-sixth part of the length of the body. Motion during progression oscillatory and rotating, on the long axis of the body. Length 1-1100", breadth 1-1800". Fresh- water tanks in the island of Bombay. These two Euglenae are remarkable for having that refractive cell or organ which I have called the “glair-cell” equatorial, instead of longitudinal as in Euglena Spirogyra, or single and in the anterior lip as in Crumenula texta. E. agilis.-Is a third species Mr. Carter would distinguish; but he has given no details, except relative to its develop- ment in the still form. 1-600". In the brackishwaters of the marshes of Bombay (A. N. H. 1856, xviii. p. 246). Genus CHLOROGONIUM (p. 195) (XVIII. 47; XX. 15–21).-Astasiae 544 SYSTEMATIC IIISTORY OF THE INFUSORIA, with a double filament. Are free and provided with an eye-speck, tail, and double filament. The only known species is of a very beautiful green colour, and has numerous transparent vesicles within it. A distinct, hyaline nucleus is perceptible in the centre of the animalcule. Self-division of the contents into four or more segments has been observed to take place, also propagation by microgonidia. Schneider and Perty concur respecting the propriety of dotaching Chlorogonium from the Astasiaea. Numerous dull-red Spocks are scattered throughout its green contents, no one of which has the clearness and distinctness of the stigma of Euglence. The primordial cnvelope, with its enclosed green contents, varies in figure; but not the external One, which is rigid. Priestley, 1-110" to 1-280", exclusive CHLoRogoNIUM euchlorum (XVIII. of the tail. It was in this species that 47; xx. 15–21).--Spindle-shaped, very pointed at both extremities; tail short; colour sparkling green. The eye-speck is so delicate that it may be easily over- looked; but when the creature is dried upon a plate of very clear glass, both the eye and the double filament are readily seen, and it may be preserved as a per- manent microscopic object, XVIII, fig. 47 represents a cluster of six, each with its double proboscis. In water-butts, on ponds, &c.; it forms the green matter of Genus COLACIUM.–Eye-speck or in this genus, although, as Ehrenberg M. Weisse thought he had discovered a form of propagation analogous to that by ova, but in fact to reproduction by mi- crogonidia Ş. 15–21). The young forms so produced, especially in their aggregate state before discharge, re- somble Uvella Bodo; and M. Weisse thinks Chlorogonium euchlorum and Glenomorum tingens only other stages of development of the same organism, stigma single. Filament not detected remarks, there can be no doubt of its existence, from the currents which are visible in coloured water near the forepart of the body; still, as these are rather feeble, it is probable that the organ is but single. Numerous transparent vesicles are seen within the body. The creatures are parasitical upon Entomostraca and Rotatoria, to which thcy attach themselves by means of a pedicle or footstalk, which is single at first, but becomes ramified by the process of self-division. CoLACIUM (P) vesiculosum.—Spindle- shaped, oval, but variable; ºil. very short, and Seldom ramified; colour sparkling green, with distinct internal vesicles. Ehrenberg says, “I have again sought in vain for the red eye (May 23, 1835), but cannot be satisfied of its non- oxistence, as it is undoubtedly present in the other species, and investigation is sometimes unproductive on account of subordinate circumstances. I have likewise failed in seeing very satis- factorily the vibratory organ, notwith- standing its action is evident enough.” Genus DISTIGMA.—Astasia, with Found upon Entomostraca, 1-860". C. stentorinum. — Form variable, but somewhat cylindrical, prolonged anteri- orly into a funnel-shaped process; colour beautiful green; vesicles indistinct; pedi- cle often ramified. The eye-speck is at one time distinct, at another Scarcely perceptible; it differs also in position so widely that sometimes it is close to the elongated neck, at others near the poste- rior end. Perty surmises it to be a larval condition of some other being, or merely a sporozoid. Found upon Entomostraca and Polyarthra trigla, 1-1150". two eye-specks. Locomotive organs not hitherto discovered; and the presumption is that they do not exist; none of the species either swim or produce perceptible currents in coloured water. Movements crecping or crawling, much like those of ecls; form variable, like that of Lacrymaria ; and they approximate to Amoeba in other respects, besides the absence of a ſlabellum. At the fore part of the body may be seen two very delicate, blackish-coloured spots, analogous to the cyc-specks in other genera. The Distigma are sometimes confounded with Proteus OF TETE ASTASIAEA OR EUGLENAEA. 545 diffluens of Müller. All the species are exquisite objects for a deep-powered microscope—for instance, one magnifying 460 diameters. Perty unites this genus with Astasia, as being indistinguishable from it by any sufficient charac- teristics. DISTIGMAtenaw (Proteus, M.).-Larger than either of the other species; proteus- like—at one time greatly distended, at another as much constricted; eye-speck rather indistinct; colour transparent yel- low. About Lemnae. 1-240". This spe- cies Perty regards as merely a larger variety of Astasia margaritifera, inca– pable of the same extent of metabolia. D. Proteus (Proteus,M.).--Smaller than the preceding ; proteus-like—sometimes greatly distended, at others constricted; blunted at both extremities; eye-specks distinct. Amongst Confervae. 1-580" to 1-400". This species, says Perty, appears nothing else than a smaller specimen of Astasia margaritifera which has lost, to a greater or less extent, its filaments, and therewith its power of swimming, whilst it retainsthe remarkable peristaltic move- ments in its internal substance. D. viridis. –Smaller than either of the other species; proteus-like some- times greatly distended, at others con- stricted; filled with green granules; eye- specks distinct. Length not exceeding 1-570". D. viridisis, in Perty's opinion, an incomplete condition of Eutreptia viridis. D. planaria.--Small, linear; proteus- like, but capable of less distension or constriction than the preceding; pointed at both extremities; colourless; eye- specks distinct. Found by Ehrenberg amongst Confervae in the Nile. 1-240". Genus PERA.NEMA (Duj.) (XXVI. 13).-Body of variable form, some- times almost globular, at others distended posteriorly, and drawn out in front, or prolonged into a long tapering filament. Movement forwards slow and uniform. The Peranemø are colourless, but contain in their diaphanous Substance granules and vacuoles. The lobes they send out in their frequent and remarkable changes of form are, unlike those of the Amoebae, covered with an integument. of dead plants. Found in stagnant marsh-water, chiefly on the surface I suspect Ehrenberg has described a species (P. protracta) of this genus under the name of Trachelius trichophorus. PERANEMA protracta.-Oblong, soft, dilated posteriorly, much extended an- teriorly. 1-838" to 1-370". Its figure undergoes changes by the movements of its contents. A trace of a red stigma often discoverable. P. globulosa (xxvi. 13). —White or pale-green, nearly globular, more or less extended anteriorly, with oblique plaits on its surface. In the Seine, and in ponds at Bern. 1-1625" to 1-1300". Perty could not discover the plaits or folds, and states that the filament is double the length of the body. Movements very active. P. virescens.—The animalcule so named occurred in the water of the Seine, was green, semi-fluid, and changed form most rapidly, like an Amaeba. 1-860" to 1-520". Requires further examination. Genus ZYGOSELMIS (Duj.) (XXVI. 12 a, b).-Animal of variable form, Swimming by means of two equal flagelliform filaments, which are constantly in agitation. Zygoselmis, says Dujardin, is distinguished from Diselmis by its contractility and its variability of form ; but such a distinction is surely insufficient. ZYGOSELMIS nebulosa (XXVI. 12 a, b).- Colourless, sometimes globular, at others top- or pear-shaped, with numerous con- tained granules. 1-1300", with two fila- ments of equal size and length. Un- common; found with Lemma; the changes of form proceed slowly. Z. indequalis (Perty).-Colourless, hya- line; one filament rather stouter than the other; both protruded in front. Ca- vity sometimes filled with clear green corpuscles, which frequently assume op- §. a red hue. Changes of figure slow ; movements sluggish. Distin- guished from Z. nebulosa by the inequa- lity of its filaments. 1-840". The assigned distinction between this and the other species appears to us insufficient. Genus HETERONEMA (Duj.) (XXVI.11).-Body of variable form, oblong, irregularly dilated posteriorly, having a fine flagelliform filament, and a second 2 N 546 SYSTEMATIC HISTORY OF THE INFUSORIA. thicker trailing one acting as a retractor. This genus, by possessing the two filaments of different characters and office, approaches the Heteromita and Anisonema, from which, however, it is distinguished by its contractile, ob- liquely striated integument. º HETERONEMA marina (XXVI. 11).- narrower in front, obliquely and closely Body oblong, irregularly dilated behind, striated. Length 1-434". In sea-water. Genus POLYSELMIS (Duj.) (XXVI. 7).-Animal oblong, of variable form, swimming by means of several flagelliform filaments which arise from its anterior extremity. The single Infusorium I have found possessing these characters resembled an oblong Euglena rounded at each end, with an anterior longer moveable filament, surrounded by three or four very fine shorter ones. PoEYSELMIS viridis (XXVI, 7).-Elon- with a red eye-speck. 1–650". Found in gated, rounded at each end; more or less a glass of marsh-water containing Lemma, dilated and folded in the middle; green, which had been kept several months. Genus EUTREPTIA (Perty) (XVIII. 53–55).-Like Chlorogonium, Zygo- selmis, and Dinema, has two filaments. It has besides the form of an Astasia, but its figure is constantly varying as it swims, and it has a red stigma. This and the following genus constructed by Perty are very imperfectly characterized, and in our opinion have slight claim to generic independence. EUTREPTIA viridis (XVIII, 53–55; XIX. a crawling movement, and not the power 18–19).-Green, with hyaline corpuscles, of swimming. Length, when extended, but sometimes quite colourless. A va- 1-240". Among Lemmae. A variety, E. riety thick and rounded posterior, with unftlis, has only a single flabellum and a the outline of Amblyophis, only presented faintly marked stigma. Genus DINEMA (Perty) (XIX. 17).-Filaments two; one projected in advance, the other trailed behind. Body Small, saccular, very contractile, and destitute of chlorophyll. DINEMA griseolum (XIX, 17). —Body dimensions. 1-250". Bern. In ponds, &c. filled with grey molecules. Movements D. pusillum.—Colourless, with few in- sluggish, and particularly so the rotation ternal granules. Very contractile, and on its long axis. Filaments about equalin changeable in figure. FAMILY DINOBRYINA. (XXII. 42, 48, 49.) THE animalcules of this family are distinctly, or to all appearance, poly- gastric, and furnished with only one aperture to the body; hence, like polypes, they can have no true alimentary canal. They are possessed of an external case or sheath, and have the power at will of changing their form, but are without appendages, except one species of Dinobryon, which has a simple filiform proboscis and a delicate red spot at the anterior portion of the body. The nutritive apparatus is obscure and undefined. The lorica is of the form of a little pitcher (urceolus), to the bottom of which the very contractile Euglena-like creature is attached. Two genera only are known. Genus EPIPYXIS (XXII. 42). —The characteristics of this genus are mostly of the negative kind; it wants the eye, and is attached. The most evident animal character possessed by the species is the funnel-shaped orifice at its anterior extremity. The soft or pulpy body is lodged within a delicate membranous (not silicious) lorica, usually affixed by a pedicle or foot. Stein presumes Epipya'is to be merely a younger condition of Dinobryon, with which it occurs frequently in company. Besides this, the peculiar cell- like nucleus occurs alike in Epipyaris and in Din. Sertwilaria. OF TELE PROTOZOA. 547 EPIPYXIS Utriculus (XXII,42).--Small, The figure represents a group of several comical, and pitcher-like, filled with yel- attached to a portion of Conferva, lowish granules; attached by a pedicle. I-640". Genus DINOBRYON (XXII. 48–49).-Distinguished from the preceding genus by possessing an eye-speck and freedom of motion. larger and looser around the body of the creature. The lorica also is Reproduction takes place by gemmae, which do not separate from the parent; hence a shrubby, forked, and polype-like cluster is produced. DINOBRYON Sertularia (xxxi, 48, 49). —Lorica (sheath) large, slightly excised and dilated at the mouth, but constricted above the base or the attached extremity. This animalcule is readily overlooked, by reason of its crystalline lorica, and often nearly colourless body; by a patient in- vestigation, however, the little colony may be perceived rolling along, and ad- vancing in the field of view. Within each lorica a pale-yellow animalcule may be noticed, in form somewhat resembling the young of Chlorogonium or of Euglena viridis. The creature is able to contract itself into a rounded mass at the bottom of its case, or it extends itself to the mouth of the lorica, but not beyond it. A red speck occurs at the anterior part of the body, from which a single thread- like filament is protruded beyond the sheath. The vibrating filaments of the several members of the colony propel it through the water like so many paddles. 1-570", cluster 1–120". Stein in the course of his researches met with a spe- cimen of Dinobryon Sertularia which he likens to a Eugleniform being, living In a crystalline goblet-like sheath, much like that of Vaginicola crystallina or of Cothurnia imberbis. The sheaths grouped on a stem are only mechanically united together, and are under no circumstances developed by progressive gemmation from the hindmost one, as Ehrenberg supposed. Each being has a clear, homogeneous, discoid nucleus near its base, containing a central nucleolus. D. (?) sociale.—Small, enveloped in a shell of a simply conical shape, truncated at the mouth. Developed in the form of a shrub-like polypary. In fresh water. 1-860", cluster 1–280". D. gracile. —Less branching (fruti- cose), lorica slightly constricted at the middle, aperture truncated. Animalcule 1–2080". In bog-water. Length of animalcule OF THE GROUP PROTOZOA (p. 199). IN the arrangement pursued in the first part of this work the Protozoa follow the Phytozoa, and are primarily divided into two chief subsections, viz. – Rhizopoda and Ciliata. These we shall treat as two groups of Infusoria, divisible into a few subgroups, and, commencing with the Rhizopoda, shall treat systematically, first those beings properly called so, and afterwards, as subgroups, the Actinophryina and the Acinetina. The Ciliata and their divi- sions will follow next. GROUP II.-RHIZOPODA (p. 201). (Plates XXI-XXIII.) THIS term and its synonym Pseudopoda are derived from the leading charac- teristic of the class, viz. the variable processes or false feet which serve as their locomotive organs. The former appellation is more in vogue, but its extent ... 2 N 2 548 SYSTEMIATIC EIISTORY OF TELE INFUSORTA. of signification is ill-defined. Some would apply it to the whole collection of animalcules composed, as far as their organic material is concerned, of the self-same simple homogeneous sarcode, whether this exist naked, as in the Amoebaea, or whether enclosed within a simple single-chambered shell, as in the Monothalamia, or in a many-chambered or compound One, as in the Poly- thalamia or Foraminifera. Siebold extends to the Rhizopoda, as a class, this wide signification. Others, and among them Ehrenberg, would so far limit it as to assign to it only the naked Amoebaea and the monolocular Arcellina. Indeed, the last-named author holds the opinion of an actual difference in organic nature between his presumed Polygastric Pseudopoda and the Fora- minifera or Polysomatia. Dujardin adopted the peculiar course of rejecting the Amoebaea from the Rhizopoda, which in his system included both mono- locular and multilocular forms. In our general history of the Rhizopoda (p. 201), we have used the term in its widest signification, to include naked monolocular and multilocular beings; but, in order to keep this systematic portion of our work within moderate bounds, we shall here give only the descriptive account of the Amoebaea and Arcellina. Were another reason required than that assigned for this proceeding, a strong one might be found in the fact of the approaching completion of an elaborate work on the Fora- minifera by Professors Williamson and Carpenter, who are so well known for their extensive acquaintance with this class of organisms. Families:–1. Amoebaea; 2. Monothalamia (Arcellina); 3. Polytha- lamia (Foraminifera); 4. Actinophryina; 5. Acinetina. FAMILY I.—AMOEBAEA OR AMOEBINA. The Amoebaea present the simplest form of organic life, and are typically represented by a microscopic particle of ‘Sarcode,” or muc0-gelatinous organic matter, possessing within itself the power of growth, of assimilation of ex- traneous substances, of movement by means of irregular and ever-changing offshoots from itself—“variable processes,”—and capable of multiplication by the severance of portions of itself, and probably of development by internal germs or gemmules. They present no definite, constant figure, although it is possible to distinguish different Amoebaea by the more frequent outline they exhibit, or by the length or figure of their pseudopodes. The general opinion is that the sarcode of which they consist is naked and homogeneous; but Auerbach (see anté, p. 205) has advanced the statement that they are all en- closed within an integument. A movement of granules is perceptible, espe- cially along the margins of the variable processes. A nucleus with a nucleolus is believed to be generally present; vacuoles are almost always distinguishable; and one, two, or even more contractile vesicles have been seen in some speci- mens. There seems evidence of the process of encysting taking place under certain conditions. Amoebiform beings are not necessarily of an animal nature; for some have latterly been proved to occur in the cycle of development of some of the simplest plants. Ehrenberg described Amoebaea as polygastric ani- malcules, having a mouth but no alimentary canal, and moving by variable processes, produced from any part of the body indifferently. He observed vacuoles (digestive sacs) in all, and self-division in Amoeba diffluens. The Amoebaea are organically related to the Arcellina and Foraminifera, from both of which groups they differ by being naked, or unenclosed in a shell (see p. 234). * Only one genus is distinguishable, viz. Genus AMCEBA, which is therefore represented by the description of the OF TELE AMCEBAEA OR AMIQEBINA. 549 family. The following species, however, are distinguished, although it is hard to define specific form in such variable AMCEBA Princeps (XXI. 4). — Colour pale yellow, processes numerous, of a cylindrical outline, with thick, rounded extremities. Its figure when in a passive or non-reptant condition is globular; but this character is of no specific value, the natural tendency of any similar semi- fluid, mucous particle being, by the force of cohesion, to assume such a form. Amongst Naviculae and Algae in fresh water. 1-140" to 1-70". A. verrucosa.--Smaller than the last; colourless; processes globular, ovoid, of a wart-like appearance. Motion sluggish, like, indeed, all Amaºbaº, Never exceeds 1-240". Amongst aquatic plants. A diffluens.—Colourless; expands into a filmy form and throws out processes which are longer than those of A. verru- cosa, and rather pointed at the ends. This species is a very interesting object under the microscope: at times it re- sembles a turbid lump of jelly-looking matter, at others a transparent gelati- nous film, with numerous outstretched processes slowly protruded at one part and withdrawn into the general mass at another, but so acted on as to serve to roduce a very slow onward movement. tS movements may be compared in ap- pearance to those which may be imagined as exhibited by a many-footed animal tied up in a sack. Usual size 1-300". Common amongst Lemmae. A. radiosa §: 1–3).-Colourless; Smaller than A. diffluens; processes nu- merous, long, slender, pointed, disposed in a radiating manner. en contracted, it resembles A. diffluensin its globose figure. Colouring matter is readily taken into its substance. In bog-water. 1-240". A. longipes, –Very Small; processes very long, one of them often four times the length of the body; acute and hya- line, without expansions, 1–2500". Cux- haven, in the sea. A. Roeselii (Duj.).—Diaphanous; pro- cesses numerous, somevery obtuse, others digitate, and others also pointed or jagged, 1-130". Large vacuoles occur about the middle of the body, looking like large globules. A. marina (D.).-Filled with granules at the centre; differs from A. diffluens Only in its dimensions and habitat, i. e. the sea. 1-260". A. Gleichenii (D.).-Varies from a glo- bular to avery long-oval figure; dividing into two or three lobes on one side; Creatures. vacuoles, and some nearly opaque gra- nular bodies, at the centre. 1-400" to 1–300". A. multiloba (D.).-This may be but a variety of A. Gleichenii, but deserves pointing out, as much from the circum- stance of its habitat as from its form. 1–1300". It seems softer than other Species, and moves actively, emitting from its border in various directions ten or twelve rounded lobes, which give it a most irregular figure. It was found in an infusion of meal which had been kept nearly two months. - A. Limaa (D.) (XXII, 4–5).-Diapha- nous, rounded on each side, more or less globose, and but slightly lobed; glides along in a nearly straight line; contains very distinct granules, and a very clearly marked vacuole. Found in Seine water kept for eight months. It may be but a more advanced degree of development of the preceding, or of the following species; its greater transparency, how- ever, and its semi-fluid consistence, seem sufficiently distinctive. 1-260" to 1-800". Auerbach suggests that this species is Only a young form of A. Princeps. A. Guttula (XXII, 6). — Diaphanous, Orbicular or ovoid; glides in a straight course, and contains very distinct gra- mules. This is one of the most common species, but may easily escape notice on account of its great transparency, the simplicity of its form, and the slowness of its movements. In river- or marsh- water, kept for Some time, containing plants. 1-520" to 1-890". A. lacerata (D.). —Symmetrical, ru- gose, plaited, and granular, rather dia- phanous, with broad expansions, looking membranous at the base, terminated by several tapering torn points; one or more evident vacuoles. 1-2800" to 1-890". In pond-water. A. brachiata (D.). —Globular; semi- transparent, porous and tubercular, with four to six very thin long and cylin- drical expansions, straight or flexuose, sometimes bifid or branching. In animal infusions. 1-190". A. crassa (D.).-More or less rounded, thick; contains numerous granules; ex- pansions rounded, numerous, not very prominent, 1-880" to 1-520". In the water of the Mediterranean. A. ramosa (D.)-Globular or ovoid; granules very numerous; expansions mu- merous, of nearly equal size, rounded at 550 SYSTEMIATIC HISTORY OF THE IN tº USORIA. the extremities, of the same length as the body, and mostly branched. Other varieties of these peculiar beings are referred to, but not specially described, by Dujardin; for one, however, he pro- poses the name of Amaeba inflata. A. quadrilineata (Carter). — 1-350". Mr. Carter has given this name to a supposed new species (A. N. H., 1856, xviii. pp. 243, 248), of which he gives a diagram, but no specific description. A. lateritia (Fresenius).-Rounded or oval, or drawn out at one end and rounded at the other. Processes thin, finely pointed; points very numerous; colour of a brick-red, becoming browner after death. In water at Walldorf with Spi- Yotamia. 1-20 to 1-10 millim. A, actinophora (Auerbach) (XXII, 12– 18).--When without processes, its form is more or less globular; and even when pseudopodes are protruded, the figure is usually not much altered, those pro- cesses being thin and spicular with pointed ends (fig. 13), though they do not exceed in length more than 1% the diameter of the body. This species is remarkable for the number of crystalline particles found in its interior, and for the processes never being entered by the granules of the interior of the body. Auerbach believes that the Actino- phrys viridis of Ehrenberg is probably no other than a large specimen of this Amoeba. It is closely allied to A. bilim- bosa, but is Smaller, its surface Smooth, its processes radiating and simple, not forked, its envelope thinner: it contains the peculiar crystals, and has no starch- globules as seen in the latter, 1-110" to 1–70". In water at Breslau. A. bilimbosa (Auerbach), (XXII, 7–11, 20–23).-Figure more or less globular when processes absent or few; pseudo- podes vary, being either wide and laminar with a spinous or dentate terminal mar- gin, or elongated and tubular. 1-50" to 1-35". A. porrecta (Schultze) (XXI. 8).-Hy- aline; processes numerous from all sides of the irregularly-shaped mass, from eight to ten times longer than the latter, divergent like so many fibres, with in- tercommunicating branches. Fissure very changeable and rapidly so; remark- ably locomotive. The fine granules seen to circulate through the processes. fresh and salt water. A. globularis (Schultze) (XXI, 2).-- Granular, delicate, yellowish-brown, central portion surrounded by a hyaline cortical lamina, from which the short, stumpy processes are very slowly pro- truded and withdrawn. Most of the processes are also remarkable from their rounded truncate ends being terminated by a retractile spine, Ancona. A. polypodia (Schultze). — Processes numerous, long, slender, with rounded or truncate extremities, and hyaline; movements tolerably active. Lagoon- water, Venice. A, Schultzii (XXI. 1).--—A species indi- cated but not named by Schultze; to distinguish it, we have applied to it that eminent naturalist's name. Central portion granular; surrounding lamina hyaline; no granules enter the interior. Processes short, tubercular, with rounded extremities. Possibly the same as A. verrucosa (Ehr.). In long-kept water from Ancona. Supplementary Genera, or Subfamily of AMCEBINA. Genus CORYCIA (Duj.).—An Amoebiform being, covered by a very expan- sible, elastic, flexible membrane or sac, which becomes folded in different directions by the movements and contractions or expansions of the animalcule, —the whole organism sometimes, after it has several times turned on itself, looking like a folded piece of linen. The membrane remains distinct after the animalcule is torn by needles, and the sarcode particles evacuated. The latter contract themselves into little balls, and, by the property of vacuolation, become hollowed by little cavities in larger or smaller numbers. The contents con- sist, besides Sarcode, of granules, vacuoles, and foreign particles; the first- named move in currents from one part to another. The expansions are not pushed forward, nor do they glide along the surface of reptation like those of Arcellina or of naked Amoebae ; they proceed from various points of the general mass or body, and seem to serve rather to change the centre of gravity than to furnish a point d'appui. 8-100" to 20-100". The name is suggested by the membranous envelope, which preserves the OF TELE ARCELLINA. 551 animalcules from being dried up during the alternations of dryness with moisture they are exposed to by their habitat in mosses. They are procured by lightly pressing the Jungermanniæ, moistened by the rains of November or December, or after they have been preserved a little time in water. This, as Dujardin remarks, is evidently a new genus, intermediate be- tween the naked and the loricated Rhizopoda, and standing in a certain relation with the Noctiluca. (A. S. N., 1852, vol. xviii. p. 240.) No species named. - Genus PAMPHAGUS (Bailey).-An Amoebiform being, covered by a deli– cate elastic integument, which, although it presents astonishing changes of form, and offers a certain amount of resistance to internal and external pres– sure, yet admits of the animalcule transfixing itself upon any denser thin portion of matter without any apparent damage (p. 220). They connect, says their discoverer, “the genus Amaeba with Difflugia, agreeing with the first in the soft body without shell, but differing in having true feelers or rhizopods confined to the anterior part of the body,” or to the region of the mouth, as in Difflugia. A specimen of Pamphagus, we may remark, is equivalent to a Difflugia without a true shell and with no ex- traneous matters to thicken and strengthen its covering. Dr. Bailey met with these animalcules in a vivarium, into which “bits of boiled beans and potatoes had occasionally been introduced as food for other animalcules,” and numerous starch granules were found in their interior. He also repre- sents it as having a mouth, and, being an adherent of Ehrenberg, as polygas- tric; but the mouth so described was the orifice of the Sac through which the pseudopodes were protruded, and therefore the homologue of the foramen of monothalamous shells. This genus is evidently very closely allied to Corycia (Duj.). The only difference of moment is that in the latter the expansions of the sac proceed from any part of the surface, whilst in Pamphagus its discoverer describes them as given off only from one spot at the anterior end. FAMILY II.-ARCELLINA (Ehr.) (Pt. I. p. 201 et seq.) (XXI, 6–17.) Amoebae invested with a single-chambered cell or lorica, having also but One opening, mouth, or foramen. The animal substance or sarcode contained within the shell is indistinguishable from that of the naked Amoebae, and is not more organized. The form of the pseudopodes given off from around the mouth of the shell are to some extent employed in defining species; but the size and conformation of the shell and of its opening are of much more im– portance systematically. * - Ehrenberg instituted this family for all one-chambered Rhizopodous shells which, in his belief, were of a silicious composition, and rejected from it Some similar shells which were of a calcareous character. This distinction, however, is based on erroneous notions (p. 219); and naturalists now concur in bringing together all unilocular Rhizopoda into one group, under the name of Monothalamia. The Arcellina were represented by Ehrenberg as polygastric animals, With an alimentary canal, and enclosed by a lorica, through the single opening of which they extended their variable processes. He also described digestive sacs, but was unable to discover either their mode of reproduction or their multiplication by fission or gemmae. Only four genera of Arcellina were enumerated by Ehrenberg; their cha- racters and mutual relations are shown in the following tabular view — 552 - SYSTEMATIC EIISTORY OF TEIE INFUSORIA. Changeable processes Lorica spherical or tum-like............... Diffugia. radiant, generally Lorica a flat spiral ........................ Spirillima. Illllllêl'OllS . . . . . . . . . Lorica discoid or shield-shaped ......... Arcella. Changeable processes broad and unbranched ........................... Cyphidium. The genus Spirillina is a very exceptional form; it has a spirally-coiled shell, apparently porous throughout, like one of the Foraminifera, and like them, too, a marine habitat. Its only affinity with the Arcellina, according to Ehrenberg’s account, is the silicious nature of the shell; but even were this established, it would not exclude it from the Foraminifera, among which silicious testae are known. Of Cyphidium little information exists; and Ehrenberg's account is by no means satisfactory. The same may be said of the figures he gives of it. Dujardin divides the “Rhizopodes,” excluding the Amoebaea, into two sec- tions, according to the form of the variable expansions. The first section cor- responds to the family Arcellina of Ehrenberg, and comprehends those species provided with short thick expansions, rounded at the extremity. Such are the Difflugiae, possessing a flexible membranous lorica, without visible tex- ture, mostly of globular form, from the aperture of which the expansions radiate: such, too, are the Arcellae, having a discoid lorica, flattened on the side along which they move (the plane of reptation), where is a central round opening, from which the expansions proceed, the latter lying thus be- tween the shell and the surface along which it glides; the lorica, moreover, is brittle, and often reticulated, or areolated. The second section, much larger, comprises beings of every variety of form, and having very numerous filiform expansions, ending by very fine extremities. Of these varieties he makes three tribes; the first distinguished from the Difflugiae only by the slender character of the expansions, except that in one genus, Trinema, the opening is lateral; the second, represented by the genus Euglypha, having a lorica beset with tubercles, or areolae, disposed spirally; and the third by the genus Gromia, having a spherical membranous shell, and very long and branching expansions. The remainder of the “Rhizopodes,” as described by Dujardin, are com- prehended in the Polythalamia by other authors. Of these he constitutes two tribes, one represented by the single genus Miliola, which, like Gromia and the examples of the first tribe, has but a single large opening in its lorica for the escape of the expansions; the other by several genera, all of which give off numerous filiform expansions from many distinct pores (foramina) of their shells, and hence called Foraminifera. Siebold included the first and second divisions of Dujardin’s class Rhizo- poda in his group of Arcellina. - M. Schultze framed the division of the Monathalamia from the structure of the shells; but he admitted amongst them the genus Orbulina, which possesses the very exceptional character of having numerous pores to its shell, instead of a single opening. The three families instituted were:— 1. Lagynida; 2. Orbulinida; 3. Cornuspirida (see p. 241). The first-named family corresponds most nearly to Ehrenberg's Arcellina, although it con- tains several genera usually described in histories of the Foraminifera, and omitted by the Berlin naturalist. The following are enumerated:—Arcella, Difflugia, Cyphidium, Trinema, Euglypha, Gromia, Lagynis, Ovulina (d'Or- bigny), Fissurina (Reuss), Squamulina, and the doubtful genera of Schlum- berger—Lecquereusia, Cyphoderia, Pseudodifflugia, and Sphenoderia. The genera Lagynis and Squamulina are two new ones formed by Schultze him- self. It will make this history more complete to introduce these new genera OF THE ARCELLINA, 553 of Lagynida, as well as the interesting Cornuspira described by Schultze. Of Fissurina we have no details. - Dr. Bailey, of New York, adds another new genus to the Monothalamia, under the name of Cadium. Genus DIFFLUGIA.—Shell of one chamber (unilocular) with a single aperture, usually of a more or less spherical or ovoid shape, but sometimes more elongated and clavate, or pitcher-shaped; thin, opaque, of a dark olive or brown colour, in general, when occupied by the living organism, but when empty, hyaline and colourless. The surface of the shell is either Smooth or sculptured, and occasionally armed with spine–like processes. In a few species, D. proteiformis, D. acuminata, and D. gigantea, the envelope does not acquire even the usual horny consistence, but is soft, and becomes strengthened by the adhesion of foreign particles of silex and other matters, which give it a rough, irregular appearance. The aperture or foramen varies in figure and size, and furnishes valuable specific distinctions. The pseudopodes are characterized as being cylindrical, not much elongated, and obtuse or rounded at the extremities. DIFFLUGIA proteiformis.-Ovate, sub- globose, covered by a coating of minute grains of sand, and either of a deep olive, black, or greenish colour. Processes hyaline, from 1 to 10. 1-240". Among Oscillatoriae. - D. oblonga.-Oblong, ovate, or orbi- cular, smooth, and of a brownish colour; processes fewer and stouter than those of the preceding species. Among Oscil- latoriae, &c. 1-200". Surface irregu- larly reticulated. D. acuminata. — Oblong and rough, with minute grains of sand; posteriorly pointed; processes hyaline. 1-70". D. Enchelys (XXI, 19 a, f).-Oval; co- lourless; translucent and Smooth, round- ed dorsally; processes transparent, slender and small; aperture lateral. This is the smallest species of the genus. 1–30" 1-15". In stagnant water. Du- jardin refers it to his genus Trinema. D. Ampulla-Oblong, club-shaped, ele- º marked by an oblique series of ots (puncta); hyaline; foramen ovate. 1–680". At Salzburg. D. spiralis (Bailey).--Sub-globose, mi- nutely granulated: upper surface un- equal, with a spiral line of two or three turns. Variable processes numerous, constantly changing position, hyaline. 1–680". Berlin and United States. Fresenius remarks that some large spe- cimens are met with coated with coarse particles, like D. proteiformis, instead of the usual finely reticulate lines. It attains, he says, in size to 1-7". D. acanthophora (XII. 64). — Ovate, oblong, loosely areolated; foramen den- tated; armed posteriorly with three or four spines (aculei). D. areolata.-Lorica and foramen as in the preceding, but the spines defi- cient. D. denticulata.-Ovate, oblong, smooth; foramen with twelve dentations. : D. Lagena.-Clavate, or of the form of a bottle; Smooth, without reticulations; margin of opening entire. D. laevigata.-Ovate, oblong, Smooth; foramen with eight dentations; ap- proaches D. denticulata. D. striolata.-Ovate, oblong, delicately striated longitudinally; foramen with a dentated border. D. Bructeri.-Oyate, surface rugose; the end presenting the aperture rather attenuate but truncate; margin of aper- ture entire. 1-1050". On moss. D. cancellata.-Oblong, obtuse; sur- face beset with imperfectly rounded cells, 5 to 6 in 1–2500”; aperture narrow, en- tire. .1–1040". On moss. D. ciliata. — Ovate, surface areolar; each posterior areola furnished with a cilium or cirrhus; constricted towards the foramen, which has 10 to 16 denti- culations. 1-936". Common in Her- cynia. D. Seminulum.—Shorter, ovate, brown, surface with narrow and small areolae ; aperture wide, very finely denticulated or entire. 1-2500" to 1-1250". On moss and stones. D. collaris.--Narrowed like a neck be- hind the aperture; straight, attenuate, pyriform or sub-clavate; surface irregu- larly cellular; cells small, but of equal size, except about the neck, where they are smaller; aperture entire. 1-840". About roots of trees. 554 SYSTEMATIC HISTORY OF THE DNFUSORIA. D. Dryas. – Ovate ; aperture entire, truncate; surface marked with longitu- dinal lines of ovate cells, which decrease in size posteriorly, 1-1170". On roots of trees. D. oligodon. — Smooth, oblong, sub- cylindrical; aperture with eight strong denticulations. 1-1000". This spacies and the two following found in Kur- distan. D. reticulata.-Ovate, surface marked by a net-work of minute cells; aperture simple, large. In its interior are mu- merous particles like aggregated buds; the margin of the foramen is sometimes dentate. 1-880". D. squamata.--Ovate, with large loose areolae, looking like Scales (squamae); aperture denticulate, truncate, contracted. 1–1450". D. spirigera.-Pyriform, smooth; neck distinct, cylindrical, truncate; orifice large, entire; opposite end turgid; round- ed. The surface presents four spiral lon- gitudinal lines. 1-36". Bavarian Alps. The first of the appended species is from Dujardin, the others from Schlum- ; (Ann, des Sciences Nat. 1845, . 254):— D. globulosa (XXI. 10).-Brown, glo- bular, or ovoid, smooth. 1-260" to 1–105". Near Paris. D. depressa,—Diaphanous, ovoid, de- pressed, resistant; its surface divided by slight fissures (lines) into numerous small and irregular polygonal sections. 1-220". Aperture with an uneven mar- gin. In springs in the Vosges. D. gigantea.—Greyish brown, rough, as if strewed with particles of sand, ovoid, elongated, and contracted an- teriorly. 1-325" to 3-325". . It ap- proaches D. proteiformis, but differs in its more elongated form, in being con- tracted anteriorly and almost pyriform, sometimes depressed, and lastly in its greater size: margin of aperture uneven. D. tricuspis (Carter).--Processes occu- ied by granules, greenish; testa ovoid, ittle incrusted; its foramen tricuspid in form, or of trefoil shape (A. N. H. 1856, xviii. p. 247). Fresenius appears to have met with this form, but considers it only a variety of D. oblonga. 1-320". D. P. marina (Bailey).-Shell silici- ous (P), ovoid or lagenoid, with a con- tracted neck and circular aperture; sur- face divided by oblique lines into quadri- lateral spaces, ºr of 1-1000", diam, 1% of 1–1000". A single specimen was found in Sound- ings taken from a depth of 2750 fathoms, which had been cleaned with acids. This resistance to acids induced Dr. Bailey to consider the shell silicious, but we now know that chitinous shells are equally unaffected. The discoverer doubted its being a Diffiugia, on account of its marine habitat. Genus SPIRILLINA.—Lorica tubular, silicious (?), rolled in a spiral manner, like a Planorbis. acids have no action on the shell). It is allied to Difflugia by its silicious lorica (for This genus probably agrees with the Spirulina of Bory de St.Vincent; but the latter name has been otherwise used by Ehrenberg to designate a genus of Polythalamia, - SPIRILLINA vivipara (XI. 37).-Shell orous, convoluted as a circular, spiral, orizontal tube, hyaline and Smooth. Young lorica may often be found con- nected with it. In the sea—Vera Cruz, Mexico. The form of this species recalls that of many undoubted Polythalamia, whilst it has no fellow amongst the Infusoria. Ehrenberg has likewise represented ap- parent dots or pores on its surface, like those through which the filiform pro- cesses of Polythalamia are protruded; and the only reason implied in Ehren- berg's account for reckoning it among the Polygastrica is its silicious shell: it is, however, most probably chitinous. It will be noted that Ehrenberg is inclined to believe it viviparous. Genus ARCELLA (XXI. 7–9, 15).-Variable processes, numerous and hyaline; single processes cleft into many, and expanded in a radiating manner; lorica flattened, shield-like. The lorica varies much in structure in the different species. For instance, in A. vulgaris it exhibits regular and delicate facets; in A. dentata the facets are large and crystalline; in A. acu- leata it is beset with spicula; and in A. hyalina it is homogeneous and clear. Vacuoles are seen filled with coloured vegetable substances; and in OF THE ARCELLDNA. 555 A. vulgaris and other species a contractile vesicle has been perceived. The processes are longer, as a rule, than those of Difflugia, fibrous, and more branched. The shells are very commonly compressed, and have a discoid figure; and in none are they soft and beset with extraneous particles, as in Difflugia, but are chitinous and elastic. - - “The Arcellae (says Dujardin) seem to differ among themselves by the intimate structure of their lorica, which sometimes appears membranous, at others finely striated, reticular, or with granules disposed in spiral lines. Some Arcella, have also spinous prolongations from the border of their lorica. Pressure fractures their lorica like a brittle substance. The contained sub- stance escapes through the cracks so formed, in the form of contractile expan- sions like those of Amoebae. I have seen one larger lobe almost separated, as if about to become an independent being. M. Peltier has observed con- tact to take place between the expansions of neighbouring Arcellae without any union being effected, while the processes of the same Arcelloe united and became blended together. “The lorica in young Arcellae is extremely diaphanous; and granulations or striae are to be seen only in those of larger size: hence it may happen, with respect to some species, that they represent but different stages of existence of the same animal.” ARCELLA vulgaris (XXI, 7, 8, 9). — Lorica round and bell-shaped, with a hemispherical or turgid back; smooth, but with rows of minute granules; colour yellow or reddish-brown. Abundant amongst Lemnae and aquatic plants. 1-570'' to 1-240." A. aculeata.-Yellowish, hemisperical, though often mis-shapen, and spinous throughout, or only around one-half of the margin; the shell is not readily de- stroyed iy heat, and is covered with short spicula. 1-210". A. dentata. — Membranous; of a he- mispherical or polygonal form ; margin dentated; colour yellow or green. Amongst Confervae. 1-570" to 1–240". A. ö) hyalina.-Membranous, Smooth, elliptical or globular, smaller than the Fº thin and soft, colourless. ound in débris at the bottom of pond- water, along with Cyphidium aureolum, &c. 1-1150 to 1-570". The shell is not quite symmetrical, one side being more convex than the other. Aperture sometimes irregular. Ehrenberg was not certain that this species is not a Diffiugia. It is indeed very like many specimens of D. Enchelys. As Americana. – Oblong; aperture Small, round, not in the median line. A. constricta.-Ovate; slightly con- tracted about the foramen, which is very large and to one side. A. disphaera. — Oblong, almost di- vided into two by a central constric- tion; one-half nearly occupied by the large foramen. This is a very doubtful Arcella, and contrary in form to the character of monothalamous cells. A comparison of Ehrenberg's account with his figures leads us to believe this sup- posed species to be no other than a young Rotalia of two cells (xx. 41), or other incomplete polythalamous shell. A. ecornis.--Large; hemispherical, not areolar; aperture round, large, placed to one side ; entire. A. lunata—Subglobose, large; with 8, yº Semi-lunar opening, seated to one SICl62. A: Nidus-pendulus. – Ovate-oblong, hyaline, loosely areolated; aperture in front, oblong, margin entire. A. Pileus.-Hemispherical, depressed, reddish, minutely . elegantly areolar; aperture central, circular. - A. P. Globulus. – Subglobose; with loosely reticular lines, appearing granu- lar; aperture large, simple. 1-780". On moss at Berlin, Potsdam, &c. A. granulata.-Oblong, hyaline. Has the habitat and size of A. hyalina, with a granular instead of a smooth surface. 1-940”. On moss in Hercynia, &c. A. caudicola,—Ovate, oblong, rounded at each end, hyaline, very delicately hispid, not areolar; aperture anterior, round, large. 1-840". Habitat of A. Nidus-pendulus. In Venezuela, on roots of plants, such as ferns, &c. . Okenii (Perty) (xxi. 15). Genus CYPHIDIUM (XXII. 24–27).-Has only one dilated variable process, and a lorica of the form of a pitcher, with protuberances issuing 556 GENERAL HISTORY OF THE INFUSORLA. from it. The lorica is combustible, and is something like a little die or stamp, mounted upon a short stem. It is very irregularly formed, having protuberances which make it appear four-cornered. The organ of locomo- tion is a broad gelatinous variable process with Smooth edges, not unlike Amoeba verrucosa. Vacuoles have not yet been observed; modes of propaga- tion unknown. * CYPHIDIUM. aureolum (XXII. 24–27).- tion they might be seen to change their Lorica cubical, with protuberances; pro- places.” Ehrenberg only once perceived cess colourless. “In March, 1835,” says the locomotive organ of the animalcule, Ehrenberg, “Ifirst observed hundreds of situated under one corner, upon which these creatures in a glass of water which it appeared to rest, and that so firmly that had stood throughout the winter, in com- six out of the eight protuberances of the pany with some specimens of the Mi- die-like lorica were visible at the same crasterias. Previously to discovering time. In fig. 26 the gelatinous variable these, the Amaeba verrucosa had been process is seen projecting from beneath abundantly generated, and afterwards the lorica. Fig.27 is a young specimen. Arcella hyalina. The creatures were in- || 1-570" to 1-430". active, although by attentive sº- - Genus TRINEMA (Duj.).—Shell membranous but resistant, diaphanous, ovoid elongated, narrower in front, with a large oblique orifice placed late- rally ; expansions filiform, as long as the shell, very thin, and but two or three in number; entirely retracted when others are to be pushed out from another side. The animal is moved onward by their alternate protrusion and contraction. This genus is accepted by Fresenius. TRINEMA Acinus. = Diffugia Enchelys (Ehr.) (p. 553). Genus EUGLYPHA (Duj.).—Shell diaphanous, resistant, membranous, elongated, ovoid, rounded at one end, terminated at the other by a very large truncated orifice, with a dentated margin ; its surface marked by emi- nences or depressions, in regular oblique series; expansions filiform, nume- rous, simple. EUGLYPHA tuberculata.-Lorica stri- E. alveolata (XXI. 11).-Lorica with ated, with rounded tubercles. Termina- regular polygonal depressions in regular tion of expansions extremely delicate. oblique (spiral) series, bearing spines at 1-295". Found in stagnant ponds. the upper or posterior end, 1-290". Genus GROMIA (XXI. 12, 16) (Duj.).—Lorica smooth, yellowish-brown, membranous, soft, globular, with a small round opening, from which the very long branching expansions proceed, tapering to very fine extremities. Found in both salt and fresh water. GROMIA oviformis-Globular, smooth, branching and amastomotic. 1-865" to aperture sorrounded by a short neck; ex- || 1-520". In rivulets. pansions very long, fibrous, branching, |, “Notwithstanding the absence of co- slightly anastomotic, colourless or pale- |lour in the shell,” says Schlumberger, yellow, transparent; animal contents “I arrange this species in the genus of a yellow or reddish-brown colour; Gromia. In size it also differs from the the processes hyaline, permeated by a other two species. The lorica, being current of granules. Shell 1-26" to transparent, admits to view some bluish 1–13". - globules, and a large hyaline glandular G. fluviatilis. – Globular, or ovoid, ovoid body, like that in the interior of without a neck; expansions palmate and other diaphanous Rhizopodes.” amastomotic. 1–290" to 1-104". G. Dujardinii (Schultze).-Shell sphe- - G. hyalina (Schlumberger, A. S. N., rical, ovoid; more constant in figure than 1845, p. 254).-Globular or rather ovoid, G. oviformis, colourless or faint yellow, smooth, soft, diaphanous, colourless; with a short neck-like elongation at the foramen round, with a very short neck, foramen, or none; animal contents dark formed by a reflexion of the lorica; ex- sepia-brown ; processes hyaline, with no pansions filiform, numerous, very fine, moving granules. Diam, 1-2". Ancona. OF TEIE ARCELLINA, 557 Genus LECQUEREUSIA (Schlumberger).—Shell ovo-globular, or retort- shaped, rather depressed, membranous, but resistant ; with a wide short neck, and circular terminal aperture, giving passage to cylindrical thick and obtuse expansions. This genus approaches Difflugia (Duj.) in the character of its expansions; but the very different form of the shell, and the position of the aperture, sufficiently mark the distinction between the two. Its distinctness is re- garded with doubt by Schultze. LECQUEREUSIA jurassica.-Shell re- aquatic plants, in many of the lakes of sistant, diaphanous, grey, of a globular the Jura chain about Neuchatel. Its figure, but rather depressed, with a short | diaphanous lorica allows its interior soft wide neck. Length about 1-250"; breadth hyaline and granular body, strewn with 1-315". brown specks, to be seen. This beautiful species is met with on Genus CYPHODERIA (Schlum.). —Lorica membranous, resistant, ovoid, elongated anteriorly, where it is curved and constricted in the form of a neck; surface marked by prominent points in oblique rows; aperture circular, oblique; expansions very long, filiform, very fine at the extremity, and simple or branching. The oblique disposition of the rows of points, the obliquity of the aperture, and the character of the expansions, bring this genus into affinity with Tri- nema (Duj.); but the constriction, forming a neck, seems sufficiently distinc- tive between the two. This genus, though admitted by Fresenius, is treated as doubtful by Schultze. CYPHODERIA margaritacea. — Lorica water of the Vosges with vegetable débris. yellow; the surface is divided into mi- The form of the . varies; at one time nute facets, which appearlike translucent the neck may be but rudimentary; at boints or rows of pearls. Processes attain another the posterior end, instead of twice the length of the shell, and are being wide and rounded, is contracted simple or branched. Length 1-395"; suddenly to a truncated apex. Aperture breadth 1-840" to 1–408". Common in the crenulate. Genus PSEUDO-DIFFLUGIA (Schlum.). — Shell membranous, ovoid or ovo-globular, smooth or striped spirally, with a wide round opening, whence proceed numerous long slender expansions, either simple or branching. This genus is allied to Difflugia by the form and character of its shell, but differs from it in the nature of the expansions; it is admitted as doubtful by Schultze. PSEUDo-DIFFLUGIA gvacilis. – Shell | filiform, very long. Ilength 1-740" to bluish brown, brittle; surface as if beset | 1–465"; breadth 1-890" to 1-740". Found with minute grains of sand, of a more or near Mulhouse. less sºft ovoid figure; expansions Genus SPHENODERIA (Schlum.).—Shell diaphanous, colourless, resistant, globular, with a flattened wedge-shaped neck; surface marked by polygonal depressions, disposed in regular oblique rows; aperture terminal, compressed, almost linear. Expansions filiform, very long and attenuated. The form of the aperture and of the neck separates this genus from Trinema and Euglypha, to which it is allied by the structure of its lorica. Schultze treats it as a doubtful genus. SPHENODERIA lenta.-Lorica as above | slender and simple, or branching, 1–650” described, expansions few, very long, to 1-520". Of all the Rhizopodes I have examined (says Schlumberger), this is the slowest in its movements, and its expansions the most difficult to discover. I have found it on tufts of moss in marshy rivulets, 558 SYSTEMATIC EIISTORY OF TEIE INFUSORIA. A glandular body and hyaline globules are seen in the internal soft sub- stance near the posterior end. In moving, the position of the shell may be perpendicular, or oblique to the surface of reptation: the hexagonal depres– sions are indistinct but large. The shell fractures along the lines of junction between the hexagons. Along with the preceding genera, Schultze, as before stated, includes in the division Monothalamia the new genera Lagymis, Squamulina, and Cornw- spºra. Genus LAGYNIS (Schultze).-Shell membranous, elastic, retort-shaped; body colourless, transparent; foramen large, but the processes few, very fine, occasionally branching. It forms the type of the family Lagynida. LAGYNIS baltica.-The transparent | The form of the shell approaches that contents rarely fill the shell, but leave a of Euglypha (P) curvata, described by space posteriorly, into which they send Perty, and found in an empty state by processes which converge towards the him on the Simplon, at an altitude of summit of the concavity of the posterior, 4000 to 5000 feet. rounded extremity. 0.05". Baltic Sea. Genus SQUAMULINA (Schultze). —Shell calcareous, plano-convex, or lenticular; adherent by the plane surface; cavity single, one large opening on the convex side; no pores. SQUAMULINA lavis-Irregularly cir- |ject to which it adheres. The yellowish cular; much flattened; convex portion animal protrudes numerous processes thick and smooth, the flat portion very from the excentric foramen. Largest thin and scarcely separable from the ob- diam. 1-26". Sea-water, Ancona. Genus CORNUSPIRA (Schultze).-Shell calcareous, spiral, like a Pla- morbis shell; Solid or finely porous; discoid ; symmetrical, i. e. with both sides alike; cavity single. One large foramen at the termination of the spiral. CoRNUSPIRA planorbis.--Shell trans- dually larger towards the termination of lucent, brown, without pores; six or the spiral; as many as seven turns seen. perhaps more turns of spiral seen. Mud ||On the coast of Mozambique. from the coast of Mozambique and D'Orbigny's Operculina inserta is pro- Trieste. bably the same form. The Spirillina de- C. perforata.-Finely porous, hyaline, scribed by Ehrenberg is somewhat like, colourless; pores circular, becoming gra- but is probably only a young Miliola. Genus CADIUM (Bailey) (XXII. 19).-Shell silicious (chitinous?) ovoid; elongated as a sort of neck, which is bent upwards and outwards, terminated by a circular foramen. This genus was instituted by the late Dr. Bailey, of New York, to include some empty Rhizopodous shells met with in the soundings taken in the gulf- stream. (Silliman's Journ. xxii. 1856.) CADIUM marinum (XXII. 19).-Shell which about 12 are visible at once, marked by numerous meridian lines, of Length 2-1000"; diam, 13-1000". Sub-group ACTINOPHRYINA. (Part I. p. 243.) (XXIII, 24–37.) A sub-class of Rhizopoda having a more constant and definite form, and furnished with long tapering retractile filaments or tentacles, which serve as prehensile organs, in the place of the usual variable processes of the class. OF THIC ACTINOPEIRYINA, 559 Their movements are excessively slow, and sometimes inappreciable; and the tentacles appear not concerned in them: conjugation is of very frequent OCCUITTOIlC6. . The genera enumerated in this section are Actinophrys, Podophrya, Tri- chodiscus, and Dendrosoma. The distinction between the two first-named genera is denied by Stein, and probably with reason, for the stem of Podo- phrya is not sufficiently characteristic (vide Part I. p. 243). Trichodiscus is little known to observers, and probably is only a variety of Actinophrys; and Dendrosoma has hitherto received little attention; its branched pedicle, how- ever, gives it a generic importance. Dujardin formed a very correct conception both of the organization and affinities of the Actinophryina, which were coupled with Amoebaea and Rhizo- poda in his second order of Infusoria. He rejected the genera Podophrya and Trichodiscus, which he merged in the genus Actinophrys. Siebold very strangely overlooked the true structure and affinities of Actinophrys, which he placed with Enchelia, in company with the very dissimilar Prorodon, among his “Stomatoda.” Perty has constituted Actinophryina a second section of Ciliata, and has adopted the genera Actinophrys, Podophrya, and Acineta. Thrichodiscus he regards as only a compressed form of Actinophrys, and treats Dendrosoma as an aggregated one, in which the individual beings are collected into colonies. Genus ACTINOPHRYS (XXIII. 28–32).-Body more or less spherical, usually compressed or discoid, Sometimes irregular in outline, owing to the projection of Superficial vacuoles. Tentacles tapering, terminated occasionally by a rounded head (i.e. capitate), pretty uniformly distributed, their length generally exceeding the diameter of the body; retractile, and for a time lost in the substance of the body, but reappearing at the same place and under the same form. The tentacles serve for prehensile instruments, but not for locomotion. Food is introduced within the body at any part, and not through , a mouth; and its excrementitious portion is in a similar manner discharged from any part of the exterior. Internally are one or two contractile vesicles, placed immediately beneath the surface, a nucleus with a nucleolus, ali- mentary vacuoles, granules, and probably small nuclear cells. Reproduction takes place by fission, and in Dendrosoma by gemmation. Germinal deve- lopment is presumed, and conjugation is a frequent phenomenon. The proboscis mentioned by Ehrenberg appears to be a sort of expansion of the sarcode of the body, homologous with a variable process, which enve- lopes and then drags the prey into the general mass. Ehrenberg believed he had discovered a mouth, anus, and polygastric structure, and that he had succeeded in demonstrating this last by feeding with coloured food. He likewise adopted Eichhorn’s statement—that the tentacles acted as locomotive organs, by giving the animalcules the power to crawl. The specific distinctions hitherto attempted are really of little worth; even the highest authorities are in doubt, and disagree among themselves, respect- ing the specific names of the animalcules they so elaborately describe; and the revision of the several forms and varieties of Actinophrys is urgently re- quired before any satisfactory separation into species can be made. We append those forms which have been accounted specific by different authors. ACTINOPHRYS Sol (xxLII. 28, 31, 32). spherical, or nearly so; the tentacles or —Colour whitish, or rather grey; figure | rays divergefrom every part of the surface, 560 SYSTEMATIC IIISTORY OF TELE INFUSORIA. and taper to their extremities, and equal the diameter of the body in length. Found in the dust-like matter upon the surface of infusions, and among Confervae and various aquatic plants. Stein asserts that these habitats are those of A. Eich- hornã, not of A. Sol, which does not oc- cur as a free being. 1-110" to 1-53." This species has been very much con- founded with A. Eichhornia. Kölliker mis- took this last for A. Sol; and Claparède wrote his description of A. Eichhornia, and afterwards discovered it was A. Sol that he had investigated. Indeed the brief characters furnished by Ehrenberg are quite inadequate to identify the species. A. Eichhorniö (XXIII, 29). — Large, white, globose; tentacles shorter than the diameter of the body, and tapering. The cortical and medullary layers arewell distinguished; the former contains nu- merous vesicles. Tentacles contractile, seen to bend themselves in the prehen- sion of food, &c. Stein affirms that the being which Ehrenberg described and figured under this name is no other than A. Sol, that the tentacles are by no means always shorter than the diameter of the body, but often longer, and that this circumstance of relative length can- not be used in the diagnosis of the spe- cies, but that the conical figure of the tentacles is distinctive. Stein's views on these specific details must be re- ceived cum grano Salis; for the influence of his Acimetiform hypothesis pervades his systematic history of the beings of the class under notice, and his figures of 4. Sol prove him to have been in error either in the observation or in the interpreta- tion of the organism ; for they indicate a member of the Acinetina rather than of the Actinophryina. Perty seems to think the largest specimens of A. Sol constitute A. Eichhorniö (Ehr.). A. oculata (Stein) (XXIII. 24, 25).-- Round, more or less discoid, with several concentric circles of vesicular spaces dis- tributed over the surface of the animal- cule, giving it an undulated outline. The tapering, pointed tentacles arise from the eminences of the surface, and are equal in length to the diameter of the body, except in small specimens, in which they rather exceed it. The periphery of the body is covered with a homo- geneous, transparent, gelatinous, appa- rently thick layer, within which the large, vesicular, non-contractile Spaces, filled with water, are found. Besides this superficial layer, a cortical and a medullary substance are clearly pro- nounced. The particles of food do not enter the medullary substance. The finely granular nucleus is central, Sur- rounded by a ring of clear medullary matter. Pressure, after the action of acetic acid, will sometimes detach it as a free body, invested by a membrane, and having within it an ill-defined granular nucleolus. Diam. 1-38" to 1-35". A. viridis (Ehr.).--Spherical, greenish; rays numerous, shorter than the diameter of the body. Diam, of body 1–620" to 1-280". Amongst Confervae. A. difformis.--Irregularly lobed, de- Fº and hyaline; rays variable in ength, some exceeding the diameter of the body, which is from 1-570" to 1-280". The animalcule thus described Stein ap- prehends to be nothing more than several young specimens of A. Eichhornii con- joined (conjugated). A. marina (Duj.).—Differs from A. Sol in its habitat, and in the more marked contractility of its rays. Amongst micro- scopic Algae in the Mediterranean. Pro- bably a mere variety of A. Sol. The claim of A. viridis, A. difformis, and A. marina to specific distinction is extremely doubtful. The green colour of the first is immaterial, and the rela- tive length of its rays to the body of no specific importance. The irregularly- lobed outline of A. difformis, again, is an immaterial condition; for the soft bodies of true Actinophryima admit achangeable outline, and the reception of food, more- over, to a certain extent involves it. Dujardin justly attributes no other value to his species A. marina, than that it may serve to indicate an Actinophrys living in the sea. A. pedicellata (Duj.)=Podophrya fica. A. digitata.-(Duj.).—Depressed; rays flexible, thicker at the base, forming, when contracted, short, thick, finger- like processes. Diam. 1-750". In fresh water containing marsh-plants. Its dis- coid body would rather place it with Thrichodiscus. A. granata (Duj.) (Trichoda granata, M.).--—Globular, opaque at its centre, Sur- rounded by rays of less length than its own diameter. A. Discus (Duj.) = Trichodiscus Sol Ehr.). ( A. ovata (Lachmann). — A species named by this naturalist in A. N. H. 1857, xix. p. 221. A. brevicirrhis (Perty).--Of a dusky yellowish green colour, rarely colourless; tentacles much shorter than the diameter of the body; not capitate, but bristle- () F THE ACTINOPEIRYINA. º 561 like. Its outline is double, with a green recognizing this organism to be an or red line. Length 1–600" to 1-500" | Actinophrys, should not have adopted Bern. Among Confervae. Dujardin's very appropriate name for it, A. Stella (Perty) = Trichodiscus Sol.— It is to be regretted that Perty, whilst rather than encumber the student with another. Genus TRICHODISCUS.—Body depressed, with a single marginal row of Setaceous tentacles; vibratile cilia and teeth absent; no pedicle; mouth truncated (Ehr.). These Infusoria, by their flat disciform shape, resemble Arcellae, but, un- like the latter, are soft and illoricated, with stiff, bristle-like rays. A central opening, and a large lateral gland (nucleus), have been recorded by Ehren- berg, who likewise states that he has seen, though indistinctly, numerous digestive cells, but neither the reception of coloured food, nor an anal orifice. This account is very unsatisfactory as a means of determining a genus. The discoid figure is not a sufficient distinction from the genus Actinophrys; and, on the other hand, the softness of the integument, compared with the lorica of Arcella, is not a generic distinction; for the so-called lorica of the latter genus is in many instances only a flexible integument. Cohn (Zeitschr. 1853, Band. iv. p. 262), after remarking on certain Acti- nophryean beings covered with adherent foreign particles of sand, Cyclo- tella-shells, &c., and surmising that such beings were no other than Difflugice engaged in the formation of a lorica, submits the opinion, in a foot-note, that Trichodiscus Sol (Ehr.) is a similar organism, because Ehrenberg describes its tentacles as proceeding from the middle of the body, which is often partially coloured with brownish corpuscles. TRICHODISCUS Sol. (Actinophrys Dis- cus, D.)-Depressed, almost flat, hyaline or yellowish, with variable rays. The motion of this species is very sluggish ; it often remains for a long time inert. Amongst Confervae. Diam., without rays, 1-430" to 1-210", Perty, as already seem, retains this spe- cies with Actinophrys, with the name of A. Stella, Genus PODOPHRYA (XXIII. 34–37). The members of this genus differ from Actinophrys Only in being stalked. Stalk single, not branched. Eh- renberg described them as Enchelia devoid of vibratile cilia and teeth, with spherical bodies, covered with setaceous tentacles; having a truncated (direct) mouth ; and in organization equivalent to Actinophrys, with a stiff stalk. PopoPHRYA ovata (Alder). — Body ovate, with a very slender and short stem ; tentacles capitate, retractile, in a single row, less numerous than in Ephe- lota apiculosa, and forming a narrow disc. Parasitic on Sertulariae. P. pyriformis (Alder). —Body pear- shaped, or rather campanulate, with a di- stinct rim around the summit, and a sin– gle circlet of delicate, capitate, retractile tentacles; stem long and slender, Pa- rasitic on Paludicella, and, unlike the preceding, an inhabitant of fresh water. These two species were first described by Mr. Alder, along with Ephelota apicu- losa, and were described in the previous edition of this work, under the name of “Alderia.” Lately, however, Mr. Alder wrote to inform us that this name had been applied to a different class of ani- mals, and therefore could not be retained. Dr. Strethill Wright has since studied these beings, and distinguished one as Ephelota apiculosa, and placed the other two among Podophrya. Mr. Alder (A. N. H. 1851, vii. p. 427) recognized their relation to Acinetae, and their affinity to Campanularian Zoophytes, between which and Infusoria, he considered them the most perfect link known. - P. fiva (Trichoda fica, M. Actino- phrys pedicellata, D.).—Body spherical, turbid, whitish, with a diaphanous pe- dicle slightly excised at the extremity. The rays or tentacles are capitate at the extremity, and equal in length the dia- meter of the body. Ehrenberg states that the seizing or catching power of this animalcule is very interesting to ob- serve. So soon as a quickly-vibrating 2 o 562 SYSTEMIATIC HISTORY OF TEIIC INFUSORLA. TrichodinaGrandinella approaches to, and comes in contact with, its tentacula, it is immediately taken prisoner, ceases to vibrate, and stretches out its cilia back- wards. On the whole, this species re- sembles Acineta; but Ehrenberg Sup- of pond-water, “and perhaps,” says Ehr., “also in the sea.” Diam. 1-430". P. libera (Perty).--Stemless, spherical; colourless, or faint yellow; periphery Smooth; tentacles hyaline, pointed in greater or less number, many very long, sometimes very few present, many seem curved. Diam. 1-380". In stale pond- Water. - posed it to possess a discharging orifice, though its situation is unknown. Found among dust-like matter upon the Surface Claparède and Lachmann have recently (Ann. d. Sc. Nat. 1857) distin- guished a number of species of Podophrya, many of which would be accounted Acinetae by Stein; however, they have no capsule like members of that genus. No characters are given. The following are noted: — 1. Podophrya Cy- clopwm, parasitic on Cyclops and Lemnae; 2. P. Carchesii, on Carchesivm polypinum ; 3. P. quadripartita, the same as the Acineta assigned by Stein to Epistylis plicatilis; 4. P. Pyrum, a large form, pear-shaped, found on Lemma trisulca; 5. P. cothwºmata, the diademiform Acimeta of Stein; 6. P. Ferrum-equinum, the Acineta of the same name of Ehr. ; 7. P. Lyngbyei, the Acineta Lyngbyei (Ehr.); 8. P. , a marine form, with extremely dila- table suckers. Genus DENDROSOMA (Ehr.).—This includes beings which resemble Actinophrys, supported on a branching pedicle. The base of the thick pedicle or trunk is fixed; and its divisions bear the animalcules at their ex- tremities. polype. In appearance, therefore, it resembles a microscopic Sertularian The question may be raised, if this genus is not the same as Anthophysa (p. 500), misinterpreted in structure; and if the organisms terminating the branches are not Uvellae instead of Actinophrydes. DENDROSOMA radians. – Corpuscles | tentacula; disposed on a soft, smooth, and (animalcules) conical, furnished with alternately branched stem. At Berlin. Genus EPHELOTA (Wright).-Similar to Podophrya ; but the tentacles, instead of being capitate, are pointed, and form a wreath or circlet. They seem also to be either slightly contractile or retractile, or only flexible. Pedicle composed of a cortical matter or integument, and a medullary or contained substance. EPHELOTA apiculosa,—Body vase- or cup-shaped, expanded, at top and set round with several circlets of numerous pointed tentacles; abruptly thickened to- wards the base. The tentacles, which are always in more than one row, enjoy little motion, curve themselves forward occasionally, and are slowly retracted at times. Pedicle stout. Found parasitic on Sertularia; by Dr. Wright on Coryne. It differs from E. coronata in having the body wider than the stem, more cup- shaped and elongated, and the tentacles more irregular,Soft, retractile, and unsup- ported by the solid matter which occurs in the interior of those of the species named. It is especially distinguished by the shape and structure of the stem, whichisof nearly equaldiameter through- out, and encloses a cortical substance formed of circular fibres passing at right angles to the fibres of the medulla, which cortical fibres are absent in E. coronata. E. coronata (Wright).-Body consists of a short cylinder of densely granular Sarcode, slightly enlarged above and be- low, so as to resemble the circlet of a crown. It is surmounted by a circle of thick, acuminate and radiating tentacles, which are capable of being slowly curved inwards, but cannot be contracted. They remain stiffly extended when the animal is immersed in alcohol. The structure of the tentacles, I believe, is unique. Under high microscopic power they are seen to consist of a bundle or framework of fine arallel rods of horny (?) texture, imbed- ded in soft contractile sarcode. The more central rods of the bundle protrude con- tinually beyond those exterior to them, OF TELE ACTINOPEIRYINA. 563 so that the point of the tentacle is formed of only a very small number. In other examples, each rod, under a power of 800 diam, assumed a bearded structure. “The animal secretes beneath itself, or from its base, a pedicle of diaphanous and colourless substance, which increases in length and breadth with the increasing growth of the animal, until it assumes the form of a glassy club, on the thick upper extremity of which the animal is seated. The whole of the pedicle is covered by a growth of scattered hairs; but it may be doubted whether these have any organic connexion with it, and whether they do not belong to one of those minute classes of Algae the structure of which eludes microscopic research. A longitudinal fibrous struc- ture is faintly seen in the axis of the pedicle, but it gradually disappears to- wards the periphery. After immersion in spirit, this fibrous structure becomes much more apparent. The action of the spirit also causes a fine membrane to separate from the surface of the pedicle, which appears to be continued down- wards from the body of the animal, and is probably analogous to the membrane which I have already shown to exist as a liming and covering to the cell of Va- ginicola valvata, and which Secretes and hides within itself the valve that closes the cell of that curious animal’’ (Edin. New Phil. Journ. 1858, p. 7). This species was twice seen by Dr. Wright, “each time in large colonies, situated within the mouth of shells in- habited by the hermit-crab, where the dense white bodies of the animalcules, seated on their transparent pedicles, form sufficiently remarkable objects.” Genus ZOOTEIREA (Wright) (XXXI. 14–15).-Body furnished with numerous contractile acuminate rays (tentacula); elevated on a contractile pedicle. tended, but not capitate. Zoot EIREA religata (XXXI, 14–15).- The body of the animalcule, when con- tracted, consists of densely granular Sar- code surrounded by a layer of more transparent substance. This external coat is capable of being prolonged into innumerable exceedingly attenuated ten- tacles or rays, from eight to ten diameters of the body in length, and resembling in structure those of Ephelota apiculosa. The animalcule is elevated on a long contrac- tile pedicle, which appears also to be Rays becoming thickened towards the point when not fully ex- continuous with the external coat of the body. I have several times seen this animal, always in colonies. When seen by oblique illumination, it has a very striking appearance. The light reflected from the rays has the appearance of two cones issuing on opposite sides of the body, and rotating in opposite directions with every movement of the lamp. Found on shells dredged from deep water in the Firth of Forth. We are indebted to Dr. Strethill Wright of Edinburgh for the knowledge of this genus and species. Dr. Wright was So kind as to transmit the account to us in manuscript, together with notes on Ephelota, the characters of the following peculiar genus Corethria, and those of several additional Infusoria. Genus CORETHRIA (Wright) (XXXI. 5, 6).-The history of this genus is thus described (in literis) by its discoverer, in the details of the structure of the only species yet found, viz.:-" Corethria Sertularice consists of a body, or oblong cushion-like mass of granular sarcode, furnished with a long club-shaped appendage, which bears at its summit a thick brush of tentacles. The body is generally homogeneous, although occasonally one or two large cells are seen within it. The mop-like appendage is seen to contain two structures, both without granules. The interior or medullary portion is a transparent and structureless cylinder, arising from a slight depression in the body of the animal. The exterior structure, also transparent, is transversely wrinkled or rugose. The tentacles are transparent, from eight to about forty in number, and have occasionally a slight waving motion: they appear to arise from the internal lamina or core of the mop. A second kind of appendage is frequently found attached to the body of Corethria, in the form of a long spindle-shaped 2 O 2 564 SYSTEMATIC EIISTORY OF THE INFUSORIA. Smass of granular sarcode, similar to the body, having a depression, perhaps an orifice, at its distal end. This is either a parasite or a gemma, as it is some- times found attached alone to the Sertularia. It appears to multiply by fission, as two are sometimes found attached together.” In another letter, Dr. Wright remarks that he has “doubts as to the Gre- garina-like body being a part of the animal, as it is often absent,” and he has “seen it fixed to neighbouring bodies.” Food is probably taken up by the Summit of the mop-like process, absorbed, and carried down to the body. Dr. Wright has found this remarkable animalcule three successive years at Granton, in great abundance, though in a limited locality. It occurs at all parts of the polypidom of the Sertularia pumila, but chiefly in the angle between the mouth of one cell and the lower part of the cell above, where two or three sometimes nestle together. Although unlike all other animalcules in shape, Dr. Wright is induced by its structure to place it near Actinophrys. Were it not for the cushion-like body, the mop-headed process would be referable to Ephelota. Subgroup ACINETINA. (Part I. p. 258.) (Plates XXIII. 1–27; XXVI, 3–4; XXVII. 13–15, 18–20; XXX. 3, 4, 8, 21–23.) A subclass of Rhizopoda, very closely resembling Actinophryina, but covered by an integument or capsule, through which the retractile tentacula or fila- ments are protruded, and usually supported on a pedicle. The Acinetoe have been supposed to have no power of nourishing them- selves by absorption of foreign matters from without, as do the Actinophryina ; but this seems to be an error; and Lachmann asserts them to be peculiarly carnivorous animals, the prey being seized by the tentacula, which have suctorial extremities. The researches of Stein went to show that the members of this family were nothing more than a developmental phase of Vorticellina; but, although this view has been accepted by a few naturalists, it has been pretty successfully controverted by Lachmann, Claparède, and others, who have witnessed the reproduction of Acineta from parent forms. The tentacles of Acinetina are not as a rule capitate; many taper, others are of nearly the same width throughout. They may be distributed pretty generally over the body, or only along a certain margin, or, again, may be collected into several bundles. To represent the known specimens of Acinetiform beings, we shall describe all those varieties described by Stein; for the truth or error of his hypothesis of transformation does not affect the value of his descriptions of them as distinguishable forms of organized beings. But before entering on the account of these, we shall reproduce the species enumerated by Ehrenberg under the head of Acineta. - - Genus ACINETA.—Has a membranous lorica, a simple pedicle, and numerous retractile, non-vibrating tentacula. Ehrenberg notes his dis- covery of vesicles (stomach–cells) in A. Lyngbyei and A. mystacina, and of a nucleus in the latter and in A. tuberosa. Self-division not observed. Repro- duction by germs, noticed by Stein, Cienkowsky, Lachmann, and others. ACINITA Lyngbyei –Spherical, pe- pale-yellow coloured body, with its thick dicle thick. It resembles a stalked Ac- crystalline stalk, is similar to a retracted tinophrys, while the circular, radiating, Vorticella. On Sertularia and other OF THE ACINETINA. 565 Polypes. This is called a Podophrya by Lachmann. Length, including stalk, 1–170" to 1-100". A. tuberosa (Vorticella tuberosa, M.) (XXVI, 3–4).-Triangular, compressed; dilated and truncate anteriorly, with three obtuse tubercles or horns, of which the two lateral are more constant, and furnished with tentacula. Pedicle simple and slender. 1-210" to 1-100". In marsh- and sea-water; on Ceramium diaphanum (XXI. 8–4). See account of Acineta of Zoothamnium affine. A. mystacina (X. 205).-Subglobose, obtusely horned, with two elongated bundles of tentacula; pedicle slender. Upon Lemna minor. 1-800" to 1-120". A. Ferrum-equinum (XXIII. 26, 27).- Ovate, white, tentacula disposed at its front; pedicle small, thick; a central gland of a horse-shoe shape. 1-240". Ber- lin. This Lachmann calls a Podophrya. A. (?)-Brightwell describes an ani- malcule with an oval sheath, of a dark colour, opake and granulated, and having a bundle of diverging rays proceeding from each extremity, many of which, by contraction or otherwise, have a globular tip. They were not observed to move or catch other animalcules. In fresh water at Oulton, Norfolk. A. patula.-A species mentioned by Lachmann (A. S. N. 1857) as developing embryos, and common on Algae and Zostera found on the coast of Norway. A. Cucullus.--Another species named, and not described, by the same naturalist. Found in the Fjord of Bergen, A. cylindrica (Perty). — Colourless, transparent, cylindrical, supported on a short stem. 1-22". Cothurnia maritima, – Its presumed Acineta bore a close resemblance to Aci- nata tuberosa (Ehr.). It had a moderately long, thin stalk, not dilated Nº. ; and the body was enclosed by a hyaline cap- sule, capped by a conical, roof-like por- tion, from which the inverted comical or pyriform granular body was suspended, more or less space intervening between it and the capsule. From each external anterior lº, proceeded a bundle of gently-tapering, fine, and slightly capi- tate tentacles, retractile and divergent. Internally was a round contractile space and an oval nucleus. Bpistylis branchiophila. —The Acineta assigned to it by Stein has usually a short, slightly curved, stiff and solid pedicle, always much thinner than the stem of the Epistylis itself. Figure pyriform; two bundles of bristly, non-capitate tentacula given off from its anterior end. The body exhibits constant changes in outline by the vermicular contractions of its tissue, and likewise alters its relative position with its stem. It likewise exhibits trans- itory folds, Swellings, and inflations of the surface. 1-240". L. crassicollis.--Stem of its Acineta transversely striped, crystalline, mostly straight, and generally like that of the Epistylis itself, except in thickness, being in this respect . thinner, save at its expansion, supporting the body of the Acineta. This last is of a rectangular figure, with rounded angles, and often inflated at the middle. Tentacula taper- ing, capitate, always few in number— from two to four at each of the four angles, and always longer than the dia- meter of the body. Length (maximum) of body 1–30", breadth I-28". Found on the Entomostraca. E. plicatilis. – Acineta-pedicle solid, longitudinally striated, much narrower than stem of the Epistylis, except at its upward dilatation, where the body was affixed, Body pyriform or ovoid, com- pressed ; in most specimens with a Smooth surface and no tentacula: when the last were present they were small, capitate, and few in number, and col- lected in four bundles, one on each lobu- lar expansion of the then expanded Aci- meta. Maxim. length 1-16", width 1-20". Opercularia articulata (XXX: 3–4).- Pedicle of Acineta rigid, solid, thin, mostly curved, and shorter than the body, After a certain height (about the half) it suddenly and greatly ex- pands to its point of articulation with the body. It is striated longitudinally, and hyaline. Body compressed, with a circular outline, or 4. ovoiá, or py- liform figure. Abruptly andwidely trun- cate at its base, where it is fixed on its pedicle: Surrounded by an apparently firm and thick integument, without aperture, and covered at slight intervals by short, thick, tubular and undulating tentacles. Maximum length 1–20" to 1–12", width 1-14" to 1-24". O. berberina (XXIII. 17–20).--Stem of Acineta very short, thick, solid, smooth or transversely striped, usually con- tracted in the centre and dilated at each end. The stem supports a very large, flattened, discoid capsule, with a para- bolic outline, and having a gently curved anterior double margin enclosing an open space. The margins are comparable to a front and back lip : the walls of the capsule thick, flexible, and hyaline, A 566 SYSTEMIATIC IIISTORY OF THIE INFUSOIRIA. portion of the contained Acimeta-body extends beyond the lips like a tongue. This process contains from four to five contractile spaces, variable both in posi- tion and size, as well as changeable in figure, from a circular to a dumb-bell shape. The rounded anterior angles of the process support numerous radiating tubular i. neither capitate nor tapering, but retractile and capable of being collected together in cylindrical bundles. The tentacles may be retracted within the lips of the capsular opening; and when this happens, the anterior mar- gin of the Acineta has a trilobate cha- racter; and very frequently a transverse fold makes its appearance behind the middle of the body, and might easily be mistaken for an indication of commenc- ing transverse fission. Sometimes two such folds are displayed. Maximum length of capsule 1-14", width across the anterior labiate extremity 1-19"; length of pedicle 1-125". º In figure and other respects this Aci- neta, remarks Stein, differs so mate- rially from those of other Acimetima, that, if these beings are to be considered independent organisms, it would require the creation of a new genus. O. Lichtensteini (XXIII. 22–23).-The Acineta varies very much both in figure and dimensions. All varieties have a short, thick, Solid stem, dilating upwards to the body of the animal. When largest, it equals half the length of the body, but is at times so short that the body seems as if sessile. The body is usually strongly compressed laterally, and in outline is a long or short oval, ovate, pyriform, or circular, except that in all cases it is narrowed at its base to equal in width that of the supporting pedicle. In short-stalked Smaller individuals, the body is mostly so very shortened and depressed, in its long axis, that the stem is quite overlaid, and the entire being has a reniform shape. A circular or oval nucleus occurs in the interior, but no contractile sac was discoverable. Maxi- mum length 1-18", width 1-24", dia- meter of smallest specimens 1-96". Ophrydium versatile (XXX. 8).--Stein does not appear satisfied with regard to the Acinetiform being to be assigned to this member of the Vorticellina (Ophry- dina). He found many cystic oval or ovoid bodies, with an irregular central nucleus, and numerous chlorophyll-cor- puscles in company with this Ophrydium; and along with these, which he concluded to be emcysted beings, other saccular organisms, of like size and figure, con- taining also a central nucleus and many chlorophyll cells, and withal furnished with a large number of tapering tubular, mostly curved or contorted, motionless processes or tentacles, distributed over the surface, recalling, in general appear- ance, the “digitate Acineta.” Spirochona gemmipara (XXX. 21–24). —Stein assigns to this peculiar member of the Vorticellina a very extraordinary Acineta, which he has named Dendro- cometes paradoxus. The body is plano- convex, circular, without pedicle, and gives off from its surface no tentacles of any of the ordinary types, but one or more large tubular processes, more or less branched. There is so great an in- constancy in the number, position, size, and ramification of these processes (says Stein), that two similar specimens are scarcely to be found. The processes on the same being differ also very much in size and mode and degree of branching. Five is the prevalent number in the most fully developed forms; above six are Scarcely ever seen; three or four are not uncommon; a single one is seen only in undeveloped examples. An entire ab- sence of such appendages is not very uncommon, the nuclear developments in their interior serving to identify them. Neither their trunk-like process nor any of its ramifications has the power of lengthening or shortening itself; but the whole process may undergo a certain amount of curvature, and extenditself in a rigid manner. Diameter of body 1-54" to 1-25". .Notwithstanding the very patent di- versity in form and constitution, Stein declares these tubular ramified processes to be morphologically and ji, identical with ordinary tentacula. Kaginicola crystallina (XXVII. 12–15). —The Acineta attributed to this being by Stein has a hyaline capsule, expanded in front and narrowed posteriorly into a sort of hollow pedicle. The dilated upper portion is infundibuliform, urceolate, or pyriform in figure, and is partially occu- pied by the granular mass of the § of the animalcule, enclosed in a membra- mous sac of its own. The body is sus- pended from the vaulted anterior surface of the capsule by an intermediate gela- tinous layer, which often appears pli- cated. Its bulk varies extremely; at times it nearly occupies the whole cavity of the capsule, except the prolonged stem-like portion, which never contains any; at others it forms only a small ball Ol' TEIE ACINETINA. 567 at the anterior end, which is then con- tracted upon it by being thrown into a few longitudinal folds. The tentacles º from the anterior surface of the Ódy and penetrate through certain fis- sures in the capsule above, diverging from the surface in a radiating manner. They are long, capitate, slightly tapering and retractile. The body contains a cir- cular mucleus and a contractile vesicle. Maximum dimensions of capsule 1-4" in height, 1-32" in width. #. minimum 1-24" high, and 1–43" wide. Stein puts this Acineta forward as one of the best illustrations to be obtained of the conversion of an encysted Vorticel- lina into an Acineta. The Acineta he identifies with the A. mystacina (Ehr.), and portrays two modes of develop- ment: one by a series of ciliated em- bryos, enveloped each in its own capsule, given off from the surface by a sort of gemmation—this process going on until the whole animal mass is exhausted; the other by the conversion of the whole mass, simultaneously, into several elon- gated-oval granular germs, covered by a membrane, but not ciliated. Vorticella microstoma. —Stein consi- ders the Actinophrys Sol and Podophrya faca (Ehr.) to be the Acinetiform re- presentatives of this species of Vorti- cella. In our opinion, as i. expressed, and which we partake in common with Cienkowski, and others, the being de- scribed by Stein under the name Actino- phrys is in fact an Acineta. It is repre- sented as covered by a firm integument, which frequently assumes the characters of a cyst, becomes plicated around it, and extended into a hollow pedicle, iving it the appearance of Podophrya. Moreover, foreign substances were never seen to enter its interior, as happens in the true Actinophrys. The further history of this Acineta has been sketched in the chapter on development of Ciliata (p. 360 et seq.). V. nebulifera.-The Acineta in Stein's estimation belonging to this species of Vorticella is found upon Lemma. The pedicle is much longer and the body more contractile, and therefore more changeable in figure, than the Acineta found on the Cyclops. When at rest, their figure is more or less compressed, and ovate or pear-shaped, with a pro- minent angle on each side of the anterior margin, from which a bundle of radi- ating retractile tentacles extends. Oval, circular, and discoid forms are not un- common. The stem is elastic, curved, and, as a rule, longer than the body it Supports, and is hollowed by a narrow canal. . It expands at its junction with the body and then spreads over it, form- ing an external sheath or capsule, except in the region supporting the tentacles, where it seems to 5. either absent or of great tenuity. Beneath this is a special govering of the Acineta body, entirely investing it. Notwithstanding these co- verings, the body is remarkable for its contractility and the mutability of its figure. It also enjoys a certain amount of movement on its pedicle, bending in this, and that direction with a peculiar jerking motion. The body contains an oval nucleus, and from one to three con- tractile spaces. It developes a ciliated embryo. The length of the body is from 1-100" to 1-20", that of the stem not above 1-10". Zoothamnium affine. — The supposed Acineta of this animalcule was found by Stein on marine Crustacea-the Gam- *marus marinus and Sphaeroma Serrata, along with the Zoothamnium. It appears identical with the Acineta tuberosa Ehr.). It is compressed, campanulate, or pyri- form, and has each external anterior angle lobate and surmounted by a group of tapering and radiant tentacula. An intermediate prominence is also frequent, but no tentacles spring from it. The body is distinctly enclosed by a hyaline elastic capsule, which is extended down- wards into a tubular pedicle, and by a softer membrane immediately investing it. The latter becomes especially pro- nounced when, as frequently happens, it is thrown into transverse folds in its narrower or posterior half during the more forcible contractions of the body. Length from 1-63" to 1-24"; maximum of stem 1-18". Carchesium pygmaum. — Stein lat- terly referred to this species an Acineta, common on Cyclops, and which he at first assigned to Epistylis digitalis. The stem is very short, often with difficulty perceptible, but never, wanting. The body is generally pyriform and com- pressed; its anterior end is rounded or truncate, and slightly emarginate, and supports at each of its angles a bundle of tentacles. Frequently the tentacula are not thus grouped in two masses, but occupy the whole anterior margin and the sides for a short distance—a circum- stance met with in Smaller specimens which have a circular, oval, or remiform figure. The mucleus is oval and small. No movements in the body are discerni- 568 SYSTEMIATIC EIISTORY OF THE INFUSORIA, ble, and the lengthening and shortening of the tentacles is very slow. This Acineta developes a ciliated embryo which resembles the Halteria Grand- nella (Duj.). Maximum length 1–30". Common size, diameter 1-50" to 1-40". ACINETA diademiformis (XXIII, 15–16). —Stein describes a peculiar Acineta found upon the roots of Lemma, under the name of the diadem-like Acineta. Its figure is compressed, disciform, transversely oval or reniform; and it is supported on its somewhat contracted base by a short, thick, solid stalk, longi- tudinally striated, and often marked by a few transverse linés. The stem is always so short that the body looks as if sessile. The latter is enveloped by a thick, structureless, Smooth and hya- line external membrane, and by a second layer beneath, closely investing the ani- mal mass. On the free margin of the body, particularly in front, a number of comparatively thick but fine-pointed tentacles are disposed at slight distances from one another. These, which are not clearly capitate, consist of a delicate mem- brane enclosing a finely granular matter, and are prolongations from the special membrane of the body; consequently they have to perforate the outer enve- lope; and Stein leans to the opinion that the latter is an excretion from the former. Usually, the tentacular pro- cesses are very slowly retracted: how- ever, when the Acineta is much disturbed, the shortening takes place much more rapidly, and renders them tortuous. A long band-like nucleus lies across the centre; and a number of transparent vesicles are disposed at equal intervals around the border, like a row of pearls around a diadem. At long intervals one or another of these sacs is seen to vanish, and after a time to reappear in the same place, like true contractile vesicles. No contractions of the body are observable; it remains stiff and motionless. It pro- duces a large ciliated embryo, which lies transversely across it in its special sac. Maximum breadth 1-14"; height 1-20", of stem 1-100". The stiff solid stem and the remarkable band-like nucleus indicate, says Stein, its derivation from some large species of Epistylis. It is the same organism as the Acineta Ferrum-equinum, according to Lachmann, A. digitata (XXIII. 21). — Under the name of the fingered or digitate Acineta, another variety of this class is charac- terized by Stein, who failed to detect the ciliated Infusorium to which, ac- cording to his hypothesis, it should owe its origin. It was found on some Ento- mostraca, and had a stemless, patella- shaped or transversely oval body, ad- herent either by the whole surface in apposition or by the central portion only. Its upper side usually presented irregular depressions and Small eminences, and was very often divided into an anterior and Osterior half by an annular constriction. from the entire upper surface, or only from its anterior section when the central constriction is present, a number of di- vergent, very thick, finger-like tentacles Spring, apparently without order and non-retractile. No contractions of the body were witnessed; but some change of outline is possible. A narrow, coiled nucleus is brought into view by acetic acid. The peculiar contractile vesicles are wanting; but from two to three un- changeable clear spaces of different sizes exist. Along with these normal speci- mens, others occurred having a smooth surface and no processes. Maximum width 1–30"; height 1–58". Genus OPHRYODENDRON. — Noticed and named in Lachmann and Claparède's paper in the Ann. d. Sc. Nat. 1857. No description given. It is said to be a very singular animal, doubtfully referable to Acinetina, found parasitic on Campanularia from the Norwegian coast. named. One species is OPHRYODENDRON abietinum.—Characters undescribed. GROUP III.-CILIATA (p. 199 and p. 266). THE group of the ciliated Protozoa, according to the scheme adopted, are resolved into two divisions:–1, mouthless (Astoma); and 2, those having OF 'THE CILIATA.—ASTOMA. 569 a mouth (Stomatoda). Of the former we have in the general history de- scribed two familes, viz. Opalinaea and Peridiniaea ; and we shall first pro- ceed to give a systematic account of their several recognized members, and in so doing redistribute certain species and genera otherwise classed by Ehrenberg,_for instance, several Opalinae described among the Bursarice. Again, in the systems of Dujardin and Perty, several mouthless genera are enumerated which must find their place in the first division of the Ciliata, as adopted by us. Such are the Leucophryina of Dujardin generally, together with a few Ploesconiens and Erviliens, and the Cobalina of Perty. The Peridiniaea of Ehrenberg, again, include two genera, Chaetotyphla and Chae- toglena, which should rightly find a place among Phytozoa ; but, to avoid disturbing the classification employed, we have retained them in the same family. Among the Stomatoda are described, not only the families enumerated by Ehrenberg (see p. 377), but also those constituted by Perty, Dujardin, and others, the place of their introduction being determined by the Ehrenbergian group to which they appear to hold the greatest affinity. We commence the systematic account of the Stomatoda with the ill-defined and imperfectly observed family Cyclidina, and take the other Ehrenbergian families in the order shown at p. 377. With the Vorticellina the Urceolarina of Dujardin and the Waginifera of Perty are conjoined, as well as several genera newly instituted. The Ophrydina embrace additional genera; and the genus Enchelia, whilst it is, on the one hand, deprived of the very heterogeneous organisms introduced into it by Ehrenberg, viz. Actinophrys, Acineta, and Tri- chodiscus, and which have already been treated as subfamilies of Rhizopoda, it has, on the other, appended to it the families Tapinia, Apionidina, and Holophryina of Perty, besides several genera named by this naturalist and by Dujardin. The history of Bursarina, Decteria, and Cinetochilina (Perty), is included in that of the Trachelina; and that of Paramecina (Duj.) and Aphthonia (Perty) in the account of Kolpodea. The Oxytrichina embrace the Keronina (Keroniens) of Dujardin; lastly, the Euplotina comprehend the Ploesconiens and Erviliens of the same writer. Division A.—ASTOMA. FAMILY I.—OPALINAEA. (Part I. p. 267.) (XXII. 46, 47; XXVI. 28, 29.) Ciliated parasitic Protozoa, consisting of a more or less oval sac, which resem- ble in figure many Bursarice, and, although often presenting an anterior fold or fossa, have no mouth. They contain, besides the usual molecular matters, a granular nucleus, and multiply by transverse fission. A globular contractile vesicle is absent in all; but in O. Planariarum and O. uncimata (of Schultze) an elongated pulsating sac occurs, recalling in character the so-called dorsal vessel of various higher animals; and in others, instead of a contractile vesicle, numerous irregularly-disposed Saccular spaces occur. The nucleus is not dis- coverable in O. Ramarwm, whilst in O. branchiarum one of unusually large volume is found. Opalinae are probably larvae of various vermes, and not independent organisms. Genus OPALINA.—The characters the same as those of the subclass. It will be seen, in the following specific descriptions, that many of the Opalince have been described by other systematic writers as members of genera of Stomatoda, such as Bursaria, Lewcophrys, and Paramecium. Stein has de- voted much attention to the Opalina ; and we accept his determination of the 570 SYSTEMATIC HISTORY OF THE INFUSORIA. characters and distinctions of species, along with the names he has assigned them. The genus Opalina was constituted by Purkinje, and has been generally accepted. Dujardin introduced Opalina into his family Leucophryina along with Leucophrys and Spathidium, and characterized that family as of a com- pressed-oval or oblong figure, clothed with closely-arranged cilia in regular Series, and apparently destitute of a mouth. OPALINA Ranarum = Bursaria Rama- Yum (E.).-The mouth described by Phrenberg in this species is merely a fold of the surface, as may be proved by add- ing a dilute solution of iodine, of alcohol, or of acetic acid, which will cause the animal to swell up and evenly distend the entire surface. Stein could find no nucleus. This species is common in the intestine and bladder of frogs. Perty makes it to include besides Bursaria JRanarum (E.), also B. Entozoon, B. Nucleus, and probably B. intestinalis. O. Planariarum (Siebold) = O. poly- morpha (Schultze), –The body has the form of a long cylindrical sac, pointed and wedge-shaped posteriorly, and expanded in front as a remarkable semicircular disc, by the central part of which it ad- heres to the surface of the intestine it occupies, the border being crowned with a wreath of long cilia. The actual point of attachment appears destitute of cilia; but the posteriorsurface is thickly studded with shorter ones. The contents consist of a homogeneous molecular substance, with numerous interspersed hyaline spaces. A long pulsating vesicle (or, from its length, a vessel) and a nucleus are also seem within the interior. The pulsating vessel extends to the extreme point of the body behind, just beneath the integment, but not in union with it, and terminates on the anterior side of the semicircular process in front. Its walls are structureless and transparent; and by its alternate contractions and ex- pansions it pushes forth the contained water alternately from each end. The position of the nucleus in the interior is not constant; it consists of a finely granular mass containing some larger granules, and is sharply defined. Fission is transverse, the nucleus and contractile vessel dividing consentaneously with the body. Stein could not discover the orifices at the end of the pulsating vessel described by Schultze. Maximum size 1-3" in length; breadth 1-20"; length of nucleus 1-25". O. Lumbrici (Stein).-Is represented by Leucophrys striata and L. modulata (Duj.), the latter being an altered form of the former, dependent on irregular endosmosis of the water in which it is placed. Transverse fission occurs in all sizes, which vary from 1-60" to 1-14". Parasitic in earth-worms (Lumbrict). O. armata (Stein) = O. Lumbric: (Duj.).—Has an oval º figure like the foregoing, from which it differs by having a strong, horny, uncinate pro- cess at the anterior extremity, on the under surface of the body, and, extending from it, a fold of the surface. The other- wise homogeneous and finely granular nucleus is remarkable by jiàº. 8, greater or less number of solid oval nuclei and elongated rods. Specimens of this species are peculiar by their uni- formity of size, which somewhat exceeds that of the largest O. Lumbrici, being from 1-12" to 1-8": hence Stein pre- Sumes that O. armata is nothing more than a further developed phase of O. Lumbrici, from which it differs only in size and in the presence of the prehensile apparatus. He surmises further that this and other Opalinae may be members in the chain of development of worms. O. Anodonta (Stein) = Leucophrys Anodonta (E.):-Mouthless, oval, turgid, transparent; ciliated equally throughout. 1-36%. Parasific in Anodºnia and if- tilus edulis. O. branchiarum.—Is characterized by its very º nucleus, which equals in volume the half of the entire organism. Its contour is also similar; and it might be taken for an imprisoned animal. Common in the ovisacs of Gammarus JPuleac. O. lineata º —Is without uncini, and has, like the last, a very large nucleus. In Nais littoralis (see Schultze’s work Beiträge zur Naturgeschichte der Turbellarien, Greifswald, 1851, p. 69). O. Wałdos (Duj.) (XXVI. 28, 29)—Is, like the preceding, unfurnished with a prehensile apparatus. Figure oval, or very elongated and nearly cylindrical, longitudinally and transversely striated: the fold extends from the anterior ex- tremity nearly to the middle. Numerous clear spaces in the interior, irregularly distributed, 1-22" to 1-11". Parasitic ÖF THE CILIATA.—STOMATODA. 571 in Naïs (one of the Annelida) (XXI. 28, 29). O. uncinata (Schultze). — Resembles O. Planariarum in general organization; it has the same sort of pulsating yessel, and a similar nucleus; it multiplies by transverse fission, and differs from all other known Opalinde by having a pair of strong, horny uncini at the anterior extremity, one on each side of the median line, giving it a bilateral character. Stein supposes this armature replaces the usual fringe of cilia, in the animals after having attained a certain age or stage. In the interior of Planaria Ulva, &c. 1-120". O. Tritonis (Perty).-Discoid, rounded in front, with a loop-like depression; colourless. 1–336". Revolves on its shorter axis. Parasitic in the intestine of Triton cristatus (the crested Water- newt). Is very like O. Ranarum, and requires further examination. O. Nucleus = Bursaria Nucleus; O. Entozoon = Bursaria Entozoon; O. intestinalis = Bursaria intestinalis. These three presumed species are nothing more than different phases of growth and development of Opalina (Bursaria, Ehr.) Ranarum. We have, however, retained the brief notes of their characters as Bursarie given by Ehrenberg. - FAMILY II.-COBALINA (Perty). Animals parasitic ; either with or without a mouth ; most of them receive only the juices of other animals. Body mostly flattened, oval, elliptic, or reniform, with numerous rows of very delicate cilia, and often with an un- cinate variety on the under Surface. An Oral-looking depression or fold fur- mished with stronger cilia commonly perceptible ; but several have no such indication of a mouth. Only those living externally upon animals are capable of receiving solid nourishment. In internal functions and in form they pre- sent a general uniformity and agreement, and are equally peculiar ; they occupy a lower position than free living forms similar to them ; their move- ments are simply automatic in character. a. With rows of cilia above, and wncini beneath. Genus ALASTOR.—The type of this genus is the Kerona Polyporum (Ehr.), and is called Alastor Polyporum. b. With delicate cilia both above and beneath. other animals. Genus PLAGIOTOMA (Duj.) (vide FAMILY TRACHELINA). PLAGIOTOMA Lumbric: ; PL. Concharum ; PL. (?) difformis. Genus LEUCOPHRYS (Duj.) (vide ante, p. 570, OPALINA Lumbrici). LEUCOPHRYS striata. Receive only the juices of Division B.—STOMATODA. FAMILY I.—CYCLIDINA. (X. 209–212). Illoricated Polygastrica devoid of eye-specks and of true alimentary canal, and having but one alimentary aperture, furnished with cilia or bristles, the various groupings and relations of which afford characters for the discrimina- tion of the genera; gastric cells (vacuoles) have been observed in two species of Cyclidium. Locomotion is effected by the vibratile cilia and a filament proceeding from the anterior extremity. The genera are distributed as follows:— Body compressed—cilia arranged in a *) Cyclidium. circle ................................................ Body round—cilia scattered all over ............ Body furnished with bristles......................................................... Body furnished with cilia IPantotrichum. Chaetolmonas. 572 SYSTEMATIC HISTORY OF TELE INFUSORIA. This family has no corresponding one in the system of Dujardin. Some of its members are represented in the family of the Enchelina as members of the genera Acomia and Enchelys. The genus Cyclidium (Duj.) is included among the Monadina of that author (p. 497), and includes beings furnished with a filament, but destitute of mouth and cilia—characters not at all analogous to those given by Ehrenberg to his genus of this name. Perty, moreover, has not retained this family in his system, although he accepts the genus Cyclidium, which he refers to a family called “Tapinia,” where it is associated with Acomia (Duj.), with Leucophrys (Ehr.) or Trichoda (Duj.), and with the following newly-instituted genera: viz. Acropisthium, Baeonidium, Opisthiotricha, Siagontherium, and Megatricha,_a set of terms not recommending themselves by their euphony, and, we presume, not wanted in a true systematic distribution to express distinct and independent forms of ciliated Protozoa. However, to render our résumé complete, these presumed new genera are appended to the family of Enchelia, to which several of their species are referred by Ehrenberg. • The family Cyclidina (Ehr.) would, in all probability, disappear from a revised system of classification. Thus Cyclidium appears to be only an em- bryonic phase of other animalcules, and Pantotrichum and Chaetomonas are not sufficiently characterized and examined by Ehrenberg to enable us with certainty to recognize them, or to determine their affinity. Moreover, the beings brought together under these genera are, some of them at least, very doubtfully referable to them, and have been so casually examined that their identification would be difficult. The ova and the polygastric organization mentioned in Ehrenberg’s account are matters only of hypothesis, Genus CYCLIDIUM.–Body compressed discoid, provided with a simple circular row of cilia. In C. Glaucoma alimentary vacuoles are distinct. The mouth is a rounded opening, situated upon the under surface of the body, either close at the anterior extremity, or towards the centre. The organs of locomotion consist, as in Kerona and Stylonychia, of a number of cilia-like feet, situated on the margin of the abdomen. It has been thought that longitudinal lines, produced by rows of very delicate cilia, were present; if so, and an anal opening be discovered, C. Glaucoma would rank with the Oaytrichina. Fission transverse. Since Ehrenberg wrote these observations, Lachmann has described not only a mouth, but also an anus on the ventral surface near the posterior extremity. This statement, taken in connexion with another, that some at least of the forms of Cyclidium are embryonic stages of other animalcules, leaves this genus in the greatest uncertainty both as to its independent existence and its systematic position. CYCLIDIUM Glaucoma (M.).-Oblong- elliptic, abdomen fringed with cilia ; delicate longitudinal striae are observed upon the back. In swimming, it re- verse self-division). They are repre- sented as fed with indigo. Abundant in vegetable infusions in the spring, 1–2880" to 1-1150". sembles Gyrinus, or Notonecta, a well- known little black water-beetle (see Microscopic Cabinet, pl. 4). Sometimes the movement is very quick; at other times the animalcules remain for a while stationary, and then presently spring with a curvetting motion to another spot. Formerly this species was con- founded with Glaucoma scintillans, but is much smaller (x. 209 is a side view, showing the cilia; fig. 211 a dorsal view; and fig. 210 a specimen undergoing trans- Betwixt this species and Enchelys nodulosa (Duj.) there is a complete agreement. The body, on a transverse Section, is triangular; hence it is (says Perty) that Dujardin has described it as sometimes assuming a triangular form. Chlorophyll granules are occasionally seen internally. Stein identifies the embryo of Chilodon Cucullulus with this i. of Cyclidium, which he would therefore exclude from the category of independent animalcules, Internally,this OF TEEE CYCLIDINA. 573 excellent observer also describes a con- tractile vesicle and a discoid nucleus; the former is the clear space mistaken by Ehrenberg for a mouth. At the same time he considers an oral aperture most probably exists somewhere near the middle of the organism, since he has seen the entrance of solid particles into the interior. Perty makes C. Glaucoma synonymous also with Enchelys triquetra (Ehr.), and probably with the Para- ºmecium Millum and Cyclidium Millum of Müller. In his system it is a member of the family Tapinia, where it is conjoined with some species of Leucophrys, with Acomia (Duj.), and several newly- created genera. - C. margaritaceum.—Orbicular, ellip- tical; the posterior end slightly º ; the dorsal surface with distinct longi- tudinal lines; cilia not distinct. 1–1500" to 1-1000". - This species is separated by Perty from Glaucoma, and constitutes in his system the representative of a genus he names Cimetochilum, which, with Glaucoma, forms the family Cinetochilima (vide GLAUCOMA). The Cin, margaritaceum is characterized as a short elliptical animal, rather compressed and with its vibratile flap on the posterior half, colourless and transparent. Movements quick; rota- tion on its axis rare. Cilia very short. Fission transverse. 1-810" to 1-720". Lachmann (A. N. H. xix. 216) appears to approve of the systematic position assigned by Perty to this being. C. (?) , planum. — Oblong-elliptic, smooth; cilia but little marked. 1-2640". C. (?) lentiforme. — Smaller than C. planum, and has no distinct striae or cilia. 1-3180". C. Arborum. – Small, suborbicular, slightly excised laterally; dorsum ru- gose; margin everywhere ciliated. Diam. 1-192". Marginal cilia used in the way of feet; Swims rapidly. Fission trans- verse. On moss of trees. This animalcule is identified by Cohn (Siebold's Zeitsch, 1851, p. 273) with the embryo developed by Lozodes (Parame- cium) Bursaria. . If this be the case, it must be rejected from the list of inde- pendent species. - Genus PANTOTRICHUM.—Body turgid, covered with moveable cilia. In P. Enchelys gastric cells (vacuoles) are distinctly visible. Ehrenberg says, “The absence of a double ali– yellow, occupy the interior. Granules, green or mentary aperture is not yet proved; nor, on the other hand, is its existence.” Pantotrichwm is not received by Perty as an independent genus, but is com- prehended by him with Lagenella and Chaetoglena, under the common appel- lation Chonemomas, and placed among the Thecamonadina. PANTOTRICHUM Enchelys.-Cylindri- cal, oblong, rounded at both ends; hya- line at extremities and turbid, the centre- colour pale yellow. X. 212 is a cluster of animalcules; those to the left are more highly magnified than the others. In swimming they revolve and glide along in the direction of the longer axis of the body. In infusions of raw flesh. 1–1150". P. volvoa (Leucophrya viridis, M.).- Ovate, spherical, of a green colour. In brackish water, 1–860". P. Lagenella'-Ovate, the ends equally rounded, anterior ciliated portion pro- duced in the form of a neck or beak. Amongst Confervae. 1-1080" to 1-570". Schneider (A. N. H. 1854, p. 329) de- scribes this species as forming around itself a cyst, which completely retains the flask-like form of the body, when the animalcule enters on a state of rest. Genus CHAETOMONAS.—Motion slow, and leaping by means of the bristles on the body, which are not vibratile. Internal organization very little known. They are parasites, living on the dead bodies of other Infusoria, and in infu- sions of flesh or other animal matters. A vibration is seen at the mouth; but whether it is produced by a filament or by cilia, is uncertain. In C. com— stricta, transverse self-division is thought to have been seen. CHAETOMONAs Globulus. – Almost spherical, of an ash-colour, furnished with setae or bristles. It often has the figure of Monas Guttula, but is larger; sometimes two cluster, together. In bad-smelling infusions of animal matter along with Pantotrichmon Enchelys, Monas Termo, &c.; also in the dead fronds of Closterium acerosum, as shown at x. 113. 1–2880". - C. constricta. — Transparent, oblong, slightly constricted at the middle, and having two setae or bristles. In dead Hydatina senta. 1–5760". 5 7 4 SYSTEMATIC IIISTORY OF TEIE INFUSORIA. FAMILY II.-PERIDINLAEA. (Part I. p. 271.) (Pl. X. 214–226; XII. 47; XXXI. 16–23.) Infusoria without an alimentary canal, covered with a lorica, upon which cilia or setae are often arranged in the form of a Zone or crown—hence the name. The lorica has only one opening. Three out of the four genera have a fila- ment besides the wreath of cilia around the middle of the body, or scattered cilia or bristles. In only Peridinium Pulvisculus and P. cinctum have artificial means succeeded in demonstrating the admission of food, the internal organi- zation being greatly obscured by the mass of coloured opake granules, which Ehrenberg called ova. A nucleus and a red stigma (eye, Ehr.) are discover- able in some species. -- The genera are disposed as follows:— Lorica having stiff bristles or short spines—no transverse | * * “” Chaetotyphla. furrowed zone........................................ . . . . . . . . . . . eye present ...... Chaetoglena. Lorica smooth or rough—a ciliated transverse zone pre- | no eye . . . . . . . . . . . . Peri - ULDOl sent ............................................................... eye present e & & # e. e. Glenodinium. Some of the presumed species have been found only in a fossil state in flint. Dujardin constitutes a family Peridiniens, agreeing in the main with that of Ehrenberg, and thus narrates its characters: “Animals without known internal Organs; enveloped in a regular, resistant, membranous lorica, which sends off a long flagelliform filament, and, in addition, has one or more furrows beset with vibratile cilia.” - The lorica would appear to have no opening ; for foreign bodies and colour- ing matter are not seen to enter it. Several have their lorica prolonged into horn-like processes; and some exhibit a coloured point (eye-speck). They are distinguished from Thecamonadina by the ciliated furrow or furrows. Dujardin observes that “as the first two of Ehrenberg's genera are with- out the furrow and vibratile cilia, and have only a filament as a locomotive Organ, they are evidently akin to, and not separable from the Thecamonadina, unless spines or asperities of the lorica are to be taken for cilia. Again, the so-called eye-speck is not a sufficient generic distinction between Peridinium and Glenodinium; the former genus, moreover, should only include spherical animalcules, whilst those concave on one side, and exhibiting horns, will rightly form a distinct genus—Cerativm.” - Perty coincides with Dujardin in detaching Chaetotyphla and Chaetoglena from the Peridiniaea, and in uniting them with Thecamonadina. Chaotoglena he merges with Pantotrichwm, and Lagenella in a genus which he names Chome- monas (p. 513). His Peridiniaea comprehend three genera, viz. Cerativºm, Glenodinium, and Peridinium: the first characterized by a cellular lorica prolonged into horns; the second by a cellular not-horned lorica; and the third by a structureless lorica. A reference to the figures of Chaetoglena and Chaetotyphla is sufficient to show that these two genera have no claim to be ranged with Peridinium : the former, in particular, indicates in its structure and general appearance a member of the Cryptomonadina ; and the latter, if not a member of the same order, is certainly not one of the Peridiniaea, but probably the encysted state of some animalcule. The imperfect descriptions attached to these genera, and the absence of sufficiently distinctive features in their illustrations, renders their exact identification with similar known forms a matter of difficulty, if not of impossibility. Again, the special differ- OF THE PERIDINIAEA. 575 ential character between Glenodinium and Peridinium, viz. the existence of a red speck in the former, is worthless; and were no other peculiarities discover- able, the two genera should be merged into one. However, the elongation of the lorica into horn-like processes supplies a differential character sufficient at least to constitute two genera out of their several members. Ehrenberg re- cognized this indication of a division, and adopted it for his eyeless Peridiniaea, making two sections:—1, Peridinium proper; and 2, Cerativºn, horned Peri- dinia. Perty, we have seen, uses the same structural peculiarity as a generic character, but, in addition, makes a third genus, marked by the absence of sculpturing on its lorica. This basis we hold to be insufficient for a generic distinction; and the whole of the Peridiniaea proper appear to us reducible to the two genera Peridinium and Cerativºrn; Glenodinium we would conse- quently cancel. The rejection of Ehrenberg’s views of internal organization, and of two of the four genera he classed as Peridiniaea, renders a revised description of this family necessary. In attempting this, we may state that the Peridiniaea are animalcules having an external, condensed, chitinous inte- gument forming a lorica, lined by a contractile membrane immediately invest- ing the organic contents. No actual oral opening is satisfactorily made out; but in most species a deep fossa or fissure is found, from the bottom of which a flabellum extends, mostly twice or more than twice the length of the body. Their figure is more or less globular or ovate ; and sometimes the lorica is ex- tended into two or three long horn-like processes, giving the whole being a very bizarre appearance. A deep furrow surrounds the body as a Zone, and in some species a vertical prolongation of it extends to one pole. These furrows are richly ciliated; yet the cilia do not appear confined to them, as Ehrenberg supposed, but may, at least in One species, cover the entire surface. The interior is occupied by masses of usually strongly-coloured brownish yellow, or reddish or greenish brown, rendering the animalcules very opake. In some species an oval nucleus has been seen ; and its presence is presumable in all. A contractile vesicle has not yet been demonstrated. They multiply by transverse, and it may be also by longitudinal fission. P. wberrimum has been found in a quiescent condition; and doubtless some mode of propagation exists; Perty endeavours to prove it is by internal germs. The zone-like ciliary furrow may be adduced as the leading characteristic. Genus CHAETOTYPHLA.—Lorica silicious, hispid or spinous, destitute of a transverse furrow or Zone, and of stigma; surface covered with little spines and bristles, which appear stronger at the posterior portion of the body. The lorica may be crushed by pressure, and the little creature within it be set at liberty. In swimming it revolves upon the longitudinal axis, probably by means of a delicate filiform proboscis, or of cilia at its mouth ; no such organs, however, have been seen. Of the internal organization, nothing positive is known. One species has been discovered in flint, and so closely resembles Yanthidium, that it is often mistaken for it. CHAETOTYPHLA armata.-Ellipsoidal, brown, ends rounded; covered posteri- Orly with short spines, where there is a circlet of black spots, as shown in the end view, x. 215. The anterior cilia, or fine bristles, are sometimes very indi- stinct; x. 214 is a variety in which they are strongly marked. In clear water, amongst Confervae. 1-620". C. aspera-Brown, oblong, rounded at both ends, and rough, with short bristles; the little spines are scattered without order at the posterior end. Found with the preceding. 1-570". C. (?) Pyrita. —Oblong cylindrical, rounded at both ends, and provided with delicate elongated bristles, *. no spines. Fossil in flint, near Delitzsch. 1-1150”. Genus CHAETOGLENA.—Lorica silicious, destitute of a transverse zone 576 SYSTEMATIC ELISTORY OF THE INFUSORIA, or furrow, but striped or covered with spines or stiff hairs, and having an eye-speck. The organ of locomotion is a simple flabellum. The interior contains Scattered transparent vesicles, and a brownish-green granular mass ; a large bright spot or nucleus is also visible. Self-division not observed. CHAETOGLENA volvocina.-Ovate, with brownish-green granules, and a red eye; between the lorica and the soft body a vae at Hampstead and Hackney. 1-1150". C. caudata. —Hispid, ovate, with a short tail; granules green; ocellus clear red; oral margin urceolate and dentate. beautiful red ring is visible in live ... er- || 1–864". Berlin. - cimens (x. 216, 218). Amongst Co Genus PERIDINTUM.—Lorica membranous, with a transverse ciliated Zone; no eye. The locomotive organs are a filament and the Zone of cilia. In P. Pulvisculus and P. cinctum, indigo and carmine are received, and de- monstrate the formation of vacuoles, which in P. acuminatwm, P. fulvum, and P. corrºwtwm are visible without having recourse to coloured food. The oral aperture is found in a hollow near the centre, as in Bursaria. The granules are generally of a brown or yellowish-brown colour, though some- times green or even almost colourless. In P. Tripos and P. Fusus an oval nucleus is visible. Self-division is longitudinal in P. Pulviscwlus and P. fuseum ; and, according to some observers, transverse in P. Fusus and P. Tripos. The structural peculiarities are sufficiently described in the chapter on Peridiniaea (p. 271). The existence of a mouth and the entrance of food are still matters of doubt. A nucleus is probably present in all; and the same may be said of the flabellum, which subsequent observers have distinctly found in cases where it eluded the observation of Ehrenberg. “ Fossil Peri- dinia,” says Perty, “are not found in recent geological formations, but only in the chalk beds of the secondary strata, in which they occur with Xan- thidia (Ehr.) and Pyazidiculae.” a. Peridinia without horns.—PERIDINIUM. PERIDINIUM cinctum (Vorticella cincta, M.).-Nearly globular, or slightly three- lobed and smooth, with a zone of cilia; not luminous. It swims slowly, with a vacillating and rolling motion. Amongst Confervae. 1-570." Instead of the red zone noted by Ehren- berg, there may be only a single speck, or even it may be absent. P. Pulvisculus.--Small, of a brown or greenish-yellow colour, and not lumi- nous; almost spherical, or slightly three- lobed; a fine filament 24 lines longer than the body may be observed; nume- rous vacuoles produced by feeding on in- digo. Amongst Confervae, with Chlamy- domonas Pulvåsculus. 1-2300" to 1-1150". Perty has met with specimens having a red speck, P. fuscum.—Is not luminous; oval, slightly compressed and pointed ante- riorly. jº to 1–280". P. Monas.—Very small, obtuse, with- out horns; remarkably social. Diam. 1–1728". In the Baltic, Perty suggests that this is merely a young stage of P. (Ceratium) cornutum. P. Planulum (Perty).-Rounded, broad, rather compressed; the two segments equal. Colour brown, usually a deep tint. Under surface rather concave. 1-720" to 1–430". Its brown contents contract. after death into a central lump. A red speck is often seen in the posterior por- tion. It is distinguished from Glenodi- mium cinctum by its greater width and deeper colour. P. Corpusculum (Perty).--Small; seg- ments very unequal, posterior one very short and cleft. 8. contents brownish-yellow, or red or green. An alteration in figure has been seem to ensue after death. 1-1120". Amongst Marchantia polymorpha. P. monadicum (Perty). —Very small; Segments unequal, the posterior one much smaller; with red stigma in the line of constriction, more seldom in the hinder half. Molecules pale green. It is the smallest known example in this family. , 1-1150". In a pond on Mount St. Gothard and at Bern, OF THE PERIDINIZEA. 577 P. wberrimum (Allman). Nearly sphe- rical; colour reddish-brown; nucleus well-defined, central. A secondary fur- row springs vertically from the annular one, and terminates at the pole. A stigma usually present at the polar ex- tremity of the vertical furrow, Swims actively by the aid of its flabellum, and of cilia generally disposed on the surface, and not confined to the furrows as Ehr- enberg represents. Occurs in a quies- cent state, 1-1000" to 1-500". Ponds, Phoenix Park, Dublin. b. Peridinia with horns.—Subgenus CERATIUM. P. (CERATIUM), (P) pyrophorum.— Ovate, spherical, with two little elevated points at its anterior extremity. It is very delicately areolate and granular. Fossil in the flints of the chalk forma- tion at Berlin. 1-570" to 1-480". P. (CERATIUM) (?) Delitiense.—Ovate, spherical; with a little stiff point near the middle laterally. Fossil in the flints of Delitzsch. 1-430" to 1–280". These two supposed fossil Peridinia and the Chaetotyphla (?) pyrita appear rather to be sporongia of Algae. * P. (CERATIUM) acuminatum.—Brown- ish-yellow; ovate, spherical, slightly three-lobed, and having a little pro- cess at the posterior end. “I observed this species,” says Ehrenberg, “in phos- phorescent sea-water from Kiel, and it is very probable that the light proceeded from this animalcule. It is the Smallest Fº sea animalcule that is own.” I-600" to 1-570". P. (CERATIUM) cornutum (Bursaria Hirundinella, M.; Ceratium Hirundinella, Duj, and Perty).-Greenish; not lumi- nous; rhomboidal and rough, with one, two, or three straight horn-like processes in front, and a single one (often curved) posteriorly. 1-280" to 1-140". Perty asserts that Ehrenberg has re- versed this animalcule in his account and illustrations, as he has likewise done in other species of this genus; for it is the single horn which advances fore- most, and indicates the anterior extre- mity. The same author, moreover, states that in the majority of speci- mens one or more red specks are to be found, generally in the posterior half, near the middle line between the large and Small horns. P. (CERATIUM) Tripos (Cercaria Tripos, M.). —Yellow, brilliantly phosphores- cent; urceolate, broadly concave, smooth, and three-horned; the two frontal horns very long and recurved; the third, or pos- terior one, straight. Ehrenberg says, “The power of this creature to evolve light is placed beyond all doubt, as I took up nine phosphorescent drops, one after the other, from the water, and I saw in each nothing else besides a single animal- cule of this species.” It is rigid, and swims with a vacillating rolling motion upon the longitudinal axis. The length of the horns is not constant, sometimes being Scarcely so long as the body, at other times much longer. x. 219, 220, repre- Sent an under and side view. In the Sea, near Copenhagen and Kiel. 1-140"; with- out the horns, 1-430". P. (CERATIUM), Michaelis. – Colour yellow; intensely phosphorescent. Lo- rica ovate and smooth, with three short, straight horns, as shown in fig. 221. A flagellum is not visible. In phosphº- cent sea-water. 1-570". Named after Dr. Michaelis, its discoverer. P. (CERATIUM.) Fusus (x. 222,223).-- Yellow, intenselyphosphorescent; ovate, oblong, and . he two horns are straight and extended in opposite direc- tions, producing a fusiform figure. Ehr- enberg states that he has seen the cilia of the furrowed zone, and the single fila- ment when at rest; also an opening or mouth in the lorica, near the insertion of the filament. With horns, 1-120" to 1–90". P. (CERATIUM.) Furca.-Yellow, very phosphorescent; urceolate, with three horms; two in front short, in the form of a fork; one behind longer. In phos- phorescent water, at Kiel. 1-120". P. (CERATIUM) divergens.—Yellow; cordate-ovate, smooth; with two diver- gent frontal acute spines, dentate at the base; posterior portion attenuated, look- ing as if shortly horned. Diam. 1-576". In the Baltic. P. (CERATIUM) macroceros.-Yellow; habit of P. Tripos, but more slender, and with longer horns, which are four times the length of the body. 1-216". In the Baltic. P. Tridens.—Yellow, with the habit of P. flavum, P. divergens, and of P. Mi- chaelis; surface granular, with three acute frontal horns, and its posterior portion attenuate. 1-576". In the Baltic. P. (CERATIUM) macroceras (Schrank) or C. longicorne (Perty) is mentioned by Perty, and does not appear quite equiva- lent to C. macroceros, to which its name is too much alike. It is the largest of - 2 P 578 SYSTEMATIC EIISTORY OF THE INFUSOIRIA. all the Peridiniaea, and (says Perty) not a variety of P. cornutum, as Ehrenberg thought: the lorica is rather concave below, and less bent than in that species, Empty loricae are clearly areolate, and the areolae round. A red Stigma is often seen in the posterior half. The anterior supports a single horn, and there are three behind, I-120" to 1-96." P. arcticum (Ehr.) resembles P. ma- croceros, but is stronger, and has its large horns all curved and three or four times longer than the body; surface rough, with little raised puncta or Spines. Length of body, 1-48", of entire being 1-18". It is phosphorescent, and found at IGingston Bay, Newfoundland, with P. Furca, P. Tridens, and P. divergens. P. longipes (Bailey).-Body triangular, rough; angles produced into very long ciliated processes, of which the two frontal ones are longest. Body crossed obliquely by a ciliated groove (XXXI. 23). St. George's Bank, New York, P. depressum (Bailey). — Lorica ob- liquely depressed, with one large conical posterior process, and two smaller comical frontal processes; the latter separated by a deep notch. Surface granular and reticulated. Both this and the preceding species, which were found together, were doubtless furnished with a proboscis when living, and, like other marine species of this genus, were probably phosphorescent. The form of P. depres- sum is closely analogous to the embryo of Nereis, whose curious changes were studied by Lovén (and referred to in Prof. Owen's Lectures on the Inverte- brata, ed. 1843, p. 147). This account of Nereis, and particularly the comparison of Prof. Owen's figure with the Peridi- nium depressum (XXXI, 21, 22), led Dr. Bailey to suspect that at least a portion of the forms now included in the genus Peridinium might be imperfectly-deve- loped or embryonic Annelida. Genus GLENODINIUM.–Peridinia with motile cilia placed in a trans- verse furrow or zone, and provided with an eye. the same, in other respects, as that of the preceding genus. The organization is much In G. cinctum a flabellum is seen to emanate from the middle, and to vibrate like the wreath of cilia. It is also probably present in the other species, though hitherto unobserved. The lorica is combustible. Vacuoles and fine granules are visible in all the species; the former are very distinct in G. apiculatum. The red speck is in the form of an elongated or horseshoe-shaped spot, and constitutes the essential character of the genus. Longitudinal self-division has been observed only in G. cinctum. Although this genus is rejected by Dujardin as indistinguishable from Peridinium, yet Perty retains it, making its point of separation from the latter genus—which, by the way, he prefers to call Ceratium—consist in the absence of horns to the lorica. The red speck he ignores, equally with Du- jardin, as a distinctive character. In this way Perty’s Glenodinium= Peri- dinium, without horns, of Ehr. GLENODINIUM cinctum = Peridinium oculatum (Duj.).—Oval, or nearly sphe- rical; Smooth; Stigma large, semi-lunar, and transverse. In fresh water, amongst Oscillatoriae. 1-570". It is seen both with and without a red speck. G. tabulatum.—Oval; yellowish-green; lorica granular and reticulate with ele- vated lines, but not spinous; truncate and denticulate posteriorly, and biden- tate anteriorly. 1-570" to 1-430". “The colour,” says Perty, “is mostly brown, especially in mature specimens, and more rarely brownish-green or greem. A red stigma is but rarely present.” G.(Peridinium) Alpinum (Perty). The sculpturing of the surface is indistinct; and very frequently there are, alternately, coloured masses of granules and hyaline spaces around the border of the lorica, broducing a notched appearance. 1-430". t is probably only an Alpine variety of G. tabulatum, in which the lorica has not attained its perfect structure. On Mount St. Gothard, and in Lake Lugano. G. apiculatum. — Oval; yellowish- green; lorica smooth, but with hispid urrows on the margin, as shown in X. 226. The stigma is oblong, and ex- tremities obtuse. Amongst Confervae. 1-570" to 1-430", OF TELE WORTICELLINA, 579 FAMILY III.--WORTICELLINA. (Part I., p. 277 et seq.) (Plates XXVII., XXIX., XXX.) Polygastrica with an alimentary canal, the extremities of which are distinct, though they approximate in consequence of its curvature (Anopisthia). They have no lorica. A few are solitary; but the majority are congregated on pedicles, which often assume elegant ramose forms, like little trees, an ani- malcule surmounting and terminating each branch or pedicle. These arbo- rescent clusters are the result of imperfect self-division. The animal organization of this family is very distinct. The entire sur- face of Stentor is covered with vibratile cilia; but in other genera they are mostly disposed in the form of a wreath around the head. In some genera, as in Vorticella, Carchesivm, and Opércularia, longitudinal and transverse muscles are seen; the mouth and discharging opening, both lying in the same lateral cavity, have been demonstrated in all. Self-division takes place in all the genera, but is least frequently observed in Zoothamnium : when it is imperfect, not affecting the pedicle, it gives rise to branching forms. Gemmation is also frequent in most genera. From their great irrita- bility when approached, may be presumed the existence of a system of sensa- tion. Colouring matter is received by all the species; eye-specks are wanting. This family affords (in form indeed rather than in structural homologies) a connecting link between the Ciliata (Polygastrica) and Rotatoria. The following curious particulars are appended by Ehrenberg, who re- garded them as indicative of an act of transformation:— “The Vorticella developes a pedicle; divides (casts its exuvia); developes posterior cilia; loosens itself from the pedicle, rambles about ; draws in (after shedding a second exuvia) the posterior cilia, sheds them, and firmly attaches itself, preparatory to putting forth another stalk. This cycle of phaenomena is repeated again and again, and possesses high physiological interest; it is a returning circle of transformations—a return to an early condition, similar to that of a butterfly, if it suddenly lost its wings and an- tennae, and again became a caterpillar, in order once more to return to the state of pupa and butterfly—or to that of an old man becoming a child, in order to run again his course of life anew.” (See Part I. p. 277 et seq., and p. 586.) - The Vorticellina live for the most part in sweet water, fresh or marine, attached to plants or shells, to Crustacea, to the larvae of insects, &c. There are, however, a few Vorticellae and Scyphideae produced in infusions, and even in fetid ones. This account of the organization of Vorticellºna from Ehrenberg requires considerable alterations and corrections from the present state of our know- ledge of these beings. In Part I. (p. 277), their organization has been largely considered; yet a few notes here may not be misplaced Any definition of the characters of the group of genera comprehended in this family by Ehrenberg would be unsatisfactory, inasmuch as some forms are included which have no sufficient affinity. Ehrenberg represents the Vorticellina as having a polygastric alimentary canal so curved that its two ends are conterminous. Now the supposed stomachs, as displayed by using coloured food, were merely Vacuoles; and no continuous alimentary canal penetrates the interior, as Sup- posed, but only a digestive tube or Oesophagus of variable length, terminating abruptly in the interior by an open mouth. The ciliary apparatus of the true Vorticellina is more complex than appeared to Ehrenberg,_the head of the animalcules being terminated by a peristom or free edge, oftentimes thickened and everted, beyond which a ciliated disc supported on a very retractile and t 2 p 2 580 SYSTEMATIC EIISTORY OF TEIE INFUSORIA. highly sensitive pedicle can be protruded. The portion of the ciliary spiral outside the vestibulum is not of equal length in all Vorticellina : in many, e.g. Vorticella, Carchesium, Zoothamnium, Scyphidia, Trichodina, some species of Epistylis, &c., it describes scarcely more than one circuit round the disc, whilst in Opercularia articulata and Epistylis flavicans it runs round the disc three times; in other species intermediate lengths occur. The ciliary wreath, moreover, consists of a double row of cilia: those of the outer one are usually somewhat shorter than those of the inner, and though inserted upon the margin nearly in the same line as the others, yet they are set at a different angle, and apparently far more strongly bent outwards. In the vestibulum and Oesophagus the cilia appear to stand in a single row. The peristom usually bears no cilia. There is no sufficient proof of the existence of muscles of the same type as those of the higher classes of animals. The contractile vesicle is single and circular; the nucleus sometimes oval, but often elongated and band—like. Besides fission and gemmation, true propagation by living germs or embryos, developed in the course of more or less complete transformations, affords an additional means of perpetuating and extending the several species. The genera are distributed as follows:— . Body covered with cilia............ Stentor. Tail absent ...... Body without stalk Body Smooth, cilia anterior...... Trichodina. Tail present ................................................ Urocentrum. / Stalk flexible, Simple......... Worticella. Form of stalked deflection spiral || Branched Carchesium. bodies similar Body stalked—often * g isłvrl; branched like a tree 4 Stalk inflexible ..................... Epistylis. IBodies of dif- ferent form ... | Stalk inflexible ..................... Opercularia. Stalk flexible, deflection spiral...Zoothamnium. Of the several genera named and distinguished by Ehrenberg, two only are accepted by Dujardin, viz. Epistylis, with a rigid pedicle, and Vorticella, with a contractile stalk, simple or branched. He places Carchesivm with the latter, maintaining that a generic character is not to be found in the simple or branched condition of the stalk alone, when the bodies are similar. More- over, he failed to meet with animalcules having the characters assigned to the genera Opércularia and Zoothamnium by Ehrenberg. A third genus, under the name of Scyphidia, is established by him for the sessile species; whilst a fourth, Vaginicola, comprises all those species invested with a membranous sheath, and corresponds, in its constituent species, to the family Ophrydina (Ehr.) after the exclusion of Ophrydium. + Perty makes a different distribution of the Vorticellina to that proposed by Ehrenberg. Like Dujardin, he rejects the genera Stentor and Urocentrum, and transfers them to a family Urceolarina. On the other hand, he adds Scyphidia of Dujardin to the true Vorticellina, and makes no mention of Carchestwm. Lachmann is another writer who rejects Urocentrum from the Vorticellina. Stein points out various defects in Ehrenberg’s grouping of Vorticellina; and whilst he would, on the one hand, detach from it Stentor, Trichodina, and Urocentrum, he would, on the other, associate with it the several sheathed genera which form the family Ophrydina, viz. Ophrydium, Vaginicola, Tintinnus, and Cothurnia. Apart from these changes in the distri- bution of admitted genera, he adds two new ones, Lagenophrys and Spirochona, remarking of the former, that, in its free condition, it constitutes a transi– OF THE WORTICELLINA. 581 tional form between the radiated type of Vorticellina and the bilateral one of Oxytrichina and Euplotina. Lastly, Lachmann states that Trichodina and Urocentrum are not Vorticellina, and makes Stentor the representative of a new family, which he calls Stentorinae. In this proposed new family he includes besides Stentor, a new genus (Chaetospira), Spirostomum, and a fourth genus which he has merely referred to without naming or de- Scribing it. In the above plans of classification there is this in common, that the genera Stentor, Trichodina, and Urocentrum are excluded from among the Vorticellina, an exclusion warranted by their difference of organ- ization and general characters. At the same time we are of opinion that the association of the Ophrydina with the Vorticellina is not correct in a systematic point of view, the existence of external sheaths being a well- marked and sufficiently distinctive character, although the homology in organ- ization is otherwise, in every essential point, very close and striking. Pro- bably Trichodina and Urocentrum should constitute an allied family or a sub-family of Vorticellina; Stentor the type of a second family; whilst the remainder of Ehrenberg's group, viz. Vorticella, Carchesivm, Epistylis, Oper- cularia, and Zoothamnium, might be called the true Worticellina. The new genus Spirochona, again, stands apart by so many peculiarities that it cannot be included within either of the groups proposed, and must be regarded as the (at present) solitary type of a new family, having the internal organization of Vorticellina, but destitute of their peculiar ciliated head. In framing his generic and specific distinctions, Ehrenberg made use of characters of no real value, such, for instance, as the occurrence of similar and dissimilar bodies (zooids) on branching stems otherwise alike, the height of the stem, the thick- ness of its branches, and the dimensions of the attached animalcules. The family Urceolarina (Duj.) is thus characterized:—“Animals variable in form, changing from a trumpet- or a hemispherical to a globular form; ciliated throughout, with a fringe of much stronger cilia along the upper and anterior margin of the body, continued as a spiral coil into the oral cavity, which is on the same border. They present the ordinary swimming move— ment, and can for a short time arrest their progress by fixing themselves by their posterior extremity to external objects.” “This family,” observes Dujardin, “ connects the Vorticellina with the Bursarina, and includes the genera Stentor, Urceolaria (Trichodina, Ehr.), Ophrydium, and Urocentrum.” The last-named genus is treated as very doubtful. As already seen, Perty adopts this family Urceolarina, but modifies it by rejecting Ophrydium, and adding Spirostomum. Genus STENTOR (XXVIII. 16, 17; XXIX. 8).-Animal without pedicle, free, or attached by the posterior extremity of the body, which is conical, although it admits of very considerable modifications of form; it is entirely covered with cilia; a wreath of larger ones surmounts the head. Ehrenberg considered the longitudinal striae along the body, and the circular ones at the anterior part, muscular fibres. The anterior ciliary wreath is coiled in a spiral manner about the head; in some species a row of longer cilia extends from the mouth, in a fringe-like manner, to the middle of the body. The Stentors increase by self-division, which is either longitudinal or oblique. The nucleus is band-like, moniliform, or round. The contractile vesicle is large, round, and placed on a level with the ciliary wreath, close to the Oesophagus; it gives off, above, an annular branch, which surrounds the head of the animalcule just beneath the fringe of cilia, and below, a straight branch extending to the posterior extremity of the animalcule (XXIX. 7). The anus may often be perceived for a considerable time both before and after the discharge of matters. It is situated on the back, close beneath the 582 SYSTEMIATIC EIISTORY OF THE INFUSORIA. ciliary circle. The Stentors are among the largest of the Infusoria, and all the species are visible to the unassisted sight. They are best examined between the plates of a large live-box, a portion of the decayed stem or leaf on which they are found being put in with them. “It is,” says M. Dujardin, “in the Stentors where we can view the several supposed internal organs isolately, that new observations will make known their real nature.” They are exclusively found in fresh standing water, or between plants where the water is still. Some of them are colourless, others green, black, or clear blue. This genus gives name to the family Stentorina proposed by Lachmann and others, and, in the classification of Dujardin and Perty, is a member of the family Urceolarina (p. 581). STENTOR Mülleri (xxvi II. 16, 17).- This is the “white funnel-like polpye.” discovered by Trembley; it is large, the crown or wreath of cilia interrupted, and the lateral crest or fringe indistinct; when outstretched it is trumpet-shaped, but in its contracted state is ovoid; and during division, or when the water around it evaporates, a muco-gelatinous mass is thrown out as an external cover- ing. When several are swimming in a glass vessel, they will gradually congre- gate, and select some particular spot, and then attach themselves, evincing, as Ehrenberg imagined, not only a degree of Sociality, . of mental activity. These animalcules receive coloured food very readily ; nucleus moniliform. Upon Lemnae and other water-plants, even under ice. Size, stretched out, 1–20"; contracted, 1-120". Ehrenberg referred to the exudation of a mucilaginous coat as the prelude to the death of the Stentor; but, as Cohn has shown (Zeitsch). Band iii. p. 263), it takes place in perfectly healthy and live- ly animals, and is an instance of the widely-pervading process of encysting. This observer, indeed, tells us that, when the conditions of existence become un- favourable, animalcules previously at- tached by their tapering posterior ex- tremity, as by a sucker resembling that of a leech, free themselves from their capsular envelope and Swim away, dis- playing then a brush of cilia at the end of the tail. The motion of a sentiment of sociality and of mental activity, sur- mised by the Berlin microscopist, de- mands the exercise of a powerful imagi- nation to realize it. Dr. Wright most kindly notices, in a letter to us, that Stentor Mülleri always secretes a gela- tinous case into which it can retract. As the zooids divide they form a gela- tinous mass, which is attached to weeds and often to the surface of the water, from which 10 or 15 Stentors aggregated together may sometimes be seen hanging with their heads downwards. The ex- ternal gelatinous sheath in Stentor and other Vorticellina and Ophrydina, Dr. Wright proposes to call the “colleto- derm,” as the homologue of the gela- tinous matter covering the polypidoms of the Hydroidae. S. Roeselii (x. 233, 234). —In form, size, and crest, this species resembles the preceding, but is of a more distinct yellowish-white colour. The nucleus is long, ribbon-shaped, and not moniliform; the contractile vesicle (seen at *) circular. Common in Summer; upon decaying plants, &c., in standing water, 1-140”; extended, 1-24" The moniliform intestine represented by Ehrenberg was very probably the chain of vesicular dilatations of the presumed vascular system connected with the con- tractile vesicle, and which is largely de- veloped in the Stentors, on one side of the body, as a canal extending from a circular sinus around the head. Dujardin regarded this species as simply a variety of S. Mülleri; and there is no apprecia- ble character truly distinctive §. them. S. caeruleus (XXIX. 8) resembles, exte- riorly, the two preceding species; but its granules are blue, nucleus articulated and chain-like (moniliform). It is trumpet- shaped when extended, ovoid when con- tracted; white or semi-transparent, ex- cept when coloured by food. The lateral crest and frontal wreath are continuous. When kept in glass vessels, they often fix themselves to the sides in clusters. They are best examined when placed in a large live-box; a magnifying power of 100 diameters is sufficient. Amongst Waucheriae. 1-480". Except its much smaller size, there OF TELE WORTICELLINA. 583 seems nothing to sufficiently distinguish it from the preceding species; for the bluish hue of the granules cannot be admitted as a characteristic. Even the difference in dimension is no satisfactory indication of a distinct species; for the Smaller animalcule may be but a younger specimen of the larger. S. polymorphus (XXIX, 7) resembles the preceding in form. Granules of a beautiful green colour; nucleus articu- lated and chain-like; lateral crest in- distinct; frontal wreath of cilia inter- rupted. This species will not receive indigo readily. Transverse self-division observed. Upon stones, decayed sticks, and leaves, in standing water. 1-120" to 1-24". Lachmann (A. N. H. 1857, xix. p. 225) seems to intimate that this species is equivalent to S. Mülleri and S. Roeselii. Both in this species and in S. caeruleus Bckhard has described reproduction by internal germs or embryos. Between the cilia, disposed in spiral series, single long hairs, similar to those of many Turbel- laria, are found, according to the testi- mony of Lachmann, S. igneus.—Less than the preceding; granules yellowish-green; surface bright yellow or vermilion; nucleus spherical; lateral crest absent; frontal wreath of cilia interrupted. Found by Ehrenberg upon the water-violet (Hottonia palus- tris). 1-72". S. niger (Vorticella nigra, M.).--Small, of a dark brownish-yellow or blackish colour; granules olive-coloured; nucleus spherical; lateral crest absent; frontal wreath of cilia continuous. This species is often so abundant that it colours large º in turfy hollows, of a dark blackish ue, resembling an infusion of coffee. The swimming movement of this species is readily seen (as in the others) with the naked eye. 1-96". S. castaneus (Wright). — A species named in a letter to us by Dr. Wright, of which the only particulars given are that it is of a dark chestnut colour, and that it selects the tops of the stems of Myriophyllum as its home, and glues all the young leaflets together with a ball of jelly, within which a crowd of zooids is imbedded. Genus TRICHODINA.—Vorticellina destitute both of tail and pedicle, distinguished from the preceding genus by the general Surface of the body being destitute of cilia. disc-shaped or comical. They possess a vibrating wreath of cilia anteriorly, on one side of which is a simple, not spiral oral opening. They are mostly T. Pediculus has the posterior end abruptly trun- cated like the front, and also surrounded with a wreath of curved setae, which it employs when crawling, in the manner of feet. In T. tentaculata there is a kind of proboscis. Coloured food is received by T. Pediculus and T. Grandinella. A kidney-shaped nucleus is seen in T. Pediculus. Many species live parasitic on freshwater Mollusca, or Zoophytes; but others have been found free in sea-water. - This description by Ehrenberg conveys a very imperfect conception of the real structure and appearance of Trichodina. The following account and figures from Stein will, however, supply its deficiencies:–“ The genus Tricho- dima consists of naked and highly contractile animalcules, subject to very con- siderable variations of form in the direction of the long axis. Their usual figure is that of a truncated come, much and suddenly distended posteriorly, and surmounted at their wider extremity by a wreath of cilia, which corre- sponds with the posterior ciliary wreath in other Vorticellina. The other, abruptly truncate extremity is furnished with an apparatus of hooks (XXIX. 15), whereby the animal can attach itself to other bodies. The mouth is circular, and placed on one side of the body, at a greater or less distance from the anterior extremity; it is furnished with a special zone of cilia to aid in the introduction of the alimentary particles.” (It is, however, not circular, but a spiral fringe of cilia, as Dujardin stated.) The genus Trichodina (Ehr.) agrees in the main with Urceolaria (Duj.). Of the several species enumerated by Ehrenberg, Stein asserts that two only are admissible, that the other three are foreign to the genus, and very 584 SYSTEMATIC HISTORY OF THE INFUSORIA. incompletely observed beings. Thus T. Grandinella and T. voraa, appear to be merely the embryos, or ötherwise the gemmae, of Vorticellina, whilst T. tentaculata is imperfectly known, and will probably always remain a ques- tionable organism. Further, this author would unite Trichodina with Urocérº- trum into a subfamily of Vorticellina. Lachmann (A. N. H. 1857, xix. p. 119) agrees with Stein in limiting the genus to the two species T. Pediculus and T. Mitra, and in rejecting the rest as not Vorticellina at all. According to him, Trichodina Grandinella and T. voraa, are rightly referable to Halteria (Duj.). TRICHODINA tentaculata (X. 227). — Discoid, destitute of the wreath of cilia, but with a fasciculus of vibratile cilia, and a styliform proboscis, 1-280". T. Pediculus (Cyclidium Pediculus, M.) = Urceolaria stellina (Duj.) (x, 228—230; XXIX. 14, 15, 17).-Depressed, urceolate, and discoid, with a wreath of vibratile cilia anteriorly, and another of short moveable uncimate cilia, or hooked setae, osteriorly. Ehrenberg remarks, “I have fed this species many times with indigo, and have seen numerous stomachs filled with the blue matter. It always runs upon the back, where there is a wreath of 24 to 28 mobile hooks (or uncinate cilia), and has the mouth and vibrating wreath of 48 to 64 cilia directed up- wards.” It appears to feed upon the little granules of the body of the Fresh- water Polype (Hydra, “Microscopic Ca- binet, pl. vii.) (Figs. 228 and 229 are side views, attached to a portion of a polype; fig. 230 is a top view). 1-570" to 1-280". T. Pediculus (XXIX, 14–17) is described in much detail by Stein (Infusionsthiere, . 175). “It has,” he writes, “a turban- shaped body; the truncated comical an- terior segment is morphological with the rotary organ of typical Vorticellina, and is shorter than the very ventricose and expanded posterior segment, from which it is separated by a deep annular con- striction or furrow, occupied by a wreath of vibratile cilia of less length than those forming the posterior zone. The oral aperture is seated in this furrow, the cilia of which are active in impelling food into the mouth. The posterior ciliary zone is parallel with the one in front, just described, and occupies the posterior surface of the hindmost segment of the body, near to the line of attachment of the circlet of uncini, as can be best seen when the animal is dead. It is this zone which principally serves for locomotion. The anterior segment can be retracted, and even vanish, by being taken up into the posterior, when the figure becomes cylindrical, with abruptly truncate ends. The posterior segment also contracts it- self considerably, and in So doing pre- sents several annular ſolds. The margin of the truncated extremity, which is much smaller thana section made through the middle of the posterior segment, is fringed by a firm cartilaginous or horny ring, having both on its outer and inner face a series of uncini, placed at equal distances from each other, and Some- what constricted behind the origin of each pair. The immer row of uncini lie in the same plane as the posterior Sur- face; but the external row are strongly turned outwards and backwards. Besides these is a structure not hitherto described, consisting of an annular, transparent, elevated rim or collar, often of a slight yellow colour, and of a horny aspect, placed around the outer margin of the corneous ring, above the base of the outer series of uncini. It is extremely flexible, directed obliquely outwards, and marked by very fine lines. The circlet of hooks is at once dissolved by acetic acid, whilst this structure remains; and, on the other hand, the whole prehensile apparatus disappears when the animal is put into alcohol.” The structure of Trichodina, as now unfolded by Stein, was both imperfectly and erroneously conceived by º; The long diameter of the largest Tri- chodina Pediculus Stein met with was 1-360"; the transverse diameter was about the same. Small specimens oc- curred of only half the size, but complete in all the details of organization. T. voraw. — Oblong, cylindrical, or slightly conical; anterior part convex, and crowned with cilia; the back rather attenuated and smooth. 1-570". This and the next species are, from their dissimilarity to T. Pediculus, re- moved by Dujardin to another genus he names Halteria, the two being equiva- lent to Halteria Grandinella, which again, in Stein's opinion, is the embryo of an Acinetiform phase of a Vorticella. T. Grandinella (M.).-Nearly spherical; sharply attenuated posteriorly; a wreath of cilia surrounds the truncated fore part. OF THE WORTICELLINA. 585 This species is liable to be mistaken, by an inexperienced observer, for a free Vor- ticella; its true distinguishing character appears to be its open wreath of cilia. 1-1500" to 1-860". T. Mitra (Siebold) (xxix. 16).--An- terior segment elongated, cylindrical, much longer than the slightly wider and more discoid posterior segment, into which it ºuiſ, expands. The outer- most margin of the posterior segment has a similar wreath ºf cilia to that of T. Pediculus; but the prehensile appa- ratus differs in the two species. T. Mitra the undulating cartilaginous ring is not armed with hooks, but has only the annular membrane, precisely like that in the other species, except that it is relatively smaller, less distinctly striped, more colourless and transparent, and therefore more readily overlooked. Between the two segments is the dee furrow in which the mouth is placed, from which a row of cilia extends to— wards each end at right angles to the posterior ciliary zone, and is homologous with the anterior wreath of cilia of T. IPediculus. Genus UROCENTRUM (X. 231, 232).—Free, with a tail-like style, but no pedicle, and no cilia, except a wreath anteriorly; oral aperture simple. Self-division transverse. Ehrenberg thinks the eyes, which Müller supposed he had seen, were most probably the traces of cilia, which he appears to have overlooked. UROCENTRUM Turbo (Cercaria Turbo, M.) (x. 231, 232).-Hyaline, ovate, tri- lateral, with a style, or Setaceous tail, one-third of its length. Ehrenberg says, ticella-stalk, but an articulated style on the back—perhaps a foot.” With Lemnae and Conſervae. Fig. 232 a dorsal, 231 a side view. 1–430" to 1–280". “The little tail is not a separable Vor- Genus VORTICELLA (XXVII. 1–5).—Crowned with cilia anteriorly; stalked when young, but at a later period, and also after self-division, sessile. The shape of the zooids, when stalked, is similar; the pedicle can be suddenly deflected spirally, by means of the long muscle within it, but it is never branched. At certain periods a second wreath of cilia is produced at the posterior part of the body. Not only, according to Ehrenberg, can numerous stomach–cells be secn, but likewise the gradual passage of the food onwards, in a twining sort of intestinal canal, though this is not easily observed, on account of the periodical deflection of the pedicle. However, in the genera Epistylis and Opércularia, whose pedicles are comparatively motionless, the nutritive apparatus may be much more perfectly investigated. The mouth and discharging orifice are separate, but lie in the same hollow, at the anterior margin. The granules are variously coloured, and constitute, in Ehrenberg’s language, clusters of ova; nucleus elongated, contractile bladder round. The animalcules are androgynous. The supposed increase by the growth of young animalcules out of the podicle (or of gemmae), like flowers on the stem of a plant, has arisen from cryoneous observation. When the animalcule loosens itself from its pedicle or stalk—a circumstance which, says Ehrenberg, “takes place at certain periods—the stalks die, or disappear, just like the shells of crabs, or as the nails and hair.” The muscular fibre within the stem requires stops, or an achromatic condenser, under the stage, to rendor it distinct. The Vorticellae being of so considerable a size, and easily procurable, have formed the subject of numerous investigations into their organization; but yet no observers have becm able to coincide entirely with the views of Ehrenberg. Among the most rocent researches are those of Prof. Stein, which have been fully put forward in the general history of these animals, to which we must refer (sco p. 277 et seq.). Suffice it to say that the Winding intestinal canal, the distinct stomach–cells, the clusters of ova, the androgynous nature mentioned in the above account from Ehrenberg of the internal organization of Vorticellae, have, not only in Stein's opinion, but in 586 SYSTEMATIC ELISTORY OF THE INFUSORIA. that of nearly every other naturalist, no existence; the appearances so inter- preted are explicable in a different manner. Adopting the results of recent discoveries, the following descriptive characters may be laid down. Body bell-shaped (campanulate), supported on a highly contractile, un- branched pedicle or stem, and surmounted at its wide upper extremity by a dilated and somewhat everted margin, or “peristom.” The wide anterior extremity is closed by a “ disc,” fringed with cilia, which commence on One side of a depression or fossa in the peristom, called the vestibulum, whence they ascend to surround the disc, and after continuing down its sides or “stem,” enter the mouth, and thence return to their starting point, thereby completing a spiral ciliary wreath, or rotary apparatus, which serves by its vibrations to draw food inwards to the mouth, and, when the animal detaches itself, as an organ of locomotion. The disc may be slightly elevated above the peristom, but less so than in other true Vorticellina; when so elevated, the ciliary apparatus is said to be expanded. On the other hand, it may be withdrawn under cover of the peristom, the cilia disappearing from view ; and when more strongly contracted, the whole disc is so drawn within the body that the entire appearance of the anterior extremity or head of the animal is lost, its ciliary mechanism being so inverted that it appears in- ternally like an irregular sigmoid cavity, in which the cilia may possibly be distinguishable, whilst the peristom is itself completely closed in upon the whole. In this state of complete contraction the Vorticella resembles a shut ovoid sac. Except the head, the rest of a Vorticella is destitute of cilia. The fossa lying between the sides of the ciliary disc and the peristom is the vestibulum, into which both the oral and anal outlets open, within a very short space of one another. The mouth opens below into a ciliated pharynx or Oesophagus, which is extended a considerable distance into the interior as a digestive tube, terminating, it would appear, suddenly by an open end. The food received at the mouth is transmitted through the oesophagus, and is formed at its extremity, with the aid of water, into a globule or vacuole, which is pushed onwards by the vis à tergo in a circular course towards the anal outlet. Besides molecules and granules derived from food (vesicular bodies composed of oily or other matters), there are always present in the interior a round contractile vesicle and an elongated curved band-like nucleus, often with several minute clear spaces or nucleoli. The vesicle is usually placed near the lower end of the digestive tube, and the curved, horseshoe- shaped nucleus lies across at the posterior third of the animalcule. The Vorticellae multiply by longitudinal self-division, and by the growth of gemmae from their base, and propagate by the resolution of the nucleus, after encyst- ing itself, into numerous Eugléma-like or Monadiform beings, and, according to Stein, by ciliated embryos through the medium of a previous conversion into Acinetae. The new beings formed from fission or gemmation are at first in a contracted condition, and on their detachment are found to be furnished with a posterior circlet of cilia to serve as a means of locomotion until they affix themselves and proceed to develope a pedicle, after which it disappears, and the Ordinary ciliary wreath of the head unfolds itself. Indeed, even when these processes of multiplication are not in operation, a Vorticella can detach itself and leave its stalk, or swim away with its pedicle when loosened from its hold. The pedicle is remarkably contractile, drawing itself into a close coil with extraordinary rapidity, and again uncoiling itself with equal quickness, regu- lating these movements by external conditions, as though possessing con- sciousness and will. The pedicle is a hollow tube, containing a thread or band within it, to which its contractile power is due. OF TEIE WORTICELLINA. 587 VoRTICELLAnebulifera (V. nebuliferaet W. Convallaria,M.).-Body campanulate; its base, to which the pedicle is affixed, may be either conical or hemispherical, according to its state of expansion or contraction; the pedicle or stalk is about five times the length of the body, and can form as many as ten coils. These Creatures usually congregate together, though each is independent of its neigh- bour; for on the approach of any foreign body to one, it withdraws, by coiling up its pedicle, while the others remain stretched out in search of food. An am- plification of 300 diameters is necessary to exhibit the cilia. During longitudinal Self-division the body becomes broader: gemmation takes place from one or other side, close to the insertion of the pedicle. Abundant, appearing like a white film, On the stalks and roots of Lemnae and other water-plants, even in winter under ice. 1-570" to 1–280". This is one of the species of Vorticella in which Stein believed he proved the development of an Acineta from the encysted animal, and also, under other circumstances, the generation of a brood of young Monadiform beings or germs. V. citrina (M.).-More hemispherical than the preceding, and the frontal mar- gin more expanded. Upon Lemnae, rarely with the former species. 1-430" to 1-210"; stalk 3 to 4 times that length. Perty speaks of this species as having a stiff stem, and apparently closely re- lated to the genus Stentor. Dujardin adopts this specific name for a Vorticella defined as being very variable in form, often campanulate, rarely conical, having a wide projecting border, variously con- torted or irregular. V. microstoma (xxvii. 1–6).-Whitish grey, ovate, marrower at the ends; frontal margin not expanded or campanulate; during contraction the animal is annu- lated; multiplies by longitudinal and transverse (?) self-division, and by gem- mation. In stagnant water. 1-2300" to lº" ; stalk six times longer than the Ody. This species was the subject of the minutest investigations by Stein, who not only represented it as becoming encysted, but also as being either trans- formed into an Acineta or Actinophrys, from which a ciliated embryo is deve- loped, or as giving origin, without such a metamorphosis, to a multitude of germs. He remarks on the immense range of size seen among different examples of this animalcule, viz. from 1-3007 to 1-3600" (XXVII. 5), the smallest equally with the largest exhibiting the same structure. The figure he describes as pear-shaped, the anterior half contracted; the ciliated disc slightly everted, not campanulate; rotary organ Small, and elevated, but slightly above the peristom. He objects to Dujardin's union of this species with V. convallaria, under the name of V. in- fusionum, as erroneous, the two being perfectly distinct beings. V. Campanula (Vorticella lunaris, M.) XXIX, 1). —Hemispherical, not annu- lated, bell-shaped, with the frontal mar- in broad, truncated, and not expanded. olour whitish-brown. This species ap- pears like a thick bluish film upon water-plants, and the single animalcules are discoverable with the naked eye. 1–120"; stalk seven times longer than the body. Perty adopts Müller's name V. lunaris for a species which he considers equiva- lent both to V. Campanula and V. patellina. V. hamata. — Small, ovate, hyaline, attenuate at both ends; body obliquely attached to the pedicle. 1-570". V. chlorostigma (Vorticella fasciculata, M.).-Green, ovate, comical, campanu- late, and annulated ; frontal margin (peristom) expanded. Often covers grasses and rushes with a beautiful green layer. 1-240"; stalk five times the length of the body. W. patellina (M.). — Hemispherical, campanulate; frontal portion very much dilated; its margin greatly expanded, and often turned backwards. 1-480"; stalk about seven times the length of the body. V. convallaria (V. craterformis, citrina, gemella, globularia, hilaris, nasuta et trun- catella; Enchelys Fritillus; Trichoda gy- rinus, M.).-Ovate, conical, campanulate, annulated; hyaline or whitish; frontal portion dilated, its margin slightly ex- panded. This appears to have been the first infusorial animalcule discovered. Leeuwenhoek, the discoverer, found it in stagnant rain-water, at Delft, in April 1675. It occurs in considerable abun- dance upon the surface of vegetable in- fusions, with V. microstoma, from which it is distinguished by its broad front, which gives to it a bell-shaped or cam- amulate appearance. Carus, in 1823, ancifully represented it as arising from spontaneous generation in oil, or from an accidental mixture of oil colour and spring-water. It has been described under various names by different natu- ralists. 1-430" to 1-24"; stalk six times its length. 588 SYSTEMATIC HISTORY OF THE INFUSORIA. This well-known animalcule is usually found attached to extraneous bodies in water; such as the leaves of duck-weed, Small aquatic shells, clusters of the ova, or the larvae of insects; an example of the latter is shown in the Microscopic Illustrations, fig. 30, where it may be considered as a parasite, or rather an epiphyte. As, when fully developed, it is mostly attached to some sta- tionary object, it affords many facilities to the microscopist for observation, and forms a good object also for ascertaining the defining power of his instrument, and his expertness in its management; for much of the clearness in structure will depend on the manner in which he manages the illumination. If this be not attended to, and the instrument has not sufficient power and penetration, it will exhibit only two cilia instead of a cir- cular row; indeed this animalcule is described and drawn in this manner by the old authors, an error which recent improvements in the microscope have demonstrated. - V. picta.-Ovate, conical, campanulate; frontal portion dilated, and its margin slightly expanded. The pedicle is very slender, and curiously marked through- out its length with red dots, 1-1150" to 1-570"; stalk four to five times as long. Perty treats V. lunaris, V. fasciculata, and V. cirrata of Müller as distinct species, instead of accepting them as varieties of others named by Ehrenberg; but he fails to give the characteristics necessary to their establishment as such. It is to be remarked, however, that V. lunaris and V. fasciculata are, he is in- clined to believe, merely varieties of the same species. Vorticella Ampulla (Müller) is treated by Lachmann as the representative of a new genus, as yet unnamed, belonging to the Stentorinae (A. N. H. 1857, xix. . 128). p V. * (Duj.) is not equivalent to V. microstoma and V. Convallaria, as he represented it to be. He describes it as commonly ovoid or nearly globular, trun- cated at the head, with a slightly pro- jecting border. The pedicle is very flexible, its surface striated obliquely. V. ramosissima (Duj.) = Carchesium polypinum (Ehr.). V. Arbuscula (Duj.) = Zoothamnium Arbuscula (Ehr.). V. lunaris (Duj.)= W. Campanula and V. patellina (Ehr.). Genus CARCHESIUM (XXX. 9).-Distinguished from the preceding genus by the spirally flexible branched pedicle. The bodies (zooids) upon the pedicle are all of the same form. The organization of this genus is not so well known as that of Vorticella and Epistylis. There is a simple wreath of cilia, which during quick vibration appears double; and, as in Vorticella, a posterior circlet is produced at certain periods; within the pedicle a trans- versely folded contractile band is observed during contraction. The mouth is lateral. Internally are whitish granules, and a contractile bladder; but the nucleus is indistinct. The growth of gemmae has been observed ; and the zooids can detach themselves from the stalk, as in the case of Vorticella. One of the best distinctive features between Carchesivm and Zoothamniwm, is that the contractile band of the former is not continuous throughout the pedicle and its branches as it is in the latter (see p. 293). This is noticed both by Stein and Dr. Wright: the latter adds, “The division of the zooids is more complete in Carchesivm than in Zoothamniwm. In the former, at each division, one of the zooids produces a new muscle not connected with that of the zooid from which it has separated.” CARCHESIUM polypinum (Leeuwen- hoek) (V. polypina, M. and Duj.) (xxx. 9).-Conical, campanulate, white; the frontal portion broad, truncate, and its margin expanded; pedicle branched in a sub-umbellate manmer. The axis matter or supposed muscle of the pedicle, first observed by Mr. Varley, is very distinct. 1-570" to 1-430". C. pygmaeum. (Zoothamnium Parasita, Stein).--Very small, ovate, white, rather dilated in front; pedicle branched in a bifid, rarely in a trifid manner. 1-2400". Berlin. On Cyclops quadricornis. C. Spectabile.—Comical, campanulate, dilated in front; branching in an oblique conical polypary, attaining two lines in height. Berlin. Genus EPISTYLIS (XXVII. 16, 22, 23; XXX. 11).-Pedicle rigid, either simple or branched; all the zooids of the same figure; or, in other words, º - OF TEIE WORTICELLINA. - 589 they are Vorticellae or Carchesia with a rigid hollow pedicle, without an internal contractile band. The situation of the mouth and anal opening is easily demonstrated by the employment of coloured food. In E. plicatilis, says Ehrenberg, the whole course of the alimentary canal can be seen. A con- tractile sac and a short band-like nucleus are observable in many; the latter, however, is spherical in E. mutans. Longitudinal self-division and gemmation frequently seen. The Epistylides are among the largest of the Vorticellina, and are exclusively found in pure water, on aquatic plants or animals. Stein’s researches throw additional light on the structure of Epistylis, which, he says, resembles generally that of Vorticella. The body has usually an ovoid or almost spindle-shaped figure, truncate in front, where a slightly everted ciliated peristom, of a sphincter- or lip-like character surrounds it, and gives to the whole being somewhat of a bell-shape. Within the peristom is a ciliary disc capable of being protruded or retracted at the pleasure of the animal, and having on One side the oral aperture. This disc is the “rotary organ ” in Stein's description, and in Epistylis its pedicle or stem is always short and thick. When retracted, the sphincter-like peristom closes over the rotary organ like a lid, and then the whole animal acquires a pear-shaped or globular figure. When the contraction has proceeded to its utmost, the peristom appears like a wedge-shaped or cylindrical process surmounting the body. The mouth opens into a slightly coiled, tapering tube, which ends abruptly towards the centre of the body; near its termination is a contractile vesicle, and not far from the last an elongated band-like or reniform nucleus. Epistylis multiplies in precisely the same manner as Vorticella, by fission and gemmation. Stein believes he has traced a cycle of changes through which it passes, between the encysted condition on the one hand, and the development of a ciliated Trichodima-like embryo from an Acinetiform phase of existence on the other. His observations tend to show that the embryonic being developed from the Acimeta of Epistylis anastatica is similar to Trichodina Grandinella (Ehr.), and probably identical with it. In E. mutans he satisfied himself of the occurrence of similar transformations, but felt less assured of their occurrence in E. grandis, E. berberiformis, E. Barba, and E. plicatilis. The stem or pedicle is inflexible. No canal, as represented by Ehrenberg, is usually discoverable; but sometimes the stem is finely striated longitudinally, and in older specimens has at varying distances transverse lines or false joints. Dujardin proposed to amalgamate the two genera Epistylis and Opercularia, since he could distinguish no generic differences between them. In this pro- posal, however, he was wrong, for, as Stein shows, there are sufficient di- stinctive peculiarities to warrant their generic independence. (See description of OPERCULARIA.) The animals seated on its branches, by their mode of articulation, enjoy considerable latitude of motion, and are also able in some degree to shorten themselves by the annular segments of their base. The stem is secreted by the animalcules it supports. When fission has taken place, two beings are for a time seen seated at the extremity of the same pedicle; but soon each begins to produce from its attached base a new pedicle for itself, and thus the original stem becomes branched, and this in a furcate or dichotomous manner. All the members of the same little tree (polypidom) are of nearly equal size. In the case of E. nutans, the largest noticed were 1-20th of a line in length; whilst in other polypidoms, whose stems and branches were propor- tionately thinner, examples were met with of very minute size (XXVII. 22, 23). In the smallest, no anterior cilia and no contained globules were visible; in larger ones, though only 1-150th of a line in length (XXVII. 23), such were found. These latter forms constitute Epistylis Botrytis (Ehr.). 590 SYSTEMATIC EIISTORY OF TEIE INFUSORIA. EPISTYLIS Galea. — Large, comical, contractile by transverse folds; mouth lateral and projecting; pedicle thick, branched, and articulated. Upon Cera- tophyllum. 1-120". E. anastatica (V. anastatica, crataegaria et ringens, M.).-Oval, without folds; frontal margin dilated and projecting; pedicle dichotomous, Smooth—or squa- mous with foreign particles. The gra- nules are white by reflected, and yel- lowish by transmitted light; the clear vesicle is often to be seen, but not its contraction; growth of gemmae un- known; self-division longitudinal. Upon Ceratophyllum and Small aquatic Miº and Entomostraca. 1-280"; height of little tree 1-140". “ E. anastatica,” says Stein, “differs from E. Digitalis, which it very closely re- sembles, by the form of its body, which is always funnel-shaped and campanulate, like that of E. plicatilis, only less elon- gated, and by the branches of its stem being outspread in a fan-like manner and acquiring a nearly equal height, or an umbellate condition.” He adds, “The three species most nearly allied, viz. E. anastatica, E. plicatilis, and E. Digitalis, have, when studied at different ages, few pºint, of separation, except that furnished y their habitats, E. plicatilis living upon the shells of Mollusca; E. amas- tatica upon the roots of Lemna; and E. Digitalis upon Cyclops quadricornis.” E. plicatilis (V. annularis et pyraria, M.).-Comical and elongated, contractile in annular folds; frontal margin dilated, truncated, , and slightly projecting; pedicle dichotomous, often corymbose, Smooth, or, when foreign bodies adhere, of a scaly appearance. This species is white to the naked eye, but somewhat yellow beneath the microscope; it is very much like the preceding, is often found with it, but is distinguished by being larger, by its ring-like folds when contracted, and by the tasselled or tufted appearance of the cluster. 1-280" to 1-210". The stem, says Stein, is solid and longitudinally striped. The nucleus, is reniform, and the contractile vesicle lies within the substance of the large rotary Organ. In old stems transverse lines or joints appear, at a distance from one another. The largest examples Stein met with were 1-168" in length. . E. grandºs. – Broadly campanulate, stalk decumbent, slender, smooth; the branches flexible and without articula- tions, but much tufted. This is not bnly the largest freshwater species of Epi- Stylis, but it also forms the greatest masses. Its proper colour is a bluish white; but it often appears of a yellow or greenish hue, from the colour of its food. Upon Ceratophyllum and Nymphaea, often like a bluish-white slime, easily broken up. In masses several feet long, and two to three inches thick. 1-140" to 1–120". E. flavicans (V. acinosa et bellis, M.). – Large, broadly campanulate, and of a yellow colour; pedicle Smooth, its branches coarctate. The branches are dilated at the axillae. In this species the alimentary canal is very evident. Size. (stretched out) 1-190"; tree 1-9" high. Although Stein represents the stem in Epistylis to be, as a rule, solid, yet, in a passing notice (p. 72) of E. flavicans, he remarks that the pedicle evidently had a hollow central canal. E. leucoa (Volvoa Sphaerula, M.). — Large, broadly campanulate; pedicle erect, Smooth, and articulated; the branches capitate or collected in a head. These animalcules are convex anteriorly, have distinct colourless granules, a sim- ple wreath of cilia, and around mouth on the margin. The nucleus is bent in the form of the letter S. 1-120"; tree 1-24". E. Digitalis (V. Digitalis, ringens et in- climans, M.). --Small, cylindrical, campa- nulate; stem dichotomous, and finely annulated. This well-marked form in- fests the Cyclops quadricornis, which it Sometimes completely covers. In the beautiful little tree this species forms by its branching, the Notommata petromyzon nestles just like a bird in a bush, and fastens its eggs to its branches. Coloured food is readily taken. 1-430”; tree 1-20". The figure is more like that of the flower of the foxglove (Digitalis), as the name implies, than bell-shaped; for the peristom is very little everted, and its diameter not greater than the middle of the body. The rotary organ protrudes Some distance, and lies very obliquely. The nucleus is band-like, and curved in a semicircle. The annulation of the stem could not be seen by Stein, except, as in verymany Epistylides, near the junc- tion or bifurcation of the branches, and occasionally in very old specimens: in these last it often has a rusty colour. E. (?) mutans (Opercularia mutans, Stein). — Ovate, attenuated at both ends; mouth two-lipped and prominent. The pedicle annulated (xxvii. 16, 22, 23). “This animalcule,” says Ehren- berg, “can push forth a bladder between OF TEIE WORTICELLINA. 591 its lips, like (si parva licet componere magnis) a camel can its palate”. 1–430"; tree 1–24". The process above alluded to by Ehrenberg as protruded from the head of this animal is undoubtedly the sort of under lip alluded to by Stein in his ac- count of Opercularia (see next page). This author, again, confirms Ehrenberg in his doubt as to the position of this species, and shows that it is an Opercularia. E. Botrytis.-Very small,ovate,Crowned with cilia. They resemble grapes upon a simple hyaline pedicle. This species together with E. Arabica and Carchesium pygmawm are, in Stein's opinion, not really distinct species, but different phases of the same animalcule. 1-2400"; tree 1-240" (see p. 589, last line). E. vegetans (Volvoz vegetans, M.). — Very small, ovate, crowned with cilia (?); disposed in clusters, like the pre- ceding, upon a branched pedicle, of a yellow colour. When the water con- taining this species is coloured with indigo, strong currents are seen at the front or head of each animalcule, evi- dently caused by a vibratile organ; but whether this is a wreath of cilia or a simple proboscis, is undetermined; if a proboscis, this creature would belong to the Monads, where it would form the pe of a new genus. In river-water, 1–3450"; tree 1-140". Brightwell says (Fauna Infusoria of Norfolk, 1848) that the armed or oval ani- malcules are furnished with a long fila- ment, that, when the water is shallow, they detach themselves, and swim about with a revolving motion. The organ of motion he states to be a long filament (proboscis); if so, the animal is not an Epistylis. Stein treats it also as a very doubtful Epistylis. E. parasitica.—Small, conical, campa- mulate, and solitary; pedicle simple and Smooth. Upon Zoobotryon pellucidus. 1-570"; with pedicle 1-120" to 1-24". E. Arabica. —Small, oval, campanu- late; pedicle but little branched, smooth, and hyaline. In the Red Sea. Size of tree 1–140". This species, as well as E. Botrytis and Carchesium pygmaum, are adduced by Stein as insufficiently marked, and re- ferred by him to the young and incom- plete forms of other species, E. Barba. — Ovate, oblong, white; branches dichotomous; longitudinally and regularly striated. On larvae of insects. E. berberiformis = Opercularia berbe- rina (Stein) (XXIX. 4). —Oblong, sub- cylindrical, white; stem dichotomous, articulated, and striated, its divisions dilated at their apices. Parasitic, Berlin. This is not, as Stein shows, a species of Epistylis, but of Opercularia, under which we shall introduce it with the de- º: account this able writer supplies. E. euchlora.—Oblong, rather expanded in front, with green ova; stem dichoto- mous. 1-13" in height, Smooth. Para- Sitic on Planorbis cornea, Berlin. E. pavonina. — Very large, helmet- shaped, elongated in front; stem very high, dichotomous, striated, and hence, by decomposing light, displays many hues. Often 1–3" in height. Berlin. E. crassicollis (Stein), (xxx. 11).- Stem of considerable height, acutely and dichotomously branched so that the seve- ral zooids it supports are brought nearly on the same level (corymbose). Branches Smooth, transparent, straight, and of equal thickness. In some specimens transverse lines or joints occur; and the stem is frequently dilated at the point of divergence of its branches. Animal- cules ovate, contracted posteriorly, and also in a slighter degree anteriorly. The annulated, hoop-like peristom surmounts the body, having a rather smaller dia- meter. The rotary disc is convex, but rises only slightly above the peristom. The Oesophagus and its intestine-like continuation curve backward almost to the posterior extremity of the body. The contractile space lies close to the lower end of the stem of the rotary organ; the nucleus is horseshoe-shaped. Contents white, frequently with specks of red. Largest specimens 1-240” in length, and 1-480" in width. Occurs on the bristles of the hind feet and of the jaws of Entomostraca. E. branchiophila (Perty). — Spherical, with a truncate base; colour grey. Stem and branches colourless and smooth. 1-360"; length of polypidom 1–96". The animalcules are sparse in reference to the dimensions of the stem : the latter often rugose at its junction with the animal it supports. When the stem contracts it does so only on One side, and not com- pletely across. Both this description and the figures given in illustration by Perty are, as Stein observes, insufficient to characterize the species. The latter writer retains the name, however, for an Jºpīstylis having a relatively thick stem, of moderate height, repeatedly forked, finely striated and somewhat curved. Of the two branches resulting from a bifur- cation, one attains a much greater length 592 SYSTEMATIC HISTORY OF TEIE INFUSORTA. than the other; hence the appearance of a main stem and a subsidiary branch. The zooids terminating the ramifica- tions are pear-shaped, the width nearly equalling the length, and almost glo- bular when the peristom is contracted. They are of a greyish hue. The rounded, lip-like, ciliated peristom is of less dia- meter than the widest part of the body; and its entire space is occupied by the rotary organ, which is only a little ele- wated above it when extended. The nucleus is elongated and vermicular. The average ji of the body is 1-360" to 1–280"; and the width 1-456" to 1-336". Gemmation may be frequently seen, the buds growing from the fore part of the body behind the peristom. Genus OPERCULARIA (XXIX. 4; XXX. 1, 2, 27).-Branched pedicle, stiff and rigid, supporting dissimilar corpuscles (zooids). The anamalcules have two lips; the Superior one, supported by a muscle, is somewhat like a lid (operculum), which is a characteristic. Opercularia = Epistylis with dis- similar corpuscles. The organs of locomotion consist of a wreath of cilia, and a long muscle within the body; this raises or depresses the frontal region, in the form of an upper lip. Food is taken into, and its effete portions dis- charged from the large vestibulum situated in front and rather to one side, and to and from which the alimentary canal is seen running. Self-division and the separation of the zooids from the stalk may be frequently observed. The large dissimilar bodies occur singly beneath the animalcules, more espe- cially in the axillae of the branches; some are very large and egg-shaped, with hairs at their point, and only a small, round, non-vibratile opening. Ehrenberg observes that such are most probably parasitic bodies. In all probability, however, they are encysted corpuscles. The following characters, contrasted with those of Epistylis, are given by Stein. The peristom is, in Opércularia, merely a single border, neither ciliated, thickened, nor everted in a campanulate manner. The body, there- fore, is elongated, ovoid, constantly narrowed anteriorly, and simply truncated. The opening of the peristom, which also forms that of the mouth, extends as a wide and deep cavity (the vestibulum) to the oesophagus, which is prolonged far into the body as a narrow digestive tube. A distinction between this last canal and the Oesophagus is indicated by a group of three or four strong cilia placed at its commencement. The rotary organ springs from the wide oral cavity, on one side, by a narrow point, which is the apex of its trumpet- shaped figure. The base of this long conical Sac is formed by its ciliated disc, which is thrust much above the peristom when extended, but can be drawn down upon it and close it : the whole organ is very moveable. The older observers looked upon the rotary organ as a valve or lid; and Ehrenberg supposed it to have a long retractile muscle which could close it upon the mouth. However, no muscle exists within the pedicle of the organ; for this is a hollow sac filled with the same substance as the general cavity of the body, and in direct communication with it. The pedicle of the ciliary disc is longer and more moveable than that of Vorticella and Epistylis. The genus Opercu- laria is further distinguished by the presence of a delicate membranous, trans- parent process which stands out from the throat like an internally fixed collar, and is elevated above the peristom, forming a sort of under lip to the rotary organ. Whether this is ciliated, or only a vibrating membrane, Stein remains in doubt. It is the same structure as is referred to by Ehrenberg in his note on Epistylis” (Opercularia) mutans as a protrusile bladder-like process (see p. 590). OPERCULARIA articulata (V. Opercu- laria, M.) (xxx. 1) occurs as a little shrub, 1–6" to 1-4" high, white and dichotomous; carmine and indigo readily taken; and Ehrenberg states he saw as many as forty-four stomach–cells filled, resembling a girdle in the middle of the body. . The stalk is very delicately striated in a longitudinal direction, and shows, at its ramifications, a transverse QF TEIE WORTICELLINA, 593. line, or joint. Upon Dytiscus marginalis. 1–430". Stein creates several additional species of Opercularia, and has entered into many details respecting the structure of O. ar- ticulata (xxx. 1, 2). According to him, the body is spindle-shaped or ovate-elon- gate, and truncate before and behind. The peristom, which is continuous with the body, forms a simple terminal edge, sometimes quite smooth, at others plaited longitudinally. Similar plaits often occur at its posterior half, when the animalcule contracts itself. The disc of the rotary organ has three circlets of cilia, is con- tractile and changeable in form. The oral cavity behind the margin of the peristom is very wide and deep, ex- panded as a capacious sac, from one corner of which, posteriorly, the digestive tube proceeds. It is lined internally by a delicate hyaline membrane, which pro- jects beyond the peristom like an upright collar. At the base of the body is a dense collection of granules, apparently of a fatty character. The nucleus is horse- shoe-shaped, and a round contractile space lies near to the digestive tube at its commencement. There is a pecu- liar glandular-looking body on each side of the oral cavity at the anterior part of the body, the nature of which is not de- termined. When in a state of contrac- tion the animal is thrown into annular folds, the rotary organ completely re- tracted, and the peristom closed over it in a sphincter-like manner, the whole body assuming a spindle-shaped form, or, when contracted to the utmost, a pyriform or orbicular figure. Reproduc- tion takes place bygemmation; but fission has not been observed: Stein believes in the transformation of the animals into Acineta, and the development from these of ciliated germs (xxx. 3, 4). The length of the body of the largest specimens, when extended, is 1–96"; and the greatest width, at the middle, 1-216". The stem is very variously branched, and is less rigid and more flexible than in other species. The transverse lines or false joints are not characteristic, and the longitudinal stria- tion is not always observable. O. berberina (Stein) (XXIX. 4) = Epi- stylis berberiformis (Ehr.).-Animalcules outstretched elongated, cylindrical, slightly contracted 'before and behind: about 24 times longer than broad, with- Qut reckoning the extruded rotary organ, No separable peristom exists at the ante- rior truncated extremity (i.e. in technical phrase, it is obsolete); rotary organ comparatively shortly stalked, its disc having a single whorl of cilia. Oral cavity capacious, as in O. articulata; its membranous lining undulating, and seen with difficulty. An amal opening ap- pears at the base of the oral cavity, not far from the orifice of the oesophagus. Even when expanded, the body is sur- rounded by thickly-placed annular folds, which become much more strongly pro- nounced when it contracts itself. The surface of the body is covered by a very firm, transparent, structureless mem- brane, . can be isolated for exa- mination without any special prepara- tion, and is often left behind after death as a distinct sheath or skeleton. Multi- plication by gemmation has not been observed; but fission is common. The largest specimens were 1-190" in length, and 1-570" in width. The form of the stem is very variable, for two similar specimens are scarcely to be found; yet in all, the animalcules are supported at different heights, on stems varying in length, and therefore not corymbose. The stem, likewise, has not the stiff, regular construction of most Operculariae and Epistylides, but is generally curved outwards, and has at variable distances transverse lines or joints; the extremity supporting the animalcule is expanded. # is through- out solid, colourless, and diaphanous, and if at all striated longitudinally, is so in a very faint manner. On aquatic animals. Stein believes he has dis- covered its Acineta (XXIII. 17, 20). O. Lichtensteinii.-Body stout, short, barrel-like, the length not being double the width; except in sparingly-branched stems, the opposite ends are little con- tracted. The rotary organ is but slightly elevated above the peristom; its stem is short, thick, and almost cylindrical, little exceeded in width by the disc surmount- ing it, which has but a single circlet of cilia. The membranous process within the oral cavity rises above the peristom, is notched, thrown into longitudinal folds, and, to all appearance, ciliated. The nucleus is always short and oval or round; its position varies; the con- tractile space is circular, in proximity to the beginning of the digestive tube or the Oesophagus. The heap of fatty corpuscles near the base is present, as in many rigid-stem Vorticellina. The maximum length is 1-190"; and the width 1-300". It differs from O. arti- culata (XXX. 1, 2) by its round mucleus, 2 Q 594 SYSTEMATIC EIISTORY OF TELE INFUSOIRIA. and from O. berberina (XXIX. 4), which it closely resembles in its general orga- nization, by its length and width being much nearer equal, and by its not being bent backwards on the stem when con- tracted. Stein describes its Acineta and the ciliated embryo resulting from it. The stem is subject to great varieties; but these all agree in the stem expanding from its base in a more or less marke manner, in the branches being all of equal length, and, in consequence, the zooids elevated at different heights. The stems of the oldest generations are low, and have but few animalcules upon them, which are seated on short, curved, and enormously thick branches, such as are seen in no other Opercularia. The whole surface of the stem is covered with numerous, closely-placed, shallow and deep transverse folds or constrictions, which give it a knotty appearance; it is also longitudinally . In younger generations the stems are more densely branched; but the branches are not ex- traordinarily thickened, being as slender as those of the larger groups of O. arti- culata, and, like these, have only here and there transverse markings, for instance, at the angles of the branches. They are also longitudinally striped, and differ further from O. berberina by their ex- pansion upwards towards the base of the Superposed animalcule. On aquatic Crustacea and Mollusca. O. Stenostoma (Stein). —Body pyri- form, widest in front of the is line, rounded anteriorly, with a very narrow peristom, and behind the middle strongly contracted, so as to assume the appear- ance of a pedicle. The disc of the rotary organ is very narrow across, fringed with a single row of cilia; the membranous process from the Oral cavity rises only so much above the peristom as to form a narrow annular ridge. Nucleus long and horseshoe-shaped; contractile space cir- cular, placed near the commencement of the oesophagus. Stem branched dichoto- ... short, whence the individual animalcules (not more than 4–6 in num- ber) are in near apposition. ... 1-900"; length of stem 1-360". The stiff stem is small relatively to the body, striated longitudinally, and obscurely wrinkled transversely. On aquatic Mollusca. O. microstoma (Stein) (XXX. 37). — Very similar to the last-named species. Like this, it forms a lowly-branched stem bearing few animalcules. The branches are comparatively thin, and mostly marked by thickly-set annular constric- tions, rendering it more or less crooked and knotty. Some stems, however, are quite smooth, and also without trace of longitudinal striae. The animals, when extended, are pear-shaped, and have a constriction behind the middle, and in front a very narrow peristom. Rotary organ with a short stem and a narrow disc; on the opposite side of the oral cavity is a tongue-like membranous pro- cess. The oral cavity is comparatively narrow; the digestive tube short, the contractile vesicle lies near its upper end, and the curved, hook-like nucleus behind the rotary organ. In contraction the animal retains its pyriform figure, and is thrown into annular folds poste- riorly. When more strongly contracted, it becomes oval. Greatest length 1-280”; width 1-450”. On the feet of Crustacea. O. mutans º = Epistylis mutans (Ehr.); but the description by Ehren- berg requires to be modified by the dis- coveries of Stein, to render it correct and characteristic. The two-lipped mouth is a º of the rotary organ and membranous process of the oral cavity, and the retractile palate is equi- valent to the rotary organ of Stein. Genus Z00THAMNIUM (XII. 67, 68, 69).—Comprehends Vorticellina with a spirally flexible branched pedicle having an internal muscle. The stalked corpuscles are of different shapes; a wreath of cilia surrounds the frontal region. been observed. The mouth simple and lateral. cells (vacuoles) can be demonstrated by artificial feedings. Numerous round stomach– Self-division has The more accurate examination of Stein supplies additional details, and corrects those above, as given by Ehrenberg. The so-called frontal region is the peristom of Stein, which presents a rounded tumid border, but no cilia; for these organs form a fringe around a ciliary disc within the circumference of the peristom, which can be protruded beyond, or retracted within it. In short, Zoothamnium, like other Vorticellina, has a “rotary organ,” which, by the Whirling of its cilia, draws inward to the mouth, situated on one side of OF TELE WORTICELLINA. 595 it, a current of water, together with the nutritive particles it may contain. Within are a curved semicircular band-like nucleus, a contractile vesicle, the So-called stomach-sacs or vacuoles, and numerous granules and molecules. The mouth opens into a wide Oesophagus, which extends backwards towards the centre of the body, where it terminates abruptly. The stem essentially differs from that of Carchestwm in its central canal being continuous through- out ; but the distinction drawn between the two genera by Ehrenberg, from the presence of dissimilar corpuscles (animalcules) being found in Zootham- niwm, and not in Carchesivtm, is worthless, as that circumstance is indicative of nothing more than a certain condition of development. The oldest portion of the stem in this genus often becomes solid and rigid, and thereby re- sembles that of Epistylis, for which it might he mistaken (see p. 293). Dr. Wright observes that the primary (parent) zooid of a polypary does not begin to develope the contractile band in its pedicle until this has attained a con- siderable length; hence, for the time, this primary zooid is an Epistylis by the structure of its stalk. Zoot HAMNIUM Arbuscula (Vorticella racemosa, M. and Duj.) (XII, 67, 68,69) has the branches in racemes or irre- gular umbels; corpuscles (zooids) white, campanulate; pedicle very thick. These beautiful little trees resemble plumes of feathers. They have the characters of Carchesium and Opercularia as respects the presence of globular bodies in the axillae of the branches, but are at once distinguished by the strength of the latter. Found upon Ceratophyllum and other freshwater plants, and also in Sea- water; visible to the naked eye. It con- tracts itself on its very elastic pedicle on every alarm. It lives but a short time when removed from its native place (Brightwell, p. 344). Size 1-430"; tree i-4", stalk one-fourth the thickness of the body. * Z. niveum (Z. plumosum, Wright). — Main stem zigzag; branches short, alter- nate, almost verticillate, given off from each angle of stem; zooids oblong, cam- panulate, white, clustered at the ends of the branches, which are filiform, the lower ones often deserted, while the upper bear clusters of club-shaped little bodies rounded anteriorly. Summit of main stem and branches curved back- wards like an ostrich-feather; hence the name plumosum, proposed by Dr. Wright. 1–210". Z, affine (Stein).--Stem dichotomous; branches attaining a nearly equal eleva- tion. The primary stem varies in length as well as the lateral ramifications; hence the arborescent polypidom varies con- siderably in its general aspect, being at one time loose and diffuse, at others com- pact and dense. When extended, the transparent branches are smooth, but during contraction are thrown into trans- verse folds, and acquire a relative in- crease of thickness. The canal is con- tinuous throughout, except at the base of attachment in specimens of some age, where the stem is solid; in its interior is the axis-matter, i.e., in Ehrenberg's language, the muscle moving the stem. The animalcules borne on the extremi- ties of the branches are oval, somewhat contracted behind, and truncate in front, where they are surmounted by a thick tumid peristom of rather less diameter than that of the body. The rotary organ is strikingly narrower, and protrudes little beyond the peristom: in the course both of the extension and retraction of the rotary disc a fold is pº which gives the appearance of a double peri- stom. A wide Oesophagus and digestive tube opens from the mouth; and near its posterior extremity is the contractile vesicle. The nucleus resembles a short Semicircular band, and lies across the body. The relative thickness of the stem is a remarkable character of this species, being one-half that of the animalcules it supports. Usuallength of animals 1-380" to I-270"; width 1–650” to 1-570". On Entomost aca, &c. Z. Parasita §. poly- pary, very Small, supporting few animal- cules: the latter agree in figure with those of Z. Arbuscula. Stein believes it identical with Carchesium pygmaeum, Ehr, the latter being an incompletely- developed form. On Entomostraca and Small aquatic Crustacea. We are indebted to Dr. Wright for a notice of the following species:— 2 Q 2 596 SYSTEMATIC EIISTORY OF TELE INFUSORIA. Z. dichotomum.—Stem very regularly drical, resembling fruit of the Rosa canina. dichotomous; pedicles long; zooids cylin- || Z. plumosum (Wright)=Z. niveum. Genus SCYPHIDIA (Duj.).—Sessile, cup-shaped, tapering at the base, covered with a reticulated integument. - - This genus is received both by Perty and Lachmann. The former notices three species, of which one, viz. Sc. patula, is new, the two others being Sc. ringens and Sc. pyriformis. Lachmann, on the contrary, although admitting the genus, rejects the species of Dujardin and Perty, “as they have a short stem, and appear to be only particular states of pedunculate Vorticellina, in which the stem has not attained its usual length; but on the other hand,” he continues, “two other beings must be referred to it, both of which attach themselves to the naked parts of small freshwater mollusca, and never form a stem, but which were often observed by me in process of division, and are easily distinguished from other forms which are, like them, attached at first, by their posteriorly-truncated form, and a projecting pad at the margin of the hinder end.” SCYPHIDIA rugosa,—Oblong, marked with distant oblique deep striae, looking like furrows. 1-565". In pond-water, amongst vegetable débris. To this genus Dujardin would also attach the Vorticella ringens and V, inclinans of Müller, and possibly also the V. pyriformis of the same author, under which name Ehren- berg has described a variety of V. conval- laria. Sc. pyriformis.-Grey, hyaline; with no pedicle, or an extremely short one; constantly contracting itself. Uncom- mon ; on Cyclops, &c. Length, in- cluding stem, 1-720" to 1-600". Is closely allied to Se, ringens. Sc.patula (Perty).-Widely campanu- late; of a bluish-grey colour; stem half the length of the body. Length, with stem, 1-360". Uncommon, with Pota- noſeto?. Vorticella hamata (Ehr.) is probably another species, and identical with V. in- climans, which Dujardin numbers among the Scyphidia. SC. limacina (Lachmann) = Vorticella limacina (Müll.) (XXIX. 3).-Body nearly cylindrical, tapering a little at each end, and ammulated; peristom narrow and not turned backwards; ciliary disc narrow, and furnished with a projecting umbi- licus in the middle; the posterior trun- cated surface provided with a thick pad- like margin. 1-240" to 1-360". Lives on small species of Planorbis. SC. Physarum (Lachmann) is longer and more uniformly cylindrical than the preceding, the peristom longer and often turned backwards (everted), and the hinder margin thinner and shorter. Lives on the naked parts of species of Physa. Genus URCEOLARIA (Lamark and Duj.).—Body not ciliated throughout, contractile, varying in shape from hemispherical or discoid to globular; sur- rounded by a plane margin fringed with a row of strong cilia planted obliquely, which makes a spiral turn inwards at the oral aperture, which is also situated on the margin. - Vorticellina of different kinds have been mistaken for examples of this genus, and Ehrenberg has placed some of its members among the Trichodinae; indeed the type of Urceolaria is the Thrichodina Pediculus of Ehrenberg. Many species of this genus are parasitic on freshwater Mollusca and Zoo- phytes; but Müller mentions some found by him in sea-water. r There appear no sufficient grounds for instituting this genus when that of Trichodina is admitted, as it is by naturalists generally. URCEOLARIA stellina = Trichodina Pe- the border of the disc ciliated. In diculus (Ehr.). U. discina = Vorticella discina (M.).- Described by Müller as orbicular, hol- lowed out above, convex beneath . . . ; sea-water. Uncommon. Ehrenberg has treated this form as identical with Tri- chodina Pediculus, but, as Dujardin thinks, erroneously. IIowever, it is impossible OF TEIB WORTICELLINA. 597 accurately to decide what the being which Müller met with is, from the ac- count he has left us. U. limacina.-Sessile, cylindrical, dia- bhamous; orifice truncated, with 2 or 4 indistinct cilia (according to Müller), or, as we may presume, with a circlet of cilia around the margin of the wider ex- tremity, and a collection of cilia at the marrower base, by which the animal at- taches itself. Parasitic on the tentacles of Bulla and Planorbis. U. Dujardinii = Vorticella bursata and V. utriculata (Müll.).-Capsular or utri- cular in shape, bellied posteriorly, cili- ated on the anterior margin. Müller distinguished this being under two forms, one of which he described as having a projecting papilla at the centre of the anterior surface, capable of elongating it- self. In sea-water. These species of Müller appear to us too indistinct to insist on as independent forms, Genus CHAETOSPIRA (Lachmann) (XXXIX. 5, 6).-The surface gene- rally covered with cilia, like the genus Stentor, from which it is distin- guished by having that part of the parenchyma of the body which bears the ciliary spiral and the anus (which in all the Stentorinae lies on the dorsal surface of the body, close under the ciliary spiral, and not in a common pit with the mouth) drawn out into a thin process. This process is narrow and bacillar; the series of cilia commences at its free extremity, and only forms a spiral when in action by the rolling-up of the lamina. The process bears the anus. The animalcules inhabit a sheath or tube, of a mucilaginous or even horny density. “It is possible that the free-swimming Stichotricha secunda of Perty, which he arranges with the Oxytrichinae, is allied to Chae- tospira; his figure, however, is very inexact, and might perhaps represent a Loxodes or Amphileptus Fasciola ; and, as he does not describe the position of the anus, which he never figures, any more than the contractile vesicle and the nucleus, I do not venture to place his Stichotricha with the Stentorinae. If it should turn out that it belongs to that family, it must be placed beside the analogous sheath-inhabiting Chaestospira, as a genus not inhabiting a sheath.” CHAEToSPIRA Milleri (XXIX. 5, 6).- Slender. The first cilia of the series upon the process are somewhat, but not re- markably longer and stronger than the rest; when rolled up, the ciliated bacillar process forms more than one thrn of a #. Sheath flask-shaped and horny. Hitherto found only in the open cells of torn leaves of Lemma trisculca, growing in fresh water near Berlin. CH. mucicola.—Enclosing tube mucous in consistence; animalcule shorter and more compressed; the rolled-up ciliary process does not form a complete turn of a spiral; the first cilia are considerably larger than the rest, the first one espe- cially being nearly twice as long as most of the others. Genus COENOMORPHA (Perty) (XXVIII. 27–30).--Small, hyaline, of a bell-like or hemispherical figure, concave at its truncated base, which has an irregularly notched margin, and a tail-like process depending from it at its Centre. Rim of the bell furnished with long cilia. Except in the absence of the long tentacula, these beings, according to Perty’s figures, have a general resemblance to minute campanulate Medusae ; or, otherwise, they may be likened to miniature parasols with fringed edges and a short handle. Perty has placed this genus in his family Urceolarina, which is equivalent to that called Stentorina by Lachmann. But, to our mind, much doubt must attach to this assigned position, for not only is there a very great departure from the general form of every genus of Vorticellina, as Perty himself could not fail to remark; but, from his figures, no characteristic, no internal organ- ization appears to establish the organic affinities of these curious beings. 598 SYSTEMATIC ELISTORY OF TTIE INFUSORIA. CoENOMORPHA Medusula (xxviii. 27— tail, 1-240" to 1-190". It swims actively 30).-Colourless, transparent, with a and rotates on itself, undergoing various small number of internal vesicles and changes in outline. Some specimens ex- molecules. Length, together with the hibit folds of the surface. Genus SPIROCHONA (Stein) (XXX. 17–20, 27, 28).-Body naked, but having a firm corneous integument; attached perpendicularly by its base, and quite motionless; of an elongated, flask-like shape, with an anterior, spirally-convoluted, funnel-like head or peristom. Posteriorly it narrows to a small base, whereby it is fixed either immediately or mediately by a very short pedicle. The infundibuliform spiral peristom surmounts a constricted portion or neck. The spiral lamina forming the peristom terminates abruptly below, so as to leave a cleft, which conducts to the mouth; its upper portion is rolled around the longitudinal axis of the peristom, and produces a solid central pivot. The innermost turn of the lamina constitutes a funnel, which surmounts the whole peristom, and with the next coil forms what Stein calls the “spiral funnel,” whilst the lowest and widest spiral represents the true peristom, homologous with the ciliary spiral or peristom of Vorticella. The latter is richly covered with cilia, which extend in less number to the second coil. Internally, a digestive tube is seen to extend a considerable distance from the mouth, having a contractile vesicle placed near its termination. A large nucleus is seated near the middle of the animal, having a clear central space or nucleolus. Fission has not been witnessed; but gemmae are fre- quently produced, which, under certain circumstances, become encysted, and, as Stein believes, undergo an Acinetiform metamorphosis (XXX. 21–28). Length 1-750" to 1-216"; breadth of largest 1-600". SPIROCHONA gemmipara (XXX.17–20). —The above, description applies spe- cially to this form. capsules of Gammarus and other Ento- mostraca, in fresh water. SP. Scheutenii (xxx. 27, 28) agrees with the foregoing in size and figure; but the peristom is more simple, consist- ing of little more than a single coil of a found on the ova- wide lamina, and has, besides, a series of stiff fibrous processes fringing it on one side. The internal face of the funnel is lined with cilia below. Found on Ento- mostraca in brackish water near Am- sterdam by M. Scheuten; they are at- tached to the long feathery bristles of the post-abdominal feet, and not to the ova-capsules, like S. gemmipara. FAMILY IV.-OPHRYDINA (WAGINTFERA). (XXVII. 10–15; XXVIII. 18–20, 23; XXX. 29–35.) Loricated polygastric animalcules, Solitary or aggregate, possessing a distinct alimentary canal, a separate mouth and discharging orifice, which approxi- mate and terminate in the same spot. In organization it resembles the family Vorticellina; in fact, continues Ehrenberg, it includes true Vorticella, or Stentors, enclosed in a gelatinous, membranous, combustible lorica. Be- sides the usual frontal wreath of cilia, there is in Ophrydium a second wreath placed posteriorly; and Tintinnus has an elastic muscular stalk or tail. Al- though, as Ehrenberg tells us, the polygastric organs of nutrition can be demonstrated in all the tribe by using coloured food, it is only in Ophrydium that an alimentary canal has been distinctly seen. Longitudinal division of the body takes place within the lorica, which continues unaffected. In Ophrydium transverse division has been doubtfully affirmed. The genera are disposed as follows:— OF THE OPEIRYDINA, 599 Forming Monad-clusters, through incomplete self-division of the lorica...... Ophrydium. to lorica * & e º e º e º e º is e º e º ſº º sº dº º is tº is s tº a ſe e g º e º e s a e e º e g º e º a º | Body furnished with an elastic pedicle attached } Tintinnus Animalcules solitary, no self-division of the lorica Lorica stalkless ............ Waginicola. Body stalkless...... Lorica stalked............... Cothurnia. Of the genera composing this family, Ophrydium is arranged by Dujardin with the Urceolarina, and Vaginicola with the Vorticellina. This author writes— “The so-called lorica of Ophrydia (Duj., or Ophrydium) is an amorphous gelatinous investment, unlike that of Vaginicola, which is a truly resistant enveloping membrane. The individual beings in the gelatinous ball of Ophrydia are elongated, cylindrical, or fusiform, and capable of varying their figure.” Eurther, Dujardin includes Tintinnus and Corthwrnia in the genus Va- givicola. Stein enumerates Tintinnus among the genera of Ehrenberg's Ophrydina, but offers no account of it. He rejects the distinction, as does Dujardin, between Vaginicola and Cothurnia, and would transfer the whole of this family, so reduced, to Vorticellina, with which its members have the greatest similarity in organization. Perty adopts the the title Ophrydina, but com- prehends under it only the single genus Ophrydium. Lachmann rejects Tintimmws from the list. The characters laid down by Ehrenberg, of this family, are very unsatis- factory. Its members cannot be said to be loricated in the same way as Colepina or Euplotina; for in these the lorica consists of a thickened, closely- adherent integument, whilst in Ophrydina the structure so called is a loose sheath, open at One extremity, which may in Some be seen gradually excreted from and built up around the animalcule, which last, moreover, has a distinct integument of its own. In the Ophrydima, therefore, it is rightly called a sheath, case, or tube. Ophrydium, indeed, is exceptional; for, though it secretes a large quantity of muco-gelatinous substance, it never builds this up around it into a sheath, but merely sends into it a long, tapering, fibrous prolongation from its posterior extremity to secure a firm hold, whilst its 'body projects freely from the mass (see Part I. p. 282). Moreover, it is this genus only that is aggregated, all the rest being Solitary. These pecu- liarities may be held to justify Perty in erecting this genus into a family. The presence of numerous stomachs and of a distinct alimentary canal, it need only be said, are details of organization required by the hypothesis of Ehrenberg, and supposed in some instances to be demonstrated by feeding with colouring matters. - As Ehrenberg rightly intimates, Ophrydina may be briefly defined as Wor- ticellina living in a sheath, instead of being supported on a pedicle. From this general definition Ophrydium is necessarily excluded as an exceptional form ; and it becomes, therefore, a matter of regret that a family should be named from a genus in no sort its true type. Perty has invented the name “Waginifera '' for a family containing the two genera Vaginicola and Co- thurnia; and it is certainly preferable to Ophrydina, whether Ophrydium be comprehended in it or not. - Genus OPHRYDIUM (XXX.5, 6)—Lorica gelatinous; animals clustered, in consequence of perfect self-division of the body, but imperfect of the lorica. This circumstance gives rise to very peculiar external appearances; 600 SYSTEMATIC ELISTORY OF TEIE INFUSORIA, for each body very frequently divides itself, the two portions separating entirely,–the gelatinous lorica forming only a separating wall. In this manner thousands and millions of connected animal-cells are quickly formed, appear- ing as gelatinous globular masses or balls. - It is a misapprehension, on the part of Ehrenberg, of the actual phaeno- mena, when he states that the large gelatinous ball formed by the multipli- cation of Ophrydia is the result of imperfect fission of the lorica; for, as we have pointed out, the animalcules have no lorica or sheath in the sense Ehrenberg intended, but are merely attached by a sort of non-contractile stalk penetrating far in the interior, upon the Surface of the gelatinous mass. When fully contracted, indeed, it is drawn down upon and slightly presses into the soft mass, raising this as a rim around it; consequently it is also an error to say that the mass is composed of numberless little cells, seeing that nothing like a cell is constructed around the animalcules. Stein found within the interior of the gelatinous mass numerous intertwining and twisted fibres, which he concluded were vegetable parasites, probably of the family Lepto- mitäe. Agardh and other botanists have described the gelatinous balls of Ophrydium as a species of Nostochineae, under the name of Nostoc prwmi- forme; but this is a great mistake, for no cellular or proper vegetable struc– ture is present. - Stein has added to the vaginated Vorticellina, or the Ophrydima, the genu Lagenophrys; and Dr. Wright (Edin. New Phil. Journ, 1858) the interesting genus Lagotia. OPHRYDIUM versatile (Trichoda inqui- becomes oval or globular. Fission is lina et Vorticella versatilis, M.) (XXIII. 5, 6).-Body fusiform, tapering to a fine extremity from behind the middle, and anterior to it contracted into a cylin- drical neck, º a funnel-shaped head surmounted by an annular peristom with a ciliated rotary disc. The mouth opens into a narrow and long ciliated cesophagus. The contractile vesicle is seated near its end; the nucleus is long, narrow, and twisted. The external sur- face is thrown into close annular folds ; and usually three longitudinal plaits ex- tend from the posterior end as far as the middle of the body, which disappear when the body contracts. A subjacent cortical lamina is evident, and, imbedded within this, numerous chlorophyll utri- cles, giving the animal a vivid green colour. hen contracted, the body as- sumes the form of a long-necked flask, and even the nucleus shortens itself. In more complete contraction the figure only longitudinal; when an Ophrydium quits its hold after fission, it swims away by means of a temporarily developed posterior wreath of cilia, just like a Vor- ticella. It is found encysted, and, Stein believes, in an Acimetiform phase (xxx. 7, 8). Vividly green, and associated in smooth and globular clusters or masses, which vary in size from a pea to a ball five inches in diameter; they are either free or attached. Ehrenberg states that, in May 1837, he saw hundreds of clusters as large as the fist, which, by the evolu- tion of gas, were at intervals elevated to the surface, and driven by the wind to the edge of the water. In sea-water; also found by Brightwell in fresh water, and in a small turf-pit, upon tendrils of roots of marsh-plants, and the stalks of the white water-lily. Length of single animalcule stretched out, 1-120" to 1-90”. Genus TINTINNUS.—Ophrydina which possess divisibility of the body, but not of the urceolate lorica; the body is attached to the interior of the sheath by a flexible pedicle (somewhat similar to the clapper of a bell); the mouth serves both as a receiving and discharging orifice; stomach–cells and traces of a yellowish ova-cluster are more or less visible; self-division was known to Müller. - • - Tintinnus, as before noted, is a genus not admitted by Dujardin; Perty likewise ignores it; and Lachmann (A. W. H. 1857, p. 119) feels the necessity of excluding it from Vorticellina (using this term in a wider sense, so as to OF THE OPEIRYDIN A. 60] include Ophrydina), since it is ciliated all round, and differs greatly from them in the form of its alimentary apparatus. Moreover, a species inhabiting a gelatinous sheath occurs in the freshwater ponds in the Thiergarten at Berlin. TINTINNUS inquilinus. – Hyaline or yellowish; lorica cylindrical, glass-like, bell-shaped. 1-570", with stalk 1–240". In Sea-water, on Algae. T. Subulatus (Vorticella vaginata, M.).- Hyaline; sheath conical, with a posterior subulate elongation. Ehrenberg observes that, if this elongation of the lorica were called a stalk, we should require a new generic name for the animalcule. Length of lorica, 1–90". T. Cothurnia.-Hyaline; sheath cylin- drical, hyaline, indistinctly annular; ra- ther attenuate and truncate posteriorly. 1–440". In the Baltic. T. Campanula.-Hyaline; sheath widely campanulate, dilated in front, pointed behind. 1–290". In North Sea and Baltic. T. denticulatus. – Sheath cylindrical, hyaline, sculptured with oblique rows of dots, front margin acutely dentate; pos- terior extremity pointed, 1–220". In the North Sea. Genus WAGINICOLA (XXVII. 10, 11; XXVIII. 18, 19).-Neither the body nor the lorica stalked; a wreath of cilia surrounds the truncated front portion, within which is the orifice or mouth. The polygastric apparatus, the passage of the food onwards, its return, and the exit of the refuse near the mouth, and coloured ova-granules, are mentioned by Ehrenberg. In- crease by longitudinal self-division of the body (not of the lorica) has been seen in all the species. To the above account must be added, according to Stein’s observations, that the body of Vaginicola has in front a peristom, from out of which a “rotary apparatus” protrudes, consisting of a ciliated disc, supported on a stout stem or pedicle, just like that of Vorticella. A mouth opens on one side of the disc, and leads into an Oesophagus; but no polygastric structure, as surmised by Ehrenberg, is visible, although numerous alimentary vacuoles are usually present. Ova-granules, again, are merely hypothetical, and, as in other Infusoria, where mentioned by Ehrenberg, represent particles of various kinds, but mostly coloured granules. In a new species noted by Dr. Wright, the tubular sheath has a peculiar structure in the form of a valve, which closes over the animalcule when it retreats to the bottom of its case (XXVIII. 18, 19). In all the particulars of internal organization, Vaginicola resembles Vorti- cella. Propagation by fission and gemmation is very distinct; by the former process more common (XXVII. 10, 11). The development of the bud takes place from the base of the parent, and within its sheath. The young being, produced by either process, is furnished, as in Vorticella, with a posterior wreath of cilia, whilst it is endowed with free locomotion (XXVII. 11). It frequently happens, as represented in the last-quoted figure, that the young being assumes on its formation a contracted ovoid form, with its frontal wreath retracted. Upon the appearance of the posterior whorl of cilia, and aided by its movements, the animal loosens itself, escapes from the parent-case, and swims freely away, elongating itself, it may be, if previously contracted, and assuming finally all the characters of a perfect Vaginicola, by developing around it its own special sheath. On the other hand, the contracted individual may become actually encased within its integument (in other words, encysted), and, as Stein believes, may thereupon assume all the characters of an Acineta, and eventually give birth to a ciliated embryo (XXVII. 11–15). This metamorphosis, however, is not generally accepted. The specific characters in this genus are for the most part deduced from the figure and dimensions of the external sheath or lorica (Ehr.), and must, therefore, as Stein points out, be admitted with much 602 SYSTEMATIC ELISTORY OF TEIE INFUSORIA. reservation; for this envelope changes greatly in figure, in size, and structure, according to the age and the different vital conditions under which the animal lives. Stein met with one example in which a short pedicle attached the Vaginicola crystallina to the bottom of its sheath: indeed he does not admit Cothurnia and Vaginicola to be generically distinct; for the stems supporting the sheath of the former are, he says, not generally longer than those belong- ing to young Vaginicolae. In this point therefore he agrees with Dujardin. We have observed how close the resemblance is between Vorticella and Vaginicola; on the other hand, the points of separation are found in the absence of a pedicle in the latter, which is fixed to the bottom of a sheath by its posterior extremity, its anterior remaining free, and its whole body capable of extension or retraction within the orifice of its case. Lastly, the figure of the body is much more elongated in Vaginicola than in Vorticella. WAGINICoEA crystallina (Vorticella stentorea et Trichoda ingenita, M.) (XXVII. 10, 11). —Sheath crystalline, straight, pitcher-shaped, slightly contracted near the open end; granules green. Length of lorica. 1-210". Upon Lemna, &c. V. tincta.—Sheath brownish-yellow, urceolate, and nearly cylindrical; body hyaline. Length of lorica. 1-280". Upon Zygnema decimum. V. decumbens.—Sheath brownish yel- low, oval and compressed, decumbent on one side, which is flattened; the body hyaline. Length of lorica. 1-280". Stein corrects this description by stating that the oval plano-convex sheath has not a simple crescentic opening, but is contracted so as to form a short tubular neck, or projecting process, with a transversely oval or reniform mouth. It has consequently the closest resem- blance to the sheath of Lagenophrys Am- pulla; but its orifice is rigid, and not con- tractile as in the latter, and, further, the animalcule is not affixed to its mar- gin, but to the bottom. On Lemma, Zygnema, &c. V. valvata (Wright) (xxvii.I. 18, 19). —Distinguished from V. crystallina by the remarkable valve existing in its case or sheath—which closes, in an inclined position, over the animal when it retreats to the bottom of its case; by the body being colourless, without the green glo- bules seen in V. crystallina; and by being an inhabitant of sea-water instead of fresh. Plentiful on zoophytes and Sea- weeds. V. vaginata.-Under the name Vorti- cella vaginata, Müller described a Vagi- nicola found in the Baltic, having a deli- cate pedicle as long as the body, which is supported by it, at the upper end of a sheath six times longer than itself, into the orifice of which it can with difficulty enter. V. pedunculata (Eichwald). —Body attached to the bottom of the sheath by a short stem. This presumed species is actually nothing more than a variety of V. crystallina, as Stein has shown. V. Ampulla.-Müller described this as larger than most animalcules, as dwelling in a bottle-shaped sheath, as very con- tractile, grey, and soft, and as occupying various positions within the case. Found in the #. and, by Mr. Brightwell, at Lowestoft. Dr. Wright (Edin. Phil. Journ. 1858, p. 5) says it has a bilobed ciliated organ, and so far resembles Lagotia. , ovata (Duj.).—Body of a lengthened ovoid figure, placed in an urceolate case. Length of i. 1-1000", of case 1-550". Apparently distinct from V. crystallina, On Zygnema in pond-water. V. ? (Brightwell) (XII. 70).- Body double, of a green colour. Pro- bably undescribed. On duck-weed and other small aquatic plants. It is doubt- ful whether this being is other than a Vaginicola in process of spontaneous fission. V. grandis (Perty).-Sheath cylindri- cal. Animals with a circular ciliated opening. Length of tube 1-108", of the extended animal 1-84". Stein considers this, species a mere variety of V. cry- stallina; but besides differing from it in size, it does so also in the figure of its sheath, which is not rounded |below, but abruptly truncate, and not narrower above, but rather wider. Animalcules hyaline, often filled with sporozoids and chlorophyll granules; when contracted it does not occupy more than a third of the tubular jº Among water-plants. Uncommon. The figure of this species presented by Perty is very rude, conveying not the slightest conception of the details of external structure or of internal organ- ization. OF TEIE OPEIRYDINA. 603 Genus COTHURNIA (XXX. 12–16).-Lorica (sheath) urceolate, and sup- ported on a rigid pedicle. A wreath of cilia is placed upon the flat frontal region; and the mouth, with the amal opening, lies on One side, within the vestibulum. The body is contractile, and can withdraw itself within the stiff sheath; fission longitudinal. It is unnecessary to enlarge on the structural details of this genus, inas- much as they are in all particulars like those of Vaginicola, from which it is separated only by its sheath being stalked. CoTHURNIA imberbis (Vorticella folli- culata, M.).--Pedicle mostly bent and much shorter than the sheath, which has, when old, a yellowish colour. Sheath tubular, narrowed anteriorly, without an everted margin. Even when outstretched, the animal extends little beyond the mouth of the sheath; its peristom is scarcely appreciably thick- ened, and not everted at all; it is evi- dently ciliated. The disc of the simple rotary organ is level on its surface, and scarcely rises above the sheath. Diges- tive tube long and narrow, extends be- yond the centre of the body, and near its commencement has from 3 to 4 long cilia. Near to it, on one side, is a round contractile vesicle, and on the other a short, band-like nucleus, almost straight or slightly reniform in figure. Longi- tudinal fission frequently observed, and sufficiently often the process of gemma- tion at the base. Length of sheath 1-288" to 1–240". Ehrenberg remarks, “This animalcule had often swallowed green Monads, and yet accepted indigo. Trichodina voraw is the enemy of this species.” Upon Cyclops quadricornis, Length of sheath 1–280". C. maritima. — Pedicle much shorter than the hyaline sheath; body hyaline and whitish. Length of sheath 1-570". C. maritima is very closely allied to Vaginicola crystallina: not the least dif- ference between the animals themselves is perceptible, and the figure of the sheath is the same, the only essential difference being that in the Cothurnia the sheath is supported on a thin, solid stem, 1-48" to 1-36" in diameter and of a length equal to its own. C. Havniensis.--Pedicle much longer than the hyaline sheath; body whitish. Length without stalk 1-280". C. Sieboldii (Stein) (xxx. 13, 14).- Sheath stalked; stalk short, thick, colour- less, transversely and deeply wrinkled, and thickened at its junction with the sheath. The last is campanulate, strongly compressed in front, dilated and bellied out posteriorly, especially on the dorsal aspect. The two angles in front are ex- tended upwards and outwards, but at the Same time curved inwards at their ex- tremities as two horns. The walls of the sheath are at first soft, colourless, and hyaline, but subsequently become yellow and leathery, and at last of a more or less deep rusty brown colour, and of a corneous consistence. The colourless and, with reference to the sheath, Small contained animal is cylin- drical in figure, contracted behind, and very similar to that of Vaginicola crystal- lina, . Its peristom forms an annular thick border, and is beset with few cilia. The digestive tube, which extends to nearly the centre of the body, has close to it the contractile vesicle, and a little further behind, the thick, short band-like and semicircular nucleus, visible without the use of chemical reagents. Multipli- cation takes place by longitudinal fission. Length of largest sheaths 1-190". On the limbs and other parts of Entomos- traca; very abundantly. C. Astaci (Stein) (xxx. 15).-Sheath Supported on a short, wrinkled, thick pedicle; having itself a tubular figure, rather contracted at the middle, and its border widened and everted, whilst its posterior half is slightly ventricose and rounded at its extremity. Its consist- ence is leathery or horny when old; it is transparent and of a pale yellow colour, but never a rusty brown. When fully outstretched, the animal protrudes a con- siderable distance beyond the mouth of the sheath, differing in this respect, as well as by its thick annular peristom and its cylindrical outline, from Cothurnia imberbis. The digestive tube attains the middle of the animal, is very narrow, and has both the contractile vesicle and the short band-like nucleus placed near its termination. Fission is longi- tudinal. Old Specimens attain a height of 1–288", and a width of 1-600". Also found on Entomostraca. It is very closely allied to C. imberbis; but, besides the differences noted between the animal- cules, the stem of the latter is relatively 604 SYSTEMIATIC HISTORY OF TEIE INFUSORIA. thinner, the posterior extremity of the sheath pointed, and the anterior con- tracted. C. curva (Stein) (xxx. 12) resembles generally a contorted specimen of C. Astaci; but old specimens have rusty- red-coloured sheaths. The pedicle of the sheath is always curved; the anterior third of the sheath is bent outwards, and the posterior half ventricose, particularly on the dorsal surface. The bending to one side causes the mouth of the sheath to be oblique. The contained animal- cule agrees generally with that of the two preceding species. Length of sheath 1-360". Upon the ova-lappets of Ento- mostraca. Stein doubts the independence of this species; for, besides being imperfectly ji by Ehrenberg, it is exceptional in the animalcule not being fixed at the bottom of the sheath. - C. Pupa (Eichwald). C. perlepida (Bailey).-Apex of sheath attenuated, slightly curved; surface en- tirely covered with spirally decussating rows of hexagonal cells; orifice crenulate. Contained animal unknown. St. George's Bank and New Haven Harbour, New York. C. Floscularia (Perty).-Hyaline; the cilia of frontal segment collected in two groups, recalling thereby the aspect of the ciliary apparatus of a Foscularia. Sheath of the same form as that of C. im- berbis. The animal lives much in a con- tracted state within its sheath, and ex- tends itself very slowly: on the contrary, the act of contraction is rapid, 1-260". Among Callitrichae, Genus LAGENOPHRYS (Stein) (XXX. 29–36).-Sheathed Vorticellina, differing especially from Cothurnia and Vaginicola by the zooids being at- tached to the circumference of the mouth of the sheath, and freely dependent from it, instead of being affixed to the bottom as in those genera. The sheath itself is without pedicle, and adheres to foreign bodies by one side, as does that of Vaginicola decumbens: this side is flattened, and may be referred to as the abdominal surface. The opposite side, or the back, is strongly vaulted. The mouth of the sheath is very much narrowed, and furnished with a prominent, flexible, double lip, which can be closed when the contained ani- malcule contracts itself. This last is closely adherent by its peristom within the margin of the orifice of the sheath, and has generally the same figure as the sheath, but not the same dimensions; hence it lies loosely within it. The mouth of the sheath and the peristom are of equal diameter; and through them a long stalked rotary organ projects, terminated by a circular ciliary disc. When the animal contracts, the rotary apparatus is withdrawn, the peristom closes like a sphincter, and the two-lipped mouth of the sheath by its closure completes the security of the whole being. place by oblique fission and by gemmation. LAGENOPHRYS vaginicola (XXX. 29– 36).-Sheath elongated cordate; in the centre of its broader and truncate end is the circular orifice, having two semi- circular, prominent, valvular processes, which tº: together when the con- tained animalcule contracts itself. The contracted posterior extremity has a very thick wall. The enclosed animal is ovate, and adherent by its narrow peristom to the orifice of the sheath, and leaves a large interspace posteriorly between itself and the enclosing wall of its sheath, ex- cept when it retracts itself. The young formed by gemmation, as well as the products of fission, can escape only when the parent being loosens its attachment from the aperture of the sheath, and so furnishes an outlet. The medium length Reproduction takes of sheath is 1-380"; the greatest width 1–640". On Cyclopsina Staphylina. L. Ampulla. — Sheath resembles a lano-convex circular lens, except in aving an anterior projecting everted rim around the oral orifice. The ani- malcule has the same figure as the sheath, and an internal organization like that of the preceding species. Diameter from 1-480" to 1-360". On aquatic animals, Entomostraca, and the like. L. Nassa,—Very similar in figure and size to L. Ampulla, but has a different profile or lateral outline. The sheath, although nearly spherical, is plano- convex, somewhat truncate in front, and emarginate on the upper surface, as is best seen in profile. #. mouth of the sheath is prolonged as a cylindrical, two- OR TELE TENCEIELIA. 605 lipped process, capable of being retracted. occurs on Gammarus and other aquatic Is more rare than L. Ampulla, but, like it, animals. Genus LAGOTIA (Wright) (XXVIII. 20–23; XXXI. 7, 8).-Sheath or case retort-shaped, with a cylindrical neck, plain or annulated ; colourless, yellowish, or dark green ; body long, cylindrical, attached by its posterior end to the bottom of the case, terminated anteriorly by a forked (furcate) head, or two long, flattened ciliated processes, between which is the opening of the oral cavity, which extends backward into the body as a tapering Oesophagus, ciliated on its free surface. The green colour of the body in L. viridis is not due to dispersed globules, but to a staining of the sarcode itself. Longitudinal fission has not been seen; but development by a free ciliated embryo, very unlike the parent, has been observed in L. producta. LAGOTIA viridis (XXVIII. 20–23). — Case resembles a flask or amphora lying on its side, having the neck bent more or less sharply upwards, and dilated into a trumpet-shaped mouth. Its colour is dark sea-green, in the larger specimens nearly opake. Animalcule green, cylin- drical; its ciliated organ, when seen in front and erect (f. 23), appears like a narrow horseshoe ; whilst from the side (f. 21) the anterior extremity of the ani- malcule bears a resemblance to the head and ears of a hare—a likeness increased by the wagging movements of the long processes. In young specimens the lobes of the furcate process are blunt and short, and the ciliary band, along which the cilia are arranged, is placed at a little distance from their margin (f:20), instead of being close to it (f. 22). Plentiful on marine shells and Algae, Firth of Forth and Tynemouth, Embryonic develop- ment has been detected by Dr. W. in this species. L. hyalina.-Colourless; lobes of cili- ated organ wider and blunter than those of L. viridis; cell buried in the substance of the shell of Alcyonidium hirsutiſm, and therefore not seen. Granton and Queens- ferry, L. atro-purpurea.—Colour of animal that of a mixture of ink and water. Cell yellowish-brown. Probably a variety in colour of L. viridis, with which it was found. L. producta (xxxi, 7–18) (Dr. Wright ân lit.):-Neck of sheath exceedingly pro- longed, ammulated; sheath of a pale yel- low-brown colour. Animalcule (zooid) two or three times the length of the sheath, attenuated; ciliated lobes erect, divergent, and recurved at tips; colour of zooid deep blackish green. Dr. Wright observed the development in this species of ciliated embryos, which, after passing through the stages seen in figs. 9 and 1.1 (XXXI.), and carrying on an active existence as free ciliated ani- malcules, form an attachment to some Surface and proceed to develope a sheath and the characteristic ciliary i. The transformation from ciliated embryos to Lagotia transpired in the course of a night, — the sheath even, during that time, being completed with its rings. The above fact constitutes an interesting ad- dition to the illustrations of embryonic development among Ciliata, quoted in the section on that subject (p. 353). ~ FAMILY W.—ENCHELIA. Animalcules having a distinct alimentary canal, with an oral and an anal orifice at the opposite ends of the body; without lorica. Locomotion effected by vibratile cllia in all the genera except three, viz. Actinophrys, Tricho- discus, and Podophrya, in which it is performed by slow-moving feelers (ten- tacles). In all but these exceptional genera, organs of nutrition have been demonstrated by the employment of coloured food; but only in one has the entire course of an alimentary canal been traced, though in most its transit through the body is indicated by its discharge through the posterior outlet. Ehrenberg states that the polygastric structure is to be seen in all the genera except the Arabian genus Disoma. A nucleus and vesicle are generally present. Complete Self-division, both longitudinal and transverse, has been observed; but not gemmation. The most curious animalcules among them are the double-bodied Disoma and the teeth-bearing Prorodon. 606 SYSTEMATIC EIISTORY OF TEEE INFUSORIA. The genera are distributed as follows:— ſ ſ (Vibratile Body simple .................. Enchelys. cilia at the Direct mouth ... Body double .................. Disoma. truncated * 4 The body co- * * Surface of º Ray-like Stalkl vered with rays } Actinophrys. body desti- (no lip)... tentacula JiKi6SS 33 tute of vi-3 not vibra- Rays at the edge Trichodiscus. ; bratile - U tile ......... *3 . cilia ...... Stalked ........................ Podophrya. *: g É 9. d | No neck .......................................... Trichoda. \ &#iº With neck ....................................... Lacrymaria. *...; Oblique truncated mouth, with lip ........................... Leucophrys. vibratile Direct truncated mouth, no lip ..................... * * * * * is “ e º e Holophrya. \ cilia ...... | Teeth present…~~~~ * * * * * * * g e s e s is a e º is $ 6 s e e s s e e s & e º e º ſº tº e º 'º º Prorodon. In the arrangement of Dujardin, and under his fourth order—comprehend- ing “ciliated Infusoria without a contractile integument, and with or without a mouth "-a family having a similar name, Enchelina (Enchelyens, so- called after a genus Enchelys) is instituted. But, most unfortunately for science, this family and this genus, with respect to the animalcules they include, in no way correspond with the similarly-named family and genus of Ehrenberg. This is remarked by Dujardin himself; and he adds, with reference to the genus Enchelys (Ehr.), that, in the whole course of his ob- servations, he never met with any Infusoria bearing the characters attributed by Ehrenberg to that genus, and he is led to conclude that the beings intended are Paramecia with a terminal mouth, or else Bursarice imperfectly examined, and the cilia of the surface overlooked. - The family Enchelina is thus briefly characterized by Dujardin:-‘‘Animals partially or entirely covered with cilia, dispersed over the surface irregularly ; mouth wanting.” The family Cyclidina (Ehr.) seems, indeed, much more nearly allied to the Enchelys of Dujardin; but its characters, as given by Ehrenberg, are not sufficiently definite to attempt an identification. Stein severely blames Dujardin for the transposition of generic names he has been guilty of in the case of this genus and Cyclidium; for, as he justly observes, it is a proceeding productive of confusion and error. The Enchelys modulosa, he adds, is the Cyclidium Glaucoma (Ehr.), and scarcely distin- guishable from E. triquetra (Duj.). Acomia. Ovulum seems nothing else than Cyclidium Glaucoma, and Uronema marina another closely-allied form, and, like Glaucoma itself, the embryo of some other animalcule. The three remaining species of Enchelys enumerated by the French writer, viz. E. cor- rugata, E. subangulata, and E. ovata, are so imperfectly observed as to be worthless, and their union in the same genus with Glaucoma quite unwar- rantable. Yet, if Dujardin has proceeded very incautiously in rejecting the En- chelia of Ehrenberg and in redistributing its genera, no apologist of the Berlin naturalist would contend that it should be left as it is ; for every person having any acquaintance with the beings brought together as En- chelia will be struck with their heterogeneous characters. Actinophrys, OF THE ENCEDELIA. 607 Trichodiscus, and Podophrya belong evidently to a type of beings altogether different from the ciliated animalcules included in the family; and we have consequently treated them as an entirely separate group from the ciliated Protozoa in our general history, and have likewise, in the present portion of the work, given their systematic descriptions apart. The genus Disoma is a very doubtful member of this family, and is even marked as such by Ehrenberg, who had very imperfectly examined it. - - The family Enchelia does not enter into the system of Perty, who disperses its members among different families according to his appreciation of their several affinities. Among the rest, his family “Tapinia” includes some species of Leucophrys of Ehrenberg and the genus Acomia of Dujardin, along with several newly-constructed genera, the account of which will be annexed to this present group. The Family “Tapinia” is thus characterized:— “Cilia scattered at large, or collected in groups, but not arranged in rows. Animals mostly very Small. Mouth not apparent, but its presence revealed by the admission of food.” This group includes the genera Acropisthium, Acomia, Trichoda (Duj.), Leucophrys (Ehr. 2), Cyclidium, Baeonidium, Opis– thiotricha, Siagontherium, and Megatricha. Another allied family, called “ Apionidina,” contains a species of Leuco- phrys (Ehr.). Perty assigns it the following characters:– “Family Apioni- dina: Body small, soft, thicker at one end than the other; cilia in longi- tudinal rows; mouth, where visible, situated at the anterior end.” The genera comprised are Ptyajidium, Colobidium, and Apionidium. The first-named genus has, as its type, the Leucophrys pyriformis (Ehr.); but the other two are advanced as new genera, founded on newly-observed beings. Both in this family (Apionidina) and in that of Tapinia, several supposed new genera are established by Perty, which, to render our compendium com— plete, we are bound to notice and describe, although we regret to record such a multitude of genera and names, as we feel highly doubtful of their claim to consideration as independent beings. Genus ENCHELYS (XXVIII. 64, 72, 73).-Vibratile cilia upon surface wanting; mouth terminal, truncated (direct, not oblique), devoid of teeth; surrounded by a Wreath of cilia. An oesophagus is not seen except during the passage of food. An anus is found in all, and in E. Farcimen a contractile bladder. Self-division is transverse and complete. Dujardin defines his genus Enchelys as having a cylindrical, oblong, or ovoid body, covered with erect uniform cilia, irregularly disposed. - Cohn (Siebold's Zeitschr. 1851, B. iii. p. 273) treats this genus as synony- mous with Enchelys (Duj.), and believes that several of its assigned species are not independent animalcules, but embryos of Loacodes, Oaytricha, and allied genera. ENCHELYs Pupa (M.) (xxvii.I. 72, 73). —Turgid, club-shaped, attenuated an- teriorly; filled with greenish vesicles, or only with molecules; neither a nucleus nor a vesicle could be found by Ehren- berg. Ehrenberg has figured (in his large work of 1838) the presumed form of the polygastric nutritive system of this species separately, stating it to be remarkably distinct. Common in stag- nant bog-water. 1-140". E. Farcimen (E. Farcimen et Vibrio in- testinum, M.) (XXVIII. 64, a-k).—Smaller, more cylindrical and slender than the preceding ; granules whitish. These creatures prey on other animalcules nearly as large as themselves, which they devour entire; this will account for the variety of forms which they assume, and which require an observer to be very watchful and cautious before he can pronounce on the identity of a species. Ehrenberg, by patient obser- vation, saw one individual undergo a great variety of forms in the act of Swallowing a young Kolpoda Cucullus; 608 SYSTEMATIC EISTORY OF TEIE INFUSORIA. illustrated in fig, 64, a-k. water. 1–430". JE. infuscata. — Oval or spherical ; whitish ; mouth not prominent, encircled by a brownish ring. When fed with indigo, numerous vacuoles become filled. In bog-water. I-280" to 1-240". E. mebulosa (M.). — Ovate, hyaline; In stagnant mouth projecting. This species receives carmine and indigo very readily. 1-230" to 1-570". B. modulosa (Duj.) = Cyclidium Glau- coma (Ehr.). E. triquetra (Duj.) is a mere accidental variety of the same animalcule. Genus DISOMA (?).—Body double, destitute of cilia; oral extremity truncated (direct); mouth ciliated, devoid of teeth. Within the bodies numerous little vesicular cells (stomachs) are observed, and the discharge of excrement may be seen to take place at the posterior extremity of each body. As already noticed, this is a very imperfectly-examined and doubtful genus. The being described may be interpreted as one undergoing longitu- dinal fission ; but there is no one character given, adequate to determine to what family of animalcules it would be referable. DISOMA vacillans consists of two onwards quickly, though in a vacillating clavate and filiform corpuscles, hyaline, manner; sometimes both bodies gaped and attenuated at the anterior extremity. Ehrenberg remarks, “Both bodies fre- quently swam parallel beside each other, widely apart from each other, but never so widely as to form a straight line. 1-380". On Mount Sinai, Arabia. and turned on their long axis, moving Genus TRICHODA.—Body devoid (?) of hairs or cilia; without a con- striction or neck; mouth obliquely truncated, destitute of teeth, but pro- vided with vibratile cilia, and a lip. Coloured food is received; the anal orifice is at the posterior extremity. The oblique direction of the mouth gives rise to a very characteristic upper-lip-like projection. In T. Pyrum only has self-division been observed. All the species are colourless. In the system of Dujardin there is both a family Trichodina and a genus Trichoda. Speaking of the relations between them and the genus Trichoda of Ehrenberg, he observes: “M. Ehrenberg has placed in his family Enchelia a genus Trichoda, which in part corresponds with ours; and he has, besides, dispersed among Lewcophrys, Enchelys, Trachelius, Loa:odes, &c., many Infu- Soria which we have brought together in this family (viz. Trichodina); but, unlike him, we are unable to see their digestive organs.” The Trichodina are soft, variable, flexible animalcules, ciliated, and have either an evident mouth, or one indicated by a varying arrangement of longer cilia. Dujardin would have it understood that this family is only provisional; to comprise a tribe of animals intermediate in organization between the Enchelina—the most simple of ciliated—and the Keronina, which conduct to the highest forms of infusorial life, having defined mouths, and an armature of styles, hooks, &c. The genera included by Dujardin in this family are Trichoda, Trachelius, Acineria, Pelecida, and Dileptus; the last two having a higher grade of organization. The first-named is thus described:— Genus Trichoda (Duj.).—Ovoid-oblong, or pyriform, rather flexible ante- riorly, with a row of cilia directed backwards, and appearing to indicate the presence of a mouth. Their surface does not appear reticulated, or ciliated in rows, as it is in Acomia and Enchelys. The Trichoda are chiefly found in putrid infusions and in stale marsh-water. TRICHODA pura (Kolpoda Pyrum, M.). — Oblong, club-shaped, attemu- ated anteriorly; mouth lateral; vacu- oles small. Common in vegetable infu- sions; usually with Cyclidium Glaucoma. 1-720". This species closely resembles Leuco- phrys pyriformis, which is somewhat Ol' TEIE ENCEUELIA. 609 larger and ciliated throughout. How- ever, the reality of T. pura as a species is very doubtful, the small size of the vacuoles, the feature most relied on by Ehrenberg as distinctive, being in reality not at all so, but prone to great varia- tions, determined by surrounding cir- cumstances. It swims slowly, revolving as it proceeds. T. Nasamomum.—Cylindrical, extre- mities equally obtuse, mouth large, and elongated laterally. 1-288". T. ovata. --Ovate, turgid, attenuated anteriorly; mouth small and lateral. 1-480". T. (?) A3thiopica.-Oblong, attenuated osteriorly; under side flat ; mouth arge. 1-600". T. Asiatica.-Oval, oblong, cylindrical, rounded at both ends; mouth Small. I-8601'. This species, together with the three immediately preceding, must be regarded as doubtful; for they were merely casually examined by their discoverer whilst tra- he had neither the means of comparing the beings with others akim to them, nor very favourable opportunities, in the rough accommodation of desert tra- velling, for careful microscopic examina- tion. T. Pyrum (Kolpoda Pyrum, M.). — Ovate, turgid, acute anteriorly. Amongst Confervae on Mount Sinai. 1–1200". A species with this name is also men- tioned by Dujardim as = Kolpoda Pyrum ? (Müller). It is thus described:—“Body ovoid, oblong, marrowed anteriorly, or pyriform; thicker in one direction than in the other;” and he goes on to say that this is the same being as the Leu- cophrys carnium (Ehr.). T. angulata (Duj.).-Oblong, obliquely and regularly plaited or angular, often with one or more superficial vacuoles. I-900". T. Lynceus.-The animalcule described under this name is (says Cienkowsky) probably no other than the young phase of various Oxytrichae and Stylonychiae velling, and when, as we must suppose, (Siebold, Zeitsch, 1855, vol. vi. p. 301). Genus LACRYMARIA (XXIV. 274, 275).-Body with a long narrow neck, slightly enlarged near the termination, where is situated the ciliated and lateral (lipped) mouth, destitute of teeth. Body not ciliated. Locomotion is performed by means of the neck, the distensible body, and the oral cilia. The proboscis-like lip is very short, sometimes distinctly articulated, and projects but little beyond the oral orifice. Coloured food is received by L. Protews, and its discharge may be seen to take place from the posterior extremity in one species; in another, green granules (ova) are present. The genus Lacrymaria of Dujardin agrees mainly with that just defined; but the French author differs entirely from Ehrenberg, by stating that the Lacrymaria, are distinctly ciliated on their surface, and that the cilia are disposed in regular series among the reticulations of the integument. Dujardin, in his notes on Lacrymaria, has some very just observations on the relation between this genus and the Phialina and Trachelocerca (Ehr.). He says, the species of Lacrymaria, which Ehrenberg noticed to be generally not ciliated on the body, have been classed by him according to the relative position of the mouth and amus, Some among the Enchelia, others, as Phialina, among the Trachelia, and others again in the genus Trachelocerca, the type of his family Ophryocercina. On this plan, Lacrymaria has the body without cilia, prolonged into a narrow neck, terminated by an obliquely truncate and ciliated mouth, at the opposite extremity to which is the anus; Phialina similar, except that the neck, instead of being terminated by a simple enlarge- nent, is notched on one side, and the mouth therefore lateral; and Trache- locerca, which he himself calls “tailed Lacymarice,” have a terminal mouth, and an amus on one side in advance of a comical caudiform prolongation of the body. These distinctions are not borne out by more critical investigations, and at most are insufficient to establish generic characters, and still more those of higher groups or families. As the result of these considerations, Dujardim has comprehended all the species distributed in the three genéra named in one, viz. Lacrymaria, which he places among the Paramecina, 2 R 610 SYSTEMATIC EIISTORY OF TEIE INFUSORIA. The doubt expressed concerning the existence of a mouth as described by Ehrenberg, has been removed by later observations. The variability of form of which the Lacrymariae are capable was noticed by Baker and other old observers, and suggested the appellation Protews, originally bestowed on them. Perty has made use of this peculiarity to constitute a section of Ciliated Protozoa, which he has named “Metabolica.” Besides Lacrymaria, it includes Trachelocerca, these two genera being combined into a family, “Ophryocercina.” His genus Trachelocerca, however, is not equi- valent to the one so named by Ehrenberg, since it also comprises the species of Phialina enumerated by that author. This employment of a recognized systematic term with a wider signification than that originally given to it, cannot be commended; and, as Perty makes no attempt to define the differ- ential characters between the two genera as understood by himself, we regard his family Ophryocercina as unsatisfactory. The Phialinae he considers only young or contracted examples of one or other genus. (See PHIALINA and TRACHELOCERCA.) LACRYMARIA Proteus (Trichoda Pro- teus, M.) (XXIV. 274,275).-Oblong, tur- gid, with delicate transverse folds. Čolour varies from grey to green. The neck is capable of considerable extension. It resembles Trachelocerca Olor; but its posterior extremity is rounded, and has at its centre the discharging orifice. Re- pºve organs unknown. Amongst emnae. Size stretched out 1–140". L. Gutta.-Body smooth and nearly spherical, with a very long neck. Perty discovered a tongue-like process above nor an enlargement is observable near the mouth. 1-570"; including neck, 1–288". L. versatilis (Duj.) (Thichoda versatilis, M.).--Fusiform; neck retractile, ciliated beneath, shorter than in L. Proteus, which it is further unlike by having the body pointed posteriorly, and by living in sea- Water. Perty declares this is not an independ- ent species, but only the immature form of Trachelocerca Olor (Ehr.). L. tornatilis.-Neck retractile, some- times disappearing entirely, presenting then only the cilia crowning its extre- mity. L. farcta-Flask-shaped, with a short neck. In ditch-water about Paris. I-260". the mouth in Some examples. Among Confervae. Size 1-1150"; including neck, 1–210". L. rugosa. — Nearly globular, and wrinkled; the neck of medium length; granules green. In Swimming, it often revolves on its long axis; neither cilia Genus LEUCOPHRYS (XXIV. 276, 277,278, 279, 280)—Covered with vibratile cilia; mouth oblique, terminal, without teeth. From the obliquity of the mouth, there is the appearance of an upper lip. The cilia which cover the body are short and disposed in rows; those around the mouth are longer, and produce very powerful currents. In Swimming, all the species revolve upon the longer axis. A serpentine alimentary canal, with more than fifty grape-like stomach–cells (XXIV. 276), terminating at the opposite extremity to the mouth, is described by Ehrenberg; in some, one or two globular nuclei and a contractile vesicle are seen. Self-division transverse and longitudinal. Leucophrys forms, in the system of Dujardin, with Spathidium and Opalina, the family “Leucophryens,” characterized by having “an oval or oblong de- pressed body, covered with cilia densely but regularly disposed; mouth not evident; foreign solid particles are not to be found in the vacuoles; hence probably these animals live only by absorption. Most of them are parasitic within Annelida and Batrachia, and soon perish in pure water, like Helmin- thoid (tape) worms.” Dujardin says, “It is to the genus Bursaria that Ehren- berg has transferred most of the true Leucophryens, in conjunction with other Infusoria having a very distinct mouth.” (See OPALINASA, p. 569.) Dujardin’s characters of Leucophrys are:—“Body depressed, oval or oblong, OF TELE ENCEIELIA. (311 equally rounded at the two ends, covered by long, very numerous, vibratile cilia, in parallel rows; no mouth. I,” says Dujardin, “ have restricted the term to animalcules parasitic within Lumbrici, but ought probably to include the form met with by Ehrenberg in the Anodontoº.” This genus requires further examination, and may probably be cancelled by the transfer of its members to other groups. It is certain that several of its enumerated species are mouthless, and that some belong to the Opalinaea ; and Dujardin clearly pursued a very right course in detaching it from the heterogeneous class Enchelia, and in bringing it into relation with Opalina. Perty has followed a similar plan, and instituted a family of parasitic animal- cules under the name of Cobalina, comprehending besides Lewcophrys (repre- sented by only One species, L. Striata) Opalina, Plagiotoma, and Alastor. Like Dujardin, also, he transfers L. patula to Bursaria; treats L. Spathwla, as identical with Spathidium hyalinum (Duj.), but places it in a family Holophryina, along with Holophrya and Enchelys (i. e. as represented by E. Farcimen and E. Pupa). Neither Ehrenberg's descriptions nor figures are sufficient to identify L. sanguinea either with Bursaria or Opalina; its colour lends no aid, since it is doubtless accidental. L. pyriformis and L. carniwm are doubtful members, and the rest named are petty clearly Opalinaea. L. carnium is treated by Dujardin as identical with Trichoda carniwm. LEUCOPHRYS patula (Trichoda patula, M.) (xxiv. 276, 277) (Bursaria patula, Duj.). — Oval, campanulate, turgid; sometimes quite pellucid, at others whitish ; mouth ample and gaping; vacuoles are very large, and fill them- selves with food in an irregular manner. When (says Ehrenberg) the animalcule is quiet, the passage of the food onwards is seen in the serpentine canal, to which the stomachs are attached like berries; even the stalk or short communicating tube is visible when they receive or dis- charge coloured food. The longitudinal rows of cilia are very numerous in full- grown specimens. The granules are white by incident light, brownish by transmitted. In the middle of the body is a small globular nucleus. Both in fresh- and sea-water. 1-280" to 1-96". L. Spathula (= Enchelys Spathula, M.) (XXIV. 278). — Lanceolate, com- pressed, whitish ; mouth narrow, situated at its anterior extremity, which is ob- liquely truncated and membrane-like. Amongst Lemnae. 1-140". Wide SPA- THIDIUM hyalinum, p. 612. L. Sanguinea (º, striata, M.) (XXIV. 279, 280).-Cylindrical, rounded at both extremities, and of the colour of blood. Ehrenberg remarked within it two bright contractile round bladders, and that on self-division one was present in each part. 1-144". L. pyriformis (Kolpoda Pyrum, M.).-- Ovate, whitish, rather more acute ante- riorly; vacuoles large. I-570" to I-280". Dujardin considers that this species should rightly be transferred to Glaucoma or Kolpoda. L. carnium (Kolpoda Pyrum, M.).- Oval, oblong, acute anteriorly, and of a whitish colour; vacuoles narrow. In putrescent animal water, and the drain- age of manure. 1-1440" to 1-430". It = Trichoda Pyrum (Perty). Perty suggests that Enchelys modulosa is referable also to this species. L. (?) Anodonta (Leucophra fluida, M.). — Oval, turgid, and transparent; rounded at both extremities. In Siberia and at Copenhagen. 1-430". Most pro- bably it is an Opalina. L. striata (Duj.),—Oblong, marked by thirty-five longitudinal granular striae. 1–325" to 1–200". In the Lumbric; (worms) of gardens. This is the only species of Leucophrys retained by Perty. On the other hand, Stein (p. 184) asserts that it is an Opa- lina, a mouthless animalcule, and there- fore rightly excluded from Enchelia. L. modulata (Duj.).—Oblong, regularly ciliated; without distinct striae, but hav- ing two series of vacuoles. . In Lumbrici. The last three supposed species are, says Stein (Infus. p. 184), Opalinae, and the last two should be united as one, which may be named O. Lumbraci. (See family OPALINAEA, p. 569.) Genus SPATHIDIUM (Duj.) (XXVI. 27).-Oblong; thicker and more rounded behind; thinner, expanded, and truncated in front. 2 R 2 (312 SYSTEMATIC HISTORY OF THE INFUSORIA. This genus is admitted by Perty, who places it in the family “Holophryina,” but, unlike Dujardin, believes it to possess a mouth. SPATHIDIUM hyalinum (XXVI. 27). — Oblong, lanceolate, hyaline ; thin and almost membramous anteriorly, and ter- minated by an oblique margin, along which some small black nodules may be seen. In pond-water, near Paris. The Enchelys Spathula of Müller would seem to be the same species; but the Leu- cophrys Spathula (Ehr.) differs from it in having a row of cilia on the ante- rior margin, with striae on each side, and in receiving indigo in its stomach- Säl,CS. Perty, however, treats them as identi- cal. Indeed, the marks of distinction Dujardin would draw are certainly in- sufficient to establish a specific differ- ence; since the absence or presence of a row of cilia may readily be unobserved, and the reception or non-reception of indigo is very much a matter of manipu- lation. Genus HOLOPHRYA (XXIV. 281).—Ovoid, oblong, or even cylindrical; covered with vibratile cilia; mouth anterior, directly truncated or terminal, and without lip or teeth. In two species the mouth and anus have been seen. Cilia disposed in longitudinal rows. In H. Ovum green granules and a posterior contractile vesicle are observable; self-division appears to be transverse in H. discolor. In the system of Perty, Holophrya gives name to a family “Holophryina,” defined as having “an anterior mouth, a posterior anus, and the surface covered with cilia in longitudinal rows.” It includes the genera Holophrya, some species of Enchelys and Spathidium (Duj.), Leucophrys (E.). The two species of Enchelys mentioned are E. Farcimen and E. Pupa ; the Leucophrys is the L. Spathula (Ehr.). Holophrya is closely allied to Prorodon; indeed its independence is very doubtful; for the only distinctive character between the two genera put for- ward is, that the “dental cylinder ’’ is absent in the former; but this is a structural peculiarity not always very obvious to the eye, liable to be over- looked, and of secondary histological importance. Holophrya and the following genus, Prorodon, are included in Dujardin's family Paramecina. HoDoPHRYA Ovum (Leucophra bursata, M.) (xxiv. 281). — Ovate, somewhat cylindrical, extremities subtruncate ; ranules green. Amongst Lemnae and É. 1-570" to 1-210". H. discolor (Trichoda horrida, M.).- White, ovate, comical, subacute at the posterior extremity; cilia long and scattered. Amongst Confervae. 1-240". This species Štein has noticed in the encysted condition, surrounded by a thick-walled cyst. Cohn, moreover, found the previous species, H. Ovum, in the same condition. Instead of being white, it is often coloured green by chlorophyll. H. Coleps (Leucophra globulifera, M.). —Oblong, cylindrical; rounded at both extremities; whitish. 1-430" to 1-280". H. brunnea (Duj.).—Brown, changing from a cylindrical to a globular form when filled with food, and also then altering in colour, Genus PRORODON (XXIV. 282; XXVIII. 8).—Is distinguished by the directly truncated mouth, and a circlet or cylinder of internal teeth. Body covered with vibratile cilia. been demonstrated by coloured food. Digestive cells, an oral, and an anal outlet have A long band-like nucleus, contractile sac, and granules are seen in P. nivews. In the system of Perty, Prorodon constitutes a member of the family Decteria, in company with Chilodon, Nassula, Habrodon, and Cyclogramma. Habrodon is annexed to this present family; but Cyclogramma will be found placed among the Trachelina, along with Chilodon and Nasswla. OF TEIE ENCEIELIA. 613 PRORODON niveus—Large, elliptical, and compressed; colour white; circlet of teeth compressed (teste Ehr.), as shown separate in XXIV. 283. Smaller examples have fewer teeth than the large. Cilia very fine. It is found encysted. Amongst Confervae in turf-pools. 1-72". Cohn intimates (Zeitschr, 1853, iv. p. 271) that this species and the next are merely varieties of the same being. P. teres (XXIV.282; xxvii.I. 8).-Ovate, cylindrical, white; circlet of teeth cylin- drical. Ehrenberg counted twenty sup- osed teeth; and when the cylinder was #. forty-five. Revolves, in swim- ming, upon the long axis, 1-140". It has been seen in the encysted State, and to undergo fission when in that condition. P. viridis.—Large, elliptic, compressed, green, with a nearly cylindrical crown of teeth. 1-120". Berlin. - In all probability this green-coloured organism is a mere variety of the pre- ceding, from which it offers no distinc- tive features. In Prorodon, as in Chi- lodon, fission occurs in encysted beings. P. voraa (Perty).-Hyaline, seldom green; dental apparatus faintly marked. Integument covered with wart-like ele- vations in rings. Movements tolerably rapid; oftentimes oscillating. Anus placed at posterior extremity. 1-240" to 1-84". It chiefly differs from P. niveus by its faintly-marked dental apparatus. We have yet to append some genera (whose affinity is with the foregoing) described by Dujardin, viz. Acomia, Gastrochaeta, Alyscum, and Uronema, and which, with the genus Enchelys, constitute his family Enchélyens (Enchelina). Acomia and Gastrochaeta are only ciliated partially—the former at one end, the latter along a longitudinal furrow on the under surface. Enchelys, Alyscum, and Uronema are ciliated throughout, -the first having but one form of cilia; the second, cilia together with some long, contractile, trailing filaments; filament. and the last, cilia with a single, straight and long posterior Genus ACOMIA (D.) (XXVI. 16, 17).--Oval or irregular, oblong, colour- less or cloudy, formed of a homogeneous glutinous substance containing unequal-sized granules, and ciliated at one end. No mouth. - Perty remarks that there is an absence of definite characters between this genus and the Enchelys (Duj.), and that the species of Acomia require further study. ACOMIA Cyclidium (XXVI. 16 a, b).- Oval, oblong, depressed, containing large ranules and some vacuoles; transverse #. In external form approaches "Cylidium (Ehr.). Marine. 1-650". A. vitrea (XXVI. 17 a, b).-Ovoid, hya- line, but rendered cloudy by granules in its posterior half; anterior borderciliated; division longitudinal. 1-1250". In fetid Water. A. ovalis.--Differs from the preceding by the granules occupying the anterior half, and by its length, 1-868". In fetid marsh-water. The difference in position of the gra- nules is valueless as a specific distinction between this and the previous species, and should be rejected. A. Ovulum.—Ovoid, presenting a no- dular or granular portion, which seems to contract itself within the interior of a diaphanous envelope. Revolves in moving, like a Dowococcus, 1-300". Stein (Infus. p. 137) declares that it is undistinguishable from Cyclidium Glaucoma (Ehr.). A. (?) Vorticella. Ovoid, nearly glo- bular, colourless, cloudy; ciliated in its anterior half; cilia curved backwards. Revolves on its axis in progressing for- wards. 1-1000". In sea-water. A, (P) costata. — Ovoid-oblong, mar– rower in front; apparently enclosed by a thick membrane, or consistent layer; nodular; modules often arranged in rows as ribs. Division transverse. 1-650" to 1–500". In sea-water, among Algae. A, varians. – Oblong, cylindrical; truncated and angular in front; dilated and compressed, by turns, in different parts of its length, and consequently alternately rounded and constricted be- hind, so as to terminate by a pointed tail. Revolves on its axis. 1-1000" to 1-450", A. inflata.—Oval, tapering anteriorly, beset everywhere with very fine cilia; colourless, or occupied with green, grey, or brown granules. Movement rapid, 614 SYSTEMATIC HISTORY OF THE INFUSORIA. revolving. Cilia often appear longer in gular; convex above, flat beneath, or front. Found by Dujardin and Perty in rather concave. Thickly ciliated all decomposing marsh-water. over, 1-670". Amongst Lemmae. A. cava (Perty).-Oval, slightly irre- Genus HABRODON (Perty).—Body subcylindrical, rather bent; thickened posteriorly, and mostly truncate in front. Mouth anterior, with a very deli– cate dental apparatus. Anus posterior. Cilia in longitudinal rows. This genus, created by Perty, is placed by him in juxtaposition with Pro- rodon, with which and Chilodon, Nassula, and a new genus, Cyclogramma, it constitutes a family called Decteria. HABRODON curvatus = Enchelys Pupa posteriorly it presents a round clear (P) (Müll).-Colour usually grey or pale space (an anus?). Movements slow. green, with numerous molecules and 1-390" to 1-132". In springs, with vesicles; anteriorly it is hyaline, and | Chara, &c., Bern. - Genus ACROPISTHIUM (Perty) (XXVIII. 61)—Circular, with an ante- rior flap, or rounded off; pointed behind. - ACROPISTHIUM mutabile. — Hyaline, more perceptible anteriorly. The figure with darker vesicles and molecules. varies much, Mouth in front (?). 1-360." Movements very rapid, revolving. Cilia to 1-320". Uncommon. cover the entire surface, very fine, usually Genus BAEONIDIUM (Perty) (XXVIII. 52–54).--Small, subcylindrical; cilia at anterior end large ; movement sluggish. BAEONIDIUM remigans.—Usually pris- movement. A slight depression some- matic and rounded; often rather times perceptible on one side, in the wrinkled; hyaline, but nearly always | position of the mouth. Fission trans- filled with green corpuscles. Cilia verse. 1-840" to 1-660". Amongst generally distributed; the large anterior Chara, but rare, in Switzerland. omes simulate pedal organs in their g Genus OPISTHIOTRICHA (Perty) (XXVIII. 55–57).--Small, elongated- cylindrical or pyriform ; cilia distributed over the body, very fine, some of those on the posterior extremity large, ciliary action sluggish. OPISTHIOTRICHA tenuis (XXVIII, 55- Large posterior cilia from two to three 57).-Colourless or slightly green, with in young specimens, five to six in old. delicate vesicles and molecules in the 1-900" to I-440". In marsh- or bog- interior. Swims very rapidly, revolv- water. Bern, &c. ing at the same time on its long axis. Genus STAGONTHERIUM (Perty) (XXVIII. 62, 63).-Very small, ex- tended anteriorly, thickened posteriorly; with a long stiff bristle extended backwards on one side of the anterior extremity. SIAGONTHERIUM tenue.-Seen on the . delicate, with internal molecules and wider side, elongated ovate; anterior vesicles. Scarce in pools. Bern, with prolongation directed forwards from the Hysginum pluviale. 1-900" to 1–760". smaller subcylindrical half. Extremely Genus MEGATRICHA (Perty) (XXVIII. 58–60).-Very small, clothed with long, scattered and slowly-moving cilia. Body entire, or divided incom- pletely into two unequal portions. “These are the most delicate and simple of all the Ciliata.” MEGATRICHA integra. - Undivided, longs to this species. 1–1440". Un- colourless, with long, delicate cilia. common. Very possibly Chaetomonas Globulus be- M. partita (xxviii. 58–60).-Divided OF TEIE ENCELELLA. 615 into a smaller, rather pointed, anterior sluggish. , Swimming often interrupted Section, and a wider posterior one; co- suddenly by a jerk in another direction. lourless. Extremely delicate; often | Fission longitudinal. 1-1560" to 1-1320”. composed, like many Monads, of only Rare, among decomposing Confervae. five molecules. Movements of cilia Genus PTYXIDIUM (Perty) (XXVIII. 40–42).-Ovate, pointed in front, with several folds. Cilia equal, very fine. PTYXIDIUM Ovulum=Leucophrys pyri- is more probably an Acomia. Perty dis- formis (Ehr.). Kolpoda Pyrum (Müll.), covered no food in the interior. which Ehrenberg cites as synonymous, Genus COLOBIDIUM (Perty) (XXVIII. 45).--When mature, ovate; in earlier condition, truncate posteriorly—frequently emarginate,_rounded an- teriorly. Cilia in longitudinal rows, those in front longer; their movements slow. CoLoRIDIUM pellucidum.—Very trans- foot-like manner.” 1-1900" to 1-600". parent, colourless or clear green; move- In turf-hollows among Confervae. Bern. ments rapid, always rotating, “The Acomía Vorticella (Duj.) is probably only longer cilia in front often moved in a a variety of this species. Genus APIONIDIUM (Perty) (XXVIII. 48, 49).-Rounded; thicker in front than behind; rows of cilia few in number. APIONIDIUM modestum. — Hyaline, cilia very fine. A round clear space with coloured §. or brown) food-par- usually visible posteriorly. Rare. 1-260" ticles. Rows of cilia from seven to nine; to 1-240". Genus GASTROCHAETA (Duj.) (XXVI. 18)—Body oval, convex on one side, and hollowed by a longitudinal furrow on the other; cilia seated in the furrow, chiefly at the two ends. GASTRocBLETA fissa (XXVI. 18). — Semitransparent, Oval, truncate in front. 1–408". In the water of the Seine. Genus ALYSCUM (Duj.) (XXVI. 20). —Body ovoid-oblong irregular, surrounded by radiating cilia, and having, besides, a lateral bundle of long retractile cilia, by means of which it leaps briskly from place to place. The single species much resembles Enchelys modulosa (Paramecium Milium, or Pantotrichum Enchelys, Ehr.) from which it is distinguished by its retractile filaments. ALyscuM saltans (xxvi. 20).-Colour- almost invisible longitudinal furrows. less, oblong, rounded at the ends, rather | 1–1300" to 1130". In infusions and in concave along the side bearing the re- the Seine. tractile filaments, and marked by Some Genus URONEMA (Duj.) (XXVI. 25).-Body long, narrower in front, rather curved; surrounded by radiating cilia, and bearing a long straight cilium behind. URONEMA marina (xxvi. 25).-Co- Stein considers this form, as in the lourless, semi-transparent, nodular, elon- instance of Cyclidium Glaucoma, to be gated; contracted in front; slightly merely an embryo of an Infusorium, and curved, with from four to five slightly- not an independent species, marked longitudinal striae. 1-595". In the Mediterranean. 616 SYSTEMIATIC IIISTORY OF THE INFUSORIA. FAMILY WI.—COLEPINA. (XXIV. 284, 285). Loricated animalcules having the mouth and anus placed at the opposite extremities of the body. The lorica is of the form of a small cask, composed either of minute plates placed in a row, or of little rings between which cilia are situated; anteriorly it is truncated, smooth or toothed, and poste- riorly terminated by three to five little points; mouth ciliated. The diges- tive vacuoles in these creatures are readily filled with coloured food, which is ejected posteriorly. Complete transverse self-division has been observed. A distinguishing character of the Ciliated Protozoa is their asymmetrical figure; but the genus Coleps is an exception to the general rule. In the act of fission a new formation of tissue appears to take place along the future line of separation, thinner and softer in consistence than the original covering. Genus COLEPS (XXIV. 284–286).-This being the only genus, its cha- racteristics are identical with those of its family. - CoLEPs hirtus (Cercaria hirta, M.) (XXIV. 284–286).-Body white, oval, with truncated ends; lorica apparently com- posed of small polygonal plates, between which the cilia are both transversely and longitudinally arranged. Anteriorly there are nineteen pointed processes, and posteriorly three. Movements very brisk; so that it is difficult to examine the lorica while the animal is living; but when it is dried, or pressed between glasses, the complex structure of the former is rendered visible. Amongst Confervae. 1-570" to 1-430." Although described by Ehrenberg as colourless or white, this is no specific character; for it may frequently be co- loured green by chlorophyll, or tinted with intermediate shades between yel- low, green, and brown, according to the food taken and its changes by digestion. C. viridis.-Green, oval, and ciliated; lorica terminating in three points. Amongst Confervae. 1-960" to 1-570". Except in the matter of colour, no distinction from the preceding is noted; its specific independence may therefore be fairly questioned. C. elongatus.-Cylindrical, elongated; lorica white, and terminating in three points; self-division transverse. 1-570." to 1-430". Between this form and C. hirtus Perty has seen every intermediate figure, and therefore regards it as a mere variety, and not a species. The colour, it hardly needs be stated, is in no way character- istic. - C. amphacanthus.-Ovate, shorter, Lo- rica, unlike that of the other species, colu- posed of rings; the anterior part crowned with unequal teeth, the posterior having three strong spines. Found in Spiro- stomum virens, 1–280". C. incurvus.-Oblong, nearly cylin- drical, and slightly curved; lorica ter- minating in five points. Amongst Con- fervab. 1-430". C. inermis (Perty).-Lorica costate, not granular; no spinous points at pos- terior end, or very feeble ones. Green corpuscles occur internally. The dis- tinctness of the ribs varies, as well as the length and thickness of the body. Mo- tions like those of C. hirčws. 1-600". Fresh water. FAMILY WII.—TRACHELINA. (XXIV., XXVIII., XXIX.) This extensive family includes those animalcules which have two distinct alimentary orifices—the receiving one lateral, the discharging one terminal. They have no lorica; but all the genera, except Phialina, are covered with vibrating cilia, generally disposed in longitudinal rows, those near the mouth being the longest. Trachelius has no neck; but the frontal portion of the body is prolonged in the form of a long trunk-like lip; in Lovodes and Chilodon it is like a hatchet-shaped broad lip. In Glaucoma there is a of THE TRACHELINA. 617 tremulous flap to the mouth, and in Chilodon and Nassula a cylinder of rod- like teeth, which sometimes projects in advance of the mouth. Bursaria and Nassula have a thick frontal protuberance. The reception and discharge of coloured matter can be seen in all the genera. In Nassula the violet-coloured specks (bile) are worthy of notice. In Spirostomum the mouth is spiral. A nucleus and one or more contractile vesicles occur in all the genera. Com- plete transverse and longitudinal self-division is frequent and complete. The genera are disposed as follows:— ſ (+. ( with a ſlip long, proboscis-like...... Trachelius. Brow con- ă brow-like º * # | No tremu- tinuous º upper lip lip broad, hatchet-shaped...Loxodes. * : 4.1- 4. +E £º gº & # { *m. §. the à brow-like prominent back ............... Bursaria. # flap. Mouth spiral .................................... Spirostomum. Gl) E- Brow interrupted in a peg-like mammer........................ Phialima. \ Mouth having a tremulous flap .................................... . . . . . . . . . . . . . . . Glaucoma. º # ſ A brow-like prominent upper lip ............................................. Chilodon. G) ºr, ë #l A brow-like prominent back .......................... • * * * * * * * * * * * * * * * * * * * * * * * Nassula. This family is not recognized by Dujardin, who rejects the supposed affini- ties of its genera as unnatural; and indeed it must be owned that the Tra- chelina, as understood by Ehrenberg, represent a heterogeneous collection rather than a natural group. Bursaria includes some mouthless Opalinae. Spirostomum evidently takes its place next to Stentor; and Chilodon and IWasswla are removed in several important details of organization from Thra- chelius and Phialima. Perty retains in his classification a family Trachelina, and places in it the genera Trachelius, Harmodirus, Amphileptus, Loacophyllum, Dileptus, Pelecida, and Loa:0&es,—adopting, however, the characters assigned by Dujardin in preference to those given by Ehrenberg. The brief character of Trachelina recorded is—“Body elongated anteriorly into a neck-like process, or pro- truding a proboscis curved on one side.” - We have retained in the preceding description of Trachelina, adopted from Ehrenberg, several notes of structural peculiarities which subsequent re- searches show to be erroneous. That the mouth is lateral and the anus ter– minal in all the members of the family is not the case. Thus, in Chilodon the discharging orifice is on One side, near the posterior extremity. Lachmann (A. N. H. 1857, xix. p. 216) speaks of the buccal orifice of Glaucoma as produced into two flaps. The teeth (so called) in Nassula, Chilodom, &c., have no real claim to that designation ; for they are no more than folds or thickenings of the oesophagus (see Part I. p. 311). The violet-coloured spots, imagined by Ehrenberg to be vesicles, are merely accidental specks of colour derived from the food (see p. 312, and notes on NASSULA elegans). Chilodon and Nassula have been proved to propagate by living embryos, after a previous emcysting-stage; and in all probability most of the other genera do so likewise. Nasswla ambigua (Stein) has been seen in the same encysted condition as Chilodon; and only the last stage, that of the internal development of a ciliated embryo, to complete the cycle as in Chilodon, has escaped observation. 618 SYSTEMATIC EIISTORY OF THE INFUSORLA. Genus TRACHELIUS (XXIV. 287–290).-Body ciliated; mouth simple, destitute of teeth, is seated on one side at the base of the very much elon- gated upper lip or proboscis. Cilia are absent in three species. In four species coloured food has been received, and in three the discharging orifice detected. It has also a collapsed Oesophagus, visible only during the passage of food. Two species increase by transverse self-division. This genus forms a member of the family “Trichodiens” (Trichodina) (Duj.), along with Trichoda and genera named Acineria, Pelecida, and Dileptus. - The account he gives of the animals differs much from the foregoing. Ac- cording to it, Trachelius is destitute of a contractile or reticulated integu- ment, and is composed of a muco-gelatinous substance (Sarcode) containing granules, which are oftentimes agglomerated in the form of nodules, disposed in rows. The apparent oviposition in T. Ovum and T. Meleagris was nothing more than the breaking up of part of the animalcule by “diffluence,” and the supposed ova only particles of “sarcode.” “The cilia at the anterior extremity are larger than those on the rest of the body. Posteriorly a large vacuole is often to be seen. distinct mouth.” There is no The last statement is contradicted by recent investigations, which prove that the animalcules belonging to this family have a mouth, and some of them, at least, an anus. TRACHELIUS Anas (Trichoda Anas et Indez, º (xxiv.287–289).--White, cla- vate, and cylindrical; proboscis thick, obtuse, not half the length of body; mouth situated close to the base of the proboscis. In exposed infusions, and freshwater swamps, amongst Confervae. The interior often contains green (chlo- rophyll) vesicles. 1-280" to 1-120". T. voraſc.—Clavate-ovate, turgid, co- lour white; proboscis thick, obtuse, shorter than half the body; mouth situ- ated near the middle of the body, and not at the base of the proboscis. Amongst Confervae. 1–120". T. Meleagris.-Compressed, lanceolate, often curved in the form of the letter S; proboscis thick, obtuse, shorter than half the body. 1-96" to 1-60". Ehrenberg described in this species a red-coloured fluid which he called bile, and a row of ten to twelve vesicles along the back, which he concluded to be sto- mach–cells filled with red gastric juice. It is now, however, admitted that these cells are really contractile, and form a vascular chain. The nucleus is oval, with a cen- tral constriction. Dujardin adopted this species as one form of a new genus, oacophyllum, hereafter described in the family Colpodea, T. Lamella (Kolpoda Lamella, M.) (XXVI. 24 a, b). — Depressed, laminar, elongated, linear-lanceolate, often trun- cated anteriorly and rounded; margin ciliated (Dujardin says, only in front). Ehrenberg considers this form may be no other than the young condition of Am- phileptus Fasciola; and Perty would add, of Spathidium hyalinum. In Sea-water. 1-900" to 1–2001'. T. Amaticula. —White, Small, ovate, pyriform, attenuated and diaphanous an- teriorly. Dujardin believes he has seen several of these animalcules become by simple contact agglutinated together, L a circumstance which would indicate the absence of a true integument. Amongst Confervae. I-570" to 1–280". T. (?) trichophorus (Vibrio strictus, M.) —Cylindrical, changeable, often clavate; º capitate, of the form of a very delicate whip. 1-1200" to 1-430". T. (?) globulifer. —Spherical, hyaline, with a very delicate whip-like acute pro- boscis. Amongst Confervae. 1-200". T. Ovum (XXIV. 290).-Large, ovate, wide or campanulate anteriorly; pro- boscis short, in the form of a beak; con- tractile vesicles numerous. “In no in- fusorial animalcule,” says Ehrenberg, “is the alimentary canal so easily seen as in this; the large mouth and contractile vesicle, lying over the lower part of the alimentary canal, are equally evident; numerous Small digestive cells and ova- granules appear in every part.” It is in this species that Lieberkühn and Lach- mann have latterly described the exist- ence of an arborescent, ramified digestive canal, quite distinct from the clear round spaces in the parenchyma of the body, OF THE TRACEDELDNA. 619 which some have supposed to be sto- machs. In stagnant bog-water. 1-72." It has been found encysted. (Wide Part I. . 309). p T. (?) laticeps.--Flattened, elliptical; anterior part (head) membranous, vari- able and wide, with a notch from which roceeds a flagelliform proboscis almost ouble the length of the body. 1-912". In North Sea. T. dendrophilus. – Ovate, subacute at each end; proboscis very fine, acute, double the length of the body. 1-288"; with filament, 1–96" to 1-72". Has the habit of a Monad, but the motion of T. trichophorus, than which it is very much Smaller. On tree-mosses. T. strictus (Duj.).—Filiform, extremi- ties rather pointed; the cilia visible only in front. 1-400". Amongst Lemnae; seen also by Perty in Switzerland. T. teres.—Filiform, cylindrical, obtuse anteriorly, pointed and tapering behind; ciliated only in the anterior margin. 1-170". In stagnant sea-water, T. Fala.-Long, depressed, lanceolate or signoid; variable; narrower and rather curved anteriorly in a sickle-like form; ciliated generally. 1-420". In pond-water. T. noduliferus (Perty).-Very slender, narrowed anteriorly, but terminated abruptly by a rounded end; colourless, but with diffused chlorophyll-vesicles at times, and granules. Cilia scarcely vi- sible, except near the head, where they are rather larger. Movements slow. The elongated neck-like portion devoid of molecules. 1-570" to 1-120" (Bern). T. apiculatus. –Slender, tapering an- teriorly, its end being obtuse. Colour- less, with diffused vesicles and molecules. Cilia very delicate. Movements rapid, like those of Trachelocerca. 1–144". T. pusillus.-Considerably elongated; rather flattened; colourless; with around opening at its narrower anterior ex- tremity. Movements tolerably quick, with slow revolutions on its axis. Perty intimates it to be the same species as Trachelius trichophorus (Ehr.) and the Peranema protractum (Duj.). Genus LOXODES (XXIV. 291–293).-Body ciliated throughout, mouth simple, devoid of teeth; upper lip continuous and broad, hatchet-shaped; locomotive cilia longer near the mouth. The contractile vesicle is round; the nucleus oval or ovoid. In L. Bursaria an oval nucleus and two contrac- tile globular vesicles have been seen. Self-division transverse. Dujardin’s characters of Loa:0des are—“Body flat, membranous, or with an apparently membranous lorica, flexible but not contractile, expanded at the centre of its superior or dorsal surface, often concave on the under surface; contour irregularly oval, sinuous and obliquely prolonged anteriorly; furnished with very fine cilia, confined to its anterior margin. In general characters,” he adds, “Loazodes approaches nearest to Trachelius (family Trichodina); but the signs of an integument are so clear as to sever it from that genus and family.” The Loazodes described by the French author are almost all of them distributed by Ehrenberg among other genera and families; and hence there is unfortunately none but the slightest relation between the similarly-named genus of the two writers. Thus the Lowodes Rostrum of Ehrenberg is the representative of a genus Pelecida, of the family Trichodina, in the system of Dujardin, and bears the name of Pelecida Rostrum. In this position it is brought into close relation with the genera Trichoda and Trachelius (Ehr.), and with two others, named by Dujardin Acineria and Dileptus. The last-mentioned genus comprises Infusoria placed by Ehrenberg with Amphileptus, in describing which we shall take the opportunity to give the characters of Dileptus, whilst Acineria and Pelecida will be included among the appended genera at the end of the present family, Trachelina. LoxoDEs Rostrum (Kolpoda Rostrum, M., Pelecida Rostrum, D.) (XXIV. 291– 293).-Body compressed, white, lanceo- late, slightly curved in the form of an S, in consequence of the lip being a little uncinated. Ehrenberg states that he has very often seen large Naviculae and Syn- edra within this creature, although it would not feed on coloured food. The cilia are very delicate. (XXIV. 291, an animalcule which has fed upon Bacil- laria; XXIV. 292, another, creeping along 620 SYSTEMATIC ELISTORY OF TEIE INFUSORIA. Confervae ; and xxv. 293, a specimen undergoing transverse self-division.) Amongst Čonfervº, i-1447 to i-36. L. Cithara (Trichoda aurantia, M.).-- Triangular and compressed; anteriorly dilated and obliquely truncated, but ointed at the posterior extremity. Co- our white. 1-430" to 1–210". L. Bursaria. —Oblong; anteriorly ob- liquely truncated and depressed; poste- riorlyhemispherical. The mouth is placed near the centre of the ventral surface, at the bottom of a deep funnel-like fossa (vestibulum), the upper border of which is longer, broader, rather concave, and truncate, and constitutes the “upper lip”.of Ehrenberg. A long Cesophagus extends far into the interior from the mouth. In bogs. 1-280". This, Focke and Stein show, is not a species of Loacodes, but of Paramecium, and therefore rightly named P. Bursaria (which see, p. 635). It was this species which was so elaborately examined by Cohn, especially with regard to its repro- duction. Young specimens are colourless; but mature beings have numerous chlo- rophyll-corpuscles diffused in their cor- tical laminaº. There are two round con- tractile spaces, which by pressure assume a stellate appearance similar to those of P. Aurelia. The rotation of the contents may be demonstrated in this species; and Cohn, Focke, and Stein have witnessed its reproduction by a living germ or em- bryo. In figure it is very like Chilodon Cucullulus, but has the oral fossa (vesti- bule) and cilia of Paramecium. L. plicatus. – Elliptical, depressed, convex on the back, and slightly plicated; the lip uncinate. On Confervae. 1-430". The species of Loacodes mentioned by Dujardin are L. Cucullulus = Chilodon Cucullus (Ehr.); and L. Cucullio = (?) Rolpoda Cucullio (M.), placed by Ehren- berg among the Kolpodea. L. reticulatus. – Oval; more slender, sinuous, and flexible anteriorly; surface granular. In long-kept marsh-water. This species is, in Stein's opinion, a mere accidental variety of Chilodon Cucul- lulus, determined by the bulk of food received. L. marinus.--Depressed, oval, almost remiform; with internal fine granules, and a row of puncta near both the ante- rior and posterior margins. 1-350". In salt water. L. dentatus.-Similar to L. Cucullulus, but having a bundle of bristles about the mouth, as in Chilodon, from which it differs by the lorica (cuirass) and by the absence of cilia on the surface. The distinction of this species and L. Cucullulus as independent, Stein rightly criticizes as an error on the part of Du- jardin, and shows (Infus. p. 131) that both of them are only accidental varieties of Chilodon Cucullulus, Loacodes Cucullulus being nothing more than Small specimens in which the Oesophagus is indistict, and L. dentatus examples in which this organ is very evident. - L. brevis (Perty). — Short, rounded, with a hyaline proboscis. 1-500". Bern, in rainwater-ponds, Genus BURSARIA (XXIV. 294–296).--Surface ciliated throughout; an– terior part convex; mouth not terminal, fringed with stronger cilia, though simple, toothless, and devoid of tremulous flap. The cilia are distinctly seen in coloured water, and are generally disposed in rows; those around the mouth are longer than the others. The nutritive system (says Ehrenberg) consists of an alimentary canal, curved forwards; it is furnished with diges– tive cells resembling little purses, which are attached to it by short stalks. The mouth is large, situated, as in Lewcophrys, obliquely at the anterior ex- tremity, so that a brow, as it were, either projects over it or else forms the end. The contractile vesicle is sometimes doubled; the nucleus oval or ovoid. The anus is placed at the posterior extremity. Self-division, longi- tudinal or transverse, has been observed in five species. Dujardin has the following remarks on this genus:—“Ehrenberg, whilst admitting a genus Bursaria, Separates from it several true species, and places some of them in his genus Lewcophrys, others in his family Kolpodea; Whilst the closely allied genera Kondylostoma and Plagiotoma are confounded with other families—the former with Oxytricha, the latter with Paramecium. Moreover, the obliquity of the mouth in Bursaria is not a sufficient distinc- tion between that genus and Lewcophrys; and, whilst assigning a large mouth OF THE TRACEIELINA. 621 to the Bursariae, he includes among them several species in which the existence of a mouth is, to say the least, doubtful.” The genus Bursaria is taken as the representative of a distinct family, both by Dujardin and by Perty. The former, who names it “Bursarina,” insti- tutes five genera, viz. Plagiotoma, Ophryoglena, Bursaria, Spirostomum, and Condylostoma. The latter adopts the same name, and ranges the family in his section Monima, comprehending Ciliata which, although very contrac- tile, and clothed by a soft integument, always retain their form. The genera included among the Bursarina by Perty are Lembadion and Bursaria, the former a new genus established by himself to receive two species which he does not find indicated by Ehrenberg. Dujardin defines the Bursarina as “animals possessing a highly contractile body, very variable in form, mostly oval, ovoid, or oblong; ciliated throughout, and having a large mouth sur- mounted by a band or surrounded by a spirally curved row of cilia.” The genus Bursaria is closely allied to Paramecium, from which it is chiefly distinguished by the row of larger, longer cilia about the mouth, ex- tending along the deep fossa in which that Orifice is contained. In Para- mecium the cilia are everywhere of the same size. Several of the Bursariae enumerated by Ehrenberg have been shown to be Opalinde, and to be destitute of a mouth. These species are B. Ramarum, B. Entozoon, B. intestimalis, and B. Nucleus, all which are further remarkable in being parasitic in Batrachia. The B. cordiformis is also a parasite of the intestime of the frog, and, although a doubtful member of the genus, has the Sanction of Stein to the generic position accorded it. a. Sub-genus BURSARIA.—The inferior (not anterior) lip reaching to the frontal margin. BURSARIA truncatella (M.). The trun- |cies has great resemblance to Urostyla cated Bursaria.--Large, visible to the naked eye; white, ovate, turgid, trun- cated and broadly excavated in front, where there is a simple row of cilia. In Some specimens, Ehrenberg saw half-di- gested Rotifera and large quantities of vegetable matter in the nutritive cells, and was able, as he thought, by means of carmine given as food, to trace an ali- mentary canal through the greater part of its course. In each vacuole the food appears surrounded by a clear fluid, which Ehrenberg calls bile. A large bright vesicle is seen below the mouth and Somewhat to the left of it, on which side is also a large curved but not articulated nucleus, reaching to the brow or frontal region. In ditches and ponds, amongst rotten beech-leaves. 1-48" to 1-36". B. Vorticella (xxiv. 294). —White; large, nearly spherical, and turgid; an- teriorly truncated and widely excavated, with a double row of cilia. Found with Chlamydomonas Pulvisculus and Gonium Pectorale, which are sometimes seen within it, as in xxIV. 294, 1–108". B. vora.c.—Large, oblong, rounded at the ends; mouth ample, being one-third the length of the body, and touching the summit of the frontal region. This spe- grandis and Stylonychia lanceolata, when their claws and styles are withdrawn. In muddy water in summer, 1-140" to 1-108". B. (Opalina) Entozoon.--Large, cylin- drical, turgid, nearly equally rounded at both extremities; mouth small, near the frontal apex. Found, with the following, in the rectum of Rana temporaria (the Frog), in Summer and winter. Perty represents this as a mere variety of B. Ranarum. He also treats B. Nucleus and probably B. intestinalis as other va- rieties of the same being, and therefore Opalinae. - B. (Opalina?) intestinalis (Vibrio Ver- miculus, M.).--Slender, cylindrical, at- tenuated posteriorly; mouth small, situ- ated below the frontal apex. In this species, as well as in others, Ehrenberg has seen transverse self-division. Found with the preceding. 1–240" to 1-120". It is probably an Opalina. B. (P) cord formis. – Reniform, front depressed, mouth slightly curved in a spiral manner; colour white. 1-210". This species Stein affirms to be a true Bursaria; but Perty makes it an Opa- lina, a view countenanced by its para- sitic nature. 622 SYSTEMATIC HISTORY OF THE INFUSORIA. B. lateritia (Trichoda ignita, M.). — colour. With Lemnae, Confervae, &c. Compressed, ovato-triangular, with the 1–430" to 1-144". front sharply crested, of a brick-red b. FRONTONIA.—Anterior part of the and is B. vernalis (Leucophra virescens, M.), Oval, turgid, rounded at the ends, and attenuated posteriorly. The mouth has a wreath of stiff, short bristles, resembling teeth; numerous digestive vacuoles are often filled with large Oscillatoriae, Na- viculae, &c. (and contain a reddish bile, Ehr.). The progressive digestion of the Oscillatoriae is interesting to follow :— they are at first elastic and rigid, and of a beautiful blue-green colour, then di- stinctly lax, flexible, and bright green, becoming afterwards yellowish green, and resolved into separate segments, which at length turn yellow. Amongst Oscillatoriae in spring. 1–144" to 1-120". B. leucas (XXIV. 295; XXX, 1). — Ob- long, cylindrical; extremities nearly equi- convex (bile colourless). This creature has a contractile bladder, with a curious jagged margin near the long open mouth. With Oscillatoriae, and on the surface of water. 1–144". B. Pupa (XXIV. 296).-White, ovate- oblong, rather acute posteriorly; mouth inferior, and near the frontal apex (see f 296). 1-280". In chalybeate water, Germany. IB. flava.-Ovate-oblong, often acute at the posterior extremity; the mouth occurs in the flat concavity immediately behind the round brow. In bog-water. I-140' to 1-96". “This species,” says Perty, “differs much, both in its figure and its narrower oral fissure, from true Bursariae, and ranges better with Panophrys.” Dujar- din, again, considers B. flava, B. leucas, and B. vernalis to be merely three va- rieties of his Panophrys farcta. B. (Opalina) Nucleus.--Small, white, ovate, attenuated anteriorly; extremities convex. In Rama temporaria and R. es— culenta. 1-240". Wide notes on B. En- tozoon. B. (Opalina) Ranarum.-Ovate-lenti- cular and compressed, Subacute ante- riorly; the back and bellycarinated; often truncated posteriorly; mouth inferior, near the frontal apex. 1–210" to 1-72". The mouth here described has been body (brow) projects beyond the mowth, CO7??)003, diligently sought for by Stein and others; but they can find nothing more than a fold of the surface, with no orifice in it, as shown by reagents. This species is therefore a member of the mouthless group Opalinaea (vide subclass OPALI- NAEA, p. 269, and Pls, XXII.46,47; XXVI. 28, 29). - B. (?) aurantiaca.-Ovate-oblong, an- teriorly obtuse, posteriorly acute; it has an ash-coloured spot near the mouth. Amongst Oscillatoriae. 1-280". B. arborum. — Oblong, compressed; very finely ciliated; ends rounded; mouth situated in the anterior third of the body, reaching its frontal extremity; a wreath of larger cilia extending around and backwards from the mouth, Length 1-40", double the breadth; vacuoles numerous, and two globular nuclei seen. On moss of trees. B. triquetra. —Ovate-lenticular; very finely ciliated; dorsum flat; venterturgid and slightly keeled, hence an imperfect triquetral figure of the animal; anterior extremity subtruncate; oral fissure long, extending from the frontal end, fringed with a row of strong cilia extending backwards; nuclei two, small; vesicle large, contractile, simple, near the pos- terior extremity. Swims slowly. 1-36". On moss of trees. B. Blattarum (Stein).-Is very like B. cordiformis, but more compressed; rounded in front, where there is a very opaque, sharply-defined, coarse-granular, and posterior to it the transverse oval nucleus. In intestine of Blatta. B. patula (Duj. and Perty)=Leuco- phrys patula º JBursaria virens (Perty) = Spirostomum virens (Ehr.); and Bursaria Spirigera. B. Loacodes (Perty)= Loacodes Bursaria (Ehr.). — Under no circumstances can this species (says.Berty) be reckoned with Lozodes (Ehr.), or with Pelecida (Duj.). B. Lumbrici (Stein)= Plagiotoma Lum- brici (Duj.) = Paramecium compressum (Ehr.) is a Bursaria, not a Parame- cium, having a row of longer cilia about the mouth and ventral surface. Genus SPIROSTOMUM (XXIV. 296–298)—Body elongated, or ribbon- shaped, flexible and ciliated, the frontal region continuous; mouth lateral, spiral-shaped, devoid of teeth, but with a tremulous flap. The locomotive OF TELE TRACEIELDNA. 623 cilia are disposed in rows; those at the mouth are longer, and form, as in Stentor, a spiral wreath around it; in S. ambiguum the brow and wreath are remarkably long. Vacuoles, to the number of ninety, have been seen filled with coloured food, and the discharge of the latter observed. The anus is placed at the posterior extremity. [Aband-like thick gland (nucleus) is seen in S. virens, and a bead-like one in other species.] The former likewise possesses a large contractile vesicle, and green granules; in S. ambigww.m. the granules are white. Self-division has not been observed, but Ehrenberg presumes that it takes place transversely. The band-like or moniliform gland mentioned by Ehrenberg is in fact a pulsating vessel extending almost the entire length of the animalcule. The genus does not belong to Trachelina, but to a family represented by Stentor, which Lachmann and others would establish with the name of Stentorina. Perty transfers Spirostomum to Urceolarina, in which family it is united with Stentor, Caenomorpha, and Urocentrum. (See remarks on WoRTICELLINA, p. 579.) From the mouth to the SPIRoSTOMUM virens (Bursaria Spiri- gera, D.) (XXIV. 296*).-Ovate-elongate, depressed; truncated anteriorly, and rounded posteriorly. The back is arched, and the under side flat. The green gra- nules are sometimes absent (f. 296*). 1-120"; ova 1-6000". S. ambiguum (Leucophrys [Trichoda] ambigua, M.) (xxiv. 297, 298.)—White, cylindrical, filiform, flexible; obtuse an- teriorly, truncated posteriorly; an elon- along the body. anterior or top of the brow runs a long ciliated furrow (xxiv. 297 and 298). In Swimming, they extend themselves, and are readily perceived by the naked eye. In ditches, among decaying oak-leaves and rotten wood. 1-12". Both Dujardin and Perty consider this animalcule to be the same as that other- wise described by Ehrenberg as Uro- leptus Filum. S. sempervirescens (Perty). — Body round, filled with green granules; tail cilia in front often appear like a pro- broad, flat, and colourless. Cilia at boscis, and were mistaken for such by anterior extremity, clearly seen. The Müller. The structure of this creature ſº colour was probably due to the is remarkable, especially the mouth, food. 1-96". Among Lemmae, but only which is only one-fifth from the tail; once. It is allied to Kondylostoma thus the frontal region or brow is very | (Duj.), which differs from it by its long, and the alimentary canal (adds marine habitat, Ehr.), first inflected forwards, returns gated frontal region or brow extends be- yond the mouth. The long vibrating Genus PHIALINA (XXIV. 299).-The frontal ciliated portion is sepa- rated from the non-ciliated body by a constriction or neck; mouth lateral, devoid of teeth. The motion of these creatures is due to the powerful wreath of cilia over the mouth. Ehrenberg says, cilia may possibly be present upon the surface of the body, since Müller described them in Trichoda ºnellitea. A contractile vesicle (perhaps two) is situated posteriorly. Self- division probably transverse. Dujardin rejects this genus; and, in Perty’s opinion, the animalcules it includes are no other than more contracted and younger specimens of Tra- chelocerca linguifera or of Lacrymaria. Amongst them are specimens with an evident terminal flap or tongue, and others with incompletely developed necks. Their movements are rapid. (See notes on LACRYMARIA, p. 609.) attenuated; neck very short. 1-280”. PHIALINA vermicularis (Trichoda ver- There is nothing distinctive in the 'micularis, M.).-Ovate, attenuated an- teriorly; neck very short; colour white, With Lemnae. 1240". P. viridis (XXIV,299).-Bottled-shaped, anterior partacute, the posterior gradually f assigned characters of this species; the slight difference in form may arise from the varying amount of contraction. The green colour is valueless. 624 SYSTEMATIC HISTORY OF THE INFUSORIA. Genus GLAUCOMA (XXIV. 300–302; XXVIII. 4–7).-Body oval, com- pressed, covered with cilia; mouth provided with a tremulous flap, but no teeth. Ehrenberg described the reception and discharge of food, and the presence of digestive vacuoles, and therefore saw, in these, indications of the existence of an alimentary canal. The large mouth, with its vibratory valves, is situated on the inferior side, in advance of the middle. The anus is situated on the ventral surface, near the posterior extremity, or at the extremity itself. The internal organs are a large Ovate gland, a star-like contractile sac, and granules. Self-division transverse or longitudinal. Glaucoma is comprised by Dujardin among his Paramecina. Perty con- structs a family out of this genus, along with Cinetochilum (vide CYCLIDIUM, p. 572), which he designates Cinetochilina, and characterizes as animalcules having a mouth on the upper side, surmounted by a vibrating valve (like a tremulous eyelid). Cilia disposed in longitudinal rows. It will be noticed that the mouth is described to be on the upper side instead of the under, as stated by Ehrenberg, with whom we agree. The anus is on the ventral surface, near the posterior extremity. Lachmann describes two flaps to the mouth, but Perty says the second is simply an expansion of the margin of the mouth. or drying the animalcules (XXIV, 300– º In natural and artificial infusions. 1-280". G. viridis (Duj.).—Green, oval, short; mouth large, situated nearer the centre than to the anterior margin. 1-860" to 1-520". In rain-water butts, GLAUCoMA scintillans (Cyclidium Bulla, M.) (xxvii.I. 4–7).-Elliptical or ovate, colourless, slightly depressed; vacuoles large. The vibrating flap appears to be semi-oval or reniform and Smooth, and to have a stiff margin. The cilia are seen by employing colour or by pressing Genus CHILODON (XXIV. 303–309; XXIX. 48–59).—Body irregularly oval, flattened, regularly ciliated : frontal region produced in the form of a broad membranous lip, on One side, resembling a beak; the mouth, situated at its base, and therefore lateral, is furnished with a tubular fascicle of teeth. A round nucleus, one or more contractile vesicles, and transverse and longi- tudinal self-division have been observed. This genus along with Nassula, Prorodom, and two newly-instituted genera, Cyclogramma and Habrodon, are grouped together in the system of Perty, as a family styled “Decteria,” which is thus characterized:—“Mouth beset with a circlet of fine bristles. In the first three genera the mouth is lateral; in the remaining two, anterior.” Stein makes Chilodon distinct from Nassula, by its body being compressed, having a distinct upper and under surface, and a lip-like process above the mouth. CHILoDoNCucullulus (Kolpoda Cucullus, M.) (xxiv. 303-307; XXIX. 48–59). — Body depressed, oblong or ovate, rounded at the ends; frontal region advancing on the right side. [Ehrenberg states he has often seen the straight alimentary canal, with its grape-like cells, filled with large Naviculae.] Contractile vesicles from two to three ; mucleus large, oval near the centre. The circlet of teeth was stated by Ehrenberg, to consist of little hard wand-like bodies, which the creature could separate so as to admit into its mouth large living bodies, and afterwards contract or close upon them (XXIV. 308, 309). The amus is at one side of the posterior extremity. In Swimming, or creeping upon the surface of Confervae, the mouth is turned under or below. Its motion is gliding; and it does not revolve in swimming. When the water is coloured, the cilia may be easily perceived, and their disposition when it is dried up. (Figs. 305 and 306 exhibit longitudinal, and 307 transverse self-division.) In fresh and salt water. 1-1150" to 1-140". This species has received a close ill- of TIE TRACHELINA. 625 vestigation by Stein. The circlet of teeth (bacillar apparatus, Lachmann) is con- structed of no actually separate portions or teeth, as Ehrenberg supposed, but is nothing more than a thickened oesopha- gus with denser rugae, or folds, of a chi- tinous composition. From its lower end a digestive tube extends to nearly the centre of the body. C. uncinatus. – Depressed, oblong, rounded at the ends. The right side of the anterior part is produced, so as to appear like a hook or beak. In vegetable infusions. 1-430". This being is, in Stein's opinion, a mere variety of C. Cucullulus: the bulging out of the side has a somewhat hook-like process; but this is a mere accidental re- sult following the process of longitudinal self-division (Infus. p. 130). It has been seen to encyst itself. C. aureus. – Ovate-conical, turgid, of a golden yellow colour; dilated and ob- tusely rostrated anteriorly, attenuated posteriorly. 1-140". C. ornatus.-Ovate subcylindrical, of a golden yellow colour, equally rounded at both ends, slightly beaked; it has a bright violet spot. 1-180". !he violet spot spoken of has no di- stinctive peculiarity; it is not a normal coloured gastric fluid, but only a collec- tion of granules, the same as in Nassula elegans. This species, together with the fore- going C. aureus and the Nassula aurea, are so very similar, that Stein doubts their independent mature, and is more dis- posed to regard them as developmental phases of the same being. C. depressus (Perty).-Irregular, with- out a beak, and rounded at both ends; compressed; almost colourless. Trans- parent, with greyish contents, Upper and under surfaces equally flat. Tooth-cylin- der very evident, Switzerland, 1-120". Stein states that the body is bilateral, presenting a distinct right and left side, an upper (dorsal) convex and a lower (ventral) flat surface. The anterior end is much flattened and transparent; and being curved towards the left side, gives the whole being a somewhat reniform figure. The depression on this side is always in advance of the middle of the body, just as in Paramecium Colpoda and Colpoda Cucullulus. The anterior, curved transparent end surmounts the body like a crescentic process, is furnished with longer cilia than elsewhere, and may not inaptly be called the lip. Vibratile cilia cover the body in regular rows, but in very young specimens are invisible ex- cept on the lip. The oval nucleus is hollowed by a cavity, within which is a nucleolus. Longitudinal and transverse fission takes place in individuals of all sizes. The former advances from the posterior extremity; the oesophageal (dental) cylinder is not divided, but is produced de novo in the newly produced Segment: this segment, when first de- tached, is the Chilodon uncinatus (Ehr.). Chilodon Cucullulus encysts itself: a soft gelatinous matter is first thrown out around it, which hardens into the cyst- wall; during this process the superficial cilia and the oesophageal cylinder disap- pear, and at length an oval cyst, with a large nucleus, and two to three contractile spaces alone appear. Gradually a cili- ated embryo is developed from the mucleus, resembling in external charac- ters a Cyclidium Glaucoma. The embryo escapes from the parent animal; and cysts are sometimes found containing the parent and its offspring side by side within it. The development of embryos may go on until the nucleus is expended. The size of the germ is determined by that of its parent. Genus NASSULA (XXIV. 310, 311; XXVIII. 2, 3, 11–15). — Covered With cilia; ovoid or oblong; turgid and prominent in front, but without the expansion or beak on one side ; mouth lateral, provided with a circlet of teeth, in the form of a wheel (massa). Numerous vacuoles are seen, and in two Species, as Ehrenberg states, the discharging orifice. The violet-coloured granular spots noticed in Chilodon ornatus occur also in the species of Nassula, and are likewise met with in Bursaria vernalis, Trachelius Meleagris, Amphi- !eptus margaritifer, A. Mcleagris, and A. longicollis. “They resemble,” says Ehrenberg, “the vesicular glands around the stomachs of the Rotatoria, and are probably of a glandular nature, analogous to biliary glands, and concerned in the process of digestion.” The nucleus is large, oval or spherical; and there are one or more contractile vesicles. Only transverse self-division has been - 2 s 626 systEMATIC EIISTORY OF THE INFUSORIA. observed. They are found in stagnant water, especially where Conferva and Oscillatoriae are present. The violet-coloured supposed digestive glands or cells are, in the opinion of others, simply vesicles coloured by the Oscillatoria on which the animal- cules feed (p. 312). This genus and the preceding, Chilodon, are very closely allied. Stein finds the best distinctions between the two in the rounded body with the ex- tremities obtuse and rounded off, in the case of Nasswla, and in the flattened, compressed body, with decided ventral and dorsal surfaces and with a lip-like process, in Chilodom. NASSULA elegans (XXIV. 310, 311; xxvii.I. 11–15). — Cylindrical or oval, slightly attenuated in front, extremities very obtuse. It is white or greenish, spotted with violet vesicles. Vacuoles, containing Chlamidomonads or other food, may often be observed ; and from fifteen to twenty rows of cilia may be seen on one aspect. The animalcule swims backward and forward, turning upon its longitudinal axis. The mouth is easily perceived by the currents when indigo is mixed with the water: it has a circlet containing twenty-six little wands or teeth, which can voluntarily diverge or converge anteriorly. Four round contractile vesicles, placed in a row, occur on the dorsal surface, and doubtless represent four expansions of a continuous contractile vessel along that region. The violet vesicles mentioned are only accidental (i. e. not necessary) collections of pigment matter, derived from the food (see p. 312). When self- division ensues, the large central nucleus divides (XXIV, 310, 311; the latter is a young one). With Lemnae and Con- fervae. 1-140" to 1-120". Nassula ele- gans is thus characterized by Cohn — Elongate with rounded extremities; oesophagus funnel-shaped; no cylinder of teeth present as in N. ornata. Con- tractile vesicles two; mucleus elliptic, with nucleolus lodged in a fossa at one end. A large mass of violet granules on under surface posteriorly. It resembles but is smaller than Paramecium Aurelia, and has a similar cuticle. With Bursaria truncatella and Ophryoglena atra. It is smaller than N. ornata. Its changes of form are remarkable; often dependent on swallowed joints of Oscillatoria. Cilia very closely disposed. N. ornata (N. viridis P, D.) (XXVIII. 65–71), Ovate or globular, depressed, of a brownish-green colour, variegated with numerous violet vesicles. The posterior part of the body has a small excavation. Ehrenberg says, there are from six to eight groups of vesicles, forming a wide circle round the mouth, filled with a violet-coloured juice, which is discharged with the excreta, and ap- pears like drops of oil, but soon mixes with and colours the water. It swims rapidly, rotating also on itself, but this only slowly. Among Swimming clusters of Oscillatoriae. 1-96"; ova 1-4800". It has been seen in an encysted State. N. aurea.—Ovate-oblong, nearly cylin- drical, very obtuse at the extremities. Its colour varies from golden yellow to a dark brown. I-120". - Stein hints it as probable that this species and N. viridis (Duj.), Chilodon aureus, and Ch. ornatus are merely dif- ferent stages of the same animal. N. ambigua (Stein) (XXVIII. 2, 3).-- Rounded, short oval; extremities equally rounded. Entire surface covered by cilia in longitudinal rows. The wedge-shaped oral opening surmounts a very wide pha- rynx (tooth-cylinder, Ehr.) which may be easily isolated. The contractile vesicle acquires a stellate figure during its com- tractions and dilatations, like that of Chilodom ornatus. The contents are ori- ginally colourless, but become tinted green, blue, and red successively, during the process of digestion of the Oscillatoria it feeds upon. It occurs encysted, in a transparent, resistant, globular cyst. Length 1-240”; width 1-420". N. concinna (Perty).-Ovate, hyaline, transparent; covered everywhere with fine granules having an annular arrange- ment. Dental apparatus particularly ãe- licate, more evident when dried. Cilia very fine ; movements sluggish; amal opening at posterior extremity. 1-216". Genus LIOSIPHON (Ehr.).--Turgid; ciliated throughout ; frontal ex- tremity advanced beyond the mouth, and not auriculate. Mouth opens into a tubular membranous pharynx, provided with a cylinder of teeth. OF TEID, TRACECELINA, 627 This is a new genus instituted by Ehrenberg. Its essential distinction from Nassula is not pointed out, the only one indicated being the prolongation of the frontal region beyond the oral aperture. LIOSIPHON Stromphil.-Obtuse, ovate; | of a variegated green colour; tube of harynx of a clavate outline. 1-36". With Oscillatoriae. The genera named by Dujardin, having a near affinity with Bursaria, are Plagiotoma, Kondylostoma, Opalina, and Panophrys. Two others, Acineria and Pelecida (Duj.), are described as allies of Trachelius. Genus OPALINA.—Already described in the Astomatous family Opalinaea (vide p. 569). Genus PLAGIOTOMA (Duj.).—Body very flat or lamellar, very flexible, irregularly oval; sinuous or emarginate on One side, and sometimes angular behind; covered with cilia in regular rows; mouth lateral, near the middle, at the bottom of the depression, with a row of strong and very numerous cilia in advance of it on its anterior margin, having a comb-like aspect. PLAGIOTOMA Lumbrici = Paramecium compressum (Ehr.).--Stein shows this to be a true Bursaria (see p. 622). P. concharum (Perty) = Leucophrys Amondonta (Ehr.).--This and the fore- going are, in Stein's opinion, Opalinae (see p. 570). of a yellowish grey colour from contained molecules. Owing to its want of trans- parency, the fine short cilia are visible only around the periphery. Motion ex- tremely languid, oscillating and revolv- ing. 1-260". In the interior of Ano- donta Cellensis. P. (?) difformis.—Irregular, thick, and Genus KONDYLOSTOMA (Duj.).—Body more or less elongated, cylin- drical or fusiform, rather crescentic, with obtuse and flattened ends; mouth very large, bordered by very strong cilia, and placed on One side near the anterior extremity; surface obliquely striated and ciliated. It swallows its food, consisting of other animalcules or of vegetable débris, rather after the manner of Planariae than of Paramecina; for it does not draw it in by the action of its cilia in producing a vortex. It lives only in Smooth and pure sea-water among Algae, &c. KonDYLosToMA patens.—Body white, modified in figure by the bulk of food or coloured by the food received; at times | Swallowed. vermiform, at others fusiform, and often Genus PANOPHRYS (Duj.) (XXVI. 33).-Ciliated throughout ; oval, depressed, contractile; becoming ovoid, or even globular, during contraction; surface marked by straight or oblique ciliated striae, crossing one another; mouth lateral. Dujardin writes—“Being desirous of characterizing Bur- saria by the row of large cilia, en moustache, which lead to the mouth, I have thought it right to establish a new genus for certain Bursaria of Ehrenberg, which are devoid of this character, and whose mouth is surrounded by only ordinary cilia.” Unlike the Paramecia, they have no anterior oblique fold or fossa, and are able to contract themselves into a ball. They differ from Holophrya by their lateral mouth. They live either in fresh smooth water, or in sea-water among plants. - In Perty's system it constitutes a member of the family Paramecina; and this is its true position, if the cilia are throughout of equal length. Indeed the characters assumed to be distinctive of it from Paramecium appear to us inconclusive. A lateral fold or vestibulum leading to the mouth is not entirely wanting, although less developed than in most Paramecia ; and as to their 2 s 2 628 SYSTEMATIC EIISTORY OF THE INFUSORIA. greater contractile power, this really is questionable, and, if true, is not a proper generic character. PANOPHRYs Chrysalis (XXVI. 33).- Ovoid, oblong, depressed, mouth accom- panied by an enlargement, and placed near the front extremity. 1-145". In sea-water. P. rubra (?)-Reniform, covered with fine cilia, and provided with a lateral mouth near the front extremity. 1-370" to 1-325". In sea-water. Only pro- visionally named. P. farcta.-Ovoid, oblong, filled with particles of a green reddish-yellow hue, or of various mingled colours; mouth lateral, placed between the centre and the anterior third of the body. Its outline is very changeable, its movements rapid. The colour is seldom green, 1-145" to 1-95". . In marsh-water among plants. I think it is the animalcule described under three names by Ehrenberg, viz. Bursaria vernalis, B. leucas, and B. flava, and is probably the same as Leucophra virescens of Müller. Although Perty acquiesces in the be- lief that the yellow-coloured specimens of this species are the Bursaria flava (Ehr.), yet he thinks Dujardin wrong in claiming B. leucas and B. vernalis as varieties. P. conspicua (Perty).--Large; cylin- drical, scarcely smaller behind than in front; mouth round. Coloured by food dark green. Swims, revolving at the same time with moderate speed. 1-95". In peaty ponds with Lemnie. . sordida (Perty).-Cylindrical, more or less elongated; colour dark, earthy- brown. Mouth small. Cilia covering the body, fine. The position of the internal molecules varies even during examina- tion, and the figure with them. 1-180" to 1-96". Among Charaº. P. griseola (Perty) (XXVIII. 31). — Broad, distended; grey, but transparent, with a fine reticulate appearance; mar- ginal concentric striae. Sometimes occu- pied with chlorophyll-granules, when | and fine. it much resembles Ophryoglena griseo- virens. The mouth appears like an elliptic fold in a shallow fossa in the anterior half. It swims and turns on itself with much activity. Transverse fission observed. 1-300" to 1-108". Among decaying plants. P. zonalis (Perty).-Elongated, ovate- cylindrical; hyaline, with a central zone of dark molecules. Extremities equally wide, and rounded. Fissure of the mouth beset with stronger cilia. Movements rather sluggish, Body ciliated through- out. 1-168". This scarcely seems a true Panophrys; for the oral cilia are said to be larger than those on the body, contrary to Dujardin's characters of the genus. Moreover its chief peculiarity, viz. the zone of darker granules, is an insufficient specific feature; and when we are told by Perty that he has only once seen a small specimen, this supposed species has few claims to notice. P. paramecioides (Perty). —Cylindri- cal, slightly curved, its posterior end somewhat thicker than the anterior; colourless; rows of cilia very numerous Its molecular structure re- Sembles that of Paramecium Aurelia. Movements emergetic, twisting. The mouth is placed in a shallow fossa on one side of the body. 1-168". An un- common form in Switzerland. There is scarcely anything in the above description which is not compatible with the belief that the animalcule in ques- tion is either a Bursaria or a Paramecium. Moreover, reference to Perty's figures lends no aid to the determination of the question; and we must confess our in- ability to find, in his illustrations of the genus Banophrys, any sufficiently detailed particulars to enable us to distinguish either of the species named as members of it from probable representatives of allied genera. * Genus BLEPHARISMA (Perty) (XXVIII. 33, 34).-Body compressed, lancet-shaped, with a pointed posterior extremity, whence a deep fossa ex- tends as far as the middle, fringed with longer and straighter cilia than cover the rest of the body. The internal molecules are disposed in longitudinal rows, over which the very fine and inconspicuous cilia are arranged. BLEPHARISMA hyalinum (XXVIII, 33, 34).-Colourless, except when occupied by swallowed chlorophyll-particles. Body thin, flexible, and changeable in form; older specimens are broader. Movements varied and tolerably rapid. Sometimes a few large and ºil. filaments appear to issue from the oral fossa. OF TELIC TRACEIELINA. 629 Among Confervae and Lemnae; not com- 1]]Oll. - B. persicinum = Trichoda striata (?) (Müll.).-Colour reddish-yellow; young Genus ACINERIA (Duj.) (XXVI Fission transverse. At Bern, with the specimens paler. 1–210" to 1–144". preceding; rare. . 21 a, b).-Body oblong, depressed, or lanceolate, with a row of cilia extending forwards on one side, which is curved like a sabre. cilia and the curvature forwards. Distinguished from Trachelius by the disposition of the row of As in Trachelius, the examples of this genus seem destitute of a mouth, and in this respect they especially differ from those of Pelécida. ACINERIA incurvata (XXVI. 21 a, b).- Contractile, oblong, compressed, almost lamellar, round or obtuse behind, con- tracted and curved in front; a row of cilia runs along the convex edge; and there are five or six granular stripes, and one or more variable vacuoles. 1-590". In the Mediterranean. It ap- pears to be without a reticulated and contractile integument. A. acuta,—Diaphanous, with granules dispersed in its interior; oblong, com- pressed, pointed at its two ends; or lanceolate, with one side more convex in front and fringed with cilia. 1-580". In pond-water. Genus PELECIDA (Duj.).—Body flexible, contractile, oblong, compressed, rounded behind, curved in the form of an axe in front, ciliated throughout, and furnished with a mouth either visible or indicated by the various objects met with in the interior of the animals. * The animalcule assumed as the type of this genus is the Loazodes Rostrum of Ehrenberg. a contractile integument. PELECIDA Rostrum (Duj.) = Loacodes to four longitudinal folds, Rostrum (Ehr.). P. costata (Perty).--Small; with two It is stated to differ from the Paramecina by the absence of Perty introduces it into his system. Colourless. 1-320" to 1-210". Bern. In ponds, &c. Genus LEMBADION (Perty) (XXVIII. 50, 51).-Body oval, rather ven- tricose; with one more or less deep and wide furrow running nearly the entire length of the ventral surface. About twenty rows of cilia on the dorsal aspect; on the margin of the furrows, and at the posterior extremity, are longer cilia. Internally from two to eight translucent large round vesicles are visible. In Perty’s classification this genus is a member of the family Bursarina (see p. 621). LEMBADION Tbullinum = Bursaria bul- lina (Müll.) (XXVIII. 50, 51).-Hyaline, filled with very delicate molecules; the spherical and often very large internal vesicles differ much, both in number and position. A proboscis-like process occurs at the anterior extremity. Movement tolerably quick, often gyrating. Trans- Verse fission has been observed. I-240" to 1-190". In spring-water. Bern, Lu- gano, &c. Ehrenberg has erroneously cited the Bursaria bullina (Schrank), which is identical with the present species, as the same organism as his Glaucoma scinţillans. L. (P) duriusculum.—Colourless, ellip- soidal, with a keel or ridge along its upper surface; the under surface some- what concave. It appears tolerably stiff and firm in consistence; the cilia are very fine, and its movements sluggish. 1-720" to 1-620". The position of this animalcule in this genus is doubtful. Genus HARMODIRUS (Perty).-Body globular, having a moveable elon- gated lip or proboscis anteriorly. It is a member of the Trachelina (Perty), and is represented as being in part equivalent to Amphileptus (Duj.) and to Trachelius (Ehr.). 630 SYSTEMATIC EIISTORY OF THE INFUSORTA, HARMODIRUs Ovum. — The proboscis is not so much a process of the substance of the body, as like a jointed finger or segment; it has a jerking movement in one direction, yet it appears frequently stretched as a stiff process from one side. Cilia extremely fine; thirty rows have been counted on one side; they are most may be frequently witnessed. 1-180" to 1-36". In fresh and bog water, with Lemmae. This species is doubtless the same as Trachelius Ovum (Ehr.) and Am- phileptus Ovum (Duj.); and we do not conceive the necessity of elevating it to the rank of a genus on account of the slight differential character of the pro- evident near the proboscis. Diastrophy | boscis, as Perty has done. Genus CINETOCHILUM (Perty) (XXVIII.35).—Small, short, elliptical, somewhat compressed; vibratile flap on the posterior half. CINETOCHILUM margaritaceum = Cyclidium margaritaceum (Ehr.) (see p. 573). Genus CYCLOGRAMMA (Perty) (XXVIII. 36,37).-Body small, having the form of Paramecium ; with concentric striae on the margin, and a lateral depression near the fore part, where a mouth, with an obscure but peculiar apparatus of from four to seven bristles, is apparent. It is a member of a family called Decteria (see p. 624). CYCLOGRAMMA rubens.—Colour yel- low, seldom green, or reddish-white. Mostly rather compressed; rarely sub- cylindrical. Cilia very fine, with the exception of those on the margin, which are arranged in circular rows. Move- ment commonly sluggish. The dental apparatus is evident in some examples, but undiscoverable in others. 1-480" to 1-300". Ponds, Belm. FAMILY WIII.—OPHRYOCERCINA. Polygastria without lorica; alimentary canal with two distinct orifices, of which only the anal one is terminal. Although their motion is rapid, cilia are perceived near the mouth only, though they probably cover the body; the long neck assists in Swimming, and indeed is sufficient alone. Granules (owa?) are seen in all the species, and a contractile vesicle in T. biceps. Self-division probable, but not observed. No such family as Ophryocercina enters into the system of Dujardin, the animalcules composing it being all referred to the genus Lacrymaria (see p. 609); and consequently that of Trachelocerca is merged in the same. On the other hand, Perty retains this family name, but, unlike Ehrenberg, comprehends in it both Trachelocerca and Lacrymaria : moreover he assigns to Trachelocerca a wider generic signification, so that it includes also Phialina (Ehr.). Again, this family is the representative of one of his three chief sections of Ciliata, viz. Metabolica, thus defined:—“Animalcules very con- tractile, undergoing protean changes of figure by the expansions and con- tractions of the body. Cilia scarcely visible upon the body, but clearly seen on its neck-like process.” Lachmann describes the Cesophagus in this family to be collapsed, or invisible, except during the passage of food, Genus TRACHELOCERCA.—Characters as above. TRACHELoCERCA Olor (Vibrio Proteus, Cygnus et Olor, M.; Lacrymaria Olor, D.) (XXIV. 317, 318, 319).—Spindle- shaped; neck very long and #. terminated by a dilated and ciliated mouth. The surface is beautifully reti- culate in this and the following species. This creature creeps at the bottom of the vessel , containing it, and twines itself gracefully about Confervae, or the roots of Lemmae, but swims awkwardly. It elongates and contracts its neck at pleasure, and is altogether an interesting object for the microscope. Greatest length 1-36". It has been found en- cysted, OF THE ASPIDISCINA AND ICOLPODEA. 631 T. viridis (Lacrymaria viridis, D.).- Spindle-shaped, neck simple, very mo- bile, long, and dilated at the mouth, which has a ciliated lip. Amongst Lemnae. Length 1-120"; contracted 1-380". Perty changes the specific name to “linguifera,” and has the very good reason for so doing that the green colour is no distinction, because it is often changed to brown, and, besides various intermediate tints, is at times greyish or cess, styled a tongue, fringed with di- stinct cilia. Perty speaks of specimens 1–72" in length. T. biceps. – Spindle-shaped, white; neck long, forked, each segment with a mouth. 1-190". This can have no claim as a species, since it is evidently nothing more than an animalcule in the act of longitudinal fission, not far advanced. T. Sagitta= Vibrio Sagitta (M.).--Fu- siform, white; neck very long; head ter- colourless. Unlike T. Olor, the neck is surmounted by a moveable flap or pro- minal, opaque. 1-120". North Sea and Baltic. FAMILY IX.-ASPIDISCINA, (XXV. 321–323.) Distinguished from the preceding family by the presence of a lorica. The alimentary canal has two orifices, of which the discharging one only is terminal. The lorica is firm, very transparent, and combustible, somewhat resembling the shell (carapace) which covers the back of a tortoise; it projects anteriorly a little beyond the body. Long flexible bristle-like organs attached to the abdomen enable the animalcules to climb, while the delicate cilia near the mouth serve both as swimming and purveying organs. Numerous vacuoles have been filled with coloured food by Ehrenberg, who has also seen the discharge of matter posteriorly. An oval nucleus and a contractile vesicle occur in both species. Müller observed self-division, but mistook it for copulation. They are not developed in large masses. Genus ASPIDISCA.—Characters as above. ASPIDISCA lynceus (Trichoda lynceus, underneath. Amongst Lemnæ and Com- M.).-Lorica nearly circular, truncated | fervº, i-IOOO" to i-376. at the posterior end, and formed into a Stein asserts that it is an error to hook or beak in front. Mouth furnished detach this species from Euplotes, with with very delicate cilia; five or six which it has the closest affinity, and to bristles (styles) are affixed posteriorly, elevate it to the rank of a family in and from five to eight hooks anteriorly, immediate contiguity with Colpodea, whereby a resemblance to Euplotes and with which it has no natural relation. Stylonychia is established. A contractile A. denticulata.-Lorica nearly circular, vesicle, near the mouth, and twenty under side truncated and denticulated, vacuoles have been seen. When burnt flat; back arched. The uncini are visible upon platina no traces remain. Gene- only when climbing. 1-76". rally swims or creeps with its back FAMILY X.—KOLPODEA OR COLPODEA. (XXIV, 312–316; XXV. 325–335; XXVI. 23, 32, 33; XXVIII. 24–26, 31, 33, 34; XXIX. 19, 20, 25–47.) Animalcules ciliated throughout; the cilia disposed in longitudinal series, and either of uniform length throughout, or of larger growth at particular parts, especially about the mouth. Both mouth and anus demonstrable, always lateral, sometimes situated on the same side, at others on opposite sides of the body. Except Amphileptus and Uroleptus, the other genera have both the mouth and anus on the ventral surface. In the former genus Lachmann likewise describes the oesophagus to be collapsed, except during the passage of food, When it presents the appearance of a canal. In all other genera of Kolpodea 632 SYSTEMATIC EIISTORY OF TEITE INFUSORIA. the oesophagus is distinct, of considerable length, and ciliated, but not thick- ened at any portion so as to produce the appearance of a dental cylinder “ or bacillar apparatus.” Coloured food received by all the species. Contractile vesicles one or two in Inumber, and in Paramecium of a stellate figure. Nucleus usually rounded, oval or reniform. A red spot, eye-speck or stigma, is common in Ophryoglema. Propagation takes place by fission, which may be either transverse or longitudinal; by the production of single living em- bryos (at least this occurs in Paramecium and Colpoda); and, in Perty and Carter’s opinion, by numerous germs or internal ova. The encysting-process has also been seen in all the genera except Uroleptus. The integument of IColpodea is reticulated, presenting a beautiful diamond-pattern, and having a cilium seated in the centre of each lozenge. The Kolpodea are highly-organized Ciliata, although inferior in this respect to the Worticellina. The single circumstance of the limitation of the cilia to the head in the latter family is of itself, according to a well-recognized law. of animal life, an intimation of a higher grade of Organization. The genera are disposed as follows:— Short protruding tongue. | absent posteriorly ............ Rolpoda. Wilia * present everywhere ......... Paramecium. Eye absent...... --- With tail and proboscis...... Amphileptus. No tongue .................. With tail, no proboscis ...... |Uroleptus. Eye present .............................................................................. Ophryoglena. This family corresponds generally with that of the Paraméciens, or Para- mecina (Duj.), thus defined:—Body soft, flexible, variable in form, but mostly oblong and more or less flattened; provided with a loose, reticulated integument, upon which numerous vibratile cilia are disposed in regular series. Mouth present. The genera included are:—Lacrymaria, Pleuronema, Glaucoma, Kolpoda, Paramecium, Amphileptus, Loacophyllum, Chilodon, Panophrys, Nassula, Holophrya, and Prorodom. Dujardin observes that Lacrymaria and Plewomema should probably be placed in a distinct family, since the mouth is rather presumed than demon- strated in them. This is, however, a reason which, in the present day, would not be held valid, as the evidence of a mouth is equally-strong in them as in others of the genera enumerated. Perty also has constructed a family Paramecina, containing the genera Ophryoglema, Panophrys, Paramecium, Blepharisma, and Colpoda, and briefly characterized as having the body covered with longitudinal rows of cilia, and a lateral mouth often within a fissure. Lastly, Mr. Carter has instituted a new genus, named Otostoma, referable to this family, being a close ally to Paramecium. - Genus KOLPODA or COLPODA.—Body ovoid, sometimes reniform; a little tongue-like member (a tuft of cilia) inserted in the oral cavity; ciliated in front and partly beneath; eye-speck wanting. The mouth, posterior termi- nation of the alimentary canal, and numerous gastric cells may be demon- strated by coloured food; the two orifices are both on the ventral surface. “Ova,” adds Ehrenberg, “occur in delicate strings, forming a sort of network; and their extrusion has been seen in One species. A round contractile vesicle is observable in two species, and two such in another. A large round or oval gland (nucleus) is found in the centre of the body.” Sclf-division both OF TELE KOLDODEA. 633 transverse and longitudinal. being few. , Dujardin, speaking of this genus, says, “Among Ehrenberg’s Kolpoda, which should possess a short tongue, and be ciliated only on the ventral surface, but one species, K. Cucullus, is with certainty numbered; the K. Ren, and K. Cucullio have been referred to the genus Loazodes, where, indeed, we still leave them. However, Ehrenberg places among the Paramecia, under the appellation of P. Kolpoda, some large animalcules, ciliated throughout, which we regard as only more developed forms of Kolpoda Cucullus.” Stein expresses himself on these views thus (Infus. p. 131):-" Under the name of Colpoda Cucullus Dujardin has described the Paramecium Colpoda, Ehr., appearing either to be unacquainted with the true Colpoda, or to have looked upon it as an undeveloped state of Paramecium Colpoda.” The distinctive characters between these two animalcules and Chilodon Cucullulws are thus laid down:—All these three forms are similar in outline, Chilodom Cucullulus and Colpoda Cucullus being really in most respects undistinguishable. Paramecium Colpoda is devoid of the peculiar lip, but has, on the other hand, an expanded anterior extremity (brow), lying over and above the oblique infundibulum, on one side of the body, leading to the mouth. Chilodon Cucullulus displays, by the action of chemical reagents, about the middle of its ventral surface its special form of pharynx or Oesophagus: it is, besides, ciliated all over; but this is a criterion determinable with difficulty, particularly in young specimens. In Colpoda Cucullus the mouth is quite simple, and placed in the lateral de- pression; the distribution of the cilia is always partial, chiefly limited to the lip. In Paramecium Colpoda the mouth (oral aperture) lies at the bottom of a deep longitudinal fold (fissure) on one side of the body, is bounded by two very motile lips, and conducts into a short, thin, walled, ciliated oesophagus; the nucleus is oval, large, homogeneous, and finely granular; and the body is very evidently ciliated all over. Kolpod A Cucullus (M.)(xxv.324–327; XXIX, 35–47). — Turgid, slightly com- pressed; kidney-shaped. The concavity Their motion is not active, the locomotive cilia of a portion of the animalcule was an act of oviposition, thought to further establish it by remarking the presence in which the oral aperture is situated is occupied by a process called by Ehren- berg a “tongue,” but which Stein has shown to be a bundle of longer cilia. The cilia are not distributed over the whole surface, but limited to the convex surface of the anterior half, augmenting in size as they approach its elongated and expanded, wide lip-like or frontal pro- cess above the oral fossa, and to a ridge extending downwards and backwards from that fossa. The granules in the interior are frequently so numerous as to render it opaque; they also give it a grey colour. The single contractile ve- sicle is seated close to the posterior extremity; the nucleus is a circular disc containing a nucleolus, and nearly cem- tral in position. This animalcule has not been seen to undergo fission whilst in the free state; the process, however, goes on after it has encysted itself, with various modifications in the results (see Part I. p. 350). Ehrenberg having adopted the motion that the breaking up of numerous Monadiform beings about it, which he concluded were developed from the supposed ova, as the first phase of future Colpoda. Such an interpreta- tion has no evidence to support it, and is rejected by Stein. (xxv. 324, the normal form ; fig. 325 represents the animalcule, as Ehrenberg conceived, de- positing its ova in a net-like mass, or, as others would interpret it, in process of diffluence; and figs. 326, 327, young animalcules, which resemble Thrichoda pyrºformis.) Common in vegetable in- fusions. 1–1800" to 1–280". R. (?) Ren. — Ovate, cylindrical, kid- ney-shaped, and rounded at the ends. In river-water. 1–288". R. (?) Cucullio (M.)=Lowodes Cucullio, (Perty).-Compressed, plane, elliptical, slightly sinuated anteriorly. Ehrenberg remarks that neither cilia nor tongue- like member was observable by him, and that its generic situation is there- fore uncertain. Perty, however, has noticed such a process, 1-900". 634 SYSTEMATIC HISTORY OF TEIE INFUSORIA. Movements slow; K. Luganensis (Perty).—Large, broad, usually numerous. 1-130'. It slightly convex on one side, Oral in- internal corpuscles green, fundibulum deep. Rows of cilia un- is probably a Kolpoda. Genus PARAMECIUM (XXV. 329–332; XXIX. 25–34).-Body oblong, compressed, ciliated on all sides; mouth lateral, with a tongue-like process; no visual point. The cilia are disposed in longitudinal series; those near the mouth are sometimes longer than the others, and are alone subservient to locomotion, except in two doubtful species. In P. Chrysalis the long oral cilia are remarkable. The digestive cells, Ehrenberg proceeds to say, are numerous, amounting to more than a hundred, and are arranged in a berry-like manner along the curved alimentary canal: in five species they have been demon- strated by artificial means, in a sixth by its usual green food. The ova in two species are seen as a granular mass. In all, except one species, male organs are visible. The curious star-like contractile vesicles in the larger species are highly interesting, when physiologically considered, as are also the little black bodies seen in P. Aurelia. In four species complete self-division, transverse and longitudinal, has been observed alternately. This genus gives name to a family Paraméciens or Paramecina in the systems of Dujardin and Perty. - Stein makes the uniformity in length and thickness of the cilia a character- istic of Paramecium, which distinguishes it both from Loacodes and Bursaria, which have larger and stronger cilia about the mouth than cover the rest of the body (see p. 285). Ehrenberg's statement that those about the mouth are longer than the rest requires correction; and the instance (P. Chrysalis) cited indicates only that this species is not a Paramecium. Other par- ticulars requiring revision are, that Paramecia have numerous stomachs dis- posed as offsets upon a curved alimentary tube; that the granular mass in the interior consists of ova. The male organs referred to are the nucleus and contractile vesicle or vesicles. In P. Awrelia and P. Bursaria Lachmann states that the anus may be frequently recognized, in the form of a small pit on the surface of the animals, even for a considerable time before and after an excretion. In our remarks on PANOPHRYS we have expressed a doubt as to the inde- pendent position of that genus apart from Paramecium. PARAMECIUM Aurelia (M) (xxv. 329– 332).-Club-shaped, cylindrical, slightly attenuated anteriorly. An oblique longi- tudinal fold borders upon the very much receding mouth. Ehrenberg states that he has seen small dark crystalline bodies abundant in the frontal region, which, he conceives, are indications of the pre- sence of nervous matter, as such cry- stalline bodies often accompany it. These creatures appear to him also to have the sense of taste, since in the same group some individuals prefer one kind of food and others another. This may be ob- served by mixing blue and red colours together, when some will feed upon the former, others upon the latter, as indi- cated by the colour of the digestive cells: in some the cells have a violet hue. After being fed with colour, they may be dried upon glass or mica, and thus preserved. According to the hypo- thesis of Ehrenberg, the rays of the star- like vesicle are spermatic ducts, through which the fluid is forced upon the ova in the vicinity by the constantly repeated acts of contraction of the vesicle. The ducts are long, and enter the ovarium at many points (see p. 312 et seq.). The expulsion of ova has frequently been ob- served. The colour of these animalcules, when bearing ova, is white by reflected light, and yellow by transmitted; hence the names “gold and silver little fishes,” so often applied to them by Joblot and others; those devoid of ova are colour- less. The cilia are best seen when the water is coloured; there are from 26 to 52 longitudinal rows along each side of the body, according to Ehrenberg, who Says that in some rows he counted from 60 to 70 cilia, making 3640 organs of OF THE ICOLPODEA. 635 locomotion, and that each cilium is placed upon a sort of little knob or articulated base (see p. 285). (Fig. 329, a dried spe- cimen; fig. 330, a creature feeding upon indigo, the particles of which around indicate the currents produced by the cilia; ſig. 332, an ideal view, to show the structure of the nutritive organs as stated by Ehrenberg; fig. 331, a young specimen, of the normal shape.) Abum- dant in vegetable infusions, and increases so rapidly in stagnant waters that some have referred their marvellous abundance to spontaneous generation from elemen- tary primitive matter. 1-120" to 1-96". P. caudatum.—Spindle-shaped; obtuse anteriorly, attenuated posteriorly. Not in infusions, but in ponds, amongst decayed sedge-leaves and Confervaº. I-120". P. Chrysalis (M.)= Pleuronema cras- sum (Duj.) (XXVI. 23). — Oblong , and cylindrical, equally rounded at both ends; cilia about the mouth very long. This species, like P. Aurelia, is often developed in such vast myriads that the water has a milky hue, the masses as- cending or descending in the fluid; this appearance may be produced by slightly shaking the water. In infusions and in Salt water. 1–240" to 1-190". If the uniform length of the cilia be admitted a generic character of Para- mecium, this species, which has several very long bristly cilia proceeding from the oral fissure, must be excluded. Both Dujardin and Perty have proposed this, and made Paramecium Chrysalis the re- presentative of a genus styled “Pleuro- nema.” It is usually filled with greyish mole- cules and vesicles, and rarely coloured with chlorophyll. Fission longitudinal. The long fibres from the lateral oral fissures are from two to twelve in num- ber, and, though frequently shorter, are at times equal to or even much longer than the body, and serve to vary its movements by their activity. P. Kolpoda (Kolpoda Ren, M.; K. Cº- cullus, D.).-Ovate, slightly compressed; ends obtuse, the anterior attenuated and slightly bent like a hook. Found espe- cially in infusions of Urtica dioica (the stinging nettle). Perty is disposed to believe this form to be an earlier stage of P. Aurelia. -1–240". P. (?) Sinaiticum. — Elliptical, com- pressed, the back and under side cari- nated (keeled); frontal cilia indistinct. Amongst Confervae, in a brook on Mount Sinai. 1–288". P. (P) ovatum. — Ovate, turgid; an- teriorly attenuated and rounded. In stagnant river-water. 1-288". P. compressum (Bursaria Lumbrici, Stein). — Elliptical or reniform, com- pressed. An oblique wreath of long cilia reaches to the middle, where the mouth, with its slight tongue-like pro- cess, is situated. Found in the river- mussel (Mya), and in the intestine of the earthworm (Lumbricus). 1-240" to 1–210”. Dujardin takes this species as the type of a newly-formed genus, “Plagiotoma,” characterized especially by its com- pressed lamellar figure, and by its para- sitic habitat. Its cilia are described as disposed in longitudinal rows over the surface (vide ante, p. 627). We agree with Stein that there is no good reason for framing the genus Pla- giotoma, as Dujardin has done, on the characters of this animalcule. If it have no mouth it should take its place among the Opalinae; and it is to be remarked that though Dujardin clearly saw a deep fold or fissure—a feature of Opalinae—he could not succeed in artificially feeding the animal with coloured food. At all events, it has certainly no right to a place among Paramecia, since the crest of longer cilia about the mouth-like fossa refers it (supposing it to have a mouth) to the Bursaria. P. Milium (Cyclidium Milium, M.).- Small, oblong, trilateral; rounded equally at both ends. In coloured water the body is seen vibrating. 1–1150". P. Bursaria = Locodes Bursaria (Ehr.) (XXIX. 25–34).--It is not a Lozodes, since all its cilia are equal and similar, Ehr- enberg being in error respecting the ex- istence of a larger sort in the infundi- bulum leading to the mouth. P. versutum (Müller) = Bursaria ver- malis (?) (Ehr.).--Perty revives this spe- cies; but Lachmann (A. N. H. 1857, xix. 215) thinks it unnecessary to do so, “as there is scarcely any certainty in the synonymy previous to Ehrenberg; and we should never again introduce an older specific name for an Infusorium if it has a name given to it by Ehrenberg, even when it is not improbable he may have overlooked an older name.” b. var. Alpina (Perty). — Smaller, plaited, stouter and more cylindrical than P. versutum. P. griseolum (Perty). — Little trans- parent, being filled with greyish mole- cules; border very delicate. Nine to ten longitudinal plaits on the surface. Move- 636 SYSTEMATIC EIISTORY OF TEIIL INFUSORIA. ment sudden, frequently oscillating. 1–430." - P. aureolum. — Transparent, peach- coloured or golden yellow; plaits strong. Movements sluggish. 1-430". IP. leucas – Bursaria leucas P Sº, On one side a horn-like process, and on the other a pair of eminences project. Movements slow. P. Stomioptycha (E.). — Oblong, ob- reniform, cilia long; body marked by circular folds; lip with peculiar appen- dages; vesicles two, stellate; nucleus elongated, cylindrical. Mouth occupies the anterior third of the body, sur- mounted, however, by its obtuse frontal end; cilia dense, in longitudinal rows; vacuoles numerous; colour yellowish- white; nucleus above one-third of the entire length, which varies from 1-24!" tusely ovate, turgid; Oral aperture large, to 1-15". Genus AMPHILEPTUS.—Tongue-like process and eye-speck absent; but the body is furnished with a proboscis and tail, and is elongated fusiform or lanceolate. Cilia numerous, disposed in longitudinal series: in one species cilia are not visible; but in this the flexible attenuated extremities of the body serve their office as locomotive organs. In Some the tail (foot) and proboscis (brow) are rudimentary. Numerous vacuoles filled with food may be fre- quently seen ; the mouth and anus are usually distinguishable. A. marga- ºritifer has a pale rose-red fluid. A contractile vesicle and a nucleus are found; the latter is globular or moniliform. Self-division occurs both transversely and longitudinally, or transversely only. Speaking of Ehrenberg’s distribution of this genus, Dujardin remarks— “This author, whilst assuming the presence of proboscis and tail (as a cha- racteristic), yet refers to the genus animalcules without tail, and dilated and rounded posteriorly; and on the other hand, whilst intent on seeking a distinctive character for his different families in the position of the anus, which he attributes to all his Enterodelous Infusoria, he has left in his genus Trachelius several species which to us appear to belong to Amphileptus, and has himself several times transferred some species from one genus to the other.” The Amphileptus Anser is taken by Dujardin as the type of a genus termed Dileptus, and A. Meleagris of one termed Loa'ophyllum. Amphileptus is the name of a genus comprehended by Perty in his family Trachelina, which appears generally equivalent to that bearing the same name in Ehrenberg’s system; but it contains besides, Trachelius voraa. Cohn remaks that it is imperfectly distinguished by Ehrenberg from Trachelius. . The Amphilepti are commonly found in the limpid water of marshes or brooks, among aquatic plants. AMPHILEPTUS Anser (Vibrio Anser et Cygnus, M. = Dileptus, D.) (XXIV, 312, 313). — Turgid, spindle-shaped; pro- boscis obtuse, same length as body; tail short and acute. The neck-like pro- boscis is in reality a brow or upper lip, the mouth being at the base. Ehrenberg thinks he has seen the anal opening upon the dorsal surface, near the tail. The motion of the body is slow, but that of the proboscis more active. It is very often coloured green with chlorophyll, received as food. Amongst dead sedge- leaves, &c. 1-120". A. margaritifer. — White, slender, spindle-shaped; proboscis acute, equals the length of the body; tail short. The most striking features are the swollen margin of the mouth, and necklace-like Series of vesicles disposed along the body. It feeds upon green Monads, like the preceding species in Ehrenberg's figures. Cilia are not shown. Amongst colonies of Vorticellae, &c. 1-72". This species is the counterpart of the pre- ceding; and the distinction found by Ehrenberg in the necklace-like vesicles has no value as such, since these vary both in number and position according to the abundance of food and other external circumstances. A. moniliger.—Turgid, ample, white; proboscis and tail short. " It has a necklace-like collection of rose-coloured vesicles. Amongst duck-weed. 1-96" to 1-72". A. viridis—Turgid, spindle-shaped, green; proboscis and tail short and OF TEIE KOLPO.D.E.A. 637 transparent. to 1-96". A. Fasciola (Vibrio Anas, Fasciola, et &ntermedius, Paramecium Fasciola, M.) (xxiv. 314-316; XXIX. 19, 20).--White, depressed, linear, lanceolate, convex above, flat beneath. When viewed from above, from ten to twelve longitudinal rows of delicate cilia may be seen, and in the middle of the body two round nuclei, and behind them a contractile vesicle (XXIV, 314, 315, 316). In infu- sions, in marshy ponds, &c. Perty states that he has found it at an elevation of 5000 feet on the Alps, and also beneath the ice. Cohn has watched its power of encysting itself. (Siebold's Zeitschr. 1854, v. p. 430). 1-720" to 1-144". A. Meleagris (Kolpoda, M.; Loacophyl- lum Meleagris, D.).--Large, compressed, membranous, broadly lanceolate in shape, with the crest of the back denti- culated. The colour of this interesting animalcule is white. On the under side there is a more or less distinct row of eight to ten bright colourless spots. These spots are, however, in no constant Amongst Lemmae. 1-120" number, as Ehrenberg supposed; for they are nothing more than coloured-food vacuoles, which sometimes completely fill the animalcule. With Lemmae. 1–72". (See notes on NASSULA, p. 625.) A. longicollis (Kolpoda ochrea, Trichoda Felis, M.).-Dilated; turgid posteriorly; attenuated and elongated anteriorly, like a sword. Amongst Lemnae. 1-120" to 1-96". A. (?) papillosus.—Depressed, lanceo- late, fringed with papillae; tail and pro- boscis Smooth. Amongst Confervae. 1-600" to I-430". A. Sphagni. — Depressed, linear or linear-lanceolate; proboscis truncate and keeled; tail acute; fringed with cilia on one side; green corpuscles oc- cupy the centre, leaving the extremities of the body colourless or hyaline. 1-48" to 1-12". Proboscis is one-fourth the length of the body. Nucleus ovate; cilia disposed spirally. Vacuoles some- times enclose Bacillaria. Ovules (?) large. Approaches A. Fasciola in general characters. On Submerged Sphagnum. Genus UROLEPTUS (XXV. 333).--Furnished with a tail; eye-speck, tongue-like process, and proboscis absent. Locomotion effected by the cilia, which cover the body, and are, in three species, evidently disposed in rows. Numerous vacuoles and a mouth have been demonstrated by coloured food; but a discharging orifice has not been Satisfactorily determined. Green- coloured granules are evident in two species, but no nucleus or vesicle. This genus of Ehrenberg (says M. Dujardin), judging from the figures of most of its species, should be in part united with Oaytricha. Thus Uroleptus Piscis seems identical with Oaytricha caudata (Duj.); U. Musculus (Ehr.) is, in figure, an Oaytricha ; whilst U. (?) Lamella is probably a Trachelius, and U. Filwm is rather allied to Spirostomum ambiguum. If these views be correct, Uroleptus should be erased from the list of genera. Three species counted in this genus by Ehrenberg are rejected from it by Perty, and allied with Oay- tricha,_viz. U. Musculws, U. Piscis, and U. Lamella. TJROLEPTUs Piscus (Trichoda Piscis, M.).-Green; in figure like an elongated top, gradually attenuated posteriorly, forming a thick tail, covered with cilia, those at the mouth largest. Found, in February and March, amongst the floccose brown coat upon dead sedge- leaves, along with Chlamydomonas and Cryptomonas. Hampstead ponds. 1-288" to 1-44". Perty doubts if there is any real di- stinction between this animalcule and the Oaytricha caudata (Ehr.). * U. Musculus (Trichoda Musculus, M.) (XXV. 383).--White, cylindrical, pear- shaped, thickened posteriorly, where it abruptly terminates in a tail. The movement rolling. It is inactive and rigid. With Oscillatoria, 1–220". U. Hospes. – Greenish, ovate-oblong and turbinate in shape; obliquely trun- cated and excavated anteriorly; poste- riorly terminated by a styliform acute tail. In frog- and Snail-spawn. 1-240". U. (P) Lamella, – Transparent, linear- lanceolate, depressed, flat, very thin. In infusions. 1–220". U. Flum (Enchelys caudata, M.). — White, filiform, cylindrical; rounded anteriorly; attenuated posteriorly, form- ing a straight long tail. It is considered a Spirostomum by Dujardin and Perty (vide ante, p. 623). In stagnant spring- water, &c. 1-48". 638 SYSTEMIATIC HISTORY OF TEIE INFUSO BLA. Genus OPHRYOGLENA (XXV. 334, 335).—Ovoid, ciliated, with an eye- speck anteriorly. Locomotion effected by the numerous regular longitudinal rows of cilia. Some of the numerous digestive vacuoles are often filled with Naviculae. The mouth is situated in a fossa beneath the brow on one side ; and the anal orifice lies upon the dorsal Surface, at the base of the little tail. A large central nucleus and one or more contractile vesicles are found; trans- verse and longitudinal self-division have been observed. A large red or black stigma is always present on the frontal region. These Infusoria are found in stagnant fresh water, but not in infusions. As Dujardin rightly remarks, this genus differs from Kolpoda only by having a stigma or eye-speck; however, he prefers to place it among Bur- Sarina, because the mouth is situated at the extremity of a row of cilia. In this transposition of Ophryoglema, Perty does not agree, seeing that it has a narrow mouth, and the closest affinity with Panophrys, with which, therefore, he replaces it, along with Paramecium, &c., in the family Paramecina. We are disposed to question its claim to a generic position; for the coloured speck is worthless as a distinctive character. OPHRYOGLENA atra (Leucophra Ma- milla, M.).-Blackish, ovoid, compressed, acute posteriorly. A black stigma is situated anteriorly near the dorsal mar- gin. The mouth is at the bottom of a funnel-shaped cavity, commencing im- mediately * the brow; within this cavity Ehrenberg thinks he has lately seen an oval bright gland. The colour- less cilia appear like silver fringe on the dusky animalcule, especially those in front. In turf-hollows. 1-180". O. acuminata (XXV. 334,335).-Brown, ovate, and compressed; tail short and acute; stigma red. The brow projects beyond the mouth about the length of the body, or, in other words, is situated about the middle. In turf-hollows. I-180". O. flavicans.—Yellow, turgid, ovate, attenuated and rounded posteriorly; stigma red, irregular in shape; the cilia near the mouth longer than in the pre- ceding species; Ehrenberg counted from twelve to sixteen rows at one view. In turf-hollows. 1–144". Nothing like a lens can be seen within the eye-speck; but close to it there is an hour-glass-shaped body, transparent and apparently structureless. Its position seems fixed, but it may be detached by diffluence of the animalcule, whenits wells up in the surrounding water and often ex- hibits a central cavity. Its presence is not necessarily associated with the coloured Stigma : in Ophryoglena atra it is ab- sent; and whilst Bursaria possesses this organ, it has no coloured speck. In other Infusoria having stigmata, such as Euglenaea, Peridiniaea, &c., no such organ is discoverable in connexion with them (Müller's Archiv, 1856, p. 21). Stein advances, as a distinctive character be- tween Oph..ſlavicans and Bursaria flava, the difference subsisting in respect of the nucleolus. O. griseovirens (Perty). — Elliptical, with more or less unequal sides; usually more pointed behind, and rounded in front, where a red or dark pigment-speck is visible. Hyaline, and when strongly magnified reticular; but frequeutly con- tains grey or green, and in rare cases brown molecules. The marginal cilia very distinct. Oral fossa in anterior half. Movements quick and revolving. 1-300" to 1-180". In ponds, Bern. O. Panophrys (Perty). — Large, oval when seen on the wider side; pointed end posterior; colour greyish yellow; without pigment-speck. When seen on the narrow side, the marginal cilia appear in concentric curved lines, whilst on the broad side the cilia are close together and apparently irregular. Movements slow. Usually swims on one of its wider sides, and but seldom revolves. Mouth wide. 1-144". Uncommon. Genus DILEPTUS (Duj.) (XXVI. 26). This genus belongs to the family “Trichodina” (ante, p. 608), and is thus defined:—Animal with a fusiform body, much elongated anteriorly, like a long neck, with a mouth Seated at the base of the prolongation; vibratile cilia cover the surface, and are of larger size in front and near the mouth. .g. Ehrenberg has arranged Dileptus with the Paramecina, although, unlike OF TEDE OXYTRICEIINA. 639 the latter, destitute of a contractile reticulated integument. The type of this genus is the Amphileptus Anser of Ehrenberg; and the A. margaritifer (Ehr.) is also referable to it. DILEPTUs Folium (Duj.) (xxvi. 26). leaf. In river-water. 1-175" to 1-130". —Very flexible; lanceolate, contracted | Perty remarks that this organism can- in front, with nodular reticulated and not be a species of Dileptus. irregular stripes, like the veins of a Genus LOXOPHYLLUM (Duj.) (XXVI. 32). Very depressed, lamellar, oblique, very flexible; sinuous or undulated along the borders; mouth lateral; cilia in wide parallel rows. Ehrenberg has comprehended Loa'ophyllum with Amphileptus. Perty makes the separation. I/OXOPHYLLUM Meleagris, the type of phyllum, as well as the Kolpoda ochrea the genus=Amphileptus Meleagris (Ehr.). of Müller, which Ehrenberg states to The Trachelius Meleagris (Ehr.) pro- agree with his Amphileptus longicollis. bably represents also another Loſco- - Genus PLEURONEMA (Duj. and Perty) (XXVI. 23), represented by the Paramecium Chrysalis (Ehr.), is thus defined by Dujardin —“Body oval, oblong, depressed; having one large lateral orifice, from which a tuft of long, floating and contractile filaments issues.” It has nothing in common with Paramecium, he adds, besides its oblong figure; whilst the bundle of long filaments has no analogy, except in the genus Alyscwm. However, he places it in his family Paraméciens, whilst Perty introduces it as the sole represen- tative of a family “Aphthonia,” characterized as having, besides locomotive cilia, other longer ones or filaments. PLEURONEMA crassum = Paramecium | the anterior fourth of the body, with Chrysalis (Ehr.). — Ovoid, much elon- long filaments, some proceeding from gated, rather depressed; with obtuse the border, others from the posterior ex- ends; finely striated. Lateral orifice at tremity. 1-120". In the Mediterranean. Genus OTOSTOMA (Carter, A. W. H. 1856, xvii. 117) (XXVIII, 24–26).- Body ovoid, of a light brown colour, covered with longitudinal lines of cilia. Mouth ear-shaped, in a depression situated about the junction of the anterior with the middle third of the infusorium ; buccal cavity broad, short, curved downwards, and a little upon itself outwards, plicated longitudinally in parallel lines. Anus terminal; gland or nucleus long, fusiform, situated between the buccal cavity and the contracting vesicles, which are double and connected with a set of vessels something like those of Paramecium . Awrelia. “It is,” adds Mr. Carter, “a Paramecium closely allied to Nasswla, and, from the likeness of the oral orifice to the human ear, I propose for it the name of ‘ Otostoma.’” Its cysts have been discovered on Nitella, and give exit to monadiform beings approaching the parent Otostoma in form. FAMILY XI.- OXYTRICHINA. (XXV. 336–344; XXVIII. 43–47.) Possess two separate alimentary orifices, neither of them situated at the extremities, and are not encased by a dense integument (lorica). Their loco- motive organs are various, consisting of setae, vibratile cilia, and non-vibratile styles or uncini, variously situated, and render the creatures active. (Poly- gastric cells, disposed upon an alimentary tube, were represented by Ehren- 640 SYSTEMATIC HISTORY OF THE INFUSORIA. berg, except in Ceratidium.) A curved line of strong cilia leads towards the mouth, which is situated about the median line at the posterior third of the body, and opens into a ciliated oesophagus. The anus is behind the mouth, on the same ventral surface, near its margin. Complete trausverse and longi- tudinal self-division is observed. The process of encysting may be presumed general; in Urostyla Cohn has seen the ulterior development of a ciliated embryo. - Brow without horns ......... Oxytricha. Cilia and setae, no styles or uncini... g Brow with horms ............ Ceratidium. With uncini, no styles ...... IKeroma. Styles, or umcini, or both............... With styles, no uncini ...... Urostyla. With styles and uncini...... Stylonychia. This family is generally similar to the Keronina of Dujardin, a family of animalcules, according to this observer, much lower in the Scale than many in the families previously described, such as Kolpoda, Paramecium, Coleps, &c. “Processes in the form of styles or hooks characterize both the ‘Réroniens’ and the ‘Ploesconiens;’ but the latter have a shield (lorica), whilst the former are soft and have no sign of an integument. Of the ‘Réroniens’ the Oaxy- tricha have neither horns nor hooks, but only cirrhi or straight processes, apparently rigid ; another genus, ‘Halteria,’ has large cirrhi like the pre- ceding, but differs considerably in its mode of life and its movements. “The Urostyla of Ehrenberg, with styles only, and no hooks (uncini), we unite with Oaytricha; and his Stylonychia, provided with both styles and hooks, with Kerona ; another genus described under the name of Ceratidium, horned anteriorly, but wanting both styles and hooks, seems to be only altered or mutilated Keronae. On the other hand, Halteria appears to be included by Ehrenberg among true Urceolaria, in his genus Trichodina, although it possesses none of the characters. The Kéroniéns are found in stagnant water, fresh and salt.” Perty has established a family Oxytrichina, which, besides containing two new genera, styled Mitophora and Stichotricha, excludes Cera- tidium and Stylomychia, referring the species of the latter genus to Kerona. After these exclusions and additions, Perty’s Oxytrichina include Oaytricha, Urostyla, Kerona, Mitophora, and Stichotricha. Genus OXYTRICHA (XXV. 336, 337; XXIX. 21–24).--Styles, uncini, and horns wanting. The body is soft, flexible, oval or oblong, more or less flattened, and provided with cilia and setae. Their movements are forwards and backwards, often by impulse, creeping, swimming, and climbing. In all the species, digestive vacuoles are evident ; in five, (ova-like) granules; in four, a nucleus; and in five, round contractile vesicles. Transverse and longi- tudinal division is observed in O. Lepus and O. Pellionella ; longitudinal only in O. Cicada, and perhaps in O. Pwllaster. The Thrichoda Nasamomum and T. Althiopica (Ehr.) and Urostyla belong, in Dujardin’s opinion, to Oxytricha, and Oxytricha Cicada (Ehr.) to the Ploesconiens. Whilst admitting a genus Oaytricha, Perty makes two divisions of it, the one corresponding generally to Uroleptus (Ehr.), and the second to Oaytricha (Ehr.). The differential characters given are:—a. Elongated posteriorly, embracing most Urolepti (Ehr.); b. Rounded posteriorly, equivalent to Oay- tricha (Ehr.). Under the first division the species enumerated are O. caudata, O. Piscis, O. Musculus, O. ambigua, and O. Lamella; under the Second, OF THE OXYTRICELINA, 641 O. proteusa, O. Pellionella, O. gibba, O. Gallina, O. Pullaster, O. Lepus?, 0. platystoma, O. decumama, and O. fusca. OxYTRICHA rubra (Trichoda Piscis et T. patens, M.). — Of a brick-red colour; linear in shape, plane on the under side, and equally rounded at the ends; pos- terior end provided with setae. In sea- water. 1-140". O. Pellionella (Trichoda Pellionella, M.) (XXIX.21–24).--White, Smooth; slightly depressed, equally rounded at both ends, often broader in the middle; head not Separate; mouth ciliated; tail provided with setae. Each animalcule has two oval nuclei, and between them a single round vesicle. When self-division com- mences, four glands are developed; and then the vesicle divides. Ehrenberg counted ten cilia anteriorly, and four or five setae posteriorly; the anal outlet is at the base of the setae. In infusions, and throughout Switzerland in swampy ponds along the Snow-line of the Alps (Perty). Auerbach has seen it encyst itself (Siebold's Zeitschr. 1854, v. p. 430). 1–720" to 1–280". Cienkowsky surmises this species, O. gibba, Stylonychia pustulata, and S. lam- ceolata to be one and the same animal- cule in different stages of growth and under different circumstances in respect of food, &c. This notion is favoured, he Says, by the fact that the animalcule which escapes from an encysted S. lan- ceolata is exactly like S. pustulata. O. caudata. — Smooth, white; linear- lanceolate in shape, rounded anteriorly, attenuated posteriorly in the form of a tail, which is provided with setae. Mouth evident. In fresh and sea-water. 1–576" to 1-84". (See STYLONYCHIA pustulata.) O. platystoma = O. eurystoma.--White, ovato-oblong, under side flat, with mar- ginal setae ; mouth large and ciliated. It Swims with a revolving and vacillating motion, and often upon the back. It creeps upon water-plants, in standing bog-water. 1-240". gibba (Trichoda gibba et foeta, M.) (xxv. 336, 337). — White, lanceolate, ends obtuse, middle enlarged, under side flat, and furnished with two series of Setae, and a large round mouth. This species resembles O. Pellionella, but is distinguished by its setae, the two or three contractile vesicles, and the mu- cleus. This creature is active, and runs nimbly along aquatic plants in fresh and brackish water. (Fig. 336 an under view, fig. 337 a side view.) 1-240". It is not equivalent to the O. gibba (Duj.). O. Pullaster (Trichoda Pullaster, Kerona Pullaster, M.). — Whitish, lanceolate, ends obtuse, ventral surface naked at the middle; the head, indicated by a con- striction, is hairy, like the tail. The mouth narrow. In water-butts, streams, and infusions. 1-430". This form and O. Lepus Perty believes to be mere va- rieties of O. Pellionella. O. Cicada (Trichoda Cicada, M.). — Ovate, or almost hemispherical, back furrowed and notched, under surface flat. Upon the surface of stagnant water. 1–1440" to 1-860". O. Lepus.--Whitish, elliptical, smooth, flat; ciliated anteriorly; provided with setae posteriorly; the mouth and dis- charging orifices not distinct; and the nucleus unobserved. In standing water, 1–540" to 1-96", The following additional species are given by Dujardin — O. incrassata.--Ovoid, long, colourless, fringed posteriorly with rigid sette. Not So long as O. Pellionella, and, unlike it, marine. In the Mediterranean. 1–350". O. Lingua. — Diaphanous, flattened, flexible, elongated, rounded at each end; without setae or apparent cilia poste- riorly; granules of surface in nearly regular rows. In ditch-water with Con- fervae. 1-212". O. ambigua.-Colourless, Oval, oblong depressed in the middle, concave on one side ; margin tumid; with very strong locomotive cilia on the concave surface, and with rigid setae behind. In Sea- water. 1–350". O. radians.—Discoid, red, Surrounded by long radiating setae. In Salt or brack- ish water, 1-520". Perty brings forward the following as new species, belonging to true Ovy- tricha, characterized by severally having a round posterior extremity:— O. proteusa (Perty).-Very long, and longer than broad. It is sometimes subcylindrical; nine to twelve times | actually four-sided, with wide upper and 2 T 642 SYSTEMATIC EIISTORY OF TEIF INFUSORIA. under surfaces. Mouth a rather curved and ciliated fissure. Cilia very fine, those of the upper surface the more di- stinct, although faint. Small specimens are colourless and transparent; but larger ones have dark grey molecules or chloro- phyll within. Movements tolerably ac- tive. Perty once thought this species and Trachelius strictus (Duj.) to be young individuals of Spirostomºm, but he subse- quently found examples 1-84" in length. behind, broadest in the middle; ends rounded; upper surface slightly convex, lower flat. Mouth wide. It differs in size from O. platystoma and in its out- line both from that species and O. fusca. In length it equals Urostyla grandis, but is much broader. Bern, in ponds. 1-96". O. fusca. —Narrow, elliptical, upper surface convex, lower concave. Oral orifice wide. Colour usually yellowish or blackish-brown. Lives in stagnant O. gallina (Perty)= Trichoda gallina § (Müller).--Anterior portion hyaline, at, with large cilia; molecules grey. Only once seen. O. decumama (Perty).-Outline rather irregular; rather smaller in front than and mouldy water. Cilia in front and about the mouth strongest; but no uncini occur there. Urostyla grandis differs from it by the uncini on its border. 1-160" to 1-84”. Genus CERATIDIUM (XXV. 338, 339).-Ciliated, with horns on the frontal region, but no styles or uncini. Little of their organization is known; and therefore their systematic position is uncertain. A power of not less than 350 diameters is required to examine these creatures. CERATIDIUM cuneatum (XXV. 388, . triangular; front truncated, as also the two horns; upper side Smooth. Ehrenberg found this whitish animalcule in 1820, amongst Confervae, but had not lately seen it. have been a mutilated Oaytricha. vibrates, runs, and climbs 1–430", Dujardin believes it to It quickly. Genus KERONA (XXV. 340, 341)—Cilia and uncini present, but no styles. Body soft, flexible, oval, flattened, and ciliated, with claws (uncini), and perhaps setae, on the under Surface. Vacuoles numerous; the oral (and probably the anal) aperture is upon the ventral Surface. One or more con- tractile vesicles and a nucleus have been seen; but self-division has not been observed. - This genus, instituted by Müller, was at first adopted by Ehrenberg with little modification; but subsequently he transposed almost all its species to his genus Stylonychia, on account of their possessing styles as well as uncini. This can scarcely be considered a sufficient reason for the construction of a new genus; and accordingly Dujardin rejects Stylomychia, and thus restores the genus Kerona nearly to its original importance. As already noted, he likewise adopts Kerona as the representative of his family Keronina. Perty coincides with the French naturalist, and rejects both Ceratidium and Stylo- nychia, treating the species of the latter as examples of Kerona. He remarks that Ehrenberg has very needlessly changed the name Kerona, given by Müller, for that of Stylonychia. The Keronae, thus understood, differ from Oaytricha only in the form of their cirrhi or processes, the base of which is commonly dilated in the form of a transparent globe, and moveable withal. Moreover they are equally voracious, are abundant in stagnant being much varied in form. IGERONA polyporum. —Whitish, de- pressed, elliptical, and reniform; a series of cilia surrounds the frontal region, ex- tended from beneath the mouth. Ehren- berg counted above forty vacuoles, many of them filled with brownish (half- water and infusions, and capable of digested green) Monads, (xxv. 340 is a back view, and 341 a side view, climbing.) Parasitic on Hydra vulgaris (Microscopic Cabinet, p. 7). Animals infested with them die. 1-144". This species is the type of a genus named OF TEIE OXYTRICHINA. 643 Alastor in Perty's system, detached from other Ciliata by reason of its parasitic habits, and placed with Plagiotoma (Duj.) and Opalina in a family named Cobalina. JK, pustulata (Duj.)= Stylonychia pus- tulata. - K. Histrio (Duj.)= St. Histrio. R. Mytilus (Duj.)= St. Mytilus. K. Silurus (Duj.) = St. Silurus. A. lanceolata = St. lanceolata. R. Calvitium (Müll.), K. fimbriata (Müll.), and Trichoda foveata and Th. Camelus (Müll.), are probably, according to Dujardin and Perty, mere varieties of JK, pustulata. R. Pullaster (Müll.) is cited by Ehren- berg as = Oaytricha Pullaster, but, as Dujardin thinks, is only an imperfectly- examined or a deformed specimen of St. pustulata. Genus UROSTYLA (XXV. 342).-Cilia and styles present, uncini want– ing ; the cilia are thickly disposed in numerous rows, and are longer near the mouth. On the ventral surface, at the posterior end, is a Small cleft, provided with non-vibratile setae. Internally are numerous vacuoles, which may be filled with particles of colour; a nucleus, a contractile vesicle, and delicate granules. UROSTYLA grandis (xxv. 342). — White, semicylindrical, rounded at the ends; slightly enlarged anteriorly, hence club-shaped; styles short; mouth large, one-fourth to one-third the length of the body. It has long cilia on both sides; the discharging orifice has from five to eight little styles on the left side only ; sto- mach-juice colourless. The young ami- malcules are flatter than the old ones. xxv. 342, an under view with glands, vesicle, and the cells filled with Bacil- laria and coloured matter. Currents Transverse self-division has been observed. produced by the vibration of the cilia about the mouth are also indicated in the drawing.) On slimy dead sedge- leaves. 1-144" to 1-96". Perty doubts the independent specific character of this form, and would rather consider it a yariety of Oxytricha fusca, or more pro- bably of O. platystoma in a further deve- loped state; for Ehrenberg admits that the uncini at the posterior extremity are Small; and if so, they can scarcely be characteristic. Genus STYLONYCHIA (XXV. 343, 344; XXVIII. 10, 74–76; XXIX. 18).-Ciliated, and armed with styles and uncini variously disposed. In one species Ehrenberg thought he had traced the course of the alimen- tary canal with its numerous digestive cells; in the others, he found, coloured food was received. Transverse and longitudinal self-division occurs in two species; transverse only in a third. Perty remarks that Ehrenberg, without any suffi- gemmae is said to occur. In S. pustulata, the formation of cient reason, has transferred many of the Keronae of Müller to Stylonychia. The granules and molecules are numerous, and often in heaps; one or two nuclei and a contractile vesicle are generally visible. STYLONYCHIA Mytilus (Trichoda My- tilus, Kerona Mytilus, M. and Perty). (XXVIII. 10). — White, flat, oblong, slightly constricted in the middle, ob- liquely dilated anteriorly in the form of a mussel. The extremities are so trans- parent that they give it the tº: of being covered with a shield; but they are soft, flexible, and ciliated. Dujardim observes that the integumentary appen- dages are very long, consisting of a row of strong cilia in front, a series of uncini and numerous styles behind. The line of cilia leading to the mouth does not reach the centre of the body. Its extre- mities are so thin and flexible that they yield before obstacles in their move- ments, like the Plaesconia Patella. It differs little from S. (K.) pustulata, ex- cept in size and the strength of its super- ficial processes. The middle of the body is sometimes filled with delicate white granules. Often, however, as Perty men- tions, the animalcule is coloured green with chlorophyll received in its food. This animalcule generally has a peculiar, thrusting, forward-and-back movement, but can climb, run, and swim nimbly, usually with the back undermost. Ehr- enberg found that a single animalcule lived mine days: during the first twenty- four hours it was developed by transverse Self-division into three animals; these in twenty-four hours more formed two each, in the same manner; so that, by self-division only (without ova), these 2 T 2 644 SYSTEMATIC EIISTORY OF TEIE INFUSORIA. animalcules increase three- or fourfold in twenty-four hours, and may thus pro- duce a million from a single animalcule in ten days. An abundant º of food favours self-division. In infusions and amongst Oscillatoria, &c., in stagnant marsh-water. I-240" to 1-96". S. pustulata (Trichoda Acarus, M.; Ke- Yona pustulata, Duj.).—White, turbid, elliptical or oval compressed, attenuated at both ends, and having a band of un- cini at the middle of the belly. Ehren- berg has seen transverse and longitudinal division, and the growth of gemmae. In infusions and stagnant marsh-water. 1–144". This species has been seen in the encysted state by Stein and Schneider (XXIX. 18). The white colour is no cha- racteristic, since it is frequently green from food received. Schneider (A. N. H. 2 ser. xiv. p. 328) observes that after exclusion from their cysts they present a remarkable resemblance to Oaytricha caudata; the posterior extremity in par- ticular is always bent round in the man- mer represented by Ehrenberg. Pineau calls this animalcule, in his history of a transformation of Vorticella, by mistake an Oaytricha (see Ann, d. Sc. Nat. 1848, ix.). Cienkowsky, however, regards both this species and St. lanceolata as phases of existence of the same being as Oxytricha Pellionella and O. gibba. S. Silurus (Trichoda Silurus, Kerona Si- Genus HALTERIA (Duj.) (XXVI. lurus, M., Duj., and Perty).--Small,white, of the form of a mussel; cilia and uncimi rather long. In fresh water, 1-280". S. appendiculata. —Elliptical, white, small, and flat; cilia and styles long; the setae disposed obliquely in fascicles. In fresh water, 1-280". S. Histrio (Paramecium Histrio, Ke- roma Histrio, M. and Perty).-Elliptical, white; middle slightly turgid, termi- mated anteriorly by a cluster of uncini; no setae. Ehrenberg states that the ab- sence of the three posterior setae in this and the following species is remarkable, inasmuch as the others possess them. Fission transverse. Amongst Confervae. Dujardin is inclined to regard this as a mere variety of S. (Kerona) pustulata. S. lanceolata. (= Kerona lanceolata, Duj. and Perty) (xxv. 343, 344).-Pale greenish; lanceolate in shape, extremities equally obtuse, under side flat; it has a cluster of uncini near the mouth, but no styles. Ehrenberg saw in one specimen a simple contractile vesicle on the left side, ii. the mouth, and near it a large oval gland. Green Monads and Bacillaria may be seen in this voracious animal, Surrounded with colourless sto- mach-juice. (XXV. 343 represents an under view, and 344 a side view.) Amongst Confervae. 1-144" to 1-120". (See note on St. pustulata.) Encysted state observed (XXVIII, 74–76). 31).-Body nearly globular or turbi- nate, surrounded by long, very fine, retractile cilia, which adhere to the glass, and by their sudden contraction enable the animal to change its place briskly, as if by leaping; a row of very strong oblique cilia occupies the circum- ference. The type of this genus is Halteria Grandinella (XXVI. 31 a, b, c), called by Ehrenberg Trichodina, and placed by him in the family Vorticellina, along with species totally different. Dujardin, however, more correctly refers them to the family called Keronina (see p. 640). Genus MITOPHORA (Perty) (XXVIII. 46, 47).-Body small, thicker behind, having on one side a row of large cilia, and posteriorly a filament of nearly the length of the body, and either with a simple or a slightly nodose extremity. - MITOPHORA dubia (XXVIII, 46, 47).- the other. Movement sluggish, revolv- Hyaline; sometimes filled with green ing. It has some resemblance to Tri- corpuscles; with the characteristic row choda praeceps (M.). 1-450". - of larger cilia along one side, and few on Genus STICHOTRICHA (XXVII. 43, 44).—Lancet-shaped, cylindrical, elongated anteriorly and flat; mouth at this portion; on one side an oblique row of cilia. STICHOTRICHA secunda (XXVIII, 43, 44)—Hyaline; usually filled with grey molecules or chlorophyll-grains; cylin- drical or rather compressed, rounded or OF TEIE EUPLOTINA. 645 truncate behind. Cilia on ventral sur- same time; sometimes it crawls, 1-240" face short, longer before and behind; 1-180". it swims rather actively, revolving at the FAMILY XII. EUPLOTINA OR EUPLOTA. (XXV. 345–353; XXVI. 22, 30). Loricated; alimentary canal with two separate orifices, neither of which is terminal. Organs of locomotion highly developed, similar to those of the preceding family. This family bears a general resemblance to the genus Asellus among the highly-developed Entomostraca. Organs subservient to nutrition are di- stinctly seen in three genera; and one is remarkable by having a cylinder of wand-like teeth, and a beautiful rose-coloured digestive juice, like that seen in Nasswla. Granules and a nucleus are found in two, and a contractile vesicle in three species; self-division, transverse and longitudinal, has been ob- served in one ; but gemmae are not produced. One form is green, the others. are colourless or whitish. This family comprises the following genera:- Teeth (Head distinguished from the body ........... ... Discocephalus. With cilia; ) absent Head not distinguished from the body............ Himantophorus. mo styles. Teeth present ...................................................... Chlamidodon. With cilia, claws, and styles ............................... ...................... Buplotes. This family Euplotina corresponds in part with that of the Ploesconiens of Dujardin, which includes animalcules of an oval or reniform depressed figure, not contractile, but only slightly flexible, and invested with an appa- rent shield (lorica), which, however, undergoes diffluence like the softer parts. Mouth furnished with vibratile cilia, and often also with cirrhi, in the form of styles or moveable hooks. They swim by means of the vibratile cilia, or crawl by the aid of the other appendages. The Ploesconiens are distributed into five genera:-Ploesconia and Chlami- dodon, with a visible mouth, the latter also having teeth; Diophrys and Coc- cwdina, without visible mouth: in the former the cirrhi or processes are grouped at the two ends, in the latter they cover the under Surface; L0&0&les has only vibratile cilia. The animalcules of the genus Ploesconia seem for the most part identical with the Euplotes of Ehrenberg; but, as the identification is in some cases uncertain, and as several new species are described by Dujardin, we shall subjoin Ploesconia, as an appended genus, along with Diophrys and Coccudina. Perty adopts the family Euplota, which he prefers to call Euplotina, and also comprehends in it the Aspidiscina (Ehr.) and the Ploesconiens (Duj.). Its genera are—Euplotes, Himantophorus, Coccudina (Duj.), and Aspidisca. Genus DISCOCEPHALUS (XXV. 345, 346).--Styles and teeth wanting, but uncini présent; the head is also distinguishable from the body. The organization is unknown, only the non-vibratile uncinated locomotive organs having been specially observed, the characteristic species having been only casually examined by Ehrenberg during his travels in the East. The genus, therefore, must be held a doubtful member of this family. 646 SYSTEMIATIC EIISTORY OF TELE INFUSORIA. DISCOCEPHALUs rotatorius (xxv. 345, (xxv. 345 is an under-, and xxv. 346 a 346).--Transparent; head smaller than side-view.) In the Red Sea. 1-380". the body; mouth rounded at both ends. Genus HIMANTOPHORUS (XXV. 347, 348).--Distinguished by the absence of styles and teeth, by having numerous uncini, and by the head not being distinct from the body. The long bent hooks, generally in pairs, appear like a broad band upon the under side, and serve as organs of loco- motion; near them is a row of cilia extending from the mouth to the middle of the body. The mouth, discharging orifice, and numerous vacuoles are distinct. At the posterior margin is a large contractile vesicle; between the row of cilia and margin on the right is a series of glandular (?) spots. Self- division has not been observed. HIMANTOPHORUS Charon (M.) (xxv. 347, 348).-Transparent, flat, elliptical, anteriorly slightly truncated obliquely; cilia short, uncini short and slender. The mouth commences anteriorly, at the lower angle of the triangular bright spot; but the true Oesophageal opening appears to be within the curved lorica, at the end of the dorsal row of cilia; the anal opening is near the base of the last cluster of four to six comb-like uncini, which supply the place of styles. (XXV. 347 is a side-, and xxv. 348 an under- view.) In stagnant water and ponds, amongst decayed leaves. 1-180". Genus CHLAMIDODON (XXV. 349).-Ciliated mouth, provided with teeth; styles and uncini absent ; an oval transparent lorica or shield covers the back, and projects around it; a margin of cilia surrounds the body; they are longer near the brow; short climbing setae probably exist posteriorly . between the cilia. There are distinct vacuoles, as also vesicles containing a beautiful rose-coloured fluid ; the mouth has a hollow cylinder of wand-like teeth. Internally are minute green granules and a large, oval, bright central nucleus. Self-division unknown. CHLAMIDODONMnemosyne (xxv. 349). —Flat, elliptical, sometimes dilated an- teriorly, as shown at xxv. 349. It is of a clear green or hyaline hue, with bril- liant rose-coloured vesicles; delicate longitudinal lines are seen upon the sur- face of the animalcule, and appear to be situated on the lorica. Ehrenberg counted sixteen wand-like teeth, disposed cylin- drically. The movement is quick and powerful, as in Euplotes. With Zostera and Scytosiphon. 1-570". Genus EUPLOTES (XXV. 350–353).-Locomotive organs highly deve- loped and various, in the form of cilia, styles, and uncini, but teeth wanting. Digestive vacuoles have been filled in four species with coloured food; the termination of the alimentary canal is indicated in one species by the dis- charge, in the rest by the projection of the little shield; the digestive juice is colourless; oval or round simple nuclei occur in three ; a single contractile vesicle exists in five, and in a sixth two such. Self-division, transverse and longitudinal, has been observed in One species, and transverse only in two or four others. (See general remarks, p. 645; and PLOESCONIA, p. 647.) Perty makes the remark that some of the assumed species of Euplotes may be modifications of the same being, due to pressure between the glasses during examination, since the so-called lorica is only relatively hard. The lorica has the form of a carapace or shield, covering only one surface, leaving the under one free. “The styles, which are trailed along, are,” says Lach- mann, “split up at the apex into as many as eight parts in many species, e.g. in E. Patella, in which, too, one style bears a number of small lateral branches.” - . . . OF TEIE EUIPLOTINA. 647 EUPLOTES Patella. — Lorica large, nearly circular, slightly truncated ante- riorly; margin transparent, broad; back elevated, gibbous, and covered with a few delicate Smooth striae. The mouth is ciliated on each side; the oesophagus is near the side, below the middle line, the discharging orifice behind the base of the styles. jth Lemnae. 1-280". E. Charon (Trichoda Charon, M.) (xxv. 350–353).-Lorica small, ovate- elliptical, slightly truncated anteriorly, and having granular striae on the back; twenty to forty cilia were counted by Ehrenberg, but no setae; a contractile vesicle and one or more nuclei have been seen. In standing water and infusions. Schneider has seen it in the encysted condition. 1-280". E. striatus.—Oblong, elliptical, slightly truncated anteriorly, uncini only upon the posterior part of the body; four smooth striae upon the back. Fission longitudinal. In sea-water, but, accord- ing to Perty, also in freshwater ponds, &c. 1–240." E. appendiculatus.—Ovate-oblong, ends rounded, provided with oblique styles and four straight setae upon the posterior part of the body. In fresh and sea water. 1-240". This, says Stein, is the Ploesconia lon- E. truncatus.-Oblong, with Smooth striae; unequally truncated, and notched anteriorly. It has setae and numerous uncini. The styles are straight. In sea- water. 1-240". Both this and the preceding, Perty be- lieves to be phases of development of lº. Charon and striatus. E. monostylus.-Elliptical, ends round- ed, no striae. It has a single style, like a tail, but no uncini. In Sea-water. 1-400", P. aculeatus.-Oblong, nearly Square, ends rounded; it has two crests upon the back, one bearing a little spine in the middle. In sea- and pond-water. 1-430", E. turritus.--Smooth, nearly circular; it has a long erect spine on the centre of the back, 1–600" to 1-430". E. Cºmew (Trichoda Cimea, M.).-Ob- long elliptical, and smooth, provided with cilia, styles, and uncini. In Sea- water, and, says Perty, in fresh pond- water. 1-430". E. viridis.--Large (ample), oblong, truncate in front, with a central obtuse tooth, dorsum flat; granules green. 1-480". Berlin. E. affinis (Perty) = Plaesconia affinis (Duj.). E. subrotundus (Perty) = Ploesconia subrotunda (Duj.). giremis of Dujardin. Genus PLOESCONIA (Duj.).—Body oval, more or less flattened, enclosed by an apparent lorica, marked by longitudinal ribs, furnished mostly on One of its plane surfaces with scattered, fleshy, thick processes in the form of stiff hairs, or of non-vibratile hooks, yet moveable and serving the purpose of feet; on the other surface, with a row of vibratile cilia regularly placed, and becoming finer as they recede from the anterior towards the posterior end, where the mouth is situated, and in the direction of which they vibrate. “In my opinion,” adds Dujardim, “a Ploesconia, notwithstanding its ap- parent complexity of structure, is yet an animal as simply organized as those previously considered—having a simple, fleshy, homogeneous substance, which assumes during life a rather complex form, but loses it at the moment of death, having no membrane or fibre to sustain it. The cilia or cirrhi, though of varied form, are still of the same nature, and, I should say, of nearly the Same consistence. They have a mouth also, but no anus; vacuoles are formed at the bottom of the mouth, as a result of an impulsive force produced by the vibratile cilia on the surrounding liquid, or they may be hollowed out in any part beneath the surface; lastly, disseminated through the mass are granules varying in kind, and which I cannot admit as determinate organs nor as ova.” We much doubt the necessity of creating this new genus, since all, or nearly all, the species referable to it might be arranged with Euplotés. Stein treats Ploesconia as synonymous with Euplotes (Ehr.), but would retain the former term to designate a new genus represented by P!. Scutum (Duj.), a Species, indeed, which is marked by the French naturalist as a doubtful member. 648 SYSTEMATIC HISTORY OF TELE INFUSORIA. It will be observed that Dujardin denies, as usual, the existence of an anus; this aperture is, however, generally stated to be found on the ventral surface, near the posterior extremity. PLOEsconIA Patella-Buplotes Patella (Ehr.). P. Vannus.-Depressed, oblong, oval; very transparent, smooth, without striae, 5 to 8 anterior hooks; and 7 to 8 straight styles behind. In sea-water. 1-218". P. (?) Scutum.–Larger than the pre- ceding, with the band of vibratile cilia extending further backwards, and the posterior styles inflected and sinuous. “This species,” says Stein º 158), “differs from the other Euplotes both in having prehensile cilia º not only on the ventral surface, at the poste- rior portion of the body, but also on the dorsal surface, and in many other pecu- liarities.” P. balteata.-Oval, rather narrower in front, diaphanous, with 5 striae (ribs); the band of cilia extending five-sixths the length of the body; styles few, feeble. In sea-water; no hooks, as in P. Vannus, 1–325". P. Cithara.-Oval, with ten regularly disposed well-marked ribs; the row of cilia semicircular, extending two-thirds its length; styles not long, and almost confined to the posterior extremity. In stagnant sea-water, 1-290" to 1-275". P. crassa,—Oval, oblong; thick, but diaphanous, with some faint signs of ribs; the band of cilia little curved, and ex- tending one-half the length; 6to 8 curved styles at anterior, and 5 to 7 straight ones at posterior extremity. With the preceding, in sea-water, 1-362". P. Charon.—Irregularly oval, truncate in front, narrower behind, with well- marked irregular ribs; styles long, not curved. Differs much from Euplotes Charon (Ehr.). P. affinis.--Differs from P. Charon, by its habitat being in fresh water, and by having its anterior portion marrower, whilst its posterior is more rounded and less º P (?) subrotunda.-Oval, thick, gra- mular within; no distinct ribs; truncated and fissured in front; styles long, thin at each end. In infusions. 1–535" to 1-475". Perty found it under the ice in a pond near the Hospice of St. Bernard, and sug- gests it to be no more than a variety of P. affinis with indistinct ribs (striae). P. (?) radiosa,—Longer than the pre- ceding, 1-520"to 1-395", with long styles radiating from each extremity. In river- water. P. longiremis.—Very depressed, irre- gularly oval, dilated on the side support- ing the cilia, where it is more transpa- rent, with 3 to 4 slightly prominent large ribs; styles numerous, very long and flexible. In sea-water. 1-400" to 1–306". P. aculeata = Euplotes aculeatus (Ehr.). Genus DIOPHRYS (Duj.) (XXVI. 22 a, b)-Body discoid, irregular, thick; concave on one side, convex on the other; with long styles grouped at each end; no mouth. DIOPHRYS marina (XXVI. 22 a, b)- cilia, and behind by 4 to 5 very long gemi- Oval, with a longitudinal excavation; terminated in front by 5 great vibratile culate styles. In sea-water. 1-580". Genus COCCUDINA (Duj.) (XXVI, 30 a, b, c). — Body oval, depressed or nearly discoid, often rather sinuous on the margin; convex, pitted or granular, and glabrous above; concave below, with vibratile cilia, and styles or hooks, serving as feet ; without mouth. Intermediate between Lovodes and Plaesconia, having the appendages of the latter, and the general figure of the former. Ehrenberg has left the Coccudince known to him dispersed among the species of Ovytricha and Euplotes. CoCCUDINA costata.-Oval, obliquely contracted, and sinuous in front; convex and furrowed beneath, where from 5 to 6 very prominent tubercular ribs are found, supporting long cilia; appendagesgrouped at each end; the anterior thinner and ponds. Aspidisca should probably be referred to this genus. vibratile. In marsh-water and swampy 1–965". C. crassa. – Oval; larger and appa- rently truncated behind; contracted and sinuous in front; convex above, with feebly-marked ribs; anterior appendages OF THE ROTATOIRTA. 649 in the form of hooks: straight styles. 1-20". corallines. C. polypoda (XXVI, 30 a, b, c).-Oval, sinuous in front; convex above, and marked with from 7 to 8 narrow ribs; flat below, and furnished with numerous long and flexible styles. In stagnant sea-water. C. Cicada.-Oval, very convex above, granular, without costae; margin round- ed; concave beneath, and there provided with long and flexible styles. Appears the same as the Trichoda Cicada of Müller, but not as its supposed synonym Oay- posterior, of Marine, among tricha Cicada (Ehr.), which is like the Coccudina costata rather than C. Cicada. 1–812". C.(?) Cimex = Stylonychia Cºmec(Ehr.). C. reticulata.-A name provisionally applied to an animalcule found in the Seine, having a granular and reticulated surface, and large styles at each end. 1-578". C. crystallina (Perty).-Hyaline, with from 6 to 7 long costae on the dorsum, and very short cilia. Outline round. The costae are less elevated than in C. costata. Wet moss and turf on the Alps. 1-900" to 1-600". OF THE GROUP ROTATORIA (p. 392). (Plates XXXII-XL., and part of XXV.) THOSE animalcules which are included in the great division Rotatoria are either destitute of a nervous system, or have merely an isolated ganglion near the head, representing the brain, with a few nervous threads proceeding from it to the body. They have no pulsating heart, nor true blood-vessels in which the blood circulates. The fluid apparently representing the blood occupies the cavity of the body and bathes the external surfaces of the various viscera, as in the lower Crustacea. The alimentary canal is tubular, variously constricted at intervals, often divided into segments, each of which appears to perform special functions. One segment, near the upper extremity of the canal, is provided with a pair of moveable appendages, between which all the food swallowed has to pass, and which may be regarded as teeth or jaws, probably analogous to the gastric teeth of Crustaceans. In many species there are caecal prolongations of the stomach; whilst the walls of the organ are thick and cellular, having a glandular aspect. The alimentary canal is, with Some remarkable exceptions, furnished with an orifice at each extremity, or mouth and anus, the latter usually opening into a cavity termed the cloaca, or common outlet for the intestine, the oviduct, and the (so-called) water- vascular canals. The interior of the canal is variously supplied with cilia, which are in constant motion. The caecal and cellular appendages are sup- posed to be glandular; but their functions, as well as relations to the liver and other chylopoetic Organs of higher animals, are doubtful. The character and instruments of the respiratory functions in the Rotatoria are alike doubtful, but most probably they are performed by the Water vas- cular canals. These are two slender tubes (XXXVI. 6 6, g) springing from the cloaca near the anal outlet, and proceeding upwards on each side of the intestine towards the head, where they branch, and sometimes the two amastomose, at others probably terminate in culs-de-sac. These canals com- mence at a pulsating organ (XXXVI. 6 v ; XL. 5), common to both, and Connected with the cloaca. In various parts of their course they are fur- nished with pyriform appendages (XXXVI. 6 a.) (tags) varying in number from two to eight on each side. In the interior of each tag is a single large cilium, which exhibits an incessant motion, resembling the flickering 650 SYSTEMATIC ELISTORY OF TELE INFUSOIRIA. flame of a candle, and which most probably promotes the circulation of the water contained in the canals. This water is apparently received from the cloaca into the pulsating appendage, and from it transmitted to the various parts of the tubular system,-a fact especially confirmed by Cohn's observa- tions on Brachionus militaris. Hence these water-vascular canals, with their vibratile appendages, appear designed to convey streams of fresh Water to the interior of the animal, and thus, by exosmosis, ačrate the fluid filling the body of the animal,—the latter being continually driven to and fro during the active muscular movements by which the creature alters its contour. The Rotatoria are provided with a reproductive apparatus, the female organs being remarkably large and conspicuous (XXXVI. 4f). In the majority of species the latter is the only portion that has hitherto been dis- covered; but in several, male organs have been found on separate indivi– duals, indicating the bisexual nature of the class—at least demonstrating the dioecious character of some of the species, a feature which will probably be found to characterize the entire family. The ovary consists of a verythin bag of structureless membrane (XXXVI. 4f), distended with clear fluid full of granular molecules, amongst which are some cellular nuclei. The latter successively attract around them portions of the granular fluid, thus forming ova. In several species two distinct kinds of ova are produćed by the same individual, one being a true generative product, the other a modified ex- ample of gemmiparous generation, and its growth independent of any sexual process. The ovary communicates with the cloaca by means of a narrow but dilatable oviduct. In examples of male animals that have been discovered, there is a remarkable absence of all viscera, except the organs of reproduction (XXXVI. 7, 8). Whether all the Rotatoria are dioecious, or whether some are hermaphrodite, the male organs having hitherto escaped detection, re- mains to be ascertained. The bodies of the Rotatoria, unlike those of the Polygastric Infusoria, re- tain a determinate form, never developing external gemmae, nor dividing by spontaneous division. Even on emerging from the egg, they possess all the essential features of the matured animal(XXXVII.16), neither passing through a larval state nor being subject to metamorphosis like Crustaceans and Insects. In the young animal some of the organs, especially the ciliated disks and other external appendages, are imperfectly developed, but they undergo little subsequent changes beyond an increase of size and definitiveness. Some organs, as the red eye-spot, often disappear as the animal progresses to ma– turity. The anterior extremities of the Rotatoria are furnished with various arrangements of the disks or bulbs supporting numerous cilia (XXXVI. 1 a. and 4 a.). These combine to form the rotatory organs, so designated from the wheel-like aspect which they present when fully expanded and with the cilia in motion. Though destitute of true articulated limbs, some species (e.g. of Melicerta) have appendages not unlike the palpi of Crustaceans and Insects, and which are probably tactile (XXXVI. 18; XXXVII. 17 d). Many forms are provided with a prolongation of the posterior part of the body, which is often pointed (XXXVIII. 1), and with the articulations slipping into one another like the joints of a telescope. This organ is sometimes furnished with a terminal disk (XXXVII. 17 b), and is used like the tail of the leech, as an organ of attachment. In other cases the disk is wanting, and its place Sup- plied by one or two digital appendages (XXXVI, 4 h), employed as anchors; whilst, in Swimming, the entire organ appears to become a rudder, regulating the direction in which the animal moves. - The cntire animal is invested by a thin pellucid membrane, which, from its extreme tenuity and transparency, readily allows the examination of the OF TEIE ROTATOIRIA. 651 internal organs whilst the creature is alive and the viscera fulfilling their functions,—a circumstance that has even made these creatures the favourites of the microscopic observer. MODES OF OBSERVING THE ROTATORIA.—The magnifying powers most useful in the examination of the Rotatoria are those varying from 200 to 400 linear. For watching their general habits, an object-glass of a half-inch focus, which with an eye-piece giving a power of about 70, is ample; but for ex- amining their internal organization, one of about 300, having an object-glass of from one-third to one-sixth of an inch, is the most useful; for the special examination of more minute structural details, still higher powers are occa- sionally, but not frequently, needed. We have already remarked that, from the transparency of their bodies, the Rotatoria can be watched with much ease, their internal organs being distinctly visible; and, as these latter are often equally transparent with the general integument, their contents, and the functions they perform, can be investigated with little difficulty. When their general habits are subjects of investigation, it is obvious they must be allowed much of the freedom enjoyed in their natural condition. For this purpose they may be introduced into a small phial of thin white glass with a long narrow strip of similar material in its interior; the latter being so fixed as to be nearer one side of the phial than the other. A blade of grass or one or two stalks of hay may now be introduced between the strip of glass and the proximate side of the bottle; these will attract the animalcules and bring them within the range of the magnifying power. If the phial be now filled with water containing the Rotatoria, they will soon find their way to the vegetable matter, especially if the bottle stands for awhile in the sun, with the side to which the plant is affixed turned to the light. The whole may now be placed under the microscope and readily examined through the lower magnifying powers. To some extent, the same object may be more readily attained by merely transferring small fragments of the half-decayed Vegetation floating in the water containing the animalcules, along with a drop or two of the water itself, to a glass slide, covering it over with a piece of thin microscopic glass. But in this case the movements of the creatures are less free, especially if they happen to be of the larger kinds, such as the Flosculariae. These are often chary of emerging from their protecting cases unless the coast be clear of all impediments. But the freedom of motion, so important to the accurate observation of their habits, wholly prevents the examination of their internal structure. Their perpetual gyration renders it impossible to trace either the forms or relative position of the viscera; con- Sequently they must be controlled. This may partly be accomplished by introducing them between the glasses already recommended without the intervention of any vegetable or other foreign substance. In this case care must be taken to adjust the relations between the size of the thin glass Covering and that of the drop of water. If the former be large and the latter Small, the chances are in favour of the animalcules being crushed. If these Conditions are reversed, their motions will not be sufficiently restrained, neither can the water be preserved from disturbance and vibration. Hence Care in hitting the medium of these conditions is essential. The Smaller the drop of water the thinner will be the fluid film when the protecting glass is placed upon it, and the more effectually will the vagrant habits of the Creatures be controlled. Sometimes it becomes necessary to rupture the animals by further compression, even whilst under examination. The diffi- Culty is to accomplish this without forcing them out of the field of the instru- ment. It may be accomplished by means of a common sewing needle fitted into a handle, by which pressure may be applied gently but firmly to the (352 SYSTEMIATIC EIISTORY OF TEIE INFUSORIA. thin glass. But this object can be still better attained by means of one of the compressoria provided by opticians: the pressure being effected with a fine screw, the movement can be regulated with the utmost nicety. Thus the animal can be merely fixed in its position, whilst its vital functions pro- ceed without interruption. On increasing the pressure, we obtain increased transparency by reducing the thickness of the animal; and on carrying the motion still further, we can rupture the integument, when the viscera become detached and discharged through the fissure. Thus their minute organization can be more accurately ascertained than when retained in situ. In some cases the forms of the various viscera can be readily ascertained from the different hues which characterize them, but in the majority of Rotatoria this guide fails us. Consequently observers have long adopted a plan of feeding the animals with brightly-coloured pigments, such as carmine and indigo, which many of the creatures consume with avidity: a very small quantity of the colour should be rubbed up with a little water, as if for artistic purposes. If the live-box be used in examining the creatures, with the water contain- ing the animalcules a little of this colour must be mixed prior to the cover being placed upon them. But when a common glass slide is employed, it generally suffices to dip a camel's-hair pencil into the diluted pigment and apply it to the edge of the thin glass. The colour usually flows between the glasses, and diffuses itself through the water sufficiently to answer every purpose. Two objects are now attained. The minute coloured particles are thrown into active motion by the ciliary movements of the trochal wreaths, beautifully demonstrating the force and direction of the aqueous vortices set up by the animalcule; and by noting the direction taken by such of the particles as are swallowed, the position of the mouth and Oesophageal canal can be traced. These particles usually accumulate in the stomach, distend- ing its parietes; and as the bright colour of the pigment contrasts strongly with the transparent walls of the viscus, its size, form, and position, as well as the structure of its walls, can be readily made out. By prolonging the observation, the same agent enables us to ascertain the direction of the intestine, anus, and cloaca, since, when the stomach becomes inconveniently full, the creature usually everts the cloaca, brings the anal orifice into contact with the surrounding fluid, and suddenly empties the stomach or bowel of its contents. - There are practical disadvantages attending the use of carmine and indigo, some of which Mr. White appears to have overcome by substituting the red pigment which lines the cornea of the eye of the common house-fly (Microsc. Journ. ii. p. 282). By means of a finely-pointed knife, or sharp-edged needle, the large cornea can easily be detached from the head of the insect ; whilst a small, stiff camel-hair, or (still better) a small sable pencil suffices to wash the pigment out of the internal concavity of the detached cornea. It is occasionally desirable to examine the animals by reflected instead of transmitted light, in order that their true colours may be exhibited, as Mr. Gosse has pointed out in the instance of Philodina citrina. TOCALITIES FOR ROTATORIA. — These are exceedingly diversified, varying from the wide ocean to the dried-up sediment of the water-spout. There are few circumstances under which water exists, in which Rotatoria may not be found, though they dislike it when its contents are undergoing decom- position. Consequently, though they occur in all vegetable infusions, they are only to be found when the first stage of decomposition has passed away, and they usually disappear again when the water becomes putrid and offen- sive. After the Momadina, Paramecia, and other smaller Infusoria have run their course, and in large measure disappeared, the Rotatoria occupy their OF TTIT, ROTATORIA. * 653 places, a circumstance that has led some observers to suggest the probability of some of these lower forms being the larval states of the higher ones—a view now known to be erroneous. Some species, especially the Rotifer vulgaris, are common wherever water has remained for a little time without disturbance, in cisterns, depressions in the gutters of houses, Saucers of flower-pots, and similar situations. A few forms have been found in the interiors of vegetable cells. Thus Rotifer vulgaris occurs in the leaf-cells of Sphagnum, and in the clavate branches of Vaucheria, feeding upon the contained chlorophyll. Notommata parasitica and N. petromyzon, found within the spheres of Volvoa globator, in like manner consume the little masses of green protoplasm; whilst Notommata TVerneckii, like the Rotifer, occurs in the cells of Vaucheria. They often abound in the damp moss from the neighbourhood of bogs, streams, and Waterfalls. But, besides these special situations, some of them are to be found in almost every ditch and pond in which Lemnae, Confervae, and other decaying masses of vegetation abound. Sometimes they play round the plants with incessant action, pushing their slender bodies into every recess in which food may lurk, then backing out again as cleverly as any of their larger aquatic companions can do with fin and tail, now anchoring themselves to Some projecting point by means of their flexible pseudopodia, drawing in their trochal disks with apparent alarm if any other creature brushes past their resting place with unmannerly rudeness; then, forgetting their fears, they again evolve their ciliated wheels, loosen from their anchor- age, and launch away into the clear stream, displaying the varied modes of progression so characteristic of different species. But it is only some of the forms which indulge these vagrant habits. The higher forms, such as Limnias, Melicerta, Floscularia, Lacinularia, and Stephanoceros, are quiet stay-at-home matrons, at least after sowing the Wild oats of their youthful days. For a short time only after leaving the ovum do they roam wild and free. They soon settle down, attaching themselves by their false feet to some fixed resting place, where they spend the rest of their lives in sober tran– quillity. These home-birds must be sought for amongst the stems and leaflets of Ceratophyllum, Chara, and the water Ranunculus, more frequently occurring in the clearer streams and ponds than do many of their smaller allies. Unlike the Momadina and other lower Infusoria, the Rotatoria rarely occur in such profusion as to colour the water. It is occasionally rendered turbid and milky by Brachiomus Palea, which, in such cases, occurs in vast profusion. Brachionus wrceolaris and B. rubens sometimes present the same conditions. Typhlina viridis, found by Ehrenberg in Egypt, coloured the water green. Lacinularia forms small transparent gelatinous masses. Limnias annulatus occasionally studs the leaves of water-plants in such number as visibly to clothe them in russet brown ; and groups of Conochilus Volvoa appear in Small clusters, adherent by the extremities of their pseudopodia, like a group of tadpoles dipped in colourloss jelly, from which they can protrude their heads or retract them at will; but sociality does not usually characterize the Rotatoria as it does Euglena and similar forms. It is only when the parasitic species have taken possession of some remarkably favourable locality that they so abound as to affect the aspect of the plants on which they dwell, and thus force themselves on the attention of the observer. Usually they must be sought for in a systematic way, without any extermal indications whether a pool will prove productive or barren. We have, how- ever, rarely been disappointed on examining the green and foul-looking drainage from the manure heap in the farm-yard. Amidst its swarms of Buglence we have usually found a rich supply of Rotatoria. The true micro- 654 SYSTEMATIC HISTORY OF TIII, INFUSORIA. scopist must not be afraid of soiling his hands, or have a weakness for kid gloves. Some few Rotatoria assume the habits of Entozoa. Albertia vér- micularis was found by Dujardin in the abdominal cavities of the earthworm and in the intestine of Limacina; whilst Albertia crystallina was discovered by Schultze in the intestine of Nais littoralis. CAPTURE OF ROTATORIA.—The modes of capturing the Rotatoria must vary with the species sought, as will be evident from the remarks made in the preceding section. The simplest mode of obtaining the majority of the forms is to collect a quantity of Confervae, Lemmae, or the half-decaying masses of the different pond-Weeds, filling the vessel with water from the pool in which plants were growing. We have usually found the shallow margins of the pond most productive. On reaching home, the vegetable mass must be well stirred up in the water, in order to detach the animalcules from the plants to which they cling; and, before they have time to re-attach themselves, the water must be poured off into another vessel, through a piece of muslim or very fine net. All the coarse material is thus got rid of, nothing passing through the strainer but water rendered turbid by fine particles of half- decayed vegetation suspended in it. But along with these vegetable atoms the Rotatoria will also pass into the receiving vessel, which must be allowed to stand for a while, allowing the sediment to sink to the bottom, where it will be followed by the animalcules which find nutriment in the half- decayed mass. A Small portion of this sediment may now be taken up by means of a narrow glass tube, one end of which must be introduced to the bottom of the vessel, whilst the opposite one is closed by the finger or thumb. On removing the latter, the sediment rushes up into the tube; and if the upper end of the tube be again closed as before, the contained material can be transferred to the live-box or the glass slide. If the tube be held for a few moments in a vertical position, the upper part being still closed with the finger, the vegetable matter and its accompanying animalcules will sink to the lowest part of the water; consequently the first drop escaping from the lower end of the tube will usually be richer than those that follow. If the drop be received upon a glass slide, it must be covered over with a piece of thin glass, when it is ready for the microscope, and, unless the pond has been uncommonly barren, the instrument will reveal a rich harvest of Algae, Con- fervae, Desmidieæ, Diatoms, and Polygastrica; whilst amongst all these the Rotatoria will be found Sailing from point to point, exploring all the recesses between the vegetable fragments, now quiescent, as if contemplating the contents of the larder, then, as if dissatisfied with the prospect, Sailing away to some more promising pasture. But when a tempting nook presents itself, this restless locomotion ceases, and they attach themselves to some fixed point either by means of a disk-like foot or by using its terminal joints as an anchor, —their trochal disks being for the time drawn in, and comfortably lodged in the anterior part of the body. Its position being fairly secured, the animalcule evolves its wheels, at first slowly, but soon increasing their speed. A violent commotion amongst the atoms abounding in the water soon indicates the pro- duction of a miniature whirlpool, which brings a continuous stream of edible matter within the reach of the hungry traveller. But, though hungry, he is a dainty gentleman, and chooses to select his fare. The bulk of what is drawn towards him by the vortex he has created, not suiting his taste, is suffered to flow by, in a continuous stream, like that left by tho rocket in its flight. But everything is not thus allowed to pass: the teeth-like jaws of the animalcule are constantly playing against each other with desperate energy, whilst sudden jerks and contractions indicate that the animalcule has made a capture ; and though it is not always easy to see his prey pass down OF THE ROTATOFIA. 655 his gullet, the gradual expansion of his stomach proves that he is not labour- ing in vain. The Monads find to their cost that he is a real Triton amongst the minnows. Another mode of capturing similar forms is by employing a small net, of very fine muslin firmly fastened to a ferruled hoop of brass or iron, a few inches in circumference, and capable of being fitted to a walking-stick or fishing-rod. It has been recommended that the exterior of this hoop should be grooved, so that nets of various degrees of fineness can readily be employed —these being attached merely by means of an elastic ring of Vulcanized indian-rubber, drawn over them and fitting into the metallic groove. By means of a net of this character, the central and deeper parts of a pond can be searched, as, if the gauze be sufficiently fine, the net will retain the larger Rotifera, whilst the water passes freely through it. After making a succes— sion of sweeps through the pond, the net may be everted into a receiver con- taining clear water, and with a little manipulation the animalcules adhering to it may be washed into the vessel. By means of the same met the fluid may be concentrated until at length the rich products of an hour's fishing may be carried home in an ounce phial. But the muslin must be very fine, or the richest of the game will escape. When the large and exquisitely beautiful Floscularian Rotatoria are the objects of search, a different method must be followed. It is but occasionally that they can be met with ; conse- quently the student must be prepared to give time and labour before he succeeds in discovering these lovely objects; but they are well worth the price. As before observed, Melicerta, Stéphanocéros, and similar forms are found attached to the slender stems and subdivided leaves of Ceratophyl- lum, Myriophyllum, Ramwmculus aquatilis, the Charge, and similar plants. The method of search which we have found the most successful has been to carry with us to the field a narrow phial of clear white glass or a chemist’s test-tube, into which portions of Such plants as a pond may contain may be introduced along with a little clean water. The unaided eye, when experi- enced, soon ascertains the presence or absence of the objects sought for ; but the search may be further facilitated by means of a pocket-lens of low magnifying power. If, after selecting several fragments drawn from different parts of a pond, these do not reveal traces of some of the Floscularians, it is probable they do not exist there, and we may proceed to some new fishing- ground; but if an isolated individual be detected, every clump of aquatic vegetation in the pond should be carefully searched; for, as is the case with Volvoa and many other microscopic organisms, there will be found in some part of the water a colony where Malthusianism has no place, and to which the isolated individual first found bears the same relation as the trappers and backwoodsmen of the west do to the Swarming communities of Boston and New York. One remarkable circumstance must be borne in mind by the animalcule- hunter. If he happens to remember a pond where some rare species abounded last year, let him not again turn thither in search of it, as the chances will not be in his favour. These creatures rarely exist in the same Water during two successive years. The reasons for this are not easily ascer- tainable. The remark is equally applicable to Volvoa and the Desmidieæ. The search will be most productive if prosecuted on new ground. It may be remarked that the Floscularian Rotatoria are usually discovered accidentally, rather than by predetermined search. Respecting the marine Rotatoria but little is known. The class appears to have but few representatives in salt Water, contrasted with their abundance elsewhere. Nevertheless some may Occasionally be observed whilst examining corallines and seaweeds under 656 SYSTEMATIC HISTORY OF TEIIL INFUSORIA. the microscope, around which objects they play after the fashion of their freshwater allies. In the ocean we have few or no counterparts of the stagnant pools found on land; those dark holes on rocky coasts, the homes of the Actiniae and the seaweeds, which would otherwise represent ponds and ditches, are too constantly disturbed by the tidal wave to admit of the accu- mulations of decaying vegetation so favourable to the existence of the fresh- water species. CLASSIFICATION.—The exact place which the Rotatoria should occupy in the zoological scale is as yet undetermined, since discordant opinions are entertained on the subject by some of our most eminent naturalists, as will be seen by a recurrence to Part I. of this work (p. 392). The question can be decided only by a careful study of their development as compared with that of other animals. Most inferior creatures are the permanent representatives of conditions which are merely transitional in the advance from the ovum to maturity of some higher form, the former beings obviously occupying a posi- tion subordinate to the latter, inasmuch as they never advance beyond a state which only occurs in the higher animal in its immature and imperfect con- dition. The Myriapod and the Worm, with their strongly-marked vegetative repetitions of parts, obviously find a temporary representative in the crawling caterpillar, but not in the fully-formed winged insect of which the caterpillar is but the rudimentary larva. Consequently the Worm and the Myriapod must alike be placed below the Insect, if we arrange animal forms in a linear series according to their development. Supposing this method of ascertaining the true Zoological position of any class of animals to be correct, the question naturally arises, what larval states of other animals are most closely repre- sented by the permanent forms of the Rotifera 2 It is clear that the Rotifera have little affinity with the Polygastric Infusoria; for, though the family of Worticellina amongst the latter animals seems to constitute a sort of inos- culating link, the affinity of the Vorticellae to the Rotatoria appears to be rather one of resemblance than of relationship. The history of the Vorticellae, as worked out by Professor Stein, reveals morphological changes wholly dis- similar from what occurs in the Rotatoria, amongst which the encysting- process, so characteristic of the Vorticellae, has no place. This process is obviously one of the phenomena of development by gemmation which is most prevalent amongst the lower animal forms, and becomes less frequent as we ascend, until, amongst the higher classes, it never occurs. In ascertaining the relation of the Rotatoria to the Vorticellae, it is necessary to inquire how far this reproduction by gemmation, as distinct from sexual reproduction, has any existence amongst the former animals; and this is precisely the question which we are as yet unable to answer. It has been suggested that, of the two forms of eggs known to be produced by some Rotatoria, one group con- sists merely of buds encased in a shell, whilst the others are the true sexual products; but such eminent observers as Professor Huxley and Dr. Cohn are at issue as to which of the two kinds of ova are to be respectively regarded as true eggs or as gemmae. Dr. Cohn Contends that the bodies ordinarily regarded as eggs are merely gemmae thrown off from the organ believed to be an ovary, without any fertilization by a male animal,—thus accounting for the extraordinary profusion in which these eggs are developed, whilst so many observers have been baffled in their attempts to discover spermatozoa or any male organization. The mode of development which Professor Huxley observed in the ova of Lacinularia, and Professor Williamson in those of Melicerta, are not incompatible with the idea of their being gemmae, and the ovary a gemmiferous stolom. Supposing all this to be true, we have, in the formation of these shelled gemmae, an analogue to the development of OF TELE ROTATORIA. 657 the Vorticella-buds from the Acimetal condition of the Vorticellae; but the encysting of the entire body of the latter animal, and especially its resolution into a multitude of gemmules, finds no parallel amongst the Rotifera; hence We cannot regard the two classes of animals as having any close affinity to One another. Professor Owen removes the Rotatoria from the Cuvierian group of Radiata and places them amongst the Articulata, in close alliance with the Crustacea. This idea is a plausible one, and has several supporters. But here we are met by the fact that all the Crustacea, not excluding the Cirripeds and the Entomostraca, pass through a larval condition, resembling which, notwith- standing the assertion of Leydig, nothing has hitherto been observed amongst the Rotatoria; whilst the latter cannot be regarded as having any resemblance to the larval conditions of these higher Crustaceans in any stage of their history. Professor Huxley’s suggestion, that they are the permanent repre- sentatives of the larval forms of his group of Annuloida (including the Echi- noidea, Annelida, Trematoda, and Nematoidea), appears to have many facts in its favour, since it connects them with the articulate division of animals without raising them to the level of true Crustaceans. Burmeister and Leydig hold similar views to those of Owen respecting the close relation existing between the Rotatoria and the Crustacea. Leydig dwells especially upon their external figure, the frequently hardened lorica, the existence in their bodies of striped muscular fibre, their nervous system, the anatomical and physiological phenomena of their sexual life, and, lastly, the supposed fact that the young, at its liberation from the ovum, has not the form of the adult animal, and consequently must undergo a metamorphosis. These argu- ments, when examined closely, afford feeble support to Leydig's opinion. External form is an unsafe criterion of Zoological position. Were it trust- worthy, it would bring the Rotatoria nearer to the cilio-brachiate polypes than to the Crustacea. The hardened lorica is nothing more than a modified exo-skeleton, which is as fully developed in the Echinoderms as in the Crustaceans; whilst in the majority of the Lerneadaº (the section of Crus- taceans to which Rotatoria bear the closest affinity) this hardened integument is wanting. The existence of striped muscular fibre proves nothing, since Mr. Busk long ago discovered this structure in some of the Acalephae. The nervous system of the Rotatoria is as yet so imperfectly understood that little reliance can at present be placed upon our knowledge of it; besides which, as Professor Huxley has pointed out, a similar condition to that of the supposed nervous system of Rotatoria exists in Turbellaria; and, lastly, the pheno- mena of sexual life amongst the Rotatoria are as little understood as is their nervous system. The few instances in which male animals have been found, present some resemblance to the phenomena seen amongst the Lerneada ; but the subject is equally involved in obscurity in each of the two classes of creatures, whilst Leydig's assertion, that the young Rotifera undergo meta- morphosis, appears entirely erroneous. The only facts positively determined indicate that nothing of the kind takes places amongst them, whilst all the Crustaceans, including the Lerneadae, undergo repeated moults before reaching maturity. We forbear enlarging on this question of the zoological position of the Rotatoria, as it has already been discussed in much detail in the first part of this work (p. 468 et seq.). • The most philosophical mode of subdividing the Rotatoria into families is almost as undetermined as their zoological affinities. Ehrenberg, who led the way in this work of classification, based his primary groups upon the number of divisions and form of the ciliated trochal wreath, sub- 2 U 658 SYSTEMATIC HISTORY OF THE INFUSORIA. dividing each division according as the animals composing it were loricated or illoricated. - The following table represents his classification :- Margin of ciliated wreath | Illoricated ... Ichthydina. entire (Holotrocha) ... Loricated...... CEcistina. With a simple continuous wreath of cilia (Mono- - trocha)..................... Margin of ciliated wreath ſ Illoricated ... Megalotrochaea. lobed or notched º \ zotrocha).................. Loricated...... Flosculariaea. With the ciliated wreath ( Illoricated ... Hydatinaea. divided into º With a compound or di- series (Polytrocha)...... Loricated...... Euchlanidota. vided wreath of cilia (Sorotrocha) ............ With the ciliated wreath ſ Illoricated ... Philodinaea. divided into two series (Zygotrocha) ............ Loricated...... IBrachiomaea. N.B. This classification is given more at length at p. 478. Siebold adopts the classification of Ehrenberg for the Rotatoria, omitting a few genera. Dujardin, on the contrary, regards the principles employed by the great Prussian microscopist in framing his division of these animals as faulty and uncertain; consequently he puts forth a classification of his own, substituting the name of Systolides for the better known one of Rotatoria. He admits four primary divisions of the class, viz.- 1. Those Rotatoria which live fixed to some foreign body by their posterior extremity. - 2. Those which employ but one means of locomotion, using their vibratile cilia as instruments, and being always swimmers. 3. Those which exhibit two modes of progression, viz. Swimming and crawling, after the manner of leeches. 4. Those which creep by uncini, and are destitute of vibratile cilia. The first of these groups includes only his Flosculariens and Melicertiens. The second contains by far the largest number, and is subdivided into two secondary groups, in One of which the animals have an integument wholly flexible, whilst in the other they have some part of it solid, constituting a lorica or shield. The third section contains only his family of Rotifera, closely corresponding with Ehrenberg’s family of Philodinaea; whilst the last comprehends the Tardigrada. These curious animals are now known to have no affinity with the Rotatoria, but belong to the Arachnida, or class of spiders. Indeed, at the time of publishing his book, Dujardin expressed doubts as to the propriety of uniting them with the Rotatoria. Leydig proposes a new classification of the Rotatoria, or as he terms them, in accordance with his views respecting their nature, Cilio-crustacea, which he arranges “according to their forms—whether they are cylindrico-conical, Sacciform, or compressed, together with which, as further characters, the condition, presence, or absence of the foot may be employed.” He adopts three primary divisions:— A. Figure between clavate and cylindrical. B. , Sacciform. C. , compressed. OF THE ROTATORIA. 659 These he again subdivides as follows:— ſ 1. With elongated, transversely-ringed, attached foot. 2. With elongated, jointed foot, retractile, like a telescope. . 3. With elongated, jointed, non-retractile foot. A.< 4. With short foot and long pedal forceps. 5. With short foot and pedal forceps which are of equal length with, or Somewhat shorter or longer than the foot. U6. Without foot. B 1. Foot short. 2. Foot absent. * * 1. With a foot. C. |: Depressed from above downwards { 2. Foot absent. b. Laterally compressed. It will be seen that the classifications of Ehrenberg, Dujardin, and Leydig agree in one feature : they are more or less artificial, being based upon peculiarities of external form and habit rather than upon internal organiza- tion. The subdivision of the trochal wreath varies in its extent with the age of the animal, the depth of its sulci increasing with the approach of maturity; consequently the defectiveness of Ehrenberg’s system becomes at once obvious. No such changes as we have just referred to affect the internal viscera, except in a minute degree ; consequently the latter alone, when thoroughly understood, can furnish the true materials for a philosophical classification. But unfortunately we do not as yet possess such a number of accurate observations as admit of our arranging the various species on this higher basis. For example, the Rotatoria are either monoecious or dioecious: a few have been demonstrated to belong to the latter class; but of the vast majority we are unable to say which of these two features characterizes them. The belief in their monoecious nature has until recently been general; but the possibility of their being all dioecious now suggests itself. Should future observations establish the fact of some Rotatoria being monoecious and others dioecious, the distinction will be one of paramount importance as a basis of classification. But of the internal organization of the vast majority of these animals we unfortunately know little or nothing. ). A very small number even of the higher forms have been submitted to rigid and accurate scrutiny; consequently the want of material for a natural classification, based on anatomical and physiological data, compels us to fall back upon such as are artificial. (See Part I. p. 477 for additional remarks On classification.) The relative value of the three systems of Ehrenberg, Dujardin, and Leydig will be a disputed question. Where the purpose to be accomplished is merely. the provision of an index (and artificial systems can be little more), the clas- sification in which the distinctions are most readily recognized will best fulfil its purpose. On these grounds we think there is little room for choice be- tween those of Ehrenberg and Dujardin. The two primary sections of the great Prussian naturalist are easily recognized, his four principal Subdivisions almost equally so; and the ultimate division of each group into a loricated and an illoricated series not only facilitates the investigations of the young student, but is an element in Dujardin’s system, who, by adopting it, re- Cognizes its value. At first sight Leydig's classification would appear to approach nearer to a natural system than either of the others enumerated; but close examination does not confirm this impression, since, in order to arrange the objects in their respective groups, such genera as Iglºº, FM'- 2 U 660 SYSTEMIATIC IIISTORY OF TENTE INFUSORIA. cularia, and Notommata have required to be subdivided, part being thrown into one subdivision and part into another. Objects which present such close resemblance as to be capable of arrangement in one generic group can scarcely be so diverse as to justify their separation into different families. The de- tachment of the fifth section from the fourth, merely because its individuals are furnished with short pedal forceps, would furnish a precedent for classi- fying birds and quadrupeds according as they have long tails or short ones. These reasons have led us to retain the classification of Ehrenberg for the present, since the advantages afforded by the two newer systems do not seem sufficiently great to justify our abandoning the general plan followed in the previous editions of this work. At the same time we are fully alive to its imperfections, both in its principles and details. Leydig's objection to Ehren- berg's employment of the term lorica is a substantial one, since it is stretching the term beyond what is admissible, to apply it to the delicate investing membranes of Floscularia and Stephanoceros, or to the gelatinous envelope of Conochilus. Consequently, though for reasons already advanced we retain the subdivisions of the Prussian microscopist, we extend his definitions of his third series of groups: instead of defining them as “loricated,” and “illoricated,” we would describe them as “loricated, or usually provided with a hard investing layer,” and “illoricated, or unprovided with a hardened investing layer.” - Leydig's objection, that such animals as Ehrenberg indicates by the terms Polytrocha and Zygotrocha have no existence, is ill founded. There is no question that the ciliated lobes of the head are divisible and distinct in a large number of species; and being so, they become as good characteristics of families as do Leydig's long or short pincers to the foot. FAMILY I.—ICHTHYDINA. Rotatoria with a single continuous rotary organ, not cut or lobed at the margin; destitute of lorica or indurated integument. In Ptygwra and Gle- mophora the wheel-like organ is in the form of a circle, and is an instrument of locomotion. In the other genera it is long elliptical, and on the ventral surface. Chaetonotus and Ichthydium have each a forked foot-like process, and the rest of the genera a simple one. A long simple alimentary canal, with a long Oesophagus, apparently without teeth, occurs in Chaetonotus and Ichthydium. Glenophora has a short Oesophagus, with two single teeth; and Ptygwra an elongated stomach and three teeth. Glands are seen only in Chaetonotus and Ptygwra. No caca exist in any of the genera. The male reproductive organs, not hitherto discovered; those of the female consist, in Ptygwra and Ichthydium, of a large ovarium containing one or more developed ova. The two red eyes seen in Glenophora are supposed by some to indicate the existence of a nervous system as yet undiscovered. - Ehrenberg's classification of this family will be found in p. 478 of the General History. It is probably the weakest which Ehrenberg has esta- . blished, being admitted neither by Dujardin nor Leydig. Dujardin does not recognize the genus Glenophora, neither does Siebold, whilst Leydig rejects both it and Ptygwra, regarding them as immature forms of some other species. Ptygwra, especially, the latter writer suggests, may be the young Melicerta ringens; but this idea Professor Williamson’s observations have shown to be erroneous; consequently the genus must be retained until its immature condition is better established than at present. Dujardin com— prehends Ptygwa in his family of Melicertiens, whilst he rejects Ichthydium OF THE ICEITEIYDINA. 661 and Chaetonotus from amongst the Rotatoria, believing them to be Polygastric Infusoria, a conclusion with which we are strongly disposed to agree. Genus PTYGURA.—Eyes and hair absent; foot simple, truncated, cylin- drical. Body campanulate, oblong. Rotary organ simple, and nearly circular. Numerous tooth-like bodies, adhering to the bulb of the oesophagus, two glands, a small narrow Oºsophagus, an elongated stomach, and a subglobular rectum constitute the apparatus of nutrition. An ovarium and a contractile vesicle have been observed, but no visual organs. This genus is comprehended in the family Melicertiens of Dujardin, along with Lacinularia, Tubicolaria, and Melicerta, and is made to include the species distributed by Ehrenberg in the several genera Ptygwra, CEcistes, and Conochilus; for Dujardin states that the individuals of these three genera present no further difference than is seen in the gelatinous envelope, which surrounds the two last, forming in OEcistes a distinct tube for each individual, whilst it includes the individuals of Conochilus in a common globular mass, and is absent in Ptygura. The same author would name (Ecistes crystallinus “Pygura crystallina,” and the Volvoa conochila “Ptygura Volvow.” PTYGURA Melicerta. — Transparent; body cylindrical, club-shaped, turgid an- teriorly, with two little curved horns at the mouth, and a single short tube at the neck (?). The tail-like foot always remains transversely folded (wrinkled), as seen in xxv. 354, which represents the under side. When swimming, a ring- like simple vibratile organ is thrust out, with a lateral notch. The two jaw-like parts of the oesophageal bulb have mu- merous teeth, as represented at xxv. 355. 1–140". Genus DASYDYTES (Gosse).—Eyes absent; body furnished with bristle- like hairs; tail simple, truncate. This genus, according to Ehrenberg's description of Ichthydina, must follow after Ptygwra. DASYDYTEs goniothric.—Hairs long, each hair bent with an abrupt angle; neck constricted. 1-146". Found at Leamington, D. antenniger.—Hair short, downy; a pencil of long hairs at each angle of the posterior extremity of the body; head furnished with two club-shaped organs resembling antennae. 1-170". Genus ICHTHYDIUM.–Tail cleft or forked, foot-like; no eyes or hair; currents at the mouth and along the ventral side indicate the existence of a vibratile organ, which not only serves for swimming but likewise for creeping. A long obsophagus, a thick simple conical alimentary canal, and sometimes a large single ovum, comprise our knowledge of their organization. It is pro- bable that a cylinder of little wand-like teeth exists (see Part I. p. 380). arched and smooth. The large dark ICHTHYDIUM Podura (Cercaria Podura, ovarium has been seen by Ehrenberg. M.). —Straight, oblong, often slightly constricted anteriorly, where it is turgid, and sometimes three-lobed. It is colour- less or whitish, but during repletion sometimes appears yellowish ; the ven- It seldom swims, but mostly creeps. xxv. 356 exhibits a full-grown animal- cule (ventral side). Among Confervoe and Oscillatoriae. 1-440" to 1-140". tral surface is flat and ciliated, the dorsal Genus CHAETONOTUS.–Dorsal surface covered with hairs; tail forked ; eyes absent. Locomotion is performed by means of a double row of cilia upon the ventral surface, forming a band-like rotary organ. The nutritive organs consist of a tubular mouth, probably provided with a cylinder of teeth, a long thin cosophagus, and a long conical stomach (trachelogastricum), upon whose 662 SYSTEMATIC HOISTORY OF THE DNFUSORIA. upper thick end (in the large species) two semiglobular glands are seen ; at certain periods from one to three large ova are formed posteriorly, but the ovarium in which they are developed has not been directly observed; male reproductive organs unknown. They are sluggish in their movements, except in creeping; they rarely swim. (See Part I. p. 380 et seq.) CHAETONOTUS maximus (xxxi. 29, 30). —Elongated, slightly constricted ante- riorly, turgid and obtusely three-lobed; hairs upon the back short and equal. From his latest observations, Ehrenberg states the mouth to possess teeth, of which he has counted more than eight; he once saw the exclusion of ova imme- diately over the foot-like tail. It creeps but slowly. 1-216" to 1-120". (See . 381. p C. Larus (Trichoda Acarus, Anas et Larus, M.). — Elongated, slightly con- stricted anteriorly, where it is turgid and obtusely triangular; the posterior hair On the dorsal surface is longest. Ehren- berg has seen only one large ovum; he states that the bodies of those bearing ova were thick posteriorly, though, under other circumstances, the head is broadest. It appears to have eight teeth. The dor- sal hairs, which are arranged in longi- tudinal rows, destroy the transparency of the body. xxv. 357 is a dorsal, and 358 a side view. Ova one-third the length of the body. In muddy water. I-720". C. brevis.-Ovato-oblong, slightly con- stricted near the turgid front; dorsal hairs few, the posterior longest ; ova small. 1-340". As before stated, Dujardin places this genus, together with Ichthydium, among the Infusoria (Polygastrica, Ehr.), but in a subclass of them, called symmetrical, along with Coleps and a doubtful genus named Planariola. These genera are distinguished by him from all other Infusoria in having a symmetrical figure. One species of Chaetonotus described by Dujardin is probably new, although it may be, as he remarks, but the C. maazimus of Ehrenberg. The following are its characters:— C. squamatus.-Elongate, narrowed at in a scale-like form toward the base, and its anterior third, but expanded in its regularly imbricated. In long-kept sea- posterior half. 1-130" to 1-135". Co- water brought from Toulouse. wered with short hairs, which are dilated Genus SACCULUS (Gosse) (XL. 17, 18)—One eye, frontal; body desti- tute of hair, and without a foot; rotary organ a simple wreath; alimentary canal very large; jaws set far forward, apparently consisting of two delicate unequal mallei and a slender incus; very evanescent; eggs attached behind after deposition. This genus comes nearest to Glenophora, but, unlike the latter, has but one eye. SACCULUS viridis.-Pear-shaped; flat- tened ventrally, the anterior end the narrower; head comical-pointed, Sur- rounded by a wreath of long cilia; di- estive canal occupying nearly the whole #. and always filled with a substance of a rich green hue in masses. 1-150". This curious animal, found in consider- able number in a little pool on Hamp- stead Heath, must be placed in this Perty’s genus Ascomorpha appears identical with Sacculus. family, according to Ehrenberg's system; but the mode of carrying its eggs indi- cates an affinity with the Brachionaea. The Ascomorpha gemanica of Leydig is identical with the above species. - Mr. Gosse has ascertained that this species is dioecious. XL. 17 represents a newly-born male, and 18 a female with ova attached. Genus GLENOPHORA (XXV. 359).—Eyes two, placed anteriorly; rotary organ frontal, circular; tail bifid, truncated. The alimentary canal is short, thick, and conical; it sometimes contains green matter. The two protruding forceps-like bodies in the middle of the rotary organ may, says Ehrenberg, OF THE CECISTINA, 663 be considered teeth; glands are indicated by knot-like turbid bodies. The eyes are sharply circumscribed, and situated at the frontal region. Dujardin and Leydig believe this genus to be based on young animals, and as such unsatisfactory. GLENOPHORA Trochus. –Ovato-coni- cal, truncated and turgid anteriorly, at- tenuated, posteriorly, with a false foot; the eyes are blackish. It swims quickly, like a Trichoda or free Vorticella. The genera Monolabis and Microcodon have similar forms. (xxv. 359, 360 represent two animalcules, the latter having the stomach filled with a green substance.) 1-570". FAMILY II.—OECISTINA. Rotatoria with a single rotary organ, entire at the margin, and an ex- ternal gelatinous envelope. This family contains only two genera, which possess a more developed internal Organization than any hitherto described. They are further provided, according to Ehrenberg, with loeomotive organs, internal muscular bands, a tail-like foot without terminal pincers; nutritive organs, among which is a crushing apparatus consisting of teeth in rows; two pancreatic glands, and red visual or eye-spots. In Conochilus alone he thinks he observed ganglia with nervous fibrillae, male organs, vessels, and two filiform tremulous organs or gills. This description is of course modified by the views Ehrenberg entertains respecting the various organs contained in the bodies of these animals. We have no evidence that the glands are pancreatic ; the “male organs” are the water-vascular canals of other writers, of which the tremulous organs or gills are external appendages; the “vessels” are muscular bands; and the nervous fibrillae and ganglia have a more than doubtful existence. Special for each animalcule CEcistes. tº it tº tº e º 'º e º tº e º ſº º ſº tº e º 'º tº g º $ tº ſº gº tº e g tº e º e External envelope ... Compound, or common to many animalcules............ Conochilus. Both the OEcistes and Conochilus are included by Leydig in his first division of Rotatorial animals. Genus OECISTES (XXV. 361-364).-Characterized by each animalcule having a separate lorica. The two eyes, situated anteriorly, become effaced as age advances. Ciliary wreath simple and frontal; the long tail-like foot has internal longitudinal muscles. Alimentary canal simple, tubular, con- tracted; stomach elongated; teeth attached in rows to two jaws situated in the pharyngeal bulb, and two glands, compose the apparatus of nutrition. The visual organs are red when the animalcule is young, and colourless in old age. The ovarium has only a single ovum. The envelope is a viscid, gelatinous, cylindrical sheath (urceolus), into which the animalcule can entirely withdraw itself, or which it may quit when a new one is desirable. The attachment to the bottom of the lorica is by the under surface of the end of the foot-like tail. S. CECISTEs crystallinus. – Lorica hya- line, viscid, floccose; body crystalline. The structure it is difficult to see. Each jaw has three distinct teeth. The de- velopment of the young from the egg is interesting to observe : , Ehrenberg saw within the shell two dark points. (eyes) near the already developed jaws; and on giving the egg a gentle pressure it burst, and the free young animal came forth (XXV. 361, a full-grown ani- malcule in the act of unfolding itself; 362, another with its rotary organ ex- panded). . Their sheaths are incrusted, and within may be seen a number of eggs (363, 364 represent them attached 664 systEMATIC IIISTORY OF THE INFUSORIA. to the pectinated leaves of the water- pocket magnifier). Length, with tail, violet, as they appear under a shallow 1-36"; without, 1-140”; lorica. 1-70". Genus CONOCHILUS (XXV. 365-370).—Animalcules social, having con- glomerate and contiguous envelopes; each has two permanent eyes. Only one species is known; its description, therefore, will include that of the genus. CoNocłIILUS Volvoa.—The compound masses white; envelope gelatinous, hya- line, consisting of from ten to forty ani- malcules united so as to form a sphere, which revolves in swimming, like the Volvoa. The frontal region of the ani- malcule is broad, truncated, and Sur- rounded with a wreath of cilia, inter- rupted at the mouth, which is lateral. On the frontal plane arise four thick conical papillae, often furnished with an articulated bristle, especially the two anterior, as seen in xxv. 365, 366, and 368. The oesophagus is short and mar- row; its head, or buib, has jaws, with teeth and four muscles; it lies imme- diately within the mouth. The stomach and rectum are oval. Two spherical glands are observed near the Oesophagus, and posteriorly an ovarium, often con- taining a large ovum, which is expelled near the base of the tail. The ovate or shortly-cylindrical body terminates in a long, thin, and strong cylindrical foot- like tail, the end having a suction-disc. The gelatinous envelope is only percep- tible in coloured water, except when infested with green parasitical Monads; the animalcules can completely withdraw themselves within it, their tails becom- ing thickened and bent. (In the group, xxv. 365–368, the lorica is not shown.) There are no anterior muscles, but three pairs of posterior ones, which disappear near the rotary organ; there are also a back and two lateral pairs. Several transverse bands appear connected with two anterior, lateral, longitudinal ones, which, Ehrenberg states, must arise from a network near the head, as in Hydatina. These are probably muscular. He has also seen two spiral bands, situated pos- teriorly. Two beautiful red visual organs lie immediately beneath the wreath of cilia, and behind them little oval bodies, which he regarded as nervous ganglia, but doubtless erroneously. In the foot- like tail are two large wedge-shaped glands, probably male organs. These creatures will feed upon carmine and indigo, but are mostly filled with a golden-coloured food, (xxv. 370 repre- sents a cluster of animalcules magnified about ten diameters, of which figs. 365– 368 represent a portion highly mag- nified; the first is an under view, the two next dorsal views, and the last a side view, xxv. 369 shows the jaws, teeth, and part of the pharyngeal bulb separate.) Size 1-60"; sphere 1-9". FAMILY III.-MEGALOTROCHAEA. No envelope or lorica. Rotary organ, which is also that of locomotion, simple, incised or flexuose at the margin. Distant muscular bands visible, by means of which the shape of the body can be modified. In Megalotrocha the alimentary canal is provided with two jaws, a stomach, two casca, and two glandular appendages. In Microcodon there are two single-toothed jaws, and a simple canal, without distinct stomach or casca. The ovarium in both genera develope a few large ova, each of which in Megalotrocha, Ehrenberg affirms, after expression, is retained in connexion with the body by means of a thread. Water-vascular canals, with tremulous tags, exist in Megalotrocha ; red eye-spots in both genera indicate a nervous system; and in Megalotrocha a radiating body, supposed to be a cerebral ganglion and to form dark glam- dular (?) spheres, are seen in the neighbourhood of the mouth. Ehrenberg's divisions of the family are given at p. 478 of the General History. - The genera contained in this family are undescribed by Dujardin and Leydig, whilst Siebold only recognizes Megalotrocha. Cyphonautes, instituted by Ehrenberg upon two animalcules found in water from the Baltic, Dujardin OF THE FLOSCULARIEA. 665 considers is a doubtful member of the Rotatorial class; and Leydig suggests that it is probably a larva of some cephalous mollusk. In the propriety of excluding it from amongst the Rotatoria we fully concur. Dujardin and Leydig also transfer Microcodon to another family, regarding its caudal process as being a free articulate foot rather than a contractile attached peduncle. Its affinities are unquestionably with Furcularia, Notommata, and Hydatina, rather than with Megalotrocha. Ehrenberg's description of the ovum of Megalotrocha albo-flavicans con- tains some grave errors. He describes the embryo as developing within the germinal vesicle, and growing at the expense of the surrounding yelk, as is the case with a vertebrate ovum. This is so contrary to what occurs in other Rotifera, in which the entire yelk is directly transmitted into the embryo, that, merely reasoning from analogy, we should be led to reject it. But Kölliker has shown that the embryo of Megalotrocha is developed in the same way as those of other Rotifera. Genus MICROCODON.—Eye single; wreath of cilia simple, bent in the middle so as to resemble the figure 8 lying transversely; alimentary canal thick and straight, without a stomach; no osophageal tube, but a sort of pharyngeal bulb and a couple of single-toothed jaws; also a turgid ovarium. Immediately behind the rotary apparatus is a small red visual organ; and at the frontal region, beside it, is a reddish knot whose function is unknown. MICRoCODON Clavus. – Campanulate, p." the styliform foot-like tail as ong as the body; in the middle of the brow are two bundles of stiff bristles; two pincer-like points, evidently teeth, project out of the middle of the rotary organ, and are in connexion with the reddish jaws. (XXXII. 371 is a back, and fig. 372 a left side view.) 1-280". Perty thinks that the so-called eye consists of two red stripes, beneath which a ribbed body is faintly discernible. Genus MEGALOTROCHA.—Eyes two, sometimes becoming effaced by age; rotary organ has two lappets. The nutritive system consists of a stomach, Caecum, rectum, and Oesophageal head, having two jaws, with teeth, and two glands; reproductive organs, a short knotted ovarium, with a few ova; muscles, three pair anterior, two pair posterior, longitudinal; two con- tractile muscles for the rotary organ, and four obsophageal; eyes frontal, of a red colour when young; four circular transverse muscular bands are also seen. The nature of four opaque white spherical bodies at the base of the rotary organ is unknown. MEGALOTROCHA alboflavicans (Vor- ticella socialis, M.). — White and free when young; yellowish, and attached in or five thus attached, and in process of further º (XXXII. 374– 376 represent different specimens; 377 radiating clusters when old, Ehrenberg states he has often perceived the red eyes within the unbroken egg; and the jaws, as if in the act of chewing, move laterally and horizontally against each other. Two ova are rarely produced at one time; the egg, when expelled from the body, remains attached to it by a thread; and the parent has often four merely the teeth and jaws separate.) Upon water-plants. Size of single ani- malcule 1-36"; of the spheres 1-6." XXIII. 1). M. velata (Gosse).-Animals separate; disc partially enveloped in a cleft, gra- nular integument; eggs not attached to the parent after deposition. 1-55". FAMILY IW.—FLOSCULARIAEA. Rotatoria surrounded by a case or envelope, and provided with a single rotary organ, flexuose at its margin and lobed or divided, having from two to 666 SYSTEMATIC HISTORY OF THE INFUSORIA, six clefts. In some genera the cilia of this organ are quiescent at intervals, not vibrating continuously; the alimentary canal is complex, usually divided transversely into several segments, and with various external appendages, believed to be glandular, the proventricular segment, gizzard, or pharyngeal bulb furnished with teeth. Lacinularia has a mouth, Oesophagus, pharyngeal bulb with teeth, a stomach constricted into three segments, and a short intestine ; the lower stomach clothed internally with a very long cilia. Melicerta has a similar arrangement, but with only two unequal segments in the stomach, both of which are ciliated interiorly. Two water-vascular canals arise from a contractile Sac opening into the cloaca, and pass upwards, one on each side of the alimentary canal to the head, where, in Lacinularia, they ramify into a network; along their course they have appended to them small tags or sacs, each containing a large vibratile cilium. These have been seen in Lacinularia, Melicerta, and Stephanoceros. In Lacinwlaria, Limnias, and Melicerta, a small lobate mass exists near the mouth, believed by Huxley to be a cerebral ganglion. Leydig assigns nervous functions to small bodies distributed through Lacinularia; but these appear to be merely the small stellate masses of viscid protoplasm described by Williamson in Melicerta, and Leydig in Stéphanoceros. Eyes exist in all the genera, except Tubico- laria, at Some stage of life. In Melicerta and Lacinularia they disappear as the animal approaches adult life. Gosse says that the same is usually the case in Floscularia, but that he has occasionally met with adult specimens in which eyes were present. Some species (if not all) have well-marked fasciculi of voluntary muscular fibre, especially running parallel to the long axis of the body, which their contraction shortens. Male reproductive organs hitherto unobserved. Female organs an ovisac composed of thin transparent mem— brane, distended with granular protoplasm, in which are distributed cells or germinal vesicles, each containing a nucleus or germinal spot. In Melicerta this ovarium communicates with the cloaca by means of an oviduct. Some species produce two classes of eggs, one being probably the true ovum, the other an encased gemma or bud. Several species retain the eggs within the envelope of the parent until the young are hatched; others set them free at an early stage of embryonic development. Ehrenberg's arrangement of the genera of this family will be found at p. 478 of the General History. Eyes present ........................................................................ Tubicolaria. One eye present (when young) ................................................... Stephanoceros. / Envelope of the single *] Limnias. Rotary organ two-parted cules distinct or separated... Cephalosiphon. Two º when full-grown......... Envelope of the single animal-l Lacinular: presen 4 cules conglomerated ......... 8,Oll llllalºla. (when young). Rotary organ four-parted when full grown .................. Melicerta. U Rotary organ five- to six-parted when full-grown ............ Floscularia. Dujardin has a family of “Flosculariens,” which, however, differs much from that of Ehrenberg, both in its distinctive characters and in the species assigned to it. The French naturalist includes only two genera, viz. Flos- cularia and Stephanoceros. Contrary to Ehrenberg's assertion, these two genera are stated by Dujardin to be destitute of a rotary organ, and indeed of vibratile cilia, and are described as having a campanulate, contractile OF THE FLOSCULARIAEA. 667 body, tapering towards the base so as to form a long pedicle, by which they affix themselves to solid bodies. Their mouths are furnished with horny jaws. Speaking of their affinities, he remarks, “The Flosculariens, like the Meli- certiens, also have a certain affinity in form with the Worticelliens and the Stentors, and also with the Campanulariae among polypes. They live in the same way, fixed to water-plants by the pedicle of their campanulate body, the margin of which presents five or six lobes, terminated by appendages or cilia, without, however, any indication of a vibratile movement. At the bottom of this wide opening is situated the mouth, provided with jaws attached to a muscular bulb, less frequent and regular in its movements than the other Rotatoria. In Floscularia the jaws are simple, and the lobes of the (anterior) margin short, but with long radiating cilia; whilst in Stéphanoceros the jaws are compound, and the marginal lobes very long and covered with short cilia.” Dujardin states further, that the gelatinous case of Floscularia may disappear, and therefore cannot be used as a generic distinction, either in the case of that genus or indeed of the other genera included in Ehrenberg’s family of the same name. Entertaining this opinion of the differences of the gelatinous envelope being accidental, not constant, Dujardin rejects the genus Limnias as not distinct from Lacinularia, whilst he denies that the latter is generically distinct from Megalotrocha—a conclusion in which Huxley is dis- posed to agree with the French naturalist. Of the remaining genera of Ehrenberg’s family Flosculariaea, viz. Tubicolaria, Lacinularia, and Melicerta, to which he adds Ptygura, already described, Dujardin constitutes a family which he terms Melicertiens. In some of these objections there is force. Floscularia and Stephanoceros undoubtedly differ from the remaining genera in the form assumed by ciliated appendages supposed to represent the trochal disk of Melicerta and Lacinularia. Gosse states that in Floscularia rotation is accomplished, not by the tufts of long setae, but by cilia set on the inner surface of the disk, which cause the currents to converge to the mouth of the animal; hence, if the setigerous bulbs of Floscularia and the ciliated arms of Stephanoceros are not the homologues of the true trochal disks of Melicerta, the propriety of Ehrenberg's definitions is seriously impaired. But we see no reason for rejecting this homology in the case of Stéphanoceros merely because the motion of the verticillate cilia is periodic and interrupted instead of continuous: and if Mr. Gosse is correct in his conception respecting Floscw- laria, it is equally entitled to its present place; for whilst, on the one hand, it is not essential to a trochal disk that its moving cilia should be arranged at its margin, on the other, these cilia do not exclude the possibility of other appendages, such as the pencils of setae in Floscularia, being attached to the same organ, though such appendages may have no homologues amongst the other Floscularian genera. Dujardin’s objection respecting the gelatinous case of Floscularia is probably based on error. Mr. Gosse has shown that in some cases it is so thin that it might easily be overlooked, without great care being taken to discover it. Leydig of course rejects Ehrenberg’s family of Floscularia, arranging the animals composing it in his first group, along with OEcistes and Conochilus, with which they have unquestionably a very close affinity. The creatures composing this family are undoubtedly among the most interesting and beautiful of Infusorial animals. Their developed organiza– tion, and singular habits, render them objects of the highest interest, both to the naturalist and the physiologist; whilst their exquisitely beautiful contour and the magnificent phenomena presented by the trochal cilia when in active rotation, never fail to impress even the most careless of observers with a sense of wonder and delight. 668 SYSTEMATIC HISTORY OF TELE INFUSORIA. Genus TUBICOLARIA (XXXII. 379–382). — Figure clavate, with a transparent gelatinous case. Rotary organ deeply fissured on the abdominal aspect, and less strongly on the dorsal side, by which it is divided into two lappets, each of which is again partially subdivided into two. Ciliary wreath double, with a space between the rows. Mouth opening directly into the osophageal bulb, in front of which is a small vesicular organ filled with pale- reddish matter. Stomach long, with thick cellular walls and four glandular organs surrounding its upper extremity. Intestine thin and clear, curving slightly forward towards the anus. Two water-vascular canals extend along the body, apparently forming a network at the head, and bearing a couple of vibratile tags. No contractile vesicle observed at their cloacal extremity. Foot, by means of which it adheres to foreign bodies, terminated by a bundle of cilia. Two tentacles extend from the abdominal surface, a little below the mouth; each has a clear fibrous-looking tract along its centre, and is terminated by a bundle of setae. Embryo with the gelatinous sheath colour- less, but acquiring consistency and a yellowish hue with advancing age. There is a small concretionary mass, apparently surrounded by a sac, affirmed by some to be urinary, in the body of the embryo. - TUBICOLARIA Najas.-The jaws have with those of the following genus; fig. four teeth; and the tactile tubes are hairy | 379 represents an animalcule within its anteriorly. This animal is described fully case, the rotary organ withdrawn; fig. in the account of the genus; and XXXII. 380, another extended, and without its 378–382 will illustrate it. 381 represents | lorica; fig. 382, the oesophagus, with the the animals of natural size, as found at- jaws and teeth separate, 1-36". tached to the roots of Lemma polyrrhiza, Genus STEPHANOCEROS (XXXII, 383; XXXVII. 1–4). — Figure clavate, with five long arms at its anterior extremity, surrounded by verticils of cilia. Sheath without parallel sides and with strong parallel folds or curves; either crystalline without any foreign admixture, or sometimes over- spread with small linear bodies like small dead Vibrios or Microglence. It apparently is not tubular, but a solid gelatinous mass envelopes the animal as high up as the base of the rotary arms. Acetic acid renders it white, and nitric acid renders its outline more clear. Beneath the cuticle is a granular layer containing nucleated cells. The cilia of the arms appear planted in a granular stratum external to the cuticle, from which they are detached in bundles when subjected to slight pressure. A deep transverse fold of the integument exists at the base of the rotary organ, and contraction, throws the peduncle into corresponding-folds. Between the skin and the viscera are numerous branching corpuscles resembling cells of connective tissue. These cells correspond with what were described by Professor Williamson in Meli– certa ringens. They look like Small globules of ductile protoplasm, and closely resemble the ductile bands seen in Noctiluca miliaris. It is not impossible that these may really be some unchanged remains of the protoplasm of the ovum, which they closely resemble. Four long muscles, contained in sarco- lemmata or sheaths, proceed from the foot anteriorly, branching dichotomously. Alimentary canal composed of a funnel-like oral cavity, opening into a still wider proventriculus having an intermediate septum and four long bristles with hooked extremities, then a globular maxillary bulb, conducting to a special stomach, which terminates in a short intestine. The oral cavity is lined with fine cilia; and the proventriculus consists of two membrancs, not in close contact, but with a narrow intermediate space. The maxillary teeth, the liming of the maxillary bulbs, and the oesophageal bristles resist the action of liquor potassae, indicating a chitinous composition. The walls of the OF TEIE FLOSCULARIAEA. 669 stomach have a thick layer of large cells filled with yellow granules or fat- corpuscles. Intestine transparent and ciliated internally. A contractile Sac connected with the cloaca, from which spring two broad water-vascular canals, which are lost anteriorly in front of a fatty mass surrounding the proventriculus. Ovarium developing but few ova at a time; these, when discharged from the ovary, are still seen to be enclosed in a membranous Oviduct, extending from the ovary to the cloaca. No male organ hitherto discovered. * Immediately above the proventriculus is a large collection of hyaline vesicles, which evidently open externally by a short duct. A dark granular vesicle appears at the posterior end of the body of the embryo, as in Tubico- laria and Melicerta, supposed by some authors, but without sufficient reason, to be a urinary concretion. Two eye-specks at the opposite extremity of the embryo. Two vibratile spaces also appear simultaneously, the one in front of the other. The vibratile action is active within the anterior one, whilst within the other a few long cilia undulate slowly. When the embryo is first distinguishable, and separable from the egg, it has a vermiform figure, and is about 124 millimetres in length. The head, supporting the eyes, is separated from the body by a constriction; its margin is furnished with numerous cilia, the whole being retractile. Within the body and behind the head are several longitudinal stripes of a doubtful nature; and still more posteriorly is a clear space with some long cilia in action, which may represent the alimentary cavity; the maxillary jaws are perceptible, and the posterior extremity furnished with some cilia. On one occasion Leydig met with another form of embryo, which retained the vermi- form aspect in its body and foot, but with the former elongated, and termi- nated by four arms. Two eye-specks present, and a proboscis in front, with two extended tubular processes terminated by cilia. Extremity of the foot devoid of cilia. The maxillae were fully developed; and, near the sac with the dark granular concretions, ciliary vibration was discernible. Leydig thinks that the dark granules of the sac escape into the cloaca, and regards them as urinary concretions accumulated in the extremity of the intestine. Cohn rejects the idea that they so escape; and we believe him to be correct on this point. The granules are affected by potash, but not by acetic acid. STEPHANOCEROS Eichhorni (XXXII. XXXII.383, the eye and tags arevisible, and 383; XXXVII. 1–4). —The case transpa- over the latter what Ehrenberg calls gan- rent, like glass; rotary organ with five glia. The case is discerned with difficulty, lobes or arms, each furnished with fifteen from its very transparent nature, unless verticils of cilia; these arms act occasion- indigo is mixed with the water. 1-36". ally as prehensile instruments. As the S. glacialis.-Only one specimen seen eggs are detained in the case until the without its stem. The five arms not youngarehatched, Ehrenbergerroneously furnished with ciliary whorls, but with considers this creature viviparous. In single bristles. 1-14". The internal organization of Stéphanocerosis well illustrated in XXXVII. 1: b is the pharyngeal bulb, resting upon a proventriculus or crop c, below which is the maxillary bulb d, containing the jaws; e is the stomach, with its large cells; whilst f is the intestine, terminating at the cloaca ; g is the ovary containing ova; k indicates delicate longitudinal muscles, extending down the peduncle; and t t the water-vascular canals with their vibratile tags. in fig. 2 the detached ovary is represented, consisting, as is usual amongst the Rotatoria, of a delicate membranous Sac, f, prolonged into an oviduct. The contained ova are seen in different stages of development. At a is the stroma or granular mass, with its germs; b is an ovum in the first stage of 670 SYSTEMATIC HISTORY OF THDE INFUSORIA. fission; at c the ovum has undergone several repetitions of the yelk-division; and at d is an ovum in which the contour of the embryo is visible. The two eye-spots seen at d, and the so-called dark urinary concretion, seen also in embryonic Melicertae and others, at k. The real nature of this last object, which is seen only in the embryonic state of these animals, is yet doubtful. Fig. 3 represents a very young Stephanoceros a little after its liberation from the ovum; and fig. 4 another immediately after its liberation from its shell. The dorsal aspect of the jaws of the maxillary bulb, according to Mr. Gosse, is represented in XL. 27, and the oblique aspect of the incus in XL. 28. Genus LIMNLAS (XXXII. 388–392; XXXVI. 2). — Eyes two ; case (urceolus) solitary; rotary organ two-lobed when fully grown, being then constricted in the middle ; alimentary canal simple, terminating at the base of the foot or tail; stomach, two jaws with teeth, and two glands also present. The ova are deposited within the case, where they are developed; neither male organs nor water-vascular canals discovered; two visual organs indicate Sensation: these in the young animalcules are red, and are even visible within the ovum; but in old age the colour disappears, and hence they are not seen. In the middle of the rotary organ, when expanded, are seen four large globules, which Ehrenberg erroneously considers nervous ganglia, or brain. LIMNIAS Ceratophylli (XXXII. 888–392; xxxvi. 2).--Case white at first, after- wards brown or blackish; Smooth, but, being viscid, often covered with extra- neous particles; its connexion with the animalcule is a voluntary act of the latter; the two red eyes and the jaws may be observed in the ova when de- veloped; by giving the latter a gentle pressure the shell bursts. XXXII, 389 exhibits an animalcule just emerged from the egg, 392; 391 a young specimen, with a rotary organ nearly circular, and two eyes; 390 a full-grown specimen, without its case, fed on indigo—the jaws (each of which has three strong teeth), the ova, and the traces of lon- gitudinal muscles are seen, the wheel is folded up; 388 another, within its case, having the lobed rotary organ ex- Fº (XXXVI. 2, is more magnified, Found upon hornwort (Ceratophyllum and other aquatic plants. Length about 1–20"; case 1-40". L. annulatus (Bailey). — The case is ribbed and semitransparent, and is com- posed of a linear series of rings. Found in a ditch at Witlingham, near Norwich, on duck weed (Brightwell); and by Dr. Bailey near New York, U.S. Genus CEPHALOSIPHON.—Rotary organ bilobed; eyes two; sheath single ; two frontal horns, including the siphon. CEPHALOSIPHON Limnias.-Sheath membranous, annulate, 1–6" to 1-5". Ceratophyllum. Berlin, July. On Genus LACINULARIA (XXXVII. 19–25). —Eyes two (in the young state); the cases (urceoli) conglomerate, or grown together; rotary organ two-lobed when full-grown, but nearly circular when young: this organ is the chief instrument of locomotion. Band-like longitudinal muscles exist within the body. Pharyngeal bulb large, with two jaws, and teeth in rows; Oesophagus short, narrow ; stomach elongated, transversely constricted, and with cascal (?) appendages; short. The ovarium is situate about the middle of the body, and opens, along with the intestine and the contractile sac of the water-vascular canals, into the caecum. Visual organs exist in the young state; red in the developed ovum, but becoming darker as they advance to maturity. Globular bodies Support the Oesophagus on each side; and below the mouth is a small organ, supposed to be the brain. OF THE FLOSCULARIAEA, 671 LACINULARIA socialis (Vorticella So- cialis et flosculosa, M.) (XXXVII. 19).-- Envelope gelatinous, transparent, in which are implanted numerous indivi- dual animals, that have unitedly thrown out the gelatinous secretion in which they are imbedded. Body elongated, co- nical peduncle (XXXVII, 19%) truncated and forming at its posterior extremity a sucker, attaching the animal to the foreign object supporting the entire group. Trochal disc at the anterior ex- tremity of the body, into which it is drawn when at rest (XXXVII. 19 a), but expanding into a horseshoe-shape, with a double row of cilia round its margin. Mouth in the notch of the trochal disk. Pharynx leading to a pharyngeal bulb (19 b), in which the jaws are planted, These are not stirrup-shaped, as described by Ehrenberg, but composed of four pieces (xxxvii. 20). CEsophagus passing through the bulb reaches the first sto- mach (19 c), into which two cellular appendages, regarded by Ehrenberg as pancreatic, open. Below this is a second dilation (1973), furnished with several short cellular caeca, and still lower a third, more globular segment (19 e), also furnished with external cellular caeca, and clothed internally with long cilia. From this a short intestime, ac- cording to Huxley, turns upwards, and outwards, terminating in a cleft of the integument on the same side as the mouth. This “intestine’’ is probably the cloaca of other writers. Two water- vascular canals (19?) arise, one on each side of the intestine (cloaca), and ascend on opposite sides of the body towards the head. They divide opposite the pha- ryngeal bulb, each into three branches, one of these uniting with its fellow, the others terminating as cæca; within these are distributed five pairs of long vibratile cilia. Vacuolar thickenings of the in- tegument exist, in several parts of the body. A small ciliated sac is located below the mouth, and still lower is a small organ believed by Prof. Huxley to be the cerebral ganglion. Two eye-spots occur on the trochal disc of the young animal (XXXVII. 11), but they disappear in the adult. No male reproductive organ hitherto discovered. Prof. Hux- ley's description of the female organs, and the development of the ova, is as follows:—“The ovary consists of a pale, slightly granular mass, of a transversely elongated form (19 h), and somewhat bent round the intestine; it is enclosed in a delicate transparent membrane, which is hardly visible in the unaltered state, but becomes very obvious by the action of acetic acid, which contracts the substance of the ovary and throws the membrane into sharp folds.” Pale clear spaces (xxxvii. 7), which sometimes seem to be limited by a distinct membrane, are scattered through the substance of the ovary; and in each of these a pale circular nucleus is contained. The nucleus is more or less opaque, but usually contains from one to three clear spots. These are the germinal vesicles and spots of the future ova. Acetic acid, in contracting the pale substance, groups it round these vesicles, without, how- ever, breaking it up into separate masses. It renders the nuclei more evident. The ova are developed thus:–One of the vesicles increases in size; and reddish elementary granules appear in the ho- mogeneous substance around it. This accumulation increases until the ovum stands out from the surface of the ovary, but invested by its membrane, which, as the ovum becomes separated, takes the place of a vitelline membrane. In the meanwhile the germinal ve- sicle has increased in size; and its nu- cleus is no longer visible. In the ovum it appears as a clear space; isolated by crushing the Oyum, it is a transparent, colourless vesicle. The perfect ova are oval, about 1-10" in diameter, and are extruded by the parent into the gela- tinous connecting substance, where they undergo their development. - The changes that take place after ex- trusion, or even to some extent within the parent, are—1, the disappearance of the germinal vesicle (as Huxley judged from one or two ova in which he couldfind none); 2, the total division of the yellº (as described by Kölliker in Megalotrocha), until the embryo is a mere mass of cells (XXXVII. 5, 6, 8, 9), from which the va- rious organs of the foetus are developed. The youngest foetuses are about 1-70" in length. The head abruptly trun- cated (XXXVII. 10), and separated by a constriction from the body. A sudden narrowing separates the other extremity of the body from the *. which is exceedingly short, and provided with a ciliated cavity (a sort of sucker) at its extremity. The head is nearly circular, seen from above, and presents a central protuberance, in which the eye-spots are situated. The margins of this protu- berance are provided with long cilia, which will become the upper circlet of cilia in the adult. In young Lacinularia, 672 SYSTEMATIC HISTORY OF TEIE INTFUSORIA. 1–30" in length, the head has become triangular (XXXVII. 11), and thus it gra- dually takes on the perfect form. The young had previously crept about in the gelatinous investment of the parents; they now begin to “swarm,” uniting together by their caudal extremities, and are readily pressed out as free-swimming colonies, resembling in this state the genus Conochilus (Huxley). But, besides the ova whose development is thus de- scribed, Professor #. observed a second class, to which he refers as fol- lows:– “In a fully-grown Lacinularia which has produced ova, the ovary, or a large portion of it, begins to assume a blackish tint (XXXVII. 22); the cells, with their nuclei, undergo no change, but a deposit of strongly refracting . *º- mentary granules takes place in the pale connecting substance. Every transition may be traced, from the deep black por- tions to unaltered spots of the ovarium; and pressure always renders the cells with their nuclei visible amongst the granules. The investing membrane of the ovary becomes separated from the dark mass, so as to leave a space; and the outer surface of the mass invests itself with a thick reddish membrane (XXXVII, 24), which is rough, elastic, and reticulated from the presence of many minute aper- tures. This membrane is soluble in both hot nitric acid and caustic potass. The nuclei and cells, or rather the clear spaces indicating them, are still visible upon }. and may be readily seen by ursting the outer coat. By degrees the ephippial ovum becomes lighter, until at last its colour is reddish-brown, like that of ordinary ova; but its contents are now seen to be divided into two masses, hemi- spherical from mutual contact (f: 21). If this body be now crushed, it will be found that an inner structureless membrane exists within the first-stated membrane, and sends a partition inwards at the line of demarcation of the two masses. The contents are precisely the same as before, viz. nuclei and elementary granules. I was unable to trace the development of these ephippial ova any further.” Professor Huxley thus indicates his belief in the existence of two classes of ova in Lacinularia, one of which he thinks probably requires sexual fecunda- tion, whilst the others do not. Cohn believes that the bodies usually termed ova by Huxley and others are not so, but internal gemmae. Genus MELICERTA (XXXII. 386,387; XXXVI. 1; XXXVII. 12–18). —With a case or envelope; solitary; rotary organ simple, with four lobes when expanded; free longitudinal muscles for the contractions of the body; alimentary canal divided into segments, in one of which (the pharyngeal bulb) are complex jaws; mouth situate at the bottom of the cleft between the two larger lobes of the rotary organ; the orifice of the cloaca near the junction of the long peduncle with the body. Male generative organization unknown; believed by Mr. Gosse to be dioecious. Female organs a large ovary filled, with granular protoplasm and germinal vesicles, as in the pre- ceding genus, but with a distinct Oviduct opening into the cloaca. Two Water-vascular canals, arising from a contractile vesicle, ascend towards the head. Two tactile appendages, with setigerous extremities, on each side the head. Two eye-spots in the young animal. MELICERTA ringens. – Case (XXXVI. 1 d) conical, granulated, resembling a honey-comb, of a brownish-red colour; it is composed of small lenticular bodies, secreted and deposited by the animalcule; these are agglutinated by a peculiar viscid matter, afterwards hardened in the water. Into this tube the soft cry- stalline or whitish animalcule can with- draw itself; and when its flower-like wheel-work (la) is expanded, the vibra- tile cilia appear to run along the margin of this organ; but, in fact, each single cilium only turns itself upon its base, their aggre- gate motion causing a little whirlpool in Nervous system uncertain. the water, directed towards the mouth, which is situated in the middle of the two large leaflets of the rotary organ; the eyes in the young animal are placed near the two other bent leaflets, which, according to Ehrenberg, are analogous to a cleft . lip of the dorsal surface: the dis- charging orifice is on the same side; and therefore the dorsal tail-like portion be- comes a ventral member or foot, (XXXII. 386, an animalcule within its case, having the rotary organ contracted; fig. 387, with the trochal disc fully expanded: the case is given in outline only, in order to show the internal structure.) On Lemma: OF THE FLOSCULARIAEA, 673 and other aquatic plants. Length 1-12"; case 1-24"; egg 1-150". The pellets forming the case were thought by Ehrenberg and others to be deposited from the cloacal orifice; but, from the careful researches of Mr. Gosse, this appears to be an error (Trans, Microsc. Soc. 1851, vol. iii. part. ii. p. 62). That observer points out the existence of a special rotating organ of a cup-like figure (XXXVI. 1 c) (the disc seen above), seated immediately above the projecting tube. This organ he saw fill and empty itself “many times in succession, until a goodly array of dark pellets were laid” down irregularly, the animal effecting their distribution by bending its head downward, so as to bring this cup and the margin of its sheath into apposition, “After a certain Uumber were deposited in one part, the animal would suddenly turn itself round in its case and deposit some in another part. It took from two and a half to three and a half minutes to make and deposit a pellet.” Coloured particles in the water “are hurled round the margin of the ciliated disc, until they pass off in front through the great sinus between the large petals;” and the atoms, if few, “glide along the facial surface, following the irregularities of the out- line with great precision, dash round the projecting chim, and lodge themselves one after another in the little cup-like receptacle beneath,” in which again they are whirled round with great rapidity, and pººl into º for the building up of the case of the animal. The internal organization of this ani- mal has been investigated by Professor Williamson. Like Lacinularia, the tro- chal disc is double at its margin, with two rows of rotary cilia, the currents created by which are directed to the mouth and pass off by the ciliated “chin” —a small additional lobe above the cili- ated cup of Mr. Gosse. On each side of the trochal head are two hollow pro- cesses or “calcars” — the respiratory tubes of Ehrenberg, but which are pro- bably tactile (XXXVII. 17 d). These ter- minate externally in a deltoid body (13), from which projects a pencil of straight setae. Along the interior of this tube is a delicate muscular band, by which the setigerous extremity can be drawn back- wards into the tube (14), and the setae thus be removed out of danger. The alimentary canal much resembles that of Lacinularia. There is a narrow ocso- phagus conducting downwards to the pharyngeal bulb (figs. 17 e and 23), in which are implanted the peculiar jaws: these are complex (f. 26), consisting of equilateral sets of numerous transverse bars, those of each set connected at their peripheral extremities by an arcuate lon- gitudinal one, and at their inner extre- mities by a double broad longitudinal One prolonged upwards into a long nar- row handle or process which meets its fellow of the opposite side at a kind of hinge-like joint. These jaws work upon one another with a crushing motion by means of the above joint, the upper part of the alimentary canal, and consequently the food swallowed, passing between them. Below the pharyngeal bulb is an oblong stomach, with cellular parietes and lined with cilia. A constriction separates this from a lower and more spherical portion (17 g), also cellular and lined with still longer cilia. This opens into a long cloaca (17 k), which turns suddenly upwards to its terminal outlet (17?). The interior of the body contains numerous free muscular bands. These are especially distinct in the pe- duncle, along the entire length of which several of them run, which shorten the body in its axial line. Each fasci- culus consists of transversely striped or voluntary muscular fibre, and is enclosed in a sarcolemma or membranous sheath (18). Diffused through the body of the animal, but specially #. at the up- per part of j. peduncle, are numerous small masses of viscid granular proto- plasmic substance, which send slender prolongations to each other and to the surrounding parts, reminding the ob- server of the pseudopodia of the Rhi- zopods and the internal threads of Noctiluca. The water-vascular system consists of two canals arising from a small pyriform contractile vesicle below the stomach, and apparently with the cloaca. One ascends on each side of the alimentary canal towards the head, where they branch. Vibratile tags are connected with them. Professor Williamson describes the ovary as “a hollow sac (xxxvii. 23%), consisting of a verythin pellucid mem- brane. It is filled with a viscid granular protoplasm of a light grey colour, in which are distributed from twenty to thirty nuclei, each having a diameter of from 1-1200" to 1-1600". Each nucleus contains a large nucleolus, varying in diameter from 1-1600" to 1-3500". In its normal state the granular protoplasm is of a uniform grey colour, flowing 2 x 674 SYSTEMATIC EIISTORY OF TEIE INFUSORIA. freely out of the ovary when the latter is ruptured. The nuclei situated nearest the centre of the ovary appear to be successively selected for development. One of these nearest the surface attracts around itself a small portion of the gra- nular protoplasm, detaching it from the remaining contents of the organ, though in close contact with them. The portion thus specially isolated gradually enlarges, assuming at the same time a darker hue, whilst, from its central position, it par- tially divides the upper from the lower half of the remaining ovarian protoplasm. At the same time the central nucleus sometimes undergoes some slight en- largement, and its nucleolus appears to become absorbed. The position of this nucleus in the centre of the ovum is now indicated by an ill-defined trans- parent spot; but on bursting the proto- plasmic mass, it is seen to be a small spherical cell about 1-1000" in diameter, having very thin pellucid walls and scarcely any visible cell-contents. When the ovum thus segmented from the ova- rian protoplasm has attained its full size (XXXVII. 17 oy, it becomes invested by a thin shell, which is apparently a secre- tion from its own surface.” “The ovum being now ready for ex- ulsion, it is slowly forced down to the ower part of the ovary, the stomachs being drawn upwards and to one side in order to make way for it. Yielding to the pressure produced by the successive contractions of the body, the ovum sweeps round the inferior border of the lower stomach, and, passing through the dilated oviduct, enters the cloaca. The latter canals become entirely everted, as is the case when the excrements are dis- charged; and by a sudden contraction the ovum is expelled.” Professor Williamson minutely de- scribes the conversion of the yelk into an embryo —the successive segmenta- tions of the nucleus, and surrounding yelk, until the whole becomes a cellular mass, as in Lacinularia. The first visible evidence of life is the production of a few moving cilia, especially near the future head, followed first by traces of the dental apparatus, then by the de- velopment of the various organs, in- cluding the two eye-spots, soon after which the young animal escapes from its shell. “Almost immediately after its escape from the egg, the young Melicerta stretches itself out, and, everting the anterior part of its body, unfolds several Small projecting mamillae (XXXVII. 16), covered with large cilia, by means of which it floats freely away. The ciliated mamillae at this stage of growth are not unlike those seen in Notommata clavu- lata, but they soon enlarge and become developed into the flabelliform wheel- organs of the matured animal.” In this stage all the organs of the perfect animal are present, showing that the creature passes through no larval form, and that it is not identical with the Plygura, as Ehr- enberg and others have thought. After swimming about some time, a dark- brown spot disappears from the posterior part of the body, followed by the eye- specks, when, the same writer adds, “the animal attaches itself by the tail to some fixed support, and developes from the skin of the posterior portion of its body a thin hyaline cylinder, the dilated extremity of which is attached to the supporting object. This structure has already been noticed by Dr. Mantell (Thoughts on Ani- malcules), though I have never seen it so largely developed as is represented in his figures. The young animal, having chosen a permanent resting-place, com- mences the formation of its singular investing case. I have verified Dr. Man- tell's account of the position occupied by the first-formed spheres. They are arranged in a ring round the middle of the body (xxxvii. 15), and are for some time unattached to the leaf or stem which supports the animal. They appear to have some internal connexion with the thin membranous cylinder. At first new additions are made to both extre- mities of the enlarging ring; but the jerking constrictions of the animal at length force the caudal end of the cylin- der down upon the leaf, to which it becomes securely cemented by the same viscous secretion as causes the little spheres to cohere.” “When the ova are discharged from the cloaca, they succes- sively fall into the cavity of the tessel- lated case, where they undergo develop- ment. I have often found as many as four in one case in various stages of progress. It is whilst the eggs are thus protected that the young animals burst their shells, swimming out at the free extremity of the case as soon as they are liberated.” Genus FLOSCULARIA (XXXII. 384, 385; and woodcuts). These crea- tures possess when young two eye-spots. Several lobes surround the head, Ö F THE FLOSCULARIAEA. 675 each surmounted by a pencil of long setae. These lobes are regarded by Ehrenberg as the rotary organ; but, according to Gosse, the upper surface of the central disc fulfils the rotatory functions. Body furnished with a long peduncle, by which the animal is fixed, and the whole surrounded by a thin diaphanous case resembling that seen in the very young Melicerta. From its transparency this can often be detected only by colouring the water with some pigment. Alimentary canal simple, conical. system resembling that of Lacinularia. Reproductive Ova deposited within the case. When viewed from above, the head of the animal resembles an Acineta. FLOSCULARIA proboscidea.—Case cy- lindrical, hyaline, gelatinous. Setigerous lobes six, with short cilia surrounding a ciliated flexible proboscis, which appears to have an opening at its extremity. Dujardin #. this proboscis may be nothing more than one of the ciliated lobes advanced towards the centre. Body ovate, with a long styliform peduncle attached to the base of the case; when extended, the body and part of the foot are protruded. Found upon the leaves of Hottonia palustris. Length when ex- tended 1-18"; case 1-36". F. ornata (Cercaria, M.) (XXXII. 384, 385).-Case or envelope hyaline; very thin at its upper extremity; thicker, and often with foreign bodies entangled in it inferiorly. It is sometimes very slug- gish, but at others moves with consider- able activity, often contracting itself very quickly within its case. The setigerous lobes, according to Gosse, are not the true rotatory organs: “yet,” he says, “there is a rotatory organ — the par- ticles of floating matter revolving in a perpendicular oval within the mouth of the disc. Hence I conclude that the rotatory cilia are set on the inner surface of the disc.” He further adds: “When the pencil of united tufts is in process of expansion the hairs have a wavy, quivering sort of motion, but when ex- pºnded they remain perfectly motionless. The two red eyes seen in the young animal ordinarily disappear in the adult; but Mr. Gosse has occasionally met with such specimens in which they were still pºly visible. He has observed the ody “to be lined with a yellowish vascular membrane, which does not ex- tend up to the petals, but terminates at the neck with a free, very mobile edge, forming an irregular opening, the out- line of which is constantly changing by the contraction and expansion of the membrane. The opacity of this lining renders it difficult to resolve the viscera.” “Ehrenberg speaks of an oesophageal head above the jaws; but I can see nothing of the kind, and am inclined to think he may have mistaken the ever- contracting opening of the lining mem- brane for one.” These animals are very fond of Chlamidomonas; and when swal- lowing large bodies, such as Naviculae, they contract the entire body. Ehr- enberg has numbered as many as five ova retained within the diaphanous case at the same time. Gosse once counted nine. These, as is also the case in Meli- certa, are generally in different stages of development, — in some the per- fectly-formed embryo being distinctly visible, its movements and its two red eyes being very manifest. With a mo- derate pressure Ehrenberg burst the shell, which, according to Gosse, is calcareous: the young animal crawled out with a slight vibratory motion; the cilia were short and not very distinct. In the mature animal the peduncle is truncate at its extremity. Upon Ceratophyllum and similar plants. I-108". In XL. 25 the dorsal aspect of the jaws is repre- sented, and in 26 their frontal aspect. Dr. Dobie writes (A. N. H. Oct. 1849): “Ehrenberg regards the Floscularia de- scribed . figured by M. Peltier, as identical with his F. ornata. Both Du- jardin and Peltier found the rotary organ five-lobed in the species observed in France; so we must either hold with Pritchard that F. ornata has sometimes five, at others six lobes, or consider the five-lobed species a variety of F. ornata. . . . . Myfriend Mr. Hallet writes me that he finds F. ornata with a six-lobed ro- tary organ and no process.” The two next species and accompanying remarks are taken from a paper by Dr. W. M. Dobie (A. N. H. Oct. 1849). F. campanulata. — Case diaphanous, fringed with very long cilia; body ovate, rotary organ with five flattened lobes, without proboscis; tail long, and termiº 2 X 2 676 SYSTEMATIC EIISTORY OF TEIE INFUSORIA. mating abruptly in a transparent fila- ment, spread out in a kind of sucker at the point of attachment. Length 1-50"when extended. Egg with two red eye-spots; contained in a large ovary. Found near Chester, on Ceratophyllum and Confervae. sº F. cornuta.-Case short, diaphanous, not very distinct; rotary organ furnished \ | \ A. Y. *\ N s *^ * R * § § Sº § º º § §§ } § tº: Š [. §§ >%§ # & º ū &- §º § wº $#º # § º-- § ss :: *§ º .* § - -: :===" sº •º t ſ ''}<ºs:::::=s**E======- with five rounded lobes, surrounded by extremely long and delicate cilia: a short, narrow, non-ciliated, flexible process (cornu) is attached to the outside of one of the lobes. Egg with two red eye- spots; young animal with vibratile cilia on the head, and rapidly locomotive. Length 1-40" when extended. In same locality as the preceding (see woodcuts), \ WN ^ Nº N wVº v. NNN \, \\ N y } º :S ^* -- x-ºf | s y | |" º º \\\\\ºllºws,' ſ º * \ſ \! ". . * sº S \, º s §§ \ S. * º º ºWºº \\ s W. 3 § §§ ſº §§§ s * ! Floscularia cornuta, Dobie. The lobes of the rotary organ of F. cornuta resemble very much those of F. ornata, but only five exist, while in the other there are six. According to Ehrenberg the F campanulata is gre- garious, whilst F. cornuta is solitary; the former is also stronger and is more active than the latter. Leydig has described a Foscularia under the name of F appendiculata º für wissenschaftliche Zoologie, July 1854). Mr. Gosse, however, believes this to be identical with the F. cornuta of Dr. Dobie, OF THE HYDATINAEA. 677 FAMILY W.—HYDATINAEA. Illoricated Rotifera, having the ciliated wreath divided into several lobes or subdivisions. - In many of the genera distinct striated muscles of the voluntary type exist, effecting the various movements and altering the form of the body. The nutritive system usually consists of a simple conical alimentary canal without a distinctly separated stomach (Coelogastrica); but a pyloric constriction exists in Hydatina, some Notommatae, and other forms. Notommata clavulata and Diglena lacustris have special caeca appended to their stomachs. Variously modified cellular appendages, supposed to be glandular, exist in all the genera. The ovarium is mostly ovate and only evolves a few ova at a time. In Notommata Myrmeleo, N. clavulata, and Diglema lacustris it is very long. In all it communicates with the cloaca, by an Oviduct of varying length. The ova vary considerably, and belong to two distinct types, respectively termed the summer and winter ova. The former have a Smooth shell, and are gene- rally regarded as mere unimpregnated gemmae, like those of Aphides amongst insects. The latter are hard, and often spinous, in which form M. Tarpin regards them as constituting the genera Bursella and Erithrinella (?) amongst plants. It is amongst the members of this group that many of the interesting researches of Dalrymple and others have been made, demonstrating the exist- ence of dioecious animals. Amongst the Rotifera the male animals of Hydatina and Asplanchna are distinct from the females. They are generally character- ized by their smaller size and by the absence of digestive organs—indicating a brief existence, during which the vis vitae derived from the ovum suffices to sustain the animals in fulfiling their several functions. According to Cohn, this absence of an alimentary canal in the males does not characterize the male of Notommata parasitica (XXXIX. 8); but this is so exceptional to all other allied discoveries as to suggest a doubt of its correctness: at the same time, we have scarcely crossed the threshold of this inquiry, and want the materials for general conclusions. Water-vascular canals, variously modified, exist in most of the Hydatinaea. The frequent association of the ... red “eye-spots” with a subjacent organ, Supposed to be a cerebral ganglion, suggests sensational functions; but no true nerves occur. Some species of Symchaeta are said to evolve light and contribute to the phosphorescence of the sea. Hydatina senta, Diglena catellina, and Triarthra are sometimes so numerous as to render the pools in which they reside milky and turbid. Ehrenberg's classification of this family is given at p. 478, Section Soro- trocha, Division Polytrocha. - The first genus (ENTEROPLEA), established to receive E. hyalina, has been shown by Leydig to have no existence, as the above animalcule proves to be the male of Hydatina senta. Genus HYDATINA (XXXII. 394; XL. 1, 2).-Eyes absent. The female has two jaws, consisting of several teeth and a forked foot. Locomotion is effected by the compound wheel organ and the pincer-like foot, acted upon by complex internal muscles. In Hydatina senta the sexes are distinct, the Enteroplea hyalina being the male form. HYDATINA senta (Vorticella senta, M.) | part of the head an interrupted row of (XXXII. 394; XL. 1).-Body of the female tufts of cilia supported on small hemi- conical, hyaline; rotary organ consisting spherical projections,—the cilia of the of a simple external wreath of cilia sur- latter broader and longer than those of rounding the truncate anterior extremity the external row. ithin these is a of the body, and enclosing at the back third uninterrupted line of cilia, Neck 678 SYSTEMATIC HISTORY OF TEIE INFUSORTA, constricted and thrown into folds or wrinkles by transverse filamentous muscles, hung like hoops within the integument, to which Cohn believes them attached only by a few interrupted oints. These muscles were regarded by £hrenberg as vessels. The contractile influence of these and similar muscles occupying the lower parts of the body is antagonized, according to Leydig, by the elasticity of the cuticle, but according to Cohn by the pressure of the compressed fluids of the body. Longitudinal con- traction of the body effected by nume- rous muscles proceeding from the head backwards to the centre of both sides of the body and thence to the foot. Ehren- berg counted mine, which number Cohn regards as correct. The latter observed vacuoles and what appeared to be nuclei in the substance of the muscles, but no transverse striae. Two bodies at the base of the toes Ehrenberg regarded as muscles moving those organs; but Cohn believes them to be glandular, secreting an ad- hesive fluid by which the creature at- taches itself to other bodies. Digestive canal consisting of an oral orifice (XL. la), buccal cavity, pharyn- geal bulb (1 c), oesophagus (1 d), stomach (le), intestine terminated by a cloacal orifice at 1.f, and gastric glands. The buccal cavity a short passage from the mouth (1a) (located on one side of the head) to the pharynx (16), which is large; and, according to Cohn, a muscular mass invests the jaws, which are complex and not easily interpreted, but consist of several parallel teeth (XXXVIII, 34) ar- ranged in two sets and attached to a complicated pyriform organ; respecting the details of their form, authors differ. A constricted passage (1 d) conducts from the pharynx to the stomach (le), which is large and oblong; its walls are Saccu- lated, or expanded into numerous lateral pouches or pockets opening into the cavity of the stomach, the whole lined by delicate cilia (XL. 4). . A narrow pylorus separates this organ from a short conical intestine, the narrow extremity of which terminates at the cloaca (1.f), opening near the posterior extremity of the body on the opposite side to that on which the mouth is situated; two large byriform bodies, supposed to be glam- §. are suspended by narrow peduncles on each side of the pharynx. Connected with the cloaca is a large contractile vesicle (1 ff), from which ascend two water-vascular canals (1 ...), convoluted at intervals and giving off Small twigs which support tremulous tags (XL. 5). Ovarium a large pyriform sac (1 h), connected with the d. by a narrow oviduct; it consists of a thin membrane distended by a granular fluid, in which are seen numerous germinal spots. A small body, supposed to be a cerebral ganglion (1%), is situated on one side of the oesophagus, and is con- nected with a small setigerous groove on one side of the neck by what Cohn be- lieves to be nerves. Male : The Ente- roplea hydatina (XXXII, 393; XL. 2) of Ehrenberg has been demonstrated by recent researches to be the male of Hy- datina senta. Like that of many other species it has no visible digestive cavity: in general form it closely resembles the female, but is much smaller. Its repro- ductive organs consist of a retractile enis (XL. 6 a.), enclosed in a fold of the cuticle (6 d), the opening of which cor- responds with that of the cloaca in the female; the base of the penis is sur- rounded by a gland (6 b), above which is the large oblong testicle containing spermatozoa, by the side of which, at its lower part, are two small vesicles (6 c), connected with the penis, and filled with numerous large granules. XL. 3 repre- sents an immature ovum of Hydatina senta, and fig. 7 the detached sperma- tozoa from the male animal. In most cases the female fixes itself to a spot by its foot, and lays several eggs upon the same place, one after another, by sudden contractions; sometimes, when it is going to lay more eggs, it " returns to the original spot. In eleven hours after the eggs were laid, vibration of the anterior cilia was observed, by Ehrenberg, within them; and in twenty- four hours the young escaped from the shell. Many of the ova are said to have a double shell, and leave a bright space between the two at one of the extremi- ties; similar ova are found in other Rota- toria, having different shapes. In these double-shelled ova the young are slowly developed. Ehrenberg names them “last- ing eggs, or winter eggs.” XXXII, 394 represents an animal completely unfolded, seen from the ventral surface. The arrows in the alimentary canal indicate a de- cussating or circulating movement of its contents, produced by delicate internal cilia, and must not be mistaken for the motion of Monads. H. brachydactyla. —Cylindrical, trun- cated anteriorly, and suddenly attenu- ated at the base of the foot; claws short, On Hottonia, &c. 1-144". of THE HYDATINAEA. 679 Dujardin would include in the genus Hydatina several Rotatoria distributed by Ehrenberg among other genera. He says: “..Notwithstanding the presence of a red eye-speck, we must consider as Hydatinae—1. Notommata tuba ; 2. N. brachionus; 3. N. tripws; 4. N. clavulata,” and, though doubtfully, N. Saccigera, for this species in form resembles a true Furcularia. “The Syn- chaetae (Ehr.), characterized by their stiff setae or styles, are true Hydatinae from their comical or campanulate form, if their jaws are really pectinated; but if not, they will constitute a genus apart. . . . . The Distemma maximum, represented by Ehrenberg with pectinated jaws, and placed as doubtful by him in the genus Distemma, characterized by a double eye-speck, appears to be a true Hydatina.” Genus PLEUROTROCHA (XXXII. 395, 396).—These have no eyes, but possess a single tooth in each jaw, and a furcate foot. The rotary organ con- sists, not of a simple wreath of cilia, but of cilia distributed in bundles near each other, the bundles being planted in muscular cases. In P. gibba there are two muscles for moving the foot; and in all the species the globular Oesophageal head has four, acting upon two single-toothed jaws (fig. 396); Oesophagus short; alimentary canal simple, conical, having anteriorly two spherical glands. The anus is at the base of the foot, upon the dorsal surface. The ovary is globular. In P. leptwra a contractile vesicle is seen. Organs of sensation are not satisfactorily known, and the nervous loop in the neck of the Hydatina appears wanting. This genus is not admitted by Dujardin. PLEUROTROCHA gibba. — Truncated anteriorly, enlarging from the front to- wards the base of the foot, where it is suddenly attenuated, the toes, or claws, short and turgid; near the mouth is a beak-like projection, forming an under lip. XXXII. 395 is a right side view; 396 the teeth and oesophageal head dis- sected out. Found with Hydatina bra- chydactyla. 1-216". P. constricta. — Elongated, conical, head separated by a stricture; front ob- lique; toes straight and slender. This Genus FURCULARIA (XXXIII. forked. Rotary organ compound. and foot-muscles in three species. animalcule is very active and powerful. Upon Ceratophyllum. 1-144". P. leptura.-Bodyturgid in centre, front oblique; foot slender; toes thin, slightly curved. Amongst Confervae. 1-144". P. renalis (Ehr.).-Elongate, slightly constricted in front, toes short, frontal portion rather oblique, truncate, pan- creatic glands kidney-shaped (reniform). I-240". Berlin. P. truncata (Gosse).--Subcylindrical; truncate behind above the foot; toes short, straight, slender. 1-175". 397, 398).--Frontal eye single; foot Longitudinal muscles exist in F. gibba, The oesophagus is very short, its head has two jaws, single-toothed (Monogomphia) in two species, but not in the others; alimentary canal simple (Coelogastrica), comical, with two ear-like glands; ovary distinct, except in F. gibba, which has only a contractile vesicle. Vessels, respiratory tubes, gills, &c., are not recognizable. The eye in F. Reinhardtii is placed upon a brain-like mass. Dujardin has the following remarks on the genus Furcularia —“The genus Furcularia, one of the most numerous, undoubtedly requires to be divided after new observations, but not according to the number and dis- position of the red points, as has been done by Ehrenberg. This author has indeed distributed some Systolides, which appear to us to have the closest relations in form and mode of living, into eight genera '' (viz. Pleurotrocha, Furcularia, Notommata, Scaridium, Diglena, Distemma, Eosphorus, and Theorus); “but many of these are purely nominal, and require a rigid I'CVISIOI). “The following are the principal species to be classed with certainty among 680 SYSTEMATIC HISTORY OF THE INFUSOR.I.A. the Furcularia —1. F. furcata=Diglema caudata (Ehr.), Diglena capitata, and Furcularia gracilis; 2. F. marina, of the same size and form as the preceding, but marine, and distinguished further by the styles of its tail, which are twice as short, and by its three-toothed but acute jaws, resembling a hook; 3. F. forcipata, placed by Ehrenberg among the Diglence; 4. F. grandis–Diglena grandis (Ehr.); 5. F. foxficula, with which must also be associated Distemma forficula ; 6. F. canicula, which Ehrenberg with doubt refers to Diglena 2 awrita; 7. F. majas, to which belong the various Systo- lides, more or less like Hydatina in their club-shaped form and articulated tail, such as Notommata petromyzon, N. majas, N. gibba, and probably also Eosphora majas, E. digitata, and E. elongata (Ehr.). We moreover refer provisionally to the genus Furcularia several other Systolides considerably dissimilar in form, some being very long, with two very long styles, of which Ehrenberg makes his Notommata longiseta, and N. dequalis, and his genus Scaridium; whilst others have an ovoid, thick body, rounded posteriorly, truncate in front, and with a short oblique tail, which Ehrenberg calls Notommata myrmeleo and N. syrina. “All these Furcularice, except F. marina, to which F. Reinhardtii of Ehren- berg must probably be added, have been found in fresh water; but it is most likely the number of those living in the sea are much more numerous; and I have indeed myself met with three or four distinct species, which I have from want of time not yet described.” FURCULARIA gibba.—Oblong, slightly (Sertularia) geniculata, in sea-water. compressed, under side flat, back convex, 1–120". toes forked, long (styliform), equal to half the body; the eye is placed . &l nervous ganglion over the mouth, clearly indicating the dorsal surface; the ova- rium has generally one large and ripe ovum. The movement of this animal- cule is somewhat slow. Found in green water, and amongst Confervae. 1-69". F. Reinhardtii. —Fusiform, truncated in front; foot elongated, cylindrical, and shortly furcate at the end; a slight stricture divides the body and head. XXXIII. 397 represents an animal. ex- tended, and 398 another, contracted ; the former is a side (right), the latter a back view. Parasitic upon Monopy.cis F. Foxficula. — Cylindrical, obtusely pointed in front, rounded and dentated at the base, on the upper side; the toes very long; the rotary organ appears to have two frontal clusters of cilia, near the eye, and a wheel-like bundle on each side. 1-144". F. gracilis.--Slender, cylindrical, Sud- denly attenuated at the base of the furcate foot; toes straight, long, but shorter than half the body. The rotary organ appears disposed on six muscular II].8 SSGS. * F. caeca (Gosse). —Cylindrical; eye wanting, or not discernible; toes slender, obtuse. Length, including toes, 1-135". Leamington. - Genus MONOCERCA (XXXIII. 399–417).-Eye single, seated upon a ganglionic mass, cervical; foot simple, styliform, resembling a tail. In two species the vibratile cilia are distributed into about six bundles, their band-like longitudinal muscles and those of the foot producing locomotion; the sides of the oesophageal head are unequal, as also the two jaws, which have one or two teeth; the Oesophageal tube is curved and long, and the simple alimentary canal conical, with two ear-like glands anteriorly. An Ovary and a con- tractile vesicle are evident. In two species a tube projects from the frontal region. MonocIRCA Rattus (Trichoda Rattus, M.; Rattulus carinatus, Duj.).—Ovate, obong, truncated anteriorly, and un- armed; foot styliform, the length of the body. This creature swims slowly, in a | stiff manner; when stationary it throws the styliform foot backwards and for- wards. The ovary has a reddish colour; ‘behind it lies a roundish contractile vesicle. The foot has a short base, with OF TEIE HYDATIN FEA, 681 a cordate internal muscle, and four un- equal bristles. Amongst Confervae, &c. I-120". Mastigocerca carinata is regarded b Perty and Dujardin as identical wit Monocerca Rattus. Dujardin identifies with this an animal he discovered and figured (xxxviii. 22), measuring 0-147 millim., or with its tail 0.29 millim. M. bicornis.--Ovate, oblong, truncated in front, armed with two spines; foot styliform, a little shorter than the body; the oblique oesophageal head exhibits delicate transverse corrugations; it has a bent and a straight jaw, with probably three teeth in each. (XXXIII, 399, an animal seen on its right side; 417 an- other, contracted, and having its rat- like tail bent.) 1-72". M. (?) valga (Vorticella valga, M.).-- Small, almost cubical, with distinct head, during contraction, shows four muscular sheaths; and the distinct red eye is placed upon a less distinct ganglion; the Ceso- phageal head is not evident. 1-288". Mſ. brachyura (Gosse).-Form that of M. Rattus, but the foot short (one-fourth of total length), slightly curved, and horizontally flattened; a large eye in the occiput, and another small one in the breast. Length, including foot, 1-135". M. Porcellus.--Thick and plump; foot short, much curved and bent under the body, dilated, flattened horizontally, and carrying a smaller spine beneath it as in a sheath ; front and chin each armed with a short sharp spine. Length, in- cluding foot, 1-110". M. Stylata. — Short, irregularly oval; foot a nearly straight spine, less than one-third of total length; eye large, red, set like a wart on the back of the occi- an elevation on the back, and a conical Fº Sac ; forehead comical, pointed. foot unequally forked; the rotary Organ, Length, including foot, 1-170". Genus NOTOMMATA (XXXIII. 416–421; XXXVI, 3–6; XXXVII. 27–32; XXXVIII.26; XXXIX. 8, 9).-These have, according to Ehrenberg, a single eye upon the neck, and a bisulcate foot, resembling a forked tail. The rotary organ compound, its cilia forming bundles on the frontal region. Bight of the larger species have numerous muscles. Of Ehrenberg's species eighteen or nineteen have two jaws, each furnished with a single tooth ; in eight the jaws have many teeth. The Oesophagus is mostly short, with a simple wide conical alimentary canal (Coelogastrica); in N. tuba only is there a stomach-like division, with a constriction (Gasterodela); and in N. Myr- meleo, N. Syrina, and N. clavulata there is also a stomach-like enlarged place, but no constriction (Gasterodela): caecal appendages are observed only in N. clavulata. The two ear-like anterior appendages of the alimentary canal, regarded by Ehrenberg as pancreatic glands, exist in twenty-four species. N. Syrina, alone was observed by Ehrenberg to contain fully- developed ova. The water-vascular system is represented in ten species by delicate tubes, with flexible and tremulous gills; only three of the smaller species have gills. In N. Myrmeleo and N. Syrina, a broad vascular network is distinct about the head. A prominent tactile tube in the neck is present in four or five species; in Some others an opening alone is seen. The visual point is red, except in N. Felis, where it is colourless; a ganglion is placed beneath the eye in twenty-six species. In N. Copews and N. centrura the brain (?) is three-lobed, and placed over the Oesophageal head; in the rest it consists of one or more nervous ganglia, situated amongst the ciliary muscles of the frontal region. This genus is especially remarkable for the parasitical habits of its members. They live upon other Rotatoria, upon the Polygastric Infusoria, and even within the globular masses of Volvoa, Globator; “but,” says Ehrenberg, “Inot like a cuckoo's egg in a hedgesparrow’s nest, but like the bear and the bee-hive, or a bird’s nest in a wasp’s nest.” Dujardin has the following criticisms on this genus:—“Five of the species appear to be Hydatinae; nine others, more or less distinct, are, in our opinion, Furculariae; three others Plagiognathi; some are imperfectly known; and only six, at most, offer sufficiently precise characters to retain the name Notommata. Such are, 1. N. copeus, 2. N. centrura, 3. N. brachyota, 4. N. 682 SYSTEMATIC HISTORY OF TEIE INFUSORIA. collaris, 5. N. awrita, and 6. N. ansata.” To these species must be added a seventh, called by Ehrenberg Cycloglena Lupus, and an eighth, which we distinguish as Notommata vermicularis. All the best observers agree that the genus Notommata requires division, being a very defective one, and containing the elements of several genera ; but all the species now composing it must be subjected to a very careful and individual examination before such a division can be made. Until this is accomplished we retain the genus as adopted by Ehrenberg, observing that the analysis of Ehrenberg’s views respecting it, as given in a preceding page, will ultimately require many modifications. Some species have already been carefully investigated by Gosse, Perty, and Leydig. a. Subgenus LABIDODON.—One tooth in each jaw. NoToMMATA Myrmeleo.—Body large, bell-shaped; foot short, lateral; teeth curved in a circular forceps-like manner (xxxLII, 420). There are two varieties: in the one (var. a), a long thin Oesopha- gus, a globular thick stomach, and a long rectum constitute the alimentary organs. Ehrenberg, by pressure, made an ani- malcule, whose dark stomach nearly filled the body, disgorge two large #. cimens of Lynceus minutus (described and figured in the Microscopic Cabinet); the animalcule afterwards vibrated away in a lively manner. Five transverse mus- cular bands and four longitudinal ones (a pair uniting to each of the first two transverse ones) represent a muscular system in this variety. . In the other (var. b), a distinct muscular network is seen at the head, but only four trans- verse bands and two longitudinal Ones going to the first. . The red eye is much larger in this variety. (XXXIII, 418, a side view of the variety b : to exhibit its organization, a small Crustacean is shown within its stomach. Fig. 420, the man- ducatory organs separated; fig. 419, the upper part of an animalcule, var. a, show- ing the Smaller eye, rotary organs, teeth, and network.) Found in clear water, in turf-hollows. 1-40". Notommata Myrmeleo, var. multiceps, according to Leydig, presents the follow- ing features:—The foot, which on a pro- file view appears given off from a lateral surface, projects from the abdominal one. The rotary organ not consisting of separate portions, but forming a con- tinuous wreath, which descends towards the mouth, forming an apparent fissure. On the free surface are four unsymme- trical lobes bearing larger Setiform cilia. Cuticle soft and thin, slightly acted on by acid, which renders it clearer; sub- jacent layer granular and homogeneous. Iaxillary head very large. CEsophagus long, thin, folded longitutinally. Stomach round, with ciliated cells : no rectum beyond the stomach, Ehrenberg being in error on this point; débris rejected by the mouth. A respiratory canal pro- ceeds from each side the contractile sac towards the head, being much convo- luted and enveloped with cell-like cor- puscles; a second smaller pair follows a similar course, joining the larger near the maxillary bulb. The smaller have not granular walls, but support numerous tags, which are absent from the larger canals. Two bands proceed backwards from the cerebral ganglion to a couple of fossae on the dorsal surface, furnished with a bundle of setae. Eye- speck dark-red or black. Ovary present- ing two horns, forming an organ like a horseshoe, the oviduct opening at the base of the tail. Winter ova spherical, bristly, with a light cortical layer con- taining clear vesicles. N. Syrina.--Large, bell-shaped; lateral: foot scarcely visible; teeth curved and bifid at the points. This species is very similar to the former, and only distin- guished from it by its small foot and by the spaces within the cilia-cluster mouth) being convex, not concave. *ound in a turf-pool. 1-40". N. hyptopus.-Bell-shaped, nearly glo- bular, rather large; foot slightly pro- minent at the middle, teeth Small; º: tile organ composed of four or five muscular bundles; Oesophagus very short. 1–72". N. parasita (XXXIX. 9).--Small, oval; foot short, teeth Small; rotary apparatus three or four lobes; Oesophageal head globose ; Oesophagus short; alimentary canal stout, simple, usually filled with green matter. This curious animalcule lives in the globes of Volvoa, Globator, where it deposits its eggs, which are therein hatched; and when of proper age, the creatures eat their way out through the hollow sphere. Summer OF THE EIYDATINAEA. 683 º Smooth; winter ova spinous. 1–40". According to Cohn, the male of this species (XXXIX. 8) is a small Rotifer 1–20" in length. Body short and sac- cular; two short toes, usually retracted; head distinguished by a slight excava- tion, and with an ear-like lappet on either side; rotary organ furnished with some stout uncini, in addition to the fine cilia; pharynx cylindrical, contain- ing two scalpel-like teeth, which can be extended beyond the mouth; stomach separated from the intestine by a con- striction. A contractile vesicle above the foot, but water-canals scarcely visible. A cerebral ganglion, resembling a long sac, within the head, and bearing a re speck at its anterior extremity. Males and females usually existing in the same Volvoac. We have considerable doubts respecting the correctness of the above account, since it differs so widely from what has elsewhere been observed amongst such male animals as have hitherto been discovered amongst the Rotifera. The absence of a complete alimentary canal has hitherto character- ized all male Rotifera. (The female is *. after Cohn in xxxix. 9.) . petromyzon. – Elongated, attenu- ated at both ends; mouth and rotary organ lateral. Ehrenberg says, in May 1835 he found one in a Volvoa Globator, whose gemmiferous masses it eats like W. parasitica. The eggs are often de- posited on Epistylis. 1-180" to 1-144". N. lacinulata (Vorticella auriculata et arcinulata, M.). — Small, conical, trun- cated and slightly lobed in front; teeth extended, often bicuspid. Alimentary canal, according to Leydig, clearly sepa- rable into a greenish yellow stomach and a clear intestine. This species is very active. Found with Chlamidomonas Pulvisculus in clear water, also in water- tubs. 1-280". N. forcipata.--Small, elongated; toes long, and often crossed; eye very large. The vibratile organ appears sometimes like a simple wreath. Amongst Lemnae. Very common in Switzerland, according to Perty, but with a small red eye-speck instead of a large pale one, as described by Ehrenberg. 1-180". N. collaris-Elongated, large, gradu- ally attenuated at both ends; neck tur- gid; toes short. It swims slowly, the vibratile organ being small in comparison with the body. 1-48". N. Werneckii.-Elongated, gradually attenuated at both ends; toes short, it has two setae near the mouth. This animalcule resembles N. collaris, but is smaller, and lives in the club-like ex- crescences of Vaucheria as an entophyte. 1–90". N. Najas.-Conical, cylindrical, stout, truncated in front; no auricles. It re- sembles Hydatina senta and Eosphora Najas; it is distinguished from the first by its cervical eye, from the latter by the want of frontal eyes. Amongst Lemnae. 1–120". N. aurita (XXXVI, 3–6).-Described by Mr. Gosse as cylindrical, but frequently pyriform. Head obliquely truncate, belly nearly straight, posterior extremity pro- duced into a retractile foot (XXXVI, 4 h) with two pointed toes, which organ, being anterior to the cloaca, is not a tail. An oval mark on each side of the head, from which the animal can suddenly project a semiglobular lobe by evolution of the integument (XXXVI. 4 a), each lobe fringed with cilia, form- ing a locomotive organ; fringe of cilia extending across the front of the face as far as the constriction of the neck. Maxillary bulb or gizzard (4 b) large, oval, nearer the ventral than the dorsal side, having imbedded within it a pair of complex jaws (XXXVI, 6 "). A duct leads from the maxillary bulb to the continuation of the alimentary canal, which is wide, subcylindrical, tapering towards the anus, not divided by any constriction, but at once stomach and intestine; walls thick, probably cellular. Cloaca between the projecting point (XXXVI, 3) and the foot. Ovary large, occupying the ventral region; some- times long and clear, containing trans- parent globules (4 f), at others gra- mulated (XXXVI, 3). A large developed egg (40) often occupying a great por- tion of the abdominal cavity. Eggs large, covered with short flexible spines. Male unknown. Water-vascular system con- sisting of two sets of tortuous vessels, commencing at the cloaca (6 a) and terminating at the head, and bearing tremulous tags. Parallel with the oeso- hageal bulb, but nearer the dorsal sur- face, is a large lobulated subglobose mass of dense matter (4 g), white by reflected light, but opaque and hence appearing black by transmitted light, occupying the bottom of a deep cylin- drical sac. A tube runs through the centre of this sac towards the rotary organ, “on which it opens, or at least impinges” (Leydig). As this opaque mass supports the eye-spot, Gosse re- 684 SYSTEMATIC HISTORY OF THE INFUSORIA. gards it as cerebral. Muscular system complex (XXXVI. 5, 6). Six or seven muscles are circular and transverse (6 t); others, arranged longitudinally (5 l), are attached to various internal viscera and to the integument. Some go to the occipital sac, others to the gizzard and to the foot, effecting various motions in all these organs. Gosse observes, “It commonly keeps the ear-like lobes con- cealed whilst crawling, but will often suddenly protrude them, and in the same instant shoot off through the water with considerable rapidity and with a smooth gliding motion, partially revolving on the longitudinal axis as it proceeds.” Leydig observes that the alimentary canal consists of two portions—stomach and intestine. 1-70". Amongst Con- fervae, &c.; also beneath ice. (XXXVI. 3–7. N. gibba.-Back swollen, front trun- cated, not auricled, no cerebral sacculi below the eye; toes short; the vibratile organs compound. In old exposed in- fusions. 1–200". N. ansata (Vorticella aurita, M.). — Turgid in the middle, suddenly trun- cated at both ends; the front auricled, no cerebral Sacculi below the eye; toes thick. In bog-water, amongst Confervae. 1–120". N. decipiens, – Cylindrical, not au- ricled; toes short; the ovarium often contains four large eggs. Perty thinks this is only the young of some other species. 1-180". . N. (?) Felis.--Small, slender; one horn in front; eye colourless; back attenu- ated posteriorly, and forked. 1-240". N. (?) Tigris (Trigoda Tigris, M.) (XXXIII. 421)—Cylindrical, curved, foot half the length of the body; toes very long, and curved downwards; it has a little horn in front; the eye is large and red. Perty has found many examples without the red eye. Amongst Oscil- latoriae. 1-72". N. longiseta (Vorticella longiseta, M.). —Cylindrical, truncated anteriorly; toes styliform, unequal, and two to four times longer than the body. It is active, and frequently leaps, being assisted by its long claws, which resemble tails. Fig. 421 is a full-grown specimen. Entire length 1-60". N. aequalis (Vorticella longiseta, M.). —Cylindrical, obtuse in front; toes sty- liform, equal the length of the body. l–J20". b. Subgenus CTENODON.—Jaws many-toothed. N. clavulata.-Bell-shaped; foot coni- cal, very short; pancreatic glands of a club-shape. This creature presents great facility for observing its internal struc- ture; but the limits of this work preclude details. Mr. Gosse kindly informs us that he has distinctly seen in it a nor- mal intestine terminating in the cloaca. 1–96". N. Tuba. — Comical, trumpet-shaped, dilated anteriorly; foot furcate and acute. It resembles, in form, Stentor Mülleri, but is more active. 1-120". N. Brachionus.-Dilated, nearly square, depressed, foot slender, eggs pendulous. This creature appears to have a shell, but Dr. E. says it has not. Ehrenberg described his N. granularis as depositing its eggs upon N. Brachionus, whence he concluded that the former, like the cuckoo, left its young to be reared by another creature. He found that some of the eggs on the dorsal surface of N. Bra- chionus produced N. granularis, Leydig solves the mystery by affirming that the latter species is the male of the former, the animal in this case being bisexual, not hermaphrodite. 1-96". N. tripus. – Oval, subtruncated, and slightly auricled in front, Dark red eye- speck with three chalky masses, giving the organ a trilobed appearance. Foot apparently trifid, but not really so, the central lobe being only the prolonged back of the animal. 1-200". N. saccigera.-Elongated, cylindrical, attenuated posteriorly; fork short. It has a curious internal pouch beneath the eye, with a group of rounded vesicles in front of the stomach, recalling, as Perty observes, the pretended agglome- ration of eyes in Theorus. N. Copews.-Large, attenuated at both ends; tail small and indurated. This curious creature has a long bristle on each side of its body; and on each side of the head a stout process, called by Ehrenberg an auricle, fringed with vibra- tile cilia at its ends, and, like the setae, standing out at right angles to the body; a thick gelatinous substance covers the body; the back terminates in a some- what hard point, which is a true tail, between which and the foot the dis- charging opening is situated. When creeping, the large vibratile arms are withdrawn, but it vibrates with the frontal cilia and proboscis. (XXXIII, 416 represents the creature extended.) 1-36". N. centrura(XXXVIII. 26).-Body large, OF TECE EIYDATIN_AEA. 685 attenuated at both ends. Usually sur- rounded by a broad gelatinous sheath, either hyaline or filled with small aci- cular bodies. According to Ehrenberg, in this sheath vegetate threads of Hy- drocrocis; but these could not be found by Leydig. Sheath wanting in young specimens. Cuticle thick, soluble in caustic potass. Behind the middle of the body, on each side, is a small conical eminence (XXXVIII. 26 b), surmounted by a bunch of long setae. Rotary organ pe- culiar, differing from Ehrenberg's repre- sentation. Anterior ciliated extremity small compared with the size of the animal; ventral portion (fig. 26 d) pro- longed in the form of a half canal or groove, constituting a kind of under lip. At the base of this is the mouth, com- municating with the maxillary bulb and Oesophagus, and opening into a stomach with walls composed of large cells (fig. 26 f), beyond which is a restriction separating it from the rectum (fig. 26 g). Three sac-like organs (fig. 26t, c) on the hinder border of the brain (fig. 26%) : the centre one composed of clear vesicles (fig. 26 c), the outer two apparently sometimes continuous with the cerebral ganglion. They are granular, nucleated, and apparent with some inorganic mat- ter, which is white by reflected and dark by transmitted light. Ovary (fig. 26 oy transversal; Perty saw only winter ova in it. (XXXVII. 25 exhibits a small por- tion of the ovary in which an ovum is forming, a being the germinal spot, b a clear space surrounding it, and c the yelk-substance. XXXVIII, 11. represents a small portion of the water-vascular canal with its tags, and fig. 12 the ter- mination of a tag with its contained cilium.) , N. brachyota.--Small, slightly attenu- ated towards the ends; no tail, auricles very small; it has two dark spots near the eye; foot forked. 1-120". N. Pleurotrocha.-Slender, cylindrical, not auricled; foot with very short toes; eye obscure, ovate, large; jaw with one tooth. 1-144". Berlin. Has the form of Pleurotrocha. N. vermicularis (Duj). --Vermiform, very contractile; of variable form, with a kidney-shaped red speck (xxxviii. 33), in which is partly imbedded a white transparent globule. 1-118". Found in the Seine. N. tardigrada (Leydig) would be re- ferable to the genus Lindia (Duj.), had not its author made the absence of cilia from the head a generic character. Fi- gure vermiform, rounded in front, pro- longed behind into a short biuncinate foot. Mouth a long fissure on the under side of the head, which is clothed with short and delicate cilia, the only part of the head so furnished. Maxillary bulb capable of being protruded. Dental ap- paratus recalling to mind that of Echinus. CEsophagus long, resembling that of N. centrura. Stomach long, yellow, with- out cilia on the free surfaces of its parietal cells. Intestine short and clear, opening at the base of the foot on the abdominal surface. Contractile sac vi- sible, giving off traces of two water- canals, but without vibratile tags. Above the maxillary bulb the “sacculus cere- bralis” of Ehrenberg, white by reflected and black by transmitted light, and soluble in liquor potassa, N. roseola (Perty). —Body of a pale rosy red, elongated, rounded in front. Rotary organ forming a cylindrical pro- cess on each side of the head. Cohn Suggests that the animal may be identical with his Lindia torulosa. N. onisciformis (Perty).-Body broad like an Oniscus, with a round lappet on each side of the head. Jaws strong, many-toothed; tail flat, rather long. Entire anterior extremity capable of being retracted. An ear-like lappet on each side of the head, between which are seen the vibratile cilia. No alimen- tary canal seen beyond the maxillary bulb. Amongst Confervae and Charae. Genus SYNCHAETA (XXXIII. 422).-Eye single, cervical; rotary organ of six to ten lobes, and armed with from two to four styles; foot furcate. The strong styles, or bristles, are situated between the clusters of cilia, and probably act as tactile organs; the body is very short, broad anteriorly, and tapers to a point posteriorly, or is comical. Internal longitudinal muscles exist in all the species; those of the foot are seen in three species: the oeso- phageal head is large, with single-toothed jaws; but in two species only is the whole chewing apparatus distinctly seen. The thin Oesophagus is long in two species, short in the rest; it leads to a simple, wide, conical alimentary Canal, which has two roundish, or, in one species, conical pancreatic glands. 686 SYSTEMATIC EIISTORY OF TEIE INFUSORIA. The ovary is rolled up like a ball; contractile vesicles exist in three, and glands in two species; transverse bands (four to ten) are visible in two species, and probably a respiratory tube in S. pectinata and S. tremula, a tremulous gill being also present in the former. The principal nervous matter is a knotty mass surrounding the head of the Oesophagus; and in the middle of it is a large, roundish, red eye. In S. pectinata three pair of ganglia and strong nerves are also said to be seen; but this is doubtful. Abdominal fluid of a reddish-yellow colour. (For remarks on the genus, see HYDATINA, p. 677.) SYNCHAETA pectinata.-Short, conical, with two styles and two crest-like horns anteriorly. “Are these horns,” asks Ehrenberg, “respiratory tubes, as in Polyarthra, and in Anuraea P" The live- liness and uniform transparency of this animalcule render it difficult to distin- guish its various organs. The styles arise from the muscle of the oesophageal head, and appear asif belonging to simple- toothed jaws. Eye blue. Egg-yellº con- taining heaps of redfat-globules. (XXXIII. 422, a dorsal view showing its organiza- tion.) Amongst Confervae. 1-120". S. Baltica.-Ovate ; rotary clusters and styles, four each; crest single, Sessile. This creature is supposed to occasion phosphorescent light in the ocean. In two samples of water received by Ehren- berg at Berlin, from Kiel, the luminous property existed; but this species, though present, did not evolve any light. Mi- chaelis, however, has noticed the produc- tion of light from this Symchaeta, as did Baker a century ago. Ehrenberg thinks it takes place only when developing ova. 1-100". S. oblonga.-Oblong, with six rotary clusters, and four styles; crest sessile and single. Distinguished from the follow- ing by the form of the pancreatic glands. Amongst Confervae in spring. fength about 1-100". S. tremula (Vorticella tremula, M.).- Body truly comical, with six rotary clus- ters, four styles; crest none; granules of elk dark coloured. Length about 1-160". Mr. Gosse thinks this may be a dioecious species. * S. mordaa (Gosse). —Body conical, subventricose; toesminute; auricles large, pendent; principal styles four, the larger (or lateral) pair sometimes branched; eye rather small, brilliant; two pairs of pro- trusile Snapping jaws. 1-72". Genus SCARIDIUM (XXXIII.423).-Eye cervical, single, flat, lenticular, the compound rotary organ armed in front with an uncinus or hooked bristle; foot forked, very long, and adapted for leaping or springing—hence the name. CEsophageal head oblique, with unequal, double-pointed (single) teeth to the jaws; Oºsophagus short, narrow, opening into a simple, wide, conical alimen- tary canal; supposed glands spherical, two. Posteriorly, above the intestine, are a ball-like ovary and a contractile vesicle. The foot has two club-shaped muscles; and its apparent articulations are very remarkable. A central gan- glion exists between the rotary lobes. Muscles with transverse striae. Shell of the ovum (winter ovum ?) clothed at both ends with scattered hairs. ScARIDIUM longicauda (Trichoda longi- cauda, M.).-Foot twice as long as the body, toes half as long as the foot; the animal springs or leaps quickly, by a rapid movement of the foot; it does not appear to have a lorica, and is distin- guished from all other Rotatoria by the length and bending-in of the foot, which, skin. Behind the eye is a transverse fold in the neck, where the head draws itself into the body; the foot has also a transverse fold when it bends, (xxxHI. 423, the animalcule extended, right side; fig. 424 the oesophageal head, with un- equal jaws, &c., extended by pressure.) Amongst Oscillatoriae. Entire length of as also the body, is covered with a stiff the body 1–72"; without the foot, 1-216". Genus POLYARTHRA (XXXIII.400–402; XXXVIII. 30).-Eye single, cervical; foot absent; provided with cirri, or pectoral fins. The rotary organ consists of four bundles of cilia, inserted in as many muscular sheaths; they sometimes appear like the double rotary organ of a Brachiomws. The form of the body resembles Anuraea; but it is soft, and the rotary organ double. OF TEIE EIYDATINAEA. 687 Laterally there arc two longitudinal dorsal muscles; the frontal region has little horns, provided with bristles; and upon the breast are six strong styles, or barbs, forming two clusters, which move in a fin-like manner. The oeso- phageal head has two single-toothed jaws; Oesophagus short; alimentary canal with a stomach-like division, produced by a constriction; supposed pancreatic glands, two. An ovary exists in both species, and in one of them a contractile vesicle; a large frontal ganglion and a round red eye indicate the system of sensation. The preceding genera of this family, together with two peculiar to himself, viz. Plagiognatha and Lindia, form, in the system of Dujardin, the family Flosculariens; but the genus Polyarthra and a few others in this family of Ehrenberg belong to the Brachiomiens of that author. From the remarks of the French naturalist, it is to be inferred that he regards the distinction between Polyartha'a and Triarthra as insufficient. PoEYARTHRA platyptera (XXXVIII, 30, also XXXIII. 400–402 & 425). — Ciliary wreath, according to Perty, not as de- scribed by Ehrenberg and Dujardin, but continuous and symmetrical, with two eminences crowded by setae, besides which are several long styliform cilia. Near the posterior end of the body are two fossae with unsymmetrically arranged setae extending from them. Alimentary canal consisting of a comical Oesophageal bulb, stomach, and intestime. Stomach- cells ciliated; contractile Sac present, but no water-vascular system seen; lon- gitudinal muscles striated; abdominal fluid yellowish-red; ovary somewhat bi- cornate; yelk of ovum with large reddish Genus DIGLENA (?).—Eyes two, frontal; foot forked. fat-globules. No winter ova seen. Em- bryo with bluish spots. Ova adhering to the exterior of the body; only one seen at a time (Leydig). It swims quickly, and often leaps, like the water flea this last motion is produced by the fins or pinnae, the former by the vibratile organs. (Figs. 400, 401, & 425 represent the P. Trigla of authors; but Leydig has decided that it is identical with P. platyptera. Fig. 425 the under side while the ami- malcule is swimming, with the pinnae depressed; fig. 400 a dorsal view while leaping or springing; and fig. 401 a side view, right.) This creature is infested * Colacium. Amongst Confervae. -140". Excepting the foot and rotary organ, they have no external prominent organ, though some protrude the teeth in a pincer-like manner. The Cesophageal bulb has single- toothed jaws; the oesophagus is very short, except in D. lacustris; alimentary canal conical, simple, in six, and constricted in two species. In all, two glands are present, which in D. lacustris are long cylindrical and two- horned ; in the rest they are spherical. The ovary in D. lacustris is band- like, in the others globose. Contractile vesicles are observed in four species. No species is viviparous; none carry their egg hanging to them; transverse muscular bands are seen in three, and in one a vascular network at the head; tremulous tags are found in three species, in two of which they appear as if attached to the water-vascular-canal glands. The cerebral ganglion is more especially developed in D. lacustris, but is indicated in all the species by the coloured eyes. DIGLENA lacustris.--Stout, Oval, cry- stalline; the front straightly truncated; foot suddenly attenuated, in length one- fourth of the body; the toes one-third the length of the foot. The transparency of this animalcule is often a great hin- drance to the discrimination of its internal organs, though they are very large; the superficial skin is delicately shagreemed. (XXXIII, 403 a side view, left, of this in- teresting animalcule, with a Lynceus— see Microscopic Cabinet, pl. vii.-in its stomach; its curious internal organiza- tion is clearly depicted. Often found in green-coloured water.), 1-70". D. grandis.-Long, slender, and cylin- drical, obliquely truncated anteriorly; toes straight, longer than the stout foot. The forked central Sacculus, near the head, is remarkable, (XXXIII.404 an ex- 688 SYSTEMATIC HISTORY OF THE INFUSORIA. tended animalcule, right side; XXXIII. 405 another, contracted, with the jaws pushed out.) 1-120" to 1-72". D. forcipata (Vorticella vermicularis, Cercaria forcipata et E. vermicularis, M.) (XL. 24).-Cylindrical, slender, obliquely truncated anteriorly; toes decurved, and longer than the stout foot. 1-110". D. (?) aurita (Vorticella Canicula, M.). —Cylindrical, slender ; front straightly truncated, auricled; foot suddenly con- stricted, toes small. The tremulous Organ observed by Corti was merely the vibra- tile lining membrane of the anterior por- tion of the alimentary canal. Amongst Confervae. 1-160". D. catellina cella Larva, M.).-Oblong, short, ends truncated; foot short, and inferior. The small size of this animalcule is unfavour- able for observing its internal organiza- tion. It is found at all seasons of the year in open water, and in infusions Cercaria catellina, Vorti- rapidly developed by genial weather, cause a milky turbidity in the water. 1–360". D. conura.-Ovate-oblong, straightly truncated in front, and gradually attenu- ated to a conical foot. Amongst Oscilla- toriae. 1-144". D. capitata.-Oblong, comical, obliquely truncated and dilated in front; toes long, without apparent base, or foot. Feeds upon Chlamydomonas and Navicula, 1–300". D. caudata (Vorticella furcata, M.).- Elongated, conical, obliquely truncated anteriorly, but not dilated; foot distinct, short; toes long. In green water. 1-200". D. (P) biraphis (Gosse).--Oblong, the head and abdomen gently swelling; toes long, slender, straight, and perfectly even in thickness; eyes placed close to- gether, frontally; jaws protrusile; alimen- tary canal very large, projecting behind and above the gizzard, always filled with covered with a green pellicle, which is often filled with its eggs; these, when Genus TRIARTHRA (XXXIII. 406–408).-Eyes two, frontal; foot simple, styliform; breast-fins two. Beside the rotary organ, internal band- like muscles are observed, and two bristles, or fins, which assist in leaping, as in Polyarthra. The oesophageal bulb has two double-toothed jaws, as in Rotifer; the oesophagus is long in one species, short in the other; alimentary canal simple, conical or constricted, with two spherical glands. An ovary and contractile vesicles are seen ; the eggs, when expelled, remain attached green matter. Length, including toes, 1–110”. by threads. upon ganglia. water, when developed in masses. T. longiseta (Trichoda, M.).-Eyes distant; the cirri or beards, and the foot, are nearly three times the length of the body. This species is distinguished from the following one by the greater length of cirri; by i. eyes, further removed from each other; by a distinct stomach, with a constriction separating it from the long portion of the alimentary canal; and, lastly, by its long Cesophageal tube. It is readily distinguished by its leaping movement whilst swimming. (XXXIII. 408, a young animal emerging from the egg, the cirri or styles being, as yet, soft; 407, back view of a young specimen—it shows the great separation of the eyes and the styles, in the position they occupy The nervous system is indicated by the two red eyes, placed Both species often produce a milky, turbid appearance in the A third species is now added. when the animal is swimming; 406 a side (right) view of a full-grown specimen— the styles are advanced, preparatory to leaping.) Found with Hydatina senta and Brachionus urceolaris. Length, with- out cirrhi, 1-140". T. myStacina (Brachionus passus, M.).— Eyes close together; two anterior cirri, or bristles; foot nearly double the length of the body; jaws very soft. 1–216". In water-tubs. + T. breviseta (Gosse), — Cylindrical ; pectoral and caudal spines each about one-fifth of totallength, and very slender. Length, including foot, 1-185". Leaming- ton. Genus RATTULUS (XXXIII. 409).-Eyes two, frontal; foot simple, styliform; no cirri or beard. The organization at present discovered com— prehends several undefined rotary muscles, an oesophageal head, without di- stinct teeth or Oesophageal tube, a simple conical alimentary canal, with two round glands, an ovary, and the eyes. OF TELE BIYDATINAEA. 689 This genus (Rattulus, or Ratulus) was established by Lamarck; but the animals included in, it by him were referred by Ehrenberg to two genera, Mastigocerca and Monocerca, and the term Rattulus conferred upon an animal placed among Cercariae, and called by Müller Trichoda lunaris. “The Mas- tigocerca carinata (Ehr.),” observes Dujardin, “is described as loricated, and enters into the family Euchlanidota ; and Monocerca Rattus, without lorica, is placed among the Hydatinaea; but the beings described under these two appellations represent but a single species, Ratulus . . . . The Monocerca bicornis of Ehrenberg would seem to be a distinct species, by reason of the horns with which it is armed in front.” RATTULUs lunaris (Trichoda lunaris, In turfy pools. 1-288". M.). —Small; eyes remote from the R. carinatus (Duj.) (xxxviii. 22}= frontal margin; foot decurved, lunate. Monocerca Rattus. No teeth are seem (XXXIII, group 409). Genus DISTEMMA.—Eyes two, cervical; foot forked; rotary organ com— pound. The Gesophageal head supports, in three species, jaws, with two teeth each ; in one species with more than two; Oºsophagus short; alimentary canal simple, conical, with two spherical glands. An ovary, and in D. (?) onarinum glands and a contractile vesicle are seen. No satisfactory details of a water—wascular system are ascertained; the eyes are red, except in one species, in which they are colourless, and in all, except D. marinum, they are situated behind the head of the oesophagus; in that one they are anterior, but below the rotary organ. The eggs are never attached to the parent, nor are they developed in large masses. DISTEMMA Foxficula. — Cylindrico- red ; toes setaceous and decurved. conical; eyes red; toes thick, recurved 1-216". and dentate at the base. The eyes are D. (?) marinum.—Ovato-comical; eyes placed at the end of a long cylindrical red, close together; foot long; toes thick, nervous ganglion; the rotary organ con- the length of the foot; jaws many- sists of four parts. XXXIII. 411 is a side toothed. In sea-water. 1-144". (left) yiew, and fig. 410 shows the jaws | D. (?) forcipatum. – Ovato-oblong ; extended for seizing prey, Perty be- eyes colourless; foot short, with stout lieves this to be identical with Fºrcw- toes. If the two colourless vesicles are laria Forſicula, having but a single eye. not eyes, it must be placed in the genus }-120". I’leurotrocha, 1–288", D. setigeratm. — Ovato-oblong ; eyes Genus TRIOPHTHALMUS (XXXIII. 412–414).-Eyes three, cervical, sessile, in a row ; foot forked; rotary organ compound. It has a large Ceso- phageal head, with two (single-toothed 2) jaws, a long thin Oesophagus, a globose stomach-like protuberance, with two oval glands, and a thin intes- tine; two muscles move the foot. Several Small tags seen in T. dorsalis. TRIOPHTHALMUs dorsalis.-Body cry- | N. Myrmeleo. (XXXIII. 412, dorsal side of stalline, turgid; central eye largest; foot an animalcule extended as it appears suddenly attenuated, its length half that when swimming and vibrating; fig. 413 of the body. This species, in form, re- one in the act of unfolding # and sembles Notommata ansata, but in size fig. 414 another contracted.) 1-40". Genus EOSPHORA (XXXIII. 415). —Eyes, according to Ehrenberg, sessile, three—two frontal, one cervical; foot forked. The rotary organ is composed of numerous muscular portions. An oesophageal head, provided with two single-toothed jaws, a short Oesophagus, a simple comical alimentary canal, with two ovate glands anteriorly, an ovary, somewhat extended, and a contractile vesicle, are also discoverable. Transverse bands are observable 2 Y 690 SYSTEMATIC HISTORY OF THE INFUSORIA. in two species, and tags in the third. Beside the three red-coloured eyes, a cerebral ganglion is seen. Distinctly striated longitudinal muscles are seen in all. - According to Leydig, what Ehrenberg has regarded as two frontal eyes have no claim to the name. Should this statement be confirmed, it would become necessary to unite Eosphora with Notommata. Eos PHORA Najas.-Conical, transpa- ricled; toes a third the length of the rent, not auricled ; toes much shorter | foot. Amongst Confervae. 1-96". than the foot. (XXXIII, 415, an animalcule | E. elongata–Elongated, almost fusi- fed upon indigo.) Amongst Confervae. form, not auricled, front truncated; toes 1-12". short, 1–72". E. digitata.-Comical, hyaline, not au- Genus OTOGLENA.—Eyes three, one being sessile and cervical, the others pedicled and frontal; foot furcated. This large animalcule, the sole repre- sentative of this genus, has considerable resemblance to Notommata Myrmeleo or N. clavulata. Four lateral longitudinal muscles, six moving the rotary organ, and two muscles of the foot are present; a toothless, and apparently jawless, Oesophageal canal leads to a somewhat thickened stomach, ending in a very thin intestinal canal. An ovary and contractile vesicles are observed. A vascular network at the neck represents a water-vascular system. An oval cerebral ganglion, with two dark appendages, and a red eye, together with two little horn-like or auricular frontal protuberances bearing two visual points, represent the nervous system. This genus has not been figured. OToGLENA papillosa. – Bell-shaped, with Volvoa Globator and Notommata turgid, scabrous with papillae. Found Myrmeleo. 1-96". Genus CYCLOGENA (XXXIV. 425, 426).—Eyes numerous (more than three), conglomerate at the neck; foot furcate. The vibratile organ is com- pound, and, with the internal muscles of the foot, serves for locomotion. The oesophageal head has two single-toothed (perhaps three-toothed) jaws; Oeso- phagus very short; alimentary canal conical, simple, with two roundish glands. An ovary and a contractile vesicle are also present. Transverse circular muscles, and six pair of tremulous Organs attached to the water- vascular canals, exist. A purse-shaped dark (colourless) body in the neck, connected by a narrow process to a large frontal ganglion, containing from six to twelve red points, of which the anterior one is most marked, possibly indicates a system of Sensation. CYCLOGENA Lupus (Cercaria Lupus, side view.) I-120". M.). — Ovato-oblong, or comical, not C. (?) elegans—Ovate, not auricled; auricled ; foot terminal, , and short. foot inferior; toes long. 1-190". (xxxiv. 425 * a back view, 426 a Genus THEORUS (XXXIV. 427–429). —Eyes numerous (more than three), disposed in two groups at the neck; foot furcate. A compound rotary organ, together with two muscles of the foot, an oesophageal head, with two one-toothed jaws, a short Oesophagus, a simple conical alimentary canal, with two glands, a ball-like ovarium, and a double group of colourless cervical eyes, are the details of the organization at present known. The frontal uncinus, or hook, is perhaps a respiratory tube. Perty doubts if Ehrenberg is correct in his interpretation of the Supposed agglomeration of the eyes in Theorws. THEORUs vernalis. –Toes small; no creature is active and vehement, like that frontal uncinus. The movement of this of an animal of prey, (xxxiv. 427, a back OF TEIE EIYDATINAEA. 691 view of this animalcule extended, with T. uncinatus. – Toes long, a frontal six colourless eyes in each group; 428, a uncinus, or hook, present. Six visual specimen with four eyes; 429, body con- points have been seen by Ehrenberg. tracted, but jaws extended.) Amongst Amongst Oscillatoriae, 1-240" Oscillatoriae. 1-140". The two next genera mentioned are from Mr. Gosse, who, however, adduces the latter one as a doubtful member of the present family. Genus ASPLANCHNA (Gosse, A. N. H. 1850, vol. vi.) (XII. 65, 66; XXXVI. 7–9; XXXVII. 27–32).-Rotatorial Hydatinæa destitute of foot, intestine and anus, but possessing eyes (ocelli) and jaws; sexes disjoined. This new genus embraces the Rotatorial animal which Mr. Brightwell introduced to notice as “a supposed new species of Notommata'' (Fauna Infusoria, Norfolk, 1849), and in which he first detected the existence of male animals distinct in Organization and character from the female. It was soon perceived that the new forms represented by Mr. Bright- well could not belong to the genus Notommata of Ehrenberg; and the discovery of other similar beings has led to the creation of this genus Asplanchna. ASPLANCHNA Brightwelli. — Jaws (mandibles) one-toothed; eye single ; stomach oval, longitudinal; vesicle lobed, larger; tremulous corpuscles (gills, Ehr.) affixed to a long filament; ovary two- hormed. Length about 1-24". (XII. 65. 66.) Males with jaws, pharynx, and stomach absent; body truncate. Length about 1-40". Found at Norwich, Lea- mington, Hampstead Heath, &c. Mr. Brightwell's account is embraced in the following extracts:— “It (the female) is furnished with an ovisac, in which the young may be clearly detected, and from which they are ex- elled through the sides of the animal. Some of the young appear to differ in form from the others, and there appear to be two kinds of ova, One, and that by far the ſº number, transparent, and hatched in the body of the parent; the other, more opaque, perhaps remain- ing unhatched, or deposited till vivified under favourable circumstances in Some ensuing season. Should this, on further investigation, turn out to be the case, we shall have, among the Rotifera, the same mode of preserving the Ova during the winter as is found in some of the Entomostraca, the Daphnia for instance.” “These [the males] are smaller than the females, and have a pyriform Sac below, from which there is an opening, and which is filled with spermatozoa ; and they have neither jaws, nor gullet, nor stomach; and it would seem they are designed, as is the case with the males of Some insects, to continue the race and then to perish. . . . I have lately repeatedly seen the male in connexion with the female. He attaches himself to her side by his sperm-tube, and re- mains attached from twenty to seventy seconds.” For a more complete description of these very interesting forms we may refer the reader to the elaborate details and figures of their organization, by Mr. Dalrymple, in the Philosophical Trans- actions for 1849, and to Part I. p. 453 et seq. of this volume. Notommata Anglica of Leydig appears to be only Mr. Gosse's Asplanchna Bright- welli. A. priodonta (Gosse).-Females: Jaws Serrated ; eyes three ; stomach hemi- spherical, transverse; vesicle spherical, Smaller; tremulous bodies attached to a twisted and plicate filament; ovary sub- globose (XXXVI, 9; XXXVIII, 28). Length about 1-48". Males: Body acute (xxxvi. 7, 8). 1-110". Found in the Serpentine river. (Figs. 10, 11 exhibit the jaws of the female detached. A. Sieboldii (Notommata Sieboldii, Ley- dig) (XXXVII. 27–32).-Females closely resemble those of Leydig's N. Anglica, but the males differ widely. Female campanulate, no foot ; anterior extre- mity widened ; ciliary wreath inter- rupted by a fissure at the mouth, into which the fine cilia descend; two large lobes (32 g) on the rotary Organ, crowded by setae, with two similar smaller ones; between these, on each side, is a fossa. with long motionless setae. Mouth open- ing into an angular maxillary bulb. Jaws (XXXVII. 31) with one furcate piece 2 Y 2 692 SYSTEMATIC HISTORY OF TEIE INFUSORIA. hooked at the end; on the inside is an aculeate process and a ridge to which strong striated muscles, working the jaws, are attached. CEsophagus long, its lower end highly muscular; two spherical glands open into the round yellowish-brown stomach (32 b); intes- time absent. Walls of the contractile vesicle (32 e), which open into the cloaca, with a muscular network. Two water-vascular canals on each side, one with granular walls, the other wider and with about fifty tags (31 & 32). Cere- bral ganglion laid across the maxillary bulb, with a dark-red or black speck above and behind it in the median line. Cells of the ganglion, according to Leydig, fusiform, and prolonged into nervous cords. A nerve is said to pro- ceed from each side to the setigerous fossa of the rotary organ, where it swells out like a ganglion; another nerve, from its posterior surface, divides to supply the smaller eminences on the rotary Organ; and another pair from the same sur- face supply the smaller eminences: but we think these supposed nerves require re-examination. Ovary horseshoe-shaped (32 c). Male and female young never si- multaneously generated within the same parent. , Winter eggs (xxxvii. 27, 28) spherical, usually one or two, never more than three; yell; yellowish-red, invested by a thin membrane, which in turn is surrounded by a thick granular tuber- culated shell, the latter rendered pale by potash, which partly obliterates the tubercles. On keeping specimens in pure water without nourishment, all the eggs deposited were winter ova. Males différ in figure (fig. 29) from females: clavate, with four conical arms; the two anterior ones (29 a) the Smallest. When swim- ming, which it does on its back, these arms are shortened. Rotary, muscular, and nervous structures as in the females. Pyriform testicle (29 c) next the con- tractile sac, filled with spermatozoa, amongst which are round vesicles, nu- cleated fusiform bodies (30 b, c), curved, nucleated, sickle-shaped objects (30a), and stiff, sharply-defined rod-like bodiés (30 f). Duct on the abdominal surface at the end of the body, and surrounded by, what look like accessory glands. Alimentary canal absent; the rudimen- tary digestive organs, represented by an irregular hº cells behind the pos- terior anus. Young males born alive. Genus TAPHROCAMPA (Gosse).-Rotary organ wanting, body fusiform, annulose; tail forked; gizzard oval; mallei incurved, shorter than the incus, which is also incurved. TAPHRocAMPA annulosa. — Occipital mass opaque, white; alimentary canal simple, wide, cylindrical; points of tail short, conical. 1-110". e . This species is evidently allied to M. Dujardin's Lindia torulosa, but differs from it in the structure of the dental apparatus, and of the digestive canal. It seems to connect the genus Chaeto- notus with the Hydatinaean genera No- tommata and Furcularia; for it has the jaws of these larviform Rotifera, and the glandular occipital mass found in some of them, with the form, simple digestive canal, and manners of Chaeto- notus. Found at Leamington. We will append here two genera of the family Furculariens of Dujardin, which that naturalist has created either to embrace new species or to dispose of those described by Ehrenberg which Dujardin cannot include with other of his genera. Likewise, before commencing with the next family (Euchla- midota of Ehrenberg), we shall take the opportunity to detail the characters of a family discovered and named by Dujardin, viz. Albertiens. Genus PLAGIOGNATHA (Duj.).—Body oblong, curved and convex on one side, or cornet-shaped and obliquely truncate in front; terminated pos- teriorly by a more or less distinct tail, bearing two styles. Jaws with parallel branches turned the same way, and recurved towards the ciliated margin with a straight central stem (fulcrum), very long and enlarged at its base; eye- specks one or two. We propose this as a genus of Furculariens. Although possessing a curved figure, with a characteristic form of jaws, Ehrenberg has distributed them in his genera Notommata, Diglena, and OF TEIE EUCHILANIDOTA. 693 Distemma, according to the number and disposition of their red points, and without consideration of the characters we employ. | PLAGIOGNATHA Felis. – The species we regard as the type of this genus is the P. Felis, called by Müller Vorticella Felis, but not answerable to the Notam- mata Felis of Ehrenberg. Its two styles are one-fourth of its entire length, and are curved backwards; the back is con- vex, abruptly truncate behind. 1-118". PL. lacinulata has been classed by Ehrenberg among the Notommatae. A variety of this º with two eye- specks may be referred to the Distemma setigera (Ehr.). One must also regard as distinct spe- cies of Plagiognatha the Notommata Tigris and the Diglena catellina of Ehrenberg. The Diglena lacustris of the same author also corresponds in form; but its jaws are not sufficiently described to deter- mine its position; whilst his Notommata hyptopus, represented with one-toothed jaws, analogous to those of our Furcu- laria, appears the same as a Systolide known to us, evidently possessing the jaws of a Plagiognatha. Genus LINDIA (Duj.) (XXXIX. 1–3).-Body oblong, almost vermicular, articulated by means of shallow transverse folds, rounded in front; protrudes, when swimming, two small clavate Organs (3 m), clothed with radiating cilia at their extremities, and forming a retractile rotary organ on each side. Jaws (fig. 2) composed of three pincer-like teeth. Eye-speck single, in front of a blackish calcareous (?) sac. extremity. LINDIA torulosa (Duj.). —Body red- dish. Length 1–6", Perty; 1-7", Du- jardin; 1-8", Cohn. Cohn, whose amended characters of the genus we have given above, thinks that Notom- mata roseola may be identical with this species: the latter differs from Notom- mata tardigrada, which it much re- Two short conical toes at the posterior rotary organ, Our author also contends, in opposition to Dujardin, that the oeso- phagus is ciliated. It is not, however, quite certain that they refer to the same animal. It is distinct from Notommata vermicularis, which it resembles. Cohn thinks the genus Lindia should be located amongst Philodinaea, sembles, in the presence of the club-like FAMILY OF THE ALBERTINA (ALBERTIENS). Body cylindrical, vermiform, round in front, with an oblique opening, from which a ciliated organ protrudes itself, almost larger than the body; termi– nated posteriorly by a short conical tail. Jaws in the form of hooks, simple, or with one tooth each. - This family comprises but One genus, and One species, Albertia vermicularis (XXXVIII, 35, 36), which is found parasitic in the intestine of Lumbric. and snails. 1-79" to 1–47". - The ova with their embryos are seen in its interior, in various stages of development. t The ciliated apparatus, in advance of the mouth, is surrounded by an appendage in the shape of a spur (calcar). FAMILY WI.—EUCHILANTDOTA. This family comprehends such Rotatoria as have a compound rotary organ with more than two subdivisions, and whose bodies are enclosed in a hardened lorica. The latter is very variable in form. Ehrenberg has remarked that it Sometimes resembles the hard carapaces of tortoises, at others the shells of crabs. In the former case the lorica is open at the extremities; and in the latter, Ehrenberg supposed it to be open inferiorly in Euchlamis; but this is 694 SYSTEMIATIC EIISTORY OF TEIE INFUSORIA. denied by Cohn, whose testimony is to be relied upon. The animal contained within this lorica presents the typical features of the Rotatorian class, just as some minute Crustaceans (Entomostraca), though enclosed between bivalved cases, retain the internal organization of their more conspicuous and shel– less allies. The Euchlanidota are provided with the various Rotatorian appendages—these exist as setae, uncimi, spurs, or tactile organs; and all are provided with the characteristic tail or foot terminating in one or two digits, this organ being largely employed in locomotion, either as a rudder or as an anchor. The hardened tegument forming the lorica is variously prolonged into spines and other appendages. Sometimes these are most developed anteriorly, at others posteriorly, whilst in Stephanops a broad expansion of the front of the lorica is developed into a curious crystalline hood. The Sur- faces of the lorica likewise are variously sculptured and ornamented. The eye-speck, to which Ehrenberg has attached such importance in his subdivision of this family, possesses, as Dujardin has pointed out, less value as a basis of classification than the Prussian observer supposed; but if the observations of Leydig prove correct, the organ acquires additional interest from the discovery of a refracting body in the eyes of Euchlamis wrvisetata and Stephanops lamellaris. Should these observations be confirmed, they will do much to remove all doubt respecting the visual character of these Organs,— doubts which are naturally suggested by the improbability of visual organs being given to the embryo encased in the egg, whilst the matured, active, bustling animalcule becomes deprived of them when its life seems to render their presence most necessary. The exact nature of the internal organization of most of the Euchlanidota is yet uncertain, and requires further study; but each form, when minutely examined, is found to approximate more closely to the Rotatorian type. Thus, whilst all are provided with a muscular system, Cohn has demonstrated that in Euchlanis the fibres are of the striped or voluntary type. The same observer has also shown that Euchlamis dilatata is bisexual, the males resembling those of Hydatina and Asplanchma in being unsupplied with an alimentary canal. These are approximations towards a general reduction of the whole class to a common type of organization of a higher character than was formerly thought to exist amongst Rotifera, but at the same time very different to what was originally attributed to them by Bhrenberg. The genus Lepadella developes itself occasionally in such myriads, in stagnant water, as to give a whitish turbidity to it. Threnberg's arrangement of the genera is given at p. 478. Dujardin includes most of the genera in his family Brachiomiens. Genus LEPADELLA (XXXIV. 430–433). — Eyes absent; foot furcate. Several trochal muscles are seen, and foot ones in two species. The jaws of the oesophageal head are single-toothed in L. ovalis and L. emarginata ; in L. Salpina triple-toothed. The oesophagus is very short in all; the alimen- tary canal below is constricted, except in L. Salpina, in which it is simple. The ovary is globular in all; in L. Salpina probably a cerebral ganglion (no eye) exists. L. ovalis is sometimes developed in myriads in stagnant water. Dujardin has the following criticisms on the genus Lepadella:-‘‘Wishing to derive his generic characters too exclusively from the eye-specks, Ehren- berg has separated all those having such specks into several genera; consti- tuting of those with two eye-points the genera Stephanops and Metopidia, and of those with four red specks the genus Squamella. But we are con- vinced that these red points may be present or absent in the same species at different periods of development. We believe, for instance, that the Lepadella ovalis and Stephanops muticus (Ehr.) are but a single species; Lépadella OF THE EUCHLANIDOTA. 695 Patella with or without red dots; so also the Metopidia Lepadella and Squa- nella bractea are the same, and what we name Lepadella rotundata. More- over the Squamella oblonga and Metopidia acuminata are two distinct species of Lepadella.” LEPADELLA ovalis (Brachionus ovalis, M.).-Lorica depressed, oval, not emar- ginate, attenuated anteriorly, the ends truncated. The alimentary canal of this animalcule is generally filled with a yel- lowish substance, except when it feeds upon colourless Monads. (XXXIV. 430, a back view; 431, a side (right) view of a young specimen; 432, the lorica; 433, the Oesophageal head.) 1-240". L. emarginata (Brachionus Spatella et ovalis, M.). — Lorica depressed, oval, broad anteriorly, extremities emargi– nate. Amongst Confervae. Length, without foot, 1-576". L. (?), Salpina. —Lorica oblong, pris- matic, obtusely triangular, back crested, denticulated. Amongst Confervae. Length of lorica, 1–200". Genus DIPLAX (Gosse).-Resembles Salpina; but the eye is wanting, and the lorica (which, as in that genus, is cleft down the back) is destitute of spines both in front and rear; foot and toes long and slender. It forms a connecting link between Salpina and Dinocharis. The name, signifying double, alludes to the gaping lorica, which forms two parallel plates. In accordance with the tabular disposition of the family, this genus follows next after Lepadella. DIPLAX compressa. — Form of lorica (viewed laterally) nearly a parallelo- gram, greatly compressed. Lorica1-176". D. trigoma—Lorica three-sided, a sec- tion forming a nearly equilateral triangle, surface delicately punctured or stippled; toes long and slender. Lorica. 1-160". Leamington, Genus MONOSTYLA (XXXIV. 434–437). — Eye single, cervical; foot simple, styliform; lorica (testula) depressed, ovate. the Oesophageal head has four muscles; in one been noted in two species species the jaws are single-toothed, in the other two-toothed. very short; stomach constricted (Gasterodela), with two glands. Numerous muscles have OEsophagus The ovary is globular; an ovum, with the vesicle of the germ within it, was seen in two species. No male organs, vessels, or respiratory tubes, are seen. Owing to the almost constant vibration of the foot-like tail, it is difficult to observe the true form of its termination, the motion producing an optical deception; hence it appears double, though in reality it is single. MonoSTYLA cornuta (Trichoda cor- nuta, M.). — Lorica hyaline, unarmed, and truncated anteriorly. Amongst Charae and Confervae. 1-250". M. quadridentata. —Lorica yellowish, anteriorly deeply dentated, resembling four horns. It is generally of a yellow leather colour, but Ehrenberg has seen it colourless. (XXXIV. 434 & 435, ventral aspect; in the latter the animal is ex- tended beyond its lorica, which happens when the rotary cilia are in motion. Fig. 436, a side view ; 437, the jaws j teeth separated.) In floccose matter about Confervae and the leaves of water- plants. 1-120". M. (?) lunaris.-Lorica hyaline, flex- ible, admitting the retraction of the head, anteriorly crescent-shaped, 1–144". Colour grey, usually so dark that no internal organs are distinguishable. Eyes red; jaws large, two-toothed; eggs few. M. Bulla (Gosse). —Body ovate, in- flated, the back very gibbous; lorica plicated on each side, with a deep fur- row; the occipital and mental deeply incised. Colour yellowish-brown. Length of lorica, 1–175". Genus MASTIGOCERCA (XXXIV. 438–440).-Dujardin and Perty be- lieve this to be identical with Monocerca. Genus EUCHLANIS (XXXIV.441–446; XXXVIII. 5,18; XXXIX.4, 5, 7)—Lorica resembling a tortoise-shell; according to Cohn not slit inferiorly, 696 SYSTEMATIC HISTORY OF THE INFUSORIA. as described by Ehrenberg. Dorsal and ventral plates United along the sides, forming an acute ridge, leaving a fissure, posteriorly, for the foot. Dorsal plate , the largest. Frontal portion of the animal retractile within the lorica; deeply cleft on its ventral aspect, with the oral orifice at the bottom of the cleft. Expanded anteriorly into lappets supporting hooked bristles. On either side is a conical process terminated by a long stiff Seta. CEsophagus capacious; jaws resembling those of Hydatina and Brachionus. Stomach thick and rounded, with two small spherical glands. Intestine pyriform, ending in a cloaca at the posterior border of the ventral plate; both ciliated. Contractile vesicle opening into the cloaca, sending up on each side a coiled water-vessel with about four vibratile tags. Longitudinal muscles strong, striated. A large trapezoid cellulo-granular organ in the head, with a red speck near its front extremity, and on each side a long, finely granular Saccular appendage. Tail with three telescope segments, ending in two long knife-like toes. Dujardin does not admit the genus Monostyla, but places its three species in the present one—Euchlamis. EUCLILANIs(?) triquetra (XXXVIII, 5a). —Lorica very large, trilateral, with a dorsal crest; sette on foot, none. This species is very diaphanous; and “there- fore,” remarks Ehrenberg, “I was never able to see the line of division on the ventral surface of the lorica. The rela- tionship of the fibres of the lateral muscles is physiologically and anatomi- cally interesting: they form three bun- dles, on each side, and show as distinct corrugations as do the muscles of larger animals.” (XXXIV. 443, a fore-shortened view ; 442, a left side view, showing the dorsal crest of the lorica: at the base of the foot an external empty fold of the skin is visible. Fig. 441, the ven- tral surface, showing an opening for the foot, but no division of the lorica; 444, the teeth and jaws separated.) In turf-pools. Length 1-48"; ovum 1-192". (XXXVIII, 5.) E. (?) Hornemanni. — Lorica thin, short, cup-shaped, truncate in front, the anterior part of the body soft (pliant) and elongated. This creature appears able to draw within the lorica, both foot and head. Sometimes longitudinal muscles are apparent. 1-432" to 1-240". E. Luna (Cercaria Luna, M.). -Lorica cup-shaped, the front excised in a lunate manner, toes with claws. The single- toothed jaw, the constriction of the ali- mentary canal, and the claws distinguish it from the other species. Amongst Ceratophyllum and Confervae, 1-144". According to Perty, specimens occur of a rosy red colour, E. macrura.-Lorica large, ovate, de- pressed; bristles at the base of the foot; toes long, styliform. This species is di- stinguished from the following one by its stronger and longer toes, “Lately,” says Ehrenberg, “I saw the division of the lorica along the ventral surface.” Each jaw has five teeth; and there are two soft maxillary appendages, each with two teeth. Amongst Confervae in clear water. Length, without foot, 1-96". Perty states that the stomach and in- testines are sometimes red. E. dilatata (Brachionus, M.).-Lorica broad, depressed, folded on the under side; foot without setae; toes long. This animalcule, when it emerges from the egg, has a very soft lorica, and re- sembles Notommata. Cohn states that the males of E. dilatata are like the female, only smaller and more slender, as well as more transparent from the absence of mouth, Oesophageal bulb, and intestine. The testis of the male occupies the centre of the body, and is a lancet- like elongated sac (XXXIX, 5 h), extend- ing from the cloaca to the cerebral ganglion, and filled with rod-like sper- matozoa. At its posterior extremity it is in connexion with a reniform body surrounding and opening into the penis. The latter has a thick wall and a ciliated canal protruding as far as the first seg- ment of the tail (5 pe). Length of lorica 1-8" to 1-20" (figs. 4, 5, 7). E. Lynceus. – Lorica ovate, turgid, deeply fluted; two little horns project anteriorly. (XXXIV. 445, a back view; and 446, a side view); the lorica is open along the middle of the under side. Length of lorica. 1-216". E. deflea'a (Gosse).-Body semioval; ventral surface of the lorica divided lon- gitudinally, and the edges of the fissure bent out at right angles; foot furnished with two pairs of bristles; toes spindle- shaped. Lorica. 1-80". E. pyriformis.-Outline (viewed dor- OF TEIE EUCEILANIDOTA, 697 sally) nearly oval, with a slight con- striction in the middle; lorica divided longitudinally along the ventral surface, the gape widening anteriorly; toes pa- rallel, edged; eye minute. Lorica. 1-62". E. Hipposideros.-Nearly oval in out- line; the ventral side flat ; the dorsal greatly arched, and ridged down the middle; lorica formed of two distinct i. the dorsal plate enveloping the ack and half down the sides; the ven- tral separated from it by a wide space, and hollowed in the middle, so as to present the figure of a narrow horseshoe, whose points are forwards; foot armed with one pair of bristles. Lorica. 1-110". E. emarginata (Eichwald).--Distin- guished from E. Luna by a projection at | the end of each tail-flap. E. bicarinata (Perty). —Body elon- gated. Dorsum of lorica with two arallel keels, rounded behind. Tail ong, with two terminal pincers; body wide in the middle, contracted towards each end. Middle joint of the tail very long ; toe-segment very short. Eye blackish-red. It is allied to E. Weissä of Eichwald, but distinguished by its long figure and long setae of tail, 1–6". Perty believes that this species connects Euchlamis with Salpina. i.i. regards it as a Salpina. E. wºmisetata (Leydig.)—Size of E. di- latata. It has a single jong bristle located on the dorsal surface of the foot-articu- lation; and, according to Leydig, the eye has a refracting lens (XXXVIII. 18), - Genus SALPINA (XXXIV. 447–453).-Eye single, cervical; foot furcate; lorica prismatic, with bulging sides, closed below, and terminated by spine- like processes or teeth. “The lorica,” says Ehrenberg, “resembles a three- sided little casket, with arched sides, flat below, and having, anteriorly and posteriorly, at the truncated extremities, little points.” entirely withdraw itself within the lorica. ridge upon the back, which in some appears to be double. The animalcule can All the species have an elevated A compound rotary organ, two short anterior lateral, and two foot muscles are seen in S. mucromata. An Oesophageal head, with three- or four-toothed jaws, a short Oesophagus, and a simple conical alimentary canal exist in all the species; in five the conical intestine has two spherical glands. The ovary is distinct. A spur or tube is observed at the neck in three species; the red eye in connexion with a cerebral ganglion is always present. They do not increase in large masses. SALPINA mucronata (Brachionus mu- cromatus, M.).—Lorica very minutely sca- brous, anteriorly with four, and poste- riorly with three horns, generally straight and of equal length. The lorica, when the creature is young, is soft and bent, but soon hardens, and produces horns. The spur, or tactile tube, in the neck, terminates in a little bristle, as seen in .xxxiv. 450. In some specimens, Ehr- enberg says, the lorica appears as if punctate or stippled. (447, 448, full- grown specimens, with the head with- drawn; the latter figure is a back view, the former an under one ; 449, a side view, head extended; 451, an egg just deposited on Lemma; 452, an egg with the young vibrating ; 450, the young one just escaped from the shell; 453, the teeth separately.) Length of lorica 1–144", S. spinigera.-Lorica with four frontal and three posterior horns; the posterior dorsal one longest, and a little recurved, Among Ceratophylla, Length of lorica 1-140" (XXXVIII. 23, 24). S. ventralis. – Lorica stippled, horns two in front, three behind, the dorsal one short and decurved. According to Perty, a faint lens seen in the eye. Amongst Confervae, &c. 1-120". S. redunca-Lorica Smooth, horns two in front, three behind; two of the latter (the under ones) hooked, the dorsal crest bifid and gaping; teeth four to each jaw. Amongst Confervae. 1-200". S. brevispina.-Lorica milky and tur- bid, but appearing bright; scabrous, horns two (small) in front, and three behind, short dorsal crest not gaping; respiratory tube unknown. Amongst Ceratophylla, 1–144". S. bicarinata.--Lorica smooth, horns four in front, three behind, short; neither lateral muscles nor respiratory tubes known, 1-216". S. Spinigera, S. ventralis, S. redunca, and S. bicarinata are probably slightly 698 SYSTEMATIC EIISTORY OF TETE INFUSORIA. variable forms of one and the same | teriorly with obtuse angles. Transparent. animal, Eye red. Tail-flaps extend to the root S. mutica (Perty). —Lorica toothless of the tail. both in front and behind, truncate pos- Genus DINOCHARIS (XXXIV. 454–456). — Eye single, cervical; foot furcate ; lorica closed below, with a sharp lateral margin, but unarmed at both ends. The compound rotary organ has five or six muscles, and in two species the foot two. An Oesophageal bulb, with single-toothed jaws, is found, except in D. tetractis, which Ehrenberg thinks has four teeth; Oesophagus very short, alimentary canal constricted; two oval glands exist in D. Pocillum and D. tetractis. An ovary is seen in all, and a contractile vesicle at the base of the foot in D. Pocillum. Traces of a water-vascular system are perhaps to be seen in D. Pocillum, though even here it is doubtful, for the apparently tremulous organ just behind the Oesophagus may be only a tre- mulous condition of an internal fold of the stomach. The only evidences of a nervous system are the eye and the long ganglion which supports it. DINoCELARIs Pocillum (Trichoda Po- cillum, M.).-Lorica nearly cylindrical, with a slight dorsal ridge; two long spines at the base of the foot, toes three. (xxxiv. 454, 455 represent this creature in different positions; and 456 the oeso- phageal j Amongst Ceratophylla, &c. 1–120". D. tetractis.-Lorica acute, triangular; horns two, at the base of the foot; toes two. This species has longer toes than the others; and the body is comparatively shorter. With Lemnae and Ceratophylla. 1–120”. D. pauper.—Lorica acute, triangular; horns two, at the base of the the foot, scarcely perceptible; toes two, short. 1–120”. - Genus MONURA (XXXIV. 457–459).—Eyes two, frontal; foot simple, styliform. The lorica is somewhat compressed and open upon the ventral surface : anteriorly is a hook-like process, which can be withdrawn. In one species, the vibratile Organ has four to six muscular bulbs; in both, an Oesophageal bulb, with two-toothed jaws, a very short Oºsophagus, and a simple alimentary canal with two spherical glands are observed; an ova- rium, with a single large ovum, has been seen. The eyes are red, moveable, and seated upon nervous masses. The species are not only difficult to di- stinguish from each other, but also from the genus Colurus, the toes of the latter appearing single until pressure is used. MoWURA Colurus. – Lorica oval, ob- tuse, obliquely, truncated posteriorly, eyes near to each other. Lorica. 1-280". Siberian specimens 1-400". M. dulcis. – Lorica ovate, anteriorly acute, posteriorly obliquely truncate; eyes distant from each other; the ali- mentary canal is often filled with green matter. They increase rapidly in glass vessels. (XXXIV. 457-459 represent three views of this animal.) Amongst Con- fervae. Length of lorica. 1-288". The two species of Monura are referred by Dujardin to Colwus, or, to adopt his appellation, to Colwrella. Genus COLURUS (XXXIV. 460–462).-They have two frontal eyes, a furcate foot, and a compressed or cylindrical lorica. The lorica is said to be open upon the under side (Sowtellum); a compound rotary organ is present in all, over which projects a retractile frontal hook; an oesophageal bulb with two jaws, in two species with two or three teeth; the oesophagus very short; two species have a constricted stomach (Gasterodela), the others have a simple alimentary canal (Coelogastrica), all with glands. The two red frontal eyes are delicate; in C, wheinatus and C. bicuspidatus they have escaped observa- OR THE EUCHLANIDOTA. 699 tion; all have peculiar vesicles at the back. They resemble Monura. Foot furcate. CoLURUS (P) uncinatus (Brachionus wncinatus, M.). — Lorica ovate, com- pressed; posterior and bi-pointed toes, very short; at the middle of the back is generally a circlet of vesicles, which at one time Ehrenberg considered eyes, but which he now regards as vesicles of oil, as they are seen in all the species, and C. caudatus. – Lorica ovate, com- º posterior points distinct; toes onger than the foot. The shell re- sembles C. uncinatus, but the toes are much longer. In fresh and sea water. Lorica. 1-288". C. deflexus.-Lorica ovate, compressed; the shell is more rounded, and very abundantly in the Cyclopida. In fresh and sea water. 1-430" to 1-288", C. (P) bicuspidatus. – Lorica ovate, compressed; the two points posterior, strong; toes short, 1-288". transparent. (XXXIV. 460–462 represent back, under, and side views; the former shows the vesicles.) In the clear water of a peaty moor. 1-240". Genus METOPIDIA (XXXIV. 463-465).—Eyes two, frontal; foot fur- cate; lorica depressed or prismatic; the frontal portion naked or uncinate, not provided with a hood; indeed they may be regarded as Lepadellae with two red frontal eyes; the lorica, which is oval and semicircular or crescentic in front, appears to be closed on the under side (testula). In two species the rotary organ has from three to four muscles; and in one species two foot muscles are observed. Two species have a frontal hook, like Colwrus. The osophageal bulb in one species has two, in another four, but in the third no distinct teeth; a short Oesophagus and two spherical glands are present in all. Two species have a distinct constricted stomach (Gasterodela). An ovary is present; and M. triptera has a contractile vesicle. Eye, according to Leydig, with a lens. METoPIDIA Lepadella. — Lorica de- pressed, nearly flat, broadly oyate, ex- cised in a lunate manner in front, rounded posteriorly; toes somewhat longer than foot. This species resembles in form Lepadella ovalis (XXXIV. 430– 433) and Squamella Bractea; but the former has two-toothed jaws and no eyes; the latter, four eyes and indi- stinctly-toothed jaws, (XXXIV.463-465, back, under, and side views, the first and last having the rotary organs ex- tended and in motion.) 1-240". M. acuminata. — Lorica depressed, nearly flat, oval in shape ; anteriorly slightly excised, posteriorly pointed. This species resembles Colurus; but in that genus the eyes are very close to- gether, and the lorica open beneath. Genus STEPHANOPS (XXXIV. Amongst Oscillatoriae. 1-240". M. triptera.—Lorica oval, triangular, back crested : a section would resemble xxxiv. 443. Amongst Confervae. 1-200". M. solida (Gosse). — Much resembles M. Lepadella, but is considerably larger; lorica circular, brilliantly transparent ; a slight punctation Surrounds the edge, like that on a coin. Lorica. 1-150". M. owysterna-Resembles M. triptera, but the dorsal keel is much higher and thinner; the anterior two-thirds of the ventral surface form a prominent ridge, terminating abruptly like the breast- bone of a bird; and the posterior portion is hollowed out lº. Viewed laterally, the outline of the back is very gibbous behind. Lorica. 1-175". 466, 467; XI. 8–10). — Eyes two, frontal; foot furcate; lorica depressed or prismatic, the front expanding into a hood or transparent shield. The lorica, in two species, has thorn-like processes posteriorly. In one species a longitudinal muscle is observed on each side (anteriorly), two muscles for moving the foot, and from three to five belonging to the compound rotary organ. The oesophageal bulb has single- toothed jaws, and a short oºsophagus. In one species the alimentary canal is constricted, in the others it is simple; two species have glands; an ovary 700 SYSTEMATIC HISTORY OF THE INFUSORLA. exists in all; a contractile vesicle in two. The red eyes are situated on each side, near the frontal head in two species; in one they are yet unknown. The hood remains extended, even when the creature withdraws within its shell (XL. 8–10). STEPHANOPS lamellaris (Brachionus lamellaris, M.), Lorica with three spines posteriorly. The rapid movement and transparency of this animalcule renders its organization difficult to observe. A process extends upwards from the oral opening and diverges into two filamen- tous appendages. Leydig affirms that the eye has a distinct hemispherical lens, and that the alimentary canal is divisible into maxillary bulb, stomach, and intes- time. The two latter ciliated. Also a contractile vesicle present. (XXXIV. 466, 467, different views with the crystalline hood or diadem. This hood is often much larger than is represented in Ehr- enberg's figures.) Amongst Confervae. Length of lorica about 1-300". S. (?) muticus (XL. 8–10). — Lorica unarmed posteriorly, entire. Two eyes, red. Head and tail larger in proportion to the trunk than represented by Ehren- berg. 1–144". - S. cirratus (Brachionus cirratus, M.). —Lorica with two spines posteriorly. This species' has a contractile vesicle. 1-240". Genus SQUAMELLA (XXXIV. 468, 469). — Eyes four, frontal; foot furcate. six muscular bulbs. The lorica is closed (testula); the rotary organ consists of five or In one species the oesophageal bulb has jaws, with two or three teeth each; its tube in one is short, in the other long and bent like the letter S. Both have a bipartite intestine (Gasterodela), with small glands; also an ovary and contractile vesicle. The eyes are disposed in pairs on each side the brow. SQUAMELLA Bractea (Brachionus Brac- tea, M.). — Lorica depressed, broadly ovate. It is very transparent; the toes thick and short, not evident. Length of lorica. 1–l44". long and slender; eyes larger than in the foregoing species. (XXXIV. 468, 469 represent back and side views of this animalcule.) In green-coloured water, with Chlamydomonas Pulvisculus, Length S. oblonga.-Lorica depressed, either of lorica. 1-280". elliptical or ovato-oblong, hyaline; toes Gemus NOTOGONLA (Perty).-Body covered by a lorica which dilates posteriorly; posterior margin occupied by two pointed processes on each side, the shorter one being directed backwards and the larger one outwards. Two eyes widely separated, on the outer margins of the anterior extremity. Jaws curved, strong, with two or three teeth. Caudal setae strong and bristle-like. - NoToGONIA Ehrenbergii. — Slightly tail, 1-14". Motions rather brisk, re- ventricose, grey. Rotary, organ com- sembling those of Brachionus. Amongst posed of a single row of cilia; eyes very | Confervae. small, pale red, Length, including the FAMILY WII.—PHILODINAEA. This family comprehends Rotatoria devoid of lorica, but possessing two simple rotary organs, resembling wheels. The body of most species is worm- like, or spindle-shaped (fusiform). Portions of the body can be thrust in and out, like the tubes of a telescope; this is effected by a sort of false joint, caused by a peculiar insertion of the muscles. In all the species the foot is furcate; and in Callidina, Rotifer, Actinwrus, and Philodina it is provided with soft processes, near the false joints, resembling horns in shape, as in the genus Dimocharis (fig. 455). Muscles are seen in the genera just named. OF TECE PEIILODIN AEA, TO1 The nutritive apparatus consists of an oesophageal bulb, with two jaws; in three of Ehrenberg’s genera these are double-toothed (Zygogomphia); in two the teeth are in rows (Lochogomphia). In the four principal genera the ali- mentary canal is filiform ; it is furnished with a bladder-like expansion at its commencement (Trachelocystea), and surrounded by a turbid cellular or glan- dular mass. In one genus the alimentary canal is conical (Coelogastrica), in the two African genera its character is unknown. In four genera the intes- time has glands; in a like number an ovary and glands are present ; a con- tractile vesicle exists only in Rotifer and Philodina, which, together with Actinwrus, are also sometimes viviparous. In Rotifer and Philodina, portions of a muscular system are visible, in the form of from nine to twelve trans- verse bands; the same genera, as also Activurus and Monolabis, have spur- like tactile tubes. In thirteen species red eyes are present; and beneath these organs, only what is supposed to be nervous matter is apparent. For Ehrenberg’s arrangement of the genera, see General History, p. 479. “The characters employed,” says Dujardim, “by M. Ehrenberg, for the distinction of his genera of Philodinaea, have certainly too slight a constancy to be admitted; that author has himself seen the red specks, which he calls eyes, vary in number and position in his Rotifers. As to the appendages of the tail (toes), they are not always alike visible, although actually present, because the animal does not extend them except at certain moments; the central terminal appendage—that by which the Rotifers affix themselves to solid bodies—is itself of greater or less length, but always present. We therefore think that but two genera can be rightly established : one, Callidina, characterized by the feeble development of its ciliated rotary Organ, and by entirely wanting red specks; the other, Rotifer, with two or several red points placed more or less near the exterior extremity, and, what is of more importance, with very highly developed rotary organs.” “The genera Hydrias and Typhlina are founded on imperfect observations made by the author during his journey in Egypt; and the genus Monolabis ought to be placed elsewhere.” The family Philodinaea thus formed is arranged parallel with Brachionaba, as though the absence of a lorica were the only difference between them. So far as Dujardin accepts of the same species, his family Rotifera and that of Philodinaea of Ehrenberg correspond. - The amazing persistence of vitality in the Rotifer vulgaris gives a great interest to this family, as also the occurrence of some of its members within the cells of aquatic plants. Dr. Morren’s observations probably ex- plain some of the latter occurrences; but it is a question whether recent discoveries in vegetable physiology may not further explain the existence of these animals within closed vegetable sacs. For instance, the origin of Some cells by the vacuolation of a soft penetrable protoplasm suggests the possibility that the Rotifera may deposit their eggs within the soft, half- organized protoplasm; and in the process of vacuolation some of these ova might readily find their way into the vacuoles about to be converted into cells, the latter change being completed before the embryonic animalcule escaped from its ovum; and when it did so emerge, the completion of the vegetable process would cause the animal to find itself imprisoned within the walls of a vegetable cell. Genus CALLIDINA (XXXIV. 470–473).--Distinguished by possessing a proboscis, and a foot furnished with processes resembling horns, and by the absence of eyes. The vibratile or rotary organ, is double, not pedicled, and is surmounted by a thickly ciliated proboscis. The furcate foot has two 702 SYSTEMATIC EIISTORY OF THE INFUSORIA, elongated toes, four little horns or processes, and six points. Muscles for moving the foot are also visible. The oesophageal bulb has two jaws, with numerous delicate teeth. The filiform alimentary canal has a bladder-like expansion posteriorly, but is not provided with glands: it is surrounded by a granular and cellular mass, whose function is unknown; Ehrenberg thinks it connected with reproduction. An ovarium, with single large ova, is seen. A little spur-like process projects from the neck. No indication of a nervous system is observable. CALLIDINA elegans.—Spindle-shaped, crystalline ; rotary organs, or wheels, small. (XXXIV, 470–472; 473, the eggs.) In bog-water and infusions of oak-bark. I-72". C. redivīva (Ehr.). — Fusiform, dif- fusely granular or else fleshy; with red, distinct ova, and strong rotary organs. 1-60" to 1-48"; ova 1-576". Berlin; in the sediment of water-spouts of houses. C. cornuta.-On each side of the head a short horn-like process. Maxillary bulb much wider behind than in C. ele- in the oesophagus. , Swims in rather an eel-like manner. C. constricta (Duj.), so named on account of the contracted form of its rotary apparatus. Its jaws pre- sent a row of closely-set parallel teeth, 1–52". C. bidens (Gosse). — Body spindle- shaped, jaws furnished with two distinct teeth. 1-45". Perhaps this is no other than C. elegans, the jaws of which Ehr- enberg describes as having many delicate teeth. I have, however, examined nu- merous specimens, and have always found gans, Ciliary motion unusually strong them distinctly two-toothed, Genus HYDRIAS (XXXV. 474).-It is devoid of eyes, proboscis, and the little horn-like processes at the foot; the two small rotary organs, or wheels, are supported on pedicles or arms. An oesophageal head, and an ovary, with a large ovum, have been seen by Ehrenberg. The form is like a naked Pterodina. This genus is constructed for an African Rotatorian imperfectly observed. HYDRIAS cornigera,_Ovate, hyaline; standing water from a small spring at foot attenuated, resembling a furcate | Siva, in the Oasis of Jupiter Ammon. tail. xxxv. 474 represents an animal- 1-190". cule extended. With Oscillatoriae, in Genus TYPHLINA (XXXV. 475).-Like the last, is an African form. Devoid of eyes, proboscis, and horn-like processes at the base of the foot; but its little wheels are sessile. It resembles a very small Rotifer, without frontal proboscis or eyes. * near Cairo in Egypt, in Such numbers as TYPHLINA viridis. – Body oblongo- to colour the water green. 1-720". conical, small (xxxv. 475). Found by Drs. Hemprich and Ehrenberg in a pool Genus ROTIFER (XXXV. 476–480; XXXVIII. 1–3).—Body fusiform. Able to retract and protrude its little foot with its appended horns. Eyes two, placed upon the frontal proboscis ; foot provided with little horn-like (corniculate) processes, and two toes bisulcate at their apices. A double rotary organ, furnished with muscles, is seen in all the species; also longi- tudinal and foot muscles in three of them ; a furcate foot and horn-like pro- cesses in four species; in R. citrinus the pincer-like portions of the foot appear to be tri-pointed; in R. erythraeus they seemed to be drawn in. In four species a muscular Oesophageal bulb, with jaws, each two-toothed, is seen; in three species the alimentary canal is filiform, with a vesicular expansion at the extremity, but no Oesophageal tube; it is moreover Sur- rounded by a cellular glandulose turbid mass ; another species has a conical, tubular alimentary canal, without the Surrounding mass or expansion at the OF THE PEIILODINAEA. 703 end; the four European species have two spherical alimentary glands, and an ovary, with a few large ova; occasionally these species are viviparous. In three of them a contractile vesicle is present. alimentary canal are two glands. In R. macrurus, near the In three species from nine to twelve parallel transverse muscular bands have been observed; and besides these, in the four European species, styliform tubes emanate from the neck, which in one species are ciliated anteriorly. Two red frontal eyes are met with in the four European forms, and beneath them, in R. vulgaris, two ganglia. ROTIFER vulgaris (Vorticella rotatoria, M.) (XXXV. 476–480). —Body fusiform, white, gradually attenuated towards the foot; eyes round. This creature, which was discovered by Leeuwenhoek, was described and illustrated in the Micro- scopic Cabinet some years ago, prior to the appearance of Ehrenberg's observa- tions. “It has the power of contracting or extending the length of the body in the following remarkable manner: — When the creature is about to shorten itself, transverse folds or joints are ob- servable, which do not appear to be con- fined in number or situation; the in- teguments, when a joint is º are drawn within the parts above, and slide out like the tubes of a telescope, when the joints disappear. It is this ower that enables it to assume the orm of a sphere, the head and tail being drawn within the body.” Anteriorly it has a proboscis-like process, with a cili- ated extremity, and a soft hook, near which are two dark red points. The body terminates posteriorly in a moderately long tail-like foot, having six processes disposed in pairs; two wreaths of cilia (the . voluntarily moveable, are placed upon short thick arms (pedicled), which can be drawn in and out at pleasure; these wreaths serve for swimming and purveying, the food approaching the mouth through the currents produced in the water by the cilia. On the dorsal Surface is a styliform horn (speculum collare, M.), at the end of which Leydig detected retractile cilia. During vibra- tion the neck has a circular fold, which appears on each margin in a front view like a lateral style. Four longitudinal muscles, two anterior and two posterior, are seen; laterally also two, club-shaped, for moving the foot, and two belonging to the rotary organ. Sometimes, says Ehrenberg, four anterior longitudinal muscles and a dorsal and ventral muscle appear to be present. It has two kinds of locomotion,--one by alternately attach- ing the mouth and foot, and, as it were, stepping along; the other by swimming, through the rotary apparatus. If the creature attach itself by the foot, and the rotary apparatus be in motion, a strong current or vortex is produced on each side the wheels, resembling two spirals in the water, which bring the nutritive particles to the mouth, from which some are chosen and the rest flow away. In order to observe this action with effect, finely-divided carmine or indigo must be mixed in the water. The oral aperture is placed just beneath the hook- like proboscis, from whence it continues backwards as a long extensible tube, as far as the oesophageal head, which has four muscles and two striated jaws with double teeth (Zygogomphia). From this point a filiform intestinal canal extends posteriorly, forming an oval expansion near its termination at the anus, at the base of the tail-like foot. A thick glam- dular cellular mass, often yellowish or greenish, Surrounds the alimentary canal; its use is unknown: anteriorly are two biliary glands. The propagative system is very interesting: the ovary is a glo- bose glandular mass; in it four or five ova. Sometimes so completely develope themselves that the young creep out of their envelopes, extend themselves, and put their wheels in motion while within the ovary; they sometimes occupy two- thirds the length of the parent. In the ovum the young are coiled up in a spiral manner. A contractile vesicle exists, and eleven or twelveparallel transversebands, probably muscular. The two red frontal eyes, with a ganglion beneath them, in- dicate a nervous system. These eyes are cells filled with a granular pigment, and sometimes separate abnormally into se- veral; Leydig affirms that they contain a refracting body. (xxxv. 476, a full- grown animal extended, and supposed to be attached to a fixed body—the currents about the trochal disc as dis- played when indigo is put in the water; 477, an under view, the wheels with- drawn, and body contracted ; 478, an extended Rotifer, wheels withdrawn ; 479, 480, upper portions more highly magnified, after submission to different degrees of pressure between the plates 704 SYSTEMIATIC HISTORY OF THE INFUSORIA, of a compressor. In XXXV. 476–478, ova are seen; some are developed, and their eyes and oesophageal bulb visible. The transverse muscles, and the tube pro- jecting from the neck, are seen in the engravings. Found in fresh and sea- water, in infusions, on the flocculent matters of water-plants, and even within the cells of some, e.g. of Sphagnum and Vaucheria, &c. (See Part I, p. 466.) I-50" to 1–24". R. (?) citrinus.--Fusiform, lower part gradually attenuated into a foot; its horn-like processes elongated ; eyes round and, according to Leydig, con- taining a refracting body; cervical tube toothed. The extremities are transpa- rent, the middle of the body of a citron colour; it often exhibits longitudinal folds, and is then less transparent. Amongst Oscillatoriae. 1-24". R. (?) erythraeus. – Small, oblong, suddenly attenuated into a long foot. 1-240". P. macrurus (Vorticella macrura, M.). —Transparent, ovato-oblong, suddenly. attenuated into a long foot; this is di- stinguished from Actinurus by its small toes, horn-like processes, and Suddenly- attenuated body. The style, or antennal tube, is ciliated in a star-like manner. The wheels are prominent. A long stomach is succeeded by a short intes- time; on each side is a convoluted water- vascular canal, but without vibratile tags. Eyes either two, hemispherical, abruptly truncate anteriorly, red, and with a refracting medium, or elongated posteriorly, becoming divided into seve- ral rows of linear points, without re- fracting media. It is altogether a choice subject for the microscope. In boggy water. 1–350". - R. tardus. – Hyaline, fusiform, gra- dually attenuated to the foot, and having deep strictures in the form of square false articulations or joints; eyes ob- º It resembles internally R. vulgaris. -80". Of the several species of Rotifer, and of the following one of Actinurus, de- scribed by Ehrenberg, M. Dujardin con- fesses his inability to discover the specific differences, although he admits diversity of habitat, and of resistance to the pro- cess of desiccation. He, however, be- lieves he has discovered a Rotifer spe- cifically distinct from any variety of IRotifer vulgaris ; this he would desig- nate R. inflatus (XXXVIII. 1–3).--It is less slender than R. vulgaris, its rotary organs of less size, and its red specks seated very near the jaws. 1-58". In water or wet moss. Of this species Dujardin infers that Ehrenberg has constructed at least four others, according to the rose or yellow colour it presents, the form of the eyes, and the length of the caudal appendages, viz. Philodina eryophthalma, § roseola, P. citrina, P. macrostyla. At the same time he would regard P. collaris, P. me- galotrocha, and P. aculeata as distinct forms of Rotifera. R. macroceros (Gosse).--Wheels large; antennal process (the respiratory tube, Ehr.) very long and mobile. 1-100". Genus ACTINURUS (XXXV. 481–484).—Eyes two, frontal; foot fur- nished with two little horn-like processes, and three toes. In other respects the organization resembles Rotifer vulgaris. ACTINURUs Weptunius (Vorticella ro- tatoria, M.). White, fusiform, gradually attenuated into a long foot, having three equal toes exceeding the horn-like pro- cesses in length. The action of the jaws in the oesophageal head is often distinctly seen. (XXXV. 481, an animal extended, with the wheels withdrawn, which is the case when crawling; the antenna is then seem, terminated by a single delicate hair-like point ; 482, contracted, head partially withdrawn; 484, the upper part, when the wheels are extended and in action; 483, the oesophagus and jaws, separated and extended under pressure.) 1-36" to I-18". Genus MONOLABIS (XXXV. 485, 486).—Eyes two, frontal red; foot with two toes, but no horn-like processes. They are provided with muscles for moving the double rotary apparatus, two for moving the foot, and four belonging to the Oesophageal bulb and jaws, which last are furnished with double teeth, or teeth in rows. A very short Oesophageal tube and a simple comical alimentary canal are seen in both species; one of them has two spherical glands; an ovarium is seen in both, but in neither have fully- OF THE PEIILODIN_AEA. 705 developed ova or male organs been observed. is present. MonoLABIs conica.--Stout, provided with a tactile tube, or spur, and three teeth in each jaw. Between the rotary In one species, a tactile tube different views from the under side.) 1–120". M. gracilis.-Has a more slender body. organs the brow can project and resemble than the last, and two teeth in each jaw, a proboscis, (XXXV. 485, 486 represent but notube Orspur. Length about 1-200". Genus PHILODINA (XXXV. 487–490; XXXVIII. 4). – Eyes two, cervical, foot with horn-like processes. All the species possess two vibratile or wheel organs upon the breast, and five of them have a frontal ciliated proboscis. Longitudinal muscles are distinct in one species, and two for moving the foot in six. The Cesophageal bulb has four muscles; its jaws are two-toothed in four species, three-toothed in two species; but in one species the oesophageal bulb has not been Satisfactorily seen. The alimentary canal is filiform, with a posterior enlargement in six species; in one it appears to have pouches or pockets. The glandular or cellular mass surrounding the filiform part of the canal sometimes becomes distinctly coloured when the creature eats coloured food, and therefore seems connected with the nutritive system, and is probably a convolution of caecal appendages. Biliary (?) glands are found in six species. The ovary developes eggs, which are usually extruded before the young are hatched. Three species possess a contractile vesicle; one, vibratile tags. A tube, in Some cases ciliated, is always present at the neck. Transverse bands are seen only in P. erythrophthalma. Eyes are found in all the spécies, and nervous ganglia connected with them in P. erythroph- thalma; sometimes the eyes are very pale; hence a solitary specimen may be mistaken for a Callidina. XXXVIII. 14 is a diagram of the head of Philo- dina as viewed in front, and fig 15 of the same viewed laterally. PHILODINA erythrophthalma (XXXVIII. 4).-White and smooth; eyes round; horn-like processes of the foot short ; jaws two-toothed. Found abundantly during the spring and summer in water- tubs and amongst Confervae. In glass vessels it increases rapidly; and, if sup- plied occasionally with two or three stems of hay, the breed may be preserved for || years. It is often met with in vegetable infusions of different kinds, 1-120" to I-48". . - - P. roseola.-Body Smooth; eyes oval, horm-like processes of the foot short. “I have observed,” says Bhrenberg, “that this animalcule, when kept in glasses, deposits its eggs in heaps, and the parent remains a long time with the young ones roduced from them, forming a sort of amily or colony, which circumstance we are not to be hindered from ascribing to a sense of company or family, though the pride of man may laugh at it.” (XXXV. 490 represents one with the wheels ex- tended.) 1-72" to 1-48". - P. collaris.-Body smooth, hyaline, or white, eyes round; a prominent annulus or collar surrounds the neck. It is especially characterized by the extent of the alimentary canal, and caecal appen- dages attached to it; so that, when the animalcule is fed upon indigo, it appears polygastric. 1-120". P. macrostyla.--White and smooth, with oblong eyes; it has three teeth in each jaw; horn-like processes of the base of the foot long. Found amongst Oscil- latoriae. 1-70". - P. citrina.—Smooth, citron-coloured in the middle; extremities white; eyes variable in form; horn-like processes slightly elongated. Found amongst Os– cillatoriae. I-70". - * P. aculeata.--White, provided with Soft spines; eyes round. The tactile tube (antenna) is thickened anteriorly in a globose manner; the jaws have each three teeth. (XXXV. 487, 488 represent this animalcule; and 489 the jaws and teeth **) 1-70". . . - . megalotrocha,_White; bodysmooth and short; wheels large; the proboscis between them long; eyes oval; jaws two- toothed. Two straight setae at the end of the tail. 1-216" to 1-108". P. hirsuta. — Of a pale yellow co- lour, and covered with a short down ; eyes oblong; foot prolonged by dorsal spines; viviparous, Length 1-72"; of egg 1-480". Berlin, *f 2 z 706 SYSTEMATIC E[ISTORY OF TEIE INFUSOIRIA. FAMILY WIII.—BRACHIONAEA. The concluding family of the Rotatoria, BRACHIONAEA, is distinguished by its members having two rotary organs and a lorica. The lorica is open at the extremities, like a tortoise's carapace. The rotary apparatus is often apparently composed of five parts, three central and two lateral; of which the latter alone belong actually to it, the others being only ciliated frontal portions, which during the vibration of the trochal disc remain stiffly extended as feelers. Besides these appendages, the disc presents in most, perhaps in all the species, two setae, as is seen also in Symchaeta. The genera Noteus and Brachiomus have a forked foot, Anuraea is destitute of feet; and Pterodina has a suctorial disc at the end of the foot, but no toes. All the genera have jaws, with teeth attached to an oesophageal head, having four muscles. In Pterodina the jaws are partly two-toothed and the teeth in a line (zygogomphia, lochogomphia), in the other genera they are many-toothed §º. In Noteus and Pterodina, the alimentary canal is constricted, orming stomachs (gasterodela); in the rest it is partly simple (coelogastrica), partly with stomachs. Glands have been observed in all the genera, as also an ovary and contractile vesicle. Many species of Amwraea, Brachionws, and Notews, carry their eggs attached to them, after expulsion. In all the genera, except Pterodina, internal tremulous tags attached to the water-vascular canals have been observed. A nervous system is supposed to be indicated by the presence of red visual points in all, except Notews, which, however, possesses what is believed to be a cerebral ganglion. Some of the Brachiomaea may become so numerous as to render the water milky and turbid. Ehrenberg’s classification of this family is given at p. 479. It was amongst the Brachiomaea that some of the most interesting of recent investigations were first made by Perty, Cohn, and Leydig. Thus, striped or voluntary muscles have been noticed in Brachionus militaris by Cohn, and in Pterodina by Leydig ; whilst, in the latter case, the same distinguished observer alleges that he finds a refracting body in the eye similar to what he had detected in Euchlamis and Stéphanops. In Brachionws wrceolaris and militaris, again, Perty and Cohn have established the existence of dioecious sexuality amongst the Rotatoria—the male animal, as in the previously de- scribed dioecious forms, being devoid of an alimentary canal; and to this list Mr. Gosse has since added B. Pala, B. rubens, B. amphiceras, B. angularis, B. Dorcas, and B. Mülleri. Its rarity, and the comparatively short period of time during which, according to Perty, the male animalcule of Brachiomws wroeolaris exists, probably explain why these creatures have been so long over- looked. Cohn observed that the contractions and expansions of the contrac- tile sac at the base of the water-vascular canals of Brachiomws militaris were accompanied by a corresponding motion in their watery contents. At each contraction, or systole, a stream was expelled into the cloaca, communicating with the water in which the creature lived, whilst an opposite movement attended the expansion or diastole of the sac. These facts strongly corro- borate the supposition that the water-vascular canals are the true respiratory organs of the Rotifera, corresponding with the remarkable analogous organs arising from the cloaca of the Holothuriae amongst the radiated animals; the pure oxygenated water being thus carried to the fluid distending the body, which fulfils the functions of the blood in higher animals, and affording an cxample of the “Phlebenterism” of the French naturalist Quatrefages. . In Brachionus militaris, Cohn has also pointed out the existence of three OF TEIE BRACEIION.E.A. 707 distinct classes of eggs—viz, winter, Summer, and male ova–all differing in their form and aspect. Genus NOTEUS (XXXV. 491–494; XXXVIII. 25).-Eyes absent; foot furcate (Brachioni wanting eyes). The two-wheeled trochal disc has between its portions a three-lobed ciliated brow, but has no long bristle-like feelers; it possesses (as also does the furcate foot) distinct muscles. The lorica has spines both anteriorly and posteriorly; an oesophageal head with jaws having many teeth (polygomphia), a constricted alimentary canal or stomach (gasterodela) with two large glands, an ovarium, and a contractile vesicle are to be recog- nized. There is also a trace of tremulous tags, a short and thick water- vascular tube, and a large central ganglion, lying between the muscles of the vibratory organs. Dujardin considers the absence of eyes insufficient to constitute this a genus apart from Brachiomws. - NoTEUs quadricornis (XXXV. 491–494; tremulous tags; a short and obscure XXXVIII, 25). — Lorica suborbicular, de- pressed, rough and urceolated, with four spines anteriorly and two posteriorly. 3otary organ simple, with a deep oral fossa; three lobes on its free surface. Alimentary canal as in Brachiomus. A contractile sac on the right of the cloaca. siphon between the large spines on the front of the body. This animalcule is large, very transparent, and of a whitish colour, (XXXV.491–493 represent dorsal, ventral, and side views; and 494 the jaws separate, and under pressure.) Found amongst decayed Sedge-leaves and Oscillatoriae. 1-120" to 1-72". giving off two canals, each bearing three Genus ANURAEA (XXXV. 495–498).-Brachionaea with a single cervical eye, but no foot (Brachiomi without feet). In Seven species the lorica has four longitudinal rows of facettes upon the back; in three it is smooth; in thirteen species it is spinous anteriorly, and in Seven posteriorly also. A. biremis has a moveable spine on each side : of one species, only the empty shell has been seen; in the rest the muscles of the rotary organ, but not the longitudinal muscles of the body, have been observed. Jaws and teeth are seen in nine species. Alimentary canal constricted (gasterodela) in four ; simple and conical (coelogastrica) in nine. Two glands are placed at the commencement of the alimentary canal; an ovary is seen in twelve species, but a contractile vesicle only in one of the larger and Smooth species, in which also four tremulous tags are found. In three species siphons emanate from the neck. The eye-speck, which is always present, is supposed to indicate the existence of a nervous system. In A. squamula, A. curvicornis, A. birémis, A. striata, and A. foliacea, what is thought to be nervous matter is seen below it. Eight species have their eggs attached to them after they are expelled. They swim freely, though not very quickly. This genus has the name of Amourella, given to it by Bory St.-Vincent, and retained by Dujardin. a. Species posteriorly devoid of spines and pedicle. ANURAEA (P) quadridentata.-Lorica curved outwards, like sickles. Surface oblong, with four horns anteriorly, its of the lorica not ridged, but rough ; pos- terior extremity obtuse. 1-144". A. curvicornis.-Nearly Square, with six frontal horns, the two middle ones larger and curved outwards and down- osterior end obtuse, back tessellated. –216" without the horns. A. Squamula (Brachionus Squamula, M.).--Smooth, obtusely square, with six wards. horns in front, obtuse behind., (XXXV. 495–497 represent different views of this animalcule, the two latter with an egg attached.) 1-240". A. falcata.-Oblong ; with six spines anteriorly, the two central of which are Dorsal surface tessellated; its large, red, round eye is seated upon a large nervous ganglion; the Oesophageal bulb has three-toothed jaws. This ani- malcule also carries the eggs attached. 1–216". 2 z 2 708 SYSTEMATIC EIISTORY OF THE INFUSORIA. A. biremis.-Linear and elongated, with four horns anteriorly; back very smooth, and having two lateral spines, like oars. The oesophageal, head has three-toothed jaws. In phosphorescent Sea-water. 1–144". A, striata (Brachionus striatus, M.).- Linear and elongated, with six horns in front, and four on the abdominal surface of the lorica; the back with twelve longi- tudinal flutings or rays, and obtuse at the end. This species is very change- able in form, owing to the membranous lorica yielding to the contraction of the body: hence it is sometimes . at others short, sometimes urn-shaped, bell- shaped, and even almost disc-shaped; the first, however, seems to be the normal form. In fresh and salt water. 1-130". b. Spinous or attenuated posteriorly. A, inermis.-Lorica oblong, attenuated and truncated posteriorly; no spines an- teriorly; back furnished with faint longi- tudinal rays. In peat-water. Length when extended, 1–144". A. acuminata.-Lorica oblong, attenu- ated and truncated at the posterior extre- mity, having anteriorly six sharp-pointed horns or spines, twelve longitudinal rays on the back. Amongst Confervae. Length about 1-120". A, foliacea.—Lorica oblong, six spines anteriorly, posteriorly terminating in a spine; dorsal and ventral surfaces longi- tudinally striated; frontal region rough, It has four-toothed jaws, and a central ganglion below the eye. 1-180", A, stipitata (Brachionus, M.).-Lorica nearly Square, or triangular; anteriorly six spines; posterior pointed like a pedicle; the back tessellated. (XXXV. 498 represents a dorsal view, with the wheels extended.) Length about 1-200". A. Testudo.—Lorica square, having anteriorly six straight spines, all of nearly the same length, and posteriorly a short one at each corner. The upper and under surfaces are rough, the former fººd like Notews. iéngth about g f f The following species are given by Mr. A. fissa (Gosse).-Lorica Smooth, hya- line, swollen at the sides and at the back; flattish on the belly, truncate in front, without any spines, attenuated and truncate posteriorly. There is a deep fold running down each side, or else the ventral plate is distinct from the dorsal 㺠* is also cleft through its medial line : eve very large, pale, 1-220". ne; ey y large, p A. tecta nearly agrees in form with A. curvicornis; but the posterior extre- mity is rather more pointed, and the tessellations are different, being larger, and arranged on each side of a medial dorsal ridge, which gives to the back the form of a vaulted roof. 1-200". A. Serrulata. —Lorica ovate, Square, with six unequal spines anteriorly, the two middle ones long and curved; it has two short spines at the posterior angles, which are sometimes scarcely apparent. The surfaces are rough, and the dorsal also tessellated, like the preceding species. Independently of the two wheels, the brow has three cylindrical ciliated pro- cesses, which are truncate at their extre- mities. 1-216". . . • , A. aculeata (Brachionus quadratus, M.).-Lorica Square, with six spines an- teriorly, the two middle longest; at the posterior angles are two long and equal spines; back rough and tessellated, under side smooth. At the brow, between the two wheels, is a single ciliated frontal rocess; a little tactile organ is situated in front of the eye. Length 1-144"; including the spines, 1-96". A. valga.-Lorica nearly square, with six spines anteriorly, the two middle ones the longest; at each posterior angle is a spine of unequal length; dorsal and ventral surfaces rough, the former tessel- lated. The jaws are five-toothed, the red eye oval, its longer axis transverse. Length, without the spines, 1-210". Gosse (Ann. Nat. Hist. 1851, vol. viii.). A. brevispina nearly agrees with A. aculeata; but the posterior spines arevery short, the frontal spines are much less curved forwards, the surface is not punctated, and it is colourless. 1-146". A. cochlearis.-Lorica spoon-shaped, with six spines in front, the medial pair curving strongly forwards; º OX- tremity attenuated into a long slender spine, inclined forwards; back ridged and tessellated, as in A. tecta. A. heptodon= Ascomorpha Helvetica, Perty. — Lorica of equal width, con- tracted posteriorly, and terminated by ºn upturned tooth in the middle line. In front are four teeth above and two below. 1-12". This species, founded on one OF TIII. BRACHIONAEA. 709 individual example, resembles.A. foliacea, the peculiar upturned tooth in the median but is less flat, more cubical, and possesses line, (XXXVIII, 6.) Genus BRACHIONUS.—Brachionaba which have a single cervical eye and a furcate foot. Figure compressed. Lorica closed at the sides; open at the extremities like a tortoise-shell. Anterior and posterior margins usually dentate; surface either smooth or rough and tuberculated, the tubercles on the abdominal surface arranged in four lines diverging posteriorly. The cuticle, which, according to Leydig, rests on a molecular layer, resists liquor potassae. The frontal processes or teeth are dentate on their inner edge. Animal able to withdraw itself within the lorica. Rotary organ simple, and, though often looking as if lobed, presenting an unbroken border, except when it is indented by descending to the mouth, whence this bilobed aspect; a median lobe and two lateral ones arise from its free surface. On its right and left side are some eminences surmounted by long bristles, in addition to a long bristle projecting backwards from each lateral margin of the rotary organ. A granular mass, the Supposed cerebral ganglion, supports the eye-speck, which is extended backwards into two points. A siphon, or tactile tube, terminated by a bunch of setae, projects from between the an– terior median teeth of the lorica. Two brown vesicles in front of the large muscular Oesophageal bulb, in which are the toothed jaws; a short Oesopha- gus; and a stomach, the latter composed of coloured cells, ciliated on their free surface. In front of the stomach two pedunculate glands. Intestine clear and ciliated. Contractile vesicle on the right of the cloaca, with two water-vascular canals proceeding from it to the neck, where they form a plexus and bear two tags. Ovary beneath the stomach. Eggs, according to Perty, of three sorts, viz. Winter ova, Summer ova, and ova bearing male embryos. Ova attached to the exterior of the animal. B. Pala, B. wrceolaris, and B. rubens sometimes increase in such quantities as to render the water milky and turbid. Several species are infested with Vorticella, Epistylis, and other parasites, which attach themselves to their shells. Like Asplanchna, Euchlamis, and others, the genus Brachiomus has acquired great additional interest from the discovery amongst some of its species of the distinct sepa- paration of the sexes. The male Brachiomi present a different form to that of the female, resembling, in this respect, Asplanchma Sieboldii rather than A. Brightwellii and Hydatina senta, in which the difference of external con- tours is mainly one of size. The multiplying discoveries of separate sexes amongst the Rotifera, combined with the manifest absence of male organs in the numerous individuals provided with ovaries, renders it increasingly probable that all the Rotifera will finally be demonstrated to be bisexual or dioeceous. 3. ? a # * * * g » BRACHIONUS Pala. — Lorica Smooth, with four spines in front, and two obtuse ones near the opening for the foot. Toes of the foot apparently bifid. This crea- ture swims in a perpendicular position, the brow being directed upwards. Lach jaw has five teeth; the alimentary canal cing constricted, forms a stomach. Length 1-36"; lorica only 1-48" (XXXIX. 14, 15). B. amphiceros.—Has a smooth lorica, with four spines, in front and poste- riorly; four sharp posterior teeth are characteristic, 1–72", B. urceolaris (Brachionus urceolaris, M.).—Whitish; lorica smooth, with six very short spines in front; posterior ex- tremity rounded; lorica slightly granu- lated; its points are shorter and less sharp than in the following species ; delicate longitudinal ridges proceed from the spines; the jaws have each five teeth. The males of Brachionus wrceolaris, according to Perty, are developed from smaller ova than the females, these eggs being also adherent to the parent in greater numbers, They are very sphe- 710 SYSTEMATIC HISTORY, OF TELE INFUSORIA. rical, reaching 1-50" in length and 1-67" in diameter. Their shell is more deli- cate and the contents clearer and more transparent, as well as of a pale yellowish hue instead of the dusky grey of the female ova. The formerlikewise contain fewer granules. The development by fission similar in both. When the egg is mature, it continues to be pale and transparent. The red eye-speck exhibits itself; but the maxillary apparatus, seen in the female ovum, is wanting. On the other hand, two or three heaps of dark ranules occur, not seen il, the females. The embryo escapes from the ovum by a transverse rupture, and is then seen to have a different contour from the female. It is but one-third the size of the latter, being, when extended, but 1-27" to 1-22" long, and from I-60" to 1-55" broad. It is destitute of a firm lorica; short, cylindrical; pro- longed anteriorly into a short head, separated by a constriction from the trunk; prolonged posteriorly into a short tubular foot about one-fifth the length of the body. Head crowned by a flat- tened disc, with a wide expanding mar- gin, clothed with long vibrating cilia and a few non-vibratile bristles. Cilia moving with extraordinary velocity, pre- venting many being seen at once; but a little strychnine added to the water checks their action and facilitates their observation. No mouth is present; hence the ciliary wreath is not twined inwards at the oral fissure; the alimentary appa- ratus is wholly wanting. A large pyri- form vesicular testicle, 1-100" in length, occupies the middle of the body; it is filled with small dark moving sperma- tozoa. The wall of the testicle is very thick, and elongated at its upper extre- mity into a thick cylindrical band, which is attached to the cephalic disc. Pos- teriorly the testicle is striated longitu- dinally, and is perforated by an aperture opening into a wide spermatic duct con- ducting to the penis. The latter organ is a short tube usually laid free on the foot and nearly extending to its extre- mity; its internal canal and outer mar- in equally furnished with vibratile cilia. The foot is transversely wrinkled, and ends in two small toes. Near the root of the penis are two club-shaped glands which pour their secretion into its canal; mear these is also a contractile vesicle with two water-canals and their ap- pººl tags. Several spherical ...iii. odies occur near the head, the larger of these, the Supposed cerebral gangliom, supporting the eye-spot. Two or three vesicles of uncertain character, filled with dark granules, rest on the testicle near its lower end. The males are much rarer than the females, and are not seen after the end of May. In fresh and brackish waters. Length of females from 1–96" to 1-72". (xxxix. 10–20; x L. 20–23.) B. rubens (B. urceolaris, M.).-Lorica smooth, with six sharp spines in front, posteriorly rounded; the body is red. 1-50". Dujardin supposes this to be a variety of B. urceolaris. Leydig recog- nizes its distinctness. (XXXVIII, 7.) B. Mülleri (Müller's Brachionus). — Lorica Smooth, with six obtuse spines in front, two short ones behind, resembling papillae. This species is somewhat larger than B. urceolaris, and has peculiarly- shaped frontal spines. The margin of the chin (brow) is smoothly truncate, with three faint indentations. The lorica is very transparent. 1-60". According to Mr. Gosse, the B. heptatomus found in sea-water is identical with this species. (XXXIX, 13.) B. brevispinus.-Lorica Smooth, having six acute unequal spines in front, an four stout spines posteriorly, the two immer ones short; two sexual glands and a contractile vesicle are present. slow running clear water, with Con- fervae. I-65". B. Bakeri (M.). —Lorica rough, its middle tessellated on the dorsal surface; six unequal acute teeth anteriorly, two elongated (lateral and dorsal) spines posteriorly, and short ones at the sheath of the foot. The lorica is covered with delicate granules; those upon the middle of the ventral surface are arranged in arallel but somewhat curved lines. –220" to 1-60". (xxxviii. 8, 9, 10–17; XL. 16.) “The following interesting observa- tions as to the development of this spe- cies have been communicated to me by a friend, an accurate and diligent observer of nature:—About two o'clock B. Ba- Jºeri was observed with one egg placed externally between the two posterior spines of the shell, and another Small egg in the left side of the animal, which increased much in size in the course of the day. At nine in the evening a motion was perceived in the exterior egg like that of the muscular Oesophagus of the parent; and about this time the internal egg was protruded and placed by the side of the other, being longer than it. At eleven the young Brachionus OF THE BRACELIONAEA. 711 burst with a bound from the egg in which the motion was perceived, and affixed itself by its tail to the lunette. At first it had the appearance of an oblong ball; by degrees the anterior part spread, and the wheel processes were developed. Soon after, the posterior shell- processes were visible in a semilunar shape, with the points nearly touching each other, which gradually expanded. The shell of the egg remained attached to the parent in the same position, quite transparent, with a longitudinal split through the whole length.” (Brightwell, . cit. *: * (M.).-Lorica Smooth, having anteriorly four long dorsal teeth or spines, six short ones at the margin of the chin (ventral), and posteriorly five dorsal spines, the two external or lateral ones very long. XXXV. 499–501 represent dorsal, side, and under views of this animal,—the first having the wheels extended, and the side view showing the siphon or so-called respi- ratory tube and an ovum attached. Length, without spines, 1-110". XXXVIII. 14, 15 represent diagrams of the head. B. militaris. – Lorica with surface divided into twelve regular pentagonal facettes, according to Cohn; its anterior border with several spinous processes; and posteriorly is a deep median ex- cavation with a curved horn on each side. The spines, 10 in number (not 12 as affirmed by Ehrenberg), viz. 2 lateral, 4 abdominal, and 4 dorsal, the latter the largest; head larger than that of B. wr- ceolaris, expanded in a funnel-shaped manner, surrounded by a circlet of cilia; its eversion is checked by the stiff spines of the lorica. Foot smaller and shorter than in B. urceolaris. CEsophageal bulb quadrangular. On each spine forming the outer posterior angle of the lorica is a circular pit with well-defined margin; from this proceeds a bunch of short bristles. Muscles of foot and head striped transversely. Contractile sac very large, occupying two-thirds of the abdominal cavity on the right side of the animal; it consists of two chambers, the ovate posterior one being the larger, their con- tractions being alternate; the posterior one opens into the cloaca by a short duct. On mingling coloured matter with the water, Cohn observed that on each systole or contraction a stream escaped from the sac, through the cloacal open- ing, and that on the diastole this move- ment was reversed, indicating a respi- ratory action. (XXXIX. 21, 22 represent the abdominal and dorsal surfaces of the female.) The ova are of three sorts:– 1. Winter ova, 1–21" long, 1–33" wide, elliptic, with thick, leathery, opaque walls, the yell; not occupying the poles (XXXIX. 23); 2. Ordinary or summer ova, of similar dimensions, but with thin transparent walls; 3. Male ova, only 1-34" long and 1-42" broad (xxxix. 24). Shell thin. Yelk subdividing in the usual way, and developing an em- bryo provided with a red eye, and two dark specks, but no maxillary organs. Cohn saw only one specimen freed from the egg, and that imperfectly. It ap- peared similar to the male of B, wr- ceolaris. P. Oon (Gosse). — Lorica ovate, the back swelling with a uniform curve, by which it is distinguished from B. Pala, which is truncate or slightly clavate posteriorly; anterior spines four, straight, wide at the base, and pointed; the occi- pital pair taller than the lateral. Lorica. I-125". rº D. Dorcas.-Lorica ovate or sub-coni- cal; occipital edge with four long slender spines, the middle pair curving forwards, and bent first from, and then towards each other, like the horns of an antelope; mental edge undulated, with a notch in the centre. Lorica. 1-60". (XL. 11 re- presents a newly-born female, and fig. 12 a newly-born male.) B. angularis. – Lorica in the female hexagonal-oval in the dorsal aspect; occi- º edge with two small teeth, divided y a rounded notch (in some specimens there are obsolete ‘traces of a lateral pair); mental edge slightly undulated, sometimes with two low points, divided by a notch like the occiput, but still more faintly; posterior extremity with two short, blunt, well-marked processes. The general surface is roughened with angular ridges, and is sometimes sub- opaque and brown, Lorica. 1-200". This curious species has relations with Noteus and with Pterodina. (XL. 19 represents a male of this species.) Genus PTERODINA.—The winged Rotatoria include such Brachiona’a as have two frontal eyes and a simple styliform foot projecting from the middle of the body. All the species have a smooth, flat, and soft lorica, like a tor- toise-shell, with curved margins; as also a more or less double rotary appa- 712 SYSTEMATIC HISTORY OF THE IN 1.''USORIA. ratus, and a simple foot with a suction-disc and sometimes a bunch of cilia at its extremity. P. elliptica has a hairy process projecting between the two lobes of the rotary organ, and P. Patina has a rounded prominence in a similar position on the dorsal surface. Muscles, often transversely striated, occur in all the species, as also a constricted alimentary canal with glandular appen- dages and an ovarium. Some have a contractile vesicle and a water-vascular system. PTERODINA Patina (Brachionus Pa- tina, M.).-Figure round, or oval com- Fº Lorica membranous, crystal- ine, somewhat scabrous near its broad margin, and slightly excavated anteriorly between the two lobes of the rotary organ. The latter not double, as de- scribed by Ehrenberg, but with an an- terior and posterior depression, from the latter of which extends a single rounded process. Cilia in two rows, prolonged to the oesophageal bulb. Stomach ciliated internally, widely expanded posteriorly. Short intestime also ciliated, and termi- nating at the base of the foot. Two yriform glands in front of the stomach. Two red specks opposite the margin of the rotary organ; their red pigment has a sharp spherical figure; according to Leydig, an obvious refracting body pro- jects from the anterior convex edge of each. Two large longitudinal muscles. On each side of the stomach a water- vascular canal, but without either tags or contractile sac. Ovary horseshoe- shaped. Free extremity of the foot with a bundle of setae. This animal was noticed by Perty to have the peculiarity of assuming an ap- parently lifeless state for half an hour or an hour at a time, lying in one spot, often on the surface of the water, with no other sign of life than that afforded by movements of the Oesophageal cilia, and occasionally of the jaws. This species is very delicate and tran- sparent. xxxy, 502 represents a side view, and 503, 504 under views, the latter having the wheels extended, the former having them withdrawn, and the anterior margin bent in, so that the eyes appear near the middle of the lorica. The internal organization is further shown in xxxviii. 29. Found in sum- mer among Lemnae and Ceratophylla. Length about 1-120". P. elliptica.-Lorica membranous, el- liptical, with a narrow, Smooth margin, front entire (not excised). The two wheels united by a brow furnished with setae. Eyes distant. Amongst Con- fervae. 1–120" to 1–108", - - P. clypeata (Brachionus clypeatus, M.). —Lorica membranous, oblong, narrow, smooth at the margin; there is a frontal portion, or brow, connecting the two wheels, but no setae. The eyes approxi- mate, (xxxv. 505 a dorsal view, with the wheels extended.) In sea-water, Length 1-120"; the shell 1-144". The next genus, Pomphone, instituted by Mr. Gosse, is considered by him to be a member of this family. g Genus POMPHOLYX (Gosse, A. N. H. 1851, vol. viii.). —Two frontal eyes; foot wanting; rotary organ double in the rear, entire in front; eggs attached behind after deposition. the lorica to a round flat smelling-bottle. The name alludes to the resemblance of PoMPHoLyx complanata. — Lorica to a central blunt point; mental ridge much depressed, nearly circular, with with two rounded lobes, divided by a the lateral edges rounded; anteriorly central notch, Lorica. 1-800". truncate; occipital edge gradually rising Of the ensuing genera, established by Ehrenberg, we have only met with the description of species; of one, indeed, with only a sketch of its relations. Genus LARELLA (Ehr.).-The following species of this new genus, the characters of which we have not met with, is named by Ehrenberg. LARELLA Piscis. – Body with equal eyes. Length 1-190" to 1-280". Berlin. setae, and three long fine hairs placed on | Werneck has also seen this species. each side the mouth, with two frontal OF THE TARDIGRADA. 713 Genus TETRASIPHON (Ehr.).—We have not met with the detail of the generic characters, but they may be gathered from the description of the following species:– * - TETRASIPHON Hydrocora. — Very | dentate, with the oblique rotary organ large, hyaline, with two prominent tu- of Pleurotrocha. Foot with slender, long bular occipital organs, and other two and acute toes; eye occipital. Length near the termination of the back; pan- 1-36" and upwards. Berlin. creatic glands four, globose ; jaws bi- - Genus DIPODINA.—Characters unknown. DIPODINA Artiscon (Ehr.) (Mentioned particular constriction of its tarsal nip- in Reports of Zoology, Ray Society).- R. (toes). Found by Ehrenberg at Approaches Notommata, but differs by a ismar, on the Baltic. The genus PolyGHAETUs (XXXVIII. 31, 32) of Perty is supposed by Leydig to be a Crustacean. CYPHONAUTES is also regarded by the same observer as dubious; whilst, as we have already observed, he regards Ptygwra and Gleno- phora as undeveloped forms of other species. OF THE GROUP TARDIGRADA. THE creatures thus named are introduced here as a group, inasmuch as they cannot be included amongst the Rotatoria. Some remarks on their organiza- tion will be found in Part I. (p. 482) of this work; and here I shall introduce further particulars, chiefly derived from the first edition of this work (1834), p. 182, and from Dujardin’s Hist, des Infusoires, p. 661. They have oblong bodies, contracted into a ball; furnished with four pairs of short feet or mammilliform processes, each terminated by simple or double hooked claws; mouth very narrow, siphon-shaped; with an internal maxillary apparatus composed of two lateral moveable pieces, and of a strong muscular obsophageal bulb, furnished with horn-like dental articulated processes. - The Tardigrada stand on the one side between the Rotatoria (Systolides, Duj.) and the Helminthidae, and on the other between the Annelida and Arachnida. These creatures are usually found attached to aquatic plants which float upon still water. I first obtained them from ponds in the Regent's Park. By placing some water with the plants in a common white hand-basin, and shaking the vegetation, they are detached and fall to the bottom of the basin, from whence they are readily taken. They are generally met with, in com- pany with the larger kinds of Rotatoria, in moss. They are very sluggish in their movements, and are commonly known under the name of “little water- bears.” Under the polarizing microscope the manducatory apparatus exhibits the same appearance as horn. They are capable of resuscitation after being dried. They vary in length from 1–20" to 1-50". M. Doyère, in an elaborate Memoir in the ‘Annales des Sciences,’ has divided the Tardigrada into four genera:- Genus EMYDIUM.–Body oval, anterior part narrow, and terminating in a pointed mouth, near to which, On each side, are flesh-like papillae. Feet 714. SYSTEMATIC HISTORY OF THE INFUSORIA. armed with four distinct claws; colour reddish. Found among moss (Bryum). (Figs. 1, 2.) Genus MACROBIOTUS.—Body more cylindrical; obtuse anteriorly; no setae; each foot furnished with two claws. Found with the preceding; also in rivulets. (See fig. 6.) Genus TARDIGRADA.—Body stout, oblong; mouth not so sharply pointed. Found in stagnant water, on aquatic plants, and on the Hypnum fluitans. (See figs. 3, 4, 5.) Genus MILNESIUM.–Characters unknown. For further particulars consult the General History, at p. 482 of this work. \ & § * Nº Wº Ass *s wº -º . } § } ; sº 3. § | º sº|º ( $. t º º | ". t ź% %| º § § y 3. | i ;} i \, º § § .: '' TARDIGRADA, OR LITTLE WATER-BEARS. Fig. 1. Emydºm, magnified 130 diameters. times. Figs. 3, 4. Tardigrada, magnified 160 times. Fig. 5. Head of same, magnified 300 times. Fig. 6. Mouth apparatus of Macrobiotus, greatly magnified. Fig. 2. Head of the same, magnified 300 OF THE DESMIDIE ZE. 715 OF THE GROUP BACILLARIA. Sub-group DESMIDIEAE of DESMIDIACEAE. (Page 1, Plates I., II., III., XVI.) [Class ALGAE, Order Chlorospermeae, Family Desmidiaceae of Botanists.] CELLs of two symmetrical valves, devoid of silex, mostly figured, their junc- tion marked by a pale interruption of the endochrome, frequently also by a constriction; increasing by the formation of two new half-cells, which become interposed between the older, so that the two newly-produced cells consist each of a new and an old half-cell; the transverse division complete or incom- plete, the cells thus either free or forming a filament; endochrome green, occasionally converted into ciliated zoospores (in the single known instance, escaping by an aperture at the apex of one or more specially formed lateral tubes); reproduction by conjugation of the contents of two distinct cells, and the formation of sporangia, the contents of which, in after-development, be- come segmented into a definite number of individualized portions, the last generation of which are set free by the bursting or solution of the containing membrane, and become the first fronds of a new vegetative cycle. We believe the foregoing diagnosis will apply to and include all the species which we look upon as undoubtedly belonging to this family, and which are introduced into this work. The claims of the genera Cylindrocystis and Mesotaenium, as true members of the Desmidiaceae, not appearing, so far as we can judge, to be satisfactorily established, they are omitted. The wonderful variety of form and beautiful symmetrical diversity of out- line of the members of this family have been dilated on at length in the General History. It seems to us, with regard to the mode of cell-division in the true species of this family, that, normally, the preliminary step in the process is the separation of the cell-contents and the formation of a septum at the central suture, the two halves of the contents becoming thus indi- vidualized, whereupon ensues the growth and extension of the primordial utricle and contents, concurrently with the production of the intermediate cell-wall ultimately to form the two new segments, and either complete sepa- ration taking place, or the cells remaining united in more or less brittle filaments. Many of the species, probably all, seem to be liable to an abnormal mode of growth, resulting from the incomplete carrying out of this process, when the new growth forms an intermediate, frequently misshapen structure, pro- ducing with the original segments but one uninterrupted cavity,+this irregu- larity seeming to be primarily due to the omission of the formation of the septum on the recommencement of the vegetative growth (III. 61, 62): vide Mrs. H. Thomas, J. M. Sci. vol. iii. pl. 5. figs. 17 & 18; also M. de Brébisson, Liste, &c. pl. 1. fig. 15; and Mr. W. Archer, Proc. Nat. Hist. Soc. Dub. 1859, vol. ii. pl. 1. figs. 9–15.) An inspection of several of the latter figures will, however, show that the intervening structure, in the first instance (from the foregoing cause, as we imagine) rendered abnormal, is not always absolutely shapeless or irregular in its form, but sometimes, its axis of growth striking off at right angles to that of the older segments, assumes the form and often the size of an entire frond. Sometimes, indeed, not only is the axis of growth 716 SYSTEMATIC HISTORY OF THE INFUSORIA. at right angles to that of the Original segments, but its plane of expansion is at right angles to their plane. In each of these latter cases the entire ab– normal specimen, therefore, forms a cross, the interior here, of course, as well as in those cases where the intervening growth does not assume any definite outline, making but one uninterrupted cavity (III. 61). The omission of the formation of a septum, however, can only be looked on as the primary cause of the aberration, the curious change in the direction of the new growth not necessarily following, as the figures, pl. 1. f. 9–11 (loc. cit.) seem to prove (III. 62). The assertion that zoospores occur in this family is based upon the observa– tions made by Mr. W. Archer on Docidium Ehrenbergii (Ralfs), and recorded and figured in Proceedings Nat. Hist. Soc. Dublin, February 1860; also Wat. Hist. Review, July 1860. These observations, though unfortunately and unavoidably not so full in their details as the interest of the case would lead us to wish for, seem to warrant the assumption that the species of this family may be occasionally propagated by Zoospores, predicating of the family that which seems to hold in the species in question (Docidium Ehrenbergii). Pedi- astreat are of course not taken into account. Briefly, the phenomenon alluded to is as follows (III.46, 47) :-From beneath the base of one of the segments, either one, two, or three (the latter rarely) lateral tubercle-like projections are formed, originating not from any portion of the segment itself, but from an extension thereto produced between the inflated base and the sutural line. When more than one is formed, they are usually opposite, but sometimes side by side. A gradual elongation of the projection (or projections) then takes place, the endochrome in the immediate neighbourhood becoming finely granular, and filling what has now become an elongate lateral tube (or tubes) like the finger to a glove, the remainder of the endochrome being as yet, not much altered, and the terminal clear space with the active granules being still in sitw. The endochrome within the lateral tube and in its immediate neighbourhood now becomes segmented into a number of definitely bounded individualized portions, which presently one by one emerge through the opened apex of the lateral tube, and become associated together in an external cluster. The remaining endochrome now becomes drawn into bands, turns brown, and speedily dies. The cluster of gonidia at the apex of the lateral tube now appear to have become encysted each within its own special coat; and the green contents can be seen twisting backwards and forwards within the con- fining membrane. After a time the contents emerge each from its cyst, by rupturing it, and slowly swim away as pyriform or ovate ciliated bodies, as we apprehend, Veritable zoospores. The author was entirely unacquainted with their after-history; but they resemble so much, in their appearance, growth, and mode of escape from the parent-cell, the similar bodies in Cla- dophora, &c., which are indubitable zoospores, that we imagine there can be little question as to the nature and function of the bodies occurring in Doci- dium. It will be noticed that this phenomenon is altogether distinct from, and we believe in no way to be confounded with, that of the active molecular movement of the ultimate granular particles of the endochrome alluded to at pages 10 and 19 of the General History, a circumstance which, indeed, some- times accompanied the special one here described, in Mr. Archer's specimens, but sometimes did not, and which is one of very general occurrence under other circumstances and in other cases, and has probably given rise to the assumption, often made in our English books, that zoospores occur in the Desmidiaceae. Nor is the production of zoospores here briefly described to be in any way confounded with the development of the parasitic plant Pythium ontophytum (Pringsheim), nor of any species of Chytridium (Braun). The OF THE DESMIDIEAE. 8 717 former, indeed, is sometimes met with in various Desmidians, such as Clos- terium Lunula, &c., as well as other Algæ. For a figure of this curious parasitic growth attacking Eremosphaera viridis (de Bary) (= Chlorosphaera Oliveri, Henfrey, the former name having, we are inclined to think, the priority), vide ‘Micrographic Dictionary, 2nd ed. pl. xlv. fig. 8. There can be little or no doubt that some such parasite as that alluded to attacking a species of Closterium has given rise to Ehrenberg’s genus Polysolemia, admitted indeed into the Desmidiaceae by Kützing, but which we here cannot but exclude. s ſ - The act of conjugation and formation of sporangia is not uncommonly to be met with in several species. The after-development of the sporangium seems to have been but very rarely witnessed; and the statement made in the diagnosis is founded on the account given by M. Hofmeister (l.c.), an extract from which is given at page 17; also on the very similar account given by M. de Bary, “Untersuchungen über die Familie der Conjugaten :’ vide pl. 6, showing the development of the sporangium of Cosmarium. Botrytis (III. 48– 54), and of C. Meneghini (III. 55–60), the number of sister-cells formed within the sporangium being fewer than in the instances cited by M. Hof- meister. But although, in the cases cited by M. de Bary, the cells resulting from the segmentation and individualization of the contents of the sporangium are eventually of a Cosmarium-shape, it is, however, not until the young fronds commence self-division in the ordinary way, that the first-formed young segments wholly assume the special characteristics of the species (III. 52, 53, 54 & 58, 59, 60). - - - The nearest affinities of this family seem undoubtedly to be, on the one hand with the Diatomaceae (with which family, indeed, they were long associated), and on the other with the Zygnemaceae (Conjugatae); while to the Palmellaceae they also approach through the genus Penium, connected with Cylindrocystis and Mesotaenium = Palmogloea (Kg.). It will be at once seen that the following arrangement of the species is for the most part based on that laid down in Ralfs's ‘British Desmidieæ,’ 1848, in addition to which the following works have been consulted:—Kützing’s ‘Species Algarum,’ 1849; Nägeli’s ‘Einzelliger Algen,’ 1849; Bailey’s (Smithsonian Contributions to Knowledge) ‘Microscopical Observations made in South Carolina, &c.’, 1850; Brébisson’s ‘Tiste des Desmidiées observées en Basse Normandie,’ 1856; de Bary (op. cit.), 1858; Papers in “Nat. Hist. Review,’ by Rev. R. W. Dixon and by Mr. Archer, 1858–60. The first and second of a series of papers by Dr. G. C. Wallich, F.L.S., descriptive of some beautiful and interesting species of Desmidiaceae collected by him in Bengal, had just made their appearance (“Annals Nat. Hist.” March and April, 1860) when we were obliged to go to press. It has seemed to us more advisable to omit any description of those species than to introduce a few only without having it in our power to do so with the whole. In indicating the sources whence we have been able to derive information as to foreign species, it is our pleasing duty to acknowledge the generous and courteous assistance of M. de Brébisson in affording by letter the requisite information which that distinguished and experienced observer has so largely at his disposal, and without which our own acquaintance with the Continental forms not known in this country would have been far more circumscribed. The following genera included in this family by Kützing in “Species Algarum ' are here excluded, as we conceive either that they are not trul Desmidian, or the unnecessary splitting up of older genera:- . . . Trochiscia, excluded; Tetraedron, excluded; Pithiscus = Cosmarium pyra- midatum (Bréb.); Stauroceras = Closterium, in part ; Polysolenia (E.) = a 718 SYSTEMATIC ELISTORY OF THE INFUSORIA, Closterium attacked by a parasitic growth (?); Microtheca, excluded; Poly- edrium, excluded; Zygoxanthium = Xanthidium, in part; Phycastrum, Aste- roxanthium, Stephanoxanthium, =Staurastrum ; Grammatonema, a diatom; Bambusina = Didymoprium Borreri; Isthmosira=Sphaerozosma ; Eucampia, a diatom; Geminella, excluded; Raphidium = Ankistrodesmus; Oocardium, excluded. The other genera included by Kützing are placed here as a distinct group, Pediastreas. Didymocladon (Ralfs) seems not distinguished from certain Staurastra by characteristics sufficient to separate it from them ; we have therefore united them, in which we follow Brébisson. - As to the new or altered genera proposed by Nägeli and de Bary, founded rather on the mode of disposition of the endochrome than on the external form, although we do not venture to deny its probably great importance, yet it seems to us that the characters relied on are in many instances not sufficiently constant for the purpose, as well as that several of the known Desmidian species could not be satisfactorily or indubitably referred to the particular genus to which, judging from analogy, they ought to belong; neither, indeed, does it seem, so far as we can judge, that those writers are themselves satisfied as to the proper place of certain species, nor does the system, as yet, appear quite without the disadvantage of disassociating kindred forms. We believe we are fortified in the opinion we here endeavour to express by that of M. de Brébisson. The genera Cylindrocystis and Mesotanium are here omitted from this family, as their claims to admission scarcely seem as yet indubitable; moreover, there seems to us little certainty as to the limitation of the species hitherto described by Kützing and others. If we have omitted some of the species described by the various authors before cited, it is from a conviction that, when either not satisfied as to their absolute distinctness, or unfurnished with what we could look upon as suffi- ciently exact details, it was the safest course we could pursue, as it seemed to us better to leave out a few species, than to insert them with a description which, owing most likely to our own want of perception, might prove insuf- ficient or inaccurate. On the other hand, Some may think we have admitted too many species, and that certain of the forms hereafter described may be but “varieties” of whichever may be assumed as the typical specific form; but in this conclusion we cannot coincide, as we are disposed to believe that the species hereafter described (with possibly, indeed, a few rare exceptions) are quite distinct, and, at least so far as British or Irish species are concerned, are always perfectly distinguishable. An ingenious method of succinctly expressing by means of symbols the ex- ternal characteristic forms of the genera Tetrachastrum, Micrasterias, and Euastrum, was propounded in a paper by Rev. R. W. Dixon, read to Nat. Hist. Soc. Dub., 3rd June, 1859. We append his own explanation, as the best that could be given :- “The typical mode of division [in the genera above named] (as exemplified in Euastrum pinnatum, E. oblongum, &c.) appears to be into three portions or subdivisions,—the first, next the line of separation of the segments, extend- ing across the frond, and embracing the two basal lobes; the second including the median lobes; and the third, the extreme or end lobe. This last, or third subdivision, is the most constant. The two former are frequently represented by a mere sinuosity or shallow indentation where the third is distinctly deve- loped; but we never find the first subdivision distinct, and the second and third imperfectly separated. The whole three, indeed, may be merely marked by slight sinuosities, as in Euastrum cuneatum; but if any one is separated, it OF THE DESMIDIE ZE. 719 is the third. And this, I may observe, is the order of development of the sub- divisions in the growing segment of the typical Micrasterias: the new seg- ment is first hemispherical; the third subdivision is then developed; and afterwards the first and second are separated. “For the purposes of description these three subdivisions might be denoted by the letters a, b, c, and their partial or complete development marked as follows:—When the subdivisions are distinctly separated, their symbols might be separated by commas, thus, a, b, c ; when any two or more are merely marked by a sinuosity, they may be represented thus, a Tö ; and if there is no trace of separation, thus, ab; and if, at the same time, the direction of the lines separating the subdivisions were noted, the full description as regards the divisions of the segments would be given. Thus— [See page 721.] CONSPECTUS OF THE GENERA. Endochrome arranged in spiral bands...... Endochrome a simple central longitudinal contracted band ... Gona TozygoN. Endochrome a single longitudinal flatten- ed band Joints constricted or with a projecting an- /Joints many times GENICULARIA. longer than broad ; neither constricted nor with lateral teeth or projections. Filament not at- tached * * * * * * * * * * * * Filament attached. LEPTocystiNEMA. < Joints broader long, seldom slightly longer than broad; more or less con- stricted, or with lateral teeth or angles, or other- \ wise figured...... mostly than | /Filament cylindri- cal or subcylin- drical tº º tº tº e º tº gº º tº tº e ſ (Joints not con- * stricted } Joints more or 4 \ less deeply: U constricted. nular rim at one or both ends ............ Joints with a bidentate process or angle at opposite sides Filament 3–4-angu- lar ; joints having the external margin plane or slightly cre- mated, united to each other by projections springing from the outer portion of each extremity, thus pro- ducing intervening central foramina ... APTogoNUM. Filament 3–4-angu- lar or compressed; joints either closely united by a thick- ened border for their entire end-margin, or by projections producing interven- ing centralforamima, as in last Filament compressed; joints united to each other by minute tu- bercles or gland- like processes ...... Eilament compressed or 3-angular; joints without intermedi- ate tubercles or pro- CeSSèS HYALOTHECA. DIDYMOPRIUM. DESMIDIUM. SPHERozos.M.A. SPONDYLosiumſ. # * e º e º $ tº 6 tº e º ſº tº e º ſº a 7 SYSTEMATIC HISTORY OF TEIE INFUSOR.I.A. 3 (Frond Frondmostly many ſ often as broad as long, rarely, if ever, as much as three times longer than broad. Sporan- gia mostly orbi- cular and spi- mous, rarely orbi- cular or quadrate and naked . times, rarely less than three times, longer than broad. Sporangia smooth (Penium annulatuºn and Spiročania mus- cicola are some- times not more than twice as long as broad)... W ſ Frond Fronds deeply con- stricted ; seg- nments more Or less deeply lobed, 3 or if merely un- dulate or taper- ing, the ends acutely notched. Fronds distinctly, mostly deeply, constricted; seg- ments mostly en- tire, or if some- what undulate, the ends not notched ......... dis- tinctly con- (Segments 3-lobed, lateral lobes attenuated, their Segments 3–5-lobed, la- teral lobes expanded, incised, their external margins dentate or rarely sinuate Segments 3–5-lobed, or sometimes only late- rally emarginate or si- muate, undulate or tapering; lateral lobes rounded, entire, or si- muately emarginate ; end-lobe mostly cen- trally emarginate or concave, the segments with variously disposed inflated circular promi- mences (the two latter characters never simul- tire, mostly rounded, rarely undulate at the margin, ends never emarginate, sometimes with a solitary central inflated prominence on each front surface ; without spines or pro- C0SS6S . . . . . . . . . . . . . . . . . . . . . Segments compressed, entire, spinous, with a central circular, cylin- 3 drical, or comical pro- jection on both front surfaces Segments compressed, en- tire, either with two or with four acute teeth or simple or geminate subulate spines placed on the external angles or prominences, with- out a central projec- tion Segments in e.V. angular U or radiate * g º e º e º e º a s s is e e º e º # 6 º' ę & ſº tº $ tº º ſº tº $ tº º e º 'º flated at the base......... Ends truncate. Segments in- | Ends trilobed. stricted at ) Segments not the middle. inflated at the base ... Jºnds notched. Frond curved or arcuate, not constricted ......... Frond straight, ends truncate or rounded, scarcely or not at all constricted JFrond straight or nearly so, endochrome spi- rally twisted * Euastrum crematuºn (Kg.) is perhaps an exception. apices entire or bifid... TETRACHASTRUM. MICRASTERIAs. U taneously absent”) ... EUASTRUM. ſ Segments not lobed, en- CoSMARIUM. XANTHIDIUM. ARTHRODESMUs. STAURASTRUM. TRIPLocERAs. DoCIDIUM. TETMEMORUS. JFrond either not at all constricted, or with a slight and gradual attenua- tion towards the middle......... ... e is e º e º e s e º & a s & e s º & e º e º 'º & CLOSTERIUM. PENIUM. SPIROTEN1A. OF THE DESMIDITE ME. 721 [Provisionally included.] Cells elongate, attenuated, entire, aggregated into faggot-like bundles... ANKISTRODESMUs. Cells rounded, compressed, deeply constricted, stipitate ................., CoSMOCLADIUM. “Euastrum cuneatum would be represented by a Tb"c. Euastrum pinnatum, 5 y 5 5 a, b, c, parallel. Euastrum oblongwm, 22 3 5 a, b, c, Subradial. Micrasterias denticulata, , , 3 y a, b, c, radial. Ewastrum ſpectinatwin, , 5 5 a^b, c, parallel. Tetrachastrum 35 3 y ab, c, parallel.” The following contractions are employed, which may require explanation :- f. V., front view ; S. V., side view ; e. V., end view ; tr. V., transverse view ; e. f., empty frond; L., length, B., breadth, of frond. The measurements are expressed in so many fractions of inch by the use of two acute marks, thus, L. 1-598"=length of frond ##sth of an inch. In most of the foreign species we are without the data to give measurements. G.B., Great Britain ; I., Ire- land; F., France; G., Germany; U.S.A., United States of America, refer- ring to the record of the occurrence of the species in those countries. It is believed that even this rough attempt at an indication of the distribution of these organisms may not be altogether without its use. Doubtless many occur, and perhaps different forms, in other countries of Europe; and information is much wanted in this respect as to other parts of the world. Where a species occurs under another name in the works above cited, we . have, as far as possible, given the synonym, but should it occur there under the same name, it is not repeated. The characters printed in italics are such as immediately distinguish each species from its nearest allies, and, the genus being known, are probably those which should be first consulted; but it is always requisite to peruse the whole of the characters applicable to each species and genus, with a view to render the identification accurate. A. Plant an elongated jointed filament. Sporangia orbicular, smooth. 1. Joints many times longer than broad. Genus GENICULARIA (De Bary).-Filament cylindrical; joints elongate, cylindrical, without a constriction or inflation, ends truncate; endochrome arranged in two or three spiral bands upon the cell-wall, sometimes irregular. Joints previous to conjugation disunited, and bent during the process; spo- rangium placed between the empty conjugated joints. GENICULARIA Spirotaenia (De Bary). rangium orbicular, smooth, placed be- —Joints ten or twenty times as long tween the conjugating joints, which are as broad, very slightly enlarged towards bent into a knee-shape, with which it their ends, on the outer surface rough remains for some time in connexion. with minute scattered granules. Spo- “B. 1-130"—1-100."” (III. 3.) G. Genus GONATOZYGON (De Bary).—Filament cylindrical; joints elon- gate, slender, cylindrical or marrow-fusiform, without a constriction or in- flation, ends truncate; endochrome a single, central, longitudinal, whdulatory, contracted band. Joints previous to conjugation disunited, and during the process bent into a knee shape; sporangium as last. GONATOZYGON Ralfsii (De Bary), — what dilated, ten to twenty times as Joints cylindrical with the ends some- long as broad, rough on * with j A 722 SYSTEMIATIC ELISTORY OF TETE INFUSORIA. numerous minute scattered granules; endochrome sometimes bifid at the ex- tremities, usually with a pale space at the centre, and with a longitudinal me- dian series of lighter-coloured dense cor- puscles. Sporangium same as preceding species. (III.1,2.) L. 1-100"; B.1–2350". Docidium asperum (Ralfs); Leptocysti- mema asperum (Archer). G.B., I., F., G. G. Brebissonii (De B.). — Joints nar- 'row-fusiform, subcapitate at ends, loosely united, often single, rough on the surface with minute scattered granules; endo- chrome usually with a pale space at the centre, and a median series of corpuscles. Sporangium as preceding. Docidium asperum (Bréb.); Lep. Portà (Archer). L. 1-200" to 1-105"; B. 1-3500". I., F., G. , 8 much smaller, and joints varying in length. . Genus LEPTOCYSTINEMA (Archer).-Filament attached, cylindrical; joints elongate, cylindrical, slender, linear, without a constriction or inflation, ends truncate; endochrome a longitudinal flattened band. tinous sheath.) (No evident gela- A genus under the above name was founded by Mr. W. Archer (Nat. Hist. Rev. vol. v. p. 250) for the reception of the single species now here included, as well as the two species of Gonatozygon (De B.), not being, however, then aware that DeBary had previously established the latter genus in ‘Hedwigia.’ However, as the reproductive condition of Lep. Kinahani (Archer) is yet unknown, we deem it more advisable to allow that species to remain under its original name, and, for the present at least, to retain the genus, distin- guishing it here from Gonatozygon by the filaments being attached (a singular circumstance in Desmidiaceae), and the endochrome a flattened band. The species is very distinct indeed from the two preceding. LEPTocystiNEMA Kinahani (Archer). —Filament 2 to 3 inches long, often breaking up into separate joints; joints 20 to 40 times as long as broad, linear, smooth; endochrome in its broader dia- meter filling the entire width of the joint—in the narrower, not more than one-third, occupying the centre of the joint, and at the central pale space curved towards the cell-wall, and hav- ing imbedded within it a longitudinal median Series of globular, light-coloured, dense corpuscles (one occupying the centre of the pale space), retracted at each end of the joint, leaving a clear space in which are active granules. porangium unknown. L. 1-200" to 1–50"; B, 1-1900". (III. 4.) I. 2. Joints mostly broader than long, very seldom slightly longer than broad. Genus HYALOTHECA (Ehr.).—Filament cylindrical, very gelatinous; joints having either a slight constriction, which produces a crenate appearance, or a grooved rim at one or both ends, which forms a bifid projection at each side; end view circular; endochrome radiate. HYALOTHECA dissiliens (Bréb.).—Fila- ment fragile, cremate; joints usually broader than long, with a shallow groove round each, dividing the endochrome into two portions. Sporangium globular, smooth, placed within the persistent connecting tube formed by the mutual fusion of a fresh extension from, and produced between, the sides opposed to each other of the conjugating pairs of i. the filament having previously broken up into single joints. (II. 32 & 35). L. 1-2105" to 1-1351"; B. 1-1308" to 1-833". = Conferva dissiliens (Smith), Gloeoprium dissiliens (Berk., Hass.), Hya- Ko.). Gº; lotheca mucosa (Kg.). G.B., I., F., G., .S.A. - H. mucosa (Ehr.).-Filament scarcely fragile, mucous sheath very broad; joints about as broad as long, not constricted, but having at one of the ends a minute bidentate projection on each margin, the adjoining end of the next joint being similar, these projections being produced by an annular grooved rim. #. 1–1250'ſ to I-660" ; B. 1-1250" to 1-1111". = Conferva mucosa (Mert., Hook, Harv.), Gloeoprium mucosum (Hass.), H. Ralfsii. G.B., I., F. dubia (Kg.).-Filament without a mucous sheat # ; joints rather broader than long, with two puncta near each margin. G. OF TELE DESMIDIE ZE. 723 Genus DIDYMOPRIUM (Kg.).-Filament gelatinous, cylindrical, regu- larly twisted; joints with a bidentate process or angle at each side; end view circular, or broadly elliptic, with two opposite projections formed by the angles; endochrome radiate. DIDYMOPRIUM Grevillii (Kg.).-Sheath distinct; joints broader than long, with a thickened border at their junction; angles bidentate; teeth angular; transverse view broadly elliptic, Sporangium orbicular, formed within one of the two conju- gating joints, the endochrome passing over from one by a narrow connecting tube produced between the otherwise but little altered broken-up single joints. L. 1-464"; B. 1-470". = Desmidium cy- lindricum (auct.), Arthrodesmus P cyl. (Ehr.), Desmidium compressum (Corda), D. Grevillii (De B.), G.B., I., F., G., Prussia, U.S.A. D. Borreri (Ralfs). — Joints inflated, barrel-shaped, longer than broad, without a thickened border at their junction; angles bicrenate, crematures rounded; transverse view circular. Sporangium elliptic, formed within the (for some time) persistent extensions from the conjugating joints, which do not previously break up into single joints, but couple, still united in the filament, in a confused or zigzag manner, some of the joints remaining unchanged. (II. 38, 39.) L. 1-939"; B. 1–1030". = Bambusina Brebissoni, (Kg., Bréb.). G.B., I., F., G., U.S.A. Genus APTOGONUM (Ralfs).-Filament 3–4-angular; joints not con- stricted, plane or cremated at the lateral margins, united only at the outer portions of each of their end margins by mutual projections, thus producing intervening central oval foramina. APTOGONUM Baileyi (Ralfs).-Joints mina broadly oval; in e.V. triangular, in f. V. quadrangular, about as broad as angles somewhat rounded. long, their lateral margins plane; fora- U.S.A. (III, 5, e.V., 6.) Genus DESMIDIUM (Ag). — Filament 3–4-angular or compressed, regul- larly twisted; joints bidentate or bicrenate at the angles or lateral margins, and either closely united throughout the whole of their end margins by a thickened border, or only at the outer portion of each by mutual projections, and thus producing intervening central oval foramina. DESMIDIUM aptogonum (Bréb.). — Joints in f. V. quadrangular, broader than long, with two rounded crenatures on each lateral margin, united at the outer portion only of each end margin by mutual projections, thus producing Žntervening central oval foramina. G.B., F., G., U.S.A. a. Filament triangular, regularly twisted, crematures rounded. L. 1-1490"; B. 1-1000". (III. 7, e.v. 8.) 6, filament compressed, crenatures shal- lower, andslightly angular. L. 1-1295"; B. 1–925". = Aptogonum Desmidium (Ralfs). D. Swartzii (Ag). — Filament trian- gular, equal, with a single longitudinal waved dark line formed by the third angle; joints in front view somewhat quadrangular, broader than long, with two slightly angular crenatures on each lateral margin, united at the whole of their end margins by a thickened border; end view triangular; endochrome three- rayed. L. 1-2000" to 1-1666"; B, 1-633", G.B., I., F., G., Italy, Sweden, U.S.A. D. Quadrangulatum (Ralfs).-Filament quadrangular, varying in breadth from its twisting, having two longitudinal waved lines; joints in f. V. broader than long, with two somewhat rounded cre- natures on each lateral margin, united by the whole of their end margins; e. V. quadrangular ; endochrome four-rayed. (II. 37, 40.) L. 1-1244"; B. 1-603" to 1-455".= D. quadrangulare (Kg.). G.B., F., G., U.S.A. D. undulatum (Corda),—Filament tri- angular; joints in f. v. with a slight central notch at each side, and four broad crematures at each lateral margin, united by the whole of their end margins. D. didymum (Corda),—Filament tri- angular; joints in f. V. bidentate, broader than long, united by the whole of their end margins; e. V. triangular; angles acutely , bifid. = Desmidium biſidum (Menegh.). G., Italy. Genus SPHAEROZOSMA (Corda)—Filament compressed; joints deeply divided on each side, thus forming two segments, and giving a pinnatifid 3 A 2 724 SYSTEMATIC HISTORY OF THE INFUSORIA. appearance to the filament, writed to each other by minute tubercles or gland- like processes. SPHZEROzosMA vertebratum (Ralfs).- Joints as long as broad, constriction deep, acute; segments reniform, gland-like processes oblique, solitary at the centre of each margin. A gelatinous sheath evi- dent. Sporangium spherical, Smooth, placed between the empty segments, the filament previously to conjugation break- ing up into single joints. L. 1-1429"; B. 1-909" to 1-666". (I, 15–17.)=Sph. elegans (Corda, Hass.), Odontella whi- dentata (Ehr.), Isthmia vertebrata (Menegh.), Isthmosira vert. (Kg.). G.B., I., F., #. U.S.A. (Kg.) S. excavatum (Ralfs). — Joints longer than broad, subquadrate, very minute; constriction a deep rounded sinus on both sides, and two sessile gland-like pro- cesses on each margin at their junction; angles sometimes with three very minute teeth; no evident gelatinous sheath. Sporangium elliptic, placed between the empty joints, the filament previously breaking up. L. 1–2575"; B. 1-3050". = Isthmosira eaccavata (Kg.). G.B., I, F., U.S.A. S. filiforme (Ehr.).-Joints about as long as broad; constriction acute; seg- ments elliptic, and united by double slender processes which include a quadrate foramen between each pair. = Isthmosira Jiliformis (Kg.). G. S. lamelliferum (Corda),—Joints about one-third broader than long, constriction deep, slightly rounded within; segments incurved, reniform; connecting processes “flattened,” colourless; a gelatinous sheath. G. Genus SPONDYLOSIUM (Bréb.)—Filament compressed or 3-angular ; joints deeply divided on each side, thus forming two segments, and giving a pinnatifid appearance to the filament, and without intermediate tubercles or processes. SPONDYLOSIUMstomatomorphum (Br.). — Joints about one-third broader than long, constriction deep, segments rent- form, ends broadly rounded; no sheath. = Isthmia stomatomorpha (Menegh.). F. S. pulchrum (Bail. sp.).-Joints twice as broad as long, constriction not deep, acute, segments elliptic; junction margins straight, forming Short connecting bands; gelatinous sheath wide. = Sphaerozosma pulchrum (Bail.). U.S.A. S. pulchellum (Archer). — Filament minute, fragile; joints about as broad as long, sharply incised; segments laterally inflated at the base, thus giving a pouting appearance to the joint, narrowing to the ends, which are straight, with Square angles; endochrome containing in each segment a single, central, lighter- coloured, globular corpuscle. No evi- dent gelatinous sheath. L. 1-2330"; B. 1-2330". (III. º I. S. depressum (Bréb.). — Joints some- what broader than long, subquadrate, constriction a rounded Sinus, angles rounded, ends straight, furnished at end margin on upper surface with three rounded protuberances; “no sheath.” (III. 9.) F. S. Serratum (Bailey, sp.). — Joints broader than long, constriction a trian- gular notch; Segments forming lateral triangular acute projections, thus giving a serrated outline to the filament; junc- tion margins straight. = Sphaerozosma serratum (Bail.). Ü.S.A. - S. secedens (De Bary, sp.), Filament very fragile, }. as long as broad, con- striction a shallow rounded sinus; seg- ments subelliptic, ends concave; no gela- tinous sheath. L. 1-287". = Sphaerozosma secedens (De Bary). G. B. Fronds simple, free, owing to complete transverse division. 1. Fronds distinctly constricted at the middle, never as much as three times longer than broad. Sporangia mostly spherical and spinous or tubercu- lated, or very rarely spherical or quadrate and naked. Genus TETRACHASTRUM (Dixon). — Frond compressed, deeply con- stricted into two 3-lobed segments; lateral lobes projecting horizontally, or sometimes divergent, broadest at their base and simply attenuated outwards; end lobe laterally expanded into a horizontal attenuated projection on each side, subtending the lateral lobes; central constriction a gradually widening incision (ab, c, vide Suprā). OF TEDE DESMIDIE ZE. 725 * Extremities of lobes entire, mucronate or acute. TETRACHASTRUM arcuatum (Bailey, sp.).--Frond rather broader than long, pinnatifid, quadrangular ; lateral lobes long, slender, arcuate, tapering, divergent from those of the opposite segment, their extremities acute; terminal lobe narrow, produced, its lateral projections abruptly transverse, slender, attenuated, acute; ends slightly concave at the centre. = Micrasterias arcuata (Bail.). U.S.A. T. expansum (Bailey, sp.). — Frond about as broad as long, somewhat stel- late; lateral lobes long, slender, Straight, conical, divergent from those of the op- posite segment, their extremities acute; terminal lobe narrow, produced, its la- teral projections somewhat divergent, short, quickly tapering, acute; ends concave. = Micr. expansa (Bail.). U.S.A. T. mucronatum (Dixon). — Frond longer than broad, subelliptic; lateral lobes very broad, straight on the margin forming the base of the segment, turgid on the upper margin, their extremities rounded, furnished on the margin with one, two, or three minute mucro-like spines, one always at the extremity or basal angle of the segment, others, when pre- sent, irregularly placed on the upper margin; terminal lobe short, very broad, its lateral projections, short, stout, quickly tapering, somewhat incurved at extremities, which are mucronate; ends rounded, with a very shallow inconspi- cuous central concavity; tr. V. broadly elliptic; e. f. punctate. L. 1-167"; B. 1–235". I. 2* Extremities of the lobes bidentate. T. oscitans (Dixon).--Frond about as broad as long, pinnatifid; lateral lobes separated from the terminal by a rounded sinus, horizontal, conical, their extremities bidentate; end lobe short, broad, its lateral projections short, conical, usually ºbidentate, narrower and shorter than the lateral lobes; ends convex at the centre; tr. V. fusiform, e. f. punctate. L. 1-256"; B. 1-211". (II. 28, 29). = Euastrum holocystis (Kg.); Holocystis oscitans gº ; Micrasterias oscitans (Ralfs). .B., I., F., U.S.A. T. Americanum (nobis). — Frond broader than long, suborbicular, pinna- tifid; lateral lobes separated from the terminal by a deep acute incision, hori- Zontal, conical, tapering, their extremities bidentate; end lobe short, its lateral pro- jections long, tapering, bidentate at their extremities, as broad and long as the lateral lobes; ends broadly rounded. = Micras- terias incisa (Kütz.), Bailey, in “Micr. Obs. in S. Carolina,’ &c., but surely not that species; we are therefore obliged to place it here under another specific Ilêll)16}. T. pinnatifidum (Dixon).--Frond ra- ther broader than long, plane, pinnatifid; lateral lobes separated from the terminal by an equal subacute incision, triangular, Subconical, horizontal, their extremities bidentate; end lobe short, its lateral |projections transverse, short, bidentate at the extremities, ends straight (colour pale). L. 1-440”; B. 1-392".= Micras- terias pinnatifida (Ralfs, Bº: JEuas- trum pinnatifidum (Kg.). G.B., F., G., U.S.A. T. did/macanthum (Nāg. sp.). Frond about as broad as long, pinnatifid; late- ral lobes separated from the terminal by a wide rounded sinus, their lower margin conver, in apposition with those of the opposite segment for a portion of their length, then slightly divergent, their upper margin nearly straight, horizontal, their extremities bidentate; end lobe long, united to the basal portion by a narrow neck, its lateral projections short, their extremities bidentate, ends slightly convex. L. 1-40"; B. 1-40”. = Euas- trum didymacanthum (Nāg.). G. T. quadratum (Bail. sp.). — Frond broader than long, pinnatifid, quadran- gular; lateral lobes separated from the terminal by a wide rounded simus, some- what inflated at their base, elongate, slightly divergent from those of the opposite segment, their produced extre- mities slender, bidentate; end lobe nar- row, produced, its lateral projections transverse, elongate, slender, bidentate at the extremities; ends with a slight central concavity. = Mic, quadrata (Bail.). U.S.A. Genus MICRASTERIAS (Ag.).--Frond mostly lenticular, as long as or slightly longer than broad, deeply constricted into two lobed segments; seg- ments usually Semiorbicular, 5- or sometimes 3-lobed ; lobes incised or divided, mostly radiant, narrower at the base and widening wipwards, their wltimate subdivisions spreading, dentate or minutely spined, or rarely only sinuate at the outer margin ; central constriction usually linear. 726 SYSTEMATIC HISTORY OF THE INFUSOR.I.A. * The subdivisions of the lobes spreading wn a plane at right angles to that of the frond, (a, b, c.) MICRASTERIAS muricata (Ralfs). — Frond quadrangular; segments sub-5- lobed, 1. opposite; basal lobes tripar- tite, middle §. bipartite; end i. exserted and laterally divergent, its lateral extensions bipartite; all the sub- divisions of all the lobes divergent and disposed in a plane at right angles to the plane of the frond, their extremities ter- minating in three or four projecting oints; the intervals between the lobes eep rounded sinuations; ends straight, entire. = Euastrum muricatum (Bailey). |U.S.A. 2* The subdivisions of the lobes spreading in the same plane as the frond. † Frond subelliptic; segments 3- or sub- 5-lobed, lobes spreading, the intervals between the lobes being wide; lateral lobes bipartite, their subdivisions di- vergent, end lobe exserted and laterally divergent. (a^b, c.) M. Baileyi (Ralfs).--Frond granulated all over; segments 3-lobed; lateral lobes deeply bipartite, subdivisions slender, their extremities bidentate, the lower subdivisions horizontal, approximate to those of the opposite segment, the upper divergent; end lobe narrow below, ex- serted, transversely expanded, its lateral extremities truncate; U.S.A. M. ringens (Bailey). — Frond some- what coarsely granulated at the margin; segments 3-lobed; lateral lobes some- what broadly bipartite, Stout, divergent from those of the opposite segment, their subdivisions having the extremities obscurely bidentate; end lobe narrow below, exserted, transversely expanded, its lateral extremities obtuse; ends con- cave. U.S.A. M. furcata (Ag). — Frond smooth; segments sub-5-lobed; basal and middle lobes bifid, their subdivisions slender, linear, divergent, and forked at the apex, bifurcation usually incurved; end i. exserted, with a rounded sinus between the considerably produced divergent ex- tensions from the angles, which are ulti- mately forked, their bifurcations in- curved. L. 1-135"; B. 1-156". = M. radiata º M. Melitensis 3 gracilis g.). G.B., U.S.A. M. Ch'ua:-Melitensis º Smooth; Segments sub-5-lo — Frond ed; basal ends concave. and middle lobes bifid, subdivisions short, Stout, and bidentate at the apex; end lobe exserted, with a rounded sinus between the produced divergent exten- sions from the angles, which are ulti- mately bidentate. L. 1-206"; B. 1-221". (I. 22). = Euastrum Cruac-Melitensis (Ehr.) ; M. Melitensis (Menegh.). G. B., F., G., Italy, U.S.A. 2t Frond angular-elliptic, subquadrate or suborbicular; segments 3-lobed; lobes spreading, the intervals between the lobes being usually wide; lateral lobes either bipartite and inciso-den- tate or truncate on outer margin ; end lobe mostly exserted, divergent. (a^b, c.) M. Americana (Ralfs).--Frond angu- lar elliptic, more or less punctate; seg- ments 3-lobed; lateral lobes broad, cuneate, their margins concave, inciso- Serrate; end lobe broad, cuneate, and exserted, bipartite at the angles, the subdivisions narrow, and minutely den- tate at the extremities; end concave. L. 1-204"; B, 1-254". (II. 44, bad). = JEuastrºm Americanum §: G. B., I., F., U.S.A. 6, margins waved rather than dentate. M. foliacea (Bailey). —Frond sub- quadrate, Smooth; Segments 3-lobed; lateral lobes deeply bipartite, inciso- dentate, their margins extending to an equal distance from the middle line of the frond, with a short rounded tooth- like projection meat the end lobe; end lobe narrow, somewhat dilated above, angles emarginate; ends concave. U.S.A. M, incisa (Kg.). —Erond about as broad as long, suborbicular; lateral lobes horizontal, sides parallel, abruptly trun- cate, with a tooth at each angle; end lobe short, very broadly cuneate, entire, its angles acute. = Buastrum Cruz-Melitensis (Ehr.). G., F., U.S.A, P M. decemdentatum º — Frond about as broad as long, suborbicular; Segments 3-lobed; lateral lobes hori- Zontal, side subparallel, obscurely bipar- tite, their Subdivisions acutely bidentate; end lobe broadly cuneate, entire, angles acute; ends rounded. L. 1-55"; B. 155". = M. Neodamensis (Braun); M. Itzigsohnii (Bréb.). F., G. 3t. Frond circular; segments 5-lobed; lobes approximate, the intervals be- tween the lobes being linear or very deep and acute incisions; basal and middle lobes dichotomously divided & OF TELE DESMIDIE ZE. 727 or deeply incised; end lobe marrow, Seldom and but very slightly exserted. (a, b, c.) M. Torrey (Bail.).-Frond smooth; segments 5-lobed; basal lobes bifid, middle lobes trifid, the subdivisions nearest the opposite segments and those nearest the terminal lobe bidentate at the apex; the intermediate three terminat- ing in acute points; all somewhat inflated and tapering; terminal lobe narrow, not exserted, spreading at the angles into divergent tapering points; ends slightly emarginate. U.S.A. M. denticulata (Bréb.).--Frond orbicu- lar, smooth; segments 5-lobed; basal and middle lobes twice dichotomous; ulti- mate Subdivisions truncato-emarginate, with rounded angles; end lobe simply thrice emarginate. Sporangium orbicu- lar, beset with scattered stout elongate spines, at first simple and obtuse, after- wards forked or trifid, their divisions finally again branched and recurved. L. i-iiš", f.i.138” (m. 22, sporangium). = Euastrum Rota (Ehr.) in part, G.B., I., F., G., Italy, U.S.A. 6, ends broader, slightly hirsute at the terminal margin (Bailey). M. rotata (Ralfs). —Frond orbicular, Smooth; segments 5-lobed; basal lobes twice, middle lobes thrice dichotomous; ultimate subdivisions acutely bidentate; end lobe very slightly exserted, its angles very slightly produced, bidentate, ends emarginate. In transverse view is seen an inflated protuberance just over the central isthmus, which may possibly exist in other species of Micrasterias. L. 1–91", B. 1-104". (I. 20.)= Euastrum Rota (Ehr.,Nāg.) in part; Euſtomia rotata (Harvey). G.B., I, F, G, Italy, U.S.A. M. fimbriata (Ralfs).--frond orbicu- lar, smooth; segments 5-lobed; basal lobes twice, middle lobes generally thrice dichotomous; ultimate subdivisions ob- tusely emarginate, each furnished with two curved acute spines; end lobe some- what exserted, the angles slightly pro- duced and rounded, and each furnished with two or three minute spines; ends concave. L. 1-108", B. 1-119". = Buas- trum. Itota º in part. G. B., U. S. A. M. apiculata (Menegh.).—Frond orbi- cular, hispid all over with Scattered spines; segments 5-lobed; basal and middle lobes once or twice incised, their external mar- gin toothed, ultimate subdivisions fur- mished with two acute spines; end lobe narrow, spinous on external margin. = Euastrum aculeatum (Ehr.). G., F. M. radioSa (Ag). —Frond orbicular, Smooth; Segments 5-lobed ; basal lobes twice, middle iobes generally thrice di- chotomous, ultimatesubdivisions inflated, attenuate towards the end, bidentate; end- lobe emarginate, its angles dentate. (I. ...) L. 1-138"; B. 1-138". = Euastrum Sol (Ehr.). G. B., I., F., U. S. A. M. papillifera (Bréb.).—Frond orbicu- lar, having the principal sinuses bordered by a row of minute granules, otherwise Smooth; segments 5-lobed; basal and middle lobes twice dichotomous, their ultimate shallow subdivisions terminated by two, sometimes three, gland-like teeth; end-lobe emarginate, its angles dentate. Sporangium as in M. denticulata, but con- siderably smaller. L. 1-221"–1-205"; B.1-238"–1–211". (I.18, spor. 19). G.B., I., F., U.S.A. 4f Frond orbicular; segments 5-lobed; lobes approximate, the intervals be- tween the lobes shallow narrow inci- Sions; the lateral lobes dentate, cremate, or slightly sinuate; end lobe broad, not exserted. (a^b, c.) M. Quadragies-cuspidata (Ralfs). — Frond hispid all over with scattered minute hair-like spines; segments 5-lobed; basal and middle lobes slightly bipartite, their Subdivisions bidentate; end lobe very broad, cuneate, truncate, its angles biden- tate. = Cosmarium quadragles-cuspidatum (Corda). G. M. truncata (Bréb.).—Frond orbicular, Smooth; segments 5-lobed; basal and middle lobes obscurely bipartite, extre- mities bidentate; end lobe very broadly cuneate, bidentate at the angles, and with a slight central concavity, L. 1-240”; B. 1–250". = Cosmarium truncatum (Corda); Euastrum Rota (Ehr.) in part; M. semi- Yadiata Gº ; Euastrum Semiradiatum (Nāg.). G.B., I, G., F., U.S.A. M. crenata (Bréb.).--Frond orbicular, Smooth; segments 5-lobed; basal and middle lobes usually cremate, or sinuate; end-lobe very broadly cuneate, rounded at the ends, entire. L. 1-244"; B. 1-263". G. B., I, U. S. A. 5+ Frond oblong, elliptic; segments 5- lobed; lobes approximate or spreading, intervals between the lobes linear or somewhat sinuous, all the lobes similar at the extremities, the end lobe the broadest, (a, b, c.) M. Jenner. º —Frond oblong, minutely granulated; segments 5-lobed; basal, middle, and end lobes cuneate, 728 SYSTEMATIC HISTORY OF TEIE INFUSORIA. obscurely bipartite, and their subdivisions emarginate, or with merely a slight central concavity; angles rounded; end-lobe at externalmarginconsiderably the broadest. L. 1-147"; B.1-209". G.B., I, a (Ralfs), #. like mere puncta, lobes slightly ipartite, subdivisions emarginate, 3 (Ralfs), granules larger, giving a dentate appearance to the margin, otherwise as a. 'y (Archer), granules giving a rough . pearance to the margin, lobes slightly concave, margins rounded, not bipartite, without emarginate subdivisions. Genus EUASTRUM (Ehr.).--Frond longer than broad, compressed; deeply constricted into two lobed or sinuated segments; segments usually pyramidal, 5- or 3-lobed or merely sinuous, possessing variously disposed circular inflated protuberances (very rarely absent); lateral lobes opposite, very rarely radiant, rounded or sinuated at the extremities; end lobes acutely incised or emarginate at the centre, rarely only concave; central constriction linear. (The inflated protuberances and the emarginate ends rarely (if ever?) simultaneously absent.) * Segments deeply lobed; separating Si- nuses directed inwards and downwards; the end lobe cuneate and partly included within the notch formed by the projection of the lateral lobes. EUASTRUM verrucosum (Ehr.).--Frond somewhat longer than broad, rough all over with conic granules; segments 3– lobed, somewhat divergent, all the lobes broad, cuneate, with a very broad shallow external sinus (ab, c). Empty frond: fiv, segments with one large circular basal inflation on surface, one smaller on each side, and two others on the end lobe; s.v. Segments inflated at the base, narrowed into a short neck, end dilated with a central sinus; e.V. oblong, with three inflations at each side, one at each end, end lobe having 4 divergent lobelets. L. 1-267”; B, 1-270". Cos- marium verrucosum (Menegh.), E. papu- losum (Kg.). G.B., I, &. F., Italy, U.S.A E. oblongum (Ralfs). — Frond rather more than twice as long as broad, Smooth, oblong; segments 5-lobed; lobes nearly equal, cuneate; lateral lobes, or the basal only, with a broad, shallow, marginal concavity, all their angles rounded, ter- minal notch linear (a, b, c). Empty frond: f. v. Seg, punctate, with three large inflations on Surface near the base, two others above and two on ter- minal lobe; tr. v. three times as long as broad, with three subdistant marginal inflations at each side, and one at each end, in 8 broader in proportion, more elliptic, and inflations close; e, y, end lobe notched at opposite external mar- gins. Sporangium orbicular, beset with numerous conical tubercles. L. 1-156"; B. 1-282". (III, 11.) = Echinella oblonga (Grev.); Euastrum Pecten (Ehr.); Cosma- rium sinuosum (Corda); Eutomia oblonga (Harv.). G.B., I., F., G., Italy, U.S.A. 3 Smaller, narrower, middle lobes rounded, without any marginal concavity. E. crassum (Kg.).--Frond about twice as long as broad, subquadrilateral, Smooth; Segments 3-lobed; basal lobes very broad, with a very broad, shallow marginal sinus, in which there is sometimes a slight in- termediate rounded projection; end lobe º rounded, terminal notch linear. ab, c. Empty frond: f. v. punctate, segments with three inflations below and two above; tr. v. two or three times longer than broad, with three lobes or inflations at each side and one at each end; e. V. end lobe sinuate at opposite external margins. L. 1-193'-1-132"; B. 1–263". =F. Pelta (Hass.). G. B., I., F., G., U. S. A. 8 smaller, margins of lateral lobes more concave, sinuations between the lateral and end lobes more closed, the latter more included. E. cornutum (Kg.).-Frond about twice as long as broad: segments 3-lobed, some- what inflated at base, outer upper angles of basal portion prolonged into a process- like projection, directed upwards; end lobe included, its notch broad, concave. Empty frond punctate. (ab, c.) G. 2 * Segments sinuously lobed, or tapering; end lobe eacserted and united to the basal portion by a distinct neck. f End lobe with a linear or acute notch, E. pinnatum (Ralfs). — Frond oblong, about twice as long as broad; segments 5-lobed in a pinnatifid manner, basal lobes slightly emarginate, middle smaller, rounded, entire, end lobe exserted, di- OIF TELE DESMIDIELEE. 729 lated, its notch linear ; the upper margin of the lobes horizontal, (a, b, c.) Empty frond: f. v. segments punc- tate, usually with two large inflations near the base, four Smaller between, three others above, and two on end lobe; s.v. central constriction deep, Segments inflated at the base, then contracted, again inflated, and again contracted be- neath the dilated terminal lobe; tr. V. with four lobes or inflations on each side, and one at each end; e.v. end lobe with a deep sinus at opposite external mar- gins, concave at the sides, so as to produce four divergent lobelets.” L. 1-188”; B. 1–454". G.B. B. humerosum (Ralfs).--Frond about twice as long as broad; segments sub- 5-lobed; basal lobes slightly emarginate; middle lobes narrow, directed upwards, resembling processes; end lobe with a short neck, partly included between the middle lobes, dilated, its notch linear. (a, b, c.) g Empty frond minutely punctate; f. V. segments with three inflations at base, two above and two on end lobe; tr. V. elliptic, with three inflations on each side and one at each end. L. 1-225"; B. 1-382". G.B., I., F. E. affine (Ralfs).--Frond about twice as long as broad; segments 3-lobed; basal lobes slightly emarginate, having inter- mediate between them and the end lobe on each side a tubercle representing mid- dle lobes, the upper margin of which is horizontal; end lobe exserted, dilated, its notch linear, (ab, c.) Empty frond: £ v. minutely punctate; the segments with four basal inflations, two above and two on end lobe; tr. V. elliptic, with four inflations on each side and one at each end; e.v. end lobe emar- ginate at opposite external margins, pro- ucing four shallow lobelets, L. 1-230"; B. 1-458". G.B., I., F., U.S.A. E. ampullaceum Gººd rather more than one-half longer than broad; segments obscurely 3-lobed, short, with broad inflated base; basal lobes not emar- ginate, having on each upper side a small intermediate tubercle between each and the end lobe; end-lobe exserted and di- lated, its notch linear, (ab, c.) Empty frond minutely punctate; f, V, inflations indistinct or confluent; S. v. narrow el- liptic, with several inflated protuber- ances, ends scarcely dilated, rounded ; tr. v. with four inflations at sides and one at each end. L. 1-274"; B. 1-394". G.B., I., F., U.S.A. . E. insigne (Hass.), Frond rather more than twice as long as broad; segments inflated at base, sides entire, without late- pal tubercles, and tapering into a long slender neck; end lobe dilated, its notch linear, (ab, c.) Empty frond minutely punctate; f, v. segments with two inflations at the base; S. v. narrower, gradually tapering to the end, which is considerably dilated; pro- jections rounded, with a sinus between; tr. V. Subquadrate, slightly concave at Sides, with a rounded lobe at the centre of each end; e.v. end lobe with a sinus at opposite external margins, angles thus protruded into four divergent rounded lobelets. L. 1-232"; B. 1-416". (III, 12.) G.B., I., U.S.A. E. Didelta (Ralfs).-Frond rather more than twice as long as broad; segments pyramidal, inflated at the base and again at the middle, end scarcely dilated, rounded, its notch linear. (a^b, c.) Empty frond punctate; f, v. segments with several inflations in lines and two at the end; tr. v. elliptic with four infla- tions at each side and one at each end: e.v. end lobe entire at margin. Sporan- gium orbicular, with subulate spines. (I. 23, 24, tr. v. 25.) L. 1-185"; B.1–357". = Cosmarium Didelta (Menegh.), E. binale (Kg). G.B., I., F., Italy, U.S.A. E. ansatum (Ehr.).--Frond about twice as long as broad; segments inflated at the base, tapering upwards without sinua- tions into a neck, end not dilated, rounded, its notch linear. (ab, c.) Empty frond punctate; f. v. segments turgid on the Surface, at the middle with- out circular inflations; tr. v. elliptic, with a single large inflation at each side; e. v. end lobe entire at the margin, its divisions circular. L. 1-315"; B. 1-654". = E. binale (Kg.), Cosmarium ansatum (Kg.). G.B., I., F., G., Italy, U.S.A. E. circulare (Hass.). — Frond about twice as long as broad, tapering upwards into a neck, end not dilated, its notch an acute incision. (ab, c.) Empty frond: segments with five basal hylations, four in a half circle round the fifth, and two others at the extremity. = Cosmarium circulare(Kg.), E. circulare, var. Hassallii (Bréb.). G.B., F., U.S.A. E. Sinuosum (Lenormand). — Frond about twice as long as broad, segments 3-lobed, basal portion emarginate at the sides ; end lobe Somewhat dilated, its notch linear, (ab, c.) Empty frond punctate; segments with Jive basal inflations and two others at ear- tremity; tr. V. elliptic, with three infla- tions at each side and one at each end, 730 SYSTEMATIC HISTORY OF THE INFUSORIA. L. 1-325"; B. 1–549". = E. circulare 8 (Rfs.), E. circulare, var. Falasiensis (Bréb.). G.B., F. E. Jenneri (nobis). —Frond scarcely twice as long as broad; segments 3-lobed, basal portion subquadrate, emarginate at the sides; end lobe somewhat dilated, its notch linear, (ab, c.) - Empty frond punctate, segments with several small inflations arranged in alter- nate lines. = E. circulare y (Ralfs), E. cir- culare, var. Ralfsii (Bréb.), G.B., F. Mr. Ralfs unites this and the two pre- ceding as three varieties of E. circulare (Hass.), ... They seem, however, to be quite as distinct as any other species de- scribed, not only in external outline, but also in the distribution of the Superficial inflations. 2 + Endlobe straight or concave without a central notch. E. pectinatum (Bréb.).—Frond rather more than twice as long as broad; Seg- ments 3-lobed, basal portion subquadri- lateral; lateral lobes horizontal, deeply emarginate, end lobe much dilated, straight or slightly concave at ends, angles entire or emarginate. (ab, c.) Empty frond #. f. v. segments with three in- ations near the base; tr. v. elliptic with three inflations at each side and two at each end; e.v. end lobe with two minute lobelets at each end, and two near them at each side. Sporangium orbicular, beset with conical tubercles. (II. 10 & 30.) L. 1-362"; B. 1-558". G.B., I., F. E. gemmatum (Kg., Bréb.). —Frond scarcely twice as long as broad; segments 3-lobed, lateral lobes horizontal, deeply emarginate, the protuberances minutely granulate; end lobe dilated, its dilata- tions inclined upwards, and minutely granulate; ends with a deep rounded emar- gination, (ab, c.) Empty frond slightly punctate; , f_v. Segments with three ranulate inflations near the base; tr. V. #. elliptic, with three granulate in- flations at each side and one at each end; e. v. end lobe cruciform, lobe- lets rounded, granulate. L. 1–443"; B. 1-641". = Euastrum (Eucosmium) JHassallianum (Nāg.). G.B., I., F., Prussia. 3* Frond without a distinct terminal lobe, frequently having a process or acute angle at corners of terminal portion. E. rostratum (Ralfs).--Frond scarcely twice as long as broad, oblong; segments with their basal portion deeply emargi– nate at the sides, connected by a broad neck with the terminal portion; ends protuberant, angular, acutely emarginate at the centre, and having at each side a horizontal subacute projection. (ab, c.) Sporangium orbicular, spinous; spines conical, attenuated. L. 1-650" to 1-580"; B. 1-1000" to 1-714". (I, 26.) G.B., I., F., U.S.A. E. pulchellum (Bréb.).—Frond rather more than one-third longer than broad, oblong; segments with the basal portion twice or thrice acutely dentate at each in- flated basal angle, and connected by a broad neck with the terminal portion;. . ends Straight, acutely emarginate at the Centre, angles acutely mucronate; e.f. bearing at the centre of each segment a Single inflated prominence bordered by an annular series of granules (in s.v. trun- cate), and a few scattered granules near the projecting parts. (ab, c.) F. E. elegans (Bréb., Kg.).--Frond minute, Scarcely twice as long as broad, oblong; segments with their basal portion emar- ginate at the sides, connected by a broad neck with the terminal portion; ends protuberant, rounded, acutely emarginate at the centre, pouting; s.v. with an infla- tion at the base of the segments, sides concave, ends rounded. (ab, c.) Sporan- gium orbicular, spinous. = E. bidentatum (Nāg.), G.B., I., F., G., U.S.A. a, neck Somewhat constricted, end portion bear- ing on each side an acute horizontal spine-like projection. L. 1-888" to 1-445"; B. 1-1441" to 1-714". , 8, seg- ments sinuated, neck not constricted and without spines. L. 1-421"; B. 1-654". 'y, neck not constricted, lateral projec- tions bearing minute spines directed ob- liquely outwards. = E. Spinosum (Hass.). L. 1-884"; B, 1-1388". E. crematum (Kg). —Frond very minute, about twice as long as broad, Segments pyramidal, their lateral margin crenate, ends broad, truncate, entire. (ab, c.) F., G. E. binale (Ralfs).-Frond very minute, scarcely twice as long as broad, oblong; segments with their basal portion either entire or bicrenate at the sides, slightly contracted beneath the ends; ends di- lated, not protuberant beyond the angles, its central notch acute, broad; tr.v. with two lateral inflations, ends truncate, angles rounded. (abc.) L. 1-1570" to 1–1428"; B.1-2400" to 1-1400". (III, 13.) = Heterocarpella binalis §§ Cos- ºnarium binale (Meneghini), E. Ralfsii (Kg.), E. lobulatum (Bréb.)? E. dubium (Nāg.). G.B., I., F., U.S.A. 6, frond rather larger, rough, with a few scattered OF THE DESMIDIE ZE. 731 granules; margins of segments crenate; acute angles of end portion slightly horizontally prolonged, its notch small, rounded .. a distinct species). E. cuneatum (Jenner).--Frond large, rather more than twice as long as broad; Segments pyramidal, broadest at base and narrowing upwards, not lobed, the sides almost Straight; ends truncate, central notch linear, (a^b \c.) Empty frond without inflated protuberances. L. 1-208"; B. 1-420". G.B., I. L. pelta (Kg.).--Frond about twice as long as broad, oblong; segments quadrate, each lateral margin with a small rounded protuberance or inflation at the base, another larger near the upper end, and another somewhat larger still at the upper angle; ends Straight, not notched. (ab, c.) = Cosmarium Pelta (Corda). G. Genus COSMARIUM (Corda),—Frond more or less constricted; segments wndivided, usually rounded, sometimes slightly sinuated, or rarely slightly contracted, somewhat extended and truncate at the ends, never notched, neither provided with spines nor processes; e.v. elliptic, and sometimes each side with a lateral opposite inflation, or circular. * Frond compressed; central constriction a deep, usually linear, incision ; e.v. compressed, either elliptic or subcruci- form, owing to the projection at each side of a protuberance or inflation. f Margins of segments entire, neither crenate nor granulate. CoSMARIUM sublobatum (Bréb. sp.).- Frond scarcely twice as long as broad, oblong; constriction linear, segments subquadrate, somewhat wider at the base, lateral and end margins slightly concave, smooth, transverse view cruciform. L. 1–523"; B. 1-646". = Euastrum P sublo- batum (Bréb.). G.B., I., F., U.S.A. C. pusillum (Bréb. sp.).--Frond very minute, slightly broader than long, con- striction acute, segments angulato-tra- pezoid, slightly narrowing upwards, smooth, angles rounded, ends slightly concave. = Euastrum pusillum (Bréb.). F. C. quadratum (Ralfs).--Frond about twice as long as broad, constriction deep, linear ; Segments quadrate, slightly pro- tuberant on each side at the base, with rounded angles at the ends, Smooth; e.v. compressed. L. 1–510"; B. 1-952". G.B., F. C. Cucumis (Corda). —Frond about twice as long as broad; constriction deep, linear ; segments as broad as long, with the basal angles rounded, broadly ºrounded at ends, smooth; e.v. elliptic. L. 1-362" to 1-257"; B. 1-568" to 1-502". = Euastrum integerrimum (Ehr.). G.B., I, F, G, Italy, U.S.A. C. Ralfsii (Bréb.). —Frond large, slightly longer than broad, orbicular, constriction deep, linear; segments semi- orbicular, rounded at basal angles, smooth; e.v. elliptico-lanceolate; endo- chrome radiate. L. 1-227"; B. 1-270". = C, Cucumis (Hass.), G.B., T., F. C. rupestre (Nāg, sp.).--Frond rather more than twice as long as broad, con- striction not deep but linear; segments broadly oval, turgid, Sides and ends broadly rounded, Smooth; e.f. punctate, puncta scattered, = Euastrum rupestre (Nāg.). G, . C. pyramidatum (Bréb.). — Frond Scarcely twice as long as broad, suboval; constriction deep, linear; segments pyra- midal, rounded at basal angles, somewhat truncate at the ends, punctate; e.v. broadly elliptic, Sporangium orbicular, tuberculated. L. 1-471" to 1–264"; B. 1-759" to 1-374", (III, 14, e.v. 15.) = Pi— thiscus angulosus (Kg.). G.B., I., F., U.S.A. C. lagenarium (Corda).--Frond about twice as long as broad, subelliptic; seg- ments triangular, pyramidal, punctate; basal angles broadly rounded, sides some- what concave, tapering, ends broadly rounded. = C. ansatum (Kg.). G. C. tinctum (Ralfs). — Frond very minute, about as long as broad, constric- tion producing an acute notch at each side; segments elliptic, about twice as broad as long, Smooth; e.v. narrow elliptic. Empty frond somewhat reddish. Sporangium quadrate, Smooth, with an empty segment of the conjugated fronds ermanently attached to each corner. . 1-2325"; B. 1-2500". G.B., I. C. bioculatum (Bréb.).—Frond minute, about as long as broad; constriction deep, producing a gaping notch at each side; segments about twice as broad as long, elliptic, Smooth; S.V. compressed; e.v. elliptic. Sporangium orbicular, with conical spines. L. 1-1416"; B, 1-1773". G.B., I., F., U.S.A. - C. depressum (Bailey). — Frond de- pressed, broader than long, constriction a deep, narrow, acute notch; segments about twice as broad as long, angular at 732 SYSTEMATIC HISTORY OF THE INFUSORIA. base, broadly rounded at ends, Smooth. .S.A. C. granatum (Bréb.).--Frond minute, somewhat longer than broad; constric- tion linear; segments broader than long, 7-apidly tapering, truncato-triangular, Smooth; s.v. compressed; e.V. elliptic. L. 1-1234"; B, 1-1602". G.B., I., F. C. polygonum (Nāg. sp.).-Frond mi- nute, about one-third longer than broad, constriction shallow, linear; segments heavagonal, sometimes punctate, lateral margins and ends Straight; e.v. elliptic with a broad rounded inflation at each Side. = Bhaastrum polygonum (Nāg.). G. C. Phaseolus (Bréb.).--Frond in fiv. about as long as broad, constriction deep, linear; segments reniform, Smooth; e.v. elliptic, with a slight conical projection at each side. L. 1-787"; B, 1-833". = E. depressum (Nāg.) P G.B., I., F. C. Papilio (Menegh.). — “Segments Smooth, triangular, with rectangular apex, sides very slightly sinuato-undu- late, lateral angles produced, acute; e.v. linear with a lobe at middle of each side.” Euastrum P Papilio (Kg.). G., Italy. 2f Margins of segments crenate or slightly undulate, surface not granu- late. C. Meneghinii (Bréb.).—Frond very minute, rather longer than broad, con- striction linear; segments subquadrate, bicrenate at the sides and ends, Smooth; e.v. elliptic. L. 1-853" to 1-735"; B. 1–1250" to 1-1176". = C, bioculatum (Menegh.), Euastrum bioculatum (Kg.), E. angulosum (Bréb.), E. crenulatum (Nãg.). G.B., I., F., G., Italy, U.S.A. C. crematum (Ralfs).--Frond minute, not quite twice as long as broad, con- striction linear; segments obsoletely quadrate, crenate at the margin, flattened at ends, surface punctate; e.v. elliptic. Sporangium orbicular, spinous; spines very short and stout, swollen at base, and divided at the apex, L. 1-474"; B. 1-678".= Euastrum P sinuosum (Kg.). G.B., I., F. C. undulatum (Corda).--Frond rather larger than last, slightly longer than broad, constriction linear; segments semiorbicular, ends and Sides broadly rounded, crenate or minutely undulate at margin; e.v. elliptic. Sporangium orbicular, spinous; spines elongate, slen- der, swollen at the base and divided at the apex. L. 1-416"; B. 1-571". (II. 33, spor. 34). = Ehtastrum crenulatum, c (Nāg.)? G.B., I., F., U.S.A. C. Nagelianum (Bréb.).—Frond in fiv. slightly longer than broad, constriction deep, linear; segments broad at the base, 7-apidly narrowing upwards, sides with Several minute sinuations, ends broadly truncate, Straight or very slightly undu- late, obscurely punctate; e.v. elliptic, Sometimes somewhat inflated at the sides. = Euastrum (Cosmarium) crematum (Nāg.). F., G. - C. tetragonum (Nāg. sp.).--Frond in fiv, about twice as long as broad, oblong, constriction linear; segments subquad- Yate, somewhat narrowing from the base, sides and end each with three slight Sinuations, those of the ends rather Smaller, in each half one large central granule; S.V. segments oval, rounded, constriction shallow. = Euastrum tetra- gonum (Nāg.). I., G. C. venustum (Bréb. sp.).--Frond some- what longer than broad, constriction deep, linear; segments slightly narrowed upwards, with two somewhat deep sinua- tions at the sides, ends broad, truncate, slightly concave at the centre. =Iºuastrum venustum (Bréb.). F. 3f Fronds rough on the surface, with early granules, which give a denticu- ate appearance to the margin. C. tetraophthalmum (Kg., Bréb.).— Frond about a third longer than broad, constriction deep, linear; segments form- &ng nearly two-thirds of a circle, rough on the surface with short and broad scattered pearly granules, giving a crenate appear- ance to the margin; e.v. broadly elliptic. Sporangium orbicular, spinous; spines swollen at base, finely branched. L. 1-232"; B. 1-1326". G.B., I, G., F. C. Brébissonii (Menegh.). —Frond Somewhat longer than broad, constric- tion deep, linear; segments Semiorbicular, rough all over with somewhat elongate- conical Scattered pearly granules; e. v. elliptic. L. 1-285"; B. 1-4.60". = C. mar- garitiferum (Kg.)? G.B., I., F., G. C. conspersum (Ralfs).--Frond about a third longer than broad, constriction deep, linear; segments quadrilateral, angles rounded, rough all over with de- pressed granules arranged in lines; e.v. elliptic. L. 1-162"; B. 1–357".= C. Brébissoni (Menegh.)? G.B., F. C. Ungerianum (Nāg.).--Frond large, rather longer than broad, constriction deep, linear; Segments much inflated at the base, angles and sides rounded, nar- rowing upwards, ends broadly truncate, rough at the margin, with a few large OF TELE DIESMIDIE ZE. 733 rounded pearly granules placed in lines, the disc punctate; e. V. broadly elliptic, the large pearly granules confined to the rounded extremities, regularly disposed in a few evident lines, the intermediate central space punctate. “L, 1–37"; B. 1-43".” = Euastrum (Cosmarium) Un- gerianum (Nāg.). G. C. ovale (Ralfs). — Frond very large, elliptic, nearly twice as long as broad, constriction very deep, linear; Segments somewhat broader than long, somewhat triangular, rounded at ends, rough near the margin, with a band of large pearly granules, producing a dentate appear- ance, the disc punctate; e. V. elliptic. L. 1-139"; B. 1-240". G.B., F., U.S.A. C. praemorsum (Bréb.).—Frond rather longer than broad, constriction deep, linear ; segments broadly reniform, sides rounded, ends somewhat truncate, rough with pearly granules, an annular series of which, more elevated than the rest, forms a ridge at the end bounding a circular depression; e. V. elliptic, F. C. margaritiferum (Menegh.).-Frond about as long as broad, constriction deep, linear ; segments reniform or Semiorbă- cular, rough all over with round and scattered pearly granules; e. V. elliptic, Sporangium orbicular, spinous; spines branched at apex. L. 1-566" to 1-806"; B. 1-694" to 1-416". (I. 1.) = Ursinella margaritifera (Turpin), Euastrum mar- #ºm (Ehr, Nāg.), C. punctulatum (Bréb.)? G.B., I., F., G., Italy, U.S.A., Mexico. C. Portianum (Archer).--Frond about one-third longer than broad, constriction deep, wide, somewhat round below, isth- mus forming a short neck; segments ellip- tic, rough all over with minute scattered pearly granules; e.v. elliptic. L. 1-600"; B. 1-930". I. s C. latum (Bréb.).—Frond large, about as broad as long, constriction deep, Sub- linear; segments reniform, rough with rounded pearly granules arranged in somewhat curved transverse lines; e.V. P. F. C. notabile (Bréb.).--Frond about one- third longer than broad, constriction somewhat deep, acute; segments slightly longer than broad, broadest at the base, gradually narrowing upwards, sides con- vea, ends truncate, rough all over with broad pearly granules, giving a crenate appearance to the margin (endochrome in bands); e. v. oval, turgid. Sporan- gium orbicular, beset with numerous short stout spines, inflated at the base, and deeply divided at the apex. F., G. C. amoenum (Bréb.).—Frond twice as long as broad, Sides parallel, ends rounded, constriction deep, linear; segments rough with crowded obtuse papilla-like pearly granules; S. V. much compressed, about thrice as long as broad; e.v. elliptic. L. 1-568"; B. 1-114.1". G.B., F., U.S.A. C. Botrytis (Menegh.).-Frond rather longer than broad, constriction deep, linear; segments twice as broad as long, broadest at base, narrowing upwards, sides rather rounded, ends truncate, rough all over with scattered rounded pearly gra- nules; e. V. broadly elliptic. Sporangium orbicular, spinous; spines elongate and slightly divided at the apex. L. 1-469" to 1-327"; B. 1-625" to 1-419", = Hete- rocarpella Botrytis (Bory), C. deltoides (Corda), Euastrum Botrytis (Ehr, Kg., Nāg.), E. angulosum (Ehr.). G.B., I G., F., Italy, U.S.A. C. protractum (Nāg. sp.).--Frond about as broad as long, constriction deep, linear; segments twice as broad as long, inflated and broadest at the base, rapidly tapering into a somewhat evident neck, sides very concave, ends abruptly truncate, rough all over with scattered pearly granules; e. V. broadly elliptic, slightly inflated at the middle, and gradually sloping to the rounded ends. L. 1-55" to I-33". = JEuastrum protractum (Nāg.). G. C. gemmiferum (Bréb. in lit. c. ic.). Frond, in f. V. about as long as broad, constriction deep, Sublinear; segments broadest at the base, gradually narrowing upwards, sides conver, ends truncate, rough all over with pearly granules, somewhat arranged in radiating lines, each segment furnished at the middle, on both surfaces, with a rounded protu. berance bordered with granules; e. v. broadly elliptic, with the central trun- cate protuberance on each side. F. C. Turpini (Bréb.).—Frond about as long as broad, constriction deep, linear ; segments, twice as broad as long, some- what triangular, much inflated and broadly rounded at the base, rapidly at- tenuated, sides concave, ends truncate, rough, all over with scattered pearly granules, and with a central granulated protuberance; e. V. narrow-elliptic, with the central broad truncate protuberance on each side. = Heterocarpella Didelta (Turpin), C. Didelta (Kg.). F., G. C. biretum (Bréb.). — Frond in f. v. about as long as broad, constriction deep, linear ; Segments quadrilateral or . heavagonal, narrowest at the base and dilated upwards, convex or somewhat truncate at ends, rough all over with Small granules arranged somewhat in • ? 734 SYSTEMATIC EIISTORY OF TEDE INFUSORIA. lines; e.v. with a rounded lobe on each side and rounded at ends. L. 1-333"; B. 1-372". G.B., F. War. triquetrum (Bréb.): e.v. with three rounded angles, sides deeply sinuous ! C. Broomei (Thwaites). — Frond in f. v. about as long as broad, constriction deep, linear; segments quadrilateral, ends straight, angles rounded, rough all over with minute granules; e.V. twice as long as broad, slightly inflated at the middle and rounded at the ends. Sporangium orbicular, smooth. L. 1-500"; B, 1-540". (r. 7.) G.B., F., U.S.A. C. caelatum (Ralfs). — Frond in f. v. about as long as broad, Suborbicular, con- striction deep, linear; segments Semior- bicular, with six broad crematures at mar- gin, rough at margin with scattered pearly granules, and at the centre with granules somewhat concentrically ar- ranged; e. V. twice as long as broad, with a broad inflation at each side. L. 1-92.1" to 1-581"; B. 1-1024" to 1-608". (II. 26.) G.B., I., F. C. ornatum (Ralfs). —Frond in f. v. about as long as broad, constriction deep, linear; segments semiorbicular or sub- reniform, with a central truncate pro- jection at the ends produced by the con- tinuation of a central inflation, rough towards the margins and on the inflation with pearly granules; e.v. with a rounded lobe on each side. Sporangium orbicular, spinous; spines elongated, dilated at the base, and slightly divided at the extre- mity. L. 1-613"; B. about the same. G.B., F., U.S.A. C. Sportella (Bréb.).—Frond about as long as broad, constriction deep, linear; segments reniform, with a central trun- cate projection at the ends, its angles slightly dilated and denticulate, rough all over with scattered pearly granules. F. C. Corbula (Bréb.). —Frond about as long as broad, constriction deep, linear; segments subreniform, a central truncate projection at the ends with its angles slightly dilated and minutely denticulate; furnished at the centre of each segment with a circular protuberance bordered with granules, and rough thereon and towards the margins with scattered pearly gra- nules. F. C. commissurale (Bréb.).--Frond small, in f. v. one-third broader than long ; constriction very deep, rounded; Seg- ments narrow-reniform, with a central somewhat truncate projection, produced by the continuation of the central inflation, rough on the inflation and on the extre- mities with somewhat large pearly gra- nules; e. V. three times longer than broad, constricted between the central in- flation and the rounded eactremities. Spo- rangium as in C. ornatum. L. 1-923"; B. 1-663" to 1-609". G., B., F. 3 acutum (Bréb.), angles sharper, C. cristatum (Ralfs). — Frond in f. v. as long as broad, Orbicular, constriction deep, linear ; segments Semiorbicular, margined by a series of obtuse papilla- like pearly granules, and having at the centre of each a circular granulate inſta- tion; e. V. linear, truncate at ends, with a slight central inflation at each side. L. 1-700"; B, 1–653". G.B., F. * , C. pluviale (Bréb. in lit. c. ic.).--Frond about one-third longer than broad; con- striction a shallow wide notch; segments Subovate, gradually tapering, ends round- ed, or broadly rotundato-truncate, rough all over with minute granules ; e. V. elliptic. F. 2 * Frond not compressed; central con- striction rarely a deep, never a linear, incision, but merely the result of the form of the contracted bases of the segments; e.v, circular, or, very rarely, compressed. f Frond rough with pearly granules, which give a denticulate appearance to the outline. • C. Colpopelta (Bréb.in lit.c. specimine). —Frond rather more than twice as long as broad; constriction a shallow contrac- tion; segments somewhat widening up- wards from the base, oval, sides and ends broadly rounded, very minutely granulate, granules scattered; e.V. circular. F. C. cylindricum (Ralfs).--Frond minute, in f. V., about twice as long as broad; segments subquadrate, narrower at the junction and gradually widening upwards, ends truncate, rough all over with pearly granules somewhat arranged in lines; e.v. circular. L. 1–588"; B. 1-1060". § 16, e.v. 17.) = Penium Ralfsii (Kg.). .B., I., F C. striolatum (Nāg. sp.).--Frond in f.v. about twice as long as broad, elliptic; constriction a shallow rounded sinus; segments with sides and ends broadly rounded, pearly granules arranged in lines and giving the margin a crenate appear- ance, eaccept at the central Sinus, which is smooth, L. 1-16"; B. 1-33". = Dy- sphinctium striolatum (Nāg.). G. C. orbiculatum º .—Frond minute, in f. v., twice as long as broad; constric- tion deep; segments Spherical, rough all over, except at the neck-like contrac- tion, with pearly granules; e. V. circular, OF TEIE DESMIDIE ZE, 735 Sporangium orbicular, spinous; spines short, stout, comical. L. 1-498" to 1-454"; B. 1-750", = Penium orbiculatum (Kg.). G.B., F. 2 + Frond smooth. C. moniliforme (Ralfs). — Frond mi- nute, in f. v. twice as long as broad; constriction deep ; Segments spherical, smooth; e. V. circular. L. 1-617"; B. 1–1131", = Tessarthronia moniliformis §º , Tessarthra moniliformis (Ehr.). .B., I., 3'., G. C. connatum (Bréb.). — Frond large, in f. v. about one-half longer than broad; constriction shallow; segments about two- thirds of a circle, coarsely punctate, and with a distinct, sometimes striated, bor- der; e.V. circular. L. 1-285"; B. 1-1155". = Dysphinctium Meneghinianum (Nāg.). G.B., F., U.S.A. C. Cucurbita (Bréb.). —Frond in f. v. about twice as long as broad; constric- tion a shallow groove; segments sub- cylindrical, or somewhat oval, with rounded ends; e. V. circular; e. f. punc- tate, the puncta scattered. L. 1-586"; B. 1-1155".= Penium clandestinum (Kg.). G.B., I., F., G. C. Palangula (Bréb.).—Frond in f. v. about two and a half times as long as broad; constriction a shallow groove; segments cylindrical; ends obtuse; e. V. circular ; e. f. minutely punctate, the puncta arranged in transverse lines. F. C. P. cruciferum (De Bary). — Frond minute, in f. v. about twice as long as broad; constriction an extremely shallow groove; segments subcylindrical; ends broadly rounded; endochrome composed of four broad plates cutting each other at right angles; e. V. circular, endochrome cruciform; e. f not punctate, L. 1-143"; B. 1-2871". G., C. Thwaitesii (Ralfs).-Frond in f. v. two or three times longer than broad; constriction a very shallow groove; seg- ments subcylindrical, with rounded ends; endochrome scattered; e. V. circular, or very slightly compressed; e.f, not punctate, or puncta very indistinct. L. 1-357"; B. 1-801". = Penium crassiusculum (De Bary) P G.B., F., G., U.S.A. C. curtum (Bréb.). — Frond in f. v. rather more than twice as long as broad; constriction very shallow; segments at- tenuated and rounded at ends; endochrome wn fillets; e. V. circular, endochrome ra– diate. L. 1-465"; B. 1-1064". = Penium curtum (Bréb., #º Dysphinctium Rege- lianum (Nāg.) P G.B., F., G. C, attenuatum (Bréb.).—Frond in f. v. fusiform, three, or sometimes four, times longer than broad; constriction very shallow ; segments comical, rapidly at- tenuated, ends angular, obtuse; e. V. cir- cular ; e. f. punctate. L. 1-420"; B. 1–1099" to 1-1068". G.B., F. C. parvulum (Bréb.).—Frond minute, in f. V. ovato-elliptic, about one and a half times longer than broad; central constriction a very shallow groove; seg- ments tapering, ends broadly rotundato- truncate; e. f not punctate. F C. turgidum (Bréb.). — Frond very large, in f. v. Oval, turgid, rather more than twice as long as broad; constriction a shallow sinus; segments somewhat tapering, broadly rounded; e. V. circular; e. f. punctate. L. 1-126"; B. 1-249". = Pleurotanium turgidum (De Bary). G.B., F., G. C. De Bary; (nobis). — Frond in f. v. about twice as long as broad; constric- tion a wide shallow notch ; segments cylindrical, with broadly rounded ends; endochrome arranged in parietal indented bands; e.V. circular; e. f. minutely punc- tate or puncta absent. = Pleurotanium Cosmarioides (De Bary). G. With great deference, we place the above species here, as described by M. de Bary, coinciding with M. de Bré- bisson in thinking the disposition of the endochrome not sufficiently constant to form the genus Pleurotaenium. Genus XANTHIDIUM (Ehr.). — Frond deeply constricted ; segments broader than long, compressed, entire, Spinous, having a circular, cylindrical or conical projection on both surfaces near the centre, which is tuberculated or dentate, or entire; end view elliptic. % Spines divided at the apex. XANTHIDIUM armatum (Bréb.). — Frond large, in f, v. twice as long as broad; constriction deep, linear ; seg- ments broadest at the base; ends rounded or somewhat truncate; Spines in pairs, principally marginal, Short, Stout, termi- mated by three or four diverging points; central projections cylindrical, truncate, the border dentate; e. f. punctate. “Spo- rangium large, Orbicular, with depressed tubercles; perhaps immature” Å; L. 1-180"; B. I-270". (I. 27, 28.) = Zygoaxanthium Echinus (Kg.). G.B., I., E., G., U.S.A. 736 SYSTEMATIC HISTORY OF THE INFUSORIA, X. (?) Artiscon (Ehr.).--Frond in f, v. about as long as broad; constriction forming a wide notch; segments narrowed at the base, with broadly rounded ends; spines numerous, restricted to the outer margin, scattered, elongate, stout, termi- nated by three or four diverging points. = Asteroacanthium Arctiscon (Kg.). G. 2* Spines subulate. X, aculeatum (Ehr.). — Frond in f, v. broader than long; constriction deep, linear; segments somewhat reniform ; spines subulate, short, Scattered, chiefly marginal ; central protuberance cylin- drical, truncate, border minutely dentate. L. (not including spines), 1-380"; B. 1–1347" to 1-393", = Zygoaxanthium aculeatum (Kg.). G.B., I., F., Italy, G. X. Brebissonii (Ralfs).--Frond in f. v. broader than long; constriction deep, acute, not linear; segments subelliptic, sometimes irregular ; spines subulate, geminate, marginal; central protuberance cylindrical, truncate, border minutely dentate. L. (not including spines)1-416"; B. 1-408" to 1-365". = X. bise?arium (Ehr.), Zygozanthium aculeatum (Kg.). (8, segments broader and more irregular, spines somewhat irregular and unequal. ë. I., F., G., U.S.A. X. fasciculatum (Ehr.).-Frond about as long as broad ; constriction deep, linear; segments somewhat reniform or subheavagonal, twice as broad as long ; spines slender, Subulate, geminate, mar- ginal, in four or six pairs; central pro- tuberance short, conical, somewhat trun- cate. a, Segts, with four pairs of spines. = X. antilopaeum (Bréb.), X. polygonum (HaSS., Bréb.). L. (not including spines) 1-454" to 1-350"; B. 432” to 408". 3, Segts, with six pairs of spines. = X, fasci- culatum, var. polygonum (Ehr.), X, fas- ciculatum (HaSS., *} L. 1-481"; B. 1-516". G.B., I., F., G., Italy, U.S.A. X, cristatum (Bréb.). — Frond rather longer than broad; constriction deep, linear; Segments Subreniform, or truncate at ends; spines straight or curved, subu- late, marginal, one at each side, at the base of the segment, solitary, the others geminate, in four pairs; central protu- berance short, comical, a, segts, remi- form, spines scarcely curved. L. (not including spines) 1–357"; B. 1–499". (II, 18 & 23.) 6, segments truncate at ends, spines uncinate. L. 1-469"; B. 1–625". G.B., I., F., U.S.A. - X. Smithii (Archer).--Frond minute, in f. V. about as long as broad; constric- tion a wide notch; segments twice as broad as long, trapezoid, lower margin Somewhat convex, sides narrowing up- wards and straight, ends broad and straight, angles rounded, each of the four angles presenting a pair of somewhat divergent, Short, minºſte, acute spines; S. v. constriction shallow, obtuse; segments with rounded sides, ends truncate, each wpper angle furnished with a minute spine, beneath each of which, about half way down, there occurs another similar spine, all the spines somewhat divergent; e. V. subelliptic, or broadly fusiform, ends blunt, rounded, furnished with three mi- nute spines, none on the sides; central protuberance a minute tubercle, apparent always in this view, but in s. v. some- times hidden by the projecting central spines, L. 1-1166"; B, 1-1272”. G.B. Genus ARTHRODESMUS (Ehr.).-Frond deeply constricted; segments compressed, either with four prominent angles and a single or geminate spine, or a tooth, at each angle, or having one spine or acute tooth only, on each side, at each upper or outer extremity; without a central projection; e.v. elliptic or fusiform. * Segments with four prominent angles and a simple or geminate Spine, or an acute tooth, at each angle, ARTHRODESMUs octocornis (Ehr., Hass., Bréb.). — Frond smooth, minute, about as long as broad; constriction a wide notch; segments much compressed, trapezoid, each angle terminated by one or two straight, Subulate, acute spines, the intervals between the angles concave. a, spine solitary at each angle. L. 1-1351"; B, 1-1538". (I, 30.) 8 larger, spines geminate at each angle, L. 1-1020”; B. 1-906". (I. 29.) = Micra- Sterias octocornis (Menegh, Kg.), Xan- thidium octocorne (Ehr., Ralfs). G.B., I., F., G., Italy, U.S.A. A. bifidus (Bréb.). — Frond smooth, very minute, about as broad as long: Segments somewhat arcuate, inner margin convex, outer concave, extremities diver- . gent, emarginate, each angle terminating ºn an acute tooth; e. v. compressed, fusi- form, with a short acute spine or tooth at each end. F. OF THE DESMIDIEGE, 737 2* Segments with a single acute tooth or Spine at each side. A. minutus (Kg.). —Frond very mi- nute, Smooth, two or three times longer than broad; constriction a minute acute notch; Segments narrow, lateral margins parallel, ends roundly concave, angles slightly produced into minute spines directed upwards. F., G. - A. Pittacium (Bréb. sp.).--Frond mi- nute, Smooth, two or three times longer than broad; constriction a minute acute notch; segments very slightly inflated at the base, Sides curved, end margin roundly concave, angles acute. = Euastrum Pit- tacium (Bréb.). F. A. Incus (HaSS.). — Frond minute, Smooth, as long as or longer than broad; constriction a deep notch or sinus; seg- ments with inner margin turgid, outer truncate, spines Subulate, acute. Sporan- gium orbicular, spinous; spines Subulate. &B. I., F., G., U.S.A., a, segments somewhat semiorbicular, connected by a distinct neck, spines diverging. L. 1-1100" to 1-1660"; B. 1-1960" to 1–1420". 3, segments gibbous near the base, spines parallel or converging, (III, 36.) L. 1-833”; B. 1-1116". A. subulatus (Kg.). —Frond minute, Smooth, about as long as broad; con- striction a wide acute-angled notch ; Segments broadly fusiform, spines hori- Zontal, straight, slender, Subulate; ends convex. G., U.S.A. A. convergens (Ehr.).-Frond smooth, broader than long; constriction deep, acute; segments elliptic, each having its lateral spines curved towards those of the other; ends conver. L. 1–1539" to 1-598"; B. 1-1477" to 1-584". = Staurastrum con- vergens (Menegh.), Euastrum convergens (Nāg.), G.B., I., F., G., U.S.A. Genus STAURASTRUM (Meyen).--Frond more or less deeply constricted at the middle; segments broader than long, often provided with spines or processes; end view angular or radiate, or circular with a lobato-radiate "margin, or very rarely compressed with a process at each eactremity. * Segments in f. v. with each of the oppo- site lateral extremities furnished with a mucro or a simple subulate acute awn or Spine, which in “e. v. terminates the angles, and without others intermediate, f Segments smooth, angles in e.V. inflated, sides concave. STAURASTRUM dejectum (Bréb.).—Seg- ments in f. V. lunate or elliptic, Smooth, mucrones or awns directed upwards, pa- rallel or convergent; e.v. with three or four angles, angles inſtated, mammillate, terminated by a mucro or awn, sides concave at the centre. Sporangium or- bicular, at first covered with minute hair- like spines, afterwards beset with stout subulate spines, and placed between the deciduous empty fronds. L. 1-833"; B. 1–757". = Goniocystis (Trigonocystis) mu- cronata (Hass.), a, segments externally lunate, awns directed outwards; 3, Seg- ments elliptic, awns parallel; y, awns converging. G.B., I., F., U.S.A. * S. apiculatum (Bréb.).—Segments in f. v. somewhat turbinate, Smooth, oppo- site lateral extremities rounded, external margin straight, furnished at each side on the upper outer margin near the lateral eactremities with a simple, short, Subulate, acute spine directed upwards; e.V. with three angles, angles inflated, mammillate, terminated by a short acute spine, sides concave. Sporangium orbicular, beset with conical spines, enlarged at the base and obtuse at the apex. F. S. Dickiej (Ralfs).-Segments in f. v. subelliptic, turgid, Smooth; spines short, curved, acute, converging with those of the opposite segment; e. V, with three angles, angles inflated, rounded, termi- mated by a spine, sides concave at the centre. L.1–855"; B. 1-929", G.B., I., F. S. brevispina (Bréb.).—Segments in f. v. elliptic or somewhat reniform, very tur- gid, Smooth; mucrones minute, inconspi- cuous; e. V. with three angles, angles inflated, broadly rounded, terminated by an inconspicuous mucro, sides concave at the centre. L. 1-502"; B, 1-510". G.B., I., F. S. cuspidatum (Bréb.).—Segments in f. V. fusiform, or truncate on outer mar- gin, connected by a long narrow band, Smooth ; awns Subulate, straight, acute, parallel or somewhat converging; e. V. with three or four angles, angles inflated, mammillate, terminated by an awn, sides concave at the centre. Sporangium or— bicular, covered all over by the enlarged bases of the few spines, which are ulti- mately much attenuated and acute. L. 1-883"; B, 1-1000". (1.31–34)= Phyc- astrum cuspidatum (Kg.), T. Spinulosum (Nāg.). G.B., I., F., G., Italy. S, aristiferum (Ralfs). — Segments 3 B 738 SYSTEMATIC EIISTORY OF THE INFUSORIA. smooth, in f. v. prolonged at each lateral extremity into a mammillate projection, which is terminated by a subulate, acute, straight awn, the awns divergent; e. V. with three or four angles; angles inflated, mammillate, terminated by an awn, sides deeply concave at the centre., L. 1-657"; B. I-1064". G.B., F., U.S.A. 2 f Segments smooth, angles in e.V. not inflated, sides straight, or nearly so. S. O’Mearii (Archer). — Segments smooth, in f. v. Somewhat cuneiform, gradually widening upwards, Outer margin truncate, awns acute, divergent; e.V. with three or four acute angles terminated by an awn, sides straight. Sporangium orbi- cular, spinous; spines subulate, acute, ultimately somewhat inflated at the base. a, e.V. with four angles, awns compa- ratively short. L. 1-1866"; B. 1-2500", 8, e.v. with three angles, awns longer. L. 1-1750"; B. 1-2300". I. S. minus (Kg.). — Segments Smooth, very minute, in e.V. with five angles, each terminated by a very minute acute Spine; sides straight, G. S. glabrum (Kg.), Segments smooth, in f. V. cuneate, ends concave or straight, spines slender, mucro-like; e.v. with three mucronate angles, sides concave, I., G. 3t Segments rough with minute granules. S. lunatum (Ralfs).-Segments in f. v. externally lunate, the inner margins con- vex, the outer somewhat truncate, and rough with minute granules; spines subu- late, acute, curved, obliquely directed out- wards and upwards; e.v. with three in- flated rounded angles, terminated by a spine, sides concave at the centre. L. 1-856"; B. 1-686". G.B. S. granulosum (Ralfs).-Segments in f. V. broadly fusiform, granulate, lateral extremities pointed, mucronate; e.V. with three subacute mucronate angles, sides convex. = Desmidium granulosum (Ehr.), S. acutum (Bréb.). F., G. 2 * Segments in f. v. with each of the op- posite lateral extremities furnished with a mucro or a simple Subulate spine, which in end view terminates the angles, and is accompanied by others interme- diate of a similar character. S. pungens (Bréb.).—Segments in f. v. externally lunate, the inner margin curved, the outer truncate, smooth ; the lateral marginal spines Subulate, curved, directed obliquely outwards and upwards, with Sia: other Spines on the outer margin, also directed outwards; e.v. with three angles, each terminated by a spine, and with two others at its base on the upper surface, and divergent at opposite sides, sides nearly straight or slightly convex. G.B., F., U.S.A. S. cristatum (Nãg. sp.).-Segments in f, v. broadly elliptic, inner margin some- what more turgid than the outer, sub- mammillate at each side, terminated by a mucro or short Spine, and possessing on the outer margin a few others directed towards the angles: e.V. with three subacute mu- cronate angles; Sides convex, with an in- wardly curved, Submarginal, single series of Short mucro-like spines directed to- wards, the angles, sometimes wanting néar the middle. L. 1-540”; IB. 1–543". = Phycastrum (Pachyactinium) cristatum ăg.), Staurastrum mitidum (Archer). • ? - ſº \ 3 * Segments with each of the opposite lateral eactremities furnished with a bifid or forked Spine, its subdivisions subulate, acute, in e. v. terminating the angles, and appearing as a mucro-like Spine, with or without intermediate spines. S. Avicula (Bréb.).—Segments in f. v. triangular or cuneate, ends truncate, Smooth, with a single forked spine on each side; e. V. with three inflated angles, the bifid spine appearing as a mucro, sides concave. L. 1-967"; B. 1-948". (III. 18, e.v. 19.) G.B., F. S. denticulatum (Nāg. sp.).-Segments in f. V. Subelliptic, inner margin some- what more turgid than the outer, both wndulate or toothed in a scolloped manner, with an unequally forked or geminate Spine on each side, the upper longer than the lower, the lateral projections having a Series of transverse rows of minute gra- nules; e. V. with three subacute angles, the spine appearing as a mucro, sides slightly concave at the centre, the mar- gîn toothed as mentioned before. “L. 1-70"; thickness 1-55".”= Phycastrum denticulatum (N º G. . S. armigerum (Bréb.).—Segments in f. V. turgid on inner margin, outer trun- cate, Smooth, with a forked spine on each side, and a few simple or forked, sometimes minute, Spines disposed at equal intervals between, on the outer margin ; e.v. with three angles, the bifid spine appearing as a mucro, and the intermediate spines projecting on each side. Sporangium or— bicular, spines numerous, elongate, sub- linear, forked at the apex. =S. spinosum (Ralfs). G.B., I., F. OF TEIE DESMIDIE ZE. 739 S. monticulosum (Bréb.). — Segments in f. v. broadly elliptic, smooth, with a forked spine on each side, and at the end six stout conical projections directed up- wards, each terminated by an acute Spine; e.v. with three or four acute angles, sides concave, the terminal projections extend- Čng on each side, confluent at their bases, from beneath which a minute, Subulate, spine-like projection arises between them and each angle. L. 1-500"; B. 1-700". =Stephanoacanthium monticulosum (Kg.). G.B., I., F. S. Ehrenbergianum.—The longitudinal outline of the segments obliquely oval, the inner margin convex, diverging, the outer margin very convex and broadly truncate at the ends; the sides in e. V. slightly undulate, membrane Smooth, having at each angle a large spine, di- vided to the middle, consisting of two legs, and on the terminal surface three pairs of Such spines, and between each of them and the angles a pair of smaller simpler *. = Phycastrum Ehrenber- gianum (Nāg.). “L. 1-66"; thickness 1-70".” We have not seen a drawing of the above species, and give the above description following as nearly as pos- sible R.H. own words, inserting it here as most probably its most fitting place. 4* Segments with numerous simple acute Spines, in f. v. no one in particular ter- minating the opposite lateral eactremities; e. v. angles entire, rounded, the Spines scattered. - S. hirsutum (Bréb.).—Segments in fiv. Semiorbicular, separated by a linear con- striction, covered with very minute, very numerous, close-set hair-like spines; e. v. with three broadly rounded angles, the spines evenly and numerously scattered; sides slightly convex. Sporangium or— bicular, beset with short spines, branched at the apex. L. 1-676" to 1-468"; B. 1-833" to 1-680". =Xanthidium hºrsutum, (Ehr, Kg.), Goniocystis { Trigonocystis) muricata (Hass.). G.B., I., F., U.S.A. S. pilosum (Nãg. sp.). —Segments in f, v. obliquely elliptic, slightly divergent, the outer margin more turgid than the inner; e.V. with three rounded angles, sides concave; scattered all over, except a Small space at the centre, with eactremely fine hair-like Spines, minutely capitate at their eactremities; surface between the spines smooth. “L. 1-55"; thickness 1-66".” Phycastrum pilosum (Nāg.), M. de Brébisson is disposed to doubt the accuracy of Nägeli's drawing (Einzell. Alg. 8 A. fig. 4), the spines are indeed So very curious. S. Brebissonii (nobis). —Segments in f. V. ovato-lanceolate, the lateral extre- mities rounded and furnished thereon with numerous short, close-set, hair-like Spines, otherwise Smooth; e. V. with three broadly rounded angles, the spines con- Jimed to the eactremities, sides concave. = S. pilosum (Bréb). F. We are obliged to alter the specific name of this species, —pilosum having been employed by Nā- geli before for the preceding species. S. erosum (Bréb).—Segments in f. v. elliptic, the lateral extremities furnished with numerous extremely short acute Spines, sometimes inconspicuous, sur- face granulated all over; e.v. with three broadly rounded angles, the spines con- fined to the angles, sides concave. F. S. echinatum º — Segments in f. v. elliptic, furnished with numerous Spines, somewhat broad at their base, eac- ceedingly acute, chiefly confined to the outer margin; e.V. with three angles; angles and sides broadly rounded, bordered all round by the spines. F. - S. teliferum (Ralfs).-Segments inf. v. elliptic or subreniform, furnished with a few scattered, elongate, Subulate, acute Spines; e.V. with three broadly rounded angles, the Spines scattered, º CO%2- fined to the eactremities, surface between the spines smooth, sides concave. Spo- rangium Orbicular, beset with numerous elongate linear spines, forked at the apex. L. 1-597"; B, 1–643". (III, 20, e, v.21.) G.B., I., F. S. Hystria (Ralfs). — Segments in f. V. subquadrate, extremities somewhat rounded, end margin nearly straight, fur- nished with a few scattered, subulate, acute spines, chiefly confined to the late- ral eactremities; e.v. with three or four broadly rounded angles, the spines scat- tered, chiefly confined to the extremities, sides concave. L. 1-1075" to 1-1020"; B. 1–1165" to 1—954". G.B. 5* Segments with numerous short, trun- cate, emarginate, Scattered Spines, prin- cipally confined to the margins; e.v. angles, rounded; if angles spinous, no Spine in particular conspicuously larger than the others terminating the angles. S. Spongiosum (Bréb.), Segments in fiv. Semiorbicular, furnished with scat- tered short, Stout, forked spines, the spines at the lower basal angle of each 3 B 2 470 SYSTEMATIC EIISTORY OF THE INFUSORIA. rather larger than the others; e.v. with three somewhat rounded angles, sides convex, and bordered all round with the spines. L. 1–506" to 1-418"; B. 1-523" to 1-476". (III. 22, e.v. 23.)= Desmidium ramosum (Ehr.), Asteroa anthium ramo- sum (Kg.), Phycastrum Griffithsianum (Nāg.). G.B., I., F., G., U.S.A. S. scabrum (Bréb.).—Segments in fiv. subelliptic or broadly fusiform, very rough or denticulate at the margin; e.V. with three rounded denticulate angles, sides straight, bordered by minute, short, truncate emarginate spines. F. S. asperum (Bréb.).—Segments in fiv. broadly elliptic, very rough, with very minute, short, truncate or forked spines chiefly confined to the outer margin; e.v. with three rounded angles, sides straight. Sporangium orbicular, beset with numerous elongate spines, twice branched at the apex. L. 1-555"; B. 1–615". G.B., I., F. 6 * Segments without spines, e.v. angles Younded. + Frond Smooth. S. muticum (Bréb.).—Segments in fiv. elliptic, Smooth, without spines; e.v. with three or four broadly rounded angles, sides concave. Sporangium beset with nume- rous elongate somewhat stout spines, forked at the apex. L. 1-674"; B. I-686". =S. trilobum (Menegh.), Phyc- astrum muticum (Kg.), P. depressum (Nág). G.B. i., §, iély, tisſã. S. orbiculare (Ralfs). — Segments in f. V. Semiorbicular, smooth, without spines; e.v. with three broadly rounded angles, sides slightly concave. L. 1–1037"; B. 1-1106". = Desmºdium orbi- culare (Ehr.), Phycastrum orbiculare (Kg.), Goniocystis (Thºgonocystis) orbi- cularis (HaSS.). G.B., I., F., G., Italy, U.S.A. S. coarctatum (Bréb.).—Segments ob- long, lateral extremities rounded, inner 7margin convex, outer somewhat concave at the centre (inversely reniform), smooth; e.V. with three inflated rounded angles, sides concave. F. S. pygmaeum (Bréb.).—Segments in fiv. cuneiform, outer margin slightly convex, smooth; e.v. with three blunt angles, sides slightly convex. Sporangium orbi- cular, “beset with protuberances bearing each two bifurcate spines at their sum- mits.” F., G. 2t Segments having the projecting por- tions surrounded by annular transverse lines (rows of puncta or minute gra- nules P). S. striolatum (Nãg. sp.). —Segments in f. V. reniform, divergent, ends concave, each of the lateral portions crossed by about five transverse lines (annular rows of closely set puncta or minute gra- nules?); e.v. with three rounded angles, sides concave, each of the projections crossed as before by about five transverse lines, the central portion Smooth. L. 1-100". = Phycastrum striolatum (Nāg.). G. 3t Fronds rough superficially with scat- tered granules. (Sometimes S. tri- corne might be thought almost to come in here ; but the extremities in that species are more prolonged into di- stinct processes, usually colourless, and mostly divided at the apex. Here, also, might S. asperum and S. scabrum seem to fall in ; but they are provided with very short and truncate spines on some part of their margin.) S. muricatum (Bréb.).-Segments sub- elliptic, the outer margin more turgid than the inner, rough all over with Scattered conic granules; e.V. with three angles, both angles and sides broadly rounded. L. 1-409"; B. J-474".= Des- midium apiculosum (Ehr.), Xanthidium deltoideum (Corda), Phycastrum apiculo- sum (Kg.), P. muricatum (Kg.), Gonio- cystis (Trigonocystis) muricata, 8 (Hass.). G.B., F., G., Italy S. punctulatum (Bréb.).—Segments in fiv. elliptic, equal, rough with scattered puncta-like granules; e.v. with three broadly rounded angles, sides concave. L. 1-704"; B. 1-881". G. B., I., F. S., rugulosum (Bréb.).-Segments in fiv. broadly elliptic, equal, rough with Scattered granules, giving a denticulate appearance to the margin, especially at the opposite lateral extremities; e.v. with three broadly rounded denticulate angles, sides straight or nearly so. F. - S. pileolatum (Bréb.). —Segments in fiv. Quadrate, the basal angles rounded and rough with minute granules, sides with , a broad shallow sinus, the upper margin terminating in three conspicious, large, rounded, conical, very slightly di- vergent projections, which are rough with minute granules; e.v. with three rounded angles, sides entire. F. - § Capitulum (Bréb.).—Segments in fiv. Quadrate, sides with a rounded sinus at the middle, the basal and upper angles crenated, rounded, tºpper margin straight; OF THE DESMIDIE ZE, 74.1 e.v. with three broadly rounded crenated angles, sides nearly straight, each with a slight shallow depression or constriction at the middle. F. S. alternans (Bréb.).—Segments in fiv. elliptic or oblong, two or three times as broad as long, separated by a wide sinus, twisted, unequal; rough with very minute pearly granules; e.v. with three obtuse and rounded angles, forming short not colourless rays, alternating with those of the other segment, sides con- cave. I.1-1037"; B.1-1106". (II. 16, 17.) = Goniocystis (Thigonocystis) heaſaceros gº S. dispar (Bréb.)? G.B., I, F., U.S.A S. dilatatum (Ehr.). — Segments in f. V. fusiform, their lateral extremities obtuse, equal, rough with puncta-like pearly granules; e.v. with four rotun- dato-truncate angles, forming short, broad, not colourless rays, sides concave. L. 1-1201"; B.1–1381". = Phycastrum di- latatum (Kg.), Goniocystis (Staurastrum) dilatata (Hass.). G.B., I., F., G., Italy, U.S.A. S. crematum (Bailey). —Segments in fiv. fan-shaped in outline, separated by a wide rounded sinus, inner margin concave, smooth, outer semicircular, cremate; e.V. with three rotundato-truncate cremate angles, sides concave, Smooth. U.S.A. 7* Segments with or without spines; in f. v. with Spines (if any) few and scat- tered; in e. v. angles emarginate or bifid, or truncate and the extremities plane and quadrangular. S. bifidum (Ralfs).-Segments in fiv. . . . . ; in e.v. with three acutely bifid or emarginate angles, the teeth acute; sides concave. = Desmidium by idum (Ehr.), Phycastrum bifidum (Kg.), nec Gonio- cystis (S.) bifida (Hass.). F., G. S. quadrangulare (Bréb.).—Segments in fiv. subquadrate, with a few short bifidor tooth-like Spines spreading laterally, otherwise smooth; e.v. with four trun- cate and emarginate angles; sides concave. L.1-1157"; B. 1-1163". (III, 24, e.v. 25.) 8, angles in e.V. broader, with four teeth at the extremity, and two minute teeth on wpper side (Bréb.). G.B., F. S. Cerberus (Bailey).-Segments in fiv. truncato-oblong, smooth; the opposite lateral extremities abruptly truncate, eac- termally plane and quadrangular, the an- gles drawn out into acute spine-like ex- tensions or teeth, two projecting upwards and two downwards; e.v. with three abruptly truncate angles, extremities as in f. v. plane and quadrangular, the teeth at the angles divergent. U.S.A. 8* Segments without spines; in fiv. and e.v. the angles terminated by either a conspicuous rounded nipple-like projec- tion, or an enlarged rounded knob, or an elongate capitate process. S. tumidum (Bréb.).--Segments in fy' elliptic, turgid, Smooth; their margin striated, and their opposite lateral ex- tremities furnished with a rounded con- Spicuous nipple-like projection; e.v. with three or four angles, the nipple-like pro- jection terminating the angles, sides conver; e. f. punctate; gelatinous in- vestment very evident. L. 1–200": B. 1–250". = S. orbiculare (Menegh.), Phyc- astrum tumidum (Kg.). G.B., I, S. globulatum (Bréb.). — Segments in fiv. fusiform, capitate; e.v. with three angles, each enlarged into a rounded granulated knob, sides nearly straight. (III. 26, e.v. 27.) F. S. bacillare (Bréb.).—Segments in fiv. Somewhat arcuate, each divergent from the opposite segment, somewhat attenuated, finally capitate, Smooth; e.v. with from three to five capitate rays. = Phycastrum bacillare (Kg.). F. 9 * Segments in fiv, with the opposite lateral extremities each tapering into a Single more or less elongate colourless process divided at the apex, which in e. v. terminates the angles, with or with- out intermediate simple or truncate Spines. t Segments smooth. S. brachiatum (Ralfs).-Segments in fiv. Smooth, narrow below, widening up- wards, ends truncate, the lateral eatre- mities each produced into a smooth, elon- gate, straight, tapering, divergent process, bifid or trifid at the apex; e.v. tri- or quadriradiate, sides concave. L. 1–1111"; B. 1-1785". = Goniocystis (S) biſida gº , Phycastrum Ralfsii (Kg.). G.B., ., F., G. . 2+ Segments rough with superficial granules, those on the processes ar- ranged in transverse lines. (S. poly- morphum has sometimes a few incon- spicuous scattered spines.) S. tricorne (Bréb.).—Segments in fiv. somewhat fusiform, often twisted, rough with minute puncta-like granules, taper- ing at each side into a short usually co- lourless process, blunt, or divided at the apex ; e.V. tri- or quadriradiate, processes 742 SYSTEMATIC ELISTORY OF TELE INFUSORIA. short, usually colourless, sides somewhat concave. Sporangium orbicular, beset with spines ultimately branched at the apex. L. 1-1275" to I-972"; B, 1-948" to 1-697". = Desmidium heasaceros (Ehr.). Phycastrum tricorne (Kg.), P. trilobatum g.)? P. hea:aceros º ?, P. Ralfsii. äg. in part). Nāg.), P. crenulatum ( G.B., T., F., G., U.S.A. S. cyrtocerum (Bréb.).—Segments in f. V. Subcuneate, gradually widening up- wards, truncate at the end margin, rough with minute granules, the lateral processes incurved, divided at the apex; e.v. triradiate, processes short, curved, sides slightly concave. L. 1-800"; B. 1–500". = Phycastrum cyrtocerum (Kg.). G.B., I., F., U.S.A. S. inflecum (Bréb.).—Segments in fiv. broadly elliptic, inner and outer margin turgid, rough with minute granules, lateral processes incurved, short, divided at the apex; e.v. tri- or quadriradiate, processes short, sides concave. F. S. brachycerum (Bréb.).-Segments in fiv. ovato-lunate, inner margin turgid, outer equally rounded, rough all over with minute granules, and on the outer mar- gin very rough with minute, acute, short, almost spine-like granules; lateral pro- cesses incurved, divided at the apex; e.V. triradiate, processes short, straight, sides somewhat concave. - S. polymorphum (Bréb.). — Segments in fiv. broadly elliptic or almost circular, rough with minute granules (sometimes with a few minute scattered spines), processes short, stout, tipped by three or four divergent spines; e.v. with three, four, five, or six angles, each produced into a short stout process. Sporangium orbicular, beset with elongate spines, forked or branched at the apex. L. 1-1000"; B. 1-1157". (II. 20, 21, 24, 25, & 31.) G.B., I., F., U.S.A. - S. gracile (Ralfs).-Segments in fiv. triangular, ends truncate, rough with minute granules, tapering at each side into elongate, Straight, slender, horizontal processes, terminated by three or four minute spines; e.V. triradiate, processes straight, sides concave. L. 1-773" to 1–539"; B. 1-348" to 1-372". (III. 28, e.v. 29.) = Goniocystis (Trigonocystis) gracilis (HaSS.), Phycastrum gracile (Kg.). G.B., I., F. S. paradovum (Meyen), — Segments in fiv, gradually widening upwards, the ends truncate, rough with minute gra- nules, processes straight, elongate, slen- der, divergent, trifid at the apex; e.v. tri- or quadriradiate, processes straight, sides straight or very slightly concave. L. 1-941"; B. 1-1165". = Phycastrum paradoxum (Kg.), Gondocystis (S) para- § (Hass.), G.B., I., F., G., Italy, .S.A. 3f Segments furnished with variously disposed spines, which are either sim- ple, or short and notched at the apex. S. proboscideum (Bréb.).--Segments in fiv, broadly cuneiform, ends somewhat convex, rough with very minute, Short, truncate spines, chiefly confined to the outer margin, processes short, thick, trifid at the apex; e. v. triradiate; processes short, stout, sides concave. L. 1-555"; B. 1-500". =S. asperum, 8 (Ralfs, Bréb.). G.B., I., F. S. controversum (Bréb.).—Segments in fv. elliptic or broadly fusiform, some- times irregular, furnished with scattered, &rregular, simple or notched Spines; pro- cesses short, generally curved, spinulose, terminated by minute spines; e. v. tri- radiate, the processes twisted or curved. Sporangium orbicular, spinous; spines twice branched. L. 1-972"; B. 1-886". Goniocystis (Trigonocystis P) aculeatum (Hass.). G.B., I S. aculeatum (Menegh.), Segments in fiv. broadly fusiform, furnished with thickly scattered simple or notched spines; processes elongate, Spinulose, Straight, ter- minated by minute spines; e.v. 3–5– radiate, the processes Straight, sides con- cave. L. 1-666"; B.1–500". = Desmidium aculeatum (Eh.), Phycastrum aculeatum (Kg.), Goniocystis (Trigonocystis) aculea- tum (Hass.). G.B., I., F., G., Italy. S. vestitum (Ralfs).-Segments in fiv. fusiform, outer margin bordered by minute emarginate Spines; processes elongate, ºrough, terminated by minute spines; e.V. triradiate, the processes elongate Straight, sides concave, furnished at the middle with a pair of conspicuous slender forked Spines, sometimes accompanied by a few others shorter either simple or notched. L. 1-625"; B. 1-384". (III, 30, e. v. 31.) G.B., I., F. S. oxyacantha (Archer).-Segments in fiv. broadly fusiform, rough with minute granules, furnished on the outer margin with Sia. Subulate acute depressed spines (four of which are apparent in this view); processes elongate, incurved, the granules thereon arranged in transverse lines, ter- minated by three or four minute spines; e. v. triradiate, the processes elongate straight, sides somewhat concave, end furnished at the middle with a pair of very slender eactremely acute subulate OF TEIE DESMIDIEAE. - 743 spines projecting to each side. L. 1-770"; B. 1-580" to 1-636". 10* Segments in f.o. with the opposite lateral eactremities terminating in one or two elongate colourless processes mostly divided at the apex ; and in e.v. either tapering into a single process at each angle, and furnished with others between or above of a similar character definite in number, or the angles fur- nished with two short processes side by side and unaccompanied by others. Segments at end view with the addi- tional processes more than one for each angle, and placed on the margin or upper surface, and diverging laterally. + S. furcatum smooth, in fiv. broadly elliptic, furnished at each opposite lateral extremity with a colourless bifid process, and with sia: others similar and divergent on eacternal margin (four only of which are usually visible); e.v. with three acute angles, each tapering into a terminal process, and each bearing two others on the upper surface, placed to each side, and º: ing laterally. L. 1-860"; B., 1-900", = Manthidium furcatum (Ehr.), Astero- acanthium furcatum (Kg.), A. bisenarium (Kg.) P G.B., I., F. S. Senarium (Ehr.). — Segments smooth, in e.v. with three angles, each terminating in a short process tipped by minute spines, and having six other short forked processes on the margins, two at each side and projecting laterally, and six others on the upper Surface, confluent at their bases, divergent at their extre- mities, and forked; sides straight, (II.7.) = Stephanoacanthium Senarium (Kg.). U.S.A. S. eustephanum (Ehr.). — Segments granulate, in e.V. with three angles, each terminating in a short process tipped by minute spines, without lateral processes, but with six others confluent at their bases on the upper surface, divergent and forked. (II. 3.) = Stephanoacanthium euste- phanum (Kg.). U.S.A. S. Ehrenbergii (Corda),—“Corpuscles ar paire, vus de côté, ovales; vus d'en aut, triangulaires, munis de six ap- pendices terminaux et latéraux, et de deux autres appendices centraux, qui sont courts, blancs, en fourchette, mais à ointes divergentes” (Corda, ‘Obs. Micr. des Animalcules de Carlsbad,’ 1840). In Corda's figure the f. V., is somewhat like that of S. furcatum. The segments are broadly fusiform, the pro- (Bréb.). — Segments cesses are all very short and stout, and the bifurcations very divergent (formed indeed somewhat like the tail of a fish). =Xanthidium Ehrenbergii (Corda, l. º S. articulatum (Corda).-‘‘Corpuscles ovales, par paire, munis aux deux bouts d’un appendice à deux cellules, qui Se divise encore en forme de fourchette, et latéralement en deux appendices plus longs à quatre cellules, et une pointe en fourchette. Sur les deux côtés plats, se trouvent deux protubérances trans- versales, également pouryues de deux allongements cellulaires en fourchette" (Corda, l.c.). In Corda's figures the seg- ments in fiv. are elliptic, the processes Stout, elongate, transversely striated (by rows of granules?), bifurcate, the bifurca- tions recurved. = X, articulatum (Corda). Neither of the figures of the foregoing is explanatory; both, however, seem to be distinct species. 2 f Segments with the additional pro- cesses one for each angle, and placed on the upper surface immediately above those terminating the angles. S. fºrcigerum (Bréb.). — Segments in f. v. twice as broad as long, separated by a deep constriction, rough with pearly granules, terminating at each side in two elongate, Stout processes, bifid at the apea, placed one above the other, the inferior horizontal, the Superior directed ob- liquely outwards and divergent, both having the granules thereon in trans- verse lines; e.V. with three or four angles, each extremity terminating in a process and having the other immedi- ately above it on the upper surface, sides concave at the centre. L. 1-333"; B. *1-357" incl. processes. (III, 32, e.v. 33.) = Didymocladon furcigerus (Ralfs), Aste- poacanthium furcigerum (Kg.), Xanthi- dium coronatum (Ehr.) P, A. coronatum (*#): G.B., I., F., G., U.S.A. . longispinum (Bail. sp.). — Segments in f. v. triangular, truncate on Outer mar- gin, Smooth, terminating at each side in two much elongated Stout processes, sub- acute at the apea, placed one above the other, divergent; e.V. with three angles, each extremity terminated by a process and having the other immediately above it on the upper surface, side straight. = Didymocladon longispinum (Bailey). 3t Segments with two processes from each angle placed side by side. S. laeve (Ralfs).-Segments in f. v. ex- termally lunate or somewhat cuneate, with 744 SYSTEMATIC HISTORY OF TELE INFUSORLA. the ends somewhat protuberant, Smooth, terminating at each side in a pair of short stout processes placed side by side (one only of which, however, is apparent), directed upwards and divergent, forked at the apex; e. v. with three or four angles, each terminated by the pair of short processes separated by a rounded sinus, sides deeply concave. L. 1-1220"; B. 1-2127". G.B., F. 11 * Segments in f. v. with each opposite lateral eactremity terminating in a colour- less process, either short, rounded, and dentate, or elongate and entire at the end; e. v. circular, margined with from jive to seven processes, or compressed, and with but two processes. (S. poly- morphum Sometimes has five rays, and the e.v. appears almost circular, but the extremities of the processes are not entire but tipped with minute spines.) † End view circular. S. Sea costatum (Bréb.).—Segments in f, v. Suborbicular, furnished on each side with a short, broad, truncate, dentate pro- cess, and with slight crenate elevations on the outer margin; e. V. circular, bor- dered by five or six short, rounded, den- tate, colourless marginal rays. L. 1-661"; B. 1-833" to 1-694". = Goniocystis (Pen- tasterias) Jenneri (Hass.), Stephanoacan- thium sea-costatum (Kg.). G.B., I., F. S. margaritaceum (Menegh). — Seg- ments in f. v. gradually widening up- wards, rough with pearly granules, outer margin convex, produced at each side ºnto a colourless, more or less attenuate short process, having the granules in transverse lines, blunt and entire at the apex; e. V. circular, bordered by from five to seven short, narrow, obtuse, co- lourless, granulate marginal rays. L. 1-1176"; B. 1-1000" incl. processes. (III, 34, e.v. 35.) = Pentasterias marga- ritacea (Ehr.), Phycastrum margaritaceum (Kg.), Goniocystis (Pent.) margaritacea gº , Phycastrum rotundatum (Kg.). .B., I., F., G., U.S.A. S. Arachne (Ralfs).-Segments in f. v. suborbicular, rough with minute gra- mules, lower margin turgid, outer convex, tapering at each side into an elongate, slender, incurved process having the gra- nules thereon in transverse lines, entire at the apex; e. V. circular, bordered by five slender, linear, colourless marginal rays, L. 1-1020"; B. 1-652" incl. pro- cesses. = Goniocystis (Pentasterias) arach- mis (HaSS.), Phycastrum Arachne (Kg.), P. radiatum (Kg.) P. G.B., F. 2t End view compressed. S. tetracerum (Ralfs). — Segments in f. V. gradually widening upwards, rough with minute granules, outer margin truncate or concave, tapering at each lateral eactremity into an elongated, very slender, colourless process, having the granules thereon in transverse lines, entire at the apex and divergent; e. V. much compressed, with a process at each extremity. L. 1–2703"; B. 1-1785". S. paradoacum (Ehr.), Goniocystis (S. P) paradoſciſm º Phycastrum para- doacum (Kg.). G.B., I., F., G., U.S.A. [S. enorme (Ralfs) is omitted, this rººf having been, as we think, shown y De Bary (op. cit.) to be a Poly- edrium.] 2. Fronds distinctly, faintly, or not at all constricted at the middle, very rarely less than three times, mostly many times longer than broad. Sporangia Smooth, and either spherical, elliptic, quadrate, or cruciform. Genus TRIPLOCERAS (Bailey).--Frond very elongate, straight, cowstricted at the middle; segments with numerous whorls of knot-like projections, ends three-lobed, lobes bidentate. Endochrome with a terminal rounded clear space, in which are active granules. TRIPLOCERAs verticillatum (Bailey). —Frond stout, suture prominent, seg- ments about eight or ten times longer than broad, with numerous whorls of prominent, broad, truncate, emarginate projections. (III. 37.) = Docidium verti- cillatum (Ralfs). U.S.A. T. gracile (Bailey). — Frond rather slender, Suture prominent, segments ten or twelve times longer than broad, with numerous whorls of prominent, some- what triangular, roundly blunt projec- tions. = Docidium verticillatum (Ralfs). |U.S.A. Genus DOCIDIUM (Bréb.).--Frond very elongate, straight, constricted at the middle; segments with an inflation at the base (very rarely not so), often OF THE DESMIDIEAE. 745 with others above, or with whorls of knot-like projections, ends abruptly t?"MºCat6. which are active granules. DOCIDIUM verrucosum (Bailey). — Frond rather stout, suture forming a rim; segments five or six times longer than broad, with numerous Small equal wndulations due to so many whorls of Small tubercle-like prominences; ends entire. U.S.A. D. nodosum (Bailey). — Frond stout, suture forming a rim; segments three or four times as long as broad, with four prominent inflated modes, including the basal, which is somewhat the largest, and which are due to so many whorls of knot-like prominences or large tubercles; ends entire; e. V. crenate. U.S.A. D. coronatum (Bréb.). — Frond stout, suture forming a thickened projecting rim ; segments four to six times as long as broad, tapering, regularly inflated up- wards from the base, so as to produce an undulated margin, the basal inflation the most prominent, the others less so, and wanting towards the ends; ends bordered by prominent tubercles, projecting all round; e. V. circular, bordered by the tubercles; e. f. coarsely punctate. F. D. undulatum (Bailey).--Frond slender, suture forming a minute rim, segments eight to ten times as long as broad, with six or eight sinuations at regular in- tervals, producing as , many inflations besides the basal, which is not larger than the others; ends and bases cremate. |U.S.A. D. Ehrenbergii (Ralfs).--Frond slender, linear; suture forming a very sharply- defined rim; segments eight to twelve times longer than broad, basal öſtation having another smaller one above it, sides otherwise straight, parallel; ends crenate, owing to a number of emarginations from the edge of the truncate extremi- ties, from three to five of the crena- tures being usually visible; e. f. punc- tate, or rough with minute granules. Sporangium suborbicular or elliptic, or slightly angular, Smooth, placed between the deciduous empty fronds. . Ciliated zoospores formed by segmentation of the cell-contents, and their emission effected through the opened apex of each of one, two, or three specially-formed lateral tubes arising from beneath the base of one of the segments (vide Suprá, p. 716; III.46,47). L. 1-71" to 1-59"; B.1–1111" to 1-96.1". (II. 8 & 11.) = Pleurotonium Ehrenbergkii (De Bary). G.B., I., F., G., |U.S.A., IEndochrome with a terminal rounded clear space at each end, in D. clavatum (Kg.). — Frond slender, suture scarcely prominent, segments eight or ten times as long as broad, slightly clavate near the ends, and ulti- mately somewhat attenuated, basal infla- tion sometimes Solitary, sometimes hav- ing another slight one above it; ends entire; e. f. punctate. L. 1-65"; B.1–813". (II. 9.) = Pleurotaenium clavatum (De Bary). G.B., I., F., G., U.S.A. D. modulosum (Bréb.). — Frond very Stout, the thickened suture forming a projecting rim; segments four to six times as long as broad, Scarcely atte- nuated, regularly inflated at intervals so as to produce an undulated margin, the basal inflation the most prominent, the others as they approach the ends less so, where they are indistinct or wanting; ends entire; e. f. coarsely punctate. L. 1-50"; B.1–428". = D. crenulatum (Ehr.), Pleurotanium modulosum (De Bary). G.B., I., F., G., U.S.A. D. truncatum (Bréb.). — Frond stout, the thickened suture forming a rim; seg- ments three or four times longer than broad, tapering, basal inflation solitary, sides otherwise gradually curved; ends en- tire; e. f. punctate. = Pleurotanium trun- catum (Nāg, De B.). L. 1-81" to 1-72"; B. 1–527" to 1-429". G.B., I., F., G. D. constrictum (Bailey).--Frond stout, Suture not prominent; segments five or six times longer than broad, not at- tenuated, with four distinct equidistant sinuations producing four equal gently curving prominences besides the basal inflation; ends entire. U.S.A. D. Baculum (Bréb.). —Frond slender, suture not prominent; segments very many times longer than broad, basal inflation very conspicuous, solitary, sides otherwise Straight, very nearly parallel, large granules of the endochrome in a single series; ends entire; e. f without puncta. L.1-111"; B.1–1937". (III, 38.) = Pleurotonium Baculum (De Bary). G.B., F., G., U.S.A. D. minutum (Ralfs). —Frond slender, suture not prominent; segments four to six times longer than broad, somewhat tapering, inſtation obsolete, sides straight, ends entire; e,f, without puncta. L. 1-212"; B. 1-1582", = Penium Ralfsii (De Bary). G.B., I., F., G., U.S.A. D. hirsutum (Bailey). — Frond rather slender, suture not prominent, segments four to six times as long as broad, 746 SYSTEMATIC IIISTORY OF TEIE INFUSOR.I.A. not tapering, ºnflation obsolete, ends en- tire, surface all over minutely Spinous, or hirsute. U.S.A. Kützing (Sp. Alg.) describes one or two other species of Docidium; but the characters given seem hardly distinctive, and appear sometimes more like generic characters re-stated. Genus TETMEMORUS (Ralfs).--Frond elongate, straight, cylindrical or fusiform, constricted at the middle; segments more or less tapering, not in- flated at the base, ends with an acwté imcision, the subdivisions rounded, . otherwise quite entire. TETMEMORUs Brebissonii (Ralfs). — Frond about five or six times longer than broad; in f. v. with parallel sides, the constriction a very shallow groove; in s. v. fusiform, the constriction very slightly deeper; endochrome with a lon- gitudinal series of light-coloured large granules; e. f. punctate, the puncta in longitudinal rows. L. 1-142"; B. 1-704". II. 12 & 13.) = Closterium Brébissonii &º , Penium monile º , P. stri- ato-punctatum (Kg.) P. G.B., I., F., G., Italy, U.S.A. 6, turgidus, larger, stouter, constriction deeper, y, (De Bary), smaller than either, otherwise externally similar, endochrome in longitudinal fillets. T. laevis (Ralfs).--Frond smaller than last, scarcely one-half its length, about three or four times as long as broad; in f. v. somewhat tapering, the constric- tion a shallow depression; in S. v. fusi- form; end sometimes with a hyaline lip-like projection extending beyond the notch; e. f. punctate, puncta faint but evident, scattered. Sporangium Smooth, in f. v. at first quadrate, afterwards broadly elliptic ; in s. v. compressed, enclosed in a central cell placed between the ultimately deciduous empty fronds. L. 1-374" to 1-336"; B. 1-1244" to 1-1073". = Penium (Tetmemorus) Bre- bissonii (Kg.). G.B., I., F., G. T. minutus (De Bary).-Frond minute, shorter than T. laevis, about three times longer than broad, fusiform, the con- striction a very shallow groove; e. f. without puncta. L. 1-41"; B. 1-118". G. T. granulatus (Ralfs). —Frond some- what longer than T. Brebissonii, about five or six times longer than broad; in both f. v. and S. v. fusiform, the constric- tion a very shallow groove, ends with a hyaline lip-like projection extending be- yond the notch ; endochrome with a longitudimal series of large granules; e. f. punctate, the puncta scattered, ex- cept near the constriction, where they are disposed in two transverse rows. Sporangium orbicular, Smooth, margin finely striated, placed between the de- ciduous empty fronds. L. 1-130”; B. 1–649". = Penium (T) granulatus (Kg.). G.B., I., F., G., Italy, U.S.A. * Genus CLOSTERIUM (Nitzsch)-Frond elongate, attenuate, more or less lunately curved or arcuate, entire, not constricted at the middle, the junction of the segments marked by a pale transverse band. Endochrome often arranged in longitudinal fillets, and at each extremity having a terminal clear space, in which are active granules; e. f. Smooth, or with longitudinal striae, never granulate. The subdivisions of this genus cannot always be rigidly adhered to, as certain species might Sometimes seem to agree almost as well with another division as with that in which they are placed. * Frond scarcely tapering, the curvature very slight, gradual and equal; lower margin nearly Straight or slightly con- cave; ends truncate or broadly rounded; e.f. with or without longitudinal stria, inclined upwards at the end; ends trum- cate, reddish; large granules in a single Series; e. f. reddish, especially near the ends, stria faint; central suture evident, sometimes accompanied by two others dividing the frond into four portions. L. 1-65"; B.1–813". (III. 39.) G.B., I, F., G. a, three transverse sutures; 8, CLOSTERIUM didymotocum (Corda).- Frond stout, six to ten times longer than broad, nearly Straight, very slightly taper- &ng to the extremities, upper margin slightly convex, lower nearly straight or very slightly concave, sometimes slightly one. = C. Subrectum (Kg.), C. Baileyanum (Bréb.). g C. obtusum (Bréb.). — Frond minute, four to ten times as long as broad, OF THE DESMIDIE ZE. 747 nearly straight, cylindrical, not tapering, ºpper and lower margin equally and but very slightly curved, ends obtusely rounded; large granules, in a single series; e. f. smooth. F. - C. Amblyonema (Ehr.). — Frond stout, very long, twenty to twenty-five times as long as broad, slightly curved, scarcely tapering, upper and lower margins equally and but gently curved ; ends broadly rounded; e. f. Smooth. U.S.A. 2 * Frond tapering, having the curvature slight; lower margin Straight or very slightly concave, and slightly inclined wpwards towards the rounded or sub- acute ends; e. f with or without lon- gitudinal Stride. C. Lunula (Ehr.).--Frond large, stout, five or six times as long as broad, semi- lunate, upper margin very convex, lower ºnearly Straight, somewhat inclined upwards towards the obtuse broadly rounded ends; endochrome with the large granules numerous, Scattered, fillets several, di- stinct; e. f. colourless, without mark- ings, central suture not evident. L. 1–62”; B. 1-330°. = Vibrio Lunula (Müller), Bacillaria Lumula (Schrank), Lunulina vulgaris (Bory). G.B., F., T., G., Italy, U.S.A., Mexico. C. acerosum (Ehr.). — Frond slender, six to fifteen times as long as broad, linear-lanceolate, gradually tapering, upper margin slightly convex, the lower nearly straight, slightly inclined upwards at the conical ends; large granules in a single central longitudinal series; fillets several, distinct; e. f. colourless, very faintly striated, central suture evident. L. 1-70" to 1-58"; B. 1-1103" to 1-510". Sporangium orbicular, Smooth, placed between the dehiscing deciduous empty fronds. = Vibrio acerosus § G.B., I., F., G., U.S.A., Mexico. C. lanceolatum (Kg.). —Frond stouter than C. acerosum, six to ten times longer than broad, Semilanceolate, gradually ta- pering ; upper margin convex, lower nearly straight, inclined upwards to- wards the tapering Subacute ends; large granules in a single central series; fillets several, distinct; e. f. colourless, usually without markings, sometimes faintly striated, central suture evident. L. 1–64"; B. 1-453". = Cymbella Hopkirki; (Moore). G.B., I., F., G., U.S.A. C. turgidum (Ehr.). — Frond stout, eight to twelve times as long as broad, semilanceolate, slightly tapering, more curved than either of the preceding, upper margin convex, with a depression near each eactremity, lower margin con- cave, inclined upwards towards the 'rounded ends; large granules, in a single longitudinal series; fillets several; e. f. Teddish, longitudinal stria close, distinct, central suture evident. L. 1-39"; B. 1-370". (III. 40.) = C, decussatum (Kg.)? G.B., I., F., G., U.S.A. C. praelongum (Bréb.). —Frond very slender, extremely long, thirty-five to forty times as long as broad, slightly curved, very gradually tapering; upper margin slightly convex, with a depres- sion near each extremity; lower concave, inclined upwards towards the rounded ends; large granules in a single series; e. f. colourless, without markings. F. C. quadrangulare (Corda). — Frond very slender, twenty-five to thirty times as long as broad, slightly curved, gra- dually tapering, quadrangular, except at the extremities, one of the angles forming a prominent longitudinal median line; upper margin equally convex, lower con- cave, very slightly inclined upwards at the blunt ends; e. f. colourless, Smooth. G. 3 * Frond tapering, the lower margin concave, often with a central inflation, and inclined downwards towards the rounded or subacute ends; e. f without narkings. t Frond slender, curvature very slight. C. Strigosum (Bréb.).--Frond slender, twelve or fifteen times as long as broad, hearly Straight, but somewhat curred down- wards towards the attenuated eactremities: upper margin slightly convex, lower concave with a gentle central inflation; ends acute; large granules in a single series ; e. f. colourless, without striae. Sporangium Orbicular, Smooth, placed between the shortly deciduous empty fronds, which conjugate soon after divi- sion, so that two of the empty segments are considerably shorter than the other two. F. C. macilentum (Bréb.). — Frond very slender, sublinear, twenty-five or thirty times as long as broad, slightly and very gradually curved, somewhat taper- ing; upper margin slightly convex, lower slightly concave; ends somewhat blunt; large granules, in a single series; e. f. colourless, without striae. Sporangium orbicular, placed between the for some time persistent empty fronds, which conjugate, as in last, soon after divi- sion, F. 748 SYSTEMATIC IIISTORY OF TEIE INIFUSORIA. C. gracile (Bréb.). — Frond very slender, about twenty-five to thirty times as long as broad, linear, nearly straight, except at the extremities, which are curved downwards; sides parallel, ends obtuse; endochrome arranged in a zigzag or subspiral manner; e. f without striae. I., F. This species resembles C. juncidum, a, in form, but differs in the arrangement of the endochrome and in the absence of striae. 2 + Frond crescent-shaped, curvature considerable. C. Ehrenbergii (Menegh.). — Frond large, Stout, about five or six times as long as broad, lunately curved, extremities tapering; upper margin very convex, lower concave with a conspicuous central inflation; ends broadly rounded; large granules, numerous, Scattered; fillets se- veral ; e. f. colourless, without striae, central suture not evident. Sporangia orbicular, smooth, placed between the but slightly connected empty conjugated fronds, the endochrome during the pro- cess of conjugation emerging from the opened apex of a short comical extension from each under side of each younger segment (or shorter cone) of each pair of recently divided fronds, the conjugating fronds being produced immediately pre- viously by the self-division of a pair of old fronds—two sporangia being thus the ultimate produce of the two original fronds. L. 1-68"; B. 1-400". (xvi. 10, 11, 12, 13, 14.) = Lunulina monilifera (Bory), C. Lunula (Ehr, Hass.). G.B., I., F., G., U.S.A. C. moniliferum ſº Smaller than the last, stout, five or six times as long as broad, lunately curved, extre- mities tapering, upper margin convex, lower concave with a central inflation, ends rounded; large granules, conspicuous, £n a single longitudinal series; e. f. colour- less, without striae, suture not evident. J. 1-75" to 1-60"; B. 1–510" to 1-466". G.B., T., F., G., Italy, U.S.A. C. obtusangulum (Corda). — Frond stout, crescent-shaped, four or five times as long as broad, rapidly attenuated, “quadrangular ” (six angles P); upper margin very convex, lower concave with- out a central inflation ; ends narrowly rounded; e. f. colourless, without mark- Ill O'S. C. Jenneri (Ralfs).--Frond small, di- stance between the extremities six or seven times the breadth, crescent-shaped, much curved, gradually tapering (some- times with an obscure central constric- tion); upper margin very convex, lower very concave without a central inflation; ends obtuse, rounded; large granules, in a single series; e. f. colourless, without striae. L. 1-281"; B. 1-1730". G.B., I., F., U.S.A. C. Leiblečni. º somewhat stout, distance between the extremities six or eight times the breadth, crescent- shaped, much curved, rapidly attenuated; upper margin very convex, lower very concave, often with a slight central infla- tion; ends Subacute; large granules, in a single series; fillets few or indistinct; e. f. somewhat straw-coloured, without striae; suture evident. Sporangium orbi- cular. L. 1-291" to 1-165"; B. 1-1632" to 1-582", (II. 1 & 5.) G.B., I., F., G., Italy, U.S.A. 3 more slender, scarcely inflated on the lower margin. C. Dianae (Ehr.). — Frond slender, crescent-shaped,six or eight times as long as broad, much curved, rapidly attenu- ated; upper margin very convex, lower very concave without a central inflation; ends subacute with a very slight emargi– nation at the upper outer eactremity; large granules, in a single series; e. f. some- what straw-coloured or faintly reddish, without striae, suture evident. L. 1-143"; B. 1-1275". = C, rigiceps (Ehr.), C. arcu- atºm º P, C. Venus (Kg.) P, C. acu- ºminatum (Kg.) P. G.B., I., F., G., Italy, C. incurvum (Bréb.).—Frond minute, somewhat stout, crescent-shaped, very much curved, rapidly attenuated, ends very acute; e. f without striae. F. 4 * Fronds gradually tapering, curvature often gradual, lower margin concave, tnclined downwards at the rotundato- trºcate or sometimes subacute ends; e. f. striated. C. indequale (Ehr.). — Frond minute, Semilunate, attenuated; upper margin very convex, lower concave; eactremities wnequal, conic, very acute; large granules, scattered; e. f. prominently striated. G. C. costatum (Corda). —Frond stout, about five or six times as long as broad, lunately curved, attenuated; upper mar- gin convex, equally arched, lower con- cave; ends obtuse, rounded; large granules, in a single series; e. f. reddish, striae few (about six), conspicuous; suture evident. Sporangium orbicular, Smooth, placed between the deciduous empty fronds. L. 1-75"; B. 1-384". = C, turgidulum (Kg.), G.B., I., F., G. - º OF TELE DESMIDII}_E. 749 C. Striolatum (Ehr.).-Frond from six to ten times as long as broad, lunately curved, attenuated; upper margin con- vex, slightly depressed at the centre, lower concave; ends very obtuse, rounded; large granules, in a single Series; e. f. reddish, especially near the ends, stria very numerous, crowded, transverse sw- tures usually three. Sporangium orbi- cular, smooth, placed between the de- hiscing deciduous empty fronds. L. 1-80" to 1-68"; B, 1–625" to 1-535". (II.2 & 6.) = C. regulare (Bréb.) P. G.B., I., F., G., Italy, U.S.A. C. intermedium (Ralfs).--Frond slen- der, twelve to fifteen times as long as broad, slightly curved, very gently taper- ºng; upper margin convex, gradually arched, lower slightly concave; ends ob- tuse, rounded; large granules, in a single series; e. f. pale straw-coloured, striae distinct, numerous, but not crowded; trans- verse sutures usually more than three. L. 1-77"–1-54"; B.1-1073". G.B., I., F. C. angwstatum (Kg.).-Frond slender, ten to twenty times as long as broad, sublinear, slightly curved, scarcely atte- muated; upper margin convex, gradually arched, lower concave; ends truncate, slightly rounded; large granules, in a single series; e. f. pale reddish, especially near the ends, stria few (about four), very distinct, transverse sutures usually three. L. 1-60"; B. 1-1142". G.B., I., F., G. C. juncidum (Ralfs).--Frond very slen- der, from about fifteen to even thirty- five times as long as broad, linear, straight eaccept towards the eartremities, which are somewhat curved downwards, ends obtuse; e. f nearly colourless, striae not numerous, faint, transverse sutures wsually three. Sporangium orbicular, smooth, placed between the dehiscing deciduous empty fronds. G.B., I., F. 8, frond stouter, less elongated. C. uncimatum (Kg.). Frond slender, tapering to a subacute point, Suddenly curved downwards; e. f., the body with striae fine and close, absent at the extre- mities. C. lineatum (Ehr.). —Frond slender, elongate, from about eighteen or twenty to twenty-five times as long as broad, gently curved, very gradually attenuated; upper margin unequally convex, being most curved near the ends, lower concave or somewhat protuberant at the centre; sides somewhat parallel for a portion of their length; the eatremities gradually ta- pering, slender, curved downwards, ends obtuse; large granules, in a single series; e. f. reddish, striae numerous, distinct, one or more transverse lines at the central Su- ture. Sporangia double, rounded, smooth, in close approximation, their opposed sur- faces flattened, placed between the de- hiscing, shortly-deciduous empty fronds, and each formed by the mutual conjuga- tion of the contents of the adjacent op- posite segments. L. 1-48"; B. 1-909". (III, 41, 42.) G.B., I., F., G., Mexico. 3, striae spiral; y, striae very faint, except at the centre of the frond (Bréb.). C. decorum (Bréb.). — Frond about twelve to twenty times as long as broad, tapering from the centre, gradually curved; upper margin equally convex, lower margin concave; extremities attenuated, slender, obtuse; large granules, in a single Series; e. f. colourless, striae numerous. F. 5* Frond gradually curved, tapering, Sud- denly contracted at the end into a comi- cal point. C. attenuatum (Ehr.).--Frond eight to twelve times as long as broad, gently curved, gradually attenuated; upper mar- gin slightly convex, lower concave; eac- tremities suddenly contracted into an obtuse comical point; large granules, in a single Series; e. f. reddish, with numerous close striae, central suture evident. L. 1-57"; B. 1-669". (III, 43.) G.B., I., F., G. 6 * Frond ventricose or narrow-lanceolate, 7-apidly tapering into a distinct beak, (Sporangia cruciform.) - - C. Ralfsii (Bréb.).--Frond stout, six to mine times as long as broad; the upper ºnargin slightly conver, the lower concave, but ventricose at the middle; each extremity tapering into a narrow, slender, reddish beak, Shorter than the body, slightly curved downwards, ends obtuse; large granules, conspicuous, in a single series; e. f. red- dish, especially near the ends, striae nu- merous, close, and distinct, central suture accompanied by Several transverse lines. L. 1-79"; B. 1–526". G.B., F. C. rostratum (Ehr.). — Frond from about ten to fifteen times as long as broad, lanceolate; upper and lower margins nearly equally convex; each extremity tapering into a narrow, setaceous, nearly colourless beak, nearly equal in length to the body, curved downwards, ends obtuse; large granules, in a single series; e. f. colourless or somewhat straw-coloured, striae numerous, close; suture solitary. Sporangium somewhat cruciform, its sides concave, its extensions truncate, attached to the empty conjugated fronds. (III, 44.) L. 1-69"; B, 1–680". C. cau- 750 SYSTEMATIC IIISTORY OF THE INFUSORLA. datum (Corda), Stauroceras Acus (Kg.). G.B., I., F., G., Italy. C. elegans (Bréb.).-Frond very slen- der (twenty-five to thirty times as long as broad), narrow-lanceolate, upper and lower margins nearly equally convex, each extremity tapering into a long, slen- der, setaceous, colourless beak, about as long as the body, ultimately curved down- wards, ends acute; large granules, in a single series; e. f without striae, F. C. setaceum (Ehr.).--Frond very slen- der, from about twenty to twenty-five times as long as broad, narrow-lanceo- late; upper and lower margins nearly equally and but slightly convex; each ex- tremity tapering into a very long, slen- der, setaceous, colourless beak, longer than the body, witämately curved down- wards, ends obtuse; e. f. colourless, striae close, faint, central suture solitary. Spo- rangium cruciform, similar to the last. L. 1–116"; B. 1-2381". = Stauroceras subw- latum § S. intermedium (Kg.), C. Fützingii (Bréb.). G.B., I., F., G., Italy, U.S.A. C. pronum (Bréb.).—Frond very slen- der (thirty to thirty-five times as long as broad), nearly straight; upper and lower margin Scarcely inflated, nearly equally though very slightly conver; very gradually attenuated at each extremity into a long, slender, Setaceous, colourless beak, ultimately somewhat curved down- wards, ends slightly enlarged and rounded; e. f. colourless, without striae. F. 7 * Frond minute, tapering, curvature very slight, neither inflated nor rostrate. (Sporangia cruciform.) C. Cornu (Ehr.).--Frond minute, from five to eight times as long as broad, slender, slightly curved, attenuated, ends blunt; endochrome not reaching to the extremities; large granules, indistinct, in a single series; e. f. colourless, without striae. Sporangium in f. V. somewhat cruciform or quadrate, with the angles produced and rounded, in s. v. elliptic, attached to the conjugating fronds. L. 1-140"; B. 1-3709". = C, tenue (Kg.). G.B., F., I, G., Italy. 8, frond more tur- gid, L. 1-226"; B. 1-2142". G.B., I., F. C. acutum (Bréb.), Frond somewhat larger than the last, about from six to twenty times as long as broad, slender, narrow-lanceolate, slightly curved, gra- dually attenuated, ends acute; e. f. co- lourless, without striae. Sporangium similar to last. L. 1-177"; B. 1-2550". G.B., I., F., G. a six to twelve times as long as broad, ends subacute. 8 ten to twenty times as long as broad, ends very acute. = Stauroceras Subulatum (Kg.)?, C. Subulatum (Bréb.)?, C. tener- rimum, (Kg.) P C. Griffithii (Berk.). —Frond minute, scarcely curved, acicular, very acute, smooth. = C, subtile (Bréb.)? G.B., I., F. 8 * Frond crescent-shaped, stout, eactre- mities furnished with a single acute Spine, - C. cuspidatum (Bailey).--Frond stout, crescent-shaped, scarcely tapering, much curved, ends rounded, furnished with a single subulate acute spine; e. f without striae. U.S.A. We are disposed to think this plant may not be a true Desmidiean, but belong to the genus Ophiocytium (Nāg.), though placed in Closterium by Bailey. Genus PENIUM (Bréb.).—Frond elongate, straight, cylindrical, elliptic, or lanceolate, either not at all constricted or but very slightly narrowed at the middle, entiré. taining active granules. * Empty frond granulate, generally 7'eddish. . PENIUM margaritaceum (Bréb.). — Frond six to ten times as long as broad, fusiform or cylindrical, with rotundato- truncate ends, rough with pearly granules arranged in longitudinal lines. Endo- chrome at each end, sometimes with a more or less distinct terminal cavity with active granules, Sporangium orbicular, Smooth. = Closterium margaritaceum (Ehr.). G.B., I., F., G. a, frond fusiform, gradually constricted at the middle, Endochrome with or without a terminal clear space, con- granules distinct. L. 1-156"; B. 1-96.1". (II. 14.) 3, frond linear, Scarcely con- tracted at the middle, granules distinct. 'y, frond linear, not contracted at the middle, granules appearing like puncta. L. 1-1697; B. 1-1515". (II. 15.) P. Cylindrus (Bréb.).--Frond minute, red, three or four times as long as broad, cylindrical, not contracted at the middle, ends rotundato-truncate, rough with minute, closely scattered, pearly granules; e. f. red. L. 1-492"; B. I760". = Closterium Cylindrus (Ehr.), Dysphinc- tium Cylindrus (Nāg.). G.B., I., F., G. OF TEIE DESMIDIE ZE. 751. P. annulatum (Nāg. sp.).--Frond mi- nute, Scarcely twice as long as broad, cylindrical or subelliptic, sides and ends broadly rounded, rough with minute gra- nules arranged in transverse lines, which give a minutely denticulate appearance to the margin, except at a very narrow central annular space, where they are absent, thus imparting a somewhat con- stricted appearance; e.V. circular, margin minutely granulate. = Dysphinctium an- mulatum (Nāg.). I., G. 2 * Empty frond smooth, colourless. P. Digitus (Bréb.).—Frond large, stout, Smooth, three or four times as long as broad, elliptic - oblong, sides and ends broadly rounded; endochrome in obscure and undulated fillets, interrupted only by the pale central transverse band, and hav- ing no clear space at the extremities. L. 1-81"; B. 1–299". = Closterium Digitus Ehr.), Penium oblongum (De Bary)? .B., I., F., G., U.S.A. P. lamellosum (Bréb.).—Frond large, stout, Smooth, about four times as long as broad, gradually contracted at the middle, and tapering to the extremities, ends somewhat truncate; endochrome in obscure and undulated fillets, in transverse view radiate, its rays divided, and hav- ing no clear space at the extremities, • 2 - . P. Naegelii (Bréb. in litt.). —Frond large, stout, Smooth, about four times longer than broad, oblong, not contracted at the middle, gradually tapering to each extremity, Sides nearly Straight, ends broadly truncate; endochrome arranged in interrupted divided planes radiating from the central acis, in f. V. being in- dented somewhat in a pinnatiñd manner, the rays touching the cell wall, some- times divided, and somewhat dilated thereat, in transverse view radiate. = Closterium (Netrium) Digitus (Nāg.). G. • 2 ºn • P. interruptum (Bréb.).—Frond large, stout, smooth, three or four times as long as broad, cylindrical, Sides parallel, eac- tremities conical, and rounded at the ends; endochrome disposed in straight, strongly marked fillets, interrupted by three trans- verse pale bands, having a rounded, well- defined clear space near the ends, in which are active granules. L. 1-116"; B. 1-571". (III. 45.) G.B., I., F., G., U.S.A. P. closterioides (Ralfs).-Frond rather large, about six times as long as broad, smooth, fusiform or lanceolate, ends broadly rounded; endochrome in distinct longitudinal fillets, interrupted only by the central transverse pale band, with a single longitudinal series of large granules, and a rounded clear space close to the ends, in which are active granules. L. 1-92"; B. 1-590". G.B., I., F., U.S.A. P. Navicula (Bréb.).—Frond minute, about three or four times as long as broad, Smooth, fusiform, ends bluntly pointed; endochrome sometimes in fil- lets, sometimes scattered, interrupted only by the transverse central pale band, with one or two large granules in each half, and a rounded clear space at the ends, in which are active granules. L. 1-420"; B. 1-750".=P. Berginii (Archer). I., F. P. truncatum (Bréb.).—Frond minute, two to four times as long as broad, cylindrical, Smooth, ends truncate. Spo- rangium orbicular, Smooth, placed be- tween the dehiscing, deciduous empty fronds. L. 1-969" to 1-555"; B. 1-2212" to 1-2100". G.B., I., F. Genus SPIROTAENIA (Bréb.).—Frond elongate, straight, cylindrical, or fusiform, entire, not constricted at the middle, ends rounded or acute; endo- chrome spiral. (Gelatinous investment very apparent; cell-division oblique; fructification unknown, therefore the position of this genus uncertain.) * Endochrome a single spiral band. SPIROTZENIA condensata (Bréb.). — Frond cylindrical, five to ten times as long as broad, ends rounded; en- dochrome a single, broad, closely-wound spiral band, its revolutions numerous. I-208"; B. 1-1048". (II. 4.) G.B., I, F., G., U.S.A. S. muscicola (De Bary).-Frond cylin- drical, two to four times as long as broad, ends rounded ; endochrome a single, broad, Smoothly-defined, widely- wound spiral band, its revolutions very few (one or two). L. 1-142” to 1-71"; B. 1-287". = Palmogloea endospira (Kg.), Cylindrocystis endospira et EndoSpira truncorum (Bréb., ##! E., G. S. erythrocephala (Itzigsohn, Braun). Frond fusiform, five or six times as long as broad, ends acute; endochrome a single, rather narrow spiral band, its revolutions few. = S. minuta (Thuret, Bréb.). F., G. 752 SYSTEMIATIC EIISTORY OF TEIE INFUSORIA. 2 * Endochrome in several spiral bands. S. obscura (Ralfs).--Frond cylindrical or fusiform, five to eight times longer than broad, extremities attenuated, ends blunt; endochrome in several slender Spi- 7'al bands, their revolutions two or three, sometimes scattered, leaving a clear space at each extremity, in which there is sometimes a free granule. L. 1-247" to Hº" B. 1-1020" to 1-907", G.B., • ? --- * C. calls stipitate. Genus COSMOCLADIUM (Bréb.). constricted at the middle, stipitate. CoSMocLADIUM pulchellum (Bréb.).— Stipes dendroid, dichotomously branched, hyaline, with a slight intermediate thick- ening between the cells; cells terminal and axillary, green, segments elliptico- reniform, smooth (III. 63). F. We here provisionally place this re- — Cells rounded, compressed, deeply markable plant, discovered by M. de Brébisson, not knowing as yet anything as to its mode of growth or development. The cells, if detached from the stipes, would scarcely be distinguishable from those of Cosmarium bioculatum. D. Cells aggregated into families, forming fasciculi or faggot-like bundles. Genus ANKISTRODESMUS (Corda).-Cells minute, smooth, elongated, attenuated, aggregated into families forming fasciculi or faggot-like bundles, each family resulting from the self-division of a single cell, which commences by the formation of a somewhat oblique septum at the middle, eventually rendered more and more oblique from the young cells growing alongside one another longitudinally until they each attain the length of the original parent- cell, the process being again and again repeated by each till the aggregated family consists of at most thirty-two cells, the family finally again breaking up into single cells. No other propagation known; the position of the genus is therefore doubtful. ANKISTRODESMUs falcatüs (Ralfs). - Cells veryslender, arcuate (rarely straight or sigmoid), gradually attenuated, ends acute. L. 1-550"; B. 1-7353". (I, 35, 36.) = Rhaphidium fasciculatum (Kg., Näg.). G.B., I., F., G., Italy. A. convolutus (Corda). — Cells much curved, crescent-shaped, somewhat ra– pidly attenuated, ends subacute. = Rha- phidium minutum (Nāg.). I., F., G. We have met with a plant (gathered near Dublin) which we now (though doubtfully) refer to this species, in which we noticed self-division of the cells, in an at first oblique, finally longitudinal manner, very much the same as that described by Nägeli (Einzell, Alg.) for the preceding species, and introduced into. §. are not quite so much curved as in ägeli's drawing of this species, and are rather more acute at the extremities: we have not noticed the fasciculi to be composed of more than 8 cells, frequently of 2 or 4 ; and while so combined the cells all look in the same direction, the con- cave surface of the One being applied to the convex surface of its neighbour. A. contortus (Thuret).-Cells slender, arcuate or sigmoid, somewhat gently in- flated at the centre, ends drawn out long and very fine. F. [Scenodesmus duplea (Ralfs) is placed in this genus by Kitzing and Nägeli under the name of Rhaphidium; ". plant may, however, be the cell of an the generic character. The cells in our Ankistrodesmus undergoing division.] Subfamily PEDIASTREAE (page 24). We shall not attempt to give anything but a very provisional diagnosis of the genera here included under the above title (which have long been asso- ciated with the Desmidiaceae, and chiefly for that reason finding a place in the present work), as, so far as we can judge, it is not yet determined whether they should remain united with the Palmellaceae, to which they have been OF THE PEDIASTRIE ZE, 753 referred by Nägeli, or, with some few other Algae, form a distinct group near Palmellaceae, and perhaps Volvocineae. They cannot, we think, continue to be considered as belonging to the Desmidiaceae. For the purposes of the present work, however, as they are introduced, we shall just indicate that the genera here described under the above head agree in the following characters:— Cells combined into a definitely formed frond or family, often either ex- ternally notched or attenuated, Sometimes spinous, not undergoing complete self-fission in the same direction into two perfect cells, but propagating by the repeated segmentation of the contents of the old cells into a definite number of portions or “gonidia,” which are either still or for a time motile, and which are either arranged according to the typical plan within the parent- cell, and by its bursting set free as a new frond or family, or become so arranged without the parent-cell, but still involved in its inner membrane, the whole having emerged by a transverse fissure. We are disposed to think that here Hydrodictyon should come; for though in this plant the development of the active gonidia is simultaneous, not successional, as in Pediastrium, Pringsheim alludes to the gonidia in Coelas- trum sphaericum (which indeed are still) as either the one or the other. Cruciagenia quadrata (Morren)=Staurogenia quadrata (Kg.), seems to pro- pagate by complete Self-fission, and, gonidia not being described, we believe cannot belong here. As to Sphaerodesmus (Nāg.) information is wanting. Genus SCENODESMUS (Meyen).—Frond or family composed of from two to eight oblong fusiform or elliptic cells, connected into a single or dowble continuous row ; propagating by means of the repeated segmentation, in parallel planes in one or two directions, of each of the cell-contents into one or more brood families (not motile), set free by the bursting of the parent- cell wall. (Nāg.) ScFNODESMUS quadricauda (Ralfs).- Cells in a single row; oblong, rounded at their ends; external cells (sometimes more turgid than the others) furnished at each eactremity with an elongate, often curved, acute spine or bristle, sometimes with another from the centre of the outer margin, L. 1-1121"; B. I-2631". I. 40, 41, 43.) = Achnanthes quadricauda §. .), Arthrodesmus quadricaudatus (Ehr.), Scenedesmus caudatus (Corda, Rg.), S. Quadricaudatus (HaSS.). G.B., I., F., G., U.S.A. 6, central cells fur- nished at one of their ends with an elongate, acute, curved spine or bristle, each half of the frond being so furnished at opposite sides, sometimes the central cells being also furnished at their other ends with a very short, minute spine, = S. Nägelii (Bréb.). (I, 42.) S. dispar (Bréb.).—Cells two or four, alternating, oblong, blunt at the ends; when four the central cells at one end at opposite sides of the frond furnished with a short acute mucro-like dejected spine, each spine directed inwards; when either two or four, the external cells with a similar spine at both ends; when four, that spine at the same side of the frond with that belonging to the central cells also directed inwards, the other directed outwards. F. sº S. antennatus (Bréb.). — Cells in a single or double row; fusiform, or semi- lunate, ends cuspidate, and each terminated by a minute orbicular globule. F. S. dimorphus (Kg.).-Cells in a single row; narrow, attenuated, and pointed at the ends; the central in apposition the most of their length, the outer externally lunate. I.1-1020" to 1-906"; B.1–8160". =Achmanthes dimorpha (Turp.), S. pec- timatus (Meyen), Arthrodesmus pectinatus (Ehr.). G.B., I., F., G. S. acutus (Meyen). — Cells in alter- nating rows; the central fusiform, in apposition only at their middle, the outer Sometimes externally lunate. L. 1-1663" to 1-1060"; B. 1-6250” to 1-6181". = Arthrodesmus acutus (Ehr.), S. acutus et obliquus (Ralfs). G.B., I., F., G., Italy. S. obtusus (Meyen).-Cells in one or two rows, all ovate or oblong, ends rounded, L. 1-2331" to 1-1961"; B. 1-4096" to 1-3623". (I, 37, 38, 39.) G.B., I., F., G., U.S.A. 3 C 754. SYSTEMATIC HISTORY OF TETE INFUSORIA, S. duplex (Ralfs).-Cells two, slender, tapering, sigmoid, acute, placed side by side for about half their length. = Rhaphi- dium duplea (Kg.), nec S. moniliformis (duplex) (Kg.). G.B., G. This plant possibly represents a cell of an Ankis- trodesmus during division. Genus PEDIASTRUM (Meyen).--Frond or family plane, circular, elliptic, or irregular, composed of several cells (a multiple of four), forming by their union a flattened star-like group, generally arranged in more or less con- centric circular series, marginal cells externally bipartite or entire; propa- gating by “macrogonidia,” which are subglobose, formed by repeated binary division of the endochrome of each of the parent-cells of the old frond, 2, 4, 8, 16, 32, or 64 (even 128) in number, and making their exit by a transverse fissure from the parent-cell, involved in its inner membrane, within which for a time they actively move, presently settling down and arranging them– selves into a new frond; “microgonidia’’ produced in the same manner, but shortly rupturing the confining membrane and swimming freely away, their fate unknown (Braun). * Lobes of the outer cells two, deeply emarginate or truncate. PEDIASTRUM Tetras (Ralfs).--Frond very minute; cells four, their interstices forming a cross, their outer margin bi- lobed, angles acute, L. 1-2941"; B. 1-2272". (II. 27.) = Micrasterias Tetras Ehr.), P. biradiatum (Tetras) (Kg.). .B., I., F., G., U.S.A. P. heptactis (Menegh.).--Frond minute; cells eight (seven disposed in a single series wound a central one), bilobed, angular. L. 1-2900"; B. 1-2500". = Micrasterias heptactis (Ehr.), Euastrum heavagonum (Corda), P. simplex. (Hass.), P. bira- diatum (heptactis) (Kg.). G.B., I., F., G., U.S.A. 3 - - - - P. biradiatum (Menegh.).-Inner cells subquadrilateral, with a linear notch, the outer quadrilateral or somewhat cuneate, approacimate for their entire length, ex- termally deeply bipartite, their incisions narrow, the subdivisions trumcate or truncato - emarginate. L. 1-1200" to 1–2550"; B. 1-1754" to 1-2040". = Mi- crasterias Rotula (Ehr.), P. biradiatum (Rotula) (Kg.). This with the two pre- ceding may possibly make but one true species, P. Ehrenbergii (Braun.). (I, 52.) ..B., I., F., G., U.S.A. P. Rotula (Ehr, emend. Braun). — Inner cells with a wide notch, and sepa- rated by wide lacunae, the outer subqua- drilateral, approacimate only at their bases, which are nearly square, externally deeply bipartite, their incisions broad, the sub- divisions marrow, inciso-dentate. F., G. P. caudatum (Braun), — Inner cells pentagonal or hexagonal, with a deep linear notch, the outer quadrangular, externally deeply bipartite, the subdivi- sions truncate, very slightly concave at the centre, and furnished at the angles with a very minute, short, bristle-like spine. = P. Rotula (Nāg.). 2* Lobes of the outer cells two, entire, attenuated, P. Selenaea (Kg.). — Cells crescent- shaped, arranged in one or more circles round one or two central ones, connecting medium coloured. = P. elegans (Hass.), P. lunare (Hass.). G.B., F., G. P. gracile (Braun). — Frond minute, of four or six cells (four external, with or without two central cells); marginal cells deeply bipartite; subdivisions ovate, tapering to a point, L. 1-1020"; B. 1-1632". = Micrasterias Coronula (Ehr.), P. Napoleonis (Hass., Menegh, Kg., néc Ralfs), P. simplex (Ralfs). G.B., F., G. P. pertusum (Kg.). — Cells arranged in circles round one or two central ones; immer cells quadrangular, sides concave and leaving angular vacant intervals; the outer cells with square bases, externally triangularly notched, the subdivisions ta- lºg to an acute point. L. 1-2266"; . 1-3268". = Micrasterias Boryana (Ehr.), P. tricyclium (Hass.), P. emargi– natum (pertusum) (Kg.). G.B., I., F., G. P. granulatum (Kg.). — Cells eight, ºrough with minute granules, six cells arranged round two central, the inner subquadrate, the outer having two taper- ing lobes. L. 1-2000" ; B. 1-1850". Gib, Í. F., G. P. Napoleonis (Menegh.).-Cells eight, six arranged round two central, the inner variable, the outer having two cuspidate lobes, the notch wide. (I. 62.) L. 1–1570." to 1-1483"; B. 1-1813" to 1-1088". = P. hea actis (HaSS.). G.B., G. OF THE PEDIASTREAE. 755 P. Boryanum (Menegh.). — Cells ar- ranged in one or more circles round one or two central; the inner variable, gene- rally concave at one side, the outer taper- ing into two long subulate points, the notch narrow. L. 1-2083" to 1-1633"; B. 1-2733" to 1-2222". (I. 59, 60, 61, 68, 69, º = Micrasterias Bory- ana (Ehr.), P. subuliferum (Kg.), P. cru- ciatum (Kg.). G.B., I., F., G., U.S.A. P. ellipticum (HaSS.). — Cells varying in number and arrangement; outer cells suddenly contracted ºnto two short, cylin- drical, obtuse processes. L. 1-1754" to I-906"; B. 1-1515" to 1-1020". 8, pro- cesses of the lobes truncato-emarginate. = Micrasterias elliptica (Ehr.), P. vagum (Kg.), P. constriction gº; Kg.), P. bi- dentulatum (Braun). G.B., I., G., U.S.A. P. angulosum (Menegh.). — Cells ar- ranged in one or more circles round one central, the inner cells roundly angular, the outer obliquely truncate, emarginate, the Subdivisions not tapering into rays. L. I-2732"; B. 1–1942". = Micrasterias angulosa (Ehr.). G.B., F., G. 3 * Outer cells with only one attenuated lobe (Monactinus). P. simplex (Meyen).--Cells eight, in a single series surrounding a central vacant interval, narrow-ovate or lanceolate, very gradually tapering, acuminate, approxi- mate only at their bases. = Monactinus simplex (Kg.), M. simplex et acutangulus Corda), M. octonarius (Bail.) P. F., G., .S.A. There seems to us to be some doubt as to the absolute distinctness of this and P. gracile (Braun), as it is pos- sible the four deeply bipartite external cells of the latter may have been mis- taken for eight simply attenuated cells as described for P. simplea (Meyen). P. duodenarium (Bailey, sp.). —Inner cells four, somewhat triangular, enclosing a central, quadrate vacant interval, an four broadly lanceolate vacant intervals between them and the outer series, to which they are united by their terminal angles ; outer cells twelve, subovate, truncate below, much attenuated, acu- minate. = Monactinus duodenarius (Bail.). U.S.A. P. ovatum (Braun).--Cells ovate, ter- minating in a long, acute point, granu- late, arranged in two series, inner three, outer ten. = Asterodictyon ovatum (Ehr.), Monactinus ovatus (Kg.). o P. Triangulum (Braun).-Cells trian- gular, Smooth, arranged in three series, the centre vacant. Asterodictyon Trian- gulum (Ehr.) = Monactinus Triangulum (Kg.). G. 4* Outer cells not lobed (Anomopedium). P. integrum (Nāg.).--Frond irregular, cells rounded or bluntly angular; outer cells not emarginate, generally possessing externally two short mucro-like spines (1, 46, 47, 48). G. Genus COELASTRUM (Nāg.).-Frond or family hollow, globular or sub- cubical, composed of polygonal (or spherical) cells writed in one layer into a hollow clathrate net-like family, the cells drawn out on the exterior into one or more lobes, or simply spherical; propagating by the segmentation of the cell-contents into a definite number of portions which become arranged into a hollow young frond resembling the parent, ultimately set free by the bursting of the parent-cell. CoELASTRUM sphaericum (Nãg.). — cells hexagonal, drawn out externally Fronds spherical or oval; cells hex- into two short truncate projections, in- agonal, drawn out externally into a terstices quadrangular, (r. 54, 56.), G. blunt cone, interstices 5–6-angular. (I. C. microporus (Nāg).--Frond globu- 49, 50, 51.) G. lar, cells exactly spherical, interstices C. cubicum (Nāg.).--Frond subcubical, minute. G. Genus SORASTRUM (Kg.).--Frond or family solid, globular, composed of cuneiform or cordate cells, somewhat compressed and united into globular families, their narrow, ends meeting in the centre and outwardly emarginate or divided. Propagation unknown. SoRASTRUM spinulosum (Nāg.):-Ex- | Subulate spines. (I. 56, 57, 58.) G. ternal margins of the cells dilated, S. echimatum (Kg.). - External mar- slightly º the rounded angles gins of the cells deeply bifid, the sub- furnished each with two minute, acute, divisions Subulate. G. 3 C 2 756 SYSTEMATIC HISTORY OF THE INFUSORIA, Sub-group DIATOMEAE or DIATOMACEAE. (Page 31, Plates IV. to XVII. and part of II.) [For reference to the species figured in this work, see Index of Diatomaceæ illustrated.] FRUSTULEs or cells, either simple or pseudo-unicellular by complete separa- tion, or united in tablets or filaments, furnished with a sculptured siliceous coat in three portions, a median one (connecting zone) and two lateral ones (valves) united by distinct sutures; internal substance yellowish-brown (rarely olive-brown); reproduction by conjugation and subsequent formation of sporangia. The general history of the Diatomaceae has been so fully treated of in the first part of this work (p. 31) that it is here only necessary to explain some terms used in the descriptions. . The Diatomaceae differ, in several respects, so widely from acknowledged Algae, that in our opinion they may be regarded rather as an order related to the Algae than as a family belonging to them. The siliceous covering is composed of three portions. The central one is sometimes called “connecting membrane'' and “cingulum;” we, however, prefer Professor Arnott's term, “ connecting Zone,” as less likely to mislead. The lateral or junction surfaces correspond to the septa of a Conferva, and are called valves. The late Professor Smith considered the central portion unessential and produced only preparatory to self-fission. We, on the contrary, regard it as of great importance, and quite unknown in the true Algae. It is conspicuous in the conjugating and, consequently, mature frustules; and we think the con- clusion illogical that it has no systematic value because obscure in newly- formed frustules. It is evidently essential in Diatoms with flat valves, since otherwise there could be no cavity to contain internal matter. We use the term “front view'' to denote that position of the frustule when the connecting zone is fully presented to the eye, and “side view " when the centre of the valve is in a similar position. When we speak of the “valve,” unaccompanied by a qualifying epithet, it must be understood as identical with “side view.” - “Longitudinal” means in the direction of the connecting Zone, and “transverse” in the opposite direction uniting the valves. When so applied to the frustule of a Diatom, these terms acquire a meaning exactly the reverse of that in which they are used when applied to the joint of a Conferva and the frond in the Desmidieæ. For example, the frustule in some Diatoms and the frond in Closterium are both described as longitudinally lunate, whilst they are really extended in opposite directions: unless the change in the meanifig of the terms be remembered, an idea of similarity will be conveyed which is altogether erroneous. The valves are sculptured, cellulose, or striated; the apparent absence of striae in some instances may be accounted for by their extreme delicacy placing them beyond the reach of our instruments, since the greater the penetration of the object-glass, and the more perfect the illumination, the greater is the number of species found to possess them. When, therefore, we use the terms “Smooth’” and “very smooth” in definitions taken from foreign works, they must be understood to mean only that the striae were too fine to be ascertained by the microscope of the describer. OF TEIB. DIATOMACEAE, 757 The word “transverse” is, for the sake of brevity, omitted before striae in the definitions, but, unless the contrary be expressed, it must always be understood. When the frustules are lunate or curved, the convex margin is called the dorsum and the opposite the venter. - We have not mentioned the Sporangia in the generic and specific descrip- tions, because the examples recorded are too few, and that condition is too seldom met with to be practically useful. With respect to the general history of the Diatomaceae, the importance of Mr. Thwaites’s discoveries can scarcely be overrated (see p. 61). We consider it, however, desirable to point. out, that whilst the similarity of their conjugating process to that of the Desmidieæ affords a powerful argument in support of the vegetable nature of the Diatomaceae, the widely different characters of their sporangia, not merely in form but in subsequent changes, furnish irresistible evidence of the pro- priety of separating the DeSmidieæ from the Diatomaceae. The resemblance of the reproductive bodies in the latter to the parent frustules, and their con- tinuous growth and increase by self-division, is so unlike what we find in the sporangia of the Desmidieæ and Conjugatae, as to appear more like an “alternation of generations” than examples of true sporangia. The first attempt at a scientific arrangement of the Diatomaceæ was by C. A. Agardh in the ‘Conspectus Criticus Diatomacearum.” He distributed them into three families—Cymbelleae, Styllarieae, and Fragilarieae, according to the form of their frustules. He considered that in each family the frus- tules might be free, stipitate, united into a filament, or enclosed in a frond. This system was greatly extended and improved by Professor Kützing; and, as we believe his arrangement (p. 101) is the best and most natural yet pro- posed, we have used it in this work, admitting, however, some judicious alterations proposed by Meneghini and others. It is true we do not meet with examples of the four conditions in each family; but they may fairly be anticipated to occur, and their absence regarded as lacunae likely to be filled up by future discoveries. We have thus brought together nearly allied genera; for it is often difficult to distinguish a Eunotia from a Himantidium, a Tri- ceratium from an Amphitetras, a Cymbella from a detached Cocconema, and an escaped frustule of Colletonema from a Navicula. The arrangements of Ehrenberg and Smith we regard as far inferior, separating, as they do, such nearly allied forms. Indeed the fame of those eminent observers must depend on their intimate knowledge of genera and species, and on their definitions being superior to those of their predecessors, and not on their primary divisions. We feel persuaded that, but for his lamented death, Professor Smith would have been led by increased acquaintance with the Diatomaceae to modify his views in that respect in a future edition of his valuable and beautiful work on the British Diatomaceae. ANALYSIS OF THE FAMILIES OF DIATOMACEAE. A. Walves with central module and median longitudimal line ......... JB, with umbilicus or pseudo-module and radiant lines or cellules ............................................................ 12 2 3 3 y with symmetrical margins .................. 6 3 y Valves dissimilar ..................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . STRIATELLEE, 4 5 similar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Walves cellulose, without transverse stria. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ANGULIFERE, not cellulose............. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1. ſ } } | ,, without a central module ....................................... 9 { Frustules in side view lunate or arcuate .............................. 3. 4. { } y 58 SYSTEMATIC EIISTORY OF THIE INFUSORIA. 5. (Valves with pervious costa or striae .................................... EUNOTIEE. tº }} a longitudinal line or keel................................. SURIRELLE.E. 6. (Frustules cuneate in the front view ............. ..................... 7 g 33 mot cuneate in the front view ............................. 11 7 ſ Frustules free; valves with alae.......................................... SURIRELLA. : ) ,, attached or united in filaments; valves without alae ... 8 8 (vº dotted, dots not forming striae ................................. EUCAMPIA. e ,, mot dotted, or the dots arranged in transverse lines......... 9 Frustules radiating from a common centre; valves obovate or 9. clavate ............................. ........................ 10 33 not radiant; valves with symmetrical ends............... FRAGILARIEE. Frustules in front view with longitudinal vittae ..................... LICMoPHOREE. 10. | 13 2 3 without longitudinal vittae (costae per- vious) .... ............................................................. MERIDIEE. 11. (Connecting zone (annulate) with imperfect internal septa......... STRIATELLEE. & 3 y ,, without internal septa .............................. 12 Lateral view with 3, or more, angles or lobes ........................ ANGULIFERE. 12. 53 » circular ...................................................... 17 33 ,, neither angular nor circular.............................. 13 Valves not conspicuous in front view, which is mostly longer 13 than broad ...................................................... 14 * , compressed, inflated, conspicuous in front view, which is mostly broader than long .................................... 15 14 Valves with a longitudinal line .................. ....................... SURIRELLE.E. º ,, without a longitudinal line .................................... PRAGILARIEE. 15 Valves in front view, rectangular, with transverse capitate vittae . TERPSINoiº. gº 53 2 3 with produced angles, processes, or spines 16 16 Valves cellulose, symmetrical............................................. BIDDULPIIIEE. e , not cellulose, mostly dissimilar ................................. CILETocFREE. Frustules saddle-shaped; valves mostly with longitudinal blank 17. Space . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CAMPYLODIscus. 35 not saddle-shaped; central blank space (if any) orbicular 18. Valves cellulºse, ............................................................ 19 & { º, not cellulose......................................................... MELOSIREE. ſ Frustules simple; lateral view more conspicuous than front...... 20 19. 2 3 either united into filaments or front view broader than lateral ....................................... tº e º & s a # s s B. & sº e º is e º a MELOSIREE. 20 Valves furnished with projecting processes ........................... |EUPoDISCEE. & ,, without processes, but sometimes with minute teeth ...... CoscINoDISCEE. 21 { Only one valve with a central module ................................ 22 Both valves with central modules ....................................... 23 22 Frustules admate, not genuflexed ....................................... Cocco NEIDEE. g 33 not adnate (often stipitate), genuflexed .................. ACHNANTIIEE. Frustules cuneate in front view; valves usually with dissimilar 23. | ends.…............................................... GOMPHONEMEE. 3 3 not cuneate; Valves with symmetrical ends ............ 24 24 Median line rib-like and distinct; modules distinct.................. 25 g y 5 not rib-like; nodules mostly obscure .................. 2 25 Side view lunate; nodule mostly excentric ...................... * * * * * 26 † 32 not lunate (rarely lunately curved); nodule central ... NAVICULEE. 26 (vº Ventricose, striae not decussating .............................. CYMBELLE.E. 4-/WJ's , not ventricose, stria decussating .............................. TOXONIDEA. - C. Individuals of ome piece, with radiating spines ..................... ACTINISCE.E. FAMILIES. * Valves without a central module. Eunotieae. Meridieæ. Licmophorea. Fragilarieae. Symedreas. Surirelleae. Stria- tellea. Terpsinoëae, Biddulphieſſe. Angulifereae. Eupodisceae. Coscinodisceae. Melosirear. Chaetocereae. 2* Valves with a median line and a central module. Cocconcidcae. Achnamthca. Cymbelleae. Gomphonemege. Naviculeac. Actimiscogo. OF TEUE EUNOTIEAE, FAMILY I.–EUNOTIEAE. Frustules free or admate, in lateral view lunate or arcuate, with transverse striae or costae, not interrupted by a central nodule or longitudinal line. The essential characters of this group are the lunate form of the frustules in the lateral view, and the striae being continuous across the valve, and not inter- rupted by a longitudinal line. It is easily distinguished, except from some species of Synedra, which, however, are linear-curved rather than lunate, and usually have an evident though faint longitudinal line. Amphiplewra inflewa, which in form more nearly resembles Eunotia, has a longitudinal line passing down the middle of the lateral valves. The Eunotieae have one surface of their connecting Zone flat or concave and the opposite one convex, the convexity being usually greater than the concavity. The lateral portions or valves are either flat or convex; in the former case they do not appear in the front view, and the frustule appears quadrilateral; in the latter, on a front view, they have an oval form. Like most Diatomaceae, the connecting Zone has two puncta at each end. Genus EPITHEMIA (K.).—Frustules lunately curved in lateral view, and furnished with transverse internal ribs (canals, Sm.); usually admate by the flat or concave surface of the connecting Zone, and not by one of the lateral valves, like Cocconeis. The lateral view has strongly-marked transverse lines, which Mr. Smith, in his beautiful work “The British Diatomaceæ,’ calls canaliculi. We consider them internal ribs; in fragments it is by no means difficult to see them, as they give a dentate appearance to the margin; their form is somewhat triangular, but we are unable to detect any internal cavity or canals. Mr. Smith, however, may have used microscopes of larger angular aperture and higher magnifying powers than we employed. Besides these ribs, the valves have transverse striae or punctated lines. The adnate frus- tules and strongly-marked ribs distinguish Epithemia from Eunotia and Himantidium. In the front view the ends of the ribs frequently produce a beautiful beaded appearance. These beads form two longitudimal lines, and are more or less remote from the margins, according to the convexity of the lateral valves. They are frequently more numerous on one side than on the other, and are not all equidistant, even in the same Series. * Front view gibbous at the centre, costa fine. ; EPITHEMIA gibba (E., K.).—Front view elongated, linear, inflated at the centre and ends. KB. p. 33, t. 4, f. 22. = Na- vicula gibba, E Inf. p. 184; Eunotia gibba, EA & M, many figures. Fresh water. Common, Ehrenberg gives about 100 habitats in Europe, Asia, Australia, Africa, and America. (XII. 27.) Striae 36 in 001"; costae 15 in .001".-Distin- guished by its elongated frustules, fine striae, and dilated ends; but, from its nearly straight side-view, its proper genus may be overlooked. * E. ventricosa (K.).—Front view ellip- tic, oblong, with gibbous middle; valves arcuate, with gibbous dorsum and atte- muated, acute, somewhat incurved ends; striae fine. KB. p. 35, t. 30. f. 9; SBD. i. pl. 1. f. 14, Fresh and brackish water. Europe. E. angulata (Perty).--Dorsum turgid, sloping to the obtuse ends; venter con- cave at the centre, striae about 12 in 1–1200". Rab Diat. p. 18, t. 1, f. 18. = Eunotia Jastrabensis, EMI. pl. 8, 1, f. 3 P Switzerland. Fossil. Hungary. Ac- cording to the figures, the frustules 3.16. gibbous or rhomboid in the front view. 2 * Front view with marginal bead-like dots formed by the capitate ends of the costae (= Cystopleura, Bréb.). E. Argus (E., K.). —Front view rect- angular, with conspicuous ocelli termi- nating the stalk-like costae, and having distinct striae interposed between them. KB. p. 35, t. 29. f. 55. = Eunofia Argus, E.A. p. 125, & M. t. 15 A, f, 59. Europe, 760 SYSTEMATIC HISTORY OF TELE TNFUSORIA. Asia, Australia, and America, (xv. 11.) Valve lunately curved. Sporangial frus- tules with somewhat angular dorsum. A common species, easily recognized by the distinct marginal striae interposed between the rather distant, conspicuous bead-like ocelli. T 'i. alpestris (K.).—Front view rectan- gular or subcuneate, with conspicuous marginal ocelli and interposed striae : valves marrow, arcuate, with the rounded apices scarcely a little recurved. KB, p. 34, t. 5. f. 16. = E. ostrantina, Rab Diat. p. 19, t. 1. f. 29? France, England. (XIII. 8.) We are unable to distinguish this species from E. Argus; for we believe that the subcuneate front view is an accidental variation, and in specimens from M. de Brébisson we find that cha- racter by no means constant. Striae are interposed between the ocelli, as in E. Argus, and are nearly, if not quite, as distant as in that species; and we doubt whether recurved extremities of the valves are not sometimes found in both. E. reticulata (Nāg.).--Front view rect- angular, margins with stronger capi- tate and intermediate finer ones; valves slightly curved, the obtuse ends some- what attenuated; striae strong, 3 to 5 in 1-1200"; the interstices regularly reticu- lated, veined, margins finely transversely striated. KSA. p. 889. Switzerland. E. longicornis (E., S.). — Front view subrectangular, with conspicuous mar- ginal ocelli and striae, as in E. Argus; valves elongated, curved, with obtuse ends and slightly angular dorsum. SI3]), pl. 30. f. 247. = Eunotia longi- cornis, EMI., several figures. Europe, Asia, and America. (XV. 6–9). Costae strong, alternating with striated spaces. T'erhaps a sporangial state of E. Argus. E. ocellala (E., K.).--Front view bar- rel-shaped, with conspicuous marginal ocelli and interposed striae; valves lu- mately curved, with rounded apices. KB. p. 34, t. 29. f. 57; SBD. pl. 1.f. 6. = Eu- motia ocellata, E. Fresh water, Europe and America. Fossil. Greece, T. Eugenia (S.).--Front view inflated, with trumcate extremities; valves lunate, with straight, truncate extremities; costae distinct, 8 in 001"; ocelli con- spicuous; striae 32 in .001". S An. Jan. 1857, p. 7, pl. 1. f. 1. Fresh water. Biarritz, France. The nearest allies of this species are E. proboscidea and E. Sorea. It may be distinguished from the first by its distinct ocelli, and from the Second by its conspicuous costae and their areola-like interspaces, S, | E. comta (E.).--Small; valves curved, with regularly convex dorsum and rounded ends; striae strong and gra- nular. = Eunotia comta, E.A. 1840, & M. pl. 6. 2. f. 17 e, f. Fossil. Greece. We are not certain whether this and the next species are correctly placed in the ocel- lated section. E. Hellenica (E.). — Valves long, curved, with regularly convex dorsum and rounded ends; costae strong, 4 in 1–1200", having very delicate striae in- tervening between them. = Eumotia Hel- lenica, EA, 1840, & M. pl. 6. 2. f. 17 a, b. Fossil. Greece. - 3* Costae not capitate. E. constricta (Bréb.). — Front view elliptical, slightly constricted at the middle; valve semilunate, with 8 distinct costae in 001". SBD. vol. i. p. 14, pl. 30. f. 248. Brackish water. France and England. Striae 30 in .001". S. E. margaritifera (Rab.).—Front view barrel-shaped, with truncate ends and striated margins; valves with three dor- Sal undulations and rounded ends; costae 4 to 5 in 1–1200"; bordered by puncta, Rab Diat. p. 17, pl. 1. f. 32. Persia. E. Musculus (K.). —Front view sub- orbicular; valves lunate, with very con- vex dorsum, concave venter, and taper- ing acute apices; costae distinct. KB, p. 33, t. 30. f. 6; SBD. pl. 1. f. 10. = Eunotia Sphaerula, EM. pl. 8, 1, f. 6? Brackish water. Europe, Asia, Africa, and America, (XIII, 18.) Striae 40 in •001". S. - . E. rupestris (S.).-Front view elliptic or elliptic-lanceolate ; valves semilan- ceolate, tapering to the subacute apices; costae distinct; striae faint, 40 in 001". SBD, vol. i. p. 14, pl. 1. f. 12. E. gibbe- rula, K.B. t. 30. f. 3; KA. p. 3. = E. Westermanni, SBD. vol. i. p. 14, pl. 1. f. 11, Fresh or brackish water. Europe and America. * E. Quinquecostata (Rab.).-Valve semi- lanceolate, with obtuse ends, and five Somewhat converging costae. Rab Diat. p. 18, t. 1, f. 35. Germany. E. Hyndmani (S.).-Front view ven- tricose with truncate ends; valves stout, lunately curved, with rounded apices; striae moniliform, 16 in .001"; costae in- conspicuous. SBD. vol. i. p. 12, pl. 1, f. 1. = Eunotia Luna, EM. pl. 15A. f. 58. Britain, Large; valve not recurved. E. Westermanni (E., K.).-Front view elliptic; valves Scmilunate, with turgid, convex dorsum gradually attenuated to the rather obtuse not prominent apices; OF THE EUNOTTEAE, 761 striae scarcely converging, 7 or 8 in 1-1200". KB. p. 23, t. 30. f. 4. = Eu- notia Westermanni, E Inf. p. 190, & M, many figures. Europe, Asia, and Ame- rica. (IV. 2; IX. 157.) In Ehrenberg's figures the frustules are large, the stout valves have the obtuse apices somewhat produced and recurved, and the inter- stices of the costae furnished with dotted lines. E. gibberula (E.).-Front view elliptic, with slightly produced apices; valves with gibbous dorsum, slightly concave venter, and attenuated, recurved apices; striae converging, 33 in 001". = Eunotia gibberula, E.A. p. 125, & M, numerous figures. = E. Sorea, KSA, p. 1; SBI). vol. i. p. 13, pl. 1. f. 9. Fresh or brackish water. Common. Europe, Asia, Aus- tralia, Africa, and America, Costae in- conspicuous. E. Saaronica (K.).-Minute; front view rectangular; valves lunately curved, at- tenuated, with obtuse not recurved ends; striae subconverging, 6 to 7 in 1-1200". KB. p. 35, t. 5. f. 15. Italy and Ger- many. 1-840". E. Teatricula (E., K.). —Valve linear, lunately curved, with rounded ends; costae stout, distant; interspaces with series of longitudinal striae. KB. p. 35, t. 29, f. 53. = Eumotia Teactricula, E.A. p. 126, & M, several figures, Europe, Asia, Australia, Africa, and America. Small; ends not recurved. E. Zebra (E., K.). —Front view sub- linear ; valves semilunate, with convex dorsum, straight venter, and very obtuse, slightly prominent apices; costæ con- vergent, 5 to 7 in 001". KB. p. 34, t. 30. f. 5; SBD. pl. 1, f. 4. = Eunotia Zebra, E. Europe, Asia, Africa, and America. Striae 33 in '001". S. E. zebrina (E., K.).-Elongated; valves with evenly convex dorsum, gradually decurrent into the obtuse, constricted apices; interspaces dotted. KB. p. 34. = Eunotia zebrina, E.A. p. 126, & M, several figures. Asia, Australia, Ame- rica, and Europe. E. turgida (E., K.).—Large; front view linear or slightly dilated at the middle; valves curved, with the slightly convex dorsum gradually attenuated to the trun- cate apices, which are neither prominent nor recurved; striae diverging, 8 or 9 in 1–1200". KB. p. 34, t. 5. f. 14. = Eunotia turgida, E Inf. t. 14. f. 5. Europe, Asia, and America, (Iv. 1; IX, 159–161.) E. granulata (E., K.). – Large; front view linear or linear-oblong ; valves slender, slightly arcuate, with obtuse, recurved apices; striae moniliform; costae distinct. #. p. 35, t, 5. f. 20. E. Faba, KB. §: 36, t, 5. f. 21. = Eumotia granu- lata, E Inf, p. 191, t. 21, f. 20 = Epithe- mia turgida, SBD, vol. i. pl. 1. f. 2. Eu- rope, Asia, Africa, and America. E. Vertagus (K.).--Large; front view sublinear, gradually dilated at the mid- dle; valves slender, arcuate, with rounded, reflexed apices; costae converging, 10 in 1–1200"; striae punctate. . p. 36, t. 30. f. 2 = E. granulata, SBD. vol. i. t, 1... f. 3. Fresh water, Europe. Re- sembles the last, but the valves are far more slender. E. Librile (E., K.).—Large; front view rectangular; valves arcuate, with con- cave venter, dorsum evenly convex at the middle, suddenly decreasing towards the obtuse, slightly revolute apices; in- terspaces between the costae dotted. KB. p. 35, t. 29. f. 45. = Eunotia Librile, E Amer. p. 126, t. 3. 1, f. 38. Asia, Africa, and America. (XII, 24, 25.) E. Porcellus (K.).—Large; front view linear, seven times as long as broad; valves with convex dorsum, concave venter, and truncate reflexed ends; striae converging, 11 in 1-1200". KB. p. 34, t. 5. f. 18, 19. Fossil. San Fiore, (xIII, 12.) 1-240" to 1-216". E. proboscidea (K.). — Small; front view rectangular with obtuse angles; valves with gibbous dorsum, slightly concaye venter, and constricted, obtuse, remarkably recurved ends; costae con- spicuous, converging. KB. p. 35, t. 5. f 13; SBD, vol. i. p. 13, pl. l. f. 8? Fossil, Lüneburg; Britain; recent, Jer- sey. Costae 5 or 6 in 1–1200". British specimens have the front view inflated, and therefore may be distinct. E. P. marina (Donkin). — Dorsal view rectangular, with longitudinal series of uncta on the connecting zone; valves inear, slightly arcuate, with produced rostrate apices; costae conspicuous; in- terspaces punctated. Donkin, TMS. vol. vi. p. 29, pl. 3. f. 14. Marine. Eng- land. A large and beautiful Diatom, whose genus is somewhat uncertain. It agrees with Amphora in having the lon- gitudinal rows of puncta confined to the dorsal surface, whilst in the form of its valves it resembles some species of Nitzschia, Costae and striae 11 in 001". Donkin. Doubtful and insufficiently known species. E. Electra = Eumotia Electra, EMI, pl. 37. 3. f. 3. Fossil, Prussia, Valve Semiorbicular, with strong, radiant striae, 762 SYSTEMATIC HISTORY OF THE INFUSORIA. !. E. Lindigii (Rab.). — Minute; front view orbicular; costae 6 to 7. Rab Diat, p. 19, pl. l. f. 20. Bogota. E. Sanct; Antoni = Eunotia Sanct; Antonii, EM. pl. 34, 5. f. 7, &c. Ame- rica. Front view rectangular, with conspicuous marginal capitate striae; valves obtusely lanceolate, straight, with strong transverse costae. Probably a Denticula. E. Beatorum = Eunotia Beatorum, EM. pl. 34. 5. f. 8. America. Front view rectangular, with marginal gland-like puncta. According to Ehrenberg, this species is allied to E. Sancti Antonii. JE. Lunula = Jºumotia Lumula, EM. l. 33.7. f. 9, & pl. 33. 14. f. 8. Ehren- erg's figures differ considerably. The first is slightly arcuate, elongated, with obtuse, slightly recurved ends; the se- cond is smaller, lunate, rapidly tapering to the obtuse ends. Both have radiant costae without intermediate dotted lines. E. mesolepta = Eunotia mesolepta, EM. pl. 9. 1. f. 26. Fossil. France. Valves elongated, slightly curved, with attenu- ated middle, and conic ends; costae alter- nating with dotted striae. E. mesogongyla- Eunotia mesogongyla, EM. pl. 9, 1. f. 27. Fossil. France. Valves linear, elongated, slightly curved, with gibbous middle, and rounded ends; costae alternating with dotted striae. E. P Faba (E., K.).—Valves semioval, slightly arcuate, with obtuse, very slightly recurved apices, and 9 moniliform striae in 1–1200".= Eumotia Faba, EMI. Seve- ral figures. Ehrenberg's figure seems to us rather to represent a Eunotia than an Epithemia. e E.? cingulata (E., K.).—Small, Smooth, with convex dorsum and tumid connect- ing zone. KB. p. 36. = Eunotia P cin- gulata, E.A. p. 126, t. 2.6. f. 34. North America. in to E. gibberula, E. E. Cocconema = Eumotia Cocconema, EM. pl. 34. 7. f. 1. Canton. Valve stout, semilunate, with regularly convex dorsum, straight venter and rounded ends, strong costae, fine intermediate striae, and a longitudinal blank line. E. Cistula = Eumotia Cistula, EM. i. 8, 1. f. 5, &c. Asia. Front view ob- ong or elliptic, with costate margins; valves Stout, lunate, with obtuse ends, strong, radiating costae, and a blank longitudinal line. Genus EUNOTIA (E.). — Frustules free, in front view quadrangular, in lateral view lunate, or arcuate, and striated. In form, Eunotia is allied to Epithemia; but the lateral surfaces of the frustules are merely striated, and want the conspicuous costae of that genus. The Superior margin is usually undulated,—an appearance caused by transverse depressions. The frustules are not adnate, and in the front view do not appear beaked. We believe that the species in this genus, as in several others, have been founded upon insufficient characters, and that those forms which differ only in the undulations should, as Professor Bailey suggests, be regarded as varieties. As this work, however, is intended to include all generally admitted species, we are content to indicate our opinion, the correctness of which must be determined by future observations. Kützing and Meneghini describe the transverse section as trapezoidal, and regard it as an important generic character; but we agree with Professor Smith in doubting the occur- rence of such a form. Several species of Eunotia have been found by Bailey and Brébisson united into short bands; and unless the generic characters of Eunotia and Himantidium can be strengthened, it will become necessary to reunite these genera. The dorsal elevations in Eunotia and Himantidium appear, in the front view, transverse darker bands. rica. Akin to E. modosa, but with in- # •zoº, ! 7 & e e Dorsal margin of valves not dentate flated and straight apices. E. EUNOTIA nodosa (E.).-Valves slightly arcuate, with inflated centre and reflexed obtuse apices. ERB.A. 1840, p. 15, & M. pl. 15 B. 3. f. 25. Asia and America. Lough Mourne deposit. E. Formica (E.).-Valves linear, with inflated centre and ends. EA, p. 126, & M, pl. 3, 4, f. 18. Australia and Ame- E. ventralis (E.). —Valves elongated, linear, curved, with tumid, rounded apices, and gibbous venter. EA. p. 126, & M, several figures. Europe, Asia, Africa, and America. E. Luna (E.).-Valves linear, lunately curved, with simply convex dorsum, gibbous venter, and obtuse apices, OF TELE EUNOTIE ZE. 763 ERBA. 1845, p. 77, & M, pl. 33. 12. f. 13. Fossil. Oregon. E. Sima (E.).-Valves linear, slightly curved, with rather concave venter; dorsum suddenly sloping down to the roduced, acute, reflexed apices. ER A. 1845, p. 77, & M. pl. 33. 12. f. 16. Fossil. Oregon. E. biceps (E.).-Valves linear, curved, with dilated, slightly revolute, broadly rounded ends. EA, p. 125, & M. pl. 5.2. f. 36. Europe and America. Some at least of Ehrenberg's figures in the ‘Mi- crogeologie' belong to Synedra flexuosa. E. Alpina (K.) = Himantidium Hal- cyonellae (Perty). — Valves with turgid convex dorsum, slightly produced sub- truncate apices, and very fine transverse striae, KB. p. 36, t. 3. f. 10, Switzer- land. E. incisa (Greg.). — Valves arcuate, slender, with obtuse or subacute apices, and subterminal notches or depressions on the ventral margin; striae fine, 44 in ‘001". Greg M.J. vol. ii. p. 96, pl. 4. f. 4. Lapland, Scotland. E. Plectrum, E.M. pl. 6. 2. f. 15. Fossil. Sweden. Valve semilunate, con- stricted beneath the capitate apices; venter straight; dorsum evenly convex. E. Hemicyclus (E.).--Small; valves linear, curved, semicircular, with obtuse apices and distinct transverse striae. = Synedra Hemicyclus, ERBA. 1840, & M. t. 16. = E. Falc, Greg MT. vol. ii. . 105; M.J. vol. iii. pl. 4, f. 1. Fossil. weden. 2 * Valves with two dorsal and three ventral wºndulations. E. Crocodilus (E.).-Valves elongated, slightly curved, with two dorsal and three ventral undulations; apices pro- duced, subacute, reflexed. ERBA. 1845, p. 77; M. pl. 34, 5 A. f. 4. Africa and America. E. Tapacumaé, E.M. pl. 34, 5 A. f. 5. America. Valve with two dorsal and three ventral undulations separated by deep sinuses; apices abruptly produced into a short beak. E. Tapacumaé seems to differ from E. Crocodilus in its stouter form, deeper sinuses, and more abruptly produced apices, 3 * Valves with dentate or cremate dorsum. E. Camelus (E.). — Valves striated, small; dorsum with two approximate rounded elevations, sloping to the atte- muated, produced, obtuse apices, EA, p. 125, t. 2, 1. f. 1. Asia, Africa, and America. E. bidentula (S.).-Valves faintly stri- ated, with two prominent, acute or rounded dorsal ridges, very straight ventral margin, and obtuse, produced apices. SBD, vol. ii. p. 83. E. Camelus, Grev ANH. 2nd series, vol. xv. pl. 9. f. 1. Britain. Differs from B. Camelus in its straight ventral margin. IE. Sella (E.).-Valve dilated; ventral margin straight; dorsum with two central ridges, from which it * with a re- gular convexity to the acute apices. E.A. p. 126, t. 2. 1. f. 7. America. E. Zygodon (E.).-Valves linear; dor- Sum with two approximate ridges, from which it passes by a curvature to the rounded apices, EA, p. 127, t. 2, 1.f. 6. America. E. declivis (E.). — Valves with plane venter; dorsum convex, with two ridges which slope to the acute apices. E.A. p. 125, t. 2. l. f. 3. America. E. impressa, EM. pl. 2. 2. f. 30, &c. America. Small, striated; valves nar- row, linear, with two slight dorsal un- dulations and obtuse . Perhaps a bicrenate state of E. tridentula. E. bactriana, EM. pl. 16. 1, figs. 29, 30, & pl. 16. 2. f. 19. ji Sweden. This seems a distinct species, with linear, nearly straight valves, and two remote, minute dorsal teeth. E. diodon (E.). —Valves stout, with two rounded dorsal ridges and broadly rounded ends; striae distinct, radiant. E Inf. p. 192, t. 21, f. 23; SBD. pl. 2. f. 17. Recent and fossil. Europe, Asia. Africa, and America.-This and the thir- teen following species of Ehrenberg we regard as mere varieties, which differ only in the number of their dorsal elevations. The species may be called E. robusta: its valves are stout, semilunate, with concave venter, broadly rounded ends, turgid convex dorsum furnished with conspicuous, rounded, diverging ridges, and the striae are strongly marked and highly radiant; as, however, the valves increase in length, according to the in- creased number of dorsal ridges each is comparatively more slender than its pre- decessor, and the ridges are smaller and resemble cremations. IE. triodon (E.). — Has three dorsal ridges; otherwise resembles E. diodom. £ff p. 192; SBD, pl. 2.f.is. Recent and fossil. Europe, Asia, Africa, and America. (IV. 4; IX, 164.) E. tetraodon, E., Sm., K., Rab. ; E. pentodon, E., K, ; E. Diadema (6 cre- 764 SYSTEMATIC HISTORY OF THE INFUSORIA. nations), E., K., Sm. ; E. heptodon, E., K. ; E, octodon, E., K. ; E. emnaodon, E., K. ; E. decaodon, E., K, ; E. hen- decaodon, E., K. ; R. dodecaodon, E., K. ; E. serrulata (13 crenations), E., K. ; E. prionotis (14 cremations), E., K. ; E. polyodon (all forms with more than 20 cremations), E., K. Fossil and recent. Europe and America.-Bréb., Rab., and Rütz, place E. tetraodon in Himanti- dium because the frustules are occa- sionally united into short tablets. We are unable to concur with them. E. Elephas(E.).-Valves stout, curved, with three dorsal teeth and broadly rounded ends, EA, p. 126, t. 1, 4, f, 5. Brazil. E. dizyga (E.). — Valves striated (?), semilunate; dorsum with four teeth, ap- proximate at the middle, EA, p. 126, t, 2. 1, f. 8. Cayenne. E. Corona (Rab.).—Valves nearly as broad as long; dorsum turgid, with five ridges; venter shorter, and separated from dorsum by a constriction. Rab Diat. p. 17, t. 1, f. 36. Italy. Striae di- stinct, radiant. E. tridentula (E.). — Small; valves finely striated, curved, narrow-linear, with three slight dorsal cremations, and obtuse recurved apices. EA, p. 126, t. 2. 1, f. 14; Grev Annals, 2nd series, xv. pl. 9. f. 2. Europe, Asia, Africa, and America.--We would unite this with the following thirteen species under the name of E. Ehrenbergii. The valves are linear, curved, with Small dorsal teeth or cremations, and become larger and longer in proportion to the number of their teeth. The striae are less radiant than in E. robusta, and the dorsum less turgid. E. quaternaria, EA, ; E, quinaria XII, 39), EA, ; E. Senaria, E. Septena, EA. = E. Septenaria, EMI. ; E, octondria, JE. monaria, E. demaria, E. undenaria, E. Terra (12 crenations), E. tridenaria, E. quatuordenaria, E. Quindenaria, E. bioctonaria. Recent and fossil, Eu- rope, Asia, Africa, and America, Ehr., Kütz. E. scalaris (E., K.).—Dorsum with 17 dorsal teeth. EM. pl. 17. 1, f. 44. Fossil. Finland. In this and the two following species Ehrenberg probably included forms belonging to E. robusta and E. Ehrenbergii. E. icosodon (E., K.).—Valves striated, linear, curved, with 20 dorsal teeth, ERBA. 1845, p. 77; Microg, pl. 33. 10. f. 3. Fossil, America. E. polyodon (E.) resembles E, icoso- don, but has more than 20 dorsal teeth. E. l.c. p. 77; Microg. pl. 17. 1, f. 45. Fossil. Finland. Doubtful and insufficiently known Species. E. triglyphis (E.) = E. triodon, Ralfs, Annals, vol. xiii. pl. 14, f 3 P Africa and America. Sussex P E. tetraglyphis (E.). Asia, Africa, and America. E. pentaglpphis, EM. pl. 16. 2. f. 22, & pl. 17. 1, f. 32. Europe, Asia, and America. Valves minute, linear, with five dorsal, approximate teeth. (Iv. 3.) E. heavaglyphis, EMI, pl. 16. l. f. 34, & pl. 16. 2. f. 24. Europe and Asia. Resembles E. pentaglyphis, but has six dorsal teeth. The above forms are probably only varieties. They seem to differ from E. Phrenbergii in more minute size, obso- lete or indistinct striae, and approximate teeth, E. Amphidicranon (E.). — Valve qua- drangular, straight, transversely striated, with constricted middle and emarginate ends. . . ERBA. 1845, p. 77; Microg. t. 33.12. f. 14. Fossil. Oregon. E. brevicornis (E.). — Oblong, dilated with Suddenly acutely rostrate ends; venter slightly concave at the middle; dorsum slightly convex, nearly smooth (very finely striated?). ERBA. 1845, p. 363. Marine. India. = A. Nitzschia P E. Creta (E.).-Valves striated, nar- row-lanceolate, acute, very gradually at- tenuated at each end. ERBA, 1844, p. 81; EMI. pl. 22. f. 55, 56. Cocoonema Cretae, E. Fossil. Sicily. E. Pileus (E.).--Small, striated, sub- quadrate; venter wider than dorsum, the latter slightly furrowed; ends ob- tuse, rather prolonged. E.M. pl. 39. 3. f 42. Siberia, Africa, and America. E. Gangetica, EM. pl. 35 A. 9. f. 2. India, Fragments large, striated, with straight venter, convex dorsum, and broadly truncate apices, which are slightly produced dorsally. JE. Australis; E. caelata; E, Cygnus; B. Paradoara, E. Serpentina, Australia, Ehr. ; E. Phrygia: E. lepida; E. Mosis; E. rostrata; E. Uralensis; E. apiculata; E. Siberica; E, borealis; E. Leptostoma; P. umbilicata, Asia, Ehr. ; E. subulis; E. curva i E. carinata, Africa, Ehr.; E. Araucaniae; E, edulis, America, Ehr, ; E. Januarii, Brazil, Ehr.; E. Guianensis; E. Demerarde: E. Pomeroni; E. Savannae; E. Synedra, Guiana, Ehr. ; E. Columbi, Columbia, Ehr. OF TEIE EUNOTIE ZE, 765 Genus AMPHICAMPA (E.).-Frustules in lateral view lunately curved, having pervious transverse striae and denticulated margins. Amphicampa is closely allied to Eunotia and Himantidium, but differs in having teeth on both margins. - AMPHICAMPA mirabilis (E.).-Valves | EMI. pl. 33. 7. f. 2. = 4. Eruca, EMI, linear, with rounded ends; dorsum with pl. 33.7. f. 1. Mexico, (IV. 5.) six or seven teeth, and venter with five, Genus HIMANTIDIUM (E.).-Frustules united into filaments or tables; lateral view arcuate or lunate, transversely striated. If all the species in Himantidium formed ribbon-like filaments, there would be no difficulty in distinguishing it from Eumotia; but this is not the case, and Kützing has well said, “It must be noticed that in many species of Himantidium the individuals are not always united into a band, and therefore the generic character is very variable and stands on a weak foundation.” Professor Smith observes that “there is no mark to distinguish the valves of the two genera unless it be in the character of the striae, which in Eunotia are radiate and in Himantidium parallel.” If the striae were indeed always radiate in the one genus and parallel in the other, a valuable diagnostic mark would be furnished; but, unfortunately, the convergent striae occur only in those species of Eumotia which have a strongly convex upper margin. In the front view Himantidium resembles the Fragilarieae, but in that family the lateral view is not arcuate. ... * Dorsum simple, HIMANTIDIUM pectinale (Dillwyn, K.). —Frustules united in long filaments; valves linear, arcuate, with flattened dorsum suddenly sloping to the obtuse apices, and slightly concave venter; striae 27 in .001". RIB. t. 16; SBL). p. 12, pl. 32. f. 280. = H. minus, KB. . 39, t. 16. f. 10; H. strictum, Rab #. t. 1, f. 1 C ; Fragilaria pectinalis, Lyngb.; Fragilaria grandis, E Inf, in art; Eunotia depressa, E.A. p. 126. Hºpe, Asia, Africa, and America, IV, 6. ( H. Soleirolii (K.).-Valves lunate, with evenly convex dorsum, concave venter, and rounded ends; striae 30 in 001". RB. p. 39, t. 16. f. 9; SBD. vol. ii. p. 13, pl. 33. f. 282. = Himantidium Faba, EM. t. 1. 2. f. 3.; Eunotia Faba, E. in art P Europe and Africa. (XIV. 13.) t might have been preferable to have adopted Ehrenberg's name for this spe- cies, since it is evident that the H. Soleiroli; of Kützing was intended to include all forms with internal siliceous cells, and his figures of the valves belong to another species. H. parallelum (E.). — Valves linear, strongly striated, curved, with simply rounded ends. EM. pl. 14. f. 58. = Eu- motia parallela, E.A. p. 126. Europe, Asia, Africa, and America. H. monodon (E.). — Frustules large, few together; valves arcuate, with some- what gibbousdorsum, and obtuse, slightly produced apices; striae 34 in 001". EA. p. 129, t. 4. = Eumotia monodon, EM, many figures. SBD. vol. i. pl. 2. f. 16. Common. Europe, Asia, Australia, Africa, and America. (xv. 16, 17.) H. praeruptum (E.). —Valves striated, elongated; dorsum very convex, with a notch-like depression near the dilated truncated apices. = Eunotia praerupta, EA. p. 126, & M, several figures. Asia, Australia, and America. According to Ehrenberg's figures, its valves scarcely differ from those of H. monodon, except by their more truncate apices, and can scarcely be placed in another genus. H. Arcus(E.).-Valves linear, arcuate; dorsum sinuated towards the rounded dilated apices. ERBA, 1840, p. 17, & M, many figures. = Eumotia Arcus, EMI. Europe, Asia, Australia, Africa, and America. 8, extremities gradually taper- ing, = H. attenuatum, Rab Diat, p. 19, t, 1. f. 10. Germany. H. gracile (E.). —Valves slender, nar- row-linear, slightly arcuate, with obtuse, somewhat recurved extremities. E.A. . 129, t. 2; SBD. vol. ii. p. 14, pl. 33. . 285. = Eunotia uncinata, EA, p. 126, & M. pl. 15 B. f. 23. Europe, Asia, Australia, Africa, and America. Habit of H. Argus, but more slender, E. Striae 27 in 001'', S. 766 SYSTEMATIC, ELISTORY OF TELE INFUSORIA. H. majus (S.).-Valves linear, arcuate, with rounded, subcapitate extremities; striae 27 in 001". SBD. vol. ii. p. 14, pl. 33. f. 286. Britain. Differs little from H. gracile, save in its greater size and elevated dorsum, and is probably a sporangial form of it or some other species, S. It scarcely differs from some of Ehrenberg's figures of H. parallelum, except in its more inflated ends. H. exiguum (Bréb.). —Valves slender, narrow-linear, arcuate, with obtuse re- curved extremities, and 42 very delicate striae in .001". KSA. p. 8. Eunotia gracilis, SBD, vol. i. p. 16, pl. 30. f. 249. Europe. H. Veneris (K.). — Valves smooth, plano-convex, with acute apices, t p. 39, t. 30. f. 7. Eunotia lavis, EMI. pl. 39. 3. f. 41. Trinidad. 2 * Valves with cremate or toothed dorsum. H. bidens (E.).-Valves with plane or slightly concave venter, biundulated dorsum, and dilated, truncate apices. EA. p. 9, & M, several figures. = Eu- motia bidens, E.A. p. 125, & M. pl. 2. 1. f. 2; Eunotia bigibba, KSA, p. 6 P. Eu- rope, Asia, and America. The dorsum has a notch-like depression near each end. H. Guianense (E.).-Valves dilated at the middle, with two dorsal undulations, and tapering, slightly reflexed ends. EA. p. 129, t. 2, 1, f. 4. Cayenne, (XII. #) H. Papilio (E.).-Valves subquadrate, with a much dilated bicrenate dorsum, constricted near the obtuse apices, EA, p. 129, t. 2. 1. f. 2. Asia and America. (xII. 45, 49–52.) H. undulatum (S.). — Valves linear, with gibbous venter, three or more slight dorsal undulations, and obtuse, somewhat recurved apices. SBD, vol. ii. p. 12, pl. 38. f. 281, Europe, Distin- guished from the other British species by its gibbous venter. H. denticulatum (Bréb.).--Valves very marrow, arcuate, with denticulated dor- sum and slightly recurved apices. RSA, p. 10. France. Dorsum mar- gined with minute teeth, constricted near the rounded apices. H. triodon (Perty). —Valves smooth, with concave venter, convex triundu- lated dorsum, and broadly rounded ends. Perty, Inf. p. 198, t. 17. f. 5. Switzer- land. Very like Eunotia diodon; but striae have never been observed. Frus- tules mostly clear as crystal. Perty. H. ternarium, EMI. pl. 34, 6 A. f. 5. Florida. Valves arcuate, with slightly concave venter, three dorsal undulations, and obtuse apices. H. quaternarium (E.). —Valves mar- row, very finely striated; dorsum a little convex, deeply four-toothed ; venter slightly concave, with attenuated and recurved apices. ERBA. 1852, p. 235. California. Joints of the chain 4 to 7, three times as broad as long, E. H. quinarium (E.). —Valves as in H. quaternarium, but with five dorsal teeth. E. l. c. p. 535. California, Asia, and Africa. Joints of the chain 14, five times as broad as long. The frustules of H. quaternarium and H. guinarium are very similar to those of Eumotia quaternaria and E. quinaria, but are distinguished by forming chains and by the attenuated ends of the valves, E. Doubtful Species. H. carinatum, EM. pl. 34, 6 A. f. 6. Florida. Frustules rectangular, Smooth, with a transverse median band. H. P. marinum (S.). — Filaments tena- cious; valves costate, slightly and regu- larly arcuate, with acute apices; costae 10 in 001". SAnnals, Jan. 1857, p. 10, pl. 2. f. 14. Marine. France. Distin- guished by its marine habitat and costate valves. Species known to us only by name : probably several of them are merely concatenated States of Eunotia and Epithemia. B. Australia, E., Australia; H. Ca- melus, E., Asia; H. Teatricula, E., Asia; B. Zebra, E., Asia; H. ventrale, E., Asia; II. amphioacys, E., Asia; H. umbilicatum, E., Asia ; H. &thiopicum, E., Asia; H. Falklandii, E., Falkland Islands. FAMILY II.—MERIDIEAE. Frustules prismatic, attenuated at the base, attached, at least when young, to a gelatinous cushion; in front view cuneate, in lateral view clavate or obovate, with pervious transverse costae or striae. Rützing places the Meridieæ between the Eunotieae and Fragilarieae; and Meneghini would unite them OF TELE MERIDIE ZE. 767 with the latter, for he “does not consider the cuneate form of the frustules of any value in an organological point of view,” because of the occasional occurrences of such frustules in Diatoma and other genera of the Fragilarieae. In the latter family, however, the cuneate frustules, when present, are in general interposed between those of the normal shape, and the lateral Surfaces have not dissimilar extremities. Kützing observes that “the forms of this family have very great similarity to those of Gomphonema, with which they may be the more easily confounded when the individuals occur singly; but they are essentially distinguished from that genus by not having a central nodule in the secondary sides, and by their uninterrupted transverse striae. Moreover, this family is much more closely united to the genus Odontidium, from which it is distinguished solely by the form of the secondary sides, which are not symmetrical at both ends.” We, however, consider its affinity with the Licmophoreae still more evident. The Meridieæ, Licmophoreae, and Gomphonemea, “form a group [the Styllarieae of Agardh] distinguished by the triangular form of the frustules, which have their smaller ends directed towards a common centre. The frustules in this group have a central and two lateral portions, as in Diatoma and Fragilaria, in which genera cuneate frustules are also occasionally met with. But in the Fragilarieae, when two or more cuneate frustules are united, the alternate frustules have their Smaller ends, in opposite directions, and hence their filaments are linear; whilst they are attached, if at all, only by the basal frustule. In this group, on the contrary, as the smaller ends are in the same direction, they point to a common centre, and when stipitate, each frustule is attached to the stipes” (Ralfs). The frustules in the Meridieæ have two puncta at the broader end, and sometimes other two, but more obscure, at the smaller end ; they want, however, the sutural or fracture-like longitudinal lines which are present in the Licmophoreae. - Genus MERIDION (Leibl., Ag.).-Frustules cuneate, united in a spiral filament; transverse costae of lateral surfaces pervious. “The species vary according to the circumstances of development, as well with respect to size as to other relations. The individuals are met with both singly among other Algae and also in masses. At times examples are found which are always composed of only few individuals; others again consist of individuals united in greater number; but generally the longer spiral ribands are rare.” (Kütz.) Professor Kützing formed a new genus (Eumeridion) for the reception of M. constrictwm ; but his reasons have been considered inadmissible by De Brébisson, Meneghini, and Smith. Meridion is remarkable for the frequent occurrence within its frustules of an obovate silicious cell, which is usually, but not invariably, divided into two symmetrical portions by a longitudinal suture; the lateral margins of the inner cell, as well as the sutural line, are crenulate like those of the original frustule. The different aspect presented by specimens in this condition has induced some observers to describe them as a distinct species. Whilst we agree with Professor Smith that the modi- fication is insufficient to warrant such a separation, we cannot coincide with him in regarding it even as a variety, since frustules with these internal cells are indiscriminately mixed with ordinary frustules in the same filament. So: common, indeed, is this occurrence, prior to the termination of individual life, that we have long been convinced that it is the normal mode of termination in this genus. MERIDION circulare (Grev., Ag.). — = M. vernale, E.; M. Zinckeni (with in- Frustules in lateral view clavate or termal cells), KB, ; B. curvatum, K. obovate. SBD, vol. ii. p. 6, pl. 33, f. 277, Frustules slightly arcuate, Common, 768 SYSTEMATIC HISTORY OF THE INFUSORIA. forming a mucous brown stratum on leaves, stones, &c., in shallow waters. 8, France. (Ix, 177, 178; xIII, 21, M. Zinckeni.) In both the primary and in- termal cells the lateral margins have a beaded appearance, produced by the ends of the lateral costae. M. constrictum (Ralfs).--Lateral valves constricted beneath the apex, otherwise as in M. circulare, SBD, vol. ii. pl. 32. f. 278. = Eumeridion constrictum, KSA. p. 11. Common. Europe. Internal cells as in M. circulare. We have received very perfect specimens from Mr. Okeden, gathered in Wales. Doubtful Species, - M. P. panduriforme (E.). — Lateral valves constricted near the ends, the capitate extremity acuminated. E Infus. pl. 16. f. 3. 1-430". Form that of Gom- phonema acuminatum. M. Povatum (Ag). — Frustules ovate, combined into a cellulose lamina. ICSA. p. 10. Sweden. M. P. coccocampyla, E.M. pl. 14. f. 79. Berlin. Perhaps a bad figure of one of the preceding species with internal cells. - * M. marinum (Greg.). — Front view Sublinear, with coarse marginal puncta; valves clavate, with 16 coarse marginal striae in 001", and a blank longitudinal median line. Greg D Clyde, p. 25, pl. 2. f. 41. Marine. Scotland. Frustules two to four together. Certainly not a true species of this genus, as its costse are not pervious. Genus ONCOSPHENIA (E.).-Frustules quadrangular, cuneate, not con- catenate; valves without an umbilicus, and also destitute of lateral apertures; and internal septa equal, but their apices unequal on account of their cuneate and uncinate form. Oncospheniae approach nearest to Podosphemiae by the absence of pedicels in the latter, but are peculiar in their uncinate form. We are unacquainted with this genus, and ignorant of the reasons which induced Professor Kützing to place it among the Meridieæ. * ONCOSPHENIA Carpathica (E.).-La- nules 11. Probably a distorted state teral valves cuneate, laxly striated; one of some other species similar to the end turgid, rounded, straight, the other | variety of Diatoma elongatum figured by attenuated and uncinate. KSA, p. 11. | Professor Smith in BD. pl. 60, f, 311. Carpathian Mountains. 1-792": pin- FAMILY III.—LTCMOPHOREAE. Frustules cuneate, longitudinally bivittate, attached or stipitate, Solitary or united in a fan-like manner; lateral surfaces striated or smooth, but not costate. The frustules in the front view are cuneate, and have, like the generality of the Diatomaceae, two puncta at each end, the upper ones, how- ever, being most conspicuous. Most frequently two longitudinal suture-like lines, corresponding to the puncta, are more strongly marked in the Licmo- phoreae than in most other families; these Kützing calls “vittae,” and has formed a tribe which from them he calls “Diatomeae vittatae.” The vittae, however, are not peculiar to this tribe ; for, as Meneghini justly remarks, “ they are merely the same longitudinal lines which run along the primary surfaces of almost all the Diatomaceae” (MeD. p. 462). Professor Smith describes them as “modifications in the outline of the valve, which in Podo- sphenia is slightly inflected at its larger extremity, causing, on a front view, the appearance of notches at the spot where the valves unite with the con- necting membrane (central portion) and the foramina exist. The apparent prolongation of this notch to the lower extremity of the frustule is nothing more than the valvular suture which is seen in all the Diatomaceae" (SBD. vol. i. p. 82). The cuneate shape of the frustules in the front view, and the dissimilar ends of the lateral surfaces, distinguish the Licmophoreae from Synedra, the species of which often resemble them in habit. OF TEIE LICMOPEIO.R.E.E. - 769 Genus PODOSPHENIA (E.). —Frustules affixed, in front view cuneate, in lateral view clavate, stipes none or obsolete. Podosphenia is identical with Styllaria (Ag). Its sessile frustules distinguish it from the rest of the Licmophoreae, and the absence of transverse costæ from the Meridieæ. “This genus represents in the Licmophoreae the genus Sphenella of the Gompho- nemea ; for, like that, it is distinguished from other genera of the same family by the more or less complete absence of the stipes. The obovate–lanceolate figure of the Secondary surfaces is precisely that of the Sphenellae and of the Gomphonemea in general. The cuneate form of the primary surfaces is, in Podosphenia, always more dilated at the summit and acute at the base, so that they resemble a triangle more than a trapezium.” (M. l. c. p. 462.) Podosph ENIAgracilis (E.).-Frustules narrow cuneate, elongated, with some- what acute base; lateral view clavate, smooth or with very obscure striae. KB. t. 9. f. 10. 1. Europe, (x, 186.) 3, minor 1–250" to 1-110". P. tenuis (K.).--Linear cuneate, elon- gated, very slender, with acute base; lateral view narrow-clavate, KB. t. 30. f. 51. Norway. P. nana (E.).--Small, Smooth, narrow linear cuneate; lateral view clavate with- outlines. EM. pl. 11. f. 18, 19. Fossil. Bilin, Bohemia. 1-2300" to 1-1720". P. debilis (K.). — Smooth, marrowly cuneate, rather acute at the base, Sub- flabellate. KB. t. 8. f. 7. Europe. 1–1380". P. tergestina (K.). — Cuneate trian- gular, geminate or ternate, conjoined in a flabellate manner, base rather acute. KB. t. 8. f. 13. Trieste. 1-1440". P. hyalina (K.). — Very hyaline, cu- neate, with approximate vittae and sub- acute base; lateral view obovate pyri- form. KB. t. 10. f. 2, 3, racemosa, K., obsoletely stipitate, t. 10. f. 3. Europe. 1-570" to 1-480". P. cuneata (Lyngb., Ag.). — Broadly cuneate with rather acute base; lateral view clavate or obovate, with obscure striae. = Styllaria cuneata, Ag, ; Podosphe- nia abbreviata, E.; P. Lingbyei, SBD. Europe. gº 13 b.) I-240". Striae 46 in 001'', S. Broader and shorter than P. gracilis. P. Jürgensii (Ag., K.). —Broadly cu- neate with truncate base; lateral view clavate, with obscure striae. SBD. i. . 83, pl. 25. f. 228. Europe. 1-432". triae 48 in .001", Š. P. ovata (S.).-Cuneate with rounded angles; lateral view obovate, tapering into an acute base; striae moniliform. SBD. i. p. 83, pl. 24. f. 226. Shoreham harbour. Striae 24 in 001", 0.033" to -0042", S. P. Ehrenbergii (K.). —Large, broadly cuneate; lateral view tapering at both ends and with distinct moniliform trans- verse striae. SBD. pl. 24. f. 225. Eu- rope. (IV. 7; XIII. 14.) 1-140". Striae 27 in .001", Š, Doubtful Species. P. Pupula, EM. Several figures. Ehr- enberg's figures have a clavate lateral valve with pervious transverse costae and with or without a constriction. All pro- bably belong to Meridion circulare and M. constrictum. He gives about twenty stations for this species in different parts of the globe, none marine. Genus RHIPIDOPHORA (K.).—Frustules stipitate, in front view cuneate, in lateral view obovato-lanceolate (“with a median longitudinal line,” S.). “We encounter the same difficulty in distinguishing Rhipidophora from Podosphenia that is experienced when practically applying the generic distinction established between Sphenella and Gomphonema and in all other similar cases (Cymbella and Cocconema, &c.); these differ only in the stipes, which is very variable in length and not always entirely wanting in the first of these two genera. “The large size of some among the species enumerated by Kützing permits us to observe clearly the conformation of the shield. Let us suppose a cylindrical articulation of Melosira, and so compress it unequally on one of its sides, and in the direction of both pairs of opposite surfaces, that the resulting form shall be cuneate, and the two incomplete diaphragms formed by the internal prominence of the longitudinal canals shall extend like these 3 D 770 systEMATIC HISTORY OF THE INFUSORIA. and lose themselves towards the pointed extremity which forms the base; such is the structure of Podosphenia and Rhipidophora. Viewed on one side, that is, on the lateral Surfaces, they present an obovate arch, marked on the periphery of the surfaces themselves. The margin of this arch is thickened by the presence of the canal, which, seen in front, presents in the curve its brightness with an appearance of perforation.” (Meneg l.c. p. 463.) Professor Smith says that “a close examination of the frustules shows us that the distinct and even moniliform striae so conspicuous in Podosphenia are almost wholly wanting in our native species of Rhipidophora.” The striae in the former genus, however, are not always detected with facility, since Meneghini remarks that “ of the nine species described and figured by Rützing, only one (P. Ehrenbergii) presents transverse striae on the secondary surfaces.” Careful observation of the species of Rhipidophora in a growing state will probably prove that several of them have been constituted upon insufficient grounds. It is to be feared, indeed, that characters taken from the comparative length and stoutness of the stipes, its simple and branched condition, and even the shorter or longer form of the wedge-shaped frustules in the front view, are more or less fallacious. We believe that at least some of the species are at first furnished with a short, thick, simple stipes, bearing the associated frustules at its apex, and that by the process of growth the frustules become longer in proportion to their breadth, and lose their flabel- late arrangement by the subsequent elongation and dichotomous division of the stipes. RHIPIDOPHORA crystallina (K.). — Shortly stalked, flabellate ; frustules shortly cuneate, rather broad, obtuse at the base. KB. t. 9. f. 10. 5. German Sea, 1–1200" to 1-1300" R. QEdipus (K.).-Veryshortly stalked, subflabellate; frustules oblong cuneate, truncate at the base; stipes hemisphe- rical. ICB. t. 18. f. 5. 5, 7, Europe. 1-600" to 1-480". B. Anglica (K.). — Shortly stalked, flabellate; frustules turgid, cuneate with truncate base and obtuse terminal angles; stipes rather long, simple, thick. KB. t. 27. f. 5. 2, 4, Europe. 1-600". R. Australis (K.). — Flabellate; frus- tules narrowly cuneate with truncate base; stipes simple, thick. KB. t. 9. f. 5. Trieste. 1–540". R. borealis (K.). — Flabellate; frus- tules large, oblong cuneate with slightly obtuse base; stipes simple, rather stout. KB. t. 9. f. 6. Heligoland. 1-310". R. Nubecula (K.).-Frustules hyaline, broadly cuneate, somewhat acute at the base, scattered, subsolitary or fasciculate, lateral and terminal; stipes filiform, elongated, subramose. KB. t. 8. f. 16. Europe. (XIII. 17.) 1-720" to 1-600". R. tenella (K.). — Minute; frustules small, broadly cuneate, conjoined in an imperfectly flabellate manmer, acute at the base ; stipes slender, very finely branched. #. t, 11. f. 3. Europe. (XIII, 15.) 1-1080" to 1-960". R. Dalmatica (K.). — Flabellate in a radiating manner; frustules oblong cu- neate; stipes short, rather stout, at length subramose, tubular. K.B. t. 9. f. 7. Europe. 1-540". Lateral view narrow- clavate with very obscure striae. R. abbreviata (Ag., K.). — Subflabel- late; frustules broadly cuneate with acute base ; stipes rather thick, at length branched. KB. t. 9. f. 14 = Licmophora abbreviata, Ag. Europe. 1-540". “Re- Sembles R. paradova, i. is distinguished by its green colour when dried.” (Ag) R. paradoaca (Lyngb., K.).—Frustules short; broadly cuneate, somewhat acute at the base; stipes slender, filiform, di- chotomous; lateral view clavate. SBD. i. p. 84, pl. 25. f. 231 = Gomphonema paradoxum, Ag. 1–540” to 1-480". Co- louring matter dull olive. The frustule, especially in dried specimens, often has its angles so much rounded as to become obovate, – a character, however, not peculiar to this species. (IV. 8.) R. tincta (Ag).-Frustules elongated, narrow cuneate, with somewhat acute base; stipes elongated, subdichotomous, slender. = Gom. tinctum, A Consp D. p. 35 ; R. elongata, K.B. t. 10. f. 6. 1-310". Colouring matter dull olive. According to Agardh, it differs from R. parado.ca in its greemer colour and longer and more slender frustules. He also states that it resembles smaller states of Licmophora flabellata, but is shorter OF TEIE LICIVIOPEI Olº EAE. 771 *N, and more lax, and without radiant frus- tules. - R. oceanica (K.). — Frustules oblong cuneate, dense; stipes elongated, slender, subdichotomous. KB. t. 10. f. 4. At- lantic. 8 flabellate, 1–390". Internal matter fulvous. R. Superba (K.).-Frustules geminate or Solitary, oblong cuneate, slightly acute at their base; stipes long, filiform, di- chotomous, Secondary branches lateral, short. KB. t. 10. f. 7. Europe. 1-310". Elegant, slender, large; internal matter golden-yellow, globose, broadly distri- buted. R. grandis (K.). — Frustules broadly cuneate, large; stipes very long, fili- form, dichotomous. KB. t. 11. f. 1. 8. arachnoidea (K.). —Frustules caducous, mostly lateral. Venice. Large, its in- ternal matter granular, globose, olive. 1–120". R. Meneghiniana (K.). —Large; frus- tules geminate, oblong cuneate, with rather broad apices; stipes much elon- gated, filiform, dichotomous. KB. t. 11. f. 2. Venice. (x|II. 19.) 1-288". In- ternal matter Scattered, globose, olive- brown. R. Craticula (Mont.).-Shortlystalked, Subflabellate, dilated at the base, cra- ticuliform; frustules two to six, lanceo- late or oblong-lanceolate, with truncate apex, and obtuse, scarcely attenuated base. Montague, A d Sci Nat. 1850, . 308. Cayenne, 1–650" to 1-450". Stipes slender. Genus LICMOPHORA (A.). — Frustules flabelliform, stipitate, in front view narrow-cuneate, laterally clavate ; stipes thick, irregularly branched. Licmophora is nearly identical with Echinella of Ehrenberg. “The frus- tules of the present genus differ in no essential respect from those of Rhipi- dophora. They are, it is true, longer and narrower, and probably less firmly silicious ; but none of these circumstances seem to be of generic importance. The separation of the genera must therefore rest upon the fan-like arrange- ment of the frustules upon the summit of an incrassate and irregularly dichotomous pedicel which occurs in Licmophora.” (S. l.c. vol. i. p. 85.) Meneghini, however, says that “the resemblance of this to the preceding genus is only apparent. But a true affinity connects Licmophora to Synedra, from which it differs only in its cuneate frustules. . . . . The Vittae in Licmophora are not to be compared with those in Rhipidophora. They are nothing more than the usual longitudinal canals projecting into the cavity, by which the apparent perforations or sections of their cavities appear very near the margin of the summit. The distribution of the internal coloured substance is different from that in the two preceding genera, and greatly resembles that of Synedra.” (M. l.c. p. 464.) LICMOPHORA Splendida (Grev.). — “Frustules nearly linear, frequently at- tenuate and rounded at the upper extre- mity; in lateral view attenuate towards the upper end.” SB. i. p. 85, pl. 32. f.233. = L. flabellata, K. ; Echinella splen- dida, E. Europe. Differs from the next species by its longer and narrower frus- tules, many of which are scattered and lateral. L. flabellata (Grev., Ag.). — Frustules cuneate, truncate; in lateral view very narrow clavate. S. pl. 32. f. 233. = L. ra– dians, K. ; L. argentescens, Ag: ; Echinella flabellata, E. Common. (IV. 9. ; X. 191—193.) “I have given, in accordance with the authority of my predecessors, two species of this genusºbut I am far from satisfied that they are truly distinct, and I am disposed to believe that a wider com- parison of specimens will necessitate their union.” (SB. i. p.85.) Being unable to determine the synonyms of Agardh, Ehrenberg, and Kützing, we have thought it better to follow Professor Smith than to risk increasing the confusion which exists. The Dicmophora argenţescens, Ag., is remarkable for its silvery lustre when dried; but we cannot detect any valid diagnostic difference. Both species are remarkable for the large and beau- tiful fan-like clusters of frustules termi- nating their branches; other frustules are lateral and scattered. L. Meneghiniana (K.). — Frustules slender, very long, linear cuneate, ter– minal Ones radiant, lateral ones scat- tered ; stipes elongated, subdivided. KSA. p. 113. Adriatic Sea. Length 3 D 2 772 SYSTEMATIC EIISTORY OF TEIE INFUSOIRIA. of frustule 1-84" to 1-72". The charac- ters given are insufficient to distinguish this species from L. Splendida. L. divisa (K.). — Frustules elongate flabellate), acute at the base; stipes short, weak, subdivided. KSA. p. 114. Adriatic Sea. (XIII. 16.) Length of frustule 1–240" to 1-180". cuneate, subsolitary or geminate (not Genus CLIMACOSPHENIA (Ehr.). — Frustules in front view cuneate, with moniliform longitudinal vittae, laterally obovate–lanceolate, divided into chambers by transverse septa. Marine. This genera resembles Podosphenia, except in having the peculiar transverse septa. “The two (first) species contained in this genus have nothing in common except the moniliform Vittàe. But in what these really consist we cannot ascertain from the figures. In the first Kützing does not delineate the lateral surfaces, and from the figure any one would say that he had drawn a Synedra. The second, again, resembles a Podosphenia.” (Meneg l.c. p. 465.). CLIMACOSPEIENIA Australis (K.). — Very shortly stalked, with smooth mar- gins. KB. t. 10. f. 8. On Algae. New Holland and Southern Africa. C. moniligera (E.). —Frustules trans- versely striated on the margin; Septa 10 to 11 in number. KB, t, 29. f. 80. Cuba, Mexico. (XI. 45, 46.) C. elongata (B.).—Lateral view elon- gated clavate, the intercostal spaces with obsolete transverse striae; stipes long, branched. BC. 1853, p. 8, pl. 1. f. 10, 11. Florida. Professor Bailey relies Genus PODOCYSTIS (K. & Bail.)= on the “elongated-clavate form of the frustules and their excessively minute striations, to distinguish this species from those previously described by Ehr- enberg and Kützing. The striae can be made out without much difficulty near the edges; but to trace them completely across the middle regions of the valve requires excellent lenses and careful management of the light.” (Bailey.) Frustules in fan-shaped groups, narrow, linear-cuneate, with conspicuous moni- liform longitudinal vittae. EUPHYLLODIUM (Shi)—Frustules stipitate, cuneate in front view with obscure vittae; valves with transverse costae, moniliform striae, and longitudinal median line. Podocystis differs from Surirella not only in its stipitate frustules, but in its moniliform striae and absence of alae; and from Rhaphoneis by its cuneate frustules. We have placed it with the Licmophoreae because of its resemblance to Podo– Sphenia, notwithstanding its obscure vittae and strong transverse costae. Marine. ToDoc YSTIs Adriatica (K.). —Valves ovate, with 11 or 12 striae in 1–1200", stipes very short. = Surirella (Podocystis) Adriatica, KB. p. 62, t. 7. f. 8; P. Ame- ricana, BMO. pl. 11. f. 38; SD. ii. p. 101; Euphyllodium spathulatum, Shadb. MT. ii. p. 11, º 4. f. 4; Doryphora P elegans, º M.J. ii. p. 284. f.3. Europe, Africa, and America. (IV. 10.) Genus SCEPTRONEIS (E.).-Frustules simple, affixed, cuneate, com- pressed, styliform; in the lateral view with moniliform transverse striae, interrupted by a median longitudinal suture. habit of a nonconcatenate Meridion central nodule of the lateral valves. SCEPTRONEIS Caduceus (E.). —Frus- tules bacillar, long, slender, inflated at centre and upper end, and tapering below. BAJ. xlviii. pl. 4. f. 11. Fossil, Ame- rica; recent, Scotland. The lateral view, the only one we have seen, is narrow, somewhat clavate, constricted beneath Marine. Sceptroneis has the and of a Gomphonema without the the head, which is rounded at its apex. Transverse striae with pear-like gra- mules. Length 1-92", exceeding the width about 18 times. Professor Gre- gory gathered a fragment of this species in Scotland. (iv. li.) OT THE FRAGILAIRIE ZE. 773 FAMILY IV.- FRAGILARIEAE. Frustules straight, free, or affixed by one angle of the basal frustules, in front view linear, in lateral view compressed, and striated or smooth, with a central module; striae or costae pervious. “The members of this family are allied in the genus Denticula to Surirella and Navicula; in the genera Odon- tidium and Fragilaria to Himantidium, Diadesmis, and the Meridieæ, and in Diatoma to Grammatophora and Tabellaria.” (Kützing.) “The character by which these genera are collected together into one family is the conformity of the two primary surfaces; nor do I know how the genus Meridion is excluded even by the minutest characters.” Kützing, indeed, “cites the affinities with Himantidium among Eunotieae, with Diadesmis among the Naviculae, and with the various genera of Striatelleae. The relation appears to us rather one of analogy than of affinity, being the polypariform association of many individuals.” (Meneghini.) Under Meridieæ we state the reasons which induce us to dissent from Meneghini’s opinion respecting the position of Meridion. The striae and costae are usually continuous across the valve; and, indeed, Kützing makes their perviousness a distinctive character, separating the Fragilarieae from the Surirelleae. We regard Meridion as far more nearly allied to some genera belonging to the latter family than to the genera mentioned by Meneghini. - Genus DENTICULA (K.). — Free, solitary, or binately conjoined, rarely more ; valves with pervious costae, which appear in front view like marginal puncta. Fresh water. Denticula differs from Odontidium in not forming a filament, and also, according to Professor Smith, in having conspicuous striae, which are wanting or obscure in Odontidium, and from Fragilaria by its strongly marked costae, which Kützing regards as always pervious. DENTICULA tenuis (K.).-Front view linear with punctated margin; valves narrow lanceolate, with 10 or 11 trans- verse costae in 1-1200". KB. p. 43, t. 17. f. 8. Europe. 1-1080". D. frigida (K.). — Front view linear, with finely striated margins; valves li- near lanceolate, with 11 or 12 costae in 1-1200". KB. p. 43, t. 17. f. 7. Europe. Smaller than D. tenuis. 1–1200", D. thermalis (K.)-Front view oblong or trapezoid, with beautifully punctated margins; valves lanceolate, with 7 or 8 costae in 1-1200". KB. p. 43, t. 17. f. 6. Italy. 1-660". D. elegans (K.). — Front view linear oblong, with obtuse angles and gland- like marginal puncta; valves lanceolate, with 6 costae in 1-1200". KB. p. 43, t. 17. f. 5. Germany. (III. 4.) 1-660". D. obtusa (K.). — Front view linear, with striated margins; valves lanceolate, with obtuse ends, and 11 costae in 1–1200". KB. p. 43, t. 17. f. 14; SBD. i. p. 19, pl. 34. f. 292. Europe. 1-336". D. crassula (Nägeli). — Front view oblong, with punctated margins; valves elliptic, with 12 to 13 fine striae in 1–1200". Nāg, in KSA. p. 889. = D. inflata, SBD. ii. p. 20, pl. 34. f. 294, Europe. D. acuta (Rab.). —Front view mostly cuneate ; valves slender lanceolate, with 6 or 7 costae in 1–1200". Rab Diat, p. 33, t. 1, f. 8. Persia, D. lauta (Bail.). — Front view linear, with gland-like marginal puncta; valves linear lanceolate, with obtuse ends and distant costae, which terminate in mar- ginal bead-like dots, BMO. p. 9, f. 1, 2. Fossil. Suisun Bay, California. D. ocellata (S.). — Front view linear, truncate, with conspicuous foramina- like marginal puncta; valves linear elliptic, with 10 costae in 001". SBD. ii. p. 20. St. Abb's Head. The frus- tules in the front view closely resemble Small specimens of Epithemia Argus. The extremities of the costae or canali- culi appear as circular foramina on the f. V., and the costae on the side view also give an ocellated appearance to the valve, S. Genus PLAGIOGRAMMA (Grev.) (HETEROMPIIALA, E.). — Frustules qua- drangular, united into a short fascia; Valves with two or more strong, pervious 774 SYSTEMATIC EIISTORY OF TITE IN INUSORIA. transverse costae, and moniliform, generally interrupted striae. Marine. Plagiogramma is a well-marked genus, identical, we believe, with Heterom- phala of Ehrenberg. We have adopted the present name, notwithstanding the prior claim of Ehrenberg's, because it is not only better defined, but the latter was founded upon imperfect knowledge, when the lateral view, which is so important, had not been observed. In the front view the torminal puncta are very conspicuous and notch-like, so that the ends appear slightly three-lobed, and the termination of the costae and striae are conspicuous along the lateral margins. The valves are always furnished with two central transverse costae, and frequently with others. In addition to the costae there are moniliform striae, the former pervious, the latter, except in one species, interrupted by a median line. We give Dr. Greville’s arrangement of the species, but must express a doubt whether the number of costae is not variable in the same species. * Valves with two centrical costae. PLAGIOGRAMMA Gregorianum (Grev.). —Front view with slightly convex mar- gins; valves lanceolate oblong, obtuse; costae two; striae pervious, 18 in 001". Grev. M.J. vii. p. 208, pl. 10. f. 1, 2, = Denticula staurophora, Greg Diat. of Clyde, p. 24, pl. 2. f. 37. Scotland. P. Jamaicense (Grev.). — Front view with straight margins; striae continued almost to the angles, 16 in 001"; costae two. Grey l.c. p. 208, pl. 10, ſ. 3. Ja- maica. The striae can scarcely be termed strictly moniliform, but rather monili- form costae. Grev. P. P tessellatum (Grev.). — Valves broadly lanceolate, obtuse; striae inter- rupted, composed of large subquadrate granules, 8 in 001"; costae two. Grev l, c. p. 208, t. 10. f. 7. Californian guano. P. interruptum (Greg.). —Front view with slightly convex margins; costae two; striae obsolete P = Denticula inter- rupta, Greg Diat. of Clyde, p. 22, pl. 2. f. 30. Scotland. Side view unknown. 2 * Valves with two centrical costae and one near each end. P. ornatum (Greg.).--Front view with convex margins, constricted beneath the dilated ends; costae four; striae obsolete P = Denticula ornata, Greg Diat. of Clyde, p. 22, pl. 2. ſ. 32. Scotland. Side view unknown. P. pulchellum (Grev.). —Valve linear oblong; costae ſour; striae robust, con- spicuously moniliform, interrupted, 11 in .001". Grev l.c. p. 209, pl. 10. f. 4–6. Californian guano; Jamaica; New Pro- vidence. P. indequale (Grev.).--Front view with straight sides; costae ſour, the terminal ones in front view longer than the cen- trical, and inflected at their apices; striae moniliform, 16 in 001". Grev l.c. p. 210, #. 10. f. 10. Jamaica and New Provi- ence. Side view unknown. P. pygmaeum (Grev.).-Minute; valves narrow oblong; costae four; striae moni- liform, interrupted, 21 in 001". Grev l, c. p. 211, pl. 10. f. 11. Distinguished for its minute size, its shape, and the Small number of striae, although re- latively closer. Grev. P. Grevillii (Ralfs). — Striae in front view broad, moniliform, costate, 8 or 9 in 001"; costae four; connecting zone with longitudinal rows of dots. = P. orna- tum, Grev l.c. p. 209, pl. 10. f. 9. Cali- fornian guano, Side view unknown. The striae are very peculiar, broad, at first sight resombling costae. Grey. P. validum (Grev.). — Valve linear, slightly dilated in the middle, rounded at the ends; costae four; striae inter- rupted, conspicuously moniliform, 12 in •001". Grey } c. p. 209, pl. 10. f. 8. Cali- fornian guano. }. view unknown. P. obesum (Grev.). — Minute valves, broadly dilated at the middle and rounded at the ends; costae four; striae 11 in :001". Grey l.c. p. 211, pl. 10. f. 12, 13. New Providence. The inflated appear- ance of the valves and the small number of striae render this a well-marked spe- cies, Grev. P. lyratum (Grev.). — Valves con- stricted at the middle, then dilated and narrowly lyriform, linear, and rounded at the extremities; costae four; striae 18 in 001". Grev l.c. p. 211, pl. 10, f. 14. New Providence. 3 * Valves with more than four costa. P. Californicum (Grev.). —Valves li- mear, with rounded ends; costae more than four; striae 18 in .001". Grev l. c. p. 211, pl. 10. f. 15–17, Californian guano. OF THE FRAGIL.ARIELE. 775 Doubtful or insufficiently known Species. P. laevis (Greg.). — Front view with slightly but sharply dilated ends and a of Clyde, p. 22, pl. 2. f. 33. Scotland. Side view unknown. P. Himantidium (E.). — Front view eight times as long as broad, with the rounded apices slightly 3-lobed, costae minute prominence in the middle of each margin; costae two?, striae delicate, about 48 in 001". = Denticula laevis, Greg Diat. two P, margin striated. = Heteromphala Himantidium, ERBA, 1858, p.13. AEgean Sea, Side view unknown. Genus ODONTIDIUM (K.).—Frustules united into a filament; lateral view linear elliptic or cruciform, with pervious costae. “The Odontidia are merely a filiform series of Denticulae.” (Menegh.) Like Denticula, this genus is distinguished from Fragilaria by its strongly-marked costae, which appear in the front view like marginal puncta. The filaments are usually extremely fragile, and when broken up the frustules scarcely differ from those of Denticula. Smith says, “It must be acknowledged that there is little to separate these genera; and I should be disposed to unite the two, were there not in the general habit of the living frustule characters which enable the observer to assign them to their respective genera. . . . . It may be left to future observers to consider whether they may not without inconvenience be united.” ODONTIDIUM mesodon (K.). — Has shorter and subquadrate frustules, with from two to four transverse costae. The last character, however, is so inconstant that, although Professor Smith adopted it in his definition, almost every frustule in his figures has a greater number. O. glaciale often has trapezoid frustules and 5 or 6 costae, whilst O. turgidulum is in- termediate between those forms and the normal frustules in length and number of costae. O. hyemale (Lyngb., K.). Front view with bead-like marginal puncta; valves elliptic-oblong or elliptic-lanceolate, ob- tuse, with conspicuous costae. KB. p. 44, t. 17. f. 4; SBD. pl. 34. f. 289; Fragi- laria hyemalis, Lyngb. t. 63; F con- fervoides, GBF. ii. p. 403; , F striata, E.A. p. 127; Odontidium turgidulum, KB. t. 17. f. 2; F turgidulum, EInf, ; Odon- tidium glaciale, KB.; O. mesodon, KB, t. 17. f. 3; SBD. ii. p. 16. Common. Europe, Asia, Australia, and America. (XIII. 24, 25.) Odontidium hyemale is easily distinguished from other filamen- tous Diatoms by its exceeding fragility, minute terminal puncta, gland-like mar- ginal ones, and the conspicuous costae of the valves. The frustules vary much in length and in the number of their costae; and several species have, we be- lieve, erroneously been constituted upon these characters. We do not hesitate to unite them, confirmed in our opinion by the doubts expressed respecting their distinctness by the late Professor Smith. O. Bogotanum (Rab.). — Very small; valves oblong, with rounded ends, and from 2 to 4 very broad transverse costae. Rab Diat. p. 34, t, 2. f. 8. Bogota. Ap- parently a state of O. hyemale. O. capitatum (Rab.). — Four to six times as long as broad; valves lanceo- late, constricted beneath the capitate apices; costae 6 or 7 in 1–1200". Rab Diat, p. 34, t. 10. f. 17. = O. chamocepha- lum, Rab D. p. 34, t. 10. f. 16; Fragi- laria? capitata, EB. 1853, p. 527; Microg. pl. 35A, 12. f. 2; F. P. leptocephala, El. c. º 527; Microg. pl. 35A, 12. f. 3. Europe, Persia, and America. O. modulosum (E., K.). — Frustules narrow linear, twelve times as long as broad; valves narrow linear, nodulose, constricted beneath the capitate ends; striae.18 in 1–200". KSA. p. 13. = Fra- gilaria nodulosa, EB. 1844, p. 267. Kur- distan. O. pinnatum (E., K.).-Frustules three to six times longer than broad; valves with rounded, not attenuated, ends, and 25 strong striae in 1-1200". KSA. p. 13. = Fragilaria pinnata, E.B. 1844, p. 202; Microg, t, 35 A. 22. f. 8. Ant- arctic Sea. O. minimum (Nãg.). — Very small; valves trapezoid, with acute apices and very faint, nearly obsolete transverse striae; front view quadrate, with margi– mal puncta. KSA. p. 889. = O. Salisbur- gense, Rab D. p. 38, t. 2. f. 7. Europe. O. rotundatum (E., K.). — Frustules often nine times as long as broad ; valves linear, with rounded ends, and 776 SYSTEMATIC HISTORY OF TELE INFUSORIA. 20 stout costae in 1-1200". KSA. p. 13. = Fragilaria rotundata, EB. 1844, p. 202; EM. pl. 1. 1, f. 1. Fossil. Philippine Islands. O. pinnatum (E., K.).-Frustules three to six times as long as broad; valves linear, with rounded ends, and 15 stout costae in 1–1200". KSA. p. 13. = Fra- gilaria pinnata, EA, p. }. Microg. many figures. Australia, Africa, and America. Akin to O. striatum and O. Syriacum, E. O. striolatum (E., K.).—Frustules three to six times as long as broad; valves linear, constricted beneath the obtuse capitate ends; striae about 18 in 1-1200". RSA. p. 13. = Fragilaria striolata, EMI. t. 28. f. 58. Europe and Australia. Ehr- enberg's figures in the ‘Microgeologie’ have the ends slightly attenuated, and not capitate. O. Syriacum (E., K.).-Frustules eight times as long as broad; valves with 10 striae in 1-1200". KSA. p. 13. = Fra- gilaria Syriaca, E.B. 1840, p. 16. Syria. O. P. polyedrum (E. K.). — Frustules oblong, angular (Sexangular P); three times as long as broad; striae very fine. KSA, p. 14. = Fragilaria polyedra, EB. 1845, p. 77. Fossil. America. 1-900". O. amphiceros (E., K.).-Valves turgid at the middle, with elongated, linear, truncate ends and pervious striae. KSA. p. 13. = Fragilaria amphºceros, E.B. 1844, p. 82; Microg. t. 18. f. 77. Vir- ginia. - O. granulatum (E., K.). — With the habit of O. amphiceros, but smaller; valves with attenuated ends and granu- lated fasciae in striae, KSA. p. 13. = Fragilaria granulata, E.B. 1844, p. 202. Antarctic Sea. O. P. Glans (E., K.).—Frustules striated, short, gibbous at the middle, constricted at the obtuse ends, and resembling the figure of an acorn with its calyx; striae 2 or 3 in 1-1200". KSA. p. 14.- Fra- gilaria Glans, E Inf. p. 185. Fossil. Finland. 1-1150" to 1-570". O. anomalum (S.). — Filament tena- cious; valves linear, suddenly constricted towards the rounded extremities; costae four to twelve. SBD. ii. p. 16, pl. 61. f.376. Alpine situations. Europe. Front view with punctate or denticulate mar- gins. Internal cells, similar to those met with in Meridion and Himantidium, are frequent in this species. . anceps (E.).--Small; valves linear- oblong, constricted beneath the subcapi- tate apices. = Fragilaria anceps, E.A. . 127; F. Pieridium, EM. pl. 34, 5 B. . 10 P North America. O. Cretae = Fragilaria Cretae, EM. pl. 53.17. f. 9; F paradoza, EM. pl. 33. 15. f. 13? Australia, Europe, and Africa. Valves linear-oblong, with rounded ends and pervious transverse costae. Genus FRAGILARIA (Lyngb., K.).-Frustules linear, united into a fila- ment; lateral valves Smooth or faintly striated, linear-lanceolate or fusiform. Fragilaria differs from Odontidium in the absence of costae; and the striae, which are probably present in all the species, are so obscure that Kützing makes their absence one of the generic characters. Diadesmis may be distin- guished from Fragilaria by the presence of a central module in the lateral valves. Professor Smith justly regrets that in the subdivision of Fragilaria sufficient regard has not been paid to the signification of the generic name. We consider that it would have been far better to have retained the name for Fragilaria hyemalis, Lyngb. (=Odontidium, K.), so remarkable for its fragility. FRAGILARIA capucina (Desm.).--Front view narrow linear, with obsolete or ob- scure terminal puncta; valves lanceolate; striae obscure. KB. p. 45, t. 16. f. 3. = F. pectinalis, Lyngb. t. 63; Ag Consp Diat. p. 62; F tenuis, Ag Consp Diat. p. 63; F. Rhabdosoma, diophthalma, mul- tipunctata, bipunctata, angusta, Scalaris, and fissa, E Inf. F. Sepes, EM. t. 38. 1. f. 8. Common, but generally in small quantities and mixed with other Diatoms. Jºurope, Asia, Australia, Africa, and America. (IX, 173, 174.) A very vari- able species. The frustules are so much compressed that it is difficult to obtain a good view of the valves; but it may usually be recognized in the front view by its obsolete terminal puncta. When dried, it has a silvery lustre. Filaments elongated. F. acuta (E.). — Valves linear, with acutely cuneate apices; striae wanting or obscure; front view linear. E Meteorp. t. 2. f. 10; Microg, many figures, = F ca- OF THE FRAGILARIE ZE. 777 pucina, SBD. pl. 35. f. 296. Asia, Africa, and America. six times longer than broad. F. corrugata (K.).-Minute; frustules geminate, corrugated at each end; valves acutely lanceolate. KB. p. 45, t. 16. f. 5. Germany. 1–1440". F. pusilla (K.). — Glassy; frustules rectangular, quadrate, or linear, united in very short fasciae ; valves narrow linear, Smooth. KSA, p. 14, Marine. France. F. Bacillum (E.). — Valves smooth, linear with rounded ends, five or six times as long as broad. EB. 1844; Microg, pl. 27. F. 36 & pi. 35.16, f.ii. Fossil. Oran and Virginia. 1-720". F. glabra (E.).-Linear, smooth, with attenuated obtuse apices, EA, p. 127. Guiana. May be a variety of F. bi- ceps, E. F. Catema (E.). —Twice as long as broad; valves oblong, Smooth. EB. 1840, p. 16. = F turgens, EMI, several figures? Europe, Africa, and Mexico. I-1152". - F. virescens (Ralfs). — Valves turgid lanceolate, suddenly contracted towards the obtuse ends; striae 44 in .001", very faint. Ralfs, Ann. xii.; SBD. ii. p. 22, pl. 35. f. 297. = Diatoma virescens, HBA. JF. pectinalis, E. Streams. Europe. Fila- ments elongated, lurid-green; frustules rather broad, with distinct terminal Fº frequently irregularly adhering y their angles like a Diatom. Easily recognized by its greenish hue when growing. - F. Venter (EM, several figures). — Minute; valves smooth, twice as long as broad, oblong lanceolate, with con- tracted, produced, obtuse ends. F. mesotyla (E.).-Bacillar with tur- gid centre, obtuse ends, and transverse granular striae. Asia. 1-480". Resembles Stauroneis granulata, but wants the lon- gitudinal band and crucial umbilicus, E. F. laevis (E.).-Resembles Odontidium amphiceros, but is without the dotted striae. EA. p. 127. Virginia. F. biceps dº.”v alves linear oblong, suddenly constricted at the ends into minute beaks; striae wanting or obscure. EA. p. 127; Microg, several figures. Europe, 1-1152"; = F gibba, EM. pl. 33.17. f. 9? Ame- rica and Europe. F. binodis (E.). — Parasitic, mostly simple; valves rostrate, sometimes con- stricted, sometimes inflated at the middle; striae wanting or obscure. EA. p. 127; Microg. pl. 5. 2. f. 26. = Odontidium ? pa- rasiticum, SBD. ii. p. 19, pl. 60. f. 375. Europe and America. 8 inflated, with- out a central constriction. Sl. c. p. 375. Frustules rarely cohering, and scarcely silicious. S. F. constricta (E.). — Frustules fre- quently cohering by their angles; valves rostrate, subacute, in general slightly constricted, sometimes inflated at the middle; striae faint, 42 in 001". EA. p. 127; Microg, several figures. = F. undata, SBD. ii. p. 24, pl. 60. f. 377. 8, valves turgid at the middle, S. Eu- * Asia, Australia, and America. . Entomon (E.). —Valves elongated, Smooth, strongly constricted at the middle, with rostrate ends. E.A. p. 127; Microg, pl. 5. 3. f. 52. North America. F. binalis, EM. pl. 14. f. 52, Germany and Mauritius. Valves smooth, con- stricted at the middle, and rounded at the ends. Doubtful and undescribed Species from JEhrenberg. F. P. Tessella, EM. pl. 20. 2. f. 29. Broadly and sharply lanceolate without markings. F. P. Synedra, EMI. pl. 39. 3. f. 60, 61. Frustules united, curved; venter gibbous at Centre. F. P. Mesogongyla, EB., 1856, p. 333, f. 48. Africa. Valves with minute in- flated middle, and slender acute rostrate ends. F. oryrhambus, EB. 1856, p. 333, f. 44, Africa; F. Trachea, Australia; F. seminuda, fossil, Georgia; F. ventralis, Anatolia; F. Himalayae, India; F. P Stylus, AEgina; F. P. Stylidium, AEgina; F P windulatum, Asia; F. Cruz, Asia; F. Tania, Africa; F. amphilepta, Africa; F. Lamella, Australia; F. amphicephala, Asia; F. ventricosa, Africa; F. frus- tulia, America; F. Eiſmotia, Africa; F. thermalis, America; F. australis, Ame- rica; F. Pomeroon?, America. Genus GRAMMONEMA (Ag.).-Frustules similar to those of Fragilaria, but scarcely silicious, and united into flexible, highly mucous filaments. “Grammonema in appearance comes very near to Fragilaria; but its habit is so very different that I am inclined, with Agardh, to keep them distinct. In Fragilaria the filaments do not adhere well to paper, the frustules are silicious and may be subjected to a red heat without any other alteration than the 778 SYSTEMIATIC EIISTORY OF TELE INFUSOR.I.A. destruction of the colouring matter, and at each end are two, more or less distinct, pellucid puncta. . . . . In Grammonema there is scarcely any silica, and the filaments are not fragile, but highly mucous, adhering firmly to paper or glass, and when dried appearing like a mere stain; the application of nitric acid or of a red heat destroys their form, and I can perceive no puncta at the ends of the frustules.” Ralfs, Ehrenberg, and Kützing place this genus with the Desmidieæ because of the absence of silica; and Meneghini says, “I think this conclusion right. It is a true Desmidiean, for it has no silicious shield; and it is to be observed that, however perfectly it may resemble the Fragi- larieae in form, it wants the longitudinal canals and terminal perforations of the primary surfaces.” - rea, Caerm. in Hook B Fl. ii. p. 403. |3. diatomoides, filaments turning greenish when dried, = Fragilaria diatomoides, Grev., Hook B Fl. p. 403. On marine Algae. Spring, Europe. (XV, 24, 25.) Grammonema Jurgensii is easily distin- guished from every species of Fragilaria by its marine habitat and flexible, highly Imucous filaments. GRAMMONEMA Jurgensii (Ag). — Valves oblong lanceolate, slightly con- stricted at the obtuse ends. Ag CD. p. 63. = Fragilaria Jurgensii, KSD. p. 59; Conferva striatula, Jurg. ; Fragilaria striatula, Lyngb Hyd Dam. p. 183, t. 63; SBD. ii. pl. 23. f. 298; Grammatonema striatulum, KSA. p. 187; Arthrodesmus striatulus, ERBA. 1840; Fragilaria au- Genus DIATOMA (Dec.). — Frustules quadrangular, partially separating, and cohering by the angles (generally by the alternate ones) into a zigzag chain. Diatoma is distinguished from Fragilaria and Odontidium by the con- nexion of the frustules at their angles in a zigzag chain. Some species of Pragilaria, indeed, have a few frustules similarly adhering; but this is a con- stant character in Diatoma, whilst the greater number of their frustules will present the usual appearance of a Fragilaria. Meneghini says, “ For my part, I think it would be much more natural to place the Smooth species (D. pec- tinale, D. vitreum, and D. hyalinum) in Fragilaria; those striated with elliptic- lanceolate surfaces (D. vulgare, D. mesodon, D. tenue, and D. mesoleptum) in Odontidium. There would remain as distinctly generic the species which have capitate extremities on their lateral surfaces. These unions would be justified on both sides; for whilst the Odontidia have forms little different from Diatoma, Diatomata are little different from Fragilaria.” * Striae obsolete. 2* Stride (costae) evident. DIATOMA hyalinum (K.). — Frustules elongated, very hyaline; valves linear lanceolate, with rather obtuse apices; striae obsolete. KB. p. 47, t. 17. f. 20; SBD. ii. pl. 41. f. 312. Marine. Europe. (Iv. 16.) D. minimum (Ralfs). —Frustules mi- nute, very hyaline; valves about twice as long as broad, oblong with rounded ends; striae obsolete. Ralfs; T Bot Soc. 2nded. p. 20; SBD. ii. p. 41, pl. 41. f. 313. = D. vitreum, KB. p.47. Marine. Europe. D. pectinale (Nitz., K.).-Frustules at first forming a fascia, afterwards zigzag ; valves acutely lanceolate; striae obsolete. KB. p. 47, t. 17. f. 11. = Bacillaria pecti- malis, Nitz; B. seriata, Ptolemaei, floccu- losa, E Inf, Fresh water. Egypt, Eu- rope, England. D. vulgare (Bory). — Valves spindle- shaped, suddenly.contracted at the ob- tuse ends; costae pervious, conspicuous, about 18 in 001". KB. t. 17. f. 15; SBD. . 39, pl. 40. f. 309; Bacillaria vulgaris, E Inf. p. 197; Diatoma tenue, Grev., HBFl. p. 406; D. flocculosum, Ag CD. p. 53. Europe, Asia, Africa, and Ame- rica. Frustules three or four times as long as broad. This species is distinguished by the greater breadth and convexity of its frustules, and by the conspicuous marginal puncta of the front view. (Iv. 13; Ix. 168.) D. mesodon (K.). — Valves ventricose lanceolate, with three to five transverse striae at the middle. KB. p. 47, t. 17. f. 13. 6. cuneatum, frustules cuneate. KB. t. 17. f. 12, - Bacillaria cuneata, E OF THE FRAGILAIRIEAE. 779 Inf. t. 15. f. 6; Diatona cuneatum, Rab D. t. 2. f. 4. Germany. (Ix. 170.) Pro- bably a state of D. vulgare. D. tenue (Ag). — Valves lanceolate, with from 9 to 12 distinct striae in 1–1200". Ag CD. p. 52; KB. p. 48, t. 9. f. 10. = Bacillaria pectinals, E Inf. p. 198, t. 15, f. 4. Europe and Asia. A protean Species; the frustules are sometimes qua- drate, sometimes linear, and sometimes Cuneate. D. mesoleptum (K.).-Frustules slightly attenuated at the middle; valves lanceo- late, with from 10 to 12 striae in 1–1200". RB. p. 48, t. 17. f. 16. Europe. 1-650". We fear it is scarcely distinct from D. text?de. D. Ehrenbergii º View at- tenuated at the middle; valves linear lanceolate, contracted beneath the sub- KB. p. 48, t. 17. f. 17; SA. 1857, xix. p. 10, pl. 1. f. 13. = Bacillaria elongata, E Inf. p. 198, t. 15. f. 5. Europe. . (IX, 169.) The inflation in the centre of the valve separates this species from D. grande, which is moreover a larger form with coarser striae, S. (IV. 15.) D. grande (S.). — Valve linear, con- stricted beneath the capitate apices; costae 24 in .001". SBD. ii. p. 39, pl. 40. f. 310. = Bacillaria australis, EMI. pl. 35. A 2. f. 3. Britain, Africa, and South America. . . D. elongatum (Ag). —Valves linear, with inflated, capitate apices; costae 7 in 1-1200". KB. p. 18, t. 17. f. 18; SBD. ii. p. 40, pl. 40. } 311.= Diatoma gracil- limum, Nāg., KSA, p. 889. Europe. Front view slender, attenuated at the middle. (IV. 14; IX, 119.) capitate apices; costae , 11 in 1-1200". Genus ASTERIONELLA (Hass.). — “Frustules linear, inflated towards one or both extremities; adhering by their adjacent angles into a star-like filament” (SBD. ii. p. 81). The frustules in this genus exactly resemble those of the capitate species of Diatoma, but are few in number; and being connected by the adjacent angles, the free extremities diverge in a stellate manner. We first observed a single specimen amongst Some freshwater Algae gathered near Dublin by Mr. D. Moore, and afterwards obtained it plentifully for two successive years in a pool near Dolgelly, when we considered it a species of Diatoma nearly allied to D. tenue. Subsequently we received a larger form from Professor Dickie, gathered near Aberdeen. The Scottish form had the free end truncated, and is probably the one described by Professor Smith as A. Ralfsii. ASTERIONELLA formosa (HaSS.). — Front view somewhat more enlarged at the base than at the summit. ‘OO24" to •0031". SBD. ii. p. 81. Fresh water. Britain. (IV. 17.) A. Bleakeleyi (S.).-Frustules linear, enlarged at the base. . .0022". SBD. ii. p. 82. Marine. England. A. Ralfsii (S.). – Frustules in front view exactly linear; valve attenuated at One end, constricted towards the other, which is rounded and capitate; striae obscure. SBD. ii. p. 81.= Diatoma stel- lare, BO. p. 39. Fresh water. Europe and America. (IV. 18.) Genus NITZSCHIA (Hass., Smith).-" Frustules free, elongated, com- pressed; valves linear, keeled, with one or more longitudinal lines of puncta; keel frequently eccentric. . . . This genus embraces a large number of species, differing in form and size, but all agreeing in a few general characters. The most important of these is the keeled form of the valves and the remarkable inequality, in many of the species, between the portions of the valve lying on either side of this prominency. This inequality (or, in other words, this eccentricity) of the keel distinguishes Nitzschia from Amphiprora, in which the keel is also present; while the presence of a keel and its accompanying line or lines of puncta, together with the absence of any form of stipes, separate the present from the genus Synedra.” Professor Smith, whose generic cha- racter and remarks we have quoted, has brought together forms from several genera, and thus has not only pointed out the remarkable character which is common to them all, but also relieved those genera of members which ill 780 SYSTEMATIC HISTORY OF THE INFUSORIA. agreed with their definitions. It is, however, probable that his characters may rather belong to a family than to a single genus, his sections forming genera. The sigmoid forms were placed by Ehrenberg in Navicula, and by Kützing, in his earlier work (Kiesel. Bacil.), in Synedra. Subsequently, how- ever, in his ‘Species Algarum, Kützing removed them from Synedra, and, under his old name of Sigmatella, placed them with the Fragilarieae because they are not affixed and have pervious transverse striae. * Minute: front view strait; valves ar- cuate with a row of dots on the ventral margin. NITzscIIIA amphioxys (E.). — Valve linear lanceolate, arcuate, with convex dorsum, concave venter, and attenuated, subrostrate, acute apices; striae 30 in •001", terminating in dots at the ventral margin. SBD. i. p. 40, pl. 13. f. 105. = Bunotia amphioxys, EA, p. 125. Fresh water, very common. Ehrenberg gives upwards of 200 habitats in Europe, Asia, Australia, Africa, and America. N. vivaa (S.). — Valve linear lan- ceolate, arcuate, with rostrate apices; striae distinct, 30 in 001", terminat- ing in marginal dots. SBD. i. p. 41, l. 31. f. 267. Fresh or brackish water. †. N. parvula (S.).-Valve with central constriction, obscure puncta, and pro- duced apices; striae faint, 70 in 001". SBD. i. p. 41, pl. 13. f. 106. Marine. Sussex. N. minutissima (S.). —Valve linear, with distinct puncta and prominent acute apices; striae obscure, 72 in 001". SBD. i. p. 41, pl. 13. f. 107. Fresh water. Beachy Head. N. Dianae (E.).-Valve linear, arcuate, with convex dorsum, concave venter, and produced slightly reflexed apices; striae 13 in 1–1200", terminating in dots on the ventral margin. = Eumotia Dianae, ERBA. 1840, p. 14; Microg. pl. 35 A. 2. f. 9. Fresh water, Europe, Asia, Africa, and America. N. amphilepta (E.). — Valve linear, arcuate, with convex, Smooth dorsum, slightly concave, striated ventral margin, and acute, gradually attenuated, slightly reflexed apices. = Eumotia amphilepta, ERBA, 1845, p. 363; Microg, pl. 34, 8, f. 4. Japan and China. N. virgata (Roper). — Valve linear lanceolate, slightly arcuate, with pro- duced, slightly recurved, obtuse apices; striae distinct, 26 in 001", dilated at in- tervals into ridges on the ventral margin. Roper JMS. vi. p. 23, pl. 3. f. 6. Ma- rine. Tenby. Differs from N. amphi- owys and N. vivaa; by the striae being dilated into bands instead of terminating in puncta, Roper. 2 * Frustules constricted at the middle, N. constricta (K.).-Front view ob- long, slightly constricted at the middle and tapering towards the somewhat truncate ends; keel very eccentric; striae obscure, 60 in 001". = Synedra con- stricta, KB. p. 64, t. 3. f. 70; Nitzschia dubia, S.B.D. i. p. 41, f. 112. Marine. Europe. - N. Entomon (E.).-Elongate, thick, striate, oblong with constricted middle and obtusely cuneate ends. = Synedra Entomon, EMI. pl. 34. 2. f. 5, Europe, Asia, Australia, Africa, and America. N. plana (S.). — Front view linear lanceolate, with attenuated middle and acutely cuneate ends; valves acutely linear lanceolate, with a single row of uncta and 56 obscure striae in 001. B.D. i. § 42, pl. 15. f. 114, Brackish water. Europe. N. Brightwellii (Kitton). — Valves broad linear-oblong, with obtuse, shortly attenuated ends, slightly constricted middle and interruptedly striate margin; surface under a low power granular, under a higher, punctato-striate; striae transverse, 25 to 30 in .001". Brackish water. Sierra Leone. Kitton in lit. (VIII.7. N. latestriata (Bréb.). —Front view large, broad linear-oblong, with a central constriction and broadly rounded ends; valves narrow lanceolate, with a central keel, double row of puncta and 56 di- stinct striae in 001". = Amphiprora late- striata, Bréb, in KSA, p. 93; Nitzschia bilobata, SBD. i. p. 42, pl. 15. f. 113. Marine. Europe. N. panduriformis (Greg.). —Broad linear-oblong, with constricted middle, acuminate ends, and punctuated mar- gins; striae fine, about 48 in 001", trans- verse and oblique, GDC. p. 57, pl. 6. f. 102. Marine. Scotland. There is a faint indication of a double keel in the middle of the valve. The striation is similar to that of Tryblionella constricta; but the present form is larger, and di- stinguished by marginal puncta; still it OF THE FRAGILAIRIE ZE. 781 resembles a Tryblionella about as much as it does a Nitzschia, Greg. 3 * Front view sigmoid (Sigmatella, Rütz.). N. sigmoidea (Nitzsch, S.). —Front view elongated, broadly linear, sigmoid with truncate ends and marginal puncta; valves marrow linear-lanceolate, with tapering ends and a single longitudinal series of puncta; striae 85 in 001". SBD. i. p. 38 º 13. f. 104. = Navicula sig- moidea, EI. t. 13, f. 15; Synedra sig- moidea, KB. p. 67; Sigmatella Nitzschia, KSA. p. 18; Nitzschia elongata, Hassall, B Alg. p. 435. Fresh water. Europe. (IX. I48.) Large, with elegantly punc- tate margins. The striae in this Diatom are sometimes strong and easily seen, while others in the same slide set at defiance every method of illumination to bring them out. Mr. Sollitt, of Hull, says, “The striae vary from 65 in the •001" up to a degree of fineness which no lenses that we now have will show.” N. Brébissonii (Kütz., S.).--Front view broadly linear, sigmoid with truncate ends and marginal puncta; valves linear, with attenuated, obtuse apices; striae 27 in .001". S.B.D. i. p. 38, pl. 31, f. 266. = Synedra Armoricana, KB. t. 4, f. 34; Sigmatella Brébissonii, KSA. p. 18. France, England. Resembles N. Sig- moidea, but is much broader in propor- tion to its length, the puncta are more conspicuous, and the lateral view is more linear. According to Professor Arnott, this species is not the Sigmatella Bré- bissonii of Kützing, the latter being a mere variety of N. sigmoidea, whilst Smith's species is distinct and a brackish- water species. N. macilenta (Greg.). — Front view elongated, linear, sigmoid, truncate; valves linear lanceolate, with acute api- ces; keel with a single row of Subremote puncta; striae very obscure. , Grey M.J. vii. p. 83, pl. 6. f. 8, 9. Marine. Scot- land. Allied to N. Sigmoidea, but de- cidedly less sigmoid. The side view very narrow; puncta separated from each other by irregular intervals, and fewer (8 in 001") than in N. sigmoidea, Gre- ville. N. Sigma (K., S.).--Front view sig- moid, linear lanceolate, gradually taper- ing to the truncated apices; keel of valves with a double row of puncta. SBD. i. p. 39, pl. 13. f. 108. = Synedra Sigma, KB. p. 67, t. 30...f. 14 Marine, Europe. Striae 56 in .001", Ş. (Iv. 20.) N. Sigmatella (Greg.).--Frontviewsig- ‘l rine. moid, linear lanceolate, gradually taper- ing to the obtuse apices; valves linear, acute, with obscure striae. Greg M.J. iii. . 4, f. 2. = N. curvula, S.B.D. ii. p. 39. resh water. Europe. Distinguished from N. Sigma by its far more delicate striae and freshwater habitat. Professor Kützing describes the Navicula curvula as straight in the front and sigmoid in the lateral view; it is therefore probably a Pleurosigma, and not this species, as supposed by Smith. N. vermicularis (K.).-Front view sig- moid, slender, linear or slightly dilated at the middle ; striae obscure. = Synedra vermicularis, K.B. t. 4, f 35 ; Sigmatella vermicularis, KSA. p. 18. Fresh water. Europe. N. Tergestina (K.). — Front view sig- moid, linear, truncate; valves narrow linear, with Suddenly contracted, pro- duced apices. = Synedra Tergestina, #. º 66, t. 4, f 33; Sigmatella Tergestina, Rab D. p. 56. Europe. 11 striae in 1–1200", Rab. N. Italica (Rab.).—Front view broad- ly linear, slightly sigmoid, truncate; valves sigmoid, with attenuated rounded ends, and 9 striae in 1-1200".= Sigmatella Italica, Rab D. p. 56, t. 4. f. 12. Italy. N. obtusa (S.):-Front view sigmoid, linear, with rounded apices; valves linear, obtuse, with a double series of puncta; striae 56 in 001". SBD. i. p. 39, pl. 13. f 109. Brackish water. Sussex. N. Smithii. H. Front view broadly linear, sigmoid, truncate, with conspi- cuous marginal capitate striae having Smaller puncta interposed between them; valves distinctly striate.-Nitzschia spec- tabilis, SBD. i. p. 39, pl. 14. f. 116. Ma- Britain. Keel nearly central, puncta in four rows. Sm. 4* Front view lunately curved. N. arcuata (Greg.). — Front view linear arcuate, with rounded ends; valves lanceolate, obtuse; puncta about 20 in 001". Grey, M.J. vii. p. 82, pl. 6. f. 4–7. Marine. Scotland. 5* Frustules straight in both views, not constricted at the middle. † Front view linear. N. scalaris (E., Sm.).--Large; front view broadly linear, with dilated truncate ends and broadly striated margins, the striae alternately longer and shorter; valves linear with shortly attenuated, obtuse ends. SBD. i. p. 39, pl. 14, f. 115. = Synedra scalaris, E.A. p. 137, t. 2, 2. 782 SYSTEMATIC EIISTORY OF TEIIL INFUSORIA, f. 18. Brackish water. Europe, Asia, Australia, and America. (IV. 21.) N. spectabilis (E.):-Large; front view broadly linear, with truncated cuneate apices; valves with rounded ends. = | Synedra spectabilis, E.A. and M, several figures. Europe, Asia, Australia, Africa, and America. The valves are figured as elongated, narrow linear, with suddenly attenuated, obtuse, reflected apices, and a row of puncta on One margin. N. insignis (Greg.). — Front view broadly linear, with rounded ends and conspicuous marginal puncta and striae; valves linear lanceolate, straight or slightly sigmoid, with subcentral keel and 30 distinct striae in 001". Greg. MT. v. pl. 1. f. 46. Marine. Scotland. Distinguished from N. sigmoidea and N. Brébissonii by its straight front view ; and from N. scalaris by its finer markings, more slender form, and nomdilated ends. Greg. N. gigantea (E.),—Very large, linear, with suddenly rounded ends; valves with attenuate subacute apices; surface finely striated in the intervals of the pin- nules. = Synedra gigantea, ERBA, 1841, . 22; Synedra Libyca, KSA. p. 48. §: of Jupiter Ammon, 1-60". N. linearis (Ag., S.). — Front view linear, with rounded or truncate apices and nearly central keel; puncta in a single row; striae obscure. SBD. i. p 39, pl. 13 & pl. 38. f. 110. = Frustulia line- aris, Ag, Fresh water. Europe. N. Palea (K., S.).--Front view linear; valves narrow, lanceolate, acute. SBD. ii. p. 89. = Synedra Palea, KB, p. 63, t. 4. f. 2; Synedra Fusidium, KB. p. 64, t. 30. f 33; Synedra fusidioides, Rab D. p. 53, . t. 4, f 47. Europe. Frustules minute. N. tenuis (S.). — Front view linear, truncate; valves narrow, lanceolate, acute; striae obscure. SBD. i. p. 40, pl. 13. f. 111. Fresh water. England. 2 + Extremities, in front view, with a hyaline wing or expansion on each side. N. spathulata (Bréb.).—IFront view lanceolate, with the truncate ends dilated on each side; valves lanceolate acute, with a single row of puncta. SBD. i. p. 40, pl. 31. f. 268. Marine. France and England. - N. distans (Greg.).--Front view broad, sublinear, with distant irregularly dis- |posed marginal puncta; apices truncate with a slight hyaline expansion on each side, GDC. p. 58, pl. 6. f. 103. Marine. Scotland. Valves lanceolate, with acute apices and central keel. N. hyalina (Greg.).--Front view sub- linear, with Small, regular marginal puncta; valves narrow linear, with con- tracted, produced apices and central keel. GDC. p. 58, pl. 6. f. 104. Marine. Scot- land. Keel apparently double; but per- haps one is seen through the very hyaline valve. Greg. 3 t Front view lanceolate. N. angularis (S.).--Front view rhom- boid-lanceolate, truncate; valves lanceo- late, with central keel; puncta in a single series and longitudinal lines. SBD. i. p. 40, pl. 13. f. 117. Marine. Sussex. This and the following species ought perhaps to be placed in Ceratoneis. N. lanceolata (S.).--Front view broadly lanceolate, acute; valves lanceolate, ros- trate, acute, with eccentric keel and longitudinal lines. SBD. p. 40, pl. 14. f. 118. Marine. Sussex. Doubtful or insufficiently described Species. N. valens (E.). — Very large, broadly linear, finely striated, with truncate ends. = Symedra valens, E.A. t. 3. 2. f. 6. Fresh water. (XII, 44.) Mexico and United States. N. curvula (K.).-Elongated, curved; front view slightly attenuated towards the truncate apices; valves acuminated, Subacute, sometimes with a longitudinal punctate line. = Synedra curvula, KB. p. 65, t. 15. f. 2. Fresh water. Prussia. 1–240". N. Ehrenbergii = Synedra amphilepta, EM. pp. 34–5, f. 11. Cape Verd. Elon- gated, straight, linear, with striated mar- gins and acutely cuneate apices. Genus CERATONEIS (Ehr.).-Frustules as in Nitzschia, but with long rostrate ends, and usually with a more or less evident central pseudo-nodule. Professor Smith, after excluding some of its species, made Ceratoneis a sec- tion of Nitzschia, and perhaps was justified in So doing; but as the forms included in it are remarkable for their filiform beaks, and there is some appearance of a central nodule, we have retained the genus, at least for the present. Some of the species resemble the Closteria in form, and have been referred to as showing an affinity between the Diatomaceae and the Desmi- dieae. The resemblance, however, is merely superficial, and, instead of showing OF TEIF SURIRELLEAE. 783 an affinity, rather proves it does not exist. In the Clostoria, division takes place across the lunate frond, or in the shortest diameter, whilst in this genus it occurs in the opposite direction. CERATONEIS longissima (Bréb.).- Valves lanceolate, with very long straight slender awns, a subcentral keel, a single row of puncta, and obscure striae. KSA. p. 891. = Witzschia birostrata, SBD. i. p. 42, pl. 14. f. 119. Marine. France, England. Front view straight, with lanceolate middle, and , long, linear, truncated beaks. (IV. 22.) C. Closterium (E.).--Front view arcu- ate, with lanceolate middle, and long, filiform, incurved awns; valves ſaintly striated, with central keel and a single row of puncta. Ehr. leb. Kreidethierchen. t. 4. f. 7. = Nitzschia Closterium, SBD. i. p. 42, pl. 15. f. 120. Europe, (XII, 59.) C. reversa (Sm.).--Front view lanceo- late, with long beaks, the extremities of which are bent in opposite direc- tions; puncta obsolete; striae obscure, 48 in 001". = Nitzschia reversa, SBD. i. p. 43, pl. 15. f. 121. Brackish water. Europe. C. spiralis (K.). —Lanceolate, with long, flat, spirally-twisted beaks. KB. p. 104, t. 4. f. 38. Marine. Europe. (XIII, 9.) C. Subulata (Bréb.). — Lanceolate su- bulate, very slender, Smooth, gradually tapering into slender beaks, which are Sometimes straight, sometimes curved or sigmoid. KSA. p. 89. Marine. France. C. acicularis (K.).--Front view narrow linear ; valves lanceolate, with straight, slender beak; striae obscure. = Synedra acicularis, KB. p. 63, t. 4. f. 3; Nitzschia acicularis, SBD. p. 43, pl. 15. ſ. 122. Fresh water. Europe. C. gracilis (Bréb.).—Elongated, very slender, linear, with rather obtuse Straight, curved, or sigmoid beaks; striae obscure. KSA. p. 89.- Nitzschia Taenia, SBD. p. 43, pl. 15, f. 123. Fresh or brack- ish water, Europe. Doubtful Species. C. Cretae (E.). — Smooth, navicular, very slightly constricted at the middle, with acute, straight, not much produced apices. ERBA, 1844; Microg. pl. 22. f. 61. Fössil. Sicily. The figure shows a distinct median line and module. C. laminaris (E.).-Broadly lanceolate, with striated margins and short rostrate apices. EA, t. 3. 7. f. 24. Asia and America. Valve with median line and central module. C. Linea.= Synedra Linea, EM. pl. 18. f 78. Fossil. Virginia. Lanceolate, with punctated margins, and narrow-linear, rostrate ends. C. rhomboides (E.).-India, Genus AMPHIPLEURA (Kütz.).-Frustules simple, elongated; valves with longitudinal ridges. considerably in their appearance. AMPHIPLEURA pellucida (K.).-Frus- tules slender, hyaline ; valves narrow lanceolate, with rather obtuse apices. KB. p. 103, t. 3. f. 32; SBD. pl. 15. f. 127. = Navicula pellucida, Ehr Inf. t. 13; Aulacocystis pellucida, Hass Algæ, p. 427, pl. 102. f. 8. Fresh water. Europe. (Iv. 30, Ix. 140 & XIII. I.) 1-800" to 1–140". Frustules often commected in flat, longitudinal band-like series by a mucous covering. A. Danica (K.).—Lanceolate, obtuse or truncated, smooth. KB. p. 103, t. 30. f, 38. Maline. º 1–390". A. rigida (K.). — Elongated, linear lanceolate, with truncate ends; front view An ill-defined genus, the species of which differ straight; valves slightly sigmoid. KB. . 104, t. 4.f.30. = Amphipleura sigmoidea, SBD. i. p. 45, pl. 15. f. 128. Marine. Europe, (XIII. 2.) It forms brown stain-like patches on marine rocks, and scarcely changes colour when gathered. A. inſtea'a (Bréb.).—Valves linear, lu- nately curved, slightly attenuated, some- what constricted beneath the rounded apices. KSA, p. 88, Marine. (IV, 31.) France and Britain. 1-430" to 1-336". Striae close, usually very indistinct. In mode of growth and colour it resembles A. rigida, but changes to a green colour as soon as gathered. FAMILY W.—SUIRIRELLEAE. Frustules prismatic or subdisciform ; striae of the lateral surfaces either interrupted by a longitudinal line or radiate. The Surirelleae comprise by no 784 SYSTEMIATIC IIISTORY OF THE INFUSORTA. means a Satisfactory group, and we believe that Synedra and the other genera with wand-like frustules should be removed from this family, whether they be united to the Fragilarieae or retained together as a distinct family; but the object of this work is rather to present an opitome of what has already been done than to introduce any extensive alterations. “The genus Campylo- discus is near to the Melosirea”, but the disk is not circular but elliptical. Surirella and the free frustules of Synedra are related to the Naviculea, but they want the middle clearly-defined nodule in the secondary sides. Bacil- laria is closely allied to the Fragilarieae, especially to Diatoma; but the striae of the frustule are interrupted in the middle, while in Diatoma they are pervious. . . . . Comparing together the genera Campylodiscus, Surirella, Bacil- laria, Synedra, it is easily perceived that the last two only deviate from the Fragilarieae by the character of interrupted striae; and the first two, deviating sensibly in the succession of species from the circular shape of the lateral surfaces, or of the transverse section, establish a transition between the Melosirea, and the group formed of these two genera, along with the Fra– gilarieae and the Meridieæ. Hence it is impossible to establish an organo- graphical character that shall embrace the entire family and strictly represent its type.” (Meneg.) Genus BACILLARIA (Gmel.).-Frustules lincar, straight, united into a short band, moving on each other by a sliding motion without separation; valves having a longitudinal punctated keel. The elongated wand-like frus- tules distinguish this from all other genera, except some species of Diatoma and Synedra. It differs from the former by the frustules not forming zigzag chains, and from the latter by its band-like filaments. “The principal organo- graphical character that distinguishes Bacillaria from the Fragilarieae is the same that allies it to a different group of the family, viz. the interruption of the transverse striae in the median line of the secondary surfaces, to which is added the parallelism of the primary surfaces.” (Menegh.) Donkin, late, hyaline; striae obsolete. Marine. TMS. vi. p. 16, pl. 3. f. 12. England. (IV. 19.) B. socialis (Greg.).-Valves lanceolate, with fine, but distinct, transverse striae. = Nitzschia socialis, Greg. TMS. v. p. 8, pl. 1, f. 45, Marine. Scotland. Frustulos in groups, striae 30 to 36 in 001, Greg. * Frustules united into a short band. BACILLARIA paradoaca (Gmel.). — Valves linear lanceolate, E Inf. p. 195; SBD. pl. 32. f. 279, Ditches in salt marshes. Europe. (IV. 18; IX, 166, 167.) 2 * Frustules bundled, B. cursoria (Donkin).-Valves lanceo- Genus HOMOEOCLADIA (Ag.). — Frustules bacillar, Nitzschoid, within subular, submembranaceous, branched filaments. The frustules are usually fasciculated; and their structure, which is that of the genus Nitzschia, sepa- rates the present from the other frondose genera (Sm.). When dried, the filaments become opake, and usually acquire a metallic lustre. HoMCEOCLADIA Martiana (Ag). — Frond umbellately branched, membrana- ceous, rugose, sº when dried; frustules crowded, linear, elongated, obtuse. Ag. CD. p. 25; ** 110, t. 30. f. 83. = H. Anglica, Ralfs, Annals, xvi. pl. 3. f. 1. Marine. Europe. (IV. 2, 3; XIV. 47–49.) Fronds much branched, flaccid when re- cent, and of a dark olive-colour, with a metallic lustre and transversely wrinkled when dried. H. A glica (Ag). — Frond trichoto- mous below, dichotomous above, opake when dry, Scarcely rugose; frustules very long, linear, obtuse. Ag CD. p. 25; KB. t. 30. f. 82. France and England. Does not adhere to paper. We are unable to determine from the fragments we have examined whether this is truly distinct from H. Martiana. H. Arbuscula (K.).-Very much and umbellately branched, upper branches OF THE SURIRELLE ZE, 785 fascicular, capillary, spuriously jointed; frustules linear, elongated, obtuse, smooth. KB. p. 111, t. 22. f. 11. Ma- rine. Venice. 1-7". H. dilatata (K.).—Much branched, Se- taceous, branches fastigiate, incrassated above, clavate ; fasciculi closely conti- guous; frustules linear, elongated, acicu- lar, obtuse. KB. p. 111, t, 23. f. 1. Ma- rine. Adriatic. 1–12". - H. moniliformis (Kütz.).-Capillary; branches slender, elongated, moniliform; fasciculi of frustules remote; frustules very long linear, obtuse. KB. p. 110, t. 22. f. 10. Adriatic. (XIV. 45,46.) H. pumila (Ag., K.).—Irregularly di- vided into equal, obsoletely-articulated, capillary branches; frustules short linear, with rounded ends. KB. p. 110, t. 22. f. 9. = Schizonema pumilum, Ag CD. p. 16. Adriatic. (XIV. 37, 38. H. penicillata (Kütz.). — Fastigiately branched ; branches divaricate, fasti- giately divided; terminal ramuli white, in pencils; primary tube thick, gelati- nous cartilaginous; frustules densely ag- gregated, slender, linear acicular, very narrow. KSA. p. 97. France. H. lubrica (Me., K.). — Gelatinous, reen, Setaceous, for the most part di- vided at the apex; frustules fascicu- late, densely aggregated, linear. KSA. p. 98. = Schizomema lubricum, Menegh. Adriatic. H. ſiliformis (S.).--Frond simple; fas- cicles of 3 or 4 frustules; front view linear-lanceolate, obtuse; valves linear lanceolate, subacute, SBD. ii. p. 80, pl. 55. f. 348. Brackish and fresh water. England. (IV. 25.) H. Sigmoidea (S.). — Frond, simple; frustules irregularly fasciculated in bun- dles of about 6; front view sigmoid; valves linear, with attenuated ends. SBD. ii. p. 81, pl. 55. f. 349. Brackish water. Britain. (IV. 26.) Genus SYNEDRA (Ehr.).-Frustules elongated, wand-like, attached by the lower end, lateral surfaces equal to or less than the front view, traversed by a smooth median longitudinal line. The true species of Synedra are distinguished from all other genera by their wand-like form and attachment by one end. They are usually either fasciculated or fixed to a distinct stipes in a fan-like manner. “As to the organographical considerations which can be instituted in this genus, they reduce themselves to the single one of length predominating over breadth and the eminently bacillary form derived from it. Thus Kützing observed of the opposite characters of Synedra and Surirella, that the lateral surfaces exceeded in one the primary surfaces in the other.” Several of the species at present placed in this genus may prove, when better known, to belong to Nitzschia. * Minute; attachment slight; striae &mdistinct or obsolete. SYNEDRA quadrangula (K.). — Very minute, in one view narrowly linear, in the other broad quadrangular. KB. p. 63, t. 3. f. 23. Marine, Norway. S. Atomus (K., Näg).—Very minute, in one view elliptic with rounded apices, in the other linear truncate. KSA, p. 40.- Amphora Atomus, K.B. t. 30. f. 70; Synedra minutissima, 8 pelliculosa, K. (according to M. de Brébisson). Fresh water. Europe. * . S. perpusilla (K.).-Very minute; front view very narrow linear; valves lanceo- late, contracted near the obtuse apices. RB. p. 63, t. 3. f. 31. Venice. S. Biasolettiana (K.).—Very minute; front view very narrow linear, arcuate; valves lanceolate, obtuse. KB. p. 63, t. 3. f. 22. Fresh water. Trieste. S. pusilla (K.), Minute; front view broadly linear ; valves oblong-elliptic, with somewhat rounded apices. KB, p. 63, t. 3. f. 29. Carlsbad. 1-1800". S. angustata (K). Front view very narrow linear; valves broader, oblong, with attenuated, rather obtuse apices. KB. p. 64, t. 4, f. 1, 3, Hot springs. Italy. 1-720". S. virginalis (K.).-Front view linear, truncate, with attenuated centre; valves lanceolate. KB. p. 64, t. 3. f. 15. Genoa. 1-600”. S. ventricosa (Rab.).--Front view nar- row linear; valves ventricose, with short, produced, beak-like apices. Rab D. p. 52, t, 4. f. 36. Apennines. 2 * Frustules in lateral view arcuate, S. lunaris (E.):-Valves marrow, linear, arcuate, slightly attenuated, obtuse; striae faint, 36 in 001". EI. t. 17. f. 4; SBD. i. p. 69, pl. 11, f. 82. Fresh water. Common. Europe, Asia, and America, - 3 E 786 SYSTEMATIC EIISTORY OF THE INFUSORIA, (x. 185.) Frustules affixed, often aggre- gated. t S. falcata(K.), Valves arcuate, linear, with obtuse apices, faint striae, undulated venter. KSA. p. 43. Paris. S. bilunaris (E.). — Valves linear, curved, bilunate, obtuse, attached, more attenuated at base; striae obscure. EI. t, 17. f. 5. Fresh water. Europe. Valves bent inwards at the middle, so as to be- come bilunate. S. longissima (Sm.).-Valvemuchelon- gated, slightly and gradually attenuated, with capitate apices; striae 28 in 001". SBD. i. p. 72, pl. 12. f. 95. Botanic Gar- den, Belfast. Is this distinct from S. biceps? S. biceps (K.).-Muchelongated; valves very slender, gradually attenuated, with capitate apices and distinct transverse striae. ICB. p. 66, t. 14. f. 18. Fresh water. Europe. 1-100" to 1-60". Front view linear, with striated margins, Some- times dilated at the ends. S. alpina (Nāg.). — Slender, faintly striated ; front view straight, linear; valves arcuate, very narrow lanceolate, with produced capitate apices. ISA. p. 43. Switzerland, 1-600" to 1-336". S. subarcuata (Nāg.).--Small; front view straight, linear, valves slightly ar- cuate, with produced capitate apices. I-2400" to 1-1200". Switzerland. Like S. alpina, but only half the size. Rab. Sjevuosa (Bréb.).—Frontview broadly linear; valves linear, curved, sometimes flexuose, with capitate apices and very fine transverse striae. = Eunotia flexuosa, KSA. p. 6; S. biceps, SBD. i. pl. 11, f.83. Freshwater. France, England. 8, valves two or three times flexed. Differs from S. biceps in having linear, not tapering valves. S. pachycephala (K.). — Front view slender, linear ; valves linear, slightly arcuate, with claviform apices and indi- stinct striae. = Eunotia pachycephala, KSA. p. 6. Fresh water, Europe. S. arcuata (Nāg.). —Smooth; front view straight, linear, with truncate ends; valves linear, arcuate, with rounded apices. KSA, p. 890. Switzerland. S. gibbosa (R.).—Front view linear; valves arcuate, tapering to the slightly constricted recurved apices; venter con- cave, gibbous at the middle. = Navicula Arcus, EI, p.182; Cymbella Arcus, HBA. p. 429; Ceratoneis Arcus, KB. p. 104, t. 6. f. 10; Eunotia Arcus, SBD. i. p. 15, pl. 2. f. 15. Fresh water. Europe. The frustules are affixed, as in other species of Synedra. - S. hamata (S.). — Valves linear or linear-lanceolate, with suddenly con- stricted, produced, incurved apices; striae marginal, 30 in 001". SBD. i. p. 73, pl. 30. f. 264. Fresh water. Sussex. 3 * Valves straight, with a circular, deft- nite central pseudo-module. S. pulchella (Ralfs, Kütz.).-Frustules in fan-shaped clusters on a compressed- dichotomous stipes; valves lanceolate, obtuse, with a median umbilicus. [B. p. 68, t. 29. f. 87; SBD. i. p. 70, f. 84. = Ctenophora pulchella, Bréb., Synedra Vertebra, Greg, M.J. iii. pl. 4. f. 22. Ponds and slow streams. England and France. Striae 33 in .001", Šm. S. minutissima (K.).-Very minute; front view narrow linear; valves lanceo- late, rather obtuse; striae 36 in 001". KB. p. 63, t. 3. f. 30; SBD. pl. 11. f. 87. Fresh water. Europe. S. gracilis (K.). — Frustules affixed, scattered; valves lanceolate, acute, with a median pseudo-module. KB. p. 64, t. 15. f. 8; SBD. i. p. 70, pl. 11. f. 85. Marine. Europe. Striae obscure, 39 in 001", Šm. S. Smithii (R.).—Frustules irregularly affixed; valves lanceolate, acute, with 36 very faint striae in 001." = Synedra acicularis, SBD. i. p. 70, pl. 11, f. 86. Brackish water. England. 4 * Valves with very long awn-like beaks (Toxarium); module obsolete. S. undulata (Bailey).-Valves slender, lanceolate at the middle, tapering into very long, linear, undulated awns, with clavate apices. SBD. ii. p. 97; Greg. DC. p. 59, pl. 6...f. 107. = Towarium undulatum, ailey, MO. p. 15, figs. 24, 25. Marine. America and Europe. Front view linear, broader; valves arcuate or straight, with 24 moniliform striae in '001". S. Hennedyana (Greg.).-Frustules as in S. undulata, but the awns not undu- late. GDC. p. 60, pl. 6. f. 108. Marine. Scotland. 5* Frustules affixed, aggregated or scat- tered; pseudo-module obscure or in- definite. - S. parvula (K.).--Front view linear, truncate; valves broad lanceolate, acute. KB. p. 64, t. 30. f.32. Fresh water. Ger- many and France. 1-1200". Sometimes free, sometimes attached and densely aggregated in a radiant manner. § ºuñs (K.). — Slender, radiant; valves narrow linear-lanceolate, very acute. KB. p. 64, t. 14. f. 2a. = Navicula OF TEIE SURIRELLE ZE. 787 Acus, EInf. p. 176, t. 13. f. 4. (Ix, 147.) Germany and France. S. dissipata (K.).—Slender, affixed, radiant; front view narrow linear, trun- cate; valves narrow lanceolate, acute. KB. p. 64, t. 14. f. 3. = S. fasciculata, EI. t. 17. f. 3. Fresh water. Europe, Australia, and Asia. S. famelica (K.).-Delicate, irregularly aggregated, very marrow linear, truncate in lateral view, front view rather acute. KB. p. 64, t. 14. f. 8. 1. Fresh water. Germany. Is a somewhat larger form of S. dissipata, Rab. S. radians (K).--Delicate, densely aggregated, radiant; front view very nar- row linear, truncate; valves narrow lan- ceolate, rather obtuse. KB. p. 64, t. 14. f. 7. Europe. 1-600". A minute species. S. tenuissima (K.). — Very slender, elongated; front view exactly linear, truncate; valves acicular, acute. ICB. p. 64, t. 14. f. 6. Stagnant waters. Germany and France. 1-180". S. tenuis (K.).--Slender, elongated; front view exactly linear, truncate; valves narrow lanceolate, with some- what obtuse apices. KB. p. 65, t. 14. ſ. 12. Fresh water. Germany and France. 1-168". S. Acula (K.), — Slender, elongated, lanceolate, in front view truncate, in lateral view very acute. KB. p. 65, t. 14. f. 20. Fresh water. Dalmatia and France. 1-72". S. laevis (E.).--Slightly and irregularly affixed; front view slightly attenuated, truncate; valves more attenuated, ob- tuse. EA. t. 2.6. f. 2. Marine. Europe and America. 1-130". S. gracillima (Rab.). —Front view elongated, very narrow linear ; valves linear, acicular, acute. Rab D. p. 53, t. 4, f. 20 d, e. Dresden. S. salina (S.). — Valves lanceolate, gradually tapering towards the somewhat obtuse apices; striae distinct, 32in 001". SBD. i. p. 71, pl. 11. f. 88. Marine. England. Š. apiculata (Rab), Very slender; valves linear, acicular, with shortly tapering apices, ſaintly striated. Rab D. p. 56, t. 5. f. 20 a, b, c, Dresden. S. amphicephala (K.).—Slender; front view linear, truncate; valves narrow lanceolate, tapering, with capitate apices. KB. p. 64, t. 3. f. 12, Fresh water. Germany. 1-360". S. fontinalis (S.).-Frustules scattered; valves linear-lanceolate or elliptic-lan- ceolate, with produced, Subcapitate apices; module indefinite; striae 27 in 001'', Sm ANH. 1857, p. 9, pl. 1, f. 9. Fresh water. Pyrenees. S. gibba (E.).--Smooth, fasciculated, elongated, narrow linear; valves broadly tumid at the middle, with gradually attenuated, obtuse apices. EA. p. 137. United States. S. delicatissima (S.). —Valves elon- gated, very narrow, gradually taperin to the subacute apices; striae 27 in .001". SBD. i. p. 72, pl. 12. f. 94, Pseudo-nodule indefinite. S. tenera (S.). — Frustules clustered; valve nearly linear or attenuated towards the slightly inflated apices; module inde- finite; striae 60 in 001". SBD. ii. p. 98. Fresh water. Britain. In outline not unlike S. delicatissima, but far smaller and with more delicate striae, Sm. S. lanceolata (K.).--Front view nar- row linear, with slightly dilated apices; valves lanceolate, distinctly striated, with a blank, rhomboid median space. KB. p. 66, t. 30. f. 31. America. 1-600" to I-310". S. debilis (K.).-Minute; front view slightly attenuated, truncate, with obso- letely striated margins; valves lanceo- late, with produced apices. KB. p. 65, t. 3. f.45. = S. porrecta, Rab D. p. 55, pl. 4. f. 27. Stagnant waters. Europe, COIDTIO, OIT. S. mesolepta (K.). —Delicate; front view dilated at the ends; valves lan- ceolate, curved or slightly sigmoid. KB. p. 66, t. 30. f. 30. America. I-160". S. notata (K.).—Small, with obsoletely striated margins; front view quadran- gular; valves elliptic-oblong, with ob- tuse ends. KB. p. 65, t. 3. f. 33. Stag- mant waters. Europe. 1-650". S. Martensiana (K.). — Small, di- stinctly striated; front view linear, trun- cate; valves rather broader, lanceolate, subacute. KB. p. 65, t. 3. f. 9. Marine. Europe. S. Vaucheriae (K.).-Minute; front view linear, truncate; valves linear- lanceolate with somewhat produced ends, indefinite pseudo-nodule, and 30 marginal striae in 001". KB. p. 65, t. 14. f. 4; SBD. i. p. 73, pl. 11. f. 99. Fresh water, especially on species of Vaucheria, Europe. S. acqualis (K.). — Front view dilated at the ends; valves linear, with rounded apices, indefinite pseudo-nodule, and 24 striae in 001". KB. p. 66, t. 14. f. 14. = S. obtusa, SBD. i. p. 71, pl. 11. f. 92. Stagnant waters. Europe. 1-140". S. investiens (S.). — Valves linear, 3 E 2 788 SYSTEMATIC ELISTORY OF TEDE INFUSORTA. slightly attenuated towards the rounded apices, nodule, obsolete; striae 26 in .001". SBD. ii. p. 98. Marine. Scot- land. - S. acuta (E.).-Front view exactly linear, truncate; valves linear, striated, suddenly acuminated near the apices. JEA. t. 1. 2. f. 22. America, Asia, Au- stralia, and Africa. 1-144". S. Oxyrhynchus (K.). — Front view linear; valves linear, narrower, suddenly contracted into a beak at the ends. KB. p. 66, t. 14, f 9–11. Germany. Di- stinguished from S. acuta by its con- | stricted ends. S. vitrea (K.).--Front view with di- lated apices; valves linear, with Sud- denly attenuated, obtuse ends. KB. p. 66, t. 14. f. 17. France. Distin- guished from S. Oxyrhynchus only by its dilated ends in the front view, Rab. S. amphirhynchus (E.):-Large; front view linear, not dilated at the ends; valves contracted into obtuse beaks. E.A. t. 3. 1. f. 25. Fresh water. Eu- rope, Africa, and America. 1-120" to 1-96". No large, median, Smooth space. S. praemorsa (E.).--Frontview broadly linear, with truncated, cuneate apices; valves linear, with rounded cuneate ends. JEA. t. 3. 6. f. 11. Mexico. S. deformis (S.). --Valves linear or linear-elliptical, suddenly constricted towards the produced and often distorted extremities; module obsolete; striae 36 in .001". SBD. ii. p. 98. Fresh water. Sussex. S. Ulna (E.). —Front view exactly linear; valves linear, slightly attenuated near the obtuse apices. EIñf. t. 17. f. 1; SBD. i. p. 71, pl. 11. f. 90. Fresh water, Europe, Asia, Australia, Africa, , and America. (x. 184.), 1-280" to 1-100". Striae 24 in 001'', Sm. - S. Splendens (K.),—Large, elongated; front view with dilated truncate ends; valves lanceolate, obtuse. KB. p. 66, t. 14. f. 16. =S. radians, SBD. i. p. 71, in part. Fresh water. Europe, Asia, and Africa. 1-72". Differs from S. Ulma merely in its dilated apices, Rab. S. Danica (K.).-Slender; front view with dilated, truncate ends; valves lan- ceolate with slightly clavate apices. KB. p. 66, t. 14. f. 13. Stagnant waters. Europe. 1-140". Is only a more slen- der form of S. splendens, Rab. S. mesocampa (Bréb.).—Size and form of S. Ulna, but in the lateral view flexed at the middle. KSA, p. 44. France. S. capitata (E.).-Valves linear, with the extremities dilated into a triangular head; striae 23 in 001". E Inf. t. 21. f 28; SBD. i. p. 72, pl. 12. f. 93. Fresh water. Europe, Asia, Africa, and Ame- rica. (IV. 29; x. 185.) Very large; length 1–120" to 1-40". S. longiceps (E.).-Very large, in form approaching very near to S. capitata, but with styliform, produced apices. ERBA. 1845. Fresh water. America. 1-12” to 1-144". 6 * Frustules attached by a distinct, mostly persistent, Stipes; pseudo-module obsolete or indefinite. f Frustules in fan-shaped clusters on a short, mostly simple, stipes. S. Acus (Kütz.).-Slender, smooth; front view slightly attenuated, truncate; Valves very narrow lanceolate, acicular. KB. p. 68, t. 15.f. 7. Hamburgh. 1-960". S. familiaris (K.).--Smooth, distinctly tabellate and flabellately disrupted; front view slightly attenuated near the truncate ends; valves lanceolate, acute. KB. p. 68, t. 15. f. 12. France. 1-320”. S. parva (K.).—Minute, smooth, nar- row linear, truncate; valves narrow lan- ceolate. KB. p. 67, t. 15. f. 9. Marine. Italy. 1-960". S. socialis (Rab.).—Front view linear, with truncated, cuneate ends; valves lanceolate, distinctly striated. Rab D. p. 56, t. 4. f. 22. Fresh water. Italy. S. Gallioni (E.).--Frustules large, on a thick, convex stipes; valves lanceo- late; striae 36 in 001", interrupted by a median line. E Inf. t. 17. f. 2; SBD. i. p. 74, pl. 30. f. 265. Marine. Europe, Asia, Africa, and America. (XII, 34, 36.) 1–120" to I-100". S. fasciculata (Ag., K.).-Frustules ta- bulate, on a thick, hemispherical stipes; front view linear, with subattenuate, truncate apices; valves lanceolate. KB. p. 68, t. 15. f. 5.5 Diatoma fasciculatum, Ag CD. p. 51. Marine. Common. S. tabulata (Ag., K.).—Frustules large, on a thick, abbreviated stipes; front View broadly linear, truncate; valves lanceolate, with subcapitate apices; striae marginal, 27 in 001". KB. p. 68, t. 15. f. 10; SBD. pl. 12. f. 96. H Diatoma tabulatum, AgCD. p. 50. Marine. Europe. S. affinis (K.).-Frustules subtabulate, on a hemispherical stipes; front view slender, linear, with subattenuate trun- cate apices; valves lanceolate, acute, with 32 marginal striae in 001". KB. 3, 68, t. 15. f. 6, 11; SBD. i. p. 73. Marine. Europe. 1-320". Frustules OF TELE SURIRELLEAE. 789 gººd in flabellate or radiating bundles, Ill. S. barbatula (K.).—Minute, tabulate; front view linear, truncate, with a ter. minal mucous appendage; valves elliptic- lanceolate. #. p. 68, t. 15. f. 10.4. Marine. Europe. 1-960". S. truncata (Grev.).-Frustules united in tablets, obscurely stipitate; front view linear, truncate; valves lanceolate, obtuse. = Diatoma and Evilaria truncata, Grew. } Evilaria fasciculata, Hass.; Synedra fasciculata, SBD. i. p. 73, pl. 11. f 100. Fresh water. Europe, Striae 40 in 001”, Sm. S. Arcus (K.).-Frustules flabellate, attached to a cushion-like stipes; front view curved; valves lanceolate, with 30 marginal striae in 001. KB. p. 68, t. 30. f_50; SBD. i. p. 73, f. 98.7 (Iv. 27.) Marine. Europe and America. 2 f Frustules on an elongated, often branched, stipes. S. Ehrenbergii (K.).-Frustules at- tenuated near the obtuse apices, terminal on a long, linear stipes. . p. 69, t. 11. f. 6. Fresh water." Berlin. S. Saxonica (K.).--Stipes a little elon- gated; frustules slender; front view linear, truncate; valves narrow lanceo- late. KB. p. 68, t. 15. f. 14, Salt Lake at Mansfeld, 1–330". S. fulgens (Grev., S.).-Frustules ter- minal on a thick, branched stipes, ge- minate linear, truncate; valves linear, inflated at centre and ends; striae 36 in -001". SBD. i. p. 74, pl. 12. f. 103.− Evilaria fulgens, Grew, ; Liemophora fulgens, KB. f. 18. f. 5. Marine. Europe and America. S. crystallina (Ag., K.).—Frustules very large, on a thickish abbreviated stipes; valves linear, inflated at centre and apices; striae distinct, 26 in 001". KB. p. 69, t. 16. f. 1; SBD, pl. 12. f. 101. = Diatoma crystallina, Ag. Marine. Europe. 1-60" to 1-48". S. superba (K.). — Stipes somewhat elongated; valves stout, linear-lanceo- late, with rounded ends; striae very di- stinct, 27 in 001". KB. p. 69, i. 15. f 13. SBD. i. p. 74, pl. 12. f. 102. Marine. Europe. S. Dalmatica (K.).--Stipes somewhat elongated and branched; frustules large, linear, slightly and gradually attenu- ated at the subtruncate ends. KB. , 69, t. 12. f. 2. Marine. Adriatic Sea. ɺle. terminal on the branches. 1–240". S. robusta, n. S. — Frustules linear; valves elliptical, ends rounded. Striæ 20 in 001", interrupted by three equi- distant longitudinal lines. 0120" to '0175". Algae, Corsica. (VIII. 3.) - S. gigantea (Lobarz.).-Frustules very long, delicate, somewhat twisted, linear, truncate; valves very narrow, with di- lated, obovate apices. Lobarzewsky, Limnaea, 1840, p. 276, t. 6; KSA, p. 48. Marine. Dalmatia. 7 * Frustules connected in tablets, at length separating, and adhering by alternate angles, as in Diatoma. S. rumpens (Kütz.).--Tablets affixed; frustules very narrow linear, with tumid obtuse apices, adhering , by alternate angles. KB. p. 69, t. 16.f. 6. Brackish water, German coast. Doubtful species from Ehrenberg. S. australis. – Linear, striated, with attenuated, obtuse apices in both views. ERBA, 1840; Microg, pl. 1. 1, f.3. In siliceous schist from the Philippine Islands. 1-432". S. paleacea.—Very narrow, Smooth, with subacute apices. E.M. pl. 1. 1, f. 1. With the last. 1-480". S. incurva. — Linear, very narrow, flexuose, smooth, round, or equally quadrangular. ERBA, 1844, p. 272. Bermuda. 1–288". Perhaps a Spongo- lithis. S. rostrata (EM. pl.9.1. f.4, and pl. 14. f_44)—Fossil. France and Germany. Valves elongated, slender, linear, with contracted, conic apices, and transverse striae. e S. elegans, Asia ; S. striata, Asia; S. lineaţa, Asia; S. Subulata, Africa; S. curvata, America. S. doliolus (Wallich). — Frustules linear; valve subarcuate, pseudo-module absent, Striae 30 in 001", 0.020" to -0050". Salpas. Indian Ocean, Atlantic. Wallich, TMS. viii. p. 48, pl. 2. f. 20. Genus DESMOGONIUM (Ehr.).-We are unacquainted with the characters of this genus; Ehrenberg's figures of it seem to show a relation to Synedra, the tablets (not single frustules) being attached to each other by a connecting Substance, end to end—an arrangement which simulates a filament. 790 SYSTEMATIC HISTORY OF THE INFUSORIA. DESMOGONIUM Guianense-EM. t. 34. (xv. 13.) Frustules not stipitate; valves 5 A. f. 3. Apparently not very uncom- without longitudinal ridges, mostly mon, since Ehrenberg gives about 50 broader than the front view. habitats in Asia, Africa, and America. Genus DIMEREGRAMMA (N., G.).-Frustules quadrangular, two or more together; valves scarcely broader than front view, having the transverse costae or striae interrupted by a smooth, longitudinal median line. The frus- tules are united as in Denticula or Odontidium, from which genera it is distinguished by the longitudinal median line. The structure is probably the same as in Staurosira (E.), the description of which, however, is altogether inapplicable to many of the species here assembled. DIMEREGRAMMA minor (Greg.). — Front view with convex striated margins, constricted beneath the comic angles; valves narrow lariceolate, with from 18 to 20 strong costae in .001". = Denticula minor, GDC. p. 23, pl. 2. f. 35. Marine. Scotland. D. capitatum (Greg.). — Front view with convex, obscurely striated margins, constricted beneath the dilated roundish apices. = Denticidata capitata, Greg l. c. . 22, pl. 2. f. 31. Marine. Scotland. s larger than D. manum, with rounded apices. Side view unknown. D. nanum (Greg.).-Front view with convex margins, constricted beneath the conic angles; valves broad, obtusely rhomboid, with rather fine striae. = Den- ticula mana, Greg l.c. p. 23, pl. 2. f. 34. Marine. Scotland. (IV, 33.) D. distans (Greg.).--Front view con- stricted beneath the comic angles; valves broad, rhombic-lanceolate, with strong, short marginal costae, and a lanceolate, blank median space. = Denticula distans, Greg l.c. p. 23, pl. 2. f. 36. Marine. Scotland. Is larger than D. minor, and its valves broader. (IV. 34.) D. Rhombus = Fragilaria P. Rhombus, EM. pl. 8, 1. f. 16. Fossil, Hungary. Valves broadly rhomboid, with marginal costae, and a smooth median space. D. fulvum (Greg.).--Front view elon- gated, with striated margins, constricted beneath the dilated apices; valves mar- row lanceolate, with dilated, Subcapi- tate apices; striae moniliform, nearly reaching the centre. = Denticula fulva, GDC. p. 24, pl. 2, f, 38. Marine. Scot- land. D. marinum (Greg.). — Front view elongated, linear, with striated margins and slightly produced angles; valves linear, with gibbous middle, obtusely comic apices, and about 10 coarsely moniliform striae in 001". = Denticula marina, Greg l. c. p. 24, pl. 2. f. 39. Marine, Scotland, D. mutabile (Sm.).-Filaments elon- gated; valves oblong or lanceolate, with 20 marginal costae in 001". = Odontidium mutabile, SBD. ii. p. 17, pl. 34. f. 290; Fragilaria amphiocys, EMI, pl. 39. 3. f. 53. Fresh water. Europe. D. Leptoceros (E.).-Valves rhomboid- linear, with longly attenuated, acute, straight ends, finely striated margins, and a smooth median space. = Fragilaria Leptoceros, ERBA, 1844, p. 82; Odonti- dium Leptoceros, KSA. p. 13, North America. D. sinuatum (Thwaites).--Front view linear, truncate; valves rhomboid-lan- ceolate, with slightly undulated margins; striae delicate, 52 in .001"; costae inter- rupted, 10 in .001". = Denticula sinuata, SBD. ii. p. 21, pl. 34. f. 295. Fresh water. Britain. (IV, 12.) D. Tabellaria (Sm.). — Filaments fra- gile; valves with constricted or inflated middle, rostrate apices, and 36 delicate costae in 001". = Odontidium Tabellaria, SBD. ii. p. 17, t. 34. f. 291. a, valves inflated at the middle, = StauroSira con- struens, Eh. P 8, valves constricted at the middle. (IV. 35.) D. birostris (E.).-Very minute; valves lanceolate, suddenly rostrate, acute; striae interrupted by a median line. = Pragilariabirostris, ERBA, 1844, p. 342; Microg. pl. 38 A. 2. f. 8. Fossil, Ger- many. 1-3120". Has nearly the cha- racters of a Staurosira, Eh. D. informe (S.). —Valves elliptical, with an irregular inflation at the centre, and hence subcruciform ; costae 18 in '001." = Odontidium informe, S Annals, 1857, p. 10, pl. 1, f. 12. Fresh water, IFrance. D. Harrisonii (Sm.). —Frustules fre- quently adhering by their angles; valves cruciform, with rounded lobes; costae distinct, 13 in 001". = Odontidium ? Harrisonii, SBD. ii. p. 18, pl. 60. f. 373. Fresh water. Hull. The valves in form resemble those of a small Tetracyclus, OF TEIE SURIRELLEAE. 791 but have interrupted costae; the front view, too, is very different. (XVIII, 6.) D. pinnatum (E.).-Valve cruciform, with angular lobes; costae as in D. Har- wisonii.-Staurosira pinnata, EM. t. 5. 2. f. 24; Odontidium Harrisonii, 8, Roper, M.J. ii. p. 6, f. 6. Europe and America. (VIII. 4.) D. Speciosum (Brightwell). — Valve subcruciform or rhomboidal ; angles rounded, naked; costae short, distinct, 16 on each side. = Odontidium speciosum, Brightwell, JMS. vii. p. 180, pl. 9. f. 8. Doubtful species. D. Surirella = Fragilaria Surirella, EM. pl. 39. 3. f. 54. Frustules large, iºd; linear, with rounded ends and marginal costae. D. Baldjickii (Brightwell). — Valve ovately rhomboidal; costae about 20 on each side, distinct, reaching nearly to the ends, but leaving a linear open space down the centre. a clay or earthy deposit from Baldjick, Mr. Norman. = Odontidium Baldjickii, Brightwell, l.c. p. 180, pl. 9. f. 10. Genus STAUROSIRA (Eh.).—“The form of this genus is that of qua- drangular Fragilariae ; it is distinguished from the much larger forms of the allied genus Amphitetras by the absence of (pseudo-) openings at the four angles.”—ERBA. 1843, p. 45. The above is the only notice of this genus we have met with, the resemblance to Amphitetras is evidently very slight. From Ehrenberg’s figures, Staurosira seems to contain forms allied to Odon- tidium and Fragilaria, which have the valve so inflated at the centre as to appear 4-lobed. This character, however, is uncertain, since Professor Smith shows that the same species has the valve sometimes inflated, and sometimes constricted at the middle. STAUROSIRA construens (E.). — Very Small, Smooth; valves spindle-shaped, with the produced angles somewhat un- S. amphilepta (E.).-Minute, smooth, two of the produced angles larger and more slender than the others. equal. FM, several figures. Asia, S. trigongyla, Asia; S. Epidendrium, Africa, and America. (xv. 5.) I-600". Chili; S. Mearicana, Mexico; S. trica- *inata, Mexico.—These species (Ehren- Compare with Dimeregramma Tabel- berg's) are known to us only by name. Jaria. Genus RHAPHONETS (E.).-Frustules simple, free or shortly stipitate : front view narrow linear ; valves much broader, with transverse dotted striae and a median longitudinal line. Marine. Rhaphoneis differs from Cocconeis and Navicula by the absence of a central nodule. The frustule has no alae; its striae are usually distinctly moniliform and divergent, and its median line more conspicuous than in Trybliomella. We have not thought it desirable to separate Doryphora; for it is doubtful whether Kützing’s only species is even specifically distinct from Some forms still retained by him in this genus. REIAPHONETS Amphiceros (Ehr.). — Valves lanceolate, about three times as long as broad, with produced, styli- form apices, and fine, dotted transverse striae. ERBA, 1844, p. 87; M. t. 18. f. 82. = Cocconeis Amphiceros, E. 1840; Doryphora Amphiceros, KB. º 74; SBD. i. pl. 24. f. 224. Marine, Europe and America. (XIV. 21.) 1-576". Striae 18 to 20 in 1-1200". Ends suddenly con- tracted and prolonged into a beak, R. Fusus (E.).-Valves slender, linear- lanceolate, usually four times as long as broad, with styliform apices, and 17 or 18 fine, transverse, granulated striae in 1–1200". ERBA. 1844, p. 87. Fossil. Virginia. 1-720". Strongly akin in habit to Fragilaria Amphiceros, but differs by its median Suture, - R. Leptoceros (E.). — Valves long lanceolate, quadrangular, rhomboid, three times as long as broad, with long styli- form apices and fine, granulated trans- verse striae. ERBA, 1844, p. 87.-R. Oregonica, EM. pl. 18. f. 83. Fossil. erica. 1-720". Striae generally 18 in 1-1200". , Has the habit of R. Amphi- ceros, but with much longer beaks. R. gemmifera (E.). — Large; valves elongated lanceolate, with long gradually. attenuated apices, usually three times as long as broad ; striae strongly granu- lated, 10 in 1-1200". ERBA, 1844, p.87. Fossil. Maryland. 1-300". R. pretiosa (E.). — Large ; valves broadly lanceolate, rhomboid, generally twice as long as broad; apices gradually attenuated into beaks; striae stout, granu- 792 SYSTEMATIC HISTORY OF TEIE INFUSORIA. lar, like series of pearls. ERBA, 1844, p. 87. Fossil. Maryland. 1-480". Striae 11 in 1-1200", R. Rhombus (E.). — Small; valves broadly lanceolate, rhomboid, sometimes suborbicular, scarcely longer than broad, with short rostrate apices and fine gra- nulated striae. ERBA, 1844, p. 87; M. pl. 33. 13. f. 19. Cuxhaven, Virginia. I-1152" to 1-864". Striae 20 to 21 in I-1200". R. scalaris (E.). — Valves slender, acutely lanceolate, furnished with a double series of striae and window-like crystalline spaces. ERBA, 1844, p. 271. Fossil. Bermuda deposit. Diameter J–960". Striae 9 in 1-1200". R. angusta (E.). — Valves elongate lanceolate, with obtuse apices, 24 striae in 1-1200", and no median Smooth space. ERBA. 1844, p. 364. India. R. lanceolata (E.).-Valves rhomboid- lanceolate with obtuse apices, 21 striae in 1–200", and a linear-lanceolate median smooth space. ERBA., 1844, p. 364; M. pl. 34. 7. f. 13. India, China, and Japan, Indica (E.). — Valves elliptic- lanceolate with obtuse apices, 15 striae in 1-1200", and a linear-lanceolate median space. ERBA, 1844, p. 365. India and Japan, R. fasciolata (E.). — Large; valves elliptic-lanceolate, twice as long as broad, with strong, finely granulated striae in transverse fasciae. ERBA. 1844, p. 204; M. pl. 35 A. 22. f. 16. Antarctic Sea. Ehrenberg's figure represents the valve as elliptic, with transverse band-like series of short longitudinal striae, alternating with smooth spaces, and interrupted by a smooth longitudinal median line. (? Lower valve of a Cocconeis.) R. Scutellum (E.). —Valves elliptic, longer than broad, with 12 or 13 stout, crenulated striae in 1–1200". ERBA. 1844, p. 204; M. pl. 35 A.I. f. 5. Ant- arctic §. 1-864". (? Lower valve of a Cocconeis.) R. fasciata (E.). — Microg. pl. 35 A. 9. f. 8. India. Valve elliptic, with broadly rounded ends, a median line, transverse fasciae of longitudinal lines alternating with smooth transverse bands, and two series of marginal striae. (? Lower valve of a Cocconeis.) Species (Eh.) known to ws only by name. IR, setacea, Sandwich Islands; R. Iºntomon, Asia Minor; R. rhomboides, Ganges; R. Gangetica, Ganges; , R. lavis, India; R. Africana, South Africa; R. Digitus, Demerara, Genus TRYBLIONELLA (S.). — “Frustules simple, free, elliptical or linear ; valves plain ; alae submarginal or obsolete, canaliculi inconspicuous, parallel.”—Smith. Tryblionella is another genus separated from Surirella by Professor Smith, who says that it “differs from Campylodiscus in the more elongated form of its frustules and the absence of the bend in its valves; the canaliculi are also more minute, and parallel rather than radiating. with Surirella in the presence of alae; It agrees but these arise from the disk.” Mr. Roper considers that Tryblionella is distinguished from Surirella by its fine (often obsolete), parallel transverse striae; whereas the latter is furnished with canaliculi or costae, which are more or less divergent. TRYBLIONELLA circumsuta (B.). — Lateral view elliptic-oblong, with a faint, longitudinal median line (indistinct or obsolete), parallel transverse striae, and marginal gland-like dots; alae very short. = Surirella circumsuta, Bailey, MO. pl. 2. f. 36; T. Scutellum, SBD. i. p. 35, }. 10. f. 74. Marine. America, Britain. rofessor Bailey describes it as having a minutely granulate surface, and a scarcely perceptible median constriction. T. gracilis (S.).--Frontviewlinear, with attenuate extremities and truncate apices; lateral view linear-acuminate ; costae parallel, extending to median line; alae distinct. SBD. i. p. 35, pl. 10. f. 75. Fresh and brackish waters. Lewes. (IV, 36.) T. navicularis (Bréb.). — Front view oblong, with truncate, slightly winged ends; lateral view elliptic-acuminate; costae distinct, marginal ; alae con- spicuous, = Surirella navicularis, Bréb. in KSA. p. 36 ; T. marginata, SBD. i. p. 35, pl. 10. f. 76. Fresh and brackish waters. France; England. T. acuminata (S.). — Lateral view linear, with attenuated ends and delicate, interrupted transverse striae; alae obso- lete; canaliculi obscure, SBD. i. p. 36, pl. 10. f. 77. Marine and brackish waters. Britain. O012" to -0021". Striae 31 in .001". (Iv. 37.) T. angustata (S.).—Resembles T. acumi- nata; but its striae are continuous. SBD. OF THE SURIRELLEAE. 793 p. 36, pl.80. f. 262. Fresh water. England, -0021" to .0040". Striæ 36 in 001". T. levidensis (S.).-Lateral view linear, with subacute extremities; costae very distinct, parallel, extending to the cen- tral line. SBD. ii. p. water. Cork City Hai. T. punctata (S.).—Lateral view ellip- tic, with acuminate ends and parallel, transverse, moniliform striae ; canaliculi obsolete. SBD. i. p. 36, pl. 30. f. 261. Marine. Sussex. T. constricta (Greg.).-Lateral view 89, Brackish panduriform, with apiculate ends and numerous, delicate, diagonal, punctated striae; costa obsolete. Greg. in MJ. iii. pl. 4. f. 13. Marine. Britain. “Its form is that of Cymatopleura Solea, but it is very much smaller.”—Greg. T. apiculata (Greg.). --Narrow, linear, slightly constricted in the middle, with apiculate extremities and about 45 fine but distinct, transverse, dotted striae in '001". Greg. in M.J. v. p. 79, pl. 1. f. 43. Scotland. ‘O015" to 0.017". Keel often strongly marked. Genus CYMATOPLEURA (S.).-Frustules free, in front view linear, with undulated margins ; laterally broader, and marked with transverse bars. Aquatic. This genus, instituted by Smith, is very distinct, and may be recognized by the lateral surfaces projecting in the front view in an undu- lated manner, the central portion being separated from the undulations by a marginal row of dots. The lateral view is usually very much broader than the front, which often renders it difficult to obtain a satisfactory sight of the latter. The lateral surfaces, however, sufficiently identify the genus, as the broad, transverse, shade-like bands or bars which correspond with the undu- lations are characteristic. The striae are generally obscure or obsolete, and the median longitudinal line is less evident than in Surirella ; the margin is usually furnished with conspicuous gland-like dots. “The undulations of the valves separate Cymatopleura from Tryblionella and Surirella; the absence of alae and canaliculi are further characters which leave no room for hesita- tion as to its distinctness.” (Smith.) CYMATOPLEURA Solea (Bréb., S.).-- Frustule elongate; laterally panduri- form, with more or less attenuated ends, sometimes apiculated ; striae delicate, 8 in 1-1200". SBD. i. p. 36, f.78. = Surirella Solea, Bréb. in KSA. p. 34; S. Librile, E.; Sphinctocystis librilis, Hass BA. p. 102, 3, War. 3, ends apiculated, = C. apiculata, S. l. c. p. 37, f, 79. Common, Asia, Africa, America, Europe. (IX, 155; XVI. 9.) Frustules, in both views, many times as long as broad; undulations six. The ends, in the lateral view are always attenuated; but their apices vary, and are sometimes obtuse, sometimes apiculate; and therefore we concur with M. de Bré- bisson in uniting C. apiculata, Smith, with this species. C. heterocyma ăgeli). — Lateral viewpanduriform, with 16 marginal strite in 1-1200"; front view broadly linear, twice undulately twisted, with six mar- ginal folds. = Surirella heterocyma, KSA. p. 889. Switzerland. 1-240". C. elliptica (Bréb., S.).-Lateral view elliptic, with three to five transverse bars; ends, in general, slightly attenuated. SBD. p. 37, pl. 10. f. 80. = Surirella oo- phaena, E. (according to Kützing); S. undulata, EMI. ; S. undata, EMI, ; S. pli- cata, EM. pl. 15 A. f. 50, 51?; S. Rützingá, Perty, Diat. p. 201, t. 17. f. 2. Aquatic. Asia, Africa, America, Europe. §: 149; XVI. 7, 8.) Professor Kützing escribes the frustules as ovate ; but we have always found them elliptic. Un- dulations three to five; lateral surfaces obscurely striated and furnished with marginal gland-like dots. We have re- ferred the Surirella plicata, E., to this species, because of its habitat, although its figure in the ‘Microgeologie' agrees better with that of C. Hibernica. C. Hibernica (S.). — Lateral view broadly elliptic, with produced ends; striae obscure. SBD. i. p. 37, pl. 10. f. 81. Ireland, France. Undulations about three; length 1-370" to 1-220"; breadth two-thirds the length. C. Regula (E.).--Lateral view linear, with cuneate ends and six transverse bars. = Surirella Regula, K.B. t. 28. f. 30. ; C. parallela, Smith, BD, pl. 30. f. 263. Mexico, France, England. Habit and size of C. Solea, but not panduriform; pinnules 10 in 1-1200", nearly obsolete. C. Ovum (Nägeli). — Lateral view broadly oval, with 8 marginal striae in 1-1200"; front view broadly linear, straight; margin with five marginal 794 SYSTEMATIC EIISTORY OF TEIE INFUSORLA. folds = surrella Ovum, Nägeli in KSA. | The characters given are insufficient to p. 889, Switzerland, 1-360" to 1-280". distinguish it from C. elliptica. Genus SURIRELLA (Turp., E., S.). — Frustules simple, free; margin striated; lateral surfaces broader than the front view, with a Smooth median longitudinal line; “margins produced into alae, canaliculi distinct, usually parallel” (Smith). Surirella thus limited by Professor Smith becomes a much more natural genus than it was constituted by preceding authors: he says, “It is well distinguished from Tryblionella by the prominency of its alae, the distinctness of its canaliculi, and the usually cuneate form of its frustules; with no other is it at all likely to be confounded.” * * Frustules pandwriform. SURIRELLA constricta (E.). — Large, oblong, in lateral view panduriform, with a median line and intramarginal crena- tions. EM. pl. 14. f. 37. Denticula con- stricta, K.B. t. 3. f. 62?. Aquatic. Berlin, (xIII. 3.) Ehrenberg's figure in the ‘Mi- crogeologie’ seems a true species of this genus; and different as is that of Denticula constricta in Kützing's work, yet, as it was copied from a figure given by Ehrenberg in an earlier work, the differences are pro- bably due to the imperfect representation. S. Smithii (K.).—Front view broadly linear, with truncate ends and rounded angles; lateral view panduriform, with attenuated ends; costae delicate, reach- ing the median line, which is often in- flated. = S. constricta, S.B.D. i. p. 31, pl. 8. f 59. Brackish water, England. Alae conspicuous, enclosing an oblong space. 1-300". The shape, in front view, re- sembles that of S. biseriata, but the costae are much finer. S. Antarctica, EM. pl. 35 A. 2. f. 20. Antarctic Sea. We have seen no de- scription of this species. , Ehrenberg's figure shows the lateral view panduri- form, with rounded ends and strongly marked striae, which nearly reach the median line. S. didyma (K.).—Oblong, with trun- cate ends, constricted middle and punc- tated margins. KB. p. 60, t. 3. f. 67. Submarine waters. Isle of Wangeroog. 1-600". This appears to us a doubtful species of Surirella; for Kützing's figure seems to represent a frustule constricted in the front view, as it shows a linear median portion truncated at its ends. S. panduriformis (Rab.). — Resembles S. didyma, but is stouter, and its mar- ginal dots appear Stalked. t. 3. f. 9. Italy. 2* Lateral view lanceolate or oblong, with ‘ts ends wsually equally attenuated. Rab. p. 29, S. Craticula (E.).-Lanceolate; costae few, reaching the median line, central ones divergent. SBD. pl.9. f. 67. Aquatic. Australia, Asia, Africa, America, Britain. (XII. 19, 20.) Costae 7 in 1-1200". 1-288". The central costae are usually more distant, leaving a transverse Smooth space bisected by the median line. Smaller than S. biseriata; its costae fewer and more divergent. S. megaloptera, EM. pl. 33. I. f. 17. Bgypt. The figure resembles that of S. Craticula; but the costae are all paral- lel, and the median line, as well as costae, are interrupted at the centre by a broad, transverse . S. biseriata (Bréb.).—Front view qua- drilateral, with conspicuous alae; lateral view oblong-lanceolate, with broad costae, which usually reach the median line. SBD. i. p. 30, pl. 8. f. 57. =S. bifrons, E. . Common. º 20–26.) Differs from S. Splendida by its parallel sides in front view. Its angles are rounded, and the alae enclose an oblong space; its costae are conspicuous in both views. 1-210" to 1-100". Striae 3} in 1-1200". S. decora (E.).-Large, linear-lanceo- late, with equal, attenuated ends and four or five marginal costae in 1–200". EMI. pl. 5. 3. f. 23. America, Ireland. Ehrenberg's figures are oblong lanceo- late, one of them constricted. - S. refleca (E.). — Lanceolate, with nearly equal, slightly reflexed, subacute ends, a distinct median suture, and strong, short striae, in the middle three or four in 1-1152". EM. pl. 33. 11, f. 13. Fossil. Connecticut. S. leptoptera (E.). —Lanceolate, with nearly equal, acute ends, a distinct, di- lated median suture, and dense trans- verse striae, which in the middle are 6 in 1-1152". KSA. p. 36. Fossil. Oregon. A specimen 1–456" long pre- sented 21 striae. S. Oregonica (E.). —Spathulate, with unequal, Subacute ends, a distinct, di- lated median suture, and strong striae, which in the middle are four or five in OF THE SURIBELLEAE. 795 1-1152". EM. pl. 33. 12. f. 27. Fossil. Oregon. A specimen 1-336" long pre- sented 19 striae. Ehrenberg's figure is elliptic-lanceolate, with a median line dilated at the centre into a large oval form; the striae short and externally ter- minating in gland-like dots, S. turgida (S.). — Elliptic-lanceolate, with tapering, sometimes contracted ends and obtuse apices; costae few (4 in ‘001"), conspicuous, separated by a me- dian lanceolate space. SBD. i. p. 31, pl. 8, f 59.-S. Caledonica, EM. pl. 15 A. f 47? Aquatic. Ireland. Distinguished by its ventricose centre. S. oblonga (E.). — Oblong-lanceolate, with obtuse ends, near the margin si- nuoso-dentate. KSA, p. 35. Aquatic. Africa; America; Mourne deposit, Ire- land. Ehrenberg's figures in the ‘Micro- geologie’ differ very much in form, but all have the costae confined to the margin. S. Brewteliana (Rab.).-Linear-elliptic, with rounded ends, five transverse costae on each side, connected at inner ends by an undulated line, and leaving a longi- tudinal median space with waved mar- gins. Rab D. p. 29, t, 3. f. 13. Aquatic. St. Kitts. S. crenulata (E.).--Small, elliptic-lan- ceolate, with crenulate margins, subacute, nearly equal ends, and a distinct median line; eleven crenules in 1-1152", extend- ing into striae, which do not reach the centre, EMI. pl. 33. f. 23. Fossil, United States, D. 1080". S. microcora (E.). — Minute, oblong- lanceolate, with somewhat acute apices, and marked near the margin with ten delicate dentations in 1-1200". EA. p. 136, t. 2. 1. f. 34; KB. t. 29. f. 15. Asia, Africa, America. S. lepida (E.). — Slender, linear-lan- ceolate, one end obtuse, the other a little more attenuated and subacute; striae nine or ten in 1-1152"; the median line di- stinctly flexuose. ERBA, 1844, p. 272; KSA. p. 36. Kurdistan. 1-768". S. tenella (K.). — Oblong-lanceolate, with rounded, obtuse apices, and five, rather lax transverse striae in 1-1200"; front view oblong, almost rectangular, with obtuse angles. KSA. p.37. Aquatic. Prussia. - S. obtusangula (Rab.). — Small, lan- ceolate, with cuneate, attenuated, obtuse ends, and six short costae in 1-1200"; front view oblong, broadly rounded. Rab. p. 29, pl. 3. f. 27. Aquatic... Germany. S. Amphioays (S.). — Elliptic-lanceo- late, with subacute extremities, and nine costae in 001"; front view linear. SBL). ii. p. 88. Haverfordwest. Ş. angusta (K.).-Minute, linear, with cuneate ends, rather obtuse apices, and 11 costae in 1-1200”; alae obsolete; front view linear, truncate. KB. t. 30. f. 52; SBD. pl. 31, f. 260. Aquatic. Europe; Lewes. S. apiculata (S)- Elliptical, ovate, Smaller extremity produced into a linear, truncate apiculum; costae 15 in 001".” SBD. ii. p. 88. Aquatic. England. Length of frustule 0008" to 0012". “A close ally, if not a variety, of S. angusta.” S. linearis (S.).-Minute, linear, with cuneate ends, distinct transverse costae, and a narrow median line. SBD. i. pl. 8. f. 58". = S. acuminata (Bréb. MS.). Aquatic. England, France. War. 3, slightly constricted at the middle, S. p. 8. f. 58°". In the front view this species resembles a small form of S. biseriata. 3* Lateral view with one end broadly rounded, the other smaller (ovate or ovate-oblong); front view usually cu- neate. - S. robusta (E.). — Large, elongated; ovate-oblong, with two stout costae (which do not reach the centre) in 1–1200". EM. pl. 15 A. f. 43. S. mobilis, SBD. pl. 8. f. 63. Aquatic. Fossil. Fin- land; Britain. 1-216" to 1-120". Di- stinguished by its large size, elongated, slightly tapering form, and large intra- marginal cremations. S. procera, EM. pl. 14. f. 33. Berlin. The figure represents a large species, slightly broader at one end, with large intramarginal cremations as in S. robusta, but the strong transverse costae are sepa- rated only by a narrow median band. S. splendida (Es, K.). — Front view cuneate, with rounded angles and pro- longed costae; lateral view ovate-oblong with conspicuous, diverging costae which reach the median line ; alae distinct. EM. t. 15 A. f. 44; SBD. i. pl. 8. f. 62. Aquatic. Common, both living and fossil. (IX. 150–152.) War. 3. linearis, smaller, lateral view narrow, slightly tapering, = S. linearis, SBD. i. pl. 8. f. 58 a. 1-210" to 1-100". As the front view has rounded angles, it is not unlike the lateral one in outline, but the ends are broader. Two or three times as long as broad. S. tenera (Greg.). — Narrow linear- oblong, with one end more tapering than the other; costæ distinct, reaching the median line. Greg M.J. iv. p. 10, pl. 1. f, 38, Scotland. It is smaller than S. 796 SYSTEMATIC HISTORY OF THE DNFUSORIA. splendida, and its alae are less conspi- cuous; but it resembles that species in form, and we doubt whether it be distinct. S. striatula (Turp.).--Front view broad cuneate, with rounded angles and short costae; lateral view ovate, with distant, curved costae, which reach the median line; alae small. SBD. i. pl. 9. f. 64. Common. Resembles S. splendida, but is shorter in proportion to its breadth. In the front view the central portion is broader, the ends more truncate, the costae shorter, and the alae less conspi- cuous. Lateral view faintly striated; striae 8 to 13 in 1–1200". S. limosa (Bai. MS.P).—Broadly ovate acuminate, faintly punctato-striate; ca- maliculi short and indistinct, not reach- ing more than 1–6", across the valve; length 0073", breadth .0035"; striae in- distinct, 22 in 001. New Zealand, Hud- son River, New York, Thames mud. Bri JMS. vii. p. 179, pl. 9. f. 5. S. brevis (E.).-Short; form and size of S. striatula, but with 16 finer striae in 1–1200". ERBA. 1844, p. 272; KSA. p. 39. Kurdistan. 1-912". S. Testudo (E.).--Large, ovate, obtuse, with 12 slender striae in its length, which is 1-288". E. l. c. 1840, p. 24; KSA. p. 39. Marine. S. Gemma (E.).--Front view narrow cuneate ; lateral view broader, ovate- elliptic, faintly striated between the de- licate, unequally distant costae, which reach the median line; alae inconspi- cuous. KB. t. 7. f. 9; SBD. i. pl. 9. f. 65. Common in marine marshes. (XII, 2-4.) Distinguished from S. striatula by its much finer costae and less conspicuous alae, which in the lateral view generally coincide with the margins. Sometimes nearly elliptic. We have rarely seen it so narrow as Professor Smith's figure represents it. S. laevigata (E.).-Elongated, Smooth, with subequal, obtuse ends, a distinct median suture, and two longitudinal lateral lines. KSA, p. 36; EMI. t. 33. 14. f. 24, Fossil. United States. 1-168". Ehrenberg's figure in the ‘Microgeologie’ is ovate, with a median line, lax intra- marginal crenations, and very short costae. S. Guatimalensis, EM. pl. 33.6. f. 7. America. Figure broadly ovate, with both ends much rounded, and minute intramarginal crenations, without me- dian line or costae. S. ichthyocephala (Rab.). — Large, ovate-oblong, with rounded ends, three broad, flexuose costae in 1-1200" and a broad linear median band. Rab D. p. 30, pl. 10, Supp. f. 6. Italy. The figure shows the costae curved, except the middle one, which is broader and straight. S. cordata (E.). — Ovate-subcordate, with four lax striae in 1-1152", conti- guous in the median line. ERBA, 1845, p. 272; KSA. p. 39. Fossil. Georgia. S. praeteata #. —Long ovate, more than twice as long as broad, with five rather lax striae in 1-1252", towards the middle broadly interrupted and not con- tiguous in the median line, hence form- ing four series with a broad linear me- dian space and two smooth lateral ones. Maritime. India. ERBA. 1845, p. 365; KSA. p. 38. S. euglypta (E.).--Small, ovate-oblong, with seven striae in 1-1200", which do not reach the centre; front view cuneate, with rounded angles at larger end. EA. p. 136, t. 3. 5. f. 2. 4; KB. t. 28. f. 27. Asia, Africa, America. S. uninervis (E.).--Small, ovate, half as long again as broad; costae reticu- lated at the margin, contiguous at the slender median line, 7 in 1–1152". KSA. p. 38. Maritime. India, Africa. S. Folium (E.). — Ovate, turgid and obtuse, slightly compressed, with 24 fine striae in 1-1150". #. Barbadoes. 1–540". S. Crumena (Bréb.).—Small, orbicular ovate, with 7 or 8 evident marginal striae in 1-1200". KSA. p. 38. Aquatic. France, Britain. Its suborbicular form in lateral view distinguishes it from every other species except S. Bright- welli. S. Brightwelli (S.). — Small, suborbi- cular, with one end subacute; costae distinct, marginal, 10 in 001"; alae in- conspicuous. SBD. i. p. 33, pl. 9. f. 69. Britain. . According to Professor Smith, this º is distinguished from S. Cru- mena by its coarser and more prominent costae and distinct striae; S. Crumena is also smaller and more orbicular. S. ovalis (Bréb.).--Small, ovate-elliptic, with 8 marginal costae in 1-1200", and one end more attenuated than the other; alae inconspicuous. KSA. p. 33; SBD. #. 9. f. 68. Aquatic. France, Britain. ront view oblong-cuneate, truncate. 1-360" to 1-280". Margin with very short, teeth-like costae. The larger end in lateral view is less rounded than in the allied species. S. ovata (K.).—Minute ovate, or ovate- elliptic, with 7 to 9 delicate, very short, OF THE SURIRELLE ZE. 797 marginal costae in 1-1200"; alae incon- spicuous. KB. pl. 7. f. 1-4; SBD. pl. 9. f 70. Europe, America. Front view broadly cuneate, truncate. 1-1200" to 1-560." ! - S. minuta (Bréb.). — Minute, ovate- elliptic, with inconspicuous alae and 14 marginal costae in 001". SBD. i. p. 34, pl. 9. f. 73. France, England. '0005" to '0009". Kitzing unites this form with S. ovata; but M. de Brébisson informs us that he is able to distinguish the two i. when in situ at the first glance; that the stratum of this species is black and very mobile, whilst that of S. ovata is brown, and adheres more firmly to the soil. S. salina (S.).-Minute, ovate-oblong, with numerous minute marginal costae and obsolete alae. SBD. i. p. 34, pl. 9. f 71. Marine or brackish waters. Eng- land. Front view wedge-shaped. S. subsalsa (S.). — Minute, ovate-lan- ceolate, with 8 distinct costae and 30 striae in 1–1200"; alae conspicuous. SBD. i. p. 34, pl. 31. f. 259. =S. pygmaea, E.M. pl. 35 A 8. f. 4 P. Fresh or brackish waters. England. S. pinnata (S.). — Minute, narrow, ovate-oblong or somewhat clavate, with large, subdistant marginal costae; alte obsolete. SBD. i. p. 34, pl. 9. f. 72. Aquatic. Lewes. Front view narrow Cumeate. 4 * Lateral view with broadly rounded, varely unequal, ends. S. Lamella (E.). — Large, narrow elliptic, with nearly equal, broadly rounded ends; intramarginal striae and granulose median area; front view nar- row linear, truncated. EMI. pl. 15 A. f. 49. Lough Mourne deposit. 1-216" to 1-180". Ehrenberg's figure has no median line. S. Liosoma º elliptic, with broadly rounded ends, a narrow margin of fine striae, and a smooth median area with a median longitudinal line. _EM. pl. 33. 14. f. 25. Maritime. India. Three times as long as broad. S. Patella (K.).—Elliptic-oblong, with equal, rounded ends, and four or five man- ginal striae in 1-1200". KB. t. 7. f. 5. Fossil at Franzensbad, S. Peruviana (E.). — Large, elliptic- oblong, with equal, rounded ends, and about 12 very short, obsolete, marginal costae in 1–1200". KB. t. 29. f. 72. Peru, S. amphiamblya, EM. pl. 14. f. 34. Berlin. The figure shows a large elliptic form with equal, rounded ends, intra- marginal crenations, and strong, parallel, transverse costae, which do not quite reach the median line. S. Mississipica, EM. pl. 35 A. 8. f. 5. America. Ehrenberg's figure is large, eillptic-oblong, with equal, rounded ends, and parallel transverse costae, separated ; * narrow linear, longitudinal median all Cl. 5* Lateral view with rounded ends; costae with dilated outer portion, and median Space finely striated. S. fastwosa (E.). — Elliptic, with rounded ends, rather distant costae, in- flated towards the margin, and a trans- yersely striated, lanceolate median space. Greg M.J. iii. p. 30, pl. 4. f. 41. Marine. Common. Europe, Asia, Africa, Ame- rica. Distinguished from all the pre- ceding species by its inflated costae re- sembling stalked flowers, and by the striated median space, which is very variable in breadth. Differs much in size, and is sometimes nearly orbicular; we have never seen it ovate, as described by Professor Smith. - S. lata (S.). — Large, broadly linear- elliptic or somewhat panduriform, with broadly rounded ends, a transversely striated median area, and distant costae externally dilated. SBD. i. p. 31, pl. 9. f 61. = Campylodiscus productus, John- ston. Marine. Not uncommon. England. Differs from S. fastuosa in its form, and usually in its larger size; but the mark- ings are similar in both. As Professor Gregory finds intermediate states, they may be, as he supposes, mere varieties. S. eximia (Grev.). — Linear-oblong with rounded ends, about 18 delicate costae on each side, reaching the narrow linear-lanceolate, transversely striated median space. Grev M.J. v. p. 10, pl. 3. f. 6. Marine. West Indies. This ex- tremely delicate and hyaline Diatom, Dr. Greville informs us, approaches S. lata in form, slight constriction, and a striated central space, but differs in every other respect. The costae equidistant, and as fine as those of S. Gemma; ala. narrow, but conspicuous. Doubtful or undescribed Species. S. P. Cocconeis, EM. pl. 35 A. 8. f. 3. Marine. India, Africa. This species, according to the figure, is small, elliptic, with obtuse ends, and parallel transversé costae separated by a smooth, narrow- lanceolate median space. S. Jenner: (Hassall). — Front view linear, with rounded ends, and distant, 798 SYSTEMATIC HISTORY OF TEIE INFUSORIA. short, teeth-like marginal costae. Hass. Br. Algæ, p. 439, pl. 102. f. 15. Aquatic. Sussex. Dr. Hassall describes it as a very distinct species, having no relation with S. biseriata. - S. ambigua (K.). — Broadly oblong, with truncated ends, and 4 straight, ob- solete, rather broad transverse striae in 1–1200". KB. t. 5. f. 17. Stagnant waters, Switzerland. 1-264". Kitzing's figure apparently represents the front view, and is broadly linear, with obscure transverse costae, leaving a narrow median portion. S. laevis (K.). — Cylindrical, Telliptic- lanceolate, somewhat obtuse, verysmooth and hyaline. IGSA. p. 36. Marine. France. 1-1080”. S. attenuata (Nāg.). —Smooth, linear- lanceolate, with gradually attenuated apices. KSA. p. 889, Switzerland. 1-240". Perhaps a Trybliomella P S. P. ornata (k.). —Elongate, pestle- shaped, truncate at each end, with obtuse angles, longitudinally dividuate, and or— namented with minute puncta disposed in decussating lines. KB. t. 3. f. 54. Marine. Genoa. Length 1-280"; breadth 1-960". Kützing's figure is linear-oblong with truncate ends, and seems to repre- sent the front view, in which the striated lateral portions approach so closely at the centre that the smooth median por- tion is visible only near the ends. Surely this is not a Surirella P S. P Amphibola (E.). —Broadly linear, with cuneate, subacute ends, and 15 striae in 1–200"; front view with obtuse ends. ERBA, 1854, p. 271. Kurdistan. 1-324". Has the general form of Tryblionella Regula. Ehrenberg remarks that he is not sure to what genus this belongs; he has sometimes fancied there was an um- bilicus, as in Pinnularia, but its equal transverse striae on each side render its form singular. S. Sicula (E.). — Smooth, broadly na- vicular, with subacute ends and longi- tudinal marginal lines. EM. pl. 22. f. 58. Fossil. Sicily. 1–528". S. liolepta (E.).-Styliform, four times as long as broad, with obtuse ends and no median line; the narrow margin finely striated. KSA, p. 36, Maritime. India. 1–360". - S. P linea (E.). -Bacillar, stout, one side cuneate at each end, the other rounded, finely transversely striated throughout. ERBA, 1843, p. 271. Ne- therlands. 1–240". S. Stylus (E.).-Large, styliform and narrow, quadrangular; one end more obtuse than the other, but neither acute; costa 54 in 1-144". ERBA, 1843, p. 271. Near Weimar. 1–144". S. rhopala, EM. pl. 33.1, f. 19. Egypt. Ehrenberg's figures show the front view large, longly cuneate with rounded ends, and numerous fine transverse striae at each side, separated by a narrow smooth median portion with two puncta at each end. S. aspera (E.).-Large, with four or five loosely disposed costae in 1-1152", with rough crests. KSA, p. 39. Volcanic earth, Hochsimmer on the Rhine. This species, named from a fragment, Ehren- berg states is perhaps a Campylodiscus. S. Australis (E.). — A fragment of a linear species with six, straight trans- verse striae in 1-1200". Africa. Another species constituted by Ehrenberg's ob- jectionable practice of naming, isolated fragments. §f lamprophylla (E.), S. Uralensis (E.), Ural Mountains; S. Sibirica (E.), Sibé- ria; S. P. curvula (E.), India, Mexico; S. Stella (E.), Maritime: India, Africa; S. Nicobarica (E.), Nicobar; S. compta (E.), Egypt; S. Zambeze (E.), River Zambezé; S. Platalea (E.), Senegal; S. Caffra (E.), S. Capensis (E.), S. clathrata (E.), Cape of Good Hope; S. Falklandica (E.), S. Meluimensis (E.), S. Insularum (E.), Falk- land Islands; S. Araucania (E.), Arau- cania; S. amphicentra (E.), S. holosticha (E.), S. insecta (E.), S. leptotera (E.), S. Polyodon (E.), Mexico. Genus CAMPYLODISCUS (E., Men.).-Valves equidistant, frustules soli- tary, disciform; disk tortuous or saddle-shaped, rotundato-elliptic, costate, costae mostly radiate. Campylodiscus has the lateral surfaces still more developed than they are in the Melosireae, whilst the central or interstitial portion is reduced to a narrow ring, a circumstance which renders it very difficult to obtain a satisfactory front view. In these respects it approaches the Coscinodisceae. Kützing referred to Surirella several species now placed in this genus. Meneghini Suggested their removal to Campylodiscus, in these terms—“One really is at a loss to find the motive that could induce Kützing to separate this generically from Campylodiscus;” and Professor Smith has, OF TEIE SURIRELLEAE. 799 we consider judiciously, adopted that suggestion. “The species included under this genus may all be recognized by the characteristic bend or con- tortion of their surfaces.”—Sm. Cocconeis differs in its Small size and cen— tral module. * Disc circular, or nearly 80, with a single series of marginal costa, † Costae all radiant, forming a marginal circle. CAMPYLODIsCUs Horologium (Wil- liamson).-Disc nearly flat, with a mal- ginal circle of numerous (about 50) equal, radiating costae, having a circle of close, very short and fine striae at its inner, and another at its outer edge, and enclosing a large, central, orbicular, smooth space. SBD. pl. 6. f. 51. Marine. Scotland. The costae are proportionally shorter in this large species than in most others, and occupy about one-third of the radius. C. limbatus (Bréb.).-Disc with a mar- ginal circle of short costae, continued by an inner fainter circle of moniliform lines, gradually lost in an indefinite, smooth central space. BD. p. 12. f. 1; GDC. p. 32, pl. 3. f. 55. Marine. France, Scotland. * Distinguished from C. Horologium by its finer costae and granulated disc,” IBréb. “Costae broad, transversely Sul- cate, so as to appear on close inspection almost moniliform. Within this mar- ginal band is another fainter band, which looks almost like the reflection in a mir- ror of the first, except that the bars are more directly moniliform,” Greg. This species might be placed with almost equal propriety in the section with double series of costae. e C. imperialis (Grev.). — Costae 3 in '001", forming a magnificent band, ac- companied at base by short bifid seg- ments; central area broadly elliptical, furnished with narrow, transverse, mO- miliform striae, interrupted by a median blank line. Gr TMS. viii. p. 30, pl. 1. f. 3. New Providence. In general . earance resembles C. limbatus, Bréb. i. differs materially from that Diatom on a closer examination. Grey. C. Kºttonianus (Gr.). — Costae elon- gated, transversely striated for two-thirds of their length. Gr, TMS. viii. p. 32, l, 1. f. 7. West Indies. Central space furnished with a median bar, as in C. no- tatus, only less conspicuous, Grey. C. stellatus (Gr.). — Valve orbicular, with a narrow marginal band of close, short costae, an inner circle of dotted lines, and a central space marked with irregular radiating lines. Gr M.J. vii. p. 157, pl. 7. f. 3. Costae 10 in 001''. C. radiosus (E.). — Disc subcircular, Small, with smooth or obscurely punctate centre, and border of about seventy . closely-set, radiating costae. KSA. t. 28. f 12. Fossil. Vera Cruz. Upper Pe- ruvian guano. We have ºãº a Cam- pylodiscus in Bolivian guano, and sup- posed it to be this species. The costae are numerous, radiating, and unequal, enclosing a quadrilateral, obsoletely punctate central space, divided by a median hyaline line, and having at its angles 3–4 converging costae. C. vulcanius (E.).--Disc large, sub- Orbicular, flexuose, with about 42 mar- ginal rays, and Smooth centre. KSA. p. 33. Peru. C. bicruciatus (Greg.).-Disc circular, with a square median space occupied by crossed striae, and prolonged to margin by four pairs of tapering, transversely striate processes in a crucial manner, each interval with four strong radiant costae. Greg MT. v. p. 78, pl. 1. f. 42. Marine. Glenshira, Scotland. A very peculiar species, but difficult to describe. The square centre is lattice-like, and itself obscurely subdivided into Smaller qua- drate portions; from it proceed to the margin, in a crucial manner, four pairs of conical prolongations; the intervals between the pairs are occupied by strong rays, which, together with the striated prolongations, are connected within the margin in a scolloped manner. Californian guano. 2 + Disc more or less evidently divided into lateral portions by a median line or band; costae imperfectly radiant. C. Hibernicus (E.). — Disc tortuous, with numerous (30 to 40) continuous, imperfectly-radiant costae, enclosing an irregularly shaped, minutely punctated central space. EMI, pl. 15A. f. 9. = C, cos- tatus, SBD. i. pl.6. f.52. Aquatic. Britain. (IV. 38.) The costae are loosely disposed (4 in 1-1152"), slightly rough from mi- nute granules, and extend in length about half the radius. Their radiant arrange- ment is somewhat imperfect, from the convergence of two or more at each end. Mr. Norman has gathered this species very pure near Hull. C. Noricus (E.). — Disc suborbicular, 800 SYSTEMATIC EIISTORY OF TELE INFUSORIA. tortuous, gradually smooth in the cen- tre ; costae numerous, continuous, their crest acute. KSA. p. 33. Aquatic. Asia; Salzberg. Fossil at San Fiore. Rays 7 in l–1152". D. 432". . Kitzingii (B.).—Disc saddle-shaped, broadly margined, marked with about 50 transverse, continuous, curved sulci. B. in Proc. Acad. Phil, 1853. Philippine Islands. C. Ralfsii (S.).-Disc small, subcir- cular, bent; costae transverse, reaching the median line. SBD. i. p. 30, pl. 30. f. 257. Marine. Britain. . The costae of one side are divided from those of the other by a longitudinal median line. C. Normanicus (Gr.).-Costae 3 to 4 in •001", imperfectly radiant, passing across a linear-oblong central depression to the narrow median blank line. Gr TMS. viii. p. 29, pl. 1, f. 1. West Indies. C. notatus (Gr.).-Costae numerous, about 12 in .001", in length more than half the radius; central space oval, with a median thick bar dilated at each end. Gr TMS. viii. p. 31, pl. 1. f. 4. Shell- cleanings. Distinguished by the mark- ings of the centre, which Mr. Norman aptly compares to the figure of a dumb- bell, Gr. C. decorus (Bréb.).--Disc circular, bent, with a simple series of long, arcuate costae, and a Smooth, narrow-lanceolate median space. BDC. p. 13. f. 2. = C. Ralfsii P #DC. p. 30, pl. 3. f. 52. Marine. France, Britain. “This species is very elegant. Its costae are, with the exception of one or two central, all curved towards the ends,” Bréb. The following re- marks are from Dr. Gregory's paper:-- “I have referred it to C. Ralfsii, S., al- though it is much larger than the form figured by him, and although there are other differences. Thus in C. Ralfsii the canaliculi reach the median line, and the row of heads or expansions lie some di- stance from the margin. But these dif- ferences cannot be regarded as specific.” C. angularis (Greg.).--Disc suborbicu- lar; costae very numerous (160 or more) and unequal, imperfectly radiant, form- ing a simple marginal band, and divided into two sets by prolongations of the large, oval central smooth space. GDC. . 30, t. 3. f. 53. , Loch Fine, Scotland. Kººi from the angular bending back of the valves. The costae are longest at the middle of each side; and, as in C. decorus, all except the central ones are curved, with the concavity towards the ends, and become also gradually smaller on approaching them. “A true median line is visible, but is very delicate. . . . . The surface of the valve, both above and below—that is, near both ends of the median line—is suddenly bent back, so as to form an angle with the rest of the valve. On the surface thus bent, short lines appear between the costae,” Greg. Distinguished from C. decorus by its more numerous costae, oval central space, and extensions of the latter separating the costae into two sets. C. Hodgsonii (S.).-Disc subcircular, bent, with a marginal series of very mu- merous (100 or upwards) imperfectly- radiating costae; the central space with transverse rows of dots divided by a narrow median Smooth line. SBD. i. p. 29, pl. 6. f. 53. Marine. Britain. “The smooth median line is formed by a ridge and two continuous furrows passing across the valve,” Smith. The costae near the ends converge. Mr. Roper finds the dots vary greatly in number, distinct- ness, and arrangement, especially in the larger specimens, and on this account considers C. eacimius not distinct from it. C. concinnus (Grev.). — Costae 5 in ‘001", radiant, forming a narrow mar- ginal band; central area oval, furnished with numerous transverse moniliform striae, interrupted by a median blank line. = C. marginatus, Johnst. in M.J. viii. p. 13, pl. 1. f. 11; Gr'TMS. viii. p. 8, f. 2. Shell- scrapings. New Providence. Californian guano. C. eximius (Greg.).-Disc subcircular, bent; costae strong, very numerous (often 150), rather short, in a single marginal Subradiating circle, enclosing a large hya- line space, furnished with scattered gra- nules and a median line. GDC. p. 31, l. 3. f. 54, Marine. Loch Fine, Scot- and. The costae of C. eacimius, like those of C. Hodgsonii, are rendered imperfectly radiant by the convergence of those near the end of the median line or raphe. C. eximius differs from that species in its less conspicuous and scattered granules, invisible except when highly magnified. Mr. Roper, however, may be right in re- garding it as a variety of C. Hodgsonii, since Professor Gregory himself states that the granules “in some instances show faint traces of a linear arrangement close to the marginal band.” 2* Disc circular or subcircular, with a double concentric series of costae. C. centralis (Greg.).-Disc with about forty, equal radiating costae, leaving a Small umbilical space; the costae conti- nuous, but divided into two series by a OIF TELE SURIRELLEAE. 801 shade-like band, the inner series fainter, GDC. §. 30, pl. 3. f. 51. Marine. Loch Fine, Scotland. Professor Gregory sup- poses that the appearance of a line which divides the costa is caused by a ridge. C. fenestratus (Grev.). —Disc circular, with marginal radiating costae divided by a line into two series, the inner one fainter and enclosing a central space occupied by four lattice-like sculptures formed by three or four bars crossing each other at right angles. Grev. in MJ. v, p. 9, pl. 3. f. 4. Marine. West Indies. The continuous costae are divided, as in C. centralis, by a line into two concentric Series. A species distinguished by the “four remarkable sculptures, exactly re- sembling square windows in miniature, the bars sharp and slender, and the panes actually appearing as if they transmitted light,” Gr. C. Ecclesianus (Grev.). — Disc subcir- cular, with a border of two concentric series of very short, radiating costae, or narrow-oblong cellules; central space with two rows of transverse broad bars, separated by a median line, from each end of which proceeds a semicircle of fine striae, Gr, l.c. p. 10, pl. 3.f. 5. Marine. West Indies. “Similar in size to the last, but somewhat more contorted, so that when one portion of the valve is in focus, the details of the remaining por- tion are less visible. The valve is con- cave; the central portion, occupied by the two rows of bars, is nearly flat; but on each side of the rows, and at their termi- nation, the dise is inflated, the lateral inflations being unsculptured, the ter- minal ones striated,” Grew. C. bicostatus (S.).--Disc suborbicular, saddle-shaped, with from twenty to forty unequal radiating costae, interrupted So as to form two concentric series, enclos- ing an oblong, Smooth central space. Ro. in MT. ii. pl. 6. f. 4; SBD. ii. p. 88. Thames; Norfolk. Diam. about 1–384". Costae distinct, their length, at sides, about half the radius, at the ends much shorter. Inner series less distinct. C. Clypeus (E.). — Disc suborbicular; rays numerous (40 to 100), radiating, partially interrupted, and forming two incomplete concentric series; the large punctated central space divided by a median smooth line. EM. pl. 10.1. f. 1; SBD. ii. p. 88. In fresh and brackish waters; also fossil, Asia, Africa, Ame- rica, Europe, England. Original draw- ings of this elegant species are given in xvi.I. 516, 518. Diam. 1-576" to 1-216". Costae punctated, continuous at the ends, but interrupted at the sides, where they form two series. In the central space are two oblong Sculptured portions, sepa- rated by the Smooth median line. C. Remora (E.). — Disc suborbicular, tortuous, with interrupted rays and a smooth centre. KSA. p. 33. Marine. Baltic. D. 480". C. marginatus (E.). —Disc Small, in the middle Smooth, subscabrous, fur- nished in the margin with a double Series of cellules, the external fine, the inner larger, evident, closed at the oppo- site ends, open and radiated in the mid- dle. KSA, p. 33. Maritime. King's Island, India, Ceylon. C. fastwosa (E.).--Disc suborbicular, curved ; costae subdistant, continuous, divided into two concentric series, the outer inflated, inner shorter, stalk-like, enclosing a finely and transversely stri- ated central space. KSA. p. 33. = C. Thureti, BDC. pl. 1, f. 41; C. simulans, Grey M.J. v. pl. 1, f. 41. Marine. Asia, France, England. C. fastuosa is easily di- stinguished from every preceding species, except C. marginatus, by its finely striate central space and the peculiar appearance of its costae, which are divided by a line into two parts, compared by Professor Gregory to a lotus-flower on a stalk. Pro- fessors Kützing and Gregory note its re- semblance to Surirella fastuosa; we be- lieve it, however, quite distinct, as, in addition to its circular and bent form, the centralstriae are finer and more numerous. C. fastwosa varies considerably in size, and in the comparative breadth of the central portion, which is sometimes a mere line, at others lanceolate, or even oval. The costae are either interrupted by the prolongation of the central por- tion to the margin, or continued all round. C. ambiguus (Gr.).-Disc suborbicu- lar; costae distant, reaching nearly to the centre, partially interrupted at the mid- dle; in the centre an jº, depression, within which is a short, linear-elliptical blank line. Jamaica, Port Natal. Gr MT. viii. p. 31, pl. 1. f. 5. = C, latus, Sh MT. ii. pl. 1, f. 13. C. parvulus (S.). — Disc Subcircular, minute; costae few (about twelve), in length about two-thirds of radius; central space obscurely striated. SBD. i. p. 30, 1.6. f. 56. England. (xv. 22, 23.) We ave found this form generally accom- panying C. fastuosa. Like that species, it is sometimes oblong, and probably is only a small variety. It is usually much bent, and is the smallest species known, 3 F 802 SYSTEMATIC EIISTORY OF TEIE INFUSORTA, 3 * Disc subcircular, with radiating series of granules or perforation-like dots. Čoronia (Ehr.). C. Echeneis (E.).--Disc bent, with nu- merous irregularly radiating series of conspicuous dots, becoming fewer and more scattered near the centre. KSA. p. 34. = C, Argus, BMO. pl. 2. f. 24, 25; C. cribrosus, SBD. pl. 7. f. 55. Marine. America, Europe, England. Diam. 1-288". The costae are nearly obsolete, and con- fined to the margin. We refer C. Argus to this species upon the authority of our lamented friend the late Professor Bailey. C. diplostictus (Norman).--Disc with conspicuous marginal, moniliform, radi- ating lines, alternate ones shorter, and a large, subelliptic, central, blank space. GrevTMS. viii. p. 31, pl. 1, f. 6. Australia. The cellules of the striae are linear-ob- long, and, being marked longitudinally by a faint line, appear doubled. C. heliophilus (E.).-Disc small, sub- orbicular, including in the broad and smooth median area a quadrate Series of granules, similar series of granules being radiately disposed in the broad margin, and in a double concentric order; the external rays simple, the inner ones binary. KSA, p. 33. Maritime. India, China. The proper arrangement of this and the next species is doubtful. C. Indicus §º. large, with a subquadrate, Smooth, median area, and a very broad margin formed of fine and dense radiating series of granules in a double concentric order. KSA. p. 33. Maritime. King's Island, India. War. 3. Concentric rays continuous. War, y, Concentric rays interrupted. 4 * Disc subcircular, with a narrow, me- dian, pervious, Smooth band, and trans- verse lateral stria, C.? striatus (E.).-Disc with two series of about 13 transverse striae on each side of the median line. EA. iii. pl. 7. f. 13; KB. pl. 28. f. 11; BriMJ. vii. p. 79, pl. 9. f. 4, " Fossil. Vera Cruz. 5 * Frustules in lateral view not circular. C. Surirella (E.).-Disc large, flexuose, oblong; the middle broad and Smooth, the margin narrower, with radiating striae. RSA, p. 33. Aquatic. Spain. C. ovatus.--Disc curved, large, ovate, obtuse, with nine very broad pinna in 1-276". = Surirella Clypeus, E. Marine. Ealtic. I-276". . C. Ehrenbergii.-Disc flexuose, Small, ovato -elliptic; ends equally rounded; margin striated, with from 10 to 12 costae in 1-1200". = Surirella Campylodiscus, E. Aquatic. Italy, Mexico. (XV. fs. 12, 13, 22 & 23.) C. spiralis (K., S.).--Spirally twisted, with a dotted margin; laterally elliptic, with about 60 nearly parallel costae; cen- tre of disc minutely punctate. SBD. i. }. 29, pl. 7, f. 54, Aquatic. Europe, gland. (IV, 39.) C. spiralis differs from C. Hibernicus in its elliptic and twisted, . not saddle-shaped frustule. We doubt if it be distinct from C. flexuosa. C. featuosa (E.).--Disc large, flexuose; costae 4 or 5 in 1-1200". = Surirella flec- wosa, E. K.B. t. 28. f. 25. Aquatic. Africa, South America, Mexico, France. (xv. f. 11.) C. elegans (E.).-Large, very broad, with subacute ends, and very finely- punctate surface. = Strirella elegans, E. KB. t. 28. f. 23. Aquatic. Germany, Mexico. Costae 4 in 1-1200". IGnown only by fragments. C. Myodon (E.).--Small, rather curved, laterally elongated, narrow, with one end rounded (the other unknown), with Small, closely-set costae, giving the mar- gin a toothed appearance. = Surrella Myodon, E. K.B. t. 28. f. 24. Mexico, Japan, Africa. Costae 6 or 7 in 1-1200". Rnown only from fragments. Q. Zonalis (Ph.)-Disc large, greatly deflected ; “radii symmetrical to two axes; concentric striation may be de- tected, and some appearance of puncta- tion on the outer edge.” Found in cre- taceous, marly deposits. Bridlington, Yorkshire. Prof. J. Phillips, 1845. Genus CALODISCUS (Rab.).—Discoid; disc subcircular, with numerous (often 64) ray-like bands, each connected at the broad, striated rim with its neighbours, and forming tooth-like straps; centre not striated, clouded, with a lighter transverse one-branched zone. The umbilical Zone is probably non- essential, and we doubt whether this genus be distinct from Campylodiscus. CALODISCUS Superbus (Rab.). —Disc a largish clouded umbilical space. Rab. large, flat, with a distinct closely striated | D. p. 12, t. 3. Aquatic, Italy. (VIII. 56.) rim, and equal radiating costae enclosing of THE STRIATELLEAE. 803 FAMILY WI.—STRIATELLEAE. Filaments compressed; the central portion of the frustule furnished with incomplete longitudinal Septa, which appear like striae or costae. The Stria- telleae form a very distinct group, distinguished from every other by having parallel longitudinal striae or costae on the central or connecting portion of the frustule. “The appearance of longitudinal striae is in fact produced by siliceous plates arising internally from the margins of the filament, and ex- tending towards but not reaching the centre. The interior is thus divided into chambers, opening into a central space. When viewed laterally, this central space resembles a canal, especially as the inner edge of each plate has a concave outline" (Ralfs, ANH. xiii.). The striae and septa are frequently conterminal; in Some genera this appearance is constant, and then the striae are said to be interrupted. We believe, however, that the striae are really continuous, although always more strongly marked where they coincide with the septa, and, on the other hand, very indistinct, especially in a young state, when they are merely formed by an internal rib. Prof. Smith adds the following explanation:—“The valves (lateral surfaces) are similar in character to those of the other Diatomaceæ, and are formed during self-division in the same manner; but, instead of the usual repetition of the process of valve- formation, we are here presented with a subsequentintervalvular development which, not confined to the exterior of the frustule, projects a plate of silex into its interior, forming a septum or partition extending towards, but not reaching, the centre of the cell, and appearing as a compressed rim or annulus of silex, whose outer or larger circumference follows the exterior outline of the frustule, and whose inner edge bounds the free space which serves as a channel of communication between the chambers into which the cell is thus divided. This process is either simultaneous, and the frustule definite, or successive, and the frustule indefinite. In the first case the annuli of silex are formed during the production of the valves in the progress of self-division, and on every repetition of such production; while in the second case the formation of the annuli is continued after the production of the valves, and is repeated an uncertain number of times before the recurrence of a new valve-production” (B.D. ii. p. 32). Kützing divides this group into Striatelleae and Tabellarieae, but we agree with Meneghini in thinking this division unadvisable. “Any One,” says the latter, “examining these beings with diligence, will entirely convince himself that the distinction of the two orders is altogether insufficient. No Tabellaria has a central nodule in the secondary surfaces at all to be compared with that of the Diatomeae constituting his order Stomaticæ in his first tribe. I firmly believe that Tabellarieae and Striatelleae ought to constitute one family, since the diaphragms, which are considered characteristic of the second ex- clusively, are not wanting in the first" (M. l. c. p. 475). Genus STRIATELLA (Ag., K.).-Filament of few frustules; stipes long; frustules longitudinally striated, laterally lanceolate, with a median line ; septa short, inner ones longest. Marine. The long stipes and absence of transverse striae on the central portion best distinguish this genus. STRIATELLA unipunctata (Lyngb., Ag). Algæ. Filaments minute, pale yellowish- – Frustules hyaline, subquadrate, with brown, glass-like, and glittering, usually numerous fine, parallel, continuous lines; composed of few frustules. The septa stipes longer than the fustule. SBD. are very short. The internal colouring ii. p. 37, pl. 39. f. 307. Not uncommon matter is generally collected into a in the autumn on Zostera and the smaller roundish central mass. (IV. 40.) 3 F 2 804 SYSTEMATIC EIISTORY OF THE INFUSORIA. Genus TESSELLA (Ehr.).—Frustules broadly tabulate, not concatenate, densely striated longitudinally; striae alternate, interrupted in the middle ; stipes none? “It is impossible to judge of the value of the characters that distinguish it from Striatella and Hyalosira whilst we do not know the organic importance or the true structure of the striae º (M. l.c. p. 466). TEssBLLA interrupta (E.).—Frustules | KB. t. 18. f. 4. Mixed with Striatella in front view subquadrate. 1-750", unipunctata, but less abundant. (VIII, 5.) Genus HYALOSIRA (K.).-Filaments stipitate; frustules quadrate, septa. alternate, interrupted in the middle, and united by very fine lines. “At first I was afraid that I was led by want of skill in observing, to believe that I could see in the two longer species of this genus a continuation of the Vittae from one margin to the other, instead of their being interrupted and alternat- ing as they are figured and described by Kützing. Continuing my observations, I succeeded at last in finding one individual exhibiting to my sight the alter- nations described ; hence I became convinced that the latter condition is not merely inconstant, but even the least frequent. elliptico-acute ’’ (M. l. c. 466). HYALOSIRA minutissima (K.). — Shortly stipitate, concatenate; frustules very minute, partially separating in a zigzag manner. 1-5700". KB. t. 18 f. 3. 2. Mediterranean Sea. H. delicatula (K.).—Shortly stipitate, concatenate; frustules minute, quadrate, partially separating in a zigzag manner. I-2640". . t. 18. f. 111, 1. France; Adriatic Sea. (IV. 42. H. rectangula (K.).-Shortly stipitate, subconcatenate, frustules subquadrate, rectangular. 1-1380". KB. t. 18. f. 3. 3. Adriatic Sea (XIV. 23). Frustules larger than in the preceding species. H. obtusangula (K.).-Longly stipi- tate, ribbon-like or subconcatenate; frus- tules quadrate, with obtuse angles. 1–1440". Adriatic Sea. (XIV. 29.) Frus- The secondary surfaces are tules larger than in the first two species. H. punctata (Bailey).-Frustules large, united in long chains, rectangular, Sub- quadrate, transversely and uninter- ruptedly vittate, alternate vittae granu- late in the middle of the frustule, the others furnished with a series of con- spicuous puncta, 1853. Tahiti. H. Beswickii (Norman, MSS.).-Septa continued across the filament as curved interrupted costae; valves oblong, with strongly inflated centre and rounded ends; striae coarse, 30 in 001". New Zealand. On Algae from Joseph Bes- wick, Esq. Frustules quadrate; valves sometimes with subcapitate apices. [We are indebted to Mr. Norman for the de- Scription of this species.] Genus RHABDONEMA (K.).—Filaments elongated, shortly stipitate; longitudinal striae uninterrupted, connected by series of transverse striae : lateral surfaces having transverse striae and a median longitudinal line. From the comparatively large size of the frustules in Rhabdonema, greater facility is afforded for examining their structure. The longitudinal striae or ribs (annuli, Sm.) are continuous, parallel, mostly equidistant, and connected by a series of transverse striae, so that, in fact, the structure has a latticed appearance. RHABDONEMA minutum (K.).-Septa R., arcuatum (Lyngb., K.). — Septa marginal, alternate ; lateral valves ob- marginal, opposite; lateral valves oblong long or spindle-shaped, inflated at the middle, transversely striated throughout. SBD. ii. p. 35, pl. 38. f. 306. = Tessella Catema, Ralfs, l.c. xii. (not E.). Europe. 1–1200". Smaller than R. arcatum, from which it differs in the inflated or gibbous centre of its lateral valves, (Iv. 41.) or linear-elliptic, the transverse striae absent near their ends. SBD. ii. p. 34, } 38. f. 305. = Striatella arouata, Ag., E.; Tessella Catena, E. Common. (x. 203, 204.) Differs from R. minutum in the form of its lateral valves, and by the absence of striae near the ends; the OF TEIE STRIATELLE ZE. 805 series of striae in the front view are also more conspicuous. Length of frustule 1-570" to 1–200”. R. Adriaticum (K.).—Frustules with four series of Septa (two marginal and two median, the latter shortest at One lateral margin, and gradually longer as they approach the other). SBD. ii. p. 35. pl. 38. f. 305. Common, especially from deep water. On Algæ, which are sold as “Corsican moss.” (XIII. 27.) 1-480" to 1-168". Easily distinguished by the median series of Septa, which, more con- spicuous than the marginal ones, are usually more or less curved or º and do not coincide with the ribs, but cross the series of striae ; they also gra- dually increase in length from one lateral margin to the other, leaving a funnel- shaped median space. R. Crozier; § — Lateral valves turgid ; apices obtuse, shortly attenu- ated; the perforated dissepiments (or spurious joints) striated, varying in number. = Striatella Crozieri, ERBA. 1853, p. 529. Assistance Bay. Striae 18 in 1-1152". (IV. 43.) Species known to us only by name, R. mirificum (S.).-‘‘A magnificent species, with filaments occasionally reach- ing 0086" in width, and with alternate and cribrose septa, Septa with several (3 to 12) irregular perforations.” SBD. ii. p. 35. Mauritius and Ceylon. Arnott, JMS. vi. p. 92; Brightw. JMS. vii. pl. 9. f. 11. (VIII, 12.) Genus STYLOBIBLIUM (E.).-Frustules cylindrical, multivalved, not concatenated, valves in a simple straight series, like the leaves of a closed book, with a large median canal, entire (not perforated) at the ends; sculp- tured; tube smooth. Fossil. Stylobiblium approaches nearest to Biblarium and Tetracyclus; but the frustules in the lateral view are orbicular—a cha- racter not met with in the other genera of this family. The species are : fossil, and occur only in a fragmentary state. STYLOBIBLIUM Clypeus (E.).-Lateral view with from 15 to 20 short, radiant marginal lines, and 3 or 4 pervious, trans- verse median ones, frustules in the front view with about 34 laminae or annuli. EM. pl. 33. 12. f. 28, 29.5-13iblarium Clypeus, E. Oregon and Siberia. Dia- meter 1-792". (IV. 45.) S. divisum (E.).--Disc large, its centre with about 10 transverse parallel lines, not reaching the margin, and separated into two series by a linear longitudinal blank band, EMI. pl. 33. 12. f. 30. Oregon. Diameter 1-600". S. eccentricum (F.).--Disc with 5 to 7 eccentric, pervious, curved lines. EMI. l. 33. 12. f. 31. Oregon. Diameter –760". A fragment of a cylinder con- tained 9 annuli. The costae in Ehren- berg's figure resemble those of Tetra- cyclus, the median one straight, and those above and below curved towards . margin in opposite directions to each Other. Genus BIBLARIUM (E.).-Frustules compressed, lamelliform, with in- ternal septa; lateral view with transverse uninterrupted costae, but without median inflation. by Ehrenberg as simple, were probably filamentous in a recent state. Fossil. All the species are fossil, and, although described The forms with inflated centre we concur with Professor Smith in removing to Tetracyclus, and indeed only retain the genus because we are unable to ascertain at present the proper situation of the other species noticed here. BIBLARIUM compressum (E.).-Lateral view elliptic-oblong, with obtuse ends and lax, parallel transverse costae: EMI. pl. 33.12. f. 1, Oregon, 1-648". Costae 5 to 7 in 1-1152", Septa 28 in each frustule. B. ellipticum (E.).--Lateral view ellip- tic, with broadly rounded ends, and 5 to 8 parallel transverse striae in 1-1152". I.M. t. 33. 12. f. 2. Siberia and Oregon. 1-1080". Differs from B. compressum only in its more elliptic lateral valves. B. Lamina (E.). — Lateral valves broadly linear, with rounded ends, slightly constricted middle, and 7 to 8 rºl. transverse striae in 1-1152", EM., pl. 33, 12. f. 4. Oregon. Ehren- berg's figure shows little or no constric- tion. B. lineare (E.).-Lateral valves nar- rowly linear, with rounded or subacute ends, and 4 to 8 parallel transverse striae 806 SYSTEMATIC HISTORY OF TEIE INFUSORIA. in 1-1152, EM. pl. 33.12. f6, Siberia || and Oregon. Ehrenberg's figures scarcely differ from those of B. Lamina, except in being narrower. B. Lancea (E.).--Lateral valves lan- ceolate, with subacute apices, and 3 to 8 parallel transverse striae in 1-1152". EMI. t. 33. 12. f. 5. Oregon. Twenty-seven septa in each frustule. 1-336". B. Castellum (E.).--Lateral view of central portion elliptic, with obtuse ends, and four marginal undulations. EMI. t, 33. 2. f. 1. Siberia. 1-900". Lateral valves unknown. (IV. 44.) B. P gibbum (E.).-Frustules smooth, bacillar; 2 to 4 together, with straight centre; lateral view gibbous at the middle. KSA. p. 117. Kurdistan. 1–1152". A doubtful member of this family. Species known to us only by name, B. Chilense (Eh. Chili.).—“Related to B. compressum,” EM. p. 301. B. constrictum (E.).-Fossil. North Asia. . Genus GOMPHOGRAMMA (Braun).-Filaments compressed, continuous, of few frustules; septa clavate, alternate, nearly equal; lateral valves elliptic, furnished with straight transverse costae. Aquatic. Gomphogramma agrees with Tetracyclus in its freshwater habitat and in the strong transverse costae of its lateral valves, but differs (as we believe, essentially) by its clavate septa, which are not continued as costae across the central canal. We are not suf- ficiently acquainted with the structure of Biblarium to decide what may be its relation to that genus; but it is not improbable that further investigation may require their union. Professor Smith thus contrasts Gomphogramma with Tetracyclus:—“In Tetracyclus the valve is cruciform, and the costae arched; in Gomphogramma the valve is elliptic, and the costae direct; but these seem rather to belong to specific than generic characters, and the pro- priety of uniting these genera hardly admits of a question ” (ANH. January 1857). GOMPHOGRAMMA rupestre (Braun).- Frustules subquadrate, with from one to three septa on each side and gland-like dots along the junction-margins. Braun in Rab D. pl. 33. t. 9, Freiburg; Pyre- nees. This seems to be a mountainous species, and most probably its detection would reward, a search in our alpine districts. In its clavate septa it some- what resembles Terpsinoë, but the re- semblance is merely superficial; for the Septa in that genus are transverse, and in this longitudinal; consequently they belong to different groups. Genus TETRACYCLUS (Ralfs).-Filaments free, elongated, inflated at the centre, striated; striae continued across the inflated centre; septa equal; lateral Surfaces costate. Aquatic. The inflated centre and strongly costate lateral Surfaces sufficiently characterize this genus. “The genus Biblarium, constituted by Ehrenberg in 1845, appears to differ from the present merely in the Solitary character of its frustules; and this character arises from the fossil nature of the gatherings from which Ehrenberg derived his specimens. I feel assured that all the species are filamentous in a living state, and that the greater number of them are casual varieties of Tetracyclus lacustris’’ (S.B.D. ii. p. 37). TETRACYCLUS lacustris (Ralfs).-La- teral view with the inflations and ends rounded. SBD. ii. p. 38, pl. 39. f. 308. = Striatella. Thienemanni, E.A. p. 136; Biblarium Stella; B. Glans and T3. Spe- ciosum, EM. pl. 33; B. Strumosum, EMI. pl. 33. 2. f. 13. Recent, Britain and celand; fossil, Oregon and Siberia. (XI, 24, 25.). The median inflation seems variable ; it is sometimes so much de- | veloped as to form a crucial figure re- sembling the quaterfoil of a Gothic win- dow, but sometimes merely a slight Swelling, as in Biblarium speciosum (E.). T. emarginatus (E., S.), — Inflations deeply notched, otherwise like T. lacus- tris, SBD. ii. p. 38. = Biblarium emargi– natum, E.M. pl. 33.2. f. 6. Recent, Britain; fossil, Siberia and Mexico. T. elegans (E.), — Inflations acute. = OF THE STRIATELLEAE. 807 Biblarium elegans, EM. t. 33. 2. f. 4. and Oregon. Fossil. Siberia. Ehrenberg's figure of this species differs from T. Rhombus merely in its more developed inflation. T. Rhombus (E.).--Lateral view rhom- boid, with subacute angles. = Biblarium Rhombus, EMI, pl. 33. Fossil. Siberia T. P. Cruz (E.). —Lateral view cruci- form, with transverse parallel striae and a median suture. = Biblarium Ch'ua, EMI. pl. 33. 2. f. 3. Siberia. Striae 18 in 1-1152". A doubtful member of this genus. Genus TABELLARIA (E.).-Frustules quadrangular, united into a fila- ment, at length partially separating and forming a zigzag chain; septa equal, straight; lateral surfaces inflated at ends and middle. Aquatic. Tabellaria differs from the other genera of this family by having three inflations of the lateral surfaces. TABELLARIA flocculosa (Roth, K.).— Joints subquadrate, with from 3 to 7 attenuate septa from each margin; la- teral view with three nearly equal infla- tions; the intermediate portions linear. SBD. ii. p. 45, pl. 43. f. 316. = Bacillaria tabellaris, E.I. p. 199. = Navicula trinodis in part, E. = Tabellaria vulgaris, E. Com- mon. (XIII, 29.) . Best distinguished from T. fenestrata by its less elongated frustules and more numerous septa, which usually alternate with those from the other margin. We believe, however, that each complete Septum has an oppo- site one which is generally rudimentary, though sometimes more developed and conspicuous. 1-860" to 1-480". T. ventricosa (K.). — Frustules as in T. flocculosa, but the central inflation of the lateral view much larger than the terminal ones. KB. t. 30. f. 74. = T, bi- ceps, EMI. Several figures, (XIII, 26.) Common. 1-960". Professor Smith unites this to T. flocculosa, and, as we believe, justly, since intermediate forms are not uncommon. T. Gastrum (E.).-Very small; lateral view with a subglobose median inflation and somewhat narrower capitate apices. ISA. p. 119. Fossil. Labrador. T. robusta (E.). —Thick, three times as long as broad, with broad gibbous centre and large subacute terminal capitula. EMI, pl. 33. f. 15. Fossil. America. 1-864". Probably another variety of T flocculosa. T. amphilepta, EM. pl. 3, 4, f.32. Fossil. Boston. Ehrenberg's figure shows the lateral view with inflated centre, as in T. flocculosa; but the extremities are not dilated. T. modosa (E.). — Small, slender, no- dose; nodules five, the median one rather largest, those adjoining oblong, EM. several figures. Siberia. Lough Mourne deposit, &c. Ehrenberg's figures are elongated, with four constrictions, and consequently five inflations, of which the median and terminal are suborbicular and the intermediate oblong. “Akin to Grammatophora undulata” (E.). T. fenestrata (Lyng, K.).--Front view linear, with two opposite septa from each end; lateral view with three nearly equal inflations and linear connecting portions. R.B. t. 17. f. 22. = Tabellaria trinodis, EM. many figures. Common. 1-600" to I-280". Species doubtful, or known to us only by 720,972.62. T. amphicephala (E.). — Very small, with strongly inflated centre and capi- tate apices. KSA, p. 119. Fossil. San Fiore. 1-1728". Scarcely distinct from T ventricosa. T. platystoma (E.), Sandwich Islands; T. rhabdosoma (E.), Asia; T. pinnularia (E.), Asia; T clavata (E.), Northern Asia; T &ndulata º Northern Asia; T. eurocephala (E.), Persia; T. Semen (E.), India; T. Bacillum (E.). Genus GRAMMATOPHORA (E.).-Frustules forming a filament, at length partially separating and becoming a zigzag chain; septa in pairs, opposite, generally curved; lateral view oblong-lanceolate, not inflated. Gramma- tophora is easily distinguished from all the other genera by its striae having commonly a curve outwards near the base; and when this curve is wanting it may be known from Tabellaria by the absence of inflation. Although Kützing describes several species of this genus as smooth, yet we believe that all the species are striated; and notwithstanding we have admitted this 808 SYSTEMIATIC EIISTORY OF TELE INFUSORIA. character into some of the definitions, we use it merely to indicate that the striae are more distinct and more easily detected. * Lateral view oblong or lanceolate, sometimes slightly constricted beneath the apices. t Septa straight or funnel-shaped. GRAMMATOPHORA stricta (E.). — Large, with straight, parallel septa ; lateral view lanceolate. KB. t. 29. f. 76. Asia, Africa, America. G. parallela, EM. pl. 21. f. 26. We know not how this form differs from G. stricta, except that the figures of the lateral valves exhibit more rounded apices. G. Tabellaria, EM. pl. 18. f. 89, 90. Fossil. Virginia. In Ehrenberg's figures the front view has the septa slightly curved and dilated iwi. (funnel- shaped); lateral view lanceolate, with a large central canal. 2 + Septa with a semicircular curve near the marginal ends; otherwise straight. G. marina (Lyng., K.). — Septa with a single curvature; lateral view linear- oblong, gradually tapering into the ob- tuse apices. KB. t. 17. f. 24. = Diatoma taniaeforme, D. marinum (Lyng.), and D. latruncularium (Ag), D. brachy- gonium (Carm.), Bacillaria Cleopatrae (E.)., B. Adriatica and B. Meneghina (Lobarzewsky), Grammatophora oce- anica. Everywhere. Common, often forming long chains. (IV.47; XI, 52, 53.) The synonyms are adopted from Kitzing, and probably some of them belong to other species. The frustules are of very variable length, sometimes nearly Square, sometimes many times longer than broad. Connecting hinge slender. G. tropica (K.).-Large, with striated margin; Septa with a single curvature; lateral view linear, with rounded apices. KB. t. 30. f. 71. Cape of Good Hope. 1-600" to 1-156". Commecting hinge tumid. G. gibba (E.).-Large, striated; septa curved at outer end, otherwise straight; lateral view linear, with slightly in- flated centre and rounded ends. KB. t. 29, f 77. Cuba, (XI. 48, 49.) G. Mearicana (E.).-Large; Septa with a single curvature; lateral view con- stricted beneath the rounded apices. KB. t. 18. f. 1–6. Europe, America. Con- necting hinge tumid. G. gibberula (K.). — Margin striated; septa once curved; lateral view lanceo- late, with tumid centre and obtuse apices. KB. t. 30. f. 81. Naples. 1-450". Con- necting hinge slender. Differs from G. Mea:icana in its distinctly striated mar- gin and more lanceolate lateral view. G. macilenta (S.). — Frustules often curved; septa as in G. marina; lateral valve linear, slightly inflated at centre and extremities; striae 60 in .001". SBD. ii. p. 43, pl. 61, f. 382. Britain; Levant. “The front view in this species is always narrower in proportion to its length than in G. marina. The striae are also far more numerous; and the frustule, espe- cially in the larger specimens, shows a decided tendency to assume a curved form.” --- 3 + Septa lunately curved, both ends hooked inwards. G. hamulifera º —Small, subqua- drate; septa curved throughout, with their concavities towards each other. KB. t. 17. f. 23. Common, especially from deep water. (XIII. 22.) I-2400" to 1-960". Distinguished by its small quadrate frustules and uniformly curved septa. It is possible, however, that it may be the immature state of one of the following species. 4t Septa undulate, inner ends incurved. G. angulosa (E.). — Septa hooked in- wards, at inner end and near the margin of frustule with angular curve inwards. jºb i. 30, £79. Kilantic and Pacific Oceans. Perhaps a variety of G. Afri- CC(720. G. Africana (E.). — Septa with three undulations, the inner ends incurved; lateral view lanceolate, obtuse. EMI. pl. 19. f. 34. Fossil, Oran; recent, not uncommon, 1–2300" to I-480". G. Islandica (E.). — Septa with three undulations, curved at the centre; lateral view navicular, striated, KSA. p. 121. Iceland. G. Serpentina (E.).-Large, with stri- ated margin; Septa with several undu- lations and incurved inner ends; lateral valves linear, with attenuated ends and obtuse apices; connecting hinge thick. SBD. ii. p. 43, pl. 42. f. 315. = G. Medi- terranea (E.), according to Kitzing. Not uncommon in sheltered bays. Remark- able for its serpentime septa, the number of curves, seeming to vary according to the length of the frustule; and we fear OR THE STRIATELLEAE. 809 that some of the allied species are not really distinct from it. Professor Smith informs us that, in this species, Mr. West finds the dots disposed in quincunx, and the lines consequently oblique. (IV. 48.) G. arguina (K.). – Large, smooth; Septa serpentime, with the interior end hooked inwards. KB. t. 17. f. 25. At- lantic and Antarctic Oceans. 1-650" to l–360". We see not how this differs from G. Serpentina, as we believe that no species in this genus is really smooth. 2* Lateral view with four constrictions. G. wrºdulata (E.).--Lateral view linear, with four constrictions and rounded ends; septa in front view undulated. KB. t. 29. f. 68. Fossil, Greece; recent, America, 1–860". 3* Lateral view lunate. G. arcuata, EM. pl. 35A. 23. f. 11, 12. Assistance Bay. The figures represent the front view with undulated septa, and the lateral one lunate, with trans- verse lines and a central canal. G. curvata, EM. pl. 35 A. 22. f. 13. Antarctic Ocean. The figure shows the lateral view, like that of G. arcuata; but its central Canal is Smaller, and there are no transverse lines. G. subtilissima. — Striae fine. A good test for high powers. Genus GEPHYRIA (Arnott).—Frustules attached; front view with sub- lamellate, finely striated connecting Zone, destitute of Septa; valves arcuate, dissimilar, with transverse costae interrupted by a longitudinal line. Marine. We place Gephyria with the Striatelleae because of its resemblance to Eupleuria; but the absence of septa renders its proper position somewhat doubtful. The lower valve differs from the upper one in having a smooth circular space at each end. The strongly arched valves and absence of septa distinguish it from Eupleuria. It differs from Achnanthes by having no central nodule. GEPHYRIA incurvata (Ar.).-Costae of G. media (Ar).-Valves obtuse, with 11 costae in '001". valve about 7 in 001"; connecting zone with stout longitudinal costae. Ar M.J. viii. p. 20. = Eupleuria incurvata, Ar M.J. vi. p. 90; Achmanthes costata, Johnstone, M.J. viii. p. 20, pl. 1. f. 14, South African Ar M.J. viii. p. 20. Achmanthes angustata, Johnstone, M.J. viii. p. 20, pl. 1. f. 13. Californian guano. G. Telfairiae (Ar.). — Valves with acute cuneate ends, and 15 costae in and Patagonian guano. '001". Ar M.J. viii. p. 20. Mauritius. Genus EUPLEURIA (Arnott). — Frustules united into short, attached filaments; front view annulate, indefinite, with short septa and beaded margins; valves dissimilar, costate ; Costae interrupted by a longitudinal line, those of lower valve fewer and central. Marine. Eupleuria differs from Rhabdonema by its dissimilar valves, the transverse costae of the lower one being confined to the middle—a character conspicuous even in the front view, since the ends of the costae are there seen as marginal bead-like dots. The valves have some resemblance to those of Achnanthes, but have no central nodule or stauros. EUPLEURIA pulchella (Ar.). — Front view with stout longitudinal costae con- nected by transverse bars, very short septa, and punctated lateral margins. Air TMS. vi. p. 89. New Zealand and Australia. The frustules, in the front view, have the cellulate structure of Rhabdomema; but the septa are so abbre- viated as to seem mere marginal dots, and the puncta on the ventral margin are confined to the middle, Annuli close, numerous; valves usually turgid at the middle and rapidly tapering to the obtuse apices (subovate), but sometimes linear- oblong. In the lower valve the costae and longitudinal line are present only at the middle portion, and leave a large hyaline inſ Space at each end. Striae between the costae, and oblique. E. ocellata (Ar.). — Front view with longitudinal lines, fine transverse striae, and costate lateral margins; costae of ventral margin longer, confined to the middle, and divergent. ArTMS. vi. p. 9. New Zealand. In E. ocellata the frustules are more hyaline than in E. pulchella, and the longitudinal costae less conspi- cuous, and not connected by transverse 810 SYSTEMATIC EIISTORY OF TELE INFUSORIA. bars. The most evident distinction, divergent. The septa seem to be rudi- however, is the clavate or capitate lines mentary, as in the preceding species. of the dorsal and ventral margins, those | Valves oblong-linear, sometimes curved, of the latter being longer, fewer, and with rounded ends. Genus ENTOPYLA (Ehr.).-Frustules prismatic, compressed, multivalved; valves contiguous, in a straight, simple Series, like the leaves of a book; internal ones traversed by a large median opening; outer ones transversely striated, unequal, one entire (not perforated), the other furnished with a large pore at each end. Marine. Entopyla, by its curved form, approaches Achnanthes; by its tabulate figure it is more akin to Tessella; but it comes nearer to Biblarium than to any other. Although, in deference to the opinion of Professor Arnott, we have kept Eupleuria distinct from this genus, we doubt the propriety of doing so. From Ehrenberg’s comparison of Entopyla with Tessella and Biblarium, and bearing in mind his peculiar views, it is evident that the “internal valves” are the “annuli” of Smith, and the “per- forations of the ventral valve” the blank spaces at each end. Since the opening in the internal valves is stated to be so large as to leave only a thin margin, the septa must be rudimentary. Both Entopyla and Eupleuria seem therefore to differ from Rhabdonema in their dissimilar valves and rudimen- tary septa, nor are we able to find any character in Ehrenberg's description which enables us to distinguish Entopyla from Eupleuria. ENTOPYLA Australis (Ehr.). —Leaves | flexuose line. ERBA, 1848, p. 42. = (annuli) about 16; transverse costae of Surirella Australis, Ehr, 1843, Pata- outer ones (or valves) 32 to more than gonian guano. 40 in number, divided by a median Genus DIATOMELLA (Grev.).-Frustules quadrangular, forming at first a plano-compressed filament, at length separating; Vittae two, interrupted in the middle and at each end.-Disiphonia, E. Aquatic. Professor Smith doubtfully referred to Grammatophora the Diatom for which this genus was constituted; but we consider the differences pointed out by Dr. Greville as sufficient, independently of its aquatic habitat, to separate it from that genus. In Grammatophora the septa are formed in the central or connecting portion, arise from the margins of the filament, and are interrupted in the middle. In Diatomella they appear to us to arise from a thickened rib connecting the lateral and central portions, and form imperfect diaphragms with three open- ings—one central, the others marginal. We have included Diatomella in this family, but, although Professor Smith states that its frustules are annulate and nearest in structure to Grammatophora, we are not sure it is rightly placed here ; for two puncta exist at each end of the frustule, as in the Fragilarieae. DIATOMELLA Balfouriana (Gr.).-La- pl. 35A. f. 7. South Africa, South Ame- teral view linear or oblong, with rounded |rica, Scotland. Front view quadrangular, ends and 45 fine striae in 001." GANH. with a smooth central portion, separated s. 2. xv. pl. 9, fº. 10–13. = Grammato- from the transversely-striated lateral phora P Balfouriana, SBD. ii. p. 43, pl. valves by the vittae. (IV, 51, 52.) 61, f. 383. = Disiphonia Australis, EMI. FAMILY WII. MELOSIREAE. Frustules disciform, cylindrical, or globose, simple or united into a filament; lateral surfaces flat or convex, circular, Smooth or with radiating striae, less frequently cellulose, granulate or punctate; front view with the central por- tion usually either obsolete or divided by one or two central furrows. “For OF TELE MELOSIRIE ZE. 811 the most part the Coscinodisceae are related to this family, with which they have been hitherto united by Ehrenberg; but I have separated them because the shell of the Coscinodiscege often has divergently arranged bands and a cellulose formation, which is wanting in the Melosirea”. Moreover the forms of the genus Melosira have in life so great similarity to the true simple Con- fervae, that they may easily be confounded even by practical Algologists. The heating of a specimen upon mica, however, distinguishes them so cer- tainly that we can never be in doubt” (Kützing). The line of demarkation between the Melosirea and Coscinodisceae is by no means well established; generally, discoid forms with cellulose structure belong to the latter, and fila- mentous or smooth species to the former. This family, however, contains some distinctly cellulose species; but they are distinguished by their inflated or vaulted segments and the absence of a central portion. We have removed some genera Kiitzing had placed here, as we consider Mr. Brightwell has proved that they are more akin to Chaetoceros. Genus CYCLOTELLA (Kiitz.).-Frustules disciform, simple or binately conjoined ; central portion ring-like ; valves plane or slightly convex. Aquatic and marine. = Discoplea, Ehr. Cyclotella differs from Melosira in not forming a filament. The recent species, according to Kützing, are either adnate or enclosed in a shapeless gelatinous substance. Some of the species approach closely in character to Coscinodiscus. We retain Kützing’s name because it has the claim of priority. CYCLOTELLA operculata (K.).-Valves depressed in the centre; striae obscure, very short ; front view with rounded angles. SBD. i. p. 28, pl. 5. f. 48. Fresh water. Europe. This species is involved in great confusion, and we confess our inability to reduce it. We have adopted Professor Smith's views, though with much hesitation. Kützing describes the margin as punctated; and his figures, though varying much in size, of the umbilical portion, show the margin closely and irregularly punctate, whilst Smith describes them as striated. Küt- zing refers here the Discoplea Kitzungi. (E.); but that form, according to the figures in the ‘Microgeologie,” is larger, with radiating striae reaching to the centre of the disc. (v. 53.) C. rectangula (Bréb.).—Similar to C. operculata; but the frustules in the front view have acute angles. Rab D. p. 11. France. By Kützing made a variety of C. operculata, by Smith of C. Kitzingi- ana. (v. 54.) C. Scotica (K.). — Frustules admate; disc plane, very smooth. KB, t. i. f. 2, 3. = C. Ligustica, K. l. c. t. 1, f. 4. On marine algae. Scotland, &c. We unite C. Ligustica to this species, since Kitzing makes no distinction except size, which in the Diatomaceae is too variable to be made the only specific difference, D. 1-960" to 1-516". (xiv. 17.) - C. maa'ima (K.).—Frustules large, ad- mate; disc nearly plane, punctated, K, l.c. t. 1, f. 5. On Algae in the Pacific. Diam. 1-300" to 1-126'. Puncta scattered. C. Coscinodiscus (E., K.).-Disc small, irregularly but densely and finely granu- late, margin Smooth. = Discoplea Cosci- modiscus, EM. pl. 33.10. f. 1, 2. Fossil. United States. Habit of Coscinodiscus minor, rather turgid on the sides. D. 1–1728". C. Mammilla (E., K.).—Disc smooth, umbonate in the centre; suture in front view tumid, produced at the margins. = Discoplea Mammilla, EMI. pl. 38. 22. f 1–3. Fossil. Patagonia. The suture between the valves is ridge-like, and consequently projects at the margins. Rim of disc striate. Diam. 1-1728". C. wºmbilicata (E.).--Disc smooth, with a central Smooth umbo. = Discoplea wºm- bilicata, EMI, pl. 35 B. B. f. 9. From Atlantic deep soundings. Ehrenberg describes this species as smooth, but figures it with a punctated centre. C. Americana (E., K.).—Frustules in front view turgid, with a transverse, tri- carinated ring ; disc punctate in the centre. KSA. p. 19. United States. Diam. 1-660". C. physoplea (E., K.).-Disc smooth, except a circlet of large vesicular-looking granules round the centre. = Discoplea physoplea, EM. pl. 33. 17. f. 8. Fossil. Virginia. Diam. 1-1152". C. conta (E., K.), Disc with a circlet of small striae near the margin, and a crowded central mass of granules. = Dis- 812 SYSTEMATIC EISTORY OF THE INFUSO.R.I.A. coplea comta, EM. pl. 38. 1 B. Asia, Africa, &c. Front view tumid at the sides. Although this species is said to have a granulated umbilicus, none of Ehrenberg's figures exhibit this cha- racter. - C. dendrochaera (E.). — Disc smooth, except a circlet of short rays. = Discoplea dendrochaera, E. On trunks of trees. Venezuela. Frustules Small, tumid in front view. Diam. of disc 1–1920"; cen- tral circlet with about ten rays. Habit of C. comta. C. atmospherica (E.). — Disc with a central, rather turgid umbilicus, from which radiatenumerousstriae. = Discoplea atmospherica, EM. pl. 39. 1, f. 17. In atmospheric dust. Diam. 1-1008". C. Sinensis (E.).--Disc with a central, rather turgid, granular umbilicus, from which radiate numerous striae; the striae separated from the umbilicus by a border. =Discoplea Simensis, EMI. pl. 39.1, f. 16. Atmospheric dust. China, &c. Diam. 1–864". Rays much closer than in C. atmospherica, and Smooth, not rough as in that species. In front view linear, with striated margins. (XV.4. C. Atlantica (E.).--Disc with a central, somewhat granular umbilicus, from which proceed numerous radiating lines. = Dis- coplea Atlantica, EMI. pl. 39. 3. f. 29. Atmospheric dust. Atlantic. Smaller than the last, and its umbilicus not cir- cumscribed by a rim; but we doubt whether this and the two preceding spe- cies are sufficiently distinct. (xv. 3.) C. Oregonica (E.). = Discoplea Orego- nica, EM. pl. 37. 2. f. 3. Oregon, Eh- renberg's figure represents a small disc with a central punctated umbilicus, from which proceed numerous rays. Front view linear, with marginal striae. Does this differ from C. Sinensis? C. venusta (E.).--Disc with granulated umbilicus and numerous Smooth rays. = Discoplea venusta, ERBA, 1852, p. 534. Alive. California. Akim to C. atmo- spherica; frustules with the stellate habit of Actinocyclus. Ehrenberg observed three specimens. In one the umbilicus was nearly equal to a fourth part of the diameter of the disc, and the entire Sur- face very nearly smooth; in another the surface was distinctly granulated, and the umbilicus, having its margin oblite- rated, was scarcely evident. C. Astraca (E., K.).—Disc with a large punctated centre and densely-rayed mar- gin. KSA, p. 19.- C. Rotula, KB. t. 2.f4; SBD, pl. 5. f. 50? ICurdistan; Ireland. JDiam, 1-636". It has the habit and size of MeloSira varians, but is not concatemate. C. Rotula is a marine species. C. Peruana (E., K.).--Disc with very fine rays, reaching to the centre. = Dis- coplea peruana, EM. pl. 38 A. 14. f. 6. In pºe from Arequipa and Santiago, Peru. Resembles C. Astraea. Diam. 1–600". The thickness of the frustule equals half its length. Although the rays are described as reaching the centre, the figures show an umbilical space. C. oligactis (E.). = Discoplea Poligactis, EMI, pl. 35 A. 9. f. 1. Ganges. Ehren- berg's figure shows a small disc, with striated rim and irregular umbilical space, from which proceed a few irregu- lar rays. C. Graeca (E.). —Disc plane, inter- ruptedly striated in a radiate manner. = Discoplea Graeca, E. = Coscinodiscus Grae- cus, KSA. p. 125; EMI. pl. 6.2. f. 1. Fossil in Greece. Diam. 1-864". C. antiqua (S.).-Valves convex; striae broad, not reaching the margin. Diam. '0009" to 0013". SBD. i. p. 28, pl. 5. f. 42. Lough Mourne and Peterhead de- posits, &c. C. picta (E., K.).—Disc plane, broadly granulated in the middle, its margin densely radiated; rays very slender, ele- gantly mixed with pairs of stouter ones. KSA. p. 20. African coast. Disc some- times large. C. Rota (E., K.). — Disc large, with numerous (52) equal rays, not reaching to the centre; surface papillose; papillae unequal, Smallest between the rays, largest at the centre. = Discoplea Rota, EM. pl. 35 A. 22. f. 6. Southern Ocean. Diam. 1-192". This and the next species are distinguished from the rest by having papillae or granules in the intervals of the rays. C. Rotula (E., K.). — Resembles C. Ičota, but is Smaller, its rays fewer in number (20), and its papillae equal. = Discoplea Rotula, EM. pl. 35 A. 22. f. 7. Southern Ocean. Diam. 1-696". As in C. Rota, the rays extend from the margin towards, but do not reach the centre. C. denticulata (E., K.).--Disc marked with straight, parallel, granulated lines, and its margin denticulate. KSA, p. 20. Bermuda. Diam. 1-672". In the character of its margin it resembles Melosira sul- cata, but in the arrangement of its gra- mules it approaches Coscinodiscus lineatus. C. undulata (E., K.).—Disc with radiat- ing lines of very minute granules, and an undulated margin. = Discopled undulata, EM. pl. 33. 18. f. 3. Bermuda. Diam. 1-576". Marginal flexures about fifteen, OF TELE MELOSIRE-ZE, 813 C. Stylorum (Br.).-Valve with styli- form rays diverging from the centre, and ending near the margin with a large circular, head; centre irregularly punc- tate. Sierra Leone. Br'TMS. viii. p. 96, pl. 6. f. 16. C. P. radiata (Br.).-Valve with simple, strongly marked radii, reaching nearly to the centre; centre Smooth; in front view the ends of the radii appear as puncta. West Indies, Monterey. Br. l.c. p. 96, pl. 6. f. 11. As many as ten frustules have been found in union; this may, therefore, belong to Melosira. C. punctata (S.).-Frustules with un- dulations; valves delicately punctate or cellulate; cellules radiate. Diam. 0008" to 0015". Fresh water, England. SBD. ii. p. 87. (VIII. 13.) C. Dallasiana (S.).-Valves with mar- ginal costae; centre cellulate; cellules irregular, Length of costae '0002"; Diam. of valve '022". Brackish water. Eng- land, SBD. ii. p. 87. Genus ACTINOGONIUM (Ehr.).-Frustules suborbicular, many-angled; disc smooth, with radiating lines. from the rest in being smooth. ACTINOGONIUM Septenarium, EMI, pl. 36. f. 39. Barbadoes. Rays (7) divid- Actinogonium, like Liostephania, differs lated border. Between the centre and border is a circlet of very short lines, two ing the disc into compartments, separated in each compartment. (V. 55.) from the margin by a regularly-undu- Genus LIOSTEPHANIA (Ehr.).—Frustules simple, orbicular; disc smooth, but with a crown of rays encircling a large Smooth central space or umbi— licus. Liostephania is distinguished by its disc being Smooth, and having a circlet of striae, which striae do not reach the margin. LIOSTEPHANIA Rotula (E.). — Disc having from six to fourteen simple rays. EM. pl. 36. f. 40. Barbadoes. (v. 57.) L. comta (E.).--Disc with from six to thirteen rays, connected exteriorly by a circlet of puncta. EMI, pl. 36. f. 41. Barbadoes. This species differs from the preceding one in the presence of puncta. - L. magnifica (E)-Disc with its rays alternating inwards with pairs of very short striae, and connected exteriorly by a circlet of puncta. EM. pl. 36. f. 42. Barbadoes. (v. 56.) Genus DICTYOLAMPRA (Ehr.).-Frustules orbicular, not concatenate; disc without an umbilicus, but having a circular cellular centre, with radiat— ing striae, which alternate with other striae from the margin. Dictyolampra differs from the other genera of this family by its disc being cellulose only in the Centre, and indeed it probably ought, together with Lio- stephania and Actinogonium, to form a distinct family; but, having seen no specimens, we are unable to decide on their proper position. DICTYola MPRA Stella (EMI, pl. 36, f | 20) short radiating lines, which alternate 38). Barbadoes. The only species. In the centre is a large, circular, loosely cel- with similar ones directed inwards from the margin; between the latter are inter- lulose umbilicus, with numerous (about | posed very short marginal striae. (v. 58.) Genus MASTOGONIA (Ehr.).-Frustules simple (unequally), bivalved; valves not cellulose, in lateral view circular, unarmed, with lines radiating from a stellate or angular umbilicus. These forms, which were formerly placed in Pyxidicula, may be recognized by their unequal and angular valves, radiating veins, and noncellular surface. The definitions of the species in this genus are unsatisfactory, depending almost entirely on the number of rays— a character which we regard as very variable. MASTOGONIA Cruz (E.). — Valves {} 33. 18. f. 8. large, one with four, the other with seven radiating lines; apex not truncated. EM. Bermuda. mbilicus stellate. * M. quinaria (E)-Valves large, one Diam, 1-396". 814 SYSTEM.A.I.LC EIISTORY OF TELE IN FujSUrt 1A, with five radiating lines, the other un- known; apex not truncate. KSA, p. 25. Bermuda. Diam. 1-480". Scarcely more than a variety of the preceding STOéCLéS. M. Rota (E.).-Valves large, one with six, the other with seven radiating lines; apices entire. RSA. p. 25. Bermuda. Diam. 1-360". Probably another variety of M. Ch'ua. M. sea-angula (E.).-Valves thin, one with six radiating lines, the other un- known; apex broadly truncate, with a hexagonal area. EM. §l. 33. 17. f. 12. Virginia. Diam, 1-1632". Resembles a truncated six-sided cone. All the above species are very smooth and crystal- line. M. heptagona (E.). —One valve with Genus STEPHANOGONIA (Ehr.). truncated apices have spinous angles. Seven, the other with nine rays; apex truncated. Bai AJS. xlviii. pl. 4. f. 12. Bermuda. Liam. 1-840". M. Oculus-Chamaeleontis (E.). —One valve having eight radiating lines and truncate apex, the other unknown. KSA. º 25. = Pyacidicula Oculus-Chamaeleontis. aryland. Diam, 1-1152". M. Actinoptychus (E.).-One valve with 9, the other with 13 flexuose radiating lines; apices broadly truncate. = Pyari- dicula P Actinoptychus, EM. pl. 18. f. 19. Virginia. This species seems distinct in its flexuose rays and the undulated mar- gin of its umbilicus. (v. 59. M. Discoplea (E.). — Valves small, conic, with 18 to 20 rays; apices smooth, truncate. KSA. p. 25. In Patagonian pumice. Diam. 1-1152". Valves as in Mastogonia, but their Distinguished by the rays being prolonged into spines, and forming a fringe round the umbilicus. STEPHANOGONIA quadrangula (E.).- Valves thin, smooth, with truncated apices, one having four, the other six ray-like angles and spines. KSA. p. 26. Bermuda. S. polygona (E.).-Valve with central portion Smooth and much elevated, united to the margin by an indefinite number of rays, the spaces between which are some- times faintly punctate ; the umbilicus sometimes surrounded with spines. Vir- ginia and Bermuda deposits. EMI. pl. 33. 18. f. 10; Br JMS. viii. p. 97, pl. 5. f. 8. (v. 57.) Genus CLADOGRAMMA (Ehr.).-The characters of this genus are un- known to us. CLADoGRAMMA Californicum (E.). — centre, and irregularly forked or divided Valve orbicular, not cellulose, marked near the margin. California. EM. pl. with flexuose lines radiating from the 33. 13. f. 1*. (VIII, 11.) Genus HYALODISCUS (Ehr.).-Frustules simple, disciform ; disc smooth, flat, its umbilical portion or centre separated by a distinct suture. Kützing unites this genus with Cyclotella; but its comparatively large hyaline disc, with a centre distinguished by an evident suture, and usually somewhat coloured, is perhaps sufficient to justify its removal. will distinguish it from Podosira. HYALODISCUS Patagonicus (E.).-Disc large, very Smooth, its margin separated from the large centre by a slightly grooved but not denticulate suture; junction-line in front view very tumid. EM. pl. 38. 22. f. 10, 11. In pumice from Patagonia. Diam. 1-432". H. laevis (E.).--Disc º: smooth, its central portion separated by a fracture- like suture. EM. pl. 33.15. f. 17. Cyclo- tella lavis, Kütz. Virginia. Diam. 1-456". Allied to Cyclotella physoplea. The Su- ture between the valves is not tumid, Its flat disc and the central portion of the disc is Smaller, and hence more distant from the rim, than in H. Patagonicus. H. Stelliger (Bai.).—Disc with a broad margin covered with distinct rectilinear rows of dots, arranged in groups so as to produce a stellate appearance. BC. vii. Abundant. St. Augustine, Florida. “The markings in this species are quite distinct; and the stellate appearance, resembling that shown by Coscinodiscus subtilis, will at once distinguish it from all other species,” B. OF TELE MELOSIRE ZE, 815 H. subtilis (Bai.).—“Disc marked like the engine-turned back of a watch, with lines of exceeding delicacy, only visible by the highest magnifiers and careful illumination; umbilical portion more coarsely granulated and in size little less than one-third of the diameter of the disc,” B. l.c. pl. 1. f. 12, Halifax, Nova Scotia. “ H. laevis differs by having a wider mar- gin and much coarser markings. This species forms an admirable test-object,” B. (v. 60) Genus LYSICYCLIA (Ehr.).-The characters of this genus are unknown to us. From Ehrenberg's figures it appears closely related to Hyalodiscus, the disc having a central, circular umbilicus, and a broad border separable at the suture, as in that genus. LYSICYCLIA Vogelii, ERBA, 1856, p. 833, f. 29. Central Africa. (VIII. 39.) Genus PODODISCUS (Kütz.).-Frustules as in Podosira, but affixed by a lateral stipes. Marine. We think that the lateral position of its stipes is scarcely sufficient to separate Pododiscus from Podosira. PopodTSCUs Jamaicensis (Kütz.). — Frustules simple, concatenate, Smooth; stipes elongated, delicate, KSA. p. 26, 1. 16. f. 28. On Enteromorpha ramulosa, amaica. Diam. 1-840". (XIII. 28.) Genus PODOSIRA (Ehr.).-Frustules united into short filaments, having a distinct central stipes; interstitial portion obsolete; valve convex. Marine. In Podosira the lateral valves are vaulted, and the central portion is at first a mere connecting ridge between them. This ridge, however, becomes gradually broader, and then double; afterwards an intermediate growth separates the halves of the frustule, which meanwhile do not increase in size; and at last, when the intermediate space equals the diameter of the original frustule, two new frustules are formed by the addition of a hemisphere on the inside of each of the separated portions. The outer silicious covering still remaining, the frustules are connected in pairs, and appear like two globules within a joint. The valves usually have a central, coloured umbi- licus—an appearance which Professor Smith attributes, in our opinion errone- ously, to an absence of silex at that point. PoDoSTRA Montagmei (Kütz.).-Frus- tules subspherical, dotted; connecting sheath with parallel annular series of minute striae. SBD. ii. pl. 49. f. 326. = P. Adriatica, Me, on Diat. ; Melosira globifera, Ra ANH. xii. Britain, France, &c. (v. 61.) P. Hormoides (Kütz.).-Frustules oval, united into short moniliform filaments; connecting sheath obscurely punctate; lateral view with umbilicus but no rays. SBD. pl. 49. f. 327. = P. nummuloides, E. (II. 45.) Atlantic, Britain, &c. Di- stinguished from the preceding species by its more depressed valves. P. maculata (S.).--Disc with a large central umbilicus, which is bordered by an irregular, fracture-like suture, from which radiate outwards several shadow- like bands; surface punctated. SBD. ii. p. 54, pl. 49. f. 328. Common in deep water, guano, &c. Britain. It may be identical with Craspedodiscus Stella, E. P. compressa, West. (VIII. 34.) P. laevis (Greg.). — Frustules trans- parent, glassy, with very delicate oblique striae and scattered puncta; connecting zone distinctly striated; disc without a distinct umbilicus. Grey M.J. vii. p. 85, pl. 6. f. 15–17. Scotland. Genus MELOSIRA (Ag).-Frustules cylindrical, discoid, or globose, con- nected into cylindrical conferva-like filaments, one or two lines passing round each frustule near the centre.-Gallionella, Ehr. Maritime and aquatic. This genus is easily distinguished from the other genera of the Diatomaceae except Pododiscus, with which the species in its first section closely correspond in character. The filaments are remarkable for their conferva-like appear- ance, but may be known by their brown colour and very fragile nature. The 816 SYSTEMATIC EIISTORY OF TEDE INFUSORIA. species are numerous, and sometimes differ very slightly; we fear indeed that several of them have been constituted upon insufficient grounds. Attempts, more or less successful, have been made to remove some species, and to form with them new genera. We have used these divisions as sections, partly because we are unable to find at present differential characters sufficient to justify a more complete separation, and partly because we cannot decide absolutely on the proper position of several species. The following are the sections we have adopted :— * Lysigonium.—Joints globose or elliptic, with a ring-like keel round each valve. In this section the frustules resemble in form those of the two pre- ceding genera, but are distinguished by their carinated valves. The suture is a ridge between the valves. 2 * Gallionella.-Joints cylindrical or suborbicular, with a single median furrow, and more or less rounded ends, generally binately connected; valves not carinated. The filaments are more or less interrupted at their margins, and the junction-surfaces are not denticulated. 3 * Aulacosira.-Joints cylindrical, bisulcate, with more or less rounded extremities. The genus Aulacosira was proposed by Mr. Thwaites for “ those species characterized by the absence in the frustule of an evident central line indicating the place of subsequent fissiparous division, but each frustule having two somewhat distant sulci or fossulae passing round it.” We have found the sulci constant; but Professor Smith believes “the characters have no real existence, and owe their apparent presence in the species Mr. Thwaites adopted as his type, viz. Melosira cremulata, Kütz., only to accident, or observation under imperfect illumination. A careful study of the specimens from Aberdeen, upon which Mr. Thwaites himself founded his remarks, and of gatherings from various other localities, has failed to satisfy” him “that any essential differences exist between this species and other Orthosirae.” 4 * Orthosira.-Joints exactly cylindrical, marked by a central line, con- nected into an uninterrupted cylindrical filament; internal cavity often spherical or subspherical (Thwaites). Orthosira contains “ those species the frustules of which are not at all convex at the extremities, and which therefore form, by their close contact, an uninterrupted cylindrical filament ’’ (Thwaites). Professor Smith distributes the species of Melosira under two genera, Melosira and Orthosira, which he thus defines. Melosira: “Fila- ments cylindrical, of numerous frustules, attached or free ; frustules spherical or subcylindrical, more or less convex at the junction-surfaces.” Orthosira: “Filaments cylindrical, of numerous frustules, continuous, attached or free; frustules and valves cylindrical; junction-surfaces plain, line of junction usually spinous or denticulated.” We regret that in the present state of our knowledge we cannot adopt Orthosira as a substantive genus. Its junction- margins, indeed, are usually denticulate or spinous, a character we do not find in Melosira as defined by Professor Smith ; but this character is not considered essential. In our opinion, too, there is greater affinity between “Melosira distans” and “ Orthosira Orichalcea ‘’ than between the latter and “Orthosira. sulcata.” Melosira is of peculiar interest, as it affords the most frequent examples of that form of reproduction in which the valves of a frustule sepa- rate, and a sporangium is formed between them, unattended by conjugation. * an ana'alo,” a “a g . 56, pl. 49. f. 329. = M. discigera, Ag. * Fºº and Marine and brackish, waters. Europe, ſ/ ySlg America. (v. 64, XI. 14.) Diam. 1-1700" MELOSIRA nummuloides (Dillwyn, to 1-860". Frustules globular, united Ag.)—Frustules spherical, very finely in pairs, forming a moniliform filament; punctured; valves carinated. SBD. ii. each divided into hemispheres by a cen- *** * S17 OF TDIE MELOSITEAE. tral ridge and crossed by fainter lines at each end. Professor Kützing describes it as of a golden colour when dry; our specimens are greenish. Sporangial frus- tules larger, concatenated, originating from the terminal frustule only. Ac- cording to Kützing, the frustules in this species are ternately, and in the next bi- mately conjoined; this does not coincide with our experience. The only species likely to be confounded with it is the following. M. salina (K.). —Smaller; valves of the binate frustules achromatic, Smooth; keels very fine. KB. p. 52, pl. 3. f. 4. = Gallionella nummuloides, EI. 167. 8, concatenata, more distinctly stipitate; frustules concatemated by a distinct isth- mus, KB. }: 3. f. 5. Brackish waters. Europe. This species differs from M. 2770mmuloides by its less conspicuous keels and more distinct stipes. Pro- fessor Smith unites them; for “forms aberrant in these respects are so fre- #. intermixed with the ordinary frustules that ” he “cannot regard such peculiarities as of specific importance.” M. Westić (S.). — Frustules sub- globular; valves conical, with truncated apices and a sutural and median sili- cious ring. SBD. ii. p. 59, pl. 52. f. 333. Stomach of Pecten, coast of Sussex. This species seems distinct in the strongly marked central and lateral ridges. 2 * Joints binately or ternately conjoined; valves weth rounded ends, neither car?- wated nor denticulated. Gallionella. M. moniliformis (Müll, Ag.).-Joints rather longer than broad, finely punc- tated, bimately conjoined, with rounded ends. KB. pl. 3, f. 2. = M. Borreri, Gr. ; Gallionella moniliformis, E. Common in brackish and marine waters. Diam, 1-800". Kitzing describes this species as having ternately conjoined frustules concatemated by a distinct isthmus. Sporangial frustules larger, concatenated, and, according to Professor Smith, origi- nating only in the terminal frustules of the filament. (v. 71.) M. lineata (Dillwyn, Ag.). — Joints cylindrical, smooth, binately conjoined, with rounded ends; pairs closely adnate. KB. p. 53, pl. 3. f. 1= Gallionella lineata, B. Marine. Europe. A single filament sometimes consists of from 1200 to 4000 frustules, forming a chaim 2 or 3 inches in length. Length of joint 1-1400" to 1–430". M, dubia (Kütz.), — Smaller; articu- lations depressed, spheroidal, Smooth. KB. p. 53, pl. 3. f. 6. Marine, near Cux- haven. Diam. 1-1200". - M. Jurgensii (Ag), Slender; joints Smooth, elongated, with two slight con- strictions beneath the silicious sheath ; junction-surfaces convex, hemispherical, closely concatenate. KB. p. 54, pl. 2. f. 15.- M. subſterilis, SBD. pl. 51, f. 331. Brackish waters. Europe. Diam. 1-800" to 1-1200". There is only one sutural line, having usually on each side of it a slight constriction. As in M. varians, the inflated joints are interstitial, and closely united to the parent frustule. M. Jurgensić differs from M. sulflewilis in its marine habitat and more closely commected joints; but we find it difficult always to discriminate them. The joints are more uniform than in M. varians, usually longer in proportion to their breadth, and with more-rounded ends, especially in the new-formed valves. (v. 63.) M. Subſleavilis (K.).-Frustules cylindri- cal, Smooth, bimately conjoined, younger ones elongated, adult shorter, depressed ends slightly convex; pairs united by a short isthmus. KB. p. 53, pl. 2. f. 13. Rivulets. Europe. Diam. 1-560". Re- sembles M. varians with the binate frus- tules connected by short interstitial pro- cesses. Professor Smith thinks this species identical with Conferva lineata, Dill. Sporangial frustules as in M. mo– miliformis. M. varians (Ag). —Joints cylindrical, irregularly binately conjoined; ends flat with rounded angles, closely admate; disc with very delicate, radiating mar- ginal striae. SBD, pl. 51. f. 332=Gallio- nella varians, Ehr, Freshwater; every- where common. 8. aqualis, all the joints quadrate; M. aequalis, Ag. This species varies much, both in size and length of joints; the margins of the filament are more or less interrupted; but the ge- minate arrangement of the frustules is often very obscure; the valves, although, as in most other Diatoms, they are really dotted, appear Smooth unless magnified. The sporangial cells are inflated and in- terstitial; Professor Smith describes them as at first globular, but afterwards dividing (as in the preceding species) and becoming cylindrical, whilst Rabenhorst gives a completely different account of them. The latter says “ that on forma- tion of the inflated cell, its granules, at first irregularly formed, become oblongo- ovate. Motion takes place as in ordinary zoospores. The cell opens, the granules 3 G 818 SYSTEMATIC EIISTORY OF THE INFUSORLA. stream forth, and two elongated cilia become visible at their hyaline Smaller end. Their movement lasts for a very short period; they settle down, and quickly equal or surpass, in size the mother-cell.” If this description be cor- rect, it will add an important fact in Sup- ort of their vegetable nature. Professor mith makes the following diagnostic remarks upon this species:—“The only species with which this form can be con- founded is M. subftecilis; but M. varians has the extremities of its frustules closely applied and partially truncate; those of M. subflewilis are often more or less separated by a mucous cushion, and di- stinctly convex. . . . M. Swiftleaſilis, when in abundance, appears as a dark-green iridescent mass. M. varians always pre- sents a rich golden-yellow or chestnut to the eye. The geminate arrangement of the frustules is conspicuous in M. Sub- flewilis, and indistinct in M. varians.” SBD. ii. p. 58. The fossil frustules of this species constitute the greater part of the earthy deposits of white powder used in polishing silver plate. (IV, 32; Ix, * 131; xv. 32.) 3 * Frustules cylindrical, bisulcate, with pounded junction-margins. M. distans (E., K.). —Slender; joints cylindrical, smooth or indistinctly punc- tated, with two distant, delicate, ring- like furrows, all closely connected; disc plane. KB, p. 54, pl. 2. f. 12. Fresh water. Europe, Asia, Australia, Africa, and America. Fossil, Bilin, &c, Diam, 1–3456" to 1-864". Joints once to twice as long as broad. M. nivalis (S.).-Joints subcylindrical; valves subhemispherical, distinctly cel- lulate; extremities more or less truncate; disc dotted. SBD. ii. p. 58, pl. 53. f. 336. = Coscinodiscus minor, SBD. i. p. 23, pl. 3. f. 36. Fresh water in Alpine di- stricts. Britain. According to Professor Smith, this form hardly differs from M. distans, except in the greater di- stinctness of the cellules, and may not be distinct. M. orichalcea (Mertens, K.).—Slender; joints obscurely punctated, mostly longer than broad, closely binately conjoined, with slightly crenulate ends and two median furrows; disc plane. KB. p. 54, t. 2. f. 14. = Gallionella aurichalcea, Ehr Inf Fresh water, Common. Europe, Asia, Africa, and America. Younger joints two or three times as long as broad; older ones shorter. This species differs from M, Italica merely in its more obscure cremations and apparently smooth disc; and perhaps Professor Smith rightly united them. Its flat and closely connected ends distinguish it from M. varians. (v. 65; VIII. 33.) M. Italica (E., K.).--Slender; joints cylindrical, longer than broad, with den- ticulated ends and two median furrows; disc with striated border. KB. p. 55, pl. 2. f. 6, = Gallionella Italica, Ehr.; G. crenata, EMI. many figures; G. crent- lata, E.A. pl. 2. l. f. 14; Melosira ori- chalcea, Ralfs, Annals, xii; Aulacosira crenulata, Thwaites; Orthosira Orichalcea, SBD. ii. p. 61, pl. 53. f. 337. Fresh water. Europe, Asia, Australia, Africa, and America. (XI.29, xv. 33.) 3. Binde- rana, Kütz., more slender; joints four to eight times as long as broad, often inflated; disc striated, KB. pl. 2. f. 1. Hamburgh. Mr. Thwaites describes the sporangium as orbicular, with its axis of elongation at right angles to that of the frustule from which it originated; but Professor Smith's experience did not en- able him fully to confirm Mr. Thwaites's observations. M. coarctata (E.).-Joints smooth. Its habit is that of M. varians, but its disc is not striated. EA, pl. 3. 5. f. 9. Mexico. (XI. 20 & 27.) Kützing unites this form with M. orichalcea. M. Roseana (Rab.). — Joints longer than broad, with two broad constrictions and dentated truncate junction-margins; disc with radiating striae and three or more central dots. Rab D. p. 13, t. 10. = Orthosira spinosa, SBD. ii. p. 61, pl. 61. f. 386, Europe. Caves, in moss, on trees, &c.; probably common. Much as they differ in appearance, the late Pro- fessor Gregory considered that he had traced the Liparogyra spiralis into this species; and certainly the two forms 8]'6) * invariably found together. V, 67. ( M. laevis (E.)= Gallionella lavis, EMI. pls, 9, 14 & 33. . . Ehrenberg gives up- wards of fifty habitats in Australia, Asia, Africa, and America. His figures of this species differ considerably from each other, and, in the absence of description, render it difficult to form any idea of the specific characters. Ehrenberg (l, c. p. 118) says it is allied to Stephanodiscus JEpidendron, and we strongly suspect that both these forms ought to be united to M. Roseana, M. pileata (E., K.).-Joints shorter than broad, smooth, with two finely pumctated, widely separated sutures. Junction-portions convex, Smooth, often OF THE MELOSIREAE. 819 narrower than the intermediate portion §º: hence the hat-like form. SA, p. 31.= Gallionella pileata, ERBA. 1844; M. pl. 35 A. 21. f. 11. Antarctic Sea. Diam, 1–648". 4 * Joints cylindrical, connected into an wninterrupted filament; internal cavity often spherical or subspherical. M, arenaria (Moore). — Filaments stout, curved; joints cylindrical, mostly shorter than broad, closely united with denticulated junction-margins and a line of puncta on each side of suture; disc with radiating striae and punctated centre. Ralfs, ANH. xii. pl. 9. f. 4. = Orthosira arenaria, SBD. ii. p. 59, pl. 52. f 334; Gallionella biseriata, EMI. pl. 15 A, f, 5–7. Fresh water. Europe. #i. recognized by its great size. (VIII, 17.) M. undulata (E., K.). —Stout; joints longer than broad, constricted within the sheath, hence undulate; disc slightly convex, very finely radiated. KSA, p. 29. = Gallionella undulata, EM. * 11. f. 2, 3. Europe and Africa. Professor Smith refers this form to M. arenaria. M. punctigera. = Gallionella punctigera, EM. pl. 12. f. 9. Fossil. Germany. Ehrenberg's figure represents a large species, perhaps not distinct from M. arenaria. Joints within a common sheath, in One figure shorter, in another longer than broad, constricted on each side of the suture, and having a series of dots along the junction-margins. Disc with numerous radiating dotted lines and a Smooth umbilicus. M. Sol (E., K.). — Joints coin-like, five times shorter than broad; disc plane, large, strongly and broadly radiated, with a smooth umbilicus and narrow Smooth rim. KSA. p. 31.= Gallionella Sol, EMI. pl. 35 A. 22. f. 12. Antarctic Sea. Rays 84; suture of valves single. Diam, 1–336". This species rivals M. arenaria in size, and somewhat resembles it in appearance, but is marine. M. Oculus (E., K.).—Habit of M. Sol, but larger, with equal and stouter rays. KSA. p. 31. ERBA, 1844, p. 202. Ant- arctic Sea. Rays 67. Diam, 1-240". Probably a state of M. Sol. M. Tympanum (E., K.). — Disc very broad, with a smooth centre and a nar- row, finely striated margin. KSA, p. 31; ERBA, 1844, p. 202. Antarctic Sea. M. calligera (E., K.). — Joints small, Smooth, having the habit of M. distans, but with a single median suture and an enclosed, double, granular mass (as in M. undulata). KSA, p. 31. = Gallionella calligera, ERBA, 1845; EM. pl. 12. f. 9 k, l, Fossil in pumice, Island of Ascen- sion. Diam. 1-1728". M. Sculpta (E., K.). — Joints not so long as broad, densely striated, and ele- gantly sculptured with horizontal punc- tated lines; suture a narrow smooth band; disc with radiating punctated lines. KSA. 31. = Gallionella sculpta, EM, pl. 33.12. f. 20, 21. Fossil. Ore- gon. Diam. 1-960". Frustules oval. M. Campylosira. = Gallionella Cam- pylosira, EMI, pl. 35 A. 13 B. f. 1–3. Elbe. Resembles M. Sculpta, but smaller. Joints suborbicular, within an uninter- rupted sheath, with horizontal dotted lines on each side of a narrow, Smooth sutural interspace; disc with marginal radiating lines. M. Californica (E.). — Joints broader than long, densely and strongly striated with horizontal punctated lines; sutural interval smooth, not distinct. = Gallio- nella Californica, ERBA, 1852, p. 534. Fresh water. California. Very much akin to the fossil M. Sculpta, and both forms closely approach M. granulata. Frequently the granulated, dome-shaped terminal discs are found dispersed amongst the truncated joints. Perhaps therefore this form, with M. Horologium, should be referred to the peculiar genus Sphaerotermia. M. Horologium = Gallionella vel Spharotermia Horologium, EMI. pl. 33, 2. f. 17. Fossil. Siberia. We have seen no description of this species, or of Ehrenberg's genus, Sphaerotermia. Frus- tule with horizontaistrie interrupted by the smooth sutural band; disc with a large, definite, Smooth umbilicus and distant radiating striae, terminating at inner ends in a circlet of gland-like dots (tubercles?). (v. 62.) M. arctica (Dickie). — Joints globose or oval, Smooth, the median sutural line generally single, but duplex in Subcu- taneous division, with a smooth band interposed. = Gallionella arctica, ERBA. 1853, p. 528; EM. pl. 35 A. f. 1, 2. Mel- ville and Kingston Bays. In Ehrenberg's figures the frustules are within a common continuous sheath, and marked with hori- zontal series of puncta. M. Sulcata (E., K.). — Joints shorter than broad, with a smooth median fur- row and pinna-like cellules on each side; disc furnished with radiating striae, which do not reach the centre. KB. p. 55, pl. 2. f. 7. = Gallionella sulcata, Ehr. ; Orthosira marina, S.B.D. ii. p. 59, pl. 53. f 338. Marine, Frequent, both recent 3 G 2 S20 SYSTEMATIC EIISTORY OF TEIE INFUSORIA. and fossil. (Ix, 131 and XI. 26.). This species, which varies considerably in size, is well marked by its short, slightly angular joints, and its transverse sculp- ture-like marks on each side of the su- ture. Margin of disc often denticulate. Diam. 1-860” to 1-600". M. coronata (E., K.).-M sulcata in habit; joints cylindrical, striated; disc smooth, slightly convex, with a cremated margin and a circlet of pearl-like gra- nules within, KSA. p. 31. = Gallionella coronata, EMI, pl. 38. 22. f. 5. Marine. Asia, Africa, Patagonia, Diam. 1-864". It differs from M. sulcata only in the more distinct cremations of the disc and the circlet of dots. M. plana (E., K.).—Habit of M. Sul- cata; but disc plane, smooth, and neither radiated nor granular. KSA. p. 31.= Gallionella plana, ERBA, 1845. Fossil. Patagonia. D. 1-1152". This form may possibly be M. Sulcata, with its markings destroyed by igneous action. M. Hetrurica (K.). — Small; joints cylindrical, smooth, twice as long as broad, with finely denticulated junction- margins; disc convex, marked with dotted rays. KB. p. 55, pl. 2. f. 6. Fossil. San Fiore, Diam. 1-3600" to 1-800”. M. granulata (E.).-Joints longer than broad, with horizontal punctated lines on each side of the median suture, and denticulated junction-margins; disc with a series of marginal puncta. = Gallionella granulata, EA, p.123; M. many figures; G. tenerrima, EMI, pl. 39. f. 50; Ortho- sira punctata, SBD. ii. p. 62, pl. 53. f. 339. Fresh water. Ehrenberg gives upwards of 50 habitats in Europe, Asia, and America. M. B. maacima. Disc with 31 mar- ginal denticulations, and strongly akin to M. Sulcata. - M. Marchica (E.). — Resembles M. granulata; but the dotted lines are pa- rallel to the suture, and not horizontal. = Gallionella Marchica, EM. several figures; G. procera, EM. pl. 15 A. f. 1. Fresh water. Europe, Asia, Africa, and Ame- l’IC8,. M. decussata (E.). — Resembles M. granulata ; but the dotted lines are dia- gonal and decussating. = Gallionella de- cussata, EM. several figures. Fresh water. Asia, Africa, and America. Kützing includes, perhaps correctly, M. Marchica and M. granulata under this species. M. lirata (E., K.).-Has the habit of M. granulata, but with more conspi- cuous lines, disposed like the strings of a lyre. KSA. p. 31.3- Gallionella lirata, EMI, pl. 2. 3. f. 33. Fossil. America. M. spiralis (E., K.).-Filaments curved and spiral; joints Small, oblique, longer than broad, or equal, loosely punctated in transverse series. KSA, p. 31. = Gal- lionella spiralis, EMI. pl. 33. 13. f. 3. Fossil. Oregon. Diam. 1-2304". M. Americana (Kütz.).-Frustules in- cluded in a jointed cylindrical tube, separated by dissepiments of the tube, elliptic, with striated margins and a median furrow; disc with radiating striae, convex, KB. pl. 30. f. 69. = Ortho- Sira Americana. Diam, 1-660". Appa- rently furnished with internal silicious cells. M. Dickień (Thwaites, K.). —Joints mostly longer than broad, Smooth or ob- scurely punctated, except by conspicuous dots bordering the suture; disc obscurely punctate; sporangia P fusiform. RSA, p. 889. = Orthosira Dickień, Thwaites, ANH, 2nd series, i. pl. 12; SBD. ii. p. 60, pl. 52. f. 335. Fresh water. Cave near Aberdeen. (XV. 29.) “The fila- ments of this beautiful species consist generally each of from two to four frus- tules, which are hyaline and perfectly Smooth ; central cavity filled with dark red-brown endochrome ; sporangium fusiform, marked with numerous annular constrictions, whose formation is pro- gressive, and which go on increasing until the sporangium is fully developed (xv. 296. 29B, a filament, the terminal cells of which have each commenced to develope a sporangium; and f. 29 C. a. mature sporangium). This formation thus occurs: at the commencement of the formation of a sporangium, the endo- chrome, at the same time that it with- draws from the end of the frustule, pro- duces at its centre an additional ring of cell-membrane; and, this process con- tinuing to take place at certain intervals, each new ring of cell-membrane exceed- ing in diameter those previously formed, produces at length the structure repre- sented in f. 29 C; or it may be a more correct explanation of the process to say that an entire new cell-membrane has been developed by the young sporangium at the time each new ring has been formed, and that thus have originated the several chambers into which the ends of the sporangium are divided; fissi- parous division subsequently takes place, and sporangial frustules are developed from each half, as shown in f. 29 D.” Professor Smith doubted whether the fusiform bodies are sporangia, as “this OF TEIB MELOSIIREE. 821 mode of development, in the formation of sporangia, stands alone and unsup- ported—a serious difficulty in the way of admitting Mr. Thwaites's conclu- Sions.” For this and other reasons, he Was disposed to refer the process to the development of internal cells, as in Meri- dion, Himantidium, Odontidium, and Achmanthes, and recorded his impression that the process was not connected with the sporangia. M. tenuis (K.).--Very slender; joints cylindrical, smooth, longer than broad, closely connected, produced at their junction. KB. p. 54, pl. 2. f. 2. In the polishing powder of Luneberg. Diam. I-5760". M. Garganica (Rab.).—Very slender; joints two or three times as long as road, with stout, protuberant, indi- stinctly dentate junctions; disc flat, punctated on the periphery. Rab D. p. 14, t. 2. f. 8. Italy. After burning, it reminds one of M. tenuis, Doubtful and imperfectly described Species, M. Dozyana (Van den Bosch)-Joints cylindrical, finely punctated; length equal to or a little longer than the breadth. KSA, p. 29. Stagnant water. Holland. Diam. 1-1152" to 1-770". M. circularis. = Gallionella circularis. EM. pl. 35 A. 9. f. 3. Asia and America. Filaments slender, curved; joints broader than long, closely connected, Smooth, with a single sutural line. M. Gallica. = Gallionella Gallica, EMI. 1. 9. 2. f. 2. Fossil. France. The frustule has one diameter twice as long as the other, and no Suture or striae. M. halophila = Gallionella halophila, EM. pl. 37. 5. f. 1. Europe. Frustules minute, Smooth, M. taeniata= Gallionella 'tamiata, EMI. pl. 39. 3. f. 65. Atmospheric dust. The figure shows a single subquadrate frus- tule, without any distinguishing cha- racter. M. trachealis = Gallionella trachealis, EM. pl. 8, 2. f. 18. Hungary. Ehren- berg's figure is too imperfect to be in- telligible. M. laminaris = Gallionella laminaris, EM. pl. 39. 3. f. 64. Asia. The imper- fect figure shows striated junction-mar- Q111S. * M. Scala = Gallionella Scala, EMI. pl. 8. l. f. 24. Hungary. The figure re- presents a slender continuous filament, divided into smooth quadrate joints, M. P. mesodon = Gallionella P mesodon (Fragilaria mesodon P), EM. pl. 11, f. 16. Bohemia. Filament slender, conti- nuous, with Smooth subquadrate joints, having two puncta at each outer margin, as in Fragilaria. M. ochracea, = Gallionella ferruginea (Ralfs),-Slender, oval, convex at both ends; Smooth. In many, perhaps in all chalybeate waters, and also in peat- Water, which contains a small proportion of iron, this is to be found; it is of the colour of iron-rust, and in mineral Springs, in which it abounds, is often taken for precipitated oxide of iron. It covers everything under water, but forms so delicate and floccose a mass, that the least motion dissipates it. In the spring of the year, this mass is com- i. of very delicate pale-yellow glo- ules, which can be easily separated from each other. They unite together in rows, like short chains, and produce an irregular gelatinous felt or floccose substance. About summer, or in autumn, they become developed into more evi- dently articulated and stiff threads, of a Somewhat larger diameter, but still form a complicated mass or web, and, either from adhering to each other or to deli- cate Confervae, appear branched; in the young condition, when examined under shallow magnifiers, they resemble gela- time; but with a power of 300 diameters, the flexible granules are discoverable, and, with dexterous management, the little chains forming the felt or floccose web can be made out. In summer, on the other hand, its structure can be ob- served much more easily and distinctly. Early in spring, the colour is that of a pale yellow ochre; but in summer, that of an intense rusty red. Diam. 1-1200". According to Kützing, this is not a species of Gallionella, but a Conferva; it has no true silicious lorica, as have true Diatomeae; and the coating of oxide of iron is not an essential element, but merely an incrustation, such as will form on well-known Confervae placed under like circumstances, i.e. in water holding salts of iron in Solution, which are sub- sequently precipitated by exposure to the air, and converted into the red oxide. The same author differs from Ehren- berg as to the part played by the so- called Gallionella ferruginea in the pro- duction of the oxide of iron in chalybeate waters, of bog-iron ore, of clay-iron ochre, &c. For, he observes, in many springs rich in iron no such organism is found, although other Confervae may be present — Conſervas, however, not peculiar to 822 OF THE INFUSORIA. SYSTEMISTIC EIISTORY such habitats, but common in Springs and ponds generally. Mr. Ralfs (op. cit. p. 352), however, in part supports Ehrenberg, declaring that, though identical with Conferva ochracea (Dillwyn), yet “Bhrenberg is no doubt correct in placing the plant in this genus, as the filaments are silicious and cylindrical.” Nägeli describes and figures a species which he refers to the genus Gallionella; but it is a doubtful member. His de- scription, however, especially that of the self-division, induces us to give it nearly in his own words, with his name (Ray Society, 1846, p. 219). M. Nägeli #. :-Shortly cylindrical; diam, '014" to 027". Marine. Naples. “Both the terminal surfaces of the cylinder are flattened; so that, when seen sideways, it appears rectangular, with the angles rounded off. It is composed of one simple cell, whose membrane is covered by a siliceous plate; and its cavity contains chlorophyll-granules, which lie upon the membrane in two circular bands. (xv. 26–28.) . Each of these bands occupies one of the obtuse angles of the cylinder, and appears annu- lar from above, rectilinear from the side. “In developing, the relative length of the cylinder increasing, a septum divides it into halves (xv. 28 c), which when complete, the latter separate as two di- stinct beings. The nascent chlorophyll- granules are either spread equally over the surface, or more frequently arranged in radii from the nucleus in the centre; they lie in the course of the currents streaming from the nucleus. Compared with a cell of Conferva, or of Spirogyra, all three agree in the forming of a septum, in the similarity of their contents, and in the depositions of extra-cellular sub- stance. But Gallionella differs from both, by the production of an individual from every cell, also by the chlorophyll forming two lateral bands, and the sili- ceous extra-cellular substance an inter- mediate one. “So far as my investigations go, Gallionella, which, according to Ehren- berg, possesses a bivalved or multivalved shield, agrees with the above-described E. in all essential particulars. The ines, for instance, which would intimate a division of the shell into two or more pieces, are the septa by which the cell- division is effected. As in the filiform Algae, these walls at first appear as deli- cate limes; then, by an increase of thick- ness, seem two clearly defined lines; and at last present themselves as two lamellae, separated by an intermediate third line. The perforations which Ehrenberg de- scribed, I look upon as nothing more than intercellular spaces, formed be- tween the two new-formed cells and the parent cell. These so-called perforations are only visible, therefore, on the two lateral borders where the wall abuts .. the membrane. The Confervoid lgae exhibit a similar appearance.” Gallionella (?) Novae Hollandia (Ehr.), Avon River, Australia; G. gibba § fossil, Georgia; G. punctata (Ehr.), Western Asia; G. tincta (Ehr.), Ural Mountains; G. gemmata (Ehr.), Siberia; G. lineolata º fossil, North Asia; G, whdata (Ehr.), Himalaya Mountains; G. curvata (Ehr.), India; G. vaginata (Ehr.), India; G. Nilotica (Ehr.), River Nile, are species known to us only by I18.]]16, Genus ARTHROGYRA (Ehr.).-The characters of this genus are unknown to us; but, judging from Ehrenberg’s figures of the species, it seems to have been constituted for the reception of those forms of Melosira which, like M. Dickieii, produce horizontal, elongated, tapering internal bodies or sporangia. ARTHROGYRA Guatimalensis, EM. pl. A. semilunaris, EM. pl. 33. 6. f. 2. 33. 6. f. 1. Fern-earth. Guatemala.- || Guatemala, Filament jointed, curved, Filament straight, jointed, with crenated with crenate margins, and semilunate * and straight, fusiform internal internal body. Oqy. Genus DISCOSIRA (Rab.).—Frustules united into a short filament, with a thick mucous covering; in lateral view circular, having a uniformly punc- tate centre, a border of numerous (24 to 33) slightly curved, oblique, ray- like lines, and a marginal crown of teeth (50 to 64). . DISCOSIRA sulcata (Rab.).-Frustules | rows, which correspond to the teeth of in front view with deep transverse fur- the lateral surface, Rab D. p. 12, t, 3. In OF THE MIELOSIRE ZE. 823 a lagoon at Manfredonia, east coast of Italy. Each tooth is minutely denticu- late, but requires the highest magnify- ing powers to ascertain it. (v. 68. Genus LIPAROGYRA (Ehr.).-Frustules simple, cylindrical, each having an internal spiral filiform band or crest. The habit of this genus closely resembles that of Spirogyra, a non-silicious genus of Algae. - LIPAROGYRA dendroteres (E.). — Frustules Smooth, crystalline, three or four times as long as broad, with an internal spiral band; margin of disc denticulated. Rab D. p. 12. = L. Spiralis, Rab. l.c. p. 12. With the preceding, and in Brazil. Ehrenberg says he is not Satisfied whether the preceding are di- stinct species, or merely varieties. Each has a smooth disc, with three central EM. pl. 34, 5A. f. 1, 3. On trunks of trees. Venezuela. Thirteen spirals in I-360". (v. 72.) L. circularis (E.).-Frustule with 13 annular turns of internal line in 1-360". apiculi. L. scalaris, EMI. pl. 34, 5A. f. 2, South America. Ehrenberg's figure represents the frustule in front view as divided by cross bars in a ladder-like manner. Genus POROCYCLIA (Ehr.).-Resembles Liparogyra, but is without spires, has interior circular rings, and the margin of its disc-like ends a circlet of deep impressions. We doubt whether this genus is sufficiently distinct from Liparogyra. PoRocycIIA dendrophila (E.). — radiating series of puncta, and 5 central Frustules smooth, with 9 annular lines; apiculi. Rab D, p. 12. On trunks of disc with 12 marginal depressions, I trees, Venezuela. L. 1-320”; w, 1-560". Genus STEPHANOSIRA (E.).-Frustules united into a short filament; disk with radiating series of minute puncta, and a marginal crown of teeth. In form this genus resembles Stephanodiscus, but differs from it, and becomes allied to Melosira by its imperfect spontaneous division, and consequent con- catenation, In Melosira, however, the circlet of spines is wanting. We are unacquainted with this genus; and its characters scarcely suffice to distinguish it from Orthosira. All the known species are found on trees. STEPHANOSIRA Epidendron (E.). — preceding species. Diameter 1-720". Front view with punctated transverse lines and furrow. Rab I), p. 14. On trees. Venezuela and Brazil. *. diameter 1-432"; smaller 1–4320". S. Hamadryas (E.). —In front view smooth, but with junction-margins stri- ated; disc having marginal radiating puncta, and its centre a few scattere S. Europaea (E.). — Frustules often broader than long, smooth, but with very faintly striated junction-margins. Rab. l, c. p. 14. Among mosses on trees at Berlin. Much smaller than the preced- ing. Chain formed of three to four frus- tules, each 1-2304" to 1-1152" in depth; rarely 1-1200" in width. dots. Tab, l.c. p. 14. On trees with the Genus STEPHANODISCUS (E.).--Disc with radiating series of puncti- form granules, and furnished with a crown of erect marginal teeth. Aquatic. Stephanodisci approximate in character to Cyclotella, but differ from them by the circlet of teeth. They also approach closely to the non-cellulose Coscinodisceae, and seem to have as good a claim to rank with that family as with the Melosirea”. Stephanodiscus differs from Odontodiscus in the same manner as Peristephania does from Systephania, and in our opinion might, without inconvenience, be united to it. STEPHANoDISCUS Berolinensis (E.), teeth (often 32) on each side, KSA, —Small, discoid; disc plane, finely radi- p. 21. Alive, Berlin. Diam. 1-1152". In- ated, and furnished with acute marginal | ternal granular substance brown, lobed, 824 SYSTEMATIC EIISTORY OF TEIE INFUSORIA, S. Agyptiacus, EMI. pl. 33. 1, f. 16. Egypt. Ehrenberg's figure represents the disc with series of puncta radiating from the centre, without a distinct um- bilicus, the teeth numerous, Subulate, and erect. (v. 69.) S. Sinensis, EMI. pl. 34, 7.f. 7. Canton. Ganges. Puncta as in the foregoing species, the rim furnished with short triangular teeth. S. Niagarae (E.). — Frustules small; disc with numerous (often 64) series of punctiform granules radiating from a large granulated umbilicus, and as many Ehrenberg's figure shows the puncta acute marginal teeth as rays. EMI. arranged as in S. AFøyptiacus, but the rim pl. 35 A. 7... f. 21, 22. Niagara. This striated, and the teeth nodule-like and intra-marginal. S. Bramaputra, EMI. pl. 35A. f. 9, 10. species is distinguished by its granulated umbilicus. Genus PERISTEPHANIA (Ehr.).-Frustules simple, discoid; disc with decussating parallel series of granules, and numerous marginal teeth. Mari- time. “The characters of this genus so well agree with Stephanodiscus that perhaps we might more correctly refer the deep-sea form to that genus. But as the hitherto known Stephanodisci are all fluviatile, and the maritime form in the order of its cellules very nearly approaches the purely maritime Cosci- modiscus lineatus, I have preferred not mixing fluviatile Stephanodisci with a doubtful maritime form. Perhaps the flow in deep water may have com- mingled a fluviatile form with the maritime ones. Should, therefore, a similar form be hereafter found in any river, this generic name must be cancelled, and the form placed in Stephanodiscus” (ERBA. 1854, p. 236). As we consider habitat altogether inadmissible as a generic distinction, we would distinguish Stephanodiscus and Peristephania by the radiating granules of the former, and their parallel arrangement in the latter genus. We should prefer to unite this genus with Systephania, which differs only in having intra-mar- ginal teeth. Perhaps even Coscinodiscus lineatus might be included, thus making the parallel arrangement of the granules the essential character. PERISTEPHANIA Eutycha (E.). — Eutycha, but its teeth are fewer and more Habit of Coscinodiscus lineatus; margin of the disc armed with numerous erect, crowded teeth. EM. pl. 35 B. 4. f. 14. | distant. EM. pl. 33.13. f. 22. Californian dº and guano. both species the teeth are minute and triangular. Deep soundings of the Atlantic. (v. 7% P. lineata (E.). — Resembles Genus PYXIDICULA (Ehr.). — Frustules simple or binately conjoined, free or adnate, bivalved; central portion obsolete; valves very convex. In Pyxidicula the frustule forms a bivalved box, and differs from Cyclotellain its vaulted valves and the absence of an interstitial portion. The same characters distinguish it from all the Coscinodisceae. As first constituted by Ehrenberg, Pyxidicula contained very heterogeneous forms; by the formation, however, of Mastogonia, Stephanogonia, Stephanopyxis, and Xanthiopyxis as distinct genera, this defect has been in a great measure removed; but we believe it still includes some doubtful species. Dictyopyxis was separated by Ehren- berg, first as a subgenus and afterwards as a genus, for those forms character- ized by the cellulose structure of the valves, leaving in the original genus the smooth and punctated species. We have thought it more desirable to regard Dictyopyxis as a subgenus only, until some of the species are more fully known. IEM, pl. 16. 1, f. 46. = P. minor, KSA. p.21. Fossil, Sweden; recent, Asia, Eng- land? Diam, 1–1440" to 1-570". Valves PXXIDICULA operculata (E.). — Frus- joined by a distinct suture. Kützing tules small, orbicular, hyaline, punctated, refers P. operculata (E.) to Cyclotella. * Frustules Smooth or minutely punctate. Pyxidicula. OF TELE MELOSIREZE, 825 P. Adriatica (Kütz.).-Adnate, sessile, of middle size; valves convex, nearly hemispherical, very smooth. RB. t. 21. f. 8. Adriatic. (x1II. 33.) Diam. 1-600". P. P. praetexta (E.).-Valves geminate, slightly hispid, neither cellulose nor radiated, but bordered by a raised limb; middle flat. KSA, p. 22. Fossil. Greece. Diam. 1-1152". - P. Purceolaris (E.).-Valves geminate, unequal, urceolate (the One more convex, elongated, the other shorter), each with a plane, raised limb; cellules nome, but about ten smooth rays in the longer, and eight apiculate ones in the shorter valve. = Dictyopya is urceolaris, EMI. pl. 18. f. 3. Fossil. Virginia. Diam. 1-1728". P. longa (E.). — Oblong, two and a half times as long as broad, cylindrical, with rounded ends; suture longitudinal. KSA. p. 22. Fossil. Virginia. L. 1-1080". 2%. Frustules cellulose. Dictyopyxis (E.). P. cruciata (E.). — Frustules oblong, with rounded ends; cellules large, ar- ranged in parallel lines; rim distinct. EM. pl. 18. f. 2. = Coscinodiscus cruciatus, KSA. p. 125. 6. Hellenica, smaller= Dictyopyacis Hel- lenica, EMI. pl. 19. f. 13. Fossil. America. Guano, &c. Frequently the disk has some series of its cellules more conspi- cuous and forming a cross, Valves cam- panulate. P. Cylindrus (E.). — Cylindrical, with rounded ends, three times as long as broad; valves with obscure rows of cel- lules. EMI. pl. 33.13. f. 8. Fossil. Mary- land. Diam. 1-960". Valves campanu- late, separated by a suture. IP. Lens (E.).-Frustules laterally de- bressed, lenticular, cellulose; valves in front view semielliptic. E.M. pl. 18. f. 5. Fossil. Virginia. Diam. 1-636". The frustule is oval in the front view, the suture forming the greatest diameter. P. areolata (E.). — Valves with a heptagonal, areolate, punctated centre, and seven lateral punctated areolae. KSA. p. 22. North America, D, 1–960". P. gemmifera (E.). — Valves turgid, crystalline, not bordered, furnished with lax series of crystalline modules, fifteen of which very nearly reach the Smooth centre. RSA, p. 22. Fossil. Maryland. Diam. 1-792". * P. compressa (Bail.).-Frustules, ellip- tic, bivalve; valves separated by a plane passing through the longer axis, slightly convex, and with transverse rows of dots, BC, ii. p. 40, f. 13, 14. Florida. P. dentata (E.). Frustules having the convex margin furnished with (irregular) slightly prominent little teeth; cellules rather large, 6 in 1-1200", KSA, p. 22. Antarctic Ocean. Diam. 1-840". P. P limbata (E.). — Frustules oblong, with a central keel; valves showing in front a central cellular surface, and 32 to 40 radiating lines; border not cel- lulose. = Stephanopya is limbata, EMI. pl. 18. f. 7. Fossil. Maryland. D. 1-792". Ehrenberg's figure is oval, and has a broad, distantly striated, but not cellu- lose rim, and in its centre scattered gra- nules. P. cristata (E.).--Frustules with gemi- mate, lenticular valves, which are close together, not winged, with a somewhat prominent margin like a thin suture; cellules of disc in rows. = Stephanopya is cristata, EMI. pl. 18. f. 6. Fossil, TVir- ginia. Diam. 1-816". Ehrenberg's figure somewhat resembles that of P. limbata; but the cellules of the oval valve are crowded, and the striated rim is mar- l'OWel’. - Obscure or doubtful Species, P. Nägelii (Kütz.).--Smooth, one side orbicular, girt with a membranous wing- like ring; the other side oval, one mar- in more convex, umbonate in the mid- dle. KSA, p. 889. Switzerland. P. Actinocyclus (E.).-Frustules with two flattened, finely cellular and ele- gantly radiated valves; rays 30 to 40, straight and dense. EM. pl. 18. f. 19. = Cſclotella Actinocyclus, KSA, p. 20. Fossil. America. Diam. 1-720". Ehren- berg figures only the lateral view, which in its radiating series of dots resembles a Coscinodiscus. P. Scarabaeus (E.). — Oblong, with unequal valves; when viewed laterally, recalling the figure of the Scarabaeus. = Dictyopya is Scarabaeus, E. Fossil. Virginia, Diam, 1–648". Cellules 14 in 1-1150". P. major (Kütz.). — Frustules large, elliptic, regularly punctated. KB. t. 1. f 25. North America; France. Diam. 1-420". Probably a state of P. cruciata, P. globata. — We insert under this name certain spherical bodies of a dia- meter varying from 1-240" to 1-1150", discovered in 1836 by Ehrenberg in flints near Berlin, and considered by him to belong to the silicious Diatomaceae. Kitzing has examined these bodies, which occur along with silicious spicula. of Sponges and species of Xanthidium and Peridinium, but does not consider them Pyxidiculae. The section of pebble 826 SYSTEMATIC ELISTORY OF TEIE INFUSORIA. containing these specimens, from which Mr. Bauer's drawings (xvii. 506–509) were made, was found on Brighton beach. The figures are magnified 100 the same as the preceding, P. P. gigas, E.M. pl. 33.13. f. 18. Fossil. California. The figure shows a large orbicular disc, with distant scattered dots, and no Suture. diameters. P. prisca, EMI. . This # 37. 7. f. 5. P. decussata (E.).-Found in the chalk species is found in flints, and is probably *. marl of Ægina, Genus STEPHANOPYXIS (Ehr.). Frustules simple or united into short filaments, in front view orbicular or oblong, composed of two cellulose valves, each having a crown of teeth, spines, or membrane; central portion obsolete ; lateral view circular. “This group includes those Pyxidiculae which have turgid forms with a cellular surface, bearing in the middle of the valves a crown of small teeth, prickles, or a membrane” (Bailey). The fossil species appear simple; but as recent specimens forming short filaments have been obtained by the Rev. R. Cresswell and Mr. Norman, probably the others also were originally so formed, but, as the crowns prevent the close union of the frustules, they become more easily disconnected. The valves agree in their turgid form, rounded ends, and cellulose structures with Pyxidicula; but their coronets will easily distinguish them. STEPHANOPYXIS Diadema (E.). — Valves hemispherical, with parallel, straight rows of cellules; centre of disc depressed, with a circlet of numerous teeth (20 to 30). = Pyacidicula Diadema, KSA. p. 21, Fossil, Virginia; guano, Diam. I-576". . We have seem two frus- tules connected. S. Turris.--Frustules cylindrical, cel- lulose, ends depressed at the centre and furnished with a crown of spines or pro- cesses, which are truncate or clavate at their apices; areolae hexagonal, 7 in •001". = Cresswellia Turris, Grev. in GDC. . 64, pl.6. f. 109. In stomach of Ascidia. Teignmouth, Hull, &c. Fossil in guano. We regret being unable to accept the genus Cresswellia, as we believe all the species of Stephanopyxis, when recent, have the frustules connected by their coronets: S. Diadema, a species closely allied to the present, we have found so united in specimens from guano. This character has probably escaped detection only because in all filamentous forms the fossil frustules are usually separated. The coronets of numerous non-attenuated spines distinguish this species. (v. 74.) S. apiculata (E.). — Frustules oblong or subcylindrical, end broadly rounded; cellules not crowded, arranged in longi- tudinal rows; centre of disc with a few elongated spines, EM. pl. 19, 13. f. 6. America, Europe, guano, &c. S. appendiculata (E.). — Frustules in front view subglobose, coarsely and closely cellulose; segments with rounded ends, each with an excentric, short, horn- like process. E.M. pl. 18. f. 4. Fossil. Virginia, Diam. 1-624", Processes trun- cate, not central; cellules forming a crenated margin. S. turgida (Grev.).-Front view cylin- drical-oblong; junction-margins subtrun- cate, with rounded angles and a crown of elongated spines with dilated apices; areolae 11 in 001. = Cresswellia turgida, Grey M.J. vii. p. 165, pl. 8. f. 14, Cali- fornian guano. This species is nearly related to S, Turris, but differs in the larger, more truly cylindrical and trun- cate frustules, and in the considerably Smaller areolation, Grev. S. feroa (Grev.).--Front view oblong; valves subglobose, campanulate, hispid, with a crown of elongated spines and a thin, hyaline, prominent Suture; areolae large, 5 in 001". = Cresswellia? feroa, Grey M.J. vii. p. 166, pl. 8. f. 15, 16, Ca- lifornian guano. The valves are ex- panded at their junction so as to form a sutural keel, as in Some species of Pyxidicula. (v. 75.) Genus XANTHIOPYXIS (Ehr.).—Walves turgid, continuous, entire, non- cellulose, hispid, setose, or winged. = Pyxidicula olim. Fossil. “These forms are Pyxidicula with bristles, setae, or wings. They have the habit of Xan- thidium and Chaetotyphla, but are bivalved and silicious.” The true affinity of this genus is doubtful: we have seem no species which is circular in the lateral view, and consequently consider them misplaced in the Melosire? ; OF TELE COSCINODISCIE ZE. 827 but, from our insufficient acquaintance with them, we are unable to decide on their proper position, and have not attempted their removal. Are they akin to Goniothecium ? XANTHIOPYXIS globosa (E.). — Frus- tules subglobose, hispid, with short setae. = Pyacidicula globosa, KSA, p. 23. Fossil. JBermuda. Diam. 1-552". X, oblonga (E.). — Frustules oblong, equally and broadly rounded at each end, densely hispid, with short setae, which are sometimes joined by a membrane. EM. pl. 33.17. f. 17. = Pyxidicula (K.). Fossil. Virginia. L. 1-552". (v. 76.) X. constricta (E.).-Frustules oblong, constricted at the middle, and broadly rounded at each end, hispid, with short setae, which are often joined by mem- brane. =Pyridicula constricta, KSA, p. 23. Fossil. Bermuda. L. 1–384". Differs from X, oblonga by its constriction. X. hirsuta (E.). -Frustules bivalved, Subglobose, not cellulose, rough with simple and obsoletely forked hairs. = Pyacidicula P. hirsuta, ERBA, 1845. Fos- of Xanthidium, but silicious. X. urceolaris (E.). —Valve urceolate, with the summit bristly; margin revo- lute. EM. pl. 33. 16. f. 14. Fossil. Vir- ginia. Diam.1-1560". “I [Ehrenberg] have only met with single valves. . In form they resemble Stephanogonia, but are not angular.” X, alata (E.).-Frustules Smooth, ob- long, each end equally and broadly rounded; margin of the valves bordered by a lacerated or deeply dentate, not Setose membrane. = Pyacidicula alata, KSA, p. 23. Fossil. Bermuda, D, 1–552". Doubtful Diatom. - X. aculeata (E.)= Pyacidicula aculeata. The figure in Microg. pl. 18. f. 124 shows a globular spinous body, resembling some sporangia of the Desmidieæ, Eh- remberg himself regards this as a very sil. Maryland. Diam, 1-115". Habit doubtful Diatom, Genus INSILELLA (Ehr.).-Frustules simple, equally bivalved, cylindrical (fusiform), with a turgid ring interposed in the middle between the valves. Marine. Resembles a cylindrical Biddulphia. INSTLELLA Africana (E.). —Frustules | others decreasing at each end, oblong; fusiform, smooth, four times constricted; each apex acuminated. KSA. p. 32. the middle joint largest, subglobose; the Mouth of the river Zambese, Africa, FAMILY WIII.—COSCINODISCEAE. Erustules disciform, mostly simple; lateral valves or discs flat or convex, cellulose, areolate or granulate, without processes, but sometimes furnished with spines or teeth; connecting Zone ring-like and generally smooth. The Coscinodisceae are closely allied to the Melosirea”, a fact noticed by Kützing himself, although in his arrangement the families are widely separated. The distinction between them is by no means satisfactory; according to Kützing, it consists in the cellulose or areolated structure of the Coscinodisceae. But whilst on the one hand we find in the Melosirea” some species of Pyxidicula and Stephanopyxis with cellulose valves, on the other hand, in this family some species are merely granulate or punctate. Practically, however, the proper situation of the species can generally be determined without much difficulty. In the Coscinodisceae the frustules never form filaments, the con- necting zone is always present, narrow and ring-like, and the lateral valves are never so convex as to be hemispherical or campanulate; SO that the disk is almost always in the field, it being difficult to obtain a good front view. Most of the forms included in this family are marine, and many are remark- able for their exceeding beauty. Genus COSCINODISCUS (Ehr.).-Frustules simple, discoid; disc cellular or dotted, without processes, defined border, internal septa, or division into radiating compartments, “The Only essential character that distinguishes 828 SYSTEMATIC IIISTORY OF THE INFUSORLA. this genus from Cyclotella is the areolation of the secondary surfaces” (Meneg.). “This genus finds its nearest allies in the Melosire2, whose genera, from their filamentous character, stand widely apart. Were the frustules of Coscinodiscus eccentricus, for example, permanently coherent after self-division, it would be difficult to separate them, in a generic point of view, from those of Orthosira nivalis, which have the same cellular structure, or from those of Melosira aurichalcea or M. Sulcata, which are furnished with a projecting fringe of silex, the homologue of the Spinous processes in C. eccentricus” (Smith, B.D. i. p. 23). Coscinodiscus is easily distinguished from most genera in this family by a disk not divided into compartments. In the greater number of species the cellules have a radiating arrangement, and become smaller near the margin; the former character, however, is fre- quently obscure, and is best seen by as low a magnifying power as will suffice to determine the cellular or dotted structure. * Disc with a few central larger (gene- rally oblong) cellules, Stellately arranged, and forming an umbilical rosette (rim striated). t Disc large, and its cellules distinct. CoSCINoDISCUS centralis (E.). — Cel- lules minute, nearly equal, in crowded radiating series; umbilical rosette of a few oblong cellules round a circular one. EM. pl. 18. f. 39; GDC. p. 28, pl. 3. f. 50. Fossil. Virginia and Sicily. A large species with striated rim. - C. omphalanthus (E.). — Cellules in radiating series, marginal ones Smaller, 7 to 8 in 1-1200", middle ones larger, 6 in 1-1200"; umbilical rosette of 7 or 8 large oblong cellules. KSA, p. 125. Bermuda deposit. Disc large. D, 1–96". Mr. Brightwell finds it difficult to distin- guish this species from the following, and considers their specific characters unsatisfactory. C. Oculus Iridis (E.). — Cellules hex- agonal, in radiating series, Smaller at the margin and near the umbilical rosette, which is formed of from 5 to 9 large oblong cellules. EM. pl. 18. f. 42. Fossil and recent. America, Europe, Milford Haven, &c. This large species, when dry, is marked with coloured rings, an effect apparently due to the peculiar arrangement of its cellules. It differs from C. centralis in its larger cellules, and from C. asteromphalus by the absence of a veil. “This species, both in the recent and fossil specimens, often ac- quires a size not much inferior to that of C. gigas” (Bailey). “C. borealis (Bail.). —Disc having at its depressed centre a conspicuous star, formed of about 6 large cellules. The rest of the surface covered with inter- ruptedly radiant lines of prominent hex- agonal cellules, which increase regularly from near the centre to the convex margin.” B. in Amer. Journ. of Science and Arts, 1856. Sea of Kamschatka. “This resembles C. Oculus Iridis; but the cellules forming the star are more rounded, and the other cellules are larger’’ (Bailey). Ö. asteromphalus (E.). — Cellules in radiating Series, Smaller towards the margin; umbilical rosette distinct; sur- face appearing as if covered by a very finely punctated veil. EM. pl. 18. f. 45. Fossil. America. Cellules large, rather tumid. C. asteromphalus differs from the other species with stellate umbilicus by its minutely punctated cellules. 2 + Disc with cellules obscure, and re- quiring the higher magnifying powers to discern them. C. concinnus (Sm.).-Disc large, with radiating series of minute puncta, and an umbilical irregular rosette of larger cellules, divided into compartments by radiating lines, which terminate at the margin in minute spines. (v. 89.) SBD. ii. p. 85; Roper, M.J. vi. p. 20, pl. 3. f. 12. Europe, Valves convex. In some spe- cimens the markings are very inconspi- cuous, and difficult to detect; in others, as in the specimens from Hull, more evident. - C. Stellaris (Roper). —Disc extremely hyaline, with very fine, inconspicuous radiating Series of puncta, and a few larger, stellately arranged umbilical cel- luids.” (v. 83.) Romij, vi. p. 3i, p. 3. f, 3. aldy, Pembrokeshire. When mounted in balsam, the disc is so hya- line, and the puncta so difficult to detect, that it is liable to be regarded as a detached ring. . Dry valves brownish, without marginal spines. - OF THIE COSCINODTSCEZE, S29 2 * Disc with a central hyaline umbilicus, which often resembles a perforation. (The Species are commonly smaller than those of the preceding section.) C. actinochilus (E.).-Granules in close lines, radiating from the distinct punc- tated umbilicus, separated from the mar- gin by a border of puncta arranged in close, short, radiating lines. EMI. pl. 35 A. 21. f. 5. Antarctic Sea. The radiating Series of granules are close, but distinct. - C. Lunae (E.). — Granules equal, ar- ranged in distinct series, radiating from the Smooth umbilicus, and separated from the margin by a border of minute puncta. EM. pl. 35 A. 21. f. 7. Antarctic Sea. Somewhat resembles C. actinochilus, but has fewer rays, the marginal puncta are more obscure, and the umbilicus is Smooth. C. gemmifer (E.). — Disk with con- spicuous granules, arranged in lax and elegantly radiating lines from a Smooth umbilicus; border minutely punctated. EM. pl. 35 A. 22. f. 3. Antarctic Sea. Bermuda deposit. The rays are fewer and more distant than in the two pre- ceding species; but all agree in having well-marked granules, distinct rays, and minute submarginal puncta. Diam. 1-456". Very like Pyaridicula gemmifera, but larger and more depressed. C. apiculatus (E.). — Cellules rather rominent, apiculate, rendering the sur- ace rough, subequal, radiating, 10 in 1–1200"; umbilicus smooth. EM. pl. 18. f. 43. America. Diam, 1-324". Has a general resemblance to Pyacidicula gemmifera. C. perforatus (E.). —Cellules, minute, arranged in close, radiating Series; um- bilicus smooth, resembling a perforation; margin finely rayed. EMI. pl. 18. f. 46. America. Diam. 1-348". JJiffers from C. fimbriatus by its umbilicus. C. disciger (E.).--Differs from C. per- foratus by its irregularly circular, not smooth, and larger umbilicus, and by its very minute and dense punctiform cel- lules. KSA. p. 123. Virginia. Diam, 1-480". Cellules about 30 in 1-1200". C. Apollinis (E.).--Disc with nume- rous series of very dense, equal, puncti- form granules, radiatings from a small umbilicus. EM. pl. 35A, 22. f. 4. Ant- arctic Sea. It differs from C. Lunae by the greater number and denseness of its rays, which, however, although nume- rous, are distinct. Diam, ilā327, 17 granules in 1-1200". C. cingulatus (E.). —Disc with very dense, punctiform granules, indistinctly radiating from a small clear umbilicus; margin with an annular band capable of being detached. EM. pl. 35 A. 21. f. 6. Fossil, America, Antarctic Sea. 26 gra- nules in 1–1200". Diam. 1-552". Resem- bles C. Apollinis, but its granules are denser and less distinctly radiating. 3* No umbilical vacancy; disc with a striated border distinct from the rim. C. fimbriatus (E.). — Cellules small, subequal, obsoletely radiating, near the margin Smaller and arranged in radi- ating lines resembling striae. E. l. c. pl. 22. f. 2. Fossil. Sicily. C. marginatus (E.).-Cellules in curved lines; marginal ones smaller and ar- ranged in radiating lines resembling striae. E. l.c. pl. 18. f. 44. Recent and fossil. America, Cuxhaven, Cellules 9 or 10 in 1–1200". C. limbatus (E.). — Central cellules largest, not radiating, outer ones small- est, crowded, arranged in radiating lines resembling striae. B. l.c. pl. 20. T. f. 29. Fossil, Greece. Diam. I-576". The largest 7 in 1-1200". & strians (K.). —Cellules irregularly crowded in the middle; margin of disc with radiating striae. KB. t. 1, f. 8. Cuxhaven. Diam. 1-456”. 4* Disc with radiating series of cellules; no distinct wºmbilicus, nor striated border distinct from the rim. C. gigas (E.).-Disc very large; cel- lules large, hexagonal, radiating, largest at the margin, decreasing towards the centre, EMI, pl. 18. f. 34, Virginia; Maryland; alive, Cuxhaven. The largest species of the genus, and well character- ized by its large hexagonal cellules gra- dually decreasing in size from the margin to the centre. Rim striated. C. excavatus (Grev. MS.).--Disk large, with hexagonal cellules decreasing in size towards the centre, which has three conspicuous depressions alternating with the same number of elevations. Pisca- taway deposit. The disc in this species is, from its large size, visible to the naked eye, and, like C. gigas, it appears ring-like, the smaller central cells being then invisible. There is no distinct um- bilicus; but the central portion,including the elevations and depressions, is thinner and is rarely found perfect. The cellules of the depressions appear smaller and more radiant than the others. (VIII, 26.) 830 SYSTEMATIC IIISTORY OF TEIE INFUSORIA, C. crassus (Bail.). — Disc without a central star, covered with interruptedly radiant lines of large, prominent, hex- agonal cellules with circular pores; cel- lules somewhat larger near the margin. B. Amer. Journ. Science, 1856. Alive, Sea of Kamtschatka; fossil, Monterey. C. profundus (E.). — Cellules of disc subequal, near the Imargin Smaller and irregularly radiating. ERBA. 1854; EMI. pl. 35B. f. 8. Atlantic. C. radiatus (E.). — Cellules rather large, arranged in radiating lines (EM. pl. 21, f. 1; SBD. pl. 3. f. 37), smaller near the margin. (xi. 39, 40.) Common, both recent and fossil. Diam. 1-860" to 1-240". The radiating arrangement is Sometimes obscure. C. Sol (Wallich).-Disc as in C. radi- atus, but surrounded by a broad, hyaline, membranous border, which is divided into compartments by numerous radiating lines. Wallich, TMS. viii. pl. 2. f. 1, 2. From Salpae, Bay of Bengal, and Indian Ocean. §. subjecting the frustule to acids, the membranous ring is at first simply detached, and after a while dis- solved (Wallich). C. Argus (E.).-Cellules large, some- what Smaller at the centre and margin; the radiating arrangement often inter- rupted. EM piºiſ; 2. Recent, Cux- haven; fossil, Oran and Sicily. May be a variety of C. radiatus, from which, how- ever, Mr. Brightwell considers it suffi- ciently distinct. He finds the cellules in that species always radiant, whilst in the present they have no definite arrangement. C. radiolatus (E.). —Granules puncti- form, equal, radiating. E. l.c. pl. 18. f. 36. Fossil, Virginia. Differs from C. Apollinis by the absence of an um- bilicus. 18 cellules in 1-1200". C. subtilis (E.).-Granules punctiform, Small, equal, radiating. E. l.c. pl. 18. f. 35. America. Similar to C. radiolatus, but with 24 cellules in 1-1200". C. Normanni (Greg.).--Disc with ra- diating series of faint areolae arranged in fasciculi of about 6 rows each; areolae equal, except near the margin, where they are smaller; rim smooth. Grev M.J. vii. p. 81, pl. 6. f. 3. In stomach of Ascidians. Hull. Areolae about 24 in .001". No distinct umbilicus. Differs from C. subtilis by having only half as many lines in each fasciculus (Grev.). C. punctatus (E.). — Cellules puncti- form, radiating, loosely disposed at the centre, very densely crowded at the margin, and forming a broad, yellowish- white border. EM. pl. 18. f. 41; KSA, p. 124. Virginia. Cellules at centre, 24 to 26 in 1-1200". Diam. 1-348". Ehrenberg gives a figure of an oval variety of this species, pl. 18. f. 40. C. tenellus (E.).-Cellules very small, equal, radiating. EB. 1854, Atlantic. 17 or 18 cellules in 1-1200". The cha- racters given are insufficient to distin- guish this species from C. radiolatus and C. subtilis. - C. granulatus (E.).-Disc Small, with dense Series of very small cellules, caus- ing a granular appearance; granules 18 to 21 in 1-1152". RSA. p. 122. Fossil. Virginia. Diam. 1-552". C. umbonatus (Greg.). — Disc densely cellulate, having a broad, nearly flai marginal zone, the central portion being nearly or quite hemispherical; cellules generally radiant, small and irregular in outline. Diam. 0045". Lamlash Bay. G.D. p. 28, pl. 2. f. 48. * 5* Cellules not radiating ; no distinct atmbilicus or striated border. f Cellules arranged in more or less perfect concentric circles, C. Patina (E.). — Disc large, with moderate-sized cellules, disposed in concentric circles and becoming Smaller towards the margin. KB. p. 1. f. 15. Fossil, Greece; alive, Cuxhaven. The young and vigorous specimens of live individuals are completely filled with yellow granules, whilst the older ones have an irregular yellow granular mass within them. Diam. 1-860" to 1–240". C. isoporus (E.). —Disc coarsely cel- lular; cellules close, arranged in con- centric circles. EMI. pl. 33. 17. f. 3. Disc of moderate size. Ehrenberg's figure bears some resemblance to C. con- cavus, but has concentric cellules, and no distinct rim. C. velatus (E.). — Cellules large, an- gular, rather distant, arranged somewhat concentrically; the disc punctated, ap- pearing as if covered with a veil. E. l. c. pl. 18. f. 37. Virginia. I)iam. 1-492". 2 + Cellules in parallel or curved lines. C. lineatus (E.). — Cellules small, cir- cular, arranged in Straight, parallel lines. KB. pl. 1. f. 10. Fossil, Sicily and Ame- rica; alive, Cuxhaven. Common. The cells in this species form parallel lines in whatever direction they may be viewed. In large and well-preserved fossil speci- mens as many as twenty-five openings (P spines) were seen near the circum- OF TEIE COSCINODISCEZE, 831 ference. Within the live forms some- times numerous yellow vesicles are seen, as in Gallionella. TXiameter of fossil 1-1150" to 1-480"; living, 1-1150" to 1–860". C. eccentricus (E.). — Cellules Small, disposed in excentric curved lines. KB. l. 1. f. 9. Common, both recent and fossil. D, 1–860 to 1-430". 3f Cellules in no determinate arrange- ment. C. concavus (E.). —Each valve very concave, the two opposite conjoined, forming an entire, very convex body; cellules coarse, equal, not radiating. EM. pl. 18. f. 38; GDC. pl. 2. f. 47. Virginia. Cellules 4 in 1-1200". An African variety has twice as many. = Melosira cribrosa, Sm ANH. xix. p. 11, pl. 2. f. 15. C. heteroporus (E.). — Cellules hex- agonal, Smaller at the margin and centre, intermediate ones largest, unequal. K.A. p. 123. Bermuda deposit. D. 1-360". This species may be recognized by the Smaller marginal and central cellules and the very unequal intermediate ones. C. minutus (IXütz.). — Disc nearly Smooth, margin with punctated rays, D. 1-1416". KB. t. 1. f. 14, Cuxhaven. C. minor (E.).-Margin smooth; disc irregularly and densely celluloso-punc- tate. Fossil, Sicily and Virginia; alive, Europe and America. E. l. c. Not C. 732?nor of SBD. C. flavicans (E.). — Disc small, with very fine non-radiating cellules, yellow by transmitted, but white by reflected light. KSA, p. 122, Peru and St. Do- mlngo. C. labyrinthus (Roper).-Disc divided by dotted lines into large, irregular, hex- agonal, minutely dotted spaces; puncta 15 in 001". Ro M.J. vi. p. 21, pl. 3. f. 2. Pembrokeshire. This species has some- what the aspect, under a low power, of a finely marked specimen of C. eccen- tricus, but differs in the absence of a spinous margin, and in the large and irregularly shaped hexagonal spaces without any clearly defined margin (RO.). Doubtful or imperfectly known Species. C. cinctus (K.). — Rim with inter- rupted radiating striae; cellules of disc crowded in the centre, the others scat- tered, remote. KSA. p. 122. C. Patina, B. Amer. Jour. of Science and Arts, 1842, pl. 2. f. 13. , Alive, Cuxhaven; fossil, Virginia. Diam, 1-324". Ehren- berg refers the Virginian specimens to C. minor. C. ovalis (Ro.).-Valves oval, brown- ish in balsam, with finely-dotted radi- ating lines and no distinct umbilicus. Ro M.J. vi. p. 22, pl. 3. f. 4. Pembroke- shire. Mºſſº very delicate and in- conspicuous. (v. 78. C. punctulatus (Greg.).--Disc marked with very fine and obscure lines, the whole surface sparsely punctate. Lam- lash Bay. G.D. p. 28, pl. 2. f. 46. C. mitidus (Greg.).-Disc marked with distant and irregularly radiant granules, larger towards the centre; margin striate, striae about 16 in 001". Lamlash Bay. Greg, l.c. p. 27, pl. 2. f. 45. (VIII, 18.) C. cervinus (Bri.). — Disc minutely punctate, puncta Scattered; centre con- vex, Diam, '0054" to 0085".= Hyalo- discus cervinus, Bri JMS. viii. p. 95, pl. 5. f. 9. Arctic regions, Genus ENDICTYA (Ehr.).-Frustules disciform, simple or forming short filaments, closely cellulose, in front view with a middle furrow, having on each side crowded parallel series of cellules. Rützing places its only species in Coscinodiscus; but we think that it is much more nearly allied to Orthosira. ENDICTYA oceanica (E.). — Disc with close cellules and a dentate rim. (v. 70.) EM. pl. 35A. 18. f. 6, 7, = Orthosira oce- anica, Bri JMS. viii. p. 96, pl. 6. f. 16. Common in Peruvian guano. Some- times the cellules of the disc are almost concentric in their arrangement, 7 in 1–1152". Diam. 1-528". This form is probably identical with Coscinodiscus concavus and MeloSira cribrosa. Genus CRASPEDODISCUS (Ehr.). — Frustules simple, disciform; disc cellulose, without striae or septa, but having a broad, well-defined, tumid border of a different structure from the centre. Craspedodiscus has the habit of Coscinodiscus, with which Kützing united it. It differs from Coscimodiscus limbatus, and similar forms, by its margin, which does not form a mere rim, but a broad border of a different structure, separated from the centre by a distinct furrow or Well-defined line. 832 SYSTEMIATIC EIISTORY OF TIIL INFUSORIA, CRASPEDODISCUS elegans (E.).-Bor- der with obliquely quadrate cellules; disc with a central rosette of five or six oblong ones, the others being circular and somewhat radiating. (XI.38.) EM. bl. 33. 18. f. 2. = Coscinodiscus elegans, &SA. p. 126. Bermuda deposit. Frus- tules large, with an elegantly marked border, the diameter of which is much less than that of the centre. This species differs from the rest in its central rosette and diagonally marked border. C. Coscinodiscus (E.).-Border broad, but of less diameter than the centre; cellules of border large, close; those of centre minute or puncta-like, and scat- tered. (v. 80.) EM. pl. 35. 16. f. 8. = Pyacidicula Coscinodiscus, E.B. 1844; Cos- cinodiscus Pyridicula, KSA, p. 126; Br JMS. viii. p. 95, pl. 5. f.4, Fossil. United States. C. microdiscus (E.). — Border very broad, its diameter greater than that of the centre; cellules of border large, close; those of centre minute, scattered. E. l. c. pl. 33. 17. f. 4. Fossil. United States. Resembles C. Coscinodiscus, from which it differs in its proportionally. Smaller Centre, Doubtful Species, C. P. Stella, EMI. pl. 35 B. B. 4. f. 11. Ehrenberg's figure sº a smooth disc with a Melosira-like umbilicus, from which radiate irregularly placed lines. C. P. Franklini, E.M. pl. 35 A. 23, f. 6. = Hyalodiscus subtilis. C. marginatus (Bri.):-Disc with hya- line margin, having about 20 rays; re- mainder of the valve minutely punctate. Diam, '0037". Barbadoes deposit. 13r JMS. viii. p. 95, pl. 5. f. 7. C. Semiplanus (Bri.). — Margin very broad, faintly radiate and punctate. One half of central part of the valve smooth, the remainder with 4 or 5 radii. Diam. .0024" to 0035". Barbadoes deposit. Br, l.c. p. 95, pl. 5. f. 12. C. coronatus º — Only fragments of this form have hitherto been found, and consequently no satisfactory specific character can be given. Br, l.c. p. 95, f. 6, Genus ODONTODISCUS (Ehr.).-Frustules simple, orbicular; disc with- out nodule or septa, but with dotted rays and erect teeth. Odontodiscus differs from Coscinodiscus and Actinocyclus by having its disc furnished with teeth, of which the others are destitute. as in Systephania. ODONTODISCUS Spica (E.). — Teeth Submarginal, numerous (48); granules in radiating series. KA, p. 129. Fossil, Virginia. Granules 19 in 1-1152". O. Uranus (E.).--Disc with numerous (32) radiating series of granules and marginal teeth. KSA, p.129. Fossil. Vir- ginia. O. Uranus has marginal teeth and fewer radiating series of granules than O. Spica; but we doubt whether they be really distinct species. O. eccentricus (E.). — Disc with its granules arranged in eccentric, curved, indistinctly radiating rows; teeth mu- The dots are radiate, not parallel, merous, marginal. (v. 90.) EMI, plá5 A. 18. f. 11. = Coscinodiscus eccentricus, SD. i. p. 23, pl. 3. f. 38. P Fossil. Guano, &c. Granules about 20 in 1-1152". D. 1-864". This species differs from Coscinodiscus only in having teeth, and may be merely that state of the latter which is described and figured by Professor Smith as spinous. We, however, have generally failed to detect the spines in the Coscinodiscus eccentricus, although they are obvious enough in the Odontodiscus, which is usually much smaller. On these accounts we cannot decide that they are identical. Genus systEPHANIA (Ehr.). – Frustules orbicular; disc cellulose, neither radiate nor septate, with an external circlet of spines or an erect membrane on the disc, not on the margin; cellules in parallel rows. “The genus has the habit of Coscinodiscus lineatus, but with lateral crowns, which, in the young state, unite two individuals” (Bailey). The spines are subulate, and appear not unlike the peristome of a moss. SYSTEPHANIA aculeata (E.). — Disc loosely cellulose; cellules distinct, spines erect, not crowded, few (12 to 15), placed on the disc near the margin. KA. p. 126. Bermuda. Cellules 8 in 1-1152". Diam. -324". This species is distinguished by its fewer spines and more conspicuous cellules. S. Corona (E.). — Disc densely cellu- lose; spines erect, numerous (40 to 50), closely set, placed on the margin.” EMI. pl. 33, 15. f. 22. Bermuda, Virginia. OF TELE COSCINODISCEAE. 833 Cellules 12 in 1–1152". Diam. 1-348". The spines are far more numerous and the cellules less distinct than in S. aculeata. S. Diadema (E.).-Disc densely cellu- lose; spines numerous, marginal, in- curved, conjoined at their extremities by a membrane. EMI. pl. 33. 18. f. 11. Bermuda. Cellules 14 in 1-1152". Diam, 1-864". Much smaller than the two preceding species. All have a variable number of teeth. Genus SYMBOLOPHORA (Ehr.). — Frustules orbicular, not concatemate; disc with striae or dotted lines, radiating from a solid angular centre. Sym— bolophora differs from Actinocyclus in having an angular or stellate hyaline Centre. Ehrenberg has placed in this genus forms which agree only in their hyaline angular umbilicus; and the species with radiating Series of dots scarcely differ from Coscinodiscus. SYMBOLOPHORA Trinitatis (E.).--Disc having a triangular crystalline umbilicus with a crenated margin, from which radiate six fascicles of very fine lines diverging towards the margin. EB. 1844, p. 88. (XI. 36.) Fossil. Maryland. We believe no one except Ehrenberg has observed this species, for which the genus was constituted; and it has been suggested that his figure may represent what he erroneously supposed to be the original form (as shown by a fragment) of Triceratium Marylandica; but in this opinion we cannot concur, because in several instances where Ehrenberg has founded species on mere fragments he has figured the fragments as he observed them, without attempting a restoration of their supposed entire figure. S. acutangula (E.). — Resembles the preceding in size and habit, but has the angles of its umbilicus acute. EB. 1845, p. 81. Fossil. Virginia. S. P. Microtrias (E.). — Disc turgid, with a stellate umbilicus, from which radiate series of puncta. Antarctic Ocean. Umbilicus triradiate = S. Microtrias, E. l, c. 1844, p. 205; EM. pl. 35 A. 21. f. 16. Umbilicus cruciate or four-rayed = S. Tetras, E. l. c. Umbilicus five-rayed=S. Pentas, EM. pl. 35 A. 22. f. 19. Umbilicus six-rayed=S. Hezas, E. l.c. This species differs from a Coscinodiscus only in the presence of the stellate umbilicus. Genus HETEROSTEPHANIA (Ehr.).-Characters unknown to us. HETERosTEPHANTA Rothii, E.M. 1. 8 or 10 marginal teeth or minute pro- 35 A. 13 B. f. 4, 5. (v. 85.) Elbe. Disc cesses, and no umbilicus. Front view with radiating series of minute puncta, with minute, erect, marginal teeth. Genus HALIONYX (Ehr.). — Frustules orbicular, not concatenate; disc rayed; number of rays definite, not starting from the umbilicus; no internal septa. It resembles Actinocyclus, except in its umbilicus not being radiate; or, in other words, its central ocellus is wanting. In like manner Coscino- discus differs from Symbolophora in its non-radiate umbilicus, which is a simple void space. HALIONYx senarius (E.).--Surface of disc with six rays; each compartment is marked by parallel lines, which de- crease by equal gradations on either side of a radiating median line; loosely and widely cellulose; umbilicus entire, punc- tated. KA. p. 130. Antarctic Ocean. Diam. 1-720". Approaches Actinoptychus wndulatus. * H. undenarius (E.).--Disc with eleven or twelve rays; umbilicus large, punc- tated, not radiant. (v. 82.) EM. pl. 35 A. 21, f. 12. = H. duodenarius, E. olim. Ant- arctic Ocean. Diam, 1-576". Ehrenberg's figure shows the disc with a granulated centre, from which proceed radiating Series of puncta and eleven darker or shade-like rays. Genus ACTINOCYCLUS (Ehr.).-Frustules simple, disciform; disc mi- nutely and densely punctated or cellulose, generally divided by radiating single or double dotted lines, and having a small circular hyaline intramarginal pseudo-nodule. We consider Actinocyclus, as limited by Ehrenberg, a well- 3 H 834 SYSTEMATIC EIISTORY OF THIS INFUSORIA. marked genus. Its confusion has arisen from Professor Kützing's retention in it of some species of Actinoptychus, and the application of its name by Professor Smith to the latter genus. The disc is not undulated; and the rays, which are often very indistinct, are dotted or interrupted, not continuous lines. From the minute size and close arrangement of the puncta, the frustules, when mounted in Canada balsam, never appear hyaline, but of a brownish or, more frequently, of a beautiful purplish colour. The disc is furnished with an intramarginal pseudo-module, which simulates an orifice. Ehrenberg in this, as in other genera of Diatomaceae, distinguished his species solely by the number of their rays; but we cannot retain them, as we con- sider species founded on such characters altogether unscientific and erroneous. In general, names once bestowed ought to be retained, even when somewhat inappropriate or defective, because less injury is done by their retention than by burdening the science with synonyms; still we believe it far better to bestow a new name when, as in this genus, numerous species are reduced to one to which the original names would be inapplicable. ACTINOCYCLUS moniliformis (n. sp.).- Disc divided into compartments by three or more rays, formed of single series of dots, in a moniliform arrangement. = A. ternarius, EMI. pl. 22. f. 9. Fossil. Europe, Africa, and America. This species in- cludes most of Ehrenberg's figures of Actinocyclifrom the deposits of Greece, Oran, Sicily, and Virginia (pls. 18, 19, 21 & 22). We have seem no specimens; but in Ehrenberg's figures the single monili- form rays differ so greatly from what we find in the following species that we must consider them distinct, although Ehrenberg, in consequence of his regard- ing the number of the rays as the essen- tial character, has mixed up its forms with those of the following species under the same names, A. Ehrenbergii (m. sp.). — Disc gene- rally iridescent, closely punctated, so as under a low power to appear waved, divided by regular equidistant rays formed of interrupted double lines, which terminate at the margin in minute teeth. Common, both recent and fossil. Very fine in Ichaboe guano. Under this name we include all Ehrenberg's species with rays composed of double lines. The rim is narrow, but generally distinct; pseudo- module minute. In fluid, A. Ehrenbergii is colourless; but when mounted in bal- Sam, it, like the next species, varies with different shades of brown, green, blue, purple, and red. The rays are formed by lines composed of linear or subulate hyaline spaces, which, more frequently than in A. Ralfsii, are in pairs, though sometimes alternate ; they are often in- distinct, especially in smaller specimens. This species is best recognized by the waved appearance of its puncta. We subjoin a list of forms included in A. Ehrenbergii, but by Ehrenberg re- garded as distinct species. Most of them may be obtained from Ichaboe guano. We unite them all in this species:– 4. ternarius, 3 rays; A. quaternarius, 4; A. quinarius, 5; A. biternarius, 6; A. Septenarius, 7; A. octonarius, 8; A. no- 7tarius, 9; A. denarius, 10; A. undena- rius, 11; A. biseñarius, 12; A. tredena- Tius, 13; A. biseptenarius, 14; A. quin- demarius, 15; A. bioctonarius, 16; A. Septemdenarius, 17; A. bimonarius, 18; A. movemdenarius, 19; A. vicemarius, 20; A. Luna, 21; A. Ceres, 22; A. Juno, 23; A. Jupiter, 24; A. Mars, 25; A. Mer- curius, 26; A. Pallas, 27; A. Saturnus, 28; 4. Terra, 29; A. Venus, 30; A. Vesta, 31; A. Uranus, 32; A. Achar- news, 33; A. Aldebaran, 34; A. Antares, 35; A. Aquila, 36; A. Arcturus, 37; A. Bet-el-gose, 38; 4. Canopus, 39; A. Ca- pella, 40; A. Form-el-hot, 41; A. Lyra, 42; A. Procyon, 43; A. Regulus, 44; A. Rigl, 45; A. Sirius, 46; A. Sol, 47; A. A. Spica, 48; A. Stella polaris, 49; A. Ninus, 50; A. Alexander, 51; A. Ptole- maus, 52; A. Davides, 53; A. Numa, 54; A. Croesus, 55; A. Dua, 56; A. Rea, 57; A. Imperator, 58; A. Plutus, 59; A. Proserpina, 60; A. abundans, 61; A. luxuriosus, 62; 4. prodigus, 63; A. for- tunatus, 64; A. locuples, 65; A. opiparus, 66; A. pretiosus, 67; A. polyactis, 68; A. magnificus, 69; A. Zoroaster, 70; A. Solon, 71; A. Cleobulus, 72; A. Chilo, 73; A. Pittacus, 74; A. Thales, 75; A. Bias, 76; A. Periander, 77; A. Socrates, 78; 4. Salomon, 79; A. Homerus, 80; 4. Hesiodus, 81; A. Tyrtacus, 82; A. Anacreon, 83; A. Sappho, 84; A. Pin- darus, 85 ; A, AEschylus, 86; A. Sophocles, 87; A. Euripides, 88: A. Virgilius, 89; A. Horațius, 90; A. Tubelcain, 91; A. OF TEIE COSCINODISCEAE, 835 Daedalus, 92; A. Callimachus, 93; A. Phidias, 94; 4. Praciteles, 95; A. Pyr- goteles, 96; A. Apelles, 97; A. Zeuscis, 98; A. Orpheus, 99; A, Apollo, 100; A. Adamas, 101; A. Achates, 102; A. Amethystus, 103; A. Astrolites, 104; A. Beryllus, 105; A. Carbunculus, 106; A. Chrysolithus, 107; A. Hyacinthus, 108; 4. Iaspis, 109; A. Jasponya, 110 ; A. Leucochrysus, 111; A. Omphus, 1.12; A. Onya, 113; A. Opalus, 114; A. Sa- phirus, 115; A. Sarda, 116; A. Sardonya, 117; A. Smaragdus, 118; 4. Topazius, 119.; A. Panhelios, 120. A. Ralfsii (Sm.). — Disc iridescent, with close radiating series of punctiform granules, interrupted by numerous subu- late hyaline spaces, which are crowded in the centre and more distant near the margin, where they form irregular rays of double broken lines; marginal teeth and pseudo-nodule as in A. Ehrenberg. E Eupodiscus Ralfsii, SBD. ii. p. 86. British coast. (v. 84.) 3. Sparsus (Greg, in lit.), granules in loose series, without angular blanks, the principal rays alone reaching the umbilicus, = Eupodiscus Sparsus, Greg TMS. v. p. 81, pl. 1. f. 47: Scotland. “The lines of cellules diminish in num- ber at distinct intervals from the margin towards the centre of the valve, giving a zoned appearance when seen under a low power” (SBD.). A. Ralfsii differs from A. Ehrenbergii in the radiated ar- rangement of its granules, the far greater number of hyaline spaces, and the more irregular distribution of the rays, in which also the blank spaces in the asso- ciated lines are usually alternate. The following remarks on the var. Sparsus are condensed from Professor Gregory's }. — Principal rays equidistant, ormed of large dots not closely set ; between the principal rays, the inner ends of which leave a small central um- bilicus, occur shorter series parallel to each other, the middle one longest, the others progressively decreasing in length on each side, and the shortest adjacent to the principal rays, which they approach at an angle. Professor Gregory finds the same arrangement in A. Ralfsii; but in that form the dots are large and very close. In A. Ralfsii the colour varies with different shades of purple, blue, green, and yellow, and sometimes brown or buff. At Professor Gregory's sug- gestion, we reduce A. Sparsus to the rank of a variety, as he finds the species to vary much in the size of the granules, in their closeness, and in colour. A. fulvus (Sm.).-‘‘Cellular structure indistinct, radiate; colour of dry valve tawny.” = Eupodiscus fulvus, SBD. i. * pl. 4. f. 40. Britain. Rays obscure. e doubt whether this species be distinct from A. Ehrenbergii, many specimens of which have very indistinct rays. A. crassus (Sm.). — Disc Somewhat opaque, purplish when dry; granules in radiating series; pseudo-nodule as in A. Ralfsii; margin Smooth. = Eupodiscus crassus, SBD. i. p. 24, pl. 4. f. 41. Britain. Mr. T. West believes this species to be an immature state of A. Ralfsii. Doubtful Species. A. Panhelios (E.). —Very large; disc with 120 very fine rays. KSA. p. 128. Cuxhaven. Diam. 1-180". * Disc generally coloured, furnished with radiating series of puncta. A, interpunctatus (Bri.). — Disc with an indefinite number of double rays running from the centre to near the cir- cumference; the rays composed of short, broken lines; the spaces between the rays are minutely punctate. California, New Zealand, West Indies. = Actino- ptychus interpunctatus, Bri JMS. viii. p. 94, pl. 6. f. 17. A. Subtilis (Greg.).-Disc very hyaline, with numerous very fine inconspicuous radiating dotted lines, a circular punc- tated umbilicus, and rather distant mar- ginal teeth. = Eupodiscus subtilis, GDC. p. 29, pl. 3. f. 50. Forming brown patches on sides of rocks. Ilfracombe, Plymouth. This species is easily distinguished by its hyaline appearance in balsam. The pseudo-nodule is minute, radiating lines indistinct, and the umbilicus is furnished with scattered dots surrounded by a dotted circle. Frustules sometimes con- tained in an indefinite mucous stratum. 2* Disk with heavagonal cellules, which are not in radiating lines. A. tessellatus (RO.). — Cellules of disc distinct, hexagonal, with a minute no- dule at each angle, not radiant. = Eupo- discus tessellatus, Ro JMS. vi. p. 19, pl. 3, f: 1. Pembrokeshire, Hull, Norfolk. Guano. This species is placed in Acti- nocyclus because of its solitary intramar- ginal pseudo-module; but in its structure it differs so much from the other species of that genus, that it might be separated from it. The reticulated disc and ab- sence of rays distinguish it. In balsam it is nearly colourless, 3 H 2 836 SYSTEMATIC IIISTORY OF TEIT, INFUSORIA. Genus ASTEROLAMPRA (Ehr.).-Frustules simple, disciform; disc orbi- cular, with marginal areolated or punctated compartments, separated by smooth rays which proceed from a hyaline central area; central area divided by lines, which radiate from the umbilicus to the apex of each compartment; compartments and rays symmetrical. Marine. The disc in this beautiful genus is generally colourless, and when mounted in balsam is far from con- spicuous, notwithstanding its comparatively large size. The marginal com- partments are usually conical, and from the apex of each a line or rib proceeds to the umbilicus. The hyaline central area seems to originate from the dilated inner ends of the rays, and its lines to be produced by their junction. Aste- rolampra is distinguished from Asteromphalus by the compartments being similar and equidistant; on which account the rays are equal, the lines all radiant, and the umbilicus central. * Umbilical lines straight. AstEROLAMPRA Marylandica (E.). — Dmbilical lines simple, straight; areo- lated compartments comical or semicir- cular. EB. 1844, p. 76, f. 10; Wallich, TM. viii. p. 47, pl. 2. f. 13, 14; Grey T.M. viii. p. 108, pl. 3. f. 1–4 = 4. Septenaria, Johns. Sill. Journ. 2nd Ser. xiii. p. 33; A. impar, Sh TM. ii. pl. 1. f. 14; A. pe- lagica, EB. 1854, p. 238. Fossil, Vir- ginia: Monterey stone, guano. Recent, India, &e. (XI. 33.) Rays 6 to 14. The disc varies greatly, not only in the mum- ber of rays, but in the elongated or de- pressed form of the compartments, pro- ducing a corresponding variation in the size of the central area. A. Rotula (Grev.). — Resembles A. Marylandica, but the areolated compart- ments have subtruncate apices; umbili- cal lines straight. Grew TM. viii. p. 111, pl. 3. f. 5. Monterey stone. Umbilical lines simple or dividing in a forked man- ner, close to the central point, A. variabilis (Grev.).--Compartments with cuneate apices; umbilical lines straight, mostly united in twos or threes near the central point. Grev TM. viii. }. 111, pl. 3. f. 6-8. Monterey stone. ays 6 to 11. - A. Grevillii (Wallich, Grev.). — Com- partments comical, with truncated apices; umbilical lines straight, variously united. = Asteromphalus Grevillii, Wall TM. viii. p. 47, pl. 2. f. 15; Asterolampra Grevillii, Grey T.M. viii. p. 113, pl. 4. f. 21. Fossil, Virginia and Wiś stone ; recent, Indian Ocean. This species approaches Asteromphalus in the appearance of the central area, but its marginal compart- ments and alternating rays are symme- trical. Rays numerous, 13 to 17. 2* Umbilical lines angularly bent. A. Brebissoniana (Grev.). —Areolated compartments truncated; umbilical lines with an angular bend in the middle. Grev TM. viii. p. 114, pl. 3. f. 9. Mon- terey stone. Umbilical lines simple or united, close to the central point, Genus ASTEROMPHALUS (Ehr.).-Frustules simple, disciform; disc as in Asterolampra, but with two of the punctated compartments approximate, and the interposed ray narrower than the others. Marine. Asteromphalus differs from Asterolampra in having two compartments closer together. The lines connecting these with the umbilicus do not radiate like the rest ; and the enclosed hyaline ray consequently differs in form from the others, and is termed the median or basal ray. * Umbilical lines radiating from a central point, two of them approacimated. As- terOmphalus. f Umbilical lines straight or curved. ASTEROMPHALUs Hookerii (E.).- Punctated compartments, comical or rounded at the apex; umbilical lines straight, the median ones parallel. EB. 1844, p. 200; EM. pl. 35A, 21. f. 2. = A. Buchii, E.B. 1844, p. 200; A. Humboldtii, E. l.c. p. 200; EM. pl. 35 A. 21. f. 3; A. Cuvierü, EB, 1844, p. 200; EM. pl. 35 A. 21. f. 1. ź ean, (x. 34.) Rays 6 to 9. We consider that forms differing only in the number of their rays are not really distinct, and have consequently united Ehrenberg's species quoted above. A. Dallasianus (Grev.). — Areolated compartments, with truncate apices; me- dian lines campanulate, = Asterolampra OF THE COSCLNO])ISCE. E. 837 JDallasiana, Grey T.M. viii. p. 115, pl. 4. f. 10. Bermuda, Tripoli. A. Wallºchianus *). — Areolated compartments, with truncate apices; umbilical lines straight. = Asterolampra Wallichiana, Grey T.M. viii. p. 115, pl. 4. f. 11. Bermuda, Tripoli. “The umbilical portion of each ray is so wide next the areolated segments, that it may be com- pared to a short-bladed trowel, while the linear part represents the handle” (Grev.). According to Dr. Greville's figure, this species differs from Astero- lampra only by its median ray being narrower than the rest. 2 + Umbilical lines with an angular bend. A. Beaumontii (E.). — Compartments with rounded. apices; umbilical lines with an angular bend; median ones straight, parallel. EB. 1844, p. 200, f. 5; Grey T.M. viii. p. 115. Antarctic Ocean. A. Darwinii (E.). — Compartments with rounded or subtruncate apices; umbilical lines with an angular bend; median ones bent or curved. ERBA. 1844, p. 200, f. 1.- Asterolampra Dar- winii, Grew T.M. viii. p. 116, pl. 4. f. 12, 13; Asteromphalus Rossii, ERBA, p.200, f. 2; EM. pl. 35 A. 21. f. 4. Antarctic Ocean, Monterey stone. (v. 86.) 2 * Disc subcircular, rays wºnequal; wºm- bilical lines radiating from the top and sides of the median ones, which latter pass beyond and enclose the central point. Spatangidium. t Umbilical lines not bent. A. flabellatus (Bréb., Grev.). — Punc- tated compartments, conic ; umbilical lines straight or slightly curved, radi- ating from apex and sides of the median ones. Grev M.J. vii. p. 160, pl. 7. f. 4, 5. = Spatangidium flabellatum, Bréb. Bull. Soc. Linn. de Normand. iii. pl. 3. f. 3; Aste- rolampra flabellata, GrevTM. viii. p. 116; Spatangidium peltatum, Bréb. l. c. pl. 3. f. 4. Peruvian and Californian guanos. Rays 10 or 11; median one clavate ; areolation of compartments very minute. A. Hiltonianus (Grev.). — Punctated compartments narrowly conic; umbilical lines radiating from apex and sides of median lines, the two lower pair Sud- denly deflexed. = Asterolampra Hilton?- ana, Grey T.M. viii. p. 117, pl. 4. f. 15, Algoa Bay guano, Indian Ocean. Rays 10 to 19, slender; umbilical lines simple or forked; areolation very minute. It is Ralfs in lit. a very transparent species, and easily overlooked, Grey. A. Arachne (Bréb.). — Disc broadly ovate; hyaline area. Small and excentri- cal; areolated compartments, very un- equal; umbilical lines straight, short ; dilated head of median ray truncate. = Spatangidium Arachne, Bréb. Bull. Soc. Linn. de Normand. iii. pl. 3. f. 1; Aste- rolampra Arachne, Grey T.M. viii. p. 123; Asteromphalus malleus, Wall TM. viii. p. 47, pl. 2. f. 11; Eccentron cancroides, (v. 66.) Peruvian guano, Indian Ocean. Distinguished by its mal- leiform median ray. Compartments with large areolation; umbilical lines less con- spicuous than in the other species. Rays usually 5, sometimes 7; median and adjacent ones straight, the anterior pair curved. When there are only five rays, this species differs greatly in appearance from the rest by having the Tanterior margin of the head of the median ray in direct contact with the anterior com- partment; but when the rays are 7 in number, the hyaline dilated portions of the anterior pair interpose between these parts, as in the other species. 2 t Umbilical lines with an angular bend. A. elegans. (Grev.). — Punctated com— partments, comic, more than half the radius; umbilical lines with an angular bend, radiating from apex and sides of the median ones, usually simple, but Sometimes two or three united. Grev M.J. vii. #. 7, pl. 7. f. 6. = Asterolampra elegans, M.J. viii. p. 118, pl. 4, f. 16, Ca- lifornian guano, Indian Ocean. (v. 87.) Areolation extremely minute; rays 13 to 29, gracefully slender. A. imbricatus (Wall.). — Areolated Compartments, conic, less than half the radius; rays numerous, robust; angular bends of umbilical lines forming unitedly an oblong-elliptical figure. Wall TM. viii. p. 46, pl. 2. f. 9. = Asterolampra im- bricata, Grev M.J. viii. p. 119, pl. 4. f. 17. Indian Ocean, Natal. Areolation con- siderably larger than in A. elegans, its nearest ally, Grev. A. Brooke: (Bail.).--Disc almost cir- cular; areolation conspicuous; compart- ments trumcated; angular bend of um- bilical lines near the outer end; umbilical portion of median ray constricted be- neath the rounded immer end, thendilated. Bail. Sill. Journ. 2 ser. xxii. p.2, pl. l. f. 1. = Asterolampra Brookei, Grey M.J. viii. p. 119, pl. 4. f. 18, Soundings, Kaunt- Schatka, Atlantic. (v. 79.) The umbi- 838 SYSTEMATIC ELISTORY OF TELE INFUSORIA. lical lines radiate from the upper half of the median ones, and are sometimes divided. The angular bend is nearer the outer end than in any other species; and at each angle is a minute spine-like pro- cess, Grev. A. Roperianus (Grev.).-Disc circular, with its hyaline area centrical; areolated compartments, truncate, almost equal; umbilical lines radiant from rounded end of median ones; median lines pass- ing round the central point in a semi- circle, then contracted, and lastly widely expanded. = Asterolampra Roperiana, Grew M.J. viii. p. 120, pl. 4. f. 14. Indian Ocean. Rays 7, robust; areolation rather large, Grev. A. Shadboltianus (Grev.). —Areolated compartments, truncate; umbilical lines radiant from the pyriform median ones, with the bend about the middle; rays not reaching the margin. = Asterolampra Shadboltiana, Grew § viii. p. 121, pl. 4. f. 19. Indian Ocean. “Rays 7, robust; areolation rather large. Its nearest ally is perhaps A. Brookei, from which it is separated by the very different median lines and by the angular bend being more in their middle” (Grev.). Dr. Greville suspects that in this species, as in A. Roperianus, A. heptactis, and 4. Arachme, the number of rays may be more constant than is generally the case in the group. A. heptactis (Bréb.).—Areolated com- partments, truncate; rays broad, linear, terminating in a lunate marginal fold, and bordered by a row of larger areolae. =Spatangidium heptactis, Bréb, Bull. Soc. Limn. de Normand. iii. p. 3. f. 2; Aste- rolampra heptactis, Grey T.M. viii. p. 122; Spatangidium Ralfsianum, T.M. vii. p. 161, 1.7. f. 7, 8, Peruvian and Californian guanos, Atlantic soundings. Rays 7, straight or slightly curved, the median one in a broad shallow groove, the linear #. faintly prolonged through the ilated portion to spurs from the bends of the adjacent umbilical lines. Areo- lation of compartments, conspicuous; disc subcircular, (VIII, 21.) Doubtful or imperfectly described Species. A. centraster (Johnston).--Disc orbi- cular ; areolated compartments with rounded apices and bordered by a series of larger areolae; umbilical lines straight, radiating from top and sides of median ones; rays terminating at the margin in modules. Johnston, Mj, viii. p. 12, pl. 1. f 10. Elide guano. (VIII, 14.) ays 11. Dr. Johnston's figure differs from every known species by having the rays continued, as Dr. Greville remarks, like distinct bars or the ribs of an umbrella, from the central point to the margin. We believe, however, that this structure is similar to what is met with in several other species of Asterolampra and AS- teromphalus (see especially Greville's figures of Asterolampra variabilis, A. Wallichiana, A. Roperiana, and A. hep- tactis), but more strongly marked, and probably exaggerated in the figure. A. Stellatus (Grev.). = Asterolampra stellata, Grew TM. viii. p. 124, pl. 4. f. 20. Indian Ocean. It is allied to A. Hilto- nianus and A. flabellatus. The lowest pair of umbilical lines are curved down- wards, as in the former species. The median lines are parallel. The valve, at a first glance, is most conspicuous for the large size of the hyaline area and the rapidly attenuated rays; but this may prove to be a worthless distinction. A. Sarcophagus (Wall.). —Valve ob- long, with inflated middle; median ray plane and continuous with the anterior ray; umbilical lines straight; areolation very large. Wallich, TM. viii. p. 47, pl. 2. f 12. = Asterolampra Sarcophagus, Grey TM. viii. p. 124. Indian Ocean. “The broadest portion of this species is always towards the extremity opposite to the median ray, thus giving the valve a some- what pyriform or sarcophagus-like shape” (Wallich). “The form of the valve is so extreme a deviation from the other- wise more or less orbicular shape of the entire series, that an impression almost forces itself upon the mind that it is simply a malformation. It is most nearly related to A. Arachme; for if we remove the terminal ray (which in many species may be either absent or present), the five remaining rays would occupy the relative position which they hold in that species, as well as in the same direction, one pair pointing upwards, the other pair down- wards. In both species the areolation is large” (Grev.). Genus ASTERODISCUS (Johnson). — Frustules simple, disciform; disc divided into punctated compartments, which do not reach the centre, by hyaline smooth rays; compartments connected to the umbilicus by an equal number of radiating lines, two united half way, the rest distinct. Fossil, (Johnson, OF TELE COSCINODISCEAE . 839 in Silliman’s Amer. Journ. 1852.) “The proximate genera, Asterolampra and Asteromphalus, are readily distinguished. In the former, all the connect- ing lines are symmetrical; in the latter, two are parallel; ” whilst in this genus one line divides half-way from the centre and proceeds to two of the Compartments, the Smooth ray between which is smaller than the others, but not parallel as in Asteromphalus. ASTERODISCUS Johnsonii – Rays and umbilical divisions from five to nine. Bermuda earth. This includes the fol- A. monarius.—Marginal rays and um- bilical divisions nine. “Front view bi-convex; compart- lowing species of Johnson:— A. quinarius.-Marginal rays and um- bilical divisions five. ments elegantly marked with minute dots, arranged in excentric curves ‘’ (Johnson), A. Senarius.-Marginal rays and um- bilical divisions six, Genus ACTINOPTYCHUS (Ehr.).-Frustules disciform, cellulose ; disc divided into equal triangular compartments by lines or internal septa (E.). = Actinocyclus, Smith, not Ehr. The circular disc is cellulose, and divided into triangular portions by lines (“internal septa,” E.) radiating from its centre. The alternate portions are usually more distinct, owing to the undu- lated form of the frustules, which causes them alternately to be nearer to or more remote from the eye. The apparent septa distinguish it from Actino- cyclus, and the absence of spines from Heliopelta and Omphalopelta. We have not the slightest doubt that Ehrenberg has properly separated Actino- cyclus from Actinoptychus. Professor Smith himself practically admits this, by placing the groups in different genera, although he has not retained the names as affixed by their author. If, however, the validity of their separa- tion be admitted, the founder of these genera has surely an undoubted right to retain the original name for whichever group he thinks fit. Professor Smith seems to have erred by choosing as the type of Actinocyclus, not one of Ehrenberg's species, but a form placed in that genus by Professor Kützing, though really belonging to Actinoptychus. ACTINOPTYCHUS ternarius (E.). — Disc with 3 or 5 radiating lines, with- out a distinct umbilicus; compartments even. KB. pl. 1. f. 19. = A. quinarius, E. Fossil, Virginia. The rays proceed directly to its centre, without leaving an umbilical space. A. undulatus (Kütz.). —Disc with its compartments alternately prominent and cellulose and depressed and punctate; umbilicus indistinct or indefinite, - Actinocyclus windulatus, KB. pl. l. f. 24; Actinoptychus biternarius, EMI. pl. 18. f. 20; A. biternatus, EMI. pl. 35 A. 16. f. 1. (v. 88.) America. Guano, &c. Com- partments six or more. A. velatus (E.). — Compartments six, loosely cellulose ; surface apparently covered by a thin punctated membrane. RSA. p. 130. Virginia. We are unac- quainted with this species, but think it may probably be a state of A. undulatus, the valves of which frequently consist of two dissimilar plates, one having the usual character, the other being triradiate and minutely punctate, and which has been described as a new species by Mr. Roper in TM. vi. p. 23 (Actinocyclus tri- radiatus), who first observed it detached from the true valve. He and others have since found the plates in situ. A. Senarius (E.). — Compartments (6 or more) alternately prominent, all loosely cellulose ; umbilicus angular, definite ; rim striated. EMI. various plates. = Actinocyclus undulatus, S.B. i. pl. 5. f. 43. (Ix. 132.) Common, both recent and fossil. Mr. Tuffen West re- gards A. Senarius and Omphalopelta areo- lata as identical. The presence of mar- ginal spines in the latter seems indeed the only essential distinction; and we have generally succeeded in detecting spines, more or less distinct, exactly such as Professor Smith has represented in one of the figures of his Actinocyclus undulatus. The determination of species in Actinoptychus is very difficult. The number of the compartments, generally relied upon, we consider unessential, and 840 SYSTEMATIC IIISTORY OF TEIE INFUSORIA. we would separate into two species all those forms in which the compartments, irrespective of their number, are di- stinctly cellulose without any particular arrangement of their cellules. A. undu- latus would thus include all those having a vague or indefinite umbilicus, and A. senarius those in which the umbilicus is separated from the cellulose compart- ments by a well-defined margin, A. splendens (Shadbolt). — Compart- ments (12 to 20) obscurely cellulose, each with a median line, which termi- nates in a clavate intramarginal module or tooth; umbilicus hyaline, definite. = Actinophaenia splendens, Sh TM. ii. p. 16; Actinoptychus sedenarius, E., Ro TM. ii. i. 74, pl. 6. f. 2. Common. Guano, Eng- and. In this species the alternate de- pressions of the compartments are often very slight; and the compartments being striated, frequently appear irregular, and are counted with difficulty. The species nevertheless has so peculiar an aspect, that, once known, it is easily recognized. The rays are most distinct where they radiate from the hyaline umbilicus, at which part they sometimes appear thick- ened. In some specimens the modules are confined to the alternate compart- mentS. A. elegans (m. sp.).-Disk divided into compartments by lines radiating from a stellate, hyaline umbilicus; compart- ments punctated, and each bisected by a moniliform row of granules. = A. octo- denarius, EMI. pl. 21. f. 21. Oran. Ehren- berg has figured more than one form as his A. octodenarius; the compartments in his figure of this species are 9, and each is bisected by a moniliform ray. A. trilingulatus (Bri.).-Valves divided by 6 alternately elevated Segments. The elevated portions gradually rise from the circumference to near the centre, where they are rounded off; each alternate one has a submarginal row of dots or trun- cated processes. Surface delicately punc- tato-striate. .0035” to "0073". est Indies. Bri M.J. viii. p. 93, pl. 5. f. 2. A. spinosus (Bri.).-Valves with 6 seg- ments, alternately slightly elevated; mar- gin occasionally spinous; each segment with 1 or 2 processes; umbilicus smooth, surface of the valve punctate. Monterey earth (or deposit). Bri M.J. viii. p. 94, pl. G. f. 15. A. dives (E.). — Disc divided into numerous (about 50) narrow compart- ments by lines radiating from a large, indefinite, punctated umbilicus, , each compartment having a single series of granules. EMI, pl. 19. f. 12.5-10iscoplea dives, E.; Cyclotella dives, K.A. p. 20. Fossil. AEgina. Doubtful Species. A. quaternarius (E.). — Disc divided into 4 compartments by as many radi- ating lines. KA, p. 130. Virginia. Diam. 1-552". A state of A. ternarius P A. P. hearapterus (E.). — Disc with 6, thick, Solid and conical rays; margin thick, undulated, denticulate internally. KA, p. 131. Fossil, Vera Cruz. (XI. 31.) A very doubtful Diatom. A. octonarius (E.).--Disc divided into 8 compartments by as many radiating lines. Guano, &c. A state of A. Senarius. A. denarius (E.).-Disc with 10 com- partments and 10 radiating lines. EMI. & 18. f. 23. Cuxhaven and Virginia. e believe this species is founded on certain forms of A. Senarius and A. Splendems. A. duodenarius (E.).--Disc divided by radiating lines into 12 compartments, which are alternately darker; in the centre of each compartment runs a nar- row line, terminating at the margin in a minute pseudo-nodule, so that as many as 24 rays may be counted. Recent and Fossil. Europe, America. K.A. p. 131. = Heliopelta Phaethon, M.J. viii. p. 13? A state of A. Splendens? The following species of Ehrenberg . distinguished by the number of rays only :— A. quatuordenarius, 14 rays=A. Splen- dens; A. vicemarius, 20 rays; A. Ceres, 22 rays; A. Jupiter, 24 rays (XI. 28). The three last are probably states of A. Splendens. Genus HELIOPELTA (Ehr.). — Frustules disciform, undulated disc cellu- lose, with external rays and internal Scpta, a striated margin, many erect submarginal teeth, and an angular centre. As in Actinoptychus, the frustule is undulated, and the disc divided into cuneate compartments or rays, which appear alternately more distinct; “but, in addition, they have near the margin a row of lateral spines, somewhat like the processes of Eupodiscus, but far more numerous, which probably connect the frustules together in the of THE COSCINODISCEAE. 841 young state. Ehrenberg has dedicated the different species of this genus to persons distinguished in the history of microscopic research'' (Bailey). As the species differ only in the number of compartments, they are probably not truly distinct. HELIOPELTA Metii (E.).--Disc having tagonal. Diam. 1-156". loosely cellulose, elevated, radiating com- partments, alternating with depressed ones marked with fine decussating lines; border a rather broad striated rim. Ber- muda deposit. (XI. 35.) Compartments 6; umbilicus stellate. Diam. 1-372". Has the habit of Actinoptychus velatus. = H. Metii, E.B. 1844, p. 268. Com- artments 8; umbilical star tetragonal. }. 1-204". H. Leeuwenhoeki (EM, pl. 33. 18. f. 5.). —Compartments 10; umbilical star pen- ií Fulcri (EM. pi. 33. 18. f. 6). — Compartments 12; umbilical star hex- agonal. Diam. 1-156". * H. Selliguerii (EB. 1844, p. 268.). — There are usually 3 teeth opposite each elevated compartment, and 2 opposite each depressed one; but sometimes, es- pecially in the larger specimens, the teeth are more numerous, whilst in the Smaller ones they are occasionally 1 less in each compartment. Genus OMPHALOPELTA (Ehr.).-Frustules simple, disciform; disc cellu- lose or punctate, divided by imperfect septa into cuneate rays; centre hyaline; spines, one to each compartment. “This genus has the habit of Actinoptychus and Heliopelta, but differs from the former in the presence of lateral spines, and from the latter in the Small number of these processes. The species of these three genera often closely agree in their form as well as in the number of their radii and cells; but the character of the spines will always distinguish them” (Bailey). “All the species of Omphalopelta resemble Actymoptychus senarius” (Kg.). Heliopelta differs from this genus in having two or more spines instead of one to each compartment, a difference we regard as more suitable for specific than generic distinction; and we believe that a better knowledge of these forms will prove the propriety of uniting them. OMPHALOPELTA cellulosa (E.). —Ba- diating compartments 6, cellulose, al- ternately tumid and º stellato- punctate; rays but slightly prominent; rim broad, striated. K.A. p. 133. Fossil. Bermuda, Virginia. Diam. 1-192". This species greatly resembles, the 6-rayed form of Heliopelta Metii, in which the compartments have sometimes only 1 and 2 spines alternately; and indeed we are not certain that they are even speci- fically distinct. O. areolata (E.). — Compartments 6, all loosely and obscurely cellulose, scarcely or but slightly depressed; rays distinct; rim broad, radiate. EM. pl. 35A. 18. f. 12. = Actinocyclus areolatus, Bri M.J. viii. p. 93, pl. 5. f. 1. Fossil. Bermuda, guano. (VIII. 15.) O. versicolor (E.). — Compartments 6, all granulated in very fine decussating lines, which cause a play of colours from tawny to red; the strong rays and hex- agonal crystalline umbilicus very conspi- cuous; rim narrow, radiant. K.A. p. 133. Fossil. Bermuda. Diam. Sometimes 1–252", but mostly less. O. punctata (E.).-Radiating compart- ments 6, all loosely punctated, 3 alter- mate ones slightly elevated; rim narrow, not distinctly radiant; spines obsolete. KA. p. 133. Fossil. Bermuda. Genus ARACHNOIDISCUS (Deane).-Frustules disciform ; disc with a central hyaline module or umbilicus, and numerous radiating lines connected by concentric lines or series of gemmaceous granules. =Hemiptychus (E.). The disc has been compared to a spider's web ; hence the name. Alternating with the long radiate lines are one to three short marginal ones, the central one of these being also longer than the other two when three are present, Professor Bailey informs us that Arachnoidiscus has been adopted instead of Hemiptychus because the latter name had previously been used in ento- mology. - 842 SYSTEMLATIC EIISTORY OF TELE INFUSORIA. ARACHNOIDISCUS ornatus (E.).-Disc having its radiating lines connected by concentric ones. = Hemiptychus ornatus, B.B. 1848, p. 7; Arachnoidiscus ornatus, EB. 1849, p. 64; Ar TM. vi. p. 16; A. Japonicus, Shadbolt; A. Nicobaricus, EM. pl. 36. f. 35 (according to Arnott). Africa, West Coast of America, Nicobar Islands. (xv. 18–21.) In deference to the opinion of Prof. Arnott, we have united A. Nicobaricus to this species; but it is desirable to examine specimens from the original stations. Ehrenberg describes all the radiating lines in his A. ornatus as equal; but he figures A. Nicobaricus with two sets of shorter, marginal, interme- diate ones. Our specimens, in this re- spect, agree with 4. Nicobaricus, but have around the umbilicus a circlet of close, short, radiant, oblong lines, which are wanting in Ehrenberg's figure. The granules, too, are apparently larger in our specimens. The lines connecting the radiating ones often anastomose. A. Ehrenbergii (Bailey). —Disc with numerous, moniliform, concentric circles of large pearly granules, the circle next the umbilicus formed of short lines; radiating lines with two series of shorter ones between. = A. Ehrenbergii, E.B. 1849, p. 64; SD. i. p. 26, pl. 31. f. 256. Recent, Coast of Oregon and California; fossil, Monterey and California. A. Ehren- bergii is easily distinguished from A. Genus PERITHYRA (Ehr.).-Characters unknown to us. ornatus by the absence of concentric lines. It is more hyaline, and the gra- nules far larger and more conspicuous. All the circles are compact, and, except the two immer Ones, have the granules slightly quadrate, and their relative di- stances somewhat irregular. The second- ary rays are sometimes half the length of the principal ones; the third series is simply marginal. A. Indicus, E.M. pl. 36. f. 34. India. We have seen neither specimen nor de- scription of this species. Ehrenberg's figure represents the disc with numerous, concentric, moniliform circles of pearly granules. The granules are distant in the first and third from the umbilical space; in all the others they are dense. rofessor Arnott (perhaps rightly) unites A. Indicus to A. Ehrenbergii; but we have thought proper to keep them sepa- rate for the present, in order to direct more attention to them, because Ehren- berg's figure of A. Indicus differs in some respects from A. Ehrenbergå. In this º there is no linear series round the umbilicus, the third circle has distant granules, all the granules are orbicular, there is only one series of shorter rays interposed between the long ones, and these are connected by an undulated line, giving the inner margin of the rim a scolloped appearance. In all these respects it differs from A. Ehrenbergii. According to Bhrenberg's figures, it seems to differ from Heterostephania by its larger tubercles. PERITHYRA demaria, EMI. pl. 35 A. 9. f. 5. = Coscinodiscus radiatus, var., Wal- lich, TMS. viii. pl. 2. f. 22? Ganges. Disc with radiating series of minute puncta, ten intramarginal tubercles, a rather broad, Smooth rim, and no umbi- licus. (VIII. 19.) P. quaternaria, EMI. pl. 35 A. 9. f. 6. Ganges. A variety of the preceding, with only four tubercles. - FAMILY IX. —EUPODISCEAE. Frustules simple, free, disciform; lateral surfaces furnished with processes. The Eupodisceae may be regarded as connecting the Coscinodisceae with the biddulphieae. They agree with the former in their discoid frustules and with the latter in having processes on the lateral surfaces. These processes, how- ever, must not be confounded with the spines or teeth which occur in some of the Coscinodisceae. It is sometimes difficult to decide whether the discs really have processes or only pseudo-nodules, since, from their circular out- line and hyaline texture, free from cellules, both these appear like orifices unless seen in profile, and perhaps Actinocyclus would be more correctly placed in this family than with the Coscinodisceae. Genus EUPODISCUS (Ehr.).-Frustules disciform; disc cellulose or gra- mulate, furnished with submarginal circular prominences. =Tripodiscus, Tetra- OF THE EUPODISCEAE. 843 podiscus, Pentapodiscus (E.), Podiscus (Bail.). usually less evident in this genus than in Coscinodiscus. The cellular structure is We have removed to Actinocyclus three species originally placed here by Professor Smith, who himself admits that they probably belong to that genus, “as the process in all is rather a pseudo-nodule than a projection from the surface of the valve.” EUPODISCUS Argus (E.). —Disc with three or more processes, subremote from the margin; cellules somewhat stellate, intervals punctated. SD, i. p. 24, pl. 4. f. 39. = E. Americanus, EB. 1844; E. quašernarius, E. guinarius, E. Germa- ºnicus, K.A. p. 134. (VI. 2; XI. 41, 42.) Recent in marine and brackish water, Europe, America; fossil, United States. This species is easily recognized by its irregular cellules and intervening puncta, which give to the disc a clouded appear- ance, very unlike the usual transparency of Diatomaceae. The processes vary from 3 to 5 in number. "“The star-shaped cells appear when seen by direct light to be placed in the centre of small bosses or protuberances, in which respect it dif- fers from all other Diatomaceae that I am acquainted with. Ro M.J. ii. p. 73. E. monstruosus (E.).--Disc with 4 pro- cesses on one side. E. l. c. p. 81. Baltic. Distinguished by the unsymmetrical dis- position of its processes. It is probably an accidental variety of E. Argus. E. Rogersii (Bail., E.). — “Frustules large, having 3 to 7 hyaline lateral pro- cesses placed on an elevated circle, within which the disc is slightly con- cave, and outside of which the surface is part of the frustum of a come. = Po- discus Rogersii, BAJ. xlvi. pl. 3. f. 1, 2; Eupodiscus Rogersii, E. l. c.; E. Baileyi, E. l. c. Recent and fossil. United States. In this species the processes are close to the rim. The whole surface is beautifully punctate. . . . As this spe- cies is the largest and most beautiful of the fossil Infusoria occurring in the strata of which Professor W. B. Rogers made the discovery, I have selected it as pe- culiarly appropriate to bear his name * (Bail. l.c.). E. radiatus (Bail.).--Disc plane, areo- lation hexagonal, with 4 (or more) sub- marginal processes. “Resembles Cosci- modiscus radiatus in size and reticulation,” BC. Bri M.J. viii. p. 95, pl. 5. f. 10. America. Genus AULACODISCUS (Ehr.).-Frustules disciform; disc granulated, and furnished with intramarginal, shortly tubular processes, each connected with the centre by a distinct furrow, or by a radiant Series of more conspicuous granules. Aulacodisci are Eupodisci furnished with bands radiating from the centré and connected with the tubercles situated just within the margin, and having the surface of their valves granulate, and not cellular. Professor Rützing makes this genus a section of Eupodiscus. * Disc bullate beneath the processes. AULACODISCUS Petersii (E.). — Disc nearly colourless, having a Small, per- foration-like umbilicus, a large kite- shaped inflation, rough with minute points, beneath each process, and minute granules arranged in lines. EB. 1845, p. 361.= Eupodiscus Petersii, KSA. p. 135; I. cruciger, Sh TM. ii. pl. 1. f. 12, South Africa, both recent and in guano; Aus- tralia and New Zealand. Disc large, with 3 to 5 orbicular processes, furnished with a central nipple and situated on the outer margin of the inflations. The granules are minute, and arranged in lines, some radiant and bisecting the intervals between the processes, the rest oblique and decussating. Raised points are present on the inflations and less conspicuously along the connecting fur- rows and about the umbilicus; margin finely striated. In order to observe the disc properly, it is necessary, on account of its unevenness, to vary the focus. Specimens from New Zealand have the granules and markings more distinct, and the inflations smaller, less definite, and further from the margin. A. formosus (Arnott, M.S.).-Disclurid, having an irregular perforation-like um- bilicus, a large cuneate inflation beneath each process, and radiating series of con- spicuous pearly granules. = A. Bright- wellii, Ralfs, MS. ; A. Boliviensis, Bréb. MS. In upper Peruvian or San Filipe guano. A. formosus agrees with A. JPeters; in having an inflation beneath each process, but differs in most other respects. From A. margaritaceus and A. Comberi, which it more nearly re- sembles in the appearance and arrange- 844 SYSTEMLATIC IIISTORY OF THE INFUSOIRIA, ment of its granules, it is easily known by its inflations. Disc large, Smoke- or lead-coloured, with a narrow, distinct, finely striated rim; inflations remote from the margin, and having a bright oint at the outer edge, placed at the ase of an elongated, clavate, not very conspicuous process. 2* Disc not bullate beneath the processes. A. scaber (Ralfs, m. sp.). — Disc with oblong submarginal processes, crowded radiating series of minute granules, and scattered raised points. Peruvian guano. Processes 3 to 5, connected by indistinct rooves with the very minute umbilicus. the front view this species resembles a Cerataulus, its lateral portions being turgid, and, in addition to the processes, rough with minute apiculi; connecting zone marked by faint longitudinal lines. A. Kittoni (Arnott, M.S.).--Disc hya- line, with 3 to 8 submarginal crescent- looking processes, connected by radiant rows of minute granules, with an umbi- lical rosette of oblong cellules. Recent, New Zealand and Monterey Bay; fossil, Monterey stone. An elegant species, distinguished by its somewhat mammi- form processes, which, being directed out- wards, appear lunate, Granules puncti- form, proceeding from umbilicus to lº in pencil-like rays; interval etween the processes bisected by similar pencils, but less conspicuous, and with- out furrows; the rest of the granules in oblique lines, as in A. Petersii. A. Johnsonii (Arnott, M.S.).--Disc pale, with a circular, perforation-like umbili- cus, and crowded radiating series of gra- mules becoming more numerous as they proceed outwards, so as to appear forked; processes within the margin, roundish, small. Algoa Bay guano. The rays, near the margin, become more numerous, with Smaller granules, so as to look like striae; sometimes the processes appear within a faint circle. A. Johnsoni; some- what resembles A. Kittoni, but is less hyaline, with more conspicuous gra- nules, and processes more distant from the margin. - A. Cruz (E.).--Disc with close, radi- ating, forked series of large pearly gra- nules, which are crowded at the centre, leaving no blank space; processes some- what distant from the margin. = A. Ch'ua, DB. 1844, p. 76; EM. t. 18. f. 47; Eu- podiscus Cruac, KA, p. 135. Fossil, Vir- ginia. We are indebted to Professor Arnott for correcting the error we had fallen into, of confounding it with A. Rittoni. In general appearance it agrees with A. Comber; and A. margaritaceus; but the processes are more remote from the margin, and the connecting furrows obscure; it differs essentially from most other species in having large granules at the centre of its disc, instead of a blank space; margin striated. A. margaritaceus (Ralfs, m. sp.).-Disc pale, with oblong submarginal processes, an irregular, perforation-like umbilicus, numerous, close, moniliform, radiating Series of large, pearly granules, and in- conspicuous connecting furrows. Patos or Californian guano. = A. Cruac, EMI. pl. 35 A. 16. f. 2. Disc large, with from 3 to 10 rather small processes; umbilicus usually irregular, hyaline, looking as if denuded of granules, sometimes very minute and SunTounded by a circlet of larger granules. Two simple series of equal granules lead to each process, be- neath which, by a slight separation, they leave a triangular hyaline space; the other series are dichotomously divided, and near the margin their granules be- come Smaller, or even punctiform, and resemble striae. - A. Comberi (Arnott, MS.).--Disc lurid; granules large, irregularly scattered round the irregular perforation-like umbilicus, the rest arranged in crowded, forked, radiating lines; processes oblong, sub- marginal, with conspicuous connecting furrows. San Filipe guano. Processes 2 to 6. A. Comber; in character ap- proaches closely to A. margaritaceus; its granules, however, are Smaller and more irregular near the umbilicus, and the furrows leading from the processes are much more conspicuous; but the most obvious distinction of this species is its lurid appearance. A. Beeveriae (Johnson, MS.). — Disc smoke-coloured, with an irregular blank umbilicus, rather distant radiating lines of large pearly granules, striated mar- gin, and (3 or 4) roundish submarginal processes. New Zealand. Of this beau- tiful species we have seen only one spe- cimen. The disc is Small, apparently nearly flat, with very distinct granules, 9 or 10 in 001", on a dark ground; two series leading to each process, wider apart and more parallel than the rest. VI. 5. ( A. }* (Norman, M.S.). — Disc coloured, with a minute umbilicus, close radiating series of granules, and two or three roundish intramarginal processes. Shell-cleanings, California and else- where in the Pacific. Fossil, Monterey OF THE EU PODISCE E. 845 stone. Disc small under a low power, bluish, with a darker, brownish border. The granules, which, according to Mr. Norman, are about 17 in 001", are so regularly arranged as to form concentric circles as well as radiating series. A. Brownei agrees in colour with A. Ore- ganus, but in the arrangement of its granules more resembles A. Beeveride. From the former it differs in the regular radiant arrangement of its granules, smaller size, fewer processes, and much flatter surface. From A. Beeveria it is distinguished by its colour and closer granules. A. Oreganus (Bailey).--Disc coloured, with circular perforation-like umbilicus, convex centre, flattened border, short cylindrical slightly emarginate marginal processes, and series of minute crowded granules. Bail. Proc. Acad. Philadelphia, 1853; Grey M.J. vii. p. 156, pl. 7... f. 2. California, both recent and fossil; Mon- terey stone, Puget's Sound. This very distinct species is easily recognized by its coloured disc and cylindrical emar- ginate processes, which are from 6 to 27 in number, and close to the margin. Under a low power its minute granules appear arranged in waved or oblique lines, but imperfectly radiant under higher powers. (VI.4. A. pulcher (Norman, M.S.).--Disc large, coloured, with from 7 to 16 marginal processes; central granules irregularly scattered or crowded, the others in di- stinct, close, radiant rows. Fossil. Mon- terey stone. A. pulcher agrees with A. Browned in its coloured, slightly and uniformly convex disc and radiant ar- rangement of granules. It differs from that species by its much larger size and more numerous processes. The most remarkable feature of this species is its granulose centre, in which respect, as well as in its radiant granules, it differs from A. Oreganus. Granules 12 in 001". (VIII, 28.) Genus AULISCUS (Ehr., Bail.).-‘‘Frustules cylindrical or discoid; lateral surfaces undulated, having two circular, flattened, mastoid, imperforate pro- cesses at some distance from the margin; umbilicus (generally present) smooth, circular, surrounded by a plumose arrangement of dots and lines; sides smooth” (BC. 1854.). “The projections on one valve are usually on a line at right angles to that on which those of the opposite valve are placed ” (B.). Kützing unites Auliscus with Coscinodiscus; but it seems more nearly allied to Eupodiscus. * Disc with a conspicuous circular wºmbilicus. AULISCUs pruinosus (B.).—“Disc with four sets of curved and sparsely punc- tate lines, two diverging from the large smooth umbilicus, while the other two converge round , the large processes.”- BC. 1854, pl. 1. f. 5–8. Recent. United States. (vſ. 1.) “Frustules large, discoid or cylindrical; edges bevelled, central portion in front view, smooth or with iongitudinal parallel lines” (B.). We have seen frustules of this species with 3 processes. e A. punctatus (B.). — Frustules like those of A. pruinosus, but their lines so crowded and closely punctate that the lumose arrangement is scarcely visible. C. pl. 1. f. 9. United States. “This may prove a variety of the preceding; but the sparsely punctate surface of the one and the closely punctate surface of the other appear to offer a sufficient distinction between them” (B.). A. caelatus (B.).—Disc with unequal, strongly marked lines proceeding from the , margin towards the centre, but leaving a well-defined central, four- lobed or cruciform figure, with waved lines radiating in four sets from the umbilicus. BC. pl. 1. f. 3, 4. In sand from West Indian sponge, and in sound- ings from Mobile Bay. Umbilicus di- stinct, Smooth, the lines proceeding from it towards the processes in converging curves, the others variously flexed and anastomosing. 2* Umbilicus wanting or obsolete. A. Sculptus (Smith). — Disc with un- equal, strongly marked short lines, radi- ating inwards from the margin and leaving a well-defined central, four- lobed space, marked with four sets of fainter lines radiating from the centre. =Eupodiscus sculptus, SBD. i. pl. 4, f.42; Bri M.J. viii. p. 94, pl. 5. f. 3. England. (VI. 3.) This species resembles A. cae- latus, but has no umbilicus. We have not seem the striae of the central quatrefoil so strongly marked as in Professor Smith's figure, but always much fainter than the 846 SYSTEMATIC HISTORY OF TEIE INFUSORIA. marginal ones; indeed sometimes they are very indistinct. A. Americanus (E.). — Disc with strongly marked lines, radiating inwards from the margin and leaving an irregular central space destitute of lines. EM. pl. 33. 14. f. 2. United States. The large processes, as well as the central space, are without the radiating lines of A. sculptus; but we think it probable that Ehrenberg's figure was taken from a specimen of that species in which those markings were more than usually inconspicuous. A. cylindricus (E.).-Frustules cylin- vian gnanos. Communicated by Mr. Kitton. This species is distinguished by its oval disc and hispid elevations. The truncated processes do not in general correspond exactly with the longer dia- meter of the valve, but are placed a little on one side in opposite directions, in which respect, as well as in the presence of hair-like spines, it approaches Cera- taulus, Doubtful Species. A. polyStigmus (E.).--Radiating series of cellules converging in two lateral obsolete whorls, which appear perforated ſº. P). Cellules "14 in 1-1200". iam. 1-360". = Coscinodiscus polystigma, KA. p. 124. North Sea. A. P. gigas (E.).-Margin of sides tu- mid, looking as if perforated, sculptured by elegant rows of dotted, imperfectly radiant lines. E.M. pl. 19. f. 63. = Cos- cinodiscus Auliscus, . p. 126. Fossil. AEgina. , Ehrenberg's figure represents a mere fragment. drical, with a plane orbicular disc on each side, having a rim and a central area marked by various radiating lines; processes resembling oblique openings. A. ovalis (Arnott, MS.). — Disc oval, with two opposite, narrow, hispid ele- vations midway between the roundish perforation-like apices of the processes; curved lines punctate, rather faint; um- bilicus obsolete. Algoa Bay and Peru- FAMILY X.—BIDDULPHTEAE. Frustules cellulose, compressed; lateral valves entering into the front view, and usually more or less produced, at one or both angles, into processes. The Biddulphieae are remarkable for the great development of the lateral valves of the frustule, which are so convex or inflated as always to enter largely into the front view, causing the central zone to appear like a band between them. The mode of growth in this family is very interesting. Instead of simple elongation and subsequent division of the central Zone by means of internal septa, new central and inner lateral valves are formed within the elongated original one, which, until ruptured, retains the frustules in pairs. The central zone is at first very narrow and merely a broad line, but it increases greatly in breadth until the new frustules are fully formed. Genus CERATAULUS (Ehr.).-Frustules with turgid lateral valves, each valve with two tubular processes alternating with the same number of horn- like spines; lateral view orbicular or broadly oval. Cerataulus seems, in some measure, to connect the Biddulphieae with the Eupodisceae, since, in a lateral view, it approaches the latter in the circular form of some of its species; the front view, however, is similar to the other genera of this family: the frus- tules are binately conjoined by an external punctated sheath, and their pro- cesses are definite in number. Ehrenberg describes the frustules as simple, by complete fission; but Professor Bailey finds them concatenate. Cerataulus is characterized by having stout horn-like spines, which are not situated on protuberances between the two processes, but alternate with them, and form part of the same circle. CERATAULUs turgidus (E.). — Pro- | f 384; Ro TMS. vii. p. 17, pl. 2. f. 23. cesses short, broad, and truncate; lateral valves broadly elliptic, with a submar- ginal band of apiculi. EB. 1843, p. 270. Biddulphia turgida, SBD. ii. p. 50, pl. 62. Europe, America. Professor Bailey thus describes this species:—“Frustules glo- bular or slightly compressed, with two large prominences at each end, cohering OF THE BIDDULPEIIEAE. 847 by alternate angles, forming zigzag chains. Between the two processes, an in a plane at right angles to that con- taining them, are placed two long horn- like processes. Two frustules are often connected by an external decussately unctate cell, as in Isthmia and Bid- ulphia.” The processes do not exactly correspond with the angles, but are situ- ated a little to the side in opposite di- rections. This species, beautifully figured in Professor Smith's excellent work, is easily recognized by its broad, truncated processes. (VI. 8. C. Smithii (Ra..).-Valves in front view turgid; processes conic, alternating with Subulate horn-like spines; lateral valves orbicular; cellules distinct. = Eupodiscus radiatus?, SBD. i. p. 24, pl. 30. f. 255 (not Bailey); Biddulphia radiata, Ro TMS. vii. p. 19, pl. 2. f. 27–29. Thames. The orbicular form and differently shaped processes distinguish this species from the preceding. The cellules are not radiant; and as Professor Smith's name was bestowed in error, and is liable to mislead, we have thought it advisable to change it. C. laevis (E.). — Frustules large, qua- drangular, with short, broad, truncate processes and straight intermediate mar- gin; valves suborbicular, obscurely punc- tate, with two minute, opposite, subme- dian spines. = Biddulphia lavis, E.B. 1843, p. 122; Ro M.J. vii. p. 18, pl. 2. f. 24–26; Odontella polymorpha, KB. 1844, pl. 29. f 90; Isthmia polymorpha, Montague. Shores of North and South America. VI. 7. C. thermalis (Me.).-Large, joints cy- lindrical, angularly concatenated by a lateral isthmion ; lateral valves very smooth. = Melosira (Pleurosira) thermalis, Menegh. ‘ On the Animal Nature of Diat.,’ p. 391. Warm springs of Eugania. Length of frustules very variable. #. ing refers this to the preceding species, —a decision from which Meneghini dis- sents. The following extracts are taken from the work of the latter:-‘‘Kützing says, “Your Melosira (Pleurosira) ther- malis is in no respects different from the Odontella polymorpha. I'have compared your specimen with that of Montague. There are even found the delicate points upon the shield, as in the other, which I have inadvertently omitted in my figure. Your specimen is certainly an Odontella, although the articulations are cylindri- cal.’”. On this opinion Meneghini makes the following comments:– “Although I have had an opportunity of examining fragments only of Montague's Isthmia polymorpha, I am positive, in treating the matter differently. It is admirably figured by Kitzing; the articulations are not cylindrical, and, though obtuse and slightly prominent, the lateral processes are very evident.” For other distinctions between them, see the work quoted, p.483. Genus BIDDULPHIA (Gray). — Frustules compressed, quadrilateral, cohering by their alternate angles, and thus forming a zigzag chain; angles equal, elongated into tooth-like projections; spines none, or confined to the intermediate rounded projections; lateral valves constricted laterally at their base. Great difference of opinion exists as to the proper arrangement of the forms here associated, whether they should be included in a single genus or not. Ehrenberg and Kützing distribute them in two genera; but although their genera appear identical, yet their definitions differ so much as to make the agreement in fact merely nominal. Professor Smith unites Cerataulus and Zygoceros, as well as Odontella, to Biddulphia, whilst Professor Bailey, whose opportunities of studying this family have been so ample, admits the propriety of conjoining Biddulphia and Odontella, but is not prepared to add Zygoceros. Brébisson, who first 'conjoined Biddulphia and Odontella, subsequently recog- nized both genera. Ehrenberg and Kützing concur in describing Biddulphia and Odontella (Denticella, E.) as concatenate, and Zygoceros and Hemiaulus as simple. Ehrenberg distinguishes Biddulphia from Odontella by the ab- sence of spines, which are present in the latter. Kützing, on the other hand, characterizes Odontella as smooth (not cellulose, though often punctate or granulate), without internal septa, and Biddulphia as regularly punctato- cellulose, with internal septa. Smith finds spines in the typical species of Biddulphia; and Bailey considers the presence or absence of spines an unim- portant accident. We retain our former opinion, that we cannot exclude any 848 SYSTEMATIC HISTORY OF THE INFUSORIA. species from Biddulphia merely on account of the absence of costae, without violating natural affinity, and dividing Isthmia also. In Biddulphia, Kützing forms his species solely from the number of lateral costae and consequent divisions (chambers); his species, however, have been generally rejected; and we think that, like similar characters in Actinoptychus and other genera, such distinctions are essentially erroneous. * Valves with undulating margins and transverse costae or depressions. PIDDULPHIA pulchella (Gray).-Frus- tules distinctly reticulated; valves with obtuse processes, and from one to five smaller intermediate projections sepa- rated by costae extending to the suture. SD. ii. p. 48, f. 321. B. trilocularis, Kütz. (with two costae); B. guinquelocularis, Rütz. (with four costae); B. Septemlocu- laris, Kütz. (with five costae); Denticella Biddulphia, E. (central projection armed with spines); B. australis, Montague; B. elongata, Montague (with broad cen- tral portion). (II.46 to 50.) . The di- stinctive character of this species is the costae or imperfect septa which separate the projections. Lateral valves oval, with undulated margins and a large pseudo- opening at each end. In the young state there is only one rib, and no interme- diate projection. B. Regina (Sm.).-Valves with three median elevations, the central one largest, unarmed; processes little ex- ceeding the median elevation in length, º rounded; cellules of elevation istinct, those of valves and central zone minute. SD. ii. p. 50, pl. 46. f. 323; Ro TMS. vii. p. 8. , Dredged off the Island of Skye. Professor Bailey refers this species to B. tridentata, and Pro- fessor Williamson, according to Pro- fessor Smith, to B. Tuomey. We have seen no specimen, but trust to the well- known accuracy of Professor Smith's figures for its distinctness in the form and comparative shortness of its pro- CéSSéS. B. tridentata (E.). — Lateral valves dotted, having elongated, obtuse, pro- cesses, and one to three unequal inter- mediate projections; constrictions ap- proaching the suture. EM. pl. 19. f. 21. = Denticella tridentata, E. (central pro- tuberance armed); Denticella Tridens, E. Fossil. America. Professor Bailey re- fers B. Regina, Sm., to this species, but, judging from the descriptions and figures, they seem to us distinct. In this species the processes are more slender, longer than the intermediate projections, and mostly constricted beneath the apex. Mr. Roper unites this species to B. Tuomeyi, and is probably right in so doing. - B. obtusa (K.).-Frustules very smooth, short, with turgid, obtuse, short horns, and a very short intermediate process. = Odontella obtusa, K.A. p. 136. Heligo- land. (XIII. 30 to 32 A. B. subaequa (K.).—Frustules oblong, very smooth; horns minute, withoutinter- mediate projections. = Odontella subaequa, KB. pl. 18.8. f. 4, 5, . Heligoland. Pro- fessor Smith is probably right in regard- ing the last two as states of B. aurita. B. laevis (E.).-Has the habit of B. aurita, but its valves are smooth and tridentate. = Denticella lavis, E.M. pl. 33. 15. f. 6. Antarctic Sea. Diam. 432". Ehrenberg's figure of this species but slightly resembles B. aurita: the horn- like processes are elongated, slender, and awl-shaped, and not the least inflated at the base; the intermediate margin also is convex, and not elevated into a central projection. B. Tuomeyi (B.).-Valves having ob- tuse horns with swollen bases, between which are from one to three shorter, rounded projections, the middle one largest, and often bearing two spines. = Zygoceros Tuomeyi, BAJ. xlvi. pl. 3. f. 3 to 9. Fossil. America, Patos guano. (VI. 10.) The central zone is narrow- linear, and slightly projects at each end; lateral valves covered with shagreen-like asperities, which are most evident on the projections; processes generally con- stricted. At the base of each swelling is a short, linear, hyaline line which re- 'sembles a perforation, but which we be- lieve is really a smooth elevation. B. polymera (E.). — Lateral valves granulated, very broad and short; angles elongated into conical processes; inter- mediate projections several (about nine), rounded, the central one largest. = Denti- cella P polymera, E., BAJ. xlviii. pl. 4. f. 20; Odontella? polymera, K.; B. Tuomeyi, Ro TMS. vii. p. 8. Fossil. Bermuda. The lateral valves are so short that the constrictions between the lobes reach nearly to the base. This species is remarkable for the great num- ber of intermediate projections, of which OF THE BIDDULPHIEAE. 849 the central one is the largest, the others decreasing regularly on each side, two of them armed. Mr. Roper unites this form, probably correctly, with B. Tuomey. 2" Valves lanceolate or elliptical, without wndulated margins (Odontella, Ag.). B. aurita (Lyngb., Bréb.).—Frustules finely º angles prolonged into slender comical horns, with an interme- diate projection, which is usually fur- nished with a few spines; valves elliptic- lanceolate. SBD. ii. p. 49, pl. 45. f. 319, = Odontella aurita, Ag., K. ; Denticella aurita, E.; Denticella gracilis, E. Ame- rica, Africa, Europe. - B. Roperiana (Grev.).-Valve elliptical oval, with central elevation, which in front view is depressed or sometimes bilobed, punctate, unarmed; angular pro- cesses scarcely produced, obtuse, largely inflated at base; connecting zone with rows of minute granules, parallel with suture of the valve. Grey JMS. vii. p. 163, pl. 8. f. 11–13, Seaweed, Mon- terey; &iº guano. “This species appears to be removed from B. aurita and its varieties by the absence of spines, and the very depressed, often two-lobed cen- tral elevation of the valve '' (Grev.). B. longicruris (Grev.).-Valve in front view with central elevation, bearing a very long spine ; angular processes very much produced, awl-shaped; surface º granulate. Grev JMS. vii. 3. 163, pl. 8. f. 10, Californian guano; ierra Leone. B. turgida (E.).--Lateral portions in front view scabrous, with produced, comical, obtuse angles, and two distant, long, intermediate spines; valves elliptic- lanceolate. = Denticella turgida, E.B. 1840, p. 207; Odontella turgida, KB. t. 18. f. 89; Biddulphia granulata, Ro TMS. vii. p. 13, pl. 1, f. 10, 11. Atlantic. Britain. Processes large, inflated at base, slightly recurved; spines generally slightly bent at the middle ; valves rough with minute apiculi. B. reticulata (Ro.). —Valves hirsute, with large hexagonal reticulations; processes obtuse, subconic, inflated and gibbous at the base. Ro TMS. vii. p. 14, bl. 2. f. 14–17. Ceylon, Natal, New Zealand. Valves elliptic; connecting zone having rows of rather conspicuous dots. B. Indica (E., Ro.).—Valves hirsute, with slender, elongated, subcapitate pro- cesses, and a long awl-shaped spine near each process, Ro TMS. vii. p. 16, pl. 2.f.20–22. = Denticella Indica, ERBA. 1845, p. 362. Natal, (v1.12.) Valves lanceolate, with the pseudo-apertures at right angles to the length of the valve, Roper. ... fumida (E., Ro.).-Valves broadly elliptic, with very fine radiating dots, and, two or three submarginal spines; in front view globose, with tapering obtuse processes. Ro TMS. vii. p. 15, pl. 2. f. 18, 19, = Denticella tumida, ERBA, 1844, p.266; Odontella tumida, KSA. p. 137. Bermuda; Californian guano, - B. Macdonaldă (Norman, MS.). — Frustules finely striated, with very short, nearly obsolete processes; valves with transverse striae interrupted by a median line. Shark's Bay, Australia. (VIII. 23.) Valves minutely dotted between the striae; frustules somewhat twisted. For the description of this species we are indebted to G., Norman, Esq. Doubtful or imperfectly known Species. B. P. brevis º-º. laterally lan- ceolato-rhomboid, smooth, tripartite with two septa; lateral portions also three-lobed; lobes small, subequal; pseudo-openings obsolete. KA. p. 138. Portugal. B. P. gigas (E.).--Large, very turgid at the centre, rough, without distinct granules, laterally five-jointed, having a large, oblong (pseudo-) opening at each attenuated apex. RSA. p. 138. Fossil. Bermuda. †. 1–144". B. P. lunata (E)-Valve three-lobed, Smooth, slightly curved, lunate, with subacute horns. EMI, pl. 18. f. 53. Fossil. Virginia. Diam. 1-864". B. P. ursina (E)-Large, turgid, not cellulose; sides hirsute, not constricted, middle part Smooth. KSA. p. 138, fragment. Antarctic regions. Diam. 1-192". Remarkable for its hairiness. B. P amphicephala (E.).--Smooth, mar- row, Wand-like, concatenate, constricted beneath each apex; hence each end capi- tate, rounded. = Odontella? amphicephala, E. ... KSA, p. 137. Mouth of the Tagus. Individual frustules resemble those of Navicula dicephala in habit. B. P. Fragilaria = Denticella? EMI. pl. 21. f. 31. Algiers. Perhaps a frag- ment of Eucyrtidium lineatum. B. P. Cirrhus (E.).-In Barbadoes earth. We have seen neither description nor figure of this species. 3 I 850 SYSTEMATIC EIISTORY OF TELE INFUSORIA. Genus PORPEIA (Bailey, MS.).—Frustules simple (?), compressed, each valve with two short obtuse processes, and two internal curved plates which do not extend to the central portion. We give this genus in deference to the opinion of our highly esteemed correspondent the late Professor Bailey, but doubt whether it is sufficiently distinct from Biddulphia. In Porpeia the septa appear like costae incurved at their inner ends. PorpFIA quadriceps (Bai. MS.).-Pro- cesses with punctated rounded ends, the intermediate margins slightly convex; lateral view narrow, with two constric- tions, and rounded ends. Gulf-stream. (VI. 6.) From drawings by Professor Bailey. “At first sight this species suggests a relation to Grammatophora; but the curved plates run at right angles to their position in that genus (i. e. not parallel to the division of the frustules, but perpendicular to it).”—B. in lit. Genus ZYGOCEROS (Ehr.).-Frustules free, compressed, not concatenated; each valve with two (apparently) perforated horn-like processes. Although we have retained this genus, yet we think it is very probable that a better knowledge of its species will justify Professor Smith in uniting it with Biddulphia, from which it differs only in its simple frustules. ZYGoCERos Rhombus (E.).-Frustules turgid, with a smooth or faintly punc- tated central portion; lateral valve rhom- boid with rounded angles, its surface having very fine granulated striae. = Biddulphia Rhombus, SBD. ii. p. 49, pl. 45. f. 320; Ro TMS. vii. p. 11, pl. 1. f. 4. America, Europe, England. 8, valves with one or more median spines, = Den- ticella Rhombus, E.; Odontella Rhombus, K. Large; striae 24 to 26 in 1-1150". Diam. 1-720". “Spines submarginal, awl-shaped, abbreviated” (Sm.). Z. radiatus (B.). — Frustules large, turgid; lateral valve rhomboid, with rounded angles and radiating series of granules. BSC. vii. Z. Balaena, EM. pl. 35. A. 23. f. 17; Bri JMS. vii. p. 181, bl. 9. f. 15. Nova Scotia. “Akin in ſº to Z. Surirella, but larger than Z. Rhombus. (Ehr.). Z. Surirella (E.). —Frustules small; lateral valve lanceolate, with constricted obtuse apices; surface with transverse granular lines, interrupted by a median longitudinal band. Ro TMS. ii. pl. 6. f. 11, 12. Alive. Europe. Thames. (XI. 50, 51.) Diam. 1-720". Central por- tion smooth, granules of valves more di- stinct than in Z. Ithombus. Distin- guished by the Smooth longitudinal line in a lateral view. Z, Bipons (E.).-Frustules laterally ianceolate, with acute ends, and two smooth median constrictions; granules delicate, not radiant. KSA. p. 139. Bermuda deposit. Diam. 1-384". Angles with small horns. May be known by having, in the lateral view, two trans- yerse lines, Central zone punctated '' Z. stiger (E.).-Frustules laxly cellu- lose ; valves with double median con- striction of the side; angles produced into long, acute, stiliform horns. KSA. p. 139. Fossil. Bermuda deposit. Diam. 1-1152", “Z. stiliger may be a species of Hemiaulus; but the constrictions resem- ble those of Biddulphia, save that they *. º wide apertures of the horns” alll’. ), Z. australis (E.).-Frustules smooth; horns obsolete; lateral valve turgid- lanceolate, with conspicuous pseudo- openings. KSA. p. 139. Antarctic Sea. Diam. 1-480". Z. PCircinus (B.).—Frustules minutely and decussately punctate; lateral valves forming truncated cones without pro- cesses, ºbut each having two long, seti- form, bent spines; lateral view elliptic. BC. vii. pl. 1. f. 19, 20. Fossil. Vir- ginia. Characterized by the comic out- line of the lateral valves, and the absence of processes. Z. Navicula, EM. pl. 19. f. 22. Fossil. Greece. Lateral valve oblong, with transverse rows of dots, a transverse Smooth median band, and a pseudo- opening at each end. Z. paradoacus (E.). —Smooth, laterally linear-oblong with rounded ends. EMI. pl. 22. f. 54. = Surirella paradoaca, EMI. Caltanisetta, Sicily. 1-576". Z. Siculus (E.). — Smooth, linear; laterally rhomboid, with obtuse ends. EM. pl. 22.f. 53.3- Surirella rhomboidea, EM. Fossil. Sicily. 1-744". Z. Mobiliensis (B.). — Frustules qua- drangular, thin, delicately punctate; valves with slender, tapering lateral | processes, and two slight intermediate OF THE BIDDULPELIEAE. 851 projections armed with one or two ver long filiform spines. BC. 1859. = Bid- dulphia Baileyi, SBD. ii. p. 50, pl. 62. f 322; Ro TMS. vii. p. 12, pl. I. f. 5–9. America. In stomach of Ascidiae. Hull, Teignmouth. (VI. 11.) Frustules fra- gile, yellowish. A well-marked species; there is nocentral projection of the valves, but two slight elevations, furnished with one or more bristles, and dividing the margin into three nearly equal portions. The elevations appear situated between the processes, but are really placed on opposite sides. Genus HEMIAULUS (Ehr.).-Frustules compressed, subquadrate; fission perfect, hence not concatenate; valves without lateral constrictions, each with two processes—that of the one side (apparéntly?) open, the other closed. The genus has the habit of Biddulphia, but is devoid of the lateral constrictions. It has the form of a Pandean pipe. As the valves are not constricted, the basal angles are rectangular, and the Outer margins of the processes (which are generally attenuated, narrow, and elongated) are straight. HEMIAULUS antarcticus (E.).-Frus- tules strongly granular; lateral processes elongated, of one valve truncate, of the other elongated; a short median rounded projection between the processes. EMI. } 35. A.22.f. 15. Antarctic Sea. (XI. 54.) iam. 1-1152". Granules in parallel TOWS. H. Polycystimorum (E.).--Angles ex- tended into very long, narrow, linear, horn-like processes, which are attenuated at the extremity, and, as well as the base, cellulose. EM. pl. 36. f. 43. Barbadoes deposit. Between the processes are from one to three slight projections; lateral view oval, bordered, having transverse bars corresponding in number to the de- pressions. H. P. Australis Sºlº strongly granulate; lateral processes rounded, intermediate one obsolete. KSA, p. 139. Antarctic Sea. H. P. Californicus (E.).-Valve granu- late, having a subquadrate base; angles extended into linear processes without intermediate projections. EM. pl. 33.13. f 15. In Californian tripoli. Genus ISTHMIA (Ag). — Frustules compressed, trapezoidal, cellulose, attached, cohering by short neck-like processes, so as to resemble irregularly branched filaments. Frustules always more or less oblique, the lower angle of each prolonged into a process by which it coheres to the one beneath, and which in the basal frustule forms the stipes by which the filament is attached. The frustules are turgid, and the reticulations of the central portion smaller than those of the sides. ISTEIMIA emervis (E.).--Lateral valves with large, somewhat quadrate cellules arranged in transverse parallel lines. = Conferva obliquata, EB. t. 1869; I. obliquata, Ag, ; I nervosa, KSA. p. 135; E Inf. p. 209, pl. 16. f. 6; SBD. ii. p. 52, 1. 48. Europe, America, Cape of Good Hope, &c. (x. 183.) The lateral por- tions are separated from the central one by rather broad lines, produced by the junction and inflection of the margins, and which form internally projecting plates or rims. The cellules bordering the sutures are -somewhat larger than the other cellules of the central portion, but less remarkably so than in the next species. I. nervosa (K.).—Lateral portions with parallel transverse costae, having two or more series of hexagonal cellules in each interval. = Diatoma obliquatum, Lyng. ; I. obliquata, E.; I nervosa, K.A. 135; S.D. ii. p. 52, pl. 47. Northern shores of Europe and America. This is usually a more northern species than I, emervis. The cellules are smaller, except a series of large conical ones bordering the inner side of the sutures, and the frustules are generally not so wide in proportion to their length; but the most evident di- stinction is the division of the lateral portions into compartments by the costae, which often anastomose. - I, minima (Harv. & B.).--Central por- . tion very finely decussately punctated; lateral portions granulated by large cellules. Proc. of Acad. of Phil. Rio de Janeiro and Sooloo Sea. Imperfectly known. I. P. Africana (E)-Large flat frag- ments resembling the central portions of 3 I 2 852 systEMATIC HISTORY OF THE INFUSORIA. Isthmia, marked by transverse rows of ERBA, 1844, p. 83. Diameter of largest very minute cellules. Oran, Africa. fragment 1-216". Genus HYDROSERA (Wallich).-Frustules quadrate, united into fila- ments, and furnished with conspicuous horizontal bands or septa; valves cellulose, compressed, or triangular, with internal Septa, and, on one side only, with minute, aperture-like appendages. Marine. Filaments elongated, attached, compressed, or prismatic. Joints rectangular, connected at the angles by mucous cushions, and marked by bands passing across the valves and connecting zone. In the lateral view the ends or angles are separated by septa. Hydrosera seems allied on the one hand to the Terpsinoëae, and on the other to the Biddulphieae and Angulifereae. HYDROSERA compressa (Wallich). — Filaments compressed; valve oblong, divided into three inflated compartments by two transverse septa. Wallich, M.J. vi. p. 252, pl. 13, f. 7–11, East Indies. Side view with blank angles, occasionally furnished with a few minute spines. VI. 8. ( H. triquetra (Wallich). — Filaments triquetrous; valves triangular, with the subcircular centre divided from the ob- tuse, somewhat produced angles by septa. Wallich M.J. vi. p. 251, pl. 13. f. 1–6. East Indies. Front view with four transverse bands; valves with un- dulated sides, reticulated, except at the angles, which are furnished with a few extremely minute spines (VI. 13.) FAMILY XI.—ANGULIFEREAE. Frustules cellulose or granulate ; in lateral view angular. This family is closely allied to Biddulphieae (and in some manner connected with the Cosci- nodisceae and Eupodisceae). As in that family, the lateral portions are seen, in the front view, having the central portion like a band between them. Hence, in order to determine their proper family, it is frequently necessary to see them laterally. The angles, however, in the front view are usually less elongated, and the intervening margin less lobed in the Angulifereae than in the Biddulphieae. Genus EUODIA, n, g. (Bailey, M.S.).-Frustules cellulose or granulate ; in lateral view lunate. Euodia agrees with the Eunotieae in the shape of its frustules, which can scarcely be called angular ; yet, notwithstanding that resemblance in form, its punctate or granulate surface induces us to place it here. EUODIA gibba (Bai, M.S.).-Frustules in lateral view semilunate, the ends somewhat comical, the lower margin gibbose; surface with radiating series of minute granules. Recent. Gulf Stream. (VIII, 22.) From a drawing by Pro- | fessor Bailey. The upper margin is very convex, the lower one less so. A con- traction near the obtuse ends makes them appear somewhat produced and conical. Professor Bailey represents the cross section as cuneate. Gondothecium amaulis, EM. t. 33. 18. f. 4, greatly re- | nate, ends scarcely produced, sembles this species, and may be iden- tical. The upper margin, however, is represented as more convex, the ends less roduced, and the granules larger and €SS Illllllel'OllS. E. P. Brightwellii. — Frustules semilu- * lower margin concave; granules somewhat concentric. = Triceratium semicirculare, BriMJ. i. p. 252, pl. 4. f. 21. Bermuda. earth. T. obtusum, EMI, pl. 18. f. 49, may probably be referred to this species. Genus HEMIDISCUS (Wallich).--Frustules free; valves cellulose, arcuate, with a ventral marginal module; cellulation hexagonal, radiate. Marine. We doubt whether Hemidiscus be distinct from Euodia, since the only di- OF THE ANGULIFEREAE. 853 stinction seems to be the marginal nodule of the former, a character perhaps overlooked by Professor Bailey. HEMIDISCUS cuneiformis (Wallich).- # pl. 2. f. 3, 4. Bay of Bengal and Valves semilunate; venter with a mar- || Indian Ocean. Cellulation distinct, ginal row of puncta, and slightly gibbous largest at the centre. Connecting zone at the middle, Wallich, TMS. viii. broadest at the dorsum. (VI, 14.) Genus TRICERATIUM (Ehr.).-Frustules cellulose, free, simple; in lateral view triangular (rarely with four or five angles). This genus has been well illustrated by Mr. Brightwell in his excellent monographs published in the ‘Journal of Microscopical Science;” so that the species can be distinguished without much difficulty. His discovery, in more than one species, of frustules with four or even with five angles, shows that in this, as in several other cases, the number of parts do not afford good generic distinctions. We were inclined to place greater reliance upon their complete fission; but Professor Bailey in- formed us that he had met with Catemate specimens. Mr. Brightwell, indeed, says that “the projection of a connecting membrane (central portion) beyond the suture of the valve, which is one of the characters of the genus Amphi- tetras, is not seen in the square forms of Triceratium;’ but we greatly doubt the validity of this distinction. “One of the difficulties attending the study of this genus, and the determination, especially in the fossil forms, of the species, arises from the difficulty of obtaining perfect frustules, and examining them in their front aspect. The imperfect frustules present only the end or triangular wall, from which alone no perfectly satisfactory specific character can be obtained?” (Br.). The descriptions, unless otherwise specified, apply to the lateral view of the frustules, and are drawn up, with few exceptions, from Mr. Brightwell’s monographs. * Lateral surfaces spinous. TRICERATIUM spinosum (B.).-Sides nearly straight; angles prolonged into horn-like processes; granules minute; spines numerous; front view constricted beneath the processes. Silliman's Jour- mal of Science, xlvi. pl. 3. f. 2. = T. Set- gerum, BC. 1854, pl. 1, f. 24; T armatum, Ro M.J. ii. p. 283; T. tridactylum, Bri M.J. i. p. 248, pl. 4. f. 3, Fossil, Ame- rica; recent, England, Florida. (VI. 19.) A variable species; its numerous spines and somewhat triradiate form best distinguish it, Larger spines are often interspersed among the Smaller ones. T. compactum (Bri, M.S.). —Spinous; front view constricted beneath the some- what inflated processes; central portion bordered by a series of large cellules, = T. armatum, 8, Bri M.J. iv, p. 274, pl. 17. f. 11. Recent. Australia. Smaller than T. spinosum, but like it in form, having a spine on the middle of each side. In the front view it is very different. T. coniferum (Bri.). — “Sides irregu- larly concave; angles drawn out into an extended cone with a short, stout horn near each; centre of frustule convex, with three setae.” Bri M.J. iv. p. 274, t. 17. f. 6. Shell cleanings. The mam- millate angles, giving the sides a waved appearance, mark the species. The gra- nules are not radiant. T. contortum (Shi)—Angles prolonged into curved horn-like processes; spines in three radiate double rows, terminating near each angle with a long bristle. Sh TMS. ii. p. 15, pl. 1.f. 7. Recent. Natal, (VI. 18.) Well distinguished by its con- torted angles. Sides straight. T. orbiculatum (Sh.).--Sides convex; angles obtuse, each with a circular pseudo-nodule accompanied by a spine; granules minute, radiating. Sh TMS. ii. p. 15, pl. 1.f. 6. Natal. The front view shows the narrow central portion marked like the lateral portions, which are large, not constricted, and terminated by three truncated comes. Mr. Brightwell enter- tains no doubt as to the identity of his specimens with Mr. Shadbolt's species; yet the latter's figure has no spines, and he describes “the margin being so in- flated as to cause the triangular outline to approach that of the circle.” T. Marylandicum (Bri.).--Sides nearly straight, with rounded angles, without 854 SYSTEMATIC EIISTORY OF THE INFUSORIA. pseudo-nodules; granules minute, radi- ating from an angular umbilicus; spines few, marginal. BriMJ. iv. p. 275, pl. 17. f. 17. Maryland deposit. There is at each angle a short spine, and sometimes another at the middle of each margin. Professor Bailey regards this species as identical with T. Amblyoceros; but we cannot believe that Ehrenberg would have omitted so remarkable a character as the angular umbilicus, nor are both species found in the same deposit. We have already given our reasons for doubt- ing the correctness of the supposition that Ehrenberg founded his Symbolo- phora Trinitatis upon this species. T. annulatum (Wallich).-Valve mi- nute, with slightly produced rounded angles and concave sides; surface marked with concentric rings, and a ray proceed- ing from the centre towards each angle. Ganges. Wallich, M.J. vi. p. 249, pl. 12. f. 15. Valves covered with minute puncta, aggregated into concentric rings. 2* Lateral surfaces with radiating vein-like lines. T. radiatum (Bri.). — Sides straight; angles obtuse; radiating lines most evi- dent at centre and margin; granules minute, radiating. Br. l.c. p. 275, pl. 17. f, 14. Barbadoes deposit. Frustules large, without horn-like processes. T. marginatum (Br.). — Valves with a triangular centre, which is surrounded by a broad border divided into compart- ments by short transverse lines. BFMJ. iv. p. 275, pl. 17. f. 13. Fossil. Sides straight, angles with double pseudo- modules; granules of centre minute, radiating, those of compartments larger and Scattered. - T. venosum (Br.). — Sides concave; angles rounded, surface dotted, and marked by three radiating pinnated lines or veins. (VI. 17.) Br § . v. p. 274, É. 17. f. 5. Barbadoes deposit. A very eautiful and distinct species. T. tabellarium (Br.).-Margin indented in foliaceous curvatures; granules nume- rous near the margin, elsewhere in atches; angles with small horns. Br M.J. iv. p. 275, pl. 17. f. 15. Honduras. This species is well distinguished by its Scolloped margin. It is doubtful whe- ther it is properly placed in this section. T. variabile (Br). — Surface with a transverse line below each angle, and Some irregular radiating veins; granules Scattered, indistinct at the ii. Br M.J. iv. p. 275, pl. 17. f. 19. Feruvian guano. Resembles T. alternans, but is larger and generally distorted; the angles are conical. Mr. Brightwell figures a quadrangular form of this species. T. truncatum (Br.).--Angles elongated into broadly truncate arms, centre di- vided into granulated compartments by radiating vein-like lines. Br M.J. iv. . 274, pl. 17. f. 4. Barbadoes earth. 3rustules triradiate. - 3* Lateral surfaces with transverse lines separating the angles from the hearagonal Centre. T. brachiatum (Br.).-Triradiate; an- gles elongated into truncate arms, and separated from centre by transverse lines. Br M.J. iv. p. 274, pl. 17. f. 3. Barbadoes earth. Distinguished by its angles pro- longed into rays. It resembles T. trun- catum in form, but is Smaller, and has no radiating veins. T. alternans (Bai.). — Sides straight, angles obtuse, granulated like the hexa- gonal centre. SBD. i. p. 26, pl. 5. f. 45. Common, recent and fossil. England, United States guano. (VI. 21.) Front view quadrate, not constricted; the angles not prolonged into processes. T. trisulcum (Bai. MS.). — Sides very concave; angles broadly rounded, sepa- rated from centre by transverse lines; granules crowded and very minute at angles, elsewhere few, large, and Scat- tered. (VIII. 27.) From a drawing by Professor Bailey. Gulf-stream shells, W. Indies. This species may be known by its distant granules. - T. castellatum (West).-Sides of the frustule deeply concave; angles forming segments of circles. Valves with con- cave sides and rounded angles, forming dome-shaped eminences; surface punc- tate, with a single row of larger puncta along the opposed margins. West, TMS. viii. p. 148, pl. 7. f. 3. Barbadoes deposit. (VIII. 29.) - T. Johnsoni (Ralfs, n.s.).-Valves with rounded angles and concave sides, sur- face with scattered granules, and a large granulated space at the angles, separated by a transverse smooth band; margin with a few short lines. Barbadoes #. posit. Johnson. Valves large, with conspicuous granules, which are few at the centre, and more numerous near the margin; each side with a few short striae like those figured by Mr. Brightwell in T. tabellarium, but the margin itself is not undulated. T. umbilicatum (Ralfs, n.s.). —Valves OF TEIE ANGULIFEREE. 855 with broadly rounded angles and deeply sinuated sides, triangular Smooth um- bilicus, radiant series of close granules, and a large punctate space at each an- gle. Barbadoes deposit. Johnson. This large and beautiful species is distin- guished by the sinuated sides and tri- angular umbilicus of the valves. Gra- mules conspicuous and dense, appearing both radiant and concentric. The large angles are separated by indistinct trans- verse lines, and appear Smooth or granu- lated according as they are more or less in focus, and they have a central round spot (probably a process), and striated margin. This species differs from T. castellatum in a distinctly radiant ar- rangement of the granules and a smooth umbilicus. . T. megastomum (E.).-Sides straight; angles obtuse, with pseudo-nodules, and separated by transverse lines from the hexagonal centre. EM. pl. 35. In guano. Small, somewhatresembling T. Reticulum, but differing in its pseudo-nodules and hexagonal centre. - 4* Sides in lateral view gibbous or un- dulate (angles without pseudo-modules; cellules minute). T. undulatum (E.). — Sides slightly convex, undulated; granules minute, radiating, Br M.J. i. p. 250, pl. 4. f. 13; ERBA. 1840, p. 273, Fossil. Bermuda and Virginian deposits. T. Brightwelli (West). — Sides of valves undulate, slightly convex, or straight; granules minute, radiating from the centre, from which proceeds a spine of considerable length; margin of valve closely set with short spines. = T. wndulatum, Br M.J. vi. p. 154, pl. 8, f. 1–5, 8; West, TMS. viii. p. 149, pl. 7. f. 6. War. 3 with 4 angles. In Noctilucae. England. The discovery of this and the following species in a living state has explained the appearance of the central pseudo-module, which has proved to be the remains of a long horn or spine. T. intricatum (West).-Sides of valves undulate; angle acute and slightly pro- duced; centre tumid; granules in lines, radiating from the centre, Scarcely dis- cernible; pseudo-module º = T. striolatum P, S.B.D. i. p. 27, p wndulatum, Bri. l. c.; West, TMS. viii. . 148, pl. 7, f. 5, . This species in its iving state forms short filaments united in a distant series. T. striolatum (E.). — Sides convex, slightly undulated; angles attenuated, ending in minute papillae, KB, t. 18. . 5. f. 46; T., f. 10. = T. membranaceum, Br M.J. i. pl. 4. f. 15. Thames mud, Cuxhaven. Wii. of the frustule extremely delicate, dotted over with very minute cellules. T. Parmula (Br.). — Sides gibbous, with produced mammiform angles; Sur- face minutely punctated. Br M.J. iv. p. 275, pl. 17. f. 2. Natal. War. 8 with 4 angles. West, TMS. viii. p. 147, pl. 7. f. 1. Frustules minute, in outline re- Sembling a shield. T. Americana.-Sides convex, slightly undulated; angles rounded; cellules minute. = T. Amblyoceros ?, Br M.J. i. § 250, pl. 4. f. 14. Fossil. Richmond, irginia. The rounded angles without appendages distinguish this species from the others in this section. T. margaritaceum (Ralfs, n. S.). — Valves with rounded angles, and straight or slightly convex sides; surface with conspicuous pearly granules, which are scattered at a triradiate central space, and arranged in radiating lines at the margin. Barbadoes deposit..' Johnson. The valve is bordered by a row of larger granules; and only a narrow inconspicu- ous terminal portion of the angles appears Smooth. - T. gibbosum (Harv. & Bail.).-‘‘Almost inflato-globose, the sides very convex, angles prominent; surface marked as in T. concavum.” Small. Proc. of Acad. of Nat. Sci, Philadelphia, 1853. Tahiti. 5* Frustules not spinous, Sulcate, veined, nor wºndulate. f Cellules large, hexagonal. T. Favus (E.). — Sides straight or slightly convex; angles obtuse, with horn-like processes; surface reticulated with large hexagonal cellules. (XI, 43, 44.)= T. megastomum, BryIJ. i. pl.4 f.73; T. fimbriatum, Wallich M.J. vi. p. 247, pl. 12. f. 4–9, Recent and fossil, not uncommon. Diam. 1-200" to 1-150". Front view with the central portion mi- nutely punctated, the lateral portions scarcely constricted beneath the short stout processes. Mr. Brightwell figures a quadrilateral form of this species with concave sides. - T. serratum (Wallich).-Valves (qua- drilateral) furnished with a horn-like process at each angle, and from 4 to 6 elongated scattered spines, with furcate apices; sides or plates of connecting zone º by dovetailed margins. Wallich, M.J. vi. p. 243. pl. 12. f. 1–3. St. Helena. Connecting zone as well as valves marked with a delicate but well-defined hexa- 856 SYSTEMIATIC E[ISTORY OF TELE DNFUSORLA. gonal areolation. This species is re- markable chiefly for the peculiar struc- ture of its connecting zone, the plates having their communicating margins serrated so as to fit into each other. T. grande (Br.). — Sides convex; angles attenuated, obtuse; hexagonal cellules numerous. Diam. 1-100". Br M.J. i. p. 249, pl. 4, f. 8. T. orientale, Harv. & Bail. l. c. Indian Seas, Min- danao, “The largest and stoutest spe- cies of this genus” (Br.). The descrip- tions do not suffice to distinguish this species from large specimens of T. Favus. T. muricatum (Br.).-Sides straight; angles ending in a stout horn-like pro- cess; cellules large, hexagonal. Br M.J. i. p. 249, pl. 4. f. 5. From the cleanings of shells. A minute species, distinguished by its pointed angles. Front view nearly Square, with the central portion smooth, and the lateral ones turgid between the prominent processes. T. ocellatum (E.).-Sides slightly con- cave; angles attenuated, obtuse; cellules unequal, large, hexagonal in the centre, gradually becoming smaller at the sides, in no distinct order. KSA, p. 141. Mouth of River Tenasserim, India. 2+ Lateral surfaces with three pseudo- nuclei, not situated at the angles. T. Sculptum (Sh,). — Sides straight; angles prolonged into conical points; granules Scattered; surface with three circular pseudo-nuclei, one opposite the middle of each side. Sh MT. ii. pl. 1. f. 4. Natal. In form this species some- what resembles T. acutum; but its pseudo- nuclei are eminently characteristic. 3t Frustules triradiate, with very concave sides. T., Solenoceros (E.).-Triradiate, with deeply concave sides; angles prolonged into long, linear, obtuse arms; cellules radiating. Br M.J. i. p. 248, pl. 4. f. 1. Bermuda earth. (VI. 15.) This species differs from every other by its long linear rays, which have neither pseudo-nodules nor processes. T. Pileus (E.).--Somewhat triradiate, with very concave sides; angles tapering, obtuse, with pseudo-modules; cellules minute, radiating. EM. pl. 19.f. 18. = T. brachiolatum, Br M.J. i. pl. 4. f. 2. Fossil, Greece; recent, New Zealand. Mr. Brightwell refers his T. brachiolatum to the next species. - T. Pileolus (E.). — Somewhat trira- diate, with very concave sides; angles produced, obtuse, with pseudo-nodules; cellules small, scattered. EM. pl. 35 A. 21, f. 17. = Tº obtusum, Br M.J. iv. * 251, pl. 4, f. 20. Antarctic Ocean. esembles T. Pileus in form, but is Smaller, and its cellules are scattered. 4t Frustules not triradiate; angles with pseudo-nodules, or minutely punc- tated. T. concavum (Harv. & Bail.).-Sides very concave; angles rounded, minutely punctated; cellules of centre arranged in simple and forked radiating lines. H. & B, Trans, of Acad. of Philadelphia, 1853. Tahiti. T. Wallichii (Ralfs). — Valves with minute radiate areolation, a row of mar- ginal puncta, and a minute horn-like rocess at each angle. = T, punctatum, allich, TMS. viii. p. 48, pl. 2. f. 21. India, Atlantic. T. arcticum (Bri.). — Valves with slightly convex or straight sides; areo- lations Small, but distinct, radiating in lines from the centre, and becoming mi- nute at the angles, which are rounded and slightly inflated. = T. Wilkesii, var. 8, with 4 angles; Amphitetras Wilkesii, Bri M.J. i. p. 250, pl. 4. f. 11; Ro TMS. viii. p. 58. Beechey Island, Arctic Regions; Puget's Sound, Vancouver's Island; and Montery stone. The speci- mens obtained from Vancouver's Island have proved that Triceratium has been erroneously considered a free form, and that its proper position is with Amphi- tetras and Biddulphia; the specimens alluded to show it attached to Zoo- phytes, and the frustules connected at the angles by a short stipes or cushion, exactly like Amphitetras. T. Montereyi. (Br.).-Sides concave; angles rounded, with pseudo-nodules; cellules minute, largest in the centre, which is much inflated. Br M.J. i. p. 251, pl. 4. f. 8. Fossil. Monterey Bay. This species is easily distinguished from T. arcticum by its central boss and larger cellules. T. punctatum (Br.). — Sides straight; cellules large, puncta-like, scattered, Smaller at the rounded angles. Br M.J. iv. p. 275, pl. 17. f. 18. Arctic Regions. (VI. 20.) 5f Angles without pseudo-nodules. T. formosum (Br). — Sides slightly concave; angles obtuse, without pseudo- nodules; cellules very minute, somewhat radiating. Br M.J. i. p. 250, pl. 4. f. 10. Shell cleanings from Hippopus maculatus. OF TELE ANGULIFEREZE. 857 Mr. Brightwell finds this species varying, with four and five angles. The front view is quadrate, not constricted, the angles produced into conical processes, between which the margin is nearly straight. T. condecorum (E.).-Sides straight or slightly convex, with obtuse angles; cellules very minute, diverging in curved series. Br M.J. i. p. 250, pl. 4. f. 12. Fossil. Bermuda. T. obtusum (E.).-Sides very convex; angles rounded, without pseudo-modules; cellules circular, scattered, EMI. pl. 18. f. 48, 49. Virginia. T. Amblyoceros (E.).—Sides concave; angles broadly rounded, without pseudo- nodules; cellules minute, somewhat radiating. EM. pl. 18. f. 51. Virginia. This species has more rounded angles and Smaller cellules than T. obtusum. T. Reticulum (E.).-Sides straight; angles subacute,without pseudo-nodules; cellules minute, numerous. EM. pl. 18. f, 50. Fossil, America; recent from shell-cleanings. Front view with a nar- row, Smooth central zone; lateral sur- faces not constricted beneath the slightly prominent angles. T. acutum $º. nearly straight; angles elongated into points; cellules not radiating, Br M.J. i. p. 251, pl. 4. f. 16. Bermuda, T. acutum is somewhat tri- radiate from its aſcuminated angles. Doubtful or insufficiently known Species. T. Scitulum (Br.), “A Small species, but varying in size. On some of the frustules I have reckoned, on an end view, about 45 cells only; sides very slightly convex; angles open, Diam. 1–350".” Br M.J. i. p. 250, pl. 4, f. 9. Indian Ocean. Varies with four sides. Except in its smaller size, we see not how this species differs from T. Favus. T. Africanum (E.). — Sides convex; angles rounded; cellules large, in radi- ating series. EMI, pl. 35 B. 19. f. 1. Recent. West Africa. In form resem- bles T. obtusum. T. comptum (E.).--Sides straight, and having a marginal fringe ; angles pro- longed into short, stout spines; cellules large, hexagonal. Ro M.J. ii. p. 283, f. 2. England. “The cellular markings are as large as in T. Favus, and I am rather doubtful whether it may not be a young form of that species; but the length of the processes, and fringe-like row of cells at the margin, appear to give it a di- stinctive character” Gº T. crassum (Sh.). — “Much smaller than T. contortum. Is characterized by the reticulations being coarse and irre- gular in form, and the horns very large as compared with the size of the valve.” Sh. in TMS. ii. p. 15. Natal. T. hyalinum (Br.). — “Small, trans- parent, surface with very minute dots or cellules; sides regular and straight.” Br M.J. iv. p. 275, pl. 17. f. 16. Barbadoes. = T. Reticulum. T. arcuatum. — Sh TMS. ii. pl. 1. f. 5. Natal. The figure resembles that of T. Pileus, but without pseudo-modules. It is probably, however, the same. C. exiguum (Sm.).-Triradiate; angles elongated into linear truncated pro- cesses; cellules very minute, scattered. S.D. ii. #. 87; Br M.J. iv. p. 274, pl. 17. f: 1. Fresh water. Ormsby, Norfolk. (VI. 14.) - T. Pentacrinus (Wallich). — Valves slightly convex, with 5 angles, with a short horn at each angle. Surface Spinous, divided into compartments by anastomosing lines or costae, which radi- ate irregularly from the centre. War. 3 with 4 angles, y with 6 angles. Wallich, M.J. vi. p. 251, pl. 12. f. 10–14. St. Helena. We scarcely see how this form differs from Amphitetras ornata of Shadbolt. T. dubium (Br.). — Valve minute, clypeate, with 6 angles, the lower one much produced; surface of valve coarsely punctate. Br M.J. vii. p. 180, pl. 9. f 12. Mauritius, Californian guano, India. “We place this form (which is not of unfrequent occurrence) provi- sionally among the Triceratia. It pro- bably forms the type of a new genus * Br. l. c.). ( T. * Br M.J. vi. p. 164, pl. 8. f. 6. Not Diatomaceous P Genus AMPHITETRAS (Ehr.). — Frustules cellulose, cubiform, cohering into a zigzag attached filament; in lateral view quadrangular, with a pseudo- opening at each angle. Since Mr. Brightwell's discovery of quadrangular states of Triceratium, the only remaining distinction between that genus and the present is, that in this the frustules form catenate attached filaments; but, according to Professor Bailey (as already noticed), even this character is 858 SYSTEMATIC HOISTORY OF TEIE INFUSORIA. not confined to Amphitetras. Professor Smith, indeed, remarks, “The pro- jection of the connecting membrane beyond the suture of the valve is a cir- cumstance which meets us for the first time in Amphitetras; ” but we believe that this occurs in every genus in which the new portions of the dividing frustules are formed within the persistent central portion, and in this respect there is no perceptible difference between Triceratium and Amphitetras. As some species have been placed in Amphitetras solely on account of their quadrate form, the correctness of their position is consequently not free from doubt. AMPHITETRAS antediluviana (E.). — Lateral view with straight or concave margins; angles rounded, each with an apparent opening; cellules large, radiat- ing, and concentric. Living, Denmark, Fngland, America, &c.; fossil, Oran, Greece... (xi. 21, 22.) A. tessellata, Sh TMS. ii. 8, sides very concave; the cellules on the central portion are smaller, and arranged in longitudinal lines. A. Adriatica (K.).— “Lateral view quadrate; cellules radiating and con- centric; primary sides plane,” KSA. p. 134. Adriatic Sea. A. parallela (E.).--Cellules in lateral view large, arranged in parallel lines. Fossil. Greece. - A. crucifera (Kitton, m. sp.).-Valyes unctate, and marked by a line passing from the centre to each angle. Front view deeply constricted on either side of connecting zone. Valves minute, with slightly convex sides, and produced mammiform angles. Cleanings of shells from West Indies. Distinguished by the cruciform lines of the valve, which taper from the centre to the angles, markings.” where they terminate in points. We have seen 4 or 5 frustules connected by the angles. Doubtful or imperfectly known Species. A. ornata (Sh.). —“Size small, mar- gins concave, and folded so that each valve is not unlike in form to a col- legian's cap; surface somewhat irregu- larly ornamented with delicate vein-like TMS. ii. p. 16, pl. 1. f. 10. Natal. War. 8, with 5 angles. (VIII. 16.) This is probably a state of some veined species of Triceratium. A. favosa (Harv. & Bail.).—“Sides scarcely concave; lateral view quadran- gular; angles almost straight, scarcely i. surface tessellated with large exagonal cellules.” Proc. of Acad, of Philadelphia, 1853. Mindanao. A. Cruz (Bri.). — Valves cruciform, with the angles widely rounded; surface coarsely punctate. Cleanings from shells, West Indies; Californian guano. Bri JMS. vii. . 181, pl. 9. f. 13. This may be a 4-angled var. of Triceratium castel- latum or T. trisulcum. Genus AMPHIPENTAS (Ehr.).-Frustules free, simple, cellulose or gra- nulate, pentagonal. Probably pentagonal forms of Triceratium. AMPHIPENTAS alternans (E.).-Sides concave; angles obtuse; the angles of the external pentagon alternating with those of a smaller central one, which has a circular umbo at its middle, K.A. . 134; EA. p. 122, pl. 2.6. f. 9. Cuba. xI. 32.) A. Pentacrinus (E.).--Pentagonal; its dorsal surface presenting a striated ring. Diam. I-240". K.A., p. 134. Fossil. Greece. Fragments like Amphitetras. A. flexuosa (B. M.S.). — Sides four or five, gibbous; angles conical; surface flat; cellules hexagonal, covered by minute puncta. Gulf-stream. (VI. 22.) From drawings by Professor Bailey. “Under a low power, the markings appear circular, as represented in the figures” (B.). The margins are undulated in consequence of their gibbous projec- tions, as in Triceratium Parmula, and may be 4- and 5-angled forms of that species. FAMILY XII.—TERPSINOEAE. Frustules quadrangular, Smooth, compressed, furnished with unequal trans- verse costae or incomplete septa interrupted at the middle. We have sepa- rated this small group from Striatelleae because, notwithstanding the great OF THE TERPSINoi;AE. 859 external resemblance of their solitary frustules, we believe them to differ essentially in structure. In Striatelleae the septa are longitudinal, and divide the central portion into chambers. In Terpsinoëae they are transverse and confined to the lateral portions, which appear in the front view as in Biddul- phieae. The relation of Terpsinoëae to the latter was pointed out by Mene- ghini. The Smooth frustules and straight lateral margins without processes distinguish the Terpsinoëae. Genus ANAULUS (Ehr.).-Frustules simple, subquadrate, smooth; septa lateral, unequal, not thickened at their extremities; lateral vic w oblong. Anaulus resembles Biddulphia, but its costae or septa are unequal, and it has no tubular processes. A genus of Mollusks has been also, but more recently, called Anaulus. .ANAULUs scalaris (E.). — Turgid in the young state; but when full-grown very wide and much flattened, having 4, 6, 8, or 14 lateral constrictions; late- rally oblong with transverse bars, giving it aladder-like appearance. EMI. pl. 35A. 22. f. 1, 2. Antarctic Sea. Diam. 1-480" to 1-180". The lateral valves, in the front view, have undulated margins, caused by the constrictions. (VIII. 37.) A. Campylodiscus (E.). — Quadrangu- lar; each valve very much compressed, triangular, with obtuse angles, and hav- ing laterally two slight constrictions. Bermuda. Diam. 1-372". It has the habit of an unequal-sided Triceratium or of a Campylodiscus, Genus TERPSINOñ(Ehr.).-Frustules concatenate; costae unequal, Capi- tate, curved so as to resemble musical notes. “If we imagine a series of frustules of Tabellaria joined together, not laterally, but the head of one to that of another, or in the direction of breadth instead of length, we shall form the most just idea of this genus’ (Ehr.). The capitate costae, which in their form so greatly resemble musical notes, distinguish Terpsinoë from every other genus. We unite Tetragramma with Terpsinoë, as Professor Bailey finds the “music-like notes” vary in number from two to at least eight on a side, and does not consider their number even specifically important. TERPSINoi; musica (E.). — Frustules finely punctated, with two or three trans- verse bands, the lateral valves having costae in each division; lateral view ob- long, showing two or three inflations and narrower rounded ends. E.A. pl. 3. 4. f. 1; Rab D. t. 10. America, Africa. (XI. 47.) Frustules with finely punctated lateral portions, between which the central zone (having two puncta at each end) appears like a band. Two or three bars cross lateral and central portions from one lateral margin to the other, and divide them obscurely into compartments. The lateral view has the margins sinuated, from constrictions corresponding with the transverse bands. T. Americana (Bailey); – Frustules quadrangular, resembling those of T. musica, but smaller, more minutely punc- tate, with two transverse bars and two costae in each lateral valve. = Tetra- gramma Americana, Bail. Smithsonian Contr. 1853, p. 7. f. 1. As in T. musica, the costae resemble notes of music, but are confined to the central compartments of the valves. In the lateral view it resembles the preceding species, but has fewer cross-bars. T. Indica (E., º – Frustules subquadrate (catenated P), compressed, two or four times constricted; lateral Valves densely granulate, central portion smooth, with two puncta at each end; median costae dilated at the end. KSA. . 119. = Anaulus Indicus, E. India, frequent. s T. Javanensis (EM. pl. 34.8. f. 16). – The figure resembles T. musica; but the central portion is marked by longitudi-, nal lines, which converge at each end. Species known to us only by name. T. Asiatica, Asia. = Tetragramma Asi- atica, E. T. Japonica (E.), Japan. T. Australis (E.), Sandwich Islands. 860 SYSTEMATIC EIISTORY OF TELE INFUSORIA. T. Libyca = Tetragramma Libycum, very Small. According to Ehrenberg, it Africa. approaches T. musica in form. Brazil. T. Brasiliensis (E.).-Music-like marks * Genus PLEURODESMIUM (Kütz.). — Frustules compressed, connected in fascia-like filaments by short thread-like processes; lateral portions punctated and furnished with music-like marks, the hyaline central smoother portion forming a band between them. Although Pleurodesmium was placed by Professor Kützing in a different family from Terpsinoë, yet these genera appeared to us so closely allied that we found it difficult to distinguish them,--a difficulty experienced also by Mr. Tuffen West on examining an authentic specimen of Pleurodesmium given us by our valued friend M. de Brébisson, which, however, was unfor- tunately not in a condition to afford a satisfactory examination. The frustules, as in Terpsinoë, agree with the Biddulphieae in having the lateral valves largely developed and entering into the front view; they are furnished with costae, enlarged at the ends and resembling notes of music. M. de Brébisson thinks this genus very distinct, the frustules being connected in straight series by thread-like points of attachment proceeding from the furrows; but these he informs us are very short indeed, for which reason Rützing, like ourselves, seems to have overlooked them. PLEURODESMIUM. Brébissonii (Kütz.). (VI. 23.) Lateral view oval, having —Frustules contracted at their junction; transverse bars and undulated sides. costae rugose. KSA, p. 115. Cayenne. Genus EUNOTOGRAMMA (Weisse).--Front view as in Anaulus; lateral view lunate, with undulated dorsal and ventral margins. Dr. Weisse observes that in the front view Eunotogramma resembles Gomphogramma, and in the lateral one Eunotia (Epithemia 2). In both instances, however, the resem- blance is evidently very Superficial, and does not require the distinctions to be pointed out. The genus doubtless belongs to the Terpsinoëae, and seems to differ from Anaulus only in the lunate form of the side view. EUNOTOGRAMMA tri- quinque– Septem- || row connecting zone, and lateral, equal, et movemloculata (Weisse).--Lateral view stout, pinna-like septa. Lateral view divided by two, four, six, or eight trans- semilanceolate, constricted at each sep- verse septa into three, five, seven, or tum, and therefore having as many mine loculi. Weisse, Bulletin de l'Acad. undulations as loculi; ends rounded. de St. Pétersbourg, xiii. p. 278, t. 3. f. 37. (VIII. 30.) - Fossil. Russia. Front view with a nar- FAMILY XIII.-CHAETOCEREAE. Frustules Smooth or faintly punctated, simple or united into awned fila- ments; lateral valves, in the nonfilamentous forms, usually unequal, inflated, lobed, and often furnished with bristles or other appendages; lateral view oval or circular. Marine, mostly fossil. Until Mr. Brightwell pointed out their true affinity, the genera included in this group were distributed amongst three families. Between Syndendrium and the Angulifereae we can perceive no resemblance; but the connexion of Chaetoceros with the Biddulphieae, and the other genera with the Melosirea, is far more plausible. In Stephano- pyxis, a true member of the latter family, the valves are crowned with bristles or spines, as in Some Chaetocereae. In Melosireae, however, all the members ought to be cylindrical, whereas in this family the shape, in the lateral view, is much oftener oval than circular. Although it is not difficult to point out differences between the Chaetocereae and other groups, yet, on OF TELE CELAETOCEREZE, 861 account of the variety in their forms, we confess our inability, in the present state of our knowledge, to give a concise definition which shall include its own members and exclude all others. We shall therefore content ourselves with pointing out those characters which will enable us to recognize with tolerable certainty those Diatoms which belong to it. The filamentous species differ by their awns so much from every other genus that they cannot be mistaken. Mr. Brightwell, in his excellent paper on Chaetoceros, regards this as the typal state: he says, “A careful examination of most of the species of Chaetoceros and other allied genera, described by Ehrenberg as found in a fossil state, have Satisfied us that most, if not all these, will, when found in a living state, turn out to belong to the singular filamentous and horned group which may for the present be comprehended in the genus Chaetoceros.” Those forms also which have dissimilar-shaped valves, espe- cially when lobed or hirsute, may be safely placed here; and it is very pro- bable that some species with unequal valves, still retained in Melosirea”, might likewise be included with propriety. The genera themselves are by no means firmly established; for, as Mr. Brightwell observes, “most of the described species have been found only in a fossil, or rather, if we may so term it, a deposit state; and in this state it is clearly difficult to form a correct idea of either species or genera, since deposits give no information as to the Diatoms being in threads or solitary frustules.” We shall not attempt to reconstruct the genera, for to do so prematurely would only increase the difficulty and cause confusion; for “much must yet be brought to light before a satisfactory classification of this group can be effected ” (Brightwell). Although only a few species have as yet been gathered in a living state, yet, as most of them are found in guano, it is probable that nearly all still exist; and when their habits are better known, we may fairly expect to obtain them. They seem to inhabit deep water, as Mr. Norman has met with them, more than once, in the stomachs of Ascidiae from such situations. Genus CHAETOCEROS (Ehr.).-Frustules without striae, united with the adjacent ones by the interlacing on each side of awns proceeding from the frustule or from a cingulum between the frustules, and so forming a filament. The filaments are imperfectly silicious and very fragile. The awns are tubular, sometimes Spinous or Serrated, and often of great length, though, according to Kützing, short in an early state. Kützing defines the genus as follows:— “Frustules concatenated, equally bivalved, turgid, with two apertures on each side, which at the earliest period are very shortly tubular and the cor- puscles contiguous, afterwards longly awned and the corpuscles distant.” If the awns be overlooked or broken off, the frustules may be mistaken for species of Melosira. No person who wishes to study this beautiful but diffi- cult genus should fail to obtain Mr. Brightwell’s valuable paper on it in the Journal of Microscopic Science. # Frustules, in lateral view, constricted at the middle. CHAETocIRos Diplomeis (E.). —Frus- tules in lateral view panduriform, in front view linear; awns Smooth. KSA. p. 138; EM. pl. 33. 18. f. 1; Bai. in Amer. Journ. of Science, xlviii. pl. 4. f. 19 (la- teral view). = C. Bacillaria, Bai. l.c. f. 18 (front view). Bermuda deposit. “Chao- łoceros Diplomeis and C. Bacillaria are merely different positions of the same species” (Bai, in lit.). In the front view the frustules are linear, three or four times as long as broad, with stout awns arising from the angles. Lateral view panduriform, with rounded ends. 2 * Frustules laterally oval or circular; awns Spinous. C. boreale º quadrate; awns very long, spinous, arising from the inner surface, not from the angles. | BC, 1854, pl. 7, f. 22, 23; Bri JMS, iv. 862 SYSTEMATIC IIISTORY OF THE INFUSORLA. p. 107, pl. 7.f. 12–15; Wallich, TMS. viii. p. 48, pl. 2. f. 18; West, TMS. viii. p. 152, 1.7. f. 13. St. George's Bank, Atlantic cean. (VI. 25.) “This species was found in considerable numbers in the contents of the stomach of the Botryo- dactyla grandis.” Awms 30 to 50 times longer than the body. e . Peruvianum (Bri.).-Valves hemi- spherical, with two very stout, long, recurved, spinous awns proceeding from the centre of the rounded ends. Br JMS. iv. p. 107, f. 16–18. In Peruvian guano. A remarkable and very distinct species, characterized by the rounded º Of the valve. Lateral view circular 3# Frustules laterally oval or circular; awns Smooth. C. Tetrachata (E.). — Frustules with four, very long, filiform, smooth awns on each side. KSA, p. 138. Antarctic Sea. Diam. without the awns, 1-1152". C. Dichaeta (E.).-Frustules with two, very long, filiform, smooth, often flexu- ose awns on each side. KSA, p. 138. Antarctic Sea. Diam. without the awns, 1-1152" to 1-720". The description is too imperfect to enable us to distin- guish the species from some of the fol- lowing ones. C. confervoides (n. sp.). — Frustules large, quadrate ; awns stout, smooth, arising a little beneath the rounded angles; lateral view circular. Mount's Bay (stomach of Ascidiae), Cornwall. We have seen only one concatenated specimen; it formed a short, very fra- gile, conferva-like filament of about 12 joints, which were equal in length and breadth and in close apposition. Internal colouring matter brownish, and collapsed into a roundish spot in the centre of each frustule. C. Wighamii (Bri.).—“Frustules cup- shaped, with a band round the mouth of the cup, and a neck or bulb proceeding from the centre; beset with minute short spines or papillae in all parts except the band; lateral view oval; awns elon- gated, smooth,” Br M.J. iv. p. 108, pl. 7. f. I9–36. In brackish water, near Brey- don, Great Yarmouth. “Boiled in acid, the filaments break up, and the frustules in an isolated state, and detached rings with the horns proceeding from them, are all that can be detected. The rings may readily be distinguished from the frustules seen endwise, as they are open and without dots, while the frustules seen endwise are dotted ” (Bri.). We have seen no perfect specimen of this interesting species; but as Mr. Bright- well's fig, 12 shows two joints similar to other species of this genus, we are inclined to regard the Goniothecia-like bodies as internal cells, of the same nature as the internal cells of Himan- tidium, Meridion, &c., which we believe to be sporangia; but whatever their true character may be, we have scarcely a doubt that Mr. Brightwell is right in supposing Goniothecium crematum, G. his- pidum, G. Navicula, and G. barbatum to be allied forms belonging to the same genus as this species, (VI. 24. C. incurvum (Bail.). — Frustules in front view linear, with smooth, filiform, recurved awns arising from the angles; lateral view oval. Bri. l.c. pl. 7. f. 9–11. Fossil. Virginia, Peruvian guano. In stomach of Ascidiae, Penzance. Easily known by its small size and slender recurved awns. C. furcillatum (Bail.). —Awns of ad- joining frustules closely approximate below, then diverging and becoming nearly parallel; lateral view oval. Bai. on Microsc. Forms in the Sea of Kamt- Schatka, p. 3, pl. 1. f. 4. Common in the Sea of kºi. The minutest spe- cies in the genus. C. didymus (E.). — Frustules longer than broad, gibbous or angular on the outer margin, and usually slightly so on the inner margin also; awns smooth, filiform, arising from the angles. Bri. l.c. pl. 7. f.3–7; KSA, p. 138; EM. t.35A. 18. f. 4. Common in Peruvian guano. Stomach of Ascidiae, Penzance. A va- riable species, distinguished by its angu- lar or gibbous margins; lateral view oval. Ehrenberg's two figures in the “Microgeologie’ 㺠from each other, as well as from any specimens we have seen. Greatest diameter 1–1080". C. Gastridium (E., Bri.).—Frustules binate, Smooth, transversely oblong, truncated at each end, abruptly dilated at the middle of the ventral surface, not contiguous, Bri. l.c. pl. 7. f. 8. = Gonio- thecium Gastridium, EM. pl. 18. f. 91. Virginian guano. Ehrenberg describes and figures it with an external umbo (gibbous), thus approaching to C. didy- 772.2/S. C. armatum (West). —Trustules qua- drangular, forming a compressed fila- ment; angles excavated; from each angle arises a long, obtuse, curved seta, with several acute ones at the base. West, TMS. viii. p. 151, pl. 7. f. 12. Abundant on various parts of the coast of England. OF TEIE CELAETOCEREZE, 863 This species, in its living state, is in- stance which has caused many doubts Vested with a mucous covering, and is as to its diatomaceous nature. Scarcely, if at all, silicious, a circum- Genus ATTHEYA (West).-Frustules compressed, annulate; annuli inde- finite; Valve elliptical-lanceolate, with a median line; angles spinous. The true position of this genus is doubtful; but, from examination, it appears to approach nearer to Chaetoceros than to any other genus excepting Striatella, from which, however, it is easily distinguished by the spinous angles and ab- sence of stipes. ATTHEYA decora (West).-Annuli 12 TMS. viii. p. 152, pl. 7. f. 15. Cresswell to 28; septa alternate; valve with me- Sands, Druridge Bay. (VIII. 35.) dian line and central nodule. West, Genus BACTERIASTRUM (Shadbolt). — Frustules awned, united into a jointed, conferva-like, cylindrical filament; valves discoidal, with marginal radiating awns. Bacteriastrum agrees with Chaetoceros in its filamentous character and in the presence of awns, but differs from it in having the awns of its discoidal valves marginal and radiant. animals, &c. BACTERIASTRUM furcatum (Sh.). — Awns Smooth, much elongated, forked. =Actiniscus seafurcatus, ERBA. 1854, p. 237; EMI. pl. 35B. 4. f. 15; A. bisepte- marius, E.; A. bisoctonarius, E. Atlantic. The awns vary in number and in the length of the forked portions. (VI. 26.) B. curvatum (Sh.). — Awns simple, elongated, Smooth, symmetrically curved in one direction. Marine. Stomachs of marine B. Wallichii (Ralfs).-Valves more or less cup-shaped, with 4 to 12 Smooth, simple, divergent awns. = Chaetoceros Bacteriastrum, Wallich, TMS. viii. p. 48, § 2. f. 16, 17. Atlantic. From Salpae. ize extremely variable. (VI. 27.) B. modulosum (Sh.). — Awns simple, straight, rough.-Awns covered with Small protuberances, like a knobbed stick, Genus DICLADIA (Ehr.).-Frustules simple, one-celled, bivalved; valves unequal, turgid, one mostly simple and unarmed, the other two-horned ; horns sometimes branched. DICLADIA Capreolus (E.).-One valve with two styles arising from conical bases, and usually branched at the end. EM. pl. 35A. 17. f. 8; Bri JMS. iv. pl. 7. f. 53–60. Virginia. Common in guano. The frustule consists of a narrow-linear central portion, projecting at each end, and two turgid lateral valves, which vary greatly in form. Usually the in- ferior one is smaller, simple, and unarmed, but is often bilobed. The larger valve is bilobed; the lobes mammiform or conical, each terminating in a style divided at its apex; occasionally, however, specimens have the upper valve unarmed or simple. D. antennata (E.). —One valve, with two simple, Setaceous, parallel, acute spines, articulated at the base, like an- tennae; the other valve unknown. EMI. l. 35A. 21. f. 9; KSA. p. 24. Antarctic §. This and the next species were constituted from single fragments. D. bulbosa (E.).-One valve with two spines, which are divergent at the base, connivent above, bulbose and slightly sulcate in the middle part; the other valve unknown. EM. pl. 35A. 21. f. 10; KSA. p. 24, Antarctic Sea. D. clathrata (E.). — Frustule with a rounded, smooth, latticed body, and two unequal frontal horns. EM. pl. 18. f. 100; KSA. p. 25. Fossil. Virginia. D. Capra (E.). —Smooth; one valve with two simple spines, the other uni- dentate or imperfectly sub-bidentate in the middle ; central portion narrow- linear. E.M. pl. 18. f. 99. = Periptera Capra, KSA. p. 26. Fossil. Virginia. D. Cervus (E.). — Smooth, large ; frontal horns long, branched. = Periptera Cervus, KSA. p. 26. Fossil. Maryland. D. Mitra (Bai.). —Valve having two conical horns coalescing below into a conical base, and bearing branched pro- cesses above. B. in Silliman's Amer. Journ. July 1856, pl. l. f. 6. Sea of Ramtschatka. Perhaps a state of D. Capreolus. 864. SYSTEMATIC IIISTORY OF THE INFUSORIA. Genus GONIOTHECIUM (E.).-Frustules simple, having a central con- striction or furrow ; each end abruptly attenuate and truncate, so as to assume an angular figure. Fossil. Like other genera in this family, this is an un- satisfactory genus. The frustules are described as cylindrical; but we believe that most, if not all of them, are oval when viewed laterally. Mr. Brightwell makes the following remarks on eight of Ehrenberg's species:– “The two largest and most common are G. Rogersii and G. Odontella; and we think it probable these will turn out, if discovered in a recent or living state, to be Chaetoceri. Of the remaining six species, we are led to conclude, from the discovery of the Breydon species, that two of them belong to the genus Chaetoceros, and are, when living, filamentous. They are G. Gastridium, of which we have found many specimens with the horns perfect, and G. crematum. A figure of a frustule of this species is given in the ‘Microgeologie’ of Ehren- berg, and it can scarcely be distinguished from the frustules of the Breydon species. G. hispidum and G. didymum scarcely appear to differ from some of the smaller frustules of the Breydon species. G. Navicula and G. barbatum are clearly allied to G. crematum, or our Breydon species.” The species differ in form, and sometimes do not correspond with the generic character. G. Gastridium (E.) is proved by Mr. Brightwell’s discovery of its awns to be a species of Chaetoceros. GONIOTHECIUM. Odontella (E.). — Valves binate, smooth, conjoined by a central process, and by their commivent apices, so as to form on each side a large oblong aperture, constricted at its middle; margin undulate. EMI. pl. 33.15. f 16; KSA, p. 23; Bri JMS. v. pl. 7. f. 47, 48. Virginia. Diam. 1-480" to 1-276". Distinguished by its large size and undulated margin, the central un- dulation forming an umbo; lateral view oval. (VI. 29.) G. Rogersii (E.). — Valves binate, Smooth, conjoined by a broad central rocess, often with commivent apices, forming suborbicular apertures; margin undulate. EM. pl. 18. f. 92,93; KSA. p. 23. Virginia. Diam. 1–588". Smaller than G. Odontella; “valves dorsally sub- quadrate, angular, with three whorls, laterally elliptic-oblong, with two or three median circles;” central undulation umbonate. Mr. Brightwell's figures are more irregular, and do not correspond so accurately with the definition. G. obtusum (E.).-Valves smooth, in- flated, with three rounded lobes; central or constricted portion forming a narrow band, EM. pl. 18. f. 95; KSA, p. 23. Virginia. Diam. 1-696". . monodon (E.). — Valves binate, Smooth, not contiguous, each linear- oblong, truncate at each end; outer side uniformly straight, the inner with a median tuberosity. EM. pl. 18. f. 97; KSA, p. 23. Virginia, California. Ehr- enberg's figures represent a canoe-shaped valve, the outer margin convex, the inner with incurved ends and a central projection (connecting P. and agrees but badly with the specific cha- racter. - G. hispidum (E.). — Frustules semi- lunate, hispid, with an umbo at the centre of inner margin. EM. pl. 18. f. 107; KSA. p. 23. Virginia. G. Navicula (E.). — Frustules small, smooth, with a linear produced central portion and a turgid or inflated valve on each side. EM. pl. 18. f. 105; KSA, p. 24. Virginia. In i. species the central portion projects beyond the lateral valves, instead of being constricted. G. didymum (E.). — Binate, smooth, transversely oblong, obtuse; one side emarginate at the centre, the other with two tubercles. EMI. pl. 18. f. 104; KSA. p. 23. Virginia. Diam. 1-1200". Ehr- enberg's figure shows two unequal valves without any interstitial portion, each valve with two rounded lobes. It re- sembles a hornless state of Dicladia, except that it wants the central portion. G. barbatum, EM. pl. 18. f. 106. Vir- ginia. Ehrenberg's figure has a narrow- linear, longly produced central portion and two unequal turgid valves—the Smaller Smooth, the larger conic with a tuft of hairs at its apex. G. crenatum, EM. pl. 39. 3. f. 74, Ehr- enberg's figure is semilunate, with a neck-like truncated cone on its inner side. This species, except in being Smooth, exactly resembles Mr. Bright- well's figures of the internal frustules of Chaºtoceros Wighamii, and doubtless be- longs either to that or to an allied species of Čhetoceros. (xv. 10.) OF THE CEIAETOCEREAE. 865 Genus OMPHALOTHECA (Ehr.).-Characters unknown to us. Judging from Ehrenberg's figure of the only species, it seems scarcely distinct from Goniothecium. OMPHALOTHECA hispida, EM. pl. 35 A. 9. f. 4*. Ganges. The figure apparently represents a frustule in the process of division. The valves are unequal; the Smaller one Smooth, the larger some- what conical and furnished with scat- tered spines; connecting-zone slightly produced beyond the valves. (VIII.44.) Genus PERIPTERA (Ehr.). — Frustules simple, compressed, unequally bivalved; valves simple, continuous, not cellulose; one valve naked, turgid, the other winged or horned; horns affixed to the extreme margin, sometimes branched. Approaches very near to Symdendrium and Dicladia. We think these three genera might be united with advantage. PERIPTERA tetracladia (E.).--Smooth, almost navicular; one valve with four equidistant spines, branched at the apex, the other simple. EMI. pl. 33. 18. f. 9. Fossil. Bermuda deposit. fin. 1–1440", including spines 1-864". Without the P. chlamidophora (E.).--Smooth, al- most navicular; one valve at the side plane and surmounted by a finely-nerved membrane, the other turgid at the mid- dle, unarmed. EMI. pl. 18. f. 96. Fossil. Bermuda. (VIII, 25.) spines, it resembles an Amphora, (VI, 30.) Genus RHIZOSOLENIA (Ehr.).-Filamentous; frustules subcylindrical, greatly elongated, silicious, annulate; annuli broadly cuneate ; surface stri- ated, extremities calyptriform, pointed with a bristle. This genus was con- stituted by Ehrenberg for the reception of certain silicious organisms found in guano and various fossil deposits. The characters assigned by him to this genus are, “lorica tubular, with One extremity round and closed, while the other is attenuate and multifid, as if terminating in little roots.” The dis- covery of this remarkable genus in a living state has, we believe, proved that the species described by Ehrenberg are only fragments of forms similar to those we are about to describe. Professor Schultze has detected in R. styli- formis and R. calcar-avis a circulation of minute granules analogous to the currents observed in the hairs on the filaments of Tradescantia procumbens, (Schultze, M.J. vii. p. 16.) RHIzosol.ENLA styliformis (Bri.). — Prustules from 6 to 20 times as long as broad; transverse lines (annuli) distinct; surface striated, striae oblique, about 40 in .001", terminal process at the base spatu- late and bifid. Found in Noctilucae, Yar- mouth; stomachs of Ascidians, York- shire; Salpae, Atlantic. Bri M.J. vi. p. 94, 1. 5. f. 5; Norman, ANH. xx. p. 158; #. Schultze, M.J. vii. p. 18, pl. 2. f. 1. (VII. 32.) From the elongated base of the calyptriform º a stout line or rib runs up on either side to nearly the apex of the cone; at base of the lines a small horn, slightly curved towards the annuli, is frequently to be detected. Self-division has been observed in this and some of the following species. R. imbricata (Bri.). — Frustules 4 to 7 times as long as broad, annuli di- stinct, surface of valve coarsely punctate, terminal process subulate, entire. Found with the preceding species. Bri M.J. p. 94, pl. 5. f. 6. The direction of the transverse lines (annuli) and puncta give this species an imbricated appear- 8.11C63, R. setigera (Bri.).—Frustules 5 to 15 times as long as broad, annuli obscure, striae very faint, terminal bristle fre- quently as long as the colourless frustule. In Noctilucae, Ascidians, and Salpae. Bri, l.c. p. 96, pl. 5. f. 7. (VII, 33.) This species is remarkable for the great length of the terminal bristle and its extreme delicacy. - R. alata (Bri).-Annuli distinct, striae faint, terminal process alate, recurved, blunt. In Ascidians, Yorkshire. Bri. l. c. p.95, pl. 5. f. 8. This curious little spe- cies is distinguished by its small but conspicuous setae attached to the base of the calyptriform process. R. calcar-avis (Schultze). — Frustules small, annuli indistinct; terminal process slightly sigmoid, the point resembling 3 K 866 SYSTEMATIC HISTORY OF THE INFUSORIA. a bird's claw. Heligoland. Schultze, M.J. vii. p. 21, pl. 2. f. 5. R. robusta (Norman, Mºº very broad, slightly sigmoid, annulinar- row, calyptriform processes with lines radiating from the apices; bristles short, delicate, nearly linear. Striae fine, about 55 in 001". Ascidians, North Sea, Teignmouth, Heligoland, Australia. Doubtful and insufficiently known Species. R. Calyptra (E.). — Valve (terminal process) broadly conico-campanulate, smooth, its apex attenuated, acute. EM. l. 35 A. 22. f. 17.; Bri. l. c. pl. 5. f. 2. outhern Ocean. (VII. 31.) This is pro- bably the terminal process of R. Styli- formis. ^ R. Campama (E.).-Valve large; apex conic, longly attenuated, varies as if terminated by little roots; surface very finely granulated. KSA, p. 24. Bermuda deposit. , ornithoglossa (E.).-Valve tubular, conical, Smooth, slender, with a much attenuated, acute apex, laterally resem- bling the tongue of a bird. EMI, plá3. 13. f. 21. Antarctic Sea. R. Americana. — Frustules Smooth, hyaline, tubular, interrupted by Septa, one end round, the other styliform, simple or branched. E.M. pl. 18. f. 98. Fossil. America. This seems a species very variable in size and form. The outline, however, of the rostrate valve bears 'some resemblance to a bottle, with the neck or beak simple or branched. R. hebetata (Bai.). —Valve calyptri- form, punctate, with a smooth, cylin- drical base; apex expanded, compressed. B. in Silliman's Amer. Journ. July 1856, p. 5, pl. 1. f. 18, 19. Seas of Kamtschatka and Ochotsk. The expanded apex re- sembles in outline the flame of a candle. The punctate conical portions are most frequently seen; but specimens with the *ial base are occasionally found, ail. R. Pileolus (E.). —Valve small, short, as broad as long; central portion linear, produced; one valve resembling an umbo, the other conical, branched at apex. EMI. l. 18. f. 103, Virginia. Diam. 1-1320". Has the habit of Dicladia or Gonio- thecium. Genus SYRINGIDIUM (Ehr.).-Frustules simple, cylindrical; valves un- equal, dissimilar, distended by a turgid middle ring. SYRINGIDIUM bicorne (E.). —Smooth, elongated, with three constrictions, one end pointed, the other subglobose, two- spined. EM. pl. 35 A. 9. f. 11*. Ganges, Africa. (VIII. 20. S. Palaomon (E.).-Resembles the pre- ceding species, but is granulated. EMI. pl. 34.8. f. 15. Japan. - S. Americanum (Bai. MS.; VII. 34, from a drawing by Professor Bailey).-- Maritime. Common in Para River, and sparingly in the soundings off the mouth of the Amazon, South America. Frustules very minute, punctated; central portion quadrangular; valves unequal, one with a quadrate base, Suddenly contracted and then tapering into a pyramidal spine terminated by a mucro; the other valve subglobose, with two short basal pro- cesses, each ending in a spine. Genus SYNDENDRIUM (Ehr.).-Frustules simple, bivalved, subquadran- gular, one-celled, without umbilicus in the middle; valves unequal, rather turgid, one Smooth, the other furnished with many styles branched at the apex; margin naked. Syndendrium differs from Dicladia only in having several instead of two spines on one of its valves; yet Kützing has placed them in different families. SYNDENDRIUM Diadema (E.).-Frus- tules lanceolate, with several spines in the centre of one valve, forked or peni- cillate (split up like a brush), their length equalling the thickness of the frustule. EM, pl. 35 A. 18. f. 13; Bri M.J. iv. p. 7. f. 49–52; Donkin, TMS. vi. p. 1. In Peruvian guano; Sea of Kamtschatka; stomach of Ascidia, Penzance. Diam. 1-1152". The central portion is narrow linear, projecting at each end, the lateral valves convex, one Smooth, the other with branched spines; lateral view oval. Genus HERCOTHECA (Ehr.). — Frustule simple, turgid, of two unequal valves; membrane of valves continuous, not cellulose, generally veined be- neath the free setae, which are permanent and assume the place of an integu- OF TELE COCCONEIDEAE. 867 ment. Hence the corpuscles on the upper, contiguous margin of each valve appear as if crowned and enveloped (as it were, shielded) by the opposite setae Or membranes. HERCOTHECA mammillaris (º). — on the margin itself, and extending be- Valves smooth, with the centre of the yond the mammillae, EM. pl. 33. 18. base fringed round (fortified) with about |f. 7. Fossil. Bermuda. (VII. 35.) twenty simple, opposite setae, inserted FAMILY XIV.—COCCONEIDEAE. Frustules elliptic, rarely bent, adnate by an inferior lateral surface, having a median longitudinal line and central nodule. “The lateral surfaces prevail So much that the central portion is reduced to a simple margin, and conse- quently it is difficult to obtain a front view” (Meneg.). Campylodiscus and Rhaphoneis, the only members of another family with which any of the Cocconeideae are likely to be confounded, are distinguished by the absence of a central nodule. Those species of Navicula which are elliptic in the lateral view somewhat resemble species of Cocconeis; but they are never adnate, and in them the central nodule is equally developed in both valves. Genus COCCONEIS (Ehr.). — Characters, those of the family. Frustules depressed or somewhat hemispherical ; the central nodule is wanting or obscure in the inferior lateral surface, and sometimes there is a transverse as well as a longitudinal line. “The general form of Cocconeis is that of a disc of an ellipsoidal figure, with surfaces more or less exactly parallel, plane, or slightly curved. . . . The characters by which the species of this most elegant genus are distinguished one from another are still very slight ° (Meneg.). The frustules in this genus are frequently furnished with an additional membranous covering, which also forms a border to them, and has been admitted into the specific definitions; but we believe this envelope generally, if not invariably, belongs to the immature state, and afterwards disappears more or less completely; and on this account we consider it an unsafe differential character. The descriptions apply to the lateral view, unless otherwise stated. she * * * g e = * * ſº Smooth; front view oblong, rectangular. * Disc smooth or with longitudinal line. KB, ... A. f. 16, Coast ; §. Cocco NEIS longa (E.):--Very minute, 1-1320". Nidulating in mucus. linear-oblong, with rounded ends, Smooth, C. elongata (E.). — Small, smooth, except a median line and nodule. EM. oblong-elliptic, plane, EMI, pl. 5. 3. f. 26. pl. 5. l. f. 25. Aquatic. Iceland. America, Europe, Africa, China. Smaller C. pumila (K.).--Very minute, curved; lateral view oblong-elliptic, Smooth, without lines or accessory border. K.B. pl. 5.9. f. 2. Aquatic. Europe. Length 1-1560". Rabenhorst describes it as destitute of median line and module. C. pygmaea (K.). — Very minute, Smooth, elliptic, girt by a cremulate ge- latinous i. RCB. t. 5.6. f. 4. Baltic Sea, on Ceramium. 1-2640". C. molesta (K.). — Minute, Smooth, elliptic-oblong, without an accessory border, densely aggregated. KB. pl. 5. 7. f. 1, 2. Marine. Venice. 1-1800" to 1–1680". C. nidulans (K.), — Elliptic-oblong, than C. Placentula, but may be a variety of that species. C. Cruz (E.). —Smooth, elliptic, thin, with a transverse linear umbilicus. KSA. p. 53. Western Asia. Diam. 1632". C. diaphana (S.).-‘‘Elliptical, scarcely silicious, diaphanous ; striae obscure. Length 0012" to 0018".” SBD. i. p. 22, pl. 30. f. 254. “B, nodule dilated into a stauros.” Sidmouth, Jersey. C. Pediculus (E.). — Small, elliptic, somewhat angular, slightly curved; disc with very fine, dotted longitudimal limes. SBD. i. p. 21, pl. 3. f. 31. Aquatic. Common. 3. Salina (K.), narrower near the margin, furnished with very delicate 3 K 2 868 SYSTEMATIC EIISTORY OF THE INFUSORTA. transverse striae : Saxony, y, minor (K.). In this species the striae are visible only when highly magnified. It is best di- stinguished by its slightly angular or rhomboid form—a character not noticed by Ehrenberg, who gives in the ‘Micro- geologie' only one figure, and five habi- tats. Diam. 1-2200" to 1-960". C. depressa (K.).-Minute, much de- pressed, plane, elliptic, furnished near the margin with punctated striae. ICB. pl. 5. f. 8. 2. Aquatic. Europe. Accord- ing to Rabenhorst, it resembles a small and flat state of the var. Salina of the preceding species. Diam. 1-1800". C. Placentula (E.). — Plane, elliptic, with faint, dotted longitudinal lines. SBD. i. p. 21, pl. 3. f. 32. (VII, 36.) Aquatic. Common. 1-1440". Ehren- berg, in his “Microgeologie,” gives many figures and upwards of sixty habitats for this species. His definition differs from that of Professor Smith, and is as fol- lows:—“Plane, elliptic, with an abrupt margin; within and without smooth.” Having seen no authentic specimens of C. Placentula and C. Pediculus, we have adopted Professor Smith's views, but do not implicitly rely on them; for not only do Ehrenberg and Smith differ in their descriptions, but whilst the latter states that both species occur in the Lough Mourne deposit, the former has excluded them from his lists of species found in it. C. praetexta (E.).--Small, elliptic, with six longitudinal lines on each side of the centre, and a dilated, Smooth, areolar margin. EA, pl. 3. 3. f. 11, Japan, India, Africa, America. C. punctata (E.).--Small, elliptic, with eight punctated longitudinal lines on each sº of the median line. KB. p. 72, pl. 29. f. 30. Australia, America, C. euglypta, EM. pl. 34.6 A. f. 2. Flo- rida. Ehrenberg's figure represents a small elliptic form, with broadly rounded ends, and a median line and module, having on each side parallel, distinctly dotted longitudinal lines. C. Striolata (Rab.). —Small, narrow- elliptic, with dense, faint longitudinal striae on each side of the median line. Rab, D. p. 28, pl. 10. f. 8. Aquatic. Salzburg. C. oblonga (K.).-Oblong-elliptic, with somewhat acute apices and longitudinal lines. KB. p. 72, pl. 5.8. f. 7. North Sea and Indian Ocean. 1-320”, C. limbata (E.).-Large, elliptic, with broadly rounded ends, very fine longi- tudinal lines, and a subentire gelatinous border. E.M. pl. 14. f. 42. Adriatic and Mediterranean Seas. 1–576". Raben- horst describes this species as like C. Placentula with a distinctly developed border-like membrane. C. oceanica (E.). — Large, roundish- elliptic, with numerous delicately punc- tated, somewhat converging longitudi- mal lines; dorsum convex. SA, p. 52. Purope, America, (XII, 42.) C. concentrica (E.). —Large, broadly elliptic, with broadly rounded ends and concentric longitudinal lines. KB. p. 72, pl. 28. f. 15. Mexico. C. undulata (E.). —Elliptic; dorsum slightly convex; exterior furrowed, with undulated concentric lines. KB. p. 72, § 5. f. 11. Baltic, Asia, Africa. 1-432". of transversely striated. C. lineata, E.M. numerous figures and habitats. Australia, Asia, Africa, Eu- rope. We have seen no description of this species; but, according to Ehren- berg's figures, it seems to differ from C. wndulata in the nonconvergence of its longitudinal striae. Apparently a very common species, as Ehrenberg gives upwards of fifty habitats. C. fasciata (E.).-Large, elliptic; disc with dotted longitudinal lines on each side the median line, intersected by a transverse median smooth band. KB. p. 72, pl. 28. f. 14, Aquatic. Peru. C. gemmata, EMI. pl. 37.2. f. 1. Ore- gon, Ægina. Ehrenberg's figure is large, broadly elliptic, with rounded ends and a smooth linear median line, having on each side five or six parallel, lon- gitudinal, moniliform series of large granules. C. aggregata (K.). — Oblong-elliptic, girt with a broadish lacerated, crenulate limb; disc having near the margin finely dotted rays, and in the middle punc- tated longitudinal lines, R.B. p. 72, pl. 5.8. f. 5. Baltic and North Seas. l–1440". - C. marginata (K.). — Elliptic, with radiatingly punctated margin and dis- coid longitudinal lines. KB. p. 72, pl. 5. 6. f. 1. Marine. Europe. 1-840". C. dirupta (Greg.). — Broadly elliptic or Suborbicular, with a smooth º line, having on each side wavy longi- tudinal and faint transverse striae. GDC. p. 19, pl. 1, f. 25. Scotland. The lon- gitudinal striae are most evident in the centre, and the transverse, which are Somewhat radiant, near the margin. Under a low power the module appears dilated into a stauros. Professor Gregory States that it differs in its brown colour OF THE COCCONEIDEAE. 869 and conspicuous striae from C. diaphana, the only allied species. 2 * Disc with radiant or transverse stria. C. striata (E.). — Elliptic-oblong, of medium size, with parallel or somewhat converging transverse striae. EMI. many figures. Aquatic. Apparently common, as Ehrenberg gives upwards of forty habitats in different parts of the world. Lough Mourne deposit. C. borealis (E.). — Elongated-elliptic or oblong with rounded ends and parallel or converging transverse striae. EM. several figures.- Ehrenberg gives about thirty habitats in Asia, Africa, &c. . Ex- cept in its more elongated frustule, it scarcely differs from C. striata. C. transversalis (Greg.).--Small, nar- now-elliptic, with fine, parallel, dotted transverse striae reaching the median line. Greg M.J. iii. pl. 4, f. 7. (VII. 37.) Scotland. C. atmospherica, EMI, pl. 39. 3. f. 9. Scirocco dust. Ehrenberg's figure is large, elliptic, with median line and module and dotted parallel transverse striae. C. hyperborea (E.). – Large, elliptic, finely punctato-striate ; striae in the middle margin of the disc, 18 in 1-1200", continued to the median furrow as puncta; the fine triple line of furrow with a single, distinct, transversely ob- long median umbilicus. ERBA, xviii. . 526; EM. pl. 35A. 23. f. 4. Assistance #. Nearly resembles C. Scutum of New Holland. Breadth rather more than half the length. C. nigricans (K). — Narrow-elliptic, densely aggregated, girt by an entire, rather broad, brownish-black border; transverse striae, 13 or 14 in 1-1200". KB. p. 72, pl. 5.8, f. 8. Trieste, 8, de- mudača, border obsolete. KB. t. 5, 8. f. 10. 1-1320” to 1-1200". C. consociata (K.). —Broadly elliptic, with a hyaline, longitudinal median line; disc with 13 punctated, almost radiant striae on each side. KB. pl. 5, 8. f. 6. Marine. Baltic. 1-1320". C. Pinnularia (K.). —Boundish-ellip- tic, transverselystriated, except a smooth, crénated, longitudinal median fascia. KSA. p. 52; KB. p. 73, pl. 5; f. 34. = Cocconets P, BAJ. xlii. t. 2. f. 34. America. This very doubtful species was constituted by Kützing from Professor Bailey's figure. C. Persica (Rab.). — Large, elliptic, with a longitudinal median line, dilated at centre and ends, and having 23 gra- mulated transverse striae on each side. Rab D. p. 27, pl. 3. f. 5. Persia. C. major (Greg.) — Very large, thin, flat, broadly elliptic or suborbicular, with numerous delicate transverse striae : median line with central and terminal nodules. GDC. p. 21, pl. 1. f. 28. Scot- land. Hyaline, without distinct border; striae about 54 in 001", somewhat con- centric with extremities. C. Scutellum (E.). — Elliptic, with finely punctated transverse striae con- centric with its extremities; striae 18 in •001". EI. p. 194, pl. 14. f. 8; SBD. i. . 22, pl. 3. f. 34. Marine. According to £hrenberg, found in every quarter of the globe; yet he gives fewer habitats for this than for some other species. (IX. 162, 163.) [8, module dilated into a stauros: S. l. c. pl. 30. f. 34, y, disc with stauros, very fine striae, and two lateral semioval markings: Ro M.J. vi. pl. 3. f. 9. Dorsum convex. 1-1150". The species thus cha- racterized is very variable in size and form and in the size of its puncta. Per- haps the varieties should be constituted distinct species. C. Arraniensis (Grev.).-Valve ovate; striae concentric with the extremities, faint, moniliform, contiguous, reaching the median line; striae 30 in 001". Grev JMS. vii. p. 80, pl. 6. f. 2. C. Speciosa (Greg.).--Small, rhomboid- elliptic, with 12 distinctly granulated transverse striae in 001", and somewhat concentric with extremities. Greg MJ. iii. pl. 4, f. 8. Scotland. So nearly allied to C. Scutellum, that, although its more distant striae are formed of fewer and larger granules, we must doubt whether these species be really distinct. C. Mediterranea (K.). — Elliptic or elliptic-oblong, with distinct puncta, regularly arranged so as to form both transverse and longitudinal series. ISB, . 73, pl. 5.6. f. 8. Mediterranean Sea. Rather large; dorsum slightly convex. 1-840" to 1-552". In Kützing's figures the striae appear somewhat concentric with extremities; and we doubt whether it be distinct from C. Scutellum. C. Peruviana (K.).-Elliptic, regularly punctate, the larger puncta quadrate, more distant. KB. p. 73, pl. 5.6. f. 7. Marine. Western shores of America. 1-840". Kützing's figure seems very similar to C. Mediterranea. C. Adriatica (K.). — Large, elliptic; striae granulated, transverse on the disc, radiating on the margin, KB. p. 73, pl. 5, 6, ºf 2 & 9, Adriatic and Medi- 870 SYSTEMATIC ELISTORY OF TELE INFUSORLA. terranean seas. 1-696" to 1-480". Dor- sum convex. The striae in Kützing's figures are concentric with the extremi- ties; and this species seems to differ from C. Scutellum in its more distinct border. C. distans (Greg.). — Elliptic, with Somewhat attenuated ends, a delicate median line and transverse series of equal, rather distant granules, GDC. § 18, pl. 1. f. 23. (VII. 38.) Scotland. his species agrees with C. Scutellum in its granulated striae, somewhat concen- tric with extremities, but it appears to us distinct. The striae are fewer, the granules far more conspicuous, and, ac- cording to Professor Gregory, equal, and situated on white, hyaline, faint bars, characters absent in C. Scutellum. C. lamprosticta (Greg.).-Large, rhom- boid or broadly lanceolate with obtuse apices, a median line, and transverse series of rather distant conspicuous granules. Greg TMS. v. pl. 1. f. 28. Scotland. This species agrees with C. distans in having conspicuous transverse Series of granules somewhat concentric with extremities, but differs in its elon- gated form. C. Splendida (Greg.). —Large, elliptic, with conspicuous, moniliform trans- verse striae, a broad margin, and a me- dian line dilated at centre and ends. GDC. p. 21, pl. 1, f. 29. Scotland. Striae somewhat concentric with extremities, their granules near the margin being closer, and thus forming a continuous rim, with the median line terminating at its inner edge. Remarkable for its large size. Length about 0.044"; breadth •0039". C. Regina (Johnston). —Valve ovate; striae 20 in 001", concentric around the extremities, distinctly granular on either side the median line, in their course out- wards faintly moniliform, more conspi- cuously so and forming a sort of border near the margin. Johnston, JMS. viii. p. 13, pl. 17. f. 1. Elide guano. C. punctatissima (Grev.). — Elliptic, densely areolato-punctate; striae monili- form, concentric with extremities; me- dian line dilated at ends; rim simply striated. Grey M.J. v. p. 8, pl. 3. f. 1. Marine. Trinidad. Striae 20 in .001". I}r. Greville says it differs from C. Mor- wisii in its finer, closer, and more mi- nutely punctated striae. C. crebrestriata (Grev.). — Elliptic- oblong, delicately, closely, and uniformly punctato-striate; striae concentric with extremities; median line straight, simple. Grev M.J. v. p. 9, pl. 3. f. 2, Trinidad. Length .0022" to 0028"; breadth .0012" to 0014"; striae 30 in .001". The figure shows the ends of the valve more atte- muated than usual in this genus. C. Grevillii (S.).-Elliptic, with trans- verse costae; striae moniliform, 15 in 001". SBD. i. p. 22, pl. 3. f. 35. Eng- land, South Africa. - C. regalis (Grev.). --Valve orbicular; striae moniliform, 5 in .001", occupying about a third of the diameter, externally continued by large distant granules, forming three or four concentric rows. GreyjśIS, vii. p. 179, p.7, fi Caii. fornian and Algoa Bay guanos. Striae coarse, Outer granules large and promi- ment, continued round the whole valve, but Smaller near the extremities. Median line abbreviated. C. pinnata (Greg.)—Valve oval; striae concentric with the extremities, large, moniliform, not reaching the median line, but leaving a narrow elliptical blank space; median line distinct. Grev JMS. vii. p. 79, pl. 6. f. 1. Lamlash Bay. C. Parmula (B.). —Broadly elliptic, with a median longitudinal line, having on each side 10 to 12 large, irregular transverse costae (or sulci); surface with transverse granulated striae. Bail. Proc. Phil. Acad. 1853, Tahiti. C. sulcata (B.). — Broadly elliptic or suborbicular, with 30 to 40 transverse arcuate sulci. Bail, l.c. Puget's Sound. C. inconspicua (Grev.).--Suborbicular, with a broad, rather strongly striated border; disc diaphanous, striae faint, con- centric with extremities, becoming ob- scure in the centre. Grev M.J. v. p. 9, pl. 3. f. 3. Trinidad. Diam. 0011"; striae 22 in 001". Dr. Greville's figure shows the striae radiating rather than concentric with the extremities, and leaving a blank median space bisected by the median line and nodule. C. ornata (Greg.). — Elliptic, with a strongly striated rim; disc with a lan- ceolate median blank space, bisected by a faint median line and large nodule; striae somewhat radiant, GDC. p. 19, pl. 1. f. 24. Scotland. C. Finnica (E.). — Ovate-oblong, slightly convex, Smooth externally, but striated within, 6 larger, elliptic, three or four times longer than broad. EMI. many figures. Ehrenberg gives about thirty habitats in Australia, Asia, Ame- rica, and Europe. (XII. 41.) 1-570" to 1-360". Ehrenberg's figures do not agree with his description. They are elliptic with finely-dotted transverse striae, and a blank, generally lanceolate longitu- OF TEIE COCCONEIDEAE, 871 dinal fascia, bisected by median line and nodule. - C. Brundusiaca (Rab.). —Very large, with very convex dorsum ; disc elliptic- oblong, with from 22 to 24 somewhat diverging, transverse, granulated costae, and an oblong central blank space bi- Sected by a linear median line. Rab D. p. 28, t. 3. f. 16. C. margaritifera (E.).-Broadly ovate, with subacute ends and transverse gra- nulated striae like rows of pearls. Marine. Bosphorus, South Africa. It is closely allied to C. Americana, but is rather larger and not curved. * C. mitida (Greg.).-Broadly oval, with Suddenly contracted, subacute, short, point-like apices, transverse rows of very large pearl-like granules, and a Inarrow-lanceolate blank median space. GDC. p. 20, pl. 1. f. 26. Scotland. The granules are so arranged as to form both longitudinal and transverse series. With- out the central nodule, which we have not detected, this species agrees with Rhaphoneis. 3 * Lateral view rhomboid. C. rhombea (E.). — Rhomboid, with about three longitudinal lines on each side the median suture. EMI, pl. 35 A. 7. f. 2. Aquatic. Niagara. 1-1200". Re- sembles C. Americana. With the excep- tion of the median line and module, Ehrenberg's figure has no markings. C. Americana (E.):-Small, rhomboid, with somewhat produced obtuse apices and faint (sometimes obsolete) dotted transverse striae, KSA. p. 53. C. Meact- cana, EA. t. 3. 5. f. 7. Mexico. (XII, 48.) 4* Stride decussating. C. decussata (E.). — Large, broadly elliptic, rough with decussating series of apiculi. K.B. p. 73, pl. 28. f. 17. Cuba, India. C. rhombifera (B.).-Broadly elliptic or suborbicular, with a sigmoid, ob- liquely longitudinal median line, run- ming through a smooth space, attenuated at the ends and enlarged at the nodule into a rhomboid figure; surface decus- sately and transversely punctate, Bail. in Proc. Acad. Philad, 1853. Puget's Sound. 5* Sºriae transverse, separated into two series on each side the median line by a blank longitudinal fascia. C. pseudo-marginata (Greg.).--Large, broadly elliptical, with median line and nodules having on each side fine trans- verse striae, interrupted and separated into two series by a longitudinal blank fascia. GDC. p. 20, pl. 1. f. 27. (VII, 39.) Scotland. Thin, transparent, the ends less rounded than in many species, me- dian line not reaching the extremities, and enclosed in the lanceolate space formed by the convergence of the two lateral fasciae. C. taeniata, EM. pl. 6. 2. f. 12. Fossil. Morea. We have seen no description of this species. The figure represents it as elliptic, having its transverse striae di- vided into two series on each side the median line and nodule by a longitu- dinal blank fascia, as in some species of Navicula. 6* Disc with longitudinal concentric lines ºnterrupted by radiating costae. C. radiata (Greg.). — Elliptic, with rounded ends, about 8 concentric lines interrupted by numerous (18) strong rays proceeding from the itmbilical nodule. Greg TMS. v. pl. 1, f. 26. Scotland. C. costata (Greg.).-Valve oval, rather broad, median line conspicuous, nodule obsolete, marked with strong entire costae reaching from the median line to the margin; spaces between the costae striate; striae at right angles to the costae. Glenshira sand. Greg TMS. v. p. 68, pl. 1. f. 27. 7* Median line and module eaccentric. C. Peaccentrica (Donkin).-Suborbicu- lar, divided unequally by the median line, which does not reach the margin, and furnished with fine, dotted, trans- verse, converging striae. Donkin, TMS. vi. pl. 3. f. 11. Marine. (VII. 40.) North- umberland. One of Dr. Donkin's in- teresting discoveries, remarkable for the excentric position of its median line and umbilical nodule, and probably the type of a new genus. The striae converge towards the umbilicus, their puncta near the margin are closer and more distinct, forming a broad border. 8 * Transverse striae and conspicuous 7margºn. C. coronata (Bri.).-Valve oval; striae transverse, reaching the conspicuous median line, surrounded by a costate band; spaces between the costae punc- tate; costae about 9 in 001"; striae 15 in .001". Bri.JMS. vii. p. 179, pl.9. f. 3. Shell cleanings. West Indies. The me- dian line reaches only to the margin of the band; breadth of band 0002". 872 SYSTEMATIC HISTORY OF THE IN f"USORIA. C. fimbriata (E.). —Valve oval, with a crenate intramarginal line ; coarse transverse puncta reaching the median line. EB. 1858; Bri JMS. vii. p. 179, pl. 9. f.43. Corsican Algæ. This species is readily distinguished by its peculiar looped margin. Doubtful and undescribed Species. C. Navicula (E).--Striated; the navi- cular side ovate; the front view narrow- linear, with an obscure median, longi- tudinal furrow. KSA. p. 53. Baltic, parasitic on Bacillaria paradoaca. 1-864". C. paradoaca, EMI. pl. 9. 2. f. 5. Fossil. Puy de Dôme. Figures Small, elliptic, Smooth, with one or two median longi- tudinal lines and no module. C. Britannica (Nāg.).-Large, elliptic, Smooth, with an accessory limb, mar- ginal outwardly curved limes, and a di- stinct median nodule. KSA, p. 890. On British Algæ. C. tenuissima (Nāg.). — Elliptic, very thin, with concave venter and con- vex dorsum, sometimes with a narrow, opaque, crenulated limb. KSA, p. 890. On TBritish marine Algae. Varies in breadth and in presence or absence of striae and accessory border. C. disciformis (E.), C. navicularis (E), C. Scutum (E.), Swan River; C stellata (E.), C. undata (E.), Western Asia; C. tumida (E.), River Jordan; C. acuta (E.), Ural Mountains; C. turgida (E.), Siberia; C. Indica (E.), C. Bramaputra gº C. angusta (E.), India; C. Sol (E.), Oasis of Jupiter Ammon, Africa; C. Stella (E), Teneriffe; C. Glans (E.), C. Brasiliensis (E.), C. lirata (E.), Brazil; C. Morrisi; (S.), Black Sea. -- FAMILY XV. ACHINANTHEAE. Frustules genuflexed downwards, either free, admate, or stipitate, each lateral Surface having a median longitudinal line and the inferior one a central nodule or stauros also. The Achnantheae, like the Cocconeideae, have a nodule only on the inferior valve; but this is almost the only point of resemblance. this family from every other. resemble the Biddulphieae. The bent frustule and dissimilar lateral surfaces distinguish In their mode of growth the Achnanthea: Genus ACHNANTHIDIUM (Kütz.). — Frustules unattached, solitary or few together, rarely numerous, in front view linear, bent; ventral valve with median line and central and terminal nodules; dorsal valve without a central module. The Achnanthidia resemble unattached frustules of Achnanthes, but are generally very minute, and their proper position is still somewhat doubtful. “Admitting it to be proved that in the species of this genus there positively exists a median nodule in one of the lateral surfaces and not in the other, and that two puncta exist in the extremities of the primary surfaces, as stated in the definition of the order and in that of the family,–admitting this, we should still have to decide whether the uncertain relations of these cha- racters to other families, and their inconstancy, will give us any right to erect a distinct genus on principles so slight and precarious” (Meneghini). rounded; striae obscure. = Navicula tri- nodis, SBD. ii. p. 94, Fresh water. Britain. (VIII. 9. A. lanceolatum (Bréb.). — Frustules * Frustules minute, smooth or obscurely striated. ACHNANTHIDIUM microcephalum (K.). – Frustules extremely minute; valves lanceolate, with capitate apices; striae obsolete, KB, p. 75, pl. 3. f. 13 & 19; SBD. ii. p. 31, pl. 61. f. 380. Fresh water. Europe, (XIV. 15.) Front view marrow-linear. 1-1680". A. trinode (Ar). — Trustules genicu- late; valves with one central and two terminal inflations; median line and central module distinct ; extremities minute; valves oblong-lanceolate, with obtuse ends and turgid centre; striae obscure. Bréb. in KSA. p. 54; SBD. ii. p. 30, pl. 37. f. 304, Fresh water. Eu- rope. Frustules 2 to 100; striae 40 in ‘001", Š. The transverse band of the lower valve sometimes extends to both margins, Sometimes is bifid, and on one half only. A. delicatulum (K.). — Frustules mi- OF TEII, ACEINANTELEAE. 873 nute; valves ventricose, with rostrate ends. KB. p. 75, pl. 3. f. 21. Falcatella delicatula, Rab D. p. 46, t. 5. f. 4. . Sub- marine. Germany. (XIV. 16.) 1-1680". A. cryptocephalum (Nāg.). — Valves lanceolate-linear, with the subacute apices attenuated or obsoletely capitate. Nāg. in KSA. p. 890. Switzerland. A. lineare (S.). — Frustules minute; walves linear, obtuse, upper with median line only, lower with median line and nodules; striae obscure. SBD. ii. p. 31, pl. 61. f. 381. Fresh water. Scotland. A. flewellum (K., Bréb.).—Valves ob- long, with gibbous middle and very obtuse ends; median line sigmoid. Bréb. KSA. p. 54. = Cymbella (?) flewella, KB. p. 80, pl. 4, f. 14; Rab D. p. 23, pl. 7. f. 15; Achnanthes Bavariea, ERBA, 1853, p. 526; Cocconeis Thwaitesii, SBD. i. p. 21, l. 3. f. 33. Fresh water. Europe. –650"; striae indistinct; front view with genuflexed venter, convex dorsum, obtuse ends, and a notch-like punctum at the middle of the lower margin. 2 * Frustules large, distinctly striated. A. coarctatum (Bréb.).—Valves elon- gated, linear-oblong, constricted at the middle, with slightly attenuated, obtuse ends, striae distinct. Bréb. in SBD. ii. p. 31, pl. 61. f 379. = Achnanthidium Otrantinum, Rab D. p. 25, pl. 8. f. 3; Achnanthes binodis, EM. pl. 34, 5 B. f. 1 P. Fresh water, Europe, Africa, America. (VII. 41.) Genus ACHNANTHEs (Boy St.-Vine, Ag). —Frustules bent, solitary or aggregate, attached to a stipes, a central module in the lower or ventral valve only. The frustules are bent downwards; so that the upper margin is convex, the lower one concave. In some species the lateral portions are turgid, the central one looking like a band between them; in others they do not enter into the front view. The superior lateral Surface differs from the lower in the absence of the central transverse pellucid line and central nodule, the latter appearing like a punctum in the front view. A median longitu- dinal line is present in both valves. In their obscure striae “three species (minutissima, easilis, parvula) present great analogy of form with the pre- ceding genus. In one of these (parvula) there is Wanting the characteristic angular bending, for which reason it becomes very similar to Odontidium and Diadesmis. The other species (striatae) differ only by very slight cha- racters from each other ” (Meneg.). * Valves divided by two constrictions &nto three lobes. ACHNANTHES ventricosa (E.).-Valves divided by two constrictions into three oblong inflations; apices rounded; striae distinct. EM. t. 1. 2. f. 9; t. 1. 3. f. 18, 19. = Monogramma ventricosa, E. Asia, Africa, America. 2 * Valves distinctly striated, not three- lobed. Marine. + Valves costate. A. longipes (Ag), Gregºrious; valves elliptic-oblong, costate, with moniliform striae between the costae. ASA, p. 1; KB. p. 77, pl. 20. f. 1; SBD. ii. p. 26, f 300. = Conferva stipitata, Eng. Bot. t. 2488; A. Carmichaëlii, Grev, in Br, Fl. ii. p. 404 (VII, 42.) On Marine Algæ. IEurope, America. Few-pointed; frus- tules large, with stout elongated stipes; front view turgid, with convex dorsum. I-570" to 1-120". 2t Valves striated, but not costate. A. brevipes (Ag). —Gregarious; valves oblong, with attenuated acute ends; striae distinct, momiliform, 20 in .001"; stipes stout, short, AgCD. p. 59; SBD. ii. p.27, pl. 37. f. 301. Marine. Europe, Ame- rica. (x, 199–202) Frustules large, very turgid in front view, with convex dor- Sum. 1-860” to 1-180". A. salina (K.). — Frustules striated, very turgid, obtuse-angled, genuflexed, with slightly notched venter ; valves broadly linear, with cuneate ends; striae punctated; stipes very short, thick. KB. } 77, pl. 20. f. 5. Salt marshes, Europe. iffers from A. brevipes only in its more linear Valves and cuneate ends. Professor Smith was probably right in uniting them. - A. intermedia (K.). — Few-jointed; frustules striated, obtuse-angled, turgid; valves sublinear, with acutely cuneaté ends; stipes short, distinct, fine, KB. p. 76, pl. 20... f. 6. On Enteromorpha intestinalis, Germany, France. Smaller 874 SYSTEMATIC ELISTORY OF TELE INFUSORIA. than A. brevipes, with less turgid dorsum and finer striae; but we doubt whether they are truly distinct. A. rhomboides (E.). —Frustules large, striated, very turgid, nearly straight; valves broadly lanceolate, almost rhom- boid, with acute apices; stipes short, thick, EA, p. 121. = A. ventricosa, KB. }. 76, pl. 20. f. 7. Marine. America, Jurope. A. multiarticulata (Ag). — Frustules striated, turgid, with rather obtuse angles; valves elliptic-lanceolate; stipes stout, short. Ag CD. p. 59; KB. p. 76, pl. 20. f. 8. Marine. Europe. 1-312". A. Capensis (K.). —Erustules striated, turgid, obtuse-angled; valves lanceolate- elliptic or oblong; stipes elongated, stout. KB. p. 76, t. 21. f. 1. Marine. Cape of Good Hope. 1-600". It varies with few or many frustules. A. bacillaris (E.). —Frustules narrow, striated, each slightly inflexed at the middle, both dorsally and ventrally equally bacillar, with rounded ends; stipes short, ERBA. 1843, p. 256. Ma- rine. Venice. Often in long series. It is Smaller than A. longipes, and more 'slender than A. brevipes, E. A. subsessilis (K.).—Scattered, of few frustules ; valves linear-oblong, with rounded ends; striae moniliform, 24 in •001"; stipes nearly obsolete. KB. p. 76, t. 20. f. 4; SBD. ii. p. 28, pl. 37. f. 302. = Achnanthes turgens, EA, p. 121. Common on filiform species of Enteromorpha in salt marshes. Europe, America. 1-1150" to 1-430". (VII. 43.) Easily recognized by its all but sessile frustules. A. angustata (Grev.). — Front view narrow; length -0060"; breadth .0004"; striae 24 in .001". Grev M.J. vii. p. 163, pl. 8. f. 9. In Californian guano. “The striae agree in number with those of A. Subsessilis; the relative length and breadth, however, of the valve, as seen in the front view, is so widely different from the proportions of the species above mentioned, that the possibility of its being a variety cannot be entertained” (Greville). A. cristata (Rab.). —Valves oblong- elliptic; striae gently curved, coarsely moniliform, distant, 9 to 10 in 001". Rab D. p. 26, pl. 8. f. 7. Italy. A. genuflewa (K.). — Frustules small, striated, turgid, obtuse-angled, strongly bent; stipes short, rather stout. KB. p. 76, pl. 21. f. 3. Marine. Genoa. A. Gregoriana (Grev.). — Front view of frustule broadly linear; striae very fine; length .0060" to 0080"; breadth '0010" to 0015". Grey M.J. vii. p. 84, pl. 6. f. 13, 14, Marine. Scotland. In point of size it rivals A. longipes, but is widely separated from it in the character of the striation alone, to perceive which requires not only a good object-glass but delicate manipulation. As in many of its congeners, the frustules vary greatly in both length and breadth (Grev.). A. pachypus (Montagne), – Frustules Small, finely striated, obtuse-angled, rather turgid ; valves elliptic-oblong; stipes stout, very short, Mont. Flor. Boliv. pl. 1; KB. p. 76, pl. 29. f. 83, Marine. Europe, Asia, America. 1-1730" to 1-1320". A, parvula (K.). — Frustules minute, nearly straight, obtuse-angled; valves elliptic-oblong, obtuse, finely striated; stipes rather stout. KB, p. 76, t. 21.f. 5. On Enteromorpha in brackish water. Europe. Frustules stouter than in A. eacilis. 3 * Very minute; striae wanting or &ndistinct. Fresh water. A. eacilis (K.). — Frustules slender, linear ; valves lanceolate, tapering to the subacute apices; striae indistinct; stipes slender, elongated. KB. p. 76, t. 21. f. 4; Ralfs, ANH. xiii. p. 14. f. 12; SBD. ii. p. 29. Fresh water. Europe, Asia, America. (VII, 44.) A. eacilis is easily known by its minute, slender, hyaline frustules from every other spe- cies except A. minutissima. From that species it differs by its tapering, more lanceolate and acute valves, and by its elongated Stipes. A. minutissima (K.).—Frustules slen- der, linear; valves linear-oblong, with rounded ends ; striae obsolete ; stipes fine, shorter than the frustule. #. p. 75, pl. 13. f. 2 c.; Ralfs, ANH. xiii. pl. 14. f. 11. Fresh water. Europe. We for- merly considered this a variety of A. eacilis, and, still doubting whether the differences are constant, think that Pro- fessor Smith may rightly have united them. Doubtful Species. A. Parenicola (Bail.).--Frustules mi- nute, rectangular or slightly curved; valves lanceolate, striate; stipes short. Bail. Sm. Cont. ii. p. 38, pl. 2. f. 19. Marine. America. # is possibly a spe- cies of Hyalosira, but requires further study (Bail.). A. australis, EMI, pl. 35 A. 2. f. 1. South Africa. Frustules linear, uni- OF TEIE CYMBELLEAE. 875 formly curved, with truncate ends and striated margin. A. P incequalis (E.). —Unequally bent and smooth, EM. pl. 16. 1, f. 45, & pl. 17. 2. f. 25. Fossil. Sweden, Finland. A. P. paradoaca (E.). —Frustules ovate, obtuse, twice as long as broad, with 16 transverse, scabrous, punctated lines in 1-1152". ERBA, 1845, p. 73. Fossil, United States, No nodule ob- served, E. 1-900". Species known to us only by name, A. turgida (E.), Australia, America; A. Indica (E.), India; A. Javanica (E.), Java; A. obtusa (E.), Africa; A. Semen (E.), America; A. Brasiliensis (E.), Bra- zil; A, incrassata (E.), America. Genus CYMBOSIRA (Kütz.).-Frustules as in Achnanthes, stipitate, con- nected into series by a gelatinous process or hinge (isthmus). Cymbosira differs from Achmanthes by the same character as Diatoma from Fragilaria. CYMBOSIRA Agardhi (K.). — Frus- tules linear, slightly curved, with rounded obtuse apices, KB. p. 77, pl. 20. f. 3. =Achmanthes seriata, Ag CD, Marine. apices; valves linear, oblong, scarcely Venice, Cayenne. (XIV. 14.). 1-960" to dilated at the middle, with rounded | 1–288". Stipes very short. Genus MONOGRAMMA (Ehr.).-Frustules furnished with transverse pin- mules, a median, transverse, linear band on one valve only, three ventral modules and two dorsal. (=Stauroptera with a stauros on one valve only, or to a solitary Achnanthes with terminal puncta-ERBA, 1843, p. 136.) Not- withstanding Ehrenberg's remarks, we cannot distinguish this genus from Achnanthidium. The species are known to us only by name. - MonoGRAMMA Achnanthes (E), India. M, trinodis (E.), Sandwich Islands, M. ventricosa (E.) = Achnanthes ven- trºcosa. FAMILY XVI.—CYMBELLEAE. Frustules cymbiform ; valves lunate, with a longitudinal line, and mar- ginal or subcentral nodule. In shape the Cymbelleae are very similar to the Lunotieae, but they differ essentially both from them and the Naviculea by the median nodules of the lateral surfaces being marginal or submarginal. Genus CYMBELLA (Ag., Kütz.).-Frustules free, cymbiform ; transverse striae interrupted by a longitudinal line having central and terminal nodules, and dividing the valve into unequal portions. The frustules, in the lateral view, have one margin (dorsum) convex, and the other (venter) straight, or at least less developed. In consequence of this form, the longitudinal line divides the surface unequally, being much nearer the lower margin. Cymbella includes species distributed in the genera Cocconema, Navicula, and Pinnu- laria of Ehrenberg’s system. * Valves with one margin triundulate. CyMBELLA Arcus (Greg.). — Valves slender, semilanceolate, with straight venter, convex, triundulate dorsum, and produced, minute, capitate apices. Greg. in M.J. iv. p. 6, pl. 1. f. 21; SBD. ii. . 85. Scotland. Minute; longitudinal É and nodules submarginal; transverse striae very fine, 40 in 001". C. sinuata (Greg.).-Valves lanceolate, with subcapitate apices, gently convex dorsum, and triundulate venter, Greg. M.J. iv. p. 4, pl. 1, f. 17. Scotland. Minute; transverse striae conspicuous, about 20 in 001", scarcely reaching the median line. 2 * Valves without triundulate margins. f Valves with produced or capitate apices. C. Ehrenbergii (K.).—Valves broadly lanceolate, with unequal sides, suddenly contracted into rather obtuse, slightly produced apices; transverse striae di- stinct, punctate, 12 in 1-1200". KB. p. 79, t. 6. f. 11; SBD. i. p. 17, pl. 2. f. 21. = Wa- vicula indequalis, E Inf. t. 13; Pinnularia tnaequalis, EMI, many figures, Common, 876 SYSTEMATIC HISTORY OF TEIT, INFUSORIA. both recent and fossil. Europe, Asia, Africa, America. (VII. 46; IX. 154.) Large; length 1-216". Differs from a Navicula only in having one margin of the valves iess convex than the other. C. heteropleura (E., K.). — Valves broadly lanceolate, with unequally con- vex sides, suddenly contracted into short, broad, very obtuse, beak-like apices; striae distinct. heteropleura, EM. pl. 5. 2. f. 11. North America. Large; allied to C. Ehren- bergii, but with more obtuse apices. C. cuspidata (K.). — Valves broadly lanceolate, with unequally convex sides, suddenly contracted into subacute, short, rostrate ºpiºs; striae delicate, 18 to 20 in 1-1200". KB. p. 79, t. 3. f.40; SBD. i. p. 18, pl. 2. f. 22. Europe. 1-576". (VII. 45.) Differs from the preceding species in its smaller size, more graceful form, and narrow beaks. C. rostrata (Rab.). — Valves semilu- mate, with dorsum strongly and venter slightly convex; ends produced into short, subacute beaks; striae dotted, con- verging, 12 or 13 in 1-1200". Rab D. p. 22, pl. 7. f. 5. Italy. Small, Very nearly allied to C. cuspidata. C. porrecta (Rab.). — Valves turgid- lanceolate, with unequal margins; ends pººl into rather long, stout, obtuse eaks; striae stout, Sohmewhat converg- ing, 6 in 1-1200". Rab D. p. 22, pl. 10. f. 10. Italy. Venter less turgid than the dorsum. C. fornicata (Rab.).-Valves lunate, with very fine convex dorsum, gibbous venter, and produced, obtuse, rostrate ends; striae fine, Smooth, 7 or 8 in 1–1200". Rab D. p. 22, pl. 10. f. 9. Persia. C. amphicephala (Nāg.). — Smooth; valves elliptic, with unequal sides and produced capitate apices; front view oblong with truncate ends. KSA. p. 890. Switzerland. C. aequalis (S.). —Valves lanceolate, nearly symmetrical, with shortly pro- duced, slightly curved, obtuse extre- mities; striae fine, 30 in 001". SBD. ii. . 84; Grev. in ANH. 2 ser. xv. pl. 9. . 4. Britain. A very distinct species, which differs from Navicula only i. the slightly curved ends, Grev. C. pachycephala (Rab.).-Valves semi- lunate, curved, with very convex dorsum and gibbous venter, strongly constricted beneath the produced capitate apices; striae granulate, somewhat converging, 7 or 8 in 1–1200". Rab D. p. 22. = C. eurycephala, Rab. t. 7. f. 10. §º. KB. p. 79, = Pinnularia C. epithemioides (Rab.).-Valves arcu- ate, with convex dorsum, concave venter, and produced, obtuse, slightly recurved ends; striae stout, somewhat converg- ing, 6 in 1-1200". Rab D. p. 22. - C. costata, Rab. t. 7. f. 16. Salzburg. Like an Epithemia, but having a central nodule. C. Gregorii (Ralfs). —Valves arcuate, with convex dorsum, straight venter, and slightly produced truncate apices; striae distinct. = C. truncata, Greg. in M.J. iii. p. 38, pl. 4. f. 3. Scotland. Small. C. turgida (Greg.). — Valves lunate, with turgid, convex dorsum, nearly straight venter, and produced, minute, acute apices; striae very conspicuous, about 24, in 2001". Greg M.J. iv. p. 5, pl. 1. f. 18. Scotland, America. C. Pisciculus (Greg.).-Valves lanceo- late, with convex dorsum, nearly straight venter, and obtuse, Subcapitate apices; striae about 30 in 001". "Greg. in MJ. iv. p. 6, pl. 1, f. 20. Britain. C. eccisa (K.). — Valves semilunate, with slightly recurved, produced apices, very convex dorsum, and a straight venter, notched at its middle; striae 16 in 1-1200". KB. p. 80, pl. 6. f. 17. Europe. Minute. 2f Apices neither rostrate nor capitate. C. affinis (K.). — Valves lanceolate, with subacute, scarcely produced apices, and the dorsal margin more convex than the ventral; striae faint, 19 in 1–1200". KB. p. 80, pl. 6. f. 15; SBD. i. p. 18, pl. 30, f 250. = Cocconema Fusidium, EMI. many figures. Europe, Asia, Australia, Africa, America. Minute; terminal modules large. 1-1150" to 1-620". C. delicatula (K.).-Valves unequally and narrowly lanceolate, smooth. KSA. b. 59. France. Minute. 1-1200". C. obtusiuscula (K.).-Valves lanceo- late, with one margin rather less convex than the other; apices somewhat obtuse, not produced; striae fine, 18 to 20 in 1-1200". KB. p. 79, pl. 3. f. 68. Europe. 1-600". Differs from a Navicula only by its slightly unequal margins. C. Helvetica (K.).-Valves elongated, Somewhat arched, slender-lanceolate, with slightly gibbous venter, and rather obtuse apices; striae fine, granulated, 13 or 14 in 1-1200". SD. i. p. 18, pl. 2. f. 24. Europe. (XIV. 24–28.) Targe. 1-264" to 1-240". Front view oblong, trum- cate. Akin to C. gastroides, but more slender, K. C. maa'ima (Nāg.), — Valves slender, with attenuated, rather obtuse ends, and OF TEITE CYMBELLEAE. 877 inflated venter; striae 16 in 1-1200." 1–1000". Front view oblong, with trun- cate ends. KSA. p. 890. Switzerland, 1-180° to I-120". C. gastroides (K.). — Valves lunate, with obtuse apices; venter slightly con- cave, with gibbous centre; striae granu- lated, 11 or 12 in 1-1200". KB. p. 79, pl. 6. f. 4 b. Europe. (XIV. 18–20.) Large. C. truncata (Rab.).—Valves as in C. gastroides, but with broadly truncate apices. Rab D. #. C. fulva, t. 7. f. 3. = C. gastroides, . p. 79, pl. 6. f. 4 a. Europe. C. leptoceras (E., K.).-Valves slender, arcuate, with gibbous venter and attenu- ate apices; striae very fine, 17 in 1-1200". KB. p. 79, pl. 6. f. 14, - Cocconema lep- toceras, EA and M. many figures. Eu- rope, Asia, Australia, Africa, and Ame- rica. Minute; front view elliptic-oblong, with rounded ends. C. maculata (K.).-Valves Semiorbicu- lar, with very convex dorsum and straight or gibbous venter; striae very fine, 12 to 13 in 1-1200". KB. p. 79, pl. 6. f. 2. = C. Lunula, Rab D. p. 23. = Cocconema Lunula, EA and M. many figures. Com- mon. Europe, Asia, Africa, America. Minute; front view elliptic, with trun- cate ends. C. obtusa (Greg.).-Valves semi-oval, with very obtuse apices, convex dorsum, and nearly straight venter; striae very fine, inconspicuous, about 36 in 001". Greg M.J. iv. p. 5, pl. 1. f. 19. Scotland. Minute. C. ventricosa (Ag). —Valves semilu- nate, with very convex dorsum, straight venter, and large, distinct terminal nodules; striae inconspicuous, 30 in .001". Ag CD. p. 9; KB. p. 80, pl. 6. f. 16; SBD. ii. p. 84, Europe. Minute. C. microstoma (Rab.).—Valves lunately curved, with broadly obtuse ends; dorsum convex, depressed at the centre; venter concave; nodules very minute ; striae smooth, 7 or 8 in 1-1200". Rab D. p. 22, t. 10. f. 3. Persia. C. Scotica (S.).-Valves slender, semi- lanceolate, with straight ventral margin and acute apices; striae 42 in 001". SD. i. p. 18, pl. 2. f. 25. Britain. C. gracilis (E., K.). —Valves slender, semilanceolate, with straight or slightly concave ventral margin and subacute apices; striae very fine or obsolete, 17 in 1–1200". KB. § 79, pl. 6. f. 9. = Cocco- nema gracile, EMI. Several figures. Eu- rope, Asia, Africa, America. Lough Mourne deposit. Small. 1-840" to 1–600". C. lunata (S.).-Valves narrow, lunate, with slightly concave venter, and rather obtuse apices; striae distinct, 24 in .001". SBD. ii. p. 84. Grev. in ANH. 2nd ser. xv. pl. 9. f. 5. Scotland. Di- stinguished from C. Helvetica by its Smaller size and concave venter, and from C. Scotica by its coarser striae and obtuse ends, Grev. C. curvata (Rab.).—Valves smooth, lunate, with convex dorsum, slightly con- cave venter, and obtuse ends. Rab D. p. 23, t. 7. f. 14. 6. Italy. C. P. Dianae, E. = Cocconema Dianae, EM. pl. 15 A. f. 100 a. Lough Mourne deposit. Small. Valves lunate, with convex dorsum, concave venter, and ob- tuse apices. C. P. Navicula = Cocconema Navicula, EM. pl. 17. 2. f. 35. Finland. —Valve lanceolate, with the dorsum rather more convex than the venter. Genus COCCONEMA (Ehr.). — Frustules cymbiform, stipitate; lateral surfaces lunate, striated, and divided unequally by a longitudinal line with median and terminal nodules. The frustules are similar in form to those of Cymbella, and when detached, their proper genus is often doubtful; the lower margin, however, is less frequently convex than it is in Cymbella. Cocco NEMA lanceolatum (E.).--Front view lanceolate, truncate; Valves elon- gated, arcuate, or semilanceolate, centre of venter gibbous; striae moniliform, 21 in .001". EI. t. 19. f. 6; SBD. i. p. 75, pl. 23. f. 219. Europe, Asia, Australia, Africa, America. (x,194, 195.) Length 1–210" to 1-120". - frustule nearly straight, with slightly gibbous centre; stipes dichotomous, articulated. - Ventral margin of C. asperum (E.).-Habit and size of C. lanceolatum, but with striae denticu- late or interrupted by puncta. EMI. many figures. Australia, Asia, Ame- rica; fossil, France. 1-288". We fear this form is scarcely distinct from C. lanceolatwºm. C. fossile, EM. t. 19. f. 57. Greece. Ehrenberg's figure represents a smaller species than C. asperum, with straight ventral margin, nearly marginal longi- 878 SYSTEMATIC EIISTORY OF TELE INFUSORIA, tudinal line and modules, and denticulate striae. C. Bremä (Nāg.).--Pulvinate; valves slender, sublunate, with attenuated ends and obtuse apices; striae very fine, KSA. p. 890. Rocks in streams. Switzer- land. . Large; stipes long, articulated; frustules in front view lanceolate. C. cornutum (E.). —Valves slender; lunate, gradually tapering into long ends, with obtuse apices; venter concave, gra- dually tumid at its middle, EMI. pl. 15 A. f. 94, America, Berlin. Lough Mourne deposit. Large; differs from C. lanceo- latum in its more slender and tapering form. C. Mearicanum (E.).--Stout; valves lunate, with obtuse, slightly produced ends; ventral margin slightly tumid; dorsum very convex; striae 18 in 1-1152", distinctly and elegantly granu- lose. EM. pl. 33. 7. f. 6, 7, Mexico. Large. 1-206". C. Cistula (E.).-Valves lunate, with very convex dorsum, and the concave venter tumid at its centre; stipes elon- gated, filiform, subsimple, EI. t. 19. f. 7; SBD. i. p. 76, pl. 23. f. 221. = Gom- phonema semi-ellipticum, Ag CD. p. 33; G. simplex, KSA. p. 37. Europe, Asia, America. (x. 196–198.) 1-1150" to 1-430". Front view elliptic-oblong, with obtuse ends. C. Graecum (E.).-Habit of C. Cistula, but with stronger and fewer striae, 12 to 3 in 1-576". ERBA, 1840, p. 12. Greece. 1-575". C.? biceps (E)-Valves turgid, semi- oval, each ends in a flat and tumid mar- gin, Suddenly rostrate, obtuse; sides longitudinally sulcate and transversely striate. ERBA. 1845, p. 362. Marine, India, 1–576". Habit of C. Cistula. C. cymbiforme (Ag., E.). —Slender; valves lunate, with somewhat obtuse apices; venter straight or slightly con- cave, with rather tumid centre; stipes intricate, forming a compact gelatinous mass. EI. pl. 19. f. 8; SBD. i. p. 76, pl. 33. f. 220. = Cymbella cymbiformis, Ag CD. p. 10; Frustulia cymbiformis, IKSA. Europe, Asia, America. (XII. 46.) 1-500" to 1-150". Transverse striae 16 in 1–1200". Front view linear- lanceolate, with truncate ends. It forms a brownish compact covering on rocks, which is frequently of considerable thickness and extent. C. P. acutum (E.). —Slender, slightly curved, smooth (?), with acute ends; ventral margin slightly tumid in the middle, EA, p. 123. Labrador, Falaise P. Small; habit of a curved Navicula am- phioaſs. C. tumidum (Bréb.).—Valves semilu- nate, with obtuse, scarcely produced ends; ventral margin nearly straight; front view lanceolate, with truncate apices. KSA, p. 60. France. Small. 1-576". Striae 16 in 1-1200". Stipes elongated, filiform, simple. C. affine (K.).-Valves lunate, with very convex dorsum ; stipes intricate. KSA. p. 59. France. Minute. Tesembles Cymbella affinis, but is stipitate. C. gibbum (E.).-Valves semielliptic, with truncate, slightly pººl apices; transverse striae very delicate. ... t. 6. f. 6. Europe, Asia. (XIII. 10.) 1-480". 8 sessile. Stipes obsolete. = Cymbella Orsiniana, Rab D. p. 23. C. Arcus (E.).-Semilunate, with ob- tuse apices; dorsum very convex, venter not gibbous, EMI. Several figures. Asia, America, Lough Mourne deposit. C. parvum (S.).-Valves lunate, with subacute ends; ventral margin scarcely gibbous; front view nearly linear, SBD. i. p. 76, pl. 23. f. 222. (VII. 47.) Cliff, Beachy Head. Minute, 0009" to 0016". Striae 21 in 001". C. Saaronicum (Rab.). —Valves semi- lunate, with acute ends; ventral margin straight or slightly concave; dorsum very convex; striae faint. Rab D. p. 24, t. 10. f. 11, Saxony. Minute. The front view is figured as oblong, with truncate ends, and the stipes dilated beneath the frustule. C. Boeckii (E.).-Valves elongated, lanceolate, with subacute apices; front view linear-lanceolate, obtuse; striae 26 in 1-1200". E Inf. t. 19. f. 5. = Gompho- nema lanceolatum, Ag CD. p. 34; Dory- phora Boeckii, SBD. i. p. 77, pl. 24. f. 223. Marine. Europe. Large. 1-210" to 1-120. Stipes dichotomously divided. (VII, 48.) This species is no doubt wrongly referred to Cocconema, since both margins of the lateral valves are symmetrical. We regard it as a stalked Navicula, and find a central, though in- conspicuous, module—a fact which, we think, forbids it being placed in Dory- phora as Professor Smith proposed. Species known to us only by name. C. subtile (E.), Asia, America; C. cingulatum $º Georgia; C. Javani- cum (E.), Java; C. Araucania (E.), America. - OF THE CYMBELLEZE. 879 Genus SYNCYCLIA (Ehr.)—Frustules cymbiform, connected in a circular manner within an amorphous gelatinous substance. “Whenever the lateral surfaces are inclined to each other by the different extension of the two pri- mary surfaces, the associated series must be formed circularly” (Meneg.). SYNCYCLIA Salpa (E.). — Frustules Semi-oval, smooth, mostly connected, in sixes, into short tubes or rings; colour- ing matter pale green. E Inf. p. 233, t. 20. f. 11; KSA. p. 61. Marine, near Wismar. (VII, 53; x. 206.) Length 1-2300" to 1-570". When dry, longi- tudinally plicate. S. Quaternaria (E.).—Frustules binate or quaternate, Smooth; colouring matter golden- or reddish-brown. ERBA. 1840, p. 22; KSA. p. 61, Marine. Europe. 1-864". Species known to ws only by name. S. granulata (E.), Georgia; S. Am- phora (E.), Palestine. Genus ENCYONEMA (Kütz.).-Frustules cymbiform, arranged in longi- tudinal series within submembranous tubular filaments. Valves divided unequally by median line and nodules. “Bricyonema differs from Schizo- nema and other frondose genera of Diatomaceæ in the form of its frustules, a single frustule resembling one of Cymbella or Cocconema. It is more probable that some bodies, which are really congeries of the ova of certain insects, will be at first sight classed with Encyonema, ; but these ova, although cymbiform and arranged in longitudinal series, are neither siliceous nor striated. . . . . The lateral surfaces of the frustule, being convex, are observed in the front view, in which also the frustules are quadrilateral, with two puncta at each end. These puncta are less easily discerned in the dorsal view, and the dorsum is longitudinally convex. The lateral view is semi- elliptic, with numerous transverse striae, which are interrupted, as in Cocco- nema, by a longitudinal pellucid line” (Ralfs). Professor Smith says that the frustules of Encyonema, even when removed from the frond, may be distin- guished from those of Cymbella, “as the terminal nodules of the median line in Cymbella are placed at the extremities of the valves, while in Encyonema they are removed to some distance above, and occupy a place nearer the central nodule.” ENCYoMEMA prostratum (Berk, Ralfs). — Filaments subsimple; valves with rounded, mostly incurved ends; striae 18 in .001". Length .0016" to .0024". Ralfs, ANH. 1st ser. xvi. º 3. f. 3; KSA. p. 61; SD. ii. p. 68, pl. 54 f. 345. = Monema prostratum, Berk B.A. pl. 4. f. 3.; Schizonema prostratum, Grey BFl. p. 414; Encyonema paradoxum, E Inf. p. 237; Glaeonema Leibleini, Ag CD. p. 31? Europe, Asia, America. The valves have a depression beneath each apex; sometimes the depression is very slight, at others so deep and notch-like that the ends become rostrate. The former condition is the E. paradoxum of Kützing. (VII.49; XIV. 22. E. Auerswaldii (Rab.). --Valves with very convex dorsum, slightly gibbous venter, and contracted, produced, obtuse ends; striae 11 or 12 in 001". Rab D. p. 24, pl. 7. f. 2. Leipzig. E. caespitosum (K.).-Filaments erect, tufted, much interwoven; valves with convex dorsum, slightlytumid venter, and straight, slightly produced, obtuse ends; striae 24 in 001". KSA, p. 61; SBD. i. p. 68, pl. 55. f. 346. = E. prostratum, KB. 82. Europe. The frustules are Smaller than those of E. prostratum, E. triangulum (E., K.).-Valves with very convex, gibbous dorsum, slightly convex venter, and produced, acute apices. KSA. p. 62. = Gloeonema trian- gulum, ERBA. I845, p. 77; EM. t. 35 A. 7. f. 10. River Niagara. Dorsum so turgid as to give the valve a triangular outline. “It is a very remarkable cir- cumstance, that I often found two differ- ent sorts of frustules in the same tube —one very delicate and straight like a Naunema, the other the large curved kind. Even to the present moment I cannot explain this phenomenon; for both sorts were in considerable quantities and quite free, and therefore it is difficult to suppose one a parasite” (E.). E. Sinensis (E.). — Valves oblong, 880 SYSTEMATIC EIISTORY OF TEDE INFUSORIA, striated, with the habit of Cocconema, but suddenly reflexed under the very obtuse apices in the manner of Eunotia. = Gloeonema Simense, ERBA. 1847, p. 484; EM. China, Java, Ehrenberg's figure represents the valve distinctly striated, with straight venter, very ob- tuse, rounded ends, and the dorsal mar- gin very convex, and curved upwards at each end. E. gracile (Rab.). — Valves slender, middle and indistinct striae. Rab D. p. 26, pl. 10. f. 1. Salzburg. Frustules minute. Doubtful Species. E. globiferum (Ag). —Eilaments ab- breviated, frustules simple or binately conjoined, hyaline, with a globule in the middle. = Gloeonema globiferum, Ag CD. p. 31. Italy. E. Arcus= Gloeonema Arcus, ERBA. with truncate apices, slightly gibbous 1856, p. 333, f. 26. Africa, Genus AMPHORA (Ehr.).-Frustules free, cymbiform; lateral view lunate or arcuate, with a nodule at the middle of the ventral margin; front view with the median lines and nodules of valves approximate and within the margin. The frustules are mostly very thin, hyaline, and imperfectly sili- cious: their form is peculiar; and Professor Arnott, who has given in the sixth volume of the ‘Microscopic Journal’ a detailed account of their structure, aptly compares it to that of “a coffee-bean rounded on the back and hollowed out in front.” Many of the species are insufficiently known ; they should be viewed in front, back, and side. Fortunately, from their hyaline nature, the dorsum and venter can in most cases be examined merely by the alteration of the focus. The lateral view closely resembles that of a Cymbella, but has the nodule marginal. The front view is usually barrel-shaped, owing to the con- vexity of the valves, which are so curved inwards that their central nodules are more or less approximate and frequently appear nearer to the connecting zone than to the margins. The portions of the valves interior to the median line are inconspicuous, and rarely afford diagnostic aid; whilst the portions exterior to the median lines are important, offer the best view of the trans- verse striae, and vary in shape according as the median line appears straight, concave, or flexed. In our descriptions we call these latter the outer por- tions, and when they project inwards at the centre in a cuneate manner, or appear inflexed, we term them canoe-shaped. The dorsum is convex, shows no nodules or lateral valves, and is mostly marked by longitudinal lines between longitudinal series of short, transverse striae, like the connecting zone of Striatella, but unaccompanied by internal plates. The late Pro- fessor Gregory, who directed attention to these facts, believed that Amphora could be divided into two groups—simple and complea, from the absence or presence of this structure. His arrangement, however, we are unable to adopt, because in many species a decision is difficult; and indeed we think that the longitudinal lines, so common if not invariable, indicate the complex structure, although the hyaline nature of the frustules may interfere with its detection. In Amphora the specific characters are taken, almost constantly, from the front view, and not from the lateral one as in most other genera of Diatomaceae; and as the connecting zone varies greatly in breadth according to the condition of the frustule, due allowance must be made for that fact. If division has recently taken place, the connecting Zone will be narrow, and the ends of the frustule less broadly truncate than just previous to that process. For the same reason we believe that the number of longitudinal lines varies and affords no aid in distinguishing the species. Amphora contains several species of Agardh’s genus Cymbella, and ought, in our opinion, to have re- tained that generic appellation. Because of its cymbiform frustules, we have removed this genus from the Naviculea, where Kützing placed it; the same reason, added to the presence of median lines and nodules, compels us to OF THE CYMBELLEAE. 881 place it with the Cymbelleae instead of with the Surirellea, as Rabenhorst has done. * Frustules in front view distinctly constricted at the middle. AMPHORA binodis (Greg.).-Frustules constricted at the middle; lobes inflated at the base, with broadly linear, Sub- truncate ends; transverse striae obscure, about 30 in .001". GDC. p. 38, pl. 4. f 67. Marine. Scotland. Resembles the next species, but is Smaller, with more rounded inflations and obscure striae, Greg. A. angularis (Greg.).-Frustules simu- ato-constricted at the middle; lobes an- gularly inflated, with short, broadly linear, truncate, produced ends; striae distinct. Greg. M.J. iii. p. 39, pl. 4. f. 6. (VII. 50.) Differs from A. binodis by having angular inflations and coarser striae. A. lyrata (Greg.). — Frustules con- stricted at the middle; lobes with in- flated base and truncate end; modules transversely dilated; striae distinct. GDC. p. 48, pl. 5. f. 82. Marine. Scot- land. Striae about 36 in 001"; connect- ing zone with longitudinal lines. A. Milesiana (Greg.). — Frustules linear, with slightly constricted middle and truncate ends, furnished with longi- tudinal lines and conspicuous transverse striae. GDC. p. 49, pl. 5. f. 83. Scot- land. Striae about 28 in .001", Greg. 2 * Frustules not panduriform ; modules transversely dilated and bar-like, A. membranacea (S.).-Frustules ellip- tic-oblong, with rounded ends; valves with a central transverse band, and very close transverse striae; connecting zone with longitudinal lines. SBD. i. p. 20, l. 2. f. 29; Ro M.J. vi. p. 24, pl. 3. f. 8. Hºli. water. Europe. * 51.) Scarcely silicious. - A. laevissima (Greg.),—Frustules very hyaline, linear-oblong, with rounded ends; outer portions of valves slender, tapering, with a transverse nodule, and obsolete or indistinct striae, GDC. p. 41, pl. 4, f 72. Scotland. A. laevis (Greg.).-Frustules very hya- line, linear, with subtruncate ends; outer portions of valves very narrow, with a transverse module and indistinct striae. GDC. p. 42, pl. 4, f 74. Scotland. Outer portion of valve canoe-shaped; striae about 60 in '001". A. minutissima (S.).-Frustules para- sitic, very minute, oval or suborbicular, with transversely dilated modules, and 64 obscure striae in 001". SBD. i. p. 20, pl. 2. f. 30. Fresh water. Para- sitic on other Diatomaceae. A. rimosa (E.).-Germany. Frustules elliptic-oblong, with rounded ends, nar- row lunate outer portions, transverse pºle. and no striae. EMI, pl. 13. 2. . 17. - A. elegans (Greg.). — Frustules oval, with truncate ends; outer portion of Valves lunate, with transverse nodule, and very fine, inconspicuous, transverse striae. Greg. TM. v. p. 70, pl. 1. f. 30. Scotland. A. ostrearia (Bréb.).-Frustules hya- line, elliptic-oblong, with rounded ends; outer portion of valves marrow, canoe- shaped, with transverse nodule and di- stinct striae ; dorsum with numerous, very delicate longitudinal lines. Bréb. in KSA, p. 94, Marine. France. Lateral view lunate, with convex dorsum and straight venter, * A. quadrata (Bréb.). —Erustules hya- line, quadrangular, with truncate ends; outer portion of valve small, inflexed, with transverse nodule; dorsum with numerous, very delicate longitudinal lines. KSA. p. 95. Marine. France. Lateral view very narrow, lunate. A. quadrata differs from A. ostrearia by its straight margins and truncate ends. A. rectangularis (Greg.). — Frustules narrow, linear, with truncate ends; valves with a transverse module, and 40 fine transverse striae in 001". Greg. TM. v. p. 70, pl. l. f. 29. Scotland. A. mobilis (Greg.). — Frustules very hyaline, barrel-shaped, with truncate ends; outer portion of valves very nar- row, arcuate, with transverse module, and fine transverse striae; dorsum with longitudinal lines. GDC. p. 49, pl. 5. f. 87. Scotland. Large; striae about 40 in 001"; ventral margin of valves COIl C8, W6. A. acuta (Greg.). — Frustules elliptic, with truncate ends; outer portion of Valves arcuate, with straight median line, transverse nodule, and distinctly moniliform, transverse striae. GDC, p. 52, pl. 5, 6...f. 93. Scotland. Large; striae about 36 in .001". A. litoralis (Donkin).-Frustules oval, with truncate ends; outer compartment canoe-shaped, with distinct moniliform striae and transverse bar-like module; dorsum with longitudinal series of short 3 L 882 SYSTEMATIC EIISTORY OF TEIIL INFUSORTA, transverse striae. Donkin in TMS. vi. . 30, pl. 3. f. 15. Marine. Northumber- and, (VII, 52.) 3* Frustules with produced or rostrate ends and roundish modules. A. aponina (K.). — Frustules lanceo- late-elliptic, with produced, truncate apices, and no longitudinal lines. KB. p. 108, pl. 5. f. 33. Italy. Minute. I-1080" to 1–650". A. coffedeformis (Ag., K.).-Frustules lanceolate, with produced, obtuse apices, strong marginal longitudinal lines, and faint or obsolete median ones. KB, p. 108, t. 5. f. 37. = Frustulia coffede- formis, Ag, ; Navicula quadricostata, E Inf. t. 21. f. 9. 3. Fischeri, with fewer marginal and obsolete median longi- tudinal lines. Carlsbad, 1-1720" to I-480". A. acutivscula (K.).—Frustules turgid- lanceolate, with acuminated, Subacute apices, and strong marginal longitudinal lines. KB. p. 108, t. 5. f. 32. Marine. Genoa. Small. 1-576”. A. lineata (Greg.).-Frustules elliptic- lanceolate, with prolonged comic ends and conspicuous longitudinal lines; transverse striae fine, obscure, about 42 in 001". GDC. p. 40, pl. 4, f 70. Scot- land. Outer portions of valves narrow lunate, with convex dorsum and straight venter. A. Ergadensis (Greg.). — Frustules elongated lanceolate, with broad, slightly produced, truncate ends; transverse striae conspicuous, about 24 in '001". GDC. p. 40, pl. 4, f 71. Scotland. Remarkable for its length. Outer portions of valves slender, with nearly straight venter. A. eacigua (Greg.).-Frustules elliptic- lanceolate, with slightly produced, ob- tuse ends; transverse striae about 28 in .001". GDC. p. 42, pl. 4. f. 75. Scotland. Small; in size and form it approaches nearest to A. lineata, but its markings are totally different, Greg. A. Semen, EM. pl. 38. 17. f. 10. Ice- land. In the figure, this species is ven- tricose, with broad, shortly produced, truncate ends, and without striae. A. Salina (S.).-Frustules elliptic-ob- long, with slightly produced, truncate extremities; valves lunate, rostrate, with 64 striae in 001". SBD. i. p. 19, pl. 30. f. 251. Brackish water. Sussex, Scarcely silicious. 0008" to 0016", S. A. turgida (Greg.).-Frustules broadly elliptic or suborbicular, with short ros- trate apices; outer portions semilunate, with capitate apices, and 24 rather coarse radiant striae in '001". GDC. p. 38, pl. 4. f. 63. Scotland. Small, A. monilifera (Greg.). — Frustules elliptic-oblong, with short, broad, ros- trate ends; outer portions arcuate, with capitate, recurved apices; dorsum with converging longitudinal rows of distant dots. GDC, p, 39, pl. 4. f. 69. Scotland. A. cymbifera (Greg.).-Frustules in- flated, with short, subcapitate, rostrate apices; outer portions arcuate, with capitate, recurved ends, and 22 rather coarse transverse striae in 001"; con- necting zone with converging longi- tudinal bars. GDC. p. 54, pl. 6. f. 97. Scotland. (VII, 54.) Large ; dorsum furnished with longitudinal series of transverse striae, separated by longi- tudinal lines or bars. A. proboscidea (G.).-Frustules linear- oblong, with produced, truncate extre- mities; valves arcuate, with rostrate, capitate ends, and 20 coarse transverse striae in .001"; dorsum with longitudinal series of transverse striae. GDC. p. 54, pl. G. f. 98. Scotland. Large. The capitate beaks of the valves are longer than in A. cymbifera, and are not re- curved, but bent forwards. A. costata (S.).-Frustules ventricose, with short, broad, truncate beaks, longi- tudinally costate; costae with a double line of moniliform puncta. SBD. i. § 20, pl. 30. f. 253. Marine. Britain. alves semilunate, with capitate ends; transverse striae coarse, about 16 in •001", Greg. A, Terroris (E.).-Valves elongated, straight, Semilunate, suddenly attenuated into stiliform beaks; transverse striae strongly granulated, 19 in 1-1200". ERBA, 1853, p. 526; EM. pl. 35A, 23. f. 2. Akin to A, fasciata, but smaller and more strongly granulate, E. A. macilenta (Greg.)—Frustules na; row elliptic-lanceolate, with short, broad, º produced apices; outer portion of valves with straight ventral margin, and about 30, rather coarse parallel striae in .001". GDC. p. 38, pl. 4, f. 65. Scotland. A. granulata (Greg.). — Frustules linear-oblong or elliptic-oblong, with short, broad, truncate, slightly produced apices; outer portion of valve with straight ventral margin, rostrate apices, and from 24 to 30 transverse striae in •001"; dorsum having longitudinal lines alternating with series of granules. GDC. p. 53, pl. 6. f. 96. Scotland. A. ventricosa (Greg.).-Frustules lan- ceolate, with turgid middle and tapering OF THE CYMBELLEAE, 883 } ! obtuse ends; outer portions slender, arcuate, with slightly concave venter, acute ends, and about 22 conspicuous transverse striae in .001". GDC. p. 39, pl. 4. f. 68. Scotland. 4* Frustules neither constricted at the middle nor rostrate at the ends ; modules roundish. A. ovalis (K.).-Frustules turgid, oval, with broadly rounded or truncate ends; outer portion of valves canoe-shaped, with 24 distinct moniliform striae in .001"; connecting zone with very fine longitudinal lines. KB. p. 107, t, 5. f 35, 39. = Navicula Amphora, E Inf. t. 14. f. 3. Fresh water, frequent. Eu- rope, Africa. (VII, 56; IX. 153.) Large. I-456'' to 1-120". A. Libyca (E.).-Frustules oval, with with broadly rounded or truncate ends; lateral view semilunate, with very con- vex dorsum, obtuse ends, and slightly concave venter. E.A. t. 3. 1. f. 42; EMI. many figures. Apparently the most common species, since Ehrenberg gives upwards of 100 habitats for it in Europe, Asia, Africa, and America. Lough Mourne deposit. (XII, 38.) We are unable to distinguish this form from A. ovalis, and probably these have been confounded; we believe they are in SBD., because there no species but A. ovalis is noticed as occurring in the Lough Mourne deposit, whilst Ehren- berg only mentions this species as found in it. Ehrenberg's figures and descrip- tion do not enable us to decide; for the latter is too indefinite, and the former vary so much as apparently to belong to more than one species. . Almost the only characters the figures have in common are the oval form and striated valves. The median line is either concave, raight, or produced at the nodule; and e connecting zone is figured sometimes smooth, and sometimes with longitudinal lines. A. pellucida (Greg.).-Frustules very hyaline, oval, with broadly rounded ends; outer portions of valves canoe- shaped, with about 30 very delicate striae in 001". GDC. p. 41, pl. 4. f.73, Scot- land. Resembles A. ovalis in form, but differs in its marine habitat, very hyaline aspect, and singular delicacy of the striae. The latter characters distinguish it also from A. incurva, Greg. A. truncata (Greg.).--Frustules barrel- shaped, with truncate ends; outer por- tions of valves canoe-shaped, striated; dorsum with longitudinal series of short transverse striae. GDC. p. 43, pl. 5. f 77. Scotland. Large. A. lineolata (E.). — Frustules turgid, elliptic-oblong, with truncate apices, strong longitudinal marginal lines, and very fine ones in the connecting zone. E Inf. t. 14. f. 14; EMI, pl. 13. 1. f. 19; Rab D. pl. 9. f. 9, 10. Fresh water. Europe, Africa, America. 1-480" to 1-140". The figures referred to represent the frustule as large, barrel-shaped, with canoe- shaped outer portions. A. Gregorii-Frustules barrel-shaped; outer portions canoe-shaped, with about 34 transverse striae in 001"; dorsum with longitudinal series of short transverse striae. = A. quadrata, GDC. p. 49, pl. 5. f. 85. Scotland. Ends truncate. A. Grevilliana (Greg.). — Frustules broad, linear, oblong or barrel-shaped; outer portions canoe-shaped, with from 28 to 34 distinct, moniliform transverse striae in 001"; dorsum with longitudinal series of transverse strie, GTVſ v. pl. 1. f. 36; GDC. p. 50, pl. 5. f. 89. = A. com- pleava, GDC. p. 51, pl. 5. f. 90; A, fasciata, GDC. p. 51, pl. 5. f.91. Scotland. Large; ends truncate. - A. sulcata (Bréb.).—Frustules hyaline, oblong or elliptic-oblong, with truncate ends; outer portions canoe-shaped, with 38 transverse striae in 001"; dorsum with longitudinal series of transverse striae. BD. pl. 18. f. 8; GDC. p. 51, 1. 5. f. 92. France, Britain. Large; differs from A. costata in its not produced but truncate apices, Bréb. A. robusta (Greg.).-Frustules broadly oval, with rounded ends and canoe- shaped outer portions; transverse striae distinct, moniliform, 16 in 001". GDC. p. 44, pl. 5. f. 79. Scotland. Large; conspicuous from its size and stoutness. A. Proteus (Greg.).-Frustules barrel- shaped or oblong; outer portions canoe- shaped, with 22 finely moniliform trans- verse striae in 001". GDC. p. 46, pl. 5. f. 81. Scotland. Large, with truncate apices. Varies much in form and length. A. Arcus (Greg.).-Frustules barrel- shaped; outer portions narrow, canoe- shaped, with 16 to 18 coarsely monili- form striae in .001"; dorsum with longi- tudinal series of moniliform transverse striae. GMJ. iii. pl. 4. f. 4; TM. v. pl. 1. f. 37; GDC. p. 50, pl. 5. f. 88. Scotland. Large, with truncate ends. The frustule has the form of a barrel, with ribs and bars. It is distinguished from A. Gre- villiana by its coarsely moniliform striae. Detached segments resemble in form a strung bow with rostrate apices. 3 I, 2 884. SYSTEMATIC EIISTORY OF TEIE INFUSORIA. A. veneta (K.). — Frustules minute, elliptic-oblong, with , truncate ends; lateral view semielliptic. , KB. p. 108, t. 3. f. 25. Marine. Venice and Con- stantinople, A. borealis (K.).—Frustules minute, oblong-lanceolate, with acute or trun- cate apices; lateral view semilanceolate. RB. p. 108, pl. 3. f. 18. Heligoland. 1–1200". A. Hohenackeri (Rab.). — Frustules minute, oblong or oblong-lanceolate, with three longitudinal lines on each side. Rab D. p. 31, pl. 9, f. 11. South Persia. A. hyalina (K.).—Frustules hyaline, elliptic-lanceolate, with acute or trun- cate apices, and a few, very delicate longitudinal lines; transverse striae ob- scure. KB. p. 108, pl. 30. f. 18; SBD. i. p. 19, pl. 2. f. 28. Marine. Europe. (vii. 58.) Imperfectly silicious, 1-600" to 1-422". A. mana (Greg.). — Frustules Small, In alſTOW elliptic-obſong, with rounded ends; outer portions with straight ven- tral margin, and about 50 transverse striae in '001". GDC. p. 38, pl. 4, f. 64. Scotland. A. elliptica (Ag., K.). — Frustules small, elliptic-lanceolate, turgid at the middle, with attenuated obtuse apices; valves distinctly striated. KB. p. 108, t. 5. f. 31. = Cymbella elliptica, AD. p. 8. Marine. Baltic. Associated in amor- phous mucus, K. A. navicularis (E.).-Frustules ellip- tic-lanceolate, with subacute ends and conspicuous transverse striae. EA. p. 122, t. 1.1. f. 12. Africa, America. (XII. 37.) A. gracilis (E.).-Frustules Small, nar- row oblong, truncate; valves slender, transversely striated. EA, t. 3. 1, f. 43; EM. t. 37. 3. f. 1. Europe, Asia, Africa, America, Australia. (XII, 26.) Outer portion of valve lunate. A. affinis (K.). — Frustules oblong, slightly attenuated, with rounded or broadly truncate apices, marked with longitudinal lines, the central ones very faint. KB. p. 107, t. 30. f. 66. France, Britain. I-960" to 1–390". A. marina (S.).-Frustules elliptic, with somewhat truncate extremities; nodule very faint; striae 40 in 001". ANH. 1857, xix. p. 7, pl. 1, f. 2. Marine. France, Britain. 0006" to 0024". (VII. 59.) Not unfrequent, but has been overlooked from its exact resemblance in outline to A. affinis; it may be known by its more delicate striae and inconspi- cuous nodules, Sm, A, dubia (Greg.).-Frustules oblong, with broadly rounded ends; outer por- tions stout, with concave venter, obtuse ends, and 24 fine transverse striae in .001". GDC. p. 42, pl. 5. f. 76. Scot- land. It has some analogy with A. marina; but the striation is coarser, and nodules distinct, Greg. A. oblonga (Greg.).-Frustules elon- gated linear-oblong or elliptic-oblong, with conic apices; outer portions very narrow, canoe-shaped, with conspicuous nodule, and 24 distinct transverse striae in 001". GDC. p. 43, pl. 5. f. 78. Scotland. Large. -- A. elongata (Greg.).-Frustules elon- gated, narrow, oblong-lanceolate, trun- cate; outer portions very narrow, canoe- shaped, with 26 conspicuous transverse striae in 001"; dorsum with longitudinal lines. GDC. p. 49, pl. 5. f. 84. Scotland. Large. A. angusta (Greg.). — Frustules mar- row linear-oblong, truncate; outer por- tions with 44 fine transverse striae in :001". GDC. p. 38, pl. 4, f. 66. Scot- land. A. obtusa (Greg.). — Frustules broad linear-oblong, with broadly rounded ends; Outer portions canoe-shaped, with 70 very fine transverse striae in .001", Greg. TM. v. pl. 1, f. 34. Scotland. Large. A. plicata (Greg.).-Frustules hyaline, broad linear-oblong, with rounded an- gles and truncate apices; outer portion canoe-shaped, very faintly striated; dorsum with longitudinal lines. Greg. TM. v. pl. 1. f. 31. Scotland. Large. The longitudinal lines give a plicate appearance to the frustule, Greg. A. crassa (Greg.).-Frustules linear or linear-oblong, with rounded or sub- truncate apices; outer portions canoe- shaped, with from 12 to 20 coarse trail verse striae in 001"; dorsum with longi- tudinal series of transverse striae. GDC. p. 52, pl. 6. f. 94. = A. Sulcata, Ro. M.J. vi, p. 18, pl. 3. f. 7 P. Britain. Large. A. Spectabilis (Greg.). — Frustules broad linear or linear-oblong, with rounded angles and subtruncate apices; outer portions canoe-shaped, with 14 to 16 distinct transverse striae in 001"; dorsum with longitudinal series of trans- verse striae. GDC. p. 44, pl. 5. f. 80. Scotland. (VII, 57.) Large. A. eaccisa (Greg.).-Frustules hyaline, broadly linear or linear-oblong, truncate; appearing notched at the sides from the marginal position of the nodules; outer portion canoe-shaped, with 52 very fine OF TEEE CYMBELLEAE. 885 transverse striae in 001"; dorsum with longitudinal series of short striae. GDC. p. 49, pl. 5. f. 86. Scotland. A. arenaria (Donkin).-Frustules hya- line, broadly linear, with rounded angles and slightly gibbous middle; outer com- * Fº of valves canoe-shaped; dorsum aintly marked with longitudinal lines. Donkin, TMS. vi. p. 31, pl. 3. f. 16. Marine. Northumberland. Large; trans- verse striae obscure. - A. amphioxys (Bailey). — Frustules linear, with subtruncate apices; lateral view arcuate, finely striated, with convex dorsum, concave venter, and rostellate recurved extremities. BMO. p. 39, pl. 2. f, 20–22. United States. The side view bears a striking resemblance to Eunotia amphioacys, Bailey. - A. biseriata (Greg.).-Frustules elon- gated linear, with rounded apices; median line marginal, except at the centre, where it curves inwards; dorsum with longitudinal series of coarse trans- verse striae. Greg. TM. v. p. 71, pl. 1. f. 32. Scotland. Large. A. tenera (S.). — Frustules narrow linear, with rounded or truncate ends; valve longitudinally rugose; striae ob- scure, 62 in 001". SBD, i. p. 20, pl. 30. f. 252. Marine. England. Scarcely silicious. Professor Smith regarded this species as the A. lineolata, E., -an opinion in which we are unable to concur, since its narrow-linear form is very unlike the broad inflated figure of the latter, and could never be described as turgid. A. bacillaris (Greg.).-Frustules mar- row linear, with slightly attenuated, ob- fuse ends, outer portions very narrow, arcuate, finely striated; dorsum with longitudinal series of granules. GDC, p. 55, pl. 6. f. 100, Scotland. Distin- guished from A. pusilla by its finer striae and granules, Greg. A. pusilla (Greg.).-Frustules narrow linear, with subtruncate apices; outer portions very narrow, canoe-shaped, with 24 conspicuous striae in 001"; dorsum with longitudinal Series of gra- nules or short striae. GDC. p. 53, pl. 6. f. 95. Scotland. A. Erebi (E.).--Lateral view arcuate, with obtuse apices, concave venter, and about 25 very fine striae in 1–1200". ERBA, 1853, p. 526; EM. pl. 35 A. 23. f. 3. Assistance Bay, North Pole. A. crystallina (E.).-Frustules smooth, crystalline, with convex dorsum, concave venter, and broadly truncate ends. ERBA. 1840, p. 10. Tjorn. 1-432". A. fasciata (E.).-Frustules with con- vex dorsum, plane venter, broadly trun- cate ends, and longitudinal series of closely set, fine striae. ERBA, 1840, p. 11. Tjorn. 1-456”. A. carinata (E.). — Frustules large, navicular, with plane sides, acute apices, and four lateral striated fasciae. ERBA. 1840, p. 10, Island of Tjorn. 1-240". A. Atomus (E.). —Very minute, on one side elliptic with rounded ends, on the other linear and truncate. 1-2640". A. AEgaa (E.).-Frustules navicular, oblong, truncate, with 10 punctated longitudinal lines, oblong umbilici, and curved lines; the space between the umbilici with two straight lines curved at each end. ERBA, 1858, p. 13. AEgean Sea. A. stauroptera (Bailey). — Frustules elliptical, elongated, with striated mar- ins; central portions crossed, as in tauroptera, by a broad band, BC. vii. p. 8, f. 14, 15. Halifax, Nova Scotia. The figure is elongated, acutely lanceolate, and the nodules connected by a trans- verse central depression, Species, the descriptions of which are wnknown to us. A. cymbiformis, EM. pl. 16. 1. f. 43. Lateral view semilunate, with convex dorsum, straight venter, obtuse apices, diverging striae, and submarginal sutural line and nodule. A. gigas, E.M. pl. 6. 2. f. 13. North Africa. Figure imperfect, large, oval, transversely º ; connecting zone with faint longitudinal lines. A, incurva, Greg, M.J. iii. pl. 4, f 5. Scotland. Lateral portion canoe-shaped and finely striated. A. paradoza (E.), A. vulgaris (E.), Asia; A. Nilotica (E.), River Nile; A. ocellata (E.), Florida. Genus RBIZONOTIA (E.).-Frustules with two median nodules (with the character and form of Amphora), but by longitudinal division often becoming a mass united together in a longitudinal series by a progeny of stolons or silicious radicles. This form is adnate on Confervae, and has many fine longitudinal striae, which appear somewhat rough or granular. The 886 SYSTEMLATIC ELISTORY OF TELE INFUSORIA. frustule is very crystalline and transparent. It has internally pale-green, almost colourless ova, E. RHIzoNoTIA Melo (E.).-The lateral | Melo, EM. pl. 35. 6. f. 14, 15 P. Swan, connecting portions of the progeny in Avon, and Canning Rivers in Western self-division mostly forked, 3 to 10. Australia. (VIII, 41.) ERBA, 1843, p. 139. = Rhizosolenia FAMILY XVII.—GOMPHONEMEAE. Frustules in front view cuneate, laterally attenuated at the base, with a median longitudinal line and a central nodule. Mostly aquatic. The Gom- phonemea differ from the Meridieæ and the Licmophoreae, and the cuneate species of Surirella, by the median longitudinal line and the central nodule. The cuneate form in the front view distinguishes it from the rest of the Diatomaceae. Genus SPHENELLA (K.).—Frustules in front view cuneate, free, neither stipitate, affixed, nor enclosed in a common gelatinous Substance. Aquatic. “The Sphenellae only differ from Naviculae in their cuneate form, perfectly similar to that of Meridion, by which, too, the associations (S. angwstata) become flabelliform and quasi-circular ; but they differ by the central nodule of the lateral surfaces. Hence there remains a greater similitude to the Naviculae; and the distinctive characters are so slight, that the generic characters of at least two species remain uncertain'' (Menegh. p. 411). ends. KB. p. 83, pl. 7. f. 12. France. 1-1020". obtusata (K.). — Small ; lateral view smooth, dilated above the middle, with rounded obtuse apices. KB. p. 83. SPHENELLA glacialis (K.). — Minute; lateral view lanceolate, with subacute ends and very delicate transverse striae. S. ICB. p. 83, pl. 3. f. 16. Monte Rosa, Alps. 1-1320". Germany, S. parvula (K.).—Minute; lateral view lanceolate, with produced ends, the base subdilated. #. p. 83, pl. 30. f. 63. France. 1-960". Striae indistinct. It cannot be distinguished from a Navicula, except on a front view. - S. angustata (K.). — Minute, flabel- lately conjoined, narrow linear, cuneate, lateral view lanceolate, with obtuse ends. KB. p. 83, pl. 8. f. 4. Germany, France. (xiv. 30.) 1-960". S. vulgaris (K.).--Small; lateral view finely striated, dilated at the middle, pl. 9. f. 1. Prussia. (xiv. 31.) 1-900". Lateral view clavate–lanceolate. S. rostellata (K.). —Solitary, Smooth, broadly cuneate; lateral view dilated at the middle, acuminate at each end. KB. p. 83, pl. 9. f. 8. 3. elongata, larger, with produced, obtuse apices. France. 1–1820" to 1-336". S. P. Italica (K.). — Broadly cuneate; lateral view obovate, slightly dilated at the middle, and with a transverse me- dian nodule. KSA. p. 63. = Gompho- nema Italicum, KB, t, 30. f. 75. and tapering to the stout beak-like Genus GOMPHONEMA (Ag).-Frustules affixed at the base or stipitate; in front view cuneate; laterally attenuated below, with a median longitudinal line and central module. “As Cocconema from Cymbella, so Gomphonema only differs from Sphenella by the stipes, on which account species are now referred to Gomphonema which formerly belonged to Sphenella. . . . Kützing supposes the Gomphonemae to be at first free, like Sphenella, and that after- Wards they affix themselves. . . . No direct observation confirms this hypo- thesis; and it is at least as just to admit the other, that the Sphenellae are at first attached like the Gomphonemae and afterwards become free. Ehrenberg Says that the Gomphonemae can become free and again adhere’’ (Menegh. p. 412). The descriptions apply to the lateral view, unless otherwise stated. OF THE GOMPEIONEMEAE. 887 * Frustules in lateral view constricted be- neath the apea, appearing urn-shaped. f Lateral view with the head apiculate Or acute, GOMPHONEMA coronatum (E.).—Slen- der, with ventricose middle, obcordate apiculate head, and lanceolate base; front view crested at apex. EM. pl. 6. 1. f. 33. = G. acuminatum 8, SBD. i. p. 79, pl. 28. f 238 3, , Europe, America, Asia, Aus- tralia. , (XIV, 36.) G. coronatum is di- stinguished from the allied forms by its inflated basal portion; but the lower inflation is sometimes very obscure, and we believe Professor Smith was justified in regarding this form as a mere variety of G. acuminatum. 1-480". G. laticeps (E.). —Habit of G. corona- tum, but shorter, and head wider than the central inflation, EM. pl. 5. l. f. 34. America, Asia. Ehrenberg's figures have the basal portion linear, not inflated. He gives about fifteen habitats. G. Sceptrum (Rab.). — Habit of G. coronatºm, but larger and more robust, the middle more inflated and much broader than the obcordate apiculated head; base stalk-like, not it. Rabl), p. 60, pl. 8. f. 8. America. G. acuminatum (E.). —Slender, taper- ing below into the stalk-like base, con- stricted above the ventricose middle; head dilated, acuminate. SBD. i. p. 79, pl. 28. f. 238. = G. trigonocephalum, EM. pl. 6, 1, f.36; G. appendiculata, Perty KL. p. 204, t. 17. f. 12. Europe, Asia, Africa, America, and Australia. (XIII. 23.) Differs from the foregoing species by a cuneate or tapering apex. In a variety figured by Professor Smith the constriction is nearly obsolete. 1-860" to 1-430". G. Brébissonii (K.).—Slender, narrow, with a longly attenuated base and a slightly ventricose middle, separated by a slight constriction from the cuneate, attenuated, somewhat obtuse head. KSA, p. 66. France. Stipes abbreviated or nearly obsolete. Akin to G. acumina- tum, but more slender, more elongated into the stipes-like base, and head and median inflation Smaller. G. Americanum (E.). — Lateral view with three inflations, separated by two constrictions ; head ovate, Subacute. EM. several figures, America, Iceland. I-864". G. elongatum (S.), Lateral view with three inflations, the median one greatest; upper one oblong, with cuneate apex; lower slender, slight. S. in ANH. 2 ser, xv. p. 6, pl. 1, f. 4. = G. Brébissonii, Greg, in Subalpine streams. M.J. ii. pl. 4. f. 18. France, England. 1-864". Scarcely distinct from G. Ame— *icantºm ; both have the inflated base of G. coronatum, and cuneate head of G. acuminatºm. 2t Head rounded, neither acute nor apiculate. G. geminatum (A.). — Frustules very large, in front view cuneate, their ter- minal puncta obsolete; lateral view in- flated at the middle, constricted above and below, with dilated, rounded ends; striae distinctly moniliform. SBD. p. 78, } 27. f. 235. = Diomphala Clava Herculis, M. pl. 15A. f. 93. (VII, 60.) On rocks Europe. This Species forms large spongy cushion-like tufts composed of densely matted fila- ments. The frustules are easily recog- nized by their large size, the absence of terminal puncta in the front view, and the conspicuous striae of their lateral valves. The neck is much constricted, and the large head broadly rounded at the end, Kützing refers G. Herculeanum (E.) to this species, but, we believe, erroneously. G. capitatum º-ºº: view tur- gid at the middle and slightly con- stricted beneath the broadly rounded head; puncta in front view evident, SBD. p. 80, pl. 28. f. 237. = G. turgidum, EMI, pl. 2. 2.f40? Furope, Asia. 1-1720" to 1-280". Striated, attenuated at its base ; stipes elongated, dichotomous. Sometimes the constriction, which is less marked than that of the next spe- cies, is nearly obsolete, and the frustules in the lateral view are obovate. G. constrictum (E.). — Lateral view ventricose at the middle, with a short neck and broadly rounded head; puncta at upper end of front view very evident. SBD. pl. 28. f. 236. = G. truncatum, EMI. many figures; G. paradoxum, EM. pl.9.1. f. 33, 34; G. pohliaforme, K., Ralfs. Forms a brown discoloration on aquatic plants. Common. (x, 187–190) 1-1720" to 1–280"; striated, attenuated at its base; stipes becoming elongated and branched. Distinguished from G. gemi- matum by its much Smaller size and distinct puncta in front view. We find this species very variable in the develop- ment of its neck; and sometimes in a young state the constriction is but slight, and the form resembles G. capitatum. G. subtile (E)-Slender, lateral view twice constricted; head Small, obtuse; neck slender, elongated. EMI. Several figures. Asia, Africa, America, Lough 888 SYSTEMIATIC EIISTORY OF THE INFUSORLA. Mourne deposit. It differs from G. con- strictum in its Inore slender form and longer neck. G. Anglicum (E.).-Twice constricted; head rounded, rather marrower than the oblong inflated middle, which tapers below into a linear stipes-like base. EMI. pl. 15 A. f. 86. Lough Mourne deposit, Treland. It is allied to G. subtile. Pro- bably both forms should be united to G. constrictum. G. Mustela, EMI, pl. 17. 2. f. 37. Fossil, Finland, France; recent, Berlin. We have seen no description of this species. Ehrenberg's figures represent the lateral view elongated, with an oblong median inflation, tapering below into a linear stipes-like base, and above into the ob- long head, which is rounded at the apex. 2% Frustules imbedded in a shapeless gela- tinous substance. (Gomphonella, Rab.) G. olivaceum (Lyngb., E.).-Frustules and stipes forming a gelatinous, mass; front view broadly cuneate, with con- spicuous terminal puncta; lateral valves obovate or subclavate, distinctly stri- ated. SBD. pl. 29. f. 244. = Gomphonella olivaceum, Rab., 8, angusta; G. angusta, R.; G. angusta, Rab D. p. 61, t. 9. f. 2. Smaller and shorter, with obsolete striae. Europe. 1-2300" to 1-1020". It forms rather large mucous masses of a pale brown colour, which, when dried, be- come pale green with a granulated appearance. G. Lenormandi (Chauvin). — Front view narrow, nearly linear ; lateral valves lanceolate acute, with indistinct striae. KSA. p. 65. = Sphenella? Lenor- mandi, K.B. pl. 30. f. 61; Gomphonella Lenormandi, Rab. Falaise, France. 1-960". Stipes slender, at length elon- gated. - G. parvulum (K.). — Frustules of the size and form of Sphenella parvula, but stipitate and aggregated into a dense mucous stratum. KSA, p. 65. = Gom- phonella parvula, Rab. 3 * Frustules in front view curved, with two longitudinal Suture-like lines or witta. G. curvatum (K.).—Frustules in front view curved, with distinct terminal puncta and longitudinal vittae; lateral valves clavate, KB, p. 85, pl. 8. f. 1–3. = G. minutissimum, E. Common. Eu- rope, Asia, Africa, America. (XII, 9–12; XIII, 11.) a, aquatic, = G. curvatum, SBD.; 8, marine, = G. marinum, SBD. This species differs considerably from the other species of Gomphonema in its curved frustules and longitudinal suture- like striae, and perhaps ought to be sepa- rated from them. It agrees with Rhi- pidophora in the latter character and with Achmanthes in having a median nodule in the ventral or concave valve only. It varies in its mode of growth, according as it is found in fresh, brack- ish, Saline, or marine waters. The frus- tules are scattered, flabellately conjoined, or aggregated in minute cushion-like tufts. The stipes is short, incrassated, and insiºn: or more or less elongated, slender, and dichotomously divided. Professor Smith makes the marine form a distinct species, and gives the following differential characters:– G. curvatum: “Stipes elongated, fila- mentous and dichotomous; striae 22 to 30 in 001”; aquatic.” G. marinum : “Stipes incrassated, branching in an irregular manner; striae 35 in 001"; marine.” Professor Smith, however, admits that it is difficult to distinguish them if we confine our attention merely to the frustules; “but,” continues he, “the general appearance of the growing plants, arising from the characters of their stipes, is very different, and their habitats are so wide apart that there can be no doubt of their distinctness.” We are unable to concur in this opinion; for our experience is quite different, and, as we stated several years ago, we find the stipes in the marine form more elon- gated than in the aquatic one. “I have attempted in vain to find some specific character to distinguish the marine form. It is more branched, has a rigid appear- ance, and the striae connecting the puncta on the front surface are strongly marked; but intermediate specimens occasionally occur, in which all these differences vanish" (ANH. xii.). 4 * Frustules in lateral view obovate or clavate, f Crested or pointed at the apex. G. cristatum (Ra..).-Frontview crested; lateral view obovate, crowned with a minute point. SBD. p. 79, pl. 28. f. 239. = G, nasutumn, EMI. pl. 2, 2. f. 41; Sphe- nella P appendiculata, Perty, p. 203, t. 17. f. 14. Europe, Asia, America. Stipes nearly simple; frustules in front view cuneate, with somewhat rounded angles, crested as in G. coronatum; terminal uncta obsolete. Ehrenberg describes #. G, nasutum as allied to G, Augur, OF THE GOMPEIONEMEAE. 889 but shorter and stouter. To G. cristatum probably belongs the Mexican form de- scribed by Ehrenberg as a variety of G. Augur, having the apex constricted into a Small terminal mucro. G. Augur (E.). — Front view linear- cuneate, lateral view rhomboid, with subacute apex and acuminated base, EM. several figures. Europe, Asia, Australia, Africa, America. 1-960". “More slender and with º: point than G. cristatum,” Rab. rofessor Kützing unites G. cristatum to this spe- cies; and certainly they, as well as G. Lagenwla, seem closely allied. Ehren- berg's figures vary considerably in form, but all have the apex more cuneate than we have ever seen it in G. cristatum. G. Lagenula (K.). — Slender, linear- cuneate, finely striated; lateral view clavate, crowned with a minute point, tapering and subacute at base. KB. p.85, pl. 30.f. 60 = G. Sphaerophorum, EMI. pl; 35 A. 7. f. 14, America, Europe. Stipes short, 1-720". This form ap- parently differs from G. cristatum only in its narrower frustule. G. apiculatum (E.).-Cuneate; lateral view obovate, with acute cuneate apex and tapering base. EM. pl. 4. 2. f. 39. Fossil. America. (XII, 28 & 53.) 6 more slender than G. apiculatum: E.M. pl. 2. 2. f. 43. G. Turris (E.). — Much elongated, clavate, its apex Suddenly acutely cu- neate. EM. several figures. Africa, America, India, Japan. Ehrenberg's figures vary in form, but are mostly clavate, with or without a slight com- striction above the middle. “Akin to G. gracile, but stouter,” E. 2+ Apex in lateral view neither acute nor apiculate. G. abbreviatum (Ag). — Frustules broadly cuneate, conjoined in a flabel- late manner; lateral view obovate, with indistinct striae and rounded apex. KB. .84, pl. 8. f. 5–7. = Echinella abbreviata, £hr. T8. longipes (K.), stipes elongated; subbranched, = G. rotundatum, E. Eu- rope, Asia, Australia, America. 1-1152" to 1-840". Stipes rather thick, usually very short and simple, but in var. 8 more elongated. G. sphenelloides (Rab.). — Obovate, smooth, with broadly rounded apex; stipes simple, stout. Rab D. p. 58, pl. 8. * Italy. Front view cuneate. Pro- bably only a form of G. abbreviatum. G. micropus (K.).--Front view linear- cuneate, truncate at each end; lateral view obovate-lanceolate. KB. p. 84, pl. 8. f. 12. Germany, France. Very finely striated P; stipes very short and obsolete, or elongated filiform and sub- Famose. “Resembles G. sphenelloides, but is smaller and more slender,” R. l. c. G. tenellum (K.). — Minute, smooth; lateral view obovate-lanceolate; stipes abbreviated, simple. , KB. p. 84, pl. 8, f. 8. Europe. T-1440". G. Persicum (Rab.). —Lateral view obovate, with rounded upper end, stri- ated; front view broadly cuneate. Rab D. p. 59, pl. 8. f. 4. Persia. The figure re- presents the front view with conspi- cuous terminal puncta and longitudinal vittae or suture-like lines. G. Hercynicum (Rab.).—Lateral view obovate-lanceolate, with obtuse ends, the upper one cuneate; striae distinct; front view broadly cuneate. Rab D. p. 59, pl. 8. f. 28. - G. subramosum (Ag). —Lateral view clavate; front view cuneate, with acute base; stipes long, slender, nearly simple. KB. p. 85, pl. 8. f. 15. = G. septatum, A CD.; G. oculatum, KSA.; G. discolor and G. clavatum, E. (according to Kützing). Common. Europe, Asia, Africa, Amé- rica. 1-1140" to 1-600". Striae very faint. We quote G. clavatum (E.) under this species in deference to Kützing's authority, because the description will not determine the question; and although Ehrenberg, in his §. figures it from more than twenty stations, yet those figures differ so greatly as to afford no decisive information: several of them are lanceolate or clavate, whilst, like G. Glans (a species indeed described as having a general resemblance to G. clava- tum), the greater number have an inflated centre. G. erosum (Rab.). — Oblong-obovate, with emarginate apex; front view narrow-cuneate ; stipes dichotomously divided. Rab D. p. 59, pl. 10. f. 12. Dresden. 5* Frustules in lateral view ventricose at the middle, attenuated at each end. G. Glams (E.).-Ovate-oblong, tumid; upper end rounded, with a slightly tu- mid neck. EM. pl. 4. 2. f. 35. Has a general resemblance to G. clavatum, but is shorter, Stouter, and more obtuse. Ehrenberg's figures represent it with ventricose centre, broadly comical above, with rounded apex, and tapering below into a short, slenderer base. - G. Oregonicum, EM. pl. 37.2. f. 12, 13. Fossil. Oregon. Ehrenberg's figure of 890 SYSTEMATIC HISTORY OF THE INFUSORIA. the lateral view has an oblong inflated centre, suddenly constricted above into a come with rounded apex, and taper- ing below into a slender base; the front view is large, broadly cuneate, with striated lateral margins, rounded base, and conspicuous puncta at upper end. It differs from G. Glans in its larger size and more elongated inflated centre. G. Mamilla, EM. pl. 37.2. f. 10. Ore- gon. Ehrenberg's figure of the lateral view resembles G. Oregonicum, but is stouter in proportion to its length, and the basal end is shorter and more truncate. • G. giganteum (E.). — Very large and turgid, distinctly striated, lanceolate, the subacute apex rather more acute than the base. ERBA, 1852, p. 534. Recent. California. It is more alkin to G. Manilla than to G. Herculeanum, but differs in its larger size and slenderer base. Centre inflated. G. Herculeanum (E.). — Very large, minutely striated, oblong, inflated at the middle; the ends attenuate and rounded, the basal one slenderer. EM. pl. 35 A. 7. f. 12, 13. Lake Michigan, Niagara, and Oregon. Stipes long, hyaline, dicho- tomous; length of frustule 1-216". Pro- fessor Kützing unites this form to G. geminatum; but according to IEhrenberg's figures, they are very different. The upper end is figured in this species as broadly conical, not dilated into a head as in G. geminatum. The front view is repre- sented as more cuneate, and furnished . conspicuous puncta at the upper GILCL. - G. intricatum 9. — Inflated at the middle, much produced at each end, narrow, obtuse; stipes rather rigid, mu- cous, extremely interwoven, dichoto- mous. KB. p. 87, pl. 9. f. 4. Germany. Forms a firm slimy stratum on rocks. 1-420". This species is described and figured by Kützing and Rabenhorst as slender, with inflated centre, whilst Smith describes the British forms as lanceolate, —a difference which renders their iden- tity problematical. Front view narrow- Cuneate. G. longiceps, EMI, pl. 7.3B. f. 9. Appa- rently common, since Ehrenberg gives thirty-eight habitats in Europe, Asia, Australia, Africa, and America. We have seen no description of this species; the figures represent it as narrow-cune- ate in the front view, and the lateral view striated, inflated at the centre, with the ends elongated into beaks, the apex obtuse, and the base truncate. G. ventricosum (Greg.). — Much in- flated at the centre, upper end conical, lower slender, constricted above the roundish base. Greg. M.J. p.4, pl. 1. f. 40. Scotland. 0013" to 0018". This form much resembles G. Glams; the base, how- ever, is dilated and rounded—characters wanting in the figures of that species. G. Cygnus (E.).--Narrow, with a lan- ceolate inflated centre, and linear, elon- gated, beak-like extremities. EMI. pl. 5.3, f. 33. America, Asia. Obtuse at apex, and truncate at base. Kützing thinks this may be identical with his Sphenella 7'ostellata. G. Vibrio (E.). – Elongated, inflated at the middle, and gradually tapering into long beak-like extremities; , the upper one subacute. EM. pl. 39. 3. f.71. Cayenne. SD. i. p. 81, pl. 38. f. 242. (XII, 35.) “Akin to G. gracile, but longer, more slender, and approaching to Pinnularia amphioacys” (E.). G. rostratum (Sm.). — Lateral view ovate-elliptical, produced at the upper extremity into a linear obtuse rostrum, slightly constricted below; striae 30 in '001". SBD. ii. p. 99. Barleylake, Co. Cork. O009" to 0012". Stipes distinct. G.? Hebridense (Greg.).--Lateral view elongated, narrow-lanceolate, with in- flated centre, acute equal apices, and very fine striae. Greg, M.J. ii. p. 99, pl. 4. f. 19. Mull deposit. Professor Gregory remarks that it seems to stand between G. tenellum and G. Vibrio, but that, only its lateral view having been seen, its genus is uncertain. 6% Frustules lanceolate in the lateral view. G. dichotomum (K.). — Lateral view narrow-lanceolate, with slightly obtuse apices, striated ; front view narrow- linear, cuneate. S.D. i. p. 79, pl. 28. f. 240. = G. gracile, EM. numerous figures. Common. 1-1150" to 1-860". Stipes usually elongated and dichotomous, but sometimes abbreviated and sub-simple. The frustules somewhat resemble those of G. olivaceum, but are narrower; their puncta also are far less distinct. This species appears generally diffused, since hrenberg gives upwards of 100 habitats, scattered over the world. G. lanceolatum (E.). — Lateral view striated, lanceolate, with acute ends; front view linear-cuneate, very gradu- ally tapering at each end, KB. p. 87, pl. 30. f. 59. America. Ehrenberg's figures represent the lateral view broader than in G. dichotomum. OF THE GOMIPEIONEMEAE. 891 G. affine (K.). — Rather turgid, elon- gate, striated; margins in front view slightly curved; lateral view sublan- ceolate, with an obtuse apex. KB. p. 86, pl. 30. f. 54. Trinidad. 1-360". sº abbreviated, subramose. “It differs from G. dichotomum in its firmer habit and broader sides; lateral apices more ob- tuse” (K.). According to Rabenhorst, it is slenderer than G. lanceolatum, but Scarcely specifically distinct. G. Fibula (Bréb.). — Slender, elon- gated, very narrow-cuneate ; lateral view acicular, very slender; stipes short, nodule obsolete. KSA. p. 65. France, England. Akin to G. dichotomum, but differs in its slenderer frustules. G. exiguum (K.). — Minute, Smooth, lateral view lanceolate; stipes slender, Subramose. KB. p. 84, pl. 30. f. 58. Ma- rine. France, Jutland, 1–1440". G. cuspidatum (Rab.).—Cumeate, often curved; lateral view smooth, lanceolate, with acute ends, Rab D. p. 59, pl. 8, f 22. Saxony. With or without a stipes. G. dequale (Greg.).--Lateral view lan- ceolate, with minutely capitate apices, an exactly central nodule, and conspi- cuous striae. Greg. M.J. iv. p. 12, pl. 1. f. 41. Scotland. 001". Striae 22 to 24 in '001". It agrees nearly with some forms of G. tenellum, from which, however, it differs in having much wider and coarser striae, and in the central position of the module, Greg. l. c. A slight constriction exists beneath each end. Professor Smith refers it to G. tenellum. G. insigne (Greg.).-Lateral view lam- ceolate, slightly rhomboid, with obtuse ends; striae 18 to 20 in .001". Greg. M.J. iv. p. 12, pl. 1. f. 39. Scotland. 0016" to 0025". “Distinguished by its size and the coarseness of its striation. Side view doubly conical, the angles at the broadest §. being strongly marked.” Professor mith thinks it may be a form of G. Sarcophagus. G. Sarcophagus (Greg.).--Lateral view clavate, lanceolate, constricted near the extremities, which are minutely capitate. Greg. M.J. iv. p. 13, pl. 1, f. 42. Scotland. •0014". art about one-third from apex. Pro- fessor Gregory compares the outline to that of a coffin. G. minutissimum (K.). -Linear-cune- ate, smooth, with a slender subbranched stipes; lateral view narrow-lanceolate. RB. p. 84, pl. 8. f. 11. Marine. Britain. (XII. T7.) T(iitzing regards this as the G. minutissimum of Greville; but that Striae 20 to 22 in 001”. Widest opinion is doubtless erroneous; for this is a marine, and Greville's was an aquatic gathering in which G. olivaceum and G. curvatum were mixed together. G. auritum (Braun.).-Broadly cune- ate in front view, the upper end truncate, with an awn at each angle; lateral view lanceolate, with a terminal awn. Rab D. p. 59, pl. 8, f. 3. Baden. Habit of G. intricatum, but furnished with awnlike Spines. G. Naviculoides (S.). —Stipes distinct and regularly dichotomous; front view Sublinear, truncate; lateral view acutely lanceolate, with the extremities equal and module central. SBD. ii. p. 98. In the Victoria Regia tank, Biſſing: According to Professor Smith, this spe- cies, in a lateral view, is not to be di- stinguished from a Navicula, as the nodule is almost exactly central. Species insufficiently described, or known to us only by name. G. digitatum (K.). — Frustules very Iminute and Smooth, linear-cuneate, fla- bellate; stipes simple, dilated above. KB. p. 84, º 21. f. 2. 2. Marine. Cux- haven. I-680", Kitzing gives no de- Scription or figure of the lateral view. G. telographicum K.). —Erustules mi- mute and very Smooth, slender, cuneate, Somewhat more acute at base, umbel- lately aggregated on a simple abbrevi- ated stipes dilated at its apex. K.B. p. 84, pl.8. f.9. Maritime. Heligoland. 1-1200". G. crassum (Rab.). — Front view broadly cuneate, truncate above, rounded at base ; the lateral margins convex, faintly striated. Rab D. p. 59, pl. 10. f. 13. Persia. Although only the front view is described and figured, yet the species seems well distinguished by the convex (not straight) lateral margins, giving it an obovate form with the broader end truncate. The puncta are conspi- cuous in the figure, as are also two lon- gitudinal lines or vittae. G. pulvinatum (Braun). — Front view broad, linear-cuneate; base Smaller than the very thick, serpentine, irregularly divided stipes, Rab D. p. 58, pl. 8. f. 16. Zurich. “Forms little, verythick, Smooth knoblike cushions of equal height.” G. P. contractum (K.). — Very minute, attenuated at the base, slightly con- stricted at the middle, with a dilated rounded apex; stipes simple, abbreviated or obsolete. KB. p. 86, pl. 14. f. 21. 3. Germany. 1–1440". Rützing's figure, which is very minute and pyriform, shows no median line, module, or striae. 892 SYSTEMATIC HISTORY OF THE INFUSORIA. G. insula'e (E.), G. tenuicolle (E.), Asia; G. Mosambicense (E.), Africa; Australia; G. longicolle (E.), Australia, G. Margaritaceum (E.), G. Savanna Asia, America; G. Jordani (E.), River (E.), British Guinea; G. lanceolatum Jordan; G. obtusum (E.), Arabia, Ame- | (E.), America; G. Palea (E.), fossil, rica; G. turritum (E.), Arabia; G. mu- Jura Mountains, France. cromatum (E.), G. rhomboideum (E.), Genus SPHENOSIRA (E.). — Frustules united into a straight compressed filament; lateral surfaces with unequal extremities and a distinct central nodule. Aquatic. The frustules in front view are scarcely cuneate; and the genus could be better placed in the Naviculea, as indeed Kützing himself suggests; it seems to differ from them only in the unequal ends of the lateral surfaces. SPHENOSIRA Catena (E.). —Frustules smooth; lateral view with a mucro at apex and a gradually attenuated, some- what obtuse base. EA, p. 98, pl. 3, 1. f 27; KB, p. 88, pl. 29. f. 47. Mexico. (XI, 30.) FAMILY XVIII.—NAWICULEAE. IFrustules free, concatenate, or included in a more or less definite frond ; front view generally linear or quadrangular; valves with similar ends, a median longitudinal line, and central nodule. “The Naviculea frequently resemble individuals in other families, but are to be distinguished by the central nodule of the lateral Surfaces, as well as by the regularity and symmetry both of these and the front view º' (Menegh.). In the minuter forms the nodules are frequently very indistinct; when present, however, they usually appear, in the front view, like a punctum at the middle of each lateral margin. In doubtful cases this appearance will often aid in ascer- taining their presence. - * Frustwles nude. Genus NAWICULA (Bory, Rab.).—Frustules simple, free, prismatic in front view, rectangular laterally, with a longitudinal median pellucid line with central and terminal nodules. Navicula was divided by Ehrenberg into two genera—Navicula with Smooth, and Pinnularia with striated valves; but this division was not received by Kützing or Brébisson, and is certainly un- sound, as it assigns the species to each genus according to the power of the author's microscope, whilst striae, we believe, are almost always, if not uni- versally, present on the valves. The late Professor Smith reconstituted Ehrenberg's genera, and made their characters depend on the presence or absence of costae. These characters were far better than those of Ehrenberg; and were the costae always plainly developed as in Pinºvularia mobilis and its allies, no difficulty could occur in determining the genera; but in many of the more minute species it is often very difficult to distinguish between striae and costae. We have not admitted Pinnularia here, partly for the reason just given, but principally because we cannot decide to which genus a large num- ber of Ehrenberg’s species should be referred. - A. Valves more or less constricted at the middle (Diplomeis, E.). NAVICULA Americana (E.).-Turgid, linear-oblong, with slightly constricted centre and broadly rounded ends; striae wanting or indistinct. EM. pl. 2. 2. f. 16. New York and Rhode Island. N. Faba (E., K.), —Turgid, oblong, slightly constricted at the middle- and rounded at the ends, marked by longi- tudinal lines; striae wanting or indi- stinct. = Diplomeis Faba, E.B. 1845, p. 365. River Tagus. The median line interrupted by the central nodule; three lines on each side continuous. N. hyalina (E., K.). — Slightly con- stricted at the middle, with oblong lobes, OF THE NAWICULEAE. 893 rounded ends, a longitudinal median fascia of lines, and a narrow pinnulated border. = Diplomeis? hyalina, E.B. * 362. Marine. India. May be more akin to Cymatopleura Solea, - N. binodis (E.). — Smooth, minute, narrow panduriform, with acuminated rostrate apices; median nodule very distinct. EB. 1840, p. 18; KB. p. 100, pl. 3. f. 35. = Fragilaria 8 binodis, E.A. p. 127. Fossil, Santa Fiore; recent in pools, &c. N. duplicata (E.). — Smooth, Small, rather broad panduriform, with attenu- ate subacute apices. EM. pl. 21. f. 35. Cuba. In Ehrenberg's figure the ends are somewhat cuneate, and the median line simple. N. incurva (Greg.).--Small, smooth, Süblinear, with a shallow sinus on each side, and ends suddenly contracted into obtuse subcapitate beaks. pl. 1. f. 26. Scotland. N. constricta, EM. pl. , 38. 17. f. 3. Volcanic ashes, Iceland, Ehrenberg re- presents it as smooth, minute, panduri- form; ends rounded, each terminated by a minute nipple-like point; median line º . emarginata, EM. pl. 39. f. 83. Ehrenberg's figure is minute, Smooth, panduriform, with each end suddenly contracted into an obtuse, broad, mam- miform beak. N. paradoaca (E.).-Large, Smooth; oblong, slightly constricted at themiddle, with four longitudinal median lines and somewhat obtuse cuneate ends. E.A. pl. 1. 3. f. 4. 6. Peru, N. imperialis º R.).—Dilated, with constricted middle and subacute apices, a simple series of conspicuous granules accompanying the middle furrow, which is smooth on both sides; lateral series alike, two perfect ones inclosing an im- perfect median sinus, all interrupted at the middle. = Diplomeis imperialis, E.B. 1845, p. 362. Marine. India. Granules large, pearl-like. N. Entomon (E.). — Large; slightly sinuato-constricted at the middle, with oblong lobes and subacute cuneate ends; striae 19 or 20 in 1–1200". EB, 1840. = Pinnularia Bntomon, E.A. pl. 1.1.f. 3, 4; Diplomeis Entomon, EMI, pl. 19. f. 30. Marine. Fossil, Greece ; recent, Eu- rope, Asia, Africa. Distinguished by its shallow stricture and Smooth striae. N. Conops (E., K.).--Small, panduri- form, very finely striated, with cordate lobes and acute apiculate apices. = Pºn- nularia P Conops, E.A. pl. 3. 7. f. 20. America. M.J. iv. p. 8, N. ºncurvata (Greg.).- Panduriform, with rounded ends; striae 30 in 001", minutely moniliform ; median line Straight, with dark shaded lines on each side. TM. iv. p. 44, pl. 5. f. 13. Marine. Scotland. N. Splendida (Greg.). — Large, pan- duriform, much constricted, with elliptic- oblong lobes, and obtusely triangular ends; striae distinctly moniliform. TM. iv. p. 44, pl. 5. f. 14. Marine. Scotland. Median line straight, and having on each side a narrow blank space. N. Proserpinae (E.). — Very large, deeply constricted; lobes almost rhom- boid, with subacute apices; sides stri- ated, lines decussating at a right angle, a broad, pellucid, Smooth median fascia divided by two lines into three parts; umbilicus circular. = Diplomeis Proser- gº EB, 1858, p. 13. Marine. Ægean €8. N. Musca (Greg). — Small, panduri- form, with turgid lobes and acute cune- ate apices; striae rather distant, coarse, moniliform, short, forming a marginal band. GDC. p. 7, pl. 1. f. 6. Marine. Scotland. Striae 18 in 001"; median line and nodule distinct. N. Bombus (E., K.). — Panduriform, with subcordate lobes and subacute apices; striae dense, coarsely moniliform, S.A. p.83. = Pinnularialbombus, ERBA, 1844; GD. pl. 1. f. 12; Diploneis Bombus, EM. pl. 19.f. 31. Europe. 1-384"; striae 21 in 1-1200". Granules of the largest striae in fours. Median line broad, with a Square central nodule. Characterized by its short turgid lobes and close, large, pearly granules. - N. didyma (E., K.). — Rather broad, slightly constricted at the middle, with short suborbicular lobes and broadly rounded ends; striae distinct, granulate. KB. p. 100, pl. 4. f.7; SD. i. pl. 17. f. 154. = Pºnnularia didyma, E.A. pl. 2, 4, f 3. Marine. Europe, Asia, Africa, America. (VII. 61; xv. 12. N. dissimilis (Rab). — Targe, pan- duriform, with broadly rounded ends; striae stout, curved, converging, not reaching the median line; front view gibbous at the centre and tapering to- wards the ends, which are truncate. = Pinnularia dissimilis, Rab. p. 45, pl. 6. f. 32. Persia. N. Pandura (Bréb.). —Large, elong- ated panduriform, with elliptic lobes and obtuse apices; costae smooth. BD. pl. 15. f. 4. = Pinnularia Pandura, GDC. p. 17, pl. 1, f. 22; N. mitida, TMI. iv. p. 44, pl. 5. f. 12. Europe. M. de Bré- 894 SYSTEMLATIC EIISTORY OF THE INFUSORTA, bisson regards this form as distinct from N. Crabro, E.; and it undoubtedly is from the Trinidad Diatom figured by Dr. Greville for that species. We con- sider, however, that N. Pandura, Bréb. not only agrees in its smooth costae with Ehrenberg's description and figure of N. Crabro, but also i. in shape than does Greville's N. Crabro, in which the constricted portion is less elongated—a fact pointed out by Greville himself. N. Crabro (E., K.). — Panduriform, deeply constricted; lobes ovate or ob- long, with subacute apices; striae di- stinct, obscurely moniliform, nitescent, 10 in 001". KA. p. 83 P; SBD. ii. p. 94; M.J. v. pl. 3. f. 11.= Pºnnularia Crabro, ERBA. 1844, p. 85?; Diplomeis Crabro, EM. pl. 19. f. 29 P Fossil, AEgina; re- cent, America, Europe. Although we defer to the opinions of Brébisson, Smith, and Greville, yet we think it highly probable that the preceding species is the one intended by Ehrenberg for D. Crabro. N. gemmata (Grev.).-Broad linear- oblong, obtuse, with straight or slightly concave sides; striae moniliform, inter- rupted, 10 in 001", with a single row of uncta near the median line. Edin. New Phil. Journ, n.s. X. pl. 4. f. 7. Cali- fornian guano. Distinguished by its distant striae, which form a linear mar- ginal band. Its affinity is with N. Crabro and its allies. N. nodulosa (Bréb., K.).-Minute, ob- long, constricted at the middle; ends contracted into obtuse mammiform beaks; transverse striae not reaching the median line. KB. p. 101, pl. 28. f. 71. = Pinnularia Termes, EMI. pl. 39. f. 100. Recent, Cuba, Mexico, Africa; fossil, Franzensbad. N. gemina (E.). — Small, striated, divided by a median constriction in both views into twolenticularlobes; in lateral view terminated by a median apiculus. EB. 1840, p. 19. Mouth of the River Elbe. 1-840" to 1-648". N. Apis (E., K.).— Oblong, so much constricted as to be nearly divided into two semiorbicular lobes; striae slender, granulate; stricture Smooth. KB. p. 100, pl. 28. f. 76. = Pinnularia Apis, E.A. iii. pl. 7. f. 18. Mexico, Africa. Distin- guished by its smooth stricture and its finely granulate striae (12 in 1-1200"). N. interrupta (K.). — Sinuato-con- stricted at the middle, with broadly ellip- tic lobes and rounded ends; striae inter- rupted opposite the nodule. KB. p. 100, pl. 29. f. 93. = Navicula, BAJ. 1842, pl. 2. f. 18. Marine, America, Jutland. B. Valves divided into three or more por- tions by two or four constrictions, but not constricted at the centre (Nodosae). N. Silicula (E.). — Smooth, linear elongated, divided by two constrictions into three nearly equal nodes; apices obtuse. EM. numerous figures. = N. ventricosa, E. Apparently common, since Ehrenberg gives upwards of fifty habi- tats in Europe, Asia, Australia, Africa, and America. This species might be placed with almost equal propriety in the following section. N. polyomca (Bréb.). —Elongated, ba- cillar, sublinear, divided by two con- strictions into three nodes, the middle One largest; ends roundish-capitate; striae wanting or indistinct. K.A. p. 85. = Pinnularia undulata, M.J. ii. p. 97, pl. 4. f. 10. France, Britain. N. Hitchcockii (E.).--Smooth, linear- oblong, each margin with three undula- tions; apices suddenly cuneate, sub- acute. EM. pl. 5. 3. f. 11. America. (VII. 62.) N. limosa (K.), Smooth or obscurely striated, linear, with two constrictions and three inflations, the middle one largest; ends cuneate, subacute. ICB. pl. 3. f. 50. Germany. N. nodosa (E.).-Linear, Smooth or ob- scurely striated, with three nearly equal inflations; ends contracted into short ob- tuse beaks. KB. p. 100, pl. 28. f. 82. Com- mon, especiallyin Small pools by theroad- side. (IX. 143.) 3, striae more evident. = Pºnnularia Legumen, E.M. many figures. 1-430". Approaches N. Hitchcockii. N. trinodis(S.).-Valves with two con- strictions, three nearly equal inflations, rounded ends, and obscure striae. N. mesolepta (E.):-Smooth, elongated, linear, with three inflations, the middle one Smallest; ends strongly contracted into short obtuse beaks. EM. pl. 17. 2. f. 17. America, France. 1-420". N. nivalis (E.).-Minute; linear, some- what narrow in the middle, with tri- crenate sides and obtuse apices. EB. 1853, p. 528; EM. pl. 35 B. A 2. f. 5. Monte Rosa. Differs from N. undosa in its stouter apices: W. nodosa is larger and more slender. Ehrenberg's figure shows the valves very minute, with four con- strictions and five nodules, including the capitate ends, which nearly resemble the others in size and form. N. Formica (E.). — Smooth, linear, with four constrictions and five oblong nodes. E.M. pl. 4; 3. f. 8. Recent, United States; fossil, Finland, OF THE NAWICULEAE. 895 N. Monile (E., K.).-Striated, linear, constricted, with five, nearly equal sub- globose nodes, including the capitate ends. = Pºnnularia Monile, EM. pl. 17. 1. f. 12; Pinnularia isocephala, EM. pl. 5. 3. f. 21. Berlin, America. It has the ends more capitate and the striae stronger than N. modosa. N. Kochi (E., K.).-Large, elongated, lanceolate, with subacute apices, each side with three undulations, the middle one most distinct; striae oblique ; the median Smooth band very broad, extend- ing to the apices. KA. p. 84. = Pinnu- laria Kochi, E.B. 1845, p. 364, Fossil. IKurdistan. N. Pyrenaica (S.).-Elongated, slen- der linear, with three inflations, the median one greatest; striae indistinct. ANH. 1857, xix. p. 8, pl. 2. f. 5. Pyre- Ile6S. N. wºndosa (E.). — Small, Smooth, broadly oblong-lanceolate, with three undulations on each side, and conical apices. EM. pl. 39. 3. f. 90. America, Africa, Asia, France. Ehrenberg de- scribes it as akin to N. Hitchcocki. Rabenhorst remarks that it resembles N. Persica in form, but is scarcely one-third its size and has no secondary undulating ribs. N. Persica (Rab.). — Large, oblong- lanceolate, with obtuse mammiform apices; each side with five undulations, and four corresponding longitudinal un- dulated lines on each side the median one. Rab D. p. 41, pl. 6. f. 55. South Persia. Broadest at the centre, and tapering in a pyramidal manner to each apex. N. integra (S.). — Small, lanceolate, with slightly undulated margins and contracted apiculate apices; striae in- distinct, 36 in 001", reaching the median line and most evident opposite the cen- tral nodule. = Pinnularia integra, S.D. ii. p. 96; N. rostrata, M.J. iv. pl. l. f. 14. Britain. N. undulata. = Pºnnularia mesotyla, EM. pl. 16. 3. f. 27. Sweden, India. Ehrenberg's figure somewhat resembles that of N, whdosa in form, but is longer and has parallel transverse striae. C. Valves elongated linear or lanceolate, with gibbous or inflated centre; central costae, when present, usually converging, and often leaving a dilated Smooth space round the median nodule. N. mesotyla (E.):-Small, smooth or indistinctly striated, narrowly linear, with a central spherical inflation and slightly contracted obtuse apices. EA, p. 131, pl. 4. 2. f. 7.; EMI. pl. 1. 3. f. 14. Asia, Africa, America. 1-420". N. inconspicua (Greg.).--Small,Smooth, hyaline, linear, with rounded ends and slightly gibbous centre; median line strong, complex, interrupted by the de- finite central module. GD. p. 6, pl. l. f. 3. Scotland. N. laevissima (K.).-Minute, vitreous, clear, linear, with broadly rounded ends and slightly gibbous centre; striae want- ing or indistinct; central nodule stauros- like. KB. p. 96, pl. 21. f. 14. = Stau- roneis rectangularis, M.J. ii. pl. 4. f. 17 º to Smith). Fossil, Santa Fiore; recent, Britain. 1-570". N. tumidula (Rab.). — Small, linear, with rounded, slightly enlarged ends, and inflated centre; central nodule stout. Rab D. p. 41, pl. 5. f. 9. Stockholm. Closely allied to N. Silicula. N. scopulorum (Bréb.). — Elongated, slender linear, with central and terminal inflations; striae very faint, reaching the median line, 56 in 001". KA, p. 81. = N. mesotyla, K.B. p. 99, pl. 5. f. 3; Pin- nularia Johnsonii, S.D. i. pl. 19. f. 179. In marine or brackish waters. France, Britain. Front view turgid at the middle. M. de Brébisson assures us that Smith's species is identical with his N. scopu- lorum; but Kitzing's figure and descrip- tion would not lead us to infer the identity. * N. gibberula (K.).—Linear, with gib- bous centre and very slightly enlarged, obtuse, Subtruncate apices; striae very fine, KB. p. 101, pl. 3. f. 50%. Europe. N. leptogongyla (E.). — Elongated, slender linear, striated, tumid in the middle ; apices slightly dilated, oblong, obtuse. #. p. 99, pl. 4. f. 9; EA, p. 130. = Pinnularia leptogongyla, EM. many figures. Europe, America. Lough Mourne deposit. Rabenhorst says that this species has double the breadth of N. Scopulorum. N. mesogongyla (E., K.). — Styliform or bacillar, striated, with gibbous middle, and broadly rounded but not dilated ends. KA, p. 81. = Pinnularia meso- gongyla, º 10. 2. f. 2. Asia, Africa, America. in to N. mobilis, but with- out dilated ends. N. mobilisº K.).-Very large, elon- gated, broadly linear, gradually dilated at centre, and broadly rounded ends; costae oblique, stout, close, not reaching the median line. KA. p. 80. = Pin- nularia nobilis, E.B. 1840, p. 20; SD. i. pl. 17. f. 161, Europe, America, Asia, 896 SYSTEMATIC ELISTORY OF THE INFUSORIA. Australia, 1–84"; modules large; costae 16 to 18 in 1–1200". N. gigas (E., K.). —Very large, elon- gated; broadly linear, with gibbous centre, and broadly rounded, slightly attenuated ends; costae broad, close, not reaching the median line. KA, p. 80. = Pºnnularia gigas, EM. pl. 2. 3. f. 1. America, Akin to N. mobilis; nine pinnules in 1–1200". N. major (K.).-Large, turgid, linear- oblong, with slightly tumid centre and broadly rounded ends; costae converg- ing at the centre, stout, 12 in 1-1200". KB. p. 97, pl. 4. f. 19, 20. = Pinnularia major, S.D. pl. 18, f. 161; Pinnularia viridis, E., in part. Common. (VII, 65; XII.15, 31; XVI, 1–6.) This species scarcely differs from N. mobilis and N. gigas, except by its somewhat Smaller size and closer pinnules. N. acrosphaeria (K.). — Elongated, slender linear, with dilated centre and ends, rounded apices, and seventeen short thick costae in 1–1200", which do not reach the median line. KB. p. 97, pl. 5. f. 2. = Pinnularia acrosphaeria, Rab D. # 45, pl. 6. f. 36; SD. pl. 19. f. 183. £urope. Front view narrow-linear. N. pachyptera (E., K.).-Large, bacil- lar, but short and stout, with gibbous centre and broadly rounded ends, which are not constricted; pinnules stout, not reaching the median line, 6 in 1-1200". ICB. p. 98, pl. 28. f. 58. = Pinnularia pachyptera, E. Labrador, Australia. N. hebes (Ralfs).--Small, oblong, with gibbous centre and broadly obtuse ends; striae distinct, 33 in 001", nearly reach- ing the median line. = N obtusa, S.D. i. p. 50, pl. 16. f. 140. Britain. N. cocconeiformis (Greg.). — Small, subelliptic, with tumid centre and slightly contracted, broad, obtuse ends; striae in- distinct, median line straight, nodule definite. M.J. iv. p. 6, pl. 1. f. 32; Grev. ANH, 2nd series, xv. pl. 9. f. 6. Scotland. It much resembles Achnanthi- dium flewellum, but its median line is quite straight, Greg. N. Macula (G.).--Small, oblong, with tumid middle, and very broad, subtrun- cate ends; striae very fine, parallel, nearly reaching the median line, except opposite the large, transverse, quadrate indefinite median space. TM. iv. p. 43, pl. 5. f. 9. Marine. Britain. Striae about 70 in ‘001". In shape not unlike large speci- mens of Achnanthidium ſleazellum, but the median line is straight. The central module is obsolete and is replaced by the large, stain-like blank space, Greg. N. gibba (E., K.).—Bacillar, striated, lanceolate, with dilated capitate ends. KB. p. 98, pl. 28. f. 70. = Pºnnularia gibba, E.A. pl. J. 2. f. 3; SD, pl. 19. f. 180. Common. Europe, Asia, Africa, America. Striae close, not reaching the median line, 30 in 001". N. Tabellaria (E., K.).--Bacillar, elon- gated, striated, rather turgid, ventricose at the middle, with dilated, broadly rounded apices. ICB. p. 98, pl. 28. f. 79. = Pinnularia Tabellaria, EA, pl. 2. 1. f. 26; SD. i. pl. 19. f. 181. Europe, Asia, Africa, America. (XII, 21.) The central dilatation tapers less than in N. gibba, and the striae are more distant. It is more slender than N. mobilis. N. porrecta (E., K.). — Large, elon- gate-lanceolate, broadly tumid at the middle, and gradually tapering into the broadly obtuse apices; striae oblique. KA. p. 81. = Pinnularia porrecta, EA, p. 133. North America. Akin to N. decurrens. N. decurrens (E., K.).—Striated, nar- row, elongate-lanceolate; tumid at the centre, somewhat narrowing towards the ends, which are broadly rounded. K.A. p. 81.= Pinnularia decurrens, EM. many figures. 8 slenderer, = Pºnnularia Tra- becula, E. y, striae obsolete, = Navicula Trabecula, E. Ehrenberg gives upwards of 80 habitats. Akin to N, gibba. N. Esoa. (E., K.). —Large, elongated, striated, narrow-lanceolate, with slightly gibbous centre and attenuated but obtuse ends; striae parallel, nearly reaching the median line. KB. p. 94, pl. 28. f. 53. = Pinnularia Esoa, EA, p. 133, pl. l. 2. f. 4. Chili, (XII, 43.) D. Valves with a smooth, transverse middle fascia. N. cardinalis (E.). — Large, broadly linear, with rounded ends; costae Stout, radiant, 9 in 001", interrupted by a smooth, transverse median band. = Pºn- nularia cardinalis, S.D. i. pl. 19. f. 166; Stavroptera cardinalis, EM. several fi- gures; Stauroneis cardinalis, KB. p. 106, pl. 29. f. 10. Europe, Asia, Australia, Africa, America. (XII. 72.) A well- marked species, easily recognized by its large size, rounded not attenuated ends, and coarse striae, which are shorter near the transverse median fascia. Perhaps this and other species having a trans- verse smooth median fascia might ad- vantageously be retained in Stauroneis, notwithstanding that the fascia is not formed by a thickened prolongation of the central module. 3. N. divergens (S.); – Large, oblong- OF THE NAVICULEME. 897 lanceolate, somewhat contracted towards the rounded ends; costae radiate at cen- tre, interrupted by a smooth transverse median fascia, 11 in 001". = Pinnularia divergens, SD. i. p. 57, pl. 18. f. 177. Britain. The costae near the central no- dule are shorter and radiant; the others are divergent. - N. Brébissonii (K.). — Linear-oblong, with obtuse ends; costae fine, indistinct, close, 30 in 001", not reaching the me- dian line, interrupted by a transverse median fascia. . p. 93, pl. 3. f. 49. = Pºnnularia stauroneiformis, S.D. i. p. 57, pl. 19. f. , 178. Europe. Front view linear, with rounded angles. N. globiceps (Greg.).-Minute, narrow linear-oblong, constricted beneath the globular ends; costae fine, distinct, not reaching the median line, interrupted by a transverse median blank band, 36 to 40 in 001".= Pinnularia globiceps, M.J. iv. p. 10, pl. 1, f. 34. Scotland. Di- stinguished by its capitate apices and transverse cross-like median band. N. parva (E.). — Linear, constricted beneath the capitate ends; costae 24 in ‘001", interrupted at the middle by a transverse, blank, cross-like band. = Stau- roptera parva, E.A. p. 135, pl. 3. 1, f. 19; Stauroneis parva, KB. p. 106, pl. 29. f. 23; Pºnnularia interrupta, SBD. i. p. 59, l. 19. f. 184, Europe, Asia, America. Transverse band dilated outwards. . N. Bohemica, EM. pl. 10. , 1. f. 4. Bohemia. Ehrenberg's figure is rhom- boid, with obtuse apices, three median lines, between which and the margins are longitudinal series of dots, all inter- rupted by a transverse median blank space, but no distinct module; front view narrow-linear, with rounded ends. N. Claviculus (Greg.).--Narrow-linear, with two constrictions; central inflation Small, Smooth; terminal ones oblong- clavate, striated; striae parallel, nearly reaching the median line, about 32 in .001". G.D. p. 6, pl. 1. f. 5. Scotland. Nodule definite ; front view linear, with rounded angles, broader than the lateral view, the margins striated except at the middle. E. Frustules in the lateral view having the striae on each side of the median line divided into two series (a marginal and a median) by a longitudinal line, blank Space, or fascia, t Valves elliptic. N. Lyra (E.). — Elliptic or elliptic- oblong, marked by two narrow longi- tudinal blank spaces, which are con- nected by the central module, in the form of a lyre; striae 22 to 24 in 001", often indistinct, the middle ones longest.= Navicula and Pinnularia Lyra, E., GD, p. 13, pl. 1, f. 13; W. Gregoriana, Grev. MJ. V. p. 10, pl. 3. f. 7. Marine. Europe, Asia, Africa, America. N. Lyra, var, recta, Grey, large, oblong-lanceolate obtuse; blank lines narrow, contracted at the no- dule, otherwise parallel with the median line; striae 24 in 001": Edin. New Phil. Jour., n.s., x, pl. 4. f. 3: Californian guano: distinguished by its large size and straight blank lines. Either N. Lyra is very variable, or more than one species has been included under the name. The valve is either rounded at the ends or (more usually) has a short, produced, conical, point. The blank spaces aré linear, inclined inwards at the nodule, and the tips, which are attenuated, usu- ally bent outwards, but are sometimes Straight or even incurved. N. approximata (Grev.). — Oblong, with produced, conic apices; striae inter- rupted, 17 in 001"; outer band broad, not dilated opposite the nodule; blank lines linear, nearly straight. Grev. Edin. New Phil. Jour., n.s., X. pl. 4. f. 10. Californian guano. Allied to N. Lyra, but distin- guished by the total absence of any con- traction of the blank spaces opposite the module. From N. Hennedy; it differs in its linear, subparallel blank spaces, and larger blank space round the module. N. irrorata Grev.).--Broad, parallelo- gramic or oblong, suddenly contracted at the ends into mammiform apices; striae 15 in 001", forming a broad-linear marginal band, and a narrow one of very unequal breadth next the median line; blank Spaces not reaching the ends. Grey, l.c. f. 1. Californian guano. N. forcipata (Grev.).--Oval or oblong, with rounded apices, and marked by two narrow longitudinal blank spaces, which diverge from the nodule in a curved mammer and converge at the apices; striae 35 in 001", the middle ones longest. M.J. vii. pl. 6. f. 10, 11, Marine. Britain. Distinguished from W. Lyra by its Smaller size, closer striae, and commivent points of the blank spaces. N. nummularia (Grev.). — Suborbi- cular; striae moniliform, about 24 in ‘001", interrupted by two narrow-linear blank lines which contract opposite the module, then curve outwards, converge, and meet at the terminal modules. Grey. Edin. New Phil. Jour., n.s., x. pl. 4. f. 6. Californian guano, Valve small; striae 3 M 898 SYSTEMATIC IIISTORY OF THE INFUSORIA. concentric with the extremities. The blank spaces have a considerable resem- blance to those of N. forcipata, Grev. N. spectabilis (Greg.).-Broadly ellip- tic, gradually tapering to the obtuse apices; blank spaces broadly linear, con- verging at nodule and ends; striae 22 in •001", coarsely moniliform, the outer series forming a broad marginal band much dilated opposite the nodule. GD, }. 9, pl. 1, f. 10. Marine. Scotland. arge (inner) bands of striae linear. Distinguished from N. Lyra by broader blank spaces and the brown colour of the striated portions; its nodule also is indefinite. N. suborbicularis (Greg.). — Small, broadly oval or suborbicular; striae con- spicuous, about 18 in 001", divided by a longitudinal line into two series, outer one broadest opposite the indefinite cen- tral module. = N. Smithi suborbicularis. GD. p. 15, pl. 1. f. 17. Marine. Scotland. N. Cowperi (Bailey). — Large, oblong, with slightly constricted sides and con- tracted mammiform apices; striae punc- tate, divided into series by two narrow longitudinal blank bands united by the transverse nodule. = Pºnnularia Couperii, BMO. p. 39, pl. 2. f. 3. United States. The outline is like that of N. paradoaca ; and the markings somewhat resemble those of N. Lyra, 8. Blank spaces con- niverit at their apices. N. Hennedy: § . — Elliptical, with rounded or mammiform ends; striae mo– niliform, divided into series by two nar- row, lunate longitudinal blank spaces, the marginal series of nearly equal breadth throughout. SBD. ii. p. 93; Greg, M.J. iv. pl. 5. f. 3. = Stauroneis an- gulata, Johnston, M.J. viii. p. 13. Marine. Britain. (VII. 69.) Striae 24 in 001", not perceptibly longer opposite the cen- tral module, which is indefinite. N. clavata (Greg.).--Broadly elliptical, with apices produced into mammiform points; striae moniliform, divided into series by two arcuate longitudinal blank spaces bent outwards at their ends; marginal Series of nearly equal breadth throughout. TM. iv. pl. 5. f. 17. Marine, Scotland, Striae 20 in 001", not per- ceptibly longer opposite the central no- dule, which is indefinite. N. nebulosa (Greg.).-Elliptic-oblong; blank spaces large, semilunate; striae fine, 34 to 36 in 001", forming a narrow marginal band of equal breadth. G.D. p. 8, pl. 1. f. 8. Marine. Scotland. Inner bands of striae, very narrow linear, close to median line. Aspect of valve hazy and indistinct; striated portions bluish under a low power; nodule indefinite. N. praetexta 9. — Large, elliptic with broadly rounded ends; striae di- stinctly moniliform, 8 to 10 in 001", forming a marginal border of nearly uni- form breadth, which is separated from the narrow median band by a large sparsely granular space on each side. EB. 1840, p. 20; GD. § 9, pl. 1. f. 11. = Pinnularia praeteata, EMI. pl. 19. f. 28. Marine, Scotland; fossil, Greece. 1-288". This species is distinguished by its large size, coarse striation, much rounded ends, and a broad semilunate space between the marginal and inner bands of striae, furnished with scattered granules. N. Californica (Grev.). — Broadly elliptic, with flattened sides; striae mo- miliform, divided into narrow marginal and median bands by a large, Semilu- mate, Smooth intermediate space on each side the median line. Grev. Edin. New Phil. Jour., n.s., x, pl. 4. f. 5. Californian and S. African guanos. Marginal striae 20 in 001". Differs from N. praetecta in having the sides of the valve flattened, and the broad intermediate space be- tween the marginal and median striae Smooth. - N. polysticta (Grev.).-Elliptical; striae moniliform, forming a narrow marginal band, separated from the median line by an irregularly punctate, lunate inter- mediate space; striae 25 in 001". Grev. l. c. f. 2. Californian guano. Valve mi- nute. Differs from N. praetexta in its Smaller size and far less rounded ends. N. Smithii (Bréb.). — Elliptic, with rounded apices; striae distinct, 21 in ‘001", interrupted on each side of the median line by a longitudinal line; the inner Series narrow, fainter. = N. elliptica, SD. i. p. 48, pl. 17. f. 152. Marine. Europe. The outer series of striae is broad, but not dilated opposite the * module. , , fusca (Greg.). — Large, elliptic- oblong, * tº, rounded ... striae coarsely moniliform, about 10 in '001", divided on each side by a longi- tudinal line into two series, the immer one fainter. = W. Smithii, 8 fusca, G.D. }; 14, pl. l. f. 15. Marine. Scotland. iffers from N. Smithii in its much larger size and more distant striae. Nodule , indefinite; median Smooth space narrow lanceolate. - N. nitescens (Greg.),—Small, elliptic- lanceolate, with obtuse apices; striae obscurely moniliform, about 16 in 001", converging at centre, divided on each OF THE NAVICULEE. 899 side by alongitudinalline into two series, reaching the median line. = N. Smithii, 'y nitescens, GD. p. 15, pl. 1. f. 16. Ma- rine. Scotland. Colourless under a low power; median line linear, module de- finite. Distinguished from W. Smithū by its Smaller size, the characters of nodule and median line, and its bright-white aspect. • . quadrifasciata (E.). — Elliptic-ob- long, with attenuated, obtuse ends; striae 20 in 1-1200", divided on each side of the median line into two linear series. E.B. 1840. = Pinnularia quadrifasciata, EM. pl. 19. f. 25–27; N. lineata, Donkin, MT. vi. p. 32, pl. 3. f. 17? Marine. Fossil, Greece; recent, Britain. 1-430". Series of striae separated by a narrow blankline. N. elliptica (K.).-Elliptic or linear- elliptic, with rounded ends; striae di- stinct, commivent, 27 in 001", divided into two series on each side the median space by a longitudinal line. = N. Par- nula, KA, p. 80; N. ovalis, SD. i. p. 48, pl. 17. f. 153. Europe. N. pygmaea (K.).—Minute, elliptic or oblong-elliptic, with rounded ends, hya- line, with very faint, close striae, and a panduriform blank median space. KA. . 77. = N. minutula, SD. i. p. 48, pl. 31. . 274. In brackish or fresh water. France, England. Although the striae, which are very indistinct, are not inter- rupted, yet the peculiar form of its me- dian space shows that its proper position is in this group. N. destiva (Donkin). —Large, narrow- elliptic, with rounded ends; striae fine, distinct, costate or obscurely momiliform, reaching nearly to the median line, crossed on either side near their inner ends by a longitudinal line. TM. vi. . 32, pl. 3. f. 18. Marine. Northum- fººd This beautiful species differs from W. Smithi; in its more gracefully elliptical figure, in its costate and much finer striae, and in the darker-brown colour when mounted in balsam. The dry valve is pale-brown. Donkin. . Allmaniana (Greg.).--Small, oval, with subacute apices; costae about 20 in •001", somewhat radiant, nearly reaching the median line, divided by a line near to and concentric with the margin. = Pinnularia Allmaniana, G.D. p. 16, pl. 1, f, 21. Marine. Scotland. The marginal series of costae , narrow, conspicuous, border-like; the inner one fainter. 2 + Valves linear, with dilated centre and ends. N. Rabenhorstii (Ralfs). —Elongated, slender, gradually dilated at centre, and broadly rounded ends; striae fine, short, divided on each side the median line by a narrow, blank, longitudinal line. = Pºn- ºvularia interrupta, Rab D. p. 44, pl., 6. f, 3, Italy. Divided by two constric- tions into three oblong portions; the interrupting line undulated like the margins. This species resembles a slen- der W. nobilis with interrupted striae. F. Valves with capitate or rostrate apices. f Valves inflated or ventricose. N. Cruz (E.). — Cruciform, with di- ºverging costae, which do not reach the median line. = Pinnularia Cruac, EM. pl. 12. f. 37. Asia, Cassel. This species has the lateral view like a Biblarium, but with median line and module. N. Trochus (E.). — With strongly in- flated middle, and obtuse, rostrate ends, longitudinally striated. EInf. p. 179, pl. 21. f. 8. Fossil. Sweden. 1-860". N. inflata (K.).—Minute; with much inflated centre, and short, obtuse, beak- like ends; striae wanting or indistinct. KB. p. 99, pl. 3. f. 36=N. Follis, EMI. several figures. Fossil, Sweden, Santa Fiore; recent, Europe. N. : amphisbana (Bory). — Inflated, elliptic, with capitate or comic apices; striae close, delicate. EInf. p. 178, pl. 13. f 7; SD. i. p. 51, pl. 17. f. 147, Common. Europe, Asia, Africa, America. (VII. 72; IX. 141.) 1-1700" to 1-240". Median nodule orbicular. The Pinnularia am– phisbaena, EMI., is probably a state of this species exhibiting more conspicuous striae. N. Placenta (E.).-Minute, ventricose, roundish-elliptic, with a nipple-like pro- jection at each apex, EMI. pl. 33. 12. f 23. Oregon. N. Sphaerophora (K.).—Elliptic-lance- olate, strongly constricted into capitate or conic apices; striae wanting or in- distinct. KB, p. 95, pl. 4. f. 17; SD. i. p. 52, pl. 17. f. 148. Europe, Asia. Very similar to N. amphisbama, but it is less inflated, and it appears destitute of striae. According to Rabenhorst, it differs also by having faint longitudinal lines, 1–320”. N, brevis (Greg.). — Small, elliptic, contracted into short, broad, mammiform ends; striae fine, about 35 in 001", nearly reaching the median line, shorter º the indefinite central nodule. G.D. p. 6, pl. 1. f. 4. Scotland. Professor Walker Kºi. is probably correct in uniting this to N. amphisbaena. 3 M 2 900 SYSTEMATIC HISTORY OF THE INFUSORIA. N. tumens (S.).-Inflated, elliptic, with the ends suddenly contracted into short, obtuse beaks; striae indistinct, 36 in •001". SD. i. p. 52, pl. 17. f. 150. Brack- ish water. #jºi N. pusilla (S.).--Small, inflated, ellip- tic, suddenly contracted into short, conic beaks; striae distinct, punctate, radiant, 26 in 001". SD. i. p. 52, pl. 17, f. 52. = N, gastroides, Greg. º . iii. p. 40, pl. 4. f. 17. Brackish water P Britain. Prof. Gregory distinguished his N. gastroides from this species by its stouter habit, larger size, and having a brown colour even in balsam ; but we unite them as Professor Smith has done, being unwill- ing to add another doubtful species to this group, which we believe is already too numerous. - N. Anglica (Ralfs).-Minute, elliptic, suddenly constricted beneath the round- ish capitate ends; striae very distinct, unctate, radiate, reaching the median ine, 24 in 001". = N. tumida, S.D. i. p. 53, pl. 17. f. 146. N. Carassius (E.). —Small, inflated, broadly lanceolate, with the ends Sud- denly contracted into short, conical beaks; striae wanting or indistinct. EA. . 130, pl. 2. 2. f. 11. France, America. }. smaller than N. amphisbana, . N. capitata (E.). — Minute, with in- flated centre, and short, obtuse, beak- like ends; striae diverging, 10 in 1-1200". E Inf. p. 179, pl. 13. f. 20. = Pinnularia capitata, EM. pl. 35 A. 1, f. 4. Europe, Asia, Australia, America. 1-1150" to 1–576". N. Semen (E.). — Small, elliptic-ob- long, slightly contracted into the broad, obtuse ends; striae obsolete or apparent. EA, pl. 4. 2. f. 8; in EM. many figures; SD. i. p. 50, pl. 16. f. 141, 8, striae di- stinct, = Pºnnularia Semen, EM. Europe, Asia, Africa, America. N. aqualis (E., K.).-Inflated, elliptic- lanceolate, Suddenly contracted at the ends into nipple-like points; striae fine. KSA, p. 77. = Pºnnularia aqualis, EA. 131; EM. many figures. Europe. Lough Mourne deposit, Iceland. N. diomphala (E.). — Striated, short, broadly lanceolate, suddenly contracted into obtuse beaks; median nodule trans- verse, divided by a longitudinal line into two parts, EA, p. 132, pl. 3. 7. f. 25. America. N. Gastrum (E., K.).--Small, striated, inflated, elliptic, contracted at the ends into short comical beaks; striae radiant. I B. p. 94, pl. 28. f. 56. = Pºnnularia Gastrum, EM. Several figures; Pin- nularia Placentula, EM. Several figures. Asia, Africa, America. N. birostrata (Greg.) — Ventricose, elliptic-oblong, with shortly rostrate apices; striaefine, close, radiant, reaching nearly to the median line. M.J. iii. p. 40, pl. 4. f. 5. Scotland. N. taeniata (E.). — Small, inflated, elliptic, suddenly contracted into minute, rounded, conical beaks; pinnules strong, forming a narrow marginal border. = Pinnularia toniata, EM. pl. 39. f. 95. The pinnules separated from the median line § a broad §. space. Perhaps a Mastogloia. (xv. 15.) N. biceps (E.). — Small, turgid, lance- olate, slightly constricted into obtuse, conical apices; striae wanting or indi- stinct. EA, p. 130; EM. many figures. Europe, Africa, America. Rather more slender than N. amphisbaena. N. crassula (Nägeli). —Smooth, ellip- tic, with capitate apices; front view broadly linear, truncate. 1-720". KSA. p. 890. Switzerland. N. sculpta, EMI. pl. 10. 1, f. 5. Bohe- mia, Asia, America. Ventricose, Sud- denly tapering into short, broad, obtuse beaks, the median line interrupted by the indefinite nodule, which extends on one side in a semicrucial Smooth band; the rest of the surface granulated. Front view linear, with rounded angles and gibbous sides. - N. Signata (E.). — Minute, inflated, prolonged into narrow beaks; striae radiant, reaching the median line, the six central ones stronger. = Pºnnularia signata, EM. pl. 34.6 A. f. 7. Florida. N. Rostellum (S.).--Small, ventricose, oval, with the apices produced into point- like beaks; striae indistinct, 80 in 001". SBD. ii. p. 93-N. apiculata, Greg, MJ. iv. pl. 1, f. 13. Britain. 2 + Valves lanceolate. N. Crassimervia (B.). — Minute, lance- olate, with shortly rostrate apices; striae wanting or indistinct. SD. i. p. 47, pl. 31. f 271. France, Britain. N. rhynchocephala (K.). — Slender, lanceolate, with longly rostrate apices; striae wanting or obscure. KB. p. 152, l. 30. f. 35; SBD. p. 47, pl. 16. f. 132. Europe. Is longer and more slender than N. cryptocephala, with more produced apices. (VII. 68. N. leptorhynchus (E.).--Small, smooth, linear-lanceolate, with straight, subacute, longly rostrate apices. #. p. 130. Mexico. Akin to N. dirhynchus, but with longer beaks. OF TEIB NAWICULEAE. 901 N. leptocephala (Rab.).--Small, lance- olate, with elongated, slender, obtuse, somewhat clavate beaks; striae wanting or indistinct, Rab D. p. 39, pl. 6. f. 69. Europe. N. eacilis (K.).—Very minute, Smooth, lanceolate, with produced, obtuse apices. KB. p. 95, pl. 4. f. 6. Germany. N. rostrata (E.). — Finely punctated, broadly lanceolate, almost rhomboid, rapidly tapering into acute beaks; cen- tral nodule large. EB. 1840, p. 18; KB. . 94, pl. 3. f. 45, Fossil. Santa Fiore. –216". Front view linear, with trun- cate apices. N. &ºus (E.).-Elongated, smooth, oblong-lanceolate, with the ends con- tracted into comic beaks. EB. 1845, p. 239; EM. pl. 35. BB. f. 12. Four times as long as broad. f N. Otrantina (Rab.). —Oblong-lance- olate, with rounded, slightly contracted ends. Rab D. p. 44, pl. 6... f. 42. N. dirhynchus (E.).--Small, narrow- lanceolate, with conic, rostrate apices; striae wanting or indistinct. EA, p. 130, pl. 3. 1, f. 11. Falaise, Mexico. N. Garganica (Rab.). — Minute, lam- ceolate, suddenly contracted into short, thick, obtuse apices; striae distinct, ob- lique, reaching the median line, six near the central module stouter than the rest. = Pinnularia Garganica, Rab D. p. 44, pl. 6. f. 41. Italy. N. amphiceros (K.).—Minute, broadly lanceolate, with produced, rostrate apices, and fine striae. T KB, p. 95, pl. 3. f. 39. Germany, Asia. N. stelligera (E., K.).-Rhomboid-lan- ceolate, with the apices suddenly atte- nuated into obtuse beaks; the very fine punctated pinnules distinctly radiating from the orbicular, Smooth umbilicºi space. KA, p. 70. = Pºnnularia Stelligera, 3B. 1845, p. 364. Marine. India. N. Petersii (E., K.)—Dilated, large at each end, suddenly attenuated into a very short beak; median line double, with a narrow, longitudinal umbilical space; pinnules very fine. KA, p. 70. =Pinnº- laria Petersä, EB. 1845, p. 364, Mouth of the river Tagus. N. guttulifera (Rab), Minute, slen- der, acicular, with a glass-like globe at each apex. R.D. p. 40, pl. 6, f. 7ſ south Persia. & N. pachycephala (Rab.). — Minute, slender-lanceolate, constricted beneath the capitate apices; striae converging; central module stout, terminal ones ob- solete. = Pinnularia pachycephala, R.D. p. 43, pl. 6, f, 40, Italy, - N. cincta. = Pºnnularia cincta, EMI. pl. 10. 2. f. 6. Bohemia. This species is figured as minute, lanceolate, with obtuse apices; striae oblique, those oppo- site the central nodule radiant and stouter than the others. N. Gregorà (Ralfs). — Small, narrow linear-lanceolate, contracted at the ends into minute beaks; striae distant, parallel, Scarcely reaching the median line. = Pºnnularia apiculata, Greg, M.J. iii. p. 41, pl. 4. f. 21. Scotland. N. angwstata (S.).-Minute, narrow- lanceolate, constricted beneath the capi- tate apices; striae indistinct, 45 in 001", SD. i. p. 52, pl. 17. f. 156. E N dicephala 8, KA, p. 76? Britain, Falaise. Front view narrow-linear. N. cryptocephala (K.).-Very minute, lanceolate, with globose, capitate apices; striae wanting or indistinct. KB. p. 95, pl. 3. f. 20. Europe. N. Veneta (K.), — Very minute, lan- ceolate, rather broad, with produced, slightly obtuse apices; striae wanting or indistinct. KB. p. 95, pl. 30. f. 76. Brackish water, Venice. Resembles W. cryptocephala, but is shorter and broader. N. Fusidium (E.). — Narrow-lanceo- late, distinctly but slightly constricted beneath the capitate apices, E.M. pl. 5, 3. f. 4. America, Asia. N. leptostylus (E.). — Lateral view turgid-lanceolate, suddenly tapering into short beaks with capitate apices. = N. Platalea, EM. pl. 15 A. f. 42. N. amphiºrhina (E.) = Pºnnularia am- phirrhina, EMI. pl. 15 A. f. 20. Lough Mourne deposit, Japan, America, Ehr- enberg figures this species as inflated- lanceolate, rapidly tapering into subacute beaks; striae parallel. N. amphirhynchus (E.). — Small; tur- gid-lanceolate, suddenly constricted at the ends into short, subcapitate beaks; striae indistinct or wanting, EA, pl. 3, 1. f. 10; KA, p. 76. Europe, Asia, Aus- tralia, Africa, America. (XII, 6.) N. amphistylus (E., K.), Elongated bacillar, with turgid middle, attenu- ated, filiform, obtuse apices, and deli- cate pinnules, KSA, p. 75. = Pinnularia amphistylus, E.B. 1845, p. 79, Fossil. oº: 1-372". , ordinata (Bréb.).-Minute, smooth, connected in a parallel manner into short, fragile filaments; valves slender- lanceolate, contracted at the ends into short, often capitate beaks. Bréb. = N. aponina 8, KA, p. 69. Falaise. N. eurycephala (Rab.). — Large, ro- bust, oblong, slightly contracted at the 902 SYSTEMATIC ELISTORY OF TELE ENFUSORIA. ends into very short and broad, truncate beaks. Rab D. p. 40, pl. 6. f. 70. Ger- many. Median line and nodule strongly developed. Tesembles Stauroneis platy- stoma, but with a rounded, not trans- verse median module. º 3 + Valves linear. N. dicephala (E.). —Blongated linear, constricted at the ends into capitate or broadly conical beaks; striae either ob- scure or distinct, 19 in 1-1200". = Navi- cula and Pinnularia dicephala, EM. many figures; Pinnularia biceps, Greg, M.J. iv. pl. 1. f. 28? Common, Europe, Asia, Africa, America. 1-860" to 1-480". N. producta (S.). — Linear, abruptly contracted at the ends intó short, obtuse beaks; striae faint, 42 to 48 in 001". SD. i. p. 51, pl. 17. f. 144. = N. amphi- rynchus, SD. i. p. 51, pl. 16. f. 142. Britain, (VII, 66. - N. birostris (E.).-Elongated narrow- linear, suddenly contracted at the ends into conical apices; striae distinct, close, parallel. = Pinnularia birostris, EMI. pl. 15 A. f. 24. Fossil. Lough Mourne de- posit; Sweden. This form seems scarcely to differ from N. dicephala, except in baving slenderer frustules. N. gracillima (Greg.).--Slender, nar- row-linear, constricted beneath the capi- tate apices; costæ fine, 27 in .001", not reaching the median line. = Pinnularia gracillina, M.J. iv. p. 9, pl. 1. f. 31; SD. ii. p. 95; Pinnularia tenuis, M.J. ii. pl. 4. f, 9 P. Britain. N. linearis (Greg.).-Minute, narrow- linear, constricted beneath the subcapi- tate ends; costae very fine, about 40 in ‘001", parallel, reaching the median line. = Pºnnularia linearis, M.J. iv. p. 8, pl. 1. f. 29. Scotland. º N. subcapitata (Greg.)-Minute, nar- row-linear, constricted beneath the capi- tate ends; striae Subdistant, conspicuous, short. = Pºnnularia Subcapitata, M.J. iv. p. 9, pl. 1. f. 30. Scotland. N. Elginensis (Greg.).-Minute, linear, constricted beneath the subquadrate capitate ends; striae fine, about 30 in ‘001", slightly oblique, reaching the median line. = Pinnularia Elginensis, M.J. iv. p. 9, pl. 1. f. 33. Scotland. N. limpida (Perty). — Rather large, striated, broadly linear-oblong, suddenly contracted at the ends into short, broad, obtuse beaks. I’erty, Mic. Org, of Alps, p. 204, pl. 17. f. 9. Alps. Front view linear, with truncate ends; striae 10 to 11 in 1–1200", N. Pisciculus (E., K.). — Elongated, slender, striated, narrow-linear, slightly contracted at the ends into comic beaks; striae very delicate. KA, p. 75. = Pin- nularia Pisciculus, E.A. pl. 2, 1, f. 30. Cayenne, India, Falaise. N. limbata (E.).--Small, linear, each end suddenly contracted into a short, broad, truncate beak, and a wide border appearing within, E.A. p. 130, pl. 1, 2. f, 16. Chili. . N. longiceps (Greg.). — Minute, nar- row-linear, with the ends contracted into short, obtuse points; module inde- finite; striae wanting or inconspicuous. M.J. iv. p. 8, pl. 1. f. 27. Scotland. N. affinis (E.).--Small, linear-oblong, with the ends suddenly contracted into short, broad, obtuse beaks; striae want- ing or indistinct. EA, p. 129, pl. 2. 2. f.7; SD. i. p. 50, pl. 16, f. 143. Very common. Ehrenberg gives upwards of seventy habitats. (XII. 32.) 1-570" to 1-420". Resembles N. dicephala. N. dubia (E.). — Small, linear-lanceo- late, with the ends suddenly contracted into conic beaks; striae wanting or in- distinct. EA, p. 130, pl. 2. 2. f. 8, , Asia, Australia, Africa, America. Akin to N. affinis. N. ambigua (E.). — Small, oblong, Somewhat inflated, with the ends Sud- denly contracted into short, comic beaks; striae wanting or indistinct. EA. pl. 2. 2. f. 9; EMI. pl. 15B. f. 15. America, Aus- tralia, Lough Mourne deposit. Re- Sembles N. affinis and N. dicephala. N. rostellata (K.). — Minute, striated, linear-oblong, with elongated, rostrate, acute apices. RB. p. 95, pl. 3. f. 65. Wangerooge. N. columnaris (E.).-Large, elongated, broadly linear, Suddenly contracted into short, very broad, rounded ends, and marked by numerous longitudinal lines, EM. pl. 14. f. 23. Berlin. N. ampliata, EM. pl. 17. 2. f. 7, & * 15 A. f. 32. Finland, Siberia, Lough Tourne deposit. Ehrenberg's figures re- present this species as large, Smooth, broadly linear, suddenly contracted at the ends into broad, rounded, mammi- form beaks. - N. Vespa (R.).--Small, linear-oblong, constricted beneath the capitate apices; nodules minute; striae parallel, close, nearly reaching the median line. = Pin- nularia Vespa, †M. pl. 33. 5. f. 9. Asia, Africa, America. N. incurva (Greg.). — Small, linear, with slightly sinuated sides; ends con- tracted into short truncate beaks; stria) OF THE NAVICULEE. 903 wanting or inconspicuous. pl. 1. f. 26. Scotland. N. apiculata (Bréb.).—Striated, linear, Suddenly attennated at each end into a short apiculus; front view broad, qua- drate, with striated lateral margins; striae strong, 14 in 001", nearly reaching M.J. iv. p. 8, the median line. Bréb DC. p. 16, pl. 1. f 20. = Pinnularia rostellata, GDC. p. 16, pl. 1. f. 20. Marine. Europe. Striae somewhat radiant. The frustules are much compressed, and very similar in the front view to those of N. retusa, 4f Valves subquadrate or elliptical, with conical terminal points, N. lacustris (Greg.). — Small, oblong or subquadrate, with acute or shortly rostrate apices; striae fine, distinct, slightly oblique, nearly reaching the median line, 28 or 30 in .001". M.J. iv. p. 6, pl. 1. f. 23. Scotland. The only species with which this could be con- founded is N. fºrma; but the latter is longer and larger, of a brown colour, with finer, less conspicuous, and parallel striae. N. humerosa (Bréb.).—Striated, sub- quadrate; ends truncate, with a minute, conic central point; striae fine, monili- form, 24 in "001", radiant, reaching nearly to the median line, shorter º, site the roundish umbilical space. SD. ii. p. 94 = N quadrata, Greg. TM. iv. p. 41, pl. 5. f. 5. Marine. Europe. Ac- cording to Dr. Donkin, the dry valve, under a low power, is hyaline and colourless. . N. granulata (Bréb.).--Striated, rather large, elliptic or subquadrate; ends with a conic central point; striae conspi- cuously moniliform, 16 in 001", radiant, reaching nearly to the median line. Donkin, TM. vi. pl. 3. f. 19. Marine. Europe. Distinguished from N. hume- 7'OS(t 5. its more distant and coarsely granulated striae. “Dry valve of a dull Bluish colour, inclining to purple * (Donkin). N. compacta (Grev.). — Small, sub- quadrate, with slightly concave sides, rounded shoulders, and the median line prolonged into comic points; striae faint, 42 in '001", reaching nearly to the me- dian line. Greg, M.J. v. p. 11, pl. 3. f. 8. Marine. Not uncommon. The striae are nearly parallel. A species well marked by its quadrate shape. º N. latissima º elliptic, with slightly produced mammiform apices; striae distinct, finely moniliform, radiant, nearly reaching the median line, shorter, and leaving an orbicular hyaline space round the central nodule. TM. iv. p. 40, pl. 5. f. 4. Marine. Britain. (VII, 70.) Distinguished from N. gra- nulata by its straw or light-brown colour in balsam, and less conspicuous granules. N. Barclayana (Greg.). — Elliptic- oblong, with minute, comic apices; striae about 38 in 001", finely moniliform, short, forming a narrow marginal band, and enclosing a large, lanceolate Smooth median space. GDC. p. 8, pl. 1. f. 9. Marine. Britain. The marginal striated band is of nearly uniform breadth, ex- cept near the base, where it becomes Ilal'l’OWe]'. N. marina (Ralfs).-Oval, with slightly produced conic apices, and 33 distinct, moniliform, radiant striae in 001", which reach the median line. = W. punctulata, SD. p. 52, pl. 16. f. 151, Marine. Eng- land. N. producta (Ralfs).-Oblong-elliptic, much constricted at each end, as if ob- tusely mucronate ; surface elegantly marked by decussating punctated lines; uncta in quincunx. = N. decussata, E.B. 843, p. 256. Habit of N. Amphisbaena, G. Valves lanceolate or rhomboid. N. rhomboides (E.). — Rhomboid-lan- ceolate, with subacute apices and 85, very faint, parallel striae in 001". EA. pl. 3, 1. f. 15; SBD. i. p. 46, pl. 16. f, 129, Mexico, Europe, Australia. N. rhombica (Greg.). — Rhomboid- lanceolate, with very fine but distinct striae, 45 in 001", reaching the median line. M.J. iii. p. 40, pl. 3. f. 16; TM. iv. p. 38, pl. 5. f. 1. Marine. Scotland. (VII. 71.) According to Professor Gre- gory, N. rhombica is distinguished from N. rhomboides by the different appear- ance of its median line and central nodule, as well as by its distinct striae. N. rhombea (E.).--Broadly rhomboid- lanceolate, with acute apices, and delicate longitudinal lines on each side; trans- verse striae wanting or indistinct, E.A. p. 131, pl. 3. 7. f. 27. Mexico. 1-480" to 1–360". N. Demerarde (E.). —Smooth, rhom- boid, tumid, strongly tapering into acute, subrostrate apices. EB. T845, p. 79. Demerara. 1-576". “Distinguished from N. rhombed only by its subrostrate ends" (Rabenhorst). N. decussata (E., K.). — Rhomboid- lanceolate, with subacute apices, an ob- solete umbilical space, and very fine, 904 SYSTEMATIC HISTORY OF THE INFUSORLA. decussating, punctated striae. KA, p. 70. = Pinnularia decussata, E.B. 1845, p. 364. Marine. India. - N. Indica (E.). — Rhomboid-lanceo- late, with somewhat obtuse apices, a small umbilicus, and thick-set, fine, lon- gitudinal, punctated lines (8 on each side). EB. 1845, p. 363. Marine. India. Somewhat resembles N. decussata. N. P asperula (E., K.).—Turgid, short, rhomboid-lanceolate, six-angled, rough with punctated striae; umbilicus subor- bicular; the longitudinal median space much dilated near the umbilicus. K p. 71.= Pinnularia? asperula, EB. 1845, p. 364, Marine. India. N. Libellus (Greg.). — Rhomboid-lan- ceolate, with obtuse ends; striae fine, uniform, about 60 in 001", reaching the median line; front view broadly linear, with the central portion longitudinally lined. GDC. p. 57, pl.6. f. 101. Scotland. In form it much resembles N. rhom- bica, but is more obtuse and broader, with uniform striae. Professor Walker- Arnott regards this species as escaped frustules of Schizomema Grevillii, an opi- nion, indeed, shared by Professor Gre- gory himself. . Subtilis (Greg.).-Elongated, trans- lucent, very slender, rhomboid-lanceo- late, with a minute, definite nodule; costae about 30 in 001", parallel, reach- ing the median line. = Pºnnularia subtilis, GīC. p. 16, pl.i.f. 19, Marine, Scot: land. N. lanceolata (Ag., K.). — Minute, narrow-lanceolate, with 44 indistinct, pº striae in 001". KB. p. 94, pl. 28. f. 38; SD. i. p. 46, pl. 31. f. 272. Europe, America. N. serians (K.). — Small, lanceolate, with fine longitudinal lines, and subacute apices; front view broadly linear, KB. p. 92, pl. 28. f. 43; SD. i. p. 47, pl. 16. f. 130. = N. lineolata, EM. Several figures. Europe, Asia, Australia, Africa, Ame- rica. 1-288". Frustules frequently co- hering. N. Subula (K.).—Elongated, slender, narrow-lanceolate, with tapering, Sub- acute apices, and fine longitudinal lines. RB. p. 91, pl. 30. f. 19. Marine. Europe. N. tenella (Bréb.). — Minute, Smooth, very narrow - lanceolate, with acute apices; front view linear, slightly con- stricted at themiddle. KA. p. 74, Europe. N. amphioacys (E.).—Elongated, nar- row-lanceolate, with acute apices; striae indistinct or wanting. EA. pl. 1. 2. f. 8; EM. many figures. Europe, Asia, Aus- tralia, Africa, America, Lough Mourne deposit, More slender than N. gracilis. Front view narrow-linear. N. Cari (E.).-Minute, smooth, lance- olate, slender, acute at both sides, with a circular median module, EI, p. 179; EMI. pl. 12. f. 20. Fossil, Cassel. 1-1150". N. oºcyphyllum (K.).-Pellucid, glassy, Smooth, slender-lanceolate, gradually tapering to the acute apices; median nodule obsolete, KB. p. 92, pl. 30. f. 17. Marine. Near Flinsburg. N. veloa (K.). — Minute, smooth, broadly or oblong lanceolate, with acute apices. KB. p. 91, pl. 3. f. 66. = N ob- longa, EA, pl. 3. 1, f. 14. Wangerooge, Mexico. - N. aponina (K.). — Minute, Smooth, slender-lanceolate, with acute, subros- trate ends. KB. p. 91, pl. 4. f. 1. Europe. Front view narrow-linear. N. Cesaţii (Rab.). — Minute, Smooth, slender-lanceolate ; front view linear, with rounded ends. Rab D. p. 39, pl. 6. f. 89. Piedmont. Very like N. aponina, but more slender in the lateral, and broader in the front view. N. digito-radiata (Greg.).--Small, ob- long-lanceolate, with obtuse ends; striae fine, distinct, about 25 in 001", reaching the median line, those near the central nodule more distinct and highly radiant. = Pinnularia digito-radiata, Mj. iv. p. 9, pl. 1, f. 32. Scotland. N. solaris (Greg). —Elongated, nar- row-lanceolate, with obtuse ends; striae fine, very distinct, 36 in 001", oblique, radiant, and shorter opposite the inde- finite central nodule. TM. iv. p. 43, § 5. f. 10. Marine. Scotland. Colour rown; striae so highly radiant round the central blank spot as to present the appearance of a Sun with rays. It is longer than N. radiosa, with finer and more inclined striae. N. Mediterranea (K.).-Minute, nar- row-lanceolate, with obtuse apices and 20 striae in 1-1200"; front view strictly linear, truncate. KB. p. 93, pl. 3. f. 17. Marine. Europe. 1-1200". - N. punctulata, EM. pl. 15A. f.34, B.f. 13, 14. Lough Mourne deposit, Sweden, Africa. Ehrenberg figures this species as rhomboid-lanceolate, with longitu- dinal, parallel, dotted lines. N. appendiculata (Ag., K.).-Minute, lanceolate, with slightly turgid middle and subrostrate obtuse ends. KB. p. 93, pl. 3. f. 28. = Frustulia and Cymbella ap- pendiculata, Ag. Europe. Front view linear, with truncate ends. In the lateral yiew the apices are somewhat produced, but scarcely rostrate. OF TEIE NAWICULEZE. 905 N. obtusa (E.). — Small, oblong-lan- ceolate, with obtuse, rounded apices. EA, p. 131. North America, Asia, Africa. Kützing thinks it probably identical with N. appendiculata. N. inflea'a (Greg.).--Small, lanceolate, with subacute apices; costae conspi- cuous, 26 in 001", highly radiant, nearly reaching the median line, except oppo- site the central nodule, where they are short, leaving a large, roundish blank º = Pºnnularia infleca, TM. iv. p. 48, pl. 5. f. 20. Scotland. Beneath each apex is a strong, dark cross-bar, pro- bably caused by a depression, Greg. N. fortis (Greg.) — Small, oblong- lanceolate or somewhat rhomboid, with obtuse apices; costae conspicuous, 16 in ‘001", not reaching the median line, gradually shorter and more radiant near the central module. = Pºnnularia fortis, TM. iv. p. 47, pl. 5. f. 19. Scotland. Turgid; costae prominent, so as to appear more distant than they actually are. N. mutica (K.).—Very minute, smooth, turgid-lanceolate, with distinct median and terminal nodules. KB. p. 93, pl. 3. f. 32. Wangerooge. 1-1560". N. Jurgensii (K.). — Minute, Smooth, turgid or oblong-lanceolate, with obtuse apices and obsolete median module; front view broadly linear, with truncate ends. KB. p. 93, pl. 3. f. 8. Island of Wan- gerooge, Germany. 1-720". N. viridula (K.). — Small, lanceolate, with obtuse, slightly produced apices; striae wanting or indistinct. KB. p. 91, pl. 4. f. 10, 15. Europe. N. carinata (E.). — Large, lanceolate; front view linear, with a broad dorsal longitudinal keel. EB. 1840, p. 18. Fossil. Shores of the Rhine, in volcanic schists. 1-216". N. diaphama (E.). — Large, Smooth, diaphanous, elongated, lanceolate, with obtuse apices; the umbilicus intercepting the double median line. EB. 1845, p. 78. Guiana, 1–192". Habit of Stau- yone's phoenicenteron. N. Schomburgkorum (E.). — Large, elongated, lanceolate, with obtuse apices, and the habit of N. diaphana, but with three longitudinal median lines. E.B. 1845, p. 79. Guiana, 1–180". N. latiuscula (K.). — Rather large, oblong or elliptic-lanceolate, with rather obtuse apices; striae shorter opposite the central nodule, 10 to 12 in 1-1200". KB. p. 93, pl. 5. f. 40. = N. patula, S.D. i. p. 49, pl. 16. f. 139, Europe, Ireland. Twice as long as broad; front view broadly linear, with truncate ends, N. Schomburgkii (E., K.). — Large, lanceolate, equal, three times as long as broad, with subacute apices, and 25 striae in 1-1152". KA. p. 71. = Pin- nularia Schomburgkii, E.B. 1845, p. 80. Guiana. Is Smaller and more obtuse than W. aqualis. . N. palpebralis (Bréb.). —Broadly lan- ceolate, with subacute apices, and 27 radiant striae in '001", which do not reach the median line. SD. i. p. 50, l. 31. f. 273. Marine. France, Britain. Striae short, leaving a lanceolate median blank space. N. angulosa (Greg.).-Broadly lanceo- late or oblong, with Subacute apices; striae conspicuous, short, forming a nar- row marginal band, shorter near the middle, and leaving a smooth, rhomboid median space. TM. iv. p. 42, pl. 5. f. 8. Marine. ºil. N. angulosa is larger than N. palpebralis, and the angular me- dian space is a good and permanent mark of distinction; nodule definite. N. radiosa (K.). — Small, slender- lanceolate, with subacute apices, and from 15 to 18 distinct, radiant striae in 1-1200". KB. p. 91, pl. 4 f. 23. = Pin- nularia radiosa, so i. p. 56, pl. 18. f. 173. Germany, Britain. ith stronger striae than N. gracilis. N. vulpina (K.).-Rather turgid, lan- ceolate, with acute apices; front view broadly linear, with truncate ends and punctate margins; striae obscure. KB. p. 92, pl. 3. f. 43. Germany. Inter- mediate between N. gracilis and N. cus- pidata. - N. cuspidata (K.). — Broadly lanceo- late, with acute apices, a very minute, orbicular central nodule, and close, very fine transverse striae. KB. p. 94, pl. 3. f. 24, 37; SD. i. p. 47, pl. 16. f. 131.=Na- vicula fulva, EM. many figures. Common. Europe, Asia, Africa, America, (XII, 5. Front view narrow-linear. 1-1150" to 1–180". The lateral view is broader and more rhomboid than in N. gracilis. N. Cantonensis (E.).-Broadly oblong- lanceolate, with acute, slightly produced apices; striae wanting or indistinct. EB. 1847, p. 484, Canton. 1-480". It differs from N. cuspidata in its shorter and acute apices. N. amphisphenia (E.). — Lanceolate, navicular, gradually attenuated into the apices, with an oblong median module; striae wanting or obscure. EA, p. 129; EM. pl. 9.1. f. 16. America, Asia, Africa, Europe. Distinguished from N. cuspi- data by its oblong module. N. phyllepta (k). — Minute, slender, 906 SYSTEMATIC HISTORY OF THE INFUSORIA. Smooth, narrow-lanceolate, with acute apices; front view strictly linear, with truncate ends. KB. p. 94, pl. 30. f. 56. Marine. Europe. - N. Meleagris (K.).--Somewhat turgid, lanceolate-acuminate, with an elegantly unctate margin. KB. p. 92, pl. 30. f. 37. Marine. Europe. Front view broadly linear. N. gracilis (E.). — Small, elongated, slender-lanceolate, with subacute ends; striae very fine, radiant, 22 in 001", reaching the median line. E. Infus. p. 176; iM. many figures. Europe, Asia, Africa, America, Lough Mourne deposit. 1–1500" to 1-560'. N. oxyptera (K.).—Elongated, slender, marrow-lanceolate, with acute apices, and fine, slightly radiant, transverse striae. ICSA. p. 69. = Pinnularia amphioacys, EMI. many figures; P. acuta, S.D. i. p. 56, pl. 18. f. 171. Europe, Asia, Australia, Africa, America. N. Kafwingensis (E.).--Small, striated, lanceolate, navicular; striae converging at the centre, 17 in 1200". EB. 1840, p. 20. = Pinnularia Kefwingensis, EMI. pl. 10, 2. f. 4, 5, Fossil. Bohemia, Asia. N. peregrina (E., K.).-Striated, nar- row-lanceolate, gradually tapering to the subacute apices; pinnules oblique, reach- ing the median line, 13 in 001". KB. p.97, pl. 28. f. 52. = Pinnularia peregrina, #. p. 133, several figures; Sl). i. p. 56, pl. 18. f. 170. Marine, Europe, Asia, Africa, America. N. leptostigma (E.). — Striated, lan- ceolate, with subacute, slightly produced apices; the transverse dotted striae in- conspicuous. EB. 1845. = Pºnnularia leptostigma, EM. pl. 33.12. f. 25. Fossil. United States. Twice as long as broad. I-432". N. Ehrenbergii (K.).—Lanceolate, with Somewhat acute apices, and fine, radi- ating striae. ICB. p. 92, pl. 3. f. 38. = Navicula lanceolata, E. Inf, pl. 13. f. 21. Europe. N. neglecta (K.).—Turgid, lanceolate, with subacute apices, margins longitu- dinally costate and transversely striated. KB. p. 92, pl. 28. f. 44. = Pinnularia lan- ceolata, EA, pl. 3. 1. f. 6. Europe, Ame- rica. Front view oblong, with incras- Sated middle and truncate ends. 1-1150" to 1-280"; striae 13 in 1-1200". N. Sempromia (Perty). — Minute, acutely lanceolate; striae not reaching the median line; front view linear, slightly narrowed towards the ends. Perty, Microsc. Org. p. 204, pl. 17. f. 8. iv. p. 42, pl. 5. f. 7. Alps. Belongs to the Smaller species, and is very like N. eacilis. & N. directa (S.). — Slender, narrow- lanceolate, acute; costæ fine, parallel, reaching the median line, 20 in 001". = Pºnnularia directa, SD. i. p. 56, pl. 18. f. 172. Marine. Sussex. º: view marrow-linear. N. pulchra (Greg.).-Broadly lanceo- late or somewhat rhomboid; striae radi- ant, strongly moniliform, nearly reaching the median line, shorter opposite the slightly dilated indefinite nodules. TM. Marine. Scotland. Rapidly tapering to the obtuse apices. N. longa (Greg.):-Much elongated, lanceolate or slightly rhomboid, acute; costae conspicuous, about 12 in 001", nearly reaching the median line, some- what shorter and radiant opposite the central nodule. = Pºnnularia longa, Greg. TM. iv. p. 47, pl. 5. f. 18. Scotland. The only known form to which it has any resemblance is N. directa, but the latter form is not rhombic, and the striae are much more numerous and parallel. N. acutivscula (Greg.). – Elongated, slender, linear-lanceolate, acute; costae distinct, about 30 in 001", reaching the median line, central ones radiant and more conspicuous. = Pºnnularia actitius- cula, TM. iv. p. 48, pl. 5. f. 21. Scotland. N. costata (K.). — Oblong-lanceolate, with obtuse apices, and longitudinal punctated lines; median module large, terminal ones minute. KB. p. 93, pl. 3. f, 56. Fossil. Santa, Fiore. Front view oblong, with broadly rounded apices. N. Norvegica (E., K.).—Broadly ob- long, with acute apices, a narrow striated border, and a Smooth median space; striae 30 in 1-1200". KA. p. 79. = Pinnularia Norvegica, E. Marine. Europe. Front view narrow-linear, truncate. 1-360". N. : Libyca (E.). — Small, striated, acutely oblong-lanceolate, with 14 striae in 1-1200"; front view quadrangular, with truncate ends. EB. T840, p. 20. Sinai. 1-550". It has the habit of N. fulva, but is wider, and not rostrate. N. Pºpula (K.). — Minute, smooth, oblong-lanceolate, with slight produced apices. , RB. p. 93, pl. 30. f. 40. Europe. N. alpina (S.). – Large, oblong-lan- ceolate, with obtuse ends, and 7 to 9 stout, distant, radiant costae in 001", which do not reach the median line. = Pºnnularia alpina, S.D. i. p. 55, pl. 18. f. 168. France, Scotland. Front view broadly linear, with truncate ends; costae shorter near the central module. OF THE NAWICULEAE. 907 N. distans (S.). — Lanceolate, with Subacute apices; costae radiant, distant, 10 in 001", not reaching the median line. = Pinnularia distans, S.D. i. p. 56, pl. 18. f. 169. Marine. Common, espe- cially from deep dredgings. Costae shorter opposite the central module. N. elegans (S.). —Broadly or elliptic lanceolate, with slightly acuminated ends; striae distinct, 24 in 001", waved, radiate, nearly reaching the median line, shorter opposite the central nodule. SD. i. p. 49, pl. 16, f. 137. Marine. iºni N. permagna (Bai.). — Large, turgid- lanceolate, with obtuse apices, a mar- ginal band of punctated striae, and a broad, lanceolate, longitudinal median blank space; nodule indefinite. = Pimmu- laria permagna, BMO. p. 40, pl. 2. f. 28 & 38. United States. H. Valves linear or oblong, neither rostrate nor constricted: t Ends scarcely cuneate. N. Bacillum (E.).-Linear, with trun- cate, rounded ends; striae indistinct, 54 in .001". EMI. Several figures. = W. bacil- laris, Greg. M.J. iv. pl. 1... f. 24. Ehren- berg gives about 50 habitats in Europe, Asia, Australia, Africa, and America. N. borealis (E., K.).--Small, striated, linear, with slightly attenuated, rounded apices; striae stout, rather distant, not reaching the median line, 13 in 001". KB. p. 96, pl. 28. f. 68–72. = Pºnnularia borealis, EM. numerous figures; Pinnu- laria latestriata, Greg. M.J. ii. pl. 4, f. 13. (VII. 74.) A very common and widely diſused species. Ehrenberg gives about 200 habitats for it, 3 longer and more dilated at the middle, = Pºnnularia Caraccana, E. Under moss on trees. The front view of this species is linear, with truncated ends and striated mar- gins, and resembles that of detached frustules of Denticula and Odontidium, N. Chilensis (E., K.).-Large, linear, with broadly rounded apices, and 11 or 12 stout costae in 1-1200". KA, p. 79. = Pinnularia Chilensis, EM. pl. 34, 11. f. 3. Australia, Asia, Africa, America. (XII. 33.) Costae parallel, equal. Approaches to N. viridis, but is shorter and broader, N. rectangulata (Greg.).-Linear, with truncate rounded ends; costae rather di- stant, 22 in 001", nearly reaching the median line, except opposite the dilated indefinite module, and there shorter and diverging, GDC, p. 7, pl. 1, f. 7. Marine. Scotland, N. Iridis (E.). — Large, elongated, linear-oblong, tapering into the obtuse apices, finely striated both longitudinally and transversely, iridescent, EA, p. 130, pl. 4, 1. f. 2. New York. N. oblonga (K.).-Elongated, slender, oblong or linear-oblong, with rounded apices; costae stout, connivent at the centre, KB. p. 97, pl. 4. f. 21. = Pinnu- laria polyptera, EA, p. 133; P. macilenta, E. Common. We follow Kützing and Smith in referring P. macilenta, E., to this species; Ehrenberg's figures, how- ever, differ from theirs in ‘being IſlCl’é linear, with less tapering apices. 1-140". N. Oregonica (E., K.). — Elongated, bacillar, uniformly and gradually de- creasing towards the rounded apices; pinnules stout, 23 in 1-1152". K.A. p. 71. = Pinnularia Oregonica, EB. 1845, p. 79. Fossil, Oregon. , 1-228". It ºne to N. Digitus, but is more slender. N. truncata (K.). — Minute, smooth, linear, with truncato-rounded ends, and an inner marginal border twice con- stricted; front view broadly linear, truncate. KB. p. 96, pl. 3. f. 34. Eu- I’Ol)62. * Liber (S.).-Linear-oblong, with rounded apices, and 48 delicate striae in 001"; colour of dry valve purplish. SD. i. p. 48, pl. 16. f. 133. Marine. Sussex. º ; N. Stylus (E.). — Elongated, narrow- linear, with rounded ends, and having longitudinal dotted lines on each side. EM. pl. 15 A. f. 36. Asia; Lough Mourne deposit. N. Ergadensis (Greg.).-Rather small, marrowly linear-oblong, with rounded ends; costae distinct, 25 in 001", nearly reaching the median line, shorter and radiant opposite the roundish, Smooth umbilical space. = Pinnularia Ergadensis, TM. iv. p. 48, pl. 5. f. 22. Scotland. N. Styliformis = Pinnularia styliformis, EM. pl. 38A, 17. f. 6. Australia, Africa, America. Ehrenberg's figure represents a portion of an elongated, narrow, strictly linear valve, with rhomboid ends, and fine, parallel striae which reach the median 1Il62. N. Dactylus (E., K.).-Large, elon- | gated, linear-oblong, passing by a very gentle curve into the slightly narrower, broadly rounded apices; pinnules 14 in 1–1200". KB, p. 98, pl. 28. f. 59.3– Pinnularia Dactylus, E.A. p. 132, pl. 4, 1. f. 8. Europe, Asia, Africa, America, | Lough Mourne deposit. N. viridis (Nitzsch, K.).-Elongated, 908. SYSTEMATIC. EIISTORY OF THE INFUSORIA. slender, linear-oblong or linear lanceo- late, with obtuse apices; 12 to 14 radiant costae in 1-1200", shorter opposite the central nodule. ... KB. p. 97, pl. 4 f. 18. = Pinnularia viridis, E., in part?; Navicula viridula, E. (IX. 133–136.) Common. 1–3000" to I-280". N. hemiptera (K.).-Narrow, linear- oblong, with obtuse, comic apices, and 14 or 15 radiant costae in 1-1200", which do not reach the median line. RB. .97, pl. 30. f. 11. = Pinnularia hemiptera, D. ii. p. 95. America, Europe. Front view linear, with rounded angles. Often overlooked from its resemblance to N. viridis, from which it is distinguished by its finer striae and narrower valve. N. aquinoctialis (Mont.). — Rather large, linear-oblong, with rounded apices, and 4 stout, radiant pinnules in 1–2600". IMontague, Annales des Sciences Nat. 1850, p. 309. Guiana. 1-260" to 1-150". In form it resembles N. Dactylus, but differs in its size and much larger striae. In the latter respect it approaches to N. pachyptera, but has not the median infla- tion of that species. N. pleurophora (K.).-Large, stout, oblong, or linear-oblong, with broadly rounded ends, and 6 stout costae in 1-1200". KA. p. 79. = Pinnularia costata, EM. pl. 4.2.f. 5; Pinnularia megaloptera, EM. pl. 3, 1.f. 4. America, Asia. N. Suecica (E.).-Oblong-elliptic, with broadly rounded ends, short, stout, rather distant marginal costae, and large central blank space. EInf. p. 189, t. 21, f. 18. = Pinnularia Suecica, EMI. Fossil. Sweden. N. lata (Bréb.).— Large, linear-ob- long, with rounded apices, and 8 stout costae in 001", which do not reach the median line, and are shorter and some- what commivent opposite the central nodule. KA. p. 79. = Pºnnularia lata, SD. i. p. 55, pl. 18. f. 167. France, Bri- tain. Front view very broad linear, with rounded angles, truncate ends, and striated margins; the central modules large. This species approaches closely in character to N. Suecica. N. Digitus=l’innularia Digitus, EMI. pl. 33.8. f. 15; rica, Java. This species is figured as large, linear-oblong, with broadly rounded ends, and stout, parallel costæ which do not reach the median line. N. Dua - Pinnularia Dua, EM. pl. 8, 2. f. 5. Fossil. Hungary. Ehrenberg repre- sents it as large, elliptic-oblong, with rounded ends and divergent costae, which do not reach the median line, and are shorter opposite the central nodule, l. 38A, 3 B. f. 1. Ame- N. ostrearia (K.), — Small, elliptic- oblong, with rounded ends, large central module, and close, fine striae. KA, p. 77. Marine. France. N. retusa (Bréb.).—Striated, narrow- linear, with rounded ends; front view. broad, quadrate, with rounded angles, truncate ends, and concave and striated lateral margins, Bréb DC, p. 16, pl. 1. f. 6. Marine. Europe. The frustules are much compressed; and consequently the front view is so much broader than the lateral surfaces, that it is difficult to obtain a good sight of the latter. N. retusa, N. apiculata, and a few allied spe- cies probably ought, as suggested by M. de Brébisson, to form a Separate group, if not a distinct genus, distinguished by the great comparative breadth of its front view, with its striated and simu- ated or constricted lateral margins. N. scita (S.).-Nitescent, linear-ob- long, with attenuated, obtuse ends; striae very faint, 45 in .001"; module small. ANH, 1857, xix. p. 8, pl. 2.f4. Pyrenees. N. parvula (Greg.).--Small, narrow linear-lanceolate, with obtuse ends and distinct costae, which do not reach the median line. = Pºnnularia parva, M.J. ii. p. 98, pl. 4. f. 11. Mull. 2+ Valves linear or oblong, with cuneate ends. N. amphigomphus (E.). — Large, broadly linear, with sharply cuneate ends, with or without obscure longitudinal limes; striae obsolete or distinct. EA. p. 129, pl. 3. l. f. 8; EM. many figures. America, Asia, Europe. Lough Mourne deposit. 8, striae distinct. = Pinnularia amphigomphus, E.M. pl. 14, f. 11. Cayenne, France. N. dilatata (E.).--Large, oblong or broadly linear, with obtuse, cuneate ends, and furnished with longitudinal lines near the margins. EM. many figures. Europe, Lough Mourne. N. disphemia (E., K.). —Linear, elon- gated, with sharply cuneate 'ends, finely striated near the margins. KB. p. 93, pl. 28. f. 54. = Pºnnularia disphenia, EA. p. 132. America, Australia. Approaches to N. amphigomphus. N. acuta (K.).-Narrow-linear, smooth, with acute, shortly cuneate apices. KB. p.93, pl. 3. f. 49, Island of Wangerooge, Australia. - N. subacuta = Pinnularia Subacuta, EMI. } 35 A. 6. f. 12. Perth, Australia. Ehrenberg's figure represents this species as linear, with cuneate apices, fine, close, OF TEII. NAWICULEAE, 909 arallel striae, which reach the median ine, and a small central nodule. N. acuminata (S.). — Linear, with acutely cuneate ends and parallel costae, which do not reach the median line. = Pinnularia acuminata, S.D. i. p. 55, pl. 18. f. 164, Premnay peat. N. minor (Greg.). — Minute; lateral view linear, with acutely cuneate ends; striae fine, nearly parallel, not reaching the median line, 36 to 40 in 001". GDC. p. 5, pl. 1. f. 1. Scotland. N. crassa (Greg.).-Linear- or elliptic- oblong, with obtusely cuneate ends; striae fine, but distinct, moniliform, radi- ant, nearly reaching the median line, but leaving an orbicular blank Space round the central module. M.J. iii. p. 41, pl. 4. f. 18. Scotland. Is of a brown colour in balsam. N. Utriculus (E., K.). — Striated, linear-oblong; ends attenuated, with a slight marginal curvature,into the obtuse apices. Rºß. p. 93. = Pinnularia Utri- culus, E.A. p. 134, Mexico. Akin to N. disphenia. N. trigonocephala (E.). - Striated, linear, with the ends dilated into large cuneate heads. = Pinnularia trigonoce- phala, EM, pl. 34.8. f. 11., Japan. Very unlike any other species in having the cuneate heads much dilated and broader than the intermediate portion. N. microstoma (K.),—Large, turgid, elongated oblong, with obtusely cuneate ends, longitudinal lines, and a very mi- nute oblong median nodule; striae nume- rous, obscure. KA, p. 71. = N lata, KB. p. 92, * 3. f. 51; N. firma, S.D. p. 48, 1.16. f. 138. Europe. Front view broadly inear, with truncate ends, rounded an- gles, and broad lateral borders, turgid at the middle, Perhaps Professor Smith was right in uniting this to N. firma, N. firma (K.),—Large, turgid, oblong- lanceolate, with obtuse, cuneate ends, º - e oval elliptic; front view broadly linear. thick borders, and large median nodule; striae wanting or obscure. KB. p. 92, pl. 21. f. 10. Fossil. Santa Fiore. N. maacima º: striated, linear, with longitudinal lines, and ob- tuse, cuneate or conic ends; striae fine, parallel, nearly reaching the median line, shorter opposite the central, nodule, about 52 in 001". GDC. p. 15, pl. 1. f. 18. Marine. Britain. (VII. 75.) Generally elongated; nodule definite, surrounded by a smooth space. Front view linear, narrowest at the middle, with striated margins. Differs from N. firma in its paler colour, finer striae, and more obtuse apices, Greg, attenuated towards the ends. p. 6, pl. 1, f. 2. Scotland. N. formosa (Greg.).-Large, striated, linear or linear-oblong, with longitudinal lines, obtuse, cuneate or conic ends; striae distinct, slightly inclined, not reaching the median line, shorter oppo- site the large central nodule, about 35 in 001". TM. iv. p. 42, pl. 5. f. 6. Marine. Scotland. Agrees in form with N. maxima, but is distinguished by its more conspicuous and slightly inclined striae which do not reach the median º leaving a longitudinal median blank 8.D.Ci. N. Kerguelensis (R.). — Oblong, with obtusely cuneate ends ; costae stout, radiant; nodule indefinite. = Pºnnularia Rerguelensis, EM. pl. 35A, 2. f. 15. Africa. I. Valves elliptic, with rounded ends. N. cocconeoides (Rab.). — Small, ellip- tic, with broadly rounded ends, and 11 to 13 parallel and distinct, but faint striae in 1-1200", which reach the median line. = Pºnnularia cocconeoides, Rab D. p. 43, pl. 6. f. 18. Stockholm. N. scutelloides (S.). — Small, subor- bicular, with 18 moniliform, radiant striae in 001", nearly reaching the median line. SD. ii. p. 91; Greg. M.J. iv. pl. 1. f. 15. Britain. N. pectinalis (Bréb.).-Linear-elliptic, with rounded ends, and 22 striae in '001". SD. ii. p. 92. Marine. France, Britain. Front view with truncate ends. N. Algeriensis (Mont.).-Elliptic-ob- long, with 10 striae on each margin. M. Fl. d’Algér, p. 190. Marine. Algiers. N. Cluthensis (Greg.).-Elliptic, with broadly rounded ends; striae conspicu- ous, moniliform, reaching the median line, about 20 in 001"; median line broadest at the central nodule, slightly DC, (VII, 73.) N. ovalis (Nāg.). — Finely striated, 1-720" to 1-600". KA, p. 890, Switzer- land. N. oblongella (Nāg.). — Smooth, ob- long-oval; front view broadly linear. 1-720" to 1-430", KA, p. 890. Switzer- land. N. fossilis, EM. pl. 10.1, f. 6: Bohemia. Ehrenberg's figure shows this species elliptic, slightly rhomboid, with rounded ends; the median suture of three lines, interrupted by the indefinite central nodule. N. nana (Greg, M.S.).-Minute, oval, obtuse; costae radiant, nearly reaching the median line; umbilical Space not 910 SYSTEMATIC IIISTORY OF THE INFUSORIA. dilated. = Pinnularia pygmaea, EMI. pl. 10. I. f. 9; M.J. iv. pl. 1, f. 8. Europe. . N. lepida (Greg.).--Minute, hyaline, oval, or oblong, with obtuse ends; striae indistinct from their transparency, slightly radiant. M.J. iv. p. 7, pl. 1. f. 25. Scotland. N. oceanica. — Elliptic-oblong, twice as long as broad, with subacute apices, small, round, clearly-defined umbilicus, and double median line; margin deli- cately but widely striated; pinnules 20 in 1-1200". Southern Ocean. 1-570". R. Median line flexuose. N. tumida (Bréb.). — Large, tumid, striated, twisted, oblong, with obtuse apices, a flexuose median line, and close, fine striae, which reach the median line. KA. p. 77. = N. Jenneri, S.D. i. p. 49, pl. 16. f. 134. Marine. France, Britain. (vſ. 55.) Front view broad linear ob- long, with rounded angles; frustules twisted, so that the hyaline central por- tion appears flexuose. N. conveza (S.).-Large, tumid, stri- ated, twisted, linear oblong, with conic apices, a flexuose median line, and 21 striae in 001", which do not quite reach the median line, SD. i. p. 49, pl. 18. f. 136. Marine. England. Front view broadly linear-oblong, with rounded angles, and a narrow, flexuose, longi- tudinal median band. - N. Westii (S.).-Broadly lanceolate, with subacute apices, and 38 delicate striae in .001", which nearly reach the slightly flexuose median line, SD. i. p. 49, pl. 16. f. 135. Marine. England. Colour of dry valve dark purple; front view linear, with rounded angles, and a narrow, slightly flexuose median band. N. P. campylogramma (E.). — Small, ovate, obtuse, smooth, with a flexuose, sigmoid median line, and orbicular cen- tral nodule. EB. 1853, p. 36. Bavaria, Rhine. Probably identical with Achnan- thidium flewellum, since Ehrenberg states | that he has seen it, together with Ach- manthes P Bavarica, distributed under the name of Cymbella flewella. N. tortuosa (E.).--Smooth, crystallime, rather turgid, and somewhat tortuous, so that one end has a more obtuse apex. EB. 1843, p. 271. 1-288". N. dissimilis (S.).-Frustules oblique ; elliptic; median line somewhat diagonal from the obliquity of the frustule, re- curved at extremities; striae obscure. ANH, 1857, xix. p.8, pl. 2. f. 6. Pyrenees. L. Frustules lunately curved in the front view. N. genuflewa (K.).--Parasitic, smooth, narrow-lanceolate, obtuse; front view linear, with truncate ends, lunately curved. KB. p. 101, pl. 2.l. f. 6. Marine. Peru. - M. Frustules lunately curved in the lateral view. N. Neapolitana (Rab.). — Lunately curved, linear, with truncate ends, and transverse striae. = Falcatella Neapoli- tana, Rab D. p. 46, pl. 5. f. 3. Italy. N. lunata (K.).—Smooth, Small, lu- nately curved, narrow-linear, with slightly rounded ends; front view linear, truncate. KB. p. 101, pl. 4. f 1.4. = Falcatella lunata, Rab D. p. 46. Italy. - N. Romana (Rab.).—Smooth, attached by a gelatinous base; lunately curved, linear, with truncate ends; front view linear lanceolate, truncate. = Falcatella Romana, Rab D. p. 46, pl. 5. f. 1. Italy. Doubtful or insufficiently described Species. N. varians (Greg.).-Form and size variable; striae oblique, 14 to 18 in .001", nearly reaching the median line, more conspicuous opposite the central module, and highly radiant. TM. iii. } 12, pl. 2. Britain. In this species rofessor Gregory disregarded form and size, considering the number and dispo- sition of the striae as the essential cha- racters. N. mutabilis (Greg.).-Form and size variable; striae as in N. varians, but finer, and from 24 to 26 in 001". TM. iii. p. 14. = Pinnularia eacigua, M.J. ii. pl. 4. f. 14, Britain. We concur in opinion with the late Professor Smith, that these species are too vaguely de- fined, and that probably they are con- stituted of forms belonging to various other species. . - N. minutissima (Rab.).-Exceedingly minute, but with distinct median module. Rab D. p. 39, pl. 6. f. 80. Persia. N. megalodon = Pºnnularia megalodon, EM. pl. 33, 14. f. 21. America. The central portion of a large, oblong species, with stout, distant, parallel costae, which do not reach the median line. N. Omphalia (E.).-Large, iridescent, with very fine, granulated, decussating lines; umbilicus orbicular, solid, hyaline, divided by the straight median line. Fossil, Fragments in Bermuda deposit, OF TEIT, NAWICULEAE. 911 N. Rhaphoneis = Pinnularia Rhapho- neis, EM. pl. 35 A. 9. f. 7. Ganges. Minute, oblong, with subacute apices, a Small central nodule, and diverging striae, N. eurysoma (E.).-Minute, smooth, elliptic, with rounded ends, and marked by two narrow, longitudinal blank lines, which converge at each end and are connected at the centre by the transverse nodule. EB. 1838. = Stauroneis eury- soma, EM. pl. 21. f. 36. Fossil, Algiers. Apparently more allied to the lyrate group of Navicula than to Stauroneis. Species from Ehrenberg, known to us only by name, men, N. amphilepta, N. obliqua, W. turgida, N. Senegalensis, N. Falklandide, N. Catha- ºrinae, N. conspersa, W. Savanna, N. aula- cophaena, N. Barbadensis, N. Euryale, N. leptoceros, N. Sphaeroptera, N. Vibrio, N. leptotermia. Pinnularia affinis, Ehrenberg gives 30 habitats. It may be a form of Navicula affinis, with more evident striae. P. ambigua, P. australis, P. insularis, P. pleuronectes, P. Preissà, P. Fusus, P. Phenana, P. Craticula, P. pterophaena, P. platysoma, P. Catharinae, P. anomala, P. Hemprichii, P. Licudrae, P. Capensis, P. Caffra, P. antarctica, P. Folium, P. microSphenia, P. pleuronectes, P. Araw- N. ceratostigma, N. Jordanº, N. Legw- I cania, P. Barbadensis. Genus STAURONETS (Ehr., Kütz.).-Frustules simple, free in front view parallelogramic ; valves with median line and nodules, central nodule trans- versely dilated. Stauroneis differs from Navicula in having the central nodule prolonged into a transverse pellucid band (stauros) free from striae. “In a few cases we meet with the semblance of a stauros in the genus Pinnularia [Navicula]; but in these instances a closer examination will show that this appearance arises from the interruption of the costae merely, and not from the dilatation of the central nodule, which is still found unchanged” (Smith). Ehrenberg divides this genus into Stauroneis and Stauroptera—the former having smooth, and the latter striated frustules; but we agree with Professor Kützing in thinking the distinction, as in Navicula and Pinnularia, unsatisfactory, and that many species would be referred by the observer to the one or other genus according to the magnifying power of the microscope used in the examination. * Valves constricted at the centre. STAURONEIS constricta (E.).--Small, oblong, deeply constricted at the centre, and slightly contracted into obtuse apices. ICA. p. 134, pl. 1. 2. f. 12 b, Chili, Australia, Africa. S. Rabenhorstii.-Linear, with broadly rounded ends and concave sides; costae stout, oblique; stauros linear. = Stattro- ptera constricta, Rab D. p. 50, pl. 9. f. 10. Italy. - - . 2# Valves with 2 or 3 undulations. S. inflata (K.).--Small, linear, with two constrictions, and three dilatations; ends broadly rounded; stauros linear, reaching the margin. KB. p. 105, pl. 30. f. 22. Trinidad. 1-480" to 1-428". S. Fulmen (Bréb.).—Lanceolate, acute, with two undulations; stauros very slightly dilated towards the margin; striae distinct, 22 in 001"; front view rectangular. 008" to 0.15". TM, yii. ). 180, pl. 9. f. 6. Fresh water. Mel- toº. This beautiful species resembles S. acuta, but is easily distinguished by its marginal undulations. S. Legumen (E.). — Small, oblong- lanceolate, each margin with three un- dulations; apices apiculated; stauros linear, reaching the margin. EB. 1844, \ 135; EMI. pl. 39. 3. f. 104; Greg. IJ. iv. pl. 1, f. 9. = Stauroneis linearis, SD. i. p. 60, pl. 19. f. 193. America, Europe, (VII. 67.) 3* Valves with a sigmoid median line. S. Sigma (E.). — Stout, lanceolate, sigmoid, with obtuse apices; stauros abbreviated. EB. 1844, p. 88; EM. 1. 18. f. 63, Fossil. Richmond deposit. t has the form and size of Pleurosigma acuminatum; but its median nodule is dilated, as if geminate. 1-240". Ehr. S. obliqua (Greg.). —Small, short, ob- long, or broadly lanceolate, with a sigmoid or oblique median line; stauros reaching the margin; striae fine, 45 in 001". Mj. iv. p. 10, pl. l. f.35. Lochleven. (VII.63.) 4* Valves with rostrate or capitate apices. S. dilatata (E.).--Small, ventricose, with minute, mammiform beaks; stauros 912 SYSTEMATIC ETISTORY OF TEEE INFUSORIA. linear, nearly reaching the margin, EA, p. 1. 2. f. 12a; Sl). i. p. 60, pl. 19. . 191. America, Australia. (XII, 16.) S. eacilis º —Very minute, ventri- cose, shortly rostrate; stauros linear. RB. p. 105, pl. 30. f. 21. Trinidad, 1-2400". - S. punctata (K.). —Small, ventricose, with rostrate apices, and 27 radiant punctate striae in 001"; stauros linear, abbreviated. KB. p. 106, pl. 21. f. 9; S.D. i. p. 61, pl. 19, f. 189, Britain. Fossil, §º. IOTe, S. anceps (E.). — Small, lanceolate, constricted beneath the Subcapitate apices; stauros linear, not reaching the margin; striae very delicate, 45 in 001". EA. p. 134, pl. 2. l. f. 18; SD. i. p. 60, pl. 19. f. 190, Europe, Asia, Africa, America. - S. Crucicula (S.). — Small, elliptic- lanceolate, somewhat ventricose, pro- duced at the ends into minute, comical beaks; stauros very narrow, linear, reaching the margin. SI). i. p. 60, pl. 19. f. 192. Marine. Ireland. (VII. 64.) S. ventricosa (K.). — Very minute, ventricose, constricted beneath the capi- tate apices; stauros linear, not reaching the margin, KB. p. 105, pl. 30. f. 27. Germany, France, Britain. S. capitata (E.).-Very small, oblong, twice as long as broad, Suddenly con- stricted beneath the capitate apices; striae 18 in 1–1560". EB. 1844, Southern Ocean. Front view linear. 1-1152". S. phyllodes (E.).--Turgid-lanceolate, with the apices produced into short, subacute beaks; stauros linear, reaching the margin. EA, p. 135, pl. 1. 2. f. 10. America, China. (XII. 7–9. S. Semen, EM. ple, 35A, and 38 A. many figures. Ehrenberg gives about 80 habitats in Asia, Africa, and Ame- rica. Lateral view Small, ventricose, with mammiform apices and linear stauroS. S. Tuscula (E.). — Small, striated, elliptic-oblong; apices suddenly con- tracted, umbonate ; stauros linear, reach- ing the margin; striae oblique. = Navicula Tuscula, EB. 1840, #. KA. p. 77; Stauroptera Tuscula, EM. pl. 6, 1, f. 13. Fossil. Santa Fiore, Siberia. Front view linear. - S. mesopachya, EMI. pl. 15 A. f. 26. Lough Mourne deposit. Large, oblong- lanceolate, Suddenly contracted into mam- miform, obtuse apices; stauros linear. S. birostris (E.). — Small, narrow- lanceolate, with produced, rostrate, sub- acute apices; stauros linear, EA, p. 134, linear, sudde rounded, mammiform beaks. p. 205, t. 17. f. 11. pl. 2. 2. f. 1. America, Africa. - S. Platalea (E.).—Lateral view slender lanceolate, constricted beneath the capi- tate apices; stauros linear. EM. pl. 15A. f. 30. Lough Mourne deposit; México. S. Siebold; (E). – Large, turgid- lanceolate, tapering into obtuse beaks; stauros linea. FM. pl. 34, 8, f. 12. Japan; S. Ehrenbergii (E.). — Small, inflated, Oval, with produced, mammiform apices; stauros linear; striae parallel. = Stau- ºroptera platystoma, EM. pl. 14. f. 13. Perlin. S. platystoma (E., K.).-Linear-ob- long, contracted at the ends into mammi- form beaks; stauros linear. KB. p. 105, pl. 3. f. 58; EM. pl. 3. 1. f. 8. = Navicula platystoma, E Inf, pl. 13. f. 8. Germany, America, Asia. (IX. 142.) 1-1100" to 1-240". r S. amphicephala (K.).—Linear-oblong, with produced, rostrate, capitate apices; stauros linear. K.B. p. 105, pl. 30. f. 25. Germany, France. S. linearis (E.). — Minute, linear-ob- long, with parallel marginal lines, at- tenuated at the apices into somewhat obtuse beaks; stauros linear, EA, p. 135, § 1. 2. f. 11. America, Europe. Lough Mourne deposit. S. macrocephala (K.).-Linear, slen- der, constricted beneath the capitate apices; transverse striae very dense. A. p. 92. = Stauroptera macrocephala, Rab D. p. 49. France. 1-425". S. platycephala – Stauroptera platyce- phala, EM. pl. 17. 2. f. 9. Fossil. Fin- land. Linear, suddenly constricted be- neath the dilated, broadly rounded ends; stauros linear, reaching the margin; striae parallel. S. eaccellensS. broadly y contracted into broadly Perty, Inf. Alps. Form and size of S. platystoma, but striated. Its nearest ally is S. microstauron, E.; but it is larger and somewhat broader, with less broadly rounded ends. S. microstauron (E., K.). — Striated, linear, Suddenly constricted beneath the broadly rounded, subcapitate apices; stauros linear. K.B. p. 106, pl. 29. f. 13. = Stauroptera microstauron, #A. bl. 1. 4. f. 1. Asia, Africa, America. S. monogramma (E.).-Oblong, turgid at the middle, and contracted at each end into a broad, rounded, conical beak. EA, p. 135; KB. p. 105, pl. 29. f. 18. Surinam, Tesembles Achnanthes ven- tricosa, OF THE NAWICULE_E. 913 1-480". S. granulata (E.). — Bacillar, with turgid middle and obtuse ends; trans- verse striae granulated. = Stauroptera granulata, EB. 1847, p. 484, Canton, Allied to Fragilaria P mesotyla, and to Ach?anthes ventricosa. 5% Valves neither constricted, rostrate, nor furnished with a sigmoid median line. f Valves lanceolate. S. Phoenicenteron (Nitzsch, E.). — Large, broadly lanceolate or somewhat rhomboid, gradually attenuated into rather obtuse apices; stauros slightly dilated outwards, reaching the margin; striae fine. EA. pl. 2. 5. f. 1; SD. i. p. 59, pl. 19. f. 185. = Bacillaria, Phoeni- centeron, Nitzsch ; Cymbella Phoenicen- teron, A.D. p. 10; Navicula Phoenicem- teron, E Inf. Common. Europe, Asia, Africa, America. (IX. 139; XII. 17, 18.) 1-400" to 1-140". S. pteroidea (E.).--Large, broadly or sharply lanceolate, with obtuse apices, and very fine, punctated, transverse striae; stauros linear, reaching the mar- gin. EA. p. 135; EM. pl. 3. 3., f. 7. America. Akin to S. Bailey; ; larger than S. Phoenicenteron, E. - S. Baileyi (E.).-Large, broadly lan- ceolate, tapering gradually to the obtuse apices; surface with very fine longi- tudinal, undulated limes; stauros linear, reaching the margin. EA, p. 134; EMI. several figures. America. Akin to S. Phoenicenteron and S. pteroidea, E. S. amphilepta (E.).--Lanceolate, little acuminated, with obtuse apices; stauros linear; striae mone, or indistinct. EA, l. 1. 2. f. 9–13. America, Africa, §bia. It is scarcely distinct from S. JPhoenºcenteron. - S. gracilis (E.). — Slender-lanceolate, gradually attenuated into obtuse apices; stauros linear, scarcely reaching the margin; striae indistinct, very delicate. EA. pl. 1. 2. f. 14; SD. i. p. 59, pl. 19. f. 186. America, Europe, Asia, Africa, Smaller and more slender than the pre- ceding species. S. apiculata (Grev.).-Oval, obtusely apiculate; stauros linear, abbreviated; striae fine, 34 in 001". IEdin. New Phil. Journ., n.s., x. pl. 4. f. 8. Californian guano. Inflated, suddenly contracted at the ends into comic beaks; stauros not reaching more than half way from the median line to the margin. S. lanceolata (K.). — Slender-lanceo- late, tapering into the narrow, subrostrate ends; stauros linear, reaching the mar- gin ; striae obsolete or indistinct. KB. p. 104, pl. 30. f. 24, Falaise. 1-180" to 1-160". - S. Atlantica (E.).--Small, lanceolate, with obtuse apices; front view linear. EB. 1845, p. 155. In pumice from the Isle of Ascension. Akin to S. amphilepta, but more obtuse. 1-1152". S. salina (Sm.).--Small, slightly con- tracted at the obtuse apices; stauros linear, nearly reaching the margin; striae faint, 45 in .001". SD. i. p. 60, pl. 19. f. 188. Marine. Britain. S. minuta (K.).—Smooth, lanceolate, rather obtuse, three times as long as broad. KA. p. 89. Thuringia. 1-1200". S. dubia (Greg.). — Minute, smooth, narrow-lanceolate, with somewhat trun- cate apices; stauros linear, nearly reach- ing the margin. M.J. iv. p. 11, pl. 1. f. 37. Scotland. When examined under a high power, the valve exhibits two parallel lines within the margin on each side. S. staurophoena (E.). — Lanceolate, Smooth, slightly contracted at the sub- acute apices; stauros linear, not reaching the margin. EA. p. 135; EMI. pl. 2. 3. f. 11. North America. Distinguished from S. Phoenicenteron by its abbreviated stauros. S. Gregorii (Ralfs).-Rhomboid-lan- ceolate, with acute apices; stauros linear, reaching the margin; striae fine, nearly parallel, 60 in 001". = Stauroneis am- phioxys, Greg, TM. iv. p. 48, pl. 5. f. 23. Scotland, Highly convex, and even in the best position showing the margin as a broad black line, Greg. S. inamis (Perty).-Striated, lanceo- late or elliptic-lanceolate, with very fine transverse striae. Perty, Inf. p. 206, pl. 17. f. 7. Alps. In form nearly agreeing with S. linearis, E., but striated. S. lineolata (E.).-Broadly lanceolate, with obtuse apices, and parallel, dotted, longitudinal lines; stauros linear, E.A. p. 135, pl. 2. 1, f. 19. Cayenne. S. pumila (K.).—Minute, elliptic-lam- ceolate, with acute apices, and short, marginal, punctated, transverse striae : stauros reaching the margin. KB. p. 106, pl. 30. f. 43. Marine. Christiania. Tront view linear, with rounded angles and truncate ends. 1–1440" to 1-1080". S. Achnanthes (E., K.). — Lanceolate, with obtuse apices; striae distinct, ob- lique; stauros linear, reaching the mar- gin. KB. p. 106, t. 29. f. 22. = Stauroptera Achnanthes, EA, p. 135, pl. 3. 3. f. 7; EM. pl. 17. 1, f. 10. Australia, Ame- rica, Falaise, 3 N 914 SYSTEMIATIC EIISTORY OF TEIE INFUSORIA. S. truncata (Rab.). —Minute, oblong- lanceolate, with very obtuse apices; stauros linear; striae distinct, oblique, 14 or 15 in 1-1200". = Stauroptera trun- cata, Rab D. p. 49, pl. 9. f. 12. Bosnia. S. acrocephala (Rab.). —Broadly lan- ceolate; turgid at the middle, rapidly tapering to the acute apices; stauros dilated outwards, reaching the margin ; striae punctate, parallel. Rab D. p. 48, pl. 9. f. 19. Saxony, S. acuta (S.). — Elongated slender- lanceolate or rhomboid, tapering to the subacute apices; stauros conspicuously dilated outwards, reaching the margin; striae oblique, 30-in .001". S.D. i. p. 59, pl. 19. f. 187. Britain. (VII. 76.) S. pulchella (S.). — Lanceolate, or linear-lanceolate; stauros conspicuously dilated outwards, reaching the margin; striae oblique, very distinct, punctate, 30 in 001". S.D. i. p. 61, Pl: 19, f. 194, Marine. Britain. (VII. 77.). Front view broad, linear-oblong, with rounded angles and constricted centre. Š. aspera (E., K.).-Turgid, lanceo- late or linear-lanceolate, with Subacute apices; striae oblique, punctate-asperate; stauros abbreviated, dilated outwards. KB. p. 106. = Stauroptera aspera, E.A. p. 134, pl. 1. 1, f. 12; BC. vii. pl. 1.f. 18. America, Europe. Front view linear, with truncate ends. 2+ Valves oval or oblong. S. Fenestra (E.).--Small, elliptic-ob- long, with parallel marginal lines, and obtuse, cuneate apices, EA, pl. 2, 1. f. 20. America, Japan. S. Peckii (Rab.).--Small, oval, with rounded ends; costae stout, 11 or 12 in 1–1200"; stauros linear, reaching the margin. = Stauroptera Peckii, Rab D. p. 49, pl. 9. f. 13. Lusatia. . . S. polygramma (E.).-Elliptic-oblong, with rounded ends and longitudinal dotted lines; stauros abbreviated. EA. p. 135, pl. 2.6. f. 30. Cuba. S. semicruciata (E.).-Very large, re- sembling Navicula viridis, but having the crucial umbilicus of Stauroneis. = Staw- roptera semicruciata. EB. 1843, p. 45. Asia, 3f Valves linear. S. dendrobates (E.). — Narrow-linear, with obtuse ends, and a densely and obliquely striated border; front view oblong-quadrate. = Stauroptera dendro- bates, E. Under moss on trees. America. 1–490". S. Roraimae = Stauroptera Roraimae, EM. pl. 34, 5.A. f. 9. Linear, with cu- neate ends, a transverse median line, and parallel striae. - S. oblonga (Bail.).-Linear, with acute, cuneate ends, and oblique punctato-as- perate striae; stauros abbreviated, dilated outwards. = Stauroptera oblonga, BC. vii. p. 10, pl. 1, f. 17. America. The size and markings of Stauroptera aspera, E., but having its valves oblong, with parallel sides, and acute angular ends, Bailey. S. Isostauron (E., K.). — Elongated, linear, with broadly rounded, slightly attenuated ends; stauros linear, reaching the margin; striae parallel. ISB. p. 106. = Stauroptera Isostauron, EA, p. 135; EM. pl. 16. 1, f. 7. Labrador, Sweden, Finland. (XII. 73. S. Liostauron (E.).-Styliform, linear- oblong, with scarcely attenuated, rounded apices; stauros linear. EA, p. 135; EM. pl. 5. l. f. 16. Iceland. Doubtful Species. S. P. explicata (Perty). — Small, not striated, with rounded ends, and much inflated centre (cruciform); enlarge- ments acute. Perty Inf. p. 205, pl. 17. f. 10, Alps. About the size of S. ven- tricosum, K., but still more inflated at the middle, and the inflations pointed, not rounded, Perty. The figure has no median line or other markings, and re- Sembles a Biblarium rather than a Stau- roneis. S. mesogongyla (E.). — Lateral view linear, with rounded ends and gibbous centre; transverse striae parallel, inter- rupted by a transverse central band. Probably a Navicula, since the figure shows a small, definite central nodule. EM. pl. 6, 1, f. 7. Guiana. Fossil, San |Fiore. S. gibba (E., K.).—Form of Navicula gibba, but furnished with an imperfect transverse fascia. KB. p. 107, pl. 29. f. 24. = Stauroptera? gibba, E.A. p. 135, #. 1. 2. f. 3. America, Africa. The gure represents a Navicula with the striae shorter opposite the dilated um- bilical space. S. paucicostata (Rab.).--Small, linear, with inflated centre, and dilated, rounded apices; costae distant, 4 or 5 in 1-1200", much inclined. = Stauroptera pauci- costata, Rab D. p. 49, pl. 9. f. 15. Eu- rope. The figure shows a rhomboid umbilical space resembling the dilated nodule seen in many Naviculae, but not a true stauros. S. maculata (Bail.). — Oval, with OF THE NAWICULEAE. 915 slightly produced, mammiform apices; surface punctato-striate, with a large Smooth central space. BMO. p. 40, pl. 2. f. 32. Florida. Resembles S. punctata, K., but is larger, and has the ends not so much produced. The figure shows a dilated umbilical space rather than a true stauros. S. Scalaris (E., K.).--Small, linear- oblong, with rounded ends; costae stout, parallel, 12 in 1-1200", not reaching the median line. KB, p. 106. = Stauroptera Scalaris, EA, pl. 4, 2. f. 3. Labrador. XII. 10, 14, 30.). Scarcely belonging to thisgenus, since Ehrenberg's figures show a definite central module. It differs from Navicula borealis by its coarser costae and their interruption opposite the median nodule. - S. amphiocys-Stauroptera amphiocys, EM. pl. 6, 1.f. 14, Fossil. Santa Fiore. Ehrenberg's figure represents an elon- gated, marrow-lanceolate Navicula, with acute apices, and a minute central nodule which is not dilated into a stauros; striae * peregrina = Stauroptera peregrina EM. pl. º f, 15, jº Šá. #iore, Ehrenberg's figure represents a small, lanceolate Navicula, with a minute central nodule, but no stauros; striae radiant. S. P. ovalis (Greg.).--Small, smooth, oval; stauros broad, indistinct, reaching the margin. MJ. iv. p. 11, pl. I. f. 36. Britain. Perhaps a Cocconeſs. Species from Ehrenberg known to us only by name. S. pusilla, S. Sphaerophoron, S. Indica, S. Placentula, S. Hologramma, S. gibbosa, S. 43thiopica, S. Amphisbana, S. Capensis, S. Galapagica, S. decurrens, S. brevirostris, Stauroptera nobilis, Stauroptera leptoce- phala, Stauroptera Distauridium, Stau- 7'optera Braziliensis, Stauroptera Tabel- laria, S. asperula, Stauroptera Siamensis, Stauroptera trinodis. Genus STAUROGRAMMA (Rab.).—Like Stauroneis, but with decussating striae, and prominent knots at the intersections, Rab. STAUROGRAMMA Persicum (Rab.).— median line dilated towards the ends. Oblong-lanceolate, with truncate apices; Rab D. p - stauros linear, reaching the margin; Rab D. pl. 9. f. 14. Persia. . 50. = Stauroptera decussata, (VIII, 36.) Genus PROROSTAUROS (E.). — Frustules simple, free; with the cha- racters of Stauroneis, except that its terminal puncta in the front view are approximate and not lateral. We doubt whether this genus can be separated from Stauroneis; for, if we understand Ehrenberg's definition, the apparent position of the terminal puncta depends upon the greater convexity of the lateral valves, which therefore appear, in the front view, like a border on each side of the connecting zone, and the puncta are within the angles. The species are unknown to us. E.B. 1843, p. 136. IP, P subulatus? (E.).-Senegal, Cape of Good Hope. At first sight it reminds one of Gomphonema gracile, E. PROROSTAUROS Splendens (E.).-River Senegal. Genus PLEUROSIPHONIA (E.). — The characters of this genus are unknown to us; but, from Ehrenberg’s figure of P. affinis, we think it is probably identical with Mastogloia. - PLEUROSIPHONIA affinis (E.). — Ob- Species known only by name. long-lanceolate, with capitate ends, me- P. Amphisband (E.), Arabia, Africa, dian line and nodules, and a marginal | Peru, Mexico; P. fulva (E.), Arabia, band of transverse striae. EB. 1856, Africa; P. Phaenºcenteron (E.), Arabia, : 32, - Fragilaria Navicula, E. 1841; Africa; P. Libyca (E.), Africa; P. obtusa #M. 33. 1, f. 14, Arabia, Africa, Peru. (E.), Africa; P. gracilis (E.) Africa. Genus PLEUROSIGMA (Smith) (Gyrosigma, Hassall, Rabenhorst, &c.). —Frustules simple, free, elongated; front view linear or lanceolate, narrower than the lateral view ; valves depressed or slightly convex, º (rarely N 916 SYSTEMATIC EIISTORY OF TELE INFUSORLA. straight), with a sigmoid median line, central and terminal modules, and fine decussating striae, which are resolvable into dots. Pleurosigma is distinguished from Donkinia and Amphiprora by the elongated-narrow front view and more depressed valves. The median line, also, is sigmoid, whilst in those genera it is usually straight, or appears sigmoid merely from the twisting of the frustule. This genus was first separated by Dr. Hassall from Navicula, under the name of Gyrosigma. Hassall, however, like Ehrenberg, erroneously considered it identical with the Sigmatella of Kützing, whereas they belong to very distinct families; and even their sigmoid forms belong to different surfaces, Sigmatella having it in the front, and this genus in the lateral view. Gyrosigma has been adopted by Rabenhorst and others; nor do we think the name so objectionable as to render its rejection necessary. If, then, we admit Professor Smith's name, we do so for the reasons given by Brébisson — “Gyrosigma (Hass.)--Peutétre ce dernier nom de genre n'était-il pas bien convenable selon les lois de la nomenclature; dans tous les cas, il est certain que, malgré son droit de priorité, il est à peu près généralement abandonné. D’ailleurs, on est d’autant moins disposé à reprocher ce changement de nom à M. W. Smith, que le soin tout monographique qu'il a apporté à l'étude des nombreuses espèces de Pleurosigma qu’il a découvertes, en fait un genre tout . à lui” (Bréb DC. p. 17). Ehrenberg does not admit Pleurosigma, because it “ does not differ in its physiological characters from Navicula” (EB. 1854, p. 236). * Frustules rostrate, † Beaks filiform. PLEUROSIGMA Fasciola (E., S.).--Tur- gid-lanceolate, with long linear beaks abruptly curved in contrary directions; striae 64 in .001", indistinct. SD. i. p. 67, 1. 21. f. 211. = Ceratoneis Fasciola, E. Marine. Europe. (XII. 60, 61.) Colour of dry valve pale-pink. 1-430". Mr. Sollitt states this Diatom near Hull is very small, the markings 90 in 001", while those from Boston in Lincolnshire are large, with only 50 striae in 001", P. macrum (S.).-Elongated slender- lanceolate, with very long filiform beaks curved in contrary directions; transverse striae 85 in 001", very indistinct, SD. i. p. 67, pl. 31. f. 276. Brackish water. England. P. prolongatum (S.). —Narrow-lance- olate, gradually tapering into slender beaks curved in contrary directions; transverse striae 65 in 001", indistinct. SD. i. p. 67, pl. 21. f. 212. Marine. England. 2. arcuatum (Donkin). — Turgid-lan- ceolate, straight, with long, very slender, strongly arcuate beaks curved in con- trary directions; striae obscure; median line straight, central. TM. vi. p. 25, pl. 3. f. 10. Marine. England. diº allied to P. macrum, but distinguished from it by the long, strongly arcuate beaks. Dry valves very pale-brown. (Donkin.) 2 + Beaks short, stout. P. distortum (S.).--Stout, turgid-lan- ceolate, produced into short, broad, ob- tuse, subrostrate extremities, which are abruptly bent in contrary directions; transverse striae obscure, 75 in 001"; median line central. SD. i. p. 67, pl. 20. f 210. Marine. England. Small; colour pale pink. 1-320". P. Astuarii (Bréb., S.). — Broadly lanceolate, rapidly tapering into sub- rostrate, obtuse ends; median line di- agonal, submarginal near the ends; striae oblique, 54 in 001"; colour pale purple. S.D. i. p. 65, pl. 31. f. 275. = Navi- cula AEstuari, #A. . 890; Gyrosigma AEstuarii, Bréb. Tarine. Europe. Rather small; 1-290". Habit of P. Thuringicum, but smaller, paler, and without the marginal notch, Kütz. P. littorale (S.). — Turgid-lanceolate, rapidly attenuated into the curved, sub- rostrate, somewhat acute ends; longitu- dinal striae conspicuous, 24 in 001", transverse 50 in 001"; colour pur- lish. S.D. i. p. 67, pl. 22. f. 214. arine. Europe. 1-200”; median line subcentral. - 2 * Valves gibbous at the middle, P. Simensis (E.). — Large, elongated, broadly linear, flexuose, sigmoid, with gibbous centre and broadly rounded, somewhat incrassated ends, which are curved in contrary directions. = Navicula OF THE NAWICULEAE. 917 22* Simensis, EB. 1847, p. 484; EM. pl. 34, 7. f. 11. China, 1–80". P. reversum (Greg.). — Elongated marrow-linear, with inflated or lanceolate centre, and dilated ends which are turned in contrary directions; median line sig- moid, subcentral except near the ends; striae extremely fine. GDC. p. 58, pl. 6. f. 105. Marine. Scotland. This form may be identical with P. Simensis; but the valves are marrower and with less- rounded apices than in Ehrenberg's figure of that species. 3 * Valves linear. P. Balticum (E., S.).--Large, broadly linear, straight, except towards the attenuated obtuse ends, which are curved in contrary directions; longitudinal and transverse striae, 38 in .001"; colour dark brown. SD. i. p. 66, pl. 22, f. 207. = Navicula Baltica, Étº 1. 13. f. 10; Gyrosigma Balticum, Rab D. p. 47, pl. 5. f. 6; P. makron, Johnston, M.J. viii. Marine or brackish waters. Common. (VIII, 33; IX. 144.) 1-70". Median line flexuose, subcentral. P. obscurum (S.).--Small, linear, with attenuated, rather obtuse ends; median, line very flexuose, not central; striae ob- lique, 75 in 001". SD. i. p. 65, pl. 20. f. 206. Marine or brackish waters. Britain. Var. 8 smaller, 1-193"; colour pale pink; median line marginal near the ends. P. Simum (E.). — Small, linear, with the ends obliquely rounded on opposite sides; median line sigmoid, nearly cen- tral. = Navicula sima, jºb. 1845, p. 363; EM. pl. 34. 7. f. 9. India. 1-430". P. Scalpellum (K.). — Small, linear, slightly sigmoid, gradually attenuated into the obtuse apices; median line sub- central. = '...}. Scalpellum, K.A. p. 85; KB. pl. 30. f. 13; Gyrosigma Scalpellum, Rab D. p. 47, pl. 5. f. 10. Trinidad, Persia. P. Sciotoensis (Sullivant). — Linear, moderately sigmoid, gradually attenu- ated into the rather obtuse ends; striae transverse and longitudinal, 40 in 001". Silliman's J. xxvii. p. 251. Fresh water. United States. 001". “Not unlike P. Spencerii, for which it has passed as a variety; but it is a larger species, with sides more parallel and ends less acute. Its striation at once distinguishes it’” (Sull.). 4 * Valves lanceolate or linear-lanceolate. i Valves linear-lanceolate. P. Wansbecki (Donkin).--Linear-lan- ceolate, with tapering, subacute, slightly sigmoid ends; median lines sigmoid, not central; longitudinal and transverse striae, about 50 in .001". Donkin, TM. yi. p. 24, pl. 3. f. 7. = P. Balticum, 8, SD. Marine. England. Pale straw-coloured. •004.5" to .005". Much smaller than P. JBalticum, and with more numerous striae. P. lamprocampum (E.). — Slender, narrowly linear-lanceolate, tapering to the rather obtuse apices; sigmoid, with fine transverse striae ; median line cen- tral; front view linear. = Navicula lam- procampa, EB 1840, p. 20; KB. p. 102, pl. 4. f. 5; Gyrosigma lamprocampum, Rabl), p. 47, pl. 5. f. 9. Marine. Europe, 1–144". P. curvulum (E.).-Linear-lanceolate, with rather obtuse apices, sigmoid. = Navicula curvula, E Inf, pl. 13. f. 14; Gyrosigma curvulum, #bº. p. 47, pl. 5. f. 8. Europe, America. P. Speciosum (S.).-Linear-lanceolate, flexed chiefly at the somewhat abrupt, obtuse ends; median line submarginal near the ends; striae oblique, 44 in 001"; S.D. i. p. 63, pl. 20. f. 197. England. Pale straw-colour. 1-85". It is shorter, less tapering, and has more rounded apices than P. formosum ; the median line also is not diagonal at the centre. P. formosum (S.).-Large, elongated, linear-lanceolate, much flexed, gradually tapering to the obtuse apices; median line diagonal; striae oblique, 36 in 001". SD. i. p. 68, pl. 20. f. 195. Marine, Eng- land. (VIII. 32.) Colour chestnut-brown. 1-66". Well distinguished by the po- sition of its median line, which, owing to a twist in the valves, appears to coin- cide with the edges for a considerable distance at either end, and then crosses in a diagonal direction. P. Longinum (Bri.). — Lanceolate, flexure moderate, extremities greatly elongated, acute; median line central; striae transverse, 36 in 001". 020" to '025". Colour pale straw, TM. vii. p. 180, pl. 9. f. 7. Arctic regions. P sinuosum (E.). — Small, striated, linear-lanceolate; striae 15 in 1–1200". 1-480". = Navicula sinuosa, EB. 1840, p. 21. Marine. Europe. Has the figure of P. Simum, but is more slender. P. subtile (Bréb.)—Very slender, pel- lucid and delicate; slightly sigmoid, very marrow linear-lanceolate, subuliform with rather obtuse apices. = Navicula subtilis, KA. p. 87. Marine. France. 1-160” to 1-120". P. tenuissimum (S.). — Very narrow linear-lanceolate, gradually tapering to a 918 SYSTEMATIC ELISTORY OF THE INFUSORLA. fine point; transverse striae 48 in 001"; median line central. SD. i. p. 67, pl. 22. f, 213. Brackish water. Essex. P. Apulum (Rab.). —Slender-lanceo- late, much curved, with obtuse ends, transversely striated; front view broadly linear, Rab D. p. 47, pl. 5. f. 7. Italy. In the figures the valves are linear, very but not symmetrically sigmoid, with tapering ends and central median line. 2 f Valves lanceolate, with oblique striae. P. delicatulum (S.). — Slender-lance- olate, gradually tapering to the acute apices; flexure moderate; median line central; striae oblique, 64 in 001". SD. i. p. 64, pl. 21. f. 202, Brackish water. Britain, Length 1-112"; breadth 1-1500". Colour pale pink. P. inflatum sºi). — Small, broadly-lanceolate, with acute apices; median line central, much flexed, as well as the valve; striae oblique. TM. ii. p. 16, pl. 1, f. 9. Marine. Natal. P. decorum (S.). — Large, elongated, rhomboid-lanceolate, uniformly flexed, gradually tapering to the subacute apices; striae oblique, 36 in 001"; median line diagonal, marginal near the ends. SD. i. }. 63, pl. 21. f. 196. Brackish water. £ngland. Colour pale chestnut. P. angulatum (Quekett, S.). — Large, broad, sigmoid, rhomboid-lanceolate, rapidly tapering to the subacute apices; median line somewhat diagonal; striae oblique, 52 in 001". SD. i. p. 65, pl. 21. f 205. = Navicula angulata, Quekett, Microsc. p. 438, pl. 8. f. 4 to 7. Marine. T}ritain. Colour pale chestnut ; flexure moderate. - P. quadratum (S.). — Large, very broad rhomboid, rapidly tapering to the Subacute apices, which are slightly flexed; striae oblique, 45 in 001”; median line central. 3. i. p. 65, pl. 20. f. 204. = P. angulatum,_ANH, 2nd series, ix. p. 7. Marine. Europe. Colour chestnut; length 1-110"; breadth 1-428". Easily recognized by its verybroad angular form. P. lanceolatum (Domkin). — Straight, broadly lanceolate, acute; median line straight or gently sigmoid, with the ter- minal modules turned in contrary direc- tions; striae very fine, oblique, about 70 in 001". TM. vi. p. 22, pl. 3. f. 4. = P. transversale, 8, Mr. Roper. Marine. Eng- land. Straw-coloured; '005.5" to 006"; front view narrow linear-lanceolate, The extremely fine striae require the most careful manipulation with very oblique light, to render them visible with a superior 1-5th objective, P. naviculaceum (Bréb.). — Rather small, lanceolate, straight, gradually tapering to the obtuse apices, which are slightly turned in contrary directions; median line sigmoid, not central; striae very fine, oblique. B. Diat. of Cherbourg, 1854, p. 17, f. 7. = Gyrosigma transver- sale, Microg, Dict, pl. 11, f., 37,385. P. transversale, S.D. ii. p. 96. Marine. Common, especially in deep waters. This species, viewed laterally, greatly resem- bles a Navicula in its lanceolate straight form. Its apices are only slightly in- clined to opposite sides. The median line, however, is sigmoid, and the striae are oblique and decussating, B. marinum (Donkin).— Broadly lan- ceolate, straight, slightly sigmoid near the obtuse ends; median line sigmoid on each side of the central module; striae oblique. TM. vi. p. 22, pl. 3. f. 3. Marine. Northumberland. Straw-coloured; striae about 45 to 50 in '001”. “0055" to 006". The well-marked sigmoid flexure, of the median line on both sides of the central nodule distinguishes this species, and renders it easy of recognition. P. Nubecula (S.).--Small, lanceolate, nearly straight, with obtuse apices, cen- tral median line, and 55 oblique striae in ‘001"; colour very pale. SD. i. p. 64, pl. 21. f. 201. Marine. England. P. intermedium º pale straw-colour, slender lanceolate, nearly Straight, tapering to the subacute apices; median line subcentral; striae oblique, 55 in 001". SD. i. p. 64, pl. 21, f. 200. Marine. England. P. rigidum (S.). —Large, stout, pale straw-colour, lanceolate, nearly straight, with rounded apices; median line cem- tral; striae oblique, 48 in .001". SD. i. p. 64, pl. 20...f. 198, Marine. England. P. validum (Sh.).-Large; lanceolate, nearly straight, with very obtuse apices, oblique striae, and slightly flexed median line. , MT. ii. p. 16, pl. 1, f. 8. Marine. Natal. P. elongatum (S.). — Large, much elongated, lanceolate, gradually tapering to the acute apices, nearly straight, ex- cept at the ends, which are slightly curved; striae oblique, 48 in 001"; median line nearly straight. SD. i. p. 64, pl. 20. f. 199. Marine. Bngland. Clear straw-colour. Length 1-75"; breadth 1-920". P. Strigosum (S.). — Large, elongated, broadly lanceolate, gradually attenuated to the obtuse apices; flexure slight; me- dian line not central near the ends; striae oblique, 44 in 001". SD, i. p. 64, OF TELE NAWICULEAE. 919 pl. 21, f. 203. Marine. Britain. 1-90"; colour pale straw; front view narrow linear-lanceolate, with obtuse apices. 3 + Valves lanceolate, with longitudinal and transverse striae. P. obtusatum (Sullivant). — Oblong- lanceolate, slightly sigmoid, with obtuse apices; 0025"; striae transverse and longitudinal, 56 in 001". Silliman's J. xxvii. p. 251. Fresh water. United States. A very small species, remark- able for the obtuse ends. It may be a Colletonema, but we have not observed it in gelatinous envelopes. P. Spenceri (Quekett, S.). — Small, lanceolate, moderately flexed, gradually tapering to the obtuse apices; median line central; striae very fine, transverse 50 in 001", longitudinal 55 in 001". SD. i. p. 68, pl. 22. f. 218. = Navicula Spenceri, Quekett. Fresh water. America, Europe. Colour pale brown, 1-270". P. Parkeri (Harrison). — Lanceolate, considerably flexed, apices produced, median line central; striae transverse, 55 to 60 in 001"; longitudinal striae faint ; colour pale yellow, Lincoln- shire. MJ. viii. p. 105. P. Wormleyi (Sullivant). — Lance- olate, conspicuously sigmoid, Suddenly attenuated into acute apices; ‘003"; striae, longitudinal and transverse, 52 in ‘001". Silliman's J. xxvii. p. 25l. Fresh water. United States. Resembles P. Spenceri, but is a Smaller species, more evidently sigmoid, and with rather ab- ruptly attenuated ends; its striae are more difficult to resolve, and the texture of its valves is thinner. IP. lacustre (S.).-Lanceolate, consider- ably flexed, gradually tapering into the obtuse apices; longitudinal and trans- verse striae, 48 in 001"; median line subcentral. SD. i. p. 68, pl. 21. f. 217. Fresh water. England. 1-144". P. Thuringicum (K.).-Lanceolate, sig- moid, gradually attenuated to the Sub- acute apices, obsoletely notched at the middle of each margin; median line central; striae wanting or indistinct. = Mavicula Thuringica, i&B, p. 102, pl. 4. f 27; Gyrosigma Thuringicum, Rab D. p. 47, pl. 5. f. 4. Thuringia. Front view narrow-linear ; 1-264" to 1-168". P. Agellus (E.). — Large, lanceolate, flexed, gradually tapering to the obtuse apices, marked longitudinally with very fine lines, and thus appearing furrowed; median line central. = Navicula Agellus, EB. 1840, p. 18; EMI, pl. 15 A. f. 31; Gyrosigma Agellus, Rab D. p. 47. Fresh water. Germany, Lough Mourne deposit, Siberia. Front view nearly linear, with Subacute apices; 180". Is more slender and longer than P. Hippocampus, E. P. attenuatum (K., S.).-Large, elon- gated, flexed, lanceolate, gradually at- tenuated into the obtuse apices; lon- gitudinal striae 30, and transverse 40 in ‘001"; median line central, SD. i. p. 68, pl. 22. f. 216. = Navicula attenuata, KB. . 102, pl. 4, f. 28; Gyrosigma attenuatum, Rab D. p. 47. Fresh water. Europe. I-120". "Colour purplish brown; front view narrow-lanceolate, with truncate ends. P. cuspidatum (Rab.). — Slender-lan- ceolate, very much flexed, with long, tapering, obtuse ends; median line cen- tral. = Gyrosigma cuspidatum, Rab D. p. 47, pl. 5. f. 5, 6, Fresh water. Europe, America. It is always mixed with P. act&minatum. P. acuminatum (K., S.).-Lanceolate, tapering into the obtuse apices; flexure considerable; median line central; lon- gitudinal striae 40 in 001", transverse 52 in .001". SD. i. p. 66, pl. 21. f. 209. = Navicula acuminata, KB. p. 102, pl. 4. f. 26; Navicula Sigma, EB. 1843, p.209; Gyrosigma Hassallii, Rab D. p. 47. Marine. Europe, Asia, Africa, America. (IX, 146.) Front view narrow-linear, with obtuse apices ; 1-162"; colour pale brown. P. Hippocampus (E., S.). — Large, elongated, broadly lanceolate, obtuse; flexure considerable; colour pale brown; striae as in P. attenuatum ; median line central. SD. i. p. 68, pl. 22. f. 215. = Navicula Hippocampus, E Inf, pl. 13. f. 9; Gyrosigma Hippocampus, HBA. pl. 102. f. 11; Rab D. p. 47. Marine. Europe. (IX. 145.) I-166"; front view linear, truncate. P. Strigilis (S.). —Large, much elon- gated, lanceolate, uniformly tapering to the subacute apices, flexed; median line central; striae, transverse and longitu- dinal, 36 to 40 in 001". SD. i. p. 66, bl. 22. f. 208. Brackish water. Eliº ength 1-80"; breadth 1-830”; colour pale brown, . Notable for its graceful form and distinct striae. P. Scalprum (Gaillon). — Small, sig- moid, gradually attenuated into the rather obtuse apices, longitudinally striated. = Cymbella Scalprºm, Al), p. 11; Navicula Scalprum, E. Inf, ; KB. pl. 4. f 25. Marine. Europe, Asia, America. Length 1-430" to 1-290". P. Normani (m. sp.). — Broadly lan- ceolate, slightly flexed, with rather ob- 920 SYSTEMATIC HISTORY OF THE INFUSORTA, tuse ends, and a slight, transverse cen- tral depression; median line stout, nearly central; striae oblique, 40 in 001". = P. lanceolatum, Norman, MS. Marine, Europe. Found in nearly every gather- ing from deep water, and in stomachs of Ascidians, Noctiluca”, Pectens, &c. Colour tawny brown; 0048" to 0110"; median line scarcely flexed, except near the ends. The description is by George Norman, Esq. P. acutum (Norman, MS) — Large, broadly lanceolate, elongated, moderately flexed, gradually tapering to the very acute apices; median line delicate, much flexed, not central; striae oblique, 50 in •001" Marine. Stomachs of Ascidians, &c. Europe, Very pale straw-colour or nearly hyaline ; 011"; median line flexed throughout. Genus TOXONIDEA (Donkin). — Frustules simple, free; lateral valves elongated convex, with the sides not symmetrical; median line arcuate, with central and terminal nodules, its ends curved towards the same margin ; striae oblique. Marine. Toxomidea is closely allied to Pleurosigma; indeed the forms placed here are regarded by Professor Arnott as distorted species of that genus. The absence, however, of a sigmoid flexure, both in the valves and median line, is so different from what we find in Pleurosigma, that we think if advisable to admit Toxonidea until Dr. Donkin’s views are disproved by more perfect observation. ToxoMIDEA Gregoriana (Donkin).-- Large, lanceolate, with the obtuse ends curved upwards; median line concurrent with the lower margin near the ends; striae fine, oblique, about 50 in .001". TM. vi. p. 19, pl. 3. f. 1. Britain. Straw- coloured; '008" to 009"; median line curved upwards near the end, and “re- sembling the figure of an unbent Scy- thian bow; " dorsum rather more con- vex than the venter. T. insignis (Donkin). — Arcuate or semi-lunate, with produced, subacute ends; median line not central, strongly arcuate; striae very fine, about 75 or 80 in 001". TM. vi. p. 21, pl. 3. f. 2, .0048" to 006"; “valves resembling a straw- coloured strung bow or a cocked hat,” with very convex or gibbous dorsum and straight venter. Professor Arnott re- gards this species as a distorted state of Pleurosigma AEstuarii. Britain. T. undulata (Norman, M.S.).-Arcuate, with three slight dorsal undulations, ob- tuse somewhat recurved apices, and con- cave venter gibbous at its centre; striae oblique, 50 in 001". From Ascidians. North Sea. Very pale straw-colour, with pinkish reflections; 0055"; longitudinal suture concurrent with the ventral mar- #. except at the inflated centre. (VIII. Genus DONRINTA (n. g.). — Frustules simple, free; front view panduri– form, as broad as the lateral view ; valves convex, keeled, with, nodules and decussating striae as in Pleurosigma. Marine. We have constituted this genus for the reception of some Diatoms possessing characters intermediate between Pleurosigma and Amphiprora, and have much pleasure in dedicating it to Dr. Donkin, who, amongst his many interesting discoveries, first directed attention to several of the species placed in it. T)r. Donkin referred the species to Pleurosigma on account of the similarity of striation; but they differ from that genus in the broad, constricted front view ; and from these characters, together with their very convex, keeled valves, we were induced to regard them as more nearly allied to Amphiprora. Indeed there is little essential difference between keel, crest, and wing, these being, in our opinion, merely different stages of development. This opinion was also adopted by Professor Arnott, whose critical knowledge of genera commands the highest deference. The species placed in Donkinia differ from Amphi- prora, not only in their decussating striae (a character sometimes difficult to verify, and of rather doubtful generic value), but also, according to Dr. Donkin, in the absence of lateral wings to the valves. DONKINIA cristata (E.), Narrow-lan- central module transversely oblong; me- ceolate, gradually subulate at each end; dian line sigmoid, crested, = Wavicula OF TELE NAWICULEAE. 92.1 cristata, EB 1854, p. 240; EM. pl. 35 B.B. 4. f. 13. Atlantic. D. inversa (E.). —Short, narrow, sig- moid, with subacute apices; front view very broad, º constricted at the middle, with broadly truncate ends and marginal glands. = Navicula inversa, EB. 1840, p. 18. Europe. 1-576". “It is allied to Amphiprora alata, but wants the winged portions” (E.). - D. carinata (Donkin).--Straight, linear- lanceolate, acute, very convex; colour dull purple; median line strongly sig- moid, marginal near each end; striae oblique, fine, about 55 to 60 in 001". = Pleurosigma carinatum, Donkin, l.c. p. 23, pl. 3. f. 5. England. 0046"; valve twisted; median line diagonal at the cen- tre, marginal near the ends. (VIII. 49.) D. compacta (Grev.). —Straight, very convex, linear, obtuse, sigmoid from having the ends sloped in contrary directions; median line much flexed, diagonal at the centre, marginal near the ends; striae very fine, 53 to 60 in 001". = Pleurosigma compactum, MJ. v. p. 12, pl. 3. f. 9; Pleurosigma rectum, Donkin, T.M. vi. p. 23, pl. 3. f. 6; Am- phiprora Ralfsii, Arnott, M.J. vi. p. 9]. Britain. '0045" to .005". According to l)r. Donkin, the striae are longitudinal and transverse; colour very pale. D. minuta (Donkin). — Short, very convex, linear-oblong, Subacute, sigmoid from the sloping of one margin near each end in contrary directions; median line much flexed; striae very fine, transverse ones distinct, about 55 in 001", longi- tudinal ones obscure. = Pleurosigma mi- nutum, Donkin, l.c. p. 24, pl. 3. f. 8. England. 0025"; colour, very pale brown. D. minuta seems to differ from D. compacta, to which Professor Arnott would unite it, chiefly in its smaller size. D. angusta (Donkin). — Very con- vex, linear, with acute, slightly apicu- lated apices; median line strongly sig- moid, marginal, except a central diagonal portion; striae obscure, longitudinal. = Pleurosigma angustum, Donkin, l.c. p. 24, pl. 3. f. 9. England. 005" to 0055"; colour dull purple. Another form closely allied to D. compacta. D. reticulata (Norman, M.S.).-Linear- lanceolate, with rather obtuse apices; median line strongly diagonal at the centre, then marginal and slightly pro- jecting; striae oblique, distinct, 22 in ‘001". Stomach of Ascidians, Shark's Bay, Australia. Collected by Dr. Mac- donald. Colour purplish brown; front view oblong, with truncate ends and con- stricted middle. For the description of this species we are indebted to George Norman, Esq. Genus AMPHIPRORA (Ehr.) (Entomoneis, Ehr.).-Frustules free, simple, in front view constricted at the middle; valves convex, with a longitudinal wing, and central and terminal nodules; striae, when present, transverse. Marine. Amphiprora is distinguished by its lateral wings, which are con- stricted at the middle, so that the frustule in front view, when not twisted (which, however, frequently occurs), is more or less panduriform, with trun- cate or broadly-rounded ends. The late Professor Smith stated that the peculiar frustules of this genus could not be confounded with any others, save those of a few species of Nitzschia. From the recent discoveries of Dr. Donkin, Amphiprora is found far more closely allied to Pleurosigma and Donkinia. From these genera it differs by its alate valves, and by having transverse striae only. According, however, to the late Professor Gregory and Dr. Donkin, the valves of Amphiprora are furnished, in addition to the median crest, with lateral ones also, similar to those of Surirella ; and certainly the frustules in the front view most frequently exhibit a longitu- dinal line on each side between the margin and the central portion—an appearance not unlikely to depend on such a formation, particularly in A. ormata and A. paludosa, in which these lines are undulated. An end view is required to ascertain whether this be really the case, since the same appearance would result from a depression along the sides of the median crest, and even the undulations may be produced by transverse ridges. AMPHIPRORAalata(E., K.).—Very hya- tinued round the ends; lateral view with line, generally twisted; front view broad- apiculate ends and a double line of puncta ly winged, strongly constricted; wingcon- | accompanying the keel; striae 42 in 922 SYSTEMATIC ELISTORY OF THE INFUSORIA. '001". KB, p. 107; SD. i. p. 44, pl. 15. f. 124.- Navicula and Entomoneis alata, EB, 1845, p. 154. Common, especially in salt-water marshes. (XIII. 5 to 7.) 1-570" to 1-430"; central portion with longitudinal lines. A. Kitzingii (Bréb.).-Very hyaline; front view slightly constricted, longi- tudinally lined, with rounded apices. KA. p. 93. France, - A. constricta (E.). — Very hyaline; front view oblong, sinuato-constricted, with rounded ends; lateral view narrow, with straight median line, and transverse stauros-likeband. EA, p. 122, pl. 2.6.f.28; SD. i. p.44, pl. 15.f. 126, Europe, America. (XII. I.) Striae very faint, 68 in 001". A. duplea (Donkin).-Broad, panduri- form, with truncate ends and rounded angles; lateral view narrow, not stri- ated; keel strongly sigmoid, unaccom- anied by puncta. TM. vi. p. 165, pl. 3. f. 13. England. Resembles A. alata in the broad, deeply-constricted front view with conspicuous alae, but differs from it in the absence of striae and puncta, and in the narrow-linear lateral view. A. plicata (Greg.).-Front view deeply constricted, with broadly rounded ends; each valve with a plate extending from its inner margin to the nodule, furnished like the wings with about 50 fine trans- verse striae in 001"; central portion with faint vertical lines or folds. GDC. p. 33, pl. 4, f 57. Scotland. Approaches nearest to A. alata, but differs from it in the folds of the middle space, and in the presence of lateral plates. Judging from the figure quoted, the longitudinal limes are similar to those present in A. alata and other species, and we doubt the distinction of the lateral plates. A. pulchra (Bailey). — Large; front view deeply constricted, with rounded ends, distinctly striated, punctate near the margin. & 18. Florida. Often twisted; central bortion narrow, sigmoid, with a few fine i. lines. A. quadrifasciata (Bailey). —Small; front view moderately constricted, with truncate or slightly rounded ends; valves striated, lanceolate, with produced ros- tellate apices. BC. ii. p. 38, pl. 2. f. 2–4, United States. When living, the colour- ing matter forms four yellowish trans- verse bands; not contorted. A. vitrea (S.). —Straight; front view oblong, with rounded ends and slight constriction ; , lateral view lanceolate ; striae 52 in 001". SD. i. p. 44, pl. 31. f. 270, Britain. BC. ii. p. 38, pl. 2. f. 16. A. elegans (S.).--Straight; front view linear-oblong, with broadly rounded ends and very slight notch-like constriction; lateral view lanceolate ; striae 40 in '001". S.D. ii. p. 90, ; GDC. p. 33, pl. 4. f 58. Britain. “Distinguished from A. vitrea by its longer and comparatively more lanceolate and slender frustule, and closer striae” (S.). Professor Arnott would unite this with A. vitrea. A. obtusa (Greg.).--Front view linear- oblong, with slightly sinuated sides and rounded ends; striae very fine. GDC. p. 34, pl. 4. f. 60. Scotland. Alae of nearly uniform breadth. A. minor (Greg.).-Front view oblong, with slightly sinuated sides and rounded ends; striae rather coarse; central smooth ortion lanceolate. TM. v. p. 75, pl. 1. . 38. Scotland. A. pusilla (Greg.). — Front view qua- drangular; alae slightly constricted, the constriction apparently overlapped by the convexity of the valve; lateral view acutely lanceolate; striae fine, about 60 in 001". GDC. p. 33, pl. 4, f 56. Scot- land. A. lepidoptera (Greg.). — Elongated; front view linear, with broadly rounded ends; the notch-like constriction of the alae, apparently overlapped by the con- vexity of the valve; lateral view lan- ceolate, apiculate; striae fine, about 48 in 001'; GDC. p. 33, pl. 4, f 59. Scot- land. The alae are carried round the ends, and in the lateral view appear like an apiculus. A. maxima (Greg.).--Front view very broad; panduriform, with rounded ends, the notch-like constriction overlapped by the convexity of the valve; striae distinct, about 36 in .001"; lateral view acutely lanceolate, GDC. p. 35, pl. 4. f. 61. Scotland. - A. comple.ca (Greg.). — Front view broadly panduriform, with broadly round- ed ends; alae with marginal puncta; striae delicate, about 45 in 001"; central por- tion oblong, with concentriclongitudinal lines. GDC. p. 36, pl. 4, f. 62. Scot- land. A. paludosa (S.).-Twisted; front view dilated, broadly winged, deeply con- stricted, with rounded or truncate ends, and a waved longitudinal line on each side between the margin and central portion; striae 60 in 001" SD, i. p. 44, ; 31, f. 269. Britain. Fresh or slightly brackish water, according to Smith; marine, according to Professor Arnott. A. ornata (Bailey).--Small; front view deeply constricted, with truncated or OF TELE NAWICULEAE. 923 rounded ends, and a longitudinal row of undulations on each side. BC. ii. p. 38, pl. 2. f. 15 & 23. America. ften twisted. “The ruffle-like rows of pin- nules distinguish this species from all others” (Bailey). Doubtful Species. A. recta (Greg.). — Front view qua- drangular, with rounded angles and very slightly constricted sides; striae fine but distinct, TM. v. p. 67, pl. 1, f. 40. Scot- land. The figure presents no appearance of alae, but only convex lateral valves, such as are seen in several species of Navicula. A. navicularis (E.). — Oblong, with obtuse ends and radiant transverse striae : front view quadrangular, with two puncta at each end. EA. p. 122; EMI. several figures. Fresh water. America. Apparently a Navicula with the ter- minal puncta of the front view less mar- ginal than usual, - Genus DIADESMIS (Kütz.).-Frustules navicular, united into a filament; valves with central and terminal nodules. Habit of Fragilaria, but the valves furnished with median line and central nodule. Diadesmis differs from Sphenosira only in having the lateral surfaces with similar ends. * Freshwater or Fossil. DIADESMTS confervacea (K.).—Breadth of articulations twice the length; valves minute, smooth, with acute, acuminate ends. KB. p. 109, pl. 30. f. 8. Trinidad. (XIV. 32, § 1-960". D. laevis (E., K.). — Smooth; breadth of articulations three to four times the length. KB. p. 109, pl. 29. f. 69. = Tabel- laria lavis, EA, pl. 1. 2. f. 17. Chili. (XII, 40.) D. sculpta (E., K.). — Articulations with striated margins; valves linear- oblong, with rounded ends and a narrow striated border. KB. p. 109, pl. 29. f. 26. = Tabellaria sculpta, EA, pl. 1. 2. f. 6. Chili. Resembles Navicula borealis, E. D. P. Bacillum (E., K.).—Articulations striated, linear-oblong, with rounded ends, and a large, oblong, longitudinal median nodule. KB. p. 109. = Navicula Pacillum, E. Fossil. Greece. D. Navicula (E.). — Frustules oblong, smooth, four or five times as long as broad, with a smooth median stricture. = Fragilaria P. Navicula, EA, p. 127, pl. 1. 3. f. 8. Peru. We place this form in Diadesmis because the frustules, in the front view, have a minute punctum at the middle of each lateral margin, an appearance, which usually indicates the presence of central nodules. D. Gallica (S.). — Filaments straight or curved; valves linear-elliptical, with about 45 obscure striae in '001". Sm. ANH. Jan. 1857, p. 11, pl. 11, f. 16. Havre. D. peregrina (S.).-Victoria tank, Glas- gow. This species is unknown to us. 2 * Mahºe. D. Williamson? (S., Greg.). — Front view linear, with central and terminal dilatations; valves linear, with attenuated ends and 16 to 18 dotted striae in 001. GDC. p. 25, pl. 2. f. 40. = Himantidium Williamsoni, SBD. ii. p. 14, pl. 33. f. 287. Marine. Scotland. Genus STIGMAPHORA (Wallich). — Frustules free, naviculoid; valves lanceolate, loculate ; loculi with central and marginal puncta. Marine. Frustules very hyaline, with two minute cells at the middle of each margin in both views; valves with median line. STIGMAPHORA rostrata (Wallich). — S. lanceolata (Wallich). — Valves Valves rostrate; beaks with a median | acutely lanceolate, without median rows row of puncta. TM. viii. p. 43, pl. 2. f. 5, 6, (VIII, 43.) India. of puncta, TMI. viii. p. 43, pl. 2. f. 7, 8, India, 924 SYSTEMATIC HISTORY OF TELE INIFUSORIA. 2 * Frustules naviculoid, enveloped in gelatine or enclosed in a définite tubular or gelatinous frond. Subfamily SCHIZONEMEAE of LACERNATAE. This group is remarkable for the great external resemblance some of its species have to acknowledged Algæ, widely as they differ in internal structure. Genus FRUSTULIA (Ag). —Frustules bacillar or navicular, immersed in an amorphous gelatinous substance. For the present we retain this genus in the Schizonemege, but believe that, in most if not all the species, the frus- tules are more like a Synedra than a Navicula, and want the central nodnle of the latter. + Striae evident, FRUSTULIA salina (E.).-Very narrow linear, transversely striated; in front view with rounded ends, in lateral view Sud- denly acute. E Inf. p. 232. Saline springs, Germany. 2f Striae wanting, or very indistinct. F. Kitzingiana (Rab.).—Smooth, lan- ceolate, with truncate apices. Rab D. p. 35, pl. 8. f. 3. = Synedra mucicola, KB. p. 68, pl. 14. f. 5. On stones in a rivulet near Nordhausen. F. minuta (Rab.). — Minute, linear, smooth, in front view with truncate apices; valves with acutely cuneate ends. Rab D. p. 35. t. 8. f. 4. = Synedra Frus- tulum, #. pl. 30. f. 77. Fresh water. Germany and Italy. It forms an olive- brown gelatinous mass on stones, and becomes green in drying. F. to facea (Braun). —Rhomboid-lam- ceolate, with obtuse apices, a stout me- dian rib, and Small central nodule. Rabl). p. 50, t. 7. f. 2. Germany. It forms dirty- yellow, rather firm, Smooth or rugged gelatinous masses about plants in bogs. An authentic specimen from Professor 1853. Marine. Braun appears to us identical with Na- vicula rhomboides. - F. Saaronica (Rab.). — Slenderer than F. to facea, with valves more acute; front view linear, with broadly rounded ends. Rab D. p. 50, t. 7. f. 1. Saxony. Forms dirty-olive-brown tremulous jelly- like masses in little cavities of damp rocks. F. Haeckeriana (Rab.).—Valves spin- dle-shaped, with acute, pointed ends; front view narrow-lanceolate, with ob- tuse apices, Rab D. p. 50, pl. 10. f. 14. Germany. Forms dirty gelatinous masses on moss in streams. F. acicularis (E.). — Bacilla slender, smooth, with acute apices; valves more acute, like a fine needle. ERBA, 1853, p. 527. Marine. Kingston Bay. Frus- tules like those of Fragilaria Rhabdo- soma, but free and heaped together without order. F. bacillaris (E.).-Bacilla linear, pin- mulate, with truncate apices in the front, and rounded in the lateral view. EB. Ringston Bay. This species, like F. acicularis, seems included in gelatine dilated like an ulva, which, when dry, appears membranaceous. In the same membrane both species are in- cluded, with many other Diatomaceae. Genus MASTOGLOIA (Thwaites).-Frustules oblong, naviculoid, annulate, in a gelatinous mammillate cushion or frond; annuli loculated; loculi open- ing by foramina along the line of suture. “The frustules of Mastogloia are notably distinct from those of the other genera of this tribe, having the annulate structure of Rhabdonema with the canaliculi of Surirella.” “The canaliculi are, however, formed differently from those of Surirella, not being connected with the valve, but with the annulus, which projects as a septum into the body of the frustule. The frustule itself is ordinarily excentric to the mucus developed around it, and sits as it were on the summit of a little nipple-like cushion of gelatine’’ (Smith). pl. 62. f. 388. = Dickieia Dansei, ANH. 1848. Brackish water. Britain. (xv. 30.) M. lanceolata (Thw.).-Valves oblong- MASToGLOIA Dansei: (Thwaites). — Valves elliptic-oblong, with 8 to 20 lo- culi; striae 42 in 001". SD. ii. p. 64, OF TEID, NAWICULEAE, 925 lanceolate, with subacute apices and 8 to 30 loculi; striae 42 in 001". SD. ii. p. 64, pl. 54 f. 340. Brackish water. Britain. M. Smithii (Thw.). — Valves oblong- lanceolate, with produced, obtuse or capitate apices, and 6 to 24 loculi; striae 42 in 001". SD. ii. p. 65, pl. 54 f. 341. Fresh or brackish water. Biº. M. apiculata (S.). — Valves elliptic- lanceolate, with slightly produced, ob- tuse, conic apices, and 30 to 50 loculi; striae 42 in 001". S.D. ii. p. 65, pl. 62. f, 387. Marine. Britain. M. Grevillii (S.).-Valves linear, with obtuse, cuneate ends, and 15 to 20 loculi; striae moniliform, 24 in 001. S.D. ii. p. 65, pl. 62. f. 389. Freshwater. Britain. M. minuta (Grev.). — Valve elliptic- lanceolate or elliptic-oval, conspicuously apiculate; loculi 12 to 18; striae very fine and close. Trinidad. Grev. M.J. v. p. 12, pl. 3. f. 10. It is a º evidently allied to M. apiculata, but differs in being scarcely half the size, and essentially in the much larger loculi; it is also much more apiculate. Genus PHLYCTAENIA (Kütz.).-Frustules navicular, included in (globose) gelatinous cells. Marine. PHLYCTAENIA minuta (K.).—Parasitic; cells hyaline, achromatic, solitary, scat- tered, or binately approximate and aggre- gated; included naviculae few, binately or quaternately conjoined, Smooth ; front view linear, with truncate apices; valves broadly lanceolate, with acumi- mated ends. KSA, p. 96, Adriatic Sea. P. maritima (E., K.). — Naviculae Smooth (?), linear, with rounded ends contained in distinct, but contiguous, gelatinous cells. KA. p. 96.- Frustulia maritima, E Inf. p. 232. Near Gothen- burg. 1–1200" to 1-1150". This species occurs as a brownish jelly-like mass on stones. In the gelatinous cells Ehr- enberg observed from one to twenty frustules. Genus DICKIEIA (Berkeley).--Frond subgelatinous, plane, attenuated to- wards the base, containing scattered, navicular, imperfectly silicious frustules. Marine. DICRIETA ulvoides (Berk.). — Frond undivided; valves elliptical. ANIH. xiv. valves elliptic-lanceolate. l. 9; SBD. ii. p. 66, ritain. (xv. 31.) Frond linear or Dickieia is distinguished by its plane frond and scattered frustules. D. pinnata (Ralfs). — Frond divided; ANH, 2nd pl. 54 f. 342. ser, viii. pl. 5. f. 6; SBD. ii. p. 66, pl. 54. f. 343. Britain. Autumn. Divisions of obovate-stipitate; striae obscure, 36 in frond subpinnate; striae obscure, 40 in ‘001"; nodule transverse, Sm. '001"; nodule punctiform, Sm. Genus RHAPHIDOGLCEA (Kütz.).--Frond globose, gelatinous, tender, filled with fusiform bundles of naviculae disposed in radiating threads. Marine. “The principal character of this genus is taken from the amor- phous disposition of the gelatinous substance in which the frustules are immersed. The frustules are mixed together in a disorderly manner in Berkeleya, whilst in Rhaphidogloea they are arranged in fusiform fasciae, confluent by the pointed extremities” (Meneg.). We think this genus might, without inconvenience, be united with Berkeleya. RHAPHIDOGLOEA medusina (K.). — Minute; fascicles lanceolate-acuminate, in irregular, reticulately-branched, con- tinuous, radiating threads ; naviculae lanceolate. KB. p. 110, pl. 22. f. 7. Me- diterranean Sea. 1-600". R. manipulata (K.). — Globose, pisi- form; rays of fascicles reticulated, not interrupted; naviculae linear-lanceolate, obtuse. KB. p. 110, pl. 22, f. 5. Europe. I-700' to 1-290". * R. interrupta (K). — Pisiform, with slender rays of fascicles, interrupted in a joint-like manner, with gradually ta- pering branches; naviculae linear, slightly attenuated at the truncate apices. ICB. p. 110, pl. 22. f. 6. Adriatic Sea. 1-300". R. micans (Lyngb., K.). --Subglobose; rays of the larger fascicles irregular, obsolete ; naviculae linear-lanceolate, Subulate, rather acute, elongated. KB. p. 110, pl. 22. f. 8. = Schizomema micans, AD. p. 17; Naunema micans, E Inf. ; Frustulia costata, Lobarzeuskyinlinnaea, 1840, pl. 5. f. 1. Europe. Mr. Tuffen West informs us that, from careful obser- vation of living specimens, he is satisfied that this species is identical with Am- phipleura pellucida, in which opinion the late Prof. Smith fully concurred, 926- SYSTEMATIC ELISTORY OF TECE INFUSORLA. Genus BERKELEYA (Grev.). — Frustules naviculoid, linear-lanceolate, included within tubular submembranaceous filaments, which are free at their extremities, but immersed below in a more or less definite tubercle. Marine. Berkeleya differs from Schizomema in having the base of the fila- ments immersed in an orbicular gelatinous tubercle. This tubercle is at first firm and definite, but finally, especially when growing on rocks, becomes enlarged, soft, and often somewhat indefinite. BERKELEYA fragilis (Grev.). — Fila- ments subsimple, minute ; frustules crowded, slender, lanceolate or linear- lanceolate, with the striae obsolete or wanting. GBF. p. 416; SD. ii. p. 67, pl. 54 f. 344. On Zostera, Algæ, and rocks. Europe. The gelatinous tubercle during growth becomes attenuated and more diffused, and sometimes forms an indefinite slimy covering about the base of the filaments. In a dried state this species acquires a metallic lustre, B. Adriatica (K.).-Filaments branch- ed; branches distinctly subdivided; frus- tules narrowly linear-lanceolate, rather obtuse. KB. p. 109, pl. 22. f. 4. Adriatic Sea, (XIV. 34, 35.) 1-300". Scarcely distinct from B. fragilis. Genus COLLETONEMA (Bréb.).—Frustules naviculoid, arranged in series within a tender, simple or divided, filiform or globose frond. Aquatic. According to Professor Smith, “the freshwater habitat and slightly divided frond distinguish the present genus from Schizonema; and [he adds] the frustules are also more firmly siliceous than those of that genus, and the character of the valve can usually be well seen after maceration in acid.” Professor Kützing describes Colletonema as having a filiform frond composed of Series of naviculae held together and enveloped by an amorphous gelatinous mucus, without an exterior gelatinous tube. We doubt if any of the above characters sufficiently distinguish Colletonema from the allied genera, because they are either inadmissible in generic definitions, uncertain, or not peculiar to the genus. The absence of an external tube, if constant, would be of generic importance ; but we sometimes find the frustule contained within an evident (although tender and evanescent) tube, whilst in Micromega, on the other hand, the presence of an external tube is sometimes doubtful. The fronds are exceedingly thin and tender, readily permitting the escape of their frustules, which may then be mistaken for species belonging to other genera; thus Professor Smith remarks that it is possible that Pinnularia radiosa may be merely the free state of Colletonema neglectum, and Navicula crassimervia the same condition of C. vulgare. COLLETONEMA eacimium (Thw., K.). — Frond filiform ; frustule in lateral view, sigmoid, striated. K.A. p. 891; S.D. ii. p. 69, pl. 56. f. 350. = Schizomema eacimium, *Nº. 1848; Gloionema sig- amoides, E.B. 1845; Encyonema sigmoides, KA. p. 62. P. Britain, Demerara P Valves linear, sigmoid from the ends sloping in opposite directions; striae 56 in 001". (VIII. 43.) C. viridulum (Bréb.).—Frond filiform; naviculae spirally and densely arranged; valves lanceolate, rather obtuse, smooth; front view linear-oblong, slightly and gradually attenuated towards the trun- cate apices. KA, p. 105. France. C. lacustre (Ag., K.).--Frond filiform, simple or Subramose, finer than a hair, enclosed in an imperceptible membrane; naviculae elliptic or parallelogramic, in a single or double series. KSA, p. 105. = Schizomema lacustre, Ag CD. p. 18. Sweden. Tufts erect, brownish yellow; in size and habit like Sphacelaria cirrosa. C. vulgare. (Thw.). — Frond filiform, simple or divided, gradually tapering, containing one or two regular rows of frustules; valves oblong-lanceolate, with slightly contracted, obtuse ends. S.D. ii. p. 70, pl. 56. f. 351. = Schizomema vulgare, ANH. 1848. England and France. Less common, according to Professor Smith, than the next species. Striae 72 in 001". C. neglectum (Thw.).--Frond slightly divided, obtuse, containing numerous and closely packed frustules; valves lan- ceolate, with obtuse ends. SBD. ii. p. 70, pl. 56. f. 352. = Schizonema neg- lectum, ANH, 1848. England. C. Subcohaerens (Thw.).--Frond glo- bose, gelatinous, pervaded by irregular rows of frustules; valves oblong, with OF THE NAVICULEAE. 927 rounded apices, SD. ii. p. 70, pl. 56. f. 353. Dorset. Striae 28 in .001". In the character of its frond this species somewhat agrees with Rhaphidogloea; but the frustules are arranged in series, not in fascicles, as in that genus. gramic, smooth; valves acutely lanceo- late. KSA, p. 105. = Naunema am- phioxys, EA, pl. 3. 2. f. 5, Mexico. (XII. 55–57.) C. P Americanum (E., K.)—Naviculae striated, large, linear, with subacute apices, densely arranged within branched tubes. K.A. p. 105. = Naunema Ameri- canum, E.B. 1845. p. 79, River Hudson. Striae 18 in 1-1200". Doubtful Species. C. Pamphioxys (E., K.).-Known only from fragments. Naviculae parallelo- Genus SCHIZONEMA (Ag., Kütz.) (Monema, Grev. ; Monnema, Meneg. ; Naunema, Ehr.), Frustules naviculoid, arranged confusedly or in a single file, within a capillary, submembranaceous, single-tubed, more or less branched frond, of nearly equal diameter throughout. This genus, constituted by Agardh, has been repeatedly divided and reunited, and the generic names altered and transposed in an arbitrary manner without regard to priority. Dr. Greville founded Monema for the species with single tubes, retaining those with compound fronds in Schizonema. This division seems judicious, and indeed has been adopted by nearly every succeeding writer, although Greville's names have been disused or differently applied. Agardh recognized the distinctions, but retained Schizomema for the species with a frond of simple structure, and founded Micromega for the species having a compound structure. As this arrangement has been followed by Kützing, and acquiesced in by Greville, we use it here. There is the greatest difference, however, in the distribution of the species, even amongst those who admit both genera. “This discordance of opinion,” observes Meneghini, “as to the arrangement of some species in one or other of the two genera, which, independently of their names, appear so distinct and so clearly defined, arises from the great difficulty of discerning the parallel tubes including the particular series of naviculae. In some species the wall of the external tube is clearly distinct, and the naviculae are confused within ; but in some others it seems as if, instead of a tube, there were a mucous mass in which the naviculae are im– mersed.” Professor Smith considered that “this great diversity of opinion owes its origin to the variableness and inconstancy of the characters adopted by the writers who arranged the species under two genera. The presence of only one or of many files of frustules is certainly, to some extent, dependent upon the stage of growth of the specimen examined; and the appearance of secondary tubes within the general mucus-envelope is more or less apparent in different portions of the same frond, or according as it is examined in the fresh or dry state. A very extensive comparison of specimens leads me to believe that in every case where the development of the frond is much advanced, as in the older or basal portions, numerous files of frustules may be observed.” For these reasons Professor Smith united the genera and divided Schizonema into two sections, “the first having frustules firmly siliceous, and fronds, in consequence, Somewhat setaceous and robust; and the second including those species whose frustules are flaccid and delicate in character.” As we consider the diagnostic differences sufficient, we have retained, with slight alteration, the arrangement of the Species in these genera given by Meneghini in his memoir upon the Diatomaceae. The frond in Schizonema is generally densely tufted and more sparingly branched than in Micromega. It is always single-tubed, and usually very slender, with even, parallel margins. The ends of the filaments, which in the early state are often empty, finally become ruptured and permit the escape of the naviculae. In a recent state these characters will generally suffice to deter- 928 SYSTEMATIC HISTORY OF THE INFUSORIA. mine the genus, even before minute microscopic examination. We place more reliance upon colour in the discrimination of species than some Writers allow. The colour for the most part depends upon the contents of the frus- tules, and, according to our experience, is subject to little variation, except in old specimens rendered unfit for comparison by the escape of the naviculae. * Central module transversely dilated. SCHIZONEMA cruciger (S.).-Filaments much divided ; maviculae crowded ; valves lanceolate, acute, striated; me- dian module transversely dilated into a stauros. SD. ii. p. 74, pl. 56. f. 354. Britain. Striae distinct, 40 in 001". 2 * Central nodule punctiform, sometimes obsolete. - S. Grevillii (Ag). — Frond membra- naceous, much branched, level-topped; naviculae in front view subquadrate ; valves oblong-lanceolate, with 60 striae in .001". Ag CD. p. 19; SD. ii. p. 77, l. 58. f. 364. = Monnema Grevillii, Meneg, ; S. Quadripunctatum, Harv. On rocks and mud. Fronds densely tufted, brown, turning to a dirty verdigris-green when dried, and adhering imperfectly to paper. Naviculae large, crowded at base, in a single file near the extremities. S. quadripunctatum of British writers is an old state, and turns of a rusty colour in drying. 1–576". S. crinoideum (Harv.). — Filaments very slender, achromatic, sparingly branched, densely woven into a pale- green or brownish stratum; naviculae very minute, disposed in an irregular loose series. Harv. Manual, p. 214. = S. tenellum, KB. p. 111, pl. 23. f. 8; Mon- nema quadripunctatum, Meneg. Europe. Filaments exceedingly slender, with long, simple, flexuose branches. Brown when recent, olive-green and glossy when dry. 1-1386". S. Dillwyni (Ag). — Frond densely tufted, rich brown, very slender; navi- culae minute; valves lanceolate-acute, smooth. SD. ii. p. 77, pl. 58. f. 366, = Monema Dillwynii, GCF, pl. 297. Rocks, mud, and Algae. Naviculae imper- fectly silicious, more or less crowded, especially near the extremities; fronds turning deep green on immersion in fresh water, and quickly acquiring an offensive smell; generally glossy when dried. 1-1000". S. implicatum (Harv.). —Frond capil- lary, densely tufted, much branched, curled, and entangled; naviculae very minute, irregularly crowded; valves lan- ceolate, rather obtuse. SD, ii. p. 78, pl. 59. f. 367. On mud in sheltered places. Tufts of a duller brown than S. Dillwynii, gradually turning in fresh water to a dark olive-green, not quickly becoming offensive. Frustules in form and size similar to those of S. rutilans. S. dubium (Harv.). — Resembles S. Dillwynī; but the long branches, naked below, are furnished towards their sum- mits with numerous curled ramuli. Harv. Manual, p. 212. = S. Dillwyni 6, KA. p. 101. ocks, &c. Tufts unequal- topped; apices of ramuli acute; naviculae veg minute and densely packed. . virescens (Harv.). — Fronds very slender, densely tufted, tenacious, very much branched from the base; ramuli numerous, curled, upper ones longest, swelling towards the tips, which are dark-coloured and end in a sudden point; naviculae minute. Harv. Manual, ; 212. North Devon. Tufts dense, rownish olive, not much altered in drying. Under the microscope it has much the appearance of S. Dillwynī; but the thickened, dark-coloured tips are remarkable. S. rutilans (Trentepohl, Ag).--Demsely tufted; filaments elongated, subsimple, brownish and empty at base, hyaline and filled with crowded linear-oblong frustules at the apex; when dry, shiming and reddish. Ag CD. p. 18; KB. p. 112, * 23. f. 6. 1, 2. = Monnema rutilans, Meneg, “It differs from S. Dillwynü by its more varnish-like lustre, reddish colour when dry, and finer and more simple filament” (Ag). S. Hoffmannii (Ag). — Filaments tufted, subsimple, arachnoid, when dry shining with a reddish lustre; naviculae Small, Smooth, crowded; valves lanceo- late. = S. rutilans, var. Hoffmanni, K.B. #. 23. f. 10; Monnema Hoffmanni, Meneg. Europe, Aberdeen. (x. 207.) Professor Kützing makes this form a variety of S. rutilans; but Meneghini observes that they differ in external characters and in the dimensions and shape of the navi- culae. I-1080” to 1-960". S. Balticum (E.).--Naviculae striated, slender, linear-lanceolate, in front view truncate, in lateral view subacute, dense, crowded in the intricately branched fila- ments, E Inf. p. 236, pl. 20. f. 15. =S. of THE NAVICULEAE. 929 7'utilans, var. viride ; Monnema octo- carpoides, Meneg. Europe, England. 1–1200". S. Ehrenbergii (K.).--Frond parasitic, lubricous, tufted, green, branched; branches crystal-hyaline, soft, obtuse at the apex; naviculae (in dried specimens) inconspicuous, tender, arranged in obso- lete series, oblong in one view, truncate in the other, with rounded ends. KB. p. 113, pl. 23.f. 9.5-Maunema Dillwynii, E Inf. p. 235, pl. 20. f. 13. Europe. 1–1320". S. Spadiceum (Grev.). —IFilaments ca- pillary, tufted, much branched, of a red- dish olive-green colour; ramuli much divaricated, ultimate ones patent; navi- culae linear-oblong, elongated. Grev. in Hooker's Br. Fl. p. 412. Scotland. Fronds often with a faint metallic lustre when dry. Filaments very slender, and of nearly equal thickness throughout. S. Adriaticum (Ag).-Filaments finer than a hair, elongated, subsimple, when dried of an opaque olive green; naviculae narrow, lanceolate, AgCD. p. 21. Venice. S. confertum (S.). — Frond filiform, sparingly divided throughout ; naviculae exceedingly crowded; valves shortly lan- ceolate, acute, with indistinct, marginal striae. SD. ii. p. 75, pl. 57. f. 359. Aber- deen. '0008" to .0011". S. lutescens (K.).—Tufted, when dry of a reddish colour, glossy; filaments Subsimple, capillary, coloured and empty at base, hyaline and filled with navi- culae at the apex; naviculae oblong-lan- ceolate, obtuse. ICB. p. 112. Europe. 1–1200". S. flavum (K.).—Frond tufted, lubri- cous, yellow; filaments tenacious, cry- stalline, achromatic, straight, fastigiate, branched; branches attenuated at the apex, erect; naviculae scattered or inter- Tuptedly aggregate, oblong or linear, with obtuse or truncate ends, KSA, p. 101. France. Naviculae rather broad. S. luteum (K.).—Frond tufted, yellow; filaments achromatic, capillary, Subfra- gile, nearly equal throughout; naviculae linear or acicular, inconspicuous, alter- mately loosely and densely compacted. KA, p. 102, France, 1-1080". S. sordidum (K.). — Fronds minute, tufted, parasitic, dull brownish-grey; filaments subdichotomous, achromatic, with equal branches; naviculae slender, truncate; valves lanceolate-linear, rather obtuse. KB. p. 113, pl. 24. f. 1. = Mon- nema sordidum, Meneg. On Zostera. Europe. 1-1440" to 1-1200". S. tenue (Ag). —Filaments arachnoid, irregularly branched; naviculae elliptic, disposed almost in a single series. RB. º 112, pl. 23. f. 2. = Monnema tenue, Meneg. Adriatic Sea. When dried it appears as a sulphur-green stain; fila- ments inconspicuous from their tenuity, Ag, Professor Kützing refers Agardh's species to his S. mucosum, but we doubt their identity. S. simplex: (E., K.). — Frond subsoli- tary; naviculae smooth, oblong, with rounded ends, in a simple series within flexible filiform tubes. KA. p. 99. = Naunema simplex, E Inf. p. 234, pl. 20. f. 12; , Monnema inconspicuum, Meneg. p. 436? Adriatic Sea. I-1150" to 1-570". S. Lenormandi (K.).—Parasitic, short, Subsimple, in woolly tufts; filaments achromatic, for the most part with empty apices; naviculae quadrangular, arranged in a simple series. KA, p. 99. = Mon- nema Lenormandi, Meneg, France. Allied to S. tenue, but with smaller frustules,. Meneg, S. tenuissimum (K.). — Filaments Crisped, Subramose, hyaline, very slen- der, densely interwoven into a compact, brown mucous stratum; naviculae very minute, linear, truncate, in obsolete series. RB. p. 111, pl. 23. f. 111, 1–3. = Monnema tenuissimum, Meneg. Adri- atic Sea. S. Striolatum (K.). — Fronds tufted, j Crisped, capillary, fastigiately ranched; filaments transversely stri- ated, nearly empty at the base, filled at the apex, crystal-hyaline throughout; naviculae, oblong, obtuse in the lateral, truncate in the front view. 8 clavigerum, branches irregular, covered with obovate or clavate ramuli, KB. p. 114, pl. 26. f. 2. = Monnema striolatum, Meneg, Ger- many and France, Genus MICROMEGA (Ag., Kütz.) (=Schizonema, Meneg.). — Frustules naviculoid, arranged in two or more longitudinal series within a gelatinous, filiform or setaceous frond, or contained within tubes united longitudinally into a compound, often membranaceous frond. Micromega is distinguished from Schizonema by its compound frond. We believe that under one genus have been comprised species belonging to two distinct types, which perhaps ought to form two genera. & 3 O 930 SYSTEMATIC EIISTORY OF TECE INFUSORIA. The first contains species having series or files of naviculae surrounded by a gelatinous covering, and by their union forming a compound, generally stout frond, externally furnished with a common epidermis. Type, M. Smithii. The species of this section are highly gelatinous, and consequently adhere firmly to paper in drying, are frequently of considerable thickness at the base, and often have their extremities lobed, proliferous, or penicillate. The margins, especially in old specimens, are generally more or less rough or irregular. The frustules are released by the destruction of the gelatine, and not by injury to the extremities, as in the case of tubular fronds. Each series of frustules seems to have its own proper gelatinous covering, and the junctions are marked by faint longitudinal lines; but these, which have been Supposed to indicate tubes, are often very indistinct; hence arises much of the difficulty in determining their proper genus. The second section contains species which have a strictly compound frond of distinct tubes longitudinally connected, each tube similar to a frond of Schizonema. The fronds are generally membranaceous, and adhere imper- fectly to paper; the frustules, arranged more or less irregularly in their tubes, are liable to escape from an opening at any part. Type, M. cornoides. If these sections, as is probable, should hereafter rank as genera, the three allied genera might be named and characterized as follows:— 1. MoWNEMA (Grev., Meneg.) (=Schizonema, Ag., Kütz.).--Frond tubular, single-tubed. . • . 2. SCHIZONEMA (Ag., Grev., Meneg.) (=Micromega, Ag., Kütz.). — Fron gelatinous, not tubular. 3. MICROMEGA (Ag., Ehr.).--Frond tubular, two- or more tubed. The branching in Micromega, especially in the species belonging to the first Section, results from the separation of the series of naviculae, and is not the branching of a tube, as in Schizonema. * Frond gelatinous, containing longitu- dinal Series of naviculae. MICROMEGA Smithi (Ag). — Frond robust, Setaceous, gelatinous, firm, simple below, much branched above, frustules in longitudinal series; valves lanceolate, acute; striae 40 in 001". = Schizomema Smithii, AD. p. 18; SD. ii. p. 76, pl. 57. f. 362. Itocks and Algae. Common. Fronds usually scattered, pale-yellowish olive; naviculae disposed in subdistant files within the colourless jelly of the frond, 1–600". M. helminthosum (Chauv.). —Fronds robust, Setaceous, gelatinous, lubricous, tufted, much branched, with acute apices; naviculae in longitudinal series; valves elliptic-oblong, with rounded ends; striae 48 in 001". = Schizonema helminthosum, A.D. p. 20; KA, p. 103; SD. ii. p. 74, p! 56. f. 355; S. Arbuscula, K.B. pl. 27. .1; Waunema Arbuscula, EInf.; W. fru- ticulosum, K.A. p. 104. Rocks. Colour olive-brown, becoming greenish-grey and without gloss in drying. 1-504". It may be known from M. Smithii by its more tufted, often gregarious, lubricous --- and darker-coloured fronds, and its larger and very obtuse valves. M. torquatum (Harv.).--Frond robust, simple below, much divided above, ulti- mate divisions much twisted; naviculae in longitudinal files; valves oblong-lan- ceolate; striae 40 in '001". = Schizomema torquatum, Me. ; SD. ii. p. 76, pl. 57. f 361; S. Smithii, 8. torquatum, Harv. Manual, p. 211; Micromega setaceum, y. torquatum, K.A. p. 107. Britain. In size and colour it agrees with M. Smithii, but is remarkable for having its branches curled; its naviculae are more distinctly in chains, shorter and broader in propor- tion to their length than in that species. I-720" to I-6907. M. Polyclados (K.).--Frond setaceous, dichotomously branched; branches elon- gated, slender, rather rigid; naviculae (membranaceous P), flaccid, in distinct tubes. KB, p. 118, pl. 28. f. 1. Europe. Spermatia diº 1–1086'' to 1-960". Meneghini unites this form with M. tor- quatum. M. nebulosum (Me.) – Frond slightly greenish, cloudy, subachromatic, forming an intricate mucous stratum; tubes gela- tinous, achromatic, obsolete; naviculae OR TELE NAWICULEAE, 931 slender-lanceolate, rather obtuse, loosely Scattered, = Schizomema nebulosum, K.A. p.99. IDalmatia. “Kützing is right in remarking that my Schizomema nebulosum corresponds to M. torquatum in the form and dimensions of the naviculae. Al- though when dried upon paper it only forms a light cloud, yet, when diligently examined, it proves similar in ramifica- tion to Harvey's species” (Me. p. 445). 1–1080". M. Wyatti (Harv.). — Frond carti- laginous, Setaceous at base, much branched ; , branches capillary, erect, straight, with acute axils, tapering to a fine point; naviculae lanceolate, densely packed in jelly. = Schizomema Wyattà, Harv. Mantial, p. 211, England. Forms globose tufts. This species comes near S. Smithii, but is much more slender, and opens more readily and with greater elasticity after being dried. M. molle (S.). — Frond gelatinous, simple below, membranous by cohesion above; margin much divided, into acute Segments; naviculae in crowded files; valves lanceolate, acute, with 48 striae in 001". = Schizonema molle, S.D. ii. p. 77, Ol. 58. f. 365. Britain. 0012" to .0015". !he naviculae are very like those of M. helminthosum, but the form and structure of the frond are altogether different. The frond is soft and flaccid, but the naviculae are firmly silicious. M. divergens (S.).--Frond simple be- low, sparingly divided or by cohesion irregularly smbmembranous above; valves oblong-lanceolate, with 42 striae in 001". = Schizomema divergens, SD. ii. p. 76, pl. 57. f. 363. Larne Lough. 0013" to -0018". Remarkable for the diffused arrangement of the #. divisions. The species is closely allied to M. Smithi; and M. torquatum. M. sirospermum (K.). — Frond rather stout, rigid, olive, cartilaginous, much branched; branches unequal, irregular, curved, setaceous; naviculae lanceolate, in dense series, often inflated into glo- bose; spermatia concatenate. KA. p. 109. = Schizomemasirospermum, Me, England. Perhaps a state of M. Smithii. 1-720". M. Setaceum (K.). — Frond setaceous, olive, rigid, subdichotomous; branches, lateral and terminal, abbreviated, spine- like; naviculae in crowded series; valves lanceolate, acute. KB. p. 117, pl. 25. f. 2, 3. = Schizomema setaceum, Me. Adri- atic Sea, -1-720" to 1-696". Spermatia elliptic-globose. M. corymbosum (Ag., K.). — Frond arborescent, rather stout at the base, firm, rigid, yellowish, much branched; branches Setaceous, rigid, here and there corymbose; naviculae in distinct, close series; valves elliptic-lanceolate. KB. p. 117, pl. 27. f. 9. = Schizonema corym- bosum, AD. p. 21. England, 1-960". M. hydruroides (K.).--Fronds greenish or brown, ultra-Setaceous, rigid; branches elongated; ramulifasciculated, capillary; naviculae in close series, minute, rather broad ; valves with rounded ends. = Schizonema hydruroides, KB. p. 114, pl. 26. f. 7. Heligoland, 1-1380". M. Bryopsis (K.).--Frond green, Seta- ceous, rigid, branched; branches scat- tered, Superior Ones patent, obtuse; na- Viculae oblong, truncate in front, and rounded in lateral view. = Schizomema Bryopsis, K.B. p. 114, pl. 26. f. 8. Heli- goland, 1-680". M. trichocephalum (K.).--Frond green- ish-yellow, ultra-setaceous, rigid, tufted, sparingly branched; inferior branches Scattered, simple; terminal ones crowded, curved, subulate, capitate; naviculae in very close series, minute. = Schizomema trichocephalum, KB. p. 114, pl. 27. f. 3. Heligoland. 1-1440". M. capitatum (K.).-Frond pale green, Setaceous; branches elongated, slender, virgate, with a corymbose, capitate, acute apex; naviculae in distinct series, minute; valves lanceolate. = Schizonema capita- tum, K.B. p. 114, pl. 27. f. 4. Heligoland. I-1200". - M. mya.acanthum (K.). — Less stout than M. corymbosum, gelatino-cartila- ginous, pale brown; branches diverging, attenuated at the base, digito-multifid at the apex; divisions patent, acute; Series of lanceolate naviculae at base few and loose, above more numerous, crowded at the apex, KB. p. 117, pl. 24. f. 8. = Schizomema myocacánthum, Me. Adriatic Sea. M. aureum (K.). — Frond arborescent, Setaceous at base, rather rigid, ochra- ceous-yellow, much branched, fastigiate; branches capillary, pale, mucous; series of naviculae and tubes distinct, crowded; valves lanceolate. KB. p. 117, pl. 27. f. 8. = Schizomema awrewm, Me, Sidmouth, 1-960". M. obtusum (Grev.). — Frond robust, Setaceous, elastic, firm, irregularly dicho- tomous, with rounded axils and obtuse apices; naviculae minute, crowded in irregular files; valves elliptic-oblong. = Schizomema obtusum, Grew BF. vi. pl. 302; S.D. ii. p. 78, pl. 58. f. 368. Britain. The naviculae are excessively crowded, and we are uncertain whether this spe- 3 O 2 932 SYSTEMIATIC EIISTORY OF TEIE INFUSORTA, cies ought not rather to be placed in Schizomema. “Frond thicker than a hog's bristle, and nearly of equal diameter throughout; colour brownish-yellow, be- coming yellowish-green in dying. handsome and distinct species, well marked by its roundish axils and obtuse apices” (Harvey). M. Blytti (Ag). —Frond elongated, filiform, many times irregularly âcho. tomous, with rounded axils, cylindrical, not attenuated; naviculae in numerous parallel series. AD. p. 23. = Schizomema I}lyttii, Me, Norway. An elegant and remarkable species; fronds erect. M. mesogloeoides (K.). — Frond stout, very gelatinous, greenish, irregularly branched; branches dense, numerous, unequal; ramuli incrassated at the apex, patent; naviculae rather irregularly ag- gregated, dense; valves with attenuated apices. = Schizomema mesogloeoides, IKA. p. 103. Aberdeen. 1-600". M. humile (K.).--Frond parasitic, very short, tufted, erect, Subramose; branches with obtuse, hyaline empty apices; naviculae acute, linear-lanceolate, ar- ranged in two to four series. = Schizo- nema humile, KB. p. 111, pl. 23. f. 7. Adriatic Sea. Naviculae in front view linear, truncate. 1–1200". M. papillosum (Me.). — Frond para- sitic, Small, very mucous, green; fila- ments ultra-setaceous, subsimple or fur- mished with acute spiniform ramuli, everywhere covered with very minute, regularly disposed papillae; valves nar- row-elliptic, rather obtuse. = Schizomema papillosum, Me. p. 452. Dalmatia. Na- viculae in series, four times as long as broad, in front view slightly elliptic, with truncate ends. The papillae appear hemispherical or slightly conical, and are arranged in quincunx, Me. M. Stalianum (Me., K.).--Fronds pa- rasitic, gelatinous, green or greenish- brown; filaments Setaceous, elongated, irregularly branched; branches diverg- ing, short; naviculae in series, six times as long as broad; valves elongated- elliptic, obtuse. K.A. p. 106, = Schizo- nema Stalianum, Me. p. 452, Dalmatia. Is very mucous and adheres strongly to paper; naviculae in front view exactly linear. 1-420" to 1-360". M. Corinald (Me.).—Frond parasitic, Small, green; filaments subsimple, Se- taceous; frustules minute, five times as long as broad; valves narrow-ellip- tic. = Schizonema Corinaldi, Me. p. 453. Marseilles. Naviculae in series, in front yiew exactly linear. The threads, slightly mucous, are usually simple; the few ra- mifications are short and divaricate, Me, M. fastigatum (K.).--Frond setaceous, olivaceous, much branched; ultimate branches subcorymbose, with lanceolate- acuminate apices; naviculae minute, ob- long, obtuse, in loose series. K.A. p. 108. Torquay. Secondary tubes obsolete. , M. medusinum (K.). — Frond cartila- gino-gelatinous, hyaline, brown, turgid at the base, separated at the apex into Fº fibres; series of naviculae oosely entangled, intermixed with flex- uose longitudinal fibres. KB. p. 118, pl. 25. f. 6. = Schizonema medusinum, Me, Adriatic Sea. Valves lanceolate. M. hyalinum (K.).--Frond colourless, hyaline, gelatino-Cartilaginous, soft, Seta- ceous at base, much branched; branches attenuated, capillary, empty at the apex; series of naviculae few, loose, intermixed with a few fibres; naviculae minute; valves oblong-lanceolate, obtuse. KB. p. 117, pl. 24. f. 6. = Schizonema hyalinum, Me. Adriatic Sea. Naviculae 1-960" to 1–780"; in front view truncate. M. tenellum (K.). — Frond colourless, hyaline, gelatino-cartilaginous, Setaceous, branched, subdichotomous ; branches delicate and empty at the apex; series of slender naviculae and internal tubes distinct. KB. p. 117, pl. 24. f. 7. = Schi- zonema tenellum, Me, Adriatic Sea. M. Hyalopus (K.). —Frond colourless and hyaline at the base, above greenish, narrow, much branched; branches fas- tigiate, subacute, full to the apices; lower series of naviculae lax, superior crowded; valves lanceolate. KB. p. 117, pl. 25. f. 5. = Schizomema Hyalopus, Me. Adri- atic and French Seas, Jersey. Internal tubes obsolete; naviculae in front view oblong, truncate; spermatia immersed, globose. M. laciniatum (Harvey). — Frond ro- bust, Setaceous below, incrassated above, very tender and gelatinous, cleft into numerous tapering branches; naviculae very minute, in close files; valves ellip- tic-lanceolate, obtuse. = Schizonema laci- niatum, Hary. Man. p. 210; SD. ii. p. 79, pl. 59. f. 371; S. scoparium, KB. p. 114, pl. 27. f. 7. Europe. Frond cleft above into numerous irregular jagged branches, 1-600". M. parasiticum (Griff, K.). —Frond gelatinous, capillary, tufted, much and intricately branched from the base; branches flexuose, with rounded axils; frustules crowded in distinct files; valves lanceolate, acute. KB. p. 116, pl. 27. f. 2. = Schözonema parasiticum, Harv. Man. OF TEIE NAWICULEAE. 933 p. 213; SD. ii. p. 79, pl. 59. f. 371. Eu- rope. Colour pale yellowish, sometimes brownish. Naviculae 1-1380". M. investens (Montagne). — Fronds parasitic, minute, lubricous, brown, opaque, fasciculated; filaments dilated at the base, diffusely ramose; branches anastomosing; naviculae large, in one or two series. = Schizomema investens, Mont. Annales des Sci. Nat. 1850, p. 308. Guiana. Naviculae with two nuclei. M. mucosum (K.).—Frond soft, highly mucous; filaments contiguous and con- fluent; branches irregular; naviculae in few files; valves elliptic-oblong, with rounded ends, delicately striated. = Schi- zonema mucosum, KB. p. 115, pl. 26. f. 9; SD. ii. p. 75, pl. 57. f. 360. Adriatic Sea, Bngland. This species can scarcely be the Schizonema tenue of Agardh, as Kützing has supposed. M. parvum (Me.).—Frond olive-green, mucous; filaments hyaline, simple (?), much entangled and curved ; naviculae in distinct, loose, oblique or straight Series; valves lanceolate. = Schizomema pareum, Me KA, p. 100. Venice, Cay- enme. Naviculae in front view linear, rectangular. 1-1200". M. Meneghinii. — Frond green, very gelatinous; filaments very hyaline, lu- bricous, fastigiately divided and laci- niated; naviculae lanceolate, in loose, rather distant series. = Schizomema bom- bycinum, Me KA. p. 100. Venice. 1–1200". M. Kützingii. — Fronds tufted, intri- cate, much branched; filaments hyaline, with rather acute apices; naviculae in distinct series; valves lanceolate, acute. = Schizomema floccosum, KB. p. 113, pl. 24. f. 3. Germany. Naviculae in front view oblong, truncate. 1-600". M. crispum (Mont.). — Fronds Small, crisped, capillary, green, branched; fila- ments obtuse, dilated and multifid at the apex; naviculae very minute, much crowded in obsolete series. = Schizomema crispum, K.B. p. 113, pl. 29. f. 71. Auck- land Islands. M. plumosum (K.). — Frond tufted, wavy, rather curled, green, fastigiately branched; filaments densely filled at the ends, dilated, multifid; naviculae distinct, very minute; valves oblong-elliptic, with rounded ends. = Schizomema plumosum, KB. p. 113, pl. 26. f. 1, Europe. Navi- culae in front view oblong, truncate. 1–1440". M. Zanardini (Me.).—Frond very fine, pale green; filaments capillary, gradually separating into corymbose arachnoid branches of one Series; naviculae in loose series, four times as long as broad; valves elliptic. = Schizomema Zanardinii, Me. p. 453. Venice. Naviculae in front view exactly linear. Fronds in globular tufts, which, dried upon paper, form uniform spots, in which the separate threads can only be distinguished by a lens. In its mode of ramification it re- sembles M. flagelliferum, Me. - M. flagelliferum (K.). — Fronds very minute, tufted, parasitic, floccose, capil- lary; branches erect, separated at the apex into flagelliform fibres; series of the very minute naviculae and internal tubes distinct. KB. p. 116, pl. 24. f. 4. = Schizomema flagelliferum, Me. 1-1920" to 1-1560". M. floccosum (K.). — Frond minute, Subcapillary, branched, rather delicate, gelatinous; series of the long, obtuse and truncate naviculae and internal tubes very distinct. KB. p. 116. Adriatic Sea. 1–720". M. intricatum (K.). — Frond delicate, Subgelatinous, nebulose, pallid yellow, irregularly branched; branches patent, upper ones abbreviated; series of navi- culae loose, intermixed with very fine longitudinal fibres; naviculae oblong, obtuse, very minute. KB. p. 116, pl. 26. f. 5. = Schizonema intricatum, Me. Eng- land. I–1440" to 1-680". M. bombycinum (K.):-Frond pale yel- low, contorted, twisted, much branched, capillary; naviculae remotely concate- nate, inconspicuous, and very minute, KB. p. 116, pl. 26. f. 6. = Schizonema bombycinum, Me, Europe, (XIV. 43,44.) M. P. Agardhi (E.). — Naviculae very narrow, acute, arranged , in a simple series within a proper tube; tubes fas- ciculately joined into a filament. = Schi- zonema Agardhi, IE Inf. p. 238, pl. 20. f. 16. North Sea. (x. 208.) Professor Kützing unites this species with M. bom- bycinum; but the frustules are apparently (judging from the respective figures) much larger. M. patens (K.).—Frond minute, para- sitic, floccose-capillary, soft, gelatinous; branches divergent or patent, with ob- tuse apices; series of naviculae and in- termal tubes distinct ; naviculae very minute. KB. p. 116, pl. 24. f. 5. = Schi- zonema patens, Me. 1-2400". M. lineatum (K.).--Frond decumbent, intricate, capillary, olivaceous, tenacious, lubricous, subramose; branches at the apex attenuated, curved, rather obtuse; series of the very minute lanceolate maviculae distinct. KB. p. 116, pl. 23, 934 OF TEIIL INFUSORIA. SYSTEMATIC HISTORY Dal- f. 4. = Schizomema lineatum, Me. matia, 1–1320" to 1-1200". M. gracillimum (S.).--Frond capillary, simple below, sparingly branched and submembranous towards the apices; na- viculae crowded in irregular files; valves lanceolate, acute. = Schizomema gracilli- mum, SD. ii. p. 79, pl. 59. f. 372, Tor- quay. 0009". M. Illyricum (K.).--Fronds forming a dull-, obscure-green, mucous, intricate stratum; filaments very fine, simple (?), soft, hyaline; naviculae acuminate, lan- ceolate, in dense series, indistinct when dried. = Schizonema Illyricum, KB. p. 111, pl. 22. f. 3. Trieste, 1-1680" to 1-1440". M. minutum (K.). — Frond parasitic, very short, fine, decumbent, subramose; branches tapering to acute apices; navi- culae acute, lanceolate, in few (2 to 4 series. = Schizomema minutum, KB. p. 111, 1, 23. f. 5. Adriatic Sea. Naviculae in front view linear, 1-1176". 2 * Frond composed of tubes longitudi- mally connected. M. comoides (Grev.).-Filaments dirty brown, coarse, membranaceous, elongated, twisted, composed of parallel tubes; frustules crowded; valves oblong-lan- ceolate; striae 48 in 001". = Schizomema comoides, Grew. (Scarcely of Agardh, certainly not the Conferva comoides of Dillwyn); Hook. Br. F. p. 413; SD. ii. p. 75,# 57. f. 358; Schizomema araneo- Stºm, . p. 113, pl. 25. f. 9. Flat rocks, often in vast quantities. It is very re- markable that this coarse, dirty-looking species should ever have been confounded with the Conferva comoides, Dillw. The latter, we were assured by Mr. Dillwyn, was totally unlike the present species, and was correctly described by him. Unfortunately Mr. Dillwyn was unable to find an original specimen of his spe- cies, but he believed that a very º, simple-tubed Schizonema, of a bright brown colour, which we once found in outside the Mumble "Lighthouse near Swansea, was the true Conferva comoides. The present species is usually twisted in a rope-like manner, retains its colour in drying, is very opaque, and does not adhere to paper. M. ramosissimum (Ag). —Frond robust, firm, membranaceous, much branched; branches short, swelling upwards; frus- tules minute, densely arranged in distinct, parallel tubes; valves oblong-lanceolate. AD. p. 22. = Schizonema ramosissimom, Harv. Man. p. 210; SD. ii. p. 78, pl. 59. f.369. Europe. Somewhat resembles M. comoides in appearance, but is less elongated and less twisted. Does not adhere to paper. M. apiculatum (Grev., Ag.). — Frond robust, ultra-setaceous, cartilaginous, irregularly dichotomous; branches with clavate ends, terminated by a mucro ; secondary tubes distinct; naviculae mi- nute, crowded; valves lanceolate. AD. p. 22; KB. p. 117, pl. 27. f. 10. = Schi- zonema apiculatum, A.A. p. 11; Harv, Manual, p. 210. Scotland. M. corniculatum (Ag). —Frond very Stout, cartilaginous, erect, rigid, Subdi- chotomous, much branched above; ulti- mate ramuli subulate and spine-like; naviculae slender, lanceolate, contained in distinct secondary tubes. AD. p. 24; KB. p. 118, pl. 28. f. 2. = Schizonema cor- niculatum, Me, Adriatic Sea. Habit of a small Fucus. 1-600". M. penicillatum (Chauv, Ag).--Frond thick and simple at the base, divided at the apex into very numerous, penicillate, fastigiate, capillary branches, AD. p. 23. = Schizomema penicillatum, Chauvin ; M. corniculatum 3, KA, p. 109. France. M. pallidum (Ag). —Frond pulvinate, rigid, Subcartilaginous, stout, much branched; ramuli suberect, abbreviated, obtuse; naviculae minute, in lax series within distinct secondary tubes. AD. p. 23; KB. p. 118, pl. 28. f. 3. = Schizo- nema pallidum, $º. Adriatic Sea. (XIV, 39–42.) Tufts hemispherical, dense; Colour pallid, verging on brown- ish yellow. 1-720" to 1-696". M. chondroides (K.).—Frond minute, cartilaginous, olive-coloured; terminal branches aggregated, clavate, obtuse, here and there with hair-like spines; Series of naviculae and secondary tubes very distinct, crowded; naviculae mem- branous, flaccid, minute. KB. p. 118, pl. 25. f. 8. = Schizonema chondroides, Me, Adriatic Sea. 1-1380" to 1-1320". Sper- e e matia immersed, globose. great abundance in April, on the rocks | M. Spinescens (K.). — Frond dwarfish, Setaceous, slightly dilated upwards; ter- minal ramuli acute, spine-like; series of naviculae and secondary tubes crowded, very distinct; valves lanceolate. KB. p. 118, pl. 27. f. 11. = Schizomema spines- cens, Me, Adriatic Sea. Naviculae in front view oblong, truncate. 1-960" to 1-720". Spermatia internal, globose. M. albicans (K.). — Frond setaceous, whitish or olive-green; branches and ramuli equal in thickness, fasciculated or whorled; naviculae in distinct series, OF TEIE ACTINISCTEAE, 935 lanceolate; secondary tubes distinct. KB. . 118, pl. 27. f. 12. = Schizomema albicans, ſe, Adriatic Sea. 1-1200" to 1-1080". Meneghinidescribes the valves as broadly elliptic. M. Berkeleyi (K.).-Frond tufted, dull olive-brown; filaments setaceous, rather rigid, branched; branches erect, attenu- ated; naviculae large; valves elliptic- oblong, in very distinct secondary tubes. KA, p. 106. Torquay. Naviculae in front view parallelogramic. 1-1080". FAMILY XIX.—ACTINTSCEAE. Individuals silicious, furnished with radiating spines. Marine. The Acti- misceae bear little or no resemblance to the Diatomaceae, and ought to be ex- cluded from them. M. de Brébisson thinks they would be more appropriately placed near the Arcella, Euglypha, or Some allied genus. On the other hand, Professor Bailey would refer them to the Polycystina. Genus ACTINISCUS (Ehr.).-Frustules solid, star-like. Actiniscus differs from Dictyocha and Mesocena in having a solid centre or body from which rays, varying in number and form, diverge. ACTINISCUS Sirius (E.). — Rays 6, acute, winged at the base. EM. pl. 33. 15. f. 1. 1-1150". Alive, Norway; fossil, America. The rays seem to arise from the disc, and not from the margin. A. Pentasterias (E.).-Rays 5, acute, not (or but partially) exserted. EM. l. 35 A. 23. f. 1. 1-1150". Alive, Nº. fossil, Greece and America. A. Tetrasterias (E.).-Rays 4, acute, not (or but partially) exserted. E.M. pl. 18. f. 62. 1-1008". Virginia. The last two forms may be varieties of A. Sirius. A. P. Stella (E.). — Stellate, with 6, marginal, obtuse rays or teeth. = Dicty- ocha, E. 1838. Africa. -- A. P. quinarius (E.).--Stellate, with 5, marginal, obtuse rays or teeth. 1-3120". Fossil. Ægina. A. P. Rota (E.).--Wheel-like, with 10, short, obtuse, spoke-like rays. 1-1920". Oran. A. P. Discus (E.).-Disciform; centre Smooth; rays 8, marginal, not exserted. 1-2304". Oran. According to Ehren- berg, the last four species may belong to Pºiº . P. Lancearius (E.).--Stellate, with 8 exserted, lanceolate rays, and some central shorter ones. 1-240". Fossil, Europe and Genus DICTYOCHA (Ehr.).-Frustules free, spinous, reticulately per- forated ; foramina large. # Foramina, or cells, two or three. DICTYoCHA Ponticulus (E.). — Frus- tules oblong, unarmed, transversely divided into 2 cells. 1-432". Fossil. Bermuda. D. Quadratum (E.).--Subquadrate or oblong, transversely divided into 2 cells, a spine at each end. 1-480". Bermuda, These two forms were first observed and figured by Professor Bailey. . D. Pons (E.).-Roundish, with 2 cells and 4 spines. 1-504". Oran. e D. triacantha (E.).—Triangular, with spinous angles; cells 3, unarmed. Mary- land. D. tripyla (E.). — Roundish, with 4 irregular spines; cells 3, unarmed. 1–492". Oran. D. trifenestra (E.). — Quadrate, 4. spined; cells 3, dentate. Recent and fossil. (xv. 35.) D. Abyssarum (E.).-Frustules trian- gular, with 2 cells; spines 3; 1 cell fur- nished with an internal tooth. EB. 1854, p. 238. Atlantic. 2* Diamond-shaped or quadrate ; 4– Spined; foramina 4 or more. D. Fibula (E.). — Cells 4, unarmed. 1-1150" to 1-560". Recent and fossil. (xv. 34.) - D. Epiodon (E.). — Resembles D. Fibula, but the cells are furnished with a tooth. Recent and fossil. D. abnormis (E.).-Cells 5, unequal, all marginal, 1-1080". Fossil. D. Cruz (E.). — Four unarmed cells round a central one. 1-624". Fossil. D. Staurodon (E.). — Resembles D. Cruac; but each marginal cell bears a tooth. 1-576". Fossil. Virginia. D. mesophthalma (E.). — Resembles the two preceding species; but each mar- 936 SYSTEMATIC ELISTORY OF TETE INFUSORIA. ginal cell has 2 ºpposite teeth, which constrict it. 1-372". Fossil, Sicily. D. bipartita (E.).-Resembles D. Cruac, but has 2 minute, cells in the centre. 1-504". Fossil. Oran and Sicily. D. Superstructa (E.). —Spines 4; cells 9, 4 marginal. 1-600". Fossil. Sicily. 3* Spines 6 (2 wsually longer). D. biternaria (E.).-Cells 6, all mar- ginal, the 3 largest next each other, 1–432". Antarctic Ocean. D. Hewathyra (E.).-Cells 6, 5 mar- § and 1 central. 1-864. Fossil. Sicily. D. Speculum (E.).-Six unarmed cells round a central one. Common, both recent and fossil. 1-860". (XII. 62, 63.) D. gracilis (K.).—Resembles D. Spe- culum; but the spines are elongated and slender. Recent. D. diommata (E.).-Six unarmed cells round 2 central ones, 1–660". Fossil, Virginia. D. aculeata (E.).-Resembles D. Spe- culum; but each marginal cell bears a tooth. Common, both recent and fossil. D. Binoculus (E.). — Resembles D. aculeata, but has 2 minute cells in the centre. 1-444". Fossil. Afgina. D. ubera (E.).-Cells unarmed, 7 mar- ginal and 2 central. 1-600". Maryland. D. triommata (E.). —Cells unarmed, 6 marginal and 3 central. 1-864". Virginia. • D. Haliomma (E.).-Cells 10, 7 mar- ginal and 3 central. 1-840". Oran. D. hemisphaerica (E.).-Hemispherical, 6-spined; 12 cells, in two circles, round a central one; the inferior aperture half closed by 6 marginal teeth. 1-744". Bermuda. D. triommata and D. diom— mata resemble, in their turgid habit, this species. 4* Spines more than 6. D. Septenaria (E.). —Spines 7; cells unarmed, 7 marginal and 1 central, 1-864". Oran. D. Ornamentum (E.).-Resembles D. Septenaria; but each marginal cell bears a tooth. 1-444". Fossil. Sicily. D. heptacanthus (E.).--Spines 7; cells 13, 7 of them marginal. 1-552". Fossil. Greece. D. octonaria (E.).-Habit of D. Orna- mentum, with 8 spines; marginal cells irregular, fewer in number at that part where the spines are increased, and with a very large central cell. 1-1152" ex- clusive of spines. Perhaps a monstrous variety of D. Ornamentum. D. Stauracanthus (E.).—Eight-spined; 4 marginal, dentate cells, round a central one. 1–648". Fossil. America. D. polyactis (E.). —Rays 9 or 10; 10 marginal cells and 1 central, arranged in a reticulate stellate form. In chalk-marl. 5* Pentagonal; angles acute, but not Spymous. D. elegans—Pentagonal, perforated by numerous small cells and 7 central large ones, of which one occupies the centre. 1-912". Fossil. Caltanisetta, Sicily. Doubtful or obscure Species, D. Navicula (E.).-Cells 8; figure ob- long, obtuse, cylindrical, reticular, with a median Septum like a Navicula. Fossil in chalk marl. Ehrenberg's figure re- sembles D. Ponticulus. D. P. splendens (E.).-Oblong, tabular, with dentate apertures (cells), 13 in number. If it be calcareous, it is similar to Coniopelta. D. anacantha (E.). — Resembles D. Speculum, with obsolete spines. EB. 1854, p. 238. North America. Perhaps a variety. D. Erebi (E.).-Resembles D. Specu- lum, with Small, subequal spines; walls of the cells thin. E. l. c. North America. A doubtful species; perhaps a variety. Genus MESOCENA (E.).-Frustules free, each forming a ring, which is mostly margined with spines or teeth. destitute of its central reticulation. MESOCENA heptagona (E.).-Frustules annular, with 7 external teeth. EMI. # 20. 1, f. 49. (XII, 71.) Actiniscus F, . Peru. M. Octogona (E.).-Frustules annular, with 8 external teeth. Peru. As this form differs from M. heptagona merely by its additional tooth, it is probably a variety. Mesocena resembles Dictyocha, but is M. bisocionaria (E.).-Frustules annu- lar, with 8 external teeth, and as many internal ones alternating with them. = M. bioctonaria, KA, p. 142; EM. pl. 35A. 18. f. 10. In Peruvian guano. M. bimonaria (E.).-Frustules annular, with 9 external teeth, and, as many internal ones alternating with them. EM. pl. 35 A. 18. f. 9. In Peruvian AIDDENDA. 937 guano, Probably a variety of the pre- ceding species. M. Circulus (E.).-Cell circular; mar- gin tuberculated. 1-576". EMI. pl. 19. f. 44. In Greek marl. M. Diodom (E.). —In the form of a smooth elliptic ring, armed at each end with a small tooth. 1-396". EM. M. elliptica (E.), — Frustules elliptic, with 4 teeth. 1-624" to 1-456”. EM. pl. 20. 1, f. 44. Fossil. Zante. - M. triangula (E.).-Triangular, with rough sides, and mucronate apices. EMI. pl. 22. f. 41. Fossil, chalk-marl. M. P. Spongiolithis (E.). —An elliptic ring, with 4 slight alternating Swellings. pl. 33. 15. f. 18. Maryland. 1–492". GENERA OF DOUBTFUL POSITION. Genus EUCAMPIA (Ehr.). — Frustules hyaline, imperfectly silicious, cuneate, without terminal puncta, united into a jointed, spiral filament. Marine. This genus, placed by Ehrenberg and Kützing with the Desmidieæ, was judiciously removed by Professor Smith to the Diatomaceæ, with which it agrees in structure and in the colour of internal matter. Professor Smith, however, considered it allied to Meridion; in our opinion it is more nearly related to the Biddulphieae, as shown by the absence of costae and terminal puncta, its dotted valves, and their prominence in the front view. EUCAMPIA Zodiacus (E.).-Frustules, f. 299. Europe. (II, 43.) - in front view, with the junction-margins | E. Britannica (S.).-Frustules cune- deeply sinuated, so as to form foramina ate, not excavated. SD. ii. p. 25, pl. 61. between the joints. E. Leb. Kreide- |f 378. Europe. Stomach of Pectens. thierchen, pl. 4, f, 8; S.D. ii. p. 25, pl. 60. Genus LITHODESMIUM (Ehr.).-Frustules not cellulose, united into a jointed, prismatic wand; valve triangular, with one side plane, and the others undulated. Lithodesmium was placed with the Desmidieæ by Ehrenberg, and with the Diatomaceae by Kützing. Its non-cellulose structure, however, prevents our associating it with the Anguliferae, as proposed by the latter. LITHODESMIUM wrºdulatum (E.). — thierchen, 1840, p. 75, pl. 4. f. 13. Frustules Smooth, veryſº valves | Marine, Cuxhaven. (II, 41, 42.) with obtuse angles. E. Leb. Kreide- Genus MICROTHECA (Ehr.).-Frustules simple, free, compressed, qua- drate. Placed by Ehrenberg and Kützing with the Desmidieæ. We remove . it to the Diatomaceæ, because of its marine habitat and golden colour; little, however, is known about it, and its nature is doubtful. MICROTHECA octoceras (E.). — Cell | colour. E Inf. p. 164, pl. 12, f. 10. quadrate, hyaline, with four spines at Marine, Kiel. (VIII, 31.) each end; internal matter of a golden - ADDENDA TO THE DIATOMACEAE. CYCLOTELLA pertenuis (B.).—Valves | cellulate or punctate; cells radiant. B. minute, slightly convex; surface minutely on Mic. Forms in the Sea of Kamtschatka, The following corrections and addition to CxcLorella are adopted from Professor Arnott's paper in JMS. viii. p. 244, For C. operculata (p. 811), substitute — C. operculata (Ag., Kutz.). --Ends of operculata, E. Fresh water. Europe. frustules undulate; valves with smooth " [Professor Arnott regards Stephano- centre, and close, short marginal striae, pyris Niagarae, and perhaps S. Egyptiacus, KB. p. 50, pl. 1, f. 1 = Frustulia and as identical with C. Astraea.] Cymbella operculata, Ag, ; Pyridicula - 938 SYSTEMATIC EIISTORY OF TEIE INFUSORLA. *. For C. rectangula (p. 811), substitute:– C. Meneghiniana centre and rather coarse marginal striae. (K.). — Front view KB. K. rectangular; valves minute, with smooth Rab D. 50, pl. 30. f. 68, C. rectangula, p. 11. Europe. Fresh water. For C. Dallasiana (p. 813), substitute:– C. Dallasiana (Sm.).-Frustules with flat ends; valves with bullate-rugose centre and coarse marginal striae, SD. ii. p. 87. = C, radiata, Bri. TMS. viii. pl. 6, f. 11. Brackish water, Europe, America. C. minutula (K).-Frustules with flat ends; valves with radiating dots or striae at centre. KB. pl. 2. f. 3. = C. operculata, SD. i. p. 28, pl. 5. f. 48. Eu- rope. (Kützing, however, describes his C. minutula as undulate.) C. Kitzingiana (Th.). — Ends of frus- tules undulate; valves with convex, Smooth centre, and long, coarse mar- ginal striae. SD. i. p. 27, pl. 5. f. 47. Brackish water. Europe. Cocco NEIS Finnica. — On careful ex- amination of several fossil deposits said by Ehrenberg to contain this species, we can find no form resembling the figures in the ‘Microgeologie,” excepting Navicula elliptica. EUPoDISCUS P Peruvianus (Kitton, MS.). —Valve orbicular, finely punc- tated, with two small, roundish sub- Imarginal processes, and a submarginal series of close minute apiculi. Peruvian and Californian guanos. We regard the genus of this Diatom as doubtful. The valve has some resemblance to an Au- liscus; but the puncta are not in flexuose lines. The processes, as seen in front view, are short and subtruncate, and the circle of apiculi which connects them shows an affinity to Cerataulus. The processes of the one valve alternate with those of the other, and are often visible at the same time. E. P. Grevillii (Ralfs, m. sp.), Disc ob- scurely punctate, with (3) clavate intra- marginal processes, and a circlet of spines between the processes and the centre. Monterey. Dr. Greville. The processes, which are rather distant from the mar- gin, resemble those of Aulacodiscus, and the circlet of spines that of Systephania; but the absence of connecting lines re- moves it from the former, and the pre- sence of processes from the latter genus. PODoSIRA P compressa (West).-Frus- tule geminate, free?; polar always shorter than equatorial diameter; valves elliptic, obscurely punctate; puncta scattered; angulum smooth. Creswell Sands, Druridge Bay, Yarmouth Sands. West, TMS. viii. p. 150, pl. 7. f. 11. (VIII. 34.) This form occurs plentifully on the sands; the frustules always occur in pairs. The absence of stipes or any attachment, the compressed valves, and the want of a thickened umbilicus, render its position in the present genus doubtful. EPITHEMIA (Eunotia, E.) Sancti An- toni = E. Beatorum = Denticula P lauta (Bail). — This species has been found by Mr. Kitton in the Monterey-stone and Richmond deposits; in the latter they occur in filaments of 6 and 7 frustules, clearly showing that they are improperly Fº in the present genus, and are pro- ably allied to Denticula. - NAVICULA bullata (Norman, n. sp.).- “Elliptical, extremities slightly pro- duced; striae in a marginal and two central bands; marginal band of un- equal width ; the blank spaces between the granules studded with a line of cir- cular bosses; striae moniliform, 14 in 001". Stomachs of Ascidians, Shark Bay, Australia” (Norman in litt.). N. Sillimanorum (E.).-Inflated at the centre; apices produced, rounded, and constricted; striae radiant, not reaching the median line. EMI. pl. 2. 2. f. 13. = Pinnularia Sillimanorum, E.A. p. 133. New York deposit. This species re- Sembles Gomphonema geminatum, but is distinguished by its less conspicuous striae and equal ends; the figure in EM. º only a fragment. N. Cyprinus (E., K.). —Small; valves oblong, slightly contracted into the very broad obtuse ends; central module ob- long; striae evident. KB. p. 99, pl. 29. f 35. = Pºnnularia Cyprinus, EA, pl.1. 11. f. 7. Chili. N. Revnickeana (Rab.). — Resembles N. cuspidata and N. rostrata; but the capitate ends are more prolonged, and the striae are only 30 in 001". Rab. Algen Sachs, No. 802. Dresden. - AULACODISCUS Sollittianus (Norman, MS.).-‘‘Disc large, hyaline, with six conspicuous processes, distant from mar- ADDIENDA. 939 gin; granules radiating, not reaching the centre, 9 in 001"; smooth round the base of the processes. Deposit from Nottingham, i. Maryland, which seems to be identical with the Bermuda tripoli, and contains several forms pecu- liar to that deposit” (Norman in litt.). A. Barbadensis (Ralfs, n.s.). — Disc large, hyaline, very minutely punctated, with small umbilicus, (3) intramarginal roundish processes, and faint connecting lines. Barbadoes deposit. Distinguished by its very obscure puncta. The rather large processes, when nearly out of focus, appear to have a central dot. TRICERATIUM crematum (Kitton, M.S.). —Sides rounded, margin crenate; gra- nules radiating from the pseudo-module, distinct at the margin, but less con- spicuous as they approach the centre. = iscoplea undulata, EMI. pl. 33. 18. f. 3. Nottingham deposit. The presence of the pseudo-module shows it to be an ally of T. Brightwellii; but the nearly orbicu- lar outline and cremate margin distin- guish it from that species. The frag- ment figured by Ehrenberg we have no doubt is identical with this form. T. Bowerbankiana (Ralfs). — Valves with two concentric circles, radiating lines between the circles, distinctly punc- tated angles, and blank or indistinctly punctated centre. Barbadoes deposit. The large valve has nearly straight sides, and obtuse angles; it is divided into three parts by two suture-like circles, the outer one with a border of bead-like dots, which are most evident nearest the sides; the limes between the circles are abbreviated, only one on each side reach- ing the inner circle. CRASPEDODISCUS Barbadensis (Ralfs, m. S.).-Border very broad, its diameter greater than that of the centre; cellules of centre very minute, those of border larger and arranged in curved, decussat- ing lines. Barbadoes deposit. Disc about the size of C. Coscinodiscus, but with a much smaller centre. It differs from both that species and C. microdiscus in having the cellules of the border in curved series. Substitute the following descriptions for the notices of CRASPEDODISCUS Stella and C. Franklini at p. 832:— C.? Stella (E.).-Valves hemispherical, with a very broad, smooth, obsoletely radiated limb, and a small, finely cellu- lose centre, having an irregular margin; rays 12, irregular. EB. 1855, p. 238; E M. pl. 35 B. B. 4. f. 11. North America. On account of its rays, this form may be the type of a new genus; but they were distinct only in a single specimen, whilst in the greater number scarcely a trace of To C. semiplanus (Bri.), add :— This Diatom, which is not uncommon in the Barbadoes deposit, is no doubt incorrectly placed in this genus. In our opinion it is closely , allied to Astero- lampra, and should either be united to that genus, or a new genus formed to To C. marginatus (Bri.), add:— We consider that this Diatom also is wrongly referred to Craspedodiscus, and, notwithstanding its large punctated centre, is really more allied to Astero- lampra,_its, marginal compartments, however, being extremely minute. ... In the Barbadoes deposit we find discs sometimes (as in Asterolampra) without any umbilical cellules, and sometimes with a large cellulose centre, and these them could be detected. It approaches to the characters of Symbolophora. C. Franklini (E.).--Disc turgid, with a deciduous, broad, hyaline, smooth marginal limb, and a very fine punctated (yellowish) centre, having an irregular margin; centre and limb of nearly the same diameter. ERBA. 1853, p. 526; EM. pl. 35 A. 23. f. 6. Assistance Bay. Akin to Coscinodiscus disciger. include this and other allied discs asso- ciated together in the deposit. Mr. Brightwell's specimen must have been imperfect, since we find the radiating lines invariably correspond in number with the marginal compartments. extremes so connected by intermediate States as to make it doubtful whether the cellulose centre is available even as a specific distinction, We hope Dr. Greville, who has paid much attention to these forms, will soon publish a monograph of them in continuation of his former admirable paper on Astero- lampra. 940 SYSTEMATIC HISTORY OF THE INFUSORLA. For CRASPEDODISCUS coronatus, substitute the following:— Genus BRIGHTWELLIA (Ralfs, n. g.).—Disc with a large granulated centre, separated from a broad punctated limb by a circlet of oblong cellules. We have constituted this genus to receive a beautiful Diatom placed by Mr. Brightwell in Craspedodiscus, but which differs so greatly from other Diatoms that we believe it should form the type of a new one, which, with much plea- sure, we dedicate to the author of the excellent monographs of Triceratium and the Chaetocereae. BRIGHTWELLIA coronata (Bri., Ralfs). — Central portion of valve with an irregular blank umbilicus and radiating series of granules, which are closer and bilicus, and interrupted by blank rays; but near the circlet of cellules they ; come more regular, and form curved, moniliform lines. The broad limb is in curved lines near the circlet of cellules. = Craspedodiscus coronatus, Bri JMS. viii. p. 95, pl. 5. f. 6. Barbadoes deposit. This species is very variable in size. In a dry state it is of a purplish or brown colour, but in balsam hyaline; the centre usually brownish when dry, and marked by numerous radiating lines, similar to those of Coscinodiscus concinnus, and have in the intervals extremely minute obliquely arranged granules. The radi- ating lines, although conspicuous in the dry state, nearly disappear in balsam, has the granules irregular near the um- After CYMATOPLEURA. Ovum (p. 793), insert:— C. multifasciata (Kütz.). — Valves | C., thermalis (Kütz.). — Slightly pan- linear, with acutely cuneate apices, and duriform, otherwise as in C. multifasciata. very fine transverse striae. = Surirella | = Surirella thermalis, KB. p. 60, pl. 3. multifasciata, KB, p. 60, pl. 3. f. 47. f. 46. Europe. . Europe. Genus CYLINDROTHECA (Rab.).—Frustules exactly cylindrical, with percurrent spires, and imbedded in an amorphous, gelatinous mucus. CYLINDROTHECA Gerstenbergeri (Rab.). §: one or three) spires. Rab, Algem —Frustules lanceolate, acute, with two achSens, No. 801. I)resden. ** Note.—Mr. Ralfs originally proposed to introduce a family Synedreae, as mentioned in p. 758, but subsequently transferred the genera to the family Surirelleae, the genera in which he distributes thus:— % Frustules bacillar ; valves keeled—NITZSCHIEE. Genera. Nitzschia, Ceratoneis, Amphipleura, Bacillaria, and Homoeocladia. 2* Frustwles bacillar ; valves scarcely broader than front view, not keeled— - SYNEDREZE. - Genera. Synedra, Desmogonium, Dimeregramma, and Staurosira. 3* Frustwles not bacillar; valves mostly broader than front view, not keeled . SURIRELLEZE. Genera. Rhaphoneis, Tryblionella, Cymatopleura, Surirella, Campylodiscus, and Calodiscus. I N D E X TO THE FIGURES ILLUSTRATING THE DIATOMACEAE, Plate Page ACHNANTHES brevipes . . . . . . . . . . . . X, 199–202 . . . . . . . . . . . . 873 exilis . . . . . . . . . . . . . . . . . . . . . . VII, 44. . . . . . . . . . . . . . . . 874 longipes . . . . . . . . . . . . . . . . . . . . VII, 42 . . . . . . . . . . . . . . . . 873 subsessilis . . . . . . . . . . . . . . . . . . VII, 43. . . . . . . . . . . . . . . . 874 ACHNANTHIDIUM coarctatum . . . . . . VII. 41 . . . . . . . . . . . . . . . . 873 delicatulum . . . . . . . . . . . . . . . . . . XIV. 16. . . . . . . . . . . . . . . . 872 microcephalum . . . . . . . . . . . . . . XIV. 15. . . . . . . . . . . . . . . . 872 trinode . . . . . . . . . . . . . . . . . . . . . . VIII. 9 . . . . . . . . . . . . . . . . 872 ACTINOCYCLUS Ralfsii . . . . . . . . . . . . V. 84 . . . . . . . . . . . . . . . . 835 ACTINOGONIUM Septenarium . . . . . . V. 55 . . . . . . . . . . . . . . . . 813 ACTINOPTYCHUS P hexapterus . . . . . . XI. 81 . . . . . . . . . . . . . . . . 840 Jupiter. . . . . . . . . . . . . . . . . . . . . . XI. 28 . . . . . . . . . . . . . . . . 840 Senarius . . . . . . . . . . . . . . . . . . . . IX, 182 . . . . . . . . . . . . . . . . 839 undulatus . . . . . . . . . . . . . . . . . . V. 88 . . . . . . . . . . . . . . . . 839 AMPIIICAMPA mirabilis. . . . . . . . . . . . IV. 5. . . . . . . . . . . . . . . . . . 765 AMPHIPENTAS alternans . . . . . . . . . . XI. 82 . . . . . . . . . . . . . . . . 858 flexuosa . . . . . . . . . . . . . . . . . . . . VI. 22a, b . . . . . . . . . . . . 858 AMPHIPLEURA inflexa . . . . . . . . . . . . IV, 31 . . . . . . . . . . . . . . . . 783 pellucida . . . . . . . . . . . . . . . . . . . . IV, 30; Ix. 140; xIII. 1 .. 783 rigida. . . . . . . . . . . . . . . . . . . . . . . XIII. 2 . . . . . . . . . . . . . . . . 783 AMPHIPRORA alata. . . . . . . . . . . . . . . XIII. 5, 6, 7 . . . . . . . . . . . . 921 constricta . . . . . . . . . . . . . . . . . . XII. 1 . . . . . . . . . . . . . . . . 922 AMPHITETRAS antediluviana . . . . . . XI. 21, 22. . . . . . . . . . . . . . 858 ornata . . . . . . . . . . . . . . . . . . . . . . VIII. 16 . . . . . . . 0 0 t tº 8 & 9 858 AMIPHORA angularis . . . . . . . . . . . . . . VII, 50 . . . . . . . . . . . . . . . . 881 cymbifera . . . . . . . . . . . . . . . . . . VII, 54 . . . . . . . . . . . . . . . . 882 gracilis. . . . . . . . . . . . . . . . . . . . . . XII, 26. . . . . . . . . . . . . . . . 884 hyalina. . . . . . . . . . . . . . . . . . . . . VII, 58 . . . . . . . . . . . . . . . . 884. litoralis . . . . . . . . . . . . . . . . . . . . VII. 52 . . . . . . . . . . . . . . . . 881 Lybica . . . . . . . . . . . . . . . . . . . . . . XII. 88. . . . . . . . . . . . . . . . 883 marina. . . . . . . . . . . . . . . . . . . . . . . VII. 59 . . . . . . . . . . . . . . . . 884. membranacea. . . . . . . . . . . . . . . . . VII, 51 . . . . . . . . . . . . . . . . 881 monilifera . . . . . . . . . . . . . . . . . . VII. 79 . . . . . . . . . . . . . . . . 882 navicularis . . . . . . . . . . . . . . . . . . XII. 37 . . . . . . . . {º º ſº tº tº e º e 884. ovalis . . . . . . . . . . . . . . . . . . . . . . VII. 56; IX, 153 . . . . . . . . 883 spectabilis . . . . . . . . . . . . . . . . . . VII, 57 . . . . . . . . . . . . . . . . 884. ANAULUS scalaris . . . . . . . . . . . . . . . . VIII. 37 . . . . . . . . . . . . . . 859 ARACHNOIDISCUS Ornatus. . . . . . . . . . XV. 18–21 . . . . . . . . . . . . 842 AstERIONELLA formosa . . . . . . . . . . IV. 17 . . . . . . . . . . . . . . . . 779 Ralfsii. . . . . . . . . . . . . . . . . . . . . . IV. 18 . . . . . . . . . . . . . . . . 779 ASTEROLAMPRA Marylandica. . . . . . . XI. 88 . . . . . . . . . . . . . . . . 836 ASTEROMPIIALUS Arachme . . . . . . . . V. 66 . . . . . . . . . . . . . . . . 837 Brookeii . . . . . . . . . . . . . . . . . . . . V. 79 . . . . . . . . . . . . . . . . 837 INDEX TO THE FIGURES OF DIATOMACEAE. Plate ASTEROMPEIALUS centraster. . . . . . . , VIII. 14 . . . . . . . . . . . . . . Darwinii . . . . . . . . . . . . . . . . . . . . V. 86 . . . . . . . . . . . . . . . . elegans. . . . . . . . . . . . . . . . . . . . . . V. 87 . . . . . . . . . . . . . . . . - heptactis . . . . . . . . . . . . . . . . . . . . VIII. 21 . . . . . . . . . . . . . . - Hookerii . . . . . . . . . . . . . . . . . . . . XI. 84 . . . . . . . . . . . . . . . . ATTHEYA decora . . . . . . . . . . . . . . . . VIII. 85 . . . . . . . . . . . . . . AULACODISCUS Beeveriae . . . . . . . . . . VI, 5. . . . . . . . . . . . . . . . . . Kittoni . . . . . . . . . . . . . . . . . , , , VIII, 24 . . . . . . . . . . . . . . Oregamus . . . . . . . . . . . . . . . . . . . . VI, 4. . . . . . . . . . . . . . . . . . pulcher . . . . . . . . . . . . . . . . . . . . VIII. 28 . . . . . . . . . . . . . . AUEISCUS pruinosus . . . . . . . . . . . . . . VI. 1. . . . . . . . . . . . . . . . . . sculptus . . . . . . . . . . . . . . . . . . . . VI, 3. . . . . . . . . . . . . . . . . . BACILLARIA cursoria. . . . . . . . . . . . . . IV. 20 . . . . . . . . . . . . . . . paradoxa . . . . . . . . . . . . . . . . . . . . Iv. 19; Ix. 166, 167 BACTERIASTRUM furcatum . . . . . . . . VI. 26 . . . . . . . . . . . . . . . . Wallichii. . . . . . . . . . . . . . . . . . . . VI. 27 . . . . . . . . . . . . . . . . BERKELEYA Adriatica. . . . . . . . . . . . . XIV, 34, 35 . . . . . . . . .. . . . BIBLARIUM. Castellum (EM. 33. 2. 1) IV. 44 . . . . . . . . . . . . . . . . BIDDULPHIA Indica. . . . . . . . . . . . . . . VI. 12 . . . . . . . . . . . . . . . . Macdonaldii . . . . . . . . . . . . . . . . VIII, 28 . . . . . . . . . . . . . . obtusa . . . . . . . . . . . . . . . . . . . . . . XIII. 30–32 . . . . . . . . . . . . ulchella . . . . . . . . . . . . . . . . . . . . II. 46–50 . . . . . . . . . . . . . . uomeyi . . . . . . . . . . . . . . . . . . . . VI. 10 . . . . . . . . . . . . . . . . CALODISCUS Superbus . . . . . . . . . . . . VIII. 50 . . . . . . . . . . . . . . CAMPYLODISCUS Clypeus . . . . . . . . . . xVII. 516–518 . . . . . . . . . . Ehrenbergii. . . . . . . . . . . . . . . . ... XII. 12, 13, 22, 23 . . . . . . flexuosa . . . . . . . . . . . . . . . . . . . . XII, 11 . . . . . . . . . . . . . . . . Hibernicus . . . . . . . . . . . . . . . . . . IV. 38 . . . . . . . . . . . . . . . . parvulus . . . . . . . . . . . . . . . . . . . . XV, 22, 23 . . . . . . . . . . . . spiralis. . . . . . . . . . . . . . . . . . . . . . IV, 39 . . . . . . . . . . . . . . . . CERATAULUS lavis . . . . . . . . . . . . . . VI, 7 . . . . . . . . . . . . . e o e º e turgidus . . . . . . . . . . . . . . . . . . . . VI. 8. . . . . . . . . . . . . . . . . . CERATONEIS Closterium . . . . . . . . . . XII, 59 . . . . . . . . . . . . . . . . longissima. . . . . . . . . . . . . . . . . . . IV. 28 . . . . . . . . . . . . . . . . spiralis . . . . . . . . . . .. . . . . . . . . . . XIII. 9 . . . . . . . . . . . . . . . . CELETOCEROS boreale . . . . . . . . . . . . VI. 25 . . . . . . . . . . . . . . . . Wighamiii . . . . . . . . . . . . . . . . . . VI, 24 . . . . . . . . . . . . . . . . CLADOGRAMMA Californicum . . . . . . VIII, 11 . . . . . . . . . . . . . . CLIMACOSPHENIA moniligera . . . . . . XI. 45, 46 . . . . . . . . . . . . CoCCONEIS Americana. . . . . . . . . . . . . XII, 48. . . . . . . . . . . . . . . . distans . . . . . . . . . . . . . . . . . . . . . . VII, 38 . . . . . . . . . . . . . . . . excentrica. . . . . . . . . . . . . . . . . . . VII, 40 . . . . . . . . . . . . . . . . Finnica. . . . . . . . . . . . . . . . . . . . . XII, 41 . . . . . . . . . . . . . . . . Oceanica. . . . . . . • . . . . . . . . . . . . . XII, 42 . . . . . . . . . . . . . . . . Placentula . . . . . . . . . . . . . . . . . . VII, 36 . . . . . . . . . . . . . . . . seudo-marginata . . . . . . . . . . . . VII. 89. . . . . . . . . . . . . . . . Cutellum . . . . . . . . . . . . . . . . . . IX. 162, 163. . . . . . . . . tº a s transversalis . . . . . . . . . . . . . . . . VII. 37 . . . . . . . • * * * * * * * * CoCCONEMA Boeckii . . . . . . . . . . . . . . VII, 48 . . . . . . . . . . . . . . . . Cistula. . . . . . . . . . . . . . . . . . . . . . X. 196–198 . . . . . . . . . . . . cymbiforme. . . . . . . . . . . . . . . . . . XII, 46 . . . . . . . . . . . . . . . . ibbum . . . . . . . . . . . . . . . . . . . . XIII. 10 . . . . . . . . . . . . . . anceolatum . . . . . . . . . . . . . . . . X, 194, 195 . . . . . . . . . . . . Dal VUIIIl . . . . . . . . . . . . . . . . . . . . VII.47 . . . . . . . . . . . . . . . . COLLETONEMA Amphioxys . . . . . . . . XII. 55–57 . . . . . . . . . . . . eximium . . . . . . . . . . . . . . . . . . . . VIII, 43 . . . . . . . . . . . . . . neglectum . . . . . . . . . . . . . . . . . . VIII, 47 . . . . . . . . . . . . . . COSCINODISCUS concinnus . . . . . . . . V. 89 . . . . . . . . . . . . . . . . excavatus . . . . . . . . . . . . . . . . . . VIII, 26 . . . . . . . . . . . . . . mitidus. . . . . . . . . . . . . . . . . . . . . . VIII. 18 . . . . . . . . . . . . . . ovalis . . . . . . . . . . . . . . . . . . . . . . V. 78 . . . . . . . . . . . . . . . . INDEX TO THE FIGURES OF DIATOMACEAE. 943 Plate Page COSCINODISCUS radiatus , . . . . . . . . . XI. 89, 40 . . . . . . . . . . . . 830 stellaris . . . . . . . . . . . . . . . . . . . . V. 88 . . . . . . . . . . . . . . . . 828 CRASPEDODISCUS Coscinodiscus . . . . v. 80 . . . . . . . . . . . . . . . . 832 elegans. . . . . . . . . . . . . . . . . . . . . . XI. 88 . . . . . . . . . . . . . . . . 832 CYCLOTELLA Atlantica. . . . . . . . . . . . XV. 8 . . . . . . . . . . . . . . . . 812 atmospherica. . . . . . . . . . . . . . . . . XV. 1, 2 . . . . . . . . . . . . . . 812 operculata . . . . . . . . . . . . . . . . . . V. 58 . . . . . . . . . . . . . . . . 811 punctata . . . . . . . . . . . . . . . . . . . . VIII, 18 . . . . . . . . . . . . . . 813 rectangula . . . . . . . . . . . . . . . . . . V. 54 . . . . . . . . . . . . . . . . 811 Scotica. . . . . . . . . . . . . . . . . . . . . . XIV. 17. . . . . . . . . . . . . . . . 811 Sinensis . . . . . . . . . . . . . . . . . . . . XV. 4. . . . . . . . . . . . . . . . . 812 CYMATOPLEURA elliptica. . . . . . . . . . . IX. 149; XVI. 7, 8 . . . . . . 793 - Solea . . . . . . . . . . . . . . . . . . . . . . IX. 155; XVI. 9 . . . . . . . . 793 CYMBELLA Arcus . . . . . . . . . . . . . . . . VII, 78. . . . . . . . . . . . . . . . 875 cuspidata . . . . . . . . . . . . . . . . . . . . VII. 45 . . . . . . . . . . . . . . . . 876 elehrenbergii • * * * g e º 'º e s p is e g º e º º VII. 46; ICX. 154 e e is e o & e e 875 gastroides . . . . . . . . . . . . . . . . . . XIV. 18–20 . . . . . . . . . . . . 877 Helvetica. . . . . . . . . . . . . . . . . . . . XIV. 24–28 . . . . . . . . . . . . 876 CYMBOSIRA Agardhii . . . . . . . . . . . . XIV. 14. . . . . . . . . . . . . . . . 875 DENTICULA elegans . . . . . . . . . . . . . . XIII, 4 . . . . . . . . . . . . . . . . 773 DESMOGONIUM Guianense . . . . . . . . XV. 18 . . . . . . . . . . . . . . . . 790 DIADESMIS confervacea. . . . . . . . . . . . XIV, 32, 33 . . . . . . . . . . . . 923 lºvis . . . . . . . . . . . . . . . . . . . . . . XII, 40 . . . . . . . . . . . . . . . . 923 DIATOMA Ehrenbergii . . . . . . . . . . . . IV. 15 . . . . . . . . . . . . . . . . 779 elongatum . . . . . . . . . . . . . . . . . . IV. 14; IX, 169 . . . . . . . . 779 hyalinum . . . . . . . . . . . . . . . . . . . . IV, 16 . . . . . . . . . . . . . . . . 778 mesodon . . . . . . . . . . . . . . . . . . . . IX, 170. . . . . . . . . . . . . . . . 778 Vulgare . . . . . . . . . . . . . . . . . . . . IV. 13; Dº. 168 . . . . . . . . 778 DIATOMELLA Balfouriana . . . . . . . . . . IV. 51 . . . . . . . . . . . . . . . . 810 DICKIEIA ulvoides . . . . . . . . . . . . . . . . XV, 31 . . . . . . . . . . . . . . . . 925 DICLADIA Capreolus . . . . . . . . . . . . . . VI. 28 . . . . . . . . . . . . . . . . 863 DICTYOCHA Fibula . . . . . . . . . . . . . . XV. 84 . . . . . . . . . . . . . . . . 935 Speculum . . . . . . . . . . . . . . . . . . XII. 62, 63 . . . . . . . . . . . . 936 ** trifenestra . . . . . . . . . . . . . . . . . . XV. 85 . . . . . . . . . . . . . . . . 935 DICTYOLAMPRA Stella . . . . . . . . . . . . V. 58 . . . . . . . . . . . . . . . . 813 DIMEREGRAMMA distans . . . . . . . . . . IV, 34 . . . . . . . e s a e e s e º s 790 Harrisonii . . . . . . . . . . . . . . . . . . VIII, 6 . . . . . . . . . . . . . . . . 790 Ilêlllllll . . . . . . . . . . . . . . . . . . . . . . IV. 38 . . . . . . . . . . . . . . . . 790 pinnatum. . . . . . . . . . . . . . . . . . . . VIII. 4. . . . . . . . . . . . . . . . . 791 sinuatum . . . . . . . . . . . . . . . . . . . . IV. 12 . . . . . . . . . . . . . . . . 790 Tabellaria. . . . . . . . . . . . . . . . . . . IV. 85 . . . . . . . . . . . . . . . . 790 DISCOSIRA sulcata . . . . . . . . . . . . . . . . V. 68 . . . . . . . . . . . . . . . . 822 DISIPHONIA australis = Diatomella -> Balfouriana. . . . . . . . . . . . . . . IV. 52 . . . . . . . . . . . . . . . . 810 DONICINIA carinata . . . . . . . . . . . . . . VIII, 49 . . . . . . . . . . . . . . 921 ENCYONEMA prostratum . . . . . . . . . . VII, 49; XIV. 22. . . . . . . . 879 ENDICTYA Oceanica. . . . . . . . . . . . . . . V. 70 . . . . . . . . . . . . . . . . 831 EPITHEMIA alpestris . . . . . . . . . . . . . . XIII. 8 . . . . . . * is a c e g º & tº e tº 760 Argus . . . . . . . . . . . . . . . . . . . . . . XV, 11 . . . . . . . . . . . . . . . . 759 gibba . . . . . . . . . . . . . . . . . . . . . . XII. 27 . . . . . . . . . . . . . . . . 759 * º, e º ºs e º e º ſº e º e . . . . . . . IX. 165. . . . . . . . . . . . . . . . 761 ibrile . . . . . . . . . . . . . . . . . . . . . . XII. 24, 25 . . . . . . . . . . . . 761 longicornis . . . . . . . . . . . . . . . . . . XV, 6–9 . . . . . . . . . . . . . . 760 Musculus. . . . . . . . . . . . . . . . . . . . XIII, 18 . . . . . . . . . . . . . , 760 Porcellus . . . . . . . . . . . . . . . . . . . . XIII, 12 . . . . . . . . . . . . . . 761 turgida. . . . . . . . . . . . . . . . . . . . . . Iv. 1; Ix. 156–161; x1, 1–8 761 Westermanni . . . . . . . . . . . . . . . . IV. 2; Ix, * 157 . . . . . . . . 760 EUCAMPIA Zodiacus . . . . . . . . . . . . . . II, 43 . . . . . . . . . . . . . . . . 937 *Eönößpentaglyphis . . . . . . . . . . . . IV. 3. . . . . . . . . . . . . . . . . . 764 quinaria . . . . . . . . . . . . . . . . . . . . XII. 89. . . . . . . . . . . . . . . . 764 944 INDEX TO THE FIGURES OF DIATOMACEZE. . Plate Page EUNOTOGRAMMA tri- quinque- Sep-. . . . . - tem- et movemloculata . , , , VIII, 30 . . . . . . . 0 & 0 tº g º º º 860 EUODIA gibba, , , , , , , , . . . . . . . , , , , , VIII, 22 . . . . . . . . . . . . . . 852 EUPLEURIA ocellata, , , , . . . . . . . .. . . , VIII, 2 . . . . . . . . . . . . . . . . 809 pulchella . . . . . . . . . . . . . . . , , , , , VIII. 8 . . . . . . . . . . . . . . . . 809 IEUPoDISCUS Argus . . . . . . . . . . . . . . VI. 2; XI. 41, 42. . . . . . . . 843 FRAGILARIA capucina. . . . . . . . . . . . . Ix. 173–175; xiv. 1, 2 .. 776 virescens . . . . . . . . . . . . . . . . . . . . IX, 176. . . . . . . . . a e a s is a tº 777 GEPHYRIA incurvata . . . . . . . . . . . . . . V, 50 . . . . . . . . . . . . . . . . 809 media . . . . . . . . . . . . . . . . . . . . . . . V. 49 . . . . . . . . ‘g s e s a tº s tº 809 GOMPHOGRAMMA rupestre . . . . . . . . IV. 46. . . . . . . . . . . . . . . . . 806 GOMPHONEMA acuminatum . . . . . . . . XIII, 23 . . . . . . . . . . . . . . 887 apiculatum . . . . . . . . . . . . . . . . . . . XII. 28, 58 . . . . . . . . . . . . 889 constrictum . . . . . . . . . . . . . , , , , , , X. 187–190 . . . . . . . . . . . . 887 Coronatum . . . . . . . . . . . . . . . . . . . XIV, 36 . . . . . . . . . . . . . . 887 curvatum . . . . . . . . . . . . . . . . . . . . XI, 9–12; XIII, 11 . . . . . . 888 geminatum . . . . . . . . . . . . . . . . . . VII, 60. . . . . . . . . . . . . . . . 887 minutissimum. . . . . . . . . . . . . . . . XI. 17. . . . . . . tº a º º s 2 s tº e is 891 Vibrio. . . . . . . . . . . . . . . . . . . . . . . . XII. 85 . . . . . . . . . . . . . . . . 890 GONIOTHECIUM crematum . . . . . . . . . . XV. 10 . . . . . . . . . . .* tº s a s a 864. Odontella. . . . . . . . . . . . . . . . . .... , VI, 29 . . . . . . . . . . . . . . . . 864. GRAMMATOPHORA gibba . . . . . . . . . . XI. 48, 49 . . . . . . . . . . . . 808 hamulifera . . . . . . . . . . . . . . . . . . XIII, 22. . . . . . . . . . . . . . . . 808 marina . . . . . . . . . . . . ... • * * * * * * * * * , IV. 47; XI. 52, 53 . . . . . . 808 Serpentina. . . . . . . . . . . . . . . . . . . IV. 48 . . . . . . . . . . . . . . . . 808 GRAMMONEMA Jurgensii . . . . . . . . . . XV. 24, 25 . . . . . . . . . . . . 778 HALIONYX undenarius . . . . . . . . . . . . V. 82. . . . . . . . . . . . . . . . . 833 HELIOPELTA Metii . . . . . . . . . . . . . . XI. 85 . . . . . . . . . . . . . . . . . 841 HEMIAULUS antarcticus . . . . . . . . . . XI. 54 . . . . . . . . . . . . . . . . 85]. HEMIDISCUS cuneiformis . . . . . . . . ... VI. 14 . . . . . . . . . . . . . . . . 853 HERCOTHECA mammillaris . . . . . . . . VII. 85 . . . . . . . . . . . . . . . . 867 EIFTEROSTEPHANIA Rothii . . . . . . . . V. 85. . . . . . . . . . . . . . . . . 833 HIMANTIDIUM Guianense . . . . . . . . . . XII, 54. . . . . . , tº £ tº º tº tº gº º tº $ 766 monodon . . . . . ... tº e º º & e s s tº a tº ... . . xII, 29; xv. 16, 17 . . . . 765 Papilio. . . . . . . . . . . . . . . . . . . . ... XII, 45, 49–52. . . . . . . . . . 766 g; g. t t t e º 'º e º e & s & B e. e. . . . . IV. 6; IX, 171–176. . . . . . 765 oleirolii . . . . . . . . . . . . . . . . . . . . XIV, 13 . . . . . . . . . . . . . . 765 HOMOEOCLADIA filiformis . . . . . . . . . . IV. 25 . . . . . . . . . . . . . . . . 785 Martiana. . . . . . . . . . . . . . . . . . . . . IV. 24; XIV. 47–49. . . . . . 784 moniliformis . . . . . . . . . . . . . . . . XIV. 45, 46 . . . . . . . . . . . . 785 pumila . . . . . . s p tº e, e s s a c e º e º e º s XIV. 37, 38..... . . . . . . . . . 785 sigmoidea . . . . . . . . . . . . . . . . . . IV. 26 . . . . . . . . . . . . . . . . 785 HYALODISCUS subtilis . . . . . . . . . . . . V. 60 . . . . . . . . . . . . . . . . 815 HYALOSIRA delicatula . . . . . . . . ... . . IV. 42 . . . . . . . . . . . . . . . . 804. obtusangula. . . . . . . . . . . . . . . . . . XIV. 29 . . . . . . . . . . . . . . 804. rectangula . . . . . . . . . . . . . . . . . . XIV. 28 . . . . . . . . . • * * * * 804. HYDROSERA compressa. . . . . . . . . ... . . . VI. 8. . . . . . . . . . . . . . . . . . 852 triquetra . . . . . . . . . . . . . . . . . . . . VI, 13 . . . . . . . . . . . . . . . . 852 ISTHMLA enervis. . . . ... . . . . . . . . ... . . X. 188 . . . . . . . . . . . . . . . . 851 LICMOPHORA divisa. . . . . . . . . . . . . . . XIII. 16. . . . . . . . . . . . . . 772 flabellata . . . . . . . . . . . . . . . . . . ... IV, 9; x. 191—193 . . . . . . 771 LIOSTEPHANIA magnifica . . . . . . . . . . V. 56 . . . . . . . . . . . . . . . . 813 Rotula . . . . . . . . . . . . . . . . . . . . . . V. 57 . . . . . . . . . . . . . . . . 813 LIPAROGYRA dentroteres . . . . . . . . . . V. 72 . . . . . . . . . . . . . . . . 823 LITHODESMIUM undulatum . . . . . . ... II, 41, 42. . . . . . . . . . . . . . 937 LYSICYCLIA Vogelii . . . . . . . . . . . . . . VIII. 89 . . . . . . . . . . . . . . 815 MASTOGLOIA Danseii. . . . . . . . . . . . . XV. 30. . . . . . . . . . . . . . . . 924 MASTOGONIA Actinoptychus . . . . . . V. 59 . . . . . . . . • * * * * * * * * * 814 MELOSIRA arenaria. . . . . . . . . . . . . . . VIII. 17 . . . . . . . . . . . . . . 819 Coarctata . . . . . . . . . e s e º g º e ..., XI. 20 & 27 . . . . . . . . . . . . 818 Dickieii . . . . . . 0 0 e º ºs º º tº t t is tº ſº tº XV, 29. , , , , , , , , , . . . . . . 820 INDEX TO THE FIGURES OF DIATOMACEAE. 945 Plate Page MELOSIRA Horologium . . . . . . . . . . . . V. 62 . . . . . . . . . . . . . . . . 819 Italica . . . . . . . . . . . . . . . . . . . . . . XI. 29; xv. 33 . . . . . . . . 818 Jurgensii . . . . . . . . . . . . . . . . . . . . V. 68 . . . . . . . . . . . . . . . . 817 moniliformis . . . . . . . . . . . . . . . . V. 71, . . . . . . . . . . . . . . . . 817 Nägeli . . . . . . . . . . . . . . . . . . . . . . XV. 26, 27 . . . . . . . . . . . . 822 mummuloides . . . . . . . . . . . . . . . . V. 64; XI, 14 . . . . . . . . . . 816 Örichalcea. . . . . . . . . . . . . . . . . . . V. 65; VIII. 33 . . . . . . . . 818 Roseana . . . . . . . . . . . . . . . . . . . . V. 67 . . . . . . . . . . . . . . . . 818 Subflexilis . . . . . . . . . . . . . . . ... . . V. 63 . . . . . . . ... • . . . . . . . 817 sulcata . . . . . . . . . . . . . . . . . . . . . . IX. 131; XI. 26 . . . . . . . . 819 Varians. . . . . . . . . . . . . . . . . . . . . . Iv. 32; Ix. *131; xv. 32 817 MERIDION circulare . . . . . . . . . . . . . . Ix. 177–179; XIII, 21 .. 767 MESOCENA heptagona. . . . . . . . . . . . . XII: 71 . . . . . . . . . . . . . . . . 936 MICROMEGA Agardhii . . . . . . . . . . . . X. 208 . . . . . . . . . . . . . . . . 933 bombycinum . . . . . . . . . . . . . . . . XIV, 43,44 . . . . . . . . . . . . 933 pallidum . . . . . . . . . . . . . .e. º a tº 6 . . XIV. 39–42 . . . . . . . . . . . . 934 MICROTHECA Octoceras . . . . . , º 0 & 0 & 0 & VIII, 31 . . . . . . . . . . . . . . 937 NAVICULA affinis . . . . . . . . . . . . . . . . XII, 32 . . . . . . . .* º e º e º e º e 902 Amphirhynchus . . . . . . . . . . . . . . XII. 6 . . . . . . . . . . . . . . . . 903, Amphisbaena. . . . . . . . . . . . . . . . . VII. 72; IX, 141 . . . . . . . , 899 borealis . . . . . . . . . . . . . . . . . . . . VII, 74. . . . . . . . . . . . . . . . 907 cardinalis. . . . . . . . . . . . . . . . . . . . XII, 72. . . . . . . . .g. e. e º & . . , 896 Chilensis . . . . . . . . . . . . . . . . . . . . XII. 33. . . . . . . . . . . . . . . . 907 Cluthensis . . . . . . . . . . . . . . . . . . VII. 73. . . . . . . . . . . . . . . . 909 cuspidata. . . . . . . . . . . . . . . . . . . . XII, 5 . . . . . . . . . . . . . . . . 905 didyma. . . . . . . . . . . . . . . . . . . . . . VII, 61; xv. 12 . . . . . . . . 893 Esox. . . . . . . . . . . . . . . . . . . . . . . . XII, 43. . . . . . . . . . . . . . . . 896 Hennedyi. . . . . . . . . . . . . . . . ... . . . VII, 69. . . . . . . . . . . . . . . . 898 Hitchcockii. . . . . . . . . . . . . . . . . . VII. 62 . . . . . . . . . . . . . . . . 894 latissima. . . . . . . . . . . . . . . . . . . . . VII, 70. . . . . . . . . . . . . . . . 903 major . . . . . . . . . . . . . . . . . . . . VII. 65; XII. 15, 31; xvi. 1–6 896 maxima . . . . . . . . . . . . . . . . . . . . . VII. 75 . . . . . . . . . . . . . . . . . 909 nodosa . . . . . . . . . . . . . . . . . . . . . • IX, 143. . . . . . . . . . . . . . . . 894 producta. . . . . . . . . .* c e g º e º 'º e o º VII, 66. . . . . . . . . . . . . . . . 902 rhombica . . . . . . . . . . . . . . . . . . . . VII, 71. . . . . . . . . . . . . . . . 903 rhynchocephala . . . . . . . . . . . . . . VII, 68. . . . . . . . . . . . . . . . 900 Tabellaria. . . . . . . . . . . . . . . . . . . XII, 21. . . . . . . . . . . . . . . . 896 teniata. . . . . . . . . . . . . . . . . . . . . . XV. 15 . . . . . . . . . . . . . . . . 900 timida . . . . . . . . . . . . . . . . . . . . . . VII, 55. . . . . . . . . . . . . . . . 910 viridis . . . . . . . . . . . • . . . . . . . . . . IX. 133–136. . . . . . . . . . . . 907 NITZSCHIA Brightwellii . . . . . . . . . . VIII, 7 . . . . . . . . . . . . . . . . 780 scalaris. . . . . . . . . . . . . . . . . . . . . . IV. 22 . . . . . . . . . . . . . . . . 781 Sigma . . . . . . . . . . . . . . . . . . . . . . IV. 21 . . . . . . . . . . . . . . . . 781 sigmoidea . . . . . . . . . . . . . . . . . . IX. 148. . . . . . . . . . . . . . . . 781 * Valens . . . . . . . . . . . . . . . . . . . . XII, 44. . . . . . . . . . . . . . . . 782 ODONTIDIUM hyemale . . . . . . . . . . . . Ix. 172; xIII. 24, 25 . . . . 775 ODONTODISCUS eccentricus . . . . . . . . v. 90 . . . . . . . . . y - e º 'º a 9 832 OMPHALOPELTA areolata . . . . . . . . . . VIII. 15 . . . . . . . . . . . . . . 841 OMPHALOTHECA hispida. . . . . . . . . . . VIII, 44 . . . . . . . . . . . . . . 865 ONCOSPHENIA P Carpathica . . . . . . . , VIII. 1 . . . . . . . . . . . , . . . , 768 PERIPTERA chlamidophora . . . . . . . . VIII. 25 . . . . . . . . . , , . . . 865 tetracladia. . . . . . . . . . . . . . . . . . . VI, 30 . . . . . . . . . . 7 º’ s = • * 865 PERISTEPHANIA Eutycha . . . . . . . . . . v. 73 . . . . . , . . . . . . . . . . 824 PERITHYRA denária . . . . . . . . . . . . . . VIII. 19 . . . . . . . . , , . . . . 842 PLAGIOGRAMMA pulchellum. . . . . . . . IV. 82 . . . . . . . . . . . . . . . . 774 PLEURODESMIUM. Brébissonii . . . . . . VI. 23 . . . . . . . . . . . . . . . . 860 PLEUROSIGMA acuminatum . . . . . , , , IX, 146 . . . . . . . . . . . . . . 919 Balticum . . . . . . . . . . . . . . . . . . . . VIII.33; IX. 144 . . . . . . 917 Fasciola . . . . . . . . . . . . . . . . . . . . XII. 60, 61 . . . . . . . . . . . . 916 formosum . . . . . . . . . . . . . . . . . . VIII. 82 . . . . . . . . . . . . . . 917 Hippocampus . . . . . . . . . . . . . . . . IX, 145, , , , , , . . . . . . . . 3. 919 INDEX TO THE FIGURIS OF DIATOMACEAE. Plate PLEUROSIPEIONIA affinis . . . . . . . . VIII. 45 . . . . . . . . . . . . . . PODOCYSTIS Adriatica. . . . . . . . . . . IV. 10 . . . . . . . . . . . . . . . . Pol ODISCUS Jamaicensis . . . . . . . . XIII, 28 . . . . . . . . . . . . . . PODOSIRA P compressa. . . . . . . . . . . VIII, 34 . . . . . . . . . . . . . . hormoides . . . . . . . . . . . . . . . . II. 45 . . . . . . . . . . . . . . . . PoDOSIRA Montagnei . . . . . . . . . . V. 61 . . . . . . . . . . . . . . . . PODOSPHENIA cuneata . . . . . . . . . . XIII, 185 . . . . . . . . . . . . . . Ehrenbergii, . . . . . . . . . . . . . . , , . IV. 7; XIII, 14 . . . . . . . . gracilis. . . . . . . . . . . . . . . . . . . . X, 186 . . . . . . . . . . . . . . . . - hyalina. . . . . . . . . . . . . . . . . . . XIII, 13 - . . . . . . . . . . . . . PORPETA quadriceps . . . . . . . . . . . . VI. 6. . . . . . . . . . . . . . . . . . PYXIDICULA Adriatica. . . . . . . . . . . XIII. 88 . . . . . . . . . . . . . . globata. . . . . . . . . . . . . . . . . . . . XVII. 506—509. . . . . . . . . . RHABDONEMA Adriaticum . . . . . . XIII, 27 . . . . . . . . . . . . . . arcuatum . . . . . . . . . . . . . . . . . . Ix. 180–182; x. 203, 204. . Crozieri . . . . . . • * * * * * * * * * * * IV. 43 . . . . . . . . . . . . . . . . minutum . . . . . . . . . . . . . . . . . . IV. 41 . . . . . . . . . . . . . . . . mirificum. . . . . . . . . . . . . . . . . . VIII, 12 . . . . . . . . . . . . . . RHAPHONEIS Amphiceros . . . . . . XIV. 21 . . . . . . . . . . . . . . RHIPIDOPHORA Meneghiniana XIII. 19 . . . . . . . . . . . . . . Nubecula . . . . . . . . . . . . . . . . . . XIII. 17 . . . . . . . . . . . . . . paradoxa . . . . . . . . . . . . . . . . . . IV. 8. . . . . . . . . . . . . . . . . . tenella . . . . . . . . . . . . . . . . . . . . XIII, 15 . . . . . . . . . . . . . . RHIZONOTIA Melo . . . . . . . . . . . . . . VIII, 41 . . . . . . . . . . . . . . RHIZOSOLENIA Calyptra. . . . . . . . . VII, 31. . . . . . . . . . . . . . . . robusta. . . . . . . . . . . . . . . . . . . . VIII, 42 . . . . . . . . . . . . . . setigera. . . . . . . . . . . . . . . . . . . VII. 88 . . . . . . . . . . . . . . . . styliformis . . . . . . . . . . . . . . . . VII. 82 . . . . . . . . . . . . . . . . SCEPTRONEIS Caduceus . . . . . . . . IV, 11 . . . . . . . . . . . . . . . . SCHIZONEMA Dillwynii. . . . . . . . . . VIII, 40 . . . . . . . . . . . . . . Grevillii . . . . . . . . . . . . . . . . . . VIII. 88 . . . . . . . . . . . . . . Hoffmannii . . . . . . . . . . . . . . . . X. 207 . . . . . . . . . . . . . . . . SPHENELLA angustata . . . . . . . . . XIV. 80 . . . . . . . . . . . . . . obtusata . . . . . . . . . . . . . . . . . XIV, 31 . . . . . . . . . . . . . . SPHENOSIRA Catena. . . . . . . . . . . . . XI. 80 . . . . . . . . . . . . . . . . STAUROGRAMMA Persicum . . . . . . VIII, 36 . . . . . . . . . . . . . . STAURONEIS acuta , , , , . . . . . . . . . . VII, 76 . . . . . . . . . . . . . . . . Crucicula . . . . . . tº e º 'º - e º a ſº e is VII, 64. . . . . . . . . . . . . . . . dilatata . . . . . . . . . . . . . . . . . . XII, 16 . . . . . . . . . . . . . . . . Isostauron . . . . . . . . . . . . § e º e º ſº XII, 78. . . . . . . . . . . . . . . . Legumen & J & J & g c & d e º 'º t e º 'º º VII. 67 . . . . . . . . . . . . . . . . obliqua. . . . . . . . . . . . . . . . . . . VII. 63. . . . . . . . . . . . . . . . Phoenicenteron . . . . . . . . . . . . Ix. 139; xII. 17, 18 . . phyllodes. . . . . . tº t e º g a tº e º e e a XII. 7–9 . . . . . . . . . . . . . . platystoma. . . . . . . . . . . . . . . . . IX. 142. . . . . . . . . . . . . . . . pulchella . . . . . . tº a tº e º 'º ºf e e º e e VII. 77 . . . . . . . . . . . . . . . . scalaris. . . . . . . . . . . . . . . . . . . . XII. 10, 14, 30. . . . . . . . . . STAUROSIRA construens . . . . . . . . XV, 5 . . . . . . . . . . . . . . . . STEPHANODISCUS AEgyptiacus V. 69 . . . . . . . . . . . . . . . . STEPHANOGONIA polygona. . . . . . . V. 77 . . . . . . . . . . . . . . . . STEPHANOPYXIS ferox . . . . . . . . . . V. 75 . . . . . . . . . . . . . . . . Turris . . . . . . . . . . . . . . . . . . . . V. 74 . . . . . . . . . . . . . . . . STIGMAPEIORA rostrata . . . . . . . . . . VIII. 48 . . . . . . . . . . . . . . STRIATELLA unipunctata . . . . . . . . IV. 40 . . . . . . . . . . . . s p = • STYLOBIBLIUM Clypeus . . . . . . . . IV. 45 . . . . . . . . . . . . . . . . SURIRELLA biseriata . . . . . . . . . . . . . . XVI. 20–26 . . . . . . . . . . . . constricta. . . . . . . . . . . . . . . . . . XIII. 8 . . . . . . . . . . . . . . . . Craticula . . . . . . • * * * * * * * * * * * * * XII. 19, 20 . . . . . . . . . . . . Gemma. . . . . . . . . . . . . . . . . . . XII. 2–4 . . . . . . . . . . . . . . splendida . . . . . . . . . . . . . . . . . . IX. 150–152 . . . . . . . . . . striatula . . . . . . . . . . . . . . . . . . . . IX, 137, 138 . . . . . . . . . . INDEx fo THE FIGURES () F DIATOMACEAE, 947 ; - Plate Page SYMBOLOPHORA Trinitatis . . . . . . . . xI. 36 . . . . . . . • * * * * * * * * 833 SYNCYCLIA Salpa . . . . . . . . . . . . . . ... VII. 53; x. 206 . . . . . . . . 879 SYNEDRA Arcus. . . . . . . . . . . . . . . . . . IV. 27 . . . . . . . . . . . . . . . . 789 capitata . . . . . . . . . . . . . . . . . . . . IV. 29; x. 185* . . . . . . . . 788 fulgens. . . . . . . . . . . . . . . . . . . . . . XIII. 20 . . . . . . . . . . . . . . 789 Gallionii . . . . . . . . . . . . . . . . . . . . XII, 34, 36 . . . . . . . . . . . . 788 lunaris . . . . . . . . . . . . . . . . . . . . . . X. 185 . . . . . . . . . . . . . . . . 785 pulchella . . . . . . . . . . . . . . . . . . . . IV. 28 . . . . . . . . . . . . . . . . 786 robusta. . . . . . . . . . . . . ‘. . . . . . . . . VIII. 8 . . . . . . . . . . . . . . . . 789 subtilis. . . . . . . . . . . . . . . . . . . . . . IX. 147. . . . . . . . . . . . . . . . 786 Ulna. . . . . . . . . . . . . . . . . . . . . . . . X. 184 . . . . . . . . . . . . . . . . 788 SYRINGIDIUM Americanum . . . . . . . . VII, 34. . . . . . . . . . . . . . . . 866 bicorne. . . . . . . . . . . . . . . . . . . . . . VIII. 20 . . . . . . . . . . . . . . 866 SYSTEPHANIA Corona. . . . . . . . . . . . . V. 81 . . . . . . . . . . . . . . . . 832 TABELLARIA flocculosa . . . . . . . . . . ... XIII, 29 . . . . . . . . . . . . . . 807 ventricosa. . . . . . . . . . . . . . . . . . . XIII. 26 . . . . . . . . . . . . . . 807 TERPSINoíš musica. . . . . . . . . . . . . . . . XI. 47 . . . . . . . . . . . . . . . . 859 TESSELLA interrupta. . . . . . . . . . . . . . . VIII. 5 . . . . . . . . . . . . . . . . 804 TETRACYCLUS lacustris. . . . . . . . . . . . XI. 24, 25; VIII. 10 . . . . 806 TOXONIDEA undulata. . . . . . . . . . . . . . VIII. 46 . . . . . . . . . . . . . . 920 TRICERATIUM alternans . . . . . . . . . . VI, 21 . . . . . . . . . . . . . . . . 854 castellatum . . . . . . . . . . . . . . . . . . VIII. 29 . . . . . . . . . . . . . . 854 contortum . . . . . . . . . . . . . . . . . . VI. 18 . . . . . . . . . . . . . . . . 853 exiguum . . . . . . . . . . . . . . . . . . . . VI. 16 . . . . . . . . . . . . . . . . 857 Favus . . . . . . . . . . . . . . . . . . . . . . XI. 43, 44 . . . . . . . . . . . . 855 unctatum . . . . . . . . . . . . . . . . . . VI. 20 . . . . . . . . . . . . . . . . 856 olenoceros . . . . . . . . . . . . . . . . . . VI. 15 . . . . . . . . . . . . . . . . 856 spinosum . . . . . . . . . . . . . . . . . . . . VI. 19 . . . . . . . . . . . . . . . . 853 trisulcum . . . . . . . . . . . . . . . . . . . . . VIII. 27 . . . . . . . . . . . . . . 854 Well08UIDO . . . . . . . . . . . . . . . . . . . . VI. 17 . . . . . . . . . . . . . . . . 854. TRYBLIONELLA acuminata . . . . . . . . IV. 87 . . . . . . . . . . . . . . . . 792 acilis. . . . . . . . . . . . . . . . . . . . . . IV. 36 . . . . . . . . . . . . . . . . 792 XANTHIOPYXIS oblonga. . . . . . . . . . . V. 76 . . . . . . . . . . . . . . . . 827 ZYGoCEROS Surirella. . . . . . . . . . . . . . XI. 50, 51 . . . . . . . . . . . . 850 Mobiliensis . . . . . . . . 4 * * * * * * * * * VI, 11 . . . . . . . . . . . . . . . . 850 3 P 2 949 DESCRIPTION OF THE ENGRAVINGS. PLATE I. (DESMIDs). Figures 1 to 14. Cosmarium margaritiferum, &c., under different stages of develop- ment: 1, 2. Frond, enclosing “vesicles” filled with moving granules; 3. Supposed early state of moving granules; 4. Early stage of self-fission; 5. Fission-products escaping the enclosing wall of parent cell; 6. Separation completed; 7. Sporangium still connected with parent frond; 8. Same with mammilliform spines; 9. Sporangium further developed; 10, 11. Supposed mature sporangia; 12. Same, broken and empty; 13, 14. Young supposed products of sporangial contents: all after Mrs. Thomas, TM, 1855, [We are disposed to think that one or two other species besides Cosmarium margaritiferum are here confounded. 4, we suggest, may possibly be C. caelatum or C. cristatum, showing nascent segments; 7, C. Broomei, the empty frond to the right showing a segment not yet fully developed; 8 and 9 appear to us as probably more likely to represent the conjugated state and sporan- gium of C. bioculatum, of which figs. 10, 11, 12, may represent the ultimately extruded inner membrane, while figs, 13 and 14 may truly be the young fronds developed from their contents, and which have not yet commenced vegetative self-division.] 15–17. Sphaero- zosma vertebratum (Ralfs): 15. A portion of a filament seen in f. v. ×200; 16. tr. V. ×400; 17. s. v. ×400. 18, 19. Micrasterias papillifera (Bréb.): 18. f. v. × 100; 19. Spo- rangium ×200. 20. M. rotata (Ralfs), f. v. × 100. 21. M. radiosa (Ag), f. v. x 100. 22. M. Crux-Melitensis (Ralfs), f. v. × 100. 23–25. Euastrum Didelta (Ralfs): 23. f. v. with endochrome; 24. e. f. in f. v.; 25. tr. v.: all × 200. 26. E. rostratum (Ralfs), f. v. ×400. 27, 28. Xanthidium armatum (Bréb.): 27. f. v.; 28. s. v.: both X200. 29, 30. Arthrodesmus octocornis (Ehr.): 29. var. 3, f. v.; 30. var. a, f. v.: both ×400, 31–34. Staurastrum cuspidatum (Bréb.): 31. f. v.; 32. showing the mascent segments; 33. tr. v.; 34. e.v.: all ×400, 35, 36. Ankistrodesmus falcatus (Ralfs), X.400. 37–39. Sceno- desmus obtusus (Meyen), after Nägeli, showing segmentation of the cell-contents, X300. 40–42. S. caudatus, after Nägeli, X300. 43. Same, segmentation of cell-contents, X.400. 44, 45. A few marginal cells of “Pediastrum Selenaea (Kg.)”=P. pertusum (?), after Nägeli, X300. 46–48. P. (Anomopedium) integrum (Nāg.): 46. x 150; 47. ×400; 48. s. v. ×400. 49–51. Coelastrum sphaericum (Nāg.): 49. ×200 ; 50, 51. ×300. 52. Pediastrum Ehrenbergii (Braun), after Braun, ×400. 53. P. Selenaea (Kg.) [non Ralfs, = P. pertusum], after Nägeli, x 150. 54, 55. Coelastrum cubicum (Nāg.), after Nägeli, X300. 56–58. Sorastrum spinulosum (Nāg.): 56. ×300; 57, 58. x600. 59–61. Pediastrum Boryanum, war. brevicornis, after Braun : 59. Two marginal cells, one empty, the other discharging the original inner membrane closely investing the micro- gonidia; 60. The same half an hour afterwards, Čonsiderably dilated, the microgonidia each with a pointed hyaline beak, and at first slowly moving ; 6l. Microgonidia, eventually emitted, swimming freely: all ×300. 62. P. granulatum (Kg.). 63. Brood of macrogonidia emerged from shell of old frond, ×400. 64. A few marginal cells of an old frond, some empty, the cell-contents of others undergoing previous segmentation, and one discharging the inner membrane investing the brood of macrogonidia (Braun), X.400. 65. Same as 63, seen from the edge, ×400. 66. Same, seen in f, V., the cells now slightly . emarginate, ×400. 67. Same, four hours after the macrogonidia have ceased to move, the marginal cells now drawn out into horns, but not yet having assumed their proper form, and all exhibiting spaces between, not yet having become closely applied to each other, ×400. 68, 69. P. Boryanum : microgonidia treated with tincture of iodime and sul- phuric acid, showing the vibratile cilia, the slightly retracted contents, and a nucleus, × 500. (Figs. 63–69 after Braun.) PLATE II. (DESMIDs). Figures 1 & 5. Closterium Leibleinii (Kg.), x200: 1. A frond filled with endochrome, and an empty one lying across it (the latter shows the central suture); 5. Sporangium lying between the conjugated, and now empty fronds. 2 & 6. Closterium striolatum (Ehr.), × 100: 2. A frond with endochrome, showing the longitudimal fillets and the single row of large granules; 6. Two empty conjugated fronds, showing the striae and the orbicular 950 DESCRIPTION OF TEIE ENGRAVINGS. sporangium lying between them, enveloped in mucus. , 3. Staurastrum (Desmidium, Ehr.) eustephanum, e.v. 4. Spirotaenia condensata (Bréb.), X200: the frond is seem with its spiral band of endochrome, and surrounded by a mucous hyaline sheath, 7. Staurastrum (Desmidium, E.) semarium. 8 & 11. Docidium Ehrenbergii (Ralfs), × 100: 8. Conjugating fronds, the sporangium in an early stage of development; 11 shows the process of develop- ment by fission, the young segments partially grown. 9. Docidium clavatum (Kg.), X 100. 10 & 30. Euastrum pectimatum (Bréb.), x200: IO. A single frond; 30. The spinous sporangium, the empty segments adjacent. 12, 13. Tetmemorus Brebissonii (Ralfs), X 200: 12. f. v.; 13. s. v. 14, 15. Penium margaritaceum (Bréb.), X200: 14. f. v. War. a ; 15. s. v. of two empty fronds, var. y, the sporangium between them. 16, 17. Staurastrum altermans (Bréb.), X.400: 16. f. v.; 17. e.v. 18 & 23. Xanthidium cristatum (Bréb.), ×400: 18. f. v.; 23. e. v. 19 & 36. Scenodesmus quadricauda (Ralfs), x400: 19. A frond of two cells; 36. One of four cells. 20, 21, 24, 25 & 31. Staurastrum polymor- phum (Bréb.), ×400; 20. e. v. (of five-rayed var.); 21 & 31. f. v.; 24. A frond multi- plying by self-division; 25. Sporangium with its furcate spines, and around it the empty. and previously conjugated fronds. 22. Micrasterias denticulata (Bréb.), X 100, sporan- gium of 26, Cosmarium caelatum (Ralfs), X300: front view of frond multiplying by self-division, the young segments partially grown and their surface still Smooth. 27. Pe- diastrum tetras (Ralfs), ×400, f, v. of a frond. 28, 29. Tetrachastrum oscitans (Dixon), × 100: 28. f. v.; 29. tr. v. of e. f. 32 & 35. Hyalotheca dissiliens (Bréb.): 32. ×200, tr. v. with investing hyaline gelatinous sheath; 35. ×400, f. v., also showing the sheath. 33, 34. Cosmarium undulatum (Corda), x400: 33. f. v.; 34. Sporangium with the empty fronds. 37 & 40. Desmidium quadrangulatum (Ralfs): 37. ×200, f. v. of fila- ment; 40. ×300, tr. v. 38, 39. Didymoprium Borreri (Ralfs), ×400: 38. tr. v.; 39. Portion of a filament, f. v. DIATOMs:–41, 42. Lithodesmium undulatum; 43. Eucampia Zodiacus. DESMID:—44. Micrasterias Americana. I) IATOMs:–45. Podosira monilifor- mis attached to Polysiphonia; 46, 47, 49, 50. Biddulphia pulchella; 48. Denticella Biddulphia. PLATE III. (DESMIDs). Figure 1. Gomatozygon Ralfsii (De Bary), three joints of, x300; 2. Same, conju- gated, showing sporangium, X300. 3. Gemicularia spirotaenia (De Bary), single joint of, X 150 (vide De Bary, op.cit. iv. 1. p. 717), X300. 4. Leptocystinema Kinahani (Archer), ×200, showing front and side views of the band of endochrome, and two joints with nascent halves. 5. Aptogonum Baileyi (Ralfs), ×400; 6. Same, e. v. 7. Desmidium Aptogonum (Bréb.), portion of a filament, x400; 8. Same, e.v. ×400. 9. Spondylosium depressum (Bréb.), X300: five joints, one dividing. 10. S. pulchellum (Archer), X450: five joints of a filament. 11, Euastrum oblongum (Ralfs), X200. 12. E. insigne (Hass.), X200. 13. E. binale (Ralfs), × 400. 14. Cosmarium pyramidatum (Bréb.), x 300; 15. Same, e. V. X300. 16. C. cylindricum (Ralfs), X300; 17. Same, e. v. x300. 18. Staurastrum avicula (Bréb.), x 300; 19. Same, e. v. x300. 20. S. teliferum (Ralfs), ×300; 21. Same, e.v. × 300. 22. S. spongiosum (Bréb.), X300; 23. Same, e.v. ×300. 24. S. Quadrangulare (Bréb.), X300; 25. Same, e. V. 26. S. globulatum (Bréb.); 27. Same, e. v. 28. S. gracile (Ralfs), X300; 29. Same, e. v. ×300. 30. S. vestitum (Ralfs), X300; 31. Same, tr. v. ×300. 32. S. furcigerum (Bréb.), x200; 33. Same, e.v. X200. 34. S. margaritaceum (Menegh.), x 300; 35. Same, e.v. × 300. 36. Arthro- desmus Incus (Hass.), X 400. 37. Triploceras verticillatum (Bailey). 38. Docidium Baculum (Bréb.), X200. 39. Closterium didymotocum (Corda), x 100, 40. C. turgidum (Ehr.), X 100. 41. C. lineatum (Ehr.), x 100; 42. Same, conjugated, showing the double sporangium, X 100. 43. C. attenuatum (Ehr.), x 100. 44. C. rostratum (Ehr.), x 100. 45. Penium interruptum (Bréb.), X200. 46. Docidium Ehrenbergii (Ralfs), X200, after W. Archer (Nat. Hist. Review, vii. p. 375): commencement of growth of lateral tube preparatory to the formation of zoospores. 47. Same, the zoospores emitted and forming an external cluster (p. 716), 48–54. After De Bary (op.cit.); all × 190, showing develop- ment of sporangium of Cosmarium Botrytis (Menegh.): 48. The immer membrane with contents escaping by bursting the outer wall of the sporangium; 49. The same escaped, somewhat further developed, preparatory to segmentation of the contents, the external membrane doubled; 50. The same, division finished; 51. The same, 13 hour after; 52. The same, at a later stage; 53. Germ-cells, ordinary vegetative division begun; 54. Product of the first division of a germ-cell, each new half (but not until now) having assumed the characteristic form of the species. 55–60. After De Bary (op. cit.), all × 390, showing development of sporangium of Cosmarium Meneghinii (Bréb.); 55. Empty out- side coat of a sporangium with an open slit or fissure by which the immer membrane (with contents) has come out; 56. The emerged inner membrane and contents; 57. A pair of germ-cells formed therein; 58. The same, one escaping; 59, 60. Products of the germ- IXESCRIPTION OF THE ENGRAVINGS. 951 cells, showing one segment the form of the germ-cell, the other, ordinary vegetative division supervening, having assumed that characteristic of the species. 6l. Euastrum didelta (Ralfs), x 150, abnormal condition of, after W. Archer (Nat. Hist. Review, vi. p. 469), showing a central irregular structure produced between the original segments, apparently owing to the non-formation of a septum on the resumption of vegetative growth, and forming with them but one uninterrupted cavity; and in this instance the new central growth having assumed the size and nearly the form of an entire frond, its axis of growth and plane of expansion are at right angles to the old segments. 62. Arthrodesmus Incus (Hass.), X300, abnormal condition of, after W. Archer, l.c., showing an abnormal growth analogous to preceding, but carried on to another vegetative generation, the middle portion being older than those produced between it and the original segments, the whole still º within but one uninterrupted cavity, 63. Cosmocladium pulchellum (Bréb.), X250. PLATE TV. (DIATOMs). [Plates IV. to VIII. are engraved by Mr. Tuffen West. Many of the figures are from original drawings, others from specimens, and all of them are magnified 300 diameters.] Figure 1. Epithemia turgida, f. and s. v. 2. E. Westermanni. 3. Eunotia pentaglyphis. 4. E. triodon, 5. Amphicampa mirabilis. 6. Himantidium pectinale, f. and s. v. 7. Podosphemia Ehrenbergii, f. and s. v. 8. Rhipidophora paradoxa. 9. Licmophora flabel- lata. 10. Podocystis Adriatica. ll. Sceptroneis Caduceus. 12. Dimeregramma simu- atum, f. and s. v. 13. Diatoma vulgare, f. and s. v. 14. D. elongatum. 15. D. Ehren- bergii. 16. D. hyalinum, f. and s. v. 17. Asterionella formosa. 18. A. Ralfsii. 19. Bacillaria paradoxa, f. and s. v. 20. B. cursoria. 21. Nitzschia Sigma. 22. N. scalaris, f, and s. v. 23. Ceratoneis longissima, f. and s. v. 24. Homoeocladia Martiana, f. and s. v. 25. H. filiformis. 26. H. sigmoidea, 27. Synedra Arcus, f. and s. v. 28. S. pulchella, f, and s. v. 29. S. capitata. 30. Amphipleura pellucida. 31. A. inflexa. 32. Plagio- gramma pulchellum, f. and s. v. , 33. Dimeregramma manum, f, and s. v. 34. D. distans, f, and s. v. 35. D. Tabellaria, f. and s. v. 36. Trybliomella gracilis. 37. T. acuminata. 38. Campylodiscus Hibernicus. 39. C. spiralis. , 40. Striatella unipunctata, f. and s. v. 41. Rhabdomema minutum, f. and s. v. 42. Hyalosira delicatula, f. and s. v. 43. Rhab- domema Crozieri, f. and s. v. 44. Biblarium Castellum (EM. 33.2.1.). 45. Stylobiblium Clypeus. 46. Gomphogramma rupestre, f. and s. v. 47. Grammatophora marima. 48. G. serpentina, f. and s. v. 49. Gephyria media, f. and s. v. upper and under valves. 50. G. incurvata, f. and S. V. ditto. 51. Diatomella Balfouriana, f, and s. v. 52, Disi- phonia australis. PLATE W. (DIATOMs). Figure 53. Cyclotella operculata, f. and s. v. 54. C. rectangula, f. and s. v. 55. Actimogonium Septemarium. 56. Liostephania magnifica. 57. L. Rotula. 58. Dictyo- lampra Stella. 59. Mastogonia Actinoptychus. 60. Hyalodiscus subtilis. 61. Podosira Montagnei, f. and s. v. 62. Melosira Horologium, f, and s. v. (EM. 33. 2. 17), 63. M. subflexilis, f. and s. v. 64. M. nummuloides, f. and s. v. 65. M. Orichalcea. 66. Aste- romphalus Arachme. 67. Melosira Roseana, f, and s. v. 68. Discosira sulcata, f. and s. v. 69. Stephanodiscus AEgyptiacus, f. and s. v. 70. Endictya oceanica, f. and s. v. 71. Me- losira Borreri, f. and s. v. 72. Liparogyra spiralis, f. and s. v. 73. Peristephania. Eutycha. 74. Stephanopyxis Turris. 75. S. ferox, f. and s. v. 76. Xanthiopyxis oblonga. TT, Stephanogomia polygona, f. and s. v. , 78. Coscinodiscus oyalis. 79. Asteromphalus Brookei. 80. Craspedodiscus Coscimodiscus. 81. Systephania Coroma. 82. Halionyx undemarius. 83. Coscinodiscus stellaris. 84. Actinocyclus Ralfsii. 85. Heterostephania Rothii. 86. Asteromphalus Darwinii. 87. A. elegans. 88. Actinoptychus undulatus, f, and s. v. 89. Coscinodiscus concinnus, 90. Odontodiscus eccentricus. PLATE WI. (DIATOMs). Figure 1. Auliscus, pruinosus. 2. Eupodiscus, Argus: a, s. v.; 5, f. V. (the latter from Kützing). 3. Auliscus sculptus: a, s. v.; b, f. V. 4. Aulacodiscus Oreganus. 5. A. Beeveriae. 6. Porpeia quadriceps: a, s. v.; b, f. V. 7. Cerataulus laevis: a, s. v.; b, filament. 8. Hydrosera compressa, s. v. 9. Cerataulus turgidus: a, S. V. ; b, f. V. 10. Biddulphia Tuomeyi: a, s. v.; b, f. v., 11. Zygoceros Mobiliensis: a, s. v.; b, f. V. 12. Biddulphia Indica. 13. Hydrosera triquetra: a, s. v.; b, filament. 14. Hemidiscus cuneiformis: a, s. v.; b, f. v. 15. Triceratium Solenoceros, 16. T. exiguum, 17. T. 952 DESCRIPTION OF TEIE ENGRAVINGS. venosum. 18. T. contortum. 19. T. spinosum. 20. T. punctatum. 2i. T. alternans: a, s. v.; b, f. v. 22. Amphipentas flexuosus: a, with five angles; b, war, with four angles. 23. Pleurodesmium Brébissonii: a, s. v.; b, f. v. 24. Chaetoceros Wighamii: a, Gonio- thecium-like frustule, f. v.; b, same, s. v.; c, s. v. of connecting zone and awns without the frustule; d, filament entire. 25. C. boreale: a, s. v.; b, f. V. 26. Bacteriastrum furcatum. 27. B. Wallichii: a, s. v.; b, filament (This figure is introduced for the sake of the f. v., which so closely resembles Bacteriastrum furcatum and B. curvatum as to be undistin- guishable in this aspect). 28. Dicladia Capreolus: a, S. V. ; b, f, v. 29. Goniothecium Odontella: a, s. v.; b, f. v. 30. Periptera tetracladia. PLATE VII. (DIATOMs). Figure 31. Rhizosolemia Calyptra. 32. R. styliformis, from a figure sent by G. Norman, Esq., Hull. 33. R. setigera. 34. Syringidium Americanum. 35. Hercotheca mam- millaris. 36. Cocconeis Placentula. 37. C. transversalis. 38. C. distans. 39. C. pseudo- marginata. 40. C. excentrica. 41. Achnanthidium coarctatum. 42. Achmanthes longipes. 43. A. subsessilis. 44. A. exilis. 45. Cymbella cuspidata. 46. C. Ehrenbergii. 47. Cocconema parvum : a, s. v.; b, f. v. 48. C. Boeckii: a, s. v.; b, f. v. 49. Encyonema prostratum (frustules): a, s. v.; b, f. V. 50. Amphora angularis. 51. A. membranacea. 52. A. litoralis. 53. Syncyclia Salpa. 54. Amphora cymbifera: a, upper surface in focus; b, lower surface in ditto. 55. Navicula tumida: a, s. v.; b, f. V. 56. Amphora ovalis. 57. A. spectabilis: a, upper surface in focus; b, lower surface in ditto. 58. A. hyalina. 59. A. marina. 60. Gomphonema geminatum. 61. Navicula didyma. 62. N. Hitchcockii. 63. Stauroneis obliqua. 64. S. Crucicula. 65. Navicula (Pinnularia) major. 66. N. producta. 67. Stauroneis linearis. 68. Navicula rhynchocephala. 69. N. Hennedyi. 70. N. latissima. 71. N. rhombica. 72. N. Amphisbaena: a, s. v.; b, f. v. 73. N. Cluthensis. 74. N. borealis. 75. N. maxima, 76. Stauroneis acuta. TV. S. pulchella. PLATE VIII. (DIATOMs). Figure 1. Oncosphemia? (Diatoma elongatum y, SBD.). 2. Eupleuria ocellata. 3. Synedra robusta. 4. Dimeregramma pinnatum. 5. Tessella interrupta. 6. Dimeregramma Harrisonii. 7. Nitzschia Brightwellii. 8. Eupleuria pulchella. 9. Achmanthidium trinode. 10. Tetracyclus lacustris, s. v. 11. Cladogramma Californicum. 12. Rhab- donema mirificum, f. V. and s. v. 13. Cyclotella punctata. 14. Asteromphalus centraster, punctations of compartments omitted. 15. Omphalopelta areolata. 16. Amphitetras ormata. 17. Melosira arenaria, s. v. 18. Coscinodiscus mitidus. 19. Perithyra demaria. 20. Syringidium bicorne. 21. Asteromphalus heptactis. 22. Euodia gibba. 23. Bid- dulphia Macdonaldii. 24. Aulacodiscus Kittoni. 25. Periptera chlamidophora. 26. Coscinodiscus excavatus. 27. Triceratium trisulcum. 28. Aulacodiscus pulcher. 29. Triceratium castellatum. 30. Eumotogramma, s. v. 31. Microtheca octoceras. 32. Pleu- rosigma formosum. 33. P. Balticum. 34. Podosira? compressa. 35. Attheya decora. 36. Staurogramma Persicum. 37. Anaulus scalaris. 38. Schizonema Grevillii. 39. Lysicyclia Vogelii. 40. Schizomema Dillwynii. 41. Rhizomotia Melo 2 42. Rhizosolemia robusta. 43. Colletonema eximium, 44. Omphalotheca hispida. , 45. Pleurosiphonia aſſimis. 46. Toxonidea undulata. 47. Colletonema neglectum, 48. Stigmaphora rostrata. 49. Donkinia carimata, s. v. 50. Calodiscus superbus. PLATE IX. (DIATOMs). Figure 131. Melosira sulcata. *131. M. varians. 132. Actinoptychus senarius. 133–136. Navicula viridis. 137, 138. Surirella striatula. 139. Stauromeis Phoenic- enteron. 140. Amphipleura pellucida. 141. Navicula Amphisbaena. 142. Stauromeis platystoma. 143. Navicula nodosa. 144. Pleurosigma Balticum. 145. P. hippocampus. 146. P. acuminatum. 147. Symedra subtilis. 148. Nitzschia sigmoidea. 149. Cyma- topleura elliptica. 150–152. Surirella splendida. 153. Amphora ovalis. 154. Cymbella Ehrenbergii. 155. Cymatopleura Solea. 156–161. Epithemia turgida (except, in group 157, those º marked with a cross). *157. Epithemia Westermanni. 162, 163. Coc- coneis scutellum. 164. Eunotia triodon. 165. Epithemia granulata. 166, 167. Bacil- laria paradoxa. 168. Diatoma vulgare. 169. D. elongatum. 170. D. mesodom. 171. Himantidium pectinale. 172. Odontidium hyemale. 173–175. Fragilaria capucina. 176. F. virescens. 177–179. Meridion circulare. 180–182. Rhabdomema arcuatum. DESCRIPTION OF THE ENGRAVINGs." 953 PLATE X. (DIATOMS AND PROTozoA). Figure 183. Isthmia enervis. 184. Symedra Ulma. #185. S. capitata. 185. S. lunaris. 186. Podosphemia gracilis. 187–190. Gomphonema constrictum. 191—193. Licmophora flabellata. 194, 195. Cocconema lanceolatum. 196–198. C. Cistula. 199–202. Achmanthes brevipes. 203, 204. Rhabdomema arcuatum. 205. Acimeta mystacima. 206. Symcyclia Salpa. 207. Schizomema Hoffmannii. 208. Micromega Agardhii. PROTozoA:—209–211. Cyclidium Glaucoma. 212. Pantotrichum Enchelys. 213. Chaetomonas Globulus. 214, 215. Chaetotyphla armata. 216–218. Chaetoglema Volvocina. 219, 220. Peridinium Tripos. 221. P. Michaelis. 222, 223. Peridinium Fusus. 224–226. Glenodinium apiculatum. 227. Trichodima tentaculata. 228–230. T. Pediculus. 231, 232. Urocentrum Turbo. 233,234. Stentor Roeselii. PLATE XI. (DIATOMs). Figures 1 to 8. Epithemia turgida (Thwaites): 1. A view of concave surface; 2. A side view ; 3. Apposition of concave surfaces in the first stage of conjugation; 4. A front view of a single endochrome, showing it to have divided into two segments; 5. The young sporangia lying transversely between the cleft parent frustules; 6. The same, viewed end- ways, showing their cylindrical figure; 7. Increased growth of the sporangia; 8. The pro- duced sporangia ultimately much larger than parent fronds, and now striated like the latter. At the commencement of conjugation the fromds are enveloped in mucus, as shown. 9, 10, 11, 12. Gomphonema curvatum (Thwaites), illustrating the process of conjugation in this being, which generally resembles that in Epithemia. 14. Melosira mummuloides (Ralfs). 17. Gomphonema minutissimum (Thwaites) conjugating. 18. Dinophysis acuta (Ehr.), f. v. 19. D. limbata (Ehr.), f. v. 20 & 27. Melosira coarctata (Ehr.), f. vs. 21, 22. Amphitetras antediluviana (Ralfs): 21. A partial s. v.; 22. filament. 24, 25. Tetracyclus lacustris (Ralfs): 24. Filament; 25. A marginal view. 26. Melosira sulcata (Ehr.), a filament. 28. Actinoptychus Jupiter (Ehr.). 29. Melosira Italica (Ehr.), filament. 30. Sphemosira Catema (Ehr.), filament. 31. Actinoptychus? hexaptera (Ehr.). 32. Amphipentas? altermans (Ehr.). 33. Asterolampra Marylandica (Ehr.). 34. Asterom- phalus Hookeri (Ehr.). 35. Heliopelta Metii (Ehr.). 36. Symbolophora Trinitatis (Ehr.). 37. Spirillima vivipara (Ehr.): a member of the family Arcellina, having a close affinity with the calcareous-shelled Polythalamia or Foraminiſera. 38. Craspedodiscus elegans (Ehr.). 39, 40. Coscinodiscus radiatus (Ehr.): 39. f. v.; 40. s. v. 41, 42. Eupodiscus Argus (Ehr.): 41. f. v.; 42. s. v. (In fig. 41, the sites of the three tubular processes, which led Ehrenberg at first to call it Tripodiscus, are seen.) 43, 44. Triceratium Favus (Ehr.): 43. f. v.; 44. s. v. 45,46. Climacosphemia moniligera (Ehr.): 45. f. v.; 46. s. v. 47. Terpsinoë musica (Ehr.). 48, 49. Grammatophora gibba (Ehr.): 48. f. v., showing the two imperfect septa (vittae, Kütz.) at each end; 49. s. v. 50, 51. Zygoceros Surirella (Ehr.); 50. s. v.; 51. f. V. 52, 53. Grammatophora marina (Ehr.): 52. f. v.; 53. s. v. 54. Hemiaulus antarcticus (Ehr.), f. v. PLATE XII. (DIATOMs, PROTozoa, &c.). Figure 1. Amphiprora constricta (Ehr.), f. v. 2, 3, 4. Surirella Gemma (Ehr.): 2, 3. f. v.; 4. s. v.: these figures were intended especially to represent the foot-like pro- cesses (cilia. 2) and the foramina through which these are protruded. 5. Navicula cuspidata (Ehr.), s. v. 6. N. amphirhyncus (Ehr.), s. v. 7, 8, 9. Stauroneis phyllodes (Ehr.): 7, 8. s. v.; 9. f. V. 10, 14, 30. Stauroneis scalaris (Ehr.): 10. s. v.; 14, Process of self- division seen on f. v.; 30. s. v. 11. Campylodiscus flexuosa (Ehr.), f. v. 12, 13, 22, 23. C. Ehrenbergii (Ehr.): 12 & 22. f. Vs. ; 23. s. v.; 13. Viewed lying on one end. 15 & 31. Navicula major (Ehr.): 15. s. v.; 31. f. v. 16. Stauromeis dilatata (Ehr.), s. v. 17, 18. S. Phoenicenteron (Ehr.): 17. f. v.; 18. s. v. 19, 20. Surirella Craticula (Ehr.): 19. f. v.; 2O. s. v. 21. Navicula Tabellaria (Ehr.), s. v. 24, 25. Epithemia Librile (Ehr.): 24. f. v.; 25. s. v. 26. Amphora gracilis (Ehr.), s. v. 27. Epithemia gibba (Ehr.), ventral surface. 28 & 53. Gomphonema apiculatum (Ehr.); 28. f. v.; 53. s. v. 29. Himantidium monodon (Ehr.), s. v. 32. Navicula affinis (Ehr.), s. v. 33. N. Chilensis (Ehr.), ventral surface, s. v. 34 & 36. Symedra Gallionii (Ehr.): 34. f. v. of four conjoined ; 36. s. v. 35. Gomphonema Vibrio (Ehr.), s. v. 37; Amphora mavicularis (Ehr.), f. v. 38. A. Libyca (Ehr.), f. v. 39. Eumotia quinaria (Ehr.), s. v. 40. Diadesmis' lavis (Ehr.), f. v. 41. Cocconeis Finnica (Ehr.), s. v. 42. C. oceanica (Ehr.), s. v. 43. Na- vicula Esox (Ehr.), s. v. 44. Nitzschia valens (Ehr.), f. v. 45, 49, 50, 51, 52. Himan- tidium Papilio (Ehr.): 45 & 5l. Filaments; 49. A single frustule seen on ventral 954 DESCRIPTION OF TEITE ENGRAVINGS. surface; 50 & 52. s. v. 46. Cocconema cymbiforme (Ehr.), s. v. 47. Peridinium con- strictum (Ehr.): the median sulcus or constriction is well seen dividing the lorica into two segments—patellae or valves, each of which is here again composed of several facettes. A distinct nucleus (sexual gland, Ehr.) is shown. 48 a, b. Cocconeis Americana (Ehr.): 48 a. s. v.; 48 b. Several frustules adherent to a portion of Conferva. 54. Himantidium Guiamense (Ehr.), f. v. of a filament. 55, 56, 57. Colletonema, Amphioxys (Ehr.); 55. s.v. of a single frustule; 56. f. v.; 57. A collection enclosed in their mucous investment, seen in different positions. 58. Sphaerozosma? ... (Brightwell): this production was found by Mr. Brightwell (see “Fauma Infusoria of Norfolk'). We cannot perceive any affinity between his drawing and the members of the genus Sphaerozosma, to which he has surmised it might belong. 59. Ceratoneis Closterium (Ehr.), s. v. 60, 61. Pleurosigma Fasciola (Ehr.). 62, 63. Dictyocha Speculum (Ehr.): 62. Viewed in front; 63. Viewed sideways. 64. Difflugia acanthophora (Ehr.): its surface illustrates what is termed an imbricate disposition of the scale-like markings; a navicular body is represented in its interior, as seen through its transparent lorica. 65, 66. Asplanchma Brightwellii (Bright- well). These two figures are from Mr. Brightwell's book: 65 is there described as “a young specimen (female), just emerged, in which the red eye and germs of other organs are seen;” in 66 “may be seen the oesophagus leading to the stomach, and above the stomach two small bodies (either salivary or hepatic glands), and under it the opaque ovisac.” 67, 68, 69. Zoothamnium Arbuscula (Brightwell): these three figures from Mr. Brightwell illustrate the curious cycle in development referred to in the text. TO. Waginicola ... ? (Brightwell): apparently a Waginicola undergoing spontaneous fission: 71. Mesocena heptagona (Ehr.). T2. Navicula cardinalis (Ehr.), s. v. 73. Stauroneis Isostauron (Ehr.), s. v. PLATE XIII. (DIATOMs). Figure 1. Amphipleura pellucida. 2. A. rigida. 3. Surirella constricta. 4. Den- ticula elegans. 5, 6, 7. Amphiprora alata. , 8. Epithemia alpestris. 9. Ceratoneis spiralis, 10. Cocconema gibbum. 11. Gomphonema curvatum. 12. Epithemia Por- cellus. 13. (left) Podosphemia hyalina; (right) P. cuneata. , 14. P. Ehrenbergii. 15. Rhipidophora tenella. 16. Licmophora divisa. , 17. Rhipidophora Nubecula. 18. Epithemia Musculus. 19. Rhipidophora Meneghiniana. 20. Synedra fulgens. 21. Meridion circulare, war. 22. Grammatophora hamulifera. 23. Gomphonema acuminatum. 24, 25. Odontidium hyemale. 26. Tabellaria ventricosa. 27. Rhab- donema Adriaticum. 28. Pododiscus Jamaicensis. 29. Tabellaria flocculosa. 30, 31, 32, 32 a. Biddulphia obtusa. 33. Pyxidicula Adriatica. PLATE XIV. (DIATOMs). Figures 1 to 12. Fragilaria capucina. 13. Himantidium Soleirolii. 14. Cym- bosira Agardhii. 15. Achmanthidium microcephalum. 16. A. delicatulum. 17. Cyclo- tella Scotica. 18, 19, 20. Cymbella gastroides. 21. Rhaphoneis Amphiceros. 22. Encyonema prostratum. 23. Hyalosira rectangula. 24–28. Cymbella Helvetica. 29. Hyalosira obtusangula. 30. Sphenella angustata. 31. S. obtusata. 32, 33. Diadesmis confervacea. 34, 35 a, b. Berkeleya Adriatica. 36. Gomphonema coronatum. 37, 38 a, b, c. Homoeocladia pumila. 39–42. Micromega pallidum. 43, 44. M. bomby- cinum. 45, 46. Homoeocladia moniliformis. 47–49. H. Martiama. PLATE XV. (DIATOMs). Figures 1, 2. Cyclotella atmospherica (Ehr.). 3. C. Atlantica (Ehr.). 4. C. Simensis (Ehr.). 5. Staurosira construens (Ehr.). 6, 7, 8, 9. Epithemia longicornis (Ehr.). 10. Goniothecium crematum (Ehr.). 11. Epithemia Argus (Ehr.). 12. Navicula didyma (Ehr.). 13. Desmogonium Guianense (Ehr.). 15. Naviculataemiata (Ehr.). 16, 17. Himantidium monodon (Ehr.): 16. Two frustules conjoined in front view; 17. s. v. 18, 19, 20, 21. Arachnoidiscus ornatus (Shadbolt): 18. External membrane, as seem when detached from the inner framework, or when viewed from the outside of the shell as an opaque object; 19. The inner framework is exhibited on a black disc as an opaque object; 20. The mem- brane and framework united, as seen by transmitted light, ×200; 21. The same, more amplified, × 500. 22, 23. Campylodiscus parvulus (Smith): 22. s. v.; 23. Partial f. V. 24, 25. Grammonema Jurgensii (Ralfs): 24. Front and s. v. of a single frustule; 25. A filament. 26, 27. Melosira Nägeli: a series of figures to illustrate the distribution of the chlorophyll (endochrome), and the presence of a nucleus: 26 a viewed from the base; DESCRIPTION OF TEIE ENGRAVINGS. 955 26 b. from the lateral surface; two bands of chlorophyll are seem on each side, and their section at the angles; 26 c. from the base; 27. Seen from below, nucleus with nucleoli and sap-currents; large and small chlorophyll-globules; 27 b. Seen from the side; the two lateral bands of chlorophyll are seen, and a parietal nucleus, with Sap-currents from it, in the centre of one side; 27 c. An individual after division, seen from the side. The chlorophyll bands appear only in section. Each secondary cell has a parietal nucleus. 28 a, b, c, d. Bacillaria Nägeli: a, viewed from the broad side, a granular mucleus in the centre; b, also the broad side, an individual before division, the nucleus primarily divided; c, division complete; d, viewed from the base (in section). 29 a, b, c, d. Melosira Dickieii (Thwaites): a, filament, in ordinary state; b, filament, the terminal cells of which are becoming converted into sporangia; c, sporangia; d, sporangial frustules becoming deve- loped from one of the halves of a previously divided sporangium, X220. 30 a., b. Mas- togloia Danseii (Thwaites): a, portion of frond, ×35; b, a part of same, X220. In it two frustules are shown, one in front, the other on side aspect. 31. a, b, c, d. Dickieia ulvoides (Ralfs): a, matural size, in different stages of growth; b, frustules (navicular bodies) highly magnified when fresh; c, one when dried; d, a lateral view of the same ; e, a portion of frond, less highly magnified, showing the simple and binate frustules. 32. Melosira varians (Thwaites) (= Gallionella, Ehr.), filament with sporangia, X220. 33. M. Italica, filament with sporangia. 34. Dictyocha Fibula. 35. D. trifenestra. PLATE XVI. (DIATOMs AND DESMIDs). Figures 1 to 6. Navicula (Pinnularia, Ehr.) major. From Schleiden’s ‘Principles of Botany,’ to illustrate the structure of the silicious valve. 1. s. v. (venter, Ehr.). “In the middle lime are two clefts, terminating at the centre, as well as at the other ends, with a little circular enlargement, more clearly seen in figs. 3 and 5. The rounded spot in the middle, and at the two ends, is not a hole as represented by Ehrenberg. That such a hole is decidedly sometimes not present, is seem in such fragments as figs, 3 and 5. In the position of the oblique lateral clefts (striae or costae, Ehr.), the valve consists of two leaves, penetrated by the clefts, which, where both the lamellae touch each other, are somewhat broader, which explaims the varying breadth of the clefts according to the alteration of the foci. Fragments in which this structure is clearly represented may be frequently obtained by crushing the valve (fig. 6). 2. A front view, showing that the rounded enlargements of the median line are but depressions on the external surface. The double contour, denoting the thickness of the wall, is well seen. This clearly shows that a passage exists from the top to the bottom of the valve, which may be easily confirmed if the valve, or better still an oblique section of it, be looked at from above; fig. 5 is such a section.” T, 8. Cymato- pleura elliptica (Smith). 9. C. Solea. 10–19. Closterium Ehrenbergii (Smith), showing the stages in its conjugation, and the formation of the sporangia: 10. A single frond in its ordinary condition; il. Two fronds approaching to conjugate; 12. Conjugating fronds undergoing self-division, the upper showing the protuberances through the torn apices of which the contents of the divided fronds pass into the sporangia; 13. Shows the passage of the endochrome-sac and its contents; 14. Conjugated fronds having perfected their spo- rangia; 15 (after M. Morren). Development of the “propagules” into young fronds; 16, 17, 18, 19 (from Morren). Development of a sporangium into a Closterium with unequal segments: the figures are all magnified 100 times. 20–26. Surirella biseriata. (Smith). To illustrate the structure of the valve and self-division of the frustule: 2O. Wiew of frustules on the completion of self-division; 21. Apertures of costal canals seen in front; 22. Silex of connecting membrane after maceration in acid; 23. f. V. (the broad median longitudimal band is the commecting zone of the two valves); 24. S. W.; 25. e. V. ; 26. Transverse section of empty frustule. PLATE XVII. (DIATOM'S AND PHYTozo A). Figures 506–509. Pyxidicula globata. 511 & 515. Xanthidium? ramosum. 512. X. hirsutum. 513, 514. X. 2 diſſorme. 516–518. Campylodiscus Clypeus. 519–531. Spirillum Bryozoon. 532,533. Astasia navalis. 534. Gyges sanguineus. PLATE XVIII. (Phytozoa). Figure 1. Monas Crepusculum, X800. 2. Monas Punctum. 3, 4. Uvella Glaucoma, × 350: 4. Detached monads. 5. Polytonia UVella. 6. Microglena monadima. 7. Gle- 956 - DESCRIPTION OF THE ENGRAVINGS. momorum tingens, x250. 8. Doxococcus ruber. 9. Bodo intestinalis, X300. 10 & 21. Momas Lens. 11 a, b. Cercomonas lobata. 12 a, b. C. trumcata. 13 a, b. Amphimomas dispar. 14. Chilomonas Paramecium, X380. 15. Monas elongata. 16. Trepomonas agilis. 17. Momas globulosa. 18. Chilomonas granulosa. 19. Momas attenuata. 20. Cercomonas acuminata. 21. Monas Lens (two figs.). 22. Cercomonas longicauda. 23. C. Globulus. 24. Spiromonas volubilis. 25. Pleuromonas jaculans. 26. Heteromita exigua. 27. Tre- pomonas agilis. 28 a, b, c, d. Trichomonas Batrachorum. 29. Cryptomonas ovata, X300. 30. Prorocentrum micans. 31. Lagenella euchlora. 32. Cryptoglema conica. 33, 34. Trachelomonas Volvocima. 35 a, b, c, d. Chonemomas Schrankii: c, d. War. C. unifilis. 36. Astasia haematodes. 37–39. Euglema sanguinea. 40, 51, 54. E. viridis, encysted and in act of fission. 41, 42. E. Pyrum, X.400. 43, 44. E. longicauda. 45. Ambly- ophis viridis. 46. Euglema viridis. 47. Chlorogonium euchlorum. 48 a, b, c, Astasia limpida. 49, 50. A. contorta. 52. Euglena spirogyra. 53, 55. Eutreptia viridis. 56, Zygoselmis inaequalis. 57. Bacterium triloculare. 58. Spirochaeta plicatilis. 59. Spirillum Undula. 60. Wibrio Bacillus. 61. Spirillum Undula. 62. Vibrio Bacillus. 63. Spirodiscus fulvus. 64. Wibrio Rugula. 65, 66. Sporomema gracile. 67, 68. Spi- rulina plicatilis. 69. Zoogloea Termo: a mucoid mass of Wibrios, the individuals of which are equivalent to Bacterium Termo of Dujardin, PLATE XIX. (PHYTozoA). Figure 1. Chromatium Weissii. 2. Menoidium pellucidum. 3. Tetramitus descissus. 4–6. Mallomonas Plöslii. 7 a, b, c, Phacotus viridis. 8. Anisonema Acimus. 9, 10. Trypemonas Volvocina. 11. T. cylindrica. 12. Chonemonas acuminata. 13, 14. Lepo- cinclis Globulus. 15. Hirmidium imame. 16. Chlamydomonas pulvisculus. 17. Dinema griseolum. 18, 19. Eutreptia viridis, 20–31. Chlamydococcus (Protococcus) pluvialis, its forms and development, after Cohn ; 20. A still cell revived after desiccation; 21. Cell with nucleus; 22. Still cell with dense external coat; 23. Fission of primordial within the parent cell; 24. Fission of a still cell, wall of parent cell become gelatinous; 25. Division of secondary cells; 26. Fission of encysted cell into four secondary, and 27. into thirty- two cells; 28. The several cells produced set free, a membrane thrown out around one; 29. An irregular-shaped, Euglema-like zoospore; 30. A cell on the point of assuming the motile condition; 31. A very small, globular, encysted zoospore. 32–37. Gonium pectorale: 32. A perfect tabular frond; 33. Detached cells, showing their contractile vesicles; 34. Four cells (gonidia) united by the radiating tubular processes of their external membrane, into which the green contents do not enter; 35. Excepting one cell of the tablet, all the others have proceeded, to a greater or less extent, by the process of fission, to generate “daughter cells,” or the rudimentary gonidia to form new tablets; each one is still surrounded by the “mother-cell” wall; 36. A tablet, of which the original gonidia are widely separated, and loosely held in Situ by the external cell-wall; fission has further proceeded, and rudimentary tablets formed from each original gonidium, consisting of sixteen “daughter cells” (macrogomidia); in 37 the connecting bonds are quite dissolved, and the sixteen secondary tablets set free: all × 500. 38–58. Stephanosphaera pluvialis, exhibiting its forms and modes of development: 38. An equatorial view; 39. Lateral view, gonidia spindle-shaped, with protoplasmic elongations; 40. Division of gonidia into four “daughter cells”; 41. Further divided into eight, united in an annular form; 42. A further-advanced stage, macrogonidia now forming distinct families, like the one repre- sented in fig. 57; 43. Division of gonidia preparatory to forming microgonidia; 44. A full-grown resting cell; .45. Beginning of division of a resting cell; 46. Division into four, outer membrane disappeared; 47. Tapering of one end of secondary or “daughter" cell preparatory to formation of cilia; 48, 49. Naked zoospores; 50. Encysted zoospore (gonidium); 51. Resolution of all the gonidia, except one, of a mature Stephanosphaera into microgonidia; 52. Detached ciliated microgonidia; 53. An encysted zoospore with protoplasmic elongations of the primordial cell; 54, 55. Division of encysted zoospore; 56. More advanced stage of division; 57. A young family of eight cells; 58. Another, with the cellular envelope still visible within the membrane of the mother cell: X500 (Cohn). 59–69. Pandorina Morum: 59. Perfect form, with sixteen gonidia, side view; 60. The same, polar view; 6l. A gonidium, side view; 62. A frond with the gonidia divided; 63. A more advanced frond; 64. A young frond of ſig. 63, after formation of cilia, set free; 65, 66. Young fronds, gonidia pushed close together; 66. A polar view; 67. End or polar view of a frond like 65, the gonidia of which are encysted and turned red and their gelatinous envelope nearly dissolved; 68. A side view of the same; 69. A single emcysted gonidium. Figs. 59 to 68 (except 61), x 100; figs. 61 & 69, x400 (Henfrey). & DESCRIPTION OF TITE ENGRAVINGS. 957 PLATE XX. (PHYTozoA). Figures 1–14. Polytoma Uvella, forms and development of: 1. Perfect form; 2. Same, acted on by chromic acid, which has separated the primordial cell from the external envelope; 3–6. Stages of fission-process; 7. Resting stage; 8. External membrane broken up into granules; 9. Fission into four; 10–12. Arrangement of secondary or “daughter” cells; 13. Contraction of body within external envelope; 14. Body retracted from ante- rior extremity: x300 (Schneider). 15–21. Fission and formation of microgonidia in Chlorogomium euchlorum. 22, 23. Pandorina Morum (?): 22. A presumed form of, with encysted immature fronds, x 150; 23. Another presumed form, x220. 24. Chlamydococcus (?), a presumed form of; the two internal globular cells of a clear ruby-crimson; the moving granules probably monads; suggested to be Spermatozoa, X220 (Currey). 25. Volvocina, a developmental phase of one of the, having encysted gonidia. 26–28. Syncrypta Volvox, x260. 29, 30. Synura Uvella: 30. Section of a group (Ehr.). 31. Uroglena Volvox. 32. Wolvox Globator. 33–49. Illustrations of structure and development of Wolvox Globator (Busk and Williamson): 33. A section showing parietal cells and contained gemmae ; 34. Portion of edge of an embryo Volvox viewed in the equatorial plane to show the common envelope and the position of the subjacent cells or gomidia; the last not passing beyond the external gelatinous (?) coat (Busk); 35. Highly magnified view of three cells; the faint lines between indicate the limits of the gelatinous envelope of each cell; 36. Section of a specimen mounted in glycerine (Will.); 37. Cells seen from above, showing radiating threads; 38. Oblique section, mounted in glycerine; 39–41. Single cells; 42—44, 46, 47. Progressive development of Volvox by fission; 45. Diagram of a superficial view of a portion of a globe (Will.); 48, 49. Winter spores of Volvox aureus: 48. An earlier; 49. A later and mature condition (Busk). PLATE XXI. (PROTozoA). Figure 1. Amoeba Schultzii, x330. 2. A. globularis, X330. 3. A. porrecta, x330. 4. A. princeps, x 100. 5 a, b, c. Amoebiform germs or “Proteans” of Spongilla. 6. Miliola vulgaris. 7–9. Arcella vulgaris; 8. A side view ; 9. Empty shell. 10. Difflugia globulosa, X 150. Il. Euglypha alveolata, empty shell, X340. 12–14. Gromia oviformis: 12. A young specimen; 13, 14. Nuclear bodies found in (Schultze), X300. 15. Arcella Okenii. 16. Gromia oviformis, X300. , 17. Difflugia pyriformis. 18 a, b. Supposed young forms of Gromial)ujardinii: a, ×72; b, ×180. 19 a-f. D. Enchelys: a, b. Different forms; c. Contents resolved into granules; d, e. Fission into two and four portions; f. Two individuals coherent. 20 a, b, Early stage of an undescribed Miliola: a, x72; ö, X330 (Schultze). 21, 22. Miliola obesa: 21. A young specimen, ×72; 22. Shell, after the removal of the calcareous matter by dilute acid. 23. M. Ancomensis. 24. Animal contents of a Miliola after dissolution of the shell by acid; displaying a constric- tion at each half turn, and the delicate membranous envelope at the lower and larger extremity. 25. Cornuspira perforata. 26. Rotalia Veneta, seen in front. 27. Rosalina ormata, portion of shell of, ×100. 28. Polystomella venusta, x72. 29, 30. P. Stella- borealis, seen in front, x72; 30. Portion of cell to show structure, X 180. 31. Rotalia Veneta, shell after action of acetic acid, × 180. 32. Nuclear body from the last chamber of Textilaria picta, X330. 33. Rotalia Veneta, X.50, 34 a, b. Acervulina acinosa; b. Natural size. 35. Acervulima globosa, portion of shell, X300. 36. Textilaria picta, × 180. 37. Acervulima globosa, section through thickness of shell, X300. 38. Polymor- phina silicea, silicious matter detached by pressure, X300, 39. Polystomella strigilata, animal substance with attached particles apparently assuming am independent existence, ×330, 40. Portion of contents of Gromia IJujardinii. (Figures 20 to 40, Schultze.) PLATE XXII. (PROTozo A). Figures 1–3. Amoeba radiosa; 2. An older specimen; 3. One nearly divided into two. 4, 5. A. Limax. 6. A. guttula. 7–11. A. bilimbosa: in 7 and 9 the external envelope strongly marked by a double outline; a clear zone within it; 9. First stage of encysting; 10. A nucleus with a central clear space, and one with two nucleoli; 11. A specimen acted on by solution of iodime; contained starch-granules coloured blue. 12–18. A. actinophora: in 13 two pulsating vesicles occur; 15. Specimen acted upon by acetic acid, showing double outline of integument; 16 contains refracting particles of a crystalline form; 17. Some such particles isolated, and more highly magnified; 18. Two coherent individuals, indicative either of fission or of conjugation. 19. Cadium marinum. 20–23. Amoeba bilimbosa: 20. Treated with iodine, the starch-granules coloured blue; 958 I).ESCRIPTION OF THE ENGRAVINGS. 21. An emcysted specimen; 22. A ruptured and empty cyst; 23. Probably the act of fission. The large circular body lying between the two halves is an encysted Oxytricha which has been taken up by the Amoeba. 24–27. Cyphidium aureolum. 28, 29. Grega- rina Sipunculi; 29. A double being, the result of fission. 30–32. Progressive develop- ment of the contents of a Gregarima from an Amnelid (Coenurus variegata) into pseudo- navicellae, in other terms, three pseudo-navicella capsules. 33. G. clavata. 34. G. Sieboldii, full-grown. 35, 36. G. Terebellae; 36 exhibits longitudimal costae. 37. A group of Psorospermia, from a cyst in the eye of a Cyprinus Timca. 38 a, b, c, Full- grown Psorospermia: a, viewed in front, x900; b, seen from above; e, on one side. From the vesicula of Gadus lota. 39. Psorospermia from a cutaneous cyst on a Gasterosteus (Stickleback), x580. 40. Psorospermia from a cyst of Gosterosteus aculeatus; a group showing the different stages of development, 41. Psorospermia burst by pressure from Cyprinus Brama; b, the contained amoebiform body isolated, ×900. 42. Epipyxis TJtriculus. 44, 45. Microtheca octoceros. 46. Opalina Lumbrici. 47. O. armata, transverse fission. 48, 49. Dinobryon Sertularia. PLATE XXIII. (PROTozoA). Figures 1, 2. Actinophrys, figured as one phase in the development of Vorticella microstoma by Stein: a, external coat; b, nucleus; c, vesicle. In 2 a ciliated embryo appears within a distinct sac. 3–5. Podophrya fixa (?), represented by Stein as another phase, besides figs. 1 and 2, in the development of Vorticella microstoma. A ciliated germ is seen in 4, which in 5 is about to escape. 6–8. Other forms of Podophryean Acineta, as figured by Stein: 6,7. As treated with acetic acid; the development of an embryo from the nucleus is shown in figs. 7 and 8. 9–14. Vorticella-cysts, after Stein's figures. In 9 the nucleus is resolved into monadiform germs; 10, 11. Development of cyst-contents into secondary cysts, which are further seen in figs. 12 and 13 as become fusiform and protruded through the wall of parent cyst, so as to discharge their monadiform germs without, as seen in fig. 14. 15, 16. Acineta diademiformis, with its embryo. 17–2O. A. linguifera, or Acineta with the tongue-like process attributed to Opercularia berberina; 20 shows an empty capsule. 21. A. digitata, or Acimeta with the finger-like processes. 22, 23. Acimeta attributed by Stein to Opercularia Lichtensteinii; 23. A specimen acted on by acetic acid. 24, 25. Actinophrys oculata; 25 represents three individuals in the act of conjugation, treated with acetic acid. The contents of two have intermingled; a large vacuole with food- particles lies between them. The individual on the other side is simply coherent. (1–26, Stein.) 26, 27. Acineta ferrum-equinum; 27 shows the escape of the ciliated embryo. The horseshoe-shaped nucleus appears as a clear space. 28. Actinophrys Sol. 29, 30. A. Eichhornii; 30. A highly magnified section to show the reticulated structure. 31, 32. A. Sol: 31. In the act of self-division (conjugation ?); 32 shows three vesicular expansions concerned in the introduction of food, and an encysted animalcule just brought to the surface. 33–35. Podophrya fixa; 34. In act of fission; 35. Segment becoming one indo- pendent and about to separate. 36, 37. Encysted Podophryae. 38, 39. Stages of Podo- phrya towards encysting. 40, 41. Acimetae with embryos. 42, 43. Transformation of the embryo into an Acimeta, figured as commencing in 43, and as completed in 42. PLATE XXIV. (PROTozoa). Figures 274, 275. Lacrymaria Proteus, , 276, 277. Leucophrys patula. 278. T. Spathula. 279,280. L. sanguinea. 281. Holophrya. Ovum, 282,283. Prorodon teres. 284–286. Coleps hirtus. 287, 287*, 288, 289. Trachelius Amas. 29O. T. Ovum. 291–293. Loxodes Rostrum. 294, Bursaria Vorticella. 295. B. leucas. 296. B. Pupa. 2.96%, Spirostomum virens. 297, 298. S. ambiguum. / 299. Phialina viridis. 3oo- 302. Glaucoma scintillans. 303-309. Chilodon Cucullulus. 310,311. Nassula elegans. 312, 313. Amphileptus Anser. 314–316. A. Fasciola. 317–319. Trachelocerca Ölor. 32O. T. biceps. PLATE XXV. (PROTozoa). Figures 321–323. Aspidisca denticulata, 324–328. Kolpoda Cucullus. 329–332. Paramecium Aurelia. 333. Uroleptus Musculus. 334, 335. Ophryoglema acuminata. 336, 337. Oxytricha gibba. 338, 339. Ceratidium cuneaturm. 340, 341. Reroma polyporum, 342. Urostyla grandis. 343, 344. Stylomychia lanceolata. 345, 346. Discocephalus rotatorius. 347, 348. Himantophorus Charon. 349. Chlamidodon Mnemosyne. 350–353. Euplotcs Charom. 354, 355. Ptygura Melicerta. 356. Ich- DESCRIPTION OF TIII) ENGRAVINGS. 959 thydium Podura. 357, 358. Chaetomotus Larus. 359, 360. Glenophora Trochus. 361-364. CEcistes crystallinus. 365–370. Conochilus Wolvox. s PLATE XXVI. (PIIYTozoA). The following figures are derived from M. Dujardin's excellent treatise, ‘Histoire des Infusoires':-Figure 1. Hexamita modulosa. 2. Anthophysa Mülleri. 3, 4. Acineta tuberosa; in 4 the cilia included. 5. Heteromita ovata. 6. Crumenula texta. 7. Poly- selmis viridis. 8. Amisonema sulcata. 9 a., b. Oxyrrhis marina. 10 a., b. Ploeotia vitrea. ll. Heteronema marina. 12 a, b. Zyzoselmis nebulosa. 13. Peramema globulosa. 14. Cyclidium distortum. 15. C. abscissum. 16 &, b. Acomia Cyclidium ; b, self-dividing. PLATE XXVII. (PROTozoa). Figures 1–9. Vorticella microstoma: 1. With a bud growing from its base; 2. A specimen about to detach itself from its stalk, and having a posterior wreath of cilia; 3. Self- division proceeding; in 4 complete; 5 a, b, c, d. Encysting-process; 5 e. A cyst ruptured by pressure, giving exit to the included Vorticella, apparently unchanged; 6. Supposed transi- tional forms from rudimentary campanulate organisms to undoubted Vorticellae; 7–9. Process of encysting, and progressive disappearance of special organs. 10–15. Waginicola crystallina: 10. Self-division; 11. One of the fission-products contracted and ready to escape by means of its posterior wreath; 12–15. Acimetae formed from Vaginicolae. 16–23. Epistylis mutans: 16. Two individuals on a stem; the ciliary apparatus protruded in one, contracted in the other; 17, 18. Supposed Acimetae; Acineta-body of the Epistyliss in 17 the wavy outline indicates the contractions taking place in the integument; in 18 the out- stretched ciliary fibres or processes, two nuclei, and a large contractile vesicle are visible; 19. Another such body, with its surface much contracted, and its contained substance wasted by the development of embryonic nuclei; 20. Another figure assumed by the Acimeta-body; 21. The ultimately withered state arrived at by the Acimeta-body of an Epistylis, after the exhaustion of its contained formative blastema by the repeated produc- tion of embryos; 22, 23. Very young forms (probably) of the Epistylis mutans, and appa- rently the Epistylis Botrytis of Ehrenberg. PLATE XXVIII. (PROTozoa). Figures 1–3. Nassula ambigua: 1. Under surface; the two long articulated filaments within are portions of Oscillatoriae; c, vesicle; d, nuclous; 2. Encysted specimen; 3. Ani- malcule forced from its cyst by pressure. 4–7. Glaucoma Scintillans: 4. Under surface; 5. An encysted being, seen in 6 undergoing transverse fission, which in 7 appears oblique, owing to a change of position of the resulting segments. , 8,9. Prorodonteres: 9. Its nucleus surmounted by a rim-like nucleolus. 10. Stylomychia Mytilus. (1–10, Stein.) 11–15. Nassula elegans: in 11 internal germs occur in a cavity (uterime) communicating externally by a canal (oviduct); 12. Germ loosing itself from the parent; 13. A fission-product enclosing a germ ; 14. Germ developing Acimetiform tentacles; 15. Nucleus terminated at its narrow end by a nucleolus. 16. Stentor Mülleri, surrounded by an envelope with monads in its interior; 17. Same, animal contracted in its case. (11–17, Cohn). 18, 19. Waginicola valvata. The valve is seen closed at bin fig. 18; fission has occurred both in this and in 19, but the animal is contracted in the former, and expanded in the latter example; in 19 the valve appears as a streak parallel with one side. 20–23. Lagotia viridis; 20. Head of a young individual; 21. Lateral view of animal and of its ciliated head; 22. Tip of one of the lobes of ciliated head; 23. Animal with front view of head. (18–23, Wright.) 24–26. Otostoma: the oral cavity is seen as an ear-shaped space; in 25 two vesicles also are seen opening externally. (Carter.) 27–30. Coenomorpha Medusula. 31. Panophrys griseola. 32. Habrodon curvatus. 33, 34. Blepharisma hyalina. 35. Cinetochilum margaritaceum. 36, 37. Cyclogramma rubens. 38, 39. Stichotricha secunda. 40–42. Pyxidium ovulum; in 42. Act of fission. 43, 44. Stichotricha secunda. 45. Colobidium pellucidum. 46,47. Mitophora dubia. 48,49. Apionidium modesium. 50, 51. Lembadiom bullimum. 52–54. Baeonidium remigans. 55–57. Opisthiotricha tenuis. 58–60. Megatricha partita. 61. Acropisthium mutabile. 62, 63. Siagontherium tenue, (27–63, Perty.) , 64 a-k. Enchelys Farcinem, illustrating change of form consequent on the introduction of food. 65–71. Nassula viridis; 65. Natural form, ×370; 66, 67. Cysts; 70, 69, 68, 71. Development of cyst-contents into monadiform germs, enclosed within saccular theeae, and at length discharged externally as in fig, 71: 960 DESCRIPTION OF TEIF ENGRAVINGS, ×300 (Cienkowsky). 72,73. Enchelys Pupa. 74–76. Stylonychia pustulata: 74. the animalcule encysted, x300. 75, 76. Rotating cells within the cysts, X220 (Cienkowsky). PLATE XXIX. (PROTozoA.) Figure 1. Worticella Campanula, viewed from the ventral aspect. 2. Carehosium polypinum, viewed in front and directly upon the ciliated disc: , the mouth; e, the anus. 3. Scyphidia limacina. 4. Opercularia berberina, seen from the back. 5, 6. Chaºtospira Mülleri: 6 represents the animal in motion. 7. Stentor polymorphus, showing vascular canal around the head and along one side. (1–7, Lachmann.) 8–13. S. caeruleus, and its supposed internal germs or embryos in different stages of development (Eckhard). 14, 15. Trichodima Pediculus: 14. A lateral view ; 15. Anterior extremity. 16. T. mitra. 17. T. Pediculus, a dead, distended specimen. (14–17, Stein.) 18. Stylonychia pustulata, encysted (Stein). 19, 20. Amphileptus fasciola: seen encysted in fig. 19, and as escaped from the cyst in fig. 20. 21–24. Oxytricha Pellionella: 21. Encysted; 22. Cyst acted upon by hydrochloric acid; 23. Animal revived in its cyst prior to its escape; 24. The free animal. 25–34. Paramecium (Loxodes, Cohn) Bursaria, its structure and develop- ment: 25 to show circulation of contents; 26. Portion of integument highly magnified ; (19–26, Cohn;) 27. Transverse fission; 28. Nucleus seen at c, the nucleolus at d, 29. Embryo attached to the nucleus; 30. Embryo escaped but still adherent by acimetiform tentacles; 31. Nucleus and attached nucleolus separated by acetic acid; 32, 33. Nucleus and nucleolus during fission of animal; 34. Nucleus, mucleolus, and commencing embryo. 35–47. Rolpoda Cucullus, illustrating its forms and development: 37. Acted on by alcohol, to bring its nucleus into view; 38. An animal contracted into a spherical shape; 39. A similar one undergoing fission; 40. Encysted Kolpoda; 41. Same, in act of fission; 42. Fission completed; 43. Specimen treated with alcohol; 44. Cyst-contents divided into four; cyst-wall soft and irregular; 45. Embryo escaping from a cyst; 46. A ruptured cyst giving exit to encysted germs, as seen in 47, 48–59. Chilodon Cucullulus: 48 b. The so-called dental cylinder; c, mucleus and mucleolus; 49. A specimen with a large upper lip, equivalent to C. uncimatus (Ehr.); 50. Transverse, and 51. Longitudinal fission; 52. Contracted prior to encysting; 53, 54. Cysts; in 54 an embryo developed; 55. Appa- rently laminated cyst discharging its contents; , 56, 57. An empty cyst, with the aperture through which its contents have escaped remaining; 58. A cyst containing a parent animal and an embryo; 59. A liberated embryo, equivalent to Cyclidium Glaucoma (Ehr.). (26–59, Stein.) PLATE XXX. (PROTozoa, after Steim). Figures 1–4. Opercularia articulata: 2. A highly magnified view of the head; 3, 4. Supposed Acineta of this species; an embryo shown in fig. 4. 5–8. Ophrydium versatile: Tm 5 the animal is seen extended, and in 6 contracted; 7. Encysted animal; 8. Its sup- posed Acimeta. 9, 10. Carchesium polypinum: 10. A highly magnified view of its stem. 11. Epistylis crassicollis, 12. Cothurnia curva. 13, 14. C. Sieboldii: 14. A side view. 15, 16. C. Astaci; 16. Animal contracted. 17–26. Spirochoma gemmipara, and its develop- ment: 17 exhibits a gemma; 18–20. Progressive development of the spiral head in a gemma; 21. Encysted gemma; 22. Supposed Acimeta (the Dendrocometes) in its early stage; 23. As fully developed; 24. Embryo (seen in 23) set free; 25. A Dendrocometes, without arms, but with a contained embryo ; 26. A free embryo revolving on its long axis. 27, 28. Spirochona Scheutenii; 28. After the action of spirit of wine. , 29–36. Lagenophrys Waginicola, its structure and development: In 29 a gemma is seen in the act of fission; in 30 the animalcule has its rotatory apparatus retracted; 31 shows the detachment of the head of the animal from the mouth of its sheath, to allow escape of a gemma; 32. Act of fission; 33. Formation of a gemma at posterior extremity; 34. Several gemmae enclosed; 35, 36. Act of fission; complete in fig. 35, where the parent segment is detached from the orifice of the sheath, leaving a portion of its interior extremity. 37. Opercularia micro- stoma: A, extended; B, contracted. PLATE XXXI. (PROTozoa). Figures 1–4. Bursaria leucas, and the position and structure of the trichocysts found in its integument: 1. X90; 2. Diagram of the margin, to show position of trichocysts in the dermal layer; 3. Trichocysts projected from the surface after the application of acetic acid; 4. Detached spiral trichocysts in the second stage of evolution from elongated oval corpuscles (Allman). 5–6. Corethria Sertulariae: in 5 the two sorts of processes are both I).ESCRIPTION OF THE ENGRAVINGS, 961 seen; that in the right is the normal form; 6. More magnified view of the fusiform process, showing the terminal depression or aperture. 7–13. Lagotia producta, its structure and development: 7. Animal extended, in 8 contracted; 9, 10, 11. Larva or embryo; IO represents it attached; 12. Diagram of structure of the sheath, showing the ectoderm (colletoderm) at a, the chitinous tube at b, and the endoderm at c, d points out the mode of overlapping of the several segments of tube; 13. Highly magnified view of a portion of tube. i4, 15. Zooteireareligata: 14. Animal expanded; 15. Contracted. (5–15, Wright.) 16–20. Peridinium uberrimum : 17. Seen on opposite side to that shown in 15; 18. Transverse fission; 19. Same specimen after the application of solution of iodime; 20. Nucleus isolated (Allman). 21, 22. P. depressum: 21. A side-, 22. A front-view. 23. P. longipes. (16–23 after Bailey.) , 24–27. Dysteria armata: 25. Parts of mouth; 26, 27. Process between two styles: 26. A front-, and 27 A side-view (Huxley). 28. Turbanella hyalina, dorsal view; d, the muscular Oesophagus; g, testis; f, mature egg; e, ovary (×350). 29, 30. Chaetomotus maximus: 29. Dorsal view (×350); 30. A lateral view. 31. Ideal section of Turbanella hyalina through the generative organs. (28–31, Schultze.) 32—39. Noctiluca militaris: (32. N. punctata, Busch; a, oral cavity or hilum; b, sharp- bordered rod; c, nucleus; d, proboscis [cilium]; f, brown corpuscles, after Busch ;) 33. Front view, a, the tooth; b, oral aperture; c, position of supposed amus (after Webb); 34. Dorsal view, showing the groove; and 35. A latero-inferior view, displaying the oral cavity with the tooth, d; the cilium a gastric pouch, e, and a presumed anal aperture (Huxley); 36–39 (after Busch): 36. A germ in process of development; 37. Brown granular body, seen at f in fig. 32; 38. A germ; 39. Further advanced, acquiring the characters of a Noctiluca. PLATE XXXII. (ROTATORIA). Figures 371, 372. Microcodon Clavus. , 373. Cyphonautes compressus. 374–378. Megalotrocha albo-flavicans. 379–382. Tubicolaria Najas. 383, 383 *. Stephanoceros Eichhornii. 384, 385. Floscularia ornata. 386, 387. Melicerta ringens. 388–392. Limnias Ceratophylli. 393. Enteroplea Hydatina. 394. Hydatina senta. 395, 396. Pleurotrocha gibba. PLATE XXXIII. (ROTATORIA). Figures 397, 398. Furcularia Reinhardtii. 399 & 417. Monocerca bicornis. 400–402, & 425. Polyarthra platyptera. 403. Diglena lacustris. 404, 405. D. grandis. 406–408. Triarthra longiseta. 409. Rattulus lunaris. 410, 4ll. Distemma Forficula. 412 & 414. Triophthalmus dorsalis. 415. Eosphora Najas. 416. Notom- mata Copeus. 418–420. N. Myrmeleo. 421. N. Tigris. 422. Synchaeta pectinata. 423, 424. Scaridium longicauda. PLATE XXXIV. (ROTATORIA). Figures 425%, 426. Cycloglena Lupus. 427–429. Theorus vernalis. 430–433. Lepadella ovalis. 434–437. Monostyla quadridentata. 438–440. Mastigocerca carinata. 441–444. Euchlamis? triquetra. 445, 446. E. Lynceus. 447–453. Salpina mucronata. 454–456. Dinocharis Pocillum. 457–459. Momura dulcis. 460–462. Colurus deflexus. 463-465. Metopidia Lepadella. 466,467. Stephanops lamellaris. 468, 469. Squa- mella oblonga. 470–473. Callidina elegans. PLATE XXXV. (ROTATORIA). Figure 474. Hydrias cormigera. 475. Typhlima viridis. 476–480. Rotifer vul- garis. 481–484. Actinurus Neptumius. 485, 486. Monolabis conica. 487–489. Philodina aculeata. 490. P. roseola. 491–494. Noteus quadricornis. 495–497. Anuraea Squamula. 498. A. stipitata. 499–50l. Brachiomus polyacanthus. 502-504. Pterodina Patina. 505. P. clypeata. PLATE XXXVI. (ROTATORIA). Figure 1. Molicerta ringens, protruded and fully expanded, with the upper part of its tube at a, b, one of the tactile tubes; the circular disc at c is the pellet-cup; at m are the Jaws and gizzard (oesophageal head); and below, the stomach; c, a * magnified Q. 962 DESCRIPTION OF THE ENGRAVINGs. specimen, partially protruded from its tube, which is here shown entire, X300. 2. Lim- mias Ceratophylli: the end is protruded beyond the smooth tube or sheath; at e is the projecting chin. 3. Notommata aurita, viewed laterally, contracted: it exhibits the Ceso- phageal head and jaws (b), the intestine, the large ovarium, the contractile sac below, the grape-like gangliomic mass in the head (g), and the tortuous vessels on each side, running the length of the body. 4. The same animal extended and rotating; the ear-like ciliated appendage, whence the specific name, is seen on each side of the head. , 4 a. The ciliated lobes of the rotary organ; b, the gizzard, with its jaws; g, the cerebral (?) mass; k, glands above the stomach; o, large matured egg in the ovary. 5. Notommata aurita, viewed dorsally, the viscera omitted, to show the muscular system; the transverse muscles are seen at £, and the longitudimal, crossing them, at l; the grape-like gangliomic mass appears connected with special muscles, as also the gizzard, traced in dotted outline, and the telescopic-working tail or foot (b); the looped band at the head (o) indicates the tubular cavities in the head-mass. 6. The same animal, showing chiefly its water-vascular system; the large sac near the bottom of its cavity (v) is the contractile bladder, from which proceed, on each side, convoluted tubes (tortuous vesicles) furnished with tremulous respiratory tags, as near a ; the transverse muscular bands seen at #. 6+. The dental apparatus of the gizzard as seen in action. T, 8. The male of Asplanchna priodonta: 7. s. v.; 8. f. V. The cavity is seen occupied chiefly by the large testes in fig. 7; the sperm-duct is represented opening externally at the pointed base. 9. The female of Asplanchma priodonta: at a are the gill-like fissures; a large oral cavity opens into a narrow oºsophagus, which ends below in a stomach. One of the strong longitudinal muscles is displayed, also tortuous vessels and ciliated tags, with an ovary. 10, 11. The jaws of the Asplanchma detached. PLATE XXXVII. (RotATORIA). Figure 1. Stephanoceros Eichhormii: a, sheath; b, pharynx; c, proventriculus, or crop; d, maxillary head with jaws; e, stomach with large glandular cells; f, intestine or rectum; g, ovary with contained ova (g at pedicle indicates the longitudinal muscles in that segment); #, respiratory canal and tags. 2. Ovary and the enveloping membramous sac, or uterus, extending from it, containing ova in different stages of development: á, stroma of ovary with inherent ova; the darker segment probably indicates the position of a winter ovum developing; b, ovum dividing; c, ovum in which division of yelk has been several times repeated; d, an ovum in which the rude outlines of the embryo are distin- guishable, the two eyes at d, and the sac with the so-called urinary concretion at k; f points to the uterime or ovarian enveloping membrane. 3. A very young Stephanoceros. 4. An embryo of Stephanoceros immediately after its exit from the shell. 5. An ovum of Lacinularia. 6. Another ovum of the same, its yelk in process of fission. 7. A portion of the ovary of the same, with four contained ova. 8. An ovum of the same, in which division has been repeated several times. 9. Another ovum, wherein fission has been repeated until the yelk is broken up into a number of cells. 10. A young embryo of Lacinularia immediately after its exit from the egg. 11. Another embryo, further developed. 12. Termination of a tentacular process of Melicerta ringens, showing the piston-like disc, capable of retraction by a muscular band affixed to it, and surmounted by a brush of cilia. 13. A view of the same process, with the brush of cilia extended. 14. The same, with the cilia retracted. 15. An embryo of Melicerta ringens, which has attached itself and has commenced the formation of its case or sheath. 16. An embryo of the same animal as it appears when swimming freely. , 17. Melicerta ringens, fully developed, with the lobes or petals of its ciliary wreath (a) fully expanded; b, uncini; c, ciliated process, representing a fifth lobe; d.d, tentacula, as shown in figs. 12, 13, 14; e, jaws; g, lower or second stomach; h, intestime; k, coloured globules; l, suctorial end of pseudopodium; m, muscles; n, gland; o, ovum. 18. Two muscular fasciculi, showing transverse markings. 19. Lacinularia Socialis: a, pharynx; b, maxillae, or jaws; c, muscular crop; d, stomach; e, lower segment of stomach, terminating in a marrow rectum and amus at 7 f, g, a glam- dular (?) process; h, ovary; i, respiratory canal; k, pedicle (Huxley). 20. Maxillae of Lacinularia socialis. 21. Winter ovum in act of division. 22. Segmentation of a portion of the ovary, of a different character from the rest, in process of forming a winter ovum. 23. Maxillae of Melicerta ringens, in bulb. 24. Winter ovum of Lacinularia. 25. A portion of ovary of Notommata centrura: a, the homogeneous germinal spot; b, the clear areola around it; c, yelk-matter. 26. Maxillae of Melicerta ringens. 27. Winter ovum of Asplanchna Sieboldii treated with solution of soda. 28. Winter ovum in its natural state. 29. Male of Asplanchma Sieboldii, viewed from the abdominal surface: a a, the anterior short arms; b b, the posterior longer arms; c, testis, or spermatic sac, filled with spermatozoa; d, water-vascular canal, 30 a, b, c, d, e, f. The corpuscles of the preceding DESCRIPTION OF THE ENGRAVINGS. .963 at c represent the earliest stage of the spermatic particles; those aſ a the mature, including the rod-like particles. 31. The maxillae of Asplanchma Sieboldii; the striated, museular bands moving them are very distinct. , 32. The female of Asplanchma, Sieboldii; 6, pharynx; b, cells of stomach; c, horseshoe-shaped ovary; d, saccular, or uterime portion of oviduct, or ovarian sac, with contained mature ovum; e, contractile vesicle; f tags of water-vascular canal; k, ditto; g, muscular (?) cushion within ciliary Wreath supporting Splmes. PLATE XXXVIII. (ROTATORIA). Figure 1. Rotifer inflatus, body extended; rotary apparatus withdrawn. 2. The same Rotifer, with the horn-like appendages of its rotary apparatus expanded., 3. The same Rotifer, strongly contracted into a globular form. . 4. Philodina erythrophthalma, in a contracted condition, as found when dried. 5. Euchlamis triquetra, viewed on the under side: a points to the lining membrane of the lorica in which the muscles are inserted; b, muscles; c, ganglionic enlargement; d, respiratory tube; e, areolar tissue of head; f, oesophagus, or tube between maxillary head and stomach. , 6. Anuraea heptodon, 7. Brachionus rubens, the young just emerged from the shell. 8–10. B. Bakeri: 8. Young from the egg; 9. Summer egg; 10. Winter egg, 11. Notommata centrura, a portion of the respiratory tube, with the ciliary tags within. 12. Termination of a tag, with the cilium within. 13. A portion of a water-vascular canal, with ciliated tags of Asplanchma Sieboldii. 14. Diagram of head of Brachiomus polyacamthus, viewed from the mouth side. 15. Diagram of head of the same, viewed from above. 16. A portion of the cerebral ganglion and of the nerves proceeding from it, and the eye consisting of two portions. I7. Eye of Brachionus Bakeri, detached. 18. Eye of Euchlamis umisetata. 19. Eye of Caligus. 20. Diagram of head (trochal disc) of Philodina. 21. Diagram of same, viewed from the mouth side. 22. Rattulus carimatus. 23, 24. Salpina spinigera. 25. Noteus quadricornis, dorsal view: a, maxillae; c, anterior spinous cornu of lorica; c c, posterior cornu; d, ovary; f, vesicle of water-vascular system; e, canal of ditto; h, stomach; 2, muscles. 26. Notommata centrura, dorsal view, surrounded by a mucous external envelope, and lined by a subtegumentary lamina or dermis; b, antemma; c, glandular sac around oesophagus; d, elongated process of rotary organ, called the under lip; e, tags of respiratory canal; f, stomach, with large glandular cells of its wall; g, intestime; h, pan- creatic glands; i, vesicle of water-vascular or respiratory system; k, cerebrum; l, canal of respiratory tube surrounded by a gramular coat; 0, ovary; p, ovum; m, muscular bands; q, chitinous liming of oesophagus; r, transverse muscles. 27. Brachionus Bakeri: a, lorica or carapace; b, posterior horns; c, anterior horms; d, lobes of trochal disc; e, siphon or antenna; f, gastric canal or Oesophagus; g, convoluted respiratory tube; l, pancreatic glands. 28. Asplanchma priodonta: a, longitudinal muscles; b, Oesophagus; c, stomach; d, ovary; e, pharynx. 29. Pterodina Patina, foot not shown: a c, convolutions of respi- ratory canal; b, longitudinal striated muscles. 30. Polyarthra platyptera: a, ciliated tubercular processes of head; c, compound feathery processes used as locomotive organs; d, mature ovum adherent externally; m, striated longitudinal muscles. 31, 32. Poly- chaetus subquadratus. 33. Maxillae of Notommata vermicularis, with the red eye, con- sisting of two portions (a). 34. Maxillae of Hydatina senta. 35. Maxillae of Albertia sº 36. Albertia vermicularis, X200. (Figured after Dujardin, Huxley, Leydig, and Perty. PLATE XXXIX. (RotATORIA). Figures 1–3. Lindia torulosa: 1. Rotary organ retracted; 2. Dental apparatus of ditto; 3. Rotary organ expanded. 4–7. Euchlamis dilatata: 4. Female, lying on its back, abdomen upwards; 5. Male, lying on its back; 6. The granular heap from a young male; 7. Male, Flying on its abdomen. 8, 9. Notommata parasita (Ehr.): 8. Male; 9. Female. 10–20. Brachionus urceolaris: 10. A summer ovum in the act of fission; 11. The embryo escaping from a summer egg, with rupture of shell; 12. A young male after its escape from the egg; 13. A male escaping from the egg; 14. A young male, older than fig. 12; 15. Female, rotary organ fully expanded; 16. Female, with four male eggs in different stages of development attached; 17. Female, rotary organ retracted, tentacular process (calcar) protruded; 18. Female, lateral view; 19. Maxillary bulb (mastax), with teeth in position; 20. A winter, ephippial, or lasting ovum, 21–24. Bra- Chionus militaris: 21. Female, lying on its back; 22. Female, lying on its abdomen; 23. A winter ovum; 24. A male ovum. (Cohn.) 3 Q 2 964 DESCRIPTION OF THE ENGRAVINGS. PLATE XL. (ROTATORIA). Figure 1. Hydatina senta, female, lateral view: a, dorsum and oral cavity, extending to an apex at 5; c, mastax with maxillae; d, canal between mastax and stomach; f, cloacal orifice; g, vesicle; h, ovary; i, coils of respiratory tube; k, cerebral ganglion; l, ciliated tactile fossa; m, longitudinal muscles. 2. Enteroplea Hydatina, the male of Hydatina senta. 3. Ova in an immature state, as found in the unimpregnated ovary of Hydatina senta: a, germinal spot; b, germinal vesicle; c, membrane of ovum occupied with granular yelk-matter. 4. The liming membrane of stomach of Hydatina senta, everted, showing cilia. 5. Vibratile tag, supported on its pedicle, attached to the respiratory canal. 6. The male sexual organs (of IEnteroplea Hydatina) detached, and highly magnified: a, penis; b, gland surrounding its bag; c, vesicles with granules; d, fold of integument surrounding penis when retracted. , 7. Detached spermatozoa. 8. Stephanops muticus, seen from beneath. 9. Same, side view. 10. Another view from beneath, or the ventral surface. 11. Brachionus Dorcas, female, newly born. 12. Same, male, newly born (Gosse). 13. B. Mülleri (male): a, head mass; b, eye; c, muscles; d, posterior mass; e, sperm- sac ; f, urinary concretion; g, foot. 14. B. Pala, male, newly born. 15. Same, male egg, nearly mature. 16. B. Bakeri. 17. Sacculus viridis, male, newly born. 18. Same, female, with male ova attached. 19. Brachionus angularis, male. 20. B. urceolaris, mastax and dental apparatus, ventral aspect: a, mastax; b, malleus; c, manubrium; d, articulation; e, uncus; f, incus; g, ramus; h, fulcrum; i, muscle connecting the uncus with the ramus; j, muscle for extending the malleus; l, muscle for throwing in the manubrium; k, muscle for bending the malleus; m, buccal funnel; m, salivary glands; o, alula. [These letters have the same signification where met with in the following figures after Gosse:] 21–23. B. urceolaris: 21. Jaws viewed nearly from above; 22. Dental apparatus, lateral aspect; 23. Buccal funnel, Salivary glands, mastax, and dental appa- ratus, dorsal aspect. 24. Diglena forcipata, jaws closed, ventral aspect. 25. Floscularia ormata, jaws, dorsal aspect. 26. The same, frontal aspect. 27. Stephanoceros Eich- hormii, jaws, dorsal aspect. 28. Same, uncus, oblique aspect, 965 I N D E X TO THE DESCRIPTION OF THE FAMILIES AND GENERA Acariatum, 503. Achmanthea, 872. Achmanthes, 873. Achmanthidium, 872. Acineria, 629. Acineta, 564. Acámečina, 564. Acomia, 613. Acropisthium, 614. Actinisceae, 935. Actiniscus, 935. Actinocyclus, 833. Actinogomium, 813. Actinophryina, 243, 558. Actinophrys, 559. Actinoptychus, 839. Actimurus, 704. Alastor, 571. Albertia, 693. Albertiems, 693. Alyscum, 615. Amblyophis, 541. Amoeba, 548. Amaebaea, 548. Amphicampa, 765. Amphimonas, 498. Amphileptus, 636. Amphipentas, 858. Amphipleura, 783. Amphiprora, 921. Amphitetras, 857. Amphora, 880. Amaulus, 859. Ancyrium, 501. Anguliferede, 852. Amisonema, 512. ' Ankistrodesmus, 752. Anthophysa, 500. Anuraea, 707. Apionidium, 615. Aptogonum, 723. Arachnoidiscus, 841. Arcella, 554. Arcellina, 551. Arthrodesmus, 736. Arthrogyra, 822. Aspidisca, 631. OF INFUSORLA. Aspidiscina, 631. Asplanchma, 691. Astasia, 539. Astasiaea, 188, 538. Asterionella, 779. Asterodiscus, 838. Asterolampra, 836. Asteromphalus, 836. Attheya, 863. Aulacodiscus, 843, 938. Auliscus, 845. BACILLARIA, 715. Bacillaria, 784. Bacteriastrum, 863. Bacterium, 532. Baeonidium, 614. Berkeleya, 926. Biblarium, 805. Diddulphia, 847. Biddulphieſe, 846. Blepharisma, 628. Eodo, 496. Brachiomaa, 706. Brachionus, 709. IBrightwellia, 940. Bursaria, 620. Cadium, 558. Calia, 529. Callidina, 701. Calodiscus, 802. Campylodiscus, 798. Carchesium, 588. Cephalosiphon, 670. Cerataulus, 846. Ceratidium, 642. Ceratium, 577. Ceratoneis, 782. Cercomonas, 497. Chaetocereas, 860. Chaetoceros, 861. Chaetoglema, 575. Chaetomonas, 573. Chaºtonotus, 661. Chaetospira, 597. Chaetotyphla, 575. Chilodon, 624. Chilomonas, 495. Chlamidodon, 646. Chlamydococcus, 522. Chlamydomonas, 146, 521. Chromatium, 502. Chloraster, 494. Chlorogomium, 543. Chonemonas, 513. CILIATA, 568. Cinetochilum, 630. | Cladogramma, 814. Clenodon, 684. Climacosphenia, 772. Closterium, 746. Cobalina, 571. Cocconeideae, 867. Cocconeis, 867. Cocconema, 877. Coccudina, 648. Coelastrum, 755. Coenomorpha, 597. Colacium, 544. Colletonema, 926. Colepina, 616. Coleps, 616. Colpoda, 632. Colobidium, 615. Colpodea, 631. Colurus, 698. Conochilus, 664. Corethria, 563. Cornuspira, 558. Corycia, 550. Coscènodisceae, 827. Coscinodiscus, 827. Cosmarium, 731. Cosmocladium, 752. Cothurnia, 603. Craspedodiscus, 831, 939. Crumenula, 511. Cryptomonadina, 140, 505. Cryptoglena, 509. Cryptomonas, 507. Cyclidina, 571. Cyclidium, 497, 572. Cycloglena, 690. 966 INDEX TO THE FAMILIES AND GENERA OF INFUSORIA. Cyclogramma, 630. Cyclotella, 811, 937. Cylindrotheca, 940. Cymatopleura, 793, 940. Cymbella, 875. Cymbelled, 875. Cymbosira, 875. Cyphidium, 555. Cyphoderia, 557. Dasydytes, 661. Dendrosoma, 562. Denticula, 773. Jesmºdiaceae, 715. IJesmidieæ, 715. Desmidium, 723. Desmogonium, 789. Diadesmis, 923. Diatoma, 778. JDiatomaceae, 756. Diatomede, 756. Diatomella, 810. Dickieia, 925. T)icladia, 863. Dictyocha, 935. Dictyolampra, 813. Didymoprium, 723. Difſlugia, 553. Diglema, 687. Dileptus, 638. Dimeregramma, 790. I)inema, 546. Dinobryina, 546. Dinobryon, 547. Dinocharis, 698. Diophrys, 648. Diplax, 695. Diplomeis, 892. Dipodina, 713. Discocephalus, 645. IDiscosira, 822. I)iselmis, 511. Disoma, 608. JDistemma, 689. Distigma, 544. I)ocidium, 744. IJonkinia, 920. I)oxococcus, 495. Drepanomonas, 513. Emydium, 713. Enchelia, 605. Enchelys, 607. Encyonema, 879. Endictya, 831. Enteroplea, 677. Entomoneis, 921. Entopyla, 810. Eosphora, 689. Ephelota, 562. Epipyxis, 546. Epistylis, 588. Tºpithemia, 759, 938. Eretes, 501. Euastrum, 728. Eucampia, 937. Euchlamidota, 693. Euchlamis, 695. Eudorina, 520. Euglema, 541. Euglenſea, 188, 538. Euglypha, 556. Eunofia, 762. Eunoãea, 759. Eunotogramma, 860. Euodia, 852. Euphyllodium, 772. Eupleuria, 809. Euplotes, 646. Euploſſéna, 645. Eupodisceae, 842. Eupodiscus, 842, 938. Eutreptia, 546. Floscularia, 674. Flosculariaba, 665. Fragilaria, 776. Fragilarieae, 773. Frustulia, 924. IFurcularia, 679. Gastrochaeta, 615. Genicularia, 721. Gephyria, 809. Glaucoma, 624. Glenodinium, 578. Glenomorum, 494. Glenophora, 662. Gloeococcus, 524. Gomphogramma, 806. Gomphonema, 886. Gomphonemede, 886. Gomatozygon, 721. Goniothecium, 864. Gonium, 152, 517. Grammatophora, 807. Grammonema, 777. Gromia, 556. Grymaea, 503. Gyges, 516. Gyrosigma, 915. Habrodon, 614. Halionyx, 833. Halteria, 644. PIarmodirus, 629. Heliopelta, 840. Hemiaulus, 851. Pſemidiscus, 852. Hercotheca, 866. Heteromita, 499. Heteronema, 545. Heterostephania, 833. Hexamita, 499. Bimantidium, 765. Himantophorus, 646. Hirmidium, 528. Holophrya, 612. Eſomoeocladia, 784. Hyalodiscus, 814. Hyalosira, 804. Hyalotheca, 722. Hydatina, 677. Hydatinaea, 677. Hydrias, 702. Hydromorina, 503. Hydrosera, 852. Ichthydina, 660. Ichthydium, 661. Insilella, 827. Isthmia, 851. JKerona, 642. Rolpoda, 632. Rolpodea, 631. Kondylostoma, 627. Labidodon, 682. Lacernata, 924. Lacinularia, 670. Lacrymaria, 609. Lagenella, 509. Lagenophrys, 604. Lagotia, 605. Lagynis, 558. Larella, 712. Lecquerousia, 557. Lembadion, 629. Lepadella, 694. Leptocystinema, 722. Leucophrys, 571, 610. Licmophora, 771. Licmophorea, 768. Limnias, 670. Lindia, 693. Liosiphon, 626. Liostephania, 813. Liparogyra, 823. Lithodesmium, 937. Loxodes, 619. Loxophyllum, 639. Lysicyclia, 815. Macrobiotus, 714. Mallomonas, 501. Mastigocerca, 695. Mastogloia, 924. Mastogonia, 813. Megalotrocha, 665. Megalotrochaea, 664. Megatricha, 614. Melicerta, 672. Melosira, 815. Melosirea, 810. Memoidium, 502. Merêdźea, 766. Meridiom, 767. Mesocena, 936. Metallacter, 537. Metopidia, 699. Micrasterias, 725. Microcodon, 665. Microglena, 493. Micromega, 929. Microtheca, 937. Milnesium, 714. Mitophora, 644. INDEx TO THE FAMILIES AND GENERA OF INFUSORLA. 967 Monadéma, 130, 485. Monas, 489. Monema, 927. Monocerca, 680. Monogramma, 875. Monolabis, 704. Monostyla, 695. Monura, 698. Nassula, 625. Naunema, 927. Navicula, 892, 938. Naviculeſe, 892. Nitzschia; 779, 940. Noteus, 707. Notogonia, 700. Notommata, 681. Octoglena, 690. Odontidium, 775. Odontodiscus, 832. CEcistes, 663. (Ecistima, 663. Omphalopelta, 841. Omphalotheca, 865. Oncosphemia, 768. Opalina, 569, 627. Opalinaa, 569. Opercularia, 592. Ophidomonas, 509. Ophrydāna, 598. Ophrydium, 599. Ophryocercina, 630. Ophryodendrom, 568. Ophryoglema, 638. Opisthiotricha, 614. Otostoma, 639. Oxytricha, 640. Oxytrichina, 639. Oxyrrhis, 512. Pamphagus, 551. Pandorina, 157, 517. Panophrys, 627. Pantotrichum, 573. Paramecium, 634. IPediaStrea, 24, 752. Pediastrum, 754. Pelecida, 629. Penium, 750. Peramema, 545. Peridiniaa, 574. Peridinium, 576. Periptera, 865. . Perislephania, 824. Perithyra, 842. JPeromium, 501. Phacelomonas, 494. Phacotus, 513. Phacus, 511. Phialina, 623. Philodina, 705. I’hilodinaea, 700. Phlyctaenia, 925. PHYTozoA, 485. Pinnularia, 892. Plagiognatha, 692. IPlagiogramma, 773. Plagiotoma, 571, 627. Pleurodesmium, 860. Pleuromonas, 502. Pleuronema, 639. Pleurosiphonia, 915. Pleurosigma, 915. IPleurotrocha, 679. Ploeotia, 512. Ploesconia, 647. Podocystis, 772. Pododiscus, 815. Podophrya, 561. Podosira, 815, 938. Podosphenia, 769. Polyarthra, 686. Polyselmis, 540. Polytoma, 504. Pompholyx, 712. Porocyclia, 823. Porpeia, 850. Prorocentrum, 509. Prorodon, 612. Prorostauros, 915. PROTozo A, 199, 547. Pseudo-difflugia, 557. JPterodina, 711. Ptygura, 661. Ptyxidium, 615. Pyxidicula, 824. Battulus, 688. Bhabdomonas, 503. Rhabdomema, 804. Rhaphidogloea, 925. Rhaphoneis, 791. Rhipidophora, 769. RIIIzopop.A, 243. Rhizomotia, 885. Rhizosolemia, 865. ROTATORIA, 392, 649. Rotifer, 702. Salpina, 697. Sacculus, 662. Scaridium, 686. Scenodesmus, 753. Sceptromeis, 772. Schizomema, 927. Schizomemea, 924. Scyphidia, 596. Siagontherium, 614. Sorastrum, 755. Spathidium, 611. Sphaerosira, 524. Sphaerozosma, 723. Sphenella, 886. Sphemoderia, 557. Sphenosira, 892. Spirillina, 554. Spirillum, 533. Spirochaeta, 533. Spirochona, 598. Spirodiscus, 537. Spiromonas, 502. Spirostomum, 622. Spirotaenia, 751. Spondylomorum, 505. Spondylosium, 724. Sporonema, 537. Squamella, 700. Squamulina, 558. Staurastrum, 737. Staurogramma, 915. Stauroneis, 91]. Stauroptera, 911. Staurosira, 791. Stentor, 581. Stephanoceros, 668. Stephanodiscus, 823. Stephanogonia, 814. Stephanoma, 529. Stephanops, 699. Stephanopyxis, 826. Stephanosira, 823. Stephanosphaera, 164, 529. Stichotricha, 644. Stigmaphora, 923. Striatella, 803. Striatellea, 803. Stylobiblium, 805. Stylonychia, 643. Surirella, 794. Surºrellede, 783, 940. Symbolophora, 833. Synaphia, 528. Symchaeta, 685. Symcrypta, 519. Syncyclia, 879. Symdendrium, 866. Symedra, 785. Synedreae, 940. Synura, 519. Syringidium, 866. Systephania, 832. Tabellaria, 807. Taphrocampa, 692. TARDIGRADA, 713. Tardigrada, 714. Terpsinoë, 859. Terpsinoëde, 858. Tessella, 804. Tetmemorus, 746. Tetrachastrum, 724. Tetracyclus, 806. Tetramitus, 501. Tetrasiphon, 713. Theorus, 690. Tintimmus, 600. Toxonidia, 920. Trachelina, 616. Trachelius, 618. Trachelocerca, 630. Trachelomonas, 510. Trepomonas, 499. Triarthra, 688. Triceratium, 853, 939. Trichoda, 608. Trichodina, 583. Trichodiscus, 561. 968 INDEX TO THE FAMILIES AND GENERA OF INFUSORIA. Trichomonas, 500. Trinema, 556. Triophthalmus, 689. Triploceras, 747. Tryblionella, 792. Trypemonas, 513. Turbanella, 381. Tubicolaria, 668. Typhlima, 702. TJrceolaria, 596. TJrocentrum, 585 º Droglema, 520. Uroleptus, 637. Uronema, 615. TJrostyla, 643. Uvella, 492. Waginicola, 601. Vaginifera, 598. Vibrio, 532. Vibrionia, 184, 529. Volvocêma, 144, 514. Wolvox, 180, 526. THE END. Worticella, 585. Vorážcellina, 579. Xanthidium, 735. Xanthiopyxis, 826. Zoogloea, 537. Zooteirea, 563. Zoothamnium, 594. Zygoceros, 850. Zygoselmis, 544. PRINTED BY TAYLOR AND FRANCIS, RED LION COURT, FLEET STREET. a 16 º e - - o - - - = º - - . º - - - - - - - - - -. º 3 co - - o - º º - - - - - Pritchards Infusora - Z/ - 33 - º 37 - . - --- - --- - º º ºgº º º º º, º º º º º º º º ".sºaggººse - | º ºf 22 - º º * West imp - | 3 |- |- |- |- ---- ---- |- ºnandº P. ！！！！！！！！！！！！！！！！！！！！！！~~~~ ----№.|- -ºs- - Tuttºn West so º º a UTIll sº Pritchard's Infusoria. i. III.) º -- U - - fE - WWest ºr Pºlas Infusoria. ſuffen West so º - º *-º-º-º: --~~~~~~ --- -- º - º --- º 2s X.300 WWestimº Tuſen west so. - - - Pritchard's Infusoria. - - º III.iimi §§ ---- |- º º º | | - In · ： ~ §@₪?> §¶√∞ √∞i√∞'， Ā№ x 300 Pºntchard's Inſusoma ：Illae ---- \ÄÛſ. ¡№ -----： ---- ſiiſ ------------------ ſ. w west imp. ºutſen west sº º º - º . . sº º Tuften Westee ºğ - Pritchard's Infusonia. -- º - -º== - º: W. West imp. - \\ | º | - º º |--~ ---- ， ， ----|-· ~ſº，· ſae !§№. 7|ſae*******！ …---- ººſ， º§ © ® è ºſſ，·nae ſaeſ.---- ..………… &ſınırıcıſı. §§§） éſ ºn Zºº /º/, /º/, （）ſae № №. "№ №. | || № ~ S|-：§ ----- ： ±（√∞ ſae----| --º -- -º-º-º-º-º-º/ º º . --- ſae \， |× |（ -º-º:º --- |（~~~~ ~~~~. ：） ├：：：：：：：：：：：： ---- ………………------ -º-º-º-º-º-º: ºw ººz. | *：'， ""：, ， ∞ → ~ . . .|（~~~~）;ſº _ |- ---- © ~|-№---- ：， ：,： ， ， · ， |-|- ºáſiſſiſſae， §¶√∞ . №ſſºſ º -º-º-º-º-º-º/-. */ º """ ul-ul-ul-ull-luluulu- ------ | "lº- º | | | ". A | ºn ºn º | º mºll - | | ºil. | - - \\ |||| || || | ------- | |. - | - | ||||||||| | - |. - - \|| || || || -- | - - º - º | Tºº -- Pritchards Infusoriº º |||||||||||||||||||||| Ès， Infusoria. |- |- ） ： ：-）№ae，- ¿?№*=¿?\· ºOº|-|-¿ſaeſº???§§|- ſºſ，ſlåſſºſºſ||3||3||3|ſ}} ſſſſſſſſſ|ſſſſſſſſſſſ ∞ √（||||||| ---- |- |×ſºſſae| --- ſae ſºſ --- Pritchards º º --- |-ſae --------|- |（LLLLLLITSELLETTILLITSELLEPITTS TL）|-№ſſºſ ¡|-\}\|\W) --- ºf ºz º.º. wº - g º º º- -- W-7 Alais, so l Pritchards Infusoria. (j): º º ºg & sº Pºº & Pritchards Infusoria º WJAlaº- Pritchard's Infusoria. // / ſº- Tº ſº. Pritchards Infusoria. Pritchards Infusoria. Pritchard's Infusoria. º Zºº”, nº- - XXV. - º E _- º - - - - -º-º-º: - - º º ſº ſº º ----- |- |-\\）\\№ ----\，\！）\\|- № №N № - - ºrd's Infusional - - - - - - - C- - - . º, , , , ” - - - - ~------- - - - ------- - - - - - - - - - - º ºg XXVII. Pritchards Inſusº |- e ：： ）; ~~~~ |- |- ， W.A. º.º.º. Pritchard's Infusoria. Pitchard's Infusoria - - - - - | - -- - - - 6. - * c - - - º . 3. W. H.º º - Pritchard's Infusoria. |- |- ）|- - . ----- |------ ¿¿.* |- ·|- -------- |-|- - - - -- -- - º- \ --- --- - ， Pritchards Infusoria. ººz ~. ---- · º -- XXXIII. - - - º - º - l º \" - - - º - -- º - - -ſ /º/, /º/, wº XXXIV. - - - -- - - º - - -> N º -- º - --- w ºn tº hard's Inſus oria Pritchards Infusoria. Mºsº. - - Pritchard's Infusoria. Infusonal Pritchards W. Alºns s Infusoria. Pritchard's * , ,- .* . . . ." · * *~~~~. • • ¡ ¿ | 704 •======-, --→=-） =======：：- =========--> | || 3 9015 O |||| tº * * * * * * * * - 2. t.e. a . . & + • *, ^ . -， + → «” } •^ ºw. ، * º *.* · · *|-ı. -, * · * * *** * ·• • ×** *ae- - * |- ----~~~~ ± ------★ →T，-~ -----* . . . . ~*~~~~ … • • • •** ~~~. . . . . . . . . . . . ） „ “- --- -|-· · --->..….`ſ. ºvº.", . . . . . * * * : *. ºr tº: ** - ºr * * *, *. ## , º. s § ** º: *: , ; * * * * * ... . . . . . . . ; gº a isiº. . . . . ºr. º: * * ſº ſº.- : # , , ºº * fºre ; : * * ...? £º º ºf * *…* .. - . ... A Fºº tº :::::: - º º º ºgº ; : * ***** ******º tºº, *::: º At ºn ºf º * † sº. 2 ºr ºf £2 sº * ºf º c- º º . * * * * * > 3 * : * ~ * - * * * * * * : - º § ; : *, *, * ºr w º - ºg * * * * º, ºriº ºf “º ºr - .* : Pº º # * * * tº. - sº tº ſº...º. rºº. . . . . . is . . . . . . . . . ºf . . . . º.º.º. . . . . . a #3 # & - - º ºr ºf s tº ºf , ººl. ºr . , , , * * * * : * ºr tº . t º **