UC-NRIF •B 177 REESE LIBRARY LIBRARY G OF THE UNIVERSITY OF Received Accessions No. _ _ / 75> 7^, 209, 211, and 212) from his articles on Corals and Cuttle-fishes in the ninth edition of the ' Encyclopaedia Britannica.' The only other point which appears to require notice relates to the classification here adopted. This classification, as in the previous editions of the work, is based essentially upon the views put forth by Professor Huxley in his masterly treatise, entitled ' Lectures on the Elements of Comparative Anatomy,' published in 1864. The reader will find a good many minor changes in this classification, necessitated by the recent pro- gress of Zoological science. Thus, the new groups of the Hydrocorallinae and Helioporidse of Mosely have been duly recognised ; the discovery of the tracheal system of Peripatus has enriched the Myriapoda with a new order: the Therio- dontia of Owen have been added to the already numerous groups of the extinct Reptiles ; the orders Odontolcae and Odontotormae of Marsh, collectively forming the new sub-class Odontornithes, are accessions to the class of Birds ; and through the researches of the last-named distinguished palaeontologist, the domain of Mammalian life has been extended by the estab- lishment of the Tillodontia and Dinocerata. In the main, however, the author has not thought it neces- sary to depart from the broad outlines of the systematic arrangement of animals originally adopted by Professor Hux- ley, to which he finds himself still able to give his hearty adhesion. The student of some of the more recent German, American, and English zoological publications would, how- ever, find himself confronted with a classification of more modern origin, and in many fundamental points essentially different from the one followed here. Thus, to speak only of conspicuous instances, he would find the Sponges placed with the Coelenterata ; the Rugose Corals would be side by side with the Jelly-fishes in the class of the Hydrozoa ; the Polyzoa and Brachiopoda would be met with in the " Vermes," in the immediate neighbourhood of the Annelides ; and in looking for the Tunicates he would either have to direct his search to Vlil PREFACE. the group just mentioned, or he might even light upon the object of his quest at the bottom of the Vertebrate sub- kingdom. That these and other similar changes have not been adopted here demands a few words of explanation. In the first place, the present work is intended principally for the guidance of general students, and the author is of opinion that it would for this reason be improper to introduce into it any schemes of classification which have not been accepted with tolerable unanimity by naturalists in general. Most or all of the above- mentioned innovations, however, though supported by many and distinguished names, are opposed by others of equal eminence. They may ultimately turn out to be based on nature, but, in the meanwhile, they have not received anything like universal acceptance. In the second place, most of these proposed changes of classification are founded upon a study of the developmental phenomena of animals. Some highly distinguished zoologists hold that embryological characters will ultimately prove to be the true basis of classification ; but in this view the author unfortunately is at present hardly prepared to concur. On the contrary, the author finds himself in the position of being un- able to believe that any general system of classification can maintain its ground unless it be based upon the morphological characters exhibited by adult animals. He would not be held as denying, or even as depreciating, the importance of embry- ological studies, but he is unable to believe that the transitory characters of the young animal can have the same general value in classification — for the purposes, at any rate, of ordi- nary students — as have the characters drawn from the fully developed organism. In the third place, if the author had here adopted one of the most modern classifications of the animal kingdom, as advocated by those who hold that embryology is the true key to taxonomy, he would have no guarantee that he might not be called upon to fundamentally alter his arrangement within a year or two. For embryologists are not agreed as to the true import of the phenomena of the development of many ani- mals, and some of our highest authorities in this department PREFACE. IX of investigation deduce diametrically opposite conclusions from their study of the same phenomena. Lastly, there are cases in which the author has preferred to retain even an antique classification, rather than accept any one of many arrangements which are based upon methods of inquiry, which are of the greatest possible value to the com- parative anatomist pure and simple, but which are unavailable for the purposes of those who merely wish to acquire a general but systematic knowledge of Zoology. The class of Birds offers a case in point. In this instance, the author has pre- ferred to retain, with some modifications, an old and only par- tially natural classification, because the only available substi- tutes are arrangements which are purely morphological, and which are based upon the observed variations in single struc- tures. Classifications of this kind, though of the utmost use to the genuine comparative anatomist, can never be thoroughly natural, and they are, at any rate, un suited for any but very advanced students of the science. In conclusion, the author can only express his regret that the fact that almost the whole of this work had passed through the press before the middle of October last, should have pre- cluded him from in any way availing himself of, or in s&me cases even from mentioning in the bibliographical lists of refer- ences, some highly valuable works of recent appearance, among which the ' Atlantic/ by Sir Wyville Thomson, the * Morphol- ogy of the Skull,' by Professor Parker and Mr Bettany, and Professor Huxley's 'Comparative Anatomy of Invertebrated Animals,' may be specially alluded to. UNITED COLLEGE, ST ANDREWS, Aprils. 1878. CONTENTS. GENERAL INTRODUCTION. PAGE Definition of Biology and Zoology — Differences between organic and inorganic matter — Differences between dead and living bodies — Nature and conditions of life — Vital force — Differences between animals and plants — Morphology and physiology — Differences between different animals— Specialisation of functions— Morpho- logical type — Von Baer's law of development — Homology, analogy, and homomorphism — Correlation of growth — Classifi- cation— Definition of species — Impossibility of a linear classifica- tion— Reproduction — Sexual reproduction — Non-sexual repro- duction—Gemmation and fission — Reproduction by internal gemmation — Alternation of generations —Parthenogenesis — De- velopment, transformation, and metamorphosis — Spontaneous generation — Origin of species — Distribution, geographical and geological, .......... 1-55 ^CHAPTER I. General characters of the Protozoa — Classification of the Protozoa — Gregarinidae — Psorospermiae, •.. . . . . . 56-60 CHAPTER II. General characters of the Rhizopoda — Monera — Amcebsa, . . 61-66 CHAPTER III. Foraminifera — Classification of the Foraminifera — Affinities of the Foraminifera — Distribution of Foraminifera in space — Distribu- tion of Foraminifera in Time, ...... 66-77 CHAPTER IV. Radiolaria — Acanthometrse — Polycystina -- Thalassicollida — Heliozoa, . . . . . ... . . 77-83 CHAPTER V. Sponges — Nature of Sponges — Chief groups of Spongida — Distribu- tion of Sponges in space and in time — Affinities of Sponges, . 83-94 Xll CONTENTS. CHAPTER VI. Infusoria — Order Ciliata — Suctoria — Flagellata — Noctiluca — Phos- phorescence of the sea — Literature of Protozoa, . . . 94-104 CHAPTER VII. General characters of the Coelenterata — Divisions of the Coelenterata — Hydrozoa— General terminology of the Hydrozoa, . . 105-111 CHAPTER VIII. Divisions of the Hydrozoa — Sub-class Hydroida — Order Hydrida— Order Corynida — Reproduction of Hydroida — Sertularida — Cam- panularida — Thecomedusse — Medusidoe, . . . . 111-131 CHAPTER IX. Siphonophora or Oceanic Hydrozoa — Calycophoridae — Divisions of Calycophoridae — Physophoridae — Divisions of Physophoridre, 131-136 CHAPTER X. Lucernarida — Steganophthalmate Medusae — Lucernariadoe — Pelagidp? — Rhizostomidae — Reproduction in Rhizostomidae — Sub- class Graptolitidse — Definition of the sub-class — Structure of Grapto- lites — Sub-class Hydrocorallinse — Millepora — Stylasteridoe, 137-149 CHAPTER XI. Distribution of Hydrozoa in space — Distribution of Hydrozoa in time — Oldhamia — Corynida — Sertularida — Graptolites — Hydrocoral- lin*, . . . , , . . . . \ .. . . I49-I5I CHAPTER XII. General characters of the Actinozoa — Zoantharia Malacodermata— Actinidae — Ily anthidse — Zoanthidae — Zoantharia Sclerobasica — Sclerobasic and Sclerodermic Corals — Antipathidae — Zoantharia Sclerodermata — Gemmation and fission amongst Corals — Divisions of Zoantharia Sclerodermata, .... 151-165 CHAPTER XIII. Alcyonaria — Alcyonidae — Tubiporidse — Pennatuliclae — Gorgonidae — Red Coral— Helioporidae, . ,,' . ,' ..... '.',, . . 165-172 CHAPTER XIV. Rugosa— Operculate Corals— Families of Rugosa, . . . . 173-175 CHAPTER XV. Ctenophora— General characters — Anatomy of Pleurobrachia — Divi- sions of Ctenophora, . . . . . . . .176-180 CHAPTER XVI. Distribution of Actinozoa in space — Coral-reefs, their structure, and mode of origin — Distribution of Actinozoa in time — Literature of Coelenterata, 180-189 CHAPTER XVII. Echinodermata — General characters of the Echinodermata — Develop- ment of the Echinodermata — Divisions of Echinodermata, . 190-193 CONTENTS. xiii CHAPTER XVIII. Echinoidea — General characters — Anatomy of Echinus — Divisions or Echinoidea, ......... 193-201 CHAPTER XIX. Asteroidea and Ophiuroidea — General characters of the Asteroidea — Divisions of the Asteroidea — General characters of the Ophiuroi- dea— Families of the Ophiuroidea, ..... 201-207 CHAPTER XX. Crinoidea, Cystoidea, and Blastoidea — General characters of Crinoi- dea — Of Cystoidea — Of Blastoidea, . , . , ;. . 207-218 CHAPTER XXI. Holothuroidea — General characters — Sub-orders of Holothuroi- dea, . • , • .-'• . . . .~" . . . 218-221 CHAPTER XXII. Distribution of Echinodermata in space — Distribution of Echinoder- mata in time — Crinoidea — Blastoidea — Cystoidea — Astercidea — Ophiuroidea — Echinoidea — Holothuroidea — Literature of Echino- dermata, . ':' V t- « •:•;.-< :-" ...... 222-226 CHAPTER XXIII. General characters of the Annulosa — Divisions of the Annulosa— General characters of the class Scolecida — Entozoa — Platyelmia — Tseniada — Structure and development of the Tapeworm — Hydatids, . -, ' , , "" ...... 227-236 CHAPTER XXIV. Trematoda and Turbellaria — General characters of the Trematoda — General characters of the Turbellaria — Planarida — Nemertida — Balanoglossus and Tornaria— Pelagonemertidse, . . 237-242 CHAPTER XXV. Nematelmia — Acanthocephala — Gordiacea — Nematoda — Parasitic Nematoids — Free Nematoids, ...... 242-248 CHAPTER XXVI. Rotifera — General characters of the Rotifera — Affinities of the Roti- fera — Literature of Scolecida, ...... 248-254 CHAPTER XXVII. General characters of the Anarthropoda — Class Gephyrea — General characters of the class Annelida, 254-259 CHAPTER XXVIII. Divisions of the Annelida — Hirudinea — Oligochseta — Tubicola — Errantia— Distribution of the Annelida in time— Class Chseto- gnatha— Literature of Anarthropoda, .... 260-273 xiv CONTENTS. CHAPTER XXIX. Arthropoda— General characters — Divisions of Arthropoda, . 274-275 CHAPTER XXX. Crustacea — Characters of the class Crustacea — General morphology of / Crustacea— Divisions of Crustacea, . •,-••:.(..• • 27S"2^3 CHAPTER XXXI. Epizoa — Ichthyophthira — Rhizocephala — Cirripedia — Characters of Cirripedia— Development — Reproduction — Divisions, . 283-292 CHAPTER XXXII. Entomostraca — Lophyropoda — Ostracoda — Copepoda — Branchio- poda — Cladocera — Phyllopoda — Trilobita — Merostomata — Xiphosura — Eurypterida, . ... . . . 292-302 CHAPTER XXXIII. Malacostraca — Edriophthalmata — Lsemodipoda — Amphipoda — Iso- poda — Podophthalmata — Stomapoda — Decapoda — Macrura — Anomura — Brachyura, ..... ; * . 302-312 CHAPTER XXXIV. Distribution of the Crustacea in space— Distribution of the Crustacea in time, . i " . . . . . . -.; . 3I2-3H CHAPTER XXXV. General characters and divisions of the Arachnida, . . . 314-319 CHAPTER XXXVI. Divisions of the Arachnida— Podosomata — Acarina — Adelarthroso- mata — Pedipalpi — Araneida — Distribution of Arachnida in -*ime, . .. -.. . 319-327 CHAPTER XXXVII. Myriapoda — General characters of the class — Chilopoda— Chilo- gnatha— Pauropoda — Onychophora — Distribution of Myriapoda in time, . 327-332 CHAPTER XXXVIII. X General characters of the Insecta — Metamorphoses of Insects — Sexes of Insects — Distribution of Insects in time, . . . 333-344 CHAPTER XXXIX. Divisions of the Insecta — Anoplura — Mallophaga — Collembola — Thy- sanura — Hemiptera — Orthoptera — Neuroptera — Aphaniptera — Diptera — Lepidoptera — Hymenoptera — Strepsiptera — Coleop- tera— Literature of Arthropoda, 344-365 CHAPTER XL. neral characters of the Mollusca — Digestive system — Circulatory system— Respiratory system — Nervous system — Reproduction — Shell, . . . . . ... . . 366-370 CONTENTS. XV CHAPTER XLI. Molluscoida — Polyzoa — Distinctions between the Polyzoa and Hy- drozoa — Polypide of the Polyzoa — Anatomy of the Polyzoa — Reproduction and development — Divisions of the Polyzoa — Affinities of the Polyzoa — Distribution of the Polyzoa in space, . - . . ^ J • 37i-38o CHAPTER XLII. Tunicata— General characters— Development— Types of— Homolo- gies — Divisions — Distribution of Tunicata in space and time, 380-388 CHAPTER XLIII. Brachiopoda — General characters — Shell — Arms — Atrial system — De- velopment of — Affinities of — Divisions of — Distribution of, in , space and time, . . . .•^'.;t.-^ . . . 388-395 CHAPTER XLIV. (.General characters and divisions of the Mollusca Proper — Lamelli- ' / branchiata — General characters and anatomy — Divisions — Distri- bution of the Lamellibranchiata in time, . . . 396-404 CHAPTER XLV. Encephala — Gasteropoda— General characters — Development — Shell of Gasteropoda, .,' ; :':.! ;;;»; V|i/. :; j. • • . 405-411 CHAPTER X'LVI. Divisions of the Gasteropoda — Prosobranchiata — Opisthobranchiata — Heteropoda — Pulmonate Gasteropoda— Distribution of Gastero- poda in space and time, ....... 411-416 CHAPTER XLVII. Pteropoda — General characters — Divisions — Families — Distribution in time, . ... -r ...... ,_.,,.i . . . . . 416-418 CHAPTER XLVIII. /Cephalopoda— General characters — Arms— Respiratory organs — Re- productive process — Shell, ....... 418-426 CHAPTER XLIX. Dibranchiate Cephalopods— General characters — Octopoda— Argon- autidse — Octopodidse — Decapoda — Teuthidse — Sepiadae — Spiru- lid^e — Belemnitidae— Tetrabranchiate Cephalopods— Structure of the Pearly Nautilus — Shell of the Tetrabranchiata — Nautilidae — Ammonitidge — Distribution of the Cephalopoda in space and time — Literature of Mollusca, ....... 426-44 1 CHAPTER L. ^General characters of the Vertebrata— Osseous system— Digestive sys- tem — Blood — Circulation — Respiration — -Nervous system — Organs of sense — Reproduction — Divisions — General litera- ture, 443-46o xvi CONTENTS. CHAPTER LI. General characters of Fishes — Integumentary system — Osseous system — Fins — Respiration — Circulation — Digestive system — Swim- bladder — Nervous system— Olfactory organs — Reproduction, 461-476 CHAPTER LIT. Pharyngobranchii — Marsipobranchii, . . . . . 477-482 CHAPTER LIII. Teleostei — Sub -orders — Malacopteri — Anacanthini — Acanthopteri — Plectognathi — Lophobranchii, 482-488 CHAPTER LIV. Ganoidei — Sub-orders— Lepidoganoidei— Placoganoidei, . . 489-494 CHAPTER LV. Elasmobranchii and Dipnoi — Sub-orders of Elasmobranchii — Holo- cephali — Plagiostomi — Dipnoi, . . •./'- . ,, ' . 494-503 CHAPTER LVI. Distribution of Fishes in time — Literature, .... 504-508 CHAPTER LVII. General characters of the Amphibia, '<£?j, form, and Xoyos, dis- course). From the second, we have to study the vital actions performed by living beings and \he functiotis discharged by the different parts of the organism. This constitutes the science of physiology. A third department of zoology is concerned with the rela- tions of the organism to the external conditions under which it is placed, constituting a division of the science to which the term " distribution " is applied. Morphology, again, not only treats of the structure of living beings in their fully -developed condition (anatomy), but is also concerned with the changes through which every living being has to pass before it assumes its mature or adult charac- ters (embryology or development). The term " histology " is further employed to designate that branch of morphology which is specially occupied with the investigation of minute or micro- scopical tissues. Physiology treats of all the functions exercised by living bodies, or by the various definite parts or organs, of which most animals are composed. All these functions come under three heads : — i. functions of Nutrition, divisible into func- tions of absorption and metamorphosis, comprising those func- tions which are necessary for the growth and maintenance of the organism. 2. functions of Reproduction, whereby the per- petuation of the species is secured. 3. functions of Correlation, comprising all those functions (such as sensation and voluntary motion) by which the external world is brought into relation with the organism, and the organism in turn reacts upon the external world. Of these three, the functions of nutrition and reproduction are often collectively called the functions of organic or vege- tative life, as being common to animals and plants ; while the DIFFERENCES BETWEEN DIFFERENT ANIMALS. 19 functions of correlation are called the animal functions, as being more especially characteristic of, though not peculiar to, animals. 7. DIFFERENCES BETWEEN DIFFERENT ANIMALS. All the innumerable differences which subsist between dif- ferent animals may be classed under two heads, corresponding to the two aspects of every living being, morphological and physiological. One animal differs from another either morpho- logically', in the fundamental points of its structure ; or physio- logically, in the manner in which the vital functions of the organism are discharged. These constitute the only modes in 1 which anyone animal can differ from any other; and they may \ be considered respectively under the heads of Specialisation of Function and Morphological type. a. Specialisation of Function. — All animals alike, whatever their structure may be, perform the three great physiological functions ; that is to say, they all nourish themselves, repro- duce their like, and have certain relations with the external world. They differ from one another physiologically in the manner in which these functions are performed. Indeed, it is only in the functions of correlation that it is possible that there should be any difference in the amount or perfection of the function performed by the organism, since nutrition and repro- duction, as far as their results are concerned, are essentially the same in all animals. In the manner, however, in which the same results are brought about, great differences are observable in different animals. The nutrition of such a simple organism as the Amoeba is, indeed, performed perfectly, as far as the result to the animal itself is concerned — as perfectly as in the case of the highest animal — but it is performed with the simplest possible apparatus. Jt may, in fact, be said to be performed without any special apparatus, since any part of the surface of the body may be extemporised into a mouth, and there is no differentiated alimentary cavity. And not only is the nutritive apparatus of the simplest character, but the function itself is equally simple, and is entirely divested of those complexities and separations into secondary functions which characterise the process in the higher animals. It is the same, too, with the functions of reproduction and correlation; but .this point will be more clearly brought out if we examine the method in which one of the three primary functions is performed in two or three examples. Nutrition, as the simplest of the functions, will best answer the purpose. 20 MANUAL OF ZOOLOGY. In the simpler Protozoa, such as the Amoeba, the process bf nutrition consists essentially in the reception of food, its digestion within the body, the excretion of effete or indigestible matter, and the distribution of the nutritive fluid through the body. The first three portions of this process are effected with- out any special organs for the purpose, and for the last there is simply a rudimentary contractile cavity. Respiration, if it can be said to exist at all as a distinct function, is simply effected by the general surface of the body. In a Coelenterate animal, such as a sea-anemone, the func- tion of nutrition has not advanced much in complexity, but the means for its performance are somewhat more specialised. Permanent organs of prehension (tentacles) are present, there is a distinct mouth, and there is a persistent internal cavity for the reception of the food ; but this is not shut off from the general cavity of the body, and there are no distinct circulatory or respiratory organs. In a Mollusc, such as the oyster, nutrition is a much more complicated process. There is a distinct mouth, and an ali- mentary canal which is shut off from the general cavity of the body, and is provided with a separate aperture for the excre- tion of effete and indigestible matters. Digestion is performed by a distinct stomach with accessory glands ; a special contrac- tile cavity, or heart, is provided for the propulsion of the nutri- tive products of digestion through all parts of the organism ; and the function of respiration is performed by complex organs specially adapted for the purpose. It is not necessary here to follow out this comparison further. In still higher animals the function of nutrition becomes still further broken up into secondary functions, for the due performance of which special organs are provided, the complexity of the organism thus necessarily increasing pan passu with the complexity of the function. This gradual sub- division and elaboration is carried out equally with the other two physiological functions — viz., reproduction and correlation — and it constitutes what is technically called the " specialisa- tion of function," though it has been more happily termed by Milne-Edwards " the principle of the physiological division of labour." It is needless, however., to remark that in the higher animals it is the functions of correlation which become most highly specialised — disproportionately so, indeed, when com- pared with the development of the nutritive and reproductive functions. b. Morphological Type. — The first point in which one animal may differ from another is the degree to which the MORPHOLOGICAL TYPE. 21 principle of the physiological division of labour is carried. The second point in which one animal may differ from another is in its " morphological type j " that is to say, in the funda- mental plan upon which it is constructed. By one not specially acquainted with the subject it might be readily imagined that each species or kind of animal was constructed upon a plan peculiar to itself and not shared by any other. This, how- ever, is far from being the case ; and it is now universally recognised that all the varied species of animals — however great the apparent amount of diversity amongst them — may be - arranged under no more than half-a-dozen primary morphologi- cal types or plans of structure. Upon one or other of these six (or perhaps seven) plans every known animal, whether living or extinct, is constructed. It follows from the limited number of primitive types or patterns, that great numbers of animals must agree with one another in their morphological type. It follows, also, that all so agreeing can differ from one another only in the sole remaining element of the question — namely, by the amount of specialisation of function which they exhibit. Every animal, therefore, as Professor Huxley has well expressed it, is the resultant of two tendencies, the one morphological, the other physiological. The six types or plans of structure, upon one or other of which all known animals have been constructed, are techni- cally called " sub-kingdoms," and are known by the names Pro- tozoa, Ccelenterata, Echinodermata, Annulosa, Mollusca, and Vertebrata. We have, then, to remember that every member of each of these primary divisions of the animal kingdom agrees with every other member of the same division in being formed upon a certain definite plan or type of structure, and differs from every other simply in the grade of its organisation, or, in other words, in the degree to which it exhibits specialisa- tion of function. VON BAER'S LAW OF DEVELOPMENT. — As the study of living beings in their adult condition shows us that the differences between those which are constructed upon the same morpho- logical type depend upon the degree to which specialisation of function is carried, so the study of development teaches us that the changes undergone by any animal in passing from the embryonic to the mature condition are due to the same cause. All the members of any given sub-kingdom, when examined in their earliest embryonic condition, are found to present the same fundamental characters. As development proceeds, however, they diverge from one another with greater or less rapidity, until the adults ultimately become more or 22 MANUAL OF ZOOLOGY. less different, the range of possible modification being ap- parently almost illimitable. The differences are due to the different degrees of specialisation of function necessary to perfect the adult; and therefore, as Von Baer put it, the pro- gress of development is from the general to the special. It is upon a misconception of the true import of this law that the theory arose, that every animal in its development passed through a series of stages in which it resembles, in turn, the different inferior members of the animal scale. With regard to man, standing at the top of the whole animal kingdom, this theory has been expressed as follows : "Human organogenesis is a transitory comparative anatomy, as, in its turn, comparative anatomy is a fixed and permanent state of the organogenesis of man" (Serres). In other words, the embryo of a Vertebrate animal was believed to pass through a series of changes corresponding respectively to the permanent types of the lower sub-kingdoms — namely, the Protozoa, Ccelen- terata, Echinodermata, Annulosa, and Mollusca — before finally assuming the true vertebrate characters. Such, however, is not truly the case. The ovum of every animal is from the first impressed with the power of developing in one direction only, and very early exhibits the fundamental characters proper to its sub-kingdom, never presenting the structural peculiari- ties belonging to any other morphological type. Neverthe- less, the differences which subsist between the members of each sub-kingdom in their adult condition are truly referable to the degree to which development proceeds, the place of each individual in his own sub-kingdom being regulated by the stage at which development is arrested. Thus, many cases are known in which the younger stages of a given animal represent the permanent adult condition of an animal some- what lower in the scale. To give a single example, the young Gasteropod (amongst the Mollusca) transiently presents all the essential characters which permanently distinguish the adult Pteropod. The development of the Gasteropod, however, pro- ceeds beyond this point, and the adult is much more highly specialised than is the adult Pteropod. The theory of development held by the supporters of the doctrine of Evolution is best expressed in the words of Prof. Haeckel. According to this eminent naturalist, " Ontogenesis " (or the development of the individual) " is the brief and rapid recapitulation of phylogenesis" (or the development of the species) "governed by the physiological functions of transmis- sion (reproduction) and nutrition (adaptation). The organic individual, during the rapid and brief course of its individual HOMOLOGY AND ANALOGY. 23 development, repeats the most important of those changes of form which its ancestors have passed through during the long and gradual course of their palaeontological development, in accordance with the laws of transmission and adaptation." 8. HOMOLOGY, ANALOGY, AND HOMOMORPHISM. When organs in different animals agree with one another in fundamental structure, they are said to be " homologous ; " when they perform the same functions they are said to be "analogous." Thus the wing of a bird and the arm of a man are constructed upon the same fundamental plan, and they are therefore homologous organs. They are not analogous, however, since they do not perform the same function, the one being adapted for aerial locomotion, the other being an organ of prehension. On the other hand, the wings of a bird and the wings of an insect both serve for flight, and they are therefore analogous, since they perform the same function. They are not homologous, however, as they are constructed upon wholly dissimilar plans. There are numerous cases, however, in which organs correspond with one another both structurally and functionally, in which case they are both homologous and analogous. A form of homology is often seen in a single animal in which (- there exists a succession of parts which are fundamentally j identical in structure, but are variously modified to fulfil dif- ferent functions. Thus a Crustacean — such as the lobster — may be looked upon as being composed of a succession of rings, each of which bears a pair of appendages, these appen- dages being constructed upon the same type, and being there- fore homologous. They are, however, variously modified in different regions of the body to enable them to fulfil special functions, some being adapted for swimming, others for walk- ing, others for prehension, others for mastication, and so on. This succession of fundamentally similar parts in the same animal constitutes what is known as serial homology. When, however, the successive parts are similar to one another, both in structure and in function, the case becomes rather one of what is called " vegetative " or " irrelative repetition." An ex- cellent instance of this is seen in the common Millipede (iulus). Homomorphism. — Many examples occur, both among animals and among plants, in which families widely removed from one another as to their fundamental structure, nevertheless pre- sent a singular, and sometimes extremely close, resemblance in their external characters. Thus the composite Hydroid 24 MANUAL OF ZOOLOGY. Zoophytes and the Polyzoa are singularly like one another — so much so, that they have often been classed together ; whereas, in reality, they belong to different sub -kingdoms. Many other cases of this resemblance of different animals might be adduced, and in many cases these " representative forms " appear to be able to fill each other's places in the general economy of nature. This is so far true, at any rate, that " homomorphous " forms are generally found in different parts of the earth's surface. Thus, the place of the Cacti of South America is taken by the Euphorbiae of Africa; or, to take a zoological illustration, many of the different orders of Mammalia are represented in the single order Marsupialia in Australia, in which country this order has almost alone to dis- charge the functions elsewhere performed by several orders. Many homomorphous forms, however, live peacefully side by side, and it is difficult to say whether in this case the resem- blance between them is for the advantage or for the disadvan- tage of either. In other cases we find certain animals putting on the external characters of certain other animals, to which they may be closely related, or from which they may be widely separated in zoological position. Such cases are said to be examples of "mimicry," and such animals are said to be " mimetic." Excellent examples of this may be found amongst certain Butterflies, or in the close resemblance of the clear- winged Moths to Bees and Hornets. In all these cases it appears that the mimetic species is protected from some enemy by its outward similarity to the form which it mimics. Finally, there are numerous cases in which animals resemble certain natural objects, and thus greatly diminish their chances of being detected by their natural foes. Excellent instances of this " protective resemblance " are afforded by the insects known as Walking-leaves (Phy Ilium, fig. 2) and Walking-sticks (Phasmid(z\ which respectively present the most singular resemblance to leaves and dried twigs. The student, how- ever, must carefully guard himself against supposing that the term " mimicry " implies any conscious action on the part of the mimetic species ; there being no evidence to support such a view. 9. CORRELATION OF GROWTH. This term is employed by zoologists to express the empirical law, that certain structures, not necessarily or usually connected together by any visible link, invariably occur in association with one another, and never occur apart — so far, at any rate, as human observation goes. CORRELATION OF GROWTH. 25 Thus, all animals which possess two condyles on the occi- pital bone, and possess non-nucleated red blood-corpuscles, suckle their young. Why an animal with only one condyle on its occipital bone should not suckle its young we do not Fig. 2.— Walking-Leaf Insect (Phyllium). know, and perhaps we shall at some future time find mammary glands associated with a single occipital condyle. Most of these correlations are physiologically difficult of explanation, and sometimes even amusing. Thus all, or almost all, male cats, which are entirely white and have blue eyes, are at the same time deaf. With regard to these and similar generali- sations we must, however, bear in mind the following three points : — 1. The various parts of the organisation of any animal are so closely interconnected, and so mutually dependent upon one another, both in their growth and development, that the characters of each must be in some relation to the characters of all the rest, whether this be obviously the case or not. 2. It is rarely possible to assign any reason for correlations of structure, though they are certainly in no case accidental. 26 MANUAL OF ZOOLOGY. 3. The law is a purely empirical one, and expresses nothing more than the result of experience ; so that structures which we now only know as occurring in association, may ultimately be found dissociated, and conjoined with other structures of a different character. 10. CLASSIFICATION. Classification is the arrangement of a number of diverse objects into larger or smaller groups, according as they exhibit more or less likeness to one another. The excellence of any given classification will depend upon the nature of the points which are taken as determining the resemblance. Systems of classification, in which the groups are founded upon mere ex- ternal and superficial points of similarity, though often useful in the earlier stages of science, are always found in the long- run to be inaccurate. It is needless, in fact, to point out that many living beings, the structure of which is fundamentally different, may nevertheless present such an amount of adap- tive external resemblance to one another, that they would be grouped together in any " artificial " classification. Thus, to take a single example, the whale, by its external characters, would certainly be grouped amongst the fishes, though widely removed from them in all the essential points of its structure. " Natural" systems of classification, on the other hand, endea- vour to arrange animals into divisions founded upon a due consideration of all the essential and fundamental points of structure, wholly irrespective of external similarity of form and habits. Philosophical classification depends upon a due ap- preciation of what constitute the true points of difference and likeness amongst animals ; and we have already seen that these are morphological type and specialisation of function. Philo- sophical classification, therefore, is a formal expression of the facts and laws of Morphology and Physiology. It follows that the more fully the programme of a philosophical and strictly natural classification can be carried out, the more completely does it afford a condensed exposition of the fundamental con- struction of the objects classified. Thus, if the whale were placed by an artificial grouping amongst the fishes, this would simply express the facts that its habits are aquatic and its body fish-like. When, on the contrary, we obtain a natural classi- fication, and we learn that the whale is placed amongst the Mammalia, we then know at once that the young whale is born in a comparatively helpless condition, and that its mother is provided with special mammary glands for its sup- CLASSIFICATION. 2/ port ; this expressing a fundamental distinction from all fishes, and being associated with other equally essential correlations of structure. The entire animal kingdom is primarily divided into some half-a-dozen great plans of structure, the divisions thus formed being called " sub-kingdoms/' The sub-kingdoms are, in turn, broken up into classes, classes into orders, orders into families, families into genera, and genera into species. We shall ex- amine these successively, commencing with the consideration of a species, since this is the zoological unit of which the larger divisions are made up. Species. — No term is more difficult to define than " species," and on no point are zoologists more divided than as to what should be understood by this word. Naturalists, in fact, are not yet agreed as to whether the term species expresses a real and permanent distinction, or whether it is to be regarded merely as a convenient, but not immutable, abstraction, the employment of which is necessitated by the requirements of classification. By Buffon " species " is defined as " a constant succession of individuals * similar to and capable of reproducing each other." De Candolle defines species as an assemblage of all those individuals which resemble each other more than they do others ; and are able to reproduce their like, doing so by the generative process, and in such a manner that they may be supposed by analogy to have all descended from a single being or a single pair. M. de Quatrefages defines species as "an assemblage of individuals, more or less resembling one another, which are descended, or may be regarded as being descended, from a single primitive pair by an uninterrupted succession of families." Miiller defines species as "a living form, represented by individual beings, which reappears in the product of generation with certain invariable characters, and is constantly reproduced by the generative act of similar individuals." According to Pritchard, a species is constituted by " separate origin, and distinctness of race, evinced by a constant trans- mission of some characteristic peculiarity of organisation." According to Woodward, " all the specimens, or individuals, * In using the term "individual," it must be borne in mind that the "zoological individual" is meant; that is to say, the total result of the development of a single ovum, as will hereafter be explained at greater length. 2$ MANUAL OF ZOOLOGY. which are so much alike that we may reasonably believe them to have descended from a common stock, constitute a species" From the above definitions it will be at once evident that there are two leading ideas in the minds of zoologists when they employ the term species ; one of these being a certain amount of resemblance between individuals, and the other being the proof that the individuals so resembling each other have descended from a single pair, or from pairs exactly simi- lar to one another. The characters in which individuals must resemble one another in order to entitle them to be grouped in a separate species, according to Agassiz, " are only those determining size, proportion, colour, habits, and relations to surrounding circumstances and external objects.** On a closer examination, however, it will be found that these two leading ideas in the definition of species — external resemblance and community of descent — are both defective, and liable to break down if rigidly applied. Thus, there are in nature no assemblages of plants or animals usually grouped together into a single species, the individuals of which exactly resemble one another in every point. Every naturalist is compelled to admit that the individuals which compose any so-called species, whether of plants or Animals, differ from one another to a greater or less extent, and in respects which may be regarded as more or less important. The existence of such individual differences is attested by the universal employment of the terms "varieties** and "races." Thus a u variety * comprises all those individuals which possess some distinctive peculiarity in common, but do not differ in other respects from another set of individuals sufficiently to entitle them to take rank as a separate species. A " race," again, is simply a permanent or " perpetuated * variety. The question. however, is this — How far may these differences amongst in- dividuals obtain without necessitating their being placed in a separate species ? In other words : How great is the amount of individual difference which is to be considered as merely " varietal? and at what exact point do these differences become ofsp&z/ic" value ? To this question no answer can be given, since it depends entirely upon the weight which different naturalists would attach to any given individual difference.* Distinctions which appear to one observer as sufficiently great to entitle the individuals possessing them to be grouped as * As an example of this, it is sufficient to allude to the feet that hardly any two botanists agree as to the number of species of Willows and Bram- bles in the British. Isles. What one observer classes as mere varieties* another regards as good and distinct species. CLASSIFICATION. 29 a distinct species, by another are looked upon as simply of varietal value ; and, in the nature of the case, it seems impos- sible to lay down any definite rules. To such an extent do individual differences sometimes exist in particular genera — termed "protean" or " polymorphic " genera — that the deter- mination of the different species and varieties becomes an almost hopeless task. Besides the individual differences which ordinarily occur in all species, other cases occur in whkh a species consists normally and regularly of two or even three distinct forms, which cannot be said to be mere varieties, since no inter- mediate forms can be discovered. When two such distinct forms exist, the species is said to be "dimorphic/' and when three are present, it is called " trimorphic." Thus, in dimorphic plants a single species is composed of two distinct forms, similar to one another in all respects except in their repro- ductive organs, the one form having a long pistil and short stamens, the other a short pistil with long stamens. In tri- morphic plants, the species is composed of three such distinct forms, which differ in like manner in the conformation of their reproductive. organs, though they are otherwise undistinguish- able (Darwin). Similar cases are known in animals, but in them the differences, though apparently connected with repro- duction, are not confined to the reproductive organs. Thus the females of certain butterflies normally appear under two or three entirely different forms, not connected by any inter- mediate links ; and the same thing occurs in some of the Crustacea. As regards, therefore, the first point in the definition of species — namely, the external resemblance of assemblages of individuals — we are forced to conclude that no two individuals are exactly alike ; and that the amount and kind of external resemblance which constitutes a species is not a precise and invariable quantity, but depends upon the value attached to particular characters by any given observer. The second point in the definition of species — namely, com- munity of descent — is hardly in a more satisfactory condition, since the descent of any given series of individuals from a single pair, or from pairs exactly similar to one another, is at best but a probability, and is in no case capable of proo£ In the case of the higher animals, it can doubtless be shown that certain assemblages of individuals possess amongst themselves the power of fecundation and of producing fertile progeny, and that this power does not extend to the fecundation of indi- viduals belonging to another different assemblage. Amongst 30 MANUAL OF ZOOLOGY. the higher animals, " crosses " or " hybrids " can only be pro- duced between closely-allied species, and when produced they are sterile, and are not capable of reproducing their like. In these cases, therefore, we may take this as a most satisfactory element in the definition of " species.5' The sterility, however, of hybrids is not universal, even amongst the higher animals ; and amongst plants no doubt can be entertained but that the individuals of species universally admitted to be distinct are capable of mutual fertilisation ; the hybrid progeny thus produced being likewise fertile, and capable of reproducing similar individuals. That this fertility is often irregular, and may be destroyed in a few generations, admits of explana- tion, and hardly alters the significance of these undoubted facts. Upon the whole, then, it seems in the meanwhile safest to adopt a definition of species which implies no theory, and does not include the belief that the term necessarily expresses a fixed and permanent quantity. Species, therefore, may be defined as an assemblage of individuals which resemble each other in their essential characters, are able, directly or indirectly, to pro- duce fertile individuals, and which do not (as far as human observation goes) give rise to individuals which vary from the general type through more than certain definite limits. The pro- duction of occasional monstrosities does not, of course, invali- date this definition. Genus is a term applied to groups of species which possess a community of essential details of structure. A genus may include a single species only, in cases where the combination of characters which make up the species are so peculiar that no other species exhibits similar structural characters ; or, on the other hand, it may contain many hundreds of species. Families are groups of genera which agree in their general characters. According to Agassiz, they are divisions founded upon peculiarities of "form as determined by structure." Orders are groups of families related to one another by structural characters common to all. Classes are larger divisions, comprising animals which are formed upon the same fundamental plan of structure, but differ in the method in which the plan is executed (Agassiz). Sub-kingdoms are the primary divisions of the animal king- dom, which include all those animals which are formed upon the same structural or morphological type, irrespective of the degree to which specialisation of function may be carried. Impossibility of a Linear Classification. — It has sometimes been thought that the animal kingdom can be arranged in a CLASSIFICATION. 31 linear series, every member of the series being higher in point of organisation than the one below it. As we have seen, how- ever, the status of any given animal depends upon two condi- tions1— one its morphological type, the other the degree to which specialisation of function is carried. Now, if we take two animals, one of which belongs to a lower morphological type than the other, no degree of specialisation of function, however great, will place the former above the latter, as far as its type of structure is concerned, though it may make the former a more highly organised animal. Every Vertebrate animal, for example, belongs to a higher morphological type than every Mollusc ; but the higher Molluscs, such as cuttle- fishes, are much more highly organised, as far as their type is concerned, than are the lowest Vertebrata. In a linear classi- fication, therefore, the cuttle-fishes should be placed above the lowest fishes— such as the lancelet — in spite of the fact that the type upon which the latter are constructed is by far the higher of the two. It is obvious, therefore, that a linear classification is not possible, since the higher members of each sub-kingdom are more highly organised than the lower forms of the next sub- kingdom in the series, at the same time that they are con- structed upon a lower morphological type. In the words of Professor Allen Thomson, "It has become more and more apparent in the progress of morphological research, that the different groups form circles which touch one another at certain points of greatest resemblance, rather than one continuous line, or even a number of lines which partially pass each other." In the same way the highest vegetables do not approximate to, or graduate into, the lowest animals ; but " each kingdom presents, as it were, a radiating expansion into groups for itself, so that the relations of the two kingdoms might be represented by the divergence of lines spreading in two different directions from a common point." BINOMIAL NOMENCLATURE. — Since the time of Linnseus it has been the practice of naturalists to designate all species by double designations, the first part of the title indicating the genus to which the animal belongs, whilst the second is the proper or specific title. Thus the Dog is known by the "binomial" designation of Cams familiaris. The "genus" Cants contains other species besides the Dog — such as the Wolf and Jackal — but the i&xs\& familiaris indicates that this title belongs to the Dog and not to either of the latter. The genus Cam's, again, belongs to the "family" Canidce, including other genera, such as the Foxes ( Vulpes). The family Canidce, further, is one of a number of families, such as the Cats (Felida), the Bears (Ursidce}, the Hyaenas (Hycznidtz), &c., which collectively con- stitute the ' ' order " of the Carnivora or Beasts of Prey. The Carnivora, 32 MANUAL OF ZOOLOGY, again, constitute one of many orders of quadrupeds, which are distinguished by suckling their young and by other common characters, and which collectively constitute the "class" Mammalia. Finally, the Mammalia are united with the classes of the Birds, Reptiles, Amphibians, and Fishes to constitute the great primary division or " sub-kingdom " of Vertebrata or " Vertebrate animals ; " since all these classes agree with one another in certain fundamental points of structure. Condensing the above, the name of Cants familiaris, as applied to the Dog, implies a large amount of information as to the precise zoological position and affinities of the animal. Its title, namely, if expressed in full, would indicate its systematic place to be as follows :— Sub-kingdom, VERTEBRATA. Class, Mammalia. Order, Carnivora. Family, Canida. Genus, Cants. Species, Cam's familiaris. ii. REPRODUCTION. Reproduction is the process whereby new individuals are generated and the perpetuation of the species insured. The methods in which this end may be attained exhibit a good deal of diversity, but they may be all considered under two heads. I. Sexual Reproduction. — This consists essentially in the production of two distinct elements, a germ-cell or ovum, and a sperm -cell or spermatozoid, by the contact of which the ovum — now said to be " fecundated " — is enabled to develop itself into a new individual. As a rule, the germ-cell is pro- duced by one individual (female) and the spermatic element by another (male) ; in which case the sexes are said to be dis- tinct, and the species is said to be "dioecious." In other cases the same individual has the power of producing both the essential elements of reproduction ; in which case the sexes are said to be united, and the individaal is said to be " her- maphrodite," " androgynous," or " monoecious." In the case of hermaphrodite animals, however, self- fecundation — contrary to what might have been expected — rarely constitutes the re- productive process ; and, as a rule, the reciprocal union of two such individuals is necessary for the production of young. Even amongst hermaphrodite plants, where self-fecundation may, and certainly does, occur, provisions seem to exist by which perpetual self-fertilisation is prevented, and the influence of another individual secured at intervals.* Amongst the * It seems to have been established as a strong probability by Darwin, Hildebrandt, and Delpino, that in the great majority of plants self-fecunda- REPRODUCTION. 33 higher animals sexual reproduction is the only process whereby new individuals can be generated. II. Non-sexual Reproduction. — Amongst the lower animals fresh beings may be produced without the contact of an ovum and a spermatozoid ; that is to say, without any true generative act. The processes by which this is effected vary in different animals, and are all spoken of as forms of "asexual" or "agamic" reproduction (" agamogenesis "). As we shall see, however, the true " individual " is very rarely produced other- wise than sexually, and most forms of agamic reproduction are really modifications of growth. a. Gemmation and Fission. — Gemmation, or budding, con- sists in the produ.ctiQri_ja£ a bud, or buds, generally from the exterior, TnTt sometimes from the interior, of the body of an animal, which buds are developed into independent beings, which may or may not remain permanently 'attached to the parent organism. Fisskp differs from gemmation solely in the fact that the new structures in the former case are pro- duced by a division of the body of the original organism into separate parts, which may remain in connection, or may under- go detachment. The simplest form of gemmation, perhaps, is seen in the power possessed by certain animals of reproducing parts of their bodies which they may have lost. Thus, the Crustacea possess the power of reproducing a lost limb, by means of a bud which is gradually developed till it assumes the form and takes the place of the missing member. In these cases, how- ever, the process is not in any way generative, and the pro- duct of gemmation can in no sense be spoken of as a distinct being (or zooid). An excellent example, however, of true gemmation is ex- hibited in such an organism as the common sea-mat (Flustra), which is a composite organism composed of a multitude of similar beings, each of which inhabits a little chamber, or cell ; the whole forming a structure not unlike a sea-weed in appear- ance. This colony is produced by gemmation from a single primitive being (" polypide "), which throws out buds, each of which repeats the process, apparently almost indefinitely. All the buds remain in contact and connected with one another, but each is, nevertheless, a distinct and independent being, tion never occurs, but the plant is fertilised by the intervention of insects. Thus, in many plants the stamens and pistil arrive at maturity at different times, whilst in others the stamens and stigma are placed at different heights in the flower, and do not always occupy the same position even in a single species. C 34 MANUAL OF ZOOLOGY. capable of performing all the functions of life. In this case, therefore, each one of the innumerable buds becomes an inde- pendent being, similar to, though not detached from, the organ- ism which gave it birth. This is an instance of what is called " continuous gemmation." In other cases — as in the common fresh-water polype or Hydra — the buds which are thrown out by the primitive or- ganism become developed into creatures exactly resembling the parent, but, instead of remaining permanently attached, and thus giving rise to a compound organism, they are de- tached to lead an entirely independent existence. This is a simple instance of what is termed " discontinuous gemmation." The method and results of fission may be regarded as essen- tially the same as in the case of gemmation. The products of the division of the body of the primitive organism may either remain undetached, when they will give rise to a compo- site structure (as in many corals), or they may be thrown off and live an independent existence (as in some of the Hydrozoa). We are now in a position to understand what is meant, strictly speaking, by the term " individual." In zoological language, an individual is defined as " equal to the totalresult of the development of a single ovum." Amongst the higher animals there is no difficulty about this, for each ovum gives rise to no more than one single being, which is incapable of repeating it- self in any other way than by the production of another ovum ; so that an individual is a single animal. It is most important, however, to comprehend that this is not necessarily or always the case. In such an organism as the sea- mat, the ovum gives rise to a primitive polypide, which repeats itself by a process of continuous gemmation until an entire colony is produced, each member of which is independent of its fellows, and is capable of producing ova. In such a case, therefore, the term " individual " must be applied to the entire colony, since this is the result of the development of a single ovum. The sepa- rate beings which compose the colony are technically called zooids. In like manner the Hydra, which produces fresh and independent Hydrae by discontinuous gemmation, is not an " individual," but a zoo id. Here the zooids are not perma- nently united to one another, and the "individual" Hydra consists really of the primitive Hydra, plus all the detached Hydrae to which it gave rise. In this case, therefore, the "in- dividual " is composed of a number of disconnected and wholly independent beings, all of which are the result of the develop- ment of a single ovum. It is to be remembered that both the parent zooid and the " produced zooids " are capable of giving REPRODUCTION. 35 rise to fresh Hydrse by a true generative process. It must also be borne in mind that this production of fresh zooids by a process of gemmation is not so essentially different from the true sexual process of reproduction as might at first sight appear, since the ovum itself may be regarded merely as a highly specialised bud. In the Hydra, in fact, where the ovum is pro- duced as an external process of the wall of the body, this like- ness is extremely striking. The ovarian bud, however, differs from the true gemmae or buds in its inability to develop itself into an independent organism, unless previously brought into contact with another special generative element. The only exceptions to this statement are in the rare cases of true " par- thenogenesis," to be subsequently alluded to. b. Reproduction by Internal Gemmation. — Before considering the pheno- mena of " alternate generations," it will be as well to glance for a moment at a peculiar form of gemmation exhibited by some of the Polyzoa, which is in some respects intermediate between ordinaiy discontinuous gemma- tion and alternation of generations. These organisms are nearly allied to the sea-mat already spoken of, and, like it, can reproduce themselves by continuous gemmation (forming colonies), by a true sexual process, and rarely by fission. In addition to all these methods they can reproduce themselves by the formation of peculiar internal buds, which are called " statoblasts." These buds are developed upon a peculiar cord, which crosses the body-cavity, and is attached at one end to the fundus of the stomach. When mature they drop off from this cord, and lie loose in the cavity of the body, whence they are liberated on the death of the parent organism. When thus liberated, the statoblast, after a longer or shorter period, ruptures and gives exit to a young Polyzoon, which has essentially the same structure as the adult. It is, however, simple, and has to undergo a process of continuous gemmation before it can assume the compound form proper to the adult. As regards the nature of these singular bodies, " the invariable absence of germinal vesicle and germinal spot, and their never exhibiting the phe- nomena of yelk-cleavage, independently of the conclusive fact that true ova and ovary occur elsewhere in the same individual, are quite decisive against their being eggs. We must then look upon them as gemnuz pecu- liarly encysted, and destined to remain for a period in a qwiescent or pupa- like state " (Allman). c. Alternation of Generations. — In the case of the Hydra and the sea-mat, which we have considered above, fresh zooids are produced by a primordial organism by gemmation ; the beings thus produced (as well as the parent) being capable not only of repeating the gemmiparous process, but also of pro- ducing new individuals by a true generative act. We have now to consider a much more complex series of phenomena, in which the organism which is developed from the primitive ovum produces by gemmation two sets of zooids, one of which is destitute, of sexuaj organs, and is capable of performing no other function than that of nutrition, whilst the other is pro- 36 MANUAL OF ZOOLOGY. vided with reproductive organs, and is destined for the per- petuation of the species. In the former case the produced zooids all resembled each other, and the parent organism which gave rise to them; in the latter case, the produced zooids are often utterly unlike each other and unlike the parent, since their functions are entirely different. The simplest form of the process is seen in certain of the Hydroid Polypes, such as Hydractinia. The embryo of Hydrac- tinia is a free - swimming ciliated body, which, after a short locomotive existence, attaches itself to some submarine object, develops a mouth and tentacles, and commences to produce zooids like itself by a process of continuous gemmation. These remain permanently attached to one another, with the result that a compound organism is produced, consisting of a num- ber of zooids, or " polypites," organically connected together, but enjoying an independent existence. None of the zooids, however, are provided with sexual organs ; and though there is theoretically no limit to the size which the colony may reach by gemmation, its buds are not detached, and the species would therefore die out, unless some special provision were made for its preservation. Besides these nutritive zooids, however, other buds are produced which differ considerably in appearance from the former, and which have the power of generating the essential elements of reproduction. These generative zooids derive their nourishment from the materials collected by the nutritive zooids, but only live until the ova are matured in their interior and liberated, when they disappear. The ova thus produced become free-swimming ciliated bodies, such as the one with which the cycle began. In this case, therefore, the " individual " consists of a series of nutritive zooids, collectively called the " trophosome," and another series of reproductive zooids, collectively called the " gonosome," the entire series remaining in organic connection. In other Hydroid Zoophytes allied to the preceding (such as Clytia\ the process advances a step further. In Clytia, the generative buds or zooids do not produce the reproductive elements as long as they remain attached to the parent colony; but they require a preliminary period of independent existence. For this purpose they are specially organised, and when suffi- ciently mature they are detached from the stationary colony. The generative zooid now appears as an entirely independent being, described as a species of jelly-fish (or Medusa). It con- sists of a bell-shaped disc, by means of which it is enabled to swim freely; from the centre of this disc depends a nutritive pro- cess, with a mouth and digestive cavity, whereby the organism REPRODUCTION. 37 is able to increase considerably in size. The substance of the disc is penetrated by a complex system of canals, and from its margin hangs a series of tentacular processes. After a period of independent locomotive existence, the Medusa attains its full growth, when it develops ova and spermatozoa. By the contact of these, embryos are produced ; but these, instead of resembling the jelly-fish by which they were immediately gen- erated, proceed to develop themselves into the fixed Hydroid colony by which the Medusa was originally produced. Still more extraordinary phenomena have been discovered in other Hydrozoa, as in many of the Lucernarida. In these the ovum gives rise to a locomotive ciliated body, which ulti- mately fixes itself, becomes trumpet-shaped, and develops a mouth and tentacles at its expanded extremity, when it is known as the " hydra-tuba," from its resemblance to the fresh- water polype, or Hydra. The hydra-tuba has the power of multiplying itself by gemmation, and it can produce large col- onies in this way ; but it does not obtain the power of gener- ating the essential elements of reproduction. Under certain circumstances, however, the hydra-tuba enlarges, and, after a series of preliminary changes, divides by tranverse fission into a number of segments, each of which becomes detached and swims away. These liberated segments of the little hydra-tuba (it is about half an inch in height) now live as entirely inde- pendent beings, which were described by naturalists as distinct animals, and were called Ephyrse. They are provided with a swiming-bell, or " umbrella," by means of which they propel themselves through the water, and with a mouth and digestive cavity. They now lead an active life, feeding eagerly, and attaining in some instances a perfectly astonishing size (the Medusoids of some species are several feet in circumference). After a while they develop the essential elements of reproduc- tion, and after the fecundation and liberation of their ova they die. The ova, however, are not developed into the free-swim- ming and comparatively gigantic jelly-fish by which they were immediately produced, but into the minute, fixed, sexless hydra- tuba. We thus see that a small sexless zooid, which is capable of multiplying itself by gemmation, produces by fission several independent locomotive beings, which are capable of nourish- ing themselves and of performing all the functions of life. In these are produced generative elements, which give rise by their development to the little fixed creature with which the series began. To the group of phenomena of which the above are examples, 38 MANUAL OF ZOOLOGY. the name "alternation of generations " was applied by Steen- strup ; but the name is not an appropriate one, since the pro- cess is truly an alternation of generation with gemmation or fission. The only generative act takes place in the reproduc- tive zooid, and the production of this from the nutritive zooid is a process of gemmation or fission, and not a process of gen- eration. The " individual," in fact, in all these cases must be looked upon as a double being composed of two factors, both of which lead more or less completely independent lives, the one being devoted to nutrition, the other to reproduction. The generative being, however, is in many cases not at first able to mature the sexual elements, and is therefore provided with the means necessary for its growth and nourishment as an inde- pendent organism. It must also be remembered that the nutritive half of the " individual " is usually, and the generative half sometimes, compound — that is to say, composed of a num- ber of zooids produced by continuous gemmation ; so that the zoological individual in these cases becomes an extremely com- plex being. These phenomena of so-called " alternation of generations," or " metagenesis," occur in their most striking form amongst the Hydrozoa ; but they occur also amongst many of the in- testinal worms (Entozoa), and amongst some of the Tunicata (Molluscoida). d. Parthenogenesis. — "Parthenogenesis" is the term employed to designate certain singular phenomena, resulting in the pro- duction of new individuals by virgin females without the inter- vention of a male. By Professor Owen, who first employed the term, parthenogenesis is applied also to the processes of gem- mation and fission, as exhibited in sexless beings or in virgin females ; but it seems best to consider these phenomena sepa- rately. Strictly the term parthenogenesis ought to be confined to the production of new individuals from virgin females by means of ova, which are enabled to develop themselves with- out the contact of the male element. The difficulty in this definition is found in framing an exact definition of an ovum, such as will distinguish it from an internal gemma or bud. No body, however, should be called an " ovum " which does not exhibit a germinal vesicle and germinal spot, and which does not exhibit the phenomenon known as segmentation of the yelk. Moreover, ova are almost invariably produced by a special organ, or ovary. As examples of parthenogenesis, we may take the cases of the Plant-lice (Aphides), the Honey-bee, and certain Crustacea; tnough in the case of the first of these it is possible that the REPRODUCTION. 39 phenomena observed may admit of explanation otherwise than as an instance of parthenogenesis strictly so called. The Aphides, or plant-lice, which are so commonly found parasitic upon plants, are seen towards the close of autumn to consist of male and female individuals. By the sexual union of these true ova are produced, which remain dormant through the winter. At the approach of spring these ova are hatched ; but instead of giving birth to a number of males and females, all the young are of one kind, variously regarded as neuters, virgin females, or hermaphrodites. Whatever their true nature may be, these individuals produce, viviparously, a brood of young which resemble themselves ; and this second generation, in like manner, produces a third, — and so the process may be repeated, for as many as ten or more generations, throughout the summer. When the autumn comes on, however, the vivi- parous Aphides produce — in exactly the same manner — a final brood, but this, instead of being composed entirely of similar individuals, is made up of males and females. Sexual union now takes place, and ova are produced and fecundated in the ordinary manner. The viviparous Aphides are either wingless or winged ; and the number of young produced is so great, that it has been calculated that a single Aphis might in this way be, during the summer months, and by the time the tenth generation was reached, the progenitor of no less than one quintillion of indi- viduals. Each viviparous Aphis possesses an ovary, which only differs from that of the fertile females in being without certain secondary adjuncts (the colleterial gland and sperma- theca). This " pseudovarium " produces egg-like bodies or " pseudova," which are directly developed into young Aphides — the latter being thus produced by " the individualisation of previously organised tissue." The differences between the " pseudova " and true ova are in no way anatomical, but are wholly physiological ; and the decision involved in the viviparous reproduction of the Aphides turns simply upon the question as to whether the viviparous individuals possess, in addition to the pseudovarium, a testis, or whether male organs are absent. Most observers maintain that the viviparous Aphides are wholly destitute of male organs of reproduction, in which case the phenomena just described can only be explained as an example of parthenogenesis. On the other hand, Balbiani maintains that the viviparous Aphides are really hermaphrodite, in which case, of course, the pheno- mena are of a much less abnormal character. In the second case of alleged parthenogenesis which we are 4O MANUAL OF ZOOLOGY. about to examine — namely, in the honey-bee — the phenomena which have been described are now generally accepted as free from doubt. A hive of bees consists of three classes of indi- viduals : i, a "queen," or fertile female; 2, the "workers," which form the bulk of the community, and are really unde- veloped or sterile females; and, 3, the "drones," or males, which are only produced at certain times of the year. We have here three distinct sets of beings, all of which proceed from a single fertile individual; and the question arises, In what manner are the differences between these produced ? At a certain period of the year the queen leaves the hive, accom- panied by the drones (or males), and takes what is known as her "nuptial flight" through the air. In this flight she is impregnated by the males ; and in virtue of this single impreg- nation, she is enabled to produce fresh individuals for a length- ened period, the semen of the males being stored up in a receptacle which communicates by a tube with the oviduct, from which it can be shut off at will. The ova which are to produce workers (undeveloped females) and queens (fertile females) are fertilised on their passage through the oviduct, the semen being allowed to escape into the oviduct for this purpose. The subsequent development of these fecundated ova into workers or queens depends entirely upon the form of the cell into which the ovum is placed, and upon the nature of the food which is supplied to the larva. So far there is no doubt as to the nature of the phenomena which are observed. It is asserted, however, by Dzierzon and Siebold, that the males or drones are produced by the queen from ova which she does not allow to come into contact with the semen as they pass throught the oviduct. This assertion is supported by the fact that if the communication between the receptacle for the semen and the oviduct be cut off, the queen will produce nothing but males. Also, in crosses between the common honey-bee and the Ligurian bee, the queens and workers alone exhibit any intermediate characters between the two forms, the drones presenting the unmixed characters of the queen by whom they were produced. If these observations are to be accepted as established — and there can be no hesitation in accepting them as in the main correct — then the drones are produced by a true process of parthenogenesis ; but some observers maintain that the devel- opment of any given ovum into a drone is really due — as in the case of the queens and workers — to the special circum- stances under which the larva is brought up.* • * In the case of Polistes Gallica, Von Siebold appears to have proved DEVELOPMENT. 41 Among the Crustaceans, parthenogenesis has been estab- lished as occurring in some of the water-fleas (Cladocera) and in various of the Phyllopods (Apus, Limnadia, Artemia, &c.) In these latter it is the female which is produced parthenogen- etically • whereas in the honey-bee and in Polistes it is the male. There are various other cases in which parthenogenesis is said to occur, but the above will suffice to indicate the general character of the phenomena in question. The theories of par- thenogenesis appear to be too complex to be introduced here ; and there is the less to regret in their omission, as naturalists have not yet definitely adopted any one explanation of the phenomena to the exclusion of the rest. From the phenomena of asexual reproduction in all its forms, M. de Quatrefages has deduced the following general- isation : — " The formation of new individuals may take place, in some instances, by gemmation from, or division of, the parent-being ; but this process is an exhaustive one, and cannot be carried out indefinitely. When, therefore, it is necessary to insure the continuance of the species, the sexes must present themselves, and the germ and sperm must be allowed to come in contact with one another." It should be added that the act of sexual reproduction, though it insures the perpetuation of the species, is very de- structive to the life of the individual. The formation of the essential elements of reproduction appears to be one of the highest physiological acts of which the organism is capable, and it is attended with a corresponding strain upon the vital energies. In no case is this more strikingly exhibited than in the case of insects, many of which pass the greater portion of their existence in a sexually immature condition, and die al- most immediately after they have become sexually perfect and have consummated the act whereby the perpetuation of the species is secured. 12. DEVELOPMENT, TRANSFORMATION, AND METAMORPHOSIS. Development is the general term applied to all those changes which a germ undergoes before it assumes the characters of beyond reasonable doubt that the males are produced by a process of par- thenogenesis. Landois, however, asserts that the eggs of insects are of no sex, that sex is only developed in the larva after its emergence from the egg, and that in each individual larva the sex is determined wholly by the nature of the food upon which it is brought up ; abundant nourishment producing females, and scanty diet giving rise to males. 42 MANUAL OF ZOOLOGY. the perfect individual ; and the chief differences which are ob- served in the process as it occurs in different animals consist simply in the extent to which these changes are external and visible, or are more or less completely concealed from view. For these differences the terms " transformation " and " meta- morphosis" are employed; but they must be regarded as essentially nothing more than variations of development. : Transformation is the term employed by Quatrefages to designate " the series of changes which every germ undergoes in reaching the embryonic condition ; those which we observe in every creature still within the egg ; those, finally, which the species born in an imperfectly developed state present in the course of their external life." Metamorphosis is denned by the same author as including the alterations which are " undergone after exclusion from the egg, and which alter extensively the general form and mode of life of the individual." Though by no means faultless, these terms are sufficiently convenient, if it be remembered that they are merely modifi- cations of development, and express differences of degree and not of kind. An insect, such as a butterfly, is the best illus- tration of what is meant by these terms. All the changes which are undergone by a butterfly in passing from the fecun- dated ovum to the condition of an imago, or perfect insect, constitute its development. The egg which is laid by a butter- fly undergoes a series of changes which eventuate in its giving birth to a caterpillar, these preliminary changes constituting its transformation. The caterpillar grows rapidly, and after several changes of skin becomes quiescent, when it is known as a " chrysalis." It remains for a longer or shorter time in this quiescent and apparently dead condition, during which period developmental changes are going on rapidly in its interior. Finally, the chrysalis ruptures, and there escapes from it the perfect winged insect. To these changes the term metamorphosis is rightly applied. These changes, however, do not differ in kind from the changes undergone by a Mammal ; the difference being that in the case of a Mammal the ovum is retained within the body of the parent, where it undergoes the necessary developmental changes, so that at birth it has little to do but grow, in order to be converted into the adult animal. From these considerations we arrive at a second generalisa- tion, which is thus formulated by Quatrefages : " Those crea- tures whose ova — owing to an insufficient supply of nutritious contents, and an incapacity on the part of the mother to pro- SPONTANEOUS GENERATION. 43 vide for their complete development within her own sub- stance— are rapidly hatched, give birth to imperfect offspring, which, in proceeding to their definitive characters, undergo several alterations in structure and form, known as metamor- phoses." Retrograde Development. — Ordinarily speaking, the course of development is an ascending one, and the adult is more highly organised than the young ; but there are cases in which there is an apparent reversal of this law, and the adult is to all appearance a degraded form when compared with the embryo. This phenomenon is known as " retrograde " or "recurrent" development; and well-marked instances are found amongst the Cirripedia and Lernaeae, both of which belong to the Crustacea. Thus, in the Cirripedes (acorn - shells, &c.) and in the parasitic Lernaeae (fig. 3), the embryo is free-swimming and Fig. 3. — A, Young of one of the parasitic Crustaceans (Achtheres) with its swimming- paddles and eye-spots, magnified ; B, Deformed and swollen parasitic adult of an- other member of the same group (Lerncea). provided with organs of vision and sensation, being in many respects similar to the permanent condition of certain other Crustacea, such as the Copepods. The adult, however, in both cases, is degraded into a more or less completely seden- tary animal, more or less entirely deprived of organs of sense, and leading an almost vegetative life. As a compensation, reproductive organs are developed in the adult, and it is in this respect superior to the locomotive, but sexless, larva. 13. SPONTANEOUS GENERATION. Spontaneous or Equivocal generation is the term applied to the alleged production of living beings without the pre-exist- ence of germs of any kind, and therefore without the pre-exist- ence of parent organisms. The question is one which has 44 MANUAL OF ZOOLOGY. been long and closely disputed, and is far from being settled ; so that it will be sufficient to indicate the facts upon which the theory rests. If an animal or vegetable substance be soaked in hot or cold water, so as to make an* organic infusion, and if this in- fusion be exposed for a sufficient length of time to the air, the following series of changes is usually observed : — i. At the end of a longer or shorter time, there forms upon the surface of the infusion a thin scum, or pellicle, which, when examined microscopically, is found to consist of an in- calculable number of extremely minute molecules (fig. 4, A). '*<- Fig. 4. — A, Living particles or molecules developed in organic infusions ; B, Bacteria developed in organic infusions, highly magnified. (After Beale.) 2. In the next stage these molecules appear, many of them, to have increased in size by endogenous division, till they form short staff-shaped filaments, called "bacteria" (fig. 4, B). Others increase in length by the same process until we get long filamentous bodies produced, which are termed "vibri°nes'" Both the bacteria and the vibrios now exhibit a vibratile or serpentine movement through the surrounding fluid. 3. After a varying period, the bacteria and vibrios become motionless, and disintegrate so as to produce again a finely molecular pellicle. 4. Little spherical bodies may now appear, each of which is provided with a vibratile cilium with which it moves actively through the infusion (Monas lens). 5. Varied forms of ciliated Infusoria — some of which possess a mouth and are otherwise highly organised — may make their appearance in the fluid. The above is the general sequence of the phenomena which have been observed, and the following are the two theories which have been advanced to account for them : — a. By the advocates of spontaneous generation, "Abio- genesis" or " Heterogeny," it is affirmed that the Infusoria SPONTANEOUS GENERATION. 45 which finally appear in the infusion are produced spontane- ously out of the molecular pellicle, the molecules of which are also of spontaneous origin, and are not derived from any pre- existing germs. b. By the " panspermists," or the opponents of spontaneous generation, it is alleged, on the other hand, that the produc- tion of Bacteria, Vibrios, Monads, and Infusoria, in organic infusions, is due simply to the fact that the atmosphere, and probably the fluid itself, is charged with innumerable germs — too minute, perhaps, to be always detectable by the micro- scope— which, obtaining access to the fluid, and finding there favourable conditions, are developed into living beings. A large number of elaborate experiments have been carried out to prove that atmospheric air is absolutely necessary for the production of these living beings, and that if the air be properly purified by passage through destructive chemical reagents, no such organisms will be produced, provided that the infusion have been previously boiled. As the results of all these experimental trials have hitherto proved more or less contradictory, it is unnecessary to enter into the question fur- ther, and it will be sufficient to indicate the following general considerations : — a. The primary molecules which appear in the fluid are ex- tremely minute, and if they are developed from germs, these may be so small as to elude any power of the microscope yet known to us. As they subsequently become converted into bacteria and vibrios, and as there can be little dispute as to these being truly living organisms, we are obliged to believe that they must have had some definite origin. It appears, however, to be hardly philosophical to assume that they form themselves out of the inorganic materials of the infusion ; since this implies the sudden appearance, or creation, of new force, for which there seems to be no means of accounting. b. The nature of the vibrios must be looked upon as un- certain. To say the least of it, they are quite as likely to be plants as animals; and the most probable hypothesis would place them near the filamentous Confervae, or would regard them as the mycelium of various species of Moulds (Penicil- lium\ The bacteria are undoubtedly of a vegetable nature, and referable to the Algce. c. What has been said above with regard to the origin of the bacteria and vibrios applies equally to the origin of the Monads, which appear in the infusion subsequently to the death of the vibrios. d. These monads, as shown by recent researches, are pro- 46 MANUAL OF ZOOLOGY. bably to be looked upon as, in some cases at any rate, the embryonic, or larval, forms of the higher Infusoria which suc- ceed them. e. Many of the Infusoria which finally appear are of a comparatively high grade of organisation, being certainly the highest of the Protozoa, and being placed by some competent observers in the neighbourhood of the Trematode Worms (Scolecida). It is therefore very unlikely that these should be generated spontaneously ; since, if this ever occurs, it is reasonable to suppose that the creatures thus produced will be of the lowest possible organisation (such as the Gregarinidse or the Monera, for example), and will be far below the Infu- soria in point of structure. f. The reproductive process in many of these same Infusoria is perfectly well known, and it consists either in a true sexual process, for which proper organs are provided (as in Paramce- cium), or in a process of gemmation or fission. It is therefore improbable that they should be generated in the manner main- tained by the heterogenists, since this mode of reproduction would appear to be superfluous. g. In the absence of any direct proof to the contrary, it is safer to adopt an explanation of the observed phenomena which does not have recourse to laws with which wre are as yet unacquainted. Thus, it is not at variance with any known law to suppose that the primary molecules are the result of the development of germs which find in the organic infusion a suitable nidus; that these primary molecules and the vibrios which they produce are referable to the Protophyta, and should probably be placed near the filamentous Conferae ; that by the death of these vegetable organisms the fluid is prepared for the reception and development of the germs of the Pro- tozoa, for which the former serve as pabulum ; and that many of the forms which are observed are the larval stages of the higher Infusoria. h. Recent researches, especially those of Dr Bastian, have established some new facts as to the possibility of spontaneous generation, but they can by no means be said to have settled the question, if only upon the ground that they require con- firmation by other experimentalists. The chief fact which ap- pears to have been established upon a tolerably firm basis is, that living beings, vegetable or animal, may make their ap- pearance in organic infusions which have been subjected to a temperature of considerably over the boiling-point, even though the said infusions have been hermetically sealed in a flask from which all atmospheric air has been previously withdrawn. The ORIGIN OF SPECIES. 47 chief deduction which appears to flow from this — assuming its correctness — is, that there are low organisms which can exist, for a certain length of time at any rate, with an extremely small amount of air ; for it is to be remembered that the pro- duction of a theoretically perfect vacuum is probably practically impossible. If it were conceded, in fact, that a perfect vacu- um had been formed in the experiments in question, the sole result would be that we should have to alter all our beliefs as to the conditions under which life is a possibility. The only tangible result of these experiments, so far, is, that any sup- posed " pre-existent germs" must have been contained, if present at all, in the infinitesimal portion of air which could not be expelled from the flasks experimented on ; or, they must have been able to withstand without injury a tempera- ture of over 212°. Mr Crace-Calvert, indeed, asserts that he has experimentally shown that vibrios can survive exposure to a temperature exceeding 300° Fahrenheit, and Messrs Dallinger and Drysdale have shown the same of the germs of bacteria. Neither of these hypotheses is wholly incredible; but the ques- tion ought to be regarded as still sub judice. Under any cir- cumstances, the entire question is one of such complexity as to be altogether unsuited for discussion here. i. Still more recent researches, carried out in a series of elaborate experiments by Professor Tyndall, have supplied us with a complete physical demonstration that ordinary atmo- spheric air is invariably charged with innumerable particles of solid matter, many of which are so immeasurably minute as to be incapable of detection by the highest known powers of the microscope. The same observer has further shown that vibrios and bacteria are never produced in organic infusions, which, subsequent to boiling, are exposed only to air from which these floating molecules have been completely removed. In the face of these observations, it is difficult to see how the doctrine of " abiogenesis " can maintain its ground. 14. ORIGIN OF SPECIES. It is impossible here to do more than merely indicate in the briefest manner the two fundamental ideas which are at the bottom of all the various theories as to the origin of species ; and it will be sufficient to give an outline of the two leading theories, without adducing any of the reasoning upon which they are based. It should be added, however, that almost all scientific men are at the present day agreed that species have been produced by a process of evolution or development, 48 MANUAL OF ZOOLOGY. though all are not agreed as to the manner in which that evolution has been carried out. I. Doctrine of Special Creation. — On this doctrine of the origin of species it is believed that species are immutable pro- ductions, each of which has been specially created at some point within the area in which we now find it, to meet the external conditions there prevailing, subsequently spreading from this spot as far as the conditions of life were suitable for it. II. Doctrine of Development. — On the other hand, it is be- lieved that species are not permanent and immutable, but that they " undergo modification, and that the existing forms of life are the descendants by true generation of pre-existing forms " (Darwin). On Lamarck's theory of the development of species, the means of modification were ascribed to the action of external physical agencies, the inter-breeding of already existing forms, and the effects of habit. The doctrine of the development of species by variation and natural selection — propounded by Darwin, and commonly known as the Darwinian theory — is based upon the following fundamental propositions : — 1. The progeny of all species of animals and plants exhibit variations amongst themselves in all parts of their organisation, no two individuals being exactly and in all respects alike. In other words, in every species the individuals, whilst inheriting a general likeness to their progenitors, tend by variation to diverge from the parent-type in some particular or other. 2. Variations arising in any part of the organism, however minute, may be transmitted to future generations, under certain definite and discoverable laws of inheritance. 3. By " artificial selection," or by breeding from individuals possessing any particular variation, man, in successive genera- tions, can produce a breed in which the variation will be per- manent, the divergence from the parent-type being usually intensified by the process of inter-breeding. The races thus artificially produced by men are often as widely different as are distinct species of wild animals. 4. The world in which all living beings are placed is one not absolutely unchanging, but is liable, on the contrary, to subject them to very varying conditions. 5. All animals and plants give rise to more numerous young than can by any possibility be preserved, each species tending to increase in numbers in a geometrical progression. 6. As these young are none of them exactly alike in all ORIGIN OF SPECIES. 49 respects, a process of " natural selection " will ensue, whereby those individuals which possess any variation, however slight, favourable to the peculiarities of the life of the species, will tend to be preserved. Those individuals, on the other hand, which do not possess any such favourable variation, will be placed at a disadvantage in the " struggle for existence," and will tend to be gradually exterminated. The individuals, there- fore, composing any species are thus subjected to a rigid pro- cess of sifting, by which those least adapted to their environ- ment are being perpetually weeded out, whilst " the survival of the fittest " is secured. 7. Other conditions remaining the same, the individuals which survive in the struggle for existence will transmit the variations to which they owe their preservation, to future generations. 8. By a repetition of this process, "varieties" are first established; these become permanent, and "races "are pro- duced ; finally, in the lapse of time, the differences thus caused become sufficiently marked to constitute distinct "species." 9. If we grant that past time has been practically infinite, it is conceivable that all the different animals and plants which we see at present upon the globe, may have been produced by the action of natural selection upon the off- spring of a few primordial forms, or, it may be, of a single primitive being. Originally, Mr Darwin appears to have believed that " natural selection " would alone be found to be a sufficient cause to have given rise to all existing species by a process of evolution from pre-existing forms. In view, however, ot certain objections which had been brought forward, Mr Darwin seems to have abandoned this position ; and a cause supplementary to " natural selection " was sought for in what Mr Darwin terms " sexual selection." The action of sexual selection in a supposed process of evolution, according to Mr Darwin's views, may be stated in the following two pro- positions : — a. The males of many species of animals are known to engage in very severe contests for the possession of the females, these latter yielding themselves to the victor. In such contests certain males will inevitably have certain advan- tages over the others, either in point of strength or activity, or in consequence of the possession of more efficient offensive weapons. There will therefore always be a probability that certain males will get possession of the females in preference to others : and thus there will be a tendency in the individuals D SO MANUAL OF ZOOLOGY. of many species of 'animals to secure a preponderance of off- spring from the strongest males. The peculiarities which enable certain males to succeed in these contests will, cceteris paribus, be transmitted to tneir male offspring, and in this way Variations may be perpetuated, initiated, or intensified. b. In the preceding cases, the females are believed to be perfectly passive, and the selection is a "natural'' one, the final result depending solely upon the natural advantages which certain males possess' over others in actual combat. It is alleged, however, that there are other cases in which the selection is truly " sexual," since its- result is determined by spontaneous preference, and not by brute force alone. -It is asserted, namely, 'that among certain species of animals, the females exercise a free choice as to the particular male with which they will pair; the males being passive agents in the matter, except in so far as each uses, or may use, his utmost exertions to secure that the choice of the female may fall upon him. The circumstances supposed to influence, and ultimately determine, the choice of the female, are of course, in the main, the personal attractions of some particular male, the female being captivated by some " beauty of form, colour, odour, or voice," which such a male may possess. If it be admitted that the females of some of the lower animals have the power of expressing and exercising a pref- erence in the manner above indicated, then it is easy to understand how variations might be transmitted or intensi- fied in this way. The male who is most attractive to the female will, other things being equal, have the best chance of propagating his species, and is likely to leave the largest number of descendants. His male offspring will inherit the peculiarities by which their sire was rendered pre-eminently attractive in the eyes of their mother, and thus a well-marked breed might be produced, by the preservation or intensifica- tion of characters of this nature. Mr Darwin is disposed to believe that colour and song in most, if not in all animals, are thus to be ascribed to the action of sexual selection, through numerous successive generations ; but other competent author- ities are unable to concur in this view. 15. DISTRIBUTION. Under this head come all the facts which are concerned with the external or objective relations of animals — that is to say, their relations to the external conditions in which they are placed. DISTRIBUTION IN TIME. 51 The geographical distribution of animals is concerned with the determination of the areas within which every species of animal is at the present day confined. Some species are found almost everywhere, when they are said to be " cosmopolitan ; " but, as a rule, each species is confined to a limited and definite area. Not only are species limited in their distribution, but it is possible to divide the globe into a certain number of geo- graphical regions or " zoological .provinces," each of which is characterised by the occurrence in it of certain associated forms of animal life. The geographical distribution of land animals is conditioned partly by the existence of suitable surroundings, and partly by the presence of barriers preventing migrations. Thus, certain contiguous regions might be equally suitable for the existence of the same animals, but they might belong to different zoolo- gical provinces, if separated by any impassable barrier, such as a lofty chain of mountains. Owing to their power of flight, the geographical distribution of birds is much less limited than that of mammals ; and many migratory birds may be said to belong to two zoological provinces. In spite of their powers of locomotion, however, birds are limited by the necessities of their life to definite areas, and a zoological province may be marked by its birds just as well as by its quadrupeds. The geographical distribution of an animal at the present day by no means necessarily coincides with its former exten- sion in space. Many species are known which now occupy a much more restricted area than they did formerly, owing to changes in climate, the agency of man, or other causes. Simi- larly, there are species whose present area is much wider than it was originally. At the present day, naturalists usually adopt either the zoo- logical provinces proposed by Prof. Huxley, or those proposed by Mr Sclater, both arrangements possessing certain features in common. Prof. Huxley proposes to divide the earth's sur- face into four primary zoological provinces, as follows, each possessing its own "fauna," or characteristic assemblage of animals : — I. OrnithogcEa, or the Novo-Zelanian Province, comprising only New Zealand. II. Antarctogaa, or the Australian Province, comprising Australia, Tasmania, and the Negrito Islands. III. Dendrogiza, or the Austro-Columbian Province, includ- ing South America, Central America, and Mexico. IV. Arctogcea, including all the rest of the world, and having as sub-provinces, — 52 MANUAL OF ZOOLOGY. 1. North America, north of Mexico. 2. Africa, south of the Sahara. 3. Hindostan. 4. The remainder of the Old World (Europe, Africa north of the Sahara, Asia generally, but without Hindostan, &c.) Mr Sclater, basing his arrangement primarily on the distri- bution of birds, divides the earth's surface into the following six provinces : — 1. The Pal&arctic Province, including Europe, Africa north of the Atlas Mountains, and Northern Asia. 2. The AZtkopian Province, including Africa south of the 'Atlas Mountains, and Southern Arabia. 3. The Indian Province, including Asia south of the Hima- laya Mountains, Southern China, and the Indian Archipelago. 4. The Australian Province, including Australia, Tasmania, New Guinea, New Zealand, and a large proportion of the islands of the Pacific Ocean. 5. The Nearctic Province, including North America down to the centre of Mexico. 6. The Neotropical Province, including the whole of South America, Central America, and Southern Mexico. The vertical or bathymetrical distribution of animals relates to the limits of depth within which each marine species of animals is confined. As a rule it is found that each species has its own definite bathymetrical zone, and that its existence is difficult or impossible at depths greater or less than those comprised by that zone. Generalising on a large number of facts, naturalists have been able to lay down and name certain definite zones, each of which has its own special fauna. The five following zones are those generally accepted : — 1. The Littoral zone, or the tract between tide-marks. 2. The Laminarian zone, from low water to 15 fathoms. 3. The Coralline zone, from 15 to 50 fathoms. 4. The deep-sea Coral zone, from 50 to 100 fathoms. 5. To these must now be certainly added a fifth or "Abys- sal " zone, extending from 100 fathoms to a depth of 3000 or 4000 fathoms. Recent researches, however, have rendered it certain that after a certain depth, say 100 fathoms, the bathymetrical dis- tribution of animals is conditioned not by the depth, but by the temperature of the water at the bottom of the sea. Similar forms, namely, are always found inhabiting areas in which the bottom-temperature is the same, wholly irrespective of the depth of water in the particular locality in question. The DISTRIBUTION IN TIME. 53 supply of food, also, and the nature of the habitat, are im- portant elements of the case. In the light, therefore, of these recent facts, it would perhaps be advisable to adopt the views of Dr Gwyn Jeffreys, and to consider that there are only two principal bathymetrical zones — namely, the littoral and the subjnarine. The researches of the Challenger Expedition have also shown that at depths beyond 500 fathoms, the fauna presents essentially the same features all over the world, deep- sea genera usually possessing a cosmopolitan range. In addition to the preceding forms of distribution, the zoologist has to investigate the condition and nature of animal life during past epochs in the history of the world. The laws of distribution in time, however, are, from the na- ture of the case, less perfectly known than are the laws of lateral or vertical distribution, since these latter concern beings which we are able to examine directly. The following are the chief facts which it is necessary for the student to bear in mind : — 1. The rocks which compose the crust of the earth have been formed at successive periods, and may be roughly divided into aqueous or sedimentary rocks, and igneous rocks. 2. The igneous rocks are produced by the agency of heat, are mostly unstratified (i.e., are not deposited in distinct layers or strata), and, with few exceptions, are destitute of any traces of past life. 3. The sedimentary or aqueous rocks owe their origin to the action of water, are stratified (i.e., consist of separate layers or strata), and mostly exhibit " fossils " — that is to say, the remains or traces of animals or plants which were in existence at the time when the rocks were deposited. 4. The series of aqueous rocks is capable of being divided into a number of definite groups of strata, which are technically called "formations." 5. Each of these definite rock-groups, or " formations," is characterised by the occurrence of an assemblage of fossil remains more or less peculiar and confined to itself. 6. The majority of these fossil forms are "extinct" — that is to say, they do not admit of being referred to any species at present existing. 7. No fossil, however, is known, which cannot be referred to one or other of the primary subdivisions of the Animal Kingdom which are represented at the present day. 8. When a species has once died out it never reappears. 9. The older the formation, the greater is the divergence between its fossils and the animals and plants now existing on the globe. 54 MANUAL OF ZOOLOGY. IDEAL SECTION OF THE CRUST OF THE EARTH. rig. 5; )o Post-Tertiary and Recent. |°- Pliocene. Miocene. Eocene. Cretaceous. Oolitic or Jurassic. Triassic. Permian. Carboniferous. Devonian, or Old Red Sandstone. Silurian. Cambrian. Huronian. Laurentian. DISTRIBUTION IN TIME. 55 10. All the known formations are divided into three great groups, termed respectively Palaeozoic or Primary, Mesozoic or Secondary, and Kainozoic or Tertiary. The Palaeozoic or Ancient-life period is the oldest, and is characterised by the marked divergence of the life of the period from all existing forms. In the Mesozoic or Middle-life period, the general fades of the fossils approaches more nearly to that of our existing fauna and flora ; but — with very few exceptions — the characteristic fossils are all specifically distinct from all existing forms. In the Kainozoic or New-life period, the approximation of the fossil remains to existing living beings is still closer, and some of the forms are now specifically identical with recent species ; the number of these increasing rapidly as we ascend from the lowest Kainozoic deposit to the Recent period. Subjoined is a table giving the more important subdivisions of the three great geological periods, commencing with the oldest rocks ?nd ascending to the present day (fig. 5). I. PAL/EOZOIC OR PRIMARY ROCKS. 1. Laurentian. (Lower .and Upper.) 2. Cambrian. (Lower and Upper, with Huronian rocks?) 3. Silurian. (Lower and Upper.) 4. Devonian, or Old Red Sandstone. (Lower, Middle, and Upper.) 5. Carboniferous. (Mountain-limestone, Millstone-grit, and Coal-measures.) 6. Permian. ( = the lower portion of the New Red Sand- stone.) 11. MESOZOIC "OR SECONDARY ROCKS. 7. Triassic Rocks. (Bunter Sandstein, or Lower Trias ; Muschelkalk, or Middle Trias ; Keuper, or Upper Trias.) 8. Jurassic Rocks. (Lias, Inferior Oolite, Great Oolite, Oxford Clay, Coral Rag, Kimmeridge Clay, Portland Stone, Purbeck beds.) 9. Cretaceous Rocks. (Wealden, Lower Greensand, Gault, Upper Greensand, White Chalk, Maestricht beds.) * III. KAINOZOIC OR TERTIARY ROCKS. \ , - ^ 10. Eocene. (Lower, Middle, and Upper.) TI. Miocene. (Lower and Upper.) ! • 12. Pliocene. (Older Pliocene and Newer Pliocene.) 13. Post-tertiary. (Post-pliocene and Recent^) :: INVERTEBRATE ANIMALS. PROTOZOA. CHAPTER I. i. GENERAL CHARACTERS OF THE PROTOZOA. 2. CLASSIFICATION. 3. GREGARINIDA. i. General Characters. — The sub-kingdom Protozoa, as the name implies, includes the most lowly organised members of the animal kingdom. From this circumstance it is difficult, if not impossible, to give an exhaustive definition, and the fol- lowing is, perhaps, as exact as the present state' of our know- ledge will allow : — The Protozoa may be defined as animals, generally of minute size, composed of a nearly or altogether structureless jelly-like sub- stance (termed " sarcode"}, showing no composition out of definite parts or segments, having no definite body-cavity, presenting no traces of a nervous system, and having either no differentiated alimentary apparattis, or but a very rudimentary one. The Protozoa are almost exclusively aquatic in their habits, and are mostly very minute, though they sometimes form colonies of considerable size. They are composed of contrac- tile, jelly-like protoplasm, often known by the name of " sar- code," which is semi-fluid in consistence, and is composed of an albuminous base with oil -globules scattered through it. Granules are generally developed in the sarcode, and in many cases there is a definite internal solid particle, termed the " nucleus." In many of the Protozoa the protoplasm is not surrounded by a definite outer envelope, -thus permanently remaining in the condition of a mere "cytode." In other cases, how- ever (Infusoria], such an outer envelope exists and a central " nucleus " is present, when the organism may be compared PROTOZOA. 57 with a single "cell" in one of the higher animals. The Sponges, again, if they are to be retained in the Protozoa, are " multicellular " organisms. / In no Protozoan are any traces known of anything like the nervous and vascular arrangements which are found in animals of a higher grade. A nervous system is universally and en- tirely absent, and the sole circulatory apparatus consists ini certain clear spaces called " contractile vesicles," which are ' found in some species, and which doubtfully perform the functions of a heart. A distinct alimentary aperture is present in the higher Protozoa, but in many there is none ; and in all, the digestive apparatus is of the simplest character. Organs of generation, or at any rate differentiated portions of the body which act as these, are sometimes present ; but in many cases true sexual reproduction has not hitherto been shown to exist. The "sarcode," which forms such a distinctive feature in all the Protozoa, is merely undifferentiated protoplasm, not possessing " permanent distinction or separation of parts," but nevertheless displaying all '; the essential properties and char- acters of vitality," being capable of assimilation and excretion, of irritability and of the power of contraction, so as to produce movements, strictly analogous, in many cases, to the muscular movements of the higher animals. In some, too, the sarcode possesses the power of producing an external case or envelope, usually of carbonate of lime or flint, and often of a very com- plicated and mathematically regular structure. The power of active locomotion is enjoyed by a great many of the Protozoa ; but in some cases this is very limited, and in other cases the animal is permanently fixed in its adult condition. The apparatus of locomotion in the Protozoa is of a very varied nature. In many cases, especially in the higher forms, movements are effected by means of the little hair-like processes which are known as "cilia," and which have the power of lashing to and fro or vibrating with great rapidity. In other cases the cilia are accompanied or replaced by one or more long whip-like bristles, which act in the same fashion, and are known as "flagella." The most characteristic organs of locomotion amongst the lower Protozoa are known as " pseudopodia," and consist simply of prolongations of the sarcodic substance of the body, which can usually be emitted from the greater portion of the general surface of the body, and are capable of being again retracted, and of fusing com- pletely with the body-substance. 2. Classification of the Protozoa. — The sub-kingdom Protozoa is divided into three classes — viz., the Gregarinida, the Rhizo- 5?'. MANUAL: OF ZOOLOGY. poda\ and the Infusoria-.. In >the Infusoria only is a mouth present, and hence these are .sometimes spoken of as the " Stomatode" Protozoa, whilst the two former classes collec- tively constitute \he"Asto?hata" The following is a tabular view of the divisions of the Protozoa : — Class I. GREGARINIDA. Glass II. RHIZOPODA. Order i. Monera. „ 2. Amo&bta. „ 3. Foraminifera. „ 4. Radiolaria^ „ 5. Spongida.\ Class III. INFUSORIA. Order i. Suctoria. „ . 2. Ciliata^ „ 3. Flagellat^ 3. CLASS I. GREGARINIDA. — The Gregarinida may be de- fined as parasitic Protozoa, which are destitute of a mouth, and do not possess the power of emitting " pseudopodia" They con^ stitute the lowest class of the Protozoa, and comprise certain microscopic animals which are parasitic in the alimentary canal of both Invertebrate and Vertebrate animals. They have, however, a special liking for the intestines of certain insects, being commonly found abundantly in the cockroach. As we shall see hereafter, in all probability a great deal of the degraded character of the Gregarinida is due to the fact that they are internal parasites, and are therefore not dependent upon their own exertions for food. Nothing anatomically could be more simple than the struc- ture of a Gregarina, since it is almost exactly that of a cell, such as the impregnated ovum (fig. 6, b). An adult Gregarina, in fact, may be said to be a single cell, consisting of an ill-de- fined membranous envelope filled with a more or less granular sarcode with fatty particles, and sometimes differentiated into a distinct contractile " cortical layer," which contains in its in- terior a vesicular nucleus, this in turn enclosing a solid particle, or nueleolus. In some the body exhibits an approach to a more complex structure by the presence of internal septa ; but it is doubtful whether this appearance may not be due to the appo- sition and fusion of two separate individuals. A separate order, PROTOZOA : GREGARINIDA. 59 however, has been founded upon individuals of this kind, under the name of Dicystidea;, the name Monocystidea being retained for the ordinary forms. As regards the size of the Gregarince, they vary from about the size of the head of a small pin up to as much as half an inch in length, when they assume the aspect of small worms. The integument or cuticle with which the protoplasmic body is enclosed may be quite smooth or striated, or it may be furnished with bristles or spines, or even in some cases with cilia. Sometimes one end of the body is furnished with uncinate processes, very similar in appearance to the hooked "head" of the common tape-worm (Tania soliuni). Essentially, however, the structure of all appears to be the same. No differentiated organs of any 'kind beyond the nucleus and nucleolus exist, and both assimilation and excretion must be performed simply by the general surface of the body. The body is, nevertheless, contractile, and slow ,. encysted; d Further stage same, with the contents divided into " pseudonavicellae ; " e Free " pseudonavi- cellse ;" / Amoebiform mass of protoplasm liberated from a pseudonavicella ; g and h Active forms ofy". All the figures are greatly enlarged. movements can be effected, not, however, by pseudopodia. Hasckel regards the Gregarinff, as Amcebce which have become degenerate by parasitism ; but this opinion is rejected by Van Beneden, and their apparently unicellular structure would 60 MANUAL OF ZOOLOGY. rather lead us to place them in the neighbourhood of the Infusoria. The presence of muscular fibres in the cortical layer will also support the view that they should be associated with the Infusorian animalcules. In spite of their exceedingly simple structure, the following very in- teresting reproductive phenomena have been observed sometimes in a single Gregarina without apparent cause, sometimes as the result of the apposition and coalescence of two individuals — the exact nature of the process being in either case obscure. In some species conjugation is in- variable ; in others it never occurs ; and it may take place either by anal- ogous or by opposite extremities. The Gregarina — or it may be two in- dividuals which have come into contact and adhered together — assumes a globular form, becomes motionless, and develops round itself a structure- less envelope or cyst, when it is said to be "encysted" (fig. 6, c). The central nucleus then disappears, apparently by dissolution, whereupon the granular contents of the cyst break up into a number of little rounded masses, which gradually elongate and become lanceolate, when they are termed " pseudonavicellse " (or "pseudonaviculse," fig. 6, d}. The next step in the process consists in the liberation of the pseudonavicellae, which escape by the rupture of the enclosing cyst (fig. 6, e). If they now find a congenial habitat, they give origin to little albuminous or sarcodic masses, which exhibit lively movements, and are endowed with the power of throwing out and retracting little processes of the body which closely resemble the " pseudopodia " of the Rhizopoda ; so that the pseudona- vicella in this condition is very similar to an adult Amceba (fig. 6, f, g, h). Finally, these amcebiform bodies are developed into adult Gregarina:. It will be seen from the above that the formation of the pseudonavicellce out of the granular contents of the body, subsequent to the disappearance of the nucleus, presents a close analogy to the segmentation of the impreg- nated ovum which follows upon the dissolution of the germinal vesicle. In Gregarina gigantea of the Lobster the embryo is a little mass of sarcode, quite like an Amceba except that it wants a nucleus and contractile vesicle. It soon gives out two little contractile processes or arms, which become detached and move about like little worms, when they are termed ' ' pseudo- filarise," from their resemblance to free Nematoids. After a period of activity, the pseudo-filarian becomes quiescent, shortens its dimensions, develops a nucleus and nucleolus, and becomes an adult Gregarina. PSOROSPERMLT.. — There occur as parasites on and within the bodies of fishes certain vesicular, usually caudate, bodies, termed Psorospermice, the exact nature of which is very problematical. According to Lieberkiihn they occasionally give origin to amcebiform bodies, similar to those which are liberated from the pseudonavicellae of Gregarinida. In this case they should probably be regarded as the embryonic forms of some Gregarina. By Balbiani, however, they are looked upon as properly belonging to the vegetable kingdom. PROTOZOA: MONERA. 6 1 CHAPTER II. RHIZOPODA. GENERAL CHARACTERS OF THE RHIZOPODA. — The Rhizopoda may be defined as Protozoa which are destitute of a mouth^ are simple or compound, and possess the power of emitting "pseudo- podia" They are mostly small, but some of the composite forms, such as the sponges, may attain a very considerable size. Structurally, a typical Rhizopod — as an Amoeba — is composed of almost structureless sarcode, without any organs appropriated to the function of digestion, and possessing the power of throwing out processes of its substance so as to con- stitute adventitious limbs. These are termed " pseudopodia," or false feet, and are usually protrusible at will from different parts of the body, into the substance of which they again melt when they are retracted. They are merely filaments of sarcode, sometimes very delicate and of considerable length, at other times more like finger-shaped processes ; and they are identical with the little processes which can be thrown out by the white corpuscles of the blood and by pus-cells. Indeed, it has been remarked by Huxley that an Amoeba is structurally "a mere colourless blood-corpuscle, leading an independent life." The class Rhizopoda is divided into five orders — viz., the Monera, the Amdbea, the Forammifera, the Radiolaria, and the Spongida, of which the last is occasionally considered as a separate class, or is removed entirely from the Protozoa. ORDER I. MONERA. — This name has been proposed by Haeckel for certain singular organisms which may provisionally be regarded as the lowest group of the Rhizopoda. They are very minute in size, and are distinguished by the fact that the body is composed of structureless sarcode, capable of emit- ting thread-like prolongations or pseudopodia, but destitute of either nucleus or contractile vesicle. The pseudopodia are mostly in the form of delicate filamentous processes of sarcode, which exhibit a circulation of minute molecules and granules in their interior and along their edges. Sometimes the pseu- dopodia may be simple, as in Protamceba (fig. 7, a), or they may be ramified and anastomosing, as in Protogenes. The form of the body, though very mutable, may be simple ; or the organism may form a kind of colony of protoplasmic masses united by their interlacing pseudopodia (as in Myxo- 62 MANUAL OF ZOOLOGY. dictyon). Sometimes the organism passes through a quiescent stage, alternating with an active and locomotive phase of Fig. 7. — Morphology of Monera. a Protamoeba, porrecta. ', b Protomyxa auran- tiaca ; c The same in an encysted condition. Greatly magnified. existence. No hard covering or "test" is ever developed. Reproduction is mostly by fission, with or without precedent encystation (fig. 7, b and c) and quiescence. All the Monera live in water, and their systematic position is uncertain. From the general nature of the pseudopodia, and the fact that the sarcode is not differentiated into an " ectosarc " and an " en- dosarc," they appear to be most nearly allied upon the whole to the Foraminifera, from which they differ chiefly in the absence of a shell defending the soft protoplasm of the body, as well as in the constant absence of a nucleus. The name of Bathybius was given by Professor Huxley to a structure believed to consist of irregular, formless, diffused masses of protoplasm, without nucleus or contractile vesicle, found at great depths in the sea ; and, if organic, the place of Bathybius would be amongst the Monera. More recently, however, Professor Huxley and Sir Wyville Thomson have expressed the opinion that Bathybitis is not really a living organism at all ; and it only requires mention here because a similar structure, the true nature of which still requires investigation, has recently been described by Bessels under the name of Protobathybius. ORDER II. AMCEBEA. — This order comprises those Rhi- zopoda which are, with few exceptions, naked ; have usually short, blunt, lobose pseudopodia, which do not anastomose with - PROTOZOA; AMCEBEA. 63 one another ; and contain a '"nucleus" and one or' more " contrac- tilevesicles •." The ' Am a class of minute animals now known to belong to the Annulosa. By modern writers, however, the term Infusoria is used strictly to designate those Protozoa which possess a mouth and rudimentary digestive cavity. They are, for this reason, often called collectively the " stomatode " Protozoa, in contradistinction to the remaining members of the sub-kingdom, which are all " astomatous." The so-called " suctorial " Infu- soria (Acinetce), however, appear to have no definite oral aper- ture; and the same is the case with the parasitic Opalina, though there is great doubt as to the propriety of placing this in the Infusoria at all. The name Infusoria itself is derived from the fact that the members of the class are often developed in organic infusions. The Infusoria or Stomatode Protozoa may be defined as Pro- tozoa which are mostly provided with a mouth and rudimentary digestive cavity, which do not possess the power of emitting pseudo- podia, but which are furnished with vibratile cilia, or with con- tractilefilamejits.- They are mostly microscopic in size, the sarcode is differentiated into an ectosarc and an endosarc, and a nucleus and contractile vesicle are present. Most modern writers regard the Infusoria as strictly speaking "unicellular" animals, each of the simple individuals corre- sponding morphologically to a single cell. Upon this view — PROTOZOA: INFUSORIA. 95 which is by no means free from difficulties — the " nucleus " of the Infusorian animalcules really corresponds with the struc- ture known by the same name in an ordinary animal or vegetable cell. The Infusoria may be divided into three orders — viz., Suctoria, Ciliata, and Flagellata — of which the second comprises the majority of the members of the class, and alone requires much consideration. I. ORDER CILIATA. — This order comprises those Infusoria in which the otiter layer of the body is more or less abundantly furnished with vibratile cilia, which serve either for locomotion or for the procuring of food. Besides cilia, properly so called, some of the ciliated Infusoria are provided with styles or jointed bristles, which are movable, and subserve locomotion ; whilst others have little hooks or uncini, with which they can attach themselves to foreign bodies. As types of the order, Paramcecium and Vorticella may be selected, the former being free, whilst the latter is per- manently fixed in its adult condition. Paramcecium (figs. 31 and 32) is a slipper-shaped animalcule, composed externally of a structureless trans- parent pellicle — the " cuticle " — which is lined by a layer of firm and consistent sarcode, which is termed the "cortical layer," or the "paren- chyma of the body," this in turn pas- sing into a central mass of softer and more diffluent sarcode, known as the " chyme- mass," or " endoplasm." The cuticle is merely the structure- less hardened external lamina of the " cortical layer," and it may in some cases form a regular protective sheath ( Vaginicola), a horny shell ( Codon- ella\ or even a reticulated siliceous envelope (as in Dictyocysta\ Beneath 'ig. 31. — Paramaechun, viewed dorsally, and greatly magnified. m Mouth ; m to g Gullet ; a Anus ; cv' and cv The contractile vesicles; I, II, III, Canals pro- ceeding from the anterior con- tractile vesicle ; n Nucleus ; i> Large cilia bounding the depres- sion ("vestibule") leading to the mouth. The arrows indicate the course in which the particles of food circulate in the semi-fluid protoplasm of the interior of the body. (After James-Clark.) 96 MANUAL OF ZOOLOGY. the " cuticle " is the layer from which the cilia are given off, and below that, again, is a finely striated or fibrillated contrac- tile layer (" myophane layer " of Haeckel), which corresponds physiologically to the muscles of higher animals. In some Infusorians there is a still more internal lamina of the " cor- tical layer," which is charged with the singular little organs known as " trichocysts." These are vesicular microscopic bodies, capable of emitting thread-like filaments, in many re- spects closely resembling the " thread-cells " of the Ccelenterata. The " cuticle " in Paramcetium is covered with vibratile cilia (figs. 3 1 and 32), and is perforated by the aperture of the mouth. Fig. 32. — A, Paramoecium^ showing the nucleus («) and two contractile vesicles (v). B, Paramoecium bursaria (after Stein) dividing transversely : n Nucleus ; n' Nucle- olus; v Contractile vesicle. C, Paramoecium aurelia (after Ehrenberg), dividing longitudinally. The mouth leads into a funnel-shaped gullet, which is not continued into a distinct digestive sac, but loses itself in the soft central protoplasm. On the line of boundary between the cortical layer and the diffluent central sarcode are placed the "nucleus" and the "contractile vesicle" (or vesicles). The " nucleus " is an oval body (in some forms band-shaped or rod- like), consisting of an outer membrane enclosing granular con- tents, and often having a smaller spherical particle applied to its exterior or immersed in its substance. This latter is the so-called "nucleolus," which must be carefully distinguished from the nucleolus of a cell, which occurs in the interior of the nucleus. The contractile vesicles are clear spaces, which con- tract and dilate at intervals, and occasionally exhibit radiating canals passing into the surrounding sarcode. Ordinarily one contractile vesicle is present, or at most two, but in some cases there may be several. It has also been maintained that the PROTOZOA: INFUSORIA. 97 contractile vesicles communicate with the exterior of the body, but proofs are wanting on this point. Whether this should ultimately be established or not, there can be little doubt but that the vesicles are a rudimentary form of vascular apparatus. Others, however, hold, with some probability, that the contrac- tile vesicles are to be regarded as excretory in function, and that they correspond more with the water-vascular system of the Scolecida than with the true blood- vascular system of higher animals. Certain other spaces termed "vacuoles" are gen- erally visible in addition to the contractile vesicles. These, however, are probably merely collections of water surrounding the particles of ingested food, and performing with them a circulation in the abdominal cavity, something like the circu- lation of granules which is seen in certain vegetable cells. It was the appearance of these " vacuoles " — which are certainly not permanent organs of any kind — which induced Ehrenberg to term the Infusoria the " Polygastrica," upon the belief that the vacuoles were so many stomachs. Paramozdum obtains its food by means of the currents of water which are set up by the constantly vibrating cilia. The nutritive particles thus brought to the mouth pass into the central abdominal cavity, along with the contents of which they undergo the circulation above spoken of. Indigestible and fecal particles appear to be expelled by a distinct anal aperture, which is situated near the mouth. Reproduction in Paramcedum may be effected non-sexually, by fission, the body dividing transversely into two halves, and the process of cleavage commencing first with the division of the nucleus (fig. 32, B). Longitudinal fission is also stated tox occur (fig. 32, C); but it is questionable whether the appear- ances which have led to this statement may not really be due to the coalescence and temporary conjugation of two indi- viduals. Most authorities further believe that Paramadiim has the power of true sexual reproduction, the "nucleus" playing the part of an ovary in the process, and the " nucle- olus " acting as a fesfis. In this process, as described by Bal- biani, two Paramceda come together, and adhere closely to one another by their ventral surfaces. The " nucleus " in- creases in size, and a number of ovules are formed in its inte- rior. In like manner, the " nucleolus " of each also enlarges, and develops in its interior a number of fusiform or rod-like bodies, which are believed to be spermatozoa. The nucleolus of each then passes into the body of the other, the act of trans- ference being effected through the mouth. Contact of the two reproductive elements then takes place, and the fecundated G 98 MANUAL OF ZOOLOGY. ovules after their liberation from the body of the parent are developed into adult Paramceria. Other observers, however, are disposed to believe that this " conjugation " of two Paramceda is not a genuine sexual pro- cess, that the " nucleolus " is not a true testis, and that the rounded bodies into which the " nucleus " breaks up can be developed into new individuals directly and without contact with a second reproductive element. Vorticella (fig. 33, C) is a beautiful flower-like Infusorian which is com- monly found in fresh water, adhering to the stems of aquatic plants. It consists of a bell-shaped body or "calyx," supported upon the extremity of a slender contractile stem or "pedicle." The other extremity of the pedicle is fixed to some foreign body, and its power of contraction is due to the presence in its interior of a spiral contractile fibre, which is some- times called the "stem-muscle." The edge of the bell or calyx is sur- rounded by a projecting rim or border, called the " peristome, " within which is a circular surface, the "disc," forming the upper extremity of the so-called "rotatory organ." The disc is surrounded by a fringe of vibratile cilia, forming a spiral line which is prolonged into the commence- ment of the digestive canal. Near the edge of the disc is situated the mouth, which conducts by its entrance or ' ' vestibulum " into a fusiform canal or ' ' pharynx, " which terminates abruptly in the abdominal cavity. The particles of food are taken in at the mouth, descend through the short alimentary canal, and enter the abdominal cavity, where they are subjected to the general rotation of the " chyme-mass," being finally excreted by an anal aperture which is situated near the mouth and within the vestibule. As in Paramcecium, the body in Vorticella is composed of an outer ' ' cuti- cle," a central "chyme-mass," and an intermediate "cortical layer," which contains a contractile vesicle and a band-like nucleus. Reproduction in Vorticella may take place by fission, or by gemmation, or by a process of encystation and endogenous division. In the first of these modes the calyx becomes indented in a longitudinal direction — viz. , from the pedicle to the disc ; and the groove thus formed becomes gradu- ally deeper until the calyx is finally divided into two halves supported upon the same pedicle. On one of these cups a "posterior" circlet of cilia is then formed in addition to the "anterior" circlet already existing (i.e., a fringe of cilia is developed round that end of the calyx which is nearest the attachment of the pedicle and furthest from the disc). The cup (fig. 33, D), thus furnished with a circlet of cilia at both extremities, is then detached, and swims about freely. Finally, the anterior circlet of cilia disappears, and this end of the calyx puts forth a pedicle and becomes attached to some foreign object. A new mouth is now formed within what was before the posterior circlet of cilia ; so that the position and function of the two extremities of the calyx are thus reversed. In the second mode of reproduction — namely, that by gemmation — exactly the same phenomena take place, with this single difference, that in this case the new individual is not produced by a splitting into two of the adult calyx, but by means of a bud thrown out from near its proximal extremity. This bud is composed of a prolongation of the cuticular and cortical layers of the adult with a caecal diverticulum of the abdominal cavity or chyme-mass. It soon develops a posterior circlet of cilia, the connection with the parent is rapidly constricted until complete separation is effected, and then the process differs in no respect from that described PROTOZOA;: INFUSORIA. 99 as occurring in the fissiparous method of reproduction. According to Stein and Greeff, however, these so-called "buds" are really small calyces, produced by fission of one Vorticella and then attaching themselves to the outside of the calyx of an6ther individual. In the third mode of reproduction the Vorticella encysts itself in a cap- sule, the cilia and pedicle disappear, and the nucleus breaks up into a number of rounded germs, which are ultimately liberated by the rupture of the cyst, and after a short locomotive stage, develop themselves into fresh Vorticella, How far this process may be truly sexual is not known, and no form of unequivocal sexual reproduction has hitherto been shown to occur in the case of Vorticella. Epistylis is a not uncommon form of fixed Infusorian which is nearly allied to Vorticella, and differs chiefly in the fact that the pedicle is much branched, and rigid and not contractile. It usually occurs in the form of a greyish-white nap on the stems of water-plants, or on the head of the common water-beetle, the Dytiscus marginalis. It consists of a plant-like branching and re-branching frond, the stems of which are quite transparent and faintly striated, but are not contractile, though capable of movement from side to side. Each branch of the entire colony terminates in an oval calyx, articulated to the stem by a distinct joint, upon which it can move from side to side. The sarcode-body enclosed within the cortical layer is of a light-brown colour, and full of minute granules, with larger food- vacuoles and a well-marked contractile vesicle, which contracts and dilates two or three times a minute. The animal can retract itself entirely within its cup, and can at will exsert a ciliated disc. Carchesium is another form which is like Epistylis in consisting of a number of calyces supported upon a branched pedicle, but differs from Epi- stylis and agrees with Vorticella in the fact that the pedicle is contractile. Stentor, or the trumpet-animalcule (fig. 33, A), is another common In- fusorian which is closely related to Vorticella. It consists of a trumpet- shaped calyx, devoid of a pedicle, but possessing the power of attaching and detaching itself at will. When detached it swims by means of the anterior circlet of cilia, just as the calyx of Vorticella will if broken from its stalk. In Vaginicola (fig. 33, B) the essential structure is much the same as in Vorticella, but the body is protected by a membranous or horny case ("carapace" or "lorica"), which is formed by a hardening of the cuticle, and within which the animal can retire. II. ORDER SUCTORIA. — This order includes a series of In- fusoria of a very anomalous nature. In Acineta or in Podo- phrya (fig. 34, A), which may be taken as types, the body is provided with a number of radiating filamentous tubes, which are furnished at their extremities with suctorial discs, and are capable both of exsertion and retraction. These retractile tubes both seize the prey and serve as vehicles for the ingestion of food : hence the term " polystome," or many-mouthed, has been proposed for the order by Professor Greene. A nucleus and one or more contractile processes are present, but they possess no cilia in their adult condition, and the body is fixed to some foreign object by a stalk-like extension of the cortical layer. III. ORDER FLAGELLATA. — This order comprises those In- 100 MANUAL OF ZOOLOGY. fusoria which, like Peridinium, find their means of locomotion in long, flexible, lash-like filaments, termed "flagella;" cilia occasionally being present as well. In some, as in Peranema and in the Monads (fig. 34, B), there is only a single one of Fig- 33- — A, Stentor Miilleri; B, Vaginicola crystallina ', C, Group of Vorticella: ', D, Detached bud of Vorticetta, showing the posterior circlet of cilia. these appendages ; in others, as in Anisonema, there are two flagella ; whilst in Heteromastix (fig. 34, G) and Pleuronema we have forms apparently transitional between the Ciliata and the Flagellata, since both cilia and flagella are present in these genera. In all their other essential characters the flagellate Infusoria do not differ from the more typical members of the class, with which they agree in possessing a cuticle, a firm cor- tical layer, and a soft granular central parenchyma, whilst they possess a nucleus and one or more contractile vesicles. They have, however, the peculiarity that, in many cases at any rate, the base of the flagellum is surrounded by a cup-like or cylin- drical membranous collar, which can be retracted at will. Many also (as Euglena, Astasia, Heteromastix} possess the sin- gular brightly -coloured mass of pigment which is known as the '•eye-spot," and which may possibly be a species of sense- organ (fig. 34). In one singular form (Phalansterium intes- tinale\ the organism consists of numerous zooids, each with a single flagellum and projecting membranous collar, enveloped basally in slimy sarcode, so as to form a cylindrical colony. Another remarkable animalcule now usually referred to this group is Noctiluca, which occurs abundantly in most oceans, PROTOZOA: INFUSORIA. IOI and to which much of the phosphoresence of the sea is due.* It is of large size and spherical in form, with an indentation or " hilum " at one side, where the mouth is situated, and beside Fig. 34. — Suctorial and Flagellate Infusoria. A, Podophrya; B, Cercomonas truncata ; C, Monas neg lecta ', D, Eiigleua sanguinea ; E, Ccdosiga pulcherrima ; F, Astasia trlchophora ', G, Heteromastix proteiforwis. _/" Flagellum ; in Collar at the base of the flagellum ; c Contractile vesicle ; n Nucleus ; e Eye-spot. (After Pritchard, Ehrenberg, and James-Clark.) which is fixed a single long flagellum. The body consists of a central vacuolated mass of protoplasm, surrounded by a superficial layer, and in turn invested by a thin cuticle. The superficial layer is connected with the central protoplasmic parenchyma by numerous radiating, branched, and anastomos- ing filaments of sarcode. The luminosity appears to reside in nucleated cellular bodies in the outer layer of the central pro- toplasm— that is to say, in the peripheral layer of sarcode im- mediately below the cuticle. * The diffused luminosity of the sea is mainly due to the Noctiluca miliaris ; but its partial luminosity is due to various phosphorescent ani- mals, amongst which are the Physalia utriculus (the Portuguese man-of- war), Medusa, Tunicata, Annelides, &c. The cause of phosphorescence is variously stated, it being supposed very generally to be the result of a pro- cess of slow combustion analogous to that which takes place in phosphorus when exposed to the atmosphere. Upon the whole, however, it appears that the phenomenon is a vital process, consisting essentially in the conver- sion of nervous force (or vital energy) into light ; just as the same force can be converted by certain fishes into electricity. This transformation appears generally to require a special apparatus for its production. 102 MANUAL OF ZOOLOGY. DISTRIBUTION OF THE INFUSORIA IN SPACE AND IN TIME. — The Infusoria have at the present day an almost universal dis- tribution, being found in all collections of fresh and salt water, where decaying organic matter is present, and where the other conditions of life are favourable. A few are parasites in the interior of other animals (Opalina\ but the true affinities of these are doubtful. Owing to the fact of their generally want- ing any hard structures which could have been preserved in a fossil condition, no true Infusoria* can be said with certainty to have existed in former periods of the earth's history, though they have doubtless abounded in past time as now. The only possible exceptions to this statement are certain microscopic bodies which occur in the Chalk-flints, and which Ehrenberg considered to be the protective carapaces of Peridinium and allied forms of flagellate Infusoria. LITERATURE. [In the subjoined list, as well as in those which will be subsequently given, it is hardly necessary to say that nothing further will be attempted than to furnish the student with a brief and limited selection from the nu- merous works and memoirs relating to the animals belonging to each sub- kingdom. It has also not appeared needful to cite the names of well- known manuals and text-books of zoological science, save where these contain special information.] GENERAL WORKS. I. 4< Die Klassen und Ordnungen des Thier-Reichs," vol. i. Amorphozoa. Bronn. ' Manual of the Protozoa." Greene. Micrographic Dictionary." Griffiths and Henfrey. The Microscope and its Revelations." 5th ed., 1875. Carpenter. Life-Histories of Animals." Packard. Recent Researches among some of the more Simple Sarcode Organ- isms." • 'Journ. Linn. Soc.,' vol. xiii., 1877. Allman. GREGARINIDA. 7. "Icones Histiologicse," vol. i. p. 7. Kolliker. 8. '« Ueber die Natur der Gregarinen." ' Miiller's Miiller's Archiv fur Anatomic,' 1848. Stein. 9. "On a new Species of Gregarina to be called Gregarina gigantea" 'Quart. Journ. Microscop. Science/ vol. x., 1870. Van Beneden. MONERA. 10. "Monographic der Moneren." « Jenaische Zeitschrift fiir Medecin und Naturwiss.,' vol. iv., 1868. (Translated in 'Quart. Journ. Micro- scop. Science,' 1869.) Heeckel. » 1 1. " Beitrage zur Kenntniss der Moneren." Schultze's ' Archiv fiir Mik- roscopische Anat.,' vol. i., 1865. Cienkowski. " Fossil Infusoria " are often spoken of as forming more or less exten- sive deposits in the earth's crust, but the organisms so named are really Diatoms and Polycystina. LITERATURE OF PROTOZOA. IO3 AMOEBEA. 12. " Etudes sur les Infusoires et les Rhizopodes," vol. i. p. 413. Cla- parede and Lachmann. 13. " Ueber die Einzelligkeit der Amoeben." ' Zeitschrift fur Wiss. Zoologie,' 1855. Auerbach. 14. "On some Fresh-water Rhizopods." 'Quart. Journ. Microscop. Science,' 1869-71. Archer. 15. "Fresh-water Rhizopods." ' Annals of Nat. Hist./ ser. 3, vol. xiii., 1864. Carter. 1 6. "Amoeba villosa," &c. 'Annals of Nat. Hist.,' ser. 3, vol. xi., 1863. Wallich. 17. " Ueber Rhizopoden und denselben nahestehende Organismen." * Ar- chiv fiir Mikr. Anat.,' vol. x., suppl. 1874. Hertwig and Lesser. 18. " Rhizopoden- Studien." ' Archiv fiir Mikr. Anat.,' vol. xi., 1875. F. Eilhard Schultze. FORAMINIFERA. 19. "Introduction to the Study of the Foraminifera " ('Ray Society'), 1862. Carpenter. 20. " Ueber den Organismus der Polythalamien." 1854. Schultze. 21. "On the Recent Foraminifera of Great Britain" ('Ray Society'), 1858. Williamson. 22. " Researches on the Foraminifera." 'Phil. Trans.,' 1856-57. Car- ' penter. 23. "Handbuch der Palaeontologie," vol. i. pp. 61-114, 1876. Zittel. 24. " Carboniferous and Permian Foraminifera" (with a general Introduc- tion). 'Monographs of the Palseontographical Society,' 1876. H. B. Brady. 25. " Mikrogeologie. " Ehrenberg. 26. " Foraminiferes Fossiles du Bassin Tertiaire de Vienne." D'Orbigny. 27. "Ueber den Kern der Foraminiferen. ' 'Archiv fiir Mikr. Anat.,' 1876. F. Eilhard Schultze. 28. " Reticularian Rhizopoda of the Challenger Expedition." 'Quart. Journ. Micr. Science,' vol. xix., 1879. H. B. Brady. RADIOLARIA. 29. " Ueber die Thalassicollen, Polycystinen, und Acanthometren des Mittelmeeres." ' Abhandl. d. K. Akad. Berlin,' 1858 (also in ' Quart. Journ. Microscop. Science,' 1859). J. Miiller. 30. " Die Radiolarien," 1862. Hseckel. 31. " Mikrogeologie." Ehrenberg. 32. " Fortsetzung der Mikrogeologischen Studien," &c. ' Abhandl. d. K. Akad. Berlin,' 1875. Ehrenberg. 33. " On Thalassicolla." ' Annals of Nat. Hist.,' 1851. Huxley. 34. " Actinophrys sol." 'Quart. Journ. Microscop. Science,' 1853. Kolliker. 35. "Heliozoa." 'Quart. Journ. Microscop. Science,' 1876, 1877. Archer. 36. " Recent Researches on the Radiolarians." 'Journ. Linn. Soc.,' vol. xiv., 1878. St George Mivart. 37. " Ueber Radiolarien, &c., des siissen Wassers." 'Archiv fiir Mikr. Anat.,' 1869. Greeff. SPONGIDA. 38. " Observations and Experiments on the Structure and Functions of the Sponges." ' Edin. Phil. Journ.,' vols. xiii.,, xiv.; and Edin. New Phil. Journ.,' vol. i., i825->27. Grant. 104 MANUAL OF ZOOLOGY. 39. "Anatomy and Physiology of the Spongiadse." 'Phil. Trans.,' 1859. Bowerbank. 40. "British Spongiadse" ('Ray Society'). Bowerbank. 41. "History of British Sponges and Li thophytes." Johnston. 1842. 42. "Die Spongien des Adriatischen Meeres," 1862-66. Oscar Schmidt. 43. "Grundztige einer Spongien-Fauna des Atlantischen Gebietes," 1870. Oscar Schmidt. 44. " Die Kalk-Schwamme." Hseckel. 1872. 45. "Anatomy and Classification of Sponges." ' Annals of Nat. Hist.,' 1875. Carter. 46. " Vitreous Sponges," 'Annals Nat. Hist.,' 1868. Wyville Thomson. 47. " Classification of Sponges." ' Proc. Zool. Soc.,' 1867.. Gray. 48. "Development of the Marine Sponges." 'Annals Nat. Hist.,' 1874. Carter. 49. "Development of the Calcispongige. " 'Annals Nat. Hist.,' 1875. (Translation.) Metschnikoff. 50. "The Spongiae ciliatae as Infusoria flagellata. " 'Annals Nat. Hist.,' 1868. James-Clark. 51. "The Depths of the Sea," 1873. Wyville Thomson. 52. " On Holtenia." 'Phil. Trans.,' 1870. Wyville Thomson. 53. "OnCliona." 'Annals. Nat. Hist.,' 1849. Albany Hancock. 54. " Ventriculitidae of the Chalk." 'Annals Nat. Hist.,' 1847, 1848. Toulmin Smith. 55. " Untersuchungen liber Hexactinelliden." ' Zeitschr. fur Wiss. Zool.,' vol. xxv., 1877. W. Marshall. 56. "Handbuch der Palaeontologie, " vol. i., part 2, 1879. Zittel. 57. "Beitrage zur Systematik fossiler Spongien." 'Neues Jahrb. filr Min. Geol. und Paleont.,' 1877, 1878. Zittel. 58. " On Haeckel's Group of the ' Physemaria,' and on the Affinities of the Sponges." ' Ann. Nat. Hist.,' ser. 5, vol. i., 1878. Saville Kent. 59. "On the genus Haliphysema." 'Ann. Nat. Hist.,' ser. 5, vol. i., 1878. A. M. Norman. INFUSORIA. 60. "Die Infusionsthierchen als volkommene Organismen," 1838. Ehren- berg. 61. " Infusoires," 1841. Dujardin. 62. " Der Organismus der Infusionsthiere," 1867. Stein. 63. " Etudes sur les Infusoires et les Rhizopodes." 'Mem. de 1'Institut National Genevois,' 1858-61. Lachmann and Claparede. 64. " Recherches sur les organes generateurs et la reproduction des In- fusoires." 'Comptes Rendus,' 1858. Balbiani. 65. "Untersuchungen iiber den Ban und die Naturgeschichte der Vor- ticellen." ' Archiv fur Naturg.,' 1870. Greeff. 66. " Zur Morphologic der Infusorien." ' Jenaische Zeitschrift,' vol. vii., 1873. Hseckel. 67. " Ueber einige neue pelagische Infusorien." 'Jenaische Zeitschrift,' vol. vii., 1873. Hseckel. 68. " History of Infusoria." Pritchard. 69. "Recent Progress in our Knowledge of the Ciliate Infusoria." 'Proc. Linn. Soc.,' 1875. Allman. 70. " Flagellate Infusoria. " ' Annals Nat. Hist.,' 1868. James-Clark. 71. "Beitrage zur Kenntniss der Monaden." ' Archiv fur Mikr. Anat.,' 1865. Cienkowski. 72. " Researches on the Life-History of the Monads." ' Monthly Micr. Journ.,' vols. x.-xiii., 1873-75. Dallinger and Drysdale. CCELENTERATA. CHAPTER VII. THE SUB-KINGDOM CCELENTERATA. i. CHARACTERS OF THE SUB -KINGDOM. 2. DIVISIONS. 3. GENERAL CHARACTERS OF THE HYDROZOA. 4, EX- PLANATION OF TECHNICAL TERMS. THE Sub-kingdom Cceknterata (Frey and Leuckhart) may be considered as a modern representative of the Radiata of Cuvier. From the Radiata, however, the Echinodermata and Rotifera have been removed, the entire sub-kingdom of the Protozoa has been taken away, and \)i\Q Polyzoa have been rele- gated to their proper place amongst the Mollusca. Deducting these groups from the old Radiata, the residue, comprising most of the animals commonly known as Polypes or Zoophytes, remains to constitute the modern Ccelenterata. The Ccelenterata may be defined as animals whose alimentary canal communicates freely with the general cavity of the body ^somatic cavity"}. The substance of the body is made up of two fundamental membranes — an oiiter layer, calltd the " ecto- derm" and an inner layer, or " endoderm." There are no distinct neural and hcemal regions, and in the great majority of the members of the sub-kingdom there are no traces of a nervous system. Peculiar urticating organs, or " thread-cells" are usually present ; and, generally speaking, a radiate condition of the organs is perceptible, especially in the tentacles with which most are provided. In all the Ccelenterata distinct reproductive organs have been shown to exist. The leading feature which distinguishes the Ccelenterata, and the one from which the name of the sub-kingdom is derived, is the peculiar structure of the digestive system. In the Protozoa, as we have seen, a mouth is only present in the higher forms, IO6 . MANUAL OF ZOOLOGY. and in no case is there any definite internal cavity bounded by the walls of the body to which the name of " body-cavity " or " somatic cavity " could be properly applied (unless it be allowed that such really exists in the sponges). In animals higher than the Cotlenterata, on the other hand, there is not only generally a permanent mouth, but the walls of the body usually enclose a permanent chamber or "body-cavity." Fur- ther, in most cases, the mouth conducts into an alimentary canal, which is always distinct from the body-cavity, never opening into it, but usually passing through it to open on the surface by another distinct aperture (the anus). In most cases, therefore, the alimentary canal is a tube which communicates with the outer world by two apertures — a mouth and anus — but which simply passes through the body-cavity without in any way communicating with it. In the Coelenterata (fig. 35) Fig- 35- — Diagrammatic vertical section of a Sea-Anemone, a Mouth ; s Stomach ; b Body-cavity ; c c Convoluted cords (" craspeda ") containing thread-cells, and form- ing the free edges of the mesentery (m) ; t, t Tentacles ; o Reproductive organ con- tained within the mesentery. The ectoderm (e) is indicated by the broad external line, the endoderm (^) by the thin line and the space between that and the ectoderm. there is an intermediate condition of parts. There is a distinct and permanent mouth, and a distinct and permanent body- cavity, but the mouth opens into, and communicates freely with, the body-cavity. In some cases (Hydrozoa) the mouth opens directly into the general body-cavity, which then serves as a digestive cavity as well (fig. 37). In other cases there intervenes between the mouth and the body-cavity a short alimentary tube, which communicates externally with the outer world through the mouth, and opens below by a wide aperture CGELENTERATA. IO/ into the general cavity of the body (Actinozoa, fig. 35). In no case is there a distinct intestinal canal. which runs through the body and opens on the surface by a mouth at one end and an excretory aperture or anus at the other. It should, however, be mentioned here that some modern zoologists, such as Gegen- baur and Haeckel, consider that the entire system of internal cavities in any Ccelenterate is truly homologous with the intes- tinal canal of other animals, and that the Ccelenterata, therefore, possess ho true body-cavity at all. To this view some of our most distinguished authorities, such as Professor Allman, have given their adhesion ; and there is no doubt that there are weighty grounds for regarding it as the correct explanation of the facts, though any discussion of these grounds would be out of place here. It need only be added that if this view be accepted, it will entirely subvert the generally received conception of the structure of the Ccelenterata as above expressed. Though of the true " radiate " type, some Coelenterates show traces of bilateral symmetry. Thus, in some Sea-anemones one of the tentacles is larger than, or differently coloured from, the others ; and in some corals two of the primary septa, opposite one another, are larger than the rest, and divide the animal into two halves. With regard to the fundamental tissues of the Ccelenterata, there exist two primary membranes, of which one forms the outer surface of the body, and is called the " ectoderm ; " whilst the other lines the alimentary canal, the general cavity of the body, and the tuBuIaf "tentacles, and is termed the " endoderm." These membranes correspond with the primi- tive serous and mucous layers (" epiblast " and " hypoblast ") of the germinal area, and become differentiated in opposite directions, the ectoderm growing from within outwards, the endoderm from without inwards. Each is primitively cellular in its minute structure, and each may be rendered more or less complex by vacuolation or fibrillation. Between the ectoderm and endoderm there is sometimes a third layer (" mesoderm " or " mesoblast "), which is commonly of a muscular nature. In connection with the integument of the Ccdenterata, the organs termed "thread-cells" (" cnidae," or " nematocysts ") must be noticed. These are peculiar cellular bodies (fig. 36), of various shapes, which probably serve as weapons of offence and defence, and which commimicate to many members of the sub-kingdom (e.g., the Sea-Blubbers) their well-known power of stinging. In the common Hydra the thread-cells (fig. 36, E) consist of " oval elastic sacs, containing a long coiled filament, barbed at its base, and serrated along its edges. When fully io8 MANUAL OF ZOOLOGY. developed the sacs are tensely filled with fluid, and the slightest touch is sufficient to cause the retroversion of the filament, which then projects beyond the sac for a distance, which is not Fig. 36.— Thread-cells of Ccelenterata, greatly magnified. A and B, The thread-cell of Caryophyllia Smithii, in the everted condition, and in two varieties ; C and D, The thread-cell of Corallimorphus profundus, in a quiescent and active condition, en- larged about 500 times ; E, The thread-cell of Hydra, in an everted condition. (After Gosse and Moseley.) uncommonly equal to many times the length of the latter " * (Huxley). Many beautiful modifications of shape are known in the thread-cells of different Coelenterates, but their essential structure in all cases is much the same as in the Hydra. It is only in few cases, comparatively speaking, that the thread-cells have the power of piercing and irritating the human skin ; but even in the diminutive Hydra it is probable that they exercise some benumbing and deleterious influence on the living organ- isms which may be captured as prey. Besides the thread- cells, the tentacles of some Hydroids are furnished with rigid hair-like processes, which are probably tactile in function, and which are known as " palpocils." The Ccelenterata are divided into two classes, termed respect- ively the Hydrozoa and the Actinozoa. * Thread-cells, though very commonly, if not universally, present in the Ccelenterata, are nevertheless not peculiar to them. Similar organs have been shown to exist in several of the Nudibranchiate Molhtsca, as well as in some Annelides (Spio seticornis). There likewise exist analogous organs trichocysts) in several of the Infusoria, and in the Planarida. CCELENTERATA : HYDROZOA. CLASS I. HYDROZOA. The Hydrozoa are defined as Ccelenterata in which the walls of the digestive sac are not separated from that of the general body-cavity, the two coinciding with one another; the reproductive organs are in the form of external processes of the body-wall. (Fig. 37, B.) Fig- 37- — A, The common Hydra (Hydra vulgaris), carrying young Hydrce which it has produced by budding, considerably magnified (after Hincks). B, Diagrammatic section of the Hydra, showing the mouth surrounded by the tentacles, and the disc of attachment ; the dark and light lines indicate the two layers of the integument, and on one side of the body is shown a single large egg. It follows from the above, that, since there is but a single internal cavity, the body of a Hydrozoon on transverse section appears as a single tube, the walls of which are formed by the limits of the combined digestive and somatic cavity. The Hydrozoa are all aquatic, and the great majority are marine. The class includes both simple and composite organ- isms, the most familiar examples being the common Fresh-water Polype (Hydra), the Sea -firs (Sertularidd), the Jelly-fishes (Medusa), and the Portuguese man-of-war (Physalia). Owing to the great difficulty which is ordinarily experienced by the stu- dent in mastering the details of this class of animals, it has been thought advisable to introduce here a short explanation of some of the technical terms which are in more general use in describing these organisms. 110 - MANUAL OF ZOOLOGY. GENERAL TERMINOLOGY OF THE HYDROZOA. Individual. — We have already seen (see Introduction) that the term "in- dividual," in its zoological sense, must be restricted to "the entire result of the development of a single fei'tilised ovum," and that in this sense an individual may either be simple, like an Amoeba, or may be composite, like a Sponge, which is produced by an aggregation of amcebiform particles. If all the parts composing an individual remain mutually connected, its development is said to be " continuous ; " but if any of these parts become separated as independent beings, the case becomes one of "discontinuous" development. We have seen, also, that however long zooidal multiplica- tion may go on, there ultimately arrives in the history of every individual a period at which sexual reproduction must be called in to insure the per- petuation of the species throughout time. This truth is expressed by Steen- strup's celebrated law of the "alternation of generations.' Amongst the Hydrozoa, the individual may be either simple or compound, and the development may be either continuous or discontinuous, the fol- lowing terms being employed to denote the phenomena which occur. Hydrosoma. — This is the term which is employed to designate the entire body of a Hydrozobn, whether it be simple, as in the Hydra, or composite, as in a Sertularian. Polypite. — The alimentary region of a Hydrozobn is called a " polypite ; " the term " polype " being now restricted to the same region in the Actin- ozoa. In the simple Hydrozoa the entire organism may be called a " poly- pite ; " but the term is more appropriately applied to the separate nutritive factors which together make up a compound Hydrozobn. By Professor All- man the term " hydranth " is used in preference to "polypite." Distal and Proximal. — These are terms applied to different extremities of the hydrosoma. It is found that one extremity grows more quickly than the other, and to this free-growing end — at which the mouth is usually situated — the term " distal " is applied. To the more slowly growing end of the hydrosoma— which is at the same time usually the fixed end — the term " proximal " is applied. These terms may be used either in relation to a single polypite in the compound Hydrozoa, or to the entire hydrosoma, whether simple or compound. Hydrorhiza.—rY\i\s term is applied to that portion of the proximal end of a Hydroid colony by which it is attached to some foreign body. Ccenosarc. — This is the term which is employed to designate the common trunk, which unites the separate polypites of any compound Hydrozobn into a single organic whole. Polypary. — The term "polypary" or " polypidom " is applied to the horny or chitinous outer covering or envelope with which many of the Hydrozoa are furnished. These terms have also not uncommonly been applied to the very similar structures produced by the much more highly organised Sea-mats and their allies (Polyzod), but it is better to restrict their use entirely to the Hydrozoa. By Professor Allman the term " peri- sarc " is given to the chitinous investment by which the soft parts of the Plydrozoa are often protected. Zobids. — In continuous development, the partially independent beings which are produced by gemmation or fission from the primitive organism, to which they remain permanently attached, are termed "zooids." In other words, " zooids " are the more or less individualised members of which the Hydroid colony is made up. In discontinuous development, where certain portions of the "indivi- dual " are separated as completely independent beings, these detached portions are likewise termed "zooids ;" that which is first formed being ' CCELENTERATA : HYDROIDA. I 1 1 distinguished as the " producing zooid," whilst that which separates from it is known as the "produced zooid." In a great number of Hydrozoa there exist two distinct sets of zooids, one of which is destined for the nu- trition of the colony, and has nothing to do with generation, whilst the functions of the other, as far as the colony is concerned, are wholly repro- ductive. For the whole assemblage of the nutritive zooids of a Hydrozob'n Professor Allman has proposed the term "trophosome," applying the term " gonosome " to the entire assemblage of the reproductive zooids. In such Hydrozoa, therefore, as possess these two distinct sets of zooids, the "individual," zoologically speaking, is composed of a trophosome and a gonosome. It follows from this that neither the trophosome nor the gono- some, however apparently independent, and though endowed with intrinsic powers of nutrition and locomotion, can be looked upon as an "individual," in the scientific sense of this term. As a rule, the zooids of the trophosome are all like one another, or are " homomorphic ; " but there are some cases (as in Hydractinia, and in the nematophores of the Plumularido>) in which some of zooids of the trophosome are unlike the others. The zooids of the gonosome, on the other hand, are normally unlike, or are "hetero- morphic, " consisting of two or three different sets of zooids, each with its special duty in the generative functions of the Hydroid colony. CHAPTER VIII. DIVISIONS OF THE HYDROZOA. SUB-CLASS HYDROIDA.* THE Hydrozoa are divided into five sub-classes — viz., the Hy- droida, the Siphonophora, the Lucernarida, the Graptolitida, and the HydrocoraUina. SUB-CLASS I. HYDROIDA. — This sub-class comprises those Hydrozoa which consist of an alimentary region or " polypite" which is, typically, provided with an adherent disc, or " hydro- rhiza" and prehensile tentacles. In some few cases the hydrosoma is composed of a single polypite only, as in the Hydrida and in some of the Corynida; but usually there are several polypites united together by means of a common trunk or "coenosarc," as in most of the Corynida and in the orders Sertularida and Campanularida. Further, in the great majority of cases, the "hydrorhiza" is permanently attached to some foreign object. The Hydroida comprise six orders — viz., the Hydrida, the * For full details as to the morphology and physiology of the Hydroid Zoophytes, the student should refer to the magnificent 'Monograph of the Gymnoblastic Hydroids,' by Professor Allman (Ray Society). The student may also consult the excellent ' History of British Hydroid Zoophytes,' by the Rev. Thomas Hincks. I 12 MANUAL OF ZOOLOGY. &i the Sertularida, the Campanularida, the Thecomedusce, and the Medusidce. ORDER I. HYDRIDA (Eleutheroblastica, Allman ; Gymnochroa, Hincks). — This order comprises those Hydrozoa whose " hydro- soma " consists of a single locomotive polypite, with tentacles and tl hydrorhiza" and with reproductive organs which appear as simple external processes of the body -wall. The hydrorhiza is discoid, and no hard cuticular layer is at any time developed. The order Hydrida comprises a single genus * only (Hydra), including the various species of " Fresh-water Polypes," as they are often called. The common Hydra (fig. 37, A) is found abun- dantly in this country, and consists of a tu- bular cylindrical body, the " proximal " extrem- ity of which is expanded into an adherent disc or foot — the "hydro- rhiza"— by means of which the animal can attach itself to some foreign body. It pos- sesses, however, the power of detaching the hydrorhiza at will, and thus of changing its place. At the opposite or " distal " extremity of the body is placed the mouth, surrounded by a circlet of tenta- cles, which arise a little distance below the mar- gin of the oral aperture. The tentacles vary in number from five to twelve or more, and they vary considerably in length in different species, being much shorter than the body in the Hydra viridis (fig. 38), but being extremely long and * If the Protohydra of Greeff be a mature form, it also belongs to this order. It differs from Hydra in having no tentacles, but it seems more probably to be the larva of some other Hydroid. Fig. 38. — The Green Fresh-water Polype {Hydra viridis), suspended head-downwards from a piece of astern of an aquatic plant, enlarged, a One of the tentacles ; b Testis or spermarium, with sper- matozoa in its interior; c A single large ovum, protruding from the side of the body ; d Disc of attachment (" hydrorhiza"). CCELENTERATA : HYDRIDA. 113 filamentous in Hydra ftisca. They are highly extensile and contractile, and serve as organs of prehension, being capable of retraction till they appear as nothing more than so many warts or tubercles, and of being extended to a length which is in some species many times longer than the body itself. (In the Hydra fusca the tentacles can be protruded to a length of more than eight inches.) Each consists of a prolongation of both ectoderm and endoderm, enclosing a diverticulum of the somatic cavity, and they are abundantly furnished with thread- cells. The cylindrical hydrosoma (fig. 37, B) is excavated into a single large cavity, lined by the endoderm, and communi- cating with the exterior by the mouth. This — the "somatic cavity" — is the sole digestive cavity with which the Hydra is provided, the indigestible portions of the food being rejected by the mouth. The Hydra possesses a most extraordinary power of resist- ing mutilation, and of multiplying artificially when mechani- cally divided. Into however many pieces a Hydra may be divided, each and all of these will be developed gradually into a new and perfect polypite. The remarkable experiments of Trembley upon this subject are well known, and have been often repeated, but space will not permit further notice of them here. Reproduction is effected in the Hydra both asexually by gemmation, and sexually — the former process being followed in summer, and the latter towards the com- mencement of winter, few individuals surviving this season. In the first method the Hydra (fig. 37, A) throws out one or more buds, generally from near its proximal extremity. These buds at first consist simply of a tubular prolongation of the ectoderm and endoderm, enclosing a caecal diverticulum of the body-cavity ; but a mouth and tentacles are soon developed, when the new being is usually detached as a perfect independ- ent Hydra. The Hydra thus produced throw out fresh buds, often before they are detached from the parent organism, and in this way reproduction is rapidly carried on. In the second or sexual mode of reproduction, ova and spermatozoa are produced in outward processes of the body- wall (fig. 38). The spermatozoa are developed in little conical elevations, which are produced near the bases of the tentacles, and the ova are enclosed in sacs of much greater size, situated nearer the fixed or proximal extremity of the animal. Ordinarily there is but one of these sacs, containing a single ovum, but sometimes there are two. When mature, the ovum is expelled through the body-wall, and is fecundated by the spermatozoa, which are simultaneously liberated. The H 114 MANUAL OF ZOOLOGY. primitive body-cavity of the non-ciliated embryo is ultimately placed in communication with the outer world by the forma- tion of the mouth, which is produced directly as an opening in the walls of the body, and not by invagination of the ectoderm. ORDER II. CORYNIDA (Gymnoblastica, Allman ; Athecata, Hincks). — The order Corynida comprises those Hydrozoa whose hydrosoma is fixed by a hydrorhiza, and consists either of a single polypite, or of several united by a ccenosarc, which usually develops a firm outer layer or " polypary." No " hydrothecee" are present. " The reproductive organs are in the form of gono- phores, which vary much in structure, and arise from the sides of the polypites,from the ccenosarc, or from gonoblastidia " (Greene). The hydrosoma of the Corynida may consist of a single polypite, as in Coryomorpha and Vorticlava, or it may be com- posed of several united by a ccenosarc, as in Cordylophora (fig. 39, a). The order is entirely confined to the sea, with the single exception of Cordylophora, which inhabits fresh water. In Tubularia and its allies the organism is protected by a well- developed external chitinous envelope or " polypary ; " but in the other genera belonging to the order, the polypary is either Fig. 39. — Morphology of Corynida. a Fragment of Cordylophora lacustris, slightly enlarged ; b Fragment of the same considerably enlarged, showing a polypite and three gonophores in different stages of growth, the largest containing ova ; c Portion . of Syncoryne Sarsii with medusiform zooids budding from between the tentacles. rudimentary or is entirely absent. The polypary of the Corynida, when present, is readily distinguished from that of the Sertularida, by the fact that in the former it extends only to the bases of the polypites ; whereas in the latter it expands to form little cups for the reception of the polypites, these cups being called " hydrothecae." Owing to the fact that neither the polypites nor the generative buds of the Corynida are en- CCELENTERATA : CORYNIDA. closed in a chitinous investment, the name of " Gymnoblastic Hydroids " is applied to them by Professor Allman. As regards the reproductive process in the Corynida, the reproductive elements are developed in distinct buds or sacs, which are external processes of the body-wall, and have been aptly termed "gonophores" by Professor Allman. Strictly speaking, Dr Allman understands by the term " gonophore " only the ultimate generative zooid, that which immediately pro- duces the generative elements.* Great variations exist in the form and development of these generative buds, and an exami- nation of these leads us to some of the most singular pheno- mena in the entire animal kingdom. In some species of Hydractinia and Coryne, the generative buds or " gonophores" exist in their simplest form — namely, as sacciform protuber- ances of the endoderm and ecto- derm, enclosing a diverticulum of the somatic cavity. In this form they are attached to the *' trophosome " by a short stalk, and they are termed " sporo- sacs " (fig. 40). They are exact- ly like the buds which we have already seen to exist in the Hy- dra, with this difference, that they are not themselves devel- oped into fresh polypites, but are Fig.4o.— Sporosac of ^rf cjmnlv rprpntarlps in whirh thp ata (after Allman). a Outer wall of mpij receptacles 111 wnicn tne the sac . b inner wall of the sac . s Col. essential elements Of generation umn developed from the floor of the — the ova and spermatozoa — are prepared, by the union of which the young Corynid is produced. The sporosac is almost invariably permanently attached to the trophosome, the only known ex- ception being in Dicoryne, in which the sporosac, previous to the discharge of its ova, liberates itself from its outer investment, and swims about freely as an independent ciliated organism. * According to Mr Hincks, the "gonophore" is the bud in which the reproductive elements are formed. " It consists of an external envelope (ectotheca), enclosing either a fixed generative sac between the walls of which the ova and spermatozoa are developed, or a free sexual zooid." The actual sexual zooid is termed by Mr Hincks the "gonozooid," whether it be fixed or free — in other words, it is the gonophore minus its external investment. The gonozooid is sometimes male, sometimes female ; and the same colony may produce one or both — the former being most com- monly the case. sporosac, and extending into its cavity. This is termed the "spadix;" it con- tains a prolongation from the cceno- sarcal canal, and the ova are developed around it Il6 MANUAL OF ZOOLOGY. In Cordylophora (fig. 41, b] a further advance in structure is perceptible. The gonophore now consists of a closed sac, from the roof of which depends a hollow process or peduncle —the " manubrium " — which gives off a system of tubes which run in the walls of the sac. For reasons which will be im- mediately evident, the gonophore in this case is said to have a "disguised" medusoid structure (fig. 41, l>). Fig. 41. — Reproductive processes of Hydrozoa. a Sporosac ; b Disguised medusoid ; c Attached medusiform gonophore ; d Free medusiform gonophore. The cross shad- ing indicates the reproductive organs, ovaria or spermana. The part completely black indicates the cavity of the manubrium and the gonocalycine canals. In certain Corynida, however, we meet with a still higher form of structure, the gonophores being now said to be " medusoid." In these cases the generative bud is primitively a simple sac — such as the " sporosac" — but ultimately develops itself into a much more complicated structure. The gono- phore (fig. 41, c) is now found to be composed of a bell- shaped disc, termed the " gonocalyx," which is attached by its base to the parent organism (the trophosome), and has its cavity turned outwards. From the roof of the gonocalyx, like the clapper of a bell, there depends a peduncle or " manubrium," which contains a process of the somatic cavity. The manubrium gives out at its fixed or proximal end four prolongations of its cavity, in the form of radiating lateral tubes which run to the margin of the bell, where they com- municate with one another by means of a single circular canal which surrounds the mouth of the bell. This system of tubes constitutes what is known as the system of the "gastro-vascular" or " gonocalycine canals." The gonophore, thus constituted, may remain permanently attached to the parent organism, as in Tubularia indivisa (fig. 41, c}\ but in other cases still fur- ther changes ensue. In the higher forms of development (fig. 42) the manubrium acquires a mouth at its free or distal ex- tremity, and the gonocalyx becomes detached from the parent. The gonophore is now free, and behaves in every respect as an independent being. The gonocalyx is provided with marginal tentacles and with an inward prolongation from its margin, CCELENTERATA : CORYNIDA. 1 1/ which partially closes the mouth of the bell, and is termed the "veil" or "velum." By the contractions of the gonocalyx, which now serves as a natatorial organ, the gonophore is pro- Fig. 42. — Free-swimming medusiform gonophore of Bougainville 'a superciliaris a fixed Hydroid. Enlarged. (After A. Agassiz. ) pelled through the water. The manubrium, with the shape, assumes the functions of a polypite, and its cavity takes upon itself the office of a digestive sac. Growth is rapid, and the gonophore may attain a comparatively gigantic size, being now absolutely identical with one of those organisms which are com- monly called "jelly-fishes," and are technically known as Medusa (fig. 42). In fact, as we shall afterwards see, many of the gymnophthalmate Medusa, originally described as a dis- tinct order of free-swimming Hydrozoa, are in truth merely the liberated generative buds, or " medusiform gonophores," of the permanently rooted Hydroids. Finally, the essential gen- erative elements — the ova and spermatozoa — are developed in the walls of the manubrial sac, between its endoderm and ecto- derm, and embryos are produced. These embryos, however, instead of resembling the organism which immediately gave them birth, develop themselves into the fixed Corynid from which the gonophore was produced, thus completing the cycle. The swimming-bell of the medusiform gonophore is believed to be formed by a great development of an inter-tentacular web, such as is sometimes present, in a rudimentary form, in the nutritive zooids. Sometimes the medusoid becomes quies- Il8 MANUAL OF ZOOLOGY. cent towards the close of its existence, and the swimming-bell becomes reversed or atrophied. Lastly, in Clavatella, the sexual zooid, though free and locomotive, is not provided with a swimming-bell, but creeps about by means of suctorial discs developed on branches of the tentacles. As we have seen, the generative buds of the Corynida may exist in the following chief forms : i. As " sporosacs," or simple closed sacs, consisting of ectoderm and endoderm, with a central cavity in which ova and spermatozoa are produced. 2. As " disguised medusoids," in which there is a central manu- brial process and a rudimentary system of gonocalycine canals ; but the gonocalyx remains closed. 3. As complete medusoids, which have a central manubrium, a complete system of gono- calycine canals, and an open gonocalyx ; but which never be- come detached. 4. As perfect medusiform gonophores (fig. 42), which are detached, and lead an independent existence for a time, until the generative elements are matured. In whichever of these forms the gonophore may be present, the place of its origin from the trophosome may vary in different species of the order, i. They may arise from the sides of the polypites, as in Coryne and Stauridia; 2. They may be produced from the ccenosarc, as in Cordylophora ; 3. They may be pro- duced upon certain special processes, which are termed " gono- blastidia," as in Hydractinia and Dicoryne. These gonoblastidia (fig. 43, g) are processes from the body-wall or coenosarc, which closely resemble true polypites in form, but differ from them in being usually devoid of a mouth, and in having shorter tentacles. They are, in truth, atrophied or undeveloped polypites. The gonoblastidia are the " blastostyles " of Prof. Allman, and are usually columniform in shape. They may carry spo- rosacs, or medusoid gonophores ; and they may be naked, or, in other orders, they may be protected within a chitinous re- ceptacle or "gonangium." As regards the development of the Corynida, the embryo is very gener- ally, though not always, ciliated at first, when it is knoM'n as a " planula ; " but in one form the embryo leaves the gonophore as a free and locomotive polypite, and in another it is non-ciliated and amoeboid. The ''planula " is a minute ciliated cylindrical body, which swims about actively in the water. The embryonic cells of which it is composed clivide into an outer and an inner layer, enclosing a central cavity, and it next passes into a condition which is common to the embryos of the Ccelenterata generally, and to which Haeckel has applied the name of "gastrula." At this stage, it consists of an ovate or rounded body, with a single central cavity, which communicates with the exterior by an aperture placed at one pole. The wall of this central cavity consists of two layers, an outer and an inner, corresponding with the ectoderm and endoderm of the adult, and also with CCELENTERATA : CORYNIDA. 119 the two primitive layers of the germ of the Vertebrata. The "gastrula " stage appears to be one very generally p_assed^through by all animals higher than the Protozoa, and by the Spongeir~amongst the latter, but there is a difference as to the manner in which the central cavity is formed. Fig- 43-. — Diagram of sporosacs supported upon a gonoblastidion (or blastostyle). a Chitinous investment (periderm) of the colony; b Ectoderm; c Endoderm ; p Poly- pite ; g Gonoblastidion, or columniform zooid, carrying sporosacs (s s) with ova in their interior. (Altered from Allman.) In some cases it is formed by the hollowing out of the original sphere, and the formation of an opening (the primitive mouth) at one end, as seems to be generally the case in the Ccelenterata ; or, in other cases, it may be produced by an invagination or inversion of the primitive vesicle in such a manner as to form a central chamber, with a single aperture opening on the exterior. By fixation of the "gastrula " at its hinder extremity to some foreign object, and by the formation of tentacles round the mouth-opening at the other extremity, a hydraform polypite is at once produced, which (if not belonging to one of the simple forms) proceeds to develop the com- posite adult by a process of gemmation. In this process in the Corynida (as also in the Sertularida and Campanularida) the new polypites are developed at or near the distal end of the hydrosoma, the distal polypites being thus the youngest ; whereas the reverse of this obtains amongst the Oceanic Hydrozoa. The subject of the reproduction of the Corynida having been treated at some length, so as to apply to the remaining Hydroida, we shall now give a brief description of the leading types of structure exhibited by the order. I2O MANUAL OF ZOOLOGY. Eudendrium, a genus of the Corynida, which is not uncommonly found attached to submarine objects, usually in tolerably deep water, may be taken as a good example of the fixed and composite division of the order. The hydrosoma consists of numerous polypites, united by a coenosarc, which is more or less branched, and is defended by a horny tubular poly- pary. The polypites are borne at the ends of the branches and branchlets, and are not contained in " hydrothecae, " the polypary ending abruptly at their bases. The polypites are non-retractile, of a reddish colour, and provided with about twenty tentacles, arranged round the mouth in a single row. Tubularia (fig. 44) is very similar to Eudendrium^ but the hydrosoma is either undivided or is very slightly branched. The hydrosoma consists of clustered horny tubes, of a straw colour, and not unlike straws to look at ; hence the common name of pipe- coralline given to this zoophyte. Each tube is filled with a soft, semi- fluid, reddish ccenosarc, and gives exit at its distal extremity to a single poly- pite. The polypites are bright red in colour, and are not retractile within their tubes, the horny polypary extending only to their bases. The polypites are some- what conical in shape, the mouth being placed at the apex of the cone, and they are furnished with two sets of tentacles. One set consists 'of numerous short tentacles placed directly round the mouth ; the other is composed of from thirty to forty tentacles of much greater length, arising from the polypite about its middle or near the base. Near the insertion of these tentacles the genera- tive buds are produced at proper sea- sons. The generative buds remain per- manently attached, but each is furnished with a swimming-bell, in which canals are present. The manubrium is destitute of a mouth, and " the swimming-bell is converted into a nursery in which the embryo passes through the later stages of its development" (Hincks). Coryomorpha nutans may be taken to represent those Corynida in which there is no polypary and the hydro- soma is simple. It is about four inches in length, and is fixed by filamentous roots to the sand at the bottom of the sea. It consists of a single whitish polypite, striped with pink, and ter- minating upwards in a spear-shaped head, round the thickest part of which is a circlet of from forty to more than one hundred long white tentacles. Above these comes a series of long, branching gonoblastidia, bearing gono- phores, and succeeded by a second shorter set of tentacles which surround the mouth. The gonophores become ultimately detached as free-swim- ming medusoids. Another remarkable example of the Corynida is Hydractinia (fig. 45). In this genus the polypites are gregarious, and the polypary forms a horny Fig. 44. — Corynida. Fragment of Tubularia indivisa, natural size. CCELENTERATA : SERTULARIDA. 121 crust which spreads over shells and other foreign bodies. The tentacles of the nutritive zooids form a single sub-alternate series. The generative buds are produced upon imperfect, non-tentaculate polypites ; and are mere sac- shaped protuberances, enclosing diverticula from the body-cavity, but not detached from the parent organism. Fig. 45.— Group of zooids of Hydractinia echinata, enlarged. (After Hincks.) a a Nutritive zooids ; b b Generative zooids, carrying sacs filled with ova. ORDER III. SERTULARIDA (Calyptoblastica, Allman; The- caphora, Hincks). — This order comprises those Hydrozoa " whose hydro soma is fixed by a hydrorhiza, and consists o several polypites, protected by hydrotheccz, and connected by a ccenosarc, which is usually branched and invested by a very firm outer layer. Reproductive organs in the form of gonophores arising from the ccenosarc or from gonoblastidia" (Greene). The Sertularida resemble the Corynida in becoming perma- nently fixed after their embryonic condition by a hydrorhiza, which is developed from the proximal end of the ccenosarc ; 122 MANUAL OF ZOOLOGY. but they differ in the fact that the polypites are invariably pro- tected by " hydrothecas," or little cup-like expansions of the polypary (fig. 46, #, b) ; whilst the hydrosoma is in all cases Fig. 46. — a Serlularia (Diphasia) pinnata, natural size ; a' Fragment of the same en- larged, carrying a male capsule (p), and showing the hydrothecae (ft) ; b Fragment of Campanularia neglecta (after Hincks), showing the polypites contained in their hydrothecae (K), and also the point at which the coenosarc communicates with the stomach of the polypite (c). composed of more than a single polypite. The mouth of the hydrotheca is generally furnished with an operculum or valve for its closure. Owing to the presence of " hydrothecae," the name of " Calyptoblastic Hydroids" has been proposed by Professor Allman for the Sertularians and Campanularians. In all these forms, also, the generative buds are similarly en- closed in chitinous receptacles — the so-called " gonothecae " or "gonangia." The ccenosarc generally consists of a main stem — or " hydrocaulus " — with many branches; and it is so plant- like in appearance that the common Sertularians are almost always mistaken for sea-weeds by visitors at the seaside. It is invested by a strong corneous or chitinous covering, often termed the "periderm." The polypites are sessile or sub-sessile, hydra-form, and in all essential respects identical with those of the Corynida, though usually smaller. Each polypite consists of a soft, con- tractile and extensile body, which is furnished at its distal extremity with a mouth and a circlet of prehensile tentacles, richly furnished with thread-cells. The tentacles have an in- CCELENTERATA : SERTULARIDA. 12.3 distinctly alternate arrangement. The mouth is simple or lobed, and is placed, in many cases, at the extremity of a more or less prominent extensile and contractile proboscis. The mouth opens into a chamber which occupies the whole length of the polypite, and is to be regarded as the combined body- cavity and digestive sac. At its lower end this chamber opens by a constricted aperture into a tubular cavity which is every- where excavated in the substance of the ccenosarc (fig. 46, b}. The nutrient particles obtained by each polypite thus serve for the support of the whole colony, and are distributed through- out the entire organism. The nutritive fluid prepared in the interior of each polypite gains access through the above-men- tioned aperture to the cavity of the ccenosarc, which by the combined exertions of the whole assemblage of polypites thus becomes filled with a granular nutritive liquid. The ccenosar- cal fluid is in constant movement, circulating through all parts of the colony, and thus maintaining its vitality, the cause of the movement being probably due in part, at any rate, to the existence of vibrating cilia. The generative buds (gonophores or ovarian vesicles) are usually supported upon gonoblastidia, and do not become detached in the true Sertularids. They A Fig. 47. — Diagrams of the gonothecae, with their con- Fig. 48. — Ovarian cap- tents, of the Sertularians and Campanularians. « sule of Diphasia (Ser- Chitinous envelope ; g Central gonoblastidion or tularia) operculata, blastostyle ; e Medusiform gonophores carried upon Linn, (after Hincks). the blastostyle, each with a central manubrium, in Greatly enlarged, the walls of which the generative elements are pro- duced ; s Sporosacs carried upon the blastostyle, each with a central pillar (spadix), round which the ova are developed. (Altered from Allman.) are developed in chitinous receptacles known as "gonothecae " (figs. 47, 48). 124 MANUAL OF ZOOLOGY. Sometimes the "gonangium" or "gonotheca" contains only a single gonophore, but more commonly it contains several, which increase in maturity as we recede from the base of the gonoblastidion (or blastostyle) and approach its summit (fig. 47, B). The buds carried on the sides of the blastostyle may have the form either of sporosacs or of medusoids. The ova may be directly discharged into the surrounding water, or may be retained for some time in a peculiar receptacle, " where they undergo further development, and which is supported upon the summit of the gonangium, and lies entire- ly external to its cavity " (Allman). In Plumularia and some of its allies there occur cer- tain peculiar structures, to which the name of " nema- tophores " has been applied. Each of these consists of a process of the coenosarc, which is invested by the horny polypary, with the exception of the distal ex- tremity,, which remains op- en. The nematophores are sometimes fixed, sometimes movable. They " consti- tute cup - like appendages (fig. 49, n n) formed of chitine, and filled with pro- toplasm, which has the pow- er of emiting pseudopodia or amoeboid prolongations of its substance, and hav- ing their cavity in commu- Fig. 49. -Portion of a branch of Antennularia nication with that of the antennina, enlarged. (After Allman.) /One mmmrm tnhp r»f fh^ hvrlrn of the polypites ; * nn Nematophores emit- COmmOll tUDC Ot tH6 nyClrO- ting pseudopodial filaments of sarcode ; n' cauluS (Allman). Whilst Nematophore with its sarcodic contents p ,1 ~J~ ' .,^1 quiescent ; c Coenosarc enclosed within the Part Of the SarCOOe in each polypary. nematophore is capable of being extended in long fila- ments resembling the pseudopodia of an Amceba, another por- tion is charged with large thread-cells, and is not capable of emission in this way. The function of these extraordinarily modified zooids is uncertain. CCELENTERATA : CAMPANULARIDA. 125 ORDER IV. CAMPANULARIDA. — The members of this order are closely allied to the Sertularida ; so closely, indeed, that they are very often united together into a single group. The chief difference consists in the fact that the hydrothecae of the Campanularida^ with their contained polypites, are supported upon conspicuous stalks, thus being terminal .in position (figs. 46, b, and 50) ; whilst in the Sertularida they are sessile or sub- Fig. 50. — Portion of the colony of Clytia (Campanularia) Johnstoni, magnified. . p Nutritive zooid ; g Capsules in which the reproductive zooids are produced. sessile, and are placed laterally upon the branchlets. The gonophores also in the Campanularida are usually detached as free-swimming medusoids, whereas they remain permanently attached in the Sertularians. Each medusoid consists of a 126 MANUAL OF ZOOLOGY. little transparent glassy bell, from the under surface of which there is suspended a modified polypite, in the form of a "manubrium" (fig. 51). The whole organism .swims gaily through the water, propelled by the contractions of the bell or disc (gonocalyx) ; and no one would now suspect that it was in any way re- lated to the fixed plant-like zoo- phyte from which it was originally budded off. The central polypite is furnished with a mouth at its distal end, and the mouth opens into a digestive sac. From the proximal end of this stomach pro- ceed four radiating canals which extend to the circumference of the disc, where they all open into a single circular vessel surrounding the mouth of the bell. From the margins of the disc hang also a number of delicate extensile fila- ments or tentacles ; and the circum- ference is still further adorned with a series of brightly-coloured spots, which are probably organs of sense. The mouth of the bell is partially closed by a delicate transparent manubrium; bb Radiating 'gastro- membrane or shelf, the so-called vascular canals; c Circular canal; ,, ., „ ~, . , , m Marginal bodies ; t Tentacles. VCll. 1 hUS Constituted, these beautiful little beings lead an in- dependent and locomotive existence for a longer or shorter period. Ultimately, the essential elements of reproduction are developed in special organs, situated in the course of the radiating canals of the disc. The resulting embryos are ciliated and free-swimming, but ultimately fix themselves, and develop into the plant-like colony from which fresh medusoids may be budded off. The ova in the medusiform gonophores are usu- ally developed in the course of the gonocalycine canals, and not between the ectoderm and endoderm of the manubrium, as is the case in the Corynida. Examples of the order are Campanularia, Laomedea, &c. The distinctions between the Sertularida and Campanularida are certainly insufficient to justify their being placed in separate orders. If united to- gether, it would probably be best to adopt the name of Calyp- toblastica (Allman) or Thecaphora (Hincks) for the order, and Fig. 51. — Free medusiform gono- phore of Clytia Johnstoni (after Hincks). a Central polypite or CCELENTERATA : MEDUSID^. I2/ to employ the names Sertularida and Campanularida for the sub-orders. ORDER V. THECOMEDUS^E. — Professor Allman has recently described under the name of Stephanoscyphus mirabilis, a very remarkable Hydrozoon, which he believes to form the type of a new order. This singular organism is invariably associated with a species of Sponge, in the substance of which it is embedded. It consists of a congeries of chitinous tubes, which permeate the sponge-substance, and which open on its surface by large openings resembling oscula. At their bases the tubes are connected by horizontal branches, and they expand widely as they approach the surface; where their contents become developed into a remarkable body, which has the power of extending itself beyond the mouth of the tube, and again of withdrawing within it. This body is furnished with a crown of tentacles, and is essentially medusiform in its structure. There is a circular canal at the base of the tentacular crown, surrounding the central opening, with four radiating canals proceeding backwards from this ; but no lithocysts, ocelli, nor velum have been detected. For this curious organism, Pro- fessor Allman proposes the formation of a new order under the name of Thecomeduscz. ORDER VI. MEDUSID^: or HYDROMEDUSID^E (Acalephce* in part). — The organisms included in this order have often been separated as a distinct sub-class of the Hydrozoa ; but they are, perhaps, best regarded as a mere order of the Hydroid Zoophytes, characterised by the fact that the hydrosoma is free- swimming and oceanic, consisting of a single swimming - bell (" nectocalyx "\from the roof of which is suspended a single poly- pite. A system of canals is developed in the walls of the swim- ming-bell, and the reproductive organs are processes of the sides of these canals or of the walls of the polypite. The Medusida comprise most of the smaller organisms com- monly known as Jelly-fishes or Sea-nettles, the last name being derived from the property which some of them possess of severely stinging the hand, this power being due to the presence of numerous thread-cells. As employed by modern naturalists, * The old sub-class of the Acalephae contained the Gymnophthalmate Medusa (— the Discophora), and the Steganophthalmate Medusa ( = the Lucernarida in part), the two being placed in a single order under the name of Pulmograda. The Acalephce also contained the Ctenophora and the Calycophoridce and Physophoridce, of which the former constituted the order Ciliograda, whilst the two latter made up the order Physograda. The Ctenophora, however, are now generally placed amongst the Actinozoa, whilst the Calycophoridce and Physophorida constitute the Hydrozoal sub- class Siphonophora. 128 MANUAL OF ZOOLOGY. the order is very much restricted, many of its members having been shown to be really the free generative buds of other Hydrozoa. As used here, it corresponds to part of the Gym- nophthalmate Medusa of Professor E. Forbes, the Steganoph- thalmate Medusa of the same author being now placed in the sub-class Lucernarida. The hydrosoma of one of the Medusida ( = a Gymnophthal- mate Medusa] is composed of a single, gelatinous, bell-shaped swimming organ, the "nectocalyx" or "disc," from the roof of which a single polypite is suspended (figs. 52, 53). The Fig. 52. *— Morphology of Medusidae. a A Medusoid (Tkaumantias) seen in profile, showing the central polypite, the radiating and circular gonocalycine canals, the marginal vesicles and tentacles, and the reproductive organs ; b The same viewed from below. The dotted line indicates the margin of the velum. interior of the nectocalyx is often called the " nectosac," and the term " codonostoma " has been proposed to designate the open mouth of the bell. The margin of the nectocalyx is pro- duced inwards to form a species of shelf, running round the margin of the mouth of the bell, and termed the " veil " or " velum," by the presence of which the nectocalyx is distin- guished from the somewhat similar "umbrella" of the Liccer- narida. The endodermal lining of the central polypite or " manubrium " (sometimes called the " proboscis ") is pro- longed into four, sometimes more, radiating canals, which run to the periphery of the nectocalyx, where they are connected by a circular canal which runs round its circumference, the whole constituting the system of the " nectocalycine canals " (often called the " chylaqueous " or " gastro-vascular canals"). From the circumference of the nectocalyx depend marginal * The form here figured (fig. 52), though in all respects anatomically identical with the true Medusa, and originally described as such, is now known to be in reality the medusoid bud of a fixed Hydroid. It illustrates the structure and form of the Medusa, however, just as well as though it were completely independent in its development. CCELENTERATA : MEDUSID.E. 1 29 tentacles, which are usually hollow processes, composed of both ectoderm and endoderm, and in immediate connection with the canal system. Also round the circumference of the Fig- 53- — Trachynema digitale, a naked-eyed Medusa, female, enlarged. (After A. Agassiz.) p Manubrium or central polypite ; t One of the tentacles ; c One of the gastro-vascular canals ; o One of the ovaries. nectocalyx are disposed certain " marginal bodies," of which two kinds may be distinguished. Of these the first are termed " vesicles," and consist of rounded sacs lined by epithelium, and containing one or more solid, motionless concretions — apparently of carbonate of lime — immersed in a transparent fluid. The second class of marginal bodies, variously termed " pigment-spots," " eye-specks," or " ocelli," consists of little aggregations of pigment enclosed in distinct cavities. The "vesicles" are probably rudimentary organs of hearing, and possibly the eye-specks are a rudimentary form of visual ap- paratus. The oral margin of the polypite may be simple, or it may be produced into lobes, which are most frequently four in number. The essential elements of generation are produced in simple expansions either of the wall of the manubrium or of the radiating nectocalycine canals. I 130 .. MANUAL OF ZOOLOGY. ) > From the • above description it will be evident that the Medusa is in all essential respects identical in structure with the free- swimming generative bud or gonophore of many of the fixed and oceanic Hydrozoa. Indeed, a great many forms which were previously included in the Medusida, 'have now been proved to be really of this nature ; and it is only in a comparatively small number of Medusa that the direct mode of development which alone would entitle them to be ranked as independent organisms has been observed. .The Trachynemida, sEginidce, and Geryonidcz appear, however, to be directly de- veloped from the ovum, and are therefore properly placed in the present order; while we may temporarily include here a number of Medusoid forms, the development of which is at present unknown. As to the development of these true Medusidcz, little is known for certain. It appears, however, that in Trachynema, sEginopsis, and other genera, the embryo is directly developed into a form resembling its parent, without passing through any intermediate changes of form. It is hardly necessary to remark that this is not the case with the embryos of a medusiform gonophore, these being developed into the sexless Hydrozoon by which the medusoid was produced. It has also been shown that various of the true Medusa (Cunina, dZgineta, &c.), have the power of producing new forms like themselves by a process of budding, the phenomena attendant upon this being some- times of great interest. In this connection, allusion may be made to the long-known fact that certain " medusiform gonophores " are likewise capable of producing independent forms directly resembling themselves by a process of gemmation, and not by one of true reproduction. Technically these are called " tritozooids," as being derived from organisms which are themselves but the generative zooids of another being. This singular phenome- non has been observed in various medusiform gonophores (e.g., Sarsia gemmifera), the buds springing in different species from the gonocalycine canals, from the tentacles, or from the sides of the polypite or manubrium. The "naked-eyed" Medusa and their allies the "medusi- form gonophores," though mostly very diminutive in point of size, are exceedingly elegant and attractive when examined in a living condition, resembling little bells of transparent glass adorned here and there with the most brilliant colours. They occur in their proper localities and at proper seasons in the most enormous numbers. They are mostly phosphorescent, or capable of giving out light at night, and they appear to be CCELENTERATA : SIPHQNOPHORA. 131 one of the principal sources 'of the luminosity of the sea. It does not seem, however, that they phosphoresce, unless irri- tated or excited in some manner. CHAPTER IX. SIPHONOPHORA. SUB-CLASS II. SIPHON OPHORA. — The members of this sub- class constitute the so-called " Oceanic Hydrozoa ; " and are characterised by the possession of a "free and oceanic hydro- soma, consisting of several polypites united by a flexible, contrac- tile, unbranched or slightly-branched ccenosarc, the proximal end of which is usually furnished with ' nectocalyces] and is dilated into a 'somatocyst' or into a ' pneumatophore ' " (Greene). All the Siphonophora are unattached, and permanently free, and all are composite. They are singularly delicate organisms, mostly found at the surface of tropical seas, the Portuguese man-of-war (Physalia) being the most familiar member of the group. The sub class is divided into two orders — viz., the Calycophoridce. and the Physophoridce. ORDER I. CALYCOPHORIDCE. — This order includes those Siphonophora whose hydrosoma is free and oceanic, and is pro- pelled by " necto calyces " attached to its proximal end. TJie hydro- soma consists of several polypites, united by an unbranched cceno- sarc, which is highly flexible and contractile, and nei'er develops a hard cuticular layer. The proximal end of the hydrosoma is modified into a peculiar cavity called the " somatocyst" The re-> productive organs are in the form of medusiform gonophores pro- duced by budding from the peduncles of the polypites. In all the Calycophoridce the coenosarc is filiform, cylindrical, unbranched, and highly contractile, this last property being due to the presence of abundant muscular fibres. " The proximal end of the ccenosarc dilates a little, and becomes ciliated in- ternally, forming a small chamber " which communicates with the nectocalycine canals. " At its upper end this chamber is a little constricted, and so passes, by a more or less narrowed channel, into a variously-shaped sac, whose walls are directly continuous with its own, and which will henceforward be termed the somatocyst (fig. 54, 3 b). The endoderm of this sac is cili- ated, and it is generally so immensely vacuolated as almost to obliterate the internal cavity, and give the organ the appearance 132 MANUAL OF ZOOLOGY. of a cellular mass " (Huxley). The polypites in the Calyco- phoridcz often show a well-marked division into three portions, termed respectively the proximal, median, and distal divisions. Fig. 54.— Morphology of the Oceanic Hydrozoa. i. Diagram of the proximal extremity of a Physophorid; a Pneumatocyst. 2. Vogtia pentacantka, one of the Calyco- phoridce: n Nectocalyces; / Polypites; t Tentacles. 3. Diagram of a Calyco- phorid: a a! Proximal and distal nectocalyces; b Somatocyst; c Coenosarc ; d Hydrophyllium or bract; e Medusiform gonophore ; f Polypite. The dark lines in figs, i and 3 indicate the endoderm, the light line with the clear space indicates the ectoderm. (After Huxley.) Of these the " proximal" division is somewhat contracted, and forms a species of peduncle, which often carries appendages. The " median " portion is the widest, and may be termed the " gastric division," as in it the process of digestion is carried on. It is usually separated from the proximal division by a valvular inflection of the endoderm, which is known as the " pyloric valve." The polypites have only one tentacle " de- veloped near their basal or proximal ends, and provided with lateral branches ending in saccular cavities," and furnished with numerous thread-cells. The proximal ends of the poly- pites usually bear certain overlapping plates of a protective nature, which are termed " hydrophyllia " or " bracts." They are composed of processes of both ectoderm and endoderm (fig. 54, 3 d), and they always contain a diverticulum from the somatic cavity, which is called a " phyllocyst." The Calyco- phoridce always possess swimming-bells, or " nectocalyces," by the contractions of which the hydrosoma is propelled through the water (fig. 54, 2). The nectocalyx in structure is very similar to the "gonocalyx" of a medusiform gonophore, as CCELENTERATA : SIPHONOPHORA. 133 already described ; but the former is devoid of the gastric or genital sac — the " manubrium " — possessed by the latter. Each nectocalyx consists of a bell-shaped cup, attached by its base to the hydrosoma, and provided with a muscular lining in the interior of its cavity, or "nectosac." There is also always a " velum " or " veil," in the form of a membrane attached to the mouth of the nectosac round its entire margin, and leaving a central aperture. The peduncle by which the nectocalyx is attached to the hydrosoma conveys a canal from the somatic cavity which dilates into a ciliated chamber, and gives off at least four radiating canals, which proceed to the circumference of the bell, where they are united by a circular vessel ; the entire system constituting what is known as the system of the " nectocalycine canals." In the typical Calycophoridcz two nectocalyces only are present, but in some genera there are more. In Praya the two nectocalyces are so apposed to one another that a sort of canal is formed by the union of two grooves, one of which exists on the side of each nectocalyx. This chamber, which is present in a more or less complete form in all the genera, is termed the " hydrcecium," and the ccenosarc can be retracted within it for protection. The reproductive bodies in the Calycophoridcz are in the form of medusi- form gonophores, which are budded from the peduncles of the polypites, becoming, in many instances, detached to lead an independent existence. In some Calycophoridcz^ as in Abyla, "each segment of the ccenosarc, pro- vided with a polypite, its tentacle, reproductive organ, and hydrophyllium, as it acquires a certain size, becomes detached, and leads an independent life — the calyx of its reproductive organ serving it as a propulsive apparatus. In this condition it may acquire two or three times the dimensions it had when attached, and some of its parts may become wonderfully altered in form" (Huxley). To these detached reproductive portions of adult Caly- cophoridfz the term ' ' Diphyozooids " has been applied. As regards the development of the Calycophoridcz, "not only the new polypites, but the new nectocalyces and reproductive organs, and even the branches of the tentacles, are developed on the proximal side of the old ones ; so that the distal appendages are the oldest " (Huxley). The pro- cess of development is therefore the reverse of what obtains amongst the Hydroida. Diphyes (fig. 55), which may be taken as the type of the Calycophoridtt) consists of a delicate filiform coenosarc, pro- vided proximally with two large mitre- shaped nectocalyces (7;, v'\ of which one lies entirely on the distal side of the other. The pointed apex of the distal nectocalyx is received into a special cavity in the proximal nectocalyx. The "hydrcecium" (h) is formed partially by this chamber in the nectocalyx, and partially by an arched groove prolonged upon the inner surface of the distal nectocalyx, within which the ccenosarc moves 134 MANUAL OF ZOOLOGY. freely up and down, and can be entirely retracted if necessary. The upper part of the ccenosarc dilates into a small ciliated cavity, from which are given off two tubes, which proceed re- spectively to the distal and proximal necto1 calyces, where they open into the central chamber from which the nectocalycine canals take their rise. The upper portion of this small ciliated cavity is prolonged proximally into the larger chamber of the " somatocyst." The ccenosarc (c) bears polypites, each of which is protected by a delicate glassy " hydrophyllium." ORDER II. PHYSOPHORID^E. — This sec- ond order of the Oceanic Hydrozoa com- prises those Siphonophora in which the hydrosoma consists of several polypites united by a flexible, contractile, unb ranched or very slightly branched ccenosarc, the proximal ex- tremity of which is modified into a " pneuma- tophore" and is sometimes provided with " nectocalyces" The polypites have either a . single basal* tentacle, or the. tentacles arise directly from the connosarc. " Hydrophyllia " are commonly present. The reproductive bodies are developed upon gonoblastidia. The ccenosarc in the Physophoridce, like that of the Calycophoridtz, is perfectly flex- Fig. 55. — Caiycophor- ible and contractile ; but it is not neces- '1S*?$£'$$3$. sarily elongated, being sometimes spheroidal * v Proximal nectoca- or discoidal. The proximal end of the lyx : i/ Distal necto- j • i i i . calyx-; k Hydrrecium ; ccenosarc " expands into a variously-shaped ; c cce'nosarc, carrying enlargement, whose walls consist of both polypites each with its -1,1 11-1 bract and tentacle. ectoderm and endoderm, and which en- closes a wide cavity in free communica- tion with that of the ccenosarc, and, like it, full of the nutritive fluid. From the distal end, or apex, of this cavity depends a sac, variously shaped, but always with tough, strong, and elastic walls, composed of a substance which is stated to be similar to chitine in composition, and more or less completely filled with air" (Huxley). The large proximal dilatation of the ccenosarc is termed the " pneumatophore," whilst the chiti- nous air-sac which it contains is termed the " pneumatocyst " (fig. 54, i). The pneumatocyst is held in position by the reflection of the endoderm of the pneumatophore over it, and it doubtless acts as a buoy or " float." In the Portuguese CCELENTERATA : SIPHONOPHORA. 135 man-of-war (Physalia} the pneumatocyst communicates with the exterior by means of an aperture in the ectoderm of the pneumatophore. In Velella and Porpita the pneumatocyst communicates with the exterior by means of several similar openings called "stigmata;" and from its distal surface de- pend numerous slender processes containing air, and known as " pneumatic filaments." The polypites of the Physophorida resemble those of the Caly cop hor idee in shape, but the tentacles have a much more complicated structure, and are sometimes many inches in length, as in Physalia. The " hydrophyllia " have essentially the same structure as those of the former order. There occur also in the Physophorida certain peculiar bodies, termed " hydrocysts " or " feelers " (•« fiihler " and " taster " of the Ger- mans). These resemble immature polypites in shape, consist- ing of a prolongation of both ectoderm and endoderm, usually with a tentacle, and containing a diverticulum of the somatic cavity, the distal extremity being closed, and furnished with numerous large thread-cells. They are looked upon as "organs of prehension and touch," and they are somewhat analogous to the " nematophores " of the Plumularians. As regards the reproductive organs, they are developed upon special processes or "gonoblastidia," and they may re- main permanently attached, or they may be thrown off as free-swimming medusoids. In many of the Physophorida the male and female gonophores differ from one another in form and size, and they are then termed respectively "andro- phores" and " gynophores." As regards their development, the Physophoridce obey the same general law as the Calyco- phoridcz. In Physophora the hydrosoma consists of a filiform coenosarc, which bears the polypites and their appendages, and dilates proximally into a pneumatophore. Below this point the coenosarc bears a double row of nectocalyces, which are channelled on their inner faces to allow of their attachment to the coenosarc. There are no hydrophyllia, but there is a series of "hydrocysts" on the proximal side of the polypites. Physalia, or the Portuguese man-of-war (fig. 56, a) is composed of a large, bladder-like, fusiform "float" or pneumatophore — sometimes from eight to nine inches in length — upon the under surface of which are arranged a number of polypites, together with highly contractile tentacles of great length, " hydrocysts," and reproductive organs. Physalia is of common occurrence, floating at the surface of tropical seas ; and fleets of it are not uncommonly driven upon our own shores. In Velella (fig. 56, b) the hydrosoma consists of a widely-expanded pneu- matophore of a rhomboidal shape, carrying upon its upper surface a dia- gonal vertical crest. Both the horizontal disc and the vertical crest are composed of a soft marginal "limb," and a central more consistent "firm part." "To the distal surface of the firm part of the disc are attached the 136 MANUAL OF ZOOLOGY. several appendages, including — i, a single large polypite, nearly central in position ; 2, numerous small gonoblastidia, which resemble polypites, and are termed ' phyogemmaria ; ' and, 3, the reproductive bodies to which these last gi've rise. The tentacles are attached, quite independently of f >g- o^- — PhysophoridcE. garis (after Gosse). a Portuguese man - of- war (Pkysatia utriculus), showing the fusiform float and the polypites and tentacles (after Huxley) ; b Velella -vul- the polypites, in a single series along the line where the firm part and limb of the disc unite. There are no hydrocysts, nectocalyces, or hydrophyllia. . . . On all sides the limb is traversed by an anastomosing system of canals, which are ciliated, and communicate with the cavities of the phyo- gemmaria and large central polypite" (Greene). Velella is about two inches in length by one and a half in height. It is of a beautiful blue colour and semi-transparent, and it floats at the surface of the sea, with its vertical crest exposed to the wind as a sail. CCELENTERATA : LUCERNARIDA. 137 CHAPTER X. LUCERNARIDA, GRAPTOLITID^E, AND HYDROCORALLIN&. SUB-CLASS IV. LUCERNARIDA (Acalephce, in part). — The mem- bers of this sub-class may be defined as Hydrozoa " whose hydrosoma has its base developed into an l umbrella? in the walls of which the reproductive organs are produced" (Greene). A large number of forms included in the Lucernarida were described by Edward Forbes under the name of Steganophthal- mate Medusa, being in many external characters closely similar to the Medusidce. These " hidden-eyed " Medusa are familiar to every one as " sea - blubbers " or "sea-jellies," and they occur in great numbers round our coasts during the summer months. The resemblance to the little jelly-fishes is especially strong between the disc or "nectocalyx" of the true Medusidce and the " umbrella" of the Lucernarida, the latter being often a bell - shaped swimming organ, with marginal tentacles, and containing one or more polypites. These analogous struc- tures (figs. 53 and 59) are, however, distinguished as follows : i. The " umbrella" of the Lucernarida is never furnished with a " velum," as is the nectocalyx of the Medusidce. 2. The radi- ating canals in the former are never less than eight in number, and they send off numerous anastomosing branches, which join to form an intricate network ; whereas in the latter they are rarely more than four in number, and though they may subdivide, they do not anastomose. 3. In the place of the separate and unprotected " vesicles " and " ocelli " of the Medusidce, the marginal bodies of the Lucernarida consist of these bodies combined together into single organs, which are termed "lithocysts," and which are protected externally by a sort of hood. The Lucernarida admit of being divided into three orders — viz., the Lucernariadce, the Pelagidce, and the Rhizostomidce. ORDER I. LUCERNARIAD^E. — This order includes those Lu- cernarida which have only a single polypite, are fixed by a proxi- mal hydrorhiza, and possess short tentacles on the margin of the umbrella. The reproductive elements " are developed in the primi- tive hydrosoma without the intervention of free zooids " (Greene). In Lucernaria (fig. 57), which may be taken as the type of the order, the body is campanulate or cup-shaped, and is attached proximally at its smaller extremity by a hydrorhiza, 133 MANUAL OF ZOOLOGY. which, however, like that of the Hydra, is not permanently fixed. When detached, the animal is able to swim with toler- able rapidity by means of the alternate Contraction and expan- sion of the umbrella. Around the mar- gin of the umbrella are tufts of short tentacular processes, and in its centre is a polypite with a quadrangular four- lobed mouth. " In transverse section the polypite maybe described as some- what quadrilateral, with a sinuous out- line which expands at its four angles to form as many deep longitudinal folds, within which the simple genera- tive bands are lodged " (Greene). Wide longitudinal canals are formed by septa passing from the walls of the polypite to the inner surface of the cup, and a circular canal runs immediately be- neath the insertion of the tentacles. The reproductive elements are pro- duced within the body of Lucernaria itself, without the intervention of any generative zooid. ORDER II. PELAGID^E. — This order is defined as including Lucernarida which possess a single polypite only, and auricula attached an umbrella with marginal tentacles. johansptonc)e.°fsea-weed(after The reproductive elements "are'devek oped in a free umbrella, which either con-^ stitutes the primitive hydrosoma, or is produced by fission from an attached Lucernaroid " (Greene). Two types, therefore, exist in the Pelagida. The one type is represented by a fixed " trophosome," resembling Luceri naria,\)\& distinguished from it by the fact that the generative elements are not developed in the primitive hydrosoma, but in a free "gonosome," which is produced for the purpose. The second type, represented by Pelagia itself, is permanently free, thereby differing from Lucernaria; which it approaches, on the other hand, in the fact that its generative elements are pro- duced in its own umbrella without the intervention of free gen- erative zooids. Pelagia, however, differs considerably in struc- ture from Lucernaria, and in all essential characters is not anatomically separable from a Steganophthalmate Medusid. The process of reproduction as displayed in the first section of the Pelagida will be considered when treating of that of the Fig- 57- — Lucernariadae. Lu- CCELENTERATA : LUCERNARIDA. 139 Rhizostomidce, there being no important difference between the two> except as concerns the structure of the generative zooids. ORDER III. RHIZOSTOMIDCE. — The members of this order are defined as being Lucernarida in which the reproductive elements are developed in free zooids, produced by fission from attached Lucernaroids. The umbrella of the generative zoo'ids is without marginal tentacles, and the polypites are "numerous, modified, forming with the genitalia a dendriform mass depending from the umbrella " (Greene). The following is a brief summary of the life-history of a member of this extraordinary order (fig. 58), the illustration, however, representing the development of Aurelia^ one of the Fig. 58.— Development of Aurefia, one of the Lucernarida. a Ciliated free-swimming embryo, or " planula ; " b Hydra-tuba; c Hydra-tuba in which fission has consider- ably advanced, and the " Strobila" stage has been reached ; d Hydra-tuba in which the fission has proceeded still further, and a large number of the segments have been already detached fo lead an independent existence. Pelagidce, in which the phenomena are essentially the same. The embryo is a free - swimming, oblong, ciliated body, termed a " planula " (a), of a very minute size, and composed of an outer and inner layer, enclosing a central cavity. The planula soon becomes pear-shaped, and a depression is formed at its larger end. " Next, the narrower end attaches itself to some submarine body, whilst the depression at the opposite extremity, becoming deeper and deeper, at length communi- cates with the interior cavity. Thus a mouth is formed, around which may be seen four small protuberances, the rudiments of tentacula. In the interspaces of these four new tentacles arise; others in quick succession make their 140 MANUAL OF ZOOLOGY. appearance, until a circlet of numerous filiform appendages, containing thread - cells, surrounds the distal margin of the ' Hydra - tuba ' (b\ as the young organism at this stage of its career has been termed by Sir J. G. Dalyell. The mouth, in the meantime, from being a mere quadrilateral orifice, grows and lengthens itself so as to constitute a true polypite, occupying the axis of the inverted umbrella or disc, which supports the marginal tentacles. The space between the walls of the polypite and umbrella is divided into longitudinal canals, whose relations to the rest of the organism, and, indeed, the whole structure of Hydra-tuba, closely resemble what may be seen in Lucernaria " (Greene, ' Manual of Ccelenterata '). The Hydra -tuba thus constitutes the fixed " Lucernaroid," or the " trophosome " of one of the Rhizosto- midcz. In height it is less than half an inch, but it possesses the power of forming, by gemmation, large colonies, which may remain in this condition for years, the organism itself being incapable of producing the essential elements of generation. Under certain circumstances, however, reproductive zooids are produced by the following singular process (fig. 58). The Hydra-tuba becomes elongated, and becomes marked by a series of grooves or circular indentations, extending transversely across the body, from a little below the tentacles to a little above the fixed extremity. At this stage the organism was described as new by Sars, under the name " Scyphistoma" The annula- tions or constrictions go on deepening and become lobed at their margin, till the Scyphistoma assumes the aspect of a pile of saucers, arranged one upon another with their concave surfaces upwards. This stage was described by Sars under the name of " Strobila " (c). The tentacular fringe which originally surrounded the margin of the Hydra-tuba now dis- appears, and a new circlet is developed below the annulations, at a point a little above the fixed extremity of the Strobila (c). " The disc-like segments above the tentacles gradually fall off, and, swimming freely by the contractions of the lobed margin which each presents, they have been described by Eschscholtz as true Mcdusida under the name of Ephyrce (d)" Each Ephyra, however, soon shows its true nature by becoming developed into a free-swimming reproductive body, usually of large size, with umbrella, hooded lithocysts, and tentacles, constituting, in fact, a Steganophthalmate Medusa. The re- productive zooid now swims freely by the contraction of its umbrella, and it eats voraciously and increases largely in size. The essential elements of generation are then developed in special cavities in the umbrella, and the fertilised ova, when CCELENTERATA : LUCERNARIDA. 141 liberated, appear as free-swimming, ciliated "planulae," which fix themselves, become Hydra-tuba, and commence again the cycle of phenomena which we have above described. As regards the size of these reproductive zooids as compared with the organism by which they are given off, it may be men- tioned that the umbrella of Cyanea arctica has been found in one specimen to be seven feet in diameter, with tentacles more than fifty feet in length, the fixed Lucernaroid from which it was produced not being more than half an inch in height. As regards the special structure of these gigantic reproduc- tive bodies, considerable differences obtain between the Rhizo- stomida and that section of the Pelagidce in which this method of reproduction is employed. In the Pelagidce, namely, the generative zooids possess a general, though chiefly mimetic, resemblance both to the genuine Medusidce and to the free- swimming medusiform gonophores of so many of the Hydrozoa, and they have the following structure. Each (fig. 59) consists of a bell shaped, gelatin- ous disc, the "umbrella," from the roof of which is suspended a large poly- pite, the lips of which are extended into lobed pro- cesses often of considera- ble length, "the folds of which serve as temporary receptacles for the ova in the earlier stages of their development." The poly- pite — manubrium or pro- boscis— is hollowed into a digestive sac, which communicates with a cav- ity in the roof of the um- brella, from which arises a series of radiating ca- nals, the so-called "chyl- aqueous canals." These canals, which are never less than eight in number, branch freely and anasto- mose as they pass towards the periphery of the umbrella, while the entire series is con- nected by a circular marginal canal. This, in turn, sends tubular processes into the marginal tentacles, which are Fig. 59. — Hidden-eyed Medusae. Generative zooid of one of the Pelagidce (Chrysaora hyoscella), after Gosse. 142 MANUAL OF ZOOLOGY. often of great length. Besides the tentacles, the margin 01 the umbrella is furnished with a series of peculiar bodies, termed " lithocysts," each of which is protected by a sort of process or hood derived from the ectoderm, and consists essentially of a combined " vesicle " and " pigment-spot," such as have been described as occurring separately in the Medu- sidce. These marginal bodies likewise communicate with the chylaqueous canals. The reproductive elements "are lodged in sacciilar processes of the lower portion of the central cavity, immediately above the bases of the radiating canals, and being usually of some bright colour, form a conspicuous cross shining through the thickness of the disc " (Greene). By a series of elaborate experiments, Mr G. J. Romanes has shown that the contractions of the swimming-bell of the Sea- blubbers obey the same laws as the contractions of muscular tissue generally, being excitable by the same stimuli, and simi- larly affected by chemical reagents. The removal of the margin of the umbrella causes a more or less total paralysis, and the same effect is produced by the excision of the mar^ ginal bodies, showing that these parts are the seat of the energy by which the movements are effected. Moreover, the severed margin of the swimming-bell continues to contract rhythmically for a considerable time after its complete separation from the organism itself. We are therefore justified in concluding that the margin of the swimming-bell contains what is functionally, if not structurally, a nervous system, though we have at present no direct anatomical evidence to demonstrate this. In the RhizostomidcB the reproductive zooids (figs. 60, 6 1), differ from those we have just described as occuring in the first section of the Pelagidce, in not possessing tentacles on the margin of the umbrella, and in having the simple central polypite replaced by a composite dendriform process, which bears numerous polypites, projects far below the umbrella, and is thus described by Professor Huxley : " In the Rhi- zostomidce (figs. 60, 61), a complex, tree -like mass, whose branches, the ' stomatodendra,' end in, and are covered by, minute polypites, interspersed with clavate tentacula, is sus- pended from the middle of the umbrella in a very singular way. The main trunks of the dependent polypiferous tree, in fact, unite above into a thick, flat, quadrate disc, the ' synden- drium,' which is suspended by four stout pillars, the ' dendro- styles,' one springing from each angle, to four corresponding points on the under surface of the umbrella, equidistant from its centre. Under the middle of the umbrella, therefore, is a chamber, whose floor is formed by the quadrate disc, whilst its CCELENTERATA : LUCERNARIDA. 143 roof is constituted by the under wall of the central cavity of the umbrella, and its sides are open. The reproductive elements are developed within radiating folded diverticula of the root Fig. 60. — Rhizostomidae. Generative zooid of Rhizostoma (after Owen), a Umbrella; bb "Stomatodendra," covered Fig. 61. — Generative zooid of with clavate tentacles and minute polypites ; c c Anasto- Rhizostoma pulmo, reduced mosing network of canals. in size. (After Gosse.) of this genital cavity." According to other authorities, how- ever, the apparent polypites of the " stomatoderidra " are really mouth -like apertures formed by the extraordinarily complex manner in which the oral lobes are folded, and there is then in reality but one single central polypite, hanging from the under surface of the umbrella. It appears, finally, that amongst the old Pulmograde Aca- lephae, or amongst what would commonly be called Jelly-fishes, we have the following distinct sets of beings, which resemble each other more or less closely in appearance, but differ in their true nature: — 1. Free medusiform gonophores of various Corynida, Cam- panularida, and the Oceanic Hydrozoa. 2. True Medusidce, entirely resembling the former in anato- mical structure, but differing in the fact that their ova do not give rise to a fixed zooid, but to free - swimming organisms exactly like the parent hydrosoma (Trachynemida, Geryonida, and ^Lginidce). 3. Hydrozoa, which are provided with an "umbrella" (with 144 MANUAL OF ZOOLOGY. all the peculiarities belonging to this structure), but which re- produce themselves without the intervention of free generative zooids produced by fission (Pelagia). 4. The free generative zooids of most of the Pelagida, with an umbrella and a single polypite, the primitive hydrosoma being fixed and sexless (Aurelia, Cyanea, &c.) 5. The free generative zooids of the Rhizostomida, with an umbrella and a complex central tree bearing many polypites (Rhizostoma, Cephea, &c.) Of these five classes of organisms, Nos. i and 2 constitute the Gymnophthalmate Medusce of Professor E. Forbes, whilst Nos. 3, 4, and 5 are the Steganophthalmate Medusce of the same naturalist. SUB -CLASS V. GRAPTOLITID^E ( = RHABDOPHORA, Allman). — The organisms mclude^^tj^resgnl under this head are all extinct, and tliey~are"in many respects so dissimilar, and their structure is so far from being entirely understood, that it is doubtful if any definition can be framed which will include all the supposed members of the family. The following definition, however, will include all the most typical Graptolites : — Hydrosoma compound, occasionally branched, consisting of numerous polypites united by a coenosarc ; the latter being enclosed in a strong tubular polypary, whilst the former were protected by hydrothecse. In the great majority of Graptolites the hydrosoma was certainly unattached; but in some aber- rant forms — doubtfully belonging to the sub-class — there is reason to believe that the hydrosoma was fixed. The poly- pites are never separated from the ccenosarc by any partition. In many cases the hydrosoma was strengthened by a chitinous rod, the " solid axis," somewhat analogous to the chitinous rod recently described by Professor Allman in the singular Poly- zoo n Rhabdopleura. From the above definition it will be seen that the nearest living allies to the Graptolites are the Sertularians. In point of fact, if we do not insist upon the presence of a "solid axis" as part of the definition, the Grapto- lites differ from the Sertularians in no essential point, save that the hydro- soma is always attached in the latter, and was certainly free in the most typical examples of the former. Indeed, certain forms at present placed among the Graptolites — such as Ptilograptus and Dendrogi-aptus — are so similar to some living Sertularians, that it might be well to remove them altogether from the Graptolitidcz, and to regard them as extinct representa- tives of the Sertularida. As regards the value of the " solid axis " as an element in defining Grapto- lites, it is doubtful if much stress can be laid upon its presence or absence. It is true that it is present in all the most characteristic members of 'the sub-class, but it has not been proved to be present in some forms, which in other respects are quite typical members of the group. CCELENTERATA : GRAPTOLITIM!. '45 Taking such a simple Graptolite as G. priodon (fig. 62) as the type of the sub-class, the hydrosoma is found to consist of the " solid axis," the " common canal," and the " cellules." The entire poly- pary is corneous and flexible, and the solid axis is a cylindrical fibrous rod, which gives support to the entire organ- ism, and is often prolonged beyond one or both ends of the hydrosoma. There is, however, every reason for believing that the so-called "solid axis" is truly hollow. The common canal is a tube which encloses the coenosarc. and gives origin to a series of cellules, these being little cups corresponding to " hy- drothecae," and enclosing the polypites. Not only are the essential details of the structure — with the exception of the solid axis — strictly comparable with that of a Sertularian, but there is good evi- dence that the reproductive process, in some forms at any rate, was also carried on in a manner similar to what we have seen in some other Hydroida — Fig- 62._A) Graptolite namely, by generative buds or gono- phores enclosed in gonangia. ograptus) priodon, Bronn, preserved in relief — lateral view, slightly enlarged ; B, Dorsal view of a fragment of the same species — consi- derably enlarged ; C, Front view of a fragment of the same, showing the mouths of the cellules — much enlarged ; D, Transverse section of the same. All from the base of the Coniston Flags. (Orig- inal.) No Graptolite, however, has hitherto been certainly proved to have been fixed by a " hy- dro rhiza," and it is only in certain aberrant forms that there are any traces of a " hydro- caulus." Besides the simple forms of Graptolites with a row of cellules on one side (monoprionidian) (fig. 62), there are others with a row of cellules on each side (diprionidian) (fig. 63). Many other modifications are known ; but there is only another peculiarity which is worthy of notice here. This is the occurrence in several genera of a basal corneous disc or cup, which is probably the homologue of the " float "or " pneumatophore " of the Phy- sophoridae. (For distribution of Graptolites see Distribution of Hydrozoa in Time. As regards their mode of occurrence, Graptolites are usually found as glistening, pyritous impressions, with a silvery lustre. In some cases, however, they are found in relief. SUB-CLASS VI. HYDROCORALLIN^E. — This name has recently been proposed by Mr Moseley for two groups of marine ani- mals which produce a regular skeleton of carbonate of lime, K 146 MANUAL OF ZOOLOGY. often of large size, and which have been generally referred to the Corals (Actinozoa). One of these groups comprises the well-known Millepora (fig. 64), which is found contributing so largely to the formation of coral- reefs in the West Indies and Pacific. The calcareous skeleton of Millepora is mostly in the form of foliaceous or laminar expan- sions, stony in texture, with a smooth surface studded with rni- nute apertures of two sizes, the larger of these being much the fewest (fig. 64, C). The larger openings are the mouths of tubes (fig. 64, B,^/), which are divided by transverse calcareous parti- tions into a number of compait- ments, only the most superficial of these being actually tenanted by the living animal. The smaller tubes are similarly septate or "tabulate," and the general tis- sue of the skeleton (fig. 64, C) is composed of calcareous tra- beculae traversed by a series of ramifying and anastomosing coe- nosarcal canals, which place the tubes occupied by the zooids in direct communication. From the presence of transverse partitions, or " tabulae," in its tubes, Millepora was generally placed amongst the so-called "Tabulate Corals," with the typical forms of which it has no affinity. Though its skeleton is abundantly obtained in the regions where it occurs, the living animal has been rarely ob- served. The late Professor Agassiz was the first to examine Millepora in its living condition, and he was led to the conclu- sion that the genus was unequivocally referable to the Hydro- zoa. A similar conclusion has recently been reached by Mr Moseley, who had the opportunity of examining the living animal minutely. According to this observer, the colony (fig. 65) of Millepora consists of two kinds of zooids. The larger zooids, or " gastrozooids," inhabit the larger tubes of the skele- ton, and possess from four to six knobbed tentacles ; while the smaller zooids, or " dactylozooids," inhabit the smaller tubes, and are either indiscriminately mixed with the gastrozooids, or Fig. 63.— DiA nidian Grapt Mnemia, Encharis, Lesueuria. 4. Taniatie, Body ribbon-like ; no oral lobes ; two tentacles. Ex. Cestum. CHAPTER XVI. DISTRIBUTION OF ACTINOZOA. i. DISTRIBUTION OF ACTINOZOA IN SPACE. 2. CORAL-REEFS. 3. DISTRIBUTION OF ACTINOZOA IN TIME. DISTRIBUTION OF ACTINOZOA IN SPACE. — The Zoantharia malacodermata appear to have an almost cosmopolitan range, Sea-anemones being found on almost every coast ; some of the tropical forms attaining a very large size. Whilst essentially littoral and shallow-water forms, a few of the members of this group have been found by the Challenger expedition to ex- tend to great depths. Thus, as shown by Mr Moseley, Edwardsia has been found at 800 fathoms, and CeriantJms at no less than 2750 fathoms; while species of Actinia itself go down to over 1000 fathoms. A few forms also (such as ArachnactiS) Nautactis, Plotactis, Oceanactis, and Minyas) are pelagic in habit, and live in the open ocean. The Antipathidcz are principally inhabitants of warm seas ; but have been found off the coast of Greenland ; while they extend to great depths. The Alcyonidce are principally inhabitants of shallow water; but the Pennatulida extend their range up to very great depths. The Gorgonidcz are likewise mostly shallow- water forms, and they attain their maximum in the seas of the tropics. The C(ELENTERATA : ACTINOZOA. l8l Red Coral of commerce is a Mediterranean species/and occurs principally at depths of from 5 to 6 fathoms, though occurring at 120 fathoms or more. The Organ-pipe Corals (Tubipord] are confined to the warm seas of the " coral region ; " and the genus Heliopora, the only recent representative of the family H(lioporid(K> is confined to the Pacific and Indian Oceans. The only living corals referred to the Rugosa are Guynia, which is found in the Mediterranean, and the Haplophyllia of the Florida seas. The Ctenophora are pelagic, free-swimming forms, and appear to be cosmopolitan in their distribution. Lastly, the Zoantharia sclerodermata are partly inhabitants of deep water, and partly shallow-water forms; and the latter, as commonly forming " coral-reefs," are so important as to de- mand special consideration. The so-called " reef-building " corals have their distribution conditioned by the mean winter temperature of the sea, a tem- perature of not less than 66° being necessary for their existence. The seas, therefore, which possess the necessary temperature may be said to be all comprised within a distance of about 1800 miles of the equator on each side. Within these limits, however, apparently owing to the influence of arctic currents, no coral-reefs are found on the western coasts of America and Africa. They are found chiefly on the east coast of Africa, the shores of Madagascar, the Red Sea, and Persian Gulf, throughout the Indian Ocean and the whole of Polynesia, and around the West Indian Islands and the coast of Florida. The headquarters of the reef-building corals may be said to be round the islands and continents of the Pacific Ocean. A " coral-reef" is a mass of coral, sometimes many hundred miles in length, and it may be two thousand feet or more in thickness, produced by the combined growth of different species of coralligenous Actinozoa. As before said, a mean winter temperature of not less than 66° is necessary for their existence, and therefore nothing worthy of the name of a " coral-reef" is to be found in seas so far removed from the equator as to possess a lower winter temperature than the above. According to Darwin, coral-reefs may be divided into three principal forms — viz., Fringing reefs, Barrier-reefs, and Atolls, distinguished by the following characters : — i. Fringmg-reefs (fig. 91, i). — These are reefs, seldom of great size, which may either surround islands, or skirt the shores of continents. These shore-reefs have no channel of any great depth intervening between them and the land, and the soundings on their seaward margin indicate that they re- pose upon a gently sloping surface. 182 MANUAL OF ZOOLOGY. 2. Barrier reefs (fig. 91, 2). — These, like the preceding, may either encircle islands, or may skirt continents. They are dis- tinguished from fringing-reefs by the fact that they occur usu- Fig. 91. — Structure of coral-reefs, i. Fringing- reef ; 2. Barrier-reef; 3. Atoll, a Sea- level ; b Coral-reef; c Primitive land; d Portion of sea within the reef, forming a channel or lagoon. ally at a much greater distance from land, that there intervenes a channel of deep water between them and the shore, and that soundings taken close to their seaward margin indicate enor- mous depths. If the barrier-reef surround an island, it is sometimes called an "encircling barrier-reef," and it consti- tutes with its island what is called a "lagoon island." As an example of this class of reefs may be taken the great barrier-reef on the N.E. coast of Australia, the structure of which is on a perfectly colossal scale. This reef runs, with a few breaches in its continuity, for a distance of more than a thousand miles, its average distance from the shore being between twenty and thirty miles, and the depth of the inner channel being from ten to sixty fathoms, whilst the sea outside is " profoundly deep" (in some places over 1800 feet). 3. Atolls (fig. 91, 3). — These are oval or nearly circular reefs of coral, enclosing a central expanse of water or lagoon. They seldom form complete rings, the reef being usually breached by one or more openings, which are always situated on the lee- ward side, or on that side which is most completely sheltered CCELENTERATA : ACTINOZOA. 183 from the prevailing winds. In their structure they are iden- tical with " encircling barrier-reefs," and differ from these only in the fact that the lagoon which they enclose does not contain an island in its centre. If a coral-reef be observed — say a portion of an encircling barrier-reef — the following are the general phenomena which may be noticed. The general shape of the reef is triangular, presenting a steep and abrupt wall on the seaward side, and having a long and gentle slope towards the land. The outer margin of the reef is exposed to the beating of a tremendous surf, whilst the soundings taken just outside the line of breakers always indicate great depths. The longer inner slope is washed by the calm waters of the inner lagoon or channel. The reef is onlyjvery partially composed of living corals, which are found to occupy a mere strip, or zone, along the seaward margin of the reef; whilst all above this, as well as all below, is consti- tuted by dead coral, or " coral-rock." As to the method in which such a reef is produced, the fol- lowing facts have been established : — A. The coral-producing polypes cannot exjjaLaLlevels higher than extreme low water* exposure tc T tfatt sun even for a short period, provmg'Tapidly fatal. It follows from this that no coral-reef can be raised above the level of the sea by the efforts of its builders. The agency whereby reefs are raised above the surface of the sea is the denuding power of the_.br£akers which constantly fall upon their outer margins. These detach Jarge masses of dead coral, and heap them up in particular places, until an island is gradually produced. The fragments thus accumulated are compacted together by the finer detritus of the reef, and are cemented together by the percolation of water holding carbonate of lime in solution. In this way the upper surface of the reef^" along a line of greater or less breadth, is more or less completely raised above the level of high water. It is obvious, however, that the reef might be entirely de- stroyed by a continuation of this process — the sea being quite competent to undo what it had done — unless some counter- acting force were brought into play. This counteracting force is found in the vital activity of the living corals, which form the seaward margin of the reef, and which, by their growth, prevent the sea from always destroying the masses of sediment which it may have thrown up. B. The coral - producing polypes are essentially shallow- water animals, and cannot exist at depths exceeding some 15 to 30 fathoms. It follows from this that no coral-reef can be commenced upon a sea-bottom deeper than about 30 fathoms. 1 84 MANUAL OF ZOOLOGY. The question now arises— In what way have reefs been pro- duced, which, as we have seen, rise out of depths of 300 fathoms or more? This question has been answered by Darwin, who showed that the production of barrier-reefs and atolls was really to be ascribed to a gradual subsidence of the foundations upon which they rest. Thus, if a fringing-reef which surrounds an island be supposed gradually to sink be- neath the sea, the upward growth of the corals will neutralise the downward movement of the land, so far, at any rate, that the reef will appear to be stationary, whilst it is really growing upwards. The island, however, as subsidence goes on, will gradually diminish in size, and a channel will be formed be- tween it and the reef. If the depression should be still con- tinued, the island will be reduced to a mere peak in the centre of a lagoon : and the reef, from a " fringing-reef," will have become converted into an " encircling barrier-reef." As the growth of the reef is chiefly vertical, the continued depression will, of course, have produced deep water all round the reef. If the subsidence be continued still further, the central peak will 'disappear altogether, and the reef will become a more or less complete ring surrounding a central expanse of water ; thus becoming converted into an "atoll." The production, therefore, of encircling barrier-reefs and atolls is thus seen to be due to a process of subsidence of the sea-bottom. The existence, however, of fringing-reefs is only possible when the land is either slowly rising, or is stationary; and, as a matter of fact, fringing reefs are often found to be conjoined with up- raised strata of Post-tertiary age. Atolls and encircling barrier- reefs, on the other hand, are not found in the vicinity of active volcanoes— regions where geology teaches us that the land is either stationary, or is undergoing slow upheaval. C. Different portions of a coral-reef are occupied by differ- ent kinds of corals. According to Agassiz, the basement of a coral-reef is formed by a zone of massive Astraans. These cannot flourish at depths of less than six fathoms of water, and consequently when the surface of the reef has reached this level, the Astrceans cease to grow. Their place is now taken by Meandrinas (Brain-corals) and Forties ; but these, too, cannot extend above a certain level. Finally, the summit of the reef is formed by an aggregation of less massive corals, such as Madreporidce, Milleporidcz, and Gorgonida. DISTRIBUTION OF ACTINOZOA IN TIME. — With the single exception of the Mollusca, no division of the animal kingdom contributes such import- ant and numerous indications of its past existence as the Actinozoa. In the Palaeozoic rocks the majority of corals belong to the division CCELENTERATA : LITERATURE. 185 Kugosa, these seeming to have filled the place now taken by the scleroder- mic Zoantharia. Until quite recently it was believed that all the Rngosa were Palaeozoic, with the exception of the genus Holocystis, represented in the Cretaceous period (Lower Greensand) by the single species H. elegans. Recent researches, however, have brought to light the existence in our present seas of at least two genera {Haplophyllia and Gtiynia), which be- long-to the Rugose family of the Cyathaxonidce ; and certain Tertiary Rugose Corals (Conosmilid) have also been described (Martin Duncan). Of the families of the Rugosa, the Cyathophyllida and Cystiphyllida are exclusively Palaeozoic ; the Cyathaxonida are Palaeozoic, but are represented by two living genera; and the Stauridte are represented in the Silurian rocks (StaTiria), Devonian {Metriophyllum}, Permian {Polyccclia\ and in Tertiary deposits (Conosmilia). The Zoantharia sclerodermata, though attaining their maximum at the present day, nevertheless are well represented in past time, beginning in the Silurian period. The Perforata are principally represented by the Favositidce during Palaeozoic time, though other forms of this section are not unknown ; but, like the Afoi'osa, they attain a much greater develop- ment in the Mesozoic and Kainozoic deposits. The Zoantharia sderobasica are hardly known as fossils, but the Miocene deposits of Piedmont (Middle Tertiary) have yielded a species of Antipalhes. The Zoantharia malacodennata, from the soft nature of their bodies, are obviously incapable of leaving any traces of their existence ; though we are by no means therefore justified in asserting that they did not exist in past geological epochs. With the reference of the Helioporidce to the Alcyonaria, the range of this order has been enormously increased in past time. Formerly no ex- ample of the order was known as occurring in any Palaeozoic stratum, the so-called Protovirgularia of the Lower Silurian being probably a Graptolite. Now we know of various abundantly distributed Alcyonarian corals in the Palaeozoic rocks, the most important being the Heliolites of the Silurian and Devonian. The allied genus Polytremacis is Cretaceous. Of the Gorgonidce two genera (Mopsea and Websteria) are found in the Eocene ; and the genus Corallium, doubtfully quoted from the Jurassic and Creta- ceous, is found in the Miocene, which has likewise yielded examples of his, Gorgonia, &c. The Pennatulidce commence in the Eocene, with Graph- ularia. The Tubiporidce (unless the Palaeozoic Syringoporida be referred here) are unknown as fossils, and the Alcyonidce are not known to occur till the Pliocene is reached. The Ctenophora, being wholly destitute of hard structures, are not known at all as occurring in the fossil condition. LITERATURE. GENERAL WORKS. 1. " Manuel d'Actinologie et de Zoophytologie." De Blainville. 1834-37. 2. " Klassen und Ordnungen des Thier-Reichs," vol. ii. ' Strahlenthiere.' Bronn. 1859-60. 3. " Manual of the Coelenterata." Greene. 1861. 4. "Essay towards a Natural History of Corallines." Ellis. 1775- 5. "Die Pflanzen-Thiere in Abbildungen." Esper. 1788-1830. 6. " Histoire des Animaux sans Vertebres," vol. ii. Lamarck. (Ed. 2, 1836.) 7. " History of British Zoophytes." Johnston. 1847. 8. " Manual of Marine Zooloq-y for the British Isles." Gosse. 1855. 1 86 MANUAL OF ZOOLOGY. 9. " Beitrage zur Kenntniss Wirbelloser Thiere." Frey and Leuckart. 1847. 10. " Icones Histlologicse." Abth. ii. 'Die Binde - Substance der Coelenteraten. ' Kolliker. 1866. 11. " Histoire Naturelle des Coralliaires ou Polypes proprement dits." Milne-Edwards and Haime. 1855-60. 12. "Zoophytes." ' Report of Exploring Expedition under. Capt. Wilkes.' Dana. 1848. 13. " On the Alternation of Generations." Steenstrup. (Eng. Trans, by Busk.) 1845. 14. " Contributions to the Natural History of the United States." (Aca- lephse, vols. iii and iv.) Louis Agassiz. 1860-62. A. HYDROZOA. I. HYDRIDA. 15. " Memoires pour servir a 1'histoire d'un genre de Polypes d'eau douce, a bras en forme de cornes. " Trembley. 1 744. 16. " Hydra, ein anatomisch entwickelungs-geschichtliche Untersuchung. " Kleinenberg. 1872. II. CORYNIDA, SERTULARIDA, AND CAMPANULARIDA. 17. "Monograph of the Gymnoblastic or Tubularian Hydroids." 'Ray Society.' Allman. 1871. (The first part of this work comprises an elaborate account of the Hydroida generally.) 18. " British Hydroid Zoophytes." Hincks. 1872. 19. " Recherches sur la Faune littorale de Belgique." (Polypes.) Van Beneden. 1866. 20. "Contributions to the Natural History of the United States." (Acalephae.) Louis Agassiz. 1860-62. 21. " North American Acalephse." ' Illust. Catalogue Mus. Comp. Zool.' No. ii. (Hydroida, pp. 64-198.) A. Agassiz. 1865. 22. "Report on the Hydroida of the Gulf- Stream." 'Memoirs of the Museum of Comparative Zoology at Harvard.' Allman. 1877. III. OCEANIC HYDROZOA. 23. "Monograph of the Oceanic Hydrozoa." ' Ray Society.' (With a general introduction.) Huxley. 1859. 24. "Die Siphonophoren oder Schwimm-polypen von Messina." Kolliker. 1853- 25. "Siphonophoren von Nizza." ' Zoologische Untersuchungen,' ii. Leuckart. 1853. IV. MEDUSID.E AND LUCERNARIDA. [The works quoted under this section deal not only with the above-men- tioned groups as here understood, but also largely with the Medusoid Gonophores of other Hydrozoa.] 26. " System der Acalephen." Eschscholtz. 1829. 27. "Die Akalephen des Rothen Meeres," &c. Ehrenberg. 1836. 28. "Acalephes." (' Suites a Buffon. ') Lesson. 1843. 29. "Monograph of the British Naked-Eyed Medusae." 'Ray Society.' Edward Forbes. 1848. 30. "Anatomy and Affinities of the Family of the Medusae." 'Phil. Trans.' Huxley. 1849. COELENTERATA : LITERATURE. l8/ 31. " Der Generation - Wechsel und die Fortpflanzung der Medusen." Gegenbaur. 1854. 32. " Versuch eines Systems der Medusen." ' Siebold and Kolliker's Zeitschrift, ' 1857. Gegenbaur. 33. "Contributions to the Natural History of the United States." (Acalephae, vols. ii. and iii.) Louis Agassiz. 1860-62. 34. "North American Acalephce." '111. Cat. Mus. Comp. Zool.,' ii. A Agassiz. 1865. . 35. "Monograph of the Gymnoblastic or Tubularian Hydroids." 'Ray Society.' Allman. 1871. 36. " Ueber eine neue Form des Generation- wechsel's, bei den Medusen," &c. ' Monatsbericht der Kon. Akad. der Wiss. Berlin,' 1865. (Trans. Annals of Nat. Hist., 1865.) Haeckel. 37. " Beitrage zur Naturgeschichte der Hydromedusen. " Haeckel. 1865. 38. " Studien liber die Entwickelung der Medusen." 'Siebold and Kolliker's Zeitschrift,' 1874. Metschnikoff. 39. "Life- Histories of Animals." Packard. 1875. V. GRAPTOLITID^. 40. " Graptolites de Boheme." Barrande. 1850. 41. " Ueber Graptolithen." Scharenberg. 1851. 42. "Die Graptolithen." ' Versteinerungen der Grauwacken-formation.' Geinitz. 1852. 43. " Graptolites of the Quebec Series. " ' Descript. of Canadian Organic Remains.' Decade ii. Hall. 1865. 44. " British Graptolites. " ' Siluria,' 4th Edition, Appendix. Carruthers. 1867. 45. "Monograph of the British Graptolitidoe." Part i., General Intro- duction. Nicholson. 1872. 46. "Morphology and Affinities of Graptolites." 'Annals Nat. Hist.,' 1872. Allman. VI. HYDROCORALLIN^. 47. " Contributions to the Natural History of the United States. " Louis Agassiz. (The animal of Millepora is figured, vol. ii., pi. xv., and the genus is referred to the Hydrozoa. ) 48. " Grundziige der Zoologie." Clans. 1874. 49. "Observations critiques sur la classification des Polypiers paleo- zoiques." Compt. Rend. t. Ixxx., 1875. Dollfus. 50. "Notes on Two Species of Millepora," &c. 'Phil. Trans.,' 1876. Moseley. (This memoir also contains a note on the structure of a Stylaster.) 51. " Structure of a Species of Millepora occurring at Tahiti." ' Annals Nat. Hist.,' 1876. Moseley. 52. " Preliminary Note on the Structure of the Stylasteridae." ' Annals Nat. Hist.,' 1877. Moseley. 53. " On the Actinozoan Nature of Millepora alcicornis." ' Annals Nat. Hist.,' 1876. Nelson and Martin Duncan. 54. "On the Structure of the Stylasteridas." ''Phil. Trans.,' 1878. Moseley. 1 88 MANUAL OF ZOOLOGY. B. ACTINOZOA. I. ZOANTHARIA. 55. " Actinologia Britannica." Gosse. 1860. 56. " Ueber die Polypen im Allgemeinen und die Actinien insbesondere. " Rapp. 1829. 57. "Memoire sur les Edwardsies." 'Ann. Sci. Nat.,' 1842. Quatre- fages. 58. " Memoire sur le Cerianthe." 'Ann. Sci. Nat.,' 1854. Haime. 59. " Structure of Actiniae and Corals." ' Sitzungsbericht Oberhess. Gesellsch. fur Natur. und Heilkunde,' 1871. Schneider and Rotteken. 60. "Edwardsia." ' Quart. Journ. Micr. Sci., 'vol. Ixii. Allman. 61. " On some New Forms of Actiniaria, dredged in the Deep Sea, with a description of certain Pelagic Surface-swimming Species." 'Trans. Linn. Soc.,' ser. 2, vol. i.. 1877. Mqseley. 62. " Report on Zoophytes" (with Atlas). ' U.S. Exploring Exped. under Wilkes.' Dana. 1849. 63. "Corals and Coral-Islands." Dana. 1872. 64. " Histoire Naturelle des Coralliaires ou Polypes proprement dits." Milne-Edwards and Haime. 1857-60. 65. " Beitrage zur physiologischen Kenntniss der Corallenthiere im Allge- meinen, und besonders des Rothen Meeres." ' Abh. k. Akad. Wiss. Berlin,' 1834. Ehrenberg. 66. " Developpment des Coralliaires." 'Archives de Zool. Experiment.,' 1872-73. Lacaze-Duthiers. 67. "Corals." 'Encyclopaedia Brit.' 9th ed., vol. vi., 1877. Nicholson. 68. " On the Structure and Distribution of Coral-Reefs." Darwin. 1874. (2ded.) 69. " Ueber die Natur und Bildung der Corallen-inseln und Corallenbanke im Rothen Meere." 'Abh. Kon. Akad. Wiss. Berlin,' 1834. Ehrenberg. 70. " Polypiers Fossiles des Terrains Paleozoiques. " Milne-Edwards and Haime. 71. "Monograph of the British Fossil Corals." ' Palaeontographical Society.' Milne-Edwards and Haime. 72. "British Fossil Corals." (Supplement to the preceding.) ' Palaeon- tographical Society.' Martin Duncan. 73. " Introduction a 1'etude des polypiers fossiles." Fromentel. 1858-61. 74. " Reports on the British Fossil Corals." ' Rep. Brit. Assoc,,' 1869-71. Martin Duncan. 75. "Deep-sea Corals." ' Illust. Cat. Mus. Comp. Zoology,' No. IV. Pourtales. 1871. 76. " On the Affinities of the Palaeozoic Tabulate Corals with Existing Species." ' Amer. Journ. Sci. and Art.,' 1872. Verrill. 77. "On the Structure and Affinities of the 'Tabulate Corals' of the Palaeozoic Period." 1879. Nicholson. II. ALCYONARIA. [Various works previously quoted are largely concerned with the Alcyo- naria, such as Nos. 62, 63, and 64 ; but the following additional works may be noted : — ] CCELENTERATA : LITERATURE. 189 78. " Anatomisch-SystematischeBeschreibungder Alcyonarien. " Kolliker. 1870. 79. " On the Structure and Relations of the Alcyonarian Heliopora ceerulea," &c. 'Phil. Trans.,' vol. 166, 1876. Moseley. 80. " Histoire Naturelle du Corail. " ' Archives Zool. Exper.,' 1872-73. Lacaze-Duthiers. III. RUGOSA. [The Jtttgosa are extensively, or even monographically, treated of in various works already quoted — e.g., Nos. 64, 70, 71, 74; but a few addi- tional sources of information may be indicated.] 81. " Monographic der Sclerodermata Rugosaausder Silur-formation Est- lands," &c. Dybowski. 1873. 82. " Beitrage zur Kenntniss Fossiler Korallen." Kunth. 1870. 83. " Guynia and Haplophyllia." ' Phil. Trans.,' 1872. Martin Duncan. IV. CTENOPHORA. [Apart from special papers, only one or two of which can be noted here, the Ctenophora are treated of in many of the works previously referred to, especially in Nos. 2, 3, 14, 21, 23.] 84. " Studien iiber Organisation und Systematik der Ctenophoren." ' Wiegm. Arch.,' 1856. Gegenbaur. 85. " Entwickelungs-geschichte der Rippenquallen. " 'Mem. Acad. St Petersburg,' x., No. 4. Kowalewsky. 1866. 86. " Embryology of the Ctenophorae." 'Mem. Amer. Acad. Arts and Sci.,' 1874. A. Agassiz. 87. " Zoologische Studien auf Capri. " Eimer. 1873. 190 ECHINODERMA TA. CHAPTER XVII. ECHINODERMA TA. THE Echinodermata, including the Sea-urchins, Star-fishes, Sea- cucumbers, &c., form a very distinctly circumscribed group of the animal kingdom, and were formerly included in the old sub-kingdom Radiata. To Professor Huxley is due the credit of having first pointed out that the Echinoderms possess cer- tain remarkable affinities with the lower Worms, and especially with those " Scolecids " which constitute the order of the Turbel- laria. So well marked are these affinities that the above-men- tioned eminent zoologist at one time proposed to unite the Echinodermata with the Scolecida, to form a common division, or sub-kingdom, under the name of Annuloida; and there are many aspects in which this arrangement presents itself as a highly convenient one. The progress of modern Zoology has, however, shown that it is not possible to establish rigidly defined primary divisions of the animal kingdom ; but that any such divisions must inevitably be more or less artificial, as including certain inosculating forms which lead by a more or less insensible gradation into neighbouring groups. Thus, in the group now in question, while there can be no doubt as to the affinities which subsist between the Echinodermata and the Scolecida, the latter, in turn, exhibit strong points of relation- ship with the lower Annulosa. While, therefore, we must not fail to recognise the points of resemblance between the Echino- derms and the Scolecids, it seems, upon the whole, best to separate the Echinodermata as a distinct primary division or " sub-kingdom," and to regard the Scolecida as a special section of the sub-kingdom Annulosa. The Echinodermata may be defined as follows : — Simple marine organisms, the body of the adult more or less conspicuously radiate, that of the young often distinctly bilateral. ECHINODERMATA. igi An alimentary canal, with or without a distinct anus, but never communicating with the body-cavity. The water-vascular (ambu- lacral] system\often subserving locomotion. Nervous system radi- ate, composed\of an cesophageal ring and radiating branches. Sexes generally distinct, rarely united. The members of this class are known commonly as Sea- urchins, Star-fishes, Brittle-stars, Feather-stars, Sea-lilies, Sea- cucumbers, &c. ; and though the fully-grown animal often ex- hibits distinct traces of bilaterality, this is usually more or less completely masked by the general radiate arrangement of the parts of the body. On the other hand, the embryonic Echino derm usually shows distinct bilateral symmetry. The outer layer of the general integument (" perisome ") is ciliated, and the inner layer is more or less hardened by the deposition of carbonate of lime in the form of plates, granules, or spicules. In all adult Echinoderms there is a system of tubes, termed the "am- bulacra! system," which generally subserves locomotion, and usually communicates with the exterior. This water-vascular system surrounds the commencement of the alimentary canal, and in almost all cases gives off secondary vessels in a radiating manner. An alimentary canal is always present, and is com- pletely shut off from the body- cavity. A vascular (pseudo- haemal?) system is generally developed in addition to the true -water -vessels. The nervous system in all the adult Echino- derms is a ring-like, usually gangliated cord, which surrounds the oesophagus and sends branches parallel to the radiating ambulacral canals. The process of development is sometimes direct ; but in the typical members of the class a characteristic form of metamor- phosis occurs. The impregnated ovum gives exit to an ovoid embryo or "planula," freely locomotive by means of cilia, which are at first diffused over the body, but which soon be- comes restricted to transverse bands, or to definite outgrowths of the body (" epaulettes ") which are disposed with bilateral symmetry. The larva or " pseudembryo " (fig. 92) next de- velops an alimentary canal, with a distinct mouth and anus, dividing the embryonic body into two bilaterally symmetrical halves. A mass of actively formative protoplasm now appears on one side of the stomach, within which are developed a circular and radial tubes, the whole being the rudiment of the ambulacral system of the future Echinoderm. A symmetrical calcareous skeleton, not converted into that of the adult, may be developed in the larva (as in the Echinoids and Ophiu- roids), or it may be wanting (as in the Asteroids and Holo- thuroids). The mass of protoplasm, above mentioned as MANUAL OF ZOOLOGY. developed on one side of the stomach, rapidly increases in size, envelops the stomach, which it appropriates, and is ulti- mately converted into the adult Echinoderm ; the remainder of the larva being absorbed or cast off as useless. The essential peculiarity of the development of the typical Echinoderms, as above summarised, is that the larva possesses provisional organs, which may be ultimately absorbed or thrown off, but which are not converted into the cor- responding structures of the adult. Thus the larva of an Eehinoid (fig. 92) possesses a mouth and alimentary ca- nal, which are not converted into, 'and in no way corre- spond with, the mouth and alimentary canal of the adult. The larva, or " pseudem- bryo," as it is termed by Sir Wyville Thomson, leads a perfectly independent exist- ence, and the true Echino- derm is produced from it by Fig. 92.-Larva of Echinus (after J. Muller). a prOCCSS of internal budding A A, Front arms with their internal skele- or rearrangement, ton; F F, Arms of the mouth-process; B, /-,- »,r • ,, rpi \ Posterior side-arm; a Mouth; a' CEsopha- Sir WyVllle ThomSOll has, gus; 3 stomach; v intestine \d ciliated further, shown that there are bands ; ff Ciliated epaulets ; c Disc of the future Echinus. various cases amongst the Echinoidea, Asteroidea, Ophi- uroidea, and Holothuroidea, in which the young are developed directly from the egg, without the intervention of a locomotive pseudembryo. In these cases, the eggs are hatched, and the young are brought up, " within or upon the body of the parent, and are retained in a kind of commensal connection with her until they are sufficiently grown to fend for themselves." There is no sort of organic connection in these cases between the young and the parent ; but the young are often brought up in a special receptacle upon the exterior of the mother, to which the appropriate name of the " marsupium " has been given. This viviparous mode of reproduction seems to obtain specially among the Echinoderms of the cold northern and southern seas. The Echinodermata are divided into seven orders — viz., the Crinoidea, Cystoidea, Blastoidea, Ophiuroidea, Asteroidea, Echi- ECHINODERMATA : ECHINOIDEA. 193 noidea, and Holothuroidea. Of these, the first is to a consider- able extent extinct, and the two next are entirely so ; they are really the lowest orders ; but their structure will be better understood if the higher orders are considered first. CHAPTER XVIII. ECHINOIDEA. ORDER ECHINOIDEA. — The members of this order — commonly known as Sea-urchins — are characterised by the possession of a subglobose, discoidal, or depressed body, encased in a "test" or shell, which is composed of numerous, usually immovably con- nected, calcareous plates. The intestine is convoluted, and there is a distinct anus. The sexes are distinct, and the larva is plutei- form, and has a calcareous skeleton. * As regards their general anatomy, the " test " of the Echinoidea is composed of numer- ous calcareous plates,*/ which are generally firmly united to one another by their edges, in such a manner that the body of the animal is enclosed in an immovable box. In the singu- lar Urchins, however, which constitute the family of the Echi- nothuridce, the plates of the test overlap one another in an imbricating manner, so that the shell becomes quite flexible ; and the same is the case with some of the Palaeozoic Echinoids. In all living Sea-urchins, and in the great majority of the ex- tinct forms, the test is composed of twenty meridional rows of plates, arranged in ten alternating zones (fig. 93, A), which typically pass from one pole of the shell to the other, and each of which is composed of two similar rows of plates. Five of these double rows are composed of large plates, which are not perforated by any apertures (fig. 93, A and B, ct}\ the zones formed by these imperforate plates being termed the " inter - ambulacral areas." The other five double rows of plates alternate regularly with the former, and are termed the "ambulacral areas," or "poriferous zones." Each of these zones (fig. 93, A and B, /) is composed of two rows of small plates, which are perforated by minute apertures for the emis- sion of the " ambulacral tubes, " or " tube-feet." In one great * The skeleton of the Echinoids is composed of calcined areolar or connective tissue, the fibres of which enclose oval or rounded meshes (fig. 96, B), exhibiting under the microscope an exceedingly characteristic appearance. N 194 MANUAL OF ZOOLOGY. group of the Echinoids, the ambulacral areas pass from the centre of the base of the shell to its summit, when they are said to be " perfect " (ambulacra perfecta) or " simple." In 3. — Morphology of Echinoidea. A, Young specimen of Strongylocentrotus '.iensis, viewed from above. B, Small portion of the test of the same, magni- fied. C, Summit of the test of Echinus sph&ra, magnified. D, Clypeaster subde- pressus, viewed from above, showing the petaloid ambulacra. E, Spine of Poroci- daris purpurata. F, Pedicellaria of Toxopneustes lividus. ct a Ambulacral areas ; i i Inter-ambulacral areas ; g Genital plate ; o Ocular plate ; m Madreporiform tubercle ; p Membrane surrounding the anus. (Figs. A, B, and D are after A. Agassiz.) another great group the ambulacral areas are not thus con- tinuous from pole to pole, but simply form a kind of rosette upon the upper surface of the shell. In these cases — as in the common Heart - urchins — the ambulacral zones are said to be " circumscript " (ambulacra circumscriptd] or "petaloid" (fig. 93, D). Growth of the test is carried on by additions made to the edge of each individual plate, by means of an organised membrane which passes between the sutures where the plates come into contact with one another. The plates of the test are studded with large tubercles, which are more numerous on the inter- ambulacral areas than on the ambu- lacral (fig. 93, B). These tubercles carry spines (fig. 93, E, and fig. 94) used defensively and in locomotion, which are articulated to their apices by means of a sort of " universal " ECHINODERMATA : ECHINOIDEA. 195 or " ball-and-socket" joint. Occasionally a small ligamentous band passes between the head of the tubercle and the centre of the concave articular surface of the spine, thus closely Fig, 94. — Cidaris papillata. (After Gosse.) resembling the "round ligament" of the hip-joint of man. Besides the main rows of plates just described, forming the so-called " corona," other calcareous pieces go to make up the test of an Echinus. The mouth is surrounded by a coriaceous peristomial membrane, which contains a series of small cal- careous pieces, known as the " oral plates ; " whilst a corre- sponding series of "anal plates" is found in the membrane (fig. 93, C, /) surrounding the opposite termination of the alimentary canal. Surrounding the aperture of the anus at the summit of the test is the " apical disc," composed of the so-called genital and ocular plates (fig. 93, C). The "genital plates " are five large plates of a pentagonal form, each of which is perforated by the duct of an ovary or testis. One of the genital plates is larger than the others, and supports a spongy tubercle, perforated by many minute apertures, like the rose of a watering-pot, and termed the " madreporiform tubercle" (fig. 93, C, m). In some cases, this tubercle is not connected with one of the genital plates, but is placed in the centre of the apical disc. The genital plates occupy the summits of the inter-ambulacral areas. Wedged in between the genital plates, and occupying the summits of the ambulacral areas, are five smaller, heart - shaped, or pentagonal plates, known as the " ocular plates," each being perforated by a pore for the reception of an " ocellus " or " eye." (The existence of an eye-spot is denied by high authorities.) \'/> M,\\r,,v.f, r,f /OOLOGY. the spines, which are sometimes of a very great length, the test Dears curious little appendages, called " pedi- :'ig. 93, F), and originally supposed to be parasitic. of these consists of a stem, bearing two or three, some- times four, blades or claws, which snap together and close upon foreign objects like the beak of a bird. Their action appears to be independent of the will of the animal, and their ;nction is not known ; but they may be regarded as peculiarly modified spines. One function performed by the pedicellari?e, in some species at any rate, is the removal of uentitious particles of food. Such particles, on being ejected from the vent, are seized by the pedicellariae, passed on from one to another, and ultimately entirely got rid of. In almost all recent Urchins, the test also carries, as shown by I, oven, curious stalked appendages, with button-like heads <(>vcrf(\ with cilia. These so-called " sphaeridia " are supposed to be organs of sense— probably of taste. Locomotion in the Echinoidea is effected by means of a '.menhir system of contractile and retractile tubes, which constitute the "ambulacra! tubes," or "tube-feet," and are 'ted with the "ambulac.ral system" of aquiferous canals (fig. 95). From the perforated " madreporiform tubercle " on rgtft of the genital plates, there proceeds a membranous canal, known as the "stone" or "sand canal " (s\ whereby water is conveyed from the exterior to a circular tube (r) sur- rounding the (f:r;ophavu<,, ;md constituting the centre of the wa NT -vascular or ambulacra! .system. The function of the tiiadi'-poriform tubercle (ni) appears to be that of permitting the ingress of water from the exterior, but of excluding any solid parhf Irs whirh might be injurious; and as its area is much larger than that of the stone-canal, it admits sea-water not only to the ambulacra! vessels, but also to the body-cavity. It .h'.nl'l !>•• .ifldrd, however, that the admission of water to ill'- I .ody cavity through tin: madH-poric tubercle is denied by Perrier. The "circular canal" (r) surrounding the gullet is itn .ted between the nervous and blood- vascular rings, and k'ivrs off five branches — the "radiating canals" — which pro- • .'.::.'.''.:. .:-. ^~~~.~.~i. die tube-feet being capable of protrusion to a length lEPCSttd* tfKlFl f fr^fTt OK toO longest spines of die body. The mechanism by which the tube-feet are protruded and retracted is as follows : Each tube foot, shortly after its origin, gives rise to a secondary lateral branch, which terminates in a vesi- cle. These vesicles or "am- puH3ew (D) are provided with circular muscular fibres, by the contraction of which their contained fluid is forc- ed into the tube-feet, which are thus protruded. Retrac- tion of the ambulacra! tubes is effected by proper mns- UK i: :lit ^.ll ::' Pofian s. Only die sack are shown tobe4eet(/X with their * of four of the and a few of cular fibres of their own, which expd again the fluid which has been forced into them by the vesicles. The walls of the stone-canal are strengthened by calcareous deposits ; and die termina- tions of the tube-feet con- tain in many forms a cal- careous rosette, often with a calcareous ring below it, whilst the walls of the tube-feet are furnished with calcareous spicules. The total area over which the tube-feet can be protruded depends upon the extent to which the "ambulacra!" or " pori- ferous " zones of the test are developed. In the typical or " Regular " Sea-urchins, the ambulacra! areas are "perfect," and extend from pole to pole; whereas in the so-called "Irregular" Urchins (such as the Heart-urchins and Cake- side of one of the radiating canals. 198 MANUAL OF ZOOLOGY. urchins), they are " interrupted," being restricted to the summit of the test, and usually being broad and petaloid (fig. 93, D). As regards the digestive system, the mouth is typically situated in the centre of the base ; but it may be excentric ; and in one singular living form (Leskia) it is protected by valvular calcareous plates. Some forms have the mouth tooth- less, but others possess a complicated masticating apparatus. In Echinus this consists of five long, calcareous, rod-like teeth, which perforate five triangular pyramids, the whole forming a singular structure, known as " Aristotle's Lantern " (fig. 96, C). Fig. 96. — A, The masticatory apparatus of an Echinoid (Toxopneustes lividns), viewed from above, with part of the alimentary canal attached to it : a (Esophagus ; b Heart, with the sand-canal (c) in a groove on one side ; */The summit of the masti- catory apparatus, with some of the muscles (e) of the same. B, Minute structure of one of the plates of the test of an Echinus (greatly magnified), showing the calci- fied areolar tissue. C, The masticatory apparatus of Sphcerechinus esculentus, viewed from the inside and laterally, as seen in place : ff Peristomial margin of the corona ; gg Two of the radiating ambulacral vessels, with their rows of ampullae. The mouth conducts by a pharynx and a tortuous oesophagus to a stomach, opening into a convoluted intestine, which winds round the interior of the shell, and terminates in a distinct anus. The mouth is always situated at the base of the test, and may be central, subcentral, or altogether excentric in position. The anus varies considerably in its position, being usually situated within the apical disc, and surrounded by the genital and ocular plates, when the test is said to be ECHINODERMATA : ECHINOIDEA. 199 "regular." Sometimes, however, the anal aperture is with- out the apical disc, and is removed to some distance from the genital plates, when the test is said to be "irregular." In this last case, the anus, instead of being apical, is marginal or submarginal. The convolutions of the alimentary canal are attached to the interior of the test by a delicate mesentery ; the surface of which, as well as that of the lining-membrane of the shell, is richly ciliated, and subserves the purposes of respiration. The proper blood-vascular system (fig. 96 A, b) consists of a central fusiform, contractile vesicle, or heart. This gives off one vessel which forms a ring round the intestine near the anus, and another which passes downwards, and forms a circle round the gullet, above the " circular canal " of the ambulacral system. From the anal vessel proceed five arterial branches, which run along the ambulacral spaces, and return their blood by five branches, which run alongside of them in an opposite direction. This system of vessels is not always present, and its true nature is doubtful. High authorities regard it as rather comparable to the " pseudohagmal " system of the Annelides, than to the blood-system of the higher animals ; while eminent observers maintain that the so-called heart is really of a gland- ular nature. The nervous system consists of a ganglionated circular cord, which surrounds the gullet below, or superficial to, the " cir- cular canal " of the ambulacral system, and which sends five branches along the ambulacral spaces, in company with the radiating ambulacral canals. The process of respiration is carried on partly by arborescent gill-like organs placed round the mouth, which are of the nature of greatly developed tube-feet, and which are not uni- versally present ; partly by the tube-feet and their secondary vesicles in general ; and partly by the vascular lining of the test and the mesentery. The sea- water is admitted to the body-cavity principally through the " madreporiform tubercle," only a portion of the area of this being occupied by the stone- canal; though, as previously remarked, recent observations would go to show that this view is incorrect. The sexes are distinct in all the Echinoidea, and the repro- ductive organs are in the form of five membranous sacs, which occupy the inter-ambulacral areas, and open on the exterior by means of the apertures in the genital plates. In the " irregular " Echinoids (such as the " Heart-urchins ") there are only four genital glands, and therefore only four genital plates in the apical disc. 200 MANUAL OF ZOOLOGY. As regards their development, most of the Echinoids pass through a metamorphosis, as spoken of previously in treating of the development of the class. In these cases the larva is so unlike the adult animal that it was originally described as a distinct animal under the name of Pluteus, from- its resem- blance to a painter's easel (fig. 92). The larva exhibits bila- teral symmetry, and is furnished with provisional organs in the shape of ciliated epaulettes, a skeleton of calcareous rods, and an alimentary canal. The adult Echinoid is developed out of a portion of its substance only; and the rest of the larva is absorbed or thrown off. In some Echinoids, on the other hand, as we have seen, the process of development is direct, and there is no " Pluteus " stage, but the young animal is produced viviparously, and simply requires to grow to be converted into the adult. The typical Sea-urchins are divided into the two great groups of the " Irregular " and " Regular " Echinoids (or the -Echinoi- dea exocyclica and Echinoidea endocyclica). The Irregular Echin- oids have the anus situated outside the apical disc, marginal or submarginal in position, and have only four genital plates. They are also mostly destitute of a masticatory apparatus ; and are generally of an oblong, pentagonal, heart-shaped, or dis- coidal figure (as in the common " Heart-urchins " and " Cake- urchins"). The "Regular" Echinoids, on the other hand, have the anus placed at the summit of the test, surrounded by the genital disc; the test is almost always circular or sphe- roidal ; and the mouth is armed with a complicated mastica- tory apparatus. Another singular group is that of the EchinothuridcB, in which the test is "regular," but the plates of both the ambulacral and inter-ambulacral areas are imbricated and overlap one another, rendering the test quite flexible. The existing genera, Asthe- nosoma (or Calveria) and Phormosoma, and the Cretaceous genus Echinothuria belong to this group. A fourth group of the Echinoids is that of the Perischoechi- nida, which is not only extinct, but is wholly confined to the Palaeozoic period. In all these ancient forms there is the pecu- liarity that the test consists of more than twenty rows of plates, there being a multiplication of either the inter-ambulacral or the ambulacral plates, though there are still only five inter- ambulacral and five ambulacral areas. Thus in Archceodaaris, Paltzchinus, Lepidechinus, and Eocidaris, the ambulacral areas agree with those of the recent Urchins in being composed of only two rows of plates ; whilst there are from three to eight or more rows of plates in each inter-ambulacral area. On ECHINODERMATA : ASTEROIDEA. 2OI the other hand, in Melonites and OHgoponis, the ambulacral areas consist, respectively, of ten and four rows of plates. In some of the Peris choechinidce the plates of the test are joined by their edges, as in the common living Urchins ; but in others (e. g., Lepidechimis] the plates overlap in an imbricating man- ner, as in the recent Echinothuridce, and the test thus becomes flexible. CHAPTER XIX. ASTEROIDEA AND OPHIUROIDEA. ORDER ASTEROIDEA (Stelleridd}. — This order comprises the ordinary Star-fishes, and is defined by the following characters : Fig- 97-— The common Star-fish ( Uraster rubens), natural size, viewed from above. — The body (fig. 97) is star-shaped or pentagonal, and consists of a central body or " disc" surrounded by five or more lobes or 202 MANUAL OF ZOOLOGY. " arms" which radiate, from the body, are hollow, and contain prolongations of the viscera. The body is not enclosed in an immovable box, as in the Echinoidea, but the integument ("peri- some"} is coriaceous, and is strengthened by irregular calcareous plates, or studded by calcareous spines. No dental apparatus is present. The mouth is inferior, and central in position ; the anus either absent or dorsal. The ambulacral ttibe-feet are protruded .from grooves on the under surface of the rays. The larva is vermiform, and has no pseud embryonic skeleton. The skeleton of the Asteroidea is composed of a vast number of small calcareous plates, or ossicula, united together by the coriaceous perisome, so as to form a species of chain-armour. Besides these, the integument is abundantly supplied with spines, tubercles, and " pedicellarias." Lastly, the radiating ambulacral vessels run underneath a species of internal skele- ton, occupying the axis of each arm, and composed of a great number of bilateral "vertebral ossicles" or calcareous plates, which are rnovably articulated to one another, and are provided with special muscles by which they can be brought together or drawn apart. The upper surface of a star-fish corresponds to the combined inter-ambulacral areas of an Echinus, and exhibits the aperture of the anus (when present), and the " madreporiform tubercle," which is situated near the angle between two rays. The inferior or ventral surface corresponds to the ambulacral areas of an Echinus, and exhibits the mouth and ambulacral grooves. The mouth is central in position, and is not provided with teeth ; it leads, by a short gullet, into a large stomach, from which a pair of sacculated diverticula are prolonged into each ray. A distinct intestine and anus may, or may not, be pres- ent ; but the anus is sometimes wanting (in the genera, Astro- pecten, Ctenodiscus, and Ltddia). The ambulacral system is essentially the same as in the Echinoidea, and is connected with the exterior by means of the " madreporiform tubercle," or " nucleus," two, three, or more of these being occasionally present. The conical or cylindrical ambulacral tube-feet are arranged in two or four rows, along grooves in the under surface of the arms (fig. 98). Each am- bulacral groove is continued along the lower surface of one of the arms, tapering gradually towards the extremity of the latter. The floor of each groove is constituted by a double row of minute calcareous pieces — the "ambulacra! ossicles" — which are movably articulated to one another at their inner ends. At the bottom of each groove is lodged one of the radiating canals of the water-vascular system or ambulacral ECHINODERMATA: ASTEROIDEA. 203 system, from which are given off the rows of suctorial feet, or " tube-feet" It follows from this that the radiating vessels of the ambulacral system are otitside the chain of ambulacral ossicles, so that these latter are to be regarded as an internal skeleton, and they do not correspond with any part of the skeleton of Echinoids * — at least they do not correspond with the perforated ambulacral plates of the Sea-urchins. The ambulacral ossi- cles, however, of the Star-fishes are of such a form that by their apposi- tion an aperture or pore is formed between each pair. By means of these pores (fig. 98, a) the tube-feet communicate with a series of little bladders or ' ' ampullae, " placed above the chain of ossicles. These per- forations, however, do not correspond with the perforated plates of the Echinoid test, and the tube-feet of the Star-fishes pass through no "por- iferous " plates on their way to the Fig. 98.— Diagram of a Star-fish (Goniaster), This may be rendered more mtel- showing the under surface, with the mouth ligible by examining" a section of the and ambulacral grooves, a Ambulacral os- arm of a Star-fish from which the sicles' ™£ the ambulacral pores between , , i , ic them ; £ Adambulacral plates, bounding the soft parts have been removed (fig. ambuiacrai grooves; m Marginal plates, 99). In such a section the ambu- (wanting in many species) ; o Oral plates, lacral ossicles (a a) are seen in the placed at the angles of the mouth. centre of the lower surface, united along the middle line by their inner extremities. They are so placed as to form a kind of elongated pent-house, and immediately beneath the line where the ossicles of one side are articulated with those of the other side is placed the ambulacral vessel (b}. Superficial to this, again, is a nerve-cord ; so that the whole chain of ambulacral ossicles is placed in the midst of the soft parts of the animal, and is thus clearly an internal skeleton. At their outer extremities the ambulacral ossicles are articulated by the intervention of the ' ' adambulacral plates" (fig. 98, £), with plates belonging to the external or integumentary skeleton. As before said, the shape of the ambulacral ossicles is such that a pore is formed by the apposition of each pair ; and by these apertures each tube-foot com- municates with a vesicle placed internal to the chain of ossicles. It will be seen, however, that the tube-feet (indicated by the dotted lines in the figure) do not pass through these apertures, or through any other pores of the skeleton, on their way to the surface. The "poriferous zones" of the Sea-urchins are part of the external skeleton, and are not represented in the Star-fishes. On the other hand, the integumentary skeleton in the Star-fishes is absent along the ambulacral areas, or along the areas occupied by the ambulacral grooves. The circulatory system of the Asteroids is represented by a group of vessels communicating ventrally with an oral ring * The structures in the Echinus, which are truly homologous with the ambulacral ossicles of the Asteroidea and Ophiuroidea, are the so-called "auriculae." 2O4 MANUAL OF ZOOLOGY. and dorsally with an anal plexus, from which branches are dis- tributed to the genital glands. There are no distinct respira- tory organs, but the surfaces of the viscera are abundantly Fig. 99. — Section of the ray of Uraster rribens. a a Ambulacral ossicles ; b Position of the ambulacral vessel ; c c Plates of the external skeleton ; n Nerve-cord. The dotted lines show the tube-feet proceeding from the ambulacral vessel. supplied with cilia, and doubtless subserve respiration; the sea-water being freely admitted into the general body-cavity by means of numerous contractile ciliated tubes, which project from the dorsal surface of the body. The nervous system consists of a gangliated cord, surround- ing the mouth and sending filaments to each of the rays. At the extremity of each ray is a pigment-spot, corresponding to one of the ocelli of an Echinus, and, like it, supposed to be a rudimentary organ of vision. The eyes are often surrounded by circles of movable spines, called "eyelids." The generative organs are in the form of ramified tubes, arranged in pairs in each ray, and emitting their products into the surrounding medium by means of efferent ducts which open round the mouth. In their development, the Asteroidea show the same general phenomena as are characteristic of the class ; but the larvae are not provided with any continuous endoskeleton. In some Asteroids the larval forms have side- lappets, and have been described under the name of Bipin- naria; and in these, as in the Pluteiis of the Echinoids, a large portion of the larva is cast off as useless. In Bipinnaria asterigem (Sars) the digestive cavity is a simple sac which sends no prolongations into the rays, and the mouth is inter- radial, instead of being placed in the centre of the ambulacral system. The mouth of the adult is at this stage closed by the soft external skin of the larva. In other Asteroids the larvae have three anterior vermiform processes, and are known as Brachiolaria. The general shape of the body varies a good deal in different ECHINODERMATA : ASTEROIDEA. 205 members of the order. In the common Star-fish (Uraster rubens) the disc is small, and is furnished with long, finger-like rays, usually five in number (fig. 97). In the Cribella the general shape of the body is very much the same. In the Solasters the disc is large and well marked, and the rays are from twelve to fifteen in number, and are narrow and short (about half the length of the diameter of the body). In the Goniasters (fig. 98) the body is in the form of a pentagonal disc, flattened on both sides ; the true " disc " and rays being only visible on the under surface of the body. In the singular genus Brisinga, we have in some respects a transitional form between the Asteroids and Ophiuroids, the arms being much longer and more slender than is the case in the typical Aster- oids, at the same time that they are much thicker and softer than is the case amongst the latter. In none of the true Star- fishes, however, are the arms ever sharply separated from the disc, as in the Ophiuroidea, but they are always an immediate continuation of it. The principal groups of Asteroidea are the following : — Family \. Asteriadae or Asterocanthiidce. — Four rows of ambulacral feet. Fam. 2. Astropectinidce. — Two rows of ambulacral feet ; back flattish, netted with tubercles, which carry radiating spines at the tip ("paxillae"). Fam. 3. Oreastridce. — Two rows of ambulacral feet ; skin granular, pierced by minute pores. Fam. 4. Asterinidce. — Two rows of ambulacral feet ; body discoidal or pyramidal, sharp-edged ; skeleton of imbricate plates ; dorsal wart single, rarely double. Fam. 5. Brisingida. — Arms long and rounded, sharply marked off from the disc. Ambulacral grooves not reaching the mouth ; two rows of ambulacral feet. ORDER OPHIUROIDEA. — Body stellate, consisting of a central "disc" in which the viscera are contained, and of elongated "arms" which are sharply separated from the disc, solid, not containing prolongations of the viscera, and not furnished inferi- orly with ambulacral grooves. Larva generally pluteiform, with a skeleton. This order comprises the small but familiar group of the "Brittle-stars" and Sand-stars," often considered as belong- ing to the Asteroidea, to which they are nearly allied. The body in the Ophiuroidea (fig. 100) is discoidal, and is covered with granules, spines, or scales, but pedicellariae are wanting. From the body — which contains all the viscera — proceed long slender arms, which may be simple or branched, but which do not contain any prolongations from the stomach, nor have 206 MANUAL OF ZOOLOGY. their under surface excavated into ambulacral grooves. The arms, in fact, are not simple prolongations of the body, as in the Asteroidea^ but are special appendages, superadded for locomotive and prehensile purposes. Each arm is enclosed by four rows of calcareous plates, one on the dorsal surface, one on the ventral surface, and two lateral. The lateral plates generally carry more or less well-developed spines. In the centre of each arm is a chain of quadrate ossicles, forming a central axis, and between this axis and the row of ventral plates is placed the ambulacral vessel. Each ossicle of the central chain is composed of two symmetrical halves, but these are immovably articulated together, and are not movable upon one another, as in the Asteroidea. The mouth is situated in the centre of the inferior surface of the body, is provided with a masticatory apparatus, and is surrounded by tentacles. It opens directly into a sac-like ciliated stomach, which is not con- tinued into an intestine, the mouth serving as an anal aperture. The stomach is destitute of lateral diverticula. The repro- ductive organs are situated near the bases of the arms, and open by orifices on the ventral surface of the body or in the interbrachial areas.* The ambulacral system is constructed upon the same plan as in the Echinoids and Asteroids ; but its place as a loco- motive apparatus is taken by the arms. The radial vessels of the ambulacral system are not provided with secondary vesicles or "ampullae," as they are in the Echinoidea and Asteroidea, and the lateral " feet " which they give off have no terminal suckers. The madreporiform tubercle is placed on the inferior surface of the body, and is often partially concealed by one of the plates surrounding the mouth. Respiration is carried on by the lining of the body-cavity, and by a circlet of modified tube-feet or tentacles placed round the mouth. The development of the Ophiuroids is sometimes direct, the young, being brought forth alive, and, in some cases, being carried by the mother for some period after hatching (Wyville Thomson). More commonly there is a pluteiform embryo, which resembles that of the Echinoids in having a continuous endoskeleton. In Euryale the body is in the form of a subglobose disc with five obtuse angles, and the arms are prehensile. In Asteropkyton, the Medusa-head star, the arms are divided from * Spontaneous fission has been observed by Ltitken and Kowalewsky to take place in some Ophiuroids, as also occasionally in some of the Asteroids. ECHINODERMATA : CRINOIDEA. 207 the base, first dichotomously, and then into many branches. In Ophiura, the Sand-star, the arms serve for reptation (creep- Fig, loo.— Ophiuroidea. a Opkiura texturata, the common Sand-star; b Ophiocoma neglecta, the grey Brittle-star. (After Forbes. ) ing), and are undivided, often exceeding the diameter of the disc many times in length. The order Ophiuroidea may be divided into two families, as follows : — Family I. Euryalidce. Arms branched ; genital fissures ten in number. Fam. 2. Ophiurida. Arms simple ; genital fissures, mostly five in number. CHAPTER XX. CRINOIDEA, CYSTOIDEA, AND BLASTOIDEA. ORDER CRINOIDEA. — The members of this order are Echino- dermata, in which the body is fixed^ during the whole or a portion 208 MANUAL OF ZOOLOGY. of the existence of the animal, to the sea-bottom by means of a longer or shorter, jointed, and flexible stalk. The body is dis- tinct, composed of articulated calcareous plates, bursiform, or cup-shaped, and provided with slender arms, which are typi- cally five or ten in number, and are grooved on their upper surfaces for the ambulacra. (The position of the body being reversed, the upper surface is ventral ; whilst the dorsal surface is inferior, and gives origin to the pedicle.) The tubular processes, however, which are given off from the radiating ambulacral canals of the Crinoidea, unlike those of the Echi- noidea and Asteroidea, are not used in locomotion, but have probably a respiratory function. The mouth is central, and looks upwards, an anal aperture being sometimes present sometimes absent. The ovaries are situated beneath the skin in the grooves on the ventral surface of the arms or pinnules, as are also the ambulacral or respiratory tubes. The arms are furnished with numerous lateral branches or "pin- nulse." The embryo is "free and ciliated, and develops within itself a second larval form, which becomes fixed by a ped- uncle" (Huxley). If we take such a living Crinoid as Rhizocrinus (fig. 101), we shall be able to arrive at a comprehension of the leading characters of this order. Rhizocrinus is one of those Crinoids which is permanently rooted to some foreign object by the base of a stalk which is composed of a number of calcareous pieces or articulations. In some cases (as in Apiocrinus) the base of the stem or "column" is considerably expanded.- In other cases the column is simply " rooted by a whorl of ter- minal cirri in soft mud" (Wyville Thomson). The joints of the column are movably articulated to one another, the joint- surfaces often having a very elaborate structure, so that the entire stem possesses in the living state a greater or lesser amount of flexibility. Each joint is perforated centrally by a canal, which by the old writers was very inappropriately termed the " alimentary canal," but which in truth has nothing to do with the digestive system of the animal. At the summit of the stem is placed the body, which is termed the " calyx," and which is usually more or less cup- shaped, pyriform, bursiform, or dis- coidal. The calyx exhibits two surfaces, a dorsal and a ventral, of which the dorsal is composed, wholly or in part, of calcareous plates articulated by their margins, whilst the former is com- posed of a more or less leathery integument, strengthened by the deposition in it of numerous small plates of carbonate of lime. The ventral surface exhibits the aperture of the mouth, which may be subcentral or may be very excentric, and which ECHINODERMATA : CRINQIDEA. 2O9 in many extinct forms is wholly concealed from view. The ventral surface also exhibits the aperture of the anus, which is usually placed excentrically in one of the spaces between the arms, and which is often carried at the end of a longer or shorter tubular eminence or process, which is called the " proboscis." Owing to the animal being supported on a stalk, it is evident that the " ventral " surface is turned upwards, and the " dorsal " surface down- wards. The column springs from the centre of the dorsal surface; and a stalked Cri- noid may therefore be com- pared to a Star-fish turned upside down, with its lower or ambulacral surface supe- rior, and its dorsal surface looking downwards. The calyx contains the digestive canal, and the central por- tions of the nervous and water- vascular (ambulacral) system ; but it does not con- tain the reproductive organs, as is the case with the vis- ceral cavity of the other Echinoderms. From the margins of the calyx, where the dorsal and ventral surfaces join one an-? other, arises a series of longer or shorter flexible processes, which are composed of a great number of small cal- careous articulations, and which are termed the "arms" (fig. 102). The arms are usually primarily five in number, but they generally divide almost immediately into two branches, each of which may again subdivide ; the branches thus pro- duced perhaps again dividing, until a crown of delicate grace- ful filaments is formed. The arms carry smaller lateral O Fig. 101. — Crinoidea. Rhizocrinus Lofotettsis, a living Crinoid (after Wyville Thomson), four times the natural size, a Stem ; b Calyx ; c c Arms. 210 MANUAL OF ZOOLOGY. branches or " pinnulae " on both sides ; and they contain the so-called "coeliac" and " subtentacular " canals, these being tubular extensions of the cavity of the body. The upper surface of the arms and pinnulae is covered with a soft mem- brane, and below this are placed the re- productive organs. The generative organs are therefore not placed within the calyx, and it follows of necessity that there is no generative opening or "ovarian aperture" in the walls of the calyx. The ventral sur- faces of the arms and pinnulae are furnished with grooves, which in the living species are seen to be covered with vibratile cilia. The brachial grooves coalesce till they constitute five primary grooves, which are continued from the bases of the arms to the mouth. The action of the cilia gives rise to a con- stant current of sea-water, bearing organic matter in suspension ; and this current pro- ceeds from the brachial grooves to the mouth. In this way the animal obtains its Fio2.-Portion of an ' As the baSCS °f . arm of Piatycrinus, rated from the mouth by an intervening showing the ralpm- ^^ it^follows ^ thfi brachial grooves are continued over the ventral surface of the calyx, till they reach the oral opening. There is no doubt that it is by the above arrangement that the living Crinoids obtain their food, and the mechanism seems to have been essentially the same in many extinct species. In the Palaeozoic Crinoids, however, there seems to have been a modification of this arrangement. In these forms, the arms. have much the structure of those of the recent Crinoids, and are deeply grooved on their ventral surfaces. The ventral sur- face of the calyx, however, exhibits no central aperture, but only a proboscidiform tube, which arises from one of the in- ter-radial spaces (/". e.t one of the intervals between two of the arms). This tube is almost certainly anal, but good observers regard it as discharging the functions of both mouth and anus. However this may be, the brachial grooves are certainly not continued over the ventral surface of the calyx, but stop short at the bases of the arms. Hence they are continued as covered passages or tunnels to a central point in the ventral surface of the disc. Here is placed the mouth, concealed by the cal- careous plates of the perisome. The dorsal surface of the " calyx " of the Crinoidea is com- ECHINODERMATA : CRINOIDEA. 211 posed of a number of calcareous plates, accurately fitted to- gether, and having the following general arrangement (fig. 104). Resting directly upon the summit of the highest joint of the Fig. 103 — Platycrinus tricontadactylus. Carboniferous. The left-hand figure shows the calyx, arms, and upper part of the stem ; and the figure next this shows the sur- face of one of the joints of the column. The right-hand figure shows the proboscis. column is a series of plates, generally three or five in number, which from their position are termed the " basals " (fig. 104, b\ Succeeding to the basals, and alternating with them, there is commonly found a second cycle of polygonal plates, which are generally termed the " parabasals " (fig. 104,^), and which in many forms are never developed.* Succeeding to the para- basals (or, in the absence of these, to the basals) are two or three cycles of plates, which are directly superimposed upon one another in longitudinal rows, and which form the foundations of the arms. These are known as the "radials" (fig. 104, r\ and are termed "primary radials," "secondary radials," and "tertiary radials," according to their distance from the basals. The last radial plates, or those furthest from the column, give * According to the high authority of Mr P. H. Carpenter, when there is only one cycle of plates between the top column-joint and the primary radials, it is the so-called "basals" (or "under-basals") which are want- ing, and the cycle that is present consists of plates corresponding with the " parabasals " of such Crinoids as have two inferior cycles of calycine plates. 212 MANUAL OF ZOOLOGY. origin to the plates of the arms. The radial plates are ar- ranged in a series of vertical columns, which radiate from the summit of the basals to the bases of the arms. Between the Fig. 104. — Diagram of the dissected calyx of Rhodocrinus, viewed from below (after Schultze). b Basals ; / Parabasals ; r First radials ; t Inter - radials ; a Anal plates. different columns of radial plates, however, there may be inter- calated certain other smaller plates, which, from their position, are termed " inter-radials " (fig. 104, /); while one of the inter- radial spaces, corresponding with the anus, is usually much wider than the others, and is furnished with an additional series of calcareous pieces, which are termed "anal plates "(fig. 104, a). Of the living stalked Crinoids, the best known is the Penta- crinus caput - Medusa of the Caribbean Sea. Another West Indian form is the curious sessile Holopus. More recently a stalked Crinoid has been discovered in the Atlantic and North Sea, and has been described under the name of Rhizocrinus Lofotensis (fig. joi). The chief interest of this form is the fact that it belongs to a group of the Crinoidea hitherto believed to be exclusively confined to the Mesozoic rocks — viz., the Apiocrinida or " Pear-encrinites." In fact, Rhizocrinus is very closely allied to the Cretaceous genus Bourgueticrinus, and it may even be doubted if it is generically separable from it. The ECHINODERMATA : CRINOIDEA. 213 late remarkable researches into the life of the deeper parts of the ocean have brought to life several new Crinoids, which will doubtless, when fully investigated, still further fill up the in- terval between the living and extinct Crinoidea. Amongst these may be mentioned Pentacrinus Wyville-Thomsoni, Bathy- crinus gradlis, and Hyocrinus Bethellianus. In the second type of the Crinoidea — represented in our seas by the forms which are commonly known as " Feather-stars," and which are grouped together under the general name of Comatula — the animal is not permanently fixed, but is only attached by a stalk when young. Taking the British Comatula (Antedon) rosacea as the type of this group, the larva, after various preliminary embryonic changes, appears as a small stalked Crinoid (fig. 105, b), in which state it was described as a distinct species under the name of Pentacrinus Europaus. Fig. 105. — Crinoidea. Comatula (Anterior?) rosacea, the Feather-star, a Free adult; b Fixed young. (After Forbes.) In its adult condition, however, the Comatula (fig. 105, a) is free, and consists of a pentagonal disc, which gives origin to ten slender arms, which are fringed with many marginal pinnulse. The mouth and anus are on the ventral surface of the disc, which in this case is again the inferior surface, since 214 MANUAL OF ZOOLOGY. the animal has the power of creeping about by means of its pinnated arms. Though capable of creeping, the animal more usually has recourse to swimming, the five left arms working as paddles simultaneously, and alternating in their action with the five right arms. The arms of Comatula rosacea exhibit-on their ventral surface a deep "brachial groove," the elevated margins of which are cut out into minute crescentic respiratory leaves, at the base of each of which is a group of three tentacles, con- nected with a cavity in the interior of the respiratory leaf, and communicating by a common trunk with the radiating ambu- lacral vessel. The floor of the brachial grooves is ciliated, and underneath each runs a radiating ambulacral vessel, together with a blood - vascular trunk, and a peculiar fibrillar "sub- epithelial band," which is supposed to be of a nervous nature. In some Comatulids (certain Actinometrce) there is the curious feature that some of the arms in some individuals may want the ventral grooves, tentacles, and nerves, while in other in- dividuals all the arms possess these structures. The dorsal surface of the calyx, again, carries a tuft of jointed filaments or cirri, by which the animal is enabled to moor itself temporarily to foreign objects. The animal feeds upon very minute organisms which are conveyed to the mouth by the action of the cilia lining the brachial grooves. The mouth in C. rosacea is sub-central, but in some Comatulids (Actinometrd) it is quite excentric ; while the anus is usually supported on a tubular projection and situated on one side. According to the researches of Dr W. B. Carpenter, the nervous system of Comatula consists of a fibrillar sheath surrounding a central quinquelocular vascular organ, and giving off a series of radial branches which differ from the radial nerve-cords of the other Echinoderms in not running along the ventral surface of the arms, but in occupying a median canal in the centre of each arm. While the principal nerve-cords have this position, and have a motor function, it has also been shown that there exists, as before remarked, a fibrillar band below the epithelial lining of the ventral furrow of each arm, and these bands are supposed to be of the nature of sensitive nerves. They spring from a circular band, which is placed round the gullet, above the ambulacral and blood-vas- cular rings. It has also been shown by modern researches, that there exists in Comatula a complicated blood-vascular system. As regards the vascular system of the Crinoids generally, there is found in Comatula, occupying the dorso-ventral axis of the body, a largish lobated structure homologous with the heart of the Asteroids, and, like it, consist- ing of numerous closely-packed vessels. Dorsally, these resolve them- ECHINODERMATA : CRINOIDEA. 215 selves into a central group (of one or more) and five peripheral vessels, the latter of which expand in the calyx into the five chambers of the "cham- bered organ," the chambers and axis alike giving branches to the dorsal cirri. In the pedunculate Crinoids in which there are no cirri, the chambers narrow again, and the group of vessels is continued down the central canal of the column. In Pentacrinus, which has cirri at regular intervals, the five peripheral vessels expand in each cirrus-bearing joint into five dilatations, which thus give rise to a miniature "chambered organ," each chamber of which gives off a single vessel to a cirrus. In the body, the vascular axis is connected with (i) a large network of vessels round the alimentary canal, (2) an extensive plexus beneath the ventral surface of the disc, in which vessels arise that run out into the arms and enclose the gen- ital glands, and (3) a plexus of convoluted tubes depending from the oral blood-vascular ring in which the radial vessels of the arms originate (P. H. Carpenter). The reproductive organs of Comatula are situated beneath the soft skin of the arms, and their ducts open into the pinnulae, by the rupture of the ventral integument of which the generative elements are set free into the surrounding water. As regards the development of Comatula, the larva is at first cylindrical, with four transverse bands of cilia, a hinder tuft of cilia, and an alimentary canal furnished with a lateral aper- ture, its general aspect closely resembling that of the embryos of certain Annelides. The skele- ton of the calyx is developed anteriorly, that of the column posteriorly, the former being the first to appear. In its early condition (fig. 106) the calycine skeleton consists of a row of five "basal" plates, which rest below upon the so-called "centro-dorsal plate," and are suc- ceeded above by a cycle of five "oral" plates, in the centre of which the permanent mouth is fin- ally developed. Five " radial " plates are next developed as a cycle between the oral and basal plates ; and to the radialsare rapidly added the plates of the arms proper (the "brachial" plates). Inferiorly, the centro-dorsal plate rests upon a short, jointed column (fig. 106, c\ the lowest plate of which is expanded to form a disc of attachment ; and the larva now passes into what is known as its " Pentacrinus stage." In the further progress of growth the arms increase in length, and the oral plates diminish in size and ultimately disappear. At the same time the centro-dorsal plate increases in size, so as to enclose the radial plates, which in turn become fused with one another, and remain only as the so-called "rosette" on the upper surface of the centro-dorsal. The latter also develops jointed cirri from its outer surface, and finally becomes detached from the next joint of the column below, when the animal enters upon its free stage of life. Fig. 106.— Larva of Comatula (Antedori) rosacea, enlarged (after Sir Wyville Thomson). o o Oral plates ; r r Radial plates ; b b Basal plates ; c d Centro-dorsal plate ; c Col- umn ; d Disc of attachment. 2l6 MANUAL OF ZOOLOGY. Numerous living forms of Comatula are known, and have been described under various subordinate types (Antedon, Actinometra, Comaster, and Phanogenia) ; and the group seems to be cosmopolitan in its distribution. ORDER CYSTOIDEA. — Body generally spheroidal, pedunculate or sessile, enclosed by calcareous articulated plates, some of which are usually porous and are connected with respiration, and perhaps with reproduction also. Arms rudimentary, mostly reduced to the pinnulce only. Reproductive organs contained within the interior of the calyx. The members of this order are all extinct, and are entirely confined to the Palaeozoic period. The body (fig. 107) was, Fig. 107. — Hemicosmites pyriformis, one of the Cystideans. The right-hand figure shows the upper surface of the calyx. typically, more or less spherical, and was protected by an ex- ternal skeleton, composed of numerous polygonal calcareous plates accurately fitted together, and enclosing all the viscera of the animal. The body was in most cases permanently attached to the sea-bottom by means of a jointed calcareous " column," or pedicle, but this was much shorter than in the majority of Crmoids, and was rarely altogether absent. Upon the upper surface of the body were two, sometimes three, apertures, the functions of which have been a matter of con- siderable controversy. One of these is lateral in position, is defended by a series of small valvular plates, and is believed by some to be the mouth, whilst by others it is asserted to have been an ovarian aperture. The most probable view, however, is that this valvular opening is really the anus. The second opening is central in position, and it is believed by Mr Billings to be the "ambulacral orifice," as it is always in the centre of the arms when these are present. The third aper- ture is only occasionally present, and its true functions are doubtful. ECHINODERMATA : BLASTOIDEA. In some Cystoidea there were no arms, properly speaking, but only small pinnulae. In a second section two arms were present, but these were bent backwards, and were immovably soldered down to the body. In one single species (Comaro- cystites punctatus, Billings), the development has gone further, the arms being free, and provided with lateral pinnulae, as in the true Crinoids. Many Cystideans are likewise provided with a system of pores or fissures, penetrating the plates of the body, and usu- ally arranged in definite groups. These groups are termed " pectinated rhombs," but their exact function is doubtful. By Mr Billings, however, they are believed, and apparently with good reason, to have admitted water to the body-cavity, and to have thereby subserved a respiratory function ; though the recent researches of Ludwig on the genital glands of the Ophiuroids would render it not improbable that they were also connected with the function of reproduction. ORDER BLASTOIDEA. — Body enclosed in an armour of closely fitting calcareous plates, attached to some foreign body by a slender stem. From the summit of the calyx radiate five transversely striated and longitudinally grooved areas, which carry a row of jointed pinnulce on each side. The members of this order, like those of the preceding, are all extinct, and are entirely confined to the Palaeozoic period. The body (fig. 108, a) was fixed to the bottom of the sea by Fig. 108. — Morphology of Blastoidea. a Pentremites pyriformis, viewed sideways, showing a portion of the column ; b Summit of the calyx of Pentremites cervinus, showing the pseud-ambulacral areas and the apical apertures ; c Side view of Grana- tocrinus tnelonoides ', d Summit of Granatocrinus neglectus. (Figs, a and b are of the natural size; c and d are slightly enlarged.) After Hall, and Meek and Worthen. means of a short, jointed pedicle ; it was globular or oval in shape, and composed of solid polygonal calcareous plates, firmly united together, and arranged in five inter-ambulacral and as many ambulacral areas. (These ambulacral areas are 2l8 MANUAL OF ZOOLOGY. termed by M'Coy "pseud-ambulacra," upon the belief that they were not pierced for tube-feet, but that they carried a double row of little jointed tentacles or arms.) The pseud- ambulacra are petaloid in shape, having a deep furrow down the centre, and striated transversely. They converge to the summit of the calyx (fig. 108, $), and each appears to have carried a row of small jointed "pinnulae" upon each side. The five pseud-ambulacra, radiating from the summit of the calyx, give the upper surface of the body somewhat the ap- pearance of a flower-bud ; hence the name applied to the order (Gr. blastos, a bud ; eidos, form). Upon the whole, it would seem most probable that the pseud-ambulacra of the Pentre- mites represent the arms of the Crinoids, anchylosed with the calyx, and that the longitudinal furrows of the pseud-ambulacra represent the " brachial grooves " of the Crinoids ; but they are peculiar in the fact they are perforated by the apertures of a number of respiratory tubes. At the summit of the calyx are six apertures, of which one is the mouth, four are ovarian, and the sixth is probably partly ovarian and partly anal. 'The Blastoidea are known more familiarly under the name of Pentremites, and they occur most commonly in the Carbon- iferous rocks. CHAPTER XXL HOLOTHUROIDEA. ORDER HOLOTHUROIDEA. — Vermiform or slug - like Echino- derms, with a leathery skin, in which calcareous granules and spicules are generally developed. Mouth surrounded by a circlet of tentacles. Sexes mostly distinct. Larva vermiform, without a skeleton. The members of this order are commonly known by the name of "sea-cucumbers," "trepangs," or " beches-de-mer," and are the most highly organised of all the Echinodermata. The body is elongated and vermiform, or rarely slug-shaped, and is not provided with a distinct test, but is enclosed in a coriaceous skin, generally, but not always, containing calcare- ous deposits in the form of scattered granules or spicules, or even imbricated scales. The ambiilacral tube -feet, when present, are typically disposed in five rows, which divide the ECHINODERMATA : HOLOTHUROIDEA. 219 body into an equal number of longitudinal segments or lobes. The mouth is surrounded by a circlet of feathery tentacles, con- taining prolongations from the central ring of the water-vascu- lar system ; and an anus is situated at the opposite extremity of the body. There is a long, convoluted intestine. A special respiratory, or water-vascular, system is often developed, in the form of a system of arborescent tubes, which admit water from the exterior. The larva is vermiform, and has no skeleton. At a certain period of their existence, the young Holothurians are barrel-shaped, with transverse rings of cilia (fig. 109, c). Fig. 109. — Holothuroidea. a Holothuria tubulosa, one of the Sea-cucumbers b and c Young stages of the same. They rotate rapidly on their long axis, and have at this stage been described as a distinct genus under the name of Auri- cularia. In the typical Holothurians, locomotion is chiefly effected by means of rows of ambulacral tube-feet, or by alternate ex- tension and contraction of the worm-like body ; but in the Synaptida, in which there are no ambulacra, and only the central circular canal of the ambulacral system is present, the animal moves by means of variously shaped spicula, which are scattered in the integument. When developed, the ambulacral system consists of a " circular canal/' surrounding the mouth, bearing one or more " Polian vesicles," and giving off branches to the tentacula; and of five "radiating canals" which run down the interspaces between the great longitudinal muscles. These radiating canals give off the tube-feet and their second- 220 MANUAL OF ZOOLOGY. ary vesicles, just as in the Echinus. In the typical forms there are five rows of tube-feet, but these organs may be scattered over the whole body, or may be restricted to the ventral sur- face. There is also a "sand -canal" which arises from the circular canal, and is terminated by a madreporiform tubercle ; but this, instead of opening on the exterior, hangs down freely in the perivisceral cavity. The fluid, therefore, with which the ambulacral system is filled, is derived from the perivisceral cavity, and not from the exterior, as is usually the case. The mouth is toothless, is situated anteriorly, and is sur- rounded by a beautiful fringe of branched, retractile tentacles (fig. no), which arise from a ring of calcareous plates, and into which are sent prolongations from the circumoral ring of the ambu- lacral system. These tentacles, ten to twenty in number, are really mo- dified tube-feet, and probably serve in part as respiratory organs. The mouth opens into a pharynx, which conducts to a stomach. The intes- tine is long and convoluted, and usu- ally opens into a terminal dilatation, termed the "cloaca," which serves both as an anus and as an aperture for the admission of sea-water to the respiratory tubes. From the cloaca arise, in many forms, two branched and arborescent tubes, the termina- tions of which are csecal. These run up towards the anterior extrem- ity of the body, and together consti- tute the so called " respiratory tree." They are highly contractile, and they perform the function of respiratory organs, sea-water being admitted to them from the cloaca. The vascular system consists of two main vessels Fig. ^.-Pentactafrondosa, show- — one dorsal, and the other ventral ing the crown of feathery tenta- Connected With a cirCUm-CeSOplia- cles round the mouth and the •, • •»->. i • r rows of tube-feet. geal ring. Development is in a few instances direct ; but in most cases there is a metamorphosis, the larva being vermiform, and devoid of a skeleton. The nervous system consists of a cord, surround- ing the gullet, and giving off five branches which run alongside of the radiating ambulacral canals. The sexes are generally, ECHINODERMATA : HOLOTHUROIDEA. 221 but not universally, distinct. The generative organs are in the form of long, ramified, caecal tubes, which open externally by a common aperture, situated near the mouth. There is thus no trace of that radial symmetry which is observed in the arrange- ment of the reproductive organs in the other orders of the Echinodermata. The skin in the Holothurians is highly contractile, and the body is provided with powerful longitudinal and circular muscles, in compensation for the absence of any rigid integu- mentary skeleton. Many of the Sea-cucumbers, in fact, are endowed with such high contractility that they can eject their internal organs entirely, if injured or alarmed. In the family of the Synaptidce. there is no respiratory tree, and the ambulacral tube-feet are wanting; whilst the skin is furnished with calcareous spic- ules of various shapes. The Synaptcz themselves burrow in the mud or sand, and have the skin furnished with innumerable an- chor-shaped spicules (fig. in) attached to special " anchor- plates " in the integument. They often form a kind of protective case or tube of sand-grains ; and they obtain their food by swal- lowing the mud, from which they extract any disseminated nutrient particles. In Chirodota the skin is provided with mi- croscopic calcareous wheels, in the place of anchors. In the OnrinolabidcR, the skin has barbed spicules, and there is no respiratory tree; but these forms differ from the Synaptidce proper in possessing tube-feet. The order Holothuroidea is divided into the two following sub-orders : — Stib-order I. Apneumona. No respiratory tree. The ambulacral tube-feet wanting (Synaptidce) , or present (Oncinolabidiz}. Sub-order 2. Pneumonophora. A respiratory tree. (Ex. Holothuria, Tkyone, Molpadia, Psolus, Cu- i) &c. ) Fig. in. — Anchor-shaped spicules of Synapta, and the plates to which these are attached. Magnified greatly. 222 MANUAL OF ZOOLOGY. CHAPTER XXII. DISTRIBUTION OF ECHINODERMATA IN SPACE AND TIME. DISTRIBUTION OF ECHINODERMATA IN SPACE. — The Crinoidea are represented by comparatively few forms in recent seas, and these have mostly a very local distribution. More than one hundred and fifty species of Comatula (in the wide sense) are known, ranging from 82° N. lat. to Kerguelen's Land, but most abundant in the tropics. Holopus is a West Indian form, and the species of Pentacrinus are principally West Indian also. Rhizocrinns Lofotensis occurs in the North Atlantic, and another species of this genus is found in the Gulf of Mexico. Lastly, the species of Bathycrimis and Hyocrinus are found at great depths in the Atlantic and Pacific. The Asteroidea, Ophiuroidea, and Echinoidea are represented in almost all seas, whether in tropical or temperate zones, ex- tending their range even into high northern and southern lati- tudes. They have also a wide bathymetrical range, extending from between tide-marks to almost the greatest depths which have yet been explored by the dredge. Some of the Sea- urchins (such as Toxopneustes lividus) have the peculiar habit of hollowing out cavities for themselves in the solid rock, in which they spend their existence. The Holothuroidea enjoy a nearly world-wide distribution ; but they have their metro- polis in the Pacific Ocean, occurring abundantly on the coral- reefs of the Polynesian Archipelago. One species (Holothuria argus) is collected in large numbers, and is exported to China, where it is regarded as a great delicacy. DISTRIBUTION OF ECHINODERMATA IN TIME. — Numerous remains of Echinodermata occur in mo.^t sedimentary rocks, beginning with the Upper Cambrian rocks, and extending up to the recent period. The two orders Cystoidea and Blastoidea, which are the most lowly organised of the entire class, are exclusively Palaeozoic ; and the Crinoidea are mostly referable to the saiiie epoch. The more highly organised Asteroidea and Ophiuroidea commenced to be represented in the Silurian period ; but the Echinoidea^ with few exceptions, have no rep- resentatives earlier than the Carboniferous rocks. The fol- lowing exhibits, the geological distribution of the different orders of the Echinodermata in somewhat greater detail :— i. CRINOIDEA. — The pedunculate Crinoidea attained their ECHINODERMATA : DISTRIBUTION. 223 maximum in the Palaeozoic period, from which time they have gradually diminished down to the present day. On the other hand, the free Crinoids are comparatively modern, and seem to have reached their maximum at the present day. As has already been described, the Palaeozoic Crinoidea differ in some important particulars from those which succeeded them. The order is well represented in the Silurian, Devonian, and Car- boniferous rocks, but especially in the latter; many Carbon- iferous limestones (crinoidal limestones and entrochal marbles) being almost entirely made up of the columns and separate joints of Crinoids. In the Secondary rocks Crinoids are still abundant. In the Trias the beautiful "Stone-lily" (Encrlnus liliiformis) is peculiar to its middle division (Muschelkalk). In the Jurassic period occur many species of Apiocrinns (Pear- encrinite), Pentacrinus, and Extracrinus. The Chalk also abounds in Crinoids, amongst which is a remarkable unat- tached form (the Tortoise-encrinite or Marsupites}. Of the non-pediculate Crinoidea, which are a decided ad- vance upon the' stalked forms, there are comparatively few traces ; but remains of forms (such as Saccosoma and Solano- crimts) allied to the recent Comatiilcz have been found in the Jurassic and Cretaceous deposits. 2. BLASTOIDEA. — The Blastoidea, or Pentremites, are entirely Palaeozoic, and attain their maximum in the Carboniferous rocks, some beds of which in America are known as the Pen- tremite limestone, from the abundance of these organisms. They are, however, also found in the Silurian and Devonian rocks. 3. CYSTOIDEA. — These, like the preceding, are entirely Palae- ozoic ; but they are, as far as is yet known, almost exclusively confined to the Upper Cambrian and Silurian rocks, being especially characteristic of the horizon of the Bala limestone. The last known forms of Cystideans occur in the Devonian rocks. The oldest known Echinoderms are two extremely simple Cystideans (Trochocystites and Eocystites) which have been discovered in the primordial zone of North America. 4. ASTEROIDEA. — These have a very long range in time, extending from the Lower Silurian period up to tho present day. In the Silurian rocks the genera Palceaster, Stenaster, Palceodiscits , and Petraster are among the more important, the greater number of forms being Upper Silurian. The next period in which Star -fishes more especially abound is the Oolitic (Mesozoic) ; the more important genera being Uraster, Luidia, Astropecten, Plumaster, and Goniaster, some of which have survived to the present day. Many Star-fishes occur, also, 224 MANUAL OF ZOOLOGY. in the Cretaceous rocks, the genera Greasier, Goniodiscus, and Astrogonium being among the more noticeable. In the Tertiary rocks few Star-fishes are known to occur, but Goniaster and Astropecten are represented in the London Clay (Eocene). 5. OPHIUROIDEA. — The "brittle-stars" are represented in the Silurian rocks by some anomalous genera, of which the best known is Protaster. In the Triassic, Oolitic, Cretaceous, and Tertiary rocks various genera of Ophiuroidea are known ; some being extinct, whilst others still survive at the present day. 6. ECHINOIDEA. — This order is represented in the Palaeozoic rocks by a single aberrant family : but it is numerously repre- sented in the Mesozoic and Kainozoic periods. Of the Palaeozoic Urchins or Perischoechinidcz, the two most abundant genera are Archceotidaris and Palachinus, both of which are principally Carboniferous, though the latter occurs in the Upper Silurian. Melonites and Oligoporus are exclusively Carboniferous ; and Lepidechinus and Eocidaris are principally so, though both commence their existence in the Devonian. The Secondary and Tertiary Echinoidea resemble those now living in being composed of not more than twenty rows of calcareous plates. The Oolitic and Cretaceous rocks are especially rich in forms belonging to this order, many genera being peculiar ; but the number of forms is too great to permit of any selection. It may be mentioned, however, that the singular genus Eckinothuria, with its flexible test, the predecessor of the living Asthenosoma and Phormosoma, is found in the Chalk. 7. HOLOTHUROIDEA. — This order, comprising, as it does, soft-bodied animals, has left but few traces of its existence in past time. The calcareous integumentary plates and spicules of Sea-cucumbers are, however, by no means absolutely un- known in the fossil condition, ranging from the Carboniferous onwards. The shield of Psolus has also been detected in Post-tertiary deposits in Bute. LITERATURE. GENERAL WORKS. 1. " Klassen und Ordnungen des Thier-Reichs," vol. ii. ' Strahlen- thiere.' Bronn. 1860. 2. "A History of British Star-fishes and other Animals of the Class Echinodermata. " Edward Forbes. 1841. 3. " Grundriss der Vergleichenden Anatomic." Gegenbaur. 1874. ECHINODERMATA : LITERATURE. 225 4. "Die Larven und Metamorphosen cler Echinodermen." ]"• Miiller. 'Abhandl. Berlin Akad.' 1848-55. 5. Article "Echinodermata." Sharpey. Todd's 'Cyclopaedia of Ana- tomy and Physiology. ' 1839. 6. "Anatomic der Rohren-Holothurie," &c. Tiedemann. 1820. 7. " Morphologische Studien an Echinodermen." H. Ludwig. 'Zeit- schr. f. Wiss. Zool.,'vols. xxviii.-xxxi. 8. ' ' Beitrage zur Anatomic der Echinodermen. " R. Teuscher. ' Jenaische Zeitschr. ,' vol. x. 9. "Peculiarities in the Mode of Propagation of certain Echinoderms of the Southern Seas." Wyville Thomson. 'Journ. Linn. Soc.,' vol. xiii. 1876. ECHINOIDEA. 10. " Monographies d'Echinodermes vivants et fossiles." Louis Agassiz. 1838-41. 11. "Catalogue raisonne des families, des genres, et des especes de la classe des Echinodermes. " Louis Agassiz and Desor. 1847. 12. "Revision of the Echini." Alexander Agassiz. 'Memoirs of the Museum of Comparative Zoology at Harvard,' vol. iii. 1872-74- 13. "Monograph of the British Fossil Echinodermata. " Thomas Wright. ' Palseontographical Society.' 14. " Monograph of the Echinodermata of the British Tertiaries." Edward Forbes. ' Palseontographical Society. ' 15. " Paleontologie Fran9aise, Terrains Cretaces," torn. vi. and vii. 'Echinodermes.' A. D'Orbigny and G. Cotteau. 1856-57 and 1861-67. 16. " Synopsis des Echinides fossiles." E. Desor. 1855-59. 17. " Etudes sur les Echino'ides. " S. Loven. 1874. 18. " Recherches sur 1'appareil circulatoire des Oursins." Perrier. 'Arch. de Zool. Exper. et Gen.,' vol. iv. 1876. ASTEROIDEA AND OPHIUROIDEA. 19. "System der Asteriaden." Miiller and Trosch el. 1843. 20. " British Fossil Echinodermata. " ' The Asteroidea. ' Thomas Wright. ' Palseontographical Society. ' 21. "Ophiuridae and Astrophytidae." Theodore Lyman. 'Illustrated Catalogue of the Museum of Comparative Zoology at Harvard.' 1865. 22. "Ueber die Larven und die Metamorphosen der Ophiuren." J. Miiller. 'Abhandl. Berlin Akad.' 1846. (See also several of the works mentioned under the head of "General works." As regards the development of the Asteroids and Ophiuroids, the English student may consult Professor Huxley's " Report upon the Researches of Professor Miiller into the Anatomy and Develop- ment of Echinoderms," in the 'Annals of Natural History,' ser. 2, vol. viii. 1851 ; or Packard's ' Life- Histories of Animals.') 23. "Beitrage zur Anatomic und Histologie der Asterien und Ophiuren." Lange. ' Morphologisches Jahrb.,' vol ii. 24. "Acklitamenta ad historian Ophiuridarum." Liitken. 1859. 25. " North American Star-fishes. " A. Agassiz. 1877. CRINOIDEA. 26. "A Natural History of the Crinoidea," &c. J. S. Miller. 1821. 27. " Memoir on the Pentacrinus Europaeus. " J. V. Thompson. 1827. P 226 MANUAL OF ZOOLOGY. 28. " Ueber den Pentacrinus caput-Medusoe." J. Miiller. 1843. 29. " Recherches sur les Crinoides du terrain carbonifere de la Belgique." De Koninck and Le Hon. 1854. 30. "Development of Comatula. " Sir Wyville Thomson. ' Phil. Trans.' '1865. 31. "The Depths of the Sea." Sir Wyville Thomson. 1873. 32. " Notice of new living Crinoids belonging to the Apiocrinidse." Sir Wyville Thomson. 'Journ. Linn. Soc.,' vol. xiii. 1876. 33. "On the Structure, Physiology, and Development of Antedon rosaceus." Dr W. B. Carpenter. ' Proc. Roy. Soc. ' 1876. 34. "Anatomy, Physiology, and Development of Comatula." Dr W. B. Carpenter. 'Phil. Trans.' 1866. 35. "The Crinoidea of the Lower Silurian Rocks of Canada." E. Bil- lings. 'Figures and Descriptions of Canadian Organic Remains,' Decade iv. 1859. 36. " Memoires pour servir a la connaissance des Crinoides vivants." M. Sars. 1868. 37. "Anatomy of the Arms of Crinoids." 'Journ. Anat. and Phys.,' vols. x. and xi. P. H. Carpenter. 38. "Anatomy of Pentacrinus and Rhizocrinus." 'Journ. Anat. and Phys.,' vol. xii. P. H. Carpenter. 39. " On the Genus Actinometra. 'Trans. Linn. Soc.' 1877. P. H. Carpenter. 40. " On the Oral and Apical Systems of Echinoderms. " 'Quart. Journ. Micro. Sci.,' vol. xviii. P. H. Carpenter. 41. " Entwickelungs - Geschichte der Comatula Mediterranea." 'Arch. f. Mikr. Anat.,' vol. xiii. 1876. A. Gotte. CYSTOIDEA. 42. " On the Cystidea of the Lower Silurian Rocks of Canada." E. Bil- lings. ' Figures and Descriptions of Canadian Organic Remains, ' Decade iii. 1858. 43. " Notes on the Structure of the Crinoidea, Cystidea, and Blastoidea." E. Billings. 'Palaeozoic Fossils,' vol. ii. 1874. 44. "Ueber Cystideen." Von Buch. 1845. (Translated in 'Quart. Journ. Geol. Soc. Lond.' 1845.) BLASTOIDEA. 45. "Monographic der fossilen Krinoideen - Familie der Blastoideen. " Ferdinand Roemer. 1851. (See also the works by Billings quoted above.) HOLOTHUROIDEA. 46. "Forms of Animal Life." G. Rolleston. 1870. (For anatomy of Cucttmaria pentactes, pp. 145-158.) 47. " Reisen im Archipel der Philippines" C. Semper. 1868. 48. " Beitrage zur Anatomic und Systematik der Holothurien. " ' Zeitschr. f. Wiss. Zool.' E. Selenka. 1867-68. 227 TTTKI • ANNUL O S A. CHAPTER XXIII. i. GENERAL CHARACTERS OF THE ANNULOSA. 2. DIVISIONS OF ANNULOSA* 3. GENERAL CHARACTERS OF THE Sco- LECIDA. 4. CHARACTERS OF THE T^NIADA. SUB-KINGDOM ANNULOSA. — The Annulose animals are charac- terised by the possession of a body which is usually more or less elongated, and is always bilaterally symmetrical, instead of being radially disposed. Very commonly the body is divided into similar (homonomous) segments, which may be definite or indefinite, and are arranged along an antero-posterior axis. Lateral appendages may be absent or present, and when present, are symmetrically disposed. A nervous system is present, and consists of one or two ganglia placed in the anterior part of the body, or of a ventr ally- placed double gangliated chain, The association of the Scolecida with the normal Annulose animals renders necessary an exceedingly general, and there- fore correspondingly vague, definition of the sub -kingdom Annulosa. The sub-kingdom may, however, be divided into the following three primary sections, each of which admits of being characterised in a sufficiently definite manner : — I. Scolecida. — This division includes the parasitic worms (Entozoa), the Wheel-animalcules, and some allied forms, and is characterised by having an elongated or a flattened body, which may have an annulated integument, but which is not at all, or but imperfectly segmented. . A water-vascular system is present, but is not concerned with locomotion. There is no true blood-vascular system, and the nervous system consists of one or two cephalic ganglia, and never has the form of a gangliated ventral chain. Lateral appendages are almost universally wanting. The Scolecida were formerly placed by Huxley along with the Echinodermata in a special sub-kingdom (Annuloidd) ; and 228 MANUAL OF ZOOLOGY. no doubt can be entertained as to the reality of the relation- ships between these two groups of animals. On the other hand, many and close points of affinity unite the higher Scoledda with the Ringed Worms (Annelida] ; and many syste- matists unite the Scoledda and Anarthropoda in a common sub-kingdom, to which they restrict the Linnean name of Vermes. II. ANARTHROPODA. — This division includes the Spoon Worms (Gephyrea\ the Ringed Worms (Annelida), and the Arrow Worms ( Chcetognathd), and is characterised by the fact that the body is composed of a number (often indefinite) of similar or nearly similar segments arranged longitudinally. A " pseudo-haemal " system of vessels is generally present. The nervous system is placed ventrally, and consists typically of a double chain of ganglia, united by longitudinal commis- sures, and forming an cesophageal collar. Cilia are generally developed. Lateral locomotive appendages are usually pres- ent, but are never jointed or articulated to the body. III. ARTHROPODA. — This division includes the Crustaceans, (Crustacea), the Spiders, Scorpions, &c. (Arachnida), the Cen- tipedes and their allies (Myriapoda), and the Insects (Insecta). The body (fig. r 1 2) is composed of a series (usually definite) Fig. 112. — Diagram of the anatomy of an insect, an Antennae ; e Eye; m Mouth; ^Gullet; sg Salivary gland ; * Stomach \f Tubes supposed to represent the kid- neys ; z Intestine ; c Chamber (cloaca) into which the intestine opens ; v Vent ; k Heart ; n Nervous system ; / Bases of the legs. of distinct rings or " somites," arranged along a longitudinal axis. A true blood-vascular system is normally present, and the heart is placed dorsally. The nervous system consists primitively of a double chain of ganglia, placed ventrally, and traversed anteriorly by the oesophagus. Limbs are almost always present, and are jointed and articulated to the body. The integument is more or less extensively hardened by the deposition in it of chitine, with or without salts of lime ; and ciliated epithelium is not developed. ANNULOSA : SCOLECIDA. 229 THE SCOLECIDA. The name of Scolecida was proposed by Professor Huxley * for the reception of the Rotifera, the Turbellaria, the Trema- toda, the Tceniada, the Nematoidea, the Acanthocephala, and the Gordiacea. Of these the Rotifera stand alone ; whilst the Turbellaria, Trematoda, and Tceniada constitute the old division of the Platyelmia (Flat Worms); and the Nematoidea, Acanthocephala, and Gordiacea make up the old Nematelmia (Round Worms or Thread-worms). For some purposes these old divisions are sufficiently convenient to be retained, though they are of little scientific value. The term Entozoa has ac- quired such a general currency that it is necessarily employed occasionally, but it has been used in such widely different senses by different writers, that it would be almost better to discard it altogether. It certainly cannot be used as synony- mous with Scolecida, many of these not being parasitic at all. It will therefore be employed here, in a restricted sense, to designate those orders of the Scolecida which are internal parasites, comprising the Trematoda, Taniada, Nematoidea (in part), Acanthocephala, and Gordiacea. The Turbellaria and Rotifera, with a section of the Nematoidea, lead a free exist- ence, and are not parasitic within other animals. The Scolecida are defined by the possession of a "water- vascular system," consisting of a " remarkable set of vessels which communicate with the exterior by one or more apertures situated upon the surface of the body, and branch out, more or less extensively, into its substance" (Huxley). No proper vas- cular apparatus is present, and the nervous system (when pre- sent) "consists of one or two closely approximated ganglia." The body is not segmented, or but imperfectly so, and lateral appendages are absent in all except certain of the Rotifers. The habits and mode of life of the different members of the Scolecida are so different, that no other character, save the above, can be predicated which would be common to the entire group, and would not be shared by some other allied division. The most important morphological feature by which the Scolecida are separated from the Annelida, is that they are destitute of the ventral gangliated nerve- chain which is so characteristic of the latter group. * More recently ('A Manual of the Anatomy of Invertebrated Animals,' 1877) Professor Huxley has abandoned the division of the Scolecida, and has separated its members into two sections (Trichoscolices and Nemato* sco lie es). 230 MANUAL OF ZOOLOGY. DIVISION I. PLATYELMIA. — This section includes those Scole- cida which possess a more or less flattened body, usually some- what ovate in shape, and not exhibiting anything like distinct segmentation. The division includes two parasitic orders — the Tceniada and the Trematoda, — and one non-parasitic order — viz., the Turbellaria. A sub-order, however, of this last, the Nemertidce, does not conform to the above definition ; but their other characters are such as to forbid their separation. ORDER I. TCENIADA (Cestoidea). — This order comprises the internal parasites, called Tape-worms (Cestoid worms), and the old order of the "Cystic Worms" (Cystica) ; the latter being now known to be merely immature forms of the Tape- worms. The Tceniada are Scolecids in which the body of the adult is elongated and composed of flattened joints, the anterior ex- tremity ("head") armed with hooklets, or suckers, or both combined. There is no mouth or alimentary canal, and the young pass through a metamorphosis. The mature animal is hermaphrodite. In their mature condition, the Tceniada (see figs. 113 and 114) are always found inhabiting the alimentary canal of some Fig. 113. — Morphology of Tceniada. a Head and a few following segments of Tcenia mediocanellata ; b A few segments of the same further removed from the head ; c and d Segments progressively further removed from the head,— all of the natural size ; e Head of the same, enlarged ; ft A single proglottis of the same, with its branched ovary and lateral genital pore, enlarged two diameters ; f Embryo of Teenia bacillaris, with six booklets ; g Cysticercus cellulose, with its booklets and suckers, its wrinkled neck, and its caudal vesicle, enlarged. (After Leuckart, Van Beneden, and Weinland.) warm-blooded vertebrate animal; and they are distinguished by their great length, and by being composed of a number of flattened joints or articulations. These joints are not, however, ANNULOSA: T^ENIADA. 231 an example of true segmentation, nor do they really constitute the Tape-worm ; the true animal being found in the small, rounded, anterior extremity, the so-called " head," or " nurse," whilst the joints are simply hermaphrodite generative segments, which the " head " throws off by a process of gemmation. The "head" (fig. 114, 3, and fig. 113, e), which constitutes the real Tape-worm, is a minute, rounded body, which is furnished with a circlet of hooks or suckers, or both, whereby the parasite is enabled to maintain its hold upon the mucous membrane of the intestines of its host. No digestive organs of any kind are present, not even a mouth ; and the nutrition of the animal is entirely effected by imbibition. The nervous system consists of two small ganglia, which send filaments backwards; but there is considerable obscurity on this point, and it has been asserted that the nervous system is entirely wanting, or that there is only a single ganglion. The " water- vascular system " consists of a series of long vessels which run down each side of the body, communicating with one another at each articula- tion by means of a transverse vessel, and opening in the last joint into a contractile vesicle. It thus appears that all the joints are organically connected together. Whilst the "head" constitutes the real animal, it nevertheless contains no repro- ductive organs, and these are developed in the joints or seg- ments (fig. 114, 3, and fig. 113, ti), which are produced from the head posteriorly by budding. After the first joint, each new segment is intercalated between the head and the seg- ment, or segments, already formed \ so that the joints nearest the head are those latest formed, and those furthest from the head are the most mature. Each segment, when mature, con- tains both male and female organs of generation, and is there- fore sexually perfect. To such a single segment (figs. 114, 4, and 113, h\ the term "proglottis" is applied, from its resem- blance in shape to the tip of the tongue. The ovary is a branched tube, which occupies the greater part of the pro- glottis, and opens, along with the efferent duct of the male organ, at a common papilla, which is perforated by an aper- ture, termed the " generative pore." The position of this pore varies, being placed in the centre of one of the lateral margins of the proglottis in the common Tape-worms of man ( Tania solium and T. mediocanellata), but being situated upon the flat surface of the segment in the rarer Bothriocephalus latus. These two elements — namely, the minute head, with its hook- lets and suckers, and the aggregate of the joints, or proglot- tides — together compose what is commonly called a "Tape- worm," such as is found in the alimentary canal of man and 232 MANUAL OF ZOOLOGY. of many animals. The length of this composite organism varies from less than an inch to several yards. Singular as is the composition of the mature Tape-worm, still more extraordinary are the phenomena observed in its development, of which the following is a brief account : — " Proglottides," or the sexually mature segments of a Tape- worm, are only produced within the alimentary canal of man, or of some other warm-blooded vertebrate. The development of the ova which are contained in the proglottides, cannot, however, be carried out in this situation ; hence the compar- ative harmlessness of this parasite, and hence the name of " solitary worm/' which is sometimes applied to it. For the production of an embryo, it is necessary that the ovum should be swallowed by some animal other than the one inhabited by the mature Tape-worm. If this does not take place, the fecun- dated ovum is absolutely unable to develop itself. To secure this, however, the dispersion of the ova is provided for by the expulsion of the ripe proglottides from the bowel, all their contained ova having been previously fertilised. After their discharge from the body, the proglottides, which for some time retain their vitality and possess some power of movement, de- compose, and the ova are liberated (fig. 114, i), when they are found to be covered by a capsule which protects them from all ordinary mechanical, and even chemical, agencies, which might prove injurious to them. In this stage, the embryo is often so far developed within the ovum that its head may be recognised by its possession of three pairs of siliceous hooklets. For further development, it is now necessary that the ovum be swallowed by some warm-blooded vertebrate, and should thus gain access to its alimentary canal. When this takes place, the protective capsule or covering of the microscopically minute ovum is ruptured, either mechanically during mastication, or chemically by the action of the gastric juice ; and the embryo is thus liberated. The liberated embiyo (fig. ii3,/)is now called a " proscolex," and consists of a minute vesicle, which is provided with three pairs of siliceous spines, fitted for bor- ing through the tissues of its host. Armed with these, the proscolex perforates the wall of the stomach, and may either penetrate some contiguous organ, or may gain access to some blood-vessel, and be conveyed by the blood to some part of the body, the liver being the one most likely. Having by one of these methods reached a suitable resting- place, the proscolex now proceeds to surround itself with a cyst, and to develop a vesicle, containing fluid, from its pos- terior extremity, when it is called a "scolex" (fig. 114, 2, and ANNULOSA: T^NIADA. 233 fig. 113, £"). In some of the Tceniada the scolices are called " hydatids," and it is these, also, which constituted the old order of the " Cystic Worms." When thus encysted within Fig. 114. — Morphology of Taeniada. i. Ovum containing the embryo in its leathery case; 2. Cysticercus longicollis; 3. "Head" of the adult Teenia solittm, enlarged, showing the hooklets and cephalic suckers ; 4. A single generative joint, or pro- glottis, magnified, showing the dendritic ovary (> Fig. 130. — Tubicola. a Serpula con- tortuplicata, showing the branchiae and operculum ; b Spirorbis corn- in unis. 266 MANUAL OF ZOOLOGY. secreted. The young Tubicolar Annelide thus resembles the permanent condition of the Errant forms ; and the stationary Fig. 131. — Development of Tubicolar and Errant Annelides A, Larva of Tercbella; o Position of the mouth ; a Anus, surrounded by the posterior circlet of cilia; c An- terior circlet of cilia ; t Tentacle. B, Polytrochal larva of Arenicola; C, Larva of Pnyllodoce. D, Larva of Spirorbis ; tt Tentacles. All the figures are greatly magnified. (After Claparede, Schultze, and A. Agassiz.) condition of the adult, accompanied by the loss of its sense- organs, may be regarded as an instance of "retrograde de- velopment." The most familiar of the Tubicola is the Serpula (fig. 130, a), the con- torted and winding calcareous tubes of which must be known to almost every one as occurring on shells or stones on the sea-shore. One of the cephalic cirrhi in Serpula is much developed, and carries at its extremity a conical plug, or operculum, whereby the mouth of the tube is closed when the animal is retracted within it. The operculum of Serpula has a more than ordinary interest in the fact that it is the only instance in the Annelida in which calcareous matter is deposited within the integument. In Spirorbis (fig. 130, b) the shelly tube is coiled into a flat spiral, one side of which is fixed to some solid object. It is of extremely common occurrence on the fronds of sea- weed and on other submarine objects. Equally familiar with Serpula is Terebella, the animal of which is in- cluded in a tube composed of sand and fragments of shell, cemented together by a glutinous secretion. In the Sabellida the tube is composed of granules of sand or mud. In Pectinaria the tube is free, membranous, or papyra- ceous, covered with sand-grains, and in the form of a reversed cone of con- siderable length. In Phoronis, the tube is membranous, and the branchiae are carried upon a horse-shoe-shaped process, which is strikingly similar to the " lophophore " of the Polyzoa, ORDER IV. ERRANTIA ( Chcetopoda, or Nereided], — This order ANNULOSA: ANNELIDA. 267 comprises /V<^ Annelides,* which possess setigerous foot-tubercles. The respiratory organs are generally in the form of tufts of ex- ternal branchice, arranged along the back or the sides of the body. The sexes are distinct, and the young pass through a metamor- phosis. This order includes most of the animals which are commonly known as Sand-worms and Sea-worms, together with the familiar Sea-mice. The integument is soft, and the body is distinctly divided into a number of rings or segments, each of which, in the typical forms, possesses the following structure. The segment consists of two arches, a lower or " ventral arc," and an upper or " dorsal arc," with a " foot-tubercle " on each side. Each foot-tubercle consists of an upper process, or "noto- podium," and a lower process, or " neuropodium," each of which carries a tuft of bristles, or "setae," (rarely, a single bristle) and a species of tentacle termed the "cirrhus" (fig. 126). The outer, cuticular layer of the body is generally more or less chitinous, and is often iridescent. Below this is a mus- cular layer, by which the movements of the animal are effected, and which encloses the " perivisceral cavity." This cavity runs the whole length of the body, and is lined by a special, often ciliated membrane, which is reflected upon the alimen- tary canal and other internal organs. It is usually more or less subdivided by imperfect partitions, and is filled with an albuminous fluid containing floating corpuscles, and corre- sponding with the blood. This so-called " chylaqueous fluid," " performs one of the functions of an internal skeleton, acting as the fulcrum or base of resistance to the cutaneous muscles, the power of voluntary motion being lost when the fluid is let out " (Owen). The anterior extremity of the body is usually so modified as to be distinctly recognisable as the head, and is provided with eyes, and with two or more feelers, which are not jointed, and are therefore not comparable with the antennae of Crus- tacea and Insects. The mouth is placed on the inferior sur- face of the head, and is often furnished with one or more pairs of horny jaws, working laterally. The pharynx is muscular, and forms a sort of proboscis, being provided with special muscles, by means of which it can be everted and again re- tracted. In most there is no distinction between stomach and * Fritz Miiller describes an errant Annelide belonging to the Amphino- mid 3)- The next two somites carry appendages, which are in the form of jaws, and are termed respectively the first and second pairs of " maxillae." Each consists of the parts afore- mentioned, but the epipodite of the first pair of maxillae is rudimentary, whilst that of the second pair is large, and is shaped like a spoon. It is termed the " scaphognathite," and its function is to cause a current of water to traverse the gill- chamber by constantly bailing water out of it. The next seg- ment carries the biting jaws or " mandibles ; " each of which consists of a large protopodite, and a small endopodite, which is termed the "palp," whilst the exopodite is undeveloped. The aperture of the mouth is situated between the bases of the mandibles, bounded behind by a forked process, called the "labium," or " metastoma," and in front by a single plate, called the "labrum" (upper lip). The next segment bears the long antennae, or feelers (fig. 136, a'\ each consisting of a short protopodite, and a long, jointed, and segmented endo- podite, with a very rudimentary exopodite. In front of the great antennae is the next pair of appendages, termed the " antennules," or smaller antennae (fig. 136, a), each composed of a protopodite, and a segmented endopodite and exopodite, 282 MANUAL OF ZOOLOGY. which are nearly of equal size. Finally, attached to the first seg- ment of the head are the eyes, each of which is borne upon an eye-stalk formed by the protopodite. The gill-chamber is formed by a great prolongation downwards of the pleurae of the thoracic segments, and the gills are attached to the bases of the legs. As regards the digestive system of the Crustacea, the ali- mentary canal is, with few exceptions, continued straight from the mouth to the aperture of the anus. There are no salivary glands, but a large and well-developed liver is usually present. A heart is generally, but not always, present. In most of the lower forms it is a long vasiform tube, very like the " dorsal vessel " of Insects. In the higher Crustaceans, the course of the circulation is as follows (fig. 138) : The heart is a muscular sac, situated dorsally, beneath the carapace, and it gives origin Fig. 138. — Diagram of the circulation of the Lobster. The systemic arteries are shaded longitudinally, the veins are dotted, and the branchial vessels are black. h Heart; a a Systemic arteries; bb Branchial vessels; cc Venous sinuses; gg Branchiae ; p Pericardium. to six arterial trunks, which convey the aerated blood to all parts of the body. The terminations of the arteries open into a series of irregular venous sinuses, whence the blood is collected into a principal ventral sinus, and distributed to the branchiae, where it undergoes aeration. From the gills the now aerated blood is carried by a series of branchial vessels to a large sac, which is badly termed the " pericardium," and which envelops and surrounds the heart. The arterial blood gains access to the cavity of the heart by means of six pairs of valvular fissures, which allow of the ingress of the blood, but prevent regurgitation. A portion of the venous blood, how- ever, is not sent to the branchiae, but is returned directly, without aeration, to the pericardium ; so that the heart finally distributes to the body a mixture of venous and arterial blood. ANNULOSA: CRUSTACEA. 283 Distinct respiratory and circulatory organs may be altogether wanting; but, as a rule, distinct branchiae are present. The exact form and structure of the gills differ in different cases, but their leading modifications will be alluded to in treating of the different orders. TABULAR VIEW OF THE DIVISIONS OF THE CRUSTACEA. Sub-class I. EPIZOA. Order i. Ichthyophthira. it 2. Rhizocephala. it 3. Cirripedia. Sub-order i. Thoradca. M 2. Abdominalia. M 3. Apoda. Sub-class II. ENTOMOSTRACA. Order 6. Ostracoda. \ T . T , M 7. Copepoda. j^7^, Lophyropoda. H 8. Cladocera. \ n 9. Phyllopoda. I Legion, Branchiopoda. ., i.o. Trilobita. ) M ii. Merostomata. Sub-class III. MALACOSTRACA. Division A. EDRIOPHTHALMATA, Order 12. Lczmodipoda. M 13. Amphipoda. M 14. Isopoda. Division B. PODOPHTHALMATA. Order 15. Stomapoda. it 1 6. De.capoda. Tribe a. Macrura. H b. Anomura. it c. Brachyura. CHAPTER XXXI. SUB-CLASS EPIZOA. THE members of this sub-class are Crustaceans which in the adult state (except the males of some forms) are destitute of the power of locomotion, being fixed parasitically to the ex- 284 MANUAL OF ZOOLOGY. terior of other animals or adherent to foreign bodies. The young are locomotive, and are -provided with eyes and an- tennae. Branchiae are wanting or rudimentary. ORDER I. ICHTHYOPHTHIRA. — Adult parasitic, deformed, often with rudimentary limbs ; mouth suctorial ; respiratory organs wanting ; females with external ovisacs. Larva locomotive, and imdergoing retrograde metamorphosis. The members of this order (Lerncea, Achtheres^ Peniculus, Caligus, Argulus, &c.) are attached in the adult condition to the skin, eyes, or gills of fishes, and when mature possess an elongated body, having a more or less distinct head, and in the females usually a pair of long, cylindrical ovisacs, depend- ing from the extremity of the abdomen (fig. 139). Some adhere by a suctorial mouth, or by cephalic processes (Cephaluna)\ others are at- tached by a suctorial disc, developed at the extremities of the last pair of thoracic limbs, which are united to- gether (Brachiund) • whilst in others (Onchuna) attach- ment is effected by hooks at the free extremities of the first pair of thoracic limbs (Owen). The males (fig. 140, b} are usually not attached, but ad- here to the females, of which, from their much smaller size, they appear to be mere para- sites. The chief anatomical Fig. 139.— Female of Acktheres Carpenteri, peculiarities of the female are magnified. The line placed alongside of ,1 r n TV, l, A \ the figure shows the real size, a Abdomen; tllC following I The head IS d Disc of attachment developed upon the provided usually with a pair last pair of thoracic limbs ; o Ovisac. r • • j j \i of jointed antennae, and the body is divided into a cephalothorax and abdomen. The alimentary canal consists of a mouth, gullet, and intestine, terminating posteriorly in a distinct anus. The nervous sys- tem consists of a double ventral cord. There are no differen- tiated breathing-organs, and respiration is effected by the sur- face of the body. The embryo (fig. 140, a) is free-swimming, and is provided with visual organs and locomotive appendages. The two sexes are now alike, and the conversion of the active embryo, ANNULOSA: CRUSTACEA. 285 or larva, into the swollen and deformed adult, must be regarded as an instance of " retrograde metamorphosis." In Achtheres percarum (fig. 140), as generally in the order, the primitive form of the young is a " Nauplius ; " * but a wholly different larva, resembling the Cyclops in shape, but with fewer limbs and somites, is prepared within the Nauplius-skin, and is liberated by the rup- ture of the same. As regards their af- finities, the Ichthyoph- thira are closely allied tO the Copepoda, and Fig. 140.— Ichthyophthira. a Free-swimming larva of rno^r \r\r\ e.(*r\ H^ v^rror-rl Achtheres percarum in its first stage ; b Adult male may, indeed, DC regard- Of the same. Enlarged. (After Owen.) ed as parasitic Cope- pods, having the mouth modified so as to form a suctorial tube or beak, resulting from the elongation of the labrum and labium. Within this are two stylets or lancet-shaped mandibles, used in piercing. The feet are often deformed by age, or wanting, but are primitively natatory. Not only does their developmental history bear out this view, but cases are known (in some Lern&cp) in which the males do not undergo retrograde metamorphosis, but remain permanently in the con- dition of free Copepods. ORDER II. RHIZOCEPHALA. — Adult parasitic, attached by ramified roots (antenna?). Body sac- like, unarticulated, with- out limbs. No mouth. Larva a locomotive " nauplius." The Rhizocephala constitute a peculiar group of Crustaceans, the adults of which are found attached parasitically to the abdomen of Crabs and Hermit-crabs. The body (fig. 141, B) is sac-like, and non-segmented, and consists of a muscular mantle in which no skeletal structures are developed, its only aperture being reproductive and closed by a sphincter. There are no limbs, sense-organs, or alimentary canal, but there are well-developed reproductive organs, each individual, according to Giard, being hermaphrodite. The sac-like body is kept in connection with its host by means of branched, root-like pro- cesses of attachment (fig. 141, B), which sink deeply into the tissues of the latter. These processes appear to correspond * The name of "Nauplius" was given by O. F. Miiller to the unseg- mented ovate larva of the lower Crustacea, with a median frontal eye, but without a true carapace ; and this name may be conveniently employed to designate all the larval forms which agree in these characters. 286 MANUAL OF ZOOLOGY. with the " cement-ducts " of the Cirripedes, and to be, there- fore, really the homologues of the antennae. By their means, the parasite draws nutriment from its host ; and as similar hol- Fig. 141. — Morphology of Rhizocephala, A, First larval form of Sacculina purpurea, greatly enlarged. B, Young of Peltogaster socialis attached to the abdomen of a Hermit-crab ; at a the root-like processes of attachment of one individual are shown. C, body of Sacculina carcini, of the natural size, the roots of attachment not shown. (A and B are after Fritz M tiller.) low nutritive processes are developed on the " peduncle " of certain Barnacles (Anelasma squalicola), there are grounds for accepting Kossmann's view that the Rhizocephala are really to be regarded as a degraded group of the Cirripedia. The embryos of the Rhizocephala (fig. 141, A) are at first " naupliiform," with an ovate unsegmented body, an unpaired median eye, and a dorsal shield or carapace. The abdomen terminates in a movable caudal fork, and there is neither mouth nor alimentary canal. In their second stage (as so- called " pupae "), the young of the Rhizocephala are enclosed in a bivalve shell, the foremost pair of limbs constitute pecu- liar organs of adhesion ("prehensile antennae" of Darwin), the two following pairs of limbs are cast off, and six pairs of powerful biramose natatory feet are formed on the thorax. There is still no mouth. The " pupae " now attach themselves to the abdomen of Crabs, Porcellance, and Hermit-crabs ; they remain astomatous ; " they lose all their limbs completely, and appear as sausage-like, sack-shaped, or discoidal excrescences of their host, filled with ova; from the point of attachment closed tubes, ramified like roots, sink into the interior of the host, twisting round its intestine, or becoming diffused amongst the sack-like tubes of its liver. The only manifestations of life which persist in these non plus ultras in the series of retro- gressively metamorphosed Crustacea are powerful contractions of the roots, and an alternate expansion and contraction of the body, in consequence of which water flows into the brood- ANNULOSA: CRUSTACEA. 28; cavity, and is again expelled through a wide orifice." (Fritz Miiller). ORDER III. CIRRIPEDIA. — Adult attached, enclosed in an integumentary sac, within which a many-valved shell is typicallv developed. Antenna modified for adhesion. Abdomen rudimen- tary. Limbs usually present, in the form of multiarticulate cirri. Sexes generally united. Young locomotive. This sub-class includes, amongst others, the common Acorn- shells and the Barnacles or Goose-mussels. All the Cirripedia are distinguished by the fact, that in the adult condition they are permanently fixed to some solid object by the anterior extremity of the greatly metamorphosed head ; the first three cephalic segments being much developed, and enclosing the rest. of the body. The larva is free and locomotive, and the subsequent attachment, and conversion into the fixed adult, is effected by means of a peculiar secretion, or cement, which is discharged through the antennae of the larva, and is produced by a special cement-gland, which is really a portion of the ovary. In the Cirripedia, therefore, the head of the adult is per- Fig. 142. — Morphology of Cirripedia. A, Lepas pectinata, one of the Barnacles, one side of the shell being removed, enlarged four times : c Peduncle ; d Cement-duct ; o Ovary ; s Ovisac ; v Vas deferens ; p Penis. B, Paecilasma fissa, enlarged five times ; c Peduncle. C, Balanus balanoides, viewed from above, of the natural size. D, Balanus tintinnabulum^ with the shell on one side removed to show the ani- mal : a One of the valves ("scutum") of the operculum; b Another valve ("tergum") of the operculum. (After Darwin and Pagenstecher.) manently fixed to some solid object, and the visceral cavity is protected by an articulated calcareous shell, or by a coriaceous envelope. The posterior extremity of the animal is free, and can be protruded at will through the orifice of the shell. This extremity consists of the rudimentary abdomen, and of six pairs 288 MANUAL OF ZOOLOGY. of forked, cirrated limbs, which are attached to the thorax, and serve to provide the animal with food. The two more import- ant types of the Cirripedia are the Acorn-shells (Balanida) and the Barnacles (Lepadidce). In the former the animal is sessile, the larval antennae, through which the cement exudes, being embedded in the centre of the membranous or calcareous " basis " of the shell. In the latter the animal is stalked, and consists of a " peduncle " and a " capitulum." The peduncle consists of the anterior extremity of the body, with the larval antennae, usually cemented to some foreign body. The capit- ulum is supported upon the peduncle, and consists of a case composed of several calcareous plates, united by a membrane, enclosing the remainder of the animal. As regards the development of the Cirripedia, the larva has the form of a "Nauplius" (fig. 143, A), with an unsegmented, pyriform body, a median eye, and a dorsal carapace. During its life as a Nauplius, the young moults several times (seven times in Lepas fascicularis, which is here taken as ex- emplifying the development of the Cirripedia in general) ; and these various castings of its integuments are accompanied with material changes of form. Fig. 143.— Development of Lepas fascicula ris. A, Early stage of the Nauplius, show- ing the three pairs of appendages, of which the hinder two pairs are bifurcate : o Eye- spot ; b Labrum ; g Gullet ; h h Lateral horns. B, the free-swimming Cypris-stage or "pupa," after the sixth moult, the antennae and feet retracted within the shell : an Antenna, with its suctorial disc, traversed by the duct of the cement-gland (eg ) ; sg Shell-gland ; o Eye ; ad Adductor-muscle ; / Feet ; c Caudal process. Both figures are greatly enlarged. (After Von Willemoes-Suhm.) When fully grown, the Nauplius has an oval or pyriform body, enclosed in a carapace, provided with long caudal and dorsal spines. There are three pairs of limbs, of which the first pair (representing the antennae) are undivided, while the two hinder pairs (fig. 143) are bifid, and all carry natatory bristles. There is a very large labrum (fig. 143, b} placed in front of the ANNULOSA: CRUSTACEA. 289 mouth, and there is a well-developed alimentary tube, which terminates by a distinct anus at the root of the caudal spine. There is at first merely a simple central eye ; but in the adult Nauplius, two compound lateral eyes are developed in addition. Ultimately, the Nauplius passes into its second condition or " Cypris-stage " (fig. 143, B), when it is often spoken of as a "pupa." It is now enclosed in an oval, bivalved, mussel-shaped shell, with an opening along the ventral margin. The second and third pairs of the appendages of the Nauplius have now disappeared, and the first pair of appendages constitute strong four-jointed antennae, the last segment of which is disc-shaped, and is pierced centrally by a pore, which is the open- ing of the excretory duct of the ' ' cement-glands, " these organs being situated at the bases of the antennae. The thorax has developed upon its sides six pairs of forked natatory limbs ; and the abdomen is rudimentary, three- jointed, with terminal forked swimming-appendages. The pupa does not feed, but is nourished by means of an extensive accumulation of fatty matter, which had been stored up by the Nauplius in the cephalic and dorsal regions of the body ; while the great labrum of the latter is now very much reduced in size. After a brief natatory life, the pupa fixes itself by means of the disc-seg- ments of the antennae to some foreign body, such as a rock, a piece of drift- wood, the skin of a Cetacean, a Sponge, the carapace of a Turtle, or the colony of an Oceanic Hydrozoon. The "cement -glands," which, as shown by Darwin, are "part of and continuous with the branching ovaria," secrete copiously an adhesive cement, which is poured forth through the central apertures of the antennal discs, and by means of which the animal is firmly and finally fastened down to the object to which it in the first place attached itself. The body now becomes enclosed in a multivalve calcareous "test," produced by a special shell-gland. The organs of the mouth become fully developed, and the lateral eyes of the locomotive pupa disappear altogether. Lastly, the six pairs of natatory limbs of the Cypris- stage are replaced by the six forked and multisegmentate "cirri" of the adult ; while the base of the abdomen carries the penis, in the form of a proboscidiform appendage. The form of the adult, as already said, differs considerably, but the two most important types are those presented respec- tively by the Sessile and by the Pedunculated Cirripedia. In the symmetrical Sessile Cirripedes or Balanidce, commonly known as Acorn-shells (fig. 142, C, D), the animal is protected by a calcareous shell, formed by calcifications within the walls of the first three cephalic segments. The animal is placed within the shell, head downwards, and is fixed to the centre of a shelly or membranous plate, which closes the lower aperture of the shell, and which is termed the "basis." The "basis " is fixed by its outer surface to some foreign object, and is some- times compact, sometimes porous. Above the basis rises a limpet-shaped, conical, or cylindrical shell, which is open at the top, but is capable of being completely closed by a pyra- midal lid or " operculum." Both the shell itself and the oper- culum are composed of calcareous plates usually differing from one another in shape, and distinguished by special names. Within the shell the animal is fixed, head downwards. The T 290 MANUAL OF ZOOLOGY. thoracic segments, six in number, bear six pairs of limbs, each of which consists of a jointed protopodite and a much-seg- mented exopodite and endopodite, both of which are bristled, and constitute the so-called " cirri," from which the name of the sub-class is derived. These twenty-four cirri — " the glass hand" of the Balanus — are in incessant action, being pro- truded from the opening of the shell, and again retracted within it, constantly producing currents of water, and thus bringing food to the animal. There are no specialised respi- ratory organs in the family of the Balanidce. Balani some- times attain a very considerable size, and Balanus psittacus is largely eaten on the coast of Chili. The remaining family of the Sessile Cirripedes is that of the Verrucidce, comprising only the single genus Verruca. In many respects the Verrucidce. approach the Balanidcz, but the shell is composed of six valves only, and is un symmetrical, whilst the scuta and terga (forming the operculum), though movable, are not furnished with a depressor muscle. In the Barnacles (Lepadidce), the anterior extremity of the animal is enormously elongated, forming, with the prehensile antennae, the cement-ducts, and their exu- dation, a long stalk or peduncle, whereby the animal is attached to some solid ob- ject. The peduncle is cylindrical, of vary- ing length, flexible, and furnished with pro- per muscles. In some species it is naked, but in others it is furnished with calcareous scales. At its free extremity the peduncle bears the " capitulum," which corresponds to the shell of the Balanoids, and is com- posed of various calcareous plates, united together by a membrane, moved upon one another by appropriate muscles, and pro- tecting in their interior the body of the ani- mal with its appendages. The thorax and limbs resemble those of the Balanus; but "slender appendages, which from their position and connections are homologous 144.— Lepas anati- with the branchiae of the higher Crustacea, are attached to, or near to, the bases of a greater or less number of the thoracic feet, and extend in an opposite direction outside the visceral sac " (Owen). All the Balanida are hermaphrodite, and this is also the case with most of the Lepadida, but some extraordinary Fig fera, the common Bar nacle. ANNULOSA: CRUSTACEA. 2QI exceptions occur in this latter order. Thus, in some species of Scalpellum the individual forming the ordinary shell is female, and each female has two males lodged in transverse depressions within the shell. These males " are very singular bodies; they are sac-formed, with four bead-like rudimental valves at their upper ends ; they have a conspicuous internal eye ; they are absolutely destitute of a mouth, or stomach, or anus; the cirri are rudimental and furnished with straight spines, serving apparently to protect the entrance of the sac ; the whole animal is attached like the ordinary Cirripede, first by the prehensile antennae, and afterwards by the cementing substance. The whole animal may be said to consist of one great sperm-receptacle, charged with spermatozoa; as soon as these are discharged, the animal dies." "A far more singular fact remains to be told; Scalpellum vulgare is, like ordinary Cirripedes, hermaphrodite, but the male organs are somewhat less developed than is usual ; and as if in compensation, several short-lived males are almost invariably attached to the occludent margin of both scuta. ... I have called these beings complemental males, to signify that they are complemental to an hermaphrodite, and that they do not pair like ordinary males with simple females" (Darwin). As regards their distribution, the Balanoids are shallow- water forms, and Balanus itself is cosmopolitan in its range, though, geologically, quite a modern genus. The Lepadoids are not only found attached to floating bodies, dead or alive, but also extend to great depths. Scalpellum, which is a com- mon Cretaceous genus, goes down to 3000 fathoms. Alcippe (which is without a shell and has only three pairs of feet), bores holes in the shells of Gasteropods. DIVISIONS OF CIRRIPEDIA.— (AFTER DARWIN.) SUB-ORDER I. THORACICA. Carapace, either a capitulum on a pedicle, or an operculated shell with a basis. Body, formed of six thoracic segments, generally furnished with six pairs of limbs j abdomen rudimentary, but often bearing caudal appen- iges. Fam. i. Balanidce. Sessile, without a peduncle ; scuta and terga (forming the operculum) provided with depressor muscles ; the rest of the valves immov- ably united together. Fam. 2. Verrucidce. Sessile. Shell asymmetrical, with scuta and terga, which are mov- able, but not furnished with a depressor muscle. Fam. 3. Lepadidcf. Pedunculated. Peduncle flexible, provided with muscles. Scuta 2Q2 MANUAL OF ZOOLOGY. • * and terga, when present, not furnished with a depressor muscle. Other valves, when present, not united into a single immovable case. SUB-ORDER II. ABDOMINALIA. Carapace, flask-shaped ; body formed of one cephalic, seven thoracic, and three abdominal segments, the latter bearing three pairs of cirri, but the thoracic segments being without limbs. Genus — Cryptophialus. SUB-ORDER III. APODA. Carapace, reduced to two separate threads serving for attachment. Body consisting of one cephalic, seven thoracic, and three abdominal seg- ments, all destitute of cirri. Mouth suctorial. Genus — Proteolepas. CHAPTER XXXII. SUB-CLASS ENTOMOSTRACA. SUB-CLASS III. ENTOMOSTRACA (Gnathopoda, Woodward). — The term Entomostraca has been variously employed, and few authorities include exactly the same groups of the Crustacea under this name. By most the division is simply denned as including all those Crustacea in which the segments of the thorax and abdomen, taken together, are more or fewer than fourteen in number — the parasitic Epizoa and the Cirripedia being excluded. By Professor Rupert Jones the following defi- nition of the Entomostraca has been given : — "Animal, aquatic, covered with a shell or carapace, of a horny consistence, formed of one or more pieces, in some genera resembling a cuirass or buckler, and in others a bivalve shell, which completely or in great part envelops the body and limbs of the animal. In other genera the animal is invested with a multivalve carapace, like jointed plate -armour ; the branchiae are attached either to the feet or to the organs of mastication ; the limbs are jointed, and more or less setiferous. The animals, for the most part, undergo a regular moulting or change of shell, as they grow ; in some cases this amounts to a species of transformation." The Entomostraca are divided into two great divisions, or " legions," the Lophyropoda and the Branchiopoda, with which the order Merostomata may be conveniently considered. DIVISION A. LOPHYROPODA. — The members of this division possess few branchiae, and these are attached to the appen- ANNULOSA: CRUSTACEA. 293 dages of the mouth. The feet are few in number, and mainly subserve locomotion ; the carapace is in the form either of a shield protecting the cephalothorax, or of a bivalve shell enclosing the entire body. The mouth is not suctorial, but is furnished with organs of mastication. This division comprises the two orders Ostracoda and Copepoda. ORDER I. OSTRACODA. — Small Crustaceans having the entire body enclosed in a shell or carapace, which is composed of two valves united along the back by a membrane. The branchice are attached to the posterior jaws, and there are only two or three pairs of feet, which subserve locomotion, but are not adapted for swimming. A distinct heart is sometimes present (Cypridina], but is more usually wanting (Cypris and Cythere\ Little is known of the development of the Ostracoda, but the young of Cypris are said to be " shell- bearing Nauplius forms" (Claus), possessing only the three anterior pairs of limbs, but protected by a bivalve shell. As in other Nauplii, the third pair of limbs, though now locomotive, are ulti- mately transformed into the mandibles. They pass through several stages, with complete moults, before arriving at sexual maturity. The young of Cythere, on the other hand, have at birth the two pairs of antennae and two pairs of jaws, with three pairs of rudimentary abdominal limbs. The order includes the Cyprides (fig. 145, a), which are of almost universal occurrence in fresh water. The common Fig. 145.— rFresh-water Entomostraca. a Cypris tris-striata : b Daphnia pulex ; c Cyclops quadricornis . Cypris is completely protected from its enemies by a bivalve carapace, which it can open and shut at will, and out of which it can protrude its feet. The closure of the carapace is effected by means of an * adductor muscle. Locomotion is mainly effected by means of a pair of caudal appendages. The Cypris is extremely prolific, and a single impregnation appears to last 294 MANUAL OF ZOOLOGY. the female for its entire lifetime. Young females, produced in this way, are also capable for some generations of producing fresh individuals without the influence of a male (partheno- genesis). The marine Ostracoda are mostly shallow-water forms, but there are deep-sea types which attain a comparatively gigantic size (nearly an inch in length). ORDER II. COPEPODA. — Small Crustaceans, having the head and thorax covered by a carapace, and ftirnished with five pairs of natatory feet. Usually there are two caudal locomotive ap- pendages. A distinct heart is sometimes absent (as in the Cyclo- pidce) but is sometimes present. Both marine and fresh- water Copepods are known. The larvae of the Copepods are Naupliiform, with unpaired eyes, three pairs of limbs (the future antennae and mandibles), and two terminal setae. Next the maxillae are produced, and then three other pairs of limbs (the foot-jaws and the two front pairs of natatory feet). At the next moult, the larva assumes the Cyclops form, but has at first much fewer limbs and somites. In the Cyclops (fig. 145, c), which is one of the commonest of the " Water-fleas," the cephalothorax is protected superiorly by a carapace, and the abdominal somites are conspicuous. In front of the head is situated a single large eye, behind which are the great antennae and the antennules. The feet are five pairs in number, each consisting of a protopodite and a seg- mented exopodite and endopodite, usually furnished with hairs, and forming an efficient swimming apparatus. The young pass through a metamorphosis, and are not capable of repro- ducing the species until after the third moult or change of skin. The female Cyclops carries externally two ovisacs, in which the ova remain till they are hatched. A single congress with the male is apparently sufficient to fertilise the female for life. The Copepoda, or Oar-footed Crustaceans, are all of small size, and are of common occurrence in fresh water in all parts of Europe. Many forms also live in the sea, sometimes in immense numbers. Thus Cetochilus is so abundant in the North and South Atlantic, as to communicate a ruddy tinge to the ocean, and to serve as one of the principal articles of diet of the whale. By good authorities the Ichthyophthira are regarded as merely Copepoda peculiarly modified to suit a life of parasitism. DIVISION B. BRANCHIOPODA. — The Crustaceans included in this division have many branchiae, and these are attached to the legs, which are often numerous, and are formed for swim- ming. In other cases the legs themselves are flattened out so ANNULOSA: CRUSTACEA. 295 as to form branchiae. The body is either naked, or is protected by a carapace, which may enclose either the entire body, or the head and thorax only. The mouth is provided with organs of mastication. The Branchiopoda comprise the Cladocera, the Phyllopoda, and probably the Trilobita, though this order departs in many respects from the first two groups. The Merostomata may be considered along with these, though these, too, are in many respects peculiar. ORDER I. CLADOCERA. — The members of this order are small Crustaceans, which have a distinct head, and have the whole of the remainder of the body enclosed within a bivalve carapace, similar to that of the Ostracoda. The feet are few in number (usually four, five, or six pairs'), and are mostly respir- atory, carrying the branchm. Two pairs of antenna are present, the larger pair being of large size, branched, and acting as nata- tory organs. The Cladocera quit the egg with the full number of limbs proper to the adult. In the Daphnia pulex (fig. 145, b}, or " branched-horned Water-flea," which occurs commonly in our ponds, the body is enclosed in a bivalve shell, which is not furnished with a hinge posteriorly, and which opens anteriorly for the protrusion of the feet. The head is distinct, not enclosed in the cara- pace, and carrying a single eye. The mouth is situated on the under surface of the head, and is provided with two man- dibles and a pair of maxillae. The gills are in the form of plates, attached to the five pairs of thoracic legs. The males are very few in number, compared with the females, and a single congress is all that is required to fertilise the female for life. Not only is this the case, but the young females pro- duced from the original fecundated female are able to bring forth young without having access to a male. Two kinds of eggs occur in Daphnia. In the first of these, or " summer eggs," the ova (from ten to fifty in number) are deposited in an open space between the valves, and are retained there until the young are ready to be hatched. In the second of these, or "winter eggs," which alone are fecundated, the ova (gener- ally two in number) are placed in a peculiar receptacle, which is formed on the back of the carapace, and is called the " ephip- pium" or saddle. After a time the ephippium is cast off, and floats about till spring, when its contained eggs are hatched by the warmer temperature of the water. ORDER II. PHYLLOPODA. — Crustacea, mostly of small size, the carapace protecting the head and thorax, or the body entirely naked. Feet numerous, never less than eight pairs, mostly foli- 296 MANUAL OF ZOOLOGY. aceous or leaf -like, branchial in function. The eyes sometimes con- fluent, sometimes distinct and sub-pedunculate. There are two horny mandibles without palps, and the first pair of feet are oar-like, with setiform terminal appendages. The remaining feet are branchial, and adapted for swimming. The Phyllo- pods undergo a metamorphosis, the youngest forms being Fig. 146. — Phyllopoda. Fairy Shrimp (Chirocephahts, or Branchip^ts, diaphanus). After Baird. "Nauplii." In Nebalia (fig. 147, C), however, which is the only marine Phyllopod, " Zoea-stages " are superadded as well. B Fig. 147. — Morphology of Phyllopoda. A, Lepidurns Angassi, viewed dorsally. B, Under side of head of the same. C, Nebalia bipes, one side of the carapace being removed, so as to show the branchial feet. D, Branchipus stagnalis, female. E and F, Young stages of the same. G, A magnified specimen of Estheria, in its living state. The Phyllopoda are chiefly interesting from their affinity to the extinct Trilobites. In the typical genera Limnadia and Apus the body is pro- tected by a carapace, which is bivalve in the former and shield-like in the latter. In Limnadia the carapace covers the greater part of the body, and opens along the ventral margin. There are from eighteen to thirty pairs of membranaceous and respiratory feet. In Apus the carapace is clypei- form and covers a portion of the abdomen ; and there are sixty pairs of feet, of which all but the first pair are foliaceous. Apus is gregarious, fresh- ANNULOSA: CRUSTACEA. 297 water in habit, and often found in great numbers in pools and ditches in Europe. The different species of Branchipus (figs. 146 and 147, D) have the transparent body unprotected by any carapace, and are found in ponds and swamps in various parts of the world. The various "Brine-shrimps" (Artemia) are found inhabiting the brine-pans in salt-works, or occur in salt-lakes in both hemispheres, being especially abundant in Great Salt Lake in Utah. In Estheria (fig. 147, G) the body is protected by a bivalve, sub-ovate carapace, which is extremely like the shell of a Bivalve Mollusc, not only in shape and appearance, but also in having the valves joined at their beaks dorsally, and marked with concentric lines of growth. The species live in fresh or brackish water. In Nebalia (fig. 147, C), the only marine type of the order, there is a bivalved carapace, which is furnished with a beak or "rostrum," and the eyes are pedunculated. There are two pairs of an- tennse, and eight pairs of leaf-like respiratory feet, followed by a series of natatory feet. There is no metamorphosis. Nebalia has decided affinities with the Stomapods, and perhaps is not properly referable to the Phyllopoda. ORDER III. TRILOBITA. — This order is entirely extinct, none of its members having survived the close of the Palaeozoic period. The Trilobites are Crustaceans in which the body is usually more or less distinctly trilobed ; there is a cephalic shield, usually bearing a pair of sessile compound eyes ; the thoracic somites are movable upon one another, and are very variable in number ; the abdominal segments are coalescent, and form a caudal shield; there is a well- developed iipper lip or " hypostome" As regards the general structure of the Trilobites, the body was protected by a well-developed shell or " crust," which covered the whole dorsal surface of the body, and which usu- ally exhibits more or less markedly a division into three longi- tudinal lobes (fig. 148), from which the name of the order is derived. The crust is composed of a cephalic shield, generally crescentic in shape, a variable number of free and movable rings, constituting the thorax, and a caudal shield or " pygi- dium," the rings of which are more or less completely anchy- losed. On the under surface of the head-shield in front, there is situated a forked or oval upper lip or " labrum," which re- sembles in form the labrum of the Phyllopodous genus Apus. Recent researches by Mr C. D. Walcott have also consider- ably increased our knowledge of the condition of the under surface of the body in the Trilobites. This observer, namely, has shown that the visceral cavity of the Trilobites (fig. 149, b) was bounded inferiorly by a thin membrane, which is attached to the lower margin of the dorsal crust all round. This ventral membrane was strengthened by calcified arches, which in turn supported the appendages beneath. As to these latter our knowledge is not yet complete, but we know that in some forms there existed a row of articulated appendages on each side of the middle line below. The thoracic appendages seem to have 298 MANUAL OF ZOOLOGY. been slender five-jointed legs, in which the terminal segment forms a pointed claw, and the basal segment carries a jointed appendage, regarded by Mr Walcott as homologous with the Fig. 148.— The skeleton of a" Trilobite (Angelina Sedgmickit), partially dissected. A, Head-shield. B, Movable rings of the thorax. C, Tail or abdomen, g Glabella, in this species without furrows ; fi Fixed cheeks ; e Eye - lobe ; o Eye ; f Facial suture; fr Free cheeks: s Head -spines; / Pleurae; pp Anchylosed pleurae of pygidium. " epipodite " of many recent Crustaceans. On each side of the thoracic cavity there is, also, attached a row of bifid spiral appendages (fig. 149, e\ of the nature of gills; and branchial appendages were probably attached to the bases of the thoracic limbs as well. With regard to the appendages of the head, the mouth is situated behind the hypostome, and is bounded by four pairs of jointed manducatory appendages, the basal joints of which are, partly or wholly, modified to act as jaws. The cephalic shield of a typical Trilobite is more or less completely semicircular (fig. 148), and is composed of a central and of two lateral pieces, of which the two latter may, or may not, be united together in front of the former. The median portion is usually elevated above the remainder of the ANNULOSA: CRUSTACEA. 299 cephalic shield, and is called the "glabella;" it protected the region of the stomach, and is usually divided into from three to four lobes by lateral grooves. At each side of the glabella, and continuous with it, is a small semicircular area, called the " fixed cheek." The glabella, with the " fixed C Fig. 149. — Transverse section of the thorax of Calymene senaria, partially restored (after C. D. Walcott). a Dorsal crust ; b Visceral cavity, continued laterally to the pleural margins of the dorsal crust; c Legs, restored; d Epipodite; e Spiral gills. Enlarged six times. cheeks," is separated from the lateral portions of the cephalic shield — termed the "movable" or "free cheeks" — by a peculiar suture or line of division, which is known as the "facial suture," and is quite unknown amongst recent Crustacea^ except for a faint indication in the Litnulus^ and more or less doubtful traces in certain other forms. The movable cheeks bear the eyes, which are generally crescentic or reniform in shape, are rarely pedunculated (being never supported upon movable foot-stalks), and consist of an aggregation of facets covered by a thin cornea. The facial sutures may join one another in front of the glabella — in which case the free cheeks will form a single piece ; or they may cut the anterior mar- gin of the shield separately — in which case the free cheeks will be discon- tinuous. The posterior angles of the free cheeks are often produced into long spines. Behind the cephalic shield comes the thorax, composed of a variable number of segments, which are not soldered together, but are capable of free motion upon one another, so as to allow the animal, in many cases, to roll itself up after the manner of a wood-louse or hedgehog. The thorax is usually strongly trilobed, and each thorax-ring shows the same triloba- tion, being composed of a central, more or less strongly convex, portion, called the "axis," and of two flatter side-lobes, called the "pleurae." The " pygidium," or " tail," is usually trilobed also, and, like the thorax, consists of a median axis and of a marginal limb, the composition of the whole out of anchylosed segments being shown by the existence of axial and pleural grooves. ORDER IV. MEROSTOMATA. — The members of this order are Crustacea, often of gigantic size, in which the mouth is fur- nished with mandibles and maxillae, the terminations of which become walking or swimming feet and organs of prehension. 300 MANUAL OF ZOOLOGY. This order comprises the recent King-crabs, and the extinct Pterygoti and Eurypteri. SUB-ORDER i. XIPHOSURA. — " Crustacea having the anterior segments welded together to form a broad convex buckler, ttpon the dorsal surface of which are placed the compound eyes and ocelli, the former sub-centrally, the latter in the centre in front. The mouth is furnished with a small labrum, a rudimentary metas- toma and six pairs of appendages. Posterior segments of the body more or less free, and bearing upon their ventral surfaces a series of broad lamellar appendages ; the telson, or terminal segment, ensiform " (Henry Woodward). The Xiphosura include no other recent forms than the Limuli (King-crabs, or Horse-shoe Crabs). They are dis- tinguished by the possession of six pairs of chelate limbs, placed round the mouth, having their bases spinous, and officiating as jaws. The anterior portion of the body is covered by a broad horse-shoe-shaped buckler (fig. 150), the upper surface of which bears a pair of larval and a pair of compound eyes. On the lower surface of the carapace is placed the aperture of the mouth, surrounded by six pairs of limbs, the bases of which are spinous and officiate as jaws, whilst their termina- tions are converted into chelae or nipping-claws. The first pair of appendages is placed in front of the mouth, and has been generally said to represent the antennae ; but according to Milne-Edwards they are not supplied with nerves from the cerebral ganglia, and therefore cannot be of this nature. Be- hind the cephalic buckler comes a second shield, composed of six amalgamated segments, below which are carried the re- productive organs and branchiae, the former protected by a thoracic plate or " operculum," the latter borne by five pairs of lamellar appendages. Lastly, articulated to the posterior margin of the abdominal shield, is a long sword-like spine or "telson" (fig. 150, /). The circulatory system of Limulus is of a very high type, though the heart is tubular. The venous blood, instead of being contained in the mere interspaces and lacunae between the tissues, is to a large extent confined within proper vessels. A remarkable peculiarity, also, is that the ventral nerve-cord is enclosed within the abdominal artery, and most of the nerves are similarly ensheathed within the arteries. The eggs of Limulus are laid in the sand, and are fertilised by the male. Just prior to the time of hatching, six segments can be recognised in the cephalothorax ; the abdomen consists of nine well-marked somites ; the bases of the legs are hardly spinose ; and the abdominal spine is quite rudimentary. In this stage (fig. 152), the larva closely resembles some of the ANNULOSA: CRUSTACEA. 301 Trilobites, such as Trinucleus and Asaphus. After hatching, the previously existing segmentation is soon obliterated, and, three or four weeks later, the telson assumes the ensifonn Fig. 150.— Xiphosura. Limulus mus, viewed from below. c The ce- phalic shield carrying the sessile eyes upon^ its upper surface; o " Opercu- lum," covering the reproductive organs ; b Branchial plates ; a First pair of an- tennae (antennules) ending in chelae. Below these is the aperture of the mouth, surrounded by the spiny bases of the re- maining five pairs of appendages, which are regarded by Woodward as being re- spectively, from before backwards, the great antennae, .the mandibles, the first maxillae, the second maxillae, and a pair of maxillipedes. All have their extremi- ties ch elate. 'j;."° polyphe- Fig. 151. — Eurypterida. Pterygotus An- The ce- glicus, restored (after H. Woodward). c c Chelate antennae ; o o Eyes situated at the anterior margin of the carapace ; m m The mandibles, and the first and second maxillae ; nn The maxillipedes — the basal margins of these are serrated, and are drawn as if seen through the me- tastoma or post-oral plate, which serves as a lower lip. Immediately behind this is seen the operculum or thoracic plate which covers the two anterior thoracic somites. Behind this are five thoracic and five abdominal somites, and lastly there is the telson (t). shape characteristic of the adult. According to the views of Van Beneden, the development of Limulus so closely resem- bles that of the Scorpions, that the former should properly be removed from the Crustacea, and placed in the Arachnida. The King-crabs are found in the Indian and Japanese seas, on the coasts of North America, and in the Antilles. They sometimes attain a large size, and both the eggs and the flesh are eaten by the Malays. SUB-ORDER 2. EURYPTERIDA. — " Crustacea with numerous, 302 MANUAL OF ZOOLOGY. free, thoradco-abdominal segments, the first and second (?) of which bear one or more broad lamellar appendages upon their ventral surface, the remaining segments being devoid of appen- dages; anterior rings united into a carapace, bearing a pair of larval eyes (ocelli) near the centre, and a pair of large marginal or sub-central eyes : the mouth furnished with a broad post-oral plate, or metastoma, and five pairs of movable appendages, the pos- terior of which form great swimming- feet : the telson, or terminal segment, extremely variable in form ; the in- tegment characteristically sculptured" (Henry Woodward). The Eurypterida are all extinct, Fig. 152.— Larva of Limuius on and are entirely confined to the Pal- ?earCDonhgrn.featly "*****' (At" ^ozoic period. Many of them at- tained to a comparatively gigantic size; Pterygotus Anglicus (fig. 151) being supposed to have reached a length of probably six feet. In their characters they present many larval features ; resembling the larvae of the Deca- poda especially in the fact that all the free somites of the abdomen (except the two anterior ones) were totally devoid of appendages. CHAPTER XXXIII. MALACOSTRACA. SUB-CLASS IV. MALACOSTRACA (Thoracipoda, Woodward). — The Crustacea of this sub-class are distinguished by the pos- session of a generally definite nnmber of body-segments ; seven somites going to make up the thorax, and an equal number entering into the composition of the abdomen (counting, that is, the telson as a somite). The Malacostraca are divided into two primary divisions, termed respectively the Edriophthal- mata and the Podophthalmata, according as the eyes are sessile or are supported upon eye-stalks. DIVISION A. EDRIOPHTHALMATA. — This division comprises those Malacostraca in which the eyes are sessile, and the body is mostly not protected by a carapace. It comprises the three orders, Lcemodipoda, Isopoda, and Amphipoda. The eyes are ANNULOSA : CRUSTACEA. 303 generally compound, but sometimes simple, and are placed on the sides of the head. The head is almost always distinct from the body, and the mandibles are often furnished with a palp. Typically there are seven pairs of feet in the adult, hence this division is called Tetradecapoda by Agassiz. In certain Isopods (Tanais) alone is there a carapace. ORDER I. L^EMODIPODA. — Small Crustaceans, with a rudi- mentary abdomen, the first two segments of the thorax amalga- mated with the head, and carrying legs. Branchice as two or three pairs of vesicles, borne on the thorax. The Latmodipoda are small Crustaceans, which are distinguished amongst the Edrioph- thalmata by the rudimentary condition of the abdomen. The first thoracic segment is amalgamated with the head, and the limbs of this segment appear to be inserted beneath the head, or, as it were, beneath the throat (fig. 153); hence the name given to the order. The respiratory organs are in the form of two or three pairs of membranous ves- icles attached to the seg- ments of the thorax, or to the bases Of the legS. The Fig. 153.— Laemodipoda. Caprellaphasma. last pair of feet are either inserted at the end of the last somite, or are followed by not more than one or two small segments. There are four seta- ceous antennae, and the mandibles are without palps. The body is generally linear, of eight or nine joints, but is some- times oval. The feet are hooked. The Lamodipoda are all marine, and one section of the order comprises parasitic Crus- taceans, of which the Whale-louse (Cyamus cefi) is the most familiar. The entire order is now generally regarded as being merely a section of the Amphipoda. ORDER II. AMPHIPODA. — The members of this order re- semble those of the preceding in the nature of the respiratory organs, which consist of membranous vesicles attached to the bases of the thoracic limbs. The first thoracic segment, how- ever, is distinct from the head, and the abdomen is well developed, and is composed of seven segments. There are seven pairs of thoracic limbs, directed partly forwards and partly backwards, the name of the order being derived from this circumstance. As in the L&modipoda, the heart has the form of a long tube extending through the six segments following the head, and having the blood admitted to its interior by three pairs of valv- ular fissures. The three posterior pairs of abdominal limbs are bent backwards, and form, with the telson, a natatory or 304 MANUAL OF ZOOLOGY. saltatorial tail. The young Amphipod acquires its full number of segments and limbs before its liberation from the egg ; and, as a rule, the young undergo little or no metamorphosis in reaching maturity. All the Amphipoda are small, the "Sand-hopper" (Talitrus locusta, fig. 154) and the "fresh- water Shrimp" (Gammarus Fig. 154.— Amphipoda. The Sand-hopper, Talitrus iocusta, enlarged. pulex) being two of the commonest forms. The Sand-hoppers and Gammari swim on their side when in the water, and the former leap with great activity on land. ORDER III. ISOPODA. — In this order the head is always dis- tinct from the segment bearing the first pair of feet. The respira- tory organs are not thoracic, as in the two preceding orders, but are attached to the inferior surface of the abdomen ', and con- sist of branchia, which in the terrestrial species are protected by plates which fold over them. The thorax is composed of seven segments, bearing seven pairs of limbs, which, in the females, have marginal plates, attached to their bases, and serving to protect the ova. The number of segments in the abdomen varies, but is never more than seven. The abdominal seg- ments are coalescent, and form a broad caudal shield, beneath which the branchiae are carried. The eyes are two in number, formed of a collection of simple eyes, or sometimes truly com- pound. The heart is sometimes an elongated tube, with three pairs of fissures (as in the Amphipoda], sometimes short or spherical, removed towards the abdomen, and with more or fewer fissures than the above. The young Isopod is developed within a larval membrane, destitute of appendages. After a time this membrane bursts, and liberates the young, which resembles the adult in most respects, but possesses only six instead of seven pairs of limbs. Of the members of this order, ANNULOSA: CRUSTACEA. 305 many are aquatic in their habits, and are often parasitic, but others are terrestrial. By Milne-Edwards the Isopoda are divided into three sections, termed respectively, from their habits, the Natatorial, Sedentary, and Cursorial Isopods. In the Natatorial Isopoda the extremity of the abdomen and the last pair of abdominal legs are expanded so as to form a swimming-tail. Some of this section are parasitic upon various fishes (Cymothod), whilst others are found in the sea (Sphceromd). In the Sedentary Isopoda the animals are all parasitic, with short, incurved, hooked feet. This section includes the single family of the Bopyridce, all the species of which live parasitically either in the gill- chambers, or attached to the ventral surface, of certain of the Decapod Crustacea, such as the Shrimps, (Crangones] and the Palamones, The Ciirsorial, or running Isopods mostly live upon the land, and are therefore destitute of swimming-feet. The most fa- miliar examples of this section are the common Wood-lice (Oniscus). Here, also, belongs the little Linmoria terebrans, so well known for the destruction which it produces by boring into the wood-work of piers and other structures placed in the sea. Other well-known Isopods are the Water-slaters (Asellus) of fresh waters, the Rock-slaters (Ligia) of almost all coasts, the Box-slaters (Idothed), the Shield-slaters (Cassidina), and the Cheliferous Slaters (Tanais). These last are remarkable as being the only Isopods in which there is a carapace. The lateral parts of the carapace, also, are highly vascular, and respiration is effected by these, and not by the abdominal feet. Many Isopods undergo an extensive metamorphosis. "In some Fish- lice (Cymothoa) the young are lively swimmers, and the adults are stiff, heavy, stupid fellows, whose short clinging feet are capable of little move- ment." In the Bopyrida the adult females are usually blind, the antennoe are rudimentary, and the abdominal appendages from natatory become respiratory organs. The males, on the. other hand, are dwarfed, and sometimes lose all the abdominal appendages and all traces of segmenta- tion ; until we get forms which, like Cryptoniscus planarioides, "would be regarded as a Flat-worm rather than an Isopod, if its eggs and young did not betray its Crustacean nature " (Fritz Miiller). DIVISION B. PODOPHTHALMATA. — The members of this divi- sion have compound eyes supported upon movable stalks or peduncles, and the body is always protected by a cephalo- thoracic carapace. Most of the Podophthalma pass through Zoea-stages in their development. It comprises the two orders Stomapoda and Decapoda, of which the latter includes all the highest and most familiar examples of the class Crustacea. U Fig. 155. — Isopoda. Woodlice (Oniscus), twice the natural size. 306 MANUAL OF ZOOLOGY. ORDER I. STOMAPODA. — In this order there are generally from six to eight pairs of legs, and the branchm, when present, are not enclosed in a cavity beneath the thorax, but are either suspended beneath the abdomen, or, more rarely, are attached to the thoracic legs. The shell, also, is thin, and often membranous. From all the preceding orders the Stomapoda are, of course, distin- guished by the possession of pedunculate eyes. The develop- ment of the Stomapoda would appear to be by means of " Zoeae." All the Stomapoda are marine, with the single exception of the My sis relicta of the great lakes of Sweden and North America; and the Locust Shrimp (Squilla mantis] may be taken as a good example of the order. In this Crustacean (fig. 156) the carapace is small, and does not cover the pos- terior half of the thorax. The eyes and antennae are attached to a somite which is not solder- ed to the cephalothorax. Sev- eral of the anterior appendages are developed into powerfully prehensile and hooked feet. The branchiae are attached to the first five pairs of abdominal feet. The three posterior tho- racic and the abdominal ap- pendages are in the form of " swimmerets," and the tail is expanded into a powerful fin. Besides the Locust Shrimps, the order includes the Glass Shrimps (Erichthys] and their allies, and the Opossum Shrimps (Mysis). ORDER II. DECAPODA. — The members of this order are the most highly organised of all the Crustacea, as well as being Fig. 156. — Squilla mantis, the Locust Shrimp. those which are most familiarly known, the Lobsters, Crabs, Shrimps, &c., being comprised under this head. For the most part they are aquatic in their habits, and they are usually pro- tected by strong resisting shells. There is always a compli- cated set of " gnathites," or appendages modified for masticat- ory purposes, surrounding the mouth. The ambulatory feet are made up of five pairs of legs (hence the name of the order) ; the first pair — and often some other pairs behind this — being "che- ANNULOSA: CRUSTACEA. 307 late" or having their extremities developed into nipping-claws. The branchiae are pyramidal, and are contained in cavities at the side of the thorax. The carapace is large, covering the head and thorax, and the anterior part of the abdomen. The heart of the Decapoda is in the form of a more or less quadrate sac, fur- nished with three pairs of valvular openings. As regards the development of the Decapods enormous differences obtain, even amongst forms very closely allied to one another. The Decapoda are divided into three tribes, termed respec- tively the Macrura, Anonmra, and Brachyura, and charac- terised by the nature of the abdomen. TRIBE A. MACRURA. — The " long-tailed " Decapods included in this tribe are distinguished by the possession of a well- developed abdomen, often longer than the cephalothorax, the posterior extremity of which forms a powerful natatory organ or caudal fin. As regards the development of the Macrura, most appear at first in the form of "Zoese;"* but there is little metamorphosis in the common Lobster, and there is said to be none in the Cray-fish (Astacus fluviatilis}. Fritz Miiller, again, has shown that the primitive form of one of the Shrimps (Peneus] is that of a "Nauplius." Lastly, the young of the Spiny Lobster (Palinurus vulgaris) are transparent Phyllosomce, resembling Stomapods in appearance. This section comprises the Lobster, Cray-fish, Shrimp, Prawn, &c., of which the Lob- ster may be taken as the type. In the Lobster (figs. 136, 137), as also in the Cray-fish (fig. 157), the somites of the head and thorax are amalgamated into a single mass, the " cephalothorax," covered by a carapace or shield, which is developed from " the lateral or epimeral elements of the fourth cephalic ring, which meet along the back, and give way preparatory to the moult. The tergal elements of the thoracic rings are not developed in either Crabs or Lobsters ; when these rings are exposed by lifting up the cephalothoracic shield, the epimeral parts alone are seen, * The young Decapod, in most cases, leaves the egg in a larval form so different to the adult that it was originally desciibed as a distinct animal under the name of Zoea. In this stage (fig. 160) the thoracic segments with the five pairs of legs proper to the adult are either wanting or are quite rudimentary. The abdomen and tail are without appendages, and the latter is composed of a single piece. The foot-jaws are in the form of natatory forked feet, and the mandible has no palp. Lastly, there are no branchiae, and respiration is carried on by the lateral parts of the cara- pace. The "Zoea" is separated from the "Nauplius" by having a seg- mented body, large paired eyes (sometimes with a median eye), and a carapace. The form proper to the adult is not attained until after several moults, constituting a genuine metamorphosis, though one which is effected by very gradual stages. 308 MANUAL OF ZOOLOGY. converging obliquely towards one another, but not joined at their apices " (Owen). The first segment of the head bears the compound eyes, which are supported upon long and movable eye -stalks or peduncles. Behind these come two pairs of jointed tactile organs, the larger called the " great antennae," the smaller the " antennules." The mouth is situated on the under surface of the front of the head, and is provided from before backwards with an upper lip (" labrum "), two " mandibles," two pairs of "maxillae," three pairs of " maxillipedes " or "foot-jaws," and a bifid lower lip, or "metastoma" (fig. 158). The five remain- Fig. 157.— The common Cray-fish {Astacusfluvi- atilis), viewed from below, a Antennules; b Large antennae ; c Eyes ; d Opening of auditory sac ; e Last pair of foot- jaws ; f One of the great chelae ; g Fifth thoracic limb ; h Swimmerets ; / The last pair of swimmerets ; j The opening of the anus below the telson. Fig. 158. — Gnathites of the Cray -fish (Astac^cs fluvia- tilis). a Mandibles ; b Max- illae ; c Second pair of max- illae ; d First pair of foot- jaws ; e Second pair of foot- jaws ; f Third pair of foot- jaws. ing segments of the thorax carry the five pairs of ambulatory legs, of which the first constitute the great claws, or " chelae ; " the next two pairs are also chelate, though much smaller ; and the last two pairs are terminated by simply pointed extremities. ANNULOSA: CRUSTACEA. 309 The segments of the abdomen cany each a pair of natatory limbs, or " swimmerets," the last pair being greatly expanded, and constituting, with the " telson," a powerful caudal fin. Most posteriorly of all is the post-anal plate, or " telson," which may be looked upon either as an azygous appendage, or as a ter- minal segment which has no lateral appendages. The mouth leads by a short oesophagus into a globose stomach, in the cardiac portion of which is a calcareous appa- ratus, for triturating the food, which is commonly called the " lady in the lobster." The intestine is continued backwards from the stomach without convolutions, and the anal aperture is situated just in front of the telson. There is also a well- developed liver, consisting of two lobes which open by separate ducts into the intestine. The heart is situated dorsally, and consists of a single poly- gonal contractile sac, which opens by valvular apertures into a surrounding venous sinus, inappropriately called the "peri- cardium." The heart is filled with oxygenated blood derived from the gills, and propels the aerated blood through every part of the body. The gills (fig. 137, 3, ^")*are pyramidal bodies attached to the bases of the legs, and protected by the sides of the carapace. They consist each of a central stem supporting numerous laminae, and they are richly supplied with blood, but are not ciliated. The water which occupies the gill-cham- bers is renovated partly by the movements of the legs, and partly by the expanded epipodite of the second pair of maxillae, which constantly spoons out the water from the front of the branchial chamber, and thus causes an entry of fresh water by the posterior aperture of the cavity. The nervous system is of the normal " homogangliate " type, consisting of a longitudinal series of ganglia of different sizes, united by commissural cords, and placed along the ventral surface of the body. The organs of sense consist of the two compound eyes, the two pairs of antennae, and two auditory sacs. The sexes are invariably distinct, and the generative pro- ducts are conveyed to the exterior by efferent ducts, which open at the base of one of the pairs of thoracic legs. The ovum is " meroblastic," a portion only of the vitellus under- going segmentation. The neural side of the body — that is to say, the ventral surface — appears on the surface of the ovum, so that the embryo is built up from below, and the umbilicus is situated posteriorly. TRIBE B. ANOMURA. — The Decapods which belong to this tribe are distinguished by the condition of the abdomen, which is neither so well developed as in the Macrura, nor so nidi- 3io MANUAL OF ZOOLOGY. mentary as in Crabs. Further, the abdomen does not ter- minate posteriorly in a caudal fin, as in the Lobster. The development in the Anomura appears invariably to take place through Zoea-forms. The entire group of the Anomura must be regarded as an artificial assemblage, composed of modified forms of both the Macrura and the Brachyura. The most familiar of the Anomura are the Hermit-crabs (Paguridce). In the common Hermit-crab (Pagurus Bernhar- dus] the abdomen is quite soft, and is merely enclosed in a membrane, so that the animal is compelled to protect itself by adopting the empty shell of some Mollusc, such as the common Whelk, which it changes at will when too small. The Hermit is provided with a terminal caudal sucker, and with two or Fig. 159. — Brachyura. The Spiny Spider-crab (Maza squinadd). three pairs of rudimentary feet developed upon the abdomen, by means of which he retains his position within his borrowed dwelling. The abdominal appendages, however, are mostly unsymmetrical. The carapace is not strong, but the claws are ANNULOSA: CRUSTACEA. well developed, one being always larger than the other. Other forms of the Anomura are the Sponge-crabs (Dromia), the Crab- lobsters (Parcel lance), and the Tree-crabs (Birgus). TRIBE C. BRACHYURA. — The "short-tailed" Decapods, or Crabs, are distinguished from the two preceding tribes by the rudimentary condition of the abdomen, which is very short, and is tucked up beneath the cephalothorax, the latter being disproportionately large. The extremity of the abdomen is not provided with any appendage, and it is merely employed by the female to carry the ova. The Crabs (fig. 159) are mostly furnished with ambulatory limbs, and are rarely formed for swimming, most of them being littoral in their habits, and some even living inland. In all the essential points of their anatomy the Crabs do not differ from the Lobster and the other Macrura; but they are decidedly higher in their organisation. This is espe- cially seen in the disposition of the nervous system, the ventral ganglia in the Crab being concentrated into a single large ganglion, from which nervous filaments are sent to all parts of the body. In the Land-crabs (Gecar- tinus} respiration is by branchiae, but there is al- most always an aperture behind the carapace for the admission of air. They are distributed over the warm countries of the Old and New Worlds, as well as Australia. They are essen- tially terrestrial in their ha- bits, and migrate in large bodies to the sea, in order to lay their eggs. Besides the true Gecarcini^ members . of other very different fam- ilies live more or less con- stantly on dry land, and have air admitted directly into the branchial chamber. Amongst these are the Calling crabs (Gelasimus) and the Sand-crabs ( Ocypoda). Fig. 1 60.— Zoea of the Spiny Spider-Crab (Maia squinado), enlarged. 312 MANUAL OF ZOOLOGY. Reproduction in the Crabs is the same as in the Macrura, but the larva is exceedingly unlike the adult, and approximates closely to the type of the Macrura, another proof that the Brachyura stand' higher in the Crustacean scale. The larval Crab was originally described as a distinct animal, under the name of Zoea (fig. 160), presenting in this condition a long and well-developed abdomen. It is only after several successive moults that the young Crab assumes its characteristic Brachyur- ous form, and acquires by gradual changes the features which distinguish the adult. The Zoece of the Crabs are usually dis- tinguished by the possession of long spines developed from the carapace. When first liberated from the egg, the Zoea is enveloped in a larval skin or membrane, which is shed in a few hours. Among the Land-crabs, there is no metamorphosis in Gecarrinus; but in some of the Gecarcinidcz the young are Zoea. CHAPTER XXXIV. DISTRIBUTION OF THE CRUSTACEA. DISTRIBUTION OF CRUSTACEA IN SPACE. — The Crustacea are distributed over the whole globe, some forms being terrestrial in their habits, but the majority inhabiting the sea or fresh water. As a rule, the development of the Crustacean fauna is in proportion to the temperature, the higher and larger forms being most abundant in warm regions. The groups of the Cirriptdia.) Rhizocephala, Xiphosura, and Lcemodipoda^ are only found in salt water. On the other hand, the Ichthyophthira, Ostracoda, Copepoda, Phyllopoda, Eurypterida (?), Amphipoda, Stomapoda, Isopoda, and Decapoda, are found both in fresh and in salt water. Of these, however, the Phyllopods are princi- pally fresh-water forms, and the Stomapods and Decapods are essentially inhabitants of the sea ; whilst the Eurypterids are certainly mainly a salt-water group, though some forms may perhaps have lived in fresh water as well. The Isopoda and Decapoda also include terrestrial forms. DISTRIBUTION OF CRUSTACEA IN TIME. — As regards the general distribution of the Crustacea in time, remains of the class are comparatively abundant in all formations except the very oldest ; as might have been expected from the generally chitinous or sub-calcareous nature of their integuments and their aquatic habits. Owing also to their habit of periodically ANNULOSA: CRUSTACEA. 313 casting their shell, a single individual may leave repeated traces of himself, and the number of fossils may considerably exceed that of the individuals which actually underwent fossili- sation. The Crustaceans appear to have commenced their existence in the Cambrian period, remains of members of this class being tolerably abundant in the higher portion of this formation. The Palaeozoic formations, taken as a whole, are characterised by the predominance of the orders Trilobita, Eurypterida, Ostracoda, and Phyllopoda, of which the two former are exclusively confined to this period. All the other orders of Crustacea which have left any traces of their past existence at all, appear to have come into existence before the close of the Palaeozoic period. Upon the whole, however, there has been a marked progression in proceeding from the older formations to the present day. The Trilobites and Eurypterids of the older Palaeozoic rocks, though highly organised so far as their type is concerned, are in many re- spects inferior to later forms, whilst they present some striking points of resemblance to the larval forms of the higher groups. The great group of the Stalk-eyed Crustaceans — undoubtedly the highest of the entire class — is not represented at all till we reach the Devonian rocks; and it is not till we come into the Secondary period that we find any great development of this group, whilst its abundance increases to a marked extent in the Tertiary period, and it attains its maximum at the pres- ent day. Similarly, of the two orders of the Merostomata, the Eurypterida are confined to the earlier portion of the Palaeozoic period, whilst the more highly organised and less larval King- crabs (Xiphosura) hardly made their appearance till the Eu- rypterids had disappeared, at the close of the Carboniferous period. 1. Cirripedia. — The Cirripedes are hardly known as Palaeozoic fossils, but valves of a singular member of this order ( Turrilepas] have been found in the Silurian rocks. With few exceptions, the Cirripedes are entirely confined in past time to the Secondary and Tertiary epochs. The Bala- nidce are the most common, commencing, with the doubtful exception of a Liassic form, in the Chalk, and attaining their maximum in recent seas. The Verrucidce commence in the Chalk, and the Lepadidce, with one or two exceptions, begin in the Jurassic rocks, and attain their maximum of development in the Cretaceous epoch. The Upper Silurian genus Tur- rilepas, above mentioned, is also referable to the Lepadoids. 2. Ostracoda.— Small Ostracode Crustacea are extremely abundant as fossils in many formations, and extend from the Cambrian period up to the present day. 3. Phyllopoda. —Remains of Crustaceans supposed to belong to this order are found in the Palaeozoic rocks. Hymenocaris is found in the Upper Cambrian, Caryocaris in the Lower Silurian, Ceratiocaris in the MANUAL OF ZOOLOGY. Upper Silurian, and Dithyrocaris in the Carboniferous Limestone. All these forms, with other similar ones, are believed to be most closely allied to the recent Apus and Nebalia. The genus Estheria, represented by many forms from the Devonian period to the present day, is also to be referred here. 4. Trilobita. — The Trilobites are exclusively Palaeozoic fossils. In the Upper Cambrian rocks — the so-called "primordial zone" — there occurs a singular group of Trilobites — the so-called primordial Trilobites — dis- tinguished by the possession of many larval characters. In the Lower and Upper Silurian rocks the Trilobites attain their maximum of develop- ment. They are still well represented in the Devonian rocks ; but they die out completely before the close of the Carboniferous epoch, being rep- resented in the Mountain Limestone by four genera only (Phillipsia^ Brachymetopus ; Proettts, and Griffit hides). 5. Eurypterida. — These, like the last, are entirely Palaeozoic, attaining their maximum in the Upper Silurian and Devonian formations, and dying out in the Carboniferous rocks. Pterygotus, Eurypterus, and Slimonia are the most characteristic genera. 6. Xiphosura. — The genus Limulus commenced, as far as is yet known, in the Permian period, and- has survived up to the present day. Its first appearance, therefore, was just at the close of the Palaeozoic epoch. Of the remaining genera, which constitute with Limulus this sub -order, Belinurus, Eupro'dps, and Prestwichia, are Palaeozoic, and are not known to occur out of the Carboniferous rocks. The genus Neolimttlus is Upper Silurian. 7. Amphipoda. — The oldest known Amphipod is the Necrogammarus of the Upper Silurian. 8. Isopoda. — The earliest known Isopod is the Praarcturus of the De- vonian rocks. 9. Stomapoda. — This order is doubtfully represented in the Carbon- iferous rocks by the genus Palceocaris, and by some allied types. 10. Decapoda. — The Macrurous Decapods commence their existence in the Carboniferous period, or perhaps in the Devonian, with a few Prawn- like forms ; and the Brachyura seem to have existed at the same period. The Decapoda are, however, well represented, in all their three tribes, in the Secondary and Tertiary epochs, attaining their maximum at the pres- ent day. The London Clay (Eocene) is especially rich in the remains of Macrura and Brachyura, CHAPTER XXXV. ARACHNID A. CLASS II. ARACHNIDA. — The Arachnida — including the Spi- ders, Scorpions, Mites, &c. — possess almost all the essential characters of the Crustacea, to which they are very closely allied. Thus, the body is divided into a variable number of somites, some of which are always provided with articulated appendages. A pair of ganglia is primitively developed in each somite, and the neural system is placed ventrally. The ANNULOSA: ARACHNIDA. 315 heart, when present, is always situated on the opposite side of the alimentary canal to the chain of ganglia. The respiratory organs, however, whenever these are differentiated, are never in the form of branchiae as in the Crustacea, but are in the form either of pulmonary vesicles or sacs, or of ramified tubes, formed by an involution of the integument, and fitted for breathing air directly. Further, there are never "more than four pairs of locomotive limbs, and the somites of the abdomen, even when these are well developed, are never provided with limbs ; " the reverse being the case amongst the Crustacea. Lastly, " in the higher Arachnida, as in the higher Crustacea, the 'body is composed of twenty somites, six of which are allotted to the head ; but in the former class, one of the two normal pairs of antennae is never developed, and the eyes are always sessile; while, in the higher Crustacea, the eyes are mounted upon movable peduncles, and both pairs of antennae are developed " (Huxley). The head of the Arachnida is always amalgamated with the thorax, to form a " cephalothorax ; " the integument is usually chitinous, and the locomotive limbs are mostly similar in form to those of insects, and are usually terminated by two hooks. In many of the Arachnida the integument remains soft over the entire body ; in others, as in the majority of Spiders, the abdomen remains soft and flexible, whilst the cephalothorax is more or less hard and chitinous ; in the Scorpions, again, the integument over the whole body forms a strong chitinous shell. The cephalothorax may be segmented (Solpugida) ; and the abdomen may or may not be segmented. Though four pairs of legs are present, the first is certainly homologous with the labial palpi of the Insecta. The typical somite of the Arachnida is constituted upon exactly the same plan as that of the Crustacea, consisting essentially of a dorsal and ventral arc ; the former composed of a central piece, or " tergum," and of two lateral pieces, or " epimera ; " whilst the latter is made up of a median " ster- num " and of two lateral " episterna." As regards the composition of the cephalothorax of Spiders, " the tergal elements of the coalesced segments are wanting, and the back of the thorax is protected by the elongation, con- vergence, and central confluence of the epimeral pieces ; the sternal elements have coalesced into the broad plate in the centre of the origins of the ambulatory legs, from which it is separated by the episternal elements. . . . The non-develop- ment of the tergal elements explains the absence of wings " (Owen). MANUAL OF ZOOLOGY. The mouth is situated, in all the Arachnida, in the anterior segment of the body, and is surrounded by suctorial or mas- ticatory appendages. In the higher Arachnida, the mouth is Fig. 161.— A, The male of the common House-Spider (Tegenaria ci-vilis), considerably magnified : c Front portion of the body, consisting of the amalgamated head and thorax ; / Maxillary palpi ; a Abdomen. B, Front portion of the head of the same, showing the eight eyes (/}, and the mandibles («). C, Under side of the head and trunk, showing the true jaws (in), the lower lip (/), and the horny plate to which the legs are attached. D, Diagram of one of the air-chambers or breathing-organs. (Figs. A, B, and C are after Blackwall.) provided from before backwards with the following appendages (figs. 161, 162): i. A pair of "fakes," or "mandibles," used for prehension ; 2. A pair of " maxillae," each of which is pro- vided with a long jointed appendage, the " maxillary -palp ;" 3. A lower lip, or " labium." In the Scorpion, an upper lip, or "labrum," is also present* * The nomenclature ordinarily applied to the parts of the mouth in the Arachnida is a misleading one, so far as the homologies of this class with the Insecta are concerned. Thus the so-called "mandibles " are really the antenna ; the "mandibles" themselves are absent, but the "chelae" of the Scorpions may really represent the " mandibular palpi; " whilst the first pair of legs really correspond with the " labial palpi," and the second pair of legs may possibly be a modification of a second pair of palps. ANNULOSA: ARACHNIDA. 317 In the Spiders (fig. 162, 4) each falx or mandible terminates in a sharp movable hook, which possesses an aperture at its extremity communicating by a canal with a gland, which is placed in the preceding joint of the mandible, and secretes a poisonous fluid. The maxillary palps in the Spiders are long, jointed appendages, terminated in the females by pointed claws, but frequently swollen, and carrying a special sexual apparatus in the males. In the Scorpions (fig. 162, i) the mandibles are short and terminate in strong pincers, or " chelicerse." The maxillary ^ \4 Fig. 162. — Morphology of Arachnida, i. Organs of the mouth in the Scorpion, on one side : m Mandibles (antennae) converted into chelae, and called the chelicerae ; / Maxillary palpi greatly developed, and forming strong chelae. 2. Telson of the Scorpion. 3. One of the abdominal segments of the Scorpion, showing the "stig- mata," or apertures of the pulmonary sacs. 4. Tegenaria chrilis, the common Spider (male), viewed from below: ^ Spinnerets ; tn Mandibles with their perforated hooks — below the mandibles are the maxillae, and between the bases of these is the , labium ; p The maxillary palpi with their enlarged tumid extremities. palpi are also greatly developed, and constitute powerful grasp- ing claws, or " chelae." In the genus Galeodes, the mandibles, like those of the Scorpion, constitute " chelicerae," though com- paratively much larger and longer ; but the maxillary palps are not developed into " chelae." With regard to antennae, these organs, as such, do not exist in the Arachnida. It is generally believed, however, that the mandibles of the Arachnida are truly homologues, not of the parts which bear the same name in the other Arthropoda, but of \heantennce; and the name of " falces " is thus best applied to them. The antennae, therefore, of the Spiders are converted 318 MANUAL OF ZOOLOGY. into prehensile and offensive weapons; whilst in the Scorpions, as in the King-crabs, they are developed into nipping-claws, or chelae. In the lower Arachnida, the organs of the mouth, though essentially the same as in the higher forms, are often enveloped in a sheath, formed by the labium and maxillae, whilst the mandibles are often joined together so as to constitute a species of lancet. The mouth conducts by an oesophagus, sometimes by the intervention of a pharynx, to the stomach, which often carries longer or shorter caeca appended to it. The intestinal canal is short and straight, no convolutions intervening between the mouth and the anus. The terminal portion of the intestine is generally dilated into a cloaca, into which open, as a rule, branched or tortuous tubes, supposed to have a renal function, and to correspond with the " Maipighian vessels " of Insects. Salivary glands are generally present, and there is usually a well-developed liver. The circulation in the Arachnida is maintained by a dorsal heart, which is situated above the alimentary canal, and is wanting in the lower forms. Usually the heart is greatly elongated, and resembles the "dorsal vessel" of the Insecta. In the lower Arachnida, however, there is no central organ of the circulation, and there are no differentiated blood-ves- sels. All the Arachnida, except some of the lowest, breathe the air directly, and the respiratory function is performed by the general surface of the body (as in the lowest members of the class), or by ramified air-tubes, termed " tracheae," or by distinct pulmonary chambers or sacs ; or, lastly, by a combina- tion of tracheae and pulmonary vesicles. The "tracheae" con- sist of ramified or fasciculated tubes, opening upon the surface of the body by distinct apertures, called " stigmata." The walls of the tube are generally prevented from collapsing by means of a chitinous fibre or filament, which is coiled up into a spiral, and is situated beneath their epithelial lining. The pulmonary sacs, or " tracheal lungs," are simply involutions of the integu- ment, abundantly supplied with blood ; the vascular surface thus formed being increased in area by the development of a number of close-set membranous lamellae, or vascular plates, which project into the interior of the cavity. Like the tracheae, the pulmonary sacs communicate with the exterior by minute apertures, or "stigmata" (fig. 162, 3), and they are to be re- garded as being simply greatly expanded tracheae. The nervous system is of the normal articulate type, but is often much concentrated. Typically there is a cephalic or ANNULOSA: ARACHNID A. 319 " cerebral " ganglion, a large thoracic ganglion, and often small abdominal ganglia. In some of the lower forms the articulate type of nervous system is lost, and there is merely a ganglionic mass situated in the abdomen. In none of the Arachnida are compound eyes present, and in none are the eyes supported upon foot-stalks. The organs of vision, when present, are in the form of from two to eight or more simple eyes, or " ocelli." In all the Arachnida, with the exception of the Tardigrada, the sexes are distinct. The great majority of the Arachnida are oviparous, and in most cases the larvae are like the adult in all except in size. In some cases, however (Acarina), the larvae have only six legs, and do not attain the proper four pairs of legs until after some moults. CHAPTER XXXVI. DIVISIONS OF THE ARACHNIDA. THE class of the Arachnida may be divided into the following orders : — ORDER I. PODOSOMATA (Pantopoda]. — Respiration effected by the general surface of the body ; limbs four pairs in number, elongated ; abdomen rudimentary, unsegmented ; sexes distinct. The members of this order, sometimes called " Sea-spiders," have been placed alternately amongst the Arachnida and the Crustacea, their true position being rendered doubtful by the fact that, though marine in their habits, they possess no dif- ferentiated respiratory organs. They possess, however, no more than four pairs of legs, and would therefore appear to be properly referable to the Arachnida. According to Dr Dohrn, however, the embryo is naupliiform, and this would support a reference of the order to the Crustacea. The commoner forms of the Podosomata (such as Nymphon and Pycnogonmn) may be found on the sea-coast at low water, crawling about amongst marine plants or hiding beneath stones. Some species of the latter genus are parasitic upon fishes and other marine ani- mals, but the common British species (P. littorale} is free when adult, and does not appear to be parasitic at any stage of its existence (fig. 164, a). The legs consist of four pairs, some- times greatly exceeding the body in length, and containing caecal prolongations of the digestive cavity for a portion of their length. The mouth is sometimes provided with a pair of 320 MANUAL OF ZOOLOGY. " chelicerae," or ch elate mandibles, and with two well- devel- oped maxillary palpi, behind which in the female is a pair of false legs which carry the ova. The abdomen is rudimentary; but the cephalothorax is segmented. Though there are no respiratory organs, there is a distinct heart. The sexes are in different individuals, and the larvae have at first only two pairs of legs. ORDER II. ACARINA or MONOMEROSOMATA. — The mem- bers of this order possess an unsegmented abdomen which is fused with the cephalothorax into a single mass. Respiration is effected by trachea, or by the integument. Most of the Acarina are parasitic, and the most familiar are the Mites and Ticks. Family i. Pentastomida {Linguatulince). — The members of this family are worm-like parasites, which in their adult state are found in the interior of the frontal sinuses, the nose, or the lungs of the Dog, and of other Vertebrate animals. When fully grown (fig. 163) they are completely vermiform, with a soft annulated integument, and pos- sessing no external organs except two pairs of retractile hooks, re- presenting limbs, placed near the mouth. The adult thus presents an external resemblance to the Tcznia, from which, however, they are separated by the details of their internal organisation. There are no differentiated organs of respira- tion or circulation, but the sexes are distinct. The larvae (fig. 163, B) are found encysted in the liver or other internal organs of various Vertebrates (including man), and possess two pairs of articulated limbs. Family 2. Tardigrada (Macro- . ., biotida or Arctisca\ — This family Fig. 163. — A, Pentastoma t&motaes, . / •* female, of the natural size; C, Male COmpriSCS the SO-Called blOth Or of the same, of the natural size ; B, (t T> „ A t-iirYiol^nl^o " \nrViirVi orp TYII Larva of the same, greatly enlarged, -bear AnimalCUlCS, WftlCn are mi- showing the two pairs of articulated croscopic animals found in damp ™oss and in the gutters of houses (fig. 165, B). In form, the body is somewhat vermiform, with four pairs of rudimentary legs. The mouth is suctorial, with rudimentary jaws or stylets. They exhibit no traces of respiratory or circulatory organs, and, un- ANNULOSA: ARACHNIDA. 321 like the other Arachnids, they have the sexes united in the same individual. Family 3. Acarida. — This family includes the Mites, Ticks, and Water-mites, some of which are parasitic, whilst others •anychus telarins, one of the Fig. 164.— Arachnida._ a Pycnogonum littorale ; b Tetr* " Sociable " mites ; c Hydrachna globulus, one of are free, and some are even aquatic in their habits. The mouth is formed for suction, or for biting. There is no definite line Fig. 165. — A, Demodex folltoiloruni, greatly magnified. B, Emydium testudo, one of the Tardzgrada, greatly magnified. C, Sarcoptes scabiei, the Itch-mite, greatly magnified. '-'•(' ' of demarcation between the unsegmented abdomen and the cephalothorax. In the true Acari (fig. 164, b), of which the Cheese-mite may be taken as an example, there are four pairs of legs, adapted for walking, and the mouth is provided with distinct mandibles. Besides the Cheese-mite (A. domesticus), another well-known species is the Acarus destructor, which feeds upon various zoo- logical specimens, and is very annoying to the naturalist. In the Sarcoptes scabiei — the cause of the skin-disease known as the " itch " — the two anterior pairs of legs are provided with X 322 MANUAL OF ZOOLOGY. suckers, and the two posterior are terminated by bristles ; the mouth, also, is furnished with bristles (fig. 165, C). In the Ticks (Ixodes) the mouth is provided with a beak, or " rostrum," which enables them to pierce the skin and retain their hold firmly. In the Hydrachnidcs (fig. 164, c\ or Water-mites, the head is furnished with two or four ocelli, and there are four pairs of hairy natatory legs. They are parasitic, during at least a portion of their existence, upon Water - beetles and other aquatic insects. They pass through a metamorphosis, the larva being hexapod, or having only three pairs of legs. The Garden-mites (Trombidida) and Spider-mites (Ganasida) live upon plants; the Wood-mites (Oribatida) and Harvest- ticks (Leptidce) are to be found amongst moss and herbage, or creeping upon trees or stones ; whilst the true Ticks (Ixodidce) attach themselves parasitically by means of their suctorial mouth to the bodies of various Mammals, such as sheep, oxen, dogs, &c. Several Mites (Thalassarachna, Pontarachna, &c.) have been found to inhabit salt water, and several species of Trombidida live habitually between tide-marks. Another member of the Acarina is the curious little Demodex folliculorum (fig. 165, A), which is found in the sebaceous follicles of man, especially in the neighbourhood of the nose. It is probable that very few, if any, individuals are exempt from this harmless parasite. ORDER III. ADELARTHROSOMATA. — The members of this order, comprising the Harvest-spiders, the Book-scorpions, &c., are distinguished from the preceding by the possession of an abdomen, which is more or less distinctly segmented, but generally exhibits no line of separation from the cephalothorax, the two regions being of equal breadth and conjoined together. The mouth is furnished with masticatory appendages, and respiration is effected by trachece, which open on the lower surface of the body by two or four stigmata. Family i. Phalangida. — The well-known "Harvest-men" belong to this family. They are characterised by the great length of the legs (fig. 166, B), and by the filiform maxillary palpi, terminated by simple hooks. The abdomen and cepha- lothorax are of about equal width, but clearly marked off from one another, and the former is segmented. There are two eyes, and the young pass through no metamorphosis. The Harvest- men are active in their habits and live upon animal food. Family 2. Pseudoscorpionidce (Cheliferidce}. — The members of this little group are readily recognised by the fact that the maxillary palpi (fig. 166, A) are of large size, and are con- verted into nipping-claws .or chelae, thus giving the animal the ANNULOSA : ARACHNIDA. 323 appearance of a Scorpion in miniature. The abdomen is seg- mented, but there is no "post-abdomen," as in the true Scor- pions. Eyes may be wanting, and the under surface of the ab- Fig. 166.— A, Chelifer cancroides, showing the chelate maxillary palpi, considerably en- larged. B, Phalangiuvt copticum, of the natural size. C, Tlielyphonus giganteiis. D, Galeodes araneoides, of the natural size. domen carries a small spinning-organ. The " Book-scorpion " {Chelifer) is commonly found in old books and in dark places. Family 3. Solpugida. — In this family (fig. 166, D) the abdo- men is not only very distinctly segmented, but is also clearly separated from the cephalothorax, which is likewise segmented. The falces or mandibles are chelate, and of immense size ; and the maxillary palpi constitute long feet. The front of the head carries two eyes, and respiration is by tracheae. Galeodes may be considered as the type of the group, all the members of which are tropical or subtropical in their range, and are nocturnal and carnivorous in habit. ORDER IV. PEDIPALPI. — Abdomen segmented, with or with- out a "post-abdomen" Respiration by means of pulmonary sacs. In this order are the true Scorpions, together with certain other, animals which are in some respects intermediate between the Scorpions and the true Spiders. The members of this order 324 MANUAL OF ZOOLOGY. are distinguished by the fact that the abdomen in all is dis- tinctly segmented, but is not separated from the cephalothorax by a well-marked constriction. They agree in this character with the Adelarthrosomata ; hence the two are sometimes united into a single order (Arthrogastra), but they are sepa- rated by the nature of the respiratory organs, the latter breath- ing by tracheae, and not by pulmonary sacs. family i. Scorpwnidce. — The Scorpions are amongst the best known of the Arachnida, as well as being amongst the largest. They are distinguished by their long, distinctly segmented ab- domen, terminating in a hooked claw (figs. 162, 167). This Fig. 167. — Scorpion (reduced). claw, which is really a modified " telson," is the chief offensive weapon of the Scorpion, and is perforated at its point by the duct of a poison-gland which is situated at its base. The abdo- men is composed of twelve somites, not counting the telson, of which the last five constitute a true "tail" or "post-abdo- men ; " but there is no evident line of demarcation between this region and the cephalothorax. The second segment of the abdomen carries below two curious comb-like organs, of uncertain use, but probably connected with reproduction. The thoracic segments carry four pairs of ambulatory feet. There are six, eight, ten, or twelve simple eyes carried on the top of the head. The maxillary palpi are greatly developed, and constitute strong nipping-claws, or "chelae" (figs. 162, 167). The mandibles (antennae) also form claws, or " chelicerae." The respiratory organs are in the form of pulmonary sacs, four on each side, opening upon the under surface of the abdomen by as many stigmata, each of which is surrounded by a raised margin, or " peritrema " (fig. 162, 3). The Scorpions are mostly inhabitants of warm regions, and their sting, though much exaggerated, is of a very severe ANNULOSA: ARACHNIDA. 325 nature. They live under stones or in dark crevices, and run swiftly, carrying the tail curved over the back. They feed on insects, which they hold in the chelate palpi, and sting to death. The largest forms, from Central Africa and South America, attain a length of nine or ten inches. Family 2. Thelyphonidce. — The members of this family in external appearance closely resemble the true Spiders, from which they are separated by the possession of a segmented abdomen, and long spinose palpi, and by the absence of spin- nerets. They are distinguished from the Scorpionidcz by the amalgamation of the head and thorax into a single mass, which is clearly separated from the abdomen by a constriction, as well as by the fact that the maxillary palpi terminate in mov- able claws instead of chelae. Further, the extremity of the abdomen is not furnished with a terminal hook or " sting." In Thelyphonus (fig. 166, C) the abdomen terminates in three post-abdominal segments, to which a long many-jointed caudal appendage is attached ; but in Phrynus the abdomen ends in a button-like segment. The first pair of legs is the longest (immensely so in Phrynus), the fakes are not chelate ; and the maxillary palpi, though of large size, and sometimes didactyle, do not form true chelae. The genus Thelyphonus is confined to the tropical parts of Asia, America, and Australia, and the genus Phrynus is also wholly tropical. ORDER II. ARANEIDA or SPH^EROGASTRA. — This order in- cludes the true Spiders, which are characterised by the amal- gamation of the cephalic and thoracic segments into a single mass, and by the generally soft, unsegmented abdomen, attached to the cephalothorax by a constricted portion, or peduncle. Respiration is effected by pulmonary sacs in combination with trachece. (Hence the name Pulmotrachearia, sometimes applied to the order.) The number of the pulmonary sacs is smaller in the true Spiders than in the Scorpions, being either two or four, opening by as many stigmata upon the under surface of the abdomen. Usu- ally there are only two pulmonary stigmata, placed just be- hind the peduncle which unites the cephalothorax with the abdomen, on the lower surface of the latter. In the Mygalidcz there are two posterior stigmata, leading into pulmonary sacs ; and in other genera there are also two additional stigmata, which, however, open into tracheae, and not into pulmonary sacs. The head bears two, four, six, or eight simple eyes ; the mandibles are simply hooked, and are perforated by the duct of a gland which secretes a poisonous fluid ; and the maxillary palpi are never chelate. The maxillary palpi of the females 326 MANUAL OF ZOOLOGY. are almost always leg-like, and are often of the same form in the males. The latter, however, commonly have the ends of the palpi tumid, in which case they appear to be employed for the purpose of conveying the seminal fluid to the female, thus exercising a reproductive function. Spiders (figs. 162, 168) are all predaceous animals, and many 168. — Araneida. Theridion riparinm (female). of them possess the power of constructing webs for the capture of their prey or for lining their abodes. For the production of the web, Spiders are furnished with special glands, situated at the extremity of the abdomen. The secretion of these glands is a viscid fluid, which hardens rapidly on exposure to air, and which is cast into its proper, thread-like shape, by being passed through what are called the "spinnerets." These are little conical or cylindrical organs, four or six in number, situated below the extremity of the abdomen, and possibly to be re- garded as modified limbs. The excretory ducts of the glands open into the spinnerets, each of which has its apex perforated by a great number of minute tubes, through which the secre- tion of the glands has to pass before reaching the air. Many spiders, however, do not construct any web, unless it be for their own habitations, but hunt their prey for themselves. The form of the web has been employed as a basis of classification of the Spiders, and amongst its numerous modifications, the following may be specially alluded to : Some forms (such as the common Garden-spiders) construct a web in the form of an incomplete or complete circle, with lines radiating from the centre. These have been termed " Orbitelarice" Others — the so-called " Retitelaria " — simply spin a thin suspended sheet for their web. Others (" Tu&itdaria") construct a silken tube, inserted in any acci- dental cavity, its mouth being open and guarded by more or fewer threads. Lastly, others (" Territelarice") spin a silken tube in a hole formed by the animal itself, and close its mouth by means of a variously-constructed lid. The Spiders are oviparous, and the young pass through no ANNULOSA: MYRIAPODA. 327 metamorphosis ; but they cast their skins or moult repeatedly, before they attain the size of the adult. Most Spiders deposit their eggs in silken nests or cocoons, often beautifully con- structed, and sometimes carried about by the females. The males are generally smaller than the females, and of rarer occurrence. DISTRIBUTION OF ARACHNIDA IN TIME. — The Arachnida are only very rarely found in a fossil condition. As far as is yet known, both the Scorpions and the true Spiders appear to have their commencement in the Carboniferous epoch, the former being represented by the celebrated Cyclophthalmus senior from the coal-measures of Bohemia, and by the Eoscorpius carbonarius of the Carboniferous strata of Illinois. Other Carboniferous Arachnida have been referred to the genera Eophrynus, Architarbus, and Mazonia. Spiders are also known to occur in the Jurassic rocks (Solenhofen Slates) and in the Tertiary period. The Mites, Harvest-spiders, and Book-scor- pions have been detected in amber. CHAPTER XXXVII. MYRIAPODA, CLASS III. MYRIAPODA. — The Myriapoda are defined as ar- ticulate animals in whith the head is distinct, and the remainder of the body is divided into nearly similar segments, the thorax exhibiting no clear line of demarcation from the abdomen. There is one pair of antenna, and the number of the legs is always more than eight pairs. Respiration is by trachece. In this class — comprising the Centipedes (figs. 169, 170) and the Millepedes — the integument is chitinous, the body is divided into a number of somites provided with articulated appendages, and the nervous and circulatory organs are constructed upon a plan similar to what we have seen in Crustacea and Arachnida. The head is invariably distinct, and there is no marked line of demarcation between the segments of the thorax and those of the abdomen. The body, except in Pauropus, always consists of more than twenty somites, and those which correspond to the abdomen in the Arachnida and Insecta are always provided with locomotive limbs. " The head consists of at least five, and probably of six, coalescent and modified somites; and some of the anterior segments of the body are, in many genera, 328 MANUAL OF ZOOLOGY. coalescent, and have their appendages specially modified to subserve prehension " (Huxley). Pauropus has only nine pairs of legs ; but, with this exception, eleven pairs of legs is the smallest number known in the order. The respiratory organs, with one exception (i.e., Pauropits), Fig. 169. — A, Lithobius forficatns, enlarged and viewed from above: an Antennae; • f Foot-jaws; h Head. B, Head of Lithobius Leachii, viewed from below (after Newport) : an Antennae ; f Hooked foot-jaws ; / Lower lip, composed of two pieces. C, Head of Lithobiits forficatus, viewed from above (after Gervais) : an Antenna ; e Eye. agree with those of the Insecta and of many of the Arachnida in being " tracheae " — that is to say, tubes, which open upon the surface of the body by minute apertures, or " stigmata," and the walls of which are strengthened by a spirally-coiled filament of chitine. The tracheae may or may not anastomose with one another as they do in Insects. The somites, with the exception of the head and the last abdominal segment, are usually undistinguishable from one another, and each generally bears a single pair of limbs. In some cases, however, each segment appears to be provided ANNULOSA : MYRIAPODA. 329 with two pairs of appendages (fig. 171). This is really due to the coalescence of the somites in pairs, each apparent segment being in reality composed of two amalgamated somites. This is shown, not only by the bigeminal limbs, but also by the arrangement of the stigmata, which in the normal forms occur on every alternate ring only, whereas in these aberrant forms they are found upon every ring. The head always bears a pair of jointed an- tennae, resembling those of many Insects, and behind the antennae there is generally a vari- able number of simple sessile eyes. In one species (Scutigera) compound faceted eyes are present; and in Pauropus the antennae are bifid, and carry many-jointed appendages, thus differing wholly from the antennae of Insects, and presenting a decided approximation to those of the Crustacea. The young in some cases, on escaping from the egg, possess nearly all the characters of the parents, except that the number of somites, and consequently of limbs, is always less, and increases at every change of skin ("moult" or " ecdysis "). In most cases, however, there is a species of metamorphosis, the embryo being at first either devoid of locomotive append- ages, or possessed of no more than three pairs of legs, thus resembling the true hexapod In- sects. It is believed, however, that the legs of these hexapod larvae do not correspond homo- logically with the three pairs of legs proper to adult Insects. In these cases the number of legs proper to the adult is not obtained until after several moults, the entire process being stated to occupy in some species as much as two years, before maturity is reached. The Myriapoda are divided into three orders — viz., the Chi- lopoda, the Chilognatha, and the Pauropoda, to which a fourth, under the name of Onychophora, must be provisionally added for the reception of the genus Peripatus. ORDER I. CHILOPODA. — This order comprises the well- known carnivorous Centipedes and their allies, and is charac- terised by the number of legs being rarely indefinitely great (usually from 15 to 20 pairs), by the composition of the an- tennae out of not less than 14 joints (14 to -40 or more), and by the structure of the masticating organs. These consist of Fig. 170. —Centipede (Scolopendra). 330 MANUAL OF ZOOLOGY. a pair of mandibles with small palpi, a labium, and two pairs of " maxillipedes " or foot-jaws, of which the second is hooked, and is perforated for the discharge of a poisonous fluid. There is not more than one pair of legs to each somite, and the last two limbs are often directed backwards in the axis of the body, so as to form a kind of tail. The body in all the Chilopoda is flattened, and the generative organs open at the posterior end of the body. Scolopendra (fig. 170), Lithobius (fig. 169), and Geophilus are common European genera of this order. The ordinary Cen- tipedes of this country are (unless in exceptional cases) per- fectly harmless ; but those of tropical regions sometimes attain a length of a foot, or more, and these are capable of inflicting very severe, and even dangerous, bites. ORDER II. CHILOGNATHA. — This order comprises the vege- table-eating Millepedes (Inlida), the Galleyworms (Polydesmus], and other allied forms. The order is characterised by the great number of legs — each segment, except the five or six T1*^™ ^v^mjiii^^ Fig. 171. — Millepede (lulus). anterior ones, bearing two pairs — by the composition of the antennae out of six or seven joints ; and by the structure of the masticating organs, which consist of a pair of mandibles with- out palps, covered by a lower lip, composed of the confluent maxillae. The generative apertures are placed in the anterior portion of the body. In the common Millepede (lulus] the body is composed of from forty to fifty segments, each of which bears two pairs of minute, thread-like legs. The lull of this country are of small size, but an American species attains a length of more than half a foot. The Glomeridce, or " Pill-Millepedes," live under stones, and have the power of rolling themselves up into a ball. ORDER III. PAUROPODA. — In this order is only an extra- ordinary little Myriapod, described by Sir John Lubbock under the name of Pauropus (fig. 172). The body is only one- twentieth of an inch in length, and consists of ten somites, furnished with scattered setae. There are only nine pairs of legs, of which one pair is carried by the 3d segment, whilst the 4th, 5th, 6th, and 7th segments carry each two pairs of legs, and may therefore be regarded as really double. The head is ANNULOSA : MYRIAPODA. 331 composed of two segments, and is not provided with jaw-feet. The antennae are five-jointed, bifid, with three long multi- articulate appendages. The body is white and colourless, and there are no tracheae, so that res- piration must be effected entirely by the skin. Pauropus is found amongst decaying leaves in damp situations, and species have been described both from Britain and America. It is separated from the Chilopoda by its small number of legs, the absence of foot-jaws, and the composition of the antennae out of no more than five joints. ORDER IV. ONYCHOPHORA (Grube). — In the West Indies, South Africa, South America, and New Zealand occur examples of a peculiar genus of animals, which has been named Peripatus, and has been at different times referred to the Errant Annelides, the Leeches, the Tapeworms, or the Myriapoda. The species of Peripatus are terres- trial in their habits, living in moist earth, in decayed wood, or under Fig ^^Pauropus Huxieyi, view- stones, active by night Only, and ed from above, and enlarged fifty 1,1 vi • r TM diameters. (After Sir John Lub- completely worm-like in form. 1 he bock.) cylindrical body (fig. 173) is annu- lated, and provided with numerous pairs of ambulatory feet, which are jointed, and terminated by one or two hooked claws (fig. 173, C and D), sometimes with a bunch of setae. The animal walks like a caterpillar, by means of its feet, and rolls up like a Millepede when alarmed. The mouth is furnished with one or two pairs of horny hooked jaws. The respiratory organs, as recently shown by Moseley, are in the form of trachea, which open externally by numerous diffused apertures, and rarely branch. From the researches of Moseley, the sexes would appear to be distinct, though the animal is stated to be hermaphrodite by Grube and Hutton. The ventral nerve- cords are widely divergent. The systematic position of Peripatus must in the meanwhile be regarded as doubtful, the animal presenting a type of struc- ture intermediate between the Errant Annelides and the Myriapoda. The presence of tracheae, however, renders it 332 MANUAL OF ZOOLOGY. impossible to place Peripatus amongst the Annelida, and the affinities of the genus appear to be closer with the Myria- pods than with any other group ; though the wide separation Fig. 173. — A, Peripatus Edwardsit, magnified two diameters. B, Head, viewed from below, enlarged five times. C and D, A single foot, viewed from above and sideways, enlarged. (After Grube.) of the ventral nerve-cords, along with other points, removes Peripatus to a considerable distance from the normal forms of the Myriapoda. If Peripatiis should ultimately be retained in the Myriapoda, it would be as well, for the sake of uniformity, to change Grube's name of Onychophora to that of Onychopoda. DISTRIBUTION OF MYRIAPODA IN TIME. — About twenty species of Myriapoda are known as fossils, the oldest examples of the order having been found in the Carboniferous epoch. From rocks of this age several species of Chilognathous Myria- pods have been discovered. The best-known forms belong to the genera Xylobius and Archiulus, and have been placed in a special family under the name of ArchiulidcE. The occurrence of air-breathing articulate animals (both Arachnida and Myria- poda) in the Carboniferous period is noticeable, as being con- temporaneous with the earliest-known terrestrial Molluscs. ANNULOSA : IN SECT A. 333 CHAPTER XXXVIII. INSECT A. GENERAL CHARACTERS OF THE INSECTA. CLASS IV. INSECTA. — The Insecta are defined as articulate animals in which the head, thorax, and abdomen are distinct ; there are three pairs of legs borne on the thorax ; the abdomen is destitute of legs ; a single pair of antenna is present ; mostly, there are two pairs of wings on the thorax. Respiration is effected by trachece. In the Insecta the body is divided into a variable number of definite segments, or somites, some of which are furnished with jointed append- ages, and the nervous and circulatory sys- tems are constructed upon essentially the same plan as in the Crustacea, ' Arachni- da, and Myriapoda. The head, thorax, and abdomen are distinct (figs. 174, 175), and the total number of somites in the body never exceeds twenty. " Of these, five cer- tainly, and six prob- ably" (according to \, • • f thorax, with the third pair of legs and the second pair ot SOme authorities, lOUr wings; e Abdomen, without limbs, but carrying ter- nnlv^ u rrmstiriitp the minal appendages concerned in reproduction ; f Femur ; Only;, i jnSUUUC UJC * Tibia ;*<* Tarsus. head, which possesses a pair of antennae, a pair of mandibles, and two pairs of max- illae, the hinder pair of which are coalescent, and form the 'labium.' Three, or perhaps, in some cases, more, somites Fig. 174. — Diagram of the external anatomy of an insect. a Head carrying the eyes (o) and antennae (an) ; b First segment of the thorax, with the first pair of legs ; c Second segment of the thorax, with the second pair of egs and the first pair of wings ; d Third segment of the 334 MANUAL OF ZOOLOGY. unite and become specially modified to form the thorax, to which the three pairs of locomotive limbs, characteristic of per- fect Insects, are attached. Two additional pairs of locomotive Fig- 175- — A, One of the Dragon-flies (sEskna grandis), slightly dissected : h Head, carrying the eyes, antennae, and organs of the mouth ; t t' t" First, second, and third segments of the thorax slightly separated from one another, each carrying a pair of legs, and the two last carrying each a pair of wings ; a Tail or abdomen. B, Young form, or "larva," of the same. C, Second stage, or " pupa." D, Head of a Dragon- fly (Libellula depressa), showing the feelers or antennae (0.11), the eyes (e e), the hinder pair of jaws (;«), and the upper lip (f). organs, the wings, are developed, in most insects, from the tergal walls of the second and third thoracic somites. No locomotive limbs are ever developed from the abdomen of the adult insect ; but the ventral portions of the abdominal somites, from the eighth backwards, are often metamorphosed into ap- paratuses ancillary to the generative function " (Huxley). The integument of the Insecta, in the mature condition, is more or less hardened by the deposition of chitine, and usu- ally forms a resisting exoskeleton, to which the muscles are at- tached. The segments of the head are amalgamated into a single piece, which bears a pair of jointed feelers or antennae, ANNULOSA: INSECTA. 335 a pair of eyes, usually compound, and the appendages of the mouth. The segments of the thorax are also amalgamated into a single piece; but this, nevertheless, admits of separa- tion into its constituent three somites (figs. 174, 175). These are termed respectively, from before backwards, the " protho- rax," " mesothorax," and " metathorax," and each bears a pair of jointed legs. In the great majority of Insects, the dorsal arches of the mesothorax and metathorax give origin each to a pair of wings. Each leg consists of from six to nine joints (see fig. 178). The first of these, which is attached to the sternal surface of the thorax, is called the " coxa," and is succeeded by a short joint, termed the " trochanter." The trochanter is followed by a joint, often of large size, called the "femur," succeeded by the so-called " tibia," and this has articulated to it the " tarsus," which may be composed of from one to five joints. The wings of Insects are expansions of the sides of the meso- and meta-thorax, these expansions being supported by slender but firm tubes, known as the "nervures." Each nerv- ure consists of a central trachea or air-tube, running in the centre of a larger blood-tube ; so that the wings not only act as organs of flight, but at the same time assist in the process of respiration. Normally, two pairs of wings are present, but one or other may be wanting. In the Coleoptera (Beetles) the anterior pair of wings become hardened by the deposition of chitine, so as to form two protective cases for the hinder membranous wings. In this condition the anterior wings are known as the "elytra," or "wing-cases." In some of the Hemiptera this change only affects the inner portions of the anterior wings, the apices of which remain membranous, and to these the term " hemelytra " is applied. In the Diptera the posterior pair of wings are rudimentary, and are converted into two capitate filaments, called "halteres" or "balancers." In the Strepsiptera the anterior pair of wings are rudimentary, and are converted into twisted filaments. The typical number of somites in the abdomen of the In- secta is eleven, and this number can often be recognised in the Neuroptera and in some other forms. In the Hymenoptera and Lepidoptera not more than ten can be recognised, and in other cases even fewer can be made out. The abdominal somites are usually more or less freely movable upon one an- other, and never carry locomotive limbs. The extremity of the abdomen is, however, not infrequently furnished with ap- pendages, which are connected with the generative function, and not infrequently serve as offensive and defensive weapons. 336 MANUAL OF ZOOLOGY. Of this nature are the ovipositors of Ichneumons and other insects, and the sting of Bees and Wasps. In the Earwig (Forficula) these caudal appendages form a pair of forceps ; whilst in many Insects they are in the form of bristles, by which powerful leaps can be effected, as is seen in the Spring- tails (Podurcz). In some insects (as the Mole-cricket and Cockroach), the ninth or tenth abdominal segment carries jointed antenniform appendages, which, though perhaps par- tially or even primarily generative in function, are certainly organs of sense, being connected with smell or hearing. The organs about the mouth in Insects are collectively termed the "trophi," or "instrumenta cibaria." Two principal types require consideration — namely, the masticatory and the suctorial — both types being sometimes modified, and occasion- ally combined. In the Masticatory Insects, such as the Beetles (fig. 176, A), the trophi consist of the following parts, from before back- \p Fig. 176. — Organs of the mouth of Insects, enlarged ; (A) of a Beetle (Carabus); (B) of the small Cabbage White Butterfly (Pontia rapee] ; (C) of the Bed-bug (Cimex lectn- larius), the mandibles and maxillae being displaced to one side. / Labrum ; in Man- dible ; mx Maxilla ; mp Maxillary palpus ; la Labium ; Ip Labial palpus ; an Base of one of the antennas. (Fig. B is slightly altered fiom Westwood.) ward : i. An upper lip, or " labrum," attached below the front of the head; 2. A pair of biting-jaws, or "mandibles;" 3. A pair of chewing-jaws, or "maxillae," provided with one or more pairs of "maxillary palps," or sensory and tactile filaments ; 4. A lower lip, or " labium," composed of a second coalescent pair of maxillae, and also bearing a pair of palpi, the " labial palps." The primitive form of the labium — that, namely, of a second pair of maxillae— is more or less per- fectly retained by the Orthoptera and some of the Neuroptera. ANNULOSA: INSECTA. 337 The lower or basal portion of the labium is called the " men- turn," or chin, whilst the upper portion is more flexible, and is termed the " ligula." The central portion of the ligula is often developed into a kind of tongue, which is very distinct in some Insects (as in Bees), and is termed the " lingua." In the typical suctorial mouth, as seen in the Butterflies (fig. 176, B) the following is the arrangement of parts: The labrum and the mandibles are now quite rudimentary ; the first pair of maxillae is greatly elongated, each maxilla forming a half-tube. These maxillae adhere together by their inner surfaces, and thus form a spiral " trunk," or " antlia " (inap- propriately called the "proboscis"), by which the juices of flowers are sucked up. Each maxilla, besides the half- tube on one side, contains also a tube in its interior ; consequently on a transverse section the trunk is found really to consist of three canals, one in the interior of each maxilla, and the third formed between them by their apposition. To the base of the trunk are attached the maxillary palpi, which are ex- tremely small. Behind the trunk is a small labium, composed of the united second pair of maxillae. The " labial palpi " are greatly developed, and form two hairy cushions, between which the trunk is coiled up when not in use. In the Bee there exists an intermediate condition of parts, the mouth being fitted partly for biting, and partly for suction. The labrum and mandibles are well developed, and retain their usual form. The maxillae and tire labium are greatly elongated ; the former being apposed to the lengthened tongue in such a manner as to form a tubular trunk, which cannot be rolled up, as in the Butterflies, but is capable of efficient suc- tion. The labial palpi are also greatly elongated. In the Hemiptera, the "trophi" consist of four lancet-shaped needles, which are the modified mandibles and maxillae, en- closed in a tubular sheath formed by the elongated labium (fig. 176, C). Lastly, in the Diptera — as in the common House-fly — there is an elongated labium, which is channelled on its upper surface for the reception of the mandibles and maxillae, these being modified into bristles or lancets. The mouth in the Masticating Insects leads by a pharynx and oesophagus into a membranous, usually folded, stomach — the "crop," or "ingluvies" — from which the food is trans- mitted to a second muscular stomach, called the "gizzard" (fig. 177). The gizzard, or proventriculus, is adapted for crushing the food, often having plates or teeth of chitine de- veloped in its walls, and is succeeded by the true digestive cavity, called the " chylific stomach" (ventriculus chylopoieticus). Y 333 MANUAL OF ZOOLOGY. From this an intestine of variable length proceeds, its terminal portion, or rectum, opening into a dilatation which is common to the ducts of the generative organs, and is termed the "cloaca." The oesophagus is furnished with salivary glands of varying size and complexity, which open into the cavity of the mouth. Besides the pro- per salivary glands, the larvae of Insects very usually possess a pair of silk-glands, which discharge their secretion by a single duct, furnished with a spinneret, and developed upon the labium. Rarely (as in Myrmeleo\ there are silk-glands opening in the abdominal re- gion. Those silk-glands which open into the mouth are to be regarded as modified salivary glands, and they are almost in- variably confined to the larvae. No true liver is present, but the stomach is lined by secret- ing cells, which appear to exer- cise an hepatic function. Be- hind the pyloric aperture of the Fig. 177- - Digestive system of a Beetle stomach, with Very few CXCCp- (Carabus auratus). a (Esophagus; b . ' • , , -, /. Crop ; c Gizzard ; d Chylific stomach ; e tlOnS, IS a Variable number of |IAnPlfgiandsbeS;/InteStine;^C10aCa; C£6Cal Convoluted tubes (fig. 177, e), which open into the intestine, and are called the "Malpighian tubes." These vessels are now generally regarded as discharging a renal function, and as corresponding with the kidneys of the higher animals. There are no absorbent vessels, and tlie products of digestion simply transude through the walls of the alimentary canal into the sinuses or irregular cavities which exist between the abdo- minal organs. The apparatus of digestion does not differ essentially from the above in any of the Insects ; but the ali- mentary canal is, generally speaking, considerably lengthened in the herbivorous species. There is no regular and definite course of the circulation in the Insects. The propulsive organ of the circulation is a long contractile cavity, situated in the back and termed the " dorsal vessel" (fig. 178, h). This is composed of a number of sacs ANNULOSA: INSECTA. 339 (ordinarily eight), opening into one another by valvular aper- tures, which allow of a current in one direction only — viz., to- wards the head. The blood is collected from the irregular Fig. 178. — Ideal transverse section of an Insect, h Dorsal vessel ; i Intestine ; n _Ven- tral Nerve-cord ; 1 1 Stigmata, leading into the branched tracheal tubes ;iv iv Wings ; a Coxa of one leg ; b Trochanter ; c Femur ; d Tibia ; e Tarsus. (After Packard.) venous sinuses which are formed by the* lacunae and interstices between the tissues, and enters the dorsal vessel from behind, and by lateral valvular openings ; it is then driven forwards, and is expelled at the anterior extremity of the body. The blood of the Insecta is corpusculated, and usually colourless. Whilst the general belief is that there is no regular system of blood-vessels (arteries and veins), and that the blood simply circulates through the interstices of the tissues, some observers affirm the partial existence of true vessels, and others maintain that the blood circulates in the spaces between the tracheae and their enveloping sheaths, which thus become converted into blood-vessels. Respiration is effected by means of "tracheae," or branched tubes, which commence at the surface of the body by lateral / apertures, called " stigmata," or " spiracles," and ramify through every part of the animal. In structure the tracheae are mem- branous, but their walls are strengthened by a chitinous fila- ( ment, which is rolled up into a continuous spiral coil. In the aquatic larvae of many insects, and in one or two adult Insects 340 MANUAL OF ZOOLOGY. (in Pteronarcys, one of the Orthoptera, and in one of the Phas- midce, of the same order) branches of the tracheae are sent to variously-shaped outgrowths which are termed " tracheal gills," and in which the blood is oxygenated. In all, however, with the exceptions above mentioned, these temporary internal or external appendages fall off when maturity is attained. The wings, also, whilst acting as locomotive organs, doubtless sub- serve respiration, the nervures being hollow tubes filled with blood and enclosing tracheae. Entomologists have generally recognised the following kinds of breath- ing-organs in Insects : — 1. The true tracheae, in the form of branched tubes, the walls of which are strengthened by a chitinous fibre. 2. Tracheal vesicles, or dilated receptacles directly connected with the proper tracheae, but having membranous walls not supported by a horny spiral fibre. 3. The modified tracheae of some adult Hemiptera and various aquatic larvae, in which the lips of the stigmata are prolonged into shorter or longer external tubes, by which the air is conveyed to the interior. 4. The tracheal gills properly so called, these usually being leaf -like plates attached to the sides of the abdomen, or tuft-like processes developed from the mucous membrane of the rectum. The nervous system in Insects, though often concentrated into special masses, consists essentially of a chain of ganglia, placed ventrally, and united together by a series of double cords or commissures. The cephalic or " prae-cesophageal " ganglia are of large size, and distribute filaments to the eyes and antennae. The post-cesophageat ganglia are united to the preceding by cords which form a collar round the gullet, and they supply the nerves to the mouth, whilst the next three ganglia furnish the nerves to the legs and wings. In larvae, thirteen pairs of ganglia may often be recognised. In the adults, however, of the higher groups of Insects (such as the Coleoptem, Hymenoptera, Diptera, and Lepidoptera), the thoracic ganglia coalesce into a single mass. The organs of sense are the eyes and antennae. The eyes in Insects are usually " compound," and are composed of a number of hexagonal lenses, united together, and each sup- plied with a separate nervous filament. Besides these, simple eyes — " ocelli," or " stemmata," — are often present, or, in rare cases, may be the sole organs of vision. In structure these resemble the single elements of the compound eyes. In a few cases the eyes are placed at the extremities of stalks or pedun- cles, but in no case are these peduncles movably articulated to the head, as is the case in the Podophthalmous Crustaceans. ANNULOSA: INSECTA. 34! The antennae are movable, jointed filaments, attached usually close to the eyes, and varying much in shape in different Insects. They doubtless discharge the functions of tactile organs, but are probably the organ of other more recondite senses in addition. The sexes in Insects are in different individuals, and most are oviparous. The ovum undergoes partial segmentation ; and the embryo has its future ventral surface turned outwards, and its dorsal surface inwards. Generally speaking, the young insect is very different in external characters from the adult, and it requires to pass through a series of changes, which con- stitute the "metamorphosis," before attaining maturity. In some Insects, however, there appears to be no metamorphosis, and in some the changes which take place are not so striking or so complete as in others. By the absence of metamor- phosis, or by the degree of its completeness when present, Insects are divided into sections, called respectively Ameta- bola, Hemimetabola, and Holometabola, which, though not, per- haps, of a very high scientific value, are nevertheless very con- venient in practice. Section i. Ametabolic Insects. — These pass through no meta- morphosis, and also, in the mature condition, are destitute of wings. The young of these insects (Aptera) on escaping from the ovum resemble their parents in all respects except in size ; and though they may change their skins frequently, they under- go no alteration before reaching the perfect condition, except that they grow larger. Section 2. Hemimetabolic Insects. — In the insects belonging to this section there is a metamorphosis consisting of three stages. The young on escaping from the ovum is termed the "larva;" when it reaches its second stage it is called the " pupa," or " nymph ; " and in its third stage, as a perfect insect, it is called the "imago." In the Hemimetabola, the " larva," though of course much smaller than the adult, or " imago," differs from it in little else except in the absence of wings. It is active and loconjotive, and is generally very like the adult in external appearance. The "pupa," again, is a little larger than the larva, but really differs from it in nothing else than in the fact tl^it the rudiments of wings have now appeared, in the form of lobes enclosed in cases. The " pupa " is still active and locomotive, and the term " nymph " is usually applied to it. The pupa is converted into the perfect insect, or " imago," by the liberation of the wings, no other change being requisite for this purpose. From the comparatively small amount of difference between these three stages, and from the 342 MANUAL OF ZOOLOGY. active condition of the pupa, this kind of metamorphosis is said to be " incomplete." In some members of this section, however — such as the Dragon-flies — the larva and pupa are aquatic, whereas the imago leads an aerial life. In these cases (fig. 175) there is necessarily a considerable difference between the larva and the adult ; but the larva and pupa are closely alike, and the latter is active. Section 3. Holometabolic Insects. — These — comprising the Butterflies, Moths, Beetles, &c. — pass through three stages which differ greatly from one another in appearance, the meta- morphosis, therefore, being said to be " complete." In these insects (fig. 179) the "larva" is vermiform, segmented, and usually provided with loco- motive feet, which do not correspond with those of the adult, though these latter are usually present as well (fig. 179). In some cases the larva is destitute of legs, or is "apodal." The larva is also provided with masticat- ory organs, and usually eats voraciously. In this stage of the metamorphosis the larvae constitute what are usually called " caterpillars " and " grubs." Having remained in this condition for a longer or shorter length of time, and having undergone repeated changes of skin, or " moults," necessitated by its rapid _ growth, the larva passes into the second stage, and be- Fig. 179.— Metamorphosis of the Magpie- ° ' moth (Phaltena grossulariata). COniCS a "pupa. The inSCCt is now perfectly quiescent, unless touched or otherwise irritated ; is incapable of changing its place ; and is often attached to some foreign object. This constitutes what — in the case of the Lepidoptera — is generally known as the "chrysalis," or "aurelia" (fig. 179). The body of the pupa is usually covered by a chitinous pellicle, which closely invests the animal. In some cases (e.g., in many Dip- terous insects) no traces of the future insect can be detected in the pupa by external inspection ; but in the Lepidoptera the ANNULQSA: INSECTA. 343 thorax and abdomen are distinctly recognisable in the pupae ; whilst in others (e.g., Hymenoptera) the parts of the pupa are merely covered by a membrane, and are quite distinct. In some cases the pupa is further protected within the dried skin of the larva ; and in other cases the larva — immediately before entering upon the pupa-stage — spins, by means of special organs for the purpose, a protective case, which surrounds the chrysalis, and is termed the " cocoon." Having remained for a variable time in the quiescent pupa- stage, and having undergone the necessary development, the insect now frees itself from the envelope which obscured it, and appears as the perfect adult, or " imago," characterised by the possession of wings. SEXES OF INSECTS. — The great majority of Insects, as is the case with most of the higher animals, consist of male and female individuals ; but there occur some striking exceptions to this rule, as seen in the Social Insects. In those organised communities which are formed by Bees, Ants, and Termites, by far the greater number of the individuals which compose the colony are either undeveloped females, or are of no fully developed sex. This is the case with the workers amongst Bees, and the workers and soldiers amongst Ants and Ter- mites. And, these sterile individuals, or " neuters," as they are commonly called, are not necessarily all alike in structure and external appearance. Amongst the Bees, all the neuters re- semble one another ; but amongst Ants and Termites they are often divided into " castes," which have different functions to perform in the general polity, and differ from one another greatly in their character. The organs of the two sexes are in no case united in the same individual, or, in other words, there are no hermaphrodite insects. (In some abnormal cases amongst Bees, Lepidoptera, &c., hermaphrodite individuals have been observed.) As has been noticed, however, before, asexual reproduction is by no means unknown amongst the Insecta, and the attendant phenomena are often of extreme interest. (See Introduction.) DISTRIBUTION IN SPACE. — The great majority of Insects, dur- ing their adult condition, are terrestrial or aerial in their habits, but in many cases, even of these, the larvae are aquatic. Many other insects live habitually during all stages of their existence in fresh water. A few insects inhabit salt water (either the sea itself or inland salt waters) during the whole or a portion of their existence. (This is the case with two or three Beetles of the families Hydrophilida and Dytiscidce^ some Hemipterous Insects, and the larvae of various Diptera.) Lastly, many in- 344 MANUAL OF ZOOLOGY. sects live parasitically upon the bodies of Birds or Mammals, or upon other Insects. DISTRIBUTION OF INSECTS IN TIME. — The most ancient remains of Insects at present known to us are from the De- vonian rocks of North America. Here occur several forms apparently belonging to the Neuroptera (or Pseudo-neiiropterd}, In the Carboniferous rocks the remains of Insects are more abundant, and we find examples of several orders (such as the Coleoptera, Orthoptera, and Neuroptera]. The orders Hymen- optera and Lepidoptera are not certainly known to occur till the Secondary period is reached; and in the Tertiary rocks we find representatives of almost all the existing orders. Amber, which is a fossil resin, has long been known to contain many insects in its interior (in certain specimens) ; and all of these appear to belong to extinct species, though amber, geologically speaking, is not an ancient product. CHAPTER XXXIX. DIVISIONS OF INSECTA. THE class Insecta includes such an enormous number of species, genera, and families, that it would be impossible to treat of these satisfactorily otherwise than in a treatise espe- cially devoted to entomology. Here it will be sufficient to give simply the differential characters of the different orders, draw- ing attention occasionally to any of the more important points in connection with any given family. As already said, the Insecta are divided into three divisions, termed Ametabola, Hemimetabola, and Holometabola, according as they attain the adult condition without passing through a metamorphosis, or have an incomplete or complete metamor- phosis. The Insects which come under the first head (viz., Ametabola) are not furnished with wings in the adult condition, and the four orders which compose this section are commonly grouped together under the name Aptera. By some, however, this division is entirely rejected, and the orders in question are placed amongst the Hemimetabola, or even grouped with the Myriapoda. Indeed, it is certain that the orders of the so-called Apterous Insects are not, strictly speaking, scientific divisions. It is, however, a matter of convenience to retain them in a separate form, as it is by no means absolutely ANNULOSA: INSECTA. 345 certain how they may most naturally be distributed amongst the higher orders. SUB-CLASS I. AMETABOLA. — Young not passing through a metamorphosis ) and differing from the adult in size only. Imago destitute of wings ; eyes simple, sometimes wanting. ORDER I. ANOPLURA. — Minute Aptera,' in which the mouth is formed for suction ; and there are two simple eyes. This order comprises insects which are commonly parasitic upon man and other animals, and are known as Lice (Pedi- culi). The common Louse (fig. 180, A) is furnished with a Fig. 180. — Morphology of Aptera. A, Pedicidus hutnanns capitis ', B, Docopkorus hamatus, one of the Bird-lice ; C, Campodea, ; D, Degeeria, one of the Poduridce ; E, Scale of a Podurid, as seen under the microscope ; F, Degeeria purpurascens. All the figures are greatly enlarged. (After Packard and Gervais.) simple eye, or ocellus, on each side of a distinctly differen- tiated head, the under surface of which bears a suctorial mouth. There is little distinction between the thorax and abdomen, but the segments of the former carry three pairs of legs. The legs are short, with short claws or with two opposing hooks, affording a very firm hold. The body is flattened and nearly transparent, distinctly segmented, and showing the stigmata very plainly. The young pass through 346 MANUAL OF ZOOLOGY. no metamorphosis, and their multiplication is extremely rapid. Many Mammals are infested by Lice, the same animal often being subject to the attacks of more than one species of Louse. Three species commonly attack man — viz., Pediculus human-its corporis, P. capitis, and P. pubis ; and a fourth species (P. tabescentiwn) is of rare occurrence, and gives rise to the loath- some disease known as Phthiriasis. The Lice are now very commonly associated with the Hemiptera, of which they are regarded as constituting a degraded and aberrant group. ORDER II. MALLOPHAGA. — Minute Aptera, in which the mouth is formed for biting, and is furnished with mandibles and maxillcz. The members of this order (fig. 180, B) are commonly known as " Bird-lice," being parasitic, sometimes upon Mammals, but mostly upon Birds. They strongly resemble the Pcdiculi, but the mouth is formed for biting, to suit their mode of life — since they do not live upon the juices of their hosts, but upon the more delicate tegumentary appendages. They are some- times regarded as constituting a degraded group of the Hemiptera. ORDER III. COLLEMBOLA. — Minute Aptera, with a semi- masticatory or suctorial mouth ; the first abdominal segment fur- nished with a ventral tube or suctorial organ; the last abdominal segment but one with appendages for leaping. This order has been established by Sir John Lubbock for the reception of a number of Insects generally known as " Spring-tails." Their scientific name is in allusion to the fact that they attach themselves to foreign bodies by a ventral suctorial tube, which contains a viscous fluid; whilst their popular name refers to their possessing saltatory appendages attached to the last abdominal segment but one. These ap- pendages (fig. 1 80, D and F) consist of a long forked process which is generally bent along the under surface of the body, and kept there by a small catch. When released, the sudden extension of the elastic process throws the insect into the air. The body is covered either with hairs or scales, and the latter exhibit under the microscope very elaborate and beautiful markings (fig. 163, E). They are generally to be found in moist dark places in gardens, or on the surface of pools, and the commonest genera are Podura, Smynthurus, and Degeeria. ORDER IV. THYSANURA. — Minute Aptera, with a mastica- tory mouth ; the end of the abdomen furnished with long bristle- like terminal appendages, used in locomotion. ANNULOSA: INSECTA. 347 The Insects of this order are closely related to those of the preceding, but the long anal bristles do not form a " spring ; " and the mouth is distinctly masticatory. The two principal genera are Lepisma and Campodea (fig. 180, C), both of which live generally under stones or in dark situations. The body is hairy, or clothed with metallic scales ; these latter organs being in Lepisma so delicately marked that they are com- monly used as test-objects for the microscope. According to Packard, the Thysanura and Collembola are to be regarded as degraded groups of Neuroptera, the former having also affinities with the Myriapoda. According to Sir John Lubbock, Campodea may be regarded as a modern re- presentative of an ancient type-form, from which the higher Insects originally took their rise. SUB-CLASS II.. HEMIMETABOLA. — Metamorphosis incomplete ; the larva differing from the imago chiefly in the absence of wings, and in size ; pupa usually active, or, if quiescent, capable of move- ment. * ORDER V. HEMIPTERA (Rhynchotd). — Mouth suctorial, beak- shaped, consisting of a jointed rostrum, composed of the elongated labium, which forms a jointed, tubular sheath for the bristle- shaped, styliform mandibles and maxilla. Eyes compound, usually with ocelli as well. Two pairs of wings in most ; some- times wanting. Pupa generally active. The Hemiptera live upon the juices of plants or animals, Fig, 181. — Hemiptera. Bean Aphis (Aphis f aba), winged male and wingless female. which they are enabled to obtain by means of the suctorial rostrum. * The Coccidtz, amongst the Hemiptera, undergo a complete metamor- phosis. In certain of the Hemiptera and Orthoptera the adult is apterous, and in these cases there cannot be said to be any metamorphosis, since the larvae differ from the adult only in size, in having fewer joints to the antennae, and in having a smaller number of facets in each of the compound eyes. 343 MANUAL OF ZOOLOGY. The order is divided into the following three sub-orders : — Sub-order a. Homoptera. — The anterior pair of wings of the same texture throughout (membranous) ; the mouth turned backwards, so that the beak springs from the back of the head. The wings fold over one another when the insect is at rest. There are ocelli between the compound eyes, and the antennae are small and composed of few joints. The females often have an ovipositor of three toothed blades. In this section are the Aphides, the Scale Insects (Cocddagmation, and into which it may be again retracted by invagination. Mouth surrounded by a circle or crescent of hollow, ciliated tentacles ; animals always forming composite colonies " (Allman). All the Polyzoa live in an associated fbnnjn colonies or "polyzoaria," which are sometimes foliaceous (fig. 197), some- times branched and plant-like, sometimes encrusting, and very rarely are- free. Each "polyzoarium" consists of an assem- blage of distinct but similar zooids arising by continuous gem- mation from a single primordial individual. The colonies thus produced are in very many respects closely similar to those of many of the Hydroid IJolypes, with which, indeed, the Polyzoa were for a long time classed. The " polyzoarium," however, of a 'Polyzoon differs from the polypidom of a composite Hy- droid in the general fact that the separate cells of the former do not communicate with one another otherwise than by the continuity of the external integument; whereas the zooids of the latter are united by an organic connecting medium, or " ccenosarc," from which they take their origin. In one group of the Polyzoa — viz., the Ctenostomata (includ- ing Vesicularia and its allies), the cells arise from a common stalk, and are thus placed in communication with one another; 372 MANUAL OF ZOOLOGY. but this hardly affects the general value of the distinction above spoken of. The homomorphism, however, which subsists between the Fig. 197. — Flustra foliacea, one of the Sea-mats, a Portion of the colony, natural size ; b A fragment magnified, to show the cells in which the separate polypides are contained. Polyzoa and the Hydroida, is shown most decisively not to be a true affinity, when the structure of the individual zooids is examined. The polypite of a Hydroid Zoophyte, as we have already seen, possesses no alimentary canal distinct from the general cavity of the body ; there are no traces of a nervous system, and the reproductive organs are in the form of exter- nal processes of the body-wall. In the zooid of all the Polyzoa (fig. 198, 3), on the other hand, there is a distinct alimentary canal, completely shut off from the somatic cavity ; a nervous system is present, and the reproductive organs are contained within the body. In the Polyzoa, the entire colony — or its entire dermal system —is called the " polyzoarium " or " coenoecium ; " the separate MOLLUSCA : POLYZOA, 373 zooids are called " polypides ; " and the little chambers in which each is contained are called the " cells," or " zocecia." It will be seen, therefore, that the term polypite is restricted to the zooid of a compound Hydrozoon, or to the entire hydro- soma of a simple member of the class. The term polype is applied to a simple Actinozoon, or to the zooids of a compound actinosoma. Lastly, the term polypide is exclusively employed to designate the zooid of one of the Polyzoa. The construction of a typical polypide of a Polyzoon is thus described by Professor Allman (fig. 198, 2) : — "Let us imagine an alimentary canal, consisting of oeso- Fig. 198. — Morphology of Polyzoa. i. Portion of the coenoecium of Flustra truncata, magnified. 2. Diagram of a Polyzoon (after Allman) : a Region of the mouth sur- rounded by tentacles ; b Alimentary canal ; c Anus ; d Nervous ganglion ; e Invest- ing sac (ectocyst); y~Testis; /' Ovary; £• Retractor muscle. 3. Bird's-head pro- cess, or "avicularium," of a Polyzoon. phagus, stomach, and intestine, to.be furnished at its origin with long ciliated tentacula, and to have a single nervous gan- glion placed upon one side of the oesophagus. Let us now suppose this canal to be bent back upon itself towards the side of the ganglion, so as to approximate the termination to the origin. Let us further imagine the digestive tube thus constituted to be suspended in a fluid contained in a mem- branous sac with two openings, one for the mouth and the other for the vent, the tentacula alone being external to the sac. Let us still further suppose the alimentary tube, by means of a system of muscles, to admit of being retracted or pro- 374 MANUAL OF ZOOLOGY. truded according to the will of the animal ; the retraction being accompanied by an invagination of the sac, so as par- tially or entirely to include the oral tentacles within it ; and if to these characters we add the presence of true sexual organs in the form of ovary and testis, occupying some portion of the interior of the sac, and the negative character of the absence of all vestige of a heart, we shall have, perhaps, as correct an idea — apart from all considerations of homology or deriva- tion from an archetype — as can be conveyed of the essential structure of a Polyzoon in its simplest and most generalised condition. " To give, however, more actuality to our ideal Polyzoon, we may bear in mind that the immediately investing sac has the power, in almost every case, of secreting from its external surface a secondary investment, of very various constitution in the different groups; and we may, moreover, conceive of the entire animal with its digestive tube, tentacula, ganglion, muscles, generative organs, circumambient fluid, and investing sacs, repeating itself by gemmation, and thus producing one or more precisely similar systems holding a definite position relatively to one another, while all continue organically united, and we shall then have the actual condition presented by the Polyzoa in their fully-developed state." The vast majority of the Polyzoa are fixed, but this is not universally the case. Thus the singular fresh-water Cristatella is free and locomotive, creeping about by means of a flattened discoid base, not unlike the foot of the Gasteropoda ; and the polyzoary seems to have been unattached in a few other forms (Selenaria, Cupularia, &c.) The two fundamental structures of the " coencecium " of a Polyzoon — viz., the immediately investing sac, and its second- ary investment — are sometimes termed the "endoderm" and " ectoderm ; " but as these terms are employed in describing the Hydrozoa, it is better to make use of the terms " endocyst " and " ectocyst," proposed by Dr Allman. The " ectocyst," or external investment of the coenoecium, is usually a brown, pergamentaceous, probably chitinous, but often highly calcareous, membrane ; and it is by the ectocyst that the "cells" are formed. In Cristatella, alone of the Polyzoa, there is no ectocyst; and in Lophopus (fig. 199, 3) and in the curious Pectinatella the ectocyst is gelatinous in its consistence. In many cases the ectocyst is provided with singular appendages, supposed to be weapons of offence and defence, or organs of prehension, termed " avicularia " (fig. 198, 3) and "vibracula." The avicularia, or "bird's-head MOLLUSCA: POLYZOA. 375 processes," differ a good deal in shape, but consist essentially of " a movable mandible and a cup furnished with a horny beak, with which the point of the mandible is capable of being brought into apposition " (Busk). In shape the avicularia often closely resemble the head of a bird, and they are in many respects comparable with the " pedicellarise " of the Echinodermata, keeping up a constant snapping movement, which continues long after the death of the general colony. In the "vibracula," the place of the mandible of the avicu- larium is taken by a bristle, or seta, which is capable of exten- sive movement. In many cases the cells are also furnished with globular sacs or pouches (" ovicells " or "oocysts"), ap- pended to them, and serving as marsupial pouches for the ova. Ovicells are only known in the marine Polyzoa, and the ova are liberated by their ultimate rupture. It is generally believed that the avicularia, vibracula, and ovicells are really undeveloped polypides or modified zooids. Good authorities also believe that the "cells" or "zooecia" themselves are not to be regarded as mere skeletal structures, but that they have a life independent of that of their con- tained polypides, and that they can continue to live and pro- duce new polypides after the death of the latter. They are regarded, in fact, as separate zooids. The endocyst is always soft, contractile, and membranous ; and, according to Sars, is wanting in Rhabdopleura. It lines the interior of the cells formed by the ectocyst, and is reflected backwards at the mouth of the cell, so as to be invaginated, or inverted into itself; and it finally terminates by being attached to .the base of the circlet of tentacles. This invagination of the endocyst is more or less permanently present in all the fresh-water Polyzoa. The epithelium lining the inner surface of the endocyst is furnished with vibratile cilia. The mouth of each polypide is surrounded by a crown of tubular, non-retractile tentacles, which have their sides ciliated, and are arranged sometimes in a circle and sometimes in a crescent. In the fresh-water Polyzoa the tentacles are united towards their bases by a funnel-shaped membrane, known as the "calyx." The tentacles are borne on a kind of disc, or stage, which is termed by Professor Allman the "lophophore." In the majority of Polyzoa — including almost all the marine species — the lophophore is circular (fig. 199, 2) ; but in most of the fresh-water forms it has its neural side extended into two long arms, so that the entire lophophore becomes crescen- tic or "horse-shoe-shaped" (fig. 199, 3); hence this section is sometimes collectively termed the " Hippocrepian " Polyzoa. 376 MANUAL OF ZOOLOGY. In all, or almost all, the Polyzoa in which this crescentic con- dition of the lophophore exists, there is also a singular valve- like organ which, springing from the anal side of the lopho- Fig. 199. — i. Fragment of Flustra truncata, one of the Sea-mats, natural size. 2. A single polypide of Valkeria, magnified, showing the orbicular crown of tentacles. 3. A polypide of Lophopus crystallinus, a fresh-water Poly2oon, highly magnified, showing the horse-shoe-shaped crown of tentacles, a Tentacular crown ; b Gullet ; c Stomach ; d Intestine ; e Anus j g Gizzard ; k Endocyst j / Ectocyst ; f. Funiculus. phore, arches over the mouth, and is termed the "epistome." The only marine forms in which the lophophore is bilateral are Pedicellina and Rhabdopleura ; the only fresh-water species in which the lophophore is orbicular are Paludicella and Urna- tella. The mouth conducts by an oesophagus into a dilated stomach. In some cases a pharnyx may be present, and in others there is in front of the stomach a muscular proventriculus, or giz- zard. From the stomach proceeds the intestine, which shortly turns forward to open by a distinct anus close to the mouth. As the nervous ganglion is situated on that side of the mouth towards which the intestine turns in order to reach its termina- tion, the intestine is said to have a " neural flexure ; " and this relation is constant throughout the entire class. Respiration in the Polyzoa appears to be carried on by the ciliated tentacles,, and by the "perigastric space," which is filled with a clear fluid, containing solid particles in suspen- sion. A kind of circulation is kept up in this "perigastric MOLLUSCA: POLYZOA. 377 fluid " by means of the cilia lining the inner surface of the endocyst. Beyond this there is nothing that could be called a circulation, and there are no distinct circulatory organs of any kind. The nervous system in all the Polyzoa consists of a single small ganglion (fig. 198, 2), placed upon one side of the oeso- phagus, between it and the anal aperture, and apparently really of a double nature. Besides the single ganglion which belongs to each polypide, there is also in some of the Polyzoa, a " colonial nervous system ; " that is to say, there is a well- developed nervous system, which unites together the various zooids composing the colony, and brings them into relation with one another. It is probably in virtue of this system that the avicularia are enabled to continue their movements and retain their irritability after the death of the polypides ; but high authorities deny that the so-called "colonial nerve-system" is really of a nervous nature at all. The muscular system is well developed, and consists of various muscular bands, with special functions attaching to each. The most important fasciculi are the retractor muscles (fig. 198, 2, g), which retract the upper portion of the polypide within the cell. These muscles arise from the inner surface of the endocyst near the bottom of the cell, and are inserted into the upper part of the oesophagus. The polypide, when re- tracted, is again exserted, chiefly by the action of the " parietal muscles," which are in the form of circular bundles running transversely round the cell. As far as is known, all the Polyzoa are hermaphrodite, each polypide containing an ovary and testis (fig. 198, 2). The ovary is situated near the summit of the cell, and is attached to the inner surface of the endocyst. The testis is situated at the bottom of the cell, and a curious cylindrical appendage, called the " funiculus," usually passes from it to the fundus of the stomach. There are no efferent ducts to the reproductive organs ; and the products of generation — i.e., the spermatozoa and ova — are discharged into the perigastric space, where fecundation takes place ; and the impregnated ova escape by special openings in the body-wall, by dehiscence of the cell, or in some manner not as yet thoroughly understood. As already mentioned, continuous gemmation occurs in all the Polyzoa, the fresh zooids thus produced remaining attached to the organism from which they were budded forth, and thus giving rise to a compound growth. A form of discontinuous gemmation, however, occurs in many of the Polyzoa, in which certain singular bodies, called " statoblasts, " are devel- 378 MANUAL OF ZOOLOGY. oped in the interior of the polypide. The statoblasts are found in certain seasons lying loose in the perigastric cavity. In form "they may be generally described as lenticular bodies, varying, according to the species, from an orbicular to an elongated-oval figure, and enclosed in a horny shell, which consists of two concavo-convex discs united by their margins, where they are further strengthened by a ring which runs round the entire margin, and is of different structure from the discs. . . . When the stato- blasts are placed under circumstances favouring their development, they open by the separation from one another of the two faces, and there then escapes from them a young Polyzoon, already in an advanced stage of de- velopment, and in all essential respects resembling the adult individual in whose cell the statoblasts were produced " (Allman). The statoblasts are formed as buds upon the "funiculus"— the cord already alluded to as ex- tending from the testis to the stomach — upon which they may usually be seen in different stages of growth. They do not appear to be set free from the perigastric space prior to the death of the adult, and when liberated they are enabled to float near the surface of the water, in consequence of the cells of the marginal ring, or " annulus," being spongy and filled with air. They must be looked upon as " gemmce peculiarly encysted, and destined to remain for a period in a quiescent or pupa-like state " (All- man). As regards the development of the Polyzoa, the embryo upon its emergence from the ovum presents itself as a ciliated, free-swimming, sac-like body, from which the polypide is sub- sequently produced by a process of gemmation. In the singu- lar Rhabdopleura the primitive bud is enclosed between two fleshy lobes or valve-like plates, attached along their dorsal margin, and giving exit in front to the rudimentary lophophore. As the development proceeds, these plates cease to keep pace in their growth with the rest of the bud ; till ultimately they appear as a peculiar shield-like organ on the haemal side of the lophophore. These lobes have been compared by Dr Allman with the mantle-lobes of the Lamellibranchiata ; and according to the most recent researches, the whole shield-like organ is a specially modified zooid, and in no way corresponds with the " epistome " of the Pkylactolczmata. DIVISIONS OF THE POLYZOA. — According to the classification proposed by Nitsche, and now generally adopted, the Polyzoa are divided into the two primary sections of the Entoprocta and the Ectoprocta, to which a third must be added, in accordance with the views of Dr Allman, under the name of Aspidophora, for the reception of the anomalous Rhabdopleura. The follow- ing are the principal groups of the Polyzoa : — A. ECTOPROCTA. Mouth within the circle of tentacles ; anus dorsal and outside the ten- tacular circle ; lophophore crescentic or circular. Sub-order I. Phylactolcemata. ii ii II. Gymnolieinata. MOLLUSCA: POLYZOA. 379 B. ENTOPROCTA. Mouth and anus both within the circle of tentacles ; lophophore horse- shoe-shaped. Tentacles solid and non-retractile, filled, like the body- cavity, with parenchyma. Ectocyst not calcified. This division includes the marine Pedicellina and Loxosoma, and the fresh-water Urnatella. Loxosoma is semiparasitic, and is attached to the bodies of Gephyreans and other marine animals. C. ASPIDOPHORA. This division includes only the singular marine genus Rhabdopleura, in which the lophophore is crescentic, and carries a discontinuous series of tentacles ; the mouth is lateral rather than terminal ; a special shield-like organ is attached to the body of the lophophore, between the mouth and the anus ; the coenoecium is chitinous and tubular, and is supported by a correspondingly divided chitinous rod, attached superiorly to a fleshy con- tractile cord, which is in turn connected with the body of the polypites ; and, lastly, the endocyst and tentacular sheath are wanting. Of the above divisions of the Polyzoa, the two most important groups are those of the Phylactolczmata and Gymnolcemata. In the former of these are included almost all the fresh-water Polyzoa, and the lophophore is bilateral and horse-shoe-shaped in all except Fredericella. The division of the Gymnolamata, on the other hand, includes the fresh-water genera Paludicella and Urnatella, and the vast majority of the marine Polyzoa. Of these latter, the sub-order of the Cheilostomata is the most important, as embracing the greater number of the common forms.- In these, the opening of the cell is sub-terminal, and is generally closed by a movable lip or shutter. On the other hand, in the sub-order Cydostomata, the cells are tubular, the orifices terminal, of the same diameter as the cell itself, and without any movable apparatus for closure. Lastly, in the singular group of the Ctenostomata (including Vesicularia, Alcyonidium, and Val~ keria\ the cells arise from a common tube, and their mouths are terminal, and furnished with a setose fringe for their closure. AFFINITIES OF THE POLYZOA. — -By many zoologists the Poly- zoa are now regarded as being an anomalous class of Worms, closely related to the true Annelides. That there are points of relationship between these apparently diverse groups cannot be doubted ; but these do not seem sufficient to outweigh the points of divergence — such, for example, as the absence of seg- mentation in the former, and the totally different form of the nervous system. The Polyzoa have also striking affinities with the Brachiopoda and Tunicata, and even with some of the Mol- lusca proper ; and it has not, therefore, appeared advisable to remove them to the division of the Anarthropoda. DISTRIBUTION OF POLYZOA IN SPACE. — The Polyzoa, like all the Molluscoida, are exclusively aquatic in their habits, but unlike the remaining two classes, they are not exclusively con- fined to the sea. The marine Polyzoa are of almost universal occurrence in all seas. The fresh-water Polyzoa, however, not only differ materially from their marine brethren in structure, 380 MANUAL OF ZOOLOGY. but appear to have a much more limited range, being, as far as is yet known, principally characteristic of the north temperate zone. Britain can claim the great majority of the described species of fresh-water Polyzoa, but 'this is probably due to the more careful scrutiny to which this country has been subjected. Fresh -water Polyzoa have also been found in the southern hemisphere, in Australia and India. DISTRIBUTION OF POLYZOA IN TIME. — The Polyzoa have left abundant traces of their past existence in the stratified series, commencing in the Lower Silurian rocks and extend- ing up to the present day. The Oldhamia of the Cambrian rocks of Ireland, and the Graptolites, have been supposed to belong to the Polyzoa ; but the former is very possibly a plant, and the latter should be referred to the Hydrozoa. Of un- doubted Polyzoa, the marine orders of the Cheilostomata and Cyclostomata are alone known with certainty to be represented. Several Palaeozoic genera — such as Fenestella (the Lace-coral), Ptilodictya, Ptilopora, &c. — are exclusively confined to this epoch, and do not extend into the Secondary rocks. Amongst the Mesozoic formations, the Chalk is especially rich in Poly- zoa, over two hundred species having been already described from this horizon alone. In the Tertiary period, the Coralline Crag (Pliocene) is equally conspicuous for the great number of the members of this class. CHAPTER XLII. TUNIC ATA. CLASS II. TUNICATA (Ascidioida). — The members of this class of the Molluscoida are defined as follows: "Alimentary canal suspended in a double-walled sac, but not capable of protrusion and retraction ; mouth opening into the bottom of a respiratory sac, whose walls are more or less completely lined by a network of blood-vessels " (Allman). Animal simple or composite. An im- perfect heart in the form of a simple tube open at both ends. Sexes mostly united ; a metamorphosis in development. The Tunicaries are all marine, and are protected by a lea- thery, elastic integument, which takes the place of a shell. In appearance a solitary Ascidian (fig. 200, C) may be compared to a double-necked jar with two prominent apertures situated close to one another at the free extremity of the animal, one MOLLUSCA: TUNICATA. 381 of these being an ingestive and branchial aperture, whilst the other serves as an excretory aperture. The covering of an Ascidian is composed of two layers. Of these the outer is — br Fig. 200. — Morphology of Tunicata. A, Diagram of the structure of a simple Tuni- cate : / Test ; t' Second muscular tunic ; j Branchial sac ; b Branchial aperture ; a Atrial aperture ; c Atrium ; o Opening of the gullet ; g Stomach, leading into the intestine; an Anal aperture ; n Nerve-ganglion. B, Botryllus smaragdus — a small portion of a colony of the natural size, and a single system of the same enlarged; co Common atrial aperture ; br Branchial aperture of one of the zooids. C, Molgula Manhattensis, a simple Ascidian. The arrows in A and C show the direction of the water-currents. called the " external tunic," or " test," and is distinguished by its generally coriaceous or cartilaginous consistence. It is also remarkable for containing a substance which gives the same chemical reactions as cellulose, and is probably identical with this characteristic vegetable product. Sometimes it con- tains spicules or plates of calcareous matter. The test is lined by a second coat, which is termed the "second tunic," or " mantle," and which is mainly composed of longitudinal and circular muscular fibres. By means of these the animal is en- dowed with great contractility, and has the power of ejecting water from its branchial aperture with considerable force. The mantle lines the test, but is only slightly and loosely at- tached to it, especially near the apertures. The ingestive or branchial aperture (fig. 200, A, b) is generally surrounded by a circlet of small, non-ciliated, non-retractile tentacles, and opens into a large chamber (fig. 200, A, s), which usually occupies 382 MANUAL OF ZOOLOGY. the greater part of the cavity of the mantle, and has its walls perforated by numerous apertures. This is known variously as the "pharynx," the "respiratory sac," or the "branchial sac." The last of these names is the best, as it is not certain that the perforated respiratory sac is really the homologue of the phaiynx. If this should be its real nature, then the bran- chial opening in the test is truly the month ; but good authori- ties regard the branchial sac as wholly unconnected with the alimentary canal. Inferiorly the respiratory sac leads, by a second aperture (fig. 200, A, o), into an oesophagus, which conducts into a capacious stomach (g). If the branchial sac be regarded as not representing a dilated pharynx, then its lower aperture is the true mouth. From the stomach an intestine is continued, generally with few flexures, to the anal aperture (an\ which does not com- municate directly with the exterior, but opens into the bottom of a second chamber, which is called the " cloaca," or " atrium " (c). Superiorly the cloaca communicates with the external medium, by means of the second aperture in the test (a). The first bend of the intestine is such that, if continued, it would bring the anus on the opposite side of the mouth to that on which the nervous ganglion is situated. The intestine, there- fore, is said to have a "haemal flexure;" whereas the flexure in the case of the Polyzoa is "neural." The intestine, however, in the Tunicata does not preserve this primary haemal flexure, but is again bent to the neural side of the body, the nervous ganglion coming finally to be situated between the mouth and the rectum. As just stated, the anus is not in direct com- munication wtth the exterior, but opens into a large cavity, called the " cloaca," or " atrial chamber," which, in turn, opens externally by the second aperture of the animal. This cloaca is a large sac lined by a membrane which " is reflected like a serous sac on the viscera, and constitutes the ' third tunic,' or 1 peritoneum.' " From the cloaca " it is reflected over both sides of the pharynx" (respiratory sac), "extending towards its dorsal part very nearly as far as that structure which has been termed the ' endostyle.' It then passes from the sides of the pharynx to the body-walls, on which the right and left lamellae become continuous, so as to form the lining of the chamber into which the second aperture leads, or the ' atrial chamber.' Posteriorly, or at the opposite end of the atrial chamber to its aperture, its lining membrane (the 'atrial tunic ') is reflected to a greater or less extent over the intestine and circulatory organs. . . . Where the ' atrial tunic ' is reflected over the sides of the pharynx, the two enter into a MOLLUSCA: TUNICATA. 383 more or less complete union, and the surfaces of contact be- come perforated by larger or smaller, more or less numerous, apertures. Thus the cavity of the pharynx acquires a free communication with that of the atrium ; and as the margins of the pharyngo-atrial apertures are fringed with cilia working to- wards the interior of the body, a current is produced, which sets in at the oral aperture and out by the atrial opening, and may be readily observed in a living Ascidian " (Huxley). As regards some points in the above description, Professor Allman does not agree with Huxley, but believes, on the other hand, " that the walls of the atrium simply surround the branchial sac, without being reflected on its sides, and that the branchial sac is therefore properly within the cavity of the atrium/' In structure, the " branchial " sac is composed of a series of longitudinal and transverse bars, which cross each other at right angles, and thus give rise to a series of quadrangular meshes, the margins of which are fringed with vibratile cilia. These bars are hollow, and are really vessels, which open on each side into two main longitudinal sinuses, the so-called " branchial " or " thoracic " sinuses — one of which is placed along the haemal side of the sac, whilst the other runs along its neural aspect. The function of the entire perforated sac is clearly respiratory. The Tunicata mostly possess a distinct heart, consisting of a simple muscular tube, which is open at both ends, and is not provided with valves. The circulation is attended with the remarkable peculiarity of being periodically reversed, the blood being propelled in one direction for a certain number of contractions, and being then driven for a like period in an opposite direction ; " so that the two ends of the heart are alternately arterial and venous." The nervous system consists of a single ganglion placed on one side of the oral aperture, between it and the anus, in all known Tunicata, except in the aberrant form Appendicularia. The only organs of sense are pigment-spots, or ocelli, usually placed between the oral tentacles, and an auditory capsule, sometimes containing an otolith. These organs, however, are not constantly present. With the exception of Doliolum and Appendicularia, all the Tunicata are hermaphrodite. Mr Saville Kent, however, is of opinion that Appendicularia is the free reproductive zooid of an Ascidian, bearing to the adult the same relation that the Medusae do to the Hydroid colony. The reproductive organs are situated in the fold of the intestine, and their efferent duct 384 MANUAL OF ZOOLOGY. . opens into the atrium. The embryo Tunicate (fig. 201, A and C) is at first generally free, and is mostly shaped like the tad- pole of a frog, swimming by means of a long caudal appendage. In one species (Molgula tubulosa) the larval form is destitute of a tail, inactive, and amoeboid, and it almost immediately at- taches itself by means of little outward processes which it de- velops. Several other species of Molgula are also destitute of a tail when in the embryo condition ; but the embryos of those species of the genus which are fixed in the adult state appear to be provided with a caudal appendage. Lastly, the larval caudal appendage has been shown to exhibit a cylindrical rod- like body, which has been paralleled with the chorda dor sails of Vertebrates. The body in question (fig. 200, A) is a kind of cellular rod, which agrees with the notochord of Vertebrates in giving insertion by its sheath to muscles, and which is said to hold an analogous position to the nervous system. In many cases, also, the caudal appendage exhibits in addition diverging rays, which have been compared with the rays of the tails of young fishes. It is impossible here to enter minutely into the structures which compose the larval Tunicate, the relations of these structures to one another and to the larva as a whole, or their precise homological import. Such im- portant theoretical conclusions have, however, been based upon the inter- pretation of these structures, that a few words may be directed to this point. According to the researches of Kowalewsky and Kupffer, the larval Tunicate differs from the Invertebrata generally, and agrees with the Verte- brata in the fact that the embryo is bicavitary, the nervous system being developed in a dorsal cavity, quite separate from the cavity in which the viscera generally are formed. The axial structures of the tail, as described by the same observers, are stated to commence as a double row of quad- rate cells, surrounded by oval muscle-cells, and projecting slightly into the body of the larva, having the visceral canal below, and the neural canal above. When complete, the axis of the tail is said to consist of a carti- laginous elastic axial rod, surrounded by a cellular envelope. According, then, to the views of the observers just mentioned, the axial rod of the tail of the larval Tunicate is the precise equivalent of the "chorda dor- salis " of vertebrate animals, seeing that it is dorsal in position, and that it is intermediate between the neural and visceral cavities. The perforated branchial sac being, further, regarded as a development of the anterior portion of the alimentary canal, is an additional support to this view ; as it can be compared with the dilated and perforated pharynx of the Lance- let (Ampkioxus) the lowest of the Fishes. The views sketched out above, though accepted and endorsed by many high authorities, have not been allowed to pass without question. The opinions originally put forward by Kowalewsky as to the essential identity of the developmental processes of the Tunicates and the Vertebrates have been attacked, and many of the most important of his alleged facts have been denied by such well-known authorities as Mecznikow, Donitz, Giard, Von Baer, and Reichert. Without entering into this controversy further, MOLLUSCA: TUNICATA. 385 it will be sufficient to enumerate the more important points which the researches of the observers just mentioned would seem to render more or less probable : — i. The axial rod of the larval Ascidian is ventral in position, and can- not, therefore, be homologically compared with the "chorda dorsalis " of the Vertebrate embryo. (Von Baer.) Fig. 201. — Development of Tunicata, A, Larva of Botryllus violaceus, greatly mag- nified : a Processes for attachment ; b Mass of primitive cells from which the diges- tive organs are developed ; c Circlet of eight cellular outgrowths ; d Eye-spot ; e Entrance to the branchial sac \f The external structureless " test ; " g Large nucle- ated cells forming the sheath of the central axis (eight rows of these cells are pres- ent). B, A portion of the tail, highly magnified ; k Central axis (/"and g, as be- fore). C, Another larva of the same, viewed from the side, and highly magnified, showing the superior and inferior fin-like prolongations (p p) of the " test," with ray- like striae (the other letters as before). D, Diagrammatic cross-section of the tail, showing the position of the fins (//), and the relations to one another of the central axis (h\ the intermediate cellular sheath (g), and the external structureless test (/). (After Reichert.) 2. The embryo of the Tunicates is not really bicavitary, and the nervous system is not developed in a chamber separate from and lying above the visceral cavity. (Donitz, Reichert.) 3. The nerve-ganglion of the Tunicates is placed upon the ventral sur- face of the larva, and does not, therefore, correspond with the cerebro- spinal nervous system of the Vertebrates. (Von Baer.) 4. The tail of the larval Ascidian is a purely provisional organ. 5. The axial structures of the tail (fig. 201, A, B, and D) consist of a 2 B 386 MANUAL OF ZOOLOGY. central homogeneous, structureless, and elastic rod, surrounded by a sheath of large nucleated cells, and the former is not primitively composed of cells. (Reichert.) 6. The perforated branchial sac is not a dilated pharynx, but appears to correspond rather with the branchial chamber of the Lamellibranchiata, From the above, therefore, the general conclusion may safely be drawn, that we are not at present in a position to give a dogmatic account as to even the most important phenomena in the development of the Tunicates. We may further conclude that the view that the development of the Tuni- cates is fundamentally identical with that of the Vertebrata is as yet not to be regarded as scientifically proved. Amongst the Salpians a species of alternation of genera- tions has been observed. A solitary Salpian produces long chains of embryos, which remain organically connected throughout their entire life. Each individual of these asso- ciated specimens produces solitary young, which are often very unlike their parents, and these again give rise to the aggre- gated forms.* The Tunicata are often spoken of as exhibiting three main types of structure, which give origin to as many sections, known respectively as the solitary, the social, and the compound forms. In the "solitary" Tunicaries (fig. 200, C), the indi- viduals, however produced, remain entirely distinct, or, if not so primitively, they become so. In the " social " Ascidians, the organism consists of a number of zooids, each like a soli- tary Ascidian, produced by gemmation and permanently con- nected together by a vascular canal, or " stolon," composed of a prolongation of the common tunic, through which the blood circulates. Finally, in the "compound" forms (fig. 200, B) the zooids become aggregated into a common mass, their tests being fused together, but there being no internal union. The Botrylli, which are familiar examples of the compound Tuni- cates, form semi-transparent masses, often of brilliant colours, attached to various submarine objects, and consisting of numerous zooids arranged in star-shaped groups. They are almost always "very small, soft, irritable, and contractile, changing their form with the slightest movement" (Stark). The atrial apertures of all the zooids of each stellate system open into a common central cloaca (fig. 200, B.) HOMOLOGIES OF THE TuNiCATA.— The general resemblance between * These cases have been, however, otherwise explained, and asserted to be an abnormal mode of sexual reproduction, the solitary and chained in- dividuals not being the offspring of each other, but being the older and younger progeny of the same parent. MOLLUSCA: TUNICATA. 387 a solitary Ascidian and a single polypide of a Polyzoon is extremely obvious ; each consisting of a double-walled sac, containing a freely sus- pended alimentary canal, with a distinct mouth and anus, and a nervous ganglion placed between the two. The chief feature in the Tunicata, as to the exact nature of which there is much difference of opinion, is the branchial or respiratory sac. By Professor Allman this is believed to be truly homologous with the tentacular crown of the Polyzoa, and the oral tentacles of the Tunicaries are believed to be something superadded, and not represented at all in the Polyzoa. By Professor Huxley, on the other hand, and by many other authorities, the branchial sac is looked upon as an enormously developed pharynx, and the oral tentacles are regarded as a rudimentary representative of the tentacular crown of the Polyzoa. Pro- bably the most correct view of the homologies of the Tunicata is taken by Rolleston, who regards the " branchial sac " as the homologue of the gills of the ordinary Bivalve Molluscs (Lamellibranchiatd), whilst the oral and atrial apertures are looked upon as corresponding to the respiratory aper- tures of these same animals. Upon the whole, the systematic position of the Tunicata must be looked upon as still unsettled ; though they are generally referred either to the Mollusca or to the "Worms." A few naturalists regard them either as a special group intermediate between " Verities" and Vertebrata, or as actually belonging to the latter sub-kingdom. DISTRIBUTION OF THE TUNICATA IN SPACE AND TIME.— The Tunicaries are exclusively marine in their distribution, and are principally littoral and shallow-water forms, though some are found at considerable depths, and many are pelagic in habit. The singular Salpidce have the branchial and atrial apertures placed at opposite ends of the body, and are found swimming in the open sea, often in immense shoals. The Appendicularia, with their permanent larval tails, are likewise oceanic, as is the cask- shaped Doliolum. Lastly, in Pyrosoma, we have a singular compound oceanic Tunicate, in which the numerous zooids form a tubular colony, which is propelled through the water by the united excurrent respiratory jets of its component members. Like the Salpians, it is brilliantly phosphorescent. ...On the other hand, the more typical Tunicates are found attached to all kinds of submarine objects, or (as in Pelonaia) embedded in mud. During the "Challenger expedition," some singular deep- sea Tunicates were obtained, and have been since described by Mr Moseley. One of these (Hypobythius) was found in the Pacific, at a depth. of nearly 3000 fathoms, attached to foreign objects by a peduncle. Its test is hyaline and trans- parent, and is strengthened by symmetrically disposed cartilagin- ous plates. Odacnemus, dredged at over 1000 fathoms, is also hyaline- and transparent, with a short stalk, but it possesses MANUAL OF ZOOLOGY. eight long radiating processes, which give it a stellate appear- ance; and the branchial sac is so flattened as to become nearly horizontal. No Tunicates are known with certainty to have been pre- served in the fossil condition, but the singular Silurian genus Pasceolus has been doubtfully referred to this class. CHAPTER XLIII. BRACHIOPODA. CLASS III. BRACHIOPODA (Palliobranchiata}. — The members of this class are defined by the possession of a body protected by a bivalve shell, which is lined by an expansion of the integ- ument, or " mantle" The mouth is furnished with two long cirriferous arms. The nervous system consists of a single gan- glion, placed in the re-entering angle between the gullet and the rectum, so that the intestine has a " neural flexure" The Brachiopoda are essentially very similar in structure to the Polyzoa, from which they are distinguished by the fact that they are never composite, and by the possession of a bivalve, calcareous, or sub-calcareous shell. They are commonly known as " Lamp-shells," and are all inhabitants of the sea. All the living forms, except Lingula pyramidata, are fixed to some solid object in their adult condition ; but there is good reason to believe that many of the fossil forms were unattached and free in their fully grown condition. From the presence of a bivalve shell, the Brachiopods have often been placed near the true bivalve Mollusca (the Lamellibranchiatd), but their organi- sation is very much inferior, and there are also sufficient dif- ferences in the shell to justify their separation. The two valves of the shell of any Brachiopod (figs. 202, 204) are articulated together by an apparatus ^f^teeth and sockets, or are kept in apposition by muscular action alone. One of the valves is always slightly, sometimes greatly, larger than the other, so that the shell is said to be " inequi valve." As regards the contained animal, the position of Jhe valves is anterior and posterior, so that they^r^lrTerefofe termed re- spectively the " ventral " and " dorsal " valves. In the ordi- nary bivalve Mollusca (Lamellibranchiata), on the other hand, MOLLUSCA: BRACHIOPODA. 389 the two valves of the shell are usually of the same size (equivalve), and "they are situated upon the sides of the animal; so that, instead of being dorsal and ventral, they are Fig. 202. — Rhynchonella suicata. A, Profile view. B, View ot the dorsal surface. C, View of the base, a Ventral valve ; b Dorsal valve ; / Base ; c Beak ; h Foramen. Lower Cretaceous. now termed "right" and "left" valves. The ventral valve in the shell of the Brachiopoda is usually the largest, and usually possesses a prominent curved beak. The beak (figs. 202, 204) is often perforated by a "foramen," or terminal aperture, through which there is transmitted a muscular peduncle, whereby the shell is attached to some foreign object. In some cases, however (as in Lingula, fig. 203), the peduncle simply passes between the apices of the valves, and there is no foramen ; whilst in others (as in Crania, fig. 203, D) the shell is merely attached by the substance of the ven- tral valve. The dorsal or smaller valve is always free, and is never perforated by a foramen. In intimate structure, the shell of most of the Brachiopoda consists " of flattened prisms, of considerable length, arranged parallel to one another with great regularity, and at a very acute angle — usually only about 10° or 12° — with the surfaces of the shell" (Carpenter). In most cases, also, the shell is perforated by a series of minute canals, which pass from one surface of the shell to the other, in a more or less vertical direction, usually widening as they approach the external surface. These canals give the shells a "punctated" structure, and in the living animal they contain caecal tubuli, or prolongations, from the mantle, which are con- sidered by Huxley as analogous to the vascular processes by which in many Ascidians the muscular tunic, or "mantle," is attached to the outer tunic, or "test." In some of the Brachiopoda (as in the Rhynchonellidce) the shell is "impunctate," or is devoid of this singular canal system. Though characteristically calcareous, the shell of the Brachiopoda may sometimes be largely composed of horny matter (as in Discind) ; or the carbonate of lime in the horny shell may be almost wholly replaced by phosphate (as in Lingicla). 390 MANUAL OF ZOOLOGY. The inner surface of the valves of the shell is lined by ex- pansions of the integument which secrete the shell, and are called the " lobes " of the " pallium," or " mantle." The diges- to a stone {alter uaviason; : p reauncie ; v ventral vaive ; a -uorsai vaive Crania Ignabergensis, attached by its ventral valve to a piece of coral (Chalk), tive organs and muscles occupy a small space near the beak of the shell, which is partitioned off by a membranous septum, which is perforated by the aperture of the mouth. The re- mainder of the cavity of the shell is almost filled by two long oral processes, which are termed the "arms," and from which the name of the class has been derived (fig. 204, D). These organs are lateral tubular prolongations of the margins of the mouth, usually of great length, closely coiled up, and fringed on one side with ciliated lateral processes, or "cirri." In many Brachiopods the arms are supported upon a more or less com- plicated internal calcareous framework or skeleton, which is sometimes called the " carriage-spring apparatus," and which in many extinct forms is coiled into a shelly spiral. The mouth conducts by an oesophagus into a distinct stomach, surrounded by 'a well-developed granular liver. The intestine has a "neural flexure," and "either ends blindly in MOLLUSCA : BRACHIOPODA. 391 the middle line, or else terminates in a distinct anus between the pallial lobes " (Huxley). Within the pallial lobes there is a remarkable system of Fig. 204. — Terebratula(Waldheimid)jlavescens. A, The shell viewed from behind, the beak, through which the muscular stalk of attachment passes. D, Longitudinal and vertical section of the animal, showing the spiral arms (a), the stomach (s), and the liver (ft). At /"is the opening in the beak, with the stalk of attachment (/) pass- ing through it. (After Davidson and Owen.) Some details have been omitted in figs. B, C, and D, for the sake of clearness. more or less branched excretory tubes, anastomosing with one another, and ending in caecal extremities. This, which has been termed by Huxley the "atrial system," communicates with the perivisceral cavity by means of two or four organs which are called " pseudo-hearts," and which were at one time supposed to be true hearts, but which are now known to be connected with reproduction. "Each pseudo-heart is divided into a narrow, elongated, external por- tion (the so-called ' ventricle '), which communicates, as Dr Hancock has proved, by a small apical aperture, with the pallial cavity ; and a broad, funnel-shaped, inner division (the so-called ' auricle ') communicating, on the one hand, by a constricted neck, with the so-called 'ventricle ;' and, on the other, by a wide patent mouth, with a chamber which occupies most 392 MANUAL OF ZOOLOGY. of the cavity of the body proper, and sends more or less branched diver- ticula into the pallial lobes " (Huxley). This system of the atrial canals has been looked upon as a rudimentary respiratory apparatus; but its function is more probably to act as an excretory organ, and it certainly serves also to convey away the reproductive elements, the organs for which are developed in various parts of its walls. By Rolleston the pseudo-hearts are looked upon as corresponding with the so-called " organ of Bojanus" of the Lamellibranchiata. The function of respiration is probably performed, mainly, if not entirely, by the cirriferous oral arms, as it appears chiefly to be by the homologous tentacular crown of the Polyzoa. A Fig. 205. — Development of Terelratulina septentrionalis (after Morse). A, Ciliated embryo. B, More advanced embryo, showing commencing segmentation and a rudi- mentary peduncle (/). C, D, E, F, Further stages of the same embryo. G, Advanced embryo, with a very long peduncle (/), and a circular oral crown of cirri (c). H, Interior of dorsal valve, showing the circular crown of cirri, and the intestine (/'). I, Another larva, at the same stage, having the valves opened, and viewed from one side. J, Part of a larva still further advanced, showing the now horse-shoe-shaped crown of cirri ; p Peduncle ; v Ventral valve of shell ; d Dorsal valve ; c Crown of oral ciiri ; i Intestine ; j Setae springing from the edge of the mantle ; / Loop of dorsal valve. (All the figures are highly magnified.) unilocular heart is present in some, but apparently not in all, of the Brachiopoda ; and the circulation seems to be mainly carried on through the interstices between the tissues. The nervous system consists of a principal ganglion of no great size, placed in the re-entering angle between the gullet and the rectum. In those Brachiopods in which the valves of the shell are united by a hinge, the nervous system attains a MOLLUSCA: BRACHIOPODA. 393 greater development, and consists of a gangliated oesophageal collar. The sexes in the Brachiopoda appear to be ordinarily distinct, but in some forms they are asserted to be united in the same individual. As regards the process of development in the class, we may take as a type Terebratulina septentrionalis, the metamorphoses of which have been most ably worked out by Professor Morse. In this form, the earliest embryo is a ciliated planula (fig. 205, A), which swims about actively, and soon (B) exhibits a division into three regions or segments, which rapidly become more conspicuous (C). Of these segments, the most inferior (/) becomes the future peduncle, and serves to attach the embryo to some foreign body (D). The middle segment then enlarges, and partially encloses the anterior seg- ment (E and F), the latter ultimately being withdrawn entirely within the former, which becomes converted into the shell-secreting pallial lobes. Next the arms begin to bud out of the sides of the mouth (G), forming at first a circular crown of cirri (c), which forcibly calls to mind the orbicular lophophore of the Gymnolsematous Polyzoa. The peduncle, at first long (as in Lingula\ becomes rapidly shorter (I), and the oral crown of tentacles becomes distinctly horse-shoe-shaped (J), thus strikingly resembling the similarly-shaped lophophore of the ' ' Hippocrepian " Polyzoa, The cir- rated " arms " of the adult are finally produced by the growth and devel- opment of the free end of the horse-shoe. AFFINITIES OF THE BRACHIOPODA. — Great differences of opinion exist at the present day as to the affinities and precise systematic position of the Brachiopoda ; but it is impossible to do more here than merely point out these differences. The relationship of the Brachiopods to the Polyzoa is admitted on all hands to be very close ; and we may regard the encrusting members of the latter class as being "communities of Brachiopods, the valves of which are continuous and soldered together, the flat valve form- ing the united floor, whilst the convex valve does not cover the ventral valve, but leaves an opening more or less ornamented for the extension of the lophophore " (A. Agassiz). Until recently, most naturalists have held that both these groups had strongly-marked relationships with the Lamellibranchiata, and many still adhere to this view. On the other hand, the view has been gaining ground, that these groups are to be regarded as comprising modified worms, and they are often placed in the immediate neighbourhood of the Annelida. The chief grounds for this view are to be found in the similarity of the development of the Polyzoans and Brachio- pods to that of the Annelides, as shewn by the elaborate researches of Morse and Kowalewsky. Apart from embryological likeness, one of the most striking links between the Brachiopods and the Annelides is the aberrant Lingula pyramidata — the genus Lingula being itself an aberrant type. This curious form (fig. 203, A), as described by Morse, differs from its congeners in not being fixed, but in living free in the sand. • Its peduncle is long and wormlike, hollow, and highly contractile, and its lower end is encased in a sand-tube, resembling that of a Tubicolous An- nelide. Whilst it must be freely admitted that the affinities between the Brachiopoda and the Annelides are much closer than any outward resem- blance between the two would lead us to expect, a sufficient case for the removal of the former from the Mollusca has hardly been made out, except in the view of those who place a supreme value upon embryological characters in classification. DIVISIONS OF THE BRACHIOPODA. — The Brachiopoda may be divided into the two orders of the Inarticulata (or Tretenterata) and the Artictilata (or Clistenterata). . 394 MANUAL OF ZOOLOGY. In the first of these orders (Inarticulatd), the valves of the shell are not united along the hinge-line, the mantle-lobes are completely free, and the intestine terminates in a distinct anus. In this division are included the three families of the Craniate, Disdnida:, and Lingnlida — all very ancient, and all represented at the present day by living forms— together with the Silurian family of the Trimerellida. In the second order (Articulata), the valves of the shell are united by teeth along the hinge-line, the lobes of the mantle are not completely free, and the intestine ends blindly. In this division are included the living families of the Terebratulida, Rhynchonellida, and the Thecidiida, and the extinct families of the Spiriferidtz, Pentameridtz, Strophomenidce, and Pro- ductidce. In the first two of these families the arms are supported upon a shelly loop, of variable shape and size (fig. 204, B) ; whilst in some of the extinct RhynchoneHidce and in the Spiriferidce, the arms were supported by large spirally-coiled calcareous lamellae (fig. 206). Fig. 206. — Spit if era hysterica, from the Carboniferous Limestone. The right-hand figure shows the interior of the dorsal valve, with the calcareous spires for the sup- port of the arms. DISTRIBUTION OF BRACHIOPODA IN SPACE. — All the known Brachiopods live in the sea, and though very local in their distribution, they may be said to have a very wide range. Though sometimes found .between tide - marks, and more commonly in comparatively shallow water, they are essentially deep-water forms, living most generally in depths of from 100 to 500 fathoms. A few forms have been found at depths of from 2000 to over 2500 fathoms. About 100 species of living Brachiopods are known. DISTRIBUTION OF BRACHIOPODA IN TIME. — The Brachio- poda are found from the Cambrian Rocks up to the present day, and present us with an example of a group which appears to be slowly dying out. Nearly four thousand extinct species have been described, and the class appears to have attained its maximum in the Silurian epoch, which is, for this reason, sometimes called the " Age of Brachiopods.'' Numerous genera and species are found also in both the Devonian and Carboniferous formations. In the Secondary Rocks Brachio- poda are still abundant, though less so than in the Palaeozoic period. In the Tertiary epoch a still further diminution takes place, and at the present day we are not acquainted with more MOLLUSCA: BRACHIOPODA. 395 than a hundred living forms. Of the families of Brachiopoda, the ProductidcCy Strophomenidce, and Spiriferidce are the more important extinct types. Of the genera, the most persistent is the genus Lingula, which commences in the Cambrian Rocks, and has maintained its place up to the present day, though it appears to be gradually dying out. According to Woodward : — " The hingeless genera attained their maximum in the Palaeozoic age, and only three now sur- vive (Lingula, Distinct, Crania) — the representatives of as many distinct families. Of the genera with articulated valves, those provided with spiral arms appeared first, and attained their maximum while the Terebratnlida were still few in number. The subdivision with calcareous spires disappeared with the Liassic period, whereas the genus Rhynchonella still exists. Lastly, the typical group, Terebratnlid' Visceral veins ; c Systemic heart ; d d Dilatations of branchial veins on entering the heart ; e e Branchial hearts ; b b Branchiae ; r r Renal organs. shadows the cranium of the Vertebrata ; this also sends out prolongations which strengthen and defend the eye, and the auditory chambers are excavated in its substance. The sexes in all the Cephalopoda are in different individuals, the males and females generally being more or less unlike externally. In this order the ducts of the generative organs open into the pallial chamber, and each individual, besides the essential organs of reproduction (testis or ovary), generally possesses an accessory gland ; that of the female secreting a viscid material which unites the eggs together, whilst that of the male coats the spermatozoa, and aggregates them into peculiar worm-like filaments, from six to eight lines in length, termed " spermatophores," or the "moving filaments of Need- ham." The spermatophore is filled with spermatozoa, and possesses the power of expanding when moistened, rupturing, and expelling the contained spermatozoa with considerable MOLLUSCA : CEPHALOPODA. 423 force. During the congress of the sexes the male transfers the spermatophores to the pallial chamber of the female, true intromission not being possible, but the mode in which this fig. 227. — i. Octopus carena (male), showing cyst in place of the third arm. 2. Ven- tral side of an individual, more developed, with the hectocotylus (a). (After Wood- ward.) transference is effected differs in different cases, and is not universally known. In the males of many of the Cuttle-fishes, one /-^/rw/Ww/cVi^ll FiS- 23°-— Argonauta argo, the "Paper Nau- tnm single-cnamtjerea sneii, jilus/, female. The animal is represented in in form Symmetrical and its shell, but the webbed dorsal arms are se- i , j i • i • parated from the shell, which they ordinarily involuted, Which IS Secret- embrace. ed by the webbed extrem- ities of the dorsal arms, but is not attached in any way to the body of the animal. It sits in its shell with the funnel turned towards the keel, and the webbed arms applied to the shell. The male Argonaut is much smaller than the female (less than an inch in length), and is not protected by any shell. The third left arm of the male (fig. 228) is developed in a cyst, and ultimately becomes a "hectocotylus," and is deposited by the male in the pallial chamber of the female. In the Octopodidce. (or Poulpes) there are eight arms, all similar to one another, and united at the base by a web. There is an interhal rudimentary shell, represented by two short styles encysted in the substance of the mantle (Owen). The body is seldom provided with lateral fins. The third right arm of the male is primarily developed in a cyst, and ultimately becomes " hectocotylised." 428 MANUAL OF ZOOLOGY. SECTION B. DECAPODA. — The Cephalopods of this section have eight arms and two additional "tentacles," which are much longer than the true arms, are retractile, and have ex- panded, club-shaped extremities (fig. 231). The suckers are D Fig. 231. — A, The common Calamary (Loligo vulgaris), reduced in size : a One of the ordinary arms ; / One of the longer arms or tentacles." B, Skeleton or " pen" of the same, one-fourth natural size (after Woodward). C, Side view of one of the suckers, showing the horny hooks surrounding the margin. D, View of the head from in front, showing the bases of the arms (a) and tentacles (t), the mouth («/), and the funnel (./). pedunculated ; the body is always provided with lateral fins, and the shell is always internal. This section comprises the three living families of the MOLLUSCA: CEPHALOPODA. 429 Teuthida, Sepiadce, and the Spiriilida, and the extinct family of the Beltmnitida. The family of the Teuthidcz comprises the Calamaries or Squids (fig. 231), characterised by the possession of an elon- gated body with lateral fins. The shell (fig. 229, b) is internal and horny, consisting of a median shaft and of two lateral wings; it is termed the "gladius" or "pen," and in old speci- mens several may be found lodged in the mantle, one behind the other. In the common Calamary (Loligo) the fourth left arm of the male is metamorphosed towards its extremity to subserve reproduction. In the family of the Sepiadce the internal shell (fig. 229, a) is calcareous (" cuttle-bone " or " sepiostaire "), and is in the form of a broad plate, having an imperfectly-chambered apex. The broad laminated plate is extremely light and spongy, and the chambered apex is called the "mucro." In the living members of the family the body is provided with long lateral fins, sometimes as long and as wide as the body itself. In the singular family of the Spirulida the internal skeleton (fig. 229, c) is in the form of a nacreous, discoidal shell, the whorls of which are not in contact with one another, and which is divided into a series of chambers by means of partitions or septa which are pierced by a ventral tube or "siphuncle." The body is provided with minute lateral fins, and the arms have six rows of small suckers. The shell of the Spirula — commonly known as the " post-horn " — is similar in structure to the shell of the Nautilus, but it is lodged in the posterior part of the body of the animal (fig. 229), and is therefore inter- nal, whereas the shell of the latter is external It really corre- sponds to the " phragmacone " of the Belemnite. Though the shell occurs in enormous numbers in certain localities, a single perfect specimen of the animal is all that has been hitherto obtained. In its internal anatomy, Spirula is a true Dibran- chiate. It has the peculiar feature that the hinder end of the body forms a kind of suctorial disc, apparently employed to moor the animal to foreign bodies. The beaks are not calci- fied. The retractor muscles of the funnel spring from the inner surface of the last chamber of the shell (as in Nautilus} ; and this chamber also lodges the hinder termination of the liver (Owen). In the extinct family of the Belemnitida, our knowledge is chiefly confined to the hard parts. Certain specimens how- ever, have been discovered, which show that the Belemnite had essentially the structure of a Cuttle-fish, such as the recent Calamary. The body was provided with lateral fins ; the arms 430 MANUAL OF ZOOLOGY. were eight, furnished with horny hooks, with two " tentacles ; " and probably the mouth was provided with horny mandibles. An ink-bag was present. The inter- nal skeleton of a Belemnite (fig. 232) consists of a chambered cone — the " phragmacone " — the septa of which are pierced with a marginal tube or " siphuncle." In the last chamber of the phragmacone is contained the ink-bag, often in a well-preserved con- dition. Anteriorly the phragmacone is continued into a horny lamina or " pen " (the " pro-ostracum " of Hux- ley), and posteriorly it is lodged in a conical sheath or " alveolus," which is excavated in the substance of a nearly cylindrical, fibrous body, the "guard" (fig. 232, g) which projects backwards for a longer or shorter dis- tance, and is the part most usually found in a fossil condition. ORDER II. TETRABRANCHIATA. — The members of this order of the Cephalopoda are characterised by be- ing creeping animals, protected by an external, many -chambered shell, the septa between the chambers of which are perforated by a membranous or calcareous tube termed the " siphuncle" The arms are numerous and are de- void of suckers ; the branchice are four in number, two on each side of the body ; the funnel does not form a com- plete tube ; and there is no ink-bag. Though abundantly represented by many and varied extinct forms, the only living member of the Tetra- Fig. 232.— Diagram of Belemnite branchiata is the Pearly Nautilus, (after Professor Phillips). r W1-,jrh V,™ hppll InnP" known bv its Horny pen or "pro-ostracum;" WHICH Ildb UCCll lOIlg KI1OYV11 uy lib p Chambered "phragmacone" beautiful chambered shell, but the ?&<£%>&?* "alveolus'" soft parts of which were first describ- ed from a perfect specimen which was examined by Professor Owen.* * The animal of the Pearly Nautilus is still one of the greatest rarities in museums. Its anatomy was originally described from a female specimen MOLLUSCA: CEPHALOPODA. 431 The soft structures in the Pearly Nautilus may be divided into a posterior, soft, membranous mass (metasoma), contain- ing the viscera, and an anterior muscular division, comprising the head (prosoma) ; the whole being contained in the capa- cious outermost chamber (the body-chamber) of the shell, from which the head can be protruded at will. The shell itself (fig. 233) is involuted and many-chambered, the animal being con- Fig. 233. — Pearly Nautilus (Nautilius pompilius). a Mantle ; b Its dorsal fold ; c Hood ; o Eye ; t Tentacles ; /Funnel. tained successively in each chamber, and retiring from it as its size becomes sufficiently great to necessitate the acquisition of more room. Each chamber, as the animal retires from it, is walled off by a curved, nacreous septum ; the communication between the chambers being still kept up by a membranous tube or siphuncle, which opens at one extremity into the peri- cardium, and is continued through the entire length of the shell. The position of the siphuncle is in the centre of each septum, but the siphuncle simply passes through the chambers, without opening into them. Posteriorly the mantle of the Nautilus is very thin, but it is much thicker in front, and forms a thick fold or collar sur- rounding the head and its appendages. From the sides of the head spring a great number of muscular prehensile processes or "arms," which are annulated, but are not provided with by Prof. Owen in 1832. Since that time examples have been described by Van der Hoeven, Vrolik, Valenciennes, Macdonald, &c. 432 MANUAL OF ZOOLOGY. cups or suckers. Four of the arms of the male are specially modified to form a peculiar organ termed the " spadix," which is connected with reproduction, and corresponds with the " hectocotylised " arm of the male Cuttle-fishes. In the centre of the head is the mouth, surrounded by a circular fleshy lip, external to which is a series of labial processes. The mouth opens into a buccal cavity, armed with two horny mandibles, partially calcified towards their extremities, and shaped like the beak of a parrot, except that the under mandible is the longest. There is also a " tongue," which is fleshy and sen- tient in front, but is armed with recurved teeth behind. The gullet opens into a large crop, which in turn conducts to a gizzard, and the intestine terminates at the base of the fun- nel. On each side of the crop is a well-developed liver. The heart is contained in a large cavity, divided into sev- eral chambers, and termed the "pericardium" (Owen). The respiratory organs are in the form of four pyramidal branchiae, two on each side. The chief masses of the nervous system are the cerebral and infra-cesophageal ganglia, which are partially protected by a cartilaginous plate, which is to be regarded as a rudimentary cranium, and which sends out processes for the attachment of muscles. The organs of sense are two large eyes, attached by short stalks to the sides of the head, two spheroidal ear- capsules, and two hollow plicated subocular processes, be- lieved to be possibly olfactory in their function. The reproductive organs of the female consist of an ovary, oviduct, and accessory nidamental gland. There is no ink-bag, and the funnel does not form a com- plete tube, but consists of two muscular lobes, which are simply in apposition. It is the organ by which swimming is effected, the animal being propelled through the water by means of the reaction produced by the successive jets emitted from the funnel. The function of the chambers of the shell appears to be that of reducing the specific gravity of the animal to near that of the surrounding water, since they are most probably filled with some gas secreted by the animal. Good authorities, however, believe that the chambers of the shell are filled with water. The function of the siphuncle is unknown, except in so far as it doubtless serves to maintain the vitality of the shell. SHELL OF THE TETRABRANCHIATA.— The shells of all the Tetrabranchiata agree in the following points : — 1. The shell is external. 2. The shell is divided into a series of chambers by plates MOLLUSCA : CEPHALOPODA. 433 or "septa," the edges of which, where they appear on the surface of the shell, are termed the "sutures." 3. The outermost chamber of the shell is the largest, and is the one inhabited by the animal. 4. The various chambers of the shell are traversed by a tube, termed the "siphuncle." Agreeing in all these fundamental points of structure, two very distinct types of shell may be distinguished as character- istic of the two families Nautilidce and AmmonitidcE^ into which the order Tetrabranchiata is divided. In the family Nautilidcz (fig. 234, dfand e), the "septa" of Fig. 234. — Diagram to illustrate the position of the siphuncle and the form of the septa in various Tetrabranchiate Cephalopoda. The upper row of figures represents transverse sections of the shells, the lower row represents the edges of the septa. a a A mmonite or Baculite ', b b Ceratite ; c c Goniatite ; d d Clymenia ; e e Nau- tiltts or Orthoceras. the shell are simple, curved, or slightly lobed ; the " sutures " are more or less completely plain ; and the " siphuncle " is central, sub-central, or internal (t.e., on the concave side of the curved shells). In the family Ammonitida (fig. 234, a, b, and c\ on the other hand, the septa are folded and complex; the sutures are angulated, zigzag, lobed, or foliaceous ; and the siphuncle is external (/.&, on the convex side of the curved shells).* In both these great types of shell, a series of representative forms exists, resembling each other in the manner in which the * In the Ammonitida, the initial chamber ("ovisac") of the shell is an egg-shaped chamber isolated from the first air-chamber by a distinct con- striction, whereas no such arrangement obtains in the Nautilidce. Such a structure, however, is found in Spirula, Belemnites, and other allied forms ; and it has recently been concluded (Munier-Chalmas) that the Amman- itidce are properly Dibranchiate, their shell being an internal skeleton or phragmacone, similar to the shell of the Spirula. 2 E 434 MANUAL OF ZOOLOGY. shell is folded or coiled, but differing in their fundamental structure. All these different forms may be looked upon as produced by the modification of a greatly elongated cone, the structure of which may be in conformity with the type either of the Nautilidcz or of the Ammonitidce. The following table (after Woodward) exhibits the representative forms in the two families : — Nautilidce. Ammonitidce. Shell straight, Orthoceras, . Baculites. „ bent on itself, . . . Ascoceras, . . Ptychoceras. curved, Cyrtoceras, . Toxoceras. spiral, Trochoceras, . Turrilites. discoidal, Gyroceras, . . Crioceras. discoidal and produced, Lituites, . . . Ancyloceras. involute, Nautilus, . . Ammonites. After the Nautilus itself, the most important form of the Nautilidce is the Orthoceras (fig. 235). In structure this was Fig. 235. — Orthoceras explorator, Billings, i. Side view of a fragment, showing the septa. 2. Transverse section of the same, showing (s) the siphuncle. doubtless essentially identical with the Nautilus, but the shell, instead of being coiled into a spiral lying in one plane, was ex- tended in a straight, or nearly straight, line. Orthoceratites of more than six feet in length have been discovered, but in all, the body-chamber, in which the animal was lodged, appears to have been comparatively small. The siphuncle is usually very complex in structure, and was calcareous throughout its entire length. The structure of the shell in the Ammonitidce is exactly that of the Pearly Nautilus, consisting of an outer porcellanous and an inner nacreous layer. The body-chamber was rather elongated than laterally expanded or dilated. The simplest form of the Ammonitidce is the Baculite, in which the shell is straight, like that of an Orthoceras, while the septa have the characters of those of an Ammonite, and the siphuncle is ex- ternal. In the Turrilite (fig. 237) the structure of the shell is the same, but it is coiled into a turreted spiral. In the Am- MOLLUSCA : CEPHALOPODA. 435 monite itself (fig. 236), the shell is discoidal and involuted, cor- responding (in form) to the shell of the Nautilus ; the body- chamber was of comparatively large size, and had its aperture Fig. 236. — Ammonites bifrons, from the Lias. closed, in some species at any rate, by an operculum. The shell sometimes attained a gigantic size, and several hundred species of the genus have been described. In Crioceras (fig. 237) the shell was a flat spiral, like that of the Ammonites, but the whorls are not in contact. In Toxoceras the shell is shaped like a bow. In Ancyloceras (fig. 237) the shell is at first discoidal, with separate whorls, then produced into a straight line, and finally bent forwards into a hook. DISTRIBUTION OF THE CEPHALOPODA IN SPACE. — All the Cephalopoda, without exception, are marine. Some of the Cuttle-fishes (such as the Octopi and Septa) live in the vicinity of land, especially frequenting rocky bottoms; while others (such as Argonauta, Spirula, Sepiola, Onychotetithis, &c.) live in the open sea, often far from land, swimming at or near the surface. Some of the Cuttle-fishes attain a gigantic size ; but all these colossal forms of the class appear to belong to the Decapoda. The Architeuthis of the North Atlantic is certainly known to attain a length of 15 feet or upwards to the body and head, and from 30 to 40 feet or more in the long tentacles. The Pearly Nautilus is confined to the Pacific and Indian Oceans, and appears to be an inhabitant of shallow water. DISTRIBUTION OF CEPHALOPODA IN TIME. — The Cephalo- pods are largely represented in all the primary groups of stratified rocks from the Upper Cambrian up to the present day. Of the two orders of Cephalopoda, the Tetrabranchiata 436 MANUAL OF ZOOLOGY. is tKe oldest, attaining its maximum in the Palaeozoic period, decreasing in the Mesozoic and Kainozoic epochs, and being represented at the present day by the single form Nautilus Fig. 237. — Shells of Secondary Cephalopods. i. Ancyloceras Matheronianus ; 2. Scaphites (zqualis; 3. Crioceras Duvalii; 4. Hamites attenuatus ; 5. Turrilites catenatus, pompilius, together with some varieties or nearly allied species. Of the sections of this order, the Nautilida proper and the Orthoceratida are pre-eminently Palaeozoic, and the Ammonitidce are not only pre-eminently, but are almost ex- clusively, Secondary. Of the abundance of the two former families in the Silurian seas some idea may be obtained when it is mentioned that over a thousand species have been de- scribed by M. Barrande from the Silurian basin of Bohemia alone. The Nautilidtz proper have gradually decreased in numbers from the Palaeozoic through the Secondary and Ter- tiary periods to the present day. The Orthoceratidce. died out much sooner, being exclusively Palaeozoic, with the exception of the genera Orthoceras itself and Cyrtoceras, which survived into the commencement of the Secondary period, finally dying out in the Trias. The second family of the Tetrabranchiata — viz., the Ammo- nitidcz — is almost exclusively Secondary, being very largely represented by numerous species of the genera Ammonites, Ceratites, Baculites, Turrilites, &c. The principal Palaeozoic genera are Goniatites and Bactrites, of which the former is found from the Upper Silurian to the Trias, whilst the latter is MOLLUSCA: LITERATURE. 437 a Devonian form ; but true Ammonites have been found in strata of Carboniferous age in India (Dr Waagen). The genus Ceratites is characteristically Triassic, but it is said to occur in the Devonian rocks. All the remaining genera are exclusively Secondary, the genera BaculUes, Turrilites, Hamites, and Pty- choceras being confined to the Cretaceous period. The only genus which passes up into the Tertiary is Ammonites, which occurs in beds believed to be of this age in America. Of the Dibranchiate Cephalopoda the record is less perfect, as they have few structures which are capable of preservation. They attain their maximum, as fossils, shortly after their first appearance in the Secondary rocks, where they are represented by the large and important family of the Beltmnitida. Some of the Teuthida and Sepiadcz are found both in the Secondary and in the Tertiary rocks, and two species of Argonaut have been discovered in the later Tertiaries. No example of a Dibranchiate Cephalopod is known from the Palaeozoic de- posits, and the order attains its maximum at the present day. LITERATURE. GENERAL. i. "Manual of the Mollusca." S. P. "Woodward. 3d ed., with " Ap- pendix of Recent and Fossil Conchological Discoveries," by Ralph Tate. 1875. ' Handbuch der Conchyliologie." Philippi. 1853. 'Malacozoa." Bronn and Keferstein. In 'Bronn's Klassen und Ordnungen des Thier-Reichs.' 1862-66. ' Genera of Recent Mollusca." H. and A. Adams. 1853-58. 'Catalogue of the Mollusca in the British Museum." J. E. Gray. ' Figures of Molluscous Animals." Mrs Gray. 1874. ' Manuel de Conchyliologie." Chenu. 1859. ' Illustrations Conchyliologiques." Chenu. (Begun in 1843. ) ' Thesaurus Conchyliorum." G. B. Sowerby. (Begun in 1842.) ' Conchologia Iconica." Lovell Reeve. (Begun in 1841.) ' Treatise on Malacology." Swainson. 1834. ' Conchology." Swainson. 1840. ' Memoires pour servir a 1'histoire et 1'anatomie des Mollusques. " Cuvier. 1816. ' History of British Mollusca." Forbes and Hanley. 19- 20. 21. 22. 23- 24. ' Manual of British Conchology." Gwyn Jeffreys. 1862-69. ' Traite elementaire de Conchyliologie. " Deshayes. 1839-59. ' American Conchology." Say. 1830-32. ' Synopsis of the Marine Invertebrates of Grand Manan." Stimpson. 1851. ' Invertebrata of Vineyard Sound." Smith and Verrill. 1874. ' Mineral Conchology of Great Britain." J. Sowerby. 1812-30. 'Traite de Paleontologie." Pictet. 1853-57. ' Cours elementaire de Paleontologie." D'Orbigny. 1849-52. 'Materiaux pour la Paleontologie Suisse." Pictet. (Begun in 1834.) 'Catalogue of British Fossils." Morris. 1854. 43 8 MANUAL OF ZOOLOGY. POLYZOA. 25. "Catalogue of the Marine Polyzoa in the Collection of the British Museum." Busk. 1852 and 1875. 26. " Monograph of the Fossil Polyzoa of the Crag." Busk. ' Paloeon- tographical Society.' 1859. 27. " Monograph of the Fresh-water Polyzoa." Allman. ' Ray Society.' 1856. 28. "Bryozoa." Ehrenberg. * Symbolse physicee. ' 1831. 29. " History of British Zoophytes." Johnston. 2cl ed. 1847. 30. " Popular History of British Zoophytes." Landesborough. 1852. 31. " Die Pflanzenthiere in Abbildungen nebst Beschreibungen." Esper. 1788-1830. 32. " Histoire des Coralligenes flexibles." Lamouroux. 1816. 33. "Histoire naturelle du literal de France." Audouin and Milne- Edwards. 1831-34. 34. "Manual of Marine Zoology." Gosse. 1855. 35. "Fauna of Cornwall." Couch. 1852. 36. "Catalogue of the Zoophytes of Northumberland and Durham." Joshua Alder. 'Trans. Tyneside Naturalists' Field Club.' 1857. 37. "Minute Structure of some of the higher forms of Polypes." A. Farre. ' Phil. Trans.' 1837-38. 38. "On Rhabdopleura, &c." Allman. 'Quart. Journ. Microscopical Science.' 1869. 39. "Om Hafs - bryozoernas utveckling och Fett - Kroppar. " Smitt. ' Ofversigt af K. Vetenskaps-Akad. Forhandl.' 1865. 40. " Beitrage zur Anatomic und Entwickelungsgeschichte der Phylacto- lamen Stiss wasserbryozoen. " Nitsche. ' Archiv fiir Anat. und Phys.' 1 868T 41. "Beitrage zur Kenntniss der Bryozoen. " Nitsche. ' Siebold und Kolliker's Zeitschrift." 1871. 42. " Petrefacta Germanise. " Goldfuss. 1826-33. 43. " Paleontologie Fran£aise " (' Terrains Cretaces et Jurassiques '). D'Orbigny. 1840-53. 44. " Polypiarien des Wiener Tertiar Beckens." Reuss. 1847. 45. " Observations on Polyzoa : Sub-order Phylactolaemata." Alpheus Hyatt. ' Proc. Essex Inst. ' 1865. 46. "Recent Progress in our Knowledge of the Structure and Develop- ment of the Phylactoloematous Polyzoa. " Allman. 'Journ. Linn. Soc.,' vol. xiv. 1879. 47. " On the Relations of Rhabdopleura. " Allman. 'Journ. Linn. Soc.,' vol. xiv. 1879. TUNICATA. 48. Article "Tunicata." T. Rupert Jones. ' Todd's Cyclopaedia of Anatomy and Physiology.' 1848. 49. "Memoire sur les Ascidies et leur Anatomic." Cuvier. 'Mem. du Museum.' 1815. 50. "Memoire sur les Animaux sans Vertebres (Recherches Anatomiques sur les Ascidies Composees," &c. ) Savigny. 1816. 51. " Anatomisk - physiologiske Undersogelser over Salperne." Esch- richt. 'Roy. Danish Transactions.' 1841. 52. "Observations sur le Generation et le Developpment des Biphores. " Krohn. ' Annales des Science Naturelles.' 1846. MOLLUSCA : LITERATURE. 439 53. " Recherches sur I'Embryogenie, 1' Anatomic, et la physiologic des Ascidies simples. " Van Beneden. ' Mem. de 1' Acad. Roy. de Belgique.' 1847. 54. "Observations sur les Ascidies Composees des Cotes de la Manche." Milne-Edwards. 1844. 55. "Anatomy and Physiology of Salpa and Pyrosoma." Huxley. ' Phil. Trans.' 1851. 56. " Observations on Appendicularia and Doliolum." Huxley. 'Phil. Trans.' 1851. 57. "Die Entwickelungsgeschichte der einfachen Ascidien." Kowa- lewsky. 'Mem. de 1'Acad. Imp. des Sciences de St Petersbourg.' 1866. 58. "Die Stammverwandschaft zwischen Ascidien und Wirbelthiere." Kupffer. 'Schultze's Archiv fur Mic. Anat.' 1870. 59. "Zur Entwickelung der einfachen Ascidien." Kupffer. ' Schultze's Archiv,' 1872. 60. "De animalibus quibusdam e classe Vermium." Chamisso. 1819. 61. " Etude critique des travaux d'embryogenie relatifs a la parente des Vertebres et des Tuniciers." Giard. ' Lacaze-Duthier's Archives de Zooiogie.' 1872. 62. " Entwickelt sich die Larve der einfachen Ascidien in der ersten Zeit nach dem Typus der Wirbelthiere?" Von Baer. ' Mem. de 1* Acad. Imp. des Sciences de St Petersbourg.' 1873. 63. "Zur Anatomic des Schwanzes der Ascidien- Larven (Botryllus viola- ceus)." H. Reichert. 'Abhandl. d. K. Akad. der Wiss. Berlin.' 1875- 64. "Ascidies simples des cotes de France." Lacaze-Duthiers. 'Ar- chives Zool. Exper.' 1874.. 65. "On Two new Forms of Deep-sea Ascidians." Moseley. 'Trans. Linn. Sec.' Ser. 2, vol. i. 1877. BRACHIOPODA. 66. " On the Anatomy of the Brachiopoda." Owen. 'Trans. Zool. Soc.' 67. "On the Organisation of the Brachiopoda." Hancock. 'Phil. Trans.' 1858. 68. "Anatomy of Brachiopoda." Gratiolet. 'Comptes Rend.,' 1853; and 'Journ. de Conchyliologie,' 1857, 1859, and 1860. 69. " Monograph of the British Fossil Brachiopoda." Thomas Davidson. ' Pabeontographical Society.' 1851-71. (The first part contains a Memoir by Prof. Owen on the Anatomy of Terebratula, and one by Dr W. B. Carpenter, on the Intimate Structure of the Shell of the Irachiopoda.) 70. Article "Brachiopoda." Davidson. 'Encyclopaedia Britannica,' 9th ed. 71. " Qu'est ce qu'un Brachiopode ? " Davidson. 'Ann. de la Soc. Malscologique de Belg.' 1876. (Translated under the name of " What is a Brachiopod?" ' Geol. Mag.' 1877.) 72. "On -he Trimerellidae." Davidson and King. 'Quart. Journ. Geol Soc.' 1874. 73. "On the Microscopical Structure of Shells." Carpenter. 'Rep. Brit Assoc.' 1844-47. 74. " On the Systematic Position of the Brachiopoda." Morse. ' Proc. Bos:. Soc. Nat. Hist.' 1873. 44° MANUAL OF ZOOLOGY. 75. "Embryology of Terebratulina." Morse. 'Mem. Bost. Soc. Nat. Hist.' 1873. 76. "Early Stages of Terebratulina septentrionalis. " Morse. 'Mem. Bost. Soc. Nat. Hist.,' 1869; and 'Ann. and Mag. Nat. Hist.,' 1871. 77. " Entwickelung der Brachiopoden." Kowalewsky. 'Mem. de 1'Acad. Imp. des Sci. de St Petersbourg. ' 1874. LAMELLIBRANCHIATA. 78. Article "Conchifera." Deshayes. ' Todd's Cyclopaedia of Anatomy and Physiology.' 1835. 79. "The Pelecypoda of the Cretaceous Rocks of India." Ferdinand Stoliczka. ' Palaeontologia Indica. ' 1875. 80. ' ' Anatomy of Anodonta cygnea. " Rolleston. ' Forms of Animal Life.' 1870. 81. "Observations on the Genus Unio." Lea. 1829-75. 82. " Synopsis of the Family Unionidse." Lea. 4th ed. 1870. 83. "Structure and Affinities of the Hippuritidae. " S. P. Woodward. 'Quart. Journ. Geol. Soc.' 1854. 84. "Bidrag till Kannedomen om utvecklingen af Mollusca Acephala." Loven. 'Kongl. Vetenskaps-Akad. Handl. Stockholm.' 1848-50. (Embryology of Lamellibranchs). 85. " Entwickelung von Cyclas." O.Schmidt. ' Miiller's Archiv/ 1874. GASTEROPODA. 86. " Voyage de 1'Astrolabe. Zoologie." Quoy et Gainard. 1832-35. 87. " Voyage de la Bonite. Zoologie." Eydoux et Souleyet. 1851-52. 88. "On the Morphology of the Cephalous Mollusca." &c. Huxley. 'Phil. Trans.' 1853. 89. ' ' Das Gebiss der Schnecken zur Begriindung einer natiirlichen Classi- fication untersucht." Troschel. 1856-76. 90. ' ' Monograph of the British Nudibranchiate Mollusc*. " Alder and Hancock. ' Ray Society. ' 1845-55. 91. " Monographia pneumonopomorum viventium." Ffeiffer. 1852. Supplement. 1858. 92. "Cretaceous Gasteropoda of Southern India." Ferdinand Stoliczka. ' Palseontologia Indica.' 1868. 93. ' ' Manual of the Land and Fresh-water Shells of Great Britain. *' J. E. Gray. 1857. 94. "Terrestrial Air-breathing Mollusks of the United States." Binney. 1851-57- 95. "Observations on the Development of the Pond-Snail." Ray Lan- kester. 'Quart. Journ. Microscop. Science.' 1874. 96. " Beitrage zur Entwickelungsgeschichte der Prosobranchiaten. " Sa- lensky. « Siebold und Kolliker's Zeitschrift. ' 1872. ~ ." . •', PTEROPODA. 97. " Untersuchungen liber Pteropoden und Heteropoden. " Gegenbaur. 1855- 98. "On the Morphology of the Cephalous Mollusca." (Ptff'opoda and Heteropoda). Huxley. ' Phil. Trans. ' 1853. 99. Article "Pteropoda." T. Rymer Jones. 'Todd's Cydopaedia of Anat. and Phys.' 1847. MOLLUSCA: LITERATURE. 441 100. " Anatomische Untersuchungen liber die Clione borealis. " Eschricht. 1848. 101 . " Histoire naturelle des Mollusques Pteropodes. " Rang and Souleyet. 1852. 102. " Entwickelungsgeschichte der Pteropoden und Heteropoden. " Krohn. ' Mailer's Archiv,' 1856-57. 103. "Etudes sur le Developpment des Mollusques." Fol. 'Archives Zool.' 1875. 104. "Pteropodes Siluriens de la Boheme." Barrande. 1867. CEPHALOPODA. 105. "Lecons de 1'Anatomie Comparee." Cuvier. 1800. 106. "Memoire sur les Cephalopodes et sur leur Anatomic." Cuvier. 1817. 107. Article "Cephalopoda." Owen. * Todd's Cyclopaedia of Anat. and Phys.' 1836. 1 08. "Histoire naturelle des Cephalopodes acetabuliferes, vivants et fossiles." Ferussac and D'Orbigny. 1835-48. 109. "Memoire sur 1'Argonauta. " Van Beneden. ' Nouv. Mem. de 1'Acad. Roy. de Bruxelles." 1838. no. "The Animal of Spirula." J. E. Gray. 'Ann. and Mag. Nat. Hist.' 1845. in. "Zoology of the Voyage of H. M.S. Samarang." Owen. 1848. 112. " Supplementary Observations on the Anatomy of Spirula australis, Lamarck." Owen. 'Ann. Nat. Hist.' Ser. 5, vol. iii. 1879. 113. "Observations on the Hectocotyli of Tremoctopus violaceus and Argonauta argo." Kolliker. ' Trans. Linn. Soc. ' 1846. 114. " Entwickelungsgeschichte der Cephalopoden. " Kolliker. 1844. 115. " Development of the Cephalopoda. " Ray Lankester. 'Ann. and Mag. Nat. Hist.' 1873; and 'Quart. Journ. Microscop. Sci.,' 1875- 116. "Belemnites from the Oxford Clay." Owen. 'Phil. Trans. 1844. 117. "Structure of Belemnites." Huxley. 'Mem. Geol. Survey.' 1864. 1 1 8. "Monograph of the Belemnltidas. " Phillips. ' Palaeontographical Society.' 1865-69. 119. " Memoir on the Pearly Nautilus." Owen. 1822. 1 20. " Bijdrage tot de outleedkundige Kennis aangaende Nautilus pom- pilius," &c. Van der Hoeven. 1856. 121. " Embryology of the Tetrabranchiates." Hyatt. ' Bulletins of the Museum of Com p. Zoology.' 1872. 122. "Cephalopodes: Etudes Generales." Barrande. 1877. VERTEBRATE ANIMALS. CHAPTER L. GENERAL CHARACTERS AND DIVISIONS OF THE VERTEBRATA. THE five sub-kingdoms which \ve have previously considered — viz., the Protozoa, Ccelenterata, JEchinodermata, Annulosa, and Mollusca — were grouped together by the French naturalist La- marck to form one great division, which he termed Invertebrata, the remaining members of the animal kingdom constituting the division Vertebrate. The division Vertebrata, though including only a single sub-kingdom, is so compact and well marked a division, and its distinctive characters are so numerous and so important, that this mode of looking at the animal kingdom is, at any rate, a very convenient one. The sub-kingdom Vertebrata may be shortly defined as com- prising animals in which the body is composed of a number of definite segments arranged along a longitudinal axis ; the nervous system is in its main masses dorsal, and the neural and hcemal regions of the body are always completely shut off from one another by a partition ; the limbs are never more than four in number, and are always turned away from the neural aspect of the body ; mostly there is the bony axis known as the " spine" or " vertebral column" and in all the structure known as the " noto- chord" is present — in the embryo, at any rate. These charac- ters distinguish the Vertebrata, as a whole, from the Inverte- brata ; but it is necessary to define these broad differences more minutely, and to consider others which are of little less importance. 444 MANUAL OF ZOOLOGY. One of the most obvious, as it is one of the most funda- mental, of the distinctive characters of Vertebrates, is to be found in the shutting off of the main masses of the nervous system from the general cavity of the body. In all Inverte- brate animals, without exception, the body (fig. 238, A) may be regarded as a single tube, enclosing all the viscera; and Fig. 238. — A, Transverse section of the body of one of the higher luvertebrata : a Body-wall ; b Alimentary canal ; c Haemal system ; n Nervous system. B, Trans- verse section of the body of a Vertebrate animal : a Body-wall ; b Alimentary canal ; c Haemal system ; n Sympathetic system of nerves ; n' Cerebro-spinal system of nerves ; ch Notochord. consequently, in this case, the nervous system is contained within the general cavity of the body, and is not in any way shut off from the alimentary canal. The transverse section, however, of a Vertebrate animal exhibits two tubes (fig. 238, B), one of which contains the great masses of the nervous system — that is, the cerebro-spinal axis, or brain and spinal cord — whilst the other contains the alimentary canal and the chief circulatory organs, together with certain portions of the nervous system known as the " ganglionic " or " sym- pathetic" system. Leaving the cerebro-spinal centres out of sight for a moment, we see that the larger or visceral tube of a Vertebrate animal contains the digestive canal, the haemal system, and a gangliated nervous system. Now this is exactly what is contained in the visceral cavity of any of the higher Invertebrate animals; and the opinion has been generally entertained that it is the sympathetic nervous sys- tem of Vertebrates which is truly comparable to, and homolo- gous with, the nervous system of Invertebrates. On the other hand, there are Invertebrates with a sympathetic system of nerves, and the development of the nerve-chain of the Annu- losa resembles that of the cerebro-spinal axis of the Vertebrata. The tube containing the cerebro-spinal centres is formed as follows : At an early period in the development of the embryo of any Vertebrate animal, the portion of the ovum in which VERTEBRATA: GENERAL CHARACTERS. 445 development is going on — the "germinal area" — becomes elevated into two parallel ridges, one on each side of the middle line, enclosing between them a long groove, which is known as the " primitive groove " (fig. 239, A, B). The ridges which bound the primitive groove are known as the " laminae dorsales ; " and they become more and more raised up, till they ultimately meet in the middle line, and unite to form a tube, within which the cerebro-spinal nervous centres are developed. It follows from its mode of formation that the inner wall of the tube formed by the primitive groove, which remains as the septum between the cerebro-spinal canal and the body-cavity, is nothing more than a portion of the primitive wall of the body of the embryo. And there appears to be little doubt, as believed by Remak and Huxley, that the cerebro-spinal nervous centres are "the result of a modification of that serous layer of the germ, which is continuous elsewhere with the epidermis " (Huxley). Another remarkable peculiarity as regards the nervous sys- tem is found in the fact that in no Vertebrate animal does the I) Fig. 239.— Embryology of Vertebrata. A, Portion of the germinal area of the ovum of a Bitch, showing the primitive groove (after Bischoff). B, Profile view of the same. C, Diagram representing the amnion and allantois : e Embryo ; a Am- nion ; u Umbilical vesicle ; b Allantois ; f Pedicle of the allantois, afterwards the urinary bladder. D, Head of an embryo, showing the visceral arches (v v). alimentary canal pierce the main masses of the nervous system, but turns away to open on the opposite side of the body. In most Invertebrates, on the other hand, in which there is a well-developed nervous system, this is perforated by the gullet, so that an cesophageal nerve-collar is formed, and some of the 446 MANUAL OF ZOOLOGY. nervous centres become prae - cesophageal, whilst others are post- cesophageal. Furthermore, the floor of the "primitive groove" in the embryo of all Vertebrates has developed in it at an early period the structure known as the " notochord " or " chorda dorsalis " (fig. 238, B, ch). This structure, doubtfully repre- sented in any Invertebrate, is a semi-gelatinous or cartilaginous collection of cells, forming a rod-like axis, which tapers at both ends, and extends along the floor of the cerebro-spinal canal, supporting the cerebro-spinal nervous centres. In some Ver- tebrates, such as the Lancelet (Amphwxus), the notochord is persistent throughout life. In the majority of cases, however, the notochord is replaced before maturity by the structure known as the " vertebral column " or " backbone," from which the sub-kingdom Vertebrata originally derived its name. This is not the place for an anatomical description of the spinal column, and it is sufficient to state here that it is essen- tially composed of a series of cartilaginous, or more or less completely ossified, segments or vertebra, arranged so as to form a longitudinal axis, which protects the great masses of the nervous system. It is to be remembered, however, that all Vertebrate animals do not possess a vertebral column. They all possess a notochord ; but this may be persistent, and in many cases the development of the spinal column is extremely imperfect. Another embryonic structure which is characteristic of all Vertebrates, is found in the so-called " visceral arches " and " clefts " (fig. 239, D). The "visceral arches" are a series of parallel ridges running transversely to the axis of the body, situated at the sides of, and posterior to, the mouth. As devel- opment proceeds, the intervals between these ridges become grooved by depressions which gradually deepen, until they become converted into a series of openings or " clefts," where- by a free communication is established between the upper part of the alimentary canal (pharynx) and the external medium. In Fishes and many Amphibians the greater number of the visceral clefts remain open throughout life ; and the visceral arches of all fishes (except the Lancelet) throw out filamentous or lamellar processes, which receive branches of the aorta and constitute branchiae. In the higher Vertebrata all the visceral clefts become closed, whilst no branchiae are ever developed upon the visceral arches. The limbs of Vertebrate animals are always articulated to the body, and they are always turned away from the neural aspect of the body. They may be altogether wanting, or they VERTEBRATA: GENERAL CHARACTERS. 447 may be partially undeveloped ; but there are never more than two pairs, and they always have an internal skeleton for the attachment of the muscles of the limb. A specialised blood-vascular or " haemal " system is present in all the Vertebrata ; and in all except one — the Amphioxus — there is a contractile cavity or heart, which never consists of less than two chambers provided with valvular apertures. In all the Vertebrata the heart is essentially a respiratory heart — that is to say, it is concerned with driving the impure or venous blood to the breathing organs; and in its simplest form (fishes) it is nothing more than this. In the higher Vertebrates, how- ever, there is superadded to this a pair of cavities which are concerned in driving the pure or arterial blood to the body. In the case of the Mammals, these two circulations are often spoken of as the "lesser" or "pulmonary" circulation, and the " greater " or " systemic " circulation. In all Vertebrates there is that peculiar modification of the venous system which is known as the "hepatic portal system." That is to say, a portion of the blood which is sent to the ali- mentary canal, instead of returning to the heart by the ordinary veins, is carried to the liver by a special vessel — the vena portcz — which ramifies through this organ after the manner of an artery. In all Vertebrates, also, is found the peculiar system of ves- sels known as the "lacteal system." This is to be regarded as an appendage of the venous system of blood vessels, and consists of a series of vessels which take up the products of digestion from the alimentary canal, elaborate them, and finally empty their contents into the veins. Lastly, the masticatory organs of Vertebrates are modified portions of the walls of the head, and never " hard productions of the alimentary mucous membrane, or modified limbs " (Hux- ley), as they are amongst the Invertebrata. The above are the leading characters of the Vertebrata as a whole ; but before going on to consider the primary divisions of the sub-kingdom, it may be as well to give a very brief and general description of the anatomy of the higher and more typical Vertebrates, commencing with their bony framework, or skeleton. The skeleton of the Vertebrata may be regarded as consisting essentially of the bones which go to form the head and trunk on the one hand (sometimes called the " axial " skeleton), and of those which form the supports for the limbs (" appendicular " skeleton) on the other hand. The bones of the head and trunk may be looked upon as essentially composed of a series 448 MANUAL OF ZOOLOGY. of bony rings or segments, arranged longitudinally, one behind the other. Anteriorly these segments are much expanded, and likewise much modified, to form the bony case which encloses the brain, and which is termed the cranium or skull. Behind the head the segments enclose a much smaller cavity, which is called the " neural " or spinal canal, as it encloses the spinal cord ; and they are arranged one behind the other, forming the vertebral column. The segments which form the vertebral column are called "vertebrae," and they have the following general structure : Each vertebra (fig. 240, A) consists of a cen- Fig. 240. — A, Lumbar vertebra of a Whale : c Body or centrum ; n n Neural arches ; s Neural spine ; a a Articular processes ; dd Transverse processes. B, Diagram of a thoracic vertebra : c Centrum ; n n Neural arches enclosing the neural canal ; 5 Neural spine ; rr Ribs, assisting in the formation of the haemal arch ; // Costal car- tilages ; b Sternum, with haemal spine. (After Owen.) tral piece, which is the fundamental and essential element of the vertebra, and is known as the " body " or " centrum " (c). From the upper or posterior surface of the centrum spring two bony arches (n n\ which are called the " neural arches " or " neurapophyses," because they form with the body a canal — the " neural canal " — which encloses the spinal cord. From the point where the neural arches meet behind, there is usually developed a longer or shorter spine, which is termed the " spi- nous process," or "neural spine" (s). From the neural arches there are also developed in the typical vertebra two processes (a a), which are known as the " articular " processes, or " zyga- pophyses." The vertebrae are united to one another partly by these, but to a greater extent by the bodies or " centra." From the sides of the vertebral body, at the point of junction with the neural arches, there proceed two lateral processes (dd\ VERTEBRATA : GENERAL CHARACTERS. 449 which are known as the " transverse processes." (In the typi- cal vertebra the transverse processes consist each of two pieces, an anterior piece or " parapophysis," and a posterior piece or " diapophysis.") These elements form the vertebra of the human anatomist, but the " vertebra " of the transcendental anatomist is completed by a second arch which is placed be- neath the body of the vertebra, and which is called the " hae- mal " arch, as it includes and protects the main organs of the circulation. This second arch is often only recognisable with great difficulty, as its parts are generally much modified, but a good example may be obtained in the human chest, or in the caudal vertebra of a bony fish. The haemal arch in the case of the human thorax (fig. 240, B) is formed by the ribs (rr) and the costal cartilages (//), and is completed in front by the breast-bone or sternum (^), which in some cases — but not in man — develops a spine (the haemal spine) which corresponds to the neural spine on the opposite aspect of the vertebra. It follows from the above, that the typical vertebra consists of a central piece or body from which two arches are given off, one of which protects the great masses of the nervous system, and is therefore said to be "neural;" whilst the other protects the main organs of the circulation, and is therefore said to be " haemal." The correspondence of the typical bony segment or vertebra with the doubly tubular structure of the body in all Vertebrates is thus too obvious to require to be specially pointed out. As a general rule, the vertebral column is divisible into a number of distinct regions, of which the following are recog- nisable in man and in the higher Vertebrata : i. A series of vertebrae which compose the neck, and constitute the " cervical region" of the spine (fig. 241, n). 2. A number of vertebrae which usually carry well-developed ribs, and form the " dorsal region " (d). 3. A series of vertebrae which form the region of the loins, or "lumbar region" (/). 4. A greater or less number of vertebrae which constitute the " sacral region," and are usually amalgamated or " anchylosed " together to form a single bone, the " sacrum." 5. The spinal column is com- pleted by a variable number of vertebrae which constitute the " caudal " region, or tail (c). As regards the skull of the Vertebrata, it has been thought advisable not to enter into any general details here, partly because the subject is one which can only be properly dis- cussed in a work specially devoted to Human or Comparative Anatomy, and partly because there is still much diversity of 2 F 450 MANUAL OF ZOOLOGY. opinion as to the exact composition of the skull. There is, however, a very general concurrence of opinion that the skull is composed of a series of separate segments, and this is a point which it is important to remember. By Owen, and by many other competent authorities, these cranial segments are looked upon as being nothing more than so many vertebrce, the neural canals of which are greatly expanded to enclose the brain, whilst the haemal arches are very greatly modified to serve different purposes. This view is not accepted by high Fig. 241. — Skeleton of an Armadillo, showing the regions of the vertebral column, c Cervical region ; d Dorsal region ; / Lumbar region ; s Sacral region ; t Caudal region or tail. authorities ; but the general fact that the skull is composed of separate segments is universally admitted. The only portion of the bony framework of the head which it is absolutely essential to understand, is the lower jaw or "mandible." The lower jaw is sometimes wanting, but when present, it consists in all Vertebrata of two halves or " rami," which are united to one another in front, and articulate separately with the skull behind. In many cases, each half, or " ramus," of the lower jaw consists of several pieces united to one another by sutures; but in the Mammalia each ramus consists of no more than a single piece. The two rami are very variously connected with one another, being sometimes only joined by ligaments and muscles, sometimes united by cartilage or by bony suture, and sometimes fused or anchylosed with one another, so as to leave no evidence of their true composition. The mode by which each ramus of the lower jaw articulates with the skull also varies. In the Mammalia the lower jaw articulates with a cavity formed on what is known to human anatomists as the temporal bone; but in Birds and Reptiles. the lower jaw articu- VERTEBRATA: GENERAL CHARACTERS. 451 lates with the skull, not directly, but by the intervention of a special bone, known as the " quadrate bone " or os quadrat um. As regards the limbs of Vertebrates, whilst many differences exist, which will be afterwards noticed, there is a general agreement in the parts of which they are composed. As a rule, each pair of limbs is joined to the trunk by means of a series of bones which also corre- spond to one another in general struc- ture. The fore-limbs, often called the " pectoral " limbs, are united with the trunk by means of a bony arch, which is called the "pectoral" or "scapular" arch; whilst the hind-limbs are simi- larly connected with the trunk by means of the " pelvic arch." In giving a gen- eral description of the parts which com- pose the limbs and their supporting arches, it will be best to take the case of a Mammal, and the departures from this type will then be readily recognised. The pectoral or scapular arch consists usually of three bones, the " scapula " or shoulder-blade, the " coracoid," and the "clavicle" or collar-bone; but in the great majority of the Mammals, the coracoid is anchylosed with the scapula, of which it forms a mere process. The scapula or shoulder-blade (fig. 242, s) is usually placed outside the ribs, and it Fig. 242.-Pectorai limb (arm forms, either alone or in conjunction with the coracoidal element of the shoulder- girdle, the cavity with which the upper arm is articulated. The coracoid, though rarely existing as a distinct bone in the Mammals, plays a very important part in other Vertebrates, as we shall see hereafter. The clavicles are often wanting or rudimentary, and they are the least essential ele- ments of the scapular arch. The fore-limb proper consists, firstly, ^of a single bone which forms the upper arm (or " brachium "), and which is known as the humerus (h). This articulates above with the shoulder-girdle, and is followed below by the fore-arm (or " antibrachium "), which consists of two bones called the radius and ulna. Of these the radius is chiefly concerned with carrying the hand (or " manus "). . The of Chimpanzee (after Owen). c Clavicle ; j Scapula or shoulder-blade ; h Humerus ; r Radius ; u Ulna ; d Bones of the wrist, or carpus; m Metacarpus ; / Phalanges of the fingers. 452 MANUAL OF ZOOLOGY. radius and ulna are followed by the bones of the wrist, which are usually composed of several bones, and constitute what is called the carpus (d). These support the bones of the root of the hand, which vary in number, but are always more or less cylindrical in shape. They constitute what is called the meta- carpus. The bones of the metacarpus carry the digits, which also vary in number, but are composed each of from two to three cylindrical bones, which are known as the phalanges (p). Homologous parts are, as a rule, readibly recognisable in the hind-limb. The pelvic arch, by which the hind- limb is united with the trunk, consists of three pieces — the ilium, ischium, and flukes — which are usually anchylosed together, and form conjointly what is known as the innominate bone (fig. 243, i). In most Mammals, the two innominate bones unite in front by ligamentous or cartilaginous union, and they constitute, with the sacrum, what is known as the pelvis. The hind-limb proper consists of the following parts : — i. The thigh - bone or femur, corresponding with the humerus in the fore-limb. 2. The bones of the shank (or " crus "), corresponding with the radius and ulna of the fore-limb, and known as the tibia and fibula. Of these, the tibia is mainly or altogether concerned in carrying the foot (or "pes"), and it is thus shown to corre- spond to the radius, whilst the fibula corresponds to the ulna. 3. The small bones of the ankle, known as the tarsus, and varying in number in different cases. 4. A variable number of cylin- drical bones (normally five), which are called the metatarsus, and which correspond to the metacarpus. 5. Lastly, the metatarsus carries the digits, which consist of from two to three of Chim anzee sma^ bones or phalanges, as in the fore-limb. {after Owen), i The digestive system of Vertebrates will be /nFe°±aortHngeh: spoken of at greater length hereafter; but a bone ; / Tibia ; s brief sketch may be given here of the general Fibula; r Tarsus; , _ <.. 9 . .. ,, , m Metatarsus ; p phenomena of digestion. All Vertebrate ani- Phaianges of the mais are provided with a mouth for the recep- tion of food, and in the great majority of cases the mouth is furnished with teeth, which are used sometimes merely to hold the prey, but more commonly to cut and bruise the food, and thus render it capable of digestion. The food is also generally subjected in the mouth to the action of " saliv- Fig. 243. — Pelvic limb (hind -limb) VERTEBRATA: GENERAL CHARACTERS. 453 ary " glands, the secretion of which serves not only to moisten the food, and thus mechanically assist deglutition, but also to render soluble the starchy elements of the food. The food is next swallowed, or, in other words, is transferred from the mouth to the stomach, this being effected by a complicated arrangement of muscles, whereby the food is forced down the gullet (cesophagus) to the proper digestive cavity or stomach. In the stomach (fig. 244, s) the food is subjected to two sets of actions ; it is mechanically triturated and ground down by the constant contractions of the muscular walls of the stomach ; and it is subjected to the chemical action of a special fluid secreted by the stomach, and called the "gastric juice." This fluid has the power of reducing albuminoid substances to a soluble form, and by its action the food is ultimately reduced to a thick acid fluid, called the "chyme." Leav- ing the stomach by its lower aper- ture (the pylorus), the chyme passes into the intestine, the first portion of which is divided into several sections, but is collectively known as the " small intestine." Here the chyme is subjected to the action of three other digestive fluids ; the bile, secreted by a special organ, the liver ; the pancreatic juice, secreted by another gland, the pancreas ; and the intestinal juice, secreted by certain glands situated in the muc- Fig. 244.— Diagram of the digestive ous membrane of the intestine itself. * G The result of the whole process is that the " chyme " is ultimately converted into a white, alkaline, milky fluid, which is called " chyle." The indigestible portions of the food pass from the small intestine into a tube of larger dimensions, called the " large intestine." Such portions of the food as are still soluble, and capable of being employed in nutrition, are here taken up into the blood, the useless remainder being ultimately expelled by an anal aperture. The last portion of the large intestine is usually less convoluted than the rest, and is called the " rectum." .ntestine ; Im Large intestine ; r Rectum, terminating in the aperture of the anus. 454 MANUAL OF ZOOLOGY. The fluid and originally soluble portions of the food, and the chyle which is formed in the process of digestion, are taken into the blood, the losses of which they serve to repair. Part of the nutritive materials of the food is taken up directly by the blood-vessels, and is conveyed by the "vena portae" to the liver, whence it ultimately reaches the great veins which go to the heart. The greater part, however, of the liquefied food, constituting the chyle, is taken up, not by the blood-vessels, but by a special set of tubes, which form a network in the walls of the intestine, and are known as the "lacteals." In these vessels, and in certain glands which are developed upon them, the chyle undergoes still further elaboration, and is made more similar in composition to the blood itself. All the lacteal vessels ultimately unite into one or more large vessels which open into one of the veins, so that all the chyle is thus finally added to the mass of the circulating blood. The blood, then, or nutrient fluid from which the tissues are built up, is formed in this way out of the materials which are taken into the alimentary canal as food. In all the Vertebrata, with the single exception of the Lancelet (Amphtoxus\ the blood is of a red colour when viewed in mass. This is due to the presence in it of an incredible number of microscopical bodies, which are known as the " blood-corpuscles," the fluid in which these float being itself colourless (fig. 245). In all the Vertebrata the blood is distributed through the body by means of a system of closed tubes, which constitute Fig. 245. — Blood-corpuscles of Vertebrata. a Red blood-discs of man ; b Blood- discs of Goose ; c Crocodile ; d Frog ; e Skate. the " blood-vessels; " and in all exceptjheLajicelet, the means of propulsion are derived from a 'CSnfractile muscular cavity or' " heart," furnished with valvular apertures. In the most complete form of circulation, as seen in Birds and Mammals, the heart is essentially a double organ, composed of two halves, each of which consists of two cavities, an auricle and a ventricle. The right side of the heart is wholly concerned with the "lesser" or pulmonary circulation, whilst the left side is concerned with driving the blood to all parts of the body (systemic circulation). The modifications of the circula- tory process will be noticed in speaking of the different classes VERTEBRATA: GENERAL CHARACTERS. 455 of Vertebrates, but a brief sketch may be given here of the circulation, in its most complete form, as in a Mammal. In such a case, the venous or impure blood, which has circulated through the body and has parted with its oxygen, is returned by the great veins to the right auricle. From the right auricle (fig. 246, a) the blood passes by a valvular aperture into the right ventricle (v), whence it is driven through the pulmonary artery to the lungs. The right side of the heart is therefore wholly respiratory in its func- tion. Having been submitted to the action of the lungs, and having given off carbonic acid and taken up oxygen, the blood now becomes arterial, and is returned by the pulmonary veins to the left auricle («'), From the left aur- icle the aerated blood passes through a valvular aperture into the left ven- tricle (vr), whence it is propelled to all parts of the body by means of a great systemic vessel, the " aorta.'*' The left side of the heart is therefore wholly occupied in carrying out the " greater " or systemic circulation. The purification of the blood is car- ried out in all Vertebrates by means of distinct respiratory organs, assisted to a greater or less extent by the skin. In the Fishes, and in the Amphibians to some extent, the process of respira- tion is carried on by means of branchuz or gills — that is, by organs adapted for breathing air dissolved in water. These are therefore often spoken of as " Branchiate " Vertebrates ; but the Amphibians always develop true lungs in the later stages of their existence. In the Reptiles, Birds, and Mammals, branchiae are never developed, and the respiration is always carried on by means of true lungs — that is, by organs adapted for breathing air' directly. These are therefore often spoken of as the " Abran- chiate " Vertebrates. The waste substances of the body — of which the most im- portant are water, carbonic acid, and urea — are got rid of by the skin, lungs, and kidneys. Under ordinary circumstances, Fig. 246.— Di of the rir- ig. 240. — L>iagram of tne cir- culation of a Mammal. The venous system is marked black ; the arterial system is left white, a Right auricle ; r Right ventricle j / Pulmo- nary artery, carrying venous blood to the lungs ; pv Pulmo- nary veins, carrying arterial blood from the lungs ; of Left auricle ; •& Left ventricle ; b Aorta, carrying arterial blood to the body; c Vena cava, carrying venous blood to the heart. 456 MANUAL OF ZOOLOGY. the lungs are mainly occupied with the excretion of carbonic acid and watery vapour. The skin chiefly gets rid of super- fluous moisture, but can also in many animals excrete carbonic acid as well. The kidneys are present in almost all Vertebrate animals, and their function is mainly to excrete water, and the nitrogenous substance known as urea. In the majority of cases the fluid excreted by the kidneys is conveyed to the exterior by means of two tubes known as the ureters, which empty themselves into a common receptacle, the urinary blad- der. In some cases, however, the ureters open into the ter- mination of the alimentary canal (rectum). The nervous system of Vertebrate animals usually exhibits a well-marked division into two parts — the cerebro-spinal sys- tem, and the sympathetic system. The cerebro-spinal system of nerves constitutes the great mass of the nervous system of Vertebrates, and usually exhibits a well-marked separation into spinal cord (myelori) and brain (encephaloii). The propor- tion borne by the brain to the spinal cord differs much in dif- ferent cases ; and in the Lancelet a brain can hardly be said to be present at all. As already said, the brain and spinal cord are always completely shut off from the visceral cavity, and they are placed upon the dorsal surface of the body. The nerves given off from the cerebro-spinal axis are symmetrically disposed on the two sides of the body, and they are mainly concerned with the functions of " animal " life — that is to say, with sensation and locomotion. The sympathetic system of nerves is unsymmetrically disposed to a greater or less extent, and presides mainly over the functions of " organic" or "vege- tative " life, being chiefly concerned with regulating the func- tions of digestion and respiration, and the circulation of the blood. In its most fully developed form it consists of a double gangliated cord placed in the visceral cavity on the under sur- face of the spine, and of a series of nervous ganglia, united by nervous cords, and scattered chiefly over the great viscera of the thorax and abdomen. The organs of the senses are well developed in the Vertebrata, and those appropriated to the senses of sight, hearing, smell, and taste are protected within bony cavities of the head. The perfection of the senses differs much in different cases, but they are probably never wholly wanting in any Vertebrate animal. There are cases in which vision must be of the most rudimen- tary character ; but even in these cases it is probable that there is a perception of light, even if there is no power of distinguish- ing objects. The only cases in which it would appear that vision is really altogether absent, are those of animals placed VERTEBRATA : GENERAL CHARACTERS. 457 under the wholly abnormal condition of spending their exist- ence in darkness (such as the Proteus anguinus of the caves of Illyria). Smell, hearing, and taste are probably rarely, if ever, altogether absent in Vertebrates ; though in many cases their organs are very rudimentary. Touch, or " tactile sensibility," is usually possessed to a greater or less degree by the entire surface of the body ; but the sense of touch is generally localised in certain particular parts, such as the appendages of the mouth, the lips, the tongue, or the digits. In all Vertebrata without exception reproduction is carried on by means of the sexes, and in all (except in some of the Serranidce among the Fishes) the sexes are in different indivi- duals. No vertebrate animal possesses the power of reproduc- ing itself by fission or gemmation ; and in no case are compo- site organisms or colonies produced. Most of the Vertebrates are oviparous — that is to say, the ova are expelled from the body of the parent either before or very shortly after impreg- nation. In other cases, the eggs are retained within the body of the parent until the young are hatched, but no direct con- nection is formed between the fcetus and the mother, and in these cases the animals are said to be ovo-viviparous. In other cases, again, not only is the egg hatched within the parent, but the embryo is retained within the body of the mother, from whom it receives nourishment by direct vascular connection, until its development has been carried out to a greater or less extent ; and these animals are said to be viviparous. Many vertebrate animals possess an exoskeleton, formed by a hardening of one or other layer of the integument. The integument is composed of two layers — an external non-vascu- lar "epidermis," and a deeper vascular "dermis" — and the exoskeleton may be formed by the deposition of horny matter, or of salts of lime, in either or in both of these. The epider- mal exoskeleton is always horny, and, when present, is gener- ally in the form of hairs (Mammalia}, feathers (Birds), scales (serpents and many lizards), or plates (Chelonians). The horny sheaths of the jaws in Birds and some Reptiles, the outer covering of the horns in some Mammals, the hoofs, claws, and nails of Mammalia, are likewise epidermic. The dermal exoskeleton may be either horny or bony ; and good examples of it are to be found in the scales of fishes, the bony scutes of the Crocodiles, and the armour-plates of the Arma- dillos. DIVISIONS OF THE VERTEBRATA. — The sub-kingdom Verte- brata is divided into the five great classes of the Fishes (Pisces), Amphibians (Amphibia), Reptiles (Reptilid), Birds 458 MANUAL OF ZOOLOGY. (Aves), and Mammals (Mammalia). So far there is perfect unanimity ; but when it is inquired into what larger sections the Vertebrata may be divided there is much difference of opinion. Here, the divisions proposed by Professor Huxley will be adopted ; but it is necessary that those employed by other writers should be mentioned and explained. One of the commonest methods of classifying the Verte- brata is to divide them into the two primary sections of the Branchiata and Abranchiata. Of these, the Branchiate sec- tion includes the Fishes and Amphibians, and is characterised by the fact that the animal is always provided at some period of its life with branchiae or gills. The Abranchiate section includes the Reptiles, Birds, and Mammals, and is character- ised by the fact that the animal is never provided at any time of its life with gills. Additional characters of the Branchiate Vertebrates are, that the embryo is not furnished with the structures known as the amnion and allanto'is. Hence the Branchiate Vertebrates are often spoken of as the Anamniota and as the Anallantoidea. In the Abranchiate Vertebrates, on the other hand, the embryo is always provided with an amnion and allantois, and hence this section is spoken of as the Amniota or as the Allantoidea.* By Professor Owen the Vertebrata are divided into the two primary sections of the H&matocrya and the Hcematotherma, the characters of the blood being taken as the distinctive character. The Hcsmatocrya or Cold-blooded Vertebrates comprise the Fishes, Amphibia, and Reptiles, and are charac- terised by their cold blood and imperfect circulation. The Hcematotherma or Warm-blooded Vertebrates comprise the Birds and the Mammals, and are characterised by their hot blood, four-chambered heart, and complete separation of the sj:>ulmonary and systemic circulations. The chief objection to this division lies in the separation which is effected between * The amnion (fig. 239, C) is a membranous sac, containing a fluid — the liquor amnii — and completely enveloping the embryo. It constitutes one of the so-called "foetal membranes," and h thrown off at birth. The allantois (fig. 239, C) is an embryonic structure, which is developed out of the middle or " vascular" layer of the germinal membrane. It appears at first as a solid, pear-shaped, cellular mass, arising from the under part of the body of the embryo. In the process of development, the allantois in- creases largely in size, and becomes converted into a vesicle which envelops the embryo in part or wholly. It is abundantly supplied with blood, and is the organ whereby the blood of the foetus is aerated. The part of the allantois which is external to the body of the embryo is cast off at birth ; but the portion which is within the body is retained, and is converted into the urinary bladder. VERTEBRATA: LITERATURE. 459 the Reptiles and the Birds, two classes which are certainly very nearly allied to one another. By Professor Huxley the Vertebrata are divided into the following three primary sections : — I. ICHTHYOPSIDA. — This section comprises the Fishes and the Amphibians, and is characterised by the presence at some period of life of gills or branchiae, the absence of an amnion, the absence or rudimentary condition of the allantois, and the possession of nucleated red blood-corpuscles. II. SAUROPSIDA. — This section comprises the Birds and the Reptiles, and is characterised by the constant absence of gills, the possession of an amnion and allantois, the articulation of the skull with the vertebral column by a single occipital con- dyle ; the composition of each ramus of the lower jaw of seve- ral pieces, and the articulation of the lower jaw with the skull by the intervention of an " os quadratum ; " and, lastly, the possession of nucleated red blood-corpuscles. III. MAMMALIA. — This section includes the single class of the Mammals, and agrees with the preceding in never possess- ing gills, and in having an amnion and allantois. The Mam- malia t however, differ from the Sauropsida in the fact that the skull articulates with the vertebral column by two occipital condyles ; each ramus of the lower jaw is simple, composed of a single piece, and the lower jaw is united with the temporal (squamosal) element of the skull, and is not articulated to a quadrate bone. There are special glands — the mammary glands — for the nourishment of the young for a longer or shorter period after birth, and the red blood-corpuscles are non-nucleated. LITERATURE. 1. "Comparative Anatomy and Physiology of Vertebrates." Owen. 1866-68. 2. " Manual of the Anatomy of Vertebrated Animals." Huxley. 1872. 3. " Principles of Comparative Physiology. " W. B. Carpenter. 4. " Forms of Animal Life. " Rolleston. 1870. 5. "General Outline of the Organisation of the Animal Kingdom." Rymer Jones. 1871. 6. "Handbook of Zoology." Van der Hoeven. Trans, by Dr W. Clarke. 1856-58. 7. ' ' Manual of Comparative Anatomy. " Blumenbach. Trans, by Laurence. 1827. 8. " Comparative Anatomy of Vertebrate Animals." Wagner. Trans. by Tulk. 1845. 9. " Grundriss der Vergleichenden Anatomic." Gegenbaur. 1874. 10. " Le Regne Animal distribue d'apres son organisation." Cuvier. 11. " Le9ons d'anatomie comparee." Cuvier. 460 MANUAL OF ZOOLOGY. 12. " System der Vergleichenden Anatomic." MeckeL 1821-33. 13. " Le£ons sur la physiologic et 1'anatomie comparee de I'homme et desanimaux." Milne-Edwards. 1857-72. 14. "Lectures on the Elements of Comparative Anatomy." (On the Classification of Animals and on the Vertebrate Skull.) Huxley. 1864. 15. " Discourse on the Nature of Limbs." Owen. 1849. 16. "On the Shoulder-Girdle and Sternum." Parker. 'Ray Society.' 1868. 17. " Lectures on Histology. " Quekett. 1852-54. 18. "The Microscope and its Revelations." Carpenter. 19. " How to work with the Microscope. " Beale. 20. " Lehrbuch der Histologie des Menschen und der Thiere. " Leydig. 1857- 21. " Embryology, with the Physiology of Generation. " Miiller. Trans. by Baly. 1848. 22. ** Elements of Embryology. " Foster and Balfour. 1876. 23. " The Geographical Distribution of Animals. " Alfred Wallace. 1876. 24. " Recherches sur les ossemens fossiles." Cuvier. 1834-36. 25. "Manual of Palaeontology." Owen. 1861. 26. " Traite de Paleontologie. " Pictet. 1853. 27. "Cours elementaire de Paleontologie." D'Orbigny. 1849. 28. " Manual of Palaeontology. " Nicholson. 2d ed. 1879. 29. "Generelle Morphologic der Organismen." Hseckel. 1866. 30. " System der thierischen Morphologic." Victor Carus. 1853. 31. " Entwickelungsgeschichte der Thiere." Von Baer. 1837. 32. " The Morphology of the Skull." Parker & Bettany. 1877. 33. " Lessons in Elementary Anatomy." St George Mivart. 1873. 46 1 DIVISION I.—ICHTHYOPSIDA. CHAPTER LI. CLASS L— PISCES. THE first class of the Vertebrata is that of the Fishes (Pisces), which may be broadly defined as including Vertebrate animals which are provided with gills throughout the whole of life; the heart, when present, consists (except in Dipnoi] of a single auricle and a single ventricle ; the blood is cold ; the limbs, when present, are in the form of fins, or expansions of the integument ; and there is neither an amnion nor allantois in the embryo, unless the latter is represented by the urinary bladder. In form, Fishes are adapted for rapid locomotion in water, the shape of the body being such as to give rise to the least possible friction in swimming. To this end also, as well as for purposes of defence, the body is usually enveloped with a coat- ing of scales developed in the inferior or dermal layer of the skin ; whereas the epidermis is represented only by the slimy mucus covering the exterior of the animal. The more impor- tant modifications in the form of these dermal scales are as follows : I. Cycloid scales (fig. 247, a), consisting of thin, flexible, horny or bony scales, i IT ,_• i • i Fig. 247.— Scales of different fishes, a Circular _ Or elliptical m Shape, Cycloid scale : (Pike); b Ctenoid scale and having a more or less com- pletely smooth outline. These are the scales which are charac- teristic of the most of the ordinary bony fishes. II. Ctenoid scales (fig, 247, b\ also consisting of thin horny plates, but (Perch); c Placoid scale (Thornback) ; d Placoid scale of Rhino,', e Ganoid scales {Palceoniscus), 462 MANUAL OF ZOOLOGY. having their posterior margins fringed with spines, or cut into comb-like projections. III. Ganoid scales, composed of an inferior layer of bone, covered by a superficial layer of hard polished enamel (the so-called "ganoine"). These scales (fig. 247, e) are usually much larger and thicker than the ordinary scales, and though they are often articulated to one another by, special processes, they only rarely overlap. IV. Placoid scales, consisting of detached bony or dentinal grains, tubercles, or plates, of which the latter are not uncommonly armed with spines (fig. 247, c and d). In most fishes there is also to be observed a line of peculiar scales, forming what is called the " lateral line." Each of the scales in this line is perforated by a tube leading down to a longitudinal canal which runs along the side of the body, and is connected with cavities in the head. The function of this singular system has been ordinarily believed to be that of secreting the mucus with which the surface of the body is cov- ered ; but this is certainly erroneous, and it seems to be more probably sensory in function, and to be connected with the sense of touch. As regards their true osseous system or endoskeleton, Fishes vary very widely. In the Lancelet there can hardly be said to be any skeleton, the spinal cord being simply supported by the gelatinous notochord, which persists throughout life. In others the skeleton remains permanently cartilaginous ; in others it is partially cartilaginous and partially ossified ; and, lastly, in most modern fishes it is entirely ossified, or converted into bone.* Taking a bony fish (fig. 248) as in this respect a typical example of the class, the following are the chief points in the osteology of a fish which require notice : — The vertebral column in a bony fish consists of vertebrae, which are hollow at both ends, or biconcave, and are technically said to be " amphiccelous." The cup-like margins of the vertebral bodies are united -by ligaments, and the cavities formed between contiguous vertebrae are filled with the gelatinous remains of the notochord. This elastic gelatinous substance acts as a kind of ball-and-socket joint between the bodies of the verte- brae, thus giving the whole spine the extreme mobility which is requisite for animals living in a watery medium. The ossifi- cation of the vertebrae is often much more imperfect than the above, but in no case except that of the Bony Pike (Lepidos- teus) is ossification carried to a greater extent than this. In * The so-called "bone" of the skeleton of Fishes is only occasionally true osseous tissue. In a great many instances it is a homogeneous or tubu- lar, bone-like substance, or it may resemble genuine dentine. VERTEBRATA : FISHES. 463 this fish, however, the vertebral column is composed of " opis- thocoelous " vertebrae — that is, of vertebrae, the bodies of which are concave behind and convex in front. The entire spinal column is divisible into not more than two distinct regions, an abdominal and a caudal region. The abdominal vertebrae pos- sess a superior or neural arch (through which passes the spinal cord), a superior spinous process (neural spine), and two trans- verse processes to which the ribs are usually attached. The caudal vertebrae (fig. 248) have no marked transverse processes ; Fig. 248.— Skeleton of the common Perch (Percafluviatilis). p One of the pectoral fins ; v One of the ventral fins ; a Anal fin, supported upon interspinous bones (z) ; c Caudal fin ; d First dorsal fin ; d! Second dorsal fin, both supported upon interspinous bones ; i i Interspinous bones ; r Ribs ; s Spinous processes of vertebrae ; h Haemal processes of vertebrae. but, in addition to the neural arches and spines, they give off an inferior or hcemal arch below the body of the vertebrae, and the haemal arches carry inferior spinous processes (haemal spines). The ribs of a bony fish are attached to the transverse pro- cesses, or to the bodies of the abdominal vertebrae, in the form of slender curved bones which articulate with no more than one vertebra each, and that only at a single point. Unlike the ribs of the higher Vertebrates, the ribs do not enclose a thoracic cavity, but are simply embedded in the muscles which bound the abdomen. Usually each rib gives off a spine-like bone, which is directed backwards amongst the muscles. Inferiorly the extremities of the ribs are free, or are rarely united to der- mal ossifications in the middle line of the abdomen ; but there is never any breast-bone or sternum properly so called. The only remaining bones connected with the skeleton of the trunk are the so-called interspinous bones (fig. 248, / /). 464 MANUAL OF ZOOLOGY. These form a series of dagger-shaped bones, plunged in the middle line of the body between the great lateral muscles which make up the greater part of the body of a fish. The internal ends or points of the interspinous bones are attached by ligament to the spinous processes of the vertebrae ; whilst to their outer ends are articulated the " rays " of the so-called " median " fins, which will be hereafter described. As a rule, there is only one interspinous bone to each spinous process, but in the Flat-fishes (Sole, Turbot, &c.) there are two. Besides the fins which represent the limbs (pectoral and ventral fins), fishes possess other fins placed in the middle line of the body, and all of these alike are supported by bony spines or " rays," which are of two kinds, termed respectively " spinous rays" and " soft rays." The " spinous rays" are simple bony spines, apparently composed of a single piece each, but really consisting of two halves firmly united along the middle line. The " soft rays " are composed of several slender spines pro- ceeding from a common base, and all divided transversely into numerous short pieces. The soft rays occur in many fishes in different fins, but they are invariably found in the caudal fin or tail (fig. 248, c). The rays of the median fins, whatever their character may be, always articulate by a hinge-joint with the heads of the interspinous bones. The skull of the bony fishes is an extremely complicated structure, and it is impossible to enter into its composition here. The only portions of the skull which require special mention are the bones which form the gill-cover or operculum, and the hyoid bone with its appendages. For reasons con- nected with the respiratory process in fishes, as will be after- wards seen, there generally exists between the head and the scapular arch a great cavity or gap on each side, within which are contained the branchiae. The cavity thus formed opens externally on each side of the neck by a single vertical fissure or "gill-slit," closed by a broad flap, called the "gill-cover" or " operculum," and by a membrane termed the " branchiostegal membrane." The gill-cover (fig. 249, p, 0, s, i) is composed of a chain of broad flat bones, termed the opercular bones. Of these, the innermost articulates with the skull (tympano-mandibular arch), and is called the " prse-operculum ; " the next is a large bone called the " operculum" proper; and the remain- ing two bones, called respectively the " sub-operculum " and "inter-oper- culum," form, with the operculum proper, the edge of the gill-cover. These various bones are united together by membrane, and they form col- lectively a kind of movable door, by means of which the branchial cham- ber can be alternately opened and shut. Besides the gill-cover, however, the branchial chamber is closed by a membrane called the " branchiostegal VERTEBRATA: FISHES. 465 membrane," which is attached to the os hyoides. The membrane is supported and spread out by a number of slender curved spines, which are attached to the lateral branches of the hyoid bone, act very much as the ribs of an umbrella, and are known as the ' ' branchiostegal rays" (fig. 249, d}. The hyoid arch of fishes is attached to the temporal bones of the skull Fig. 249. — Skull of Cod (Morrkua viilgarls) — Cuvier. a Urohyal; b Basihyal; c Ceratohyal; d Branchiostegal rays ; / Prae-operculum ; o Operculum proper; s Sub- operculum ; i Inter-operculum ; w Mandible ; n Inter-maxillary bone. by means of two slender styliform bones, which correspond to the styloid processes of man, and are called the " stylohyal " bones (fig. 250, /). The rest of the hyoid arch is composed of a central portion and two lateral branches. Each branch is composed of the following parts : I. A tri- angular bone attached above to the stylohyal, and termed the " epihyal bone" (fig. 250, e) ; 2. A much longer bone, known as the "ceratohyal" (d). The central portion of the hyoid arch is made up of two small poly- hedral bones— the "basihyals" (b). From the basihyal there extends forwards in many fishes a slender bone, which supports the tongue, and is termed the " glossohyal " or "lingual" (a). There is also another com- pressed bone which extends backwards from the basihyals, and which is known as the "urohyal bone" (c). This last-mentioned bone is of im- portance, as it often extends backwards to the point of union of the cora- coid bones, and thus forms the isthmus which separates the two branchial apertures. From the outer margins of the epihyal and ceratohyal bones on each side arise the slender curved "branchiostegal rays," which have been previously mentioned. There are usually seven of these on each side. Above the urohyal, and attached in front to the body of the os hyoides, is a chain of 2 G 466 MANUAL OF ZOOLOGY. bones, placed one behind the other, and termed by Owen the " basibran- chial bones." Springing from these are four bony arches— the "branchial arches "—which proceed upwards to be connected superiorly by ligament with the under surface of the skull. The branchial arches— as will be sub- sequently described— carry the branchiae, and each is composed of two main pieces, termed respectively the " cerato - branchial " and " epi- -. 6 Fig. 250. — Os hyoides, branchiostegal rays, and scapular arch of the Perch (after Cuvier). ss Supra-scapula ; s Scapula ; co Coracoid ; cl Supposed representative of the clavicle ; a Glossohyal bone ; b Basihyal ; c Urohyal ; d Ceratohyal ; e Epihyal ; f Stylohyal ; br Branchial arches ; t Branchiostegal rays. branchial " bones. The second and third arches are connected with the skull by the intervention of two small bones, often called the ' ' superior pharyngeal bones," but termed by Owen the " pharyngo - branchial " bones. The limbs of fishes depart considerably from the typical form exhibited in the higher Vertebrates. One or both pairs of limbs may be wanting, but when present the limbs are almost always in the form ofjfins — that is, of expansions of the integu- ment strengthened by bony or cartilaginous fin -rays. The anterior limbs are known as the pectoral fins, and the posterior as the ventral fins ; and they are at once distinguished from the VERTEBRATA: FISHES. 46; so-called " median " fins by being always disposed in pairs, usually symmetrically. Hence they are often spoken of as the paired fins. The scapular arch (figs. 250, 251) supporting the pectoral limbs is usually joined to the skull (occipital bone), and consists of the following pieces on co Fig. 251. — Pectoral limbs of Fishes (after Owen). A, Cod (Morrhita -vidgaris) : B, Angler (Lophius). ss Supra-scapula ; j Scapula ; co Coracoid ; r Radius ; « Ulna ; cc Carpal bones ; f Fin-rays, representing the metacarpus and phalanges of the fingers. each side : I. The supra-scapula (ss) ; 2. The scapula (s), articulating with the former ; and, 3. The coracoid (co), attached above with the scapula, and united below, by ligament or suture, with the coracoid of the opposite side, thus completing the pectoral arch. Lastly, there is often another bone, sometimes single, but oftener of two pieces, attached to the upper end of the coracoid, and this is believed to represent the collar-bone or clavicle. * * These are the views entertained by Owen as to the composition and nature of the pectoral arch of fishes ; but they are dissented from by Mr Parker, one of the greatest living authorities on this subject. 468 MANUAL OF ZOOLOGY. The fore-limb possesses in a modified form most of the bones which are present in the higher Vertebrata. The humerus, or bone of the upper arm, is usually wanting, or it is altogether rudimentary. A radius and ulna (fig. 251, r, u) are usually present, and are followed by a variable number of bones, which represent the carpus, and some of which some- times articulate directly with the coracoid. The carpus is fol- lowed by the " rays " of the fin proper, these representing the metacarpal bones and phalanges. The pectoral fins vary much in size and in other characters. In the Flying Gurnard (Dac- tylopterus], and the true Flying Fish (Exoccztus), the pectorals are enormously developed, and enable the fish to take exten- sive leaps out of the water. The hind-limbs or " ventral fins " are wanting in many fishes, and they are less developed and less fixed in position than are the pectoral fins. In the ventral fins no representatives of the tarsus, tibia and fibula, or femur, are ever developed. The rays of the ventral fins — representing the metatarsus and the phalanges of the toes — unite directly with a pelvic arch, which is composed of two sub-triangular bones, united in the middle line and believed to represent the ischia. The imperfect pelvic arch, thus constituted, is never united to the vertebral column in any fish. In those fishes in which the ventral fins are " abdominal " in position (/. £., placed near the hinder end of the body) the pelvic arch is suspended freely amongst the Fig. 252. — Outline of a fish (Perca granulate?) , showing the paired and unpaired fins. /> One of the pectoral fins ; v One of the ventral fins ; d First dorsal fin ; d' Second dorsal fin ; a Anal fin ; c Caudal fin. muscles. In those in which the ventral fins are " thoracic " or "jugular" (i.e., placed beneath the pectoral fins, or on the sides of the neck), the pelvic arch is attached to the coracoid VERTEBRATA : FISHES. 469 bones of the scapular arch, and is therefore wholly removed from its proper vertebra. In addition to the pectoral and ventral fins — the homologues of the limbs — which may be wanting, fishes are furnished with certain other expansions of the integument, which are "me- dian" in position, and must on no account be confounded with the true " paired " fins. These median fins are variable in number, and in some cases there is but a single fringe run- ning round the posterior extremity of the body. In all cases, however, the median fins are " azygous " — that is to say, they occupy the middle line of the body, and are not symmetrically disposed in pairs. Most commonly, the median fins consist of one, two, or three expansions of the dorsal integument, called the " dorsal fins" (fig. 252, d, d')-, one or two on the ventral surface near the anus — the "anal fins" (fig. 252, a)-, and a broad fin at the extremity of the vertebral column, called the " caudal fin " or tail (c). In all cases, the rays which support the median fins are articulated with the so-called interspinous bones, which have been previously described. Though called " median," from their position in the middle line of the body, and from their being unpaired, the median fins of fishes, as shown by Goodsir and Humphry, are truly to be regarded as formed by the coalescence of two lateral elements in the mesial plane of the body. The caudal fin, or tail, of fishes is always set vertically at the extremity of the spine, so as to work from side to side, and it is the chief organ of progression in the fishes. In its vertical position, and in the possession of fin-rays, it differs altogether from the horizontal integumentary expansion which constitutes the tail of the Whales, Dolphin, and Sirenia (Dugong and Manatee). In the form of the tail, fishes exhibit some striking differences. In some of the Bony Fishes and Ganoids, the caudal extremity of the spine is not bent upwards, but divides the caudal fin-rays into two nearly equal portions, and the symmetrical tail-fin thus produced is said to be " diphycercal." In the great majority of the Bony Fishes the tail-fin appears on inspection to be divided into two equal lobes, and it is then said to be "homocercal" (fig. 253, A). This apparent symmetry is due to the fact that the spinal column seems to terminate in the centre of a triangular bony mass, to the free edges of which the fin -rays are symmetrically attached. In reality, however, the unossified notochord is prolonged into the upper lobe of the tail ; and as there is a much larger number of fin-rays below the bent-up notochord than above it, the tail is truly unsymmetrical in its fundamental structure. Lastly, in 4/0 MANUAL OF ZOOLOGY. the Elasmobranchii, and most Ganoids, the tail is conspicu- ously unsymmetrical (fig. 253, B), and is then said to be Fig. 253. — A, Sword-fish, showing homocercal tail ; B, Sturgeon, showing the heterocercal form of tail. " heterocercal." In these cases, the lower lobe of the tail is conspicuously larger than the upper, owing to the dispropor- tionate development of the haemal rays, and the spinal column is prolonged into the upper lobe of the tail. In a recently published and important memoir, Professor A. Agassiz has shown that in Pleuronectes and various other living Bony Fishes, the tail of the early embryo is rounded, and is symmetrically developed at the hinder end of the straight notochord ("leptocardial stage"). Soon the chorda becomes arched upwards, and there appears the first trace of a separa- tion of the tail-fin into two portions, only one of which is destined to remain permanently. The superior of these two divisions; when both have become fully marked out, surrounds the end of the upturned chorda (fig. 254, a), and it must be regarded as an embryonic structure, since it finally disappears. The inferior of the two divisions, on the other hand, is placed below the embryonic tail, and is ultimately developed into the permanent tail. At first the permanent caudal fin has the appearance of a distinct lobe, which looks like a second anal fin. In process of growth, however, the embryonic caudal becomes thrown more and more upwards, and the rays of the permanent caudal acquire a fan -like arrangement. At the stage figured below (fig. 254) the tail is truly "heterocercal," and is wonderfully similar in appearance to the tail of many Palaeozoic Fishes. Finally, however (fig. 255), the turned-up end of the notochord becomes replaced by the long " uro-^ style j " the embryonic caudal diminishes in size and disap- VERTEBRATA: FISHES. 471 pears; and the permanent caudal increases in size, and is gradually transformed from a ventral into a terminal append- age, the tail -fin thus assuming its permanent " homocercal " Fig. 254. — Tail of young Flounder (PZeuronectes) in its heterocercal stage of develop- ment, a Embryonic caudal fin ; b Permanent caudal fin, occupying an inferior position ; c Bent-up end of the notochord. (After A. Agassiz.) form. It would thus appear that the really earliest stage of the tail in the Bony Fishes and Elasmobranchs is the " lepto- cardial " stage, in which the tail is symmetrical and the noto- chord straight. This stage is in progress of growth superseded by the " heterocercal " condition, which sub- sists throughout life in the Elasmobranchs. Finally, the heterocer- cal tail of the young Bony Fish is in the adult succeeded by the Fig. 255.— Tail of adult Flounder. (After A. Agassiz.) v Vertebral column ; » Turned-uj» end of the noto- chord ; h Hypural bones permanent "homocer- cal " or " diphycercal " tail. The process of respiration in all fishes is essentially aquatic, and is carried on by means of branchial plates or tufts devel- oped upon the posterior visceral arches, which are persistent, and do not disappear at the close of embryonic life, as they do in other Vertebrates. In the Lancelet alone, respiration is effected partly by branchial filaments placed round the com- mencement of the pharynx, and partly by the pharynx itself, which is greatly enlarged, and has its walls perforated by a series of transverse ciliated fissures. The arrangement and 472 MANUAL OF ZOOLOGY. structure of the branchiae differ a good deal in the different orders of fishes, and these modifications will be noticed sub- sequently. In the meanwhile it will be sufficient to give a brief description of the branchial apparatus in one of the bony fishes. In such a fish, the branchiae are connected with the hyoid arch, and are situated in two special chambers, situated one on each side of the neck. The branchiae are carried upon the outer convex sides of what have been already described as the " branchial arches ; " that is to say, upon a series of bony arches (figs. 250 and 256) which are connected with the hyoid arch inferiorly, and are united above with the base of the skull. The internal concave sides of the branchial arches are usually furnished with a series of processes, constituting a kind of fringe, the function of which is to prevent foreign substances finding their way amongst the branchiae, and thus Fig. 256. — Gills and heart of the Perch exposed by the removal of the gill-cover on the left side, a First of the four bony arches which carry the gills (b b) ; b' The lower edges of the gills on the right side ; k Heart. (After Van der Hoeven.) interfering with the proper action of the respiratory organs. The branchiae, themselves, usually have the form of a double series of cartilaginous leaflets or laminae. The branchial la- minae are flat, elongated, and pointed in shape, and they are covered with a highly vascular mucous membrane, in which the branchial capillaries ramify. The blood circulates through , the branchial laminae, and is here subjected to the action of aerated water, whereby it is oxygenated. The water is con- 1 stantly taken in at the mouth by a movement analogous to swallowing, and it gains admission to the branchial chambers by means of a series of clefts or slits, the " branchial fissures," which are situated on both sides of the pharynx. Having passed over the gills, the deoxygenated water makes its escape VERTEBRATA : FISHES. 473 ba posteriorly by an aperture called the " gill-slit " or "opercular aperture," one of which is situated on each side of the neck. As we have seen before, the gill-slit is closed in front by a chain of flat bones collectively constituting the " gill-cover," or " operculum ; " and the gill- covers are finally completed by a variable number of bony spines — the " branchiostegal rays " — which articulate with the hyoid arch, and support a membrane — the " branchi- ostegal membrane." The heart of fishes is, pro- perly speaking, a branchial or respiratory heart. It con-i sists of two cavities, an aur- icle and a ventricle (fig. 257), and the course of the circu- lation is as follows : The ven- ous blood derived from the liver and from the body gen- erally is poured by the vena cava into the auricle (ait), and from this it is propelled into the ventricle (v). From the ventricle arises a single aortic arch (the right), and the base of this is usually dilated into a cavity or sinus, called the "bulbus arterios- us " (ab). The arterial bulb is sometimes covered with a special coat of striated mus- cular fibres, and may be pro- vided with several transverse rows of valves. In these cases, the bulbus acts as a kind of continuation of the ventricle, being capable of rhythmical contractions. The blood is driven by the ventricle through the branchial artery (b) to the gills, through which it is distributed by means of the branchial vessels, the number of which varies (there are three on each side in a few fishes, four in most of the Bony Fishes, five in the Skates and Sharks, and six or seven in the Lampreys). The Fig. 257. — Diagram of the circulatory system in a Fish, the vessels containing venous blood being longitudinally shaded, and those con- taining arterial blood being cross-shaded, vc Vena cava ; vp Vena portse ; au Auricle ; v Ventricle ; ab Bulbus arteriosus ; b Branchial artery ; ba One of the divisions of the bran- chial artery going to the gills, from which the c esponding branchial veins, by the union of which the subvertebral proceeds one of t veins, by the uni aorta (so) is formed ; z Intestine ; k Kidney. 474 MANUAL OF ZOOLOGY. aerated blood which has passed through the gills is not re- turned to the heart, but is driven from the branchiae through all parts of the body ; the propulsive force necessary for this being derived chiefly from the heart, assisted by the contrac- ; tions of the voluntary muscles. In some fishes (as in the Eel) the return of the blood to the heart is assisted by a rhythmically contractile dilatation of the caudal vein. The essential peculi- arity, then, of the circulation of fishes depends upon this — that (the arterialised blood returned from the gills is propelled [through the systemic vessels of the body, without being sent iback to the heart. """The Lancelet (Amphioxus}^ alone of all fishes, has no special heart, and the circulation is effected by contractile dilatations developed upon several of the blood-vessels. In the Mud-fishes (Ltpidosiren) the heart consists of two auricles and a single ventricle. The blood-corpuscles of fishes are nucleated (fig. 245, e), and the blood is red in all except the Amphioxus. As regards the digestive system of fishes there is not much of peculiar importance. The mouth is usually furnished with a complicated series of teeth, which, in the Bony Fishes, are not only developed upon the jaws proper, but may be also situ- ated upon other bones which enter into the composition of the buccal cavity (such as the palate, the pterygoids, vomer, branchial arches, the glossohyal bone, &c.) The oesophagus is usually short and capacious, and generally opens into a large and well-marked stomach. The pyloric aperture of the stomach is usually furnished with a valve, and behind it there is usually a number (from one to sixty) of blind appendages, termed the "pyloric caeca." These are believed to represent the pancreas, but there may be a recognisable pancreas either alone or in addition to the pyloric cseca. The intestinal canal is a longer or shorter, more or less convoluted tube, the ab- sorbing surface of which, in certain fishes, is largely increased by a spiral reduplicature of the mucous membrane, which winds like a screw in close turns from the pylorus to the anus. The liver is usually large, soft, and oily, and a gall-bladder is almost universally present ; but in the 'Amphioxus the liver is doubtfully represented by a hollow sac-like organ. The kidneys of fishes are usually of great size, and form two elongated organs, which are situated beneath the spine, and extend along the whole length of the abdominal cavity. The ureters often dilate, and form a species of bladder, the doubt- ful representative of the allantois. Whilst the respiration of all fishes is truly aquatic, most of VERTEBRATA: FISHES. 475 them are, nevertheless, furnished with an organ which has been generally believed to be the homologue of the lungs of the air-breathing Vertebrates. This — the "air" or "swim bladder" — is a sac containing gas, situated beneath the ali- mentary tube, and often communicating with the gullet by a duct. In the great majority of fishes the functions of the air- , bladder are certainly hydrostatic — that is to say, it serves to I maintain the necessary accordance between the specific gravity of the fish and that of the surrounding water. In the singular • Mud-fishes, (as also in a few Bony Fishes), however, it acts as a respiratory organ, and is therefore not only the homologue, but also the analogue, of the lungs of the higher Vertebrates. In most fishes the air-bladder is an elongated sac with a single cavity, but in many cases it is variously subdivided by septa, or it may give off more or less complicated caeca (fig. 258). In the Mud-fishes the air-bladder is composed of two sacs, completely separate from one another, and divided into a number of cellular compartments. The duct (ductus pneumaticus) leading in many fishes from the air-bladder, and opening into the oeso- phagus, is the homologue of the windpipe (trachea). The air contained in the swim- bladder is composed mainly of nitrogen in most fresh-water fishes, but in the sea- fishes it is mainly made up of oxygen. The fishes which live habitually at the bottom of the sea, such as the Flat-fishes, possess no swim-bladder, and it is much reduced in size in those which live prin- cipally at the surface. The nervous system of fishes is of an inferior type of organisation, the brain be- ing of small size, and consisting mainly of ganglia devoted to the special senses. Fig. 258. — Swim-bladder As regards the special senses, there is So^^SSSS one peculiarity which deserves particular notice, and this is the conformation' of the nasal sacs. The cavity of the nose is usually double, and is lined by an olfac- tory membrane, folded so as to form numerous plicae. An- teriorly, the water is admitted into the nasal sacs by a single or double nostril, usually by two apertures; but posteriorly the nasal sacs are closed, and do not communicate with the pharynx by any aperture. The only exceptions to this state- ment are to be found in the Myxinoids and in the Mud-fishes. 476 MANUAL OF ZOOLOGY. The essential portion of the organ of hearing (labyrinth} is present in almost all fishes, but in none is there any direct communication between the ear and the external medium. In some cases, however, there is a communication between the ear and the swim-bladder, thus foreshadowing the Eusta- chian tube in man. As regards their reproductive system, fishes are, for the most part, truly oviparous, the ovaries being familiarly known as the " roe," The testes of the male are commonly called the " soft roe," or " milt." The products of the reproductive organs are often set free into the peritoneal cavity, ultimately finding their way to the external medium by means of an abdominal pore (or pores) ; or they are directly conveyed to the exterior by the proper ducts of the reproductive organs. 477 DIVISIONS OF FISHES. CHAPTER LII. « PHARYNbUBJiANCHII AND MARSIPOBRANCH1L THE class Pisces has been very variously subdivided by dif- ferent writers ; but the classification here adopted is the one proposed by Professor Huxley, who divides the class into the following six orders, in the subdivisions of which Professor Owen has been followed : * ORDER I. PHARYNGOBRANCHII ( = Cirrostomi, Owen ; and Leptocardia, Miiller). — This order includes but a single fish, the anomalous Amphioxus lanceolatus, or Lancelet (fig. 259), the organisation of which differs in almost all important points from that of all the other members of the class. The charac- ters of Amphioxus, in fact, are so aberrant, that Haeckel pro- poses to divide the sub-kingdom Vertebrata into two primary sections — the one (Leptocardia] comprising the Lancelet alone, whilst the other (Pachycardia) includes all other Vertebrates. The order is defined by the following characters, which, as will be seen, are mostly negative : — No skull is present, nor lower jaw (mandible), nor limbs. The notochord is persistent ; and there are no vertebral centra nor arches. No distinct brain nor auditory organs are present. In place of a distinct heart, pul- sating dilatations are developed upon several of the great blood- vessels. The blood is pale. The mouth is in the form of a longitudinal fissure, surrounded by filaments or cirri. The walls of the pharynx are perforated by numerous clefts or fis- sures, the sides of which are ciliated, the whole exercising a respiratory function. * Cuvier divided the class Pisces into the great orders of the Chondrop- ierygii(or Cartilaginous Fishes), the Acanthopterygii (or Fishes with spinous rays in the paired fins), and Malacopterygii (or Fishes with soft rays in the paired fins). Agassiz divides Fishes, from the character of the scales, into the four orders, Cycloidd, Ctenoidei, Ganoidei, and Placoidei. Miiller divides the Fishes into the five orders Leptocardia, (Lancelet), Cydo- stomata (Lampreys and Hag-fishes), Teleostei, (Bony Fishes), Ganoidei, (Ganoid Fishes), and Selachia (Sharks and Rays). 478 MANUAL OF ZOOLOGY. The Lancelet is a singular little fish, from one to two inches in length, which is found burrowing in sandbanks, in various seas, but especially in the Mediterranean. The body (fig. 259) is semi-transparent, destitute of an exoskeleton, and lanceolate in shape, and is provided with a narrow mem- branous border, of the nature of a median fin, which runs along the whole of the dorsal and part of the ventral surface, and expands at the tail to form a lancet-shaped caudal-fin. No true paired fins, representing the anterior and posterior limbs, are present. The mouth is a longitudinal fissure, situated at the front of the head, and destitute of jaws. It is surrounded by a cartilaginous ring, composed of many pieces, which give off prolongations, so as to form a number of ciliated cartilaginous filaments or " cirri " on each side of the mouth. (Hence the name of Cirrostomi, proposed by Professor Owen for the order.) The throat is provided on each side with vascular lamellae, which are believed by Owen to perform the function of free branchial filaments. The mouth leads into a dilated chamber (fig. 259, £), which is Fig. 259. — The Lancelet (Amphioxus lanceolatiis), enlarged to twi,^, „.<, uunm... 010^. 0 Mouth ; b Pharyngeal sac ; g Stomach ; h Diverticulum representing the liver ; 1 Intestine: a Anus : n Notochord : /Rudiments of fin-ravs : 2* / ' ' ' ' its natural size. IYJ.UULII , i/ j. iicti y ugcdi sen* , £ OLuniacu , ri J-/IYCI Liuuium icpi eventing the ll> Intestine ; a Anus : n Notochord ; y Rudiments of fin-rays ; p Abdominal pore. believed to represent the pharynx, and is termed the " pharyn- geal" or "branchial sac." It is an elongated chamber, the walls of which are strengthened by numerous cartilaginous filaments, between which is a series of transverse slits or clefts, the whole covered by a richly-ciliated mucous mem- brane. This branchial dilatation has given rise to the name Branchiostoma, often applied to the Lancelet. Posteriorly the branchial sac opens into an alimentary canal, to which is ap- pended a long and capacious sac or caecum (h\ which is believed to represent the liver. The intestinal tube termi- nates posteriorly by a distinct anus (a), which is situated at the root of the tail a little to the left of the median line ; and the intestinal mucous membrane is ciliated. Respiration is effected by the admission of water taken in. by the mouth into the branchial sac, having previously passed over the free VERTEBRATA: FISHES. 479 branchial filaments before mentioned. The water- passes through the slits in the branchial sac, and thus gains access to the abdominal cavity, from which it escapes by means of an aperture with contractile margins situated a little in front of the anus, and called the " abdominal pore " (/). There is no distinct heart, and the circulation is entirely effected by means of rhythmically contractile dilatations which are de- veloped upon several of the great blood-vessels. In other words, the heart retains its primitively tubular condition, and special contractile dilatations are developed upon other vessels (those carrying the blood to the pharynx). The blood itself is colourless. No kidneys have as yet been certainly identi- fied, and there is no lymphatic system. There is no skeleton properly so called. In place of the vertebral column, and constituting the whole endoskeleton, is the semi-gelatinous cellular notochord (n), enclosed in a fibrous sheath, and giving off fibrous arches above and below. The notochord is, further, peculiar in this, that it is prolonged quite to the anterior end of the body, whereas in all other Vertebrates it stops short at the pituitary fossa. There is no cranium, and the spinal cord does not expand anteriorly to form a distinct cerebral mass. The brain, however, may be said to be represented, since the anterior portion of the nervous axis gives off nerves to a pair of rudimentary eyes, and another branch to a ciliated pit, believed to represent an olfactory organ. The generative organs (ovaria and testes) are not furnished with any efferent ducts (oviduct or vas deferens). The generative products, therefore, are shed into the abdominal cavity, and gain the external medium by the " abdominal pore." ORDER II. MARSIPOBRANCHII ( = Cyclostomi, Owen ; and Cydostomata, Muller). — This order includes the Lampreys (Petromyzonidcz) and the Hag-fishes (Myxinidcz), and is defined by the following characters : — The body is cylindrical, worm- like, and destitute of limbs. The skull is cartilaginous, without cranial bones, and having no lower jaw (mandible). The noto- chord is persistent, and there are either no vertebral centra, or but the most rudimentary traces of them. The heart consists of one auricle and one ventricle, but the branchial artery is not furnished with a bulbus arteriosus. The gills are sac-like, and are not ciliated. The type of piscine organisation displayed in the Marsipo- branchii is of a very low grade, as indicated chiefly by the persistent notochord without vertebral centra, the absence of any traces of limbs, the absence of a mandible, and the struc- ture of the gills. 48o MANUAL OF ZOOLOGY. Both the Lampreys (fig. 260, B) and the Hag-fishes (fig. 260, A) are vermiform, eel-like fishes, which agree in possess- Fig. 260. — Morphology of Marsipobranchii. A, Myxine glutinosa, showing the sucker- like mouth, and the two ventral openings (K) by which the water escapes from the gills. B, The River Lamprey or Lampern (Petromyzon fluiriatilis), showing the seven branchial apertures on the side of the neck. C, Branchial organs of Myxine ; g The gullet laid open, showing the openings (six on each side) by which the water enters the branchial sacs (s) ', c Canal carrying the water away from the gills, to be discharged by the two ventrally-placed branchial apertures (h, K) ; i Aperture by which the water is admitted to the gullet and thence to the gills. ing no paired fins to represent the limbs, but in having a median fin running round the hinder extremity of the body. The skeleton remains throughout life in a cartilaginous condition, the chorda dorsalis is persistent, and the only traces of bodies of vertebrae are found in hardly perceptible rings of osseous matter developed in the sheath of the notochord. The neural arches of the vertebrae, enclosing the spinal cord, are only represented by cartilaginous prolongations. There is a par- tially cartilaginous cranium, which is not, however, movable on the spinal column. The mouth in the Hag-fish (Myxine) is of a very remarkable character, and enables it to lead a very peculiar mode of life. It is usually found, namely, embedded in the interior of some other large fish, into which it has suc- ceeded in penetrating by means of its singular dental apparatus. The mouth (fig. 260, A) is sucker-like, destitute of jaws, but provided with tactile filaments or cirri. In the centre of the palate is fixed a single, large, recurved fang, which is firmly attached to the under surface of the cranium. The sides of this fang are strongly serrated, and it is by means of this that the Hag-fish bores its way into its victim, having previously attached itself by its sucker- like mouth, assisted by the action VERTEBRATA : FISHES. 481 of the piston-like toothed tongue. In the Lampreys the mouth has also the form of a circular cup or sucker, and is also destitute of jaws ; but in addition to the palatine fang of the Myxine. the margins of the lips bear a number of horny processes, which are not really true teeth, but are hard struc- tures developed in the labial mucous membrane. The tongue, also, is armed with serrated teeth, and acts as a kind of piston ; so that the Lampreys are in this manner enabled to attach themselves firmly to solid objects. Sometimes the oral cavity is strengthened by a basket-shaped cartilaginous apparatus, and sometimes a similar apparatus supports the gill-sacs. The alimentary canal is simple and straight, the liver not sac-like, but of its ordinary form, and the kidneys distinct and well developed. The Marsipobranchii are peculiar amongst Vertebrate ani- mals in possessing only one median nasal sac, opening on the exterior of the head by a single unpaired nostril. The Hag- fishes further differ from all the members of the class, except the Mud-fishes (Dipnoi} in the fact that the nasal cavity com- municates behind with the pharynx. In the Lampreys, on the other hand, the nasal sac is closed posteriorly. Another very remarkable point in the Hag-fishes and Lam- preys is to be found in the structure of the gills, from which the name of the order is derived. The gills, namely, are in the form of fixed pouches, instead of being free vascular struc- tures contained in a common chamber, opening externally by a gill-slit, as in the typical Bony Fishes. In the Hag-fishes there are six of these branchial sacs on each side of the oeso- phagus (fig. 260, C). The water is admitted to the gullet (g) by a special aperture situated on the ventral surface, whence it passes into the branchial pouches by six apertures on each side. Having passed over the complicated and highly vascular interior of the branchial sacs, the water escapes by a corre- sponding series of tubes opening into a common canal (c] on each side, and these canals finally discharge the effete water by two apertures situated on the ventral surface behind the head (/i, //). In the Lampreys the gills have the same fixed and pouch-like arrangement, but there are some marked differences from the above. The water is admitted from the gullet to seven branchial pouches on each side, but the mode of admission is by means of two special canals which lie beneath the oeso- phagus on each side, communicating each by its own aperture with the mouth in front, terminating blindly behind, and send- ing off a branch to each pouch. The effete water, also, escapes by a special tube to each sac, so that there are seven branchial 2 H 482 MANUAL OF ZOOLOGY. apertures in the form of slits or holes on the side of the neck (fig. 260, B). The reproductive organs are ductless, and the generative elements are shed into the abdomen, whence they escape by an abdominal pore. The Lampreys are, some of them, inhabitants of rivers ; but the great Sea-lamprey (Petromyzon marinus) only quits the salt water in order to spawn. The mouth in the Pettomytonida is a circular cartilaginous ring, formed by the amalgamation of the palatine and mandibular arches, and carrying numerous teeth and small tubercles. The tongue is armed with a double series of small teeth, and acts like a piston, enabling the animal to attach itself to stones and rocks. There is no air-bladder. The body is cylindrical, compressed towards the tail, and destitute of scales. The skeleton consists of a series of cartilaginous rings without ribs. The young Petromyzon undergoes a metamorphosis, being so unlike the parent that a new genus (Ammocates) was originally founded for its reception. In the Myximda the mouth is circular and membranous, with eight cirri. The palate carries a single fang, and the tongue is armed with a double row of small teeth on each side. There may be seven branchial apertures on each side (Heptatrema), or the branchial pouches open into a common tube on each side, and each of these terminates in a distinct aperture situated under the heart on the lower surface of the body (Myxine or Gas- trobranchus}. The Hags pour out so much mucus through the lateral line that they can surround themselves with jelly; hence the name of the com- mon species (Myxine glutinosa). The Glutinous Hag is a native of the North and British seas, and is chiefly found in the interior of the Cod and Haddock (often five or six individuals in one fish). CHAPTER LIU. TELEOSTEI. ORDER III. TELEOSTEI.— This order includes the great ma- jority of fishes in which there is a well-ossified endoskeleton, and it corresponds very nearly with Cuvier's division of the "osseous" fishes. The Teleostei are defined as follows : — The skeleton is usually well ossified ; the cranium is provided with cranial bones ; and a mandible is present ; whilst the vertebral column almost always consists of more or less completely ossified vertebra. The pectoral arch has a clavicle; and the two pairs of limbs, when present, are in the form of fins supported by rays. The gills are free, pectinated or tufted in shape ; a bony gill-cover and branchiostegal rays being always developed. The branchial artery has its base developed into a bulbus arteriosus ; but this is never rhythmically contractile, and is separated from the ventricle by 110 more than a single row of valves. VERTEBRATA : FISHES. 483 The order Teleostei comprises almost all the common fishes \ and it will be unnecessary to dilate upon their structure, as they were taken as the types of the class in giving a general description of the Fishes. It may be as well, however, to recapit- ulate very briefly some of the leading characters of the order. I. The skeleton, instead of remaining throughout life more or less completely cartilaginous, is now always more or less thoroughly ossified. The notochord is not persistent, and the vertebral column, though sometimes cartilaginous, consists of a number of vertebrae. The bodies of the vertebrae are what is called " amphiccelous " — that is to say, they are concave at both ends. It follows from this, that between each pair of vertebrae there is formed a doubly-conical cavity, and this is filled with the cartilaginous or semi-gelatinous remains of the notochord. By this means an extraordinary amount of flexi- bility is given to the entire vertebral column. In no fish except the Bony Pike (which belongs to the order Ganoidei} is the ossification of the vertebral centra carried further than this. The skull is of an ^extremely complicated nature, being com- posed of a number of distinct cranial bones ; and a mandible or lower jaw is invariably present. II. The anterior and posterior pairs of limbs are usually, but not always, present, and when developed they are always in the form of fins. The fins may be supported by " spinous " or "soft" rays, of which the former are simple undivided spines of bone, whilst the latter are divided transversely into a num- ber of short transverse pieces, and also are broken up into a number of longitudinal rays proceeding from a common root. (The fishes with soft rays in their paired fins are termed " Malacopterygii " — those with spinous rays, " Acan- thopterygii") III. Besides the paired fins, representing the limbs, there is a variable number of unpaired or azygous integumentary ex- pansions, which are known as the " median fins." When fully developed (fig. 261), they consist of one, two, or three fins on the back — the " dorsal " fins ; one or two on the ventral surface — the "anal" fins; and one clothing the posterior extremity of the body — the " caudal " fin. The caudal fin (fig. 253, A) is set vertically, and not horizontally, as in the Whales and Dolphins ; and in all the bony fishes its form is " homocercal " —that is, it consists of two equal lobes, and the vertebral column is not prolonged into the superior lobe.* In all the * Though to all appearance symmetrical, the tail of the bony fishes is in reality generally unsymmetrical. The appearance of symmetry is due to the bony spinal column terminating in the centre of a wedge-shaped 484 MANUAL OF ZOOLOGY. median fins the fin-rays are supported upon a series of dagger- shaped bones, which are plunged in the flesh of the middle Fig. 261.— The common Perch (Perca Jluviatilis). o Gill-cover, with the gill-slit be- hind it ; / One of the pectoral fins, the left ; i> The left ventral fin ; ^The first dorsal fin ; d' The second dorsal fin ; c The caudal fin or tail ; a The anal fin ; / Lateral line. line of the body, and are attached to the spinous processes of the vertebrae. These are the so-called " interspinous " bones. IV. The heart consists of two chambers, an auricle and a ventricle, and the branchial artery is furnished with a bulbus arteriosus. The arterial bulb, however, is not furnished with a special coat of striated muscular fibres, is not rhythmically con- tractile, and is separated from the ventricle by no more than a single row of valves. V. The respiratory organs consist of free, pectinated, or tufted branchiae, situated in two branchial chambers, each of which communicates internally with the pharynx by a series of clefts, and opens externally on the side of the neck by a single aper- ture (or " gill-slit "), which is protected in front by a bony gill- cover (fig. 261) and is also closed by a " branchiostegal mem- brane," supported upon " branchiostegal rays." The branchiae are attached to a series of bony branchial arches (generally five on each side, but only the anterior four bearing gills), which are connected inferiorly with the hyoid bone, and superiorly with the skull ; and the water required in respira- tion is taken in at the mouth by a process analogous to swal- lowing. "hypural bone," to the free edges of which the caudal fin-rays are sym- metrically attached. The actual termination of the notochord is bent up, and is never ossified ; but its sheath usually becomes calcified, forming a spine ("urostyle") which coalesces with the dorsal edge of the hypural bone, the latter being formed by the anchylosis of ossicles developed from the ventral face of the notochordal sheath. VERTEBRATA: FISHES. 485 VI. The nasal sacs never communicate posteriorly with the cavity of the pharynx. VII. The exoskeleton usually has the form of overlapping horny scales of the cycloid or ctenoid character ; but it is sometimes absent, sometimes composed of scattered plates of true bone, sometimes ganoid, and sometimes formed of sha- green-like bony spines. VIII. The stomach is capacious ; pyloric caeca are present ; the intestine has no spiral valve; and the rectum usually opens separate from and in front of the urinary and genital apertures. The air-bladder may or may not be present, and may or may not communicate with the gullet. The kidneys are well de- veloped. The reproductive organs may be solid, and may liberate their contents by rupture into the abdominal cavity; but they are usually hollow organs, with ducts which open beside or behind the urinary aperture. The subdivisions of the osseous fishes are so numerous, and they contain so many families, that it will be sufficient to run over the more important sub-orders, and to mention the more familiar examples of each. SUB-ORDER A. MALACOPTERI, Owen ( = Physostomata, Miil- ler). — This sub-order is defined by usually possessing a com- plete set of fins, supported by rays, all of which are " soft" or many-jointed, with the occasional exception of the first rays in the dorsal and pectoral fins. A swim-bladder is always present, and always communicates with the oesophagus by means of a duct, which is the homologue of the windpipe. The skin is rarely naked, and is mostly furnished with cycloid scales ; but in some cases ganoid plates are present. This sub-order is one of great importance, as comprising many well- known and useful fishes. It is divided into two groups, according as ventral fins are present or not. In the first group — Apoda — there are no ventral fins; and the most familiar examples are the common Eels of our own country. The Eels (Mur&nida) have an elongated, almost cylindrical body, with the scales deeply sunk in the skin, and scarcely ap- parent. A swim-bladder is present, and the operculum is small and mostly enveloped in the skin. More remarkable, however, than the ordinary Eels is the Gymnotus electricus, or great Electric Eel (fig. 262), which in- habits the marshy waters of those wonderful South American plains, the so-called " Llanos," and which shares with various fishes of diverse affinities (the Torpedo, the Malapterurus electricus, &c.) the power of generating electricity by means of special organs. The second group of the Malacopteri is that of the Abdominalia, in which there are ventral fins, and these are abdominal in position. Space will not permit of more here than merely mentioning that in this section are con- tained amongst others the well-known and important groups of the Chtpeida (Herring tribe), the Pikes (Esocida>\ the Carps, Barbels, Roach, Chub, Minnow, £c. (Cyprinida:), and the Salmonidce, comprising the various 486 MANUAL OF ZOOLOGY. species of Salmon and Trout. Also belonging to this group are the Sheat- fishes (Siluridcz), which are chiefly noticeable because they are amongst the small number of living fishes possessed of structures of the same nature as the fossil spines known as "ichthyodorulites." The structure in question consists of the first ray of the pectoral fins, which is largely developed, and Fig. 262 — Electric Eel (Gymuotus electricus). constitutes a formidable spine, which the animal can erect and depress at pleasure. Unlike the old "ichthyodorulites," however, the spines of the Sihtridce have their bases modified for articulation with another bone, and they are not simply hollow and implanted in the flesh. The " Siluroids " are also remarkable for their resemblance to certain of the extinct Ganoid fishes (e.g., Pterichthys, Coccosteus, &c.), caused by the fact that the head is protected with an exoskeleton of dermal bones. The largest European species is the Silurus glanis of the Swiss lakes, and of various European rivers. Another remarkable member of this family is the Malapterurus of the Nile and West Coast of Africa, which is endowed with electrical powers. SUB -ORDER B. ANACANTHINI. — This sub -order is distin- guished by the fact that the fins are entirely supported by " soft " rays, and never possess " spiny " rays ; whilst the ven- tral fins are either wanting, or, if present, are placed under the throat, beneath or in advance of the pectorals, and supported by the pectoral arch. The swim-bladder may be wanting, but when present it does not communicate with the oesophagus by a duct. As in the preceding order, the Anacanthini are divided into two groups, distinguished by the presence or absence of the ventral fins. In the first of these groups (Apoda) are only a few fishes, of which one of the most familiar examples is the little Sand-eel (Ammodytes lancea\ which occurs on all our coasts. In the second group (Sub-brachiata), in which ventral fins exist, are the two important families of the Gadidcz and Pleuronectida. The Gadidcz or Cod family, comprising the Haddock, Whiting, Ling, and Cod itself, is of great value to man, most of its members being largely consumed as food. In the Pleuronectidcz or Flat-fishes are comprised the Sole, Plaice, VERTEBRATA: FISHES. 487 Turbot, Halibut, Brill, and others, in all of which there is a very curious modification in the form of the body. The body, namely, in all the Flat-fishes (fig. 263) is very much compressed Fig. 263. — Pleuronectidse. Rhombus fanctatus. Natural size (after Gosse). from side to side, and is bordered by long dorsal and anal fins. When young, the body is symmetrical, the eyes are bilaterally situated, and the animal swims in a vertical position. Soon, the habit of lying on one side (sometimes the right, but more commonly the left, side) is commenced, and then the eye upon the lower side is gradually translated to the upper side of the head \ this translation being effected by an actual movement of the lower eye, or by its passing through the at that time soft tissues of the head, a partial twisting of the cranial bones assisting to bring about the final result. When adult, both eyes are situated upon one side of the head (fig. 263), and the fish now keeps this side uppermost, and is dark-coloured on this aspect; whilst the opposite side, on which it rests, is white. From this habit of the Flat-fishes of resting upon one flat surface, the sides are often looked upon as the dorsal and ventral surfaces of the body. This, however, is erroneous, as they are shown by the position of the paired fins to be truly the lateral surfaces of the body. The mouth has its two sides unequal, the pectorals are rarely of the same size, the ventrals look like a continuation of the anal fin, and the branchiostegal rays are six in number. SUB-ORDER C. ACANTHOPTERI. — This sub-order is charac- terised by the fact that one or more of the first rays in the fins are in the form of true, unjointed, inflexible, " spiny " rays. The exoskeleton consists, as a rule, of ctenoid scales. The ventral fins are generally beneath or in advance of the pecto- rals, and the duct of the swim-bladder is invariably obliterated. 488 MANUAL OF ZOOLOGY. This sub-order comprises two families : — a. The Pharyngognathi, in which the inferior pharyngeal bones are an- chylosed so as to form a single bone, which is usually armed with teeth. The family is not of much importance, the only familiar fishes belonging to it being the "Wrasses" (CyclolabridcE). b. The Acanthopteri veri, characterised by having always spiny rays in the first dorsal fin, and usually in the first rays of the other fins, whilst the inferior pharyngeal bones are never anchylosed into a single mass. This family includes many subordinate groups, and may be regarded as, on the whole, the most typical division of the Teleostean fishes. It will not be necessary, however, to do more than mention as amongst the more import- ant fishes contained in it, the Perch family (Percida), the Mullets (Mugi- lidce), the Mackerel family (Scomberidtz), the Gurnards (Sclerogenidce}, the Gobies (Gobiidce), the Blennies (Blenniida:}, and the Anglers (Lopkiida). The Percidce form by far the most important member of this group, and are distinguished by having ctenoid scales, the operculum and prse-operculum variously armed with spines, teeth on the vomer and palate as well as on the jaws, and the branchiostegal rays from five to seven in number. SUB-ORDER D. PLECTOGNATHI. — This sub -order is charac- terised by the fact that the maxillary and prsemaxillary bones are immovably connected on each side of the jaw. The endo- skeleton is only partially ossified, and the vertebral column often remains permanently cartilaginous. The exoskeleton is in the form of ganoid plates, scales, or spines. The ventral fins are generally wanting, and the air-bladder is destitute of a duct. The most remarkable fishes of this section are the Trunk-fishes (Ostraci- ontidce, in which the body is entirely enclosed, with the exception of the tail, in an immovable case, composed of large ganoid plates, firmly united to one another at their edges. Besides the Trunk-fishes, this section also includes the File-fishes (fialis- tidce) and the Globe-fishes (Gymnodontidce). SUB-ORDER E. LOPHOBRANCHII. — This is a small and unim- portant group, mainly characterised by the peculiar structure of the gills, which are arranged in little tufts upon the branchial arches, instead of the comb-like plates of the typical Bony Fishes. The endoskeleton is only partially converted into bone, and the exoskeleton, by way of compensation, consists of ganoid plates. The swim-bladder is destitute of an air-duct. The singular Sea-horses (Hippocampidcc), now kept in most of our large aquaria, belong to this sub-order, but the only point about them which re- quires notice is the curious fact that the males in this family are provided with a sort of marsupial pouch, into which the eggs are placed by the female, and to which the young, when hatched, can retire if threatened by any danger. This singular cavity is only found in the males, and is situated at the base of the tail. More familiar than the Sea-horses are the Pipe-fishes (Syngnathid characterised by having a " heart, with a contractile bulbus arteriosus, intestine, with a spiral valve, and optic nerves non-decussating." 504 MANUAL OF ZOOLOGY. CHAPTER LVI. DISTRIBUTION OF FISHES IN TIME. THE geological history of fishes presents some points of pe- culiar interest. Of all the classes of the great sub-kingdom Vertebrata, the fishes are the lowest in point of organisation. It might therefore have been reasonably expected that they would present us with the first indications of vertebrate life upon the globe ; and such is indeed the case. After passing through the enormous group of deposits known as the Lauren- tian, Huronian, Cambrian, and Lower Silurian formations — representing an immense lapse of time, during which, so far as we yet know with certainty, and leaving the " Conodonts " out of sight, no vertebrate animal had been created — we find in the Upper Silurian rocks the first traces of fish. The ear- liest of these, in Britain, are found in the base of the Ludlow rocks (Lower Ludlow Shale), and belong to the Placoganoid genus Pteraspis. Also in the Ludlow rocks, but at the summit of their upper division, are found fin-spines and shagreen, probably belonging to Cestraciont fishes — that is to say, to fishes of as high a grade of organisation as the Elasmobranchii. So abundant are the remains of fishes in the next great geo- logical epoch — namely, the Devonian or Old Red Sandstone — that this period has frequently been designated the " Age of Fishes." Most of the fishes of the Old Red Sandstone belong to the order Ganoidei, but the order Dipnoi appears to be also represented. In the Carboniferous and Permian rocks which close the Palaeozoic period, most of the fishes are still Ganoid, but the former contain the remains of many Elasmobranchii. At the close of the Palaeozoic and the commencement of the Mesozoic epoch, the Ganoid fishes begin to lose that predom- inant position which they before occupied, though they con- tinue to be represented through the whole of the Mesozoic and Kainozoic periods up to the present day. The Ganoids, therefore, are an instance of a family which has endured through the greater part of geological time, but which early attained its maximum, and has been slowly dying out ever since. Towards the close of the Mesozoic period (in the Cre- taceous period) the great family of the Teleostean or Bony Fishes is for the first time known certainly to have made its appearance. The families of the Marsipobranchii and Pharyn- gobranchii have not left, so far as is known, any traces of their VERTEBRATA: FISHES. 505 existence in past time. Judging from analogy, however, it is highly probable that both of these must have had a vast antiquity, and it is not impossible that the so-called " Cono- donts " of the Palaeozoic period may yet be shown to be the teeth of fishes allied to the Lampreys. Leaving these unrepresented orders out of consideration, the following are the chief facts as to the geological distribution of the other great groups : — I. Ganoidei. — As far as is yet known with certainty, the oldest representatives of the fishes belong to this order. The order is represented, namely, in the Upper Silurian rocks by the remains of at least four genera. In the Devonian rocks, or Old Red Sandstone, the Ganoids attain their maxi- mum both in point of numbers and development. The Placoganoid division of the order is represented by the singular genera Pterichthys, Cephalaspis (fig. 267), Pteraspis, and Coccosteus. The Lepidoganoid division of the order is now also abundantly represented for the first time, the genera Dipterus, Osteolepis (fig. 265), Glyptolepis, Holoptychius, Dipla- canthus, and many others, belonging to this section. As regards the further distribution of the Placoganoids, the section of the Ostracostci, characterised by the great development of the cephalic buckler, appears to have died out at the close of the Devonian period. The other section, however — namely, that of the Sturionidce — is represented in the Liassic period (Mcsozoif) by the genus Chondrosteus, and in the Eocene (Kainozoic] by a true Sturgeon, the Acipenser toliapicus. The Lepidoganoids continue from the period of the Old Red in great profusion, and they are represented by very many genera in the Carboniferous and Permian rocks. In the earlier portion of the Mesozoic period — /.rma1 Hvr» ities;// Phalanges of fingers. StltUtCQ by the normal t\\O bones, the radius and ulna (fig. 324, r, u), of which the radius is the smaller and more slender, and the ulna the larger and stronger. The ulna and radius are followed inferiorly by the bones of the wrist or carpus ; but these are reduced in number to two small bones, one radial and one ulnar, " so wedged in between the anti- brachium and metacarpus as to limit the motions of the hand to those of abduction and adduction necessary for the folding up and expansion of the wing ; the hand is thus fixed in a VERTEBRATA: AVES. 581 state of pronation ; all power of flexion, extension, or of rota- tion, is removed from the wrist-joint, so that the wing strikes firmly, and with the full force of the contraction of the de- pressor muscles, upon the resisting air " (Owen). One other bone of the normal carpus (namely, the " os magnum ") is present, but this is anchylosed with one of the metacarpals. There are thus really three carpal bones, though only two appear to be present. (According to Morse, there is a fourth carpal, which early anchyloses with the base of the meta- carpal of the middle finger.) The carpus is followed by the metacarpus, the condition of which agrees with that of the carpal bones. The two outermost of the normal five meta- carpals are absent, and the remaining three are anchylosed — together with the os magnum — so as to form a single bone (fig. 324, m). This bone, however, appears externally as if formed of two metacarpals united to one another at their extremities, but free in their median portion. The metacarpal bone which corresponds to the radius is always the larger of the two (as being really composed of two metacarpals), and it carries the digit which has the greatest number of phalanges. This digit corresponds with the " index " finger, and it is com- posed of two, or sometimes three, phalanges (fig. 324, p}. At the proximal end of this metacarpal, at its outer side, there is generally attached a single phalanx, constituting the so-called "thumb" (fig. 324, /), which carries the " bastard-wing," and is sometimes furnished with a claw. The digit which is attached to the ulnar metacarpal corresponds to the middle finger, and never consists of more than a single phalanx (fig. 324). In the Apteryx and the Cassowary there is only one complete digit to the hand. As regards the structure of the posterior extremity or hind- limb, the pieces which compose the innominate bones (namely, the ilium, ischium, and pubes) are always anchylosed with one another ; and the two innominate bones are also always an- chylosed, by the medium of the greatly-elongated ilia, with the sacral region of the spine. In no living bird, however, with the single exception of the Ostrich, are the innominate bones united in the middle line in front by a symphysis pubis. The stability of the pelvic arch, necessary in animals which sup- port the weight of the body on the hind-limbs alone, is amply secured in all ordinary cases by the anchylosis of the ilia with the sacrum. As in the higher Vertebrates, the lower limb (fig. 325, A) consists of a femur, a tibia and fibula, a tarsus, metatarsus, and phalanges ; but some of these parts are considerably obscured 582 MANUAL OF ZOOLOGY. by anchylosis. The femur or thigh-bone (fig. 325, A, f) is generally very short, comparatively speaking. The chief bone of the leg is the tibia (/), to which a thin and tapering fibula (r) Fig. 325. — A, Hind-limb of the Loon (Colymbus glacialis) — after Owen : z" Innominate bone ; f Thigh-bone or femur ; t Tibia, with the proximal portion of the tarsus an- chylosed to its lower end ; r Fibula ; m Tarso-metatarsus, consisting of the distal portion of the tarsus anchylosed with the metatarsus ; p p Phalanges of the toes. B, Tail of the Golden Eagle; s Ploughshare-bone, carrying the great tail-feathers. is anchylosed. The upper end of the fibula, however, articu- lates with the external condyle of the femur. The ankle-joint is placed, as in Reptiles, between the proximal and distal portions of the tarsus. The proximal portion of the tarsus, consisting of two bones, representing the astragalus and cal- caneum or the former only, is undistinguishably amalgamated with the lower end of the tibia. The distal portion of the tarsus is anchylosed with the second, third, and fourth meta- tarsals to constitute the most characteristic bone in the leg of the Bird — the " tarso-metatarsus " (m). In most of the long- legged birds, such as the Waders, the disproportionate length of the leg is given by an extraordinary elongation of the tarso- metatarsus. VERTEBRATA: AVES. 583 The tarso-metatarsus is followed inferiorly by the digits of the foot. In most birds the foot consists of three toes directed forwards and one backwards — four toes in all. In no wild bird are there more than four toes, but often there are only three, and in the Ostrich the number is reduced to two. In all birds which have three anterior and one posterior toe, it is the posterior thumb or hallux (that is to say, the innermost digit of the hind-limb) which is directed backwards ; and it invariably consists of two phalanges only, its metatarsal being incomplete and united as a rule to the tarso-metatarsus by ligament only. The most internal of the three anterior toes (the "index") consists of three phalanges; the next ("middle") has four phalanges ; and the outermost toe (" annularis ") is made up of five phalanges (fig. 325, A). This increase in an arithmetical ratio of the phalanges of the toes, in proceeding from the inner to the outer side of the foot, obtains in almost all birds, and enables us readily to detect which digit is sup- pressed, when the normal four are not all present. Variations of different kinds exist, however, in the number and disposi- tion of the toes. In many birds — such as the Parrots — the outermost toe is turned backwards, so that there are two toes in front and two behind, whilst in the Trogons the inner toe is turned back with the hallux, and the outermost toe is turned forwards. In others, again, the outer toe is normally directed forwards, but can be turned backwards at the will of the ani- mal. In the Swifts, on the other hand, all four toes are pres- ent, but they are all turned forwards. In many cases — especially amongst the Natatorial birds — the hallux is wholly wanting, or is rudimentary. In the Emeu, Cassowary, Bus- tards, and other genera, the hallux is invariably absent, and the foot is three-toed. In the Ostrich both the hallux and the next toe (" index ") are wanting, and the foot consists simply of two toes, these being the third and fourth digits. The toes are mechanically flexed during the sleep of most birds by the action of a special muscle which runs from the pubis outside the knee to join one of the flexors of the toes (the flexor digi- torum perforatus), and which is therefore put on the stretch whenever the leg is bent upon the thigh. The digestive system of birds comprises the beak, tongue, gullet, stomach, intestines, and cloaca. Teeth are invariably wanting in living birds, and the jaws are encased in horn, con- stituting the bill. Dental papillae, sometimes covered with a cap of dentine, have, however, been observed in the embryos of some Parrots. In the extinct Odontopteryx, moreover, the osseous substance of the jaws is prolonged into tooth -like 584 MANUAL OF ZOOLOGY. processes of two sizes; and in the Odontornithes of the Cre- taceous period the jaws are furnished with true teeth implanted in distinct sockets. The form of the bill varies enormously in different birds, and it is employed for holding and tearing the prey, for prehensile purposes, for climbing, and in some birds as an organ of touch. In these last-mentioned cases the bill is more or less soft, and is supplied with filaments of the fifth nerve. In many birds, too, in which the bill is not soft, the base of the upper mandible is surrounded by a circle of naked skin, constituting what is called the " cere," and this, no doubt, serves also as a tactile organ. The tongue of birds can hardly be looked upon as an organ of taste, since it is generally cased in horn like the mandibles. It is, in fact, principally employed as an organ of prehension ; but in some cases — as in the Parrots — it is soft and fleshy, and then, doubtless, is to some extent connected with the sense of taste. It is essentially composed of a prolongation of the hyoid bone (the glosso-hyal), which is sheathed in horn, and is variously serrated or fringed. Salivary glands are invariably present, but they are rarely of large size (they are very large in the Woodpeckers and Swifts), and they have often a very simple structure. In accordance with the structure of the neck, the gullet in birds is usually of great length, and it is generally very dilat- able. In the carnivorous, or Raptorial, and in the granivorous birds, the gullet (fig. 326, o] is dilated into a pouch, which is situated at the lower part of the neck, just in front of the merry - thought. This is what is known as the " crop " or "ingluvies" (<:), and it may be either a mere dilatation of the tube of the gullet, or it may be a single or double pouch. The food is detained in the crop for a longer or shorter time, according to its nature, before it is subjected to the action of the proper digestive organs. The oesophagus, after leaving the crop, shortly opens into a second cavity, which is known as the " proventriculus " or " ventriculus succenturiatus " (/). This is the true digestive cavity, and its mucous membrane is richly supplied with gastric follicles which secrete the gastric juice. The proventriculus, however, corresponds, not with the whole stomach of the Mammals, but only with its cardiac, portion \ and it opens into a second muscular cavity, which corresponds to the pyloric division of the Mammalian stomach. The gizzard (g) is situated below the liver, and forms in all birds an elongated sac, having two apertures above, of which one conducts into the duodenum, or commencement of the small intestine, whilst the other communicates with the pro- VERTEBRATA: AVES. 585 ventriculus. The two chief forms of gizzard are exhibited respectively by the Raptorial birds, which feed on easily- digested animal food, and the Rasores and some of the Nata- d Fig. 326. — Digestive System of the common Fowl (after Owen), o Gullet : c Crop ; p Proventriculus ; g Gizzard; sm Small intestine; k Intestinal caeca; / Large in- testine ; cl Cloaca. tores, which feed on hardly-digested grains. In the birds of Rapine the gizzard scarcely deserves the name, being, as a rule, nothing more than a wide membranous cavity with thin walls. In the granivorous birds, whose hard food requires crushing, the gizzard is enormously developed ; its lining coat is formed of a thick, horny epithelium, and its walls are ex- tremely thick and muscular. This constitutes a grinding apparatus, like the stones of a mill ; whilst the " crop " or cesophageal dilatation may be compared to the " hopper " of a mill, since it supplies to the gizzard " small successive quan- tities of food as it is wanted" (Owen). Supplementing the action of the muscular walls of the gizzard, and acting in the place of teeth, are the small stones or pebbles, which, as is so well known, so many of the granivorous birds are in the habit of swallowing with their food, or at other times. In fact, there can be no doubt but that the gravel and pebbles swallowed by these birds are absolutely essential to existence, since the 586 MANUAL OF ZOOLOGY. gizzard, without this assistance, is unable properly to triturate the food. The intestinal canal extends from the gizzard to the cloaca, and is, comparatively speaking, short The secretions of the liver and pancreas are poured into the small intestine as in Mammals. The commencement of the large intestine is al- most always furnished with two long "caeca" or blind tubes, the length of which varies a good deal in different birds (fig. 326, k). They are sometimes wanting (Parrots, &c.), or there may be only one ; and their exact function is uncertain ; though they are most probably connected partly with digestion and partly with excretion. The large intestine is always very short — seldom more than a tenth part of the length of the body — and it terminates in the "cloaca" (fig. 326, d). This is a cavity which in all birds receives the termination of the rectum, the ducts of the generative organs, and the ureters ; and serves, therefore, for the expulsion of the faeces, the gene- rative products, and the urinary secretion. Respiration is effected in Birds more completely and actively than in any other class of the Vertebrata, and as the result of this, their average temperature is also higher. This extensive development of the respiratory process is conditioned by the the fact that, in addition to true lungs, air is admitted into a greater or less number of the bones, and into a number of cavities — the so-called air-receptacles — which are distributed through various parts of the body, and which are present in all birds except the Apteryx. By this extensive penetration of air into various parts of the body, the aeration of the blood is effected not only in the lungs, but also over a greater or less extent of the systemic circulation as well ; and hence in Birds this process attains its highest perfection. The cavities of the thorax and abdomen are not separated from one another by a complete partition, the diaphragm being mostly only present in a rudimentary form. The lungs are two in number, of a bright-red colour, and spongy texture. They are confined to the back of the thorax, extending along each side of the spine, from the second dorsal vertebra to the kidney. They differ from the lungs of the Mammals in not being freely suspended in a pleural membrane. The pleura, on the other hand, is reflected only over the anterior surface of the lungs. The bronchi, or primary divisions of the windpipe (fig. 327), diminish in size as they pass through the lung, by giving off branches, which, in turn, give off the true air-vesicles of the lung. When the bronchial tubes reach the surface of the lung, they open, by a series of distinct apertures, into a series of VERTEBRATA: AVES. 587 " air-sacs." These are a series of membranous sacs formed by the continuation of the lining membrane of the bronchi, and supported by reflections of the serous membrane of the thora- cico-abdominal cavity. There are nine proper air-sacs — two abdominal (the only ones present in some birds, such as the Pen- guin), two in the hinder part of the thorax, two in the front part of the thorax, two on the sides of the neck, and one between the branches of the furculum. The air-cells not only greatly reduce the specific gravity of birds, and thus fit them for an aerial life, but also assist in the mechanical work of respiration, and must also greatly promote the aeration of the blood. In connection with the air-re- ceptacles, arid as an extension of them, is a series $f cavities occu- pying the interior of a greater or less number of the bones, and also containing air. In young birds these air-cavities do not ex- ist, and the bones are filled with i -. .- i rm marrow, as in the Mammals. The extent also to which the bones are " pneumatic " varies greatly in different birds. In the Penguin — which does not fly — all the bones contain marrow, and there are no air-cavities. In the large Running birds (Cursores), such as the Ostrich, the bones of the leg, pelvis, spine, ribs, skull, and sternum, are pneumatic ; but the bones of the wings, with the exception of the scapular arch, are without air - cavities, and permanently retain their marrow. All birds which fly, with the singular exception of the Woodcock, have air admitted to the humerus. In the Pelican and Gannet, all the bones of the skeleton, except the phalanges of the toes, are penetrated by air ; and in the Horn- bill even these are pneumatic. The functions discharged by the air-cavities of the bones appear to be much the same as those of the air-receptacles — namely, that of diminishing the specific gravity of the body and subserving the aeration of the blood. Fig. 327. — Lung of Goose (after Owen). a Main bronchus dividing into sec- ondary branches as it enters the lung, these giving off smaller branches, the openings of which are seen on the back of the bronchial tubes : b b Bris- tles passed from the bronchi through the apertures on the surface of the lung by which the bronchi communi- cate with the air-receptacles. MANUAL OF ZOOLOGY. The heart in all Birds consists of four chambers, two auricles and two ventricles. The right auricle and ventricle, constitut- ing the right side of the heart, are wholly concerned with the pulmonary circulation ; the left auricle and ventricle, forming the left side of the heart, are altogether occupied with the systemic circulation; and no communication normally exists i in adult life between the two sides of the heart. In all essen- ; tial details, both as regards the structure of the heart itself I and the course taken by the circulating fluid, Birds agree with Mammals. The venous blood — namely, that which has circu- lated through the body — is returned by the venae cavae to the right auricle, whence it is poured into the right ventricle. The right ventricle propels it through the pulmonary artery to the lungs, where it is aerated, and becomes arterial. It is then sent back by the pulmonary veins to the left auricle, whence it is driven into the left ventricle. Finally, the left ventricle pro- pels the aerated blood to all parts of the body through the great systemic aorta. The chief difference between Birds and Reptiles as regards the course of circulation is, that in the Birds the two sides of the heart are completely separated frorJI one another, the blood sent to the lungs being exclusively venous, whereas that which is sent to the body is exclusively arterial. In Reptiles, on the other hand, the pulmonary and systemic circulations are connected together either in, or in the immediate neigh- bourhood of, the heart; so that mixed venous and arterial blood is propelled both through the lungs and through every part of the body. In accordance with their extended respiration and high mus- cular activity, the complete separation of the greater and lesser circulations, and the perfect structure of the heart, Birds main- tain a higher average temperature than is the case with any other class of the Vertebrata. This result is also to a consid- erable extent conditioned by the non-conducting nature of the combined down and feathers which form the integumentary covering of Birds. The urinary organs of Birds consist of two elongated kid- neys, and two ureters, but there is no urinary bladder. The ureters open into the cloaca, or into a small urogenital sac which communicates with the cloaca. As regards the reproductive organs, the males have two testes placed above the upper extremities of the kidneys, and their efferent ducts (vasa deferentid] open into the cloaca along- side of the ureters. A male organ (penis] may or may not be present, but there is no perfect urethra. The female bird VERTEBRATA: AVES. 589 is provided with only one ovary and oviduct — that of the left side — the corresponding organs of the right side being rudimentary or absent. The oviduct is very long and tor- tuous, and the egg, during its passage through it, receives the albuminous covering which serves for the nutrition of the embryo, and which is known as the " white " of the egg. The lower portion of the oviduct is dilated, and the egg receives here the calcareous covering which constitutes the "shell." Finally, the oviduct debouches into the cloaca, into which the egg, when ready, is expelled. The further development of the chick is secured by the^ process of "incubation" or brooding, for which birds are peculiarly adapted, in consequence of the high temperature of their bodies. The development of the ovum belongs to physiology, and does not concern us here. It is sufficient to notice the means by which the chick is ultimately enabled to escape from the egg. When development has reached a stage at which ex- ternal life is possible, it is of course necessary for the chick to be liberated from the egg, the shell of which is often extremely hard and resistant. To this end the young bird is provided with a^little calcareous knob on the point of the upper mandible, arm by means of this it chips out an aper- ture through the shell, at its blunt end. Having effected its purpose, this temporary appendage then disappears, without leaving a trace behind. The state of the young upon exclusion from the egg is very different in different cases, and in accordance with this, Birds have been divided into the two sections of the Autophagi or Aves prcecoces, and the Heterophagi or Aves altrices. In the Autophagi the young bird is able to run about and help itself from the moment of liberation from the egg. In the Hetero- phagi the young are born in a blind and naked state, unable to feed themselves, or even to maintain unassisted the neces- sary vital heat. In these birds, therefore, the young require to be brooded over and fed by the parents for a longer or shorter period after exclusion from the egg. As regards their nervous system, the brain of Birds is rela- tively larger, especially as regards the size of the cerebrum proper, than the brain of Reptiles, but the chief mass of the latter consists of the corpora striata, and it does not cover the cerebellum. The cerebellum is less developed than in Mammals, the lateral lobes and Pons Varolii being rudiment- ary. The corpus callosum is absent, and the surface of the cerebral hemispheres is devoid of convolutions. As regards the organs of the senses, the eyes are always well 59O MANUAL OF ZOOLOGY. developed, and in no bird are they ever rudimentary or absent. The chief peculiarity of the eye is that the cornea forms a segment of a much smaller sphere than does the eyeball pro- per, so that the anterior part of the eye is obtusely conical, whilst the posterior portion is spheroidal. Another peculiarity is that the form of the eye is maintained by a ring of from thirteen to twenty bony plates, which are placed in the anterior portion of the sclerotic coat. Eyelashes are almost universally absent ; but in addition to the ordinary upper and lower eye- lids, Birds possess a third membranous eyelid — the " membrana nictitans " — which is sometimes pearly-white, sometimes more or less transparent.* This third eyelid is placed on the inner side of the eye, and possesses a special muscular apparatus, by which it can be drawn over the anterior surface of the eye, like a curtain, moderating the intensity of the light. As to the organ of hearing, most birds possess no external ear or concha, by which sounds can be collected and transmitted to the internal ear. In some birds, however, as in the Ostrich and Bustard, the external meatus auditorius is surrounded by a circle of feathers, which can be raised and depressed at will. The Nocturnal Birds, also, especially Owls, have the external meatus auditorius protected by a musculo-membranous valve, which foreshadows the cartilaginous concha of the majority of Mammals. The external nostrils in Birds are usually placed on the sides of the upper mandible, near its base, in the form of simple perforations, which sometimes communicate from side to side by the deficiency of the septum narium. In the singular Apteryx of New Zealand, the nostrils are placed at the extreme end or tip of the elongated upper mandible. Some- times the nostrils are defended by bristles, and sometimes by a scale (Rasores). Taste must be absent, or almost absent, in the great majority of birds, the tongue being nothing more than a horny sheath surrounding a process of the hyoid bone, and serving for deglutition or to seize the prey. In the Parrots, however, the tongue is thick and fleshy, and some perception of taste may be present. Touch or tactile sensibility, too, as already remarked, is very poorly developed in Birds. The body is entirely, or almost entirely, covered with feathers ; the anterior limbs are converted into wings, and rendered thereby * The membrana nictitans is simply a fold of the conjunctiva on the inner side of the eye. It occurs in some Fishes (e. g.t some Sharks), in some Reptiles and Amphibians, in Birds, in Monotremes and Marsupials, and in some of the higher Mammals. In Man, however, in Monkeys, and in most of the higher Mammals, it is rudimentary, and constitutes the so-called "plica semilunaris." VERTEBRATA: AVES. 591 useless as organs of touch ; and the posterior limbs are covered with horny scales or feathers. The bill, certainly, officiates as an organ of touch, but it cannot possess any acute sensibility, as in most birds it is encased in a rigid horny sheath. In some birds, however, such as the common Duck, the texture of the bill is moderately soft, and it is richly supplied with filaments of the fifth nerve ; so that in these cases the bill doubtless constitutes a tolerably efficient tactile organ. The " cere," too, or the fleshy scale found at the base of the bill in some birds, is in all probability also used as a tactile organ. The last anatomical peculiarity of Birds which requires notice is the peculiar apparatus known as the " inferior larynx," or " syrinx," by which the song of the singing birds is con- ditioned. " The air-passages of birds commence by a simple superior larynx, from which a long trachea extends to the an- terior aperture of the thorax, where it divides into the two bronchi, one for each lung. At the place of its division, there exists in most birds a complicated mechanism of bones and cartilages, moved by appropriate muscles, and constituting the true organ of voice ; this part is termed the inferior larynx " (Owen). The inferior larynx may be developed from the trachea only, before the division of this tube into the bronchi ; or, it may be developed wholly from the bronchi; or, last- ly, and more commonly, it may be developed at the junction of the trachea and bronchi and out of both. The structure of the vocal apparatus is extremely complicated, and there is no necessity for entering upon it here. It is to be remem- bered, however, that those modifications of the voice which constitute the song of birds, are produced in a special and complex cavity placed at, or near, the point where the trachea divides into the two bronchi, and not in a true larynx situated at the summit of the windpipe. The syrinx is wanting in a few birds (e.g., the RatilcB). Lastly, the trachea of birds is always of considerable proportionate length, and it is often twisted or dilated at intervals, this structure, doubtless, having something to do with the production of vocal sounds. Before passing on to the consideration of the divisions of Birds, a few words may be said as to the migration of birds. In temperate and cold climates comparatively few birds remain constantly in the same region in which they were hatched. Those which do so remain, are called " permanent birds " (aves manentes). Other birds, such as the Woodpeckers, wander about from place to place, without having any fixed direction. These are called " wandering birds " (aves erraticcz), and their irregular movements are chiefly conditioned by the scarcity or 592 MANUAL OF ZOOLOGY. abundance of food in any particular locality. Other birds, however, at certain seasons of the year undertake long jour- neys, usually uniting for this purpose into large flocks. These birds — such as the swallows, for instance — are properly called " migratory birds " (aves migratorice). The movements of these birds are conditioned by the necessity of having a cer- tain mean temperature, and consequently they leave the cold regions at the approach of winter, and return again for the warmer season. DISTRIBUTION OF BIRDS IN TIME. — As regards the geolo- gical distribution of Birds, there are many reasons why we should be cautious in reasoning upon merely negative evi- dence, and more than ordinarily careful not to infer the non- existence of birds during any particular geological epoch, simply because we can find no positive evidence for their presence. As Sir Charles Lyell has well remarked, "the powers of flight possessed by most birds would insure them against perishing by numerous casualties to which quadrupeds are exposed during floods;" and "if they chance to be drowned, or to die when swimming on water, it will scarcely ever happen that they will be submerged so as to become pre- served in sedimentary deposits," since, from the lightness of the bones, the carcass- would remain long afloat, and would be liable to be devoured by predaceous animals. As, with a few utterly trivial exceptions, all the deposits in which fossils are found have been laid down in water, and more especially as they are for the most part marine, these considerations put forward by Sir Charles Lyell afford obvious ground against the anticipation that the remains of Birds should be either of frequent occurrence or of a perfect character in any of the fossiliferous rocks. In accordance with these considerations, as a matter of fact, most of the known remains of birds are either fragmentary or belong to forms which were organised to live a terrestrial life, and were not adapted for flight. The earliest remains which have been generally referred to birds are in the form of footprints (fig. 328) impressed upon certain sandstones in the valley of the Connecticut River in the United States. These sandstones are almost certainly Triassic ; and if the ornithic character of these footprints be admitted, then Birds date their existence from the commence- ment of the Mesozoic period, and, for anything we know to the contrary, may have existed during the Palaeozoic epoch. In the fact that these footprints are three-toed, and are cer- tainly the tracks of bipedal animals, we have strong evidence that they were produced by birds. On the other hand, it is VERTEBRATA: AVES. 593 certain that some of the Deinosaurian Reptiles of the Triassic period walked on their hind-legs only, and it is highly probable that they were the real authors of the prints in question. If Fig. 328. — Footprint supposed to belong to a Bird. Triassic Sandstones of Connecticut. truly ornithic, we must admit the existence in the Triassic period of a considerable number of kinds of Birds, some of which must have been of colossal dimensions, but this question does not admit of final settlement at present. The first unmistakable remains of a bird have been found in the Solenhofen Slates of Bavaria, of the age of the Upper Oolites. A single unique specimen, consisting of bones and feathers, but unfortunately without the skull, is all that has until recently been discovered; and it has been named the Archczopteryx macrura. The characters of this singular and aberrant bird, which alone constitutes the order Saururce, will be given in treating of the order. In the Cretaceous rocks, not only do we find the remains of Birds of the type now existing, but we meet with the ex- traordinary " Toothed Birds" (Odontornithes), which seem not to have survived this period, and which will be spoken of in greater detail later on. Lastly, almost all the existing orders of Birds are represented by the time we reach the middle of the Tertiary period, and the distribution and characters of the more important fossil forms will be treated of in discussing the several orders in question. 2 P 594 MANUAL OF ZOOLOGY. CHAPTER LXIV. DIVISIONS OF BIRDS. i. GENERAL DIVISIONS OF AVES. 2. CURSORES. OWING to the extreme compactness and homogeneity of the entire class Aves, conditioned mainly by their adaptation to an aerial mode of life, the subject of their classification has been one of the greatest difficulties of the systematic zoologist. By Professor Huxley the birds are divided into the following three orders : — 1. SAURUR^E. — In this order the caudal vertebrae are nume- rous, and there is no ploughshare -bone. The tail is longer than the body, and the metacarpal bones are not anchylosed together. This order includes only the single extinct bird the Archceopteryx macrura, in which the long lizard-like tail is only the most striking of several abnormalities. 2. RATIT/E. — This order comprises the Running birds, which cannot .fly, such as the Ostriches, Emeus, and Casso- waries. It is characterised by the fact that the sternum has no median ridge or keel for the attachment of the great pec- toral muscles. The sternum is therefore raft-like (from the Lat. rates, a raft), hence the name of the order. 3. CARINAT^:. — This comprises all the living Flying birds, and is characterised by the fact that the sternum is furnished with a prominent median ridge or keel (carina); hence the name of the order. The numerous subdivisions of this order are mainly founded upon the structure of the palate. As regards the above primary divisions of Birds, there can be no doubt as to their being very natural sections. A fourth division, of equal rank, must now be added for the extinct Odontornithes, and all four divisions may be best considered as sub-classes, and not as mere orders* No difficulty, also, is to be found in subdividing the Ratita, Saururce, and Odon- tornithes ; but there is the greatest difficulty in establishing natural subdivisions amongst the great sub-class of the Cari- nattz, since this includes by far the greater number of known birds. The classification of this group proposed by Professor Huxley (like that of Mr Garrod), descending, as it does, to a great number of secondary groups, is not only too compli- * If this view be taken, it will be advisable to give the name of Sauror- nithcs to the sub-class, and to reserve the title of Saururce for the order. VERTEBRATA : AVES. 595 cated to be available for the general student, and therefore to be useful in a work of the present nature ; but it is intended primarily for the anatomist, and not for the systematic zoolo- gist. The latter requires a classification based upon all the characters, internal and external ; whereas the morphological method of arrangement selects simply single structures in the anatomy of the bird, and fixes its place by means of these. Thus, Prof. Huxley founds his classification of the Carinatcz upon the structure of the bony palate. This method of classi- fication, however, though of the greatest use to the compara- tive anatomist, cannot be made to coincide with any purely zoological mode of arrangement. It has, therefore, seemed preferable for the purpose of the present work to adhere, with some modifications, to the old classification of Birds, which is to be found, in one form or another, in almost all the'Standard works on ornithology. In using, however, the six old orders of this system, with their familiar and long current names, the student must remember that they bear very unequal values. Some of them — such as the Natatores, Grallatores, Rasores, and Raptores — are essentially natural groups, and cannot be seriously mutilated in any system of classification. The order Insessores is also, in the main, a natural one, though it in- cludes groups which can only be artificially connected with it. On the other hand, the order Scansores is a conspicuously unnatural one, and is retained here simply as a matter of convenience. SUB-CLASS I. RATITVE. ORDER CURSORES. — The first order of Birds is that of the Cur sores, or Runners, comprising the Ostriches, Rheas, Cassowaries, Emeus, and the singular Apteryx of New Zealand. The Cur sores are characterised by the rudimentary condition of the wings, which are so short as to be useless for flight, and by the compensating length and strength of the legs. In accordance with this condition of the limbs, many of the bones retain their marrow, and the sternum (fig. 329, A) is destitute of the prominent ridge or keel, to which the great pectoral muscles are attached (hence the name of Ratitcz, applied by Huxley to the order). In the Ostrich, the pubic bones of the pelvis unite to form a symphysis pubis, as they do in no other bird ; and in all, the pelvic arch possesses unusual strength and stability. The legs are extremely robust and powerful, and the hind-toe is entirely wanting, except in the Apteryx, in which it is rudimen- tary. The anterior toes are two or three in number, and are MANUAL OF ZOOLOGY. provided with strong blunt claws or nails. The plumage pre- sents the remarkable peculiarity that the barbs of the feathers, instead of being connected to one another by hooked barbules, as is usually the case, are remote and disconnected from one another, presenting some resemblance to hairs. The order Cursores may be divided into the two sections of the Struthionida and the Apterygidcc — the former characterised by the absence of the hallux, and comprising the Ostrich, Rhea, Emeu, and Cassowary, with several extinct forms ; the latter comprising only the Apteryx of New Zealand, and char- acterised by the possession of a rudimentary hallux. The African Ostrich (Struthio camelus] occurs in the desert plains of Africa and Arabia, and is the largest of all living birds, attaining a height from six to eight feet. The South African Ostrich is often considered as a distinct species, under the name of S. australis. The head and neck are nearly naked, and the quill -feathers of the wings and tail have their barbs wholly disconnected, constituting the ostrich-plumes of commerce. The legs are extremely strong, and are terminated by two toes only, these consisting respectively of four and five phalanges, showing that it is the hallux and the innermost toe which are wanting. The internal one of the two toes is much the larger, and is clawed ; the outer toe is small and clawless. The pubic bones (fig. 329, B) are united in a ventral sym- physis, and the wing is furnished with a long humerus. The Ostriches run with extraordinary speed, and can outstrip the fastest horse. They are polygamous, each male consorting with several females, and they generally keep together in larger or smaller flocks. The eggs are of great size, averaging three pounds each in weight ; and the hens lay their eggs in the same nest, this being nothing more than a hole scratched in the sand. The eggs appear to be hatched mainly by the exertions of both parents, relieving each other in the task of incubation, but also partly by the heat of the sun.* The American Ostriches or Rheas are much smaller than the African Ostrich, and have the head feathered, whilst the feet (fig. 329, E) are furnished with three toes each. The wings are rudimentary, and the phalanges are plumed and terminated by a spur. They inhabit the great plains of South America, and are polygamous. Three species are known, extending from Patagonia to Peru, but each inhabiting its own specific area. The Emeu (Dromaius Novce-Hollandia] is exclusively found * Mr Sclater, however, states that the duty of incubation is entirely taken by the males. VERTEBRATA : AVES. 597 in the Australian continent, and nearly equals the African Ostrich in size, attaining a height of from five to seven feet. The feet are furnished with three toes each, and the head is Fig- 329- — Morphology of Cursores. A, Sternum of the Ostrich (Struthio camelus) : s Scapula ; c Coracoid. B, Side view of the pelvis of the Ostrich : i Ilium ; / Pubis ; is Ischium ; / Femur. C, Foot of Apteryx australis. D, Tarso-metatarsus of the Apteryx, showing the hallux placed high up on its posterior surface. E, Foot of the Rhea americana. < feathered. The throat, however, is naked, and the general plumage resembles long hairs, the feathers hanging down on both sides of the body from a central line or parting which runs down the middle of the back. The Emeus are mono- gamous, and the eggs are dark green in colour. The male Emeu is smaller than the female, and undertakes all the duties of incubation. Two varieties, or species, of the Emeu are known — one on the eastern and the other on the western side of Australia. The last living group of the Struthionidce. is that of the Cas- sowaries, best represented by the Galeated Cassowary (Casu- arius galeatus), which inhabits the Moluccan Islands and New Guinea, and was first brought alive to Europe by the Dutch. It stands about five feet in height, and possesses a singular horny crest upon its head. The head and neck are naked, with pendent wattles, the wing has a short humerus, and the feet have three toes each. The general plumage is black, and the feathers more or less closely resemble hairs. The wings are rudimentary, each with five naked pointed quills. The male is much the smaller, and sits upon the eggs. Besides 598 MANUAL OF ZOOLOGY. the Galeated Cassowary, other species have been described from the Malayan Archipelago and North Australia, at least nine species being now known to exist in all. The second section of the Cursorial birds is that, of the Ap- terygidcz, comprising only the singular "Kiwis" (Apteryx] of New Zealand. The beak in the Apteryx is long, slender, and slightly curved, the tip being obtuse, and the nostrils placed at the extremity of the upper mandible. The legs are com- paratively short, and there is a rudimentary hind-toe or hallux, forming a kind of spur, furnished with a claw (fig. 329, C and D). The wings are entirely rudimentary, and are quite con- cealed by the feathers, each terminating in a sharp claw. The feathers are long and narrow, and the tail is short and incon- spicuous. The species of Apteryx are wholly confined to New Zealand, and are nocturnal in their habits, living upon insects and worms. Four species have been described, of which A. australis (fig. 330) is the best known. As regards the distribution of the Cursores in time, it seems Fig. 330. — Apteryx australis. (Gould.) probable that some of the footprints of the Connecticut Trias (if ornithic at all) have been produced by birds belonging to this group. Leaving these doubtful instances out of sight, the Eocene Tertiary has yielded the first certain traces of Cursorial birds (the Dasornis of the London Clay). The most interesting VERTEBRATA: AVES. 599 remains of Cur sores have, however, been found in the Post- Tertiary deposits of the southern hemisphere, and more espe- cially in New Zealand. In this island have been found the remains of a number of large wingless birds, which form the family of the Dinornithida, of which Dinornis (fig. 331) itself is the most important genus. All the members of this group (Dinornis, Palapteryx, &c.) are large Cursorial birds, the wings being useless for flight, and furnished with a rudimentary hume- Fig. 331.— Skeleton of Dinornis elephantopus, greatly reduced. Post-Pliocene. New Zealand. (After Owen.) rus. The hallux is wanting (Dinornis} or present (Palapteryx). The largest species is the Dinornis giganteus, one of the most gigantic of living or fossil birds, the tibia measuring a yard in length, and the total height being at least ten feet. Another species, the Dinornis elephantopus (fig. 331), though not stand- 6OO MANUAL OF ZOOLOGY. ing more than about six feet in height, was of an even more ponderous construction — " the framework of the skeleton being the most massive of any in the whole class of Birds," whilst ''the toe-bones almost rival those of the Elephant" (Owen). The feet in Dinornis were furnished with three toes, and are of interest as presenting us with an undoubted bird big enough to produce the largest of the footprints of the Triassic Sand- stones of Connecticut. New Zealand has now been so far explored, that it seems questionable if it can retain in its re- cesses any living example of Dinornis ; but it is certain that species of this genus were alive during the human period, and survived up to quite a recent date. Not only are the bones very numerous in certain localities, but they are found in the most recent and superficial deposits, and they still contain a considerable proportion of animal matter ; whilst in some in- stances bones have been found with the feathers attached, or with the horny skin of the legs still adhering to them. Charred bones have been found in connection with native " ovens ; " and the traditions of the Maories contain circumstantial accounts of gigantic wingless Birds, the " Moas," which were hunted both for their flesh and their plumage. In Madagascar, bones have been discovered of a bird as large as, or larger than, the Dinornis giganteus, which has been described under the name of the ALpiornis maximus. With the bones have been found eggs measuring from thirteen to fourteen inches in diameter, and computed to be as big as three ostrich-eggs, or one hundred and forty-eight hen's eggs. Though generally referred to the Cursores, ALpiornis has been sometimes regarded as a gigantic member of the Raptores. Lastly, the Post-tertiary deposits of Australia have yielded the remains of an extinct Struthious bird allied to the Emeu, which has been described under the name of Dromaomis. CHAPTER LXV. SUB-CLASS II. CARINAT&. NATATORES, GRALLATORES, AND RASORES. ORDER I. NATATORES (Palmipedes}. — The order of the Natatorts, or Swimmers, comprises a number of Birds which are as much or even more at home in the water than upon VERTEBRATA: AVES. 6oi the land. In accordance with their aquatic habit of life, the Natatores have a boat- shaped body, usually with a long neck. The legs are short, and placed behind the centre of gravity of the body, this position enabling them to act admirably as paddles, at the same time that it renders the gait upon dry land more or less awkward and shuffling. In all cases the toes are "webbed" or united by membrane to a greater or less extent (fig. 332, A). Fig. 332. — Natatores. A, Foot of Cormorant (Phalacrocorax) ; B, Beak of the Bean-goose (A nser segetum). In many instances the membrane or web is stretched com- pletely from toe to toe, but in others the web is divided or split up between the toes, so that the toes are fringed with membranous borders, but the feet are only imperfectly webbed. As their aquatic mode of life exposes them to great reductions of temperature, the body of the Natatorial birds is closely covered with feathers, and with a thick coating of down next the skin. They are, further, prevented from becoming wet in the water by the great development of the coccygeal oil-gland, by means of which the lustrous plumage is kept constantly lubricated and waterproof. They are usually polygamous, each male consorting with several females; and the young are hatched in a condition not requiring any special assistance from the parents, being able to swim and procure food for themselves from the moment they are liberated from the egg. The Natatores are divided into the following four families : — Fam. i. Brevipennatce. — In this family of the Swimming birds the wings are always short, and are sometimes useless as organs of flight, the tail is very short, and the legs are placed very far back, so as to render terrestrial progression very difficult or awkward. The family includes the Penguins, Auks, Guillemots, Divers, and Grebes. In the Penguins (Spheniscidce) the wings are completely rudimentary, without quills, and covered with a scaly skin. They are useless as far as flight is 602 MANUAL OF ZOOLOGY. concerned, but they are employed by the bird as fins, enabling it to swim under water with great facility, and they are also used on the land as fore-legs. The feet are webbed, and the hinder toe is rudimentary or wanting. The Penguins live gregariously in the seas of the southern hemisphere, on the coasts of South Africa and South America, especially at Tierra del Fuego, and in the solitary islands of the South Pacific. When on land the Penguins stand bolt upright, and as they Fig. 333. — Jackass Penguin (Spheniscus demersus). usually stand on the shore in long lines they are said to present a most singular appearance. The best-known species are the Jackass Penguin (Spheniscus demersus) of the Falkland Islands, and the King Penguin (Aptenodytes Patagonica) of the Straits of Magalhaens. Some Penguins have the extraordinary habit of forming no nest, but of carrying their egg about with them in a temporary pouch of the abdominal integument. In the Auks (Alcidtf) the wings are better developed than in the Penguins, and they contain true quill-feathers ; but they are VERTEBRATA: AVES. 603 still short as compared with the size of the body, and are of more use as fins than for flight. The Great Auk or Gare-fowl ( Aka impennis) is remarkable for being one of the birds which appear to have become entirely extinct within the human period, having been, in fact, destroyed by man himself. It abounded at one time on both the American and European sides of the North Atlantic, and used to visit the shores of Scotland in summer for the purpose of breeding. The Little Auk (Mergulus alle) occurs still in abundance in the seas of northern regions. Other well-known members of this group are the Razor-bill, the Puffins (Fratercula arctica], and the Guillemots ( Urid). The Guillemots have a short tail, narrow and pointed wings, short feet, and no hallux. Like the other members of the family they inhabit northern and polar regions. In the Divers {ColymbidcK}^ comprising the true Divers and the Grebes, the power of flight is pretty well developed, but the bird still is much more active in the water, swimming or diving, than on land. The Grebes are not uncommon in Britain, and are largely killed for making muffs, collars, and other articles of winter dress. They have the membrane between the toes deeply incised. They haunt the sea as well as lakes and rivers, and swim and dive admirably. In the Divers proper the front toes are completely united by a mem- brane. The Northern Diver or Loon (Colymbus glacialis) is a familiar example, and is found on the coasts of high northern latitudes. Fam. 2. Longipennatce. — This family of Natatores is charac- terised by the well-developed wings, the pointed, sometimes knife-like, sometimes hooked bill, and by never having the hallux united with the anterior toes by a membrane. The following are the more important groups coming under this head : — a. Laridce, or Gulls and Terns, having powerful wings, a free hinder toe, and the three anterior toes united by a membrane. The Gulls form an exceedingly large and widely distributed group of birds ; and the Terns or Sea-swallows are equally beautiful, if not quite so common. The Terns are distin- guished by their long and pointed wings, forked tail, and comparatively -'short legs. They fly with great rapidity over the surface of the sea, from which they pick up their food. b. Procellaridce, or Petrels, closely resembling the true Gulls, but having a rudimentary hinder toe, and having the upper mandible strongly hooked. The smaller species of Petrel are well known to all sailors under the name of Storm-birds and Mother Carey's Chickens. They are nocturnal or crepuscular 604 MANUAL OF ZOOLOGY. in their habits, breed in holes in the rocks, lay but one egg, and are almost all of small size and more or less sombre plumage. The largest member of the group is the gigantic Albatross (Diomedea exulaus], not uncommonly found far from land in both the northern and southern oceans. The Albatross sometimes measures as much as fifteen feet from the tip of one wing to that of the other, and the flight is powerful in proportion. Pam. 3. TotipalmatcB, characterised by having the hinder toe or hallux more or less directed inwards, and united to the innermost of the anterior toes by a membrane (fig. 332, A). In this family are the Pelicans, Cormorants, Gannets, Frigate- birds, Darters, and others. They all fly well, and have short legs, and amongst them are almost the only Natatorial Birds which ever perch upon trees. The Pelicans (Pdicanidcz) are large birds, which subsist on fish, and are found in Europe, Asia, Africa, and the New World. They sometimes measure as much as from ten to fifteen feet between the tips of the wings, and most of the bones are pneumatic, so that the skeleton is extremely light. The lower mandible is composed of two flexible branches which serve for the support of a large "gular" pouch, formed by the loose unfeathered skin of the neck. The fish captured by the bird are temporarily deposited in this pouch, and the parent birds feed their young out of it. The bill is long and straight, and the upper mandible is strongly hooked at the tip. In the Cormorants (Phalacrocorax) there is no pouch be- neath the lower mandible, but the skin of the throat is very lax and distensible; the nail of the middle toe is serrated. They are widely distributed over the world, one species being very abundant in many parts of Europe. The Gannets (Sula) have a compressed bill, the margins of which are finely crenate or toothed. They occur abundantly on many parts of the coasts of northern Europe, one of the most noted of their stations being the Bass Rock at the mouth of the Firth of Forth. Another species (Sula variegata) is of greater import- ance to man, as being one of the birds from the accumulated droppings of which guano is derived. The Frigate - birds (Tachypetes) are chiefly remarkable for their extraordinary powers of flight, conditioned by their enormously long and powerful wings and long forked tail. They occur on the coasts of tropical America, and are often found at immense distances from any land. The Tropic -birds (Phaeton) inhabit inter- tropical regions, and are found far out at sea. They have short feeble feet, and long pointed wings. VERTEBRATA: AVES. 605 The Darters or Snake-birds (Plotus] are somewhat aberrant members of this group, characterised by their elongated necks and long pointed bills. They occur in America, Africa, and Australia, and catch fish by suddenly darting upon them from above. Fam. 4. Lamellirostres. — The last family of the Natatores is that of the Lamellirostres, including the Ducks, Geese, Swans, and Flamingoes, and characterised by the form of the beak (figs. 332 and 334), which is flattened in form and Fig. 334. — A, Head of the Grey Lag Goose ; B, Foot of the domestic Goose. covered with a soft skin. The edges of the bill are further furnished with a series of transverse plates or lamellae, which form a kind of fringe or " strainer," by means of which these birds sift the mud in which they habitually seek their food. The bill is richly supplied with filaments of the fifth nerve, and doubtless serves as an efficient organ of touch. The feet are furnished with four toes, of which three are turned forwards, and are webbed, whilst the fourth is turned backwards, and is free. The trachea in the males is often enlarged or twisted in its lower part, and co-operates in the production of the pecu- liar clanging note of most of these birds. The body is heavy, and the wings only moderately developed. The groups of the Ducks (Anatidcz), Geese (Anserince), and Swans (Cygnidcz), are too familiar to require much special notice. The Anatidce, or true Ducks, have the hallux furnished with a 606 MANUAL OF ZOOLOGY. very narrow membranous lobe, and the laminae of the upper mandible generally projecting. As examples may be taken the Mallards and Teals (Boschas}, the Widgeons (Mareca), the Shoveller (Anas), and the Pin- tail Ducks (Dafila). The Sea- ducks (Fuligulina) frequent the sea chiefly, and have the hallux furnished with a wide membranous lobe. Good examples are the Eider-duck (Somaterid), the Surf-duck (Oidemia), the Canvass-back Duck and Pochard (Fuligula), and the Golden- eye (Clangula). The Anserince are distinguished from the Ducks chiefly by their stronger and longer legs, and comparatively shorter wings. Good examples are the Grey Lag (Anser ferus), the Canada Goose (A. canadensis), the Bean-goose (A. segetum), and the Snow-goose (A. hyperboreus) . All the domesticated varieties of Geese appear to be undoubtedly descended from the " Grey Lag " Goose, a common wild species which is found in marshy districts in Europe generally, in Northern Africa, and as far east as Persia. In the Swans the neck is extremely long, and the legs are short. In the Hooper Swan (Cy gnus ferns] the sternal keel is double, and forms a cavity for the reception of a convoluted portion of the trachea. This is not the case, however, with the Mute Swan (C. olor], the Black Swan (C. atratus\ or the Trumpeter Swan (C buccinator], all well-known members of the group. The Flamingoes, however, forming the group of the Phxnicop- teridce, require some notice, if only for the fact that the legs are so long and slender that they have often been placed in the order Grallatores on this account. The three anterior toes, however, are webbed or completely united by membrane, and the bill is lamellate, so that there can be little hesitation in leaving the Flamingo in its present position amongst the Nata- tores. The bill is singularly bent, both mandibles being sud- denly curved downwards from the middle. The common Flamingo (Phcenicopterus ruber) occurs abundantly in various parts of southern Europe. It stands between three and four feet in height, the general plumage being rose-coloured, the wing-coverts red, and the quill-feathers of the wings black. The tongue is fleshy, and one of the extravagances of the Romans during the later period of the Empire was to have dishes composed solely of Flamingoes' tongues. Other species occur in South America and Africa. As regards the distribution of the Natatores in time, the earliest traces of the order are found in the Cretaceous rocks. In deposits of this age in the United States, Professor Marsh VERTEBRATA: AVES. 607 has exhumed the bones of several forms (Graculavus and Laornis) ; and other forms (Cimolornis) have been described from the Cretaceous of Europe. In the Eocene Tertiary are found several Natatorial birds, the most interesting of which are the Gastornis Parisiensis and Agnopterus of the Paris basin, the former being apparently a huge and wingless goose, whilst the latter is allied to the Flamingoes. Under this order also probably comes the extraordinary fossil bird, recently described by Professor Owen, from the London Clay (Eocene) of Sheppey under the name of Odontopteryx toliapicus. In this singular bird (fig. 335) the alveolar margins of both jaws are furnished with tooth-like denticulations, which differ from true teeth in being actually parts of the osseous substance of the jaw itself, with which they are continuous. They are of triangular or compressed conical form, and are of two sizes, the larger ones resembling canines. From the consideration of all the discovered remains of this bird, Professor Owen con- Fig. 335. — Skull of Odontopteryx toliapicus, restored. (After Owen.) eludes that " Odontopteryx was a warm - blooded feathered biped, with wings ; and further, that it was web-footed and a fish-eater, and that in the catching of its slippery prey it was assisted by this Pterosauroid armature of its jaws." Upon the whole, Odontopteryx would appear to be most nearly allied to the Anatidce, but the denticulation of its jaws is an entirely unique character. Leaving the Eocene, the Miocene and later Tertiary de- posits have yielded the remains of numerous Swimming Birds, as has also the Post-tertiary ; but no special interest attaches to any of these, unless the great Cnemiornis of the Quaternary of New Zealand be rightly referred here, since this has the peculiarity of having been unable to fly. ORDER II. GRALLATORES. — The birds comprising the order of the GrallatoreS) or Waders, for the most part frequent the banks of rivers and lakes, the shores of estuaries, marshes, 6o8 MANUAL OF ZOOLOGY. lagoons, and shallow pools, though some of them keep almost exclusively to dry land, preferring, however, moist and damp situations. In accordance with their semi-aquatic amphibious habits, the Waders are distinguished by the great length of their legs ; the increase in length being mainly due to the great elon- gation of the tarso-metatarsus. The legs are also unfeathered from the lower end of the tibia downwards. The toes are elon- gated and straight (fig. 336, A), and are never completely palmate, though sometimes semi-palmate. There are three anterior toes, and usually a short hallux, but the latter may be wanting. The wings are long, and the power of flight usually considerable ; but the tail is short, and the long legs are stretched out behind in flight to compensate for the brevity of the tail. The body is generally slender, and the neck and beak usually of con- siderable length (fig. 336, B). They are sometimes polygam- Fig. 336. — Grallatores. A, Leg and foot of the Curlew ; B, Head of Snipe ; C, Beak of the Avocet. ous, sometimes monogamous, and the young of the former are able to run about as soon as they are hatched. The most typical Waders — those, namely, which are semi- aquatic in their habits — spend most of their time wading about in shallow waters or marshes, feeding upon small fishes, worms, shell-fish, or insects. Others, such as the Storks, live mostly upon the land, and are more or less exclusively vegetable- feeders. The Grallatores are divided into the four families of the Macrodactyli, the Cultirostres, the Longirostres, and the Pressi- rostres. Fam. i. Macrodactyli. — In this family the feet are furnished VERTEBRATA: AVES. 609 with four elongated, sometimes lobate, toes, and the wings are of moderate or less than average size. In many of their char- acters a considerable number of the birds of this family ap- proach the Rasorial birds, and differ from the true Waders. The beak is mostly short, rarely longer than the head, and is compressed from side to side, or wedge-shaped. The legs are strong and not particularly lengthy ; but the toes are often of great length, and are furnished with long claws. The neck is not very long, and the tail is very short. Some of them are strictly aquatic in their habits, and, like the Coots, approach in many respects to the Natatores; others, again, are exclusively terrestrial. The most familiar members of this family are the Rails (Rallus], Water-hens (Gallinula), the Coots (Fulica), and the Jacana (Parra jacana). The Water-hens and Coots are aquatic or semi-aquatic, swimming and diving with great ease. In the Coots the toes are semi-palmate, being bordered by membranous lobes, like the toes of the Grebes, but the toes are not fringed in the Gallinules. Amongst the Coots should probably be placed the Notornis (Owen), long supposed to be extinct, but recently proved to be still living in the Middle Island of New Zealand. The Notornis is much larger than the ordinary Coots, and is remarkable in the fact that, like many extinct and some living New Zealand birds, the wings are so rudimentary as to be useless for flight. The true Rails, comprising the common Water-rail (Rallus aquaticus], and the Land- rail or Corn-crake ( Crex pratensis) of Britain, and the Marsh-hen (Rallus elegans), and Virginian Rail (R. Virginianus) of North America, live almost exclusively on land, though the first of these usually frequents damp or marshy places. In the Jacanas, lastly, the feet are furnished with excessively long and slender toes, which enable the bird to run about upon the leaves of aquatic plants; whilst the carpus is armed with formidable spurs. They are natives of South America, Africa, and India. Closely allied to the Jacanas are the Screamers (Palamedea) of South America, of which the Horned Screamer (P. cornuta) is the best known. It has a long frontal horn, and has spurs implanted on the edge of the wing. JFam. 2. Cultirostres. — In this family of the Grallatores are some of the most typical and familiar forms contained in the entire order. The bill in this family is long — usually longer than the head — and is compressed from side to side ; the legs are long and slender, having a considerable portion of the tibiae unfeathered ; and the feet have four toes, which are usually connected to a greater or less extent at their bases by 2Q 6 10 MANUAL OF ZOOLOGY. membrane. In this family are the Cranes, Herons, Stork, Ibis, Spoonbill, and others of less importance. The Cranes (Gruida) are large and elegant birds, and are chiefly remarkable for their long migrations, which were noticed by many classical authors. In these journeys the Cranes usually fly in large flocks, led by a single leader, so that the whole assemblage assumes a wedge-like form; or they fly in long lines. The common Crane (Grus cinered] breeds in the north of Europe and Siberia, and migrates southwards at the approach of winter. The Numidian Crane or Demoiselle in- habits Asia and Africa, the Stanley Cranes (Anthropoides) are natives of the East Indies, and the Crowned Cranes (jBalearica) are African. In many respects the Cranes are more nearly allied to the Rails than to the Herons. The Herons (Ardeidte) are familiarly known to every one in the person of the common Grey or Crested Heron (Ardea cinerea, fig. 337). It was one Fig. 337. — Crested "RvcoTi (Ardea cinerea). Europe. of the birds most generally pursued in the now almost extinct sport of falconry. Various species of Heron are found over the whole world, both in temperate and hot climates. Here, also, belong the various species of Night Heron (Nycticorax\ the Bitterns (Botaurus), and the Boat-bills (Cancroma). VERTEBRATA : AVES. 6ll The Ibises (Tantalince] form a group of beautiful birds, species of which occur in all the warm countries of the world. They are distinguished by their metallic colours, long, cylin- drical, curved bill, and more or less naked head. One, the Ibis religiosa, was regarded by the ancient Egyptians as a deity, and was treated with divine honours, being often embalmed along with their mummies, or figured on their monuments. The Storks (CiconiruB) are large birds, of which one, the common Stork (Ciconia alba), is rarely found in Britain, but occurs commonly on the Continent, where it is often semi- domesticated. The Storks live in marshes, and feed on frogs, fishes, &c. Nearly related to the true Storks are the gigantic Marabout (Mycteria Marabou) and Adjutant (M. Argala] of Africa and India, which possess a sausage-shaped appendage in front of the neck. The Spoonbills (Plataleadce) are also large birds, very like the Storks, but the bill is flattened out so as to form a broad spoon -like plate. The common White Spoonbill (Platalea leucorodid] is found commonly on the Continent, but is of very rare occurrence in Britain. Fam. 3. Longirostres. — The third family of Waders is that of the Longirostres, characterised by the possession of long, slender, soft bills, grooved for the perforations of the nostrils (fig- S36, B). The legs are sometimes rather short, sometimes of great length; the toes are of moderate length, and the hallux is usually short, and is sometimes absent. The bill in these birds serves as an organ of touch, being used as a kind of probe to feel for food in mud or marshy soil. To fulfil this purpose, the tip of the bill is furnished with numerous filaments of the fifth nerve. They feed mostly upon insects and worms, and are not strictly aquatic in their habits, mostly frequenting marshy districts, moors, fens, the banks of rivers or lakes, or the shores of the sea. In this family of the Long-billed Waders are the various species of Snipe and Woodcock (Scolopaddce), the Sandpipers (Triuga), the Curlews (Numenius), the Turnstones (Strepsilas\ the Ruffs (Machetes), the Redshanks (Totanus), the Godwits (Limosa), and others which need no special notice. Fam. 4. Pressirostres. — The members of this family are characterised by the moderate length of the bill, which is seldom longer than the head, and has a compressed tip. The legs are long, but the toes are short, and are almost always partially connected together at their bases by membrane. The hallux is short, and is often wanting. The wings are long, and they can both fly powerfully and run with great swiftness. In 6l2 MANUAL OF ZOOLOGY. this section are two very distinct sub-families, the Charadriidce or Plovers, and the Otidce or Bustards. In the former of these the legs are long and slender, the toes are united at their bases by a small membrane, and the hind-toe is very small and raised above the ground, or is entirely wanting. In this group are the true Plovers and Lapwings ( Charadrius and Vanellus), the Pratincoles (Glareola], the Long-shanks (Himantopus\ the Oyster-catcher (Hamatopus\ and the Thick-knee ( (Edicnemus). In the Otidce or Bustards, the legs are long, and the toes are short and furnished with stout claws. The hinder toe or hallux is entirely wanting • and these birds are chiefly interesting from the affinities which they exhibit to the Rasores on the one hand, and to the Cursores (Ostrich, &c.) on the other. The wings, however, are of ample size, and the tail is comparatively long, the reverse being the case in the Cursores. The Bus- tards are entirely confined to the Old World, and two species were formerly not uncommon in Britain. They are found in plains and downs, and rarely fly, but run with great swiftness, using the wings to accelerate their course. They are polygam- ous, and the males are generally brighter and more variegated in plumage than the females. As regards their distribution in time, the earliest known remains of Grallatores have been found in the Cretaceous rocks of North America (Telmatornis and Palceotringa). The Eocene Ter,tiary of both Europe and North America has yielded the remains of Waders, one of the most remarkable being a gigantic Rail (Gypsornis] from the Paris basin. The later Tertiaries also contain the remains of various Grallatorial birds allied to, or identical with, living types. In the Post- tertiary deposits of Mauritius are found the bones of the Aphanapteryx, a large Ralline bird, allied to the living Ocy- dromus, but incapable of flight. It survived into the human period, and was exterminated at a comparatively late date. ORDER III. RASORES. — The third order of Carinate Birds is that of the Rasores, or Scratchers, often spoken of col- lectively as the " Gallinaceous " birds, from the old name of " Gallinae," given to the order by Linnaeus. The Rasores are characterised by the convex, vaulted upper mandible, having the nostrils pierced in a membranous space at its base. The nostrils are covered by a cartilaginous scale. Taking the Gallinacei as the type of the crder, the legs are strong and robust, mostly covered with feathers as far as the joint between the tibia and tarso-metatarsus. There are four toes, three in front and one be- Jiind, the latter being short, and placed at a higher level than the other toes. All the toes terminate in strong blunt claws suitable VERTEBRATA: AVES. 613 for scratching (fig. 338, A). The food of the Scratchers or Gallinaceous birds consists chiefly of hard grains and seeds, and in accordance with this they have a capacious crop and an extremely strong and muscular gizzard. They mostly nidificate, or build their nests, upon the ground, and the more typical members of the order are polygamous. The males take no part in either nidification or incubation, and the young are generally " precocious," being able to run about and provide themselves with food from the moment they quit the egg. The young of the Pigeons and Doves, however, are brought forth in a comparatively helpless condition. The wings in the A ^"^ Fig- 338.— Rasores. A, Foot of Fowl (Callus Bankiva) ; B, Head of Guinea-fowl. majority of the Rasores are more or less weak, and the flight is feeble and accompanied with a whirring sound. Many of the Pigeons, however, are capable of very powerful and sus- tained flight. The order Rasores is divided into two sub-orders, called re- spectively the Gallinacei and the Columbacei, or sometimes, from the characters of the sounds which they utter, the Clama- tores and the Gemitores. Stib-order i. Gallinacei or Clamatores. — This sub-order com- prises the typical members of the order Rasores, such as the common Fowls, Turkeys, Partridge, Grouse, Pea-fowl, and a number of allied forms. Its characters are therefore those of the order itself, but it is especially distinguished from the Columbacei by being less fully adapted for flight. The body is much heavier, comparatively speaking, the legs and feet are stronger, and the wings shorter and less powerful. On the whole, therefore, these birds are worse fliers than the Colum- bacei, and are better adapted for living upon the ground. The hallux (fig. 339, A) is elevated above the anterior toes, and merely touches the ground in walking. The back of the tarsus, too, is usually furnished in the males with a spur (calcar\ which is used as an offensive weapon, and has some- 614 MANUAL OF. ZOOLOGY. times been looked upon as a rudimentary toe.* Lastly, the Gallinacei are mostly polygamous, and the males are usually much more brilliantly coloured than the females, this being an adaptive modification of the plumage to meet this peculiarity in their mode of life, t The following are the most important families of the Gallinacei: — The Tetraonidcz, or Grouse family, com- prises the various spe- cies of Grouse (Tetrao\ the Ruffed Grouse (Bo- nasa), the Cock of the Plains ( Centrocercus), and the Ptarmigans (Lagopus). The Perdiridce, or Partridge family, com- prises the Partridges (Perdix\ the Francolins (Francolinus), the Quails ( Coturnix), the Mary- land Quail (Ortyx\ the B Tufted Quails (Lophor- Upper and under views of the foot of the /y-vA Rrc Wood-pigeon (Colnmba palumbiis). * '' The Phasianida, or Pheasant family, comprises the Turkeys and Guinea-fowl (Meleagrmce), the common Pheasant (Phasianus Cokhicus}, the Golden and Silver Pheasants, the common Fowl (Gallus domesticus), and the Pea-fowl (Pavonina). None of these birds — all of which can be domesticated, and most of which are of great value to man — are natives of this country, though they will all breed readily, and thrive even in confinement. The domestic Turkey (Meleagris gallopavo) is originally a native of North America, where it still occurs in a wild con- dition, having been brought to Europe about the beginning of the sixteenth century. The Guinea-fowl (Numida meleagris] is * In some cases (as in the Java Peacock) the female possesses spurs as well as the male; and sometimes (as in Polyplectrori] there are two or more spurs on each leg of the male. t The Guinea-fowl, Red Grouse, Ptarmigan, and Partridge are mono- gamous, in a state of nature at any rate. IJ Fig. 339.— A, Foot of Black-cock (Tetrao tetrix). nd C, VERTEBRATA: AVES. 615 originally an African bird. The common Pheasant (Phasianus Colchicus), though now regarded as an indigenous bird, truly belongs to Asia, and it is asserted that it was really brought to Europe from Colchis by the Greeks ; hence its specific name. The common Fowl is certainly not a native of Europe, and it is usually thought to be a native of Asia or of some of the Asiatic islands ; but its exact original habitat is uncertain, as is the species from which the domestic breeds are descended (commonly said to be the Galhis Bankiva of Java). The introduction of the Fowl into Europe is lost in the mists of antiquity, and it is wholly unknown whence the original stock may have been brought ; though there is really every ground for believing that the typical breed — the Game breed — is truly descended from the Jungle Cock, or Gallus Bankiva. The domestic Fowl has, however, been found to be a member of the Cave-fauna of France in the early Stone period, which would throw far back its alleged introduction from the East. The Pea-fowl (Pavo) are really natives of Thibet and Hindostan, and were originally brought to Greece by Alex- ander the Great. They were formerly much esteemed as food, but are now regarded merely from an ornamental point of view. The Pterodidce, or Sand-grouse, are confined to the Old World, being principally Asiatic and African, and in their long and pointed wings they make an approximation to the Pigeons. The Turniridce, or Bush- quails, on the other hand, make an approach to the Charadriidce. amongst the Grallatores. They are found in Europe, Africa, Asia, and Australia. The Megapodid&i or Mound-birds, belong to India and Aus- tralia, and have very large feet and long claws. They build immense mounds, often six or eight feet high, and twenty or thirty feet in diameter. They lay their eggs in the centre of these mounds at a depth of two or three feet, and leave them to be hatched by the heat produced by the fermentation of the vegetable matter of the mass. The Cracidce, or Curassows, are large heavy birds, allied to the preceding, belonging to Central and South America, and to a great extent arboreal in their habits. The best-known species is the crested Curassow (Crax alector) of Mexico and Brazil. Lastly, the Tinamidce, or Tinamous, form an aberrant group of the Gallinacei, with many remarkable features in their inter- nal organisation, and with the striking external character that the tail is exceedingly short or totally wanting. They inhabit South America, and are in many respects intermediate between 6l6 MANUAL OF ZOOLOGY. the Struthionidtf, and the true Galling, such as the Grouse. Many of the sutures of the skull are persistent, and the brain is very small. There is the lacertilian character that there exists a row of supra-orbital bones. Sub-order 2. Columbacd. — The second sub -order of the Rasores is that of the Columbacd or Gemitores, comprising the Fig. 340. — Columbidae. Rock-pigeon (Cohcmba livid). Doves and Pigeons, and often raised to the rank of a dis- tinct order under the name of Columba. The Columbacei are separated from the more typical members of the Rasores by being furnished with strong wings, so as to endow them with considerable powers of flight. In place, therefore, of being chiefly ground -birds, they are to a great extent arbo- real in their habits, and in accordance with this the feet are slender, and are well adapted for perching. There are four toes, three in front and one behind, and the former are never united towards their bases by a membrane, though the base of the outer toe is sometimes united to that of the middle toe. The hallux is articulated on the same plane as the other toes, and touches the ground in walking. Lastly, they are all monogamous, and pair for life ; in consequence of VERTEBRATA: AVES. 6l/ which fact, and of their being readily susceptible of domesti- cation, they present an enormous number of varieties, often so different from one another that they would certainly be de- scribed as distinct species if found in a wild state. It seems certain, however, that all the common domestic breeds of Pigeons, however unlike one another, are really descended from the Rock-pigeon (Columba lima\ which occurs wild in many parts of Europe, and 'has retained its distinguishing peculiarities unaltered for many centuries up to the present day. Finally, the young of the Columbacei are born in a naked and helpless state, whilst those of the Gallinacei are "preco- cious," and can take care of themselves from the moment of their liberation from the egg. Of the various living birds included in this section, the true Pigeons (Columbida) are too well known to require any de- scription ; but the Ground-pigeons (Gourida) depart to some extent from this type, being ground-loving birds, more closely allied to the ordinary Gallinacei. The Treronida, or Tree- pigeons, are exclusively found in the Old World, in its warmer parts, and are arboreal in their habits, living principally upon fruits. The Didunculidcz are a small group, comprising only the little Didunculus strigirostris of the Navigator Islands. In this curious bird the wings are well developed, enabling it to lead an arboreal life, and the upper mandible of the beak is strongly arched and hooked towards its tip. The Didunculus is of special interest as having certain relationships to the now extinct Dodo, the representative of the family Didida. The Dodo (Didus ineptus, fig. 341) formerly inhabited the island of Mauritius, in great numbers, but the last record of its occur- rence dates from the year 1681. It was a large and heavy bird, bigger than a swan, and entirely unlike the Pigeons in general appearance. The wings were rudimentary and completely useless as organs of flight. The legs were short and stout, the feet had four toes each, and the tail was extremely short, carrying, as well as the wings, a tuft of soft plumes. The beak (unlike that of any of the Columbacei except the little Didunculus strigirostris] was strongly arched towards the end, and the upper mandible had a strongly-hooked apex, not at all unlike that of a bird of prey. The Dodo owed its exter- mination to the fact that it was good to eat, and that it was unable to fly. At present all the known remains of this singular bird that exist are some old, but apparently faithful, oil-paintings, and a few fragmentary remains, to which explor- ations in the Recent deposits of the island have added a large number of bones. Allied to the Dodo, and, like it, incap- 6i8 MANUAL OF ZOOLOGY. able of flight, is the Solitaire (Pezophaps) of Rodriguez, a small island lying about 300 miles to the east of Mauritius. Its last recorded appearance was in the year 1693. It Fig. 341.— Skeleton of the Dodo (Didus ineptus], restored. (After Owen.) had longer legs than the Dodo, and its bill was less strongly arched. As regards the distribution of the Rasores in time, the order is not known to have made its appearance sooner than the Eocene Tertiary (the Palceortyx of the Paris basin). In the Miocene period occur the remains of both Gallinaceous and Columbaceous birds, one of the most noticeable of the former being a Turkey (Meleagris antiquns) from the Miocene of Colo- rado. The later Tertiary and Post-tertiary deposits have also yielded the bones of various Rasorial birds. VERTEBRATA: AVES. 619 CHAPTER LXVL SUB-CLASS C A RIN AT &— Continued. SCANSORES, INSESSORES, AND RAPTORES. ORDER IV. SCANSORES. — The order of the Scansorial or Climb- ing birds is easily and very shortly defined, having no other distinctive and exclusive peculiarity except the fact that the feet are provided with four toes, of which two are turned back- wards and two forwards. Of the two toes which are directed backivards, one is the hallux or proper hind-toe, and the other is the outermost of the normal three anterior toes. This arrange- ment of the toes (fig. 342, B) enables the Scansores to climb Fig. 342. — A, Skull of a Parrot (Psittacus erythacus). B, Foot of the same : a Hallux ; b Index ; c Middle toe ; d Outer or ring toe. (After Blanchard.) with unusual facility. Their powers of flight, on the other hand, are generally only moderate and below the average. Their food consists of insects or fruit. Their nests are usually made in the hollows of old trees, but some of them have the remarkable peculiarity that they build no nests of their own, but deposit their eggs in the nests of other birds. They are all monogamous. The order Scansores, as above defined, must be looked upon as a. purely artificial assemblage, comprising birds which pos- sess in common the peculiarity of a scansorial foot, but which otherwise are widely different The order is only retained here because it can hardly be dispensed with otherwise than by raising the three principal groups contained in it to the rank of separate orders (viz., the Cuculidce, Picidce, and Psittaridce). 620 MANUAL OF ZOOLOGY. The most important families of the Scansores are the Cuckoos (Cuculidce), the Woodpeckers and Wry-necks (Picida), the Par- rots (Psittaridce\ the Toucans (Rhampttastida), the Trogons ( Trogonidce), the Barbets {Buaonida), and the Plantain-eaters (MusophagidcB). The Cuculidcz, or Cuckoos, are chiefly remarkable for the extraordinary fact that many of them, instead of nidificating and incubating for themselves, lay their eggs in the nests of other birds. The only bird not belonging to this family which has the same " parasitic " habit, is the Cow-bunting (Molothrus pecoris} of the United States. As a rule, only one egg is de- posited in each nest, and the young Cuckoo which is hatched from it, is brought up by the foster-parent, generally at the expense of the legitimate offspring. The large Channel-bill (Scythrops Novce-Hollandice] is said to possess the same curious habit, but many species of this group build nests for themselves in the ordinary manner. Beside the typical Cuckoos (Cuculus) this group contains the American Cuckoos (Coccygus), the Anis (Crotophaga\ the Honey-guides (Indicator], and other less im- portant forms. The second family of the Scansores is that of the Picidce, and comprises the Woodpeckers and Wry-necks. These birds feed chiefly upon insects, and the tongue is very extensible, barbed at the point, and covered with a viscid secretion, so as to enable them to catch their prey by suddenly darting it out. The bill is strong and wedge-shaped, and the claws crooked. The tail- feathers terminate in points, and are unusually hard and stiff, assisting the bird in running up the trunks of trees. The Wood- peckers are widely distributed throughout both hemispheres, and the Wry-necks ( Yunx) are European. The next family is that of the Parrots (Psitfatidtz), the largest group of the Scansores, comprising several hundred species. The bill in the Parrots is large and strong, and the upper man- dible is considerably longer than the lower, and is hooked at its extremity (fig. 343). The bill is used as a kind of third foot in climbing, thus allowing the feet to be used in prehension. At the base of the upper mandible is a " cere," in which the nostrils are pierced. The tongue is soft and fleshy. The feet are especially adapted for climbing, some, however, of the. Par- rots moving about actively on the ground. The colours of the plumage are generally extremely bright and gaudy ; and they live for the most part upon fruits. The Psittacida are distri- buted throughout the tropics, and in the southern hemisphere as far south as the 52d parallel. They are monogamous, and VERTEBRATA : AVES. 621 make their nests in holes in trees, and in the rocks. Their natural voice is harsh and grating. The true Parrots (Pstttacus) are mostly inhabitants of tropical America, and their prevailing colour is green. Other well-known forms are African. The Cockatoos (Plyctolophus], the Love-birds (Agapornis), and the Lorikeets (Trichoglossus) belong to the Melanesian and Austra- lian province. The Lories (Lorius) inhabit the Melanesian province. The true Macaws (Araince) are exclusively Ameri- can ; and the true Parrakeets (Pezoporince) are exclusively con- fined to the eastern hemisphere, being especially characteristic of Australia. Fig- 343.— Head of Cockatoo. Among the more remarkable of the Psittacidtz may be men- tioned the singular "Kakapo" (Strigops habroptilus] of New Zealand, which makes an approach to the Owls. This curious Parrot differs from the ordinary members of the order in not being gregarious in its habits, in only being active by night, in forming burrows in the ground, in which it spends the day, and in being limited in its powers of flight. One species of Parrot (Lophopsittacus Mauritianus) has become extinct during the human period, and the Philip Island Parrot (pfestor productus}, of the New Zealand province, has not been known to occur since the year 1851. In the next family of the Scansores are the Toucans (Rham- phastidce), characterised by having a bill which is always very large, longer than the head, and sometimes of comparatively gigantic size (fig. 344). The mandibles are, however, to a very great extent hollowed out into air-cells, so that the weight of the bill is much less than would be anticipated from its size. 622 MANUAL OF ZOOLOGY. The tongue is very long, notched at its side, or feathered with delicate lateral processes. The Toucans live chiefly upon fruits, and are all confined to the hotter regions of South America, frequenting the forests in considerable flocks. The Trogons have short and weak feet, a short triangular bill, the gape bordered with strong bristles, and short wings. The plumage is soft and loose, and generally of the most gor- Fig. 344. — Head of Toucan. geous description. They inhabit the most retired recesses of the forests of the intertropical regions of both hemispheres, and show many decided points of affinity to the Goatsuckers. The Barbets (Bucconidtz] are South American, but also occur in Africa and in the Indian province. Lastly, the Plantain- eaters or Touracos (Musophagidce) are exclusively confined to Africa. The range of the Scansores in time does not appear to be extensive, the earliest known representative of the order being from the Lower Tertiary. The Eocene beds of Wyoming have yielded remains of a Woodpecker (Uintornis), and Parrots, Trogons, Cuckoos, and Woodpeckers are known to have lived during the later Tertiary and Post-tertiary periods. ORDER V. INSESSORES. — The sixth order of Birds is that of the Insessores, or Perchers — often spoken of as the Passeres, or " Passerine " Birds. They are denned by Owen as follows : " Legs slender, short, with three toes before and one behind, the two external toes united by a very short membrane" (fig. 345, E, F). " The Perchers form the largest and by far the most numer- ous order of birds, but are the least easily recognisable by dis- tinctive characters common to the whole group. Their feet, VERTEBRATA: AVES. 623 being more especially adapted to the delicate labours of nidi- fication, have neither the webbed structure of those of the Swimmers, nor the robust strength and destructive talons which characterise the feet of the Birds of Rapine, nor yet the extended toes which enable the Wader to walk safely over marshy soils and tread lightly on the floating leaves of aquatic Fig. 345. — A, Head of Hoopoe ( Upupa epops), showing the Tenuirostral type of beak. B, Head of Red-backed Shrike (Lanius collurio), showing the Dentirostral type of beak, C, Head of White-bellied Swift (Cypselus inelbd)^ showing the Fissirostral type of beak. D, Head of Corn-bunting {Einberiza iniliaria), showing the Coni- rostral type of beak. E, Foot of the Yellow Wagtail (Mo tori Ha sulphured). F, Foot of a Finch (Fringilld). plants ; but the toes are slender, flexible, and moderately elongated, with long, pointed, and slightly curved claws. 624 MANUAL OF ZOOLOGY. " The Perchers in general have the females smaller and less brilliantly coloured than the males ; they always live in pairs, build in trees, and display the greatest art in the construction of their nests. The young are excluded in a blind and naked state, and wholly dependent for subsistence during a certain period on parental care. The brain arrives in this order at its greatest proportionate size ; the organ of voice here attains its greatest complexity, and all the characteristics of the bird, as power of flight, melody of voice, and beauty of plumage, are enjoyed in the highest perfection by one or other of the groups of this extensive and varied order." The structure of the feet, then, gives the definition of the order, but the minor subdivisions are founded on the nature of the beak ; this organ varying in form according to the nature of the food, " which may be small or young birds, carrion, in- sects, fruit, seeds, vegetable juices, or of a mixed kind" (Owen). In accordance with the form of the beak, the Insessores have been divided into four great sections or sub-orders, known as the Conirostres^ Dentirostres, Tenuirostres, and Fissirostres. Sub-order i. Conirostres. — In this section of the Insessores the beak is strong and on the whole conical, broad at the base and tapering with considerable rapidity to the apex (fig. 345, D). The upper mandible is not markedly toothed at its lower margin. Good examples of the conirostral type of beak are to be found in the common Sparrow, Hawfinch, or Bullfinch. The greater number of the Conirostres are omnivorous; the remainder are granivorous, or feed on seeds and grains. The sub-order includes the families of the Horn-bills (Bncerotidcc), the Starlings (Sturnidce), the Crows (Corvida), the Cross-bills (Loxiadg), and the Finches and Larks (FrtngiUidct). In the Horn-bills the conirostral shape of the beak is masked, partly by its being of very great size, and partly by the fact that above the upper mandible is placed a hollow appendage like a kind of helmet. Both the beak and the appendage above it are rendered light by the presence of numerous air-cells. The Horn-bills are exclusively confined to the warm countries of the eastern hemisphere, and are the largest of all the Insesso- rial birds, sometimes attaining the size of a goose ; and they must be regarded as only provisionally placed in this order. They live on fruits, and make their nests in the holes of trees. The best-known species is the Rhinoceros Bird (Buceros rhino- ceros) of India and the Indian Archipelago. The family of the Corvidce, or Crows, is an extremely exten- sive one, and includes a large number of very dissimilar-look- VERTEBRATA: AVES. 625 ing birds, all characterised by their long, strong, and com- pressed beaks, the tip of the upper mandible being slightly hooked and more or less notched. In this family are the Jays (Gam4in&)\ the true Crows or Coruince (comprising the Rooks, Carrion-crows, Ravens, Jackdaws, Magpie, Chough, &c.), and the Birds of Paradise (Paradiseida}. These last differ considerably from the ordinary Corvida, but can hardly be separated as a distinct family. They are amongst the most beautiful of all birds, and are entirely confined to New Guinea and the neighbouring islands. They feed upon insects and fruit, and are largely destroyed for the sake of their feathers. The natives who capture them usually cut off their legs ; hence the notion formerly prevailed that the Birds of Paradise were destitute of these limbs. It is only the males which possess the brilliant plumage, the females being soberly dressed ; and in accordance with this fact, it is stated that the Birds of Par- adise are polygamous, being in this respect an exception to almost the entire order of the Insessores* " They are char- acterised by extraordinary developments of plumage, which are unequalled in any other family of birds. In several species large tufts of delicate, bright -coloured feathers spring from each side of the body, forming trains, fans, or shields ; and the middle feathers of the train are often elongated into wires, twisted into fantastic shapes, or adorned with the most brilliant metallic tints. In another set of species, the accessory plumes spring from the head, the back, or the shoulders ; whilst the intensity of colour and of metallic lustre displayed by their plumage, is not to be equalled by any other birds, except, perhaps, the Humming-birds, and is not surpassed by these." (Wallace.) The family of the Starlings (Sturnidce) is not separated from that of the Crows by any important characters. Besides our common Starlings, it includes a number of other more or less singular birds, of which the Bower-birds of Australia are per- haps the most peculiar. These curious birds have the habit of building very elaborate bowers, often very beautifully con- structed and of considerable size, in which they amuse them- selves and apparently make love to one another. These bowers are wholly independent of their nests, which they construct elsewhere. The last family of the Conirostres is that of the Fringittid&\ comprising the Finches, Linnets, and Larks. In these birds * The Humming-birds are thought to be polygamous, and this is cer- tainly the case with the Whydah Finch (Vidua). 2 R 626 MANUAL OF ZOOLOGY. the bill is stout and conical, with a sharp apex, but not having the upper mandible toothed. The toes are adapted for perch- ing, and are provided with long and curved claws, that of the hinder toe being usually longer than the rest. They are almost all monogamous, and they build more or less elaborate nests. In this family are the true Finches (Fringilla), the Sparrows, (Pyrgita), the Linnets and Goldfinches (Carduelis\ the Whydah Finches (Vidua), the Grosbeaks (Coccothraustes], the Bullfinches (Pyrrhuld), and many others, but their num- bers are so great that any further notice of them is im- possible here. It may be mentioned, however, that the Finches of the Old World are represented in the tropical parts of America by the Tanagers (Tana- grida), remarkable for their brilliant colours. Fig. 346. — Head of the common Bullfinch T'hp nnlv rfrrminincr mpvn (Pyrrhula vnlgaris), showing the coniros- L nC °mY remaining mein- trai beak. bers of the Conirostres which require notice are the Cross- bills (Loxiada?), which are sometimes placed with the Finches, and sometimes considered as a separate family. In these birds the structure of the beak is so peculiar that its conirostral character is completely masked, and it has been looked upon as a deformity. Both mandibles, namely, cross one another towards the tip, giving the entire bill a most remarkable ap- pearance. In point of fact, however, instead of being a defor- mity, the bill of the Cross-bills is a beautiful natural adapta- tion, enabling the bird with the greatest facility to tear in pieces the hard fir-cones, on the seeds of which it feeds. Sub-order 2. Dentirostres. — The birds in this section are characterised by the fact that the upper mandible is provided with a distinct notch in its lower margin near the tip (fig. 345, B). They all feed chiefly upon insects. This sub-order in- cludes the Shrikes (Laniidce), the Fly-catchers (Muscicapidce), the Thrushes (Merulida), the Tits (Paridce\ and the Warblers (Sylviadce). The Muscicapidce, including the numerous species of Fly- catchers, are the most insectivorous of the Dentirostres. The gape is wide and bordered with bristles, and the legs are short and weak. They are mostly sedentary, catching their prey from a fixed point. VERTEBRATA: AVES. 627 The Shrikes are highly predaceous birds, which in many respects make a close approach to the true Birds of Prey. They feed, however, mostly upon worms and insects, and only occasionally destroy small birds or mice. The great family of the Thrushes (Merulidce) comprises not only the true Thrushes, Fieldfares, and Blackbirds, but a number of exotic forms, of which the most familiar are the Orioles, so well known for their brilliant plumage and their beautifully-constructed nests. In the Sylviadce, amongst other forms, are the Wagtails (Motacillince) and the Pipits (Anthus), the Titmice, Robins, Hedge-sparrow, Stonechat, Redstarts, and other well-known British birds. The Titmice (Paridce) are often placed in the sub-order of the Conirostres. The Nightingale also belongs to this family. Sub-order 3. Tenuirostres. — The members of this sub-order are characterised by the possession of a long and slender beak, gradually tapering to a point (fig. 345, A). The toes are very long and slender, the hind-toe or hallux especially so. Most of the Tenuirostral birds live upon insects, and some of these present a near resemblance in many of their characters to the Dentirostres, but it is asserted that some live partially or wholly on the juices of flowers. The chief families of the Tenuirostres are the Creepers (Ctrikida)) the Honey -eaters (Meliphagidcz), the Humming- birds (Trochilidtz), the Sun -birds (Promeropida>\ and the Hoopoes ( Upuptda\ of which only the Creepers and Hum- ming-birds need any further notice. The family Certhidcz includes several familiar British birds, such as the little brown Creeper (Certhia familiaris), the Nuthatch (Sitta Europaa), and the Wrens (Troglodytes). With these are a number of exotic forms, of which the singular Lyre-birds of Australia are the most remarkable. The family of the Trochilida, or Humming-birds, includes the most fragile and brightly coloured of all the birds, some not weighing more than twenty grains when alive, and many exhibiting the most brilliant play of metallic colours. The Humming-birds are pre-eminently South American, but extend northwards as far even as the southern portions of Canada. The bill is always very long and slender, as are the toes also. The tongue is bifid and tubular, and appears to be used either to catch insects within the corollas of flowers, or to suck up the juices of the flowers themselves. The plumage of the males is always brilliant, with metallic reflections, that of the 628 MANUAL OF ZOOLOGY. females generally sombre. The legs are short and weak, but the wings are proportionately very long, and the flight is exceedingly rapid. The Sun -birds represent in the Old World the Hum- ming-birds of the western hemisphere, and the Australian Honey-eaters show also many points of resemblance to the Trochilidce. Sub-order 4. Fissirostres. — In this sub-order of the Insessores the beak is short but remarkably wide in its gape (figs. 345, C, and 347), and the opening of the bill is fenced in by a number of bristles (vibrissce). This arrangement is in accordance with the habits of the Fissi- rostres, the typical mem- bers of which live upon insects and take their prey upon the wing. The most typical Fissirostral birds, in fact, such as the Swal- lows and Goatsuckers, fly about with their mouths widely opened; and the insects which they catch in this way are prevented Fig. sTr.-Head of Goatsucker (Ca^nui^, fr°™ escaping partly by showing the fissirostral form of beak. the bristles which border the gape, and partly by a viscid saliva which covers the tongue and inside of the mouth. The group of the Fissirostres, with various additions (notably with that of the Humming-birds), is often raised to the rank of a distinct order (the Volitores of Professor Owen). The typical Fissirostres, characterised by the structure of the beak, comprise three families — the Swallows and Martins (Hirundinida), the Swifts (Cypselida*), and the Goatsuckers (Caprimulgidce). These three families differ in many important respects from one another, but it would be inconvenient to separate them here. The Swifts, especially, are remarkable for the peculiarity that whilst the hallux is present, it is turned forwards along with the three anterior toes. The Goatsuckers, again, hunt their prey by night, and they are provided with the large eyes and thick soft plumage of all nocturnal birds. Besides the above, there remain the two families of the King- fishers and Bee-eaters, which are generally placed amongst the Fissirostres, though in very many respects the arrangement appears to be an unnatural one. These families are charac- terised by their stronger and longer bills, and by having the VERTEBRATA: AVES. 629 external toe nearly as long as the middle one, to which it is united nearly as far as the penultimate joint. In consequence of this peculiar conformation of the toes, these families were united by Cuvier into a single group under the name of Syndactyli. The Caprimulgidce are intermediate between the Owls and the Passerine Birds. Their plumage is lax and soft, and they have a hawking flight. The eyes and ears are large, the feet short and weak, and the gape of enormous size and bordered by vibrissae. Amongst the more remarkable members of the family may be mentioned the Whip-poor-will (Antrostomus vociferus) of North America, the More-pork (Podargus Cuvieri) of Australia, and the extraordinary Guacharo Bird (Steatornis Caripensis) of the valley of Caripe in the West Indies. The Hirvndinid(Z have a wide gape, with few or no vibrissae, the wings being very long and the feet short and weak. All the Swallows feed upon insects, which they catch upon the wing, and they have a cosmopolitan range. The Swifts (Cypselidith a short down (fig. 350). In this group are the typical ""Vul- tures " ( Vultur, Neophron, &c.), and the great Bearded Vultuv> or Lammergeyer (Gypaetos barbatus) of the mountain-ranges of the south of Europe and the west of Asia. The American Vultures form the separate family of the Cathartidce. They have no eyebrows ; the head and upper part of the neck are unfeathered ; the bill is not powerfully raptorial ; the feet have the anterior toes partially webbed ; the talons are blunt and little curved ; there is no inferior larynx ; and the gullet dilates into a very large crop. They all feed VERTEBRATA: AVES. 633 principally upon carrion, and are filthy and cowardly birds. The wings, however, are long and strong, and they possess great powers of flight. This group comprises the Californian Vulture (Cathartes Californianus) of Western North America, the King Vulture (Sarcoramphus papa) of tropical America, and the famous and gigantic Condor (Sarcoramphus gryphus) of South America. Lastly, the family of the Gypogeranidce, includes only the single genus Gypogeranns or Serpentarius, including only the curious " Secretary Bird " of Africa. In this singular bird, the legs are long and slender, with an unfeathered tarso-metatarsus, thus resembling a typical Wader ; whilst the wings are long and armed with blunt spurs. The Secretary-bird lives principally upon Snakes and other reptiles, which it kills by blows from its feet and wings. As regards their distribution in time, the Raptores seem to make their first appearance in the Eocene Tertiary, where both sections of the order are represented, the Diurnal forms by the Lithornis vullurinus of the London Clay, and the Nocturnal by the Bubo leptosteus of the Eocene of Wyoming. Amongst the later representatives of the group may be mentioned the Har- pagornis of the Post-Tertiary of New Zealand, a colossal Bird of prey, which was a contemporary of the Moas. CHAPTER LXVIL SAURORNITHES AND ODONTORNITHES. SUB-CLASS III. SAURORNITHES. ORDER I. SAURUR^E. — This order includes only the extinct bird, the Archceopteryx macrura (fig. 351), a single specimen of which — and that but a fragmentary one — has been dis- covered in the Lithographic Slates of Solenhofen (Upper Oolites). This extraordinary bird appears to have been about as big as a Rook ; but it differs from all known birds in having two free claws belonging to the wing, and in having a long lizard-like tail, longer than the body, and composed of separate vertibrcz. The tail was destitute of any ploughshare-bone, and each vertebra carried a single pair of quills. The metacarpal lones, also, were not anchylosed together as they are in all other 634 MANUAL OF ZOOLOGY. known birds, living or extinct, and two of the digits appear to have been ungniculate. The sub-class Saurornithes includes only the single order Saurura, of which no other representative is known than the Fig. 351. — ArcJuzopteryx macrura, showing tail and tail-feathers, with detached bones. Jurassic Archaopteryx. From the presence of feathers it may be inferred that Archaopteryx was hot-blooded, and this char- acter, taken along with the structure of the extremities, is sufficient to justify the reference of this unique fossil to the Birds. In the long lizard-like tail, composed of numerous free vertebrae, each of which bears a pair of tail-feathers, in the fact that the metacarpals were not anchylosed together, and in the possession of two free clawed digits to the manus, Archceopteryx differs from all other known birds, living or extinct. There is also some reason to believe that the jaws were furnished with teeth sunk in distinct sockets. SUB-CLASS IV. ODONTORNITHES. ORDER I. ODONTOLC^E. — This order has been founded by Marsh for the reception of the extraordinary Hesperomis regalis, from the Cretaceous rocks of North America. In this wonderful fossil we have a gigantic diving-bird somewhat resembling the true "Divers" or " Loons " (Colymbus), but having the jaws furnished with numerous conical recurved teeth, sunk in a deep continuous groove (fig. 352, b and d\ The front of the upper jaw does not carry teeth, and was probably encased in a horny beak. The breast-bone is entirely VERTEBRATA: AVES. 635 destitute of a central ridge or keel, and the wings are minute and quite rudimentary ; so that Hesperornis^ unlike Ichthyornis, Fig. 352. — Toothed Birds (pdontornithes) of the Cretaceous rocks of America. «, Left lower jaw of Ichthyornis disbar, slightly enlarged ; b, Left lower jaw of Hesperornis regalis, reduced to nearly one-fourth of the natural size ; c, Cervical vertebra of Ichthyornis dispar, front view, twice the natural size ; c', Side view of the same ; d, Tooth of Hesperornis regalis, enlarged to twice the natural size. (After Marsh.) must have been wholly deprived of the power of flight, in this respect approaching the existing Penguins. The tail consists of about twelve vertebrae, of which the last three or four are amalgamated to form a flat terminal mass, there being at the same time clear indications that the tail was capable of up and down movement in a vertical plane, this probably fitting it to serve as a swimming-paddle or rudder. The vertebrae of the cervical and dorsal regions are of the ordinary ornithic type. The legs were powerfully constructed, and the feet were adapted to assist the bird in rapid motion through the water. The known remains of Hesperornis regalis prove it to have been a swimming and diving bird, of larger dimensions than any of the aquatic members of the class of Birds with which we are acquainted at the present day. It appears to have stood between five and six feet high, and its inability to fly is fully compensated for by the numerous adaptations of its struc- ture to a watery life. Its teeth prove it to have been carnivor- ous in its habits, and it probably lived upon fishes. From the next order, the present is readily distinguished by the fact that the vertebrae, resemble those of recent birds, the ster- 636 MANUAL OF ZOOLOGY. 11 um is without a keel, the wings are rudimentary, and the teeth are implanted in a groove in the jaw and not in separate sockets. ORDER II. ODONTOTORM^E. — This order has been founded by Marsh for the reception of two remarkable birds, which he has named Ichthyornis dispar and Apatornis celer, both from the Cretaceous rocks of North America. In Ichthyornis dispar, which may be taken as the type of the order, the teeth (fig. 352, a) were sunk in distinct sockets, and were " small, compressed, and pointed, and all of those pre- served are similar. Those in the lower jaw number about twenty in each ramus, and are all more or less inclined back- wards. . . . The maxillary teeth appear to have been equally numerous, and essentially the same as those in the mandible. The skull was of moderate size, and the eyes placed well forward. The lower jaws are long and slender, and the rami were not closely united at the symphysis. . . . The jaws were apparently not encased in a horny sheath. " The scapular arch, and the bones of the wings and legs, all conform closely to the true ornithic type. The wings were large in proportion to the legs, and the humerus had an extended radial crest. The metacarpals were united, as in ordinary birds. The bones of the posterior extremities re- semble those of swimming birds. The vertebrae (see fig. 352, c and c') were all biconcave, the concavities at each end of the centra being distinct and nearly alike. Whether the tail was elongated cannot at present be determined ; but the last vertebra of the sacrum was unusually large. "The bird was fully adult, and about as large as a pigeon. With the exception of the skull, the bones do not appear to have been pneumatic, though most of them are hollow. The species was carnivorous, and probably aquatic." (Marsh.) Apatornis agrees with Ichthyornis in most of the above char- acters, but the structure of its jaws is not fully known. It follows from the above that the order Odontotormce is char- acterised by the possession of distinct teeth sunk in separate sockets in the jaw and not in a continuous groove, by the fact that the vertebra are biconcave, and by the possession of a carinate sternum and well-developed wings. LITERATURE. [In addition to many of the works mentioned in the list of treatises re- lating to the Vertebrata in general, the following are some of the more im- portant sources of information as to recent and fossil Birds : — ] i. Article "Aves." Owen. 'Todd's Cyclopaedia of Anat. and Phys.' 1836. VERTEBRATA : LITERATURE. 637 3- 4- 5- 6. s! 9. 10. ii. 12. 1 6. 17- 1 8. 20. 21. 22. 23- 24. 25- 26. 27. 28. 29. 32. 33- 34- II: 37- 38. 39- 40. 41. 42. 43- 44. 45- Article "Birds." Newton and Parker. 'Encyclopaedia Britannica.' 9th edt. 1875. "Genera of Birds." G. R. Gray. 1844-49. " System der Pterylographie." Nitzsch and H. Burmeister. 1840. " Pterylography." Nitzsch. Translated by Sclater. 'Ray. Soc.' 1867. "Manuel d'Ornithologie." Temminck. 1820. "Natural History and Classification of Birds." Swainson. 1836. "On the Classification and Distribution of the Alectoromorphce and Heteromorphae." Huxley. ' Proc. Zool. Soc.' 1868. " On the Classification of Birds." Huxley. * Proc. Zool. Soc.' 1867. "Aves." Selenka. ' Bronn's Klassen und Ordnungen des Thier- reichs.' 1869. " Elements of Embryology." Foster and Balfour. 1874. "On the Osteology of Gallinaceous Birds and Tinamous." Parker. 'Trans. Zool. Soc.' 1866. " On the Skull of the Ostrich. " Parker. ' Phil. Trans. ' 1866. " Essai sur 1'appareil locomoteur des Oiseaux." Alix. 1874. " Animal Locomotion." Pettigrew. 1873. "Recherches Anatomiques et Paleontologiques pour servir a 1'histoire des Oiseaux fossiles de la France." Alphonse Milne-Edwards. 1867-77. " British Fossil Mammals and Birds. " Owen. 1846. " Memoir on the Apteryx. " Owen. ' Proc. Zool. Soc.' 1842. " Anatomy of the Southern Apteryx." Owen. 'Trans. Zool. Soc.' 1838 and 1842. "On Dinornis." Owen. 'Trans. Zool. Soc.' 1839-64. " Osteologia Aviuni. " Eyton. 1861-64. " Osteology of the Dodo. " Owen. 'Trans. Zool. Soc.' 1867. " The Dodo and its kindred." Strickland and Melville. 1848. " Archoeopteryx macrura. " Owen. ' Phil. Trans.' 1863. "On the Odontornithes or Birds with Teeth." Marsh. 'Geol. Magazine.' 1876. " Geographical Distribution of Animals." Wallace. 1876. " General History of Birds." Latham. 1821-28. " Anatomic und Naturgeschichte der Vogel." Tiedemann. 1810-14. " Histoire Naturelle, generale et particuliere, des Oiseaux." BufFon. Ed. by Sonnini. An. xiv. (Eng. Translation by Smellie. 1793.) "History of British Birds." Bewick. 6th ed. 1826. " History of British Birds. " Macgillivray. 1839-41. ' ' History of British Birds. " Yarrell. "Catalogue of Birds in the British Museum." Bowdler Sharpe. 1874, 1875, 1877. " Birds of Europe. " Gould. 1832-37. " Birds of Australia. " Gould. 1 840-48. " Monograph of the Trochilidae. " Gould. " Monograph of the Rhamphastidae. " Gould. 1833-35. ' Illustrations of Ornithology. " Jardine and Selby. 1825-39. ' Monograph of the Anatidoe." Eyton. 1838. ' Monograph of the Alcedinidae." Sharpe. 1871. Des Murs. 1849. 1826. (Abridged from the larger work.) ' Iconographie Ornithologique. " ' Birds of America. " Audubon. 'Birds of America." Audubon. 1840-44. 'American Ornithology." Wilson. 1808-14. ' Catalogue of North American Birds." Baird. 1859. 638 MANUAL OF .ZOOLOGY. 46. " Key to North American Birds. " Coues. 1872. 47. " Fauna Boreali Americana." Richardson. (The Birds by Swainson.) 1831. 48. " Distribution and Migration of American Birds." Baircl. 'Amer. Journ. Sci. and Arts.' 1866. 49. "Manual of the Ornithology of the United States and Canada.'' Nuttall. 2d ed.. 1840. 50. "Birds of India." Jerdon. 1862-64. 639 . 6S33T DIVISION III.— MAMMALIA. CHAPTER LXVIII. GENERAL CHARACTERS OF THE MAMMALIA. THE last and highest class of the Vertebrata, that of the Mam- malia, may be Shortly defined as including Vertebrate animals in which some part or other of the integument is always provided with hairs at some time of life ; and the young are nourished, for a longer or shorter time, by means of a special fluid — the milk — secreted by special glands — the mammary glands. These two characters are of themselves sufficient broadly to separate the Mammals from all other classes of the Vertebrate sub-king- dom. In addition, however, to these two leading peculiarities, the Mammals exhibit the following other characters of scarcely less importance : — 1. The skull articulates with the vertebral column by means of a double articulation, the occipital bone carrying two con- dyles, in place of the single condyle of the Reptiles and Birds. 2. The lower jaw or mandible consists of two halves or rami, united anteriorly by a symphysis, but not necessarily anchylosed ; but these are each composed of a single piece, instead of being complex and consisting of several pieces, as in the Reptiles and Birds. Further, the lower jaw always articulates directly with the squamosal element of the skull, and is never united to an os quadratum, as in the Satiropsida. 3. The two hemispheres of the cerebral mass, or brain proper, are united together by a more or less extensively developed " corpus callosum " or commissure. 4. The heart consists — as in Birds — of four cavities or chambers, two auricles and two ventricles. The right and left sides of the heart are completely separated from one another, and there is no communication between the pulmonary and systemic circulations. The red blood - corpuscles are non- nucleated, and, with the exception of those of the Camelidce, 640 MANUAL OF ZOOLOGY. they are circular biconcave discs. There is only one aorta — the left — which turns over the left bronchus, and not over the right, as it does in Birds. 5. The cavities of the thorax and abdomen are completely separated from one another by a muscular partition — the dia- phragm or midriff. 6. The respiratory organs are in the form of two lungs placed in the thorax, but none of the bronchi end in air-recep- tacles, distributed through the body, as in Birds. 7. The embryo mammal is invariably enveloped in an am- nion, and an allantois is never wanting. The allantois, how- ever, either disappears at an early period of life, or it develops the structure known as the "placenta." The placenta is a vascular organ which serves as a means of communication between the parent and the foetus, but it will be noticed more particularly hereafter. 8. In no Mammal do the visceral arches and clefts of the embryo ever carry branchiae, as they do in the fishes and Amphibians. These are the essential characters which distinguish the Mammalia as a class, but it will be necessary to consider these, and some other points, in a more detailed manner. In the first place, with regard to the osteology of the Mam- mals, the following points should be noticed : — With the exception of the Whales and Dolphins (Cetacea), and the Dugongs and Manatees (Sirenia), the vertebral column is divisible into the same regions as in man — namely, into a cervical, dorsal, lumbar, sacral, and caudal or coccygeal region (see fig. 241). In the Cetacea and Sirenia the dorsal region of the spine is followed by a number of vertebrae which com- pose the hinder extremity of the body, but which cannot be separated into lumbar, sacral, and caudal vertebrae. In spite of the great difference which is observable in the length of the neck in different Mammals, the number of vertebrae in the cervical region is extraordinarily constant, being almost invariably seven, as in man. In this respect there is no difference between the Whale and the Giraffe. The only exceptions to this law are the Manatees (Manatus) which have but six cervical vertebrae ; the three-toed Sloth (Bradypus tridactylus), which is commonly regarded as posses- sing nine, though competent anatomists would refer the pos- terior two of these to the dorsal region ; and one of the two- toed Sloths (Cholozpus Hoffmannt), which has only six cervical vertebrae. The dorsal vertebrae are mostly thirteen in number, but they VERTEBRATA: MAMMALIA. 64! vary from ten to twenty-four. In man there are twelve, in one of the Armadillos only ten, and in the two-toed Sloths and the Hyrax the maximum is attained. The lumbar vertebrae are usually six or seven in number, rarely fewer than four. In Man they are five in number, and they are reduced to two in the two-toed Sloth, one of the Ant-eaters, and the Duck-mole. The first vertebra, or atlas, always bears two articular cavi- ties for the reception of the two condyles of the occipital bone ; and the second vertebra, or axis, usually has an " odontoid " process, on which the head rotates. In the true Whales, how- ever, in which the cervical vertebrae are anchylosed together to a greater or less extent, and the neck is immovable, the odontoid process is also wanting. In almost all Mammals the spinous processes of the dorsal vertebrae are very largely developed for the attachment of the structure which is known as the ligamentum nuchce. This is a great band of elastic fibrous tissue, which is attached in front to the occipital bone and spinous processes of the cervical vertebrae, and which relieves the muscles of the task of support- ing the head in those Mammals which progress with the body in a horizontal position. The development of the ligamentum nuchce is consequently, as a rule, proportionate to the size of the head and the length of the neck. In Whales no such apparatus is necessary, owing to the fixation of the cervical vertebrae by anchylosis; and in Man, who walks erect, the ligamentum nuchce can hardly be said to exist as a distinct structure, being merely represented by a band of fascia. The number of lumbar and sacral vertebrae, as we have seen, varies in different Mammals ; but ordinarily some of the verte- brae are anchylosed into a single bone, and have the iliac bones abutting against them, thus constituting the "sacrum" of human anatomists. In the Celacea and Sirenia, in which the hind-limbs are wanting, and the pelvis rudimentary, there is no " sacrum/' The thoracic cavity or chest in Mammals is always enclosed by a series of ribs, the number of which varies with that of the dorsal vertebrae. In most cases each rib articulates by its head with the bodies of two vertebrae, and by its tubercle with the transverse process of one of these vertebrae (the lower one). In the Monotremata (e.g., the Duck-mole), the ribs articulate with the body of the vertebra only ; and in the Whales, the hinder-most of the ribs, or all of them, articulate with the trans- verse processes only, and not with the centra at all. There are usually no bony pieces uniting the ribs with the sternum or breast-bone in front, as in Birds ; but the so-called 2 S 642 MANUAL OF ZOOLOGY. "sternal ribs" of Aves are represented by the "costal carti- lages " of the Mammals. In some cases, however, the carti- lages of the ribs do become ossified and constitute sternal ribs. Sometimes, as in the Armadillos, there is a joint between the vertebral ribs and sternal ribs. More rarely, as in the Mono- tremes (fig. 357, D), an intermediate piece is found between the vertebral and costal portions of the rib. .Only the anterior ribs reach the sternum, and these are called" the " true " ribs ; the posterior ribs, which fall short of the breast-bone, being known as the " false " ribs. The sternum or breast-bone (fig. 353) is formed of several --/ 3-3 i— i 3—3 4—4 The hind-limbs in the Bandicoots are considerable longer than the fore-limbs, and their progression is therefore by a series of bounds. The fore-limbs have really five toes each, but only the central three of these are well developed, the outermost and innermost digits being rudimentary. The three functional toes are armed with long strong claws, with which the Bandi- coots burrow with great ease. The marsupial pouch — and this is a singular point — opens backwards instead of forwards. In the nearly-allied genus Charopus, also from Australia, the fore-foot has only two functional digits (the 2d and 3d), the ist and 5th digits being wanting, and the 4th being rudimen- tary; while the 4th digit of the hind-foot is the only func- tional toe. The second family of this section — namely, the true Opos- sums or Didelphidcz — is remarkable in being the only group of the whole order which occurs out of the Australian province. The Didelphidce, namely, are exclusively found in North and South America, where they are known as "Opossums." A considerable number of species is known, but they are mostly of small size, the largest measuring not more than from two to three feet, inclusive of the tail. The Virginian Opossum (Didelphys Virginiana) is the only member of the family which is found in North America, and it was the earliest Marsupial known to science ; its place in South America being taken by the widely-distributed Didelphys D'Azara. Most of the Opos- sums are carnivorous, feeding upon small quadrupeds and birds, but they also eat insects, and sometjmes even fruit. One species (Didelphys cancrivora) lives chiefly upon Crabs ; and the Yapock (Cheironectes) has webbed feet, and leads a semi-aquatic life. All the Diddphidce have the hallux nail-less and opposable to the other toes, so as to convert the hind-feet into prehensile hands, and all have a more or less perfectly prehensile tail, these being adaptations to an arboreal life. The marsupial pouch is sometimes not present in a complete form, but is merely represented by cutaneous folds of the abdomen concealing the nipples. In the Didelphys dorsigera, in which this peculiarity obtains, the young soon leave the nipples, and are then carried about on the back of the mother, to whom they cling by twining their prehensile tails round VERTEBRATA : MAMMALIA. 667 hers. The dentition of the Opossums (fig. 366) is remarkable for the great number of the incisor teeth, the dental formula being — 5-5 ,5ml; /w3-3 .,,4-4 4—4 i— i 3—3 ;;/ - — - = so. 4—4 The canines are well developed, and the crowns of the molars are cuspidate. Fig. 366. — Dentition of Opossum (Didelphys). The Banded Ant-eater {Myrmtcobius fasciatus) is a small but extremely elegant little animal, which inhabits Western and Southern Australia, and lives upon insects (fig. 367). The tail is bushy, and differs from that of the Didelphida in not being prehensile. The fore-feet have five toes armed with claws ; the hind-feet have only four toes. The Myrmecobius is remarkable for the extraordinary number of molar teeth, in which it exceeds any existing Marsupial, and is only surpassed by some of the Armadillos. The dental formula is — 4—4 . I T c ; pm ° — 2- ; vi ~ ~ 3—3 6—6 6—6 = 54- e. Sarcophaga. — This is the last section of the existing Mar- supials, and includes a number of predaceous and rapacious forms, which fill the place held elsewhere by the true Carnivora. They are distinguished by the fact that the intestine is desti- tute of a caecum, and by their strictly carnivorous dentition, the canines being strong, long, and pointed, whilst the molars and prsemolars have cutting edges furnished with three cusps (fig. 364, C). The best-known species of this section are the Thy- lacinus cynocephalus and the Dasyurns ursinus. The former of these is the largest of the rapacious Marsupials, being about as big as a shepherd's dog. It is a native of Van Diemen's Land, and is known to the colonists as the " hyaena." Its head 668 MANUAL OF ZOOLOGY. is very large, and the back exhibits several transverse black bands. The marsupial bones are peculiar in being represented only by permanent cartilages, and the marsupium opens back- ward. It lives in caverns and amongst the rocks in the wildest parts of the colony, and its numbers have been very much reduced by the constant war waged upon it by the settlers. The Dasyurus ursinus is also a native of Van Diem en's Land, where it is known as the " native devil/' Though smaller than the Thylacine, the Dasyurus is extremely ferocious, and is capable of committing great havoc amongst animals even as large as sheep. The dental formula of Dasyurus is — . 4 — 4 i — i 2 — 2 4 — 4 t ±— ~ : c ; pm — — : m - — " - 42. 3—3 i— i 2—2 4—4 The praemolars and molars are remarkable in the fact that they, all of them, possess sharp, serrated, cutting edges. As regards their distribution in time, the Marsupials are probably the oldest of Mammals hitherto discovered ; but owing to the detached and fragmentary condition of almost all Mammalian remains — consisting mostly of the ramus of the Fi j. 367. — My rinecobius fascia tus. lower jaw, or of separate teeth — it is not possible to state this with absolute certainty. The Microkstes of the Trias, the oldest, or nearly the oldest, of the Mammals, known only by its molar teeth (fig. 369), was probably a Marsupial ; but the evidence upon this point is not conclusive. In the Triassic rocks of America, also, perhaps at a lower horizon than that at which Microlestes occurs in Europe, has been found the jaw of VERTEBRATA: MAMMALIA. 669 a small Mammal, which is probably Marsupial, and has been named Dromatherium (fig. 368). 68. — Lower jaw of Dromatherium sylvestre. rias, North Carolina. (After Emmons.) Fig. 369. — a Molar tooth of Micro- lestes antiquus, magnified; b Crown of the same, magnified still further. Trias, Germany. In the next mammaliferous horizon, however — namely, that of the Stonesfield Slate in the Lower Oolites — there is no doubt but that some of the Mammalian remains, if not all, belong to small Marsupials (fig. 370). From this horizon the two genera, Phascolotherium and Amphitherium are almost certainly refer- able to the Marsupialia ; the latter seeming to be most nearly related to the living Myrmecobius, whilst the former finds its nearest living ally in the Opossums of America. The Stereo- gnathus of the Stonesfield Slate is in a doubtful position. It may have been Marsupial ; but, upon the whole, Professor Owen is inclined to believe that it was placental, hoofed, and herbivorous. In the middle Purbeck beds (Upper Oolite), where fourteen species of Mammals are known to exist, it is probable that all Fig. 370. — Oolitic Mammals, natural size. i. Lower jaw and teeth of Phascolotherium 2. of Triconodon ; 3. of A mphitherium ', 4. of Flag iaulax. were Marsupial. All the Purbeck Mammalia were of small size, the largest being no bigger than a polecat or hedgehog. They form the genera Plagiaulax, Triconodon, and GaZestes, of which Plagiaulax is believed to be most nearly allied to the living Kangaroo-rat (Hypsiprymnus) of Australia. In the Tertiary series of rocks Marsupials are of rare occur- 6;o MANUAL OF ZOOLOGY. rence ; but Opossums, closely allied to the existing American forms, have been discovered in the Miocene and Eocene rocks of Europe, and have been referred to a distinct genus under the name of Peratherium. It is also interesting to note that the Upper Jurassic beds have recently yielded to the researches of Professor Marsh the first fossil Marsupials which have been detected in the North American continent in beds older than the Post-pliocene, and that these belong to an extinct type of the at present exclusively American family of the Didelphidce. The next occurrence of Marsupials is in the later Tertiary (Pliocene) and in the Post-tertiary epoch ; and here they are represented by some very remarkable forms. The remains in question have been found in the bone-caves of Australia — the country in which Marsupials now abound above every other part of the globe ; and they show that Australia, at no distant geo- logical period, possessed a Marsupial fauna, much resembling that which it has at present, but of forms comparatively of a much more gigantic size. In the remains from the Australian bone-caves almost all the most characteristic living Marsupials of Australia and Van Diemen's Land are represented ; but the extinct forms are usually of much greater size. .We have Wombats, Phalangers, Flying Phalangers, and Kangaroos, with carnivorous Marsupials resembling the recent Thyla- dnns and Dasyurus. The two most remarkable of these ex- tinct forms are Diprotodon and Thylacoleo. In most essential respects Diprotodon resembled the Kangaroos, the dentition, especially, showing many points of affinity. The hind-limbs, however, of Diprotodon were by no means so disproportionately long as in the Kangaroos. In size Diprotodon must have many times exceeded the largest of the living Kangaroos, since the skull measures three feet in length (fig. 371). The affinities of Thylacoleo are disputed. The great feature in the dentition is the presence in either jaw of one huge, compressed, and trenchant prsemolar. This is regarded as corresponding to the great cutting prsemolar of the Kangaroo-rats (Hypsiprymnus). Upon the whole, there- fore, Professor Flower concludes that " Thylacoleo is a highly modified and aberrant form of the type of Marsupials now represented by the Macropodidce and Phalangistidce, though not belonging to either of these families as now restricted," and Fig- 371.— Skull of Diprotodon australis. VERTEBRATA: MAMMALIA. 671 he believes that its diet was of a vegetable nature. On the other hand, Professor Owen is of opinion that Thylacoleo was probably carnivorous in its habits. This distinguished natu- ralist thus regards Thylacoleo as an ancient form of the Dipro- todont Marsupials (Kangaroos, &c.), adapted for carnivorism, but not anatomically related to the true Carnivorous or Poly- protodont Marsupials (such as Thylacinus and Dasyurus}. Under any view of its habits, Thylacoleo is a very remarkable type of the Marsupials ; and it must have attained a very great size, since the length of the crown of the great praemolar is not less than two inches and a quarter. 672 PLACENTAL MAMMALS. CHAPTER LXX. EDENTATA. ORDER III. EDENTATA or BRUTA. — The lowest order of the placental or monodelphous Mammals is that of the Edentata, often known by the name of Bruta. The name Edentata is certainly not an altogether appropriate one, since it is only in two genera in the order that there are absolutely no teeth. The remaining members of the order have teeth, but these are always destitute of true enamel, are never displaced by a second set, and have no complete roots. Ftirther, in none of the Edentata are there any median incisors, and in only one species (one of the Armadillos'] are there any incisor teeth at all. Canine teeth, too, are almost invariably wanting. Clavicles are usually present, but are absent in the Scaly Ant-eater (Manis). All the toes are furnished with long and powerful claws. The mammary glands are usually pectoral, but are sometimes abdominal in position. The testes are abdominal in position. The skin is often covered with bony plates or horny scales. The placentation of the Edentates varies, the placenta being discoidal and deciduate in the Sloths (e.g., Cholctpus Hojfmanni), but diffuse and non-deciduate in Manis (Turner) — a fact which throws some doubt on the propriety of using the placental char- acters in classification. The order Edentata is conveniently divided into two great sections, in accordance with the nature of the food, the one section being phytophagous, the other insectivorous. In the former section is the single group of the Sloths (Bradypodidcz). In the latter are the two groups of the Armadillos (Dasypodidce), and the various species of Ant-eaters (the latter constituting Owen's group of the Edentuld}. The order Edentata is but sparingly represented in modern times, and its geographical distribution is peculiar. The true VERTEBRATA: MAMMALIA. 673 Ant-eaters, the Armadillos, and the Sloths, are entirely confined to South America, in which country a group of gigantic extinct Edentates existed in Post-tertiary times. The Scaly Ant-eater or Manis is common to Asia and Africa, and the genus Oryc- teropus is peculiar to Africa. The family Bradypodida (or Tardigradd] comprises some exceedingly curious animals, which are exclusively confined to South America, inhabiting the vast primeval forests of that continent. The Sloths have a remarkably short and rounded face, and the body is covered with hair. The mammae are two in number and pectoral in position ; and the tail is short or quite rudimentary. The incisor teeth are altogether want- ing (fig. 372, A), but there is always a small number of simple Fig. 372--A, Side -view of the skull of Bradypus c^^cull^ger; of Dasypus gigas. (After Giebel. ) B, Side-view of the skull molars, and in the Two-toed Sloths or Unaus the first tooth in each jaw on each side is so much larger than the others, and so much more pointed, that it has been regarded as a canine. The malar bone is not directly articulated with the temporal bone, and it sends backwards two long processes, directed re- spectively upwards and downwards (fig. 372, A). The stomach is complex, somewhat resembling that of the Ruminants. The cervical vertebrae are more than the normal seven in number in the Three-toed Sloth, and less than the normal in one of the two- toed species; and the long bones have no medullary cavities. 2 U 6/4 MANUAL OF ZOOLOGY. The most striking peculiarities, however, about the Sloths are connected with their mode of life. The Sloths, in fact, are constructed to pass their life suspended from the under surface of the branches of the trees amongst which they live ; and for this end their organisation is singularly adapted. The fore- limbs are much longer than the hind-limbs, and the bones of the fore-arm are unusually movable. All the feet, but especially the fore-feet, are furnished with enormously long curved claws (fig. 373), by the aid of which the animal is enabled to move Fig. 373. — Hand of Three-toed Sloth {Bradypus tridactylus). (After Owen.) about freely, suspended back downwards from the branches. Not only is this the ordinary mode of progression among the Sloths, but even in sleep the animal retains this apparently unnatural position. Owing to the disproportionate size of the fore-limbs, as com- pared with the hind-limbs, and owing to the fact that the hind- feet are so curved as to render it impossible to apply the sole to the ground, the Sloth is an extremely awkward animal upon the ground, and it has therefore recourse to terrestrial pro- gression only when absolutely compelled to do so. Whilst the name of " Sloth " may thus appear to be a merited one from the point of view of a terrestrial Mammal, it is wholly unde- served when the animal is looked upon as especially adapted for an arboreal existence. In the Ai or Three-toed Sloth (Bradypus tridactylus] there are three toes to each foot, and these are short, completely rigid, and so enveloped in the in- tegument as to leave nothing visible except the enormously long and crooked claws. The hand and foot are jointed to the arm and leg obliquely, so that the palm and sole cannot be applied to the ground, but are turned inwards. The ungual phalanges are also so articulated that the claws are bent in- VERTEBRATA: MAMMALIA. 675 wards towards the palm or sole. There are sixteen pairs of ribs. The molars are - — -, or = , rootless, growing from 4 — 4 5 — 5 permanent pulps, and consisting of a simple cylinder of den- tine enveloped in cement. In the Unau (Cholazpus) the fore- feet are two-toed, and there are twenty-three pairs of ribs, the greatest number known in the Mammals. The second family of the Edentata is that of the Dasypodidce or Armadillos. These are found exclusively in South America, as are the Sloths, but they are very different in their habits. The Armadillos are burrowing animals, furnished with strong digging-claws and well -developed collar-bones. They feed upon insects, worms, carrion, roots, and fruits. The jaws are provided with numerous simple molars (fig. 372, B), which attain the enormous number of nearly one hundred in the great Armadillo (Priodontes gtgas). The upper surface of the body is covered with a coat of mail, formed of hard bony plates or shields united at their edges (fig. 374). A portion of this Fig- 374- — The three-banded Armadillo (Tolypeiites conurus), one-third of the natural size. (After Murie.) armour covers the head and shoulders, and another portion protects the hind-quarters; whilst between these is generally a variable number of movable bands which run transversely 6/6 MANUAL OF ZOOLOGY. across the body and give the necessary flexibility to this singu- lar dermoskeleton. In most species this flexibility is so great that the animal can roll itself up like a hedgehog. The tail is likewise mostly covered with bony scutes. The spinous pro- cesses of the second cervical and of all the dorsal vertebrae are specially developed to carry the dermal shield. The sternum and first rib are expanded, and sternal ribs are present. The Armadillos are confined entirely to America, ranging from Mexico to Patagonia. In this country, also, have been found the remains of the gigantic armour-plated animals allied to the Armadillos, which will be subsequently described under the name of Glyptodon. Amongst the best-known species of Armadillo are the Peba (Dasypus Peba), the Poyou (D. sex- cinctus), the Tatouay (D. Tatouay), the Pichiy (D. minutus\ the Peludo (D. villosus), and the Great Armadillo (Priodontes gigas). A somewhat aberrant form is the Chlamyphorus, or Chlamydophorus, of Chili, the total length of which is only about six inches. The remaining members of the Edentata are the various Ant-eaters ; but these are so different from one another in their characters that they form three distinct families, also dis- tinguished by their geographical distribution. a. Myrmecophagidcz. — This family is exclusively confined to South America, as are the two preceding, and it contains only the Hairy or true Ant-eaters. These curious animals feed chiefly upon Ants and Termites, which they catch with their long sticky tongues. The jaws are wholly destitute of teeth ; the body is covered with hair ; there is a long tail ; and the feet are armed with long and strong, curved digging-claws. The toes are united by skin up to the bases of the claws, as in the Sloths ; the ungual phalanges are articulated in the same way ; and the palms of the hands are similarly turned inwards, their sides carrying a callous pad. The best-known species of this family is the Great Ant-eater (Myrmecophaga jubata)* This singular animal attains a length of over four feet, and has an extremely long and bushy tail. The jaws are produced to form a long and slender snout, which is entirely enclosed in the skin, till just at its extremity, where there is an aperture for the protrusion of the thread-like tongue. A bird -like character is the horny gizzard -like stomach. The anterior feet have four, and the posterior feet five toes, all armed with strong curved claws, which, in the case of the fore-feet, when not used in digging, are bent in- wards, so that the animal walks on the sides of the feet ; whereas the soles of the hind-feet touch the ground. The VERTEBRATA: MAMMALIA. 6// animal is perfectly harmless and gentle, when unmolested, and leads a solitary life. It lives mainly upon Termites, into the nests of which it forces its way by means of the powerful claws. When the Termites rush out to see what is the matter, the Ant-eater captures them by thrusting out its glutinous tongue, an action which can be repeated with marvellous rapidity. In the closely-allied genus Tamandua the feet are four-toed, and the animal is arboreal in its habits, as is also the case with the Cy dot hums. In the latter the fore-feet are two-toed, and the hind-feet are four-toed, with a rudimentary hallux. In ac- cordance with their mode of life these forms have prehensile tails, and in the last-mentioned genus well-developed clavicles are present. b. Manidce. — This family includes only the Scaly Ant-eaters or Pangolins, all exclusively confined to the Old World, and found in both Africa and Asia. The whole of the body, limbs, and tail in the Manidce is covered with an armour of horny imbricated plates, overlapping like the tiles of a house, and apparently consisting of agglutinated hairs. The legs are short, and furnished with four or five toes each, ending in long and strong digging-claws; but there are no clavicles. The tongue resembles that of the Hairy Ant-eaters in being long and contractile, and capable of being exserted for a consider- able distance beyond the mouth. It is covered with a glutinous saliva, and is the agent by which the animal catches ants and other insects. The jaws are wholly destitute of teeth. When threatened by danger, the Pangolins roll themselves up into a ball, like the hedgehogs. The tail is comparatively long, and is covered with scales. Though very strong for their size, only one of the species ( M. gigantea, of Africa) attains a length of more than three or four feet, inclusive of the tail. The best-known species are the Manis pentadactyla of India, and the Manis tetradactyla of Africa. Other species occur in Java, Sumatra, and China. c. Oryderopidce. — The last family of the living Edentata is that of the Oryderopidce, comprising only the single genus Oryderopus. This genus comprises two or three species, the best known being O. capensis, which is peculiar to South Africa, and is known by the Dutch colonists as the " Aardvark " or Ground-hog. The animal is nocturnal in its habits, and lives upon insects. The body is elongated, and the tail is long, the species attaining a total length of four feet or more. The zygomatic arch is complete. The legs are short, and the feet plantigrade, the anterior pair having four unguiculate toes, the posterior five. The claws are strong and curved, and enable 678 . MANUAL OF ZOOLOGY. the animal to construct extensive burrows. The skin is very thick, and is thinly covered with bristly hairs ; and the tail is hairy. The head is elongated, and the mouth small — devoid Fig. 375. — Skull of Orycterofius capensis. of incisor and canine teeth (fig. 375), but furnished with a number of cylindrical molars {^—\ The crowns of the molars are flat, and they are composed of dentine traversed by nu- merous dichotomising pulp-cavities, their cross-section resem- bling a piece of bamboo cut across. The tongue is long, flat, and slender, and is covered by a sticky saliva, by the aid of which the animal catches insects. The head is long and attenuated, the snout truncated and callous, and the ears large, erect, and pointed. Other species of Orycteropus occur in Senegal and Southern Nubia. As regards their distribution in time^ the oldest Edentates at present known occur in Europe, in which country no members of the order now exist. These are the Macrotherium and Ancylotherium of the Miocene Tertiary, both apparently allied to the Orycteropida, with affinities to the Manidce. The Plio- cene deposits of North America have yielded to the researches of Professor Marsh two large Edentates of the new genus Moro- therium, and the Miocene deposits of the same country con- tain remains of another Edentate type {Moropus}. It is, how- ever, in the Post-tertiary deposits of the American continent, and especially of South America — the present metropolis of the order — that we find the most abundant and the most re- markable remains of Edentate animals. Here, both in Post- pliocene superficial deposits and in cave-earths of the same age, we meet with the remains of numerous Edentates often of gigantic size, but in the main representing the existing types. Thus the existing Sloths are represented in the Brazilian bone -caves by a number of extinct genera of Bradypodidcz, VERTEBRATA : MAMMALIA. 6/9 whilst the Post-pliocene sands and gravels of the open country have yielded the bones of various huge Edentates, resembling the Sloths in most essential respects, but adapted for a terres- trial instead of an arboreal life. Of these great " Ground- sloths" (Gravigrada), the most remarkable are the Megathe- rium (fig. 376), which attained a length of eighteen feet, with Fig. 376. —Skeleton of Megatherium. Post-tertiary, South America. bones as massive as, or more so than, those of the Elephant ; and the Mylodon and Megalonyx, both of which extended their range into the United States. In the same way the little banded Armadillos of South America were formerly represented by gigantic species, con- stituting the genus Glyptodon. The Glyptodons (fig. 377) dif- Fig- 377. — Glyptodon clavipes. Pleistocene deposits of South America. fered from the living Armadillos in having no bands in their armour, so that they must have been unable to roll themselves up. It is rare at the present day to meet with any Armadillo over two or three feet in length ; but the length of the Glyp- todon clavipes, from the tip of the snout to the end of the tail, was more than nine feet. The trunk-armour of Glyptodon is formed of nearly hexagonal bony scutes, forming a massive dome, for the support of which the skeleton is specially modified. Thus the last cervical 680 MANUAL OF ZOOLOGY. and first two dorsal vertebrae are anchylosed to form a single bone (" trivertebral bone " of Huxley), which articulates by a movable hinge-joint with the remaining dorsal vertebras, which are likewise anchylosed to form a kind of " tunnel or arched bridge of bone." The last two lumbar vertebrae are also fused with the sacral and caudal to form a continuous bony mass, whilst the ilia are of enormous size. Numerous extinct forms of genuine Armadillos have also been found in the Brazilian bone-caves, one of them (Chlamydotherium) being as big as a Rhinoceros. Lastly, the South American Myrmecophagida are represented in the Brazilian cavern-deposits by the extinct Glossotherium. CHAPTER LXXI. SIRENIA AND CETACEA. .ORDER IV. SIRENIA. — This order comprises no other living animals except the Dugongs and Manatees, which have been often placed with the true Cetaceans (Whales and Dolphins) in a common order. There is no doubt, in fact, but that the Sirenia present certain alliances to the Cetacea ; and though they are to be regarded as separate orders, yet, from one point of view, they may be considered as belonging to a single section, which has been called Mutilata, from the constant absence of the hind-limbs. The Sirenia agree with the Whales and Dolphins in their complete adaptation to an aquatic mode of life (fig. 378) ; especially in the presence of a powerful caudal fin, which differs from that of Fishes in being placed horizontally, and in being a mere expansion of the integuments, not supported by bony rays. The hind-limbs are wholly wanting ; * and there is no sacrum. The anterior limbs (fig. 379) are converted into swimming-paddles or "flippers" The snout is fleshy and well-developed, and the nostrils are placed on its upper surface, and not on the top of the head, as in the Whales. Fleshy lips are present, and the upper one usually carries a moustache. Ears are wanting. The skin is covered with scattered bristles. The head is not dispropor- tionately large, as in the true Whales, and is not so gradually prolonged into the body as it is in the latter. There may be * All the Sirenians possess a rudimentary pelvis, and in the extinct Halt- therium a small femur is present in addition. VERTEBRATA: MAMMALIA. 68 1 only six cervical vertebrae. The teats are two in number and are "thoracic," i.e., are placed on the chest. There are no clavicles, and the digits have no more than three phalanges Fig. 378. — A, Side-view of young Manatus Americanus ; B, The same viewed from above ; n Nostrils. (After Murie.) each. The testes are retained throughout life within the ab- domen, but vesicular seminales are present. The animal is diphyodont (Manatus\ or monophyodont (Halicore) ; the perma- nent teeth consisting of molars with flattened crowns adapted for bruising vegetable food, and incisors which are present in the yotmg animal, at any rate. In the extinct Rhytina it does not appear that there were any incisor teeth; while in all the existing genera, the front of the upper and lower jaws is pro- vided with rough horny pads or plates. The only existing Sirenia are the Manatees (Manatus} and the Dugongs (Halicore}, often spoken of collectively as " sea- cows," and forming the family of the Manatidce. The Manatees (fig. 380, B) are characterised by the posses- sion of numerous 9—9 :. n—1 9-9 to ii — ii broad molars, which are never' all in use at one time, while there are two small upper incisors, which do not cut the gum. The tail-fin is oblong or oval in shape, and the anterior limbs (fig. 379) are furnished with nails to the four outer digits. One species (Manatus Ameri- canus) occurs on the east coast of North America, especially 682 MANUAL OF ZOOLOGY. in the Gulf of Mexico, and another (M. Senegalensis) is found on the west coast of Africa. They are generally found in con- Fig. 379. — Fore-limb and hand of the Manatee (Manatus Americanus). siderable numbers about the mouths of rivers and estuaries, often ranging far inland, and they appear to live entirely upon Fig. 380. — A, Side-view of the skull of the Dugong (Halicore), showing the tusk-like upper incisors ; B, Side-view of the skull of Manatee (Mauatus). (After Cuvier.) sea-weeds, aquatic plants, or the littoral vegetation. They are large, awkward animals, with a dense, rugose, hairy skin, attaining a length of from eight to ten feet as a rule, but sometimes growing to a length of nearly twenty feet. 5-5 6-6 The Dugongs (Halicore, fig. 380, A) have or 5-5 6-6 molar teeth in the young condition, but these are never all in use at one time. The molars are without enamel, and are single-rooted. Inferior incisors are present in the young ani- mal, but are wanting in the adult. The upper jaw carries two VERTEBRATA: MAMMALIA. 683 permanent incisors, which are entirely concealed in the jaw in the females, but which increase in size in the males with the age of the animal, till they become pointed tusks. Both upper and lower jaws are strongly bent down in front, and the de- flexed portions of the jaws bear horny plates. The anterior extremities are nail-less, and the tail-fin is crescentic in shape. In their general appearance and in their habits the Dugongs differ little from the Manatees, and they are often killed and eaten. They attain a length of from eight to ten, twelve, or more feet, and are found on the coasts of the Indian Ocean and its islands, extending their range to the north coast of Australia. The bones are remarkable for their extreme den- sity, their texture being nearly as close as ivory. The Manatees and Dugongs, as before said, are the only living Sirenia; but besides these there is a very singular form, the Rhytina Stelleri, which is now extinct, having been exter- minated by man within a comparatively recent period. This remarkable animal was discovered about the middle of the eighteenth century in a little island (Behring's Island) off the coast of Kamtchatka. Upon this island the celebrated voyager Behring was wrecked, and he found the place inhabited by these enormous animals, which were subsequently described by M. Steller, who formed one of his party. The discovery, however, was fatal to the Rhytina, for the last appears to have been seen in the year 1768. The Rhytina was an animal of great size, measuring twenty-five to thirty-five feet in length, and twenty feet at its greatest circumference. There can hardly be said to have been any true teeth, but the jaws con- tained -r— large lamelliform fibrous structures, which offici- ated as teeth, and may be looked upon as molars. These singular structures are not teeth, in the true sense of this term ; but they are similar to the horny tuberculated plates found in the front of the mouth of the Dugong and Manatee, and the upper ones may be regarded as the equivalent of the anterior palatine pad of the Ruminants (Murie). The epidermis was extremely thick and fibrous, and hairs appear to have been wanting. There was a crescentic tail -fin, and the anterior limbs alone were present. As regards the distribution in time of the Sirenia, the oldest- known remains referable to the order are found in the Eocene Tertiary (Eotherium). Of the same age is probably the inter- esting form described from the Tertiary deposits of Jamaica by Owen under the name of Prorastomus sirenoides. This type 684 MANUAL OF ZOOLOGY. is remarkable as possessing upper and lower canines in addi- tion to molar and incisor teeth. The Miocene and Pliocene deposits of Europe have yielded remains of numerous Sireni- ans belonging to the genus Halitherium, in which there are tusk -like upper incisors (as in Halicore), combined with en- amelled molars (as in Manatus}, and in which a rudimentary femur is attached to the pelvis. Re- mains of Rhytina occur in the Post- pliocene of Siberia. ORDER V. CETACEA. — In this order are the Whales, Dolphins, and Por- poises, all agreeing with the preceding in their complete adaptation to an aquatic life (figs. 384, 386). The body is completely fish-like in form; the ante- rior limbs are converted into swimming- paddles or "flippers ;" the proximal bones of the fore-limbs are much reduced in length, and the succeeding bones are shortened and flattened, and are enveloped in a tendinous skin, thus reducing the limbs to oar-like fins, the phalanges of some of the digits being sometimes in- creased in number (fig. 381); there are no external ears ; the posterior limbs are completely absent ; and there is a power- ful, horizontally -flattened, caudal fin, sometimes accompanied by a dorsal fin as well. In all these characters the Cetacea agree with the Sirenia, except in the one last mentioned. On the other hand, the nostrils, which may be single or double, are always placed at the top of the head, constituting the so-called "blow-holes" or "spiracles ;" and they are never situated at the end of a snout. The body of the adult is in general com- bTglts"; r~Rad~ius; u uina; pletely hairless. The testes are retained fif^hTmclfpaf First and throughout life within the abdomen, and there are no vesiculae seminales. The teats are two in number, and are placed upon the groin. The head is generally of disproportionately large size, and is never separated from the body by any distinct constriction or neck. The lumbar region of the spine is long, and, as in the Sirenia, there is no sacrum, and the pelvis is represented by a single Fig. 381. — Hand of Round- headed Dolphin. I— V, VERTEBRATA: MAMMALIA. 685 bone (the ischium) on each side. A rudimentary femur may be present, and Balcena mysticetus has a cartilaginous tibia as well. There are no clavicles, and the sternum is broad and flat in form. Lastly, the adult is either destitute of teeth, or, with the single exception of the Zeuglodontidcz, is monophyodont — that is to say, possesses but a single set of teeth, which are never replaced by others. When teeth are present, they are usually conical and numerous, and, except in the Ztuglodonts, they are always of one kind only. The skull is often un symmetrically developed, and the maxillae and praemaxillae are greatly prolonged. The nasal bones are short, and the nasal passages are vertically directed ; the epiglottis and laryngeal cartilages being prolonged behind the soft palate in the form of a cylindrical tube, which is practically continuous with the posterior nares, thus allowing the animal to swallow under water without choking. The Cetacea may be divided into the five families of the Bala- nidcz or Whalebone Whales, the Delphinidce or Dolphins and Porpoises, the Catodontidcz or Sperm Whales, the Rhynchoceti or Ziphioid Whales, and the Zeuglodontida. Of these the Balce- nidce are often spoken of as the " toothless " Whales, whilst the other four families are called the "toothed" Whales (Odontoceti). Fam. i. Halcenidce. — The Balanidce. or Toothless Whales are characterised by the total absence of teeth in the adult (fig. 382). Teeth are, however, present in the foetal Whale, Fig. 382.— Skull of the Right Whale (Balcena mysticettts). (After Owen.) but they never cut the gum. The place of teeth is supplied by a number of plates of whalebone or "baleen" attached to the palate; hence the name of "whalebone whales" often given to this family. They are the largest of living animals, and may be divided into the two sections of the Smooth Whales, in which the skin is smooth and there is no dorsal fin (as in the Greenland Whale), and the Furrowed Whales, in which 686 MANUAL OF ZOOLOGY. the skin is furrowed and a dorsal fin is present (as in the so- called Finner Whales and Hump-backed Whales). The Greenland or ' ' Right " Whale (Bal&na mysticetus) will illustrate almost all the leading points of interest in the family. The Greenland Whale is the animal which is sought after in the whale-fishery of Europe, and hence the name of "Right" Whale often applied to it. It is an inhabitant of the arctic seas, and reaches a length of from forty to sixty feet. Of this enormous length, nearly one-third is made up of the head, so that the eye looks as if it were placed nearly in the middle of the body. The skin is completely smooth, and is destitute of hairs in the adult. The fore -limbs are converted into "flippers" or swimming -paddles, but the main organ of progression is the tail, which often measures from twenty to twenty- five feet in breadth. The mouth is of enormous size, the upper jaw much narrower than the lower, and both completely destitute of teeth. Along the middle of the palate runs a strong keel, bordered by two lateral depressions, one on each side. Arranged transversely in these lateral depressions are an enormous number of horny plates, constituting what is known as the "baleen" plates, from which the whalebone of commerce is derived. The arrangement of the plates of baleen is as follows (fig/ 383) : Each plate is triangular in shape, the shortest side or base being deeply sunk in the palate. The outer edge of the plate is nearly straight, and is quite unbroken. The inner edge is slightly concave, and is fur- nished with a close fringe formed of detached fibres of whalebone. For simplicity's sake each baleen-plate has been regarded here as a single plate, but in reality each plate is composed of several pieces, of which the outer- most is by far the largest, whilst the others gradually decrease in size towards the middle line of the palate. The large marginal plates are from eight to ten or more feet in length, and there may be over one hundred on each side of the mouth. The object of the whole series of baleen-plates with which the palate is furnished, is as follows : The Whale is a strictly carnivorous or zoophagous animal, but owing to the absence of teeth and the comparatively small calibre of the oesophagus, it lives upon very diminutive animals. The Whale, in fact, lives mostly upon the shoals of small Pteropodous Molluscs, Crustacea, Ctenophora and Medusa, which swarm in the arctic seas. To obtain these, the whale swims with the mouth opened, and thus fills the mouth with an enormous mass of water. The baleen - plates have the obvious function of a ' ' screening apparatus. " The water is strained through the numerous plates of baleen, and all the minute animals which it contains are arrested and collected together by the inner fibrous edges of the baleen- plates. When, by a repetition of this process, the Whale has accumulated a sufficient quantity of food within the central cavity of the mouth, it is enabled to swallow it, without taking the water at the same time. We have now to speak of a phenomenon which has given rise to a con- siderable amount of controversy — namely, what is known as the "blow- ing" or "spouting" of the whale. In all the Cetaceans the nose opens by a single or double aperture (the latter in the Balanidce) upon the top of the head, and these external apertures or nostrils are known as the "blow-holes" or "spiracles." The act known to the whalers as "blow- ing," consists in the expulsion from the blow-holes of a jet of what is apparently water, or at any rate looks like it. This act is performed by the whale upon rising to the surface, and it is usually by this that the whereabouts of the animal is discovered. The old view as to what takes place in the act of blowing is, that the whale is really occupied in getting VERTEBRATA: MAMMALIA. 687 rid of the surplus water which it has taken in at the mouth and strained through the baleen- plates. The modern and undoubtedly correct view, however, is, that the water which has been strained through the baleen really makes its escape at the sides of the mouth, and does not enter the pharynx to be expelled through the nose. Upon this view the apparent Fig. 383. — Diagram of the baleen-plates of a Whale, a a Section of the palatal surface of the upper jaw, showing the strong median ridge or keel ; b b Baleen-plates sunk at their bases in the palate ; ff Fibrous margin of baleen-plates. column of water emitted from the blow-holes in the act of blowing con- sists really of the expired air from the lungs, the contained watery vapour of which is suddenly condensed on its entrance into the cold atmosphere. With the expired air there may be such water as may have gained access to the nose through the blow-hole, for the expulsion of which proper pro- vision exists in the form of muscular diverticula of the nasal cavity. It is also possible that the column of air in being forcibly expelled from the blow-hole may take up with it some of the superincumbent water. The skin in the Right Whale is perfectly smooth and naked, but it is underlaid by a thick layer of subcutaneous fat, which varies from eight to fifteen inches in thickness, and is known as the "blubber." The blubber serves partly to give buoyancy to the body, but more especially to protect the animal against the extreme cold of the medium in which it lives. It is the blubber which is chiefly the object of the whale-fishery, as it yields the whale-oil of commerce. The whale which is captured in the South Atlantic is not the same species as the Greenland Whale, and is termed the Balana atistralis. It is much about the size of the Right Whale, averaging about fifty feet, but the head is proportionately smaller. Another Atlantic species is the B. Biscayensis. In the South Pacific occurs Balcena antipodarum, and in the 688 MANUAL OF ZOOLOGY. North Pacific we meet with the B. Japonica along with the B. mysticetus or Right Whale of the North Atlantic (Van Beneden). The only remaining members of the Balcenidce which require notice are the Rorquals and Hump-backed Whales, constituting the group of the ' ' Furrowed " Whales. These are collectively distinguished by having the skin furrowed or plaited to a greater or less extent, whilst the baleen-plates are short, and there is a dorsal fin. The specific determination of these animals is a matter of great difficulty, but there would appear to be prob- ably three well-marked genera : I. The genus Megaptera, including the so-called Hump-backed Whales, in which the flippers are of great length, from one-third to one-fifth of the entire length of the body. 2. The genus Balcenoptera, comprising the so-called Rorquals or Piked Whales, in which the flippers are of moderate size. 3. The Finner Whales proper (Physalus). In all these genera there is a dorsal adipose fin, so that they are all "Finner Whales." The Balanopterce reach a gigantic size, being some- times as much as eighty or one hundred feet in length. They are very active animals, however, and their whalebone is comparatively valueless, so that the whalers rarely meddle with them, though they are not uncom- mon, and are often driven ashore on our own coasts. Fam. 2. CatodontidcB. — The family of the Catodontida or Physeteridcz comprises the Sperm Whales or Cachalots, with which we commence the series of the toothed Whales (Odon- toceti). They are characterised by the fact that the palate is destitute of baleen- plates, and the lower jaw possesses a series (about fifty-four) of pointed conical teeth, separated by inter- vals, and sunk in a common alveolar groove, which is only imperfectly divided by septa. The upper jaw is also in reality furnished with teeth, but these do not cut the gum. The best-known species of this family is the great Cachalot or Sper- Fig. 384. — Spermaceti Whale (Physeter macrocephalus}. maceti Whale {Physeter macrocephalus, fig. 384). This animal is of enor- mous size, averaging from fifty to seventy feet in length, but the females VERTEBRATA: MAMMALIA. 689 are a good deal smaller than the males. The head is disproportion- ately large, as in the Balcenida, forming more than one-third of the entire length of the body. The snout forms a broad truncated muzzle, and the nostrils are placed near the front margin of this. The Sperm Whales live together in troops or "schools," and they are found in various seas, especially within the tropics. They are largely sought after, chiefly for the substance known as "spermaceti ;" but besides this they yield oil and the singular body called "ambergris." The spermaceti is a fatty sub- stance, which has the power of concreting when exposed to the air, being in life a clear white oily liquid. It is not only diffused through the entire blubber, but is also contained in special cavities of the head. The sperm- oil yielded by the blubber is exceedingly pure, and is free from the un- pleasant odour of ordinary whale-oil. The ambergris is a peculiar sub- stance which is found in masses in the intestine, and is probably of the nature of a biliary calculus, since it is said to be composed of a substance very nearly allied to cholesterine. It is used both as a perfume itself, and to mix with other perfumes. Fam. 3. Delphinidce. — This family includes the Dolphins, Porpoises, and Narwhal, and is characterised by usually pos- Fig- 385.— Side-view of the skull of Delphinus tursio. (After Cuvier.) sessing teeth in both jaws : the teeth being numerous, and conical in shape (fig. 385). The nostrils, as in the last fam- ily, are united, but they are placed further back, upon the top of the head. The single blow-hole or nostril is transverse and mostly crescentic or lunate in shape. The head is by no means so disproportionately large as in the former families, usually forming about one-seventh of the entire length of the body. The most noticeable members of this family are the true Dolphins, the Porpoises, and the Narwhal. The Dolphins have an elongated snout, separated from the head by a transverse depression. The common Dolphin (Del- phinus delphis, fig. 386) is the best-known species. It aver- ages from six to eight feet in length, and has the habit of swimming in flocks, often accompanying ships for many miles. The female, like most of the Cetacea, is uniparous. The Dolphin occurs commonly in all European seas, and is espe- cially abundant in the Mediterranean. The common Porpoise {Phoccena communis} is the commonest and smallest of all the Cetacea, rarely exceeding four feet in length. The head 2 X 690 MANUAL OF ZOOLOGY. is blunt, and is not produced into a projecting muzzle. The Porpoise frequents the Atlantic, Pacific, Mediterranean, and Arctic Oceans, and the North Sea, and is commonly seen off our coasts. Another British species is the Grampus (Orca gladiator] , but this is much larger, attaining a length of from eighteen to twenty feet. Nearly allied to the Grampus is the so- called ' ' Caing " Whale, or, as it is sometimes termed, the Bottle-nosed Whale (Globicephalus melas or Phoc&na globiceps). This species occurs not Fig. 386. — The common Dolphin (Delphinus delphis). uncommonly round the Orkney and Shetland Islands, and attains a length of as much as twenty-four feet. It is gregarious in its habits, and is often killed for the sake of its oil. Closely allied to the true Dolphins are some curious Cetaceans, belonging to three genera, but all inhabiting fresh waters. One of these is the Gan- getic Dolphin (Platanista Gangetica), which inhabits the Ganges, especially near its mouth. This singular animal is characterised by the great length of its slender muzzle, and by the small size of the eyes. It attains the length of seven feet, and the blow-hole is a longitudinal fissure, and there- fore quite unlike that of the -typical Delphinidce. Closely allied to this, or identical with it, is the Platanista Indi of the Indus ; while the Orcella fluminalis inhabits the Irawaddy. Another fresh-water form is the Inia Boliviensis, which inhabits the rivers of Bolivia, and is found at a distance of more than two thousand miles from the sea. Lastly, the Pontoporia Blainvillii is a small Dolphin which inhabits the rivers of the Argentine Republic and of Patagonia. The last of the Delphinidtz is the extraordinary Narwhal or Sea-unicorn (Monodon monoceros). The Narwhal is an inhabitant of the arctic seas, and attains a length of as much as fifteen feet, counting in the body alone. The dentition, however, is what constitutes the great peculiarity of the Narwhal. The lower jaw is altogether destitute of teeth, and the upper jaw in the females also exhibits no teeth externally, as a general rule at any rate, though there are two rudimentary canines (often looked upon as in- cisors) which do not cut the gum. In the males, the lower jaw is likewise edentulous, but the upper jaw is furnished with two molar teeth concealed in the gum, and with two canines. Of these two upper canines, that of the right side is generally rudimentary, and is concealed from view. The left upper canine, on the other hand,, is developed from a permanent pulp, and grows to an enormous size, continuing to increase in length through- out the life of the animal. It forms a tusk of from eight to ten feet in length, and it has its entire surface spirally twisted. As an abnormality, both the upper canines may be developed in this way so as to form pro- jecting tusks ; and it is stated that the tusk is occasionally present in the female. The function of this extraordinary tooth is doubtless offensive. VERTEBRATA: MAMMALIA. 691 Fam. 4. Rhynchoceti. — This family is allied to the Cachalots or Sperm Whales, and includes the so-called " Ziphioid Whales." They are distinguished by the possession of a pointed snout (the "beak" or "rostrum"), single blow-hole, small dorsal fin, and dentition. The upper jaw is greatly extended and is edentulous, any teeth which may be present not cutting the gum. The lower jaw, on the other hand, possesses usually a single pair of teeth, sometimes two pairs, which are sometimes tusk-like, but which in other cases are concealed by the gum, and are always most conspicuous in the males. The rostrum of these Cetaceans is of great density, and has often been preserved in a fossil state, usually presenting itself as a bony cylinder or elongated cone, generally more or less water-worn. The most important living genera are Hyperoodon and Ziphius, of which the former is found in the North Atlantic, and the latter in the Mediterranean and South Atlantic. The genera Berardius and Mesoplodon belong to the New Zealand province, species of the latter having been obtained at the Cape of Good Hope and on the coasts of Britain and France. Fam. 5. Zeuglodontidce. — The members of this family differ from all existing Odontoceti in the possession of molar teeth implanted by two distinct fangs. Incisor teeth are likewise present, and the animal is diphyodont The Zeuglodonts are entirely extinct, and they are exclusively confined to the Eocene, Miocene, and Pliocene periods. The chief genera are Zeuglodon and Squalodon. Zeuglodon (fig. 387) is distinguished by its elongated snout, Fig. 387. — Znuglodon cetoides. A, Molar tooth, natural size ; B, Vertebra, reduced. From the Middle Eocene of North America. (After Lyell.) conical incisors, and molar teeth with triangular serrated crowns, implanted in the jaw by two roots. Each molar looks 692 MANUAL OF ZOOLOGY. as if it were composed of two separate teeth united on one side by their crowns ; and it is this peculiarity which is ex- pressed by the generic name. The species of Zeuglodon are Eocene and Miocene. The species of Squalodon are Miocene and Pliocene. As regards the distribution of the Cetacea in time, no mem- ber of the order has yet been detected in any Secondary deposit. The Zeuglodonts, as just remarked, extend from the Eocene to the Pliocene, Zeuglodon itself being the oldest Cetacean at present known. The Ziphioid Whales begin in the Pliocene, as do the Catodontidce ; but the Delphinida are known to occur in the Miocene. The Balcenidce are not known to have existed earlier than the Pliocene. CHAPTER LXXII. UNGULATA. ORDER VI. UNGULATA. — The order of the Ungulata, or Hoofed Quadrupeds, is one of the largest and most important of all the divisions of the Mammalia. It comprises three entire old orders — namely, the Pachydermata^ Solidungula, and Ruminantia. The first of these old divisions — that of the Pachydermata — included the Elephants, Rhinoceros, Hippopotamus, Tapirs, and the Pigs, all characterised, as the name implies, by their thick integuments. The name is still used to express this fact, though the order is now abandoned, and is merged with that of the Ungulata; the Elephants alone being removed to a separate order under the name of Proboscidea. The second old order — that of the Solidungula or Solipedes — included the Horse, Zebra, and Ass, all characterised by the fact that the foot terminates in a single toe, encased in an expanded hoof. The name Solidungula is still retained for these animals, as a section of the Ungulala. The third old order — that of the Ruminantia — includes all those animals, such as Oxen, Sheep, Goats, Camels, Giraffes, Deer, and others, which chew the cud or "ruminate," and have two functional toes to each foot, encased in hoofs. The name Ruminantia is still retained for these animals, as consti- tuting a most natural group of the Ungulata. All these various animals, then, are now grouped together VERTEBRATA: MAMMALIA. 693 into the single order of the Ungulata, or Hoofed Quadrupeds, and the following are the characters of the order : — All the four limbs are present, and that portion of the toe which touches the ground is always encased in a greatly-expanded nail, constituting a " hoof" Only in a few extinct forms (the Cory- phodontidce] are there more than four full-sized toes to each limb. Owing to the encasement of the toes in hoofs, the limbs are useless for prehension, and only subserve locomotion ; hence clavicles are always wanting in the entire order. There are always two sets of enamelled teeth, so that the animal is diphyodont. The molar teeth are massive and have broad crowns, adapted for grinding vegetable substances. In accordance with the number of the digits (fig. 388), the Fig. 388. — Feet of Ungulata. A, Fore-foot of Tapir (Tapirus Malayanus) ; B, Perisso- dactyle fore-foot of Rhinoceros Sumatrensis; C, Artipdactyle foot of Pig (Sus scrofa). The figures indicate which of the normal five digits are present in each foot. (After Flower.) order Ungulata is divided into two primary sections : The Perissodactyla, in which the toes or hoofs are odd in number (one or three, or, in the extinct Coryphodontida, five), and the Artiodactyla, in which the toes are even in number (two or four). PERISSODACTYLE UNGULATES. SECTION A. PERISSODACTYLA. — The section of the Perisso- dactyle Ungulates includes the Rhinoceros, the Tapirs, the 694 MANUAL OF ZOOLOGY. Horse and its allies, and some extinct forms, all agreeing in the following characters : — The hind-feet are odd-toed in all (fig. 388, B), and the fore-feet in all except the Tapirs and Brontotheridce. The dorso-lumbar vertebra are never less than twenty-two in number. The femur has a third trochanter. The horns, if present, are not paired (except in the extinct genus Diceratherium, and in the family of the Brontotheridce). Usually there is only one horn, but if there are two, these are placed in the middle line of the head, one behind the other (fig. 392). In neither case are the horns ever supported by bony horn-cores. The stomach is simple, and is not divided into several compartments ; and there is a large and capacious ccecum. The three existing groups of Perissodactyle Ungulates — namely, the Horses, Tapirs, and Rhinoceroses — are widely removed from one another in many important characters ; but the intervals between them are largely filled up by an extensive series of fossil forms, commencing in the Lower Tertiary strata. The section of the Perisso- dactyle Ungulates includes the following seven families : — Fam. i. Coryphodontidce. — This family comprises only a (Mter number of extinct Tapir-like animals, belonging to the Eo- cene period. The skull is of the Perissodactyle type, hornless, with small nasal bones. The brain is remarkably small, and the dentition is complete, the dental formula being — 3—3 i— i 4-4 3—3 The canines are not excessively developed, and the molars are of the Tapiroid type, having two transverse crests or ridges. The limbs are short, and both the fore-feet (fig. 389) and the hind-feet are furnished with five complete toes, all of which carried hoofs. The genus Coryphodon is the principal or only one comprised in the family; and as it contains the only Ungulates with the complete number of five digits on each foot, it might with propriety be raised to the rank of a distinct section, equal with the sections of the Perissodactyla and VERTEBRATA: MAMMALIA. 695 Artiodactyla, to which the name of Teleodactyla might be applied. Fam. 2. Rhinocerotidce. — This family comprises only a single living genus, the genus Rhinoceros, unless, indeed, the little Hyrax is to be retained in this order. The Rhinoceroses are extremely large and bulky brutes, having a very thick skin, which is usually thrown into deep folds. The muzzle is rounded and blunt, and there are ?-h? grinders, with tuberculate crowns. 7 — 7 The typical dental formula is — ,°=2; /*|4=4. «3n3 Ora8. o— o' 4—4 3—3 There are no canines ; and the incisors are often wanting in the adult (as in the living two-horned species), or may be in- creased in number (as in the extinct Accrothcrium}. The crowns of the praemolars and molars (fig. 390) exhibit two principal tracts of dentine, not filled up by cement. Fig. 390. — Teeth of the upper jaw of Rhinoceros Indiciis^ (after Cuvier). wz1, mz Molars ; /;«!, pnfi Prsemolars ; i Incisor. The skull (fig. 391, B) is pyramidal, and the nasal bones are generally enormously developed. The nasal bones usually support one or two horns, which are not paired in any living form. The horn is composed of longitudinal fibres, which are agglutinated together, and are of the nature of epidermic growths, somewhat analogous to hairs. When two horns are present, the hinder one is carried by the frontal bones, and is placed in the middle line of the head behind the anterior horn. The posterior horn is usually much shorter than the anterior one; and if not, it differs in shape. In the extinct genus Diceratherium of Marsh, from the Miocene of Oregon, there are two horns placed transversely and symmetrically upon the 696 MANUAL OF ZOOLOGY. nasal bones. This singular form further differs from the typical Rhinoceroses in having four toes to the fore-feet, whilst the hind-feet have only three. The development of the nasal bones in the Rhinoceroses varies greatly in accordance with the varying condition of the horns. In the extinct Acerotherium, in which there are no horns, the nasal bones are greatly reduced in size. In the horned forms, on the other hand, not only are the nasal bones prolonged forwards over the nasal cavity; but the septum narium may be partially or completely ossified, thus strength- ening the basement of the anterior horn in the bicorn species. Fig. 391. — A, Side-view of the skull of Tapirus A mericanus ; B, Side-view of the skull of Rhinoceros bicornis. (After Giebel.) The Rhinoceroses live in marshy places, and subsist chiefly on the foliage of trees. They are exclusively confined at the present day to the warmer parts of the Old World; but several extinct species formerly ranged over the greater part of Europe. Of the one-horned species, of which there are three, the best known is the Indian Rhinoceros (R. Indicus or umcornis), which was probably the " Unicorn " of the ancients. Another VERTEBRATA: MAMMALIA. 697 species with one horn (J?. Sondaicus) inhabits the Malay Peninsula, Java, Sumatra, and Borneo. Of the two-horned species, one (R. Sumatrensis) is found in Sumatra and the Malay Peninsula, and is remarkable for the comparative absence of cutaneous folds. The best known, however, is the African Rhinoceros (R. bicornis) which occurs abundantly in Cape Colony and in the southern parts of the African con- tinent, extending its range to Nubia (fig. 392). Another Fig. 392. — Head of two-horned Rhinoceros (R. bicornis). African species is the White Rhinoceros (R. simus), distin- guished from the preceding by its colour, the shortness of its upper lip, and the great length of the anterior horn ; and at least two other two-horned species are said to occur in the same country. Fam. 3. Tapirida. — The Tapirs are characterised by the possession of a short movable proboscis or trunk. The skull (fig. 391, A) is pyramidal, like that of the pigs, and the nasal bones poject over the nasal cavity. The skin is hairy and very thick. The tail is extremely short. The fore-feet (fig. 388, A) have four toes each, but these are unsymmetrical (the little toe being smaller than the rest and not touching the ground), and the hind-feet have only three toes, all encased in hoofs. The dental formula of the Tapirs is — . 7 — t i — i 4 — 4 3 — 3 z 2 — £ • c ; pm - — - ; m * — ^ = 42. 3—3 i— i 3—3 3—3 The canines are of comparatively small size, and do not form projecting tusks ; and the molars and prasmolars are of the " bilophodont " type, the crown of each showing two trans- verse or oblique ridges separated by shallow valleys. 698 MANUAL OF ZOOLOGY. Several species of Tapirs are known, of which the most familiar is the American Tapir (T. Americanus), which in- habits the vast forests of South America. It is a large animal, something like a pig in shape, but brownish black in colour, and having a mane. It is nocturnal in its habits, and is strictly phytophagous. The proboscis is employed in conveying the food to the mouth, and the nostrils are placed at its extremity. It attains altogether a total length of from five to six feet. Another species, with longer hair (T. villosus), inhabits the Andes, and a still larger species (T. Malayanus) is found in Sumatra, Borneo, and Malacca. In this last, there is no mane, and the general colour is black ; but the back, rump, and sides of the belly are white. The Elasmognathus Bairdii occurs in Central America, and one or more species of the genus Tapirus (T. Roulini and T. leucogenys] have been dis- covered in the elevated regions of Ecuador and New Granada. Fam. 4. Brontotheridtz. — We may provisionally place here the large fossil Mammals from the Miocene of North America, which Professor Marsh has described under the name of Bron- totheridce. In these, the fore-feet have four nearly equal toes, Fig- 393-— Skull of Brontotherium ingens. (After Marsh.) and the hind-feet three, thus resembling the Tapirs. The skull is elongated, and a pair of very large horn-cores are carried upon the maxillaries and the anchylosed nasal bones in both sexes. The dental formula in Brontotherium is — ?2=|j ,i=I; pm 4=4 3-3 = 3g> 2—2 i— i 3—3 3—3 The incisors are small ; and the canines are short and not separated from the praemolars by any diastema, these latter being much smaller than the molars. The neck was long, and there seems to have been a long tail. The nose was probably VERTEBRATA: MAMMALIA. 699 elongated and flexible, but there would not appear to have been a long proboscis. The Brontotheridcz seem to be the successors of the Dinocerata of the Eocene. The chief genus is Brontotherium, with which the Symbprodon and Miobas ileus of Professor Cope are more or less entirely synonymous. The genera Titanotherium, Megacerops, and Diconodon, also belong to this group. Fam. 5. Palceotherida. — This family includes certain extinct Ungulates from the Eocene and Miocene Tertiary. They are characterised by the possession of three toes to all the feet, by having canines, and by the fact that the lower molars have a doubly crescentic form. The canines are longer than the other teeth, and the dental formula is — c*=±-,pm 4=4;* 5-3 = 44- 3—3 i— i 4—4 3—3 The chief genus in this family is Palaotherium itself. Several species of this genus are known, varying in size from a sheep Fig. 394. — Grinding-surface of the molar and praemolar teeth of the upper jaw of Palceotherium crassum. (After Owen.) up to a horse. From the form and size of the nasal bones it is deduced, with great probability, that the Palceotheridce pos- sessed a short movable proboscis or trunk. Fam. 6. Macrauchenida. — This family comprises the single genus Macrauchenia from the late Tertiary deposits of South America. The animals included in this genus were of large size, with three-toed feet, and a third trochanter to the femur, but having cervical vertebrae of the type of those of the Came- lidce. The general form of the skull is horse-like, and the in- cisors have a coronal pit. The teeth form nearly a continu- ous series, and the dental formula is — i 3lZl . c IZZI ; pm 5^5 . m 3n3 = 46. 3—3 i— i 4—4 3—3 Fam. 7. Solidungula or Equida. — This family comprises the Horses, Asses, and Zebras, characterised by the fact that the feet, in living forms, have only a single perfect toe each, en- closed in a single broad hoof, without supplementary hoofs 7OO MANUAL OF ZOOLOGY. (figs- 355 and 397, D). The functional toe is the 3d, and the 2d and 4th digits are represented only by rudiments of their metapodials ("splint-bones"), hidden beneath the skin. There is a discontinuous series of teeth (fig. 395) in each jaw; Fig. 395. — Skull of the Horse {Equus caballus). and in the males, canines are present, but these are wanting in the females. The dental formula is — 1-3=3. c i^l fQT ?=?V pm 3=3. « 3=3 = 40 or 38. 3—3 i— i \ o— oJ 3—3 3—3 The skin is covered with hair, and the neck is furnished with a mane. As regards the dentition of the recent Equidce, there are sometimes - - praemolars, but the first praemolar usually dis- 4 — 4 appears in adult life. The canines are of small size. The outer side of the molars (fig. 396) is deeply grooved, with two parallel sulci, to which internal ridges correspond, their length being very great, and the whole external surface being thickly coated with cement ; while the enamel-ridges and folds of the crown are filled in with the same substance. The enamel cover- ing the incisors is folded in at the crown, like the inverted finger of a glove, the tube thus formed being filled in with soft cement ; and it is the wearing down of this with age which con- stitutes the " mark." The family Equidcz is divided by Dr Gray into two sections or genera : JEguus, comprising the Horse • and Asinus com- VERTEBRATA: MAMMALIA. 701 prising the Asses and Zebras. Many authorities, however, place all the existing forms under the single genus Equus. The genus Equus is distinguished by the fact that the animal is not banded, and has no dorsal line ; both the fore and hind legs have warts, and the tail is hairy throughout. The genus appears to contain no more than one well-marked Fig. 396. — Grinding-surfaces of the last praemolar and of the three true molars of the upper jaw of the Horse. (After Cuvier.) species, if the Asses be excluded, and as far as living forms are concerned — namely, the Equus caballus. From this single species appear to have descended all the innumerable varieties of horses which are employed by man. The native country of the horse appears to have been Central Asia, but all the known wild individuals of the present day appear to be de- scendants of domestic breeds. The Ass (Asinus vulgaris) is characterised by the fact that there is always a distinct dorsal line, and the body is more or less banded; the fore-legs alone have warts, and the tail has a tuft of long hair at its extremity. The Ass is probably a native either of Northern Africa, or of South-western Asia, and it has been supposed to be the descendant either of the "Djig- getai" (Asinus hemionus\ or the "Onager" (Asinus onager), both wild existing species : though a more probable stock for it is to be found in the Asinus tceniopus of Abyssinia. According to Lenormant, the Ass was domesticated in Egypt at the very earliest periods of its history, long before the introduction of the Horse ; and it may therefore be the descendant of a wild African form. The striped and banded asses are known as Zebras and Quaggas, and are distributed over the greater part of Africa. Several genera (Anchitherium, Hipparion, Orohip- pus, Miohippus, Pliohippus, &c.) have been founded upon the 702 MANUAL OF ZOOLOGY. remains of fossil Equidce. Many of these are of special in- terest, as showing an almost perfect series of gradations be- tween a foot with three complete toes and a foot with only one complete digit. Some of them also exhibit other curious tran- sitional characters. The most ancient type of the Equidm Isolated praemolar. (After Giebel.) side in front, separated by slight intervals. The most anterior of these is a conical incisor; the central one is a canine, and the hindmost is the first prasmolar, which is separated by a wide gap from the rest of the molar series, and is pointed in foim. In the lower jaw there is also a canine, placed a little beaind the incisors, and a detached laniariform praemolar (the latter sometimes absent). In the Llamas these isolated prae- moars do not exist. Each foot terminates in two toes, which are provided with imperfect nail-like hoofs, covering no more thai, the upper surface of each toe. The two hinder toes, which are mostly present in the Ruminants, are here altogether want- ing, and the animal walks upon the hinder surfaces of the toes, 712 MANUAL OF ZOOLOGY. which are directed downwards, and are protected by pads of callous horny integument. The stomach is complex, but the manyplies is wanting. As regards their further characters, the head of all the Camdida is destitute of horns in both sexes ; the nostrils can be closed at the will of the animal; the upper lip is hairy and partially cleft ; and the red blood- corpuscles are oval. The family of the Camelidcs is represented in the Old World by the Camels (Came/us), and in South America by the Llamas and Alpacas (Auchenia). There is also an extensive series of Tertiary forms, one of which (viz., Protolabis} is specially in- teresting as possessing the full number of upper incisors, namely, three on each side of the jaw. The true Camels are peculiar to Asia and Africa, and two species are known, distinguished from one another by the possession of a double or single adipose hump on the back. The African or Arabian Camel (Camelus Dromedarius) is often called the Dromedary, and has only one hump on its back. The two toes are united together by the callous sole ; and the chest, shoulders, and knees are furnished with callous pads, upon which they rest when they lie down. The hump is almost entirely composed of fat, and appears to act as a kind of reserve supply of food, as it is noticed to diminish much in size upon long journeys. The Camel can likewise support a very prolonged privation of water, as the paunch is furnished with large cells, which the animal fills when it has access to water, and then makes use of subsequently as occasion may require. The structure of the Camel adapts it admirably for locomotion in the sandy deserts of Arabia and Africa ; and as it is very docile and good-tempered, it is almost exclusively employed as a beast of burden in the countries in which it occurs. The Bactrian Camel (C. Bactrianus] is distinguished by the possession of two humps ; but in other respects it does not differ from the Dromedary. It is found in Turkestan, Persia, Mongolia, and Thibet. The two species are said to breed together, and the hybrid offspring is stated to be occa- sionally fertile. The place of the Camels is taken in the New World b;" the Llama and Alpaca, with two other nearly-allied forms. These anima's form the genus Auchenia, and are in many respects similar to the trie Camels. They are distinguished, however, by having no hump upon tie back, and by the fact that the two toes are not conjoined and supported by a callous pad, as in the Camels, but are separate, with separate pads, and w:th strong curved nails. The neck is long and the head comparatively snull, whilst the upper lip is mobile and deeply cleft vertically. The Llamas ire chiefly found in Peru and Chili. They live in flocks in mountainous regions, and are much smaller than the Camels in size. The true Llami is kept as a domesticated animal, and used as a beast of burden, its wild form being known as the "Guanaco." The Alpaca is still smaller than the Llama, and is not very unlike a sheep, having a long woolly coat. It is partially domesticated, and the wool is largely imported into Europe. Its wild form is the so-called " Vicuna." b. Tragulida. — This group comprises certain small Rumi- nants, the so-called " Chevrotains " ( Tragulus\ which have been VERTEBRATA: MAMMALIA. 713 generally associated with the true Musk-deer (Moschus) in a single family, under the name of Moschida. The researches of Milne-Edwards and Flower, however, would prove that Moschus itself is really one of the Cennda or Deer proper, and that the Chevrotains form a group by themselves. The TragulidcR are characterised by the total absence of horns in both sexes, and by the presence of canines in both jaws, those in the upper jaw being in the form of tusks in the males, but much smaller in the females. The third stomach, or " psalterium," is wanting, and the placenta is diffuse. The feet have supplementary toes, and the metacarpals of the middle and ring digits either unite in late life to form a canon- bone, or remain (as in Hyomoschus) permanently separate. The family includes at the present day only the Hyomoschus of Western Africa, and some four or five species of Tragulus from the Indian province. The best known are the Tra- gulus Javanicus, or " Napu " of Java, and the T. meminna of Fig. 408.— Side-view of the skull of Tragulus Javanicus. (After Giebel.) India. They are all very small elegant animals, and, though commonly called " Musk-deer," they have no musk-gland. c. Cervidcz. — This family is of much greater importance than that of the Tragulidcz, including as it does all the true Deer. They are distinguished from the other Ruminants chiefly by the nature of the horns, which are wanting in the genera Mos- chus, Hydropotes, and Lophotragns. With the single exception of the Reindeer, these appendages are confined to the males amongst the Cervida^ and do not occur in the females. They do not consist, as in the succeeding group, of a hollow sheath of horn surrounding a central bony core, nor are they perma- nently retained by the animal. On the other hand, the horns — or, as they are more properly called, the antlers — of the Cervida are deciduous, and are solid. They are bony through- out, and are usually more or less branched (fig. 410), and they are annually shed and annually reproduced at the breeding 7H MANUAL OF ZOOLOGY. season. They increase in size and in the number of branches every time they are reproduced, until in the old males they may attain an enormous size. The antlers are carried upon the frontal bone, and are produced by a process not at all unlike that by which injuries of osseous structures are made good in man. At first the antlers are covered with a sensitive hairy skin or "velvet"; but as development proceeds, the vessels of the skin are gradually obliterated, and the skin dies and peels off; a bony ridge or "burr" being formed on the antler just above its base of attachment to the frontal bone. Fig. 409. — Side-view of the skull of the Roebuck (Capreolus caj>rced). (After Giebel.) In all the Deer there is a sebaceous gland, called the " lach- rymal sinus," or " larmier," which is placed beneath each eye, and secretes a strongly-smelling waxy substance. When fully developed, the antlers of the Deer consist of a main stem or " beam," carrying one or more branches or " tynes." In the second year after birth, when the antlers are first produced, and in a few Deer through- out life, the antler consists only of the "beam," and is dagger-shaped and unbranched, the animal being known now as a " brocket." In the horns of the next year, the antler develops a basal branch or ' ' brow-tyne. " In the antlers of the next year there is produced above the brow-tyne a second branch or " tres-tyne," which is directed forwards, the hinder portion of the beam constituting the "royal." If the antler develops beyond this point, it is by the more or less complex branching of these two divisions of the beam, the "royal tyne," in particular, being very liable to become divided in successive years. The following are the principal types of antlers among the Deer : — (A.) Rusine type. — The brow-tyne simple, the beam simply divided (fig. 410, A). This form of antler occurs in the Sambur Deer (Riisa Aristotdis) and in the Axis Deer of India. (B.) Rucervine type. — The two primary divisions of the beam above the VERTEBRATA : MAMMALIA. 715 brow-tyne again bifurcated, and both divisions approximately equal, as in the Rucervus Schomburgki of Siam (fig. 410, B). In a modification of this type, the royal tyne is reduced in size (fig. 410, C), and the tres-tyne is large ; while in a still more extreme type, the royal tyne is reduced to a mere snag. (C.) Elaphine type. — Brow-tyne reduplicated (by the presence of a "bez- tyne ") ; the royal tyne large and divided. This type occurs in the Red Fig. 410.— A, Antler of the "Rusine" type (Sambur Deer); B, Antler of the " Ru- cervine " type (Rucervrts Schomburgki)\ C, Modified Rucervine type of Antler (Rucervus Duvaucelli) in which the "royal" tyne is reduced in size ; D, Antler of the "Capreoline" type (Capreolus caprced); E, Antler of the Muntjak (Cervus muntjak); F, Antler of the Red-deer (Cervus elaphus) of the second year ; G, Antler of the full-grown Red-deer, showing the "elaphine" type. Deer (Cervus elaphtu, fig. 410, F and G). In the " sub-elaphine " type (as in the Cervus sika of Japan), the brow-tyne is simple. (D.) Capreoline type. — The beam dividing into a short anterior and a longer posterior branch, the latter, when fully developed, again bifurcated at its extremity (fig. 410, D). This type of antler occurs in the Roebuck (Capreolus capraa). (E.) Type of the Muntjak. — Antler supported upon an osseous pedicle arising from the frontal bone; a short brow-tyne; the beam undivided. Occurs only in the Muntjak (Cervus muntjak}. The Cervidcz are very generally distributed, but no member of the group has hitherto been discovered in either Australia or South Africa, their place in the latter continent seeming to be taken by the nearly-allied Antelopes (distinguished by their MANUAL OF ZOOLOGY. hollow horns). Africa, in fact, has no Deer except the Barbary Deer alone, and this occurs north of the Sahara only. Very many species of Cervida: are known, and it is not possible to allude to more than a few of the more familiar and important forms. Three species occur in Britain — namely, the Roebuck, Red -deer, and Fallow-deer, the last being a doubtful native. The Roebuck (Capreolus caprcza) \vas once very generally distributed over Britain, but is almost confined to the wilder parts of Scotland at the present day. It is of small size, and ranges over Northern Europe and Asia. The Red-deer or Stag (Cervus elapJius) is a much larger species, with well-developed spreading antlers. The Red- deer of Britain is represented in North America by a still larger species, known as the Wapiti (Cervus Canadensis}. The third British species is the Fallow-deer (Dama platyceros], charac- terised by the fact that the antlers are palmated — that is, dilated towards their extremities. It is a doubtful native, and is never found in a wild state at the present day. Allied to the Fallow-deer is a gigantic extinct species, the Megaceros Hibernicus, which inhabited Ireland, the Isle of Man, Scotland, and probably the greater part of Europe, up to a comparatively modern date, probably having survived into the human period. It is often, but incorrectly, spoken of as the Irish ' ' Elk, " but it is really a genuine Stag. The animal was of very great size, and was furnished with enor- mous spreading and palmate antlers, which measure from ten to twelve feet between the tips. Of all the Deer, the largest living form is the true Elk (A Ices palmatus), which is generally distributed over the northern parts of Europe, Asia, and America, being often spoken of as the Moose. The antlers in the Elk are of a very large size, and are very broad, terminating in a series of points along their outer edges. The only completely domesticated member of the Cervida; is the Rein- deer (Cervus tarandus], which is remarkable for the fact that the female is furnished with antlers similar to, but smaller than, those of the males. At the present day the Reindeer (if the Caribou be regarded as distinct) is ex- clusively confined to the extreme north of Europe and Asia, abounding especially in Lapland. Remains, however, of the Reindeer are known to occur over the greater part of Europe, extending as far south, at any rate, as the Alps, and occurring also in Britain. From this fact, taken along with many others, the existence of an extremely cold climate over the greater part of Europe at a comparatively recent period may be safely in- ferred. The Reindeer lives chiefly upon moss and a peculiar kind of lichen (Lichen rangiferina), and they are extensively used by the Lap- landers both as beasts of burden and as supplying food. The ''Caribou " of North America, if not absolutely identical with the Reindeer, would seem to be at most a well-marked variety of it. The so-called "Brockets," such as the " Guazu-pita" (Subulo rufus) of South America, have simple horns in the form of a stiletto ; whilst the singular Muntjak of India, Burmah, China, and the Indian Archipelago has the horns supported on long bony pedicles springing from the frontal bone ; and the males have large upper canines. The true Musk-deer (Moschtis moschiferus] possess no horns, and the males have a musk-gland. There are canine teeth in both jaws, and the upper canines of the males have the form of long tusks. The Musk-deer are elegant little animals, which agree with the typical Deer in the fact that they have spotted young, and that the placenta is cotyledonary, whilst they depart from the ordinary cervine type in the absence of antlers. They inhabit Central Asia. VERTEBRATA: MAMMALIA. The curious Water-deer (Hydropotes) of China is related to Moschus, and also has no horns. Another curious Chinese form is the Elaphurtts, in which there is a long tufted tail, and the antlers, in place of an anterior basal branch, possess a long posterior branch, the end of which is dilated and prolonged into several short points. d. Camelopardalida. — This family includes only a single living animal — the Camelopardalis Giraffa, or Giraffe — some- times called the Camelopard, from the fact that the skin is spotted like that of the Leopard, whilst the neck is long, and gives it some distant resemblance to a Camel. There are no upper canines in the Giraffe, and both sexes possess two small frontal horns, which, However, are persistent, and remain per- manently covered by a hairy skin, terminated by a tuft of long stiff bristles. These are not mere out-growths of the frontals, but are independent ossifications placed on the sutures between the frontal and parietal bones. There is also a central horn, if it may be so called, which is of the nature of an epiphysis, and is placed upon the sagittal suture. It becomes early an- chylosed with the skull, as do ultimately the other two horns. The neck is of extraordinary length, but, nevertheless, consists of no more than the normal seven cervical vertebrae. The fore- legs appear to be much longer than the hind-legs, and all are terminated by two toes each, the supplementary toes being altogether wanting. The tongue is very long and movable, and is employed in stripping leaves off the trees. The Giraffe is the largest of all the Ruminants, measuring as much as from fifteen to eighteen feet in height. It is a harmless and inoffen- sive animal, but defends itself very effectually, if attacked, by kicking. It is found in Nubia, Abyssinia, and the Cape of Good Hope. Remains of gigantic Ruminants allied to the Giraffe have been found in France and Greece (Helladotheriuni) ; but the Sivatherium, sometimes referred to this family, appears to have been more nearly allied to the true Antelopes. e. Cavicornia. — The last family of the Ruminants is that of the Cavicornia, comprising the Oxen, Sheep, Goats, and An- telopes. This family includes the most typical Ruminants, and those of most importance to man. The upper jaw in all the Cavicornia is wholly destitute of incisors and canines, the place of which is taken by the hardened gum, against which the lower incisors bite. There are six incisors and two canines in the lower jaw, placed in a continuous series, and the molars are separated by a wide gap from the canines. There are six grinders on each side of each jaw. Both sexes have horns, or the males only may be horned, but in either case these append- 718 MANUAL OF ZOOLOGY. ages are very different to the " antlers " of the Cervida. The horns, namely, are persistent, instead of being deciduous, and each consists of a bony process of the frontal bone — or " horn- core" — covered by a sheath of horn (fig. 411). In the Prong- buck (Antilocapra\ however, the sheath of the horn is shed annually. The feet are cleft, but are mostly furnished with accessory hoofs placed on the back of the foot. Fig. 411. — Skull of the Cape Buffalo (Bubalus coffer), viewed from above, showing the horn-cores. (After Cuvier.) The Cavicornia comprise the three families of the AntiZopidce, Ovidce, and Bovida. The Antelopes form an extremely large section, with very many species. They are characterised by their slender deer-like form, their long and slender legs, and their simple cylindrical annulated or twisted horns, which are sometimes confined to the males, but often occur in the females as well (fig. 412). Accessory hoofs are generally, but not always, present. The Antelopes must on no account be con- founded with the true Deer, to which they present many points of similarity. The structure of the horns, however, is quite sufficient to distinguish them. The Antelopes are further dis- tinguished by rarely having a beard or dew-lap, and by the general possession of " inguinal pores" and'" lachrymal sinuses." The inguinal pores are the apertures of two involutions of the integument of the groin,, secreting a viscous substance, the use VERTEBRATA : MAMMALIA. 719 of which is unknown. The lachrymal sinuses, or " tear-pits," have already been mentioned as occurring in the Cervida, and are not found in any of the Cavicornia except the Antelopes. Fig. 412.— Head of the Koodoo (Strepsiceros Koodoo). Each consists of a sebaceous sac placed beneath the eye, and secreting a yellowish waxy substance. The function of these glands is uncertain, but it is probably sexual. The Antelopes are especially numerous, both in individuals and in species, in Africa, in which country they appear to take the place of the true Deer (only one species of Deer being indigenous to Africa). Amongst the better-known African species of Antelopes are the Springbok, Hartebeest, Gnu, Eland, and Gazelle. The only European Antelopes are the Chamois (Rupicapra tragus), which inhabits the Alps and other mountain - ranges of southern Europe, and the Saiga of eastern Europe. Amongst the more remarkable Antelopes may be mentioned the Prong -buck (Antilocapra Americana) of N. America, in which there are no accessory hoofs, lachrymal sinuses, or inguinal pores ; the females have very small horns, and the horns of the male have a snag or branch in front. The horn-core, however, is conical, and does not extend above the snag. The horns are also very remarkable for the fact that their sheath is annually shed, and annually reproduced. Another curious form is the Chickara (A. quadricornis) of India, in which the females are hornless, but the males have four horns. The Sheep and Goats (Ovidce) have mostly horns in both sexes, and the horns are generally curved, compressed, and turned more or less backwards. The body is heavier, and the legs shorter and stouter, than in the true Antelopes. In the true Goats (Capra) both sexes have horns, and there are no 720 MANUAL OF ZOOLOGY. lachrymal sinuses. The throat is furnished with long hair, forming a beard; and this appendage is usually present in both sexes, though sometimes in the males only. The goats live in herds, usually in mountainous and nigged districts. The domestic Goat (Capra hircus) is generally believed to be a descendant of a species which occurs in a wild state in Persia and in the Caucasus (the " Paseng," or Capra agagrus). The true Sheep (Ovis} are destitute of a beard, and the horns though triangular and transversely ridged, are more cylindrical than in the Goats, and are generally twisted into a spiral. Horns may be present in both sexes, or in the males only.'" Lachrymal sinuses are invariably absent. Numerous varieties of the domestic sheep (Ovis aries) are known, but it is not certainly known from what wild species these were originally derived. Some, at any rate, of the domesticated breeds, more especially the smaller short-tailed breeds, with crescent-shaped horns, appear to be descended from the wild species known as the "Moufflon," which is found in Corsica and Sardinia. The Merino Sheep (a Spanish breed) and the Thibet Sheep are particularly celebrated for their long and fine wool. With the excep- tion of one species (the Big-horn, Ovis montana), all the Sheep appear to be originally natives of the Old World. The Big-horn, however, inhabits the Rocky Mountains from their termination in latitude 68° to 40°. The true Oxen (Bovida) are distinguished by having simply rounded horns, which are not twisted in a spiral manner. There are no lachrymal sinuses. Most of the oxen admit of being more or less completely domesticated, and some of them are amongst the most useful of animals, both as beasts of burden and as supplying food. The parent stock of our numerous breeds of cattle is not known with absolute certainty ; the nearest approach to British Wild Cattle being a celebrated breed which is still preserved in one or two places. These " Chillingham Cattle " are a fine wild breed, which at one time doubtless existed over a considerable part of Britain. They are pure white, with a black muzzle, the horns white, tipped with black. Though degenerate in point of size, the Chillingham Cattle are probably the descendants of the " mountain-bull" or " Urus," which existed in a wild state in Gaul at the time of Coesar's invasion. The smaller breeds of European Cattle appear to be descended from a now extinct species, the "British Short -horn" (Bos longifrons). Another large Ox, which formerly existed in Britain, and abounded over the whole of Europe, is the Aurochs or Lithuanian Bison (Bos bison). The Aurochs is of very large size, considerably exceeding the common Ox in bulk. It still occurs in the forests of the Caucasus in a wild state, but it no longer occurs wild in Europe, if we except a herd maintained by the Czar in one of the forests of Lithuania. * In the Merino Sheep, and in some other breeds also, the males only are horned. VERTEBRATA: MAMMALIA. 721 Nearly allied to the Aurochs is the American Bison or Buffalo (Bison Ainericanus], This species formerly occurred in innumerable herds in the prairies of North America, but it has been gradually driven westwards, and has been much reduced in numbers. It has an enormous head, a shaggy mane, and a conical hump between the shoulders. Two other very well known forms are the Cape Buffalo (Bubalus caffer) and the common Buffalo (Bubalus bubalis). The former of these occurs, with two allied forms, in southern and eastern Africa, and the latter is domesticated in India and in many parts of the south of Asia. The horns in both species are of large size, and their bases are confluent, so that the forehead is protected by a bony plate of considerable thickness. Amongst the more remarkable Asiatic Oxen may be mentioned the Zebu (Bos Indicus] distinguished by the fatty hump over the withers at the back of the neck, and the Yak (Poephagus grunniens] of Thibet, remarkable for its long silky tail, and the possession of a fringe of long hair along its shoulders, flanks, and thighs. The "humped" Cattle of the East are almostly certainly descended from a stock different to that which has given origin to the humpless races. They are known from Egyptian monuments to have been domesticated at an extremely early period ; but their wild form is unknown. The last of the Oxen which deserves notice is the curious Musk-ox (Ovibos moschat^ls}. This singular animal is at the present day a native of Arctic America, north of latitude 60°, and is remarkable for the great length of the hair. It is called the Musk-ox, because it gives out a musky odour. Like the Reindeer, the Musk-ox had formerly a much wider geo- graphical range than it has at present ; the conditions of climate which are necessary for its existence having at that time extended over a very much larger area than at present. The Musk-ox, in fact, in Post-tertiary times is known to have extended over the greater part of Europe, remains of it occurring abundantly in certain of the bone-caves of France. Good author- ities regard the Musk-ox as being a sheep, and therefore truly referable to the Ovidce. As regards the distribution of the Ungnlata in time, the order is not known to have commenced its existence earlier than the Eocene Tertiary ; but it presented itself throughout the whole Tertiary period under such numerous and such varied types that it will not be possible in this place to do more than simply indicate the geological range of the principal families. Of the Rhinocerotida, hornless forms (Acerotherium) occur in Miocene and Pliocene strata ; but the best-known fossil species is the two-horned Woolly Rhinoceros (R. tichorhinus). This curious species occurs in Post-pliocene deposits, and must have ranged over the greater part of Europe. It was adapted to a temperate climate, and, like the Mammoth, possessed a thick covering of mixed wool and hair. This has been demonstrated by the discovery of a frozen carcass in Siberia. The curious genus Diceratherium, with its transverse pairs of horns, is from the Miocene of North America. The Tapiridce are represented in the Eocene and Miocene 2 z 722 MANUAL OF ZOOLOGY. by the genus Lophiodon. (Coryphodon, which has generally been placed here, has been shown by Marsh to have five toes to both feet, and it, therefore, forms the type of a special family of Perissodactyles.) The genus Tapirns itself begins in the Miocene. The Brontotheridcz are wholly extinct, and are confined to the Miocene of North America. The Palaotherida are likewise completely extinct, and are confined to the Eocene and Miocene. The Macrauchenidce. are confined to the Pliocene and Post- pliocene of South America. The distribution of the Equidce in time has already been spoken of (see p. 702). The oldest genus of the family is the Eohippus of the American Eocene. Amongst the Artiodactyles, the earliest representative of the HippopotamidcR is the Hexaprotodon of the Upper Miocene (Pliocene?) of India, which differs from Hippopotamus proper only in having six lower incisors, in place of four. The latter genus appears in Europe in the Pliocene. A very large number of fossil forms of Suida are known from the Tertiaries of both the Old and New Worlds, beginning in the Eocene (Chceropotamus, &c.) The Oreodontidce are wholly confined to North America, and belong to the Miocene and Pliocene. The Anoplotherida are wholly extinct, and are confined to the Eocene and Miocene periods. The CamelidcB are first represented in the Miocene deposits of North America (Poebrotherium, &c.), and the later Tertiaries and Post-tertiaries of the same country have yielded several other extinct types of this family. Fossil remains of Camelida. also occur in the Upper Miocene (Pliocene?) of India; and early types of the Llamas occur in the Pliocene of South America. The Tragulida are first known to have come into existence during the Miocene period (Amphitragulus and Dremotherium) , but it is possible that some Eocene types (Xiphodon and Caino- therium] are really referable here. The Ceruida appear for the first time in the Miocene (Dorca- therium, Dicrocerus, &c.) Cervus itself appears in the Upper Miocene, and of the same age is the genus Amphimoschus, re- lated to the living Musk-deer. The first representative of the Camelopardalidce, so far as known, is the Helladotherium of the Upper Miocene of France, Greece, and India. The Antilopida appear in forms closely allied to recent ones in the Miocene of Europe ; and in beds of Upper Miocene VERTEBRATA: MAMMALIA. 723 (Pliocene ?) age in India we have the aberrant four-horned types which constitute the genera Sivatherium and Bramatherium. True Bovidce occur in the Miocene (Pliocene?) of India, and the Pliocene of Europe, whilst Ovidce, resembling existing types are not known from deposits earlier than the Post-pliocene. CHAPTER LXXIII. DINOCERATA, TILLODONTIA, AND TOXODONTIA. ORDER VII. DINOCERATA. — This order comprises certain extraordinary extinct Mammals from the Eocene of North America, which are regarded by Prof. Cope as an aberrant group of Ungulates, whilst Prof. Marsh considers them as a distinct order intermediate between the Perissodactyle Ungulates and the Proboscidea. The members of this order are all of gigantic dimensions, and of massive construction. Both the hind-feet and fore-feet possessed five well-developed toes. The nasal bones were elongated, and do not seem to have supported a proboscis. The cranium carries three pairs of horn - cores, which were probably envel- oped in horny sheaths. There are no upper incisors, and the upper canines have the form of long tusks directed downwards. (These characters are taken from Dinoceras, the best-known genus of the group.) The order is distinguished from the Proboscidea by the absence of upper incisors, the presence of canines, the possession of three pairs of horn-cores, and the absence of a proboscis. In Dinoceras itself, which may be taken as the type of the group, we have a large animal equal in dimensions to the living Elephants, which it resembles also in the osteology of its limbs, in most essential respects. It is in the skull (fig. 413) and dentition, however, that the most striking pecu- liarities of Dinoceras are to be found. As regards the denti- tion, the front of the upper jaw was destitute of incisors, and probably carried a palatine pad, but there were two very large canines in the form of tusks directed perpendicularly down- wards ; and there was also a series of six small grinders on each side. In the lower jaw are six incisors, small canines, and twelve prsemolars and molars, six on each side. The dental formula is thus — 724 MANUAL OF ZOOLOGY. . o — o i I c -j pm 3zz3. . m 3~3 _ 3—3 ' i—1 ' ' 3—3 ' 3—3 Superiorly each maxillary bone carried a well-developed pro- cess, probably of the nature of a horn-core. The nasals sup- Fig. 413. — Skull of Dinoceras mirabile, after Marsh. From the Eocene Tertiary. port two similar but smaller horn-cores ; and the frontals are developed behind into two larger bony projections most prob- ably also of the nature of horn-cores. The animal thus pos- sessed three pairs of horns, one carried by the upper jaw- bones, one by the nasals, and one by the frontal bones ; though it is possible that some of these cores were simply covered by a callous integument. The nasal bones are long, and there is no evidence of any proboscis. The limbs are short, the fore- legs shorter than the hind-legs ; and the femur was not pro- vided with a third trochanter. The tail is short and slender, and the ribs are furnished with rudimentary uncinate processes. As regards the mental powers of Dinoceras, Prof. Marsh re- marks : " The brain-cavity of Dinoceras is perhaps the most remarkable feature in this remarkable genus. It proves con- clusively that the brain was proportionately smaller than in any other known Mammal, recent or fossil, and even less than in some reptiles. It is, in fact, the most reptilian brain in any known Mammal. In D. mirabile, the entire brain was actu- VERTEBRATA : MAMMALIA. 725 ally so diminutive that it could apparently have been drawn through the neural canal of all the prsesacral vertebrae, cer- tainly through the cervicals and lumbars." The chief genera which are included amongst the Dinocerata by Marsh are Dinoceras, Tinoceras, and Uintatherium. All the remains of this singular group which have hitherto been brought to light, are from the Eocene rocks of North America. ORDER VIII. TILLODONTIA. — This order has been estab- lished by Prof. Marsh for the reception of some singular Mam- mals from the Eocene Tertiary of the United States. The following are the characters of the order, so far as published : The molar teeth have grinding crowns, as in Ungulates, and may have distinct roots, or may grow from permanent pulps ; small canines are present in both jaws ; and each jaw carries two long scalpriform incisors, resembling those of Rodents in form and in growing from persistent pulps. The feet are plantigrade and pentadactyle, and the digits were apparently unguiculate. The femur has a third trochanter, and the radius and ulna and tibia and Jibula are distinct bones. The order includes two distinct families, — one, the Tillothe- rid&, having molar teeth with distinct roots ; whilst the other, Stylinodontidce, possessed rootless molars, which grew from persistent pulps. All the known forms of the order are from the Eocene Tertiary, and the typical species seem to have been from one-half to two-thirds of the size of the Tapir. The type-genus of the order is Tillotherium, which presents a remarkable combination of the characters of the Ungulata, Rodentia, and Carnivora. The general form of the skeleton most closely resembles that of the Carnivores, the skull being like that of the Bears in many respects, whilst the feet are five- toed, with the whole sole applied to the ground, and having ungual phalanges similar to those of the Ursidce. The brain- cavity is of small size, and the cerebral hemispheres did not extend over the cerebellum or the olfactory lobes. The orbits are not complete, but open into the temporal fossae. The prsemolars and molars have grinding crowns, the canines are of small size, and the praemaxillae carried a pair of large scalpri- form incisors (fig. 414), which resemble those of the Rodents in having chisel-shaped crowns, and in growing throughout the life of the animal. As in Rodents, there is a correspond- ing pair of scalpriform incisors in the lower jaw. The dental formula is — . i — i i — T i — * •* — 3 i - - ', c - ; pm •- — - ; m ° -- = 30. !_!> !_!> * 2_2' 3—3 726 MANUAL OF ZOOLOGY. ORDER IX. TOXODONTIA. — This order includes certain large extinct Mammals from the later Tertiary deposits of South Fig. 414. — Tillodontia. Side-view of the skull of Tillotherhtmfodiens, with the lo\ jaw displaced downwards, one-fourth of the natural size. (After Marsh.) America, the true systematic position of which is still very doubtful; since they present affinities to the Ungulata, the Rodents, and the Edentates. The skull is massive and the dentition is very peculiar. The molars and praemolars are Fig. 415 — A, Right upper jaw of Toxodon Bnrmeisteri, and(B) left lower jaw of the same ; c Lower canine. (After Byrmeister.) Greatly reduced in size. bent so as to be strongly convex outwards and concave inwards, with flat grinding-surfaces (fig. 415), and presenting the pecu- liarity that they are rootless and grow from persistent pulps. Canines are present in the lower jaw; but are of very small VERTEBRATA : MAMMALIA. 727 size (fig. 415, c) and are placed in the interval between the in- cisors and praemolars. In the upper jaw only the sockets for the canines are left. There are four upper and six lower incisors, which are separated by a wide diastema from the praemolars. The dental formula is — . 2 — 2 o — o 4 — 4 3 — 3 z - - ; c — ; pm : m - - = 38. 3-3' i— i' 3—3' 3-3 There is no third trochanter to the femur, but the structure of the manus and pes is quite unknown. The only known genera are Toxodon and Nesodon. CHAPTER LXXIV. HYRACOIDEA AND PROBOSCIDEA. ORDER X. HYRACOIDEA. — This is a very small order which has been constituted by Huxley for the reception of two or three little animals, which make up the single genus Hyrax. These have been usually placed in the immediate neighbour- hood of the Rhinoceros, to which they have some decided affinities, and they are still retained by Owen in the section of the Perissodactyle Ungulates. The order is distinguished by the following characters : There are no canine teeth, and the incisors of the upper jaw are long and curved, and grow from permanent pulps, as they do in the Rodents (such as the Beaver, Rat, &c.) The lower incisors are directed forwards. The molar teeth are singularly like those of the Rhinoceros. According to Huxley, the dental formula of the aged animal is — **£?; ,°-°; ^4=4 m 3~3 = 6> 2—2' o—o 4—4' 3—3 The fore-feet are tetradactylous, the hind-feet tridactylous, and all the toes have rounded hoof-like nails, with the exception of the inner toes of the hind-feet, which have an obliquely-curved nail. There are no clavicles. The nose and ears are short, and the tail is represented by a mere tubercle. The placenta is deciduate and zonary, whereas in the Ungulates it is non-deciduate. Several species of Hyrax are known, but they resemble one another in all essential particulars, and, with the exception of 728 MANUAL OF ZOOLOGY. H. Syriacus, they are exclusively confined to Africa. They are all gregarious little animals, living in holes of the rocks, and capable of domestication. Some forms (Dendrohyrax) are arboreal in their habits. The "coney" of Scripture is Fig. 416.— Skull of Hyrax. (After Cuvier.) believed to be the Hyrax Syriacus, which occurs in the rocky parts of Syria and Palestine. Another species — the Hyrax Capensis, or "Klipdas" ("badger of the cliffs ") — occurs com- monly in South Africa, and is known by the colonists as the " badger." No fossil remains have as yet been discovered which can with certainty be referred to this order. ORDER XI. PROBOSCIDEA. — The eleventh order of Mammals is that of the Proboscidea, comprising no other living animals except the Elephants, but including also the extinct Mastodon and Deinotherium. The order is characterised by the total absence of canine teeth; the molar teeth are few in number, large, and transversely ridged or tuberculate; incisors are always present, and grow from per- sistent pulps, constituting long tusks (fig. 417). In living Ele- phants there are two of these tusk-like incisors in the upper jaw, and the lower jaw is without incisor teeth. In the Deinotherium this is reversed, there being two tusk-like lower incisors and no upper incisors. In the Mastodons, the incisors are usually developed in the upper jaw, and form tusks, as in the Ele- phants, but sometimes there are both upper and lower in- VERTEBRATA: MAMMALIA. 729 cisors, and both are tusk - like. The nose is prolonged into a cylindrical trunk, movable in every direction, highly sensitive, and terminating in a finger-like prehensile lobe (fig. 417). The nostrils are placed at the extremity of the proboscis. The feet ^ Fig. 417. — Skull of the Indian Elephant (Elephas Indicus) : i Tusk-like upper incisors ; m Lower jaw, with molars, but without incisors ; n Nostrils, placed at the end of the proboscis. (After Owen.) are furnished with five toes each (fig. 419), but some of those toes may not be provided with hoofs. The feet are furnished with a thick pad of integument, forming the palms of the hands and the soles of the feet. There are no clavicles. The testes are abdominal throughout life. There are two teats, and these are placed upon the chest. The placenta is deciduate and zonary. The recent Elephants are exclusively confined to the tropical regions of the Old World, in the forests of which they live in herds. Only two living species are known — the Asiatic Elephant (Elephas Indicus} and the African Elephant (E. Afri- canus). There can be no doubt, however, but that the Mam- moth (Elephas primigenius) existed in Europe within the human period. 730 MANUAL OF ZOOLOGY. In both the living Elephants the " tusks " are formed by an enormous development of the two upper incisors. The milk- tusks are shed early, and never attain any very great size. The permanent tusks grow throughout the life of the animal, and often reach six or seven feet in length, and from fifty to seventy pounds in weight, or even up to one hundred and fifty pounds in aged males. In the Indian Elephant, and its variety the Ceylon Elephant, the males alone have well-developed tusks, but both sexes have tusks in the African species, those of the males being the largest. The lower incisors are absent, and there are no other teeth in the jaws except the large molars, Fig. 418. — A, Left ramus of lower jaw of Elephas Indicus, viewed from above (after Cuvier). B, Grinding-surface of molar tooth of Elephas Africamts (after Giebel). which are of very large size, and are composed of transverse plates of enamel, surrounding tracts of dentine, and bound together by cement. As the tooth wears down, the enamel plates come to project, enclosing islands of dentine, which are narrow and elongated in the Indian Elephant (fig. 418, A), but are lozenge-shaped in the African Elephant (fig. 418, B). In reality, there are six molars on each side of each jaw, but owing to their large size, and the manner in which they succeed each other, there is never more than one (or part of two) in use on each side of each jaw at one time. The first three teeth of the grinder - series, which would ordinarily be sup- posed to be prsemolars, are in reality true molars, as they have no predecessors or successors. None of the molars, in fact, undergo vertical displacement, but the whole series gradually moves forward in the jaw, and the place of each tooth as it slowly advances is taken by the tooth next behind it in the series, each succeeding tooth being usually larger than its predecessor, and having more numerous plates of enamel. VERTEBRATA: MAMMALIA. 731 The Indian Elephant is the only species which is now caught and domesticated, and as it rarely breeds in captivity, the de- mand for it is supplied almost entirely by the capture of adult wild individuals, which are taken chiefly by the assistance of those which have been already tamed. The Indian Elephant is distinguished by its concave forehead, its small ears, and the characters of the molars. Its skull is pyramidal, and it has five hoofs on the fore-feet, and only four on the hind-feet. Its colour is generally pale brown. (The so-called " White Ele- phants "are merely albinos.) The African Elephant, on the other hand, has a strongly convex forehead and great flapping ears. Its colour is darker, its skull is rounded, and it has four hoofs on the fore-feet, and only three on the hind-feet. The African Elephant is chiefly hunted for the sake of its ivory, and there is too much reason to believe that the pursuit will ultimately end in the destruc- tion of these fine animals. A great deal, however, of the ivory of commerce conies from Siberia, and is really derived from the tusks of the now ex- tinct Mammoth, which formerly inhabited the north of Asia in great numbers. The Elephants are all phy- II. IV. tophagous, living entirely on the foliage of shrubs and trees, and other vegetable matters, which they strip off by means of the prehensile trunk. As the tusks prevent the animal from drinking in the ordinary manner, the water is sucked up by the trunk, which is then inserted into the mouth, into which it empties its contents. Closely allied to the true Elephants are the Mastodons, characterised by the fact that the crowns of the molar teeth have nipple-shaped tubercles placed in pairs (fig. 420). Gen- erally speaking, the two upper incisors formed long curved tusks, as in the Elephants, but in some cases there were two lower incisors as well. The various species of Mastodon all belong to the later Tertiary and Post-tertiary periods. Fig 419.— Hind-foot of the Indian Ele- phant (Elepkas Indicus). (After Cuvier.) 732 MANUAL OF ZOOLOGY. The last of the Probosddea is a remarkable extinct animal, the Deinotherium . This extraordinary animal has hitherto only been found in Miocene deposits, and little is known of it except its enormous skull. Molars and prsemolars were Fig. 420.— A, Skull of Mastodon giganteum ; B, Side-view of the second true molar of Mastodon giganteum. (After Owen.) present in each jaw, and the upper jaw was destitute of can- ines and incisors. In the lower jaw were two very large tusk- like incisors, which were not directed forwards as in the true Fig. 421. — Skull of Deinotherium giganteum. Miocene Tertiary. Fig. 422. — A, Side-view of the third molar of Deinotherium giganteum; B, Grinding surfaca of the same. Miocene Tertiary. (After Kaup.) Elephants, but were bent abruptly downwards (fig. 421). The animal must have attained an enormous size, and it is probable VERTEBRATA: MAMMALIA. 733 that the curved tusks were used either in digging up roots, or in mooring the animal to the banks of rivers, for it was prob- ably aquatic or semi-aquatic in its habits. The whole of the praemolars and molars were in use at one time, and their crowns are crossed by strong transverse ridges, which give them a marked Tapiroid character, while in some respects they resemble the teeth of the Mastodons. It is placed by De Blainville in the Sirenia, being regarded as a Dugong with tusk-like lower incisors ; but this view has been rendered un- tenable by the discovery of limb-bones of a distinctly Pro- boscidean type. As regards the distribution of the Proboscidea in time, the order came into existence in the Miocene period, where it is represented by all its three sections, Deinotherium, Mastodon, and Elephas. The genus Deinotherium, as just mentioned, is exclusively confined to the Miocene period. The genus Mastodon is characteristic in Europe of the Mio- cene and Pliocene ; but in North America it is represented in the Post-pliocene, and it occurs also in deposits of the same age in South America. No Elephant has yet been discovered in the Miocene rocks of Europe, but six species are known from Miocene (Pliocene ?) strata in India. In the Pliocene period Europe possessed its Elephants (viz., JE. priscus and JS. meridionalis) ; but the best known of the extinct Elephants, as well as the most modern, is the Mammoth (E. primigenius}. This enormous animal is now wholly extinct, but it formerly abounded in the northern parts of Asia and over the whole of Europe. It occurred also in Britain, and unquestionably existed in the earlier portion of the human period, its remains having been found in a great number of instances in connection with human implements. From its great abundance in Siberia, it might have been safely inferred that the Mammoth was able to endure a much colder climate than either of the living elephants. This inference, however, has been rendered a certainty by the discovery of the body of more than one Mammoth embedded in the frozen soil of Siberia. These specimens had been so perfectly preserved that even microscopical sections of some of the tissues could be made; and in one case even the eyes were preserved. From these specimens we know that the body of the Mam- moth was covered with long woolly hair. 734 MANUAL OF ZOOLOGY. CHAPTER LXXV. CARNIVORA. ORDER XII. CARNIVORA. — The twelfth order of Mammals is that of the Carnivora, comprising the Ferce, or Beasts of Prey, along with the old order of the Pinnipedia, or Seals and Wal- ruses, these latter being now almost universally regarded as merely a group of the Carnivora modified to lead an aquatic life. The Carnivora are distinguished by always possessing two sets of teeth, which are simply covered by enamel, and are always of three kinds — incisors, canines, and molars — differing from one another in shape and size. The incisors are generally (except in some seals) ; the canines are always - — , and are invariably much larger and longer than the incisors. The prce- molars and molars are mostly furnished with cutting or trenchant edges ; but they graduate from a cutting to a tuber culate form, as the diet is strictly carnivorous, or becomes more or less miscellaneous. Fig. 423.— Permanent dentitition of the Lion (Felts leo). In the upper jaw the letter /3 indicates the upper carnassial, while in the lower jaw the letter m indicates the lower carnassial. In the typical and most highly specialised Carnivores (such as the Felida), the last praemolar in the upper jaw, and the first molar in the lower jaw (fig. 423, pm* and m) are specially developed, and are known as the " carnassial " teeth, having a VERTEBRATA: MAMMALIA. 735 sharp cutting-edge ; whereas in other cases the corresponding teeth are blunt and " tuberculated." Even in their most tren- chant condition, the carnassial tooth commonly has a more or less developed tuberculated process or heel, on the inside of its cutting edge. In various Carnivores a number, or all, of the praemolars and molars may be " tuberculate," their crowns being adapted for bruising rather than cutting. As a general rule, the shorter the jaw, and the fewer the praemolars and molars, the more carnivorous is the animal. The jaws are so articulated as to admit of vertical but not of horizontal move- ments ; the zygomatic arches are greatly developed to give room for the powerful muscles of the jaws ; and the orbits are not separated from the temporal fossae. The intestine is com- paratively short. In all the Carnivora the clavicles are either altogether ivanting, or are quite rudimentary. The toes are 'provided with sharp{ curved claws. The teats are abdominal ; and the placenta is deciduate and zonular. The order Carnivora is divided into three very natural sec- tions : — Section I. P'mnigrada or Pinnipedia. — This section comprises the Seals and Walruses, in which the fore and hind limbs are short, and are expanded into broad webbed swimming-paddles (fig. 424, B). The hind-feet are placed very far back, nearly irada, Foot of Bear ; Fig. 424.— Foot of Carnivora (after Owen). A, Plantign B, Pinnigrada, Hind-feet of Seal ; C, Digitigrada, Foot of Lion. in a line with the axis of the body, and they are more or less tied down to the tail by the integuments. Section II. Plantigrada. — This section comprises the Bears, 736 MANUAL OF ZOOLOGY. and their allies, in which the whole, or nearly the whole, of the foot is applied to the ground, so that the animal walks upon the soles of the feet (fig. 424, A). Section III. Digitigrada. — This section comprises the Lions, Tigers, Cats, Dogs, &c., in which the heel of the foot is raised entirely off the ground, and the animal walks upon the tips of the toes (fig. 424, C). SECTION I. PINNIGRADA or PINNIPEDIA. — This section of the Carnivora comprises the amphibious Seals and Walruses, which differ from the typical Carnivores merely in points con- nected with their semi-aquatic mode of life. The body in these forms is elongated and somewhat fish-like in shape, covered with a short dense fur or harsh hairs, and terminated behind by a short conical tail. All the four limbs are present, but are very short, and the five toes of each foot are united together by the skin, so that the feet form powerful swimming- paddles. The hind-feet are of large size, and are placed far back, their axis nearly coinciding with that of the body (figs. 424, 425). From this circumstance, and from the fact that the Fig. 425. — The Greenland Seal (Phoca Grcenlandica). integument often extends between the hind-legs and the sides of the short tail, the hinder end of the body forms an admir- able swimming apparatus, similar in its action to the horizontal tail-fin of the Cetacea and Sirenia. The tips of the toes are furnished with claws, but the powers of terrestrial locomotion are very limited. On land, in fact, the typical Seals can only drag themselves along laboriously, chiefly by the contractions of the abdominal muscles. On the other hand, the Eared Seals (Otariadce) can use their hind-limbs freely upon the land. The ears are of small size, and are mostly only indicated by VERTEBRATA: MAMMALIA. 737 small apertures, which the animal has the power of closing when under water. The bones are light and spongy, and beneath the skin is a layer of fat or blubber. The dentition (fig. 426) varies, but teeth of three kinds are always present, in Fig. 426. — Dentition of the common Seal (Phoca vitulina). the young animal at any rate. The canines are always long and pointed, and the molars are generally furnished with sharp cutting-edges. The lower incisors may be reduced to four or to two in number, or may even be wanting (Walrus) ; and the upper incisors may fall below the normal six. The dental formula of the common Seal (fig. 426) is — 3 — 3 i — 4 — 4 i — The section Pinnigrada includes the three families of the Earless Seals (Photidce), the Eared Seals (Otariadcz), and the Walruses ( Tricheddce). The typical Seals (Phocidce] are distinguished from the Walruses by the presence of incisor teeth in both jaws, and by canines of moderate size ; while the absence of ears and the inability to use the hind-limbs on land separate them from the Otariadce. They form a veiy numerous family, of which species are found in almost every sea out of the limits of the tropics. They abound, however, especially in the seas of the Arctic and Antarctic regions. They live for the most part upon fish, and when awake, spend the greater part of their time in the water, only coming on land to bask and sleep in the sun and to suckle their young. They appear to be univer- sally polygamous. The body is covered with a short fur, interspersed with long bristly hairs ; and the lips are furnished with long whiskers, which 3A 733 MANUAL OF ZOOLOGY. act as organs of touch. The seals are very largely captured for the sake of their blubber and skins. The only common British seal is the Phoca vitulina, which occurs not uncommonly on the northern shores of Scotland, and ranges over almost the whole of the shores washed by the North Atlantic and the seas of Greenland. It is yellowish-grey in colour, and measures from three to five feet in length. Other seals attain a much greater length — the Great Seal measuring from eight to ten feet, and the Elephant Seal (Macro- rhinus) of the South Pacific, reaching a length of twenty feet. The Eared Seals or Sea-lions (Otariada:) differ from the typical Seals in the possession of small conical ears, and in the much greater freedom of the limbs, enabling the animal to walk with comparative ease on land. The Eared Seals are principally found on the shores of the continents and islands washed by the Pacific ; but they are also found in the extreme southern part of the Atlantic as far northwards as the mouth of the Rio Plata. The third family of the Pinnigrade Carnivores is that of the Triche- cidce, comprising only the Walrus or Morse (Trichecus rosmarus). The chief peculiarity by which the Walrus is distinguished from the true Seals is found in the dentition. According to Owen, there are six incisors in the upper jaw and four in the lower ; but these are only present in the young animal, and soon disappear, with the exception of the outermost pair of upper incisors. The upper canines are enormously developed, growing from persistent pulps, and constituting two large pointed tusks, which attain a length of over fifteen inches (fig. 427). The direction of Fig. 427. —Skull of the Walrus (Trichecus rosmarus), after Owen. i Tusk-like upper canines. the tusks is downwards and slightly outwards, and they project consid- erably below the chin. The upper jaw has three prsemolars and two molars, with flattened crowns, on each side, and the lower jaw has the same VERTEBRATA: MAMMALIA. 739 number of praemolars and a single molar on each side ; but the true molars are caducous, so that the dental formula of the adult animal is — = i*. o—o i— i 3—3 o—o Except as regards its dentition, the Walrus agrees in all essential re- spects with the Seals. It is a large and heavy animal, attaining a length of from ten to fifteen feet or upwards. The body is covered with short brownish or yellowish hair, and the face bears many long stiff bristles. There are no external ears. The chief use of the tusk-like canines appears to be that of assisting the unwieldy animal to get out of the water upon the ice; but they doubtless serve as weapons of offence and defence as well, and they are used for digging up burrowing shell-fish out of the sand. The Walrus is hunted by whalers, both for its blubber, which yields an excellent oil, and for the ivory of the tusks. It is found, living in herds, in the Arctic seas, being especially abundant at Spitzbergen and Nova Zembla. SECTION II. PLANTIGRADA (ARCTOIDEA). — The Carnivorous animals belonging to this section apply the whole or the greater part of the sole of the foot to the ground (fig. 424, A) ; and the portion of -the sole so employed is destitute of hairs in most instances (the sole is hairy in the Polar Bear). From the structure of the foot, the Plantigrada have great power of rearing themselves up on the hind-feet. They approach the Insectivora in their comparatively slow movements and their nocturnal habits, and in possessing no caecum. They mostly hibernate, and their feet are always pentadactylous. The typical family of the Plantigrade Carnivora is that of the Ursidtf. or Bears, in which the entire sole of the foot is applied to the ground in walking. The Ursidce, are much less purely carnivorous than the majority of the order, and, in ac- cordance with their omnivorous habits, the teeth do not ex- hibit the typical carnivorous characters. The incisors and canines have the ordinary carnivorous form, but the " carnas- sial " teeth have tuberculate crowns, instead of a sharp cutting- edge. The dental formula in Ursus (fig. 428) is — ,'3-3. c*=} pm 4=4 .m2-2 = 3—3 i— i 4—4 3-3 The dental formula of the Bears is thus the same as that of the Dogs ; but the second and third praemolars are small and usually deciduous; while the first prsemolar is also often caducous. The last praemolar and all the molars have tuber- culate crowns, and the carnassials are not of specially large size, these characters being equally present in the flesh-eating Polar Bear and the strictly vegetarian Sun-bear. The claws are formed for digging, large, strong, and curved, but are not retractile. The tongue is smooth ; the ears small, 740 MANUAL OF ZOOLOGY. erect, and rounded ; the tail short ; the nose forms a movable truncated snout ; and the pupil is circular. As shown by their smooth tongues and tuberculate molars, the Bears are not peculiarly or strictly carnivorous. They eat Fig. 428. — Dentition of the Polar Bear (Thalassarctos maritimus). flesh when they can obtain it, but a great part of their food is of a vegetable nature. The Bears are very generally distributed over the globe, Australia and Africa alone having no representative of the family. The common Brown Bear (Ursus arctos) was at one time an inhabitant of Britain, and also existed over the whole of Europe. At the present day the Brown Bear is only found in the great forests of the north of Europe and in Asia, and in the Arctic portions of North America. It feeds on roots, fruits, honey, insects, and, when it can obtain them, upon other Mammals. It attains a great age, and hibernates during the winter months. Very nearly allied to the Brown Bear is the Black Bear of America (Ursus Americanus}. Both are of some commercial value, being hunted for the sake of their skins, fat, and tongues. A much larger American species is the Grizzly Bear (Ursus ferox], found in many parts of the American continent. It is about twice as large as the ordinary Bear, but it is said to subsist to a great extent upon vegetable food, such as acorns. The most remarkable, however, of the Bears is the great White Bear ( Thalassarctos maritimus\ which is exclusively a native of the Arctic regions. It is a very large and powerful animal, the fur of which is cream-coloured. The paws are very long, and the soles of the feet are covered with coarse hair, giving the animal a firm foothold upon the ice. The Polar Bear differs from the other Ursidce in being exclusively carnivorous, since vegetable food would be generally unattainable. It is as much at home in the water as on land, and lives chiefly upon seals and fish, and the carcasses of Cetaceans. Amongst the other Bears may be mentioned the Sun-bears (Helarctos] of the Malayan Archipelago, the Honey-bears (Prochilus or Melursus) of India, and the Spectacled Bear (Helarctos or Tremarctos ornatus] of the VERTEBRATA: MAMMALIA. 741 Peruvian and Chilian Andes, the sole representative of the Ursidcs in South America. The family Procyonidos includes a number of small American Carnivores, which are nearly allied to the Bears. The Racoons (Procyon, fig. 429) are natives of tropical and northern America, Fig. 429.— Skull of Racoon (Procyon lotor}. (After Giebel.) and have a decided external resemblance to the Bears. They have tolerably long tails, however, and sharp muzzles. The commonest species is the Procyon lotor of North America, which derives its specific name from its habit of soaking its food in water before eating it. The dental formula of Procyon is — • . ^ — 3 i — i 4 — 4 2 — 2 i 2 — .-2 • c : pm - — * : m = 40. 3—3 i -i 4—4 2—2 The Coatis (Nasua) are very closely allied to the Racoons, and are exclusively confined to the American continent. The Kinkajous (Cercoleptes) are inhabitants of South America, ex- tending their range northwards to Mexico, and, as is the case with so many of the animals of this continent, they are adapted for an arboreal life, to which end their tails are prehensile. They appear to represent in the western hemisphere the Lemurs of the Old World, to which they present certain points of affinity. Forming a transition between the Procyonidtz and the Civets (Viverridce)^ is the curious Cacomixle (Bassaris astuta\ which is a native of California, Texas, and parts of Mexico, and is arboreal in its habits. Nearly related to the preceding is the family of the sEluridce, comprising the well-known "Wah" or "Panda" (^Elurusfulgens] of India and Thibet, and the ^Eluropus of the latter country. The former is a cat-like animal, chestnut-brown above and 742 MANUAL OF ZOOLOGY. black inferiorly, with a white face and ears, and the latter is almost completely white in colour. Like the Kinkajous, but unlike the Coatis and Racoons, the sEhinis has retractile claws. The only remaining family of the Plantigrada is that of the Melidce. or Badgers, characterised by their elongated bodies and short legs, and forming a transition between the Ursidce and Mustelidce. They agree with the latter group in the pos- session of odoriferous anal glands. The dental formula of the Badger is as follows (Baird) — ''™^; = 34(36). The first prsemolar in the lower jaw is very minute, and is soon lost; the upper carnassial has a well-marked internal tubercle; and the upper molar is of comparatively large size, nearly equalling the carnassial in its dimensions. The common Badger (Meles taxus\ which may be regarded as the type of this group, occurs in Britain, and is one of the most inoffensive of animals. It is nocturnal in its habits, and is a very miscellaneous feeder, not refusing anything edible which may come in its way, though living mainly on roots and fruits. The Badger burrows with great ease, and can bite very severely. The European Badger is represented in the United States and Canada by the " SifHeur " (Taxidea Labradoricd), and in the hilly parts of India by the Indian Badger (Meles or Arctonyx collaris). The Glutton (Gulo luscus), often called the Wolverine, is of common occurrence in the northern parts of Europe, Asia, and America. It is from two to three feet in length, and though doubtless a tolerably voracious animal, it is certainly not so much so as to deserve the name of Glutton. The Grison (Galictis) is a closely-allied form which is found in South America. These two genera are often placed among the Mustelidce. The Ratels or Honey-badgers (Mellivora) are much like the common Badger in their habits and appearance, but they have only one lower molar (the carnassial) on each side. They are natives of southern and eastern Africa, and India. The Skunks (Mephitis) are sometimes placed in this family, to which they are allied through the singular Mydaus of Java and Sumatra. SECTION III. DIGITIGRADA. — In this section of the Carnivora the heel is raised above the ground, with the whole or the greater part of the metacarpus and metatarsus, so that the animals walk more or less completely on the tips of the toes (fig. 424, C), No absolute line, however, of demarcation can VERTEBRATA: MAMMALIA. 743 be drawn between the Plantigrade and Digitigrade sections of the Carnivora, since many forms (e.g., Mustelida and Viver- ridce) exhibit transitional characters, and it has even been pro- posed to place these in a separate section, under the name of Semi-plantigrada. Moreover, the Mtislelidce and Melidcz are so nearly allied that they can with difficulty be kept apart. The first family of the Digitigrada is that of the Mustelida or Weasels, including a number of small Carnivores, with short legs, elongated worm-like bodies, and a peculiar gliding mode of progression (hence the name of Vermiformes, sometimes applied to the group). The dental formula of Mustela proper is — 3—3 i— i 4—4 2—2 In the nearly-allied genus Putorius (fig. 430) there is a prae- molar less above and below. Among the best known of the Mustelidcz are the common Weasel (Putorius vulgaris], the Polecat (Putorius fatidus\ and Fig. 430.— Skull of the Polecat (Putorius fcetidus). the Ferret (Putorius furo), the last being usually regarded as an albino variety (now permanent) of one of the Polecats. It is really an African form, but it has been long domesticated in Europe. Nearly-allied types are the Ermine or Stoat (Pu- torius erminea), and the Minks (P. vison and P. lutreold] of North America and Europe. Among the species of Mustela proper may be mentioned the Pine-marten (M. martes) and Stone-marten (M. foind] of Europe and Asia, the Pekan or "Fisher" (M. Pennantii) of North America, the true Sable (M. zibellina) of northern Asia, and the American Sable (M. Americana). The Mustelida are of commercial importance as yielding beautiful and highly- valued furs, the skins of the 744 MANUAL OF ZOOLOGY. Sable, Ermine, Black Mink, and Pekan, being specially sought after. Almost all the Weasels have a very disagreeable odour, produced by the secretion of greatly-developed and modified sebaceous glands, placed in the neighbourhood of the anus, and known as the anal glands. In this respect, however, the nearly-allied genus Mephitis, comprising the Ameri- can Skunk, is facile princeps. The Skunk is a pretty little animal, with a long bushy tail, and when unmolested it is perfectly harmless. If pursued or irritated, however, it has the power of ejecting the secretion of the anal glands to a greater or less distance with considerable force. The odour of this secretion is so powerful and persistent that no amount of washing will remove it from a garment, and its characters are said to be of the most in- tensely disagreeable description. Nearly related to the family of the Mustelidce. are the Otters (Lutra\ distinguished by the possession of webbed feet adapted Fig. 431. — Skull of common Otter (Lntra vnlgaris), viewed from one side. (After Coues.) Fig. 432. — Under view of the skull of the common Otter. (After Coues. ) for swimming. The body is long, the legs short, and the tail long, stout, and horizontally flattened. The common Otter (Lutra vulgaris, figs. 431, 432) is a native of Britain, frequent- VERTEBRATA : MAMMALIA. 745 ing the banks of streams and lakes. It lives upon fish, and is highly destructive to salmon. A closely-allied form is the American Otter (Lutra Canadensis]. In the Sea- otters (Enhydris) the tail is very short. They are found on both sides of the North Pacific, and yield a very valuable fur, being much more strictly aquatic in their habits than the ordinary Otters. Besides Enhydris, a species of Sea-otter belonging to the genus Nutria is found on the shores of North and South America, ranging from California to Chili. The second family of the Semi-plantigrade Carnivores is that of the Viverrida, the Civets and Genettes. They are all of moderate size, with sharp muzzles and long tails, and more or less striped, or banded, or spotted. The dental formula of Viverra is — I — i c - -\ pm 4 — 4 2, — 2 m - - = 40. 2—2 3—3 i— i 4—4 The upper carnassial (the 4th praemolar) and the lower carnassial (the ist molar) have cutting edges (fig. 433) ; while Fig. 433. — Dentition of the Civet-cat (yiverra civetta). The upper figure shows the upper jaw, the lower figure gives the lower teeth. both the upper molars and the last lower molar have tubercu- late crowns. The canines are long, sharp, and pointed. The tongue is roughened by numerous priclcly papillae. The claws are semi-retractile, and the pupils can contract, on exposure to light, till they resemble a mere line. In most of their charac- 74-6 MANUAL OF ZOOLOGY. ters, therefore, the Civets are much more highly carnivorous than are any of the preceding families, and they approach in many respects very close to the typical group of the Digitigrada (viz., the Felidce), having especially very close affinities with the Hyaenas. Many of the species of the family are furnished with anal glands, which secrete the peculiar fatty substance known as " civet." All the Viverridcz belong to the Old World. The true Civet-cat is the Viverra civetta, a native of North Africa and Eastern Asia. It is a small nocturnal animal, which climbs trees with facility, and feeds chiefly upon small mammals, reptiles, and birds, but also upon roots and fruits. It furnishes the greater part of the "civet" of commerce, which was formerly in great repute both as a perfume and as a medicinal agent. It is a pomade-like substance, with a strong musky odour, and is secreted by a deep double pouch beneath the anus. The Genette ( Viverra genetta) is very closely related to the preceding, and is a native of Africa and Southern Europe, being not uncommonly domesticated and kept like a cat. The anal pouch in the Genette is much reduced in size, and has hardly any perceptible secretion. Another nearly-allied form is the Ichneumon (Herpestes], one species of which is kept as a domestic animal in Egypt, and lives upon Snakes, Lizards, the eggs of the Crocodile, and small Mammals. Among the numerous other forms which are referred to the Viverridcz may be mentioned the Paradoxtirus of the Indian province ; the prehen- sile-tailed "Benturongs" (Arctictis] of India, and Sumatra and Java ; the web-footed Cynogale of Bor- neo; the "Mangue"(Cr0ssarchus)of Western Africa ; the " Suricate " (Rhyzcena} of South Africa ; and the curious Cryptoprocta of Madagascar. Forming a transition between the Viver- ridcz and the Felidce, is the family of the Hycenidce, distinguished by the fact that, alone of all the Carnivora, both pairs of feet have only four toes each. The hind-legs are shorter than the fore-legs, so that the Fig 434.— Crown of the trunk sinks towards the hind-quarters, and left upper carnassial , ., • , mi • i j of the striped Hysena the tail IS SllOrt. Ihe tOJlgUC IS TOUgll and SurafS?' °f the Prickly. The head is extremely broad, the muzzle rounded, and the muscles of the jaw extremely powerful and well developed. The claws are non-retractile. All the praemolars and molars are trenchant except the last upper molar, which is tuberculate. The upper carnassial has an internal tubercle (fig. 434), and the lower carnassial is wholly trenchant. The, dental formula is — . 3 — 3 i — i 4 — 4 i — i t - — - : c - - : pm - - : m — - = -24. 3—3 i— i 3 3 i— i All the known species of Hyaena are confined to the Old World. The striped Hyaena (H. striata) is found in North VERTEBRATA : MAMMALIA. 747 Africa, Asia Minor, Arabia, and Persia, ranging into India. The spotted Hyaena (ff. crocutd) occurs all over Africa south of the Sahara ; and the Brown Hyaena (H. brunnea) is also found in the south of Africa. Closely allied to the Hyaenas is the .curious Aardwolf (Pro- teles), of South Africa, sometimes raised to the rank of a dis- tinct family (Protelidcz), which has decided affinities with the Civets. It has the fore-feet pentadactylous, and the hind-feet tetradactylous (as in the Dogs). It is a nocturnal burrowing animal, about as large as a Fox, and of a yellowish-grey colour, with black stripes on the sides, and it feeds on White Ants and carrion. The next family is that of the Canidce, comprising the Dogs, Wolves, Foxes, and Jackals. The members of this family are characterised by having pointed muzzles, smooth tongues, Fig. 435. — Dentition of the Wolf (Canis lupus) : p± Upper carnassial ; w1 Lower carnassial. and non-retractile claws. The fore-feet have five toes each, the hind-feet have only four. A large caecum is present (being small in the Cats and absent in the Bears). The snout is pro- longed, and there is a numerous series of teeth (fig. 435), the dental formula of the Dog being — 4 — 4 2 — 2 ; pm - - ; m — - = 42. 4— 4' 3—3 3—3 i— MANUAL OF ZOOLOGY. Some of the anterior praemolars, and especially the first, may disappear in late life, and the carnassial teeth are of large size. Both of the upper molars and the last two of the lower molars on each side are tuberculate. The true Dogs (i.e., the Dog and Wolf) have round or oblique pupils, and a tail which is of moderate length and rarely very hairy. The Foxes ( Vulpes] have very long bushy tails, and the pupil contracts to a mere line. The Dog (Cants familiaris) is only known to us at the present day as a domesticated animal. Such wild dogs as there are, are probably merely derived from the domestic dog ; and the original stock, or stocks, from which our numerous varieties of dogs have sprung, is still uncertain. It is worth while remembering, however, that all our varieties of dogs are cap- able of interbreeding ; and there is a strong probability that the Wolf is the parent stock of at least some of our domestic breeds. The Dog, in fact, will interbreed with both the Wolf and the Jackal. The "native dog" (Cam's dingo] of Australia is generally supposed to be only a variety of the Cants familiaris ; and this is certainly the case with the so-called "native dog " of New Zealand. The genus Canis, besides the Dog, contains the well-known Jackal (Cants aureus) and the Wolf (Cants lupus), and many writers place the Foxes in the same genus. The Foxes, however, are better considered as forming a separate genus ( Vulpes), of which there are many species, all more or less like the common Fox ( Vulpes vulgaris). One of the most remarkable species is the Arctic Fox ( Vulpes lagopus\ which abounds in the Arctic regions, and changes its colour with the season, being brown or bluish in summer, and white in winter. The soles of its feet are hairy. Other well-known Foxes are the Red Fox ( V. fulvus) of North America, the Deccan Fox ( V. Bengalensis} of India, and the Caama ( V. Caama) of Africa. The Jackals have a round pupil, a long muzzle, and a dental formula like that of the Dogs. They inhabit Asia and Africa, are gregarious, hunt in packs, and burrow in the ground. Other species are found in South America. One of the most aberrant members of the Canidce is the curious Lycaon pictus or "Hunting Dog " of South Africa, which agrees with the Dogs in its dentition and osteology, but resembles the Hyaenas in the fact that all the feet are tetradactylous. Other aberrant members of the Canidce are the long-eared Megalotis Lalandii of South Africa, and the Racoon-Dog (Nyctereutes procyonoides) of Eastern Asia. The last group of the Digitigrada is that of the Felida or Cat tribe, comprising the most typical members of the whole order of the Carnivora, such as the Lions, Tigers, Leopards, Cats, and Panthers. The members of this family all walk upon the tips of their toes, the soles of their feet being hairy, and the whole of the metacarpus and heel being raised above the ground (fig. 424, C). The jaws are short, and owing to this fact, and to the great size of the muscles concerned in mastication, the head assumes a short and rounded form, with an abbreviated and rounded muzzle. The molars and prae- VERTEBRATA : MAMMALIA. 749 molars (fig. 423) are fewer in number than in any other of the Carnivora (hence the shortness of the jaws), and they are all trenchant, except the last molar in the upper jaw, which is very small and is tuberculate. The upper carnassial has three lobes, and a blunt heel or internal process. The lower car- nassial has two cutting lobes, and no internal process. The dental formula is — '& ' • f" tl ; - r i - 3°- The legs are nearly of equal size, and the hind-feet have only four toes each, whilst the fore-feet have five. All the toes are furnished with strong, curved, retractile claws, which, when not in use, are withdrawn within sheaths by the action of elastic ligaments, so as not to be unnecessarily blunted. The ungual phalanges (fig. 436) are strongly bent near their middle, and the resistance of the ligaments which retract the claws is overcome (when the claws are to be protruded) by the con- traction of the flexor profundus perforans. The tongue is Fig. 436. — Bones and ligaments of the toe of a Cat, showing the claw retracted (A) and protruded (B). roughened and rendered prickly by the presence of horny papillae, thus rendering it a most efficient rasp in licking the flesh from the bones of the prey. All the members of this group are exceedingly light upon their feet, and are exces- sively muscular, and they have all the habit of seizing their prey by suddenly springing upon it. It is questionable if any good genera have hitherto been established in this family, as far as recent forms are concerned, 750 MANUAL OF ZOOLOGY. and all the living species may be considered as belonging to the single genus Felis. The species of Fdid i— i o—o 2—2 3—3 The clavicles are imperfect. The fore-legs are furnished with five toes, and are considerably shorter than the hind-legs, which have only four toes. The two orbits communicate by an aperture in the septum. There is a short erect tail. The common Hare (Lepus timidus) is dispersed over the whole of Europe, but is not met with in Northern Scandinavia, its place there being taken by the Mountain-hare (white in winter), which occurs commonly in Scotland. As a rule, the Hares occur in temperate regions, but some are found in Africa, and one species (Lepus glacialis) is a native of the Arctic regions, whilst the common American Hare (L. Americanus) extends from Canada to Mexico. The Rabbit (Lepus cunicu- lus) is also a native of temperate regions, but appears to thrive, to a more than average extent, in Australia. Fam. 2. LagomydcE. — In the Calling Hares or Pikas (Lago- mys\ which form this family, the legs do not differ much in size, there is no visible tail, and the clavicles are nearly com- plete. There are only five back teeth (instead of six) on each side of the upper jaw, but there are two rudimentary incisors besides the central ones. They resemble the Guinea-pigs in form, and are found in Russia, Siberia, and North America. VERTEBRATA: MAMMALIA. 755 Fam. 3. Caviidcz. — In this family the tail is rudimentary; the incisors are short ; the back teeth are rootless ; the clavicles are rudimentary or wanting ; the feet are, typically, three-toed, and the claws are in the form of hoof-like nails. They are all South American. The Capybara (Hydrochozrus capybard) is the largest of living Rodents, attaining a length of three or four feet. It leads a semi-aquatic life, and has the feet incom- pletely webbed. The Cavia aperea has short legs and ears, and is believed to be the parent stock of the domesticated Guinea- pigs; while other species of Cavy are also found in South America. The Agoutis and Pacas are sometimes separated as a distinct family (Dasyproctidcz), having long incisors, molars at first root- less, but afterwards rooted, rudimentary clavicles, and five- toed fore-feet. The Agouti (Dasyprocta Aguti) is found in Guiana, Brazil, and Peru. Its fore-feet are five-toed, but the hind-feet have only three toes. The Paca ( Ccelogenys paca) has five toes on both the hind and fore feet. It has the zygomatic arches enormously inflated, the maxillary portions being hollowed out into chambers which are lined by mucous membrane, and open into the mouth, and the use of which is quite unknown. It inhabits Central and South America. Fam. 4. Hystricidce. — In this family are the well-known Por- cupines, distinguished from the other Rodents by the fact that the body is covered with long spines or " quills," mixed with bristly hairs. They have four back teeth on each side of each jaw, and they possess imperfect clavicles. The true Porcupines (Hystrix) have n on -prehensile tails, which are mostly furnished with long hollow spines, but some- times with scales and bristles. As at present restricted, they are found in the Old World only. They are mostly inhabi- tants of hot climates, with the exception of the common Por- cupine (ff. cristata), which occurs in Southern Europe and in the north of Africa. In the genus Atherura of Asia and the Indian Archipelago, the tail is long and scaly, and is termi- nated by a bundle of flattened horny strips. Fam. 5. Cercolabidce. — This family is hardly separable from the preceding, the chief difference being that the animals com- posing it spend more or less of their lives in trees, and are therefore adapted for climbing. The Cercolabidtz comprise the American Porcupines, of which the principal genera are Erethizon and Cercolabes. In the genus Erethizon, represented by the Canada Porcupine (E. dorsatum) of North America, the quills are short, and are half hidden in the hair, and, though the animal is arboreal in habit, the tail is non-prehensile. 756 MANUAL OF ZOOLOGY. The nearly-allied genus Cercolabes or Sphingurus is South and Central American, and it is distinguished from the preced- ing by the possession of a long prehensile tail. In fact, the species of Cercolabes, like so many of the inhabitants of this wonderful continent, are adapted for an arboreal life, instead of being confined to the ground. Fam. 6. Octodontidce. — This family includes a large number of Rodents which are principally South American and African (Octodon, Echimys, Ctenomys, &c.) The best -known species is the beaver-like Coypu (Myopotamus coypus) of South Ame- rica, in which the hind-feet are webbed, and the tail is long and rounded. It inhabits burrows in the sides of streams, and it leads a semi-aquatic life. Among the other Octodontidce, the species of Octodon live in South Ame- rica, and are rat-like Rodents, with short tufted tails, the molars being, typically, of a simple type. In Ctenomys, also South American, the toes of the hind-feet carry laterally a sort of comb of bristles. The Spiny Rats (Echimys) are found in the West Indies and in Africa, and have the hair mixed with fine spines, while the molars have complicated enamel-folds. Petromys is an African type. Fam. 7. Chinchillida. — This family includes some South American Rodents, of which the true Chinchillas (Chinchilla] are the best known. They are small, squirrel-like, nocturnal animals, with large ears, and excessively soft fur, strictly ter- restrial in their habits, and having the hind-legs considerably longer than the fore-legs. The Alpine Viscachas (Lagidium) live on the Andes up to heights of 16,000 feet; and the Vis- cacha of the plains (Lagostomus) inhabits the South American pampas. Fam. 8. Castor ida. — The best-known example of this family is the beaver (Castor fiber). The distinctive peculiarities of the family are the presence of distinct clavicles, the posses- sion of five toes to each foot, and the fact that the hind-feet are webbed, adapting the animal to a semi-aquatic life. The Beaver is a large Rodent, attaining a length of from two and a half to three feet. Naturally it is a social animal, living in societies, and this is still the case in America,* but in northern Europe and Asia, where the animal has been much hunted, it leads a solitary life. When living in social commu- nities the beavers build dams across the rivers, as well as habi- tations for themselves, by gnawing across the branches of trees or shrubs, and weaving them together, the whole being after- wards plastered with mud. There is no doubt but that the * The American Beaver is sometimes considered to be a distinct species '-(Castor- Canadensis], VERTEBRATA: MAMMALIA. 757 Beaver shows extraordinary ingenuity in these and similar operations; but there can be equally little doubt as to the greatly-exaggerated stories which have been set afloat in this connection. The tail is greatly flattened and scaly, and the animal gives the alarm by striking it upon the water. The Beaver is hunted chiefly for the sake of the skin, but also for the substance known as castoreum. This is a fatty substance, secreted by peculiar glands, and employed as a therapeutic agent. Fam. 9. Sa#omyd&. — This family comprises the so-called Pouched Rats and Gophers of North America, all of which have large external cheek-pouches. Some of them (Geomys and Thomomys) have the fore -feet greatly developed, and adapted for burrowing ; whilst the so-called " Kangaroo-rats " (Dipodomys] have very long hind-legs, and the fore-limbs are not specially developed. The Gophers (Geomys, &c.) possess a pair of cheek-pouches, which are hairy inside, and open out- side the mouth, their use being to carry provender. The best- known species is the common Pocket - gopher (Geomys bur- saritts) of the Mississippi valley and Canada. Fam. 10. Spalacidce. — Nearly related to the American Go- phers are the Mole-rats (Spalax] of the Old World. These have a thick body, short legs, the tail rudimentary or absent, the molars rooted, and the feet five-toed. The Mole-rats are burrowing animals, in which the eyes are very small, and may be covered over by the skin, so as to be functionally useless. They live upon vegetable food, unlike the Mole, and some of them lay up a winter store. Georychus and Bathyergus are African forms of the group. Fam. ii. Muridce. — The next family of Rodents is that of the Muridce, comprising the Rats, Mice, and Lemmings. In this family the tail is long, always thinly haired, sometimes naked and scaly. The lower incisors are narrow and pointed, and there are complete clavicles. The hind-feet are furnished with five toes, the fore-feet with four, together with a rudi- mentary pollex. The family comprises over three hundred living species, distributed over the whole world, except the islands of the Pacific, some of the species (such as the Brown Rat and the common Mouse) being similarly cosmopolitan in their range. The Rats (Mus rattus and Mus decumanus], the common Mouse (Mus musculus), the Field-mouse (Mus sylvaticus), and the Harvest-mouse (Mus messorius) are all well-known examples of this family, and are too familiar to require any description. The three first are also common in North America, though not MANUAL OF ZOOLOGY. indigenous. Closely allied to the true Rats are the Hamsters ( Cricetu's, fig. 440), and the Voles (Arvicola} ; the latter repre- sented by many species in both Europe and America. The molars of the Voles (fig. 439) are composed of alternating tri- Fig. 439.— Molar teeth of the Water-rat (Arvicola amphibius], angular prisms. Three species of Arvicola (the Water-rat, the Field-vole, and the Black Vole) are found in Britain. A less familiar example of this family is the Lemming (Myodes lemmus). This curious little Rodent is found inhabiting the mountainous regions of Norway and Sweden. It is chiefly re- Fig. 440. — Common Hamster (Cricetus vulgaris). markable for migrating at certain periods, generally towards the approach of winter, in immense multitudes and in a straight line, apparently in obedience to some blind mechanical im- pulse. In these journeys the Lemmings march in parallel columns, and nothing will induce them to deviate from the straight line of march, the migration always terminating in the VERTEBRATA: MAMMALIA. 759 sea, and ending in the drowning of all that have survived the journey. The Gerbilles (Gerbillus), though closely related to the Jerboas, are generally placed in this family. Here also may be placed the Musquash or Ondatra (Fiber zibethicus) of North America, which leads a semi-aquatic life, and has the tail com- pressed, and the hind-feet partly webbed. Fam. 12. Dipodidcz. — The next family of the Rodents is that of the Dipodidcz or Jerboas, mainly characterised by the dis- proportionate length of the hind-limbs as compared with the fore-limbs. The tail also is long and hairy, and there are complete clavicles. The Jerboas live in troops, and owing to the great length of the hind-legs, they can leap with great activity and to great distances. They are all of small size, and inhabit Russia, North Africa, and North America. The best-known members of this family are the common Jerboa (Dipus ^Egypticus} of Africa and south-west- ern Asia, which lives in societies and constructs burrows ; the Jumping Hare (Pedetes Capensis] of South Africa, and the Jumping Mouse (Zapus or Meriones Hudsonicus] of North America. Fam. 13. Myoxidce. — The members of this family are com- monly known as Dormice, and they are often included in the following family of the Squirrels and Marmots. They only require to be mentioned, as they must not be confounded with the true Mice (Muridce) on the one hand, or the Shrew-mice (Soriridce) on the other; the latter, indeed, belonging to an- other order (Insectivora}. The common Dormouse (Myoxus avellanarius] is a British species, and must be familiarly known to almost everybody. No species of this family have yet been described from the New World. In form, the Dormice are Squirrel-like, with a long and hairy tail. There are four rooted molars on each side ; the pollex is rudimentary; and the intes- tine is destitute of a caecum. Fam. 14. Sduridcz. — This is one of the most characteristic and familiar of the divisions of the Rodents, and it comprises the true Squirrels, the Flying Squirrels, and the Marmots. The molars are rooted, five in number in the upper jaw on each side (the first being often deciduous), and four on each side of the lower jaw ; their crowns, when unworn, being tuberculate. The true Squirrels (Sdurus) are familiarly known in the person of the common British species (Sdurus vulgaris), and the equally common Grey Squirrel (S. cinereus] of the United States. Numerous species (about one hundred in number) 760 MANUAL OF ZOOLOGY. more or less closely allied to these occur in other countries, and they are especially abundant in North America. In the genera Pteromys and Stiuropterus, or Flying Squirrels, there is a peculiar modification by which the animal can take extended leaps from tree to tree. The skin, namely, extends in the form of a broad membrane between the hind and fore legs, and this acts as a kind of parachute, supporting the animal in the air. There is, however, no power whatever of true flight, and the structure is identically the same as what we have previously seen in the Flying Phalangers (Petaurus], which take the place of the Flying Squirrels on the Australian continent. The Flying Squirrels are found in southern Asia, Polynesia, the north-east of Europe, Siberia, and North America. The Marmots {Ardomys), unlike the true Squirrels, are ter- restrial in their habits, and live in burrows, having short tails, thick bodies, and short legs. Various intermediate forms, how- ever, are known, by which a transition is effected between the typical Squirrels and the Marmots. Such, for example, are the Ground Squirrels (Tamtas) of Europe, Asia, and North America. There are numerous species of this family inhabit- ing various parts of Europe and northern Asia, and generally distributed over the whole of North America. Good examples are the Alpine Marmot (A. Alpinus) of Europe, and the Prairie Dog (Cynomys Ludovicianus) of North America. The Pouched Marmots (Spermophilus] have cheek-pouches, and are widely distributed over North America, northern Europe, and northern Asia. As regards the distribution of the Rodentia in time, very many fossil forms are known, the oldest appearing in the Eocene Tertiary, but the ex- tinct forms offer few points of special interest. The fam- ilies of the Stiuridce, Muridce, My oxides, and Octodontidce (?), have representatives in the Eocene, and the families of the Dipodida, Castorid(E,Hys- triridce, Cavidcz (?), and Lago- posits. The Leporida do not seem to have made their appearance earlier than the Pliocene. Amongst the fossil Rodents perhaps the most interesting are the extinct genera of Beavers. Of these the genera Steneofiber and Palaocastor are Miocene; Chalicomys is Pliocene; the VERTEBRATA: MAMMALIA. 761 great Trogontherium (fig. 441) is Pliocene and Post-pliocene, and the equally gigantic Castoroides of North America is also found in the Post-pliocene deposits. CHAPTER LXXVII. CHEIROPTERA. ORDER XIV. CHEIROPTERA.* — This order is undoubtedly "the most distinctly circumscribed and natural group" in the whole class of the Mammalia. The most obvious peculiarity of the Bats is the modification of the hand for the purpose of supporting a flying-membrane ; but with this are correlated other structural characters of importance. The Cheiroptera are essentially characterised by the fact that the anterior limbs are longer than the posterior, the digits of the fore-limb, with the exception of the pollex, being enormously elon- gated (fig. 442). These elongated fingers are united by an ex- panded membrane or " patagium," which is also extended between the fore and hind limbs and the sides of the body, and in many cases passes also between the hind-limbs and the tail. The pata- gium thus formed is naked, or nearly so, on both sides, and it serves for flight. Of the fingers of the hand, the pollex, and sometimes the next finger as well, is unguiculate, or furnished with a claw ; but the other digits are destitute of nails. In the hind-limbs all the toes are unguiculate, and the hallux is not in any respect different from the other digits. Well-developed clavicles are always present, and the radius has no power of rotation upon the ulna. The mammary glands are two in number, and are placed upon the chest. There are teeth of three kinds, and the canines are always well developed. The molars are tiiberculate or grooved in the frugivorous forms, and cuspidate in the insectiv- orous species. The ulna is rudimentary. The bones are not pneu- matic. The testes are abdominal except during the breeding season. The stomach is complex and the intestine long in the fruit-eating Bats ; but the reverse of this obtains amongst the insectivorous forms. The Cheiroptera are cosmopolitan in their distribution, and the oldest known species is from the Eocene rocks. * The Cheiropfera'-WQrz placed by Linnaeus in his order Primates, which contained also the Lemurs, the Apes, and Man. 762 MANUAL OF ZOOLOGY. The most striking features in the structure of the Cheiroptera are those connected with the conformation of the limbs (fig. 442). The fore-limb is larger than the hind-limb, the strong and moderately long humerus ar- ticulating with a very large scapula. The clavicles are complete, and the sternum is keeled. The radius is long and well developed, but the ulna Fig. 442. — Skeleton of the Mouse-coloured Bat (Vespertilio murinus). a Humerus ; b Scapula ; d Radius, with the rudimentary ulna at its proximal end ; e Carpus ; f Thumb ; gg Metacarpal bones; ss Sternum;^ Pelvis; z Supplementary bone attached to the calcaneum. is reduced to a mere splint-bone, which is anchylosed with the proximal end of the radius, all power of rotation of the fore-arm being thus lost. The thumb is short, and its last phalanx carries a claw. The index is long, but is shorter than the other digits, and often consists of its metacar- VERTEBRATA: MAMMALIA. 763 pal only, in other cases with two short phalanges in addition. It is usu- ally clawless, but may (as in most of the Pteropidce) be unguiculate. Of the remaining digits the medius is the longest ; and all are clawless, and possess two or three phalanges. In the hind-limb, the fibula is mostly incomplete, and the foot is fur- nished with five clawed toes. To the os calcis is attached, in most Bats, a cartilaginous or bony process or spur, which is directed inwards along the lower margin of the inter-femoral membrane, and serves to put this upon the stretch during flight. The Bats are all crepuscular and nocturnal in their habits, and are sometimes carnivorous, sometimes frugivorous. The eyes are small, but the ears are very large, and their sense of touch is most acute. During the day they retire to caves or crevices amongst the rocks, where they suspend themselves by means of the hind -feet, which are provided with curved claws. In their flight, though they can fly in the genuine and proper sense of the term, and can turn with great ease, they are by no means as rapid and as active as are the true birds. The tail is sometimes short, sometimes moderately long, and is usually included in a continuation of the leathery patagium, which stretches between the hind-legs, and is termed the " inter-femoral membrane." The body is covered with hair, but the patagium is usually hairless, or nearly so. Most of the Bats hibernate. The Cheiroptera are conveniently divided into the two sec- tions of the Insedivora and Frugivora, according as the diet consists of insects or of fruits. SECTION A. INSECTIVORA (Microcheiroptera). — In this section are the four families of the Vespertilionidce, RhinolophidcB, Noctilionidcz, and Phyllostomida. Fam. i. VespertilionidcE. — In this family are the ordinary Bats, distinguished by having a dentition very like that of the order of the Insectivorous Mammals, the molar teeth being furnished with small pointed eminences or cusps, adapted for crushing insects, and the incisors being of small size. The nose is not furnished with leaf-like appendages, and the tail is elongated, and enclosed in a large inter-femoral membrane. The species of this family are generally distributed over the temperate and warm regions of both the Old and New Worlds. About fifteen species of this family have been described as British, but of these only two are at all common. Of these two, the Pipistrelle ( Vespertilio pipistrelld} is the commonest species, occurring over the whole of Britain. The long-eared Bat (Plecotus auritus] is also not uncommon, and is distin- guished by its greatly elongated ears, which are confluent above the forehead. The largest British species is the Noctule 764 MANUAL OF ZOOLOGY. ( Vespertilio noctula), which measures as much as fifteen inches in expanse of wing. Fam. 2. Rhinolophidcz. — The second family of the Insec- tivorous Bats is that of the Rhinolophidce or Horse-shoe Bats which in most respects are very similar to the Vesperlilionidcz, but are distinguished by the possession of a complex leaf-like apparatus appended to the nose. In the typical forms of the family the ears have no tragus or earlet. Of this family, two British species are known— the Greater and Lesser Horse-shoe Bats (Rhinolophus ferrum-equinum and R. hipposideros). Most of the Horse-shoe Bats are Asiatic and African, a few being found in Australia. The genera Nycteris and Megaderma are sometimes separated to form a distinct family (Nycteridce), distinguished by having very large ears, with a well-marked tragus or earlet. Fam. 3. Nodilionidcz or Emballonurida. — In this family are a number of Bats which are principally South American, African, and Asiatic, and which are distinguished from the Vespertilion- idce by the fact that the tail usually perforates the inter-femoral membrane at or about its middle, and the incisors are of large size. Fam. 4. Phyllostomida. — This is the only remaining family of the Insectivorous Bats, and comprises the well-known Vam- pire-bats (fig. 444, A), distinguished by having leaf-like nasal appendages, and by the fact that the ears are of small size ; whereas in the preceding they are always very large (Rhi- nolophus}, and are of- ten confluent above the forehead (Megaderma}. They are all of large size, and are natives of South America, extend- ing northwards to Mex- ico and California. The Vampire-bat (Phyllosto- Fig. 443 —Skull of the Javelin Bat (Phyllostoma has- ma spectrum] has an CX- tatnm), showing the large canines, and cuspidate r r , molars. panse of wing of two feet and a half, and lives chiefly upon insects. Some species of the family have the habit of sucking the blood of sleeping animals, appearing sometimes to attack even man, though apparently never doing any substantial or lasting injury. VERTEBRATA: MAMMALIA. 765 SECTION B. FRUGIVORA (Megacheiroptera). — In the fruit- eating section of the Cheiroptera are only the Pteropidcz or the Fox-bats, so called from the resemblance of the head to that of a fox (fig. 444, B). The head in these bats is long and Fig. 444.— A, Head of Vampire-bat (A lectors ater) ; B, Head of Fox-bat (Pteropus personatus). (After Gray.) pointed. The ears are simple and of moderate size, and the nose is destitute of any appendages. Cutting incisors and canines are present in both jaws, and the Fox-bats do not altogether refuse to eat small birds or mammals. They live, however, almost exclusively upon fruits, and the molars are therefore not cuspidate, but are furnished with blunt tubercular crowns. The tail is very short, or is entirely absent. The inter-femoral membrane is much reduced in size; and the index (as well as the pollex) is almost always clawed. The Pteropidce are amongst the largest of the Bats, one species — the Pteropus edulis, or Kalong — attaining a length of from four to five feet from the tip of one wing to that of the other. The Pferopidce are especially characteristic of the Pacific Archi- pelago— Java, Sumatra, Borneo, &c. — but they also occur in Asia, Australia, and Africa. They do not occur, however, in either North or South America. As regards the distribution of the Cheiroptera in time, the order dates from the Eocene Tertiary, where we find the re- mains of Vespertilionidce, essentially similar to existing forms. Professor Marsh has also detected the remains of the first American Tertiary Bats hitherto discovered in the Eocene of Wyoming. No fossil remains of Pteropidce are known, but the bone-caves of Brazil (Post-pliocene) have yielded traces of several species of Phyllostomidce. ;66 MANUAL OF ZOOLOGY. CHAPTER LXXVIII. INSECTIVORA. ORDER XV. INSECTIVORA. — The fifteenth order of Mammals is that of the Insectivora, comprising a number of small Mammals which are very similar to the Rodents in many respects, but want the peculiar incisors of that order, and are likewise almost always furnished with clavicles. In the Insectivora, all the three kinds of teeth are usually pres- ent, but the exact nature of the dentition varies considerably in different cases. The incisors and canines present little special, but the molars (fig. 445) are always serrated with numerous small pointed eminences or cusps, adapted for crushing in- sects. With one exception (Potamogale), clavicles are always present in a com- plete form. All the feet are ustially furnished with five toes ; all the toes are furnished with claws ; and the animal walks on the soles of the feet, or is plantigrade. The testes pass periodically from the abdomen into a temporary scrotum ; and the placenta is deciduate and discoidal. They are mostly nocturnal and subterranean, and generally hibernate. They are all of small size, and are found everywhere, except in the continents of South America and Australia, where their place is filled by Marsupials. The order Insectivora has been divided variously by different authorities, but the following are the principal families : — Fam. i. Talpida. — The body in this family is covered with hair ; the feet are formed for digging and burrowing, and the toes are furnished with strong curved claws. external ears ; and the eyes in the adult are may be covered by the skin. The clavicles are strong, the arm very short, the hand wide, and the palm turned outwards and backwards. The fur is short and velvety, and the tail very short or wanting, in most cases. The common Mole (Talpa Europcea, fig. 446) is the only Fig. 445. — Dentition of the common Mole (Talpa Europced). There are no very small, or VERTEBRATA : MAMMALIA. 767 British species of the family, and is too well known to need any description. The dental formula of the Mole is — 11 4 3-3 3 3— 3 i— i 4—4 3—3 The nearly-allied Talpa caca of Southern Europe has the eyes covered by a membrane, pierced by a small central aperture. Other species of Talpa are found in India, China, and Japan. Fig. 446. — European Mole (Talpa Europcea). The star-nosed Moles (Condylura) are North American, and are distinguished by a fringe of elongated membranous car- uncles surrounding the nostrils. The tail is much longer than in the typical Moles ; the eyes are very minute ; and there are no external ears. Also North American is the genus Scalops, comprising the so-called Shrew-moles. In this genus the tail is short, the muzzle is long, with the* nostrils at its extremity, and the eyes are very small and are hidden in the fur. The common Shrew- mole (Scalops aquaticus) has the hind-feet webbed, and is found everywhere in the United States east of the Mississippi. The Golden Moles (Chrysochloris) of South Africa are often regarded as forming a special family. They are like the Moles in form and general habit ; but the hairs of the fur have the power of dispersing the rays of light, and thus of giving rise to beautiful metallic colours. The fore-feet have four toes, the second and third being very large and armed with immense claws; while the clavicles are not shortened (as they are in Talpa). The eyes are very minute, and covered by the skin. The dentition is quite peculiar, the dental formula being — i — x 6 — 6 5—5 ; pm - - ; m — - or - — - = 36 or 40. V^ 3— 3' 5—5 4—4 6 768 MANUAL OF ZOOLOGY. Lastly, in the curious genus Urotrichns (sometimes referred to the Myogalid(Z\ of Japan and the north-west of America, the nose is long and cylindrical, terminated by a naked fleshy bulb, and extremely sensitive, the tail is moderately developed and hairy, and the fore-feet are adapted for burrowing. Allied forms have also been recently discovered in North China and Thibet Fam. 2. Potamogalida. — This family merely requires to be mentioned as founded for the reception of a single genus (Potamogale), comprising only a single species (P. velox). This animal is a curious Otter-like Insectivore, which leads a semi- aquatic life, to which end it has a long compressed tail. Cla- vicles are also entirely wanting. It is confined to the west of Africa. Fam. 3. Soridda. — The Soricidce or Shrew-mice are distin- guished by having the body covered with hair, and the feet not adapted for digging ; whilst there are mostly external ears, and the eyes are well developed. The tail is nearly naked, and scaly ; the central upper and lower incisors are very large ; the tibia and fibula are united; and there is no caecum. Of all the Insectivora, no division is more abundant or more widely distributed than that of the Shrew-mice, their range extending over North America and the whole of the Old World, In general form and appearance the Shrews very closely resemble the true Mice (Muridcz)^ and the Dormice (Myoxida), but they are in reality widely different, and must not be confounded with them. The Common Shrew (Sorex vulgaris\ the Garden Shrew \Crocidura araned), and the Water-Shrew (Crossopus fodtens) are well-known British species of this family. The smallest known Mammal is one of the Shrews (Sorex Etrus- cus\ which is not more than two and a half inches in length, counting in the tail. Ths Desmans or Musk-rats, forming the genus Myogale, are sometimes placed here, sometimes in the family of the Talptdce, and are often raised to the rank of a distinct family (Myogalida). They have the nose prolonged into a kind of flexible proboscis, whilst the feet are webbed, and the tail is compressed, thus adapting the animal for a semi-aquatic life. The dental formula is — . 2 2 I T q tj 3 — ? i - ; c - ; pm « — * ; m - — - = 44. 2—2 i— i 5—5 3—3 The central incisors and the lateral lower incisors are very large and pyramidal ; and the hind-legs are longer than the VERTEBRATA: MAMMALIA. 769 fore-legs. Two species are known, one found in south-eastern Russia, the other in the Pyrenees. Fam. 4. ErinaceidcR. — The fourth family of the Insectivora is that of the Hedgehogs, characterised by the fact that the upper Fig. 447. — Skull of the common Hedgehog (Erinaceus Eriropezus). part of the body is covered with prickly spines, the feet are not adapted for digging, and they have the power of rolling them- selves into a ball at the approach of danger. The dental formula of the Hedgehog is — /3-Zl; ;S£fg ^4±4. m3=3 6. 3—3 o—o 2—2' 3—3 The central upper and lower incisors are longer than the others ; and the first praemolars are the largest of all the teeth present. The first upper praemolars are sometimes regarded as canines. The common Hedgehog (Erinaceus Europaus) is in every way a typical example of this family, but is too well known to require any description. Other species of the family are found in North and South Africa and in Asia. Fam. 5. Centetidce. — The most typical members of this family are the " Tenrecs " (Centetes) of Madagascar. These are small animals resembling the Hedgehogs in appearance and habits, and having the back covered with hair intermixed with fine prickles or spiny bristles, but mostly destitute of the power of rolling themselves into a ball. They have a long proboscis- like nose, and the tail is generally rudimentary or absent. The genera Ericulus, Echinops, and Geogale of the island of Mada- gascar, are allied to Centetes, the last having relationships with the SoriddcK. Likewise related to the Tenrecs is the curious genus Solenodon of Cuba and Hayti, in which the nose is very long and pointed, the tail is long and scaly, and the body is 7/O MANUAL OF ZOOLOGY. covered with coarse fur, without spines. The two central incisors of the lower jaw are small, and are placed between long conical lateral incisors, which are deeply grooved on their inner surfaces. We may also place here the singular Gymnura of Borneo, Sumatra, and the Malay Peninsula. In this genus, the body is covered with long, coarse fur, the tail is long and scaly, the snout is long, and the feet are five-toed. Fam. 6. Tupaiida. — The best known members of this family are the "Banxrings" or "Squirrel- shrews" (Ttipaia) of India and the Malay Archipelago. These are squirrel -like Insec- tivores, with long bushy tails, the feet plantigrade, five-toed, with naked soles, and sickle -shaped claws. They climb actively amongst the trees, and also run with facility upon the ground. Closely allied to the TitpaUe is the little Ptilocercus of Borneo, in which the tail is very long, and the hairs towards its extremity are arranged like the barbs of a feather. Fam. 7. Macroscelidce. — This family includes only the little " Elephant-shrews " (Macroscelides) of Southern and Northern Africa. They are readily distinguished by their extraordi- narily elongated trunk-like nose, resembling the proboscis of an Elephant, and their very long Kangaroo-like hind-legs. Fam. 8. Galeopithecidce — This family has been constituted for the reception of a very singular animal which forms a kind of connecting link between the orders of the Insectivora and Qiiadrumana, having been sometimes placed in the one and sometimes in the other, or having been regarded as the type of a separate order. The family includes only the single genus Galeopithecus, comprising two species of the so-called " Colu- gos" or "Flying Lemurs." The genus is confined to the Indian Archipelago, and the best-known species is the Galeo- pithecus volans of Malacca, Sumatra, and Borneo. The most characteristic point in this singular animal is the presence of a flying membrane, presenting some superficial resemblance to the patagium of the Bats, but in reality very much the same as the integumentary expansions of the Flying Squirrels and Flying Phalangers. This membrane in the Galeopithecus ex- tends as a broad expansion from the nape of the neck to the arms, from the arms to the hind-legs, and from the hind-legs to the tail, forming an inter-femoral membrane. The fingers are not elongated, and do not support a patagium, as in the Bats, so that the animal has no power of true flight, and can simply take extended leaps from tree to tree. The feet are furnished with five toes -each, united by a membrane, but neither the hallux nor the pollex are opposable to the other digits. The dental formula is — VERTEBRATA: MAMMALIA. 771 .2 — 2 i — I 2 — 2 3 — 3 t c — ' ) Pm ~> m = 34- 3—3 l~ l 2~2 3—3 The upper incisors are separated by a wide central space, and the six lower incisors (fig. 448) are split into narrow strips, like the teeth of a comb. The Galeo- pitheci seem to live chiefly upon fruits, and other vegetable matters. They are nocturnal animals, arbo- real in their habits, and they sleep head downwards, suspended by their prehensile tails. As regards the distribution of the Insedivora in time, the earliest undoubted, remains of the order OCCUr in the Miocene, at Which pe- Fi riod the families of the Talpidx, Soricidtz, Erinaceida, and Centetida, appear to have been already differentiated. The geological distribution of the order, however, presents no points of spe- cial interest. CHAPTER LXXIX. QUADRUMANA. ORDER XVI. QUADRUMANA. — The sixteenth order of Mam- mals is that of the Quadrumana, comprising the Apes, Mon- keys, Baboons, Lemurs, &c., characterised by the following points : — The hallux (innermost toe of the hind-limb) is separated from the other toes, and is opposable to them, so that the hind -feet become prehensile hands. The pollex (innermost toe of the fore- limbs) may be wanting, but when present, it also is usually oppos- able to the other digits, so that the animal becomes truly quadru- manous, or four-handed. ty 2 *? . _. i *? The incisor teeth generally are - — , and the molars — , with broad and tuber culate crowns. Perfect clavicles are present. The teats are two in number, and (except in Cheiromys) are pectoral in position, and the placenta is discoidal and deciduate. The Quadrumana are divided by Owen into three very 772 MANUAL OF ZOOLOGY. natural groups, separated from one another by their anatomical characters and by their geographical distribution as follows : — Section A. Strepsirhina. — The members of this section are characterised by the nostrils being curved or twisted, whilst the second digit of the hind-limb has a claw. This section includes the true Lemurs and a number of allied forms. It is chiefly referable to Madagascar as its geographical centre ; but it spreads westwards into Africa, and eastwards into the Indian Archipelago. Section B. Platyrhina.—^^s section includes those Quad- rumana in which the nostrils are placed far apart ; the thumbs of the fore- feet are either wanting, or, if present, are not oppos- able to the other digits • and the tail is generally prehensile. The Platyrhine Monkeys are exclusively confined to South America. Section C. Catarhina. — In this section the nostrils are ob- lique, and placed close together. The thumb of the fore-limb Fig. 449. — Green Monkey or Guenon (Cercocebus sabceus). (After Cuvier.) (pollex), with one exception, is present, and is always oppos- able to the other digits. The Catarhine Monkeys are restricted entirely to the Old World, and, with the single exception of a Monkey which inhabits the Rock of Gibraltar, they are exclu- sively confined to Africa and Asia. It is in the Catarhine sec- VERTEBRATA: MAMMALIA. 773 tion of the Quadrumana that we have the highest group of the Monkeys — that, namely, of the Anthropoid or Tail -less Apes. STREPSIRHINA. This section of the Quadrumana, as before said, is charac- terised by the possession of twisted or curved nostrils, placed at the end of the snout. The incisor teeth are generally much modified, and are in number - — - as a rule ; the lower incisors 3—3 ^ *+ 2 _ 2 are produced and slanting ; the praemolars are ^—^ or — - — and the molars are tuberculate. The second digit of the hind-limb has a claw, and both fore and hind feet have five toes each, all the thumbs being generally opposable. In the true Lemurs, all the digits, except the second toe of the hind- feet, are furnished with nails. This section is often called that of the Prostmice, and it in- cludes several families, of which the Aye-ayes, Loris, and true Lemurs are the most important. In many works the Galeo- pithecus is also placed in this section. Milne-Edwards and Gervais, from an examination of the placentation of the Lemuroids and of their cerebral charac- ters, conclude that the group should be raised to the rank of a distinct order intermediate between the Carnivora and the Quadrumana. The family of the Aye-ayes (Cheiromydce) includes only a single animal, the Cheiromys Madagascariensis. In appearance the Aye-aye is not very unlike a large Squirrel, having a hairy body and a long bushy tail. There are no canines, and the molars (fig. 450) are separated by a wide interval from the incisors; while there is the additional Rodent-like character that the incisors are ploughshare-shaped, and grow from per- manent pulps. The dental formula is — i— i o— o o— o 3—3 The fore-feet have five toes, armed with strong claws, but the pollex is scarcely opposable to the other digits. The middle finger is about as long as the ring-finger, but only about half as thick, its last two joints being hairless. The hind-feet have also five toes, of which the hallux is opposable, and the second digit is furnished with a long claw ; as are all the toes 774 MANUAL OF ZOOLOGY. except the hallux, which has a flat nail. As far as is yet known, the Cheiromys is entirely confined to Madagascar. The family of the Tarsiidce includes only the singular Tar- sius spectrum of Borneo, Sumatra, Celebes, and Banca, remark- Fig. 450. — Skull of the Aye-aye (Cheiromys), viewed laterally and from the front. (After Owen.) able for the extraordinary elongation of the hands and feet. It has a long tail, and is arboreal in its habits. In the Nycticebidtz are the Loris and the Slow Lemurs, in which there is no tail, or but a rudimentary one ; the limbs are nearly equal in size ; the ears are short and rounded, and the eyes are large, and are placed close together. The species of this family are all of small size, and are exclusively confined to the eastern portion of the Old World, occurring in Java, Ceylon, the southern parts of Asia, and other localities in the same geographical area. They are nocturnal in their habits, living mostly on trees, and feeding upon insects ; and from the slow- ness with which some of them progress, they are sometimes spoken of as " Slow Lemurs." The best-known species are the Slender Loris (Loris or Stenops gradlis) of Ceylon, and the Nycticebus tardigradus of the East Indies. Here also belong the " Potto " (Perodicticus] of Sierra Leone, in which the index-finger is rudimentary, and the Arctocebus of Old Calabar, in which this digit is completely wanting, and the tail is rudimentary. The largest and most important of the families of the Strep- sir hina is that of the Lemurida or Lemurs. In this family the muzzle is elongated, the feet are all furnished with opposable thumbs, and the nails on all the toes are flat, with the excep- tion of the second toe of the hind-foot, in which there is a long VERTEBRATA: MAMMALIA. 775 and pointed claw. The body is covered with a soft fur, and the tail is usually of considerable length, and is covered with hair. They are easily domesticated; and though capable of B'ig. 451.— Side-view of the skull of a Lemuroid (Nycticebus or Stenops tardigradris). (After Giebel.) biting pretty severely, their disposition is gentle and docile. They are mostly about the size of cats, and not unlike them in appearance, being often termed u Madagascar cats " by sailors. They are found almost exclusively in the great forests of Madagascar, moving about amongst the trees with great activ- ity, by means of their prehensile tails. They appear to fill in Madagascar the place occupied by the higher Quadrumana upon the adjoining continent of Africa. One of the best-known species is the Indri (Indris laniger) which occurs, with other species of the genus, in Madagascar. The genus Lemur itself includes the so-called " Makis," the most familiar of which is the Ring-tailed Lemur (L. catta). The dental formula is — 2— 2 T^ *=± 53=; 3 6. ' 2—2 i— i 3—3 3—3 The " Galagos" (Galago), sometimes raised to the rank of a distinct family, are the only members of the Lemuridce which occur out of Madagascar, and they are confined to Africa, being most abundant in the western part of this continent, but one species extending its range to Senegal and the southern borders of the Sahara. All have long bushy tails, large eyes, and large membranous ears. PLATYRHINA. The section of the Platyrhine Monkeys is exclusively con- fined to South America, and one of its leading characters is to be found in the very general possession of a prehensile tail ; 776 MANUAL OF ZOOLOGY. this being an adaptive character by which they are suited to the arboreal life which so many of the South American Mam- mals are forced to lead. There are neither cheek-pouches nor natal callosities, and there is an additional praemolar, and sometimes a molar less than in Man and the Old World Monkeys. The nostrils are simple, separated by a wide septum, and opening laterally. The praemolars are - ----- in 3—3 number and have blunt tubercles. The thumbs of the fore- hands are either wanting altogether, or, if present, are but slightly opposable, though versatile. The Platyrhine Monkeys are divided into the two principal sections of the Hapalidce and Cebidce. Fam. i. Hapalidce (Arctopitheci). — In this family the number of teeth is the same as in the Old World Monkeys and in Man, but there is an additional prsemolar on each side of each jaw, and a molar less. The dental formula of the Mar- moset is — 2 — 2 i — i 3 — 3 2—2 i - - ; c — - : pm ; m - — = 32. 2—2 ' i— i ' 3 — 3 ' 2—2 The molars, however, are tuberculate, and though the num- ber of teeth is the same as in the Catarhine Monkeys, in their other characters, the Marmosets are genuine Platyrhines. The hind-feet have an opposable hallux with a flat nail, but all the other toes are unguiculate, and the pollex is not at all opposable. The tail is long and thickly haired, but is not prehensile. The Hapalidce are all small monkeys, mostly about as big as Squirrels, and they are exclusively South American, occur- ring especially in Brazil. The best-known species is the com- mon Marmoset (Hapale penicillata\ but several species are domesticated and kept as pets. The genus Midas comprises small Monkeys which differ from the Marmosets chiefly as regards their dentition. Fam. 2. Cebidce. — In this family are all the typical Platy- rhine Monkeys, in which the dentition differs from that of the Hapalidce, in having an additional molar, so that the molars are the same as in the Catarhina and in Man, but the prse- molars are more numerous. The dental formula is — /2~2; ,532; ^3=3 „ 3_-3 6. 2—2' i— I9 3—3' 3—3 There are neither cheek-pouches nor " callosities ; " and the VERTEBRATA : MAMMALIA. 777 face is usually more or less naked, though sometimes whis- kered. The tail is long, and is mostly prehensile ; though in rare instances it is non-prehensile, and has its extremity clothed with hairs. The thumb of the fore-hand may be wanting, and, if present, is not opposable. All the fingers are furnished with flat nails. Their diet is miscellaneous, consisting partly of insects and partly of fruit. The Cebida are exclusively confined to the warmer parts of South America, in the vast forests of which they are met with in large troops, climbing amongst the trees. The Spider Monkeys (Ateles), the Howling Monkeys (Mycetes), the " Sapa- jous" or "Capuchins" (Cebus], and the Squirrel Monkey (CaZlithrix), may serve as typical examples of this section of the Quadrumana. In Ateles the tail is long, slender, and powerfully prehensile ; and the limbs are very long and slender. The pollex is absent, or is quite rudimentary. In Mycetes there is a bony drum which is formed by a convexity of the os hyoides and communicates with the larynx. The voice is thus rendered extraordinarily resonant. The pollex is not oppos- able, but is placed on a line with the other fingers. In the so-called " Sakis " (PitJieciida) the tail is sometimes long (Pitheaa\ sometimes short (Brachyurus), but is never prehensile, while the lower incisors are inclined forwards. The little "Night-apes" (Nyctipithecus) also have non-prehensile tails, but the lower incisors are vertical, and the eyes, in accordance with the nocturnal habits of the animal, are of immense size. CATARHINA. The third and highest section of the Quadrumana is that of the Catarhina or Old World Monkeys. In this section the nostrils are oblique, and are placed close together, and the septum narium is narrow, the nostrils looking downwards. The thumbs of all the feet are opposable, so that the animal is strictly quadrumanous. In Colobus alone the anterior thumbs (pollex) are wanting. The dental formula is the same as in man, viz.: — . 2 — 2 i — i 2 — 2 3 — 3 i - - • c - - : pm - - ; m - — - = 32. 2— 2' I — I ' 2—2' 3—3 The incisors, however, are projecting and prominent, and the canines — especially in the males — are large and pointed. Moreover, the teeth form an uneven series, interrupted by a diastema or interval. The tail is never prehensile, and is 7/8 MANUAL OF ZOOLOGY. sometimes absent. Cheek-pouches* are often present, and the skin covering the tubera ischii is mostly callous and destitute of hair, constituting the so-called " natal callosities." With the single exception of a Monkey which inhabits the Rock of Gibraltar, all the Catarhina, as before remarked, are natives of Africa and Asia. There are three well-marked groups or tribes of the Cata- rhine Monkeys. In the first of these the tail is long, and there are generally both cheek-pouches and natal callosities. In this tribe is the genus Semnopithecus, in which cheek-pouches are absent, the hind-limbs are long, and the thumb is small, and all the species of which are natives of Asia and the Indian Archipelago. One of the best-known species is the Sacred Monkey of the Hindoos (Semnopithecus entellus). Closely allied to the Semnopithed is the genus Colobus of Africa, in which cheek-pouches are also absent, and in which, alone of all the Catarhine Monkeys, the pollex is either altogether absent or totally rudimentary. Closely allied to Semnopithecus also, is the Proboscis Monkey or Kahau (Presbytis nasatis), distinguished by its elongated proboscidiform nose, short pollex, and long tail. It is a native of Borneo. Here also come the little Gueno.ns (Cercocebus and Cercopithecus, fig. 449), all of which are confined to Africa. Also referable to this division is the genus Macacus or Inuus (comprising the Ma- caques), which includes most of the Monkeys which are ordi- narily brought to this country. It is a Macaque which occurs at the Rock of Gibraltar, and is the only wild Monkey which is found in Europe at the present day. Most of the Macaques are Asiatic, and. a good example is the Wanderoo (M. Silenus) of India. All the Macaques have cheek-pouches and callosi- ties, and the tail is sometimes long, sometimes rudimentary, and sometimes wanting. The second tribe of the Catarhine Monkeys is that of the Baboons (Cynocephalus). In these forms the tail is mostly short, and is often quite rudimentary. The head is large, and the muzzle (fig. 452) is greatly prolonged, having the nostrils at its extremity. The facial angle is about 30°, and the whole head has much the aspect of that of a large dog. The natal callosities are generally large and conspicuous, and usually of some bright colour. The Baboons are large strong animals, extremely unattractive in outward appearance, and of great ferocity. The fore and hind limbs are nearly of equal length, and, more than any other of the Monkeys, they employ the * The cheek-pouches are sacs or cavities in the cheeks, which open into the mouth and serve to hold any superfluous food. VERTEBRATA : MAMMALIA. 779 fore-limbs in terrestrial progression, running upon all -fours with the greatest ease. They are mainly inhabitants of Africa, and one of them, the Mandrill (Cynocephalus Maimon\ attains very nearly the height of a man. The best-known species are the Chacma (Cynocephalus porcarius], the Derrias or' 'Sacred Fig. 452. — Side- view of the skull of a Baboon (Cynocephalus ursin-us)^ (After Giebel.) Baboon" (C. Hamadryas), the common Baboon (C. papio\ and the Mandrill. The Derrias is found in Arabia and Abys- sinia, and occurs both embalmed and sculptured upon ancient monuments in Egypt and Nubia. The Mandrill is rendered probably without exception the most disgustingly hideous of living beings by the possession of large blood-red natal cal- losities and of enormous cheek -protuberances striped with brilliant colours in alternate ribs. The genus Cynopithecus includes a baboon-like monkey which is found in Celebes and the Philippine Islands. The third family of the Catarhine Monkeys is that of the Anthropomorphous or Anthropoid Apes, so called from their making a nearer approach in anatomical structure to Man than is the case with any other Mammal. The members of this family are Apes in which there is no tail, and cheek-pouches are absent, whilst in some cases there are also no natal callo- sities. They agree with Man in the possession of a broad flat sternum (whence their name of " Latisternal" Apes), in having an appendix vermiformis to the caecum, and in the fact that the liver, except in the Gorilla, is of a very simple structure. The hind-legs are short — shorter than the fore-limbs — and the animal can progress in an erect or semi- erect position. At the same time, the thumbs of the hind-feet (hallux) are oppos- able to the other digits, so that the hind-feet are prehensile 780 MANUAL OF ZOOLOGY. hands. The spine shows a single curve, and articulates with the back part of the skull. The canine teeth of the males are long, strong, and pointed, but this is not the case with the females. The structure, therefore, of the canine teeth is to be regarded in the light of a sexual peculiarity, and not as having any connection with the nature of the food. In this tribe are the Gibbons (Hyhbates), the Orang-utan {Simla satyrtis\ the Chimpanzee, and the Gorilla. The Gibbons form the genus Hylobates, and they belong to southern Asia and the Indian Archipelago. The anterior limbs are extremely long, and the hands nearly or quite reach the ground when the animal stands in an erect posture. There is no tail, but there are natal callosities. The body is covered with a thick fur. The sternum is wider than in the other Apes, and the chin is better developed. One of the best known of the Gibbons is the Siamang (Hylobates syndaJylus), which has been sometimes regarded as making a nearer ap- proach to Man than any other of the Monkeys. It is a native of Sumatra. It is the largest of the Gibbons, and derives its specific name from the fact that the index and middle toes of the hind-foot are united to one another by skin as far as the nail-joint. Another well-known species is the common Gibbon (H. tor). In the Orang or " Mias'" (Simia satyrus) there are neither cheek-pouches nor natal callosities, and the hips are covered with hair. As in the Gibbons, the arms are excessively long, reaching considerably below the knee when the animal stands in an erect posture. The hind-legs are very short, and there is no tail. When full grown the Orang stands about four feet high. It never progresses with the help of a stick, or walks erect at all, except along the branches of trees, supporting itself by a higher branch, or when attacked. When young, the head of the Orang is not very different from that of an average European child; but, as the animal grows, the facial bones become gradually produced, whilst the cranium remains in a tolerably stationary condition ; great bony ridges are developed for the attachment of the muscles of the jaws and face ; the incisors project ; and ultimately the muzzle becomes as pro- nounced and well-marked a feature as in the typical Carnivora (fig. 453, A). The Orangs are inhabitants of Sumatra and Borneo. They are arboreal in their habits, and form for them- selves a sort of nest or shelter amongst the trees. The fore- head is rounded, the cerebrum is greatly convoluted, and the canine teeth of the full-grown males are very large. The genus Troglodytes contains the Chimpanzee (71 niger) VERTEBRATA: MAMMALIA. 78l and the Gorilla (71 Gorilla), with some other imperfectly known forms. The Chimpanzee is a native of western Africa, extending its. range eastwards to Abyssinia ; and has the arms much shorter, proportionately, than in the Gibbons and Orangs ; still they are much longer than the hind-limbs, and Fig. 453. — A, Skull of the Orang-utan. B, Skull of an adult European. they reach beneath the knee when the animal stands erect. The ears in the Chimpanzee are large, and the body is covered with dark-brown hair. The animal can stand erect, but the natural mode of progression is on all-fours. The hands are naked to the wrist, and the face is also naked, and is much wrinkled. The Chimpanzee lives in society in wooded dis- tricts, constructs huts, and can defend itself against even the largest of its foes. The Gorilla is in most respects the same as the Chimpan- zee, but is much larger, attaining a height of between five and six feet. The hind-limbs are short, and the ears are small. It is an enormously strong and ferocious animal, and is found in Lower Guinea and in the interior of equatorial Africa. It possesses a laryngeal sac, has a most appalling voice, and is polygamous. Its habits are mainly arboreal, and the male builds a kind of nest in the trees, in which the female brings forth the young. The Gorilla has been often regarded as the most human of the Anthropoid Apes, but many of the highest authorities believe that the Gibbons have a greater claim to occupy this position. As regards the distribution of the Quadrumana in time, the earliest representatives of the order appear to be found in the Eocene Tertiary. In deposits of this age in Wyoming, Pro- fessor Marsh has discovered several forms apparently related 782 MANUAL OF ZOOLOGY. to both the Lemuroids and the Platyrhines. They form the two families of the Lemuravidce, of which the principal genus (Lemuravus) has forty-four teeth, and Limnotheridtz, in which there are only forty teeth. Remains of Lemuroids have also been found in the Eocene of Europe. The first remains of the higher Quadru- mana appear in the Miocene. The two most important of these are Pliopithecus (fig. 454)andZ>r>v//- thecus, both of which are European, and both of which belong to the section of the Catarhine Monkeys, which are at present characteristic of the Old World ; the former being most nearly allied to the living Semnopitheci, the latter to the Gibbons. It is interesting to notice that the South American fossil Monkeys — from the later Tertiary deposits of South America — belong to the divi- sion of the Qiiadrumana now peculiar to that continent — to the section, namely, of the Platyrhine Monkeys. Fig. 454. — Lower jaw of Pliopithecus autiquus. Miocene. CHAPTER LXXX. BIMANA. ORDER XVII. BIMANA. — This, the last remaining order of the Mammalia, comprises Man (Homo] alone, and it will therefore require but little notice here, the peculiarities of Man's mental and physical structure properly belonging to other branches of science. Zoologically, Man is distinguished from all other Mammals 'by his habitually erect posture and bipedal progression. The lower limbs are exclusively devoted to progression and to sup- porting the weight of the body. The anterior limbs are shorter than the posterior, and have nothing whatever to do with pro- gression. The thumb is opposable, and the hands are pre- VERTEBRATA: LITERATURE. 783 hensile, the fingers being provided with nails. The toes of the hind-limb are also furnished with nails, but the hallux is not opposable to the other digits, and the feet are therefore useless as organs of prehension. The foot is broad and plantigrade, and the whole sole is applied to the ground in walking. The dentition consists of thirty-two teeth, and these form a nearly even and uninterrupted series, without any interval or diastema. The dental formula is — 2 — 2 I — I 2 — 2 3—3 The brain is more largely developed and more abundantly furnished with large and deep convolutions than is the case with any other Mammal. The mammae are pectoral, and the placenta is discoidal and deciduate. Man is the only terrestrial Mammal in which the body is not provided, at any rate dorsally, with a covering of hair. The zoological or anatomical distinctions between Man and the other Mammals are thus seen to be of no very striking nature, and certainly of themselves would not entitle us to con- sider Man as forming more than a distinct order. When, how- ever, we take into account the vast and illimitable psychical differences, both intellectual and moral — differences which must entail corresponding structural distinctions — between Man and the highest Quadrumana, it becomes a question whether the group Bimana should not have the value of a distinct sub-kingdom ; whilst there can be little hesitation in giving Man, at any rate, a class to himself. At any rate, man's psychical peculiarities are as much an integral portion, or more, of his totality, as are his physical characters, and, as Dr Pritchard says, — " The sentiments, feelings, sympathies, inter- nal consciousness, and mind, and the habitudes of mind and action thence resulting, are the real and essential character- istics of humanity." As regards the distribution of the order Bimana in time, we have doubtless yet much to learn. So far as is certainly known at present, no remains of Man, in the form of bones or imple- ments, have as yet been detected in deposits of greater age than the later half of the Post-Pliocene period, at which time Man was associated in Western Europe with a number of ex- tinct Mammalia. LITERATURE. [In addition to many of the works mentioned in the bibliographical list relating to the Vertebrata in general, and especially to Owen's " Compara- 784 MANUAL OF ZOOLOGY. live Anatomy and Physiology of Vertebrate Animals," and Huxley's "Manual of the Vertebrata," the following are some of the principal sources of information as to recent and fossil Mammalia : — ] 1. "Osteology of Mammalia." Flower. 1870. 2. " Characters, Principles of Division, and Primary Groups of the Class Mammalia." Owen. 'Proc. Linn. Soc.' 1858. 3. " Saiigethiere. " Giebel. * Bronn's Klassen und Ordnungen des Thier- reichs.' 1874 (in course of publication). 4. " Die Saiigethiere in zoologischer, anatomischer, und palseontologischer Beziehung umfassend dargestellt. " Giebel. 1855. 5. " Recherches pour servir a 1'histoire naturelle des Mammiferes." H. & A. Milne-Edwards. 1868. 6. " Recherches sur les ossemens fossiles. " Cuvier. 4th ed. 1835-37. 7. " Allgemeine Naturgeschichte. " Oken. 1838. 8. " Histoire naturelle, generale et particuliere." Buffon and Dauben- ton. 1753-67. 9. "Lectures on the Comparative Anatomy of the Placenta." Turner. 1876. 10. " Natural History of Mammalia. " Waterhouse. 1845-48. 11. " Odontography. " Owen. 1840-45. 12. " History of British Quadrupeds, including Cetacea." Bell. 1837. 13. "History of Quadrupeds." Bewick. 8th ed. 1824. 14. " Histoire naturelle des Mammiferes." Etienne Geoffrey Saint- Hilaire, and Fred. Cuvier. 1819-35. 15. " Comparative Anatomy of the Domesticated Animals." Chauveau. Trans, by Fleming. 1873. 16. " Handbuch der Vergleichenden Anatomic der Haus - Saiigethiere. " Gurlt. 1860. 17. "Naturgeschichte der Saiigethiere." Schreber. (Continued by Wagner.)' I775'I855- 1 8. "Classification of the Mammalia." Gill. 'Proc. Amer. Assoc. for the Advancement of Science.' 1870. 19. " On the Characteristics of the Primary Groups of the Class of Mam- mals." Gill. Ibid. 1871. 20. "Geographical Distribution of Animals." Wallace. 1876. 21. " Geographical Distribution of Mammals. " Andrew Murray. 1866. 22. " Geographische Verbreitung der Thiere. " Schmarda. 1853. 23. "Zoologie et Paleontologie francaises, nouvelles recherches sur les animaux vertebres." Gervais. 2d ed. 1859. 24. " Histoire naturelle des Mammiferes." Gervais. 1854. 25. " Variation of Animals and Plants under Domestication." Darwin. 1868. 26. "Mammals of North America." Baird. 1859. 27. " Mammals of India." Jerdon. 1867. 28. " Mammals of Australia." Gould. 1845-60. 29. "Fauna boreali Americana." Sir John Richardson. Mammalia by Harlan. 1825. 30. Article " Monotremata." Owen. ' Todd's Cyclopaedia of Anat. and Phys.' 1841. 31. "Mammary glands of Ornithorhynchus. " Owen. Phil. Trans. 1832. 32. "Young of Ornithorhynchus paradoxus." Owen. 'Trans. Zool. Soc.' 1834. 33. " Memoire sur le genre Ornithorhynche. " Van der Hoeven. 'Nova Acta Acad. Leopold.' 1823. VERTEBRATA: LITERATURE. 785 34. " Natural History and Habits of the Ornithorhynchus paradoxus.' E. T. Bennet ' Trans. Zool Spc.' 1835. 35. " Ornithorhynchi paradoxi descriptio anatomica. " Meckel. 1826. 36. Article " Marsupialia." Owen. 'Todd's Cyclopaedia of Anat. and Phys.' 1841. 37. "Structure of the Brain in Marsupial Animals." Owen. 'Phil. Trans.' 1837. 38. " Classification of the Marsupialia." Owen. 'Trans. Zool. Soc.' 1839. 39. "Generation of Marsupial Animals." Owen. ' Phil. Trans.' 1834. 40. " Osteology of Marsupialia. " Owen. * Trans. Zool. Soc. ' 1841 and 1845. 41. " Fossil Mammalia of Australia." Owen. ' Phil. Trans. ' 1858 and 1865. (Thylacoleo.} 42. "Fossil Mammalia of Australia." Owen. 1877. 43. "Fossil Mammalia of the Mesozoic Formations. Owen. 'Paloe- ontographical Society.' 1871. 44. "Marsupialia." Waterhouse. 'Jardine's Naturalists' Library.' 1841. 45. " Monograph of the Macropodidae." Gould. 1841-44. 46. " Untersuchungen iiber die Edentaten." Rapp. 2d ed. 1852. 47. Article " Edentata." Bell. ' Todd's Cyclopaedia of Anat. and Phys.' 1836. " Memoir on the Megatherium." Owen. 1860. " Skeleton of the Mylodon. " Owen. 1842. " Memoir on the Extinct Sloth Tribe of North America. " Leidy. 1853. "Classification of Edentata." Turner. « Proc. Zool. Soc.' 1851. ' ' Osteology of Edentata. " Turner. ' Annals and Magazine Nat. Hist.' 1853. 53. "Form and Structure of the Manatee." Murie. 'Trans. Zool. Soc.' 1872. 54. " Ausfiihrliche Beschreibung von sonderbaren Meerthieren. " Steller. 1753- 55. " Untersuchungen iiber die ehemalige Verbreitung und die ganzliche Vertilgung der von Steller beobachteten Nordischen Seekuh. " Von Baer. 'Mem. de 1'Acad. Imp. des Sci. de St. Petersbourg.' 1838. 56. "Anatomy of the Dugong." Owen. ' Proc. Zool. Soc.' 1838. 57. Article "Cetacea." F. Cuvier. 'Todd's Cyclopaedia of Anat. and Phys.' 1835. Also> " Hist- Nat- des Cetaces." 1836. 58. " Die Cetacen zoologisch-anatomisch dargestellt. " Rapp. 1837. 59. " Cetace's du littoral de la Belgique. " Van Beneden. 1861. 60. " Synopsis of the Species of Whales and Dolphins in the British Museum." J. E. Gray. 1868. 61. " Untersuchungen iiber die Nordischen Walthiere. " Eschricht. 1849. 62. " Osteology of Inia and Pontoporia." Flower. ' Trans. Zool. Soc. ' 1867. 63. "Monograph of the Crag Cetacea." (Ziphioid Whales.) Owen. ' Palaeontographical Society.' 1870. 64. Article " Pachydermata." Rymer Jones. 'Todd's Cyclopaedia of Anat. and Phys.' 1839. 65. Article " Solipedia." Rymer Jones. Ibid. 1847. 66. Article " Ruminantia. " Spencer Cobbold. Ibid. 1859. 67. "The Horse." Youatt. 1843. 68. "Naturgeschichte des Pferdes." D' Alton. 1810-16. 69. " Gigantic Fossil Mammals of the Order Dinocerata." Marsh. ' Amer. Journ. Sci. and Arts.' 1873. 786 MANUAL OF ZOOLOGY. 70. " Short-footed Ungulata of the Eocene of Wyoming. " Cope. ' Proc. Amer. Philosoph. Soc.' 1873. 71. "Structure and Affinities of the Brontotheridse." Marsh. 'Amer. , Journ. Sci. and Arts.' 1874. 72. "Principal Characters of the Brontotheridse." Marsh. 'Amer. Journ. Sci. and Arts.' 1876. 73. " Principal Characters of the Dinocerata. " Marsh. ' Amer. Journ. Sci. and Arts.' 1876. 74. " Principal Characters of the Tillodontia. " Marsh. ' Amer. Journ. Sci. and Arts.' 1876. 75. Article " Carnivora." Bell. ' Todd's Cyclopaedia of Anat. and Phys.' 1835. 76. " Anatomic Descriptive du Chat." Strauss-Durckheim. 77. Article " Rodentia." Rymer Jones. ' Todd's Cyclopaedia of Anat. and Phys.' 1847. 78. "OntheChinchillidse." E.T.Bennett. 'Trans. Zool. Soc.' 1833. 79. " Systematisk Ofversigt af de Gnagande Daggdjuren, Glires." Lillje- borg. 1866. 80. Article "Cheiroptera." Bell. 'Todd's Cyclopaedia of Anat. and Phys.' 1835. 81. " Monograph of the Asiatic Cheiroptera." Dobson. 1876. 82. "Classification of Insectivora." Mivart. 'Proc. Zool. Soc.' 1871. 83. Article "Insectivora." Bell. 'Todd's Cyclopaedia of Anat. and Phys.' 1836. 84. "De Solenodonte." Brandt. ' Mem. de 1'Acad. Imp. des Sci. de St. Petersbourg.' 1838. 85. Article " Quadrumana. " Vrolik. ' Todd's Cyclopaedia of Anat. and Phys.' 1847. 86. Article ' ' Apes. " Mivart. ' Encyclopaedia Britannica. ' 9th ed. 1875- 87. " Appendicttlar Skeleton of Primates." Mivart. 'Phil. Trans.' 1867. 88. "On the Zoological Rank of the Lemuroidea." Mivart. 'Proc. Zool. Soc.' 1873. 89. " Man and Apes." Mivart. 1874. 90. " Evidence as to Man's Place in Nature." Huxley. 1874. 91. "The Human Skeleton." Humphry. 1858. 92. " Monograph on the Aye- Aye. " Owen. 1868. 93. " Recherches sur le Chimpanse." Vrolik. 1841. 94. "Natural History of Man." Pritchard. 1843. 95. "Researches into the Physical History of Mankind." Pritchard. 3d ed. 1844. 96. " De generis humani varietate nativa." Blumenbach. 3d ed. 1795. 97. " Types of Mankind." Nott and Gliddon. 1854. 98. "Descent of Man." Darwin. 1871. 99. " Fauna der Vorwelt." Giebel. 1847. 100. "Fauna Antiqua Sivalensis." Falconer and Sir Proby Cautley. 1846-49. 101. "British Fossil Mammals and Birds." Owen. 1846. 102. "Catalogue of the fossil Organic remains of Mammalia and Aves in the Museum of the Royal College of Surgeons of England." Owen. 1845. 103. " Extinct Mammalia from Nebraska Territory." Leidy. 1852. 104. " Animaux fossiles et Geologic de 1'Attique." Gaudry. 1864-68. 105. " Monograph of the British Fossil Pleistocene Mammalia." Daw- kins and Sandford. ' Palseontographical Society. ' 1866-71. GLOSSARY. ABDOMEN (Lat. abdomen; from abdo, I conceal. Sometimes regarded as a contraction of adipomen, from adeps, fat. ) The posterior cavity of the body, containing the intestines and others of the viscera. ABERRANT (Lat. alerro, I wander away). Departing from the regular type. ABIOGENESIS (Gr. a, without ; bios, life ; genesis, origin). Spontaneous gene- ration, or the production of living beings without pre-existent life. ABNORMAL (Lat. ab, from ; norma, a rule). Irregular ; deviating from the ordinary standard. ABOMASUM. The fourth cavity of the complex stomach of the Ruminants. ABRANCHIATE (Gr. a, without ; bragchia, gills). Destitiite of gills or bran- chiae. ACALEPH.E (Gr. akalepM, a nettle). Applied formerly to the Jelly-fishes or Sea-nettles, and other Radiate animals, in consequence of their power of stinging, derived from the presence of microscopic cells, called "thread- cells," in the integument. AcANTHOCEPHALA (Gr. akantha, a thorn ; kephale, head). A class of para- sitic worms, in which the head is armed with spines. ACANTHOMETRINA (Gr. akantha ; and metra, the womb). A family of Pro- tozoa, characterised by having radiating siliceous spines. ACANTHOPTERYGII (Gr. akantha, spine; pterux, wing). A group of bony fishes with spinous rays in the front part of the dorsal tin. ACARINA (Gr. akari, a mite). A division of the Arachnida, of which the Cheese-mite is the type. ACEPHALOUS (Gr. a, without; kephale, head). Not possessing a distinct head. ACETABULA (Lat. acetdbulum, a cup). The suckers with which the cephalic processes of many Cephalopoda (Cuttle-fishes) are provided. ACETABULUM. The cup-shaped socket of the hip-joint in Vertebrata. ACONTIA (Gr. akontion, a javelin). Long filaments, charged with thread-cells, attached to the free edges of the mesenteries of Sea-anemones. ACRITA (Gr. akritos, confused). A term sometimes employed as synonymous with Protozoa, or the lowest division of the animal kingdom. ACTINOMERES (Gr. aktin, a ray ; meros, a part). The lobes which are mapped out on the surface of the body of the Ctenophora, by the ctenophores, or comb-like rows of cilia. ACTINOSOMA (Gr. aktin ; and soma, body). Employed to designate the entire body of any Actinozotin, whether this be simple (as in the Sea-anemones), or composed of several zooids (as in most Corals). ACTINOTROCHA (Gr. aktin, ray ; trochos, wheel). The form of Invertebrate larva seen in some of the Annelides, &c., in which there is a circlet of cilia round the anterior extremity. ACTINOZOA (Gr. aktin; and zoon, an animal). That division of the Coclen- terata of which the Sea-anemones may be taken as the type. 788 GLOSSARY. ADELARTHROSOMATA (Gr. adelos, hidden ; arthros, joint ; soma, body). An order of the A rachnida. AGAMIC (Gr. a, without ; gamos, marriage). Applied to all forms of repro- duction in which the sexes are not directly concerned. ALLANTOIDEA. The group of Vertebrata in which the foetus is furnished with ail allantois, comprising the Reptiles, Birds, and Mammals. ALLANTOIS (Gr. alias, a sausage). One of the " membranes" of the foetus in certain Vertebrates. ALVEOLI (Lat. dim. of alvus, belly). Applied to the sockets of the teeth. AMBULACRA (Lat. ambulacrum, a place for walking). The perforated spaces or " avenues" through which are protruded the tube-feet, by means of which locomotion is effected in the Echinodermata. AMBULATORY (Lat. ambulo, I walk). Formed for walking. Applied to a single limb or to an entire animal. AMETABOLIO (Gr. a, without ; metdboU, change). Applied to those insects which do not possess wings when perfect, and which do not, therefore, pass through any marked metamorphosis. AMNION (Gr. amnos, a lamb). One of the foetal membranes of the higher Vertebrates. AMNIOTA. The group of Vertebrata in which the foetus is furnished with an amnion, comprising the Reptiles, Birds, and Mammals. AMCEBA (Gr. amoibos, changing). A species of Rhizopod, so called from the numerous changes of form which it undergoes. AMCEBIFORM. Resembling an Amoeba in form. AMORPHOZOA (Gr. a, without ; morph'e, shape ; zoon, animal). A name some- times used to designate the Spwiges. AMPHIBIA (Gr. amphi, both ; bios, life). The Frogs, Newts, and the like, which have gills when young, but can always breathe air directly when adult. AMPHICCELOUS (Gr. amphi, at both ends ; koilos, hollow). Applied to Verte- brae which are concave at both ends. AMPHIDISCS (Gr. amphi, at both ends ; disfcos, a quoit or round plate). The spicula which surround the gemmules of Spongilla, and resemble two toothed wheels united by an axle. AMPHIOXUS (Gr. amphi, at both ends ; oxus, sharp). The Lancelet, a little fish, which alone constitutes the order Pharyngobranchii. AMPHIPNEUSTA (Gr. amphi, both ; pneo, I breathe). Applied to the "perenni- branchiate " Amphibians which retain their gills through life. AMPHIPODA (Gr. amphi ; andpous, a foot). An order of Crustacea. ANAL (Lat. anus, the vent). Connected with the anus, or situated near the anus. ANALLANTOIDEA. The group of Vertebrata in which the embryo is not fur- nished with an allantois. ANALOGOUS. Applied to parts which perform the same function. ANAMNIOTA. The group of Vertebrata in which the embryo is destitute of an amnion. ANARTHROPODA (Gr. a, without ; arthros, a joint ; pous, foot). That division of Annulose animals in which there are no articulated appendages. ANCHYLOSIS or ANKYLOSIS (Gr. ankulos, crooked). The union of two bones by osseous matter, so that they become one bone, or are immovably joined together. ANDROGYNOUS (Gr. aner, a man ; gune, a woman). Synonymous with her- maphrodite, and implying that the two sexes are united in the same indi- vidual. ANDROPHORES (Gr. aner, a man ; and phero, I carry). Applied to medusiform gonophores of the Hydrozoa, which carry the spermatozoa, and differ in form from those in which the ova are developed. ANNELIDA (a Gallicised form of Annulata). The Ringed Worms, which form one of the divisions of the Anarthropoda. ANNULATED. Composed of a succession- of rings. ANNULOIDA (Lat. annulus, a ring; Gr. eidos, form). The sub-kingdom com- prising the Echinod&rmata and the Scolecida (= Echinozoa). GLOSSARY. 789 ANNULOSA (Lat. annulus). The sub-kingdom comprising the Anarthropoda and the A rthropoda or A rticulata, in all of which the body is more or less evidently composed of a succession of rings. ANOMODONTIA (Gr. anomos, irregular ; odous, tooth). An extinct order of Reptiles, often called Dicynodontia. ANOMURA (Gr. anomos, irregular ; oura, tail). A tribe of Decapod Crustacea, of which the Hermit-crab is the type. ANOPLUKA (Gr. anoplos, unarmed : oura, tail). An order of Apterous In- sects. ANOURA (Gr, a, without ; oura, tail). The order of Amphibia comprising the Frogs and Toads, in which the adult is destitute of a tail. Often called Batrachia. ANTENNJE (Lat. antenna, a yard-arm). The jointed horns or feelers possessed by the majority of the Articulata. ANTENNULES (dim. of antennae). Applied to the smaller pair of antennae in the Crustacea. ANTIBRACHIUM ((Jr. anti, in front of ; brachion, the arm). The fore-arm of the higher Vertebrates, composed of the radius and ulna. ANTLERS. Properly the branches of the horns of the Deer tribe (Cervidce), but generally applied to the entire horns. ANTLIA (Lat. antlia, a pump). The spiral trunk or proboscis with which But- terflies and other Lepidopterous Insects suck up the juices of flowers. APHANIPTERA (Gr. aphanos, inconspicuous ; pteron, a wing). An order of Insects comprising the Fleas. APLACENTALIA. The section of the Mammalia, comprising the two divisions of the Didelphia and Monodelphia, in which the young is not furnished with a placenta. APODA (Gr. a, without; podes, feet). Applied to those fishes which have no ventral fins. Also to the footless Ccecilice amongst the Amphibia. APODAL. Devoid of feet. APODEMATA (Gr. apodaio, I portion off). Applied to certain chitinous septa which divide the tissues in Crustacea. APTERA (Gr. a, without ; pteron, a wing). A division of Insects, which is characterised by the absence of wings in the adult condition. APTEROUS. Devoid of wings. APTERYX (Gr. a, without ; pterux, a wing). A wingless bird of New Zealand, belonging to the order Cursores. AQUIFEROUS (Lat. aqua, water ; fero, I carry. Water-bearing : applied to all vessels or canals by which water is distributed through an organism. ARACHNIDA (Gr. arachne, a spider). A class of the Articulata, comprising Spiders, Scorpions, and allied animals. ARBORESCENT. Branched like a tree. ARCH,EOPTERYX (Gr. archaios, ancient ; pterux, wing). The singular fossil bird which alone constitutes the order of the Saururce. ARCHENCEPHALA (Gr. archo, I overrule; egkephalos, brain). The name ap- plied by Owen to his fourth and highest group of Mammalia, comprising Man alone. ARENACEOUS. Sandy, or composed of grains of sand. ARTICULATA (Lat. articulus, a joint). A division of the animal kingdom, com- prising Insects, Centipedes, Spiders, and Crustaceans, characterised by the possession of jointed bodies or jointed limbs. The term Arthropoda is now more usually employed. ARTIODACTYLA (Gr. artios, even; daktulps, a finger or toe). A division of the hoofed quadrupeds ( Ungulata) in which each foot has an even number of toes (two or four). ASCIDIOIDA (Gr. askos, a bottle ; eidos, a form). A synonym of Tunicata, a class of Molluscous animals, which have the shape, in many cases, of a two- necked bottle. ASEXUAL. Applied to modes of reproduction in which the sexes are not concerned. ASIPHONATE. Not possessing a respiratory tube or siphon. (Applied to a division of the Lamellibranchiate Molluscs.) 790 GLOSSARY. ASTEROID (Gr. aster, a star ; and eidos, form). Star-shaped, or possessing radi- iug lobes or rays like a star-fish. ASTEROIDEA. An order of Echinodermata, comprising the Star-fishes, char- acterised by their rayed form. ASTOMATOUS (Gr. a, without ; stoma, mouth). Not possessing a mouth. ATLAS (Gr. the god who holds up the earth). The first vertebra of the neck, which articulates with and supports the skull. ATRIUM (Lat. a hall). Applied to the great chamber or " cloaca," into which the intestine opens in the Tunicata. AURELIA (Lat. aurum, gold). Applied to the chrysalides of some Lepidoptera, on account of their exhibiting a golden lustre. AURICLE (Lat. dim. of auris, ear). Applied to one of the cavities of the heart, by which blood is driven into the ventricle. AUTOPHAGI (Gr. autos, self ; phago, I eat). Applied to birds whose young can run about and obtain food for themselves as soon as they escape from the egg. AVES (Lat. avis, a bird). The class of the Birds. AVICULARIUM (Lat. avicula, dim. of avis, a bird). A singular appendage, often shaped like the head of a bird, found in many of the Polyzoa. Axis (Gr. axon, a pivot). The second vertebra of the neck, upon which the skull and atlas usually rotate. AZYGOUS (Gr. a, without ; zugon, yoke). Single, without a fellow. BACTERIUM (Gr. bakterion, a staff). A microscopic organism occurring in fluids containing organic matter, and having a staff-shaped form. BALANID.E (Gr. balanos, an acorn). A family of sessile Cirripedes, commonly called "Acorn shells." BALEEN (Lat. balcena, a whale). The horuy plates which occupy the palate of the "whalebone" Whales. BATIDES (Gr. batos, a bramble). The family of the Elasmobranehii comprising the Bays. BATRACHIA (Gr. batrachos, a frog). Often loosely applied to any of the Am- phibia, but sometimes restricted to the Amphibians as a class, or to the single order of the Anoura. BELEMNITIDJ;! (Gr. belemnon, a dart). An extinct group of Dibranchiate Cepha- lopods, comprising the Belemnites and their allies. BICAVITART (Lat. fris, twice ; cavus, hollow). Consisting of or possessing two cavities. BIFID. Cleft into two parts ; forked. BILATERAL. Having two symmetrical sides. BIMANA (Lat. bis, twice ; manus, a hand). The order of Mammalia compris- ing Man alone. BIPEDAL (Lat. bis, twice ; pes, foot). Walking upon two legs. BIRAMOUS (Lat, bis, twice ; ramus, a branch). Applied to a limb which is divided into two branches (e.g., the limbs of Cirripedes). BIVALVE (Lat. bis, twice ; valvce, folding-doors). Composed of two plates or valves ; applied to the shell of the Lamellibranchiata and Brachiopoda, and to the carapace of certain Crustacea. BLASTOIDEA (Gr. blastos, a bud ; and eidos, form). An extinct order of Echi- nodermata, often called Pentremites. BLASTOSTYLE (Gr. blastos, a bud ; and stulos, a column). Applied by Prof. Allman to certain columniform zob'ids in the Hydrozoa which are destined to bear generative buds. BRACHIOPODA (Gr. brachion> an arm ; pous, the foot). A class of the Mol- luscoida, often called " Lamp-shells," characterised by possessing two fleshy arms continued from the sides of the mouth. BRACHIUM (Gr. brachion, arm). Applied to the upper arm of Vertebrates. BRACHYURA (Gr. brachus, short ; oura, tail). A tribe of the Decapod Crusta- ceans with short tails (i.e., the Crabs). BRACTS. (See Hydrophyllia). BRADYPODIDJE (Gr. bradus, slow ; podes, feet). The family of Edentata, com- prising the Sloths. GLOSSARY. 791 BRANCHIA (Gr. bragchia, the gill of a fish). A respiratory organ adapted to breathe air dissolved in water. BRANCHIATE. Possessing gills or branchiae. BRANCHIFERA (Gr. bragchia, gill ; and phero, I carry}. A division of Gastero- podous Molluscs, in which the respiration is aquatic, and the respiratory organs are mostly in the form of distinct gills. BRANCHIO-GASTEROPODA ( = Branchifera). BRANCHIOPODA (Gr. bragchia : and penis, foot). A legion of Crustacea, in which the gills are supported by the feet. BRANCHIOSTEGAL (Gr. 'bragchia, gills ; stego, I cover). Applied to a membrane and rays by which the gills are protected in many fishes. BREVILINGUIA (Lat. brevis, short ; lingua, tongue). A division of the Lacer- tilia. BREVIPENNAT.E (Lat. brevis, short ; penna, a wing). A group of the Natato- rial Birds. BRONCHI (Gr. brogchos, the windpipe). The branches of the windpipe (trachea), by which the air is conveyed to the vesicles of the lung. BRONTOTHERID^E (Gr. Brontes, the name of a giant ; therion, beast). An extinct order of Tertiary Mammals. BRUTA (Lat. brutus, heavy, stupid). Often used to designate the Mammalian order of the Edentata. BRYOZOA (Gr. bruon, moss ; zoon, animal). A synonym of Polyzoa, a class of the Molluscoida. BUCCAL (Lat. bucca, mouth or cheeks). Connected with the mouth. BURSIFORM (Lat. bursa, a purse ; forma, shape). Shaped like a purse ; sub- spherical. BYSSIFEROUS. Producing a byssus. BYSSUS (Gr. bussos, flax). A term applied to the silky filaments by which the Pinna, the common Mussel, and certain other bivalve Mollusca, attach themselves to foreign objects. CADUCIBRANCHIATE (Lat. caducus, falling off ; Gr. bragchia, gill). Applied to those Amphibians in which the gills fall off before maturity is reached. CADUCOUS. Applied to parts which fall off or are shed during the life of the animal. C^CAL (Lat. ccecus, blind). Terminating blindly, or in a closed extremity. CAECUM (Lat. ccecus). A tube which terminates blindly. OESPITOSE (Lat. ccespes, a turf). Tufted. CAINOZOIC. (See Kainozoic.) CALCAR (Lat. a spur). Applied to the "spurs" of Easorial Birds; and also to the rudiments of the hind-limbs in certain snakes. CALCAREOUS (Lat. calx, lime). Composed of carbonate of lime. CALICE. The little cup in which the polype of a coralligenous Zoophyte (Aciinozoon) is contained. CALYCOPHORID.E (Gr. kalux, a cup ; and phero, I carry). An order of the Oceanic Hydrozoa, so called from their possessing bell-shaped swimming organs (nectocalyces). CALYPTOBLASTIC (Gr. kaluptos, covered ; and blastos, a bud). Applied by Prof. Allman to those Hydrozoa in which the nutritive .or generative buds are provided with an external protective receptacle. CALYX (Lat. calyx, a cup). Applied to the cup-shaped body of Vorticella (Protozoa), or of a Crinoid (Echinodermata). CAMPANULARIDA (Lat. campanula, a bell). An order of Hydroid Zoophytes. CANINE (Lat. cards, a dog). The eye-tooth of Mammals, or the tooth which is placed at or close to the praemaxillary suture in the upper jaw, and the corresponding tooth in the lower jaw. CAPITULUM (Lat. dim. of caput, head). Applied to the body of a Barnacle (Lepadidce), from its being supported upon a stalk or peduncle. CARAPACE. A protective shield. Applied to the upper shell of Crabs, Lob- sters, and many other Crustacea ; also to the case with which certain of the Infusoria are provided. Also the upper half of the immovable case in which the body of a Chelonian is protected. 792 GLOSSARY. CARINAT.E (Lat. carina, a keel). Applied by Huxley to all those birds in which the sternum is furnished with a median ridge or keel. CARNIVORA (Lat. caro, flesh ; voro, I devour). An order of the Mammalia. CARNIVOROUS (Lat. caro, flesh ; voro, I devour). Feeding upon flesh. CARNOSE (Lat. caro). Fleshy. CARPOPHAGA (Gr. karoos, fruit ; phago, I eat). A section of the Marsu- pialia. CARPUS (Gr. karpos, the wrist). The small bones which intervene between the fore-arm and the metacarpus. CATARHINA (Gr. kata, downwards ; rhines, nostrils). A group of the Quadru- mana. CAUDAL (Lat. cauda, the tail). Belonging to the tail. CAVICORNIA (Lat. cavus, hollow; cornu, a horn). The "hollow-horned" Euminants, in which the horn consists of a central bony " horn-core " sur- rounded by a horny sheath. CENTRUM (Gr. kentron, the point round which a circle is described by a pair of compasses). The central portion or "body" of a vertebra. CEPHALIC (Gr. kephale, head). Belonging to the head. CEPHALO-BRANCHIATE (Gr. kephale ; and bragchia, gill). Carrying gills upon the head. Applied to a section of the Annelida, which, like the Serpulce, have tufts of external gills placed upon the head. CEPHALOPHORA (Gr. kephale; an&phero, I carry). Used synonymously with Encephala, to designate those Mollusca which possess a distinct head. CEPHALOPODA (Gr. kephale ; and podes, feet). A class of the Mollusca, com- prising the Cuttle-fishes and their allies, in which there is a series of arms ranged round the head. CEPHALOTHORAX (Gr. kepliale; and thorax, chest). The anterior division of the body in many Crustacea and Arachnida, which is composed of the coalesced head and chest. CERCARIIFORM (Lat. cercaria, a tailed animalcule ; and forma, shape). Cer- caria (Gr. kerkos, tail) is the name of a tadpole-shaped animalcule ; and the epithet " cercariiform " is applied to all organisms of a similar shape (e.g., the larval Tunicates). CERE. The naked space found at the base of the bill of some birds. CERVICAL (Lat. cervix, neck). Connected with the region of the neck. CESTOIDEA (Gr. kestos, a girdle). An old name for the Tceniada, a class of intestinal worms with flat bodies like tape (hence the name Tapeworms). CESTRAPHORI (Gr. kestra, a weapon ; phero, I carry). The group of Elasmo- branchii represented at the present day by the Port Jackson Shark. CETACEA (Gr. ketos, a whale). The order of Mammals comprising the Whales and Dolphins. CH^TOGNATHA (Gr. chaite, bristle ; gnathos, jaw). An order of the Anarthro- poda, comprising only the oceanic genus Sagitta. CHJETOPHORA (Gr. chaite ; phero, I carry). Applied as a common name to the Tubiculous and Errant Annelides, both of which have bristle-bearing foot- tubercles, together with the Earth-worms and their allies (Oligochceta), which have locomotive bristles. CHEIROPTERA (Gr. cfieir, hand ; pteron, a wing). The order of Mammals com- prising the Bats. CHEL.E (Gr. chele, a claw). The prehensile claws with which some of the limbs axe terminated in certain Crustacea, such as the Crab, Lobster, &c. CHELATE. Possessing chelae ; applied to a limb. CHELICERJB (Gr. chele, a claw ; and keras, a horn). The prehensile claws of the Scorpion, supposed to be homologous with antenna. CHELONIA (Gr. chelone, a tortoise). The order of Keptiles comprising the Tor- toises and Turtles. CHELONOBATRACHIA (Gr. chelone, a tortoise ; batrachos, a frog). Sometimes applied to the Amphibian order of the Anoura (Frogs and Toads). CHILOGNATHA (Gr. cheilos, a lip ; and gnathos, a jaw). An order of the My- riapoda. CHILOPODA (Gr. cheilos; and podes, feet). An order of the Myriapoda. GLOSSARY. 793 CHITINE (Gr. chiton, a coat). The peculiar chemical principle, nearly allied to horn, which forms the exoskeleton in many Invertebrate animals, especially in the Arthropoda (Crustacea, Insecta, &c.). CHLOROPHYLL (Gr. chloros, green; andphullon, a leaf). The green colouring matter of plants. CHROMATOPHORES (Gr. chroma, complexion, or colour ; and phero, I carry). Little sacs which contain pigment-granules, and are found in the integument of Cuttle-fishes and other animals. CHRYSALIS (Gr. chrusos, gold). The motionless pupa of butterflies and moths, so called because sometimes exhibiting a golden lustre. CHYLAQUEOUS FLUID. A fluid consisting partly of water derived from the ex- terior, and partly of the products of digestion (chyle), occupying the body- cavity or perivisceral space in many Invertebrates (Annelids, Echinoderms, &c.), and sometimes having a special canal-system for its conduction (chly- aqueous canals). CHYLE (Gr. chulos, juice). The milky fluid which is the result of the action of the various digestive fluids upon the food. CHYLIFIC (Gr. chulos, juice [chyle] ; and Lat./aa'o, I make). Producing chyle. Applied to one of the stomachs, when more than one is present. The word is of mongrel origin ; and " chylopoietic " is more correct. CHYME (Gr. chumos, juice). The acid pasty fluid produced by the action of the gastric juice upon the food. CHYME-MASS. The central, semi-fluid sarcode in the interior of an Infusorian. CILIA (Lat. cilium, an eyelash). Microscopic, hair-like filaments, which have the power of lashing backwards and forwards, thus creating currents in the surrounding or contiguous fluid, or subserving locomotion in the animal which possesses them. CILIOGRADA (Lat. cilium ; and gradior, I walk). Synonymous with Ctenophora, an order of Actinozoa. CINCLIDES (Gr. kigklis, a lattice). Special apertures in the column walls of some Sea-anemones (Actinidw), which probably serve for the emission of the cord-like " craspeda." CIRRI (Lat. cirrus, a curl). Tendril-like appendages, such as the feet of Bar- nacles, and Acorn-shells (Cirripedes) , the lateral processes on the arms of Brachiopoda, &c. CIRRIFEROUS or CIRRIGEROUS. Carrying cirri. CIRRIPEDIA, CIRRHIPEDIA, or CiRRHOPODA (Lat. cirrus, a curl ; and pes, a foot). A sub-class of Crustacea with curled jointed feet. CIRROSTOMI (Lat. cirrus, a tendril ; Gr. stoma, mouth). Sometimes used to designate the Pharyngobranchii. CLADOCERA (Gr. klados, a branch; keras, a horn). An order of Crustacea with branched antennae. CLAVATE (Lat. clavus, a club). Club-shaped. CLAVICLE (Lat. clavicula, a little key). The "collar-bone," forming one of the elements of the pectoral arch of Vertebrates. CLOACA (Lat. a sink). The cavity into which the intestinal canal and the ducts of the generative and urinary organs open in common, in some In- vertebrates (e.g., in Insects), and also in many Vertebrate animals. CLYPEIFORM (Lat. clypeus, a shield; and/orma, shaped). Shield-shaped; ap- plied, for example, to the carapace of the King-crab. CNID^I (Gr. knide, a nettle). The urticating cells or " thread-cells" whereby many Coslenterate animals obtain their power of stinging. COCCOLITHS (Gr. kokkos, a berry ; lithos, stone). Minute oval or rounded bodies, which are found .either free or attached to the surface of cocco- spheres, and which are probably of vegetable origin. COCCOSPHERES (Gr. kokkos ; and sphaira, a sphere). Spherical masses of sar- code, enclosed in a delicate calcareous envelope, and bearing coccoliths upon their external surface. COCCYGEAL. Connected with the coccyx. COCCYX (Gr. kokkux, a cuckoo). The terminal portion of the spinal column in man, so called from its resemblance to a cuckoo's beak. 794 GLOSSARY. COCOON (French, cocon, the cocoon of the silk -worm; connected with Fr. coque, shell, which is derived from the Lat. concha). The oxiter covering of silky hairs with which the pupa or chrysalis of many insects is protected. The chitinous capsules in which Leeches and Earth-worms deposit their eggs. The silken cases which Spiders weave for their eggs. CODONOSTOMA (Gr. kodon, a bell; stoma, mouth). The aperture or mouth of the disc (nectocalyx) of a Medusa, or of the bell (gonocalyx) of a medusi- form gonophore. CCELENTERATA (Gr. koilos, hollow ; enteron, the bowel). The sub-kingdom which comprises the Hydrozoa and Actinozoa. Proposed by Frey and Leuckart in place of the old term Radiata, which included other animals as well. CCENENCHYMA (Gr. koinos, common ; encJiuma, tissue ; literally, an infusion). The common calcareous tissue which unites together the various corallites of a compound corallum. COBNCECIUM (Gr. koinos, common; oikos, house). The entire dermal system of any Polyzob'n; employed in place of the terms polyzoary or polypidom. COJNOSARO (Gr. koinos, common ] sarx, flesh). The common organised me- dium by which the separate polypites of a compound Hydrozob'n are con- nected together. COLEOPTERA (Gr. koleos, a sheath; pteron, wing). The order of Insects (Beetles) in which the anterior pair of wings are hardened, and serve as protective cases for the posterior pair of membranous wings. COLLEMBOLA (Gr. kolla, glue; embolos, a sharp beak or pointed projection). An order of Apterous insects furnished with an adhesive ventral process. COLUBRINA (Lat. coluber, a snake). A division of the Ophidia. COLUMBAOEI (Lat. columba, a dove). The division of Easorial Birds compris- ing the Doves and Pigeons. COLUMELLA (Lat. dim. of columna, a column). In Conchology, the central axis round which the whorls of a spiral univalve are wound. Amongst the Actinozoa, it is the central axis or pillar which is found in the centre of the visceral chamber of many corals. COLUMN. Applied to the cylindrical body of a Sea-anemone (Actinia) ; also to the jointed stem or peduncle of the stalked Crinoids. COMMENSAL (Lat. cum, with ; mensa, table). Living at the same table with, a messmate : Applied to animals which live on or in other animals for part or the whole of their life, simply sharing the food of their host, without . being parasitic on him. COMMISSUBAL (Lat. committo, I solder together). Connecting together : usually applied to the nerve-fibres which unite different ganglia. CONCHA (Lat. a shell). The external ear by which sounds are collected and transmitted to the internal ear. CONCHIFERA (Lat. concha, a shell ; fero, I carry). Shell-fish. Applied in a restricted sense to the bivalve Molluscs, and used as a synonym for Lamelli- branchiata. CONDYLE (Gr. kondulos, a knuckle). The surface by which one bone articu- lates with another. Applied especially to the articular surface or surfaces by which the skull articulates with the vertebral column. CONIROSTRES (Lat. conus, a cone ; rostrum, a beak). The division of Perching Birds with conical beaks. COPEPODA (Gr. kope, an oar ; podes, feet). An order of Crustacea. CORACOID (Gr. korax, a crow ; eidos, form). A separate bone which enters into the composition of the pectoral arch in Birds, Keptiles, and Mono- tremes. In most Mammals it is a mere process of the scapula, having, in man, some resemblance in shape to the beak of a crow. CORALLIGENOUS. Producing a corallum. CORALLITE. The corallum secreted by an Actinozoon which consists of a single polype ; or the portion of a composite corallum which belongs to, and is secreted by, an individual polype. CORALLUM (from the Latin for red coral). The hard structures deposited in, or by, the tissues of an Actinozoon — commonly called a "coral. CORIACEOUS (Lat. corium, hide). Leathery. GLOSSARY. 795 CORPUS CALLOSUM (Lat. the " firm body "). The great band of nervous mat- ter which unites the two hemispheres of the cerebrum in the Mammals. CORPUSCULATED (Lat. corpusculum, a little body or particle). Applied to fluids which, like the blood, contain floating solid particles or "corpuscles." CORTICAL LAYER. The layer of consistent sarcode, which in the Infusoria encloses the chyme mass, and is surrounded by the cuticle. Sometimes called the "parenchyma of the body." COST^E (Lat. costa, a rib). Applied amongst the Crinoidea to designate the rows of plates which succeed the inferior or basal portion of the cup (pel- vis). Amongst the Corals the "costse" are vertical ridges which occur on the outer surface of the theca, and mark the position of the septa within. COSTAL (Lat. costa, a rib). Connected with the ribs. CRANIUM (Gr. kranion, the skull). The bony or cartilaginous case in which the brain is contained. CRASPEDA (Gr. kraspedon, a margin or fringe). The long, convoluted cords, containing thread - cells, which are attached to the tree margins of the mesenteries of a Sea-anemone. CREPUSCULAR (Lat. crepusculum, dusk). Applied to animals which are active in the dusk or twilight. CRINOIDEA (Gr. krinos, a lily ; eidos, form). An order of Echinodermata com- prising forms which are usually stalked, and sometimes resemble lilies in CROCODILIA (Gr. krokodeilos, a crocodile). An order of Reptiles. CROP. A partial dilatation of the gullet, technically called "ingluvies." CRUSTACEA (Lat. crusta, a crust). A class of articulate animals, comprising Crabs, Lobsters, &c., characterised by the possession of a hard shell or crust, which they cast periodically. CTENOCYST (Gr. kteis, a comb ; kustis, a bag or cyst). The sense-organ (prob- ably auditory) which occurs in the Ctenophora. CTENOID (Gr. kteis, a comb ; eidos, form). Applied to those scales of fishes, the hinder margins of which are fringed with spines or comb-like pro- jections. CTENOPHORA (Gr. kteis, a comb ; an&phero, I carry). An order of Actinozoa, comprising oceanic creatures, with swim by means of "ctenophores," or bands of cilia arranged in comb-like plates. CURSORES (Lat. curro, I run). An order of Aves, comprising birds destitute of the power of flight, but formed for running vigorously (e.g., the Ostrich and Emeu). CUSPIDATE. Furnished with small pointed eminences or " cusps." CUTICLE. (Lat. cuticula, dim. of cutis, skin). The pellicle which forms the outer layer of the body amongst the Infusoria. The outer layer of the in- tegument generally. CUTIS (Lat. skin). The inferior vascular layer of the integument, often called the cutis vera, the corium, or the dermis. CYCLOID (Gr. kuklos, a circle ; eidos, form). Applied to those scales of fishes which have a regularly circular or elliptical outline with an even margin. CYCLOSTOMI (Gr. kuklos ; and stoma, mouth). Sometimes used to designate the Hag-fishes and Lampreys, forming the order Marsipobranchii. CYST (Gr. kustis, a bladder or bag). A sac or vesicle. CYSTICA. The embryonic forms (scolices) of certain intestinal worms (Tape- worms), which were described as a distinct order, until their true nature was discovered. CYSTOIDEA (Gr. kustis, a bladder ; and eidos, form). An extinct order of Echinodermata. DECAPODA (Gr. deka, ten ; podes, feet). The division of Crustacea which have ten ambulatory feet ; also the family of Cuttle-fishes, in which there are ten arms or cephalic processes. DECIDUOUS (Lat. decido, I fall off). Applied to parts which fall off or are shed during the life of the animal. DECOLLATED (Lat. decollo, I behead). Applied to univalve shells, the apex of which falls off iu the course of growth. 796 GLOSSARY. DEINOCERATA or DINOCERATA (Gr. deinos, terrible ; Iceras, horn). An extinct order of Tertiary Mammals. DEINOSAURIA or DINOSAURIA (Gr. deinos, terrible ; saura, lizard). An extinct order of Eeptiles. DENDRIFORM, DENDRITIC, DENDROID (Gr. dendron, a tree). Branched like a tree, arborescent. DENTIROSTRES (Lat. dens, a tooth ; rostrum, a beak). The group of Perching Birds in which the upper mandible of the beak has its lower margin toothed. DERMA or DERMIS. (See Cutis.) DERMAL (Gr. derma, skin). Belonging to the integument. DERMOSCLERITES (Gr. derma, skin ; skleros, hard). Masses of spicules which occur in the tissues of some of the Alcyonaria (Actinozoa). DESM.IDI2E. Minute fresh- water plants, of a green colour, without a siliceous epidermis. DEUTEROZOOIDS (Gr. deuteros, second ; zoon, animal ; eidos, form). The zooids which are produced by gemmation from zooids. DEXTRAL (Lat. dextra, the right hand). Eight-handed ; applied to the direc- tion of the spiral in the greater number of univalve shells. DIAPHRAGM (Gr. diaphragma, a partition). The " midriff," or the muscle which in Mammalia forms a partition between the cavities of the thorax and abdomen. DIASTEMA (Gr. diet, apart ; histemi, I place). A gap or interval, especially between teeth. DIASTOLE (Gr. diastello, I separate or expand). The expansion of a contractile cavity such as the heart, which follows its contraction or " systole*." DIATOMACE^E (Gr. diatemno, I sever). An order of minute plants, which are provided with siliceous envelopes. DIBRANCHIATA (Gr. dis, twice ; Iragchia, gill). The order of Cephalopoda (comprising the Cuttle-fishes, &c.) in which only two gills are present. DICYNODONTIA (Gr. dis, twice ; kuon, dog ; odous, tooth). An extinct order of Reptiles. DIDELPHIA (Gr. dis, twice ; delphus, womb). The subdivision of Mammals comprising the Marsupials. DIGIT (Lat. digitus, a finger). A finger or toe. DIGITIGRADA (Lat. digitus ; gradior, I walk). A subdivision of the Carnivora. DIGITIGRADE. Walking upon the tips of the toes, and not upon the soles of the feet. DIMEROSOMATA (Gr. dis ; meros, part; soma, body). An order of Arachnida, comprising the true Spiders, so called from the marked division of the body into two regions, the cephalothorax and abdomen. The name Araneida is often employed for the order. DIM Y ART (Gr. dis, twice ; muon, muscle). Applied to those bivalve Molluscs (Lamellibranchiata) in which the shell is closed by two adductor muscles. DICECIOUS (Gr. dis, twice ; oikos, house). Having the sexes distinct ; applied" to species which consist of male and female individuals. DIPHY DONT (Gr. dis, twice ; phuo, I generate ; odous, tooth). Applied to those Mammals which have two sets of teeth. .DIPHYOZOOIDS. Detached reproductive portions of adult Calycophoridce, an order of oceanic Hydrozoa. DIPNOI (Gr. dis, twice ; pnoe, breath). The order of fishes represented by the Lepidosiren. DIPTERA (Gr. dis, twice ; pteron, wing). An order of insects characterised by the possession of tAvo wings. DISCOID (Gr. diskos, a quoit ; eidos, form). Shaped like a round plate or quoit. DISCOPHORA (Gr. diskos, a quoit ; phero, I carry). This term is applied to the Medusas, or Jelly-fishes, from their form ; and is sometimes used to designate the order of the Leeches (Hirudinea) from the suctorial discs which these animals possess. DISSEPIMENTS (Lat. dissepio, I partition off). Partitions. Used in a restricted sense to designate certain imperfect transverse partitions, which grow from the septa of many corals. DISTAL. Applied to the quickly growing end of the hydrosoma of a Hydro- GLOSSARY. 797 zob'n ; the opposite, or "proximal," extremity growing less rapidly, and being the end by which the organism is fixed, when attached at all. DIURNAL (Lat. dies, day). Applied to animals which are active during the day. DrvERTicuLUM (Lat. diverticulum, a by-road). A lateral tube with a blind extremity springing from the side of another tube. DORSAL (Lat. dorsum, back). Connected with the back. DORSIBRANCHIATE (Lat. dorsum, the back ; Gr. bragchia, gill). Having ex- ternal gills attached to the back ; applied to certain Annelides and Molluscs. The term is of mongrel composition, and " notobranchiate " is more correctly employed. ECDERON (Gr. ek, out ; deros, skin). The outer plane of growth of the externa integumentary layer (viz., the ectoderm, or epidermis). ECDYSIS (Gr. ekdusis, a stripping off). A shedding or moulting of the skin. ECHINOCOCCI (Gr. echinos, a hedgehog ; kokkos, a berry). The larval forms (scolices) of the tapeworm of the dog (Tcenia echinococcus), commonly known as "hydatids." ECHINODERMATA (Gr. echinos ; and derma, skin). A class of animals compris- ing the Sea-urchins, Star-fishes, and others, most of which have spiny skins. ECHINOIDEA (Gr. echinos; and eidos, form). An order of £chinodermata, com- prising the Sea-urchins. ECHINOP2EDIUM (Gr. echinos, a hedgehog ; paidion, a child). A term applied to the embryo or larva of the Echinodermata. ECHINULATE. Possessing spines. ECTOCYST (Gr. ektos, outside ; kustis, a bladder). The external investment of the C03no3cium of a Polyzoon. ECTODERM (Gr. ektos; and derma, skin). The external integumentary layer of the Ccelenterata. ECTOSARC (Gr. ektos; sarx, flesh). The outer transparent sarcode - layer of certain Rhizopods, such as the Amoeba. EDENTATA (Lat. e, without ; dens, tooth). An order of Mammalia, often called JBruta. EDENTULOUS. Toothless; without any dental apparatus. Applied to the mouth of any animal, or to the hinge of the bivalve Molluscs. EDRIOPHTHALMATA (Gr. hedraios, sitting ; ophthalmos, eye). The division of Crustacea in which the eyes are sessile, and are not supported upon stalks. ELASMOBRANCHII (Gr. elasma, a plate ; bragchia, gill). An order of Fishes, including the Sharks and Kays. ELYTRA (Gr. elutron, a sheath). The chitinous anterior pair of wings in Beetles, which form cases for the posterior membranous wings. Also ap- plied to the scales or plates on the back of the Sea-mouse (Aphrodite). EMBRYO (Gr. en, in; bruo, I swell). The earliest stage at which the young animal is recognisable in the impregnated ovum. ENALIOSAURIA (Gr. enalios, marine ; saura, lizard). Sometimes employed as a common term to designate the extinct Reptilian orders of the Ichthyosauria and Plesiosauria. ENCEPHALON (Gr. egkepfutlos, brain). The portion of the cerebro-spinal ner- vous axis contained within the cranium. ENCEPHALOUS (Gr. en, in ; kephale, the head). Possessing a distinct head. Usually applied to all the Mollusca proper, except the Lamellibranchiata. ENCYSTATION (Gr. en, in ; kustis, a bag). The transformation undergone by certain of the Protozoa, when they become motionless, and surround them- selves by a thick coating or cyst. ENDERON (Gr. en, in ; deros, skin). The inner plane of growth of the outer integumentary layer (viz., the ectoderm or epidermis). ENDOCYST (Gr. endon, within ; kustis, a bag). The inner membrane or integu- mentary layer of a Polyzoon. In Cristatella, where there is no " ectocyst," the endocyst constitutes the entire integument. ENDODERM (Gr. endon ; and derma, skin). The inner integumentary layer of the Ccelenterata. ESDOPODITE (Gr. endon; and pous, foot). The inner of the two secondary joints into whicn the typical limb of a Crustacean is divided. 798 GLOSSARY. ENDOSARC (Gr. endon; and sarx, flesh). The inner molecular layer of sarcode in the Amoeba, and other allied Rhizopods. ENDOSKELETON (Gr. endon; and skeletos, dry). The internal hard structures, such as "bones, which serve for the attachment of muscles, or the protection of organs, and which are not a mere hardening of the integument. ENSIFORM (Lat. ensis, a sword ; forma, shape). Sword-shaped. ENTOMOPHAGA (Gr. entoma, insects; phago, I eat). A section of the Mar- supialia. ENTOMOSTRACA (Gr. entoma, insects ; ostrakon, a shell). Literally, shelled insects — applied to a division of Crustacea. ENTOZOA (Gr. entos, within ; zob'n, animal). Animals which are parasitic in the interior of other animals. EOCENE (Gr. eos, dawn ; kainos, new or recent). The lowest division of the Tertiary rocks, in which species of existing shells are to a small extent re- presented. EPHIPPIUM (Gr. ephippion; Lat. ephippium, saddle). A receptacle on the back of the Daphnia, in which the winter eggs are deposited. EPIDERMIS (Gr. epi, upon ; derma, the true skin). The outer non-vascular layer of tne skin, often called the scarf-skin or cuticle. EPIMERA (Gr. epi, upon ; meron, thigh). The lateral pieces of the dorsal arc of the somite of a Crustacean. EPIPODIA (Gr. epi, upon ; pous, the foot). Muscular lobes developed from the lateral and upper surfaces of the "foot" of some Molluscs. EPIPODITE (Gr. epi, upon ; pous, foot). A process developed upon the basal joint, or "protopodite," of some of the limbs of certain Crustacea. EPISTERNA (Gr. epi, upon ; sternon, the breast-bone). The lateral pieces of the inferior or ventral arc of the somite of a Crustacean. EPISTOME (Gr. epi ; and stoma, mouth). A valve-like organ which arches over the mouth in certain of the Polyzoa. EPITHECA (Gr. epi; and theke, a sheath). A continuous layer surrounding the thecse in some Corals externally. EPIZOA (Gr. epi, upon ; zob'n, animal). Animals which are parasitic upon other animals. In a restricted sense, a division of Crustacea which are parasitic upon fishes. EQUILATERAL (Lat. cequus, equal ; latus, side). Having its sides equal. Usu- ally applied to the shells of the Brachiopoda. When applied to the spiral shells of the Foraminifera, it means that all the convolutions of the shell lie in the same plane. EQUIVALVE (Lat. cequus, equal ; valvce, folding-doors). Applied to shells which are composed of two equal pieces or valves. ERRANTIA (Lat. erro, I wander). An order of Annelida, often called Nereidea, distinguished by their great locomotive powers. EURYPTERIDA (Gr. eurus, broad; pteron, wing). An extinct sub-order of Crustacea. EXOPODITE (Gr. exo, outside; pous, foot). The outer of the two secondary joints into which the typical limb of a Crustacean is divided. ExosKELETON (Gr. exo, outside ; skeletos, dry). The external skeleton, which is constituted by a hardening of the integument, and is often called a " dermoskeleton"" FASCICULATED (Lat. fasciculus, a bundle). Arranged in bundles. FAUNA (Lat. Fauni, the rural deities of the Romans). The general assem- blage of the animals of any region or district. FEMUR. The thigh-bone, intervening between the pelvis and the bones of the leg proper (tibia and^ifotZa). FIBULA (Lat. a brooch). The outermost of the two bones of the leg in the higher Vertebrata ; corresponding to the ulna of the fore-arm. FILIFORM (Lat. filum, a thread ; forma, shape). Thread-shaped. FISSILINGUIA (Lat. findo, I cleave ; lingua, tongue). A division of Lacertilia, with bifid tongues. FISSION (Lat. findo, I cleave). Multiplication by means of a process of self- division. GLOSSARY. 799 FISSIPAROUS (Lat. findo ; and pario, I produce). Giving origin to fresh struc- tures by a process of fission. FISSIROSTRES (Lat. findoy I cleave; rostrum, beak). A sub-order of the Perching Birds. FLAGELLUM (Lat. for whip). The lash-like appendage possessed by many In- fusoria, which are therefore said to be " flagellate." FLORA (Lat. Mora, the goddess of flowers). The general assemblage of the plants of any region or district. FOOT-JAWS. The limbs of Crustacea, which are modified to subserve masti- cation. FOOT-SECRETION. The term applied by Mr Dana to the sclerobasic corallum of certain Actinozoa. FOOT-TUBERCLES. The unarticulated appendages of the Annelida, often called parapodia. FORAMINIFERA (Lat. foramen, an aperture ; fero, I carry). An order of Pro- tozoa, usually characterised by the possession of a shell perforated by numerous pseudopodial apertures. FRUGIVOROUS (Lat. frux, fruit"; voro, I devour). Living upon fruit. FURCULUM or FURCULA (Lat. dim. of furca, a fork). The "merry-thought" of birds, or the V-shaped bone formed by the united clavicles. FUSIFORM (Lat. fusus, a spindle ; and forma, shape). Spindle-shaped, or pointed at both ends. GALLINACEI (Lat. gallina, a fowl). Sometimes applied to the whole order of the Rasorial Birds, but properly restricted to that section of the order of which the common Fowl is a typical example. GANGLION (Gr. gagglion. a knot). A mass of nervous matter containing nerve- cells, and giving origin to nerve-fibres. GANOID (Gr. ganos, splendour, brightness). Applied to those scales or plates which are composed of an inferior layer of true bone covered by a superior layer of polished enamel. GANOIDEI. An order of Fishes. GASTEROPODA (Gr. gaster, stomach ; pous, foot). The class of the Mollusca comprising the ordinary univalves, in which locomotion is usually effected by a muscular expansion of the under surface of the body (the "foot"). GASTRULA (Gr. dim. of gaster, stomach). A name applied by Hseckel to that developmental stage in various animals, in which the embryo consists of two fundamental membranes, an outer and an inner, enclosing a central cavity. GEMMAE (Lat. gemma, a bud). The buds produced by any animal, whether detached or not. GEMMATION. The process of producing new structures by budding. GEMMIPAROUS (Lat. gemma, a bud ; pario, I produce). Giving origin to new structures by a process of budding. GEMMULES (Lat. dim. of gemma). The ciliated embryos of many Ccelenterata ; also the seed-like reproductive bodies or " spores " of Spongilla. GEPHYREA (Gr. gephura, a bridge). A class of the Anarthropoda, comprising the Spoon-worms (Sipunculus) and their allies. GIZZARD. A muscular division of the stomach in Birds, Insects, &c. GLADIUS (Lat. a sword). Applied to the horny endoskeleton or "pen" of certain Cuttle-fishes. GLENOID (Gr. glene, a cavity ; eidos, form). A shallow cavity ; applied espe- cially to the shallow articular cavity in the shoulder-blade to which the head of the humerus is jointed. GNATHITES (Gr. gnathos, a jaw). The masticatory organs of Crustacea. GONANGIUM (Gr. gonos, offspring; and aggeion, a vessel). The chitinous receptacle in which the reproductive buds of certain of the Hydrozoa are produced. GONOBLASTIDIA (Gr. gonos, offspring ; Uastidion, dim. of blastos, a bud). The processes which carry the reproductive receptacles, or " gonophores," in many of the Hydrozoa. GONOCALYX (Gr. gonos ; and kalux, cup). The swimming -bell in a medusiform gonophore, or the same structure in a gonophcre which is not detached. 800 GLOSSARY. GONOPHORE (Gr. ffonos ,• and phero, I carry). The generative buds, or recep- tacles of the reproductive elements, in the Hydrozoa, whether these become detached or not. GONOSOME (Gr. gonos; and soma, body). Applied as a collective term to the reproductive zooids of a ffydrozob'n. GONOTHECA (Gr. gonos; and theke, a case). The chitinous receptacle within which the gonophores of certain of the Hydrozoa are produced. GRALLATORES (Lat. grallce, stilts). The order of the long-legged Wading Birds. GRANIVOROUS (Lat. granum, a grain or seed ; voro, I devour). Living upon grains or other seeds. GRAPTOLITID,® (Gr. grapho, I write ; lithos, stone). An extinct sub-class of the ffydrozoa. GREGARINIDA (Lat. gregarius, occurring in numbers together). A class of the Protozoa. GUARD. The cylindrical fibrous sheath with which the internal chambered shell (phragmacone) of a Belemnite is protected. GYMNOBLASTIO (Gr. gumnos, naked ; and blastos, a bud). Applied by Prof. Allman to those ffydrozoa in which the nutritive and reproductive buds are not protected by horny receptacles. GYMNOL.EMATA (Gr. gumnos, naked ; laimos, the throat). An order of the Polyzoa in which the mouth is devoid of the valvular structure known as the "epistoine." GYMNOPHIONA (Gr. gumnos, naked ; ophis, a snake). The order of the Am- phibia comprising the snake-like Ctecilice. GYMNOPHTHALMATA (Gr. gumnos; and ophthalmos, the eye). Applied by Edward Forbes to those Medusas in which the eye-specks at the margin of the disc are unprotected. The division is now abandoned. GYMNOSOMATA (Gr. gumnos ; and soma, the body). The order of Pteropoda in which the body is not protected by a shell. GYNOPHORES (Gr. gune, woman ; phero, I carry). The generative buds, or gonophores, of ffydrozoa, which contain ova alone, and differ in form from those which contain spermatozoa. GYRENCEPHALA (Gr. guroo, I wind about ; egkephalos, brain). Applied by Owen to a section of the Mammalia in which the cerebral hemispheres are abundantly convoluted. H.EMAL (Gr. haima, blood). Connected with the blood-vessels, or with the circulatory system. H.EMATOCRYA (Gr. haima, blood ; cruos, cold). Applied by Owen to the "cold-blooded" Vertebrates — viz., the Fishes, Amphibia, and Reptiles. H^MATOTHERMA (Gr. haima, blood; thermos, warm). Applied by Owen to the "warm-blooded" Vertebrates — viz., Birds and Mammals. HALLUX (Lat. allex, the thumb or great toe). The innermost of the five digits which normally compose the hind foot of a Vertebrate animal. In man, the great toe. HALTERES (Gr. halteres, weights used by athletes to steady themselves in leap- ing:). The rudimentary filaments or "balancers" which represent the posterior pair of wings in the Diptera, an order of Insects. HAUSTELLATE (Lat. haurio, I drink). Adapted for sucking or pumping up fluids ; applied to the mouth of certain Crustacea and Insecta. HECTOCOTYLUS (Gr. hekaton, a hundred ; kotulos, a cup). The metamorphosed reproductive arm of certain of the male Cuttle-fishes. In the Argonaut the arm becomes detached, and was originally described as a parasitic worm. HEUOZOA (Gr. helios, sun ; zoon, animal). An order of Protozoa, with radi- ating pseudopodia. HELMINTHOID (Gr. helmins, an intestinal worm). Worm -shaped, vermiform. HEMELYTRA (Gr. hemi, half ; elutron, a sheath). The wings of certain Insects, in which the apex of the wing is membranous, whilst the inner portion is chitinous, and resembles the elytron of a beetle. HEMIMETABOLIO (Gr. hemi, half; metabole, change). Applied to those Insects which undergo an incomplete metamorphosis. GLOSSARY. 80 1 HEMIPTERA (Gr. hemi; andpteron, wing). An order of Insects in which the anterior wings are sometimes "hemelytra." HERMAPHRODITE (Gr. Hermes, Mercury; Aphrodite, Venus). Possessing the characters of both sexes combined. HETEROCERA (Gr. heteros, diverse ; kercts, horn). Applied to the Moths amongst the Lepidoptem, on account of the great variety of shape in their antennae. HETEROCERCAL (Gr. heteros, diverse ; kerkos, tail). Applied to the tail of Fishes when it is unsymmetrical, or composed of two unequal lobes. HETEROGANGLIATE (Gr. heteros, diverse; gagglion, a knot). Possessing a nervous system in which the ganglia are scattered and unsymmetrical (as in the Mollusca, for example). HETEROGENESIS or HETEROGENY (Gr. heteros, diverse ; genesis, origin, birth). The production of living beings without pre-existent living beings. Or, the supposed production of a living being of one kind from a part or the whole of the matter of another living being of a perfectly different kind. HETEROMORPHIC (Gr. heteros; morphe, form). Differing in form and shape. HETEROPHAGI (Gr. heteros, other ; phago, I eat). Applied to Birds the young of which are born in a helpless condition, and require to be fed by the parents for a longer or shorter period. HETEROPODA (Gr. heteros, diverse ; podes, feet). An aberrant group of the Gasteropods, in which the foot is modified so as to form a swimming organ. HEXAPOD (Gr. hexa, six ; pous, foot). Possessing six legs ; applied to the Jnsecta. HILUM (Lat. hilum, a little thing). A small aperture (as in the gemmules of sponges), or a small depression (as in floctiluca). HIRUDINEA (Lat. hirudo, a horse-leech). The order of Annelida comprising the Leeches. HISTOLOGY (Gr. histos. a web ; logos, a discourse). The study of the tissues, more especially of the minuter elements of the body. HOLOCEPHALI (Gr. holos, whole ; kephale, head). A sub-order of the Elasmo- branchii comprising the Chimcerce. HOLOMETABOLIC (Gr. holos, whole ; metabole, change). Applied to Insects which undergo a complete metamorphosis. HOLOSTOMATA (Gr. holos, whole ; stoma, mouth). A division of Gasteropodous Molluscs, in which the aperture of the shell is rounded, or "entire." HOLOTHUROIDEA (Gr. holothourion ; and eidos, form). An order of Echinoder- mata, comprising the Trepangs. HOMOCERCAL (Gr. homos, same ; kerkos, tail). Applied to the tail of Fishes when it is symmetrical, or composed of two equal lobes. HOMOGANGLIATE (Gr. homos, like ; gagglion, a knot). Having a nervous sys- tem in which the ganglia are symmetrically arranged (as in the Annulosa, for example). HOMOLOGOUS (Gr. homos; and logos, a discourse). Applied to parts which are constructed upon the same fundamental plan. HOMOMORPHOUS (Gr. homos ; and morphe, form). Having a similar external appearance or form. HUMERUS. The bone of the upper arm (brachium) in the Vertebrates. HYALINE (Gr. hualos, crystal). Crystalline or glassy. HYDATIDS (Gr. hudalis, a vesicle). The vesicle containing the larval forms (Echinococd) of the tape- worm of the dog. HYDRAFORM. Kesembling the common fresh- water polype (Hydra} in form. HYDRANTH (Gr. hudra, water-serpent; and anthos, flower). The "polypite" or proper nutritive zooid of the Hydrozoa. HYDROCAULUS (Gr. hudra, a water-serpent ; and kaulos, a stem). The main stem of the coenosarc of a Hydrozoon. HYDROCYSTS (Gr. hudra; and kustis, a cyst). Curious processes attached to the ccenosarc of the Physophoridce, and termed " feelers " (Fiihler and Taster of the Germans. HYDRCECIUM (Gr. hudra; and oikos, a house). The chamber into which the coanosarc in many of the Calycaphoridce can be retracted. 3 E 802 GLOSSARY. HYDROIDA (Gr. hudra; and eidos, fonn). The sub-class of the Hydrozoa, which comprises the animals most nearly allied to the Hydra. HYDROPHYLLIA (Gr. hudra; and phullon, a leaf). Overlapping appendages or plates which protect the pplypites in some of the oceanic Hydrozoa, (Calycophorida and Physophoridce). They are often termed " bracts," and are the " Deckstiicke" of the Germans. HYDBORHIZA (Gr. hudra ; and rhiza, root). The adherent base or proximal extremity of any Hydrozoon. HYDROSOMA (Gr. hudra ; and soma, body). The entire organism of any Hydrozoon. HYDROTHECA (Gr. hudra; and theke, a case). The little chitinous cup in which the polypites of the Sertularida and Campanulas ida are protected. HYDROZOA (Gr. hixlra; and zoon, animal). The class of the Ctelenterata, which comprises animals constructed after the type of the Hydra. HYMENOPTERA (Gr. humen, a membrane ; pteron, a wing). An order of In- sects (comprising Beetles, Ants, &c.) characterised by the possession of four membranous wings. HYOID (Gr. U ; eidos, form). The bone which supports the tongue in Verte- brates, and derives its name from its resemblance in man to the Greek letter U. HYPOSTOME (Gr. hupo, under ; stoma, mouth). The upper lip, or "labrum," of certain Crustacea (e.g., Trilobites). HYRACOIDEA (Gr. hurax, a shrew ; eidos, form). An order of the Mammalia constituted for the reception of the single genus Hyrax. ICHTHYODORULITE (Gr. ichthus, fish ; dorus, spear ; lithos, stone). The fossil fin-spines of Fishes. ICHTHYOMORPHA (Gr. ichthus ; morphe, shape). An order of Amphibians, often called Urodela, comprising the fish-like Newts, &c. ICHTHYOPHTHIRA (Gr. ichthus ; phtheir, a louse). An order of Crustacea com- prising animals which are parasitic upon Fishes. ICHTHYOPSIDA (Gr. ichthus ; opsis, appearance). The primary division of Vertebrata, comprising the Fishes and Amphibia. Often spoken of as the Branchiate Vertebrata. ICHTHYOPTERYGIA (Gr. ichthus ; pterux, wing). An extinct order of Reptiles. ICHTHYOSAURIA (Gr. ichthus ; saura, lizard). Synonymous with Ichthyo- pterygia. ILIUM. The haunch-bone, one of the bones of the pelvic arch in the higher Vertebrates. IMAGO (Lat. an image or apparition). The perfect insect, after it has under- gone its metamorphoses. IMBRICATED. Applied to scales or plates which overlap one another like tiles. INCISOR (Lat. incido, I cut). The cutting teeth fixed in the intermaxillary bones of the Mammalia, and the corresponding teeth in the lower jaw. INEQUILATERAL. Having the two sides unequal, as in the case of the shells of the ordinary bivalves (Lamellibranchiata). When applied to the shells of the Foraminifera, it implies that the convolutions of the shell do not lie in the same plane, but are obliquely wound round an axis. INEQUIVALVE. Composed of two unequal pieces or valves. INFUNDIBULUM (Lat. for funnel). The tube formed by the coalescence or apposition of the epipodia in the Cephalopoda — commonly termed the " funnel" or " siphon." INFUSORIA (Lat. infusum, an infusion). A class of Protozoa, so called be- cause they are often developed in organic infusions. INGUINAL (Lat. inguen, groin). Connected with, or situated upon, the groin. INOPERCULATA (Lat. in, without ; operculum, a lid). The division of pul- monate Gasteropoda in which there is no shelly or horny plate (operculum) by which the shell is closed when the animal is withdrawn within it. INSECTA (Lat. inseco, I cut into). The class of Articulate animals commonly known as Insects. INSECTIVORA (Lat. insectum, an insect ; voro, I devour). An order of Mammals, INSECTIVOROUS. Living upon Insects. GLOSSARY. 803 INSESSORES (Lat. insedeo, I sit upon). The order of the Perching Birds, often called Passeres. INTERAMBULACRA. The rows of plates in an Echinoderm which are not per- forated for the emission of the " tube-feet." INTERMAXILLJB or PR^MAXILLJE. The two bones which are situated between the two superior maxillae in Vertebrata. In man, and some monkeys, the pnemaxillae anchylose with the maxillae, so as to be irrecognisable in the adult. INTUSSUSCEPTION (Lat. inhis, within ; suscipio, I take up). The act of taking foreign matter into a living being. IN VERTEBRATA (Lat. in, without ; vertebra, a bone of the back). Animals without a spinal column or backbone. TSCHIUM (Gr. ischion, the hip). One of the bones of the pelvic arch in Verte- brates. [SOPODA (Gr. isos, equal ; podes, feet). An order of Crustacea in which the feet are all like one another and equal. JUGULAR (Lat. jugulum, the throat). Connected with, or placed upon, the throat. Applied to the ventral fins of fishes when they are placed beneath or in advance of the pectorals. KAINOZOIC (Gr. kainos, recent ; zo$, life). The Tertiary period in Geology, comprising those formations in which the organic remains approximate more or less closely to the existing fauna and flora. KERATODE (Gr. keras, horn ; eidos, form). The horny substance of which the skeleton of many Sponges is made up. KERATOSA. The division of Sponges in which the skeleton is composed of keratode. LABIUM (Lat. for lip). Restricted to the lower lip of Articulate animals. LABRUM (Lat. for lip). Restricted to the upper lip of Articulate animals. LABYRINTHODONTIA (Gr. laburinthos, a labyrinth ; odous, tooth). An extinct order of Amphibia, so called from the complex microscopic structure of the teeth. LACERTILIA (Lat. lacerta, a lizard). An order of Reptilia comprising the Lizards and Slow-worms. LJEMODIPODA (Gr. laimos, throat ; dis, twice ; podes, feet). An order of Crus- tacea, so called because they have two feet placed far forwards, as it were under the throat. LAMELLIBRANCHIATA (Lat. lamella, a plate ; Gr. bragchia, gill). The class of Mollusca, comprising the ordinary bivalves, characterised by the possession of lamellar gills. LAMELLIROSTRES (Lat. lamella, a plate ; rostrum, beak). The flat - billed Swimming Birds (Natatores), such as Ducks, Geese, Swans, &c. LARVA (Lat. a mask). The insect in its first stage after its emergence from the egg, when it is usually very different from the adult. LARYNX. The upper part of the windpipe, forming a cavity with appropriate muscles and cartilages, situated beneath the hyoid bone, and concerned in Mammals in the production of vocal sounds. LENTICULAR (Lat. lens, a bean). Shaped like a biconvex lens. LEPIDOPTERA (Gr. lepis, a scale ; pteron, a wing). An order of Insects, com- prising Butterflies and Moths, characterised by possessing four wings which are usually covered with minute scales. LEPIDOTA (Gr. lepis, a scale). Formerly applied to the order Dipnoi, con- taining the Mud-fishes (Lepidosiren). LEPTOCARDIA (Gr leptos, slender, small ; cardia, heart). The name given by Mliller to the order of Fishes comprising the Lancelot, now called Pharyn- ffolranchii. LIGAMENTUM NUCILE (Lat. nucha, the nape of the neck). The band of elastic fibres by which the weight of the head in Mammalia is supported. LINGUAL (Lat. lingiw, the tongue). Connected with the tongue. LISSENCEPHALA (Gr. lissos, smooth ; egkephalos, brain). A primary division 804 GLOSSARY. of Mammalia, according to Owen, in which the cerebral hemispheres are smooth or have few convolutions. LITHOCYSTS (Gr. lithos, a stone ; kustis, a cyst). The sense-organs or "mar- ginal bodies" of the Lucernarida or Steganoxththalmate Medusce, LONGIPENNAT.E (Lat. longus, long ; penna, wing). A group of the Natatorial Birds. LONGIROSTRES (Lat. longus ; rostrum, beak). A group of the Wading Birds. LOPHOPHORE (Gr. lophos, a crest ; and phero, I carry). The disc or stage upon which the tentacles of the Poly zoo, are borne. LOPHYROPODA (Gr. lophouros, having stiff hairs ; and podes, feet). A section of Crustacea. LORTCA (Lat. a breast-plate). Applied to the protective case with which cer- tain Infusoria are provided. LORICATA (Lat. lorica, a cuirass). The division of Reptiles comprising the Ghelorda and Cwcodilia, in which bony plates are developed in the skin (derma). LUCERNARIDA (Lat. lucerna, a lamp). An order of the Hydrozoa, LUMBAR (Lat. lumbus, loin.) Connected with the loins. LUXATE (Lat. luna, moon). Crescentic in shape. LYENCEPHALA (Gr. luo, I loose ; egkephalos, brain). A primary division of Mammals according to Owen. MACRODACTYLI (Gr. makros, long ; daktulos, a finger). A group of the Wading Birds. MACRURA (Gr. makros, long ; oura, tail). A tribe of Decapod Crustaceans with long tails (e.g., the Lobster, Shrimp, &c.). MADREPORIFORM. Perforated with small holes, like a coral ; applied to the tubercle by which the ambulacral system of the Echinoderms mostly com- municates with the exterior. MALACOSTRACA (Gr. malakos, soft ; ostrakon, shell). A division of Crustacea. Originally applied by Aristotle to the entire class Crustacea, because their shells were softer than those of the Mollusca. MALLOPHAGA (Gr. mallos, a fleece ; phago, I eat). An order of Insects which are mostly parasitic upon birds. MAMMALIA (Lat. mamma, the breast). The class of Vertebrate animals which suckle their young. MANDIBLE (Lat. mandibulum, a jaw). The upper pair of jaws in Insects ; also applied to one of the pairs of jaws in Crustacea and Spiders, to the beak of Cephalopods, the lower jaw of Vertebrates, &c. MANTLE. The external integument of most of the Mollusca, which is largely developed, and forms a cloak in which the viscera are protected, Techni- cally called the "pallium." MANUBRIUM (Lat. a handle). The polypite which is suspended from the roof of the swimming-bell of a Medusa, or from the gonocalyx of a medusiform gonophore amongst the Hydrozoa. MANUS (Lat. the hand). The hand or fore-foot of the higher Vertebrates. MARSIPOBRANCHII (Gr. marsipos, a pouch ; bragchia, gill). The order of Fishes comprising the Hag-fishes and Lampreys with pouch-like gills. MARSUPIALIA (Lat. inarsupium, a pouch). An order of Mammals in which the females mostly have an abdominal pouch in which the young are carried. MASTAX (Gr. mouth). The muscular pharynx or "buccal funnel" into which the mouth opens in most of the Rotifera. MASTICATORY (Lat. mastico, I chew). Applied to parts adapted for chewing. MAXILLAE (Lat. jaws). The inferior pair or pairs of jaws in the Arthropoda (Insects, Crustacea, &c.). The upper jaw-bones of Vertebrates. MAXILLIPEDES ( Lat. maxillce, jaws ; pes, the foot). The limbs in Crustacea and Myriapodct, which are converted into masticatory organs, and are com- monly called "foot-jaws." MEDULLA (Lat. marrow). Applied to the marrow of bones ; or to the spinal cord, with or without the adjective " spinalis." MEDUS.E. An order of Hydrozoa, commonly known as Jelly-fishes (Disco- GLOSSARY. 805 pfiora, or AcalepJm), so called because of the resemblance of their tentacles to the snaky hair of the Medusa. Many Medusas are now known to be merely the gonophores of Hydrozoa. MEDUSIFORM. Resembling a Medusa in shape. MEDUSOID. Like a Medusa; used substantively to designate the medusiform gonophores of the Hydrozoa. MEMBRANA NICTITANS (Lat. nicto, I wink). The third eyelid of Birds, &c. MENTUM (Lat. the chin). The basal portion of the labium or lower lip in Insects. MEUOSTOMATA (Gr. meron, thigh ; stoma, mouth). An order of Crustacea in which the appendages which are placed round the mouth, and which offi- ciate as jaws, have their free extremities developed into walking or pre- hensile organs. MESENTERIES (Gr. mesos, intermediate ; enteron, intestine). In a restricted sense, the vertical plates which divide the somatic cavity of a Sea-anemone (Actinia) into chambers. MESOPODIUM (Gr. mesos, middle ; pous, foot). The middle portion of the ''foot of Molluscs." MESOSTERNUM (Gr. mesos, intermediate; sternon, the breast -bone). The middle portion of the sternum, intervening between the attachment of the second pair of ribs and the xiphoid cartilage (xiphisternum). MESOTHORAX (Gr. mesos; and thorax, the chest). The middle ring of the thorax in Insects. MESOZOIC (Gr. inesos ; and zoe, life). The Secondary period in Geology. METACARPUS (Gr. meta, after ; karpos, the wrist). The bones which form the "root of the hand," and intervene between the wrist and the fingers. METAMORPHOSIS (Gr. meta, implying change ; morphe, shape). The changes of form which certain animals undergo in passing from their younger to their fully-grown condition. METAPODIUM (Gr. meta, after ; pous, the foot). The posterior lobe of the foot in Mollusca; often called the " operculigerous lobe," because it develops the operculum when this structure is present. METASTOMA (Gr. meta, after; stoma, mouth). The plate which closes the mouth posteriorly in the Crustacea. METATARSUS (Gr. meta, after ; tarsos, the instep). The bones which intervene between the bones of the ankle (tarsus) and the digits ki the hind-foot of the higher Vertebrates. METATHORAX (Gr. meta, after ; thorax, the chest). 'She posterior ring of the thorax in Insects. METAZOA (Gr. meta, implying change ; zob'n, animal). Applied to animals in which the primitive indifferent tissue of the embryo becomes converted into cells, which in turn may or may not be developed into more complex tissues. Under this head are included all animals except the Protozoa. MIMETIC (Gr. mimetikos, imitative). Applied to organs or animals which resemble each other in external appearance, but not in essential structure. MOLARS (Lat. mola, a mill). The "grinders " in man, or the teeth in diphyo- dont Mammals which are not preceded by milk-teeth. MOLLUSCA (Lat. mollis, soft). The sub-kingdom which includes the shell- fish proper, the Polyzoa, the Tunicata, and the Lamp-shells ; so called from the generally soft nature of their bodies. MOLLUSCOIDA (Mollusca; Gr. eidos, form). The lower division of the Mollusca, comprising the Polyzoa, Tunicata, and Brachiopoda. MONADS (Gr. monas, unity). Microscopical organisms of an extremely simple character, developed in organic infusions. 'GNERA (Gr. moneres, single). An MONERA (Gr. moneres, single). An order of Protozoa, comprising animals composed of simple undifferentiated sarcode. MONOCULOUS. Possessed of only one eye. MONODELPHIA (Gr. monos, single ; delphus, womb). The division of Mammalia in which the uterus is single. MONOECIOUS (Gr. monos, single ; oikos, house). Applied to individuals in which the sexes are united. MONOMYARY (Gr. monos, single ; mum, muscle). Applied to those bivalves 8o6 GLOSSARY. (Lamellibranchiata) in which the shell is closed by a single adductor muscle. MONOPHYODONT (Gr. monos ; phuo, I generate ; odous, tooth). Applied to those Mammals in which only a single set of teeth is ever developed. MONOTHALAMOUS (Gr. inonos ; and thalamos, chamber). Possessing only a single chamber. Applied to the shells of Foraminifera and Mollusca. MONOTREMATA (Gr. monos ; trema, aperture). The order of Mammals corn- prising the Duck-mole and Echidna, in which the intestinal canal opens into a "cloaca" common to the ducts of the urinary and generative organs. MULTILOCULAR (Lat. multus, many ; loculus, a little purse). Divided into many chambers. MULTIVALVE. Applied to shells which are composed of many pieces. MULTUNGULA (Lab. multus, many; ungula, hoof). The division of Perisso- dactyle Ungulates, in which each foot has more than a single hoof. MYELON (Gr. muelos, marrow). The spinal cord of Vertebrates. MYRIAPODA or MYRIOPODA (Gr. murios, ten thousand ; podes, feet). A class of Arthropoda comprising the Centipedes and their allies, characterised by their numerous feet. NACREOUS (Fr. 'nacre, mother-ofcpearl, originally Oriental). Pearly ; of the texture of mother-of-pearl. NATATORES (Lat. nare, to swim). The order of the Swimming Birds. NATATORY (Lat. nare, to swim). Formed for swimming. NAUTILOID. Resembling the shell of the Nautilus in shape. NECTOCALYX (Gr. necho, I swim ; kalux, cup). The swimming-bell or "disc" of a Medusa or Jelly-fish, NEMATELMIA (Gr. nema, thread ; helmins, a worm). The division of Scolecida comprising the Round-worms, Thread-worms, &c. NEMATOCYSTS (Gr. nema, thread ; kustis, a bag). The thread-cells of the Coelenterata. (See Cnidse.) NEMATOIDEA (Gr. nemo,, thread ; eidos, form). An order of Scolecida com- prising the Thread- worms, Vinegar-eels, &c. NEMATOPHORES (Gr. nema, thread ; phero, I carry). Csecal processes found on the coenosarc of certain of the Sertularida, containing numerous thread-cells at their extremities. NEMERTIDA (Gr. Nemertes, proper name). A division of the Turbellarian Worms, commonly called " Ribbon -worms." NERVURES (Lat. nervus, a sinew). The ribs which support the membranous wings of insects. NEURAL (Gr. neuron, a nerve). Connected with the nervous system. NEURAPOPHYSIS (Gr. neuron, a nerve ; apophusis, a projecting part). The " spinous process " of a vertebra, or the process formed at the point of junc- tion of the neural arches. NEUROPODIUM (Gr. neuron, a nerve ; pous, the foot). The ventral or inferior division of the "foot-tubercle" of an Annelide; often called the "ventral oar." NEUROPTFRA (Gr. neuron; andpteron, a wing). An order of insects charac- terised by four membranous wings with numerous reticulated nervures (e.g., Dragon-flies). NEUTER (Lat. neither the one nor the other). Having no fully developed sex. NIDIFICATION (Lat. nidus, a nest ; facio, I make). The building of a nest. NOCTURNAL (Lat. nox, night). Applied to animals which are active by night. NORMAL (Lat. norma, a rule). Conforming to the ordinary standard. NOTOBRANCHIATA (Gr. notos, the back ; and bragchia, gill). Carrying the gills upon the back ; applied to a division of the Annelida. NOTOCHORD (Gr. notos, the back ; chorde, string). A cellular rod which is developed in the embryo of Vertebrates immediately beneath the spinal cord, and which is usually "replaced in the adult by the vertebral column. Often it is spoken of as the " cliorda dorsalis." NOTOPODIUM (Gr. notos, the ba;.k; and pous, the foot). The dorsal division of one of the foot-tubercles or parapodia of an Annelide; often called the "dorsal oar." GLOSSARY. 80; NUCLEATED. Possessing a nucleus or central particle. NUCLEOLUS. 1. The minute solid particle in the interior of the nucleus of some cells. 2. The minute spherical particle attached to the exterior of the "nucleus" or ovary of certain Infusoria, performing the functions of a testicle. NUCLEUS (Lat. nucleus, a kernel). 1. The solid or vesicular body found in many cells. 2. The solid rod, or band-shaped body found in the interior of many of the Protozoa, and having, in certain of them, the functions of an ovary. 3. The " madreporiform tubercle" of the Echinodermata. 4. The embryonic shell which is retained to form the apex of the adult shell in many of the Mollusca. NUDIBRANCHIATA (Lat. nudus, naked; and Gr. bragchia, gill). An order of the Gasteropoda in which the gills are naked. NYMPHS. The active pupae of certain Insects. OCCIPITAL. Connected with the occiput or the back part of the head. OCEANIC. Applied to animals which inhabit the open ocean (= pelagic). OCELLI (Lat. diminutive of oculus, eye). The simple eyes of many Echino- derms, Spiders, Crustaceans, Molluscs, &c. OCTOPODA (Gr. octo, eight ; pous, foot). The tribe of Cuttle-fishes with eight arms attached to the head. ODONTOCETI (Gr. odous, tooth; ketos, whale). The "toothed" Whales, in contradistinction to the "whalebone" Whales. ODONTOID (Gr. odous; eidos, form.) The "odontoid process" is the centrum or body of the first cervical vertebra (atlas). It is detached from the atlas, and is usually anchylosed with the second cervical vertebra (axis), and it forms the pivot upon which the head rotates. ODONTOPHOEE (Gr. odous, tooth ; phero, I carry). The so-called " tongue " or masticatory apparatus of Gasteropoda, Pteropoda, and Cephalopoda. ODONTOPTEEYX (Gr. odous, tooth ; pterux, wing). An extinct genus of Birds. ODONTORNITHES (Gr. odous, tooth ; ornis, bird). The extinct sub-class of Birds comprising forms with distinct teeth in sockets. OESOPHAGUS. The gullet or tube leading from the mouth to the stomach. OLIGOCH^ETA (Gr. oligos, few; chaite, hair). An order of Annelida, compris- ing the Earth-worms, in which there are few bristles. OMASUM (Lat. bullock's-tripe). The third stomach of Kuminants, commonly called the psalterium, or many -plies. OMNIVOROUS (Lat. omnia, everything ; voro, I devour). Feeding indiscrimi- nately upon all sorts of food. ONYCHOPHORA (Gr. onux, claw or nail ; phero, I carry). The order of which Peripatus, with its hooked feet, is the type. OOCYSTS (Gr. oon, egg ; kustis, bladder). Chambers appended to the cells of certain of the Polyzoa, which serve as a receptacle for the eggs. Sometimes called "ovicells." OPERCULATA (Lat. operculum, a lid). A division of pulmonate Gasteropoda, in which the shell is closed by an operculum. OPERCULUM. A horny or shelly plate developed, in certain Mollusca, upon the hinder part of the foot, and serving to close the aperture of the shell when the animal is retracted within it ; also the lid of the shell of a Bala- nus or Acorn-shell ; also the chain of flat bones which covers the gills iL many fishes. OPHIDIA (Gr. ophis, a serpent). The order of Reptiles comprising the Snakes. OPHIDOBATRACHIA (Gr. ophis; batrachos, a frog). Sometimes applied to the order of Snake-like Amphibians comprising the Ccecilice. OPHIOMORPHA (Gr. ophis; morphe, shape). The order of Amphibia compris- ing the Ccecilice. OPHIUROIDEA (Gr. ophis, snake ; oura, tail; eidos, form). An order of Echino- dermata comprising the Brittle-stars and Sand-stars. OPISTHOBRANCHIATA (Gr. opisthen, behind ; bragchia, gill). A division of Gasteropoda, in which the gills are placed on the posterior part of the body. OpiSTHOCffiLOUS (Gr. opisthen, behind ; koilos, hollow). Applied to vertebrae the bodies of which are hollow or concave behind. 8o8 GLOSSARY. ORAL (Lat. os, mouth). Connected with the mouth. ORNITHODELPHIA (Gr. ornis, a bird ; delphus, Avomb). The primary division of Mammals comprising the Monotremata. ORNITHOSCELIDA (Gr. ornis, bird ; skelos, leg). Applied by Huxley to the Deinosaurian Eeptiles, together with the genus Compsognathus, on account of the bird-like characters of their hind-limbs. ORTHOCERATIDJS (Gr. orthos, straight ; keras, horn). A family of the Nau- tilidce, in which the shell is straight, or nearly so. ORTHOPTERA (Gr. orthos, straight ; pteron, Aving). An order of Insects. OSCULA (Lat. diminutive of os, mouth). 1. The large apertures by Avhich a sponge is perforated ("exhalant apertures"). 2. The suckers with which the Tceniada (Tape-worms and Cystic Worms) are provided. OSSICULA (Lat. diminutive of os, bone). Literally small bones. Often used to designate any hard structures of small size, such as the calcareous plates in the integument of the Star-fishes. OSTRACODA (Gr. ostrakon, a shell). An order of small Crustaceans which are enclosed in bivalve shells. OTOLITHS (Gr. ous, ear ; and lithos, stone). The calcareous bodies connected with the sense of hearing, even in its most rudimentary form. OVARIAN VESICLES or CAPSULES. The generative buds of the Sertularida. OVARY (OVARIUM). The organ by which ova are produced. OVIPAROUS (Lat. ovum, an egg ; andpario, I bring forth). Applied to animals which bring forth eggs, in contradistinction to those which bring forth their young alive. OVIPOSITOR (Lat. ovum; and pono, I place). The organ possessed by some in- sects, by means of which the eggs are placed in a position suitable for their development. OVISAC. The external bag or sac in which certain of the Invertebrates carry their eggs after they are extruded from the body. OVOVTVIPAROUS (Lat. ovum, egg ; vivus, alive ; pario, I produce). Applied to animals which retain their eggs within the body until they are hatched. OVUM (Lat. an egg). The germ produced within the ovary, and capable under certain conditions of being developed into a new individual. PACHYDERMATA (Gr. pachus, thick ; derma, skin). An old Mammalian order constituted by Cuvier for the reception of the .Rhinoceros, Hippopotamus, Elephant, &c. PALAEONTOLOGY (Gr. palaios, ancient ; onta, beings ; and logos, discourse). The science of fossil remains or of extinct organised beings. PALAEOZOIC (Gr. palaios, ancient ; and zoe, life). Applied to the oldest of the great geological epochs. PALLIOBRANCHIATA (Lat. pallium, a cloak ; and Gr. Iraychia, gill). An old name for the Brachiopoda, founded upon the belief that the system of tubes in the mantle constituted the gills. PALLIUM (Lat. a cloak). The mantle of the Mollusca. Pallial; relating to the mantle. Pallial line or impression; the line left in the dead shell by the muscular margin of the mantle. Pallial shell ; a shell Avhich is secreted by, or contained within, the mantle, such as the "bone" of the Cuttle-fishes. PALPI (Lat. palpo, I touch). Processes supposed to be organs of touch, de- veloped from certain of the oral appendages in Insects, Spiders, and Crus- tacea, and from the sides of the moiith in the Acephalous Molluscs. PANSPERMY (Gr. pan, all ; sperma, seed). The theory that living beings are never produced except from pre-existent living beings. PAPILLA (Lat. for nipple). A minute soft prominence. PARAPODIA (Gr.^ara, beside ',podes, feet). The unarticulated lateral locomo- tive processes or " foot-tubercles " of many of the Annelida. PARIETAL (Lat. paries, a wall). Connected with the Avails of a cavity or of the body. PARIETOSPLANCHNIC (Lat. paries; Gr. splagchna, viscera). Applied to one of the nervous ganglia of the Mollusca, Avhich supplies the Avails of the body and the viscera. GLOSSARY. 809 PARTHENOGENESIS (Lat. parthenos, a virgin ; and gignomai, to be born). Strictly speaking, confined to the production of new individuals from virgin females by means of ova without the intervention of a male. Sometimes used also to designate asexual reproduction by gemmation or fission. PATAGIUM (Lat. the border of a dress). Applied to the expansion of the in- tegument by which Bats, Flying Squirrels, and other animals support themselves in the air. PATELLA. The knee-cap or knee-pan. A sesamoid bone developed in the tendon of insertion of the great extensor muscles of the thigh. PAUROPODA (Gr. pauros, little ; podes, feet). An order of Myriapoda. PECTINATE (Lat. pecten, a comb). Comb-like ; applied to the gills of certain Gasteropods, hence called Pectinibranchiata. PECTORAL (Lat. pectus, chest). Connected with, or placed upon, the chest. PERENNIBRANCHIATA (Lat. perennis, perpetual ; Gr. Iragchia, gill). Applied to those Amphibia in which the gills are permanently retained throughout life. PEDAL (Lat. pes, the foot). Connected with the foot of the Mollusca. PEDICELLARL-E (Lat. pedicellus, a louse). Certain singular appendages found in many Echinoderms, attached to the surface of the body, and resembling a little beak or forceps supported on a stalk. PEDICLE (Lat. dim. of pes, the foot). A little stem. PEDIPALPI (Lat. pes, foot ; and palpo, I feel). An order of Arachnida com- prising the Scorpions, &c. PEDUNCLE (Lat. pedunculus, a stem of stalk). In a restricted sense applied to the muscular process by which certain Brachiopods are attached, and to the stem which bears the body (capitulum) in Barnacles. PEDUNCULATE. Possessing a peduncle. PELAGIC (Gr. pelagos, sea). Inhabiting the open ocean. PELECYPODA (Gr. pelekus, an axe ; podes, feet). A name often applied to the Lamellibranchiata, on account of many of them having a hatchet-shaped or sickle-shaped foot. PELVIS (Lat. for basin). Applied, from analogy, to the basal portion of the cup (calyx] of Crinoids. The bony arch with which the hind-limbs are con- nected in Vertebrates. PERGAMENTACEOUS (Lat. pergamena, parchment). Of the texture of parchment. PERICARDIUM (Gr. peri, around ; kardia, heart). The serous membrane in which the heart is contained. PERIDERM (Gr. peri, around ; and derma, skin). The hard cuticular layer which is developed'by the coenosarc of certain of the Hydrozoa. PERIGASTRIC (Gr. peri, around ; and ff aster, stomach). The perigastric space is the cavity which surrounds the stomach and other viscera, corresponding to the abdominal cavity of the higher animals. PERIOSTRACUM (Gr. peri ; and ostrakon, shell). The layer of epidermis which covers the shell in most of the Mollusca. PERIPLAST (Gr. peri; and plasso, I mould). The intercellular substance or matrix in which the organised structures of a tissue are embedded. PERISARC (Gr. peri, around ; sarx, flesh). Employed by Prof. Allman as a general term for the chitinous envelope secreted by many of the Hydrozoa. PERISOME (Qr.peri; and somay body). The coriaceous or calcareous integu- ment of the Echinodermata. PERISSODACTYLA (Gr. perissos, uneven ; daTctulos, finger). Applied to those Hoofed Quadrupeds (Ungulata) in which the feet have an uneven number of toes. PERISTOME (Gr. peri; and stoma, mouth). The space which intervenes be- tween the mouth and the margin of the calyx in Vorticella ; also the space between the mouth and the tentacles in a sea-anemone (Actinia) • also the lip or margin of the mouth of a univalve shell. PERIVISCERAL (Gr.peri; and Lat. viscera, the internal organs). Applied to the space surrounding the viscera. PETALOID. Shaped like the petals of a flower. PHALANGES (Gr. phalanx, a row). The small bones composing the digits of the higher Vertelrata. Normally each digit has three phalanges. 8 10 GLOSSARY. PHARYNGOBRANCHII (Gr. pharugx, pharynx; bragchia, gill). The order of Fishes comprising only the Lancelet. PHARYNX. The dilated commencement of the gullet. PHRAGMACONE (Gr. phragma, a partition ; and Amos, a cone). The chambered portion of the internal shell of a Belemnite. PHYLACTOL.EMATA (Gr. phulasso, I guard ; and laimos, throat). The division of Polyzoa in which the mouth is provided with the arched valvular process known as the "epistome." PHYLLOOYSTS (Gr. phullon, leaf; and kustis, a cyst). The cavities in the in- terior of the u hydrophyllia " of certain of the Oceanic Hydrozoa. PHYLLOPODA (Gr. phullon, leaf; and pous, foot). An order of Crustacea. PHYOGEMMARIA (Gr. phuo, I produce ; and Lat. gemma, bud). The small gonoblastidia of Velella, one of the Physophoridce. PHYSOGRADA (Gr. phusa, bellows or air-bladder ; and Lat. gradior, I walk). Applied formerly to the Physophoridce, an order of Oceanic Hydrozoa, in which a " float" is present. PHYSOPHORIDCE (Gr. phusa, air-bladder ; and phero, I carry). An order of Oceanic Hydrozoa. PHYTOID (Gr. phuton, a plant ; and eidos, form). Plant-like. PHYTOPHAGOUS (Gr. phuton, a plant; and phago, I eat). Plant -eating, or herbivorous. PINNATE (Lat. pinna, a feather). Feather - shaped, or possessing lateral processes. PINNIGRADA (Lat. pinna, a feather ; gradior, I walk). The group of Carni- vora, comprising the Seals and Walruses, adapted for an aquatic life. Often called Pinnipedia* PINNULE (Lat. dim. of pinna). The lateral processes of the arms of Crinoids. PISCES (Lat. piscis, a fish). The class of Vertebrates comprising the Fishes. PLACENTA (Lat. a cake). The " after-birth," or the organ by which a vascu- lar connection is established in the higher Mammalia between the mother and the foetus. PLACENTAL. Possessing a placenta, or connected with the placenta. PLACOID (Gr. plax, a plate ; eidos, form). Applied to the irregular bony plates, grains, or spines which are found in the skin of various fishes • (Elasmobranchii). PLAGIOSTOMI (Gr. plagios, transverse ; stoma, mouth). The Sharks and Rays, in which the mouth is transverse, and is placed on the under surface of the head. PLANARIDA (Gr. plane, wandering). A sub-order of the Turbellaria. PLANTIGRADE (Lat. planta, the sole of the foot ; gradior, I walk). Applying the sole of the foot to the ground in walking. PLANULA (Lat. planus, flat). The oval ciliated embryo of certain of the Invertebrates. PLASTRON. The lower or ventral portion of the bony case of the Chelonians. PLATYELMIA (Gr. plains, broad ; and helmins, an intestinal worm). The division of Scolecida comprising the Tape-worms, &c. PLATYRHINA (Gr. platus, broad ; rhines, nostrils). The group of the Quad- rumana. PLEURA (Gr. the side). The serous membrane covering the lung in the air- brecithing Vertebrates. PLEURON (Gr. pleuron, a rib). The lateral extensions of the shell of Crustacea. PLUTEUS (Lat. a pent-house). The larval form of the Echinoidea. PNEUMATIC (Gr. pneuma, air) Filled with air. PNEUMATOCYST (Gr. pneuma, air ; and kustis, cyst). The air-sac or float of certain of the Oceanic Hydrozoa (Physophoridce). PNEUMATOPHORE (Gr. pneuma, air ; and phero, I carry). The proximal dilatation of the coenosarc in the Physophoridce which surrounds the pneu- matocyst. PNEUMOSKELETON (Gr. pneuma; and skeletos, dry). The hard structures which are connected with the breathing organs (e.g., the shell of Molluscs). PODOPHTHALMATA (Gr. pous, foot ; and ophthalmos, eye). The division of Crustacea in which the eyes are borne at the end of long foot-stalks. GLOSSARY. 8 II PODOSOMATA (Gr. pous, foot ; soma, body). An order of Arachnida. POEPHAGA (Gr. poe, grass, phago, I eat). A group of the Marsupials. POLLEX (Lat. the thumb). The innermost of the five normal digits of the anterior limb of the higher Vertebrates. In man, the thumb. POLYCHJ3TA (Gr. polus, many; chaite, bristle). A name often applied to. the Tubicolar and Errant Annelides to distinguish them collectively from the Oligochceta (Earthworms, &c.). POLYCYSTIXA (Gr. polus, many ; and kustis, a cyst). An order of Protoza, with foraminated siliceous shells. POLYGASTRICA (Gr. polus ; and gaster, stomach). The name applied by Ehrenberg to the Infusoria, under the belief that they possessed many stomachs. POLYP ABY. The hard chitinous covering secreted by many of the Hydrozoa. POLYPE (Gr. polus, many ; pous, foot). Kestricted to the single individual of a simple Actinozob'n, such as a Sea-anemone, or to the separate zooids of a compound Actinozoon. Often applied indiscriminately to any of the Ccelen- terata, or even to the Polyzoa. POLYPIDE. The sepai-ate zooid of a Polyzob'n. POLYPIDOM. The dermal system of a colony of a Hydrozoon or Polyzoon. POLTPITE. The separate zooid of a Hydrozoon. POLYSTOME (Gr. polus, many ; and stoma, mouth). Having many mouths ; applied to the Acinetae amongst the Protozoa. POLYTHALAMOUS (Gr. polus ; and thalamos, chamber). Having many cham- bers ; applied to the shells of Foraminifera, and Cephalopoda. POLYTROCHAL (Gr. polus, many ; trochos, wheel). An epithet applied to those larvae of Annelides and other Invertebrates, in which there are successively- disposed circlets of cilia. POLYZOA (Gr. poluj; and zoon, animal). A division of the MoUuscoida, com- prising compound animals, such as the Sea-mat. Sometimes called Bryozoa. POLYZOARIUM. The dermal system of the colony of a Polyzoon (= Polypi- dom). PORCELLANOUS. Of the texture of porcelain. PORIFERA (Lat. porus, a pore ; and fero, I carry). Sometimes used to desig- nate the Foraminifera, or the Sponges. POST- ABDOMEN. That portion of the "abdomen" of Crustacea, Arachnida, and Myriapoda which lies behind the segments corresponding with the abdomen of Insects. POST-ANAL. Situated behind the anus. POST-GESOPHAGEAL. Situated behind the gullet. POST-ORAL. Situated behind the mouth. PR^-MAXILLJE. (See Intermaxillae. ) PR.EMOLARS (Lat. prce, before ; molares, the grinders). The molar teeth of Mammals which succeed the molars of the milk-set of teeth. In man, the bicuspid teeth. PR.E-CESOPHAGEAL. Situated in front of the gullet. PR^E-STERNUM. The anterior portion of the breast-bone, corresponding with the manubrium sterni of human anatomy, and extending as far as the point of articulation of the second rib. PRESSIROSTRES (Lat. pressus, compressed; rostrum, beak). A group of the Grallatorial Birds. PROBOSCIDEA (Lat. proboscis, the snout). The order of Mammals comprising the Elephants. PROBOSCIS (Lat. or Gr. the snout). Applied to the spiral trunk of Lepidop- terous Insects, to the projecting mouth of certain Crinoids, and to the cen- tral polypite in the Medusw. PROCCELOUS (Gr. pro, before ; koilos, hollow). Applied to vertebrae, the bodies of which are hollow or concave in front. PROGLOTTIS (Gr. for the tip of the tongue). The generative segment or joint of a Tape-worm. PRO-LEGS. The false abdominal feet of Caterpillars. PRONATION (Lat. pronus, lying on the face, prone). The act of turning the palm of the hand downwards. 812 GLOSSARY. PROPODIUM (Gr. pro, before; pous, foot). The anterior part of the foot, in Molluscs. PROSCOLEX (Gr. pro, before ; scolex, worm). The first embryonic stage of a Tape- worm. PROSOBRANCHIATA (Gr. proson, in advance of; bragchia, a gill). A division of Gasteropodous Molluscs in which the gills are situated in advance of the heart. PROSOMA (Gr. IJTO, before ; soma, body). The anterior part of the body. PROTHORAX (Gr. pro; and thorax, chest). The anterior ring of the thorax of insects. PROTOPHYTA (Gr. protos, first ; and phuton, plant). The lowest division of plants. PROTOPLASM (Gr. protos; andplasso, I mould). The elementary basis of or- ganised tissues. Used synonymously with the ' ' sarcode " of the Protozoa. PROTOPODITE (Gr. protos, first; and pous, foot). The basal segment of the typical limb of a Crustacean. PROTOZOA (Gr. protos; and zoon, animal). The lowest division of the animal kingdom. PROVENTRICULUS (Lat. pro, in front of; ventriculus, dim. of venter, belly). The cardiac portion of the stomach of birds. PROXIMAL (Lat. proximus^ next). The slowly -growing, comparatively-fixed extremity of a limb or of an organism. PSALTERIUM (Lat. a stringed instrument). The third stomach of Ruminants. (See Omasum.) PSEUDEMBRYO (Gr. pseudos, falsity ;. embruon, embryo). The larval form of an Echinoderm. PSEUDOBRANCHIA (Gr. pseudos, falsity; bragchia, gill). A supplementary gill found in certain fishes, which receives arterialised blood only, and does not, therefore, assist in respiration. PSEUDOILEMAL (Gr. pseudos, falsity ; and haima, blood). Applied to the vas- cular system of Annelida. PSEUDO - HEARTS. Certain contractile cavities connected with the atrial system of Brachiopoda, and long considered to be hearts. PSEUDO-NAVICELL^E (Gr. pseudos, false ; and Navicula, a genus of Diatoms). The embryonic forms of the Gregarinidce, so called from their resemblance in shape to the Navicula. PSEUDOPODIA (Gr. pseudos ; and pous, foot). The extensions of the body- substance which are put forth by the Jthizopoda at will, and which serve for locomotion and prehension. PSEUDOVA (Gr. pseudos; Lat. ovum, egg). The egg-like bodies from which the young of the viviparous Aphis are produced. PTEROPODA (Gr. pteron, wing ; and^ows, foot). A class of the Mollusca which swim by means of fins attached near the head. PTEROSAURIA (Gr. pteron, wing ; saura, lizard). An extinct order of reptiles. PUBIS (Lat. pubes, hair). The share-bone ; one of the bones which enter into the composition of the pelvic arch of Vertebrates. PULMOGASTEROPODA (=Pulmonifera). PDLMONARIA. A division of A rachnida which breathe by means of pulmonary sacs. PULMONATE. Possessing lungs. PULMONIFERA (Lat. pulmo, a lung; and/ero, I carry). The division of Mol- lusca which breathe by means of a pulmonary chamber. PUPA (Lat. a doll). The stage of an insect immediately preceding its appear- ance in a perfect condition. In the pupa-stage it is usually quiescent — when it is often called a " chrysalis ; " but it is sometimes active — when it is often called a "nymph." PYLORUS (Gr. paloros, a gatekeeper). The valvular aperture between the stomach and the intestine. PYRIFORM (Lat. pyrus, a pear ; and forma, form). Pear-shaped. QUADRUMANA (Lat. quatuor, four; manus, hand). The order of Mammals comprising the Apes, Monkeys, Baboons, Lemurs, &c. GLOSSARY. 813 RADIATA (Lat. radius, a ray). Formerly applied to a large number of animals which are now placed in separate sub-kingdoms (e.g., the Ccelenterata, the Echinodermata, the Infusoria, &c.). RADIOLARIA (Lat. radius, a ray). A division of Protozoa. RADIUS (Lat. a spoke or ray). The innermost of the two bones of the fore- arm of the higher Vertebrates. It carries the thumb, when present, and corresponds with the tibia of the hind-limb. RADULA (Lat. radula, a scraping-iron). An epithet often given to the toothed lingual ribbon or " odontophore " of the higher Mollusca. RAMUS (Lat. a branch). Applied to each half or branch of the lower jaw or mandible of Vertebrates. RAPTORES (Lat. rapto, I plunder). The order of the Birds of Prey. RASORES (Lat. rado, I scratch). The order of the Scratching Birds (Fowls, Pigeons, &c.). RATITJS (Lat. rates, a raft). Applied by Huxley to the Cursorial Birds, which do not fly, and have therefore a raft-like sternum without any median keel. RECTUM (Lat. rectus, straight). The terminal portion of the intestinal canal, opening at the surface of the body at the anus. REPTILIA (Lat. repto, I crawl). The class of the Vertebrata comprising the Tortoises, Snakes, Lizards, Crocodiles, &c. RETICULOSA (Lat. reticulum, a net). Employed by Dr Carpenter to designate those Protozoa, such as the Foraminifera, in which the pseudopodia run into one another and form a network. RETICULUM (Lat. a net). The second division of the complex stomach of Ruminants, often called the "honeycomb-bag." REVERSED. Applied to spiral univalves, in which the direction of the spiral is the reverse of the normal— i.e., sinistral. RHABDOPHORA (Gr. rhabdos, a rod ; and phew, I carry). Employed by Prof. Allman as a name for the Graptolites, in consequence of their commonly possessing a chitinous rod or axis supporting the perisarc. RHIZOPHAGA (Gr. rhiza, root ; phago, I eat). A group of the Marsupials. RHIZOPODA (Gr. rhiza, a root ; andpous, foot). The division of Protozoa com- prising all those which are capable of emitting pseudopodia. RHOPALOCERA (Gr. rhopalon, club; keras, horn). A name given to the But- terflies among the Lepidoptera in allusion to the fact that the antennae are clubbed at the end. RHYNCHOLITES (Gr. rhunchos, beak ; and lithos, stone). Beak-shaped fossils, consisting of the mandibles of Cephalopoda. RODENTIA (Lat. rodo, I gnaw). An order of the Mammals ; often called Glires (Lat. glis, a dormouse). ROSTRUM (Lat. rostrum, beak). The "beak" or suctorial organ formed by the appendages of the mouth in certain insects. ROTATORIA ( = Rotifera). ROTIFERA (Lat. rota, wheel ; and fero, I carry). A class of the Scolecida (Annuloida) characterised by a ciliated "trochal disc." RUGOSA (Lat. rugosus, wrinkled). An order of Corals. RUMEN (Lat. the throat). The first cavity of the complex stomach of Rumi- nants ; often called the " paunch." RUMINANTIA (Lat. ruminor, I chew the cud). The group of Hoofed Quadru- peds (Ungulata) which "ruminate" or chew the cud. SACRUM. The vertebrae (usually anchylosed) which unite with the haunch- bones (ilia) to form the pelvis. SAND-CANAL (= STONE-CANAL). The tube by which water is conveyed from the exterior to the ambulacral system of the Echinodermata. SARCODE (Gr. sarx, flesh ; eidos, form). The jelly-like substance of which the bodies of the Protozoa are composed. It is an albuminous body con- taining oil-granules, and is identical with protoplasm. SARCOIDS (Gr. sarx; and eidos, form). The separate amcebiform particles which in the aggregate make up the " flesh " of a Sponge. SAURJA (Gr. saura, a lizard). Any lizard-like Reptile is often spoken of as a 8 14 GLOSSARY. "Saurian ; " but the term is sometimes restricted to the Crocodiles alone, or to the Crocodiles and Lacertilians. SAUROBATRACHIA (Gr. saura; batrachos, frog). Sometimes applied to the order of the tailed Amphibians ( Urodela). SAUROPSIDA (Gr. saura ; and opsis, appearance). The name given by Huxley to the two classes of the Birds and Reptiles collectively. SAUROPTERYGIA (Gr. saura ; pterux, wing). An extinct order of Reptiles, called by Huxley Plesiosauria, from the typical genus Plesiosaurus. SAURURJ3 (Gr. saura ; oura, tail). The extinct order of Birds comprising only the Archveopteryx. SCANSORES (Lat. scando, I climb). The order of the Climbing Birds (Parrots, Woodpeckers, &c.). SCAPHOGNATHITE (Gr. skaphos, boat ; and gnathos, jaw). The boat-shaped appendage (epipodite) of the second pair of maxillae in the Lobster, the function of which is to spoon out the water from the branchial chamber. SCAPULA (Lat. for shoulder-blade). The shoulder-blade of the pectoral arch of Vertebrates ; in a restricted sense, the row of plates in the cup of Crinoids, which give origin to the arms, and are usually called the " axillary radials." SCLERENCHYMA (Gr. skleros, hard; and enchunia, tissue). The calcareous tissue of which a coral is composed. SCLERITES (Gr. skleros). The calcareous spicules which are scattered in the soft tissues of certain Actinozoa. SCLEROBASIC (Gr. skleros, hard ; basis, pedestal). Applied to the coral which is produced by the coenosarc in certain Actinozoa (e.g., Red Coral), and which forms a solid axis which is' invested by the soft parts of the animal. It is called " foot-secretion " by Mr Dana. SCLERODERMIC (Gr. skleros ; and derma, skin). Applied to the corallum which is deposited between the tissues of certain Actinozoa, and is called " tissue- secretion " by Mr Dana. SCLEROTIC (Gr. skleros, hard). The outer dense fibrous coat of the eye. SCOLECIDA (Gr. skolex, worm). A division of the Annuloida. SCOLEX (Gr. skolex). The embryonic stage of a Tape- worm, formerly known as a " Cystic worm." SCUTA (Lat. scutum, a shield). Applied to any shield-like plates ; to those which are developed in the integument of many Reptiles. SELACHIA or SELACHII (Gr. selachos, a cartilaginous lish, probably a shark). The sub-order of Elasmobranchii, comprising the Sharks and Dog-fishes. SEPIOSTAIRE. The internal shell of the Sepia, commonly known as the " cuttle-bone." SEPTA. Partitions. SERPENTIFORM. Resembling a serpent in shape. SERTULARIDA (Lat. sertum, a wreath). An order of Hydrozoa. SESSILE (Lat. sedo, I sit). Not supported upon a stalk or peduncle ; attached by a base. SET^B (Lat. bristles). Bristles, or long stiff hairs. SETIFEROUS. Supporting bristles. SETIGEROUS ( = Setiferous) . SETOSE. Bristly. SILICEOUS (Lat. silex, flint). Composed of flint. SINISTRAL (Lat. sinistra, the left hand). Left-handed ; applied to the direc- tion of the spiral in certain shells, which are said to be "reversed." SINUS (Lat. sinus, a bay). A dilated vein or blood-receptacle. SIPHON (Gr. siphon, a tube). Applied to the respiratory tubes in the Mol- lusca; also to other tubes of different functions. SIPHONOPHORA (Gr. siphon ; andphero, I carry). A division of the Hydrozoa, comprising the Oceanic forms (Calycophoridve and Physophoridce). SIPHONOSTOMATA (Gr. siphon ; and stomia, mouth). The division of Gasteropo- dous Molluscs, in which the aperture of the shell is not "entire," but possesses a notch or tube for the emission of the respiratory siphon. SIPHUNCLE (Lat. siphunculus, a little tube). The tube which connects together the various chambers of the shell of certain Cephalopoda (e.g. , the Pearly Nautilus). GLOSSARY. 8 1 5 SIPUNCDLOIDEA ( Lat. siphunculus, a little siphon). A class of Anarthropoda (Annulosa). SIRENIA (Gr. seiren, a mermaid). The order of Mammalia comprising the Dugongs and Manatees. SOLIDUNGULA (Lat. solidus, solid ; ungula, a hoof) . The group of Hoofed Quadrupeds comprising the Horse, Ass, and Zebra, in which each foot, in the living forms, has only a single solid hoof. Often called Solipedia. SOMATIC (Gr. soma, body). Connected with the body. SOMATOCYST (Gr. soma ; and kustis, a cyst). A peculiar cavity in the coenosarc of the Calycophoridce (Hydrozoa). SOMITE (Gr. soma}. A single segment in the body of an Articulate animal. SPERMARIUM. The organ in which spermatozoa are produced. SPERMATOPHORES (Gr. sperma, seed ; phero, I carry). The cylindrical capsiiles of the Cephalopoda, which carry the spermatozoa ; sometimes called the "moving filaments of Needham." SPERMATOZOA (Gr. sperma, seed ; and zoon, animal). The microscopic fila- ments which form the essential generative element of the male. SPH^RIDIA (Gr. sphairidion, a little ball or sphere). Minute stalked appen- dages with button-shaped heads carried by most living Sea-urchins, and supposed to be organs of sense. SPICULA (Lat. spiculum, a point). Pointed needle-shaped bodies. SPINNERETS. The organs by means of which Spiders and Caterpillars spin threads. SPIRACLES (Lat. spiro, I breathe). The breathing-pores, or apertures of the breathing-tubes (tracheae) of Insects. Also the single nostril of the Hag- fishes, the " blow-hole " of Cetaceans, &c. SPLANCHNOSKELETON (Gr. splagchna, viscera ; skeletos, dry). The hard struc- tures occasionally developed in connection with the internal organs or viscera. SPONGE-PARTICLES. (See Sarcoids.) SPONGIDA (Gr. spoggos, a sponge). The division of Protozoa commonly known as sponges. SPORES (Gr. spora, seed). Germs, usually of plants ; in a restricted sense, the reproductive " gemmules " of certain sponges. SPOROSACS (Gr. spora, seed; and sakkos, a bag). The simple generative buds of certain Hydrozoa, in which the medusoid structure is not developed. SQUAMATA (Lat. sqitama, a scale). The division of reptiles comprising the Ophidia and Lacertilia in which the integument develops horny scales, but there are no dermal ossifications. STATOBLASTS (Gr. statos, stationary ; Hastes, bud). Certain reproductive buds developed in the interior of Polyzoa, but not liberated until the death of the parent organism. STEGANOPHTHALMATA (Gr. steganos, covered ; and ophthalmos, the eye). Ap- plied by Edward Forbes to certain Medusce, in which the sense-organs ("marginal bodies") are protected by a sort of hood. The Steganophthal- mata are now separated from the true Medusidce, and placed in a separate division under the name Lucernarida. STELLERIDA (Lat. stella, star). Sometimes employed to designate the order of the Star-fishes. STELLIFORM. Star-shaped. STEMMATA (Gr. stemma, garland). The simple eyes, or " ocelli," of certain animals, such as Insects, Spiders, and Crustacea. STERNUM (Gr. sternon). The breast-bone. STIGMATA. The breathing- pores in Insects and Arachnida. STOLON (Gr. stolos, a sending forth). Offshoots. — The connecting processes of sarcode in Foraminifera ; the connecting tube in the social Ascidians ; the processes sent out by the coenosarc of certain A ctinozoa. STOMAPODA (Gr. stoma, mouth ; pous, foot). An order of Crustacea. STOMATODE (Gr. stoma}. Possessing a mouth. The Infusoria are thus often called the Stomatode Protozoa. STREPSIPTERA (Gr. strepho, I twist; pteron, wing). An order of Insects in which the anterior wings are represented by twisted rudiments. 8l6 GLOSSARY. STREPSIRHINA (Gr. strepho, I twist ; rhines, nostrils). A group of the Quad- rumana, often spoken of as Prosimios. STROBILA (Gr. strobiles, a top, or fir-cone). The adult Tape-worm, with its generative segments or proglottides ; also applied to one of the stages in the life-history of the Lucernarida. STYLIFORM (Lat. stylus, a pointed instrument ; forma, form). Pointed in shape. SUB-CALCAREOUS. Somewhat calcareous. SUB-CENTRAL. Nearly central, but not quite. SUB-PEDUNCULATE. Supported upon a very short stem. SUB-SESSILE. Nearly sessile, or almost without a stalk. SUPINATION (Lat. supinus, lying with the face upwards). The act of turning the hand with the palm upwards. SUTURE (Lat. suo, I sew). The line of junction of two parts which are im- movably connected together. Applied to the line where the whorls of a univalve shell join one another; also to the lines made upon the exterior of the shell of a chambered Cephalopod by the margins of the septa. SWIMMERETS. The limbs of Crustacea, which are adapted for swimming. SYMPHYSIS (Gr. sumphusis, a growing together). Union of two bones in which there is no motion, or but a very limited amount. SYNAPTICUL.E (Gr. sunapto, I fasten together). Transverse props sometimes found in Corals, extending across the loculi like the bars of a grate. SYSTOLE^ (Gr. sustello, I contract). Applied to the contraction of any contrac- tile cavity, especially the heart. TABULA (Lat. tabula, a tablet). Horizontal plates or floors found in some Corals, extending across the cavity of the " theca," from side to side. TACTILE (Lat. tanpo, I touch). Connected with the sense of touch. TJEXIADA (Gr. talnia, a ribbon). The division of Scolecida comprising the Tape-worms. T.&NIOID (Gr. tainia ; and eidos, form). Kibbon-shaped, like a Tape-worm. TARSO-METATARSUS. The single bone in the leg of Birds produced by the union and anchylosis of the lower and distal portion of the tarsus with the whole of the metatarsus. TARSUS (Gr. tarsos, the flat of the foot). The small bones which form the ankle (or " instep " of man), and which correspond with the wrist (carpus) of the anterior limb. TECTIBRANCHIATA (Lat. tectus, covered ; and Gr. bragchia, gills). A division of Opisthobranchiate Gasteropoda in which the gills are protected by the mantle. TEGUMENTARY (Lat. tegumentum, a covering). Connected with the integument or skin. TELEOSTEI (Gr. teleios, perfect; osteon, bone). The order of the "Bony" Fishes. TELSON (Gr. a limit). The last joint in the abdomen of Crustacea ; vari- ously regarded as a segment without appendages, or as an azygous ap- pendage. TENUIROSTRES (Lat. tennis, slender ; rostrum, beak). A group of the Perch- ing Birds characterised by their slender beaks. TERGUM (Lat. for back). The dorsal arc of the somite of an Arthropod. TERRICOLA (Lat. terra, earth ; and colo, I inhabit). Employed occasionally to designate the Earth-worms (Luriibricidis, 358. Aplacental Mammals, 654, 656. Aplysiadce, 412. ^oda (Cirripedia), 283, 292; (Amphi- bia'), 513; (Fishes), 485, 486. Apodemata, 279. Aporosa (Corals), 164. Appendicularia, 383, 387. Aptenodytes, 602. Aptera, 341, 344. Apterygidce, 596, 598. Apteryx, 590, 595, 596, 597, 598. ^ws, 41, 296, 297. Aquiferous system (see Water - vascular system). Arachnactis, 155, 156, 180. Arachnida, 274, 275; characters of, 314; somite of, 315 ; organs of the mouth of, 316; respiratory process of, 318 ; distri- bution of, in time, 327. Araince, 621. Araneida, characters of, 325; webs of, 326 ; distribution of, in time, 327. Arcadce, 399, 403. Arcella, 65. Arcellina, 65, 66, 72. Archceocidaris, 200, 224. Archceopteryx, 575, 593, 594, 633, 634. Archegosaurus, 524. Architarbus, 327. Architeuthis, 435. Archiulidce, 332. Archiulus, 332. Arctictis, 746. Arctisca, 320. Arctocebus, 774. Arctoidea, 739. Arctomys, 760. Arctonyx, 742. Arctopitheci, 776. ^irdm, 610. Ardeidce, 610. -drem'coZa, 270. Argonauta, 419, 423 ; shell of, 425, 426 ; 822 INDEX. reproductive process of, 427; hectoco- tylus of, 424. Argonautidce, 427. Argulus, 284. Aristotle's Lantern, 198. Ark-shells, 403. Armadillos, 672, 675, 676, 680. Arms of Star-fishes, 203 ; of Ophiuroidea, 206; of Crinoidea, 208; of Comatula, 214 ; of Cystoidea, 217 ; of Brachiopoda, 390; of Cuttle-fishes, 419; of Nautilus, 431, 432. Artemia, 41, 297. Arthrogastra, 324. Arthropoda, 228; characters and divisions of, 274. Articulata, 274. Articulata (Brachiopoda), 393, 394. Artiodactyla, 693, 702. Arvicola, 758. Ascaris, 245, 247. Ascidians, solitary, social, and compound, 386. Ascidioida (see Tunicata). Ascoceras, 434. Asellus, 305. JLsmws, 700. Asiphonida (Lamellibranchiata), 403. Aspidophora, 378, 379. Aspidorhynchus, 493. Asplanchna, 251. Ass, 701. ^Istactts, 307, 308. ^stasia, 100, 101. Asteriadce, 205. Asterinidce, 205. Asterocanthiidce, 205. Asteroid Polypes, 165. Asteroidea, 192; general characters of, 201 ; families of, 205 ; distribution of, in space, 222 ; in time, 223. Asthenosoma, 200, 224. Astomata (Protozoa), 58. Astrcea, 163. Astrceidce, 164. Astrogonium, 224. Astropecten, 202, 223. Astropectinidce, 205. Astrophyton, 206. Astrorhiza, 69. Athecata, 114. Atherura, 755. Atlantidce, 414. Atolls, 181, 182. Atrial system (Brachiopoda), 391. Atrium (Tunicata), 382. J.«a, 360. Auchenia, 712. Auk, 602, 603. Aulopora, 165. .Awrefta, 139, 144. Aurelia, 342. Auricularia, 219. J.wricuZid<#, 415. Aurochs, 720. Autolytus, 269. Autophagi, 589. Aves, 458 ; general characters of, 571-592 ; feathers of, 572-574 ; vertebral column of, 574 ; beak of, 576 ; pectoral arch and fore-limb of, 578 e£ seg. ; hind-limb of, 581 et seq. ; foot of, 583 ; digestive sys- tem of, 583-586 ; respiratory system of, 586 ; circulatory system of, 586, 588 ; nervous system and organs of sense of, 589, 590; reproductive system of, 588; migrations of, 591 ; divisions of, 594- 595 ; orders of, 595-636 ; distribution of, in time, 592; literature, 636. Avicularia, 374, 375, 377. Aviculidce, 403. Avocet, 608. Axinella, 84. Axolotl, 515, 516, 517. Aye-aye, 773. Azorica, 90. Baboon, 778, 779. Babyroussa, 706. Bacteria, 10, 44, 45, 47. Bactrites, 436. Baculites, 434, 436, 437. Badger, 742. Balcena, 685, 686, 687. Balcenidce, 685, 686, 692. Balcenoptera, 688. Balancers, 335, 354. Balanidce, 288, 289, 290, 291 ; distribution of, in time, 313. Balanoglossus, 241. Balanus, 287, 290, 291. Balatro, 249. Balearica, 610. Baleen, 685, 686, 687. Balistidce, 488. Banded Ant-eater, 667, 668. Bandicoot, 665, 666. Banxring, 770. Barbadoes Earth, 80. Barbel, 485. Barbets, 620, 622. Barnacles, 287, 288, 290. Barrier-reefs, 181, 182. Bascanion, 543. Basiliscus, 550. Bassaris, 741. Bathybius, 62. Bathycrinus, 213, 222. Bathyergus, 757. Batides, 598, 599. Batrachia, 518. Bats, 761 et seq. Beaked Rays, 500. Bear, 739, 740, 751. Bear-animalcules, 320. Bearded Vulture, 632. Beaver, 756. Bed-bug, 349. Bee-eaters, 628, 629. Bees, parthenogenesis of, 40 ; communi- ties of, 3£3. Belemnites, structure of, 492, 430. Belemnitidce, 429, 437. Belinurus, 314. Bellerophina, 416. Bellerophon, 416. Belodon, 558. Beluga, 493. Benturong, 746. Berardius, 691. Beroe, 179, 180. Beroidce, 179, 180. Bighorn Sheep, 720. INDEX. 823 Bimana, general characters of, 736. Binomial nomenclature, 31. Biology, definition of, 1. Bioplasm, 8. Bipes, 545. Bipinnaria, 204. Bird-lice, 346. Bird's-head process, 373, 374. Birds of Paradise, 625. Birds of Prey (see Raptores}. Birgus, 311. Bison, 721. Bittern, 610. Bivalve Shell-fish, 396. Black Corals, 157. Black Snake, 543. Bladder, contractile, of Rotifera, 250. Blastoidea 192; general characters of, 217 ; distribution of, in time, 223. Blastostyle, 123, 124. Blatta, 349. Blattidce, 349, 350. Blenniidce, 488. Blind-worm, 548. Boa, 543. Boatbill, 610. Boat-fly, 349. Bolina, 180. Bombidce, 359. Bonasa, 614. Bony Pike, 490, 492, 493. Book-scorpion, 323. Bopyridce, 305. Bos, 720. Bosehas, 606. Botaurus, 610. Bot-flies, 355. Bothriocephalus, 231, 235. Botryllus, 381, 385, 386. Bourgueticrinus, 212. Bovidce, 718, 720. Bower-birds, 625. Box-slaters, 305. Brachiolaria, 204. Brachiopoda, 366, 367, 368, 371 ; general characters of, 388 ; shell of, 389 ; arms of, 390 ; atrial system of, 391 ; nervous system of, 392; divisions of, 393; dis- tribution of, in spacepSW; mtime, ib. ; development of, 393. Brachiuna, 284. Brachymetopus, 314. Brachyura, 307 ; characters of, 311 ; de- velopment of, 312. Brachyurus, 777. Bracts (see Hydrophyttia), 132. Bmdypodidce, 672, 673, 678. Bradypus, 673, 674. Bramatherium, 723. Branchellion, 260, 262. Branchial arches (Fishes), 466, 472. Branchial hearts (Cuttle-fishes), 421. Branchial sac (Tunicata), 382, 383, 384, 387 : (Lancelet), 478. Branchiata (Annelida), 259. Branchiata (Gasteropoda), 411. Branchiata (Ve.rtebrata), 458. Branchifera, 411. Branchiobdella, 262. Branchiogasteropoda, 407, 411. Branchiopoda, 283, 292, 294. Branchiostegal rays, 465, 466, 473. Branchwstoma (see Amphioxus). Branchipus, 296, 297. Brevilinguia, 547. Bfevipennatce, 601. Brill, 487. Brine-shrimp, 297. Brisinga, 205. Brisingidce, 205. Brittle-stars, 205. Brocket Deer, 716. Brontotheridce, 698, 699. Brontotherium, 698. Bruta (see Edentata). Bryozoa (see Polyzoa. Bubalus, 718, 721. Bubble-shells, 412. Bubo, 633. Buccinidce, 412. Buccinum, 406, 407, 411. Bucconidce, 620, 622. Buceros, 624. Bucerotidce, 624. Buffalo, 718, 721. Bufo, 522. Bufonidce, 521. Bulbus arteriosus, 473, 484, 492, 495, 503. Bullfinch, 626. Bullidce, 412. Bull-frog, 522. Bumble-bees, 359. Bungarus, 543. Bunodonts, 703. Buprestidce, 362. Burying Beetles, 362. Bush-quails, 615. Bustards, 612. Butterflies, 337, 342, 355, 356. Buzzards, 632. Byssus (of Lameliibranchiata), 402, 403. Cachalot, 688. Cacomixle, 741. Caddis-flies, 351. Caducibranchiata (Amphibia], 510, 511, 517. Cseca, intestinal (of Birds), 586. Cgeca, pyloric (of Fishes), 474. Ccecilice, 512, 514, 515. Caiman, 557, 558. Cainotherium, 722. Cake-urchins, 200. Calamaries, 428, 429. Calamoichthys, 489, 493. Calcarea (Sponges), 88, 92, 93. Calcarina, 71, 76. Calceola, 174, 175. Calcispongice, 88, 92, 93. Calice (Corals), 160. Californian Vulture, 633. Caligus, 284. Calling Crabs, 311. Calling Hares, 754. Callithrix, 777. Callograptus, 150. Callorhynchus, 497. Calveria, 200. Calycophoridce, 131 ; polypites of, 132 ; reproduction of, 133 ; development of, ib. ; distribution of, 150. Calyptoblastic Hydroids, 121. Calyptrceidce, 412. - 824 INDEX. Calyx (of Vorticella), 98 ; (of Crinoids), 210, 211. Camelidcv, 651, 710, 711, 722. CamelopardaUdce, 717, 722. Camelopardalis, 717. Camelus, 711, 712. Campanularia, 126. Campanularida, 112, 125 ; medusiform gonopliores of, 126. Campodea, 345, 347. Canals, of Sponges, 86; of Alcyonaria, 166, 169; of Ctenophora, 177, 178. Cancroma, 610. Canidce, 747, 748, 752. Canis, 747, 748. Cantharidce, 362. Canvass-back Duck, 606. Capitulum (Lepadidce), 288, 290. Capra, 719, 720. Caprella, 303. Capreolus, 714, 715, 716. Caprimulgidce, 628, 629. Capuchin Monkeys, 777. Capybara, 755. Carabidce, 362. Caracal, 751. Carapace, of Difflugia, 65; of Arcella, ib. ; of Vaginicola, 99; of Crustacea, 279, 305 ; of Lobster, 279, 307 ; of Crab, 311 ; of Chelonian Reptiles, 531, 534. Carcharias, 499. Carcharodon, 506. Carchesium, 99. Cardiadce, 403, 404. Carduelis. 626. Caribou, 716. Carinaria, 369, 414. Carinatce, 594, 600. Carnivora, general characters of, 734 ; divisions of, 735-751; distribution of, in time, 751, 752. Carp, 488. Carpophaga, 664. Carriage-spring apparatus (Brachiopoda). 390. Caryocaris, 313. Caryophyllia, 160. Cassidina, 305. Cassidulinidce, 74. Cassis, 410. Cassowary, 596, 597, 598. Castor, 756. Castoridce, 756, 760. Castoroides, 761. Casuarius, 597. Catarhina, 727, 731, 736 Cathartes, 633. Cathartidce, 631.632. Catodontidce, 685, 6S8, 692. Cats, 74*, 750, 751. <7ama, 755. Cavicornia, 717. Caviidcp, 755, 760. Cebidce, 776. Te&MS, 777. CecMomyia, 355. Cells, of Polyzoa. 373, 374. Cellulose in Ascidiaiis, 15, 381. Cement-gland of Cirripedes, 287, 289. Centetes, 769. Centetidce, 7^9, 771. Centipedes, 327, 329. Centrocercus, 614. Cephalaspis, 494, 505. Cephalobranchiata (see Tubicola}. Cephalophora (Mollusca), 396. Cephalopoda, 367, 368, 369, 396 ; general characters of, 418; arms of, 419 ; funnel of, 420; ink-bag of, 421; mandibles of, i&. ; digestive system of, i&. ; branchiae of, ib. ; nervous system of, ib. ; repro- ' duction of, 422-424; skeleton of, 425, 426 ; divisions of, 426-435 ; distribution of, in space, 435 ; in time, 435-437. Cephaloptera, 500. Cephalothorax, of Crustacea, 278; of Ar- achnida, 315. Cephaluna, 284. Cephea. 144. Cerastes, 542. Ceratiocaris, 313. Ceratites, 433, 437. Ceratudus, 490, 491, 500, 501, 502, 503, 507. Ceratophrys, 513. Cercocebus, 778. Cercolabes, 756, 757. Cercolabidce, 756. Cercoleptes, 741. Cercopitkecus, 778. Cere, of Birds, 584, 591. Cerianthus, 155, 157, 180. Cerithiadce, 412. Cert.hia, 627. Certhidce, 627. Cervidce, 713, 722. Cervus, 715, 716. Cer^/^, 629. Cestoidea (see Tceniada}. Cestracion, 498, 505. Cestraphori, 498, 506. Cestum, 180. Cetacea, 640, 641, 642, 643, 645, 646, 650, 651, 653, 680; general characters of, 684 ; groups of, 685 ; distribution of, in time, 692. Cetiosaurus, 558, 567. Cetochilus, 294. Cetonia, 361. Chacma, 779. Chceropotamus, 722. Chceropsis, 705. Chceropus, 666. Chcetoderma, 255. Chcetognatha. 254, 271. Chcetonotus, 249. Chcetophora, 259. Chalcididce, 547. Chalicomys, 760. Challengeria, 73. Challengerida, 73. Chamceleo, 552. Chamceleontidce, 552. Chamidce, 403, 404. Chamois, 7x9. Channel-bill Cuckoo, 620. Charadriidce, 612. Charadrius, 612. Cheese-mite, 321. Cheetah, 751. Cheilostomata, 379, 380. Cheiromydce, 773. Cheiromys, 773, 774. Cheironectes, 666. Cheiroptera, general characters of, 761 ; divisions of, 763 ; distribution of, in time, 765. INDEX. 825 Cheirotherium, 523. Chelae, 281 ; of King-crab, 300 ; of Scorpion, 317, 324; of Book-scorpion, 322. ChelicersE, 317. Chelichnus, 536. Chelifer, 323. Cheliferidce, 322. Cheliferons Slaters, 305. Chelone, 535. Chelonia, general characters of, 53P-535; subdivisions of, 535 ; distribution of, iii time, 536. Cheloniidce, 535. Chelonobatrachia (see Anoura). Chelydidce, 553. Chelydra, 536. Chevrotains, 711, 712. Chigoe, 353. Chilognatha, 330. Chilopoda, 329. Chimcera, 496. Chimceridce, 497. Chimpanzee, 781. Chinchilla, 756. Chinchillidce, 756. Chirocephahis, 296. Chirodota, 221. Chirotes, 545, 547. Chiton, 369. Chitonidce, 412. Chlamydosaurus, 551. Chlamydotherium, 681. Chlamyphorus, 676. Chlorophyll in animals, 15. Cholcepus, 640, 672, 675. Chondropterygidce, 477, 494. Chondrosfeidce, 492, 493. Chondrosteus, 505. Chorda dorsalis (see Notochord). Chromatophores, 419. Chrysalis, 342. Chrysaora, 141. Chrysochloris, 767. Chrysopa, 351. Chub, 485. Chylaqueous canals (Medusce), 128. Chylaqueous fluid, of Rotifera, 250; of Annelida, 258. Chylific stomach of Insects, 337. Chyme-mass of Infusoria, 95. Cicada, 348. Cicindelidce, 362. Ciconia, 611. Ciconince, 611. Cidaris, 195 Ciliata (Infusoria), 95. Ciwez, 349. "Cinclides, 156. Cimolornis, 607. Cirrhatulus, 268. Cirrhopoda (see Cirripedia). Cirripedia, 283 ; general characters of, 287 ; development of, 288 ; shell of, 289, 290 ; reproduction of, 291 ; divisions of, 291, 292 ; distribution of, in time, 313. Cirrostomi (see Pharywjobranchii). Civet, 745. Cladocera, 283 ; characters of, 295. Cladochonus, 165. Clamatores, 613. Clangula, 606. Classification, 26. Clathrulina, 83. Clavatetta, 118. Cleodora, 417, 418. Clepsine, 262. Climacograptus, 150. Cliona, 92. Clisiophyllum, 175. Clistenterata, 393. Clitellum. 263. CfoMo, 542. Clupeidce, 455. Clymenia, 433. Clypeaster, 194. Clytia, 126. Cnemiornis, 607. Cnidse, 107. Coati, 741. Cobra, 543. Coccidce, 347, 348. Coccinellidce, 362. Coccosteus, 494. 505. Coccothraustes, 626. Coccus, 348. Coccygus, 620. Cochliopodium, 65. Cockatoo, 621. Cockle, 404. Cockroach, 349, 350. Cocoon, 343. Cod, 486. Codonella, 95. Ccelenterata, characters of, 105 ; thread- cells of, 107 ; divisions of, 108. Coelogenys, 755. Ccenenchyma, 162. Coancecium, 372, 374. Coenosarc, 110; of Oceanic Hydrozoa, 131 ; of Physalia, 135 ; of Velella, 136. Ccenurus, 235. Coleoptera, 335; mouth of, 336; charac- ters of, 361 ; sections of, 362. Collembola, 346. Collocalia, 629. Collosphcera, 80. Collozoum, 80. Colobus, 777, 778. Colossochelys, 537. Coluber, 543. Colubrina, 543. Colugo, 770. Columba, 614, 616, 617. Columbacei, 613, 616. Columbidce, 617. Columella, of Corals, 161 ; of the shells of Gasteropoda, 410. Column, of Actinidce, 154. Colymbidce, 603. Colymbus, 603. Comarocystites, 217. Comaster, 216. Comatula, 213, 214, 215, 216, 222, 223. Compsognathus, 567. Conchicolites, 271. Conchifera, (see Lamellibranchiata). Condor, 633. Condylura, 767. Conidce, 412. Conirostres, 624. Conodonts, 504, 505. Conosmilia, 175, 185. Contractile vesicle, of Protozoa, 57 ; of , 64 ; of Paramcecium, 96. 826 INDEX. Conularia, 418. Coot, 609. Copepoda, 283 ; characters of, 294. Cophobelemnon, 168. Coral (see Corallum). Coral-reefs, 181 et seq. Coral-snakes, 543. Corallistes, 90. Corallite, 163. Corallium, 169, 170. Corallum, 153, 157, 158, 162, 166, 167, 169, 170, 173. Cordylophora, 114; gonophores of, 116; distribution of, 149. Cormorant, 604. Cornulites, 271. Cortical layer, of Infusoria, 95, 96; of Noctiluca, 101. Corvidce, 624. Coryne, 115, 118. Corynida, 112; characters of, 114; repro- duction of, 115; types of, 120; devel- opment of, 118 ; distribution of, 149. Corynoides, 150. Coryornorpha, 120. Coryphodon, 694. Coryphodontidce, 693, 694. Cossus, 357. Coturnix, 614. Coypu, 756. Cow Bunting, 620. Cowries, 412. Crab-Lobsters, 311, Crabronidce, 358. Cracidce, 615. / Crane, 610. Crane-fly, 354, 355. Crania, 389, 390, 395. , Craniadce, 394, 395. Craspeda, 156. Crax, 615. Creepers, 627. Crex, 609. Cribella, 205. Cricetus, 758. Crickets, 350. Crinoidea, 192; general characters of, 207 et seq. ; distribution of, in space, 222 ; in time, 223. Crioceras, 434, 435, 436. Cristatella, 374. Cristellaridea, 74. Crocidura, 768. Crocodilia, 527, 528, 529, 530; general characters of, 555 ; divisions of, 557. Crocodilus, 556, 558. Crop of Insects, 337 ; of Birds, 585. Crossarchus, 746. Cross-bill, 626. Crossopterygidce, 491, 492, 493. Crossopus, 768. Crotalidce, 540, 541, 542. Crotalus, 539, 541, 542. Crotophaga, 620. Crows, 625. Crust, of Crustacea, 275; of Trilobites, 297. Crustacea, 228, 274; general characters of, 275etseq.; morphology of a typical Crus- tacean, 276 et seq.; divisions of, 283 ; dis- tribution of, in space, 312 ; in time, 313. Cryptobranchus, 517, 524. Cryptohelia, 174. , 305. Cryptophialus, 291. Cryptoprocta, 746. Cryptostegia, 74. Crystalline stylet, 400. Cte?iacanthus, 506. Ctenocyst, 178. Ctenodipterini (Dipnoi), 503, 507. Ctenodiscus, 202. Ctenodus, 503, 507. Ctenoid scales of lishes, 461, 487. Ctenomys, 756. Ctenophora, 154; characters of, 176; hpmologies of, 178; divisions of, ISu; distribution of, 181. Ctenophoral canals, 177, 179. Ctenophores, 177. Ctenoptychius, 506. Ctenostomata, 371, 379. Cuckoo, 620. Cuculidce, 619, 620. Cucumaria, 221. Culicidce, 354, 355. Cultirostres, 609. Cunina, 130. Cupularia, 374. Curassow, 615. Curlew, 611. Cursores, characters of, 595, 596; distri- bution of, in time, 598. Cuscus, 659. Cuticle, of Amoeba, 63 ; of Infusoria, 95. Cuttle-bone, 425, 429. Cuttle-fishes, 418, 419, 420, 421, 423, 424, 425, 426, 428. Cuvieria, 417, 418. Cyamus, 303. Cyanea, 14], 144. Cyathaxonia, 175. Cyathaxonidce, 175, 185. Cyathophyllidce, 175, 185. Cyathophyllum , 175. Cycladidce, 403, 404. Cyclas, 401. Cyclobranchiata, 412. Cyclodus, 547. Cycloid scales of fishes, 461. Cyclolabridce, 488. Cyclophthalmus, 327. Cyclopoidea, 277. Cyclops, 293, 294. Cydostomata(Polyzoa), 379, 380 ; (Fishes), 479. Cyclostomi (Fishes), 479. Cyclostomidce (Gasteropoda), 415. Cyclothurus, 677. Cydippe, 176. Cygnidce, 605, 606. Cygnus, 606. Cymothoii, 305. Cyncehtrus, 751. Cynipidce, 358. Cynocephalus, 778, 779. Cynodictis, 752. Cynodraco, 568. Cynogale, 746. Cynomys, 760. Cynopithecus, 779. Cyprceidce, 412. Cypridina, 293. Cyprinidce (Mollusca), 403, 404; (Fishes), 485. INDEX. 827 Cypris, 293. Cypeelidce, 629. Cyrtoceras, 434, 436. Cyrtolites, 416. Cysticerci, 230, 233, 234, 235. Cystic Worms, 230, 233, 234, 235. Cystiphyllidce, 175, 185. Cystiphyllum, 174, 175. Cystoidea, 192 ; general characters of, 216 ; distribution of, in time, 223. Cythere, 293. Cytherea, 397. Dacelo, 629. Dactylethra, 521. Dacti/localyx, 89, 90. Dactylopterus, 468. Dafila, 606. Dakosaurm, 558. Dama, 716. Daphnia, 293, 295. Darter, 605. Darwinian theory, 48. Dasornis, 598. Dasypodidce, 672, 675. Dasyprocta, 755. Dasyproctidce, 755. Dasypus, 676. Dasyurus, 67, 668. Dawsonella, 416. Death-adder, 542. Decapoda (Crustacea), 306; distribution of, in time, 314 ; (Cephalopoda), 419, 427, 428. Decollated shells, 370. Deer, 713-716. Degeeria, 345, 346. Deinosauria (see Dinosauria). Deinotherium, 728, 732. Delphinidce, 689, 692. Delphinus, 689, 690. Demodex, 321, 322. Dendroccela, 240. Dendrogrdjrtus, 144, 150. Dendrohyrax, 728. Dendrolagus, 663. Dendrophyllia, 159. Dendrostyle, 142. Dental formula, 649, 650. Dentalidce, 412. Dentalium, 409. Dentirostres, 624, 626. Derrias, 779. Desman, 768. Desmognathce, 577. Development, 41 ; Retrograde, 43 ; of Gregarinidce, 60 ; of Foramini/era, 69 ; of Sponges, 91 ; of Hydra, 113 ; of Cor?/- m'cZa, 118; of Calycophoridce, 133; of Physophoridce, 135 ; of Medusidce, 130; of Lucernarida, 139 ; of Actinidce, 156 ; of Pleurobrachia, 178 ; of Echinoder- mata, 191 ; of Echinoidea, 200 ; of .4ste- roidea, 204 ; of Ophiuroidea, 206 ; of Comatula, 215; ofHolothuroidea,219; of Tceniada, 232 ; of Trematoda, 237, 238 ; of Nemertida, 241 ; of Balanoglossus, ib. ; of Acanthocephala, 243 ; of Tri- china, 246 ; of the Guinea-worm, i&. ; of Gephyrea, 256 ; of Hirudinea, 262 ; of Tubicolar Annelides, 265 ; of Errant Annelides, 269 ; of Crustacea, 277 ; of Ichthyophthira, 284 ; of Rhizocephala, 286; of Cirripedia, 288; of Ostracoda, 293 ; of Copepoda, 294 ; of Pliyllopoda, 296 ; of Limulus, 300 ; of Isopoda, 304, 305; ofAmphipoda, 304 ; ofStomapoda, 306; of Macrura, 307; of Anomura, 310; of Brachyura, 312 ; of^lrac/midrt, 319; ofMyriapoda,329; oflnsecta, 341 etseq.; of Polyzoa, 378; of Tunicata, 384 ; of Brachiopoda, 393 ; of Lamelli- branchiata, 402 ; of Gasteropoda, 408 ; of Amphibia, 509 et se Hyperoodon, 691. Hypobythius, 387. Ilypochthon, 516. Hypostome of Trilobites, 297. Hypsiprymnus, (562, 664. tly Hyracoidea, general characters of, 727. Hyrax, 641, 727, 728. Hystricidce, 755, 760. Hystrix, 755. Ibis, 611. Ichneumon, 746. fchneumonidce, 358. Ichthyodorulites, 486, 495, 506. 1 chthyomorpha, 515. Ichthyophthira, 283, 284. Ichthyopsida, 459. Ichthyopterygia, 530 ; characters of, 559. Ichthyornis, 571,636. Ichthyosauria, 559. Ichthyosaurus, 559, 500, 5(51. Ictitherium, 751. Idothea, 305. Idyia, 180. Iguana, 546, 550. Iguanidce, 550. Iguanodon, 567. Ilyanthidce, 156. Ilyanthus, 156, 157. Imago, 341, 343. Imperforata (Foraminifera), 66, 73. Implacentalia (Mammalia), 654. Inarticulata (Brachiopoda), 393, 394. Indicator, 620. Individuality, general definition of, 34. Indris, 775. Infusoria, spontaneous generation of, 44, 46 ; characters of, 94 ; divisions of, 95 ; Ciliated, to.; Suctorial, 99; Flagellate, 99 ; compared with Rotifera, 252. Inia, 690. fnoperculata, 415. Inorganic and organic matter, differences between, 2-5. Insecta, 274, 275 ; general characters of, 333 et sflq. ; organs of the mouth of, 336 ; wings of, 335 ; digestive system of, 337 ; tracheae of, 339; circulation of, 338; me- tamorphoses of, 341 ; parthenogenesis of, 38 et seq.; sexes of, 341 ; orders of, 344 et seq. ; distribution of, in time, 344. Insectivora, general characters of, 766 ; families of, 766-770 ; distribution of, in time, 771 ; (Bats), 763. Insessores, 595; characters of, 622; sec- tions of, 624. Integro-pallialia, 401, 403. Inuus, 778. Invertebrate, general characters of, 444. Irish Elk, 716. Irregular Echinoids, 197, 200. Ischiodus, 497, 507. /sis, 169, 185. Isopoda, 283, 302 ; characters of, 304 ; de- velopment of, 304, 305 ; distribution of, in time, 314. Itch-mite, 321. lulidce, 330. lulus, 330. Jxodes, 322. Ixodidce, 322. Jacana, 609. Jackals, 747, 748. Jaguar, 750. Jelly-fishes, 127 ; urticating powers of, 127 ; nature of, 130 ; former classifica- tion of, 127. Jerboa, 759. Jumping-hare, 759. Jumping-mouse, 759. Kakapo, 621. Kangaroo, 659, 662, 663. Kangaroo-bear, 664. Kangaroo-rat, 662, 663. Keratode, 87. Keratosa (Sponges), 87. Keyhole Limpets, 412. King-crabs, 300. Kingfishers, 628, 629. King Vulture, 633. Kinkajou, 741, 742. Kiwi, 598. Koala, 664. Koleops, 243. Koodoo, 719. Labyrinthodon, 523, 524. Lab'yrinthodontia, 512, 522, 523, 524. Lacerta, 549. Lacertidce, 549. Lacertilia, 530 ; general characters of, 545 ; families of, 547-554 ; distribution of, in time, 554. Lady-birds, 362. Lcemodipoda, 283,302; characters of, 303. Lagena, 68, 69. Lagenida, 74. Lagidium, 756. Lagomydce, 754, 760. Lagomys, 754. Lagopus, 614. Lagostomus, 756. Lamellibranchiata, 36", 367, 368 ; general characters of, 396 ; shells of, 397, 398 ; digestive system of, 399; circulatory system of, 400 ; mantle of, 399; bran- chiae of, 400 ; reproduction of, 402 ; muscles of, ib. ; habits of, 403 ; divi- sions of, ib. ; distribution of, in time, 404. Lamellicorn Beetles, 362. INDEX. 833 Lamellirostres, 605. Lammergeyer, 632. Lamprey, 473, 479, 480, 481, 482. Lamp-shells, 388. Lampyris, 362. Lancelot, 462, 474, 477 ; anatomy of, 478, 479. Land-crabs, 311, 312. Land-salamanders, 518. Land-tortoises, 536. Laniidce, 626, 627. Lantern-fly, 348. ; • «• Laomedea, 126. Laornis, 607. Laridce, 603. Lark, 625. Larva, of Echinodermata, 191, 192 ; of Echinoidea, 200 ; of Asteroidea, 204 ; of Ophiuroidea, 206 ; of Crinoidea, 215 ; of Uolothuroidea, 219 ; of Tceniada, 232 ; of Trematoda, 237 ; of Nemertida, 241 ; of Acanthocephala, 243 ; of Gor- diacea, 244 ; of Gephyrea, 256 ; of Tubicola, 265 ; of Errantia, 269 ; of fchthyophthira, 284 ; of Rhizocephala, 286 ; of Cirripedia, 288 ; of Ostracoda, 293 ; of Copepoda, 294 ; of Cladocera, 295 ; of Phyllopoda, 296 ; of Limulus, 300 ; of Macrura, 307 ; of Brachyitra, 312; of Myriapoda, 329 ; of Lnsecta, 341, 342 ; ofPolyzoa, 378 ; of Tunicata, 384, 385 ; of Brachiopoda, 393 ; of Lainelli- branchiata, 402 ; of Gasteropoda, 408 ; of Amphibians, 509, 510, 511, 514, 517, 518, 520. Latisternal Apes, 779. Laurillardia, 629. Leathery Turtle, 535. Leech, 260 et seq. Leiodermatium, 90. Lemming, 758. Lemur, 775. Lemuravidce, 782 Lexwuivus, 782. />«S|Ktf>, 774, 775. Leopard, 750. Lepadtdce, 288 ; characters of, 290 ; dis- tribution of, in time, 313. Lepas, 287, 288, 290. Lepidechinus, 200, 224. Lepidoganoidei, 492, 505. Lepidoptera, 335, 340, 343, 344; mouth of, 337 ; characters of, 355. Lepidosiren, 474, 500, 501, 502, 503 : char- acters of, 500, 501. Lepidosteidce, 492. Lepidosteus, 462, 489, 490, 492, 493. Lepidota (see Dipnoi). Lepidurus, 296. Lepisma, 347. Leporidce, 754, 760. Leptidce, 322. Leptocardia (see Pharyngobranchii). Leptoglossa, 547. Lepus, 754. Lerncea, 43, 284, 285. LesKa, 198. Lestosaurus, 555. Lesueuria, 180. Libellula, 334. Libellulidce, 351. Life, nature and conditions of, 7-13. , 305. Ligula, 337. Limacidce, 415. Limacina, 409. Liniacinidce, 417. Li>napontia, 412. Limaa;, 369, 415. Liinicolce, 263. Limnadia, 41, 296. Limncea, 416. Limnceidce, 415. Limnoria, 305. Limnotheridce. 782. Li'inosa, 611. Limpet, 412. Limulus, 300, 301, 314. Lingua (Insects), 337. Lingual Ribbon (see Odontophore). Linguatulina, 320. Lingula, 388, 389, 390, 393, 395. Lingulidce, 394, 395. Linnets, 626. Lion, 734. Lithistidce, 89, 90. Lithobius, 328, 330. Lithocysts, 137. Lithodomus, 403. Lithornis, 633. Lithostrotion, 175. Littorina, 412. Littorinidce, 412. Lituites, 434. Lituolida, 73. Liver-fluke, 238. Living bodies, characters of, 5-7. Lizards, 527, 530, 545, 546. Llama, 711, 712, 722. Lobster, morphology of, 277 e£ seq1. ; gen- eral anatomy of, 307 ei seg. Lob-worm, 270. Locustidce, 350. Locust-shrimp, 306. Loggerhead Turtle, 533, 534, 535. Loligo, 428, 429. Longicarnia, 362. Longipennatce, 603. Longirostres, 611 Lonsdaleia, 163, 175. Loon, 603. Lophiidce, 488. Lophiodon, 722. Lophobranchii, 488 Lophophpre, 375, 376. Lophopsittacus, 621. Lophopus, 374, 376. Ijophortyx, 614. Lophotragus, 713. Lophyropoda, 283, 292. Loricata, 528. Lorikeet, 621. £om, 774. Lorius, 621. Louse, 345. Love-bird, 621. Loxiadce, 626. Loxosoma, 379. Lucernaria, 137, 138. Lucernariadce, 137. Lucernarida, 37, 111 ; general characters of, 137 ; umbrella of, 137, 141 ; divisions of, 137; development of, 139; structure of reproductive zooids of, 141, 142. G 834 INDEX. Lucinidce, 403, 404. Luidia, 202, 223. Lumbricidce, 262. Lurnbricus, 263. Lutra, 744, 745. Lycaon, 748. Lycosaurus, 568. Lyncus, 751. Lynx, 751. Macacus, 778. M'Andrewia, 90. Macaw, 621. Macellodon, 554. Machairodus, 752. Machetes, 611. Mackerel, 488. Maclurea, 416. Macrauchenia, 699. Macrauchenidce, 699. Macrobiotidce, 320. Macrodactyli, 608. Macropodidce, 662. Macropus, 662. Macroscelidce, 770. Macroscelides, 770. Macrotherium, 678. Macrura, 283 ; characters of, 307 e« seg. Mactridce, 404. Madreporaria, 158. Madreporidce, 164. Madreporiform tubercle, of Echinoidea, 195, 196 ; of Asteroidea, 202 ; of Ophiu- roidea, 206 ; of Holothuroidea, 220. Jlfaia, 310, 311. Makrospondylus, 558. Malacodermata (Zoantharia), 154. Malacopteri, 485. Malacopterygii, 477, 483. Malacostraca, 283, 302. Malapterurus, 485, 486. Mallard, 606. Mallophaga, 345. Malpighian tubes, of Insects, 338. Mammalia, 458, 459; general characters of, 639; osteology of, 640 e£ se#.; teeth of, 648 e£ seg. ; digestive system of, 650 ; circulatory system of, ib. ; respiratory system of, 651 ; nervous system of, 652 ; reproductive system of, 651 ; integu- mentary system of, 652; primary divi- sions of, 654 ; orders of, 656 e£ seg. ; dis- tribution of, in time, 653 et seq. Mammoth, 731, 733. Manatee, 640, 680, 681, 682. Manatidce, 681. Manatus, 640, 681, 682. Mandibles, of Lobster, 281 ; of Arachnida, 316; of Myriapoda, 330; of Insecta, 336; of Cephalopoda, 421; of Verte- brates, 450. Mandrill, 779. Mangue, 746. Manidce, 677. Manis, 648, 652, 673, 677. Mantis, 350. Mantle, of Tunicata, 381 ; of Brachiopoda, 390 ; of Lamellibranchiata, 399 ; of Gas- teropoda, 405 ; of Cephalopoda, 419 ; of Nautilus, 431. Manubrium, 116, 117, 118, 128, 141. Marabout, 611. Mareca, 606. Marginal bodies, of Mcdusce, 129 ; of Lu- cernarida, 137. Marmoset, 776. Marmot, 760. Marsipobranchii, general characters of, 479-481 ; families of, 482 ; distribution of, in time, 504. Marsupial bones, 655. Marsupialia, general characters of, 650 : families of, 661 et seq. ; distribution of, in space, 659 ; in time, 668 et seq. Marsupites, 223. Martens, 744. Martins, 628. Mastax, 249. Mastodon, 728, 731, 732, 733. Maxillae, of Lobster, 281; of Arachnida, 316; of Insecta, 336. Maxillipedes, of Lobster, 281 ; of Centi- pedes, 330. May-flies, 351. Mazonia, 327. Meandrina, 164. Measles, of Pig, 234 ; of Ox, 235. Medusidce, 112 ; structure of, 127, 12S; exact nature of, 130. Megacerops, 699. Megaceros, 716. Megacheiroptera, 765. Megaderma, 764. Megalonyx, 679. Megalosaurus, 567. Megalotes. 748. Megalotrocha, 248. Megapodidce, 615. Megaptera, 688. Megatherium, 679. Melania, 416. Melaniadce, 412, 415. Meleagrince, 614. Meleagris, 614, 618. Meles, 742. Melicerta, 248, 250, 251. Melidce, 742, 743. Meliphagidce, 627. Mellivora, 742. Melolontha, 361. Melonites, 201, 224. Melursus, 740. Membrana nictitans, of Birds, 590 ; of Mammals, 652. Menobranchus, 512, 515, 517. Menopoma, 515, 517. Mentum, 337. Mephitis, 742, 744. Mergulus, 603. Meriones, 759. Meropidce, 629. Merostomata, 283 ; characters and divi- sions of, 299. Merulidce, 627. Mesenteries, of Actinozoa, 152, 155, 160, 165, 175, 179. Mesohippus, 702. Mesopodium, 406, 414. Mesothorax, 335. Metamorphosis, 42 ; of Myriapoda, 329 ; of Insecta, 341 ; incomplete, ib. ; com- plete, 342. Metapodium, 406, 414, 416. INDEX. 835 Metasoraa, 419. Metathorax, 335. Metriophylluin, 175, 185. Mice, 757. Microcheiroptera, 763. Microconchus, 271. Microgromia, 72. Microlestes, 653, 668. Midas, 776. Midge, 355. Miliola, 68, 69. Miliolida, 73, 74. Millepedes, 327, 330. Millepora. 146, 147, 150, 151. Mimicry, 24. Mink, 743. Minnow, 485. Minyas, 155, 180. Miobasilcus, 699. Miohippus, 701, 702. Mites, 320, 321. Mnemia, ISO. Moa, 599, 600. Mole, 766, 767. Mole-cricket, 350. Mole-rat, 757. Mollusca, general characters of, 366-370 ; digestive system of, 366 ; circulatory system of, 367 ; respiratory organs of, ib. ; nervous system of, 368 ; sense-or- gans of, ib. ; reproduction of, ib. ; shell of, 369 ; divisions of, 370. Mollusca Proper, 370 ; characters of, 396; divisions of, ib. Molluscoida, 370; characters and divisions of, 371 et seq. Moloch, 550. Molothrus, 620. Molpadia, 221. Momotus, 629. Monads, 44, 45. Monera, characters of, 61, 62, 100, 101. Monitor, 547, 550. Monkeys (see Quadrumana). Monocystidea, 59. Monodelphia, 655. Monodon, 690. Monograptus, 145. Monomerosomata, 320. Monomyaria, 402. Monothatamia, 69. Monotremata, 641, 642, 643, 652, 655 ; gen- eral characters of, 656 ; distribution of, in space, 657 ; iii time, 659. Mopsea, 169, 185. Moropus, 678. Morotherium, 678. Morphology, 18. - Morse, 738. Mosasauridce, 554, 555. Mosasaurus, 554. Moschidce, 713. Moschus, 713, 716. Mosquitoes, 355. Motacillince, 627. Mother-of-pearl, 369. Moths, 342, 355, 356. Motmots, 629. Moufflon, 720. Mound-birds, 615. Moving filaments of Needham, 422. Mud-eel, 516. Mud-fish, 474, 475, 500. Mud-turtles, 535. Mud-worms, 263, 264. Mugilidce, 488, Mullet, 488. Multi valve shells, 369, 409 411 Muntjak, 711, 715, 716. Murcenidce, 485. Muricidce, 412. Muridai, 757. Mus, 757. Muscicapidce, 626. Muscidce, 355. Musk-deer, 713, 716. Musk-ox, 721. Musk-rat, 768. MusopUagidas, 620, 622 Mussel, 403. Mustela, 743. Mustelidce, 743, 751 Mutilata, 680. Mya, 399, 400, 403. Myacidce, 404. Mycetes, 777. Mycteria, 611 Mydaus, 742. Mygalidce, 325. Myliobatis, 500. Mylodon, 679. Myodes, 758. Myogale, 768. Myogalidce, 768. Myopotamus, 756. Myoxidce, 759. Myoxus, 759. Myriapoda, 228, 274, 275; general charac- ters of, 327 ; development of, 329 ; dis- tribution of, in time, 332. Mynnecobius, 653, 667. Myrmecophaga, 648, 676. Myrmecophagidce, 676, 680. Myrmeleo, 338. Afyrmeleontidce, 351. Jfysis, 306. Mytilidce, 403. Mytilus, 403. Myxine, 480, 481, 482. Myxinidce, 479, 482. Myxinoids, 475. Myxobrachia, 78. Myxodictyon, 61. Myxospongice, 87. Nacreous shells, 369. Naididce, 263, 264. jIVaw, 264. Mya, 541, 542, 543. Narwhal, 689, 690. Nasua, 741. Natatores, 595 ; general characters of, 600 ; families of, 601-606 ; distribution of, in time, 606. Naticidce, 412. Natural selection, 49. Nauplius, 285. Nautactis, 155, 180. Xautilidce, 433, 434, 436. Nautiloid Foraminifera, 70. Nautilus (Pearly), 419, 420 ,421, 425, 426, 430, 431, 434, 435, 436. Nebalia, 296, 297. 362. 836 INDEX. Nectocalyces, structure of, 128 ; in Caly- cophoridce, 132 ; in Medusidce, 128 ; dis- tinguished from the umbrella of the Lucernarida, 137. Neetosac, 128. Needham, moving filaments of, 422. Nematelmia, 229 ; characters of, 242. Xernatocysts, 107. Nematoda, 229, 242 ; characters of, 244 ; parasitic forms of, 245 ; free forms of, 247. Nematophores, 124. Nemertes, 241. Nemertida, 230, 239 ; characters of, 240 ; development of, 241. Neolimulus, 314. Neophron, 632. Nepa, 348, 349. Nephthys, 270. Nereidce, 270. Nereidea, 266. Nereis, 269. Neritidce, 412. Nervures,.335. Nesodon, 727. Nestor, 621. Neuropodium, 257, 267. Neuroptera, 335, 344; characters of, 350. Newts, 511, 517. Nidamental ribbon, 368. Night Heron, 610. Noctilionidce, 764. Noctiluca, 100. Nodosaria, 68, 70. Nonionina, 67. Nothosaurus, 562. Notidanus, 506. Notochord, 446. Notommatina, 251. Notonecta, 349. Notopodium, 257, 267. Notornis, 609. Nototrema, 511. N ucleobranchiata (see Heteropoda). Nucleolus of Paramcecium, 97. Nucleus, of Protozoa, 56 ; of Gregarina, 58 ; of Amoeba, 64 ; of Infusoria, 95, 96 ; of Vorticella, 98 ; of the shell of M ol- lusca, 369. Nudibranchiata, 369; characters of, 412, 413. Numenius, 611. Numida, 614. Nummulina, 71, 72, 77. Nummulitic limestone, 77. Nummulitidea, 74. Nuthetes; 554. Nutria, 745. Nyctereutes, 748. Nycteridce, 764. Nycteris, 764. Nycticebidce, 774. Nyctwebus, 774. Nycticorax, 610. Nyctipithecm, 777. Nymph, 341. Nymphon, 319. Oceanactis, 155, 180. Oceanic Hydrozoa, 131 ; distribution of, in space, 150. Ocelli, of Medusae, 129 ; of Echinoidea, 195; of Asteroidea, 204; of Planarida, 240 ; of Rotifera, 251 ; of Annelida, 259 ; of Chcetognatha, 272 ; of Limulus, 300 ; ofArachnida, 319 ; of Myriapoda, 329 ; of Insecta, 340 ; of Tunicata, 383 ; of Lamellibranchiata, 368 ; of Gastero- poda, 406. Octacnemus, 387. Octodon, 756. Octodontidce, 756, 760. Octopoda, 427. Octopodidce, 427. Octopus, 423, 435. Oculinidce, 164. Ocydromus, 612. Ocypoda, 311. Odontaspis, 506. Odontoceti, 685, 688. Odontolcce, 634. Odontophora, 396, 405. Odontophore, 396, 405, 407, 417, 421. Odontopteryx, 583, 607. Odontornithes, 584, 594, 634. Odontotormce, 634. CKdicnemus, 612. (Edipoda, 350. Oidemia, 606. Oldhamia, 150, 380. Oligochteta, 262, 263. Oligoporus, 201, 224. Omnivora ( Ungulata), 704. Omphyma, 175. Onager, 701. Onchuna, 284. Onchus, 505. Oncidiadce, 415. Oncinolabidce, 221. Oniscus, 305. Ontogenesis, 22. Onychophora, 329, 331, 332. Onychoteuthis, 419, 435. Oflcyst, 375. Operculata, 415. Operculum, of Balanidce, 289 ; of Gaster- opoda, 406 ; of Fishes, 464. Ophiderpeton, 523. Opkidia, 530; general characters of, 537 e£ seg-.; divisions of, 541 ; distribution of, in time, 544. Ophidobatrachia, 513. Ophiocoina, 207. Ophiomorpha, 513. Ophisaurus, 548. Ophiura, 207. OpkiuridcK, 207. Ophiuroidea, 192 ; general characters of, 205; families of, 207; distribution of, in space, 222 ; in time, 224. Opisthobranchiata, 411, 412, 415. Opisthoccelia (Crocodilia), 557, 558. Opisthodelphys, 522. Opossum, 664, 666. Opossum-shrimp, 306. Orang-utan, 780, 781. Orbitoides, 77. Orbitulitidea, 74. Orca, 690. Orcella, 690. Oreaster, 224. Oreastridte. 205. Oreodon, 70S. INDEX. 837 Oreodontidce, 707, 722. Organ of Bojanus, 392, 401. Organ-pipe Corals, 167. Organic and inorganic matter, differences between, 2. Organs of the mouth of Insects, 336 et seq. Oribatidce, 322. Oriole, 627. Ornithodelphia, 655. Ornithorhynchus, 648, 652, 655, 656, 657, 658. Ornithosaiiria, 563, 565. Orohippus, 701, 702. Orthoceras, 434, 436. Orthoceratidce, 436. Orthoptera, 336, 340, 344; characters of, 349. Ortonia, 271. Orlyx, 614. Orycteropidce, 677. Orycteropus, 673, 677, 678. Oscula, of Sponges, 83, 87 ; of Tapeworm, 231, 233. Osteolepis, 491, 505. Ostraciontidce, 488. Ostracoda, 283 ; characters of, 293 ; dis- tribution of, in time, 313. Ostracostei, 492, 449, 505. Ostrea, 403. Ostreidce, 403. Ostrich, 577, 578, 581, 583, 594, 595, 596. Ostrich (American), 596. Otarladce, 736, 737, 738. Otidce, 612. Otter, 744. Oudenodon, 563. Ounce, 751. Ovarian vesicles of Sertularida , 122, 123. Ovibos, 721. Ovicells (Polyzoa], 375. Ovidce, 718, 719, 723. Ovipositor, 336, 357, 358. Ovis, 720. Ovulitidea, 74. Owls, 630, 631. Oxen, 720, 721. Oxyuris, 245, 246. Paca, 755. Pachycardia, 478. Pachydermata, 692. Pachyglossa, 547. Paddle-fish, 494. Paguridce, 310. Pagurus, 310. Palceaster, 223. Palcechinus, 200, 224. Palceichthyes, 503. Palceocastor, 760. Palceocaris, 314. Palceocoryne, 150. Palseocrinoids, 210, 223. Palcpodiscus, 223. Palceogithalus, 629. Palceonyctis, 751. Palceophis, 544, 545. Palceortyx, 618. Palceosiren, 524. Palceotheridce, 699. Palceotherium, 699. Palceotringa, 612. Palamedea, 609. Palapteryx, 599. PaUnurus, 307. Pallial line, 399, 401. Pallial sinus, 401. Palliobranchiata, 388. Pallium (see Mantle). Palmipedes, 600. Paludicella, 376, 379. Paludina, 416. Paludinidce, 412, 415. Palythoa, 157. Pamphagus, 65. Panda, 741. Pangolin, 677. Panorpidce, 351. Panspermy, 45. Panther, 750. Pantopoda, 319. Paper Nautilus (see Argonaut). Paradiseidce, 625. Paradoxurus, 746. Paramcecium, structure of, 95-97 ; repro- duction of, 97. Paramuricea, 174. Parapodia, 257. Paridce, 626, 627. Parkeria, 76. Parra, 609. Parrakeets, 621. Parrots, 576, 580, 583, 586, 619, 620. Parthenogenesis, 38 e£ seg. Partridge, 614. Pasceolus, 388. Passeres, 622. Patella, 409. Patellidce, 412. Pauropoda, 329, 330. Pauropus, 327, 328, 329, 330, 331. Pa«o, 615. Pavonaria, 168. Pavonince, 614 Peachia, 154, 155, 157. Pea-fowl, 615. Pear-enerinites, 212, 223. Pearl-mussels, 403. Pearly Nautilus, 420, 421, 425, 426, 430 ; anatomy of, 431; distribution in space, 435. Peccary, 707. Pecten, 403. Pectinaria, 265, 266. Pectinatella, 374. Pectunculus, 397. Pedation, 251. Pedetes, 759. Pedicellarise, 196, 202. Pedicellina, 376, 379. Pediculus, 345, 346. Pedipalpi, 323. Pelagia, 138. Pelagidce, 137, 138, 139 ; structure of generative zooids of, 141. Pelagoneinertidce, 242. PeZias, 539, 541. Pelican, 604. Pelicanidce, 604. Pelonaia, 369, 387. Peltogaster, 286. Pen of Cuttle-fishes, 425, 429. Peneus, 307. Peneroplidea, 74. 838 INDEX. Penguin, 574, 587, 601, 602. Peniculus, 284. Pennatula, 167, 168. Pennatulidce, 166, 167, 169, 180 ; distribu- tion of, in time, 185. Pentacrinus, 212, 213, 222, 223. Pentacta, 220. Pentamera (Coleoptera), 362. Pentameridce, 394. Pentastoma, 320. Pentastomida, 320. Pentatoma, 349. • Pentremites, 217, 218, 223. Perameles, 663. Peramelidce, 665. Peranema, 100. Peratherium, 670. Perca, 463, 468, 484. Perch, 484, 488. Perchers, 622. PercidcK, 488. Perdicidce, 614. Perdix, 614. Perennibranchiata (Amphibia), 510, 511, 515, 516, 517. Perforata(Foraminifera),66, 73; (Corals), 164, 185. Pericardium, of Crustacea, 282 ; of Nauti- lus, 432. Peridinium, 100, 102. Perigastric space of Polyzoa, 376. Periostracum, 369. Peripatus, 329, 331, 332. Perischoechinidce, 200, 224. Perissodactyla, 693. Peristome, of Vorticella, 98 ; of the shell of Gasteropoda, 410. Peristomial space of Actinia, 155. Peritoneum (Tunicata), 382. Perivisceral space of Actinozoa, 151, 152. Periwinkle, 412. Perlidce, 351. Perodicticus, 774. Peromela, 513. Petalodus, 506. Petaurus, 664. Petraster, 223. Petrel, 603. Petrogale, 663. Petromyzon, 480, 482. Petromyzonidce, 479, 482. Pezophaps, 618. Pezoporince, 621. Phacochcerus, 707. Phcenicopteridce, 606. Phcenicopterus, 606. Phaeton, 604. Phalacrocorax, 604. Phalcena, 342. Phalangers, 665. Phalangidce, 322. Phalangista, 665. Phalangistidce, 665. Phalangium, 323. Phalansterium, 93, 100. Phanogenia, 216. Pharyngobranchii, 477, 504. Pharyngognathi, 488. Pharynx, of Ascidians, 382, 384, 385 ; of Lancelot, 471, 478. Phascolarctos, 664. Phascolomys, 661. Phascolosoma, 256. Phascolotherium, 653, 669. Phasianidce, 614. Phasianus, 614. Phasmidce, 340, 350. Pheasant, 614. Phillipsia, 314. P/ioca, 737, 738. Phoccena, 689, 690. Phocidce, 737. Pholadidce, 369, 404. Pholas, 396, 403. Phormosoma, 200, 224. Phoronis, 266. Phosphorescence of the sea, 101. Phragmacone, 369 ; of Spirula, • 429 ; of Belemnite, 430. Phryganeidce, 351. Phrynus, 325. Phylactolcemata, 378, 379. Phyllidiadce, 412. Phyllirrhoidce, 413. Phyllium, 25. Phyllocyst, 132. Phyllopoda, 283 ; characters of, 295, 296 ; distribution of, in time, 313. Phyllosoma, 307. Phyllostoma, 764. Phyllostomidce, 764, 765. Phyogemmaria, 136. P%m, 416. Physalia, 109, 131, 135, 136. Physalus, 688. Physeter, 688. Physeteridce, 688. Physiology, 18. Physopftora, 135. Physophoridce, 1 31 ; characters of, 134 e£ se<7. ; tentacles of, 134 ; reproduction of, 135 ; distribution of, in space, 150. Physostomata, 485. Picidce, 619, 620. Piddock, 403. Pieris, 356. Pigeons, 616, 617. Pigment-spot, of Infusoria, 100 ; of /?ota- /era, 251. Pikas, 754. Pike, 485. Pilidium, 239, 241. Pill-millepede, 330. Pinna, 403. Pinnigrada, 735, 736, 751. Pinnipedia, 734, 735, 751. Pintail Duck, 606. Pipa, 591, 521. Pipe-fish, 488. Pipidce, 521. Pipistrelle, 763. Pipits, 627. Pisces, 457; general characters of, 463; scales of, i&. ; skeleton of, 464 e£ seg ; limbs of, 466-469; tail of, 469-471; respiratory system of, 471-473 ; heart of, 473; digestive system of, 474; swim- bladder of, 475 ; nervous system of, ib. ; reproductive system of, 476 ; orders of, 477 e« seg.; distribution of, in time, 504 Pithecia, 777. Pitheciidce,. 777. Placenta, 654. INDEX. 339 Placentalia (Mammalia'), 654, 655. Placodus, 562. Placoganoidei, 492, 493, 505. Placoid scales of Fishes, 461, 462, 495. Placoidei, 477. Plagiaulax, 654, 669. Plagiostomi, 496, 497, 498. Planaria, 239. Planarida, 239, 240. Pla.norbis, 409, 415. Plantain-eaters, 620, 622. Plantigrada, 735. Plant-lice, 348. Plants and animals, differences between, 13. Planula, 118. Plasmopora. 172. Plastron, 531, 532, 533. Platalea, 611. Plataleadce, 611. Platanista, 690. Platycrinus, 211. Platyelmia, 229 ; characters of, 230. Platijrhina, 772, 775, 782. Plecotus, 763. Ptectognathi, 488. Plectropterus, 576. Plesiosauria, 561. Plesiosaurus, 561, 562. Pleura, of Lobster, 279 ; of Trilobite, 299. Pleuracanthiis, 506. Pleurobrachia, 176 ; ctenophores of, 177 ; canal-system of, 177 ; development of, 178 ; homologies of, ib. Pleurobranchidce, 412. Pleuronectes, 470, 471. Pleuronectidce, 486. Pleuronema, 100. Pliohippus, 701, 702. Pliopithecus, 782. Plotactis, 180. Pfofrws, 605. Ploughshare-bone, 575. Plumaster, 223. Plumularia, 124. Pluteus, 192, 2i iO. Plyctolophus, 621. Pneumatic filaments of Physophoridce, 135. Pneumatocyst, 134. Pneumatophore, 134, 135. Pochard, 606. Pocillopora, 162, 164. Podophrya, 99, 101. Podophthalmata, 302 ; characters of, 305. Podosomata, 319. Podura, 336, 345, 346. Poebrotherium, 722. Poecilasma, 287. Poephaga, 662. Poephagus, 721. Pole-cat, 743. Polian vesicles, 196. Polistes, 40, 41. Polyarthra, 251. Polyccelia, 175, 185. Polycystina, 77, 79, 80. Polydesmus, 330. Polygastrica (of Ehrenberg), 97. Polymorphinidea, 74. Pohjnoe, 268. Polypary, 100. Polype, 153. Polypide, 373. Polypidom, 110. Polypite, 110. Polyplectron, 614. Polyprotodontia, 661, 665. Polypterus, 489, 490, 491, 492, 493. Polystome Infusoria, 99. Polystomella, 71. Polystomellidea. 74. Polythalamia (Foraminifera), 70. Polytrema, 76. Polytre'tnacis, 172, 185. Polyzoa, ,366, 367, 368 ; characters of, 371 ; distinctions from Hydrozoa, 371, 372 ; typical polypide of, 373 ; avicularia of, 374 ; lophophore of, 375 ; digestive sys- stem of, 376; nervous system of, 377; reproduction of, «'&. ; statoblasts of, 377, 378; development of, 378; divi- sions of, i&. ; affinities of, 379 ; distri- bution of, in space and time, 379, 380. Polyzoarium, 372. Pond-snails, 415. Pontarachna, 322. Pontobdella, 262. Pontoporia, 690. Porcellana, 311. Porcellanous shells, 369.' Porcellia, 416. Porcupine, 755. Porous, 706. Pores of Sponges, 84, 86. Porifera, 83. Porites, 184. Poritidce, 164. Porocidaris, 194. Porpita, 135. Porpoise, 689. Port Jackson Shark, 498. Portuguese man-of-war. 109, 131, 134,135, 136. Potamochcerus, 706. Potamogale, 768. Potamogalidce, 768. Potoroo, 662. Pouched Marmots, 760. Pouched Rats, 757. Poulpe, 427. Prcearcturus, 314. Prairie Dog, 760. Praya, 133. Preabytis, 778. Pressirostres, 608, 611. Prestwichia, 314. Primates, 761. Primnoa, 174. Priodontes, 675, 676. Pristis, 500. Proboscidea, characters of, 728 ; distribu- tion of, in time, 733. • Proboscis, of Medusce, 128 ; of Crinoidea, 209 ; of Planarida, 239 ; of Nemertida, 240 ; of Acanthocephala, 243 ; of Ge- phyrea, 255 ; of Errantia, 267 ; of l doptera, 337 ; of Proboscidea, 729. Proboscis Monkey, 778. Procellaridce, 604. Prochilus, 740. Proecelia (Crocodilia), 557. Procyon, 741. Procyonidce, 741, 751. 840 INDEX. Productidce, 394, 395. Proglottis, 231, 232, 284. Pro-legs, 356. Promeropidce, 627. Prong-buck, 718, 719. Pro-ostracum, 430. Propodite, 279. Propodium, 406, 414. Propora, 172. Prorastomus, 683. Prorhynchus, 241. Proseolex, 232, 234. Prosimice, 773. Prosobranchiata, 411. Prosoma, 419. Prostomium, of Planarida, 239 ; of Anne- lides, 258 Protanweba, 61, 62. Protaster, 224. Proteles, 747. Protelidce, 747. Proteolepas, 292. Proteus, 512, 515, 516. Proteus-animalcule, 63. Prothorax, 335. Protobathybius, 62. Protococcus, 14. Prot.ogenes, 61. Protohydra, 112. Protolabis, 712. Protomyxa, 62. Protoplasm, 8, 9. Protopodite, 279. Protopterus, 502. Protomis, 629. Protorosauria, 547. Protorosaurus, 554. Protovirgularia, 185. Protozoa, 14, 20 ; general characters of, 56 e< se?. ; classification of, 57 e« se?. Proventriculns, of Earthworm, 263 ; of Birds, 584. Psammodus, 506. Pseudembryo, 191. Pseudobranchia, 491. Pseudochlamys, 65. Pseudohsemal system, 258. Pseudo-hearts, 391. PseudonavieellR', 59, 60. Pseudopodia, 57, 61, 64, 67, 77, 78, 79, 81, 85. Pseudopus, 545, 548. Pseudoscorpionidce, 322. Pseudoneuroptera, 351. Psittacidce, 619, 620. Psittacus, 621. Psolus, 221,224. Psorospermice, 60. Ptarmigan, 614. Pteranodon, 564, 565. Pteraspis, 494, 504, 505. Pterichthys, 494, 505. Pteroclidce, 615. Pterodactylus, 564, 565. Pterodon, 752. Pteromys, 760. Pteronarcys, 340. Pteropidce, 763, 765. Pteropoda, 367, 396, 405 ; general charac- ters of, 416 ; foot of, t'6. ; shell of, 417 ; divisions of, ib. ; distribution of, in space and time, 417, 418. Ptcropus, 765. Pterosauria, 530; general characters of 563 ; distribution of, in time, 565. Pterygotus, 301, 302, 314. Ptilocercus, 770. Ptilodictya, 380. Ptilograptus, 144, 150. Ptilopora, 380. Ptychoceras, 434, 437. Puff-adder, 542. Puffin, 603. Pulex, 353. Pulicidce, 353. Pulmogasteropoda, 407, 411, 414. Pulmonata (MollusccC), 411. Pulmonifera (Mollusca), 411, 414. Pulmotrachearia, 325. Puma, 750. Pupa, 341, 342, 356. Ptt^a, 416. Pupipara, 355. Purples of wheat, 247. Putorius, 743. Pycnogonum, 319, 321. Pygidium, 297, 299. Pyramidellidce, 412. Pyrgia, 165. Pyrgita, 626. Pyrosoma, 387. Pyrrhula, 626. Python, 537, 543. Pythonina, 543. Pythonomorpha, 555. Quadrate bone, 526, 537, 570. Quadrula, 65. Quadrumana, characters of, 771 ; sections of, 773-777; distribution of, in time, 781. Quagga, 701. Quail, 614. Rabbit, 754. Racoon, 741. Madiata, 105. liadiolarm, 58 ; characters of, 77. Radula (see Odontophore). .Raia, 499. Rail, 609. .RaZZtur, 609. ^an«, 519, 520, 522. Raniceps, 525. Ranidce, 521, 522. Raptores, 585, 595 ; characters of, 630 ; sections of, ?'&.; distribution of, in time, 633. Rasores, 595 ; characters of, 612 ; sec- tions of, 613 ; distribution of, in time, 618. Rat, 757. Ratel, 742. RatitCK, 591, 594, 595. Rattlesnake, 539, 540, 541, 542. Rays, 494, 495, 497, 499, 500, 506. Razor-bill, 603. Razor-shells, 404. Receptaculites, 76. Red Coral, 169, 170, 181. Red Deer, 716. Redshank, 611. Redstart, 627. Regnum Protisticum, 14. Regular Echinoids, 197, 200. INDEX. 841 Keiudeer, 715, 716. Renilla, 169. Reproduction, general phenomena of, 32 et seq. ; sexual, ib. ; non-sexual, 33 et seq. Reptilia, 457 ; general characters of, 526 : jaw of, 527; teeth of, 528; circulation of, ib., 529; respiration of, ib., 530; orders of, ib. et seq. Respiratory tree of Holothurians, 220, 221. Respiratory tubes of Rotifera, 250. Reticulosa (see Foramlnifera), 67. Reversed shells, 370, 398. Rhabdoccela, 240. Rhabdoidea, 74. Rhabdophora, 144. Rhabdopleura, 375, 376, 378, 379. Rhamphastidce, 620, 621. RhamphorhyncJms, 565. Rhea, 596. Rhinatrema, 515. Rhinobatis, 500. Rhinocerotidcc, 695. Rhinoceros, 695, 696, 697. Rhiuolophidce, 764. Rhinolophus, 764. Rhinophrynus, 521. Rhipidogorgia, 170. Rhizocephala, 283 ; characters of, 285. Rhizocrinus, 208, 209, 212,. 222. Rhizophaga, 661. Rhizophylluiii, 175. Rhizopoda, 58 ; characters of, 61 ; pseudo- podia of, i&. ; divisions of, ib. Rhizostoma, 143, 144. RhizostomidcK, 137 ; definition of, 139 ; development of, 139 ; structure of re- productive zooids of, 140. Rhodope, 413. Rhombus, 487. Rhopalocera, 356. Rhynchocephalia, 553. Rhynchoceti, 685, 691. Rhynchonella, 389, 395. Rhynchonellidce, 389, 394, 395. Rhynchophora, 362. Rhynchosaurus, 554, 5*53. Rhynchota (see Hemiptera). Rhytina, 648, 681, 683. Rhyzcena, 746. Ribbon-worms, 240. Right Whale, 686, 687. Ringed Snake, 543. River-snails, 412. Roach, 485. Robins, 627. Robulina, 70. Rock-kangaroos, 663. Rock-slaters, 305. Rock-snakes, 543. Roebuck, 715, 716. Rodentia, general characters of, 752 ; fa- milies of, 754 et seq. ; distribution of, in time, 760. Rorqual, 688. Rot of Sheep, 238. Rotalia, 70 Rotalidea, 74. Rotatoria (see Rotifera). Rotifera, 10, 229 ; characters of, 248 ; wheel-organ of, 249 ; masticatory or- gans of, ib.; water-vascular system of, 250; affinities of, ib. ; vitality of, 10; distinctions from Infusoria, 252. Round-worms, 244. Rucervus, 715. Ruff, 611. Rugosa, 154 ; characters of, 173 ; families of, 175 ; distribution of, in time, 185. Ruminantia, 692, 703 ; characters of, 708 ; dentition of, 709 ; families of, 711-721 ; distribution of, in time, 722. Rupicapra, 719. Rusa, 714, 715. Sabella, 265. Sabellaria, 264, 265. Sabeltidce, 266. Sable, 743. Saccammina, 76. Saccomydce, 757. Saccosoma, 223. Saccutina, 286. Scemiridce, 263. Sagitta, 'ill, 272. Saki, 777. Salamanders, 516, 517, 518, 524. Salamandra, 518. Salamandrdla, 525. Salmon, 485. Salmonidce, 485. Salpidce, 387. Sand-crab, 311. Sand-grouse, 615. Sand-hopper, 304. Sand-lizard, 549. Sand-pipers, 611. Sand-stars, 205. Sand-worms, 267. Sanguisuga, 262. Sapajou, 777. Sarcode, 56. Sarcodictyon, 166. Sarcoids of Sponges, 84, 85, 86, 87. Sarcophaga, 667. Sarcophyton, 167. Sarcopsylla, 353. Sarcoptes, 321. Sarcorhamphus, 633. Sarsia, 130. Sauranodon, 560. Satiria, 546. Saurillus, 554. Saurobatrachia (see Urodela). Sauropsida, 459, 526. Sauropterygia, 530; general characters of, 561 ; distribution of, in time, 562. Saurornithes, 504. 633. Saururoe, 594 ; characters of, 633. Saw-fish, 500. Saw-flies, 357, 358. Scalaria, 413. Scale-insects, 348. Scallop, 402, 403. Scalops, 767. Scalpellum, 291. Scansores, 595 ; characters of, 619 ; fami- lies of, 620. Scaphirhynchus, 489, 490, 494. Scaphites, 436. Scaphognathite, 281. Scaphopoda, 412. Schizognathce, 578. Scincidce, 548, 549. 842 INDEX. Scincus, 549. Sciuridce, 759, 760. Sciuropterus, 760. Sciurus, 759. Sclerenchyma, 159. Sclerites, 170. Sclerobasica (Zoantharia), 154, 157, 185. Sclerobasic corallum, 158, 159. Sclerodermata (Zoantharia), 154, 168; divisions of, 164, 165. Sclerodermic corallum, 159, 160. Sclerogenidce, 488. Sclerostoma, 245, 246. Scolecida, 227 ; characters and divisions of, 229 et seq. Scolex, 232, 233, 234, 235. Scolopacidce, 611. Scolopendra, 329, 330. Scomberidce, 488. Scorpion, 314, 316, 317, 323, 324, 327. Scorpion-flies, 351. Scorpionidce, characters of, 324; distribu- tion of, in time, 327. Screamer, 609. Scutigera, 329. Scyllaridce, 277. Scyphistor>na, 140. Scythrops, 620. Sea-anemones, 154. Sea-cows, 681. Sea-cucumbers, 218. Sea-firs, 121. Sea-hares, 412. Sea-horses, 488. Sea-lemons, 413. Sea-mouse, 267, 270. Sea-otter, 745. Sea-pens, 167. Sea-shrubs, 169. Sea-slugs, 412. Sea-spiders, 319. Sea-worms, 267. Seals, 737, 738. Secretary Bird, 633. Segmental organs of Leeches, 260 ; of Earthworm, 263 ; of Errant Annelides, 258. Selachii, 498. Selenaria, 374. Selenodonts, 703. Semnopithecus, 778. Sepia, 425, 435. Sepiadce, 429, 437. Sepiola, 419,435. Sepiostaire, 425. Septa, of Corals, 160 ; of the shell of Tetra- branchiate Cephalopods, 431, 433. Serpentarius, 633; Serpents (see Snakes). Serpula, 264, 265, 266. Serpulites, 271. Sertularia, 122. Sertularida, 111, 112 ; characters of, 121 ; hydrothecae of, 122 ; polypites of, ib. ; reproduction of, 123, 124 ; distribution of, in space and time, 150. Setse of Annelides, 258, 259, 263, 264, 267. Sexual selection, 49, 50. Sharks, 473, 477, 494, 495, 497, 498, 499, 506. Sheat-fishes, 486. Sheep, 719, 720. Sheep-ticks, 355. Shell of Mollusca, 368-370 ; of Brachio- poda, 388, 389 ; of Lamellibranchiata, 396-399; of Gasteropoda, 409-411; of Heteropoda, 414; of Pteropoda, 417; of Argonauta, 426, 427 ; of Nautilus, 426, 431 ; of Tetrabranchiate Cephalopods, 432. Sheltopusiks, 548. Shield-slaters, 305. Ship-worm, 404. Shoveller, 606. Shrew-mice, 768. Shrew-mole, 767. Shrikes, 626, 627. Sialidce, 351. Siamang, 780. Sieboldia, 517. Silicispongice, 88, 89, 93. Siluridce, 486. Silurus, 486. Simia, 780. Simosaurus, 562. Sinupalliatia, 401, 403. Siphonia, 93. Siphonida, 403. Siphonophora, 111 ; characters of, 131 ; divisions of, 131 et seq. Siphonops, 514, 515. Siphonostomata (Gasteropoda), 410, 411, 416. Siphons, of Lamellibranchiata, 401 ; of Gasteropoda, 508. Siphuncle, of the shell of Nautilus, 426, 431, 432, 433 ; of Spirilla, 429 ; of fielem- nites, 430 ; of Tetrabranchiata, 433 ; of Orthoceras, 434. Sipunculoidea, 255. Sipunculus, 255, 256. Siredon, 516, 517 Siren, 512, 515, 516. Sirenia, 640, 643, 646 ; characters of, 680 et seq. ; distribution of, in time, 683. Sirenidce, 515. Sirenoidei (Dipnoi), 503. Sirex, 359. Siricidce, 357. Sitta, 627. Sivatherium, 712, 723. Skates, 473, 499. Skink, 549. Skunk, 744. Slaters, 305. Sloth, 640, 641, 673, 674, 675. Sloth-animalcules, 320. Slow Lemurs, 774. Slow-worm, 548. Slugs, 414, 415. Smynthurus, 346. Snails, 414. 415. Snake-birds, 605. Snakes, 527, 537, 538, 539, 540, 541, 542, 543, 544, 545. Snapping-turtle, 536. Snipe, 611. Soft Tortoises, 535. Solanocrinus, 223. Solaster, 205. Sole, 486. Solenidce, 404. Solenodon, 725. INDEX. 843 Solipedia (see Solidvngula). Solitaire, 618. Solpugidce, 323. . Somateria, 606. Somatic cavity, of Caelenterata, 106, 107 ; of Hydrozoa, 106, 109 ; of Hydra, 113 ; of Actinozoa, 107, 151. Somatocyst, 131. Somite, 274; of Crustacea, 279 ; of Arach- nida, 315. Sorex. 768. Soricidce, 768, 771. Spalacidw, 757. Spalacotherium, 654. Spalax, 757. Sparrows, 626. Spatularia, 489, 490, 494. Species, definition of, 27, 28; origin of, 47-50. Spectacled Bear, 740. Spermatophores, 422. Spermophilus, 760. Sperm-whale, 688. Sphseridia, 196. Sphcerogastra, 325. Sphceroma, 305. Sphcerozoum, 80. Sphcerularia, 244. Sphagodus, 506. Sphargis, 535. Spheniscidce, 601. Spheniscus, 602. Sphenodon, 553. Sphingurus, 756. Spicula, of Sponges, 87, 88, 89, 90 ; of Jta- diolaria, 78. 80 ; of Actinozoa, 157, 166, 167, 168, 169, 170. Spider-crab, 310, 311. Spider-mites, 322. Spider-monkey, 777. Spiders, 314, 315, 316, 317, 325, 326, 327. Spinax, 496, 497. Spinnerets, of Spiders, 326; of Caterpillars, 328. Spio, 108. Spin/era, 394. Spiriferidce, 394, 395. Spirillinidea, 74. Spirorbis, 265, 266, 271. Spirula, 425, 429, 435. Spirulidce, 429. Sponge-crab, 311. Spongia, 87. Spongida, 83 ; skeleton of, 87, 88 ; sarcoids of, 84, 85 ; aquiferous system of, 86 ; reproduction of, 90; development of, 91 ; classification of, 93 ; distribution of, in space, 92 ; in time, ib. Spongilla, 87, 90, 92; reproduction of, 90. Spoon-bill, 611. Spoon-worms, 254, 255. Sporosac of Corynida, 115. Spring-tails, 346. Squalidce, 499. Squalodon, 691, 692. Squamata (Reptilia), 528. Squamulinidea, 74. Squids, 429. Squitta, 306. Squirrel, 759. Squirrel Monkey, 777. Staggers of Sheep, 235. Stagonolepis, 558. Staphylinidce, 362. Starlings, 625. Star-nosed Mole, 767. Statoblasts, 35, 377. Stauria, 173, 175, 185. Stauridce, 175, 185. Stauridia, 118. Steatornis, 629. Steganophthalmata (Medusae), 127, 128, 137, 138, 140, 144. Stellerida, 201. Stellio, 550. Stem-muscle of Vorticella, 98. Stemmata (see Ocelli). Stenaster, 223. Steneofiber, 760. Steneosaurus, 558. Stenops, 774. Stenostomata, 179, 180. Stentor, 16, 99, 100. Stephanoceros, 248, 251. Stephanoscyphus, 127. Sterelmintha, 237. Stereognathus, 653, 669. Sternum, of Crustacea, 279 ; of Arach- nida, 315 ; of Chelonia, 353 ; of Aves, 578 ; of Mammalia, 642. Stick-insects, 350. Stigmata, of Physophoridce, 135 ; of Leeches, 260; of Arachnida, 318; of Insecta, 339. Sting-rays, 500. Stolons, of Foraminifera, 70 ; of social Tunicata, 386. Stomapoda, 283 ; characters of, 306 ; de- velopment of, ib. ; distribution of, in time, 314. Stomatodendra, 142, 143. Stone-chat, 627. Stone-flies, 351. Stork, 611. Strepsilas, 611. Strepsiptera, 335, 360, 361. Strepsirhina, 772, 773. Streptospondylus, 558. Strigidce, 630. Strigops, 621. Strix, 631. Strobila, of Rhizostomidce, 140 ; of Tceni- ada, 233, 234. Stromatopora, 76. Strombidce, 368, 406, 412. Strombodes, 175. Strongylocentrotus, 194. Strophomenidce, [394, 395. Struthio, 596. Struthionidce, 596. Sturgeon, 470, 493. Sturionidce, 493, 494. Sturnidce, 625. Stylaster, 149. Stylasteridce, 147. Stylinodontia, 725. Stylops, 360. Sub-brachiata, 486. Sub-kingdoms, 21. SfoZmto, 716. Suchosaurus, 558. Suctoria (Infusoria), 94, 95, 99. , 705, 722. 844 INDEX. Sula, 604. Sun-bear, 740. Sun-birds, 627. Surf-duck, 606. Surinam Toad, 521. Sus, 705, 706. Swallow, 628, 629. Swan, 605, 606. Swifts, 583, 628, 629. Swim-bladder of Fishes, 475. Swimmerets of Lobster, 279, 309. Swimming-bells, 132. Sycandra, 84, 85. Sycon, 88. Syllidea, 260. Syllis, 269. Sylviadce, 626, 627. Symborodon, 699. Sympodium, 167. Synapticulse, 161. Synaptidce., 219, 222. Syndactyli, 629. Syndendrium, 142. Syngnathidce, 488. Syringoporidce, 185. Syrinx, 255. Syrinx, 591. Tabanidce, 355. Tabulse of Corals, 161, 162. Tabulata, 164. Tabulate Corals, 164. Tachyglossus, 657, 658. Tachypetes, 604. Tadpole, 520. Tcenia, 230, 231, 233, 234, 235, 236. Tceniada, 229 ; characters and develop- ment of, 230 et seq. Talitrus, 304. Talpa, 766, 767. Talpidce, 766, 771. Tamandua, 677. Tamias, 760. Tanagridce, 626. Tanais, 303, 305. Tank-worms, 246. Tantalince, 611. Tape-worm (see Tcenia). Tapir, 698. Tapiridce, 697, 721. Tapirus, 693, 696, 697, 698, 722. Tardigrada, 319, 320. Tarsiidce, 774. Tarsius, 774. Taxidea, 742. Teal, 604. Tectibranchiata, 412. Teqenaria, 316, 317. Teleodactyla, 694. Teleosaurus, 558. Teleostei, characters of, 482 e£ se^. ; sub- divisions of, 485 et seg. ; distribution of, in time, 507. Telephorus, 362. Telerpeton, 554. Tellinidce., 404. Telmatornis, 612. Telson, of Crustacea, 276; of Lobster, 279 ; of Limulus, 300, 301 ; of Scorpion, 324. Tenebrionidce, 362. Teurec, 769. Tentacles, of Hydra, 112, 113 ; of Tubula- ria, 120; of Calycophoridce, 132; of Physophoridce, 134 ; of Medusidoe, 129 ; of Hydra-tuba, 139 ; of Actinia, 155 ; of Alcyonaria, 165; of Pleurobrachia, 177 ; of Holothuroidea, 220 ; of Polyzoa, 375 ; of Tunicata, 381 ; of Cuttle-fishes, 419, 428. Tentaculites, 271, 418. Tenthredinidce, 357. Tenthredo, 358. Tenuirostres, 624, 627. Terebella, 265. 266. Terebratula, 391. Terebratulidce, 394, 395. Terbratulina, 392, 393. Teredo, 404. Tergum, of the exoskeleton of Crustacea, 279; of Arachnida, 315. Tern, 603. Terricola, 262. Termites, 343; communities of, 351. Terrapin, 535, 536 Test, of Foraminifera, 66, 68 ; of £c/