ALBERT R. MANN LIBRARY AT CORNELL UNIVERSITY In Honor of The Reverend Mary Bunton Adebonojo || Ordained April 15, 1980 Given by Mildred Settle Bunton The physiology of the Invertebrata, PHYSIOLOGY OF THE INVERTEBRATA THE PHYSIOLOGY OF THE INVERTEBRATA Ves BY + yf A. B. GRIFFITHS, Pu.D., F.R.S. (EDIN.), F.C.S. MEMBRE DE LA SOCIETE CHIMIQUE DE PARIS; MEMBER OF THE PHYSICO-CHEMICAL SOCIETY OF ST. PETERSBURG AUTHOR OF “ RESEARCHES ON MICRO-ORGANISMS," “THE DISEASES OF CROPS,” BTC. ETC. LONDON LREEVE AND CO. 5 HENRIETTA STREET, COVENT GARDEN, W.C. 1892 [Al rights reserved] ‘ hog: QL _ 3b4 OSS A-45626 i UNIVERSITY SN LIBRARY 2 y TO Pror. T. H. HUXLEY, LL.D, F.RS., F.LS., F.ZS. Correspondant de l'Institut de France . Past-President of the Royal Society, etc. etc. WHO HAS CREATED A NEW EPOCH IN BIOLOGY ; AND WHOSE GENIUS HAS DONE SO MUCH TO AWAKEN THE KEENEST INTEREST IN THE STUDY AND POPULARISATION OF SCIENCE This Work is (by permission) Dedicated AS A TOKEN OF ADMIRATION AND RESPECT BY THE AUTHOR PREFACE. “ Physiology ts to a great extent applied physics and chemistry.” Pror, Huxley. “A true knowledge of biology must be based on a Inowledge of chemistry and physics.”—M. M. P, Murr. “ Biology being the science which deals with the matter and energy of living things, manifestly rests on physics and chemistry, since it involves the appli- cation of the laws and principles of these sciences to the special case of living matter.” —R. J. H, GIBSON. “ Chemistry lies at the basis of physiology,” —A. BINET, “ It is impossible that physiology can ever acquire a scientific foundation without the aid of chemistry and physics.”—J. von LiEBIG. THE branch of biology detailed in the following pages has had only a few workers; for the reason that the majority of biologists are not chemists, and consequently have not the necessary: manipulative skill in applying a science like chemistry to the solution of biological problems. The true functions of the various organs of the Invertebrata have always been, until recent years, more or less prob- lematical. Morphology and histology alone could not answer correctly the questions involved ; but physiology with chemical and physical methods of: research have illuminated very many obscure problems concerning the functions of the various organs and tissues of the Jnvertebrata ; and no doubt viii PREFACE. they are destined to play an important part in the elucidation of many problems still requiring solution. The following work gives an account of some of the most important researches on the subject, which have been published during the past fifteen or twenty years; and I have also included an account of my own researches in the present volume, more especially as these have appeared in the Proceedings of the Royal Societies of London and Edinburgh, and have also attracted the attention of the Académie des Sciences (l'Institut de France), to the extent that its Council thought proper to award me an “honourable mention” in connection with the Prix Montyon, which is given annually for researches in experimental physiology and physiological chemistry. Besides, several well-known biologists have informed me that a work on the physiology of the Inverte- brata would be a welcome addition to biological literature. Consequently, I hope that this work (although I am fully cognisant of its many imperfections and shortcomings) may prove of some utility to those scientists and students who are desirous of investigating biological problems involving the applications of chemistry and physics. I take this opportunity of expressing my gratitude and best thanks to Sir Richard Owen, K.C.B., F.R.S., for the great interest he has always taken in my investigations, and for the many letters of friendly criticism which I have received from him, I am also grateful to Mr. F. E, Beddard, F.R.S.E. ; the Rev. W. H. Dallinger, LL.D., F.R.S, ; Mr. H. H, Dixon (of the University of Dublin); Prof. J. C. Ewart (of the Univer- sity of Edinburgh); Prof. Léon Fredericq (of the University of Liége); Dr. A. Giard (of Paris); Mr, S. T. Griffiths; PREFACE. ix Mr. A. Johnstone, F.G.S. (of the University of Edinburgh) ; Dr. C. A. MacMunn, F.C.S.; Prof. P. Mantegazza (of the University of Rome); Dr. A. C. Maybury, F.G.S.; Prof. A. von Mojsisovics (of the University of Gratz); Mr. E. B. Poulton, F.R.S.; Dr. G. J. Romanes, F.R.S.; Prof. G. O. Sars (of the University of Christiania); and Dr. C. Zeiss, for valuable assistance in various parts of the book. My obligations are due to the President and Council of the Royal Society of Edinburgh for the loan of certain wood-blocks used in illustrating my own papers on the Invertebrata, and which were originally printed in the Society’s Proceedings. In conclusion, I here record the name of my sister (Miss Mildred H. Griffiths), for her help in preparing, under my direction, certain drawings for the illustrations. Figures 32 and 33 are supplied by Dr. Carl Zeiss, optician, Jena, from his catalogue of microscopes. A. B. GRIFFITHS. Epesasron, Feb. 1892. CONTENTS. CHAPTER I. Introduction: Definition of Physiology—The Actions of Living Matter—Cells and their Functions—The Function of the Sarcode of the lowest Animals—Dual and Triple Functions of an Organ —Law of Von Baer—Classification of the Jnvertebrata—Division of Physiological Labour, &c. CHAPTER II. The .Chemistry of Protoplasm: ‘‘ The Physical Basis of Life ’— Analyses of Albumin—Chemical and Physical Properties of Albumin—Lieberkiihn’s Formula for Albumin—Schorlemmer on the Synthesis of Albumin—Loéw and Bokorny’s Researches— Researches of Reinke, Mori, Kretzschmar, Griffiths, Schtitzen- berger, Palladin, Schulze, and Kisser, on Alboumin—Decomposition Products of Albumin or Protoplasm—Latham’s Formula for Albumin—Spencer’s Definition of Life, &c. CHAPTER III. Digestion in the Invertebrata: DIGESTION IN GENERAL—Modes of Nutrition—Digestion in the Protozoa—-Phosphorescence and Digestion—Digestion in the Porifera, Coelenterata, Echinodermata, Trichoscolices, Nematoscolices, Cheetognatha, Arthropoda, Polyzoa, PAGE 10 xii CONTENTS. PAGE Brachiopoda, Mollusca, Hernichordata, and Urochordata—General Remarks concerning Digestion in the Invertebrata : eee CHAPTER IV. Digestion continued: DIGESTION IN PARTICULAR—Digestion in the Protozoa: No specialisation of parts—Digestion in the Porifera and Cclenterata ; Researches of Greenwood, Lankester, Haéckel, Voigt, Cienkowski, MacMunn, Fredericq —Digestion in the Echinodermata : Researches of Fredericq, Griffiths, MacMunn— Digestion in the Trichoscolices: Experiments of Fredericq— Digestion in the Annelida: Researches of Frederic and Griffiths ; the Pancreatic Function of the so-called “Liver ’’—Digestion in the Insecta and Arachnida: Researches of Griffiths on the Salivary Glands and “Livers” of the Jnsecta; Lowne on the Malpighian Tubules of Calliphora; Von Planta, Leuckart, and Schonfeld onthe Food Stuff of Bees; the Researches of Griffiths and Johnstone on the Salivary Glands and ‘‘ Liver ” of the Spider —Digestion in the Crustacea; Investigations of Griffiths on the “ Livers’ of the Brachyura and Macroura ; Stamati's Investiga- gations on the Gastric Juice of the Crayfish—Digestion in the Lamellibranchiata: Researches of Fredericg, Griffiths, and MacMunn—Digestion in the Gasteropoda: Investigations of Griffiths, Levy, and Fredericq—Digestion in the Cephalopoda : Researches of Griffiths, Krukenberg, Fredericq, and De Bellesme on the “ Liver ”’ (Pancreas) of Sepia—Digestion in the Tunicata— Constituents of the Secretions of the Salivary Glands and Pancreas (so-called “liver"’) in the Jnvertebrata, &c. * ‘ - 79 CHAPTER V. Absorption in the Invertebrata: No Distinct Set of Vessels—The Function of the Typhlosole—Absorption by the Alimentary Canal and Blood-vessels—Absorption in the Protozoa : Protozoan Absorp- tion due to Excitability or Irritability of the Cell—Absorption in the Porifera, Calenterata, Echinodermata, Cestoidea, Annelida, Myriapoda, Insecta, Arachnida, Crustacea, Polyzoa, Brachiopoda, and Mollusca—General Remarks on Absorption, &c i a ‘CONTENTS. xiil CHAPTER VI. PAGE The Blood in the Invertebrata: The Size of some Invertebrate Cor- puscles—Coagulation of Invertebrate Blood—The Protozoa and Porifera devoid of Blood—The Blood in the Actinozoa and Echinodermata—The Blood in the Myriapoda: Three distinct Corpuscles—The Blood in the Annelida: The Fluids of the Perivisceral Cavity and the Pseudo-hzmal System ; First appear- ance of a Coloured Corpuscle ; Researches of MacMunn, Lankester, Delle Chiaje, Schwalbe, Krukenberg, and Milne-Edwards—The Blood in the Insecta: Pigments of the Blood; Researches of Poulton and Fredericq ; Coagulation of Insects’ Blood—The Blood in the Crustacea: Investigations of Fredericq; Percentages of Saline Matter in Crustacean Blood; Densities of Crustacean Blood; Blood of the Mollusca: Researches of Griffiths, Cuénot, Fredericg, and Krukenberg ; Transport of Oxygen by means of Hemocyanin; Percentages of Saline Matter in Molluscan Blood; Saline Composition of Molluscan Blood—The Chro- matology of Invertebrate Blood: Researches of MacMunn, Poulton, and others; The Hemoglobin of Lumbricus ; Micro- spectroscopes—Griffiths’ Researches on the Gases of the Inverte- brate Blood—General Remarks, &c. . . . . 125 CHAPTER VII. Circulation in the Invertebrata : Fusion of Circulation and Digestion in the Protozoa, Porifera, and Ccelenterata—Blood and Vascular Systems in the Echinodermata and Annelida—Circulation in the Trichoscolices, Arthropoda, Polyzoa, Brachiopoda, Mollusca, and Tunicata, &e. . ‘ ; ‘ ‘ ; :. . ‘ . . 182 CHAPTER VIII. Respiration in the Jnvertebrata : Respiration in the Protozoa, Porifera, Coelenterata: Respiratory Pigments; Researches of Moseley, MacMunn, M‘Kendrick, Krukenberg, and De Negri; Internal or Tissue Respiration ; Respiration in the Echinodermata ; Investi- gations of Dugés, MacMunn, and Feettinger—Respiration in the Trichoscolices and Annelida: Researches of MacMunn, Geddes, Beddard, and Vejdovsky—Respiration in the Nematoscolices : xiv _ CONTENTS. Bunge’s Investigations on Respiration in Ascaris—Respiration in the Myriapoda and Insecta: Griffiths and Lyonnet on the Power .of certain Insects resisting Asphyxia; Trachez and Tracheal Gills; Tissue Respiration—Respiration in the Arachnida: Respira- tion by Trachez, “ Lungs,” and the General Surface of the Body— Respiration by Branchie and Pigments—Activity of Respiration— Respiration:in the Polyzoa, Brachiopoda, Mollusca, and Tunicata— General Remarks on Invertebrate Respiration, &c. . : . CHAPTER IX. Secretion and Excretion in the Invertebrata: General Remarks on Secretion and Excretion—The Protozoan Contractile Vacuole— Secretion of Lime Carbonate in the Cwlenterata: Researches of Murray and Irvine—The Excretory Organs in the Echinodermata : Investigations of Griffiths on the Renal Organs of Uraster—The Renal Organs to the Annelida and Nematoidea—The Secretion of Viscid Matter by the Prototracheata—Excretory Function of the Malpighian tubules in the Myriapoda—Poisons secreted by Insects : Researches of Poulton; The Salivary Glands in the Lepidoptera and their Function ; Griffiths” Researches on the Renal Function of the Malpighian Tubules in the Insecta—The Arachnida : Poison Glands of the Arthrogastra and Araneina ; The Arachnidium of the Araneina ; Investigations of Griffiths, Johnstone, and Weinland on the Renal Organs in the Araneina—The Crustacea : The Shell- gland a Renal Organ ; Researches of Griffiths on the Green Glands of Astacus—The Brachiopoda: Secretion of the Shell; the Functions of the Pseudo-hearts—The Mollusca: Secretion of Lime Carbonate by these Animals; Formation of Pearls; Re- searches of Irvine and Woodhead on Shell-formation ; Researches of Griffiths and Follows on the Organ of Bojanus; Researches of MacMunn, Griffiths, and others on the Function of the Nephridia in the Mollusca; Secretion of Mucus by the Pulmo- gasteropoda—Nerves and the Phenomena of Secretion—The Invertebrate Kidney—Comparison of the Invertebrate Kidney with that of the Vertebrata, &c. . ‘ : CHAPTER X. Nervous Systems of the Invertebrata : General remarks; Nerve-centres, Nerve-fibres ; Functions of Nerve-fibres—The Diffused Nervous PAGE 207 - 241 CONTENTS. xv PAGE System of the Protozoa—Ledenfeld’s Investigations on a Nervous System in the Porifera—The Nervous System of the Cwlenterata : ‘Researches of Kleinenberg, Romanes, Haéckel, Hertwig, and others ; Experiments of Romanes on the Nervous System of the Meduscee; Eimer’s Investigations on Ctenophora—The Nervous System of the Echinodermata: Researches of Romanes, Ewart, Fredericq, Prouho, and Hamann; Internal and External Nerve- plexuses of Echinus—Nervous Systems of the Trichoscolices, Anne- lida, Nematoscolices, Chetognatha, Prototracheata, and Myriapoda— The Nervous Systems of the Insecta: The Cerebral Ganglion or Brain—The Nervous Systems of the Arachnida and Crustacea : Investigations of Sars, Fredericq, Vandevelde, and Griffiths—The Nervous Systems of the Polyzoa, Brachiopoda, Mollusca, and Tunicata, &c. . 5 ‘ . 3 3 2 . 293 CHAPTER XI. The Organs of Special Sense, &c., in the Invertebrata : Tactile Sensi- bility and Sight in the Protozoa and Porifera—The Coelenterata: Rudimentary Eyes and Olfactory Organs in the Meduse—The Echinodermata : Tactile Sensibility ; Sense of Smell: Experiments of Griffiths; Sense of Hearing ; Eyes: Researches of Romanes and Ewart—The Sense-organs in the Trichoscolices, Annelida, Nematoscolices, Cheetognatha, and Myriapoda—Serse-organs in the Insecta: Tactile Organs ; The Senses of Taste, Smell, and Hearing ; Simple and Compound Eyes of Insects, Mosaic Vision; The “Voices ” of Insects—Sense-organs in the Crustacea : Blind Cave- crabs, Cirripedia, Crayfishes, &c.—Sense-organs in the Mollusca: Organs of Touch, Taste, Smell, Hearing, and Sight; The Cepha- lopod Eye—Intelligence or Reason in certain Invertebrates, &c. . 345 CHAPTER XII. Movements and Locomotion in the Invertebrata: In the Protozoa: Pseudopodia, Flagella, and Cilia as locomotive organs; Researches of Dallinger and Drysdale ; The Muscular Fibre in the Peduncle of Vorticella—Movements in the Porifera—Locomotion, &c., in the Celenterata: Researches of Romanes—Locomotion, &c., in the Trichoscolices, Annelida, Nematoscolices, and Myriapoda; Loco- xvi CONTENTS. motion, &c., in the Insecta: The Flight of Insects—Locomotion, &c., in the Arachnida, Crustacea, and Mollusca, &c. CHAPTER XIII. Reproduction and Development in the Invertebrata: Spontaneous APPENDIX . INDEX OF AUTHORITIES . SuBJEcT INDEX Generation, Gemmation, Fission, Endogenous Cell Formation, Parthenogenesis, Sexual Reproduction, Hermaphroditism, Sexual Elements of Reproduction, Fecundation, Development of the Embryo, and Conjugation—Reproduction in the Protozoa: Investi- gations of Dallinger and Drysdale and others—Reproduction, &c., in the Porifera, Cclenterata, Echinodermata, Trichoscolices, Anne- lida, Nematoscolices, Cheetognatha, Onychophora, and Myriapoda— Reproduction, &c.,in the Insecta: their Odours, Colours, Dances, and Music, as Agents in the Reproduction of the Insecta—Repro- duction in the Arachnida, Crustacea, Polyzoa, Brachiopoda, Mollusca, and Tunicata—Concluding Remarks: Pleomorphism, Origin of Life, &c. PAGE 374 + 399 + 457 . 461 - 465 THE PHYSIOLOGY OF THE INVERTEBRATA. CHAPTER I. INTRODUCTION. ANIMAL physiology may be defined as that branch of biology which is concerned in the elucidation of the various functions which take place in the animal economy. It is a branch of study quite distinct from morphology, chorology, and etio- logy ; and as a separate branch of biological science we propose to treat it in the following pages. Researches undertaken to investigate accurately the proper physiological functions of the various organs and tissues of the Invertebrata were greatly needed; and it is only during the last few years that certain biological chemists—fully equipped with the necessary manipulative skill—have con- siderably advanced this important but much-neglected branch of biology. If one studies any particular organ from only one aspect, incomplete or erroneous conclusions are apt to be drawn. For instance, the vesicular tissue lying in the rectal loop in Ascidia, and in some species extending over the intestine, is well known to be renal in function. This vesicular tissue is a true kidney physiologically ; morphologically it is another A 2 PHYSIOLOGY OF THE INVERTEBRATA. matter, and depends upon one’s definition of a true kidney. Embryologically these vesicles are the remains of a part of the original colon. As more attention has been paid to the morphology of the Tnwertedrata, it is not our object to speak of that branch of the subject further than is necessary; but in some cases the function of an organ or a tissue cannot be comprehended without referring to its anatomy. According to the great apostle* of biological thought, “the actions of living matter are termed its functions ; and these functions, varied as they are, may be reduced to three categories. They are either—(1) Functions which affect the material composition of the body, and determine its mass, which is the balance of the processes of waste on the one hand, and those of assimilation on the other. Or (2) they are functions which subserve the process of reproduction, which is essentially the detachment of a part endowed with the power of developing into an independent whole. Or (3) they are functions in virtue of which one part of the body is able to exert a direct influence on another, and the body, by its parts or as a whole, becomes a source of molar motion. The first may be termed sustentative, the second generative, and the third correlative functions. In the lowest forms of life the functions which have been enumerated are seen in their simplest forms, and they are exerted indifferently, or nearly so, by all parts of the protoplasmic body ; and the like is true of the functions of the body of even the highest organisms, so long as they are in the condition of the nucleated cell, which constitutes the starting-point of their development. But the first process in the development is the division of the germ into a number of morphological units or blastomeres, which eventually give rise to cells; and as each of these possesses the same physiological functions as the germ itself, it follows that each morphological * Prof, Huxley. PHYSIOLOGY OF THE INVERTEBRATA. 3 unit is also a physiological unit, and the multi-cellular mass is strictly a compound organism, made up of a multi- tude of physiologically independent cells. The physiological activities manifested by the complex whole represent the sum, or rather the resultant, of the separate and independent physio- logical activities resident in each of the simpler constituents of that whole. “The morphological changes which the cells undergo in the course of the further development of the organism do not affect their individuality; and, notwithstanding the modification and confluence of its constituent cells, the adult organism, however complex, is still an aggregate of morpho- logical units. Nor is it less an aggregate of physiological units, each of which retains its fundamental independence, though that independence becomes restricted in various ways. “ach cell, or that element of a tissue which proceeds from the modification of a cell, must needs retain its susten- tative functions so long as it grows or maintains a condition of equilibrium; but the most completely metamorphosed cells show no trace of the generative function, and many exhibit no correlative functions. Contrariwise, those cells of the adult organism which are the unmetamorphosed derivatives of the germ exhibit all the primary functions, not only nourishing themselves and growing, but multiplying and frequently showing more or less marked movements.” The cell theory, first ably worked out by Schwann, has led physiology, aided by chemical means, to. scrutinise more ‘profoundly the mechanism of the vital acts; it has taught it to refer them to their ultimate agents—that is, to the histo- logical elements themselves, which vary in function and in form in complex beings, and which we must consider as playing a part in the mechanism of organised beings analogous to that of atoms in chemical molecules. In the lowest animals all functions are performed by all ‘tissues: the sarcode of an amceba assimilates, breathes, 4 PHYSIOLOGY OF THE INVERTEBRATA. excretes, and reproduces—for no special part is set aside for the functions of digestion, of respiration, of excretion, of re- production. There seems to be in the lowest Invertebrates a confusion of organic materials and functions. Many of the Protozoa are endowed with motility and sensibility, with a sort of instinct ;* and yet, as far as we know at present, they are destitute of muscular and nervous elements. Possibly the sarcode is the rudiment, still undivided, of muscular fibre. But as we ascend gradually from lower to higher forms the differentiation becomes more marked, and we find par- ticular parts of the body reserved for special actions. But this differentiation passes through various stages before arriving at the most differentiated forms of animal life. As already stated, the single cell of the amceba performs many functions; and even when an organ has arrived at such a stage that it is quite distinct, it may have a dual or triple function—as, for instance, the pentagonal pyloric sac of Uraster rubens (one of the Asteridea) has been proved to have a dual function.t It is a digestive gland as well as an excretory organ, separating the nitrogenous products of the waste of the tissues, &c., from the blood in the form of uric acid, which is to be found in the five pouches of that organ. In The Origin of Species (chapter vi.) Darwin mentions the fact that “numerous cases could be given among the lower animals of the same organ performing at the same time wholly distinct functions: thus, in the larva of the dragon-fly . . . . the alimentary canal respires, digests, and excretes.” But as we pass from the lower to the higher forms of animal life the various organs have special functions assigned them. This rule not only applies to the physio- logical functions of various organs, but also to their ana- * See Binet’s Psychic Life of Micro-Organisms. + See Dr. A. B. Griffiths’ papers in the Proceedings of Royal Society of London, vol. 44, p. 325 ; and the Proceedings of Royal Society of Edinburgh, vol. 15, p. III. PHYSIOLOGY OF THE INVERTEBRATA. 5 tomical elements. The more simple is the organisation of an animal, taken as a whole, the simpler is also the structure of each of the orders of anatomical elements. Tor example, the muscular fibres of the Radiata, Annulosa, and Mollusca are simpler than the same elements in the crab (Robin), But in the higher animals there is a complete differentiation of parts into organs having special physiological functions and varied degrees of structure. In fact, the important law of Von Baer —the law of progress from the general to the special ”— reigns supreme in the organic world. In the higher Invertebrates the various organs are localised in different parts of the body. One area is restricted to digestion, another to circulation, a third to respiration, and a fourth to reproduction. The more highly organised the animal, the more divided is its body into separate and dis- tinct organs, each endowed with its own special function. The main object of this volume will be to consider in detail the physiological functions of the various organs in the Invertebrata ; but as it is impossible to investigate func- tions without a knowledge of the organs performing them, we shall refer (when necessary to a proper understanding of the mechanism described) to their anatomy. As we shall have to allude to numerous classes, &c., of animals, a classification of the Invertebrata will hardly be out of place in concluding the present chapter. The following tables are founded on the classifications of Professor Huxley :— PROTOZOA. Monera. Protoplasta. Gregarinida, Catallacta. Infusoria. Foraminifera. Radiolaria. (a) Heliozoa. (6) Cytophora. PHYSIOLOGY OF THE INVERTEBRATA. 6 ‘eleiodeipey, (48s0dny) e[[eLoovyo, xesorody (f) seprdung (a) xbye1opieg (p) epryjueo, (2) epiyyedyuy (q) vaprloyselg epluryoy (7) epoorquy, (7) ‘vpltaseolpy . elpelooexa yy eraesig (2) é " vopriség spiodrqny, (a) eyenyosjog ‘Baploullo ezptiodorpay (p) B}eVYOOSII[O Baplo}yseD vaplulyony epruofsory (v) Bal[e1090.1pAFT wt8uodstae9 Boulpuiiy, BpoyeUely, vapid wpiuosi0y (9) eioydoipsyy wrsuodstoritg vardydey BIOTTIOY vaplieysy exprnyeuueg (”) eiroydoosiq sersuodsojzvieg vyemoysozs BlIIV{[aqAuy, vaplunyyoloy B][210003009 eioydouoydig eersuodsox AJ ‘eplpuuy *SadT[OOSONOIL, “eyRULIApOUTyo eee ai i ‘episuodg . ~eye19qU9{O IO BIOFIIO ‘SHIMMY GIOTANNY ‘IIT “SaTaaS . IVNYAGONIHOR "II "SUIUAY OILAHAOOZ ‘J ‘VOZV.LEW 7 PHYSIOLOGY OF THE INVERTEBRATA. BINOIO’ A vrlncpoulg ernowouy epodeutoyg ; epodosy epodryduy wiped tig B.aydoalog ereydeooziyy vioydousm {py epodadoy viaqdoi1neN epooel4soQ VBIySesOIyILY e1aydopidaT BIDN0PRTO eulouvIy eioqdiq vpodol[éqg BUlLleVoy vyoqoucyy epododiq BIQOTL, epruosouodg | viaydodyotpoxyeg | vpodtjodryory eleydaooyjuvoy vausoydrx Bo0TyO1Y e103doywO evpodoriyo , eyoudys1oyeuleN| epneydding | eptmojseyueg einueskyy, | eyyeudadsojorg | Byvayousjoj}OIg VyLseg BaployeuUaN “@90e]SNIO “epluyovly “eqyoosuy “epoderid ‘eroydoyo sug, “epodoiqyiy ‘eyyeusoyeyQ | ‘saotjoosoyeulaN ‘SHIUDG OLOZOMHLUY "AT *ponuiquoo—Y¥ OZV LAN 8 PHYSIOLOGY OF THE INVERTEBRATA. METAZOA—continued. V. MALACOZOIC SERIES. Malacoscolices. Polyzoa. Brachiopoda. Mollusca.” VI. PHARYNGOP- NEUSTAL SERIES. Podostomata Phylactolemata Gymnolemata Tretenterata Clistenterata Lamellibran- chiata Scaphopoda Hemichordata Urochordata (Tunicata) Pedicellinea Polyplacophora Heteropoda Gasteropoda (a) Pulmogas- teropoda (6) Branchio- gasteropoda Pteropoda Cephalopoda (a) Dibran- chiata | (bd) Tetra- branchiata If animals are looked upon as machines for doing work, they differ from one another in the extent to which this work is subdivided. ‘Each subordinate group of actions or Junctions is allotted to a particular portion of the body, which thus becomes the organ of those functions; and the extent to which this division of physiological labour is carried differs in degree within the limits of each common plan, and is the chief cause of the diversity in the working out of the common plan of a group exhibited by its members. Moreover, there are certain types which never attain the same degree of physiological differentiation as others do. ‘Thus, some of the Protozoa attain a grade of physiological complexity as high as that which is reached by the lower PAYSIOLOGY OF THE INVERTEBRAT\1, 9 Metazoa. And notwithstanding the multiplicity of its parts, no Kchinoderm is so highly differentiated as a physiological machine as isasnail..... It is not mere multiplication of organs which constitutes physiological differentiation; but the multiplication of organs of different functions in the first place, and the degree in which they are co-ordinated, so as to work a common end, in the second place. Thus, a lobster is a higher animal, from a physiological point of view, than a Cyclops, not: because it has more distinguishable organs, but because these organs are so modified as to per- form a much greater variety of functions, while they are all co-ordinated towards the maintenance of the animal by its well-developed nervous system and sense-organs. But it is impossible to say that, v.y., the Arthropoda, as a whole, are physiologically higher than the Mollusca, inasmuch as the simplest embodiments of the common plan of the Arthropoda are less differentiated, physiologically, than the great majority of Mollusks.” (Huxley.) CHAPTER II. THE CHEMISTRY OF PROTOPLASM. BEFORE commencing our study of the physiology of the Invertebrata in detail, we offer a few remarks concerning the chemical nature and supposed composition of protoplasm,* or albumin. As the complex molecule of albumin is the basis of all physiological functions—in fact, “the physical basis of life”—no apology is needed in bringing this chapter before the attention of our readers. Many chemists have submitted albumin to ultimate ana- lyses. Among these may be mentioned the following :— ae | & s = = a 2a | 28 ge: ) Fe ae: poe |e ee | ae a Carbon 53-4 | 52-9 | 53-3 | 53-5 | 53-4 | 54-3 | 53-1 | 52.6 Hydrogen . Jet 7.2 Jos 7:2 7.0 7.1 7.0 7.1 Nitrogen . 15.8 | 15.6 | 15.7 | 15.8 | 15.7 | 15.9 | — | 16.3 Oxygen _ — | 22.1 Sr 122.3) |) = = Sulphur — _ 18 | 1.7 16 | — 1.3 | 18 Besides the above elements, there is always present in proto- plasm. a small, but variable, amount of ash, which contains phosphorus and other elements in infinitesimal quantities. 1 * From mpdros (first), and mAdoua (formed substance). PHYSIVULOGY OF THE INVERTEBRATA. II Albumins are incapable of being crystallised, or, if they are present in some tissues in an apparently crystalline condition, they are not crystals in the true sense of the word. These pseudo-crystals are readily recognisable beneath a microscope, for they dissolve in a dilute solution of potash, and are stained yellow by nitric acid. A solution of iodine colours albumin or protoplasm brown, while sulphuric acid colours it red. Carmine deeply stains dead protoplasm, but has no action on living protoplasm. Dilute mineral acids and alcohol coagulate albumin; but it is soluble in concentrated hydrochloric acid. According to Dr. F. Hoppe-Seyler,* albumin has a specific rotatory power of from — 35.5° to—56°. A temperature of about 50° C. co- agulates albumin ; 7.¢., it is converted into an isomeric modi- fication by the action of heat, as well as by dilwtr acids, as already stated. Albumin combines with hydrochloric, sulphuric, phosphoric, and acetic acids, forming albuminates. It also combines with certain bases and salts, forming similar compounds. It was the albuminate of potash which gave Lieberkiihn the means of ascertaining the empirical formula of this complex chemical compound. Lieberkiihn’s formula for albumin is represented as follows :— CHa 2Oy8- The above formula gives no idea of the atomic constitution of albumin. Dr. C. Schorlemmer, F.R.S. (Rise and Development of Organic Chemistry, p.123) says: ‘The enigma of life can only be solved by the discovery of the synthesis of an albuminous compound.” The direct synthesis of albumin has not yet been performed ; but during the past nine or ten years some excellent work has been done by Loéw and Bokorny in this line of research, which opens a vast field of inquiry for the physiological chemist. These chemists have paved the * Handbuch der Physiologisch- und Pathologisch- Chemischen Analyse. 12 PHYSIOLOGY OF THE INVERTEBRATA. way for the synthesis of this compound; and in their re- - searches * on living and dead protoplasm, they have arrived : at the conclusion that living protoplasm contains an alde- hydic group of elements. In their experiments on the living protoplasm of the fresh-water algze, Spirogyra and Zygnema, growing in spring-water containing 0.1 per cent. of dipotas- sium phosphate and ammonium nitrate, Loéw and Bokorny Sine eet. found that the living cells had the power of reducing silver © from very dilute alkaline solutions of salts of that metal. — Dead cells do not give this reaction. Loéw and Bokorny have experimented (with the same result) upon the cotyledons of Helianthus annus, the epidermal hairs of plants, the sap of the pine and oak, the cells of fruits, fungi, and also many of the Jnfusoria. They conclude from these observations that living protoplasm contains an aldehydic group of elements, whereas there is no such group in dead protoplasm. Reinke (Berichte der Deutschen Chemischen Gesellschaft, vol. 14, p. 21443 vol. 15, p. 107) says that the aldehydic nature, as tested by an alkaline silver solution, is only a property of the protoplasm of the chlorophyll, for he failed to find it in the protoplasm of cells in unopened buds ; therefore he thinks it is probable that it is formed only in the presence of sunlight by the chlorophyll corpuscles. Mori (Chemisches Centralblatt [3], vol. 13, p. 565) considers that formic aldehyde is the first product of assimilation, for he detected (by the action of a solution of silver nitrate) a substance which reduced the nitrate in plants containing chlorophyll which had been exposed to sunlight. When the same plants were left for about forty-eight hours in a dark place, so that on applying the test again the first products of assimilation might be used up, no reduction of silver nitrate * Dre Chemische Kraftquelle im lebenden Protoplasma; also Berichte der Deutschen Chemischen Gesellschaft, vol. 14, p. 2508; vol. 15, p. 6953 Pfliiger’s Archiv fiir Physiologie, vol. 25, p. 150; vol. 45, p. 199; and Bot. Centr. 1889, :p. 39- PHYSIOLOGY OF THE INVERTEBRATA. 13 took place. Therefore, both Reinke and Mori support Baéyer’s theory that formic aldehyde is formed by chlorophyll under the influence of light from the carbonic acid of the atmosphere in the presence of water: CO, = CO + O 3% 246 H,O = H, + O COH. Dr. Kretzschmar (Biedermann’s Centralblatt fiir Agricultur- Chemie, 1882, p. 830), on the other hand, states that the protoplasm of living and dead cells reduces silver from an alkaline solution of the salts of that metal, and so concludes that this reagent fails to distinguish between living ans dead protoplasm. The author * has also shown that the alkaline solutions of copper (cupric) and silver salts are reduced by both living and dead protoplasm. In fact, these reagents fail to dis- tinguish between living and dead protoplasm, but these investigations do not disprove Loéw and Bokorny’s idea that protoplasm (i.c., living and dead) contains an aldehydic group of elements; but this particular group of elements is only one of many combinations of elements forming the complex molecule of albumin. When we study the decomposition of albumin (both animal and vegetal) by the agency of different chemical reagents, we begin to see that its chemical constitution is not repre- sented by any simple group of elements. Many of the substances found in the animal body are products of the metabolism of protoplasm—eg., urea (CN,H,O), creatine (C,H,N,O,), creatinine (C;H,N,O), cholesterine (C,,H,,O,), uric acid (C,H,N,O,), guanin (C, H 5N;0), leucin (C,H,,NO,), tyrosin (C,H,,NO,), &c. Professor P. Schiitzenberger (Comptes-Rendus, vol. 106, p. 1407) has shown experimentally that when albumin is boiled with barium hydroxide, it yields leucin, leucein, and the products of hydration of urea and oxamide; and Dr. W. * The Chemical News, vol. 48, p. 179; Journal of Royal Microscopical Society, 1884, p. 249; Journ. Chem. Soc. 1884, p. 202. 14 PHYSIOLOGY OF THE INVERTEBRATA. Palladin (Berichte der Deutschen Botan. (tescllschaft, vol. 6, p- 296), and Drs. Schulze and Kisser (Landw. Versuchs-Stat., os 36, p. 1), have shown that vegetal protoplasm can be made to yield tyrosin, leucin, xanthine, hypoxanthine, and similar compounds, which are undoubtedly some of the pro- ducts of the decomposition of albumin occurring in the bodies of living animals. If protoplasm or albumin gives rise to such compounds as the above, we have good reason to believe that its constitution is more complex than Loéw and Bokorny would have us suppose. Many of the substances formed during the decomposition of albumin have been artificially prepared in the laboratory. For instance, leucin is very largely diffused in the animal organism, and has been obtained artificially by oxidising amylic alcohol with potassium bi- chromate and sulphuric acid, and then distilling, when the following reaction occurs : 2C,H,,HO + 0, = 2C,H,COH + 2H,0. [Amylic alcohol.] [Valeric aldehyde.] When valeric aldehyde is treated with ammonia, valeral ammonia is formed, and if the latter compound is digested with hydrocyanic and hydrochloric acids it is converted into leucin : («) C,H,COH + NH, = C,H,CH(NH,)OH. [Valeral ammonia.] (0) C,H,CN(NH,)OH + HCN + H,O = NH. CHLON{ Cob8 ‘ec . . [Leucin.] Amido-isovaleric acid (a substance which occurs in the pancreas of the ox), amido-butyric acid, and amido-propionic acid, have been obtained by Schiitzenberger* from albumin ; and all these substances have been obtained artificially in the Jaboratory. * See Comptes-Tendus, vols. 81 and 84. PHYSIOLOGY OF THE INVERTEBRATA. 15 Dr. Guckelberger (Liebig’s Annalen, vol. 64, p. 39) obtained caproic, valeric, butyric, propionic, acetic, and formic acids by oxidising albumin with potassium bichromate and sulphuric acid. As these organic acids can be obtained artificially from cyan-alcohols, it has been stated that albumin or protoplasm is a compound of cyan-alcohols or cyanhydrins united to a benzene nucleus. By looking upon albumin as built up of cyan-alcohols, we can readily account for the formation of such compounds as glycocine, leucin, the acids of the C,H.,,,COOH series, as well as those of the lactic series—occurring in the animal body. In the year 1828 Wohler converted ammonium cyanate into urea; and Dr. Pfliiger (Pfliiger’s Archiv, vol. 10, p. 337), in calling attention to the great molecular energy of the cyanogen compounds, suggested that the functional meta- bolism of protoplasm by which energy is set free, may be compared to the conversion of the energetic unstable cyanogen compounds into the less energetic and more stable amides. In other words, that “ammonium cyanate is a type of living, and urea of dead nitrogen, and the conversion of the former into the latter is an image of the essential change which takes place when a living proteid dies.”* Dr. P. W. Latham, in “ The Croonian Lectures” for 1886, ably argues from experimental data that albumin or proto- plasm has the following constitutional formula : * See Foster’s Text-bool: of Physiology (4th ed.), p. 749. 16 PHYSIOLOGY OF THE INVERTEBRATA. SO,H-—C HO \ C_H (OH C:Hw» 1 GNOH { CH CNOH HH Cs «| ONOH a. Cus (CNOHL HH, | CH \CNOH PHYSIOLOGY OF THE INVERTEBRATA. 17 This substance, whose composition is C,,H,,,N,,0,,S, differs from Dr. Lieberkiihn’s empirical formula (C,,H,,,N,,0,.5) only by six atoms of hydrogen. According to Latham, albumin “is a compound of cyan- alcohols united to a benzene nucleus, these being derived from the various aldehydes, glycols, and ketones, or that they may be formed in the living body by the dehydration of the amido-acids; that from a body so constituted all the different substances may be obtained which have been extracted from albuminoid tissues; that lactic acid is obtained in two ways, either from CHE on or from changes and condensation in ci with the simultaneous development of carbonic anhydride, a result which is brought about when a muscle contracts or when it dies; and that urea may be obtained from one series of cyan-alcohols with the production of a cyan-alcohol higher in the series. “Such a compound of cyan-alcohols therefore, presenting so much resemblance in its properties to albumin, cannot differ very widely (though perhaps not absolutely correct) from the molecular constitution of albumin. “Taking this view, then, of the constitution of albumin, the following may be given as a summary of the nutritive changes: The amido-acids—glycocine, leucin, tyrosin, &c.—in passing from the alimentary canal to the liver, are dehydrated, forming a series of cyan-hydrins or cyan-alcohols attached to a benzene nucleus, and then pass into the circulation. In the tissues these cyan-alcohols, partly by condensation, partly by hydration and oxidation, give rise to the various effete products which are eliminated from the system in the form of carbonic acid and urea.” There is no doubt that the theory of protoplasm being a complex molecule,* derived from various aldehydes, glycols, * See also a paper by Dr. P. Schiitzen in the Comptes-Rendus, tome 112, p. 198. B 18 PHVSIOLOGY OF THE INVERTEBRATA. and ketones, aids us considerably in understanding the origin of various secretory products found in the Invertebrata as well as in the Vertebrata. Living protoplasm is a substance which is constantly undergoing chemical changes. It is the chemical and physical properties of this complex substance, diversely’ modified, which underlie all the vital functions—nutrition, | secretion, growth, reproduction, motility, &c. Of ‘hess functions the most important is nutrition, the double and perpetual movement of molecular renovation of the living substance. Without nutrition there can be no growth, no reproduction, no movement, and in fact no physiological function whatsoever. It has been stated that “life can be conceived of as reduced to its most simple expression, to- mere nutrition. A being capable of nourishing itself, and. destitute of every other property or function, which, after all,. is only a simple extension of the nutritive property, its life will be only an individual life;” a time will come when the nutritive functions will have less energy—then “the nutritive residue, incompletely expulsed, will impregnate the living tissues and liquids obstructing them.” Such obstruction necessarily interferes with physiological activity, and ulti- mately ends in complete arrest. When this stage arrives,. the organism, no longer capable of adjusting its “internal relations to external relations,”* undergoes those chemico- biological changes which finally result in its molecules (as: new combinations) once more re-entering the mineral king- dom—or the world of inanimation. On the other hand, if the nutritive activity of a living organism “is sufficiently energetic to rise, as it were, to excess, even to growth and reproduction, the being is sure of living in its offspring; it: fills its place in the innumerable crowd of living beings, and can even, according to the doctrine of evolution, become the source of a superior organised type, can ascend in the hierarchy of life,” * Mr. Herbert Spencer's definition of “life.” PHYSIOLOGY OF THE INVERTEBRATA, 19 From what has been said in this chapter it will be gathered that “(a mass of living protoplasm is simply a molecular machine of great complexity; but it must not be supposed that the differences between living and not-living matter are such as to bear out the assumption that the forces at work in the one are different from those which are to be met with in the other. Considered apart from the phenomena of con- sciousness,” Professor Huxley says, “the phenomena of life are all dependent upon the working of the same physical and chemical forces as those which are active in the rest of the world.”. CHAPTER III. DIGESTION IN THE INVERTEBRATA. Digestion in General. In this chapter we have to trace the function of digestion from its lowest or most general form to that stage when it nearly approaches in complexity the digestive process occur- ring in the backboned animals. Digestion is that process whereby food is taken into an organism, and there made fit to become part thereof—i.ze., the digested food becomes assimilation, for in the living organism, however low in the animal scale, there is never any repose. The organism has to reckon with its environ- . ment; oxidation is always going on, therefore the digested food is employed in the work of reparation and of recon- ' struction. Animal organisms cannot live without constantly © absorbing complex organic substances. As they cannot manufacture these substances, they obtain them from other animals or from plants; hence we may divide even the lowest animals into either carnivorous, herbivorous, or omni- vorous forms. For the process of digestion the organism is furnished with either a general or a special apparatus, whose office consists in forming a kind of physiological kitchen to modify the raw materials, which renders them more suitable for assimilation or absorption. This apparatus is the digestive system. Many of the lowest animals are comparable to the lowest plants—in fact, the two great kingdoms may be said to over- PHYSIOLOGY OF THE INVERTEBRATA. 21 lap, for there is no sharp line of demarcation, as far as digestion is concerned, between the Protozoa and the Bacteria. For instance, if one compares the Gregarine (a parasite) to a bacterium or any other fungus, both forms live by assimilating the products of decomposed organisms, or rather organic matter ; thus showing that the lowest members of the animal kingdom are closely allied to the lowest members of the vegetal kingdom. The mode of nutrition among the lowest animals is not uniform—a fact which ought not to appear remarkable when we bear in mind that these animals are made up of all manner of heterogeneous beings that have nothing in common save the microscopic smallness of their bodies and the simplicity of their structure. In the animal kingdom three main types of nutrition may be distinguished :— (1) Holophytic or vegetal nutrition. (2) Saprophytic or endosmosis nutrition. (3) Animal nutrition. The first type of nutrition or digestion is found in animal cells that contain chlorophyll, and that nourish themselves by forming assimilable substances from ingredients taken from the medium in which they live. It should be borne in mind that the function of chlorophyll in the animal as well as in the vegetal kingdom is essentially that of nutrition, and not of respiration; although we shall see later in this volume that many of the animal chromophylls (using the word in its widest sense) have respiratory as well as other functions. A large number of the lower animals contain chlorophyll, but these animals are met with chiefly among the Flagellata. Their assimilative or digestive organs hear the name of chro- matophores. These chromatophores are small granular masses of protoplasm impregnated with a colouring substance. In the centre of the chromatophore is a small bright globule which is said to possess the same chemical reactions as 22 PHYSIOLOGY OF THE INVERTEBRATA. nuclein. Dr. Schmitz has named this small globule pyrenoid.* The function of the pyrenoid is the formation of starch and similar carbohydrates. This is a process of digestion akin to the vegetal kingdom. It is interesting to note that “the Huglene (belonging to — the Flagellata) might nourish themselves as animals do, for they have a mouth and a digestive apparatus, The buccal, or oral, aperture opens in the anterior end at the base of the Fic. 1.—EuGLENA. A= C, contractile vacuole; E, eye or ocular spot; P, disk of paramylone; N, nucleus; Ch, chromatophores. B = M, mouth; E, eye; D, contractile reservoir; C, contractile vacuole, flagellum, and is connected with a short gullet or esophagus (Fig. 1). Nevertheless the Huglena is never seen using its mouth for swallowing alimentary particles. A curious problem - is involved here. If it is true, as has been claimed, that it is the function that makes the organ, how do we explain the existence, and especially the genesis, of this digestive apparatus, which performs no function?” The second type of nutrition or, digestion in the animal * From mvp, a nucleus. PHYSIOLOGY OF THE INVERTEBRATA. 23 ‘kingdom is that of saprophytic or endosmosis nutrition, It occurs in the Gregarinida, &c,, and is the simplest type of nutrition, for the organism simply nourishes itself by absorbing, through the whole surface of its body, the liquids containing decomposing or digested animal and vegetal substances. The third and highest type of nutrition occurs in all animals except those coming under the previously mentioned types. In the highest type of nutrition the organism ‘seizes solid alimentary particles, and nourishes itself after the fashion of an animal, whether it be by means of a permanent mouth, or by means of an adventitious one, improvised at the moment of need.” Before describing in detail the great physiological functions, it may be stated that “in organised beings, from the lowest to the highest, the most differentiated, there is a graduated hierarchy. From the physiological confusion which exists at the lowest step of the ladder we pass, step by step, through series of organic models, better and better finished, to the most perfect specialisation. Nothing is more interesting than this seriation of organs, especially from the point of view of the great doctrine of evolution, which more and more -vivifies all the branches of natural history.” THE PRoTOzOA. (a) The Gregarina.—This animal (Fig. 2, 4) infests the interior of cockroaches, earthworms, and other Invertebrates. It well illustrates an example of endosmosis or saprophytic nutrition, for it absorbs or imbibes fluid nutriment by every part of its surface, and most probably the effete matter is likewise given out at every part of its surface. Although the anatomical structure of the Gregarina gives it a higher rank in the zoological scale than the Amba, the latter organism is certainly its superior in the matter of digestion. It may be stated that the gradual specialisation of 24 PHYSIOLOGY OF THE INVERTEBRATA. different functions do not follow the same lines in the anima! series. Nor will the advance of particular functions keep pace with the advance in anatomical structure. As far as ae FIG. 2.—VARIOUS PROTOZOA. A = Gregarina. B= Amceba. C= Magosphzra. D = Actinophrys. E = Actinospherium. F = Part of E highly magnified. v = contractile vacuole. 2 = nucleus. structure is concerned, the Gregarina ranks higher than the Ameba. ; (b) The Amaba.—In the Protoplasta, to which the Amaba belongs, we have a distinct advance in the mechanism of ‘PHYSIOLOGY OF THE INVERTEBRATA. 25 digestion, for in this order one beholds the very birth of the digestive function. The Amada (Fig. 2, B) seizes its food by extending some portion of its cell. The extended portion is known as a pseudopodium. The pseudopodium, after seizing the particles of food, retract, and the food becomes incorporated in the interior of the cell, which has the property of digesting and absorbing the nutritive portion of the food and ejecting the non-digested portion. In some forms of the Protoplasta pseudopodia are extended from any part of the protoplasmic cell; whereas in others (e.g., Pamphagus) these non-differentiated prehensile organs are extended from one particular region only of the cell, In Arcella and Difiwgia, having an external covering or shell, the pseudopodia are extended only from the single opening present in each shell. There is another point of difference between the Gregarina and the Ameba—namely, the latter organism has a contractile vacuole. It is possible that this vacuole is in some way directly connected with the function of digestion, but there is no doubt that it performs more than one function, for the author has shown that at times the contractile vacuole of the Ameba acts as a renal organ (see later in this volume). As far as the function of digestion is concerned in the Protoplasta, every part of the protoplasm may be made to serve as a digestive cavity in enveloping the food particles. “A mouth region and an anal region are marked off for each particular particle of food, but there is no mouth and there is no anus.” (c) The Foraminifera.—These complex Protozoa may be looked upon as-colonies of Amabe connected together and surrounded by a complex shell. They have been divided into the Perforata and the Imperforata, according to whether the shell is either perforated or imperforated. In the former class, the shell contains many apertures, through which the pseudopodia of the particular individual dwelling within that 26 PHYSIOLOGY OF THE INVERTEBRATA. division of the shell are protruded. In the Imperforata “the food for the whole colony is seized and taken in by the pseudopodia given off by the individual segment found in the last-formed, and therefore most free cavity of the shell.” Nearly all the Foraminifera are marine animals; whereas the Amebe chiefly inhabit fresh water, although some are found in the sea. (d) The Catallacta.—There is a morphological difference. between this order and the Protoplasta, although the mechan- isms of their digestive functions are closely allied. Magosphera (Fig. 2,c) which represents the Catallacta, protrudes pseudopodia which are broad at the base, while the other extremities break up into a number of very fine filaments. We may term these secondary pseudopodia. Magosphera has a well-marked contractile vacuole. (ec) The Radiolaria.—One of the most common of this order is Fee Opening. bss Fic. 25.—(¢ and 4) SALIVARY GLAND OF BLATTA. the crop. A quantity of the secretion* was extracted by crushing about sixty glands of cockroaches, which had been recently killed. The secretion was alkaline to test-papers. A portion of the secretion was added to a small quantity of starch, which was converted into glucose in twelve minutes. * Griffiths, in Proc. Roy. oc, Edinb., vol. 14, p. 234; and Chemical Neva, vol, 52, p. 195. PHYSIOLOGY OF THE INVERTEBRATA. 93 The presence of glucose was proved by the formation of red cuprous oxide by the action of Fehling’s solution. Another portion of the secretion was distilled in a minia- ture retort (made of glass tubing) with dilute sulphuric acid. To the distillate ferric chloride was added, which produced a red colour, indicating the presence of sulphocyanates. The secretion of these glands yields a small quantity of ash, which contains calcium phosphate. The soluble ferment of this secretion may be isolated by precipitating an infusion of the glands obtained from a large number of these insects with dilute phosphoric acid, adding lime-water, and filtering. The precipitate is then dissolved in distilled water, and re-precipitated by alcohol. This precipitate converts starch into glucose, but has no action on fibrin; in other words, it has a similar action to ptyalin —the ferment of the saliva of the higher animals. It is probable that in Blatta there are terminations of the nerves in these salivary glands. It may be that these nerve- endings affect the protoplasmic substance of the cells forming the ferment, which has the property of converting starch into glucose. The crop of Blatta simply acts as a receptacle to store up the rapidly swallowed food until time is afforded for the food to be passed on to the true stomach. The gizzard or proventriculus has been described in the last chapter. It is considered by some to be an internal masticatory apparatus, but M. Plateau* considers that the proventriculus of Blatia acts simply as a strainer. The chylific ventriculus may be termed the true stomach of Blatta, for it is probable that digestion is more active in this than in any other part of the alimentary canal. It is lined with epithelium, and often contains peptones, The pyloric ceca, situated in front of the chylific ventri- * See his papers on the digestion in the Myr iapoda, Insecta, and Arachnida, published in the Bulletin de Académie Royale des Se‘ ences -de Be'gique, 1874-78. 94 PHYSIOLOGY OF THE INVERTEBRATA. culus, have been directly proved by the author* to be pancreatic in function. The secretion from these ceca flows into the chylific ventriculus, where digestion proceeds. a 4 = @ Bo & & Ss ow n = | Il v L gg Aas Bs a o 6 x 1 8 OD o ~ Pp i Ros “8 of = a "Ss S 4 4 ae & < me at By 8 Pe s 2 it Ba EBs o GB 2 a €ou., Oo o & OF vg oO @ | 3S aux a < “3 #2 Zo. we 5 8 all 4am 3 a %&% ~ bf 2 a ai 8. <6 an ee ne a 8 ~~ 8 = 8 3 a 2 4 dl xa tw Es | sf ey S 4 65 ; bP eS ge = Br ag S| a 4 ss Il g 8 iS a s 8 a 5 y a < og In the carnivorous Libellula (the dragon-fly) there is no crop or gizzard, only the chylific ventriculus is present; the * Griffiths, in Proc. Roy. Soc. Edinb., vol. 14, p. 237. PHYSIOLOGY OF THE INVERTEBRATA. 95: fluids within this organ are always slightly alkaline, and an infusion of about twenty of these organs readily converted starch into glucose, and digested fibrin. (6) The Lepidoptera—As an example of this important order we describe the physiology of the alimentary canal of the larva and imago of Pontia brassicw (the large white cabbage butterfly). The alimentary canal of the larva (Fig. 26, a) agrees closely with the general Lepidopterous type. The mouth opens into a pharynx lined by a dark, firm cuticula, and into the latter open two ducts from a pair of well-developed salivary glands. These glands form elongated tubes, gra- dually diminishing in diameter towards the posterior ends. The cesophagus is very narrow and short. It leads into a long chylific stomach, which opens into a short duct. Behind the stomach the intestine consists of four parts: first, a short, constricted piece; second, a dilated, oval division; third, the short rectum; and fourth, the anal tube. The stomach has an epithelium lining, which is thrown up into folds so as to form imperfectly differentiated glandular follicles. At the posterior end of the stomach are the Malpighian tubules. Fig. 26, B, represents the alimentary canal of the imago of Pontia. The pharynx passes into a narrow, but long, ceso- phagus leading to the crop or food receptacle. This crop is entirely absent in the larval, but is developed in the pupal stage. The stomach is much smaller than in the larva, but its lining is also thrown up into glandular follicles. The posterior end of the stomach leads into a long and peculiarly coiled small intestine. The intestine passes into the wide terminal division, the rectum, from the front end of which there is a curved blind caecum or pouch. In the imago of Pontia there are also a’ pair of well- developed salivary glands. The secretion of the salivary glands is alkaline to test- papers, and readily converts starch into glucose. It has, 96 PHYSIOLOGY OF THE INVERTEBRATA. however, no action on fibrin. It contains sulphocyanates, proved by the red colour produced by ferric chloride with a drop of the secretion. The stomach of both the larva and imago contains glandular follicles. These secrete a digestive : fluid, which answers in every way to that of a Vertebrate pancreas. The Malpighian tubules are well-developed in the imago, as well as in the larva of Pontia. Their function is that of a renal organ, but this subject will be considered in detail in our chapter on excretion. It may be stated in passing, that according to Dr. B. T. Lowne, F.L.S.,* the Malpighian tubules of Calliphora erythrocephala (the blow-fly) are “hepatic” in function. If by hepatic he means that these tubules have the function of a Vertebrate liver, his conclusions are erroneous, for neither biliary acids nor glycogen are present in these tubules. Again, if Dr. Lowne means by “ hepatic” that they have a pancreatic function, this is also erroneous, because these tubules do not yield any digestive ferment or ferments. On the other hand, the Malpighian tubules of the Diptera, including Calliphora, readily yield uric acid; and there is little doubt that they are physiologically the kidneys of the animal; although, concerning their place of develop- | ment from the alimentary canal, as well as from other considerations, they are the homologues of hepatic organs (liver). (¢) The Hymenoptera.—The structure of the alimentary canal of Apis (the bee) has ‘already been given. The long stomach is furnished internally with small. glandular follicles, and by making an alkaline extract of the stomachs obtained from a large number of bees (which had been kept for some time without food), the extract contained a ferment which hydrolyzes starch, and digests fibrin, although feebly. In fact, it answers to the characteristic tests of trypsin or pancreatin. An alcoholic extract of the bee’s stomach does * The Anatomy, Physiology, Morphology, and Development of the Blowjfly (1890). PHYSIOLOGY OF THE INVERTEBRATA. 97 not contain the smallest trace of biliary acids, pigments, or glycogen. Dr. A. von Planta* has recently investigated the juice, or the sticky substance, which the working bees store in the cells of the larvee of the queens, drones, and workers. Leuckartt regarded it as the product of the true stomach (see Fig. 8c) of the working bees, which they vomit into the cells in the same way that honey is vomited from the honey-bag (see Fig. 8b). Fisher and others regarded it as the product of the saliyary glands of the bees. Schinfeld has more recently shown that Leuckart’s original view is the correct one. He showed that the saliva can be easily obtained from the salivary glands of the head and thorax, and that it is very different from the food-juice deposited in the cells by the bees; and that, moreover, the juice is similar, both chemically and microscopically, to the contents of the bee’s true stomach; he showed also, from the consideration of certain anatomical and physiological pecu- liarities of the bee, such as the position of the mouth, the inability of the bee to spit, &c., that the view of this substance being saliva is quite untenable. Certain observers have to this replied, that a bee cannot vomit the contents of its true stomach, because of a valve which intervenes between it and the honey-stomach or bag (see Fig. 82) ; but Schénfeld has shown that the structure, mistaken for a valve, has not the function of one, but is in reality an internal mouth, over which the animal has voluntary control, and by means of which it is able to eat and drink the contents of the honey- stomach when necessity or inclination arises. By light pressure on the stomach, and stretching out the animal’s neck, the contents of the stomach can be easily pressed out. Dr. A. von Planta’s investigations entirely confirm Schén- feld’s view, that the food-juice comes from the bee’s true stomach. The subject was investigated from the point of * Zeitschrift Physiol. Chemie, vol. 12, p. 327. + Deutsche Bienenzeitung, 1854-5. 98 PHYSIOLOGY OF THE INVERTEBRATA. view of its chemical composition, and care, also, was taken to investigate, individually, the juice as occurring in: the cells of three varieties of bees—queens, drones, and workers. Some preliminary microscopical examinations of this sub- stance yielded the following results, which are quite in accord with the subsequent chemical analyses :— (1) The food of the queen-bee larvze is the same during the whole of the larval period ; it is free from pollen grains, which have been reduced to a thickish but homogeneous juice by ue digestive action of the bee’s stomach. (2) The food of the larval drones is also, during the first four days of the larval period, free from pollen, and appears to have been completely digested previously. After four days their food is rich in pollen grains, which have, however, under- gone a certain amount of digestion. The food-stuff of the larvee is probably formed from bee-bread. The following table gives the average percentages obtained from several analyses :— Food-stuff of— Female or | Drones or Neuters or Queen Bees. Males, Working-Bees Water z : 69.38 % 72.75 % | 71.63 % Total solids. : ‘ ‘ 30.62 ,, 27.255, ; 28.375, Nitrogenous matter 45-14,, 43-79 5; | 51.21 ,, Inthe | Fat. 3 ‘ 13.55 5 8.32 ,, 6.84 ,, Solids |Glucose . ‘ 20.39 ,, 24.03 ,, 27.65 Ash. 2 e r 4.06 ,, 2.02 ,, _ __All these food-stuffs are rich in nitrogen; all were of a greyish white colour; and that of the queen-bee was the stickiest, while that of the working-bees was the most fluid. The greater part of the nitrogenous matter of the food was proteid. The sugar present was always invert-sugar, whereas the sugar in pollen grains is invariably sucrose. AN PHYSIOLOGY OF THE INVERTEBRATA. 99 The preceding table shows certain differences in the compo- sition of the different kinds of larval food, more especially in the composition of the solids present. Its composition is, moreover, quite different from that of the bee’s saliva, which contains no sugar. The difference between the proportional amount of the different solids present in the different forms of larval food is a constant one, and no doubt this variation has in view the particular requirements of the larve in ‘question. Certain small but constant differences were also observed in the chemical composition .of the food of the larval drones during the first four days and at eae periods. Not only is there a difference in the quality, but there is also one in the quantity of the food supplied. The juice from 100 queen-bee cells yielded 3.6028 grammes of dry matter, that from 100 drones’ cells 0.2612 gramme, and that from 100 workers’ cells, 0.0474 gramme. (d) The Araneina.—As the spider’s web has indirectly to do with digestion a few remarks on the subject may not be out of place. There is no doubt that “one of the most characteristic organs of the Araneina is the arachnidium, or apparatus by which the fine silky threads which constitute the web are produced. H. Meckel,* who has fully described this apparatus as it occurs in Hpeira diadema, states that, in the adult, more than a thousand glands, with separate excretory ducts, secrete the viscid material, which, when exposed to the air, hardens into silk. These glands are divisible into five different kinds, and their ducts ultimately — enter the six prominent arachnidial mammille, which, in this species, project from the hinder end of the abdomen. Their terminal faces are truncated, forming an area beset with the minute arachnidial papille by which the secretion of the glands is poured out.” The secretion of these glands is insoluble in water, and fas a nitrogenous basis. Web-spinning has several objects in * Miiller’s Archiv, 1846. 100 PHYSIOLOGY OF THE INVERTEBRATA. view: (1) itis a means by which the spider obtains a livelihood ; (2) it is subservient to propagation of the species *—-the silk being used as a cocoon for the reception of eggs, a nest for the young, as well as forming aéronautic gossamer lines for the dispersion of the young brood on the approach of maturity; (3) in the genus Hydrachna (belonging to the Acarina) it serves to attach the moulting individual to an aquatic plant by the anterior part of the body, when it struggles to withdraw itself from its exuvium; (4) it forms a home for the spider. The secretion of the salivary glands of Tegenaria domestica (the common house-spider) contains a diastatic ferment and sulphocyanates. These were proved by the tests previously given. The so-called “liver ducts” of Teyenaria domestica have been investigated by Mr. A. Johnstone, F.G.S.,+ and the author,} with the following results :-— When examined microscopically these ducts are seen to consist of cellular tissue; and the secretion is poured into the intestine. The secretion obtained from a large number of animals, as well as an extract made of the intestines of a very large number of spiders, gave the following reactions :— (1) The secretion and extract form emulsions with neutral oils, yielding subsequently fatty acids and glycerol. (2) The secretion and extract decompose stearin with the formation of stearic acid and glycerol :— C;,H,,,0; + 3H,O = 3C,,H,,0, + C,H,O,. (3) The secretion and extract act upon starch paste with the formation of dextrose. The presence of dextrose was proved by the formation of red cuprous oxide with Fehling’s * solution. , (4) The secretion and extract dissolve coagulated albumin with the formation of peptones, which are readily recognised. * See Dr. H. C. McCook’s American Spiders and their Spinning Work. . + Demonstrator in Geology in the University of Edinburgh. ¥ Proceedings of Royal Society of Edinburgh, vol. 15, p. 113. PHYSIOLOGY OF THE INVERTEBRATA. oI by the rose colour produced in the cold by potash and copper sulphate. (5) Tannic acid produces a white precipitate with the sec- retion. (6) When a few drops of the secretion of these ducts were examined chemico-microscopically, the following reactions were observed : on running in a solution of iodine (in potas- sium iodide) between the slide and cover-glass, a brown de- posit was obtained; and on running in concentrated nitric acid, on another slide containing the secretion, yellow xantho- proteic acid was formed. These reactions prove the presence of albumin in the secretion of the organ in question. The presence of albumin was further confirmed by the tests of Palm.* (7) The soluble ferment, or enzyme, secreted by the cellular tubes was extracted, although with some difficulty, by the Wittich-Kistiakowsky method. This ferment converts fibrin into leucin and tyrosin. (8) The albumins in the secretion and extract are not converted into taurocholic or glycocholic acids, for not the slightest traces of these biliary acids could be detected by the Pettenkofer and other tests. (9) The secretion contains approximately four per cent. of solids. The slight residue (solids), which contains some com- bination of sodium, effervesced on the addition of dilute acid. (10) No glycogen was found in the secretion or extract. From these investigations, which have been repeated on several occasions, the so-called liver of the Araneina is proved to have a similar function to the pancreas of the Vertebrata. Tue CRUSTACEA. (1) The Brachyura.—As a type of this order, the alimentary canal of Carcinus menas will be considered in detail. This animal is a voracious feeder; its food consists of * Zeitschrift fir Analytische Chemie, vol. 24, pt. i. 102 PHYSIOLOGY OF THE INVERTEBRATA. animal and vegetable substances. These contain albuminoids, - fatty and starchy matters, and earthy salts. The food is torn to pieces by means of the chele. The wide and short cso- phagus leads into a large globular stomach. containing chi- tinous teeth, the object of these teeth being to sub-divide the food so that it may be acted upon by the digestive fluid poured into the intestine. The only lateral appendage of the alimentary canal of Carcinus is the so-called liver. It is an organ of considerable size, and consists of two symmetrical halves. Its secretion has the following reactions :— ‘It decomposes fats and oils with the formation of glycerol and fatty acids. It converts starch into dextrose, and dis- solves albumin. The action of the secretion upon milk is to render it transparent. The secretion contains leucin and tyrosin, no doubt produced by the metamorphoses of certain albuminous substances. In the words of Prof. M. Foster, F.R.S.,* “one result of the action of the pancreatic juice is the formation of considerable quantities of leucin and tyrosin.” These organic compounds are not formed in a liver, for they are “dehydrated in a true liver, forming a series of cyanhydrins or cyanalcohols attached toa benzene nucleus, which then pass into the circulation.” The principal mineral ingredient found in the ashes (incin- erated at a low temperature) of the so-called liver of Careinus was sodium carbonate. In the ash of a Vertebrate liver the chief mineral constituents are potassium and phosphoric acid. The soluble ferment is readily extracted by the Wittich- Kistiakowsky method, or by the method recently introduced by Dr. N. Kravkoff.t This method consists in precipitating the soluble ferments and albuminoids by means of ammonium sulphate. By treatment with alcohol, the albuminoids become insoluble, and the ferments are then extracted with water. The ferment so extracted converts fibrin into leucin and tyrosin ; as well as hydrolyzes starch. * Text-book of Physiology, (4th ed.), 438. + Journal of Russian Chemical Society, 1887, p. 387. PAVSIOLOGY OF THE INVERTEBRATA. 103 The secretion of the so-called liver of Curcinus does not ‘contain glycocholic and taurocholic acids, or glycogen. By using the methods of M. Zaleski* for ascertaining the presence of ferrous, ferric, and ferrosoferric compounds in a true liver, the author of the present volume‘could jot detect the presence of iron in the organ or its secretion, From the above reactions the conclusion to be drawn is, that this bilobed organ is essentially pancreatic in function. THE MACROURA. The general details of the alimentary canal of -4stacus have been described in the last chapter. The principal organs are the stomach and the “liver.” The gastric juice of the crayfish has recently been investi- gated by M. Stamatit By means of a gastric fistula, the gastric juice can be easily collected from the crayfish. This secretion is of a yellowish colour, somewhat opalescent, and alkaline to test-papers. It digests fibrin, rapidly forming peptones which give the ordinary reactions: it also transforms starch into glucose. It appears also that fats are emulsified and fatty acids liberated. This so-called gastric juice of M, Stamati was in fact nothing more than the secretion of the “liver,” which pours its secretion into the anterior part of the intestine, and no doubt finds its way into the pyloric portion of the crayfish’s stomach. After the stomach of Astacus has been thoroughly washed out with water, an extract of the organ does not digest fibrin, nor does it act upon starch. This proves that Stamati’s gastric juice was in reality the secretion of the “ liver.” The so-called liver of Astacus fluviatilis has been proved by the author § to be pancreatic in function. Its secretion * Zeitschrift fiir Physiologische Chemie, vol. 10, pp. 453-502. + Dr. A. B. Griffiths’ paper in Proc, Roy. Soc. Hdin., vol. 16, p. 178. $ Comptes Rendus de la Société Biologique, [2], t. 5, p. 16. gk § Griffiths’ paper in Proc. Roy. Soc. Edin., vol. 14, p. 237. 104 PHYSIOLOGY OF THE INVERTEBRATA. contains about five per cent. of solids, and readily digests fibrin and hydrolyzes starch. Similar reactions to the above are also produced by the so-called livers of Homarus and Palemon. There is no doubt that the “liver” of the Macroura is a true pancreas. THe LAMELLIBRANCHIATA. Dr. Léon Fredericq has investigated the alimentary canal of Mya arenaria (see Fig. 18) and Mytilus edulis (the mussel). The secretions of the so-called livers of these two animals digest fibrin analogous to the pancreas of higher forms.* When neutral and alkaline extracts of the organ are prepared, they have the characteristic reactions already given under the head of Carcinus menas; but Fredericq states that he has extracted glycogen from the secretion of the “liver” of Mya. It is, however, probable that glycogen is only present in this organ and other tissues of Mya during certain periods of growth. It may be remarked that in Carcinus, where development is achieved by sudden bounds—by moultings— the “liver” contains glycogen during these periods of rapid . growth, but at other times there is not the slightest trace of the carbohydrate in that organ or any part of the alimentary canal. The contents of the digestive canal of Mya are acid. This acid is chlorohydric acid, and is found chiefly in fluids obtained from the stomach. It is possible that the function of the stomach, as a separate digestive organ, becomes more differ- entiated in the Lamellibranchiata. Is it possible that it gives rise to a secretion similar to the gastric juice of higher forms ? The so-called liver of Ostrea, Pecten, Anodonta, and Cardium functionates as a true pancreas. Dr. C. A. MacMunn} has extracted enterochlorophyll from * Proc. Roy. Soc. Hdin., vol. 14, p. 237. ¢ Philosophical Transactions of Royal Society, 1886, pt. i, p. 235. ‘PHYSIOLOGY OF THE INVERTEBRATA. 105 the “liver” pigments of certain genera of the Mollusca, as well as from a large number of other Invertebrates. Among the Mollusca experimented on were—Mytilus, Ostrea, Ano- donta, Cardiwm, Unio, Octopus, Buccinum, Patella, Helix, and Limaz. In some Molluscs—as Patella—the “liver” contains enterohzematin besides enterochlorophyll. It might be suggested in reference to the discovery by Tredericq of glycogen (C,H,,0,) in the “liver” of Mya that it was pro- duced by the enterochlorophyll present in the organ; as enterochlorophyll is allied to chlorophyll. But MacMunn (loc. cit., p. 257) states that he has made “ various sections of Invertebrate ‘ livers’ obtained from animals feeding and fast- ing, but never obtained a trace of starch (C,H,,0,) or cellulose with iodine in iodide of potassium, Schulze’s fluid, or with iodine and sulphuric acid. These experiments were made on the ‘livers’ of Heli aspersa, Anodonta cygnea, Patella vulgata, Ostrea edulis, Mytilus edulis, Astacus fluviatilis, the ceca of star fishes, &c. The precautions recommended by Geddes* of previously digesting the tissues in alcohol, and in caustic potash, and neutralising with acetic acid, having been adopted in each case.” It appears that the “ enterochlorophyll occurs dissolved in oil globules, also in granular form, and sometimes dissolved in the protoplasm of the secreting cells of the ‘ liver.” The probable function of this and other pigments will be alluded to in a subsequent chapter. Tur GASTEROPODA. The secretion of the salivary glands of Heli aspersa has been examined by the author.t 1t contains a ferment which converts starch into glucose. The ferric chloride test failed to show the presence of sulphocyanates. The mineral ingre- dients found were calcium and chlorine; but no phosphates * Proc. Roy. Soe. Edin., vol. 11, p. 377- t Tbid., vol. 14, p. 235- 106 PHYSIOLOGY OF THE INVERTEBRATA. or carbonates could he detected in the salivary glands of Helix, Similar results have been obtained with the salivary glands of Limax flavus, and Limaxe maximus. The so-called livers of Helix aspersa, Limav flavus, and Limax maximus are pancreatic in function. Dr. M. Levy* has recently carefully examined the so-called | liver of Helia pomatia, The weight of its organic constituents is very constant, being the same in summer and winter, and in great measure they are the same in kind in all periods of the year. The alcoholic extract of the gland when examined by the spectroscope gave the spectrum of enterochlorophyll. The digestive ferments present are a diastatic, a peptic, but not a tryptic one. The peptic ferment appears to be iden- tical with the late Dr. Krukenberg’s helicopepsin. The diastatic ferment disappears during the winter sleep; it is capable of digesting raw starch, but has no action on cellulose, A fat emulsifying action is shown by the secretion in the summer-time, but this also disappears during hibernation. The ferment, by means of which this action. is brought about, is not identical with the one described by Dr. Schmiede- bergt as histozyme. Histozyme, which was separated from pigs’ kidneys, is concerned in the splitting up of hippuric acid. ‘The snail’s ferment has no such action. According to Dr. Levy, glycogen with sinistrin is generally present in the organ, but all tests for bile gave a negative result. Jecorin was also absent. Dr. Levy has separated the following sub- stances from the so-called liver of Helin pomutia :— Enterochlorophyll Lecithin Oleic acid In the alcoholic extract ( Fatty acids ; Chlorine Ash Phosphoric acid Sulphuric acid. In the ethereal extract ! A trace of fat. * Zeit. Biol. vol. 27, p. 398. \ t Archiv. Exper, Path, und Pharm., vol. 14. PHYSIOLOGY OF THE INVERTEBRATA. 107 Sugar Globulin ee at 66° C.) Glycogen Sinistrin Hypoxanthine* Potassium Sodium In the aqueous extract Calcium Magnesium Ash Tron (traces) Manganese Chlorine Phosphoric acid ‘Sulphuric acid. In winter animals, silica was also found as an ash con- stituent. Dr. Fredericq has investigated the nature of the secretions of the salivary glands and “liver” of Avion rufus. The secretion of the salivary glands readily acts upon starch, but has no action upon fibrin and neutral oils. ‘The secretion of the “liver” is a brown liquid, and can be collected in a sufficiently large quantity by killing a large number of fresh snails. It suffices to dissect them lengthways to extract the viscera, and to collect the liquid which flows from the cut end of the intestine. If the secretion is extracted after the ani- mals have just been feeding, it is most likely that the secretion will be slightly acid (acidity due to food); in that case the digestion of fibrin takes about twenty-four hours. On the other hand, if the secretion is extracted when alkaline, or if the acid secretion is rendered slightly alkaline by a small quantity of scdium carbonate, its activity is greatly increased. In an acid solution the ferment is inactive, and this is readily observed when a small quantity of acidulated water is added to the digestive fluid of the snail, for it completely stops the digestion of fibrin. The “liver” and its secretion furnish a diastatic ferment transforming starchy matters into glucose. The so-called t * And other bases precipitable by phosphotungstic acid. 108 PHYSIOLOGY OF THE INVERTEBRATA. liver of Arion rufus, as well as Helix, is a digestive gland which is comparable to the pancreas of the Vertebrata. It contains neither biliary pigments nor biliary acids. If one considers that the Vertebrate liver is not a digestive gland in the proper sense of the word, since neither bile nor an infusion of hepatic tissues contains digestive ferments, we may conclude that the name of liver is in no way applicable to the diges- tive gland of the Gasteropoda. It is stated by Barfurth that the liver of the Gasteropoda performs the functions of a hepato-pancreas. It is certainly pancreatic in function; but there are no chemico-physio- logical reasons for saying that it also possesses a hepatic function. The salivary glands and “liver” of Patella vulgata have been investigated by the author.* The limpet (P. vulgata), with its conical shell adhering to the rocks of our coasts, is well known to every sea-side wanderer. This member of the Gasteropoda, has been the subject of many scientific memoirs in ancient and modern times. Amongst naturalists, Aristotle was the earliest who gave an account of some of the limpet’s habits, and Cuvier was the first to describe its anatomy. Although this interesting little animal has attracted the attention of many naturalists, it is only within the last decade that the true functions of its internal organs have been satisfactorily worked out. The “liver” of Patella vulgata isa yellowish saccular gland, and the greater bulk of this organ is encircled by the super- ficial coil of the intestine. Its secretion acts upon starch- paste converting the starch into glucose, as proved by Fehling’s solution. The secretion, as well as the organ itself produces an emulsion with oils and fats, yielding subsequently glycerol and fatty acids. The soluble ferment secreted by the columnar cells of the epithelium of the gland is readily extracted by either the Wittich-Kistiakowsky or Kravkoff * Dr. Griffiths in Proceedings of Royal Society of London, vol. 42, p. 3933 vol. 44, p. 328. ‘ PHYSIOLOGY OF THE INVERTEBRATA. 109 methods. The isolated ferment, as well as the organ and its secretion, digest fibrin. Neither the organ nor its secretion contains biliary acids or glycogen, From these investigations there is no doubt that the so-called liver of Patella vulgata is similar in function to the pancreas of the Vertebrate division of animal life. The two salivary glands of Patella are well-marked, and situated anteriorly to the pharynx, lying beneath the pericar- dium on one side and the renal and anal papilla on the other. They are of a yellowish-brown colour, and give off four ducts. The secretion of these glands was examined by the same method applied to the salivary glands of Sepi« officinalis (see later in this chapter), and with similar results. The following table represents the constituents found in the salivary secretions of the two orders of the Ao/lusea :— _+ = Present. — = Absent. Cephalopoda. Gasteropoda, : : Pulmogastero- | Branchiogas- Dibranchiata. poda. teropoda, Soluble diastatic ferment + + + Mucin + Sulphocyanates + : + Calcium phosphate ; + 2 + Calcium . é . , ae + + Chlorine . : . 7 : + ? The “liver” and salivary glands of Buccinwm (whelk) have similar functions as the same organs in Putella. THE CEPHALOPODA. In a memoir published in the Chenvical News, vol. 48, page 37, and the Journal of the Chemical Sovicty, 1884, page 94, the author gave an account of a peculiar excretory 110 PHYSIOLOGY OF THE INVERTEBRATA. product found in the Sepia’s “liver.” This product was proved to be albumin in pseudo-crystalline aggregations when examined under the microscope. These bodies are not of a coustant occurrence in this organ of Sepia officinalis. Two years after the publication of the above-mentioned memoir the author * made a thorough examination of this organ in Sepia which substantiated and extended the observa- tions of Krukenberg, Fredericq,{ and Jousset de Bellesme.§ After carefully dissecting the organ out of the cavity of the body of a fresh Sepia, the following experiments were performed :— (1) A small portion of the organ was placed on starch- paste. The starch granules disappeared, with the exception of the celluloid covering, and on treating with water, and testing the solution with Fehling’s solution, sugar in the dextrose form was found. (2) The organ gave an akaline reaction to litmus paper. (3) When a small portion of the organ was agitated with a small quantity of oil, an emulsion was produced—this emulsion had first au alkaline reaction, and after some time became acid, owing to the formation of butyric and other acids of the fatty series. (4) The action of it on milk was to render the milk trans- parent in four hours; 15 cc. of milk were rendered trans- parent by 6 milligrammes of the organ. (5) A chemico-microscopical examination of the secretion of the organ revealed the presence of albumin. The Isolation of the Ferment.—The process used to obtain the ferment or ferments (in a crude state) from the secretion of the organ was that devised by Wittich and used by Kistiakowsky|| in his researches on pancreatic ferments. * Proceedings of Royal Society of Edinburgh, vol. 13, p. 120. + Untersuch. Physiol. Inst. Heidelberg, Ba. 1, p. 327 [1878]. t Bull. Acad. Sciences Belgique, tome 56, p. 761 [1878]; Revue Intern. Sciences, t. 3, p. 263 [1879]. § Comptes Rendus, t. 88, pp. 304, 428 [1879]. || Pfliger’s Archiv. fiir Physiologie, vol. 9, p. 438. prraeede PHYSIOLOGY OF THE INVERTEBRATA. 11I The process consists in hardening the organ in alcohol for three days, and then cutting it up into very small pieces, ex- tracting with glycerol and filtering. On the addition of alcohol to the filtrate, the ferment is precipitated. The action of this ferment or ferments on starch was the complete conversion of the latter into dextrose or right- handed glucose, which was proved by the action of Fehling’s solution ; and the formation of crystals (C,H;,0, NaCl, H,O) with a solution of sodium chloride, a distinction from levulose or left-handed glucose, which does not form these crystals with sodium chloride solution. The action of the ferment on fibrin was the formation of leucin (a- amido- caproic acid, C,H,,NO,) and tyrosin (paraoxyphenylamido- propionic acid, C,H,,NO,); for on treating the fermented mass with hot water and filtering, a solution is obtained which contains leucin and tyrosin. When acetic acid was added to this solution, acicular crystals were deposited. These crystals are insoluble in ether, but soluble in boiling water. The aqueous solution produced a red flocculent pre- cipitate on the addition of a neutral solution of mercuric nitrate ; this reaction is characteristic of tyrosin. The acetic acid solution, after precipitating the tyrosin, was evaporated, when leucin was deposited in white shining plates, which melt at 98°C. These crystals of leucin were heated with barium oxide, the result of the action being the formation of amylamine and carbon dioxide :— C,H,,NO, = N(C,H,,)H, + CO, By digesting the organ itself with boiling water and filtering, the filtrate contained leucin and tyrosin. The ferment has no action on cellulose. From these investigations, the so-called liver of Sepia officinalis is proved to be a pancreas, for the juices of the organ are purely digestive in function, digesting starch, oil, and similar bodies, and transforming fibrin into leucin and tyrosin. Then, again, albumin is present in its secretion, which is 112 PHYSIOLOGY OF THE INVERTEBRATA. characteristic of the pancreatic fluid of the higher animals— no albumin being found in the liver, for albuminoids are decomposed by that organ. No glycocholic and taurocholic acids or glycogen were obtained from the organ. Not the slightest trace of these biliary compounds could be detected in the organ or its secretion. There is no doubt that these investigations prove that this so-called liver of the Cephalopoda is a true pancreas or digestive organ. The author in his paper entitled, “ Further Researches on the Physiology of the Invertebrata,”* gave the following account of the salivary glands of the cuttle-fish: There are two pairs of salivary glands in Sepia officinalis, The posterior pair, which are the larger (see Fig. 20) lie on either side of the cesophagus. The secretion of the posterior glands is poured into the cesophagus, while the secretion of the smaller anterior pair of glands passes directly into the buccal cavity. A quantity of the secretion was extracted by using several freshly-killed cuttle-fishes. It was alkaline to test-papers! » A portion of the secretion was added to a small quantity of starch, the starch being converted into glucose in fifteen minutes. The presence of glucose was proved by the formation of red cuprous oxide by the action of Fehling’s solution, The soluble enzyme, or ferment, contained in the secretion (which is capable of causing the hydration of starch), was isolated by precipitating the secretion with dilute normal phosphoric acid, adding lime-water and then filtering. The precipitate produced was dissolved in distilled water and reprecipitated by alcohol. This precipitate converts starch into glucose. When a drop of the clear secretion was allowed: to fall into a beaker containing dilute acetic acid, stringy flakes of mucin were easily obtained. The presence of mucin was confirmed by several well-known tests. Another portion of the secretion was distilled (with the * Proceedings of Royal Society of London, vol. 44, p. 327. PHYSIOLOGY OF THE INVERTEBRATA. 113 utmost care) with dilute sulphuric acid, and to the distillate ferric chloride solution was added, which gave a red colour, indicating the presence of sulphocyanates. The inorganic constituents, as far as the author could make out, consisted only of calcium phosphate. No calcium carbonate could be detected. There is much in favour of the supposition that the diastatic ferment in these secretions is produced as the result of the action of nerve-fibres (from the inferior buccal gan- glion) upon the protoplasm of the epithelial cells of the glands. THE TUNICATA. The very fine, branched, and ampullated tubules (sometimes known as Savigny’s tubules), ramifying over the wall of the intestine in nearly all the Tunicata, form a digestive gland, which is certainly pancreatic in function. The common duct of this gland opens into the stomach. The latter organ always contains a secretion having similar chemical properties to those produced by the pancreatic tubules. The two following tables summarise our studies of the salivary glands and the so-called livers of the Jnverte- brata :— PHYSIOLOGY OF THE INVERTEBRATA. 114 + + + + + + + + + eyeuoqies TaNTOTeD ; suory) . mantoyey eyeydsoyd wnroreg * soqeuefooyding ulonyl qUoUMIey O17e9SVIG. seqetqoueaqi *epodoiay ssegzoryourig “epod -O19]SUZ0W Ng “epodoyeyday *epodo.iaysexy) ‘eupuery | ‘etoydouamfy] |*e103doptdey | -e10}doy310 “BqaIOS ITO ‘quesqy = - ‘“Juasatig = + ‘'SGNVID AUVAITVS SHI () 115 PHYSIOLOGY OF THE INVERTEBRATA. ‘sTTO9 ONssTz-dATJOaTUOD a4 Aq vosnyoF_ ay} UL pataLojsed st UOTJOUNZ oTMESOOATS 9Y]} Ye} Soyeys ouOyspuNtg + : ‘usar Apearre ‘vaynuod wyazy JO ,, LAAT] ,, 94} UO STOTFVSIysaaut s,AAoT OSTR 230 » 1 3 = =f x ¢ | # | | a wHIpog | |, oS aN ae me Pe Sed ee Sp ee) ea Ga cael wasoo4T x os ns = = = = = 2 2 2 = a - - plow o1foqooo 4TH 7 mn S es et bes 2 =: s ele 2 es ZB - 0 plow oroyoomney, fe | | 23 +i +t+y4 |] - uyngyTy + + Ee + a + 7 utso14y, ae) ak +f +] 4 ]4 4] - * ujoney tye] + + +) + +] +) 4 )]4]- * souoydeg +] 4]+4] + +} +] +rit e+] +] tf] +]-] 4] 44° * ulyeeroueg +} ti 4+ ]o# tt] tr] +) +] 4] ] +t] ep - ] 4] 4 ]- qUOULIEg o1yeyseIq Q 2 du oz aR 8 iy e O° cS me Se eter ee |e lee |e ley Blea | 5 SS 8 Ee 8 8 5 8 = S 2 5 2 & z Ss) 8 |g | 881 2¢ /2)e),8s | Sis} s |B] 8 e | F e.|3s|/2 1]? | 3 )8 | F}2 ls} | 8 le]& |] es] | ae ae Bi dpe CR SSR RES | ame te ROOM see a Bia (| + * 1 : ° P (quesqy = - ‘yueserg = +) (LON 4O GALVIENGUTAAIG UAHLIA) UAAIT AATIVO-OS AH (9) 116 PHYSIOLOGY OF THE INVERTEBRATA. The chief digestive glands of the Invertebrata are the pancreas (the so-called liver) and the salivary glands. There appears to be no organ, from the lowest to the highest Invertebrate animal, corresponding with the Vertebrate liver. Dr. C. Letourneau, in his La Biologie, says: “Does the pancreas exist in the Invertebrates? This is a question of comparative physiology which still waits for a reply. We do not begin clearly to recognise the pancreas except in fishes, and then only in a rudimentary state.” After the recent researches of Krukenberg, Fredericq, Jousset de Bellesme, Plateau, Hoppe-Seyler, as well as those of the author, the problem now requiring solution is the following :—Does a true liver exist in the Invertebrata? The pancreas appears to be the chief digestive organ of the earlier forms of animal life. On the other hand, some biologists look upon the Verte- brate liver, pancreas, and salivary glands as differentiated bodies of an original pancreas of the Jnvertebrata. But have not many forms of the lower animals similar salivary glands to those found in the Vertebrata? And is not the so-called liver of the Jnvertebrata a true pancreas, capable of producing the same chemical and physiological reactions as the pancreas. of higher forms ? CHAPTER V. ABSORPTION IN THE INVERTEBRATA. In Chapters III. and IV. the processes of digestion in the Invertebrata were considered in detail. The digested food becomes tissue; but before this is attained the said digested. food, which is still enclosed in the alimentary canal (if present), must. first pass through its walls and gain entrance into the blood or tissues. This process is known ,as absorption. The function of absorption in the Vertebrata is carried on by a distinct set of vessels, but these are entirely wanting in the Invertebrata. In the higher animals absorption takes place partly in the stomach and partly in the intestine. “The mucous membrane of the stomach and intestine con- tains an abundant supply of capillaries; the walls of these vessels are only one cell thick; consequently the soluble peptones and sugar will diffuse readily into their interiors.” In the intestine the area of absorption is largely increased by means of the villi in the Vertebrata, and by means of the typhlosole in those Invertebrates whose intestine is provided with such an arrangement. There are no openings in the substance of the villi and typhlosoles; consequently the nutritive, fluids pass directly through their substance by a kind of transudation or imbibi- tion (endosmosis). Every animal membrane will absorb certain fluids with greater or less facility. Thus most of them will absorb pure water more abundantly than a solution of sodium or potassium chloride; or a solution of sugar more 118 PHYSIOLOGY OF THE INVERTEBRATA. readily than one of gum; and the same liquid will be ab- sorbed more readily by one membrane, and less so by others. Thus every membrane has a special power of absorption for certain fluids, which it will take up in greater or smaller quantity, according to their nature and composition. In all cases, however, there is a natural limit to this quantity, beyond which absorption will not continue. In the higher animals there is absorption by the blood- vessels and absorption by the lacteals; but, as already stated, there are no distinct vessels in the Invertebrata set apart for the function of absorption. In the lower Mollusca, Echino- dermata, &c., the digested food is absorbed by the walls of the alimentary canal. In the higher Mollusca and Arthropoda, the digested food or nutritive fluids are absorbed by the blood- vessels in the walls of the alimentary canal. In both of the above cases, the two functions of absorption and digestion are not completely differentiated from each other. In the Invertebrata the digested food is brought into con- tact or close relationship with the various tissues in three ways: (1) The food particles (as in Ameba), during the process of digestion, are brought into contact with the tissues (using the term in its widest sense), that are to be nourished or renovated by them. In this case there is a fusion of the two functions of absorption and digestion. The digested food immediately becomes tissue. (2) The digested food or nutritive fluid transudes through the walls of the alimentary canal into the somatic or body cavity, and is consequently absorbed by the walls of, and the organs suspended in, that cavity. In this case, the nutritive fluid passes through a transitory condition, in such a state being known as the “chylaqueous” fluid. The so-called chylaqueous fluid is found in the body cavity, and is never enclosed in any distinct vessels; it undoubtedly represents the blood of the higher animals. (3) The digested food contained in the alimentary canal is . PHYSIOLOGY OF THE INVERTEBRATA. 119 absorbed by the blood-vessels distributed on the walls of the digestive system. Through the medium of blood-vessels the products of digestion are carried to all parts of the body. ‘In this case there is a fusion of the functions of absorption and circulation; the products of digestion become incorpo- rated with the blood ere they reach the tissues for which they are destined. Therefore, in the Invertebrata the function of absorption does not exist as an entirely separate function, as one finds in the Vertebrata. It is either fused with the function of digestion or the function of circulation. THE PROTOZOA. The Gregarimida, being parasitic organisms, pass their existence in the chyle or nutritive fluid of the higher animals. They absorb by the whole surface of their bodies the nutritive fluids of their hosts; such fluids are already in such a state as to form a nutritive material for these low organisms. Probably the nutritive material does not undergo any fur- ther change after passing into the body of a Gregarina. “ Perhaps no other animals present such a complete want of differentiation between the functions of digestion and ab- sorption ” as do the Gregarinida. In the Rhizopoda (eg.,.Amaba) food is taken in at any part of the cell, but only at one region of the cell at one given time—i.¢., the whole surface of the cell can ingest food, but only one portion of it ingests at atime. In these animals the intimate contact of the food particles, absorbed within the living substance, is aided by the contractions of the sarcode, by the emission and retraction of the pseudopodia. The sarcode of these organisms absorbs nutrient matter from the food particles, There is no distinct channel through which the food particles pass. What causes the sarcode to absorb nutrient matter from the heterogeneous materials introduced into the cells by the pseudopodia ? There is no doubt that 120 PHYSIOLOGY OF THE INVERTEBRATA. itis due to the excitability* or irritabilityt of the cell, caused indirectly by the presence of food particles. Speaking of the Rhizopoda, M. Richet says that “irritability is their life complete.” The presence of food particles excites digestion and absorption, but only the digested particles are absorbed. This power of selection is possessed by the protoplasm of the cell; it is a physiological property of that complex substance whose composition has already been alluded to in the early part of the work. In the compound Fhizopoda, only certain regions of the sarcode take in food particles. ‘The food so ingested passes through more or less of a compound Rhizopoda in a similar fashion to that met with in the simple forms.” In the Infusoria the tood particles may possibly undergo a preliminary digestion in the short cesophagus (¢.g. Para- mecium). After this the food gives rise to food vacuoles in the sarcode, These food vacuoles undergo a rotatory move- ment round the cell, just below the cuticular layer. “Only the sarcode immediately in contact with the food vacuoles, as they pass round, can be regarded as truly absorptive. Here is, then, the first marking off of a region (only a region) of the sarcode, whose work is that of absorbing nutrient materials from the food, and transferring them to other parts of the sarcodic body.” THE PORIFERA. In the Porifera the food particles, along with water, enter through the inhalent apertures, and pass into the gastro- vascular cavity, which is lined with flagellate cells; but the functions of digestion and absorption in the Porifera do not differ very much from those occurring in the Rhizopoda. | THE Ca:LENTERATA. In the Hydrozoa the function of absorption is somewhat * See Dr. Romanes’ Mental Evolution. + Richet’s Essai de Psychologie Générale. PAYSIOLOGY OF THE INVERTEBRATA. 121 more complicated than in the Rhizopoda. The digestive and somatic cavities are not differentiated, for they form one common cavity. The digested food is absorbed by the cells of the endoderm. In the Protozoa the function of absorption is effected by the sarcode, whereas in the Hydrozoa the “sarcode” becomes differentiated into cellular membranes, the internal one (endoderm), lining the digestive cavity. The endoderm of the Hydrozoa is the absorptive layer and is the means of transferring the absorbed fluids to the ectoderm. Although there are many points in the mode of absorption in the Hydrozoa comparable to those of the Rhizopoda, yet the former class marks a distinct advance on that of the latter; for the food is first digested in the “chylaqueous ” fluid contained in the digestive and somatic cavity, whereas in the Rhizopoda the food particles are brought into actual contact with the sarcode, which performs both the functions of digestion and absorption. In the Actinozoa the function of absorption comes under the second method already described. The digested food transudes through the linings of the digestive cavity, or passes directly through the posterior aperture into the somatic cavity. The somatic cavity, which is distinct from the digestive cavity,* contains a ‘‘chylaqueous” fluid. This fluid consists largely of water, and contains albuminoid spherules, which are possibly the precursors of the white corpuscles of chyle and of blood in the higher animals. ‘The nutrient matter of the digested food, having passed into the somatic cavity, is absorbed by the endodermic cells’ of that cavity and by the mesenteries, THE ECHINODERMATA. As far as the function of absorption in the Echinodermata is concerned, there is very little difference from that of the * In Actinozoa the digestive cavity is suspended in the somatic cavity. 122 PHYSIOLOGY OF THE INVERTEBRATA, Actinozoa. The alimentary canal, or digestive system, is sus- pended in the somatic cavity ; and the digested food transudes through the walls of the former into the latter. The nutrient fluid is then absorbed by the walls of the somatic cavity, as well as by the various organs suspended therein. The somatic or peritoneal cavity in the Asteridea contains a watery cor- pusculated fluid. The corpuscles are nucleated cells; this fluid therefore represents the blood of the higher animals. It will be noticed that in the Actinozoa, as well as in the Echinodermata, the function of absorption is distinct from that of digestion, but it is not performed by any special organs. THE CESTOIDEA. As already stated, the Cestoidea are reversions to a lower or simpler type. They are immersed in the chyle or the tissues of the higher animals ; consequently they absorb the digested food, &c., by the whole of the external surface. Although these animals are much higher in the zoological scale than the Gregarinida, there is in the functions of digestion and absorption a close analogy between these two orders. In both, the processes of absorption and digestion are not differentiated. THE ANNELIDA. The digestive tube is suspended in the perivisceral cavity. The digested food transudes into this cavity, and there becomes mixed with a colourless corpusculated fluid. This fluid fills the perivisceral cavity, and is analogous to the blood of other Invertebrates, This colourless fluid is not contained in any vessels, although there is in Zwmbricus, for example, a red fluid contained in a well-developed system of vessels, in addition to the colourless fluid already mentioned. The nutrient matters, after having passed into the peri- visceral cavity or chambers—as the perivisceral cavity is generally divided into chambers by means of thin muscular PHYSIOLOGY OF THE INVERTEBRATA. 123 mesenteries—are absorbed by the pseudo-hzemal vessels, as well as by the various tissues, &c., suspended in the peri- visceral cavity. THE MYRIAPODA AND INSECTA. In these two classes of the Jnvertebrata there is a distinct advance, in the mode of absorption, on all the forms alluded to in the present chapter. Over the external surface of the alimentary canal there are distributed blood-vessels ; and the nutrient matter of the food is chiefly absorbed by these vessels, and more especially by those carrying venous blood. Here the digested food is absorbed by distinct vessels, although there may be some transudation directly into the somatic or body cavity, especially in some of the lower orders of these two classes. The vessels which absorb the digested food are not special vessels (like the lymphatics of the Vertebrata) set apart for the function of absorption, for they perform the ordinary func- tion of veins, as well as “ carrying away from the tissues of the alimentary canal the effete products resulting from the work of those tissues. But in addition to this there is laid upon them the office of receiving the fresh material introduced into the system through the alimentary canal. These vessels are not only transmitting blood, but are absorbing ‘ chyle’; there is a fusion of the functions of absorption and circulation.” THE ARACHNIDA. The function of absorption in this class is performed in a similar manner to that of the Myriapoda and Insecta. The digested food passes into the veins, and is conveyed to the dorsal vasiform heart. THE CRUSTACEA. The digested food passes from the intestine into the blood- vessels or veins, which are distributed on its walls. No other 124 PHYSIOLOGY OF THE INVERTEBRATA. vessels are known to convey the digested food into the circu- latory system ‘‘than the irregular venous receptacles which are in contact with the parietes of the intestine.” THE POLYzoA AND BRACHIOPODA. The function of absorption in the Polyzvu and the Brachio-' poda is not so highly differentiated as the Myriapoda, Insecta, Arachnida, and Crustacea. In the latter, the digested food passes into vessels, or, in other words, into the circulatory system; but as there are no vessels in the Polyzoa and the Brachiopoda, the function of absorption is analogous to that of the Actinozoa. There is an alimentary canal suspended in a somatic or body cavity. The digested food transudes through the walls of the digestive system, and is then absorbed by the external endoderm of the body cavity, as well as by the organs suspended therein. THE MOoLLusca. The function of absorption in the Mollusca is placed under the head of our third category. The digested matter is absorbed by vessels, but these perform the dual functions of absorption and circulation. There are no special absorbent vessels in the Znvertebrata. But although there is no special apparatus set apart for absorption, the nutrient fluids, absorbed by either the sarcode, somatic linings, or blood-vessels, are spread wherever they are required, the distribution being in some animals effected slowly, in a way analogous to absorption. In others the distribution of the nutrient fluids is accomplished rapidly by the establishment of currents, which serve also to remove ‘the excretory products eliminated from the organs. This originates another function, the circulation of the blood, and another set of organs by which this is performed. CHAPTER VI. THE BLoop IN THE INVERTEBRATA. In animals of the simplest structure all the fluids of animal economy resemble one another. “ It seems, indeed, to be only water charged with a certain amount of organic particles ; but in animals higher in the scale of being, the humours cease to be of the same nature, and there is one, distinct from all the others, destined to nourish the body; this fluid is the blood. It not only nourishes the body, but is the source whence are drawn all the secretions, such as the saliva, urine, bile, and tears.” In the Mammalia, Aves, Reptilia, Amphibia, Pisces, and in most of the Annelida, the blood isof a red colour. But in the greater number of the Invertebrata the blood presents various colours and densities, being often thin or watery, and slightly yellow or green, brown, rose-coloured, or lilac. The majority of the Jnver- tebrata have white blood; ¢g., the Insecta, Crustacea, Mol- lusca, &c. The blood of the Invertebrata, like that of the Vertebrata, is not homogeneous, for it consists of a transparent or semi-trans- parent liquid, and a number of small, solid corpuscles, which float in this liquid. In the higher animals the corpuscles are of two kinds, red and colourless ; but in the Invertebrata there are, as a rule, only colourless corpuscles. The red blood of Annelides is different from the red blood of the Vertebrata, inasmuch as the plasma is coloured, and the corpuscles are colourless in the former, while in the latter the plasma is colourless, 126 PHYSIOLOGY OF THE INVERTEBRATA. and there are present coloured and colourless corpuscles, The perivisceral fluid of the Annelida is colourless, and contains colourless nucleated corpuscles. The corpuscles in the blood of the Invertebrata are of different sizes, and the size varies much in the same in- dividual. The size of the corpuscles in the earthworm and leech are as follows :— Lumbricus , : - yy inch in diameter. Hirudo . 7 F + gesivy inch in diameter. Their form, however, is generally spherical; and- their surface has a raspberry appearance. In the higher Invertebrata the blood clots after a variable period of time. Drs. J. B. Haycraft and E. W. Carlier* have recently examined the coagulation of the blood in certain forms of the Invertebrata. According to their investigations, “in Inverte- brate blood the clot is formed, at any rate for the greater part, by the welding together of blood-corpuscles. These 4 a throw out processes, which interlace to form a solid mass.” Haycraft and Carlier have examined the blood of a crab and a sea-urchin. ‘‘Orab’s blood clots in about five minutes, when the opaque pinkish fluid becomes water-clear, with a branching clot within it. During and after coagulation the clot becomes of a brown-black colour, from the development within the corpuscles of a pigment.” “The blood of the sea-urchin varies very much in the number of corpuscles present in the different specimens. In most cases, when allowed to coagulate, the clot is very small, and not easy to demonstrate in a few drops of blood.” The blood of the higher Invertebrates generally darkens rapidly on exposure to air. For example, Mr. E. B. Poulton, F.R.S.,f has shown that the blood of Lepidopterous larve and * Proc. Roy. Soc. Hdinb., vol. 15, p. 423. + Proceedings of Royal Society, 1885, p. 294. PHYSIOLOGY OF THE INVERTEBRATA. 127 pups becomes black: and Dr. C. A. MacMunn* has shown that the blood of Helix pomatia assumes a blue tinge on ex- posure to air. Concerning the composition and nature of the Invertebrate blood generally, further remarks will be given later in this chapter. THE PROTOZOA AND PORIFERA. These animals are without blood, for no part of the sarcode can be regarded as blood. The sarcodic substance lining the canals, which traverse the skeleton of the Porifera, is also devoid of any fluid analogous to the blood of the higher Invertebrata, In some of the Cestowdea and allied forms the blood or nutritive fluid found “in those interstices of the mesoderm that represent the somatic cavity of other animals, is said to be free from corpuscles.” The simplest form of Invertebrate blood is present in the Nematoidea. In the Polyzoa the fluid contained in the perivisceral cavity consists largely of water, and has but few, if any, corpuscles. This nutritive fluid (the chylaqueous fluid of some writers), derived in the first instance from the food that has been digested in the alimentary canal, and which has transuded through the walls of that canal, is, without doubt, analogous to the blood of higher forms. In the Hydrozoa, which are provided with blood, the blood isof a very watery nature. The amount of fibrin is extremely small; consequently the fluid is non-coagulable, and it is almost devoid of corpuscles. ‘That the so-called chylaqueous fluid is analogous to the blood of higher forms is demonstrated by the fact that the perivisceral fluid of the Annelida yields on investigation “not only albumin and fibrin, but crystals which are derived from the water that constitutes so large a part of the nutritive fluid.” From the above remarks it will be observed that the blood * Quarterly Journal of Microscopical Science, 1885. 128 PHYSIOLOGY OF THE INVERTEBRATA of many of the Jnvertebrata is devoid of corpuscles; and the young of many of these animals (which in the adult form have corpusculated blood) have blood without corpuscles. This is another fact which proves that “development is a progress from the general to the special, from the lower to the higher form, and that the earlier stages of the history of higher animals are similar to the adult forms of lower” ones.” ; Although many forms of the Invertebrata have blood devoid, or nearly devoid, of corpuscles, other forms have corpusculated blood. Tue ACTINOZOA AND ECHINODERMATA. The “ chylaqueous” fluid in the Actinozoa and Echinodermata is analogous to the blood of higher forms. In both these classes the blood is corpusculated; some of these corpuscles are distinct cells with wall ahd nucleus, but the majority of the corpuscles in the blood of the Actinozoa and Echinoder- mata are of a very rudimentary nature. “They are probably small masses of matter with no definite limiting membrane on their exterior, akin, perhaps, to the albuminous molecules in our chyle.” . THE MyRIApopDa. In this class the blood is contained in some part of its course in blood-vessels. It contains three distinct corpuscles, which are devoid of cell-walls. “The simplest kind are pellucid central nuclei invested by a few granules. Next rank the oat-shaped corpuscles, where the nucleus is still very evident. The third and most perfect form presents a central nucleus, surrounded and almost obscured by a large number of granules. As yet no definite cell-wall is to be seen on the exterior of the granules.” . PHYSIOLOGY OF THE INVERTEBRATA. 129 Tur ANNELIDA,. The perivisceral cavity, communicating with the excretory or segmental organs, contains a corpusculated fluid which is nutritive. The corpuscles are oval, flat, granular, colourless bodies without a limiting membrane. Besides these corpuscles, the blood of the Annelida contains “ actual cell corpuscles of fusiform shape, and devoid of granules. Here, then, are some corpuscles with a true wall, but all the solid, floating particles of the blood are not yet of that high order of structure.” The fluid present in the pseudo-heemal system or vessels of the Annelida contains a substance allied to hemoglobin ; and according to Dr.MacMunn, this red colouring matter func- ~ tionates in a similar manner to the histohaematins of other Invertebrates, 7.¢., it has a respiratory function. It will be noticed, that there is in the case of the pseudo-hemal system of the Annelida a fusion of the functions of circulation and respiration. This hemoglobin is dissolved in the fluid and does not belong tothe corpuscles. It is questionable whether this “respiratory blood,” as Prof. Huxley* calls it, possesses any nutritive properties ; it appears to be entirely devoted to the function of respiration. In the Gephyrea, represented by Sipunculus, the blood corpuscles contain a coloured fluid between the external wall and the central nucleus. This is the first appearance of a coloured corpuscle, but it differs essentially from the coloured corpuscles of the Mammalia, for in the latter the colouring matter is distributed throughout the corpuscle. Prof. E. Ray Lankester, F.R.S.,f has shown that the perivisceral cavity of Sipunculus nudus contains a pale madder-like colouring matter, “which is due to a large number of coloured corpuscles from 3355 t0 goo Of an * The Anatomy of the Invertebrated Animale, P- 57. + Proceedings of Royal Society, v vol. 21, p. 71. 130 PHYSIOLOGY OF THE INVERTEBRATA. inch in diameter, and that this colouring matter, also found in other parts of the worm, is not hemoglobin.” Delle Chiaje showed that in Sipwnceulus balanorophus and S. echinorhynchus “the arterial blood is red, the venous brown. G. Schwalbe* found that the body fluid of Phascolo- soma elongatum (a Gephyrean) is a bright-rose or greyish-red colour, and is cloudy owing to the presence of morphological elements, and that on standing in the air it gets darker and darker until it assumes an intense Burgundy-red colour. By long standing in the air this colour goes into a dirty brown owing to decomposition, and in drying the whole assumes a dirty green colour. Krukenbergf found the blood of Sipunculus nudus to contain the same colouring matter as that observed by Schwalbe ; he finds that it is the oxygen of the air which brings about the colour change, and that the colour is removed by CO,. This colouring matter gives no absorption band either in the oxidised or reduced condition. _Krukenberg calls this pigment hamerythrin, and the chro- mogen belonging to it hemerythrogen. The colouring matter is decomposed by H,S. The oxygen in the oxidised blood-pigment seems, according to Krukenberg, to be more firmly fixed than in oxyhemoglobin. Milne-Edwards{ in 1838 discovered that certain Annelids possessed green blood, his observations being made on Subella. “Prof. Ray Lankester § on examining the blood of Sabella ventruabrum and Siphonostoma (sp. ?) with the spectroscope discovered the interesting fact that it only gives a banded absorption spectrum, but is capable of being oxidised and reduced, and it behaved in such a way with potassium cyanide and ammonium sulphide, as to have led him to conclude that hemoglobin and this colouring matter (chloro- . cruorin) ‘ have a common base in cyanosulpheem, and perhaps * Archiv. fiir Mikr. Anat., vol. 5, p. 248, et seq. t+ Vergleich. Physiol. Studien, p. 85. t Annales des Sciences Naturelles, 1838, vol. 10, p. 190. § Journal of Anatomy and Physiology, 1868, p. 114 ; 1870, p. 119. PHYSIOLOGY OF THE INVERTEBRATA. 1310 in Stokes’ reduced hematin.’* .... Prof. Lankester could not obtain derivatives of chlorocruorin, owing, as he has stated, to the apparent instability of this body, which decomposes rapidly.” Dr. MacMunn has recently examined spectroscopically the behaviour of chlorocruorin with certain reagents, but his investigations will be de- scribed later in this chap- ter, when we consider in detail the chromatology of the Invertebrate blood. The red blood of ZLum- bricus can be made to yield crystals of oxyhe- moglobin (Fig. 27), and a solution of these crystals gives an absorption spec- trum (Fig. 28). Heemoglobin is also pre- sent in special corpuscles Fic. 27.—CRYSTALS OF OXYHEMOGLOBIN of the blood of Glycera FROM BLOOD OF LUMBRICUS. (one of the Polycheta) ; as well as in the vascular fluid of Nephelis and Hirudo. It c Dia BEd F TTT TTT TT [TTT PTAA TTT TTT TTP ATT TTT TTT TTT 60 70 80 90 100 110 = «120130 0s Fic, 28.—ABSORPTION SPECTRUM OF OXYHAMOGLOBIN FROM BLOOD OF LUMBRICUS. appears that this particular colouring matter is speciro- scopically identical with Vertebrate hemoglobin. THE INSECTA. In a large number of insects the blood is colourless ; although sometimes it is of a green, yellow, or red hue. This colour * Heemochromogen. 132 PHYSIOLOGY OF THE INVERTEBRATA. is not due to the flat, oat-shaped, granular corpuscles with their well-defined walls and nuclei, but is due to the liquid in which they Hoat. In the case of Phytophagous larvee, Mr. E. B. Poulton, F.R.S.,* has shown that they owe their colour and markings to two causes:—(1) “Pigments derived from their food- plants, chlorophyll and xanthophyll, and probably others; (2) pigments proper to the larve or larval tissues made use of because of some (merely incidental) aid by either or both of these groups of factors. It may be generally stated that all green colouration without exception, is due to xantho- phyll. All other colours (including black and white) and some yellows, especially those with an orange tinge, are due to the second class of causes... .. Derived pigments often occur dissolved in the blood, or segregated in the subcuticular tissues (probably the hypodermic cells), or even in a chitinous layer, closely associated with the cuticle itself.” In some cases, the colour of the blood changes before the pupal stage is reached, while in others it remains the same as in the larval condition. On this point Mr. Poulton (loc. cit., p. 277) says:—‘‘the superficial derived pigments of Sphinx Ligustri become brown in the dorsal region, before pupation, while the colour of the blood is unchanged. In Dicranura Vinula the whole larva becomes reddish-brown, and in this case the green blood changes to brownish-yellow. The true larval pigment also changes before pupation, except when it is cuticular. Thus the larva of #. Angularia becomes transparent by the disappearance of dark pigment, and the green blood gives its colour to the larva. The green colour of the blood is generally retained in the pupal state, and it is often of great importance.” According to Mr. Poulton, the blood of Phytophagous larve and pup is acid to litmus-paper, with the exception of that of Ephyra punctaria, which seemed to be neutral. This acid, which is volatile, is readily extracted with ether; butits * Proc. Hoy. Soc., 1885, p. 270. PHYSIOLOGY OF THE INVERTEBRATA. 133 nature has not been determined, The corpuscles of Phyto- phagous blood are amceboid. Coagulation.—“ The blood clots after a very variable period of time, but generally darkens in about five minutes, ultimately forming a solid black clot which is due to oxida- tion. If blood be sealed in a tube, the small quantity of oxygen present will form a thin black film on the surface of the blood, and the action then ceases.” Mr. Poulton has shown “how blood can be kept indefinitely without clotting in a section of tube with a cover-glass over one end, and the other cemented to a glass slide.” He has kept “ the blood of Pygera Bucephalus in this way for a month, quite unchanged, and on then breaking off part of the cover-glass a thick black crust was formed on the surface, while the blood beneath became translucent instead of clear and transparent. On removing the crust a second thin one was formed, but on removing this, no further coagulation took place. If in sealing up blood, or placing it in a tube section, a bubble of air is accidentally included, coagulation takes place round the bubble, but not elsewhere. This black substance is the normal clot, for the injured places on larvee which have healed are always black, notably the horns of Sphina larvee which have been nibbled off by others of the same species. The coagulation takes place after the addition of water, or of a saturated solution of neutral salt (sodium sulphate). The occurrence of a reducing agent in the blood appears to be very remarkable, but it is possible that the substance is capable of again yielding up its oxygen, and so acting as a carrier. It has been observed that if fresh blood be added to that which is turning black on the surface, the black clouds are redissolved. If this be not so, it is difficult to see how the blood can be the internal medium for the supply of oxygen in these animals, and one is tempted to the supposi- tion that in the tracheal system we have a means for the supply of oxygen direct to the tissues.” Another suggestion which occurred to Poulton was that “the coagulation is a 134 PHYSIOLOGY OF THE INVERTEBRATA. very similar process to the darkening of cuticular pigment on larvee, and the darkening of the pupal covering. It has always been assumed that this darkening is due to light, but it takes place rapidly and completely in pupe buried several inches under ground, in compact and opaque cocoons, or sometimes in the heart of a tree.” Furthermore, Poulton has never observed that darkness made the least difference to the darkening of pupe. It is, therefore, “‘ very probable that this will also prove to be due to oxidation, and possibly to the formation of a substance similar to the black clot of the blood.” Poulton has observed that “the brown and colourless blood darkens as well as the green.” The Action of Reagents——The action of (a) alcohol (fifty per cent.) on the blood of P. Bucephalus was to precipitate proteids; and if the mixture is shaken, “the proteids and pigments are precipitated as yellowish-green clouds, and in a few minutes the upper part of the liquid becomes blue, and ultimately black, from the formation of coagulum. The proteids are decolourised and sink, the alcohol remaining yellow with xanthophyll (the chlorophyll disappearing). Absolute alcohol does not lie on the top of the blood (like diluted alcohol), but mixes with it at once. (b) Chloroform behaves in the same manner as ether, but it dissolves nothing coloured from the green coagulum ; the latter contracts in a few hours, and a clear blue liquid appears between it and the sides of the tube. The exposed surface of the coagulum (the chloroform having sunk to the bottom) rapidly becomes black. (c) Distilled water, like weak spirit, lies on the top of the blood with a cloud of precipitated proteid (probably globulin) above the junction. On shaking, the cloud disap- pears, and the blood only seems diluted ; if now more water be added (altogether many times the volume of the blood), in a few minutes the whole fluid becomes cloudy, remaining dark-greenish. On filtering, a blue solution comes through, which slightly darkens for some hours. With less water the ‘PHYSIOLOGY OF THE INVERTEBRATA. 135 blood coagulates normally, although after a longer interval of time. (d) Carbon disulphide had no effect for a consid- erable time. ventually the blood was coagulated (green) but nothing coloured was dissolved out.” The Action of Heat.— The blood of the pupa of Sphina Ingustry was heated in a glass tube in a water-bath; no change was seen till the temperature reached 132° F., when part of the blood became slightly dim. By 141° the whole of the blood was distinctly cloudy, but it was not till 180° that the blood became quite coagulated—solid-looking and opaque, the proteids being yellow with xanthophyll. In the interstices of the clot was a clear yellow fluid. The xantho- phyll in the coagulum was easily extracted by ether or alcohol.” Dr. L. Fredericq* has also investigated the nature of the blood in the Insecta. He experimented upon the blood of the larvee of Oryctes nasicornis (belonging to the Coleoptera). The blood was extracted by making a small slit (with fine scissors) across the skin of the back and the walls of the dorsal vessel ; into this slit a slender glass canula was inserted when the blood of the animal immediately rose in the tube. The blood is a colourless liquid having somewhat the aspect of the lymph of the Mammalia, and holding in suspension a large number of colourless globules which slightly interfere with its transparency. The blood of Oryctes quickly coagu- lates. This coagulation is not arrested by the addition of sodium chloride, magnesium sulphate, &c. But a slightly elevated temperature (54° C.) sufficed to prevent coagula- tion. When exposed to the air the blood of this insect becomes a dark brown colour ; but the brown colour has not the same intensity throughout the fluid ; it is of a deeper colour in the vicinity of the mass of globules. Light has no action in changing the colour; the change being due to oxidation. After being coagulated with hot water, the blood of Oryctes * Bulletins del Académie Royale de Belgiyzue, 3° série, tome i. 136 PHYSIOLOGY OF THE INVERTEBRATA. changes to a brown colour in contact with air. But the coagulum produced by alcohol is not acted upon by air. When the oxidised or brown blood is examined by the spectroscope, it does not show any characteristic absorption bands. At first sight the blood of Oryctes appears to contain a substance acting under the influence of oxygen in a similar manner to hemoglobin or hemocyanin. The substance which becomes brown in air, does not probably play any réle in the respiration of the animal. The blood in the vessels is perfectly colourless; the brown colour which is produced after it has been extracted from the body is probably a cadaveric or post mortem phenomenon comparable to the spontaneous coagulation which equally occurs in this: liquid. In fact, the colourless substance, which becomes brown on exposure to air is not contained in the blood which circulates, but is formed at the moment of spontaneous coagulation. If one carefully plunges the larvee of Oryctes into warm water (50° to 55° C.) for a quarter of an hour before opening it, the blood extracted from the dorsal vessel neither coagulates nor colours in air. The production of the colourless substance (susceptible of becoming brown in contact with air) has probably been prevented by the temperature of 50° to 55° C. For when once this substance has been produced, the temperature of boiling is incapable of preventing its combination with oxygen, and a change of colour which it indicates. Finally, the most important fact which proves that the phenomenon of colouration does not play any réle in the respiration of the animal, is that the brown substance once formed constitutes a stable combination, which is not decom- posed by acids or alkalies, and is not decolourised when placed in vacuo or in a sealed tube. The phenomenon of colouration which the blood of the larvee of Oryctes presents when it is exposed to air, appears to be a cadaveric phenomenon, and as already stated, com- PHYSIOLOGY OF THE INVERTEBRATA. 137 parable to spontaneous coagulation. The substance which becomes brown in air does not form any intermediate vehicle between the exterior air and the tissues which require it. The existence of such an intermediate vehicle is most doubtful, especially when one bears in mind the anatomical disposition of the respiratory apparatus in the Insecta, i.c., the air penetrates by the trachez among all the living tissues. By means of the trachez the function of respiration is carried on in every part of the body. THE CRUSTACEA. Dr. Léon Fredericq* has examined the blood of various Crustacea. The blood of crabs, lobsters, &c., which live in the sea, has exactly the same taste as sea water; which leads one to suppose that the blood or nourishing fluid of these animals has the same saline composition as the waters in which they live. According to an analysis of Backs, and cited by Pelouze and Fremy,t the water of the North Sea contains a little more than three per cent. of soluble salts :— Sodium chloride : « 2.358 Potassium chloride . . O10 Magnesium chloride. - 0.277 Magnesium sulphate. . 0.199 Calcium sulphate. . O.LIT 3.046 It tastes strongly salt and bitter. In support of the idea that the blood of certain Crustacea living in the North Sea, has the same saline composition as the medium in which they live, Fredericq obtained the following result after analysing the blood of an Ostend lobster (Homarus vulgaris) :— 3.040 per cent. of .soluble ashes. * Bulletins de V Académie Roya'e de Belgique, 3° série, tome iv. + Traité de Chimie, 3° éd., tome I, p. 252. 138 PHYSIOLOGY OF THE INVERTEBRATA. The blood of a large female lobster (bled by making a cut in the claws) weighed 26.49 grammes. This blood was dried at a moderate heat in a covered crucible; then heated to complete carbonisation. The porous carbon was exhausted with warm water. The filtered solution was evaporated to dryness, the residue allowed to cool in a dessicator, and weighed with the usual care. The 26.49 grammes of blood yielded 0.8055 gramme of soluble salts, equal to 3.040 per cent. 23.01 grammes of the blood of the crabs (Carcinus manas) of Roscoff yielded 0.708 gramme of soluble salts, equal to 3.07 per cent. The crabs (C. menas) of Roscoff living in sea water of a density of 1.026 were also examined; 14.78 grammes of the blood of these animals yielded 0.445 gramme of soluble salts, equal to 3.001 per cent. The hermit crab (Platycarcinus pagurus) of Roscoff, whose blood had a density of 1.037, was examined by Fredericg; . 13.54 grammes of this blood yielded 0.419 gramme of soluble salts or equal to 3.101 per cent. In the case of another hermit crab the blood had a density of 1.036, and 31.08 grammes of it yielded 0.965 gramme of soluble salts, equal to 3.104 per cent. In the case of the sea crayfish (Palinurus vulgaris) of Roscoff, 22.94 grammes of blood yielded 0.666 grammes of soluble salts, equal to 2.9 per cent. In the case of Maja squinado of Roscoff, 15.60 grammes of blood yielded 0.476 gramme of soluble salts, equal to 3.045 per cent. : The sea water of Roscoff in which the above Crustaceans lived was also analysed with the following results :—27.312 grammes of sea water yielded on evaporation 0.929 gramme of saline residue which is equal to 3.401 per cent. In another determination 26.266 grammes of the same water yielded 0.894 gramme of saline residue, which is equal to 3.407 per cent. PHYSIOLOGY OF THE INVERTEBRATA. 139 The Maja squinado of Naples lives in sea water which is exceptionally rich in saline matter ; 20.669 grammes of this water yielded 0.821 gramme of saline residue, equal to 3.9 per cent; 14.807 grammes of the blood of Maja yielded 0.498 gramme of soluble salts, equal to 3.37 per cent. Not only has Fredericq examined the blood of various Crustaceans inhabiting sea water but he has also examined the blood from those living in brackish and fresh water. 6.48 grammes of the blood of Carcinus menas inhabiting brackish water yielded 0.096 gramme of soluble salts, equal to 1.48 per cent: To examine the blood of fresh water Crustaceans seven crayfishes (Astacus fluviatilis) were used in the experiments. A large quantity of blood was obtained by making an incision in the claws. Its. taste was only slightly saline; 23.453 grammes of it yielded 0.221 gramme of soluble salts, that is less than one per cent. (0.94 per cent.) The following table gives a summary of the results obtained concerning the saline matter of the blood of various Crustaceans and the medium in which they live :— PROPORTION OF SALINE MATTER IN THE BLOOD OF CRUSTACEANS. Water in which th Blood: Thniaiale liveds . Per- Density. ee Density. Lee of ; salts. Astacus fluviatilis . _ 0.940 — fresh water Carcinus menas . a 1.480 ? brackish water. i $e _— 1.650 1.007 | about 0.9 ee 4 —_ 1.560 1.010 a 23 ” ” —= 1.990 1.015 5 1.9 ” ” — 3.001 |° 1.026 3.40 ” pet) a a8 ~~ 3-007 as 3-49 Homarus vulgaris . : aoe 3-040 1.026 3-41 Platycarcinus pagurus . 1.037 | 3-101 | 1.026 3-40 3 5 1.036 3.104 1.026 3.40 | Palinurus vulgaris _— 2.900 | 1.026 3-40 Maja squinado : : — 3.045 1.026 3-40 Pe 9% 3 3 a aS 3.370 2 3.90 140 -PHVSIOLOGY OF THE INVERTEBRATA. The blood of crabs living in brackish water contains a smaller percentage of saline matter than those living in sea water; and the blood of crayfishes living in rivers contains only a very small amount of saline matter—generally less than one per cent. According to the above investigations it appears that there is an exchange of salts, forming a kind of equilibrium between the composition of the blood and the external medium in which these Crustaceans live. This equilibrium is the result of the simple laws of diffusion. Among the fresh water Crustaceans the albuminoid substances of the blood probably retain a little more of the soluble salts than is contained in the external medium. It is probable that this exchange of dissolved salts is established by the respiratory organs—the branchie. The delicate walls of the branchiee, which separate the blood from the external medium, allow the respiratory gases to pass by simple diffusion: and most likely these delicate walls actin a similar manner to a dialyzer with easily diffusible salts. The albuminoid substances of the blood do not pass into the external medium. The nourishing fluids, to which the illustrious physiologist —Claude Bernard—gave the name of “milieu intérieur,” have not (with the animals previously mentioned) the constant chemical composition and independence of the conditions of the “ milieu extérieur ” which characterises the blood of the higher animals. Among fishes (Pisces) the branchial walls allow equally to pass the oxygen and carbonic anhydride of respiration. One can therefore understand that there is a similar exchange of salts between the blood and the external medium. But experience proves that it is the inverse of that which takes place among the Crustaceans and other Invertebrates ; for the blood of marine fishes has a saline composition which is entirely different from that of sea water. The blood of a sole, a PHYSIOLOGY OF THE INVERTEBRATA. 141 haddock, and a weever does not contain more soluble salts than the blood of fresh water fishes. ; Among fishes the interior fluid constituting the blood is isolated more or less from the external medium in which the animal lives. In regard to this there is an advance on that which occurs among Invertebrates. The blood of the Crustacea contains corpuscles which are very well defined. They are oval in shape, granular, and present a very distinct wall externally and nucleus within. THE Mo.Luusca. The blood of the lower Mollusca (Lamellibranchiata and Gasteropoda) is corpusculated, but the nuclei (which are generally present) are sometimes very indistinct. The percentages of saline matter contained in the blood of Anodonta and Mytilus were found to be the following* :— | I. IL, Ill. IV. | Average. Anodonta cygnea . 5 . | 1.002 | 0.998 | 1.006 | 0.996 1.000 Mytilus edulis we . | 1.796 | 1.799 | 1.810 | 1.800 1.801 It will be observed that the blood of the fresh water mussel contains a smaller amount of saline matter than that of the marine form. The blood of the Mollusca is principally colourless, but Dr. L. Cuénott has recently shown that the blood from the heart of Aplysia depilans (one of the Gasteropodc) has a distinct rose colour, due to the presence of 0.636 per cent. of an albuminoid which is precipitated by alcohol, acids, mercuric chloride, and the usual reagents. Its colour has no relation to the presence of oxygen, and it seems improbable that it plays any part in respiration. When the blood is dialyzed, * See Dr. Griffiths’ paper read before the Royal Society of Edinburgh on June 1, 1891 (P. &. S. £,, vol. 18, p. 288). + Comptes Rendus, vol. 110, p. 724. 142 PHYSIOLOGY OF THE INVERTEBRATA. or exposed for a long time to air, it decomposes spontaneously, part of the albuminoid remaining in solution and part separating in a white, flocculent form. This albuminoid is entirely distinct from hemocyanin, and has been called heemorhodin. If the blood is concentrated im. vacuo and heated, it becomes opalescent at 58° C., and coagulates completely at about 70° C. The blood of Aplysia punctata is quite different, and contains 1.77 per cent. of a perfectly colourless heemocyanin which is not affected by air, and coagulates at about 76° C. This albuminoid probably plays no part in the absorption of oxygen. In the Gasteropoda, Cephalopoda, as well as in the Crustacea and Arachnida, the function of respiration is brought about by an albuminoid substance analogous to hemoglobin, but contains copper instead of iron. This substance, which Fredericq* named hemocyanin, combines with oxygen, form- ing a very unstable combination. The blue colouring matter of the blood of Octopus vulgaris is due to the absorption of oxygen, for if the blood is placed in vacuo it loses its colour, but regains it in the presence of air or oxygen. Heemocyanin occurs in the arteries of the living Octopus. Krukenbergt examined the blood of Sepia _ officinalis, Carcinus menas, Homarus vulgaris, Squilla mantis, as well as other species of the Mollusca and Crustacea, and observed that the blood becomes blue by shaking with oxygen or air; and that the blue colour disappears more or less with carbonic anhydride. ‘“ Krukenberg also found great differences in the blood of individual Gasteropod Molluscs, which led him to assume that perhaps the oxygen in such cases is in a firmer combination with the hemocyanin than is the case in Crabs and Cephalopods. He also made the interesting observation * Archives de Zoologie. Expérimentale, 1878; see also Fredericq’s La Lutte pour 0 Existence, p. 84. t Vergleich. Physiol. Studien, 1st R., 3 Abh., 1880, 8. 72. PHYSIOLOGY OF THE INVERTEBRATA. 143 that the blood of Crabs and Cephalopods on treatment with carbonic oxide became colourless, but regained its blue colour on shaking with air. This behaviour is different from that of hemoglobin when similarly treated. It was further found that blood which had become blue by the reception of oxygen if allowed to stand in a test-tube exposed to the air did not lose its blue colour from above downwards, but from below upwards, whence he concludes that the blueing is not due to suspended particles, but to the presence of a chromogen which becomes blue by the reception of oxygen. .... He could find no hemocyanin in the blood of several Molluscs (e.g., Tethys fimbria, Doris tuberculata, Aplysia depilans, &c).” Although the blood of the higher Invertebrates, as a rule, contains copper, in some this element is replaced by man- gapese. Krukenberg has shown that the blood of Pinna squamosa (one of the Lamellibranchiata) as well as the organ of Bojanus are rich in manganese. If a borax bead is dipped into the blood of Pinna and then heated in the oxidising blowpipe flame, the bead becomes a distinct violet colour, and in the reducing flame it remains colourless. It is probable that copper, manganese, and possibly other metals play the same part in the blood of the Invertebrata as iron plays in the Vertebrata. The author* of the present volume has also extracted copper from the blood and organs of Sepia officinalis ; but the process was entirely different from those of Fredericq and Krukenberg. In the majority of the Jnvertebrata the carrier of oxygen to the tissues is hemocyanin contained in the blood; but in many of the Annelida, as well as in nearly all Vertebrates, the transport of oxygen from the surrounding medium (air or water) to the living tissues is made by means of the hemoglobin of the blood. * See Dr. Griffiths’ paper in Chemical News, vol. 48, p. 37; Journal of Chemical Society, 1884, p. 94. 144 PHYSIOLOGY OF THE INVERTEBRATA. This substance (as is well known) forms an oxygenised combination which is very unstable, and which is carried by the blood across the tissues of the animal, and is there dissociated, yielding its oxygen to the elements of those tissues which require it, Prof. Ray Lankester discovered that in some Annelids the hemoglobin is replaced by a green-colouring matter (chloro. cruorin). Reverting once more to the saline matter contained in the blood of the Mollusca, the author* obtained the following results (i. é., percentages) :— Dr. L. Fredericq+ found 3.016 per cent. of soluble and insoluble salts in the blood of Octopus vulgaris, ‘The author of the present volume has submitted to analysis the ashes of the blood of several Invertebrate animals. The ashes were obtained by incinerating the blood, I. Il. III. Average. é Hehx pomatia . «| 1.065 1.072 1.069 1.068 oS 2 Helix aspersa . + | 1.079 1.080 | 1.062 1.077 eH ® : é a Liimneeus stagnalis. | 1.200 | 1.203 1.210 1.204 an 3 Limax flavus. «| e122 1.100 I.1I5 1.112 "a : 3 # Limax maximus . - | WIIQ | 1.127 | 1.114 1,120 2 a g Buccinum undatum . | 1.699 1.710 | 1.698 1.702 a ad 3 g, &.| Patella vulgata . - | 1.706 | 1.721 | 1.719 1.715 = 1 Oe S 3 Sepia officinalis . » | 2.840 | 2.862 | 2.851 2.851 a3 2 & | Octopus vulgaris - | 3.004 | 3.032 | 3.020 3.018 partially covered in a platinum dish, at a very low tempera- 2 * A paper read before the Royal Society of Edinburgh on June 1, 1891. t Bulletins de UV Académie Royale de Belgique, 3° série, tome iv. PHYSIOLOGY OF THE INVERTEBRATA. 145 ture. By so doing the alkaline metals are not volatilised as they are when a high temperature is used. The following results represent the averages of three analyses in each case :— Cancer | Carcinus| | - 2 clot. Echinochrome in ‘‘ Serum.” Do. + Stan- nous chloride. a ees f Echinochrome ae ES ; in blood clot. Fe Do. + NaHO. 4 [ & Do. in absolute alcohol. u Do. with acetic i acid. Reed ie Do. with’stan- nous chloride. ey Dried clot i in ether. ANDY Do. in chloro- form. Do. in carbon bisulphide. pe rata Do. in benzene Fresh clot in glycerine.. Do. with stan- nous chloride. FIG. 29.—SPECTRA OF PERIVISCERAL FLUID OF STRONGYLOCENTROTUS LIVIDUS. (After C. A. MacMunn.) the colour changed to dark purple” and showed the bands in the spectrum a (Fig. 29). MacMunn says that the deepening of colour which echinochrome undergoes on exposure to the air must be in PHYSIOLOGY OF THE INVERTEBRATA. 151 part due to the oxidation of a chromogen, if so we may infer the existence of such, and name it echinochromogen. Echinochrome differs from the blood pigments of most Invertebrates, as it is readily dissolved by a great number of solvents. It can be obtained in solution and isolated by two methods :—‘(a) The fresh blood-clot can be extracted with the solvents mentioned before, or (0) the clot may be separated from the serum by filtering, the pigment dried at the tempera- ture of the air (as it changes by using heat) and the dried pigment thus obtained treated by solvents. By the adoption of the latter method it can be obtained in a purer condition.” “The ‘serum ’ after separation of the clot is a faint yellow colour and shows two faint bands in the green, but if allowed to stand some time in contact with the clot it becomes a faint violet red,” and then gives the spectrum seen in Fig. 29,6. On the addition of stannous chloride to the serum dark bands (Fig. 29, c) make their appearance. These bands have the following positions, X 541.5 to A 532 and 2 506 to d 486.5. Inthe oxidised condition the serum has a spectrum of the same kind but the bands are feebler. The serum is “faintly acid or neutral, faintly opalescent on heating, opalescent with absolute alcohol, and faintly so with ether.” Spectra Fig. 29, d and ¢ are those of the brownish-red clot, after standing in contact with the serum and with sodium hydroxide respectively. The red alcoholic solution of the clot gives the spectrum represented in Fig. 29,f. These bands read: first, A 55 7 to d 545-5; second, 524.5 to A Sor; third, A 494.5 to A475. On the addition of ammonium sulphide two new bands make their appearance. The first is from A 531 to 4507; and the second, 4494.5 to 4475, the colour of this solution being changed to yellow, and on shaking with air remained the same. On the addition of acetic acid to an alcoholic solution of the fresh clot, the spectrum given in Fig. 29,g is seen. ‘“ The spectrum of the original absolute alcohol solution is that 152 PHYSIOLOGY OF THE INVERTEBRATA. of the neutral pigment, as can be proved. Hydrogen peroxide did not affect the bands. Hydrochloric: acid produced the same effect as acetic acid; the bands reading: first, X 545.5 to XA 529.5; second, A 511.5 to A 488. When the alcohol solution is treated with stannous chloride the colour changes to yellow, and two very well-marked bands appear (Fig. 29, h). Dark part of the first band, A 535 to A 511.5; second, d 496.5 to 477. Sodium hyposulphite changed the colour to yellow, but the original bands could be seen, although faint.” Dr. MacMunn has also examined solutions of echinochrome in chloroform, water, ether, carbon disulphide; some of the spectra of these solutions are given in Fig. 29. Echinochrome is only partially soluble in water and alcohol, but is soluble in chloroform, ether, beuzene, glycerol, carbon disulphide, and petroleum ether. It is capable of existing in two states of oxidation, therefore its function is of a respiratory nature. Hchinochrome has not been obtained in. the crystalline condition. (2) The Annelida.—The blood of many Annelids contains hemoglobin; some contain pigments allied to chlorophyll, while others contain lipochromes. The blood of Arenicola piscatorum (one of the Polycheta) contains, besides hemoglobin, a lipochrome or lipochromes, Dr. MacMunn obtained a dark brown-green extract by treating this worm with a solution of caustic potash. This solution gave no bands. But he has extracted from the digestive system and the integument of Arenicola certain lipochromes, which have well-defined absorption spectra. The spectrum of the blood of Nereis Dumerillii consists of a single band like that of reduced hemoglobin. The spectrum of an aqueous solution of the blood of this worm consisted of two feeble bands; “the first was like that of the first of oxyhemoglobin, but the second was rather narrower than is the second blood-band. These bands read approximately: the first, from X 584.5 to 4574, the second, about d 550.5 to d 536, and a third one at the blue end of the green, from about PHYSIOLOGY OF THE INVERTEBRATA. 153 507 to A 474(?) was visible. Sulphide of ammonium caused these bands to disappear,” but Dr. MacMunn could not then detect that of reduced hemoglobin. The various colouring matters contained in the blood and organs of certain worms are given in the following table :— : : Chlorocruorin. | Lipochromes. diel pereate Hemoglobin. Polynée ; — present _ absent Aphrodite . @ = = —_ present Nereis cd _— present — = Sabella . : present = _ — Siphonostoma . present _— _— — Serpda. ‘ present ae _ _ | Cirratulus . ¥ _ i present _ present Terebella . . — present — present Lumbricus 5 — present _ present Hirudo. z _ = _— present -| Chetopterus . _— absent present = Arenicola . “ — . present = a Pontobdella , a = present aa Glycera. 5 _ —_ present Phoronis . 5 —_ = _— present ~ Dr. MacMunn has examined the green fluid (containing chlorocruorin) of Sabella by means of the microspectroscope. The spectrum (Fig. 30,@) consists of a dark band before D, and a feeble one between D and E. The green blood has “a reddish tinge with reflected gaslight, and in most cases is green with transmitted daylight, and reddish with transmitted gaslight. On dilution with water this fluid gave two bands: 154 ‘PHYSIOLOGY OF THE INVERTEBRATA. the first from \ 618 to X 593, the second from A 576 to A 554.5.” On adding ammonium sulphide, the spectrum Fig. 30, d is produced. The first of these bands extends from d 625 to d 596.5 (?), but this, and also the second band, says MacMunn, wt BC D Eb F G Oxychloro. ° = aye cruorin, * ‘ if ‘ The same i + NH4HS. ay Do. + NaHO, Aq. sol. + NaHO, then NH4HS. Blood of Ser- pula, living animal. Blood of another Serpula, Do. from a dilated part of blood-vessel. Do. from same part, a third specimen, Do. from same part, a fourth specimen. : j * Aqueous solu- i tion of blood , of Serpula. q Do. other specimens. Do. + NaHO, then NH4HS, Sane Gills of Serpula. : Operculum of : Serpula. FIG. 30.—SPECTRA OF THE BLOOD OF SABELLA AND SERPULA. (After C. A. MACMunN.) “were very faint.” After the addition of sodium hydroxide to this solution, a dark band is seen covering D, “which recalls to mind the band of alkaline hematin (Fig. 30,¢), and this band extends from A 595 to A 576.” PAYSIOLOGY OF THE INVERTEBRATA, 155 When the blood is treated with alcohol and potassium hydroxide and filtered, a yellow-coloured solution is obtained “free from bands, but on adding ammonium sulphide a band appears covering D” (Fig. 30,d). “On treating aqueous solutions with acetic acid the bands faded away, and the colour of the solution changed to a brownish colour (gaslight).” MacMunn tried the action of alcohol acidulated with sulphuric acid on chlorocruorin, and obtained a greenish solution, which showed a faint shading in the green, too indistinct to map. “ Hence none of the decomposition products of hemoglobin or hematin could be obtained, the pigment, as Prof. Lan- kester had already shown, being destroyed by the reagents required to produce acid hematin and hematoporphyrin. The blood of the pseudo-hemal system of Serpula contortu- plicata presents some resemblance to that of Sabella, There are slight differences in the blood spectra of some specimens, which doubtless are due to the pigment being present in different states of oxidation, and on comparing some of these spectra with those of the histohematins and with the decomposition products of hemoglobin, a striking likeness is apparent.” “On putting a Serpula into the compressorium, and bring- ing gentle pressure to bear on the upper surface of the animal, and examining with the microspectroscope, using a good achromatic substage condenser, a series of spectra are obtained when the various parts of the animal are moved under the objective ; what these parts are is seen by looking down the left-hand tube of the microscope. In this way we can differentiate the blood-vessels, intestine, gills, opercu- lum, and other parts, and study the spectrum of each.” With the pseudo-hemal system of Serpula, MacMunn obtained a spectrum represented in Fig. 30,¢c The band before D is like that of Lankester’s chlorocruorin, but the first after D and also the second are different. An aqueous solution of the blood from the pseudo-hemal system is yellow by daylight, reddish-yellow by gaslight, and 156 PHYSIOLOGY OF THE INVERTEBRATA. its spectrum is represented in Fig. 30,¢. The band before D was from A 620.5 to A593, the second about A 583.5 to A 572, the third uncertain (about \ 551 to’ 532). After the addi- tion of ammonium sulphide, “the only band seen with cer- tainty was that before D, which seemed slightly nearer the violet.” In an alcoholic solution only a faint band was visible from about » 501 to A477. In a specimen in which the blood appeared a bright carmine-red colour, MacMunn obtained the spectrum repre- sented in Fig. 30,7. The second band of this spectrum resembles the first band of hemochromogen, and is really the same as Fig. 30, 0. Fig. 30,g represents the spectrum of the blood from a dilated part of the principal blood-vessel of Serpula. ‘‘The darkness of the second band at once distinguishes the pigment from chlorocrurorin.” Fig. 30, 4 and i also represent the spectra. of the blood from the same part of a third and fourth specimen. “An aqueous solution of blood obtained from a dozen specimens, whose blood gave the above spectra, was yellow, aud showed the three bands represented in Fig. 30, /, and these gave the following readings :—First band, \ 618 to ) 593, second, A582 to 1570.5; third, A551 to A529.5 (?) On treatment with sulphide of ammonium the solution became slightly greener; no bands could then be seen after D, and that before it was very faint. Hence it would appear that the two- and three-banded spectrum denotes the oxidised state.’ “In some Serpula, whose blood was not red but brown, the bands before and after D reminded one of chlorocruorin (Fig: 30, %). An aqueous solution of the blood of these speci- mens had a reddish tint by gaslight, and gave three bands, which read as follows:—First, X 620.5 to. 595; second, d 538.5 toA 570.5; third, A551 to A532. On adding sul- phide of ammonium, the band before D read 2620.5 to d 598, and a second band was visible after D, which could not ..be measured. On adding to this reduced fluid some caustic soda, at first the only change produced was the disappearance PHYSIOLOGY OF THE INVERTEBRATA, 157 of the faint band after D; but, after standing, the spectrum given in Fig. 30,/ appeared, of which the bands read: first, 4623 to (607; second, A 596.5 toA579. This shows that the blood of these Serpulew did not contain the same kind of chlorocruorin as Sabel/a, but a pigment very closely related to it, probably nearer to hematin than it.” MacMunn has also investigated spectroscopically the gills and opercula of Serpula. The pigment present is allied to, if not identical with, tetronerythrin. The use of this pigment is not of a respiratory nature. “It is not unlikely that, especially when its likeness to Kiihne’s chromophanes is taken into consideration, it may be of use in absorbing rays of light concerned in some obscure photochemical process.” * From what has been said, it will be seen that the blood of the Annelida contains various pigments; and that hemo- globin and the lipochromes are uniformly distributed among these animals. Krukenbergt observes: “ Chlorophane und rhodophane tragen auch bei Wiirmern in manchen Fallen viel zu einer lebhaften pigmentirung bei.” (3) The Jnsecta.—Mr. E. B. Poulton, F.R.S., has examined spectroscopically the blood of Lepidopterous larvee and pupe. He used Zeiss’ microspectroscope in these researches, which was found “to be extremely delicate and convenient on all occasions.” Asa means of illumination a paraffin lamp was at first used, “‘ and it acted very well for the less refrangible half of the spectrum, but in all later work bright sunlight was alone employed, because of its immense superiority at the violet end.” Concerning Zeiss’ and other microspectroscopes used in researches on the chromatology of the Invertebrate blood, a description of these instruments will be given later in the present chapter. The greatest care is required in obtaining the blood of insects so as to prevent any admixture with food particles of * Quarterly Journal of Microscopical Science, 1885. + Grundziige einer vergl. Physiol. d. Farbstoffe und der Farben, 1884, p. 137- 158 PHYSIOLOGY OF THE INVERTEBRATA. the alimentary canal or any secretions. As the blood in Lepidopterous larvae exists under considerable. pressure, it is readily obtained by making a minute prick in the hypodermis, Tn larvee, Mr. Poulton generally pricked the distal parts of the claspers; and then examined a drop of the blood under the microscope to see if any food particles were mixed with it. The blood should be perfectly clear, containing only colourless corpuscles, fat-cells, and minute spherules of fat. The blood of pupz was obtained by making a prick in the cuticle of the wings. The blood at once issues, being under considerable pressure. ‘‘ The whole of the blood was obtained by pushing the abdominal segments inwards, and ultimately by gradually increasing compression of the pupa. Owing to histolytic changes, the weak and thin-walled digestive tract is broken, and a red fluid escapes, which is mixed with the last of the blood. By carefully watching for the first appear- ance of the red fluid, the blood may be obtained in a perfectly pure state, exactly resembling that of the larva in clearness and in microscopic contents. The blood is received into sections of glass tubes of various lengths, with the ends care- fully ground. One end is cemented with Dammar varnish ° to a glass slide, and when the tube is filled with blood a cover-glass is placed upon the open end, and becomes fixed by the drying of the blood. In most cases the blood so pre- pared will keep for months without change. If, however, air be admitted, an opaque black clot is formed on the sur- face, and the rest of the blood becomes cloudy. It will also keep indefinitely in sealed tubes.” * Mr. Poulton has examined the blood of the larve ot Philogophora meticulosa. These larvee assume various shades of colour between green and brown. The green blood was taken up by a capillary tube (0.75 mm. internal diameter); and allowed to stand four days, during which time it was reduced to about half its volume (due to evaporation). The tube was then sealed. The spectrum produced by using a | * Proc. Roy. Soc., vol. 38, p. 283. PHYSIOLOGY OF THE INVERTEBRATA, 159 paraffin lamp was the following: “a broad band in the red, of which the extreme edges extended from 64.5-68.5, and when this band was best seen the violet end was cut off at 51, and the green was darkened to 52. There was no absorption of the red end. When the blood was fresh and less concentrated, the blue came through on the violet side of the darkening at 51, thus showing a broad dark band between this part and the green. A more concentrated sample of similar blood, prepared in the same way and at the same time, gave a darker band in the red with the sume limits, but with more defined edges. The violet end was similarly absorbed. There were indistinct traces of a broad dim band about 59-61.5.” “The fresh blood of another individual of the same species which was dark greenish-brown, due to a combination of subcuticular pigment and green blood, was examined in a capillary tube. The compound character of the larval colour- ing was proved by gentle pressure. The pale green blood with a thickness of about 1 mm. gave the band in the red from 65-68, the violet end, being completely absorbed at 45, darkened to 51 (when the slit was narrowed so as to render the band distinct). A greater thickness of blood darkened the band, and cut off the violet end at 50, darkening to 52 (when the band was distinct). A still greater thickness produced more marked results with nearly the same limits. On widening the slit, no blue appeared at the absorbed end, The dark band now seemed to extend to 68.5. The whole spectrum was much dimmed, but this was probably due to the accidental presence of fat in the blood. In this case the thickness of fluid was 3.3 mm., and the colour was bright green.” The fresh blood of a dark-brown larva (P. meticuwlosa) pro- duced a spectrum with a faint band in the red. After the blood had been exposed to the air for 24 hours it became brown, but the spectrum was not altered. The spectrum of the green fluid contents of the alimentary 160 PHYSIOLOGY OF THE INVERTEBRATA. a band in the red from 65.5-68.5, while the blue was cut of at so, darkened to 52. : Poulton remarks that “this observation upon the green fluid from the digestive tract is important, because it serves to identify the chlorophyll in the blood with that taken’in ag: food. It is likely, however, that a greater thickness‘of fluid and the use of sunlight would bring out some differences between the derived pigment dissolved in the ee secre- tions, and that united with a proteid in the blood... . .. It seems quite certain that the derived pigments of the’ blood and tissues are only protective, and play no further parting the physiology of these organisms. Thus there are nox marked differences between the physiological processes’ the brown and green individuals of the same brood ina, dimorphic species, or in the processes of a green larva, whic] r has become brown, or vice versd. It seems that the pigmef are entirely harmless, and are often retained when they would have no effect upon colour. Thus, in Pygwra Bucephalus, the blood is bright green, although the larva and pupa are ~ entirely opaque, while the eggs are white. It is possible™ that in this case the conspicuous colours—which warn enemies that the species is distasteful—have been recently acquired, 4 and in consequence of the complete opacity, there would be no advantage in losing the colour of the blood.” In the experiments just mentioned, Poulton used a paraffin lamp as a means of illumination, but he afterwards found that by the aid of sunlight the spectra were further developed. The concentrated green blood of the larva of P. meticulosa, when examined by sunlight, gave the spectrum represented in Fig. 31, sp. 1. ‘The band in the red, reaching from 64.5-68, was very black, except at the edges. When this band was most distinct and clear, the violet end was absorbed to 51, darkened to 52. On opening the slit a little, the blue came through (though dimmed) at 48, the violet end being absorbed at 43. When the slit was very narrow, traces of canal of another brown individual of the same species on = PHYSIOLOGY OF THE INVERTEBRATA. 161 Fic. 31.—SPECTRA OF THE BLoop oF LEPIDOPTEROUS LARVA AND Pupa&. (After E. B. PouLton.) Spectrum 1.—The blood of the larva of P. Weticulosa (green variety) examined in a thickness of about .75 mm. by sunlight. The blood had been allowed to remain in an open capillary tube for about four days, and was then sealed up after it had evaporated to half its bulk. Spectrum 2.—The fresh and unaltered blood of the pupa of S. Ligustri, examined in a thickness of 35 mm. by sunlight. Spectrum 3.—The fresh and unaltered blood of the pupa of P. Bucephalus, examined in a thickness of 23 mm. by sunlight. Spectrum 4.—Two fresh calceolaria leaves, gently compressed, and examined by sunlight. Spectrum 5.—Five ditto ditto. ‘Spectrum 6.—The fresh and unaltered blood of the pupa of S. Ligustri, examined in u thickness of 3mm. by illumination from the bright sky near the sun. L 162 PHYSIOLOGY OF THE INVERTEBRATA. another band, from 59.5-61.5, were faintly seen. .... The two chief bands and the absorption of the violet end were also seen in the blood of a living larva by passing the light through one of the claspers.” Poulton has also examined the blood of the pupee of the Pygera Bucephalus, Sphinx Ligustri, Cherocampa Elpenor, Smerinthus Ocellatus, Smerinthus Tilie, Smerinthus Populi, Dicranura Vinula, Papilio Machaon, Ephyra Punctaria, and the ova of Ennomos Angularia, S. Tilie, S. Ocellatus, and Sphinx Ligustri. He has also made a comparison between the spectra of the pigments contained in the blood of Lepi- dopterous larvee and pupee, and the spectra of unaltered plant pigments (see Fig. 31). The spectrum of the green blood of the pupa of P. Bucephalus is represented in Fig. 31, sp. 3. ‘The characteristic band in the red ends sharply at 71, gradually at about 64.5, pass- ing into a lesser absorption of the red, which is continuous with the second band, extending from about 58-60.5, but with very indistinct limits. When these appearances are best seen, the violet end is completely absorbed to 52, dark- ened to 52.5. On opening the slit a little, the dimmed blue comes though from 48-42. The band in the blue now sharply ends at 52, gradually at 48. Diminishing the thickness of the blood to 8 mm. (the previous thickness being 23.5 mm.) produces nearly the same spectrum, the band in the red being a little narrower, while the band at D cannot be detected. On diminishing the thickness still further to 1 mm., another band appears in the violet. The spectrum is as follows: The characteristic band from 65-70; the chief band of the blue end, 48-51; the second band of the blue end, 45-46.75 ; the violet being absorbed at 41. The second band of the blue end is much fainter than the first band, and it is not seen in a thickness of 5 mm.” Fig. 31, sp. 2, represents the spectrum of the fresh blood of the pupa of Sphinx Ligustri. The characteristic band extends from 70 to 64.5, becoming gradually continuous with PHYSIOLOGY OF THE INVERTEBRATA. 163 a less absorption, extending to D, of which “the part from 59-60 corresponds to the second band of the less refran- gible part of the spectrum and the third band of true chloro- phyll. The violet end is completely absorbed from 51.5, dimmed to 52, but on widening the slit a little, blue comes through on the violet side of 48, but very dimly.” With a thickness of 3 mm. the blood gives no absorption of the red, but shows three bands at the violet end (Fig, 31, sp. 6). The blood of the pupa of S. Ligustri is a yellow colour in those individuals which have fed upon privet in the larval state, and greenish-yellow in those which have fed upon lilac. ‘Comparing the spectra of the blood from pupz of which the larvee had fed upon different foods, it was found that the lilac-fed individuals showed greater effect at the red end than the privet-fed individuals, while the converse was true of the violet end. The comparison was made in a thickness of about 8 mm. and by sunlight.” The table on p. 164 gives the spectra of the blood obtained from various Lepidopterous pupe. After adding absolute alcohol to the blood of the pupa of S. Ocellatus, a bright yellow solution of xanthophyll was ob- tained, which gave ‘“‘the characteristic spectrum (shifted to the violet) 49-47, 45.25-44, the violet being absorbed at qo? Alcoholic extracts of the ova of #. Angularia, S. Tilie, S. Ocellatus, and Sphinn Ligustri gave each the spectrum of xanthophyll. Poulton has made a comparison of the above results with those yielded by unaltered plant pigments. In Fig, 31, sp.4 and 5, are given the spectra of two and five calceolaria* leaves (superposed) respectively. ‘Comparing these two spectra with those of green blood (Fig. 31, sp. 1, 2, and 3), the re- semblance is seen to be very great, the chief differences being in the second and third bands of the red end, which are con- tinuous (Fig. 31, sp. 2 and 3), while the third is developed * The same results were seen in the leaves of other plants, PHYSIOLOGY OF THE INVERTEBRATA. 164 ‘eb-EP \ ‘prryy !Sb-SZ'ob ‘puooes {£:0S-gh ‘paeq jo1qg v ; ED ‘cS 04 pous -yrep ‘19 4e@ yo yno pua yajota ' 69- ee ‘pueg # HeReaUSHACUSR | * * RRE 8 “Sul ‘pasn dury -WapIA TO YSno1yy stavo anyq t 16 07 peueyIep | I : 4 z mn -uygered jo yySrq7 ‘ob 03 poqrosqe pua yojo[a ‘66-99 ‘pueg “SUIUOPIM uo ysnoiy4y omvo entq ou £19 0} pemuIp \ $ maady : ‘aur “st ‘oS 0} peqiosqe pues yefora ‘of-S'bg ‘pueg ‘soTqoliva [[@ WoIT ‘Iv ye paqiosqe pua yejora £ zv-£b af) ¢¢ MOTIOX a uonyoyy ‘gq ames uinzjooedg {| ‘paryy §Sb-Sz-gh ‘puooes { gb-o$ ‘pueq jJeryO ‘pesn dur ‘0S 03 -uyyered jo yqsrT dn paqtosqe pue yeTora 4nq ‘a[qIsta spueq ON } she MMOLO-MSIDDOe. |i BNA “TE ‘Ib 4B poqrosqe pus yepora {eb-£b ‘paryy § Sb-Sz-gb ‘puooes | fz uMOIq-Ystppey | * ° Louadya ‘9 $gb-S.0$ ‘pueq jorqo £ $9-S.69 Mory pueg ) *pautwexa “syIvwey “4ysiqung YT vaijoedg poorg, jo “wu *poorlg Jo anojop9 _ ‘adag UT ssaUyoTY, PHYSIOLOGY OF THE INVERTEBRATA. 165 before the second (Fig. 31, sp. 1). Considering the chemical change which must have taken place in the chlorophyll during digestion, rendering possible the passage of the walls of the digestive tract, and considering its chemical union with a proteid constituent of the blood, the resemblances of the spectra are very striking; in fact, the two spectra are far nearer to each other than the ordinary spectrum of chloro- phyll in alcoholic solution is to the unaltered chlorophyll of leaves.” Alcoholic solutions of chlorophyll are very unstable, the reason being that the alcohol precipitates the proteid which was orginally united to the colouring matter in the living plant or animal. Consequently, in the alcoholic solution the combination is no longer the same. Both the chlorophyll and xanthophyll in caterpillars’ blood are united chemically with a proteid; hence their great stability. The separation of these pigments from the proteid is at once effected by the addition of alcohol. The former pass into solution, while the latter is precipitated. The solution of the pigments is very fugitive; an alcoholic solution of chlorophyll changing in a few seconds, so rapidly is it acted on by light. “But while the pigments exist unchanged in the blood of many larvee for a long time, in other species they are entirely destroyed during the comparatively short period preceding ecdysis, when some green larvae become brown; and con- versely the pigments may appear in the blood equally suddenly. The former change must be due to an active destruction or excretion of the pigments, and is probably also accompanied by changes in the digestive tract, whereby no more pigment is passed through its walls. And so also the proportions of xanthophyll and chlorophyll may be changed during the life of a caterpillar.” From Poulton’s interesting investigations it will be observed that Lepidopterous larvee and pupz make use of a modified chlorophyll, as well as other plant pigments, derived from 166 PHYSIOLOGY OF THE INVERTEBRATA. their food, because of the protective * colour which they acquire from its presence in their blood and tissues. (4) The Arachnida.—Professor Ray Lankester t has shown that the blood of Scorpio becomes blue. on exposure to air, It contains hemocyanin. The blood of Epeira, Tegenaria, and Pholcus also contains hemocyanin. (5) The Crustacea.—Concerning the blood of the Crustacea, Genth in 1852 first observed the blue colour of the blood of Limulus cyclops; and in 1857, Professor Haeckel t observed that the blue blood of Homarus became, after many hours’ exposure to the air, a violet colour. In 1873, Rabuteau and Papillon § experimented on the blood of crabs, and found that it became blue in contact with air, but lost this property when submitted to the action of carbonic anhydride. It, however, recovered its blue colour on shaking with air. “ Jolyet and Regnard || showed in 1877 that on shaking crabs’ blood with air it showed a beautiful blue or brownish colour, according to the manner in which it was examined; it gradually loses this colour, becoming reddish and then feebly yellow; but on treatment with pure oxygen its original colour is restored. They found two colouring matters in crabs’ blood: one is blue, and is precipitated by alcohol with the albumin of the blood; the other is reddish, and remains in the alcoholic filtrate.” In 1879, Dr. Léon Fredericg { proved that the blue blood of Homarus contained hemocyanin, and that it was blue with reflected and brown with transmitted light. The blue pigment —hzemocyanin—is a proteid containing copper. The red pig- ment in crabs’ blood is also present in the blood of Homarus. But this pigment does not belong to the proteid constituents of the blood ; it does not contain copper, iron, or manganese, * From enemies. + Quarterly Journal of Microscopical Science, 1878, p. 453- ¢ DMiller’s Archiv, 1857, p. 511, Anm, i. § Comptes-Rendus, t. 77, Pp. 137+ || Archives de. Physiologie, 2 série, t. 47. GY Bulletins de ? Académie Royale de Belgique, 2 série, t. 47. : ‘ PHYSIOLOGY OF THE INVERTEBRATA. 167 and it has nothing to do with the change in the colour of the blood. It may be remarked in passing that Dr. W. D. Halliburton, FE.R.S.,* has shown that the blood plasma of Homarus contains a red pigment, which is soluble in alcohol, ether, and chloro- form; but it is possible that this pigment belongs to the histoheematins which Dr. MacMunn has found to be pretty generally distributed in the tissues and organs of the Invertebrata. The blood of Homarus, Cancer, Carcinus, and Astacus does not show any absorption bands when examined by the microspectroscope. The blood in all these animals contains heemocyanin. The blood of Apus, one of the Phyllopoda, is of a red colour, and, according to Lankester, this colour is due to haemoglobin. Another Crustacean which has red or violet blood is Gam- marus. ' (6) The Polyzoa.—Several of the Polyzoa contain lipo- chromes; and in Flustra foliacea MacMunnt has shown there exists a chlorophylloid pigment which is soluble in alcohol. The spectrum of this pigment somewhat resembles that of modified chlorophyll. The alcoholic solution is a yellow colour, and has a red fluorescence. Its chief dark band reads from X 681°5 to X 656, its darker part from 4678 to d 662. “Tt showed another before D; the third chlorophyll band was missing, and there was one lipochrome band.” (7) The Mollusca.—The blood of many Molluscs contains the pigment hemocyanin. In 1816, Erman simply recorded the fact that the blood of Heliz was of a blue colour. Harless and Von Bibrat (in 1847) stated that the blood of Helix pomatia acquired a blue colour on exposure to air, but this colour was discharged by shaking the blood with carbonic anhydride. They also * British Medical Journal, 1885. + Proc. Physiol. Soc., 1887; and Quart. Journ. Micro. Science, vol. 30, p. 79- t Miller's Archiv, 1847, p. 148. 168 PHYSIOLOGY OF THE INVERTEBRATA. observed “that ammonia removed the blue colour, which came back on neutralising with hydrochloric acid. They stated that this blood contains copper, but no iron; but Gorup-Besanez* found iron also in its ash.” In 1858, Dr. Witting recorded in his paper, “ Ueber das Blut einiger Crustaceen und Mollusken,”{ that the blood of Unio pictorum had a slight blue tinge. Similar observations were made by Rougett in 1859 on the blood of Octopus vulgaris, In 1867, the late Dr. Paul Bert§ described the blood of Sepia as “ feebly bluish, especially in the veins of the gills, and that it acquired a bright blue colour on exposure to air. This colour belongs to the plasma, and is not lost by boiling.” Rabuteau and Papillon|| in 1873 examined the blood of Octopus, which became blue on exposure to air. They also examined spectroscopically the blood of this animal, and arrived at the conclusion that it gives no bands. But the most remarkable paper on the blood of Octopus vulgaris is that of Dr. Fredericq,# published in 1878. He proved that the blood contained hemocyanin, and that the substance was a proteid combined with copper. There is no doubt that the blueing of the Molluscan as well as Crustacean blood is due to the oxidation of hemocyanin, and that hemocyanin is the carrier of oxygen within the system. The blood of Helix and Avion was also shown by Fredericy to contain hemocyanin, and to give no absorption bands, Among the Mollusca, the late Dr. Krukenberg** examined the blood of Eledone moschata, Sepia officinalis, Limneus * Lehrbuch der Physiologischen Chemie, p. 369. + Journal fiir Practische Chemie, Bd, 73, s. 121-132. +t Journal de lu Physiologie, t. 2, p. 660. § Comptes-Rendus, t. 65, p. 300. || Comptes-Rendus, t. 77, p. 137. { Bulletins de V Académie Royale de Belgique, 2 série, t. 46. ** Vergleichend-physiologische Studien, 1st Reihe, 3 Abth., 1880, s. 72. PHYSIOLOGY OF THE INVERTEBRATA. __ 169 stagnalis, Helia pomatia, and Helix aspersa ; and in all these he observed that the blood became blue by shaking with air and oxygen, and that the blue colour disappeared in the presence of carbonic anhydride. Krukenberg states that in the blood of the three last-named Molluscs there exists a body very nearly related to, but different from, hemocyanin ; but there is no doubt that hemocyanin exists in the blood of these animals. Krukenberg could find no hemocyanin in the blood of Tethys fimbria, Doris tuberculata, Aplysia depilans, and Pleurobranchus. Many years ago the blood of Anodonta cygnea was examined by Schmidt,* who described it as colourless; but the blood of this Lamellibranch contains, without doubt, heemocyanin. Among the Mollusca, MacMunnt has examined the blood of Heliz pomatia, Helix aspersa, Paludina vivipera, and Limneus stagnalis, The blood of these animals gave no absorption bands when examined by the microspectroscope. “The blood of Helix aspersa was found to be a bluish-white colour by daylight, but by gaslight it had a purplish tinge; after twenty-four hours’ standing that had disappeared, and it was then very slighly brownish. Examined in a deep layer, no bands could be seen; on treatment with ammonia, the blue colour persisted, and no bands came into view. With acetic acid the blue colour persisted, and no bands . appeared. After repeated filtering the blue colour remained ; hence it can hardly have been due to particles in suspension. On treatment with reducing agents the blue colour was lost, and no bands appeared.” The blood of Helix pomutia “assumed a distinct blue tinge on exposure to air, and gave no absorption bands, but absorbed a little of the violet end of the spectrum. On treatment with ammonia its colour was not so well marked, * Lehmann’s Handbuch der Physiologischen Chemie. + Quarterly Journal of Microscopical Science, 1885. 170 PHYSIOLOGY OF THE INVERTEBRATA. and it had a faintly reddish tinge, but no bands could be seen, nor after treatment with acetic acid, which did not remove the colour. On treatment with ammonium sulphide the blue colour disappeared, and could not be again brought back by shaking with air for some time; the fluid had assumed a bronze colour, and with gaslight a faint violet tint, but no bands were seen.” The blood of Zimneus stagnalis assumed a whitish-blue colour on exposure to air, “ gave no bands, nor after treat- ment with ammonia, acetic acid, or ammonium sulphide; the last discharged the colour completely, which could not be restored on shaking with air.” The blood of Paludina vivipara “is frequently exuded when the animal is pricked with a needle or otherwise irri- tated, and is of a blue colour. It is quite free from bands. Ammonia slightly diminishes the colour, but does not remove it; acetic acid does not remove it. With neither reagent nor ammonium sulphide could any distinct bands be obtained.” The blood of the majority of the Mollusca contains heemo- cyanin, that of a few contains hemoglobin (¢.g., Planorbis), while that of others, according to Krukenberg, is devoid of either of these substances. Microspectroscopes. As the examination of the colouring matters of the blood necessitates the use of a microspectroscope, we now proceed to describe two forms of this important instrument of re- * search. The one used by Mr. E. B. Poulton, F.R.S., in his investi- gations on the blood of the Lepidoptera is illustrated in Fig. 32. This instrument has the slit mechanism between the lenses. The upper achromatic lens is adjustable to the slit; an Amici prism is placed over the eyepiece, and the whole connected with the body by a clamping screw. The mechanism worked by the screw F is for contracting and expanding the slit by the symmetrical movement of both PHYSIOLOGY OF THE INVERTEBRATA. 171 edges. This opens so widely as to permit a view of the whole visual field. The slit is shortened by the screw H, so that when the comparison prism is inserted the aperture is contracted to such an extent that the image of the object under investigation completely fills it. There is a comparison prism, with lateral frame and clips to hold the compared object and the ‘mirror; all these parts are fixed in a drum combined with the eyepiece. Above the eyepiece there is Fic. 32.--THE ABBE-ZEISS MICROSPECTROSCOPE. I = Microspectroscope (half actual size). 2 = Drum with mechanism of the slit (actual size). an Amici prism of great dispersion, which turns aside on a pivot, leaving the eyepiece unobstructed for adjustment to an object K; the axial position of the prism is indicated by the spring L, which keeps it in place. A scale is projected on the spectrum by means of a small scale-tube and mirror attached to the mount of the prism. The divisions of the scale give the wave-lengths of that section of the spectrum on which they fall in fractions of a micromillimetre, whereby the second decimal place may be read off directly, and the 172 PHYSIOLOGY OF THE INVERTEBRATA. third calculated by estimation. The position of the scale relative to the spectrum is adjusted by a screw P on the jacket of the Amici prism. Fig. 33 represents Dr. Engelmann’s microspectrometer, which is constructed on the principle of Vierordt’s spectro- photometer for quantitative microspectrum analysis. In place of the eyepiece, the box A is attached to the body of Fic, 33.—THE ENGELMANN MICROSPECTROMETER, the microscope by the tube R; it contains two independent, conaxial, movable slits in juxtaposition, which are sym- metrically opened and closed by opposed reverse-threaded screws. The width of each slit is read off on the drums T and ‘TY accurately to ool mm., and by estimation to o‘oo1 mm. One slit is occupied by the image of the object under investigation, and the other by light from the source PHYSIOLOGY OF THE INVERTEBRATA. 173 of comparison, which is brought to it by a superimposed reflecting prism and lateral tube d with collimator lens, diaphragm carrier n, and mirror S, or incandescent lamp. In the upper opening of the box A is placed either an eyepiece in a sliding jacket, which is accurately adjusted to the slit; or, instead of this (after proper adjustment of the FIG, 33-—THE ENGELMANN MICROSPECTROMETER. image of the specimen in the objective slit) the spectroscopic apparatus a'A’BC, which is fixed in the proper azimuth by an arresting mechanism. This apparatus consists of the box A' which on one side (the upper end of a’) contains a col- limator lens /, to render parallel the cone of rays proceeding from the objective before they fall on a Rutherford prism P of great dispersion. By the lens /' on the other side (at the 174 PHYSIOLOGY OF THE INVERTEBRATA. lower end of B) the parallel rays proceeding from the prism are again brought to a focus, and this’ real spectrum is observed by an eyepiece L. By two slit mechanisms at right angles to each other, actuated by the screws ¢¢', wu’ in the focal plane of the eyepiece, the visual field can be limited at pleasure according to the procedure of Vierordt. By means of two lenses shown at C an image of a wave- length scale is projected on the spectrum by reflection from the end-surface of the Amici prism, which is illuminated by the mirror S’ and put out of action by closing the shutter d’. Adjustment of this scale is made by inclining the whole scale-tube C with the screw w, which is opposed by a counter- spring v (Fig. 33). Both of these instruments are of the utmost importance for investigating the chromatology of the Invertebrata. Although Dr. MacMunn* uses the microspectroscope, he says that, “when the amount of material is sufficient for the purpose, it is best to measure the position of bands by the chemical spectroscope and reduce the readings to wave-lengths by means of a curve plotted out on logarithm paper, as directed in Watts’ Index of Spectra. Similarly, the readings of others can be reduced to wave-lengths by laying a scale— say of millimetres—along the top of their maps, and noting the readings of the Fraunhofer lines, and then, by means of an index of spectra (such as Watts’), finding the wave-length of these lines, and laying them down in accordance with these data on the logarithm paper. One can also detect an error in the map of any observer by this method. ‘So delicate is this graphical method of detecting error, that ‘by its means we might very readily detect error in tables of logarithms or trigonometrical functions.’ In using the diffraction grating it is nearly a straight line, and Sir George Stokes, F.R.S., says that by using the reciprocals of the wave-lengths instead of the numbers themselves, one has a straight line instead of a curve.” * Proceedings of Birmingham Philosophical Society, vol. 5, p. 180. PHYSIOLOGY OF THE INVERTEBRATA. 175 Dr. MacMunn uses in his researches three spectroscopes— (1) a microspectroscope, (2) a Hilgers’s “ Student’s Kensing- ton Spectroscope,” and (3) a large spectroscope with one dense flint-glass prism, which is replaceable by a reflection diffraction grating. He has curves adapted to each, so that he can easily correct any error of observation by comparison. “The wave-length record of bands has raised the chroma- tology of plants and animals from a state of chaos to one which is daily assuming shape and symmetry, and we are now beginning to perceive relationships and the shadows of generalisations which when made will undoubtedly be of great help to biology.” From the above remarks it will be seen that the spectro- scope is an instrument of the greatest value not only to the chemist and physicist, but also to the biologist and physiolo- gist. “ Until the spectroscope was applied to physiology no one knew what the true colouring matter of the blood was, and the chaotic state of medical knowledge with regard to the cause of the colour of the various animal secretions (of which survivals are still found in many text-books) is sufficiently proved by a perusal of the older text-books, in which one finds the pretended knowledge of the authors cloaked under the adoption of meaningless names, which may have, at the time they were written, brought conviction home to those incapable of judging for themselves, but which show us now what physiological chemistry alone could do, unaided by spectroscopic analysis, in detecting animal pigments and enabling us to follow their metabolism ” (MacMunn). Tur GASES OF THE BLOOD. Very little is known concerning the composition and nature of the gases in the blood of the Invertebrata. The author* has ascertained the approximate composition ‘* A paper read before the Royal Society of Edinburgh on June 1, 1891; and also in Revue Générale des Sciences pures et appliquées, 1891, Pp. 395. 176 PHYSIOLOGY OF THE INVERTEBRATA. FIG, 34.—APPARATUS FOR EXTRACTING THE GASES OF THE BLOOD. - e of the gases in the blood of certain Invertebrate animals. The apparatus used for this purpose was that of Gautier slightly modified (Fig. 34); and the method allows the col- PHYSIOLOGY OF THE INVERTEBRATA. 177 lection of the blood in vacuo (from the time of leaving the vein, &ec.) without any alteration in its composition. The glass receiver ACD (left-hand figure), in which the vacuum is made, has a canula E fastened to its lower:end. The canula is drawn out into a fine capillary point, which is pushed into the artery, vein, or under the hypodermis, as the case.may be. After introducing the canula into the blood system, the tap B is opened, and the blood rises into the receiver, The gases are evolved almost immediately, and by means of the pump they are collected over mercury in the tube ab, where their composition is ascertained. After the introduction of the blood into the receiver the tap B is turned off; the receiver is then attached to the pump. Before opening the tap A, the receiver is placed in a bath of water heated to about 40° C. The heat assists in the liberation of the gases from the blood. Coagulation is pre- vented by previously introducing a small quantity of sodium chloride into the receiver (i.¢., before the introduction of the blood).* The pump and pneumatic trough do not require description, as they are of the usual kind. The volume of the mixed gases collected at ab having been ascertained, the percentage of each gas is estimated by the ordinary methods of gas analysis. The carbonic anhydride is absorbed by potash, the oxygen by pyrogallic acid, whilst the amount of nitrogen is represented by what remains. (a) Blood of Sepia officinalis, A hundred volumes of the blood of the cuttlefish contained the following volumes of the three gases—the volumes being reduced to 0° C. and 760 mm. :— * The liberation of carbonic anhydride is accelerated by previously introducing into the receiver a small quantity of a hot solution of tartaric acid. 178 PHYSIOLOGY OF THE INVERTEBRATA. I. Il. Ill. IV. | Ve | Vi. Oxygen . ‘ - | 13.26 | 12.91 | 13.14 | 14.62 | 14.21 | 14.34 | ' Carbonic anhydride . . | 30.12 | 31.21 | 32.10 | 30.14 | 29.12 | 29.89 |! Nitrogen . : 2 . | 1.60] 2.00] 1.51 | 1.41 1.73] 1.23 The nitrogen is simply dissolved in the blood, but the oxygen and carbonic anhydride are partly dissolved and partly in a state of loose chemical combination with certain constituents of the blood. The oxygen, with the hemocyanin, and possibly the greater part of the carbonic anhydride, is united to certain salts contained in the blood. (b) Blood of Cancer pagurus. The blood was obtained from very large individuals by opening the carapace, and passing the capillary point of the canula directly into the heart. A hundred volumes of the blood yielded the following volumes of oxygen, carbonic anhydride, and nitrogen after being reduced to 0° C. and 760 mm. :— » i I. II. m | iw | Oxygen 2 oe ee | gezg | 14.88 | 14.96 | 14.85 | Carbonic anhydride. : - | 28.62 | 27.21 | 27.14 | 28.39 Nitrogen . ‘ = . A 1.01 1.20 1.22 1.30 | (c) Blood of Palinurus vulgaris. A hundred volumes of the blood of this animal gave the following results :— . PHYSIOLOGY OF THE INVERTEBRATA. 179 Te II. III. | IV. | Oxygen . ah 5 . 14.62 14.71 14.29 14.76 Carbonic anhydride ‘ ‘i . | 30.00 | 29.62 28.92 29.79 Nitrogen a : 5 7 1.82 1.60 1.20 1.34 (2) Blood of Homarus vulgaris, A hundred volumes of the blood obtained from several large lobsters yielded the following results :— : I ll. I. Oxygn. . . .. , 14.99 14.81 14.85 Carbonic anhydride ‘ Z 31.11 28.84 29.26 Nitrogen A P ‘ 1.76 1.82 1.85 (¢) Blood of Octopus vulgaris. A hundred volumes of. the blood yielded the following results :— I | IL | Id | Oxygen . ‘ : , - 13.33 13.28 13.65 Carbonic anhydride ‘ 30.23 31 29 31.22 Nitrogen 1.45 1.30 1.29 (f) Blood of Acherontia atropos. A hundred volumes of the blood of the larve of this moth yielded the following results :— 180 PHYSIOLOGY OF THE INVERTEBRATA. I. If. Oxygen . 3 - F é 16.21 16.79 Carbonic anhydride . 3 4 32.92 34.24 Nitrogen. fs ‘ 5 ate 1.09 1.98 It may be stated that the oxygen and carbonic anhydride in the blood of the Jnvertebrata do not behave according to the law of Dalton (the law of partial pressures) in regard to the absorption of a mixture of gases by a simple fluid. A portion of each gas combines chemically with some con- stituent or constituents of the blood. It was Magnus*™ who first demonstrated that the oxygen and carbonic anhydride of the Vertebrate blood did not obey the law of Dalton; and the same is true concerning the gases of the blood of the LInwertebrata. Surveying the Invertebrata as a whole, we find animals like the Protozoa devoid of blood; next, animals, as some Trematoda and Cestoidea, with blood devoid of corpuscles or solid particles; then such creatures as the Echinodermata, where the blood is corpusculated. In some of these forms, the corpuscles merely consist of solid particles of proto- plasm, devoid of cell walls and nuclei; while in others the blood contains walled and nucleated corpuscles. In the Myriapoda the blood contains three distinct corpuscles, and during a portion of its course is contained in blood-vessels. In the Crustacea the corpuscles are walled and nucleated, but are colourless, or nearly so; while in the Gephyrea the cor- puscles have a limiting membrane, nucleus, and coloured contents. Asa rule, the colouring matter of the Invertebrate blood belongs to the plasma, and not to the corpuscles; but there are exceptions to this rule, which have already been alluded * Poggendorf''s Annalen, vol. 40, p. 583. PHYSIOLOGY OF THE INVERTEBRATA. 181 to in this chapter. Concerning the colouring matter itself, it offers a greater diversity of individual pigments than the blood of the Vertebrata. In some forms we find chlorophyll and allied pigments; while others contain one or more of the following pigments:—Echinochrome, chlorocruorin, hemo- cyanin, hemoglobin, and the lipochromes. “To contrast the various conditions of the blood corpuscles of the Znvertebrata with the stages in the development of our own red corpuscles is not without interest. There is a time in the history of the highest mammal when there is no blood developed; there is a time when only fluid blood, destitute of corpuscles, is to be seen; possibly our blood corpuscles commence as minute fragments or protoplasm derived from the digested food. These minute granules may coalesce in the absorbent vessels and form free nuclei; the nuclei may become surrounded by granules, a wall be de- veloped on the exterior of these, and a white corpuscle (leu- cocyte) would result.” The colourless corpuscle, in its turn, is transformed into a red corpuscle; but the history of this transformation belongs to the physiology of the Vertebrata rather than to that of the Jnvertebrata. CHAPTER VII. CIRCULATION IN THE INVERTEBRATA. THE circulation of the blood in the higher animals was dis- covered by Harvey in 1619. In order to nourish all the parts of the body, it is necessary that the blood should be conveyed to these parts; but the mode in which it is conveyed differs considerably in the lower animals. Among the Invertebrates we find that the mode of circulation becomes more and more specialised as they rise in the zoological scale. From the Protozoa to the Celenterata, the circulatory and digestive systems are still fused together, for they are not differentiated. In the Echinodermata and Annelida we find the first true blood or vascular system. In most worms one of the blood-vessels forms a pulsating tube, or so-called heart, by which the blood is driven towards the periphery of the body through certain vessels, returning by others. In the Mollusca there is a contractile vessel, which has a much closer resemblance to the Vertebrate heart than the above. This heart consists of two or three chambers ;—(a) One or two auricles, which serve for the reception of the blood, brought to them by the veins ; (0) the ventricle which serves for the propulsion of the blood into the arteries. Et ~wri—be-noticed M~rom—the Above-remarks that the-circulatery_system; like all others, -was—~not—perfected—at—once. Nature~made~ numberless attempts; adding successively new—pieces~to the—system-or complieating tittle—by-litthe those-whieh—existed-already. In other words, the circulatory system became more and more PHYSIOLOGY OF THE INVERTEBRATA, 183 differentiated under the influence of natural selection and the struggle for existence. As already stated, in the lowest Invertebrates the digestive and circulatory systems are not differentiated, but among the higher Invertebrates these two systems become distinct. The circulatory system only shapes itself after the digestive system; consequently one may look upon the former as an appendage to the latter. In the higher animals the blood is made to pass through. the respiratory organs in order to expose it to the oxidizing action of the air. In certain of the lower animals the air penetrates into the body; but in all the higher animals, and in many of the lower, there exists a complex apparatus for the circulation of the blood: (1) A system of blood-vessels to convey the blood into the various parts of the body. (2) Ax ergen-featiet the heart) destined to put this fluid in motion. Most animals, from man to the Annelida, have a heart. Tue Protozoa. In these creatures there is no true blood, yet there is a curious foreshadowing of a circulation. In the Rhizopoda* the only structures which may be said to have a circulatory function are the contractile vacuoles. The spaces are filled with a clear fluid, and exhibit fairly regular and rhythmic expansion and contraction (diastole and systole). During the systoles radiating canals or vessels extend from these vacuoles; these widen as the vacuole lessens in diameter. Presently the vacuole begins to expand, whilst the radiating canals become narrower in diameter and ultimately. disappear. The contractile vacuole performs more than one function, and among these is probably that of circulation. There is a pulsating central “organ” with conducting canals proceed- ing therefrom. Does not this look very much like a primitive circulatory system ? * The Rhizopoda includes the Protoplasta, Foraminifera, and the Radic- laria, 184 PHYSIOLOGY OF THE 1NVERTEBRATA. “In the Jnfusoria, contractile vacuoles ure present, and there is also a curious movement of the outer layer of the sarcode in company with the food vacuoles. It will be remembered that these food vacuoles pass, after quitting the abrupt termination of the cesophagus, through the sarcode along a very definite line. They trace the outline of the in- fusorial body as they pass along just within the contractile layer of the animal. With them the outer layer of the sar- code is said to move.” THE PORIFERA. In the Porifera or Spongida, there is no true blood, but there is a circulation of water carrying food particles and air for respiration. This circulation is brought about by the action of cilia, which cause the currents of water to enter the inhalent pores, and after traversing the internal canals, finaily take their exit through the exhalent pores. These currents of water containing nutritive matter act as carriers of tissue- forming materials as well as of waste products, consequently we may regard them as representing the circulatory system among these Invertebrates. Although the water currents in the Porifera have a circulatory function, they also perform the functions of respiration and digestion. THE Ca@LENTERATA. In these animals the blood or nutritive fluid is not con- tained in any vessels, but is free in the somatic cavity or enteroceele. This fluid is moved by “the contractions of the body, and, generally, by cilia developed on the endodermal lining of the enteroccele.” By this means a kind of circula- tion is constantly maintained. The movements of the body of the animals belonging to the Celenterata cause a move- ment of the corpusculated blood in the body cavities, a flux and reflux, a flowing and an ebbing of the nutritive fluid. Here is the most general form of circulation. There are no PHYSIOLOGY OF THE INVERTEBRATA. 185 vessels and no special pumping apparatus, for the whole body is concerned in the performance of this function. ‘“ In the compound Celenterata, this motion of the corpusculated fluid of the body cavity affects also the fluid in those extensions of FIG. 35.—CIRCULATION IN MEDUS#. the body cavities, through the common flesh or ccenosare, that place in communication the interiors of the various members of the compound animal.” Fig. 35 represents the circulatory system in the Meduse. THE ECHINODERMATA. All the Echinodermata are furnished with distinct organs of circulation, consisting of a “heart or corresponding organ, and a complicated system of vessels. This circulatory system consists of two vascular rings surrounding the orifice of the digestive tube. These rings are connected with each other, they emit radiating ramifications, and one of them receives vessels proceeding from the intestine.” Such is a general description of the circulatory apparatus in the Echinodermata, but since the time of Cuvier and Tiedemann “the presence or absence of a blood-vascular system in the Asteridea has been alternately asserted and denied.” The investigations of Greef,* Hoffmann,t and Teuscher} are in favour of “ the * Marburg Sitzungsberichte, 1871-2. + Niederliindisches Archiv, vol. 2. t Jenaische Zeitschrift, vol. 10. 186 PHYSIOLOGY OF THE INVERTEBRATA. existence of the anal ring, and of an extensively ramified system of canals, connected with it and with the neural canals.” But according to Prof. Huxley, “ the facts, as they are now known, do not appear to justify the assumption that these canals constitute a distinct systern of blood-vessels,” Prof. Huxley doubts the special circulatory function of the neural canals, and he does not consider that the sinus which accompanies the madreporic canal is in reality a heart. He states that this sinus and canals “are mere sub-divisions of. the interval between the parietes of the body and those of Fic. 36.—CIRCULATION IN ECHINODERMATA (Sea-urchin). the alimentary canal, arising from the disposition of the. ambulacral vessels and that of the walls of the peritoneal cavity ; both of which, as their development shows, are the result of the metamorphosis of saccular diverticula of the alimentary canal, which have encroached upon, and largely diminished, the primitive perivisceral cavity which exists in the embryo. The peritoneal cavity of the body and rays is filled with a watery corpusculated fluid (blood); a similar fluid is found in the ambulacral vessels, and probably fills all the canals.” Fig. 36 represents the circulatory system in Echinus. PHYSIOLOGY OF THE INVERTEBRATA. 187 THE T'RICHOSCOLICES. “In the Turbellaria, Trematoda, and Cestoidea, the lacuns of the mesoderm and the interstitial fluid of its tissues are the only representatives of a blood-vascular system. It is probable that these communicate directly with the terminal ramifications of the water-vascular (respiratory) system. In the Rotifera, a spacious perivisceral cavity separates -the mesoderm into two layers, the splanchnopleure, which forms’ the enderon of the alimentary canal, and the somatopleure, which constitutes the enderon of the integument. The ter- minations of the water vessels open into this cavity.”* Tur ANNELIDA. In the Annelida there is a perivisceral cavity (perienteric space) communicating with the segmental or excretory organs. This cavity contains a colourless fluid consisting of a coagul- able albuminous plasma and numerous colourless corpuscles. The perivisceral fluid is not only nutritive, but acts as a liquid fulcrum to the muscular movements of the body. If this fluid is let out the power of voluntary motion is lost. It has been stated that “the vermicular motions of the intestine are aided or determined by its resistance and support ; it favours circulation by obviating _the pressure upon the blood-vessels, which follow the contact of the intestine with the integument, and is, perhaps, the source, or one of the sources, of the blood itself.” This fluid con- tains albumin, fibrin, and certain salts. In addition to the perivisceral cavity and its fluid, there is in most of the Annelida a system of vessels with contractile walls. These vessels, known as the pseudo-heemal system, are filled with a fluid, which may be red or green, and corpusculated or non- corpusculated. In some Annelids. the pseudo-hzemal system communicates with the perivisceral cavity ; but in the majority of these animals it is shut off from it. * Huxley’s Anatomy of Invertebrata, p. 57. 188 PHYSIOLOGY OF THE INVERTEBRATA. Professor Huxley considers that the perivisceral fluid represents ordinary blood as far as being a carrier of nutri- ment to the tissues ; and that the pseudo-hzemal fluid is 9 ROH supra-neural d 4 = lateral neural vessels. Transverse section. D= hearts. s= ¢ = transverse vessels. & = dorsal vessel. sub-neural vessel. FiG. 37.—THE CIRCULATORY SYSTEM CF LUMBRICUS. f ée = nerve. alimentary canal. vessel. & = segmental organ. A = Dissection from dorsal side, with the alimentary canal turned on one side. a B = Looking down on nerve with supra-neural vessel removed. probably only engaged in the function of respiration ; hence the reason that he calls it ‘‘ respiratory blood.” After these general remarks we proceed to detail at length the pseudo-hemal-systems of Zumbricus and Hirudo. («) In Lumbrieus, there are three principal vessels which PHYSIOLOGY OF THE INVERTEBRATA. 189 traverse the body in a longitudinal direction (Fig. 37, a, B, C, D). The dorsal or supra-intestinal vessel is situated on the dorsal side of the alimentary canal. The supra-neural or sub-intestinal vessel is situated along the ventral side of the alimentary canal ; and the sub-neural vessel lies directly beneath the great ventral ganglionic nerve cord. Besides the three principal vessels, there are two lateral neural vessels situated on either side of the nerve (Fig. 37, B). The dorsal vessel (which is contractile, and consequently drives the blood from behind forward) is connected with the supra- neural vessel in nearly every segment by pairs of transverse vessels—1.¢., one vessel on each side of the body connects the dorsal to the ventral trunk. a In the anterior portion of the body the longitudinal vessels break up into a blood plexus, consequently in this region (i.¢., first seven segments) there are no distinct transverse vessels. Between the seventh and tenth segments, the dorsal vessel becomes dilated into. what is known as the “hearts” of Lumbricus. These “ hearts” contract so as to force the blood from the dorsal to the ventral side of the body. The dorsal vessel also sends out branches to the body wall, mesenteries, and to the walls of the alimentary canal. The supra-neural vessel sends out branches to the nervous system, and also transverse vessels which unite with the sub-neural trunk (Fig. 37, D). Certain transverse vessels also unite the dorsal to the sub-neural vessel ; these vessels supply the segmental organs and integument with blood. (b) The body or perivisceral cavity in Hirudo is only im- perfectly differentiated from the vascular system. It is filled with loose connective tissue in which are dorsal, ventral, and lateral spaces (sinuses) containing blood. The vascular system (Fig. 38) consists of a ventral blood- vessel or sinus, and two wide lateral vessels which run along the sides of the body. There is also a median dorsal vessel. All these vessels anastomose with each other, and send off 190 PHYSIOLOGY OF THE INVERTEBRATA. branches which also anastomose and give rise to a fine net- work of blood-vessels situated on the organs of generation, nephridia, and in the muscular mesodermic layer. The red blood contained in these vessels has already been described. In the Polycheta the perivisceral cavity is continued into all the important appendages of the body, consequently they are filled. with blood. ‘The circulation of this fluid is effected partly by the contraction of the body and its appendages, partly by the vibratile cilia, with which a greater Fic. 38.—DIAGRAM OF THE PSEUDO-HZMAL VESSELS OF HIRUDO. (After GRATIOLET.) a = dorsal vessel and branches. 4 = lateral vessel and branches, ¢ = ventral vessel and branches. d@ = branches. or less extent of the walls of the perivisceral cavity is covered. In a great number of Polychaeta no part of the body is specially adapted to perform the function of respiration, the aération of the blood probably taking place wherever the integument is sufficiently thin; and, even when distinct branchiz ordinarily exist, members of the same family may be deprived of them.” PHYSIOLOGY OF THE INVERTEBRATA. 1g In many of the Polychwta, the pseudo-hemal system is entirely absent (¢.9., Polynoé squamata), while in others it varies greatly in the arrangement of the principal vessels; ‘but they commonly consist of one or two principal longitu- dinal dorsal and ventral vessels, which are connected in each somite by transverse branches. Where branchie exist, loops or processes of one or other of the great trunks enter them.” The dorsal and ventral vessels are generally con- tractile ; and the direction of the contractions “ is usually such that the blood is propelled from behind forwards in the dorsal vessel, and in the opposite direction in the ventral vessel ; but the course which it pursues in the lateral trunks is probably very irregular.” THE ARTHROPODA, The various classes belonging to the Arthropoda present a system of vessels, partially at least, shut off from the somatic or body cavity. But the blood-vascular system is not com- plete in any Invertebrate animal. In some part or parts of the body the vessels will be found to terminate, and the blood will flow through lacunz or spaces not bounded by any limiting membrane. From this remark it will be observed that the old form of circulation once more comes uppermost-— i.e., the blood passes into the general body cavity. This primitive form of circulation is met with in all Invertebrates, but the higher forms have partially developed a system of blood-vessels, which is, however, incomplete, consequently the lower the animal, the more extensive is the lacunar circulation. In the Invertebrata, the arteries have not the three coats, such as are met with in the higher animals. The heart is generally situated in a dorsal position ; and its pulsations drive the blood at once over the body generally, and not to the organs of respiration first. ‘The word ‘pericardium,’ used by some writers in describing the blood systems of the Jnver- tebrata, is an unfortunate and a misleading one. The pericardium of the Jnsecta and Crustacea has no homology 192 PHYSIOLOGY OF THE INVERTEBRATA. with the serous membrane, that invests the heart of the Vertebrate animals. It is, in truth, a large venous sinus, surrounding that long segmented vessel in the dorsal region of the body that is generally called the heart. From this sinus, blood passes into the heart by certain lateral openings provided with valves opening inwards. Yet another unfor- tunate name has been used in thisconnection. Certain parts of the venous system in the Znsecta and Myriapoda have been designated portal. They represent, however, in no manner the portal system peculiar to the Vertebrata.” In the Arthropoda, there are no pseudo-hemal vessels; and “the blood-vascular system varies from a mere perivisceral cavity without any heart (Ostracoda, Cirripedia) up to a complete, usually many-chambered heart with well-developed arterial vessels. The venous channels, however, always have the nature of, more or less, definite lacunz. The blood cor- puscles are colourless, nucleated cells.” * In all those Arthropods where a heart is present, the blood returns to that organ by the lacunar spaces situated between the organs. These conduits, without special walls, debouch into a so-called pericardiacal reservoir, and the blood pene- trates afterwards into the heart by cardiacal clefts. In the Brachyura and Macrowra (Fig. 39) the blood, before returning to the heart, is oxidised in passing through the branchie. In the Myriapoda, the heart has many chambers, and it is nearly as long as the body. The blood enters this organ by a pair of clefts, and leaves it partly by the communication with the adjacent chamber, and partly by the lateral arteries. “A median aortic trunk continues the heart forwards, and the lateral trunks encircle the cesophagus and unite into an artery which lies upon the ganglionic chain. The arterial system in the Chilopoda is, in fact, as complete as that of the Scorpions.’f In the Jnsecta, circulation is chiefly effected by means of * Huxley’s Anatomy of the Invertebrata, p. 252. + See Newport in the Philosophical: Transactions of the Royal Society, 1863. PHYSIOLOGY OF THE INVERTEBRATA. 193 the heart, which is a tubular organ running along the back of the insect, and hence called the dorsal vessel (Fig. 40). This. Gill. Afferent branchial vessels, Nephridium « (kidney). Auricle. Ventricle. vu eo Post. vena cava. one Capillaries. ‘Post. aorta, Fic. 46.—BLoopD SYSTEM AND NEPHRIDIA OF SEPIA. (3) The Cephalopoda.—tThe circulatory system of Sepia is seen in Fig. 46. “The heart is placed upon the posterior face of the body, on the heemal side of the intestine, and receives the blood by branchio-cardiac vessels, which correspond in number with the gills ; and, as they are contractile, might be regarded as auricles. The gills themselves have no cilia, and PHYSIOLOGY OF THE INVERTEBRATA. 205 are, in somé cases, if not always, contractile. The arteries end in an extensively developed capillary system, but the venous channels retain, to a greater or less extent, the charac- ter of sinuses. The venous blood, on its way back to the heart, is gathered into a large longitudinal sinus—the vena cava—which lies on the posterior face of the body, close to the anterior wall of the branchial chamber, and divides into as many afferent branchial vessels as there are gills. Each of these vessels traverses a chamber, which communicates directly with the mantle cavity, and the wall of the vessel, which comes into contact with the water in this chamber, is sacculated and glandular.” In Loligo media “ the sacculated afferent veins and branchial hearts contract about sixty times a minute. The pulsations of these veins and of the branchial hearts are not synchronous. The branchial veins and the lamellee of the branchie also contract rhythmically,” but the branchial arteries do not contract. ‘‘ The portion of the branchial vein which lies between the base of the gill and the systemic ventricle is very short, and it is hard to say whether it contracts independently or not. Mechanical irritation causes contraction both of the afferent branchial veins and of the branchial hearts.” (Huxley.) In Eledone cirrhosus Professor Huxley has “ observed regu- lar rhythmical contractions of the vena cava itself, as well as of its divisions, the sacculated afferent branchial veins, of the branchial hearts, and of the branchio-cardiac vessels.” Toe TUuNICATA. In the Ascidians the function of circulation differs entirely from other Invertebrates. The peculiarity of this circulation is the reversal at regular intervals of the direction of the blood current. The heart is devoid of valves, and contracts with a wave-like movement. If the wave is from below upwards, “the blood passes into an abdominal vessel, thence into transverse ascending canals that lead to the extraordinary 206 PHYSIOLOGY OF THE INVERTEBRATA. network of vessels connected with the respiratory structures, into a dorsal vessel, and thence by a connecting branch to the posterior end of the heart. After a certain period, the wave of contraction through the heart, and the course of the blood, are generally reversed in direction; and the blood now flows from the ventral heart into the dorsal vessel, down through the branching network into the abdominal or ven- tral vessel, and so to the anterior end of the heart.” The blood consists of a clear plasma containing colourless corpuscles. In Appendicularia flabellum, Professor Huxley states that there are no corpuscles, and “the direction of the pulsations of the heart is not reversed at intervals, as it is in the Ascidians in general. M. Fol,* however, states that, in other Appendiculariw the reversal of the contractions of the heart takes place... . . There are no distinct vessels, but the colourless fluid which takes the place of blood makes its way through the interspaces between the ectoderm and endoderm and the various viscera.” Concerning. the velocity of the circulation in the Jnwverte- brata very little is known; but it may’ be stated that the blood in these animals is animated by a much slower move- ment of translation than occurs in the Vertebrata. * Htudes sur les Appendiculaires, 1872. CHAPTER VIII. RESPIRATION IN THE INVERTEBRATA. Ir is well known that the presence and absorption of oxygen is essential to the life of every tissue, and that one of the products of the action of oxygen on the tissues, &c., is the production of carbonic anhydride, a gas which is inimical to life. Even the lowest members of the animal kingdom re- quire oxygen—without oxygen, no animal life. The Amwba and Parameciwm, when introduced into a medium contain- ing no oxygen, or containing an excess of carbonic anhydride, very soon die. In all animals there is an interchange be- tween the gases of the organism and the gases of the medium in which they live; and this interchange, which is known as respiration, is continuous throughout life. In the lowest forms no special mechanism is necessary for facilitating the gaseous interchange; for they absorb fluids containing oxygen in solution. In higher forms, canals, along which the air passes, seem to be necessary ; and in still higher forms respiration is performed by the movement of the branchie, or by trachez (air-tubes) and lungs. The absorption or respiration of oxygen is one of the first con- ditions of nutrition. All organised beings absorb oxygen, and this absorption goes on in all stages of the existence of living matter. The organs (using the word in its widest sense) of respira- tion differ considerably in different animals, but they have all the same physiological function to perform—that of sup- plying oxygen to the tissues and blood; and the elimination 208 PHYSIOLOGY OF THE INVERTEBRATA. of the gaseous products of. decay. In fact we may define respiration as “the elimination of the gaseous products of tissue-combustion, and the introduction of the oxygen neces- sary for that combustion.” The lower forms of the animal kingdom respire directly by changes between the general surface of the body and the medium in which they live; but in the higher forms, respira- tion is a twofold process: (#) internal respiration, or the interchanges between the gases of the blood and the tissues ; and (b) external respiration, or the interchanges between the gases of the blood and the gases in the air-cells of the lungs. These interchanges, however, are not always confined to the lungs; thus there is a true cutaneous respiration in the skin, an intestinal respiration in the intestines, and most probably interchanges of a like nature take place in other organs; for it may be remarked that many organs of the Invertebrata contain various pigments, which have a res- piratory function. The respiratory apparatus is always in intimate relation with the organs of circulation. THe PRoTozoA. In most of the Protozoa, respiration takes place all over the general surface of the body; but these animals differ somewhat in the mechanism of respiration. In the Gregarimida the interchange of gases takes place all over the body. In the majority of the Infusoria and Rhizopoda there is a differentiation of the function of respiration, for even in these low forms the interchange of oxygen and carbonic anhydride takes place at certain specialised regions (con- tractile vacuoles), but the air is not brought into direct con- tact with the circulating fluid. The oxygen or air for res- piration is dissolved in water. The contractile vacuoles of these organisms perform several functions, among these being that of respiration. The contractile vacuoles contain PHYSIOLOGY OF THE INVERTEBRATA. 209 liquids, and during contraction send out radiating canals. This system probably communicates with the exterior. By this primitive respiratory organ the working tissues are brought into contact with oxygen dissolved in water. THE PORIFERA. In the Porifera (Spongida) respiration is effected by means of the oxygen dissolved in the water, which permeates through the various canals, and thereby brings it into intimate relation with the whole mass. In the circulation of this water through the ordinary fresh-water sponge (Spongilla) there is a fusion of the functions of digestion, circulation, and respiration. “Sponges absorb oxygen and give off carbonic anhydride with great rapidity ; and the manner in which they render the water in which they live impure, and injurious to’ other organisms, suggests the elimination of nitrogenous waste matter.” It is possible that the oxygen is retained in the substance of a sponge by certain respiratory pigments—probably a histohematin. Sponges are rich in chlorophyll, but this pigment has another function—viz., the formation of fatty matter.* THE CaELENTERATA. In the lower Calenterata the function of respiration is performed by the general surface of the body. The fluids in these animals are in close relationship to the water in which they live ; and consequently the ectodermic lining serves as an organ of respiration. In other words the lower Ccelenterates respire by the skin. In some of the higher orders of this group the respiratory function is performed in the water- vascular tubes along with other functions performed by the same vessels. But there is no doubt that the chief mode of respiration in * MacMunn in Journal of Physiology, vol. 9. 210 PHYSIOLOGY OF THE INVERTEBRATA. the Ccelenterates is by means of the ectodermic lining, for this lining is very largely impregnated with respiratory and other pigments, as shown by Prof. Moseley* and Dr. MacMunn.tf The respiratory pigments are capable of existing in a state of oxidation and reduction, and no doubt play an important part in the function of respiration. Professor Moseley discovered a pigment called poly- perythrin in various Ccelenterates, and Dr. MacMunn has carefully examined the brown colouring matter of jelly-fishes, and various pigments in the Actinie. In Chryscora hysocella a brown pigment is present in ‘the radiating triangular areas on the upper surface of the umbrella, and in dark patches, thirty-two in number, all round the margin of the disc, also in the tentacles; but in each of these situations it possesses the same properties. It also occurs dotted on the surface of the umbrella between the triangular pigmented areas. Microscopically, it occurs in granules, and is limited to the surface; these granules are yellowish in colour under a high power.” Dr. MacMunn could not extract the brown pigment with alcohol, ether, chloroform, alcohol and sulphuric acid, and alcohol and potassium hydroxide. But he obtained an extract by allow- ing portions of Chrysaora to stand, “the sea-water contained in the tissues dissolved the pigment, forming an orange- brown solution,. showing a broad dark band at the blue end of the green. When more pigment went into solution, the fluid became a dark brown colour. Boiled in fresh and sea- water the colour went into solution, but showed no bands except the shading at the blue end of the green. A deep layer of this solution only transmitted red and some green. Ammonia and caustic potash precipitated the colouring * Quarterly Journal of Microscopical Society, vol. 17; and Jowrnal of Physiology, vols. 7 and 8. + Quarterly Journal of Microscopical Science, vol. 30; and Journal of Marine Biological Association, 1889. wae ve PHYSIOLOGY OF THE INVERTEBRATA. 211 matter. Hydrochloric acid did not discharge the colour at first, although it became much lighter; strong sulphuric acid and nitric acid discharged it after some time. Absolute alcohol also precipitated the pigment, the fluid becoming flocculent after a while. The colouring matter in the fresh state showed no bands except some shading at the blue end of the green; it also absorbed the violet end of the spectrum.” Dr. MacMunn’s investigations on the respiratory pigment of Chrysaora confirms those of Dr. J. G. M‘Kendrick, F.R.S.,* who has also investigated the pigments from Cyanea and Aurelia by allowing fragments of these organisms to macerate in sea-water for about thirty-six hours. “In these cases ammonia precipitated the colouring matter from its solutions, and it dissolved in acids.” Dr. M‘Kendrick states that after death ‘the body becomes slightly acid, the protoplasm disintegrates, and the colouring matter diffuses out.” ‘When examined by the microspectroscope the fresh pig- ment from Cyanea, as well as an infusion of the organism, gave two bands, one in the orange and the other in the red. The spectrum of the blue pigment of Rhizostoma Cuviert consists of three bands, one in the red, a dark one at D, and an extremely faint band in the green. There is little doubt that the same colouring matter occurs in Rhizostoma as in Cyanea. This pigment has been termed cyanein by the late Dr. Krukenberg,t and he compared it with the blue pigment found in Velella limbosa by A. and G. De Negri.t Cyanein is soluble in water, insoluble in benzene, ether, carbon disulphide, and chloroform. On the addition of alkalies, cyanein is changed into an amethyst colour, while acids colour it red. * Journal of Anatomy and Physiology, vol. 15, p. 261. + Vergl. Physiol. Studien, zweite Reihe, dritte Abth., 1882, s. 68. + Gazetta Chimica Italiana, vol. 7 [1877]. 212 PHYSIOLOGY OF THE INVERTEBRATA. In 1884, Krukenberg stated that cyanein occurs in Velella, Aurelia, Cyanea, and Rhizostoma. Dr. MacMunn* has examined the pigments from the following Actiniw :—Actinia mesembryanthemum, Bunodes crassicornis, B. ballu, Sagartia bellis, S. dianthus, 8. para- sitica, S. viduata, S. troglodytes, and Anthea cereus. (a) When the solid portions from the ectoderm, endoderm, and tentacles of the red-coloured specimens of Actinia mesem- bryanthemum were examined by the microspectroscope, they gave a band which closely resembled that of reduced heemo- globin, accompanied by two other bands nearer the violet end of the spectrum. The extreme edges of the shading of the band extend from ) 600 to A 560, while its darkest part is from A 580 to A 563. “These measurements vary accord- ing to the colour of the specimen, for in brown specimens the dominant band is nearer the violet, and in some a band is also present before D.” The latter spectrum is said to belong to modifications of the same pigment, as the same decomposition products are obtained in both cases. The spectrum of the brown specimens of this species has a close resemblance to the histohematins. MacMunn has named this pigment actiniohematin. Actiniohzematin is soluble in glycerol, but it is insoluble in alcohol, ether, chloroform, carbon disulphide, benzene, &e. This pigment is also extracted (but in a changed condition) by treating with alcohol and potassium hydroxide (either hot or cold). By the latter treatment a reddish solution is always obtained, which gives a band at D, generally extending from A 625 to X 589, recalling to mind the spectrum of alkaline hematin. When ammonium sulphide was added to the alkaline alcoholic extract, the band at D was replaced by two bands which are undistinguishable from the spectrum of hemochromogen. MacMunn has also observed that all the red pigments in the Actiniw gave after this treatment in the * Philosophical Transactions of Royal Society, 1885 (part ii.), p. 641; and Quarterly Journal of Microscopical Science, vol. 30. PHYSIOLOGY OF THE INVERTEBRATA. 213 solid state (i.e., examined in the compressorium) the spectrum of hemochromogen. It may be remarked that Professor F. Hoppe-Seyler* found that when solutions of hemoglobin are treated with potassium or sodium hydroxide in the absence of air, the hemoglobin is converted into heemochro- mogen. In the solid tissues of the Actinia, says MacMunn, a similar reaction occurs, but in the solution used to extract the pigment the hematin becomes oxidised as it comes out of the tissue, and shows the alkaline hematin spectrum, which, however, can be reconverted into hemochromogen by the addition of ammonium sulphide. MacMunn could not obtain acid hematin, but he. did succeed in converting the pigment into hematoporphyrin. “ By digesting portions of an Actinia in sulphuric acid, and filtering through asbestos, a purple-red solution was obtained, which showed bands like those of acid heematoporphyrin, a little rectified spirit being added to the acid solution; but the band nearer the violet is not placed exactly in the same position as the corresponding band of hmatoporphyrin obtained from hemoglobin. The first band extended from 605 to A 595, and the second from A 563 to A551, but owing to the presence of biliverdin and proteids these measure- ments may not be quite reliable; still, they possess a certain value when the results are compared with other cases. If this spectrum be that of a kind of hematoporphyrin, it ought to be changeable into alkaline hematoporphyrin, and such is the case.” From the above remarks there can be no doubt that in Actinia mesembryanthemum a pigment is present which can be changed into hemochromogen and hemato- porphyrin. MacMunn has also extracted (by means of alcohol and alcohol and sulphuric acid) the green pigment situated beneath the ectoderm of many specimens of this species of Actinia. This pigment gives the reactions of biliverdin (C,,H,N,O,?). “Hence A. mesembryanthemum contains in * Zeitschrift fir Physiologische Chemie, vol. 1, p. 138. 214 PHYSIOLOGY OF THE INVERTEBRATA. its mesoderm and elsewhere a colouring matter undistinguish- able from biliverdin” of the Vertebrata. As biliverdin is derived from the decomposition of Vertebrate hemoglobin, its presence in Actinia is further proof that these organisms contain pigments closely allied to hemoglobin. MacMunn has proved that the hematin-yielding pigment of A. mesembryanthemum is not the same as Prof. Moseley’s actiniochrome, although the latter pigment is present in certain species of the Actiniw. The band of actiniochrome is nearer the red than that of MacMunn’s pigment (actinio- hematin), and the two pigments yield entirely different decomposition products under similar treatment. After a careful examination of the glycerol extracts, MacMunn found that “every specimen of Actinia mesembryanthemum, whether its colour was red, reddish-brown, brown, or greenish-brown, gave to the glycerol, after some days’ extraction, a certain amount of colouring matter, which in every case could be made to change into hemochromogen, while actiniochrome never could be changed into it; hence the respective pig- ments are very different. Oneisarespiratory colouring matter (actiniohematin), the other (actiniochrome) is an ornamental one.” The glycerol extract made from the ectoderm of an anemone yielded actiniohzematin, which, on the addition of potassium or sodium hydroxide and ammonium sulphide, was rapidly changed into hemochromogen. “It appears that this hematin-yielding pigment does not give the same spectrum in brown specimens as in red; but the spectrum of the glycerol extract of red Actiniw has a close resemblance to that of the spectrum of the solid ectoderm and other parts of brown specimens. This does not show that the pigment has been altered by extraction with glycerol, but its mole- cular condition may be altered. It is well known that the spectrum of a pigment may differ in the solid and liquid state without any necessary change in its composition (Vogel and Kundt).” PHYSIOLOGY OF THE INVERTEBRATA. 215 ) Bunodes crassicormis.—Moseley * examined this Actinia, and he found in two specimens the tentacula were a rose colour, the colour being due to actiniochrome. MacMunn has more recently examined the pigments of this species of Bunodes ; and he found that the colour and spectra differ considerably in different cases. The conclusions arrived at are that “in Bunodes crassicornis we find actiniohematin with tolerable constancy, occasionally actiniochrome and also biliverdin, besides the lutein-like (lipochromes) pigments. In the ectoderm, as well as in the endoderm, and sometimes in the tentacles, actiniohematin is present. In none of the specimens were ‘yellow cells’ present, and by no other solvents except glycerol, and alkaline and acid alcoholic solutions, could any pigments be got into solution.” (c) Bunodes balliiThe tentacles and mesenteries of his anemone, when examined by the microspectroscope, gave a number of bands, which showed the presence of a chlorophyll- like pigment. In the large variety of this species the tentacles are packed with “yellow cells” t lodged in part in their endodermal lining. It appears that these “yellow cells” replace the red pigment of other species, since the latter is present in mere traces. No “yellow cells” are present in the tentacles or elsewhere in the small variety of Bunodes ballii, The inner tentacles of this variety gave the spectrum of actiniochrome; but no hemochromogen was produced from these anemones. Still, the fact is interesting, that the pigment of the ectoderm resembles, with regard to the first band of its spectrum, that of A. mesembryanthemum ; and MacMunn remarks that ‘‘it may have been a pigment which is intermediate between actiniochrome and actiniohzmatin. The replacement of this pigment by the colouring matter of the ‘yellow cells’ in the large variety is of great interest, and teaches that the presence of the colouring matter has * Quart. Journ. Micro. Soc., vol. 12, p. 143. + Symbiotic alge. 216 PHYSIOLOGY OF THE INVERTEBRATA. something to do with the absence of ‘yellow cells’ in the small variety.” (d) Sagartia dianthus.—The brown and white specimens both contain a hematin-yielding pigment, which is un- doubtedly actiniohzematin. (e) Sagartia vidwata.—On extracting the ectoderm for twenty-four hours in alcohol and caustic potash a yellow solution was obtained. This gave achlorophyll-like spectrum, but faint traces of hamochromogen were detected on the addition of ammonium sulphide. (f) Sagartia parasitica—In this species MacMunn dis- covered the presence of actinioheematin and another pigment, which is different from any other he had previously examined. This latter pigment is peculiar to this species. “In its colour-changes with acids it has a very remote resemblance to the purple pentacrinin of Professor Moseley, also to the colouring matter of Aplysia, but differs in spectrum and in some colour-changes.” “Yellow cells” are absent in S. parasitica; its colouring matter is capable of uniting with oxygen and of giving it up again ; consequently it has a respiratory function. (g) Sagartia troglodytes—The solid ectoderm of this species yielded a pigment which is related to hemochromogen. MacMunn believes that this pigment is a histohzematin. (h) Sagartia bellis—The tentacles of this species were found packed with “yellow cells.” The spectroscopic exami- nation of the tentacles showed a banded spectrum reminding one of chlorophyll, or rather chlorofucin. This spectrum belongs to the mass of ‘yellow cells” which are embedded in the endodermal linings of the tentacles. The ectoderm and endoderm do not contain hematin. The examination of solutions of the tentacles revealed the presence of a small amount of other pigments; but it appears that the presence of the “ yellow cells” has something to do with the absence or suppression of respiratory pigments. (i) Anthea cerus——‘‘In some specimens the ectoderm was PAYSIOLOGY OF THE INVERTEBRATA. 217 a pale red, also the base, and the tentacles a pale green tipped with- violet. In the violet apices of the tentacles, actiniochrome was detected. The rest of the tentacles gave a spectrum resembling that of chlorophyll.” The base in some specimens of this species contained actiniohematin. Besides the above-mentioned pigments, there are “ yellow cells” present in the body cavity and ectoderm. The ‘‘vellow cells” on treatment with Schulze’s solution gave the reaction for cellulose. These cells contain starch. Anthea cereus contains symbiotic unicellular alge, and MacMunn has proved that the chlorofucin in Anthea cereus, Bunodes ballii, and Sagarita bellis, is without doubt due to the so-called “ yellow cells” ; and in those anemones possess- ing “yellow cells” there is more or less suppression of the respiratory pigments found in other Actiniw. The extracts of the “ yellow cells,” prepared by Sir G. Stokes’s fractional method, yielded chlorophyll and chlorofucin, proving that the colouring matters of the alge are several, for there are present at least one chlorophyll, one chlorofucin, and certain lipochromes, and perhaps other pigments, all of which belong to the “ yellow cells.” These “yellow cells” are parasitic alge and have not a hepatic function as supposed by the late Dr. Krukenberg. In no Invertebrate “liver” are such bodies found. The Invertebrate /¢ver-pigment, or enterochlorophyll, occurs mostly dissolved in oil, or in granules, or diffused through the protoplasm of the lining cells of the “liver” tubes.* The colouring matters of these “ yellow cells” belong to the chlorophyll group, and bear no relationship whatever to enterochlorophyll, which is in direct opposition to Kruken- berg, who stated that the pigment of the “ yellow cells” is a hepatochromate, which is his name for enterochlorophyll. The function of animal chlorophyll is of use in the respiratory processes of animals.f * MacMunn in Proe. Roy. Soc. 1885; and Prilos. Trans. 1886, part i. + Regnard in Comptes Rendus, vol. 101, p. 1293. 218 PHYSIOLOGY OF THE INVERTEBRATA. (j) Cornynactis viridis.—MacMunn has examined the red specimens of this little sea anemone. On putting one of these animals into a compressorium and examining it by means of an achromatic condenser and a microspectroscope, a spectrum was obtained whose bands do not correspond with either those of actiniohematin or actiniochrome, for they are nearer the violet and differ in other respects. Yet they belong to a pigment which is related to actiniohematin, for this pigment can readily be changed into hemo- chromogen. No “yellow cells” are present in either the red or green varieties of C. viridis. There is no doubt that this anemone contains a respiratory pigment allied to actinio- heematin. 7 The important researches of MacMunn and others have shown: (1) That a respiratory pigment is largely present in many Actinie. That it must be respiratory is shown by the fact that one of its decomposition products is capable of existing in a state of oxidation and reduction. That it is closely related to hemoglobin is proved by the fact that it is capable of being converted into hemochromogen (reduced hematin) and hematoporphyrin,* which are undistinguish- able from the same products obtained from hemoglobin. (2) The respiratory pigment in the Actiniw cannot be looked” upon as a carrier of oxygen, but as a means to keep it in com- bination until it is wanted by the cells for metabolic pur- poses. ‘As it is’ distributed all over the surface of some Actinie, the whole body of such an animal may, in a physio- logical as well as in a morphological sense, be considered comparable to a single organ of a higher animal, so far, at least, as internal respiration is concerned.” (3) In every species of Actiniw, even in those almost destitute of colour, the presence of respiratory pigments has been detected. The coloured proteids, which are concerned in tissue-respiration, enable the anemone to abstract oxygen * Moseley’s poly perythrin is identical with MacMunn’s hematoporphyrin. + That is, tissue-respiration. PHYSIOLOGY OF THE INVERTEBRATA. 219 from the sea-water in which it lives, and to hold the oxygen in its tissues. (4) In animal tissues chlorophyll or allied pigments may be of use in furnishing oxygen to the animal ; and in those | 2s ao 26 In grammes, | In parts of sea g aa lime carbonate water. a 5 per litre. One part in Coral sand . 3 5 3 27 12 0.0320 32,000 Harbour mud, Bermuda .| 27 12 0°0410 25,000 | Isophyllia dipsacea eo) 327, 12 0.0410 25,000 Millepora ramosa 27 12 0.0360 28,000 Madrepora aspera -| 27 12 0.0730 14,000 Montipora foliosa A arf) 27 12 0.0430 23,000 Goniastreea multilobata . | Io 12 0.0730 14,000 Porites clavaria . 3 : Il 12 0.0930 11,000 Oculina coronalis . 5 e 10 96 0.0237 42,600 Their experiments prove that ‘there is very great diversity as to the amount of carbonate of lime that will pass into solu- tion in sea water from various calcareous structures in a given time.” The more dense varieties of coral are less soluble than the porous varieties. ‘The rate of solution is also much greater when the water is constantly renewed than when the same water remains in contact with the coral, and the solution approaches to saturation.” (i) From the investigations and observations of Murray and Irvine “it is evident that a very large quantity of car- bonate of lime is in a continual state of flux in the ocean, now existing in the form of shells and corals, but after the death of the animals passing slowly into solution, to go again through the same cycle.” “On the whole, however, the quantity of carbonate of lime that is secreted by animals must exceed what is re-dissolved by the action of sea-water, and at the present time there is a vast accumulation of carbonate of lime going on in the ocean. It has been the same in the past, for with a few insignificant exceptions all the carbonate of lime in the geological series of the rocks has been secreted from sea water, and owes its origin to organisms in the same way as the carbon of the car- boniferous formations. The extent of these deposits appears 254 PHYSIOLOGY OF THE INVERTEBRATA. to have increased from the earliest down to the present geological period.” THE ECHINODERMATA. We have already alluded to the secretion of the protective skeleton in these animals; consequently we proceed tv describe the excretory organs of the -Asteridea, being an im- portant order of the Echinodermata. The autlior * has shown that the five sacs of the stomach of Uraster rubens sometimes act as renal organs. With a quantity of the fluid obtained from a large number of star- fishes the following experiments were performed :— (1) The clear liquid from these sacs was treated with a hot dilute solution of sodium hydroxide. On the addition of pure | hydrochloric acid a slight flaky precipitate was obtained, after standing seven and a half hours. These flakes, when examined beneath the microscope (4 in. obj.) were seen to consist of various crystalline forms, the predominant forms being those of the rhomb. On treating the excretion alone with alcohol, rhombic crystals were deposited which were soluble in water. When treated with nitric acid and then gently heated with ammonia, these crystals yielded reddish- purple murexide crystallised in microscopic prisms. (2) Another method was used for testing the fluid contents of the sacs of the stomach of Uraster. These fluid contents were boiled in distilled water, and evaporated carefully to dryness. The residue obtained was treated with absolute alcohol and filtered. Boiling water was poured upon the residue, and to the aqueous filtrate an excess of acetic acid was added. After standing some hours, crystals of uric acid were deposited, and easily recognised by the chemio-micro- scopical tests mentioned above. The above-mentioned alcoholic filtrate was tested for urea. * See Dr. A. B. Griffiths’ paper in Proceedings of Royal Society, vol. 44, P- 325. PHYSIOLOGY OF THE INVERTEBRATA. 255 To do this, the alcoholic solution was diluted with distilled water, and boiled over a water-bath until all the alcohol had vaporised. The warm aqueous solution (A) remaining was now tested for urea in the following manner :— (a) On the addition of mercuric nitrate to a portion of the above solution, no white precipitate was obtained. (6) To another portion of the solution (A), a solution of sodium hypochlorite was added. No bubbles of nitrogen were disengaged. (c) No crystals of urea nitrate were formed in a small quantity of the solution (A) [concentrated by evaporation] after the addition of nitric acid. (d) The distillation of a small quantity of the solution (A) with pure sodium carbonate in a chemically clean Wiirtz’s flask attached to a small Liebig’s condenser, failed to produce in the distillate any coloration with Nessler’s reagent. The above tests clearly prove the entire absence of urea in the excretion under examination. No guanin or calcium phosphate could be detected in the excretion, although the author has found the latter compound as an ingredient in the renal excretions of the Cephalopoda and the Lamelli- branchiata.* From these investigations, the isolation of uric acid proves the renal function of the five pouches or sacs of the stomach ‘of the Asteridea.{ There is no doubt that the stomach of starfishes performs a dual function: it is an excretory organ as well as a digestive gland, and separates the nitro- genous products of the waste of the tissues, &c., from the blood or nutritive fluid in the form of uric acid, which is at certain times to be found in the five pouches of that organ. In the Invertebrata there are numerous examples where an organ performs a dual and even a triple function. * Proceedings of Royal Society of Edinburgh, vol. 14, p. 230. + See also Durham in Quart. Journ. Micros. Science, 1891. 256 PHYSIOLOGY OF THE INVERTEBRATA. THE ANNELIDA. (1) The Hirudinea.—The author* has examined the nephridia of Hirudo medicinalis. These nephridia are in pairs, extending from the second to the eighteenth segments (somites). Each nephridiumf consists of a much-convoluted cellular tube. :'The cells of the tube are perforated by small ducts. The nephridia (segmental organs) open externally on the ventral side of the body. In Lumbricus the nephridium communicates internally by a wide funnel-shaped aperture (which is ciliated) with the perivisceral cavity, but in Hirudo it opens internally by a “cauliflower-headed” portion (the analogue of the funnel-shaped aperture in Lwmbricus) into the perinephros- tomial sinus. Each nephridium consists of five principal parts—(a) posterior lobe, (0) anterior lobe, (c) apical lobe, (d) the testis lobe, (¢) the vesicle, with its duct, which opens externally. The nephridia of Hirudo are covered with a pigmented connective tissue. These pigments are no doubt the histohematins of Dr. C. A. MacMunn, for he says: “I have found that throughout the whole animal kingdom in each tissue and organ there are present colouring matters.” { In examining the physiology of the nephridia or segmental organs of the Hirudinea, the author obtained the excretions from a large number of freshly killed leeches. These excre- tions were examined by the same chemical and microscopical methods used in the examination of the segmental organs of the Oligocheta and the renal organs of the Asteridea. The nephridia of Hiruwdo contain uric acid and sodium; and it may be that the uric acid is in combination with sodium as sodium urate. * Proceedings of Royal Society of Edinburgh, vol. 14, p. 346. + From vedpés, a kidney. A : £ Proc. Birmingham Philosophical Society, vol. 5, p. 211; Proc. Roy. Soc, 1886 ; and Philosoph. Trans., 1886. PHYSIOLOGY OF THE INVERTEBRATA. 257 (2) The Oligocheta.—The renal system of Lwmbricus consists of a large number of coiled tubes (Fig. 47) distributed in pairs, one pairin each somite of the body. Each tube or segmental organ (nephridium) consists of three distinct parts—(a) A much-convoluted thin portion, terminating in a funnel-shaped opening ; (0) a thick-walled glandular portion; (¢) a thick Cuticle. ee Dorsal vessel. Epidermis. Circular mus- - & T | __s, Middle loop of cular layer. xf SENS. Boe nephridium. i . 69, : ; goo Typhosele. Longitudinal : SUSY ’ a Pees muscular P| / / layer. P s Hepatic cells, , Ht g so-called Outer loop of : 4 : liver: nephridium. | > |________» Inner loop of i M nephridium. Ny ro ‘ Ms \ Epithelium of ZS "A oY a < : intestine. So, ORE Ventral v. < LArh Se Ccelom. = ; ea LOR hb Po] bod Internal open- xterna ‘ PT Pf I ing of neph. opening of WE, PAL Ppl |____s Vent. ea nephridium, y a cord. AG j +> Subneural HIN vessel. FIG. 47.—NEPHRIDIUM OF LUMBRICUS. muscular portion (the outer loop), which opens externally by an aperture near the ventral side of the body. The nephri- dium as a whole lies on the posterior side of the septum, but the funnel-shaped aperture opens on the anterior surface ; that is to say, into the cavity of the segment in front of that in which the main body of the nephridium lies. This is the case in every segment containing these organs. The septa, or mesenteries dividing the body into segments, are richly R 258 PHYSIOLOGY OF THE INVERTEBRATA. supplied with blood-vessels, many of which are intimately con- nected with the folds of the nephridia. There is little doubt that the nitrogenous waste matters are absorbed by the glandular portions of these coiled tubes, and ejected by the contractile parts to the exterior. ; The author * has isolated uric acid from the excretion of the nephridia or segmental organs of Lwmbricus terrestris, The contents of these organs do not contain guanin, urea, or calcium phosphate. The segmental organs in the Oligocheta are therefore renal in function, eliminating the nitrogenous waste matters con- tained in the blood, in the perivisceral cavity. The largest amount of uric acid was found in the excretion contained in the muscular part of the segmental organ (Fig. 47, outer loop of nephridium). The following table is a summary of the constituents of the nephridia or segmental organs of the Annelida :-— Hirudinea. Oligochata, Polychaeta, Uric acid. 3 : : present present (2) Urea. é ; . . absent absent _ Guanin . - ‘ i : absent absent — Calcium phosphate. absent absent _ Sodium 7 3 ‘ ‘ present _ oe The minute structure of the excretory organs in the Oligo- cheta, especially those of Lumbricus terrestris, have been worked out by Dr. E. Claparéde, and detailed in his “ Histo- logische Untersuchungen iiber den Regenwurm,” ft and also by Prof. C. Gegenbaur. t * Proceedings of Royal Society of Edinburgh, vol. 14, p. 233. + Zeitschrift fiir Wissenschaftliche Zoologie, vol. 19. t Ibid. vol. 4, PHYSIOLOGY OF THE INVERTEBRATA. 259 - Tae NEMATOIDEA. In a paper read before the Royal Society of Edinburgh on July 1, 1889, the author stated the results of his examina-~ tion of the renal organs of the Nematoidea. The body of the “‘thread-worms” is elongated, round, and thread-like, tapering (more or less) towards the anterior and posterior ends. The Nematoidea are not divided into segments, and they have no segmental organs. In the species (Anguillula brevispinus) selected for investi- gation the renal organ is a glandular mass situated in front of the gizzard. This organ has a well-developed excretory duct, which opens externally by a tranverse slit (the vascular pore) on the ventral side of the body. When a section of the glandular organ of Anguillula is examined under the microscope, the epithelial lining is seen to consist of nucleated cells, similar to those of the Malpighian tubules of the Jnsecta (see later in this chapter). The organ contains a clear fluid, which can be made to yield microscopic crystals of uric acid. The author has extracted uric acid from a large number of these organs (obtained by dissection under the microscope) by boiling them in distilled water. The filtrate, tested by the methods already described, yielded uric acid and murexide crystals. A fresh “ glandular organ” was placed upon a microscope slide and crushed ; then a drop of dilute acetic acid added, and the whole covered by a cover-glass. On examining with the microscope it was observed that rhombic plates and other crystalline forms had deposited. The cover-glass was slightly raised, and on the addition of a drop of nitric acid, followed by ammonia and gently heating over a spirit lamp, prismatic crystals of murexide were formed. No urea, guanin, calcium phosphate, d&c., could be de- tected in the excretion of this organ. These reactions prove that the so-called “ glandular organ ” of the Mematoidea is physiologically a kidney. 260 PHYSIOLOGY OF THE INVERTEBRATA. THE PROTOTRACHEATA. This order is represented by the genus Peripatus, which contains several species. These animals have the power of “throwing out a web of viscid filaments when handled or otherwise irritated.” This viscid matter is secreted by two large ramified tubular glands situated on the sides of the digestive tube, and open externally by the perforations of the oral papille. Peripatus breathes by means of trachez, hence the reason that Prof. Huxley has referred the order to which Peripatus belongs to the Arthropoda. From these remarks it will be observed that respiration in Peripatus is on the insect-type—ce., by means of tracheal tubes; but the other excretory organs differ from those of the Insecta. In the Insecta the renal organs are the Malpighian tubules, but no such appendages to the alimentary canal are present in Peripatus. The kidneys are segmental organs or nephridia, like those of the worms, but of a more highly complex type. There is a pair of these organs in each segment. They open in- ternally into the body cavity, and externally at the base of the limbs. THE MyriapoDa. The intestines of the animals belonging to this class are provided with Malpighian tubules which perform an ex- cretory function ; in other words, they are physiologically the kidneys. THE INSECTA. Before describing the excretory organs, it is perhaps desirable that we mention certain secretions, and the organs (as far as possible) which give rise to them. (a) The poison which certain insects secrete is a fluid strongly impregnated with formic acid. In many cases this fluid is secreted by a special gland, and poured into a re- ceptacle connected with the sting (¢.9., in Apis and Vespa). : PHYSIOLOGY OF THE INVERTEBRATA. 261 The larva of Dicranura vinula possesses a gland which secretes formic acid. The duct of this gland opens in a horizontai slit on the red margin below the true head, and is thus placed in such a position that its contents are ejected in an anterior direction. Disturbance causes the larva to withdraw its head still further, and to inflate the red margin, especially in the region of the gland duct, and at the same time the head is always turned in the direction of the dis- turbance. Thus the fluid is thrown towards the cause of the irritation, and the terrifying appearance of the larval full- face is also brought to bear upon it (Poulton). The acid ejected by the larva of D. vinula is a defensive fluid, and no doubt is a means of protection against enemies. ‘This defensive fluid is ejected from a transversely placed aperture on the ventral surface of the prothorax, immediately below the head. Mr. E. B. Poulton, F.R.S., Prof. R. Mel- dola, F.R.S., and Prof. W. R. Dunstan have proved by chemical tests that this fluid secreted. by the larva of D. vinula is formic acid. ‘The smell is also quite characteristic, and affords an indication of the large proportion of acid present in the secretion. It is also an interesting fact that the freshly-made and moist cocoon of D. vinula is powerfully acid to test-paper.” The secretion consists of a pure aqueous solution of formic acid, containing an average of 33 per cent. of anhydrous acid. A mature larva will eject 0.05 gramme of the secretion, con- taining 40 per cent. of acid. The rate of secretion is slow ; starvation lessens its amount and decreases the quantity of ‘acid; but there is no difference in the nature of the acid when the larva is fed on poplar instead of willow.* “The larva appears to depend entirely upon tactile stemule for the direction in which to move its terrifying full-face, and towards which to eject the irritant acid secretion. Visual sensations appear to play no part as guides in the assumption of the defensive attitude.” * See Report of British Association, 1887, p. 765. 262 -PHYSIOLOGY OF THE INVERTEBRATA. The larva of Dicranura furcula does not eject an irritant secretion, but it possesses an eversible “gland” as a defensive organ. A similar structure is present in the larva of D. vinula, but it is unable to evert its prothoracic ‘“‘ gland ” voluntarily. This structure is eversible in the larvee of Melitwa artemis, Orgyia pudibunda, Orgyia antiqua, and Liparis auriflua ; and there is no doubt that these defensive structures are of con- stant occurrence in Lepidopterous larvee. The power of everting the “gland” in the larva of D. vinula has been lost, due to the fact that the “larva has acquired the remarkable power of ejecting the intensely irritant secretion to a considerable distance by forcing it through the narrow ‘chink, with its closely approximated lips, which constitutes the mouth of the duct leading to the sac. Such a formidable means of defence may readily have supplemented the more usual method of eversion, a method which can only give rise to the discharge of vapour into the air, instead of a well- directed stream of fluid, which, if volatile, as it is in these larvee, of course produces abundance of vapour.” The eversible glands of the larva of Liparis auriflua are not often completely everted, but they are very sensitive to tactile impressions, and on “stimulation a clear, transparent secretion appears in the lumen, being probably raised. by partial eversion. The secretion is not acid to litmus paper, but it possesses a peculiar and penetrating odour.” The ejection of defensive fluids and vapours are not con- fined to the anterior parts of insects, for in the Bombardier Beetles, according to Dr. Léon Dufour, a pungent vapour, resembling nitric acid in its properties, is ejected from the anus. Brachinus displosor will furnish twelve such discharges, but subsequently explosion with noise is replaced by the emission of a yellowish or brownish fluid, which readily vaporises. These discharges are meant to arrest the onset of larger predacious beetles. Brachinus crepitans is sometimes gregarious, and when one individual is disturbed the whole PHYSIOLOGY OF THE INVERTEBRATA. 263 discharge in unison, but after about twenty explosions they only emit a white fluid. M. F. Pouchet * says :— L’instinct de la défense est telle- ment inhérent a la tribu des Bombardiers, qu’au seul coup de canon d’alarme de l’un d’eux, tous les autres crépitent en méme temps: c’est un feu roulant sur toute la ligne.” There is something in these insects discharging the fluid in unison which seems to point out that they are guided not merely by instinct, but by that which is the equivalent of mind. The, chief enemy of B. crepitans, which inhabits Great Britain, is Calosoma inquisitor (Fig. 48). Fic. 48.—BOMBARDIER BEETLE AND ITS ENEMY. (After F. A. POUCHET.) The secretory glands of the Bugs are situated exterior ‘to the insertion of the posterior legs, and emit foetid effluvia on seizure. The ground bettles of the genus Carabus, when disturbed, eject a fluid which is caustic if applied to the skin. In conclusion, it may be remarked that a very large number of insects eject liquids or vapours as a means of * DT’ Univers, p. 137+ 264 ‘PHYSIOLOGY OF THE INVERTEBRATA. protecting themselves, more or less, from the attacks of : various enemies.* (6) There are two pairs of salivary glands of the larval Lepidoptera (see Fig. 7). The posterior or second pair secrete the viscous substance, which hardens on exposure to the atmosphere and forms silk. This silk is the material in which the larvee or caterpillars invest themselves. The vis- cous substance from these glands is made into threads and spun into cocoons by means of a slender tubular organ called a spinneret, which is situated on the labium. Most caterpillars spin silken threads to secure themselves from falling, and many of them, as already stated, spin a cocoon in which to pass the pupal state. In Myrmecoles and the Hemerobide the silk is furnished by the rectum. (c) The glow-worm, or Lampyris splendidwla, and many other insects have the power of emitting light. According to Schulze,t the males of the glow-worm have a pair of photogenic organs, “ which lie on the sternal aspects of the penultimate and ante-penultimate abdominal somites. Each is a thin, whitish plate, one face of which is in contact with the transparent chitinous cuticula, while the other is in rela- tion with the abdominal nerve-cord and the viscera. The sternal gives out much more light than the tergal face. The photogenic plate is distinguishable into two layers, one occupying its sternal and the other its tergal half. The former is yellowish and transparent, the latter white and opaque, in consequence of the multitude of strongly refract- ing granules which it contains. Tracheze and nerves enter the tergal layer, and for the most part traverse it to terminate in the sternal layer, which alone is luminous. * For further information on the defensive fluids and the eversible glands of Lepidopterous larve, see the papers by Mr. E. B. Poulton, F.R.S., in the Transactions of Entomological Society of London, 1885, p. 322; tbid., 1886, p. 1563 tbid., 1887, p. 295; Report of British Association, 1887, p. 765; and his excellent book, The Colours of Animals. + Archiv fiir Mikroskopische Anatomie, 1855. PHYSIOLOGY OF THE INVERTEBRATA. 265 Each layer is composed of polygonal nucleated cells. The granules are doubly refractive, contain uric acid, and probably consist of urate of ammonia. Hence the cells of the layer which contain them are termed by Schulze the ‘urate cells,’ while he calls the others the ‘parenchyma cells. The branches of the tracheee which ramify among the parenchyma cells end, like those of other parts of the body, in stellate nucleated corpuscles, one process of the corpuscle passing into a ramification of the trachea. Schulze is inclined to think that the other processes end in paren- chyma cells. The nerves of the photogenic plates are derived from the last abdominal-ganglion ; they branch out between the parenchyma cells into finer and finer branches, which eventually escape observation.” (Huxley.) Lampyris can vary at will the intensity of the phosphoric light. It has been stated that the light is connected with the action of oxygen upon a fatty material secreted by the photogenic organs, and the light so produced is reflected by means of the granules already alluded to. The function of the Malpighian tubules of insects were not definitely established until a few years ago. Some zoologists stated that they represented the “liver,” while others main- ‘tained that they were renal in function. The Malpighian tubules of Blatta (Periplancta) have been shown by the author* to contain uric acid and urea. Dr. C. A. MacMunn f has confirmed the author's investiga- tions, for he has extracted uric acid from the Malpighian tubules of Periplaneta orientalis. These tubules were crushed, boiled with distilled water, the extract evaporated to dryness, washed with hot alcohol, and again dissolved in boiling water and filtered. To the filtrate excess of acetic acid was added, and in some hours uric acid crystals of various forms, and giving the murexide test, were formed. * Chemical News, vol. 52, p. 195. t+ Journal of Physiology, vol. 7, p. 128. 266 PHYSIOLOGY OF THE INVERTEBRATA. The author* has also examined the Malpighian tubules of Lnbellula depressa (Figs. 49 and 50), and has proved that they have a renal function. Co — CORT AAA ERROR b BLRARL AA SSR EMS oe No. Ei tl 4 Hh, Le He fy H I Lt 2 aes BS £7 wes LQ eH Me Lj wa Be g SS SSK CO tf 7 a Uy SS W wi S > oe KS ESR FIG. 49.—MALPIGHIAN TUBULES OF LIBELLULA. Libellula depressa (the dragon-fly) is a voracious insect, which lives in water, during its earlier stages, where it undergoes an imperfect metamorphosis, the pupa finally creeping out of the water, and chang- ing intothe imago. By ex- perimenting with a large number of the larval forms of Libellula, the author has extracted (from the larva) : uric acid crystals, by using Fic. 59.—MALPIGHIAN TUBULES OF. similar methods to those ee already described in this A= Longitudinal section showing the va- rious states of the epithelial lining. chapter. ; B = Transverse section of tubule. X 230. In the imago or mature form of the dragon-fly the Malpighian tubules number from sixty to seventy, and are branched. Under the microscope, a Malpighian tubule is *. Proc. Roy. Soc. Edinb., vol. 15, p. 401. PHYSIOLOGY OF THE INVERTEBRATA. 267 seen to consist of a connective tissue layer, a delicate “tracheal tube,” a basement membrane, and an epithelial layer of comparatively large nucleated cells (Fig. 50). The internal cavity of one of these tubules is very irregular, as is seen by examining various parts of it in a transverse section. The uric acid contained in these tubules can be extracted by boiling a large number of them in water, filtering, and then evaporating the filtrate to dryness. The residue is treated with alcohol, filtered, and the residue so formed is dissolved in boiling water to which acetic acid is added. After standing for several hours, crystals of uric acid (C,H,N,O,) are deposited. These crystals are readily con- verted into murexide, Then, again, if a fresh Malpighian tubule is placed upon a slide under the microscope, and crushed, a drop of dilute acetic acid added, and the whole covered by a cover-glass, rhombic and other crystalline forms are deposited.’ These crystals are also readily converted into murexide by the action of nitric acid and ammonia. No other substance besides uric acid could be detected in the Malpighian tubules of Libellala depressa. From the above-mentioned reactions it is evident that the Malpighian tubules of the Jnsecta are physiologically true renal organs. As already mentioned some zoologists of the older school stated that these appendages of the alimentary canal repre- sented the “liver,” and this statement has been recently revived by Dr. B. T. Lowne in his work on Calliphora. But the Malpighian tubules of the Diptera (including Calliphora) readily yield uric acid when the proper tests are skilfully applied; and they do not contain the least trace of biliary acids, glycogen, or even ferments. The Malpighian tubules of the Insecta are undoubtedly true kidneys, although they are developed -from the alimentary canal, 268 _PHYSIOLOGY OF THE INVERTEBRATA. THe ARACHNIDA. (a) In the Scorpion the posterior extremity of the abdomen is armed with a sort of hooked claw, which, when the animal is in motion, is always carried over the back in a most threatening attitude. This claw-like organ is the sting, and at its base are situated two poison-glands whose ducts pass into the point of the sting, so that when the animal strikes with its weapon, a small portion of the poison or vemon is instilled into the wound. The sting is a weapon of offence. (b) In the Avraneina the poison gland is lodged in the cephalo-thorax, and the duct of it opens at the summit of the terminal joint. It will be noticed that in the Arancina the poison gland is situated in the anterior part of the body, whereas in the Arthrogastra it is in the posterior part. But “the most characteristic organ of the Araneina is the arachnidium, or apparatus by which the fine silky threads which constitute the web, are produced.” In Zpeira diadema this apparatus contains a thousand glands with separate ducts. These ducts secrete the viscid material which ultimately hardens into silk. “The glands are divisible into five different kinds (aciniform, ampullate, aggregate, tubuliform, and tuberous), and their ducts ulti- mately enter the six prominent arachnidial mammille, which in this species project from the hinder end of the abdomen. The superior and inferior mammille are three-jointed ; the middle one is two-jointed. Their terminal faces are trun- cated, forming an area beset with the minute arachnidial papillee by which the secretion of the glands is poured out.” The Spider usually commences its thread by applying the spinnerets to some fixed object ; to this the viscous secretion attaches itself, when the movements of the animal are sufficient to draw out the materials necessary for the con- PHYSIOLOGY OF THE INVERTEBRATA. 269 tinuation of the thread. This power of spinning threads from the secretion of these glands is of the greatest import- ance to all these animals (%.¢, those belonging to the sedentary class), as it not only serves many of them for the “ Qo 3 & Le [a AS { a hm oO & 8 a is liver ducts* malpighian tubes E °° Oo ~ Fic. 51, A AND B.—MALPIGHIAN TUBES OF TEGENARIA. construction of dwellings, and of webs for the capture of prey, but isconstantly employed in securing them from falls whilst in motion, or in descending in a. direct line from an elevated position to some object below them. Many spiders 270 PHYSIOLOGY OF THE INVERTEBRATA. have the power of emitting this secretion in the form of threads, one end of which floats freely in the air until it meets with some object to which it adheres. By this means spiders often form natural bridges, by means of which they can pass over brooks and rivers, in some cases twenty and even fifty feet wide. Another purpose to which this secretion is applied by all spiders is the formation of silken cocoons for the reception of the ova, which a few species (i.c., wandering spiders) carry about with them. FIG. 52, @ AND 4,—CRYSTALS OF URIC ACID AND MUREXIDE. a = the uric acid crystals. %4 = murexide crystals. Concerning the excretory apparatus in the Araneina, Mr. A. Johnstone, F.G.S., and the author* have examined the Malpighian tubules of Tegenaria domestica (Fig. 51, A and B). The intestines of this species form a tube-like body, which dilates into a short rectum, and into this rectum the Mal- pighian tubules open. An aqueous extract of a large number of these tubules yielded uric acid (Fig. 52). The secretion is neutral to test papers. * Proc. Roy. Soc. Edinb., vol. 15, p. 111. PHYSIOLOGY OF THE INVERTEBRATA. 271 The uric acid was extracted by both of the methods used for testing the pyloric sacs of Uraster (see p.) 254. The uric acid is present as sodium urate, for sodium is easily detected in the secretions of these organs. No doubt some sodium compound is a normal constituent of the blood of Tegenaria. “No urea, guanin, or calcium phosphate could be de- tected in the secretion. But it may be stated that Dr. C. Weinland* has recently extracted crystals of guanin from the excrements of certain spiders. .The guanin so extracted is stated to have answered to all the reactions of that substance as described by Capranica.t There is no doubt that the Malpighian tubules of the Arachnida are renal in function. THE CRUSTACEA. Among the lower Crustacea the renal organ is represented by the so-called shell-gland. It consists of a coiled tube with clear contents. In Apus (belonging to the Phyllopoda) this gland opens by a duct “on the base of the first pair of thoracic appendages, immediately behind the second maxille,” In his paper on Cyclestheria hislopit Dr. G. O. Sars says that the only organ to which an excretory function has been attributed is the so-called shell-gland (see Fig. 11). Its structure is glandular, but of what nature the secretion is, and in what manner performed in this species, has not yet been satisfactorily ascertained. Some naturalists state that this peculiar organ secretes the material of which the shell is built up, but it is far from evident that such is its real function. On examining the organ, Dr. Sars failed to detect in this species any secreting orifice, the whole organ appear- ing to constitute a convoluted canal or duct recurring in itself. * Zeitschrift fiir Biologie, vol. 25, p. 390. + Zeitschrift fiir Physiologische Chemie, vol. 4, p. 233. t Christiania Videnskabs-Selskabs Forhandlinger, 1887, p 43. 272 PHYSIOLOGY OF THE INVERTEBRATA. But there is no doubt that in other forms of the lower orders of the Crustacea the secretion of the shell-gland does‘ contain uric acid, proving the renal function of the organ in question. In the Decapod Crustacea * the excretory organs are re- presented by the so-called green glands. Dr. Rawitz has recently examined the anatomical structure of these glands in Astacus fluviatilis, and his results may be summarised as follows :—The gland is uniformly green on the ventral side, but on the dorsal side only at the periphery ; elsewhere white, with a round yellow-brown speck in the centre. When examined microscopically the gland is seen to consist of two tubules closely interwoven. The cells of the green part contain a round grass-green drop of protoplasm, and the yellow-brown cells a uniformly yellow-brown coloured nucleus. The tubules anastomose, the yellow-brown cells being the terminal portions of tubules ie ee and secretory. ee ee The author} has made a com- @ = glandular portion. b = sac- + ‘ ; like portion. ¢ = opening of plete study of the function of quch = = Herve Wh cama the pres plands of Asa 5 i b 5 . “76 cations. X 2 (about) fluviatilis, and the results of these researches may be stated as follows:—The so-called green glands of the fresh-water crayfish lie in the cavity of the head below the front part of the cardiac division of the stomach (see Fig. 13). The openings of these organs are situated at the base of each antenna. The organ, carefully dissected out of the head of a fresh-killed crayfish, is seen to consist of two principal parts (Fig. 53): a dorsal or upper- * The Decapoda includes the Brachyura and the Macroura. + See Dr. Rawitz’s paper, read before the Berlin Physiological Society on January 28, 1887. / < Dr. Griffiths’ paper in Proceedings of Royal Society of London, vol. 38 (1885), p. 187. PHYSIOLOGY OF THE INVERTEBRATA. 273 Murexide. B= Uric acid. Fic. 4.—Uric AcibD CRYSTALS FROM GREEN GLAND OF CRAYFISH, A 274 PHYSIOLOGY OF THE INVERTEBRATA. most one which is a transparent and delicate sac-like body filled with a clear fluid, and a ventral or an underlying portion of a green colour, glandularin appearance, containing granular cells. As is well known, these green glands were formerly believed to be the auditory organs of Astacus; but in 1848 Drs. Will and Gorup-Besanez* stated that this organ probably contained guanin, and from this supposition the green glands have been considered as excretory organs. The secretion of these glands is acid to litmus paper, and on treating the secretions, obtained from a large number of green glands, with hot dilute sodium hydroxide solution, and then adding hydrochloric acid, a slight flaky precipitate was obtained, and on examining these flakes under the microscope they were seen to consist of small crystals in rhombic plates. On treating the secretion with alcohol these rhombic crystals (Fig. 54 A) were deposited; they were soluble in boiling water. When these crystals were moistened with dilute nitric acid, alloxanthine (C,H,N,O,) was produced, and on heating this substance with ammonia, reddish-purple murexide (Fig. 54 B) or the ‘ammonium purpurate” [C,H,(NH,)N,0,] of Prout was obtained. The murexide so obtained crystallises in prisms, which by reflected light exhibit a splendid green metallic lustre, and by transmitted light are a deep reddish- purple. On running in a solution of potassium hydroxide upon a microscopic slide containing some of the murexide crystals they were dissolved. It is evident (from the above reactions) that these rhombic crystals are deposits of uric acid (C;H,N,O,) from the secretion of the green gland of the crayfish. These deposits of uric acid crystals were covered more or less with a very thin and superficial coating of some brown colouring matter, probably one of the pigments already described. * See Minchen Gelehrie Anzeigen, No. 233, 1848. PHYSIOLOGY OF THE INVERTEBRATA. 275 The secretion of the green gland of Astacus contains guanin, which is proved by treating the secretion with boiling hydro- chloric acid. A solution is obtained containing flakes of uric acid in suspension, these are filtered off, and the filtrate set aside to cool, when a few crystals (guanin hydrochlorate) separate which are soluble in hot water. On the addition of ammonia to this hot aqueous solution a precipitate is obtained of guanin (C,H,N,O), the precipitated guanin being composed of a number of minute microscopic crystals. On running in warm dilute nitric acid (on to the slide), these crystals dis- appeared, but they where precipitated again on the addition of a drop of silver nitrate in the form of the nitrate of silver compound (C,;H,N,0O,AgNO,) of guanin. This investigation proves that the so-called green gland of Astacus fluviatilis is a true urinary organ, its secretion containing uric acid and traces of the base guanin. The green gland is, therefore, physiologically the kidney of the animal.* The nerve, which comes off from the supra-cesophageal gan- glion, passes to the neck of this gland (see Figs. 13 and 53), and ramifies over its surface between the outer and inner membranes of which it is composed. In the Edriophthalmic Crustacea, there are occasionally present one or two tubules which open into the posterior part of the alimentary canal. These are renal organs and contain uric acid. They are analogous to the Malpighian tubules of the Jnsecta. In this respect the Amphipoda and Isopoda differ from other Crustacea. THE BRACHIOPODA. The shell of these animals is “a cuticular structure secreted by the ectoderm, and consists of a membranous basis, hardened * For further details see Dr. Griffiths’ papers in Proceedings of Royal Society, vol. 38, p. 187 ; Chemical News, vol. 51, p. 121; Journal of Chemical Society, 1885, p. 680 ; Science Gossip, 1886, p. 57. 276 PHYSIOLOGY OF THE INVERTEBRATA. by the deposit of calcareous salts, sometimes containing a large proportion of phosphate of lime (Lingula).” In Waldheimia and other Brachiopods, “the perivisceral cavity communicates with the pallial chamber by at least two, and sometimes four, tubular organs, which have been described as hearts, but are now known to have no such nature.” These organs are funnel-shaped, the wide parts of which open into the perivisceral cavity. The narrower parts of these organs pass through the anterior wall of the visceral chamber, and terminate in small openings in the pallial cavity. According to Dr. Morse, the ova pass through these organs in Terebratulina septentrionalis. The so-called pseudo-hearts have a double function, being renal organs and genital ducts, They are the homologues of the organs of Bojanus of the Mollusca, and of the segmental organs of worms. Tue MoLuusca. The excretion of carbonate of lime is an important function in a large number of Molluscs. In Anodonta, which is taken as a typical example of the Lamellibranchiata, the shell is a “cuticular excretion from the surface of the mantle,” and consists of variously disposed lamelle of organic matter impregnated and hardened by the. deposition of calcareous salts (chiefly carbonate of lime, mineralised as arragonite). The shell has no cellular ‘struc- ture; “but from the disposition of its lamellz, and from the manner in which the calcareous deposit takes place in. them, it may present varieties of structure which have been distin- guished as nacreus, prismatic, and epidermic ” (Fig. 55). In the young Lamellibranch shell there is a much larger percentage of calcium phosphate present than in the adult shell: the calcium phosphate being gradually replaced hy calcium carbonate as the animal arrives at maturity. The ligament which unites the valves together is an uncal- cified chitinous material. This material is continuous with PHYSIOLOGY OF THE INVERTEBRATA. 277 the horny cuticle which spreads over the external surface of the valves, and is reflected over the ventral edges into the mantle or pallium. The pearly or nacreus layer has a laminated texture, and is secreted by the mantle. The production of pearls (¢9., in Meleagrina margaritifera, the “pearl oyster”) is as follows: A grain of sand, or other hard substance, gets in between the pallium and the shell. Con- sequently the external surface of the pallium becomes irri- tated, and the laminated mo- ther-of-pearl layer (nacreus FIG. 55. layer) is secreted by the pal- section or SHELL oF GAPER. lium, during the remainder of a = cuticula. 4 = prismatic layer. the animal’s life, around this ¢ = nacreus layer. d = epithelium. ite é = mantle. irritant nucleus.* The exoskeletons of the Brachyura and Macroura have a similar structure to the Lamellibranch shells;t and it has been shown that the particular combinations of lime requisite for the formation of these shells, &c., are calcium chloride, calcium carbonate, or calcium phosphate. The sulphate of lime present in sea water cannot be utilised for shell formation unless it is first converted into one of the above forms. The researches of Irvine and Woodhead + prove that “ shell forma- tion in the crab is somewhat different from egg-shell formation in the hen, and occupies an intermediate position between * According to Dr. G. Harley, F.R.S. (Proc. Roy. Soc., 1888) pearls have the-following composition :— Calcium carbonate . : a ‘ » 91.72 Organic matter (animal) . 7 3 - 5-94 Water . . . ; . : #12323 99.89 + See Vitzou’s paper in Archiv de Biologie, tome 10, p. 659. ¥ Proc, Roy. Soc. Edin., vol. 15, p. 308; vol. 16, p. 324. 278 PHYSIOLOGY OF THE INVERTEBRATA. such egg-shell formation and bone formation, as the carbonate of lime is deposited in the chitinous portion of growing epithelial cells in the crab shell.” “Tn the secreting layer of the mantle of certain Molluscs the lime in the epithelial cells is principally phosphate, whilst the fluid bathing its outer surface and the shells them- selves contain the lime, principally in the form of a carbonate. If there is a definite interval between the secreting surface and the area of deposition, or if much chitin or other tissue is developed between the actively secreting cells and the tissue in which the lime is deposited, there is always a greater tendency to the formation and deposition of carbonate of lime.” Phosphates of the alkalies and alkaline earths occur in the blood or nutritive fluid, and the latter acts as a carrier of lime, &c., to every part of the body where carbonic anhydride may be given off; thus carbonate of lime is formed, and the phosphoric acid re-enters the circulation. As already stated, the embryonic and young shells of the Lamellibranchiata are richer in phosphate of lime than the shells of the fully-grown animal. No doubt as greater activity goes on a larger amount of carbonic anhydride is produced, and by this means more carbonate of lime is de- posited than phosphate of lime. When alkaline phosphates, associated with lime and albumin, preponderate in the blood, the lime so separated is in the form of phosphate, as in bone formation; when these are partially replaced by an excess of alkaline carbonates, as in the majority of marine animals, the lime is secreted as car- bonate. The corals have a secreting layer of cells which, according to Irvine and Woodhead, produce chitin—chitin infiltrated with calcium carbonate, and almost pure calcium carbonate, with a small quantity of cementing organic material. The carbonate of lime is formed by the ammonium car- bonate produced by the decomposition of the effete products PHYSIOLOGY OF THE INVERTEBRATA. | 279 of animals, as urea, &c., decomposing the calcium sulphate in the sea water with the formation of calcium carbonate. In the blood of the lime-secreting Invertebrates there are phosphates of lime and soda, along with alkaline chlorides, carbonates, and sulphates associated with albuminous matter, carbonic anhydride and oxygen being also present in varying quantities. This blood is alkaline, which is due to the pre- sence of alkaline phosphates and carbonates. Dr. Schmidt found that the blood of Anodonta cygnea was slightly alkaline; and on evaporation it yielded crystals of calcium carbonate resembling gaylussite. “ These could not have been present originally in the alkaline fluid, and it is probable that they were produced by the formation of ammo- nium carbonate from the decomposition of urea* and nitro- genous organic matter.” The membrane which secretes chitin also brings lime to the surface, and in performing its protoplasmic function car- bonic anhydride is set free; this readily forms calcium car- bonate after decomposing certain lime salts. “ But it must be noted that the chitin is directly in contact with the upper secreting cells, in fact, the younger layers of chitin still form the upper or oldér portion of the cell.” Irvine and Wood- head “maintain that the direct contact allows of the dialysis into the chitin of a portion of the phosphate of lime before it is completely transformed into the carbonate. As the car- bonate of lime is formed the free phosphoric acid is apparently reabsorbed and utilised afresh. In proof of this fact, and as bearing on the whole question of lime secretion, we refer to the investigations of Schmidt, who, in speaking of Unio, Anodonta, and Helix, describes the structure of the secreting membrane of the mantle as a layer of hexagonal cells on which is a structureless transparent membrane in which the lime is deposited, and ascribes to it the function of decomposing the blood, of secreting a compound of albumin with phosphate of * Urea and uric acid are present in the excreta of Anodonta, see the author’s paper in the Chemical News, vol. 51, p. 241. 280 PHYSIOLOGY OF THE INVERTEBRATA. lime next the shell, which is decomposable even by the carbonic anhydride of the air or of the water, but of retaining the phosphoric acid and returning it to the organs which require it for the process of cell formation. In proof of this he gives the following analysis of the ash of the secreting layer of the mantle: I. IL. Calcium phosphate . > 3 ‘ 14°85 14°91 Calcium carbonate, sodium phosgene: 2.71 3.45 sodium chloride,and calcium sulphate : : showing how large a proportion of the lime salts must, in | this secreting layer, be in the form of phosphates. As: further proof he gives analysis of the mucus which is found between the shell and the mantle, in which he finds much albuminate (basic) of lime, a small proportion of carbonic anhydride, but not a trace of phosphate. In the delicate membrane in which the lime is deposited we have an analo- gous membrane to that of egg-shell membrane (of birds), separated from the secreting layer of cells by a fluid containing albumin, carbonic anhydride, and lime salts, in whatever way combined, and deposited in the structureless membrane. According to analysis of the ash, the lime salts present are in the following proportion : Anadonta. Helix, Calcium carbonate . . : 99-45 .. 99.06 Calcium phosphate . ‘ ‘i 0.55 vee 0.94 So that Schmidt was able to trace the transition stages through the excess of phosphate in the mantle, the albu- minate in the intermediate bathing mucus, and the carbonate in the shell.” Irvine and Woodhead believe that the carbonic anhydride in this case was the result of metabolic processes going on in the mantle, and that the carbonate of lime formed was gradually passed on in this condition from the lime-mucous solution (if present in that condition) into the membrane again by dialysis. PHYSIOLOGY OF THE INVERTEBRATA. 281 “As the process of shell-formation must necessarily go on slowly, it is not at all astonishing that such a small propor- tion of carbonic anhydride should be found in the mucous material. It is used up as it is formed in laying down the carbonate of lime of the shell. “As regards the proportion of the lime salts and chitin, Schmidt found that the amount of earthy phosphate increases in proportion to the quantity of chitinous tissue present in the basement structure : : Crayfish. Squilla. Lobster, Chitin . : » 46.73 sie 62.84, oie 22.94 Lime salts. - 53-27 ie 37-17 = 77.06 100.00 a 100.00 ss 100.00 Calcium phosphate 13.17 si 47.52 aH 12.06 Calcium carbonate 86.83 ite 52.48 ea 87.94 100.00 ate 100.00 oat 100.00 “He argued from this that the calcium (lime) phosphate is in intimate relation with cell-formation.” But Irvine and Woodhead think that as the chitin becomes older and thicker the cellular layer becomes less active, less carbonate is formed, and that there is thus a more direct passage out- wards of the phosphate. In their papers already mentioned, Irvine and Woodhead give the following analyses as showing the comparative amount of calcareous and organic matter in the common edible crab : Water, blood, salts, kc. . . : . 6,646 grains Flesh (gave 14.56 of ash containing a 94 iiiite phosphate) « 2905» Outer calcareous structure a , _ « 2,956 5 Inner calcareous structure : : ‘ , a - 103 4 10,000, The calcareous structure consisted of : 282 PHYSIOLOGY OF THE INVERTEBRATA. ' Lime Total. | Chitin. eters ae Percentage. Carapace . . | 817 | 150.32 | 656.80 | 9.87 Gian. Chelze : . | 1184 | 236.80 | 933.00 | 14.20 Chitin Bae Ambulatory limbs | 736 | 147.20 | 579.97 | 8.83 CaCO, . 7880 Abdominal f 156 31.20 | 122.93 | 1.87 Ca,P,0, . 1.20 segments “\( 63 {| 12.60} 49.64 | 0.76 100.00 Outer — struc-) . = Gare anconek 2956 | 587.12 | 2342.34 | 35-53 INNER. 103 | 35.00} 66.98] 1.02 | Chitin . 34.00 CaCO, . 65.00 (se (mandibles) weighed . 17 grains. | Ca,P,0, . 1.00 Inner _ struc- ture aoe . Stomachical teeth (horny mat- 100.00 ter) weighed . - 2 QP oy The nutritive fluid (blood) of an edible crab weighing _ about 8000 grains contained :— Calcium phosphate . , : : : - 11.10 grains Phosphoric acid a % 5 ; : : 15-78 4 Having alluded to the secretion of the shells and exo- skeletons in the Mollusca and Crustacea, we now proceed to describe the organ of Bojanus in Anodonta cygnea and other Lamellibranchiata. The function of this organ has been investigated by Mr. Harold Follows, F.C.S., and the author.* It is a paired, elongated, oval, glandular sac with folded walls. It is situated beneath and behind the pericardium, and in front of the posterior adductor muscle (see Fig. 18). This organ is composed of a yellowish or brownish spongy tissue, which is covered with a closely ciliated cellular layer. Its secretion is acid to litmus paper, and it contains uric acid, urea, and calcium phosphate... The presence of these com- pounds were proved by the methods already described in this chapter. * Chemical News, vol. 51, p. 241; Journal of Chemical Society, 1885, p. 921i Proceedings of Royal Society of Edinburgh, vol. 14, p. 233. PHYSIOLOGY OF THE INVERTEBRATA. 283 Mr. Follows and the author also examined the blood (of Anodonta) contained in the vena cava before it enters the organ of Bojanus, and it was proved that the blood contains uric acid and urea. After leaving the vena cava the blood passes into the organ of Bojanus and thence to the branchie. The blood in the branchize does not contain uric acid or urea. The investigation proves—(w) that the organ of Bojanus is physiologically the kidney of the animal, eliminating the nitrogenous waste matters (in the form of uric acid and urea) contained in the impure blood as it is brought to this organ by the vena cava; (0) that after the blood has passed through the organ of Bojanus, it is freed from urea and uric acid. The secretion of the organ of Bojanus in Mya arenaria (see Fig. 18) contains uric acid, urea, and calcium phosphate. Drs. Will and Gorup-Besanez* stated that they found guanin in the organ of Bojanus of the fresh-water mussel, but subsequently Voit could not detect the least trace of this base in the organ in question. Mr. Follows and the author entirely agree with the conclusions of Voit, for we also could not detect guanin in the organ of Bojanus in Anodonta cygnea, although it may be remarked that guanin is present in the green glands of Astacus and Homarus.t The organ of Bojanus appears to be well-developed in the majority of the Lamellibranchiata, but in Ostrea and Teredo it seems to be present in only a very rudimentary form.t The nephridia of Helix aspersa and Limax flavus contain uric acid, and were proved by MacMunn§ to have a renal function. * Ann. der Chem. und Pharm., vol. 59, p. 117; and Dliinchen Gelehrte Anzeigen, 1848. ‘ + See Dr. Griffiths’ papers in Proc. Roy. Soc. of London, vol. 38, p. 187 ; and Proc. Roy. Soc. of Edinburgh, vol. 14, p. 233- + See the papers of Lacaze-Duthiers in Annales des Sciences Naturelles, 1854-1861. § Journal of Physiology, vol. 7, p. 128. 284 PHYSIOLOGY OF THE INVERTEBRATA. The author has confirmed MacMunn’s investigations, and he has also proved the renal function of the nephridia in Limax maximus, Helix pomatia, Limax variegatus, Arion ater, and other Gasteropods. They contain, in addition to uric acid, urea and calcium phosphate. Many of these organs also contain some of the histohematins; and in the case of “ Arion ater the nephridium showed a spectrum resembling that of myohematin, and this spectrum is remarkable for its resemblance to that of the kidney of Vertebrates.” (MacMunn.) The Gasteropoda are provided with numerous glands which secrete mucus. The epiphragm of Helix is secreted by mucous glands, but it becomes hardened and strengthened by the deposition of calcareous matters. This epiphragm (perforated) is secreted before hybernation (%.¢., the winter sleep), and closes the shell-opening when the animal is retracted. The epiphragm is cast off in the spring when the animal awakes. The secretion of the mucous glands of slugs is of value to the animals as a means of protection against the attacks of enemies. The mucus secreted is often pigmented, and it gives a polished appearance to the pigments which resemble certain metallic hues; such pigments are spoken of as protec- tive colours. : Having referred to certain secretions of the Pulmogastero- poda, we have now to consider those of the Branchiogasteropoda. The author™ has investigated the nephridia of Patella vulgata. These organs consist of two parts—left and right lobes. The left nephridium is very small in comparison to the right. The anatomy and histology of these organs have been fully described by Professor E. Ray Lankester, F.R.S.,f J. T. Cunningham,} and Harvey Gibson.§ * Proceedings of Royal Society, vol. 42, p. 392. t Annals and Magazine of Natural History, vols. 20 (1867), and 7 (1881). + Quarterly Journal of Microscopical Science, vol. 22, p. 369. § Transactions of Royul Society uf Edinburgh, vol. 32, p. 617. PHYSIOLOGY OF THE INVERTEBRATA. 285 After dissecting the nephridia from the bodies of a large number of fresh limpets, the secretions of the left nephridia were examined separately from those of the right nephridia. Both secretions were examined chemically by two separate methods as follows: (a) The clear liquid from the nephridia was treated with a hot dilute solution of sodium hydroxide. On the addition of HCl a slight flaky precipitate was obtained after standing for some time. These flakes when examined microscopically were seen to consist of small rhombic plates and other forms. On treating the secretion alone with alcohol, rhombic crystals were deposited, which were soluble in water. When these crystals were treated with nitric acid and then gently heated with ammonia, reddish-purple murexide was obtained. (6) The second method for testing the secretion of the nephridia of Patella was as follows: The secretion was boiled in distilled water, and then evaporated carefully to dryness. The residue so obtained was treated with absolute alcohol and filtered. Boiling water was poured upon the residue, and to the aqueous filtrate an excess of pure acetic acid was added. After standing about seven hours, crystals of uric acid (C,H,N,O,) were deposited, and readily recognised by the chemico-microscopical tests mentioned above. The secretions of both the left and right nephridia yield uric acid. It has been suggested by Professor R. J. Harvey Gibson (in his masterly memoir on the “ Anatomy and Phy- siology of Patella vulgata ”*) that the secretions of the two nephridia may be chemically distinct. The author could not extract or detect (after a most searching investigation) the presence of any other substance besides uric acid in the secretion of either nephridium. The isolation of uric acid proves the renal function of the nephridia of Patella vul- gata. The nephridia of the Cephalopoda have also been examined * Transactions of Royal Society of Edinburgh, vol. 32, p. 601. 286 PHYSIOLOGY OF THE INVERTEBRATA. by the author.* Taking Sepia officinalis as a type of the Cephalopoda, it was proved that the nephridia of the animal are true renal organs. The venous blood, as it passes from the vena cava, is distributed by a number of afferent branchial vessels which communicate with the sacculated and glandular nephridia; it then passes into the branchis, and hence it is sent back to the heart. The secretion of the nephridia contains uric acid and calcium phosphate, but urea, guanin, calcium carbonate, and magnesium carbonate are absent. Uric acid is also present in the blood of the vena cava before it enters the nephridia, but the blood after passing. into the branchie contains no uric acid. The nephridia of the Cephalopoda are true renal organs, eliminating the nitrogenous waste matters in the form of uric acid, contained in the impure blood as it is brought to these organs by the vena cava. As already stated no urea could be detected in the nephridia of Sepia, and the same remark applies to those of Octopus. The muscular tissues of these animals do not yield urea; but it may be remarked that the muscular tissues of certain Lamellibranchs do contain this base. For instance, 100 grammes each of the adductor muscles and foot of Mya arenaria (large individuals) were chopped into small frag- ments and were allowed to remain in contact with alcohol. for twelve hours. The alcohol was then squeezed out and evaporated on a water-bath. The residue obtained was dissolved in water, placed in the receiver of a mercury pump, and treated with sodium hypobromite. By this method the following results were obtained :— I. II. Ill. Adductor muscles : . 42.6 chs 56.2 we 56.8 Foot. : : : , 48.9 its 52.0 wed 58.6 * Proc. Roy. Soc, Edin., vol. 14, p. 230. PHYSIOLOGY OF THE INVERTEBRATA. 287 These results are expressed in milligrammes of urea per 100 grammes of muscular tissue.* It is most probable that the formation of urea takes place in the muscles. It is certainly present in the blood of Mya and Anodonta. Milne-Edwards states that “it is probable that in all cases the secreted matter exists in the blood already formed. It was thought, for example, that the urea found in urine must be formed by and in the kidneys, since it could not be detected by chemical analysis in the blood; but if these organs be destroyed in a living animal, or re- moved, urea will, after a certain time, be formed in the blood, thus clearly proving that the kidneys do not form it.” In the higher animals an abundant alimentation gives rise to a greater excretion of uric acid and urates. On the con- trary, in abstinence the uric acid and its salts disappear, but urea is excreted in greater quantity. This applies not only to Vertebrates but also to many Invertebrates. Ureaisa product of more or less complete oxidation of organic sub- stances, and is formed, as already stated, in muscular tissues, by the disintegration of the anatomical elements. Uric acid, on the other hand, is the result of an incomplete oxidation, and is produced for the most part in the bood or its equivalent, when such fluid is surcharged with peptones which the tissues are unable to assimilate. Secretion and excretion can be traced back to the phenomena of nutrition—that is to say, to the molecular acts effected in the midst of glandular cells, which means that it can be accomplished without the inter- vention of the nervous system. Such is the case with the lowest Invertebrates; but in the higher forms, possessing a more or less complete nervous system, secretion and excretion are largely influenced by nerves. It may be probable that if the commissural cords connecting the supra-cesophageal with the sub-cesophageal ganglion were severed nervous stimulus would not be supplied to the green glands of ' * See also Smith’s new method for estimating urea in the Pharm. Journ. Trans. [3], vol. 21, p. 294. 288 PHYSIOLOGY OF THE INVERTEBRATA. Astacus, and consequently the secretion ‘of urine would be most probably influenced. At any rate, this is a question for research. In the Vertebrata there is no doubt that the nervous centres do greatly modify the secretions. Forty-six years ago, Schiff demonstrated that lesions of the cerebral peduncles rendered the urine albuminous and acid. Claude Bernard* proved that punctures of the roof of the fourth cerebral ventricle gave rise to the formation of glucose sugar in the urine. Lesions of the isthmus and of the lower part of the cervical marrow can prevent the urinary excretion; or in other words, produce anuria. There is no doubt that in the Jnvertebrata the nerves play an important part in the phenomena of secretion, and even in the lower orders, where there are no traces of nervous elements, the protoplasm of the cells, being irritable, is capable of bringing into play the phenomena which we have been discussing in the present chapter. Experimental evi- dence shows that the Amba, for instance, excretes, digests, and respires; but so far at least as present microscopic expedients reach, this organism appears to be simply a small mass of protoplasm, nevertheless it has the power of adjust- ing its low organisation to the environment. “In the organism lies the principle of life; in the environment are the conditions of life. Without the fulfilment of these con- ditions, which are wholly supplied by environment, there can be no life.” The wonderful adaptations of each organism, and of each part of every organism to its environment, inspire us with a sense of the boundless resource and skill of Nature in perfect- ing her arrangements for each single life. The causes of these adaptations are to be sought in the numberless structural modifications brought about by means of natural selection and by the direct action of the environment. As already stated, not only an organism as a whole, but each organ is also capable of undergoing modification. Hence * Lecons de Physiologie Opératotre. PHYSIOLOGY OF THE INVERTEBRATA. 289 the reason that there are strange facts to confront in deter- mining the nature of anorgan. For instance, the Malpighian tubules of the Jnsecta are diverticula of the alimentary canal, consequently they have been described as livers, and morpho- logically they ought to have the function of a liver. But when physiology, aided by chemical methods, steps in, we find that these organs have solely a renal function. Is it possible that the Malpighian tubules had originally the function of a liver? This is improbable, but it is well known that an organ may lose its original function, and yet persist because it is of use for some other purpose: one of these predominate at one time, another at another, and the organ undergo structural modification in consequence.* The variety of modifications or forms of the renal organs in the Invertebrata may be illustrated by the table on pp. 290-1. The table on p. 292 is a summary of the constituents (present and absent) in the renal organs of the higher Invertebrata. In the lower Jnvertebrata the kidney performs other functions besides that of a renal organ; but in the higher forms a special organ is set apart for that function, and it resembles in many respects the Vertebrate kidney. On this point Prof. Huxley says: ‘In the Vertebrata, the renal apparatus is constructed on the same principle [as the renal organs of the Mollusca] . . .. The Vertebrate kidney is an extreme modification of an organ, the primitive type of which is to be found in the organ of Bojanus in the Mollusc, and in the segmental organ of the Annelid ; and, to go still lower, in the water-vascular system of the Turbellarian. And this, in its lowest form, is so similar to the more com- plex conditions of the contractile vacuole of a Protozoon, that it is hardly straining analogy too far to regard the latter as the primary form of uropoietic as well as of internal respiratory apparatus.” * In the higher animals, for example, we have the formation of a lung from a swimming bladder, and of the ear passage from a gill cleft. x .PHYSIOLOGY OF.THE INVERTEBRATA. 290 ‘UBSIO [BUSI B JO Jey} S¥ [JAA SB SUOTIOUNF 13y40 ‘prow orn) | prow ong } | ° ‘poe ony | ° ‘prow ong | * (i) (| * “prow og + ‘(a}vAN TANTpos se) plow on : “plore Off) GQ) | - P @ 1° ‘prowong | “ “ ) 66 6c (seqng uriqerdyem) saynqny re[nTT99 suvSio [eyueUsag ,, SUBBLO Ie[NpUeLy ,, ( 5 ) i (sweS10 TequdmZes) “ s > + (erprgdou) saqny ren TT99 s (uoTjouns [eNp wv sey YORMoys) ORM04s 94} Jo sayonod say ory, ,W9qsKS FE[NOSVA-1972 Ay * ,SOfONdBA 9TIJOVIJUOD * * ySaTONOBA a [TJOVIZUOD wuojied esau, , renee = * eraqdoy4I0 (9)} epodoiyyry eyeayorr}oqyorg (oy) BaployeMaN (wv) sadljoosojeUlaN * vyxzyodtog (a) eyeyoost[O (¢) ‘ eprpuuy > vourpnaty (0) vaplieysy (vp) eyeMIepoulyoR : : : * eyerequalao eraydoiman (2) | 5 ‘ epr8uodg io ereyOg eyosnjuy (9) 2 * 80Z0J01g eyse[doyorg (2) ] “UOIpaIOVg UT yuasaid syonpoIg —&q payuesaadaa Louptyy ‘ow ‘s1apIQ ‘sessv[Q (‘ssyounasas s.coyinp ay? wo1f papdwog) ‘AGNGIM GALVUIALYAANI GHL 291 PHYSIOLOGY OF THE INVERTEBRATA. *(j) prow om, ‘aqeyd -soyd wmnpoeo ‘prow org ‘proe ony) ‘ayeydsoqd Tnroyeo ‘vain ‘plow og ‘ayeydsoyd wantoreo ‘vain ‘plow O11, (3) ‘ulUeNsS PUR plo LIQ. “poe ony) ‘uruend ‘(ayein WINIpOS Sv) plow O11 "prow ON, | | | 4 4 suvsi0 suedi0 * (erpriqded) AZ[NpULLS puv pozvpnooes Jo srg (etprzqdeu) Je[npuels puv payepnooes jo seg (mantpiaydeu) purls repnqyao . snuvlog Jo suvSio ,, IepnT]aO (sue8i0 re[nqn4) syteoy-opnesg (,,Spuels uses ,,) . Spurs 1e[NTTIO (soqny uviysidjey) soynqn re[nTEO | | | ! | | vyergouriqevayzay, (z) equryoursqid (1) * — epodoyeydag (2) epodo.e4 -sesorqourig (z) ‘ epod | -oroysedomjug (1) ° epodosaysey (9) ‘ Bqurqouviqiteuey (v) * ByereqUa4sTTQ (77) * emmoieyl (7) ‘ vindyovig (4) . ermyeqaqydorpy (Sf ) eulouety (a) 3 eraydosjop (p) * BOSNT[ON . ‘ epodommorig * epodoryyi1y PHYSIOLOGY OF THE INVERTEBRATA. 292 t SI vozhjog sUIIeM ay} UT UOTJIOXe JeYy UMOYS svY (16QI ‘soUdIK ‘soup ‘wunor "Q4oN~)) IOMTIVA A'S “IW (1) ‘moryouny A103910x9 Ue aA “9490 ‘ppusapouryoy oY4 UL ,, ST[2O SULIOpUeA ,, a} FVY4 Sadorjeq (16gI ‘aug ‘soLnp “ULnor “yzonf)) WeyING ‘| ‘H “IW (z) ‘yeuvo ArejuouTye ayy Jo sTjeM 944 Aq pue onssty aATyooUUOD oY] Aq 4U94xXe OTIOS 04 PUP ‘sT[a0 OTMIIeposetM very Aq UO poTIIVO “DD.Lga,LaQUuy oy} Ul UoT}JeIOxe uo parvedde savy sioded omy ‘sxoqutid oy} Jo spuvy oy} Url poowfd sem YIOM sIyy eoUIGS— ‘ALON (06€ -d ‘Sz ‘fos ‘abojng unf prsyosnag) puerta ry 0} Surproooe ‘st yey, + F ‘ppodosajyspbowjpsupigg 94 UL YUeSqY + ry + é é i : i " uwnIpog = a = - + at + ‘ oyeqdsoyd unto[e9 oe = ae + = = : . * ulueny = = + = - + at - n> 30 + + + + + + + + + : prov ong “Baurpniiy | ‘TyZqooS[Q | ‘vaployewoN |} ‘ejoasuy ‘eplayoery | “eaovysns9 be sie, ie canning ‘quosqy = — : ‘quasaIg = + CHAPTER X. THE NERVOUS SYSTEMS OF THE INVERTEBRATA. ‘NERVOUS tissue consists of two distinct structural parts: (a) nerve-cells and (0) nerve-fibres. The nerve-cells are usually found in aggregates, termed ganglia or nerve-centres ; and ganglia are united to ganglia by nerve-cords or bundles, which consist of many delicate nerve-fibres. The latter act as the conductors of nervous force; in fact, ‘ the characteristic function of nerve-fibres is.that of conducting stimuli to a distance. The function of nerve-cells is different, viz., that of accumulating nervous energy, and, at fitting times, of dis- charging this energy into the attached nerve-fibres. The nervous energy, when thus discharged, acts as a stimulus to the nerve-fibre; so that if a muscle is attached to the end of a fibre, it contracts on receiving this stimulus. When nerve- cells are collected into ganglia, they often appear to discharge their energy spontaneously; so that in all but the very lowest animals, whenever we see apparently spontaneous action, we infer that ganglia are probably present.” There is another important point, viz., the difference between muscles and nerves under the influence of a stimulus. “A stimulus applied toa nerveless muscle can only course through the muscle by giving rise to a visible wave of contraction, which spreads in all directions from the seat of disturbance as from a centre. A nerve, on the other hand, conducts the stimulus without sensibly moving or undergoing any change of shape. Therefore muscle-fibres convey a visible wave of contraction, and nerve-fibres convey an invisible, or 294 PHYSIOLOGY OF THE INVERTEBRATA. molecular, wave of stimulation, Nerve-fibres, then, are functionally distinguished from muscle-fibres—and also from protoplasm—-by displaying the property of conducting in- visible, or molecular, waves of stimulation from one part of an organism to another, so establishing physiological con- tinuity between such parts, without the necessary passage of waves of contraction.” (Romanes.) Nerve-fibres may be functionally divided into five groups —motor, sensory, vascular, secretory, and inhibitory. When a nerve-fibre is stimulated from some nerve-centre, it may give rise to the contraction of a muscle or a blood-vessel, in- creased secretion from a gland, or a diminution or arrest of some other kind of nervous action. In all these cases, “ the nervous influence travels outwards from a ganglion or nerve-centre towards the periphery, thus presenting an analogy to ordinary motor nerves.” Perhaps the best classification of nerve-jibres, from a physiological point of view, is the following ; > 4 a ( Motor (efferent), excite contraction of muscles. & & (6) Vascular (vaso-motor), excite contraction of blood-vessels. a6 (ce) Secretory, excite secretion. 2 > (d) Inhibitory, affect other nerve-centres so as to moderate or Be destroy their action. 8 (e) Connecting, which connect motor-cells in nerve-centres. 2 (1) General, “convey to nerve-centres in brain influences which cause sensations of a vague character (not permanent).” = (a) Sensory (2) Special, “convey to nerve-centres in brain $ 7 influences which cause visual, auditory, 8 $ gustatory, olfactory, or tactile sensa- = es tions.” s é (b) Afferent, “convey to nerve-centres influences which cause no = 8 sensation, and which may or may not be followed by further a ' nervous activity.” o (c) Connecting, ‘‘ which connect sensory cells in nervous centres.” The centrifugal nerve-fibres convey influences outwards from a nerve-centre ; while the centripetal nerve-fibres con- vey influences inwards towards a nerve-centre. It should be PHYSIOLOGY OF THE INVERTEBRATA. 295 borne in mind that the different nerve-fibres merely act as conductors, the effects depend upon the arrangements or apparatuses at the end of the fibres. It is the totality of the properties which nerve-cells and nerve-fibres are capable of giving rise to, which constitutes innervation. When nerve-centres or ganglia are excited the activity or energy produced is not the same in each case. Some produce the sensations of light, sound, pain, &c. ; others are the cause of secretion or locomotion; others are associated with psychical states; while a fourth exerts an influence over other nerve-centres. These nerve-centres may be classified as follows: (a) “‘ Receptive centres, to which influences arrive which may excite sensations or some kind of activity not associated with consciousness. (b) Discharging centres, whence emanate influences which, according to structures at the other ends of the nerves connected with them, may cause movements (muscles), secretion (glands), or contractions of vessels. (¢) Psychical centres, connected with sensation, in the sense of conscious perception, feeling, volition, intel- lectual acts, and will. (ad) Inhibitory centres, which inhibit, restrain, or even arrest the action of other centres.” In the majority of cases there are terminal organs at the commencement of sensory, and the terminations of motor nerves. Such organs are seen in the rods and cones of the retina and the terminal plates of muscle; but in some few cases nerve-fibres may terminate in loops towards the periphery of the body or in the interior of organs. We now proceed to describe the nervous systems in the Invertebrata. Tue Protozoa. In none of these animals has any trace of a nervous system been discovered; nevertheless, as nervous elements are nothing more than the products of the differentiation of protoplasm, it is logical to assume that certain parts of the protoplasmic 296 PHYSIOLOGY OF THE INVERTEBRATA. cells of the Protozoa, are the means of conveying nervous energy. If no nervous system is anatomically differentiated, there is every reason to believe that the protoplasm contains a “diffused nervous system” (Gruber). In these organisms innervation is rudimentary; and the nervous function devolves upon the protoplasm, which is the cause of the phenomena of contraction, secretion, &c., and according to M. Binet, of certain psychical acts. Certainly no definite nerve-tracts have been discovered in these animals; “but any one who has attentively watched the ways of a Colpoda, or still more of a Vorticella, will probably hesitate to deny that they possess some apparatus by which external agencies give rise to localised and co- ordinated movements. And when we reflect that the essential elements of the highest nervous system—the fibrils into which the axis fibres break up—are filaments of the extremest tenuity devoid of any definite structural or other characters, and that the nervous system of animals only becomes con- spicuous by the gathering together of these filaments into nerve-fibres and nerves, it will be obvious that there are as strong morphological, as there are physiological, grounds for suspecting that a nervous system may exist very low down in the animal scale, and possibly even in plants.” (Huxley.) THE PORIFERA. No differentiated nervous system has been discovered, but there is little doubt that nervous function is traceable in the protoplasm of these animals. The nervous system of the horny sponges has been recently examined by Dr. R. von Ledenfeld.* He gives an account of Euspongia anfractuosa, which differs in some particulars from Euspongia officinalis (the bath sponge). The fine membrane which extends from the tips of the horny * Sitzungsberichte der Kgl. Preussischen Akademie der Wissenschaften in Berlin, 1885, p. 1015. PHYSIOLOGY OF THE INVERTEBRATA. 297 fibres consists of parallel spindle-shaped cells, which are set perpendicularly to the outer surface of the sponge; they end in extraordinarily fine tips. The protoplasm contains small, but highly and doubly refractive, granules embedded in a single refractive substance. The granules are so arranged as to give the appearance of a kind of transverse striation. These are muscle-fibres. If the investigations of Ledenfeld are correct, we have in these animals the beginning of a true nervous system. THe CcLENTERATA. Kleinenberg has shown that in Hydra the cells of the ectoderm terminate internally in delicate processes from which fine longitudinal filaments are produced. These fila- ments form a layer between the ectoderm and endoderm. According to Kleinenberg, these filaments are the represen- tatives of both muscle and nerve; in fact, he regards them as neuro-muscular elements in an undifferentiated state. But Prof. Huxley believes that Kleinenberg’s fibres “are solely internuncial in function, and therefore the primary form of nerve. The prolongations of the ectodermal cells have indeed a strangely close resemblance to those of the cells of the olfactory and other sense-organs in the Vertebrata ; and it seems probable that they are the channels by which impulses affecting any of the cells of the ectoderm are con- veyed to other cells and excite their contraction.” Dr. G. J. Romanes, F.R.S.,* has shown that in the Meduse . we find phenomena similar to nervous transmission sent along definite tracks, or sometimes diffused from one part of the body to the other, without any histological trace of differen- tiated nerve-fibre. As in the Protozoa, we have in these animals the early stages of the evolution of a nervous system. * Philosophical Transactions of Royal Society, 1875, p. 269 ; ibid. 1877, Pp. 659; ibid. 1879, p. 161; and his book, Jellyfish, Starfish and Sea Urchins, 298 PHYSIOLOGY OF THE INVERTEBRATA. Prof. E. Haeckel * has described the nervous system of the Geryonide. It forms a circle all round the margin of the nectocalyx (umbrella), “following the course of the radial (nutrient) tubes throughout their entire length, and pro- ceeding also to the tentacles and.marginal bodies.” There is a ganglion at the base of each tentacle from which the above-mentioned nerves take their origin. These ganglia contain fusiform and nucleated cells of high refractive power. .“The nerves that emanate from the ganglia are composed of a delicate and transparent tissue, in which no cellular elements can be distinguished, but which is longitu- dinally striated in a manner very suggestive of fibrillation. Treatment with acetic acid, however, brings out distinct nuclei in the case of the nerves that are situated in the marginal vesicles, while in those that accompany the radial canals, ganglion-cells are sometimes met with.” Haeckel’s researches have been confirmed by Allman, Claus, Harting, Romanes, and others, According to Drs. O. and R. Hertwig,} the nervous system of the naked-eyed Medusw consists of two parts, a central and a peripheral. ‘The central part is localised in the margin of the swimming-bell, and there forms a nerve-ring, which is divided by the insertion of the veil into an upper and a lower nerve-ring..... In all species the upper nerve-ring lies entirely in the ectoderm. Its principal mass is composed of nerve-fibres of wonderful tenuity, among which are to be found sparsely scattered ganglion-cells. .... The fibres which emanate from them are very deli- cate, and, becoming mixed with others, do not admit of being further traced.” “Beneath the upper nerve-ring lies the lower nerve-ring. It is inserted between the muscle-tissue- of the veil and. umbrella, in the midst of a broad strand wherein muscle- fibres are entirely absent.” The lower nerve-ring belongs * Beitr dge zur Naturgeschichte der Hydromedusen, 1865. + Das Nervensystem und die Sinnesorgane der Medusen. PHYSIOLOGY OF THE INVERTEBRATA. 299 to the ectoderm, and consists also of nerve-fibres and ganglion-cells, In these respects there is no difference between the lower and upper nerve-rings; but it may be remarked that a difference is distinguishable between the two. In the former there are many nerve-fibres of con- siderable thickness, whereas in the latter the nerve-fibres are exceedingly slender, and there are few ganglion-cells. “The two nerve-rings are separated from one another by a very thin membrane, which, in some species at all events, is bored through by strands of nerve-fibres which serve to connect the two nerve-rings with one another.” “The peripheral nervous system is also situated in the ectoderm, and springs from the central nervous system, not by any observable nerve-trunks, but directly as a nervous plexus composed both of cells and fibres. Such a nervous plexus admits of being detected in the sub-umbrella of all Meduse, and in some species may be traced also into the tentacles.” This nerve-plexus is situated between the muscle-fibres and the epithelium. “There are also described peculiar tissue elements; such as, in the umbrella, nerve-fibres which pro- bably stand in connection with epithelium-cells; nerve-cells which pass into muscle-fibres, similar to those which Kleinen- berg has called neuro-muscular cells; and in the tentacles neuro-muscular cells joined with cells of special sensation. No nervous elements could be detected in the convex surface of the umbrella, and it is doubtful whether they occur in the veil.” (Romanes.) The nervous system of the covered-eyed differs from that of the naked-eyed Meduse. In the former the central nervous system consists of separate centres unconnected with commissural cords. There are eight, twelve, or sixteen (but generally eight) of these nerve-centres situated in the margin of the umbrella. They consist of cells of special sensation and a thick layer of delicate nerve-fibres. These nerve-fibres are merely prolongations of epithelial cells, as true ganglion-cells are entirely absent. 300 PHYSIOLOGY OF THE INVERTEBRATA. Professor E, A. Schifer, F.R.S.,* has shown the presence of “an intricate plexus of cells and fibres overspreading the sub-umbrella tissue” of Aurelia awrita. Dr. Claus has also described the presence of numerous ganglion-cells in the sub-umbrella of Chrysaora. It appears that as far as the nervous system is concerned, the naked-eyed are more highly developed than the covered- eyed Meduse. It is now our intention to briefly allude to the important researches of Dr. G. J. Romanes,f which have been made from the stand-point of experimental physiology. He has studied—(a) the effects of excising the entire margins of the nectocalyces of both the naked-eyed and the covered-eyed Meduse ; (b) the effects of excising certain portions of the margins of the nectocalyces ; (c) the effects upon the manu- brium of excising the margin of a nectocalyx (swimming organ); and he has arrived at the following conclusions :— “With a single exception to hundreds of observations upon six widely divergent genera of naked-eyed Meduse, I find it to be uniformly true that the removal of the extreme periphery of the animal causes instantaneous, complete, and permanent paralysis of the locomotor system. In the genus Sarsia, my observations point very decidedly to the conclu- sion that the principal locomotor centres are the marginal bodies, but that, nevertheless every microscopical portion of the intertentacular spaces of the margin is likewise endowed with the property of originating locomotor impulses. “In the covered-eyed division of the Medusce, I find that the principal seat of spontanéity is the margin, but that the latter is not, as in the naked-eyed Medusw, the exclusive seat of spontaneity. Although in the vast majority of cases I: have found that excision of the margin impairs or destroys the spontaneity of the animal for a time, I have also found that the paralysis so produced is very seldom of a permanent * Philosophical Transactions, 1878. + Ibid. 1875, p. 279. PHYSIOLOGY OF THE INVERTEBRATA. 301 nature. After a variable period occasional contractions are usually given, or, in some cases, the contractions may be resumed with but little apparent detriment. Considerable differences, however, in these respects are manifested in different species, and also by different individuals of the same species. Hence, in comparing the covered-eyed group as a whole with the naked-eyed group as a whole, I should say that the former resembles the latter in that its repre- sentatives usually have their main supply of locomotor centres situated in their margins, but that it differs from the latter in that its representatives usually have a greater or less supply of their locomotor centres scattered through the general contractile tissue of their organs. But although the locomotor centres of a covered-eyed Medusa are thus, generally speaking, more diffused than are those of a naked-eyed Medusa, af we consider the organism as a whole, the locomotor centres in the margin of a covered-eyed Medusa are less diffused than are those in the margin of a naked-eyed Medusa. In no case does the excision of the margin of a swimming organ produce any effect upon the movements of the manubrium.” Romanes has proved the effects of various stimuli upon the Meduse. After the removal of the locomotor centres (ganglia) all these animals invariably respond to stimulation, but the degrees of irritability in responding to stimuli differ con- siderably in different species. The covered-eyed, and a few of the naked-eyed Medusw respond with one or more contractions to the action of light. In the case of Sarsia tubulosa, a flash of light causes it to respond ; in fact, light acts as a stimulus. It has been ob- served that the marginal bodies of Sarsia are organs of special sense, adapted to respond to luminous stimulation; in other words, they perform the function of sight—in fact, the marginal bodies are rudimentary eyes. Romanes has shown that when these marginal bodies are excised, the mutilated animals did not seek the light, “ but 302 PHYSIOLOGY OF THE INVERTEBRATA. swam hither and thither without paying it any regard.” Sarsia tubulosa and Tiaropsis polydiademata are probably the only two naked-eyed Medusw sensitive to light. But the action of light on Sarsia and Tiaropsis differs considerably. In the case of the latter, sunlight causes it to go into a kind of tonic spasm—the whole of the nectocalyx being drawn to- gether. The period of latency* in Sarsia is instantaneous with all stimulations (mechanical, electrical, luminous, &c.) ; but in Ziaropsis the period of latency is not instantaneous with luminous stimulation, for a little more than a second elapses after the first occurrence of the stimulus. With all other stimulations, in Tiaropsis, the period of latency is in- stantaneous. Romanes has shown “that the enormously long period of latent excitation in response to Juminous stimuli was not, properly speaking, a period of latent excitation at all; but that it represented the time during which a certain summation of stimulating influence was taking place in the ganglia, which required somewhat more than a second to accumulate, and which then caused the ganglia to originate an abnormally powerful discharge.” The ganglionic matter of Tiaropsis represents, according to Romanes, the most rudi- mentary type of visual organ. All the excitable parts of the Medusw are highly sensitive to electrical stimulation, but the most sensitive parts are those which correspond with the distribution of the main nerve- trunks. The external or convex surface of the nectocalyx, and the whole of the “gelatinous substance to which the neuro-muscular sheet is attached,” are insensitive to stimulation. The extreme sensitiveness of the tissues to electrical stimula- tion suggested to Romanes the idea of ascertaining whether there is any localization of definite excitable tracts in these animals. In the case of Sursia, “the apex of the swimming- bell is much the least excitable portion of the animal; and * ‘The time which elapses between the application of a stimulus and the response to that stimulus. ° PHYSIOLOGY OF THE INVERTEBRATA. 303 from this point downwards to the margin there is a beautiful and uninterrupted progression of excitability, the latter being greatest of all when the electrodes are placed upon the string of cells described by Agassiz as nerve-cells.” In regard to “the marginal tract of excitable tissue, the degree of ex- citability differs slightly in different parts.” In other parts of the nectocalyx there is ‘a marked difference between the excitability of this organ when the electrodes are placed upon any one of the four radiating canals (and so upon the ascend- ing nerve-chains described by Agassiz), and when the electrodes are placed upon the tissue between any of the canals. The ratio is generally about 9 centims. to 64 centims.” Concerning the action of electrical stimulation the following conclusions have been arrived at by Romanes :— (1) “The excitable tissues of the Medusq, in their behaviour towards electrical stimulation, conform in all respects to the rules which are followed by the excitable tissues of other animals. Thus closure of the constant current acts as a much stronger stimulus than does opening of the same, while the reverse is true of the induction-shock. (2) “ Different species of the Medusw manifest different degrees of sensitiveness to electrical stimulation, though in all cases the degree of sensitiveness is wonderfully high. (3) ‘When the constant current is passing in a portion of the strip of a severed margin, the nectocalyx sometimes manifests uneasy motions during the time the current is passing. It is possible, however, that these motions may be merely due to accidental variations in the intensity of the current. (4) “When the intrapolar portion of the severed margin of Staurophora laciniata happens to be spontaneously contract- ing prior to the passage of the constant current, the moment this current is thrown in, these spontaneous contractions often cease, and are then seldom resumed until the current again is broken, when they are almost sure to recommence. 304 PHYSIOLOGY OF THE INVERTEBRATA. This effect may be produced a great number of times in succession. (5) ‘‘ Exhaustion of the excitable tissue of the nectocalyx may be easily shown by the ordinary methods. Exhausted tissue is much less sensitive to stimulation than is fresh tissue. Moreover, so far as the eye can judge, the contrac- tion is slower, and the period of latent stimulation prolonged. (6) “The tetanus produced by faradaic electricity is not of the nature of an apparently single prolonged contraction (except, of course, such among the naked-eyed Medusw as respond to all kinds of stimuli in this way), but that of a number of contractions rapidly succeeding one another—as in the heart under similar excitation.” Romanes, in his important papers (Joc. cit.), has shown the amount of section which the neuro-muscular tissues of the Meduse will endure without suffering loss of their physiolo- gical continuity ; and this is in the highest degree astonishing. He has also investigated the rate of transmission of stimuli; as well as the regeneration of excitable tissues in these animals (1.¢., after injury). Jt may be remarked that if the contractile sheet, which lines the nectocalyx is completely severed throughout its whole diameter, it again reunites, or heals up, in from four to eight hours after the operation. The nervous system of the naked-eyed Medusw is more highly developed than it is in the covered-eyed Medusw ; and Romanes has demonstrated the occurrence of reflex action in the Medusw. This reflex action occurs “ only between the marginal ganglia (in Sarsia) and the point of the bell from which the manubrium is suspended—it being only the pull which is exerted upon this point when the manubrium con- tracts and acts as a stimulus to the marginal ganglia.” Romanes has brought much physiological evidence to bear on the distribution of nerves in Sarsia and it may be stated that his researches prove “‘ that nervous connections unite the tentacles with one another and also with the manubrium ; or perhaps more precisely, that each marginal body acts as a PHYSIOLOGY OF THE INVERTEBRATA. 305 co-ordinating centre between nerves proceeding from it in four directions—viz., to the attached tentacle, to the margin on either side, and to the manubrium.” “The nervous connections between the tentacles and the manubrium are of a more general character than those between the tentacles themselves; that is to say, severing the main radial nerve-trunks produces no appreciable effect upon the sympathy between the tentacles and the manubrium. “The nervous connections between the whole excitable surface of the nectocalyx and the manubrium are likewise of this general character, so that, whether or not the radial nerve-trunks are divided, the manubrium will respond to irritation applied anywhere over the internal surface of the nectocalyx. The manubrium, however, shows itself more sensitive to stimuli applied at some parts of this surface than itis to stimuli applied at other parts, although in different specimens there is no constancy as to the position occupied by these excitable tracts.” Romanes has examined the distribution of nerves in Tiaropsis (especially 7. indicans*), Stawrophora, Aurelia, and other Meduse. In all these forms primitive nerves are well developed. By the word “nerves” is meant certain physio- logically differentiated tracts of tissue, which either stimu- lation or section prove to perform the function of conveying impressions to a distance. Romanes has also studied the subjects of co-ordination and natural and artificial rhythm in the Meduse ; but it is not our object to detail these important investigations, as a full account of them will be found in the Philosophical Trans- actions of the Royal Society, to which our readers are referred. Nevertheless, the following may be taken as a general summary of the results :— (1) That in the covered-eyed Medusw the lithocysts are * This species was first described by Romanes; see peat Linn. Soc. (Zool.), vol, 12, p. 524. U 306 PHYSIOLOGY OF THE /NVERTEBRATA. the exclusive seats of spontaneity, so far as the “ p movements ” are concerned. (2) The rate of the natural rhythm has a tendency « an inverse ratio to the size of the individual, though, be remarked, that size is not the only factor in deter such, rate. (3) The cutting off the manubrium (polyprite) or a } of the nectocalyx (swimming-bell), causes, first accel of the rhythm, and then a progressive decline to a < point below the original rate. The rate then x stationary at this point, but may again be made temp to rise and permanently to fall by removing another of the nectoculyx. “In these experiments the rl besides becoming permanently slowed, is also often re: permanently irregular. Again, paring down the cont tissues from around a single lithocyst* has the effect, the tissue is greatly reduced, of giving rise to enor long periods of inactivity. During such period, ho stimulation may initiate a bout of rhythmical contra to be followed by another prolonged pause. These fact to show that the apparently automatic action of the litl is really due to a constant stimulation supplied by parts of the organism.” (4) ‘Temperature exerts a profound influence on tl of rhythm. This influence may be best observed moderate limits of variation ; for water below 20° C. su: spontaneity and even irritability, while water above permanently slows the rhythm after having temp quickened it. But water between 50°and 60° C. perma quickens the rhythm during the time that the Medusa, have been removed from colder water, are exposed influence. In very cold water the loss of spontaneil gradual though rapid. process, as is also its return in ¥ water. After having been frozen solid, Aurelia will 1 * The marginal bodies in the covered-eyed Medusc occur in the little bags of crystals ; hence they have been termed lithocysts. PHYSIOLOGY OF THE INVERTEBRATA. 307 on being thawed out, but the original rate of rhythm was not observed fully to return.” (5) Oxygen accelerates the rhythm, while carbonic anhy- dride retards it, and in strong doses destroys both sponta- neity and irritability. Deficient aération of the water in which the Meduse are living, causes irregularity of their rhythm, as well as the occurrence of pauses; until at last spontaneity altogether ceases; but on now removing the animals to fresh sea-water, their recovery is surprisingly sudden. (6) As regards stimulation, Romanes has shown that a few drops of hot water allowed to run over the excitable tissues of these animals cause a responsive contraction. Single mechanical or chemical stimuli applied to paralyse the nectocalyces of covered-eyed Meduse frequently produces in response a small series of rhythmical contractions. (7) Light acts as a powerful stimulus to some species of Meduse; and it may be stated that the stimulus has been proved to be light per se, and not the sudden transition from darkness to light. (8) The period of latent stimulation in the case of Aurelia aurita is greatly modified by certain conditions. Of these, temperature exerts the greatest influence, but the most im- portant influence, from a physiological point of view, is that of the summation of stimuli. At the bottom of a “ stair- case” the latent period is 3 of a second, while at the top of a “staircase” it is only 3 of a second. Summation of stimuli also greatly increases the amplitude of the contrac- tions; so that it both develops in the tissue a state of ex- pectancy and arouses it into a state of increased activity. (9) The excitable tissues of Awrelia may be thrown into tetanus by means of strong faradaic stimulation ; and Romanes has proved that the the tetanus is due to the summation of contractions. (10) Reflex action occurs in various species of Meduse. In Sarsia definite nervous connections of constant occurrence 308 PHYSIOLOGY OF THE INVERTEBRATA. have been shown to exist between the tentacula, but not between the tentacula and polypite. Section of the neuro- muscular sheet proves that in the case of this genus physio- logical harmony may, as a rule, be easily destroyed, although it occasionally happens that such is not the case. (11) Romanes has shown that the essentially nervous function of maintaining excitationul continuity is able to persist in these primitive nervous tissues after they have been subjected to the severest forms of section. This fact “cannot be explained by Kleinenberg’s theory of double- function cells; for sometimes contractile waves will become blocked by section before the tentacular waves, and sometimes vice versd. We seem, therefore, driven upon the theory of a nerve-plexus, whose constituent elements are capable of vicarious action in almost any degree.” (12) Contractile waves in Awrelia travel at the rate of 18 inches per second, if the temperature of the water is normal; but the rate is greatly modified by temperature, straining, anesthetics, and various foreign substances. Stim- ulus-waves only travel at the rate of 9 inches per second, if the stimulus which starts such a wave is not strong enough at the same time to start a contractile wave; but if the stimulus is strong enough to start both waves, they both travel at about the same rate. (13) There appears to be no further co-ordination among the lithocysts of the covered-eyed Medusw than such as arises from contractile waves coursing rapidly from one of the number, and, as it passes the others, causing them succes- sively to discharge; but, in the case of the naked-eyed Meduse, true co-ordination has been proved to occur between the marginal ganglia, and the tracts through which it is effected have been proved to be the marginal nerves. Slightly cutting the margin of a naked-eyed Medusa exerts a very deleterious influence upon the vigour of the animal; and violent nervous shock, while it always suspends both spontaneity and irritability, will sometimes also destroy PHYSIOLOGY OF THE INVERTEBRATA. 309 co-ordination for a considerable time after spontaneity returns. (14) Romanes has ascertained the effects of the following poisons—chloroform, amylic nitrite, caffein, strychnia, mor- phia, curare, veratrium, digitalin, atropin, nicotin, alcohol, and potassium cyanide—upon the Medusw.* He has shown that there is a wonderful degree of resemblance between the actions of the above-mentioned poisons on the Meduse and on the higher animals. This is a most important discovery, especially ‘when we remember that in these nerve-poisons we possess so many tests wherewith to ascertain whether nerve-tissue, where it first appears upon the scene of life, presents the same fundamental properties as it does in the higher animals.” In fact the primitive nervous tissues of the Meduse adhere to the rules of toxicology that are followed by nervous tissues in general. ‘In one respect, indeed, there is a conspicuous and uniform deviation from these rules; for it has been observed that in the case of every poison mentioned, more or less complete recovery takes place when * Fresh water acts as a deadly poison to the Medusw,; and brine acts as an anesthetic. The fresh-water Medusa (Limnocodium Sorbii) is even more intolerant of sea water than are the marine species of fresh water; and brine acts as a poison to the fresh-water form. ‘“ We have thus a curious set of cross relations. It would appear that a much less profound physio- logical change would be required to transmute a sea-water jellyfish to a jellyfish adapted to inhabit brine, than would be required to enable it to inhabit fresh water. Yet the latter is the direction in which the modifica- tion has taken place, and taken place so completely that the sea water is ‘ now more poisonous to the modified species than is the fresh water to the unmodified. There can be no doubt that the modification was gradual— probably brought about by the ancestors of the fresh water Jledusa pene- trating higher and higher through the brackish waters of estuaries into the fresh water of rivers—and it would be hard to point to a more remarkable case of profound physiological modification in adaptation to changed con- ditions of life. If an animal so exceedingly intolerant of fresh water as is a marine jellyfish, may yet have all its tissue changed so as to adapt them to thrive in fresh water, and even die after an exposure of one minute to their ancestral element, assuredly we can see no reason why any animal in earth or sea or anywhere else may not in time become fitted to change its element.” (Romanes.) 310 PHYSIOLOGY OF THE INVERTEBRATA. the influence of the poison has been removed, even though this has acted to the extent of totally suspending irritability, In other words, there is no poison in the above list, which has the property, when applied to the Meduse, of destroying life till long after it has destroyed all signs of irritability.” As an explanation of this peculiarity it should be borne in mind “that in the Medusw there are no nervous centres of such vital importance to the organism that any temporary sus- pension of their functions is followed by immediate death. Therefore, in these animals, the various central nerve-poisons are at liberty, so to speak, to exert their full influence on all the excitable tissues without having the course of their action interrupted by premature death of the organism, which in higher animals necessarily follows the early attack of the poison on a vital nerve-centre.” Then, again, the mode of administering the poisons to the Meduse was different from that which is generally used when administering them to the higher animals. (15) Romanes’ researches prove that the phenomena of muscular tonus, as they occur in Sarsia, tend more in favour of the exhaustion, than of the resistance, theory of ganglionic action. ‘The exhaustion theory supposes that the rhythm is largely due to the periodic process of exhaustion and recovery on the part of the responding tissues.” Besides the researches on the nervous systems of the Meduse, Dr. Kimer* has investigated the nervous system of the Ctenophora. In these animals the mesoderm contains numberless fibrils, varying in diameter from zy4g5 t0 gshor of an inch. ‘These fibrils present numerous minute varico- sities, and, at intervals, larger swellings which contain nuclei, each with a large and refracting nucleolus, These fibrils take a straight course, branch dichotomously, and end in still finer filaments, which also divide, but become no smaller, They terminate partly in ganglionic cells, partly in muscular fibres, partly in the cells of the ectoderm and endoderm. Many of * Zoologische Studien auf Capri, 1873. PHYSIOLOGY OF THE INVERTEBRATA. 311 the nerve fibrils take a longitudinal course beneath the centre of each series of paddles, and these are accompanied by ganglionic cells, which become particularly abundant towards the aboral end of each series. The eight bands meet in a central tract at the aboral pole of the body; but Eimer doubts the nervous nature of the cellular mass, which lies beneath the lithocyst, and supports the eye spots.” Professor Huxley says that “the nervous system of the Ctenophoran is, therefore, just such as would arise in Hydra, if the development of a thick mesoderm gave rise to the separation and elongation of Kleinenberg’s fibres; and if special bands of such fibres, developed in relation with the chief organs of locomotion, united in a central tract directly connected with the higher sensory organs. We have here, in short, virtual, though incompletely differentiated brain and nerves.” In the Actinozoa, there is a plexus of fusiform ganglionic cells connected by nerve-fibres at the base of the body; and at the base of the tentacula of the Actinie, near the pigment- cells (eyes ?) isolated nerve-cells have been discovered. THE ECHINODERMATA. Among these animals the nervous system consists of a number of ganglia, connected by commissural cords, so as to form a ring, from which nerve-fibres pass to various parts of the body. “The internal nervous system of Echinus consists of five radial trunks, which may be traced from the ocular plates along the ambulacral areas, external to the radial canals to the oral floor, where they bifurcate and unite with each other, so as to form a pentagonal nerve-ring. This ring lies between the cesophagus and the tips of the teeth, which project from the lantern. Small branches leave the ring and supply the esophagus, and lateral branches arise from the several trunks to escape with the pedicels through the apertures of the pore 312 PHYSIOLOGY OF THE INVERTEBRATA. plates. Each trunk lies in a sinus (Fig. 56, ¢) situated between the lining membrane of the shell (Fig. 56, @) and the ambulacral radial canal (Fig. 56, ¢); the lateral branches, Fic. 56.—DIAGRAM SHOWING PORTIONS OF AMBULACRAL AND NERVOUS SYSTEMS OF ECHINUS. (After ROMANES and EWART.) a = ampulle. = radial nerve. c¢=neuralradialsinus. d= lining membrane of shell, e¢ = radial ambulacral canal. f = lateral branch of radial canal. g = pedicel. 4 = spine. 7 = pedicellaria. 4 = layer of fibres external to shell. Z = subepidermic nerve-plexus. ? = plexus extending over base of spine. 2" = plexus extending over pedicellaria towards base of mandibles. 2 = epider- mis. 7 = lateral branch from nerve-trunk. o = continuation of lateral branch. p = portion of lateral branch. 7 = ambulacral plate. which accompany the first series of pedicels through the oral floor are large and deeply pigmented; the other branches within the auricles are small; those external to the auricles PHYSIOLOGY OF THE INVERTEBRATA. 313. gradually increase in size until the equator is reached, and from the equator to the ocular plates they again diminish.” The nerve-trunk is enveloped by a fibrous sheath containing FIG. 57.—STRUCTURE OF A NERVE-TRUNK OF ECHINUS. (After ROMANES and Ewart.) pigmented cells. The nerve-trunk consists of delicate fibres, and of fusiform cells (Fig. 57). The cells are nucleated. “The lateral branches of the nerve-trunk escape along with, and are partly distributed to, the pedicels; the remainder breaks up into delicate filaments, which radiate from the base of the pedicel under the surface epithelium (Fig. 56, 2). When one of the large branches is traced through the oral floor after sending a branch to the foot, it breaks up into delicate fibres, some of which run towards the bases of the adjacent spines and pedicellarie, while others run inwards a short. distance towards the oral aperture.” There is also an external plexus situated under the surface epithelium, and extending from the shell to the spines and pedicellariz. ‘The fibres (Fig. 58) of this plexus closely resemble those of the lateral branches of the trunk; but generally they are smaller in size, and have a distinct con- nexion with nerve-cells. The cells consist of an oval nucleus and of a layer of protoplasm, which is generally seen to project in two, or sometimes in three, directions—the several processes often uniting with similar processes from adjacent cells, so as to form a fibro-cellular chain or network:” Romanes and Ewart * have succeeded in tracing the plexus over the surface of the shell between the spines and pedi- * Philosophical Transactions, 1881, pt. iii. p. 836. op 314 PHYSIOLOGY OF THE INVERTEBRATA. cellarize; and from the surface of the shell to the capsular muscles at the bases of the spines (Fig. 59). Fic. 58,—EXTERNAL NERVE-PLEXUS OF EcHINUS. (After ROMANES and Ewart.) “Tn the case of the pedicellariz, the plexus on reaching the stem runs along between the calcareous axis and the FIG. 59.—NERVE-CELLS LYING AMONG MUSCULAR FIBRES AT THE BASE OF A SPINE IN ECHINUS, (After ROMANES and Ewart.) surface epithelium, to reach and extend over and between the muscular and connective tissue-fibres between the calcareous PHYSIOLOGY OF THE INVERTEBRATA. 315 axis and the bases of the mandibles (Fig. 56, J”, and Fig. 60). The plexus, now in the form of exceedingly delicate fibres connecting small bipolar cells, reaches the special muscles of the mandibles... . . Although this plexus is especially Fic. 60,—NERVE-PLEXUS LYING OVER MUSCULAR FIBRES NEAR BASE OF MANDIBLES OF PEDICELLARIA. (After ROMANES und Ewart.) related to the muscular fibres—lying over and dipping in between them—it is also related to the surface epithelium, and delicate fibres often extend from it to end under or between the epithelial cells.” Romanes and Ewart have shown that the Echinodermata respond to all kinds of stimulation. The period of latency varies considerably in different species, and in different parts of the same animal. “The external nerve-plexus supplies innervation to three sets of organs—the pedicels, the spines, and the pedicellaric ; for when any part of the external surface of Echinus is touched, all the pedicels, spines, and pedicellariee within reach of the point that is touched immediately approximate and close in upon the point, so holding fast to whatever body may be used as the instrument of stimulation. In executing this combined movement the pedicellaris are the most active, the spines somewhat slower, and the pedicels very much slower. If the shape of the stimulating body admits of it, the forceps of the pedicellariee seize the body and hold it till the spines and pedicels come up to assist.” The function of the pedicellarieze is to aid locomotion by 316 PHYSIOLOGY OF THE INVERTEBRATA, grasping hold of sea-weeds, é&c., when an Hchinus is climbing perpendicular or inclined surfaces of rock. Starfishes (with the exception of Brittle-stars) and Eechini. are attracted by light, but when their eye-spots are removed, they no longer are so. Romanes and Ewart have demon- strated that severing the ray-nerve destroys all physiological coutinuity between the pedicels on either side of the division, Severing the nerve at the origin of each ray, or severing the Fic. 61.—NERvous SysTEM OF STARFISH. a =nerve-ring. 4 = ambulacral nerve. c¢ = eyes. nerve-ring (Fig. 61) between each ray, has the effect of totally destroying all co-ordination among the rays; “ there- fore the animal can no longer crawl away from injuries, and when inverted it forms no definite plan for righting itseli— each ray acting for itself without reference to the others, there is, as a result, a promiscuous distribution of spirals and doublings, which as often as not are acting in antagonism to one another. This division of the nerves, although so com- PHYSIOLOGY OF THE INVERTEBRATA. 317 pletely destroying physiological continuity in the rows of pedicels and muscular system of the rays, does not destroy, or perceptibly impair, physiological continuity in the external nerve-plexus; for however much the nerve-ring and nerve- trunks may be injured, stimulation of the dorsal surface of the animal throws all the pedicels and muscular system of the rays into active movement. This fact proves that the pedicels and muscles are all held in nervous connexion with one another by the external plexus, without reference to the integrity of the main trunks.” The function of the spines and pedicellariee in Echinus are dependent upon the external nerve-plexus ; for if the latter is injured they have not the power of localising and closing, round a seat of stimulation. But “ other nervous connexions, upon which another function of the spines depends, are not in the smallest degree impaired by such injury. This other function is that which brings about the general co-ordinated action of all the spines for the purposes of locomotion. That this function is not impaired by injury of the external plexus is proved by severely stimulating an area within a closed line of injury on the surface of the shell; all the spines over the whole surface of the animal then manifest their bristling movements, and by their co-ordinated action move the animal in a straight line of escape from the source of irri- tation.” It will be apparent from the above remarks that there is a local reflex function of the spines and pedicellariz, which is entirely dependent upon the external nervesplexus. There is also the universal reflex function of the spines, which con- sists in their general co-ordinated action for the purposes of locomotion, and which is entirely independent of the external nerve-plexus. The nerves which give rise to the universal reflex function are distributed over the internal surface of the shell—that is they form an internal nerve-plexus. The internal nerve-plexus of Zchinus has been recently 318 PHYSIOLOGY OF THE INVERTEBRATA. discovered by Dr. J .C. Ewart, of Edinburgh University. He has found that this “internal plexus spreads all over the inside of the shell, and is everywhere in communication with the external plexus by means of fibres, which pass between the sides of the hexagonal plates of which the shell of the animal is composed.” The nerve-centres in Hchinus are to be found in the nerve- ring, for as soon as the latter was removed, the animal lost, completely and permanently, all power of co-ordination among its spines—.e., the function of locomotion was entirely lost. Although locomotion was destroyed, the spines were not entirely paralysed or motionless, for they still retained the power of closing round a seat of irritation on the external surface of the shell. This is due to the fact that all the spines and pedicellarie are connected with the external plexus, and when it is irritated, all the spines and pedicellarize in the vicinity move over to the seat of irritation. ‘On the other hand, it is the internal plexus which serves to unite all the spines to the nerve-centre which surrounds the mouth, and which alone is competent to co-ordinate the action of all the spines for the purposes of locomotion.” Dr. Romanes* has shown experimentally that the am- bulacral feet of Echinus are co-ordinated by the nerve-centre, quite as much as are the spines. The nervous system of LEchinus consists of the following parts (Table, p. 319). Dr. L. Fredericqt has also investigated the nervous system of Echinus. He finds that the pentagonal nerve-ring and its five radial nerve-trunks are contained in as many sheaths, which are expansions of the lining membrane of the shell. The lateral branches of these nerves are also contained in a similar sheath ; the latter pass out of the ambulacral pores in company with the pedicels, which they serve to enervate, a delicate nerve running along the whole length of each pedicel to terminate at its distal end in a tactile organ. The * See Jellyfish, Starfish, and Sea- Orchins, pp. 307-317. + Archiv. de Zool. Experi. et Générale, tome 5, pp. 429-440. PHYSIOLOGY OF THE INVERTEBRATA. 319 Nervous System. Situation. Function. Unites feet, spines, and pedicellariz together, so that they all move over to a seat of irritation in that plexus. External a External to shell. plexus. _Brings feet, spines, and pedicellariz into rela- face of shell and Internal nerve- is in communica- plexus. tiou-with external tion with co-ordinating nerve-centre. plexus. Presides over co-ordinated | ; action of spines and feet. Nerve-centre. Mainly round mouth It gives rise to nerve- trunks. Over internal sur- | pentagonal nerve-ring sends off, in addition to the am- bulacral trunks, the nerve-cords to the intestine. The physiological experiments of Frederic (see p. 436 of his paper, Joc. cit.) are almost entirely in accordance with those of Romanes and Ewart. Dr. H. Prouho* has investigated the nature of the external nerve-plexus in Lchinus acutus; and Dr. O. Hamannf has found and traced nerves in the various pedicellarize of the Hchinidea, and he finds that from the main nerves branches are given off to sense organs and glandular sacs. All the pedicellarie: are tactile organs, as the nerve-terminations indicate; the tri- foliate ones seem to remove sand, Protozoa, &c. The large pedicellarize serve to keep off layers of living bodies—e.y., worms, and therefore act as weapons, as well as for organs of attachment when the animal is moving about. There is. no doubt that the latter function is the most important; in other words, the pedicellarize aid locomotion. In Echinus microtubercwatus the gemmiform gland-bearing . pedicellarize hold fast sea-weeds, &c., when the animal is at: * Comptes Rendus, tome 102, p. 444. + Sitewngsberichte Jenaisch. Gesell. fiir Med. und Naturwiss. 1886. 320 PHYSIOLOGY OF THE INVERTEBRATA. rest; these help to hide it, and the secretion from the glands is therefore of the greatest service. It will be noticed that the nervous system of the Hchino- dermata is much more highly developed than that of the Coelenterata. THE TRICHOSCOLICES. According to De Quatrefages the nervous system of the Turbellaria consists of two ganglia situated in the anterior end of the body, from which, in addition to other branches, a longitudinal nerve-cord extends backwards on each side of the body. As a general rule, the lateral trunks exhibit ganglionic masses, and from these ganglia nerves are given off. These ‘““may become approximated on the ventral side of the body, thereby showing a tendency to the formation of the double ganglionated chain characteristic of higher worms.” In the Rotifera, the nervous system consists of a large ganglion situated on one side of the body near the trochal disc. This ganglion, sometimes divided into two portions, gives off nervous filaments. The nervous system of the Cestoidea consists of two longitudinal lateral nerve-trunks, which run down the body externally to the main canals of the excretory system. In the so-called head of the animal, where they are swollen (ganglia), they are united by a transverse commissure. Dr. G. Joseph * has recently examined the nervous system of the Cestoidea. The results arrived at are—(a) That the two cerebral ganglia are in many cases (Tenia transversalis, T. rophalocera) connected, not by a single dorsal commissure, but by two, separated by a matrix and muscle-processes ; (0) that each cerebral ganglion is triple, consisting of a median and two smaller (dorsal and ventral) ganglia separated by muscle-processes, as is best seen in Tania crassicollis ; (c) that in the bladder-worm, before evagination of the hooks, the * Biologisches Centraiblatt, vol. 6, p. 733. PHYSIOLOGY OF THE INVERTEBRATA. 321 central system exhibits six equatorial ganglionic masses, which afterwards form a nerve-ring by the growth of bipolar processes. THE ANNELIDA. The nervous system of the Gephyrea surrounds the ceso- phagus, and from it a simple or ganglionated nerve-cord proceeds backwards in the ventral median line. This nerve- cord gives off branches. The nerve-ring surrounding the esophagus usually has a ganglionic mass. This mass is connected with rudimentary eyes. ; The nervous system of the Hirudinea, and of Hirudo in particular, is highly developed. It consists of large supra- cesophageal ganglia, which send off five pairs of nerves to the five pairs of eyes. These ganglia are connected with a sub- esophageal ganglion by a circum-cesophageal nerve-ring. They also communicate with the buccal ganglia situated over and in front of the mouth. From the sub-cesophageal ganglion two longitudinal, ventral, and ganglionated cords proceed along the median line of the ventral aspect of the body. The ganglia of the two ventral longitudinal cords are united together in pairs by transverse commissures. Hach pair of ganglia sends off, to the right and left, two nerves. There are twenty-three pairs of ganglia on the ventral cords, in addition to the sub-cesophageal ganglion, which is com- posed of three or four pairs which have coalesced, and the caudal ganglion, which lies in the region of the posterior sucker, and is composed of seven coalesced ganglia. There is also a system of visceral nerves, consisting of a nerve, which proceeds from the supra-cesophageal ganglia, and runs above the ventral ganglionated nerve-chain, giving off along its course branches to the ceca of the stomach. The nervous system of the Oligocheta, as represented by Lumbricus, consists of two cerebral ganglia situated on the dorsal side of the pharynx in the third segment. These xX 322 PHYSIOLOGY OF THE INVERTEBRATA, ganglia are connected by two nerves, which embrace the pharynx, with the sub-cesophageal ganglia. The latter ganglia are the first of the ventral ganglionated nerve-cord. This ventral nerve has a double ganglionic enlargement in every segment posterior to the third. A large nerve, which divides and sub-divides, proceeds forward from each of the cerebral ganglia. Four or five nerves run backward from the upper part of each half of the circum-pharyngeal ring, and are distributed in the muscular walls of the pharynx. Nerves are also given off from the lower portion of this ring to the muscles of the fourth segment. Two pairs of nerves from each bilateral ganglionic enlargement of the ventral cord, proceed to the viscera and muscles of each segment. Two nerves, one from each side, pass off from the ventral nerve at a point nearly half-way between the double ganglionic masses, These supply the posterior sides of the mesenteric septa. When examined under high power the nerve-rods of A B Fic. 62,—NERVOUS SYSTEMS OF POLYCH/ETA. A = Polynée squamata, B = Savella flabellata. C = Nereis regia. a = cerebral ganglia. 4 = cesophageal commissures, ¢ = longitudinal commissures of ventral ganglia, Lumbricus are seen to contain a large number of nerve- cells along with the nerve-fibres, This is a characteristic feature of Lwmbricus and Peripatus. In Hirudo the nerve- PHYSIOLOGY OF THE INVERTEBRATA. 323 cells are confined to the ganglia; in this respect the nerves of the leech are like those of Astacus and the spinal cord of the Vertebrata. “The nervous system of the Polychaeta usually consists of a chain of ganglia—one pair for each somite—connected together by longitudinal and transverse commissures, which diverge between the cerebral ganglia and the succeeding pair, to allow of the passage of the cesophagus. The most important differences presented by the nervous systems of the Polychceta result from the varying length of the transverse commissures, In Vermilia, Serpula, Sabella, these commis- sures are very long, so that two distinct and distant series of ganglia appear to run through the body, while, in Nepthys, the two series of ganglia are fused into a single cord enlarged at intervals, .... In most Polycheta a very extensive series of visceral nerves supplies the alimentary canal.” THE NEMATOSCOLICES. In the Nematoidea the nervous system consists of a nerve- ring surrounding the cesophagus, From this ring proceed six nerves in an anterior, and two in a posterior direction, Two of the anterior nerves proceed in the lateral lines—that is, one in each—and four in the interspaces between the lateral and median lines. The posterior nerves proceed to the tip of the tail—one in the dorsal, and the other in the ventral median line of the body. Near to the nerve-ring, in front and behind it, arranged in dorsal, ventral, and lateral groups, lie certain ganglia. These are respectively known as dorsal or supra-cesophageal, ventral or sub-cesophageal, and lateral ganglia. In addition to these, there are groups of ganglia in the median and lateral lines, in the posterior part of the body ; these are known as caudal ganglia. In the Acanthocephala, represented by Echinorhyncus, the nervous system consists of a simple ganglion, which is situated 324 PHYSIOLOGY OF THE INVERTEBRATA. at the base of the proboscis. Nerves are given off from this ganglion to the proboscis, and through the retinacla to the muscular wall of the body. THE CHATOGNATHA. This class contains only one genus—Sagitta. The nervous system consists of a cerebral ganglion (brain) on which the eyes are placed, and a ventral ganglion situated near the middle of the body. These two ganglia are united by commissures. Near the mouth there are a pair of sub- cesophageal ganglia, which are united to each other, and to the cerebral ganglion by commissures which embrace the cesophagus. Ture PROTOTRACHEATA. The nervous system of Peripatus consists of two large supra-cesophageal ganglia, and two imperfectly-ganglionated, widely-separated nerve-trunks, which proceed to the posterior part of the body. From these two trunks many lateral nerves pass outwards and inwards; and, according to Grube,” the latter act as commissures between the two nerve-trunks. THE MyRiapopa, The nervous system of these animals forms a ventral chain, with a pair of ganglionic enlargements for each segment of the body. The anterior pair is united by commissures with the cerebral ganglia. The ventral chain gives off on each side a number of lateral nerves. The nervous system of the Myriapoda has been compared to that of the larve of the Insecta. The cerebral ganglia furnish nerves to certain sense organs, such as the eyes. The ganglia are constituted of cells, and the cords of nerve- fibres. * Archiv fir Anatomie, 1853. PHYSIOLOGY OF THE INVERTEBRATA. 325 THE INSECTA. Tn these animals there is always a well-developed cerebral ganglion or brain connected by nerve-trunks with a series of ventral ganglia. One of the reasons of the great develop- ment of the brain is assuredly the greater perfection and the more important office of the organs of the special senses in the Insecta. According to Gegenbaur, many Diptera, Hymenoptera, Lepidoptera, and the large-eyed Libellule, have powerful cerebral ganglia. The cerebral ganglion or brain of the ants, of bees, and of the spinning spiders (among the Arachmda), is remarkable for its size, and even for its conformation. Though Apis is a much smaller insect than Melolontha, it possesses a cerebral ganglion more highly developed, and relatively three times larger, if we take into consideration the difference of size. The cerebral. ganglion of the ant is proportionally larger still. Besides, the surface of these ganglia or brains is mammillated; and there are convolutions. According to M. Dujardin,* the brain of Apis has avery singular form. “We perceive a disc with stel- lated strisee surmounting like a hood the superior ganglion ; and from certain experiments of M. Faivre,f the cerebral ganglion has, like the cerebral hemispheres of the Vertebrates, the property of being insensible to punctures and lacerations.” The nervous system of the Insecta (speaking in general terms) consists of a cerebral ganglion connected to a gan- glionated nerve-trunk or trunks, which passes backwards along the ventral surface of the animal. Lateral nerves are given off from these ganglia to the organs of sense, limbs, viscera, é&e. Fig. 63 represents the nervous systems of various in- sects; and numbers 4 and 5 of the same figure represent the nervous system of Periplaneta. The nervous system of Periplaneta consists of supra- cesophageal ganglia (brain), which are connected by short, * Annales des Sciences Naturelles, 1850. + bid. 4 s., tomes 8 et 9. 326 PHYSIOLOGY OF THE INVERTEBRATA. thick commissures with the sub-cesophageal ganglion, which corresponds to several pairs of ganglia fused together. This e = gizzard. eye. the brain and visceral nerves of Feripluneta. @d c = crop. 5 = Periplaneta (Orthoptera). Fic. 63.—NERVOUS SYSTEMS OF THE INSECTA. 4 = visceral nerves. x a gS = & 2 9 x S & 2= Dytiscus ( Coleoptera) 3 = Musca (Diptera). 4 a = brain. Formica, I sub-cesophageal ganglion leads into a ventral ganglionated chain, which has three pairs of coalesced ganglia in the thorax, and six pairs of closely connected and smaller ganglia: Z PHYSIOLOGY OF THE INVERTEBRATA. 327 in the abdomen. The brain gives off nerves to the sense organs (eyes, antennee), the sub-cesophageal ganglion supplies the mouth, and the other ganglia the rest of the body. The visceral nervous system is well developed in the Insecta. (Fig. 63, 4). In the Insecta, “the ner- yous system varies very much in the extent to which its com- ponent ganglia are united to- gether. In most Orthoptera and Neuroptera, and in many Coleoptera, the thoracic and abdominal ganglia remain dis- tinct and are united by double commissures as in Blatta (Peri- planeta). In the Lepidoptera, Ra yOuS Sate On Cae: the thoracic ganglia have coa- 4% =opticnerve. 4 = antennary lesced into two masses united oe ee ae by double commissures; while e = nerve-cord of abdomen. in the abdomen there are five = ganglia, with single or partially separated commissural cords. The concentration goes furthest in some Diptera and in the Strepsiptera, in which the thoracic and abdominal ganglia are fused intoa common mass.” In many insects there are respira- tory nerves, whose branches are distributed to the muscles of the stigmata. The inner ends of these nerves form a plexus, which is situated “over the interval between two of the ganglia of the central nervous cord, and they are connected by longitudinal cords with one another, and with these ganglia.” Fic. 64. THe ARACHNIDA. In the Arthrogastra, there is a bilobed cerebral ganglion or brain connected by commissures with the sub-cesophageal ganglion: from this passes a nerve-trunk (consisting of two 328 PHYSIOLOGY OF THE INVERTEBRATA. closely-applied commissural cords) to the three ganglia situated in the region of the twelfth to the fourteenth somites of the body. The abdomen contains four ganglia, from the last of which leads two nerves terminating in the extremity of the body. The cerebral ganglion, as in the Insecta, gives off nerves to the eyes and other sense organs; while branches from the sub-cesophageal ganglion are distributed to the maxille and following somites. The visceral nervous system is well developed in these animals, In the Araneina, the nervous system is more concentrated than in the last-mentioned order. It consists of cerebral and sub-cesophageal ganglia with branch-nerves, which proceed to the organs of sense and other parts of the body. In fact it will be observed that in the Araneina the ganglia are con- centrated round the cesophagus. The same arrangement occurs in the Acarina. THE CRUSTACEA. As a representative of the lower Crustacea we describe the nervous system of Cyclestheria hislopi, belonging to the Phyllopoda. The nervous system of this animal has been recently worked out by Dr. G. O. Sars.* The cerebral ganglion or brain (see Fig. 11) is located within the pre-oral part of the head, posterior to the compound eye and im- mediately below the anterior part of the alimentary canal. It is rather large and of a somewhat irregular form, but very difficult to examine minutely on account of its being to a great extent concealed by the scape of the antenne. From the upper part of this ganglion, and somewhat in front, the strong optic nerves originate. These nerves are not united, but quite separate throughout their whole length, each giving rise, at the end, to a ganglion, lying at a short distance posterior to the eye and sending off to this organ numerous * Christiania Videnskabs-Selshabs Forhandlinger, 1887. PHYSIOLOGY OF THE INVERTEBRATA. 329 fine nerve-fibres. The anterior corner of the cerebral ganglion is exserted to a narrow point, appliedagainst the posterior angle of the ocellus. The antennular nerves, apparently originat- ing from the posterior part of the cerebral ganglion, may be easily traced as a delicate stem running along the axis of the antennule and dividing at their extremity into a number of nerve-fibres, which end with numerous ganglionic cells, filling up the dilated terminal part of these organs at the base of the sensory filaments. The nerves of the antennsz do not seem to arise from the cerebral ganglion itself, but from the strong commissures encompassing the cesophagus. The closer structure of these nerves, and the mode by which they innervate the several parts of the antenne, Dr. Sars has not succeeded in tracing out. The ventral nervous system, and especially its anterior part, is very difficult to examine. By carefully dissecting the trunk, and spreading it out in a ventral aspect after the intestine had been removed, Dr. Sars has succeeded in partly tracing out the double nerve-cord, which seems to agree in structure precisely with that in other known Phyllopoda, exhibiting the peculiar ladder-like appearance characteristic of those animals. In the Cirripedia, “the nervous system consists of a pair of cerebral ganglia situated in front of the cesophagus, and connected by long commissures with the anterior of five pairs of thoracic ganglia, whence nerves are given off to the limbs. In the middle line, the cerebral ganglion gives off two slender nerves, which run parallel with one another in front of the stomach and enlarge into two ganglia, when they are con- tinued to a double mass of pigment, representing the eyes. From the outer angles of the cerebral ganglion arise the large nerves, which proceed into the peduncle and supply the sac. These appear to correspond with the antennary and frontal nerves of other Crustacea; and Mr. Darwin describes an extensive system of splanchnic nerves.” * * Huxley’s Invertebrata, p. 295. 330 PHYSIOLOGY OF THE INVERTEBRATA, S Thoracic canghz Saute yt! oa 6 Abdominal Ganglia See gin Ta ess see Ae eee ~ 4 fe % 1 my w be Lae cate ae FIG. 65. NERvVousS SYSTEM OF ASTACUS. a=brain. d=optic nerve. c= “collar.” d = sub-cesophageal ganglion. e = visceral nerve. f= posterio-lateral nerve. g = “hepatic” nerve. The stomach is turned on one side to show its nerves. | In some Crustacea, such as the shore-crab (Carcinus manas), there is a large cere- bral ganglion which gives off nerves to the eyes and antenns; while the ventral chain of ganglia (of other forms) is fused into one mass (Fig. 64). From this mass radiate the nerve-cords, The nerve-cords connecting the cerebral ganglion with the nervous mass form the cesophageal ring or collar. There isin Carcinus a degree of concentration of the gan- glionic cells, greater, in some respects, than in the Verte- brates themselves. The nervous system of Astacus fluviatilis (Fig. 65, and see also Fig. 13) con- sists of thirteen ganglia joined together by means of commissures. These ganglia are divided as follows: one cerebral, one sub-cesopha- geal, five thoracic, and six abdominal ganglia. The cerebral ganglion or brain gives off nerves to the eyes; to the auditory organs; to the antenns; to the cara- pace in front of the cer- vical suture; to the green glands; to the visceral nervous system; and to the sub- PHYSIOLOGY OF THE INVERTEBRATA. 331 esophageal ganglion. The latter nerves form the cesophageal collar. The sub-cesophageal ganglion supplies the somites, from the fourth to the ninth, and their appendages, and gives off also delicate nerves to the cesophagus. The five anterior ab- dominal ganglia supply the muscles and the appendages with nerves; while the sixth and last abdominal ganglion sends nervous branches to the telson (tail). The sixth abdominal ganglion also sends out two nerves, which unite into one common trunk, and from which nerve-fibres are given off to the intestine. The genital organs are supplied with nerves from the third, fourth, and fifth thoracic ganglia. “The size of the ganglia is in direct ratio with the development of the segments and their appendages, to which they belong” (Von Siebold). The physiology of the nerves of the Macrowra (under stimulation) have been investigated by Drs. L. Fredericq and G. Vandevelde.* They experimented upon the nerves of the flexor muscles of the chelee of Homarus. The nerves of Homarus when dissected out of the body very rapidly lose their excitability. When a nerve is submitted to section the excitability disappears progressively from the surface of the section to the extremity of the periphery. Concerning Homarus, Fredericq and Vandevelde state: “ Ainsi, sur une pince séparée du corps de I’animal, il arrive un moment ot lexcitation électrique du nerf prés de la surface de section ne produit plus de contraction musculaire, alors que la méme excitation appliquée sur un point plus rapproché du muscle y provoque de violentes secousses.” These experimenters have shown that the nerves of Homarus present the same distribution of electric tensions, and the same negative variation, as those of the frog (Rana). They have also ascertained the rate of transmission of motor nervous influx in the nerve connected with the flexor muscle of the dactylopodite. In these experiments they had. recourse to the graphic method employed by Helmholtz. By * Bulletins de ? Académie Royale de Belgique, 2 série, t. 47 [1879]. w 332 PHYSIOLOGY OF THE INVERTEBRATA. exciting the nerve at a point near the muscle, and notin moment of excitation and the moment of contraction, « able to ascertain the time which, elapses between thi phenomena: the same experiment is then repeated on a of the nerve further from the muscle. The difference i time observed in these two experiments—that is to sa Fic. 66.—APPARATUS FOR STUDYING THE TRANSMISSION OF MOT‘ EXCITATION IN THE NERVE OF THE CHELA, M = myograph carrying claw of Homarus. 5 = style attached to the opodite. vy = elastic spring which holds the dactylopodite. a= electrodes. 4 = another pair of electrodes. C=commutator. P=] E = registration cylinder. BB’ = the two coils. A = steel needles for the circuit at each revolution of the cylinder. lapse of time between the second contraction and the fi gives the time employed by the motor excitation to ru , distance between the two excited points. Knowing distance, one can calculate the rate of transmission. Fredericq and Vandevelde exposed the nerve (in a: lobster) which leads to the claw by two openings. A: * The style used was that of Dr. Marey, the distinguished Profe: Experimental Physiology in the College of France. ‘ PHYSIOLOGY OF THE INVERTEBRATA. 333 was attached to the dactylopodite of the chela (Fig. 66), and all firmly fixed, by the aid of bands, upon the horizontal plate of the myograph. The dactylopodite was held by means of a horizontal elastic spring; the object being to keep it away from the other portion of the claw. (Fig. 66). The distance between the starting points of the two curves represents about 100th of a second. Fredericq and Vandevelde measured the distance of the two excited points of the nerve, putting the points of the compass at each pair of electrodes, with those of the wire which were turned to the side of the muscle. This distance’= 56 millimetres. The rate of transmission was consequently 100 x 0°56 = 5°6 metres per second. The following results were obtained in these experiments :— A lobster (2) weighing 559 grammes (without blood); the right chela being used; and the length of the nerve was 59 mm. Experiments A, interval in hundredths ofa second . . 0.9 or 6.49 m. per second. B, ” ” ” > = OS ” 6.8 ” C, ” ” ” = ® 1.0 ” 5-9 ” D, » ” ” - + 08 ” 6.8 9 A lobster (3) weighing 487 grammes (without blood); the left chela being used; and the length of the nerve was 56 mm. Experiments E, interval in hundredths of asecond . . 1.1 or 5.04 m. per second. Fo ” ” + + LI 4, 5.04 ” G, ” ” ” ee DOlry, 5.60 ” A, ” ” ” » + OD sy 6.16 ” PHYSIOLOGY OF THE INVERTEBRATA. 335 The mean of these eight determinations is 5°95 metres, or in round figures 6 metres, per second. The motor nervous excitation is transmitted, then, with infinitely more slowness in the lobster than in the frog or man. In Fig. 67 the distance AC, which separates the beginning of the curve CD from the point A, corresponds to about sooths of a second. ‘This duration represents the sum of the two periods: Ist, the time which is lost from the excita- tion produced’ at the point a to run the length of the nerve as far as the termination of it in the muscle; and 2nd, the time of latent excitation of the muscle. The latter is known and artes Peer a nen nw was Fic. 67.—A GRAPHIC TRACING FOR DETERMINING THE RATE OF . TRANSMISSION OF MOTOR EXCITATION. A = moment of excitation of nerve. CD = curve of contraction obtained by the excitation of the nerve at u (Fig. 63). EF = curve of contraction ob- tained by the excitation of the nerve at 4 (Fig. 63). (Hundredths of a second.) determined, among other things, upon the same muscle. It suffices to obtain a graphic tracing of the muscular contrac- tions by directly placing the exciting electrodes upon the flexor muscle of the dactylopodite. This time was found to be 1.500ths of a second, and that it did not exceed 200ths of a second. There remained, then, at least 5 - 2=300ths of a second, which represented the necessary time for the motor excitation to travel from the point a along the nerve to the interior of the muscle. The length of this portion of the nerve could not be directly determined ; but it was very probably less than sooths in these experiments, and did not certainly reach 1000th. That gave a velocity of 1.66 m. per second in the first hypothesis, and 3.33 m. in the second. From these 330 PHYSIOLOGY OF THE INVERTEBRATA. investigations it is evident, that the rate of transmission of the motor nervous influx in its passage from nerve to muscle finds in the last nervous ramifications considerable delay. The following conclusions have been arrived at by Fredericq: and Vandevelde :— (1) There appears to be a complete identity in the pro- perties of the muscles of Homarus and those of Rana. (2) The motor nerves of Homarus present, from a physio- logical point of view, great points of resemblance to those of Rana. The most characteristic difference consists in the slowness with which the motor excitation travels the length of the motor nerves. In Homarus it is 6 metres, and in Rana 27 metres per second, The slow rate of transmission of the motor excitation proves in Homarus a considerable slackening in the muscular terminations of the motor nerves. The difference in the rate of transmission may be due to the difference in the composition of the nervous matter of the two animals, The following table represents the chemical com- position* of the nerves of Homarus and Rana respectively :— Homarus, Rana, L II I II. Albuminoids : 20.61 21.00 29.20 30.00 Lecithine . ‘ a 7-79 8.11 9.92 9.90 Cholestrine and fats .| 58.34. 57.67 47-13 46.44 Cerebrine ‘ : . 8.26 8.03 9.78 9.75 Insoluble substances (in ' 4.10 4.26 3.50 3.46 ether) . Salts 5 , ‘ ‘ 0.90 0.92 0.47 0.45 100.00 99.99 100.00 100,00 * Dr, A, B. Griffiths’ analyses. PHYSIOLOGY OF THE INVERTEBRATA. 337 The composition of the ashes of the nervous matter in each case is represented in the following table :— Homarus. Rana Potash . s : ‘ : 2 , 33.00 36.24 Soda. : é Z i : < 11.98 10.87 Magnesia : 3 : z : 1.87 1.30 Lime. ‘ 5 : : 0.99 0.81 Tron oxide. . : : ; . 0.16 0.21 Phosphoric acid (combined) . ‘ ; : 41.51 40.32 Phosphoric acid (free) . é ‘ ‘ 6.81 7.92 Sulphuric acid é 3 . 0.90 0.72 Chlorine : . z : : 1.96 1.21 Silica . 4 és i ‘ i : 0.82 0.40 100,00 100.00 The first table gives the chemical composition of the ner- vous matter in a dry state; the following table gives the composition of the nervous matter with its accompanying water :— Homarus. Rana. Water . - 4 é ‘ A : : 70.21 66.42 Solids : “ : : fs : 29.79 33-58 100.00 100.00 The last two tables represent the averages of six analyses in each case. Y 338 PHYSIOLOGY OF THE INVERTEBRATA. The difference in the composition of the nervous matter of the two animals, may possibly account for the difference in the rates of transmission as observed by Fredericq and Vandevelde. Tue PoLyzoa. The nervous system of these animals is very simple, and consists of a ganglion, situated between the mouth and the anus (see Fig. 17), which gives off many nerve-fibres to the tentacula and the alimentary canal. THE BRACHIOPODA. The nervous system of the Clistenterata consists of a ganglion on the ventral side of the oral aperture. From this ganglion proceeds a commissure, which surrounds the cesophagus, and bears two small ganglia. ‘The latter probably answer to the cerebral, the former to the pedal, ganglia of the Lamellibran- chiata. Immediately behind the pedal mass, from which two large nerves to the dorsal or anterior lobe of the mantle are given off, are two elongated ganglia, connected by a commis- sure of their own, which possibly correspond with the parieto- splanchnic ganglia of the higher Molluscs. The nerves to the ventral lobe of the mantle, and those to the peduncle arise from these ganglia.” The nervous system of the Tretenterata has not been so thoroughly worked out as that of the Clistenterata ; but in Lingula, Sir Richard Owen, F.R.S., has shown that the visceral nerves are more developed than those of Terebratula, which belongs to the latter order. ‘Filaments to the muscles are also more distinct: a pair, which come off from the sub- cesophageal ganglion, diverge as they pass backwards along the visceral chamber, then converge to their insertion in the anterior muscles ; a second pair, also from the sub-cesophageal ganglia, run more parallel as they pass along the ventral aspect of the anterior muscles to go to the posterior muscles. PHYSIOLOGY OF THE INVERTEBRATA, 339 Liagula has also the pallial and brachial systems of nerves as well developed as in Terebratula.” * THE Mo.uusca. In the Mollusca there are usually at least three ganglia with radiating nerves—one in the head, one in the foot, and one posterior and above the alimentary canal. ye ob rer A B Cc Fic. 68.—NERVOUS SYSTEMS OF THE MOLLUSCA. A = diagram of nervous system of Axodonta. a = cerebral ganglia. 6 = pedal ganglia. c¢ = parieto-splanchnic ganglia. B = nervous system of Zimax. a= cerebral ganglia. dc = pedal parieto-splanchnic ganglia. d@ = nerves to foot. = nervous system of Sefza. @ = posterior buccal ganglion. 6 = anterior buccal ganglion. ¢ = pedal ganglion. dd = parieto- splanchnic ganglion. ¢ = cerebral ganglion. / = optic nerve and ganglion. .g = splanchnic ganglion. % = ganglion stellatum. As an example of the Lamellibranchiata, we describe the nervous system of Anodonta. There are three pairs of ganglia.(a) Thecerebral ganglia, which are united by a com- missure, aré situated at the sides of the mouth. They send * Owen’s Comparative Anatomy and Physiology of the Invertebrate Animals, P- 492 (2nd ed.) ; 349 PHYSIOLOGY OF THE INVERTEBRATA. off nerves to the anterior portion of the pallium; to the anterior adductor muscle ; to the labial palps, &c.; and tothe branchiz. (6) The pedal ganglia are situated in the foot, or in the corresponding part of the body when the foot is absent, asis the case in some of the Lamellibranchiata. These ganglia are fused together on the median line of the body, and are connected by commissures with the cerebral ganglia. The pedal ganglia send off nerves to the foot.(c) The parieto- splanchnic or visceral ganglia lie on the ventral side of the posterior adductor muscle. They are united with the cerebral ganglia by commissures (Fig. 68 A), which traverse the organ of Bojanus (kidney). These ganglia send off nerves to the branchize ; to the posterior and middle parts of the pallium ; to the posterior adductor muscle ; to the heart ; to the siphons —as in Mya; and to the viscera generally. In the Gasteropoda, represented by Helix, the nervous system consists of the following parts: (a) The cerebral or supra-cesophageal ganglia, lie on the dorsal side of the ceso~ phagus, and are joined close together by a transverse nervous band (Fig. 68 B). Each ganglion sends off a commissure to the pedal ganglia, which are situated close together on the ventral side of the cesophagus. Commissures also join the cerebral ganglia with the so-called parieto-splanchnic ganglia (a group of paired ganglia), which come into close relationship with the pedal ganglia; in fact, they are fused together with the latter ganglia. The cerebral ganglia supply nerves to the eyes, tentacula, &c., and also give off a pair of nerves— one on either side of the cesophagus—to the buccal ganglia. (6) The pedal ganglia are closely united. (c) As already stated, the parieto-splanchnic ganglia are fused with the pedal ganglia. They send off nerves to the nephridia, heart “lung,” sexual and olfactory organs, and pallium.(d) The small paired buccal ganglia are situated above and below the buccal mass. These regulate the movements, &c., of the mouth ; and they have been regarded by some investigators as sympathetic in function. PHYSIOLOGY OF THE INVERTEBRATA. 341 In the Cephalopoda, the nervous system consists of a cerebral or supra-cesophageal, pedal and parieto-splanchnic ganglia situated around the cesophagus, and connected by commis- sures. “In addition to these, buccal, visceral, branchial, and pallial ganglia may be developed on the nerves which supply the buccal mass, the alimentary canal, heart, branchie, and mantle.” In the Dibranchiata (Fig. 68 C), the cerebral ganglia send off nerves to the eyes, &c., and to the buccal ganglia; in the Letrabranchiata, the same ganglia supply. nerves to the eyes, &c., and to the buccal mass. The pedal ganglia, in the Dibranchiata, supply the arms, funnel, and they are connected with the auditory nerves. In the Zetrabranchiata, the pedal ganglia supply the branchieze and the funnel. In both sub- orders of the Cephalopoda, the parieto-splanchnic ganglia supply the branchia, but in the Dibranchiata they also send nerves to the pallium and sexual organs. In the last-men- tioned sub-order, “each parieto-splanchnic ganglion gives off a nerve, which runs along the shell-muscles to the anterior wall of the mantle, and there enters a large ganglion—the ganglion stellatum.” The anterior and posterior buccal ganglia give off nerves to the cesophagus and stomach. The nervous system of the Cephalopoda is characterised by its great concentration and high development. Notwithstanding the apparent irregularity of its general arrangements, the nervous system of the Mollusca is modelled upon the same plan as that of the Arthropoda. In the Mollusca, we still find the cesophageal ring, giving off from its central portion a ganglionic peripheral nervous system, distributing itself to the various organs, but without sym- metiy, as, however, the general conformation of the body ‘demands. The cerebral or super-cesophageal ganglia are very small in the Lamellibranchiata; but are not exceptionally so, ‘as these animals have no head provided with sense-organs. The cerebral ganglion is, however, very large in the Cephalopoda, due to the highly developed sense-organs. 342 PHYSIOLOGY OF THE INVERTEBRATA. The cerebral or supra-cesophageal ganglion of the Mollusca appears to have special functions. According to M. Vulpian,* if this ganglion in Helix is removed, the animal survives the operation four or five weeks, but remains completely motion- less, On the other hand, the removal of the sub-cesophageal ganglion kills the animal in twenty-four hours. Mechanical or electrical stimulation of the supra-cesophageal ganglion of the Mollusca produces little or no effect; but with the sub- cesophageal ganglion, both kinds of stimulation cause vigorous muscular agitation. Electrical stimulation often causes the heart to stop, in the state of diastole: Exactly the same phenomenon occurs when electrical stimulation is applied to the pneumogastric nerves in the Vertebrata.t These facts would seem to confirm the theory of the German school of evolutionists, who connect the genealogy of the Vertebrata with the Mollusca ; but this theory has had its day, and the latest embryological researches explain the origin of the Vertebrate brain and spinal cord as the outcome of the nervous system of the Arthropoda. The nervous system of the acranial Vertebrates can be considered as a coalescent ganglionic nervous system. The central nervous system of Amphiorus (one of the acranial Vertebrates) is a spinal cord with a series of ganglionic enlargements, each of which corresponds with the origin of a pair of nerves. An enlargement, which is comparable to the central ganglion of the Arthropoda, terminates (anteriorly) the spinal cord of the acranial Vertebrata. It does not perceptibly differ from the others, but gives off five pairs of nerves, among which are the optic and auditory nerves. The great difference between the Arthropoda and the Vertebrata is the complete absence in the latter of an cesophageal nervous ring; and that the nerve-cord has a dorsal aspect in the Vertebrata, * Lecons sur la Physiologie Générale et Comparée du Systéme Nerveux, Pp. 757-761. ; + From these investigations it is difficult to decide whether the supra- or the.sub-cesophageal ganglion represents the brain in the Mollusca. PHYSIOLOGY OF THE INVERTEBRATA 343 whereas it is situated ventrally in the Arthropoda. Never- theless there is a certain amount of homology between the spinal cord of the cranial and acranial Vertebrata on the one hand, and the ganglionic chain of the Arthropoda on the other. In both the Vertebrata and the higher Invertebrata, there is a special nervous network, which supplies the alimentary canal, the respiratory and urino-genital organs, and the circulatory system. In both of these sub-kingdoms this system has its origin, or at least its roots, in the great nervous centres. In concluding these remarks, it may be stated that on the whole, every nervous system, whether Invertebrate or Verte- brate, resolves itself into a number of cells, and into a number of fibres, which connect the cells or terminate therein. The parts of the system where the cells accumulate in great number are the nervous centres. The parts are almost wholly composed of fibres from the nervous cords, and if we look at the animal kingdom as a whole, we see that where the cellular centres are the more voluminous and tbe less numerous, the higher the animal is in the zoological scale. In fact, the mammal has been said to be ‘“‘a sort of summary of the entire kingdom. In him are combined all the tissues, all the apparatus scattered through the entire series: he has a special nervous system, but he possesses, nevertheless, a portion of the ganglionic system of the Invertebrates, and in him, as in them, this ganglionic system is constituted essentially of fibres,” derived in the first instance from a protoplasmic basis. Tur TUNICATA. The nervous system of these animals consists of an elongated cerebral ganglion situated on the dorsal side of the pharynx. Nerves are given off from this ganglion to the entrance of the pharyngeal sac, &c.; nerves are also sent out laterally and posteriorly. In the Ascidian larva the nervous 344 PHYSIOLOGY OF THE INVERTEBRATA. “system is composed of a cerebral ganglion, which has at first the form of a cord containing a cavity. This ganglion is constricted into three parts, and is connected with ganglia in the tail. The first or anterior part of this ganglion gives off nerves to the margin of the pharyngeal aperture. 'The middle portion of this ganglion has on it the auditory vesicle, the optic organ, and a stalked ciliated olfactory organ. The optic and auditory organs degenerate just before the adult condition is reached. The third or posterior portion of the ganglion is continued into a long nerve, which at the base of the tail forms a ganglionic enlargement. This ganglion gives rise to a nervous cord, which passes into the tail; where it forms a number of small ganglia. Just before the animal reaches maturity, the tail aborts, the muscles and notochordal sheath degenerate, and the notochordal axis contracts. The nervous system and sense-organs also degenerate, and the cavity in the nerve-cord and cerebral ganglion disappears. In concluding the chapter it may be stated that Prof. E. Ray Lankester* states that “the structure and life-history of the Ascidians may be best explained on the hypothesis that they are instances of degeneration; that they are the modified descendents of animals of higher, that is, more elaborate structure, and, in fact, are degenerate Vertebrata, standing in the same relation to fishes, frogs, and men, as do the barnacles to shrimps, crabs and lobsters.” f * Degeneration, p. 4I. + For further information relative to the above'subject see the papers of Dr. A. Giard in the Archives de Zoologie Expérimentale, t. i (1872); Associa- tion Frangaise pour l’Avancement des Sciences, t. 3 (1874): Revue Scientifique du i1 juillet 1874; Revwe des Sciences Naturelles, septembre 1874; et Comptes Rendus, 1874-5; and also Dr. W. A. Herdman’s papers in the Challenger Reports. CHAPTER XI. THE ORGANS OF SPECIAL SENSE, ETC., IN THE INVERTEBRATA. As we have already seen, all nerves have not the power of transmitting sensations to the brain or its equivalent ; some, on the contrary, are clearly nerves of motion, whether acted on by will or excited by other means. Some nerves, as the optic, transmit only the impressions received from colours—- . i.¢., due to the action of light; to other stimulants this nerve is insensible. The olfactory nerve is sensible to various odours, but it is insensible to the action of light or sound. To these modifications of the sensibility of nervous elements are due the phenomena of special senses. The senses of touch, taste, smell, hearing, and seeing, are so many distinct faculties putting the animal kingdom in relation with the various qualities of the external world. The apparatus or mechanism of the sensibility is not com- posed only of the different parts of the nervous system, whose use we have already alluded to; for the sense-nerves do not terminate freely in the exterior, so as to receive directly the contact of the producing agents of sensations, but terminate in various mechanisms destined to collect the excitation, and to prepare it in such a way as to assure its action. These mechanisms are the sense-organs, and it is essentially by the intermedium of these organs that the sensations reach the brain or its equivalent ; but it may be remarked that they are ot indispensable for the exercise of all the special senses ; the tactile sensibility may be called into play everywhere, where nerves exist adapted to conduct the ordinary sensa- 346 PHYSIOLOGY OF THE INVERTEBRATA. tions, and it is only by the senses of taste, smell, hearing, and sight, that this intermediate organ between the nerve and the external world is a necessary condition. We now proceed to describe the sense-organs in the principal divisions of the Jnvertebrata. .THE Protozoa. As these organisms are destitute of any true nervous system, it would be consistent, on & priort grounds, to assume that they have no special sense-organs. But would it be consistent to assume that these lowly organisms do not digest, respire, and excrete, because there are present no special organs set apart for the functions of digestion, respiration, and excretion? Certainly not, and there is every reason to believe that one or more of the special senses are represented in the Protozoa. Tactile sensibility is generally distributed over the whole surface of the body; frequently, however, it is concentrated on processes and appendages of it. This is more or less true in the whole animal kingdom. In the Protozoa, the whole surface of the body is exceedingly sensitive; but it may be stated that the protoplasmic expansions called pseudopodia have been regarded as fulfilling the function of organs of touch as well as of locomotion. In other forms (¢.g., Para- macium, see Fig. 3) the vibrating cilia are considered by Dr. Stein to be organs of touch; and the long rigid bristle in Cryptochilum, according to M. Maupas, has a similar function, its principal use ewe “to advise the animal of the wont of other Infusoria.” In touch, sensibility is brought into play by simple shock, or contact of bodies: it is spoken of as the least perfect of the senses, and is also the one; which offers the least variety in the different animal classes, compared among themselves. Of all the sense-organs, the eye is the one which is first PHYSIOLOGY OF THE INVERTEBRATA. 347 differentiated ; and a large number of the lowest organisms possess an ocular spot, which is a differentiated, organ having the function of sight. In the Protozoa, this organ is chiefly found in the group of Monads or Flagellata, and is generally coloured red. Klebs has studied the structure of these ocular spots in the Euglene. When one of these organisms is treated with a solution of sodium chloride (1 to 1co), the contractile vesicle, which is in close proximity to the ocular spot, dilates enormously, and consequently causes the same thing to occur in the ocular spot itself. By this means Klebs observed that the spot “is a small discoid or triangular mass, of jagged and irregular outline (see Fig. 1); it is formed of two parts: for a base it has a small mass of reticulated protoplasm, and in the meshes of the protoplasm there are smail drops of an oily substance coloured red.” “What is the physiological significance of these spots? Ehrenberg considered them as eyes; hence the name Luglena (word for word, pretty eye), which he had given to a species of the Flagellata provided with ocular spots. This interpre- tation had been questioned by all the authors of his time, and especially by Dujardin.” At the present day, however, many distinguished French naturalists hold the same opinion as Ehrenberg—viz., that the so-called ocular spots of the ‘Protozoa are true visual organs. According to M. Pouchet, the ocular spot of Glenodinium polyphemus (one of the Peri- dinew) has without doubt the function of an eye. It always occupies a fixed and definite position in the cell, and it is composed of two parts—a crystalline humour and a choroid. “The crystalline humour is a strongly refractive, hyalin, club-shaped body, rounded at its free end, which is always directed forwards, while the other end is immersed in the mass of pignient which represents the choroid. The latter is clearly determined; it forms a sort of hemispherical cap, enveloping the posterior extremity of the crystalline humour. In fact, the visual organ of this organism is composed of 348 PHYSIOLOGY OF THE INVERTEBRATA. exactly the same parts as the eye of a Metazoon, with one exception, the absence of the nerve-element.” The ocular spots of other Flagellata had been previously investigated by Kiinstler, Claparéde, and Lachman, and they found crystalline humours and pigmented capsules (a choroid); but what their true function was, they did not know, as no nerve-apparatus fitted to perceive the impressions received was, in the least, demonstrable in these organisms. On the other hand, certain French savants state that “the co- existence of a pigment and of a crystalline humour amply suffices to characterize a visual organ. As to the nerve- apparatus susceptible of perceiving impressions, it is re- placed by the protoplasm, which, as is well known, is sensi- tive to light.” It has also been stated, by some observers, that the red pigment in the ocular spots of the Protozoa exhibits similar reactions to the pigment, which is present in the rods of the retina of the Vertebrata. But it should be borne in mind that pigment is not indispensable for the sensation of light, because there are many eyes of complicated structure from which pigment may be altogether absent. Therefore the only reasons which those observers, who state that a visual organ is present in certain Protozoa, have for such an assertion is, that the ocular spot has a definite position, and it possesses a crystalline humour. Are these facts sufficient to speak of it as an eye? The Rev. W. H. Dallinger, F.R.S., and Dr. J. Drysdale,* who examined the ocular spots in various Monads, failed to discover the function of these bodies after a most searching inquiry. In concluding this account of the sense-organs in the Protozoa, it may be stated that the vesicles of Miller in Loxodes rostrum (one of the Ciliata) have been considered as possessing an auditory function. * The Monthly Microscopical Journal, vol. 11, p. 8 PHYSIOLOGY OF THE INVERTEBRATA. 349 THE PorIFERA OR SPONGIDA. In these animals the sense-organs are not further differen- tiated than those of the Protozoa. THe Ca@LENTERATA. The sense of touch in these animals is believed to be chiefly located in the tentacula, which surround the mouth, but in Hydra, as well as in other forms, every cell is sensitive to tguch. ‘The small pits in connection with nerves, and provided with an epithelial lining of hair-bearing sense cells, in the Meduse, are regarded as the simplest olfactory organ. They are situated round the margin of the bell; in fact in all the Meduse the sense-organs are marginal. The small pigmented spots are undoubtedly eyes ; and according to some writers, otolithic sacs or simple auditory organs are also situated on the edge of the bell. The rudimentary eyes of the Meduse are much better developed than those which are supposed to exist in the Protozoa ; for in certain species, nerves penetrate manifestly into the capsule (Gegenbaur). But the exact function of the ocular spots in these animals was not understood until Dr. G. J. Romanes, F.R.S.,* investigated their nature from a physiological standpoint. His mode of investigating this subject was to put two or three hundred Sarsie into a large bell-jar, and then to completely shut out the daylight from the room in which the jar was placed. By means of a dark lantern and a concentrating lens, he cast a beam of light through the water in which the Sarsiw were swimming. “From all parts of the bell-jar they crowded into the path of the beam, and were most numerous at that side of the jar which was nearest to the light. Indeed, close against the glass they formed an almost solid mass, which followed the light wherever it was moved. The individuals composing * Philosophical Transactions, 1875, p. 295; ibid., 1879, p. 189. 350 PHYSIOLOGY OF THE INVERTEBRATA. this mass dashed themselves against the glass nearest the light with a vigour and determination closely resembling the behaviour of moths under similar circumstances. ‘There can thus be no doubt about Sarsia possessing a visual sense.” To prove that the ocular spots of these animals are really eyes, Dr. Romanes experimented in a like manner with a dozen vigorous specimens; nine of which had previously had their ocular spots removed, while three specimens were left intact. The difference in the behaviour of the mutilated and the unmutilated individuals was very marked. The three unmutilated individuals sought the light as before, while the nine blind or mutilated individuals swam hither and thither without. paying it any regard. It was suggested by Professor L. Agassiz, that it was the heat, or ultra-red rays of the spectrum, which was the real cause of the above phenomenon, but Dr. Romanes has shown that when a heated piece of iron (“just ceasing to be red”) was placed against the bell-jar containing the specimens of Sarsia, not one of the organisms approached the heated metal. These investigations prove that in Sarsia the faculty of appreciating luminous (but not heat) rays is present, and that this faculty is lodged exclusively in the ocular spots. Dr. Romanes has also shown that the lithocysts of the covered-eyed Medusew resemble, in function, the marginal bodies of the naked-eyed Medusw—that is, they are rudi- mentary or incipient organs of vision. The lithocysts are stimulated by the approach of a candle or the access of day- light, but if the lithocysts are removed, the approach of a luminous object produces no stimulating effect. The ocular spots in the Actinozoa, and especially in, Actinia mesembryanthemum, have been investigated by Schneider, Rétteken, Duncan, and MacMunn. These coloured bodies are situated in the oral disc outside the tentacula; and they are diverticula of the body wall. Be- neath the surface “lies a layer of strongly refracting spherules, followed by another layer of no less strongly PHYSIOLOGY OF THE INVERTEBRATA, 351 refracting cones. Subjacent to these, Professor P. M. Duncan, F.R.S.,* finds ganglionic cells and nerve-plexuses, It would seem, therefore, that these bodies are rudimentary eyes.” The colouring matter of the blue ocular spot of the above-mentioned species of Actinia has been spectroscopically investigated by MacMunn,f and these investigations have led him to believe that it is possible that this pigment is capable of absorbing certain rays of light, so as to enable the animal to distinguish light from darkness. THE ECHINODERMATA. The sense of touch is well developed in the Lchinodermata, and seems to have its seat in the ambulacral feet, pedi- cellarize, and tentacula situated in the neighbourhood of the buccal orifice. Romanes and Ewart state that ‘all the Echinodermata seek to escape from injury. Thus, for in- stance, if a starfish or sea-urchin is advancing continuously in one direction, and if it be pricked or cut in any part of an excitable surface facing the direction of advance, the animal immediately reverses that direction.” There is no doubt that the sense of touch is present in these animals. The sense of smell also appears to be developed to a certain extent in starfishes. If several of these animals (contained ina tank) are advancing in the direction of a luminous portion of the water,{ they immediately retract their steps, if a small quantity of bromine or sulphuretted hydrogen water is gently poured into the luminous portion of the water. This fact appears to support the idea of a sense of smell in the Asteridea. - According to Leydig § certain Echinodermata appear to be provided with auditory vesicles, in which float powerfully * Proceedings of Royal Society, 1873. + Philosophical Transactions, 1885, pt. 2, p. 660. + The water was illuminated by means of a small incandescent lamp. § Histologie Comparée, p. 316, 352 PHYSIOLOGY OF THE INVERTEBRATA. refracting homogeneous granules. These vesicles receive nerves, and sometimes even rest on the central ganglia of the nervous system. The eyes or ocular spots in the Asteridea are five in number, and they are situated at the end of each ray. These organs are spheroidal, pedunculated, and pigmented prominences; being expansions of the ectoderm, and con- tinuous with the ambulacral or radial nerve (see Fig. 61). Each eye contains a number of clear oval bodies surrounded by a pigment. These are said to répresent the crystalline cones of a compound eye. In the Echinidea the five ocular spots are situated on a similar number of small plates, which form the apex of each ambulacral segment. The ocular along with the five genital plates surround the anus. The true function of the ocular spots in the Echinodermata have been ascertained by Drs. Romanes and Ewart.* The Asteridea and Echinidea (but not the Ophiuridea) crawl towards, and remain in, the light; but when their ocular. spots are removed they no longer do so. On the other hand, if only one of the five ocular spots were left intact, the animal crawled towards the light as before. It may also be stated that when their ocular spots are left intact, these animals can distinguish light of very feeble intensity. THE TRICHOSCOLICES. In the Turbellaria the organs of touch are distributed over the whole surface of the body, but the cilia are the chief tactile organs. Some of these animals have auditory sacs provided with otoliths; and most of thems possess eyes. Many Planarie have first of all in the embryonic state pigmented spots in the place where, at a later period, eyes with crystalline cones are developed. In the Rotifera, the tactile organs are cutaneous, and have * Philosophical Transactions, 1881, pt. 3, pp. 856, 873, 877. PHYSIOLOGY OF THE INVERTEBRATA, 353 the form of papille or prominences covered with hairs, or of tubular prolongations of the skin. In some of these animals there is a sac filled with calcareous granules attached to the ganglion. This sac is most likely an auditory organ. One or more ocular spots are sometimes situated on the ganglion in the Rotifera. In some of the Z'rematoda, ocular spots have been observed, but no other sense-organs. THE ANNELIDA. In these animals the sense-organs are variously distributed. The organs of touch are cutaneous, and they have the form of bristles (setee), &c., in connection with sensitive fibres. According to Leydig, these tactile organs are sometimes, in the Hirudinea, grouped in large numbers at the bottom of cup-shaped depressions. In Hirudo, there are about sixty of the cup-shaped depressions in the head, and others in the posterior part of the body. They are in connection with the terminations of nerves given off to those in the head from the supra-cesophageal ganglia, and to those posteriorly situated, from the caudal ganglion. These organs are also of an olfactory function (Leydig). In the Gephyrea rudimentary or incipient eyes are some- times connected with the cerebral ganglion. Simple eyes are usually present on the anterior segment in the Hirudinea. These are supplied by nerves from the supra-cesophageal * ganglia, In Hirudo the eyes are situated on the dorsal surface of the first three segments. In Lumbricus (one of the Oligochwta) no eyes or other special sense-organs are present, Although devoid of sense- organs, Lumbricus “ possesses a generalised sensitiveness, due to the plentiful distribution of nerve-fibres through the body, and which, in many respects, takes the place of a series of specialised organs, corresponding to the senses of touch, taste, Zz 354 PHYSIOLOGY OF THE INVERTEBRATA. sight, hearing, and smell. Its sensitiveness to touch and its dislike to sunlight are well known; and, though not possessed of organs of sight or smell, it is able easily to find its way to stores of food, and to retreat from sources of danger into a burrow ” (Gibson). In Alciope (one of the Polychwta) the eyes are large and well developed. As already stated the visual organs in the Annelida are usually situated in the anterior part of the body ; but in “ the remarkable genus Polyophthalmus, De Quatrefages discovered, besides the ordinary cephalic eyes, a double series of additional visual organs, one pair being allotted to each somite. In Branchiomma, eyes are situated at the ends of the branchial plumes. Ehrenberg has described two caudal eyes in Amphicora, and De Quatrefages has shown that similarly placed eyes exist in three other species of Polycheta, two of which are closely allied to Amphicora, while the other is an errant form, related to Lumbrinereis. Auditory sacs, containing many otoliths, have been observed upon each side of the cesophageal ring in Arenicola, and similar organs have been noticed in other 7ubicola; but hitherto their existence has not been certainly determined in the Hrrantia” (Huxley). THE NEMATOSCOLICES. In the Nematoidea, the papille and hairs situated chiefly in the region of the mouth are organs of touch. In non-parasitic Nematodes (¢.g., Hnoplus) pigmented ocular spots are present on the cesophageal nervous ring. THE CHETOGNATHA. The eyes in Sagitéa are situated on the supra-cesophageal or cerebral ganglion. PHYSIOLOGY OF THE INVERTEBRATA, 355 THE MyRIApoDa. Concerning the sense of touch in these animals, there are on the antennz and other appendages, filiform prolongations —these transmit the effects of mechanical pressure, d&c., to the nerves attached to these organs. Although some species of the tad are blind, the majority have eyes; and these organs are either simple or compound eyes. Prof. H. Grenacher has recently investi- gated the eyes in this Arthropod class. He distinguishes those of (1) Scolopendride, (2) Lithobius, (3) Julus, (4) Glomeris, and (5) Scutigera ; all except the last are stemmatia. Scutigera has compound eyes of a very anomalous type, in no wise resembling those of the Insecta and Crustacea. The eyes of the Chilopoda are more polymorphic and more com- plex than those of the Chilognatha (Diplopoda). Physiologi- cally, the simple eyes of at least some of the Myriapoda must be very unlike the ordinary stemmata of spiders or insects. These are true eyes. In the Myriapoda, on the other hand, each stemma has its retinal elements, or their representatives so disposed in regard to the axis of the cornea-lens, and there- fore to the incident rays of light, that it seems very doubtful whether such eyes can do more than distinguish between degrees of light and darkness. The sense of smell appears to be feebly developed in the Myriapoda. THE INSECTA. “The sense of touch appears to be seated in the Jnsecta in very different parts of the body. It is chiefly located in the palpi of the mouth, which, for this purpose, are usually terminated by a soft surface. The antenneze also serve as tactile organs, but in a very variable manner, according to their forms, the degree of their development, and the habits of the species. These organs receive, each, directly from the cerebral ganglion, a nerve; these nerves perceive the slightest dis- 356 PHYSIOLOGY OF THE INVERTEBRATA. turbances occurring in the antennal integuments, which are solid and often provided with hairs and bristles. Among those Znsecta in which these organs are very long, filiform, and movable in various directions, they serve, like the vibrissz of many Mammalia, to announce the presence of external bodies. With very many other Insecta, they are very movable, and are distinctly used as tactile organs, like the fingers of the human hand. It is also by means of these organs that insects perceive the various conditions of the atmosphere, especially the temperature, and thereby regulate their movements and actions. With those Insecta, where the parts of the mouth are modified into organs of suction, it is quite evident that the extremity of the proboscis is the seat of a very delicate sense of touch. Also with those female insects having an ovipositor, which is used to deposit their eggs in holes of various depth, the apex of this organ must be endowed with the same power.”*- The extremities of the limbs in many Jnsecta are also tactile organs. Besides these special devices, the skin of the Znsecta is sensitive to touch. In spite of the chitinous covering, these animals feel strongly the contact of external objects at any point of their own bodies. This is due to the sensitiveness of the underlying membrane. The sense of taste is confined to the mouth and pharynx. This sense is, as a general rule, connected with the tactile sensation of the buccal cavity, and also with the olfactory sensation. In the Insecta, as well as in other Arthropoda, a specific sensory epithelium is present at the entrance to the buccal cavity : this is stated to possess a gustatory function. In the Jnsecta the cuticular appendages of the antenne, in which the ganglionated extremities of nerves occur, are con- sidered to be olfactory fibres. Dr. G. Hauserf has recently examined the olfactory organs of the JZnsecta. In all the * Siebold’s Anatomy of the Invertebrata (American edition), p. 414. + Zeitschrift fir Wissenschaftliche Zoologie, vol. 34, p. 367. PHYSIOLOGY OF THE INVERTEBRATA. 357 Orthoptera, Diptera, Lepidoptera, Neuroptera, Hymenoptera, and Coleoptera, a strong nerve arising from the cerebral ganglion passes into the antenna, and there is a sensory terminal organ, formed by cells developed from the hypodermis, with which the nerve-fibres are connected. The function of this organ was ascertained by extirpating the antenne, and the insects which turned away from carbolic acid, turpentine, &c., before the antennze were cut off, now showed no repugnance at all in the presence of these compounds. It was also found that when the antennze were removed the insects did not rush to food. , The author has entirely confirmed Hauser’s investigations ; and there is no doubt that in the antenneze of these animals, there resides the sense of olfaction; but it should be borne in mind that the antennz are also tactile organs—i.c., they have a dual function. The sense of hearing is somewhat well developed in the Insecta.* “The only organs which can safely be regarded as auditory in insects, are those which occur in grasshoppers (Acridide), crickets (Achetidw), and locusts (Locustidw), and which were first accurately described by Von Siebold. They have since been studied by Leydig, Hensen, Ranke, and Oscar Schmidt, but it must be confessed that much obscurity still hangs over their. minute structure. In the Acridide, the chitinous cuticula of the metathorax presents on each side, above the articulation of the last pair of legs, a thin tympani- form membranous space surrounded by a raised rim. On its inner face, the cuticular layer of the tympaniform membrane is produced into two processes, one of which is a slender stem ending in a hollow triangular dilatation. A large tracheal vesicle lies over the tympanic membrane, and between its wall and the latter, a nerve derived from the metathoracic * The weevils (Sitona crinita and Sitona lineata), which feed upon the leaves of beans and peas, are very sensitive to sound, and if approached they usually drop from the leaves to the ground, (See Dr. Griffiths’ The Diseases of Crops, p. 26.) 358 PHYSIOLOGY OF THE INVERTEBRATA. ganglion, passes to the region occupied by the processes, and there enlarges into a ganglion, the outer face of which, beset with numerous glassy rods arranged side by side, is in contact with the tympaniform membrane. A nerve arising from the ganglion passes along the groove to the ‘ stem,’ and ends in a ganglion in its dilatation. From this ganglion certain fine filaments proceed. In. the Achetide and Locustida, the tibize of the fore-legs present similar tympaniform membranes, which are easily seen in the common cricket, but, in other forms, become hidden by the development over them of folds of the cuticle of the adjacent region of the limb. Two spacious tracheal sacs occupy the greater part of the cavity of the tibia, and a large nerve ends in a ganglion in the remain- ing space. Upon this ganglion a series of peculiar short rod- like bodies are set.” For a tolerably full réswmé concerning the auditory organ in the Insecta the reader is referred to Mr. A. H. Swinton’s Insect Variety: Its Propagation and Distribution, pp. 230- DED. Asa general rule, the Jnsecta have a pair of compound eyes, which are sessile and are situated upon the sides of the head. The compound eye is literally an agglomeration of simple eyes, having each a cornea, a vitreous humour of conical form, a pigmented layer, and a nervous filament. In some insects a compound eye contains upwards of twenty-five thousand of these simple eyes. All the small corneze are hexagonal, and unite together so as to form a kind of common cornea, whose surface presents a vast number of facets. The retina of such eyes has a hemispherical form, the convex surface being directed outwards, and consists of large compound nerve-rods and retinule, which are separated from each other by pig- mented sheaths. In front of these rods are placed the strongly refractile crystalline cones, and in front of these again the lens-shaped corneal facets. The compound eye is enclosed by a firm chitinous layer, which following the sheath of the PHYSIOLOGY OF THE INVERTEBRATA. 359 entering optic nerve surrounds the soft parts, and reaches as far as the cornea.* Almost all the Insecta have a pair of.these compound eyes; but they are sometimes replaced by simple eyes, and at other times both kinds are present. In a few cases there are neither compound nor simple eyes; among these are certain species of Ptiliwm, that live under the bark of trees; the Nycteribia, which is parasitic on the skin of certain animals ; the Anophthalmus,t which lives in dark caves; and the Claviger, which dwells in the nests of ants. .The larve of the Diptera and Hymenoptera, and most of the apodal larvae of the. Coleoptera are also blind. The second form of eye. occurring in the Znsecta is the simple eye, ocellus, or stemma. It contains the following parts :— sclerotica, cornea, lens, vitreous humour, and choroid; and it is of globular form. ‘‘ But the lens appears to be always a mere thickening of the cuticle, which constitutes the cornea, and the so-called vitreous humour is partially or wholly made up of crystalline cones, analogous to those which are found in the compound eye. In this respect the ocellus of the insect resembles the simple eye in the Arachnida and Crustacea.” The larvee of the Lepidoptera, Newroptera, Coleoptera, and some Hymenoptera and Diptera have only ocelli. T'wo or three of these ocelli remain, but with superadded compound eyes, in the majority of the winged orders except the Coleoptera, in which only compound eyes are present in the perfect state. Simple eyes are present in the following Insecta:—Pediculide, Coccide, Poduride, Nirmide, and the larve of the Phryganide, Hemerobide, Myrmeleonide, and Raphidide. The sense of sight must be keen in the Insecta, but their mode of vision is essentially different from that of the higher Vertebrata. On this point, Professor C. Lloyd Morgant says : “ Remember.their compound eyes, with mosaic vision, coarser * Claus’ Lehrbuch der Zoologie. | t See Darwin’s Origin of Species, p, 111. {£ Animal Life and Intelligence (1891). ‘ 360 PHYSIOLOGY OF THE INVERTEBRATA. by far than our retinal vision, and their ocelli of problematical value, and the complete absence of muscular adjustments in either one or the other. Can we conceive that, with organs so different, anything like a similar perceptual world can be elaborated in the insect mind ?. I, for one, cannot. Admitting, therefore, that their perceptions may be fairly surmised to be analogous, that their world is the result of construction, I do not see how we can for one moment suppose that the percep- tual world they construct can in any accurate sense be said to resemble ours.” “The sounds produced by insects are, in a great proportion of cases, effected by the friction of the hard parts of the integument one against the other. ... Landois, however, found that the thorax of a bluebottle fly continued to buzz after the separation of the head, the wings, the legs, and the abdomen. ... The acoustic apparatus, in fact, lies in the immediate neighbourhood of the thoracic stigmata... . The vocal organ of the fly appears to be a modification of the occlusor apparatus of the stigmata, just'as the organ of voice of mammals is a modification of the occlusor apparatus of their respiratory opening.” In Apis the voice organs are three-fold, the vibrating wings, the vibrating rings of the abdomen, and the true vocal apparatus in the breathing aperture or spiracle; the first two produce the buzz; while the hum—surly, cheerful, or colloquially significant—is due to the vocal membrane. Some of the bee’s notes have been interpreted. ‘“‘Huumm” is the cry of con- tentment ;* “wuh-wuh-wuh” glorifies the incessant accouche- ments of the queen; “shu-u-u” is the frolic note of young bees at play; “ssss” means the muster of a swarm; “brrr” the slaughter or expulsion of the drones; the “ tu-tu-tu” of newly-hatched young queens is answered by the “ qua-qua- qua” of the queens still imprisoned in their cells. * The poet Byron says in Don Juan (c. i. v. 123)—‘‘ Sweet the hum of bees,” PHYSIOLOGY OF THE INVERTEBRATA. 361 THE ARACHNIDA. The palpi are the principal seat of the sense of touch, being in connection with nerves arising from the cerebral ganglion. The feet are also very sensitive tactile organs. The eyes are always simple, like the ocelli of the Jnsecta ; and there are usually from two to twelve* in number. Audi- tory organs have not been discovered in the Arachnida, but we have many proofs of the existence of this sense in these animals, and it would even appear that some of them are sensible “to the charms of music.” The parasitic Acarina, and allied groups, are entirely devoid of organs of vision. THE CRUSTACEA. The sense of touch is well developed in these animals. Its principal seat is in the antenna, which also contain nerves from the supra-cesophageal ganglion. Often the mouth organs have one or more pairs of tactile appendages ; and no doubt the limbs, especially the anterior ones, are also the means of giving rise to tactile impressions. In the lower Crustacea, Dr. G. O. Sars has shown that the principal seat of the sensation of touch is in the antenne. The antennulee have no such function. The olfactory organ is situated in the antennule. In ‘Astacus, this organ is situated in the delicate sete of the endopodite of each antennule (Fig. 69, A); these sete are provided with nerves. A similar arrangement occurs in many Crustacea besides the Decapoda. If the antennule of Astacus are removed, the animal will approach a small cup containing bromine placed at the bottom of the tank in which the animal lives. On the other hand, if the antennulz are left intact, the animal will not approach the cup. Other obnoxious liquids of high density give rise to similar results. * Scorpionide (Von Siebold) 362 PHYSIOLOGY OF THE INVERTEBRATA. This proves that the sense of smell is developed in Astacus and that the olfactory organs are the antennule. Auditory organs have been observed in the higher Crustacea, especially in the Decapoda. In Astacus (Fig. 69, D), there is an auditory sac lodged in the basal joint of each antennule. The upper face of the basal joint has a small oval aperture, the outer lip of which is invested by hairs directed inwards. This aperture leads into a wide delicate sac, which contains a fluid in which minute sandy particles (otoliths) are suspended. A ridge, formed of the Fic, 69.—THE OLFACTORY AND AUDITORY ORGANS OF ASTACUS. A = Antennule, with setz at d. C =d enlarged, showing olfactory nerve (¢). B= Antennule complete : a@=exopodite; 4 = endopodite; ¢ = protopodite. D = auditoryorgan: f/=nerve; g = auditory hairs (sete); = otoliths. posterior and inferior wall of the sac, projects into its interior. Each side of this ridge is covered with a series of delicate sete (auditory sete), which project into the fluid, An auditory nerve, which enters the sacs, breaks up into fine fibrils that are distributed to the sete. A fibril passes through the base right up to the summit of each seta, where it terminates in a peculiar rod-like body. The sonorous waves, transmitted through the water in which -Astacus lives to the fluid and sandy contents of the auditory sac, are taken up by the delicate nerve-endings and conveyed through the auditory nerve to the brain or supra-cesophageal ganglion. PHYSIOLOGY OF THE INVERTEBRATA, 363 In Astacus, Homarus, and other Decapoda, it may be re- marked that both the olfactory and auditory organs are lodged in the antennule. The eyes of the Crustacea are formed on a plan very similar to those of the Insecta. Sometimes they are simple; but generally they are compound eyes, and in all the higher Crustacea they are carried on movable peduncles, an arrange- ment not met with in any of the other classes of the Arthropoda. “The Cirripedia, the Penellina, and the Lernwodea alone are without an organ of vision; and even here this deficiency occurs only during the last phases of their retrograde meta- morphosis, when these animals remain fixed to foreign bodies.* There is, moreover, in the other orders, here and there a genus, which contains blind individuals: such is the case with the females of certain parasitic Zsopoda;{ and the same remark applies to some subterranean Myriapoda.” t The eyes of Astacus and other Decapoda are two in number —one seated at the extremity of each of the ophthalmic peduncles, the cuticle of which is continuous with the transparent cornea. The corneal membrane is divided into numerous minute square facets, each of which corresponds * The adult Cirripedia, notwithstanding the absence of eyes, are very sensitive to light (Von Siebold). + Bopyrus, Jone, Phryxus (i.e., the ?). + Polydesmus, Cryptops, Geophilus, and Blaniulus. The blindness of these and other animals is generally attributed to the effects of disuse. Concerning the blind cave-crabs, Darwin in the Origin of Species (p. 110) says: “In some of the crabs the foot-stalk for the eye remains, though the eye is gone..... As it is difficult to imagine that eyes, though useless, could be in any way injurious to animals living in darkness, their loss may be attributed to disuse.’”? On the other hand, Mr. W. P. Ball says: “The cave-crabs which have lost their disused eyes, but not the disused eye-stalks, appear to illustrate the effects of natural selection rather than of disuse. The loss of the exposed, sensitive, and worse-than- useless eye, would be a decided gain, while the disused eye-stalk, being no particular detriment to the crab, would be but slightly affected by natural selection, though open to the cumulative effects of disuse.” (See Ball’s book: The Liffects of Use and Disuse, p. 17.) 364 PHYSIOLOGY OF THE INVERTEBRATA. with the base of a crystalline cone. Each cone passes inwardly into a nerve-rod, and then thickens into a striated spindle-shaped body. The inner extremities of the striated spindles become narrow again, and then pass into the optic nerve (Fig. 70). Fic. 70.—THE EyE OF THE DECAPODA. A = Eye of Astacus. B= Eye of Homarus. a= cornea. 6 = crystalline cones. ¢ = nerve rods. d = striated bodies. e = optic nerve, J = lenticular bodies. g = fenestrated membrane. #% = layer not present in Astacus. k = pigment cells between cones. C = cornea of Decapoda. D = cornea of /xsecta. There are certain species of crayfishes which -are blind; among these may be mentioned Cambarus setosus (Faxon), which lives in the caves of south-western Missouri, and Cambarus pellucidus, the well-known species from the Mam- moth Cave. Mr. G. H. Parker* has recently examined the question of ‘degeneration of these organs. He states that * Bulletin of the Museum of Comparative Anatomy at Harvard College, vol. 20 (1890). : PHYSIOLOGY OF THE INVERTEBRATA. 365 not only has the finer structure of the retina been affected, but the shape of the optic stalks has been altered. The optic stalks are not only proportionally smaller than those of crayfishes possessing functional eyes, but they have in these two cases characteristically, different shapes. In crayfishes with fully developed eyes, the stalk is terminated distally by a hemispherical enlargement; in the blind crayfishes it ends as a blunt cone. In both forms of crayfishes the optic ganglion and nerve were present, the latter terminating in some way undiscoverable in the hypodermis of the retinal region. In C. setosus this region is represented only by undifferentiated hypodermis, composed of somewhat crowded cells, while in C. pellucidus it has the form of a lenticular - thickening of the hypodermis, in which there exists multi- nuclear granulated bodies; these are shown to be degenerated clusters of cone-cells. Tur MoLuvsca. The sense of touch, according to Gegenbaur, is chiefly confined to certain cutaneous cells with setiform prolonga- tions, disseminated where the body is not covered with hard pieces. These cells are provided with nerves, which offer here and there ganglionic expansions. In the Lamellibranchiata, there are frequently tentacula around the branchial and anal openings of the pallium, and the orifice of the siphon. These and similar devices receive nerves from those of the pallium. The tentacula and the ciliated labial palps are the tactile organs of the Lamellibranchiata. In the Gasteropoda, represented by Helix, all the parts of the body (excepting the shell) are capable of feeling when touched, The tentacula, the edges of the lips, and the lobes of the pallium and foot, however, have the sense of touch developed in a specially high degree. : In the Cephalopoda, the sense of touch is well developed. It is situated in the arms, the fringed labial membranes, and in the whole of the cutaneous covering. 366 PHYSIOLOGY OF THE INVERTEBRATA. In the Mollusca there appears to be special organs of taste, in the form of a specific sensory epithelium at the entrance of the buccal cavity. In the Cephalopoda, “the fleshy point of the tongue is undoubtedly a gustatory organ. It is concealed in the anterior angle of the lower jaw, and its rounded surface is covered with numerous soft villosities, which very probably serve ag gustatory papille.” The olfactory organ of the Branchiogasteropoda has been examined by Dr. J. W. Spengel.* He finds that in Trochus, Turbo, and Vermetus, the so-called “rudimentary gill,” or colour gland of T. Williams, is an olfactory organ. This organ consists of a large mass of nervous matter, invested by a layer of epithelium, into which nerve-fibres distinctly pass. Spengel has also proved that the ciliated organs of eee in the Pteropoda have an olfactory function. Dr. D. Sochaczewerf has also examined the ‘ini organs in the Pulmogasteropoda. In these animals, the tentacula, the organ of Semper, and the pedal gland have each been considered to have the function of an olfactory organ. Sochaczewer has tried the following experiments: (a) Having cut off the tentacula of Helix pomatia, the wound was allowed to heal. The -snails were then placed on a flat plate, the edge of which was smeared with turpentine. Both the mutilated and unmutilated specimens turned away from the edges. This shows that the tentacula are not the seat of the olfactory organ. (0) The organ of Semper is small in Helix, Arion, and Limneus; but is well developed in Limaz. Here it has the form of four or five glandular lobate processes, which are set at the sides of the mouth. This organ is supplied with four nerve-fibres. The two median are mus- cular in character, while the lateral branches are the proper labiales, which give off, one on either side, a fine nerve-branch to the glandular branches of Semper’s organ. The cells of * Leitschrift fiir Wiss. Zoologie, vol. 35, p. 333- + Lbid. p. 30. PHYSIOLOGY OF THE INVERTEBRATA. 367 the constituent lobes resemble the glandular cells of the salivary glands; in other words, this organ has not an olfactory function. (¢) The pedal or foot gland is looked upon by Sochaczewer as an olfactory organ. It is well supplied with nerves; but experiments are difficult to try in such an , organ. The olfactory organs of the Cephalopoda are situated near the eyes. They are either depressions or papille of the integument. The nerves which . supply these organs arise from the optic ganglion of the ceso- phageal nerve-ring. The auditory organs (Fig.71) of the Lamellibranchiata con- sist of a pair of vesicles or sacs. FIG. 71. These vesicles are filled with a ‘Te AupiTory Orcan or CycLas fluid (endolymph) containing a=capsuleorsac. 4 = ciliated otoliths; and they are attached SNe eee by short nerves to the pedal ganglia. In the Mollusca generally, a delicate sensory epi- thelium marks the percipient portion of the inner wall of the auditory sac. The auditory organs of the Gasteropoda, as represented by Helix, are in pairs, close to and connected with the pedal ganglia. Hach auditory. organ or otocyst consists of an in- ternally ciliated vesicle or sac containing a fluid and otoliths ; an auditory canal which may communicate with the exterior ; and an auditory nerve from the cerebral ganglia. A pair of auditory vesicles are always present in the Pteropoda. In the Dibranchiata, the auditory organs are situated in the cavities of the cephalic cartilage. The internal walls of the auditory vesicles in the Octopoda are smooth; but in the Loligina they are raised into papille. In the Tetrabranchiata, represented by Nautilus, the auditory organs are attached to the pedal ganglia, and are 368 PHYSIOLOGY OF THE INVERTEBRATA: not situated in the cranial cartilage. In both ordérs, the auditory nerve gives rise to nerve-filaments within the sac; and in the Dibranchiata there is a single, irregular, white otolith of a crystalline texture (CaCO,). On the other hand the auditory sac of the Tetrabranchiata contains many otoliths.* In the Mollusca, organs of sight are met with in various degrees of development. They are absent in the fixed Mollusca. Certain of these, which in the state of mobile larvee had eyes, lose them by degeneration when they have. becomeimmobile. Certain spe- cies of the Lamellibranchiata have as eyes sometimes only pigmented spots, and some- times brilliant organs, dissemi- nated on the edge of the pallium. Fic, 72.—THE Eyre OF PECTEN, @=cornea. 4=Ilens. c= sclerotica. d = optic nerve (2). e = retina. In Pecten, there are a large f= opticnerve(x). g= pigment number of simple emerald- layer. A = vitreous humour. : Aaya green coloured eyes situated round the edge of the pallium. Each eye (Fig. 72) consists of a cornea, lens, sclerotica, retina, choroid, and vitreous humour. The eye is peduncu- lated, and it has a double optic nerve. The table on p. 369 gives the colour, &c., of the eyes of various Lamellibranchiata, The Scaphopoda and Polyplacophora have no eyes. In the Pulmogasteropoda (e.g., Helix) there are a pair of simple eyes situated on the summits of the large tentacula. The eye of Helix consists of the following parts: sclerotica, choroid, lens, cornea, vitreous humour, and an optic nerve which expands into an outer and inner retina. The eye in these animals is much more highly developed than the simple * Dr. J. D. Macdonald in Proc. Roy. Soe., 1855. PHYSIOLOGY OF THE INVERTEBRATA. eyes of other Invertebrata. are also present in the Branchiogasteropoda. 369 Highly-developed simple eyes Cotovr. REMARKS. Pholas . Pecten . Venus . Yactra Arca Solen Pinna . Tellina Anomia Lima . Spondylus Plicatula Ostrea . Pectunculus . yellowish-brown green yellowish-brown reddish-blue reddish-brown yellowish-brown brownish-yellow reddish-brown reddish-yellow brown green green green brown non-pedunculated. pedunculated. non-pedunculated. non-pedunculated. non-pedunculated. non-pedunculated. short peduncles. non-pedunculated. pedunculated. non-pedunculated. pedunculated. pedunculated. pedunculated. short peduncles. In the Pteropoda the visual organ is rudimentary. either absent or it is In the Cephalopoda the organs of vision are large and highly developed ; in fact, the eyes of the typical Dibranchiate Cephalopoda are more highly organised than those of any other Invertebrate animal, A pair of eyes are situated in the orbital cavities at the sides of the head in all the Dibranchiata. The eye (Fig. 73) is more or less of globular form and con- sists of the following parts: cornea, tapetum, ciliary body, crystalline lens, vitreous humour, sclerotica, retina, white glandular body, and the optic ganglion* and nerve. * A great part of the eyeball is occupied by the optic ganglion. 2A 370 PHYSIOLOGY OF THE INVERTEBRATA. In the Tetrabranchiata, as represented by Nautilus and its allies, the eye has no cornea, lens or vitreous humour. It is @ mere cup or cavity lined by the retina. ae f ence — wo ve! P aN al \ a! WHS OTN NW) — u AN rp C u 7] ‘ : t a Fic. 73.—EYE oF Sepia. (After GEGENBAUR.) a= lens. 4 = anterior chamber. c = cornea. d = ciliary body. e = cartilage ofiris. = sclerotica. g=tapetum. = cephalic cartilage. 7 = optic. ganglion, & = white glandular body. = pigment layer. o = outer and inner layers of retina. 2 = optic nerve. In Onychoteuthis, Ommastrephes, and allied’ genera, the crystalline lens is exposed to the sea water; this is due to the entire absence of the cornea. The eye of the Dibranchiata has been stated to resemble the Vertebrate eye, but this resemblance is merely superficial. In fact, “the rods and cones of the Vertebrate eye exactly correspond with the crystalline cones, &c., of the Arthropod eye; and the reversal of the ends, which are turned towards the light in the Vertebrata, is a necessary result of the extra- ordinary change of position which the retinal surface under- goes in them.” The aboveis an additional fact substantiating PHYSIOLOGY OF THE INVERTEBRATA. 371 the theory, that the Vertebrata have been developed from the Arthropoda rather than from the Mollusca, (See Chapter X.). In this chapter we have seen that many of the lower animals have tolerably well-developed organs of sense, and as such organs are the means of awakening consciousness, it is reasonable to conclude that, on the whole, every nervous system, however little developed, in the Invertebrata as well as the Vertebrata, may be traced to a conscious cellular part, in continuous relation with two nervous systems, the one afferent, through which sensory excitation is conveyed, the other efferent, by which motor incitation is transmitted. The mode of action of such a mechanism is evidently reflex action, and, in fact, there is not a central nervous act, from the Protozoa to the highest Vertebrata, which cannot be traced to reflex nervous acts. rst of all, the reflex action is absolutely unconscious; but in a later phase the nervous cell becomes conscious of vibration of its molecules; it experiences the sensations of touch, taste, smell, &c., more or less varied ac- cording as the organ or organs are more or less differentiated. At the same time it has impressions of pain, but in the lower animals these impressions are only momentary—there is no memory. Later still, however, this faculty becomes mani- fested ; which is followed by the co-ordination of impressions, sensations, &c., in other words—understanding, intelligence, or reason, comes into play. But behind all this labyrinth of ‘psychical phenomena there are simply reflex acts, transformed sensations and impressions. It has often been stated that animal “intelligence” is merely due to instinct and not to reason; that instinctive actions are not the result of ex- perience or of previously acquired knowledge through the senses, whilst those of reason can be readily traced to these sources. Many acts of the Insecta and the Arachnida, for example, such as slave-making, cell-making, web-making, &c., are described as due to instinct; but there are many actions among these Invertebrates which appear to come under the head of reason. Among these may be mentioned the 372 PHYSIOLOGY OF THE INVERTEBRATA. following: (a) Certain moths formerly entered the hives of the working-bee, and thereby caused great damage to the comb, &c. To prevent this nuisance the bee built a barrier, which now prevents the entrance of the larger intruders, yet at the same time allows the entrance of the rightful owner. (6) On the authority of an American naturalist, a pastrycook in Chicago found his shop invaded by a colony of ants, who feasted nightly on the delicacies deposited on a certain shelf. After cudgelling his brains for some time in order to discover a plan for stopping the depredations of the active insects, he resolved to lay a streak of treacle around the tray containing the coveted food. In due time the ants came forth in their hundreds, and were led towards the feast by their chief, On reaching the line scouts were then sent out to survey, and eventually “the word of command ” was passed around, and instantly the main body of the ants made for a part of the wall, where the plaster had been broken by a nail. Here each snatched up a tiny piece of mortar and returned to the spot indicated, where their burdens were deposited upon the molasses, By this means, and after an infinite amount of labour, a bridge was formed, and the triumphant army marched forward to partake of the fruits of victory, the pastry- cook meanwhile standing by filled with wonder. (¢) The dens or burrows of the trap-door spiders having been entered by large predacious insects, these spiders constructed smaller lateral burrows, provided with trap-doors, into which they can now retreat in case the dens are forcibly entered. In this way these spiders protect themselves against enemies. (d) The modes of building webs across various streams; the strengthening of webs by buttress-like devices, when they are constructed in gorge-like and windy situations: these facts, combined with the power of the spider to adapt itself’ to every possible circumstance, seem to point out that the , spider (as well as many other Invertebrates) is not guided merely by “blind instinct,” but by that which is the equiva- PHYSIOLOGY OF THE INVERTEBRATA. 373 lent of mind, and which is capable of developing with every generation—7.c., according to the Darwinian law. But it is not our intention to go fully into the subject of animal intelligence as displayed in various groups of the Invertebrata ; such information the reader will obtain by con- sulting special treatises devoted to this fascinating subject.* * Morgan’s Animal Life and Intelligence; Romanes’ Animal Intelligence ; and Lubbock On the Senses, Instincts, and Intelligence of Animals, with special reference to Insects. CHAPTER XII. MOVEMENTS AND LOCOMOTION IN THE INVERTEBRATA, In this chapter we give an account of locomotion and other movements in the Jnvertebrata. There is scarcely any species in the animal kingdom, which is not more or less endowed with the power of movement or motility ; but it is not essentially a property inherent in organised matter ; for many histological elements are destitute of it, and when an animal is only differentiated in a small degree, motility is the attribute and the function of a special tissue, at least in its most perfect mode. In the lowest animals, where there is no differentiation of parts, the whole body is constituted of a substance which is contractile and which changes its form perpetually— emitting and retracting pseudopodia unceasingly. The pseudopodia are the first organs of motion; but they are simply expansions of the substance of the body—viz., the sarcode. The first effort of differentiation appears to be the formation of cilia and flagella. In this case these expansions are no longer transitory; for they have a fixed and definite form. They are persistent organs, constituting the principal organs of locomotion in the Jnfusoria. As we ascend in the zoological scale muscles become differentiated ; and by the alternate shortening and lengthening of these muscles, move- ments of the body are brought about. Muscles are present in all but the simplest animals—i.e., in all animals higher than the Protozoa and Porifera. PHYSIOLOGY OF THE INVERTEBRATA. 375 THE PROTOZOA. In these animals a distinct muscular tissue has not been demonstrated, but the sarcode of their bodies is contractile. It may be mentioned, however, that the contractile stalk or peduncle of Vorticella contains a differentiated, longitudinal muscular fibre, which is capable of contracting so as to give the stalk the form of a spiral. The organs of locomotion in the Protozoa are the pseudo- podia, flagella, and cilia. In the Ameba it is by means of pseudopodia that the animal moves; ‘it emits them in the direction in which it is going, then it retracts them, while other parts of the mass are in their turn elongated. The whole body moves by creeping. This organism in moving has the aspect of a drop of oil moving along. ‘To explain the mechanism of this movement, it must be supposed that the extended pseudo- podium seizes some point of support with its free end, then, in contracting, draws the entire mass of the body up to this.” According to M. Rouget the retraction of the pseudopodia is the analogue of muscular rigidity, the emission of these organs being due to internal pressure; and that the hyaline substance of the pseudopodia is a kind of hernia of the ectosarc, “resulting from a diminution of the elastic resistance at the point where each pseudopodium appears, with an increase of elasticity in those parts of the ectosarc where pseudopodia are not produced. When the elastic tension of these parts diminishes, and returns to its original state the pseudopodium re-enters into the mass.” M. Rouget further states that in Ameba terricola, the most external portion of the ectosarc shows “strie of a granular appearance which may be identical with the strie or contractile fibrils of the ectosarc of the ciliated Infusoria—Stentor, Spirostomum, Paramecium, &e.” The Gregarina moves in a worm-like, gliding, fashion, but 376 PHYSIOLOGY OF THE INVERTEBRATA. very slowly. This movement, which only occurs occasionally, is due to the contractile nature of its body. The Flagellate Infusoria are provided with flagella; these are appendages which have a dual function, being organs of locomotion as well as of prehension. “ The Protozoon with its flagellum executes the most varied movements, moving first in one direction, then in another, and in different planes; sometimes the animal curves about entirely; but most frequently, when it uses the flagellum as an organ of prehension, it extends the whole length of the organ; the basal part remaining completely immovable and rigid, while the free end alone executes movements destined to drive food to the mouth, which is generally situated at the base of the flagellum.” In certain genera of the Flagellata (among these the Peridinew), there are organisms which have the power of throwing off their flagella before entering into a dormant — state ; and they can as readily regenerate these important organs. (Biitschli.) “In Anthophysa, there are two motor organs—the one a stout and comparatively stiff flagellum, which moves by occasional jerks, and the other a very delicate cilium, which is in constant vibratory motion.” Drs. Dallinger and Drysdale* (who have so thoroughly worked out the life-history of several species of Monads or Flagellata) state that in some of these organisms there is a peculiar structure, which is intimately connected with the bases of the flagella, this appears to be muscular and is the probable cause of movement in the flagella. They also state, “that in every instance where there was only one flagellum, or where the two arise and move from the same point, their insertion in the, body-sarcode was always in front; so that the flagellum or flagella had a pulling motion like that of the paddle of an ancient coracle ; never the pushing motion from the stern like the sculling or rowing of a modern boat. This ie Monthly Microscopical Journal, 1874, p. 264; and 1875, p. 190. | ( | PHYSIOLOGY OF THE INVERTEBRATA. 377 evidently arises from the complete flexibility of the flagella, by which a propelling motion plainly could not be ap- plied.” The diameter of the flagellum of some forms is only 0.000004885 26 or the 552,qth of an inch.* In the Ciliata, the outer surface of the body is provided with vibratile cilia. These are organs of locomotion, touch, and prehension; and they may also aid in the function of respiration by causing a renewal of the water, which furnishes the necessary air for the function of respiration. The cilia of these animals are homogeneous structures con- tinuous with the ectosarc. . The Ciliata are divided as follows— CrLta. They are of equal length and distributed Holotricha . . all over the body, : Heterotricha . the whole surface of the body. They are situated only on the ventral Hypotricha . side of the body. They form a zone round the anterior They are of unequal length, but cover Peritricha . part of the body. As already stated certain Jnfusoria have a portion of the protoplasm differentiated, so as to suggest a body comparable to the muscular fibres of the higher animals. This filament, or myophane, occurs in the peduncle of the Vorticelle ; and it is by this means that the stalk or peduncle is capable of forming a spiral, when the animal is disturbed. * See the paper by the Rev. W. H. Dallinger, F.R.S., inthe Transactions of the Royal Microscopical Society, 1878, p. 174. 378 PHYSIOLOGY OF THE INVERTEBRATA. THE PORIFERA OR SPONGIDA. Movements in these animals are caused by the contractile material of the body-substance and of the flagella; the latter . being used to aid respiration, &c. The embryos of certain Porifera are richly ciliated, and thereby become free-swimming larvee. THE C@LENTERATA. The movements of Hydra are performed partly by true muscular fibres, and partly also by the contractions of the body-wall. The tentacula are used for locomotion as well as for prehension. In the Actiniw, locomotion is brought about by the contractions of the disc of the foot. Dr. G. J. Romanes* has made a thorough examination of the locomotor system of the Medusew, from the standpoint of experimental physiology. As these researches would fill a volume in themselves, we must refer the reader desirous of information on the subject to the original memoirs mentioned in the foot-note. However, ‘it is known to every one that the Meduse are naturally locomotive animals, the various species‘ swimming more or less rapidly by means of an alternate contraction and dilatation of the entire swimming- organ. It may not be so generally known’ that these swimming-movements, although ordinarily rhythmical, are, at any rate in the case of some species, to a limited extent voluntary—using the latter term in the same sense as it is applicable to invertebrated animals in general. For instance, if Sarsia or Aurelia, &c., be gently irritated, the swimming- motions immediately become accelerated, and the acceleration persists for some time after the irritation has been withdrawn; but to secure this result, the irritation must not be of such a character as an inanimate object might supply. Again, individuals belonging to some discophorous species of the * See Philosophical Transactions of the Royal Society, 1875, p. 269; 1877, Pp. 659; 1879, p. 161. PHYSIOLOGY OF THE INVERTEBRATA. 379 naked-eyed Medusw exhibit peculiar movements on being alarmed; but I am not sure whether these are, as is most probable, purely involuntary, or performed with the view of affording protection to the more vital parts of the animal. Possibly the object may be to decrease the buoyancy of the nectocalyx, and so escape from the source of injury by sinking in the water. At any rate, these peculiar movements consist of a sudden folding together of the entire nectocalyx, con- sequent on an abnormally strong contraction of the swimming- muscles; and this contraction, besides being of unusual strength, is also of unusual duration. Thus the last idea of this movement will perhaps be gained by regarding it as a sort of spasm. The time during which this spasmodic con- traction lasts is pretty uniform in different individuals of the same species ; but it varies in different species from three to six seconds or more. In all cases the disappearance of the spasm is comparatively gradual, the nectocalyx re-expanding in a slow and graceful manner, instead of with the rapid motion characteristic of ordinary swimming. These move- ments only occur when the animal is being injured, or threatened with injury.” (Romanes.) Romanes has shown that the lithocysts are the exclusive seats of spontaneity, so far as the so-called “ primary move- ments” are concerned ; aud he has failed to detect the slightest evidence of spontaneity on the part of the contractile zones, as asserted by Dr. Eimer. The tentacula of the Meduse are prehensile organs aut of seizing upon and destroying animals of far more complicated structure than themselves. THE ECHINODERMATA. In these animals the muscular system is well developed ; its fibres are flat and without transverse striz. The natural movements of the Hchinodermata have been 380 PHYSIOLOGY OF THE INVERTEBRATA. studied by Drs. Romanes and Ewart ;* and they have shown that the ambulacral system is instrumental in the locomotion of all these animals, except the Ophiwridea. " The Asteridea.—(a) The common starfish (Uraster rubens) crawls upon a flat horizontal surface at the rate of two inches per minute. “The animal usually crawls in a determinate direction, and, while crawling, the ambulacral feet at the end of each ray are protruded forwards as feelers ; this is parti- cularly the case with the terminal feet on the ray, or rays, facing the direction of advance. When in the course of their advance, these tentacular feet happen to come into contact with a solid body, the animal may either continue its direction of advance unchanged, or may deflect that direction towards the solid body.” Uvaster rubens has the power of ascending per- pendicular surfaces, and also of attaching itself to solid bodies, The ambulacral feet are so strong in holding on to a perpen- dicular surface, that the feet of one or two rays are sufficient to support the animal when its body is distended in a hori- zontal position (Fig. 74). If Uraster is turned over on its dorsal surface upon the flat floor of a tank, it does not occupy more than half a minute in righting itself. This is done by, a number of the ambulacral feet of three rays getting a firm hold of the floor of the tank; this being done, the animal turns a complete somersault—the disc and inactive rays being thrown over the active ones with considerable rapidity. (>) The sun-stars (Solaster) move about in a similar manner to Uraster ; but the method of righting themselves is slightly different from that just described. (c) Astropecten aurantiacus—Romanes and Ewart state that the ordinary locomotor movements of this species are highly peculiar. The general form of the animal resembles Uraster, although its disc is proportionally larger, and the whole animal smaller. Its ambulacral feet are pointed tubes, about a quarter of an inch long, and unprovided with any * Philosophical Transactions, 1881, p. 829. 381 PHYSIOLOGY OF THE INVERTEBRATA. “When the animal is not walking, these sucker at the tip. feet are nevertheless in a constant state of movement, and their movements are then of a peculiar writhing, almost CLIVMY PuY SANVNOY -4/p) “aOVaNaAS AVINOIGNATUTG V OL NO DNIGION waLsvaQ—'?Z ‘og vermiform character—twisting about in various directions, and frequently coiling round each other. When fully pro- truded, however, they are perfectly straight and stiff.” A ’ 382 PHYSIOLOGY OF THE INVERTEBRATA. number of these feet are continually being retracted, while others are being protruded, and this state of affairs goes on alternately.* These animals can crawl up perpendicular surfaces, but are very soon tired. This is due to the absence of any dif- ferentiated structures in the form of sucking discs. The mode of locomotion of Astropecten is peculiar. Upon a dry, flat surface, it “ points all the feet of all the rays in the direction of advance, and then simultaneously distends them with fluid ; they thus become so many pillars of support, which raise the animal as high above the flat surface as their own perpendicular length. The fluid is then suddenly with- drawn, and Astropecten falls forward flat with a jerk. This manceuvre being again and again repeated at intervals of about a quarter of a minute, the animal progresses in a uni- form direction at the rate of about an inch per minute. In this mode of progression, all the feet of all the rays are co- ordinated in their action for determining one definite direction of advance—those in the ray facing that direction acting forwards, or centrifugally, those in the hinder rays backwards, or centripetally, and those in the lateral rays sideways.” When Astropecten is walking along a flat horizontal surface under water, its mode of locomotion is the same as the above, only the motion is very rapid. “It appears, however, as if the feet, besides being used as walking poles in the manner just described, are also used to sweep backwards along the floor of the tank, and so to assist in propelling the animal forwards after the manner of cilia. Therefore, while walking in water, Astropecten is kept stilt-high above the surface on which it is walking, by some of its feet, while others of its feet are engaged in these sweeping movements.” Astropecten has a rapid rate of movement, being between one and two feet per minute. When placed upon its back, it ° has the power of righting itself very rapidly. * The feet usually remain extended for a quarter to half a minute, but very suddenly collapse. PHYSIOLOGY OF THE INVERTEBRATA. — 383 (d) The Ophiuridea.—tIn the brittle-stars the ambulacral feet are only rudimentary, although exceedingly active; they are devoid of suckers; and their mode of protrusion and re- traction is exactly like that of Astropecten, but more rapid in . ne tS (After ROMANES and EWART.) Fic. 75.—LOCOMOTION OF OPHIURA, action. These animals are much the most actively locomotive of all the starfishes; ‘‘ and the reason is, that having discarded the method of crawling by.the ambulacral. system, which is common to nearly all the other Echinoderms, they have adopted instead a completely new, and a much more effectual 384 PHYSIOLOGY OF THE INVERTEBRATA. method. ‘The muscular system of the rays is very per developed, enabling these long and snake-like appenda perform with energy and quickness a great variety of s like writhings. As the movement of all the arms is co nated, the animal is able by these writhings to shuffle along flat horizontal surfaces at a considerable speed. when it desires to move still more rapidly, it adopts a1 plan. If the animal is advancing in the direction c arrow (Fig. 75), one of its rays, I, is pointed straighti direction ; the two adjacent rays, 2 and 3, are throw: wards as far as possible, and then, by a strong ‘contr downwards upon the floor of the tank, these two rays ° elevate the disc, and, while keeping the disc so ele throw themselves violently backwards into the for crescents, as represented in 2’ and 3’. The result o movement is to propel the animal forwards—ray 1 pushed into the position 1', while rays 4 and 5 are dr along into the position 4’and 5’. As soon as the rays 2 have assumed the position 2’ and 3’, they are again, w an instant’s delay, protruded straight, to be again ins thrown into the form of the curves 2' and 3’. Tht animal advances by a series of leaps and bounds, whicl between 14 and 2 inches in length, and which follo another with so much rapidity, that a lively Ophiur easily travel at the rate of 6 feet per minute. While travelling, the ray, I, is usually kept straight pointe partly uplifted—doubtless in order to act as a feelex sometimes the animal varies its method of progression, to use two pairs of arms for the propelling movement in this case the remaining arm is, of course, dragged b and so rendered useless as a feeler. Ophiwra is able any pair, or pairs, of its arms as propellers. indifferentl in all cases it so uses them by resting their outer, or thirds wpon the tank floor, and at each leap raising remaining two-thirds, together with the anterior part: disc, off the floor; at the end of each leap, howeve PHYSIOLOGY OF THE INVERTEBRATA. 385 whole animal (except, perhaps, the elevated feeler-ray) lies flat upon the floor.” (Romanes and Ewart.) Ophiura when placed on its back has the power of righting itself; but it is unable to ascend perpendicular surfaces owing to the rudimentary condition of its ambulacral ap- paratus. (e) The Hehinidea.—Unlike the rapid movements of the starfishes, the Echini have a slow rate of locomotion. Along a horizontal surface it is six inches per minute, while up a perpendicular surface it is only a quarter of an inch per minute. The ambulacral feet or pedicels have a greater power of anchorage than the same appendages of the star- fishes. In Hchinus the pedicels are also used as feelers. When a perpendicular surface is reached, the animal may either ascend it or crawl along for an indefinite distance, feeling it all the way with its pedicels. When an Echinus is inverted upon its aboral pole, it has the power of righting itself, although it is a much more difficult task than is the case with the starfishes. This is due to the formation of its body—for it is a rigid, non-muscular, and globular mass, whose only motive power available for conducting the evolu- tion is that which is supplied by relatively feeble pedicels. _ The spines and lantern* are also used in locomotion. When the animal is taken out of the water and placed upon a table, Romanes and Ewart observed that it began to walk in some definite direction—i.¢., in a straight line, and in doing so the only organs used for the purposes of locomotion are the spines and the lantern, the ambulacral feet under these circumstances not being protruded at all, The rate of locomotion is very slow—viz., about one inch per minute. The so-called “ Aristotle’s lantern” is capable of being protruded and retracted; and these movements are perfectly rhythmical, at the rate of three or four revolutions per minute. The pedicellarize of Hchinus assist in locomotion. It is by means * “ Aristotle’s lantern,” or dental apparatus, in Hehinus is worked by thirty muscles. 28 386 PHYSIOLOGY OF THE INVERTEBRATA. of these small forceps or grasping organs, that the animal is capable of “climbing perpendicular or inclined surfaces of rock, covered with waving sea-weeds.” In the Asteridea and the Holothuridea, the pedicellariee are only rudimentary— changed habits of life on the part of these animals have caused the inherited appendages to dwindle from disuse. For instance, “the Ophiwridea never climb sea-weed covered rocks at all, and those starfishes which do so have their ambulacral feet restricted to the ventral surface; it would therefore be useless for these animals to have well-developed pedicellarize, adapted to hold sea-weeds steady in the manner which may be of so much use to the globular Echinus, who throws out on all sides feet feeling for attachments.” Spatangus (one of the Hchinidea) crawls about somewhat slower than Hchinus; and it is incapable of climbing per- pendicular surfaces. When placed upon its back it has even a greater difficulty in righting itself than Echinus. It rights itself entirely by its long and mobile spines. (f) The Holothuridea.—These animals “ craw] slowly, and indulge in prolonged periods of quiescence. They are, how- ever, able to climb perpendicular surfaces.” THE TRICHOSCOLICES. The Yurbellaria—Although the parenchyma of these animals is contractile, they have only a very feebly-developed muscular system. The muscular fibres appear to be un- striated. The 7urbellaria are divided into (a) the Rhabdocela and (0) the Dendrocwla. The smaller species of the first- mentioned sub-order swim by means of their ciliated epithe- lium; whereas the larger species appear “to float from place to place by means of their epithelium.” The Dendrocela, on the other hand, crawl along somewhat in the manner of the Gasteropoda. Sometimes the tentacle-like processes (situated at the anterior end of the body) are used as oars when these animals move upon the surface of the water. According to PHYSIOLOGY OF THE INVERTEBRATA. 387 - Martens,* Planaria lichenoides moves by means of the pro- truded lobes of its muscular pharynx. The Rotifera—The muscular system of these animals is composed. of unstriated fibres. The most characteristic ap- paratus is the so-called “wheel.” By its agency these animals swim freely about, or, when at rest, create certain water currents. The “ wheel” or trochal disc and its append- ages vary in different genera. The edge of this disc is generally ciliated, but in some forms (¢.g., Stephanoceros) it is produced into ciliated tentacula. Besides being organs of locomotion, the appendages of the trochal disc are indirectly prehensile organs. The Zrematoda and -Cestoidea.—The movements of the body are due to sucking-cups and cavities (i.c., suctorial organs), horny hooks and spines, THE ANNELIDA. Muscular tissues are highly developed in the Annelida. In Hirudo, the muscular system into which the integument is continued, forming a dermo-muscular tube, consists ex- ternally of a circular muscular layer, and internally of a longitudinal muscular layer. Both these layers are traversed by radial muscle-fibres, which run from the interior of the body to the surface. At the lateral edges of the body, the radial muscles pass directly from the dorsal to the ventral surface. Certain muscle-fibres run obliquely. In Hirudo, locomotion is chiefly effected by means of the suckers, which contain both circular and radiating muscle-fibres. The posterior sucker is attached to something, then the animal stretches itself forward to its fullest extent and fixes its anterior sucker. After releasing the posterior sucker the body is powerfully contracted. The posterior sucker now attaches itself close to the anterior sucker, which is then loosened and thrust forward as before. Hirudo can also * Mémoires de V Académie Impériale des Sciences de St. Pétersbourg, tome 2. 388 PHYSIOLOGY OF THE INVERTEBRATA. swim, though its motion in water is rather slow. ‘ Whilst - swimming, the body becomes flattened by the contraction of the vertical muscle-fibres, which pass from the dorsal to the ventral surface; and then by perpendicular quick serpentine undulations, it progresses like a wavy ribbon.” The muscle-fibres are developed, as in the higher animals, out of nucleated, spindle-shaped, muscle-cells. The fibres are not transversely striated, but they are enveloped in a structureless sheath. In the Oligocheta, represented by Lwmbricus, the muscular system is somewhat similar to that already described. Beneath the cuticle and hypodermis there is an external layer of circular muscle-fibres and an internal one of longi-~ tudinal muscle-fibres ; there are also radiating and obliquely intertwisted fibres. On the ventral surface of each somite (in Lumbricus) four pairs of minute pits occur, from each of which projects a long hook-like seta or bristle. The sete or bristles can be projected or retracted at will, and they aid locomotion in a somewhat similar manner to the suckers of Hirudo. Both these devices are the means of anchorage, while the subcutaneous muscles produce the vermicular motions of the body. The Polychaeta, or marine worms, are usually provided with parapodia (rudimentary limbs), having numerous chitinous seta embedded in them. In the body-wall the circular and longitudinal muscle-fibres are well developed. The sub- order Lrrantia contains the free-swimming Polycheta. The head of these animals contains tentacula, and generally cirri, and the anterior portion of the pharynx is like a pro- boscis, being eversible. The parapodia are well developed in the Lrrantia. The Tubicola, or sedentary Polychwta, have no cirri, and the parapodia are only slightly developed. None have a proboscis or eversible pharynx. The Zubicola are not free and actively locomotive animals like the Errantia. They live in tubes, which they construct either by gluing together PHYSIOLOGY OF THE INVERTEBRATA... 389 sand and pieces of shells, or ‘by secreting a chitinous or calcified shelly substance.” Locomotion in the Annelida is aided by means of aciculi and sete. These are used as fulcra when they creep, or as oars when they swim. THE NEMATOSCOLICES. The general movements of the body in the Nematoidea are due to a subcutaneous circular muscle-layer; and its longitudinal and transverse muscles are quite distinct from each other. In most of the Nematoidea the longitudinal muscles form four large bands—two on the ventral and two on the dorsal surface. These animals are devoid of limbs, though they may sometimes be provided with setiform spines or papillee. Tue MyYRIAPoDA. Great advance is observed in the mode of locomotion in the Arthropoda. There is no longer any contractile envelope like the Annelida and their allies, for here the muscular fibres are all grouped into distinct masses or individual muscles, which are inserted into such and such a limb or part of the body by means of tendons. In the Arthropoda all the muscles are transversely striated, Locomotion in the Myriapoda is produced by means of the limbs. Almost all the segments bear at least a pair of articulated limbs terminated by claws. The Chilopoda (centipedes) usually live in the earth or under stones; they run with considerable swiftness in pursuit of their prey, and can even progress backwards by the aid of their tail-like posterior limbs, which at other times are dragged helplessly behind them. The Diplopoda or Chilognatha (millipedes) possess two -pairs of limbs on each segment except the posterior segment, which is devoid of these organs. The movements of these animals, 390 PHYSIOLOGY OF THE INVERTEBRATA. notwithstanding their immense number of limbs, are always very slow, and they generally try to escape danger by rolling themselves up into a ball. Tue INSECTA. In this class the thorax always bears the organs of loco- motion, which, in most insects, consist of six ambulatory limbs and four wings. The form of these organs is very various, but their general anatomy is always similar. The centre of the ventral surface of the thorax is occupied by a narrow piece termed the sternum, which frequently projects as a ridge externally, and generally gives off an internal process for the insertion of muscles. On each side of this are the sockets for the legs, of which each segment of the thorax bears a pair. The first joint or coxa of the legs is sometimes immovably attached to the thorax, sometimes articulated with it by a sort of ball-and-socket joint. The next four joints are termed respectively—the trochanter, femur, tibia, and tarsus. The tarsus or foot sometimes con- sists of one, but generally of from three to six joints. The terminal or sixth tarsal joint is furnished with two curved and pointed claws or ungues, often toothed, and in many cases accompanied by a pair of soft membranous organs or pulvilli, which are very distinct in Musca (house fly). These adhere, like suckers, to any object against which they may be applied, and thus enable their possessors to walk securely even in a reversed position. The ambulatory limbs and their various joints undergo very many modifications in the different orders and groups of the Insecta ; always, however, in exact coincidence with the habits of the individuals—in leaping or jumping insects, such as Eupteryx,* Locusta, and Gryllus, the posterior limbs are much lengthened and the femoravery thick, forming powerful jumping organs. In Mantis, the anterior limbs are so much * See Dr. Griffiths’ The Diseases of Crops, p. 51 (Bell & Sons). PHYSIOLOGY OF THE INVERTEBRATA. 391 three. When the tripod which is moving has come to the developed as to give the insect a praying attitude—these limbs are used as prehensile organs. The anterior limbs of Gryllotalpa (the mole cricket) are modified to suit this insect to its burrowing habits. In those insects which swim, such as Dytiscus, the tarsi are generally flattened, ciliated, and disposed like oars. In fact, Dytiscus possesses organs of natation, of burrowing, of reptation, and of flight. This Cole- opterous insect is, in a sense, comparable to the great epic poet’s fiend in the nature of its various movements, and also the different elements in which it is capable of living :— “Through strait, rough, dense, or rare, With head, hands, wings, or feet, pursues its way, And swims, or sinks, or wades, or creeps, or flies.” * These wonderful modifications of a general plan are certainly strong points in the theory of natural selection. “It may metaphorically be said that natural selection is daily and hourly scrutinising, throughout the world, the slightest variations; rejecting those that are bad, preserving and adding up all that are good; silently and insensibly working, whenever and wherever opportunity offers, at the improvement of each organic being in relation to its organic and inorganic conditions of life. We see nothing of these slow changes in progress, until the hand of time has marked the lapse of ages, and then so imperfect is our view into long-past geological ages, that we see only that ihe forms of life are now caterers from what they formerly were.” t Mr. H. H. Dixon, of Trinity College, Dublin, has recently made some observations on the locomotion of various insects, and he finds that in the case of those which move quickly, the best method for observation is instantaneous photography. Instantaneous photographs of moving flies show that they move the front and hind legs of one side almost simultangously with the middle leg of the other, while they stand on the other. * Milton’s Paradise Lost. + Darwin’s Origin of Species (6th ed.), p. 65. 392 PHYSIOLOGY OF THE INVERTEBRATA. ground, the other tripod is raised, and so on. Dixon’s observations show, however, that while no leg of one tripod ever moves simultaneously with any leg of the other, yet there ‘is a succession in the movements of the legs of each ‘tripod, The hind leg on one side is first moved, then the middle on the other, and when the hind leg has been moved forward and almost reached the ground, the front leg of that side is raised. The middle leg andthe front leg of the opposite sides come to the ground almost simultaneously. It is usually just when the hind leg is reaching the ground, and the front leg is beirig raised, that the tripod on which the fly is resting thrusts the body forward. After the movement of each tripod there appears to be a short pause, during which all six legs are on the ground together. Dixon has also observed the tripodic walk in earwigs, water scorpions, aphides, and some beetles. In the case of some slowly moving beetles and aphides, which can be observed without photographic means, quite irregular movements have been observed. By cooling aphides, they can be made to move very slowly. In this condition one was observed to move its legs in slow succession in the following order:— (a) Right hind, (0) right middle, (¢) right front, (d) left hind, (¢) left middle, (/) left front. This walk was continued for some time, occasionally interrupted by the following order, or some other quite irregular walk:—(a) Right hind, (0) right middle, (¢) left hind, (d) left middle, (¢) left front, (7) right front. In caterpillars the legs forming a pair seem to move simul- taneously ; the motion begins at the posterior end of the body, and proceeds regularly forward till the most anterior. pair of legs are moved.* ' According to Darwin,} Papilio feronia, of Brazil (one of the * Mr. Dixon kindly sent the author several photographs illustrating the above movements, but unfortunately they cannot be reproduced as wood- cuts. t+ Journal of Researches (chaps ii.). PHYSIOLOGY OF THE INVERTEBRATA. 393 Lepidoptera), uses “its legs for running,” this being an ex- ceptional habit among butterflies. The wings of insects are appendages attached to the meso- thorax and metathorax. They are composed of a double membrane, supported internally by a variable number of nervures. These serve to keep the wings extended. There are never more than two pairs of wings, sometimes only one, and they vary in form. When they really serve for flight they are thin, translucent, and covered with microscopic scales as in the Lepidoptera; but the anterior wings often become hard and opaque, and becoming useless as organs of flight, form elytra—z.e., protecting sheaths, for the posterior pair of wings: such an arrangement occurs in the Coleoptera. Although the wings of insects are usually four in number, the posterior pair is frequently absent, and, in fact, the Diptera is characterised by the possession of only one pair of wings. In these insects a pair of small knobbed filaments, situated on the sides of the thorax behind the wings, and which are called halteres, have been regarded as the representatives of the posterior wings. In almost every order of the Insecta there are genera, species and individuals, as certain female aphides, which are apterous or wingless. “The movements of the wings are produced by two extensor and several smaller flexor muscles,* which arise from the middle and posterior thoracic segments, and are inserted on the tendinous process at the base of each wing. The size of these muscles is proportionate to the size of the wings and their mode of use in flight. They are, consequently, all equally developed when the four wings participate equally * Dr. Allen Thomson has measured the diameters of the muscular fibres in the Insecta with the following results :— Greatest diameter e : , 3 . sto inch. Least “6 s < . - & 3 : i rts on Average ,, : atu on F : Distance of transverse striz 3 ‘ ; . woot on 394. PHYSIOLOGY OF THE INVERTEBRATA. in the act of flying, as is the case with the Lepidoptera, Hymen- optera, the majority of the Newroptera, the Libelludide, Perlide, and finally, the Cicadide, and the Aphidide. The muscles of the anterior wings are comparatively smaller than those of the posterior, when the first are not used, properly speaking, except to cover the latter, as is the case with the Coleoptera, the Bugs, and many of the Orthoptera.” (Von Siebold.) There are also certain accessory organs which aid in the phenomenon of flight. Prof. Huxley says that “the air-sacs doubtless assist flight by the diminution of the specific gravity of the insect, which follows upon their distention.” Concerning the phenomenon of flight Sir Richard Owen has justly remarked that “in no part of the animal kingdom is the mechanism for flight so perfect, so apt to that end, as in the class of insects. The swallow cannot match the dragon~ fly in its aérial course ; this insect has been seen to outstrip and elude its swift pursuer of the feathered class: nay, it can do more in the air than any bird—it can fly backwards and sidelong, to right or left, as well as forwards and alter its course on the instant without turning.” * Tue ARACHNIDA. In the Arachnida the organs of locomotion are all fixed to the cephalo-thorax, and consist of eight pairs of limbs, strongly resembling those of the Jnsecta ; and almost always terminated by two hooks. The length of these organs is generally con- siderable, and they easily break; but, as in the Crustacea, the stump, after having cicatrised, reproduces a new limb, which increases by little and little, and ends by becoming similar to that of which the animal had been deprived. * The flight of the bee exceeds twelve miles an hour, and it will go four miles in search of food. Its wings, braced together in flight by a row of hooklets, bear it forward and backward, upward, downward, or suddenly arrested course, by a beautiful mechanical adaptation. (See Cowan’s Honey Bee.) For a full exposition of the flight of insects the reader is referred to the work of Chabrier in Jdém. du Muséum, tomes 6-8 PHYSIOLOGY OF THE INVERTEBRATA. 395 The Arachnida are entirely devoid of wings, and the organs of locomotion are never inserted on the abdomen. The Araneina may be conveniently divided into two groups —the wandering and the sedentary spiders. In the former group belong the swift-runner, the side-walker, and the vault- ing or leaping spiders. All the wandering spiders trust to their swiftness of movement in securing their food; and some of them can run in any direction. THE CRUSTACEA. In the lower Crustacea, represented, for example, by the Phyllopoda, Dr. G. O. Sars states that there are two modes of locomotion. In the case of Cyclestheria hislopi, one of these is accomplished when the animal is freely suspended in the water; in the other it takes place while it is at the bottom of the water; in the former case, it is a swimming motion; in the latter, a creeping or more generally a burrowing, motion. The swimming motion is performed exclusively by the aid of the antenne, the repeated strokes of which propel the animal through the water. During this motion, the antenne, together with the anterior part of the head, remain exserted from the front part of the shell, being moved laterally to a greater or less extent. The locomotion effected by this means is not very rapid, nor abrupt or jerking, but a perfectly even run through the water, whereby the animal as a rule turns the dorsal part uppermost. Not rarely, however, this attitude becomes changed, and the animal is often observed to revolve several times before breaking off the motion and sinking to the bottom. On the whole, the swimming motion appears to be effected with considerable effort, especially when the individuals are carrying a young brood; and hence this motion is never continued for any length of time, but takes place at intervals, the animal being more frequently found resting on the bottom or affixed to some submerged object. 396 PHYSIOLOGY OF THE INVERTEBRATA. The creeping or burrowing mode of locomotion, which takes place while the animal is on the bottom, is effected partly by the antennze, but more especially by the flexion and powerful extension of the trunk, the caudal plate being thus exserted from the shell inferiorly and moved rapidly behind, as it strikes against the bottom. This mode of locomotion has sometimes a distinctly jerking character. Often, by repeated strokes of the tail, the shell will be turned round several times in succession, and may thus get rather deeply buried in the loose muddy deposit at the bottom of the water. Dr. Sars, in his important paper (loc. cit., p. 33), also describes the movements of the shell, head, trunk, tail, eye, antennule, antenne, &c., but it is not our object to refer to these separate movements. In the higher Crustacea the organs of locomotion or limbs are connected in pairs with the different thoracic segments; there are frequently seven pairs, as in the Isopoda (eg., Oniscus), the prawns, and the Talitri (sand-hoppers); but in other Crustacea—eg., the crabs, crayfishes, and lobsters—there are only five pairs of limbs. The structures of these append- ages differ considerably: in some forms they are wholly foliaceous, membranous, and exclusively adapted for swim- ming; in others they have the form of small flexed columns, articulated, and disposed only for walking; in others, still, besides remaining adapted for this mode of locomotion, they become suited to act as so many small spades wherewith to dig the earth, and in that case they are enlarged and lamel- lated towards the extremity ; and still, finally, in others they terminate in forceps, and become prehensile organs, perform- ing at the same time the function of locomotion. In the swimming Crustacea, such as Astacus, Homarus, Palemon, &c., the abdomen terminates in a tail-fin, which is the principal organ of locomotion; but in those individuals which walk more than they swim, the tail-fin is, as a rule, very small, and folded under the thorax: in the crabs, for example, this .PHYSIOLOGY OF THE INVERTEBRATA. 397 portion of the body is reduced almost to nothing, and con- stitutes then a movable apron placed on the lower surface of the body between the limbs. In Astacus the ambulatory limbs are composed of seven separate joints: the basal joint being the coxopodite which is followed in succession by the following joints :—the basi- podite, ischiopodite, meropodite, carpopodite, propodite, and dactylopodite. THE Mo.uvusca. The movements in these animals are, as a rule, executed by means of a muscular organ, termed the foot, which varies greatly in its form, in accordance with the habits of the animal. The foot consists of a mass of muscular fibres, run- ning in various directions, by the contraction of which its movements are effected. Tn many of the Mollusca, the foot forms a flat disc, which adheres to any substance to which it may be applied, and thus, by the alternate contraction and dilatation of its different parts, enables the animal to crawl slowly along. In other forms, the foot is bent upon itself, so that its sudden extension causes the animal to perform a con- siderable leap (¢g., Cardiwm and Trigonia). This organ is also the means by which the burrowing species bury them- selves in the sand or mud; and in those species which bore in the solid rock, the foot is also called into requisition ; its surface in these cases being covered with minute silicious varticles, which assist greatly in the enlargement of its owner's wy dwelling. . 3ut although most Mollusca possess a greater or less power of :ocomotion, others are confined to a single spot, during all but the earliest period of their existence, when they are free- swimming organisms. In the non-locomotive Mollusca the foot is either wholly undeveloped (e.g., Ostrea), or serves merely to support a glandular organ, from which a chitinous or shelly substance is secreted, which serves to attach the 398 PHYSIOLOGY OF THE INVERTEBRATA, animal to submarine objects. This modification occurs in Mytilus, Pinna, &c.* : In the Pteropoda the function of swimming is performed by the flapping epipodia, which are muscular expansions, but it may be remarked that in these Mollusca “the rest of the foot is always small, and often rudimentary, in correspondence with the small size of the neural face of the body.” The locomotive organs of the Cephalopoda are the tentacula, which are arranged round the head, and furnished on their inner surface with numerous sucking-cups, which enable the animal to take a firm grasp of any object. By means of the tentacula t the Cephalopoda creep along the bottom of the sea with the head downwards. These animals also swim rapidly by the expulsion of the water from the branchial chamber, * For an account of the movements of various parts of certain bivalve Molluses, see the papers by D, M‘Alpine in the Proc, Roy. Soc, Edinb., vol. 15, p. 1733 vol. 16, p. 725. { The tentacula are also prehensile organs. CHAPTER XIII. REPRODUCTION AND DEVELOPMENT IN THE INVERTEBRATA. Every living organism possesses the power of reproducing its kind. The process by which this reproduction or pro- creation is maintained may be either asexual or sexual; and some scientists * assert a third mode of “ reproduction ”—viz., by spontaneous generation, abiogenesis, or heterogenesis, 4.¢., the origin of living organisms de nove, without parents. It is not our object to discuss the arguments for and against the theory of spontaneous generation, suffice it to say that the researches of Pasteur, Tyndall, Dallinger, and others, point out that “ no definite instance of life originating de novo has heen proved,” and their experiments appear to negative its possibility.t Yet, it has been stated that the facts adduced against the theory “do not appear to invalidate the possibility * See Dr. Bastian’s Beginnings of Life (1872); Bennett’s Physiology, p. 421; Pouchet’s Nouvelles Expériences sur la Géneration Spontanée et sur la Résistance Vitale, p, 110; and also the works of Prof. P. Mantegazza and MM. Bernard, Pennetier, Joly, and Musset. {+ Concerning the controversy on spontaneous generation, Prof. Huxley states that biogenesis (life from previous life) has been “ victorious along the whole line;” but at the same time he remarks ‘that with organic chemistry, molecular physics, and physiology yet in their infancy, and every day making prodigious strides, it would be the height of presumption for any man to say that the conditions under which matter assumes the qualities called vital, may not some day be artificially brought together.” And further the great biologist remarks, “that as a matter not of proof but of probability, if it were given me to look beyond the abyss of geologically recorded time, to the still more remote period when the earth was passing through chemical and physical conditions, which it can never see again, I should expect to be a witness of the evolution of living protoplasm from non-living matter.” 400 PHYSIOLOGY OF THE INVERTEBRATA. of abiogenesis occurring in certain conditions, and it is un- philosophical to assert the impossibility of its occurrence now or in some past time. The intimate relations known to exist between physical, chemical, and vital phenomena, depending on the laws of the conservation and transmutation of energy, and the theory of evolutional development, indicate the pro- bability of abiogenesis, and it is one of the problems of biological science to ascertain the conditions in which this may occur.” “In the domain of science any logical and necessary de- duction or induction ought to be admitted, though it may shock old ideas and shatter old dogmas. The same religious and metaphysical prejudices, which have been so deeply dis- quieted by the doctrine of evolution are still more alarmed and annoyed by the idea of spontaneous generation. But this may be changed as time rolls on, as has been the case with the Darwinian theory..... Not many years ago the majority of naturalists believed in the immutability of all organised beings, and, as every epoch had its special fauna and flora, it was necessary to recognise, as did the immortal Cuvier, a series of successive creations. When God, irreve- rently compared to the machinist of an opera, whistled once, an implacable cataclysm annihilated all the living world; when He whistled a second time, but creatively, a new fauna and a new flora rose to life. Thus had things to go on at every geological epoch. From the trilobite to the mammoth every species had thus to be formed by ‘ magical crystallisa- tion.’ Assuredly there was here spontancous generation of the most astonishing kind, but it shocked no one, because it was in more or less tacit accordance with metaphysical and religious ideas.” But all this is now changed, for the majority of, if not all, naturalists firmly believe in the doctrine of evolution, or the mutability of organised beings, as revealed by the genius of Darwin. Although spontaneous generation is, at the present time, ‘not proven,” we mention the fact that it is still looked PHYSIOLOGY OF THE INVERTEBRATA. 401 upon by some scientists as one of the “ modes of reproduc- tion.” ASEXUAL REPRODUCTION includes the processes of gem- mation, fission, endogenous cell formation; and a variety of asexual reproduction is known by the name of partheno- genesis. (a) Gemmation—In this mode of reproduction a small portion of the body enlarges and gradually increases in size. When fully developed this bud may either become detached from the parent and develop into a free organism (like the parent), or it may remain permanently attached to it, giving rise to a colony. (0) Fission.—This mode of reproduction, common in the lower animals (and of special importance in the formation of new cells), consists simply of a division of the animal into two or more parts. Each part then grows and ultimately assumes the same form as the parent; and possesses the same power of reproducing its kind. Should the division, how- ever, remain permanently incomplete, colonies of the animal will be produced. (c) Endogenous cell formation—This mode of asexual reproduction or agamogenesis occurs in the Protozoa. The animal becomes ehcysted—i.e., it surrounds itself with a cover- ing or cell-wall. After this, the nucleus becomes constricted and ultimately may be divided into many portions. The protoplasm then divides in a similar manner, and there may result two, four, eight, &c., cells, in each/ of which there is at least one nucleus.* These cells finally rupture the parent- cell and are set free. (d) Parthenogenesis.—As already stated parthenogenesis is a variety of asexual reproduction. In this case the whole development of the embryo is effected without the succour of fecundation. Parthenogenesis is the production of young, apparently without any previous congress with the male * Such a process is termed segmentation, and may be seen in the early stages of the development of the embryo of higher forms, 2 C 402 PAYVSIOLOGY OF THE INVERTEBRATA. organism ; and it is illustrated by the development of various forms of Medusw, Tenia, and of Aphides. SEXUAL REPRODUCTION.—This mode of reproduction, or gamogenesis, is the result of the fusion of two distinct elements—a male element, or spermatozoon, and a female element or ovum. These are differentiated cells, produced. in special organs, of the parent or parents, and by their coalescence a series of changes take place, which ultimately give rise to a new organism. These elements (3% and ¢ ) may be produced in the same individual (as in many Annelida and Mollusca): such a condition is termed hermaphroditism ; but in the majority of the Invertebrata the male and female organs are on different individuals, in other words, the sexes are completely separate. Prof. Huxley states that it is probable that hermaphro- ditism “was the primitive condition of the sexual apparatus, and that unisexuality is the result of the abortion of the organs of the sex, in males and females respectively.” Although some Invertebrates have both sexual organs on the same individual, these organs are often.so arranged that self-fertilisation is almost impossible. As already stated certain Mollusca and Annelida are hermaphrodites, but these all pair. Darwin* states that he had ‘not found a single terrestrial animal which can fertilise itself. This remarkable fact, which offers so strong a contrast to terrestrial plants, is intelligible on the view of an occasional cross being indispens- able; for owing to the nature of the fertilising element there are no means, analogous to the action of insects and of the wind with plants, by which an occasional cross could be effected with terrestrial animals without the concurrence of two individuals. Of aquatic animals, there are many self- fertilising hermaphrodites; but here the currents of water offer an obvious means for an occasional cross.” Darwin also remarks that he failed “to discover a single hermaphrodite animal with the organs of reproduction so perfectly enclosed . ” Origin of Species (6th ed.), p. 79. PHYSIOLOGY OF THE INVERTEBRATA. 403 that access from without, and the occasional influence of a distinct individual, can be shown to be physically impossible.” Darwin concludes, from a large number of observations and facts that ‘an occasional intercross between distinct individuals is a very general, if not universal, law of nature.” The male element or spermatozoon varies in form and size in different animals, but consists of a head and filiform appendage or appendages.* The spermatozoa move by vibrations in a fluid called the semen, where they exist in large numbers. The female element or ovum is a nucleated cell developed in the ovary. In all animals the ovum is nearly identical. Tt consists of a vitelline membrane, a protoplasmic contents or vitellus, a germinal vesicle (nucleus), and a germinal spot (nucleolus). As already stated it is the union of these two elements which give rise to offspring. Fecundation is brought about by various methods in the animal kingdom. But as far as the Invertebrata are concerned, these methods will be described more in detail later in this chapter. Suffice it to say that in the majority.of the unisexual Invertebrata copulation or the union of the sexes takes place. In animals higher in the zoological scale—for instance in fishes, the male discharges the semen over the spawn or ova of the female, for there is no act of copulation. In many of the Amphibia and Reptilia, the male clings to the back of the female, and then discharges the seminal fluid or semen over the ova as they pass through the uro-genital aperture. In the Aves and Mammalia, and also in many of the Invertebrata, the semen is introduced by the penis into the genital organs of the female. By any one of the above acts the ovum becomes fertilised : a series of changes occur which result in a more or less complete segmentation. If this segmentation or division is complete—i.e., involves the whole vitellus—it is called * In Astacus there are many appendages. 404 PHYSIOLOGY OF THE INVERTEBRATA. holoblastic. Holoblastic segmentation occurs in the Mam- malia, Batrachians, the lower Crustacea, Vermes, &c.; but ifthe segmentation is incomplete or involves only a portion of the vitellus, so that the remaining portion may be utilised as nourishment during the early stages of the development of the embryo, it is termed meroblastic. Meroblastic segmenta- tion occurs in the ova of Aves, Amphibia, Cephalopoda, the higher Crustacea, and the Insecta. The detailed description of the changes which occur in the ovum after fecundation belongs to embryology, consequently it is beyond the province of this volume, which treats of the Junctions of animals after birth. Nevertheless, we shall allude, in passing, to the broad outlines of the development of the fecundated ovum.* Besides the above-mentioned mode of sexual reproduction (viz., that of the fusion of two different elements), there is another mode termed conjugation, or the union of two similar protoplasmic masses. These may be derived from different parts of the same individual, or from two individuals of the same species. The union of these similar masses ultimately results in the development of a new organism. This mode of reproduction occurs in some Protozoa, THE Protozoa. The mode of reproduction in the Monera and Protoplasta is either by fission or by endogenous cell formation. In the former the cell divides into two portions, each portion gives rise to a perfect organism. In the latter mode of repro- duction a cyst is formed, and within this the protoplasm of the original cell divides into a number of segments which ultimately rupture the parent cell and escape as separate individuals. * For further details on the subject of embryology the reader is referred to Balfour’s Treatise on Comparative Embryology; and Foster and Balfour's Practical Embryology. PHYSIOLOGY OF THE INVERTEBRATA. 405 In the Gregarine reproduction occurs by endogenous division of the encysted body. Sometimes two full grown organisms come together, adhere, and then surround them- selves with a cyst. The result in each case is the forma- tion of segments, which become spindle-shaped cells, called pseudo-navicellae. These grow and finally rupture the cyst, and thereby are set free. The pseudo-navicelle are sur- rounded by cell-walls, but these burst, and the protoplasmic contents of each escapes as a moner-like cell resembling Protameba. The moner now becomes differentiated into ectosare and endosarc, and the young Gregarina is now amcebiform. In this stage of the development two arm-like projections appear: one of these lengthens and separates, forming a perfect Gregarina. The other elongates and absorbs the rest of the mass and also becomes a perfect Gregarina. This elongating stage has been termed by Van Beneden, the pseudo-filaria phase. Afterwards the body becomes shorter and broader, and a nucleus appears, the animal then passes into the adult form. The Jnfusoria propagate by fission, endogenous division, gemmation, and conjugation. In the Jnfusoria flagellata multiplication by longitudinal fission occurs in several genera. For instance, in Codosiga, the flagellum is first retracted and then fission takes place ; in Anthophysa the cell becomes encysted before the division occurs. / Drs. Dallinger and Drysdale have investigated the life- cycle of many genera and species of the Jnfusoria flagellata. Many of these forms multiply by— (a) Fission (with or without encystment). (6) Conjugation. In the case of conjugation, the body which is formed becomes encysted for a time, but ultimately the contents of the cyst divide into either large or small bodies, which are destined to assume the parental form. The complete life-history of Amphiplewra pellucida is 406 PHVSIOLOGY OF THE INVERTEBRATA. described by Drs. Dallinger and Drysdale* as follows— “development from a germ or sporule of extreme minuteness, and on the attainment of maturity multiplication by fission,t constantly and for an indefinite time; but-the vital power is at‘ intervals renewed by the blending of the genetic elements, effected by the union of two, when both are in an amceboid condition, from which a still sac results, in which germs or sporules are formed, which eventually escape, and again originate the life-cycle.” Drs. Dallinger and Drysdale have shown that the in- vestigations of Bastian, Gros, and others, on heterogenesis and the transformation of living forms, are erroneous. They state that as far as their researches on the Monads go, they are bound to say that not the slightest countenance is given to the doctrine of heterogenesis. ‘‘On the contrary, the life- cycle of a Monad is as rigidly circumscribed within defined limits as that of a mollusc or a bird. There is no indication of any unusual or more intense methods of specific mutation than those resulting from the secular processes involved in - the Darwinian law, which is held to furnish the only legitimate theory of the origin of the species.” The Infusoria tentaculifera multiply by (1) longitudinal fission, (2) “the development of ciliated embryos in the interior of the body. These embryos result from the separation of a portion of the endoplast, and its conversion into a globular or oval germ, which, in some species, is wholly covered with vibratile cilia, while in others, the cilia are confined to a zone around the middle of the embryo. The germ makes its escape by bursting through the body wall of its parent.” This free swimming organism rapidly assumes the adult form. (3) Conjugation takes place in these organisms, which * Transactions of Royal Microscopical Society, 1875, p. 195. + In the case of Tetramitus rostratus, fission proceeds for from six to eight hours; and in that of Dallingeria Drysdali there are from seven to eight acts of fission in an hour, for the first four hours, and about five per hour during the next two hours, after which acts are performed at longer intervals. 1 PHYSIOLOGY OF THE INVERTEBRATA. 407 is followed by endogenous division. (4) Gemmation, as in Vorticella. The Infusoria ciliata multiply by division or by conjugation. The first mode of reproduction is effected by a constriction of the adult cell in a transverse direction. The cell ultimately. becomes divided into two portions which separate; each portion finally developing into separate organisms. Paramecium bursaria conjugates in pairs when the anterior ends of two individuals unite and remain united for five or six days. According to: Balbiani,* the nucleolus and nucleus of each organism, at this period of their life-histories, become converted into sexual organs. The nucleolus ¢ is converted into an oval body which acquires a striated structure ; ulti- mately it divides into two or four parts. These parts again divide, giving rise to capsules containing rods which are pointed at one end. These rods represent the spermatozoa of higher forms. The nucleus Q gives rise to bodies analogous to ovules. The result of conjugation is the forma- tion of cells which escape as young Puramecia. During the act of conjugation the two organisms, as already stated, are always united together at their anterior ends; in other words at the apertures which form the mouth. “It has been thought that this aperture must play the part of a sexual orifice through which the two organisms in copulation effect the exchange of reproductive matter; it has also been suggested, moreover, that a special sexual orifice is present close to the mouth; but these questions of structure are still doubtful.” . Balbiani’s investigations have been confirmed by Claparéde, Lachmann, Kolliker, Stein, Biitschli, Griiber, and others. It should be borne in mind that in these low organisms the nucleus of the cell is the all-important agent in producing many physiological functions—without it, the above mode of reproduction cannot take place. In fact, it has been stated that “the nucleus plays the primordial ré/e in the cell; if, to use an old comparison of Aristotle’s, we compare the proto- * Journal de la Physiologie, tome 1 (1858) 408 PHYSIOLOGY OF THE INVERTEBRATA. plasm to the clay, we must compare the nucleus to the potter that fashions it. The nucleus comprehends all the physio- logical properties, the totality of which goes to constitute life.” Concerning the first mode of reproduction—viz., that of transverse fission, Balbiani states, that in forty-two days Paramecium can produce 1,384,116 young, that is to say that a single individual organism measuring 0.2 mm. long, grows 277 metres in bulk.* THE PORIFERA. Reproduction takes place asexually—by fission and by gemmation; and sexually—by the production of spermatozoa and ova. The needle-shaped spermatozoa lie in small pockets lined with cells until required. The ova, derived from the cells of the mesoderm, are naked ameceboid cells with a germinal vesicle and spot. They are fertilised before leaving the parent. The impregnated ovum divides into two, four, eight, and more cells, and thereby passes into the morula condition. The cells of the morula subsequently become separated into two layers—an epiblast and a hypoblast. These layers give rise respectively to the ectoderm and endo- derm of the young animal. The embryo sponge is a free swimming larva, and in such a condition it is stated to be in the planula stage of its life-history. After a time the ciliated cellular portion or hypoblast of the free swimming embryo invaginates, and the dark granular cells or epiblast grow over it. The latter form the ectoderm and the mesoderm is also derived from them. The invaginated cells (ciliated) give rise to the endoderm of the gastric cavity. This constitutes the gastrula stage in the development of the Porifera. After a time the young sponge becomes more or less cylin- drical, and an osculum and inhalent pores are produced; and calcareous spicules appear in the mesoderm. * For further information on the reproduction in the Infusoria, see Mantegazza’s Ricerche sulla generazione degli Infusorii, e descrizione di alcune nuove specie (1852); and W. Saville Kent’s Manual of Infusoria. PHYSIOLOGY OF THE INVERTEBRATA. 409 THE Cc:LENTERATA. The modes of reproduction in Hydra are by gemmation, fission, and sexual reproduction. Gemmation is the most common mode of multiplication. The buds may remain attached, or may become separated from the parent; and consequently lead an independent life. The bud of Hydra ‘consists always of a simple fold of the wall of the stomach and the skin, so that the stemach of the young individual is in direct communication with that of the parent, and the chyme (nutritive fluid) can pass freely from one to the other.” When the foot of this new being has acquired a proper development, it is completely detached at its inferior extremity. In regard to the second mode of reproduction—by natural fission—it may be stated that it is comparatively rare. Fission takes place longitudinally or transversely, and each part repairs itself, and ultimately develops into a new Hydra identical with the parent. In some forms of the Celenterata the fission may or may not be complete. ‘ When it is com- plete the cells of the corallum are definitely limited, as in Astrea, Favia, and Caryophyllia, but when incomplete, the cells are branched, lobulated, and of irregular contour, as in Agaricia, Meandrina, Monticularia, &c.” Sexual reproduction takes place in Hydra; but the animal is hermaphrodite. In the summer, testes are developed at the base of the tentacula ; and one or more ovaries at the base of the column near the disc. The testis is simply a mass of inner ectodermal cells, by the division of whose nuclei, sperma- tozoa are formed. A spermatozoon consists of a small oval head and a long filament. This filament by its rapid move- ments enables the spermatozoon (when liberated) to swim about in the water; and in this medium it retains its fertilis- ing properties for many days.* * The retention of the fertilising properties of spermatozoa after expul- sion from the body, varies in different animals, In trout the property is 410 PHYSIOLOGY OF THE INVERTEBRATA. The ovary in Hydra is a small group of ectodermal or interstitial cells. Orie cell, however, lying in the centre of the group is larger and clearer than the rest; from this central cell the naked amoeboid ovule is produced. In Hydra, as already stated, the sexes are united in the same individual; but in other Celenterata they are distinct; “with the colonial polyps the sexes are separate, and each colony may be composed of individuals which are androgynous, or of one sex alone. Some species are sexless, and remain so; but they produce by gemmation individuals of a particular character, which have sexual organs.” In Hydra when gemmation takes place there is ultimately a complete separation of the buds, but in some Coelenterata, there is gemmation without separation of the young; this occurs, for example, among the Coralligena. Concerning the development of Hydra, the following is an outline of the process: After the ovule or egg-cell escapes from the ovary it is fecundated by spermatozoa, which are discharged from the testes into the surrounding water. There is no act of copulation. As the result of fecundation the - naked egg-cell acquires a cell-wall, and segmentation of its mass follows; that is, a morula or blastosphere is formed. After this a chitinous shell is elaborated which envelopes the embryo. The embryonic cells fuse together, giving the embryo the appearance of an unsegmented egg-cell. In the centre of this mass a small cavity (the beginning of the body cavity) is produced. This gradually widens and lengthens so that the embryo becomes a closed sac. After several weeks the above-mentioned shell is ruptured, and the hollow germ escapes enveloped in a thin membrane. The protoplasmic lost ina few minutes. Spermatozoa in the seminal reservoir of the female bee retain their powers for several years. In mammals the seminal elements retain their powers of fertilisation for some time in the genital passages of the female; in the female rabbit Balbiani found them twenty- four hours after coition ; and Drs. E. van Beneden, Benecke, Eimer, and Fries have observed spermatozoa in the uterus of bats for several months. PHYSIOLOGY OF THE INVERTEBRATA, Als mass which surrounds the body or somatic cavity differentiates or divides into an ectoderm and endoderm. During all this embryological development, the embryo has been growing in length. At one end of the elongating embryo, a mouth is formed by rupture of the tissues. “It first appears as a star-shaped cleft which gradually becomes more or less round. The tentacula next appear simultaneously. The animal then bursts the thin membrane, comes out of it, and starts life on its own account as a ‘perfect Hydra. There is no meta- morphosis in the development of Hydra (no invagination, and no ciliated planula as in many other Hydroids). The young Hydra passes into the adult condition by continuous growth.” In the Meduse the sexes are separate; the females have yellowish-coloured ovaries, while the males possess rose- coloured genital glands. The ova undergo their embryonic development in the oval tentacula. The embryonic develop- ment.of these animals presents the following phases :—. (a) egg; (0) morula (blastosphere) ; (c) gastrula (by invagi- nation); (d) planula (ciliated larva), this stage is formed by the closing of the gastrula mouth and the “ciliating” of the ectodermal cells; (¢) next appears the hydra-form or scyphistoma, which is produced by the planula becoming fixed and developing tentacula and a mouth at the free end. During the scyphistoma stage there is at first multiplication by gem- mation, but afterwards fission occurs, and the animal then reaches the strobila stage; (f) the detached segments of. the strobila swim away in the ephyra form; (g) the ephyra form after some weeks is converted into the adult animal (in this case, Awrelia). In the development of Aurelia it will be observed there is an alternation of generations; the asexual generation being represented by scyphistoma and strobila. In the Actiniw the sexes are united. The testes and ovaries form closely convoluted tubules and the generative products are discharged into the somatic or digestive cavity, 412 PHYSIOLOGY OF THE INVERTEBRATA. The embryo arises from the fecundated ovum without any metamorphosis. The ovum (Fig. 76, /) undergoes segmenta- tion within the ovary, and the embryo is born alive as a ciliated larva, possessing a somatic or digestive cavity. and a mouth. After this two mesenteric tissues are produced which divide the internal chamber into two unequal parts. Two new mesenteries subsequently arise in the larger or anterior » opel RS A - ¢ 4 e : ovel ; 4} FIG. 76.—SPERMATOZOA AND OVA OF CERTAIN INVERTEBRATES. a= Lumbricus. 4 = Pagurus. c¢ = Pisa. d= Grapsus. e¢ = Astacus(é). jf = Actinia. g = Astacus (9). chamber. A third pair are next developed in the posterior chamber, and then a fourth pair in the lateral spaces. Next the tentacula are developed ; and afterwards four new mesen- teries appear, these are situated one on either side of the two primary mesenteries, so that in all twelve somatic cavities are formed which ultimately become of equal size. The Actine are also reproduced by gemmation or budding. For fuller details the reader is referred to special books and memoirs on the subject.* Tse ECHINODERMATA. These animals propagate by sexual organs, and the sexes are distinct; hermaphroditism is very rare. The ova are * See also Prof. A. Giard’s paper in Comptes Rendus de l Académie des Sciences, 1877. PHYSIOLOGY OF THE INVERTEBRATA. 413 covered by a delicate chorion, and contain a variously coloured vitellus with germinal vesicle and spot; the ova also contain a little albumin. The spermatozoa are nearly always com- posed of a round or oval body and a delicate hair-like filament. “With a few exceptions, the embryo leaves the egg as a bi- laterally symmetrical larva, provided with ciliated bands, and otherwise similar to a worm-larva, which may be termed an Echinopedium. The conversion of the Eehinopediwm into an Echinoderm is effected by the development of an enteroccele, and its conversion into the peritoneal cavity and the ambu- lacral system of vessels and nerves; and by the metamorphosis of the mesoderm into radially disposed antimeres, the result of which is the more or less complete obliteration of the primitive bilateral symmetry of the animal.” (Huxley.) The external appearances of the sexual organs in the Echinodermata are somewhat similar, but at the period of pro- creation they frequently differ in colour. They are composed of efther simple or branched tubules with or without excretory ducts. In the latter case, the contents of the organ, male or female as the case may be, are discharged by rupture into the body cavity, from whence they pass out through the respiratory openings. The Echinodermata are devoid of copulatory organs; the ova being fecundated by the spermatozoa in the water in which these animals live. In the Holothuridea, there is only one testis and ovary in male and female respectively.. Both are composed of a tuft of highly-branched tubules, which unite to form a common duct, which opens externally near the mouth. The early stages in the development of Holothwria are like those of the Asteridea, which will be described later in this chapter.. The free-swimming larva is called an Awricularia. The larva is transparent, vermiform, and has four or five bands of cilia; and while still growing, the young Holothurian begins to bud out by the side of the larval stomach, The larva or Auricularia is gradually absorbed by the developing AI4 PHYSIOLOGY OF THE INVERTEBRATA. Holothurian; and the adult form of the animal is attained without any further changes. Although the sexes are distinct, there is one exception among the Holothuridea, and that is the genus Synapta. These animals are hermaphrodites. According to De Quatre- fages,* the testes and ovaries are united so as to form one organ. This organ consists of branched tubules and secretes both spermatozoa and ova; its excretory duct opens near the oral end of the body. In the Asteridea, the sexes are separate. The genital organs are very similar in appearance, but the colour of the ova is either yellow or red and the seminal fluid is white. The ova are fecundated in the water. There are five pairs of genital glands, one pair lying in each ray. They are saccu- lated or racemose organs, whose ducts open externally by a narrow orifice on the dorsal side of the body. Dr. G. O. Sars has shown that in Brisinga endecacnemos the genital organs consist of many distinct glands forming two well-marked series, which are situated one on each side of the middle line of the central half of each ray. Concerning the development of Asterias (a typical example of the Asteridea), the following may be.taken as an outline of what occurs:--(a) The ovum, after fecundation, becomes totally and equally segmented—thus forming the morula stage. (b) The segmented ovum gives rise to a spheroidal embryo consisting of an external ciliated cellular wall and an internal gelatinous substance. (c) A depression of the ex- ternal wall now makes its appearance, and gives rise to the first rudiment of the alimentary canal. The opening of this depression ultimately becomes the anus. This is the gastrula stage.. (d) The ciliated embryo lengthens and four surfaces can now be distinguished. There is a continuous band of cilia which has a locomotory function. The alimentary canal, which in this stage acquires a mouth, becomes modified into three portions—cesophagus, stomach, and intestine. * Annales des Sciences Naturelles, tome 17, p. 66. PHYSIOLOGY OF THE INVERTEBRATA. AIS Before the formation ‘of the mouth, two lobe-like bodies are formed from the upper part of the alimentary canal. These lobes ultimately separate and form two distinct cavities. These develop into two water-tubes which elongate until they surround the alimentary canal, extending on the other side of it beyond the mouth where they join, giving rise to ‘a Y-shaped canal. (¢) The ventral. ridge containing the ~ band of' cilia becomes prolongated into processes of various shapes. These processes are arranged with close regard to bilateral symmetry (Bipinnaria and Brachiolaria, or bilateral larval stage). (f) At this point the body of the future starfish begins to develop from the larva. ‘On one of the branches of the united water-tubes the feet or tentacula are produced as'a series of lobes, while on the opposite branch of the water-vascular canal many small calcareous rods are elaborated. These rods afterwards form a regular network, and indicate the dorsal side of the young Asterias.” (g) At this stage the larva Brachiolaria shrinks and drops to the bottom of the water, where it fixes itself by means of its short arms. (h) That portion of the larva which is more developed into the true starfish form than the remaining portion, now absorbs the latter and acquires a conical and disc-like form, with a crenulated edge. In this stage the organism remains for two or three years. Then the rays or arms lengthen and the mature form is assumed. According to Greef,* parthenogenesis appear to occur in Uraster rubens. In the Ophiwridea, the sexes are distinct,f and the genital organs consist of lobular, pedunculated sacs, which are situated, in: pairs, in the inter-radial spaces of the disc. These organs pour their secretions into the peritoneal cavity ; the latter, however, is in communication with the external medium by narrow apertures situated inter-radially on its margins. The ova are fecundated in the water, and in that * Marburg Sitzungsberichte, 1871. + Ophiolepis sqguamata is hermaphrodite. 416 PHYSIOLOGY OF THE INVERTEBRATA. medium the embryos are developed; but in the case of Ophiolepis ciliata, the embryo is developed within the body cavity of the parent. The early stages of the embryological development of most Ophiuridea are similar to those of other Echinodermata; nevertheless, in some forms the embryo passes directly into the adult condition without first becom- ing an Echinopedium. “Where an Echinopedium stage exists, the larva is a Pluteus. The dorsal wall of the body of the embryo exhibits a medium conical outgrowth ; along the course of the ciliated band symmetrically disposed processes are developed ; and these outgrowths are supported by a calcareous skeleton, which is also bilaterally sym- metrical.” In the Echinidea* there are five unpaired ovaries or testes, which are situated inter-radially. As a rule, they project far into the body cavity, and are composed of ramified tubules. The ducts of the genital glands open externally by five apertures in the genital plates which surround the apical pole. The early stages in the embryological development of Echinus are similar to those of the starfish. The free- swimming larva, however, assumes the Pluteus form, and in this respect it is similar to the Ophiuridea. The Pluteus form has eight long slender arms, which are supported by calcareous rods extending from the body. The adult form of Echinus is developed within the body of the larva, the alimentary canal and dorsal sac (the commencement of the ambulacral system) alone persisting. The larval body is gradually absorbed by the developing and growing Echinus, the spines and pedicels of the latter increasing in size and number until the animal assumes the adult form. It may be remarked that Professor A. Giard + has shown that at certain times the genital glands of the Hchinidea secrete small crystalline concretions of a brownish colour. These concretions consist of calcium phosphate, which is * The sexes are distinct. + Comptes Rendus del Académie des Sciences, 1877. PHYSIOLOGY OF THE INVERTEBRATA. 417 destined to furnish the vitellus and spermatozoa with phos-: phorus—an element which is present in large quantities in the genital products.* In the Crinoidea, the sexes are distinct; and the tubular genital organs are situated under the perisoma of the pinnule. In ) by sexual organs. In the smaller Rhabdocela, the first mode of reproduction is the rule, for no genital organs are present. These animals are both moncecious and dicecious; and the “ genital and copulatory organs of both sexes are situated upon one and the same individual so that they are capable of self-impregnation ; but there is generally a reciprocal copulation.” * In the higher Turbellaria the female genital organs consist of the following parts: a germarium which develops ova; a vitellarian gland in which the vitellus or food yolk is formed; an oviduct; a uterus and vagina; and a sperma~ theca—the function of which is to store the semen after the act of coition. The male genital organs consist of a testis, vas deferens, and penis; the latter “is often eversible and covered with spines.” The impregnated ova are enclosed within a hard shell. In some genera the hard shell is only formed on the winter ova, while the summer ova are only covered by a soft vitelline membrane. The rhabdoccelous ovum undergoes complete segmentation and the embryo passes directly into the adult form. In the marine Planariw, there is no vitellarium, and in some of these animals the embryo after leaving the ovum differs considerably from the adult. The Planarie are hermaphrodites, but Planaria dioica is unisexual. The Proc- tucha are nearly always hermaphrodites, and the ova and spermatozoa are discharged externally by the dehiscence of the integument. Nemertes is dicecious, and the genital organs ($ and 9) have the same structure, being sacs filled with spermatozoa * Coition has been observed in Planaria, Mesostomum, &c. ‘PHYSIOLOGY OF THE INVERTEBRATA. 419 or ova according to the sex of the animal containing them. The genital organs are situated in the lateral part of the body between the pouch-like diverticula of the intestine. They are arranged in pairs along the body and open externally by paired apertures. The development of Nemertes occurs with metamorphosis. The following are the stages through which the embryo passes: (a) Before hatching—egg, morula, and planula. (6) After hatching—a ciliated larva or Pilidiwm is formed ; and the adult condition is attained by direct growth, or by budding out from the. Pilidium. In the Rotifera the sexes are distinct, and the male animals are much smaller than the females. The genital apparatus of the male consists of a testis, in which the spermatozoa are produced and stored; the testis opens by a duct situated | near the posterior end of the body, usually on a muscular protruberance or penis. The male Rotifera are short-lived, and are only born into the world to impregnate the ova of the females. The genital apparatus of the female consists of a round sac-like ovarium or ovary, filled with ova in various stages of development, and a short oviduct which opens into the cloaca. The female produces both summer and winter eggs. According to Prof. Huxley the winter eggs are produced parthenogenetically—.e., without previous im- pregnation. In fact, he says in regard to Lacinularia that the winter eggs appear to be “ segregated portions of the ovarium.” On the other hand, Cohn believes that it is the summer eggs which are produced parthenogenetically, while the winter eggs are impregnated. The egg undergoes complete and irregular segmentation; then a two-layered embryo is formed. An involution of the epiblast occurs, giving rise to the primitive mouth, which remains permanently open. The trochal disc grows out of the walls surrounding the epiblastic depression ; and the nerve-ganglion is also produced from the epiblast. At the. bottom of the primitive depression, the true mouth is formed; while the cesophagus and the remaining portion of the alimentary canal are developed from the hypoblast. 420 PHYSIOLOGY OF THE INVERTEBRATA. The Zrematoda are nearly always hermaphrodites; and the genital apparatus consists of the following parts: the ovary, vitellarium, oviduct, uterus, vagina, common genital vestibule, testis, vasa deferentia (internal and external), and the penis and its sac. The ovum, as it passes into the oviduct, is devoid of a vitelline membrane, and the vitellus or yolk is clear; but after fecundation, which takes place in the oviduct, a shell is developed and the accessory yolk is added by the action of the vitellarium. The oviduct, which is ciliated internally, communicates with a duct which proceeds from the testis; it also receives the vitellarian duct. The ovi- duct then passes into the uterus, which terminates by the vagina and common genital vestibule in close proximity to the male organs. The oval-shaped testis, situated posteriorly to the ovary, does not contain spermatozoa, but simply a granular mass. The external vas deferens comes into contact with the ovary, and then passes, after several bends, into the anterior part of the body, terminating in the penis, which occupies, in common with the uterus, the genital vestibule. In the case of Aspidogaster (the above being an account of its reproductive organs), the embryo assumes the adult form without any metamorphosis; but in other species, the development is either direct* or accomplished by a com- plicated metamorphosis,f accompanied by alternation of generations. The ova of Aspidogaster, as they pass down the oviduct, are impregnated, “either by the spermatozoa conveyed by the internal vas deferens, or by those received by the vagina, when copulation with another individual, or possibly self- impregnation, occurs.” As already stated, nearly all the Zrematoda are herma- phrodites, but among those that are dicecious is the parasitic Bilharzia, which lives in the blood-vessels of man. The female Bilharzia is much smaller than the male; and a * Polystomum, Gyrodactylus. + Distoma, Monostomum. PHYSIOLOGY OF THE INVERTEBRATA. 421 curious mode of pairing occurs—for the male, not content to unite with the female, retains the latter in a gynzcophore or canal; but it may be stated that very little is known concerning the reproduction and development of this Tre- matode. So far we have seen that the Trematoda only multiply sexually ; but some of these animals also multiply. by conju- gation and by a kind of gemmation. For instance, in. the genus Diporpa, two individuals (devoid of sexual organs) conjugate, and the result is a double-bodied Diplozoon paradocum, which ultimately develops sexual organs. In the case of Gyrodactylus, a kind of internal gemmation occurs. The Cestoidea are hermaphrodites in the mature condition, but in the earlier stages of their growth they are devoid of sexual organs (i.¢c., in the cystic form). Some, like Caryo- phylleus, have only a single set of hermaphrodite organs ; and Zigula is an unsegmented form with many sets of these organs. The Tape-worms are segmented animals, and in each proglottis or segment there are male and female organs. The male organ consists of innumerable pear-shaped vesicles or testes, scattered in the parenchyma of the body. The vasa efferentia open into the common duct—the vas deferens ; the latter lies in the cirrus sheath. By the contraction of the cirrus sheath, the vas deferens (“cirrus”) can be forced through the vagina.* In this case the vas deferens acts as a copulatory organ or penis. The female organ consists of the following parts: An ovary leading into a single oviduct, which has an enlarged portion or pouch, termed the receptaculum seminis. Branch- ing out from the oviduct are the vitellaria or yolk glands, whose efferent tubes ultimately coalesce with the oviduct forming a common duct. At the point where the ducts of the vitellaria unite with the oviduct, the shell gland is * The vagina and vas deferens open into a cloaca or genital vestibule, which is situated on the lateral margin of the proglottis. 422 PHYSIOLOGY OF THE INVERTEBRATA. attached. This gland secretes a substance which becomes the investment of the ova. The terminal portion of the oviduct passes into the uterus. The vagina is usually a long canal, and at its inner end is the receptaculum seminis. The small ova are either oval or round. They are formed by three glands—the ovary, vitellarium, and shell gland.* As already stated, the Tape-worms are composed of many segments or proglottides, and at the end of the body the segments become detached. In this condition they retain their vitality for some time. The uterus of the proglottis contains, very many ova; and the embryo (ciliated or hooked) is developed in a similar manner to that of the Trematoda. The Tape-worms live a portion of their life in one animal (cystic condition), and the other portion in an entirely different one (cestoid condition). or instance, the following diagram illustrates the life-history of Tenia soliwm, which infests man :— Teenia in man (sexual condition). Cystic form in pig /~ \ Six-hooked or ciliated (measly pork). embryo. “The Tape-worms are rarely met with in both the cystic and cestoid conditions in the same animal; but the cystic form is found in some creature which serves as prey to the animal in which the céstoid form occurs.” Tor ANNELIDA. The Myzostomea are small unsegmented worms, parasitic on Comatula (Antedon). These animals are hermaphrodites. The two oviducts open into the cloaca; and the male organ * The ovary forms the nucleus, the vitellarium the yolk, and ‘the shell gland the external covering of the egg. PHYSIOLOGY OF THE INVERTEBRATA. 423 opens externally by separate ducts—the vasa deferentia—on each side of the ventral surface of the body. The Gephyrea are also unsegmented worms, but they are dicecious (7.¢., the sexes are distinct), and the spermatozoa and ova are developed from the epithelial cells, which line the walls of the perivisceral cavity, or they are developed in simple cecal glands. The earlier stages in the development of these animals are similar to those of the Oligocheta and Polychaeta. The adult state is attained from the embryonic condition by a metamorphosis. In the genus Bonellia, the males, which are minute, rudimentary, and Planarian-like, live in the uterus of the female.* The Hirudinea are hermaphrodites.t The male organs of Hirudo consist of nine pairs of testes, situated in successive segments. The first pair are in the segment behind that which contains the eversible penis ; and the others are in the following eight segments, a little in front of the nephridia or segmental organs. From each testis a duct passes into the vas deferens (situated laterally), which, in front of the anterior pair of testes, becomes much coiled, forming the vesicular seminalis. The latter opens into a duct, which passes for- ward to the ventral median line, and, along with the same duct of the vas deferens of the other side of the body, opens into the prostate gland. A duct proceeds from the prostate gland, which forms a sheath of the eversible penis, and opens in the twenty-fourth segment. The spermatozoa are enclosed jn a case, called a spermatophore. The female organs are situated in the segment behind that which contains the penis. They consist of two small ovaries provided with oviducts; the latter open into the uterus, which is surrounded by an albumin gland. The uterus proceeds into a vagina, which opens by a small orifice situated between the twenty-ninth and thirtieth segments. It will be noticed that the external orifices of the genital organs are unpaired. * This is different from Bilharzia (one of the Trematoda), for the male retains the female within its own body. + Except Histriobdella and Malacubdella, which are dicecious. 424 PHYSIOLOGY OF THE INVERTEBRATA. The impregnation of the ova takes place within the body ; and the ova, when laid, are enclosed in a cocoon which is secreted by the integument. Although these animals are hermaphrodites, copulation between two separate individuals takes place. ‘The female copulatory organs are upon the ventral surface of the anterior part of the body, and behind the male organs—so that two individuals, by placing together their anterior ventral surfaces in an inverse position, can be mutually impregnated.” (Von Siebold.) The ovum of Hirudo passes through a metamorphosis, the mesoblast undergoing division into segments, which ultimately give rise to the characteristic structure of this and other seg- mented animals. The Oligocheta are hermaphrodites; ae the genital organs are situated (like Hirudo) in the anterior part of the body. In the fresh-water Oligochata (Nais and Tubifex), these organs have no genital ducts, but the ova and spermatozoa are con- veyed outwards by the nephridia, which are situated in those segments of the body containing the genital glands. “In Nais and Chetogaster, agamic multiplication occurs by the development of posterior segments of the body into zooids, which may remain associated in chains for some time, but eventually become detached and assume the parental form.” In Lumbricus, the testes are two pairs of white sacs situated on the posterior sides of the septa, separating the ninth and tenth, and the tenth and eleventh segments. The spermatozoa are not fully developed on leaving the testes, and they are known in this condition as spermospores. The spermospores are further developed by a process of budding, which takes place in the vesiculee seminales (two pairs of reservoirs).. The fully developed spermatozoa (Fig. 76 a) are conveyed out- wards by four ducts—the vasa deferentia; but the two vasa deferentia on either side of the body unite, forming one duct, which opens on the ventral side of the fifteenth segment. The female genital organs consist of a pair of small ovaries PHYSIOLOGY OF THE INVERTEBRATA. 425 (7s in. long), situated in the thirteenth segment. The ova when fully developed rupture the walls of the ovaries, and pass into the body cavity. Ultimately the ova find their way into the oviducts, which are quite distinct from the ovaries. The pair of oviducts are small, funnel-shaped, ciliated tubes; the funnel-shaped portion opens internally in the thirteenth segment, whereas the opposite end opens externally by a small aperture on the ventral side of the fourteenth segment. Although Zumbricus is hermaphrodite, copulation takes place between two separate individuals, the impregnating seminal fluid being stored in four small spherical sacs or spermathecze, which open externally between the ninth and tenth, and the tenth and eleventh segments. The ova are impregnated externally by the seminal fluid from the sperma- thecee. Groups of these ova become surrounded by mucous and chitinous secretions termed cocoons. These cocoons sometimes contain forty or fifty ova, an albuminous substance, and packets of spermatozoa. In the development of the Oligochecta, the segmentation of the ovum is total and nearly regular, giving rise to a flattened ciliated blastosphere. The latter invaginates, and a gastrula is formed; and between the epiblast and hypoblast in this stage of the development a mesoblast is formed. “On the ventral side of the embryo, the mesoblast divides into a row of quadrate masses, which are symmetrically arranged on each side of what becomes the median line of the adult body. This series of symmetri- cally placed quadrate masses resembles the protovertebrze of the embryo of a Vertebrate animal.” After this ‘a cavity forms in the interior of each quadrate mesoblastic mass, making it into a kind of sac. The adjacent anterior and posterior walls of the row of sacs unite, and this union gives rise to the dissepiments of the somites, while the cavities become the body cavity or perivisceral chambers.” (Johnstone. ) The epiblast now thickens inwardly, along the median line, ultimately. giving rise to the ganglionic nervous 426 PHYSIOLOGY OF THE INVERTEBRATA. system.* -The nephridia or segmental organs begin as out- growths from the posterior face of each septum; and finally the adult form is attained just before the hatching of the egg. The Polycheta are dicecious and rarely hermaphrodite.t Some of these animals multiply by fission and gemmation. In Syilis, transverse fission takes place; while in Myrianida gemmation occurs giving rise to zooids. In some other Polychzetous forms reproduction is produced by a combination of fission and gemmation. The genital organs of the Polychwta are very simple in structure, and the genital products ultimately float about in the perivisceral cavity, probably passing outwards through the apertures at the bases of the parapodia. In some Polycheta, the nephridia act as genital ducts. The ova of these animals undergo a somewhat similar metamorphosis to those of the Oligocheeta and Hirudinec ; “ but the embryos of the Polychaeta differ from those of the Oligocheta and Hirudinea in being ciliated.” , THE NEMATOSCOLICES. The Nematoidea are nearly all dicecious, unsegmented worms.{ These animals and their genital products are pos- sessed of great vitality. According to M. Devaine, the ova of Ascaris lumbricoides§ are capable of withstanding the action of a solution of chromic acid (2 per cent.) for five years; and Mr. W. Carruthers, F.R.S., states that vitality was restored in some Nematodes, after they had been in the botanical department of the British Museum for more than thirty years. || * The nervous system, almost throughout the animal kingdom, has an epiblastic origin. + Protula is hermaphrodite. + Pelodytes is hermaphrodite ; and Ascaris nigrovenosa, which at first pro- duces spermatozoa, afterwards only produces ova. § The 2\pive orpoyyvdog of Hippocrates. || See Dr. Griffiths’ Diseases of Crops, pp. 18 and 119. PHYSIOLOGY OF THE INVERTEBRATA. 427 As a rule, the male organ consists of a single cecal tube opening on the ventral side into the cloaca or the posterior end of the intestine. The spermatozoa,* which are amceboid in shape, are developed from the blind end of the cecal tube, whose remaining portion has the function of a vas deferens. One or two, sometimes long, chitinous spicula are developed in the cloacal region of the male. These spicula are used by the male during copulation—the object being to distend the vulva of the female, inorder to allow the seminal fluid to pass freely into the vagina and uterus. The spermatozoa undergo further changes in the female organs of reproduction, but ultimately fuse with the ova. The female organ consists of a single or double tube, which is blind at one end. The blind end of this tube contains internally a protoplasmic substance or rhachis, from which the ova are developed; this portion of the tube is, therefore, physiologically the ovary of other forms. The tube then becomes differentiated into an oviduct, and later into a uterus. The ova are free in the oviduct, and they are im- pregnated in the uterus, where they become surrounded by a hard shell. The uterus then passes into the vagina, which opens on the ventral surface, usually near the centre of the body. The vitellus of the fecundated ovum becomes segmented, and gives rise to a single row of cells, which ultimately become indented on one side—7.e., the ovum forms a kind of in- vaginated gastrula.t The body wall and the alimentary canal are developed from two layers of cells, which are produced by the invagination of the above-mentioned single layer. At this point the embryo rapidly assumes the adult form; and is found rolled up within the shell. After hatching, the young Nematode casts its cuticle, which is shed a second time when it acquires its sexual organs—+.¢., theré is a period * In the Nematoidea, the spermatozoa retain the character of cells. "+ The ova of Ascaris dentata and Oxyuris ambigua are unsegmented after fecundation. 428 PHYSIOLOGY OF THE INVERTEBRATA. in which the Nematoidea are sexless worms. In the genera Mermis and Gordius, the anterior ends of the embryos are provided with spines—the spines being used to pierce holes in the bodies of insects, in which these Nematodes live a portion of their life-history. According to Sir John Lubbock, the male of Spherularia becomes permanently fixed to the female.. Many of the Nematodes are only parasitic in the sexless stage of their existence; but some are free in the larval or sexless stage; and some again are parasitic both in the sexless and sexual condition. In the Acanthocephala—represented by Echinorhynchus— the genital organs are attached to the posterior end of the proboscis sheath by the ligamentum suspensorium, which traverses the body cavity. The sexes are distinct. The female organ consists of a tubular ovary; a uterine bell—the mouth of which opens into the body cavity, while the upper portion leads into the uterus; the uterus then passes into the vagina, which opens externally at the posterior end of the body. The ova, discharged from the ovary into the body cavity, are ultimately taken up by the mouth of the uterine bell, which is continually expanding and contracting, and thence the ova pass into the uterus. The male organ consists of two oval testes provided with vasa deferentia, which proceed to the posterior end of the body. At this point the vasa deferentia fuse together, forming a bulb-like structure, called the ductus ejaculatorius, which is usually provided with six or eight glandular sacs. The ductus ejaculatorius is furnished with a long penis placed in the centre of the bottom of a bell-shaped bursa situated at the posterior end of the body. The development of the fecundated ovum com- mences with an irregular and a complete segmentation. This gives rise to an embryo, which is enclosed in the membranes. The embryo, at this stage, is provided anteriorly with small spines. The ova (containing the embryo) are usually “swallowed” by various Amphipoda, Isopoda, and Insecta (larvee) ; in this stage the membranes are dissolved by the PHYSIOLOGY OF THE INVERTEBRATA. 429 secretions of the alimentary canal, and the embryos becoming free, bore their way through the walls of the intestine of their host. While in the alimentary canal of the host, the embryo loses its spines, and develops into an elongated larva. In this condition, the skin gives rise to the muscular body wall, the dermal vessels, and the lemnisci of the adult; all the other organs are developed from the “ embryonic nucleus,” which makes its appearance early during the embryonic development—.c., before the ovum is ‘“‘ swallowed” by one of the above-mentioned Invertebrates. Finally, the embryo finds its way into the alimentary canal of one of the Vertebrata (e.g., fishes, aquatic birds, pigs, &c.), and while there, it develops sexual organs. THE CHATOGNATHA. This group contains only one genus—Suagitta. These animals are hermaphrodites; and the male and female organs are situated at the sides of the posterior end of the body. There are two tubular ovaries, the ducts of which open externally on each side of the anus. The tubular testes, situated behind the ovaries in the caudal region of the body, open by short ducts at the sides of the tail. The fecundated ovum becomes completely segmented, giving rise to a blasto- sphere. By invagination, the hemispherical, two-layered, cup- shaped gastrula is formed. The primitive opening now closes, and a permanent mouth is formed at the opposite end. At this point the embryo has an oval shape, but it finally elon- gates and acquires the adult form before leaving the egg. THe ONYCHOPHORA. Professor H. N. Moseley* has shown that in Peripatus the sexes are distinct. The testes are egg-shaped; and they are provided with coiled vasa deferentia, which ultimately unite, forming a common duct. This duct opens on the ventral * Philosophical Transactions of the Royal Society, 1874. 430 PHYSIOLOGY. OF THE INVERTEBRATA. side of the rectum. Like the testes, the ovary is situated in the posterior end of the body. It is a small, single, bilobed organ provided with two long oviducts, which unite before passing into a short vagina. The vagina opens externally on the ventral side of the rectum. The oviducts are provided with uterine dilatations, and in these the ova are developed, Peripatus being a viviparous animal. For details concerning the development of Peripatus, the reader is referred to Moseley’s original paper, already cited. . THe Myrriapopa. The Myriapoda are dicecious. The testes, in the Chilopoda, assume various forms; but in most of these animals, the testes are said to be “‘fusiform acini united by delicate ducts with a median vas deferens; and two, or four, pairs of accessory glands are connected with the opening of the male apparatus.” According to Favre,* the testis, in Zithobius, is a single tube connected with the vas deferentia, the latter being situated on each side of the rectum. A vesicula seminalis opens into each vas deferens. In the Chilognatha (Diplopoda), the tubular testes are situated between the alimentary canal and the nervous system. The testes are provided with lateral tubules, the former being connected with the latter by transverse ducts. There are two penes connected with the bases of the seventh pair of legs. In Scolopendra (centipede), Geophilus, and Cryptops, the spermatozoa are enclosed in spermatophores. In both the Chilopoda and Chilognatha, the ovary is a long single tube. It is situated above the alimentary canal in the Chilopoda, and between the alimentary canal and the nervous system in the Chilognatha. The female organ in each order is provided with double vaginz, which open beneath the anus in the Chilopoda, and behind the bases of the second pair of legs in the Chilognatha. Two spermathece are generally present in the Myriapoda. * Annales des Sciences Naturelles, 1855. PHYSIOLOGY OF THE INVERTEBRATA. 431 “The Chilognatha copulate.. In Glomeris and Polyxenus, the genital apertures of the two sexes are brought together during copulation; but in Jwlus, the penes of the male are charged with the spermatic fluid before copulation takes place, and it is by their agency that the female is impregnated. The Chilopoda have not been observed to copulate, indeed the female shows a tendency to destroy the males, as among the Araneina, The male Gophilus* spins webs, like those of spiders, across the passages which he frequents, and deposits a spermatophore in the centre of each.” The development of the embryo of the Myriapoda has been worked out by Metschnikoff,t whose papers the reader is referred to for important information. THe INSECTA. The Jnsecta multiply by means of genital organs, and the sexes are distinct. According to M. Lacaze-Duthiers, t the copulatory organs in these animals present wide and manifold variations. Among the colonies of ants, bees, and wasps, besides the males and females, there are large numbers of neuter individuals. The sexual organs of the Jnsecta are developed chiefly during the pupal stage; but the rudiments of these organs exist in the larve—e.., the female genital ‘organs exist in the larvee of Apis, and it is due to an increase in the quantity of nourishment that the larva become females or queens. Among the Aphidw, parthenogenesis occurs; for many successive generations of females are born viviparously with- out copulation with the males. As a typical example of the genital organs in the Insecta, we describe in detail those of Periplaneta (the cockroach). The male organ consists of numerous short testicular sacs attached to a short vas deferens. It is situated above the * Belonging to the Chilopoda. + Zeitschrift fiir Wissenschaftliche Zoologie, 1874-5. + Annales des Sciences Naturelles, tomes 12, 14, 17, 18, and 19. 432 PHYSIOLOGY OF THE INVERTEBRATA. posterior abdominal ganglion. The anterior end of the vas deferens is dilated ; and this duct in the adult male always contains spermatozoa. The spermatozoa appear to be formed in the testis or mushroom-shaped gland of the young, and then accumulate in the vas deferens, for in the adult cock- roach the testis atrophies. The two ovaries, each of which consists of eight tubules, are situated in the posterior part of the abdomen. The ovarian tubes or the contracted portion of the ovaries pass into two short oviducts. The two oviducts unite in the middle line of the body, and open externally by a very short but wide vagina. Behind the union of the oviducts with the vagina, there is the spermatheca or seminal receptacle; and behind the latter are two much-branched tubular colleterial glands which secrete the chitinous substance of the egg-cases. There are sixteen eggs enclosed in each case. ‘‘ The female carries the egg-case about for a week or more, before depositing it. The young leave the eggs as minute active insects, colourless, except for the large dark eyes.” Peri- planeta does not pass through any pupal stage ; but undergoes seven ecdyses or moultings of the skin; and attains its mature condition during the fifth year. The penes or male copulatory organs in the Insecta are often very complex in structure. ‘“ Kraepelin,* who has examined the development of these parts in the Drone, and the modifications found in hermaphrodite Bees, is led to the conclusion that they are developed from the eighth and ninth somites of the abdomen, and therefore are the homologues of the parts of the sting in the female. In the male Blatta (Periplaneta), however, it is obvious that the male copulatory apparatus belongs to a more posterior somite than that upon which the female gonapophyses are developed.” In most Insecta, the vitellus of the ovum undergoes only partial segmentation; but in some Poduridw segmentation is complete. During the development of the embryo, there are * Zeitschrift fiir Wiss. Zoologie, 1873. PHYSIOLOGY OF THE INVERTEBRATA. 433 certain parts * which are comparable to the amnion of the Vertebrata. This amniotic investment is not, however, universal among the Insecta, although it is present in the Orthoptera (Libellula), Diptera, Lepidoptera, Hymenoptera, Coleoptera, and Hemiptera. As material agents in the propagation of the Insecta, the following may be mentioned: their odours, colours, dances, and music. For instance, (1) in some Lepidopterat there are two glands, situated near the opening of the vagina, which secrete an odorous substance that excites copulation; and one could give many examples where odours play an important part in the amours of various insects. (2) Female Libellule and flies with bright metallic colours may often be noticed reposing on plants in the sunshine, “attracting ever and anon the attention of some passing male, who, staying his course, remains for a while, as seized with an ecstasy, suspended over their charms like a hawk marking his quarry, and seeming as if dazed by the glow of pigment beneath him. This is very characteristic of the Libellule and Syriphide.” In other insects it is the males which have the gorgeous colours. (3) The aérial dances of certain Diptera, Lepidoptera, Newroptera, &c., are said to be means favouring copulation. The males of some Newroptera dance and collect, and when joined by their attracted females they pair. (4) Stridulation or.instrumental music is a character- istic phenomenon in many insects. “The musical organs sexually common in most beetles, butterflies, and moths, as in a grasshopper genus, assume generally masculine differ- entiation in the Orthoptera, indicating dermal alteration and induration; they are either duplicate, paired, and similarly situate as regards the bodies’ median line, or their develop- ment is single, as the alar organ of leaf-crickets, or quasi unique, as in the family of bugs, and the longicorn beetles. Reciprocating stimulatory friction of articulate parts to * The lamina of the sternal band. + Argynms, Zygnena, Mekitea. 434 PHYSIOLOGY OF THE INVERTEBRATA. express emotion postulates adaptive acquisition, consequent on assumed integumental tendency under attrition to determine a smooth undulatory surface, and propagation by hereditary transmission; a rudimentary structure of this description exists in the Stag Beetle at the inferior and pos- terior extremity of the head; and whenever a number or group of insects is capable of music, we may establish a degradation of the organs almost invariably in mute indi- viduals of the opposite sex, or inother members of the genus or family. Practically, the microscope establishes the essential constituent, the file (lima), to be a dermal or skin excrescence, with a systematic exaggeration or coalescence of external callosities, wrinkles, tubercles, or a protrusion of the'spiral thread of the wing-veins or other tracheal organ. Theo- retically, this active or passive source of sonorous vibration is a variously-placed more or less /-shaped tumour, provided with denticulations more or less regular, which are vibrated and sounded diagonally over a narrow raised callosity or ridge, on the chitinous integument or modified alar vein. These latter, constituting the passive or active clasping organ, assume the function of a violin bow or plectrum.” Many of the musical sounds emitted by insects are said to express fear, anger, and “the more complex emotions of love and rivalry, causing, at certain seasons, the music to assume the character of a stimulus to reproduction and migration.” “The action of stridulation with the majority of beetles and one of the bee group is a more or less rapid protrusion and contraction of the abdominal segments, a respiratory movement which we shall show results from tracheal dis- position in the Insecta. In some moths and grasshoppers, music is implicated with a bladdery inflation of the skin; but in other insects it is not directly dependent on respira- tion. With some the action is a sharp nid-nodding, performed by the elevator and depressor muscles of the prothorax or head. Many butterflies and the crickets pro- duce their music by wing friction, resulting from a rapid PHYSIOLOGY OF THE INVERTEBRATA. 435 movement of the extensor and deflexor muscles; and the grasshoppers to the same end employ the subtile elevator and depressor muscles of their agile leaping legs.” The following table gives the orders of the Insecta which possess the power of emitting musical sounds :— Sexes, &e. Certain genera of the Coleoptera 3 . | both sexes stridulate é 2 » — Orthoptera : ; re einsdulaica) the 4 female is mute | ” ” » Hemiptera i fe sa | (Heteroptera) | both sexes stridulate | ” ” ” Hemiptera* \ vocal music 2 | (Homoptera) 55 3 » 4lymenoptera . .| both sexes stridulate 4% i 5, Lepidoptera : . | both sexes stridulate ” ” » Diptera (2) ‘ . | waale stridulates (?) Many sounds emitted by insects are certainly not musical to the human ear; nevertheless, as the latter is only capable of appreciating sonorous vibrations within narrow limits, the sounds produced by the Insecta may be musical to them; at any rate these sounds have their uses, or the organs which produce them would not be so well developed as they are in the Insecta. If many of us are incapable of appreciating insect music, the ancients, and especially the Greeks, appear to have regarded it with feelings of great satisfaction; and the Cicada is often referred to by certain Greek poets. Anacreon, for instance, has devoted an ode to singing the happiness of this insect. An element of this happiness, according to Zenachus, is, that the Cicade{t “all have voiceless wives,” an opinion which will probably find sup- porters in the present day. Besides stridulation, many insects produce sounds by means of their wings (wing-beating), and stigmata, spiracles, * Various Cicada, + For a full description of these insects, see Buckton’s Monograph of the British Cicade or Tettigide. 436 PHYSIOLOGY OF THE INVERTEBRATA. or “‘breathing-slits.” These sounds are said to give rise to various emotions—fear, anger, and love; consequently the musical sounds produced by “ wing-beating” and the “ vocal organs” are material agents in the reproduction of many Insecta ; for it should be borne in mind that those females which are mute always “alight near” * the musical males, and many insects (of either sex) know the particular notes of their kind. From what has been said in the last few pages, it will be seen that odours, colours, dances, and music are important agents in bringing about sexual reproduction in many orders and genera of the Insecta. We now consider the subject of parthenogenesis or virginal reproduction, which occurs in certain insects. In Chermes ahietis and Coccus hesperidum, the females produce ova which give rise only to females, for no males have been discovered.- In the Aphide both sexes are developed in the autumn; these copulate, when the females lay eggs, which are hatched in the following spring. But instead of producing individuals of both sexes, these eggs give rise only to female insects, which produce living young without any congress with the male; the brood thus brought forth again produces living young in the same manner, and this goes on throughout the whole summer, without the appearance of a single male insect. In the autumn again, male and female individuals are produced, the latter lay eggs which are to continue the species until the following summer. The production of parthenogenetic females has no definite limit, but is regulated to a certain extent by temperature and food supply. To retain the parthenogenetic function, the Aphidw require warmth and a plentiful supply of food; for on the failure of either of these conditions the parthenogenetic females give rise to both males and females’ The genital organ of a * Darwin’s Descent of Man, vol. 1, chap. Io. + For further information, see Swinton’s Insect Variety, pp. 102-229; and Von Siebold’s Invertebrata, p. 406. PHYSIOLOGY OF THE INVERTEBRATA. 437 parthenogenetic or viviparous female is different from the oviparous form; for in the former the spermathece and colleterial glands are entirely absent, whereas these organs are present in the latter.* “The unimpregnated, apterous, caterpillar-like females of the Lepidopterous genera Psyche and Solenobia, lay eggs out of which only females issue. The males occur but rarely and locally, and, from the impregnated eggs, males and females issue in about equal numbers.” Among ants, wasps, and humble-bees, the ovaries of the neuters often contain ova; and in the two last-mentioned insects these ova give rise to young (sex ?). In Polistes gallica the so-called neuters (2) lay ova, which develop only male insects; and the unimpregnated females of Nematus ventricosus lay ova which give rise to males. Parthenogenesis among hive-bees is an established fact; the young unwedded queen-bee lays ova profusely, but all of them give rise to males or drones. The impregnated ova, however, give rise to females, which become either queens or neuters, according to the supply of food given to them. If a queen-bee dies, the inmates of the hive feed a selected female larva on “chyle-food,” elaborated in the so-called chyle-stomach of the nurses, until it assumes the pupal change, from which it emerges a perfect female. The future worker or neuter is weaned on the fourth day, and fed henceforth on honey and digested pollen, with the result that its ovaries are rudimentary and sterile, while its further genital struc- ture renders it incapable of mating. The fecundation of the queen-bee takes place within a few days of her quitting the cell, and lasts for life; the millions of spermatozoa dis- * See Prof. Huxley’s paper in Zransactions of the Linnean Society, 1857 ; Balbiani’s paper in Annales. des Sciences Naturelles, 1869-72; and Von Siebold’s Anatomy of the Invertebrata, + Parthenogenetic females which produce male young are termed arren- tokous, while those which produce female young are termed thelytokous. 438 PHYSIOLOGY OF THE INVERTEBRATA. charged by the males are retained in the spermatheca of the queen-bee, and they only escape one by one to fertilise each ovum as it is laid. Insects in their most complete character pass through four stages of existence—the ovum, the larva, the pupa, and the imago. In none of these, except the larval stage, does the insect increase in size. Some insects (Aptera) pass only three stages—the ovum, the “younger stage,” and the imago; and in others the perfect state or imago, is attained without passing through more than two. The ova of insects are usually deposited externally (this deposition in many cases being assisted by an ovipositor), but in some few cases they are hatched in the body of the parent. In the larval stage, the insect moults several times, and after each ecdysis attaining a sudden and rapid increase in size. The larva does not always take the form of a grub or maggot; for in the Aptera, Hemiptera, and Orthoptera, it assumes a good deal of the appearance of the perfect insect. In this imperfect metamorphosis it changes its skin as the maggots do, and it does not assume a different form for the pupal stage. In the Diptera, Hymenoptera, Newroptera, Lepidoptera, and Coleoptera, the larve, on their last change of skin, assume the pupal stage, in which they remain dormant until the last change takes place, when they come out as perfect insects. In some cases the pupa remain on or in the earth; while in others, cocoons or cases are made by the larve in which they pass the pupal stage. In concluding our remarks concerning the modes of re- production and development in the Jnsecta, it may be stated that a-very full account of the genital organs and their countless modifications in the various orders, genera, &c., are given in Von Siebold’s Anatomy of the Invertebrata,* to which the reader is referred. * This is one of the best books on the subject ever written, and is still indispensable to the biologist. PHYSIOLOGY OF THE INVERTEBRATA. 439 THe ARACHNIDA. In the Pentastomida, the ovary of the female is a large sac-like organ, with oviducts which pass off from its anterior end. The oviducts terminate in an aperture situated near the anus. The ova are developed in the ovary. The testis of the male is situated on the ventral side of the intestine. It is provided with two vasa deferentia, which pass in an anterior direction, and terminate in two dilatations, which contain long, chitinous penes (1.¢., a penis in each dilatation). These animals are parasitic, and the parasitism is almost similar to that of the Cestoidea—eg., Pentastomum denticula- tum, which is sexless, inhabits the liver of rabbits and hares ; but in the sexual state this parasite, known as Pentastomum tenioides, infests the nasal cavities of wolves and dogs. In the Arctisca or Tardigrada, the sexes are not distinct, for these microscopic animals are hermaphrodites. The ovary is a sac-like organ, situated on the posterior half of the digestive canal, and opens into the cloaca, which-is a dilatation of the rectum. The ova of Hmydium, Milnesium, and Macrobiotus wrsellus are invested by a chorion, and they are deposited in an ephippium, which is in reality the cuticle of the parent. The vitellus undergoes complete segmentation, but there is no metamorphosis.* The Pycnogonida are dicecious, and ‘the testes and ovaria are lodged in the legs and open upon their basal joints. The embryo emerges from the egg as a larva provided with a rostrum, and with three pairs of appendages, which represent the short anterior three pairs in theadult. (A. Dohrn.) The four pairs of great limbs of the adult are produced by outgrowths from a subsequent posterior elongation of the body.” In the Acarina, the sexes are distinct. The male organs are formed on distinct types. The testes of Ixodes, for * See Kaufmann's paper in Zeitschrift fiir Wiss. Zoologie, 1851. 440 PHYSIOLOGY OF THE INVERTEBRATA. instance, consist of a group of five pairs of follicles which unite in the abdomen.. There are two vasa deferentia which terminate in the base of the so-called chin-like process. The male introduces this process, together with the chelicera, ‘into the vagina of the female during copulation. In Trom- bidium, the testis consists of twenty follicles attached to a vas deferens which opens between the posterior legs. Although there are twenty follicles comprising the testis of Trombidiwm, that of Gamasus has only two; but each of these has its own vas deferens. Many Acarina (e.g., Oribates, Bdella, Gamasus) possess a penis, which is situated in a similar position to that of the vulva of the females. As accessory organs of repro- duction, some of the legs are used by the males to. retain the females during coition. The female organ consists of a pair of ovaries, whose ducts open in a common vulva situated, as a rule, in the middle of the abdomen on the ventral side of the body. In Gamasus and Ixodes, the genital aperture is situated on the thorax. The two oviducts of Ixodes ricinus open into a pyriform uterus, whose neck, according to Von Siebold, communicates laterally with a large cecum coming from the vulva. The cecum is a receptacle for the spermatic fluid during copulation ; which, after the act, flows into the uterus and oviducts. This caecum is also in connection with two small glands, filled with transparent cells, which secrete a substance for enveloping the ova. The oviduct of many VaEOVLSNYO ViLOASNI vosn TION PHYSIOLOGY OF THE INVERTEBRATA. 455 stability of the organic world? Nothing would be at one stay. “‘There could be no permanence in anything living. The philosophy of modern biology is that the most complex forms of living creatures have derived their splendid complexity and adaptations from the slow and majestically progressive variation and survival fron the simpler and the simplest forms. If, then, the simplest forms of the present and the past were not governed by accurate and unchanging laws of life, how did the rigid certainties that manifestly and admittedly govern the more complex and the most complex come into play ? If our modern philosophy of biology be, as we know it is, true, then it must be very strong evidence indeed, that would lead us to conclude that the laws seen to be universal break down, and cease accurately to operate, where the objects become microscopic,* and our knowledge of them is by no means full, exhaustive, and clear. Moreover, looked at in the abstract, it is a little difficult to conceive why there should be more uncertainty about the life-processes of a group of lowly living things, than there should be about the behaviour, in reaction, of a given group of molecules. The triumph of modern knowledge is a knowledge—which nothing can shake—that Nature’s processes are immutable. The stability of her processes, the precision of her action, and the universality of her laws, are the basis of all science, to which biology forms no exception. Once establish, by clear and unmistakable demonstration, the life-history of an organism, and truly some change must have come over Nature as a whole, if that life-history be not the same to- morrow as to-day; and the same to one observer, under the same conditions, as to another. “No amount of paradox would induce us to believe that the combining proportions of hydrogen and oxygen had altered in a specified experimenter’s hands in synthetically * Biichner, Sattler, Grawitz, and others state that certain microbes are capable of being transformed into other microbes. 456 PHYSIOLOGY OF THE INVERTEBRATA. producing water. We believe that the melting-point of platinum and the freezing-point of mercury are the same as they were a hundred years ago, and as they will be a hundred years hence. Now carefully remember that, so far as we can see at all, it must be so with life. Life inheres in protoplasm ; but just as one cannot get abstract matter—that is, matter with no properties or modes of motion—so one cannot,” says Dr. Dallinger, “get abstract protoplasm. Every piece of living protoplasm we see has a history: it is the inheritor of countless millions of years. Its properties have been determined by its history. It is the protoplasm of some definite form of life’ which has inherited its specific history. It can be no more false to that inheritance than an atom of oxygen can be false to its properties. All this, of course, within the lines of the great secular processes of the Darwinian law, which could not operate at all if caprice formed any part of the activities of Nature.” In addition it may be remarked that pleomorphism is entirely opposite to the Darwinian law, but abiogenesis (as already stated at the commencement of the present chapter) is not: in opposition to evolution. It is one of the theories which have been brought forward to explain the origin of life in the world. Protoplasm consists of carbon, hydrogen, oxygen, nitrogen, with a little sulphur and phosphorus, and still fainter traces of other elements, combined in extreme complexity. ‘Given the matter which composes it, and the play of forces and energies of which that matter is the vehicle, wherein lies the difference which gives as one result non-living substance, and as another result living substance ? The answer obviously is that, the ingredients being the same, the difference must lie in the mixing;” and-it is this “mixing” which the scientist has to find out to explain the origin of life, or, before abiogenesis can be.considered to be more than one of the theories which have been put forth during historic times to account for it. APPENDIX. — + I. Tue Composition or Hamocyanin. Tue author* has ascertained the approximate composition of hemocyanin (see p. 142 e¢ seg.). ‘The hemocyanin derived fromthe blood of Homarus, Sepia, and Cancer respectively was submitted, after purification, to chemical analysis. The percentage composi- tion of this important substance is very constant. In this respect it differs from hemoglobin. We are, therefore, justified in caleu- lating an empirical formula for hemocyanin as follows :— O67 A ig63N o5Cu8,0,,5. The blood of the lower, and some of the higher, Invertebrates is a watery fluid, called the hydrolymph. But in the majority of the higher Invertebrates, the blood is less watery and much richer in albuminoids ; it is sometimes termed a hemolymph. II. InvERTEBRATE CARTILAGE. Invertebrate cartilage is very similar, chemically and_histo- logically, to that of the Vertebrata. Dr. W. D..Halliburtont has recently examined the head cartilage of Sepia, and the entosternite of Limulus. ‘The basis in both structures is chrondrin; there is, however, in addition, a certain proportion of chitin, in the case * Comptes Rendus de V Académie des Sciences, tome 114, p. 496. + Proceedings of Royal Society, vol. 38; and Quart. Jour. Micro. Science, vol, 25. ‘ 458 APPENDIX. of Limulus 1.01, and in that of Sepia 1.22 per cent. These results are especially interesting, as showing that chitin is not a substance which is exclusively epiblastic in origin, but here, at least, we have it occurring in mesoblastic structures.” IIT. Curtin anp OTHER SUBSTANCES. Chitin.—This substance, which is frequently impregnated with salts (calcareous salts in the Crustacea, silica in the lingual ribbon of certain Mollusca), “has a very wide distribution among the Invertebrata. It is in the Arthropoda that it is found to the greatest extent ; it forms the membrane of the ovum, the cuticle of the adult, with its appendages, the supporting substance in the trachee of insects, dc. It is also found in the Mollusca (jaws and odontophore); and in worms (e.g., the sete of the Annelida). It forms the membrane of the ova in other groups, and the cyst-wall in encysted forms of the Protozoa, &c.” Chitin is readily prepared by treating the shells of crabs and lobsters with HCl, so as to dissolve out the calcareous salts. It is also obtained by digesting the wings of beetles and other insects in a solution of NaHO. In both cases the chitin remains undis- solved. The residue is then dissolved in strong HCl, and re- precipitated from this solution by the addition of water. This operation is repeated two or three times, when the chitin is obtained in a state of purity. Chitin is a colourless substance, devoid of crystalline structure, and is only soluble in strong mineral acids. When heated with strong acids, it is decomposed into acetic acid and glucosamine :— 2C,,H,,N,0O,, + 2H,O = 30,H,O, + 4C,H,,NO,. Conchiolin (C,,H,,N,O,,) is the skeletin or basis of the shells of the Gasteropoda. Cornein (C4H,,N,O,;) is the skeletin of Gorgonia and other corals. Spongin is the skeletin of the Porifera. Its composition is unknown. Fibrorin is the substance of which the webs of spiders are com- posed. APPENDIX. 459 These four substances all yield leucin and glycocine on decom- position. Hyalin is allied to chitin, and is found in the Echinodermata and other Invertebrates. It has the following composition :— C= 45.3 to 44.1; H=6.5 to6.7; N=5.2 to 4.5; O=43 to 44.7 per cent, Tunicin is the carbohydrate found in the Tunicata, Ophry- dium, &c. It is represented by the formula (C,H,,0,),.* IV. Tue Inx-pac or Sepia. The secretion of the ink-bag (see p. 73) is used to colour the water and cover the flight of the animal. It contains from 70 to 87 per cent. of solids, of which the black or brown pigment is the chief constituent ; it also contains mucin, magnesium carbonate, sodium sulphate, calcium carbonate, and sodium chloride. Accord- ing to Nencki and Sieber,t the pigment contains an acid, which has been termed sepiaic acid. It has been suggested that the ink-bag corresponds to a liver ; but its secretion contains neither biliary acids nor glycogen, and it has no digestive properties. ? V. WAVE-LENGTHS. The sign A (p. 151 eé seg.) denotes wave-lengths. For instance, A506 means a wave-length equal to 506 milliontlis of a millimetre. Sometimes the letters W.L. are used instead of X. * For further information, see Gautier’s Chimie Biologique (1892), pp. 163, 165, 188; and Halliburton’s Chemical Physiology and Pathology. + Chem, Centralblatt, 1888, p. 587. INDEX OF AUTHORITIES. Acassiz, L., 303, 350 Allman, G. J., 298 Anacreon referred to, 435 Aristotle, 108, 407 BACKS, 137 Baéyer, A. von, 13 Balbiani, 407, 408, 410, 437 Balfour, F. M., 404 Ball, W. P., 363 Barfurth, 108 Bastian, H. C., 399, 406 Beddard, F. E., 225 Benecke, 410 Beneden, E. Van, 146, 405, 410 Beneden, P. J. Van, 36 Bennet, 399 Bernard, Claude, 140, 288, 399 Bert, Paul, 168 Bibra, Von, 167 Binet, A., 4, 296 Bischof, 252 Blundstone, 115 Bokorny, T., 11,.12, 14 Brady, G. 8., 55, 56 ‘Brandt, 81 Biichner, 455 Buckton, G. B., 435 Bunge, G., 227 Biitschli, 376, 407 Byron quoted, 360 CAHOURS, 10 Capranica, 271 Carlier, E. W., 126 Carruthers, W., 426 Chabrier, 394 Chandelon, 76- Cienkowsky, 27, 81 Claparéde, E., 258, 348, 407, 441 Claus, 2098, 300, 359, 444 Cohn, F., 419 Cowan, 394 Cuénot, L., 141 Cunningham, J. T., 284 Cuvier, 72, 75, 108, 185, 400 DALLINGER, Rev. W. H., 27, 348, 376, 3771 399) 495, 406, 453, 456 Dalton, J., 180 Darwin, C., 4, 56, 85, 239, 249, 329, 359, 363, 391, 392, 400, 402, 403, 436, 443, 444 De Bellesme, J., 110, 116 Delle Chiaje, 130 De Negri, G., 211 De Quatrefages, 320, 354, 414 Devaine, 426 Devaux, H., 233 Dixon, H. H., 391, 392 Dohrn, A., 439 Drysdale, J., 27, 348, 376, 405, 406 Dufour, L., 262 Dugés, 219 Dujardin, 325, 347, 440 Dumas, J. B., 10 Duncan, P. M., 350, 351 Dunstan, W. R., 261 Duthiers, Lacaze-, 45, 283, 431 EHRENBERG, 347, 354 Eimer, 310, 311, 379, 410 Engelmann, T., 172 Erman, 167 Ewart, J. C., 312-319, 351, 352, 380, 383, 385 FAIVRE, 325 Favre, 430 Fisher, 97 Follows, H., 282, 283 Fol, M., 206 Foster, M., 15, 102, 404 462 Fredericq, L., 82, 85, 87, 88, 89, 91, 104, 107, 110, 116, 135, 137, 139, 142, 143, 144, 166, 168, 318, 319, 331-336 Fremy, 137 Fries, 410 GAUTIER, A., 176, 459 Geddes, P., 105, 149, 224, 226 Gegenbaur, C., 193, 258, 325, 365, 366, 370 Genth, 166 Giard, A., 344, 412, 416, 453 Gibson, R. J. H., 284, 285, 354 Gmelin, 90 Goodsir, 443 Gorup-Besanez, 168, 274, 283 Graber, V., 194 Gratiolet, 190 Grawitz, 455 Greef, 185, 415 Greenwood, 79 Grenacher, H., 255, 462 Griffiths, A. B., 4, 10, 13, 27, 30, 58, 83, 85; 88, 89, 92, 94, 95, 100, 102, 103, 105, 108-112, I16, 141, 143, 144-147, 175-180, 229, 246-248, 254, 256, 257, 259, 265, 266, 270, 272, 275, 279, 282-287, 336, 351, 357, 301, 390, 426, 453, 457 Gros, 406 Gruber, 296, 324, 407 Guckelberger, 15 HA#CKEL, E., 80, 81, 82, 166, 298 Halliburton, W. D., 148, 167, 457 Hamann, O., 319 Harless, 167 Harley, G., 277 Harting, 298 Harvey, 182 Hauser, G., 356, 357 Haycraft, J. B., 126 Helmholtz, 331 Hensen, 357 Herdman, W. A., 344 Hertwig, O., 298 Hertwig, R., 298 : Hippocrates quoted, 426 Hoffmann, 185 Hoppe-Seyler, F., 11, 116, 213 Huxley, T. H., 2, 5, 9, 19, 26, 31, 36, 39, 43, 56, 61, 129, 186, 187, 188, 192, 201, 205, 206, 230, 237, 260, 265, 289, 296, 207, 311, 329, 304, 399, 402, 413, 417, 419, 437, 443 INDEX OF AUTHORITIES. IRVINE, R., 63, 245, 249, 252, 253, 277- 282 JOHNSTONE, A., 100, 270, 425 Joly, 399 Jolyet, 116, 233, 235 Joseph, G., 320 KAUFMANN, 439 Kent, W.8., 26, 408 Kishinouye, K., 441 Kisser, 14 Kistiakowsky, 110 Klebs, 347 Kleinenberg, 297, 299, 308, 311 K6lliker, A., 407 Kraepelin, 432 Kravkoff, N., 102, 108 Kretzschmar, 13 Krukenberg, 106, 110, 116, 130, 142, 143, 157, 168, 169, 170, 211, 212, 217, 222, 238-240, 244 Kiihne, W., 148, 157 Kundt, 214 Kiinstler, 348 LACHMAN, 348, 407 Landois, 360 Lankester, E. R., 77, 80, 81, 129, 130, 131, 144, 146, 155, 166, 167, 226, 238, 284, 344,452 Latham, P. W., 15, 17 ° Ledenfeld, R. von, 296, 297 Letourneau, C., 116 Leuckart, R., 97 Levy, M., 106, 115 Leydig, 351, 353) 357 Lieberktihn, 10, 11, 17 Loéw, O., 11, 12, 14 Lowne, B. T., 95, 267 Lubbock, Sir John, 373, 428 Lyonnet, 229 MAcDONALD, J. D., 368 Macleod, 230 MacMunn, C. A., 81, 82, 85, 91, 104, 105, 127, 129, 131, 146-157, 167, 169, 174, 209-226, 230, 231, 233- 240, 256, 265, 283, 284, 350, 351 Magnus, 180 : M‘Alpine, D., 398 Mantegazza, P., 398, 408 Marey, 332 Martens, 387 Maupas, 346 McCook, H. C., 100 Meckel, H., 99, 442 Meldola, R., 261 INDEX OF AUTHORITIES. Merejkowsky, 148, 149 Metschnikoff, E., 431 : Milne-Edwards, 130, 248, 287, 451 Milton quoted, 391 M‘Kendrick, J. G., 211 Mojsisovics, A. von, 451, 452 Moleschott, 235 Morgan, C. L., 359, 373 Morgan, T. H., 442 Mori, 12, 13 Morse, 276 Moseley, H.N., 40, 210, 215, 216, 218, 225, 429 Miilder, 10 Miiller, 348 Murray, J., 245, 249, 252, 253 Musset, 399 NENCKI, 459 Newport, 192, 229 Owen, Sir Richard, 200, 338, 339, 394, 442 PALLADIN, W., 14 Palm, R., 84, 101 Papillon, 166, 168 Parker, G. H., 364 Pasteur, L., 399 Pelouze, 137 Pennetier, 399 Pettenkofer, 84, 90, 101 Pfliiger, 15 Planta, A. von, 97 Plateau, 93, 116 Pouchet, F. A., 263, 347, 399 Poulton, E. B., 126, 132, 133, 134, 146, 157, 158, 160-165, 170, 261, 6 204 Prouho, H., 319 QUATREFAGES, J. L. A. de, 320, 354, 414 RABUTEAU, 166, 168 Ranke, 357 Rawitz, 272 Regnard, 166, 217 Regnanlt, 233, 235 Reinke, 12, 13 Reiset, 233, 235 Richet, 120 Robin, C., 5 Romanes, G. J., 120, 294, 297-320, 349-352, 373; 378-385 Rotteken, 350 Rouget, 168, 375 Riiling, 10 463 Sars, G. O., 34) 51, 53, 54, 55, 575 196, 197, 199, 217, 232, 271, 328, 329, 361, 395, 396, 414, 442 Sattler, 455 Savigny, 48, 113 Schafer, EH. A., 300 Scherer, 10 Schiff, 288 Schmidt, 169, 279, 280, 357 Schmiedeberg, 106 Schmitz, 22 Schneider, 350 Schénfeld, 97 Schorlemmer, C., 11 Schiilze, 14, 217, 264, 265 Schiitzen, P., 17 Schiitzenberger, P., 10, 13, 14 Schwalbe, G., 130 Schwann, 3 Sieber, 459 Siebold, L. von, 331, 356, 357, 361, 363, 394, 424, 436, 437, 438, 440, 444, 452 Smith, 287 Sochaczewer, D. 366, 367 Spencer, Herbert, 18, 250 Spengel, J. W., 366 Stamati, 103 Stein, 29, 346, 407 Stokes, Sir George, 131, 174 Swinton, A. H., 195, 358, 436 TEUSCHER, 185 Thomson, A., 393 Tiedemann, 90, 185 Tyndall, J., 399 VAN DER HOEVEN, 51 Vandevelde, G., 331-336 Vejdovsky, 225 Verne, Jules, referred to, 249 Vierordt, 172 Vitzou, 277 Vogel, 214 Voigt, 81, 283 Vulpian, 342 WATTS, 170 Weinland, C., 271 Will, 274, 283 Williams, T., 366 Wittich, 110 Witting, 168 Woodhead, G. 8., 63, 277-282 Wiirtz, A., 10, 233 ZALESKI, M., 103 Zeiss, C., 157, 171 246 Zenker, 443 Zonachus referred to, 435 SUBJECT INDEX. ABIOGENESIS, 399, 400, 456 Absorption in Annelida, 122 Arachnida, 123 Brachiopoda, 124 Cestoidea, 122 Celenterata, 120 Crustacea, 123 Echinodermata, 121 Insecta, 123 Invertebrata, 117-124 Mollusca, 124 Myriapoda, 123 Polyzoa, 124 Porifera, 120 Protozoa, 119 Acanthocephala, 38, 39, 323, 428 Acarina, 47, 100, 231, 328, 361, 439, 440 Acarus, 231 Acherontia atropos, 179 Achetide, 357, 358 Acinetie, 26, 28, 29 Acridide, 357 | Actinic, 34, 77, 81, 83, 210, 212, 213, 214, 217, 218, 219, 311, 351, 378, 4II, 412 ; Actinia mesembryanthemum, 212, 213, 214, 350 Actiniochrome, 214, 215, 217, 218, 219 Actiniohematin, 212, 214, 215, 216, 217, 218 Actinophrys, 24, 26 Actinospherium, 24, 26 Actinozoa, 32, 33, 121, 122, 128, 245, 311; 350 Activity of respiration, 233 Aolosoma Headleyi, 226 quarternarium, 226 ienebrarum, 225 variegatum, 226 Aischna, 230 Aitiology, 1 Agaricia, 409 Albumin, 10, 11, 13 Aldekydic nature of albumin, 12 Alimentary canal of Acarina, 47 Amphipoda, 56 Araneina, 48, 99 Aretisca, 47 Arthrogastra, 50 Brachiopoda, 66 Brachyura, 58, 101 Cephalopoda, 72-75, 109 Chilopoda, 41 Cirripedia, 56 Cladocera, 54 Coleoptera 46 Copepoda, 55 Diplopoda, 41 Diptera, 43 Echinodermata, 34, 82 Gasteropoda, 70-72, 105 Gephyrea, 37 Hemichordata, 75 Hirudinea, 38, 87 Hymenoptera, 45, 96 Isopoda, 57 Lamellibranchiata, 67, 104 Loaner 43, 44, 95 ‘acroura, 59-63, 103 Nematoidea, 39 Neuroptera, 45 Oligocheta, 38, 87 Orthoptera, 41, 92 Ostracoda, 55 Pentastomida, 47 Peripatus, 40 Phyllopoda, 51 Polycheeta, 38, 91 Polyplacophora, 69 Polyzoa, 64-66 Pteropoda, 72 Pycnogonida, 47 466 Alimentary canal of Rhynchota, 43 Sagitta, 40 Scaphopoda, 69 Stomapoda, 57 Thysanura, 41 Tunicata, 76 . Xiphosura, 50 Amebee, 23-26, 31, 207, 246, 288 Ameba terricola, 375 Ameba, the sarcode of, 3 Amphicora, 354 Amphilina, 36 Amphioxus, 80, 342 Amphipleura pellucida, 405 Amphipoda, 56, 428, 444 Amplhaptyches, 36 Ampullaria, 237 Anatomy, 5 Anguillula brevispinus, 259 Animal physiology, 1 Annelida, 37, 122, 125-128, 130, 143, 152, 157, 182, 187, 223, 224, 226, 243, 245, 256, 258, 353) 354, 387, 389, 402, 422, 448 Annulosa, 5 Anodonta, 67, 104, 105, 141, 169, 202, 233, 237-239, 276, 279, 282, 287, 339, 448 Anomoura, 57, 444, 446 Anophthalmus, 359 Antedon, 417, 422 Anthea cerus, 81, 212, 216, 217 Anthophysa, 376, 405 Anus, improvised, 30 Apertures, exhalent, 31, 32 inhalent, 31, 120 Aphides, 43, 394, 402, 431, 436 Aphrodite, 153, 226 Apis, 96, 229, 260, 325, 360, 431 Aplysia depilans, 141, 143, 169 punctata, 142, 216 Appendicularia flabellum, 206, 452 Appendix, 457 Aptera, 438 Apus, 51, 167, 271, 443 Araneina, 48, 99, 101, 230, 231, 268, 270, 328, 395, 440, 442 Arachnida, 40, 47, 48, 64, 91, 123, 142, 166, 196, 230, 268, 325, 327, 359, 361, 394, 439 Arachnidium of spider, 99, 268 Arcella, 25 Aretisea, 47, 63, 439 Arenicola, 146, 153, 224, 226, 354 piscatorum, 152 Argonauta, 72 Argynnis, 433 SUBJECT INDEX. Arian ater, 238, 284, 366 rufus, 107, 108, 168, 237, 239 Aristotle’s lantern, 385 Arthrogastra, 50, 63, 231, 268, 327, 442 Arthropoda, 9, 40,. 63, 64, 191, 192, 260, 341, 342, 370, 371, 389 Ascaris acus, 227 dentata, 247 lumbricoides, 227, 426 marginata, 86 megalocephala, 227 mystax, 227 nigrovenosa, 426 Asexual reproduction, 401, 411 Aspidogaster, 420 Assimilation, 2, 20 Astacus fluviatilis, 59, 60, 61, 103, 105, 139, 167, 200, 232, 234, 272, 274, 275, 283, 323, 330, 361, 362, 364, 396, 412, 445, 446 Astacus, gastric juice of, 103 stomach of, 61 Asteracanthion rubens, 234 Asterias glacialis, 221 Asteridea, 4, 34, 83, 85, 122, 185, 243, 246, 254, 255, 256, 317, 351, 352, 380, 386, 414, 417 Asterina gibbosa, 221 Astrea, 409 Astropecten aurantiacus, 380, 382 Atlanta, 70 Auditory organs, 349, 351, 352, 354, 357, 361, 362, 363, 367, 368 Aurelia, 211, 212, 300, 305, 306, 307, 378, 411 Auricularia, 413 Bacillus anthracis, 453 subtilis, 453 Bacteria, 21, 27 Balanoglossus, 75 Balanus balenoides, 443 Barnacles, 56 food of, 56 Bdella, 440 Bees, food of, 98 Belanus, 56 Bilharzia, 420, 423 Biliary acids, 89, 90, 101, 108 Bilirubin, 73 Biliverdin, 73, 213, 214, 215 Biogenesis, 399 Bipinnaria, 415 Blastoccele, 36, 37 Blastomeres, 2 Blatta, alimentary canal of, 92, 327 Blatte, 41, 42, 93, 265 SUBJECT INDEX, Blind crustaceans, 363 insects, 359 Blood, chromatology of, 146-170 copper in, 145 gases of, 175-180 in Invertebrata, 125-181 of Lepidopterous larvee, 157-166 of various worms, 153 saline matter in, 139, 141, 144 Blood-vascular systems, 185, 187, I9I, 192, 201, 231 Blood-vessels, 123, 124, 155, 180, 182, 186, 190, 197, 199, 200, 224, 228, 236, 239 Bojanus, organ of, 68, 143 Bombardier ‘beetles, 262, 263 Bombyx, 64 Bonellein, 225 Bonellia, 224, 423 Bopyrus, 363 Brachiolaria, 415 ; Brachiopoda, 64, 65, 66, 201, 236, 275, 338,447), Brachinus crepitans, 262, 263 displosor, 262 Brachyura, 58, 60, 101, 192, 444, 446 Branchiz, 56, 140, 192, 193, 199, 200, 202, 207, 224, 230, 232, 236, 237, 240, 286 Branchiogasteropoda, 70, 72, 236, 284, 366, 450 Branchiomma, 354 Branchiopoda, 50, 53, 124. 232, 443 Buccinum, 72, 105, 109, 238 Bugs, the, 43, 263, 433 Bunodes balliz, 212, 215 217 crassicornis, 212, 215 CALCIFEROUS glands, 87, 88 Calcium phosphate, 255, 282, 284, 416 Calliphora, 96, 267 Calosoma inquisttor, 263 Calyptrwa, 70 Cambarus pellucidus, 364, 365 setosus, 364, 365 Campodea, 41 Cancer, 167, 178, 233, 234 Capitella, 146 Carabus, 263 Carcinus meenas, 101, 103, 104, 138, 139, 142, 167, 233, 320 Cardiwm, 67, 104, 105, 234, 238, 397, 448 Cartilage, Invertebrate, 245, 368, ot? ll ‘ laryophyllia, 40 Cutallnet, 26 467. Cell theory, 3 Centipedes, 41 Cephalopoda, 70, 72, 109, 142, 143, 202, 204, 236, 255, 285, 341, 305, 369, 398, 404, 451 Cestoidea, 35, 36, 85, 86, 122, 127, 180, 187, 243, 320, 387, 421 Cherocampa Elpenor, 162 Cheetifera, 37 Cheetogaster, 424 Cheetognatha, 39, 324, 354, 429 Cheetonotus, 39 Chetopterus, 153, 226 Chetura, 39 Cheirocephalus, 146 Chela, 50, 102 Cheliceree, 48 Chelifer, 442 Chemistry of protoplasm, 10-19 Chermes abietis, 436 Chilognatha, 41, 355, 389, 430, 431 Chilopoda, 40, 41, 192, 355, 389, 430 Chironomus, 14 Chitin, 39, 56, 63, 278, 279, 458 Chitinous spines, 40, 42 Chiton, 69 Chlorocruorin, 130, 131, 153, 155, 156, 157, 181, 225' Chlorofucin, 217, 236 Chlorophyll, 21, 80, 81, 82, 90, 132,. 134, 152, 153, 165, 181, 209, 217, 225, 226, 23 Cholesterine, 13 Chorion, 412 Chorology, 1 Chromatophores, 21 Chromophanes, 157 Chromophylls, 21 Chrysaora hysocella, 210, 300 Chylific ventriculus, 42-46, 93 Cicadee, 43, 394, 435 Cilia, 29, 39, 65, 67, 352, 374, 375+ 377 Ciliata, 28, 30, 348, 377 Circulation in Annelida, 187 Arthropoda, 191 Brachiopoda, 201 Celenterata, 184 Echinodermata, 185 Invertebrata, 182-206 Mollusca, 201 Polyzoa, 200 Porifera, 184 Protozoa, 183 Trichoscolices, 187 Tunicata, 205 Cirratulus, 153, 226 Cirri, 56, 224 468 Cirripedia, 56, 192, 196, 329, 363, 443 Cladocera, 54, 55 Classification, 5-8 Classification of nerves, 294 Claspers, 48 Claviger, 359 Cho, 450 Clistenterata, 66, 338 Coagulation of blood, 126, 133, 135 Cobites, 85 Coccus hesperidum, 436 Cockroaches, 41, 431 Codosiga, 405 Celenterata, 32, 33, 79, 80, 120, 182, 209, 243, 248, 297, 320, 349, 378, 409, 410 Coleoptera, 46, 63, 326, 327, 357) 359 393, 394, 433» 435) 438 Collospheera, 26 Colours of eyes of Lamellibranchiata, 369 Colpoda, 296 Concheecia, 196 Concluding remarks, 453-456 Conjugation, 405, 407, 421 Constituents of so-called liver of Helix, 106 Contractile vacuoles, 25, 26, 28, 30, 3, 183, 184, 208, 240, 243, 246, 2 4: Convoluta, 35, 36 Copepoda, 50, 55, 196 Coralligena, 33, 410 Coral reefs, &c., 250-254 Cornynactis viridis, 218 Corpuscles, blood, 125, 126, 132, 149, 150, 181 Correlative functions, 2, 3 Covered-eyed Medusce, 299-305 Crayfish, stomach of, 61 Creatine, 13 Creatinine, 13 Cribella oculata, 221 Crickets, 41 Crinoidea, 34, 417 Crustacea, 40, 50, 51, 59, 60, 63, 101, 123, 125, 137, 142, 166, 180, 191, 196, 199, 200, 231, 271, 272, 282, 328, 359, 361, 395, 396, 404, 442 Cryptochilum, 346 Centar, 363, 430 Ctenophora, 33, 310, 311 Cyanea, 211, 212 Cyanein, 211 Cyanosulpheem, 130 Cyclas, 367, 448 SUBJECT INDEX. Cyclestheria, food of, 53 mode of feeding in, 54 hislopi, 51, 53, 196, 197, 232, 271, 328, 395 Cyclops, 9, 55 Cyprea, 72, 350 Cypridina, 196° Cyprinotus dentato-marginatus, 55 Cypris, 196, 443 Cystidea, 34 Cytherea, 69, 196, 443 Dallingeria Drysdali, 406 Dalton’s law, 180 Daphnia, 54, 146, 443 Darwinian law, 453, 456° Dasyditis, 39 Dead protoplasm, 12 Decapoda, 72, 272, 361, 363, 364, 6 Degeneration, 36, 39, 56, 122, 205, 344, 363, 365 Dendrocela, 386 Dentalium, 69 Diaptomus orientalis, 56 Diastase, 89 Dibranchiata, 72, 236, 341, 367, 368, 370 Dicranura furcula, 262 vinula, 132, 162, 261, 262 Difugia, 25 Diffused nervous system, a, 296 Digestion in Celenterata, 80-82 Echinodermata, 82-85 eneral, 20-78 trudinea, 87 Invertebrata, 20-116 Oligochceta, 87-91 Ler 79-116 olychceta, 91 Trichoscolices, 85-87 types of, 21 Digestive cavities, 33, 121-123 Digestive system, a rudimentary, 32 Dilatable sacs, 32 Fpete, 63 Diplopoda, 41, 355, 389, 430 Diplozoon paradoxum, 421 Diporpa, 421 Diptera, 43, 96, 267, 325, 327, 357, 359; 393) 433) 435) 438 Disc, trochal, 35 Distoma, 420 Doris tuberculata, 143, 169 Dragon-fly, larva of, 4, 85, 266 Dragon-fly, the, 41, 260, 394 Dytiscus, 326, 391 SUBJECT INDEX. a 34, 319, 352, 385, 386, 416, 41 Echinochrome, 149-152, 181 Echinochromogen, 151 Echinodermata, 9, 34, 82, 121, 122, 128, 147, 149, 180, 182, 185, 2109, 243, 245, 254, 311, 320, 351, 379, 412, 413, 416, 417 Lichinopeedium, 413, 416 LEichinorhynchus, 39, 323, 428 Echinus, 149, 186, 311, 315, 317, 385, 386, 416 Echinus acutus, 319 microtuberculatus, 319 spheera, 149 Lichiurus, 224 Eledone cirrhosus, 205 moschata, 168 Embryology, 404 Endogenous cell formation, 401, 404, 405, 407 Endolymph, 367 Ennomus Angularia, 162, 163 Enoplus, 354 Enterochlorophyll, 85, 90, 91, 104, 105, 106, 217, 220, 221, 238 Enteroceele, 37, 184, 413 Enterohzmatin, 105, 238, 239 Linteropneustra, 239 Lintomostracea, 79, 200 Lintozoa, 86 eira diadema, 99, 166, 231, 268 hemera, 64 hyra, 41t Angularia, 132 punctaria, 132, 162 Epiphragm of Helix, 284 Epipodia, 72 Errantia, 354, 388 Euglence, 22, 347 Eunice, 146 Euspongia anfractuosa, 296 officinalis, 296 Eupteryx, 390 Hurypterida, 50 Eversible glands, 262 Evolution of Invertebrata, 454 Excretion in Invertebrata, 30, 41, 241-292 Exhalent apertures, 31, 32, 184 Exoskeletons, secretion of, 245, 277 Eyes, the, 52, 301, 311, 316, 321, 328, 341, 346, 348, 349, 350, 352-355) 358; 361, 363, 364, 368, 369 FAT GLANDS, 244 Favia, 409 Feet, thoracic, 57 469 Fission, 401, 405, 408, 409, 426 Flagella, 27, 28, 29, 32, 374, 375s 377 Flagellata, 21, 22, 27, 347, 348, 376 Flagellata, chromatophores of, 21 Flagellate cells, 31, 32 Flustra foliacea, 167 Food of larval drones, 98 working-bees, 98 queen-bee larvz, 98 vacuoles, 29, 30, 120 Foraminifera, 25, 26 Formica, 326 Formic acid, 45, 260, 261 Formule of albumin, 11-17 Fresh-water worms, 38 Functions, correlative, 2, 3 generative, 2, 3 sustentative, 2, 3 Fusus, 238 Gamasus, 440 Gammarus, 167, 234 Ganglia, 298, 301, 302, 304, 320-344, 352, 357 Gas apparatus, 176 Gases of blood, the, 175-180 Gasteropoda, 70, 105, 108, 141, 142, 202, 203, 340, 364, 367, 386, 448 Gastric juice of Astacus, 103 Gastroliths, 61, 63 Gastrotricha, 39 Gastro-vascular spaces, 30-33, 120 ee 37, 408, 411, 414, 417, 429, 44 Gemmation, 33, 401, 405, 407, 409 410, 411, 421, 426, 447 Generative functions, 2, 3 Genital organs, 411, 412, 414, 416- 424, 427-453 Geophilus, 363, 430, 431 Gephyrea, 37, 129, 180, 224, 321, 353, 423 | Geryonide, 298 Gills, 155, 157, 168, 199, 230, 232, 236, 240, 448 Glands, pedal, 367 rectal, 42 salivary, 38, 40-42, 47, 49, 50, 60, 63, 64, 70, 73, 87, 91, 92, 94, 95, 97, 100, 105, 107, 108, 112, 114 Glandular organ of Nemutoidea, 259 Glenodinium polyphemus, 347 Glomeris, 355, 431 Glow-worm, 264 Glycera, 131, 146, 153 Glycocholic acid, 101, 103, 112 470 Glycogen, 96, 97, 101, 103, 104, 112, II Glycogenic function in Mollusca, Il Gnathopoda, 50 Goniaster equestris, 221 Goniastreea multilobata, 253 Gordius, 428 Grapsus, 412, 446 Grasshoppers, 41 Green glands, 272, 274, 287 Gregarina, 21, 23, 34, 119, 208, 375, 404, 405 Gryllotalpa, 391 Gryllus, 390 Guanin, 13, 255, 271, 274, 275, 283 Gustatory organs, 356, 366 Gymnolemata, 66 Gyrodactylus, 420, 421 Halocryptis, 196 Hematin, 155, 157, 213, 216 Hematoporphyrin, 155, 213, 218, ‘220, 221, 223, 238 Hemerythrin, 130 Hemerythrogen, 130, 156 Hemochromogen, 90, 131, 212, 213, 215, 216, 218, 220, 239, 244 Hemocyanin, 142, 143, 147, 166, 167, 168, 181, 457 Hemoglobin, 90, 129, 130, 131, 142, 143, 146, 147, 152-157, 167, 181, 213, 218, 222, 225, 226, 238 Hemophsis vorax, 87 Hemorhodin, 142 Hearts, 68, 123, 182, 185, 189, 192- 206, 237, 286 Helianthus annus, 12 Helicopepsin, 106 Helicorubin, 239 Helix, 70-72, 105, 108, 167, 168, 203, 237, 239, 243, 279, 283, 340, 365, 366, 368, 448, 449 Helix aspersa, 105, 106, 169 pomatia, 106, 127, 167, 169, 284, 66 3 Hemerobidee, 359 Hemichordata, 75 Hemiptera, 433, 435, 438 Hepatochromates, 217, 238 Hepato-pancreas, a, 108 Hermaphrodites, 56, 409, 414, 415, 418, 420-429, 439, 442, 443, 448- 451 Hermaphroditism, 402, 412 Hermit-crabs, the, 58 Heterogenesis, 399, 406 Heteropoda, 70, 448 SUBJECT INDEX, Heterotricha, 377 Hexapoda, 46 Hirudinea, 37, 87, 223, 225, 256, 321, 322, 353) 423 Hirudo medicinalis, 37, 87, 126, 131, 146, 153, 188, 189, 190, 224, 234, 256, 321, 353, 387, 388, 424 Fister, 4 Histohematins, 129, 155, 167, 212, 216, 220, 222, 231, 237, 238, 256, 284 Histriobdella, 423 / Holothuria nigra, 147, 148, 221 Holothuridea, 34, 219, 224, 249, 386, 413, 414, 417 Homurus, 59, 104, 137, 166, 167, 179, 193, 199, 232, 233, 283, 331-336, 363, 364, 396 Honey-bag of bees, 46, 97 Hyalea, 72, 450 Aydra, 32, 34, 81, 297, 378, 409, 411 Hydrachna, 100, 440 Hydra fusca, 79, 80 viridis, 80, 81 Hydrozoa, 31-33, 120, 127 Aymenoptera, 45, 96, 325, 357, 359) 394) 433: 435, 438 Hypopharynx, 42 Hypotricha, 377 Hypoxanthine, 14 Ibla, 443 diyocryptus longiremis, 54 Imbibition, 23, 36, 117 Imperforata, 25, 26 Indol, 90, 91 Infundibulum, an, 236 Infusoria, 12, 26, 34, 81, 120, 184, 208, 375; 377, 405, 406, 407 Infusoria ciliata, 26, 29, 407 Jflagellata, 26, 27, 31, 405 tentaculifera, 26, 27, 406 Ingluvies, 42 Inhalent apertures, 31, 120, 184, 408 Ink-bag of Sepia, 73, 459 Insecta, 40-43, 64, 91, 123, 125, 131, 137, 157, 191-195, 228, 230, 244, 259, 267, 325, 327, 355, 359) 390 393, 404, 428, 431, 433 Integumentary organs, 244 Intermesenteric chambers, 33 Intestinal canal, a rudimentary, 30 Intestines, 40, 42, 44, 50, 51, 53, 55) 56, 65, 87, 270 Introduction, 1-9 Invertebrata, absorption in, 117-124 blood in, 125-181 circulation in, 182-206 SUBJECT INDEX. Invertebrata, digestion in, 20-116 . excretion in, 241-292 locomotion in, 374-398 nervous systems in, 293-344 organs of sense in, 345-373 reproduction in, 399-453 respiration, 207-240 Invertebrate kidney, the, 290-292 liver, so-called, 115 Isophyllia dipsacea, 253 Isopoda, 67, 363, 396, 428, 444 Ixodes, 47, 439, 440 ricinus, 440 Tapys, 41 Jaws, 40 Jellyfishes, 210 Jone, 363 Juice of working bees, 97 Fulus, 355; 431 KIDNEY, Invertebrate, 1, 30, 42, 55, 96, 242, 243, 245-248, 254, 256, 257; 259, 260, 266, 275, 283, 286, 290 King-crabs, 50, 457 Lacinularia, 419 Lamellibranchiata, 67, 104, 141, 202, 243, 255, 276, 278, 282, 338, 339, 365, 367, 368, 448 Lampyris splendidula, 264, 265 Larve, Lepidopterous, 162, 165, 262 Phytophagous, 132 Latonopsis australis, 54. Leeches, 37 Lepas, 56 | Lepidoptera, 43,44, 45, 63,95, 194, 325, 327) 357; 359) 393: 394, 433, 438 Lepidoptera, heart of, 195 Lepidosiren, 237 Lepisoma, 41 Lepralia foliacea, 236 Lernceodea, 363 Leucein, 13 Leucin, 13, 14, 73, 82, 90, 101, 102, IIL Libellula depressa, 42, 94,95, 194, 230, 266, 325, 394, 433, 435 Libelludide, 394 Ligula, 45 Limazx flavus, 106, 238, 283, 366 maximus, 106, 237, 284 vartegatus, 238, 284 Lime carbonate, secretion of, 244, 248, 249, 250, 276-282 Limnadia gigas, 443 Limneus stagnalis, 169, 170, 237, 238, 239, 366 471 Limnocodium Sorbit, 309 Limulus, 50, 457 cyclops, 166, 200 Lingua, 42, 44 Lingula, 67, 201, 276, 338, 339 Liparis auriflua, 262 Lipochromes, 148, 149, 152, 153, 157; 167, 181, 215, 217, 220, 221, 226, 23 Lithobius, 355, 430 Lithocysts, 306, 308, 350, 379 Ltttorina, 237, 238, 239 Liver pigments, 89, 90 Liver, so-called, 49-51, 53, 57-63, 67, 68, 72, 73, 88, 91, 100-108, III, 115- 117, 217, 238 Living protoplasm, 12 Locomotion in Arachnida, 394 Crustacea, 395 Insecta, 390 Invertebrata, 374-398 Mollusca, 397 Myriapoda, 389 Locomotor system of Echinodermata, 379 Locomotor system of AMedusiw, 379 Locusta, 390 viridissima, 229 Locustide, 357, 358 Loligina, 367 Loligo media, 205 Lophophore, 65 Lophyropoda, 50 Loxodes rostrum, 348 Loxosoma, 447 Lucanus cervus, 229 Lumbricus, 87-91, 122, 126, 131, 146, 153, 188, 189, 223, 226, 257, 258, 321, 322, 353, 388, 412, 424 Lumbrinereis, 354. “Lungs,” 207, 230, 237, 240 Lutein, 148 Macrobiotus, 47, 48 ursellus, 439 Macrothriz spinosa, 54 Macroura, 58-60, 103, 104, 192, 331, 444, 446 Madrepora aspersa, 253 Maygosphera, 24, 26 Maja squinado, 138, 139 * Malacobdella, 38, 423 Malacoscolices, 64 Malacostraca, 50 Males, complemental, 56, 443 Malpighian tubes, 41, 42, 44-49, 57, 94- 96, 243, 259, 260, 265, 266, 270, 271, 275, 289 472 Mandibles, 40-43, 45, 51, 58, 60 Mantis, 390 Manubrium of Medusce, 304-306 Mastax, 35, 39 . Material agents in reproduction, of Insecta, 433-436 Maxille, 41-45 Maxillary apparatus, rudimentary, 6 7, Mazxillipeds, 57 Mayflies, 41 MMedusee, 185, 245, 297-310, 349, 350, 378, 379; 402, 411 Meleagrina margaritifera, 277 Melitcea, 433 artemis, 262 Melolontha, 325 Mermis, 39, 428 Merostomata, 50 Mesenteries, 33 Metastoma, 50, 58, 60 Metazoa, 9, 30, 32, 221, 245 Micrococet, 27 Microspectroscope, the, 153,155, 157, 169, 170-175, 215, 21 Millepora ramosa, 253 Millipedes, 41 Milnesium, 439 Mimicry, 82 Maandrina, 409 Molar motion, 2 Mollusca, 5, 9, 67, 105, 124, 125, 141, 167, 201, 233, 236, 244, 276, 278, 282, 339, 341, 342, 365, 367, 397, 402, 448 Mollusca, glycogenic function in, 115 salivary secretions in, 109 Monads, 26, 29, 347, 348, 376, 406 Monas vulgaris, 27 Monera, 404. Monostomum, 420 Monticularia, 409 Montipora foliosa, 253 Morphological units, 2 Morphology, 1 gene 37, 408, 410, 411, 417, 429, 44 Mucous glands, 245, 284 Murchisonia, 450 Murexide, 247, 248, 254, 259, 270, 274 Musca, 326, 390 Muscular fibres, 375, 387-389, 393 pharynx, 35, 40 Musical organs of insects, 433-436 Mya, 67-69, 104, 105, 283, 286, 287, 340 Mygale, 48 Myohzmatin, 219, 222, 231, 238, 284 SUBJECT INDEX. Myrianida, 426 Myriapoda, 40, 41,.46, 123, 127, 180, 192, 228, 260, 324, 355, 363, 389, 430 e es 264 ‘yrmeleonidce, 359 Mytilus, 67, 104, 105, 141, 234, 237, 238, 398 Myzostomatas, 37, 422 Nais, 79, 424 Naked-eyed Meduse, 298-308 Natica, 450 Natural selection, 250, 288, 391 Nautilus, 74, 202, 367, 370, 451 Nectocalyx of Medusce, 298, 300, 302, 304-306, 379 Nematoscolices, 38, 39, 227, 323, 354, 3890, 426 Nematoidea, 38, 39, 86, 127, 227, 259, 323, 354, 389, 426, 428 Nematorhyncha, 38, 39 Nematus ventricosus, 437 Nemertes, 418, 419 Nephelis, 131, 146 Nephridia, 204, 243, 256, 257, 260, 283-286 Nephrops, 232 Nepthys, 323 Nereis, 38, 91, 153, 226 Dumerillii, 152 regia, 322 Nerve-cells, 293, 299, 303, 3135 322 Nerve-centres, 295, 310, 319 Nerve-fibres, 293, 294, 299, 322, 353 Nerve-plexuses, 299, 313, 317, 319, 327, 351 Nerve-poisons, 309 Nerve-rings, 311, 316, 318, 321, 323, 342 Nerve-tracts, 296, 302 Nerves, inhibitory, 294 motor, 294 : of ce eae composition of, 336- 33 secretory, 294 sensory, 294 transmission of motor excita- tion in, 331-336 vascular, 294 Nervous systems, 292-344 Neuro-muscular elements, 297, 299, 302, 304, 308 Neuroptera, 45, 327, 357, 359, 394 433; 438 Nirmidee, 359 SUBJECT INDEX. Noctiluca, 27 Nuclein, 22 Nucleolus, 403, 407 Nucleus, 22, 24, 180, 310, 401, 407 Nutrition, types of, 21 Nycteribia, 359 Obisium, 442 Ocelli, 329, 359, 361 Ocnus brunneus, 221 Oculina coronalis, 253 Octopoda, 72, 367 Octopus, 72, 105, 142, 144, 168, 179, 202, 234, 239, 286 Odontophora, 70 Odontophore, 69, 72 Cisophageal glands, 38 Cisophagus, 34-36, 38-44, 47, 49-52, 55-60, 65, 79, 87, 92 Olfactory organs, 349, 351, 352, 356, 361, 363, 366, 367 Oligocheta, 37, 38, 87, 90, 223, 256, 257, 321, 388, 424 Omentum, an, 60 Ommastrephes, 370 Onchidum, 237 Oniscus, 57, 396 Onychophora, 40, 429 Onychoteuthis, 370 Operculum, an, 155, 157, 450 hiactis virens, 220 yhiolepis ciliata, 416 squamata, 415 Ophiura, 385 Ophiuridea, 34, 352, 380, 383, 386, 415, 416, 418 ee, 81 'chestia, 243 Organ of Bojanus, 48, 143, 202, 204, 243, 276, 282, 283 Organ of Semper, 366 Organs of special sense, 345-373 Orgyia antiqua, 262 udibunda, 262 Oribates, 440 Origin of life, 456 Orthoptera, 41, 42, 46, 63, 194, 327, 357, 394, 433, 435 ryctes nasicornis, 135, 136 Oscula, 31, 243, 408 Ostracoda, 55, 63, 192, 442, 443 Ostrea, 67, 69, 104, 105, 234, 237, 238, 283, 397, 448 Ovipositor, a modified, 45 Ovipositors, 356, 438 Oxychlorocruorin, 154 Oxyhzmoglobin, 131 Oxyuris ambigua, 427 473 Pagarus, 233, 412, 446 Paguride, 58, 446 Pacodinjonors, 43 Paleemon, 59, 104, 396 Pallium, 66, 70, 365 Palinurus quadricor nis, 234 vulgaris, 138, 178 Palpi, 42-45, 67, 361, 441 Paludicella, 66 Paludina vivipera, 169, 170, 237-239 Pamphagus, 25 Pancreas, the Invertebrate, 35, 38, 4°, 49-51, 55-58, 60, 64, 67, 72; 73: 76, 88, 91, IOI, 103-108, III, 116, 238 Pancreatin, 82, 89, 96 Pandora, 448 Pantostomate being, a, 26 Papilio feronia, 392 Machaon, 162 Paraglossz, 45 Paramecia, 28, 30, 81, 120, 207, 240, 346, 375, 407, 408 Parapodia, 224, 388, 426 Parenchyma cells, 265 Parthenogenesis, 401, 415, 419, 431, 436, 437; 447 Patella vulgata, 72, 105, 108, 237, 238, 239, 284, 285 Pearls, formation of, 277 Pecten, 67, 104, 368, 448 Pectostraca, 50, 56 Pedicellina, 447 Pediculidce, 359 Pelagic organisms, 250, 251 Pelodytes, 426 Penellina, 363 Pentacrinin, 216 Pentastomida, 439 Pentastomum, 47, 439 Peptones, 93 Perforata, 25 Pericardium, a, 191, 193, 282 Peridinece, 347, 376 Peripatus, 40, 260, 322, 324, 429 Periplaneta, 265, 325, 326, 327, 431, 432 | Peritricha, 377 Perivisceral cavity, 122, 127, 128 129, 189, 200, 224, 236, 256, 276 Perlide, 394 Phallusia mentula, 76 Pharynx, a, 35-40, 48-50, 65, 87, 236, 239, 387, 388 Phascolosma elongatum, 130 Phlogophora meticulosa, 158-161 Pholas, 69 Pholcus rivulatus, 49, 166 474 Phoronis, 37, 146, 153 Phosphorescence and digestion, 27 Photogenic organs, 264 Phryganide, 359 Phryxus, 363 Phylactoleemata, 65 Phyllocyanin, 226 Phyllodoce-green, 225 Phyliodoce viridis, 224, 226 Phyllopoda, 51-54, 167, 196, 232, 271, 328, 395 Physiological labour, division of, 8 units, 3 Physiology, animal, 1 Physopoda, 42 Phytophagous larve, 132, 133 Pigments, liver, 89, 108 respiratory, 210, 214, 216, 218, _ 223; 225, 227, 233, 236, 237 Pilidiwm, 419 Pinna, 398 squamosa, 143 Pisa, 412, 446 Planarie, 352, 387, 418 Planaria lichenoides, 387 Planorbis, 146, 170 Planula, 411 Platycarcinus pagurus, 138 Pleomorphism, 453, 455, 456 Pleurotomaria, 450 Pluteus, 416 Podostomata, 64 Poduridee, 359, 432 Poison-claws, 41, 268 of Hymenoptera, 45 Poisons, action of, on Medusce, 309 Polia sanguirubra, 146 Polistes gallica, 437 Polycheeta, 37, 38, 91, 131, 152, 190, 191, 224, 322, 323, 388, 426 Polydesmus, 363 Polynée, 38, 153, 191, 226, 322 Polyophthalmus, 354 Polyperythrin, 210, 218 Polyplacophora, 69, 70, 368, 448 Polystomum, 420 Polyxenus, 431 Polyzoa, 64, 65, 124, 127, 167, 200, 235, 338, 447 Pontia-brassice, alimentary canal of, 94. Pontobdella, 153, 225, 226 Porifera, 30, 32, 79, 82, 120, 127, 184, 209, 243, 245, 248, 296, 349, 378, 408 Porites clavaria, 253 Porpita, 81 Priapulus, 224 SUBJECT INDEX. Proboscis, 37, 38, 42, 44, 76, 91, 324, 6 3 Proctucha, 418 Protameba, 405 Protoplasm, chemistry of, 10-19 Protoplasta, 24-26, 404 Prototracheata, 40, 260, 324 Protula, 426 Proventriculus, a, 38, 42, 70, 93 Protozoa, 4, 8, 21, 23, 31, 79, 119, 127, 182, 183, 208, 243, 245, 246, 295, 346, 347, 375, 401, 404 Psendo-filaria, 405 Pseudo-hzmal vessels, 123, 129, 155, 187, 191-193, 223, 224, 240 Pseudo-hearts of Brachiopods, 276 Pseudo-navicellz, 405 Pseudopodia, 25, 26, 28, 29, 110, 346, 374, 375 Psyche, 437 Pteropoda, 70, 72, 237, 367, 367, 369, 398, 450 Ptyalin, 93 Pulmonary sacs, 204, 240 Pulmogasteropoda, 70, 72, 237, 238, 243, 366, 368, 448 Pupe, 45, 46, 438 Purpura, 237, 238, 239 Pycnogonida, 47, 439, 442 Pygera Bucephalus, 133, 134, 160, 161 Pyrenoid, 22 QUEEN-BEE larve, food of, 98 Radiolaria, 26, 28, 80 Radula, a, 72 ‘Raphidide, 359 : Reason in Arachnida, 371-373 Insecta, 371-373 Rectal glands, 42, 43, 230 Rectum, 42-45, 60, 70, 94, 270 Renal organs, 30, 68, 143, 202, 203, 243, 245, 247, 248, 254, 257, 25% 260, 266, 275, 276, 280 Reproduction in Annelida, 422 Arachnida, 439 Brachiopoda, 447 Coelenterata, 409 Crustacea, 442 Echinodermata, 412 Insecta, 431 Invertebrata, 399-453 Mollusca, 448 Myriapoda, 430 Nematoscolices, 426 Onychophora, 429 Polyzoa, 447 - SUBJECT INDEX. 475 Reproduction in Porifera, 408 Protozoa, 404 Trichoscolices, 418 Tunicata, 452 Respiration, activity of, 233 Respiration in Annelida, 223 Arachnida, 230 Brachiopoda, 236 Ceelenterata, 209 Crustacea, 231 Echinodermata, 219 Insecta, 228 Invertebrata, 207-240 Mollusca, 236 Myriapoda, 228 Nematoscolices, 227 Polyzoa, 235 Porifera, 209 Protozoa, 208 Trichoscolices, 223 Tunicata, 239 “ Respiratory blood,” 129, 188 Respiratory pigments, 210, 214, 216, 218, 223, 226, 227, 233, 236, 237 Reversions, 36, 39, 56, 112, 205, 344, 6 363 Rhabdocala, 386, 418 Rhabdopleura, 64, 65 Rhizocephala, 56 Rhizopoda, 34, 119, 120, 183, 208 Rhizostoma, 212 Cuviert, 211 Rhodophan, 148 Rhynchota, 43 Fotifera, 35, 36, 39,187, 224, 320, 352, 387, 419 Rudimentary digestive system, 32 intestine, 30 Sabella, 130, 153, 154, 155, 322, 323 ventrilabrum, 130 Sagarlia bellis, 212, 216, 217 dianthus, 212, 216 parasitica, 212, 216 troglodytes, 212, 216 viduata, 212 Sagitta, 39, 40, 324, 354, 429 Salivary glands, 38-50, 60-70, 73, 87, QI-116 secretions in Mollusca, 109 Sarcode of Amaba, 3 Sarsia, 300, 302, 304, 310, 349, 350, 8 37: tubulosa, 301, 302 Savigny tubules, the, 76, 113 Scalpellum, 443 ornatum, 56 rostratum, 56 Scalpellum, vulgare, 56 Scaphopoda, 69, 70, 368, 448 Scari, 249 Scolopendra, 430 Scolopendride, 355 Scorpio, 166, 192, 230, 231, 268, 361, 442 Scutigera, 228, 355 Scyphistoma, 411 Secreting glands of bugs, 263 Secretion in Invertebrata, 241-292 Secretion of lime carbonate, 244, 248, 250, 276-282 Secretion of silk, 264 Segmental organs, 243, 256, 257, 258, 260 Segmentation of vitellus, 403, 404 Sense-organs, 345 373 Sepia officinalis, 72-74, 109, 110, 112, 142, 143, 168, 177, 204, 286, 339, 379, 451, 452 Serpula, 153-157, 323 contortuplicatu, 155 Seta, 40, 353, 361, 388 Shell-glands, 52, 55, 243, 271 Shells, structure of, 277 Siphonophora, 433-435 Siphonostoma, 130, 153 Sipunculus, 129 balanorophus, 130 echinorhynchus, 130 nudus, 129, 130 Sitona crinita, 357 lineata, 357 Smerinthus ocellatus, 162, 163 populi, 162 tile, 162, 163 Sodium urate, 256, 271 Solaster, 380 papposa, 221 Solecurtus strigillatus, 238 Solen legumen, 146, 238 Solenobia, 437 Somatopleure, 187 Sounds produced by insects, 360, 433 436 Spatangus, 386 Spectra of Invertebrate blood, 150, 154, 161 Spermatozoa, various, 412 Spherularia, 428 Spheerozoum, 26 Sphinx Lngustri, 132, 134, 135, 161, 163, 195 Spider, heart of, 196 Spines, chitinous, 40 Spinning glands, 44, 48, 245, 268 Spirogyra, 12 476 Spirostomum, 375 Splanchnopleure, 187 ongida, 30, 184, 209, 349, 378 spongilla, 31, 81, 209 Spontaneous generation, 399, 400 Squilla, 57 mantis, 142 Staphylinus olens, 244 Staurophora laciniata, 303, 305 Stemmata, 355, 359 Stentor polymorphus, 81, 375 Stephanoceros, 337 Sternaspis, 224 Stetheophyma grossum, 194 Stigmata, 228, 231 Sting, bee’s, 45 Stomach of Astacus, 61 Stomachs, 40, 42, 44, 48, 51, 56, 58, 59, 65, 66, 67, 70, 72 Stomapoda, 44 Strepsiptera, 327 Stridulation, 433, 435 Strobila, 411 Strongylocentrotus lividus, 149, 150 Suckers, 28, 36 Sustentative functions, 2, 3 Syllis, 426 Bynapte, 414 Synthesis of albumin, 11 Syriphide, 433 Teenia, 36, 320, 402 crassicollis, 320 rophalocera, 320 serrata, 85 transversalis, 320 Talitri, 396 Tape-worms, 36, 37, 320, 402 Tardigarda, 47, 439 Taurocholic acid, 101, 103, 112 Teeth, chitinous, 37, 38, 42, 58, 68 Tegenaria domestica, 49, 100, 166, 269, 270 Telson, 50, 331, 396 Tentacula, 28, 29, 37, 40, 64, 65, 366, 379; 387, 398 Tentaculifera, 2 Terebella, 153, 226 Terebratula, 338, 339 Terebratulina septentrionalis, 276 Teredo, 283 Tethys fimbria, 143, 169 Tetrabranchiata, 72,74, 236, 341, 367 368, 369 Tetramitus rostratus, 406 Tetronerythrin, 148, 149, 157 Tettigide, 435 Thalassema, 224 SUBJECT INDEX. Thalassicolla, 80 Thoracic feet, 57 Thread-worms, 39 Thrips, 42 Thysanura, 41 Tiaropsis indicans, 305 polydiademata, 302 Tissue-respiration, 208, 218, 231, 237, 240 Trachez, 40, 137, 207, 228, 229, 231, 240, 260, 264, 265 Trematoda, 35, 36, 86, 180, 187, 387, 420, 421, 422, 423 Tretenterata, 66, 338 Trichoscolices, 35, 85, 187, 223, 320, 352, 386, 418 Trigonia, 397 Trilobita, 51, 400 Trochal disc, 35, 387, 419 Trochus, 366 cinerarius, 238 Trombidium, 440 Trypsin, 82, 86, 89, 96 Tubicola, 354, 388 Tubifex, 424 Tunvcata, 75, 113, 205, 239, 245, 343, 452 Turbanella, 39, 187 Turbellaria, 35, 36, 320, 352, 386, 8 41 Turbo, 366 Turritella, 450 Types of nutrition, 21 Typhlosole, 69, 70, 117 Tyrosin, 13, 14, 73, 82, 90, IOI, 102, III UMBRELLA of Meduse, 298, 299 Unio, 105, 237, 239, 279 Units, morphological, 2 physiological, 3 Uraster rubens, 4, 83, 85, 220, 254, 380, 415 “Urate cells,” 265 Urea, 13, 252, 265, 279, 282, 284, 286 Uric acid, 13, 96, 246, 247, 248, 254, 256, 257, 259, 265, 266, 267, 270, 271, 274, 279, 281, 283-286 Urochordata, 75 VACUOLES, contractile, 25, 26, 28, 29, 30, 183, 184, 208, 240, 243, 246, 248 gastric, 28, 120, 184 Vascular systems, 35, 182, 185, 189 Veil of Medusce, 298 Velella, 81 limbosa, 211 SUBJECT INDEX. Vermes, 404 Vermetus, 366 Vermilia, 323 Vertebrates, cranial, 89 Vespa, 260 Voice-organs, 360 Voluta, 450 Vortex viridis, 81 Vorticellee, 28, 29, 249, 247, 296, 375, 377; 407 Waldheimia, 276 Water-vascular systems, 35, 187, 223, 240, 243 | " Web-spinning, objects of, 99 477 Wheel-animalcules, 35 Worms, blood of, 153 XANTHINE, 14 Xanthophyll, 132, 134, 135, 163, 165 Xanthoproteic acid, ro1 Aiphosura, 50, 63 “ YELLOW cells,” 80, 81, 215-219 ZOANTHODEMES, 33 Zoophytes, 234 Zygneena, 433 Zyynema, 12 PRINTED BY BALLANTYNE, HANSON AND CO. LONDON AND EDINBURGH ERRATA. Page 20, line 7, for assimilation, read assimilated. » 86, ,, 28, for Some Ascares marginate, read Some worms (Ascaris marginata), » 289 ,, 12, for predominate, read predominates. WORKS PUBLISHED by L. REEVE & CO. Under the Auspices of the Government of India. Now publishing in' parts, 4to, with Coloured Plates, 153. each. LEPIDOPTERA INDICA. By F. Moont, F.Z.8., F.E.S. Now publishing in parts, with Coloured Plates, 58. each. THE LEPIDOPTERA OF THE BRITISH ISLANDS. By CHARLES G. BARRETT, F.E.8. Prospectus and Form for Sub- scribers may be had on application. . Now publishing in parts, with Coloured Plates, 58. each. THE HEMIPTERA HETEROPTERA OF THE BRITISH ISLANDS... By Epwarp SAUNDERS, F.L.S. Prospectus and Form for Subscribers may be had on application. : Just completed in Five Vols. THE COLEOPTERA OF THE BRITISH ISLANDS. A De- scriptive Account of the Families, Genera, and Species indigenous to Great Britain and Ireland, with Notes as to Localities, Habitats, &c. By the Rev. Canon Fow.er, M.A., F.L.8. Large Edition, complete in five vols., with 180 Coloured Plates, containing up- wards of 2300 Figures, £14. Small Edition, complete in five vols., with 2 Structural Plates, £4. THE BUTTERFLIES OF EUROPE. Illustrated and described by Henry CHARLES Lane, M.D., F.L.S., &c., Member of the Entomological Society of London. Complete in two vols., super- royal 8vo, with 82 Coloured Plates, containing upwards of goo Figures, £3 18s. THE LEPIDOPTERA OF CEYLON. By F. Moons, F.LS. Complete in three vols. Medium 4to, with 215 Coloured Plates. Cloth, gilt tops, £21 12s. Published under the auspices of the Government of Ceylon. BRITISH INSECTS. A Familiar Description of the Form, Struc- 3 ture, Habits, and Transformations of Insects. By E. F. STAVELEY, Author of “ British Sipders.” Crown 8vo, with 16 Coloured Plates, and numerous Wood Engravings, 14s. : BRITISH BEETLES; an Introduction to the Study of our In- digenous Coleoptera. By C. E. Ryz. New Edition, revised and in part re-written by the Rev. Canon FowEr, M.A. Crown 8ro, 16 Coloured Steel Plates, and 11 Wood Engravings, tos. 6d. BRITISH BEES; an Introduction to the Study of the Natural History and Economy of the Bees indigenous to the British Isles. By W. E. SuuckaRp. Crown 8vo, 16 Coloured Plates, and Wood- cuts of Dissections, Ios. 6d. BRITISH BUTTERFLIES AND MOTHS; an Introduction to the Study of our Native Lepidoptera. By H. T. STAINTON. Crown 8vo, 16 Coloured Plates, and Wood Engravings, Ios. 6d. BRITISH SPIDERS; an Introduction to the Study of the Araneidz found in Great Britain and Ireland. By. F. STAVELEY. Crown 8vo, 16 Coloured Plates, and 44 Wood Engravings, Ios. 6d. BRITISH ZOOPHYTES; an Introduction to the Hydroida, Actinozoa, and Polyzoa found in Great Britain, Ireland, and the Channel Islands. By ARTHUR S. PEnNineToN, F.L.S. Crown 8vo, 24 Plates, tos. 6d. - L. REEVE & CO., 5 HENRIETTA STREET, COVENT GARDEN, LONDON. WORKS PUBLISHED BY L. REEVE & CO. CURTIS'S BRITISH ENTOMOLOGY. Illustrations and Descrip- tions of the Genera of Insects found in Great Britain and Ireland, containing Coloured Figures from Nature, of the most rare and beautiful Species, and, in many instances, upon the plants on which they are found. Eight vols., royal 8vo, 770 Coloured Plates, £28. Orders. Plates. £ 8s. d. Orders. Plates. £ s. d. APHANIPTERA . 2 . 0 2 0O| HYMENOPTERA .125 . 6 5 0 COLEOPTERA . . 256 .12 16 O | LEPIDOPTERA. . 193 913 0 DERMAPTERA. . I . 0 I O| NEUROPTERA. . I3 . 013 0 DICTYOPTERA. . I Oo 1 0] OMALOPTERA. . 6.0 60 DIPTERA . . . 103 5 3 0] ORTHOPTERA. . 5 05 0 HEMIPTERA . . 32 112 O | STREPSIPTERA . 3 0 30 HOMOPTERA . . 21 I 1 oO| TRICHOPTERA . 9 ° ° “Curtis’s Entomology,” which Cuvier pronounced to have “reached the ultimatum of perfection,’ is still the standard work on the Genera of British Insects. The Figures, executed by the author himself with wonderful minuteness and accuracy, have never been surpassed, even if equalled. The price at which the work was originally published was 443 I6s. HARVESTING ANTS AND TRAP-DOOR SPIDERS; Notes and Observations on their Habits and Dwellings. By J. T. Moc- GRIDGE, F.L.S. With a Supplement of 160 pp., and 8 additional Plates, 17s. The Supplement separately, cloth, 7s. 6d. ELEMENTS OF CONCHOLOGY ; an Introduction to the Natural History of Shells, and of the Animals which form them. By LovELL REEVE, F.L.S. Royal 8vo, two vols., 62 Coloured Plates, £2 16s. CONCHOLOGIA ICONICA; or, Figures and Descriptions of the Shells of Mollusks, with remarks on their Affinities, Synonymy, and Geographical Distribution. By LOVELL REEvE, F.L.S., and G. B. SOWERBY, F.L.S., complete in twenty vols., 4to, with 2727 Coloured Plates, half-calf, £178. A detailed list of Monographs and Volumes may be had. TESTACEA ATLANTICA; or, the Land and Freshwater Shells of the Azores, Madeiras, Salvages, Canaries, Cape Verdes, and Saint Helena. By T. Vernon WOLLASTON, M.A., F.L.S., demy 8vo, 25s. THE EDIBLE MOLLUSCA OF GREAT BRITAIN AND IRELAND, including the Oyster, Mussel, Cockle, Scallop, Limpet, Whelk, Periwinkle, and many others less generally known, with much curious and interesting information respecting them ; with the Modes of Cooking them. By M.8. LoveLn. Crown 8vo, with 12 Coloured Plates. New Edition, rewritten and much enlarged, Tos. 6d. NATAL; a History ‘and Description of the Colony, including its Natural Features, Productions, Industrial Condition and Prospects. By HENRY BROOKS, for many years a resident. Edited by Dr. R. J. Many, F.R.A.S8., F.R.G.8., late Superintendent of Education in the Colony. Demy 8vo, with Maps, Coloured Plates, and Photographic Views, 21s. ST. HELENA. A Physical, Historical, and Topographical Descrip- tian of the Island, including its Geology, Fauna, Flora, and Meteorology. By J. C. Meuuiss, A.I.C.H., F.G.S., F.L.S. In one large vol., super-royal 8vo, with 56 Plates and Maps, mostly Coloured, 42s. For other Works see Catalogue at end. L. REEVE & CO., 5 HENRIETTA STREET, COVENT GARDEN, LONDON. . LIST OF WORKS ON NATURAL HISTORY, TOPOGRAPHY, ANTIQUITY, AND SCIENCE. CONTENTS. Page Page Borany 3 SHELLS aNnD Mo.tuusxs 10 Ferns . 8 ENTomoLoGcy ; . 1) Mosses 8 ZOOLOGY. : . 13 Funconoeyr , 9 ANTIQUITY . 5 . 13 SEAWEEDS 9 MISCELLANEOUS. . 14 PUBLISHED BY L. REEVE AND CoO., PUBLISHERS TO THE Home, CoLoniat, AnD INDIAN GOVERNMENTS, 5, HENRIETTA STREET, COVENT GARDEN, W.C. 4 2 L. Reeve & Co,.’s Crown Series of Natural History. For descriptive details, see Catalogue. British Beetles. By E. C. Ryz. 2nd Hdition, revised by Rev. Canon Fowzzr, M.A., F.L.S. 16 Coloured Plates, and Woodcuts, 10s. 6d. British Zoophytes. By AxntHur S. PENNINGTON, FILS. 24 Plates, 10s. 6d. British Insects. By EH. F. Stavetzy. 16 Coloured Plates and Woodcuts, 14s. British Butterflies and Moths. By H. T. Stainton. 16 Coloured Plates, and Woodcuts, 10s. 6d. British Bees. By W. E. Sxuonarp. 16 Coloured Plates, and Woodcuts, 10s. 6d. British Spiders. By E. F.Stavenzy, 16 Coloured Plates, and Woodcuts, 10s. 6d. The Edible Mollusca of Great Britain and Ireland, with Recipes for Cooking them. By M. 8S. Lovet. Second Edition. 12 Coloured Plates, 10s. 6d. Synopsis of British Mosses. By OC. P. Hosxirg, F.L.S. Revised Edition, 7s. 6d. British Grasses. By M. Puvzs. 16 Coloured Plates, and Woodcuts, 10s. 6d. British Ferns. By M. Pivss. 16 Coloured Plates, and Woodcuts, 10s. 6d. British Seaweeds. By 8S. O. Gray. 16 Coloured Plates, 10s. 6d. Handbook of the British Flora. By G. Bentaay, F.R.S. 5th Edition, Revised by Sir J. D. Hooxzr, C.B., K.CS.L, F.B.S., &., 10s. 6d. Illustrations of the British Flora. Drawn by W.. H. Fircn, F.LS., and W. G. Smire, F.L.S. 1311 Wood Engravings, 2nd Edition, revised and enlarged, 10, 6d, 3 BOTANY. The Species of Ficus of the Indo-Malayan and Chinese Countries. By Gzorcz Kine, M.B., LL.D., F.LS. Part I., Small folio, 91 Plates in Portfolio, 25s. Part It:; 137 Plates in Portfolio, 40s. Appendix to Vol. L, 12 Plates, 10s. 6d. Vol. IT., 104 Plates, 32s. 6d. The Natural History of Plants. By H. Barton, President of the Linnzan Society of Paris, Professor of Medical = Natural History and Director of the Botanical Garden of the mip Faculty of Medicine of Paris. Super-royal 8vo. Vols. J. to VIIL., with 3545 Wood Engravings, 25s. each. Handbook of the British Flora; a Description of the Flowering Plants ‘and Ferns‘indigenous to, or naturalized in, the British Isles. For the use of Beginners and Amateurs. By GzoreE Bentuam, F.R.S. 5th Edition, revised: by Sir J. D. Leet Hooxzr, C.B,, K.C.8.1., F.R.S., &. Crown 8vo, 10s. 6d. Illustrations of the British Flora; a Series of Wood Engravings, with Dissections, of British Plants, from Drawings by W. H. Fitcn, F.L.S8., and W. G. Surrz, E.LS., forming an Illustrated Companion to BrntHam’s “ Handbook,” and other British Floras. New Edition, revised and enlarged. 1311 Wood Engravings, 10s. 6d. Outlines of Elementary Botany, as Introductory to Local Floras. By Groraz BentHam, FRS,F.LS. New Edition, 1s. British Wild Flowers, Familiarly Described in the Four Seasons. By Tomas Moorz,F.L.S. 24 Coloured Plates 16s. a » The Narcissus, its History and Culture, with v Coloured Figures of all known Species and Principal Varieties. //) | By F. W. Bursrpez, and a Review of the Classification = by J. G. Baxgezr, F.L.S. Super-royal 8vo, 48 Coloured Plates, 32s." 4 2 4 The Botanical Magazine; Figures and Descriptions of New and Rare Plants suitable for the Garden, Stove, or Greenhouse. By Sir J. D. Hooxer, K.C.8.1., C.B., F.R.S., late Director of the Royal Gardens, Kew. Royal 8vo. Third Series, Vols. I, to XLVIL., each 42s. Published Monthly, with 6 Plates, 3s. 6d., coloured. Annual Subscription, 42s. Re-Issvux of the Tarrp SzRixs in Monthly Vols., 42s. each; to Subscribers for the entire Series, 36s. each. The Floral Magazine; New Series, Enlarged to Royal 4to. Figures and Descriptions of the choicest New Flowers for the Garden, Stove, or Conservatory. Complete in Ten Vols., in handsome cloth, gilt edges, 42s. each. First Sertes complete in Ten Vols., with 560 beautifully-coloured Plates, £18 7s. 6d. The Young Collector’s Handybook of Botany. By the Rev. H. P. Dunster, M.A. 66 Wood Engravings, 3s. 6d. Laws of Botanical Nomenclature adopted by the International Botanical Congress, with an Historical Intro- duction and a Commentary. By ALPHONSE DE CANDOLLE. 2s. 6d. Report on the Forest Resources of Western Australia. By Baron Frrp. Murtuzr, C.M.G., M.D., Ph.D., F.R.S., Government Botanist of Victoria. Royal 4to, 20 Plates of the Eucalyptus, 12s. Flora Vitiensis; a Description of the Plants of the Viti or Fiji Islands, with an Account of their History, Uses, and Properties. By Dr. BertHoip REpHANN, F.L.S. Royal 4to, Coloured Plates. Part X., 25s. Flora Hongkongensis; a Description of the Flowering Plants and Ferns of the Island of Hongkong. By Grorce Bunruam, F.R.S. With a Map of the Island, and a Supplement by Dr. Hancz. 18s. Published under the authority of Her Majesty’s Secretary of State for the Colonies. The Sup- plement separately, 2s. 6d, 5 Flora of Mauritius and the Seychelles ; a Descrip- tion of the Flowering Plants and Ferns of those Islands. By J.G. Barer, F.L.8. 24s. Published under the authority of the Colonial Government of Mauritius. Flora of British India. By Sir J. D. Hooxer, K.C.S.I., C.B., F.R.S., &c. ; assisted by various Botanists. Parts I. to XIII., 10s. 6d. each, XIV. to XVII., 9s. each. Vols. I. to IV., cloth, 32s. each; Vol. V., 38s. Published under the authority of the Secretary of State for India in Council. Flora of Tropical Africa. _By DantEn Ottver, FE.BS., F.L.8. Vols. I. to III., 20s. each. Published under the authority of the First Commissioner of Her Majesty’s Works. Handbook of the New Zealand Flora; a Systematic Déscription of the Native Plants of New Zealand, and the Chatham, Kermadec’s, Lord Auckland's, Campbell’s, and Mac- quarrie’s Islands. By Sir J. D. Hooxzr, K.C.S.1, F.RS. 42s. Published under the auspices of the Government of that Colony. Flora Australiensis; a Description of the Plants of the Australian Territory. By Grorcr BrntHam, F.R.S., assisted by Ferpinanp Mur.uzr, F.R.S., Government Botanist, Melbourne, Victoria. Complete in Seven Vols., £7 4s. Vols. I. to VI., 20s. each; Vol. VII., 24s. Published under the auspices of the several Governments of Australia. Flora of the British West Indian Islands. By Dr. GriseBacu, F.L.S. 42s. Published under the auspices of the Secretary of State for the Colonies. Flora Capensis; a Systematic Description of the Plants of the Cape Colony, Caffraria, and Port Natal. By Wituram H. Harvey, M.D., F.R.S., Professor of Botany in the University of Dublin, and Orro Witaem Sonpsr, Pb.D. Vols. I. and II., 126, each, Vol. IUT., 188. 6 Flora of West Yorkshire ; with an Account of the Climatology and Lithology in connection therewith. By FrEDERIC Aznotp Lzzs, M.R.C.S. Eng., L.R.C.P. Lond., Recorder for the Botanical Record Club, and President of the Botanical Section of the Yorkshire Naturalists’ Union. 8vo, with Coloured Map, 21s. Flora of Hampshire, including the Isle of Wight, with localities of the less common species. By F. TowNsEND, M.A,, F.L.S. With Coloured Map and two Plates, 16s. ‘ Contributions to the Flora of Mentone, and to a Winter Flora of the Riviera, including the Coast from Marseilles to Genoa.. By J. Tranerne Moceriper, “.L.8. Royal 8vo. Complete in One Vol., with 99 Coloured Plates, 63s. On the Flora of Australia: its Origin, Affinities, and Distribution; being an Introductory Essay to the “ Flora of Tasmania.” By Sir J. D. Hooxer, F.R.S. 10s. Wild Flowers of the Undercliff, Isle of Wight. By Cuarztotre O’Brizn and C. Parkinson. Crown 8vo, 8 Coloured Piates, 7s. 6d. Icones Plantarum. Figures, with Brief Descrip- tive Characters and Remarks, of New and Rare Plants, selected from the Author’s Herbarium. By Sir W. J. Hooxer, F.R.S. New Series, Vol. V. 100 Plates, 3ls. 6d. Illustrations of the Nueva Quinologia of Pavon, with Observations on the Barks described. By J. E. Howazp, F.L.S. With 27 Coloured Plates. Imperial folio, half-morocco, gilt edges, £6 6s. The Quinology of the East Indian Plantations. By J. E. Howazp, F.L.S. Complete in One Vol., folio. With 13 Coloured and 2 Plain Plates, and 2 Photo-prints, 84s. Parts VJ. and TIT.. cloth, 7 Genera Plantarum, ad Exemplaria imprimis in Herbariis Kewensibus servata definita. By Gzoraz BenTHam, F.RS., F.L.S., and Sir J. D. Hooker, F.R.S., late Director of the Royal Gardens, Kew. Complete in 7 Parts, forming 3 Vols., £8 2a. Revision of the Natural Order Hederaces ; being a reprint, with numerous additions and corrections, of a series of ‘ papers published in the “ Journal of Botany, British and Foreign.” By Bertuoip Seemann, Ph.D., F.L.S. 7 Plates, 10s. 6d. Orchids ; and How to Grow them in India and other Tropical Climates. By Samvzn Jennrnes, F.LS., F.R.H.S., late Vice-President of the Agri-Horticultural Society of India. Royal 4to.. Complete in One Vol., cloth, gilt edges, 63s. A Second Century of Orchidaceous Plants, selected from the Subjects published in Curtis’s “ Botanical Magazine” since the issue of the “ First Century.” Edited by Jamzs Batr- MAN, Esq., F.R.S. Complete in One Vol., Royal 4to, 100 Coloured Plates, £5 5s. Dedicated by Special Permission to H.R.H. the Princess of Wales, Monograph of Odontoglossum, a Genus of the Vandeous Section of Orchidaceous Plants. By James Bateman, Esq., F.R.S. Imperial folio, in One Vol., with 30 Coloured Plates, - and Wood Engravings, cloth, £6 16s. 6d. The Khododendrons of Sikkim-Himalaya; being an Account, Botanical and Geographical, of the Rhododendrons recently discovered in the Mountains of Eastern Himalaya, by - Sir J. D. Hooker, F.R.S. By Sir W. J. Hooxen, F.R.S. Folio, 20 Coloured Plates, £4 14s. 6d. British Grasses; an Introduction to the Study of the Graminez of Great Britain and Ireland. By M. Piuzs. Crown 8vo, with 16 Coloured Plates and 100 Wood Engravings, 10s. Gd, Botanical Names for English Readers. By Ranpa H, Aucock. &8vo, 6s. 8 Elementary Lessons in Botanical Geography. By J. G. Baxsr, F.L.S. 3s. FERNS. British Ferns; an Introduction to the Study of the Ferns, Lycopops, and EquisETa indigenous to the British Isles. With Chapters on the Structure, Propagation, Cultivation, Diseases, Uses, Preservation, and Distribution of Ferns. By M. Prvuzs. Crown 8vo, with 16 Coloured Plates, and 55 Wood Engravings, 10s. 6d. The British Ferns; Coloured Figures and Descrip- tions, with Analysis of the Fructification and Venation of the Ferns of Great Britain and Ireland. By Sir W. J. Hooxer, F.R.S. Royal 8vo, 66 Coloured Plates, £2 2s. Garden Ferns ; Coloured Figures and Descriptions with Analysis of the Fructification and Venation of a Selection of Exotic Ferns, adapted for Cultivation in the Garden, Hothouse, and Conservatory. By Sir W. J. Hooxer, F.R.S. Royal 8ve, | 64 Coloured Plates, £2 2s. Filices Exotice ; Coloured Figures and Description of Exotic Ferns. By Sir W. J. Hooxzr, F.R.S. Royal Ato, 100 Coloured Plates, £6 11s. Ferny Combes; a Ramble after Ferns in the Glens and Valleys of Devonshire. By CHartotre CHanteR. Third Edition. Feap. 8vo, 8 Coloured Plates and a Map of the County, 5s. MOSSES. Synopsis of British Mosses, containing Descrip- tions of all the Genera and Species (with localities of the rarer ones) found in Great Britain and Ireland. By CHarizs P. Hosrizx, F.LS., &c., &c. New Edition, entirely revised. Crown 8vo. 7s. 6d. 9 Handbook of. British Mosses, containing all that are known to be natives of the British Isles. By.the Rev. M.-J. Burxuny, M.A., F.L.S. 24 Coloured Plates, 21s. The British Moss-Flora. By R. Brarruwairs, M.D., F.L.S. Vol. 1, Imperial 8vo, with 45 finely executed Plates, 50s. Part XI., 8s., Part XII., 7s., Part XIII, 6s. FUNGI. British Fungi, Phycomycetes and Ustilagine. By Gzorcz Masses (Lecturer on Botany to the London Society for the Extension of University Teaching). Crown 8vo, with 8 Plates, 7s. 6d. Outlines of British Fungology. By the Rev. M. J. Berxetzy, M.A., F.L.S. With a Supplement of nearly 400 pages by WortHineTon G. Situ, F.L.S., bringing the work down to the present state of Science. Two vols., 24 Coloured Plates, 86s. The SuppLement separately, 12s. The Hsculent Funguses of England. Containing an Account of their Classical History, Uses, Characters, Develop- ment, Structure, Nutritious Properties, Modes of Cooking and Preserving, &. By C. D. BapHam, M.D. Second Edition. . Edited by F. Currey, F.R.S. 12 Coloured Plates, 12s. Clavis Agaricinorum; an Analytical Key to the British Agaricini, with Characters of the Genera and Sub-genera. By Wortuineron G. Smita, F.L.S. 6 Plates, 2s. 6d. SEAWEEDS. British Seaweeds ; an Introduction to the Study of the Marine Ate of Great Britain, Ireland, and the Channel Islands. By S. 0. Gray. Crown 8vo, with 16 Coloured Plates, 10s, 6d, 10 Phycologia Britannica; or, History of British Seaweeds. Containing Coloured Figures, Generic and Specific Characters, Synonyms and Descriptions of all the Species of Alge inhabiting the Shores of the British Islands. By Dr. W. H. Harvey, F.R.S. New Edition. Royal 8vo, 4 vols. 360 Coloured Plates, £7 10s. Phycologia Australica; a History of Australian Seaweeds, comprising Coloured Figures and Descriptions of the more characteristic Marine Alge of New South Wales, Victoria, Tasmania, South Australia, and Western Australia, and a Synopsis of all known Australian Alge. By Dr. W. H. Harvey, F.R.S. Royal 8vo, Five Vols., 300 Coloured Plates, £7 13s. SHELLS AND MOLLUSKS. Elements of Conchology; an Introduction to the Natural History of Shells, and of the Animals which form them. By Loven Reeve, F.L.S. Royal 8vo, Two Vols., 62 Coloured Plates, £2 16s. Conchologia Iconica ; or, Figures and Descriptions of the Shells of Mollusks, with remarks on their Affinities, Syno- nymy, and Geographical Distribution. By Loven Reeve, F.L.S., and G. B. Sowzrsy, F.L.S., complete ix Twenty Vols., 4to, with 2727 Coloured Plates, half-calf, £178. A detailed list of Monographs and Volumes may be had. The Edible Mollusca of Great Britain and Ireland, including the Oyster, Mussel, Cockle, Scallop, Limpet, Whelk, Periwinkle, and many others less generally known, with much curious and interesting information respecting them; with the Modes of Cooking them. By M.S. Lovezn. Crown 8vo, with 12 Coloured Plates. New Edition, rewritten and much enlarged, 10s. 6d. Testacea Atlantica; or, the Land and Freshwater Shells of the Azores; Madeiras, Salvages, Canaries, Cape Verdes, and Saint Helena. By T. Vernon Woutaston, M.A., F.1S. Demy 8vo, 25s. 1] ENTOMOLOGY. The Hemiptera-Heteroptera of the British Islands. By Epwarp Sauwpers, F.L.S., Large Paper Illustrated Edition with Coloured Plates, in monthly Parts, 5s. each. Prospectus on application. The Lepidoptera of the British Islands. By Cuarues G. Barrett, F.E.S., Large Paper Illustrated Edition with Coloured Plates, in monthly Parts, 5s. each. Prospectus on application. The Coleoptera of the British Islands. A Descriptive Account of the Families, Genera, and Species indigenous to Great Britain and Ireland, with Notes as to Localities, Habitats, &c. By the Rev. Canon Fowzzr, M.A. F.LS. With two Structural Plates and Wood Engravings, complete in 5 Vols., £4. Large Paper Illustrated Edition, with 180 Coloured Plates, containing 2300 figures, £14 net. The Butterflies of Europe; Illustrated and De- scribed. By Henry Cuartes Lane, M.D., F.L.S. Complete in Two Vols., super-royal 8vo, with 82 Coloured Plates, con- taining upwards of 900 Figures, cloth, £3 18s. *," Tue Systematic List or Evrorgan Borrerruizs from the above work _ separately, price 8d.; or printed on one side of the paper only for Labels, 1s, The Lepidoptera of Ceylon. By F. Moors, F.L.S. Three Vols., Medium 4to, 215 Coloured Plates, cloth, gilt tops, £21 12s. Published under the auspices of the Government of Ceylon. British Insects. A Familiar Description of the Form, Structure, Hubits, and Transformations of Insects. By E. F. Sraverey, Author of “ British Spiders.” Crown 8vo, with 16 Coloured Plates and numerous Wood Engravings, 14s. British Beetles ; an Introduction to the Study of our indigenous Coteoprera. By HE, C. Ryg. 2nd Edition, revised by Kev. Canon Fowner. Crown 8vo, 16 Coloured Steel Plates, and 11 Wood Engravings, 10s. 6d. . 12 British Bees; an Intrcduction to the Study of the Natural History and Economy of the Bees indigenous to the British Isles. By W. E. SHuckarp. Crown 8vo, 16 Coloured Plates, and Woodcuts of Dissections, 10s. 6d. British Butterflies and Moths; an Introduction to the Study of our Native Leriporrera. By H. T. Sratnton. Crown 8vo, 16 Coloured Plates, and Wood Engravings, 10s. 6d. British Spiders ; an Introduction to the Study of the ARANEIDH found in Great Britain and Ireland. By EH. F. StavELEy. Crown 8vo, 16 Coloured Plates, and 44 Wood Engravings, 10s. 6d. Harvesting Ants and Trap-door Spiders; Notes and Observations on their Habits and Dwellings. By J. T. Moeeriper, F.L.S. With Suprrement, 17s. The Supple- ment separately, cloth, 7s. 6d. Curtis’s British Entomology. Illustrations and Descriptions of the Genera of Insects found in Great Britain and Ireland, containing Coloured Figures, from Nature, of the most rare and beautiful Species, and in many instances, upon the plants on which they are found. Eight Vols., Royal 8vo, 770 Coloured Plates, £28. Or in Separate Monographs. Orders. Plates, £ 8. d. Orders. Plates. £8, d, APHANIPTERA . . 2 0 2 0 | HymenorrzRaA . . 125 6 56 0 ConEorPTERA. . . 266 1216 0 | Lepiporrera . 198 913 0 DERBMAPTERA. . . 1 0 1 0 | Nevroprera. .. 13 013 0 DictyorpTeRA. . . 1 010 OMALOPTERA. . . 6 060 DietzRA ww se 103 5 3 0 ORTHOPTERA . . 6 0650 HEMIPTERA . . . 32 112 0 STREPSIPTERA . . 3 030 Homorrzpa . . . 21 1 1°01 Tricnoprera .. 9 090 “ Curtis’s Entomology,” which Cuvier pronounced to have “reached the ultimatum of perfection,” is still the standard work on the Genera of British Insects. The Figures executed by the author himself, with wonderful minuteness and accuracy, have never been surpassed, even if equalled. The price at which the work was originally published was £43 16s. Insecta Britannica; Diptera. Vol. ILI. By Francis Wanker. F.L,8. 8vo, with 10 Plates, 25s. 18 The Structure and Life History of the Cockroach (Periplaneta Orientalis). An Introduction to the Study of Insects. By L. C. Mraxz, Professor of Biology in the Yorkshire College, Leeds, and Aurrep Denny, Lecturer on Biology in the Firth College, Sheffield. Demy 8vo, 125 Woodeuts, 7s. 6d, ZOOLOGY. The Physiology of the Invertebrata. By A. B. Gairritus, Ph.D., F.R.S.E. Demy 8vo, 81 cuts, 15s. net. British Zoophytes; an Introduction to the Hy- droida, Actinozoa, and Polyzoa found in Great Britain, Ireland, and the Channel Islands. By Anruur S. Pennineton, F.LS. Crown 8vo, 24 Plates, 10s. 6d. Handbook of the Vertebrate Fauna of Yorkshire ; being a Catalogue of British Mammals, Birds, Reptiles, Amphi- bians, and Fishes, found in the County. By Wi.t1am Eaeie and Witt1am Denison Rozsuck. 8vo, 8s. 6d. Handbook of the Freshwater Fishes of India; giving the Characteristic Peculiarities of all the Species known, and intended as a guide to Students and District Officers. By Capt. R. Bravan, F.R.G.S. Demy 8vo. 12 Plates, 10s. 6d. The Zoology of the Voyage of H.M.S8. Samarang, under the command of Captain Sir Edward Belcher, C.B., during the Years 1843-46, By Professor Owen, Dr. J. E. Gray, Sir J. Ricwarpson, A. Apams, L. Rezve, and A. WHirE. Edited by Artuur Apams,F.L.S. Royal 4to, 55 Plates, mostly coloured, £3 10s. ANTIQUARIAN. Sacred Archeology; a Popular Dictionary of Ecclesiastical Art and Institutions from Primitive to Modern Times. By Mackenzie ®. C. Watcort, B.D. Oxon., F.S.A., Precentor and Prebendary of Chichester Cathedral. 8vo, 18s. A Manual of British Archeology. By CHARLES Bovrett, M.A. 20 Coloured Plates, 10s. 6d. » 14 MISCELLANEOUS. _ Collections and Recollections of Natural History and Sport in the Life of a Country Vicar. By the Rev. G.C, GREEN. Illustrated with Woodcuts from Sketches by the Author. Crown 8yo, 7s. 6d. : West Yorkshire; an Accountof its Geology, Physical Geography, Climatology, and Botany. By J. W. Davis, F.LS., and F, Arnotp Luss, F.L.S. Second Edition, 8vo, 21 Plates, many Coloured, and 2 large Maps, 21s. Natal; a History and Description of the Colony, including its Natural Features, Productions, Industrial Condition and Prospects. By Henry Brooxs, for many years a resident, Edited by Dr. R. J. Mann, F.R.AS., F.R.G.S., late Superin- tendent of Education in the Colony. Demy 8vo, with Maps, Coloured Plates, and Photographic Views, 21s. St. Helena. A Physical, Historical, and Topo- graphical Description of the Island, including its Geology, Fauna, Flora, and Meteorology. By J. C. Mztutss, A.I.C.E., F.G.S., F.L.S. In one large Vol., Super-royal 8vo, with 56 Plates and Maps, mostly coloured, 42s. The Young Collector’s Handy Book of Recreative Science. By the Rev. H. P. Dunster, M.A. Cuts, 3s. 6d. The Geologist. A Magazine of Geology, Palzont- ology, and Mineralogy. Edited by S.J. Macxiz, F.G.S., F.S.A. Vols. V. and VI., each with numerous Wood Engravings, 18s. Vol. VIL, 9s. Everybody’s Weather-Guide. The use of Meteoro- logical Instruments clearly explained, with directions for secur- ing at any time a probable Prognostic of the Weather. By A. Steinmetz, Esq., Author of “ Sunshine and Showers,” &c. Is. The Artificial Production of Fish. By Piscartts. Third Edition. 1s. The Gladiolus: its History, Cultivation, and Exhi- bition. By the Rev. H. Honywoop Domuratn, B.A. Is. Meteors, Aerolites, and Falling Stars. By Dr. T. L. Purpson, F.C.S. Crown 8vo, 25 Woodcuts and Lithographic Frontispiece, 6s. 15 ' Papers for the People. By One or Tuem. No. 1, OUR LAND. 8vo, 6d. (By Post, 7d. in stamps.) The Royal Academy Album; a Series of Photo- . graphs from Works of Art in the Exhibition of the Royal Academy of Arts, 1875. Atlas dto, with 32 fine Photographs, cloth, gilt edges, £6 6s.; half-morocco, £7 7s. The same for 1876, with 48 beautiful Photo-prints, cloth, £6 6s.; ; half-morocco, £7 7s. Small Edit. Royal Ato, cloth, gilt edges, 63s. On Intelligence. By. H. Tatnz, D.C... Oxon. Translated from the French by T. D. Hays, and revised, with additions, by the Author. Complete in One Vol., 18s. Manual of Chemical Analysis, Qualitative and ‘ Quantitative ; for the use of Students. By Dr. Henry M. Noap, F.R.S. New Edition. Crown 8vo, 109 Wood Engravings, 16s. Or, separately, Part I., “QUALITATIVE,” New Edition, new Notation, 6s.; Part IT. “QUANTITATIVE,” 10s. 6d. PLATES. Floral Plates, from the Floral Magazine. Beauti- fully Coloured, for Screens, Scrap-books, Studies in Flower-painting, &e. 6d.and1s. each. Lists of over 1000 varieties, One Stamp. ‘Botanical Plates, from the Botanical Magazine. Beautifully-coloured Figures of new and rare Plants. 6d. and 1s. each. Lists of nearly 3000, Three Stamps. _ SERIALS. The Botanical Magazine. Figures and Descrip- tions of New and Rare Plants. By Sir J. D. Hoong, C.B., F.R.S. Monthly, with 6 Coloured Plates, 3s. 6d. Annual subscription, post free, 42s. ° Re-issue of the Third Series, in Monthly Vols., 42s. each ; to Sub- scribers for the entire Series, 36s. each. : “The Naturalist. Monthly, 6d.; per annum, post- free, 5s., in advance. The Hemiptera of the British Islands. By Epwarp Saunpers, F\L.S. Illustrated Edition. Monthly, 5s. 16 THE VICTORIA LIBRARY. A New Series of Standard and Popular Works in all departments of Literature, to be issued monthly, in handy pocket volumes, well printed and neatly bound in whole cloth, yellow edges, price 1s. each; or in paper covers, cut or uncut -edges, 6d. each. _ The Series willcomprise Selected Works, in Poetry and Prose, from our Classic Literature, Biographies of Men and Women who have distinguished themselves in Literature, Science or Art, including great Statesmen, Generals, Admirals, Explorers, Inventors, Philanthropists, é&c., &c.; Histories of Important Events and Epochs, Descriptions of Places of Note and Interest; with occasional Volumes of approved Fiction. Vol. L, British Oratory, containing Six famous Speeches, viz.; Grattan on Irish Independence, Pitt on Union, Peel on Corn Laws, Bright on Reform, Jones on Democracy, Gladstone on Qaths. Vol. II. Enerisn Dramas: The Birth of Merlin, and Thomas Lord Cromwell. Vol. III. Ow tHe Stupy anp Us or History: By Lord Bolingbroke. Vol. IV. Exeriso Dramas: By Congreve, ‘“ The Way of the World,” and “ The Mourning Bride.” . Vol. V. A Tanz or a Tus: By Dean Swift. With notes and translations, Vol. VI. Spenszr’s Farry Quezn: A selection of the most beautiful passages in modernized orthography, with analyses ot each book. Notes and explanations of archaic words. Vol. VIL. Lire or Wituram Pitt: By T. Evan Jacob, M.A. Vol. VIII. ExizapetHan Sones anp Sonnets. Now Ready, Parts I. to X., with Coloured Plates, each 15s. LEPIDOPTERA INDICA. By FREDERIC MOORE, Fellow of the Zoological and Entomo- logical Societies of London, A.L8., A. Asiat. Soc., Bengal, &c. Prospectuses with full particulars may be had on application to the Publishers. ¢ London: L. REEVE & CO.,5, HENRIETTA STREET, COVENT GARDEN, GILBERT AND RIVINGTON, LD., ST.. JOHN’S HOUSE, CLERKENWELL, E.C.