EN SON SS x Sek AY BAN RAN AN Nabe ANecte A TN a are ‘ ao NS Se SS LAAN SEN AN wh kh RNSERNNN OC si Scr Sa Sedna Re Sh Sra re Se . sats a oo WOR Se Sener as OS . , Pees y SSS ASSN SN S = wes AN Saas SS a SES es a s RN XX Sua a SN \\ SN ae a AX aN % SS ‘ A \ SS x ck aC hh ohn ane rhe ance a es Nice No Qu. CORNELL UNIVERSITY it f ; THE 8 lower Heterinary Library FOUNDED BY ROSWELL P. FLOWER for the use of the N. Y. STATE Veena COLLEGE This Volume is the Gift of Dr. William t.. Weitg oo. — 5577 Cornell University Library QL 47.P11 1886 Zoology for high schools and colleges, 3 1924 001 021 603 vet PRINTEOINUS A DATE DUE 4g 7 ER maa, + THE AMERICAN SCIENCE SERIES FOR HIGH SCHOOLS AND COLLEGES, The principal objects of the series are to supply the lack—in some subjects very great—of authoritative books whose principles are, so far as practicable, illustrated by familiar American facts, and also to supply the other lack that the advance of Science perennially creates, of text-books which at least do not contradict the latest generalizations. The books of this series systematically outline the field of Science, as the term is usually employed with reference to general education. ‘Ihe scheme includes an Advanced Course, a Briefer Course, and an Elementary Course. The books arranged for in the ADVANCE CoURSE are as follows. Those with the prices affixed have been published. ES" In ordering be cereful to state which course is desired Advanced, Briefer or Elementary Physics. Zoology. By GeorGe F, Barker, Professor : ; By A. §. Packarp, Professor in the University of Pennsylvania. of Zoology and Geology in Brown University, Editor of the American Naturalist. Advanced Course, $3.00. Briefer Course, $1.40. Elementary Course, $1.00. Chemistry. By Ira Remsen, Professor in the Johns Hopkins University. Briefer Course, $1.40. Elementary Course. Astronomy. By Simon Newcoms, Professor in the Johns Hopkins University, and Epwarp 8, Ho.pen, Director of the Lick Observatory. Advanced Course, $2.50. Briefer Course, $1.40. The Human Body. By H. NewELi Martin, Profes- sor in the Johns Hopkins Univer- sity. Advanced Course, $2.75. Copies without the Appendix on Repro- duction will be sent when specialiv ordered. Briefer Course, $1.50. Elementary Course, 90 cents. Biology. By Wiu.iam T. Sep@wick, Pro- fessor in the Massachusetts Insti- ‘tute of Technology, and EpmunD ‘B. Wixson, Professor in Bryn Mawr College. Political Economy. Botany. By C. E. Brssey, Professor in the University of Nebraska; formerly ia the Iowa Agricultural College. By Francis A. WALKER, Presi- dent Massachusetts Institute of Technology. . Advanced Course, $2.75. Briefer Course, $1.35. Advanced Course, $2.25. Briefer Course, $1.50, HENRY HOLT & CO., Pusursuers, NEW YORK. AMERICAN SCIENCE SERIES LOOLOG Y FOR HIGH SCHOOLS AND COLLEGES BY A. 8. PACKARD, M.D., Pu.D. MEMBER OF THE NATIONAL ACADEMY OF SCIENCES; PROFESSOR OF ZOOLOGY AND GEOLOGY IN BROWN UNIVERSITY FIFTH EDITION, REVISED NEW YORK HENRY HOLT AND COMPANY 1886 : /p 20 FI oD Y/ Copyright, 1879, 1886. by HENRY Hour & Co. Lf ne | . Mb6 re - be 7? Pil 1 S8é PREFACE. THIs book is designed to be used quite.as much in the la- boratory or with specimens in hand, as in the class-room. If. Zoology is to be studied as a mental discipline, or even if the student desires simply to get at a genuine knowledge, at first hand, of the structure of the leading types of animal life, he must examine living animals, watch their movements and habits, and finally dissect them, as well as study their mode of growth before and after leaving the egg or the parent. as the case may be. But the young student in a few weexs’ study in the laboratory cannot Jearn all the principles of the science. Hence, he needs a teacher, a guide, or at least a manual of instruction. This work is an expansion of a course of lectures for college students, but has been pre- pared to suit the wants of the general reader who would ob- tain some idea of the principles of the science as generally accepted by advanced zoologists, in order that he may under- stand the philosophical discussions and writings relating to modern doctrines of biology, especially the law of evolution — and the relations between animals and their surroundings. The book has been prepared, so far as possible, on the in- ductive method. The student is presented first with the facts; is led to a thorough study of a few typical forms, taught to compare these with others, and finally led to the principles or inductions growing out of the facts. He has not been assailed with a number of definitions or diagnoses applicable to the entire group to which the type may belong before he has learned something about the animals typica! iv PREFACE, of the order or class ; but these are placed after a description | of one or a few examples of the group to which they may belong. The simplest, most elementary forms are first no- ticed, beginning with the Protozoa and ending with the Ver- tebrates. In working up from the simplest forms to those more complex, it is believed that this is the more logical and philosophical method, and that in this way the beginner in the science can better appreciate the gradual unfolding of the lines of animal forms which converge toward his own species, the flower and synthesis of organic life. Still the learner is ad- vised to begin his work by a study of the first part of Chap- ter VIII., on Vertebrates, and to master, with a specimen in hand, the description of the frog, in order that he may have a standard of comparison, a point of departure, from which to survey the lower forms. Particular attention has been given to the development of animals, as this subject has been usually neglected in such manuals. Some original matter is introduced into the book ; a new classification of the Crustacea is proposed, the orders being grouped into the subclasses Neocarida and Paleocar- ida. Most of the anatomical descriptions and drawings have been made expressly for this book, and here the author wishes to acknowledge the essential aid rendered by Dr. C. 8S. Minot, who has prepared the drawings and descriptions of the fish, frog, snake, turtle, pigeon, and cat. In compiling the book, the author has freely used the Jarger works of Gegenbaur, Huxley, Peters and Carus, Claus, Rolleston, and others, whose works are enumerated at the end of the volume, and in many cases he has paraphrased or even adopted the author’s language verbatim when it has suited his purpose. Besides these general works many mon- ographs and articles have been drawn upon. In order to secure a greater accuracy of statement, and to render the work more authoritative as a manual of Zoology, PREFACE. Vv the author has submitted the manuscript of certain chapters to naturalists distinguished by their special knowledge of certain groups. The manuscript of the sponges has been read by Professor A. Hyatt ; of the worms and Mollusca, by Dr. Charles 8. Minot; of the Echinederms, by Mr. Walter Faxon; of the Crustacea, by Mr. J. 8. Kingsley. Proofs of the part relating to the fishes have been revised by Professor T. Gill, whose classification as given in his ‘‘ Arrangement of the Families of Fishes,” has been closely followed, his defin- itions having been adopted often word for word. The man- uscript of the Batrachians and Reptiles has been read by Professor E. D. Cope, whose classification, given in his “‘Check-List of North American Batrachia and Reptilia,” has been adopted. Proofs of the part on birds have been read by Dr. Elliott Coues, U.S.A., whose admirable ‘ Key to the Birds of North America” has been freely used, the author’s words having been often adopted without quotation- marks. Dr. Coues has also revised the proofs of the pages re- ferring to the Mammals. To the friendly aid of all these gentlemen the author is deeply indebted. As to the illustrations, which have been liberally provided by the publishers, a fair proportion are original. The full- page engravings of the anatomy of the typical Vertebrates have been drawn expressly for this work by Dr. C. 8. Minot ; a number have been prepared by Mr. J. 8. Kingsley ; Prof. W. K. Brooks has kindly contributed the drawing of the nervous system and otocyst of the clam, and a few of the sketches are by the author. The publishers are indebted to Prof. F. V. Hayden for illustrations kindly loaned from the Reports of the U.S. Geological Survey of the Territories; a few have been loaned by Prof. S. F. Baird, U.S. Commissioner of Fish and Fisheries, and the members of the U.S. Entomological Com- mission ; a number have been loaned by the Peabody Acad- vi PREFACE. emy of Science, Salem, Mass.; by the publishers of the ‘American Naturalist, and by the Boston Society of Natural History, while forty of the cuts of birds have been electro- typed from the originals of Coues’ Key, and Tenney’s Zoology. Measurements are usually given in the metric system ; in such cases the approximate equivalent in inches and fractions of an inch are added in parentheses. Should this manual aid in the work of education, stimu- late students to test the statements presented in it by person- al observations, and thus elicit some degree of the inde- pendence and self-reliance characteristic of the original in- vestigator, and also lead them to entertain broad views in biology, and to sympathize with the more advanced and more natural ideas now taught by the leading biologists ‘of our time, the author will feel more than repaid. Brown UNIVERSITY, Providence, 8. I., October 25, 1879, PREFACE TO THE FIFTH EDITION. More radical changes have been made in this than any former edition. The Tunicata have been transferred to a position next below the Vertebrates in the group Chordata. The Merostomata, together with the Trilobites, have been placed in a class called Podostomata (in allusion to the fact that the head and mouth appendagesare fvot-like). Their po- sition is between the Crustacea and Arachuida. The branch Arthropoda is divided into six classes, viz.: 1, Crustacea ; 2, Podostomata ; 3, Malacopoda ; 4, Myriopoda; 5, Arach- nida ; 6, Insecta. ‘The orders of insects have been increased from eight to sixteen, according to the arrangement on pp. 365, 366. For the order of Mayflies we propose the name Plectoptera (Gr. plectos, a fine net, in allusion to the finely net-veined wings), and for the Panorpide, the ordinal name Mecaptera (Gr. mecas, long, in allusion to the long, narrow wings). Numerous minor changes and corrections have also been made. PROVIDENCE, June, 1886. CONTENTS. 3 PAGE INTRODUCTION (aed ces side segae sss Ses be sewcie ada ca6 Paes Bed R 1 Definition of Zoology... 20... ccc eee cece ee cere e ee sees 1 IMGEPHOlORY vicie. 25s scacsie. Staak ates dieee ek did 8 ass sues tsguneesee he posed Saas 5 Organs and tueir Functions........ 0.006. cece eee ee eee 8 Correlation of Organs... co.cc ee ce cece cee eee eee 9 Adaptation of Orgins....... cece eee eee een teen eee eens 10 Analogy and Homology... 2.0.6.6 ee cece cece eee cee ween 12 Physiology..............45 Pauala(daits le pad is 4 Gesu al aval Ging oa. 12 Pay Gh ology oa siisssccsalcte a Red va san shoe secede an aes rene gees SS 12 Reproduction ccies- ; oc pened educa Mate ty Mreede ew tobaaas 13 Hmbryologyns.ccsnesss% oa4 oeeme eee ea saiad qamaee se ee eats 13 Claas fi cation yas saciece ghar eames Wetec we ae Fe wary LS LOGLCOBLAPDY sigue o,vkecdara bee aseceuus ca haan icdustdlsre diners oP was a 16 CHAPTER I. Branch 1. PROTOZOA............cceseeeeee onan 17 Il. « 2. PORIFERA (Sponges)................-- 42 Til. «3, CasLENTERATA (Hydroids, Jelly-fishes, and Poly p8)s.0.0<0.ssses ewe suey ey 51 IV. « 4, ECHINODERMAaTaA (Crinoids, Starfish, Sea Urchins, etc............-.005 96 Vv. «5. VERMES (Worms)...........0 0.50 ee ee 138 Vi. «6. Mox.usca (Bivalves, Snails, Cuttles)... 220 VIL. «7, ARTHROPODA (Crustaceans and Insects) 265 VII. (8. VERTEBRATA: oc oie ces cue ncinine ose ot 369 IX. COMPARATIVE ANATOMY OF ORGANS..........+-- 631 Organs of Digestion, the Mouth and Teeth... 631 Organs of Circulation..............ceeereee 635 Organs of Respiration............0eeeeereee 637 The Nervous System............00eseeeeeee 638 Organs Of Senge... wees aes sies eve vse sers 640 viii CHAPTER X. XI. XII. XIII. XIV. Xv. XVI. CONTENTS. PAGE DEVELOPMENT....... 00sec cscececcscscccceeestes 644 Metamorphosis........... 0.00 cee ee ee teens 651 Parthenogeuesis and Alternation of Genera- HONS esa Ves cee. ws Kaeo at ae 652 Dimorphism and Polymorphism............. 654 Individuality occ s ccecv aa wemeaee cages ses 656 FY Didi ysis... hecneisseaie ns eagepeee ines eee 657 THE GEOGRAPHICAL DISTRIBUTION OF ANIMALS 658 Means of Dispersal...............-00505 eee 660 Division of the Earth into Faune............ 661 Distribution of Marine Animals............. 664 Chief Zoological Faune of the Earth........ 666 THE GEOLOGICAL SUCCESSION OF ANIMALS...... 668 THE ORIGIN OF SPECIES.......... 00 cece eee 671 PROTECTIVE RESEMBLANCE........-..ceeeee eee 675 INsTINCT AND REASON IN ANIMALS............ 680 GHOSSARYiciedcdiad Sek daa d cu.0s erm avelnate dated Ga creas 689 VIL: ANDES: ele Manchin ted eaves aed Beene te coeeess 697 ZOOLOGY. INTRODUCTION. Definition of Zoology.—That science which treats of liv- ing beings is called Biology (ios, life ; Adyos, discourse). It is divided into Botany, which relates to plants, and Zo- ology (C@orv, animal ; Adyos, discourse), the science treating of animals. It is difficult to define what an animal is as distinguished from a plant, when we consider the simplest forms of either kingdom, for it is impossible to draw hard and fast lines in nature. In defining the limits between the animal and vegetable kingdoms, our ordinary conception of what a plant or an animal is will be of little use in dealing with the lowest forms of either kingdom. A horse, fish, or worm differs from an elm tree, a lily, or a fern in having organs of sight, of hearing, of smell, of locomotion, an¢ special organs of digestion, circulation, and respiration, but these plants also take in and absorb food, have a circulation of sap, respire through their leaves, and some plants are me- chanically sensitive, while others are endowed with motion —certain low plants such as diatoms, etc., having this power. In plants, the assimilation of food goes on all over the organism, the transfer of the sap is not confined to any one portion or set of organs as such. It is always easy to distinguish one of the higher plants from one of the higher animals. But when we descend to animals like the sea-ane- mones and coral-polyps which were called Zoophytes from their general resemblance to flowers, so striking is the exter- nal similarity between the two kinds of organisms that the 2 ZOOLOGY. early observers regarded them as ‘‘ animal flowers ;’”’ and in consequence of the confused notions originally held in regard to them the term Zoophytes has been perpetuated in works on systematic zoology. Even at the present day the com- pound Hydroids, such as the Sertularia, are gathered and pressed as sea-mosses by many persons who are unobservant of their peculiarities, and unaware of the complicated anat- omy of the little animals filling the different leaf-like cells. Sponges until a very late day were regarded by our leading zoologists as plants. The most accomplished naturalists, however, find it impossible to separate by any definite lines the lowest animals and plants. So-called plants, as Bacte- rium, and so-called animals, as Protameba, or certain mo- nads, which are simple specks of protoplasm, without gen- uine organs, may be referred to either kingdom ; and, in- deed, a number of naturalists, notably Haeckel, relegate to a neutral kingdom (the Protista) certain low- est plants and animals. Even the germs (zo- ospores) of monads like Uvella (Fig. 1), and those of other flagellate infusoria, may be mistaken for the spores of plants ; indeed, the active fla- Fig. 1.—Uvel- gellated spores of plants were described as in- Ja,a flagellate fusoria by Ehrenberg ; and there are certain so- infusorian, or monad. with called flagellate infusoria so much like low -two large ci- lia called plants (such as the red snow, or Protococcus), flAagella.: Greatly mag- in the form, deportment, mode of reproduc- ae tion, and appearance of the spores, that even now it is possible that certain organisms placed among them are plants. It is only by a study of the connecting links between these lowest organisms leading up to what are un- doubted animals or plants that we are enabled to refer these beings to their proper kingdom. Asa rule, plants have no special organs of digestion or circulation, and nothing approaching to a nervous system. Most plants absorb inorganic food, such as carbonic acid ‘gas, water, nitrate of ammonia, and some phosphates, silica, etc. ; all of these substances being taken up in minute quan- tities. Low fungi live on dead animal matter, and promote the process of putrefaction and decay, but the food of these DISTINCTIONS BETWEEN ANIMALS AND PLANTS. 3 organisms is inorganic particles. The slime-moulds called Myzxomycetes, however, envelop the plant or low animals, much as an Ameba throws itself around some living plant and absorbs its protoplasm ; but Afycxomycetes, in their man- ner of taking food, are an exception to other moulds. The lowest animals swallow other living animals whole or in pieces ; certain forms like Amada (Fig. 2) bore into minute alge and absorb their pro- toplasm ; others engulf sili- cious-shelled plants (diatoms) absorbing their protoplasm. No animal swallows silica, lime, ammonia, or any of the phosphates as food. On the other hand, plants manu- , 2,2 Ames, Protozoan, Therisht facture or produce from in- Te itopadia aes onltcaenea ig 4 fe tude, organic matter starch,* sugar mass. and nitrogenous substances which constitute the food of animals. During assimilation, plants absorb carbonic acid, and in sunlight exhale oxygen; during growth and work they, like animals, consume oxygen and exhale carbonic acid. Animals move and have special organs of locumotion ; few plants move, though some climb, and minute forms have thread-like processes or vibratile lashes (cilia) resem- bling the flagella of monads, and flowers open and shut, but these motions of the higher plants are purely mechanical, and not performed by special organs controlled by nerves. The mode of reproduction of plants and animals, however, is fundamentally identical, and in this respect the two king- doms unite more closely than in any other. Plants also, like animals, are formed of cells, the latter in the higher forms combined into tissues. - As the lowest plants and animals are scarcely distinguish- able, it is probable that plants and animals first appeared contemporaneously ; and while plants are generally said to form the basis of animal life, this is only partially true ; a large number of fungi are dependent on decaying animal matter; and most of the Protozoa live on animal food, as * Starch has been found by Bergh in Cilio-flagellate Infusoria. 4 ; ZOOLOGY. do a large proportion of the higher animals. The two kingdoms supplement each other, are mutually dependent, and probably appeared simultaneously in the beginning of things. It should be observed, however, that the animal kingdom overtops the vegetable kingdom, culminating in man. In speaking as we have of low animals and high animals, we are comparing very unequal quantities; the distance be- tween monad and man is well-nigh infinite. But there is a series or chain, sometimes broken and often with lost links, connecting the extremes ; and as there are wide differences in form, so there are great extremes in the organs and de- gree of complication of function of the simple as compared with the more complex forms. The improvised stomach of ‘an Amoeba is not comparable with the stomach of an hydra, nor is the stomach of the latter creature with that of a horse ; there is a gradual perfection and elaboration or spe- cialization of the stomach as we ascend in the animal series. So it is with organs of locomotion ; the pseudopods and cilia of the Protozoans are replaced in the star-fishes and worms by hollow tentacles or various fleshy soft appendages ; in crabs and insects by stiff, jointed limbs, with different lev- erage systems; and these are replaced in vertebrates by genuine limbs supported by bones. A comparative view of the origin and structure of organs succeeds in this book the systematic account of the animals themselves. We thus see that the organs of the higher animals are merely modifications of organs often having the same general functions as in the lower animals; the lower or simpler have preceded in geological history the higher or more specialized forms, and thus we are, in ascending the animal series, going from the simple to the complex. For this reason the plan of this work has been to lead the stu- dent from the simpler forms of animal life to the more complex ; and though the vertebrate animals, such as fishes and dogs, are more familiar and interesting to us, the seri- ous student of zoology will feel that it is more logical and better in the end to study the animal world in the order in which the different forms have appeared—as we believe, MORPHOLOGY. 5 through the orderly operations of physical and biological laws, under the guidance of an Infinite Intelligence—a Creator whose modes of working are-revealed to us in what we call the laws or processes of nature. Zoology is subdivided thus : i Morphology or gross Anatomy, and minute Anatomy (Histology). Physiology and Psychology. Zoology. < Reproduction and Embryology. Systematic Zoology or Classification. Paleontology. Zoogeography. Morphology.—In order to properly understand Zoology, one should first study Morphology—+.e., the general struc- ture of animals. The student should first thoroughly ac- quaint himself with the anatomy of a vertebrate animal, | such as a frog, as compared with that of a toad or salaman- der. The examination and comparison of the organs of animals belonging to distinct groups, is called Comparative Anatomy. The study of Morphology also includes the rela- tion of the different organs to one another, and of all to the walls of the body. Finally, we need also to study the com- position of the tissues of the different organs ; each kind of tissue being formed of different kinds of elements or cells. This department of Comparative Anatomy is called Histol- ogy (Greek, tords, web or tissue; Adyos, discourse). It treats of the cell, and the combination of cells into germ- layers, tissues, and organs. The Cell.—The primary elements of the bodies of animals are called cells. They are microscopic portions of proto- plasm either with or without a wall. Protoplasm largely — consists of protein, which is a complex compound of car- bon, hydrogen, oxygen, and nitrogen, associated with a large proportion of water. Cells are originally more or less spherical sacs, and the protoplasm forming the cell-mass is the dynamic part of the cell. The protoplasm of animal as well as vegetable cells, the protoplasm of eggs and of the cells forming the different tissues of the animal body, as 6 ZOOLOGY. well as the entire Amceba or monad, is complex. It is com- posed of carbon, hydrogen, oxygen, and nitrogen, combined in nearly the same proportions. The protoplasm of different cells exerts widely different forces and capabilities. An egg- cell becomes a man, whose brain-cells are the medium of the intellectual power which enables him to write the history of his own species, and to be the historian of the forms of life which stand below him. The cell is the morphological unit of the organic world. With cells the biologist can in the imagination reconstruct the vegetable and animal worlds. The primitive form of a cell, when without a nucleus or nucleolus, is called a cytode; genuine cells have a nucleus, the latter containing a nucleolus. Animals composed of but a single cell, such as the Ameba or an Infusorian, are said to be unicellular. Cells grow by absorbing cell-food—i.e., by the assimilation of matter from without, and this matter may be in masses of considerable size when seen under the microscope. Cells multiply by self-division. The egg-cell undergoes division of the yolk into two, four, eight, and afterward many cells; the cells thus formed become arranged into two layers or sets called germ-layers. The outer is called the ectoderm and the inner the endoderm. A third germ- layer arises between them, called the Fig. 3.—Germ of Sagitta, ™esoderm or middle germ-layer. From. a. eevectoderm ; en.endoderm: these germ-layers, or cell-layers, the both layers formed of nu- cleated cells. tissues of the body are formed, such as muscle, bone, nerve, and glandular tissue. These tissues form organs, hence animals (as well as plants) are called or- ganisms, because they have certain parts formed of a partic- ular kind of tissue set apart for the performance of a special sort of work or physiological labor. This separation of parts for particular or special functions is called differentia- tion ; and the highest animals are those whose bodies are most differentiated, while the lowest are those whose bodies are least differentiated ; hence high animals are specialized, and, on the other hand, low animals are simple. Thus dif- CELLS AND TISSUES. 7 eile of organs involves the division of physiological abor. Tissues.—Of the different kinds of tissues there is, first, epithelial tissue (Fig. 4) consisting of cells with a nucleus and nucleolus, and placed side by side, forming a layer. All the organs develop originally from epithelium, which is the prim- itive cell-structure and forms the tissues of the germ-layers. Epithelial cells form the skin of animals, and also the lining of the digestive canal. The cells of the latter may, as in sponges, bear a general resemblance to a flagellate infuso- Fig. 4.—Vertical section through the skin of an embryonic shark, showing at Z the epithelial cells, forming the epidermis; c, corium; e, columnar epithelium.—After Gegenbaur. rian, as Codosiga, or they may each bear many hairs, called cilia, which by their constant motion maintain currents of the fluids passing over the surface of the epithelium. The tissue forming glands is simply modified epithelium. Connective tissue is formed by isolated rounded or elon- gated cells with wide spaces between them filled with a ge- latinous fluid or protoplasm, and occurs between muscles, etc. An analogous (but hypoblastic) tissue forms the “no- tocord,” a rod supporting the bodies of vertebrate embryos. Gelatinous tissue is a variety of connective tissue found in the umbrella of jelly-fishes (Aurelia, etc.). Fibrous and elastic tisswe are also varieties of connective tissue. Cartilaginous tissue is characterized by cells situated in a 8 ZOOLOG Y. still firmer intercellular substance ; and when the intercel- lular substance becomes combined with salts of lime form- ing bone, we have bony tissue. The blood-corpuscles originate from the mesoderm as independent cells floating in the circulating fluid, the blood- cells being formed contemporaneously with the walls of the vessels enclosing the blood. In the invertebrates the blood- cells are either strikingly like the Amebda in appearance, or are oval, but still capable of } changing their form. Thus blood- * corpuscles arise like other tissues, of a water beotle—After Minot. oe that they finally become ree. Muscular tissue is also composed of cells, which are at first nucleated and afterward lose their nuclei. From being at first oval, the cells finally become elongated and more or less spindle-shaped, forming fibres; these unite into bundles forming muscles. ach fibre is ensheathed in a membrane called sarcolemma. Muscular fibres may be simple or striated (Fig. 5). The contractility of muscles is due to the con- tractility of the protoplasm 7 originating in the cells forming the fibres. Nervous tissue is made up of nerve-cells and fibres pro- ceeding from them; the for- mer constituting the centres of nervous force, and usually ‘massed together, forming a ganglion or nerve-centre from which nerve-fibres pass to the Fig, = anglion in the clam, with periphery and extremities of "°'Y®* © 9 % proceeding from it. the body, and serve as conductors of nerve-force (Fig. 6). Organs and their Functions.—Having considered the different kinds of cells and the tissues they form, we may now consider the origin of organs and their functions. The Protam@ba may be considered as an organless being. In Ameba (Fig. 11) we first meet with a specialized portion of the body, set apart for the performance of a special function. ORGANS AND THEIR FUNCTIONS. 9 Such is the nucleus ; so that Ameba is a genuine organism. © Ascending to the flagellate Infusoria (Fig. 1), we have the flagella developed as external, permanent organs of locomo- tion. In the Hydra (Fig. 36) the tentacles are organs whose functions are generalized. In the worms we have or- gans arranged in pairs on each side of the body, and in gen- eral among the higher invertebrates, especially the crusta- ceans and insects, and markedly in the vertebrates, we have the bilateral symmetry of the body still farther emphasized in the nature and distribution of the appendages. Of the internal organs of the body, the most important is the digestive cavity, which is at first simple and primitive in the gastrula or embryo of all many-celled animals, and as we ascend in the animal series we witness its gradual special- ization, the digestive tract being differentiated into dis- tinct portions (7.e., the esophagus, stomach, and intestine), each with separate functions while the organs of respiration, digestion, secretion, and excretion originate as offshoots or outgrowths from the main alimentary tract. In like man- ner the skeleton is at first simple and afterward is extended into the different organs, the various parts of the ap- pendicular skeleton corresponding to the increased flexi- | bility and diversified leverage power ; so that limbs become subdivided into joints, and these joints still further subdi- vided as we go from the points of attachment to the peri- phery or extremities, as seen in the tendency to an irrelative repetition of joints in the limbs and feelers of crustaceans and insects, and the digits of the lower vertebrates. Correlation of Organs.—Cuvier established this princi- ple, showing that there is a close relation between the forms of the hard and soft parts of the body, together with the functions they perform, and the habits of the animal. For example, in a cat, sharp teeth for eating flesh, sharp curved claws for seizing smaller animals, and great muscular activ- ity coexist with a stomach fitted for the digestion of animal rather than vegetable food. Soin the ox, broad grinding teeth for triturating grass, cloven hoofs that give a broad support in soft ground, and a several-chambered stomach coexist with the habits and instincts of a ruminant. Thus 10 ZOOLOGY. the form of the teeth presupposes either a ruminant or carni- vore. Hence this prime law of comparative anatomy led to the establishment by Cuvier of the fundamental laws of paleontology, by which the comparative anatomist is en- abled to restore from isolated teeth or bones the probable form of the original possessor. Of course the more perfect the series of bones and teeth, or the more complete the re- mains of insects or mollusks, the more perfect will be our knowledge, and the less room will there be for error in re- storing extinct animals. Adaptation.—An organ with a certain normal use or function may be adapted, in consequence of a change in the habits of the animal, to another use than the original one. To take an extreme case, the Anadas, or climbing fish, may use its fins to aid it in ascending trees. On the other hand, by disuse organs become aborted or rudimentary. The teeth of the whalebone whale are rudimentary in the young, and are replaced by whalebone, which is more useful to the animal ; the eyes of the blind-fish are rudimentary, func- tionless. Those of certain cave-insects are entirely wanting, being lost through disuse, owing to a change of life from the light, outer world to totally dark caverns, and the con- _ Sequent disuse of their eyes. Nature is economical. Every thing that is not of use as a rule disappears. It would bea waste of material to nourish and care for an organ in a cave- animal, or a parasitic insect or crustacean, which would be of no use to the animal. On the other hand, if the leg or tail of a newt is snipped off by some rapacious fish, it grows out again. Moreover, the animal organism is far more pliable than is generally supposed. Not only is nature continually repair- ing wounds and waste, not only is the body being contin- ually made over again, but certain animals undergo a change of form, either generally or in particular parts. It the environment is unchanged, the animal remains true to its species. The dogma of the invariability or stability of species is a fallacy. Change the climate, moisture or dryness, the nature of the soil ; introduce the natural enemies of the animal or remove them ; destroy the balance of nature, in LAW OF INHERITANCE AND TRANSMISSION. 11 other words, and the organism changes. The plants and animals of the mummies and monuments of Egypt are prob- ably the same as those now living in that country, because the climate and soil have remained the same. The assemblages of life that have successively peopled the surface of the earth, and which are geological time-marks, have probably become extinct because they could not adapt themselves to more or less rapid oscillations of continents and islands, to consequent changes of climate and the in- coming of destructive types of life. This probably accounts for the origin, culmination, and extinction of different types of life. The earth has been, and still is, in a state of unstable equilibrium. Organic life has been and is even now, in a degree, being constantly readjusted in harmony with these changes of the earth’s surface and climate. Thus this adaptation of organs to their uses, of animals to their environment, the laws controlling the origination of new forms of life and the extinction of those which have acted their part and are no longer of service in the economy of nature, is part of the general course of nature, and evinces the Infinite Wisdom and Intelligence pervading and contin- ually operating in the universe.* Coupled with variability is the law of inheritance and transmission of variable parts, and the habits thus induced by the variation of parts. It should be observed that the portions which vary most are the peripheral parts—i.e., fingers and toes, tentacles and antennae, the skin and scales and hair; it is by modifications and differences brought about in those parts most used by animals that the multi- tudes of specific forms have resulted. There is, as Darwin states, a general tendency of organisms to vary; the laws accounting for this tendency to vary have yet to be formu- lated ; though the attempts of Lamarck in this direction laid the way for the discovery and application of the funda- * That animals and plants are self-evolved, that the world has made itself, and that all is the result of so-called physical and biological laws operating from within outward, is as inconceivable as the medieval dogma that animals and plants and the earth they inhabit were made in the twinkling of an eye. See the concluding chapter on Evolution, 12 ZOOLOGY. mental laws of evolution. On the other hand, pure Dar- winism—viz., natural selection—accounts rather for the preservation than the origixation of the forms of life. Analogy and Homology.—When we study the Inverte- brates alone we see that it is often easy to trace a general identity in form between the more important parts. The parts of the sting of a bee are originally like the feet or jaws of this insect, though the functions of these parts may be quite unlike; these are therefore examples of a general identity in structure or homology between two organs. A closer homology implies a more apparent identity of form, as seen in the resemblance in structure of the fore-limbs of a whale and a seal, or the pectoral fins of fishes and the arms of man, or the wing of a bird and the human arm. Analogy implies a dissimilarity of structure of two organs with identity in use, as the wing of an insect and of a bird ; the leg of an insect and the leg of a frog; the gill of a worm and the gill of a fish. Homology implies blood-relationship ; analogy repudiates any common origin of the organs, however physiologically alike. The most general homologies are those existing in organs belonging to animals of different branches ; the most special between those of the same orders and minor groups. Thus it is fundamentally a question of near or remote con- sanguinity. Physiology treats of the mode in which organs do their work ; or, in other words, of the functions of different or- gans. Thus the hand grasps, the fins of a fish are its swim- ming organs ; the function of the nose is to smell, of the liver to secrete bile, of the ovary to secrete protoplasm which forms eggs. Psychology is the study of the instincts and reasoning powers of animals ; how they act when certain parts are irritated ; so that while this term is generally applied to man alone, Comparative Psychology deals both with the simplest automatic acts and the whole series of psychic pro- cesses—from those exercised by the Protozoans, such as Ameba, up to the complicated instinctive and rational acts of man. REPRODUCTION AND EMBRYOLOGY. 13 Reproduction.—The simplest form of reproduction is cell-division, one cell budding or separating from another. This mode of growth is called self-division or fission. Where one cell separates from another, the separating part being smaller than the original cell, or where a number of cells separate or bud out from a many-celled animal, such as a Hydra, the process is called gemmation. A third mode of reproduction is sexual, the sperm-cell of the male coalescing with the nucleus of the egg ; the commingling of the pro- toplasm of the two nuclei resulting in a series of events leading to the formation of a germ or embryo. Embryology is, strictly speaking, a study of the develop- ment of animals from the beginning of life of the egg up to the time the animal leaves the egg or the body of the parent —namely, up to the time when it begins to shift for itself , but the term embryology may also be applied to the grow- ing animal from the egg to the adult condition. Many of the lower animals undergo a metamorphosis, suddenly as- suming changes in form, accompanied by changes in habits and surreundings ; so that at different times it is, so to speak, a different animal. For example, the caterpillar lives on solid food, crawls on the ground, and has a worm- like form ; it changes to a chrysalis or pupa, lying quies- cent, taking no food; then it changes to a butterfly and flies in the air, either taking no food or sipping the nectar of flowers : in all these three stages it is virtually different animals with different surroundings. Many animals besides ‘insects have a metamorphosis, and their young are called larve ; thus there are larval polyps, larval star-fish, larval worms—these larve often differing remarkably in form, habits, and in their environment or surroundings, as com- pared with the mature or adult forms. Classification.—After thoroughly studying a single ani- mal, its external form, how it acts when alive, its external and internal anatomy after death, and the development of other individuals of its own species, the student is then ready to study the classification of animals. The best method of studying classification, or Systematic Zoology, is to make an exhaustive examination of one an- 14 ZOOLOGY. imal, and then to study in the same thorough manner an allied form, and, finally, to compare thetwo. For example, take a frog and compare it with a toad, and then with a newt, or a land salamander ; thus, by a study of the different types of Batrachians, one may arrive at a knowledge of the affinities of the different species of the class. The methods of research are, then, observation and comparison. The best and most philosophic observers are those who compare most. Then, passing on to other animals, the student will place in one group animals that are alike. He will find that . Many agree in certain general characters common to all. He will thus form them into classes, and those that agree in less general characters into orders, and so on until those agreeing in still less important characteristics may be placed in categories or groups termed families, genera and species, varieties and races. For example, the cat belongs to the following groups : Kingdom of Animals ; Sub-kingdom, or branch, Vertebrates ; Class, Mammalia ; Order, Carnivora ; Family, Felide ; Genus, Felis ; Species, Felis domesticus -Linneus ; Variety, Angorensts. But these different groups are insufficient to represent the almost endless relationships and series called the System of Nature, which our classifications attempt to represent. Hence we have sub-species, sub-genera, sub-families and super-families, sub-orders and super-orders, and sub-classes and super-classes, and the different assemblages may be grouped into series of orders, families, etc. The relations of the members of these different groups may be represented in the same manner as the genealogi- cal tree of the historian, or like a tree, with its trunk and branches and twigs; or on a plane by a cross-section through the tree, the different groups or ends of the branches resembling a constellation, and embodying one’s HIGHT BRANCHES OF THE ANIMAL KINGDOM. 15 idea of the complicated relations between animals of differ- ent groups. The Animal Kingdom may be divided primarily into two series of branches; those forthe most part composed of asingle cell, represented by a single branch, the Profo- zoa, and those whose bodies are composed of many cells (Metazoa), the cells arranged in three fundamental cell- layers—viz., the ectoderm, mesoderm, and endoderm. The series of Metazoa comprises the seven higher branches—i.e., the Porifera, Coelenterata, Echinodermata, Vermes, Mol- lusca, Arthropoda, and Vertebrata. Their approximate relationships may be provisionally expressed by the follow- ing TABULAR VIEW OF THE EIGHT BRANCHES OF THE ANIMAL KINGDOM. VIII. Vertebrata. Ascidians to Man, VII. Arthropoda. Crustaceans and Insects. | VI. Mollusca. Clams, Snails, Cuttles. Flat and Round Worms, Polyzoa, Brachiopods, Annelids. | IV. EHehinodermata. Crinoids, Starfish, etc. | | V. Vermes. Ill. Celenterata. Hydra, Jelly-fishes, TI Porifer a ay cael eee Merazoa. Many-celled animals, with 3 cell-layers. I. Protozoa. Single-celled animals. It should be understood by the student that the classifi- cation presented in this book is a provisional one, bused on cur present knowledge of the structure of the leading types 16 ZOOLOGY. of the animal kingdom, and may be regarded as rudely in- dicating the blood-relationship or pedigree of animals. It differs in some important respects from the classifications given in the books ordinarily in use by American students. Some authors retain the four types of Cuvier, but it should be remembered that since Cuvier’s classification was proposed in 1812 our knowledge has been greatly extended. The microscope has revealed an immense mass of new mi- croscopic forms, and many facts regarding the structure and development of the larger forms. The embranchments of Cuvier are in all cases, except the Vertebrates, unwieldy, het- erogeneous, and, in the light of our present knowledge, un- natural assemblages of animals. New discoveries do away with old systems, and the classifications adopted by differ- ent authors represent the standpoint from which they re- gard the system of nature. It isnot of so much consequence to the student to know what the system may be, as to learn the leading facts of animal morphology and development. Paleontology-—With a thorough knowledge of the anat- omy of animals and their classification, the student is pre- pared to study the remains of extinct animals, to restore so far as possible their forms, and to classify them. With a knowledge of the hard parts of existing animals, and of the interaction of the tendons, ligaments, muscles, and bones, the paleontologist can, in accordance with the law of cor- relation of parts, refer fossils to their respective orders, families, genera, or species. Zoogeography, or geographical distribution, is the study of the laws of distribution of animals over the surface of the earth or over the bottom of the sea. ‘The assemblage of animals inhabiting any area is called a fauna. Thus we have an arctic fauna, a tropical fauna, a North American fauna, or Australian fauna. The fauna of the ocean is sub- divided into different subordinate faune. CHAPTER I. BRANCH I.—PROTOZOA. General Characters of Protozoans.—We can imagine no more elementary forms of life than certain members “of this branch, whose bodies in the simplest forms are merely masses of albumen, without any distinct permanent organs, or portions set apart for the performance of any special function. Yet the primary acts of animal life, such as tak- ing food, its digestion and assimilation, and reproduction, are carried on as effectively by these lowest as by the high- est forms. The simplest Protozoans are like minute drops of protoplasm or albumen, having a gliding motion, and constantly changing their forms, throwing out temporarily root-like projections called pseudopodia, which serve to § gather food-particles. Fig. 7 illustrates a typical Proto- zoan. It is the common Ameba of standing water. Most Protozoans are provid- ed with a central organ or nucleus, which corresponds ' to the reproductive organs of the many-celled animals. The Protozoa are one-celled in distinction from all other animals, from the sponges to man, which are many-celled, though it is claimed that a few shelled forms (Rhizopods) are composed of several indistinct cells. Thus a Protozoan cor- responds to an egg or to any one of the cells composing the bodies of higher animals. They may be naked, asin Prota- meba or Ameba, or may secrete a silicious or calcareous shell. The Infusoria, forming the highest class, are quite complicated, with permanent cilia, a mouth, throat, repro- Fig. 7. —Ameeha, the nucleus not shown. 18 ZOOLOGY. ductive nucleus, and several contractile vesicles, rudely an- ticipating the heart of higher animals. Protozoans repro- duce by self-division and the formation of motile germs (zoospores), and in the Infusoria of ciliated young. There is thus a great range of forms leading from the most primi- tive type (Protameba) to the most specialized forms, such as the bell animalcule ( Vorticella.) Crass I.—Monera (Moners). General Characters of Moners.—This group comprises the simplest forms of Protozoans, whence the name Monera (uorvnpes, simple). The lowest forms are almost identical in appearance with the lowest plants, and they can only Fig. 8.—Protomoas amyli, greatly magnified. A, when encysted; 2, germs or ZO- ospores; y, food-mass. B, germ freed from the parent-cyet. C, D, older germs. £, adult encysted 3; y, food ; s, projection inward of the cell-wall ; x, wall of the cyst; ¢, germs.—After Cienkowski. be claimed to be animals from their resemblance to higher forms leading to Ameba, which, in turn, is connected by a series of forms leading to undoubted animals, such as the shelled Rhizopods (Fig. 14). The Monera differ from the Rhizopods (Amebda, etc.) in wanting a nucleus and contractile vesicles. Their body- substance is homogeneous throughout, not divided into a tenacious outer and softer inner mass, as in Ame@eba. They move by the contraction of the body, and the irregular pro- trusion of portions of the body forming either simple pro- cesses (pseudopodia) or a network of gelatinous threads, The food, assome diatom, desmid, or protozoan, is swallowed MONERA. 19 whole, being surrounded and engulfed by the body, and the protoplasmic matter is then absorbed, serving for the nour- ishment and growth of the Moner. The simplest form known, and supposed to be really a living being, is Haeckel’s Protameba. It may best be described by stating that it is like an Ameda, but without a nucleus and vacuoles (or little cavities). It reproduces by simple self-division, much as in Amebda (Fig. 11). In Protomonas the body is very changeable in form, the pseudopods often being very slender, thread-like. Fig. 8, A represents this Moner during the formation of the young (zoospores) in the cyst-like body, or resting-stage of the creature ; B, one of these germs freed from the cyst and capable of moving about by the two thread-like pseudopo- dia; CD, the Ameba-like form which the young after- ward assumes, and which at maturity passes into the en- cysted or resting-stage Z. A still better idea of what a Moner is may be seen by studying the Protomyza aurantiaca Haeckel. This Moner was discovered at the Canary Islands. It is from half to one millimetre in diameter, and is a perfectly simple mass of orange-red jelly. When hungry numerous root-shaped threads (pseudopodia) radiate from the central mass. Fig. 9, # represents the Protomyxa after having absorbed into its body-mass a number of shelled Infusoria. When about to become encysted (4 B) it rejects the shell of its victims, retracts its false feet, and soon becomes fast- ened as minute red balls to the surface of some dead shell. The ball becomes enclosed by a thick covering (A), and then the contents become divided into several hundred small, round, thoroughly structureless spheres, which become germs (B). The germs finally burst through the cyst-wall, as in C, a, c, d, and assume various monad-like and amoeboid shapes, and finally attain, by simple additions of the proto- plasm of its food (diatoms and infusoria), the adult form (D #). Other Moners exist in fresh water. We have been dealing with the simplest living forms, be- ings showing no trace of organization, much lower and simpler than the Am@ba, with its nucleus. The individual 20 ZOOLOGY. Moner—for example, Prot.meba—is simply a speck or drop of transparent, often colorless, viscid fluid, scarcely of more consjstency than, and in all apparent physical characters identical with, the white of ahen’s egg. And yet this drop of protoplasm has the power of absorbing the protoplasm of other living beings, and thus cf increasing in size—t.e., growing ; and in taking its food makes various movements, one or more parts of its body being more movable than .—Protomyxa aurantiaca. A, encysted. B, cyst filled with germs. C, germs Fig. 9. @ d ¢) issuing from the cyst. D, a young Protomyxa swallowing a diatom (a). adult after enclosing or swallowing several shelled Infusoria.—After Haeckel. others, the faculty of motion thus being for the moment specialized ; it has apparently the power of selecting one kind of food in preference to another, and, finally, of repro- ducing its kind bya process not only of simple self-division, but also of germ-production. In short, we may say of the Moner what Foster says of the Amceeba—viz., (1) it is con- tractile ; (2) it is irritable and automatic ; (3) itis receptive MONERA. al and assimilative ; (4) it is metabolic and secretory in the sense that the Moner digesis and separates the portions necessary for food from those which it rejects as waste ; (5) itis respiratory, the changes involved in taking food, es- pecially oxygen, causing the production of and excretion of carbonic acid ; (6) it is reproductive. It is difficult to conceive of a simpler form of life than Protameba or Protomonas. Are the Moners animals or plants, or do they represent a neutral division or group of forms? It was formerly thought that Ameba was the sim- plest possible form of life, but we shall see that that animal is an undoubted organism, possessing a permanent organ, the nucleus. Moreover, the Amoeba intergrades with the other Rhizopods which are undoubted animals, while the simplest Monera have no characters which absolutely sepa- rate them on the one hand from the plants or on the other from the animals. Their relation to the plants is seen in the fact that, besides the resemblance to the lowest plants, the cyst of Protomonas is composed of cellulose, while the granular contents of the body become colored with chlo- vophyll.* For these reasons, Haeckel, the discoverer of the Monera, regards them as neutral beings, neither plants nor animals. But by comparison with other Protozoa, we shall see that the Monera only differ from tke monads and Amebe by the absence of a nucleus. This may yet be found to occur in the Monera, and from this fact we separate the group only provisionally from the Rhizopoda. The Gregarine also pass through a true Moner-stage. This indicates that the Monera are allied rather to animals than plants. Another point of difference from plants is the fact that, like the Ameba, they engulf living plants (desmids, etc.) and ani- mals (Infusoria), the only plants known to do this being the singular Myxomycetes, whose position is uncertain, some naturalists (Allman) regarding it as an animal. It is probable that the Monera were the earliest beings to * On the other hand, cellulose occurs in the integument of Tunicates, and various parts of Articulates and Vertebrates, while chlorophy!l occurs in the Infusoria and Hydra. 22 ZOOLOGY appear, and that from forms resembling them all other organ- isms have originated. We can conceive at least of no simpler ancestral form; and if organized beings were originally pro- duced from the chemical elements which form protoplasm, one would be naturally led to suppose that the earliest form was like Protameba. It would follow from this fact that the Monera are as low as any plants, and that animals appeared contemporaneously with plants. Having studied a few typical forms of Monera, we are prepared to briefly define the group and tabulate the sub- divisions of the class. Cuass I.—MONERA HaerckeE.. Beings consisting of transparent protoplasm, containing granules, some- times forming a net-work, but with no nucleus* or contractile vacuole ; capable of automatically throwing out pseudopodia, and reproducing by simple self-division of the body-mass into two individuals, or by division into a number of germ-like or spore-like young, which increase in size by absorption of the protoplasm of other organisms. Group 1. Gymnomonera, comprising the genera Protameba, Protogenes, and Myxodictyum, which do not become encysted. Group 2. Lepomonera, which become encysted and protected by a case, as in the genera Protomonas, Protomyxa, Vampy- rella, and Myxastrum. Crass II.—Rurzopopa (Root Animalcules). General Characters of Rhizopods.— \ Fig. 59.—Section of a reef.—From Dana, \ | : H NX . SN XN . SRO XO . if \S a KY BANS . BOS oS . \ \ Cad \ INN WN PRS S el Za GtaeeNS te ANS ~ ae \ ee S RS \ MX MAY \\ NS << \ \S: . . a 7 the submarine: slopes, like massy structures of artificial masonry ; some forming a broad flat platform or shelf ranging around the land, and others encircling it like vast FORMATION OF CORAL REEFS. 89 ramparts, perhaps a hundred miles or more in circuit.” Darwin has estimated that some reefs in the Pacific Ocean are at least 2000 feet in thickness. Thus far we have spoken of reefs surrounding mountainous islands ; coral islands or atolls (Fig. 58) resemble such reefs, except that they surround a lake or lagoon instead of a high island, the coral island itself being seldom more than ten or twelve feet above the sea, and usually supporting a growth of cocoanut trees, while the sea may be of great depth very near the outer edge of the atoll, which ‘‘ usually seems to stand as if stilted up in a fathomless sea ’’ (Dana). These reefs and atolls are formed and raised above the sea by the action of the winds and waves, in breaking up the living corals, comminuting it and forming with the débris of shells and other limestone-secreting animals and plants, banks or de- posits of coral mixed with a chalky limestone, as the base of the reef. When it rises above the waves, cocoanuts and other seeds are caught and washed up on the top, and gradually the island becomes large enough to support a few human beings. The Bermudas are the remnants of a single atoll, and are situated farther from the equator than any other reefs. Most barrier reefs and coral islands or atolls are formed in an area of subsidence, where the bottom of the ocean is gradually sinking ; this accounts for the peculiar form and great thickness of many reefs. On the other hand, the coral reefs of the West Indies are, generally speaking, in an area of elevation. A section of a coral reef is shown by Fig. 59: 2 is the point where the shore slopes rapidly down within the lagoon (which lies to the right), and m is where the reef suddenly descends toward the open ocean. Between 6 ¢ and de lies the higher part of the reef. The shore toward the lagoon slopes away regularly from d to n ; while toward the open ocean there is a broad horizontal terrace (a to 6 c) which becomes uncovered at low water. The theory of the formation of barrier reefs is shown by the diagram, Fig. 60. The island, for example, the volcanic island Coro, which is slowly sinking, at the ancient sea-level I is surrounded by a fringing reef //, a small rock-terrace 90 ZOOLOGY at the former level of the sea. Where the island has sunk to the level of the water-line II, the reef appears at the sur- face as at 0’ f’,b f. There is now a fringing and a barrier reef, with a narrow canal between them ; 0’ is a section of the barrier reef, e’ of the canal or lagoon, and /' of the fringing reef. After a farther submergence to the sea-level III, the canal e” becomes much wider. On one side (f/f) the reef is present, on the other side it has disappeared, ow- ing to the agency of ocean-currents. Finally, at the water- level IV, there are two small islands surrounded by a wide lagoon, with two reef-islets 7’”, 7'", resting upon two sub- marine peaks. The coral reef has now grown to great di- mensions, and covered almost the entire original island, and though the reef-building coral polyps cannot live below yu” 2 ms ge “a 2 a” a a ee Ce i ee FS ME Ds Stine Pe zs Fe Fig. 60.—Schematic section of an island with reefs. a point fifteen or twenty fathoms below the surface, yet ow- ing to the slow sinking of the island, they build up the reef as rapidly as the former subsides, and in this way after many centuries a coral reef sometimes two thousand feet thick may be built up in mid-ocean. Semper has called attention to the influence of ocean currents, and their varying strength and direction, in shap- ing the forms of coral islands and reefs ; and Moseley holds nearly the same view ; neither of these authors accepts the theory of subsidence. Coral reefs are mainly confined to the Western and Cen- tral Pacific and the Indian Oceans, and to the Caribbean Sea. None occur on the west coast of North America or of Africa, and only limited patches on the eastern coast of South America. There were paleozoic reefs, such as the fossil coral reef extending across the Ohio River at Louis- ville. ACTINOZOA. 91 _ Crass II.—THE ACTINOZOA. Calenterates with a digestive sac partially free from the body-cavity open- tng into tt below and held in place by six or eight mesenteries radiating from the digestive cavity and dividing the perivisceral space into chambers. Mouth surrounded with a circle of tentacles, which are hollow, communicating di- rectly with the perivisceral chambers. A slightly marked bilateral symmetry. To the edges of the mesenteries (usually the free ones) are attached the repro- ductive glands, both male and female, or of one sea alone , also the craspeda, or mesenterial filaments, which contain a large number of lasso-cells. Body either entirely fleshy, or secreting a calcareous or horny coral-stock, und when the species is social connected by a cenenchyme. In some forms (sea- pens) the entire colony capable of limited locomotion. No well-marked nervous system, but a plexus of fusiform ganglionic cells connected by nerve- fibres in the base of Actinians. Reproduction by self division, gemmation, or by ova, the sexes being separate or united in the same individual ; the young undergoing a morula and gastrula condition, and then becoming fived. Order 1. Zoantharia.—Mesenteries and tentacles usually six or in mul- tiples of six, corallum with calcareous septa. Mesenterial fila- ments abundantly developed (Astreea, Madrepora, Actinia). Oraer 2, Aleyonaria.—Mesenteries and tentacles always eight in num- ber. Coral-stock without true septa. Mesenterial fila- ments not usually numerous. Corallum usually horny, and the whole colony in the Pennatulacea capable of locomo- tion (Aleyonium, Gorgonia, Pennatula, Renilla). VIEW OF THE CLASSIFICATION OF THE ACTINOZOA, Aleyonaria. (Alcyonium.) Zoantharia. (Actinia.) si ACTINOZOA. Laboratory Work.—Verrill has preserved Actinise completely ex- panded by slowly adding a saturated solution of picric acid to a small quantity of sea-water in which they had expanded. When dead they “should be transferred to a pure saturated solution of the acid, and allowed to remain for from one to three hours, according to size, etc. They should then be placed in alcohol, which should after a day or two be renewed. Thus hardened they can be cut into sections. Corals can be studied by grinding or sawing sections, and, if desirable, treated as in the case of the corallum of the Millepores. 92 ZOOLOGY. Crass III.—CrenopHora (Comb-bearers). _ General Characters of Ctenophores.—These beautiful an- imals derive their name Ctenophora, or ‘‘ comb-bearers,’’ from the vertical rows of comb-like paddles (ctenophores) situated on meridional bands of muscles which serve as lo- comotive organs, the body not contracting and dilating as in the true jelly-fishes. In their organization they are more complicated than the Actinozoa, as they have a true digestive cavity passing through the body-cavity, with two posterior outlets (it will be remembered that Cerianthus has one at the end of the body). From this alimentary canal are sent off chymiferous or water-vascu- lar canals (Fig. 61) which correspond in their mode of origin with the water- tubes of the Echinoderms. As regards the rows of paddles, each vertical row consists of a great number of isolated, transverse, comb-like fringes placed one above the other, and movable, either isolately or in regular succession or simultaneously (Agassiz). As these rows of paddles are connected for their whole Fig. 61.— View of the length with a chymiferous tube, they aetro-vascular canals of a probably aid in respiration. These ani- leurobrachia, from which a the two retractile | arms mals also stand much higher in the scale from one side, the mouth. of life than the other Ccelenterates by font whe math ond being more truly bilateral, the radial PELE a symmetry so marked in the Actinia or in the jelly-fish being in these animals less apparent, as the parts are developed on opposite sides of a median plane. The nervous system, as originally described by Grant, con- sists of a ganglion situated at the aboral end (end opposite to the mouth) of the Pleurobrachia, from which, among other nerves, eight principal ones are distributed to the eight rows of paddles. A nerve also proceeds to the so- called otolitic sac (lithocyst) seated upon the ganglion. Eimer has lately shown that the nervous system of the AFFINIVIES OF OTENOPHORES. 93 Ctenophora, as, for example, that of Beroé, agrees in general with that of the jelly-fishes, with the difference that in the Ctenophores the nerve-centres are not situated on the edge, but at the pole of the body opposite the mouth. On the other hand, the nervous system is not radiated as in the jelly-fishes or as in the Echinoderms. Our commonest example of this class is the Pleurobrachia rhododactyla Agassiz. It is a beautiful animated ball of transparent jelly moving through the water by means of eight rows of minute paddles, throwing out from a sac on each side of the body two long ciliated tentacles. It is abundant in autumn ; sometimes thousands may be seen stranded on the shore at low water. That the Ctenophores have affinities to the sea-anemones (Actinozoa) is seen in the form and relations of the diges- tive tract, though it differs in hanging free, not being held in place by radiating mesenteries, and in this respect they approach the Echinoderms. From their possessing a dis- tinct digestive tract, the Ctenophores need not be confounded with the jelly-fishes (Hydrozoa). On the other hand, they present some advance over the Actinozoa, and in some respects connect the Hydrozoa and Actinozoa with the Echinoderms. For example, the water-vascular system arises in the Ctenophores as outgrowths from the digestive sac, as they do in the young star-fish and sea-urchins. This indicates that in the mode of development of both the di- gestive tract and the water-vascular system the Ctenophores are allied to the Echinoderms rather than to the Hydrozoa, in which the water-vascular tubes arise as simple hollows in the body-mass. Moreover, they are less radiated than in the Hydrozoa or Echinoderms. In Bolina alata Agassiz the body is plainly bilateral and the water-vascular tubes are very distinct. In Idyia roseola Agassiz the mouth is large, the stomach wide, and the body is of an intense roseate hue. This beautiful species after death, late in summer, is very phosphorescent ; all Cteno- phores, however, even their eggs and embryos, are phospho- rescent. In the Ctenophores the ovaries and spermaries occur in the same individual and form blind sacs attached to the 94 ZOOLOGY. water-vascular tubes, and are developed locally, asin Cestum, or along the whole length of the tubes, the sexually-differ- ent glands being placed in Beroé and allies on opposite sides of the tube. When ripe the eggs pass into the perivisceral space, and finally pass out through the openings of the body. The eggs of Plewrobrachia escape singly ; in Bolina they are laid in strings, while those of Idyia are deposited in a thick slimy mass. They spawn late in the summer and in the autumn. The young develop in the autumn, becoming nearly mature in the following spring. Development is di- rect, the young hatching nearly with the form of the adult, there being no metamorphosis. The species are widely distributed, a number being com- mon to both sides of the Atlantic, and the same species, ap- parently, of Plewrobrachia and Idyia occur on the east and west coast of North America. The most widely distributed forms are the Beroids. While the genus Mertensia is en- tirely arctic, the larger number of species are either tropi- cal or subtropical. The classification of the group isshown in the following summary. Cuass III.—CTENOPHORA. Spherical or oval, somewhat bilateral, scarcely radiated aninwls, with jelly-like, transparent bodies. The digestive tract opens at the posterior end into the perivisceral cavity ; from the canal pass off eight water-vas- cular tubes, which are in close relation with eight vertical meridional series of comb-like locomotive organs. Usually a pair of tentacles, which may become withdrawn into sacs, and are provided with thickset lasso-cells on the tentacular fringes. Nervous system consisting of an aboral ganglion, sending off eight nervous filaments to each of the eight rows of paddles. The sexual glands seated in the same individual. No metamorphosis, the young when hatched resembling the adult. Order 1. Hurystomee.—Body oval, with a large mouth and capacious stomach. The water-vascular tubes connected with the ctenophores, and forming numerous ramifications, commu- nicating by means of a circular canal near the mouth (Berot, Idyia). CLASSIFICATION OF CTENOPHORES. 95 Order 2. Saccate.—Body more or less spherical, with two long tenta- cles capable of being wholly retracted in a sac (Pleuro- brachia). Order 3. Taniata,—Body ribbon-like, being very much compressed in the direction of the lateral diameter (Cestum). Order 4, Lobate.—Body lateral, compressed, bilobed (Bolina). ‘VIEW OF THE CLASSIFICATION OF THE CTENOPHORA, Lobata. (Bolina.) Teniata. : (Cestum.) Saccata, (Pleurobrachia.) 4 Hurystomee. (Idyia.) | CTENOPHORA. Laboratory Work.—The Ctenophore should be studied while alive. They may be collected with a drag or tow-net from a boat when the surface of the ocean is calm. For studying the fine anatomy and tissues they should be treated by the same methods as the smaller jelly- fishes. , CHAPTER IV. BRANCH IV.—ECHINODERMATA (StAR-FIsH, SEA; URCHINS, SEA-CUCUMBERS, ETC.) General Characters of Echinoderms.—We now come to animals of much more complicated structure than any of the foregoing branches, and in which the radiated arrange- ment of the parts of the body is in most cases as marked as the jointed or ringed structure of worms or insects ; for not only are the body-walls of the star-fish or sea-urchin, or even many of the Holothurians (though less plainly), di- vided into five wedge-shaped portions (spheromeres), or pro- duced into five arms as in the common star-fish or five- finger, but the nervous system, the reproductive organs, the blood and water-vascular systems, and the locomotive appendages of the latter, are usually arranged in accordance with the externally radiated form of the body. Still these animals are in many cases, as in the higher sea-urchins, plainly bilateral, while in the larval forms of all Echino- derms whose development is known the young are not radiated, but more or less bilateral, asin the larve of worms and mollusks. The most trenchant character, however, separating the Echinoderms from the Ceelenterates, and ally- ing them to the worms, is the genuine tube-like digestive canal which lies free in the body-cavity (perivisceral cavity), and may be several or many times the length of the body. The student can gain a correct idea of the general struc- ture of the Echinoderms from a careful examination of the common star-fish (Aséerias vulgaris Stimpson), which is the most common and accessible Echinoderm to be found on the New England shores. After placing a star-fish in some sea- water and noticing its motions, the thrusting out of the am- bulacral feet or suckers by which it pulls or warps its clumsy STRUCTURE OF COMMON STAR-FISH. 97 body over the mussel-beds, or rocks, or weeds, the arms being capable of slightly bending ; after observing the red eye-spot at the end of each arm or ray, and the movements of the numerous spines which are attached to the separate plates forming the calcareous framework of the body- walls, and examining the movements of certain modified spines called pedicellarie, which are pincer-like bodies situ- ated among the spines, the student will be ready to study the external and internal anatomy. First, as to the calcareous framework of the star-fish. In order to study this, a transverse section should be made through an arm, and a vertical one through the body and along the middle of a single arm, and finally the animei should be divided into two halves, an upper and lower. It will then be seen that the calcareous framework or so-called skeleton consists of a great number of limestone plates or pieces attached by a tough membrane and covered by the skin. Between the plates are spaces by which the water enters the body-cavity through the skin. These plates are arranged so as to give the greatest strength and lightness to the body. There is also to be seen an oral (actinal) side on which the mouth ig situated, and an aboral (abactinal) side, the re- spective limits of which areas vary greatly in the different groups of Echinoderms. Each arm or ray is deeply chan- nelled by the ambulacral furrow containing four rows of suckers or ‘‘ambulacral feet,’? which are tentacle-like protrusions of the skin growing out through orifices in the ambulacral plates, and are a continuation of the water- sacs or “‘ampulle’’ within. The madreporic plate is a flattened hemispherical body situated on the disk between two of the arms. It is perforated by canals. The nervous system of Echinoderms consists of a plexus of cells and fibres overlying the surface of the shell. The oral ring and radial nerves may be seen without dissection. By closely examining the mouth, a pentagonal ring is seen sur- rounding it, each angle slightly enlarging* and sending off * Owfsiannikoff states that the nervous ring is a flat band, con- taining no swellings or ganglia, and not differing in structure from the ambul:cral nerves, which latter possess nerve-cells as well as fibres. 98 ZOOLOGY. a nervous cord to the eye at the end of the ray. It may be discovered by pressing apart the ambulacral feet along the median line of each arm. Fine nerves are sent off to each sucker, passing through the opening between the calcareous plates and extending to each ampulla, thus controlling the movements of the ambulacral feet. SSSEO WE china — OT OTTO ee Fig. 62.—Longitudinal section through the body and one arm of Asterias vulgaris. m, mouth; s, stomach; /, lobe of stomach extending into the arm; a, anus; 77, ner- vous ring ; 7, radial nerve; vr, water-vascular ring, sending a radial vessel (v) into the arm; mp, madreporic plate; ¢, stone canal ; 2, hemal canal ; ov, oviduct ; 0, ovary ; am, ampulle, the ambulacral feet projecting below; 5, ceca or liver.—Drawn by A. F, Gray, under author's direction. The mouth (Fig. 62, m) is capacious, opening by a short esophagus into a capacious stomach (Fig. 62, s) with thin distensible walls, and sending a long lobe or sac (Fig. 62, /) into the base of each arm ; each sac is bound down by two retractor muscles attached to the median ridge lying be- tween the two rows of water-sacs (ampulle, see also Fig. 63). Fig. 63.—Diagram of the cross-section of an arm. A, of Asterias rubens; B. of Ophiura texturata ; p, ambulacral feet ; p’, ampulle ; ¢, dermal tentacles ; 7, nervous cords ; w, ambulacral plates ; m, muscles ; a@,ambulacral vein ; 0, ventral plate ; ¢, lat- era] plates; @, dorsal plate; &, calcified portion of the integument.—After W. Lange from Gegenbaur. The stomach ends in a short intestine, the limits between the two not distinctly seen. The intestine suddenly con- tracts and ends in a minute rectum situated in an angle between two of five fleshy ridges radiating from the centre STRUCTURE OF COMMON STAR.FISH. 99 of the aboral disk. The anus (Fig. 62, a) is minute and difficult to detect, being situated between the short spines, and is evidently not used in the expulsion of fecal matter unless the urinary secretions, if there be such, pass out of it. It would seem as if the opening were rudimentary and that the star-fish had descended from Echinoderms like the Crinoids, in which there is a well-marked external terminal opening of the digestive tract. Appended to the intestine are the ‘‘ ceca ’’ or “‘ liver” (Fig. 62, 4), consisting of two long, tree-like masses formed of dense branches of from four to six pear-shaped follicles, connecting by a short duct with the main stem. The two main ducts unite to form a short common opening into the intestine. The cceca are usually dark, livid green, and secrete a bitter digestive fluid, representing probably the bile of the higher animals. The star-fish is bisexual, but the reproductive glands are much alike, the sexes only being distinguishable by a micro- scopic examination of the glands. The ovaries (Fig. 62, 0) are long racemose bodies lying along each side of the in- terior of the arms, and the eggs are said to pass out by a short narrow oviduct (ov) through an opening between two plates on each side of the base of the arms, the opening be- ing small and difficult to detect. The water-vascular system consists of the madreporic body, the “‘ stone-canal ’’ (Fig. 62, ¢), the ring or circumoral canal (vr), and the radial vessels (v) ending in the water- sacs (am) and ambulacral feet. The stone-canal begins at the outer and under side of the sieve-like madreporic body, passing directly forward and downward in a sinuous course to the under side of the circumoral plates. The madreporic body (mb) is externally seen to be perforated by linear apertures radiating and subdividing toward the pe- riphery. The sea-water in part enters the body-cavity through the fissures in the madreporic body, while most of it enters the stone-canal, which is a slender tube scarcely one fourth the diameter of the entire madreporic body. The water entering the stone-canal (Fig. 62, ¢) passes di- rectly into the water-vascular ring (Fig. 62) and then into the ten Polian vesicles and the five radial canals, whence 100 ZOOLOGY, it is conveyed to each water-sac or ampulla (Fig. 62, am). These pear-shaped water-sacs, when contracted, are supposed to press the water into the long slender suckers or ambulacral feet, which are distended, elongated, and by a sucker-like ar- rangement at the end of the prehensile foot act in conjunc- tion with the others to warp or pull the star-fish along. Besides locomotion the ambulacral feet serve for respiration and perception (Simroth). Hoffman shows that the feet of the sea-urchins can be projected or thrust out without the aid of the ampulle. It will thus be seen that the water-vascular system in the star-fish is in its functions partly respiratory and partly locomotive, while it is in connection with the vascular sys- tem, and thus partly aids in circulating the blood and chyle. Of the true vascular or blood system the student can ordi- narily only discover one portion, the so-called ‘‘ heart ’’ or “* pulsating vessel,’’? which we may call the hemal canal (Fig. 62 4), and which runs parallel to the stone-canal from the madreporic body to near the ring-canal.* It is nearly as large as the stone-canal, slightly sinuous, muscular, and with the latter is surrounded by a loose investing membrane like a pericardium. Some observers deny the existence of a vas- cular (sometimes called ‘‘ pseudohemal ’’) system, but it has been recently studied by Hoffman and subsequently by Teu- scher, who maintains that in all Echinoderms there are two systems of blood-vessels, which belong, one to the viscera and the other to the nervous system, forming an oral or nervous ring and an analring. The two rings are in direct com- munication in the star-fishes, Ophiurans and sea-urchins, but not in the Holothurians. The radial nerves are ac- companied by a vessel which subdivides and distributes branches to the ambulacral feet in star-fishes, Echini, and Holothurians. 'Teuscher considers that the ‘“‘ heart ’’ found in the star-fishes and Echini connecting the wsophageal (or nerve-ring) and anal ring, is neither a gland nor a pulsating vessel, as different authors have supposed, but perhaps only * Simroth states that in Ophiurans (Ophiactis) the stone-canal opens in common with the ‘‘ heart’’ into the madreporic plate. CRINOIDS. 101 a relict of an earlier period of development. In the Ophi- urans the oral canal opens directly into the body-cavity ; in Echinothrix directly connects with the outer world by means of the interradial canals. Finally, he regards the nervous vessel as homologous with the ventral vessel of the Worms. Having made ourselves acquainted with the general struc- ture of the Echinoderms as exemplified in the star-fish, we are prepared to study the modifications of the Echinoderm plan in the different classes. Cuass I.—CRrrINorpEa (Stone-lilies, Encrinites, etc.) Order 1. Brachiata.—The living representatives of those Crinoids which lived in paleozoic and early mesozoic times are few in number, and for the most part live in deep water, or, as in the case of Rhizocrinus and its living allies, at great depths. They are like Limulus and Nebalia, rem- nants of an ancient fauna. There are but eight genera known—viz., Holopus, Rhizocrinus, Bathycrinus, Hyoert- nus, Pentacrinus, Comaster, Actinometra, and Antedon (Comatula). Of the first five genera the species are attached by a stalk to the sea-bottom, while the last three genera are in their young state stalked, but finally become detached. The body or calyx divides into arms bearing pinnule or sub- branches. The Pentacrinus lives attached to rocks from twenty to thirty fathoms below low-water mark in the West Indies. The stem is about a foot long, the joints pentagonal, send- ing off at intervals whorls of unbranched cirri. “‘ No dis- tinct basal piece is known, but the calyx appears to begin with the first five radialia ’’ (Huxley). Pentacrinus ca- put-meduse Miller (Fig. 64) and P. Millert Oersted are West Indian species. P. Wyville-Thompsont Jeffreys was dredged in deep water on the coast of Portugal. In the fossil P. subangularis the stalk was more than fifty feet long. Bathycrinus gracilis Wyville-Thompson is closely allied 102 ZOOLOGY. to Rhizocrinus, and was dredged in the Bay of Biscay at the depth of 2435 fathoms. 8B. Aldrichianus occurred in 1850 fathoms, latitude 1° 47’ N., longitude 24° 26’ W., off the coast of Brazil. With it and also near the Crozet Islands occurred the interesting Hyocrinus Bethellianus Wyville-Thompson, which bears in some points resemblance to the paleozoic genus, Platycrinus. Fig. 64.—a, Pentacrinus caput-meduse, half natural size; 6, calyx-disk seen from above, natural size.—From Brehm’s Thierleben. The most widely distributed species is the Rhizocrinus lofotensis of Sars (Fig. 65), which is closely related to the Bourquetticrinus of the chalk formation, and forms the transitional type connecting the Apiocrinide with the free-moving, unstalked Antedon. It occurs at the depth of STRUCTURE OF CRINOIDS. 103 from one hundred to one thousand fathoms in the North Atlantic and Floridan seas, and is acharacteristic member of the abyssal.g fauna. This crinoid®s consists of a jointed stalk, a cup-shaped body (calyx), from the edge of which from five to seven (the number varies) arms (brachia) radi- ate, which subdivide into a double alter- nate series of pin- nule. The mouth is situated in the centre, while the anus is situ- ated on a conical pro- jection on one side of the oral disk, between the bases of two of the arms. Rk. Raw- sont Pourtales occurs in from eighty to one hundred and twenty fathoms at Barba- does. In Holopus, ashort, stout form with no true stalk, but at- tached by a broad en- crusting base, there are ten arms originat- ing from five axial joints. ‘‘ When con- Fi tracted the arms are size” mics . 65.—Rhizocrinus lofotensis Sars, twice natural —After Wyville Thompson. 104 ZOOLOGY. rolled in a spiral and press laterally against one another so as to enclose a hermetically closed cavity.”’ The pinnules are formed of broad flat joints, and are ‘‘ rolled spirally to- ward the ambulacral channel of the arms when contracted ”’ (Pourtales). The only species yet known is H. Rangit D’Orbigny, from Barbadoes. In Antedon (Comatula) the body is at first stalked, but ‘afterward drops off, when it represents the calyx and arms of the ordinary Crinoids. It thus passes through a Rhizo- crinus condition, showing that it is a higher, more recent form. The mouth opens into a short, broad csophagus, and a wide stomach which makes a turn and a half, ending in the anal cone placed between the base of two of the arms. Within the five triangular plates is a circle of tentacles. From the space between each pair of oral plates the ambu- lacral grooves radiate to the arms and their branches. 4H. Ludwig maintains that Antedon possesses a true water-vas- cular system formed on the typical Echinoderm plan ; there being a ring-canal, with radial vessels arising from it. The tentacles of the perisome are connected with the ring- canal, and the tentacles of the arms and pinnule are con- nected with the radial vessel. Ludwig has also discovered in Antedon a system of blood-vessels (‘‘ pseudo-hemal ”’ system) consisting of an ural ring-canal and five vessels radiating from it, which send branches to the tentacles, as in Asterias. He also detected a ‘‘ dorsal organ,’’ which ‘he, contrary to Perrier and P. H. Carpenter, considers to be the central organ of the whole system of blood-vessels. Both Ludwig and Carpenter, however, regard it as homolo- gous with the so-called ‘‘ heart ’’ or hemal canal of Echini and Asterias. The nervous system consists of an oral ring with branches extending into the arms. The body-cavity extends into the arms, and the ovaries for the most part lie in the cavity of the arms, as in Asterias. The internal anatomy of Rhizocrinus has been investi- gated by Ludwig, who finds that it agrees very closely with that of Antedon. The water-vascular system, nervous sys- tem, alimentary canal and its appendages, have the same DEVELOPMENT OF CRINOIDS. 105 relations as in the unstalked Crinoids (Antedon and Actin- ometra), only they are on a simpler plan, there being a close similarity between Rhizocrinus and the pentacrinoid stage of Antedon. The ovaries of Antedon open externally on the pinnules of the arms, while there is no special opening for the prod- ucts of the male glands, and Thompson thinks that the spermatic particles are ‘‘ discharged by the thinning away and dehiscence of the integument.’’ The ripe eggs hang for three or four days from the opening like a bunch of grapes, and it is during this time that they are fertilized. The following account is taken (sometimes word for word) He. 66.—Development of a Crinoid (Antedon). A, morula; ZB, free larva, with bands of cilia; C, young crinoid.—After Wyville-Thompson. from Wyville-Thompson’s researches on Antedon rosaceus (Fig. 67) of the European seas. In the first stage the egg undergoes total segmentation (Fig. 66). A represents the egg with four nucleated cells, an early phase of the mul- berry or morula stage. After the process of segmentation of the yolk is finished, the cells become fused together into .a mass of indifferent protoplasm, with no trace of organiza- tion, but with a few fat cells in the centre. This pro- toplasmic layer becomes converted into an oval embryo, whose surface is uniformly ciliated. The mouth is formed with the large cilia around it before the embryo leaves the 106 ZOOLOGY. egg. When hatched, the larva is long, oval, and girded with four zones of cilia, with a tuft of cilia at the end, a mouth and anal-opening, and is about eight millimetres long. The body-cavity is formed by an inversion of the primitive layer which seems to correspond to the ectoderm. Within a few hours or sometimes days, there are indica- tions of the calcareous areolated plates forming the cup of the future crinoid. Soon others appear forming a sort of trellis-work of plates, and gradually build up the stalk, and lastly appears the cribriform basal plate. Fig. 66, B, ¢, rep- resents the young crinoid in the middle of the larva, whose body is somewhat compressed under the covering-glass. Fig. 67.—Antedon, stalked and free.—From Macallister. Next appears a hollow sheath of parallel calcareous rods, bound, as it were, in the centre by the calcareous plates. This stalk (B, ¢) arises on one side of the digestive cavity of the larva, and there is no connection between the body- cavity of the larva and that of the embryo crinoid. Two or three days after the appearance of the plates of the crinoid, the larva begins to change its form. The mouth and digestive cavity disappear, not being converted into those of the crinoid. The larva sinks to the bottom, there resting on a sea-weed or stone, to which it finally ad- heres. The Pentacrinus form is embedded in the larval body FOSSIL CRINOIDS. 107 (the cilia having disappeared), now constituting a layer of protoplasm conforming to the outline of the Antedon. Meanwhile the cup of the crinoid has been forming. It then assumes the shape of an open bell; the mouth is formed, and five lobes arise from the edges of the calyx. Afterward five or more, usually fifteen tentacles, grow out, and the young Antedon appears, as in Fig. 66,C. The walls of the stomach then separate from the body-walls. The animal now begins to represent the primary stalked stage of the Crinoids, that which is the permanent stage in Rhizocrinus, Pentacrinus, and their fossil allies. After liv- ing attached for a while (Fig. 67), it becomes free (see right- hand figure) and moves about over the sea-bottom. Fig. 68.—A Blastoid, Pentremites, seen from the side and from above.—After Liitken. There are two species of Antedon on the New England coast, one (A. Sarsit) inhabiting deep water in about one hundred fathoms, and the other (A. Zschrichtii Miller) shallower water (twenty-five fathoms) in the Gulf of Maine. Order 2. Blastoidea.—No forms have been discovered later than the Carboniferous period. The group began its existence as species of Pentremites (Fig. 68) in the Upper Silurian, and culminated in the Carboniferous age. It connects the Crinoids with the Cystideans ; the species have no arms, are supported on a short, jointed stalk, and the oral plates, when closed, as they are in a fossil state, make the calyx look like a flower-bud. There is a mouth and eccentric anal outlet and five radiating grooves, along 108 ZOOLOGY. each side of which are attached a row of pinnules. Be- sides Pentremites are the typical genera Hiwacrinus and Eleatherocrinus. Order 3. Cystidee.—This group is likewise extinct. In the fossil Pseudocrinus there is a short-jointed stalk, while in Caryocystites (Fig. 69) there is no stalk and no arms, the Fig. 69.— Caryocys- tites, a ,Cystidean.— After Liitken, Fig. 71.—Agelacrinus, a Cystidean, on the shell of a Brachiopod.—After Liatken. Fig. 70.— Pseudocri- nus, a Cystidean.— After Liitken. body being angulo-spherical, composed of solid plates. The Cystideans (Figs. 69 to 71) originated in the Cambrian for- mation, attained their maximum development in a number of species in the Silurian, and became mostly extinct in the Carboniferous period. Cuass I.—CRINOIDEA. Spherical or cup-shaped Echinoderms, without a madreporic plate, usu- ally attached by a jointed stem, a few free in adult life, with five arms sub- dividing into pinnule; the ambulacral feet in the form of tentacles arising around the mouth in the furrows of the calyx or situated on the jointed arms. In the Blastoidea and certain Cystideans the arms are ab- sent, but the pinnule are usually present, though absent in Caryocystites. Circulatory, water-vascular, and sexual organs much as in other Echine derms , the digestive canal ending in a distinct eccentric aperture. GENERAL STRUCTURE OF STAR-FISHES. 109° Order 1. Brachiaia (True Crinoids).—Calyx with large pinnulated arms, without dorsal calical pores, mostly stalked (Encri- nus, Pentacrinus, Apiocrinus, Rhizocrinus, Holopus, Ante- don, Actinometra, Phanogenia). Order 2, Blastoidea.—Armless, but with five series of pinnule, and with a stalk (Pentremites. No living representatives). Order 3. Cystidea.—Usually armed, with jointed pinnule, and a short stalk, the latter sometimes absent, as in Caryocystites. (All fossil forms, as Edriaster, Caryocystites, Spheeronites, etc.) Laboratory Work.—The living Crinoids are great rarities, and few students have access even to alcoholic specimens. The recent re- searches on their internal anatomy have been made in large part by cutting thin sections for the microscope, and staining them with car- mine, etc., after the methods of the histologist. Crass IIJ.—ASTEROIDEA (Star-fishes). General Characters of Star-fishes.— Having already studied the structure of the common star-fish, we are pre- pared to understand the classification of the class. The star-fishes have star-shaped, flattened bodies, with round or flattened arms, a madreporic plate, and two or four rows of ambulacral feet. Order 1. Ophiuridea (Sand-Stars).—This division is characterized by the body forming a flattened disk, with cylindrical arms, the stomach not extending into the arms, and there is no intestine or anal opening. ‘The ambulacral furrow is covered by the ventral shields of the tegument, so that the ambulacral feet project from the sides of the arm. They have no interambulacral spaces or plates. The am- bulacral feet or tentacles do not have a sucker at the end, but are provided with minute tubercles. They move faster than the true star-fishes, the arms being more slender and flexible. The madreporic body is one of the large circular plates in the interambulacral spaces around the mouth, The external openings for the exit of the eggs form distinct fissures or slits, one on each side of each arm. ' The ovaries are situated in the body, not extending into the arms, the 110 ZOOLOG Y. eggs being expelled into the perivisceral cavity, and thence finding their way out into the water through the interradial ‘slits.* The Ophiurans are bisexual, but one species being known to be unisexual, viz., Ophiolepis squamata, accord- ing to Metschnikoff. While most Ophiurans pass through a metamorphosis, the young of Ophiclepis ciliata is developed within the body of the parent, adhering by a sort of stalk (Krohn). In Ophiopholis bellis development is direct, there being no metamorphosis. An Ophiuran which has accidentally lost its arms can re- produce them by budding. Liitken has discovered that in species of Ophiothela and Ophiactis the body divides in two spontaneously, having three arms on one side and three on the other, while the disk looks as if it had been cut in two by a knife and three new arms had then grown out from the cut side. Simroth has made farther extended researches on self-fission in Ophiactis. The Ophiurans in most cases undergo a decided meta- morphosis Jike that of the star-fish, which will be described at length farther on. The larva, called a pluteus, is free- swimming, though in some species the young, in a modified larval condition, reside in a pouch situated above the mouth of the parent, finally escaping and swimming freely about (A. Agassiz). In Ophiocoma vivipara Ljungman, which occurs in the South Atlantic, the young at first live in the body of the parent and afterward cluster on the surface of her disk. The eggs are hatched successively, the young being found in a regularly gradated series of stages of growth (Wyville- Thompson). It appears probable, as in the case of the sea- urchins, that the Ophiurans of the cooler portions of the South Atlantic, in most cases at least, have no metamor- phosis. Several native forms are also viviparous. Our most common sand-star is Ophiopholis bellis Lyman (Fig. 72), which may be found at low-water mark, and espe- cially among the roots of Laminaria thrown up on the * On the other hand, Ludwig denies that the eggs pass into the peri- visceral cavity, but insists that they collect in pouches formed by an in- troversion of the integument. SAND-STARS AND STAR-FISHES.. 111 beach. It is variable in color, but beautifully spotted with pale and brown, its general hue being a brick-red. Am- phiura squamata Sars has long slender arms and is white ; it lives below tide-marks. The basket-fish, me- dusa’s head, or Astrophyton Agassizii Stm., is of large size, the disk being two in- ches across, and the arms subdividing into a great number of tendril-like branches. It lives from ten to one hundred fathoms in the Gulf of Maine. sep Ophiurans are widely dis- - CS tributed, and live at depths eo oo pears between low-water mark and . ; two thousand fathoms. Fos- Fig. 72.—ophiopholis ellis, common Sand- sil Ophiurans do not occur “**—After Morse. in formations older than the Upper Silurian, where they are represented by the genera Protaster, Palwodiscus, Acroura, and Hucladia ; genuine forms closely like those now living appear in the muschelkalk beds of Europe (Middle Trias). Order 2. Asteridea.—In the true star-fishes the arms are direct prolongations of the disk, and the stomach and A ¢ Fig. 73.—Three forms of Star-fish, A, B, C, seen from above, showing the different development of the ambulacral and interambulacral areas. The ambulacra are indi- sated by rows of dots; 0, mouth; 7, arms; é, interradial or interambulacf#al areas. C Pleraster; B, Goniodiscus; A, Asteriscus.—After Gegenbaur. ovaries or spermaries project into them, and there is a deep ambulacral furrow, while the interambulacral spaces vary much in development (Fig. 73); the feet are provided with 112 ZOOLOGY. suckers, excepting those at the end of the arms, which are tentacle-like. We have already described the common star- fish of our north-eastern coast, Asterias Forbesii of Desor (Fig. 74). This and the allied varieties are abundant on mussel and oyster beds, being very injurious to the latter, which serve them as food. The star-fish projects its capa- cious stomach, turning it inside out, between the open _ valves of the oyster, and sucks in the soft parts, in this way doing much damage to the oyster-beds of the southern coast of New England. Be bas ee oes eS es Be ms eo aa SS) Se PeCHOos One ee 38 jews Fig. 74.—Asterias Forbesii, natura) size.—After A. Agassiz. The bodies of star-fishes as well as sea-urchins (Echini) are covered with pedicellariw, which in the former are situ- ated around the base of the spines on the upper side of the body. They are pincer-like, consisting of but two prongs. In the *sea-urchins they are three-pronged, and scattered ir- regularly over the surface of the body. Their use is not really known. Star-fish have the sense of smell. The development of this species (and its ally or variety, A. berylinus) has been studied by A. Agassiz. After pass- DEVELOPMENT OF STAR-FISHES. 113 ing through the morula and gastrula stages, the cephalula or larval stage is reached, the mouth, digestive sac and its posterior opening being formed, a cephalic end being dis. tinguished from a posterior end. The larva is now bilater- ally symmetrical. At this time two lobes arise from each side of the mouth. These separate from their attachment and form two distinct hollow cavities,and by the time the larva attains the Brachiolaria stage the development of the Fig. 76.—Brachiolaria of Asterias viugaris, en- larged, with the star-fish Fig. %.—Bipinnaria with the star- (7) developing at the fish budding from it. ¢, e’,d’, 9, 9g aboral end. e. median protuberances of the body comparable anal arm; e*, odd termi- with the “arms” of the Brachiolaria nal oral arm; /, brachio- figured in the adjoining engraving. lar ai 1, branch of 6, mouth; 0, vent of the larva; A, germ water-tube (w’) leading of the star-fish; A, ciliated digestive into f” odd brachiolar tract; 7, ambulacral rosette (germ of arm, f’”, eurface-warts the water-vessels).—After Miiller, from at base of odd brachiolar Gegenbaur. arm f”.—After A. Agas- siz. body of the star-fish begins, for these two cavities subse- quently develop into two water-tubes. On one of these cav- ities the back of the star-fish is afterward developed, while on the other the under side with the feet or tentacles arise. The fully-grown larva is called a brachiolaria, as it was originally described with this name under the impression that it was an adult animal, as was the case with the plu- 114 ZOOLOGY. teus of the sand-stars, the dipinnaria (Fig. 75) of certain star-fishes, and the awricularia of the Holothurians. Fig. 76 shows the star-fish developing on the aboral end of the brachiolaria, whose body it is now beginning to ab- sorb. The brachiolaria soon shrinks, falls to the bottom, and attaches itself by its short arms. The star-fish com- pletely absorbs the soft body of the larva, and is conical, ' disk-shaped, with a crenulated edge. In this stage it re- mains probably two or three years before the arms lengthen and the adult form is assumed. In Leptychaster kerguelenensis Smith, of the South Paci- fic, a form allied to Luidia or Archaster, the young develop directly in a sort of marsupium, according to Wyville- Thompson. Pteraster militaris was found by Sars to be viviparous. In Brisinga the arms number from nine to twenty, are long, cylindrical, and, like the body, bear long spines. The species are abyssal. 2B. endecacnemos Asbjornsen lives on the Norwegian coast, at a depth of about 200 fathoms, and was dredged in abundance by the Challenger Expedition in 1350 fathoms, at a station due south of St. George’s Banks, associated with other species of star-fish (Zoroaster and As- tropecten), and again in eighty fathoms on La Have Bank, off Nova Scotia. A common form living in mud in usually from ten to thirty fathoms is Ctenodiscus crispatus Retzius, in which the body is almost pentagonal, the arms being very short and broad. Archaster is a genus of star-fishes occurring at great depths, A. vexillifer Wyville-Thompson (Fig. 77), occurring off the Shetland Islands, in from 300 to 500 fath- oms. Luidia is called the brittle star-fish, as when brought up from the bottom and taken out of the water it breaks up into fragments. It has five long arms. L. clathrata is com- mon on the sandy shores of the Carolinas, and ranges from New Jersey to the West Indies. Astropesten articulatus (Say) has the same range. <). germ passing through a Fig. 145.—Earth-worms pairing. After Curtis. morula (blastula ), ead a, embryo (blastula) soon after segmentation of trula and neurula stage, the yolk ; 0, embryo further advanced ; 0, mouth; c, embryo still older; &, primitive streak; d, the worm, when hatch- neurula ; 0, its mouth.—After Kowalevsky. a g, 9 esembling the pa- rent, except that the body is shorter and with a much less number of segments. While the earth-worms are in the main beneficial, from their habit of boring in the soil of gardens and ploughed Le ANATOMY OF NEREIS VIRENS. 211 lands, bringing the subsoil to the surface and allowing the air to get to the roots of plants, they occasionally injure young seedling cabbage, lettuce, beets, etc., drawing them during the night into their holes, or uprooting them. The next and highest type of Annulata is the common sea-worm of our coast, Nereis virens Sars. It lives between tide-marks in holes in the mud, and can be readily obtained. The body, after the head, eyes, tentacles and bristle-bearing feet have been carefully studied, can be opened along the back by a pair of fine scissors and the dorsal and ventral red blood-vessels with their connecting branches observed, as well as the alimentary canal and the nervous system. The anatomy of this worm has been described by Mr. F. M. Turnbull. It is very voracious, thrusting out its pharynx and seizing its prey with its two large pharyngeal teeth. It secretes a viscid fluid lining its hole, up which it moves, pushing itself along by its bristles and . ligule. At night, probably during the breeding season, they leave their holes, swimming on the surface of the water. The body consists of from one hundred to two hundred seg- ments. The head consists of two seg- ments, the anterior and buccal, the for- _ : mer with four eyes tae Saeed ehcerewah, — dick, caiculas layer with the pore-canals ; m, muscular layer; m’, and two pairs of muscles of the bristles, s, which retract the central antenne The sec- foot-lobe, while others pass to its dorsal glandular projection, d.—After Gegenbaur. ond segment bears four antenne (tentacular cirri). Each of the other segments bears a pair of paddle-like appendages (rami), which may be best studied by examining one of the middle segments which 212 ZOOLOGY. has been separated from the others. For the finer structure of the body-walls see Fig. 146. The alimentary canal consists of a mouth, a pharynx armed with two large teeth and much smaller. ones. The pharynx is entirely everted during the act of taking its food. Into the esophagus empty two large salivary glands; the remainder of the alimentary canal is straight and tubular. The circulatory system is very complicated ; it is closed and the blood is red. Both the dorsal and ventral vessels are contractile, the blood flowing forward in the dorsal vessel. and backward in the ventral vessel. The two small vessels, one on each side, in each segment of the body, branch off from the ventral vessel and subdivide, each sending a branch to the ventral ramus of the foot of the segment behind, and another larger branch around the intestine to the dorsal ves- sel, receiving also, on its way, a vessel from the upper ramus of the foot of its own segment. ‘‘ Besides these principal -lateral vessels, there are five other vessels on each side in each segment, coming from the ventral vessel. These form a loose but regular net-work that surrounds the in- testine and is connected with five other convoluted vessels, which join the dorsal vessel. This net-work on the intestine probably supplies the hepatic organ with material for its secretion, and very likely may receive nutritive material from the digested food.”. (Turnbull.) The blood is aérated in the finer vessels of the oar-like feet and in those situated about the alimentary canal. The neryous system consists of the ‘‘ brain” and ventral double ganglionated cord. The sexes of Nereis virens are separate ; the eggs during the breeding season fill the body-cavity, and pass out through certain of the segmental organs, which act as oviducts, while others, probably the more anterior ones, are excretory, like the kidneys of vertebrates, as urea has been detected in them. These organs are situated at the base of the lower ramus of each foot. In some species of the Capitellide Hisig has found that it is normal for several segmental organs to be present in asingle segment. While the mode of development of our Nereis has not \ LARVA OF ANNELIDS. 213 been studied, the eggs are probably laid in masses between tide-marks, and the young, when hatched, swim freely on the surface of the sea. The eggs of other worms are carried about in lateral pouches. The germ undergoes a cleavage phase and a gastrula stage. We have observed, in Salem harbor, the development of Polydora (probably P. ciliatum Clap.) which may be found in August, in all stages, on the Fig. 147.—A,.earliest observed stage of Polydora; B, Cephalula stage; Cand D, ater stages.—Author del. surface of the water. When first observed (Fig. 147, A) the body was spherical, with a short, broad intestine, and two sets of large locomotive bristles. It then passed into the cephalula state, the head clearly indicated and forming a large hood. This stage is seen at B, which represents the under side of the cephalula, the mouth being situated be- tween the two large ciliated flaps (like the velum of larval mollusks) of the hood ; the body is now segmented, with a third set of bristles and a band of cilia on the penultimate segment ; afterwards as at C, dorsal view, additional rings are present ; the eyes are distinguishable, and there are two more sets of bristles. ‘The new segments are, as usual in all 214 ZOOLOGY. articulates, interpolated between the penultimate and ter- minal segments of the body. At D, the body is many- jointed, the tentacles well developed, the large temporary bristles have been discarded, and the worm can be identified as a young Polydora. It is probable that Polydora is hatched as a trochosphere like that of Polyzoa, Brachiopoda and certain mollusks. The young Terebrellides Stroemti, and of Lumbriconereis, - are at first trochospheres, 7. ¢., the free-swimming germ is spherical, with a zone of cilia, two eye- | spots, and no bristles. Thus the earliest stages of Polyzoa, Brachiopoda, Lamellibranchiata, Gastro- A poda, and even of a Cephalopod (Fig. 215), Nemer- Fig. 14g— tina, and Annelides are almost identical. Farther Phylowoce along in their developmental history, the cepha- ae eee ‘lula of the Annelides (Fig 147, A, B, and 149), ‘is like that of certain Echinoderms (Fig. 149), Gephyrea, Polyzoa, Brachiopoda, and Mollusca. It may here be observed that the free-swimming larve of these types of invertebrate animals are the young of more or less seden- wy lh M TO att Fig. 149.—Cephalula stage of Echinoderms and Worms, lateral view. A, Holo- thurian, B, Star-fish, C, D, of Annelides. 0, mouth ; 4, stomach ; a, vent ; v, preoral ciliated band, in B, C, D, independent ; in A surrounding an oral region.—From Gegenbaur, ‘ tary parents. In this way the species becomes widely dis- tributed through the action of the marine currents, and too close in-and-in breeding is prevented. Certain Annelides sometimes multiply by self-division, the process being called strodilation. This is commonly observed BUDDING OF ANNELIDS. 215 in the fresh-water worm Nais, also in Syllis and Myrzanida, as wellas in Pilograna, Protula, etc. Autolytus, a com- mon worm on the coast of New England, produces one gen- eration by budding (parthenogenesis). There is, in fact, an alternation of generations, an asexual Autolytus, giving Fra. 151. Fig. 150.—Clymenella torquata.—After Verrill. Hig. 151.—Amphitrite cirrata, enlarged twice. 0, branchia; c, uncini, enlarged 50C diameters.—After Mulmgren. rise to a brood of males and females, the sexual and asexual forms being so unlike each other as to have been mistaken. for different species and even genera. . In Syllis and allies certain long, slender processes of the 216 ZOOLOGY. feet are jointed, thus anticipating He jointed appendages of the Crustacea and Insects. “The Annelides are divided into two suborders. The first suborder, Oligocheta, comprises Lumbricus, Nais, etc., while the second suborder, Chetopoda, embraces Syilis, Autolytus, Nereis, Polydora, Aphrodite, and Polynoé, which are free- swimming, while the tubicolous worms which respire by spe- aa 152.—Cistenides Goulilii, and its tube. —athed Verrill. “Fig. 153 —Euchone elegans, enlarged. cron Verrill. cial branchie, or gills, on the Boe live in tubes of sand or ‘in limestone shells. ‘Those which live in sand or mud-tubes are Cirratulus (Fig. 154), Clymene and Clymenella (Fig. 150), “which has no branchie, Amphitrite (Fig. 151), Teredrella, Cistenides (Fig. 152), Sabella, and Huchone (Fig. 1538), while Protula, Filograna, Serpula, and Spirorbis secrete more or less coiled limestone tubes. The large solid shells of the Serpule assist materially in building up coral reefs, SILURIAN WORM TRACKS. 217 especially on the coast of Brazil. The minute nautilus-like shells of Spirorbis live attached to the fronds of sea-weeds, especially the different kinds of Fucus. e i O AF ( os oi MOIS) Her Sak “Gen oe SS Ci | A ke ia S aS) i] Zp NCE ead Me) SW ip Oy ae Zp A ete S i Fig. 154.—Cirratulus grandis.—After Verrill. Many sea-worms are highly phosphorescent, the light emit- ted being intensely green. The tracks of worms like the Nereis of to-day occur in the lower Silurian slates; their bristles, however, were spinulose, as in the larval worms. Thus the type, though highly specialized, has, unlike most specialized groups, a high antiquity, the specialized Anmne- ides existing side by side with the generalized Polyzoa and Brachiopoda. At the present time the Annelides are widely distributed in the seas of the globe, the tropical forms being exceedingly abundant among coral stocks and in sponges, while the arctic seas abound with Annelid life. They also sparingly exist at great depths, one species of a worm allied 218 ZOOLOGY. to Clymene, having been dredged by the Challenger Expedi- tion at the enormous depth of over three miles (about 5000 metres). Cuiass [X.—ANNULATA. Body long, bilaterally symmetrical, cylindrical, consisting of numerous segments, either unarmed, or more usually provided with sete alone or with sete and paddlelike appendages (rami). Head simple, with a few simple eyes, or provided with tentacles (antenna) alone, or with tentacles and bran- chie. Aneversible pharynx, armed with teeth, usually present. Alimentary system straight, the tubular stomach sometimes sacculated ; vent always situated in the last segment of the body. Nervous system well developed, consisting of a brain and ventral ganglionated cord. Circulatory system closed, with a dorsal and ventral and lateral vessels connected by anasto- mosing branches in nearly each segment. A system of numerous paired segmental organs. Sexes united or separate. Embryo passing through a cleavage-stage (morula or blastula), gastrula, sometimes a neurula stage, and after hatching, development is either direct. or there is a marked met- amorphosis, the larva passing through a trochosphere and cephalula stage. Order 1. Hirudinea—Body unarmed, finely segmented; with a pos- terior sucker. (Hirudo, Nephelis.) Order 2. Annelides.—Suborder 1. Oligocheta (Lumbricus, Nais), Sub- order 2.—Chetopoda (Arenicola, Syllis, Autolytus, Aphro- dite, Polynoé, Amphitrite, Terebrella, Sabella, Serpula, Spirorbis). TABULAR VIEW OF THE CLASSES OF WoRMS (VERMES). Annulata, Brachiopoda. Einteropneusta. Polyzoa, Gephyrea. at i Rotatoria. | | ; Nemertina. Nematelminthes. Ee EN | VERMES. ANNULATA. 219 Laboratory Work.—Worms should be dissected at once after be- ing killed by ether or in aicohol, before the circulation has ceased ; and transverse sections made to observe the relation of the appendages to the body-walls, and of the different systems within the body-walls. The worms should also be hardened in alcohol, and thin sections stained with carmine be made for histological study. A portion of the worm can be put in paraffine and sliced by hand with the razor or by the microtome, 2D é S Ay LD 2 ae Amphitrite ornata, CHAPTER VI. BRANCH VI.—MOLLUSCA. General Characters of Mollusks.—The characters which separate this branch from the others, especially the Vermes arc much less trenchant than those peculiar to other groups of the same rank, and indeed the author only retains the Mollusks as a special branch in deference to the general usage of zoologisty believing that the Mollusca are probably only a highly specialized group of Vermes, where they were originally placed by Linneus, and bearing much the same relation to the true worms as do the Rotatoria, the Tuni- cata, the Brachiopoda, etc. It will be seen from the fol- lowing account of the mollusks, that they travel along, appar- ently, the same developmental road as the genuine worms, and then suddenly diverge, and the divergence is not an ad- vance in a parallel direction, but if anything the road turns back, or, to change the simile, the branch of the genea- logical tree bends downwards. It is, and always has been, extremely difficult to define the Mollusca, their original bilateral symmetry being partially effaced in most of the Gastropoda and in some Lamellibranchs, ¢. ¢, in those Gastropods with a spirally-twisted shell like the snail, or in fixed bivalve forms like the oyster, etc. The Mollusca are usually defined as animals with laterally symmetrical, un- jointed bodies protected by a shell, with a foot or creeping disk, and usually with lamellate gills, which are folds of the mantle- or body-walls. The special organs characterizing the Mollusks are the foot and, in nearly all except Lamel- libranchs, the odontophore ; but the foot of a snail is simply a modified part of the mantle, and in reality in many forms but a specialized ventral surface, as is that of certain non- segmented worms, like the Planarians and Nemerteans ; while MORPHOLOGY OF MOLLUSKS. | 221 the odontophore or lingual ribbon, often absent, is appar- ently a modification of the pharyngeal teeth of Annelides. . Mollusks in general have a heart consisting of a ventricle and one or two auricles, and in this respect they are more like the Vertebrates than other invertebrated animals; the highly developed eye of the squids and their imperfect car- tilaginous brain-box are also special characters analogous to the eye and brain-box of Vertebrates. Still these features are not homologous with the corresponding parts in the Vertebrates, and we have already seen that the Tunicata. and even the Annelides, are much more closely allied to the Vertebrata than are the Mollusks, which should, perhaps, be interpolated between the Brachiopods and Tunicates. The affinities of the Mollusks are, then, decidedly with the worms, rather than with the Vertebrates. ; That the Mollusca are a highly specialized and comparax tively modern group is shown by,the fact that they began to abound after the Brachiopods had had their day in the Silurian seas, and had begun to decay and die out as.a type; _ the shelled Mollusca supplanted the shelled Vermes or Brachi- opods. For the upper Silurian period, and those later, the Mollusks prove useful as geological time-marks, especially j in the Cainozoic period, and so much so that Lycll based his divisions of Tertiary time mainly on the shells which abound in Tertiary strata. Although morphologically the shell of a Mollusk is not the most important feature of the animal, it is very charac- teristic of them and of great use in distinguishing the species of existing, but more especially of fossil, forms; still it is liable to great variation, and mollusks of quite different families, and even orders, sometimes have shells much alike, so that the characters of shells, like many of those drawn from the peripheral parts of the body, are liable oftentimes to mislead the student. That the Mollusca are a highly specialized group is also seen by the enormous number of existing species, and their wide geographical and bathymet- rical range. There are about 20,000 living and 19,000 fossil species known, and the group ranks next to the winged insects, also a comparatively recent. and highly 22 ZOOLOGY. specialized group, in the number of species and indi- viduals. CLASS I.—Lamernrprancurata (Acephala, Bivalves). General Characters of Lamellibranchs.— This group is represented by the oyster, clam, mussel, quohog, scallop, etc. By a study of the common clam (Mya arenaria Linn.) one can obtain a fair idea of the anatomy of the entire class, as it isa homogeneous and well-circumscribed group. The clam is entirely protected by a pair of solid limestone shells, connected by a hinge, consisting of a large tooth (in most bivalves there are three teeth) and ligament (Fig. 155 C 1). The shells are equivalve, or with both valves alike, but not equilateral, one end (the anterior) being distinguishable from the other or posterior, the clam burrowing into the mud by the anterior end, that containing the mouth of the mollusk. The hinge is situated directly over the heart, and is there- fore dorsal or hemal. On the interior of the shells are the two round muscular :mpressions made by the two adductor muscles and the pallial impressios, parallel to the edge of the shell, made by the thickened edge of the mantle. On carefully opening the shell, by dividing the two adductor muscles, and laying the animal on one side in a dissecting trough filled with watcr, and removing the upper valve, the mantle or body-walls will be disclosed ; the edge is much thickened, while within, the mantle where it covers the el- liptical rounded body is very thin. The so-called black head, or siphon, is divided by a partition into two tubes, the upper, or that on the hinge or dorsal side, being excurrent, the lower and larger being incurrent—a current of sea-water laden with minute forms of life passing into it. Each orifice ig surrounded with a circle of short tentacles. This siphon is a tubular prolongation ofthe mantle-edge, and is very ex- tensible, as seen in Fig. 155, 4; it is extended, when the clam is undisturbed, from near the bottom of its hole to the level of the sea-bottom. In the fresh-water mussel (Unio, Fig. 156) the two siphonal openings are above the level of ANATOMY OF THE CLAM. 223 the sandy bottom of the water, when the mussel is plough- B ing its way through the sand with its tongue- shaped foot, which is a muscular organ attach- ed to the visceral mass, and is a modification of the under lip of the larval mollusk. In the foot is an orifice for the passage in and out of water, but the spurt- ing of water from the clam’s hole, observed in walking over the flats,is the stream eject- ed from the siphon. The inflowing currents of water pass from the inner end of the mus- cular siphon below the lenticular visceral mass to the mouth, which is situated at the anterior end of the shell, oppo- site the siphon. The - opening is simple, un- armed, without lips, and often difficult to detect. On each side of the mouth is a pair of flat, narrow-pointed appendages called pal- pi. The digestive ca- nal passes through a dark rounded mass, mostly consisting of the liver, covered ex- ternally by the ovarian A ' Fig. 155,—A, Mya arenarta with its siphons ex- tended; in its natural position in the mud head- end downwards; 8, transverse section of Unio, showing the position of the spring opening the shell; M, adductor muscle ; the ligament represent- ed by dark mass; C, section of Mya, showing the position of the spring to open the shell; JZ, liga- ment ; D, ideal transverse section of Unio; J, intes- tine; F foot; V, ventricle; A, auricle; G, gills; M. mantle; S, shell.—After Morse. 224 ZOOLOGY. masses. There is no pharynx armed with teeth as in the Cephalophora and Cephalopoda, but the esophagus leads to a tubular stomach and intestine, the latter loosely coiled sev- eral times and then passing straight backwards along the dor- sal side under the hinge and directly through the ventricle of the heart, ending posteriorly opposite the excurrent division Fe re re cre yr of the siphon. Through the visceral mass passes a curious slender cartilaginous rod, whose use is unknown, unless it be to support the voluminous viscera. The gills or branchie are four large, broad, leaf-like folds of the mantle, two on a side, hanging down and covering each side of the visceral mass (Fig. 155, D, a). The heart (Fig. 157) is contained in a deli- / \ cate sac, called the pericardium, and is situ- et +q ated immediately under the hinge ; it consists infty at of a ventricle and two auricles ; the former is i : easily recognized by the passage through it of i i the intestine (Fig. 155, D, v), usually colored Hig. 1si-—Heart dark, and by its pulsations. The two wing- of the clam. V like auricles are broad, somewhat trapezoidal ventricle; A, au- 4 ricles: G, bare’ inform. Just behind the ventricle is the so- Horse. called “‘aortic bulb.” The arterial system is quite complicated, as is the system of venous sinuses, which can be best studied in carefully injected specimens. At the base of the gills, however, is the pair of large collective branchial veins. The kidney, or “organ of Bojanus,” is a large dusky glandular mass (Fig. 158, 4) lying below but next ANATOMY OF THE CLAM. 225 to the heart; one end is secretory, lamellar and glandular, communicating with the pericardial cavity, while the other is excretory and opens into the cavity of the gill, The. neryous system can be, with care and patience, worked out in the clam or fresh-water mussel. In the clam (Mya arena- Fig. 158. Circulatory system of Anodonta, a fresh-water mussel, after Bojanus. 1, ventricle; 2, arterial system; 14 and 15, veius which follow the border of the mantle. The veins lead the blood in part directly towards the organ 4, which is the xidney or “organ of Bojanus,”’ and in part to the venous sinus of the upper surface of this organ; 5, veins which carry back the blood from the gills, the rest going to the sinus, 6, where arise the branchial arteries; 7, 8, the branchial veins, and 9, the gill.—From Gervais et Van Beneden. ‘ ria, Fig. 159) it consists of three pairs of small ganglia, one above (the ‘‘brain”) and one below the cesophagus (the pedal ganglia) connected by a commissure, thus forming an cesophageal ririg; and at the middle of the mantle, near the base of the gills, is a third pair of ganglia (parieto-splanch- nic), from which nerves are sent to the gills and to each division of the siphon. This last pair of ganglia can be usually found with ease, without dissection, especially after the clam has been hardened in alcohol. The ear of the clam is situated in the so-called foot; it bears the name of otocyst (Fig. 160, 7), and is connected with a nerve sent off from the pedal ganglion. It is a little white body found by laying open the fleshy foot through the middle. Microscopic ex- amination shows that it is a sac lined by an epithelium, rest- ing on a thin nervous layer supported by an external coat of connective tissue. From the epithelium spring long hairs; the sac contains fluid and a large otolith. The structure of this octocyst may be considered typical for Invertebrates. 226 ZOOLOGY. The ovaries or testes, as the sex of the clam may be, are bilaterally symmetrical, blended with the wall of the visce- ral or liver-mass, and are yellowish. The genital openings b N, = Fig. 159.—Nervous system of the clam, natural size. a, cesophageal ganglion; 8, commissure anterior to the mouth ; c, pedal commissure ; d, pedal ganglia ; e, parieto- splanchnic commissures ; /, parieto-splanchnic ganglia ; g, branchial nerves; 4, 2, pal- lial nerves ; i, epoeuel nerves ; %, anal nerves ; 7, nerves to the anterior adductor.— Drawn by W. K. Brooks. are paired and lie near the base of the foot. Both eggs and semen arise from the epithelium of the sexual glands. The eggs pass out into the body-cavity, or accumulate between the ANATOMY OF THE CLAM. 227 gills, where the embryos in some species partially develop. Impregnation probably takes place within the branchial Fig. 160.— Pedal ganglia and oto- cysts (ears) of the clam, magnified 10 diameters. d, pedal ganglia; e, pedal commissures; /, line of union of gan- glia; g, nerve from commissure to muscles of foot; 4, auditory nerve ; i, otocyst; 4, nerves from ganglia to the pedal muscles.—Drawn by Ww. Brooks. chamber, the spermatozoa being swept in with the respiratory current, and coming’ in contact with the eggs as they are dis- charged. An excellent general view of the relation of parts to the body-walls and shell may be seen by hardening a clam, or better a fresh-water mussel, Unio (see Fig. 155, D) in alco- hol, and then making trans- verse sections. A section can be floated off in water and ex- amined with a lens. The per- K. fect bilateral symmetry of parts will thus be seen. The above description will answer for the majority of la- Fig. 161.—Zima htans, flying through the water, its long numerous filaments ex- tended.—From Brehm’s *‘ Thierieben.” . mellibranchiate mollusks ; in the oyster (Ostrea) or in Ano- 228 ZOOLOGY. mia the shell is inequilateral, one, usually the lower, being fixed to some object, and the intestine does not pass through the ventricle; in Arca the ventricle is double. In Lucina and Corbis there is but one gill on each side, and in Pecten, Spondylus and Trigonia the gills are reduced to comb-like Fig. 162.—Mytilis edulis, common mussel. @, mantle; 5, foot: c, byssus; d and e, muscles retracting the foot ;_/, mouth ; % palpi; 2, visceral mass + 2, inner gill; j, outer gill.—From Brehm’s ‘ Thierleben.” processes. There are usually no eyes present; in the scallop (Pecten), however, there is-a row of bright shining eyes with tentacles along the edge of the mantle, and contrary to the habits of most bivalves, the scallop can skip over the surface of the water by violently openmg and shutting its shell. 'rigonia is also capable of leaping a short distance ; while Lima (Fig. 161) is an active flyer or leaper. The Ameri- can oyster* is dicecious, while most mollusks are monoscious or hermaphroditic. ‘The foot varies much in form; in the mussel (Mytilus, Figs. 162, 163), Pinna, Cyclocardia (Car- dita) (Fig. 164), and the pearl-oyster it is finger-shaped and * The European oyster is clearly hermaphroditic (Ryder). TYPICAL BIVALVKS. 229 grooved, with a gland for secreting a bundle of threads, the byssus, by means of which it is anchored to the bottom. Fig. 164. Fig. 163.—Mytilus edulis, common mussel, with its fringe expanded, and an- chored by its byssus.—After Morse. Fig. 164.—Cyclocardia novanglie, natural size.—After Morse. The foot in the quohog (Fig. 165 A, Venus mercenaria), Mulinia (166 B) and Clidiophora (Fig. 167) is large, these Fig. 165 4.— Venus mercenaria, quohog, natural size, with the foot and siphons. Fig 166 B.—Mactra (Mulinia) lateralis, natural size.—After Verrill. mollusks being very active in their movements. In Glyei- meris (Fig. 168) the fringe is toothless, much as in the oyster. In Mactra (Fig. 169) the middle tooth is large, the 230 ZOOLOGY. corresponding cavity large and triangular. In Saxicava and Panopea (Fig. 170), the pallial line is represented by a row of dots. In Macoma (Fig. 171) the siphons are very long. Lithodomus, the date shell, one of the mussels, bores into corals, oyster shells, etc. ; the aes common Sazicava excavates ee one Witineeta, nee holes in aud and soft lime- stone, as does Gastrochena, Pholas and Petricola. Many boring Lamellibranchs are said to be luminous. Fig. 168.—G@lycimeris siligua, natural size.—After Morse. A very aberrant form of bivalve mollusk is Clavagella, in which the shell is oblong, with flat valves, the left cemented to the sides of a deep burrow. The tube is cylindrical, fringed above and ending below in a disk, with a minute central fissure, and bordered with branching tubules. In Aspergillum, the watering-pot shell, the small bivalve shell is cemented to the lower end of a long shelly tube, closed below by a perforated disk like the ‘‘rose” of a watering- pot. The most aberrant Lamellibranch is the ship-worm, Teredo navalis Linn. (Fig. 174), This species is now cosmopolitan, and. everywhere. attacks the hulls.of ships. and the piles of wharves. It is one of the most destructive to human inter- ests of all animals. The body is from one to two feet long, slender, fleshy; it lives in a burrow lined with limestone, while the shell itself is globular, and lodged at.the farther FORMATION OF PEARLS. 231 end of the tube or burrow. The mantle lobes of the ani- mal are united, with a minute opening for the foot, which is small, suvker-like. The heart is not pierced by the intes- Fig. 169.—Mactra ovalis, natural size.—After Morse. tine, while the siphons are very long and furnished with two shelly styles. Pearls are sometimes produced in bivalve shells by particles of sand getting in between the mantle and the shell, which Fig. 170.—Panopea arctica, natural size.—After Morse, cause an irritation to the tissues of the:mantle.and the for- mation of a nacreous shelly matter around the nucleus, Excellent pearls are sometimes found in fresh-water mussels, 232 ZOOLOGY. but the purest occur in the pearl oyster, Meleagrina marga- ritifera (Linn.), which occurs at Madagascar, Ceylon, the Persian Gulf, and at Panama. The largest pearl known measures two inches long, four round, and weighs 1800 grains. All bivalves pass through a metamorphosis after birth, The development of the oyster is a type of that of most La- mellibranchs. A single oyster may lay about . 2,000,000 eggs; they are yellow, and after leaving the ovary are dor the nal ea Se Poaeina, maosh ‘part retained among the gills. In America the oyster spawns from June till September ; during their growth the eggs are en- closed in a creamy slime, growing darker as the “spat” or young oyster develops. The course of development is thus: after the segmenta- tion of the yolk (morula stage), the embryo divides into a clear peripheral layer (ectoderm), and- an opaque inner layer containing the yolk and representing the inner germinal layer (endoderm). A few filaments or large cilia arise on what is to form the velum ot the future head. The shell then begins to appear at what is destined to be the posterior end of the germ, and before the digestive cavity arises. The digestive cavity is next formed (gastrula stage), and the anus appears just behind the mouth, the alimentary canal being bent at right angles). Meanwhile the shell has grown enough to cover half the embryo, which is now in the “ Veliger” stage, the ‘‘velum” being composed of two ciliated lobes in front of the mouth-opening, and comparable with that of the gastropod larve. The young oyster, as figured by Salen- sky, is directly comparable with the Veliger of the Cardium (Fig. 172). Soon the shell covers the entire larva, only the ciliated velum projecting out of an anterior end from be- tween the shells. In this stage the larval oyster leaves the mother and swims around in the water. According to Brooks the American vyster becomes a free-swiming larva in six hours after the egg is fertilized. When about .03 mm. in diameter it becomes fixed. ‘The oyster is said to be EMBRYOLOGY OF CARDIUM. 233 three years in attaining its full growth, but is able to propa- gate at the end of the first year. The development of the cockle (Cardiwm pygmeum), is better known. After passing through a morula and gastrula stage, the embryo becomes ciliated on its upper surface and already rotates in the shell. On one side of the oval em- bryo is an opening or fissure, on the edges of which arise two tubercles which eventually become the two “sails” of the velum. The next step is the differentiation of the body into head and hind body, 7.e., an oral (cephalic) and postoral region. Out of the middle of the head grows a single very large cilium, the so-called flagellum (Fig. 172 A, fl; », Fig. 172.—The development of the cockle shell (Cardium), .A, the trochosphere 3; v, ciliated crown ; ji, flagellum. B, Veliger stage, with the shell developing ; 2, velum ; m, mouth ; /i, liver lobes; ¢, stomach Th intestine ; mz, mantle ; 7, foot; mil, muscle ; 7, nervous ganglion.—After Lovén. velum). ‘The shell (B, sh) and mantle (mt; ml, muscle) now begin to form. From the inner yolk-mass are developed the stomach, the two liver lobes (i) on each side of the stomach (¢), and the intestine (7). The mouth (m), which is richly ciliated, lies behind the velum, the alimentary canal is bent nearly at right angles, and the anus opens behind and near the mouth. The velum (Fig. 172 B, v) really consti- tutes the upper lip, while a tongue-like projection (B, f) be- hind the mouth is the under lip, and is destined to form the large unpaired “foot,” so characteristic of the mollusks. The shell arises as a cup-shaped organ in both bivalves and univalves, but the hinge and separate valves are indicated very early in the Lamellibranchs. At the stage represented 234 . ZOOLOGY. by Fig. 172 B, the stomach is divided into an anterior and posterior (pyloric) portion. The liver forms on each side of the stomach an oval fold, and communicates by a large open- ing with its cavity; while the intestine elongates and makes more of a bend. The organ of hearing then arises, and be- hind it the provisional eyes, each appearing as a vesicle with ° dark pigment corpuscles arranged around a refractive body. The nerve-ganglion (z) appears above the stomach. The two ciliated gill-lobes now appear, and the number of lobes increases gradually to three or four. The foot grows larger, and the organ of Bojanus, or kidney, becomes visible. The shell now hardens; the mouth advances, the velum is with- drawn from the under side to the anterior end of the shell. In this condition the Veliger remains for a long time, its long flagellum still attached, and used in swimming even after the foot has become a creeping organ. Latest of all appears the heart, with the blood-vessels. Upon throwing off the Veliger condition, the velum con- tracts, splits up and Lovén thinks it becomes reduced to the two pairs of palpi, which are situated on each side of the mouth of the mature Lamellibranch. The provisional eyes disappear, and the eyes of the adult arise on the edge of the mantle. ; In the fresh-water mussels (Unio) the developmental his- tory is more condensed. ‘The velum of the embryo is want- ing or exists in a very rudimentary state. The mantle and shell are developed very early. The young live within the parent fastened to each other by their byssus. The shell DS) (Fig. 173) differs remarkably from that of iis! the adult, being broader than long, trian- gular, the apex or outer edge of the shell Fig. 173.—Young Unio. Hooked, while from different points within —After Morse. project a few large, long spines. So dif- ferent are these young from the parent that they were sup- posed to be parasites, and were described under the name of Glochidium parasiticum. They are found in the parent mussel during July and August. The ship-worm (Zeredo navalis Linn. Fig. 174) after the ! " \ DEVELOPMENT OF THE SHIP-WORM. 235 segmentation of the yolk (Fig. 175 A) passes through a veliger stage, the shell begins to grow, and when five days Fig. 174.—The Ship-worm. ¢, siphons; 7, pallets; ¢, collar; s, shell ; 7, foot.— After Verrill. : , ts and a half old the germ appears as in Fig. 173, B, the shell almost covering the larva. Soon after this the velum becomes larger, and then decreases, the gills arise, the audi- tory sacs develop, the foot grows, though not reaching to the edge of the shell, and the larva can still swim about free in the water. When of the size of a grain of millet, it becomes spherical, as in Fig. 175, C, brown and opaque. The long and slender foot projects far out of the shell, and the velum assumes the form of a swollen ring on which is a double crown of cilia. The ears and Fig. 175.—Development of the Ship-worm. A, egg, with the yolk once divided; B, the eyes develop more, and qellieer enclosed ig. the bivalve shells; C, ad- the animal alternately ee oe foot (f) and velum swims with its velum, or walks by means of the foot. At this stage Quatre- fages thinks it seeks the piles of wharves and floating wood, into which it bores and completes its metamor- phosis. On the coast of New England the ship-worm lays eggs in May and probably through the summer. 236 ZOOLOGY. Indeed most mollusks spawn in the summer. Species of Kellia, Galeomma, and Montacuta are viviparous. Some bivalves get their growth in asingle year. The fresh- water muscles live from ten to twelve years and perhaps longer ; while Tridacna gigantea probably lives from sixty years to a century. Of about 14,000 known species of Lamellibranchs, from 8000 to 9000 are fossil. , Cuass I.—LAMELLIBRANCHIATA., Bilaterally symmetrical mollusks, with two valves lined by the mantle, con- aected by a dorsal hinge and ligament; no head ; mouth unarmed, with two pairs of labial palpi; intestine coiled in the visceral mass, usually passing through the ventricle, and always ending at the posterior, usually siphon-bearing, end of the body. Foot small, sometimes nearly wanting, never used asacreeping disk. Usually two pairs of large leaf-like gills on each side of the visceral mass. Sexes usually in separate individuals. Fimbryo passing through a so-called morula, gastrula, and free-swimming veliger condition. Order 1. Asiphonia.—Body-wall or mantle without siphons. Shell sometimes inequivalve. (Ostrea, Anomia, Pecten, Melea- grina, Mytilus, Arca, Trigonia, Unio, and Anodonta.) Order 2. Siphoniata.—Siphons present. Shell equivaive. (Chama _ Tridacna, Cardium, Venus, Mactra, Tellina, Solen, Clava- gella, Aspergillum.) Laboratory Work.—In dissecting the clam, etc., the work should be performed under water, in a dissecting trough. One shell should be removed by cutting the adductor by a pointed scalpel, the mantle dis- sected off and thrown aside, so as to expose the gills, heart, and kid- neys. In dissecting the nervous system it is well to introduce a probe into the mouth, and then cut down towards it from above, when the white supracesophageal ganglia or ‘‘ brain” will be found, and the other ganglia can thence be traced by the commissures leading from the “brain.” To find the pedal ganglia and otocyst, cut the foot vertically intwo. The heart can be readily found, and the large vein at the base of the gills, but the arterial and venous systems can only well be studied after making careful injections, For ordinary or even quite fine injections, Sabatier used a mixture of lard and turpentine, some- times adding a little suet or wax to thicken the paste, which was colored chrome yellow, vermilion, or blue. For histological exami- nation he used essence of turpentine, colored as before, or gelatine SCAPHOPODA. 237 colored by carminate or ammonia, or Prussian blue dissolved in oxalic acid, or the precipitate of chromate of lead, or he even injected air into the vascular cavities. The mollusk should, before injection, be allowed to slowly die for several days, and the,fluids to leave the body. The injection should be made before decomposition has set in, otherwise the vessels will burst. Some anatomists plunge mollusks into water to which.has been added alcohol and chlorhydricacid. After remaining in this fluid fora day or two they can be injected. The arterial system can best be injected by the aortic bulb, or aorta; the venous system may be filled from the foot through the aquiferous orifice, by the adductor muscle, or by any of the large veins.‘ After injection the animal should be plunged into cold water to hasten solidification and then placed permanently in alcohol. Crass II:—CrpHatopHora (Whelks, Snaits, ete.). General Characters of Cephalophores.—We now come to Mollusca with a head, distinguishable from the rest of the body, bearing eyes and tentacles ; but the bilateral symmetry of the body, so well marked in the Acephala, etc., is now in part lost, the animal living in a spiral shell ; still the foot and head are alike on both sides of the. body; while the foot forms a large creeping flat disk by which the snail glides over the surface. Moreover, these mollusks have, besides two pharyngeal teeth, a lingual ribbon or odontophore. In a shelless land-snail (Onchidiwm) Semper has discovered the existence of dorsal eyes, constructed, as he claims, on; the Vertebrate type. They are in the form of little black dots scattered over the back of the creature, and their nerves arise from the visceral ganglion. Familiar examples of the _Cephalophora are the sea-snails, the sea-slugs, and the genuine air-breathing snails and slugs. Order 1. Scaphopoda.—A very aberrant type of the class is Dentalium, the tooth snail, common in the ocean from ten to forty fathoms deep, on our coast. It lives in a long slender tooth-like shell, open at both ends, while the animal has no head, eyes, or heart, and the foot is trilobed.. Owing to the presence of a lingual ribbon, we would retain it in the present class, though it is a connecting link between this and 238 ZOOLOGY. the preceding class, and is, by some authors, regarded as the type of a separate class (Scaphopoda). The sexes of Fig. 176.—Development of Dentalium. A, morula; B, trochosphere; C, annu- lated larva; D, larva with its rudimentary shell; z, velum ; a, shell; #, young much farther advanced, the shell or body segmented ; d, rudimentary tentacles ; j, sub- ene atid” Aneaeepeiaa. oe eee Denialium are distinct. The young isa trochosphere and =: afterwards becomes segmented, and the univalve shell then appears. (Fig. 176.) Order 2. Pteropoda.—In these winged-snails the head is slightly indicated and the eyes are rudimentary ; while they are easily recognized by the large wing-like appendages (epipodium), ne on each side of the head. The shell is conical or helix-like. The species are hermaphroditic. Cavolina tridentata Lamarck and Styliola vitrea Verrill (Fig. 178) are pelagic forms, occurring on Fig. 177.Den- the high seas, and are occasionally taken with the tatium Indiano- rum.’ Used a8 tow-net off the southern coast of New England. shell money. — : * i : : After Stearns. Limacina arctica Fabr. is of the size of, and looks like, a sweet pea, moving up and down in the water. It is common from Labrador to the polar regions. PTEROPODA. 239 A common form, occurring at the surface in harbors north of Cape Cod, as well as many miles off shore, is Spiri- alis Gouldii Stimpson, the shell of which resembles a conical Helix. The largest form on the eastern coast of North America, extending from New York to the polar seas, is the beautiful Clione papillon- acea of Pallas, which has a head and lin- gual ribbon. It is rare on the coast of New England, but abundant from Labra- dor northward. We have observed it rising and falling in the water between the floe-ice on the coast of Labrador. It is an inch long, the body fleshy, with no shell, the wings being rather small. The larve of the Pteropods pass through a trochosphere stage, being, as in Cavolina, ee spherical, with a ciliated crown. It after- wards assumes a veliger form. Fig. 179 represents a worm- like, segmented, Pteropod larva, the adult of which is unknown. In other genera the larve are annulated, resem- bling the larve of Annelides. The Pteropods are, in some degree, a generalized type. They have a wide geographical distribution and a high antiquity; forms like Cavolina, viz.: Theca, Conularia, Tentaculites, Cornulites, etc., dating back to the paleozoic formation ; Theca-like forms (Pugiunculus and Hyolithes) occurring in the primordial rocks. Order 3. Gastropoda.—This great assemblage of mollusks is represented by the sea-slugs. i, limpets, whelks (Figs. 180-183), snails, and .Ptero- slugs. The head is quite distinct, bearing one, and sometimes, as in the land-snails, two pairs of tentacles, with eyes either at the bases, or at the ends of the tentacles, or, as in Trivia californica (Fig. 184), they are situated on projections near the base of the tentacles. All the Gastropods move or glide over the surface by the broad creeping-disk, a modification of the foot of the clam, 17 pod ere ie. 240 ZOOLOGY. etc. The head is alike on each side, but posteriorly the body Fie. 180. Fie 181. Fia. 182, Fic, 183, Fig. 180.—A Whelk. Buccinum cretaceum. Labrador. Fig. 181.—A Whelk. Buccinum ciliatum.—After Morse. Fig. 182.—Strombus pugilis. West Indies.—From Tenney’s Zoolo; Fig. 183.—Pelican's Foot, Aporrhais occidentalis. sy. Northern New England.— After Morse. ANATOMY OF THE SNAIL. 241 1s, in those species inhabiting a spiral shell, asymmetrical and wound in a spiral, the visceral mass extending into the apex of the shell. In the Nudibranchs (Figs. 190, 192), and the slug, the body being naked is symmetrical on each side. The digestive tract is doubled on itself, the vent ending on one side of the mouth. In some Nudibranchs the intestine has numerous lateral offshoots, or gastro-hepatic branches, which resemble similar structures in the Plana- rian and Trematode worms. A heart is always present, except in the parasitic Hntoconchap and sometimes, as in Chiton, Neritina, and Haliotis, it is perforated by the intestine. In some genera there are two auricles to the heart, but as a rule but one is present. The Gastro- yf Jiiimgnn pods breathe by gills either free, or contained gnlarged twice — in a cavity in the mantle, while in the land- snails (Pulmonata) the air is breathed directly by a lung-like gill in a mantle-cavity. The kidney is single. The sexes are either distinct or united in the same individual. An excellent idca of the structure of a typical Gastropod may be obtained by a dissection of Natica (Lunatia) heros. -This is a large mollusk, common between tide-marks from Labrador to Georgia. On taking it up the student will notice the large, round, swollen, porous foot, from which the water pours as if from the ‘‘rose” of a watering-pot. The shell is large, composed of several whorls, with a small flattened spire or apex. ‘The aperture is large, lunate in shape, and can be closed by a large horny door or oper- culum. (In some mollusks, Natica, Turbo, etc., the oper- culum is of solid limestone, and small ones are used as ‘‘ eye- stones,” being inserted in the eye and moved about by the action of the lids, thus cleansing the eye of irritant particles of dust, etc.) The animal should then be placed in a dish of salt water, and its movements observed. There are but two short, broad, flattened tentacles, situated on a flap or head-lobe (prosoma) of the mantle or body-walls. No eyes are present 242 ZOOLOGY. in this species. The mouth is situated in front of the foot and at the base of the head-lobe, and is bounded by large puck- ered swollen lips. Cutting down from between the tentacles, a large buccal mass, the pharynx, is exposed. The mouth- cavity is roofed with two broad quadrant-shaped, flat thin teeth, with the free-edge serrated. On the floor of the mouth lies the ‘‘ tongue,” or lingual ribbon (Odontophore),. which is folded once on itself, and is a thin band composed. of seven rows of teeth, those forming the two outer rows long and much curved, those of the central row being stout and three-toothed. The long slender csophagus is tied down, near its middle, by the brain (supracwesophageal gan-: glion); just behind and beneath which are the two large: salivary glands. The csophagus suddenly dilates into a. large stomach-like pouch, which is much larger in this: species than in other forms allied to it. It is a sort of crop or proventriculus (the organ of Delle Chiaje), and rarely oc- curs in the Gastropods. On laying it open, it may be seen to be spongy at its anterior end, and posteriorly divided by numerous transverse partitions into small cavities. The cesophagus beyond it is again slender, and leads to the stomach situated in the apex of the shell, partly embedded. in the liver-mass which lies mainly beyond it. From the stomach the intestine returns to the head, widely dilat- ing into a large sacculated cloaca, before the free up- turned vent, which is situated on the right side behind and. to the right of the right tentacle. The nervous system is. represented by a pair of large ganglia, forming the brain (supracesophageal ganglia) situated just below and behind. the pharynx. The two other ganglia were not traced, but as. arule in all Cephalophora there are three pairs of ganglia, t.é., the brain (supracesophageal ganglia) with commissures passing around the gullet to the pedal or infraesophageal ganglia, thus forming the esophageal nervous ring, while the visceral or parieto-splanchnic ganglia are placed at a varying distance behind the head. The heart, contained in its pericardial sac, and consisting of a ventricle and auricle, is situated near the posterior end of the gills. The latter are disclosed by laying aside the man- DEVELOPMENT OF GASTROPODS. 243 tle on the left side of the body behind the head. In a !arge Lunatia it isan inch long, with a vein at the base, the gill- lobes arranged like the teeth in a comb. A smaller, much narrower gill lies within and parallel to it. The ovary is situated near the stomach, the ovi- duct ending near the vent. The eggs are laid in capsules (Fig. 185, Purpura lapillus and two egg- capsules) of varied form attached to rocks or, as in Trochus and the Nudibranchs, in masses of jelly at- Nd tached to sea-weeds or stones. Gioibies ibe ites colanea Asa type of the mode of devel- After Morse. opment of Gastropods may be cited that of Calyptrea si- nensis, represented in our waters by Calyptrea striata Say (Fig. 186). Fie, 188, Fig. 186.—Calyptrea striata, natural size.—After Moree, f Fig. 187.—Veliger of Calyptrewa. jf, foot; v, velum ; m, mouth; ce, ectoderm ; ‘ve, tmesoderm.-—After Salensky. Fig. 188.—Veliger of Cutyptrea farther advanced. m, mantle; v, velum ;/, foot; /, larval heart ; 7, permanent ; x, primitive kidney ; s, crosses the shell and rests on the yolk.—After Salensky. According to Salensky, after segmentation of the yolk into eight cells the first four cells or ‘‘spheres of segmenta- tion” subdivide, enclosing the yolk-mass, and constituting the ectoderm or outer germ-layer, the yolk-mass forming the endoderm. The cells of the outer germ-layer multiply and form the blastoderm, from which the skin, mantle, and ex- ternal organs, as well as the walls of the mouth, arise. The *€ primitive” mouth of the gastrula is formed by the invagi- 244 ZOOLOGY. nation of the outer germ-layer ; the sides of the primitive mouth form the two sails of the velum or swimming organ, and the embryo now assumes the veliger stage (Fig. 187). Soon the middle germ-layer (mesoderm) arises, and from the cells composing it are developed the muscles of the foot and head, as well as the heart itself. The mantle or body- wall next develops, and from it the shell, which originates in a cup-like cavity which is connected only around the edge with the mantle, being free in the centre. The eyes and ears, or otocysts, next appear, both organs arising as an infolding of the outer germ-layer. Hitherto symmetrical, the alimen- tary canal now begins to curve to the left, and the visceral sac, or posterior part of the embryo hangs over on one side. The nervous system is the last to be developed. Fig. 188 represents the asymmetrical larva with the shell enveloping a large part of the body, and the ciliated velum (v) and foot (f) well developed. A temporary larval heart (4) assumes quite a different position from the heart of the adult, and the primitive, deciduous kidney () is situated in quite a different place from the permanent kidney. The further changes consist in a gradual development of the hel- met-like shell, the disappearance of the temporary larval structures, and the perfection of the organs of adult life, the gills appearing quite late. The development of Trochws, the top-shell, exhibits more strikingly the trochosphere and veliger stages of molluscan life, and most Gastropods develop like this form. The velum at first forms a ciliated ring (Fig. 189, A, v) on the front end of the trochosphere. Fig. 189, B, represents the veliger state. It thus appears that the tem- Fig. 189.—Larval Trochus. A, tro- : chosphere ; , velum ; B, veligerstate; porary larval or veliger form of Shiencey. Fr foot 8, shell—Aftet the Gastropods are of vermian origin, the organs last to be de- veloped, 7. ¢., the foot, shell and lingual ribbon, which are the distinctively molluscan characters, being the last to appear. NUDIBRANCH MOLLUSKS. 245 The Nudibranch mollusks, such as the Holis and Doris and allied forms, breathe by external gills, arranged in bunches on the back, as seen in Fig. 190, dolis (Mon- tagua) pilata (Gould), a common species on the coast of New England. In Doris (Fig. 192), they are confined to a circle of pinnate zills on the hinder part of the back. They are Fie 190. Fie. 191. Fie. 192, Fig. 190,—olis,a Nudibranch. soak ji —Vellget of Tergipes, v, velum; s, shell; d, foot; b, otocysts.—After Fig. 192,—Doris bilamellata. New England coast. shelless, and not uncommon just below low-water mark, laying their eggs in jelly-like masses coiled up on stones and the surface of sea-weeds. Though the adults are shelless, the embryos at first have'a shell (Fig. 191, s), indicating that the Nudibranchs have descend- ed from shelled Gastropods. Fig. 191 rep resents the veli- Trig. 193.—Physa heterostropha. Com- ger of Tergipes lacinulatqa mon pond-enail.—After Morse. Schultze, allied to Doris, with its large ciliated velum, and protected by a deciduous shell, which finally disappears with the velum. The air-breathing mollusks, Pulmonata, are represented by the pond-snails, Physa (Fig. 193) and Limneus (Figs. 194, 195), and the land-snails and slugs. Fig. 200 represents a slug suspended by a mucous thread from a twig. The common snail, Helix albolabris Say, is a type of the air-breathing mollusks. Fig. 196 represents this snail of natural size, in its shell. The opening to the lung is seen at a, and at B are represented the heart and lung of the gar- den slug (Limax flavus). Fig. 197 represents Helix albo- labris with the shell removed, and the mantle thrown back, 246 ZOOLOGY. showing the lung and heart (/) and the mouth (m) as well as the four tentacles, with an eye at the end of the two upper tentacles. Fig. 198 shows the brain and pedal ganglia of Helix albola- bris. The tentacles when carefully exam- ined may be found to contain both the eyes (¢) with the optic nerve (op) and the olfactory nerve (Fig. 201, 0). Fig. 199 represents the jaw and lingual ribbon of Helix. The eggs of the pond- -snails are laid in transparent capsules attached to sub- merged leaves, etc. Those of Physa heterostropha are laid in the early spring, and three or four weeks later from fifty to sixty embryos with well-formed shells may Fig 194.—Limnensap- be found in the capsule. bressus— After Morse. he egos of Limneus are laid late in the spring in capsules containing one or two eggs, and sur- rounded by a mass of jelly. After passing through the mo- Fig. 195.—Zimneus elodes, a common pond-snail, showing its variations.— After Morse. rula, gastrula, and trochosphere stages a definite veliges stage is finally attained. The foot is large and bilobed, the mantle and shell then arise, and the definite molluscan char. acters are assumed, the shell, creeping foot, mantle-flap, eyes, and tentacles appearing, and the snail hatching in about twenty days after development begins. Land-snails and slugs lay their eggs loose under damp’ leaves and stones, and development is direct, the young snail hatching in the form of the adult. HELIX ALBOLABRIS. 247 Fie. 198. Fig. 199. . Fig. 196.—Helia albolabris, natural size. a, orifice of lung. Also the heart and ‘ung of Liman flavus, magnified. Fig. 197.—Helix albolabris, with the shell removed to show the heart (/) and the tng ; m, mouth.—This and Figs. 201-204 after Leidy. Fig. 198.—Nerve-centres of Helix albolabris. Fiy. 199.—Jaw (lower figure) aud side and top view of teeth of lingual ribbon of Helix albolabris. 248 ZOOLOGY The group of mollusks represented by Chiton (Fig. 202, Chiton ruber) have been referred to the worms by Jhering, on account of the segmented appearance of the plated shell, and the nervous sys- tem, which consists of two parallel cords, connected by several commis- 1 sures ;* as well as from the fact that the intestine ends at the hinder end of the body. The young is oval when hatch- ed, ard is a trocho- sphere, having a ciliated ring in the Fig. 200.-Slug. Nat- middle of the body esi with a long tuft of large cilia on the head. Afterwards it becomes segmented, as in Fig. 203, and is remarkably worm-like, the limestone plates of the adult corre- sponding to the primitive larval rings. Certain Gastropods are useful either as food or in the arts. In Europ == Littorina littorea, the limpet (Patella eee eee vulgata), the whelk (Buccinum un- Dts % olfactory nerves. datum), and the Roman suail (Helix pomatia) are eaten, The sea-ear ‘ (Haliotis) is roasted in the shell. L cena) The animal of Cymba, Strombus gi- gas, Turbo, Trochus, and Conus are eaten in the tropics, while many of the larger forms are used for fish- bait. Pearls are sometimes found in frit Fra. 203. the species of Haliotis and Turbo. Fig. 202.-Chiton ruber. j rej Fig, 208, —segmented larva Ihe beautiful shell of Cassis is made of Chiton. into cameo pins, and the shell of Strombus gigas is in the West Indies made into ornaments. *In Fissurella and Haliotis the two nerve-cords from the pedal gan- glia are also united by nine transverse commissures, so that here also we have an approach to the double ganglionated cord of worms. FOSSIL GASTROPODS. 249 Various shells, such as Marginella, Turbinella, etc., are strung in bracelets and armlets by savages. Cypr@a moneta, the cowry (Fig. 204), is used for money, and other shells are worked into various shapes for wampum or aboriginal money. Fig. 205 represents an Olivella, used by the Cal- ifornian Indians as money. Murex and Purpura afford the Tyrian dye. While a few Gastropods are pelagic, living upon the high seas, such as Janthina and the Nudibranch Glaucus, most of the species are submarine and live in all seas ; the hardier, most widely diffused species living between tide-marks, the more delicate forms in deep water, ranging from low-water Fie. 204, . Fig. 205. Fia. 204.—Cyprea moneta.—After Stearns Fria. 205.— Olivella biplicata.—After Stearns. mark to fifty or one hundred fathoms. ‘The abyssal fauna at the depth of from 500 to about 2000 fathoms has a few char- acteristic mollusks. Many live on land and in fresh water. The largest, most highly colored shells live in the tropics, while those found in the temperate zones are less beautiful, and the arctic species are the smallest and dullest in color. The shells of the eastern coast of North America are divided into several assemblages, or faune, the West Indian or tropical shells, in some cases, reaching as far north as ’ Cape Hatteras ; between this point and Cape Cod a north temperate assemblage occurs, and north of Cape Cod the molluscan fauna is essentially Arctic; many species being common to the arctic and subarctic seas of the circumpolar regions. 250 ZOOLOGY. Marine shells in time date back to the lowest Silurian period ; such are Maclurea, Holopea, Murchisonia, Pleuro- tomaria, etc., which occur fossil in rocks of the Potsdam period. The Paleozoic Gastropods are few in number com- pared with those occurring in Cretaceous and especially Ter- tiary formations. The earliest land-snails occurred in the Coal Period s the living species are exceedingly numerous, and often much re- stricted in range, especially in the tropics; the arctic forms are very scarce, but four or five species occurring in Green- land, There are over 22,000 species of Cephalophora known, of which 7000 are fossil. There are 6500 species of Pulmo- nata. Subclass 4. Heteropoda.—The Heteropods form a distinct subclass, the systematic position of which was for a long time unsettled ; but they are now classed among the Gas- tropods, being in fact related to the Opisthobranchiata. Their most striking peculiarity is the form of their foot, the anterior and middle portions of which are expanded to ‘form a leaf-like fin, which often bears a sucker ; the pos- terior part of the foot is much elongated, and, reaching far backwards, appears to form a tail-like continuation of the body. The Heteropods are more or less transparent, and are found swimming upon the surface of the ocean, upon their backs with their foot upwards. The shell may or may not be developed ; when present it may be either simple or coiled. The nervous system resembles closely that of the true Gastropods, but is more highly developed; the brain consists of several supracesophageal ganglia forming part of an cesophageal ring. From the brain arise the optic and auditory nerves. The two large eyes lie in special capsules near the feelers, and are movable by several muscles. The otocysts are also large, and contain a large spherical otolith. The otocysts are lined by an epithelium with bundles of long vibratile hairs, and with a cluster of sensorv cells, form- ing a macula acustica. Organs of touch have also been described. The sensory apparatus of the Heteropods are highly: specialized, and have been studied bv Claus, Boll, Flemming, and others. The odontophore 1s well developed ; THR TETEROPOD MOLLUSKS. 251 the tongue or radwula has highly characteristic teeth, which serve these rapacious animals to seize their prey. The in- testine runs straight back from the mouth, and after mak- ing one or two coils ends in the, yent. The excretory organs open near the anus; the contractile tube opens internally into the pericardial cavity, and resembles in form and posi- tion the excretory organ of the Pteropoda. The circula- tion is imperfect, the blood passing from the wide sinuses of the body to the ventricle of the heart. From the auricle springs the aorta, which subdivides into several branches that open freely into the body-cavity. The circulation can be easily watched, owing to the transparency of the body. The aération of the blood is effected partly through the skin, partly through gills, except in a few species. The branchize are either thread- or leaf-like ciliated appendages, which may either be free or enclosed in the mantle-cavity. The sexes are distinct. The males can be readily recognized by the large copulatory organ, which hangs free on the right side of the body. The sexual glands fill the posterior por- tion of the visceral cavity, and are partly imbedded in the liver. The oviduct is complicated by the presence of an albumen gland and a receptaculum seminis. It opens on the right side of the body. The Heteropods are exclusively marine, but are found in all quarters of the world. The number of species is small, and there are two orders only—the Pterotracheide with a small or no shell and free gills, and the _ the yolk-sac, its epithelium first : appearing in the liver-sac. The Zz heart is the last to be formed. Ex- ternally the antenne in Oniscus Fie. 253, andalso Asellus are the first to bud Mouth-parts ‘of ont; the remaining appendages of Serolis. m, man- dible; ma’, first the head and thorax arise contem- © maxilla ; ma", Fr 254. —A second t ete poraneously, and subsequently the i ot servile. — bras oe abdominal feet. The abdomen in gingtey” 7 * the Isopods is curved upwards and ieee while in the embryo Amphipods it is bent be- neath the body. The development of the Amphipods or beach-fleas is nearly identical with that of the Isopods. The eggs of cer- tain species undergo total segmentation, while those of other species of the same genus (Gammarus) partially segment, as in the spiders, and in a less degree the insects. Standing next below Cymothoa, which is of the general Isopod shape, but which lives parasitically on the tongue and other parts of fishes, but which from their purasitic habits become slightly changed in form, the females espe- cially, sometimes becoming blind, is the family of which Bopyrus is arepresentative. The females (Fig. 257) are par- asitic under the carapace of various shrimps. In B. palemon- eticola Packard, the females are many times larger than the males ; the ventral side of the body is partly aborted, having been absorbed by its pressure against the carapace of its host, which is swollen over it ; it retains its position by ISOPODA, 289 Fie, 256, Fia. 257. Fig. 255.—Section of the embryo pill-bug. 4, intestine; 2, epithelium form- ing the walls of the two lobes of the liver ; g, transverse section of the nervous cord . h, walls of the body.—After Bobretzky. Fig, 256.—Section of more advanced embryo pill-bug. A, heart; hp, hypoder- mal layer or body-walls ; m, muscular wall of the intestine; ¢, epithelial lining of the intestine ; p, dividing cell-wall between the heart and intestine; 7, two lobes of the liver ; g, ganglion. the clear space being filled with the fine granular substance of the ganglion.—After Bobretzky. Fig. 257.—Bopyrus. A, ventral, B, dorsal side of the female; C, lateral and D, dorsal view ot the male ; c!, head and first thoracic segment ; ¢?, antenne—all en- larged.—Packard, del. 290 ZOOLOGY. the sharp hook-like legs around the margin of the body. The head has no eyes nor appendages. The male (Fig. 257, C, D) is but shghtly modified, is very minute, and is lodged partly out of sight under the ventral plates of the female, whose body is about five millimetres (a fifth of an inch) in length. Fig. 258.—Arcturus Bafini, with its young clinging to its antenne.—After Wyville- Thompson. Various species of Porcellio (sow-bugs) live under stones on land; and allied to Asellus, the water sow-bug, is the marine Limnoria lignorum White, which is very injurious to the piles of bridges, wharves, and any submerged wood. The highest Isopods are Jdotewa, of which I. irroratus Say (Fig. 250) is our most abundant species, being common in eel-grass, etc.. between and just below tide-marks ; and Arc- turus (Fig. 258, A. Baffint Sabine), from the Arctic seas. PHYLLOCARIDA. 291 The series of Amphipods begins with Cyamus ceti (Linn.), the whale-louse, passes into Caprella, with its linear body and spider-like legs, to Hyperia, which lives as a mess-mate of the jelly-fish, Cyanea, and culminates in the water-flea (Gammarus ornatus Edwards) and sand-flea (Orchestia agilis Smith), abundant and leaping in all directions from under dried sea-weed at high-water mark. Fig. 259 represents Gammarus robustus Smith, a fresh- water form common in the western territories. Fig. 259.—Gammarus robustus Smith. Utah. Enlarged.—After Smith. Order 5. Phyllocarida.—This name is proposed for a group of Crustacea, the forerunner of the Decapoda and hitherto regarded as simply a family (Nedaliade), in which there is an interesting combination of Copepod, Phyllopod, and Decapod characters, with others quite peculiar to them- selves. The type is an instance of a generalized one, and is very ancient, having been ushered in during the earliest Si- lurian period, when there were (for Crustacea) gigantic forms (Dithyrocaris was over one foot in length) compared with those living at the present day. The order connects the Decapods with the Phyllopods and lower orders. The mod- ern Nebalia is small, about a centimetre (.40-.50 inch) in length, with the body compressed, four of the abdominal segments projecting beyond the carapace, the last abdominal segment bearing two large spines. There is a large rostrum overhanging the head ; stalked eyes, and two pairs of anten- ne, the second pair nearly as long as the body and many- jointed. The mandibles are succeeded by two pairs of max- 292 ZOOLOGY. ile. Behind these mouth-parts are eight pairs of short, leaf- like respiratory feet, which do not project beyond the edge of the carapace. These are succeeded by four pairs of large, long swimming feet, and there are two additional pairs of small abdominal feet. ‘There is no metamorphosis, develop- ment being direct, the young hatching in the form of the adult. Of the fossil forms, Hymenocaris was regarded by Salter as the more generalized type. The genera Peltocaris and Discinocaris characterize the Lower Silurian period ; Ceratiocaris the upper ; Dictyocaris the Upper Silurian and Lowest Devonian strata ; Dithyrocaris and Argus the Car- boniferous period. Our northeastern and arctic species is Nebalia bipes (Fabricius), which occurs from Maine to Green- land. Order 6. Thoracostraca.—In the Stomapods, represented by Squilla, the gills are attached to the base of the hinder ab- dominal feet. Sgwilla lives in holes below low-water mark. The suborder Decapoda (Shrimps, Lobster).— A general knowledge of the Crustacea representing this, the high- est group of the class, may be obtained by a study of the craw-fish and lobster. All Decapods have twenty seg- ments in the body, a carapace covering the thorax and con- cealing the gills, which are highly specialized and attached to the maxillipedes and to the legs; usually a pair of stalked eyes, two unequal pairs of antenns, the hinder pair the larger and longer ; a pair of mandibles, often provided with a palpus, two pairs of lobed maxillw, three pairs of maxilli- pedes, while the name of the order is derived from the fact that there are five pairs of well-marked legs, or ten in all. To the abdomen are appended six pairs of swimming feet. called ‘“‘swimmerets.” Another distinctive characteristic of most, in fact all the higher Decapods, is the short, or five or six-sided heart. The early phases of embryological development in the De- capods are much asin the Edriophthalma. Most Decapods leave the egg in a larval state called the Zoéa. In the shrimps, Lucifer and Peneus, the young is a Nauplius, like a young Entomostracan, having but three pairs of feet, and asingle eye. The Zoéa has no thoracic feet, and usually at first DECAPODA. 293 no abdominal feet ; the compound eyes are large and usually sessile, and the carapace is often armed with a long dorsal and frontal spine. Fig. 260 represents the Zoéa, or larva of the common shore crab (Cancer irroratus Say). After sev- Fig. 260.—Zoéa of the common Crab. Cancer. Much enlarged.—After Smith. eral moults, the thoracic legs appear, the mouth - parts change from swimming -legs to appendages fitted for pre- paring the food to be swallowed and digested. This stage in the short-tailed Decapods or crabs, is called the Mega- lops stage (Fig. 261); certain immature crabs having been mistaken for and described as mature Crustacea, under the name Megalops. After swimming about the surface in the Zoéa and Megalops conditions, the body becomes more bulky, more concentrated headwards, and the crab descends to the bottom and hides under stones, etc. The development of the individual crab is, in a general sense, an epitome of the development of the order. In the lowest genera, as in Cuma and Mysis, the form is some- what like an advanced Zoéa, while the remarkable concentra- tion of the parts headwards, seen in the crabs, is a great 294 ZOOLOGY. step upwards. Dana’s law of cephalization, or transfer of parts headwards, is more strikingly manifested in the Crus- tacea than in any other animals. Nearly all Decapods undergo this decided metamorphosis ; in only a few forms, such as the craw-fish, lobster, and a few shrimps and crabs, do the young leave the egg in the general form of the adult, the Zoéa stage being rap- idly assumed and dis- carded during em- bryonic life. Most Crustacea bear their eggs about with them ; in only a few cases, as the Squilla and the land-crab of the West Indies, are the eggs left by the parent in holes or on the sea-shore. Thoracostraca in- clude Stomapods, the Schizopoda, rep- resented by Mysis ; the Cumacea, repre- sented by Cuma ; the long-tailed Decapods, Fig. 261.—Megalops of the Crab.—After Smith, SUch as the shrimps and lobster, called Macrura, and the genuine short-tailed Decapoda, or Bra- chyura. Most of the species of the crabs are confined to tropical seas and live in shallow water. The Decapods appeared in the Coal Period, and were rep- resented by somewhat generalized forms, such‘as Anthra- palemon (Fig. 262) from the coal measures of Illinois. Recently a genuine shrimp (Paleopalemon) has been de- scribed by Whitfield from the Upper Devonian formation of Ohio. Crustacea, especially shrimps and crabs, are sensitive to FOSSIL CRABS, 295 snocks and sounds. When alarmed, lobsters are said to cast off their large claws, but the latter are again re- newed. It is more probable, however, that the claws are torn off during their contests with each puner Hensen found that crabs and shrimps liv- ing in water do not notice sounds made in the air. The hairs about the mouth are the organs of tac- - tile sense, and have been made by Hensen to vibrate to certain sounds. The eyes may be greatly devel- oped in shrimps living at great depths ; thus Thalascaris, a shrimp living near the bottom of the At- lantic Ocean, is remarkable for the v large size of its eyes. In the spe- cies of Alpheus, which live in holes in sponges, etc., the eyes are small. qe of the blind Willemesia, cits hs Antirapalann eek and Worthen. dredged at great depths by the “Challenger” Expedition, are rudimentary, though in the young the eyes are better developed. This is the case with the young of the blind craw-fish Cambarus pellucidus (Tell- kampf, Fig, 263) of Mammoth and other caves. The fact that the eyes in the young are larger than in the adult indi- cates that this species has descended from other forms living in neighboring streams, and well endowed with the sense of sight. The eye (Fig. 264) of the blind craw-fish differs from that of the normal species in its smaller size, conical form, the absence of a cornea (indicated by the dotted lines in A), the pigment cells being white instead of black, and by differences in the form of the brain, that of the blind species being fuller on the sides. Crabs breathe by gills, but the palm crab breathes by lungs. Crass II.—PopostTomMaTa. Podostomata.—This class is proposed for the king- crab (Limulus), the only survivor of a large number of fossil Merostomata, which dominated the Silurian seas. 296 ZOOLOGY. It comprises the order of Merostomata represented at the present day by the king-crab, and the order Trilodita, which is wholly extinct. The organization of the king-crab is so Fig. 263.—Cambarus pellucidus, the blind craw-fish of Mammoth Cave. Natural size. wholly unlike that of the Crustacea, when we consider the want of antennsx, the fact that the nervous system is PODOSTOMATA., 297 peculiar in form and also ensheathed by arteries, and the peculiar nature of the gills of the abdominal feet, as well as the highly developed system of blood-vessels; that we are obliged to place it with the Trilobites in a division by itself. Fig. 264. =Zh Brain and eye of a normal Cambarus from Iowa. B, The same of the blind craw-fish from Mammoth Cave. Cc Cornea.—Packard, del. Recent researches also on its development prove that the Podostomata should form a distinct class of Arthropods, equivalent on the one hand to the Crustacea and on the other to the Arachnida, but from the fact that they breathe like most Crustacea by external gills, we prefer to retain them in a position between the Crustacea and Arachnida. Order 1. Merostomata.—The only living representative of this order is the king-crab, belonging to the genus Limulus, represented in American waters by Limulus Polyphemus Linn., which ranges from eee Bay, Maine, to Florida and the West Indies. The body of the king-crab is very large, sometimes nearly two feet in length ; it consists of a cephalo-thorax composed of six segments and an abdomen with nine segments, the ninth (telson) forming a long spine. The cephalo-thorax is broader than long, in shape somewhat like that of Apus, with a broad flat triangular fold on the under-side. Above are two large lunate compound eyes, near the middle of the head, but quite remote from each other, and two small sim- ple eyes situated close together near the front edge of the, head. There are no antenne, and the six pairs of append- 298 ZOOLOGY. ages are of uniform shape like legs, not like mandibles or maxille, and are adapted for walking; the feet are pro- vided with sharp teeth on the basal joint for retaining the food. The mouth is situated between the second pair; the first pair of legs are smaller than the others. All end in two simple claws, except the sixth pair, which are armed with several spatulate appendages serving to prop the crea- ture as it burrows into the mud. The males differ from the females in the hand and opposing thumb of the second pair of feet. These cephalo-thoracic appendages are quite as dif- ferent from those of most Crustacea as those of the mites and spiders, which have a pair of mandibles and maxille, the latter provided with a palpus. Appended to the ab- domen are six pairs of broad swimming feet, all except the first pair of which bear on the under side two sets of about one hundred respiratory leaves or plates, into which the blood is sent from the heart, passing around the outer edge and returning around the inner edge. This mode of respiration is like that of the Isopods. The alimentary canal consists of an oesophagus, which rises directly over the mouth, a stomach lined with rows of large chitinous teeth, with a large conical, stopper-hke valve projecting into the posterior end of the body ; the intestine is straight, ending in the base of the abdominal spine. The liver is very voluminous, ramifying throughout the cephalo- thorax. The nervous system is quite unlike that of the Crustacea ; the brain is situated on the floor of the body in the same plane as the rest of the system, and sends a pair of nerves to the compound eyes, a single nerve supplying the ocelli.* The feet are all supplied with nerves from a thick ring surrounding the esophagus. The nerves to the six pairs of abdominal legs are sent off from the ventral cord. * The nervous system of Limulus is quite unlike that of the Scorpion, where the brain is situated in the upper part of the head and supplies the maxille with nerves, and is situated directly over the infraceso- phageal ganglion; and, besides, there is no cesophageal ring as in Limulus, only the two commissures connecting the brain with the infracesophageal ganglion as usual in the Crustacea ‘and Arachnida in general, ANATOMY OF THE KING-CRAB. 299 The heart is tubular, with eight pairs of valvular openings for the return of the venous blood which flows into the pericardial sac from all parts of the body ; the arterial blood Fig. 265.—Nervous and part of the circulatory system of Limulus polyphemus, the King-Crab. a, vent ; @, esophagus ; 3, brain; 0, nerve to the emaller eyes; o’, nerve to the larger eyes; s, nerve-ring around the esuphagus. All the nerves are surround- ed by an arterial coat.—After Milne Edwards. is sent out from the arteries branching from the front end of the heart flowing around the upper side of the edge of the cephalo-thorax through numerous minute vessels. Also there - are a pair of branchial arteries, and two arteries in the base of the spine. 300. ZOOLOGY. The arrangement of the ventral system of arteries 1s very peculiar and quite characteristic of this animal. The ceso- phageal nervous ring, and in fact the entire nervous cord, is ensheathed in a vascular coat, so that the nervous system and its branches are bathed by arterial blood. The veins are better developed than usual ; there being in the cephalo- thorax two large collective veins along each side of the in- testine. — Closely connected with the two large collective veins are two large yellowish glandular bodies each with four branches extending up into the dorsal side of the cephalo-thorax. They are probably renal in their nature. Both the ovaries and testes are voluminous glands, each opening by two papille on the under side of the first ab- dominal feet. At the time of spawning the ovary is greatly distended, the branches filled with green eggs. Unlike most Crustacea, the female king-crab buries her eggs in the sand between tide-marks, and there leaves them at the mercy of the waves, until the young hatch. The eggs are laid in the Northern States between the end of May and al Fig. 206. Fie. 267. Fig. 266.—Embryo of King-crab, enlarged ; am, serous membrane ; ch, chorion. Fig. 267.--The same, more advanced. early in July, and the young are from a month to six weeks © in hatching. After fertilization the yolk undergoes total segmentation, much as in spiders and the craw-fish. When the primitive disk is formed the outer layer of blastodermic cells peels off soon after the limbs begin to appear, and this constitutes EMBRYOLOGY OF THE KING-CRAB. 301 the serous membrane (Fig. 266, am), which is like that of insects. Then the limbs bud out; the six pairs of cephalic limbs appear at once as in Fig. 266. Soon after the two basal pairs of abdominal leaf-hke feet arise, the abdomen be- comes separated from the front region of the body, and the segments are indicated as in Fig. 26% A later stage (Fig. 268) is signalized by the more highly developed dorsal portion of the embryo, an increase in size of the abdomen, and the appearance of nine distinct abdominalsegments. The segments of the cephalo-thorax are now very clearly defined, as also the division between the cephalo-thorax and abdomen, the latter being now nearly as broad as the cephalo-thorax, the sides of which are not spread out as in a later stage. SS LUED Fig. 268.—King-crab shortly before hatching ; trilobitic stage, enlarged ; side and dorsal view. At this stage the egg-shell has split asunder and dropped off, while the serous membrane, acting as a vicarious egg- shell, has increased in size to an unusual extent, several times exceeding its original dimensions and filled with sea- water, in which the embryo revolves. Ata little later period the embryo throws off an embry- onal skin (amnion), the thin pellicle floating about in the egg. Still later in the life of the embryo the claws are de- veloped, an additional rudimentary gill appears, and the abdomen grows broader and larger, with the segments more 302 ZOOLOGY. distinct ; the heart also appears, being a pale streak along the middle of the back extending from the front edge of the head to the base of the abdomen. Just before hatching the head-region spreads out, the ab- domen being a little more than half as wide as the cephalo- thorax. The two compound eyes and the pair of ocelli on the front edge of the head are quite distinct ; the append- ages to the gills appear on the two anterior pairs, and the legs are longer. The resemblance to a Trilobite is most remarkable, as seen in Fig. 268. It now also closely resembles the fossil king-crabs of the Carboniferous formation (Fig. 269, Prest- wichia rotundatus, Fig. 2%0, Huprodps Dane). N ig ae 1 go 1 mi AZ ! Ke Fig. 269.—Prestwichia, natural size.— Fig. 270.—Euprodps, natural size.— After Worthen. After Worthen. In about six weeks from the time the eggs are laid the embryo hatches. It now differs chiefly from the previous stage in the abdomen being much larger, scarcely less in size than the cephalo-thorax ; in the obliteration of the seg- ments, except where they are faintly indicated on the car- diac region of the abdomen, while the gills are much larger than before. The abdominal spine is very rudimentary ; it forms the ninth abdominal segment. The reader may now compare with our figures of the re- RELATIONSHIP OF LIMULUS TO TRILOBITES. 303 cently hatched Limulus (Fig. 271), that of Barrande’s larva of Trinucleus ornatus (Fig. 272, natural size and enlarged). He will see at a glance that the young Trilobite, born with- out any true thoracic segments, and with the head articu- lated with the abdomen, closely resembles the young Limu- lus. In Limulus no new segments are added after birth ; in the Trilobites the numerous thoracic segments are add- ed during successive moults. The Trilobites thus pass through a well-marked metamorphosis, though by no means so remarkable as that of the Decapods and the Phyllopods. Fig. 272.—Larva of a Trilo- bite, Trinucleus ornatus.— After Barrande. Fig. 271.—Larva of the King-crab. The young king-crabs swim briskly up and down, skim- ming about on their backs like Phyllopods, by flapping their gills, not bending their bodies. In asucceeding moult, which occurs between three and four weeks after hatching, the abdomen becomes smaller in proportion to the head, and the abdominal spine is about three times as long as broad. At this and also in the second, or succeeding moult, which oc- curs about four weeks after the first moult, the young king- crab doubles in size. It is probable that specimens an inch long are about a year old, and it must require several years for them to attain a length of one foot. The Limuit of the Solenhofen slates (Jurassic) scarcely differed in appearanee from those of their living descend- ants. Limulus, Prestwichia, Bellinurus, and Huproéps form 304 ZOOLOGY. the representatives of the suborder Xiphosura. The second suborder Hurypterida is represented by extinct genera Ptery- gotus, Hurypterus and allies which appeared in the upper Silurian Period and became extinct in the Coal Period. In these forms the cephalothorax is small, flattened and nearly square, while the abdomen is long, with twelve or thirteen segments, the last one forming a spoon-shaped or acute spine. The appendages of the cephalothorax were adapted for walking, one pair sometimes large and chelate; the hinder pair paddle-like. The gills were arranged like the teeth in a rake, the flat faces being fore and aft. While the king-crab burrows in the mud and lives on sea-worms, the Eurypterida probably swam near the surface, and were more predatory than the king-crabs. The Merostomata are a gen- eralized type, with some resemblances to the Arachnida as well as to the genuine Crustacea, resembling the former in . the want of antenne, and their mode of development. Order 2. Trilobita.—The members of this group are all extinct. The body has a thick dense integument like that of Limulus, and is often variously ornamented with tuber- cles and spines. The body is divided into three longi- tudinal lobes, the central situated over the region of the heart as in Limulus. The body is more specialized than in the Merostomata, being divided into a true head consisting of six segments bearing jointed appendages, somewhat like ‘those of the Merostomata, with from two to twenty-six dis- tinct thoracic segments (probably bearing short jointed limbs not extending beyond the edge of the body, which support- ed swimming and respiratory lobes). The abdomen consisted of several (greatest number twenty-eight) coalesced segments, forming a solid portion (pygidium), sometimes ending in a spine, and probably bearing membranous swimming feet. The larval trilobite was like that of a king-crab, and after a number of moults acquired its thoracic segments, there being a well-marked metamorphosis. The Trilobites (Paradoxides, Agnostus, etc.) appeared in the lowest Silurian strata, cul- minated in the upper Silurian, and died out at the close of the Coal Period. CLASSIFICATION OF CRUSTACEA. 305 Cuass. I. CRUSTACEA. Arthropoda breathing by gills situated on the legs, or respiring through the body-wails. Body in the higher forms divided into two regions, a cephalo-therax and abdomen. Two pairs of antenne ; mandibles usu- ally witha palpus. Heart nearly square, or in the lower forms tubular. Often a distinct metamorphosis. Sexes distinct, except in a few cases (certain burnacles, etc.). Order 1. Cirripedia.—Sessile often retrograded ; antenne not devele oped, living parasitically, the appendages of the head some- times forming net-like organs. Young hatched in the nau- plius state. Suborder 1.—Rhizocephala (Sacculina, Pelto- gaster). Suborder 2.—Genuine Cirripedia (Balanus, Lepas.) Order 2. Entomostraca.—A cephalo-thorax developed ; mandibles and three pairs of maxille ; five pairs of thoracic feet, no ab- dominal feet ; without any gills. The parasitic forms more or less modified in shape, with sucking mouth-parts ; all the young of the nauplius form. Suborder 1. Copepoda (Cyclops). Suborder 2. Siphonostoma (Lernea, Caligus, and Argulus). Order 3. Branchiopoda. Thoracic feet leaf-like ; one to three pairs of maxille ; number of body-segments varying from a few to sixty ; cephalo-thorax often well developed, and forming a bivalved shell. Young usually a Nauplius. Suborder 1, Ostracoda (Cypris). Suborder 2. Cladocera (Daphnia). Sub- order 3. Phyllopoda (Limnadia, Apus, Branchipus, and Ar- temia.) Order 4, Edriopthaima.—No cephalothorax, thoracic segments dis- tinct; respiration often carried on by the abdominal feet. Suborder 1. Jsopoda (Idoteza, Asellus), Suborder 2. Am- phipoda (Gammarus). : Order 5. Phyllocarida.—Body compressed ; rostrum distinct from the carapace ; thoracic feet leaf-like ; no metamorphosis. (Ne- balia.) Order 6. Thoracostraca.—Cephalothorax well marked, abdomen often : pent beneath the cephalothorax; breathing by gills attached to the maxillipedes and legs. Heart often nearly pentagonal. Usually a well-marked metamorphosis; young called a Zoéa. Suborder 1. Cumacea (Cuma). Suborder 2. Syncarida (Acanthotelson). Suborder 3. S/omapoda (Squilla). Sub- order 4. Schizopoda (Mysis). Suborder 5. Decapoda (Cran- gon, Astacus, Homarus, Cancer). £06 ZOOLOGY. Cuass IIL—PODOSTOMATA. Appendages of the cephalothorax in the form of legs, spiny at the base ; no antenne ; brain supplying nerves to the eyes alone, nerves to the cephalothoracie appendages sent off from an asophageal ring ; nervous system ensheathed by a ventral system of arteries ; metamorphosis slight. Sexes distinct. Order 1, Merostomata.—No distinct thoracic segments and appendages. (Limulus, Eurypterus.) Order 2. Trilobita.—Numerous free thoracic segments and jointed ap- pendages. (Agnostus, Paradoxides, Calymene, Trinucleus, Asaphus; all extinct.) : CLASSIFICATION OF THE ORDERS OF CRUSTACEA AND PODOSTOMATA. 8 = rh s 8 $s s Ss © s = 8 g S [2 2 SS & = $ = 8&8 & § 9 ‘'S 8 & 8 - & ™ 3 3 s s Sa fy > 2 an - 8 Sin S 2 8 8 = i J 2 oe 3 § = 2 s 3 = = 2 ~ RQ = BS a Le i) ? CRUSTACEA. PoDOsTOMATA. Laboratory Work.—In dissecting the lobster, the shell or crust may be removed by a stout knife ; the whole dorsal portion of the cephalo- thorax and each segment behind, including the base of the telson, should be removed, care being taken not to injure the brain, which lies just under the base of the rostrum. The hypodermis, or reddish, mem- pranous, inner layer of the integument, should then be dissected away, exposing the heart, the stomach, the liver, and the large muscles of the abdomen, The arterial system can be injected with carmine GENERAL CHARACTERS OF INSECTS. 307 through the heart, and the finer arteries traced into the large claws and legs. In the crab, the entire upper side of the carapace may be removed by the point of a knife. The smaller Crustacea, especially the water-fleas, may be examined alive under the microscope as trans- parent objects. In the larger forms the stomach may be laid open by the scissors in order to study its complicated structure. The eyes of the lobster should be hardened in alcohol and fine sections made for the microscope. This is an operation requiring much care and expe- rience. Experts in embryology have sliced the eggs of certain Crusta- cea and studied their embryology with great success. THE AIR-BREATHING ARTHROPODA (Centipedes, Spiders, Insects). General Characters of Insects.—While in the worms there is no grouping of the segments into regions, we have seen that in most Crustacea there are two assemblages of segments—+. e., a head-thorax and abdomen. In the insects there is a step higher in the scale of life, a head is separated from the rest of the body, which is divided into three regions, the head, thorax, and hind-body (abdomen). More- over, the insects differ from the Crustacea in breathing by internal air-tubes which open through breathing-holes (spiracles) in the sides of the body. The six-footed insects also have wings, and their presence is correlated with a differentiation or subdivision of the two hinder segments of the thorax into numerous pieces. The number of body-segments in winged insects is seven- teen or eighteen—. ¢., four in the head, three in the thorax, and ten or eleven in the hind-body. In spiders and mites there are usually but two segments in the head, four in the thorax, and a varying number (not more than twelve) in the abdomen ; in Myriopods the number of segments varies greatly—z. e., from ten to two hundred. The appendages’ of the body are jointed, and perform four different func- tions—7. ¢., the antenne are sensorial organs, the jaws and maxille are for seizing and chewing or sucking food ; the 308 ZOOLOGY. ‘thoracic appendages are for walking, and the spinnerets of the spider, as well as the sting or ovipositor of many insects, are subservient in part to the continuance of the species. Of the winged insects there are two types : first, those in which the jaws and maxille are free, adapted for biting, as in the locust or grasshopper, and, second, those in which the jaws and maxille are more or less modified to suck or lap up liquid food, as in the butterfly, bee, and bug. -Nearly all insects undergo a metamorphosis, the young being called a larva (caterpillar, grub, maggot) ; the larva transforms into a pupa (chrysalis), and the pupa into the adult (Imago). : In order to obtain a knowledge of the structure, external and internal, of insects, the student should make a careful study of the anatomy of a locust or grasshopper with the aid of the following description ; and afterward rear from the egg a caterpillar and watch the different steps in its metamor- phosis into a pupa and adult. The knowledge thus acquired will be worth more to the student than a volume of descrip- tions. On making a superficial examination of the locust (Calop- tenus femur-rubrum, or C. spretus), its body will be seen to consist of an external crust, or thick, hard integument, pro- tecting the soft parts or viscera within. This integument is at intervals segmented or jointed, the segments more or less like rings, which, in turn, are subdivided into pieces. These segments are most simple and easily comprehended in the abdomen or hind-body, which is composed of ten of them. The body consists of seventeen of these segments, variously modified and more or less imperfect and difficult to make out, especially at each extremity of the body— 1.e., in the head and at the end of the abdomen. These seventeen segments, moreover, are grouped into three re- gions, four composing the head, three the thorax, and ten the hind-body, or abdomen. On examining the abdomen, it will be found that the rings are quite perfect, and that each segment may be divided into an upper (tergal), a lateral (pleural), and an under (sternal) portion, or arc (Fig. 273, A). ANATOMY OF INSECTS. 309 These parts are respectively called tergite, pleurite, and - sternite, while the upper region of the body is called the Thabrum (FA) Oe, Kandible(F Tar aug : d © g Tirta, mt 2 a ? me OF Femur Fig. 278.—External anatomy of Caloptenus spretus, the head and thorax disjointed, up, uropatagium ; f, furcula: ¢, cercus.—Drawn by J. S. Kingsley. tergum, the lateral the pleurum, and the ventral or under portion the sternum. 310 ; ZOOLOGY. As these parts are less complicated in the abdomen, we will first study this region of the body, and then examine the more complex thorax and head. The abdomen is a little over half as long as the body, the tergum extending far down on the side and merging into the pleurum without any suture or seam. The pleurum is indicated by the row of spiracles, which will be noticed further on. The sternum forms the ventral side of the abdomen, and meets the pleu- rum on the side of the body. In the female (Fig. 273, B), the abdomen tapers some- what toward the end of the body, to which are appended the two pairs of stout, hooked spines, forming the oviposi- tor (Fig. 273, B,r, r'). The anus is situated above the upper and larger pair, and the external opening of the oviduct, which is situated between the smaller and lower pair of spines, and is bounded on the ventral side by a movable tri- angular acute flap, the egg-guide (Fig. 273, B, eg, and Fig. 276). The thorax, as seen in Fig. 273, consists of three seg- ments, called the prothorax, mesothorax, and metathorax, or fore, middle, and hind thoracic rings. They each bear a pair of legs, and the two hinder each a pair of wings. The upper portion (tergum) of the middle and hind segments, owing to the presence of wings and the necessity of freedom of movement to the muscles of flight, are divided or differ- entiated into two pieces, the scu¢wm and scutellum* (Fig. 273), the former the larger, extending across the back, and the scutellum a smaller, central, shield-like piece. The protergum, or what is usually in the books called the pro- thorax, represents either the scutum or both scutum and scutellum, the two not being differentiated. The fore wings are long and narrow, and thicker than the hinder, which are broad, thin, and membranous, and most active in flight, being folded up like a fan when at rest and tucked away out of sight under the fore wings, which act as wing-covers. * There are in many insects, as in many Lepidoptera and Hymenop- tera and some Neuroptera, four tergal pieces—é. e., preescutum, scutum, scutellum, and postscutellum, the first and fourth pieces being usually very small and often obsolete. dll ANATOMY OF INSECTS. Fig. 274.—Locust, Caloptenus, side-view, with the thorax separate from the head and abdomen, and divided into its three segments. 312 ZOOLOGY. Turning now to the side of the body under the insertion of the wing (Fig. 274), we see that the side of each of the middle and hind thoracic rings is composed of two pieces, the anterior, episternum, resting on the sternum, with the epimerum behind it; these pieces are vertically high and narrow, and to them the leg is inserted by three pieces, called respectively coxa, trochantine, and trochanter (see Fig. 274), the latter forming a true joint of the leg. The legs consist of five well-marked joints, the femur (thigh), ¢idia (shank), and tarsus (foot), the latter consist- ing in the locust of three joints, the third bearing two large claws with a pad between them. The hind legs, especially the femur and tibia, are very large, adapted for hopping. The sternum is broad and large in the middle and hind thorax, but small and obscurely limited in the prothorax, with a large conical projection between the legs, The head is mainly in the adult locust composed of a sin- gle piece called the epicranium (Figs. 274 and 275, £), which carries the compound eyes, ocelli, or simple eyes (Fig. 275, e), and antenne. While there are in real- ity four primary segments in the head of all winged insects, corresponding to the four pairs of appendages in the head, the posterior three segments, after early em- bryonic life in the locust, become obsolete, and are mainly represented by their ap- pendages and by small portions to which the appendages are attached. The epicranium represents the antennal segment. .and vine ofits head ono mostly corresponds to the tergum of the seg- spretus. E, epicrani- ment. The antenne, or feelers, are in- um; C, clypeus; Z, labrum; 00, ocelli; e, 7 ayer 7 antenney, ood! serted in front of the eyes, and between mandible; mz,portion them is the anterior ocellus, or simple eye, of maxilla uncovered e i 7 by the labrum; p, while the two posterior ocelli are situated . maxillary palpus; p’, 5 : labial palpus.—Kings- above the insertion of the antenne. In sib front of the epicranium is the clypeus (Fig. 275), a piece nearly twice as broad as long. To the clypeus is attached a loose flap, which covers the jaws when they are at rest. This is the upper lip or labrum (Fig. 275). MOUTH-PARTS OF INSECTS. 313 There are three pairs of mouth-appendages : first, the true jaws or mandibles (Fig. 2738), which are single-jointed, and are broad, short, solid, with a toothed cutting and grinding edge, adapted for biting. The mandibles are situated on each side of -the mouth-opening. Behind the mandibles are the maxille (Fig. 273), which are divided into three lobes, the inner armed with teeth or spines, the middle lobe unarmed and spatula-shaped, while the outer forms a five- jointed feeler called the maxillary palpus. The maxille are accessory jaws, and probably serve to hold and arrange the food to be ground by the true jaws. The floor of the mouth is formed by the labiwm (Figs. 273 and 274), which in real- ity is composed of the two second maxille, soldered together in the middle, the two halves being drawn separately in Fig. 273; to each half is appended a three-jointed palpus. Within the niouth, and situated upon the labium, is the tongue (lingua), which is a large, membranous, partly hol- low expansion of the base of the labium ; it is somewhat pyriform, slightly keeled above, and covered with fine, stiff hairs, which, when magnified, are seen to be long, rough, chitinous spines, with one or two slight points or tubercles on the side. These stiff hairs probably serve to retain the food in the mouth, and are, apparently, of the same struc- ture as the teeth in the crop. The base of the tongue is narrow, and extends back to near the pharynx (or entrance to the gullet), there being on the floor of the mouth, behind the tongue, two oblique slight ridges, covered with stiff, golden hairs, like those on the tongue. The internal anatomy may be studied by removing the dorsal wall of the body and also by hardening the insect several days in alcohol and cutting it in two longitudinally by a sharp scalpel. The esophagus (Fig. 2%6, @) is short and curved, contin- uous with the roof of the mouth. There are several longi- tudinal irregular folds on the inner surface. It terminates in the centre of the head, directly under the supra-cesopha- geal ganglion, the end being indicated by several small coni- cal valves closing the passage, thus preventing the regurgita- tion of the food. The two salivary glands consist each of a 31.4 ZOOLOGY. bunch of follicles, emptying by a common duct into the floor of the mouth. The cesophagus is succeeded by the crop (ingluvies). It dilates rapidly in the head, and again enlarges before pass- ing out of the head, and at the point of first expansion or enlargement there begins a circular or oblique series of folds, armed with a single or two alternating rows of simple spine- like teeth. Just after the crop leaves the head, the ruge or folds become longitudinal, the teeth arranged in rows, each row formed of groups of from three to six teeth, which point backward so as to push the food into the stomach. In alcoholic specimens the folds of the crop and esophagus are deep blood-red, while the muscular portion is flesh-col- ored. It is in the crop that the “‘ molasses ’’ thrown out by the locust originates. The proventriculus is very small in the locust, easily over- looked in dissection, while in the green grasshoppers it is large and armed with sharp teeth. A transverse section of the crop of the cricket shows that there are six large irreg- ular teeth armed with spines and hairs (Fig. 277). It forms a neck or constriction between the crop and true stomach. It may be studied by laying the alimentary canal open with a pair of fine scissors, and is then seen to be armed with six flat folds, suddenly terminating posteriorly, where the true stomach (chyle-stomach, ventriculus) begins. The chyle-stomach is about one half as thick as the crop, when the latter is distended with food, and is of nearly the same diameter throughout, being much paler than the red- dish crop, and of a flesh-color. From the anterior end arise six large gastrie ceca, which are dilatations of the true chyle-stomach, and probably serve to present a larger surface from which the chyle may escape into the body-cavity and mix with the blood, there being in insects no lacteal vessels or lymphatic system. The stomach ends at the posterior edge of the fourth ab- dominal segment in a slight constriction, at which point (pyloric end) the urinary tubes (vasa uwrinaria, Fig. 276, ur) arise. These are arranged in ten groups of about fifteen tubes, so that there are about one hundred and fifty long, fine tubes in all. 315 ANATOMY OF INSECTS. 2 Fig. 276.—Internal anatomy of Caloptenus femur-rubrum. at, antenna and nerve leading to it from the “ briin” or supra-cesophageal ganglion (sp), oc, ocelli, anterior and vertical ones, with ocellar nerves leading to them from the “ brain ;” ©, esophagus ; m, mouth: 6, labium or under lip ; i/ infra-cesophageal ganglion, sending three pairs of nerves to the mandibles, maxilla, and labium Tespectively (not clearly shown in the engraving) ; sm, sympathetic or vagus herve, starting from a ganglion resting above the cesophagus, and counecting with another ganglion (sg) near the hinder end of the crop; sal, salivary glands (the termination of the salivary duct not clearly shown by the cngraver); nv, nervous cord and ganglia; ov, ovary; wr, urinary tubes (cut off, leaving the stumps): ovt, oviduct; sb, sebaceous gland: be, bursa copulatrix; ovt’, site of Opening of the oviduct (the left oviduct cut away); 1-10, abdominal segmuuts. “The other organs labelled in full.—Drawn Rom his original dis sections by Mr. Edward Burgess, 316 . ZOOLOGY. The intestine iam) lies in the fifth and sixth abdominal segments. Behind the intestine is the colon, which i is smaller than the intestine proper, and makes a partial twist. The colon suddenly expands into the rectum, with six large rectal glands on the inside, held in place by six muscular bands attached anteriorly to the hinder end of the colon. The rectum turns up toward its end, and the vent is situated just below the supra-anal plate. Haviug described the digestive canal of the locust, we may state in a summary way the functions of the different divisions of the tract. The food after being cut up by the jaws is acted upon while in the crop by the salivary fluid, \, which is alkaline, and pos- Gi) sesses the property, as in ver- tebrates, of rapidly transform- ing the starchy elements of the food into soluble and as- similable glucose. The diges- tive action carried on in the crop (ingluvies) then, in a veg- etable-feeding insect like the Fig 277.~Transvr e-section of the locust, results in the conver- crop of Grylls cinereus of Europe; muc, muscular walls 5.7. oe ridge etween Sion of the starchy matters the large teeth.—After 4 Inot. into glucose or sugar. This process goes on very slowly. When digestion in the crop has ended, the matters submitted to an energetic pressure by the walls of the crop, which make peristaltic contrac- tions, filter gradually through the short, small proventricu- lus, directed by the furrows and chitinous projections lining it. The apparatus of teeth does not triturate the food, which has been sufficiently comminuted by the jaws. This is proved by the fact, says Plateau, that the parcels of food are of the same form and size as those in the crop, before passing through the proventriculus. The six large lateral pouches (ceca) emptying into the commencement of the stomach (ventriculus) are true glands, which secrete an al- DIG ES TI ON IN INSECTS. 317 kaline fluid, probably aiding in digestion. In tne stomach (ventriculus) the portion of the food which has resisted the action of the crop is submitted to the action of a neutral or alkaline liquid, never acid, secreted by special local glands or by the lining epithelium. In the ileum and colon ac- tive absorption of the liquid portion of the food takes place, and the intestine proper (ileum and colon) is thus the seat of the secondary digestive phenomena. The reaction of the secretion is neutral or alkaline. The rectum is the ster- coral reservoir. It may be empty or full of liquids, but never contains any gas. The liquid products secreted by the urinary tubes are here accumulated, and in certain cir- cumstances here deposit the calculi or crystals of oxalic, uric, or phosphatic acid. Insects, says Plateau, have no special vessel to carry off the chyle, such as the lacteals or lymphatics of vertebrates ; the products of digestion—viz., salts in solution, peptones, sugar in solution, and emulsion- ized greasy matters—pass through the fine coatings of the digestive canal by osmosis, and mingle outside of this canal. with the currents of blood which pass along the ventral and lateral parts of the body. Into the pyloric end of the stomach empty the urinary tubes, their secretions passing into the intestine. These are organs exclusively depuratory and urinary, relieving the body of the waste products. The liquid which they secrete contains urea (?), uric acid, and urates in abundance, hip- puric acid (?), chloride of sodium, phosphates, carbonate of lime, oxalate of lime in quantity, leucine, and coloring mat- ters. The nervous system of the locust, as of other insects, con- sists of a series of nerve-centres, or so-called brains (ganglia), which are connected by two cords (commissures), the two cords in certain parts of the body in some insects united into one. There are in the locust ten ganglia, two in the head, “three in the thorax, and five in the abdomen. The first ganglion is rather larger than the others, and is called tne *‘brain.’’? The brain rests upon the cesophagus, whence its name, supra-cesophageal ganglion. From the brain arise the large, short, optic nerves (Fig. 276, not lettered, but repre- ZOOLOGY. and from the front arise -Uvs oTeydao-orpaur aq} TIM aArau v Aq payauuod ‘Apoq Sururys ~JOP OY] JV aINSY oy} UT SUTPUS ‘oad [RYVUIO]S AY) SB IVs vB O} APIS OM] BILSUBS d80Y} JO Yous wo1g{ ‘do1d ayy Jo apis Japun oy} uo (SZ) wSuLT o (sd) wosuvs o1eydes-orpaul ayy WOIJ ast YOIYA\ SaAdoT UTBUL OMY OY) Aq pajuasaidad oav BILs *(0J8 “LOYISOMIAO oY} O} SayOUIG SUIPUAS PUL "ysaF1R] ay) YIJT oy}) BISUBs [RuLUIOpge aay ‘G-T | asuydosa-wijur ‘/2 $ (sn{je0o 4Jaq ay Jo AOYs sdoqs JO AUT] PoIJOp ay{}) SN[[e00 YoVe 0} aAJoU ILT[IVO UR pur ‘sata oy} Croqine oy) Aq opvuT suOTDessIp WO UOWOWA “Ap Aq UMTIG) ‘WMOTYUN ornyzeU aT ‘WOTs punod Bi “UOl[ZURd o;ovL0Y} puodas ayy Avou ‘% AMI] Pay Bl B pus ‘dodo ay} Jopun juUas a1¥ sAAIOM AM] pus snsvydosa ay} aaoqv pur uo Surat Uv dAIOU 9 BlBUBS D1DBI0N} ‘E ‘ZS ‘T * UOTE aatou o1ydo asi] oy} HO Surpuas ‘uoysuvs [vosvydosea-vidns ‘ds ‘snjaudy snuagdopng Jo wWo}sh8 SNOAIAN—'S!8 “SLA / From immediately in front, low down, arise sented by the circle behind the brain, sp; Fig. 278, op), which go to the compound eyes, 318 oe. daee----}-~2n4 L eens toons} Benn--f-F5 the three slender filaments which are sent to the three ocelli (Fig. 276, oc). NERVOUS SYSYEM OF INSECTS. 319 the antennal nerves (Fig. 276, a¢). The simple brain of the locust may be compared with the more complicated brain of an ant, as seen in Fig. 279. The infra-cesophageal ganglion (Fig. 278, if), as its name implies, lies under the esophagus at the base of the head, un- Fig. 279.—Right half of an ant’s-brain; uG, infra-cesophageal ganglion ; @r, brain; C, central connective portions ; W, semi-circular bodies of the small-celled portion of the brain lying next to the basal portion of the brain, from which the nerves to the simple eyes (av) arise; Au, optic lobes; An, antennal lobes (the bodies appearing like cells are rounded masses of the network of the substance ol the cord; 7, celln- Jar cortical substance of the brain; Xo, twofold body of the commissure connecting the brain wich the iufra-cesophageal ganglion.—After Leydig, from Graber. der abridge of chitine, and directly behind the tongue. It is connected with the supra-cesophageal ganglion by two com- missures passing up each side of the esophagus. From the ander side of the infra-cesophageal ganglion arise three pairs of nerves, which are distributed to the mandibles. 320 ZOOLOGY. maxille, and labium. The mandibular nerves project for- ward and arise from the anterior part of the ganglion, near the origin of the supra-cesophageal commissures, while the maxillary and labial nerves are directed downward into those organs. The sympathetic ganglia are three in number ; one situ- ated just behind the supra-cesophageal ganglion (Fig. 273, as), resting on the esophagus, and two others situated each side of the crop, low down. Each of Fy the two posterior ganglia is supplied by a nerve from the anterior ganglion. Two nerves pass under the crop con- necting the posterior ganglia, and from each posterior ganglion a nerve is sent backward to the end of the we x” proventriculus. A pair of nerves pass under the cesophagus from each side of the anterior sympathetic ganglion, and another pair pass downward to a round white body, whose nature is unknown (Fig. 273, u).. Fig. 280 represents an enlarged view of the brain and sympathetic nerve of amoth. The heart is a long tube lying in the abdomen, dilating Fig. 280.— Supra-cesopha- geal ganglion and visceral (or sympathetic) nervous system of the silk-worm moth (Bom- byx mori). —g8, Supra-ceso- phageal ganglion (“‘ brain”’) ; a, antennary nerve ; 0, optic nerve ; 7, azygos trunk of the visceral nervous system ; 7”, its roots arising from the supra-cesophageal ganglion ; s, paired nerve with its gangli- onic enlargements s’ 8".— After Brandt, from Gegen- baur. at six places along its course, and ending in a conical point near the end of the abdomen ; it is held in place by fine muscular bands. All insects breathe by means of a complicated system of air-tubes rami- fying throughout the body, the air entering through a row of spiracles, or air-holes, or breath- ing-holes (stigmata), in the sides of the body. There are in locusts two pairs of thoracic and eight pairs of abdominal spiracles. The first thoracic pair (Fig. 281) is situated on the membrane connecting the prothorax and mesothorax, and is covered by the hinder edge of the protergum (usually ealled prothorax). The second spiracle is situated on the RESPIRATORY ORGANS OF INSECTS. 321 posterior edge of the mesothorax. There are eight abdominal spiracles, the first one situated just in front of the auditory sac or tympanum (see Fig. 274), and the remaining seven are small openings along the side of the abdomen, as indicated in Fig. 281. From these spiracles air-tubes pass in a short distance and connect on each side of the body with the spi- racular trachea (Fig. 281, s, Fig. 282, s),as we may call it. The air-tubes consist of. two coats, in the inner of which is developed the so-called spiral thread (tenidium). These spiracular trachese begin at the posterior spiracle, and extend forward into the mesothorax, there subdividing into several branches. Branches from them pass to the two main ven- tral trachese (Fig. 281, v), and to the two main dorsal tra- chee (Fig. 281, D, Fig. 282, D). The main tracheal sys- tem in the abdomen, then, consists of six tubes, three on a side, extending along the abdomen. The pair of ventral trachexe extend along the under side of the digestive canal; the dorsal trachee rest on the digestive canal. These six tubes are connected by anastomosing trachee, and, with their numerous subdivisions and minute twigs and the sys- tem of dilated trachex or air-sacs, an intricate network of traches is formed. The system of thoracic air-tubes is quite independent of the abdominal system, and not so easy to make out. The tubes arising from the two thoracic stigmata are not very well marked; they, however, send two well-marked trachez into the head (Fig. 281, c, Fig. 282, c), which subdivide into the ocular dilated air-tube (Fig. 281, oc, Fig. 282, oc) and a number of air-sacs in the front of the head. The series of large abdominal air-sacs, of which there are five pairs (Fig. 282, 3-7), arise independently of the main traches directly from branches originating from the spira- cles, as seen in Fig. 281. They are large and easily found by raising the integument of the back. There is a large pair in the mesothorax (Fig. 282, 2) and two enormous sacs in the prothorax (Fig..282, 1), sometimes extending as far back as the anterior edge of the mesothorax. All these sacs are superficial, lying next to the hypodermis or inner layer of the integument, while the smaller ones are, in many cases, ZOOLOGY. 322 RESPIRATION IN INSECTS, 323 buried among the muscles. Besides the ordinary air-sacs, there is in the end of the abdomen, behind the ovaries, a plexus of six dilated air-sacs (Fig. 282, I, IL, III), which are long, spindle-shaped, and are easily detected in dis- secting. There is a system of dilated trachee and about fifty air- sacs in the head. In the legs two trachez pass down each side of the femora, sending off at quite regular intervals numerous much-branch- ing, transverse twigs ; there is one large and a very small trachea in the tibia, and the main one extends to the ex- tremity of the last tarsal joint. ' By holding the red-legged locust in the hand, one may observe the mode of breathing. During this act the por- tion of the side of the body between the spiracle and the pleurum (Fig. 273, A) contracts and expands ; the contrac- tion of this region causes the spiracles to open. The gen- eral movement is caused by the sternal moving much more decidedly than the tergal portion of the abdomen. When the pleural portion of the abdomen is forced out, the soft pleural membranous region under the fore and hind wings contracts, as does the tympanum and the membranous por- tions at the base of the hind legs. When the tergum or dorsal portion of the abdomen falls and the pleurum con- tracts, the spiracles open ; their opening is nearly but not always exactly co-ordinated with the contractions of the pleurum, but as a rule they are. There were sixty-five con- tractions in a minute in a locust which had been held be- tween the fingers about ten minutes. It was noticed that when the abdomen expanded, the air-sacs in the first ab- Fig. 281._Showing distribution of air-tubes (tr: chee) and air-sacs—side view of the hud. v, Main ventral trachea (only one of tue two shown); s, left stigmatal trachea, connecting by vertical branches with D, the left main dorsal trachea; ¢, left cephalic trachea ; oc, ocular dilated trachea, From the first, second, third, and fourth spiracles arise the first four abdominal air-sace, which are succeeded by the plexus of three pairs of dilated trachee, I, JI, III, in Fig. 287. Numerous air-sace and trachez are represented in the head and thorax. The two thoracic spiracles are rep- resented, but not lettered. Fig. 282.—D, left dorsal trachea; .S, left stigmatal trachea ; T, IT, TIT. first, second, and third pairs of abdominal dilated trachew, forming a plexus behind the ovaries ; 1, pair of enormous thoracic air-sacs ; 2, pair of smaller air-sacs ; 3-7. abdominal air-sacs ; oc, ocular dilated trachea and air-racs ; c, cephalic trachca. The relationa of the heart to tne dorsal trachee are indicated.—Drawn by Emerton from dissec- tions by author. 824 ZOOLOGY. dominal ring contracted. This would indicate that the air rushes into the spiracles during the contraction of the abdomen, and that the air-sacs are not refilled until the spiracles are closed ; thus the air in the air-sacs is perhaps constantly changing. It is evident that the enormous powers of flight possessed by the locust, especially its fac- ulty of sailing for many hours in the air, is due to the presence of these air-sacs, which float it up in the atmospheric sea. Other insects with a powerful flight, as the bees and flies, have well- developed air-sacs, but they are less numerous. It will be seen that, once having taken flight, the locust can buoy itself up in the air, con- stantly filling and refilling its internal buoys or balloons without any muscular exertion, and thus be borne along by favorable winds to its Fig, 293, destination. It is evident that the process of Longitudinal respiration can be best carried on in clear, sunny section of the ; trachea of Hy- weather, and that when the sun sets, or the or oalebertie weather is cloudy and damp, its powers of flight ou, chicula sy are lessened, owing to the diminished power of Pxtter Minot’ tespiration. The finer structure wf the trachea is seen in Fig. 283. It is difficult to explain many of the actions of insects, from the fact that it is hard for us to appreciate their men- tal powers, instincts, and general intelligence. That they have sufficient intellectual powers to enable them to main- - tain their existence may be regarded as an axiom. But in- sects differ much in intelligence and also in the degree of perfection of the organs of sense. The intelligence of in- sects depends, of course, largely on the development of the organs of special sense. The sense of sight must be well developed in the locust, there being two large, well-developed compound eyes, and three simple ones (oceliz), situated between the former, sup- plied with nerves of special sense. Fig. 284 represents the eye of a moth greatly enlarged to show the finer structure. SENSES OF INSECTS. 325 The antenne are, in the locust, organs of smell. The palpi are not only organs of touch, but probably, as in some other insects, are endowed with the sense of taste, enabling the locust to discriminate between the different kinds of food, and select that best adapted to suit its wants. It is possible that the labial nerves send branches of special sense to the tongue. Fig. 284.—Longitudinal section of the facetted eye of asphinx: the eye-capsule or sclera facetted externally (f), and sieve-like within, shows the rod-like ending of the optic nerve-fibres ; %, layer of the crystalline lens; 3, iris-like-pigment zone; ch, choroid composed of pigment cells ; sn, optic nerve ; ¢7, trachea lost in fine bundles of fibrille.—After Leydig, from Graber. The ears are well developed in the locust, and we know that the sense of hearing must be delicate, not only from the fact that a loud alarum with kettles and pans affects them, but the movements of persons walking through the grass invariably disturb them. Besides this, they produce a fid- dling or stridulating sound by rubbing their hind legs against their folded wing-covers, and this noise is a sexual 326 ZOOLOGY. sound, heard and appreciated by individuals of the other sex. Any insect which produces a sound must be supposed to have ears to hear the sound pro- h c duced by others of its species. In the antenne, palpi, and a abdominal appendages of dif- Sheeenee ferent insects are seated mi- 2 b er ‘ nute olfactory organs consisting ace Aurea on est oF nite alone (Fig, 285), or of cupae of Fava -autoraen aR perforated at the end, and pegs associated with the pits. The ears (or auditory sacs) of the locust are situated, one on each side, on the basal joint of the abdomen, just be- ae KX Fig. 286.—Ear of a locust (Caloptenus italicus) seen from the inner side. 7’, tym- panum ; 7'R, its border ; 0, u, two horn-like processes ; 03, pear-shaped vesicle ; 7, auditory nerve ; ga, terminal ganglion; s¢, stigma ; 7, opening and m/’ closing mus- cle of the same; 2, tensor muscle of the tympanum-membrane.—After Graber. hind the first abdominal spiracle (Fig. 274). The ap- paratus consists of a tense membrane, the tympanum, sur- rounded by ahorny ring (Fig 286). ‘* On the internal sur- ORGANS OF HEARING. 327 ‘face of this membrane are two horny processes (ow), to which is attached an extremely delicate vesicle (7) filled with a transparent fluid, and representing a membranous labyrinth. This vesicle is in connection with an auditory nerve (7) Fig. 287—A Carabus beetle in the act. of walking or running. Three legs (Z}, R?, ZL), are directed forward, while the others (f#!}, L?, #%), which are directed back- ward toward the tail, have ended their activity. @ 0, cd, and ¢/f are curves described by the end of the tibie and passing back to the end of the body; 0h, d i, andy’ g are cues described by the same legs during their passive change of position.—After raber. which arises from the third thoracic ganglion, forms a gan- glion (ga) upon the tympanum, and terminates in the im- mediate neighborhood of the labyrinth by a collection of 328 ZOOLOGY. cuneiform, staff-like bodies, with very finely-pointed ex- tremities (primitive nerve-fibres?), which are surrounded by loosely aggregated ganglionic globules.’’ (Siebold’s Anatomy of the Invertebrates.) In walking, the locust, beetle, or, in fact, any insect, raises and puts down its six legs alternately, as may be seen by observing the movements of a beetle (Fig. 287). While the structure of the limb of a ver- tebrate and insect is not homol- ogous, yet the mechanism or functions of the parts are in the main the same, as indicated in Figs. 288 and 289. The footprints of insects are sometimes left in fine wet sand on the banks of streams or by the seaside. In Fig. 290 the black dots are made by the fore, the clear circle by the middle, and the black dashes by the hind legs | (Graber). The wings are developed as folds of the integument, and strengthened by hollow rods called ‘‘ veins ;’’ their branches Fig. 288,—Section of the fore leg of Called ‘‘ venures.’’ There are a Stag beetle, showing the muscles. S. ; - . < etentor: B, flexor of the leg; s, ex. in the wings of most insects bit 7 muons? chum, loses SIX main veins—t.e., the costal, es mexer gt the femere;ubial the subcostal, median, subme- dian, internal, and anal. They are hollow and usually contain an air-tube, and a nerve often accompanies the trachea in the principal veins. The arterial blood from the heart (as seen in the cockroach by Moseley) flows directly into the costal, subcostal, median, and submedian veins ; here it is in part aérated, and returns to the heart from the hinder edge of the wings through the hinder smaller branches and the main trunks of the internal FLIGHT OF INSECTS. 329 and anal veins. So that the wings of insects act as lungs as well as organs of flight. For the latter purpose, the principal veins are situated near the front edge of the wing, Fig. 289.—Diagram of the kuee-joint of a vertebrate (A) and_an insect’s limb (B). a, upper, b, lower shank, united at A bya capsular joint, at B by a folding joint ; d, extensor or lifting muscle ; @!, flexor or lowering muscle of the lower joint. The dotted line indicates in A the contour of the leg.—After Graber. called the costa, and thus the wing is strengthened when the most strain comes during the beating of the air in flight. The wing of an insect in making the strokes during flight describes a figure 8 inthe air. A fly’s wing makes 330 revolutions in a second, executing t therefore 660 simple oscillations. The sexes are always distinct in insects, the only known exception being certain very low s aquatic Arthropods called Tardigrada, in a which both sexual glands occur in the same ?) individual. The testes of the common red- 6... legged locust form a single mass of tubular [ “|. (< glands, resting in the upper side of the third, ead fourth, and fifth segments of the hind body. “ Figs. 291 and 292 represent this structure in o. other insects. The ovaries consist of two sets “O 16 of about twenty long tubes, within which the | eggs may be found in various stages of de- velopment. The eggs pass into two main fig. 290—Foot- tubes which unite to form the single oviduct UA08,, of Mec: which lies on the floor of the abdomen. Natural size—At Above the opening of the oviduct is the sebific gland and its duct. This gland secretes a copious supply of -a sticky fluid, which is, as in many other insects, poured 330 ZOOLOGY. out as the eggs pass out of the oviduct, thus surrounding them with a tough coat. The external parts consist of the ovipositor (Fig. 273, B, and Fig. 276), which is formed of two pairs of spines (rhab- dites) adapted for boring into the earth; and of the egg- guide (Figs. 273 and 276, eg), a triangular flap guarding the under side of the opening of the oviduct. Fig. 291.—Male sexual apparatus of a bark-beetle. su al wate al, vas deterens ; ho, testis ; bi, seminal vesicle; ag, of Acheta campestris.—After ductus ejaculatorius.—After Graber. Gegenbaur. There is a remarkable uniformity in the mode of develop- ment of the winged insects. In general, after fertilization of the egg, a few cells appear at one end of the egg ; these multiply, forming a single layer around the egg, this layer constituting the blastoderm. This layer thickens on one side of the egg, forming a whitish patch called the primitive streak or band. The blastoderm molts, sloughing off an outer layer of cells, a new layer forming beneath ; the skin thus thrown off is called the serous membrane; the second germ-layer : (ectoderm) then arises, and a second Fig, 203.—Section of Sphinx Membrane (called amnion, but not embryo, erm imm j in The yolks, eerous nen homologous with that of vertebrates) mn nner gemmiayer, we peels off from the primitive band just as the appendages are budding out, so that the body and appendages of the embryo insect are en- cased in the amnion as the hand and fingers are encased by a glove. As seen in the accompanying Figs. 293-298, the DEVELOPMENT OF INSECTS. 331 appendages bud out from the under side of the primitive band, and antenne, jaws, legs, ovipositor (or sting), and the abdominal feet of caterpillars are at ternal organs, the ner- vous system first origi- nates; the alimentary Fig. 294.—Embryo of Sphinx canal is next formed ; much more advanced. f, heart; and at about this time Sralinestary muscularbanierem, the stigmata and. air- Hesuiing of a wicker Ue and tubes arise as invagina- stan Kowaleveee “8% #83295 tions of the outer germ- layer. The development of the salivary glands precedes that of the uri- nary tubes, which, with the genital glands, are originally offshoots of the primitive digestive tract. Finally the heart is formed. When the insect hatches, it either cuts its way through the egg-shell by a temporary egg-cut- ter, as in the flea, or the expansion of the head and thorax and the convulsive movements of the body, as in the grasshopper, burst the shell asunder. The serous membrane is left in the shell, but in the case of grasshoppers the larva on hatching is still enveloped in the am- nion. ‘This is soon cast as a thin pellicle. The principal change from the larval to the adult locust or grasshopper is the acquisition of wings. In such insects, then, as the Orthoptera and Hemiptera, in which the adults differ from the newly hatched larva mainly in the posses- sion of wings, metamorphosis is said to be in- first all alike. Soon the appendages begin to assume the form seen in the larva, and just before the insect hatches the last steps in the elabora- tion of the larval form are taken. As to the development of the in- Fig. 295.— Primitive band or germ of a Sphinx moth, with the fegments in- dicated, and their rudimen- tary append- ages. c¢, upper lip ; at, anten- ne ; md, man- dibles; ma, me’, first and second maxil ler, 0, ot legs ; ul, abde minal legs. complete. In the beetle, butterfly, or bee, the metamorphosis 1s complete ; the caterpillar, for example, is a biting insect, 332 is voracious, and leads a different life from the quiescent, © sleeping pupa or chrysalis, which takes no food ; on the other hand, the imago or butterfly has mandibles, which are rudimentary, and incapable of biting, while the maxille, or ‘“tongue,’’ which were rudimentary in the caterpillar, become now greatly developed; and the butterfly takes Fig. 296.—Embryo of a Water-beetle (Hydrozhilus). E, egg ; A, head ; o/, upper lip: m, mouth 3 an, antenne ; *,, man- dibles; Xa, kg, maxille; B, thorax ; 6,, boy bys legs 3 hy-Ayos ten pairs of rudimentary abdo- minal legs, of which all except 2, disappear before the insect hatches; @, anus,—After Kowa- levsky. Fig. 297.—Profile view of embryo Honey-bee, lettering as in Fig. 296. BM, uervous cord; 0G, brain; D, digestive canal; sch, the ceso- phagus ; S¢, stigmatal openings of the tracheal system; 2, heart.— After Bliitschli. liquid food and but little of it, while its surroundings and mode of life are entirely changed with its acquisition of wings. Thus the butterfly leads three different lives, differ- ing greatly in structure, externally and internally, at these three periods, and with different environments. METAMORPHOSIS OF INSECTS. 333 Most caterpillars moult four or five times; at each moult the outer Jayer of the skin is cast off, the new skin arising from the hypodermis, or inner layer of the in- tegument. The skin opens on the back behind the head, the caterpillar drawing itself out of the rent. In the change from the caterpillar to the chrysalis, there are re- markable transformations in the muscles, the nervous, digestive, and circulatory system, inducing a change of form, external and internal, characterizing the ce stages in the metamorphosis. While the changes in form are comparatively sudden in flies and butterflies, the steps that lead to them are gradual. How gradual they are may be seen by a study of the metamorphosis of a bee. In the nest of the humble or honey bee, the young may be found in all stages, from the egg to the pupa gayly colored and ready to emerge from its cell. It is difficult to indicate where the chrysalis stage begins and the larva stage ends, yet the metamorphosis is more complete—namely, the adult bee is more unlike the larva, than in any other insect. Besides the normal mode of de- velopment, certain insects, as the rie eee or mouse, plant-louse (Aphis), the bark-louse as, antennee 5 vk Sorehead.—After (Coccus), the honey-bee, the Po- listes wasp, the currant saw-fly (Nematus), the gall-flies, and a few others, produce young from unfertilized eggs. Certain moths, as the silk-worm moth. (Bombyx mort) and others, have been known to lay unfertilized eggs from which caterpillars have hatched. This anomalous mode of repro- duction is called parthenogenesis, and fundamentally is only a modification of the mode of producing young by budding which is universal in plants, and is not unusual, as we have 334 ZOOLOGY. seen, among the lower branches of the animal kingdom. The object or design in nature, at least in the case of the plant-lice and bark-lice, as well as the gall-flies, is the pro- duction of large numbers of individuals, by which the per- petuity of the species is maintained. Insects are both useful and injurious to vegetation. Were it not for certain bees and moths, orchids and many other plants would not be fertilized ; insects also assist in the cross-fertilization of plants. For full crops of many of our fruits and vegetables, we are largely indebted to bees, flies, moths, and beetles, which, conveying pollen from flower to flower, ensure the production of abundant seeds and fruits. - Mankind, on the other hand, suffers enormous losses from the attacks of injurious insects. Within a period of four years, the Rocky Mountain locust, migrating eastward, in- flicted a loss of $200,000,000 on the farmers of the West. In the year 1864, the losses occasioned by the chinch-bug in the corn and wheat crop of the valley of the Mississippi amounted to upward of $100,000,000. It is estimated that the average annual losses in the United States from insects are about $100,000,000. On the other hand, hosts of ichneumon flies and Tachina flies reduce the numbers and prevent undue increase in the numbers of injurious insects. The number of species of insects is estimated to be about 190,000. Of these there are about 25,000 species of Hyme- noptera (bees, wasps, etc.) ; about 25,000 species of Lept- doptera (butterflies and moths) ; about 24,000 Diptera (two- winged flies), and 90,000 Coleoptera (beetles) ; with about 4600 species of Arachnida (spiders, etc.), and 800 species of Myriopoda (millepedes, centipedes, ete.) Insects are distributed all over the surface of the earth. Most of the species are confined to the warmer portions of the globe, becoming fewer in the number of species as we approach the North Polar regions. Many are inhabitants of fresh water; a very few inhabit the sea. Insects, except a Silurian Blattid, first appeared in the Devonian rocks; these were Newroptera and Orthoptera, with ~ representatives of other groups which seem generalized in their structure. But if highly developed flying insects, be- longing, at least the May fly, to existing families, appeared PERIPATUS. 335 in the Devonian period, it is reasonable to suppose that other insects, besides forms like cockroaches, must have inhabited the dry land of the Silurian period. While true scorpions have been found in the Upper Silu- rian rocks of Scotland, Sweden, and New York, the oldest insect-remains are the wing of Paleodlattina douvillet, an insect probably allied to the cockroach, and found in the Middle Silurian rocks of France. In the Devonian of St. Johns, N.B., have been discovered fragments of the wings either of a May-fly or dragon-fly, and five other species of doubtful position. In the Carboniferous formation insect-remains are more numerous; they belong to the Thysanura, Orthoptera, May- flies, dragon-flies, Hemiptera, with composite forms (Huge- reon) and genuine Neuroptera, allied to Stalis and Corydalus. No insects with a complete metamorphosis (except the Meu- roptera) are yet known to have lived before the Mesozoic age. Crass I.—Matacopopa (Pertpatus). Characters of Malacopoda.—This group is represented by a single animal, the strange Peripatus of tropical coun- tries, in which the body is cylindrical, the integument, an- tenne, and limbs soft, not chitinized, with the head not separate from the body, and bearing a pair of many-jointed extensible antenne, with two pairs of rudimentary jaws {mandibles and maxille), and from fourteen to thirty-three pairs of feet. There is a pair of nephridia to each segment. It differs from other Arthropods in the two widely separated minutely ganglionated nervous cords sent backward from the brain; also in the minute, numerous tracheal twigs arising from numerous minute oval openings (rudimentary spiracles) situated irregularly along the median line of the ventral surface of the body. The feet are soft, fleshy, and end in two claws. Peripatus is viviparous. According to the description and figures of Mr. Moseley, the young develop much as in the chilopodous Myriopods (Geophilus), show- ing that Pertpatus is nearer to the Myriopods than any other group. That it is a tracheate animal was also proved by Mr. Moseley; but owing to the nature of the nervous system, the minute trachee and their numerous irregular 336 ZOOLOGY. spiracular openings, with no chitinous edge, this form cannot be placed among the Myriopods. It is certainly not a worm, but, on the whole, connects the worms with the sucking Myriopods, and suggests that the insects may have descended from forms somewhat like Peripatus. Peripatus tuliformis inhabits the West Indies, and either P. Edwardsit Blanch- ard, or an undescribed species about four centimetres in length (with twenty-seven pairs of legs), inhabits the Isth- mus of Panama. The name Malacopoda was proposed by De Blainville, who suggested that Peripatus connected the Myriopods with the Annelids. Crass II].—Myriopopa (Centipedes, etc.). ’ Characters of Myriopoda.—The centipedes and millepedes are distinguished by their cylindrical body, the abdominal seg- ments being numerous and similar to the thoracic segments, all provided with a pair of feet. The head bears a pair of antenne, but the jaws are not homologous with those of in- sects. The internal organization is simple, like that of the larvee of insects. Some Scolopendre are said to be viviparous. Order 1. Diplopoda.—To this group belong the mille- pedes, Julus, etc. (Figs. 299-302). The first maxille are absent. The segments are round or flattened, and the feet are inserted near together, the sternum being undeveloped. In some forms (Fig. 299, Scoterpes Copei Packard, from Mammoth Cave) the body is hairy. They are all harmless. The eggs are laid in large numbers an inch or two beneath the surface of the earth. They undergo total segmentation, _ and in a few days the larva (Fig. 300) hatches. At this time it bears a resemblance to a Podura, having but three pairs of feet, the third pair attached to the fourth thoracic seg- ment. After a series of moults, new segments and new feet appear, and thus these Myriopods undergo a distinct meta- morphosis. The species feed on dead leaves and fruit. Order 2. Pauropoda.—The two orders of Myriopods are connected by Pauropus, which by Lubbock is regarded as the type of a distinct order (Pauropoda). Our only species, Pauropus Lubbockii Pack. (Fig. 304), consists of six seg- ments besides the head, and the young Pauropus has but MYRIOPODS. 337 Fig. 300.—Larva of C Julus. a, third ab- He 301. dominal segment, with —Polydes- the new limbs just mus ery- budding out; 4, new thropygus segments arising be- >common tween the penultimate Poly des- Fig. 299.—Scoter- and the last segment.— mus. pes copei of Mam- After Newport. moth Cave. ‘ Fig. SA toiarceemels causes, tae Utah, op and sice view. a. antenna; 6, a segment . co and leg; c, dorsal view of two segments show- Fig. ae eae ing ornamentation ; d, side view of two terminal e segments of the body—all magnified. 338 ZOOLOGY. three pairs of feet, and in this and other respects resembles Podura. Asecond form, Zurypauropus, of Ryder, has six segments, with nine pairs of feet wholly concealed from above by the expanded seg- ments. The antenne end in a terminal globular hyaline body with a long pedicel, as in Pauropus, and the mouth-parts are as in that genus. #. spinosus Ryder is reddish brown, and one mm. in length. Order 3. Chilopoda.—This group is rep- resented by the centipede and Lithobius, in which the body is flattened, the sternal region being well developed. In Geophilus (Fig. 803, G. bipunecticeps Wood) and allies there are from thirty to two hundred seg- ments. Our most common form is Litho- bius Americanus Newport, found under logs, etc. The centipede (Scolopendra : heros Girard) is very poisonous, the poison- poe ee sae being lodged in the two large fangs or jarged. Pig. 2.20; first pair of legs. In Cermatia the body is earer feck, and frst short, with compound eyes and remarkably long slender legs. C. forceps Rafinesque, of the Middle and Southern States, is said to be poisonous; it preys upon spiders. Crass III].—ARracHNnrIpA (Spiders, etc.). Characters of Arachnida.—The bodies of spiders and scor- pions, etc., are divided into two regions, a head-thorax and abdomen, the head being closely united with the thorax. There are no antenne, only a pair of mandibles and a pair of maxille, with four pairs of legs. There are never any compound eyes. The young are usually like the adult, except in the mites, in which there _ Fig. 305.—Head of Paur is a slight metamorphosis. In all Fee ene Arachnida there is a liver, this organ not being present in the winged insects. PYCNOGONIDA., 339 The type of this class is the spider, which is character- Fig. 366.—Anatomy of a spider, diagrammatic longitudinal section through the body. au, simple eyes and nerves leading to them from the brain (supra-cesophageal ganglion, 0@) ; @no, mandibles ; td, palpus of maxilla ¢,; do, first pair of legs, b,-5 , Succeeding pairs; A, head; Br, thorax ; H, hind-body or abdomen; Ri, heart or dorsal vessel; Z, lung in front of the opening of the oviduct @; the spinning-glands (sp) con- nect with the spinnerets. sp W. The digestive tract is ~haded, and in the abdomen enveloped in the liver.—After Graber. ized by the pos- session of two or three pairs of spinnerets, which are jointed ap- pendages ho- mologous with the legs. Be- sides trachee, spiders have a so-called lung (Fig. 306, L), composed of several leaves, into which the blood flows, and is thus aérated. In Lycosa the blood flows through the heart from the head backward. There is a great range of structure, from the lowest mites to the spiders, certain mites having no heart, no trachez, very rudimentary mouth-parts, and no brain, there being but a single ganglion in the abdomen. Order 1—~The Pyenogonida are marine forms, without air- tubes, with four pairs of long legs, into which cecal prolonga- tions of the stomach pass, as seen in Fig. 307. Order 2. Tardigrada.— The bear animalcules (Fig. 308) are related to the mites. In these singular beings the ovary and testis exist in the same individual. Macrobiotus Americanus Pack. swamps. noides. Fig. 307.— Ammotho#@ pycnogo- a, stomach with cceca (b, b, b, 6) extending into the legs.— From Gegenbaur. is common in sphagnum Like the Rotatoria, these low forms are capable of revivifying after being apparently dead and dried up. 340 ZOOLOGY. Order 3. Linguatulina.—This group comprises remark- able worm-like forms, which are parasites. The young are mite-like, the body spherical, with boring jaws, and two \ Fig. 308.—Milnesium tardigradum, X Fig. 309.—Pentastoma teenioides. 120 times. 1, nee b, alimentary Natural size.—From Verrill. canal; ov, ovary.—After Doyere. 7 Fig. 310.—Ixodes albiptctus trom a partly domesticated moose. The tick natural size, gorged with blood, and its six-legged young, much enlarged. a, beak or man- dibles armed with teeth; b, maxilla, and c, maxillary palpus; d, a foot with sucker Fig. 311.—Izodes bovis. Natural size and claws, enlarged. and enlarged. THE MITES. 341 pairs of short-clawed feet. Pentastoma (Fig. 309) occurs in the lungs and liver of man, and in horses and sheep. Order 4. Acarina.—The mites are degenerate Arach- nida, the body being oval in form, the head usually small, more or less merged with the thorax, while the latter is not differentiated from the abdomen. ‘There is a slight metamorphosis, the mite ae when first hatched having but—_ 7 three pairs of legs, the fourth we ie =) y M <— €_f Fig. 312.—Sugar-mite. Much Fig. 313.—Carolina scorpion (Buthus enlarged. Carolinianus). Natural size. (and last) pair being added after a moult. A typical mite, though above the average size of the members of the group, is the tick (Fig. 310, Izodes ailbi- pictus Pack). Closely allied to this is Ixodes bovis Riley, the cattle-tick (Fig. 311), which buries its head in the skin, anchoring itself firmly by means of the backward-pointing teeth of its jaws. Other examples of mites are the cheese and sugar mites (Fig. 312, Tyroglyphus sacchari). ‘The lat- ter appear as white specks in sugar, and to them is due the disease known as grocers’ itch. Certain mites live under the epidermis of the leaves of . trees, often forming galls. Fig. 314.—Chelifer cancroi- des. Magnified. 342 ZOOLOGY. Order 5. Arthrogastra.—In this group belong scor- pions (Fig. 313), false scorpions (Fig. 314), the whip scor- pions, and the harvest-man (Phalangiuwm). In all these forms the abdomen is plainly segmented, the segments not being visible in the mites or spiders. Usually the maxillary palpi are much enlarged, and end in claws. The scorpion is viviparous, the young being brought forth alive. The young scorpions cling to the back of the mother. The sting of the scorpion is lodged in the tail, which is perforated, and contains in the bulbous enlargement un active poison. Though producing sickness, pain, and swelling in the arm, the sting of the scorpion is seldom fatal. The little false-scorpions (Chelifer, Fig. 314) often occur in books, under the bark of trees, and under stones. The whip- scorpion is confined to warm countries. Thelyphonus gigan- teus Lucas occurs in New Mexico and Mexico. Its abdomen ends in a long lash-like appendage. Its bite is poisonous. The harvest-men, or daddy-long-legs, are common in dark places about houses. They feed on plant-lice. Our common species is Phalangium dorsatum Say. Order 6. Araneina.—The spiders are always recogniza- ble by their spherical abdomen, attached bya slender pedicel to the head-thorax. They breathe, like the scorpions, both by lungs as well as by trachex, and the young resemble the parent in having four pairs of feet. The development of the spider has some peculiarities not found in the higher insects. The egg undergoes total seg- mentation, The germ is somewhat worm-like, as in Fig. 315, then, as in C, the primitive band forms, with head and tail end much alike. Afterward (Fig. 316) the head ac- celerates in development, and the appendages begin to bud out, six pairs of abdominal limbs appearing and then totally disappearing, except the three pairs of spinnerets, as if the spiders were descended originally from some Myriopod-like form. The mandibles are vertical, and end in hollow points, through which the poison exudes, the two poison-glands being situated in the head. The male spider is usually much smaller than the female ; the latter lay their eggs in silken cocoons. The tarantula (Zycosa) usually lives in ’ TRAP-DOOR SPIDERS. 343 holes in the ground, and sometimes conceals the opening by eovering it with a few dead leaves. Our largest spider is Nephila plumipes of the Southern States. The common garden spider is Hpeira vulgaris Hentz. It lives about B A : C Fig. 315.—Development of the Spider.—A, worm-like stage ; B, primitive band ; C, the same more advanced, with rudiments of limbs. houses and in gardens ; its geometrical web is very regular. The large trap-door spider (Mygale) has four lung-sacs in- stead of two, as in the other spiders, and only two pairs of spinnerets. Mygale Henzii Girard inhabits the Western plains and Utah ; Mygale avicularia Linn. of South America is known to seize small birds, and suck their blood. There are probably about six or eight hundred species of spiders in North America; their colors are often brilliant, and sometimes, from the harmony in their colora- tion with that of the flowers in which they hide, or the leaves on which they ae Tesh lade uhe Fig. 816.—Embryo Spider, still grasp of insectivorous birds. more advanced. This and Fig. 815 In their instincts and reasoning “"@* “lparede. power, spiders are quite on a level with the insects, as proved by their nest- and web-constructing abilities. 344 ZOOLOGY. Cuass VI.—INSECTA. General Character of Insects.—The triregional division of the body is better marked in the genuine winged insects than in the Myriopods and spiders. ‘They usually have com- ‘pound as well as simple eyes; usually two pairs of wings; three pairs of thoracic legs; often a pair of jointed abdomi- nal appendages, besides an ovipositor or sting which mor- phologically represents three pairs of abdominal legs. Order 1. Thysanura.—The spring-tails (Podura) and bristle-tails (Zepisma) represent this group. They are wing- less, with some affinities to the Myriopods; and the typical form: Campodea (Fig. 319) is regarded as the ancestral form of the six-footed insects, as it is a generalized type, and forms like it may have been the earliest insects to appear. In Podura, the spring-tail, and also in Smynthurus (Smynthurus quadrisignatus ‘Pack., Fig. 317), the characteristic organ is a forked abdominal appendage or ‘‘spring,” held in place by a hook; when released the spring darts backward, sending the insect Fig. 317.—Smyn- 4. , © s jiuria. 2 apriue high in the air. il. Enlarged. : ee Haare Our commonest Poduran is Tomocerus plumbeus Linn. (Fig. 318), found all over the northern hemisphere, in North America and Europe. The snow-flea, Achorutes nivicola Fitch, is blue-black, and is often seen leaping about on the snow in forests. The Podurans belong to the suborder Collemdola; the higher forms, which bear a greater resemblance to the larve of Neuropterous insects and to the young cockroach, are the Cinura, to which belong the genera Campodea (Fig. 319), Lepisma, and Machilis. In the group Cinwra there is no spring, but the tail ends in two or three bristles; and in Machilis, the highest form, there are compound eyes. In all there are jointed abdominal appendages, which structures are unique among Hexapodous insects. Campodea staphylinus (Fig. 319) is a small white DERMAPTERA AND ORTHOPTERA. 345 slender form, with long, many-jointed antenne, and two long, slender, jointed caudal ap- pendages. It lives under stones, and C. Cookei lives in Mammoth Cave. Order 2. Dermaptera. — The earwigs (Forficula) have a flat Fig. 318.—A Poduran (Tomocerus) and its scales. Much enlarged. body, ending in a forceps; while the < fore-wings are small, the large hind- %* wings being folded under them. Order 3. Orthoptera.—The insects of this group, so called from the straight-edged fore-wings of the grass- hoppers, locusts, crickets, etc., are characterized by their net- veined wings and incomplete metamorphosis. Organs of hearing may be situated: either on the fore-legs, as in the green grasshoppers, katydids, or at the base of the abdomen, as in the locusts. Most Orthoptera have a large ovi- positor, by which they burrow in the earth or into soft wood, and deposit their eggs singly or in masses. Mantis . (Fig. 320) lays its eggs in a cocoon- Fig. 319.—Campodea. a, like mass. mandibles; b, maxilla. Many Orthoptera, as the crickets, green grasshoppers, 346 ZOOLOGY. katydids, etc., and iocusts, produce loud, shrill sounds, which are sexual calls. They stridulate in three ways—i.e., first, by rubbing the base of one wing-cover on the other (crickets and green grasshoppers); second, by rubbing the inner surface of the hind legs aguinst the outer surface of the front wings (some locusts); third, by rubbing together the upper surface of the front edge of the hind wings and Fig. 320.—An African Mantis, or soothsayer, with its egg-mass.—From Mon- teiro’s Angola. the under surface’ of the wing-covers during flight (some locusts). Order 4. Platyptera.—This group comprises the bird- lice, Psocide, Perlide, and white ants (Zermitide). The body is flattened, the head horizontal. The pronotum is usually large, broad, and square. The bird-lice (Maillophaga) are more nearly related to the wingless Psocide, such as the death-tick (Atropos) than to the Hemiptera, among which they are usually placed, since their free jaws and mouth- parts generally ure like those of the Psocide. They prob- WHITE ANTS. 347 ably form a suborder of Platyptera. In the larval and pupal Perla (Fig. 321), tufts of gills are situated on the under side of the prothorax, and in the adult winged Péeronarcys these gills are ° retained. The white ants top the Platypterous series; they live in stumps and fallen trees, and in the tropics do much harm by undermining the sills of houses, and destroying furniture, books, etc. The colonies are very large and populous. In our Zermes flavipes there are males and females, workers and soldiers; the workers being small, ant-like, with small round heads, while the soldiers have = c Fig. 321.—Perla, larva. a Fig. 322.Pupa of a Drag- Fig. 323.—Agrion, natural size, and a, its on-fly (Eschna). larval gill, much enlarged. large square heads, with long jaws; the pups are active. Fritz Miller found in Brazil that one species of, Termes was differentiated into six different kinds of individuals: viz., a set of winged and wingless females; winged and wingless males; workers and soldiers. A male always lives with a female, and a wingless male and female may, on the death of a winged normal male and female, replace them. He 348 ZOOLOGY. found a male (king) living with thirty-one complemental females. Order 5. Odonata.—Here belong the dragon-flies, in which the prothorax is remarkably small, the thorax nota- ble for the great development of the side-pieces, the dorsal pieces being rudimentary. The wings of both pairs are large, of nearly equal size, and finely net-veined. The larve are all aquatic, some of them having gills (Fig. 323, a) at the end of the ‘body. Order 6. Plectoptera.—The May-flies have rudimentary mouth-parts; while the hind-wings are small, sometimes wanting, and the hind-body ends in three long filaments. The larve are aquatic and breathe by gills De on the sides \ of the hind-body. 4 MH \,S Fig. 824.—May-fly and Jarva, the latter enlarged. Fig. 325.—Thrips. Order 7. Thysanoptera.—This group is represented by Thrips, and belongs nearer to the Hemiptera than any other order. The mouth-parts are united to form a short conical “ sucker. The mandibles are bristle-like, bulbous at the base, and situated inside of the maxille, which are flat, triangular, with palpi shorter than those of the labium. ‘The wings are narrow and fringed, sometimes wanting; the pronotum is large, and the two-jointed feet are swollen at the ends, being without claws. The metamorphosis is incomplete; the pupa is active, its limbs and wings encased by a membrane, and the antenna are turned back on the head. Order 8. Hemiptera.—Insects of this group are called HEMIPTERA. 349 bugs. They all have sucking mouth-parts, the mandibles and first maxille being bristle-like, and ensheathed by the labium or second maxille. Their metamor- phoses are incomplete, the larva being like the adult, except that the wings are absent. Many bugs secrete a disagreeable fluid from glands seated in the metathorax. The lice are low, wingless parasitic Hemiptera. The squash-bug (Fig. 826, Coreus tristis) and chinch-bug (Blissus leucopterus Uhler) are types of the order. ee mee While most insects live but a year or two, or three at the most, the seventeen-year locust (Cicada sep- temdecim Linn., Fig. 327) lives over sixteen years as a lar Vas ~ Fig. 327.—Seventeen-year Locust. a, b, pupa; d, incisions for eggs.—After Riley. finishing its transformations on the seventeenth; there is also, according to Miley, a thirteen-year variety of this species. The froth insect (Piyelus lineatus) abounds on grass in early summer. The cochineal insect (Coccus cacti) belongs to the Coccide, or bark-lice; the dried female is used as a dyestuff, and abounds in Central America. 350 ZOOLOGY. The plant-louse (Fig. 330, Aphis mali Fabr.) is provided with two tubes on the hind-body from which honey-dew drops, which attracts ants, wasps, etc. In summer the gee Fig. 829.—Apple Aphis. et size and size and enlarged. enlarged. plant-lice reproduce asexually, and as there may be nine or ten generations, one virgin aphis may become the parent of millions of children and grandchildren. Order 9. Neuroptera—We now come to insects with a complete metamorphosis. All the foregoing orders are \ 999% 9 ametabolous, the species passing through an incom- "Pink. plete metamorphosis, the Fig. 30.—Chrysopw aud group of stalkea /arvee resembling the adult. eges. S This order is now restricted to those net-veined insects with a complete metamorphosis, the mouth-parts free, adapted for biting, with the ligula entire and large, broad, flat, and rounded, while the pro- thorax is large, broad, and square. The group comprises the Sialide (Corydalus) and the Hemerodiide (Chrysopa, Mantispa, Rhaphidia, and Hemerobius). Order 10. Mecaptera.—The scorpion-flies are represented by a single family (Panorpide), with the typical genera Panorpa and the wingless Boreus. ‘They are net-veined insects, but differ from the Newropéera in the caterpillar- like larve and in the imagines having a minute rudimentary ligula, the head being elongated, with minute mandibles atthe end of the snout. The maxille are long, and connate with the labium. Order 11. Trichoptera.—The group of caddis-flies, whose MECAPTERA., 351 ® cylindrical larve are called case-worms, differ from the Neuroptera in features which ally them to the Lepidoptera. The mandibles are obsolete, but well developed in the larva Fig. 331_—Mantispa interrupta _ Fig. 332.—Fresh- Fig. 332a.—Larva of the , Sav; and side view of the saire ly hatchedlarvaof same, but older, before the without wings. Natural size— Mantispa styria- first moult. Enlarged.— Emerton del. ca, Enlarged. After Brauer. Fig. 233.—Panorpa. Fig. 3341.—Case-worm; a, its case. and pupa; the maxilla are connate with the labium, while the palpi of both pair are well developed. The general proportions of the head and body and of the legs are much as in the Tineid moths. 352 ZOOLOGY. ‘Order 12. Coleoptera.—The beetles form a homogeneous and easily circumscribed group, all having the fore-wings thickened, not used in flight, and forming sheaths (elytra Fig. 335 —Pine weevil. a, larva; b, pupa. or wing-covers) for the hinder pair. The mouth-parts are free and adapted for biting. The metamorphosis is com- plete. The young or larve of beetles are called grubs. Examples of beetles and their transformations are the pine ‘Fig. 336 —June Beetle and its transformation=, 1, pupa; 2, larva.—After Riley. weevil (Fig. 335, Prssodes strobt Peck) and the June beetle (Fig. 336, Lachnosterna fusca Frohl.). The oil beetle is remarkable for passing through three larval stages (Fig. OIL BEETLE. 353 337, Meloé angusticollis Say), the first larva being minute and parasitic on bees, sucking their blood, while in the Fig. 337.—Oil Beetle. a, firstlarva; }, second larva; c, third larva; d, pupa. _ second and third stages it feeds on the pollen mass designed for the young bees. Fig. 338.—Stylops children, male, dorsal and side view. Much enlarged The blister beetles (Lytta marginata) undergo a similar series of transformations called a hypermetamorphosis. « 354 ZOOLOGY. The most aberrant of beetles is Stylops (Figs. 338 and 339, S. childreni Westwood), the male of which has minute fore SS Fig. 339.—Stylops childreni, female. Fig. 340.—Astraptor illwminator, larva, 2, parasitic in the abdomen of a bee; b, top view of the same. Much en- larged. ae oO Se Fig. 342.—The early stages of the common House-fly. A, dorsal and side view of the larva; a, air-tubes; sp, spiracle. C, the epiracle enlarged. 7, head of the same larva, enlarged ; dd, labrum (7); md, mandibles; ma, maxille ; at, antenne. Fa peu spiracle much enlarged. D, puparium; sp, spiracle, All the figures much enlarged. wings. The female is wingless, grub-like, imperfectly de- veloped, and is viviparous, the young issuing from her body THE HOUSE-FLY. 355 in all directions. A few beetles are phosphorescent. Such are the fire-flies, the cucuyo of the West Indies, the glow- worm, and certain grubs, such as Astraptor illuminator (Fig. 340), Melanactes, and the young of a snapping beetle. Fig. 343.—Bot-fly of the ox and its larva. Order 13. Stphonaptera.—The fleas (Fig. 341) are wing- less, with sucking mouth-parts; all the palpi four-jointed. Order 14. Diptera—The common house fly (Fig. 342) is a type of this division, all the members of which have but two wings, while the tongue is especially developed for lap- ping up liquids. ‘The common house- fly lives one day in the egg state, from five days to a week as a maggot, and from five to seven days in the pupa state. It breeds about stables. . The Tachina-fly is beneficial to man, from its parasitism in the bodies of caterpillars and other injurious insects. The bot-fly (Fig. 3438, Hypoderma bovis DeGeer) is closcly allied to the gave *44—Syrhus politus house-fly, but the maggot is much larger. The larval bot-fly of the horse lives in the stomach, that of the sheep in the frontal sinus. The Syrphus flies (Fig. 344, Syrphus politws Say) mimic wasps ; they are most useful in devouring aphides, while in 356 ZOOLOGY. h 4 Uy 4 iY, a 4 Va ae te He Ma li al a Yi y M 4 Yi i M4 14 Fig, 341,—Metamorphosis of Sarcopsylla penetrans, or jigger, which lives in the toe of the natives of tropical America, 1, egg; 2, embryo; 3, larva; 4, cocoon; 5, pupa; 6, fecundated female ; 7, the same on the third day from its entrance under the skin of its human host; 8, the same after several days’ residence in the skin of its host ; 9, fully grown female magnified four times ; 10, head of the came still more enlarged ; 11, the female before it has entered the skin of its host ; 12, the mouth-parts, much entered ; m, mandibles ; d, maxillary palpi ; wv, under-lip or Jabium,—After Karsten and Guyon. THE HESSIAN-FLY. 357 the larva state. They may be recognized as greenish maggots living among groups of plant- lice. In the two-winged gall- flies (Fig. 345, Cecidomyia destructor Say, or Hes- sian-fly) the body is small and slender, with long antenne. The crane-flies (Tipula) are large flies, standing near the head of the order, and, like the gall-fly, the chry- salis has free append- ages, there being no puparium or pupa-case, as in the lower flies. Lastly, we have the mos- quito (Figs. 346 and 347), whose larva is aquatic, and breathes by a process on the end of the body, containing a trachea. Order 15. Lepidoptera. — The butterflies and moths form a well-defined group, and are known by their scaly bodies (Fig. 348), the spiral maxille or tongue, rolled up between the two large labial palpi, and their usually broad wings. As the butterfly, the type of the order, has been described at some length, we will only enumerate some of the Fig. 345.—Hessian-fly. a, larva; b, pupa; c. incision in wheat stalk for larva. (Mag- nified).—After Fitch. Fig. 346.—A, larva; ec, its respiratory tube. B, pupa; d, respiratory tube; a, two paddles at the end of the hoy. Fig. 347,—Head and mouth parts of mos- quito. e, eye; a, antenne; lbr, labrum; h, hypopharynx; m, mandibles; mz, maxillee; map, maxillary palpus; 1b, jabium: c, cly peas. (Magnified.) 358 ZOOLOGY, typical forms. The lowest group are the plume-moths (Pterophorus), in which the wings are fissured. Above HALT yt H i Fig. 348.—Showing mode of ar- rangement of thescales on the wings of a Moth, b a Fig. 350.—Grain Moth, Tinea _granella. a, larva; 6, pupa, nat, size and enlarged ; ¢, grain of wheat held together by a web.—After Curtis. Fig. 351.—Army-worm Moth. a, male ; >, female; c,eye; @, male; e, portton of female antenna. Much magnified.—After Riley. them stand the clothes and grain moths (Figs. 349 and 350), which are minute moths with narrow wings. THE COTTON-WORM. : 359 The larger moths are represented by the canker-worm, the grass army-worm (Fig. 351), and the cotton army-worm (Fig. 352), so destructive to vegetation; the silk- worm moth (Bombyx mori Linn.), of the Old World, and the American silk-worm (TZélea Polyphemus Linn.). Certain species of the silk- worm family, called basket-worms (Gceticus), live in cases con- structed of short or long strips Fig. 352. Eee, caterpillar, and moth (Fig. 353. Our native species Of hth argillacea, the Cotton Army- jg Thyridopterys. ephemereefor- mis Haworth. The hawk-moths (Sphinx) are distinguished by their large size and very long tongue. The butterflies differ from the moths in having knobbed anten- nz, while the chrysalides are often ornamented with golden or silvery spots. Order 16. Hymenoptera.—The bees stand at the head of the insect series in perfection and specialization of parts, especially the organs of the mouth, and from the fact that in the course of the metamorphosis from the larva to the pupa the first ab- dominal segments hecome transferred to the thorax—a striking instance of the principle of transfer of parts headward. In the large head, spheri- cal thorax, and short, conical abdo- men, the bees are opposed to the dragon-flies and other Neuroptera, in which the abdomen is long, the pé;,' Worms. Natural size. thorax composed of three homogene- ous segments, and the mouth-parts only silapied for biting. In the bee there is a marked differentiation of the parts of ‘360- ZOOLOGY. the first and second maxille ; the tongue or fleshy prolonga- tion of the second maxille (/abiwm, see Fig. 354, gy) being very long and adapted for lapping up liquid food in the bottom of flowers. The Hymenoptera are represented by the saw-flies, the gall-flies, the ichneumon-flies and the ants, the sand-wasps, mud-wasps (Fig. 363), paper-making wasps, and bees. The lowest family is the Uroceride, or horn-tails (Fig. 355, larva of Tremex columba Linn.), whose fleshy white Fig. 854.—Side view of the front part of the head of the Humble Bee. a, clypeus covered with hairs; 06, labrum; c, the fleshy epipharynx partially concealed by the base of the mandibles (ad); é, lacinia or blade of the maxille, with their two-jointed palpi (/) at the base ; j, the:Jabium to which is appended the ligula (¢g) ; below are the labial palpi; 2, the two basal joints ; %, compound eyes, larve bore in trees. The adults are large, with a long, saw- like ovipositor. In the saw-flies (Tenthredinide, Fig. 356, the pear-slug, Selandria cerasi Peck) the larva strongly re- sembles a caterpillar, having eight pairs of abdominal feet. The gall-flies (Fig. 857, Cynips) are small Hymenoptera which lay eggs in the leaves or stems of the oak, etc., which, from the irritation set up by their presence, causes the de- formation termed a gall. HABITS OF ANTS. 861 The ichneumon-flies (Fig. 358) are very numerous in Bpe- cies and individuals ; by their ovipositor, often very long, they pierce the bodies of caterpillars, inserting several or many eggs into them ; the larve develop feeding only on the fatty tissues of their host, but this usually causes the death of the caterpillar before its transformation. Certain minute species, with veinless wings (Fig. 359, Platygaster), of the canker-worm eggs, are egg-parasites, Ovipositing in the eggs of butterflies, dragon-flies, etc. Fig. 355. —Horn- tail : larvaof 7re- mexcolumba, Nat. Fig. 358,—An Ichneumon-fly, size. Fig. 356.—Pear Slug, — YG natural size, gnawing leaves. a, larva en- Fig. 359.—Egg parasite of Canker. larged ; 2, the fly. worm, Highly magnified. ‘The family of ants is remarkable for the differentiation of the species and the consequent complexity of the colony, the division of labor and the reasoning powers manifested by the workers and soldiers, which, with the males and females, constitute the ant-colony. . Certain ants enslave other species; have herds of cattle, the aphides ; build complicated nests or formicaries (Fig. 361), tunnel broad rivers, lay up seeds for use in the winter- 362 ZOOLOGY. time, are patterns of industry, and exhibit a readiness in overcoming extraordinary emergencies, which show that Fig. 860.—CEcodoma, or Leaf-cutter Ant of Nicaragua.—After Belt. they have sufficient reasoning powers to meet the exigencies of their life ; their ordinary acts being instinctive—namely, Fig. 361.—Diagram of an ant’s nest (Ecodoma), the chambers below containing the ant food.—After Belt. the results of inherited habits. The leaf-cutter ants of Central and South America (Fig. 360) are famous from MUD-WASPS. — 363 their leaf-cutting habits ; the soldiers have large triangular heads, while the workers have much smaller rounded heads. Fig. 362 represents a species of Hciton. Fig. 362,—Eciton. Fig. 363.—Mud-dauber. The mud-daubers (Pelopeus, Fig. 363) build their nests against stone walls, of pellets of mud, while the sand- and mud-wasps dig deep holes (Fig. 364, Sphex ichneuwmonea Fig. 364.—Sand-wasp (Sphex). Natural size. Linn.) in gravelly walks, and have the instinct to sting grasshoppers in one of the thoracic ganglia, thus paralyzing the victim, in which the wasp lays her eggs; the young 364 ZOOLOGY, hatching, feed upon the: living but paralyzed grasshoppers, ‘the store of living food not being exhausted until the larval wasp is ready to stop eating and finish its transformations. The genuine paper-making wasps are numerous in species; here the workers are winged, and only differ from the females or queens in being rather smaller and with unde- veloped ovaries. The series of genera from Odynerus, which builds. cells of mud, and in “which there are no workers, up to those which have work- ers and build paper cells, such as Polistes, is quite continu- ous. The genuine paper- making wasps, such as Vespa, build several tiers of cells, ar- ranged mouth downward, and enveloped by a wall of several thicknesses of paper. In the Vespe, the females found the colony, and raise a brood of workers, which early in the summer assist the queen in completing the nest. The bees also present a gradual series from _ those which are solitary, living in holes in the earth, like the ants (Fig. 365, nest of a sot tn Yi, oo uly by “Yd ‘Uli “Maine “shee ‘yy, ty 4p my “Ws CLASSIPIVLATION OF INSECTS. 365 pollen in some subterranean mouse-nest or in a stump, and the young hatching, gradually eat the pollen, and when it is exhausted and they are fully fed, they spin an oval cylin- drical cocoon ; the first brood are workers, the second males and females. ‘The partly hexagonal cells of the stingless bees of the tropics (Melipona) are built by the bees, while the hexagonal cells of the honey-bee are made by the bees from wax secreted by minute subcutaneous glands in the abdomen. Though the cells are hexagonal, they are not built with mathematical exactitude, the sides not always being of the same length and thickness. The cells made for the young or larval drones are larger than those of the workers, and the single queen cell is large and irregularly slipper-shaped. Drone eggs are supposed by Dzierzon and Siebold not to be fertilized, and that the queen bee is the only animal which can produce either sex at will. Certain worker-eggs have been known to transform into queen bees. On the other hand, worker-bees may lay drone eggs. The maximum longevity of a worker is eight months, while some queens have been known to live five years. The latter will often, under favorable circum- stances, lay from 2000 to 3000 eggs aday. The first brood of workers live about six weeks in summer, and are suc- ceeded by a second brood. Cuass VI.—_INSECTA. A distinct head, thorax, and abdomen, breathing by trachee; winged; usually with a metamorphosis, which is either incomplete or complete. Serres I. Ametabola, or with an incomplete metamorphosis. Order 1. Thysanura.—Wingless, minute, with a spring; or ab- domen ending in a pair of caudal stylets; usually no com- pound eyes; no metamorphosis (Podura, Campodea, Lepis- ma). Order 2. Dermaptera.—Body flat; the abdomen ending in a for- ceps; fore-wings small, elytra-like; hind-wings ample, folded under the first pair (Forficula). 366 ZOOLOGY. Order 8. Orthoptera.—Wings net-veined; fore-wings narrow, straight, not often used in flight; metamorphosis incom- plete; pupa active (Caloptenus, Locusta, Phaneroptera, Acheta). Order 4. Platyptera.—Body usually flattened; pronotum usually Jarge and square; often wingless (Mallophaga or bird-lice, Perla, Psocus, white ants). Order 5. Odonata.—Prothorax small; thorax spherical; both pairs of wings of nearly the same size, net-veined. Larva and pupa aquatic; labium forming a large mask (Agrion, Libel- lula). Order 6. Plectoptera.—Mouth-parts nearly obsolete; wings net- veined, hinder pair small, sometimes wanting; abdomen ending in three filaments. Larve aquatic, with large jaws, and with gills on the side of the hind body (Ephemera). Order . Thysanoptera.—Mouthb-parts forming a short conical sucker; palpi present; wings narrow, fringed; abdomen end- ing in a long ovipositor (Thrips). Order 8. Hemiptera.—Mouth-parts forming a sucking beak; pro- thorax usually large; fore-wings often thickened at base; pupa active (Coreus, Arma, Pentatoma, Cicada, Coccus, Aphis). Series II. Metabola, or with a complete metamorphosis. Order 9. Neuroptera.—Wings net-veined; mouth-parts free, adapted for biting; ligula large, rounded; prothorax large, square. lLarve often aquatic (Corydalus, Chrysopa, Myr- meleon) Order 10. Mecaptera.—Wings somewhat net-veined, or absent. Larvee like caterpillars (Panorpa, Boreus). Order 11. Trichoptera.—Wings and body like those of moths; mandibles obsolete in imago. Larve usually aquatic, liv- ing in cases (Phryganea). Order 12. Coleoptera.—Fore-wings thick, ensheathing the hinder pair, which are alone used in flight; mouth-parts free, adapted for biting; metamorphosis complete (Doryphora, Clytus, Lucanus, Harpalus, Cicindela). Order 18. Siphonaptera. — Wingless; mouth-parts adapted for sucking. Larva maggot-like, but with a well-developed head and mouth-parts (Pulex). Order 14. Déptera.—But one pair of wings; mouth-parts adapted for lapping and sucking; a complete metamorphosis (Musca, Gistrus, Syrphus, Cecidomyia, Tipula, Culex). CLASSIFICATION OF INSECTS. 367 Order 15. Lepidoptera.—Body and wings covered with scales; maxille lengthened into a very long tongue; larve (cater- pillars) with abdominal legs (Tinea, Geometra, Noctua, Bombyx, Sphinx, Papilio). Order 16. Hymenoptera.—Wings clear, with few veins; mouth- parts with a variety of functions, 7.¢., biting, lapping liquids, etc. In the higher families the thorax consists of four segments, the first abdominal segment of the larva being transferred to the thorax in the pupa and imago. Metamorphosis complete (Tenthredo, Cynips, Ichneumon, Sphex, Vespa, Apis). TABULAR VIEW OF THE SIXTEEN ORDERS OF INSECTA. Hymenoptera. Lepidoptera, s iS 3 oo Boge a § §§ s > 3 a, & . 8 i ss £& § 5 s & & 3 ‘ [72 Ff § Ss €& § 3 he Ss 8 * S§ §S 8 E 8g | Ss SF 8 § = Ss —O a | | S$ & a oe | et ! | | Metabola | Ametabola. Thysanura. (Campodea.) Laboratory Work.—In dissecting Myriopods, spiders, and insects, the dorsal portion of the integument should be carefully removed with fine scissors, leaving the hypodermis untouched; this should then be raised, disclosing the delicate heart or dorsal vessel. The alimentary canal will be found passing through the middle of the body; it should be laid open with the scissors, or, better, a hardened alcoholic specimen can readily be cut in two longitudinally, and if the section is true, the cesophagus and crop—for example, of a locust—can be laid open, and 368 ZOOLOGY. the rows of teeth examined. The thoracic and abdominal portions of the nervous system, which lies loosely on the floor of the body, can be readily found by raising the alimentary canal; but the brain and infra- esophageal ganglia can best be detected by a longitudinal section of the head. The ovaries always lie above the intestine, and the two oviducts unite below the nervous cord to form the common duct which opens on the ventral side of the third segment in front of the anus, which is situated dorsally. Insects should be dissected in a shallow pan lined with wax or cork, and the parts floated out ; fresh specimens are desirable. The body may also be dissected, each segment with its appendages being separated and glued in their true sequence to a card. By simply dissecting an insect in this way, the student will acquire a valuable knowledge of the external structure of insects. Dragon-fly (Diplax Elisa). CHAPTER VIII. BRANCH VIII—VERTEBRATA. General Characters of Vertebrates.— The fundamental characters of the Vertebrates are the possession of a segmented vertebral column, enclosing a nervous cord, and a skull which contains a genuine brain; yet these features, though common to most Vertebrates, are wanting in the lancelet (Amphiozus) and in a degree in the hag-fish, and even the lamprey ; but the essential character is the division of the body-cavity by the notochord (in the lancelet, etc.), or by the back-bone of higher Vertebrates into two sub- ordinate cavities, the upper (neural) containing the nervous cord, and the lower (enteric) the digestive canal and its ap- pendages and the heart. These are the only characters which will apply to every known Vertebrate animal (compare p. 206 with Figs. 366, 370, and 371). In general, however, the Vertebrates are distinguished from the members of the other branches by the following characters: they are bilaterally symmetrical animals, with a dorsal and ventral surface, a head connected by a neck with the trunk; with two eyes and two ears, and two nasal open- ings, always occupying the same relative position in the head ; an internal cartilaginous or bony, segmented skeleton, con- sisting of vertebre, from the bodies of which are sent off dorsal processes which unite to form a cavity for a spinal cord, the latter sending off spinal nerves in pairs * correspond- ing to the segmentations (vertebre) of the spinal column. * Except in Amphioxus, in which the spinal nerves arise right and left alternately. 370 ZOOLOGY. From the underside of the vertebre are sent off processes articulating with the ribs, which enclose the digestive and central circulatory organs. There is a skull formed by a con- tinuation of the vertebral column, enclosing a genuine brain, consisting of several pairs of ganglia. To the vertebral col- umn are appended two pairs of limbs, supported by rays ir- regularly repeated, or a series of bones of a definite number, Ve 7am Fig. 346.—Transverse section of a worm, of Amphioxus, and of a Vertebrate con- trasted. a, outer or skin layer; 5, dermal connective layer; c, muscles; d, seg- mental organ: 4, arterial, and é, venous blood-vessel ; g. intestine ; /, notockord.— After Haeckel. attached to the vertebral column by a series of bones called respectively the shoulder and pelvic girdle. It will be observed that the fact of segmentation, so prom- inent a feature in the Worms and Arthropods, survives, or at least reappears in a marked degree in the Vertebrates, as , seen not only in the vertebral column, but in the arrangement of the spinal nerves. It is perceived also in the arrangement of the muscles into masses corresponding to the vertebrae ; and in the segmental organs or tubes forming the kidneys of the sharks and rays, while segmentation is especially marked in the disposition of the primitive vertebre of the early em- bryos of all Vertebrates. The digestive canal consists of a mouth with lips or jaws, armed with teeth, a pharynx leading to the Jungs ; an cesoph- agus and thyroid gland ; sometimes a crop (ingluvies), often a fore-stomach (proventriculus) ; a stomach and intestine, cloaca and vent. Into the beginning of the intestine passes a duct leading from a large liver; a gall-bladder, usually a pancreas, and aspleen, also communicating with the intestine. The products of digestion do not all pass through the walls of the stomach and directly enter the circulation, as in the invertebrates, but there is a system of intermediate vessels NERVOUS SYSTEM OF VERTEBRATES. 371 called the lacteal system or absorbents, which take up a part of the chyle from the digestive organs and convey it to the blood-vessels, There is a true heart, with one, generally two, auricles, and one or two ventricles with thick, muscular walls, and besides arteries and veins, a capillary system, 7. e., minute vessels connecting the ends of the smaller arteries with the smaller veins. There are no genuine capillaries in the lower animals exactly comparable with those of the Vertebrates. The blood is red in all the Vertebrates except the lancelet, and contains two sorts of corpuscles, the white corpuscles like the blood-corpuscles of invertebrates, and red corpuscles not found in invertebrates, and which are said by some authors to be derived from the white corpuscles. While fishes and larval Amphibians breathe by gills, all land and amphibious Vertebrates breathe the air directly by means of cellular sacs called lungs, and connected by a trachea with the pharynx, the trachea being situated beneath the cesopha- gus, and the opening from the mouth into the pharynx lead- ing into the trachea being placed below the throat or passage to the esophagus. The air filling the cells or cavities of the lungs passes by osmose through the walls of the cells into the blood sent by the heart through the pulmonary artery, and after being oxygenated, the blood returns by the pulmonary vein to the heart. On the other hand, carbonic acid passes from the blood out of the lungs through the trachea. The nervous system of Vertebrates consists of a brain and spinal cord. The brain consists of four pairs of lobes, 2%. ¢., the olfactory lobes, cerebral hemispheres, the optic thalami (Thalamencephalon) and pineal gland, and the optic lobes; and two single divisions : the cerebellum and the beginning of the spinal cord, called the medulla oblongata. The olfactory lobes are the most anterior, and send off the nerves of smell to the nose. The cerebral hemispheres in the fishes and amphibians are little larger than the adjoining lobes, but in the reptiles become larger, until in the mammals, and especially in the apes and man, they fill the greater part of the brain-box and overlap the cerebellum ; the latter, in the mammals, also exceeding all the other lobes in size, excepting the cerebrum. 372 ZOOLOGY. Attached to a downward prolongation (infundibulum) of the optic thalami is the curious pituitary body. The medulla sends nerves to the skin and muscles, giving sensibility and motion to the face, eyes and nose, to the larynx and sensitive portion of the lungs; a pair also is sent to the lungs and heart. If the spinal marrow is severed, the parts below are paralyzed ; if the medulla is cut or broken up mammals die at once, while the lower Vertebrata die sooner or later. The brain in an embryo originally consists of three vesi- cles or primitive lobes; and the correspondence between Fig, 367.—Diagrammatic, longitudinal and vertical section of a Vertebrate brain. Mb, mid brain; what lies in front of this is the fore brain, and what lies behind, the hind brain. JZ, iamina terminalis; Olf, olfactory lobes; Hmp, cerebral hemi- spheres; 7h EF, thalamencephalon; Pn, pineal gland ; Py, pituitary body; FW, fo- ramen of Munro; CS, corpus striatum ; 7h, optic thalamus; CQ, corpora quadri- gemina; CO, cruracerebri; Cd, cerebellum ; fy pons varolii; 270, medulla oblon- gata; J, ee IT, optici ; ZZZ, point of exit from the brain of the Motores oculorum ; JV, of the pathetici ; VJ, of the abducentes ; V—XZI, origin of the other cerebral nerves ; 1, olfactory ventricle ; 2, lateral ventricle ; 3, third ventricle; 4, fourth ventricle.—After Huxley, the three primitive lobes, called respectively the fore, mid, and hind brain, may be seen by the following table : TABULAR VIEW OF THE SUBDIVISIONS OF THE VERTEBRATE BRAIN Olfactory lobes or ganglia, with their ventricles (rhinen- cephalon). Cerebrum or cerebral lobes or hemispheres (with the two lateral or first and second ventricles, forming the prosencephalon or prothalami). Optic thalami, with the third ventricle and conarium above aud hypophysis (pituitary body) below (Thalamencephalon pineal gland). Fore brain. NERVOUS SYSTEM OF VERTEBRATES. 373 Optic lobes, corpora bigemina or quadrigemina (mesen- cephalon). Crura cerebri. Optic ventricle or Iter a tertio ad quartum ventriculum. Mid brain. Cerebellum (with its ventricle and the pons varolii, form- Hind brain. ing the metencephalon). Medulla oblongata and fourth ventricle. The accompanying sketches represent the typical nervous system of an amphibian, which also resembles that of many fishes, and even the lower Reptilia. The spinal cord (Fig. 368) usually extends through the whole length of the spinal canal, except in the toads and frogs, birds and many mammals, where it stops short of the end of its canal. In those Vertebrates with limbs, the cord enlarges where the nerves which supply them are sent off ; these are the cervical.or thoracic, and lumbar enlargements, especially large in turtles and birds. The white and gray substance of the brain continues in the cord. As the most essential characteristic of Vertebrates is the internal skeleton (endoskeleton) we will enter more into detail in describing it, and afterwards notice the external skeleton (exo- Fig. 368,—Brain and spinal skeleton). cord of the frog. A, from 7 above, B, from below. a, ol- In the embryos of higher Vertebrates qoote, Fateen pee ce tral and in the adult lancelet, hag-fish and hemispheres; c, optic lobes ; d, cerebellum in the form of a lamprey, the vertebral column is rep- lamella bridging over the : : ‘ fourth ventricle (8) ; mm, spinal resented by a rod-like axis (notochord cord; 4 tenniual corde After or chorda dorsalis) which is composed °°2°"™"™™ of indifferent, or only partly organized cells, the substance of the chord resembling cartilage. These chordal cells secrete a membrane called the chordal sheath. Thenotochord is not 374 ZOOLOGY. segmented. In all Vertebrates above the lamprey, the verte- bral column grows around the notochord, which finally Sy Fig, 369. Fie. 371. Fig. 369.—Transverse section through the spinal cord of a calf. a, anterior, 3, posterior longitudinal fissure ; c, central canal; @, anterior, e, posterior cornua; J, substantia gelatinosa; g, anterior column of the white substance ; /, lateral, 7, pos- terior column ; &, transverse commissures.—After Gegenbaur. Fig. 870.—Section through the vertebral column of Ammoccetes (lamprey). Ch, no- tochord; cs, chordal sheath ; m, spinal chord ; a, aorta; 2, veins. Fig. 371.—Section through the spinal column of a young salmon. Ch, notochord ; cs, chordal sheath; m, spel chord ; X, superior, X’, inferior arch (rudimentary) ; a, aorta; v, veins.—After Gegenbaur. forms the central portion of the bodies of the vertebra, and in the higher Vertebrates is wholly effaced ; the centra or LIMBS OF VERTEBRATES. 375 bodies of each vertebra of a lizard, bird or mammal being solid bone. Figs. 370 and 371 represent the relations of the notochord in an adult lamprey and a young fish. The vertebra of a bony fish or higher vertebrate consists of a body, with a dorsal or neural spine; a pair of odlique processes (zygapophyses) arching over and enclosing the spinal cord; and ¢ransverse processes, bending downwards, to which the ribs are articulated ; certain of the thoracic ribs uniting with the sternum or breast-bone Fig, 372.—Diagram of a Vertebra (Figs. 372 and 373). wath ae body (5), rib (), breast bone Vertebrex like those of fishes, Mot chitane preceseéa o£ gueveree which are hollow or concave at Poe ss® each end, are said to be amphicelous ; those hollow in front and convex behind procelous, as in most toads and frogs and crocodiles, and most existing lizards, and those convex in front and concave behind opisthocwlous, as in the garpike, some Amphib- jans (the salamanders and cer- tain toads, Pipa and Bombinator). sie are aula stata ot Vertebrates never have more buzzard (Buteo vulgaris). c, centrum than two pairs of limbs, an an- or body; s, superior spinvus pro- . : : cess; ¢7, transveree process; io, terior and hinder pair ; the pecto- rib; a, tuberculum of the rib; 3, ca- . pitulum of the rib.—After Gegen- ral pair of fins of fishes represent Daur. the fore limbs of Amphibians and higher Vertebrates, and the arms of man; the two ventral fins represent the hind legs of higher Vertebrates, and the legs of man. Each pair of limbs is connected by ligaments and muscles to a girdle or set of bones, called respectively the shoulder girdle and pelvic girdle, each girdle being con- nected by muscles to the vertebral column. The shoulder girdle consists of a clavicle (or collar-bone), scapula (or shoulder-blade), and coracotd bone, usually a process of the scapula. These bones differ greatly in the different classes, 376 * ZOOLOGY. and are reduced to cartilaginous pieces in sharks. The pelvic girdle, or pelvis, consists of three bones, 7.e., one dorsal, the ilium, and two ventral, the anterior of which is called pubis, and the posterior ischium. The limbs each consist of a single long bone, succeeded by two long bones, followed by two transverse rows of short wrist or ankle bones, and five series of long finger or toe bones, called phalanges. For example, in the fore limb of most Vertebrates, as in the arm of man, to the shoulder gir- dle, i.e., at the point of junction of the three bones com- posing it, is articulated the humerus ; this is succeeded by Fie. 374, Fia 3%, Fig. 374.—Sternum and shoulder girdle of Frog (Rana temporaria). p, body of the sternum ; sc, scapula; sc’, supra-scapula; co, coracoid bone, fused in the middle line with its fellow of the opposite side (s) ; al, clavicle ; e, epis- ternum. The extreme shaded double portion below pis the xiphisternum. The cartilaginous parts are shaded.—After Gegenbaur. Fig. 3875.—Fore-leg of a seal. S, scapula; 4, humerus; O, olecranon or tip of elbow; #, radius; U, ulna; Po, pollex, or thumb. : Fig. 876.—Pelvis or pelvic bones on one side of a marsu- pial eee 62, ilium; @, situated on the pubic bone (pubis) indicates the acetabulum or concavity for the artic- ulation of the head of the femur; 63, ‘echium, consolidated with the pubis. The three bones thus consolidated form the os innominatum ; m, marsupial bones ar- ticulated to the pubic bones.—After Owen. the ulna and radius, the carpals, the metacarpals, and the fin- ger-bones or phalanges, the single row of phalanges forming a digit (fmger or toe). To the point of union (acetabulum, Fig. 376, a) of the three pelvic bones is articulated the fe- mur, or thigh; this is succeeded by the ¢idia and fibula (shank-bones), the tarsal (ankle-bones) and metatarsal bones, and the phalanges or bones forming the digits (toes). Figs. 378-380 represent the simplest form of the posterior limbs in the higher Vertebrates, that of the bird showing an COMPOSITION Of THE SKULL. 377 extreme modification in form. At first all limbs arise as little pads, in which the skeletons subsequently develop, and in early life the limbs of all Vertebrates above the fishes are much alike, the mod- ifications taking place shortly before birth. Ac- cording to Gegenbaur and others, the limbs of Vertebrates have been probably derived from the pectoral and ventral fins of fishes in which the fin-rays are irrela- tively repeated. * In the fins of fishes there is a simple system of leverage ; in the limbs au of higher air-breathing Fig. 377.—a, skull; 4, vertebra; ¢, sacrum, 5 and é, its continuation (urostyle) ; f, euprascap- Vertebrates, formed by ula; 1, hnmerus; 2, fore-arm hones ; 4, wrist ir om- bones (carpals and metacarpals) ; d, ilium ; m. walking on land, a CORY thigh (femur) ; , leg bone (tibia, 0, elongated pound system of lever Bi pi of ae baais su) van Tx age (Wyman). The head of all Vertebrates above the lancelet is supported by a more or less perfect cartilaginous or bone framework, the skull (cranium), or brain-box (Fig. 381). It is a contin- aation of the vertebral column, and protects the brain, besides forming the support of the jaws, tongue-bone (hyoid bone), and branchial arches. The series of lateral (visceral or branchial) arches varies, but there may be nine ; the most anterior (if it be counted as the ‘first one, Fig. 382, a, b, c) is formed by what are called the labial carti- lages; next comes the mandibular arch (0, 2), which is suc- ceeded by the hyoid arch (II.) and the six branchial arches. in the embryos of all Vertebrates these visceral arches are * A modified form of this theory is advocated by Balfour and J. K. Thatcher, who attempt to show that the limbs with their girdles were derived from a series of similar simple parallel rays, and that they were originally a specialization of the continuous lateral folds or fins of embryo fishes, and probably homologous with the lateral folds of the adult lancelet (Amphioxus). 378 ZOOLOG ¥. well marked; of the slits or openings between them, the first is destined to form the mouth, the next pair of slits Fia. 378, Fia. 379. Fig. 380, Fig. 378.—Hind Jeg of a larval Salamander. The dotted lines are drawn through the rays to which the different.pieces belong. We, femur: 7, tibia; F, fibula; 4, ¢, ¢, 7, tarsal bones; é, os intermedium; ¢, tibiale; /, fibulare; c, centrale; 1-5, the five tarsals. The first row of phalanges are called metatarsals (in the hand, meta- carpals). ‘ig. 379.—Bones of the foot of a Reptile (lizard) A, and an embryo bird, B. J, fe- mur ; ¢, tibia; 7, fibula; ¢s, upper, ¢2, lower pieces of the tarsus; m, metatarsus ; 1-J, metatarsalia of the toes. _ Fig. 380.—Leg of the Buzzard (Buteo vulgaris). a, femur; 0d, tibia; UY, fibula; ¢, tarso-metatarsiis ; c’, the same piece isolated, and seen from in front; dda’, ad”, a”, the four digits or toes.—After Gegenbaur. in the Amphibia and higher Vertebrates forms the ear-pass- age, while the other slits may remain open in fishes, form- COMPOSITION OF THE SKULL. 379 ing gill-slits or spiracles, but are closed in the higher Verte- brates. As a rule, the skull is symmetrical, exceptions being found in the flounders and the bones about the nose of cer- tends CA, yee mn SANS Fig, 381.-Skull of the Lion. 2, occipital condyle: 7, Parietal bone and sagittal crest ; 8, péroccivital ; 27”, squamosal bone ; 27, zygomatic arch ; 26, malar bone ; 11, frontal bone ; 12, post-orbital process ; 15, nasal bone; 21, maxillary bone ; 22, premaxillary bone ; 32, mandible ; 3, occipital crest ; c, canine teeth ; p?, second pre- molar ; ml, molar tooth.—After Owen. tain whales and porpoises. The base of the skull is perfo- rated for the exit of the nerves proceeding from the base of the brain, and the hinder bone (occiput) is perforated ( fora- men magnum) for the passage of the spinal cord from the medulla oblongata. It is probable that there is a general parallelism between the head of Insects and _ Vertebrates. While the head of Fig. 382.—Skul! and vi-ceral skeleton of a Selachian : ‘ (diagram). occ, eopual region; da, wall of the laby- winged insects, for rinth; eth, ethmoidal region ; 7, nasal pit; @, first, 4, ¢, : second labial cartilage ; 0, suverior, n, inferior portion example, consists of of the mandibular arch I.; IL, byoid arch; I20.- VI. + (1-6), branchial arches.—After Gegenbaur, a certain number of segments, homologous with those of the rest of the body, and with mouth-parts homologous with the limbs; so the skull is also segmented, and an expansion and continuation of the vertebral column. Gegenbaur even maintains that the various arches of the head are homologous with the limbs, 380 ZOOLOGY. On the other hand, while the brain of insects is a single pair of ganglia like those of. the rest of the body, the differ- ent. ganglia forming the brain of Vertebrates are concen- trated in the head alone; still the different pairs of nerves sent off from the base of the brain are homologous with the spinal nerves, sent off at intervals corresponding to each vertebra. There are two theories of the composition of the skull. That of Oken, Goethe, and of Owen, who believed that the skulls of the bony fishes and mammals were composed of three or four segments. It should be noticed that these views are based on an examination of highly specialized ver- tebrates. From a study, however, of the more generalized types of fishes (such as the sharks), and the embryos of ver- tebrates belonging to different groups, the old vertebrate theory of the skull has been discarded, and the view of Ge- genbaur, confirmed by Salensky, is probably nearly the cor- rect one. As stated by Gegenbaur: | 1. The skull is comparable to a portion of the vertebral column, which contains at least as many vertebral segments as there are branchial arches. This view is borne out by the following facts : a. The notochord, which forms the foundation of the vertebral column, passes through the cranium in the same way as it passes through the vertebral column. 6. All the nerves which pass out of the base of the skull (or that portion traversed by the notochord) are homologous with the spinal nerves. ce. The difference between the skull and vertebral col- umn consist of secondary adaptations to certain con- ditions, which are external tothe skull, and are. partly due to the development of a brain, 2. The skull may be divided into two regions, a vertebral ° portion and an anterior evertebral portion, lying beyond the end of the notochord. 3. The number of vertebrae which enter into the forma- tion of the skull are nine at least (according to Salensky, in the sturgeon, seven) ; the exact number is immaterial. TEETH OF VERTEBRATES. 381 In the fancelet there is no skull, or even the rudiments of one (unless the semi-cartilaginous supports of the tentacles be regarded as such), hence the Vertebrates are divided into the skulless or acraniate (Acrania, represented by the lance- let alone) and the skulled or craniate (Craniota), the latter series comprising all forms from the hag-fish to man. In the Craniota the skulls may be, according to Gegenbaur, di- vided into two groups. In the hag and lamprey the noto- chord is continued into the base of a small cartilaginous capsule, enclosing the brain, and which représents the skull of higher Vertebrates (Craniota). This capsule behind is continuous with the spinal column. With the skull of the second form two jaws are developed, hence all the vertebrates above the hag and lamprey form a series (Gnathostomata) opposed to the former, or Cyclos- tomata. In the Gnathostomata there is a gradual modification and perfection of the skull. In the sharks it may be quite sim- ple and cartilaginous ; in the bony fishes it is highly special- ized, consisting of a large number of separate bones. In ~ the Amphibians we first meet with askull consisting of few bones, easily comparable with those of mammals; in the reptiles and birds the ear-bones are external, forming the large quadrate-bone by which the lower jaw is articulated to the skull. A progress is seen in the mammals where the quadrate-bone becomes internal—one of the ear-bones (mal- leus). Now, also, the brain becoming much larger, evincing amuch higher grade of intellect, the skull is greatly en- larged to accommodate the great increase in size of the cerebrum and cerebellum, the perceptive and reasoning fac- ulties predominating over those regions of the brain and skull devoted to perceiving, grasping, and masticating the food. Though not properly forming part of the skeleton or de- veloped with it, we may here consider the teeth. The teeth of Vertebrates are formed from the modified epidermis and cutis, or dermis; the former secretes the enamel and the latter is changed into the pulp or dentine. The simplest form of tooth is conical. In the jawless hag there are no teeth in the lips, but a single median tooth on 382 ZOOLOGY. the palate and two rows of comb-like teeth on the tongue. In the lamprey the edges of the circular mouth are provided with circular rows of conical horny teeth. The teeth of higher Vertebrates are derived from the cells of the mucous membrane of the mouth, which is formed of connective tis- sue as well as epithelium. The teeth of fishes are developed not only in one or several rows in the lip, but may also arm the bony projections into the mouth-cavity of the palate, vomer and parasphenoid bones and the hyoid and bran- chial arches. In the Amphibia teeth survive on the palatine and vomerine bones, more rarely on the parasphenoid ; among the reptiles, the snakes and lizards alone have teeth on the palatine and pterygoid bones, while in the crocodiles and in mammals the teeth are confined to the maxillary bones. In the geckos, snakes and the crocodiles, as well as the mam- mals, the teeth are inserted in sockets (alveoli) of the jaw. (Gegenbaur.) In certain extinct birds (Odontornithes) there were teeth in the jaws, though all existing birds are toothless. It is said that rudimentary teeth were found by Geoffroy St. Hilaire in the jaws of a parrot. Blanchard afterwards found the germs of teeth there, though © they never come through. In the Mam- mals the teeth are dif- Fig. 383.—Teeth of the Tasmanian devil. The ferentiated into inci- incisors are situated in front of the large conical : canine teeth. 2, 3, premolars; m,1-4, four molar SOTS, Canines, premo- She Sn lars and molars (Fig. 383). In descriptive anatomy the teeth are for convenience expressed by a formula, the number of teeth of the upper jaws being placed like the numerator of a fraction, and those of the lower jaw like the denominator, the initials of the names of the teeth being placed before the figures, thus 2-2 4,3—3 + 72-2 wll, * the dental formula of man is ia Cc <7 ae ae SCALES, HAIRS, AND FEATHERS. 383 In the fishes, Amphibians and reptiles, the worn-out teeth are replaced by a succession of new ones ; in mammals (ex- cept cetaceans, where there is no change) there is but a single change, the first (milk) teeth being replaced by a second set of permanent teeth. The teeth of the lower Vertebrates are shed while swallowing the food. In the boa (Python) the tecth thus shed are found scattered along the intestinal canal and are discharged with the remnants of the food (Wyman). The dermal or exoskeleton consists of the scales of fishes, reptiles and certain mammals, such as the armadillo, the Fig. 884.—Vertical section through the skin of an embryonic shark. (, corium or dermis ; c,c, ¢, layers of the corium ; d, uppermost layer ; p, papilla; 2, epidermis ; é, its layer of columnar cells; 0, euamel layer.—After Gegenbaur. / feathers of birds and the hairs of mammals. Most scales arise from dermal papille (Fig. 384, p), and are covered over by a layer of enamel (Fig. 384, 0) developed from the epider- mis; so that the scales of sharks and rays, and turtles, arise from both the dermis and epidermis. A hair or feather is a modification of a scale; the papilla is sunken in a pit of the dermis, the conical cap of epi- dermis arising from it ultimately forming the hair or feather. The plates of turtles, the scales of snakes and lizards, and feathers of birds are epidermal. In the horns of mammals, as of the rhinoceros, and the hoofs of the horse, the epi- dermal substance is penetrated by numerous long dermal papille. 384 ZOOLOGY. The head of the sturgeon, garpike, and of other ganoid fishes, is protected by solid dermal bones, and the shells of turtles are dermal structures. The color of the skin of Vertebrates is due to pigment- granules situated either in the epidermis or dermis, and in the chameleon they are contained in special sacs (chromatophores) which are under the control of the nervous system. > The muscular system - of Vertebrates arises _ from the middle germ- layer (mesoderm), and Fig. 385.—Placoid scale of dog-fish (vertical sec- - dion masmbed). a, enamel layer b, dentine of the 1M the germ the muscles spine on the scale.—After Owen. in part arise from the primary segments indicated by the protovertebre, while in the adults of fishes and certain salamanders, the muscular system is distinctly segmented, corresponding to the seg- mentation of the ver- tebral. column, the : four lateral trunk- Z 5 ———e muscles being divided i = i : ce into a number of seg- LTT ee ments by tendinous 5 bands, which corre- spond in number to the vertebres (Gegen- | baur). The eye in Verte- brates in its develop- mentalhistory belongs to a different type of structure from that of ea any invertebrates, un Fig. 386.—Cyloid scale of roach, magnified, seen in less it be the larva] Section, 4, and from the surface, B.—After Owen. Ascidians, for in both types the eye is said by Gegenbaur not to be directly developed from the ectoderm, but from the EYES AND EARS OF VERTEBRATES. 385 anterior portion of the central nervous system. The differ- ence between the highly-developed eye of a cuttle-fish and a bony fish, for example, consists in the fact that the rods and cones (similar to those of the invertebrate eye) forming a layer (the bacillar layer) behind the retina, are in the ver- tebrate eye turned away from, while in the invertebrates they are directed toward the opening of the eye. The ear of Vertebrates is at first a primitive otocyst, or ear-vesicle, which is gradually cut off and enclosed, forming a cavity of the skull. As we rise towards the mammals, the ear becomes more and more developed until the inner, middle, and outer ear is formed ; the Eustachian tube being a modification of the first branchial cleft, forming the spiracle in the sharks (Selachii) and Ganoids. In the lancelet a head is scarcely more set apart from the rest of the body than in many invertebrates. In the fishes and Amphibians the head is not separated by a neck from the trunk ; in reptiles the neck begins to mark off a head from the thorax, while in the birds and mammals the head is clearly demarked, the degrees of cephalization and trans- fer headward of those features subordinate to the intellec- tual wants of the animal becoming more striking as we ascend through the mammalian series to the apes, and finally man. The development of Vertebrates can scarcely be epitomized in a few lines. The mode of growth of Amphioxus is a general expression for that of all Vertebrates, for all develop from fertilized eggs, which undergo total or partial segmen- tation of the yolk, become three-layered sacs and assume the pecuhar vertebrate characters, the development of the mam- mals differing from that of the other classes only in compar- atively unimportant features. The Vertebrates or Chordata are divided into three series or sub-branches: the Urochordata, the Acrania, and Crant- ota. The Urochordata are represented by the class Z21- cata. The sub-branch Craniota is divided into six classes, the Marsipobranchs, fishes, amphibians, reptilia, birds, and mammals. . 386 ZOOLOGY, Ciass I.—Tunicata (Ascidians, Sea Squirts). General Characters of Tunicates.—These animals were once regurded as mollusks, and in former editions of this book they were assigned a position among the worms, between the Brachiopods and the Nemertina. Recent advances in our knowledge of Ascidians on the one hand. and of the primitive features of the Vertebrates on the other, show quite conclusively that the Ascidians, par- ticularly the adult form Appendicularia, and the larve of those Ascidians which undergo a metamorphosis, have the fundamental characters of Amphioxus and the embryos of genuine Vertebrates, such as the lamprey. It will be remembered that these fundamental characters are the presence of a notocord, over which lies the central nervous system. No invertebrate is known to possess this dorsal position of the nervous system to the dorsal cord, unless we except Bulanoglossus, which, as Mr. Bateson hus shown, has a notocord lying under a central nervous cord. If the larva of this form was not like that of the worms and | Echinoderms, presenting no vertebrate features, we might adopt Bateson’s view that Balanoglossus should be placed at or near the base of the Vertebrate series, in a group Pro- tochordata. The result of admitting the Tunicates into the same branch or type as the Vertebrates has led to the proposal of a group Chordata, including the Tunicates and the genuine Vertebrates; but as Amphioxus seems to be a connecting- link between the Tunicates and the genuine Vertebrates, beginning with the hag-fish and the lamprey, we will, for convenience, retain the familiar word Vertebrata for all ani- mals having a notocord situated between a neural and an enteric cavity. Fig. 386° will show the close resemblance of the larval as- cidian to the embryo lamprey. It will be seen that even the larval Ascidian has an incipi- ent brain, consisting of two ganglia, from which arise a spinal nervous cord, with even spinal nerves. The intestine in the larval Ascidian is bent and ends in front, but in the adult tadpole-shaped Appendicularia the end of the intes- tine is ventral and opens directly outwards. POSITION OF THE ASCIDIANS. 387 While all Tunicates, except Appendicularia, are more or less degenerate, losing their vertebrate characters, in Appen- dicularia these are retained. The heart is situated ventrally, occupying nearly the same relation as in Fig. 386’, Accord- ing to Claus,* ‘‘the elongated cerebral ganglion is divided by constrictions into three parts; it is connected with a cili- ated pit and an otolithic vesicle, and is prolonged into a nerve-cord of considerable size. The latter is continued into the tail, at the base of which it swells out into a gan- glion; in its further course it forms several small ganglia, ed Bb Fig. 386?.—Diagram of larval Ascidian. Letteringas in Fig. A. m, mouth; 7. digestive tract; sp, spiracles in the pharyngeal portion: ht, heart; e, eye; er, ear; br, brain; nc, nervous cord; b/, b’’, mid-brain; cl, cerebellum; sj, spinal nerves; n, notocord; ol, nasal cavity; s, suckers (their homologues alsv occur in young garpikes and tadpoles). whence lateral n-rves pass out. In consequence of a torsion of the axis of the tail, the originally dorsally-placed caudal nerve comes to have a lateral position. The segmentation of the nerve-cord in the tail (as shown by the ganglionic swellings) corresponds to the segmental divisions of the muscles, which recall the myotomes of Amphioxus. The large chorda (nrochord), which extends along the whole length of the tail, constitutes another point of resemblance to Amphioxus.” * Text-book of Zoology, English translation, ii, p. 100. 388 ZOOLOGY. Oraer 1. Ascidiacea.—As an example of (Fig. 386’) Tuni- cates, we will now study the internal anatomy of Boltenia. On examining the test of this Ascidian, which is mounted on a long stalk, the oral or incurrené orifice is seen at the insertion of the stalk, and the atrial or excurrent orifice on the same side near the opposite end. On cutting open the thick test and throwing the flap over to the left, the deli- cate mantle or tunic is disclosed ; it extends a short distance into the stalk or peduncle This thin hyaline mantle is crossed. by two scts of narrow raised muscular bands ; the transverse fibres are arranged concentrically to the two ori- fices, so as to close or vpen them, the longitudinal ones curv- ing outward from the left side. Currents of sea-water laden with organic food pass into the oral orifice, which is surrounded by a circle of tentacles pointing inward, and thence into a capacious saccular bran- chial chamber within the mantle, which contracts at the bottom, where the csophageal opening is situated. The walls of this chamber, which is over an inch long in a good- sized specimen, and gathered into fringed folds, is sieve-like with ciliated perforations (compare Fig. 386’ e), making the walls like a lattice-work, the blood coursing through the ves sels passing between the meshes of the sieve-like waiis. The cesophagus, which lies at the bottom of this branchial chamber, is also situated near the intestine passing over the anal end into the short stomach. The intestine is long, passing up to the insertion of the stalk, where it is held in place by muscular threads extending into the stalk and attached to the mantle ; it then suddenly bends back and passes straight down to the vent, which opens opposite to the atrial orifice ; the end of the intestine is in part revolute and provided with a fringe of about twenty filaments. The liver forms a broad and flat mass of a bright livid green, and consists of three flat lobes each composed of eight or nine lobules, with very short ducts enveloping the inner aspect of the intestine. The ovaries are two yellowish, large and long lobulated masses extending nearly the whole length of the body, while the right one is a little smaller, and situated in the fold of the intestine. The atrium is that region of the STRUCTURE OF APPENDICULARIA., 389 body-cavity which lies between the end of the intestine and the atrial or excurrent orifice; into this atrial region the feces, eggs, etc., pass on their way to and out of the atrial orifice. The simplest form of Tunicate is Repaiacutabias which is tadpole-shaped, bearing a general resemblance to the larva of an ordinary Ascidian, so that it may be properly called a larval form. The Appendicularia isa pelagic animal, usually about one-half of an inch in length, found floating at or near the surface when the ocean is calm, and occurring in all seas a few miles from land or in mid-ocean. It swims by means of its large, long, broad, flat tail, the body being Fig. 3862.—Anatomy of Boltenia.—Drawn by J. 8. Kingsley from the author's dissections. oval or flask-shaped. In Appendicularia flabellum, as de- scribed by Huxley, the caudal appendage is three or four times as long as the body. The mouth leads into a large pharyngeal or branchial sac; a narrow cesophagus at the bottom of this sac leads to a spacious stomach, with two lobes, from the left one of which the intestine arises, curves and ends midway between the mouth and insertion of the tail. In the middle of the hemal side (that side in which the heart is situated and bearing the atrial opening) is a fold of the wall of the pharyngeal cavity called the endostyle On each side of this endostyle is an oval ciliated aperture 390 ZOOLOGY. corresponding to the numerous branchial slits in the other ee es FBP IOS oS z BZ EAS J re et Fig. 888, — Struc- ture of a compound Ascidian, Amare- cium. A, branchial sac ; m, stomach ; &, intestine ; c, mouth ; o/, testis ; rr’. effer- ent duct of the tes- tis; C, ovary; p’, egg in the bouy-cav- ity; p’, eggs in the atrium ; 7, anus; 0, shows the site of the heart; ¢, liver; e, openings in wal's of branchial chamber. —From Macalis er. Ascidians, but in Appendicularia each oral aperture leads into a funnel-shaped atrial canal, the open end of which terminates beside the rectum. The heart is a large pulsatile src situated between the two lobes of the stomach. The nervous system is much more fully developed than in other Tunicates, and is constructed on the Vertebrate type, consisting first of a ganglion situated below the mouth on the side opposite the atrial opening and opposite the anterior end of the endostyle. This nerve-centre throws off nerves to the sides of the mouth, and from it posteriorly extends a long cord past the esophagus to the base of the tail, thence it extends along one side of the axis of the tail (urochord), swelling at regular intervals into small ganglia, from which from two to five small nerves radiate. On the cephalic ganglion a round ear-vesicle is attached. Behind the posterior turn of the digestive canal is the testis and ovary, the Appendicularia being hermaphrodite, as Fol claims, though the ovary is developed later than the testis. The Appendicularia has no test, but secretes a fibrous envelope, which is at first gelatinous, loosely surround- ing the whole body, and allowing the creature the freest motion within its cavity. The general structure of an Ascidian may perhaps be more readily comprehended by a study of acompound Ascidian (Amarecium), which grows in white or flesh-colored masses on sea-weeds, etc. On removing an Ama- rectum from the mass and placing it under the microscope, its structure can be per- ceived. The body is long and slender, as seen in Fig. 386°. The mouth leads by the capacious bran- STRUCTURE OF ASCIDIANS. 391 chial sac (A) to the stomach, while the intestine (B) is flexed, - directed upwards, ending at the bottom of the atrium not. far from the atrial opening. The reproductive glands are situated behind or below the bend of the intestine, the eggs. being fertilized as they pass into the atrium, and the heart lies in the bottom of the body-cavity, being directly opposed to the nerve-ganglion (not represented in the figure), which lies between the two openings. In the perfectly transparent Perophora, which grows on the piles of wharves on the coast of Southern New England, one individual after another buds out (as also in Clavellina) from a common creeping stalk like a stolon. In this form the circulation of the blood-disks in the branchial vessels and the action of the heart can be studied by placing living ani- mals in glasses under the microscope. The heart is a straight tube, open at each end, and situated close to the hinder end of the branchial sac. After beating for a number of times, throwing the blood with its corpuscles in one direction, the beatings or contractions are regularly reversed and the blood forced in an opposite direction. Renal organs are apparently represented in Phallusia by a peculiar tissue, consisting of innumerable spherical sacs containing a yellow concretionary matter. In Molgula and Ascidia vitrea Van Beneden, an oval sac containing concre- tions of uric acid lies close to the ovary. In the forms already considered the plan of structure is complicated, owing to the difficulty of distinguishing an anterior or posterior, a dorsal or ventral aspect of the animal. In Salpa and Doliolum, however, the body is more or less barrel-shaped, the hoops of the barrel represented by the muscular bands which, at regular intervals, surround the body. The mouth is near the centre of the front end, the pharyngeal sac is very large, and the digestive tract makes less of a turn than in the ordinary Ascidians, while the atrial opening lies directly at the posterior opening. The heart is truly a dorsal vessel, and the nervous ganglion is situated on the opposite side of the body. This relation of the anatomical systems is most clearly shown in the, genus Doliolum, and we have here a slight approach to the sym- 392 ZOOLOGY metrical relation of parts seen in the true worms, and which strongly suggest the conclusion that the Tunicates are mod- ified worms. This conclusion is strengthened by the fact that in Appendicularia the ventral nervous cord is gangli- onated at intervals, as in the Annelids, while the twisted digestive tract is much as seen in Polyzoa and Brachiopods. - Furthermore, the branchial sac is strongly analogous to the pharyngeal or gill-sac of Balanoglossus, and this structure in the Ascidian and whale’s-tongue worm anticipates the pha- ~ ryngeal or gill-sac of Amphioxus and vertebrate embryos. The simple Ascidians attain to a large size, Ascidia callosa being about ten centimetres in diameter, quite round, and in form and color bears a strong resemblance to a potato. Ascidia gigas, dredged by the Challenger Expedition, is from thirty to forty centimetres in diameter, and has a ganglion nearly as large as a pea. A floating colony of Pyrosoma gigas is sometimes five feet long. Cynthia pyriformis Rathke may be called the sea-peach, from its size, form, and the rich bloom and reddish tints of its test. It is common in deep water from Cape Cod to Greenland and Scandinavia. While the Ascidians as a rule do not live below a depth of 150 fathoms, the stalked Hypobythias calycodes Moseley was dredged by the Challenger Expedition in 2900 fathoms in the North Pacific Ocean; it is stalked, and about twenty inches high. The aberrant Octacnemus bythius Moseley was also dredged in 1070 fathoms near the Schouten Islands, ‘Tasmania. Panceri has described the luminous organs of Pyrosoma, which is highly phosphorescent ; the substance from which the light is emitted is probably a fatty matter. Ascidians multiply by budding and by eggs. Examples of budding or germination are seen in the compound or social Ascidians, such as Amarecium, etc., where the individuals of the colony bud out from the primitive one just as it has left the larval condition and has become fixed. In Didemnium buds arise from masses of cells floating free within the test. They multiply by division as soon as the digestive and repro- ductive organs are indicated. In Botryllus the zooid which vesults from the tadpole-like larva serves, according to DEVELOPMENT OF ASCIDIANS. 393 Huxley, merely as a kind of stalk, from which new zooids bud out, and this process, in his opinion, “leads to the still more singular process of development in Pyrosoma, in which the first formed embryo attains only an imperfect develop- ment, and disappears after having given rise to four ascidio- zooids.” In Clavellina and Perophora the original parent Ascidian throws off branches or stolons from which develop new individuals. The usual mode of development in the simple and com- pound Ascidians (forming the order Ascidiacea) is by fertil- ized eggs. We will give the life-history of an Ascidian as based on Kowalevsky and Kupffer’s researches on Phallusia mammiliata Cuvier, in which the embryonic stages were ob- Cc Fig. 3864.—Embryo Ascidian. A, a, primitive opening; h, primitive digestive cavity; c, segmentation-cavity or primitive body-cavity: B, 7, pharynx; 7, nerve- cavity; ¢, epithelium forming the body-wall; «, rudimentary notocord; C, sec- tion of a fish embryo; , nervous tube, open in front and situated dorsally; ch, notocord; bb, mouth; e, alimentary canal; a, place of vent; m, mesoderm. served, and Ascidia intestinalis, whose larva was studied. Tne egg consists of a yolk unprotected by a yolk-skin, but surrounded by a layer of jelly containing yellow cells. The yolk undergoes total segmentation. The next step is the invagination of the ectoderm, a true gastrula state resulting. Fig. 386‘, A (after Kowalevsky), represents the gastrula; h, the primitive digestive cavity; a, the primitive opening, which soon closes; and c, the segmentation-cavity or primi- tive body-cavity. After this primitive opening (a) is lost to view, sometime before the embryo has reached the stage B, another cavity (7) appears with an external opening. This cavity is formed by a union of two ridges which grow out 394 ZOOLOGY. from the upper part of the germ. This is the central ner- vous system, and in the cavity are subsequently developed the sense organs. We thus see, says Kowalevsky, a com- plete analogy in the mode of origin of the nervous system of the Ascidians to that of the vertebrates, the nervous cavity, where the embryo is seen in section, being situated above the digestive cavity in both types of animals. The next important stage is the formation of the tail. The pear-shaped germ elongates and contracts posteriorly until of the form indicated at Fig.386*, B. At this period. appears the axial string of nucleated cells, called the chorda dorsalis, as it is homologous with that organ in Amphioxus and the embryo of higher vertebrates. The nervous system consists of a mass of cells extending halfway into the tail and directly overlying the chorda, but extending far beyond the end of the latter as seen in the figure. The nerve-cav- ity (B, n) after closing up forms the nerve-vesicle, a large cavity (Fig. 386°,@), m which the supposed auditory organ (e) and the supposed eye (a) arise ; this cavity finally closes, and the sense-organs are indicated by certain small masses of pigment cells in the fully grown Ascidian larva. As the embryo matures, the first change observed in the cord is the appearance of small, refractive bodies between the cells. Between the neighboring cells soon appear in the middle minute highly refractive corpuscles which increase in size, and press the cell-contents out of the middle of the cord. After each reproductive corpuscle grows so that the central substance of the cell is forced out, it unites with the others, and then arises in the middle of the simple cel- lular cord a string of bodies of a firm gelatinous substance which forms the support of the tail. After this coalescence the substance develops farther and presses out the proto- plasm of the cells entirely to the periphery. The cord when complete consists of a firm gelatinous substance surrounded by acellular sheath which is formed of the remains of the ‘5ells originally comprising the rudimentary cord. The cells lying under the epithelial layer form a muscular sheath of which the cord (Fig. 386°, c) is the support or skeleton. The alimentary cavity arises from the primitive cavity 395 (Fig. 138, A, h); whether the primitive opening (Fig. 386‘, A, a) is closed or not, Kowalevsky says is an interesting question. According to analogy with many other animals DEVELOPMENT OF ASCIDIANS. it probably closes. The larva hatches in from forty-eight to sixty hours af- ter the beginning of segmen- tation, and is then of the form indicated by Fig. 386° (copied with some additions and omissions from Kupffer’s figure, being partly diagram- matic). This anatomist dis- covered in the larva of As- cidia canina, which is more transparent than Kowaley- sky’s Phallusia larva, not only a central nervous cord overlying the chorda dorsalis and extending well into the tail, while in the body of the larva_it becomes broader, elub-shaped, and surrounds the sensitive cavity (a), but he also detected three pairs of spinal nerves (s) arising at regular intervals from. the spinal cord (h, h’) and dis- | tributed to the muscles (not represented in the figure) of the tail; Kupffer calls f the middle and g the lower brain- ganglion. The pharynx (8), or respiratory sac, is now very large; it opens pos- teriorly into the stomach and intestine (7); 2 represents one of the three appendages uct ee Fig. 3865.—Larval Ascidian. a, sense cavity containing the eye; 0, pharynx or respiratory sac ; c, notochord ; e, supposed auditory organ ; 7, middle, g, lower brain- ganglion; h, h, spinal cord ; s, s, s, three sets of spinal nerves; i, intestine; ¢, body-wall, consisting of epithelial cells.— Copied with some changes from Kupffer. by which the larva fastens itself to some object when. about to change into the adult, 396 . ZOOLOGY. sessile condition; ¢ indicates the body-wall, consisting of epithelial cells. We will now, from the facts afforded us by Kowalevsky, trace the changes from the larval, free-swimming state to the sessile adult Ascidia, which may be observed on the New England coast in August. After the larva fastens itself by the three processes to some object, the chorda dorsalis breaks and bends, the cells forming the sheath surrounding the broken axial cord. The muscular fibres degenerate into round cells and fill the space between the chorda and the tegument, the jelly-like substance forming a series of wrin- kles. With the contraction and disappearance of the tail be- gins that of the nerve-vesicle, and soon no cavity is left. The three processes disappear ; the pharynx becomes quadrangu- lar ; and the stomach and intestine are developed, being bent under the intestine. A mass of cells arises on the an- terior end beneath the digestive tract, from which originate the heart and pericardium. In a more advanced stage, two gill-holes appear in the pharynx, and subsequently two more slits, and about this time the ovary and testis appear at the bottom, beyond the bend of the alimentary canal. The free cells in the body-cavity are transformed into blood-cells, and indeed the greater part of those which composed the nervous system of the larva are transformed into blood-corpuscles. Of the embryonal nervous system there remains a very small ganglion, no new one being formed. The adult Ascidian form meanwhile has been attained, and the very small indi- viduals differ for the most part only in size from those which are full-sized and mature. It will be seen that some highly important features, recall- ing vertebrate characteristics, have occurred at different pe- riods in the life of the embryo Ascidian. Kowalevsky remarks that ‘‘ the first indication of the germ, the direct passage of the segmentation cells into the cells of the embryo, the for- mation of the segmentation-cavity, the conversion of this cavity into the body-cavity, and the formation of the diges- tive cavity through invagination—these are all occurrences which are common to many animals, and have been observed in Amphiozus. Sagitta, Phoronis, Echinus, etc. The first RELATION OF ASCIDIANS TO VERTEBRATES. 397 pomt of difference from other animals in the development of all vertebrates is seen in the formation of the dorsal ridges, and their closing to form a nerve-canal. This mode of yormation of the nervous system is characteristic of the vertebrates alone, except the Ascidians. Another primary character allying the Ascidians to the vertebrates, is the presence of a chorda dorsalis, first seen in the adult Appen- dicalaria by J. Miller. This organ is regarded by Kowal- evsky to be functionally, as wellas genetically, identical with that of Amphioxus. ‘This was a startling conclusion, and stimulated Professor Kupffer, of Kiel, to study the embry- ology of the Ascidians anew. He did so, and the results this careful observer obtained led him to fully endorse the con- clusions reached by Kowalevsky, particularly those regarding the unexpected relations of the Ascidians to the vertebrates, and it would appear from the facts set forth by these emi- nent observers, as well as Metschnikoff, Ganin, Ussow, and others, that the vertebrates have probably descended from some type of worm resembling larval Ascidians more perhaps than any other vermian type, though it is to be remembered that certain tailed larval Distome appear to possess an organ resembling a chorda dorsalis, and farther investigation on other types of worms may lead to discoveries throwing more light on this intricate subject of the ancestry of the verte- brates. At any rate, it is among the lower worms, if any- where, that we are to look for the ancestors of the Vertebrates, as the Celenterates, Echinoderms, the Mollusks, Crustacea and Insects, are too circumscribed and specialized groups to afford any but characters of analogy rather than affinity. For example, the cuttlefish, with its ‘‘ bone,” brain-cap- sule and highly-developed eye, is, on the whole, more remote from the lowest vertebrate, Amphioxus, than the Appendi- cularia or the larval Ascidian. Certain (three) species of Molgula have been found by Lacaze-Duthiers to have a nearly direct development, not producing tailed young. There is a slight metamorphosis, however, the young having five temporary, long, slender processes. In Ascidia ampuiloides the larva has a tail, no- tochord and pigment spots, which are wanting in the young 398 ZOOLOGY. of several species of Molgula, but it has the five long decid- ‘uous appendages observed in young Molgule. Among the compound Ascidians, Botryllus and Botrylloides have tailed ‘young, while in other forms there is no metamorphosis, de- velopment being direct. Order 2. Thaliacea.—On the whole, we may regard this order, represented by Salpa (Fig. 386°), and Doliolum, as comprising the more specialized forms of Tunicates. Salpa is pelagic, one species occurring in abundance off the shores of Southern New England, while the cthers mostly live on the high seas all over the tropical and sub- tropical regions of the globe. Late in the summer our Salpa spinosa of Otto can be captured in multi- tudes by the tow-net in Long Island Sound. ie There are in Salpa two kinds of individuals, 7.e:, the solitary, and aggregated or chain-Salpz. The ‘body of the solitary or asexual form is more or less barrel-shaped, with a series of circular bands of muscles, like the hoops of a barrel, ‘and situated on the inner side of the outer tunic. The test is trans- Fig. 386°.—Salpa spinosa, An parent, though very thick, while individual from ameturechain; the outer tinic lines tle cavity of three-quarter view, enlarged. a, atrial opening ; 6, mouth ; ¢, pro- . 7 couses by which the members of ‘he test as in other Tunicates. In ies ee ict ~ the members of this order the oral Sie Kepors” Sess from Ver- aperture of the mantle is at one end of the body, and the atrial opening at the opposite end, the minute digestive canal be- ing but slightly curved, the body-cavity being largely occu- pied by the pharyngeal or respiratory sac. Moreover, the dor- sal or hemal side of the body is clearly distinguishable from the ventral or neural side, as well seen in Doliolum, where the well-marked tubular heart lies above the digestive organs, and is directly opposed, as in worms generally, to the nervous STRUCTURE OF SALPA. 395 system, which is situated ventrally between the mouth and vent. We thus have in these Tunicates a front and hind end of the body, a dorsal and ventral, as well as a distincr bilateral symmetry of the body. This is seen in Appendi- cularia as well as in Doltolum and Salpa, however much this symmetry may be obscured in the more typical Ascidi- ans, such as Ascidia, Molgula, Boltenia, etc. The oral aperture leading into the respiratory sac is large, being as wide as the body ; the respiratory sac is more com- plicated than in other Ascidians, and more so than in Doli- olum, where it is a wide, deep passage, the cesophagus at the hinder end, the sac itself perforated by two rows of bran- chial slits, four or five slits in each row. In Salpa, how- ever, the respiratory sac, as described by Brooks, is attached to the outer tunic, around the edges of the mouth, as in other Tunicates. There are only two branchial slits, one on each side; these are very large, and cover almost the whole surface of the branchial sac, except the median dorsal and hemal lines. On the neural side the branchial slit opens directly into the atrium, the ciliated line where the two tunics unite being niarked by the so-called ‘ gill” (Brooks). In Salpa, according to Brooks, the branchial sac, though ciliated within, is not so directly concerned in the respiratory act asin other Tunicates, since respiration is effected largely by the action of the muscles, which also assist deglutition, and are the organs of locomotion. These contract rythmi- cally, with great regularity, and at each contraction the water is expelled from the branchial sac through the atrial aperture ; and when the muscles are relaxed, the elasticity of the test distends the chamber, and a fresh supply is drawn in through the branchial aperture, the lips of which readily admit its passage in this direction, while a similar set of valves allows its passage out of the atrial aperture, but pre- vents its return.” Thus a chain of individuals move with a ‘uniform motion, while the solitary individuals and those which have been set free by the breaking up of a chain, move by jerks. The digestive canal is small, curved on itself, the esopha- gus leading from the bottom of the pharyngeal or respiratory 400 ZOOLOG ¥Y. sac into a small stomach, the intestine bending back on itself, and the vent being near the mouth. The entire diges- tive canal is immovable, the food being driven through the permanently distended cavity by means of the cilia lining its inner surface. The great posterior blood-sinus surrounds the digestive system on all sides, the nutriment being di- rectly absorbed from its surface and mixed with the blood. The nervous system is, in adaptation to its locomotive life, more specialized than in the sessile forms, and highly spe- cialized organs of sight and hearing are present. The heart is a short, complicated organ, lying in the sinus-system. Its action is often reversed ; the reversal of the beats tending to clear the sinuses of the blood-disks overcrowding them. In one species of Salpa Prof. Brooks states that the blood- channels are in all cases sinuses, which are parts of the body- cavity and have no special walls, though in species investi- gated by other writers there are said to be true blood-vessels, lined with epithelium. The hermaphroditic, aggregated or chain-salpa differs from the solitary asexual form in being less regularly barrel- shaped, and without the two long posterior appendages of the latter; in the proportions of the different organs, the two forms are essentially alike. The young chain is easily perceived in the solitary indi- viduals in the posterior part of the body, curving around the digestive organs. When first set free from the body of the solitary Salpa, the chain is about half an inch long, and the single, individual Salpz composing it are about two and a half millimetres in length. They grow very rapidly, and soon reach their full size, when the chains are often a foot or a foot and a half long; the individuals composing them when fully grown being about two centimetres in length. The chain easily falls apart, and the individuals are capable of living a solitary life, Huxley stating that the chain-individu- als of the species observed by him were generally found soli- tary; for this reason we should regard the chain-salpe as individuals, not zootds, being capable of leading an inde- pendent existence, and with a structure almost identical with that of the solitary Salpe. DEVELOPMENT OF SALPA. 401 Brooks has studied the mode of development of the female and male Salpa spinosa (Fig. 386°). When a Salpa-chain is discharged from the body of the asexual Salpa, each indi- vidual of the chain contains a single egg which is fertilized by sperm-cells of individuals belonging to some other chain, and after passing through the mulberry stage and entering the gastrula stage, the germ is in most intimate relation with the body of its parent. The vase-shaped gastrula is lodged in a brood-sac. Its body-cavity, originally formed by invagination of the ectoderm, opens directly into the sinus- system of its nurse, and the blood now circulates in and out of the primitive digestive cavity as well as around the out- side of the embryo. But as the embryo grows and fills the brood-sac, so that the outer surface of the gastrula becomes intimately connected with the wall of the brood-sac, the blood no longer bathes the outside of the embryo. At this time the ‘‘ placenta” is formed. Brooks believes that it originates directly from the blood, ‘by the aggrega- tion and fusion of its corpuscles,” not being derived from any of the parts of the parent or embryo. Soon after its appear- ance it consists of an inner chamber communicating with the sinus of the nurse, and haying no communication with any of the cavities of the embryo ; its cavity being a part of the original ‘‘ primitive stomach” of the gastrula. It finally has two chambers, an inner and outer one, and Huxley describes* the fcetal circulation in the placenta, a deciduous organ analogous in function, but by no means homologous in struc- ture, with the vertebrate placenta. When the embryo of the solitary Salpa is nearly one millimetre (s!, inch) long, and while still in the brood-sac of the parent, the tube which is to give rise te the chain ap- * « The blood-corpuscles of the parent may be readily traced enter ing the inner sac on one side of the partition, coursing round it, and finally re-entering the parental circulation on the other side of the par- tition ; while the fcetal blood-corpuscles, of a different size from those of the parent, enter the outer sac, circulate round it at a different rate, and leave it to enter into the general circulation of the dorsul sinus. More obvious still does the independence of the two circulations be come when the circulation of either mother or foetus is reversed.” 402 ZOOLOGY. pears within its body. We will now briefly trace the devel- opment of the chain-salpa, condensing Brooks’s statement. The aforesaid tube is at first simply a cup-like protrusion of the outer tunic into the cellulose test which now surrounds the embryo; the cavity of the cup is an offshoot from the sinus-system, the blood passing in and out of it. A small bud-like protrusion now appears upon the surface of the per- icardium, and lengthens to form a long rod or stolon, ex- tending across the sinus and projecting into the cavity of the cup. At about this period a long, club-shaped mass of pro- toplasm appears within each of the sinus-chambers of the tube, and soon after the outer wall is constricted at regular intervals, each segment being destined to form the outer tu- nics of the chain-salpe, the constrictions indicating the bodies of the latter. By the deepening of these constrictions, each of the sinus-chambers, which are diverticula from the body-cay- ity of the solitary Salpa, becomes divided up to form the body-cavities of the Salpz on one side of the chain. From the central tube of the stolon arises a row of buds on each side, which become the branchial and digestive organs of the Salpe on each side of the chain ; while a similar double row, upon the other edge, gives rise to the ganglia. The club- shaped organs within the sinus-chambers become divided up into single rows of eggs, one of which passes into the body- cavity of each chain-salpa at a very early period of develop- ment. Thus, as Huxley states, budding occurs, not from the outer wall alone, as in Hydroids and Polyzoa, ‘‘ but, from the first, several components, derived from as many distinct parts of the parental organism, are distinguishable in it, and each com- ponent is the source of certain parts of the new being, and of these only.” Prof. Brooks adds that while these changes are going on the constrictions on the surface deepen, the wall protruding from them, and each is soon seen to mark off, on each side of the stolon, the body of a young Salpa, which soon becomes visible to the naked eye. They do not increase in size gradually from one end of the stolon or tube to the other, but develop in sets of from thirty to fifty each, GENERATIONS OF SALPA. 403 and the development of all which are embraced within a set progresses uniformly ; there are usually three of these sets upon the tube of an adult solitary Salpa.* Thus the Salpa reproduces parthenogenetically as in some Crustacea and insects, and we have here a true case of “ alter- nation of generations, * Tn 1819 Chamisso stated ‘“‘that a Salpa mother is not like its daughter or its own mother, but resembles its sister, its granddaughter, and its grandmother. ¢ Immediately after the publication of Brooks’ researches on Salpa spinosa, those of Salensky on Salpa democratica- mucronata (a species said to be closely allied if not identical with S. spinosa) appeared. According to the Russian ob- server, as stated by Huxley, who adopts his conclusions, the chain- -salpa is a hermaphrodite, and the egg while still in the ovarian follicle is fertilized, when the oviduct shortening and widening forms a single uterine sac, the maternal and *The Development of Salpa, by W. K. Brooks. Bulletin of the Museum of Comparative Zoology, III., No. 14, Cambridge, 1876. We have presented quite fully the author’s account of the mode of devel- opment of the young asexual (his female) Salpa, without, however, adopting his interpretation of the sexes of the two kinds of individuals of Salpa ; believing his “female” Salpa to be asexual, and his “ male” Salpa to be hermaphrodite, with an ovary and testis, as he has not ap- parently observed the fact of the introduction of an egg into the body of his ‘‘male” Salpa. On the contrary, it appears to be developed originally in a true, simple ovary or “ ovarian follicle ;” the testis being immature and the egg fertilized by sperm-cells of other hermaphro- dites, in-and-in breeding thus being prevented. + This view has been endorsed by Steenstrup, Sars, Krohn, and others, especially by Leuckart in the following words quoted by Brooks: “It is now a settled fact thet the reproductive organs are found only in the aggregated individuals of Salpa, while the solitary individuals, which are produced from the fertilized eggs, have, in place of sexual organs, a bud-stolon, and reproduce in the asexual manner exclusively, by the formation of buds. Male and female organs are, so far as we yet know, united in the Salpe in one indi- vidual. The Salpe are hermaphrodite.” On the other hand, Todaro, in an elaborate memoir (1876), considers the Salpa as the synthetic type of all the vertebrata, presenting features peculiar to each class, even including the mammals. In his opinion it is an allantoidian ver- tebrate, developed in a true uterus, the neck of which, after the life of the embryo begins, becomes plugged with mucus. 404 ZOOLOGY. embryonic parts of the placenta arising, respectively, from the wall of the ovarian sac and from certain large cells (blas- tomeres) on the adjacent (hamal) face of the embryo. Thus the asexual development of the Salpa is like that of the germ- masses destined to form the Cercarie developed in the body of the Redia of the Distoma ; and is also like that of the plant lice (Huxley). This is a reaffirmation and extension of the original view of Chamisso. To recapitulate, the life-history of the Salpa is as follows : There are two kinds of individuals : a, solitary, asexual ; ), social, aggregated, and hermaphroditic. (1.) The solitary, asexual Salpa produces by budding a chain of hermaphrodite Salp ; the latter produce a fertil- ized (2.) Egg, which passes through a— (3.) Morula and— (4.) Gastrula stage, contained and growing in a placenta- like organ, where the embryo is directly nourished by the blood of the parent, the embryo finally becoming— (5.) A solitary asexual Salpa. We thus have a true alternation of generations, like the sexless Hydroid and its sexual Medusa, the asexual Aphis and its last brood of males and females; the asexual Redia and the sexual Distoma ; in all these cases the offspring (8) of the asexual individual (a) is unlike the parent, but the off- spring (c) of the second generation (4) is like (a) the grand- parent. “Tn Doliolum the reproductive processes are much more complicated, for not only do the sexually produced young undergo a metamorphosis, but a’ new series of generations is introduced into the life-history. The eggs are laid, and the larve which issue from them are provided with tails and re- semble Ascidian larve. They develop into asexual forms, which differ from the sexual forms, and are provided with a dorsal stolon; the ventral stolon (stolon of Salpa) is rudimen- tary. Two different kinds of buds are formed on this dorsal stolon, viz., median buds and lateral buds. The lateral buds have a slipper-like form, and are without the cloacal cavity; they do not reproduce themselves, but are concerned with the nourishment of the asexual form. The latter as it increases CHARACTERISTICS OF TUNICATES. 405 in size, loses its gills and alimentary canal, while its muscu- lar system becomes powerfully developed. The median buds develop into individuals, which resemble the sexual animals, except that they are without genital organs; they, therefore, represent a second generation of asexual forms, which become free and produce the sexual generation from a ventral sto- lon.” * : Crass IL—TUNICATA. Body usually subspherical, or sac-like, obscurely symmetrical ; some times barrel shaped, bilateral, with a dorsal and ventral symmetry, pro- tected by a@ transparent or dense test, containing cellulose, lined within by a tunic surrounding the body-cavity. Two openings in the test, one oral, the other atrial; mouth leading into a capacivus pharyngeal res- piratory sac, opening posteriorly by an esophagus tuto a stomach, which is provided with a liver, intestine flexed, vent opening near the esophagus, the feces passing into an atrium or cloacal space, and thence out of the atrial opening. Nervous system bilateral, forming a double ganglio- nated chain (Appendicularia), but usually reduced to a single ganglion, sttuated within the tunic between the two openings ; a tubular heart, open- ing at each end, lodged in a sinus-system, an’ its beatings often reversed, the blood flowing in and out at either end. Sexes usually united ; in some forms asexual individuals ; reproducing by eggs or budding partheno- genetically, or by gemmation. Order 1. Ascidiacea. — Body sac-like, subspherical, usually sessile, sometimes stalked, simple or compound, minute individuals growing in a common mass; the oral and atrial openings contiguous ; often acomplete metamorphosis. (Appendicu- laria, Botryllus, Amarcecium, Clavellina, Perophora, As- cidia, Boltenia, Pyrosoma). Order 2. Thaliacea —Body barrel-shaped ; free-swimming, test thick, hyaline ; with circular muscular bands; respiratory sac widely open; reproducing by alternation of generations. (Salpa, Doliolum), Laboratory Work.—The Tunicates can well be studied only in a living state; or sections of hardened Salps may be made. The young, caught with the tow-net, should be immediately examined, as they are very short-lived. Delicate sections of hardened eggs and larve are made with great difficulty, but are necessary to examine in con- nection with the living, more or less transparent animals. * Claus, Zoology, English edition, ii. p. 107. 406 ZOOLOGY. Crass I. Luprocarpit (Lancelet). The lancelet is the only type of this class. From its worm-like form it was regarded as a worm by some authors, and as a mollusk (‘‘Limax’) by water mark, ranging on our coast from the mouth of Chesapeake Bay to Florida; it also occurs on the South American coast, and in the European seas and the Hast Indies, the species being nearly cosmopolitan. — As this is the lowest Vertebrate, its structure and mode of development merit careful study. a> oh cwaee2 ee gee Pallas. The body is four or five cen- ZEES wp timetres in length, slender, com- BHOES e Teel 4 pressed, pointed at each end, hence Reser the generic name (Amphioxus, augr, Exe ES, ‘ both, o&us, sharp), the head-end be- e228- ie 4 ing thin, compressed. The muscu- Bon BL i lar segments are distinct to the Bae oe a | naked eye. From the mouth to the By SEE Ea é vent is a deep ventral furrow, and’ BQ QE q| a slight fin extends along the back £ E oe g | and ventrally as far front as the vent. BEE : - The lancelet, A. lanceolatus (Pal-. 5 Zune t- las), lives in sand just below low- Boye H ® 5 © ¢ { [RUBS DAYSAHIp ay} Jo Worjtod ILi43@. My ‘sawty Jey B PUB OM] payt } JO JBOY ‘Oo : BARD BABA OY) Jo WAwAY ‘uw $ soLINqIV [BIYOURIG aq) JO sJUETHA. g : g Hy. e . N The mouth is oval, surrounded Boe Ni with a circle of ciliated tentacles oar. \ supported by semi-cartilaginous pro- gz \ cesses arising from a circumoral ring. See i Ni The mouth leads directly into a large a8 VM broad pharynx or “branchial sac” 32 e i (Fig. 387, d), protected at the en- ee trance by a number of minute cili- a ated lobes. sto 3 sad The walls of this sac are perforated by long ciliated slits, comparable with those of the bran DEVELOPMENT OF THE LANCELET. 407 chial sacs of Ascidians and of Balanoglossus. The water which enters the mouth passes out through these slits where it oxygenates the blood, and enters the general body-cavity, thence passing out of the body through the abdominal pore (Fig. 387, c). The pharynx leads to the stomach (e), with which is connected the liver or coecum (f). There is a pulsatile vessel or tubular heart, beginning at the free end of the liver, and extending along the underside of the phar- ynx, sending branches to the sac and the two anterior branches to the dorsal aorta. ‘‘ On the dorsal side of the pharynx the blood is poured by the two anterior trunks, and by the branchial veins which carry away the aérated blood from the branchial bars, into a great longitudinal trunk or dorsal aorta, by which it is distributed throughout the body.” ({Iuxley.) There are also vessels distributed to the liver, and returning vessels, representing the portal and hepatic veins. The blood-corpuscles are white and nucleated. The vertebral column is represented by a notochord which extends to the end of the head far in front of the nervous cord ; and also by a series of small semi-cartilaginous bodies above the nervous system, and which are thought to repre- sent either neural spines or fin-rays. The nervous cord lies over the notochord ; it is not divided into a true brain* and spinal cord, but sends off a few nerves tu the periphery, with nerves to the two minute eye-spots. There are no kidneys like those of the higher Vertebrates, but glandular bodies which -may serve as such. The reproductive glands are square masses attached in a row on each side of the walls of the body-cavity. The eggs may pass out of the mouth or through the pore. Kowalevsky found the eggs issuing in May from the mouth of the female, and fertilized by sper- matic particles likewise issuing from the mouth of the male. The eggs are very small, 0-105 millimetres in diameter. The eggs undergo total segmentation, leaving a segmentation- cavity. The body-cavity is next formed by invagination. The blastoderm now invaginates and the embryo swims about as a ciliated gastrula. The body is oval, and the germ does not differ much in appearance from a worm, starfish, * Langerhans has figured an olfactory lobe; and all observers agree that a ventricle is present ; thus there is a slight approximation to a brain. 408 : ZOOLOG F. or ascidian in the same stage of growth. No vertebrate features are yet developed. Soon the lively ciliated gastrula elongates, the alimentary tube arises from the primitive gastrula-cavity, while the edges of the flattened side of the body grow up as ridges which afterwards, as in all vertebrate embryos, grow over and en- close the spinal cord. When the germ is twenty-four hours old it assumes the form of a ciliated flattened cylinder, and now resembles an Ascidian embryo (Fig. 138, &), there being a nerve-cavity, with an external opening, which after- wards closes. The notochord appears at this time. In the next stage observed the adult characters had ap- peared, the mouth is formed, the first pair of gill-openings are seen, eleven additional pairs appearing. It thus appears that while the lancelet at one time in its life presents Ascidian features, yet as Balfour states ‘all the modes of develop- ment found in the higher Vertebrates are to be looked upon as modifications of ‘that of Amphioxus.” A second form of this group, from Moreton Bay, North- ern Australia, has been described by Peters under the name of Epigonichthys cultellus. It differs from Amphioxus in the presence of a high dorsal fin, in the want of a distinct caudal and anal fin, with some differences in the structure of the mouth and oral tentacles. It is from thirteen to twenty-three millimetres in length. Crass II.—LEPTOCARDII. Comprising the lowest Vertebrate known ; body lancet-shaped, with no skeleton ; notochord persistent, no brain ; no cranium ; no paired fins ; blood colorless ; a metamorphosis ; gustrula ciliated, free-swimming. A single order (Pharyngobranchi), family (Amphioxini), and genus (Amphioxus), each with the characters of the class. Laboratory Work.—The structure of the lancelet can only be imper- fectly made. out by a triplet lens and higher powers ; but by sections stained with carmine the anatomy can be well studied. Brooks has found the young in the later free-swimming stages on the surface of the ocean near Fortress Monroe. : GHNERAL CHARACTERS OF MARSIPOBRANCHS, 409 Cuass ITI. Marstpoprancuil (Lampreys, or Cyclustomt). General Characters of the Cyclostomatous Vertebrates. —In the hag-fish and lamprey, representatives of the jaw- less Vertebrates, the body is long and slender, cylindrical, the skin smooth, scaleless, with only a median dorsal and ventral fin (or in Myzine only a small lower median fin) ; the mouth is circular, and in the lampreys armed with nu- merous conical teeth. There is no bony skeleton; the spinal column is represented simply by a thick rod (dorsal cord, notochord) surrounded by a sheath. The skull is car- tilaginous, not movable on the vertebral column; is very imperfectly developed, having no jaws, the hyo-mandibu- lar bones and the hyoid arch existing in a very rudimentary state. The few teeth present in the hag-fish are confined to the palate and tongue; those of the lamprey are numerous, conical and developed on the cartilages supporting the lips. The nervous system is much as in the fishes, the brain with its olfactory, cerebral lobes, thalami, optic lobes, and medulla being developed, the cerebellum in Myxine blended with, in the lamprey free from the medulla. The digestive canal is straight, with no genuine stomach, but the liver is much as in higher Vertebrates. The respiratory organs are very peculiar, being purse-like cavities (whence the name Marsipobranchii), in the lamprey being seven in number on each side of the pharynx, opening externally by small aper- tures ; internally they connect with a long cavity lying under the cesophagus, and opening anteriorly into the mouth. The heart is like that of fishes, as are the kidneys. The eyes are minute, sunken in the head and under the skin in the hag (Myzine), but larger in the lamprey. Another extraordinary feature in the class is the single nasal aperture, as opposed to the two occurring in all higher Vertebrates. The aperture leads to a sac, which in the Myzine communicates with the mouth (pharynx), put in the lamprey forms a cul-de-sac. The ovaries and male glands (the sexes being distinct) are unpaired plates suspended from the back-bone, and have no 410 ' ZOOLOGY. ducts, the eggs breaking through the walls of the ovary, fall- ing into the abdominal cavity and passing out of the abdom- inal pore. Theeggs of Myzine are very large in proportion to the fish, enclosed in a horny shell, with a filament at each end by which it may adhere to objects. The hag-fish is about afoot long and an inch thick, with the head small, a median palatine tooth, and two comb-like rows of teeth on the tongue. There is a single gill-opening a long way behind the head; there are large mucous or slime-glands on the side of the body, for these fishes are very slimy. The hag lives at considerable depths in the sea ; we have dredged one at 114 fathoms in soft deep mud off Cape Ann. It is often parasitic, attaching itself to the bod- ies of fish, and has been found to have made its way into the body-cavity of sturgeons and haddock. The lamprey lives both in fresh and salt water. The eggs of the common lamprey, Petromyzon marinus (Linn.), are laid in early spring, the fish following the shad up the rivers, and spawning in‘fresh water, seeking the sea in autumn ; small individuals, from five to seven inches long, have been seen by Dr. Abbott attached to the bellies of shad, sucking the eggs out of the oviducts. The lamprey when six inches long is quite unlike the adult, being blind, the eyes being concealed by the skin ; it is tooth- less, and has other peculiarities. It is so strangely unlike the adult that it was described as a different genus (Ammocetes). P. nigricans. Lesueur is smaller, and occurs in the lakes of New York and eastward, while P. niger Rafinesque is still smaller, and lives in the Western States. Crass ITIL MARSIPOBRANCHI. Worm-like Vertebrates, without paired fins ; notochord persistent ; single nasal sac, six or ten pairs of purse-like gill-sacs, no jaw-bones. Order 1. Hyperotetra.—Nasal duct leading into the mouth. (Myxine.) Order 2. Hyperoartia.—Nasal duct a blind sac, not connecting with the mouth. (Petromyzon.) GENERAL CHARACTERS OF FISHES. 411 Laboratory Work.—The anatomy of these animals is exceedingly in- teresting ; the respiratory sacs and nasal duct can be exposed by a lon- gitudinal section of the head ; the relations of the notochord can be best seen by transverse sections ; the heart and vessels should be in- jected. Preparations of the brain should be made, and with care the skull prepared. Cuass IV. Pisces (Sharks, Rays, Sturgeons, Garpikes, and bony fishes). General Characters of Fishes.—We now come to Verte- brates which have genuine jaw-bones and paired fins, and which, in short, are affiliated to the Batrachians, and through them with the reptiles, birds, and mammals. All the fishes agree in having a true skull, to which is attached a movable lower jaw. ‘The brain is well developed, with its lobes for the most part, at least, equivalent to or homologous with those of the reptiles, birds, and mammals, though the cere- bral hemispheres are small, and in most fishes of nearly the same size as the optic lobes; the cerebellum is also generally Cauda, = Anal. Ventral. Pectoral. Fig. 388.— The Mud-Minnow. of moderate size. The head forms part of the trunk, there being no neck (except in the Hippocampide), and the body is usually compressed and adapted in shape for rapid motion in the water. Paired fins are always primitively developed, though the posterior or ventral fins, at least, are in many cases wanting through the atrophy of parts developed in embryonic life. The pectoral and ventral fins (Fig. 388), which represent the fore and hind legs of higher Vertebrates, are attached to the body or trunk by a shoulder and pelvic girdle. The shoulder 412 ZOOLOG Y. girdle is either lyre-shaped or forked, like a bird’s wish-bone, curved forward, and with each side connected below; the . fishes in this respect differing from the Batrachians (Gill). The shoulder girdle is usually closely connected by a series of intervening bones with the skull, and makes its first ap- pearance opposite the interval between the second and third vertebrae. The skull and skeleton may be either cartilaginous or bony, and the bones of the head and skeleton very numerous. In some sharks there are 365 vertebra ; in some bony fishes 200, while in the Plectognatni (fishes like the sun-fishes and Ba- listes) there may be no more than fifteen; thus in some fishes there may be about one thousand separate bones. No fishes have a well-defined sternum or breast-bone, this bone appearing for the first time in the Batrachians. The verte- bre are almost always biconcave ; this is the simplest, most primitive form of vertebra ; it forms a weak articulation, admitting, as Marsh states, of free, but limited motion. All fishes breathe by gills, which are supported generally on four or five cartilaginous or bony supports or arches. The gills are never purse-shaped, as in the lampreys, and are mostly situated within the head, in front of the scapular arch. The mouth is generally armed with teeth varying greatly in number and form, and in the bony fishes especially, not only the jaws, but any bony projections, such as the palatine, pterygoid and vomerine bones, as well as the tongue and pha- ryngeal bones may be armed with teeth, so that the food is retained in the mouth and more or less torn and crushed be- fore being swallowed. Fish have no salivary glands. The tongue moves only as a part of the hyoid apparatus upon which it is attached. After being crushed and torn in the mouth the food passes through a short throat or cesophagus into the stomach. The intestine is generally provided at the anterior end with several or numerous cecal appendages which are especially abundant in the cod. The gut is twisted once or twice be- fore reaching the vent, but is usually much shorter than in the air-breathing Vertebrates, while the vent is placed much neaver the mouth than in the tailed Amphibians, thus sepa- STRUCTURE OF FISHES. 413 rating the trunk into a thoracic and caudal portion. To make up for the short intestine, its absorbing surface is greatly increased in all except the bony fishes by a peculiar fold called the “‘spiral valve.” The rectum always opens in front of the urinary and genital outlets; except when the latter communicates directly with the rectum, thus forming a cloaca. All fishes have a well-developed liver, usually a gall- bladder, with several gall-ducts ; and in general a yellowish pancreas. The heart consists of a ventricle and auricle, the latter branchial with a venous sinus (sinus venosus) ; while to the ventricle is added an arterial bulb, which subdivides into five pairs of arteries, one for each gill-arch. The Dipnot ap- proach the Amphibians in the possession of a second auricle as well as of genuine lungs, 7.e., cellular air-sacs. The lungs are fundamentally comparable with the air-bladder or swim- ming bladder. It is generally situated below the back-bone, and is developed originally as an offshoot of the cesophagus. It is either free, not connected with the digestive tract, or its original attachment may be retained in the form of the ‘‘pneumatic duct,” which, when persistent, opens into the ‘cesophagus. In the sharks it is either absent or exists in a rudimentary state. The kidneys are two voluminous, dark-red lobulated or- gans, lying close together next to the back-bone, behind, 7. e., above the air-bladder, and occupying nearly the whole length of the abdominal cavity. The efferent ducts (ureters) either pass along in front of or by the side of the kidney, and some- times unite to form a single sac, the outlet of which is situ- ated either behind or below the generative orifice. It has been found that the minute structure of the kidneys of em- bryo sharks resembles somewhat the segmental organs of worms, the original kidney being composed of bundles of ciliated funnels, like those of worms, combined, however, with Malpighian bodies and renal lobules which do not exist in worms, while all these parts have a common duct, the ureter, which also does not exist in worms, being character- istic of Vertebrates. in the fishes, the sexes nite, with a very few exceptions, dis- 414 ZOOLOGY. tinct. The ovaries are large bodies, either discharging the eggs directly, as in the eel, salmon, and trout, into the body- cavity, thence passing along a fold of the peritoneum out of a minute opening situated directly behind the vent, or, as in most bony fishes, there is a duct leading from each ovary. to the common outlet. In the sharks and skates (Hlasmo- branchs) the ovary is single, and the oviducts unite behind to serve as a uterus in such sharks as are viviparous ; or the same parts secrete a shell in the egg-laying sharks (Scylliwm) and skates. The reproductive glands of most fishes are, except in the breeding season, so much alike, that it is difficult to distin- guish them except by a microscopic examination. In the breeding season the ovaries of the cod, perch, and smelt are very large and yellowish, while the testes are small and white. Fishes, like some Amphibians and many invertebrates, may be able to perform the reproductive functions before they are fully mature ; in fact, some fishes continue to grow as long as they live. The fishes are not a homogeneous or ‘‘ closed,” 7. ¢., well- circumscribed, type, as the birds and mammals, for the form of the body is liable to great variation, the differences be- ° tween the subdivisions or orders, families and genera being much greater than in birds and mammals. The class is divided into three subclasses, viz. : the Zlas- mobranchit (sharks and rays), the Ganoidei (sturgeons, gar- pikes, etc.), and the Zeleoste’, or bony fishes. The classifi- cation we adopt is that of Professor Gill. Subclass 1. Elasmobranchii (Selachians, or Sharks and Rays).—These are the most generalized as well as among the oldest of all fishes. In some respects they stand above the bony fishes, with some features anticipating the Amphibians, while in their cartilaginous skeleton, their numerous gill-openings, ,and their general appearance they are scarcely higher than the embryos of the bony fishes. It would seem as if a shark were an embryo fish, which had been hurried by nature into exist- ence with some parts more perfect than others, in order to serve in the Upper Silurian and Devonian times as destructive * © SHARKS AND RAYS. 415 agents to the types of invertebrate life which then became extinct, partly through their means. These and ganoid fishes having thus accomplished their work were replaced in the later ages by more highly elaborated and specialized forms, *i.e., the bony fishes. Sharks and skates are engines of de- struction, having been since their early appearance in the . Upper Silurian age the terror of the seas. Their entire structure is such as to enable them to seize, crush, tear, and rapidly digest large invertebrates, and the larger marine members of their own class. Hence their own forms are gigantic, soft, not protected by scales or armor, as they have in the adult form few enemies. Hence they do not need a high degree of intelligence, nor special means of defence or protection, though from their activity the circulatory system is highly developed. In the general form the sharks are long and somewhat cylin- drical, with the head rather large, often pointed, sometimes, in in the hammer-headed shark, extraordinarily broad, with a capacious mouth, situated in the under-side of the head. The body tapers behind, and the caudal portion is unequally lobed, the upper lobe being much longer than the lower, upturned and supported by a continuation of the vertebral column, while the tail-fins of bony fishes are equally lobed and consequently called homocercal; those of sharks are unequally lobed, and are therefore said to be heterocercal. In this respect they resemble an early stage in the development of bony fishes, such as the trout or herring. Sharks, like bony fishes, have two pectoral and generally two ventral fins ; these two pairs of fins corresponding to or homologous with the limbs of air-breathing Vertebrates, and besides this there is one or usually two dorsal fins, and an anal fin, the latter situated behind the vent. The skin is either smooth or covered with minute placoid scales (see Fig. 385); the integument of such species as are provided with these fine scales forming shagreen. While the spinal column is in the sharks usually cartilaginous, and easily cut with a knife, there are different grades of devel- opment from certain forms, as the Chimera, to a well-marked 416 ZOOLOGY. column or series of biconcave vertebre, with the cartilage in part replaced by bone, forming radiating leaves or plates ; while in the rays or skates the anterior part of the column is bony. ‘ The ribs are small, sometimes rudimentary. The skull is rudimentary, without membrane-bones, embryonic in char- acter, forming a simple cartilaginous brain-box, without pre- maxillary or maxillary bones, the constitution of the jaws be- ing quite unlike that. of the bony fishes, the jaws being formed of elements, 7. e., ‘‘ cartilaginous representatives of the pri- mary palatoquadrate arch and of Meckel’s cartilage.” (Hux ley.) ee are no opercular bones such as cover the gill-open- ings in bony fishes, their place being taken by cartilaginous filaments. The mouth is armed in most sharks with numerous sharp, flattened, conical teeth, arranged in transverse rows and pointing backwards; they are never fixed in sockets, but imbedded in the mucous membrane of the upper and under jaws. In the Heterodontide, represented by Cestracion or Port Jackson, shark, the teeth are much blunter than in other living sharks, the middle and hinder teeth having broad, flattened crowns, forming a pavement of rounded teeth. The Devonian sharks were in most cases like the Cestracion in this respect. In the Carboniferous age, sharks with teeth more like those of modern forms came into ex- istence ; and they must have been of a more active nature, the sharp teeth directed backward indicating the rapacity of these monsters, which darting after and seizing their prey were enabled to retain it by the backward-pointed teeth ; while the more sluggish Devonian Cestracions kept near the bottom and devoured the shelled mollusks, ete., possibly Or- thoceratites, Nautili, and Trilobites, which became nearly extinct about the time the type of pavement-toothed sharks culminated. The teeth of the skates or rays have obtuse points. In Myliobatis the teeth are flattened and united to form a solid pavement, so that the mouths of these large rays are fur- DEVELOPMENT OF SHARKS AND RAYS. 41? nished with an upper and nether millstone for crushing and comminuting the thick, solid shells of mollusks. The mouth in both sharks and rays is always situated on the underside of the head, all being ground-feeders. Such sharks as rise to the surface for food seize it by turning over before closing their jaws on the luckless victim. The throat or cesophagus is wide ; the stomach a capacious sac, and the intestine short, separated from the stomach by a pyloric valve. The spiral valve of the intestine is a fold projecting into the cavity of the gut, the fixed edge forming a spiral line around the inner wall of the intestine. The heart consists of a ventricle and auricle, with an aortic bulb which pulsates as regularly as the heart ; and the blood must be sent forward with great force, as the very mus- cular bulb is provided within with three rows of semi-lunar valves. The gills are pouch-like, generally five, rarely six or seven, in number, the external openings or gill-slits being usually of moderate size, but sometimes long and large, as in the basking shark. While the clefts open on the side of the neck in sharks, in the skates they are placed beneath the neck. A spiracle or opening leads, in some sharks, from the up- per side of the head into the mouth. According to Wyman this is the remnant of the first visceral cleft of the embryo. In the brain the optic thalami are separate from the optic lobes, the olfactory lobes being large and long in the skates and some sharks. The medulla forms the larger part of the brain. The optic nerves unite, asin higher Vertebrates, form- ing acommon stem or chiasma, before diverging to the eyes. The eyes of some sharks have a third lid or nictitating membrane analogous to that of birds. The ear, except in Chimera, has the labyrinth completely surrounded by carti- lage. There are two testes, and usually two ovaries, but in the dog-fishes and the nictitating sharks there is but a single ovary. The oviducts are true ‘“ Fallopian tubes,” expanding posteriorly into uterine chambers, which unite and open into the cloaca. (Huzley.) . : The sharks and skates are not prolific; having but few 418 ZOOLOG Y. enemies they do not lose much ground in the struggle for life. The oviparous forms such as certain sharks, skates, and Chimera, lay large eggs enclosed in tough, leathery, purse-shaped cases. The other Elasmobranchiates are vivip- arous, bringing forth their young alive. In Mustelus and Carcharias a rudimentary “placenta” analogous to that of Mammals is developed from the yolk. The following ac- count of the development of the dog-fish (Mustelus), which * is condensed from Balfour, may be found to be applicable to sharks in general : The blastoderm or germinal disk is a large round spot darker than the rest of the yolk, bordered by a dark line (really a shallow groove). Segmentation occurs much as de- scribed in the bony fishes, reptiles, and birds. The upper germ-layer (epiblast) arises much as in the bony fishes, the Batrachians and birds, while the two inner germ-layers are not clearly indicated until a considerably later stage. The segmentation-cavity is formed nearly as in the bony fishes. There is no invagination of the outer germ-layer to form the primitive digestive cavity, as in Amphioxus, the lamprey, . Sturgeons, and Batrachians, but the Selachians agree with the bony fishes, the reptiles, and birds, in having the alimen- ‘tary canal formed by an infolding of the innermost germ- layer, the digestive track remaining in communication with the yolk for the greater part of embryonic life by an umbilical canal. This mode of origin of the digestive cav- ity, Balfour regards as secondary and adaptive, no “ gas- trula” (Heckel) being formed as in Amphioxus, etc. The embryo now rises up as a distinct body from the blastoderm, just as in other Vertebrates, and there is a medullary groove along the middle line, and by the time this has appeared the middle and inner germ-layers are clearly indicated. After this development continues in much the same manner as in the chick. At this time the embryo dog-fish externally resembles the » trout; the chief difference is an internal one, the outer germ-layer not being divided into a nervous and epidermal sublayer as in the bony fishes. DEVELOPMENT OF SHARKS AND RAYS. 419 The next external change is the division of the tail-end into two caudal lobes. The notochord arises as a rod-like thickening of the third germ-layer, from which it afterwards entirely separates, so that the germ, if cut transversely, would appear somewhat as in the embryo bird. The primitive vertebre next arise, and about this time the throat becomes a closed tube. The head is now formed by a singular flattening-out of the germ, like a spatula, while the medullary groove is at first entirely absent. The brain then forms, with its three divisions, into a fore, middle, and hind brain. Soon about twenty primitive vertebre arise, and by this time the embryo is very similar, in external form, to any other vertebrate embryo, and finally hatches in ‘the form of the adult. The skate was found by Wyman to be at first long and narrow, the dorsal and anal fins extending to the end of the tail, as in the eel. Soon after it becomes shark-shaped, and finally assumes the skate form. Thus skates pass through a shark-stage, and this accords with the position in nature of skates, since they are, as a whole, a more specialized as well as more modern group than the sharks. Wyman found that there are in the skate at first seven branchial fissures, the most anterior of which is converted into the spiracle, which is the homologue of the Eustachian tube and the outer ear-canal ; the seventh is wholly closed up, no trace re- maining, while the five others remain permanently open. The Elasmobranchs are subdivided into two orders (re- garded by Gill as super-orders, the Plagiostomi, represented by the sharks and rays, and the Holocephali, the type of which is Chimera. Order 1. Plagiostomi.—In the sharks and skates the teeth are very numerous ; the gill-slits are unavvered. The rays or skates differ from the sharks in their broad, flat bodies, with the gill-slits opening below; the great breadth of the body is due to the enlargement of the pectoral fins which are connected by cartilages to the skull ; there is likewise no median articular facet upon the occiput or base of the skull, for the first vertebra. The most common of our Selachians is the mackerel shark 420 ZOOLOGY. ° or Jsurus punctatus (Fig. 389). The head is conical, with the nostrils under the base, and the lobes of the tail are nearly equal. It is from four to eight feet in length, and is often taken in fish-nets, being a surface-swimmer. In the thresher shark (Alopecias vulpes Cuvier), the upper lobe of the tail is nearly as long as the body of the shark itself. It grows twelve or fifteen feet in length, and lives on the high seas of the Atlantic. Nearly twice the size of the thresher is the great basking shark, Selache (Cetorhinus) maxima Cuvier, of the North Atlantic, which becomes nine to thirteen metres (thirty or forty feet) in length. It has very large gill-slits, and is by no means as ferocious as most sharks, since it lives on small Fig. 389.—Mackerel Shark.—From Tenney’s ‘ Zoology.” fishes, and in part, probably, on small floating animals, strain- ing them into its throat through a series of rays or fringes of an. elastic, hard substance, but brittle when bent too much, and arranged like a comb along the gill-openings, the teeth being very small. Among the smaller sharks is the dog-fish (Squalus Amert- canus Storer), distinguished by the sharp spine in front of each of the two dorsal fins. It is caught in great numbers for the oil which is extracted from its liver. The dog-shark (Mustelus canis Dekay), which is a little larger than the dog-fish, becoming over a metre (four feet) long, brings forth its young alive. In the European Mustelus levis Risso a so-called placenta is developed, while it is wanting in the Mustelus vulgaris of Miller and Henle. SHARKS AND RAYS. 421 Among the more aberrant sharks is the hammer-headed Sphyrna zygena (Linn.), which grows to the length of twelve feet, and is one of the most rapacious and formidable of the order. Of the rays and skates, the saw-fish approximates most to the sharks. Its snout is prolonged into a long, flat bony blade, armed on each side with large teeth. Pristis antiquorum Latham (Fig. 390), the common saw- fish, inhabits the Mediterranean Sea and the Gulf of Mexico ; it is vivipa- rous (Caton.) Pristis Perroteli lives in the Senegal River, while Carcharias gangeticus is found sixty leagues from the sea. j The genuine skates or rays have the body broad and flat, rhomboidal (ow- ing to the great extension of the thick pectoral fins). Portions of the ventral fins in the males are so elon-. gated and modified as to form intro- mittent and clasping organs. They swim close to the bottom, feeding upon shell-fish, crabs, etc., crushing them with their powerful flattened teeth. The spiracle is especially developed in the rays, while, as observed by Gar- man, in the majority of the sharks which swim in midwater or near the surface, the water enters the mouth and passes freely out of the gill-open- ings, but in the rays, which remain at ™"" the bottom, the purer sea-water enters deuntten Gel, feats the spiracle from above to pass out of mag ee, ane Tater the gill-slits. The smallest and most common skate of our northeast- ern Atlantic coast is Raja erinacea Mitchell. It is one half of a metre (twenty inches) in length, and the males are smaller than the females. The largest species is the barn- door skate, Raja levis Mitchell, which is over a metre (forty- AR2 ZOOLOGY. two inches) long. Aaja eglanteria Lacepéde (Fig. 391) ranges from Cape Cod to the Caribbean Sea. The smaller figures in Fig. 391 represent respectively the mouth and gill-slits, and the jaws of Myliobatis fremenvillii Lesueur. In the torpedo the body is somewhat oval and rounded. Fig. 392 represents Torpedo marmoratus, of the Mediter- ranean Sea. Our native species, found mostly in winter, especially on the low sandy shores of Cape Cod, is Zorpedo occiden- talis Storer. Its bat- teries and nerves are substantially as in the European spe- cies. The electrical organs are construct- ed on the principle of a Voltaic pile, consisting of two series or layers of hexagonal cells, the space between the numerous fine trans- verse plates in the cells filled with a trembling jelly-like mass, each cell representing, so to ee Soh ee en ae Rout ae gill- speak, a Leyden jar, its, jaws and teeth o iobatie fremenvillit 2. Si te There are about 470 cells in each battery, each provided with nerves sent off from the fifth and eighth pairs of nerves. The dorsal side of the apparatus is positively electrical, the ventral side nega- tively so. The electrical current passes from the dorsal to the ventral side. When the electrical ray is disturbed by the touch of any object, the impression is conveyed by the sen- sory nerves to the brain, exciting there an act of the will which is conveyed along the electric nerves to the batteries, THE ELECTRICAL RAY. 423 producing a shock. The benumbing power is lost by fre- quent exercise, being regained by rest; it is also increased by energetic circulation and respiration. As in muscular Fig. 392.— Torpedo murmvratus, a, cerebrum: 0, the medulla; ¢, spinal cord; d@ and b’, electric portion of the trigeminate or fifth pair of nerves; ee’, electric portion of the pneumogastric or eighth pair of nerves; /, recurrent nerve ; g, left electric organ entire ; g’, right electric organ dissected to show the distribution of the nerves; h, the last of the branchial chambers ; i, mucus-secreting tubes.—From Gervais and Van Beneden. exertion the electrical power is increased by the action of strychnine (Owen). Marey has more recently made interesting experiments on the torpedo, examining the discharge of this fish with the 424 ZOOLOGY. telephone. Slight excitations provoked a short croaking sound. ach of the small discharges was composed of a dozen fluxes and pulsations, lasting about one fifteenth of a second. The sound got from a prolonged discharge, how- ever, continued three to four seconds, and consisted of a sort of groan, with tonality of about mz (165 vibrations), agree- ing pretty closely with the result of graphic experiments. Marey has also studied the resemblance of the electrical apparatus of the electrical ray or torpedo and a muscle. Both are subject to will, provided with nerves of centrifugal action, have a very similar chemical composition, and re- semble each other in some points of structure. A muscle in contraction and in tetanus executes a number of successive small movements or shocks, and a like complexity has been proved by M. Marey in the discharge of the torpedo. The sting-rays (Zrygon) have no caudal fin, but the spinal column is greatly elongated, very slender, and armed with a long, erect spine or “‘sting.” Some live in fresh water ; several species of sting-rays (Potamotrygon) inhabit the large rivers of Brazil and Surinam, as the Amazon, Tapajos, Ma- deira, and Araguay, digging holes in the sand, in which they lie flat and await their prey. In this connection it may be said that Raja fluviatilis of India has been taken near Ram- pur, nearly 1000 miles above tide-reach. Myliobatis has the teeth forming a solid plate or pavement. The devil-fish (Cephalopterus diabolus Mitchell) of the coast of South Carolina and Florida is the largest of our rays, be- ing eighteen feet across from tip to tip of its pectoral fins, and ten feet in length, weighing several tons. It sometimes seizes the anchors of small vessels by means of the curved processes of its head and swims rapidly out to sea, carrying the craft along with it. Order 2. Holocephali.—This small but interesting group is represented by Chimera of the north Atlantic, and Cal- lorhynchus of the antarctic seas. In these fishes the four gill-openings are covered by an opercular membrane ; thus approaching the true bony fishes, and there are but four teeth in the upper and two in the lower jaw. The brain of Chi- mera is said by Wilder to combine characters of those of GANOID FISHES. 425 Selachians, Ganoids, and Batrachians. Chimera plumbea Gill lives in deep water off the coast of New England. Subclass 2. Ganoidei (Garpikes, Lung - Fishes).—The term Ganoid was applied to these fishes from the form of the scales, which in most of the species are angular, square, or rhomboidal and covered with enamel, as seen in the com- mon garpike. In others, however, as in the Amia and Dip- noans, the scales are rounded or cycloid. These fish, z.e., both the. genuine Ganoids and Dipnot, were the character- istic fishes of the Devonian age, which has consequently been called the Age of Fishes, there being no bony fishes (7Tedeos- tei) at that time. The forms were much larger than at present, far more numerous in species, genera, and families, and they, with the sharks, were the rulers of the sea. At the present day the type is nearly extinct, being repre- sented by such isolated forms as the sturgeon, the paddle- fish, the lung-fish (Dipnot), the garpikes, and the American mud-fish (Amia). Like most of the paleeozoic types of life, the Ganoids were both generalized forms and also combined the characters of classes of animals not then in existence ; in other words they were synthetic or comprehensive types. Thus in forms like Amia, the Teleostean fishes were antici- pated ; in the Dipno?, with their external gills and lungs, not only the Amphibians, but even the reptiles were indica- ted in their hearts with two auricles, just asthe Trilobites and Merostomata, as indicated by the structure of the living king-crab, combined with the structure of Crustaceans, fea- tures which became in a degree reproduced in the terrestrial scorpions and spiders which subsequently appeared. Owing to this intermixture of ancient and modern characteristics, this reaching up and out of the piscine type of life over into the amphibian and reptilian boundaries, the classification, 7.@., actual position in nature of the Ganoids, becomes very difficult, and the views of naturalists regarding their system- atic position are very discordant. If, as insisted on by Gill, we recognize the fact that the Ganoids are an older, more generalized, and therefore more elementary group, and the osseous fishes a newer, more highly specialized group, and 426 ZOOLOGY. that there is a natural series of forms leading from the stur- geon, which is nearest the Elasmobranchs, up through the Dipnoans to the true Ganoids, and that the latter, through zlmia, leads to the bony fishes, we shall have a clue to the intricate relations existing between them and the other sub- classes of fishes. * The Ganoids of the present day are well nigh confined to fresh water, the sturgeons alone living in the sea as well as ascending rivers; though the Devonian and carboniferons forms occur as marine fossils. In synthetic forms, like the Ganoids, it is difficult to find absolute characters separating them from the Elasmobranchs on the one hand and the Teleosts on the other. The diag- nostic characters are the following: the skeleton is either wholly cartilaginous, or partly or wholly bony; the skin is either smooth, or with cycloid, or usually with ganoid scales ; the gills are free ; the gill-opening is covered with an oper- cular bone ; the first fin-rays generally sharp ; the air-blad- der with a pneumatic duct ; the embryos sometimes with ex- ternal gills. The spinal column is usually cartilaginous; in the Dip- noans, the sturgeons, the paddle-fish and allies, the notochord, with its sheath, is persistent ; while in Polypterus and Amia the spinal column is completely bony, the vertebre being amphicelous, t, e.,biconcave ; while in the garpike (Lepidos- teus) the vertebree are convex in front and concave behind. The cartilaginous skull is covered by broad, thin membrane- bones, as seen in the sturgeon. The tail is heterocercal, the lobes being, in Amia, nearly equal. The brain is as in the bony fishes, but the optic nerves unite in a chiasma. The heart and aortic bulb are as in the Elasmobranchs, and all but Lepidosteus have a well-devel- oped spiral valve in the intestine, the valve being rudimentary * Although strongly inclined to regard the Dipnoans from their am- phibian and reptilian characters as types of a subclass, Dipnoi, yet in deference to the principles stated by Gill, which we had previously fol- lowed independently in the classification of the neocaridan and paleo- caridan Crustacea, we here adopt the classification of Prof. Gill. DEVELOPMENT OF THE STURGEON. 427 in the garpikes. The oviducts communicate with the ure- ters as in the sharks and amphibians. The different modifi- cations of Ganoid structure may be observed in the examples of the different orders. Many of the Ganoids of the Upper Silurian and Devonian rocks belonged to the groups Cephalaspide and Placoder- mata. In the Cephalaspids, represented by the singular Cephalaspis Lyellii of Agassiz, the broad head was covered by a single semi-circular plate, with large orbits above, the mouth being below. The pectoral fins were rayless folds of the skin; the body behind the head was covered with rhom- boidal scales, and provided with adorsal fin. The Pteraspis had a kead-shield composed of seven pieces. Among the Placoderms, Pterichthys had a plated head half as long as the body, the tail short and scaled. These fishes, the earliest known Vertebrates, were bottom-feeders. Nothing is known as to the nature of their jaws or teeth. Order 1. Chondroganoidei.—In these Ganoids the dorsal chord is not ossified ; the skull is cartilaginous, covered with membrane-bones ; they are either toothless or with small teeth. The skin is naked as in the paddle-fish, or protected as in the sturgeons with very large, bony, solid plates. The sturgeons have the snout long and pointed, with the mouth underneath, and toothless. Actpenser sturio Linn. is the common sea-sturgeon of our coast, ascending rivers. The shovel-nosed sturgeon, Scaphirhynchops platyrhynchus has a spade-like snout. It inhabits the waters of the Mississippi Valley. Salensky has studied the embryology of the Russian sturgeon. The freshly-laid eggs are two millimetres in di- ameter, the yolk undergoes nearly total segmentation, thus connecting most Vertebrates in which the eggs only partially segment, with the Amphioxus, lampreys, and amphibia, in which segmentation is total. The skeleton is developed much as in the Elasmobranchs. The sheath of the noto- chord develops in three weeks after hatching. At the end of the third week the upper and lower vertebral arches appear, arising as in other fishes. The skull is indicated in two or three weeks after hatching. 428 ZOOLOGY. The singular spoon-bill, Polyodon folium Lacepéde, is five feet long; it is smooth-skinned and has a snout one-third as long as the body, and spatulate, with thin edges. It has a very wide mouth with minute teeth, and lives on small Crustacea. It abounds in the Mississippi, and its larger tributaries. Order 2. Dipnoi.—The lung fishes are so called from the fact that often being in pools and streams liable to dry up, they breathe air directly, having true lungs, like those of Amphibians, as well as gills. From the nature of their lungs and heart, the Dipnoans are quite different from all other fishes, anticipating in nature the coming of Amphibians, while on the other hand the notochord and sheath is persist- ent, and as they were characteristic and more numerous in Devonian times, they may be said to be a prematurative type. The body of the Dipnoans is somewhat eel-shaped, though not very long in proportion to its thickness, and is covered with cycloid scales. The pectoral and ventral fins are long, narrow, and pointed, and there is a long caudal fin which is protocercal, a term proposed by Wyman to designate the form of the caudal fin of embryo sharks. In fact, the tail of the young garpixe, as of embryo Teleosts or bony fishes, is at first protocercal, afterwards’ being heterocercal in adult Ganoids, such as the garpike, and in the embryo and early free stage of most bony fishes ; the tail in the latter becoming finally homocercal or equal-lobed. Thus the tail of the Dipnoans may be said to be embryonic, 7.e., protocercal. The spinal column is represented by a simple notochord and sheath ; within the latter the basal ends of the bony neural arches and ribs, and near the tail the lower (hemal) arches are imbedded. The skull is cartilaginous. The extremity of the lower jaws supports large tooth-like plates (dentary plates) which shut in between the few palatine teeth ; in Ceratodus these plates are single, and in all Dipnoans these single den- tary plates are very characteristic of the group. The narrow pectoral and ventral fins are supported by.a single, median, LUNG FISHES. 429 many-jointed cartilaginous rod, to which is attached fine fin- rays, supporting the thin edge of the fin. The spiral valve and cloaca are present in the intestinal tract. In Polypterus the cerebral hemispheres are larger than the olfactory lobes, and there 1s an optic chiasma ; the heart has besides the right large auricle, a left smaller one which receives the blood from the lungs, and a single ven- tricle, as in Amphibians and most reptiles; they have true nostrils. The lungs are like those of Amphibians, and in addition they possess both internal and external gills (Hig. 393), the latter nearly aborted in the adult. The genus Ceratodus was originally named by Agassiz, pee ie EA ee sone Po- from teeth found in Jurassic and Triassic strata in Europe. Living specimens were found by Mr. Krefft in Queensland, Australia, and called Ceratodus Fostert Krefft (Fig. 394). This fish is rather more elemen- ‘tary in form than Lepidosiren, the body being stouter, and the large scales of the body, with the fin-like paddles and distinctly rayed vertical fins, cause it to resemble more closely ordinary bony fishes than Lepidosiren (Giinther). Moreover ace Nee Fig. 394.— Ceratodus, or Australian Lung-Fish. (The tail in nature ends in a point.) —After Giinther ; from Nicholson. the lung is single, and not used so much as the two perfect lungs of Lepidosiren. It attains a length of six feet. It can breathe by either gills or lungs alone. When, Gtinther thinks, the fish is compelled to live during droughts in thick muddy water charged with gases which are the product of decomposing organic matter, it is obliged to use its lungs. The gills are more like those of ordinary bony fishes than those of Lepidostren. It lives on the dead leaves of aquatic grasses, etc. The local English name is “flat-head,” the 430 ZOOLOG ¥. native name being “‘barramundi.” Nothing is known of its breeding habits or mode of development. The eggs when ready to be laid are 2.5 millimetres in diameter. The lower part of the oviduct is much asin Menopoma. Fossil teeth of Ceratodus occur in the Jurassic beds of Wyoming, and two species have been found in still older beds in Ilinois, regarded by Cope as either Upper Carboniferous or Permian. Thus, Fig. 395.—-Protopterus annectens, a Lung-fish of Africa. One third natural size. as remarked by Giinther, we have in Ceratodus a genus which has survived from the Triassic period. The lung-fish are distinguished by two well-formed lungs, and the narrow ribbon-like fins. In Lepidosiren paradozxa Fitzinger, there are five gill-arches, with four slits, and the body is rather longer, more eel-like, with a blunter snout than in Protopterus. It grows to one metre in length, and Fig. 396.—Skeleton of Protopterus annectens, showing the protocercal tail and the simple rod-like limbs, the pelvic and shoulder girdles, and the nature of the jaws. ch, notochord ; p, bones representing the hemal arches attached to the notochordal sheath ; 4s, hemal spines ; in, zh, rays of the caudal fin.—After Owen. inhabits the rivers of Brazil. This is represented in Africa by the closely allied Protopterus annectens Owen (Figs. 395 and 396 skeleton), which has six gill-arches, with three pairs of external gills in the young. It is 40-70 centimetres in length. It lives on leaves in the White Nile, Quilimani, Niger, Gambia, and their tributaries. It buries itself in the mud afoot deep. Ginther states that numerous examples POLYPTERUS. 43) of Lepidosiren “have been kept in captivity, but none have shown a tendency to leave the water.” The modern Dipnot represent the Devonian fishes Holop- tychius, Dipterus, and Phaneropleuron, and the American ,Dinichthys Torrellt of the Devonian rocks of Ohio, which is said by Newberry to have been about five metres (from fifteen to eighteen feet) in length, and a metre in thickness, being inferior only in size to the Astero- lepis, a Placoderm of the old red sand- stone of Great Britain. Order 3. Branchioganoidet.—Here be- longs the Polypterus of the Nile and Senegal. In these Ganoids the tail is either protocercal or heterocercal; the scales are cycloid or rhomboid. The dorsal fin is iong, subdivided into divis- ions, each with a separate ray and spine. Polypterus bichir Geoffroy (Fig. 397) has a protocercal tail. The young has external gills (Fig. 393). It inhabits the river Nile, P. senegalus the Senegal. Calamoichthys differs in having no ven- tral fins and in its elongated form. It inhabits the rivers of Old Calabar. Al- lied to these living forms are the De- vonian Osteolepis, Celacanthus, and Ho- loptychius. Order 4. Hyoganoidei.—This group is represented by the garpike and Amia or mud-fish of the United States, which is an annectant form connecting the Ganoids with the Teleosts. In these 4, 397.—Polypterus bi- fishes the spinal column is bony, the #r—From Cuvier. tail partially heterocercal. In Lepidosteus (Fig. 398, L. ossews Agassiz) the body is long, the jaws long and armed with sharp tceth, the vertebra" are opisthocelous, and the scales are large and rhomboidal, 432 ZOOLOGY. while the air-bladder is cellular, lung-like. Fossil species oe- cur with those of Ama in the tertiary rocks of the West. Lepidosteus osseus Agassiz, the bony gar, with a long, slender snout, is sometimes five feet long; L. platystomus Rafin. has a short nose, while the alligator gar, L. spatula Lacé- péde, has a short and wide snout, and grows to a larger size (nearly three metres) than the other species, and inhabits the Mississippi Valley. The garpikes are carnivorous, very rapacious, and are said to destroy large numbers of food- fishes. They usually remain near the surface of the water, emitting bubbles of air and apparently taking in a fresh supply. Wilder has observed Amita inhaling air, and re- marks that ‘‘so far as the experiments go, it seems probable that, with both Amia and Lepidosteus, there occurs an inha- lation as well as exhalation of air at pretty regular intervals, the whole process resembling that of the Menobranchus and other salamanders, and ‘the tadpoles, which, as the gills Fig. 398.—Garpike. From Tenney’s Zoology. shrink and the lungs increase, come more frequently to the surface for air.” Both of these fishes are very tenacious of life and withstand removal from water much better than bony fishes and sturgeons, on account of the lung-like nature of their air-bladder. Wilder shows that there is a series of ‘forms, mostly Ganoids, from the Amia and Lepidosteus in which the pneumatic duct enters the throat on the dorsal side, up to Lepidosiren in which it enters the throat on the ventral side, like the air-tube or trachea of Amphibians and higher Vertebrates. The breeding habits and ed changes in form of the garpikes have been described by Mr. A. Agassiz, The gars, which are nocturnal in their habits, appear on the shores of Lake Ontario,near Ogdensburg, in immense numbers between MUD FISH. 433 the middle of May and the 8th of June, remaining at other times of the year in deep water. ‘The young begin to hatch about the end of May. At first the embryo gar possesses an unusually large yolk-sac, while the notochord is very large; otherwise posteriorly it resembles the young of bony fishes. It differs, however, in its large mouth, which is surmounted with a hoof-shaped depression edged with a row of projecting suckers, by which it attaches itself, hanging immovable, to stones; the eye and brain is smaller than in bony fishes. The tail is at first protocercal, beginning on the second day to become hetero- cercal. On the third day the gill-covers form rectangular flaps, and the first traces of the pectoral fins appear, while the snout becomes longer. By the fifth day the traces of the dorsal, caudal, and anal fins appear. When a little over three weeks old it assumes a more fish-like form ; the suck- ing disk has nearly disappeared, the lower jaw greatly length- ened, and the gill-covers extend to the base of the pectoral fins. When between two and three weeks old the young gar-fish is 20 millimetres (inch) long. The young rise to the surface to swallow air, as in the adult. Soon after this it is of the form first discovered and figured by Wilder. The gar-fish, according to Agassiz, bears some resemblance to the sturgeon in certain stages of growth, and in the forma- tion of the pectoral fins from a lateral fold, as well as by the mode of growth of the gill-openings and the gill-arches, while it closely resembles the young of bony fishes in the develop- ment of the posterior part of the body, by the mode of origin of unpaired fins from the embryonic fin-fold, and by the mode of formation of the fin-rays, and of the ventral fins. The mud-fish, Ama calva Linn., is like an ordinary bony fish in form, with rounded scales; the caudal fin “ masked heterocercal,” the snout is short and rounded, and the air- bladder is large and cellular. It attains a length of two thirds of a metre, and occurs in the Mississippi Valley and as far east as New York. A fossil form closely allied to Amia dates back to the Cretaceous Age, and the genus Caturus is a Liassic and Oolitic genus. 434 ZOOLOGY. Subclass 3. Teleostei (Bony fishes).—We now come to a type of fishes which, within very recent geological times as well as during the present period, has become differentiated or broken up into thousands of species, corresponding to the complexity of their physical environment as compared with the simple features of the physical geography of De- vonian and Carboniferous land-masses. Like most of the larger groups of animals, as the Decapod Crustacea, and especially the insects, as well as the mollusks, the bony. fishes have attained an astonishing amount of specialization, as if the tree of icthyic life, taking root in the Silurian Age, and sending out but a few branches in later Paleozoic times, had suddenly, in the Cretaceous and Tertiary Ages, thrown out a multitude of fine branches and twigs intertwining and spreading out in a way most baffling to the systematist. The essential, diagnostic characters of the bony fishes, 7.¢., such as separate them from the Elasmobranchs and Ganoids, are as follows: The skeleton is bony, the vertebre being sep- arate ; the outer elements of the scapular arch are simple, the inner elements for the most part bony and usually three or two in number ; the pectoral fins are without any bone rep- resenting the humerus, and are connected with the scapular arch by several (generally four) narrow bones (Gill). The optic nerves cross one another. The gills are free, usually four on each side, and with several opercular bones. The heart is without a cone, but with an arterial bulb, and with but two valves at the origin of the aorta. The intestine is destitute of a spiral valve. The student should dissect a typical Teleost, such as a fresh-water or sea perch, with the aid of the following ac- count of its anatomy. The drawing and account here given of the anatomy of the sea-perch have been prepared by Dr. C. Sedgwick Minot. The common sea-perch or cunner (Tautogolabrus adspersus Gill, Fig. 399) resembles the fresh- water perch very closely in its anatomy, the most note- worthy difference being the absence of the cceca at the pyloric end of the stomach in the marine species; with this exception the following description applies almost equally well to the fresh-water perch, so that this account will be ANATOMY OF THE CUNNER. 435 available for western students who have not access to speci- mens of the cunner. The perch has the general form of a flattened spindle, for it tapers down at either end and is compressed laterally. There is no neck marked off externally, and the head ap- pears as the direct continuation of the body, but separated from it by a fissure on either side; this is the opening of the gills, which extends from above downwards and curves forward, nearly meeting its fellow on the median line of the under jaw ; upon opening the gill-slit the pectinate or comb- like gills or branchiz are seen within. There are four sets of branchial filaments, each set attached to a separate de- scending arch, in front of each of which is a slit leading into the cavity of the mouth ; but there is no slit behind the last gill. The branchie are protected externally by the gill- cover or operculum, which is attached in front, but is free behind, where it forms the front edge of the gill-slit ; it is composed of four distinct parts: 1. The preoperculum nearest the eye, and with its lowest corner almost a right angle; its posterior and vertical edge is furnished with numerous minute projecting spines. 2. Appended to the underside of the margin thus armed is the operculum. 3. Below the preoperculum is the interoperculum, which par- tially covers up 4, the suboperculum. ach of these parts has a separate bony support; all four bones are developed only in the Teleosts; in sturgeons, for example, there is only an operculum, to which in other Ganoids other parts are added; in Selachians the whole apparatus remains undeveloped. The mouth is placed in front ; the upper lip is capable of independent motion, being supported by the pramaxillary bones, which are but loosely attached to the cranium, though in many other fishes the union is closer. The eyes are large and lidless; just in front of each eye is an opening of the size of a pin’s head ; these openings lead into the nasal sacs, of which there are two, but both are without communica- tion with the mouth; in higher vertebrates, from the Dip- not upwards and in My.cine, there is such a communication. In the Marsipobranchii there is but a single median nasal sac. 436 ZOOLOGY. The ear has no external opening, being completely encased in bone. Nearly parallel with the line of the back extends a continuous row of yellow spots marking the lateral line (Fig. 399, Z), along which are found the pore-like open- ings of the so-called muciparous glands. Ali fish have fins of two kinds—unpaired and paired ; the latter, four in number, correspond to the limbs of other Ver- tebrates. The unpaired fins are first developed on a contin- uous median flap of integument, which extends along the back, around the tail, and on the underside as far forward as the anus; cartilaginous or bony rays are developed in it as a support. In the adult fish the fold is generally discontinu- ous, being usually separated into three distinct fins—dorsal, caudal, and anal ; the dorsal fin is frequently, the anal fin sometimes subdivided. The fin-rays are (1) either simple pointed rods, or (2) jointed and branching. All the rays of the caudal fin, and the posterior rays of the dorsal and anal fins, are branching. In some Malacopterygians all the rays are branching ; in many, however, the first ray is simple in the dorsal and anal fins, while fishes like the perch and cun- ner are distinguished by having several or many of the an- terior raysof the dorsal and anal fins simple and pointed. In the cunner half the rays of the dorsal and the first two of the anal fin are simple. The pectoral fins are attached to the side of the body and are large and rounded. ‘The ventral fins le further back near the median ventral line ; they are smaller than the pec- torals. The position of the ventrals varies in different fish, and is much used in classification. The anus lies immedi- ately in front of the anal fin. The body is covered by scales, which overlap one another ‘from before backward ; their free edges are rounded and smooth, hence they are called cycloid. These scales, as in all Teleosts, are ossifications of the underlying cutis, and are covered by the epidermis ; they were formerly wrongly sup- posed to be epidermal structures. 'To dissect a perch the side-wall of the mouth must be re- moved, then the gill-cover ; study the arrangement of the gills. Next make an incision along the median ventral line ANATOMY OF THE CUNNER. 43% from the level of the pectoral fins to just before the anus, and following the upper edge of the body-cavity upward and for- ward cut away the body-wall, taking care not to injure the large swimming-bladder above, nor the heart in front. Now open the pericardial cavity, which lies ventrally immedi- ately behind the gills (see Fig. 399, Ht). Cut away the mus- cular masses around the back of the head ; expose the cavity of the brain, and remove the loose cellular tissue around the nervous centres. If the gills of one side are excised and the intestine drawn out, the dissection will appear very much as in Fig. 399. The cavity of the mouth widens rapidly and continues as the branchial chamber or pharynx (), whence we can pass a probe outward through any of the gill-slits. There isa single row of sharp-pointed teeth in front on both the under and upper jaws; in the pharynx above and below there are rounded teeth. At the side of the pharynx are the four gill- slits and the four arches ; the inner surface of the anterior three arches is smooth, while the arch behind the fourth slit is much modified in shape and is armed with tubercles and teeth. The entrance of each slit is guarded in front and behind by a row of projecting tubercles appended to the arches. On the outside of each arch, except the fourth, is a double row of filaments, richly supplied with blood-vessels which, shining through, give a brilliant red color to the gills; on the fourth arch there is but a single row. At the upper and posterior gorner of the pharynx is the small open- ing of the short cesophagus. . The branchial chamber has an upward extension on the sides of which lie the pseudobran- chize (Ps), accessory respiratory organs not connected with the gills proper, and receiving their blood-supply from distinct arteries. There are no salivary glands. The esophagus dilates almost immediately to form the stomach (partly concealed in the figure by the liver, Zi), which seems hardly more than a dilatation of the intestine (dn). This last isof nearly uniform size throughout, and after making three or four coils terminates at the anus, immedi- ately in front of the urinary and genital apertures. When in situ, the terminal portion of the intestine or the rectum 438 ZOOLOGY. extends straight along the median ventral line. The liver (Z7) forms an elongated light-brown mass resting upon the stomach. The elongated gall-bladder lies between the liver and stomach, somewhat imbedded in the substance of the former. There is no pancreas, though it is present in some fishes. The spleen (Sp) lies between the stomach and intestine, in the mesentery ; it is dark reddish-brown in color. The air-bladder (8) is a single large sac, placed in the dor- sal part of the body-cavity. Its glistening walls are com- posed mainly of tough fibrous tissue. The pneumatic duct, by which the bladder communicates with the esophagus in many fishes, is wanting in the perch as in nearly all other Teleosts. The air-bladder normally contains only gases. It conceals most of the kidneys, which extend the whole length of the body-cavity on either side of the middle line, as two long strips of a deep though dull red. They project beyond the air-bladder in front (A?) and behind (A7v’). Their an- terior ends are somewhat separated from one another by the intervening pharynx. The ureters open into a urinary bladder (47) behind the anus. The ovary is single and varies greatly in size according to the season. In the male the sexual glands are double. Each testis (2) is an elongated, whitish, lobulated organ, placed im- mediately below the swimming-bladder, and continues pos- teriorly with the spermiduct, which opens immediately be- hind the anus. The heart (H7#) lies in the triangular pericardial cavity ; it consists of two portions, the dark-colored venous chamber, or auricle, above, and the lighter-colored arterial chamber, or ventricle, below. The auricle receives from above two large veins, one from either side ; these veins are called the ductt Cuviert. Each Cuvierian duct, as can be seen in the figure, ascends beside the cesophagus, and there receives a large jug- ular vein from in front, and a large cardinal vein from be- hind. Furthermore, a large vein, the sole representative of the vena cava of higher Vertebrates, passes from the liver, near its anterior end, through the pericardium, and empties into the Cuvierian ducts near their common auricular orifice. ANATOMY OF THE CUNNER. 439 The walls of the auricle are comparatively thin ; the auriculo- ventricular orifice is provided with valves, which prevent the blood flowing back into the auricle. The walls of the ventricle are thick and very muscular ; from the upper end of the ventricle close to the base of the auricle springs the bulbus arteriosus, a muscular cylinder, which, running hori- zontally forward, passes out through the pericardium, and is continued as the less muscular aorta (4) underneath the branchial arches along the median line ; the aorta gives off branches on both sides, one to each arch to supply the bran- chiw ; the vessels after ramifying are gathered together, to again form a single trunk, which passes backward immedi- ; Fig. 399.— Anatomy of the Cunner, maie. Z, lateral line ; ¢, heart ; G, pharynx ; Ps, pseudobranchia ; Sp, spleen ;_S, air-bladder; Ki, Ki’, kidneys ; b/, bladder; 7, tes- tis ; A, aorta; B, brain ; Jn, intestine ; Zi, liver ; @, gills.—Drawn by C. S. Minot. ately underneath the spinal column ; it is called the descend- ing aorta. The body and pericardial cavities are called serous, because their lining membranes are always moist with serum, a watery fluid, very much like blood-plasma. The lining of the body- cavity is named the peritonewm, and forms a continuous cov- ering around the viscera. It is important to observe that the various organs simply project into the body-cavity and do not lie really inside of it. In fishes we find the disposition of the parts to correspond more closely with the fundamental type of Vertebrate structure than it does in higher forms, in which further modifications have supervened. The pharynx still has its distinctive character ; the pericardium lies at the 440 ZOGLOG Y. base of the neck, instead of in the thorax as in the higher Ver- tebrates. The heart still preserves its primitive division ; on the other hand, the swimming-bladder is a special adaptation ‘of the piscian type, while the frequent absence of the pan- ereas is a peculiarity of fishes the meaning of which is not yet understood. The brain (B) does not occupy the whole of the cranial cavity, but is imbedded in a large accumulation of cellular tissue. In order to study the brain satisfactorily, it should be exposed from above, laying bare at the same time the optic nerves and muscles. The two olfactory lobes are followed by two lobes (#7), the cerebral hemispheres, and immediately behind them two larger lobes (Q), the corpora bi- or quadrt- gemina (optic lobes, not optic thalami) ; further back follows a single median lobe (C8), the cerebellum, somewhat conical in shape and resting upon the medulla oblongata (I), from which spring various nerves, and which, tapering backward, is continued as the spinal cord. In front appear the very large and conspicuous optic nerves (Op), the right nerve passing obliquely to the left eye, the left nerve to the right eye running under the right nerve, but forming no chiasma; each optic nerve is a plaited membrane, folded somewhat like a fan when shut up, an arrangement occurring only among fishes. In a side-view of the brain (ig. 400, Z), the mode of origin of the optic nerves and their origin from the optic lobes can be clearly seen ; it further shows the various forms of the lobes of the brain, and the large inferior lobes (Z) below the corpora quadrigemina ; these lobes are very remarkable and difficult to homologize. _ The eyes lie in two sockets, separated by an interorbital septum (Fig. 400, 8). The eyeball has the form of an ob- late spheroid, and is moved, as in all Vertebrates, by four recti and two obliqui muscles. The recti spring from around the exit of the optic nerve from the brain-case, and thence diverge to be inserted into different parts.of the eyeball ; above is the rectus superior (Rs) ; towards the interorbital septum (S) rectus internus (Ri), opposed to the last is the rectus externus (Re), and below is the rectus inferior, not shown in the figure. In Teleosts both oblique muscles, the ANATOMY OF THE CUNNER. 441 superior (Os) and inferior (Ot), arise from the front of the orbit near the interorbital septum. The disposition of the a 400.—Anatomy ofthe brain of the Cunner, dor-al and side view. B, OU, olfac- tory lobes ; the crura and the thulami not represented.—Drawn by C. S. Minot. recti is very constant, but the obliqui vary considerably in their origin in different Vertebrates. If a perch be cut through transversely, so that the section passes through the fore-part of the air-bladder, and the anterior portion then looked at from behind, a very instructive view will be obtained, as in Fig. 401. The best sections can be made by first freezing the fish. The vertebral column (V) appears a little above the middle; overlying it is the neural canal with the spinal cord ; im- mediately below it is the descending or 4 dorsal aorta (Ao), on either side of which follow the kidneys (A), resting directly upon the air-bladder (Bd). Lowermost is the body-cavity, with _ the stomach (S), and intestine (Jn), throtuh tlemulddie of he body surrounded by the liver, which has $f, Cunner—Drawn by'C. 8. been almost entirely removed. The rest of the section is occupied by muscles, which, it will thus be seen, make up the main bulk of the body. (Minot.) 442 ZOOLOGY. The so-called ‘* mucous canal” or lateral line of fishes an,” Amphibians is sensory. It consists of small masses of nerve-epithelium, arranged in linear series along the sides of the head and body, having hair-cells continuous with nerves. They are called ‘‘nerve-buttons” or “ nerve-heaps.” Accord- ing to Schultze, their office appears to be to appreciate mass- movements of the water, and more particularly vibrations, which have longer periods than those appreciated by the ear (Dercum). In the blind-fish of the Mammoth Cave a row of sense-papillz is situated on the front of the head, sup- plied with nerve-fibres sent from the fifth pair of nerves (Wyman). The angler (Lophius piscatorius) has long been known to possess hinged teeth, capable of being bent inward toward the mouth, but by virtue of the elasticity of the hinge at once resuming the upright position when pressure is removed from them. . EE chians as in fishes, and Fig. 428.—Skeleton of a Frog. a, skull; 0, bony parts are developed vertebrae ; ¢c, sacrum, and e, its continuation | : : 7 (urostyle); f, suprascapula ; g, homcrus; 2, foree jn Gonnection with it arm bones; i, wrist bones (carpals and meta- mn ; carpals); d, ilium; m, thigh (femur); %, leg which essentially corre- bone (ulna): 0, elongated first pair of ankle- bones (tarsals) ; p, 7, foot bones or phalanges. Spond to those of fishes. —After Owen. (Gegenbaur. ) The suspensorium is immovably joined to the skull, and with it is connected the hyoidean arch. The branchial arches in the tailed forms persist in varying numbers, 7. e., from two to four, but are dropped in the toads and frogs. The skulls of certain Labyrinthodonts are roofed in by broad, flat bones, so that they bear a strong resemblance to certain Ganoids represented by the garpike, while Gegenbaur states that there are many bony parts in the skull of the Batra- chians which resemble those in the Dipnoan fishes. The ex- ANATOMY OF BATRACHIANS, 467 tinct Archegosaurus had in its larval life branchial arches, and in fact so close are the affinities of some Amphibians to the Ganoids that it is probable that both types have had a com- mon origin ; while on the other hand the bones of certain extinct scaly Labyrinthodonts have been regarded by some authors as reptilian ; for example, the Carboniferous Mas- todonsaurus was described as a reptile, but has been referred to the Amphibians by modern writers. The sternum or breast-bone (Fig. 429, s) first appears in the Batrachians. The shoulder-girdle is in great part carti- Jaginous. In the toads and frogs (Anwra) the fore limbs, the radius, and ulna, and in the hind limbs the tibia and fibula, grow together; there are four toes in the fore feet, and five toes in the hind feet. In the Siren the hind legsare pig. 429-sternum and shoulder-girdle of Frog (Rana temporaria). p, body of wanting 5 in the congo-snakes the sternum ; sc, scapula ; sc’, supra-scap- . ‘ ula; co, coracoid-bone, fused in the mid- (Amphiuma) the limbs are dle line with its fellow of the opposite either tao or three-toed, extrome shaded double, portion Délow p T'he teeth of modern Ba- is the xiphistemum. The cartilaginous ig i parts are shaded.—After Gegenbaur. trachians are conical or lobate, and microscopically are simple, while those of the extinct forms are mostly complicated by the labyrinthine infolding of the walls, as seen in microscopic sections; the teeth of many Ganoids have a similar, though much simpler struc- ture. They are usually of the same size, and may be ar- ranged on projecting portions of different bones of the mouth, a.é., the premaxillary, maxillary, mandibular, vomerine, pal- atine, and pterygoid bones, as in fishes. In tadpoles and in Stren the jaw-bones are encased in horny beaks like those of turtles and birds. In many Labyrinthodonts two tusks were developed on the palate. The nasal canal is much as in the Dipnoan fish, the internal opening being situated in the Perennibranchiates just within the soft margin of the mouth. In the, salamanders and frogs it is bordered with firmer parts of the jaw. The labyrinth of the ear is large, and the tympanum or drum of the ear is external, Am- 468 ZOOLOGY. phibians having a middle ear in addition to the internal ear of fishes. In toads and frogs the tongue is quite free and capable of being protruded, except in Pipa and Dactyle- thra, where it is entirely wanting. In other forms the tongue is much as in fishes, not being capable of extension from the mouth. As in fishes, there are no salivary glands. The gills: of Am- phibians consist of two or three pairs of branched, fleshy appendages, which | grow out from as many arches. While in the toad and frog the gills are small and remain but for a short time, in the Jarval salaman- ders, especially the axolotl (Fig. 430), the gills are still longer retained, while in the mud-puppy (Necturus) they persist throughout life. The digestive canal is us- ually simple, straight, there being no enlargement form- ing a stomach; in other species, both tailless and tailed, the canal dilates into a stomach, which in the toad lies across the body- ig. 430.— Axolotl, or larval Salamander, = : deena tke gills, heart (H), aortic branches Cavity. In tadpoles, which and lungs ( P, pulmonary arteries; 7; = Pp, easy veins; A, bulbus arteriosus live on decaying vegetable f hich th jar arches (B : ‘est ciate whlch, Wee eaalae : the eae neean matter, the digestive tract cava: V, descending aorta,—From Gervais is very long and. closely coil- et Van Beneden. . ed (Fig. 431). The lungs are long, slender sacs, much like those of the Dipnoan Lepidosiren, which extend backwards into the ab- domen, as in the lizards and snakes, no diaphragm existing to confine them in a thoracic cavity. The larynx exists in a very rudimentary state, though the vocal powers of the ANATOMY OF BATRACHIANS. 469 toads and frogs are so highly developed. The trachea ig short. The heart has two auricles, the right one the larger, and a single ventricle ; but in Protews the auricles connect with each other, and in the salamanders there is a hole in the par- tition separating the auricles. There are also indications of Fig. 431.—Mouth and digestive canal of a Tadpole. A, mouth; 3, intestine coiled on itself ; ¢, liver ; d, hepatic duct; e, pancreas; Jf, rudimentary hind legs ; g, rectum. —After Gervais and Van Beneden. a partition in the ventricle. Fig. 432 represents the circulatory or- : Fig. 432.—Tadpole of a Frog. 1, gans of a tadpole, after the gills yeng'cavay zrigheauricle ; 3° pal, have become absorbed, and before Movary vein and its origin in the two lungs; 4, left auricle; 5, ven- the aortic arches are reduced in tticle; 6, arterial bulb ; 7, branchial artery and its internal branches; 8, number. branchial veins ; 9, aorta; 10, pul- monary artery and its subdivisions The nervous system is much _ inthe jungs.—After Gervais and Van as in reptiles ; but the optic lobes *°"°*™ are rather small ; the cerebrum is small. The kidneys are in many respects like those of fishes, especially sharks, as is the internal reproductive system. The ovaries are greatly enlarged during the breeding season. The sperm is usually passed to the kidney, and thence through the ureters out of the cloaca. The oviducts and ureters have a common outlet 470 ZOOLOGY. into the cloaca. In the salamanders the end of the oviduct. serves as a uterus. There are also fat-bodies (Fig. 433) at- tached to the anterior end of the reproductive glands of the toads and frogs, the use of which is unknown. For a gene- ral idea of the structure of Amphibians the student should dissect a frog or toad in connection with the following de- scription and accompanying illustration (Fig. 433), prepared by Dr. C. 8. Minot. The frog is one of the types of Vertebrates most valuable to the student, being readily obtained and easily dissected. The accompanying figure represents the anatomy of the spotted or leopard frog, Rana halecina, male. The skin is smooth, having neither scales, feathers, nor hairs, and contains numerous microscopic glands, of which there are said to be two kinds—one having an acid, the other an alkaline secretion (L. Hermann). It is pigmented on the dorsal surface, but whitish underneath. The head is broad, triangular, with two large nasal openings in front, large and prominent eyes, two tympanic membranes formed. by a part of the integument stretched across a hard ring, and an cnormous moyth. The neck is short and not con- stricted. The body tapers slightly posteriorly, and has the opening of the cloaca upon the posterior end of its back. Each limb consists of the three divisions: in the front leg, brachium, antebrachium, and manus with four digits, of which the fourth is very much thickened in the male; the sexes may be distinguished by this mark. In the hind leg the three divisions are the femur, crus, and pes, with five long digits, between which the membranous web is stretched. If the web is examined in a living frog with a microscope,. the circulation of the blood in the capillaries can be studied. The current of corpuscles and plasma is constant, and in a given vessel passes only in one direction ; by following the stream backwards and forwards it will be found to issue from larger vessels, the arteries, and to enter into other and different vessels, the veins. The pigment corpuscles can also be seen in the web; they are branching bodies, capable of drawing in or expanding their processes, and they can be made to contract by an electrical shock from an induction apparatus. ANATOMY OF THE COMMON FROG. ATI Slit open the skin along the median ventral line the whole length of the animal, turn the skin back, and then cut through the muscular walls of the abdomen, being care- ful not to injure the underlying organs. The viscera will then be exposed : the coiled intestine, the large liver, and in the female the sexual organs at either side; finally, pos- teriorly, the thin-walled bladder, B. The next step is to seize the posterior end of the sternum with a pair of for- ceps, lift it up, cut the fibres which run from its under sur- face, and cut with a pair of strong scissors along both sides of the sternum and around its anterior end, so as to remove itentirely. Underneath the sternum lies a thin-walled bag, the pericardium, enclosing the heart. On either side are the lungs. To complete the preparation dissect out the intestine, by cutting through the mesentery ; follow it to the stomach, which must be separated from the esophagus and drawn aside together with the intestine, while the liver must be turned over to the right of the animal. The pericardium — must be cut through and removed without injury to the heart; finally, the skin must be removed from the hind legs. If the dissection is of a male, it will then appear very much as in the figure. The heart is conical in shape ; ; its apex points backwards, and is formed by a single chamber, the ventricle, with thick muscular walls, from which springs on the ventral surface a little to the right the truncus arteriosus (Ao), which runs forward and divides into the two aortic arches. The base of the heart contains two chambers, the right and left auricles, the separation of which is not marked externally. a SY Fig. 484,—Metamorphosis of the Toad.—After Owen ; from Tenney’s Zoology. In certain Batrachians as the Alpine salamander, the Su- rinam toad (Pipa) and the Hylodes of Guadaloupe in the West Indies, the metamorphosis is suppressed, development, being direct ; though the young have gills, they do not lead an aquatic life. In the axolotl there is a premature devel- opment of the reproductive organs, the larve as well as the adults laying fertile eggs. The Batrachians are inhabitants of the warmer and tem- perate zones. Frogs extend into the arctic circle. The Amblystoma mavortium breeds at an altitude of about 8000 feet in the Rocky Mountains. Rana septentrionalis Baird extends to Okak, Northern Labrador, where the climate is as extreme as that of Southern Greenland ; frogs have also been 478 ZOOLOGY. observed at the Yukon River in lat. 60° N., but the climate there is milder than that of Labrador. The common toad and a salamander (Plethodon glutinosa Baird ?) extend to Southern Labrador. Nearly 700 species of existing Batrachians are known, 101 of which are North American, and about 100 fossil forms have been described. There are five orders of Batrachians, Professor Cope’s classification being adopted in this work. Those Batrachians with persistent gills are sometimes called Perennibranchiates. Order 1. Trachystomata.—The sirens have a long eel-like body, with persistent gilis ; there is no pelvis or hind limbs, and the weak, small fore legs are four or three-toed. The great siren, Siren lacertina Linn., is sometimes a metre in length, and has four toes in the fore leg ; it lives in swamps and bayous from North Carolina and Southern Illinois to the Gulf of Mexico. A small siren with three toes and small gills is Pseudobranchus striatus Le Conte. It occurs in Georgia. Order 2. Proteida.—This group is represented by the Proteus of Austrian caves and the mud-puppy (Necturus) of the United States. These Batrachians have bushy gills, with gill-openings and well-developed teeth. In Proteus, which is blind, there are three toes in the fore feet and two in the hinder pair. In the mud-puppy, Nectwrus (formerly Menobranchus) Jateralis Baird, each foot is four-toed. The head and body are broad and flat, brown with darker spots. It has small eyes and is about half a metre (from 8 inches to 2 feet) in length. It inhabits the Mississippi Valley, extend- ing eastward into the lakes of Central New York. The Proteus as well as the mud-puppy lay eggs. Order 3. Urodela.—The tailed Batrachians or Salaman- ders rarely have persistent gills, these organs being larval or transitory ; the body is still long and fish-like, the tail some- times with a caudal fin-like expansion as in the newts, but is usually rounded, and the four legs are always present. With only one or two viviparous exceptions, most of them lay eggs in the water. The eggs of Triton are laid singly on sub- merged leaves; those of Diemyctylus viridescens are laid SALAMANDERS, 4% singly on leaves of Myriophyllum, which adhere to the glu- tinous egg, concealing it. (Cope.) Those of Desmognathus are laid connected by a thread both on land and in water. The common land salamander, or Plethodon erythronotum Baird, lays its eggs in summer in packets under damp stones, leaves, etc. ; the young are born with gills, as is the case with the viviparous Salamandra atra of the Alps. The possession of gills by land salamanders, which have no use for them, and which consequently drop off in a few days, leads us justly to infer that the land salamanders are the de- scendants of those which had aquatic larve. The lowest form of this order is the aquatic Congo-snake or Amphiuma means Linn., in which the body is large, very long, round and slender, with small rudimentary two-toed limbs ; there are no gills, though spiracles survive. It lives in swamps and sluggish streams of the Southern States. A step higher in the Urodelous scale is the Menopoma, which is still aquatic, with large spiracles, but the body and feet are as in the true salamanders. The Menopoma Alleghani- ense Harlan, called the hellbender or big water lizard, is about half a metre (14-2 feet) in length, and inhabits the Mississippi Valley. Allied to the Amphiuma is the gigantic Japanese salamander, Cryptobranchus Japonicus Van der Hoeven, which is a metre in length. Allied in size to this form was the great fossil salumander of the German Tertiary formation, Andrias Scheuchzeri, the homo diluvii testis of Scheuchzer, thought by this author to be a fossil man. In the truesalamanders the body is still tailed, the eyes are rather large ; there are no spiracles ; they breathe exclusively by their lungs, except what respiration is carried on by the skin. The genus Amdlystoma comprises our largest salamanders ; they are terrestrial when adult, living in damp places and feeding on insects. The larve retain their gills to a period when they are as large or even larger than the parent. The most interesting of all the salamanders is the Amdblystoma mavortium, whose larva is called the axolotl, and was origi- nally described as a perennibranchiate amphibian under the name of Siredon lichenoides Baird. This larva is larger than 430 ZOOLOGY. the adult, terrestrial form, sometimes being about a third of a metre (12 inches) in length, the adult being twenty centim- etres (8 inches) long, forming an example of what occurs in the Amphibians and also certain insects, of the excess in size and bulk of the larva over the more condensed adult form. This law is also strikingly observed in the Pseudes (Fig. 437). This fact of prematuritive, accelerated, vegetative development of the larva over the adult is an epitome of what has happened in the life of this and other classes of animals. The fossil, earliest representatives of the Amphibians, as we shall see farther on, were enormous, mon- strous, larval, prem- ature forms com- Fig. 485.—Siredon or larval Salamander.—From pared with their de- " Tenney’s Zoology. scendants. The same law holds good in certain groups of Crustacea (trilobites), insects, fishes, reptiles and mammals. The axolotl or siredon abounds in the lakes of the Rocky Mountain plateau from Montana to Mexico, from an altitude of 4000 to 8000 or 9000 feet ; the Mexican axolotl being of a different species, though closely allied to that of Colorado, Utah and Wyoming. The Mexicans use the animal as food. Late in the summer the siredons at Como Lake, Wyoming, where we have observed them, transform in large numbers into the adult stage, leaving the water and hiding under sticks, etc., on land. Still larger numbers remain in the lake, and breed there, as I have received the eggs from Mr. William Carlin, of Como. Thousands of the fully-growa siredons are washed ashore in the spring when the ice melts. They do not appear at the surface of the lake until the last of June, and disappear out of sight early in September. The eggs are laid in masses, and are 2 millimetres in diameter. Mr. F. F. Hubbell has observed in Como Lake, July 23d, young siredons four to six centimetres (14-24 inches) in length, and September 3d specimens eight centimetres (3 inches) long. In Utah, Mr. J. L. Barfoot raised in 1875 HABITS OF THE AXOLOTL. ; 481 several adults from the larva, and I have been told that sire- dons in the mountains among the miners’ camps near Salt Lake City leave the water and transform. It thus appears that inthe elevated plateaus* as well as at the sea-coast, some siredons transform while others do not. Mexican siredons have for a number of years been bred from eggs in the aquaria of Europe, laying eggs the second year. The change from the larva to the adult consists, as we have observed, in the absorption of the gills, which disappear in about four days ; meanwhile the tail-fins begin to be absorbed, the costal grooves become marked, the head grows smaller, the eyes larger, more protuberant, and the third day after the gills begin to be absorbed the creature becomes dark, spotted, and very active and restless, leaving the water. Their metamorphosis may be greatly retarded and possibly wholly checked by keeping them in deep water. The internal changes in the bones of the head and in the teeth are very marked, according to Dumeril. ; Experiments made in Europe show that the legs and tail of the axolotl, as of other larval salamanders, may be repro- duced. We cut off a leg of an axolotl the first of November ; - it was fully reproduced, though of smaller size than the others, a month later. The tail, according to Mr. L. A. Lee, if partly removed, will grow out again as perfect as ever, vertebree and all. The Tritons or water-newts, represented by our common, pretty spotted newt, Diemyctylus viridescens Rafinesque, are also known in Europe to become sexually mature in the larval state when the gills are still present, as has been observed by three different naturalists. The female larva of Lissotriton punctatus: has been known to lay eggs. Order 4. Gymnophiona.—The blind snake with its several allies is the representative of this small but interesting order. * It has been stated by De Saussure, Cope, Marsh, and more recently by Weismann, that the siredon does not change in its native elevated home. No naturalist has seen the Mexican siredon transform into an Amblystoma, but as it does so in abundance in Wyoming and Utah, it probably transforms in Mexico. (The adult Mexican form has recent- ly been found, and is at the Smithsonian Institution.) 482 ZOOLOGY. The body is snake-like, being long and cylindrical ; there are no fect and no tail, the vent being situated at the blunt end of the body. The skin is smooth externally, with scales embedded in it, but with scale-like transverse wrinkles. The eyes are minute, covered by the skin. The species inhabit the tropics of South America, Java, Ceylon, and live like earthworms in holes in the damp earth, feeding on insect larve. They are large, growing several feet in length. Cecilia lumbricoides Daudin inhabits South America. Ce- cilia compressicauda of Surinam is viviparous, the young being born in water and possessing external gills which are leaf-shaped sacs resting against the sides of the body ; when the animal leaves the water they are absorbed, leaving a scar. (Peters.) Siphonops Mexicana Dumeril and Bibron, is a Mexican form. Order 5. Stegocephala.—Here belong an order of extinct Batrachians, with three suborders, Labyrinthodontia, Gano- cephala, and Microsauria (Cope). In these forms the skulls were either somewhat like those of the frogs, or the crania were roofed in by solid flat bones, similar to those of ganoid fishes. The vertebrae were biconcave. The limbs of the Labyrinthodonts were like those of the tailed Batrachians, of small size and weak, compared with the great size of the body. Von Meyer states that Archegosaurus possessed branchial arches when young, and that probably other Laby- rinthodonts resembled it in this respect. It had paddles instead of feet, the head had an armor of plates, and the body was covered with overlapping ganoid scales. It had teeth like those of ganoid fishes; it had a notochord, the bodies of the vertebr being neither bony nor cartilaginous. Owen regards it as combining the characters of the perenni- branchiate Amphibians and the Ganoid fishes. It was a little over a metre (34 feet) in length. It is a representative of the suborder Ganocephala. While the older text-books in the restorations of Laby- rinthodon represented it as like a toad, with large legs and tailess, it is now known that some of the gigantic prede- cessors of the salamanders and tritons had long tails, while others had long, cylindrical, snake-like bodies. Unlike exist- LABYRINTHODONT BATRACHIANS. 483 ing Batrachians, their fossil ancestors had an armor of large breast-plates, with smaller scales on the under and hinder part of the body. But the largest forms were the true Labyrinthodonts repre- sented in the Carboniferous rocks of this country by Baphetes, and in Europe by Anthracosaurus, Zygosaurus, and in the Permian beds of Texas by Eryops. Labyrinthodonts also abounded in the Triassic Period, and forms like the Euro- pean Labyrinthodon or Mastodontosaurus must have been colossal in size. Footprints occur in the Subcarboniferous rocks of this country which indicate forms still larger than any yet discovered in the Old World. A large number (thirty-four species, referable to seventeen genera) of medium- sized Labyrinthodonts have been described from the coal measures of Ohio by Cope which were characterized by their long, limbless, snake-like bodies and pointed heads, forming a still more decided approach to the Ganoids. This was the lowest group of. Stegocephala, called Microsauria by Dawson. Thus we have in these Labyrinthodonts synthetic or an- nectant forms, which connect the fishes with the Am- phibians, and on the other hand point to the incoming of the reptiles. They were thus prematuritive, larval forms, which in certain characters anticipated the coming of a higher type of Vertebrate. The reptiles were ushered in during the Permian Period, the rocks of this age imme- diately overlying the coal measures, though it should be stated that there are obscure traces of reptiles in the Carbon- iferous rocks. It is not improbable that evidence will be found to substantiate the impression that the reptiles, together with but independently of the Amphibians, branched off from the Ganoid fishes, or from extinct forms related to them. Order 6. Anura.—The toads and frogs represent this order, which comprises tailless Batrachians, with the four limbs present, the toes being very long (dus to the great length of the calcaneum and astragalus), while the body is short and broad, the skin soft and smooth, scaleless, though small plates are sometimes embedded in it. The lower jaw is 484 ZOOLOGY. usually toothless. The larve are called tadpoles, and repre- sent the adult form of the Perennibranchiates. The exter- nal gills are in the adult replaced by shorter internal ones. Among the lower frogs or arciferous Anura of Cope, 7.¢., those with the acromial and coracoid bones divergent and connected by distinct carcilage plates, are certain forms, as Alytes, Pelobates, and Pelodytes, whose breeding habits are peculiar and interesting. The eggs of Pelodytes are deposited in small clusters in the water, those of Pelo- dates in a thick loop. The male of the European Alytes obstetricans winds a string of eggs which it takes from the female, and goes into the water, where it remains ‘until the young (which have no gills) are hatched. The American Scaphtopus, or spade-footed toad, is not known to have this obstetrical habit. This singular toad appears sud- denly and in great numbers. It remains but a day or two in the water, where it lays its eggs in bunches from one to three inches in diameter. ‘The tadpoles hatch in about six days after the eggs are laid; their growth is rapid, the young toads leaving the water in two or three weeks. The croaking of this toad is harsh, peculiar, and need not be confounded with that of any other species. (Putnam.) As the spzde-footed toads are rarely seen, it is possible that they burrow in the soil, like the European Alytes. Another peculiarity in the reproductive habits of -Alytes, Pelobates, Cultripes, and Pelodytes is that they spawn at two seasons instead of one, and that their larvae, like Pseudes (Fig. 437), attain a greater size than those of other frogs before completing their metamorphosis. (Cope.) Among the tree-toads, Polypedates of tropical Western Africa, contrary to the usual habits of frogs, deposits its eggs in a mass of jelly attached to the leaves of trees which bor- der the shore overhanging a pond. On the arrival of the rainy season, the eggs become washed into the pond below, where the male frog fertilizes them. Our common piping tree-toad (Hyla Pickeringti Le Conte), about the middle of ‘April, in the neighborhood of Boston, attaches her eggs simply to aquatic plants. The young are hatched in about twelve days. SUPPRESSED METAMORPHOSIS. . 485 As an example of a suppressed metamorphosis, due ap- parently to a radical difference in the physical environment of the animal, may be cited the case of a tree-toad in the island of Guadaloupe. There are no marshes on this island, consequently in a species of Hylodes the development of the young is direct; they hatch from the eggs which are laid under moist leaves, without tails, and are otherwise, ex- cept in size, like the adults. On the other hand, a tree-toad of the island of Martinique (Hylodes Martinicensis, Fig. 436) has tadpoles, which it carries on its back. The female of Nototrema marsupiatum Dumeril and Bibron, of the Andes, has a marsupium or sac on its back in which the young are carried. The Notodelphys of South America has similar habits ; for example, the female Opisthodel- phys (Notodelphys) ovifera has a dor- sal sac a centimetre deep in which the eggs are carried. In the young of this and of (Castrotheca also of Central America, Peters found traces of external gills. The Pipa, or Suri- nam toad (Pipa Americana Laurent), which has no tongue, neither teeth in the upper jaw, has similar breeding _ pig. 436.—rhe Martinique habits. In this interesting toad the 7re¢-tpad carrying the young young, according to Prof. Wyman, are provided with small gills, which, however, are of no use to them, as the tadpoles do not enter the water, but are carried about in cavities on the back. The eggs are placed by the male on the back of the female, where they are fertilized. The female then enters the water; the skin thickens, rises up around each egg and forms a marsupial . sac or cell, The young pass through their metamorphosis in the sacs, having tails and rudimentary gills ; these are absorbed before they leave their cells, the limbs develop, and the young pass out.in the form of the adult. The toad (Bufo lentiginosus Shaw) is exceedingly useful as a destroyer of noxious insects. It is nocturnal in its habits ; is harmless, and can be taken up with impunity, though it 486 ZOOLOGY. } UZ LZ. 4 . yyy 7 ye <5 LV) DI Y Y a yy) | 9 17, Es SE WW, Wl Ta ee > at ” © § Minot wards, to reunite posteriorly just in front of the retractor muscles, their union forming the single median descending aorta; 3d. The pulmonary aorta (pa), which soon divides into a branch for each lung. The left aorta gives off a branch (d) which persists as a mere cord, the remnant of the ductus arteriosus, which originally united the aorta with the pulmonary artery. The right aorta gives off an innominate branch, that soon divides, and from each division springs 510 ZOOLOGY. the carotis (car), and subclavian artery of the same side. The veins are two in number, as they enter the heart: 1st. The pulmonary veins (pv) unite to form a very short trunk emptying into the left auricle; while (2d) the two vene cave supertores unite with the cava inferior (V) to empty through the sinus venosus into the right auricle. The kidneys lie at the posterior end of the body against the vertebral column. In the figure they are concealed by the bladder and oviducts. (Minot.) There are about forty species of Chelonians in America north of Mexico. The lower forms of turtles are the marine species. Such is the great sea-turtle (Sphargis coriacea Gray) of the Atlantic and Mediterranean, which is the largest of all existing turtles, and is sometimes eight feet long, weighing from eight hundred to twelve hundred pounds. Next to this species is the loggerhead turtle (Thalassochelys caouana Fitzinger), which is sometimes seen asleep in mid- ocean. Still another is the hawk-bill or tortoise-shell turtle (Lretmochelys imbricata Fitz.), the plates of whose shell is an article of commerce. The green-turtle of the West Indies weighs from two hundred to three hundred pounds, and is used for making delicious soups and steaks; being caught at night when laying its eggs on sandy shores. All the foregoing species have large, flat, broad flippers or fin-like limbs, while in the pond and river turtles the feet are webbed, and the toes distinct. A very ferocious species is the common soft-shelled turtle (Aspidonectes spinifer Lesueur), whose shell is covered with a thick leathery skin. It is carnivorous, voracious, living in shallow muddy water, throwing itself forward upon small animals forming its prey. The snap- ping-turtle (Chelydra serpentina Schweigger) sometimes becomes four feet long; its ferocity is well known ; the flesh makes an excellent soup. . The terrapins belong to the genus Pseudemys ; the pretty painted turtle (Chrysemys picta Agassiz) is common in the Eastern States, while the Nanemys guttatus (Agassiz), or spotted tortoise, is black, spotted with orange. In the land tortoises the feet are short and stumpy. The Testudo Indica © of India is three feet in length. The great land tortoises of THE ICHTHYOSAURS. 511 the Galapagos Islands, the Mascarine Islands (Mauritius and Rodriguez), and also of the Aldabra Islands, lying northwest of Madagascar, are in some cases colossal-in size, the shells being nearly two metres (six feet) in length. The fierce Mas- carine species were contemporaries of the dodo and solitaire, and are now extinct. The bones of extinct similar species have been found in Malta and in one of the West Indian islands. The land tortoises are long-lived and often reach a great age. Certain tortoises of the Tertiary Period, as the Colossochelys of the Himalayas had a shell twelve feet long and six feet high. The turtles extend back in geological time to the Jurassic, a species of Compsemys being char- acteristic of the Upper Jurassic beds of the Rocky Moun- tains. (Marsh. ) The eggs of turtles, as those of birds, are of large size ; they are buried in June in the sand and left to be hatched by the warmth of the sun. It is probable that turtles do not lay eggs until eleven to thirteen years of age. The develop- ment of turtles is much as in the chick. By the time the heart becomes three-chambered, the vertebrae develop as far as the root of the tail, and the eyes are completely enclosed in their orbits. The shield begins to develop as lateral folds along the sides of the body, the narrow ribs extending to the edge of the shield. In the lower forms of turtles (the Ohelonioida), the paddle-like feet are formed by the bones of the toe becoming very long, while the web is hardened by the development of densely packed scales, so that the foot is nearly as rigid as the blade of an oar. Order 5. Rhynchocephalia.—The only living represeata- tive of this order is the Sphenodon or Hatteria of New Zea- land ; a lizard-like form of simpler structure, however, than the lizards in general. This rare creature somewhat re- sembles an iguana in appearance, having a dorsal row of spines. It is nearly a metre (32 inches) in length. In this group the vertebra are biconcave ; the quadrate bone is im- movable, and there are other important characters based on a study of the living and fossil forms, the latter represented by the Triassic Rhynchosaurus and Hyperodapedon. Order 6. Ichthyopterygia.—This order is entirely extinct. 512 ZOOLVGY. The Ichthyosaurs were colossal reptiles from two to thirteen metres (six to forty feet) in length, swimming in the ocean by four paddle-like limbs consisting of six rows of digital bones Fig. 448.—Skull of Ichthyosaurus ; lateral view. Pmax, premaxillary bone ; Mz, maxillary ; N, nasal; Fr, frontal; Prf, prefrontal; Poy, postfrontal ; Pa, parietal LZ, lachrymal; M, malar; Qj, quadratojugal ; @, quadrate ; Fob, postorbital ; Sg squamosal; D, dentary; Ang, angular; Aré, articular; 9. Ar, subarticular ; Pler pterygoid.—After Cope. the head was very large, the neck very short, and the orbits were enormous; the vertebrae were remarkably short and bi- concave. ‘They were carniv- orous, and powerful swim- mers, and common in the Ju- rassic seas of Europe; one form existed in the Jurassic times in Wyoming. Order %. Theromorpha.— This order is divided into the Pelycosauria and neck in the so-called hybernation-glands. There are about 3500 species of mammals described, of which 2100 are living; of these 310 inhabit America north of Mexico. Mammals live all over the earth’s surface, but mostly in the tropical region, those of the arctic zones having been derived from the south since the end of the Tertiary period. The range in space of certain species is very great— for example, the cougar, panther, or puma ranges from Brit- ish to South America (Chili). The mammalian fauna of the Tertiary deposits of the west was far more abundant than now, the remains of over five hundred species having been already discovered by Leidy, Cope, and Marsh in the few spots ex- amined. The earlier (Eocene) mammals were generalized ORIGIN OF DOMESTIC MAMMALS. O71 forms, combining in a remarkable degree characters more elaborated, and in great detail, in different orders of living mammals, especially the Ungulates. For example, from the Hocene Coryphodon, a generalized ungulate animal, have probably been derived the ruminants, the tapirs, hog, hip- popotamus-like forms, the rhinoceros, and, finally, the horse. This inference is based on the fact that the bones and teeth of Coryphodon present characters which are no longer combined in any one species of mammals, but which are found worked out in detail in the members of the differ- ent orders referred to. Moreover, the early Tertiary mammals had brains much smaller than in any existing forms, and with only one ex- ception, without convolutions—showing that the develop- ment of the size of the brain and its convolutions, and con- sequently of the intellect, has kept pace with the successive stages in the specialization shown in existing forms, and which agree with the increasing complexity of the Ameri- can Continent and the subdivision of the western part of the continent into distinct basins, with separate mountain systems and river-valleys. The result of all this apparent waste of generalized forms, and the survival of the few favored types now existing, has been the preservation of animals which have been domesticated by man, such as the dog, pig, horse, ox, camel, elephant, and of others useful as food or as intelligent servants ministering to his every-day wants. The earliest mammals were small insectivorous or gnaw- ing marsupials, none larger than a cat, and first appearing in Jurassic strata. The Mammalia are divided into three sub-classes—viz., the Ornithodelphia (duckbill and Echidna), the Didelphia or marsupials, and the Monodelphia, comprising all the higher mammals. Sub-class 1. Ornithodelphia.—The duckbill and spiay ant- eater (Fig. 493, Echidna hystriz) are the only representatives of the sub-class, of which there is but a single order, called Monotremes, and are distinguished by the following char- acters. The oviducts, vasa deferentia and ureters, open into 572 ZOOLOGY. the cloaca, as in birds. The sternum is provided with a pecu- liar T-shaped bone, and there are important features in the Fig. 493.—Spiny Ant-eater (Zchidiu hystrix).—From Brehm’s Thierleben, brain separating them from the members of the higher sub- classes. Hchidna lays large eggs, 2 cm. long, placing them DUCKBILL AND KCHIDNA. 513 in a mammary pouch, where the young hatch. The duck- bill also lays large eggs. The embryonic development is meroblastic, as in reptiles. The toothless jaws are long and narrow in the #chidna, or broad and flat in the duckbill (Ornithorhynchus paradozus Blumenbach), where it is cov- ered by a leathery integument; the external ear is wanting. Fig. 494.—Skeleton of Echidna hystriz.—From Brehm’s Thierleben, In the aquatic duckbill the feet are webbed, with claws of moderate size. It is covered with a soft fur, and is about half a metre (17-22 inches) long. Its i habits are like those of a muskrat, fre- Hf quenting rivers and pools in Australia and Van Dieman’s Land, sleeping and breeding in holes extending from un- der the water up above its level into the banks, and with an outlet on shore. It lives on mollusks, worms, and water-insects. Young duckbills, five em. long, have been found in their nests. The spiny ant-eater (Figs. 493 and 494) is represented by three species, the Echidna hystrix Cuvier, of Aus- tralia, H. Lawesti Ramsay, from Port Moresby, New Guinea, also by a re- 23 ug cently discovered form inhabiting the wien af io hoe a a elevated portions of Northern New marsupial bones. : Guinea, and called by Gervais Acanthoglossus Bruijnit. In these singular animals the bill is long and slender, tooth- M63 5v4 ZOOLOGY. — less, while the palate is armed with rows of strong, sharp spines ; the tongue is long and slender, like that of the ant- eater, while the body is armed with quills like those of a porcupine ; the claws are very large and strong, adapted for tearing open ant-hills. All the species are from one third to one half of a metre (12-19 inches) in length. Fig. 496.—Skeleton of the Kangaroo.—_From Brehm's Thierleben, Sub-class 2. Marsupialia.—These are singular forms, rep- resented by the opossum in this country, and the kangaroo, with a number of other forms, in Australia. They differ from all other mammals in having a pouch (marsupium) for the reception of the young immediately upon birth, where MARSUPIALS. 575 they are attached to the nipples at the bottom of the pouch. This large pouch (absent in some opossums and in the Dasyuride@) is supported by two long slender bones attached to the front edge of the pelvis and projecting forward (Fig. 495 m and Fig. 497), In Thylacinus, the Tasmanian wolf, these bones are car- tilaginous. In the opossum, the kangaroo, and probably most marsupials, the young remains in the pouch attached to the nipple, which fills the mouth. ‘‘ To this it remains at- tached fora considerable period, the milk being forced down its throat by the contraction of the cremaster muscle. . The danger of suffocation is avoided by the elongated and coni- cal form of the upper extremity of the larynx, which is em- braced by the soft palate, as in the Cetacea, and thus respi- ration goes on freely, while the milk passes, on each side of the laryngeal cone, into the esophagus” (Huxley). In the car- nivorous forms the brain is low in struc- ture, the olfactory lobes being very large, completely exposed, while the cerebral hemispheres are smalls gy or pets withthe marsupial bones. and quite smooth. The dentition of marsupials is characteristic, none having three incisor teeth upon each side, above and below, and none but the wombat (Phascolomys), with an equal num- ber of incisors in each jaw, there being usually more in the upper than in the under jaw. The lowest marsupial is the Tasmanian wolt ( Thylacinus), which is rather smaller than the wolf. The Tasmanian devil (Dasyurus ursinus Geoffroy, Fig. 383) is a vicious, trouble- some creature, about the size of a badger. The opossums inhabit North and South America. They have a long tail and a plantigrade step—i.e., they walk on the sole of the whole foot. The Virginian opossum (Fig. 497, Didelphys Vir- ZOOLOGY. 576 Lawson says that ‘“the female doubtless breeds her young at her teats, for 1 have seen them stick fast thereto when they have been no giniana Shaw) lives chiefly in trees. cee yy, yc LEI, iy = ey jy, fi VY g “DOQaPaIGL & Wyo wo1g—‘(sndowovyy) oomwduvy OUT —'s6p ‘Sta aA GyGAy ijl GUN ae ! She has a paunch, or false belly, wherein she carries her young after they are from those teats, till they can shift for bigger than a small rasberry and seemingly inanimate. EDENTATE MAMMALS. 577 themselves. Their food is roots, poultry, or wild fruits. They have no hair on their tails, but a sort of a scale or hard crust, as the beavers have. If a cat has nine lives, this creature surely has nineteen ; for if you break every bone in their skin and mash their skull, leaving them for dead, you may come an hour after and they will be gone quite away, or perhaps you may meet them creeping away.’”’ (“* Perfect Description of Virginia,” 1649.) There are squirrel-like flying marsupials (Petaurus), marsupial rats, marsupial bears, and marsupial ant-eaters (Myrmecobius), but the most characteristic Australian ani- mals are the different kinds of kangaroo (Macropus thetidis, Fig. 498). The largest species, WM. giganteus Shaw, is 1-8 metres, or nearly six feet long. Kangaroos go in herds, and move by a succession of long leaps. All marsupials are stupid, low in intelligence, and, in the insectivorous and carnivorous forms, of vicious temper. With the exception of the opossums, all are confined to Aus- tralia, New Zealand, and New Guinea. Sub-class 3. Monodelphia.—While in the marsupials the termination of the oviduct is double, in the present group it is always single, whence the name Monodelphia. The members of the group are also called placental Mammalia, because the young at birth are of considerable size and nearly perfect in development, being nourished until born by a highly vascular mass or thick membrane ( placenta) supplied with arteries and veins, developed originally from the allantois, which is a temporary embryonic membrane. The brain, as a rule, presents an advance over that of any of the preceding mammals, the corpus vallosum being better developed, while the anterior commissures are all reduced. There are no marsupial bones, though in some Carnivora certain small cartilages appear to represent them. There are twelve orders, as follows : Order 1. Bruta or Edentata.—These creatures, repre- sented by the sloths, ant-caters, pangolins, and armadillos, stand next above the non-placentals or marsupials, as the brain is but little better developed, the hemispheres in some 578 - ZOOLOGY, forms being nearly smooth, while, in point of their general structure and intelligence, they stand at the foot of the sub- class. The teeth may be entirely undeveloped, as in the common ant-eater, but when developed they are not encased Fig. 499.—Skeleton of the Ai, or Three-toed Sloth.—After Owen in enamel. In most Edentates the incisors are absent, but the lateral one may exist in the armadillo (Dasypus). The feet are formed for grasping or digging, and end in large straight or curved claws. They are either hairy or pro- SLOTHS AND THEIR ALLIES. 579 tected, as in the pangolins (Fig. 501) and armadillos (Fig. 502), with large thick scales. They feed on insects and de- cayed animal matter, or on leaves. They are of moderate size, though certain extinct forms were colossal in stature. The leaf-eating forms, viz., the sloths, differ from the other Bruta in the very long and slender limbs, the hinder pair the shorter. There are five teeth above and four below, which become sharp with use, like chisels ; the stomach is said to be remarkably complex. In disposition these crea-* tures are types of sluggishness ; they live in trees, being absolutely helpless on the ground, not being capable of walking on the bottom of the foot. Waterton says that, in climbing, the ai (Bradypus tridactylus, Figs. 499 and 500) uses its legs alternately ; that its hair ‘‘is thick and coarse at the ex- tremity and gradually tapers to the root, where it becomes fine as a spider’s web. His fur has so much the hue of the moss which grows on the branches of the trees, that it is very difficult to make him out when he is at rest.’’ Only two Edentates now occur in the United States, but formerly colos- sal, sloth-like forms, with some resem- fs blance to the ant-eaters, ranged over | Fig. 500.—Ai, or Threo- the Southern and Middle States as far tude.— After Wood, from north as Pennsylvania, their bones oc- eee curring in waves. Such was the Megatherium, a gigantic, sloth-like creature, which extended from Pennsylvania to the pampas of South America, and whose skeleton is over five metres (18 feet) Jong. With it was associated the Meg- alonyz, first described by Thomas Jefferson ; it was as large as a bison, as was the Mylodon. ‘'Thes> animals walked on the soles of the feet, could rise on their hind legs and partly support themselves by their thick tails, pulling down large trees and feeding upon the leaves and smaller branches. Tn the ant-eaters the jaws are toothless, but very long, and the tongue is of great length and very extensile ; the sub- 580 ZOULUG ¥. maxillary glands are very large, so that the viscid salivary fluid is very abundant. They burrow into ant-holes, thrust- ing the tongue among the ants, which stick in multitudes to the viscid, writhing rod, and are withdrawn into the mouth. The pyloric end of the stomach is gizzard-like. The ant- eaters (Myrmecophaga) inhabit South America. : The pangolins, or species of Manis, are mail-clad ant- eaters,- the body and long tail being covered with large overlapping scales. When molested they roll up the body. In walking the hind feet rest on the soles, while the fore- feet are supported by the upper side of the long bent claws. Ve Ee a Or an aoe (Xperts or ah Fig. 501.—Pangolin (Manis longicaudata) robbing white ant-nests.—After Monteiro. @ The long-tailed pangolin of the West Coast of Africa (Fig. 501) tears open with its long claws the nests of the white -ants. It is nearly 2 metre (28-30 inches) in length. The armadillos (Fig. 502) are small mammals covered with a carapace, consisting of from three to thirteen transverse rows of movable scales ; by rolling into a ball, these singu- lar creatures become thoroughly protected from their ene- mies. Dasypus novem-cinctus Linn. is much like the Peba armadillo, and extends from South America to Texas. The strange extinct armadillo-like Glyptodon of South Amer- ica, which was over two metres (8 feet) long, was covered THE ARMADILLO. 581 by a heavy, solid coat-of-mail consisting of polygonal plates soldered together immovably. The three following orders have by most authors been placed near the Primates (monkeys, etc.), but Owen, from nm eS ag ors = Sose See 2°N ze BoL "es 3 S 2 3 3. ° oS “OPIPVUUB BYgeg Jo TOJ[VYS—"ae “9 ‘eIqn ‘99 $(1ayUBqION parq3 oy) Jo yuod ay} aus0ddo Zar [I] Io Tepnra ‘yy tunidvs *¢ 14} 10 Inulas ‘cg SuoL qs [euLIeptda Jo sarpi1d ay} Jo eUT[JNO 94} YITA ‘uoTsa.1 [es10p ‘T— — tun ‘gg tsniauinyg ‘zg {eindros ‘Tq imag SI Jaquintt oy) euoq- the characters afforded by the brain, has shown that they be- long at or near the bottom of the scale. Gill has shown that not only by the brain, but by other characters corre- lated with the low development of the brain, the Rodents, 582 ZOOLOGY. Insectivora, and bats should be associated with the Edentates in Bonaparte’s division (or, as Gill terms it, super-order) of Ineducabdilia (which corresponds to Owen’s sub-class Lissencephala). In these four orders, then, the cerebrum is small, smooth, with none or few convolutions; in front it does not cover the olfactory lobes, and behind leaves the cerebellum wholly or partly uncovered. On the other hand, in the super-order Hducabilia, com- prising the following order: Cete, Sirenia, Proboscidia, Hy- racotdea, Toxodontia, Ungulata, Carnivora, and Primates, the brain has a relatively large cerebrum, behind overlap- ping much, or all, of the cerebellum, and in front much, or all, of the olfactory lobes (Gill). The cerebrum is also con- voluted ; the convolutions increasing in number and com- plexity, until we reach the apes and man, and accompanied by increasing intelligence and capability for mental im- provement. Other important characters are mentioned by Owen and by Gill in support of this arrangement. In the smooth small cerebrum, as well as in other re- spects, the Zneducabilia are related, together with the mar- supials and duckbill, to the birds and reptiles. In the cloaca, the convoluted trachea, the long, slender, beak-like, toothless jaws and the gizzard of the ant-eaters, the quills of the porcupine and hedge-hog, the proventriculus or crop of the dormouse and beaver, in the growing together of the three chief metatarsals of the jerboa, asin birds, in the keeled sternum and wings of the bats, there are points of resem- blances to birds. Owen, whom we have quoted, also adds the aptitude of the bats, insectivores and certain rodents “‘to fall, like reptiles, into a state of torpidity, associated with a corresponding faculty of the heart to circulate car- bonized or black blood.’’ However, there are points in which these orders are re- lated to the lemurs and monkeys. Order 2. Glires. (Rodentia.)—The rats, squirrels, por- cupine, and beaver are common examples of this extensive group. They differ from other orders in the large incisors, the dental formula of which is normally § ($ in Leporide and Lagomyid@), and in the absence of canine teeth. The ORDER OF RODENTS. 583 condyles of the lower jaw are longitudinal, not received in spe- cial glenoid sockets, but gliding freely backwards and forwards in longitudinal furrows. The feet are adapted for walking and climbing or burrowing, the claws being well developed. A peculiarity in the incisors is that they grow out as fast as they are worn down ; this is due to the fact that the pulp is persistent ; the enamei in front causes them to wear away Fig. 503.—American Flying Squirrel (Sciuropterus volucella) behind so that they are chisel-shaped. The species are pro- lific, live mostly on vegetable food, and are of small size; the muskrat, beaver, and capybara being the largest mem- bers of the group. The flying squirrels (Fig. 503) take short flights by means of the expansion of the skin between the fore and hind legs. The Norway lemmings are notice- able for their remarkable migrations from the elevated 584 ZOOLOGY. plateaus of Scandinavia down and into the sea; the object and origin of which are inexplicable, and are not indicative of much intelligence. From this and their nest-building habits, rodents are, as a rule, not unlike birds ; and Owen, for these reasons, ascribes to them a low degree of intelligence. Granting that this is the case, an exception to this rule is seen in the social beavers, which evince a high, exceptional degree of intelligence. Beavers build a dam in a running stream so as to create an artificial pond as a refuge when at- tacked, as well as a subaquatic entrance to their lodges and to their burrows in the banks of the streams they inhabit. Bea- ver dams are built at first by a single pair or family, and are added to from year to year, and afterwards maintained for centuries by constant repairs. They are built of sticks and mud, usually curve up stream, with a sloping water-face. Beavers lay up stores of wood for winter use in the autumn ; they can gnaw through trees eighteen inches in diameter; they work mostly at night. They often construct artificial canals for the transportation of the sticks of wood to their lodges. This, in the opinion of Mr. Morgan ‘‘is the highest act of intelligence performed by beavers.” When ponds do not reach hard-wood trees or ground in which they can burrow for safety, they will build canals with dams, and so excavate them that they will hold the surface drainage. Morgan describes one canal about 161 metres (523 feet) long which ‘served to bring the occupants of the pond into easy con- nection, by water, with the trees that supplied them with food, as well as to relieve them from the tedious, and per- haps impossible, task of moving their cuttings five hundred feet over uneven ground, unassisted by any descent.” Bea- vers, in swimming, use their tail as a scull, and the hind feet beg webbed, its propelling power while swimming is very great. They carry small stones and earth with their paws, holding them under the throat, and walking on their hind feet. They use the tail in moving stones, working it under so as to “ give it a throw forward.” Beavers are very social, working together and storing up wood in common. “A beaver family consists of a male and female, and their offspring of the first and second years, or more properly. HABITS OF THR BEAVER. 585 under two years old. The females bring forth their young from two to five at a time, in the month of May, and nurse them for a few weeks, after which the latter takes to bank.” They attain their full growth at two years and six months, and live from twelve to fifteen years, * Allied to the beaver, Fre. 504. —Sewellel or Showt’l, Much reduced. but forming the type —From American Naturalist, of a distinct family, is the singular sewellel or showt’l Fig. 505.—Alpine ‘Hare of the Rocky Mountains.—After Hayden. (Haplodon rufus Coues, Fig. 504) of the mountains of west- ern Oregon and Washington Territory. It is nearly as large * The American Beaver and his Works. By Lewis H. Morgan. 1868. 586 ZOOLOGY. as a muskrat, is nocturnal in its habits and, therefore, rarely seen, and burrows in the earth, feeding on roots. The lowest in intelligence are, perhaps, the hares, rep- resented by the common varying hare (Lepus America- nus Erxleben, Fig. 505), of which an interesting variety, L. Bairdii, lives on the Alpine summits of the Rocky Moun- Pick Mase IRN LES iS Fig. 506.—The Spalax or Blind Rat.—After Owen. tains. The largest of all existing rodents is the Capy- bara of South America, which looks like a pig. This is succeeded by the porcupine, which either lives in trees or burrows in the earth, while the more intelligent, active forms are the beaver, muskrat, the European blind rat (Spalax, Fig. 506) the rats and mice, squirrels, and lastly the marmots. The domes- tic mouse and the two rats, the brown or Norway rat (Mus decumanus Pallas). ip the black rat (Mus rattus if Linn.), and the common Gy ANGIA~ house mouse (Mus muscu- Fig. 507—Jumping Mouse (Zapus hud. lus Linn.), are cosmopoli- sonius).—From Tenney’s Zoology. tan animals. The jumping mouse (Fig. 507) has remarkably long hind legs and short fore legs. Peculiar to the western plains is the prairie-dog, (Cynomys ludovicianus) which represents the marmots of the Old World ; it is semi-social and takes in perforce as boarders the owl and rattlesnake, which devour its young. MOLES AND SHREWS. 587 Order 3. Insectivora.—In the moles the incisors, the canines, and molars are well developed, and the molars have the crown surmounted by conical projections called cusps. The fore feet are plantigrade, with ee claws, and the en- tire limb is short, thick, mus- cular, and fossorial,7.e., adapted for burrowing in the soil (Fig. 508). The shrews comprise the smallest mammals. Nearly all are nocturnal, burrowing under the surface, and never seen by day; consequently, their eyes are small, and most- ly hid under the fur; while the ears are small and concealed by the hair. The shrews are mouse-like, having feet of the normal form, and a long nose. In our com- Fig. 508.—Bones of fore leg of a Mole. 52, the cubital scapula; 53, humerus ; 54, ulna; 55, radius.--Af- ter Owen. mon shrew (Sorex platyrhinus Wagner, Fig. 509), the nose is long, and the tail shorter than the head and body. The genuine moles are the characteristic forms of the order ; the most peculiar being the star-nosed mole, Condy- HRLNICHOL SSC. Fig. 509.—-Common Shrew.—After Coues. lura cristata Linn., which occurs from the Atlantic to the Pacific Ocean, while the common mole (Fig 510) is abundant: in the Eastern United States. A flying form with a superficial resemblance to the bat, and 588 ZOOLOGY. with the same habit of sleeping, head downward, holding on by its hind feet, is the Galeopithecus of the East Indies. This singular creature has been placed among the lemurs by some authors. Gi. volans Pallas inhabits Java, Sumatra, Borneo, and Siam. Fig. 510.—Common Mole (Scalops aquaticus Linn.).—After Coues. Order 4. Chiroptera.—The bats form a well-circumscribed group of mammals, very distinct from any other, especially in the greatly modified fore-limbs, the radius and ulna being united, and the second to the fifth metacarpal bones and phalanges being very long and slender, supporting a thin. leathery membrane or skin, extending to the hind legs, and wholly or partly enclosing the tail ; the hind toes being, how- ever, free, as when at rest or in the vegetarians when feeding, bats hang head downwards, holding on by their claws. The sternum is slightly keeled for the attachment of the mus- cles of flight. The mammary glands are pectoral. In other respects, especially the dentition, the bats resemble the Insectivora. The form of the teeth differs from the ordi- nary insectivorous bats in those which live on fruit. The vegetable-eating or fruit-eating hats have a superficial resem- blance to the flying Jemurs; and becanse their mamme are pectoral, have been placed next to the Primates. HABITS OF BATS. 589 Bats live in caves and in the hollow of trees by day ; all hibernate in the same situations, going into winter quarters in the autumn, and reappearing in the warm twilight of spring. Though the eyes are small, and the sight, so far as Fig. 511.—Skeleton of a fruit vat (Pteropus).—After Owen. we know, deficient in keenness, they show wonderful skill in avoiding objects during their rapid flight. The ears are very large, and in the vampires the nose is adorned with 590 ZOOLOGY. sensitive, leaf-like growths of complicated form. Certain bats are known to enter houses, and suck the blood from Fig. 612,—Skull of adult sperm whale sen from above and from the side. 60, basioccipital bone ; eo, exoccipital ; so, supraoccipital ; p, parietal ; s, squamosal ; /, irene ; pl, palatine; /, jugal ; sh, stylohyoid ; bh, basihyoid ; 72, thyrohyoid.—After ower. the extremities of sleeping persons, who awaken to find their feet covered with blood. ‘he true vampire is harmless. CETACEANS. 59l The largest bats are the fruit bats or flying foxes (Ptero- pus) of the Hast Indies ; one species of which expands one and a half metres (nearly five feet) from a to tip of the wings. Our commonest species is the little brown bat, Vespertilio subulatus of Say; nearly as com- mon is the red bat, Atalapha no- veboracensis Coues. Order 5. Cete (Cetacea).—We now come to the Hducadilia, in which the brain is more highly de- veloped, and begin with two very aberrant orders, the whales and Sirenians, in which the body is fish-like, though the tail is hori- zontal ; the pelvis and hind limbs are wanting, either wholly, or mi- nute rudiments may be present ; and they are aquatic, occasionally leaping out of the water, but usu- ally only showing the dorsal fin or nose when at the surface to breathe. The whales and porpoises have a large, broad brain, with numer- ous and complicated deep convolu- tions. In the skull (Figs. 512, 513) the aperture for the spinal cord (fora- men magnum) is entirely posterior in situation and directed some- what upward. The lower jaw is straight, with no ascending ramus, the narrow condyles being situated at the end of the jaw, at the point indicated by the angle of the ramus in other mammals. The teeth are conical, with a single root, but are Fig. 513.—Skull of the sperm whale, longitudinal section show- ing the relative size and form of the cranial cavity. mm, maxilla ; pm, premaxilla.—After Flower. sometimes wanting. There is no neck; the cervical verte- bre are sometimes confluent, forming a single mass. The 592 ZOOLOGY. limbs form a pair of paddle-like appendages just behind and under the head, which are supported by short, flattened limb-bones, the carpals and phalanges often separated by car- tilage ; the second digit being composed of more than three phalanges. There are two mamme situated near the anus. The external nostrils are either single or double, and are sit- uated on the top of the head ; they are modified to form the spiracles or ‘‘ blow-holes ;” certain folds of the skin prevent the water from entering the air-passages. The vapor blown from the holes does not consist of water, but of the mucus from the nostrils, and the moisture in the breath. The blow-holes vary in form in different kinds of whales. The ‘“spout” of the sperm-whale issues in a single short stream from the extreme end of the snout, and curls over in front of the head; that of the fin-back whale forms a single column of vapor about ten feet high ; the right, humpback and sulphur-bottom whales each ‘“‘blow”.in a double stream which is directed backward toward the tail. Whales are rarely over fifty feet long; the sperm-whale has been known to reach a little over twenty-three metres (76 feet) in length, but Professor Flower questions whether the sperm-whale frequently, if ever, when measured in a straight line, exceeds a length of sixty feet. The largest of all whales, as of all existing animals, is the fin-back or ror- qual (Balenoptera boops), which sometimes measures thirty- four metres in length. The smallest Cetacea are the por- poises. In the Mysticete or whalebone whales, the teeth, present in the embryo, become reabsorbed into the gums before birth and are replaced by plates of whalebone (Fig, 514), three hun- dred of which may be present on each side of the mouth. The inner edges of these plates have projecting fibres, form- ing arude strainer ; these whales feed on small pelagic jelly- fish, molluscs and crustacea, by taking in a mouthful of water, and then pressing the tongue against the roof of the mouth, expelling the water through the openings between the plates, the fibres acting as a strainer. Three thousand five hundred pounds of whalebone have been obtained from a single bow-head or Greenland whale (Balena mysticetus). THE SPERM WHALE. oY8 The cachelot or sperm-whale (Fig. 515) has an enormous head, and is without the power of smell. Above the nasal, frontal, and maxillary bones are cavities filled with a fatty fluid called spermaceti, used in the manufacture of candles, ointments, and cosmetics, such as cold cream. A large sperm- Fig. 514.—Head and tongue of finback whale, Budenop/era (the latter (a) swollen by the gases of decomposition); , whalebone plates. whale will yield 2500 kilograms of this substance. Another valuable substance is ambergris, a morbid product, the result of injury to the intestine by the beaks of cuttle-fishes, upon which animals the toothed whales largely prey. It isa kind of bezoar or gall-stone, fatty, aromatic, burning with a clear flame. It is composed of benzoic acid, united with chlorine, of a balsamic substance, and ambrein. Jt is used in making perfumes. Fig, 515,—Outline of the cachelot, showing how the blubber is removed; @, the aitaation of the ‘‘case ’’; c, the junk’; d, the bunch of the neck ; 2, the hump ; 3, ibe ridge; k, the small ; f, the tail or flukes: between the oblique dotted iines are the spiral strips or blanket pieces.—After Beale, from Gill. But the chief use of whales is the oil extracted from the fat enveloping the body, called blubber by whalers. The most valuable of the whales is the Greenland whale, as it contains the most oil, individuals having been known to yield nearly three hundred barrels. 594 ZOOLOGY. The whale-fishery first sprang up in the twelfth century in the Bay of Biscay. In the New England colonies whales were pursued in boats from the shore. In 1854 the fishery culminated ; since then it has decreased. It is principally carried on by Americans, New Bedford being now the lead- ing port from which whalers are sent out to the Arctic Fig. 516.—Hogi + Flow 1i.—After Grayson, from Gill. regions and Behring’s Straits, one hundred and ten vessels having been sent out in 1876 from this port. Closely allied to Physeter macrocephalus Lacépéde, are the pigmy whales, represented on the Californian coast by Kogia Floweri Gill (Fig. 516), which is nearly three metres Fig. 517 Skull of Callignathus simus, seen from the side and from below.— After Owen. (nine feet) in length, with a conical head. In Callignathus simus Owen (Fig. 517) the skull is short and broad ; it is found on the coast of Madras, India. The narwhale (Monodon monoceros Linn.) is distinguished by the long, spirally-twisted, horn-like tusk of the male, formed of the left upper incisor, which becomes nearly three SIRENIANS OR SHA-COWS, 595 metres long, the female having no visible teeth ; there being two rudimentary incisors which never appear through the gum. It ranges from Hudson's Straits to the Arctic seas, having formerly been seen along the coast of Labrador. To the family of dolphins and porpoises belong the white whale or Delphinapterus leucas Pallas, which ranges from the Gulf of St. Lawrence northward; the grampus (Grampus griseus Cuvier) ; the blackfish, of which there are two species, one Globicephalus melas Trail, ranging north of New York, and one G. brachypterus Cope, to the southward, and the por- poises, of which the most common on our coast is Phocena brachycium Cope; the rarer is P. lineata Cope. On the coast of Labrador, as well as northward, occurs the thrasher whale or killer (Orca gladiator Gray) which has large teeth, and a high dorsal fin ; it attacks whales, gouging out the flesh from their sides. Certain fossil whales were pigmies in size; while the Zeuglodon of the Alabama Eocene Ter- tiary beds, was an enormous serpent-like whale, which must have measured over seventy feet in length. Order 6. Sirenia.— In the few species of sea-cows represent- ing this order, the lower jaw is more as in other mammals, having well developed ascending rami and normal transverse condyles and coronoid processes. The teeth are well developed, both incisors and molars, the latter with flattened or ridged crowns, adapted for the trituration of vegetable food. A neck is indicated; the two nostrils are situated at the upper part of the snout, and the lips are beset with stiff bristles, while the mamme are pectoral. The fore limbs are of moderate length, with five well-developed digits, but still fin-like and bent at the elbow. The brain is narrow com- pared with that of cetaceans, and the heart is deeply fissured between the ventricles. The manatees of America and the dugong of Australia and India (Fig. 518) live in the mouths of large rivers, feeding on seaweeds, aquatic plants, or the grass along the shore. The Florida manatee (Manatus Ameri- canus Desmarest) grows to a length of from two to nearly three metres. It ranges from Florida to the Amazons, where it is called Vacca marina ; itascends the river as far as Pebas, Peru, and is killed and eaten, its flesh resembling beef. 596 ZOOLOGY. Steller’s manatee (Rhytina Stelleri) was in the last century found in abundance on the shores of Behring’s Island on the coast of Kamtchatka; twenty-seven years afterwards (in 1768) it was totally exterminated by the sailors ; a few im- perfect skeletons exist in the National museum. This is the Fig. 518.—The Dugong.—From Brehm’s Thierleben, ' i | | i ANAL nO largest Sirenian known ; it was over six metres in length. It differed remarkably from the other forms, in having no teeth, but was provided with a very large, horny, palatine plate, and a corresponding one covering the enlarged point of union, or symphysis, of the lower jaws. In the Tertiary : ( THE PROBOSCIDIANS. 597 Period a fossil Sirenian (Halitheriwm) inhabited the shores of western Europe. In the structure of the skull, their dentition and their her- bivorous habits the Sirenians in a degree connect the Ceta- ceans with the Ungulates, and elephants. Order 7. Proboscidia.—Only two representatives of this group are now in existence, the Asiatic and African elephant, a number of other forms having become extinct. The group is well circumscribed, when we consider the living species, but in the early (Eocene) Tertiary Period there existed forms which indicate that the Proboscidians and Ungulates had a common origin, In the elephants the up- per incisors are enor- mously developed, while there are none in the lower jaw. There are no canine teeth, while the few molars are large, trans- versely ridged. In the elephants the ridges are numerous, the spaces between them filled with cement. The young mastodon has cement on the up- fen fens ob Te ap claeue a lephant ; 22 es tooth ; the ridges af- itlary'bone containing the root of the tuak, £y 15, terwards become free 25, malar zygomatic arch: flower jaws cr eppet and covered with Ce maxilla; 11, frontal; g, enamel. A peculiari- ty in the elephant’s skull is its large size, the brain cavity being very small in proportion to the bulk of the skull itself. To give lightness to what would be otherwise an insupportable weight, the cranial bones contain numerous large air-cells (Fig. 520). Another remarkable feature, from which the group takes its name, is the trunk or proboscis, a long, thick, fleshy, flexible snout, growing from the front edge of the nasal 598 ZOOLOGY. bones (Fig. 520, a). The trunk ends in a finger-like, highly sensitive point, below which are situated the nostrils. The brain has a large cerebrum, with numerous convolutions, but more of the cerebellum is exposed than in any of the succeed- ing orders ; in this respect and in the large incisors the Pro- boscidians approach the Rodentia. In the nature of the limbs, especially from the fact that elephants walk on their toes, a relation to the Ungulates is cue indicated. They are AK five-toed, but the dig- \ < its are represented ex- ternally only by the five broad. shallow hoofs, the foot being supported by thick, broad pads. The legs are almost wholly free from the body. The placenta is zonary, non-deciduate. The skin is naked in the existing elephants, but the extinct mam- moth was covered sparsely with hairs. Elephants live in herds, browsing on the leaves of trees Fig. 520.—Section of an elephant’s skull, showin, the s-uall size of the brain cavity as compared to the and herbs. They at- male seal ond tg mamgion? 459 au salt; tain a height of from Renee ttated ttterolmen =o *mIeM three to four metres (10-12 feet). The Asiatic elephant has a concave forehead and small ears, while the African species has a full, rounded forehead and large ears, with four hoofs on the fore feet and three on the hind feet, the Asiatic elephant having one more hoof on each foot. The fossil mammoth (Elephas primigenius Blumenbach), which was contemporaneous with early man, was not much larger than the existing species. Its tusks, however, were of MAMMOTH AND MASTODON. 599 great size, some being five metres long. It formerly ranged in herds over northern Hurope and Asia, as well as America, bones occurring under swamps in the Northern and Middle United States. A carcass frozen in the ice, with the hair still on, was discovered near the mouth of the Lena River in Siberia. A pigmy, extinct Maltese elephant of the late Ter- tiary Period was only 1.7 metres in height. The Mastodon was characterized by having incisors in both jaws of some of the species. The mastodon had molars with fe goxo Fig. 521.—Dinotherium.—¥rom a restoration by Brandt. conical cusps, and was 33-4 metres (12-13 feet) in height. The mastodon (Mastodon gigantewm Cuvier) was an earlier type than the elephant, and formerly inhabited the North American continent. In the Dinotheriwm of the Middle Tertiary (Fig. 521) there were only two incisors, and they grew out from the under jaw. It was elephantine in its form, according to Brandt. Order 8. Hyracoidea.—With some affinities to the Ro- dentia, and a decided resemblance in some particulars to 600 ZOOLOGY. the rhinoceros among the Ungulates, the members of this small order are in general characterized by having long, curved incisors ; and by feet provided with pads as in Ro- dents and Carnivora, the toes being encased in hoofs (four in front and three behind). The Hyraz, a little gregarious animal living in holes among rocks, of which there are two or three species known, one South African, and another in the Holy Land and Arabia, thought to be the coney referred to in the Bible, is the only genus. Order 9. Toxodontia.—Of this group, of which no spe- cies are now living, the types are Toxodon and Nesedon. They are placed by many authors among the odd-toed Ungu- lates, not far from the tapirs. Their incisors were § or 4. Toxodon in its skull bore some resemblance to the Sirenians, and in the teeth were in certain respects like the Edentates. The species lived in South America during the early Tertiary Period. Order 10. Ungulata.—The larger proportion of mammals belong to this interesting order, which comprises nearly all those species of mammals useful to man, such as the ox, camel, pig, deer, and horse. They are, in general, charac- terized by walking, so to speak, on their toes, each toe being at the end encased in a horny hoof; not more than four toes being completely developed on a foot. The teeth are usually ' well developed, with six incisors in each jaw, but these are often, especially in the upper jaw less in number or entirely absent, as in the sheep, deer, and ox. The collar-bone is absent. The brain still remains small compared with the bulk of the skull, and the intestinal canal is of unusual length compared with that of animals of the previous orders. The Ungulates have been divided by Owen into two sub- orders, according to the odd number of toes (Perisso- dactyla) or even number (Artiodactyla). In the Perisso- dactyles there may be three toes on each foot, as in the rhi- noceros, or one, as in the horse ; while in the Artiodactyles ‘there may be four toes (Hippopotamus), or two, as in the giraffe, or two functional and two rudimental, as in the ox and deer, 7. e., most Ruminants. The more generalized ex- isting form of Ungulates is the tapir; the most specialized ORDER OF UNGULATES. GOL type is the horse, with its single toe on each limb. A large number of extinct Tertiary Ungulates in the Western States and Territories, and the Tertiary basins of Paris and Lon- don, more or less allied to the tapir, especially Coryphodon, Anoplotherium, Paleotherium, etc., were generalized or ancestral forms, from which the modern, more specialized types have probably been evolved, and a study of these fossil Ungulates shows that there was then (7. ¢., in Eocene times) an essential unity of organization in all Ungulates, including the Ruminants; the breaking up of the Ungulate stem into special groups, along favored lines or paths of development, having resulted in a gradual improvement and _ elabora- tion of particular parts, which rendered them more fitted for their present life, and more intelligent in meeting and overcoming the emergencies their more complex surround- ings subjected them to. Thus in the Eocene Ungulates, such as Coryphodon, the cerebrum was small, without convo- lutions, indicating a slight degree of intelligence compared with the modern Ungulates, while the gradual differentiation of the horse, with its single toe and hoof, from its tapir-like ancestors, is a marked example of the intelligent, beneficent selection of favored, useful types which has gone on from the earliest geological times. All this specialization of type involved the destruction of great numbers of forms unfitted to withstand changes in their surroundings, or not sufficiently intelligent or wary to avoid the attacks of carnivorous forms, and thus the present number of Ungulates is much exceeded by the fossil forms. Perissodactyles. The odd-toed Ungulates, on the whole, stand lower than the even-toed forms. They all have at least twenty-two dorsal and lumbar vertebre, and a simple stomach, with a large, sacculated caecum. The tapirs are the more elemental, generalized forms. Fossil tapirs occur in the older Tertiary beds of the West. The snout is _almost proboscis-like, and the legs are moderately long, with four toes in front, three toes behind. The tapirs inhabit the tropics of the New World and Sumatra. They are succeeded _ by the rhinoceros, represented in this country by a number of extinct Tertiary allies, the living species being restricted 602 ZOOLOG ¥. to Africa and the East Indies. The skinis remarkably thick and dense, while these animals have either one or two long median horns growing from the skin of the nose. A rhinoc- eros contemporary with early European man formerly inhab- ited England, France, and Germany, and extended into Si- beria. A number of fossil forms lead up to the family compris- ing the horse, ass, zebra, and quagga, etc., in which there is a single toe, being the third on each limb. Their den- tion is— 6 ,1-1 ,4- 3—3 te? Pas The genealogy or series of ancestral extinct Ungulates leading from tapir-like forms to the modern horse has been worked out partly by Huxley, and especially by Marsh, who has with Leidy discovered a large series of remains in the Ter- tiary beds of central and western United States, America being the original home of the horse. The earliest member of the series directly leading up to the horse was Zohippus, an older eocene form, about as large as a fox, which had four well- developed toes and the rudiments of a fifth on each fore-foot, and three toes ‘behind. In later eocene beds appeared an animal (Orohippus) of similar size, but with only four toes in front and three behind. In newer beds, 7. e., lower miocene, are found the remains of Mesohippus, which was as large as a sheep and had three toes and the splint of another in each fore-foot, with but three toes behind. In later miocene beds another form (Anchitherium or Miohippus) had the same number of toes, but with the ‘‘ splint bone of the outer or fifth digit reduced to a short remnant.” The splint bones, then, represent two of the digits of several-toed animals. The suc- ceeding forms were still more horse-like. ‘In the Pliocene above, a three-toed horse (Hipparion or Protohippus), about as large as a donkey, was abundant, and still higher up a near ally of the modern horse, with only a single toe on each foot (Pliohippus) makes his appearance. A true Equus, as large as the existing horse, appears just above this horizon, and the series is complete.” (Marsh.) Fossil horses extended over portions of North and South America, but became ex- tanct before the present Indians appeared. THE HORSE AND ITS VARIETIES. 603 _ The horse (Zquus cabailus Linn.) is the most useful of all domestic animals, and next to ships a prime means of the diffusion of civilization. By artificial selection a great num- ‘Waqaelyy, 8, WYoIg wosg —‘snuvjododdiy oy} Jo Woya[oyS—'eeg "SL ber of varieties, races, and strains have been produced, adapted for the performance of different kinds of work. The horse only exists in a domesticated state. Sanson states that 604 ZOOLOGY. the horse in the Orient has five, and in the west (Africa) six lumbar vertebrz ; in Arabia both forms occur ; in the horse with but five lumbar vertebra the shape of the skull is also different. The Hemippus, the tarpau and muzir of Tartary, as well as the white, shaggy horse of the elevated plains of Pamir in central Asia which is often regarded as the original stock, may be a race which has returned to a wild state, since partly wild horses occur in Syria, on the Don, and live in great herds on the llanos and pampas of South America. There are two primitive races of horses, the Oriental and Western. To the first belong three types : the Arabian, with Fig. 523.—Stomach of a ruminant (sheep), oes the four compartments ; @, cso- phagus ; 0, paunch ; ¢, honeycomb or reticulum ; @, liber psalterium or manyplies ; true digestive stomach ; J, beginning of the intestine: After Owen. er the Berber, Andalusian, Neapolitan; and in England the blood horse; the Nizaischan type of the Deccan, India, to which belong the Persian, Turkestan, Turkish horses, and the Tartarian. The western races comprise the Frieseland, to which belong the Brabant, Holstein, Mecklenburg, and the English farm-horse, and among others the Percheron horse, of France. Ponies are dwarf horses produced in cool, mountainous areas, such as the Shetland Islands. The wild ass (Hqwus onager Brisson) ranges from the Indus to Meso- potamia. Hguus hemionus Pallas, the Dschiggetai or Kiang, goes in herds in central Asia and Mongolia. The hinny and EVEN-TOED UNGULATES. 6045 mule are infertile hybrids of the horse and ass (Hgwus asinus Linn.). Artiodactyles.—The even-toed Ungulates comprise the peccary, pig, hippopotamus, and the Ruminants represented by the deer, sheep, ox, and camel. The pig and peccary are the descendants of a number of extinct earlier forms which flour- ished in the Tertiary Period; the pig, as Marsh observes, having held its own with characteristic pertinacity. ‘The Hippopotamus (Fig. 522) has a large head, with large canines, a clumsy body, and short, four-toed legs. Hippopotamus amphibius Linn., ranges from the Upper Nile to the Cape of Good Hope, and westward to Senegambia. It is nearly % metres (11 feet) in length. Ruminantia.—The remaining Artiodactyles are called Ruminants, from the fact that they chew their cud. The molars are provided with two double crescent-shaped folds (compare Fig. 490). The stomach (Fig. 523) is divided into at least three, usually four compartments, 7.¢., the paunch, the reticulum or honeycomb, so named from the polygonal cells on its interior, the psalterium or manyplies, and lastly the rennet or true stomach. When a sheep, cow, or any other Ruminant feeds, it thrusts out its long tongue, seizes a bunch of grass, and bites it off by pressing the incisors of the lower jaw against the toothless gum of the opposing part of the upper jaw; the mouthful of grass is then swal- -lowed, mixed with much saliva. When its appetite is satis- fied it seeks a retired spot away from its carnivorous ene- mies, if not a domesticated animal, and after lying down, suddenly regurgitates a ball of grass, the cud,* which it slow- ‘ly grinds up between its molar teeth into a pulp. The cropped grass passes into the honeycomb and paunch; the manyplies serves as a strainer for the pulp, which in the fourth stomach is digested by the gastric juice. Among a number of fossil forms leading up to the exist- *The regurgitation o‘ the cud is probably due to a sudden and sim- ultaneous contraction of the diaphragm and of the abdominal muscles, which compresses the contcnts of the rumen and reticulum, and drives the sodden fodder against the cardiac aperture of the stomach, which opens and the cud is propelled into the mouth. (Huxley.; 606 ZOOLOGY. Fig. 524.—Restoration of buck, doe, and young Sivatherium.--After Hawkins. EVEN-TOED UNGULATES. oT Fig. 526.—Virginian Deer.—From Caton. 608 ZOOLOGY. ing deer and antelopes is the Sivatherium (Fig. 524, 525) of the Tertiary beds of the Himalaya Mountains, which had two pairs of horns, and were gigantic creatures. nearly as * th ad rH pal teleoaallaw valli ni + So 1h IW fiw. --—= Fig. 527.—Elk or Wapati.—From Caton's Antelope and Deer of America. Nn bulky as an elephant, and of the singular form approxi- mately indicated by the accompanying illustrations, having affinities to the antelopes and the giraffe. The deer family (Cervid@) is represented in the United THE SHEEP AND ITS VARIETIES. 609 States by the common Virginian deer (Cariacus Virginianus Gray, Fig. 526), the clk or wapiti (Cervus Canadensis Erxle- ben, Fig. 527), and the caribou (Rangifer caribou Audubon and Bachman), which is probably a variety of the European reindeer (2. tarandus Sundevall). In these beautiful, grace- ful forms the solid antlers are cast off annually ; with the exception of the reindeer the females or does have no antlers. The prong-horn antelope (Antilocapra Americana Ord, Fig. 528.—Head of young Prong-horn Antelope.—After Hays. Fig. 528) so characteristic of the western plains, also drops its horns in the autumn, though they are hollow when shed and with a persistent core as in the ox and goat. It crops grass, not, like the deer, cating leaves of trees and shrubs ; “in fleetness it excels all other quadrupeds of our conti- nent,” though it is short winded, and does not run a great distance (Caton). In its horns, hollow when cast off, and the gall bladder, which is absent .in the Cervide, the prong-horn 610 _ ZOOLOGY. connects the deer family with the Bovide, represented by the sheep, goat, antelope, gazelle, and ox. The domestic sheep (Ovis aries Linn.) is not a natural species, but an association of races whose specific origin is obscure. Some authors regard the turf sheep of the stone age of Europe as the ancestor of the domestic sheep, as forms. like it are now living in the Shetland Isles and in Wales. It was of small size, with slender limbs, and erect, short horns. This sheep was supplanted by a curved, large-horned form, the modern domestic sheep. ‘This latter form is pos- sibly the descendant of the Ovis argali Pallas, of Asia, which in North America is represented by the Ovis montana Cuvier, the Rocky Mountain sheep or big-horn (Fig. 530), still com- mon on the less accessible summits along the upper Missouri and Yellowstone Rivers, as wer as the mountains of Wy- > oming and Montana. In the same, though higher and more inac- cessible situations lives the rare mountain goat, Aploceros monta- nus Richardson, whose horns are jet black and polished, slender and conical, like those of the Swiss chamois. It is found sparingly in the higher summits of Fig. 529.—Horns at different ages of the Prong- : born Antelope, showing the hollow structure of the Rocky Mountains the horn when shed.—After Hay:. and the Cascade range ; > an individual has within a few years been shot on Mount Shasta, California. Passing by the gazelles and true an- telopes we come to another characteristic American an- imal, the musk sheep (Ovibos moschatus Blainville, Fig. 531), now confined to the arctic regions. A closely allied species, Ovibos priscus of Riitimeyer, formerly during the post-glacial period existed in England, France, and Ger- many. Closely allied to the musk sheep is a fossil form (Bobtherium of Leidy) which is regarded by Rittimeyer and THE BISON. 611 others as a musk sheep (Ovibos priscus Rutimeyer). If this is the case the musk sheep, or a species closely allied to it,” formerly extended to the Middle States at or near the close of the glacial period. We now come to the bison and ox. The American bison Fig. 580.—Rocky Mountain Sheep or Big-Horn.—From Brehm’s Thiereben. (Bison Americanus Gmelin) formerly ranged from Virginia and Lake Champlain to Florida, and westward from the northern limit of trees to the Rocky Mountains and eastern Mexico. It is nowin danger of extermination, being mainly restricted to a few herds on the plains. It is closely 612 ZOOLOGY. allied to the European bison, (Bison Europeus Owen), the “auroch,” now preserved in the forests of Bialowicza, and living wild in Caucasus. Bos primigenius Bojanus, which Fig. 531.—Musk Sheep.—From Brehm ’s Thierleben, in the time of Cesar lived in Germany and England bear- ing the name ‘“‘urus,” is the ‘‘ur’ of the Niebelungen song. From it has descended the half-wild cattle in certain THE OX AND ITS VARIETIES. 613 English parks, also certain large domestic races, such as the Holstein and Friesland breeds. From another fossil species (Bos longifrons Owen) arose the so-called brown cattle of Switzerland, and the ‘‘runts” of the Scottish Highlands. Still other domestic races are traced back to another fossil ee Soe ‘WMO LOIJV—"MOD oYseTI0G Jo uoJafeHS—‘seg “Fy quaternary species, Bos frontosus Nilsson. Our present races of domestic cattle, however, do not represent a genuine species, but a number of races which have descended from several fossil species; the name Bos taurus (Fig. 582) is simply, then, a conventional name (Carus’ Zoologie), The ‘bison is known to breed with cattle in the Western States, 614 ZOOLOG ¥. though whether the hybrids thus produeed are fertile or not is unknown. The ox is succeeded by the giraffe, with its long neck, which makes it the tallest of all quadrupeds. The last family of Ungulates, the Camelide, comprises the camels of the Old World, and the llama and vicuna of South America. In former (Tertiary) times a llama-like animal inhabited the Pacific coast to Oregon. In the camels the upper lateral incisors are present; the stomach is less distinctly divided into four chambers, the third stomach, as such, is wanting, though the second stomach has the deep cells, which suggested the fable that the camel stores up a supply of water in its stomach for its march over deserts. Fig. 533.—Skull of Lion. The toes have very large, thick pads, while the hoofs are reduced to nail-like proportions. Order 11. Carnivora (Fere).—The bear, cat, tiger, and lion recall the leading forms of this order. The skull is massive, though the head is small or of moderate size: the teeth are all well developed, especially the canines : the mo- lars usually have two or three roots, and the feet have large claws. The stomach is simple. The cerebral hemispheres of the lower carnivores have usually but three distinct con- volutions, while the latter are much more numerous and complicated, the brain itself being broader, in the aquatic forms (Pinnipedia). The group is divided into two sub- orders, 7.¢. the Pinnipedia or seals, and the land species (Fis- sipedia). In the former group the feet are webbed, the toes BEARS AND THEIR ALLIES, 615 being connected ; the wrist and foot only projecting beyond the skin of the body, and there are no external ears, or only small ones. The walrus (Fig. 534), the seals, and the eared seals or sea-lions (Otariide) are the types of the aquatic Carnivores ; the sea-lions can walk on all fours, and in certain peculiarities of the skull they resem- ble the bears. Of the terrestrial, normal Carnivora, the raccocn, coati, Cerco- leptes, and bear, to- gether with a number of extinct forms, are she more generalized or lower types. They are plantigrade, and while standing at the base of the carnivorous series, have some fea- tures suggesting and anticipating those of the lemurs, and mon- keys. The raccoon, Procyon lotor (Linn.), abounds throughout the United States. Al- lied to it is the coati (Nasua) of Central America, a creature about the size of, and with the general hab- its of the raccoon, being an exceedingly knowing and mis- chievous animal. A number of extinct Eocene mammals are also allied to a small plantigrade, long- tailed carntvore, Cercoleptes, which resembles the Primates ia 1ts two cutting “MoQea[Ialy,L, §,LUYyaIg WOI—'snI[e MA OY} JO UOJ[OYS—Feg “BLT 616 , ZOOLOGY. pre-molars and three true molars; while the rami of the mandible are codssified; for these reasons it was placed by F. Cuvier between the orders Carnivora and Primates (Cope).. It is allied to the raccoon, is called the kincajou, and lives in northern South America. The bears have a thick, clumsy body, with a rudimentary * tail, and the teeth are broad and tuberculated, so that they can live indifferently on fish, insects, or berries. Our North American species are the polar bear (Ursus maritimus Linn.) and Ursus arctos Linn., with its varieties of brown, ~ Sansa SOR so A, a Nig, © 2 pat, pena penrow ye Fig. 535.—Skeleton of the Polar Bear, ehowine the plantigrade feet. 51, scapula; 58, humerus; 54, radius; 55, ulna; 62, ilium; 63, ischium; 65, femur; 66, tibia; 67, fibula ; cl, calcareum ; C, cervical vertebree.—After Owen. cinnamon and grizzly bears; and the true black bear, Ursus Americanus Pallas. The bears are succeeded by the Mustelid@, or the otter, skunk, badger, wolverene, weasel, mink, ermine, etc., nearly all of which are valuable for their furs. The dog family (Canide) is represented by the fox, wolf, and dog. The gray fox (Urocyon Virginianus Erxleben) the common red fox ( Vulpes vulgaris Fleming), with its varie- ties, tle cross, silver, and black fox, as well as the wolf (Canis lupus Linn.), are valuable for their furs. The wolf is mostly gray northward, becoming ‘southward more and THE SPECIES OF DOGS AND CATS. 617 more blackish and reddish, till in Florida black wolves pre- dominate, and in Texas red ones.” (Jordan’s Manual of Vertebrates.) The prairie wolf or coyoté (Canis latrans ’ Say), is characteristic of the Western plains and Pacific coast. _ The Indian dogs breed with the coyoté, and the offspring is fertile. (Coues.) This fact appears to support the theory that the domestic dog (with its conventional name Canis familiaris Linn.) is a descendant of the wolf. On the other hand, Fitzinger in his ‘‘ Researches on the Origin of the Dog,” states that fourteen kinds of dogs can be distinguished in the Roman and Greek records; of these he considers five to be principal types or species, five others climatic varieties, the remainder being either breeds artificially produced or hybrids. As regards the Egyptian dogs, seven kinds may be distinguished, besides the jackall, three of them being dis- tinct species. He believes that wolves, jackalls, foxes, etc., are species quite distinct from the domestic dog; they may have interbred with the latter, and thus influenced cer- tain breeds ; but they are not the parents of the domestic dog. He concludes that there are seven species among our dogs :—C. domesticus, extrarius or spaniel and Newfound- land dogs, vertagus or badger dog, sagax or hound, molossus or bulldog, leporarius or greyhound, and the naked dog, C. caribeus. Among half-wild dogs is the dingo or hunt- ing-dog of Australia, which goes in packs. — The Viverra and Genetta or civet cats, and the hyenas lead to the cat family, which stands at the head of the Car- nivora. The panther, leopard, tiger, and lion belong to the genus Felis. The Felis concolor Linn., cougar or puma, ranges over both continents ; it is 1-1-3 metres in length. The domestic cat, Felis domestica Linn., was first domes- ticated in Egypt, the Greeks and Romans not possessing it; the cat and common marten were in use as domesticated animals side by side; and at the same time in Italy, nine hundred years before the crusades. It appears that the do- mestic cat of the ancients was Mustela Soina (Rolleston). Of the lynxes there are two species in North America, Lynx rufus Rafinesque, the American wildcat, and the Canada lynx, Lynx Canadensis Rafinesque, the latter being much the larger species. 618 ZOOLOGY. Order XII. Primates.—The last and highest order of mammals contains a series beginning with creatures resem- bling squirrels and bats, 7. ¢., the lemurs, and comprising monkeys, apes, and ending with man. In all the Primates, the legs are exserted almost or quite free from the trunk, with the great toe of the hind foot usually enlarged and op- posable to the others; nails, except in the marmosets, replace claws ; the teeth are usually of the following formula : © 72-2 {1-1 ,3- : 3-8 tye eat’ * gene gee with one aoe oS teeth are Eee present ; pre- molars are usuall v2 eos - but in the American monkeys = oa a The hemispheres of the brain may in the lower forms be quite smooth, but in all there is a well-developed ‘‘ calcarine furrow,” giving rise to a ‘‘ hippocampus minor” within the posterior cornu of the ventricle, by which the posterior lobe of the cerebrum is traversed (Flower). The collar-bones (clavicles) are for the first time in the series well developed. The placenta is also different in shape from that of other mammals, being disk or cake-like, but in lemurs it is *‘ diffuse.” The Primates are divided into two sub-orders, 2. ¢., the Prosimie and Anthropotdea. The former group embraces the lemurs, which vary in size from that of a rabbit to a large monkey. They are covered, the face as well as the rest of the body, with a dense fur; walk on all-fours, usually have long tails, though the lori is tailless, while the fore limbs are shorter than the hind limbs. The skull is small, flattened, and narrow in front; the brain-cavity small in proportion to the rest of the skull, 7. ¢., the face compared with the monkeys. The cerebral hemispheres are small and ‘flattened, the frontal lobes narrow and pointed, and behind they only slightly cover the cerepellum. By some authors the lemurs are separated from the Pri- mates, the Insectivora and Cheiroptera being placed between the Prosimie and the other Primates. They have characters in which they resemble Jnsectivora, Rodentia, and Carnivora, but the weight of organization, or the sum of their charac- ters, ally them nearest to the monkeys. They are therefore essentially a generalized or ancestral tyve. Recent discov- THE PRIMATES. 619 eries have led to the hypothesis, that from still older, more generalized types, four lines of development, respectively. culminating in the typical Carnivores, Cetaceans, lemurs, and monkeys, have taken their origin. That the lemurs, though now restricted to Madagascar, eastern Asia, and South Africa, were preceded by still more generalized types on the American Continent, is indicated by the discovery of fossil bones in the Eocene beds of the Recky Mountains, referred by Marsh and Cope to the Primates; Marsh stating that the principal parts of the skeleton are ‘‘much as in some of the lemurs.” Allied to the true lemurs is a very puzzling creature, the aye-aye or Chiromys, of Madagascar, whose dentition differs from that of all other Primates, and resembles that of the Rodents ; the thamb also is not ¢ruly opposable, and all the hind digits, except the great toes, have claw-like nails. The Gaiago, of West Africa, somewhat recalls the Jnsectivora, while ‘‘in the more active and flexible-bodied Lemuride, the trunk-vertebre resemble in proportions, connections, and direction of neural spines those of the agile Carnivora.” (Owen. ) The genuine Primates or suborder Anthropoidea are, in biief, characterized by the large, convoluted cerebral hemi- spheres which nearly, or in the higher apes and man, conceal the cerebellum when seen from above.* 'Theears are rounded, with a distinct lobule, and the two mamme are pectoral. These Anthropoidea are divided into two subdivisions, the first comprising the monkeys and apes, and the second, man. In the first group (Simi), the body is prone, the animal walking on all-fours, only the orang and gorilla walking partly erect 5 the great toe is rather short, thumb-like, and opposable to the fingers, while the body is very hairy. The monkeys of the New World have a wide septum to the nose, and are hence called Platyrhine ; they als» have long tails. The little, squirrel-like, gregarious marmosets are the small- est of the monkeys and nearest allied to the lemurs. They walk on all-fours, the anterior extremities being like the *In the low Hapale and onus however, the cerebrum projects backward as far or even farther than in man (Gill). 620 ZOOLOGY, hind feet, and resting on the same plane, serving as a paw ; the teeth ure sharply tubercled, and the nails, except those of the great toe, are claw-like. The cerebral hemispheres are nearly smooth, though relatively large. Jacchus and Midas are the typical genera, inhabiting South America. While the marmosets (Midide) have but thirty-two teeth, in the true platyrrhine monkeys there are thirty-six teeth ; there being an additional molar on each side of each jaw, and the thumb is slightly opposable to the fingers (though a true thumb is wanting in the spider monkeys). The New World monkeys also have long prehensile tails, so useful in climb- ing as to be sometimes called a fifth hand, as seen in the spider ‘monkeys (Ateles), in which the tail underneath is naked and very sensitive. The skull varies greatly in the dif- ferent genera, as does the brain, which in Chrysothriz, etc., is nearly smooth, while in Cebus the hemispheres are nearly as much convoluted as in the catarrhine apes. (Huxley.) The monkeys of the Old World intergrade with the apes, and are thus more specialized or highly developed than those of the New World. The septum of the nose is narrow, hence they are said to be catarrhine or thin-nosed, while the tail is short and not prehensile. The catarrhine monkeys (Cercopithecide) walk on all- fours ; the body being horizontal or prone ; they have thirty- two teeth, as in man, though the canines are large and sharp; the thumb is well developed, and they are truly quadrumanous; the skull has a comparatively large facial angle, and the hemispheres of the brain are well furrowed. They have highly-colored, naked callosities over the ischiatic bones, and cheek-pouches for the temporary reception of the food. Of the baboons, with their dog-like muzzles and short tails, the mandrills are the most noticeable, with their white beards, scarlet lips, and blue cheeks; they are less arboreal than the macaques of Asia, running about over rocks on all-fours. The common monkeys of menageries are the macaques (Macacus) of India. All the foregoing catarrhine monkeys have a simple stomach, as in man, but in the sacred monkey of India (Semnopithecus) and the African thumbless Colobus, the stomach is more complex, and there are no cheek pouches. THE MONKEYS AND APES. 621 The apes live in trees, only occasionally walking on the ground ; their posture is semi-erect; they are tailless, the fore legs are much longer than the hind legs, and used as arms, the radius being ca- pable of complete prona- tion and supination. In the form of the skull, of the brain with its convolu- tions, and in the teeth, there is a still nearer ap- proach to man. There are three typical forms or genera of apes, 1.¢., the gibbon (Hylobates, Fig. 536); the orang (Mfi- metes pithecus) and chim- panzee (M. niger, Fig. . 587), and the gorilla. The gibbons are nearest to the monkeys; they are little less than a metre (3 feet) in height, and are very slender, with very long arms, so that they are rapid, agile climbers, also run- ning over the ground with ease and rapidity ; when standing erect the fingers touch the ground; only the thumbs and great toes have true nails, in all the higher apes the nails of all the digits being flattened ; the spinal column is nearly straight; they have four- teen pairs of ribs and ae 536.—Skeleton of Siamang Ape, a rib- on.—After Owen. eighteen dorso-lumbar ver- tebre, there being i in the other apes usually seventeen, as in man. The siamang lives in the forest of Sumatra; others inhabit Java, Borneo, Cambogia, etc. 622 ZOOLOGY. The orang-outang 1s 1-38 metres (4-44 feet) high ; it has twelve pairs of ribs, the same number as in man ; the arms are very long, reaching the ground, so that in walking they rest on their knuckles, swinging the body through their long arms as if walking on crutches; their posture is only par- tially erect. The forehead is less strongly marked than in Al Fig. 537.—The Chimpanzee, variety Tshego.—From Brehin’s Thierleben. the other apes, showing better the shape of the skull. The volume of the brain, both of the orang and chimpanzee is about twenty-six or twenty-seven cubic inches. The follow- ing table will show, according to Wyman, the relative capacity of the skull in the different apes as compared with man : CHIMPANZEE AND GORILLA. 623 The examage capacliy se the Caucasian skull is 92 cubic inches. Australian “ %5 ae 66 “¢ se Gorilla ce 29 to near 35 cubic inches. “ se ee Chimpanzee “ 26 fe ce ce ee Orang ce 95 ce According to Wyman, the range of variation in different races of men, as seen in seventeen skulls, is from 92 to 75 cubic inches ; in the gorilla from 34 to 25 cubic inches, nine skulls having been measured. There is but a single species of orang, which is restricted to Sumatra and Borneo. It is said to be very intelligent, to possess a voice so loud as to be heard one or two miles, and to build a nest to sleep on. The chimpanzee and gorilla are only found on the west coast of Africa. The chimpanzee (Mimetes niger Geoffroy with its variety Tschego, Fig. 537) inhabits the coast from Sierra Leone to Congo. It is about 14 metres (5 feet) in height. It can stand or run erect, but it usually leans for- ward, resting on its knuckles ; the arms span about half as much again as the creature’s height. Both the chimpanzee and gorilla have fourteen pairs of ribs. The chimpanzee lives on fruit, is an active climber, and nests in trees, changing its rude quarters according to circumstances. Rey. Dr. Savage states that “they generally build not far above the ground. Branches or twigs are bent, or partly broken, and crossed, and the whole supported by the body of a limb or a crotch. Sometimes a nest will be found near the end of a strong leafy branch twenty or thirty feet from the ground.” The gorilla, like the chimpanzee, goes in bands, but the company is smaller, and led by a single adult male. They make similar nests, which, however, in the case of both apes, afford no shelter, and are only occupied at night. The gorilla sometimes reaches the height of about 13 metres (53 feet) and weighs about 200 pounds. Its ordinary attitude is like that of the chimpanzee ; there is a web between the first joints of all the fingers and three of the toes, and both hands and feet are broader, while the body is much more robust than in the other apes, being very broad across the shoulders. The span of the arms is to the height as three to two, or a little over eight feet. The skull is thick, and the strength 624 ZOOLOGY. and ferocity of the creature is evinced by the thick supra- orbital ridges and the high sagittal and lambdoidal crests on the top of the skull; the face is wide and long, the nose broad and flat, the lips and chin prominent. The gorilla walks like the chimpanzee, though it stoops less. It is very ferocious, bold, never running when approached or attacked by man. It lives on a range of mountains in the interior of Guinea, its habitat, so far as known, extending from a little north of the Gaboon River to the Congo. Thus, to recapitulate, while the gibbons are most remote from man, the orangs approach him nearest in the number of the ribs, the form of the cerebral hemispheres, and other less obvious characters ; the chimpanzee is nearest related to him in the form of the skull, the dentition and the propor- tions of the arms, while the gorilla resembles him more in the proportions of the leg to the body, of the foot to the hand, in the size of the heel, the curvature of the spine, the form of the pelvis and the absolute capacity of the skull (Huxley). Anatomists have and do differ as to whether the chimpanzee or the gorilla is nearest to man. The question whether man (Homo sapiens Linn.) considered simply as an animal, is the representative of a distinct sub- class, order, suborder or family, is and may never be settled ; though the tendency among zoologists is to leave him among the Primates, where he was placed by Linneus. When we consider the slight absolute anatomical differences separating man from the apes, and take into account the great variations in form between the different genera of apes, and still more in the monkeys, it seems best, throwing out, as we have to do in a purely zoological classification, the intellectual and moral faculties of man, to adopt the view that man is the representative of a group of Primates.* The absolute differences of man from the apes consist in the greater num- ber and irregularity of the convolutions of the cerebral hemi- * Geoffroy St. Hilaire placed man in a kingdom by himself ; Owen assigned him to a subclass ; by others he is generally regarded as a representative of an order Bimana, as opposed to the order Quadru- mana, or monkeys and apes; while from recent comparative studies man is considered as belonging either to a separate suborder or a fam. ilv. DIFFERENCES OF MAN FROM THE APES 625 spheres, which are also much larger compared with the cere- bellum, and completely cover the latter; the entire brain being at least double the size proportionately of that of the gorilla ;* it is also stated that two muscles exist in man which have not yet been found in any ape, the extensor primi internodit pollicis and the peroneus tertius, belonging to the thumb and foot respectively (Huxley).+ There are also points in the origin of certain muscles which are peculiar to man, but Huxley adds that all the apparently distinctive peculiarities of the muscles of the apes are to be met with, occasionally, as varieties in man. On the other hand, the relative differ- ences of the skulls of the gorilla and man are, as Huxley states, ‘‘immense.” In man the cranial box overhangs the orbits ; in the gorilla the forehead is hollowed out. The hinder portion of the brain is also much more developed in man than in the apes, and in the hinder part of the hemi- spheres the convolutions are more numerous than in the chimpanzee, this part in monkeys losing its convolutions altogether (Wyman). Man stands erect; his arms span a distance equal to his height; the spinal column has four curves; the skin of the hands and feet of man is highly sensitive, compared with that of the apes. Finally, as Cuvier stated, the grand distinctive zoological character separating man from the other animals is the possession of the power of speech. Sometimes in man the coccyx has one or two more joints than the normal number, but the apes have no tail; though the human embyro, like other young animals, has a tail, * «Tt must not be overlooked, however, that there is a very striking difference in absolute mass and weight between the lowest human brain and that of the highest ape—a difference which is all the more remarkable when we recollect that a full-grown gorilla is probably pretty nearly twice as heavy as a Bosjes man, or as many an European woman, It may be doubted whether a healthy human brain ever weighed less than thirty-one or two ounces, or that the heaviest gorilla brain has exceeded twenty ounces.” In another place Huxley states that “‘an average European child of four year’s old has a brain twice as large as that of an adult gorilla.”’—Man’s Place in Nature. + Dr. Chapman has found in the arm of a gorilla a distinct extensor primi internodit pollicis muscle, but no trace of the flecor longs pollt- cis.— American Naturalist, June, 1879, p. 395. 626 ZOOLOGY. though as observed by His, it does not contain any vertebre, and is thus not like the tail of other embryo mammals. The black and Australian races are slightly nearer the apes than civilized peoples. In apes, as in the lower mammals, the pel- vis is higher than wide; when there is a degradation in the human pelvis it tends to become higher than wide, as seen in the pelvis of the Hottentots. In civilized man the legs are one half the height of the body, but in the South Afridan, Hottentot, and Bushman the legs are a little less than half the height, and the thigh bone is flattened from side to side, asin the gorilla. The waist is broader in the African than in the European ; the os calevs is not longer in negroes than in the white man, the larger heel of the former being simply a due to an expansion of the = soft parts. Me, Nig ‘The form of the skull va- ries greatly in the different races, and even in individ- uals of the same race of inert = mankind. This is seen in eae rn RO the difference of the facial Fig. 538.—Skull of a Negro, showing its angle. This is obtained by prognathism.—After Owen. f drawing a line from the occipital condyle along the floor of the nostrils, and inter- secting it by a second, touching the most prominent. parts of the forehead and upper jaw; the angle they make is an index of the cranial capacity, and of the degree of in- telligence of the individual. The facial angle in the reptiles is very slight, as it is in the birds; in the dog it is 20°, in the. gorilla 40°, in the Australian 85°, in the civilized Caucasian it averages 95°, while the Greek sculptors adopted an ideal angle of 100°. (Owen.*) When the lower part of the face protrudes, as in the negro, the face is said to be prognathous (Fig. 538) ; where the facial angle is high, and the face straight, as in the more intellectual forms, the cranium is * Pagenstecher states that the facial angle in the Caucasian Euro- pean is 80°-85°, and even over 90°; in the Mongolians 75°-80°; in negroes 70°-75°; in the tribe of Makoias in South Africa 64°; in the tribe of Tikki-Tikki, or Akka negroes, the dwarfs described by Schweinfurth, only 60°.—Allgemeine Zoologie, i., p. 250. THE VARIETIES OF MAN. 627 said to be orthognathous. Those skulls which are high and narrow, 1.¢., with the longer diameter to the shorter, as 100 to 65, are said to be dolichocephalic, while those with the diameters as 100 to 85 are called brachycephalic, but these dis- tinctions have been found to be quite arbitrary. The classification of the human races is in as an unsatis- factory state as that of the domestic animals. Naturalists are now agreed that there is but one species of man. Blu- menbach, from the shape of the skull and the color of the skin, divided mankind into three varieties, the white or Cau- casian, the brown or Mongolian, and the black or Ethiopian, considering the American variety as connecting the Caucasian and Mongolian, and the Malayan as intermediate between the Caucasian and Ethiopian. Hamilton Smith divided man into three varieties, Caucasian, Mongolian, and Tropi- cal; Latham, also, into three, Japetide, Mongolide, and Atlantide ; and Pickering into white, brown, and black varieties, with intermediate races. Huxley divides the dif- ferent races into two primary groups, the Ulotricht, with crisp or woolly hair, and the Leiotrichi with smooth hair. The average height of Englishmen is 5-8-5-10 feet ; in the universities more. In America, the average height of medical and military men is 5-93 feet. The Patagonian men are nearly six feet high on an average; the women 5:10 feet; the Bushman and Esquimaux 4-7, the latter being the small- est people on the earth. The smallest dwarfs in Europe were 33 and 28 inches in height respectively ; while Pat- rick Cotter, the Irish giant, was 8 feet 7 inches tall. It is claimed by some naturalists that man has descended from some generalized type of animal which gave rise to several series of forms culminating in the monkeys, apes, and man respectively, and by others that he is a direct descendant of forms like the chimpanzee or gorilla; but it is probable that from the want of sufficient data, the question as to the origin of man can never be def- initely settled. Setting hypothesis aside, in ascending the mammalian series, we have seen in the forms lead- ing from the extinct Eocene generalized types of Eud- ucabilia to the Carnivora and Primates, a tendency to an extreme specialization of those parts ministering to the 628 ZOOLOGY. intellectual behests of the creature. On the other hand, in - all general points, man’s limbs are those of the primitive type so common in the Eocene. Period. As Cope remarks : ‘‘He is plantigrade, has five toes, separate carpals and tar- sals; a short heel, rather flat astragalus, and neither hoofs nor claws, but something between the two. The bones of the fore arm and leg are not so unequal as in the higher types; and remain entirely distinct.from each other, and the ankle joint is not so perfect as in many of them. In his teeth his character is thoroughly primitive. He possesses, in fact, the original quadrituberculate molar with but little modification. His structural superiority consists solely in ‘ the complexity and size of his brain.” Whether man in common with other animals is the result of divinely ordered processes or biological laws, appearing at the head of a long series of forms, and, as probably many other animals have, with comparative suddenness, being at the outset in all essential respects man, though a savage, and not with a long pedigree of morphologically impossible Dar- winian ‘‘ missing links,”—whether he thus originated, or by an independent creative act, the result is a being concerning whom the fact that he is physically an animal, is after all the least important characteristic of the nature of him who is the historian of his own and other species; who is capable of studying and in a degree comprehending the universe in which he lives, and who whatever his physical origin may have been, has intellectual, moral, and spiritual capabilities which render his nature susceptible of endless improvement, endowing him with immortality and all that it involves. Crass VITIL—MamMaAtta. Body covered with hair ; young nourished with milk secreted in mam- me ; lower jaw articulating directly with the skull, the quadrate bone be- coming one of the ear-bones (malleus) ; a diaphragm dividing the body- cavity into thoracic and abdominal portions ; heart with the aorta reflect- ed over the left bronrhus ; blood-corpuscles non-nucleated ; brain large, especially the cerebral hemispheres ; viviparous ; uterine gestation. Subelass IL Ornithodelphia.—Order Monotremata.—Urinary and gen- ital outlets opening into the cloaca. Laying large eggs (Echidna, Ornithorhynchus). CLASSIFICATION OF MAMMALS. 629 Subclass IL. Didelphia.—Order Marsupialia—Mammals with a mar- supium and bones supporting it. (Macropus, Didelphys.) Subciase III. Monodephia.—Placental mammals. Super-order I. Ineducabilia.—Brain with a relatively small, smooth cerebrum. Order 1. Bruta.—Incisors absent; sometimes toothless. (Bradypus.) Order 2. Glires.—Rodents, incisors large. (Sciurus.) Order 3. Insectivora.—Fore limbs often peculiarly adapted for burrowing ; molars with conical cusps. (Scalops.) Order 4, Chiroptera.—Fore limbs adapted for flight. (Ves- pertilio.) Super-order II, Educabilia.—Brain with a relatively large, con- voluted cerebrum. Order 5. Cete-—Cetaceans; fish-like in form, no hind limbs. (Balzna.) Order 6. Sirenia.—Fish-like in form, but with ascending rami to the lower jaw; teeth ruminant-like. (Mana- tus.) : Order 7. Proboscidea.—Snout prolonged into a proboscis. (Elephas. ) Order 8. Hyracoidea.—Long curved incisors; feet with pads; toes encased in hoofs. (Hyrax.) Order 9. Toxodontia.—Extinct forms, with well developed incisors. (Toxodon.) Order 10. Ungulata.—Ungulates ; toes encased in hoofs. (Equus, Bos.) Order 11. Carnivora.—Teeth pointed; claws large. (Felis, Canis.) ; Order 12. Primates.—Brain with cerebrum nearly or quite covering the cerebellum ; nails usually present; body quadrupedal, quadrumanous, or erect and bimanous. (Cebus, Gorilla, Homo.) Laboratory Work.—All the craniate vertebrates may be dissected in the same general manner, either under water in pans, or, if large, upon the dissecting table. The necessary tools are a scalpel, forceps, scis- sors, and tenaculum or hook for suspending the specimens or portions 630 ZOOLOGY. of large subjects for better facility in dissecting. A small sharp- pointed narrow-bladed scalpel, besides a large one, curved, as we.] as sharp-pointed scissors are useful, with a German silver blow-pipe for temporarily distending vessels; and also a blunt-pointed copper wire or probe made for surgeon’s use, will be necessary. All these in- struments, put up in a compact box, can be purchased at the surgical instrument maker's, as well as syringes for injecting the circulatory organs and vascular parts of the viscera. TABULAR VIEW OF THE EIGHT CLASSES OF VERTEBRATES. VIII. Mammatia.—Mammals. 3 $ a oe ‘ z bo a = q = a = 7 g 5 , a os) mn 3 qa a a 3 Ss R q < | 4 a 4 3s Ki 3 “a > 3 | ; EOC ; = I a al fa x sg & fo S a a i a ee 5 > a I a a ‘ | e B i aaa ca * ~ > g = | - : poy ei = ° | | B a a < = wi — | Sus-srancu III.—CRANIOTA. Sup-BRANCH II.—ACRANIA. I. Leprocarpr (Lancelet). SuB-BRANCH I.—UROCHORDATA. I. Tunrcata. CHAPTER IX, COMPARATIVE ANATOMY OF ORGANS. “Havine studied the morphology of animals in a system- atic way, it will be well for the student to make a brief re- view of those facts stated in the foregoing chapters bearing on the origin and successive degrees of complication of the most important organs. Organs of Digestion—The Mouth and Teeth.—The most important organs in the animal system are those relating to ‘digestion, as an animal may respire solely through its body- walls, or do without a circulatory or nervous system, but must eat in order to live and grow. The opening by which the food is taken into the alimentary canal is called the mouth, whether reference is made to the ‘‘ mouth’ of a hydra or of a vertebrate ; although the structure of the edges may differ radically, still in all Metazoa the mouth is due to an inpushing of the ectoderm, however differently the edge of the mouth may he supported and elaborated. The edges of the mouth are usually called the lips, but true lips for the first time appear in the Mammalia. The trituration or mastication of the food is accomplished among the in- vertebrates in a variety of ways, and by organs not always truly homologous. Hard bodies serving as teeth occur for the first time in the animal series in the sea-urchins, where a definite set of cal- careous dental processes or teeth (Figs. 78 and 79), with solid supports and a complicated muscular apparatus, serves for the comminution of the food, which consists of decaying an- imals and sea-weeds. In those Echinoderms which do not havea solid framework of teeth, the food consists of minute forms of life, protozoans and higher soft-bodied animals, 632 ZOOLOG ¥. or the free-moving young of higher animals, which are carried into the mouth in currents of water or swallowed bodily with sand or mud. Among the worms true organs of mastication for the first time appear in the Rotatoria (Fig. 122), where the food, such as infusoria, etc., is crushed and is partly comminuted by the well-marked horny or chitinous pieces attached to the mastax. In most other low worms the mouth is unarmed. In the leeches there are three, usually in the annelids two, denticulated or serrate, chitinous flattened bodies situated in the extensible pharynx of these worms, and suited for seizing and crushing their prey. In the higher mollusks, such as the snails (Cephalophora) and cuttles, besides broad thin pharyngeal teeth, compara- ble with those mentioned as existing in the worms, is the lin- gual ribbon already described (p. 276, Fig. 215), and admira- bly adapted for sawing or slicing sea-weeds and cutting and boring into hard shells, acting somewhat like a lapi- dary’s wheel ; this organ, however, is limited in its action, and in the cuttles the jaws, which are like a parrot’s beak, do the work of tearing and biting the animals serving as food, which are seized and held in place by the suckered arms. In the crustaceans and insects we have an approach to true jaws, but here they work laterally, not up and down or vertically, as in the vertebrate jaws ; the mandibles of these animals are modified feet, and the teeth on their edges are simply irregularities or sharp processes adapting the mandi- bles for tearing and comminuting the food. It is generally stated that the numerous teeth lining the crop of crustacea and insects (Fig. 282) serve to further comminute the food after being partially crushed by the mandibles, but it is now supposed that these numerous points also act collectively as a strainer to keep the larger particles of food from passing into the chyle-stomach until finely crushed. The king-crab burrows in the mud for worms (Nereids, etc.) ; these may be found almost entire in the intestine, having only been torn here and there and partly crushed by the spines of the base of the foot-jaws, which thus serve the COMPARATIVE ANATOMY OF ORGANS. 633 purpose effected by the serrated edges of the mandibles of the genuine Crustacea and insects. Among vertebrates, the lancelet is no better off than the majority of the Ceelenterates and worms, having no solid parts for mastication ; and we have seen that the jaws and teeth of the hag-fish and even the lamprey eel form a very different apparatus from the jaws and its skeleton in the higher vertebrates ; and that, even in the latter, the bony elements differ essentially in form in the different classes, though originating in the same manner in embryonic life. In the birds we have seen that the mandible and maxilla are encased in horny plates, that true teeth are remarkably ex- ceptionable, the gizzard being, however, provided with two hard grinding surfaces ; on the other hand, mammals with- out teeth are exceptionable. The teeth of fishes are developed, not only in the jaws, but on the different bones projecting from the sides and roof of the mouth, and extend into the throat. In many cases, in the bony fishes, these sharp recurved teeth serve to prevent the prey, such as smaller fish, from slipping out of the mouth. On the other hand, the upper and lower sides of the mouth of certain rays (Myliobatis) are like the solid pavement of a street, and act as an upper and nether mill- stone to crush solid shells. In the toothless ant-eaters the food consists of insects, which are swallowed without: being crushed in the mouth ; true teeth in the duckbill are wanting, their place being taken by the horny processes of the jaws, while in Steller’s manatee the toothless jaws are provided with horny solid plates for crushing the leaves of aquatic succulent plants. Examples of the most highly differentiated teeth in verte- brates are seen in those animals, like the bear, whose food is omnivorous, consisting of flesh, insects, and berries, where the crown of the molars are tuberculate; while the canines are adapted for holding the prey firmly as well as for tearing the flesh, and the incisors, for both cutting and tearing the food. The simplest form of a genuine digestive or enteric canal is to be found in the Hydra, and in a more advanced stage in the marine Hydroids. For the technical name of the 634 ZOOLOGY. digestive tract we may adopt Haeckel’s term enteron. In the jelly-fishes the stomach opens into four or more water- vascular canals or passages, by which the food, when par- tially digested and mixed with sea-water, thus forming a rude sort of blood, supplies the tissues with nourishment. In the sea-anemones and coral polyps, the digestive cavity is still more specialized, and its walls are partly separated from the walls of the body, though at the posterior end the stomach opens directly into the body-cavity. In the Echi- noderms and worms do we find for the first time a genuine digestive tube, lying in the pertvisceral space (which, with Haeckel, we may call the cwlom), and opening externally for the rejection of waste matter. In the worms the digestive canal now becomes separated into a mouth, an cesophagus, with salivary glands opening into the mouth, and there is a division of the digestive tract into three regions—t.e., fure (esophagus), middle (chyle- stomach), and hind (intestine) enteron. In the mollusks and higher worms there is a well-marked sac-like stomach and an intestine,with a liver, present in certain worms (in the ascidians and mollusks), opening into the beginning of the intestine. All these divisions of the digestive tract ex- ist still more clearly in the crustacea and most insects. In the latter, six or more excretory tubes (Malpighian vessels) discharge their contents into the intestines, and in the “‘ res- ‘piratory tree ’’ of the Holothurian and the excretory vessels -of certain worms we have organs with probably similar uses. In the vertebrates, from the lancelet to man, the alimen- tary canal has, without exception, the three divisions of ces- ophagus, stomach, and intestine, with a liver. In this branch the lungs are either, as in the lancelet, modified parts of the first division of the digestive tract or originally sac-like dilatations of the digestive tract. The intestine is also subdivided in the mammals into the small and large intestine and rectum, a cecum being situated at the limits between the small and large intestine. We thus observe a gradual advance in the degree of specialization of the digestive or- gans corresponding to the degree of complication of the an- imal. COMPARATIVE ANATOMY OF ORGANS. 635 Organs of Circulation.—Intimately associated with the digestive canal are the vessels in which the products of di- gestion mix with the blood and supply nourishment for the tissues, or, in other words, for the growth of the body. In the Infusoria the evident use of the contractile vesicles is to aid in the diffusion of the partly digested food of these mi- croscopic forms. In the Hydra the food-stuff is directly taken up by the cells lining the celum, while the imper- fectly formed blood also finds access to the hollows of the tentacles. The mode in which the cells lining the canals in the sponge take up, by means of the large cilia, micro- scopic particles of food, directly absorbing them in their substance, is an interesting example of the mode of nourish- ment of cellular tissues of the lower animals. The sea-anemone presents a step in advance in organs of circulation ; here the partly digested food escapes through the open end of the stomach into the perivisceral chambers, the action of the cilia, with the contractions of the body, churning the blood, consisting of sea-water and the particles of digested food, and a few blood-corpuscles, hither and thither, and forcing it into every interstice of the body, even into the tentacles, so that the tissues are everywhere supplied with food. The water-vascular system of the Celenterates presents an additional step in degree of complexity ; but it is not until we reach the Echinoderms on the one hand, and such worms as the Nemerées and allies on the other, where defi- nite tubes or canals, the larger ones contractile, and in the latter type at least formed from the mesoderm, serve to convey a true blood to the various parts of the body, that we have a definite blood system. In the Echinoderms a true hemal or vascular system may co-exist with the water- vascular system. In the annelids, such as the Nereis, one of the blood-vessels may be modified to form a pulsating tube or ‘‘ heart,’’ by which the blood is directly forced out- ward to the periphery of the body through vessels which may, by courtesy, be called arteries, while the blood returns to the ‘‘ heart ’’ by so-called veins. The mollusks have a circulatory system which presents a 636 ZOOLOGY. nearer approach to the vertebrate heart and its vessels than even the crustaceans and insecis, for the ventricle and one or two auricles, with the complicated arterial and venous sys- tem of vessels of the clam, snail, and cuttle-fish, truly fore- shadow the genuine heart and systemic and pulmonary cir- culation of the vertebrates. The mollusks, and king-crab, and the lobster present some approach to the capillaries of vertebrates. The circulation in certain worms, from We- mertes upward, may be said to be closed, the vessels being continuous ; but they are not so in insects, where true veins are not to be found, the blood returning to the heart in channels or Jacune in the spaces between the muscles and viscera. We have seen that in vertebrates the ‘aortic heart ” of the lancelet or Amphiorus is simply a pulsating tube, and there are portions of other vessels which are pulsatile, so that there is, as in some worms, a system of “hearts.” A gen- uine heart, consisting of an auricle and a ventricle only, first appears in the lamprey. This condition of things survives in fishes, with the exception of those forms, such as the lung- fish (Dipnoans), whose heart anticipates in structure that of the amphibians and reptiles, in which a second auricle ap- pears. Again, certain reptiles, such as the crocodiles, antici- pate the birds and mammals in having two ventricles—i.e., a four-chambered heart. It should be borne in mind that in early life the heart of all skulled vertebrates (Craniota) is a simple tube, and as Gegenbaur states, ‘‘ as it gradually gets longer than the space set apart for it, it is arranged in an S-shaped loop, and so takes on the form which the heart has later on.’? Owing to this change of form, it is divided into two parts, the auricle and ventricle. . Astriking feature first encountered in the craniate ver- tebrates is the presence of a set of vessels conveying the nutrient fluid or chyle which filters through the walls of the digestive canal to the blood-vessels ; these are the lym- phatics. In the lancelet, as well as in the invertebrate ani- mals, such vessels do not occur, but the chyle oozes through the stomach-walls and directly mixes with the blood. COMPARATIVE ANATOMY OF ORGANS. 637 Organs of Respiration.—Always in intimate relation with the circulatory system are the means of respiration. The process may be carried on all over the body in the simple animals, such as Protozoa or sponges, or, as in Celenterates, it may be carried on in the water-vascular tubes of those animals, while in the so-called ‘‘ respiratory tree’? of Echin- oderms it may go on in company with the performance of other functions by the same vessels. Respiration, however, is inclined to be more active in such finely subdivided parts of the body as the tentacles of polyps, of worms, or any filamentous subdivisions of any of the invertebrates ; these parts, usually called gills, though only the gills of fishes are traly such, present in the aggregate a broad respiratory sur- face. Into the hollows of these filamentous processes, which are usually extensions of the body-walls, blood is driven through vessels, and the oxygen in the water bathing the gills filters through the integument, and immediately gains access to and mixes with the blood. The gills of the lower animals appear at first sight as if distributed over the body in a wanton manner, appearing in some species on the head, in others along the sides of the body, or in others on the tail alone ; but in fact they always arise in such situations as are best adapted to the mode of life of the creature. The gills of many of the lower animals afford an admira- ble instance of the economy of nature. The tentacles of polyps, polyzoans, brachiopods, and many true worms serve also, as delicate tactile organs, for grasping and conveying food to the mouth, and often for locomotion. The suckers or ‘‘ feet’? of star-fish or sea-urchins also without doubt perform the office of gills, for the luxuriously branched, beautifully-colored tentacles of the sea-cucumber are simply modifications of the ambulacral feet. One of the readiest ways of judging of the mental condition, so to speak, of a worm, such as Sadella or Terebrella or of a polyzoon or a brachiopod, is to watch the movements of their beautiful delicate gills, which are thrust in or out, waved back and forth, slowly or suddenly, according to the degree of tran- quillity or disquietude of their possessors. 638 ZOOLOGY. In the mollusks, especially the snails and cuttle-fish, the gills are in close relations with the heart, so that in the cut- tle-fish the auricles are called ‘‘ branchial hearts.’’ The gills of crustaceans (Fig. 259) are attached either to the thoracic legs or are modified abdominal feet, being broad, thin, leaf-like processes, into which the blood is forced by the contractions of the tubular heart. Respiration in the insects goes on all over the interior of the body, the tracheal tubes distributing the air so that the blood becomes oxyge- nated in every part of the body, including the ends of all the appendages. The gills of aquatic insects are in all cases fila- mentous or leaf-like expansions of the skin permeated by traches (Fig. 326) ; they are, therefore, not strictly homolo- gous with the gills of crustaceans or of worms. The gills of fishes are so situated as to be constantly bathed by fresh water ; in the amphibians and lung-fishes, lungs, which are outgrowths of the enteric canal, replace the air-sacs of the fishes, the air being now swallowed by the mouth and gaining access by a special duct, the larynx, to highly specialized organs of respiration, the lungs, which are situated in the thoracic cavity near the heart. The Nervous System.—We have seen that animals of com- paratively complicated structure perform their work in the animal economy without any nervous system whatever. It has been only recently discovered that in a few jelly-fish is there, for the first time in the animal series, a consecutive nervous system, with definite nerve-centres or ganglia. In most Acalephs none has been found, so that the majority of Celenterates perform their complicated movements, swimming about for food, taking it in, digesting it, and re- producing their kind, without the aid of what seems, when we study vertebrates alone, as the most important and fundamental system of organs in the body. The Protozoa, sponges, and most Celenterates depend, for the power of motion, on the contractility of the protoplasm of the body, whether or not separated into muscular tissue. In the Hydra for the first time appear the traces of a ner- vous tissue in the so-called nervo-muscular cells, one por- COMPARATIVE ANATOMY OF ORGANS. 639 tion of a cell being muscular, the other nervous in its func- tions. A more definite nervous organization is the disconnected bodies and rod-like nerve-cells, and other nervous bodies found near the eye-spots, and the nerve-cells and fibres at the base of the sea-anemone ; but, as has been stated, a gen- uine nervous system for the first time appears in certain naked-eyed jelly-fishes, in which it is circular, sharing the radiated disposition of parts in these animals. The Echin- oderms have a well-developed nervous system, consisting of a ring (without, however, definite ganglia, though masses of ganglionic cells are situated in the larger nerves), surround- ing the esophagus, and sending a nerve into each arm ; or in the Holothurians situated under the longitudinal muscles radiating from that muscle closing the mouth. In all other invertebrate animals, from the worms and mollugca to the crustaceans and insects, the nervous system is fundamentally built upon the same plan. There is a pair of ganglia above the cesophagus called the ‘‘ brain ;’’ on the under side is usually asecond pair ; the four, with the nerves or commissures connecting them, forming aring. This ar- rangement of ganglia, often called the ‘‘ esophageal ring,”’ constitutes, with the slender nerve-threads leading away from them, the nervous system of the lower worms, in many of which, however, as also in the Polyzoa and Brachiopoda, the subeesophageal ganglia are wanting. Now to the cesophageal ring with its two pairs of ganglia add a third pair of visceral ganglia, and we have the nervous system of the clam and many mollusks. In the higher ringed worms, the Annulata, and in the Crustacea and Insects, a chain of ganglia, or brains, which is ventral, lying on the floor of the coelum or body-cavity, completes the highest form of nerve-centre found in the invertebrate animals, unless we except the mass of ganglia, partly enclosed in an imperfect cartilaginous capsule of the Cephalopods, which hints at the brain and skull of Vertebrates. The nervous cord of the Appendicularia, an Ascidian, is constructed on the same plan as in the Annulata, but the mode of origin and apparently dorsal position of the nervous system of the 640 ZOOLOGY. tailed larval Ascidian presents features which apparently anticipate the state of things existing among the lower ver- tebrates, such as the lancelet. In the last-named animul the nervous cord has a dorsal position—t.e., rests above the alimentary canal; but as yet no brain appears, only a very slight enlargement of the an- terior end of the nervous cord from which a few nervous threads are distributed to minute sense-organs in the head. In all the craniate Vertebrates, from the lamprey upward, the brain is a series of close-set ganglia, having a definite site, enclosed by a skull or brain-box, and with definite re- lations to the sense-organs. Attention has already been given in a general way, in the foregoing pages, to the increas- ing complexity of the brain, especially to the relative size and markings of the cerebral hemispheres and cerebellum, as we rise from the fish to man. Organs of Sense.—While all animals, perhaps without exception, unless it be the root-barnacles, and a few other parasitic forms, have the sense of touch, which, in the lower Protozoa is so slight as to be compared with the contractility common to all living protoplasmic matter, whether existing in cellular tissue or one-celled, independent animals ; not all of the lower animals have, however, definite sense-organs. The Eye.—The most important of these are undoubtedly eyes, as they are the most commonly met with. The sim- plest form of eyes are perhaps those of the sea-anemone, in which there are, besides pigment cells forming a colored mass, refractive bodies which may break up the rays of light impinging on the pigment spot, so that these creatures may be able to distinguish light from darkness. The next step in advance is where a pigment mass covers a series of refract- ive cells called ‘‘ crystalline rods’’ or ‘‘ crystalline cones,” which are situated at the end of a nerve proceeding from the ‘‘ brain.”’ Such simple eyes as these, often called ‘‘ eye- spots,’ may be observed in the flat worms, and they form the temporary eyes of many larval worms, Echinoderms and mollusks. In some nemertean worms, such as certain species of Polia and Nemertes, true eyes appear, but in the ringed worm, NMeophanta celox, Greef describes a remarka- COMPARATIVE ANATOMY OF ORGANS. 641 bly perfect eye, consisting of a projecting spherical lens covered by the skin, behind which is a vitreous body, a layer of pigment separating a layer of rods from the exter- nal part of the retina, outside of which is the expansion of the optic nerve. Eyes are also situated on the end of the body in some worms, and in a worm called Polyophthalmus each segment of the body bears a pair of eyes. The eyes of mollusks are, as a rule, highly organized, un- tilin the cuttle-fish the eye becomes nearly as highly de- veloped as in fishes, but still the eye of the cuttle-fish is not homologous with that of Vertebrates, since in the former the crystalline rods are turned toward the opening of the eye, while in Vertebrates they are turned away from the opening of the eye, so that, as Huxley as well as Gegen- baur show, the resemblance between the eye of the Ce- phalopods and of the Vertebrates is a superficial one. While, as we have seen, the eyes of the worms and the mollusks are situated arbitrarily, by no means invariably placed in the head, in the Crustaceans the eyes assume in general a definite position in the head, except in a schizo- pod crustacean (Huphausia), where there are eye-like organs on the thorax and abdomen. In insects there are both sim- ple and compound eyes occupying definitely the upper and front part of the head. The eyes of the lancelet are not homologous with those of the higher Vertebrates, being only minute pigment spots comparable with those of the worms. In the skulled Ver- tebrates the eyes are of a definite number, and in all the types occupy a definite position in the head. The Bar.—The simplest kind of auditory organ is to be found in jelly-fishes, where an organ of hearing first occurs. In these animals, situated on the edge of the disk, are minute vesicles containing one or more concretionary bodies or crystals. Reasoning by exclusion, these are supposed to rep- resent the ear-vesicles or otocysts of worms and mollusks ; and the concretions or crystals, the otoliths of the same kind of animals. The otocysts or simple ears of worms and mollusks are minute and usually difficult to find, especially the auditory 642 ZOOLOGY. nerve leading from them to the nerve-centres. In the clam it is to be looked for in the so-called foot. In the snails the auditory vesicles are placed in the head close to the brain, as also in cuttle-fish. The ears of Crustacea are sacs formed by inpushings of the integument filled with fluid, into which hairs project, and which contain grains of sand which have worked in from the outside, or concretions of lime. These are situated in the shrimps and crabs at the base of the inner antennae, but in certain other lower Crusta- cea, as in Mysis, they are placed at the base of the lobes of the tail. In the insects the ear is a sac covered by a tympanum, with a ganglionic cell within, leading by a slender nerve-fibre to a nerve-centre, and in these animals the distribution of ears isvery arbitrary. In the locust they are situated at the base of the abdomen (Fig. 279) ; in the green grasshoppers or katydids and the crickets in the fore tibiz ; and it is probable that in the butterflies the antennz are organs of hearing. | The vertebrate ears are two in number and occupy a dis- tinct, permanent position in the skull, however much modi- fied the middle and outer ear become. - Organs of Smell.—The sense of smell is obscurely indi- cated by special organs in the invertebrate animals, nasal organs as such being characteristic of the skulled Vertebrates. Whether organs of smell exist in any worms or not is un- known ; there are certain pits in some worms which may possibly be adapted for detecting odors. In some insects at least the organs of smell are without doubt well developed ; the antenne of the burying beetles are large and knob-like, and evidently adapted for the detection of carrion. It is possible that certain organs situated at the base of the wings of the flies and on the taudal appendages of the cockroach and certain flies (Fig. 290) are of use in detecting odors. ® CHAPTER: X, ‘DEVELOPMENT AND METAMORPHOSES OF ANTI. MALS. Embryology.—The development of the individual is often an epitome of the classification of the order or class to which it belongs, as well as of the development or appearance in geological history of the different members of the order or class to which the individual belongs. The changes under- gone by the animal within the egg are often so sudden and marked that the separate chapters of its history as an em- bryo can be read side by side with the history of the succes- sion of the different genera and families of its type in past ages. Moreover, it is now generally supposed by naturalists that these critical periods in the development of the individ- ual have a constant relation to external causes which have acted on the ancestors of the animal, and hence that these changes are the result of influences and changes in the sur- roundings of the forms which have preceded. So much in- terest, therefore, attuches to the subject of the early develop- ment of animals, that much prominence has in the foregoing ‘pages been given to the matter. We may now briefly review the more striking phenomena of development in the invertebrate animals, and close with a summary of the mode of development of Vertebrates. The eggs of all animals consist of three portions, the egg proper, consisting of a mass of protoplasm enveloped by the yolk or food-stuff, the nucleus or germinative vesicle, and the nucleolus or germinative spot. Before the egg is ready for fertilization it undergoes a special process of maturation, involving the following series 644 ZOOLOGY. of events: 1. Transportation of the germinal vesicle to the surface of the egg; 2. An absorption of the membrane of the nucleus or germinative vesicle and a change in the ger- minative spot; 3. The portion of the nucleus surviving as- sumes a spindle-shape, this portion being largely formed from the nucleolus ; 4. One end of the spindle enters into a protoplasmic prominence at the surface of the egg; 5. The spindle divides into two halves, one remaining in the egg, the other in the prominence, the latter separating from the egg and forming the polar cell ; 6. A second polar cell forms in the same manner as the first, part of the spindle still re- maining in the egg; 7. The part of the spindle remaining in the egg, after the formation of the second polar cell, is converted into a nucleus, the female pronucleus, and finally, just before fertilization, the female pronucleus takes its po- sition at the centre of the egg. © OF Sw > Fig. 539.—Development of the sperm-cells of a blind worm (Epicrium glutinosum), a, testis-cell; 0, the same, more numerous; c, d, €, becoming more numerous and finally forming spermatozoa (/). Highly Imagnified.—After Minot. After this, the first step in the development of many-celled animals is the fusion of the protoplasm of the female pronu- cleus with that of the sperm-cell ; for this end the latter is exceedingly minute and provided with a vibratile cilinm or ‘*tail,’? so that it may force its way in toward the centre of the egg. These sperm-cells are developed in the testis of the male. On close examination with very high powers of the microscope, certain cells, called ‘‘ mother cells,’’? may be found developed in fine tubules forming the gland ; these are known to possess several nuclei, which are destined to be- come spermatozoa (Fig. 539, a and 0) ; these multiply until they become very numerous, elongated, and packed side by DEVELOPMENT OF ANIMALS. 645 side in bundles (¢) ; from each one acilium or “tail” grows out, when they are set free from the mother-cell. In this tailed form they are very active, and effect the fertilization of the egg of an animal of the same species. This is due to contact of one spermatozoon with the female pronucleus situ- ated in the egg. Immediately after the spermatozoon has penetrated into the egg, its ‘‘head’’ is converted into a nucleus, called the male pronucleus ; after this, radiating strie make their appearance around its surface ; then the male pronucleus travels toward the female pronucleus, and finally the male and female pronuclei fuse together and form the first ‘‘ segmentation nucleus.”’ This nucleus subdivides, and the result is a mass of cells resembling a mulberry, and hence called the morula. The outer circle of the cells of the morula may hereafter form what is called the blastoderm ; after a while it pushes in at one point, and the portion thus forced is called: the inner germ-layer (endoderm) and the outer is called the ectoderm or outer germ-layer, and in this condition the germ is called a gastrula. Subsequenily, a third layer develops from the endoderm, which is called the mesoderm, and after this the different tissues become developed. All animals, from sponges to man, become first two- and afterward three-layered sacs ; so that all animals above the Protozoa not only, as a rule, originate from eggs, but may be said to travel, up to a certain point, the same developmental path. From this point the members of different types of life diverge. How different are the modes of development of animals has been set forth in the different life-histories related in the foregoing pages of this book.* But the laws of growth are as stable and uniform—certain causes pro- ducing certain results—as the laws of the motions of the heavenly bodies. When the workings of these laws of development are in- terfered with by sudden accidents, by too scanty nourish- ment, and by the transmission of the effects of such acci- * For a fuller, more consecutive, though still fragmentary account, the reader is referred to the author’s ‘‘ Outlines of Comparative Em- bryology, or Life Histories of Animals, including Man.” 646 ZOOLOGY. dents or abnormal products from parents who have been affected by them, the results are usually abnormal, more or less distorted forms, with greater or less defects ; and here again have been observed laws governing the production of abnormalities, the study of these being called teratology. We may study the mode of development of the domestic fowl or hen as the best known example to illustrate the changes undergone by an embryo vertebrate, for this pur- pose condensing the statements of Foster and Balfour in their ‘‘ Elements of Embryology.” Fig. 540.—Blastodermic disk and germ of a rabbit about one day old, seen from the back. a, edge of the head-end of the amnion, b, fore-brain; c¢, lateral expansion of the same, or primitive eye-vesicle; d, middle, e, hind brain. There are eight protover- tebree, between which is situated the spinal cord. Enlarged ten times.—After Bischoff. First Day.—After fertilization of the egg, segmentation of the egg occurs, but instead of being total, forming a morula or mulberry mass, it is, as in all birds and in the majority of fishes and reptiles (except the lancelet and lamprey eel), par- tial, or confined to the periphery of the yolk, resulting in the formation of a blastoderm, the oval more apparent por- tion being called the ‘‘ blastodermic disk,’’ which is the be- ginning of the embryo. In six or eight hours after fertili- zation the three germ-layers appear. From the outer germ- DEVELOPMENT OF ANIMALS. 647 layer are destined to arise the skin and wall of the body with the nervous system; from the second (mesoderm, in the embryo called the mesoblast) are formed the heart and the vascular system, as well as the stomach and intestines. The middle layer now thickens, causing the mark known as the ‘‘ primitive streak,’’ along the middle of which runs the ‘‘ primitive groove.’’ The notochord now appears and the muscle-plates (called protovertebre, Fig. 540). The am- nion arises as a membrane, splitting off from the outer germ- layer of the embryo, and finally forms a cavity which is filled with a fluid. About this time the allantois arises as an offshoot of the alimentary canal, budding out at the hinder end of the embryo, and finally curving over the em- bryo, serving as a foetal respiratory membrane. Second Day.—The three portions or vesicles of the brain now appear (Fig. 540), as well as the alimentary tract and heart, both arising in the head-fold or enlargement (Fig. 540, a to c), and soon the blood-vessels arise as channels in which blood-corpuscles appear, originating as amoba-like cells separating from the cellular mass of the mesoderm.’ Dur- ing the second day also the eyes and ears begin their devel- opment, being at first simply folds or inpushings of the outer germ-layer. Third Day.—This is one of the most eventful days, as im- portant steps in the elaboration of the different organs are taken ; the different parts of the brain, of the alimentary tract and its appendages being sketched out, and the rudi- ments of the lungs, the liver, pancreas, nose, and different parts of the eye and ear appearing. On the fourth day the wings and legs grow out, appearing first as flattened buds. The notochord, which is indicated by the second day, by the sixth begins to diminish in size, disappearing by the time the chick is hatched, while by the twelfth day the deposition of bcne in the bodies of the vertebree commences. Between the eightieth and one hundredth hour the internal differences in the sexes appear, the testes beginning to arise on the sixth day. Fifth Day.—The limbs have by this time developed so as to show the knee- and elbow-joints, as well as the cartilages 648 ZOOLOGY. Fig. 541.—Five schematic figures showing the development of the foetal egg-mem- branes, where in all except the last the embryo is represented as if seen in longitudinal section. 1. Diagram of egg with zona pellucida, blastoderm (a, ¢), germinal disk, and) embryo, 2. Egg with the first traces of the yolk-sac (@) and amnion (Xs, ss, and am. 3. Egg with the amnion uniting and forming a sac; the allantois (a/) budding out. 4, Egg with the villi of the serous membrane (sz); the allantois larger ; embryo with mouth and anal opening. 5. Egg in which the vascular layer of the allantois lies close to the serous layer and has grown into the villi of the same, constituting the true chorion (ch). Yolk-sac much smaller, about to be drawn into the cavity of the amnion, DEVELOPMENT OF ANIMALS. 649 which precede the formation of the bones of the digits and limbs. The primitive skull also arises from the mesoderm. Until the sixth day it would be impossible to say whether the embryo was that of a bird, reptile, or mammal, but now the characters peculiar to birds appear. The wings and legs manifest their bird-like characters, the crop and intestinal coca are indicated, ‘‘ the stomach takes the form of a giz- zard, and the nose begins to develop into a beak, while the incipient bones of the skull arrange themselves after the avian type. . . . From the eleventh day onward, the embryo successively puts on characters which are not only avian, but even distinctive of the genus, species, and variety ”’ (Balfour). By the ninth or tenth day the feathers originate in sacs in the skin, while the nails and scales begin to ap- pear on the thirteenth day, and at this time the various muscles of the body can be distinguished. Development is thus seen to be from the general to the special, from the simple to the complex ; the trunk is first indicated ; while the peripheral parts—i.¢., the extremities, the digits, the skin, feathers or scales, or hair, whatever be the type of Vertebrate—are the last to be elaborated ; in other words, the characters of the branch, class, and order are the first to be evolved, those of the family, genus, and species the last. The development of the rabbit, guinea-pig, or any mam- mal, including even man, follows much the same order as in the chick, there being, however, a well-marked morula ; the differences are due to the fact that the embryo mammal d, yolk-skin ; d’, villi of the yolk-skin ; sh, serous membrane; s2, villi of the serous membrane ; ch, chorion (vascular layer of the allantois); chz, true villi of the chorion (arising from the projections of the chorion and the sac of the serous membrane); am, amnion ; ks, head-fold of the amnion ; ss, tail-fold of the amnion ; ah, cavity of the amnion; as, sheath of the amnion for the navel-string ; a, the first beginning of the embryo arising from a thickening of the outer layer of the blastoderm a/; m, thickening forming the germ in the middle layer of the blastoderm (m/), which at first only reached as far as the germinal disk, and afterward forms the vascular layer of the yolk-sac (df) which connects with the intestino-muscular layer (darmfaserblatt); st, sinus terminalis ; dd, infeotne-slendaiar layer (darmdrusenblatt) arising out of a part of i, the inner layer of the blastoderm (afterward the epithelium of the yolk- sac); kh, cavity of the blastoderm, which afterward becomes (d@s) the cavity of the yolk-sac ; dg, passage way of the yolk; ai, allantois; e, embryo; 7, original space between the amnion and chorion, filled with albuminons fluid ; o/, anterior body-wall in the region of the heart ; 2A, cavity of the heart without the heart itself. In Figs. + and 3, the amnion is, for the sake of clearness, represented as situated too far away from the embryo; so also the cavity of the heart 1s drawn too small and the embryo too Jarge, since, except in Fig. 5, they are only drawn diagrammatically.—From Kol- liker’s ‘‘ Entwickelungsgeschichte des Menschen und der hdheren Thiere.” 650 ZOOLOGY. develops in a specialized portion of the oviducts, the uterus or womb, and that the growing germ until birth is supplied not with yolk as food, but by the nourishment in the ma- ternal blood. In fact, while the eggs of reptiles and birds are enormous, it was not known with certainty until 1827 that mammals developed from eggs. The eggs of these an- imals are very minute, owing in part to the minute amount of yolk they contain ; that of man being less than a quarter of a millimetre (74> inch) in diameter. The mammalian embryo, nourished as it is through the maternal circulation, needs additional temporary organs ; these are the chorion (Fig. 541, ch), formed from the vitelline membrane (present in birds as well as mammals), which sends off villi or processes extending into the walls of the womb. Besides this, in the higher or placental mammals, the pla- centa or after-birth is formed, which serves as an organ of respiration as well as to supply the embryo or fetus with nourishment, and to carry off its effete products by means of the maternal circulation. It is comparatively late in embryonic life that the mam- malian features appear; in the dog it is twenty-five days before it can be told whether the embryo is a mammal or not. All mammals may be said to pass through a morula and gastrula stage. In the next stage when the nervous chord and notochord arise, the mammalian germ is on the same footing with an Ascidian larva. In a succeeding stage, when the protovertebre appear, an Amphioxus stage is reached ; when a brain is formed, the level of the fishes is reached ; after the limbs bud out the young mammals may be said to assume the condition common to the embryos of all Amphibian and higher Vertebrates. When the allantois begins to appear the amphibian feature (the want of an allantois) is dropped. When the placenta has developed the avian characters are surpassed and the mammalian feat- ures assumed. Thus the development of the individual mammal is an epitome of that of the branch or type to which it belongs, and the successive steps in the degree of specialization of the individual mammal are also paralleled METAMORPHOSES OF ANIMALS. » G51 by the geological succession of the representatives of the different classes, as without much doubt lancelets (or at least acraniate, boneless forms) were the first Vertebrates to ap- pear, and we know that fishes appeared before Amphibians, that their type culminated before the reptiles held full sway in Mesozoic times, and that birds, after them mam- mals, and, last of all, man appeared, who crowns the series of vertebrate forms. Metamorphosis.—While many animals are hatched like the chick with the form of the parent, others pass through a series of changes of form called metamorphoses ; these changes of form adapt the animal to changes in its sur- roundings, involving alterations in its mode of life—slight if the change of body-form is slight, thorough-going and radi- cal if its body becomes profoundly modified. As an exam. ple of.a complete metamorphosis may be cited the life-his- tories of the jelly-fishes, the star-fish, sea-urchins, sea-cu- cumbers, the marine-worms, the mollusks, the crustaceans, insects, and the salamanders and toads and frogs, already de- scribed in the foregoing pages. If thestudent will read and compare these different accounts, and then consider the striking differences between the complicated histories of cer- tain species, compared with the direct mode of growth of other species of the same order or family, or even of the same genus, the inquiry will arise, What is the purpose or use of such a series of changes? If he look carefully into the embryological changes of those species which are born - or hatched with the form of the adult, he will see that their embryological history is, in point of fact, a condensed sum- mary of the changes undergone after hatching by their co- species, which, to gain the same adult form, have been sub- jected by nature to a series of complicated, and, at first sight, superfluous changes of form and environment. - Most shrimps and crabs undergo a complicated metamor- phosis ; in the different changes of forms they lead different lives, and are subjected to different surroundings, the larve, for the most part, being free-swimming and living near the surface of the water, while the parents are stationary. The barnacle, when very young, swims near the surface of the . 652 ZOOLOGY. sea, afterward, as a pupa, becoming fixed to a rock; the young oyster-spat swims freely about, finally becoming fixed to the bottom. ‘This change of life and of form undeubted- ly tends to prevent the extinction of the species, since, if at a given moment the parents were swept out of existence, the young living in a different station would continue to represent the species. This law is seen to hold good among insects, where many’species are represented in the winter- time by the egg alone, others by the caterpillars, others by the chrysalis, while still others hybernate as imagines. Again, in the marine species, the free-swimming young are borne about by ocean and tidal currents, and in this way what in adult life are the most sedentary forms become widely dis- tributed from coast to coast and sea to sea. On the other hand, the larval forms of fixed marine animals serve as food for fishes, especially young fishes and numerous inverte- brates, while their stationary parents afford subsistence for still other forms of life ; thus were it not for the metamor- phoses of animals, many species would become extinct sooner than they do, while the great overplus of larval forms gives to many other species of animals a hold on ex-- istence. Metamorphosis among the invertebrate animals, espe- cially, is perhaps the rule and not the exception. Where ani- mals develop directly, as in certain insects, crustaceans, cer- tain salamanders, toads and frogs, this is due to some change in the environment; in the case of Amphibians, perhaps the want of water, or some other cause, there always being an adaptation in the case of the direct mode of de- velopment to the surroundings of the animal and the require- ments of its existence. Parthenogenesis, and Alternation of Generations.— Having traced the normal process of development of ani- mals, we may turn to certain unusual or abnormal modes of production. Asan example of what is known as ‘‘ alternation of generations,’’ may be cited the mode of development of the jelly-fish, such as the naked-eyed meduse (Melicertum and Campanularia), which at one time of life develop by budding, at another by eggs ; of the trematode worms, the adult forms ALTERNATION OF GHNERATIONS. 653 of which lay eggs, while the redia or proscolez of the same worm produces cercarie by internal budding. Here also may be cited the cases of strobilation of the Aurelia, the tape-worm, the Nais, Syllis, and Autolycus, among Anne- lids. Thusamong Celenterates and worms, as well as some Crustacea, a large number of individuals are produced, not from eggs, but by budding. Similar occurrences take place among insects, as the Aphis or plant-louse, in which a virgin Aphis may bring forth in one season nine or ten generations of Aphides, so that one Aphis may become the parent of millions of young. These young directly develop from eggs or buds which are never fertilized, hence the term parthenogenesis, or virgin-reproduction, sometimes called agamogenesis (or birth without marriage). The bark-lice as well as the Aphides develop in this manner during the warm wea- ther ; but at the approach of cold both male and female Aphides and Coccide appear, the females laying fertilized eggs, the first spring brood thus being produced in the normal, usual manner. Still more like the production of young in the redia of the Trematode worms is the case of the larva of a small gall- gnat (Miastor), which during the colder part of the year from autumn to spring produces a series of successive generations of larve like itself, until in June the last brood develops into sexually mature flies, which lay fertilized eggs. While the larval Miaster produces young like itself, the pupa of another fly, Chironomus, also lays unfertilized eggs. A number of moths, including the silk-worm moth, are known to lay unfertilized eggs which produce caterpillars. Among the Hymenoptera, the currant saw-fly, certain gall- flies, several species of ants, wasps (Polistes), and the honey- bee, are known to produce fertile young from unfertilized eggs ; in the case of the ants and bees, the workers lay eggs which result in the production of males, while the fertilized eggs laid by the female ant or queen bee produce females or workers. Taking all these cases together, parthenogenesis is seen to be due to budding, or cell-division, or multiplication. Now, 654 ZOOLOGY. it will be remembered that the egg develops into an animal by cell-division, so that fundamentally parthenogenesis is due to cell-division, the fundamental mode of growth; hence, normal growth and parthenogenesis are but extremes of a single series. In this connection, it will be remembered that all the Protozoa reproduce by simple cell-division, that among them the sexes are not differentiated, that they do not reproduce by fertilized eggs ; hence, so to speak, among Protozoa parthenogenesis is the normal mode of re- production ; and when it exists in higher animals it may . possibly be a survival of the usual protozoan means of stocking the world with unicellular organisms, with which _ we know the waters teem. And this leads us to the teleol- ogy or explanation of the cause why parthenogenesis has sur- vived here and-there in the world of lower organizations ; it is plainly, when we look at the millions of Aphides, of bark-lice, the hundreds of thousands inmates of ant-hills and bee-hives, for the purpose of bringing immediately into existence great numbers of individuals, thus ensuring - the success in life of certain species exposed to great vicis- situdes in the struggle for existence. That this unusual mode of reproduction is all-important for the maintenance of the existence of most of the parasitic worms, is abundantly proved when we consider the strange events which make up the sum total of a fluke or tape-worm’s biography. With- out this faculty of the comparatively sudden production of ‘large numbers of young by other than the slow, limited process of ovulation, the species would be stricken off the roll of animal life. Dimorphism and Polymorphism.—Involving the produc- tion of young among many-celled animals (Metazoa) by what is fundamentally a budding process, we have two sorts of individuals. When the organism is high or specialized enough to lay eggs which must be fertilized, we have a differentiation of the animal into two sexes, male and fe- ‘male. Reproduction by budding involves the differentia- tion of the animal form into three kinds of individuals— ‘4.€., males, feniales, and asexual individuals, among insects often called workers or neuters. These have usually, as in DIMORPHISM. 655 ants and bees, a distinct form so as to be readily recog- nized at first sight. Among the Celenterates and worms the forms reproducing by parthenogenesis are usually larval or immature, as if they were prematurely hurried into ex- istence, and their reproductive organs had been elaborated in advance of other systems of organs, for the hasty, sud- den production, so to speak, of large numbers of individu- als like themselves. In insects, as we have stated elsewhere,* dimorphism is intimately connected with agamic reproduction. Thus the summer wingless, asexual Aphis and the perfect winged autumnal Aphis may be called dimorphic forms. The per- fect female may assume two forms, so much so as to be mis- taken for two distinct species. ‘Thus, an oak gall-fly (Cy- nips guercus-spongifica) occurs in male and female broods in the spring, while the autumnal brood of females were de- scribed originally as a separate species under the name C. actewlata. Walsh considered the two sets of females as di- morphic forms, and that Cynips aciculata lays eggs which produce C. quercus spongifica. Among butterflies, dimor- phism occurs. Papilio memnon has two kinds of females, one being tailless, like the tailless male, while Papilio Pam- mon is polymorphic, there being three kinds of females be- sides the male. There are also four forms of Papilio Ajax, the three others being originally described as distinct species under the name of P. Marcellus, P. Telamonides, and P. Walshit. Our Papilio glaucus is now known to be a dark, dimorphic, climatic form of the common Papilio Turnus. There are dimorphic males among certain beetles, as in the Golofa hastata Dejean, of Mexico, in which one set of males are large and have a very large erect horn on the prothorax, and in the other the body is much smaller, with a very short conical horn. Temperature is also associated with the production of polymorphic forms in the temperate regions of the earth, as seen in certain butterflies, southern forms being varieties * Guide to the Study of Insects, sixth edition, p. 52. 656 ZOOLOG ¥Y. of northern forms, and alpine “‘ species ’’ proving to be va- rieties or seasonal forms of lowland species. For example, Weismann states that the European butterflies, Lycaon amyn- tas and polysperchon, are respectively summer and spring broods. Anthocharis Simplonica is an alpine winter form of Anthocharis Belia, as is Pieris bryonie of Pieris napi. In this country, as Edwards has shown, two of the polymorphic forms of Papilio Ajaz—i.e., Walshii and Telamonides—come from winter chrysalids, and P. marcellus from a second brood of summer chrysalids. It thus appears that poly- morphism is intimately connected with the origin of species. Perhaps the most remarkable case of polymorphism is to be seen in the white ants (Zermites), where in one genus there are two sorts of workers, two sorts of soldiers, and two kinds of males and females, making eight sorts of individuals ; in the other genera there are six. Among true ants there are, besides the ordinary males, females, and workers, large- headed workers. In the honey-ant (Myrmecocystus Mezi- canus), besides the usual workers, there are those with enormous abdomens filled with honey. Other insects, es- pecially certain grasshoppers, are dimorphic. Certain par- asitic Nematode worms are dimorphic; and among the Coelenterates, especially the Hydroids, there is a strong ten- dency to polymorphism. Individuality.—Perfect individuality among animals is the rule, each individual being capable of maintaining an independent existence ; but we have seen that there are many of the lower animals in which it is difficult to determine whether the different members of a colony are really in- dividuals or simply individualized organs. The student, in referring back to the account of the Por- tuguese man-of-war, will find it difficult to say whether the four kinds of members of the floating colony are organs or individuals, and he will probably agree with the view that it is best to provisionally call them zooids or individualized organs ; for the feeders, the reproductive zooids, the digest- ive zooids, and the swimming float, or the swimming bells of the other Siphonophores, are highly specialized organs, and only differ from true individuals in lacking the power INDIVIDUALITY AND HYBRIDITY. 657 of free motion and of maintaining an independent existence. So with many other Ccelenterates and with the tapeworm, whose proglottides or segments are finally capable of sepa- rate existence. Among the higher invertebrates, even the different members of a colony of white or true ants lack a certain amount of individuality, the workers performing labors upon which the maintenance of the very existence of the colony depends, so that there are different grades of in- dividuality, from examples like the Hydractinia and the Siphonophores up to those insects which live socially ; and we see that the most perfect individuality exists in those animals which can most efficiently provide for their own sustenance and for the continuance of their species. Hybridity.—It is rare that two species, even of the same genus, can produce offspring ; when such cases occur. the result is called a hybrid. For example, the mule is a hybrid, being bred from a female horse and an ass; but the mule is not fertile, and hybrids are very rarely fertile. The In- dian dog and coyote are said by Coues to interbreed, and on the Upper Missouri we have seen dogs which had every appearance of being such hybrids. Dogs also cross with the fox (Darwin). The American bison is known to breed with the domestic cattle, and it seems to be a well-established fact that the hybrids are fertile. Fish readily hybridize. Darwin states that he knows of no thoroughly well-au- thenticated cases of perfectly fertile hybrid animals, though he adds, ‘‘I have reason to believe that the hybrids from Cervulus vaginalis and Reevesii and from Phasianus col- chicus with P. torquatus are perfectly fertile.’’ The hare and rabbit are supposed to have fertile offspring ; the hy- brids of the common and Chinese geese (Anser cygnoides) are fertile. The crossed offspring from the Indian humped and common cattle interbreed. Caton has hybridized the Virginia deer with the Ceylon deer and the Acapulco deer ; “the hybrids seem perfectly healthy and prolific.” Among insects over 100 cases of hybridity have occurred. Hybrids between the brown and polar bear, the leopard and jaguar, Equus onager and LE. hemippus, EB. burchelli with the com- mon horse, and with the common ass and #. hemionus ; have been raised. CHAPTER, 2), THE GEOGRAPHICAL DISTRIBUTION OF ANI- MALS. THE assemblage of animal life peopling any one locality or area is called its fauna, as the plants of a place consti- tute its flora. Where the physical geography—i.e., the con- tour of the surface, the plains, valleys, and hills—is of iden- tical character and the climate the same, the fauna is much the same, but when these characteristics of soil and climate change, as in passing from lowlands to highlands, or from south to north, the assemblage of animals will be found to change in a corresponding ratio. And as there are no definite limits to any large area of the earth’s surface, the physical features of one area merging insensibly, as a rule, into adjoining districts, so adjoining faunz merge into one another, and a certain proportion of the species may range through two or more faunal areas. There are in nature causes tending to restrain animals within their faunal limits, and others tending to diffuse them, or to cause them to migrate from their specific cen- tres or centres of creation—namely, the point where the in- dividuals of a species are most abundant, and where, ac- cordingly, they are supposed to have originated. Barriers to the Spread of Animals from their Specific Centres.—Among the most important are the oceans and their basins. The animals of the opposite sides of the Pa- cific Ocean are entirely unlike, no species being common to the two sides; while, of the immense numbers of animals peopling the coast of Brazil and the opposite coast of Af- riva, only two or three are known to be identical. Differ- ence in climate is also a great barrier, the animals of the GHOGRAPHICAL DISTRIBUTION. 659 ‘tropics, as a whole, being unlike those of the temperate zones ; while arctic and antarctic animals have features in common. Mountains serve as most important barriers, re- straining animals within their limits ; thus the basins be- tween or surrounded by continuous ranges of mountains harbor faune differing from those on the opposite sides of the mountains. For example, the majority of the animals of the Great Basin between the Rocky Mountains and the Sierra Nevada differ from those of the Pacific slope or the prairie lands lying east of the Rocky Mountains, as the meteorological and geological features are different. The Cordilleras of South America form a barrier to the diffusion westward of Brazilian animals. Still this fact is not to be taken too literally, as the mountains are divided by valleys and rivers, which afford means of communication and an interchange of specific forms; thus certain species of ani- mals of the Rocky Mountain plateau occur on each side of the range, as do those in the Alleghany district of the At- lantic coast. In the West Indian and especially the Hawa- iian Islands, where the species of land snails are very numer- ous, certain forms are restricted to the deep narrow valleys, being confined to very restricted areas. So also the cold Alpine summits of the White Mountains of New Hamp- shire, of the Rocky Mountains, of the Alps and Scandina- vian mountains harbor a few species either peculiar to those extremely limited tracts or found northward in the Arctic regions. Deserts may act much as inland seas to separate the ani- mals of the adjoining more fertile tracts, and they afford dwelling-places for animals which are incapable of living elsewhere. Desert faune have a general facies the world over, though the original elements out of which the faune have been made up may radically differ. The distribution of plants also has much to do with that of those animals which are dependent on them for food ; as a rule, the distribution of both plants and animals de- pends on the same physical causes. Large rivers sometimes act as barriers, but more often, perhaps, aid in the diffusion of the smaller forms, such as 660 ZOOLOGY. insects, mollusks, and crustaceans. Different systems of riv- ers have distinct sets of fluviatile animals ; for example, the fishes of the Ohio and Upper Mississippi and its tributaries differ from those of the Hudson River and the New England rivers, and the latter from those draining the Southern At- lantic States. The fresh-water mussels, so abundant and characteristic of the waters of the Mississippi and its tribu- taries are confined to the region lying west of the Allegha- nies and east of the Great Plains. The fishes and mollusks of the rivers of the Pacific slope differ from those of the scanty waters of the Great Basin. Means of Dispersal._The most general are the alterna- tions of winter and summer, leading birds and mammals to migrate great distances to and from their breeding-places. Ocean-currents are most important factors in the dispersal of many marine and some land animals. By means of such great currents as the Gulf Stream, tropical animals are borne to temperate and even subarctic regions ; and, on the other hand, arctic and temperate animals are borne southward, and thus marine faune interdigitate and merge insensibly into one another. By this agency also new coral islands are peopled from the mainland, and peninsulas are colo- nized from adjoining continents or islands ; for example, the southern extremity of Florida has been visited by trop- ical plants and animals borne by currents and winds from the West Indies, thus lending a purely tropical aspect to the southern part, a semi-tropical fauna occupying the mid- dle and northern part of the State. Trade winds play an important part in scattering insects, and especially the minute forms of life; whirlwinds and tornadoes catch up larger forms and transport them from stream to stream, pond to pond, and from lowlands to highlands, and even to Alpine summits, where may some- times be found, under loose stones, multitudes of insects which have been borne up from below by strong gales or ascending currents of air. The direction of the migrations of the Rocky Mountain locust seems to be mainly dependent on the direction of pre- vailing winds. Insects as well as birds are blown off-shore GHOGRAPHICAL DISTRIBUTION. 661 sometimes for hundreds of miles, and in this apparently haphazard way islands are, in part at least, supplied with their quota of animal life. Great rivers, like the Missouri, Mississippi, and the Ama- zons, afford means of transportation from one part of a con- tinent to another, from the interior to the seaboard, of which many fishes, insects, and especially fluviatile mollusks, avail themselves. Artificial means of crossing broad rivers are offered, to insects especially, by country-roads and bridges and railroad bridges, of which the potato-beetle and the cabbage-butterfly have fully availed themselves. The Colo- rado beetle has advanced steadily eastward, suddenly ap- pearing in isolated points in New England, having appar- ently been transported by through grain-cars from Chicago, and has been carried to Europe in vessels. The European cabbage-butterfly introduced into Quebec spread southward into Maine along the Grand Trunk Railroad, into New York along the railroads from Montreal to New York, and then along the railroads to Washington. Geological changes, such as the rise and submergence of the edges of continents, and also the incoming and wane of the glacial period, were still more general and fundamental means of the dispersal and rearrangement of faune. Division of the Earth into Faune.—When we go from Maine to California we shall find that the faunistic features of the country radically change three times. Leaving the moist, temperate, forest-clad Atlantic region with its char- acteristic animals, and entering on the broad, treeless, dry, elevated plateau of the Rocky Mountains, we shall notice that the Atlantic fauna has been replaced almost wholly by anew and strange assemblage ; and when we descend the Pacific slope of the Sierra Nevada, there will be found to be a second replacement, though much less marked than the first. Again, when we pass from Labrador to the Isthmus of Panama, we shall find several distinct faune, from an arctic one to a purely tropical one. If we pause at Wash- ington and analyze the fauna of that point, we shall see that it is made up mainly of animals common to the Middle Atlantic States, with an infusion of northern and southern 662 . ZOOLOGY. forms. Indeed, at almost any point in temperate North America the fauna is found to consist of three elements— 1.¢., mainly a temperate, with a certain percentage of boreal or subarctic and of southern or semi-tropical forms; and if the point be situated near some lofty range of mountains, a fourth element—i.e., a purely arctic or alpine feature—is superadded. The earth’s surface may then be mapped out into general and special divisions. First, a tropical, tem- perate, and arctic or circumpolar fauna or realm, and, sec- ondly, each continent may form asmaller subdivision or spe- cific centre—t.¢., the Europeo-Asiatic, the African, the Aus- tralian, and the South and North American regions, for each of these continental divisions have been peopled with animals which have been from the earliest geological times the original possessors of the soil, though they may have adopted members of each other’s fauna. Confining ourselves to the North American Continent, let us examine the distribution of life on its surface. We shall have to throw out the arctic regions, which belong with the arctic regions of Europe and Asia, to a distinct circumpolar fauna or realm, and then map out the rest of the continent into five provinces—i.e., the Canadian, the Alleghanian, the Central or Rocky Mountains, the Pacific or Californian, and the Mewican ; all of these provinces are bounded by natural geological limits and differ in tempera- ture and moisture. While the cougar, or Felis concolor, is common to each one of them, and the bison and black bear range throughout the Canadian, Alleghanian, and Central provinces, there is a certain percentage of animals which are confined to each province ; and on closer examination, each province, especially on the Atlantic and Pacific coasts, will be found capable of minuter subdivision into more lo- cal faune or faunile. It will also be found that the animals, especially the insects, of the Atlantic province have certain elements reminding us of Northeastern Asia, while on the Pacific slope—i.e., the Californian province, a few insects, shells, and crustacea, as well as the birds, remind us of European types, which are wholly wanting east of the Rocky Moun- tains. GHOGRAPHICAL DISTRIBUTION. 663 On inquiring into the origin of the North American fauna, in the light of the geological history of the conti- nent, we shall find, first, that immediately preceding the glacial period, Arctic America was peopled by a flora and fauna of which the larger proportion of the animals of the continent north of latitude 30° are probably the descend- ants ; and, second, that a number of species migrated north- ward from the South American Continent. Now, when the glacial period came in, the semi-tropical and warm tem- perate animals of the northern two-thirds of the continent were mostly swept out of existence ; a scanty arctic fauna took their place ; as the ice melted and retreated to its pres- ent limits, the present assemblage of temperate animals, mostly modified descendants of those originally driven south, migrated back again and colonized the region laid compara- tively bare by the ice and cold of the glacial period. This is an illustration of the sweeping extinctions, recolonizations, and extended migrations of animals on our continent in former times, by which the existing relations of faunz have been brought about. Parallel events have occurred on the Europeo-Asiatic Continent, and thus geological extinctions and widespread migrations and recolonizations have taken place ; and it is only in this way that the existing relations in the geographical distribution of animals as well as plants can be accounted for. It should also be observed that in the beginning of things the continents were built up from north to south— such has been at least the history of the North and South American and the Europeo-Asiatic and African Conti- nents ; and thus it would appear that north of the equator, at least, animals slowly migrated southward, keeping pace, as it were, with the growth and southward extension of the grand land masses which appeared above the sea in the Pa- leozoic Age. Hence, scanty as are the arctic and temperate regions of the earth at the present time, in former ages these regicns were as prolific in life as the tropics now are, the latter regions, now so vast, having all through the Tertiary and Quaternary ages been undisturbed by great geological revolutions, and meanwhile been colonized by emigrants driven down by the incoming cold of the glacial period. 664 ZOOLOGY. It appears, then, that each continent has had from the first its distinct assemblage of life, and thus opposing con- tinents, such as South America and Africa, have fundament- ally different faune, because they have had a separate geo- logical history. Though the climate, moisture, and extent of forests of Brazil and the West Coast of Africa may, for example, be nearly identical, the animals are of a different type. At the present day, Australian trees may be trans- planted to California, and flourish there, and camels from the Orient may breed in Southern California, because at the present day the climate and soil are so much alike in the two countries. Distribution of Marine Animals.—Nearly all that has been said thus far applies to land animals. Marine species are assorted into faunz which are nearly as well marked as terrestrial assemblages of species. The barriers restraining them within their faunal limits are the temperature of the water, this being modified more or less by the ocean-cur- rents, the nature of the shore, whether rocky or muddy or sandy, and the nature of the sea-bottom, whether also rocky, muddy, orsandy. Many marine animals live attached to rocks and stationary pebbles, others are found only in coarse or in fine sand, while the muddy bottoms of harbors, bays, and gulfs, or the soft, deep ooze of the ocean-depths harbor a different assemblage of mud-loving species. The temperature of the water is the most important agency now in operation in the limitation of marine animals. Thus there is a tropical, north and south temperate, an arctic and probably an antarctic zone, and these are, along the shores of the different continents, subdivided into distinct faune. For example, along the coast of Eastern North America, the arctic or circumpolar fauna extends from the polar regions to Labrador and Newfoundland ; a second, the Acadian, to Cape Cod; between Cape Cod and Cape Hatteras another assemblage (the Virginian) is found ; from Cape Hatteras to Southern Florida a fourth, and the Flor- idan peninsula belongs to the tropical regions. Along these different areas the water is of different temperatures. We also find a large proportion of circumpolar animals in the GEOGRAPHICAL DISTRIBUTION. 665 Acadian fauna and a few in the Virginian fauna, as the Labrador or polar current passes down along the coast, bathing the New England coast north of Cape Cod, and even extending under the warm surface-water as far as New Jersey. On the other hand, the great volume of heated tropical water forming the Gulf Stream issuing from the Straits of Florida makes its influence most sensibly felt as far as Cape Hatteras, and in a diminished degree to Cape Cod, and even southern shells, etc., are found as outliers of more southern faune near Portland, Me., and Nova Scotia. As we descend from the shore into deep water, the tem- perature becomes lower and lower the deeper we go, until we come toa stratum or zone of water about 32°-36° Fahr., where circumpolar or arctic life alone abounds. Wherever deep abysses off the coast or at the bottom of bays or gulfs occur, the water is found to be colder than elsewhere ; just as when we ascend a mountain the air becomes colder, un- til at the Alpine summits we find an arctic temperature and fauna ; thus, in the sea, increase of depth is paralleled by increase of height on land. Usually, off the coast of the United States, north of New York, there is a distinct zone of life between high and low water, a second extending to the depth of about fifty fathoms, anda third to one hundred fathoms or over. Ata depth of from one or two hundred fathoms in the Northern Atlantic, and from five hundred to one thousand fathoms in the sub- tropical and tropical seas, down to the deepest parts of the ocean, now known in a few points to be about five miles in depth, the water is about 32° Fahr. and the animal life is polar in its nature. The water of the ocean all over the globe, as shown by the results of the ‘‘ Challenger’ and other expeditions for the exploration of the sea at great depths, everywhere below a depth of one thousand fathoms, is of an arctic temperature, overlaid by the heated water of the tropics. The abysses or deeper parts of the ocean-bed support a nearly uniform assemblage of life, which may be called the deep-sea or abyssal fauna, The animals largely consist of Echinoderms, notably Crinoids, with Celenterates, mollusks, worms, and Crustacea, and it is an interesting fact 666 ZOOLOGY. that a few of the Echinoderms belong to genera which flour- ished in the Cretaceous Period ; so that in a sense the abys- sal fauna may be said to be an extension in time of the Cretaceous fauna ; the physical features of the deeper parts of the sea having remained nearly the same, while the shallower parts have risen and fallen so as to undergo great changes, and have wrought corresponding changes in the life along the shores of the continents. The following tabular view of the chief zoological faunas of the earth, proposed by Mr. J. A. Allen, is based on a study of the mammals, but will primarily apply to most land animals. The arctic realm is most distinctly charac- terized by the distribution of marine invertebrates, where 1t becomes of primary value : I, Arctic realm, undivided. _ IL North Temperate realm, with two regions, viz. : 1. American region, with four provinces, viz.: a. Boreal. b. Eastern. c. Middle. ad. Western. 2. Europzo- Asiatic region, also with four provinces, viz. : a. European. b. Siberian. c. Mediterranean. ad. Manchurian. III. American Tropical realm, with three regions, viz. : 1. Antillean, 2. Central American, 3. Brazilian. IV. Indo-African realm, with two regions, viz. : 1. African region, with three provinces, viz. : a. Eastern. b. Western. ce. Southern. GHOGRAPHICAL DISTRIBUTION. 667 2. Indian region, with two provinces, viz. + a. Continental. 6. Insular. V. South American Temperate realm, with two provinces, viz. : a. Andean. 6, Pampean. VI. Australian realm, with three regions, viz. : 1. Australian, with two provinces, viz. : a, Australian, b. Papuan, 2. Polynesian. 8. New Zealand. VII. Lemurian realm, undivided. VIII. Antarctic or South Circumpolar, undivided. Migrations of Animals.—Intimateiy connected with zoogeog- raphy are the migrations of animals, especially birds. Nearly all the pirds of the United States which breed in the central and northern portions pass southward in the autumn, and winter in the Southern States or in Central America and the West Indies. Most of the birds * which breed in Northern and Central Europe fly at the approach of cold weather into Southern Europe or across the Mediterranean into Northern Africa. The causes of this regular periodical migration are probably due, primarily, to the changes of the seasons and to the want of food in the colder portion of the year, and, secondarily, to the breeding habits of birds. : The periodical migrations of fishes from deep to shoal water are connected with their breeding habits, the marine fish being in most cases compelled to spawn in rivers or in shoal-water. The migratory movements of fishes along the coast are probably connected with the presence or absence of their accustomed food. The partial, occasional migrations of locusts depend on the undue increase in the numbers of the insects, and the consequent lack of food, while the direction of the swarms is largely dependent on the general course and force of the winds. CHAPTER AIT, THE GEOLOGICAL SUCCESSION OF ANIMALS. THE different systems of rocks, from the Silurian to the Quaternary or present age, contain the fossil remains of ani- mals, which show that in the beginning the animals were, as a whole, unlike those now living, the later types becom- ing more and more like those now constituting the earth’s fauna. The oldest set of animals, the Paleozoic, comprised species of nearly all the branches of invertebrates, with a few fishes. A large proportion of these animals belonged either to simple or to what are called generalized types, though some were as specialized as any invertebrates now living. Progress upward has involved the disappearance of most of the generalized types, and their replacement by more or less highly specialized types. Thus the earliest corals were mostly of the Rugose type, which were succeeded by the more complicated recent forms ; the Brachiopods or shelled worms were replaced by mollusks ; the generalized trilobites gave way to the genuine specialized shrimps and crabs ; the existing generalized king-crab, with its affinities to spiders, has survived a number of still more generalized or synthetic allies. The generalized sharks and ganoids abounded at a time when there were no bony fishes like the cod and her- ring. Nearly nine thousand species of bony fishes have appeared since the extinction of the earlier types of cartila- ginous and mail-clad fishes. The highly specialized horse was preceded by a number of more generalized species and genera, the oldest of which approached the tapir, one of the most generalized of mammals. The succession of forms leading up to the horse is paralleled by the succession of GHOLOGICAL SUCCESSION OF ANIMALS. 669 sea-urchins and of ammonites, the older being of simpler, more generalized forms, and the later with a greater specialization or elaboration of the different, especially ex- ternal, hard parts of the hody. When we ascend to the Amphibians, the reptiles and the mammals, we shall find that there has been an elaboration or working out into great detail, of the parts most used by the animal, this differentiation being more and more marked as we approach the present time; and this has been in ac- cord with the building up of the continental masses, and the differentiation or specialization of the surface of the different continents into plains, plateaus, highlands, and mountain ranges, with their different climatic features, and the: dividing up of the waters into mediterranean seas, friths, fiords, rivers, and lakes. Thus the extinction of successive faune all over the globe has been followed by the appearance of new sets of animals, each assemblage be- ing adapted to the new and improved condition of things. Having seen that the earlier forms of life were of a sim- pler form, though often combining the features of diverse classes and orders of animals which appeared afterward, so that Agassiz called them, in some cases, prophetic types, combining as they did characters which have been trans mitted to two or more later groups, and these specially elab- orated, so that such generalized or prophetic types serve as points of departure from which several series of forms have arisen—having traced the law or principle underlying the geological succession of animals, we may inquire whether this has been paralleled by the development of any one of the members of a group. That this is the case has been ‘proved by Hyatt, who shows that the development of the individual Ammonite is paralleled by that of the geological succession of the members of the order to which it belongs. Stalked Crinoids were the style in Paleozoic ages, while free Crinoids are more abundant at the present day ; and we have seen that in the individual development of the existing Antedon, the young is stalked at first, afterward becoming free. The young, bony fish has at first a cartilaginous skeleton and a heterocercal tail, these being characteristics 670 ZOOLOGY. of early fishes. The earlier Batrachians were tailed, the tailless toads and frogs in general appearing last, as the tadpole precedes the frog condition. Extinction of Species.—The laws governing the extinction of animals are obscure, but we know that geological extinc- tions must have been due to natural causes, since the earth has at different periods evidently undergone great changes, sufficient to account for the death of such species as were unable to withstand the oscillations and changes of climate. In Paleozoic times existed multitudes of animals which, judg- ing by their descendants of later times, belonged to old-fash- ioned, obsolete, useless types. They cumbered the ground, and were destroyed by the beneficent action of unerring natu- ral laws promoting the decay and extinction of antiquated forms, and the recreation, by the laws of transmission with modification, of new, improved types, useful in their day and generation as stepping-stones to a still higher, more improved stock. That the extinction was due to causes acting pri- marily from without, and secondarily from within by trans-. mission force, seems demonstrated when we take into ac- count the destruction of life which we know took place during and at the close of the Glacial Period, when the earth was swept with glaciers, and afterward garnished with the vegetation and fresh life of the post-glacial times, and made ready for the abode of man. Thus the death of species by the action of laws that we can comprehend in- volves the recreation of new and improved animal forms by laws that we can at least in part, if not fully, understand. CHAPTER XIII. THE ORIGIN OF SPECIES. THE extinction of species was in some cases gradual, in others sudden, so in all probability as different assemblages of life became slowly extinct new forms as slowly originated from them by genetic descent and took their places. While here and there certain species, under favorable circumstances, suddenly appeared, if we could have been there to look on, it would perhaps have been as difficult to have observed the process as it is at the present day to observe the changes going on in the relation of existing faune. We know, however, that changes are going on in the world of life about us, that the balance of nature is being disturbed. The nature of the evidence tending to prove that species have originated through the agency of physical and biologi- cal laws is mainly circumstantial, there being comparatively few facts in demonstration of the theory, the direct act of transformation of one species into another under the eye of scientific experts having never been observed. Reasoning @ priori, we assume that organisms, both plant and animal, have been created by development from pre-existent forms because it agrees with the general course of nature. All the events in geology, as in physics and as- tronomy, being due to the operation of natural laws, it is reasonably supposed that the production of all the species of plants and animals from original simple forms, like the Monera or bacteria, have been the result of the action of natural law. The study of the early forms of life found in the Paleozoic strata ; the laws of the succession of types ; the correlation existing between the development of the indi- 672 ZOOLOGY. vidual and of the members of the class to which it belongs ; the parallelism between the formation and differentiation of the land-masses of the globe and the successive extinc- tions and creations of plants and animals—all these facts, notwithstanding the imperfections of the geological record, and the fact that many of the older forms of animals were nearly as much specialized as those now living ; tend strongly to prove that, on the whole, the world as it now exists has been the result of progressive development, one form com- ing genetically from another ; the animal and plant worlds constituting two systems of blood relations, rather than sets of independent creations. When to more special studies of those species which live in extraordinary environments, such as cave-animals, para- sitic animals, brine-inhabiting animals, Alpine forms and certain deep-sea species, we add the study of rudimentary organs in adult animals, of temporary, deciduous organs in young or larval animals; when we compare the metamor- phoses of some species congeneric with others which undergo no transformations ; when we study the delicate balance in nature as observed in the geographical distribution of ani- mals ; the harmony in nature between species and their en- vironment ; protective coloration and resemblance in form, the relations between carnivorous and herbivorous creatures, the struggle for existence between animals, we are forced to acknowledge that the operations of nature, as a whole, tend, on the one hand, to the origination of new forms and the preservation of those which are useful, or, in other _ words, arein harmony with their surroundings ; and, on the other hand, to the destruction of those which are incapaci- tated by changes in their environment for existence in what has been and now is a constantly changing, progressive world. Again, reasoning by induction, as an actual fact we know that species vary ; that hardly any two experts agree exactly as to the limitation of species ;* that varieties tend to break * As one of many examples, we may cite the fact that fifty-nine nom- inal species of the squirrels have been described as inhabiting tropical America, but lately the number has been reduced to twelve. THE ORIGIN OF SPEUIES. 673 up into races, and that no two individuals of a race are ex- actly alike. Where the climate and soil remain the same, the species tends to remain fixed and stable ; remove the stability in the environment, or subject the individuals of a species to changes of soil and temperature, and expose it more than usual to the attacks of its natural enemies, it then begins to undergo a change. This is seen in those in- dividuals of a species which live on the borders of lowlands and highlands, of deserts and fertile tracts, of salt and brackish water, of shallow and deep water, and of polar and temperate zones, or to the influence of alternating cold and warm weather. When, as in some cases, climatic or other agencies suddenly change, we may have species and even genera suddenly appearing, as is known to be the case in the change of one genus to another of brine shrimps when the water changes from brackish to a brine, as worked out by Schmankevitch in Russia. The struggle for existence resulting in the survival of the fittest is a fact now generally observed. ‘The cod may de- posit several millions of eggs, but of this immense number only one or a few pair of adults survive ; there are probably no more codfish now than two centuries since—indeed, not as many; the eggs are devoured by different animals, the young fish, as soon as hatched, form the food of larger fish, half-grown cod serve to supply the wants of larger animals, until finally the survivors may be to the original number of eggs as one to a million. The queen bee may, during her whole life, lay more than a million of eggs, the queen white ant may lay eighty thousand eggs a day, an Aphis may be the mother of a hundred young, those hundred may each produce their centesimal offspring until the result in one season, at the end of the tenth generation, amounts toa quintillion of plant-lice ; but most of these insects serve as food for other species, many die of disease and cold, until | at the end of the season only one or several pairs survive to lay a few eggs, which represent the species in the winter-time. Lastly, the variation in domestic animals, the result of the subjection of the species to influences not felt in what we call a state of nature, is an indication that animals not 674 ZOOLOGY. exposed to human interference may vary when subjected to changes in their environment. Also the fact that man can, by careful selection, breed races of horses adapted for draught, speed, or the road ; races of cows for different qualities of milk ; beeves for meat ; races of sheep for pre-eminence in the quality of their wool or mutton, or races of doves or poultry for beauty, usefulness, or other qualities ; the fact that gentleness, and generally good mental qualities, can be made to replace viciousness in horses, cattle, dogs—all these and many other facts, in the art of breeding animals known to fanciers, indicate that nature has, through the past ages, by the operation of natural laws, evolved races and species of animals which have followed constantly improving lines of development, the outcome of which are creatures the best fitted to withstand the struggle for existence, the most use- ful in the scheme of nature, and the most in harmony with the world about them. Progress, on the whole, therefore, has been beneficent, the best proof of which is the last product of evolution, man, the paragon of creation. CHAPTER XIV. PROTECTIVE RESEMBLANCE. CLosELy related to the foregoing subjects is the protective resemblance or ‘‘ mimicry’’ of natural objects by which spe- cies of animals are preserved from extinction. Animals may ‘“‘mimic’”’ or imitate, or be assimilated in shape or in color to natural objects, as stones, lichens, dry bushes, the bark of trees, or portions of leaves, or entire leaves, fresh or dried, and their stems, or so closely imitate other animals which enjoy an immunity from attack as to escape notice or attacks from their enemies, and thus prolong their own lives and that of their species. The animal is, as a rule, unconscious that it is thus pro- tected ; though there are examples, as in the case of the trap-door and other spiders, which cover their holes in such a way to avoid notice that it would appear as if they were semi-conscious or aware of what they were doing. In the first place, we know that animals may be deceived, as is proved by the various subterfuges employed by hunters in tolling or deceiving the larger quadrupeds, the use of decoy-ducks, by which water-fowl are often thoroughly de- ceived and brought within reach,of the gun. The disguises worn by animals, the exquisite adaptation of the colors of their fur or feathers to their surroundings, are part of the general harmony existing throughout nature. Desert animals are rusty or light-colored ; birds and insects and lizards, as well as frogs and tree-toads, which live among trees, are green; those which live among the trunks and larger branches of trees assimilate in color to the color of the bark. The cougar, which clings to the trunk of some 676 ZOOLOGY. tree, prepared to spring upon the deer passing underneath, 1s protected from observation by its brown neutral color, while the bars and lines of the tiger are said to resemble the lights and shades of the jungle grass in which it lies in wait for its prey. The prairie-dog, the deer, buffalo and ante- lope on the Western plains, are concealed by their resem- blance in color to the soil, or to the bushes on its surface. Among insects, the grasshoppers nearly always harmonize in color with the general hue of the fields in which they abound ; insects on light-colored sandy beaches are often pale, as if bleached ont by the sun’srays. Alpine and arctic butterflies and moths, which have limited powers of flight, when nestling on lichen-covered rocks, are difficult to detect. Fig. 542.—A Katydid-like form resembling a leaf. Certain orthopterous insects resemble leaves; such are certain katydids (Fig. 542), and especially the famous leaf- insect, Phyllium siccifoliwm Linn. (Fig. 543), which strik- ingly resembles a green leaf. The stick-insects (Fig. 544) also would be easily mistaken for the twigs of trees or stalks of leaves, one species (Fig. 544) representing a moss-grown twig. The under sides of the wings of our native Grapta butterflies have the color of dead Jeaves, so that when they are at rest they resemble a withered dry leaf. The most perfect resemblance to a leaf with its stem is the Kallima butterfly when setting at rest with its wings folded over its PROTECTIVE RESEMBLANCE. 677 back. The caterpillars of the geometrid moths often won- derfully mimic the stems of the plants they feed upon, in color and markings, even to the warts and tubercles on their skin. As an example of possibly con- scious mimicry or effort at conceal- ing their nest from the search of their enemies, may be cited the trap- door spider observed by Moggridge in Southern Europe. This spider digs its hole among moss and small ferns, and after the trap-door is made the top is covered with growing Hen arena ftw ferns, etc. transplanted by the spider, and the deception is so perfect that Mr. Moggridge found it difficult to detect the position of the closed trap, even when holding it in his hand. Mimicry of other insects is of very frequent occurrence, certain flies resembling bees in appearance and the sounds or buzzing they make ; the Syrphus flies closely imitate wasps. Fig. 545 illustrates a case observed by Belt in Nicara- gua, where a wasp (Priocnemis) is mimicked by a hemipterous insect (Spiniger luteocornis Walker, the left-hand figure) in every part, even to its vibrating, brown, semi- transparent wings and its wasp-like motions. Here the bug is evidently protected by its resemblance to the wasp, for whose ferocity and sharp sting all unarmed insects have great respect. Some butterflies are distasteful Fig. 544,—Stick insect, to birds, and there are other but- terflies which have no bad taste, but closely resemble in color such species as are passed over by birds. Thus, 678 ZOOLOGY. Danais archippus, a common large butterfly, is not eaten by birds on account of its pungent odor, which is disagree- able to them. Another butterfly, Limenitis disippus, a smaller but similarly colored butterfly, which is inodorous, is supposed to be mistaken by the birds for the Danais, and thus escapes destruction. Belt says that in Central America stinging ants are not only closely copied in form and movements by spiders, but by species of Hemiptera and Coleoptera; as stinging ants are not usually eaten by birds, this disguise is thought to protect the various forms which imitate them. Many highly-colored caterpillars, which live exposed on the leaves of plants, are not eaten by birds, owing to their bad taste. This and other bright-colored insects may be said Fig. 545 —Wasp mimicked by a bug.—After Belt. to hang out danger-signals to warn off hungry birds. Mr. Belt, in his ‘“‘ Naturalist in Nicaragua,’’ suggests that the skunk is an example of this kind. ‘‘ Its white tail, laid back on its black body, makes it very conspicuous in the dusk when it roams about, so that it is not likely to be pounced upon by any of the Carnivora mistaking it for other night-roaming animals.’? He also cites the case of a very poisonous, beautifully banded coral snake (Zvaps), which is ‘“marked as conspicuously as any noxious caterpillar with bright bands of black, yellow, and red.’’ This author also found that while the frogs in Nicaragua are dull or green- colored, feeding at night, and all preyed upon by snakes and birds, one little species of frog, dressed in a bright liv- PROTECTIVE RESEMBLANCE. 679 ery of red and blue, hops about in the day-time, and, as he proved by experiment, is thoroughly distasteful to fowls and ducks. We have seen that many animals resemble externally those above them in the scale of life ; in the synthetic or general- ized types from which the more specialized forms have prob- ably originated, there are characters which cause them to resemble more recent, new-fashioned types. It is possible that in many cases the older types, doomed as they were to destruction, have had their existence prolonged by their protective resemblance to modern types. For example, the Newroptera as a group are geologically of high antiquity ; owing to geological extinction, but few species, compared with those of other orders, have survived ¥ and those which are now living often resemble members of higher, more recent orders. The inference is, then, that the mimickers have survived by reason of their resemblance to the more abundant forms which appeared, as the more old-fashioned types were waning or dying out. Certain Brazilian species of the lepidopterous family, Zygenide and Bombycide, mimic in form and coloration certain butterflies, especially the Heliconide, which abound in Brazil. The former groups are evidently the older geo- logically, as there are wide gaps between the genera; and the indications are that these butterfly-like moths have likewise, from their resemblance to the more abundant Heli- conide, been preserved. It thus appears that protective mimicry may be an important factor in the preservation of species. CHAPTER XY. INSTINCT AND REASON IN ANIMALS. We have seen that animals have organs of sense, of per. ception, in many cases nearly as highly developed as in man, and that in the mammalia the eyes, ears, organs of smell and touch differ but slightly from those of our own species ; also that the brain and nervous system of the higher mam- mals closely approximate to those of man.- We know that all animals are endowed with sufficient intelligence to meet the ordinary exigencies of life, and that some insects, birds, and mammals are able, on occasion, to meet extraordinary emergencies—in other words, to rise with the occasion. These occurrences indicate that what usually goes by the name of ‘‘instinct’’ is more or less pliable, unstable ; that animals are ina limited degree free agents, with powers of choice. Moreover, those naturalists who observe most closely and patiently the habits of animals do not hesitate to, state their belief that animals, and some more than others, possess reasoning powers which differ in degree rather than in kind from the purely intellectual acts of man. As a matter of not infrequent observation, animals exer- cise the power of choice, they select this or that kind of food, prefer this or that kind of odor, and have their likes and dislikes to certain persons, and all this aside from mere physical stimulation of the senses. Moreover, animals are subject to the passions, they show anger, even when not hungry or under the domination of the reproductive in- stincts ; their sounds express dissatisfaction or contentment. Indeed, many facts could be stated showing that animals INSTINCT AND REASON. 681 not only have feelings, intelligence, and volition, but are possibly, in a very slight degree, self-conscious. The fact that animals exercise discrimination in the selection of food, in the choice of a flower or object of one color in preference to another, in perceiving likeness or unlikeness in two objects, indicates that they can exercise the power of intelligent discrimination, as has been said by Mr. G. H. Lewes :* ‘‘ When there is no alternative open to an action it is impulsive ; when there is, or originally was, an alter- native, the action is instinctive ; where there are alterna- tives which may still determine the action, and the choice is free, we call the action intelligent.” _ Indeed, animals have the principle of similarity strongly developed. It is the bond that holds together the social or- ganizations of such insects as live in colonies, and such fish, birds, or mammals as go in schools, flocks, or herds. Were it not for this mental quality some species would tend to die out. Animals possess memory, which consists in storing up in the mind the results of external impressions, so that they are enabled to perceive the points of resemblance or differ- ence between two objects, after having been out of sight of them for a greater or less length of time. Bain defines memory, acquisition or retention, as ‘‘ being the power of continuing in the mind impressions that are no longer stim- ulated by the same agent, and of recalling them afterward by purely mental forces.’ With the aid of memory, birds make their migrations, bees and ants find their way back to their nests. As we have elsewhere said, ‘‘ No automaton could find its way back to a point from which it had once started, however well the machine had been originally wound up. Nor does the common notion of an inflexible instinct meet the case. Memory is often due to a repetition of certain experiences, and experiences lay the foundation for instinctive acts ; it is the sum of these inherited experiences which make up the total which passes under the name of instinct.’’t * Article on Instinct in Nature, April 10th, 1873. + Half Hours with Insects, p. 374. 682 ZOOLOGY. It would appear, then, that animals have in some slight degree what we call mind, with its threefold divisions of the sensibilities, intellect, and will. When we study animals in a state of domestication, especially the dog or horse, we know that they are capable of some degree of education, and that they transmit the new traits or habits which they have been taught to their offspring ; so that what in the parents were newly acquired habits become in the descend- ants instinctive acts. We are thus led to suppose that the terse definition of instinct by Murphy, that it is ‘‘ the sum of inherited habits,’’? is in accordance with observed facts. Indeed, if animals have sufficient intelligence to meet the extraordinary emergencies of their lives, their daily, so- called instinctive acts, requiring a minimum expenditure of mental energy, may have originated in previous genera- tions, and this suggests that the instincts of the present generation may be the sum total of the inherited mental ex- periences of former generations. Descartes believed that animals are automata. Lamarck expressed the opinion that instincts were due to certain in- herent inclinations arising from habits impressed upon the organs of the animals concerned in producing them. Darwin does not attempt any definition of instinct ; but he suggests that ‘‘ several distinct mental actions are com- monly embraced by this term,’’ and adds that “a little dose, as Pierre Huber expresses it, of judgment or reason often comes into play, even in animals low in the scale of nature.’? He indicates the points of resemblance between instincts and habits, shows that habitual action may become inherited, especially in animals under domestication ; and since habitual action does sometimes become inherited, he thinks it follows that ‘‘ the resemblance between what origi- nally was a habit and an instinct becomes so close as not to be distinguished.’? He concludes that, by natural selection, slight modifications of instinct which are in any way useful accumulate, and thus animals have slowly and gradu- ally, ‘‘ as small consequences of one general law,’’ acquired, through successive generations, their power of acting in- INSTINCT AND REASON. 683 stinctively, and that they were not suddenly or specially endowed with instincts. Rev. J. J. Murphy, in his work entitled ‘‘ Habit and In- telligence,”’ seems to regard instinct as the sum of inherited habits, remarking that ‘‘ reason differs from instinct only in-being conscious. Instinct is unconscious reason, and reason is conscious instinct.’? This seems equivalent to saying that most of the instincts of the present generation of animals is unconscious automatism, but that in the begin- ning, in the ancestors of the present races, instincts were more plastic than now, such traits as were useful to the or- ganism being preserved and crystallized, as it were, into the instinctive acts of their lives. This does not exclude the idea that animals, while in most respects automata, occa- sionally perform acts which transcend instinct ; that they are still modified by circumstances, especially those species which in any way come in contact with man ; are still in a de- gree free agents, and have unconsciously learned, by success or failure, to adapt themselves to new surroundings. This view is strengthened by the fact that there is a marked de- gree of individuality among animals. Some individuals of the same species are much more intelligent than others, they act as leaders in different operations. Among dogs, horses, and other domestic animals, those of dull intellect ‘are led or excelled by those of greater intelligence, and this indicates that they are not simply automata, but are also in a degree, or within their own sphere, free agents. BIBLIOGRAPHY.* GENERAL ZOOLOGY. Elements of Comparative Anatomy. By Carl Gegenbaur. London, 1878. A Manual of the Anatomy of Vertebrated Animals. By T. H. Hux- ley. London, 1871. A Manual of the Anatomy of Invertebrated Animals. By T. H. Huxley. New York, 1878, Forms of Anima: Life. By George Rolleston. Oxford, 1870. Grundziige der Zoologie. Von C. Claus. Leipzig, 1876. Fourth edition, 1879. : Handbuch der Zoologie. Band 1, Wirbelthiere, Mollusken und Mol- luscoiden, von J. Victor Carus, Leipzig, 1868-1875 ; Band 2, Arthropo- den, von A. Gerstaecker ; Raderthiere, Wirmer, Echinodermen, Ccelen- teraten und Protozoen, von J. Victor Carus, Leipzig, 1863. Bronn’s Classen und Ordnungen der Thierreichs. Protozoa, Radiata, Crustacea, Amphibia. (Other partsincomplete.) Leipzig und Heidel- berg. Zoologie. Won L. K. Schmarda. 2t¢, Auflage. Band 1,2. Wien, 1877-78. The Anatomy of Vertebrates. By R. Owen. 8vols. London, 1868. A Key to the Birds of North America. By Elliott Coues. Boston, 1872. The Birds of North America. 3 vols. By §. F. Baird, T. M. Brewer, and R. Ridgway. Land Birds. Boston, 1874. Contributions to the Natural History of the United States. By L. Agassiz. 4 vols. Boston, 1857-1862. Mind in Nature. By H.J. Clark. New York, 1865. Manual of the Vertebrates of the Northern United States. By D. 8. Jordan. Second edition. Chicago, 1878. Seaside Studies in Natural History. By B.C. Agassiz and Alexander Agassiz. Radiata. Boston, second edition, 1871. Introduction to Entomology. By W. Kirby and W. Spence. 4 vols. London, 1828. * Works used in the preparation of this volume, with the titles of others indispen- sable to the student. 686 ZOOLOGY. Manual of Entomology. By H. Burmeister. London, 1836. Guide to the Study of Insects. By A. 8. Packard, Jr. Highth edition. New York, 1888, Invertebrate Animals of Vineyard Sound. By A. E. Verrill. (Re- port U. S. Commissioner of Fish and Fisheries.) Washington, 1873. Invertebrata of Massachusetts. By A. A.Gould. Edited by W. G. Binney. Boston, 1870. First Book of Zoology. By E. 8. Morse. Second edition. New York, 1875. : Manual of the Mollusca. By S. P. Woodward. Second edition. London, 1868. _ Corals and Coral Islands. By J. D. Dana. New York, 1872. Introduction to the Osteology of Mammalia. By W. H. Flower. London, 1870. Elementary Text-book of Zoology. By C. Claus. Translated by A. Sedgwick. 2 vols , 8vo, London, 1884-5. Elementary Biology. By T. H. Huxley and H. N. Martin. New York, 1876. With the works and monographs of Dana, Wyman, Leidy, L. and A. Agassiz, H. J. Clark, Cope, Gill, Hyatt, Verrill, Scudder, Binney, Allen, Coues, Smith, Baird, Ridgway, Brewer, Dall, Cooper, Wilder, Riley, Uhbler, Edwards, Grote, Le Conte, Hagen, Scammon, Stimpson, Jordan, Morse, Thomas, Gould, Bland, Prime, Tryon, Gabb, Packard, and others, and the standard works of Linnzeus, Cuvier, Von Baer, Leuckart, Gegenbaur, Haeckel, St. Hilaire, Huxley, Mivart, Allman, Hincks, Shuckard, Westwood, P. J. and E. Van Beneden, Brandt, Ratzburg, Burmeister, Oscar Schmidt, Metschnikoff, Kowalevsky, Kupffer, and many others. The student should also consult the following serials : American Jour- nal of Science and Arts, New Haven, Conn. ; The American Naturalist, Philadelphia ; Nature, London ; Quarterly Journal of Microscopical Science, London; Archiv fiir Naturgeschichte, Berlin; Annals and Magazine of Natural History, London ; Annales des Sciences Naturelles, Zoologie, Paris ; Siebold und Kolliker’s Zeitschrift, Canadian Ento- mologist, London, Canada; Psyche, Cambridge. Descriptions of North American animals and essays on their anatomy, physiology, and development are to be found in the Transactions and Proceedings of the following scientific societies: American Academy of Arts and Sciences, Boston ; American Philosophical Society, Phila- delphia ; Academy of Natural Sciences, Philadelphia ; Boston Society of Natural History ; Smithsonian Institution ; American Entomologi- cal Society, Philadelphia ; Museum of Comparative Zoology, Cam- bridge, Mass. ; Essex Institute ; Peabody Academy of Science, Salem; Academy of Sciences, San Francisco, Cal. ; and other societies in Port- land, Me. ; Buffalo, N. Y.; Davenport, Iowa; St. Louis, Mo., and Charleston, 8. C. ; New York and New Haven. BIBLIOGRAPHY. 687 HISTOLOGY. Handbook of Human and Comparative Histology. By S. Stricker. New York, 1872. And the monographs or essays of Leidy, Clark, and C. 8. Minot. PHYSIOLOGY. Treatise on Human Physiology. By J. C. Dalton. Philadelphia, Elementary Lessons in Physiology. By T. H. Huxley. Fourth edition. London, 1870. ‘Text-Book of Physiology. By M. Foster. London, 1877. The Human Body. By H. Newell Martin, N. Y., 1881. EMBRYOLOGY, _ Entwicklungsgeschichte der Thiere. Von Baer. _ Konigsberg, 1828. Entwicklungsgeschichte des Menschen. Von A. Kodlliker. zig, 1861." Elements of Embryology. By M. Foster and F. M. Balfour. 1874. A treatise on Comparative Embryology. By F. M. Balfour. 1880. With the monographs of Wolff, Harvey; Barry, Coste, Pouchet, Von Baer, Remak, Bischoff, L. and A. Agassiz, Weismann, Metsch- nikoff, Huxley, Balfour, Parker, Packard, and others. Leip- ZOOGEOGRAPHY. The Geographical Distribution of Animals. By A. R. Wallace. 2 vols. New York, 1876. With the essays of Agassiz, Baird, Allen, Verrill, Ridgway, Gill, Packard, and others. EVOLUTION AND RELATION OF ANIMALS TO THEIR ENVIRONMENT. Philosophie Zoologique. &J.B.de Lamarck. 8vo, 2 vols. 1809. On the Origin of Species. By Charles Darwin. New York, 1871. The Origin of Genera. By E, D. Cope. Philadelphia, 1861. Contributions to the Theory of Natural Selection. By A. R. Wal- lace. New York, 1970. On the Origin of Species. By T. H. Huxley. New York, 1863. With the essays of Cope, Hyatt, Wagner, Weismann, Haeckel, Kupffer, Palmén, Lubbock, Semper, Packard, and others. NATURAL HISTORY OF MAN. De Generis Humani Varietate Nativa. Von J. F. Blumenbach. Editio 3. Gottingen, 1795. 688 : ZOOLOGY. Researches into the Physical History of Mankind. By J. C. Prich- ard. London, 1851. Types of Mankind. By J. C. Nott and G. R. Gliddon. Philadel- phia, 1854. Natural History of the Varieties of Man. By R. G. Latham. Lon- don, 1850. Races of Man. By Charles Pickering. London, 1863. Evidence as to Man’s Place in Nature. By T. H. Huxley. New York, 1863. Prehistoric Times. By Sir John Lubbock. London, 1872. Natural History of the Human Species. By H. Smith. Edinburgh, 1882. With the works and essays of Reizius, Wilson, Mortillet, Broca, Lartet, Von Baer, St. Hilaire, 8. Van der Kolk, Vrolik, Schaaffhausen, Riitimeyer, Busk, Morgan, Wyman, Squire, Davis, Schmerling, Wag- ner, Vogt, Rolle, Quatrefages, Tylor, and others. : GLOSSARY. AB-DO’MEN. In mammals the part of the trunk below or behind | the thorax; in insects the third region of the body, or hind body. AB-ER'RANT. Departing from the regular or normal type. AB-O’RAL. Opposite the oral or mouth region. A-BRAN'CHI-ATE (Gr. a, without; bragchia, gills). Without bran- chie or gills. A-cU'MI-NATE. Ending in a pro- longed point. AL-VE'0-Lus. A cavity forming the socket in the jaws of verte- brates for the teeth. AM-BU-LA'CRUM (Lat. from ambu- lare, to walk, a garden-walk). The perforated space or arca in the shell of the sea-urchin or the arm of a star-fish, through which the foot-tubes or ambu- lacral feet are protruded. A-ME-Ta'BG-LIc (Gr. a, without ; metabole, change). Referring ‘to insects and other animals which do not undergo a meta- morphosis. A-mMor’PHOUus (Gr. a, without; morphe, form). Without a defi- nite figure; shapeless ; espe- cially applicable to sponges. AM-PHI-Ca@’'Lous (Gr. koilos, hollow). vertebrae which concave, ends. A-NAL’'O-Gy (Gr. analogia, propor- tion). The relation between organs which differ in struc- ture, but have a similar func- tion; as the wings of insects and birds. A-NnaAs-To-mMo’siInG. Inosculating or running into each other like veins. AN-CHY-LO'sIs. The growing to- gether of two bones'so as to prevent motion between them. AN'NU-LATE. When a leg or an- tenna is surrounded by narrow rings of a different color. A'PLA-CEN-TAL. Referring to those mammals in which the embryos are destitute of a pla- centa. A'po-pous. Footless. Ap’TE-ROUS (Gr. a, without; pter- on, wing). Destitute of wings. A-QUI'FE-ROUS (Lat. agua, water; JSero, I carry). Applied to the water-carrying or water-vascu- lay system, of the sponges, etc. A-RACH'NL-DA (Gr. arachne, a spi- der). The class of Arthropods, amphi ; Applied to are doubly or hollow at both 690 embracing the spiders, scor- pious, and mites. A'RE-0-LATE. Furnished with small areas; like a network. A-RIS'TATE, Furnished with a hair. AR-THRO’PO-DA (Gr. a, without ; arthros, a joint; pous, podos, foot) Those Articulata with jointed feet. AR-TI-CU-LA'TA (Lat.ar sient di- minutive of artus, a joint). Cuvier’s subkingdom of worms, ' crustacea, and insects. AR-TI-O-DAC'’TY-LA (Gr. artios, even; daktulos, finger or toe). Those Ungulates with an even number of toes, as the ox. A-sEx'u-aL. Applied to animals, especially insects, in which the ovaries or reproductive organs are imperfectly developed; and which produce eggs or young by budding. AU-RE'LI-A. Old term for the pupa of an insect. AU'RI-CLE (Lat. auricula, a little ear). One of the cavities of the heart of mollusks and verte- brates. Az'y-aos (a, without ; zugon, a yoke, a pair). An organ, such as @ nerve or artery, situated in the middle line of a bilater- ally symmetrical animal, which has therefore no fellow. Bz-no'Po-pa (Gr. baino, to walk). The thoracic legs of insects. Bz'No-soME (Gr. baino, to walk; soma, body). The thorax of in- sects. BrFip. Divided into two parts; forked. GLOSSARY. BLAs’T0-DERM (dlastos, a bud or sprout; derma, skin). The outer layer of the germ-cells of the embryo. BLAs'TO-PORE. the gastrula. BLAs'T0-8PHERE. The embryo when consisting of a single cell-layer. Bran’cur-a. A gill or respiratory organ of aquatic animals. BrRan'cHr-aAL. Relating to the gills or branchie. Boc'cau. Relating to the mouth cavity; orrarely to the cheeks. Buu'LaTe. Blistered. The mouth of CA-DU-CI-BRAN'CHI-ATE (Lat. ca- ducus, falling off; Gr. bragchia, gills). Applied to those Ba- trachia in which the gills be- come absorbed before adult life. CaL'Ca-RA-TED, Armed with spurs. Ca'Lyx. A little cup; often ap- lied to the body of a Crinoid. Cap't-TaTE. Ending in a head or knob. CEN-TRUM. The body or central part of a vertebra. CrE-PHAL'IC. Relating to the cephalum or head. CE-PHAL'0-MERE. A cephalic seg- meut of an Arthropod. CE-PHAL'0-SOME. The head of in- sects, Arachnida and Myrio- poda. CER-cO'PO-DA (Gr. cercos, tail; pous, podos, foot). The last pair of jointed abdomiual appen- dages of insects; the ‘‘cerci.” CuE'LA. The terminal portion of a limb with a movable lateral part, like the claw of a crab; as GLOSSARY. in the chelate maxilla of the scorpion. Cur-as’Ma (Gr. chiasma, a cross- ing). The commissure of the optic nerves in most verte- brates. Cur'trin (Gr. chiton, a tunic). The horny substance in the skin of insects, etc. CuHYLE (Gr. chulos, juice). The milky fluid resulting from the action of the digestive fluidson | the food or chyme. CHyME (Gr. chumos, juice). The acid, partly fluid or partly digested food, produced by the action of the gastric juice on the food. Cru’ UM (pl. cla). Microscopic filaments attached to cells, usually within the body, and moving usually rhythmical- ly. Cirrus. A slender process on the body of worms. Cuo’a-ca (Lat. a sewer). The common.duct or passage at the end of the intestine into which the oviducts and urinary ducts open, as in reptiles, birds, and monotreme mammals. Cas'caL. Ending blindly or ina cul-de sac. Ca'cum. A blind sac; usually applied to one or more append- ages of the digestive canal. Cas-NEN'CHY-MA (Gr. kornos, com- mon; chumos, chyme or juice). Applied in polyps to the coral mass containing the chymifer- ous or nutritive canals connect- ing the different polyps. - Cou'Lo-PHORE. The sucker-like organ extended from the under 691 side of the abdomen of Podu- rans. CoM-MI8s’sURE. The nerves con- necting two ganglia. Con-cot'o Rous. Of the same color as another part. Con'DYLE (Gr. kondulos, a knuckle). The articular sur- face of a bone, especially of the occiput. Cor'Tr cau. Relating to the cor- tex or inner skin; external, as opposed to medullary. Cos'TaL (Lat. costa, a rib). lating to the ribs. CRIB'RI FORM (Lat. eribrum, a sieve; forma, form). With perforations like those of a sieve. Crop. LULL LENG Gee ee TA he Ae RTE PTA Seas << WES SE st ANS “ ‘ A oS AC we SEIN RUN eS ws ead atl Re WAY Sa SO NS Re Aveo Sra x . x xy mee wo oe EAN SSR oe ~% Suet Sukie = es EN = SHeeseR NN tea REN o ha ye it ei ‘ ‘\ Nt SCS A Ra 2 y SANs Se Ses OAS DS SS es SS AONE a es RENN OP po Se Sa . ee so SANS x ecu WR a See et i KS RON RY Soth Se oe SENG a x Lae Pest pera : SSS: