QL #6 NOV 11 1930 Vor CORNELL UNIVERSITY THE Hlower Veterinary Library FOUNDED BY oT. ROSWELL P. FLOWER for the use of the N. Y. STATE VETERINARY COLLEGE 1897 This Volume is the Gift of Dr. P. A. Pish. 5577 eo University Library iii | QL 48.N xt-book of zoology for schoo il wi Cornell University Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http :/Awww.archive.org/details/cu31924001022429 TEXT-BOOK OF ZO Ee FOR SCHOOLS AND COLLEGES. BY H. ALLEYNE NICHOLSON, M.D, D.Sc, M.A, Pu.D., F.R.S.E, F.G.8, Erc, PROFESSOR OF NATURAL HISTORY AND BOTANY IN UNIVERSITY COLLEGE, TORONTO} FORMERLY LECTURER ON NATURAL HISTORY IN THE MEDICAL 8CHOOL OF EDIN- BURGH; AUTHOR OF “MANUAL OF ZOOLOGY FOR THE USE OF STUDENTS,” “TEXT-BOOK OF GEOLOGY,” “INTRODUCTORY TEXT-BOOK OF ZOOLOGY,” “GEOLOGY OF CUMBERLAND AND WESTMORELAND,” ETO., ETO. NEW YORK: D. APPLETON AND COMPANY, 1, 83, anv 5 BOND STREET. 1884, ¢> 27/4 lex 89 Mt. /09 v0 ENTERED, according to Act of Congress, in the year 1871, by D. APPLETON & CO., In the Office of the Librarian of Congress, at Washington, PREFACE. In bringing out a Text-book of Natural History, intended mainly for the use of schools, there are a few remarks which it may be as well to make by way of preface, if only to ex- plain the principles upon which the work has been written. In the first place, more space has been devoted, compara- ’ tively speaking, to the Invertebrate Animals than has usually been the case in introductory works, upon the belief that any practical Zoological work likely to be undertaken by young students will certainly be in connection with these rather than with the Vertebrate Animals. Secondly, the Author has devoted considerable space to a discussion of the principles of Zoological classification, be- lieving that it is of paramount importance that the student should have a clear idea of the principles upon which the Animal Kingdom has been systematically divided. At the same time, the introductory portion of the work is more especially intended for the teacher; and there is much in it that the learner may perhaps hardly understand till he has arrived at some clear idea of Natural History as a whole. Thirdly, while the Author trusts that the style of the work will be found clear and intelligible, he does not believe in the existence of any royal road to learning in Natural History, any more than in any other department of human knowledge. If Natural History is ever to be taught in ie PREFACE. schools, with any satisfaction to the teacher, or any profit to the learner, it must be taught as systematically and as un- flinchingly as Mathematics and Greek have been taught for many generations. The Author is one of those who believe that the time is now approaching, if it be not already here, when the Natural Sciences will take their true place in school education, as second to no other branch of knowledge, either as regards their intrinsic value and interest, or rezarded mere- ly as a means of developing the mental powers. Acting upon this belief, the Author has, therefore, treated his subject in a purely scientific spirit; and, while avoiding as much as pos- sible the use of technicalities, he has not endeavored to lend his subject any false glitter or embellishment; firmly beliey- ing that there is even a certain mental training involved in the recognition that a strictly scientific description is not without its own charms and beauties. While the use of tech- nical terms has been as far as possible restricted, it is believed that an explanation of every unavoidable term wili be found in the glossary, or is appended in the text. Lastly, the illustrations, with few exceptions, have been drawn on the wood by the Author, and he has thought it wise to wholly eschew the use of pictorial illustrations, as unneces- sary in a scientific work, however elementary it may be. TABLE OF CONTENTS. INTRODUCTION. Definition of Biology and Zoology—Characters of dead and unorganized bodies—Characters of living and organized bodies—Differences between animals and plants—Principles of Zoological classification—The great Physiological Functions—Homology and Analogy— General Divisions of the Animal Kingdom—lInvertebrata and Vertebrata, . Pages 1-24 CHAPTER I. General characters of the Protozoa—Classification of the Protozoa—Gregarinidw, . p. 25-23 CHAPTER II. General characters and orders of the Rhizopoda—Anatomy of the Amebea—Foraminifera— Affinities—Distribution of the Foraminifera in Space and in Time—Radiolaria—Acan- oe ee of a Sponge—Reproduc- tion of Spongilla—Distribution of Sponges in space, F + + oe Pp, 20-44 CHAPTER IIl. ‘General characters of the Infusoria—Anatomy of Paramecium—Structure of Epistylis— Orders of Infusoria—Distribution of Infusoria in space—Tabular view of the divisions ofthe Protozoa, . 6. we ee ee Pe 48D CHAPTER IV. General characters of the Celenterata—Divisions of the Celenterata—General characters of the Hydrozoa—General terminology of the Hydrozoa, . r a a » p. 50-56 CHAPTER V. Divisions of the Hydrozoa—Hydroida—Hydrida—Anatomy of Hydra—Corynida~Repro- duction in the Corynida and in the Hydroid Zoophytes generally—Alternation of gen- erations—Sertularida—Campanularida, . . . .« «6 «© «+ . p. 57-69 CHAPTER VI. Siphonophora or Oceanic Hydrozoa—Calycophoride—Physophoridx, . » oe Pp. TO-73 CHAPTER VI. Discophora or Medusidw—Structure of Naked-eyed Meduse—Their nature, . Pp. TAT paid vi TABLE OF CONTENTS. CHAPTER VIII. Lucernarida—Hidden-eyed Bee of Lucernarida—Rhizostomida—Grap- tolitide, . . . ' 3 : a ‘ a é ‘ 3 Pages 78-83 CHAPTER IX. General characters of the Actinozoa—Zoantharia—Anatomy of a Sea-Anemone—Zoantharia Sclerodermata—Sclerodermic and Sclerobasic Corals—Coral-reefs—Zoantharia Sclero- basica—Alcyonaria—Gorgonide—Red Coral—Rugose Corals—Ctenophora—Anatomy of Pleurobrachia—Tabular view of the divisions of the Celenterata, . . . p. 84-94 CHAPTER X. General characters of the Annuloida—General characters of the Echinodermata—Divisions of the Echinodermata—Echinoidea—Anatomy of Echinus—Asteroidea—Ophiuroidea— Crinoidea—Cystoidea and Blastoidea—Holothuroidea, . . . . + p. 95-107 CHAPTER XI. General characters of the Scolecida—Divisions of the Scolecida—Teniada—Devel it of a Tape-worm—Cystic worms—Trematoda—Turbellaria—Acanthocephala—Gordiacea— Nematoda—Rotifera—Tabular view of the divisions of the Annuloida, + p. 108-117 CHAPTER XII. General characters of the Annulosa—Characters of the Anarthropoda—Gephyrea—Annelida —Divisions of the Annelida—Hirudinea—Oligochxta—Tubicola—Errantia, p. 118-125 CHAPTER XIII. General characters of the Arthropoda—Divisions of the Arthropoda, . . . p. 126,127 CHAPTER XIV. General characters of the Crustacea—Decapoda—Macrura— Anomura—Brachyura—Isopoda —Merostomata—Trilobita—Cladocera, Copepoda, and Ostracoda—Cirripedia—A ppendix of the remaining orders of Crustaceans, . . . moe . + « p. 128-188 CHAPTER XY. General characters of the Arachnida—Podosomata—A carina—Pedipa!pi—Araneida, p. 189-143 CHAPTER XVI. Ceneral characters of the Myriapoda—Centipedes—Millipedes . + 4 pe 144, 145 CHAPTER XVII. General characters and anatomy of Insects—Mctamorphoses of Insects, . . p. 146-152 CHAPTER XVIIL Orders of Insects—Anoplura—Mallophaga—Thysanura—Hemiptera—Orthoptera—Neurop- tera—Aphaniptera—Diptera—Lepidoptera— Hymenoptera—Strepsiptera—Coleoptera— Tabular view of the divisions of-the sub-kingdom Annulosa, + 6 . p. 158-163 TABLE OF CONTENTS. vii CHAPTER XIX. General ch ters of the Mollusca—Primary divisions of the ‘attesee, . Pages 164-167 CHAPTER XX. Molluscoida—General characters of the Polyzoa—General characters of the Tunicata—Gen- eral characters of the Brachiopoda, . fs 7 Fig. 7.—a Siliceous shell of Collorphera; b Thalassicolia, showing the radiating pseude- podia and groups of siliceous spicula (after Miiller). term a sponge is really a colony or aggregation of separate masses of sarcode, greatly resembling Amcbe in structure, and having the power of secreting a skeleton or supporting framework common to the whole assemblage. Sponges, in fact, may be defined as compound Rhizopoda, forming masses which are traversed by canals opening on the surface, and supported by a framework of horny fibres or of calcare- ous or flinty needles. There are, then, two essential elements in the structure of a sponge—namely, the sarcode-bodies which constitute the animal itself, and which are collectively termed the “ sponge- flesh,” and the hard framework or “skeleton ” upon which the flesh is supported. To understand the nature of these fully, we may take an ordinary horny sponge, such as we are con- stantly in the habit of using. As we see the sponge in this country, we are only acquainted with the skeleton, which is composed of an enormous number of horny fibres, all interlaced and interwoven with one another, but leaving numerous holes and canals between their bundles (Fig. 9, d@). In its living condition, however, the whole of this skeleton is covered in- side and outside—saturated, in fact—with a kind of slimy ma- terial very like white-of-egg to look at. This is the so-called sponge-flesh, and, upon examining this with a microscope, it is found to be composed of an enormous number of minute RHIZOPODA. 41 masses of sarcode, all more or less completely independent of each other, and each very closely resembling an Amba. These separate “ sponge-particles,” or “sarcoids,” as they are called, consist, in fact, of granular sarcode, capable of pushing out little processes or threads of sarcode in the form of pseudo- podia, and sometimes furnished with an internal solid mass or nucleus (Fig. 3, c). In some cases each sarcoid carries a single lash-like vibrating filament or cilium (Fig. 3, a, ¢). Each sarcoid has the power, if detached, of independent move- ment, and each can obtain food for itself. As the sponge, however, is a fixed animal, some provision is necessary by which food shall be conveyed to the sarcoids in the interior of the mass. This is effected by a remarkable water-carrying or “aquiferous” system in the following manner: The entire sponge is riddled in every direction by an immense number of canals, all opening on the surface, and communicating freely Fic. 8.—Diagrammatic section of Spongilla (after Huxley). a a Outer or superficial layer of the sponge; 0 b Inhalant apertures, or “pores;” cc Ciliated chambers; @ An exha- lant aperture, or “osculum.” ‘The arrows indicate the direction of the currents. with one another in the interior of the mass. The canals are of different sizes, and, as can readily be observed in an ordinary sponge, their external openings are also of different sizes. A few of the holes are of much larger size than the others, and these, for reasons which will be seen directly, are called the “ exhalant apertures,” or “oscula.” The great majority of the holes are very minute, and these are known as the “inhalant apertures,” or “ pores.” In a living sponge a more or less constant circulation of water is carried on by means of this canal system. The water is admitted by means of the pores (Fig. 8, 66), is driven into the interior of the sponge, and is finally expelled in steady streams from the oscula (Fig. 8, d). The mechanism by which this circulation of water is effected, 42 INVERTEBRATE ANIMALS. was long unknown, but it is now known to consist in aggrega- tions of sponge-particles provided with cilia which all work toward the interior of the sponge (Fig. 8, ¢c). The circula- tion of water in this manner can be readily observed in many of our common marine sponges, and it is under the control of: the animal to a great extent. The large apertures or oscula are permanent, but they can be closed and opened at will; while the smaller apertures or pores appear to be formed afresh, wherever they are wanted, at any point of the surface, By means of the currents of water each individual sarcoid or sponge-particle is enabled to obtain food, so that the whole sponge, as remarked by Huxley, “represents a kind of sub- aqueous city, where the people are arranged about the streets and roads in such a manner that each can easily appropriate his food from the water as it passes along.” It is also not improbable that the process is at the same time a rudimentary form of respiration. #Ie.9.—a Gemmule of Spongilla; h Hilam; } Diagrammatic section of the gemmule showing the outer layer of spicules or amphidiscs, and the inner mass of cells; 2 Hilum; ce One of the epnieises seen in profile; @ Fragment of the skeleton of a horny sponge fener Bowerbank), showing the interlacing horny fibres with spicula. All much magni- ied, Such, then, are the general phenomena exhibited by any sponge, and the chief variations which occur among the sponges are to be found in the nature of the skeleton. In the sponges of commerce the skeleton consists of matted fibres composed of a substance nearly allied to horn. In other forms the skeleton is calcareous, or composed of lime; and in other cases, again, it is siliceous, or composed of flint. The Venus’s flower-basket (Euplectella), which looks like a goblet woven RHIZOPODA. 43 of spun glass, is a familiar example of the flinty sponges. In most cases, the skeleton, and often the flesh as well, is fur- nished with more or less numerous needles or spicula, gener- ally of flint, but sometimes of lime, which assume a great vari- ety ot shapes, and appear to exercise different functions (Fig. 9, ¢, d). ae regards the reproductive process in the sponges, it will be sufficient to state very briefly the leading phenomena which have been observed in the fresh-water sponge (Spongilla fluviatilis). If a specimen of Spongilla be observed toward the approach of winter, its deeper portions will be found to be filled with numerous small, rounded bodies, like seeds, which have been called “ gemmules.” Each gemmule (Fig. 9, a, 6) exhibits at one point a small aperture, and is found to be com-. posed of a leathery membrane, surrounded by a layer of sar- code, in which are imbedded a number of spicula. These spicula consist each of a central rod or axle carrying a toothed wheel or disk at each end (Fig. 9, ¢c). In the interior of the capsule thus formed is a mass of cells, of which the central ones contain numerous reproductive germs. When the spring comes, these masses are discharged into the water through the aperture of the gemmule, and become developed into fresh Spongille. In addition to this method of reproduction, the fresh-water sponge during the summer months has the power of producing true eggs or ova, and sperm-cells. The impreg- nated ova develop themselves into embryos, which are pro- vided with numerous cilia or vibrating hairs, by means of which they swim about freely. Finally, upon finding a suit- able locality, they fix themselves to some solid object, lose their cilia, and grow up into Spongille. Indeed, as a general if not universal rule, the embryos of the sponges are provided with cilia, and are thus capable of active locomotion, In this way is secured the extension over a wide area of these other- wise fixed and plant-like organisms. Distribution of Sponges in Space.—It remains only to add a few words on the distribution of sponges in space. With the single exception of Spongilla, all known sponges are in- habitants of the sea; but the former is to be found in lakes and rivers in most parts of the world. The marine sponges are found mostly attached to stones and other foreign objects between tide-marks and in deep water. The sponges of com- merce are mostly obtained from the Grecian Archipelago, but inferior kinds are imported from the Bahama Islands. One common sponge (Cliona), instead of incrusting other objects, 44 INVERTEBRATE ANIMALS, inhabits branching cavities in shells, which it excavates for itself. It apparently lives upon the animal matter contained in the shell, and few oyster-shells can be picked up upon our shores which do not exhibit the perforations and mines of some species or other of this genus. Fossil shells, also, often occur, which show that these mining sponges have enjoyed a vast antiquity. ; CHAPTER IIL InFusortia, Tue last class of the Protozoa is that-of the Infusoria, so called because of their being frequently developed in organic infusions under the following singular circumstances: If some water be taken, and any animal or vegetable substance be soaked or boiled in it, a solution is formed containing organic matter, or, in other words, an “organic infusion.” It is un- necessary to say that if this infusion be examined under the microscope, after boiling, nothing will be detected in it— nothing living, at any rate. If examined, however, at the end of a few days’ time—if the circumstances have been favor- able—a vast number of living forms will now be found in it. Among these will be found several of the members of the present class, and hence the name applied to them of Infusorian animalcules, or Jnfusoria. It is unnecessary to enter here into the question how these living beings are produced, since the subject is one of great obscurity, and opinions are still divided upon it. It is sufficient to remark that there are emi- nent observers who hold that the appearance of the Jnfusoria in this fashion is to be explained upon the theory that they have been spontaneously produced out of the inorganic ma- terials of the infusion, in opposition to the general view that they are derived from preéxistent germs. The position of the Znfusoria is somewhat doubtful, and it appears probable that they will ultimately have to be re- garded as a separate sub-kingdom, or as a branch of a higher sub-kingdom (Annuloida). In the mean while it is most con- venient to retain them in their present place, at the head of the sub-kingdom Protozoa. Regarded in this light, the Jn- Jusoria present a great advance in structure over all the forms which we have hitherto studied—an advance which is especially seen in the constant presence of a permanent 46 INVERTEBRATE ANIMALS. mouth. The Infusoria may be defined as Protozoa which are provided with a mouth, and generally a rudimentary digestive canal, They do not possess the power of emitting pseudopodia, but are furnished with vibratile cilia or con- tractile filaments. They are mostly microscopic in size, and their bodies usually consist of three distinct layers. They are mostly simple free-swimming organisms, but they some- times form colonies by budding, and are fixed to some solid object in their adult condition. As types of these two sec- tions of the Infusoria, we may take respectively Paramecium and Hpistylis. ; Paramecium (Fig. 10) is a beautiful slipper-shaped little Fia. 10.—Ciliated Infusoria. A. Paramecium, showing the nucleus (7) and two con- tractile vesicles (v); B. Paramecium bursaria (after Stein), dividing transversely, n Nucleus; 7’ nucleolus; 9 Contractile vesicle; C. Paramecium aurelia (after Ehren- berg), dividing longitudinally. creature, which may be found commonly in stagnant waters or in artificially-prepared infusions. The body is nearly quite transparent, and consists of three layers—1. A structureless, transparent, external film or pellicle; 2. A central mass of soft semi-fluid sarcode; and 3. An intermediate layer of firm and consistent sarcode. The external membrane or cuticle is richly covered with minute vibrating hairs or cilia, which ap- pear, however, to be really derived from the middle layer. The cuticle is also perforated by the aperture of the mouth, which is continued into a short, funnel-shaped gullet. The gullet, however, is not continued into any distinct stomach, but opens directly into the soft, semi-fluid sarcode which con- stitutes the central abdominal cavity. The particles of food INFUSORIA. 47 on passing through the gullet are directly received into the central mass of diffluent sarcode, where they undergo a kind of slow circulation or rotation. As in the case of the Ameba, each particle of food generally carries with it a little water, so that the appearance is produced of a number of little clear spaces in the central sarcode. These are now called vacuoles, or food-vacuoles; but they were originally described by Ehren- berg, the famous Prussian microscopist, as so many distinct stomachs, in consequence of which he named the Infusoria the Polygastrica (Gr. polus, many; and gaster, stomach). The vibrating cilia which clothe the surface of Paramcecium serve partly to drive the animal rapidly through the water, and partly to set up currents by means of which food is conveyed to the mouth, All the nutrient particles obtained in this way undergo the circulation in the central garcode above spoken of, where they are partially or completely digested. The indigestible portions of the food appear to be got rid of by a second aper- ture (anus) placed near the mouth. The only other organs possessed by Paramecium are the so-called nucleus and nucleolus, and the contractile vesicle (or vesicles), all of which appear to be situated in the cortical layer of the body. The nucleus (Fig. 10, ”) is a little solid body, composed of an ex- ternal membrane, with granular contents, and having the nucleolus (v’) firmly attached to its exterior in the form of a little spherical particle. Both appear to be organs of repro- duction, the nucleus being an ovary, and the nucleolus a spermarium. ‘The names, therefore, of nucleus and nucleolus are extremely inappropriate, as they lead to confusion with the wholly. distinct structures which receive these names in an ordinary animal or vegetable cell. The contractile vesicle (v) has exactly the same structure as in the Ameba. It is simply a little contractile cavity filled with a fluid apparently derived from the digestion, and contracting and dilating at regular intervals. There is usually only a single vesicle present, but there may be two or more. Reproduction in Paramcecium may be effected by fission— that is to say, by a simple splitting of the body of a single in- dividual into two portions, each of which becomes a fresh being. The process of fission may commence at the surface, or it may begin at the nucleus. In other cases, two Para- moecia come together and adhere closely to one another. The nucleus and nucleolus enlarge, and the nucleolus of each is transferred to the other, apparently through the mouth. As the result of this, numerous germs are produced, which, after 48 INVERTEBRATE ANIMALS. their liberation from the body of the parent, are developed into fresh individuals. i Epistylis, which is a good example of the fixed Infusoria, may be regarded as essentially similar to Paramecium in its anatomical structure. In place, however, of a single free- swimming organism, we have now a colony of more or less closely related beings, the whole assuming a plant-like form, and being rooted to some solid object. The colonies of Epistylis may not uncommonly be found adhering to the stems of water-plants or to the backs of our common water- beetles, and the trained eye readily recognizes them as a grayish-white down or nap. On placing a portion of this under the microscope, we see a number of little oval cups or “calyces” supported upon a branched stem. Each cup con- tains a sarcode-body, essentially the same as Paramecium in structure, consisting of granular sarcode, with vacuoles, a nucleus, and a contractile vesicle. The end of the cup farthest from the stalk terminates in a rounded aperture, through which there can be protruded a ciliated disk. On one side of this disk is the aperture of the mouth, leading into a kind of gullet, which is also furnished with large vibrating cilia. This, in turn, opens directly into the soft, granular sarcode of the abdominal cavity, which exhibits a constant though slow rotation. Fie, 11.—Ciliated Infusoria. @ VPaginicola, b Stentor Miilleri, the Trumpet Animalcule; ce Group of Vorticelle ; d@ Detached bud of Vorticedla. A still commoner and equally beautiful example of the Stalked Infusoria is the so-called Bell-animalcule ( Vorticella. Fig. 11, ¢), which may be found in any stagnant pool attached INFUSORIA. 49 to the stems of aquatic plants. The body in Vorticella forms a kind of cup or “calyx” supported upon a long stalk, which is in turn fixed to some solid object. The stem contains a contractile fibre in its interior, and the animal can by this means push itself out or coil itself up with the utmost rapidity. The vibrating filaments or cilia are not scattered over the whole surface of the bell-shaped body, but are collected to form a kind of fringe or circle round the mouth of the calyx. Nearly in the centre of this ring, or on one side, is placed the aperture of the mouth, which leads by a short gullet straight into the central soft sarcode of the interior of the body. A nucleus and contractile vesicle are also present, so that in the essential points of its anatomy Vorticella does not differ from a free-swimming Infusorian such as Paramecium. Indeed, a transition between the two forms is found in the so-called Trumpet animalcule or Stentor (Fig. 11, 6), which can detach itself and swim about at will, at the same time that it is ordinarily fixed by its thinner extremity to some solid object. In Vaginicola (Fig. 11, 4), again, we have an animalcule closely related to Stentor, but having the body protected by a horny or membranous sheath. All the Infusoria we have been hitherto considering belong to a section of the class in which the surface is furnished with more or less numerous cilia, There are other forms, however, in which there are no cilia, but the body is furnished with a number of radiating filamentous tubes, the extremi- ties of which form little sucking-disks. Finally, there is another section in which the organs of locomotion are in the form of long, contractile filaments, termed “ flagella,” which may be combined with cilia, or may be the only locomotive organs present. In accordance with these differences, the Jnfu- soria are divided into the three orders of the Ciliata, Suctoria, and Flagel- lata, of which the ciliated forms are by far the most numerous and most im- portant. Distrisotion or Inrusorta IN Space.—As regards the distribution of Infusoria in space, there is little to say, except that they are of universal occurrence in fresh water over the whole globe, and that they occur also in the sea. In fact, the only conditions which appear to be necessary for their existence are a certain quantity of water holding organic matter in solution. Wherever these contitions ure fulfilled, Infusoria are certain to make their appearance. The attached forms of Jnfusoria, however (such as Vorticella, Epistylis, Stentor, and others), do not appear to be ever developed in artifi- cial infusions, and they are to be sought for on the stems of water-plants, and in other similar localities. It seems hardly necessary to remark that, as before defined, the occurrence of fossil Jnfusoria is not to be looked for, as they possess no hard structures which are capable of permanent preser- vation. It is only to be added in this connection that, if the animalcule known as Noctiluca be rightly referred to this class, the Infusoria take a very decided share in producing the diffused phosphorescence or luminosity of the sea, which is occasionally such a beautiful spectacle even in our own climate. SUB-KINGDOM IL—CG@LENTERATA. CHAPTER IV. 1. Cuaracters or Tux Sus-Kinepom. 2. Drvistons. 3. GENERAL CHARACTERS OF THE Hyprozoa. 4, EXPLANATION OF TECHNICAL TERMS. In the sub-kingdom Celenterata are included the sea- anemones, corals, sea-jellies, sea-firs, and other allied animals, and the whole division may be looked upon as forming the most typical section of the animals formerly called by Cuvier Radiata. In addition, however, to the above-mentioned ani- mals, Cuvier included in his Radiata all the members of the modern sub-kingdom Protozoa, together with the sea-mats or lowest class of the Mollusca, and the sea-urchins, star-fishes, wheel-animalcules, internal parasites, and others which are now placed in a separate sub-kingdom by themselves (Annu- loida). The old Radiata, therefore, was an extremely hetero- geneous assemblage, and there is no advantage to be derived from its employment even in works such as this present. The division Coelenterata, or “hollow-entrailed” animals (Gr. koilos, hollow ; and enteron, intestine), includes all those radi- ate animals which are more or less closely allied to the sea- anemones on the one hand, and to the sea-firs on the other. Most of the Coelenterata come under the conveniently loose term of “ zoophytes,” or plant-animals, from the external re- semblance which many of them show to plants. The Coelenterata may be defined as animals whose aliment- ary canal communicates freely with the general cavity of the body (“somatic cavity”). The body %s essentially com- posed of two layers or membranes, an outer layer or * ecto- derm,” and an inner layer or “ endoderm.” No circulatory organs exist, and in most there are no traces of a nervous CELENTERATA. 51 system. Peculiar stinging organs, or “thread-cells,’ are usually if not always present, and in most cases there is a radiate or star-like arrangement of the organs, which is - especially perceptible in the tentacles, which are in most in- stances placed round the mouth. Distinct reproductive organs exist in all. The leading feature which distinguishes the Cclenterata, and the one from which the name of the sub-kingdom is de- rived, is the peculiar arrangement of the digestive system. In the Protozoa, as we have seen, a mouth is only very rarely present, 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. In most of the higher animals, on the other hand, not only is a permanent mouth present, but the walls of the body enclose a distinct and permanent chamber or body-cavity. Further, in most cases the mouth opens into an alimentary or digestive tube, which is always distinct from the body-cavity, and never opens into it, usually passing through it to open on the sur- face 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 an anus—but which simply passes through the body-cavity with- out in any way communicating with it. In the Celenterata (Fig. 12) the condition of parts is intermediate in its arrange- a . ‘ 1 1 ’ i) 1 1 1 ‘ 1 ' Fia. 12.—Diagrammatic vertical section of a Sea-anemone (Actinia). a Stomach; 6 Mesen- tery; ¢ Convoluted cord or ‘craspedum;” @ Tentacle. The dark line indicates the “ectoderm,” the fine line and clear space adjacent mark the “ endoderm.” ment. There is a distinct and permanent mouth, and there is a distinct and permanent body-cavity, but the mouth opens 52 IN VERTEBRATE ANIMALS. into, and thus communicates freely with, the body-cavity. In some cases the mouth opens straight into the general body- cavity, which then serves as a digestive cavity as well (Fig. 13, a In other cases there intervenes between the mouth . and the body-cavity a short alimentary tube, which communi- cates externally with the outer world through the mouth, aud opens below by a wide aperture into the general cavity of the body. In no case is there a distinct intestinal tube which runs through the body-cavity and opens on the surface by a mouth at one end and an excretory aperture or anus at the other. Another leading character of the Coelenterata is the composition of the body out of two fundamental membranes (Fig. 12), which are usually of a very simple structure, but which may be more or less complicated by the development of muscular fibres and other tissues. The outer of these layers or membranes is known as the “ectoderm,” and it forms the whole of the outer surface of the body, terminating at the margins of the mouth. The inner layer is known as the “endoderm,” and it lines the whole of the interior of the body, being prolonged into the tubular tentacles round the mouth, Both of these membranes, but especially the endoderm, are usually more or less richly furnished with vibrating cilia. The peculiar microscopic organs called “ thread-cells,” or “net- tle-cells,” which communicate to many of the Celenterata (such as the sea-jellies) their peculiar power of stinging, are structures found in the integument of almost all the mem- bers of this sub-kingdom, and sometimes in internal parts as well. They are very beautiful objects of microscopical ex- amination, and differ very considerably in the details of their structure. They are, however, in most respects essentially the same as in the common Aydra or fresh-water polype, in which the thread-cells (Fig. 13, @) are “oval elastic sacs, con- taining a long, coiled filament, barbed at its base and serrated along its edges. When fully 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 uncommonly equal to many times the length of the latter” (Huxley). In accordance with the above-mentioned differences in the arrangement of the digestive system, the Cclenterata are divided into two great classes, termed respectively the Hy- drozoa and the Actinozoa. In the Hydrozoa, there is no body-cavity distinct from the digestive cavity—or, in other words, the body-cavity ds the digestive cavity. In the Acti- CCELENTERATA, 53 nozoa, on the other hand, there is a distinct digestive cavity, but this opens directly into the general body-cavity, so that the two form distinct but freely-communicating divisions of the same chamber. Crass I.—Hyprozoa. The Hydrozoa are defined as Coelenterata in which the walls of the digestive sac are not separated from those of the general cavity of the body, the two coinciding with one an- other. The reproductive organs are external, in the form of outward processes of the body-wall (Fig. 18, a, b). The Hydrozoa are all aquatic in their habits, and, with the exception of two genera, all are inhabitants of salt water. The class includes both simple and composite organisms, of which the most familiar are the sea-firs and their allies (Hy- droid zoophytes), the fresh-water polype or Hydra, the sea- jellies (Meduse), and the Portuguese man-of-war (Physalia). Owing to the extremely complicated nature of many of the Hydrozoa, it appears advisable to preface their description by an explanation of some of the more important terms which are employed in connection with various members of the class. GENERAL TERMINOLOGY OF THE Hyprozoa. Individual.—In order to understand fully the meaning which is attached to the term “ individual” in zoological lan- guage, it is necessary to glance briefly at the general features of reproduction as displayed in different sections of the ani- mal kingdom. Reproduction is the process by means of which new individuals are produced and the perpetuation of the species insured. This end may be attained in various ways, but these all come under the two heads of “sexual” and “non-sexual” reproduction. In sexual reproduction, by which alone can fresh beings be produced among the higher ani- mals, the essential element of the process consists in the formation of two distinct structures, a germ-cell or ovum, and a sperm-cell or spermatozoid. By the union of these distinct reproductive elements fresh beings can be produced. Asa general rule, the germ-cell is produced by one individual (female), and the sperm-cell by another (male); but among the lower animals it is not uncommon for the same individual to produce both of these elements, in which case the indi- vidual is said to be “hermaphrodite.” Among the lower animals, however, fresh beings may be produced without the 54 INVERTEBRATE ANIMALS. contact of a sperm-cell and an ovum—that is to say, without any genuine act of reproduction. The processes by which this can be effected in different animals vary considerably, but they are all spoken of as forms of “non-sexual” reproduction. The only varieties, however, of the process which require considera- tion, are those in which fresh beings are produced by what is called “ gemmation” or “ fission.” Gemmation (Lat. gemma, a bud) consists in the produc- tion of a bud or buds, usually from the outside, but sometimes from the inside, of an animal; which buds become developed into more or less completely independent beings. The fresh beings thus produced by budding are all known as zodids, and are not spoken of as distinct animals for reasons which will be immediately evident. When the zodids produced by budding remain permanently attached to one another and to the parent organism which produced them, the case is said to be one of “continuous” gemmation, and the ultimate result of this is to produce a colony or composite structure, composed of a number of similar and partially independent beings, all pro- duced by budding, but all remaining in organic connection. This is seen very well in the sponges, in the compound Fora- minifera, and in a great number of the Hydrozoa. When, on the other hand, the zodids produced by budding become finally detached from the parent organism, we have a case of what is’ called “ discontinuous ” gemmation. In this case, the detached zodids become completely independent beings; and they are often wholly unlike the original zodid in structure and in habits, so much so that .they have in various cases been de- scribed as altogether distinct animals. Discontinuous gem- mation is very well seen in many of the Zydrozoa, and in them the case is still further complicated by the coexistence of discontinuous gemmation with the continuous form of the process. Thus, it is not an uncommon thing among the Hydrozoa to find a composite organism or colony produced from a primordial zodid by continuous gemmation, and hav- ing at the same time the power of giving rise to detached and completely independent beings by a process of discontinuous gemmation. In what is called “fission” (Lat. findo, I cleave), exactly the same results are attained as in gemmation, but in a slightly different manner. In gemmation the new beings are produced by means of buds thrown out by a primitive zodid. In fission the new beings are produced by a cleavage or division of a primitive zodid into two or more parts, each of CCQELENTERATA. 55 which becomes finally developed into a new and more or less completely independent being. In fission, as in gemmation, the new beings or zodids may remain permanently in con- nection with one another, when the process is a continuous one, and a composite organism is produced, as in many corals. Or, in other cases, the new zodids produced by fission are de- tached to lead an independent existence, as in some of the Hydrozoa, the process thus becoming a discontinuous one. We are now able to understand what is meant, in strict zoological language, by the term “individual,” as applied to animals, Zoologically speaking, an individual is defined as “equal to the total result of the development of a single ovum.” In the higher animals there is no sort of difficulty about this, for each ovum gives rise to no more than one single animal, which cannot produce fresh beings in any other way than by producing another ovum. In this case, there- fore, each animal is an individual. In the lower animals, however, the being produced by an ovum has often the power of giving rise to fresh beings by a process of gemmation or fission, and these beings may either remain attached to one another so as to form a colony, or may become detached to lead independent lives. In either case, the term “individual” can only be properly applied to the whole assemblage of be- ings produced in this way, however much they may differ from one another in appearance, structure, cr mode of life. In these cases, therefore, the individual may be, jirstly, a single independent being—as, for instance, an Amcba, or an Infusorian such as Paramecium ; secondly, a colony or com- posite organism composed of a number of more or less nearly similar beings or zodids, produced by budding from a primi- tive zovid—as, for instance, a sponge, or such an Infusorian as Hpistylis ; and thirdly, an assemblage of zodids produced by budding or fission from a primitive being, but not neces- sarily remaining connected with one another or exhibiting any common features of likeness, as we shall see is the case in many of the Hydrozoa. Lastly, cases may occur in which the individual consists partly of similar zodids which remain permanently connected with one another, and partly of dissimilar zodids which are detached to lead an independent life, all alike being the result of the development of a single ovum, Zovid (Gr. zo6n, animal; eidos, form),—The term “zodid” is indifferently applied to all the more or less completely in- dependent beings which are produced by budding, or by 56 ; INVERTEBRATE ANIMALS. cleavage from a primitive organism. It does not matter, therefore, for the purposes of this definition, whether these beings remain permanently attached to the original organism, or whether they are finally separated to enjoy an independent existence. ; Hydrosoma (Gr. hudra, a water-serpent; soma, body).— The term “hydrosoma” is one which is very conveniently ap- plied to the entire organism in any Hydrozoén, whether this be simple, or whether it be composite and made up of a num- ber of connected zodids. Polypite——That portion of any Hydrozoin which is con- cerned with the process of digestion, or, in other words, the “alimentary region,” is termed the “polypite”—the more generally current term of “polype” being now restricted in meaning to the same region in the higher Celenterata (Ac- tinozoa). In such of the Hydrozoa as the fresh-water polype or Hydra, in which the hydrosoma is simple, the whole or- ganism ig termed a-polypite; but the term is more generally . employed to indicate the nutritive zodids of any compound Hydrozobn, Cenosare.—The term “ccenosarc” (Gr. koinos, common; sare, flesh) is employed to designate the common trunk or flesh by which the separate polypites of any compound Hy- drozoén are united into a single organic whole. Polypary.—The term “ polypary ” or “ polypidom ” is ap- plied to the horny or chitinous outer covering or envelope with which many of the Hydrozoa are furnished. These terms have also been not uncommonly employed to designate the very similar structures produced by the much more highly or- ganized sea-mats and their allies (Polyzoa), but it is better to restrict their use entirely to the Hydrozoa. CHAPTER V. Divisions oF THE Hyprozoa. Tar Hydrozoa are divided into four great divisions, each of which requires some notice, as presenting points of special interest. These divisions or sub-classes are known by the names of Hydroida, Siphonophora, Discophora, and Lucernarida. SUB-CLASS HYDROIDA. This sub-class comprises all the sea-firs and their allies, commonly known to naturalists as the “ Hydroid zoophytes,” from their resemblance to the fresh-water polype (Hydra), which is also a member of this division. The Hydroitda are defined by the fact that they consist of an alimentary region or “ polypite,” which is furnished with a mouth and prehensile tentacles at one end, and with an adherent disk at its other extremity. In some few cases the hydrosoma consists of but one such polypite (as in the Hydrida and some of the Co- rynida) ; but generally the hydrosoma is composed of a greater or less number of similar polypites all united by a coenosarc or common trunk (as in the majority of the Corynida, and in the Sertularida and Campanularida). In the great majority of cases, also, the hydrosoma is not unattached, but is fixed to some solid object by one extremity. The Hydroid zoophytes exhibit three principal types of structure, which constitute so many orders, Orver I. Hypripa.—In the first order we have only the well-known. fresh-water polypes or Hydra, of which we may take the common green Hydra (7. viridis) as the type. This singular little creature may be found with a little trouble in most of our streams and pools, and it is quite visible to the naked eye, though it can only be satisfactorily examined hy 58 INVERTEBRATE ANIMALS. the help of the microscope. "When uncontracted, the body of the Hydra is in the form of a cylindrical tube (Fig. 13, a, 0), composed of the two fundamental layers, the ectoderm and endoderm, of which the former contains many thread-cells, and is likewise furnished with numerous green granules, stated to be identical with “chlorophyll,” or the green coloring- matter of plants, At the base of the cylindrical body is a kind of disk-shaped sucker, by means of which the animal can attach itself at will to any foreign body. Its favorite position appears to be that of hanging head-downward, suspended from the stem of some water-plant. It is not, however, per manently fixed, but it can detach itself and change its place at will, At the opposite extremity of the body is placed the aperture of the mouth, surrounded by a circle of from five to fifteen small tubular filaments, which are termed the “tenta- Fie. 18.—Morphology of Hydrozoa. a Diagrammatic section of Hydra: the dark line is the ectoderm, the fine line and clear space adjacent indicate the endoderm; b Hydru viridis, showing a single ovum contained in the body-wall near the lower extremity, and two conical elevations containing sperm-cells near the bases of the tentacles, e Hydra vulgaris, with an undetached bud—enlarged ; d@ Thread-cell of the Hydra, greatly magnified. cles” (Fig. 13,6). Each tentacle consists of a tubular prolon- gation of both ectoderm and endoderm, and encloses a canal which opens at its base into the general cavity of the body. The ectoderm of the tentacles is richly furnished with thread- cells, and they are also well supplied with muscular fibres. They exhibit the most extraordinary contractility, being capa- ble of retraction till they appear as nothing more than so many little warts or tubercles, and of being extended to a DIVISIONS OF THE HYDROZOA. 59 length which is in some species many times longer than the body itself. (In Hydra fusca the tentacles can be protruded to a length of more than eight inches.) The tentacles are the organs by means of which the Hydra obtains its food, con- sisting chiefly of minute aquatic organisms, such as small worms, insects, Crustacea and Rotifera. These are seized by the tentacles and gradually drawn into the mouth; but in addition to this merely mechanical action, the tentacles ap- pear to exercise a benumbing or even fatal influence upon the animals grasped by them—this being apparently due to the thread-cells with which they are furnished. The mouth in the Hydra opens directly into a capacious cylindrical cavity, which is excavated along the whole length of the body, and which is both the body-cavity and the stomach in one. This cavity (Fig. 13, a, 6) is filled with water derived from the exterior, and also with the nutritive particles derived from the food. Indigestible fragments appear to be rejected by the mouth, though an anal aperture has been asserted to be het There are no internal organs of any kind. Physio- ogically, therefore, the Hydra presents little advance upon the higher Protozoa, such as the Infusoria. There is a per- manent mouth, surrounded by permanent and special organs adapted for the seizure of food. There is also a permanent internal cavity for the reception and digestion of the food, but this is not shut off from the general cavity of the body. There is no organ for the propulsion of the nutritive fluid through the body, no nervous system or organs of sense, and no special respiratory or excretory organs. Another and striking proof of the essentially low position of the Hydra in the animal scale is to be found in its extraordinary capacity of resisting mutilation, or, in fact, mechanical injury of any kind short of absolute annihilation. The briefest illustration of this fact is all that can here be given, but with that the . name of Trembley of Geneva must be associated. This well- known observer, in a long series of experiments, most of which have been successfully repeated by subsequent nat- uralists, discovered that the Hydra could be mechanically divided with a knife into any number of fragments, with the sole result that each and all of these possessed the power of developing themselves into fresh and independent polypites. Further, the animal could even be turned inside out, with a necessary transposition of the ectoderm and endoderm, without any apparent inconvenience or interference with its health. 60 INVERTEBRATE ANIMALS. Reproduction in the Hydra is effected non-sexually by gemmation, and sexually by the production of ova and sperm- cells; the former process being followed in summer and the latter in autumn, few individuals appearing to survive the winter. In the first or non-sexual method, the Hydra throws out one or more buds, usually from near the fixed extremity (Fig. 13, c). These buds at first consist simply of a tubular proicngation of the ectoderm and endoderm, enclosing a cavity which communicates with the general cavity of the body. A new mouth and tentacles are soon developed at the free end of this bud, and after a longer or shorter period the new Hydra, thus produced, is detached to lead an independent life. Hach Hydra can produce many such buds during the summer season, and the liberated buds can also repeat the same process, s0 that in this way reproduction is rapidly carried on, In the second or sexual method of reproduction, ova and sperm-cells are produced toward the winter in ex- ternal processes of the body-wall. The spermatozoa are de- veloped in little conical elevations, which are produced near the bases of the tentacles; and the ova are formed in much larger elevations, of which there is ordinarily but one, placed nearer to the fixed extremity of the animal (Fig. 13,0). When mature, the ovum is fertilized by the sperm-cells, both being set free into the water by the rupture of the body-wall. The embryo Hydra is at first covered with vibrating cilia, and swims freely about, until it meets with a suitable locality. It then fixes itself by one extremity, the cilia drop off, and a mouth and tentacles are developed at the free end of the body. Orver IJ. Corynipa.—In the second order of the Hydroid zoophytes, known as the Corynida or Tubularida, we have a number of organisms which in their essential structure are closely related to the Hydra, but which differ considerably in the nature of the reproductive process. All of them are marine, with the single exception of the genus Cordylophora, which inhabits fresh water. Some of the members of the order are simple, consisting of no more than a single polypite. In these cases there is an exceedingly close approach to the structure of the common Hydra, but the polypite is per- manently fixed without the power of voluntarily changing its lace, while the reproductive process is considerably different. n the majority of the Corynida, however, the hydrosoma is compound, consisting of a greater or less number of separate DIVISIONS OF THE HYDROZOA. 61 polypites or zodids, all connected with one another by a com- mon flesh or ccenosare, and all forming parts of a plant-like rooted colony. In some of the Corynida the polypites are naked, but in most cases the ccenosare is protected by a horny-looking chitinous* envelope or “ polypary,” as in Tubularia indivisa (Fig. 14). In no case, however, is this horny covering so prolonged as to ; form little cups in which each poly- pite is contained. It always stops short at the bases of the polypites, and in this way the Corynida can al- ways be distinguished from their near allies, the sea-firs (Sertularida). As a good example of the Cory- nida, the common pipe - coralline (Tubularia indivisa) may be taken. In this animal (Fig. 14) we have a gregarious zoophyte consisting of numerous clustered horny tubes, fixed by their bases to shells or stones, and inhabiting most seas. The tubes are usually unbranched, though often con- siderably interwoven together. Each tube is filled with a soft, semi-fluid, reddish ccenosare, and gives exit at its free extremity to a single poly- pite. The polypites are bright red in color, and are not retractile within their tubes, the horny polypary ex- tending only to their bases. The polypites are somewhat conical in #6 14—Hragment of Pubularta shape, the mouth being placed at the ; apex of the cone, and they are furnished with two sets of ten- tacles. One set consists of numerous short tentacles placed directly round the mouth, the other is composed of from thirty to forty tentacula of much greater length arising from the polypite about its middle or near its base. Near the in- sertion of these tentacles the generative buds are produced at proper seasons. In Hudendrium (the branched pipe-coral- line) the essential structure is much the same as in Zubularia, but the hydrosoma is now truly compound, consisting of a number of non-retractile reddish polypites, united by a cceno- * Chitine is a substance which is nearly allied to horn, but is distinguished from it by the fact that it is not soluble in caustic potash. i : 4 : 62 INVERTEBRATE ANIMALS. sarc, which is furnished with a horny polypary, the whole colony assuming a singularly close resemblance to a plant. In Cordylophora—the only fresh-water member of the order—we find also a branched composite hydrosoma carrying numerous polypites, and having the ccenosarc defended by a horny sheath (Fig. 15, a, 6). In Coryomorpha, finally, we have a type of the Fig. 15.—a Fragment of Cordylophora lacustris, slightly enlarged; Fragment of the same, considerably enlarged, showing a polypite and three gonophores in different stages of growth; ¢ Portion of Syncoryne Sarsii, with medusiform zodids budding be- tween the tentacles. Corynida, in which the hydrosoma consists of no more than a single polypite, and there is no polypary. It is about four inches in length, and is fixed by filamentous roots to the bot- tom of the sea. It consists of a single whitish polypite, striped with pink, and terminating upward in a pear-shaped head, furnished with two sets of tentacles, the shortest of which form a circlet round the mouth. As regards the generative process in the Corynida, it may be as well to consider the general phenomena of reproduction as carried on by all the Hydroid zoophytes, the general char- acters of the process being of a most remarkable nature. As has been already explained, the individual in the case of the compound Hydrozoa consists of an aggregation or colony of partially independent beings or zodids, produced by gemma- tion or fission from a primordial organism. This is the case in all composite animals, such as sponges, sea-mats, corals, and many others. In many of the compound Hydrozoa, how- ever, the case becomes still further complicated. In many of these organisms, namely, the zotids differ very much from one another both in structure and in function. One set of zodids DIVISIONS OF THE HYDROZOA. 63 is entirely devoted to the duty of providing food for the col- ony, and in these no reproductive organs are ever developed. ‘These nutritive zodids are all like each other in form, and the whole assemblage of them has been appropriately termed the “trophosome” (Allman), from the Greek trepho, I nourish; and soma, body. The colony or trophosome thus formed by the nutritive zodids can go on increasing by the production of fresh zoéids for an almost indefinite period; but in all cases there ultimately comes a time when it becomes necessary to produce the essential elements of reproduction in order to secure the perpetuation of the species. The nutritive zodids, as just stated, cannot produce the ova and sperm-cells, being destitute of reproductive organs, and the colony is therefore compelled to produce a second set. of buds, which have the power of producing the essential elements of reproduction. These buds are collectively called the “gonosome” (Gr. gonos, offspring; and soma, body). The generative buds have the further peculiarity that not only can they produce the generative elements, but they are altogether unlike the nutritive zoéids in appearance. This difference in external appearance and in structure is sometimes so great as to lead to a most remarkable series of phenomena. In the simplest form in which these generative buds or “ gonophores” appear, they have the form of mere protuberances of the ectoderm and endoderm (Fig. 16, a), enclosing a cavity derived from the body-cavity. In these buds the generative elements— ova and spermatozoa—are developed (Fig. 15, 5). In other instances, the generative buds have a more complicated struct- a Fa. 16.—Generative buds or gonophores of the Hydrozoa diagrammatically represented, a Simple gonophore, consisting merely of a protuberance of the ectoderm and endo- derm ; ¢ Gonophore which has the structure of a Medusa (medusoid), but is not de- tached; @ Free medusiform gonophore. ure. They consist now (Fig. 16, c) of a bell-shaped disk, which is attached by its base to the parent organism, and has its cavity turned outward (see also Fig. 15,¢). From 64 INVERTEBRATE ANIMALS. the roof of this disk there is suspended a kind of handle, which corresponds to the clapper of the bell, and is termed the “manubrium” (Lat. for handle). From the fixed or proxi- mal extremity of the central process or manubrium proceed four canals, which extend to the margin of the bell, where they all open into a circular canal surrounding the mouth of the bell. This bell-shaped reproductive bud may attain no higher development than this, and may remain permanently attached to the parent organism from which it is produced. In other cases, however, a higher state of development is reached (Fig. 16, @). The generative bud or gonophore be- comes detached from its parent colony; the manubrium or central process develops 2 mouth at its free extremity; the mouth of the bell becomes partially closed by an inward pro- longation or shelf, called the “veil;” and a series of ten- tacles are developed from its margin. The generative bud, thus liberated, leads a wholly independent existence. The manubrium, having developed a mouth, assumes the func- tions of a true polypite, and its cavity acts as a digestive sac. The whole organism swims about freely, and has the power of assimilating food, and thus of attaining to a com- paratively gigantic size. This independent existence, how- ever, only goes on till such time as the elements of reproduc- tion can be produced. The ova and sperm-cells are developed in specialized portions of this generative bud, and then it ceases to exist. The ova, however, when fertilized, do not develop themselves into the free-swimming bell-shaped or- ganisms in which they were actually produced, but into the plant-like, rooted, and compound zoophyte, from which the generative buds were originally given forth. These free- swimming bell-shaped reproductive buds or gonophores, as . we shall see, are identical structurally with the smaller forms of the so-called sea-jellies or Meduse ; and it is now known that most if not all of these Medusw, though originally de- scribed as distinct beings, are really nothing more than the free generative buds of the fixed Hydrozoa. We have here, then, an instance of what has been not quite appropriately called “alternation of generations.” We have a compound fixed animal, in many respects comparable to a plant, pro- ducing a special series of buds which are devoted to the pro- cess of reproduction. These buds are cast off as independent beings to lead an independent life, and they are furnished with the necessary organs to preserve their existence till they are able to mature the reproductive elements. When once DIVISIONS OF THE HYDROZOA. 65 able to consummate this, they die; but the young to which they give origin are wholly unlike themselves. The young, namely, instead of being free-swimming “ medusiform” beings, become developed into the fixed, plant-like colony from which the generative buds were originally produced. The term “alternation of generations” is not an altogether good one, and does not quite express the facts of the case. There is not any alternation of generations, but there is an alternation of generation with gemmation or budding. The only true generative act takes place in the reproductive zoéid or gono- phore, in which the ova and sperm-cells are developed. The production of this gonophore from the parent organism (tro- phosome) is a process, not of generation, but of gemmation or budding. The whole process, therefore, is, properly speak- ing, not an “alternation of generations,” but an alternation of generation with gemmation. To recapitulate, then—the process of reproduction in the Hydroid zoophytes is carried on by means of reproductive buds or gonophores, which are produced at special seasons, and in which the reproductive elements are developed. These generative buds differ a good deal in their character, but three chief kinds may be distinguished: 1. Simple closed sacs or protuberances formed out of both ectoderm and endoderm, and having the special elements of generation developed in their interior. 2. Bell-shaped buds, attached to the parent colony by their bases, and having a central process or manu- brium, which is furnished with a mouth and central cavity, from which there is given off a system of canals to ramify in the substance of the disk. The reproductive elements are developed either in the walls of these canals or between the ectoderm and endoderm of the manubrium. From the resem- blance of these buds in anatomical structure to the so-called sea-jellies or Medusw, they are usually spoken of as “ medusi- form gonophores,” or simply as “ medusoids.” In this form, however, though highly organized, the buds never become de- tached from the parent colony. 3. Buds which become de- veloped into bell-shaped medusiform bodies exactly similar in structure to the last, but detached to lead an independent ex- istence. These free-swimming medusiform gonophores are anatomically indistinguishable from ordinary Meduse , and it is now known that most, if not all, of the so-called “ naked- eyed” Medusw, are really the detached generative buds of other orders of Hydrozoa. The special elements of reproduc- tion are developed in these detached buds, but the resulting 66 INVERTEBRATE ANIMALS. embryos are not developed into Medusc, such as produced the ova and sperm-cells, but straightway grow up into the plant-like, sexless colony, from which the medusiform gono- phores were originally budded forth. In these cases, there- fore, the individual Hydroid consists of a fixed, rooted colony or trophosome, producing fresh zodids by a process of budding, but incapable of producing the essential elements of reproduc- tion, together with a free and independent series of generative buds, or gonosome, in which the elements of reproduction are developed. Orver III. Serruraria.—In this order of the Hydroida we have the most familiar and best known of all our zoophytes —namely, the sea-firs and their allies. The horny, plant-like polyparies of the Sertularida are familiar to every visitor at the sea-side, and by those unacquainted with their true nature they are almost universally set down as sea-weeds. ' The Sertularida are very closely allied to the compound forms of the Corynida, resembling them in being rooted, plant- like colonies, composed of a number of similar polypites or zodids, produced by budding from a primitive zodid. As in the Tubularians among the Corynida, the whole ccenosare is enveloped in a horny or chitinous envelope or polypary (Fig. 17, a), and this is the structure which is most familiarly known to sea-side observers. The Sertwlarida, however, are distinguished from the Corynida by two points: Firstly, none of the Sertularida are simple, but are all compound, con- sisting of more or less numerous polypites, united by a branched ccenosare. Secondly, the polypary of the Sertwlarida differs from that of the Corynida in not simply reaching to the bases of the polypites, but in being prolonged to form a number of little cups or “ hydrothece ” (Fig. 17, a, 6) within which the polypites are lodged. Each polypite has a cup of its own, within which it can entirely withdraw, and from which it can protrude its free extremity. The polypites of the Sertularida have essentially the same structure as in the Corynida, and each may be compared to a little Hydra. Each, namely, consists of a soft, contractile, and extensile body, which is furnished at its free extremity with a mouth and a circlet of prehensile tentacles, richly furnished with thread-cells. The mouth opens into a chamber which occupies the whole length of the polypite, and which is to be regarded as the combined body-cavity and digestive sac. At its lower end this chamber opens by a constricted aperture DIVISIONS OF THE HYDROZOA. 67 into a tubular cavity, which is everywhere excavated in the substance of the ccenosarc (Fig. 17, 6). The nutrient parti- cles obtained by each polypite thus serve for the support of Fig. 17.—a Sertularia (Diphasia) pinnata, natural size; a’ Fragment of the same en- larged, carrying a male capsule (0), and showing the hydrothece (%); 6 Fragment of Campanularia neglecta (after Hincks), showing the polypites contained in their hy- drothece (7), and also the point at which the ccenosare communicates with the stomach of the polypite (c). the entire colony, and are distributed throughout the entire organism. The nutritive fluid prepared in the interior of each polypite gains access through the above-mentioned aperture to the cavity of the ccenosarc, which, by the combined exer- tions of the whole assemblage of polypites, thus becomes filled with a granular nutritive liquid. This ccenosarcal 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 process of reproduction varies somewhat in different members of the order. In all alike, however, the ordinary polypites are incapable of producing the essential elements of reproduction, and for this purpose special generative buds have to be developed. In the typical Sertularians the re- productive buds are developed at certain seasons in great numbers, and they constitute what used to be called the 68 INVERTEBRATE ANIMALS, “ ovarian vesicles” or “capsules.” These reproductive buds are enclosed in horny cups or receptacles, often of a very beautiful shape, and much larger in size than the ordinary hydrothece (Fig. 17, a, a'). Each bud may be compared to a polypite destitute of a mouth and tentacles, being composed of a protuberance of the ectoderm and endoderm, containing a prolongation from the general cavity of the ccenosarc. The essential elements of reproduction are developed between the ectoderm and endoderm of the bud, and the resulting embryo is finally liberated as a little oval body covered with cilia, with which it swims freely about, until it meets with a suitable. locality, when it fixes itself, loses its cilia, and by budding soon develops another colony. In one division of this group—often described as a separate order, under the name of Campanularida—some points of difference are observable. In the typical Sertularians the little cups or hydrothece for the polypites are placed on the sides of the branches, and they are not stalked (Fig. 17, a’), while the reproductive elements are pro- oe duced in fixed buds. Inthe Campanu- hp : ® Jarida, on the other hand (Fig. 17, 5), the hydrothece are supported upon stalks, and are placed at the ends of the branches, while the generative buds are usually detached to lead an inde- pendent existence. In these forms the reproductive zodids or gonophores start as simple buds; but they become grad- ually developed into free-swimming \ medusoids, such as have been before } t alluded to. Each medusoid consists of a little transparent, glassy bell, from the under surface of which there is sus- pended a modified polypite, in the form of a manubrium (Fig. 18). The whole organism swims gayly through the { water, propelled by the contractions of the bell or disk; and no one would sus- } pect now that it was in any way related to the fixed, plant-like zoophyte from Fic. 18—Gonophore of one of Which it was originally budded off. The the Campanularida. central polypite is furnished with a mouth at its distal end, and the mouth opens into a digestive sac. From the upper end of this stomach DIVISIONS OF THE HYDROZOA. 69 proceed four radiating canals which extend to the margins of the bell, where they all open into a circular vessel which runs round the mouth of the bell. From the circumference of the bell hang also a number of delicate extensile filaments or tentacles; and the margin is further adorned with a series of brightly-colored spots, which are probably rudimentary organs of vision and hearing. The mouth of the bell is partially closed by a delicate transparent membrane or shelf, the so- called “veil.” Thus constituted, these beautiful little beings lead an independent and locomotive existence for a longer or shorter period. Ultimately ova and sperm-cells are produced in special organs, which are developed in the course of the radiating canals of the disk. The resulting embryos are minute free-swimming bodies, covered with cilia, which finally fix themselves, and develop into the plant-like colonies from which the medusoids were derived. CHAPTER VL SUB-CLASS SIPHONOPHORA. Tue animals included under the name of Siphonophora are often known as the “oceanic Hydrozoa,” as they are not fixed like the Hydroid zoophytes, but are found swimming at the surface of the open ocean, far from land. They are all singularly delicate and beautiful organisms, but they require little notice here. They are distinguished from the Hydroid zoophytes, which we have been just considering, by the fact that the hydrosoma consists of numerous polypites, united by a common trunk or ccenosarc, which is very rarely branched, and is never furnished with any hard outer covering or poly- pary, so that it remains permanently soft and flexible through- out life. Asin the Hydroida, the reproductive organs are in the . form of special buds, which have the power of developing the essential elements of generation, and which are often detached as free-swimming medusoids. The entire sub-class is divided into two great groups or orders, and it will be sufficient to consider shortly a typical form of each. In the first order—that of the Calycophorida— the coenosarc is thread-like, cylindrical, unbranched, and highly contractile. The cavity of the ccenosarc dilates at one end into a peculiar ciliated chamber, which is the distinguishing character of the order. The name of Calycophoride (Gr. kalux, a cup; and phero, I bear) is, however, derived from another circumstance—namely, that one end of the ccenosarc is always furnished with a series of bell-shaped disks, which are known as “swimming-bells” or “nectocalyces.” Each nectocalyx consists of a bell-shaped cup (Fig. 19, v, v’), at- tached by its base to the ccenosarc, and having its cavity turned outward. In the substance of the disk run at least four canals, which communicate with the cayity of the cceno- SIPHONOPHORA. val sarc, and proceed to the margin of the bell, where they all open into a circular vessel, The mouth of the bell is also furnished with a delicate ledge, which runs round its circum- ference, and is known as the “veil.” The structure, there- fore, of the nectocalyces is very similar to that of an ordinary medusiform gonophore, the chief difference being the absence _ in the former of the central polypite or manubrium. The nectocalyces are highly muscular, and have the power of alter- nately contracting and dilating, thus driv- ing the whole organism through the water. In Diphyes (Fig. 19), which may be taken as the type of the group, there is a long thread-like trunk or “coenosare” (¢c) which bears at intervals minute polypites, each of which is protected by a delicate glassy overlapping plate, termed a “bract.” At one extremity of the ccenosarc are two large mitre- shaped swimming - dells or nectocalyces (v, v'), by the contractions of which the entire organism is driven through the water. The ccenosare with its polypites can be withdrawn, when necessary, into a kind of chamber be- tween the two swimming-bells; but when unretracted the organism often attains a length of several inches. Its name is derived from the fact that the two nectocalyces can be separated from the ccenosarc by the least oe and it was for this reason origina supposed 8 ; to consist of two distinct auinale feces aN ade dane se: attached to one another. The tentacles — Prorid@ (after Kolliker), : 5 , v, g-bells; ¢ are comparatively speaking ofgreatlength, — Cenosare, carrying the and are furnished with lateral branches Lt ee eae i containing numerous thread-cells. The — 4 bract. mouths of the polypites are not pro- vided with a circlet of tentacles, but each has a single long tentacle arising from near its base. The reproductive organs of the Calycophoride are in the form of medusiform gono- phores, which are budded from the stalks of the polypites, and which are mostly detached to lead an independent ex- istence. The second order of the oceanic Hydrozoa is that of the 72 INVERTEBRATE ANIMALS. Physophoride (Gr. physa, a bladder; and phero, I carry), of which the most familiar, though not the most typical, example is the Portuguese man-of-war, Physalia utriculus (Fig. 20, a). The Physophoride are distinguished from the organisms which we have been just considering by the fact that one extremity of the ccenosarc is developed into a structure which is known as the “float” or “ pneumatophore” (Gr. pneuma, air; and phero, I carry). The float contains a larger or smaller sac, composed of some elastic, horny substance, proba- bly chitine, often communicating with the exterior by one or more apertures, and always more or less completely filled with air. This sac is enclosed in a reflection of the ectoderm and endoderm, so that it is really outside the cavity of the cceno- sarc. The function of the float is no doubt that of enabling the organism to maintain its position at the surface of the sea. Asin the Calycophoride, the ccenosarc is always per- fectly flexible, contractile, and soft, and is rever furnished with any chitinous covering or polypary. There may or may not be swimming-bells, and the tentacles are very complicated in structure, and often attain a length of many inches. The polypites present no special points of interest, but are often furnished with the protective plates, which have been already spoken of as “ bracts.” As a good example of the Physophoride, the Portuguese man-of-war may be taken (Fig. 20, a). It is composed of a large, spindle-shaped float, often of several inches in length, upon the under surface of which are arranged a number of polypites, together with highly-contractile tentacles of great length, and reproductive organs. The tentacles are richly furnished with thread-cells ; and it has the power of stinging very severely. Physalia is commonly found floating at the surface of tropical and sub-tropical seas, and fleets of it are occasionally driven upon temperate shores. Another very beautiful member of the Physophoride is the Velella vulgaris, which occurs abundantly in many seas. It is about two inches in length by one and a half in height. One end of the ccenosare is greatly expanded and flattened out into an oval disk, which carries a vertical triangular crest, running obliquely across its upper surface (Fig. 20, 0). The whole organism is semi-transparent and of a beautiful bluish color, and it floats at the surface of the sea with the vertical crest exposed to the influence of the wind, and thus officiating as asail. From the under surface of the disk are suspended the various appendages of the organism, consisting of a single SIPHONOPHORA. 73 large central polypite, a number of processes, like polypites in shape, and carrying medusiform gonophores; and lastly, a single series of tentacles which arise from the ccenosarc quite independently of the polypites. ?, nM al é t ¥ x £ & a é a S Fic. 20.—a Portuguese man-of-war (after Huxley); 6 Veledia vulgaris (after Gosee). CHAPTER VII. SUB-CLASS DISCOPHORA. Tue group of Hydrozoa here spoken of as Discophora or Meduside comprises most of the familiar organisms known to visitors at the sea-side as sea-jellies, jelly-fishes, or sea-netties ; this last name being derived from the power possessed by some of them of stinging pretty severely in virtue of the pos- session of numerous thread-cells. Under the name, however, of sea-jellies are included a number of large organisms, ex- tremely common at certain seasons in our seas, but now known to be properly referable to another group of the Hy- drozoa (viz., Lucernarida). It is these large forms which alone possess any power of stinging man, and to these the term of “sea-nettles” ought properly to be restricted. They are better known under the name of “ hidden-eyed” Medusa, applied to them by the late Edward Forbes. Under the present group of the Discophora are included only a number of small jelly-fishes, found in great abundance at certain times, floating in the open sea, but nevertheless very little known to the general public in consequence of their very minute size. These delicate and diminutive organisms were originally described by Edward Forbes, for reasons to be immediately stated, as the “naked-eyed” Medusw. It is now known, however, that most of these naked-eyed Medusc are in reality nothing more than the free-swimming generative buds, or medusiform gonophores, produced by budding from so many of the other Hydrozoa, and then. detached, as we have formerly seen, to lead an independent existence. That this is their true nature, is shown by the fact that the eggs which they produce develop themselves, not into fresh Me- dusce, but into various other forms of Hydrozoa, which are fixed or oceanic. Under these circumstances, therefore, the DISCOPHORA. 45 naked-eyed Meduse which can be shown to be of this nature, cannot, of course, be regarded as distinct animals at all. Still, there remains a considerable group of naked-eyed Meduse to which this explanation has not hitherto been shown to apply. In most of the members of this group the course of develop- ment is quite unknown, and therefore their true nature is a matter of doubt. Two families, however, of this group are stated to produce eggs which develop directly into Meduse, such as those which gave origin to the eggs; and, if this ob- servation is confirmed, these, at any rate, must be regarded as true Discophora. In the mean while, therefore, it is best to regard the group of the Discophora or Meduside as of a questionable nature, and as including forms which may ulti- mately be shown to be nothing more than the detached zodids of other Hydrozoa. Under these circumstances it will not be requisite to do more than very briefly to describe the anatomical structure of a typical Medusid ; and this is the less necessary, since it will be seen at once that the structure is in all essential respects identical with what has been already described in speaking of the free medusiform gonophores of the Hydroid zoophytes. In all the naked-eyed Medusce, of which Modeeria (Fig. 21) Fic. 21.—Naked-eyed Medusm. a Sarsia gemmifera; b Modeeria formosa; ¢ Polyxe- nia Alderi (after Gosse). 76 INVERTEBRATE ANIMALS. may be taken as a good example, the general structure is briefly as follows: The hydrosoma is perfectly free and is oceanic, being found swimming near the surface in the open ocean. The body is composed of a thick, transparent, gelatinous disk or swimming-bell (the nectocalyx), by the pulsations of which the animal is driven through the water. From the under surface or roof of this bell-shaped disk is suspended a single polypite (the manubrium), which bears to the disk the same relative position as the clapper does to an ordinary hand- bell. The distal end of the central polypite is furnished with a mouth, the lips of which are often prolonged into four longer or shorter lobes or processes. The mouth opens into a digestive sac, occupying the axis of the polypite; and from the upper end of this proceed four radiating canals, which run in the substance of the disk to its margin, where they are united by a single circular vessel, the whole system con- stituting the so-called ‘ gastro-vascular” canals, The margin of the bell is narrowed by a kind of shelf, which runs round the whole circumference, leaving a central aperture, and which is known as the “veil.” From the margin of the disk hang more or less numerous tentacles, which are hollow processes of the ectoderm and endoderm, and which communicate with the circular vessel of the canal-system. Also round the cir- cumference of the swimming-bell are disposed certain “ margi- nal bodies,” which are doubtless organs of sense. Some of these marginal bodies consist of little rounded sacs or “ vesi- cles,” filled with a transparent fluid, and containing mineral particles, apparently of carbonate of lime. These are probably rudimentary organs of hearing. Others of the marginal bodies are in the form of little masses of coloring-matter or pigment, often of a strikingly bright color, enclosed in distinct cavities. These are known as the “ pigment-spots” or “ eye-specks,” and they are believed to be rudimentary organs of vision. They are placed in a conspicuous and unprotected position on the margin of the disk, and hence these organisms were termed “naked-eyed” Medusce by Edward Forbes. The reproductive organs are mostly developed in the course of the radiating gastro-vascular canals, but are sometimes situated in the walls of the central polypite. The above is the essential structure of any of the ordinary naked-eyed Meduse ; and it is hardly necessary to remark that it is exactly similar to what has been formerly described as distinguishing the undoubted free- swimming reproductive buds of the fixed Hydrozoa. The probabilities, therefore, as before said, are in favor of the belief DISCOPHORA. 77 that the entire group of the Discophora will have to be ulti- mately done away with. The naked-eyed Medusc are all exceedingly elegant and attractive, when examined in a living condition, resembling little. bells of the most transparent glass, adorned here and there with the most brilliant colors. They occur, in their proper localities and at proper seasons, in enormous numbers, and they constitute one of the staple articles of diet to the Greenland whale. They are mostly phosphorescent, or capa- ble of giving out light at night, and they appear to be one of the principal sources of the luminosity of the sea. It does not seem, however, that they phosphoresce unless disturbed or irritated in some way. CHAPTER VIII. SUB-CLASSES LUCERNARIDA AND GRAPTOLITIDZ. Tue last remaining group of the living Hydrozoa is that of the Lucernarida (Lat. lucerna, a lamp), under which name are included a considerable number of forms, differing from one another to a great extent in exter- nal appearance. It will be sufficient here to describe one or two typical forms, One group of the Lucernarida is represented by Lucernaria itself (Fig. 22), which occurs not uncommonly in temperate seas. In Lucernaria we have a cup-shaped body, of a more or less gelatinous consistence, usually found attached by its smaller extremity to sea-weeds, this end of the body being developed into a small sucker. Like the Hydra, however, Lucernaria is not fixed, but can detach itself at will, and can even swim freely by means of the alternate contraction and expansion of the cup-shaped body (or “ umbrella,” as it is termed). Round the margin of the cup are tufts of short tentacular processes, and in its centre is fixed a single polypite, furnished with a four- Fig. 22.—Two specimens of Zu. !Obed mouth. The essential elements Hida Re Bodom of reproduction are developed within Johnston). (her the body of Lucernaria itself, and it does not give off any generative buds, as so commonly occurs in other forms. LUCERNARIDA AND GRAPTOLITIDZ. 79 Another type of the Zucernarida is represented by the organisms formerly termed “hidden-eyed” MMeduse, and familiarly known as sea-nettles or sea-blubbers. Every sea- side visitor is familiar with the great circular disks of jelly which are left upon the sands by the retreating tide during the summer months; and many must have noticed on a calm day the large, transparent disks of these same creatures slowly flapping their way through the water. Nota few, too, must have learned by painful experience that some of these singular organisms have the. power of stinging most severely, if in- cautiously handled. The forms included under the old name of “ covered-eyed” Medusce differ considerably from one an- other in their nature, and even in their structure, though they all present, in spite of their much greater size, a decided re- semblance to the naked-eyed Meduse already described. Some of the covered-eyed Medusce produce eggs which are developed into organisms resembling themselves; but most of them are now known to be nothing more than the free-swimming re- productive buds of minute rooted Hydrozoa. It will be suf- ficient here to describe shortly the life-history of one of the more remarkable forms of this section. If we commence with the young form of one of these sin- Fia. 23.—Development of Lucernarida (Cirysaora). a Ciliated embryo; 6 Hydra-tuba; c Hydra-tuba beginning to divide by transverse cleavage; @ The cleavage still further advanced; ¢ A form in which the cleavage has proceeded still further, and a fresh circle of tentacles has been produced near the base; / Free-swimming, generative zodid, pro- duced by fission from the Hydra-tuba. gular animals, we find that the egg gives origin to a little microscopic ciliated body, which swims about freely by means of the cilia with which its surface is covered (Fig. 23, a). 80 INVERTEBRATE ANIMALS. This little body, on finding a suitable locality, fixes itself by one end, and develops a mouth and tentacles at the other, when it is known as a “ Hydra-tuba” (Fig. 23, 6), from its resemblance in shape to the fresh-water polype or Hydra, The Hydra-tuba is only about half an inch in height, and it possesses the power of forming large colonies by gemmation, while it is incapable of developing the essential elements of reproduction. Under certain circumstances, however, repro- ductive zodids are produced by the following singular process: The Hydra-tuba becomes elongated, and exhibits a number of transverse grooves (Fig. 23, c). These grooves go on get- ting deeper and deeper, and become lobed at their margins, till the whole organism assumes the aspect of a pile of saucers placed one above the other (Fig. 23, @). The tentacles now disappear, and a fresh circle is formed close to the base of the Hydra-tuba (Fig. 23, ¢). Finally, all the saucer-like segments above the new circle of tentacles drop off one by one, and pre- sent themselves in the form of independent, free-swimming Meduse (Fig. 23, f). These reproductive zodids or Meduse eat voraciously, and increase rapidly in size, becoming not only comparatively, but often actually, gigantic. Thus, in one case the reproductive zodid has been known to attain a size of seven feet across, with tentacles fifty feet in length, though the fixed organism from which it was produced, was no more than half an inchin height. These gigantic repro- ductive bodies live an independent life until they are able to produce ova and sperm-cells, when they die. The fertilized ege, however, develops itself, not into the monstrous organism by which it was produced, but into the little fixed sexless Hydra-tuba, from which the generative bud was detached. We have, then, here another instance of the so-called “ alterna- tion of generations.” It is now known, then, that most of the great sea-blubbers which abound around our coasts in summer are really the detached reproductive buds of minute fixed Hydrozoa ; and it may be as well to mention the leading features in their struct- ure, and the points by which they may be distinguished from the smaller or naked-eyed Medusc, to which they have a de cided superficial likeness. In the commonest forms of these zovids (such as the familiar sea-blubbers, Aurelia and Cyanea), the body consists of a great bell-shaped gelatinous disk or “umbrella,” from the roof of which is suspended a single polypite, the lips of which are extended into lobed processes, often extending far below the margin of the disk (Fig. 24). LUCERNARIDA AND GRAPTOLITIDA. 81 The digestive cavity of the polypite gives out from its upper extremity a series of radiating gastro-vascular canals, which proceed toward the margin of the umbrella. These radiating canals are never less than eight in number, and on their way to the margin of the disk they break up into a great number of smaller vessels, which unite with one another to form a complicated net-work. At the margin of the bell they all Fig. 24,—Generative zodid of one of a TS dedi (Chrysaora hysoseclia). (After osse. open into a circular vessel, which in turn sends processes into a series of marginal tentacles, which are often of extraordinary length. Besides the tentacles, the margin of the umbrella is provided with a number of marginal bodies, each of which consists of a little collection of pigment or “ eye-speck,” and a little sac filled with fluid and containing mineral particles. Each of these marginal bodies is covered and concealed from view by a kind of hood derived from the ectoderm. Hence the name of “hidden-eyed” Medusw applied to these forms, in contradistinction to the “naked-eyed ” Meduse, in which the eye-specks are exposed to view. ‘The reproductive organs are usually of some bright color, and “form a conspicuous cross shining through the thickness of the disk.” 82 INVERTEBRATE ANIMALS. From the above description it will be evident that there is considerable resemblance between the so-called “ hidden-eyed” Meduse, or the reproductive zodids of many of the Lucernarida, and the medusiform gonophores of so many of the Hydrozoa, as well as the true Discophora or naked-eyed Meduse. The differences, however, between them are these: The swimming- disk of the naked-eyed Meduse and of any medusiform gono- phore is furnished at its mouth with an internal shelf or veil ; the radiating gastro-vascular canals are very rarely more than four in number, and, should they subdivide (as in rare oases they do), they do not form an intricate net-work; lastly, the marginal bodies are simply placed in an uncovered situation on the margin of the disk. In the reproductive zodids of the Lucernarida or hidden-eyed Meduse, on the other hand, the swimming-disk or umbrella is destitute of any marginal shelf or veil; the radiating gastro-vascular canals are never less than eight in number, and they split up into numerous branches, which unite to form an intricate net- work; lastly, the marginal bodies are concealed from ‘view by a kind of hood. There still remains another family of the Lucernarida (viz., Ehizostomide) in which the reproductive process is carried on in the same way as in the forms we have just described, but the structure of the reproductive zodids is somewhat different. In these, as in Rhizostoma, the generative zodid is much like those just mentioned ; but the umbrella is destitute of ‘marginal tentacles ; and, in place of a single central polypite, there hangs from the under surface of the umbrella a com- plex tree-like mass, the branches of which end in, and are covered by, small polypites and club-shaped tentacles. The umbrella itself does not exhibit any difference as compared with those already described, but the ova are produced in a genital cavity which is placed on the under surface of the umbrella. Sup-cLass GRaProLit1p£.—Before leaving the Hydiozoa, it will be as well to notice very briefly a group of extinct organisms which certainly belong to this class, and which probably find their nearest allies in the Sertularians. The Grapitolitide are without a single living representative, and their anti- quity is, indeed, very high, since it is doubtful if they ever pass above the group of rocks known to geologists as the Silurian formation. The most typical forms of the group agree with the living Sertularians in having a horny polypary, and in having the polypites protected by little horny cups or hydrothecw, all springing from a common flesh or coenosare. The typical Graptolites, however, differ from all known Sertularians in the fact that the hydrosoma was not fixed to any solid object, but was permanently free. LUCERNARIDA AND GRAPTOLITIDA. 83 Most of them, also, exhibit a very anomalous and remarkable structure, termed the “solid axis.” This is a peculiar fibrous rod, which no doubt served to strengthen the polypary, and which is often prolonged beyond one or both ends of the polypary in a naked state. There is also good evidence that the reproductive process in the Graptolites was carried on in a manner somewhat similar to what is seen in the living Sertularians—namely, by means of reproductive buds enclosed in horny capsules. Graptolites most usually present themselves as beautiful silvery impressions, covering the sur- face of the black shales of various parts of the Silurian system. CHAPTER IX, ACTINOZOA. Tur second great class of the Celenterata is that of the Actinozoa, comprising the sea-anemones and their allies, the corals, the sea-pens, the sea-shrubs, and various other organ- isms.’ They are all defined as Coelenterate animals in which there is a distinct digestive sac which opens below into the general cavity of the body, but is nevertheless separated from the body-walls by an intervening space, which is divided into a number of vertical compartments by a series of partitions or “ mesenteries,” to the faces of which the reproductive organs are attached. The Actinozoa (Fig. 12), therefore, differ fun- damentally from the Hydrozoa in this, that whereas in the latter the digestive cavity is identical with the body-cavity, in the former there is a distinct digestive sac, which opens truly into the body-cavity, but is nevertheless separated from it by an intervening space. The result of this is, that while the body of a Hydrozoén exhibits on transverse section a single tube only, formed by the walls of the combined diges- tive and somatic cavity, the body of an Actinozoén exhibits two concentric tubes, one formed by the digestive sac and the other by the general walls of the body (Fig. 25, A). Further, in the Actinozoa the reproductive organs are always internal, and are never in the form of external processes of the body- wall as in the Hydrozoa, In their minute structure the tissues in the Actinozoa dif: fer little from those of the Hydrozoa. The body is essen- tially composed of two fundamental layers—an ectoderm and endoderm; but there are often well-developed layers of mus- cular fibres, somewhat obscuring this simplicity of structure. Thread-cells are most commonly present in abundance. Cilia are very generally developed, especially in the endoderm lining ACTINOZOA. 85 the body-cavity, where they serve to maintain a circulation of the contained fluids. The only digestive apparatus consists of a tubular or sac-like stomach, which opens inferiorly directly into the body-cavity (Fig. 12, a), and communicates © Mm Fic. 25.—A. Transverse section of an Actinozodn. a Digestive sac; > Outer-wall of the body or ectoderm; b’ Endoderm; m Mesenteries, connecting the stomach with the boty wal and dividing the space between the two into a number of vertical chambers. B. Transverse section of the body of a Hydrozodn, showing the single tube formed by the walls of the body. with the outer world through the mouth. A nervous system has not been shown to exist in any of the Actinozoa except the Ctenophora, and in none are there any traces of a circula- torysystem. Distinct reproductive organs are always present, and true sexual reproduction occurs in all the members of the class. In a great many forms, however, of the Actinozoa we _ have composite organisms or colonies, produced by a process of “continuous” gemmation or fission, the zodids thus origi- nated remaining attached to one another. In these cases— as in most of the corals—the separate beings or zodids thus produced are termed “polypes,” the term “ polypite” being restricted to the Hydrozoa. In the simple Actinozoa, how- ever, such as the sea-anemones, the term “ polype” is applied to the entire organism, as consisting of no more than a single alimentary region. It follows from this, that the entire body of any Actinozodn may be composed of a single polype, or of several such produced by budding or cleavage, and united to one another by a common connecting structure or coenosarc. Most of the Actinozoa are permanently fixed, like the corals; some, like the sea-anemones, possess a limited amount of locomotive power; and one order, the Ctenophora, is com- posed of highly-active free-swimming organisms. Some of them are unprovided with hard structures or supports of any kind, as the sea-anemones and Ctenophora ; but a great many v 86 INVERTEBRATE ANIMALS. secrete a calcareous or horny skeleton or framework which is known as the “coral”? or “ corallum.” The Actinozoa are divided into four orders—viz., the Zoan- tharia, the Alcyonaria, the Rugosa, and the Ctenophora. Orver I. ZoantHaria (Gr. zodn, animal; anthos, flower). —The Zoantharia comprise those Actinozoa in which the polypes are furnished with smooth, simple, usually numerous tentacles, which, like the mesenteries, are in multiples of jive or siz, The Zoantharia are divided into three groups, dis- tinguished from one another by the presence or absence of a coral, and by its structure when present. The first of these groups is termed Zoantharia malacoder- mata, or “ soft-skinned” Zoantharia, because the polypes are either wholly destitute of a coral, or, if there is one, it consists merely of little scattered needles or spicules of carbonate of lime, Generally, too, the organism is simple, and consists of Fic. 26.—Morphology of Actinide. a Actinia rosea; b Arachnactis albida (after Gosse).. no more than a single polype. The best known of the mem- bers of this group are the beautiful sea-anemones or animal- flowers (Actinide), which occur so plentifully on every coast (Fig. 26, a). It will be as well to describe the structure of a sea-anemone somewhat in detail, as in this way a clear notion may be obtained of the general anatomy of the Actinozoa. The body of an ordinary sea-anemone (Fig. 26, @) is a truncated cone or short cylinder, termed the “column,” and is of a soft, leathery consistence. The two ends of the column are termed ACTINOZOA. 87 respectively the “base” and the “disk,” the former constitut- ing a kind of sucker, by means of which the animal can attach itself at will, while the mouth is placed in the centre of the latter. The mouth is surrounded by a flat space, destitute of appendages, and the circumference of the disk is in turn sur- rounded by numerous simple tubular tentacles, arranged in alternating rows. The tentacles consist of both ectoderm and endoderm, enclosing a tube which communicates with the body-cavity. By the muscular contraction of the walls of the column, the fluid contained in the body-chambers can be forced into the tentacles, which can be thus protruded a great length, while they can also be usually retracted. In some cases the tentacles are furnished with perforations at their extremities. The mouth (see Fig. 12, a) leads directly into the stomach, which is a wide, membranous tube, opening by a wide aperture into the body-cavity below, and extending about half-way be- tween the mouth and the base. The wide space between the stomach and body-walls is subdivided into a number of sepa- rate compartments by radiating vertical plates, which are called the “mesenteries,” and to the faces of which the re- productive organs are attached, in the form of reddish bands, containing either ova or sperm-cells. Below the stomach, attached to the free edges of the mesenteries, are a series of singularly twisted threads or cords (Fig. 12, ¢), which are filled with thread-cells, and are termed “craspeda.” The function of these is not well understood; but it is believed ‘that in some cases they can be emitted through apertures, which are occasionally found in the walls of the column, The sea-anemones are mostly to be found between tide-marks, in rock-pools, or on ledges of stone, adhering by means of the expanded base. They are not, however, permanently fixed, but can change their place at will. In the nearly allied Ltyanthus and Arachnactis (Fig. 26, 6) the base is tapering, and it appears that the animal spends the greater part of its existence in an unattached, free condition. The true sea- anemones, as already said, are all simple, each consisting of a single polype; but there are closely-related forms (such as Zoanthus) in which the organism is compound, consisting of numerous polypes united by a creeping, fleshy trunk or coeno- sare, The second group of the Zoantharia is termed that of the Zoantharia sclerodermata, from the nature of the skeleton or coral, In this group are all the so-called “ reef-building” corals, which are the makers of the well-known “ coral-reefs.” 88 INVERTEBRATE ANIMALS. The members of this‘group all possess the power of secreting carbonate of lime within their tissues, so as to form a more or less continuous skeleton or corallum. From the fact that this corallum is secreted by the inner layer of the polypes, and is therefore truly within the body, it is said to be “ sclero- dermic,” in opposition to the kind of coral produced by other forms (such as the red coral), where the skeleton is secreted by the outer layer of the polypes, and is therefore outside them. In this latter case the coral is said to be “ sclerobasic.” (For illustrations of these different kinds of corals, see Fig. 29.) In the typical form of sclerodermic coral, the skeleton is in the form of a conical cup, the upper part of which is hol- low. The lower part is divided into a series of compartments by vertical plates, which are called the “septa,” and which correspond to the mesenteries of the living animal. Some- times the space contained within the walls of the cup cr “corallite” is broken up by horizontal plates called “tabulz;” but, when these are present, there are generally no septa. In the form of coral just described we have a single corallite, produced by one polype, and this simple condition may be maintained throughout life. In the great majority of cases, however, the polypes bud, so as to form a colony, all bound together by a common flesh or ccenosarc. When such a colony, therefore, produces a sclerodermic coral, in place of a single corallite, we have a composite skeleton composed of a number of little cups or corallites, each of which was produced by one polype, and all of which are united by means of a oe calcareous basis secreted by the coenosare (Fig. 29, a). In accordance with their mode of formation, an ordinary compound sclerodermic coral may be distinguished from a sclerobasic coral by the fact that it would show a number of little cups in which the polypes were contained, whereas these cups would be absent in the latter. In accordance, also, with the fundamental character of the order Zoantharia, the corals of the present group always show septa which are some mul- tiple of five or six. When it is understood that compound corals, such as we have been speaking of, are produced by the combined efforts of a number of polypes, essentially the same in structure as our ordinary sea-anemones, it is readily intelligible that under favorable circumstances large masses of coral may be produced in this way. When these masses attain such a size as to be of geographical importance, they are spoken of as “ coral-reefs,” and the phe- nomena exhibited by these are of such interest as to demand some notice. The coral-producing polypes require for their existence that the average ACTINOZOA. 89 temperature of the sea shall not be less during winter than 66°; and coral- reefs are, therefore, not found in temperate seas. Reefs, however, abound in all the seas not far removed from the equator, being found chiefly on the east coast of Africa and the shores of Madagascar, in the Red Sea and Persian Gulf, throughout the Indian Ocean and the whole of the Pacific Archipelago, around the West-Indian Islands, and on the coast of Florida. The headquarters, however, of the reef-building corals may be said to be around the islands and continents of the Pacific Ocean, where they often form masses of coral many hundreds of miles in length. According to Darwin, coal-reefs may be divided into three principal forms—viz., Fringing- reefs, Barrier-reefs, and Atolls, distinguished by the following charac- ters: 1. Fringing-reefs (Fig. 27, 1).—These are reefs, usually of a moderate size, which may either surround islands or skirt the shores of continents. These shore-reefs are not separated from the land by any very deep channel, and the sea on their outward margins is not of any great depth. 2. Barrier-reefs (Fig. 27, 2).— These, like the preceding, may either encircle islands or skirt continents. They are distinguished from fring- ing-reefs by the fact that they usually occur at much greater distances from the land, that there intervenes a channel of deep water between them and the shore, and soundings taken close to their seaward margin indicate great depths. Fig. 27.—Structure of Coral-reefs. 1. Fringing-reef; 2. Barrier-reef; 8. Atoll; @ Sea- level; } Coral-reef; ¢ Primitive land; @ Portion of sea within the reef, forming a chan- nel or lagoon. As an example of this class of reefs may be taken the great barrier-reef on the northeast coast of Australia, the structure of which is on a gigantic scale. This reef runs, with a few trifling interruptions, for a distance of more than a thousand miles, with an average breadth of thirty miles, and an area of 90 INVERTEBRATE ANIMALS. thirty-three thousand square miles. Its average distance from the shore is between twenty and thirty miles, the depth of the inner channel is from ten to sixty fathoms, and the sea outside is “profoundly deep” (in some places over eighteen hundred feet). 8. Atolls (Fig. 27, 3).—These are oval or 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. They agree in all particulars with those barrier-reefs which surround islands, except that there is no central island in the lagoon which they enclose. The last group of the Zoantharia comprises composite or- ganisms in which the ccenosare is supported upon a central axis or sclerobasic skeleton. These Zoantharia sclerobasica require no notice, except simply to remark that they are dis- tinguished from other sclerobasic corals (such as the Gor- gonide) by the fact that each polype possesses tentacles which are a multiple of stx in number. Orpver II. Atcyonarta.—The second great order of living Actinozoa is distinguished by the fact that the polypes are furnished with fringed tentacles, and that these, as well as the mesenteries and somatic chambers, are always some mul- tiple of four. With one doubtful exception, all the Al cyonaria are composite, their polypes being connected to- gether by a ccenosarc. The body-cavities of the polypes are connected with a system of canals which are excavated in the coenosare, and communicate freely with one another, so that a free circulation of nutrient fluids is thus kept up. The struct- ure of the polypes of the Alcyonaria is, in all essential -anatomical features, the same as in the sea-anemones, the number of the mesenteries and tentacles being the chief dis- tinction. Of the various different organisms included under this order, one of the best known is the “ Dead-men’s-fingers,” or Alcyo- nium, which occurs commonly in most seas. It forms spongy- looking masses of a yellow or orange color, attached to shells and other marine objects. The whole mass is covered with little star-shaped apertures, through which the delicate pol- ypes can be protruded and retracted at will. Another well- known member of this order—the type of another family—is the “sea-rod” (Virgularia mirabilis), which occurs not very rarely in shallow seas. Vérgularia occurs in the form of along rod-shaped body of a light flesh-color, supported upon a cal- careous rod, somewhat like a knitting-needle, which is covered by the ccenosare. From the ccenosare are given out lateral ACTINOZOA. 91 processes, each of which bears numer- ous polypes. Closely allied to Virgu- laria is the “ Cock’s-comb” Pennatula (Fig. 28); but in this the lower end of the coenosare is naked and fleshy, and the polype-bearing fringes are considerably longer, giving the whole organism very much the appearance of a feather. Another family of the Aleyonaria is represented by the so-called “Or- gan-pipe corals,” of which Tubipora musica is a well-known example. In this there is a well-developed sclero- dermic coral consisting of numerous cylindrical tubes, which are not di- vided by vertical partitions (septa), but which are connected by strong transverse plates. The coral is bright red in color, and the polypes are usually bright green. The best known, however, of the Alcyonaria is the family Gorgonide, represented by the sea-shrubs, fan- Fie. 28.—Pennatulide, The Cock’s- ' corals, and the red coral of commerce. — comb (Pennatula phospho- A few of the members of this family "° ‘#e Johnson) live in temperate waters, but they attain their maximum in point of size and numbers in the seas of the tropics. In all the Gorgonide the organism consists of a composite structure made up of numerous polypes united by a common flesh or coenosare (Fig. 29, 5), the whole supported by a central branched axis or coral. The coral varies in composition, be- ing sometimes calcareous—as in red coral—sometimes horny, and sometimes partly horny and partly calcareous, as in sis (Fig. 29). In all cases, however, the corallum differs alto- gether from the sclerodermic corallum, which has been de- scribed as so characteristic of the reef-building corals. The coral in the present instance is always what is called “ sclero- basic ”—that is to say, it always forms an internal axis, covered by the ccenosare with the polypes produced therefrom. It is, therefore, outside the polypes, and bears to the coenosarc the same relation that the trunk of a tree bears to its investing bark. This is well shown in Fig. 29, 6, where there is repre- sented one of these sclerobasic corals in which the corallum 92 INVERTEBRATE ANIMALS. consists of alternate horny and calcareous joints. The pol- ypes of all the Gorgonide agree, of course, with their order in having eight tentacles each, and by this they are distin- guished from the few Zoantharia in which there is a sclero- basic coral. Fic. 29.—Sclerodermic and Sclerobasic Corals. a@ Portion of branch of Dendrophyllia nigrescens, a sclerodermic coral (after Dana); 6 Longitudinal section of Isis hippuris, a sclerobasic coral, exhibiting the external bark or ccenosare, with its imbedded polypes, supported by the internal axis or skeleton (after Jones). The best known of the Gorgonide is the Corallium rubrum, or “red coral” of commerce, which is largely imported from the Mediterranean. In this species there is a bright-red, finely-grooved, calcareous coral, usually more or less repeatedly branched. The coral is invested by a bright-red coenosarc or bark, which is studded with numerous little apertures. The polypes can be protruded from these openings at will, and are milk-white in color, with eight fringed tentacles each. The entire coenosare is excavated into a number of communicating canals, with which the cavities of the polypes are connected, the whole system being filled with a nutritive fluid known as the “milk.” Orver III. Rueosa (Lat. rugosus, wrinkled).—This order merely requires mention, as all its members are extinct, and are therefore only known to us by their hard parts or skele- ACTINOZOA. 93 tons. They agree with the Zoantharia sclerodermata in having a well-developed sclerodermic corallum, but differ from them in the fact that the septa are always some multiple of four ; and there are generally transverse plates or tabule combined with the vertical plates or septa. On the other hand, they agree with the Alcyonaria in having their parts in multiples of four, but differ from them in having a well- developed sclerodermic corrallum in which septa are present. Orper IV. Crenopnora (Gr. kteis, a comb; phero, I carry).—The fourth and last order of the Actinozoa is that of the Ctenophora, comprising a number of free-swimming oceanic creatures, very different in appearance from any of the forms which we have hitherto been considering. They are all trans- parent, gelatinous, glassy-looking creatures, which are found near the surface in the open ocean, swimming rapidly by means of bands of cilia. The cilia are arranged in a series of trans- verse ridges, which are disposed in longitudinal bands, the whole constituting locomotive organs which are known as “‘ctenophores.” In none are there any traces of a corallum or skeleton, and thread-cells are asserted to be universally present. Fic. 80.—Ctenophora. Plewrobrachia pileus. As the type of the order, we may take one of the commoner forms, which is known by the name of Pleurobrachia or Cy- dippe (Fig. 30). The body of Pleurobrachia is transparent, colorless, gelatinous, and melon-shaped, and exhibits two poles, at one of which is placed the mouth. The globe-like body is 94 INVERTEBRATE ANIMALS. divided into a number of crescentic lobes by eight ciliated bands or ctenophores, which proceed from near the mouth to near the opposite pole of the body. Besides the cilia there are two very long and flexible tentacular processes, which are fringed on one side by smaller secondary branches. The ten- tacles arise each from a kind of sac, one placed on each side of the body, and they can be instantaneously and completely retracted within these sacs at the will of the animal. ‘he mouth of Pleurobrachia opens into a spindle-shaped digestive sac or stomach, which in turn opens below into a wider and shorter cavity termed the “funnel;” from this there proceed in the axis of the body two small canals, which open at the opposite pole of the body. The funnel communicates with a complicated system of canals, which are ciliated internally, and are filled with a nutrient fluid, In the angle between the two canals which run from the base of the funnel to the sur- face is a little vesicle or sac, believed to be a rudimentary organ of hearing, and placed upon this is a little mass which is generally believed to be of a nervous nature. If this is correct, this is the first indication which we have hitherto en- countered of a genuine nervous system. The reproductive organs are developed in the walls of the canal-system, The only other form of the Ctenophora which deserves mention is the “Venus’s girdle” (Cestwm Veneris), which agrees in essentials with Pleurobrachia, but is greatly enlon- gated in a direction at right angles to the alimentary canal, till we have a ribbon-shaped body produced, four or five feet in length and two or three inches high. Cestwm is not un- common in the Mediterranean, and has the power of phospho- rescence, appearing at night as a moving and twisting band of flame, SUB- KINGDOM III.—ANNULOIDA. CHAPTER X. ECHINODERMATA. Tue third primary division of the animal kingdom is known by the name of Annzloida, and includes two groups of organ- isms which are extremely unlike one another in appearance, and are termed respectively the Hchinodermata and the Sco- lecida. In the former we have the sea-urchins, star-fishes, and their allies, formerly classed in the old sub-kingdom Radiata ; in the latter are a number of internal parasites, with some minute aquatic creatures, all formerly referred elsewhere. Dif- ferent as are these two groups in appearance and habits, they are nevertheless united by the following peculiarities:* They possess a@ distinct alimentary canal, usually communicating with the outer world by two apertures (a mouth and a vent), but in any case completely shut off from the general cavity of the body. In all there is a distinct nervous system ; and in all there is a peculiar system of canals termed the “ water-vascu- lar ” or “aquiferous” vessels, which usually communicate with the exterior of the body. It should be mentioned that many naturalists dissent from this grouping together of the Echinodermata and Scolecida into a single sub-kingdom, Annuloida. Many other arrangements have been proposed, most of which present some special advantages and,some dis- advantages. In the mean while, in the confessedly uncertain state of this department of Natural History, it has been thought well to adhere to the arrangement proposed by Prof. Huxley, an arrangement with many obvious drawbacks, and at best but provisional. * Some of the internal parasites of this sub-kingdom have no alimentary canal at all, but this docs not affect the value of the above definition. 96 INVERTEBRATE ANIMALS. Crass I.—EcuiInopERMATA. The members of this class are popularly known as sea- urchins, star-fishes, brittle-stars, feather-stars, sea-cucumbers, etc., and derive their name of Echinodermata (Gr. echinos, a hedgehog; and derma, skin) from the generally prickly nature of their integuments, In all, the skin is possessed of the power of secreting carbonate of lime, but in very different degrees, In the sea-urchins this goes so far that the body becomes en- closed in an immovable box, composed of numerous calcareous plates firmly jointed together. In the star-fishes and their allies the skin is rendered prickly by grains, tubercles, or spines of calcareous matter, and the body is either destitute of regular plates or is only partially enclosed by them. In the sea-cucumbers, again, the calcareous matter is mostly only present in the form of minute grains scattered in the skin. When adult, they all show a more or less distinctly radiate structure, which is most conspicuous in the star-shaped star- fishes and sand-stars, but can be detected in all the members of the class. When young, however, they almost always ex- hibit what is called “bilateral symmetry ”—that is to say, they show similar parts on the two sides of the body. In all Echino- derms there is a water-vascular system of tubes, which is termed the “ambulacral system,” which generally communi- cates with the exterior, and which in most cases is used in locomotion, An alimentary canal is always present, and is always completely shut off from the general cavity of the body. A vascular or circulatory system is sometimes present. There are always distinct organs of reproduction, which are almost always placed in different individuals, so that the sexes are distinct. The nervous system is in the form of a ring sur- rounding the gullet and sending branches in a radiating man- ner to different parts of the body. : The Echinodermata are divided into seven orders, as fol- lows : 1. Eehinoidea (Sea-urchins). 2. Asteroidea (Star-fishes). 3. Ophiuroidea (Sand-stars and Brittle-stars). 4, Crinoidea (Feather-stars), 5. Cystoidea (extinct). 6. Blastoidea (extinct). %. Holothuroidea (Sea-cucumbers). This is by no means a true arrangement of these orders, but it is convenient to consider them in this sequence. ECHINODERMATA. 97 Orver I. EcuryomEa.—The animals included in this order vary from the shape of a sphere or globe to that of a disk, and they are all commonly known as “sea-urchins” or “ sea-eggs.” They are all characterized by the fact that the body is encased in a “test” or “shell” (Fig. 31, 2) composed of numerous cal- careous plates mostly immovably jointed together so as to form a kind of box. The intestine is convoluted, and there is a distinct vent, or anal aperture. The test of a sea-urchin, as just said, consists of many cal- careous plates accurately fitted together, and united by their edges. In all living forms the test is composed of ten zones of plates, each zone consisting of a double row. In five of these zones (1 a, 2 a) the plates are of large size, and are per- Fic. 31.—Morphology of Echinoidea. 1. Portion of the test of a sea-urchin (@alerites), enlarged, showing the ambulacral areas (6) and interambulacral areas (a). 2. Test of the same, viewed from above: @ Interambulacra; 6 Ambulacra. 8. Genital disk of a sea-urchin (Hemicidaris) enlarged: ¢ Ocular plate; d@ Genital plate; e Anal aperture; J Madreporiform tubercle. 4, Spine of the same. (After Forbes.) forated by no apertures. These are termed the “interambu- lacral areas.” In the other five zones (1 6, 2 6) the plates are of small size, and are perforated by little apertures for the emission of delicate locomotive suctorial tubes (the so-called “ambularcal tube-feet”). These zones are therefore called the “ambulacral areas.” Besides these main rows of plates which collectively make up the greater part of the test, there are other plates placed in the leathery skin round the mouth and vent. The most important of these form a kind of disk, which is placed at the summit of the shell. This disk (Fig. 31,3) is composed of two sets of plates—one called the “geni- 98 INVERTEBRATE ANIMALS. tal plates,” perforated for the ducts of the reproductive organs; the other set smaller, and each carrying a little “eye,” hence their name of “ocular plates.” One of the genital plates is also larger than the others, and carries a spongy mass which is called the “ madreporiform tubercle,” and which protects the entrance of the water-vascular or ambulacral system. The whole of the test is covered with numerous tubercles of dif- ferent sizes, which carry longer or shorter spines (Fig. 32). The spines are jointed to the tubercles by a sort of “ ball-and- Fic. 82.—Cidaris papillata (after Gosse). socket” or “universal” joint, and they are completely under the control of the animal, so as to be used both in locomotion and apparently as defensive weapons. In most common species the spines are short, but in many tropical forms they attain a very great length. Besides the spines, the outer surface of the test is furnished with curious little bodies called “ pedi- cellarize,” which were long believed to be parasitic. They consist of two or three blades mounted upon a flexible stalk and constantly employed in snapping together like the beak of a bird. They occur in many other Echinodermata, and their use is obscure. Locomotion is effected in the sea-urchins by a curious system of contractile tubes which are known as the “ambu- lacral tubes” or “tube-feet,” and which are appendages of the water-vascular system. The following is essentially the arrangement of the whole aquiferous system. From the madreporiform tubercle on the largest of the genital plates ECHINODERMATA. 99 there proceeds a membranous canal by which the outer water is conducted to a central tube, which forms a ring round the gullet. The tubercle is spongy, and is perforated with little holes, and its function is probably to act as a filter, and prevent foreign particles gaining access to the interior. From the “circular canal” round the gullet proceed five “ radiating canals” which take their course toward the summit of the shell, underneath the ambulacral areas. In its course each radiating canal gives off numerous short lateral tubes—the ambulacral tubes or tube-feet—which gain the exterior of the shell by passing through the apertures in the ambulacral plates of the shell, and which terminate in little sucking- disks. The tube-feet can be distended with water by means of a series of little muscular bladders placed at their bases, and they can thus be thrust far out beyond the shell, into which they can be again withdrawn at the will of the animal. However long the spines may be, the animal can protrude the tube-feet to a still greater length; and by the combined action of the little suckers at their extremities locomotion is effected with moderate rapidity, considering the bulk of the body. The digestive system in the chinus consists of a mouth armed with a curious apparatus of calcareous teeth, which opens into a gullet, which in turn conducts to a distinct stomach, From the stomach there proceeds a long and con- voluted intestine, which is attached to the interior of the shell by a delicate membrane or “mesentery,” and terminates in a distinct vent, The surface of the mesentery, as well as that of the lining membrane of the shell, is richly ciliated, and thus serves to distribute the fluids of the body-cavity to all parts of the body. In this way, also, respiration is subserved, though it is probable that the chief agent in this function is to be found in certain specialized portions of the ambulacral system. The circulatory system consists in its central portion of two rings placed round the opposite ends of the alimentary canal, and united by an intermediate muscular cavity or heart. The nervous system consists of a gangliated cord placed round the gullet, and sending five radiating branches along the ambulacral areas. The sexes are distinct, but in both the re- productive organs are in the form of five membranous sacs placed in a radiating manner in the interambulacral areas, and opening at the genital-plates. The embryo of the Hchinus is at first a little free-swimming ciliated organism, and it passes through an extraordinary development, which can only be 100 INVERTEBRATE ANIMALS. alluded to here. In its later stages it was originally described as a distinct animal under the name of “ Pluteus.” In this state the larva is a curious, easel-shaped body, with a distinct alimentary canal and an internal calcareous skeleton, and ex- hibiting distinct bilateral symmetry. The remarkable point, however, about its further development is, that the young Echinus is developed out of only a portion of the Pluteus, and the greater part of the latter, including the skeleton, is cast away as useless. The majority of the sea-urchins are found at moderate depths in the sea, especially in the neighborhood of oyster- banks. Others spend their existence buried in the sand; and one species excavates holes for itself in the solid rock, ap- parently by some mechanical action. Orver II. Asteromea (Gr. aster, star; eidos, form).— As the structure of the sea-urchins may be taken as embody- ing the most important anatomical peculiarities of the Echino- dermata, and as this has been described at some length, it will not be necessary to do more than briefly indicate the more important characteristics of the remaining orders. In the present order are included all the true star-fishes, the sand- stars and brittle-stars being generally regarded as a distinct Kis& Fig. 83.—Cribella oculata (after Forbes). group. The body in all the Asteroidea is more or less ob- viously star-shaped (Fig. 33), consisting of a central disk sur- rounded by five or more lobes or arms, which radiate from the ECHINODERMATA. 101 body, are hollow, and contain prolongations from the stomach. The body is not enclosed in an immovable box or test, as in the sea-urchins, but the integument is of a leathery nature, and is richly furnished with calcareous plates, tubercles, and spines. The true star-fishes are distinguished from the nearly allied brittle-stars (Ophiuroidea) by the fact that the arms are direct prolongations of the body, that they contain prolonga- tions of the stomach, and that they are deeply grooved on their under surfaces for the radiating vessels of the water- vascular system, which are further protected by a sort of in- ternal skeleton. The upper surface of the body and arms is richly furnished with calcareous matter, in the form of prickles, tubercles, spines, and pedicellarize, these last being peculiarly- modified spines. The upper surface, also, exhibits the madre- poriform tubercle in the form of a concentrically-striated disk placed at the angle between two of the rays, and also the aperture of the anus, when this is present. The mouth is placed in the centre of the lower surface, and is not furnished with teeth. Jt leads by a short gullet into a stomach which usually terminates on the upper surface by an anal aperture; but this is occasionally wanting. From the stomach in all the Asterotdea proceeds a series of much-branched membra- nous sacs, two of which are prolonged into each ray. The water-vascular or ambulacral system is in most essential re- spects identical in structure with that of the sea-urchins, making due allowance for the different shape of the body. The nervous system consists of a gangliated ring surrounding the mouth and sending branches along each of the arms. The reproductive organs, like the nervous system, exhibit a radiate condition, being arranged in pairs in each ray. The star-fishes are found on all shores, but many forms are properly inhabitants of deep water. They differ much in the general shape of the body. In the common cross-fish ( Uraster rubens) the disk is small, and is furnished with long, finger-like rays, which are properly five in number. In the Cribellw (Fig. 33) the general shape is much the same. In the sun-stars (Solodeny the disk is large and well marked, the rays are from twelve to fifteen in number, and they are shorter than the diameter of the disk. In the cushion-stars (Goniaster) the body is in the form of a five-angled disk, more or less flattened on both sides, the rays being only marked out by the ambula- cral grooves upon the lower surface. Orver III, OruivrorpEa (Gr. ophis, snake; oura, tail; ei 102 INVERTEBRATE ANIMALS. dos, form).—In this order we have only the common sand-starg (Ophiura) and brittle-stars (Ophiocoma), all closely allied to the true star-fishes in external appearance, especially in their strikingly radiate form. The body in the Ophiuride consists of a circular central disk covered with small calcareous plates, and giving off five long, slender, snake-like arms (Fig. 34, a, b), which may be simple or branched, but which do not contain any prolongations from the stomach, nor have their under surfaces excavated into grooves for the protrusion of ambu- lacral tube-feet. The arms, in fact, are not prolongations or lobes derived from the body itself, but are special appendages added for purposes of locomotion and prehension. The arms sam fed EER RS cee Hi eres a wr HYY cities -s>y annie, Fie. 84—Ophiuroidea. a Ophiura texturata, the common sand-star; & Ophiocoma neglecta, the gray brittle-star (after Forbes). are very much longer than the diameter of the disk, and are protected by four rows of calcareous plates—one above, one below, and one on each side. In the centre of each arm is a row of calcareous pieces which form a kind of internal axis ECHINODERMATA, 103 or skeleton, below which is placed the radiating ambulacral vessel, All the internal organs are contained within the disk, and none of them pass into the arms except the nerve-cords and ambulacral vessels. The mouth is placed in the centre of the under surface of the disk, and opens into a globular, simple stomach, which is not furnished with an anal aperture, all indigestible particles being’ got rid of through the mouth. In various points of their anatomy the Ophiuroidea differ considerably from the true star-fishes, to which they are most nearly related, but these differences do not require further notice. The habits of the brittle-stars and sand-stars are various, but many of them may be found in rock-pools or under stones at low water on most shores, Lz hs J SRE MEE SESE NG if) . G43; ae y ti Wes yp CAN Wie 4a? NN Wie Zi WS GUN Z4u ZA y S77 Fic. 35.—Comatula rosacea. a Free adult; 6 Fixed young (after Forbes). Orver IV. Crinowea (Gr. krinos, a lily; eidos, form).— In this order are comprised Echinodermata, in which the body is fixed, during the whole or a portion of the existence of the animal, to submarine objects by means of a jointed flexible stalk or column. The Crinoidea were formerly very 104 INVERTEBRATE ANIMALS. numerous, both individually and in types, but they are rep- resented at the present day by no more than three or four living forms, of which one only (the feather-star) is at all of common occurrence. The body in the Crinoids con- sists of a central disk or cup formed of calcareous plates, and protecting the body of the animal. From the mar- ) gins of this cup spring five 49 or more arms which are ar- ranged in a radiating manner, so as to form a more or less feathery crown. In one ef our living forms, the animal, when full grown, is free; but in all other living genera, and in the great majority of fossil forms, the body was attached throughout life to the sea- bottom by means of a jointed stalk attached to the lower surface of the cup (Fig. 36), thus somewhat resembling a lily. The commonest living spe- cies is the rosy feather-star (Comatula rosacea), which occurs not very rarely on European coasts (Fig. 35). This beautiful animal consists of a central body or disk, from which proceed five ra- diating arms, which divide almost directly after their Fic. 86.—Rhézocrinus lofotensis, a living Origin into two secondary soi re Ge esl emt) branches, so that ultimately Cup; ec Arms, there are produced ten long and slender rays. Each arm is furnished on both sides with a number of little jointed lateral processes or “ pinne,” so as to assume a feather-like appearance, from which its popular name is derived. The digestive system is furnished with both a mouth and a vent; ECHINODERMATA. 105 the water-vascular or ambulacral system appears to take no part in locomotion, and the reproductive organs are lodged in the lateral processes of the arms, The most remarkable point, however, about the Comatula is the manner in which it de- velops itself. When fully grown (Fig. 35, a) it presents no small superficial resemblance to some of the Ophiuroidea. When young (Fig. 35, 6) the Comatula is so different in ap- pearance from the adult, that it was originally described as a distinct animal. It consists now of a little cup-shaped disk with ten radiating arms above, produced by the splitting into two of five primary rays, and furnished inferiorly with a little flexible column or stalk composed of a number of calcareous joints. By this jointed stem the body is at this period of life fixed to sea-weeds or other submarine objects. When sufficiently mature, however, the body drops off its stalk, and then only requires to grow in size to become a fully-developed Comatula. The stalked condition which we have just seen to consti- tute a merely temporary stage in the life-history of the Coma- tula is, on the other hand, the permanent state of parts in almost all the “stone-lilies” and other fossil Crinoidea, and in two or three living forms. Of these recent species, one of the most remarkable is one which has been recently discovered in the Atlantic and North Seas, and which has been described under the name of Rhizocrinus lofotensis. This curious species (Fig. 36) consists of a little thread-like, jointed stem support- ing a calcareous cup, from which proceed five branched and jointed arms; and the stalked condition is here permanently re- tained during life. Orvers V. anp VI. CysToIDEA AND |X BuasrorpEa.—These orders merely require to be mentioned here, as all the forms in- cluded in them are extinct, and are unrep- resented at the present day by living spe- cies. In both, the body is enclosed in a kind of box formed by jointed calcareous plates (Fig. 37), and it was in most cases permanently fixed to the sea-bottom by a Fig. 31 Cystoides. jointed stalk or column. The arms, which i ° form so conspicuous a feature in the true Crinoidea, were either absent or very rudimentary. Both orders are most closely allied to the Crinoidea, and they constitute probably 106 INVERTEBRATE ANIMALS, the least highly-developed sections of the whole class of the Echinodermata. Orver VII. Hototuvromera.—In this order are comprised the highest of the Echinodermata, all very different in out- ward appearance from any of the forms we have hitherto con- sidered. They are commonly known as sea-cucumbers, or tre- pangs, but they are mostly rare and inconspicuous animals at the best. They are all more or less worm-shaped or snail-like in form, and they are either altogether destitute of calcareous matter in the skin, or with rare exceptions have only scattered grains and spines of this material. As a rule, the skin is simply leathery, and is endowed with wonderful contractility by means of powerful longitudinal and transverse muscles. In consequence of this, they can, in many cases, eject all or almost all their internal organs, and can sometimes divide their bodies into several parts when injured or alarmed. Loco- motion is effected by alternate extension or contraction of their worm-like bodies, by anchor-shaped spicules of lime contained in the skin, or by rows of ambulacral tube-feet, like those of the sea-urchins, protruded through the integument. Some- times the tube-feet are scattered over the whole surface of the body, and sometimes they are altogether absent. There is always a mouth at one extremity of the body, and a distinct vent at the other. The mouth is situated anteriorly, and is surrounded by a circlet of feathery tentacles (Fig. 38), which Fig. 88.—Holothuroidea. Thyone papillosa (after Forbes). are believed to be modified tube-feet. The water-vascular or ambulacral system is sometimes quite rudimentary, but in other cases it much resembles that of the sea-urchins, except that the madreporiform tubercle is not placed on the outside of the body, but hangs down freely in the interior of the body. In most of the Holothuroidea there are appended to the ter- mination of the intestinal canal two much-branched tubes, ECHINODERMATA. 107 which are filled with sea-water from without, and are believed to exercise a respiratory function, hence the name of “respi- ratory tree” often applied to them. The ordinary species of Holothurians, as already said, are all rare, and are mostly only to be obtained by dredging in tolerably deep water. Some of the tropical forms attain a large size, and some are largely searched after to be sold in the Chinese market, being regarded in that country as a delicacy. CHAPTER XI. Cuass IL—Sco.ecrpa. In the second class of the sub-kingdom Annuloida are in- cluded a number of organisms which are, in many cases, very unlike one another in external appearance, but which, never- theless, agree in one or two structural points of importance. The most important of these are.the possession of a system of water-vascular vessels, the absence of a vascular system, and the possession of a nervous system composed of no more than one or two nervous masses or ganglia. The points by which the Scolecida are distinguished from the Echinodermata are, the absence of calcareous matter in the skin, the absence of any traces of a radiate arrangement of their parts, especially of the nervous system, the constant absence of any blood- circulatory apparatus, and the course of their development. The Scolectda (Gr. skolex, a worm) are often vermiform in shape, but many of them exhibit no worm-like characters, and one whole order is entirely microscopic. A great many of the Scolecida are internal parasites in other animals, and these are often collectively spoken of as Entozoa (Gr. entos, within ; zodm, an animal). These parasitic forms subsist by an imbibition of the juices of their host through their delicate integument. They have, therefore, no necessity for acquiring food for themselves; and we find, in consequence, that many of them are wholly destitute of an alimentary canal, and that in all the organs of “relation” are very rudi- mentary. The Scolecida are divided into the following seven groups or orders: 1. Teniada (Tape-worms). 2. Trematoda (Flukes). 8. Zurbellaria (Ribbon-worms and Planarians), SCOLECIDA. 109 4, Acanthocephala (Thorn-headed worms). 5. Gordiacea (Hair-worms). 6. Nematoda (Round-worms and Thread-worms). 4, Rotifera (Wheel-animalcules). Orver I. Tzntapa (Gr. tainia, a ribbon).—In this order are comprised the ribbon-shaped Tape-worms (Fig. 39, 5) and Fia. 89.—Morphology of Tzeniada. 1, Ovum containing the embryo in its leathery case; 2. A bladder-worm (Cysticercus longicollis), magnified; 3. Head of the adult Tenia solium, enlarged, showing the suckers and crown of hooklets; 4. A single generative joint, enlarged to show the branched ovary (0), the generative pore (@), and the water- vascular canals (0); 5. Fragment of Tenia soliwm, showing the generative joints and the alternate arrangement of the generative pores. the bladder-worms or cystic worms (Fig. 39, 2). These were formerly described as distinct groups; but it is now known that the latter are merely the young forms of the former. The peculiarity which distinguishes the development of the Tveni- ada, and which led to the cystic worms being described as distinct animals, is that the different stages of growth are always found inhabiting different animals or “hosts.” If the fully-grown tape-worm is found in one animal, then its young form or cystic worm will always be found in another. Many animals are infested by tape-worms; but all the leading points of interest in the order will be brought out by a consideration of the commonest of the three tape-worms to which man is subject—namely, the common tape-worm, or Tenia solium, : 6 110 INVERTEBRATE ANIMALS. The common tape-worm is found inhabiting the intestines of man, one only being generally present in the same individual. In shape (Fig. 39; 5) it is an extremely elongated, flattened, tape-like body, many feet in length, and composed of a num- ber of flattened joints (Fig. 39, 4) all loosely united to one another. At one extremity the joints become much smaller and narrower, till ultimately a point is reached where the organism is firmly fixed to the mucous membrane of the in- testine by means of a minute rounded head (Fig. 39, 3), The organs by which attachment is effected are, in this spe- cies, a crown of recurved hooks and four suckers. The head is in reality the true animal, and all the long, jointed, tape- like body which follows this, is really produced by a process of budding from the head. The head contains no repro- ductive organs, and is not furnished with a mouth or diges- tive organs of any kind, its nutrition being entirely effected by imbibition of the nutritive fluids elaborated by its host. A nervous system, in the form of one or two ganglia, sending filaments backward, is said to be present; but there is some doubt on this point. The water-vascular system (Fig. 39, 4) consists of two long vessels which run down each side of the body and communicate at each articulation by a transverse vessel, the whole opening in the last joint into a contractile vesicle. Hach joint is sexually perfect, or hermaphrodite, containing both male and female reproductive organs (Fig. 39, 4), which open on the surface by a small raised aperture, the “generative pore.” Almost the whole of each of the mature joints is filled up bya much-branched ovary. As the head is the true animal, and the numerous joints are only pro- duced by budding, it follows that the entire organism is to be regarded as a kind of colony, constituted by a single sexless zodid or “nurse,” and numerous sexual zodids, produced by budding from the former. The process of development—that is to say, the process by which this composite organism, commonly known as the tape-worm, is produced—is a very remarkable one, and is briefly as follows: Hach generative segment or joint, as al- ready said, is hermaphrodite, and contains innumerable ova. These eggs, however, cannot be developed within the body of the animal infested by the tape-worm itself, but they are compelled to gain access to the body of some different species of animal, if development is to proceed. To secure this end, the mature joints of the colony break off, and are ‘expelled from the alimentary canal of the host. The joints thus ex- SCOLECIDA. 111 pelled die and decompose, and their contained eggs are thus set free. Hach egg (Fig. 39,1) is covered with a little leathery capsule which protects it from injury, and contains a minute embryo in its interior. If this microscopically small egg be swallowed—as in many ways it easily may be—by another warm-blooded animal (in this particular case by the pig), then a fresh series of changes ensues. The leathery case of the ovum is dissolved in the stomach of the new host, and the embryo is set free, when it bores its way through the walls of the stomach by means of little siliceous hooks with which it is provided. Having reached a suitable locality, the young tape-worm proceeds to surround itself with a kind of cyst, and it develops from its hinder end a kind of bladder filled with fluid (Fig. 39, 2). It is now a bladder-worm, or cystic worm, and as such would formerly have been regarded as a distinct animal. In the particular case of the Tenia solium which we are now considering, the cystic worm is found imbedded in the muscles of the pig, and it constitutes in that animal the disease known as the measles. In this cystic stage the young tape-wo1m may remain for an ap- parently indefinite period, being quite incapable of develop- ing eggs, though sometimes fresh bladder-worms may be produced by a process of budding. For its further develop- ment it is necessary that it should now be introduced into the alimentary canal of man. If a portion of measly pork be eaten with these cystic worms imbedded in it, then the young tape-worm is liberated from its cyst: it fixes itself by means of its suckers and hooklets to the mucous mem- brane of the intestine, and its caudal bladder drops off. It is now converted into the head of the adult tape-worm. It finally commences to throw out buds from its hinder extremity, and in these buds or joints the reproductive elements are pro- duced, so that ultimately we get the long, flattened jointed colony with which we started. . This extraordinary series of phenomena is now known to occur in other cases, but space will not admit our dwelling upon these. Another of the tape-worms of man (the Tenia mediocanellata) is developed in the same way from the measles of the ox. The tape-worm of the cat is the mature form of the bladder-worm of mice, and the tape-worm of the fox is derived from the cystic worm of hares and rabbits, Lastly, man is not only liable to be infested with the tape-worms derived from the cystic worms of other animals, but may be attacked by the cystic or immature forms of the tape-worms 112 INVERTEBRATE ANIMALS. of other animals. Thus the disease known as “hydatids” in the human subject is caused by the presence in his tissues of the cystic worms which are ultimately developed into the tape- worm of the dog. Orper II. Tremaropa (Gr. trema, a pore or sucker).— The “ suctorial” worms, or “ flukes,” as the members of this order are commonly called, are all internal parasites, inhabit- ing various situations in different animals, but especially af- fecting birds and fishes. They are all more or less flattened and rounded in shape, and are furnished with one or more suckers, by which they adhere. They are distinguished from the Zaniada by always possessing an alimentary canal, which is often much branched (Fig. 40, 1), is simply hollowed out Fic. 40.—Trematoda. 1. Distoma hepaticum, the “liver-fluke,” showing the branched alimentary canal: 2. Anterior extremity of Distoma lanceolatum, enlarged; a An- terior sucker; } Posterior sucker; ¢ Generative pore; @ Gullet; ee Bifurcating aliment- ary canal (after Owen). of the tissues of the body, and is never provided with a dis- tinct anus, The best known of the Zrematoda is the common liver-fluke (Distoma hepaticum, Fig. 40, 1), which inhabits the gall-bladder or ducts of the liver in sheep, and is the cause of the disease known as the rot. In form it is ovate, flat- tened on the two sides, and presenting two suckers, of which the anterior is perforated by the aperture of the mouth. A branched water-vascular system is present, and opens pos- teriorly by a small aperture. The alimentary canal bifurcates shortly behind the mouth, the two divisions thus produced being much branched, and terminating posteriorly in blind extremities. In Distoma lanceolatum (Fig. 40, 2) the intes- tine is divided into two branches, but these are simple tubes, and are not branched. SCOLECIDA. 113 Orver IT]. Turpettarta.—The animals included in this order differ altogether from the Zrematoda and Teniada in being almost all aquatic in their habits and being all non- parasitic. They never possess sucking-disks or hooklets, and their integument is always furnished with vibrating cilia. A water-vascular system is always present, but it appears some- times not to communicate with the exterior. The alimentary canal is sometimes simply hollowed out of the tissues and destitute of an anus, as in the Zrematoda, or at other times suspended in a free space (body-cavity) and furnished with an anus. It may be simple or much branched. The best known of the members of this order are certain little jelly-like, soft-bodied, ovate, or elliptical creatures, which are commonly found in fresh water or on the sea-shore, and are known as Planarians. The skin in these curious little ani- mals (Fig. 41, 1, 2) is richly furnished with cilia, and also contains numerous cells which have been compared to the Fie, 41.—Turbellaria. 1. Planaria torva: m Mouth; g Nerve-ganglion; ¢ Eyes; ov Ovary; ¢Spermarium ; g7 Genital opening: 2. Planaria lactea, showing the branched intestine: 3. Larva of one of the marine Turbellarians: 4. Pilidiwm, the larva of one of the Nemertide. “nettle-cells” of the Coelenterata. The intestine may be either straight or branched, but always terminates behind in blind pouches, and is never provided with an anus. The water-vascular system communicates with the exterior. The nervous system consists of two ganglia, placed in front of the mouth, and united by a cord. There are generally rudimen- tary eyes or pigment-spots, which vary in number from two to sixteen. The remaining members of the Turbellaria are known as ribbon-worms (Nemertide), and are not uncommonly found on the sea-shore. They differ from the Planarida in being 114 INVERTEBRATE ANIMALS. worm-like in shape, by the fact that the alimentary canal is furnished with a distinct anus, and by the absence of an ex- ternal opening to the water-vascular system of the adult, in some cases at any rate. Their development sometimes shows phenomena very similar to what occurs in the Echinodermata, the larva (Fig. 41, 4) being a free-swimming, ciliated organ- ism, of which only a portion is employed in producing the adult animal, the remainder being cast off as useless. Orpver IV. AcanrnocepHata (Gr. akantha, thorn; ke- phate, head).—The “ thorn-headed worms” included in this order are all internal parasites. They are worm-like in shape, marked with transverse wrinkles, and destitute of any mouth or alimentary canal. The anterior extremity of the body forms a kind of proboscis or snout, which is armed with recurved hooks, and has placed at its base a single nervous ganglion. Beneath the skin is a net-work of canals, containing a clear fluid, and believed to represent the water-vascular system. The thorn-headed worms include some of the most formidable parasites with which we are as yet acquainted, the best known being the various forms of Echinorhynchus, which are found inhabiting the alimentary canal in many mammals, birds, and fishes, but not as yet in man. OrpER V. GorpiacEa.—The Gordiacea, or “hair-worms,” are thread-like parasites which in the earlier stages of their existence inhabit the bodies of various insects, chiefly beetles and grasshoppers. They possess a mouth and alimentary canal, The sexes are distinct, and they leave the bodies of the insects which they infest to breed, subsequently deposit- ing their eggs in long chains either in water or in some moist situation. In form the Gordiacea are singularly like hairs, and they often attain a length very many times greater than that of the insect in which they live. Orprr VI. Nematopa (Gr. nema, a thread).—In this order are the “round-worms” and “thread-worms,” both of which are parasitic, together with a number of worms which lead a permanently free existence, All the Nematoda (Fig. 42) are elongated and cylindrical or thread-like in shape. They possess a distinct mouth, and an alimentary canal which is freely suspended in an abdominal cavity, and which termi- nates in a distinct anus. They possess a system of canals which are believed to represent the water-vascular system; SCOLECIDA. . 115 and the nervous system is in the form of a gangliated cord surrounding the gullet, and sending filaments backward. Among the best known of the parasitic Nematodes are the common round-worm (Ascaris lumbricoides) and the thread- worm (Oxyuris) of the human subject, both of which inhabit the alimentary canal, and the guinea-worm (Filaria), which spends a portion of its existence in the cellular tissue of man, especially of the legs, and which attains a length of several feet. More dan- gerous than any of these is the Trichina, which spends its immature stages encysted in the muscles of some such animal as the pig, and only attains maturity and becomes capable of producing eggs, when in- troduced into the alimentary canal of some other warm-blooded verte- brate animal, When this takes place, a train of symptoms are originated which sometimes re- semble rheumatic fever, and appear to be very generally fatal, Of the free Nematode worms, which are never parasitic at any time of their lives, about two hun- dred species have been described, most of which inhabit fresh water or the shores of the sea. One of the most familiar is the so-called “vinegar-eel” (Anguillula aceti, Fig. 42, A). A Fic. 42.—Nematoda. A. Vinegar-eel Orver VII Rortrrera (Lat. Wet shale ieaea wanes rota, wheel; jfero, I carry).—The __ living in stagnant water. Rotifera, or “ wheel-animalcules,” derive their popular name from the fact that the anterior end of the body is furnished with one or two circlets of cilia (Fig. 43) which, when in motion, vibrate so rapidly as to produce the illusory impression of a quickly-rotating toothed wheel. The Rotifera are almost all aquatic, and are mostly inhabitants of fresh water. They are all microscopic in size, none attaining a greater length than one-thirty-sixth of an inch. In the females there is a distinct mouth, intestinal canal, and nant Sao sears ntl 116 INVERTEBRATE ANIMALS. anus. A nervous system is also present, consisting of gan- glia placed near the anterior extremity of the body and send- ing filaments backward, There is, finally, a well-developed water-vascular system. : : Most of the Rotifera are free-swimming, active little ani- mals (Fig. 43, A), but some are permanently fixed, as in Melicerta (Fig. 43, B), or in the crown-animalcule Stephano- ceros), They are usually simple, but they are sometimes com- posite, forming colonies. As a rule, the male and female Rotifera differ greatly from one another, the males being smaller than the females, devoid of any masticatory or diges- Fig. 43.—Rotifera. A. Diagrammatic representation of Hydatina senta (generalized from Pritchard): @ Depression in the ciliated disk leading to the digestive canal; b Mouth; e¢ Pharyngeal bulb with masticatory apparatus; @ Stomach; e Cloaca; / Contractile pladder; gg Respiratory or water-vascular tubes; 2 Nerve-ganglion, giving filament to ciliated pit (£); o Ovary. B. Melicerta ringens (after Gosse). tive apparatus, and more or less closely resembling the young forms of the species. The males, in fact, merely lead a tran- sient existence, and die as soon as they have succeeded in fertilizing the females. The body in most cases is very dis- tinctly ringed or annulated (Fig. 43, A), but is not composed of distinct rings separated by partitions. The integument is usually provided with bundles of muscular fibres taking a longitudinal and transverse direction. In the free forms the SCOLECIDA. 117 anterior ciliated disk acts somewhat like the propeller of a screw-steamer in driving the organism through the water—in all cases it has the action of producing currents in the water by which particles of food are brought to the mouth. The posterior end of the body is usually developed in the free forms into a kind of tail or foot (Fig. 43, A), which may take the shape of a kind of pincers or of a little suctorial disk. As regards their internal anatomy, in the females of almost all the Kotifera there is a well-developed alimentary canal, which is completely shut off from the general cavity of the body. The mouth (Fig. 43, A 6) opens into a dilated cham- ber (c), which contains a complicated apparatus of horny teeth. This in turn opens into a capacious stomach (d), con- tinued into an intestine which terminates by a chamber known as the “cloaca” (e), which forms the common outlet for the water-vascular and generative systems. In both sexes there is a well-developed water-vascular system consisting of a con- tractile chamber or bladder (f°), opening into the cloaca, and giving origin to two complicated tubes which are known as the “respiratory tubes” (g g), and which terminate near the anterior end of the body, apparently by blind extremities. The nervous system is in the form of a large double ganglion placed above the gullet, and having one or two eye-specks placed upon it. The ovaries (0) constitute conspicuous organs in the female Rotifera, but in summer the young Rotifers ap- pear to be produced by the females without having access to the males, The Rotifera were long confounded with the Infusoria, in consequence of their great similarity in external appearance. They are, however, of an obviously much higher grade of structure. One of the most remarkable phenomena presented by the Fotifera is found in the undoubted fact that, in spite of their complex organization and aquatic habits, they can be dried, and again brought to life by the addition of a little water, and that this desiccation and restoration to life can be apparently repeated many times in succession without injury. SUB-KINGDOM IV.—ANNULOSA. CHAPTER XII. ANARTHROPODA. Sus-Krinepom AnnuLosa.—In this sub-kingdom are com- prised an enormous number of animals which agree in the following characters (Fig. 44): The body is composed of a number of segments or rings arranged along a longitudinal axis. There is a distinct alimentary canal (6), placed cen- trally as compared with the other organic systems, and com- pletely shut off from the general cavity of the body. The Fic. 44.—Diagram of an Annulose animal. a Blood-vascular or hemal system; } Digestive system; c Neural system. blood-vascular system may be absent, but, when present, it is always situated on the dorsal aspect of the body (a). The nervous system is always present, and is placed along the ventral surface of the body. In its typical form it consists of two nervous cords running along the whole length of the ventral surface, and having a pair of ganglia developed in each ring. The first pair of ganglia is always placed above the gullet, and the second below, so that ‘the gullet is. sur- rounded by the two cords uniting these ganglia (constituti the so-called wsophageal collur). The limbs (when present are always turned toward the neural aspect—that is to say, ANARTHROPODA. 119 toward that side of the body upon which the nervous system is situated, (See also the transverse section of an Annulose animal, Fig. 1.) The entire sub-kingdom of the Annulosa is divided into two great divisions termed Arthropoda and Anarthropoda, according as the body is provided with jointed appendages or not. In the Arthropoda, in which the body- rings are furnished (some or all) with jointed appendages, are included the Crustaceans (lobsters, crabs, etc.), the spiders and scorpions, the centipedes, and the insects. In the Anarthro- poda, in which there are no true jointed appendages, are in- cluded the spoon-worms, leeches, earth-worms, tube-worms, and sand-worms.* Division I. Anarruropopa (Gr. a, without; arthros, joint ; podes, feet),—In this division of the Annulosa, the locomotive appendages are never distinctly jointed or articulated to the body. In this division are included two principal classes—the Gephyrea and the Annelida.t Cxiass I. Grrayrea.—This class is a very small one, and includes a number of worm-like animals, which in most re- spects are very similar to the following class of the Annelida, but are distinguished by having no locomotive appendages at- tached to the sides of the body. They were long placed among Fia. 45.—Gephyrea. Syrinw nudus (after Forbes), the Echinodermata, having a decided relationship to the worm- like Holothurians. They are distinguished, however, by never secreting calcareous matter in the skin, and by having no water-vascular or ambulacral system. There can be no doubt, * The Anarthropoda are often united with the Scolecida into a common sub-kingdom under the name of Vermes; in which case the Echinodermata are retained apart in a special sub-kingdom. + A third class has been constituted under the name of Chetognatha for some singular marine animals, transparent and worm-like in form, with lateral fins at the hinder end of the body, and having the mouth armed with bristles. They form the genus Sagitta. 120 INVERTEBRATE ANIMALS. however, that the Gephyrea are, on the whole, very nearly related to the Holothurians, and it is chiefly from the total absence of any radiate arrangement of the nervous system and internal organs that they appear to be more properly classed with the worms. The Sipunculus or spoon-worm is found burrowing in the sand of many sea-coasts, or inhabiting the cast-away shells of univalve shell-fish, A considerable num- ber of species of this class have been recorded as occurring in European seas, and one of the more characteristic forms is figured above (Fig. 45). Crass II, Annewipa (Lat. annulus, a ring).—The Annelida or ringed-worms are distinguished from the preceding by the possession of definite segmentation, the body being composed of a number of rings which are all similar to each other ex- cept at the two ends of the body. All the Annelida are more or less worm-like in shape, and in all, except the leeches, the segments are (some or all) provided with lateral appendages which mostly subserve locomotion, but which are never jointed to the body. In the typical Annelida each segment (Fig. 46) Fic. 46.—Diagrammatic transverse section of a typical Annelide. @ Dorsal arc; 0 Ventral arc; » Branchiw or gills; a@ Dorsal oar; 2 Ventral oar—both carrying bristles and 4 jointed filament. consists of two arches, termed, from their position, respectively the “dorsal arc” (d@), and the “ventral arc” (v), Each seg- ment carries a lateral process on each side, which are known as the “foot-tubercles” ( parapodia). Each foot-tubercle in turn may consist of an upper piece or “dorsal oar” (a), and a lower piece or “ ventral oar” (6), both carrying a tuft of bris- tles and a soft jointed filament. The nervous system consists essentially of a double gan- gliated chain placed along the ventral surface of the body, and ANARTHROPODA. 121 traversed in front by the gullet, so that the first ganglion lies above the gullet (Fig. 44). The digestive system consists of a mouth, generally with a protrusible proboscis, and sometimes horny jaws, a gullet, stomach, intestine, and a distinct anus. As a rule, the alimentary canal runs straight from one end of the body to the other without describing any convolutions in its course. In almost all cases the alimentary tube is placed in a distinct cavity, which contains a fluid with solid par- ticles in it, believed to correspond to the blood of the higher Annulosa. In most, if not in all, there is an additional system of vessels which carry a fluid containing solid particles, which are contractile, and which send branches to the respiratory organs, when these exist. This system is believed not to cor- respond to the blood-vascular system of the higher animals, and it has, therefore, been termed the “ pseudo-hemal” system (Gr. pseudos, falsity; and haima, blood). It is believed, on the other hand, to be truly homologous with the water-vascu- lar system of the Annuloida, Respiration is effected by the general surface of the body, or by distinct gills or branchiz. In most cases, also, there exists a series of peculiar involutions of the integument, which are known as the “segmental or- gans” or “respiratory pouches,” and which are believed to be partially concerned in the respiratory process. The sexes in the Annelida are sometimes distinct, sometimes united in the same individual. The embryos are almost always ciliated, and many of them pass through a metamorphosis. The Annelida may be divided as follows: Section A. Aprancatata.—Without gills or branchia. 1. Hirudinea.—(Leeches.) 2. Oligocheta.—(Earth-worms.) Sxcrion B. Brancutara.—With branchiz. 3. Tubicola.—Tube-worms.) 4. Errantia.—(Sand-worms.) Orver I. Hirvupryea (Lat. hirudo, a horse-leech).—This order comprises only the leeches, some of which are marine, while others inhabit fresh water. The leeches (Fig. 47) are all characterized by the fact that the body is destitute of lateral bristles or foot-tubercles, but is provided with a suck- ing-disk at one or both extremities. In the typical forms, as in the common medicinal leech, there are sucking-disks at both ends of the body, and in those in which only the hinder sucker is present, the head can be converted into a suctorial 122 INVERTEBRATE ANIMALS. cavity. Locomotion is effected either by means of the alter- nate fixation and detachment of the suckers, or by a serpentine bending of the body. The body is obviously ringed or annulated, but none of the rings carry lateral appendages of any kind. The mouth is sometimes destitute of teeth, but is occasionally armed with complex jaws. The alimentary canal is short, with lateral dilatations, and united to the skin by means of a spongy vascular tissue, so that the body- cavity is obliterated. The pseudo- heemal system is well developed, and consists essentially of four great longi- tudinal vessels. Respiration appears to be effected, in part, at any rate, by means of the segmental organs, which have the form of little sacs . opening externally by minute aper- , tures. The nervous system has its j usual form, and the ganglia in front of the gullet (“prce-cesophageal” ganglia) give off branches to a number of simple eyes which are placed on the head. The sexes are united in the same in- dividual. a ella, igh The most familiar of the leeches are oficinalis), natural’ size? the common horse-leech (Hamopsis), Anterior extremity of the and the medicinal leech (Sanguisuga same magnified, showing the % a 5 sucker and triradiate jaws; Officinalis, Fig. 47). The former has See ne ee canoe small and blunt teeth, but the latter is toothed margin. provided with three semicircular tooth- ed jaws (Fig. 47, 5, c), which meet in a point, and are sufficiently powerful to cut through the human skin. The medicinal leech is a native of fresh waters through- out the south and east of Europe, and it is imported in large numbers from Hungary, Bohemia, and Russia. Orver II. Oxrcocn.zta.—In this order are included the earth-worms (Lumbricide), and the water-worms (Naidide). They are all distinguished from the preceding by the fact that the body is furnished with rows of bristles which take the place of the foot-tubercles of the higher Annelida, and which are the organs of locomotion. They are distinguished from the higher forms by the fact that the locomotive bristles ANARTHROPODA. 123 are comparatively few in number, hence the modern name of the order (Gr. oligos, few; and chaite,a bristle). In the com- mon earth-worm (Lumbricus terrestris) the body is cylindrical, attenuated at both ends, and furnished with eight rows of locomotive bristles. The mouth is destitute of teeth, and opens into a gullet which leads to a muscular crop, succeeded by a second muscular dilatation or gizzard. The intestine is continued straight to the anus, and is constricted in its course by numerous transverse partitions springing from the walls of the body-cavity. The pseudo-hemal system is well de- veloped; and there exists in even greater numbers than in the leeches the series of segmental organs, or lateral pouches, which open externally by pores. The JVaididc are chiefly noticeable on account of their power of producing fresh indi- viduals by a process of budding before they attain sexual maturity. One of the commonest of them is a little worm which occurs abundantly in many pools and streams (Zubifea rivulorum), and which exhibits a fine red color, owing to the pseudo-hemal system being visible through the transparent integument. : Orper III. Tustcora.—The Annelides included in this - group derive their name from the fact that they have the power of protecting themselves by means of tubes (Lat. tuba, a tube; and colo, I inhabit). In some cases (Fig. 48) the tube is composed of car- bonate of lime, and is a genuine secretion from the body. In all the Zubicola the respiratory organs are in the form of branched fila- mentous external gills, in which the fluid of the pseudo-hemal sys- tem is subjected to the action of the outer water. They are, there- fore, “ branchiate” Annelides. As Fie. 48.—Tubicola. a Serpula con- they live in tubes, however, and yy ree aes Spirorbia do not voluntarily expose more = communis than the anterior end of the body, the branchiz are all placed on or near the head. The filaments of which the gills are composed (Fig. 48, a) are richly ciliated, and, as the pseudo-hemal fluid is usually red, they have gen- erally a beautiful scarlet color. 124 INVERTEBRATE ANIMALS. The most familiar of the Tubicola is the Serpula (Fig. 48, a), the contorted and winding tubes of which must be known to every one as occurring on shells or stones on the sea-shore. One of the cephalic filaments in Serpula is much developed, and its extremity forms a kind of conical plug which serves to close the mouth of the tube when the animal is retracted within it. In Spirorbis (Fig. 48, 6) the shelly tube is coiled into a flat spiral, which is fixed to some solid object, It is of extremely common occurrence on the fronds of sea- weed, and on other submarine objects. Orper IV. Errantia.—The Annelides comprised in this order are called “errant” (Lat. erro, I wander), or “roving,” from the fact that they all lead a free existence, and are never confined in tubes. They have always lateral unjointed ap- pendages, or foot-tubercles (Fig. 49), which carry tufts of Fig. 49.—Errant Annelides. A. Hairy Bait (Nephthys); B. Sea-Mouse (Aphrodite); CG. : Lobworm (Arenicola). (After Gosse.) bristles and a soft, jointed filament. The anterior rings of the body are usually so modified as to form a sort of head, which is provided with eyes and with two or more feelers, which differ from the antennz of insects and Crustaceans in not being jointed. The mouth is placed on the inferior sur- face of the head, and is sometimes furnished with one or more pairs of horny jaws, which work from side to side. The upper ANARTHROPODA. 125 part of the alimentary canal is muscular, and can be turned inside out, or protruded beyond the true opening of the mouth. The pseudo-hzmal system is well developed, and its contained fluid is mostly red. Respiration is effected by ex- ternal processes, gills, or branchiz, arranged in tufts placed along the sides or back of the body, and not confined to the immediate neighborhood of the head, as in the Tudicola. The sexes are in different individuals, and the young pass through a metamorphosis. Among the best known and commonest of the Errant Anne- lides are the common lob-worm (Arenicola piscatorum) of our coasts, which is constantly used by fishermen for bait; and the sea-mnice (Aphrodite and Polynoe), some of which attain a large size, and are conspicuous for their iridescent bristles. Other less abundant forms may be readily obtained by searching under stones at low water. CHAPTER XIII. ARTUROPODA. Division II. Arruroropa or ARTICULATA.—The members of the sub-kingdom Annulosa comprised under this head are generally known as Articulate animals, or as Arthropoda (Gr. arthros, a joint; and podes, feet). They are all distinguished by the possession of jointed appendages articulated to the body. The body is composed of a series of distinct rings or segments (technically called “ somites”) arranged longitudinally one be- hind the other. The skin is more or less completely hardened by a horny deposit of “ chitine,” with or without lime, so as to form a resisting shell, to the inner surface of which the muscles are attached. There is consequently no necessity for any in- ternal skeleton. The nervous system in the: young of all Articulate animals has its typical form of a chain of ganglia placed along the ventral surface of the body, and traversed in front by the gullet. In the adult, however, this typical state of the nervous system is often lost or modified. The blood- circulatory system may be absent; but, when it is present, it is placed dorsally (Fig. 44), and consists of a true blood-system containing corpusculated blood, and furnished with a contractile cavity or heart. Respiration is sometimes effected simply by the general surface of the body, but there are generally special organs adapted for breathing air, either directly or through the medium of water. Jointed appendages are always present, and may be developed from any segment of the body. The Arthropoda are divided into four great classes—viz., the Crustacea (crabs, lobsters, etc.), the Arachnida (mites, spiders, and scorpions), the Myriapoda (centipedes and gally- worms), and the Jnsecta (or true insects). These are roughly distinguishable from one another by the following charac- ters ARTHROPODA. 127 1, Crusracea.—Animal more or less truly aquatic; respiration by gills, or by the general surface of the body; two pairs of antennz (feclers); loco- motive appendages more than eight in number, borne by the segments of the thorax, and usually of the abdomen also. 2. ARacunipa.—Respiration aérial, by pulmonary sacs, by air-tubes (trachez), or by the general surface of the body; head and thorax amalga- mated ; antenne (as such), absent; legs eight; abdomen without jointed appendages. 3. Myrtaropa.—Respiration by air-tubes (trachea); head distinct; re- mainder of the body composed of nearly similar segments; one pair of antenna ; legs numerous. 4. Insecta.—Respiration by air-tubes (tracher); head, thorax, and abdomen distinct ; one pair of antenne; thre> pairs of legs borne on the thorax ; abdomen destitute of limbs; generally two pairs of wings on the thorax, CHAPTER XIV. CRUSTACEA. Crass I, Crustacea (Lat. crusta, a crust, or external shell).—The members of this class are commonly known as crabs, lobsters, shrimps, prawns, king-crabs, barnacles, acorn- shells, wood-lice, etc. They are nearly allied to the succeeding class of the Arachnida (spiders and scorpions), but are dis- tinguished by their adaptation to a more or less purely aquatic life, by having jointed appendages upon the hinder segments of the body (abdomen), and by the possession of two pairs of antenne. As a class, the Crustacea are distinguished by being usually furnished with branchize or respiratory organs adapted for breathing air dissolved in water, by having more than four pairs of legs, by having a well-developed chitinous or partially calcareous “crust” or external skeleton, by the fact that some of the appendages are generally so modified as to act as organs of mastication, and by passing through a meta- morphosis before attaining their adult condition. The body in a typical Crustacean is composed of twenty-one (or, according to some writers, twenty) distinct segments or somites, placed one behind the other. These segments are distributed in three distinct divisions, known respectively as the “head,” the “thorax” or chest, and the “abdomen” or tail, each of which is usually regarded as being composed of seven segments. In very many cases, however, the fourteen segments belonging to the head and chest are amalgamated together into a single mass, which is termed the “ cephalo- thorax,” thus leaving seven segments to the abdomen. It will be unnecessary, however, to dwell here longer upon the structure of the Crustacea, as the general morphology of the class will be given at somewhat greater length in speak- ing of the lobster. The classification, also, of the Crustacea CRUSTACEA. 129 is so complex that it will be as well to omit altogether the less important orders, merely giving the names and leading characters of these in an appendix. It has also been thought advisable to invert the usual order here adopted, and to com- mence with the consideration of the highest sections of the class first. Orprer Decaropa.—The Crustacea included in this order derive their name from the fact that they all possess five pairs of legs (Gr. deka, ten; podes, feet). They belong to a large section known as the “stalk-eyed” Crustaceans, from the fact that the eyes are supported by long, movable stalks, They include the lobsters, shrimps, cray-fish, crabs, hermit-crabs, and other forms, and are the most highly organized and most familiar of the whole class of the Crustacea. They are divided into three very well marked groups or tribes, all of which can be exemplified by the well-known British species. A. Macrura.—The name of Macrura (Gr. makros, long; and oura, tail) is given to those ten-footed Crustaceans which have a long and well-developed tail. Among these are the lobster, shrimp, prawn, and cray-fish, of which the lobster may be selected as a good typical example. In the lobster (Fig. 50) the body is at once seen to be composed of two parts, familiarly called the “head” and “tail.” The so-called head is covered by a great shield termed the “carapace” (Fig. 50, ca), and it is in reality the cephalo- thorax, being composed of the amalgamated segments which belong to the true head and to the thorax. The so-called tail is really the abdomen, and it is composed of a number of segments which are not immovably united together, as in the cephalo-thorax, but are movably jointed together. The vari- ous appendages of the animal are arranged in pairs on the under surface of the body; and, where the segments are com- pletely amalgamated (as in the cephalo-thorax), their existence may, nevertheless, be determined by the presence of a pair of appendages. The first segment of the head carries a pair of _ compound eyes, made up of a number of simple lenses aggre- gated together, and supported upon long and movable eye: stalks. Behind these come two pairs of jointed organs of touch, which are known as the “antenna.” The front pair is much smaller than the hinder pair, and they are known re- spectively as the “lesser antenne,” or “antennules,” and the “great antenna.” Behind these, again, comes the mouth, which is placed on the under surface of the head, and is pro- 130 INVERTEBRATE ANIMALS. vided with a complicated series of masticatory organs. It is unnecessary to describe these minutely, but it should. be noticed that they are all modified limbs, and therefore differ AES Ja ‘ X 7h WL LV? coer qu aor NneTvesaee ca Fig. 50.—Common Lobster (Homarus vulgaris), 1. First pair of legs, constituting the great nipping-claws; 2 and8. Second and third pairs of legs, also ending in nipping- ape 4and 5. Last two pairs of legs; @ Smaller antennm; ga Greater antenne; ca arapace. ; . altogether from the jaws of the Vertebrate animals. That this is their real nature is shown most obviously in the hind- most pairs of these jaws, which are so little altered from ordi- nary legs that they are known as “ foot-jaws.” The last five CRUSTACEA, 131 -segments of the thorax carry five pairs of walking-legs, hence the name Decapoda applied to the order. Of these legs, the first three pairs have their extremities converted into nipping- claws or “chelz,” and the first pair is much larger than the others, and constitutes the well-known great claws of the lob- ster. The last two pairs of legs simply terminate in pointed extremities, and not in pincers. The segments of the abdo- men, with the exception of the hindmost, carry each a pair of paddle-like appendages, which are used in swimming, and are called the “swimmerets.” The last pair of swimmerets are attached to the last segment but one, and are very greatly ex- panded, so as to form a very powerful tail-fn. The last seg- ment of all is known as the “telson,” and is not provided with any lateral appendages. The mouth in the lobster leads by a short gullet into a globular stomach, which is furnished with a calcareous appa- ratus for grinding down the food, commonly called the “lady in the lobster.” The intestine is continued backward from the stomach without convolutions, and opens by a distinct anus placed in front of the telson. A well-developed liver is also ‘present. The heart is placed dorsally, and is filled with aérated blood derived from the gills, which it propels through every part of the body. The gills, or branchiz, are pyrami- dal bodies attached to the bases of the legs, and placed in a kind of chamber formed beneath the great shield, or cara- pace, on each side of the body. They consist each of a central stem supporting numerous lateral branches, and they are richly supplied with blood. The water which fills the gill-chambers is constantly renewed by the movements of the legs, and thus the gills are kept constantly supplied with fresh water. The nervous system is placed along the ventral surface of the body, and has its usual form. The organs of sense are the two pairs of feelers or antennz, the compound eyes, and two organs of hearing. B. Anomura.—The most familiar members of this tribe are the hermit-crabs (Paguride@) which occur so commonly on every shore. They are distinguished by the fact that the ab- domen is quite soft, and is not protected by a chitinous crust. The animal, therefore, is compelled to protect the defenceless part of the body in some artificial manner, and this it effects by appropriating the empty shell of some dead mollusk, such as the common periwinkle or whelk. The abdomen is pro- vided with special appendages to enable the intruder to re- tain firm hold of his borrowed dwelling, at the same time that 132 INVERTEBRATE ANIMALS. he can change, it at will when too small or otherwise incon- venient. The first pair of legs are developed into pretty powerful nipping-claws or chelz, and one of them is always much larger than the other, and acts as a kind of plug, block- ing up the entrance of the shell when the animal is retracted within it, C. Brachyura.—The decapod Crustaceans included in this tribe are familiarly known as crabs, and they derive their name of Brachyura (G. brachus, short; and owra, tail) from Fig. 51.—Brachyura, The Spiny Spider-crab (Ifaia sguinado). the rudimentary condition of the abdomen. The abdomen, in fact, is not only extremely short, but it is always tucked up beneath the greatly-developed cephalo-thorax, so that it is not visible at all, except when the animal is looked at from below (Fig. 51). The crabs are very various in their habits, but they are mostly denizens of the shore, hiding beneath stones or sea- CRUSTACEA. 133 weed, in cracks of rock, or in pools near the line of low water. Some of them, however, can swim with tolerable activity, and some of them (the land-crabs) even live habitually inland. One group, the “pea-crabs,” is distinguished by the singular habit of living semi-parasitically within the shells of bivalve mollusks, such as the great horse-mussel. The young or larval crab is exceedingly unlike the adult, and has a long and well-developed abdomen, thus approximat- ing to the type of structure which is permanently retained in the Macrura. Orpvrr Isopopa (Gr. ésos, equal; podes, feet).—In this order are. a number of Crus- taceans of which some in- habit the sea, others are parasitic in their habits, and others are terrestrial. The best known are the common wood-lice ( Oniseus, Fig. 52), which are found so com- monly under stones, or in the crevices of old walls. The Isopods all belong to a group of Crustaceans in which the eyes are not sup- ported upon stalks, and they are therefore said to be “ses- sile-eyed.” The head is dis- tinct from the segment bear- | ing the first pair of feet. The thoracic feet are all similar to one another, and the bran- chia are developed on the abdominal legs. Fic. 52.~Isopoda, Wood-lice (Oniscus). Orprr Mrrosromara.—lIn this order are only the living king-crabs (Zimulus), and some large extinct forms nearly allied to them. They are all distinguished by the fact that the appendages which are placed round the mouth act by their bases as jaws, but have their extremities developed into swimming-paddles, walking-feet, or nipping-claws. The King-crabs or Horseshoe crabs (Fig. 53) constitute a special group called Xiphosura (Gr. xiphos, a sword; and ” 134 INVERTEBRATE ANIMALS. oura, tail), from the fact that the end of the abdomen is furnished with a long sword-like spine (Fig. 53, ¢). The mouth is surrounded by six pairs of appendages, the bases of which are spinous and act as jaws, while their free extremities are developed into nipping-claws or chela. The whole of the upper surface of the body is protected by a kind of buckler, composed of an anterior semicircular shield, and a posterior somewhat hexagonal plate, the under surface of which carries Fic. 58.—Xiphosura, Limulus poly- Fic. 54.—Eurypterida. Prerygotus a ener viewed from below. oon restored (after H. Wood. ward). branchial plates, while the sword-like telson is jointed to its hinder margin. The king-crabs attain a large size, and are often called “ Molucca crabs” from their occurrence in the Moluccas. Both the eggs and the flesh are eaten by the Malays. Closely allied to the king-crabs is the extinct family of the Lurypterida, an example of which is figured above (Fig. 54). This species is supposed to have attained a length of probably six feet, but other forms were very much smaller. CRUSTACEA. 135 OrpvER Trimopira.— The Trilobites constitute another wholly extinct order of the Crustacea, and deserve a short notice from their great geological importance. They derive their name from the fact that the body exhibits a more or less conspicuous division into a central and two lateral lobes (Fig. 55, 1). The entire shell or crust is composed of an anterior Ria. 55.—Trilobita. 1. Angelina Sedgwickii; 2. Diagram of the cephalic shield of a Trilobite (after Salter). semicircular shield, covering the head (Fig. 55, 2), a series of movable rings, constituting the thorax, and a tail-piece com- posed of amalgamated segments, and representing the abdo- men. On the under surface of the shell nothing had ever been discovered except the upper lip, but recently traces of limbs have been made out. The cephalic shield usually bears a pair of compound eyes (Fig. 55, 2 0), but these are sometimes wanting. It is probable that most of the Trilo- bites possessed the power of rolling themselves up into a ball, much as our modern wood-lice. The Trilobites are only known as occurring in the older rocks of the earth’s crust, and they are chiefly characteristic of the period known to geologists as the “ Silurian.” Orprrs CLapocrra, CopEpopa, AND Ostracopa.—These orders deserve mention more from the extreme abundance of their commoner forms than for any other reason. They in- clude a number of minute Crustaceans, most of which are commonly called “ water-fleas,” and abound in fresh waters in most parts of the world. They are, however so small that, though visible to the naked eye, they can only be satisfac- torily examined under the microscope. As an example of the 136 INVERTEBRATE ANIMALS. Cladocera may be taken the “branched-horned water-flea” (Daphnia pulex, Fig. 56, 6), thousands of which may be captured in any pond in summer. In this pretty little species the whole body is enclosed in a bivalve shell, which is so transparent that the whole organization of the animal is clearly visible through it. The head is distinct, and carries a single Fie, 56—Fresh water Entomostraca. a Cypris tris-striata; b Daphnia pulex; ¢ Cyclops quadricornis. eye. The greater antennz are branched. The males are smaller than the females, and much fewer in number; and it appears to be a well-established fact that the female, when once fertilized by the male, can not only lay eggs for the rest of her life, but can transmit the power of producing fertile ova to her young for several generations. Of the Copepoda one of the commonest is the Cyclops (Fig. 56, c), in which the cephalo-thorax is covered by a shield, and there is a well- developed abdomen. The female carries on either side a kind of pouch or ovisac, in which the eggs remain till they are hatched. The little Ostracoda (Fig. 56, a) are all minute Crustaceans, which occur in both fresh and salt water. They are distinguished by the fact that the body is entirely enclosed in a shell, which is made up of two lateral halves or valves. The valves of the shell are united by a membrane along the back, but can be opened below, so as to allow of the protrusion of the feet. Orver Crrripepia.—tThe last order of Crustacea which re- quires mention is that of the Cirripedia (Lat. cirrus, a curl; and pes, foot), comprising the so-called barnacles and acorn- CRUSTACEA. 137 shells, both extremely unlike Crustaceans to look at. All the Cirripedes are distinguished by the fact that, while they are quite free when young, and very similar to some of the little Crustaceans just described, when adult they are immovably fixed by their heads to some solid object. In this fixed con- dition the body and internal organs are, in most cases, pro- tected by means of a calcareous shell, composed of many pieces, and the only part of the body which remains movable is the legs, which are constantly thrust out of the shell and again drawn in in quest of food. The Cirripedia were formerly de- scribed as “multivalve” shell-fish (Mollusca), owing to their possession of a regular calcareous shell. Two distinct types of structure are known among the Cirripedia (Fig. 57), con- stituting the two families of the barnacles (Lepadide), and the acorn-shells (Balanide). In the barnacles (Fig. 57, 5), the anterior end of the body Fig. 57.—Cirripedia. a Sessile Cirripede (Balanus); 6 Stalked Cirripede (Zepas). is much elongated, and is converted into a kind of stalk, by means of which the animal is attached to some solid object, such as a rock, a floating log of timber, or even some marine animal, In the acorn-shells (Fig. 57, a), which occur in myriads upon every solid object between tide-marks, there is no stalk, but the head is firmly cemented to the centre of a membranous or shelly plate. The body is enclosed in a limpet- shaped or conical shell, composed of several pieces, and having an aperture at its summit. This opening is closed by a mov- able lid, and from it the animal can protrude its delicate legs or “cirri,” which look like a “ glass hand,” and are constantly employed in sweeping the water in search of food, In accordance with the fixed condition of the adult, almost all the Cirripedia are hermaphrodite, possessing both male 138 INVERTEBRATE ANIMALS. and female organs of reproduction. In some cases, however, males exist, but these are much smaller than the females, and quite different to them in appearance, and they spend their existence within the shell of the female. , APPENDIX, GIVING THE REMAINING ORDERS or CRUSTACEA. Order Rhizocephala.—Minute Crustaceans, free when young, but when adult parasitically attached to the abdomen of various crabs. When adult they are completely deformed, destitute of limbs, and attached to their host by means of numerous branched tubes or roots which ramify deeply among the internal organs. Ex. Peltogaster. Order Ichthyophihira, —Minute Crustaceans, free when young, but when adult parasitic upon various kinds of fishes; adult usually deformed and soft ; young with eyes and swimming-feet. Ex. Rl Phyllopoda.—Thoracic feet leaf-like and acting as branchie. Ex. Onde Lemodipoda.—Eyes sessile; abdomen rudimentary; respiration by means of little vesicles attached to the thoracic segments or legs. Zz. Cyamus (the whale-louse). Order Amphipoda.—Kyes sessile ; abdomen well developed ; respiratory organs in the form of vesicles attached to the thoracic limbs. Zz. Sand- hopper ( Zalitrus) ; Fresh-water shrimp (Gammdrus). Order Stomapoda.—Eyes stalked; gills unprotected, usually suspended beneath the abdomen. x, Locust-shrimp (Squilla). CHAPTER XV. ARACHNIDA. Crass Il. Aracuntpa (Gr. Arachne, a spider).—This class includes the mites, ticks, scorpions, and spiders, and, as a whole, is very nearly related to the preceding. The Arachnida, however, are distinguished from the Crustacea by being adapted. in most cases for a strictly terrestrial life, so that when any distinct breathing-organs are present these are never in the form of gills, but are always either pulmonary sacs or air- tubes (trachew). In none of the Arachnida, further, are there ever more than four pairs of legs, and the segments of the ab- domen never carry limbs of any sort. The eyes are always sessile, and never supported upon stalks; if antennz exist at all, they are much modified, and the head is always amal- gamated with the thorax, so as to form a cephalo-thorax. The integument usually produces chitine more or less abundantly, so as to constitute a resistent shell; but in some cases the skin remains permanently soft. The mouth is situated in the anterior portion of the body, and in the higher forms is furnished with a pair of prehensile jaws, called “ mandibles,” a pair of chewing-jaws, called “maxilla, and a lower lip. In the scorpions an upper lip is present as well. In the true spiders each mandible terminates in a sharp movable hook, perforated by a canal which communicates with a poison-gland situated near its base. By means of this poisonous fluid the spiders kill such animals as they capture. In the scorpions the mandibles are short, and terminate in strong pincers. In them, too, the maxille are furnished with enormously-de- veloped nipping-claws or chele.* In all the Arachnida the mandibles are believed to correspond to the antennz of the * These nipping-claws in the scorpions are produced not by the maxilla themselves, bat by two appendages to the maxilla, which are known as “maxillary palpi.” 140 INVERTEBRATE ANIMALS. Crustacea. In the lower Arachnida, such as the ticks, the organs of the mouth are modified to enable them to imbibe fluids. The mouth in the Arachnida opens into a pharynx, which is of extraordinarily small diameter in the true spiders, which live simply on the juices of their prey. The intestinal canal is usually short and straight, and is continued without convo- lutions to the aperture of the anus. Salivary glands are also present, as well as ramified tubes which are believed to act as kidneys. The circulation is maintained by means of a dorsal heart, which is situated above the alimentary canal. All the Arach- nida breathe air directly, and the function of respiration is performed by the general surface of the body (as in the lowest members of the class), or by branched air-tubes termed “ tra- cheze,” or by distinct pulmonary chambers or sacs, or, lastly, by a combination of tracheze with pulmonary sacs. The tra- chez are essentially similar in structure and function to the breathing-tubes of the Myriapoda and Insecta, and consist of tubes, which open on the surface of the body by distinct aper- tures called “ spiracles.” The walls of the tube are prevented from collapsing by means of a spirally-coiled thread or filament of chitine, which is wound round their walls within their inner lining. The pulmonary sacs which occur in the Arachnida are simple chambers formed by an inversion of the skin, which constitutes a number of closely-set plates or folds. The whole of the interior of the pulmonary sacs is richly supplied with blood, and air is admitted by means of minute external open- ings. The nervous system is of the regular articulate type, but the ganglia of the ventral chain are often massed together in particular situations. In no case are compound eyes present; and, when distinct organs of vision exist, these are in the form of from two to eight simple eyes. ORDERS OF THE ARACHNIDA. OrpeEr J. Poposomatra.—In this order are included the “ Sea-spiders,” which are wholly marine, and were long be- lieved to be referable to the Crustacea on this account, As they have no respiratory organs of any kind, the question can- not be definitely settled, but they have no more than four pairs of legs, and would therefore seem to be properly refer- able to the Arachnida. In some forms the legs attain an ex- ARACHNIDA. 141 traordinary length, and contain prolongations from the stom- ach. They are all grotesque-looking animals, found at low water upon stones or marine plants, or parasitically attached to marine animals. One of the commonest forms is figured below (Fig. 574, a). Orpver II. Acarma.—The most familiar members of this order are the Mites and Ticks (Fig. 574, 6, ¢). They are dis- tinguished by the fact that the abdomen is amalgamated with the cephalo-thorax to forma single mass. Respiration is ef- fected by the general surface of the body or by air-tubes (trachez). The habits of the mites are extremely varied. Some are found upon different plants (Fig. 574, 6); others are parasitic upon water-insects when young, but swim about freely when adult (Fig. 574, ¢); others are permanently parasitic upon Fie. 57¢.—Arachnida. a Pycnogonum littorale; b Tetranychus telarius, one of the “Sociable” mites; ¢ Zydrachna globulus, one of the “ Water-mites.” other animals, such as sheep, dogs, insects, etc.; and others inhabit decaying provisions, as is the case with the well-known “ cheese-mite” (Acarus domesticus). Two species have a con- siderable medical interest as attacking man. One of these causes the skin-disease which is known as the “itch,” and the other is found inhabiting certain glandular follicles of the skin, probably without an exception even in favor of the most cleanly people. Orper JII. Pepreatpr.—In this family are the most for- midable of all the Arachnida—namely, the Scorpions. They are all distinguished by the fact that the abdomen is divided into distinct segments, and is continued into the cephalo- thorax without any well-marked boundary or constriction. In 142 INVERTEBRATE ANIMALS. the true scorpions the end of the abdomen (Fig. 58) is com- - posed of a hooked telson, which is perforated for the duct of a poison-gland, situated at its base. It is by means of this that the scorpions sting ; and the poisonous fluid which they secrete Fig. 58.—Scorpion (reduced). is sufficiently powerful to render their wounds troublesome and painful, if not positively dangerous. The mandibles in the scorpions, as already said, are developed into pincers, and the so-called “maxillary palpi” constitute powerful nipping- claws. The respiratory organs are in the form of pulmonary sacs, four on each side, opening on the under surface of the abdomen by as many distinct apertures or spiracles. The scorpions live in the warmer regions of the temperate zone and in tropical countries, and are generally found hiding under stones or in crevices of walls. Their sting, though much exaggerated, is certainly capable of producing very un- pleasant symptoms.* : Orver IV. Aranrrpa.—In this order are the true Spiders, readily distinguished from the insects, with which they are popularly confounded, by having four pairs of legs, as well as by other characters. In all the true spiders (Fig. 59) the seg- ments of the thorax and head are united to form a single mass or cephalo-thorax, to which the soft and unsegmented ab- domen is joined by a constricted stalk, or neck. Respiration is effected by means of pulmonary sacs, usually conjoined with tracheze. The pulmonary sacs are two or four in number, and open on the surface of the abdomen by as many apertures. * Nearly allied to the Scorpions are the so-called “ Harvest-spiders” (Phalangtde), and oat aia “Book-scorpion” (Chelifer), which is commonly to be found among old ooks, ARACHNIDA. 143 The head bears from six to eight simple eyes; the mandibles are hooked, and carry the duct of a poison-gland; and the maxillary palpi are not developed into nipping-claws. The spiders are all predaceous and rapacious animals, and many of ‘i Reg Fic. 59.—Araneida. Theridion riparion (female). them possess the power of constructing webs, either for the capture of their prey, or simply for lining their habitations. 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 rapid- ly on exposure to air, and which is cast into its proper thread- like shape by passing through what are called the “spin- nerets.” These are little conical or cylindrical organs placed at the end of the abdomen, and perforated by a number of ex- tremely minute tubes, through which the secretion 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 simply hunt their prey for themselves. The spiders are oviparous, and their young pass through no metamorphosis, but they cast their skin, or “moult,” re- peatedly before they attain the size of the adult, ry CHAPTER XVI. MYRIAPODA. Crass II. Myriapopa (Gr. murios, countless; podes, feet).—This class is an extremely small one, and includes only the Centipedes and the Millipedes. In all the Myriapoda the head is distinct, and not amalgamated with the thorax. There is no clear boundary-line between the thorax and the ab- domen, both being composed of nearly similar segments. The body, with one exception, always consists of more than twenty rings, and the hinder segments, which correspond to the ab- domen, always carry locomotive appendages, whereas the abdominal rings in Arachnida and Jnsecta are always des- titute of locomotive appendages. One pair of antenne is present, and the number of the legs is always more than eight pairs. Respiration is carried on by branched air-tubes or trachez. In most of their characters the Myriapoda closely re- semble the true insects, with which, indeed, they are not un- commonly classed. The true insects, however, always have the head, thorax, and abdomen, distinct from each other, and have never more than three pairs of legs. In most of the Myriapoda the young, or “ larvee,” are more like insects than the adult, since they have only three pairs of legs, or are alto- gether destitute of feet. In some cases, however, the young Myriapod, on escaping from the egg, possesses nearly all the characters of the parents, except that the number of body- rings, and consequently of legs, is smaller, and increases with every change of skin (“moult”). The class is divided into two leading families, represented by the common Centipedes and Millipedes. The Centipedes (Fig. 60) are carnivorous in their habits, and the organs of the mouth are adapted for a life of rapine. MYRIAPODA. 145 In addition to the parts of the mouth proper, they have two pairs of “ foot-jaws,” of which the second is hooked and per- forated for the discharge of a poisonous fluid. The bite of the common European species is perfectly harmless to man, but some of the tropical forms attain a length of a foot or more, and are consequently able to inflict extremely severe and even Fis. €0.—Centipede (Scolopendra). dangerous bites. The true centipedes are further distinguished by the number of legs not being indefinitely great (usually from fifteen to twenty pairs), and by the fact that the antennz are composed of not less than fourteen joints each. The Millipedes (Fig. 61) are repulsive-looking but perfectly Fic. 61.—Millipede (Zulus). innocent animals, which feed principally upon decaying vege- table matter. The body, in the ordinary millipedes, is round- ed and worm-like, and the segments are so amalgamated that each apparent body-ring gives origin to two pairs of minute, thread-like feet. The mouth is destitute of the powerful jaws which are found in the centipedes, the legs are indefinitely numerous, and the antennz are short, and are composed of no more than six or seven joints each, The European millipedes are all of small size, but an Amer- ican species is stated to attain a length of more than half a foot. A third family has been established for a curious little creature called Pauropus. In this the body consists of only ten segments, and there are no more than nine pairs of legs. The antenne are five-jointed, forked, and provided with jointed appendages. There are no trachex, and respiration is carried on by the skin. It is very small, and is found inhabiting decayed leaves and damp situations. CHAPTER XVII. INSECTA. Crass IV. Insecta.—The true Insects are distinguished from the preceding classes of articulate animals by the fact that the three divisions of the body, namely, the head, thorax, and abdomen, are always distinct from one another , there . are never more than three pairs of legs in the adult, and these are borne upon the thorax ; the abdomen is destitute of loco- motive appendages. Respiration is effected by means of air- tubes or trachez, and, in most insects, two pairs of wings are developed from the back of the second and third segments of the thorax. The integument in insects is more or less hardened by the deposition of chitine in it, and the body is deeply cut into segments—hence the name Jnsect (from the Latin insectus, cut into). The head in insects (Fig. 62, a) is composed of several segments amalgamated together, and carries a pair of jointed feelers or antenney, a pair of eyes, usually compound, and the appendages of the mouth. The thorax in insects (6, ¢, @) is composed of three segments, which are amalgamated together, but are generally pretty easily recognized. Each of these segments of the thorax carries, in perfect insects, a single pair of jointed legs, so that there are three pairs in all. To the back of the two hinder segments of the thorax, in most insects, there are also attached two pairs of wings. In their typical form, the wings are membranous expansions, supported by more or less numerous hollow tubes, known as the “nerv- ures.” One or both pairs of wings may be wanting, and when all are present the anterior pair may be much modified by the deposition of chitine in it. These modifications will be treated of in speaking of the orders of insects. The abdo- men in insects (e) is properly composed of rine segments, INSECTA. 147 Aree Fic. 62.—Diagram of the external anatomy of an insect: a Head, carrying the eyes and antenne; b First segment of the thorax, with the first pair of legs; ¢ Second segment of the thorax, with the second pair of legs and the first pair of wings; @ Third seg- ment of the thorax, with the third pair of legs and the second pair of wings; ¢ Abdo- men, without limbs, but carrying terminal appendages concerned in reproduction. which are usually more or less freely movable upon one an- other, and which never carry locomotive limbs, as is so com- monly the case in the Crustacea. The extremity of the abdo- men is, however, often furnished with appendages which are primarily connected with reproduction, but which are often converted into weapons of offence and defence. Of this nature are the “ovipositors” of ichneumons, the stings of bees and wasps, and the forceps of the common earwig. The organs of the mouth in insects require a brief consid- eration, as being in the closest possible relation with their habits and mode of life. Two chief types of mouth are recog- nizable in insects, termed respectively the “masticatory ” and “ suctorial,” according as the mouth is fitted for biting and chewing, or simply for imbibing fluids. The masticatory mouth is seen in perfection in the beetles, in which the follow- ing organs are present: 1. An upper lip or “labrum” at- tached below the front of the lead. 2. A pair of biting-jaws 148 INVERTEBRATE ANIMALS. or “mandibles.” 3. A pair of chewing-jaws or “ maxille” provided with jointed filaments, called the “ maxillary palpi.” 4, A lower lip or “labium” which also carries a pair of jointed filaments, known as the “labial palpi.” In the typical suctorial mouth, as seen in the butterflies and moths, the fol- lowing is the arrangement of parts: The upper lip and man- dibles are quite rudimentary; the maxilla are greatly length- ened, and form a spiral tube fitted for sucking up the juices of flowers; and the labial palpi are much developed, and form two hairy cushions between which the trunk can be coiled up when not in use, In many insects, the organs of the mouth are essentially adapted for suc- tion, but are also fitted for pierc- ing solid substances, such as the skin of animals or the stems of plants. In these the lower lip forms a kind of sucking-tube or sheath, within which are con- tained the maxille and mandi- bles, which are modified so as to form piercing organs or lan- cets. In the common bee, the masticatory and suctorial types of mouth are combined. The mandibles or biting-jaws are re- tained, to enable the honeycomb to be manufactured, and there is also a tubular trunk fitted for sucking up the juices of flowers. In the butterflies, too, in which the mouth of the adult is strict- ly adapted for suction, the cater- pillar is furnished with a mas- ticating mouth, so that it can feed upon leaves or other solid Fia. 63.—Digestive apparatus of a Beetle : (Carabus auratus). a Gullet; & Crop; substances. é Gizard; @ Chylific stomach; ¢ Mal- The mouth in the mastica- youn Tubes J Intestine; g Cloaca; % ting Insects (Fig. 63, a) leads into a membranous and often folded cavity, termed the “crop” (0), from which the food passes to a second muscular cavity or “gizzard” (c). The gizzard is adapted for crushing the food, and often has plates or teeth of chitine developed in its walls. It is succeeded by the true digestive cavity (d), which is termed the “ chy- INSECTA. 149 lific stomach.” From this there proceeds an intestine (/), of variable length, which usually terminates in a chamber (9) called the “cloaca” (Lat. cloaca, a sink), into which the ducts of the reproductive organs open. The commencement of the gullet is furnished with glandular appendages, which are believed to discharge the functions of salivary glands. Imme- diately behind the posterior aperture of the stomach are a variable number of cecal convoluted tubes (e), which are known as the “ Malpighian vessels,” after their discoverer Mal- pighi, and which are generally looked upon as representing the liver. Close to the cloaca may be other tubes, which are _be- lieved, from their position, to exercise the functions of kid- neys (/). The circulation in insects is mainly carried on by a long, contractile tube, placed along the back, and termed the “ dor- sal vessel.” The blood, collected from the various tissues and organs of the body, enters the dorsal vessel from behind, and is driven forward to the anterior extremity of the body. Res- piration is effected by means of air-tubes or tracheze, which commence at the surface by so many apertures or spiracles, and branch repeatedly as they proceed inward through the tissues. They have essentially the same structure as in the Arachnida, consisting of membranous tubes strengthened by means of a spirally-coiled filament of chitine. The nervous system in insects, though sometimes some- what modified, has essentially the regular annulose form of a ventral chain of ganglia, traversed in front by the gullet. The organs of sense are the eyes and antenne. The eyes are usually “compound,” and are composed of numerous six-sided lenses, united together, and each supplied by a separate ner- vous filament. As many as eight thousand of these lenses have been counted in one of the eyes of the common cock- chafer, and this number is sometimes greatly exceeded. Be- sides these compound eyes there are sometimes “simple” eyes, identical in structure with the single lenses of the com- pound eyes; and in rare cases these are the only organs of vision. The feelers or antennz, with which all insects are furnished, are jointed filaments attached close to the eyes, and assuming very different shapes in different insects. They ap- pear to be certainly organs of touch, but they very probably minister to other senses as well, and there is some reason to suppose that they are connected with the sense of hearing in particular. The sexes in insects are distinct, and most of them are 150 INVERTEBRATE ANIMALS, oviparous, Generally speaking, the young insect is extremely different in external character from the adult, and it requires, before reaching maturity, to pass through a series of changes which collectively constitute what is called the “metamor- phosis. In some insects, however, there is no proper meta- morphosis, and in some the changes which take place are not so complete and striking as in others. By the dbsence of met- amorphosis, or by its completeness when present, insects are divided into three convenient, though perhaps not strictly natural, sections, as follows: Section IL Ametabolie Insects.—The insects belonging to this section are said to be “Ametabolic” (Gr. a, without; metabole, change), because they pass through no metamorpho- sis. The young, on their escape from the egg, resemble the adult in every respect except in size, and they undergo no alteration in reaching maturity, except that they grow larger. All the insects of this section are destitute of wings in the adult state, and they are therefore often called “ Aptera” (Gr. a, without; pteron, a wing). Section IT, Hemimetabolic Insects——In the insects be- longing to this section (Gr. hemi, half ; and metabole, change), there is a metamorphosis consisting of three stages, but these stages do not differ much from one another in appearance. The young, on escaping from the egg, is known as the “larva,” and it is not only much smaller than the adult, but is desti- tute of wings. After several changes of skin, the larva enters into the second stage, when it is termed the “pupa.” The pupa is active and locomotive, and rarely differs much from the larva, except that it is bigger, and rudimentary wings have now appeared on the back of the thorax. After a cer- tain period, and after some changes of skin, the wings burst from their sheaths, and the pupa is now converted into the third and final stage, when it is known as the “imago” or perfect insect. In all the insects belonging to this section— such as grasshoppers, dragon-flies, etc.—the second stage or pupa is active and locomotive; and for this reason the meta- morphosis is said to be “ incomplete.’ Section III. Holometabolic Insects (Gr. holos, entire; and metabole, change).—The insects belonging to this section— such as butterflies, moths, and beetles—pass through three stages, just as do the preceding, but these stages differ from INSECTA. 151 one another very much in appearance, and the metamorphosis is therefore said to be “complete” (Fig. 64). In these insects the larva is worm-like, segmented, and usually furnished with loco- motive feet, which do not correspond with the three pairs proper to the adult (see Fig. 71, 6), though these are usually present as well. The larva is also provided with masticating organs, COU el Fic. 64.—Metamorphosis of the Magpie-moth (Phalwna grossulariata). and eats voraciously. In this stage of the metamorphosis, the larvee constitute what are popularly known as “caterpillars ” or “grubs.” Having remained in this condition for a longer or shorter time, and having undergone repeated changes of skin, necessitated by its rapid growth, the larva passes into the second stage, and becomes a pupa (Fig. 64—see also Fig. 71). In this stage the insect remains quiescent, unless irri- tated, and it is very often attached to some foreign object, so as to be quite incapable of changing its place. In the case of the butterflies and moths, the pupa constitutes what is so familiarly known as the “ chrysalis.” The body is protected by a chitinous pellicle, and in some cases this is still further protected by the dried skin of the larva; while in other cases the larva—immediately before entering the pupa stage—spins 152 INVERTEBRATE ANIMALS. for itself a protective case of silken threads, which surrounds the chrysalis, and is known as the “cocoon.” Having re- mained for a variable time in this inanimate, quiescent pupa- stage, during which rapid changes have been going on in the interior of the animal, the insect now frees itself from the en- velope which obscured it, and appears as the perfect winged adult or imago, CHAPTER XVIII. ORDERS OF INSECTS. Tuer known number of insects is so enormous, their forms are so various, and their habits and instincts are not only so remarkable but have been so fully described, that it were hopeless to attempt here to do more than give the briefest possible outline of the leading characters which distinguish the different orders. The student desirous of further informa- tion on this head must have recourse to treatises specially de- voted to entomology. Section I. Amrtazouic Insects.— Young not passing through a metamorphosis, and differing from the adult in size only. Perfect insect (imago) destitute of wings; eyes simple, sometimes wanting. Orver J. Awnortura (Gr. anoplos, unarmed ; owra, tail). —tThe insects comprised in this order are parasitic upon man and other animals, and they are commonly known as Lice. They are all very minute in size, destitute of wings in the adult state, having a mouth formed for suction, and having either two simple eyes or none. Orper II. Matrorpaea (Gr. mallos, a fleece; phago, I eat).—These are known as “ Bird-lice,” and are all minute parasites on different birds. They are distinguished from the true lice by not living upon the juices of their host, but upon the more delicate and tender appendages of the skin. The mouth is, consequently, not suctorial, but fitted for biting. Orver II]. Taysanura (Gr. thusanoi, fringe; oura, tail), —The most familiar members of this order are the “ Spring- 154 INVERTEBRATE ANIMALS. tails” (Podure), which are commonly found under stones or in cellars and such like situations. They are distinguished by having the extremity of the abdomen furnished with bristles, by the sudden straightening of which the insect can effect pow- erful leaps. In many cases the body is covered with delicate scales which form beautiful objects under high powers of the microscope. Section II. Hemmeraporic Insecrs. — Metamorphosis incomplete ; the larva differing from the perfect insect chiefly in the absence of wings and in size; pupa usually active, or, Uf quiescent, capable of movement. Orvrer IV, Heniprera (Gr. hemi, half; pteron, wing).— In this order the mouth is formed for suction; the eyes are compound, but simple eyes are often present in addition. Two pairs of wings are always present. The Hemiptera live upon the juices of plants or animals, which they are enabled to obtain by means of their suctorial mouths, All the four wings are generally present, but the condition of these varies in different sections of the order. In one group all the four wings are membranous (Fig. 65); but in the other the posterior wings and the tips of the anterior Fic. 65.—Hemiptera. Bean Aphis (Aphis faba); winged male and wingless female. wings alone are membranous. The inner portions of the an- terior wings are hardened by chitine, and they are known as “hemelytra” (Gr. hemi, half; and elutron, a sheath). Among the more familiar examples of the Hemiptera are the numer- ous species of Plant-lice (Aphides), the Field-bug (Penta- toma), the Boat-fly, the Cochineal insects, and the Cicadas. The Cochineal insects are of considerable commercial im- portance, as the dried and powdered bodies of the female con- stitute the substance known as Cochineal, from which is ob- ORDERS OF INSECTS. 155 tained the brilliant pigment carmine. The male insect is winged, and is smaller than the female, which is wingless. They live upon different species of Cactus (Opuntia,) and are mainly imported from Mexico, Algeria, and the Canary Islands. Numerous species of Aphides or Plant-lice (Fig. 65) are known, and they are among the greatest pests of the gar- dener and farmer, as they are extraordinarily prolific, and live upon the juices of plants. One of the most curious points about the Plant-lice is that they secrete a sweet and stick fluid, which is expelled from the body by two little tubular filaments placed near the end of the abdomen. Ants are excessively fond of this fluid, and hunt after Aphides in all directions in order to ob- tain it; and it is a well-established fact that the Plant-lice are actually pleased with this, and voluntarily yield up the coveted fluid to the importunity of the ants. Orper V. OrtHoprera (Gr. or- thos, straight; pteron, wing).—The mouth in this order is strictly masti- catory ; there are four wings present in most, but the anterior pair is smaller than the posterior, and of a different texture. The posterior wings are membranous, and are fold- ed lengthwise, like a fan; the ante- rior wings are leathery, and consti- tute cases for the posterior wings (elytra). This order includes the Crickets (Achetina), Grasshoppers (Gryllina), Locusts (Locustina), Cockroaches (Blattina, Fig. 66), { and others. Some of them are fy, 66.—Orthoptera. The com- formed for running, all the legs on Cooua tua neni: being nearly equal in size; others have the first pair of legs greatly developed, and constituting powerful organs of prehension; while others, such as the Lo- custs and Grasshoppers, have the hindmost pair of legs much longer than the others, giving them a considerable power of leaping. All the Orthoptera are extremely voracious, and every one is acquainted with the terrible ravages occasionally caused in hot countries by swarms of locusts. 156 . INVERTEBRATE ANIMALS. The most destructive species is the Migratory Locust (Acrydium migratorium, Fig. 6%), which is very abundant in Africa, India, and throughout the whole of the East. Owing to the rapidity with which they devour every thing they can possibly eat, and owing to their enormous numbers, the Lo- custs are compelled to be constantly on the move, looking for “fresh fields and pastures new.” It is from these migrations Fig. 67.—The Migratory Locust (Acrydium migratorium). in vast bodies in search of food that the Migratory Locust takes its name. When one of these destructive hosts visits a district, it only needs a few hours to convert the most fer- tile country into a howling wilderness. In an incredibly short space of time, every green thing on their line of march is destroyed, every leaf is stripped from every tree, every blade of grass and corn is eaten down, and it is not until the ground is utterly bare and brown that the locusts take wing and seek out some fresh region to devastate. OrpEer VI. Nevroprera (Gr. neuron, nerve; pteron, wing).—The mouth in this order is fitted for mastication; the wings are four in number, generally nearly equal in size, all membranous, and traversed by numerous delicate nervures, which interlace so as to form a delicate net-work (Fig. 68). The metamorphosis is generally incomplete, but is sometimes complete. This order includes the well-known and rapacious Dragon- flies (Libellulidce), the Caddis-flies (Phryganeide), the May- flies (Ephemeride), the Ant-lion (Myrmeleo), the Aphis-lion (Fig. 68), Termites, etc. The last of these—namely, the Ter- mites or white ants—are social insects, living in organized communities, and exhibiting many remarkable phenomena. They are mostly inhabitants of hot countries, and cause im- mense mischief by destroying wood-work of all descriptions. ORDERS OF INSECTS. 157 Though called “ white ants,” it is to be remembered that they are not related in any way to the true ants. They build mounds of different shapes and sizes, sometimes several feet in height, formed of “ particles of earth worked into a mate- rial as hard as stone.” Each 24s, & ere family of Termites (Fig. 69) SN possesses a king and queen, - which are always kept together closely guarded in a chamber placed in the centre of the nest. The king (Fig. 69, a) and the queen (8) both origi- nally possessed wings, but they lose these as soon as they foundacolony. Both are much larger than the bulk of the community, the queen im- Sj mensely so, owing to the Fie. 683—Neuroptera, Aphis-lion (/Zemero- enormous distention of her ab- SCRE ROUGE aa OS PEER domen with eggs. The ordinary Termites are all sterile fe- males, incapable of laying eggs, and they are divided into two distinct sets or “castes,” both destitute of wings, and differ- ing in the armature of the head. The one caste includes the Fia. 69.—Termites (Zermes bellicosus); a King, before the wings are cast off; 0 Queen, with the abdomen distended with eggs; c Worker, @ Soldier. so-called “ workers,” who perform all the ordinary work of the colony, while the “soldiers” have greatly-developed jaws, and are simply Gpeupiel in defending the nest against all enemies. 158 INVERTEBRATE ANIMALS. Section II. Hotomzranora.— Metamorphosis complete ; the larva, pupa, and imago, differing greatly from one an- other in external appearance. The larva worm-like, and the pupa quiescent. Orper VII. Apnanrprera (Gr. aphanos, inconspicuous ; pteron, wing).—In this order are only the Fleas (Pulicide), in which the mouth is suctorial, the metamorphosis is complete, and the wings are rudimentary, being represented by four minute scales placed on the last two segments of the thorax, The larva of the common flea is a footless grub, which in about twelve days spins a cocoon for itself, and becomes a quiescent pupa, from which the imago emerges in about a fortnight more. OrveErR VIII. Dirrera (Gr. dis, twice; pteron, wing).— The insects of this order, as implied by its name, have only a single pair of wings—namely, the anterior pair. The poste- rior wings are rudimentary, and are represented by two Fra. 70.—Diptera. Crane-fly ( Zipula oleracea). clubbed filaments called “balancers” or “ poisers” (Fig. 70). The mouth in the Diptera is suctorial. ORDERS OF INSECTS. 159 The Diptera constitute one of the largest orders of insects; the House-flies and Flesh-flies (Zusea), the Gnats ( Culex), the Crane-flies (Zipula), the Forest-flies (Hippobosca), and the Gad-flies (Zabanide), constituting good examples. Orprr IX. Leprpoprera (Gr. lepis, scale; pteron, wing). —This well-known and most beautiful of all the orders of in- sects comprises the Butterflies and Moths, the former being active by day (diurnal), and the latter mostly toward twilight (crepuscular), or at night (nocturnal). In all the Lepidoptera the mouth of the adult insect is purely suctorial, and is pro- vided with a spiral trunk fitted for imbibing the juices of flowers. The wings are four in number, and are covered more or less completely with modified hairs or scales, which are pretty objects under the microscope, and from which the wings derive their beautiful colors. The larve of the Lepidoptera (Fig. 71) are generally known as caterpillars. They are worm- like, provided with masticatory organs fitted for dividing solid Fic. 71.—Large white Cabbage-butterfly (Pontia brassicae). a Larva or caterpillar; 3 : Pupa or chrysalis; ¢ Imago or perfect insect. substances, possessing false legs in addition to the three pairs proper to the adult, and having attached to the under lip a tubular organ or spinneret, by which silken threads can be manufactured. The butterflies or diurnal Lepidoptera are characterized by being active during the daytime, by keeping their wings most- 160 INVERTEBRATE ANIMALS. ly erect when at rest (Fig. 71, c), by having club-shaped an- tenn, and by having a chrysalis (), which is almost always naked and angular, and is generally attached to some solid object by silken threads variously disposed. The Moths are mostly active during the night-time, when they are said to be nocturnal. Many of them, however, are “ crepuscular ”’—that is to say, they are active during the hours of twilight; and a few come out in broad daylight and in the brightest sunshine. The pup, or chrysalides, are never an- gular, as in the case of the butterflies. Apart from the destruction committed by the Caterpillars of some of the Lzpidoptera, the only members of the order which are of importance to man are the various species of Bombyx, from which silk is derived. Several species are cul- tivated for this purpose, but by far the most valuable is the common Silk-moth (Bombyx Mort), which owes its name to the fact that the larva feeds upon the leaves of the common Mulberry (Morus nigra). It is hardly necessary to say that raw silk is derived from the “ cocoon,” or silken case in which the caterpillar enwraps itself before becoming a chrysalis. Most of the raw silk is derived from France, Italy, China, and the East Indies. Orprer X. Hymenoptera (Gr. hiumen, membrane; pteron, wing).—lIn this order all the four wings are present, as a rule, and they are all membranous in texture, with few nervures (Fig. 72). The mouth is always furnished with biting-jaws or mandibles, but often is adapted for suction as well. The fe- males have the extremity of the abdomen furnished with an instrument connected with the process of laying eggs (ovi- positor) ; and in very many cases this becomes the powerful defensive weapon known as the sting. The metamorphosis is complete. The Hymenoptera form a very extensive order, comprising the Bees (Apidae), the Wasps ( Vespida), the Ants (Pormi- cide), the Saw-flies (Zenthredinidw, Fig. 72), and the Ich- neumons. The Bees and Wasps are well known as forming social communities, though solitary members of both are not uncommon, In both groups these organized communities con- sist of a vast number of undeveloped females, or “ neuters ”— the so-called “ workers ”—presided over by a single fertile fe- male, or “ queen,” or containing several such. The males are only produced at certain seasons, and they constitute the so- called “drones” of a hive of bees. The workers discharge all ORDERS OF INSECTS. 161 the duties necessary for the preservation of the colony, such as procuring food, building the nest, and feeding the young. As there is only one set, or “caste,” of neuters, the duty of Fig. 72.—Gooseberry Saw-fly (Tenthredo grossularia), larva, pupa, and imago. ) defending the nest falls to the lot of all the workers, and is not delegated to a special class of soldiers. The queen is the founder of the colony, and her sole function, after starting the community, is to lay eggs. The drones, or males, do no work, as a rule, and they either die, or are killed by the workers, as soon as the female is fertilized. The Ants likewise form communities, consisting of males, females, and neuters, The males and females, like those of the very different “White Ants,” or Termites, are winged (Fig. 73, a), and are produced in great numbers at particular times of the year. They then quit the nest and pair, after which the fecundated females lose their wings and form fresh societies. The workers (Fig. 73, 6) are sometimes all of one kind, but they are often divided into two, or even three, distinct classes or “castes.” The Ants exhibit many most extraordinary and interesting instincts and habits, of which 162 INVERTEBRATE ANIMALS, Fic. 73.—The Red Ant (Myrmica rufa). a Winged male; b Wingless female. Magnified. their custom of “milking” the little Plant-lice has been al- ready mentioned. Another very singular habit of some Ants may be just alluded to—their habit, namely, of capturing the pupz of other species of Ants and bringing them up as slaves, The relations, however, between the masters and slaves vary a good deal in different cases. In the case, for instance, of the Russet Ant (Formica rufescens) the masters are so entire- ly dependent upon their slaves that they cannot even feed themselves, and the only work which they perform unassisted is the capturing of fresh slaves. In the Blood-red Ant (for- mica sanguinea), on the other hand, the slaves are much fewer in number, and the masters are much less dependent upon their good offices. In all cases, the slaves exhibit the greatest devotion to their masters, and are invariably taken the greatest care of by their captors. Orver XI. Srrepsiprers (Gr. strepho, 1 twist; pteron, wing).—This is an extremely small order of insects, which merely requires to be mentioned. It includes only certain minute parasites, which are found on bees and other Hy- menoptera, The females are destitute of wings or feet, and are merely soft, worm-like grubs. The males are active, and possess a single pair of large membranous wings. Unlike the Diptera, it is the posterior pair of wings which is present, and the anterior pair is quite rudimentary, and is only represented by curious twisted filaments, from which the name of the order is derived. OrpEer XII. Corzorrera (Gr. Koleos, a sheath; pteron, wing).—The twelfth and last order of insects is that of the Coleoptera, including the well-known insects familiar to every ORDERS OF INSECTS. 163 one under the name of “beetles.” The leading peculiarity of the Coleoptera is to be found in the fact, that though all the four wings are present, only the posterior pair are mem- branous, and perform the function of wings. The anterior pair of wings are no longer capable of being used in flight, but are hardened by the deposition of chitine, and constitute pro- Fig. 74.—Coleoptera. The common Cockchafer (Melolontha vulgaris), with the elytra closed, and in flight. tective cases, which cover the hind-wings, and are known as “elytra” (Gr. elutron, a sheath). The mouth in all the beetles is masticatory, and is furnished with biting and chewing jaws. The larve of the beetles are all worm-like grubs, with masticatory mouths, and they all pass through a complete meta- morphosis, generally requiring a protracted period for its com- pletion. The known number of different kinds of beetles can- not be estimated with any certainty, but it is probably little short of 50,000 species, and this estimate has been doubled by some writers. They are, as a general rule, remarkable for their hard, chitinous skin, their glittering, often metallic, colors, and their voracious habits, though many of them feed upon vegetable matters. Of the enormous number of known Beetles, the only one which can be said to be of any decided use to man is the so- called “ Blister-beetle,” or “Spanish Fly” (Cantharis vesica- toria). This handsome insect is a native of Southern Europe, especially of Italy, Spain, and France, and lives upon the leaves of the ash, lilac, elder, and poplar. It is largely col- lected and exported for medicinal purposes, as it yields one of the most generally used and efficient of blisters, SUB-RINGDOM V.—MOLLUSCA. CHAPTER XIX. Sup-Kinepom Mottusca.— The Mollusca (Lat. mollis, soft), as implied by their scientific name, are mostly soft- bodied animals, but their popular name of “ shell-fish” ex- presses the fact that their soft body is usually protected by an external skeleton or “shell.” All the Mollusca are fur- nished with a distinct alimentary canal, which is completely shut off from the general cavity of the body (Fig. 75, a). There is sometimes no distinct blood-circulatory apparatus ; but, when there is, its central portion (i. e., the heart) is placed upon the dorsal aspect of the body. The chief peculiarity, however, aif 2 Fig. 75.—Diagram of a Mollusk. @ Alimentary canal; 2 Heart; £ Foot; m Cerebral gan- glion; 2’ Pedal ganglion; ’’ Parieto-splanchnic ganglion. of the Mollusca is found in the nature of the nervous system. In the lower forms (Fig. 76, 2 d), the nervous system consists essentially of a single ganglionic mass, giving off filaments in various directions. In the higher Mollusca (Fig. 75, 1), the nervous system consists of three scattered ganglia, united to one another by nervous cords. One of these ganglia is placed above the gullet or cesophagus, and is known as the “supra- cesophageal” or “cerebral” ganglion. A second supplies MOLLUSCA. 165 nerves to the great locomotive organ of most Mollusks, the “foot,” and is therefore called the “pedal” ganglion, The third is known by the cumbrous name of the “ parieto-splanch- nic” ganglion, because it supplies nervous filaments to the walls (parietes) of the body, and also to the internal organs (splanchna). In all the higher Mollusks it is this scattered condition of the nervous masses which distinguishes them so sharply from all other animals. Distinct respiratory organs may or may not be present, and they may be adapted for breathing air directly or through the medium of water. All the higher Mollusca are simple animals, and perpetuate their kind by means of the sexes, but many of the lower forms have the power of producing colonies by continuous gemma- tion, much as we have formerly seen in the Hydroid Zoo- hytes, . *The digestive system in all the Mollusca consists of a mouth, gullet, stomach, intestine, and anus, with the excep- tion of a few forms in which the intestine ends blindly. In some the mouth is surrounded by ciliated tentacles (Polyzoa, Fig. 77) ; in others, it is furnished with two long ciliated arms (Brachiopoda); in the bivalves (Lamellibranchiata), it is mostly furnished with four membranous processes or “ palpi” (Fig. 80, p); in others, it is furnished with a complicated toothed organ or “odontophore ” ( Gasteropoda, Fig. 83, and Pteropoda); and lastly, the Cephalopoda,.in addition to an odontophore, possess horny mandibles, forming a kind of beak, very like that of a parrot. The blood is colorless, or nearly so. In the lowest class of the Mollusca (Polyzoa), the circulation is carried on by means of cilia, and there is no distinct heart, nor any definite course of the circulating fluid. In the Sea-squirts (Zunicata), there is a distinct heart, but the structure of this is very simple, consisting of a mere tube, open at both ends, so that the course of the circulation is periodically reversed. In the higher Mollusca, there is a distinct heart, consisting of two chambers, of which one (the auricle) receives the aérated blood from tlie gills, while the other (the ventricle) drives it through the body. , Respiration is very variously effected among the Mollusca. In the Polyzoa (Fig. 7) respiration is discharged mainly by the crown of ciliated tentacles surrounding the mouth. In the sea-squirts (Fig. 78), respiration is effected by a greatly-devel- oped pharynx, which is perforated by numerous ciliated aper- tures. In the lamp-shells and their allies (Brachiopoda), the 166 INVERTEBRATE ANIMALS. long, ciliated arms, which spring from the sides of the mouth, seem to be the main agents in respiration. In the bivalve- shell-fish, the cuttle-fishes, and most of the univalves, the breathing-organs are in the form of gills or branchiz, adapted for breathing air dissolved in water. In the remainder of the univalves (e. g., snails and slugs), the breathing-organs are adapted for breathing air directly, and have the form of an air-chamber or pulmonary sac, produced by the folding of a portion of the mantle. The air is admitted to the chamber by a round opening, situated on the side of the neck, and capable of being closed at will. The lining membrane of the chamber is richly supplied with blood-vessels, and thus the necessary purification of the blood is carried out. In accordance with the scattered or rudimentary condition of the nervous system, the Mollusca are not characterized by acuteness of senses, nor by any great power of locomotion. Organs of sight exist in some of the lower and many of the higher Mollusca, attaining in the cuttle-fishes (Fig. 89) an ex- tremely high type of organization. The common bivalve shell- fish, such as the scallop, possess numerous simple eyes placed along the margins of the mantle, but, in many cases, even these are absent. Locomotion is very variously effected, but seldom with much vigor or activity. The lowest classes of the Mol- fusca are, in the great majority of instances, fixed when adult. The common univalve shell-fish, such as whelks, snails, slugs, etc., creep about slowly by means of a flattened disk, devel- oped on the under surface of the body, and known as the “foot.” Other Univalves and many Bivalves can effect short leaps by means of the foot, but many of the latter are perma- nently fixed to solid objects, or buried in the sand. The mi- nute Mollusca, known as the Pteropoda (Fig. 88), swim freely at the surface of the ocean by means of two fins, formed by a modification of the foot, and attached to the sides of the head. The only Mollusks which enjoy really active powers of loco- motion are the predacious cuttle-fishes, which swim rapidly by means of fins, or by ejecting a jet of water from the cavity of the mantle, and which can also creep about by means of the “arms ” placed around the mouth (Fig. 89). The last feature in the Mollusca which requires to be men- tioned is the “shell.” The shell is not invariably and univer- sally present in the Mollusca, many being either destitute of a shell altogether, or having one so small that it would not com- monly be recognized as such. In these cases, as in the com- mon slugs, the animal is said to be “naked.” In all the Mol MOLLUSCA. 167 lusea which possess a shell, this is secreted by the integument, or by what is technically called the mantle, and, in all cases, it is composed of carbonate of lime. The methods in which the lime is arranged differ in different cases, but all living shells have an outer covering of animal matter, which is known as the “epidermis.” In a great many of the higher Mollusca, such as the whelks, periwinkles, snails, and others, the shell consists of only a single piece, when it is said to be “ uni- valve.” In many others, such as oysters, mussels, scallops, etc., the shell is composed of two pieces, and is then said to be “bivalve.” In afew forms, the shell consists of several pieces, and it is then said to be “multivalve.” The more important variations in the shells of the Mollusca will be noticed in speaking of the different classes of the sub-kingdom. In accordance with the nature of the nervous system, the Mollusca are divided into two great divisions, known respec- tively as the Molluscoida and Mollusca proper. In the Mol- luscoida, the nervous system consists of a single ganglion, or principal pair of ganglia, and there is either no circulatory organ or an imperfect heart. In this division are included the three classes of the Sea-mosses (Polyzoa), the Sea-squirts (Zu- nicata), and the Lamp-shells and their allies (Brachiopoda). In the Mollusca proper, the nervous system consists of three principal pairs of ganglia, and there is a well-developed heart, consisting of at least two chambers. Under this head come all the ordinary forms of shell-fish. CHAPTER XxX. MOLLUSCOIDA. Criass I. Potyzoa (Gr. polus, many; z0dn, animal.) — The members of this class are the lowest of all Mollusca, and they are generally known by the popular names of “ Sea- mosses” and “Sea-mats.” They are invariably compound, forming associated growths or colonies, each consisting of a number of distinct but similar zodids, produced by gemmation from a single primordial individual. The colonies thus pro- duced are very generally protected by a horny or chitinous integument, and they are so like the Hydroid Zoophytes that they were long described as such. The only absolute distinc- tion between the two classes is to be found in the internal structure of the zodids of each; but they may be generally separated by the fact that the separate cells in a compound Hydroid are all united to one another by means of a common flesh or coenosarc; whereas in the Polyzoa the separate cells composing the colony are merely connected externally, but very rarely have any direct communication with each other. The separate beings or zovids which collectively constitute the colony of any Polyzoén are spoken of as “polypides ”—the term polypite being only used in connection with the Hydro- zoa, and the term polype being similarly restricted to the Actinozoa. Each polypide in a typical Polyzodn has the following structure (Fig. 76, 2): The body of the animal is enclosed in a double-walled sac, of which the outer layer is usually chitinous or calcareous, and constitutes a “cell” in which the zovid is contained. This outer layer is known as the “ ectocyst,” to distinguish it from the ectoderm of the Celenterata. The cell, thus formed, is lined by a much more delicate membra- nous layer, which is known as the “endocyst.” This membra- MOLLUSCOIDA. 169 nous sac, formed by the endocyst, is pierced by two openings. One of these is the mouth, and it is always surrounded by a circle or crescent of hollow ciliated processes or tentacles (Fig. 76, 2, a). These ciliated tentacles serve partly as respi- ratory organs, and partly to set up a current of water by which floating particles of food are brought to the mouth. The mouth and tentacular crown can be partially or com- pletely pulled into the sac by means of a muscle which is fixed to the gullet (2, g). The mouth leads into a gullet, and that Fia. 76.—Morphology of Polyzoa. 1. Fragment of one of the Sea-mats (Flustru truncata), magnified to show the cells. 2. Diagram of a single polypide of a Polyzodn (after Allman): @ Mouth surrounded by the ciliated tentacles; imentary canal; c Anus; @ Nervous ganglion; ¢ Investing sac or “ectocyst;” #7 Reproductive organs; g Muscle. 8. Bird’s- head process. again into a stomach, sometimes with a muscular gizzard be- tween. From the stomach proceeds an intestine of variable length, which terminates by a distinct anus at the upper part of the sac (2, c). On one side of the gullet, between it and the anus, is placed a single nervous ganglion (d). Distinct reproductive organs (77) are also present, and the whole cay- ity of the sac is filled with fluid. From the above description it will be evident that the typical polypide of a Polyzoin differs from the polypite of a Hydrozoén in having a distinct alimentary canal suspended freely in a body-cavity, and hav- ing both a mouth and vent, in having a distinct nervous sys- tem, and in having the reproductive organs contained within 170 INVERTEBRATE ANIMALS, the body. On the other hand, in the Hydrozoa, there is no alimentary canal distinct from the body-cavity, there is no nervous system, and the reproductive organs are in the form of external processes of the body-wall. ieee Pease CdS tits Fig. 77.—1. Fragment of Flustra truncata, one of the Sea-mats, natural size. 2. A single polynde of Valkeria, magnified, showing the circular crown oftentacles. 38. A polypide of Lophopus erystallinus, a fresh-water Polyzotn, highly magnified, showing the horse- shoe shaped crown of tentacles: a Tentacular crown; b Gullet; cStomach; d Intestine; e Anus; g Gizzard; & Endocyst; 7 Ectocyst. The foregoing gives the essential structure of the polypide of any Polyzoén, but in nature this simplicity is lost. In all cases in nature the primitive polypide possesses the power of producing fresh zodids by a process of budding; and these zodids remain attached to one another, so that ultimately there is produced a compound growth or colony. Further, in almost all the Polyzoa, the outer layer of the polypide is more or less hardened by the deposition in it of chitine or of carbonate of lime. The skeletons thus formed are the parts of the colony which are most familiarly known, and in the case of the com- mon Sea-mats (Fig. 77, 1) they are very well known to sea- side visitors, and are generally regarded as sea-weeds, Exam- ined in its dead state, such a skeleton only shows a number of little horny chambers or cells (Fig. 76, 1), each with a little aperture. When alive, however, each of these cells was ten- anted by a single zodid or polypide, capable of protruding its MOLLUSCOIDA, 171 ciliated head from the aperture, and of again retiring within it, if alarmed. The skeleton is, in some cases, furnished with curious organs, which are known as “ bird’s-head processes” (Fig. 76, 3), from their resemblance to the beak of a bird. ‘The parts of this beak keep constantly snapping together, very much like the little pincer-like organs called “ pedicella- riz” in the sea-urchins and star-fishes; but it is difficult to see what service they perform. They continue their movements long after the death of the polypides, and this appears, in some cases, at any rate, to be due to a peculiar system of nerves known as the “colonial” nervous system. In addition, namely, to the single ganglion with which each polypide is furnished, it has been shown that in many forms the zotids composing the colony are united together by a well-developed nervous system, and are thus brought into organic connection with one another. The vast majority of the Polyzoa are fixed, and thus as- sume a very plant-like-appearance. There is one fresh-water species, however (viz., Cristatella), in which the colony can creep about upon a flattened base very like the foot of a slug. In this same form, also, alone of all the Polyzoa, there is not any outer covering or ectocyst to the polypides. The Polyzoa are partly inhabitants of the sea and partly of fresh water, and they are thus divided into two groups which differ from one another very much in anatomical struc- ture. In most of the fresh-water Polyzoa the tentacles are borne upon acrescentic disk or stage (Fig. 77, 3), so that the crown of tentacles assumes the shape of a horseshoe. In almost all the marine forms, on the other hand, the tentacles (Fig. 7'7, 2) are simply arranged in a circle. All the Polyzoa are hermaphrodite, each polypide being furnished with the reproductive organs proper to the two sexes. The eggs are simply liberated into the body-cavity, where they are fertilized; but it is uncertain how the fertilized ova escape into the external medium. Besides true sexual reproduction, and besides the power of producing colonies hy continuous budding, fresh individuals can be produced in many cases by a process of discontinuous gemmation. Crass II. Tuntcata (Lat. tunica, a cloak).—The mem- bers of this class are not uncommonly called Ascidian Mol- lusks (Gr. askos, a wine-skin) from the resemblance which many of them exhibit in shape to a two-necked leather bottle (Fig. 78, 2). They are popularly known as “Sea-squirts,” from their power of forcibly ejecting water from the orifices - 172 INVERTEBRATE ANIMALS. of the bottle. Their scientific name, again, of Zunicata, is derived from the fact that the body is enveloped in a leathery elastic integument, which consists of different layers, and which takes the place of a shell, The outer covering of the animal is of a gristly or leathery consistence, and is known as the “test.” It is remarkable for containing a considerable propor- tion of a substance apparently identical with cellulose, which is one of the most characteristic of all vegetable products, The test is lined by a second coat, which is highly muscular, and confers upon the animal its power of contracting itself and squirting out water. Of the two necks which are placed at the anterior end of a simple Ascidian (Fig. 78), one is per- Fic. 78.—Morphology of Tunicata. 1. Diagram of a Tunicary (after Allman): @ Oral aper- ture; b "Atrial D sartares c Respiratory sac, with its rows of ciliated apertures; @ Ali- mentary canal; e Anus; f Cloaca or atrium; g Nervous ganglion. 2. A simple Ascidian (Cynthia papillosa). forated by the aperture of the mouth, while the other serves as an excretory aperture. These two apertures are known respectively as the “oral” and “atrial” apertures. The oral aperture (a) is usually furnished with a circle of small non-retractile tentacles, and opens into a great chamber known by various names, but best as the “respitatory sac.” This sac occupies the greater part of the cavity of the body (Fig. 78, 1, c), and has its walls perforated by numerous aper- tures, the sides of which are ciliated. At the bottom of the respiratory sac is a second opening (the mouth of some MOLLUSCOIDA. 173 writers) which leads by a short gullet into a capacious stom- ach (d). From the stomach an intestine is continued to te7- minate by a distinct anus, which does not communicate direct- ly with the exterior, but opens into a second great chamber, known as the “cloaca” or “atrium” (e). The cloaca, in turn, opens on the exterior by the second, or atrial aperture, in the test (0). These two great chambers—namely, the respiratory sac and the cloaca—occupy the greater part of the body-cavity, and, where their walls come into contact, a free communication is established between the two by means of the ciliated aper- tures already spoken of as perforating the respiratory sac. The cilia which fringe these apertures all work toward the cloaca, and thus a constant current of water is caused to set in by the oral aperture, through the respiratory sac, into the cloaca, and out again by the atrial aperture. In this way respiration is effected, the walls of the respiratory sac being almost made up of blood-vessels. A distinct heart is present in all the Tunicata, but it has a very simple structure (1, A’). It consists of a simple tube, open at both ends, and not pro- vided with valves. In consequence of this, the circulation in the majority of Tunicaries is periodically reversed, the blood being driven for a certain number of contractions in one direc- tion, and then propelled for a like period in an opposite direc- tion; so that “the two ends of the heart are alternately arterial and venous.” The nervous system in the Zunicata consists of a single ganglion placed on one side of the oral aperture. With one or two exceptions all the Znicata are hermaph- rodite, the organs of reproduction being situated in a fold of the intestine, and opening into the cloaca. The embryo is at first free, and in most swims about by means of a long tail, so that it presents considerable resemblance to the tadpole of a frog. The Tunicata are all marine, but differ a good deal from one another in form. In the so-called “simple” Ascidians the animal has the shape figured above, and is fixed to some solid object by one end of the test. In the “social” Ascidians the organism consists of a number of zoéids, produced by con- tinuous budding, and connected together by a common tube, through which the blood circulates. In the so-called “com- pound” Ascidians the tests are fused together into a com- mon gelatinous mass, in which the individuals are imbedded in groups. Some of the Tunicata are oceanic — that is to say, are found floating, or swimming, at the surface of the 174 INVERTEBRATE ANIMALS. open ocean—and some exhibit the phenomenon of phospho- rescence, In the foregoing description it has been found impossible to convey even the most elementary outline of the anatomy of a Tunicate without having recourse to technical terms. There still remain a few points of homology which should be mentioned. In the foregoing, the so-called ‘‘ oral aperture” of the animal has been regarded as truly the mouth, this being the simplest view, and the one held by Prof. Huxley. Upon this view the “ respiratory sac,” into which the mouth opens, must be regarded as a greatly-developed pharynx (i. e., the upper portion of the alimentary tube). Similarly, on this view, the /ower aperture of the respiratory sac will have to be regarded as the opening of the gullet, By Prof. Allman, again, the respiratory sac is looked upon as formed by a great modification of organs corresponding to the ciliated tentacles of the Polyzoa, so that the lower aperture of the respira- tory sac is the true mouth, Lastly, by Prof. Rolleston the respiratory sac is looked upon as corresponding to the gills of the Bivalve shell-fish (Lamelh- branchiata), and the oral and atrial apertures are regarded as corresponding to the “respiratory siphons” of these same animals. On this view, the lower aperture of the respiratory sac is again looked upon as the true mouth. The question cannot be regarded as settled, and Huxley’s view has been here adopted merely as being the most readily intelligible to learners. Cuass III. Bracniopopa.—The members of this class are little known to the general public, being all marine, often in- ~ habiting considerable depths in the sea, and being much more abundantly represented by fossil forms than by living ex- amples. They are often placed with the ordinary Bivalve shell- fish (Lamellibranchiata), in consequence of their universally possessing a shell composed of two pieces or valves (Fig. 79), but they are really of a much lower organization. In their essential structure they show many points of affinity to the Polyzoa, but they are always simple animals, never forming colonies, and they always have a bivalve shell. The two pieces of which the shell is composed are always placed one in front and one behind, so that they are “ventral” and “ dorsal,” and not “right” and “left” as in the true Bivalves. The two valves of the shell are also always slightly, and sometimes greatly, different to one another in size, so that the shell is said to be “inequivalve.” The ventral valve is usually the largest, and often possesses a prominent curved beak, which is generally perforated by an aperture through which there passes a muscular stalk by means of which the shell is at- tached to some solid object. In some cases, however, as in Lingula (Fig. 79), the stalk of attachment simply passes be- tween the valves, and is not transmitted through a distinct aperture. Jn other cases the shell is simply attached by the substance of the ventral valve. MOLLUSCOIDA. 175 The inner surface of the valves of the shell is lined by expansions of the integu- ment, which are called the “ mantle-lobes,” and which secrete the shell. The digestive organs and muscles occupy a small space near the apex or “beak” of the shell, which is partitioned off by a membranous partition, perforated by the aperture of the mouth. The remainder of the cavity of the shell is almost filled by two long processes, derived from the sides of the mouth, fringed with lateral ‘branches, and termed the “arms.” These arms are usually closely coiled up, and serve to obtain food for the animal. It is from these organs that the name of the class is derived (Gr. brachion, arm; and podes, feet). The arms also serve as respiratory organs, and in many forms they are supported on an internal calcareous framework or skeleton, sometimes called the “ carriage-spring apparatus.” The mouth is placed between the bases of the arms, and is not furnished with any apparatus of teeth. It conducts by a gullet . into a distinct stomach, surrounded by a well- Sinaia, aogng developed granular liver. The intestine may the musenlar stall : : ee y which the shell or may not be furnished with a distinct anus, __ is attached. but in no case does it open into the body- cavity. Within the lobes of the mantle, there is a remarkable system of branched tubes, which commence by blind extremi- ties, and finally communicate with the mantle-cavity by means of certain organs, which were formerly believed to be hearts, and are now known as “ pseudo-hearts.” This system of tubes appears to be mainly, if not entirely, connected with repro- duction. A true heart, however, is present in most, if not in all, of the Brachiopoda. The nervous system consists of a single principal ganglion, connected in some cases with others so as to form a collar round the commencement of the gullet. In some cases, how- ever, the nervous system appears to be very rudimentary. The sexes appear to be sometimes distinct and sometimes united in the same individual. The embryo, in some cases, at any rate, is locomotive, moving from place to place by means of the ciliated arms or by ventral spines. CHAPTER XXL MOLLUSCA PROPER, TE higher Mollusca or Mollusca proper comprise those members of the sub-kingdom in which the nervous system consists of three principal pairs of ganglia; and there is always a well-developed heart, consisting of at least two chambers. In this division are included the following classes : 1. Lamellibranchiata, without a distinct head. 2. Gasteropoda, a a distinct head and a masticatory 8. Pteropoda, apparatus or “ odontophore.” 4, Cephalopoda, Crass I. LamELiiprancuiata.—These are well known as bivalve shell-fish, such as mussels, oysters, scallops, etc., and they are all either marine or inhabitants of fresh water. They are distinguished from the other Mollusks by having no dis- tinct head, and by having the body more or less completely protected by a bivalve-shell composed of two pieces. They are called Lamellibranchiata (Lat. lamella, a plate ; Gr. brag- chia, gill), from the fact that the organs of respiration are in the form of leaf-like gills or branchize, two of which are placed at each side of the body, constituting what is-:known in the oyster as the “beard.” The body of the Lamellibranchiata is more or less completely enclosed in an expansion of the integument which constitutes the “mantle,” and which is divided into two halves or “lobes,” which are placed on the sides of the animal, and secrete the shell. The shell, there- fore, of the true bivalves is composed of two valves, which are “right” and “left,” and not “dorsal” and “ ventral,” as in the Brachiopoda. Moreover, the valves of the shell are usually of the same size, so that the shell is “ equivalve,” and, MOLLUSCA PROPER. 177 lastly, the shell is more developed on one side than the other, so as to become “inequilateral” (Fig. 81, 2). The lobes of the mantle are sometimes quite free ; but, at other times, they are more or less united to each other, and leave only two openings. Through one of these openings (the ante- rior) the “ foot” is protruded (Fig. 80, #); and through the other pass the respiratory tubes or “siphons” (s). The foot in the bivalves is a mus- cular organ developed upon the lower surface of the body, but not forming a creeping flattened disk, as in the ordi- nary univalves. In many cases, it is quite rudimentary ; and even when it is employed in locomotion it is usually small, Most generally, it is hatchet-shaped or pointed (Fig. 80, f), and serves to enable the animal to make short leaps. In many cases, as in the common mussels, the foot is subsidiary to a special gland, which secretes a viscous fluid, which hardens rapidly on exposure to the air. This fluid is moulded by the foot into silky threads (the so-called “ byssus”), by means of which the shell is firmly fixed to some solid object. Besides the muscular foot, other muscles are pres- ent as well in the ZLamelli- branchiata. Of these, the most important are the muscles which close the shell, and are called the “ adduc- 5 R > Fie. 80,—Anatomy ot a Bivalve Mollusk. Mya arenaria (after Woodward). The left valve and mantle-lobe, and half the siphons are removed. 8 Respiratory siphons, tha arrows indicating the direction of the cur- rents; a a/ Adductor muscles; 6 Gills; A Heart ; 0 Mouth, surrounded by (7) labial palpi; f Foot: v Anus; m Cut edge of the mantle. tor” muscles. In one group of the bivalves (Fig. 81, 3), there ‘ 178 INVERTEBRATE ANIMALS. is only one adductor muscle, but ordinarily there are two (Fig. 81, 2). These muscles leave distinct scars or “muscular im- pressions” in the dead shell, so that it is easy to determine how many were present in any given shell, The margin of the mantle, too, is muscular, and leaves upon the shell a dis- — tinct line where it was attached, this being known as the “pallial line” (Lat. pallium, a mantle), as shown in Fig. 81. As regards the shell of the bivalves, the following are the chief points to be noticed. Each valve of the shell (Fig. 81) is to be regarded as essentially a hollow cone, the apex of which is turned more or less to one side. The apex of the valve is known as the “umbo” or “beak,” and is turned tow- ard the mouth of the animal. Consequently, the side of the Fic. 81.—Shells of Lamellibranchiata. 1. Cyclas amnica, a shell with two adductor rouscles, and an “entire” mantle-margin. 2. Tapes pullastra, a shell with two adduc- tors, and an indented pallial line. 8. Perna ephippiwm, a shell with one adductor muscle: @ Pallial line; Scars left by the adductors; ¢ Siphonal impression. shell toward which the beaks are turned is known as the “anterior” side, and it is usually much shorter than the oppo- site or “posterior” side. The side of the shell at which the beaks are situated is known as the “ dorsal” margin ; and here the valves are united to one another for a longer or shorter distance along a line which is known as the “hinge-line.” The union between the valves is usually effected by means of interlocking parts or “teeth,” and there is often a band of horny fibres passing between the two valves just behind the beaks. In many cases, there is also a series of horny fibres placed perpendicularly between the beaks, so as to be com- pressed when the shell is shut. By the elasticity of these, and of the external ligament, when present, the valves of the shell are opened, without any effort of the animal, simply by relaxing the adductor muscles. The valves are shut again by the contraction of the adductor muscle or muscles. MOLLUSCA PROPER. 179 As already said, the margin of the mantle leaves on the shell a distinct impression—the “ pallial line ”—and, by inspec- tion of this, important conclusions can be drawn in any given case as to the mode and life of the animal. In certain shells, namely, the pallial line (Fig. 81, 1) is unbroken or “ entire,” and in these the mantle-lobes were either quite free, or if attached to one another and drawn out into respiratory tubes, these were not furnished with special muscles by which the tubes could be retracted within the shell. In other bivalves, on the other hand (Fig. 81, 2), the pallial line is indented to a greater or less extent, showing that the mantle-lobes were more or less united to one another, and were drawn out into long respiratory tubes or siphons, which were furnished with spe- cial muscles by which they could be withdrawn within the shell. This difference expresses a real distinction among the bivalves, due to their mode of life. In all alike, the respiratory organs are in the form of membranous leaf-like gills, of which there are generally two on each side of the body. The gills are composed generally of tubular rods (Fig. 80, 6) richly supplied with blood-vessels, and covered with vibrating cilia. For the proper maintenance of respiration, however, it is necessary that the gills should be constantly supplied with fresh water. In those bivalves in which the animal is free and the mantle- lobes not attached to one another, this is effected without any special mechanism. In those forms, however, in which the animal lives buried in the mud and sand, and the mantle-lobes are more or less completely united, there are two orifices, one of which admits fresh water, while the effete water is got rid of through the other. These orifices, in the shells just spoken of, are extended into two long tubes which are known as the “respiratory siphons.” The water passes in by one siphon, is swept over the surface of the gills, and then reaches the mouth (Fig. 80,ss), when it is returned in the opposite direction to escape by the other siphon. The same current of water, therefore, both carries oxygen to the gills, and serves to convey food to the mouth. The two siphons may be quite distinct from one another, but they are very often united together so as to look like a single tube (Fig. 80). They are often very small, and then they leave no traces of their ex- istence in the dead shell; but, when they are very long, they are furnished with muscles to retract them within the shell, and it is the scar left by these muscles which causes the pallial line to be indented. This indentation, therefore, as seen in the dead shell, is an indication that the animal possessed long 180 INVERTEBRATE ANIMALS. retractile respiratory siphons, and lived, therefore, most prob- ably imbedded in sand or mud. There is always a distinct heart, composed of two or three chambers, and in all cases acting as a mere arterial heart, That is to say, the heart propels the aérated blood derived from the gills through the body, and has nothing to do with the propulsion of the non-aérated or venous blood through the gills. There is never any distinct head in any of the Bivalves, and for this reason they are sometimes called the “ headless” (acephalous) Mollusks. The mouth is simply placed at the anterior end of the body, and is never furnished with teeth, though usually provided with membranous processes or “ palpi” (Fig. 80, ). The mouth cpens into a gullet which conducts to a stomach. The intestine is convoluted, and usu- ally perforates the ventricle of the heart, ultimately terminating in a distinct anus, which is always placed near the respiratory aperture. A large and well-developed liver is also present. The nervous system has its normal form of three principal masses—the cerebral, the pedal, and the parieto-splanchnic ganglia. The majority of the bivalve Mollusks have the sexes dis- tinct, but they are sometimes united in the same individual. The young are hatched before they leave the parent, and, when first liberated, are ciliated and free-swimming. The habits of the Lamellibranchiata are very various. Some, such as the Scallops (Pecten), habitually le on one side, the lower valve being the deepest, and the foot rudimen- tary or wanting. Others are fixed to the bottom of the sea by the substance of one of the valves. Others, such as the common Mussel, are moored to some foreign object by a tuft of silky fibres, constituting a “ byssus.” Many, such as the Gapers (Mya) and Razor-shells (Solen), spend their existence sunk in the sand of the sea-shore or the mud of estuaries. Others, such as the Pholades, bore holes in rock or wood, in which they live. Finally, many are permanently free and locomotive. Crass II. Gasrmropopa (Gr. gaster, belly ; podes, feet).— This class includes an enormous number of Mollusks, such as the land-snails, sea-snails, whelks, limpets, slugs, sea-lemons, etc., which agree in many fundamental characters, but nevertheless present many striking differences. From the very common occurrence of a shell composed of a single piece, the Gastero- poda are often spoken of in a general way as the “ univalve 2 MOLLUSCA PROPER. 181 Mollusks. In many, however, there is either no shell at all, or one so small that it would not generally be recognized as such ; and in a few the shell is composed of several pieces (‘ multi- valve”). In none, however, is the shell composed of two pieces or “bivalve.” The great majority of the Gasteropoda are further distinguished by the great development of the foot, which constitutes a broad, flattened disk upon which they creep about, as may readily be observed in the common slugs. Some, however, have the foot much modified and adapted for swimming. In many cases, also, the foot carries behind a horny or shelly plate which is known as the “operculum” (Fig. 82, 0), and which serves to close the shell when the animal is withdrawn within it. Fig. 82.—Gasteropoda. Ampullaria canaliculata, one of the Apple-shells: o Operculum ; s Respiratory siphon. The head in most of the Gasteropoda, unlike the Bivalves, is very distinctly marked out, and carries two long feelers, and two eyes, often placed upon stalks (Fig. 85). The mouth, also, differs from that of the Bivalves in being furnished with a singular apparatus of teeth, constituting what is known as the “ odontophore” (Fig. 82), or “lingual ribbon.” This con- sists essentially of a number of siliceous teeth, of different shapes in different species, supported upon a kind of strap which can be made to work backward and forward over a cartila- ginous cushion, thus acting like a chain-saw. In addition to the odontophore there are sometimes horny jawsas well. The mouth leads by a gullet into a distinct stomach, which some- times is provided with calcareous plates for grinding down the food. The intestine is long, and always terminates in a distinct anal aperture. Distinct salivary glands are usually present, and the ince is well developed. 182 INVERTEBRATE ANIMALS. A distinct heart is almost always present, and consists of two chambers, an auricle and aventricle. Respiration is very variously effected—one great division being constructed to breathe air by means of water, while in another section the respiration is aérial. In the former of these—often spoken of as the “ branchiate” Gasteropods—respiration may be carried on in three ways: Firstly, there may be no special breathing- organ, the blood being simply exposed to the action of the water, as it circulates through the thin walls of the mantle-cavity. Secondly, the breathing-organs may be in ' the form of outward processes of the skin, w exposed to view on the back or sides of the , animal (Fig. 85). Thirdly, the breathing- organs are in the form of plume-like gills, contained in a more or less complete cham- ber, formed by a folding of the mantle. In i many members of this group the water ob- tains access to the gill-chamber by means of Fie. 88.—Portion of the a tubular prolongation or folding of the a pe aes mantle, forming a siphon (Fig. 82, s), and so (after Wood- often the effete water is expelled by another : tube which is similarly constructed. In the second great section—often called the “pulmonate” Gaste- ropods—respiration is effected by a pulmonary chamber or lung, formed by a folding of a mantle, and having air admitted to it by a distinct aperture. The sexes in the G'asteropoda are mostly distinct, but they are sometimes united in the same individual. The young, when first hatched, are always provided with an embryonic shell, which may be entirely lost in the adult, or may simply become concealed by a fold of the mantle. In the water- breathing forms the young is protected by a small nautilus- shaped shell, within which it can entirely withdraw. It is en- abled to swim about freely by means of two ciliated lobes spring- ing from the sides of the head, and in this stage it is very like the permanent adult condition of the Pteropoda (Fig. 88). As regards the shell of the Gasteropoda, the following points may be noticed: The shell is composed either of a single piece (univalve), or of a number of plates placed one behind the other (multivalve). The univalve shell is to be looked upon as essentially a hollow cone, the apex of which is placed a little on one side. In the simplest forms, as in the Limpets, the conical shell is MOLLUSCA PROPER. 183 retained throughout life without any alteration. In the great majority of cases, however, the cone is considerably elongated so as to form a tube, which may retain this shape (as in the “tooth-shell”), but which is usually coiled up into a spiral. The “spiral univalve” may, in fact, be regarded as the typical Fie. 84.—Gasteropoda. a@ Shell of the Turritella communis, showing a round mouth; b Shell of the common whelk (Buccinwm undatum), showing the mouth notched for a respiratory siphon. form of the shell in the Gasteropoda (Fig. 84). The coils of the spiral are termed the “whorls,” and are usually more or less amalgamated on one side. In most cases, too, the whorls are wound obliquely round a central axis or pillar, increasing gradually in size to the mouth. The last whorl is the largest, and is termed the “body-whorl.” The mouth of the shell in many forms is unbrokenly round or “ entire ” (Fig. 84, a), and it is found that most of these shells subsist upon vegetable food, as, for instance, the common periwinkles. In others, again (Fig. 84, 5), the mouth of the shell is notched or is pro- duced into a canal, as in the common whelk, and it is found that these live upon animal food, or are “ carnivorous.” There may be more than one of these canals or tubes, but they do not necessarily indicate the nature of the food, as their func- tion is to protect the respiratory siphons. The Gasteropoda are divided into a good many groups, of which the more important may be briefly noticed, the fore- going applying chiefly to the ordinary forms, which, therefore, need no further description. The remaining members of the 184 : INVERTEBRATE ANIMALS, water-breathing Gasteropods are divided into two sections, differing a good deal from the typical forms of the class in many respects. As examples of the first of these may be taken the sea- slugs and sea-lemons (Mudibranchiata), specimens of which may at any time be found creeping about on sea-weeds, or at- tached to the under surface of stones at low water, These slug-like animals (Fig. 85) are wholly destitute of a shell when fully grown, but possess an em- bryonic shell when young. When there are any distinct respiratory organs, these are in the form of gills, placed, without any protec- tion, upon ‘the back or sides of ' : ; the body. The head is furnished i pe ga er eee nada with tatutles which do not ap- pear to be used as organs of touch, but are more probably connected with the sense of smell; and behind the tentacles are generally two eyes. The nervous system is extremely well developed, and would lead to the be- hef that the Sea-slugs are among the highest of the Gastero- poda. Locomotion is effected, as in the true Slugs, by creep- ing about on the flattened foot. The last remaining group of the “ branchiate ” Gasteropods is that of the Heteropoda (Fig. 86), comprising a number of curious forms which are found swimming at the surface of the Fic. 86.—Heteropoda. Carinaria_cymbium; p Proboscis and mouth; /Dentucless g Gills; s Shell; f Foot; d@ Disk (after Woodward). open sea, instead of creeping about at the bottom of the sea. In order to adapt them for this mode of life, the foot, instead of forming a creeping disk, is modified to form a compressed fin (f). The Heteropoda are to be regarded as the most MOLLUSCA PROPER. 185 highly organized of all the Gasteropoda, at the same time that they are not the most typical members of the class. Some of them can retire completely within their shells, but others have large bodies, and the shell is either small or entirely absent. In VUarinaria, which may be taken as a good example of the group, there is a little limpet-shaped shell protecting the gills (6) and heart. The animal swims, back downward, by means of a vertically-flattened ventral fin (7), on one side of which is a little sucking-disk (¢), by which the animal can ad- here at pleasure to floating sea-weed. Carinaria is found in the Mediterranean and other warm seas, and is so transparent that the course of the intestine can be seen along its whole length. The last group of the class is that of the “air-breathing ” Gasteropods, so well known as Land-snails, Pond-snails, and Slugs (Fig. 87). All the members of this group are formed to breathe air directly, instead of through the medium of water, and they, therefore, never possess gills or branchie. Fic. 87.—Limaz Sowerby, one of the slugs (after Woodward). In place of these they have a pulmonary chamber or lung, formed by a folding of the mantle, and having air admitted to it by a round hole on the right side of the neck, which can be opened and closed at will, Though thus adapted for breath- ing air directly, many of the members of this group can only live in damp or moist places, while others habitually live in fresh water. The common Pond-snails are examples of these last. The condition of the shell varies much. Some, such as the common Land-snails, have a well-developed shell within which the animal can completely withdraw itself for protec- tion. Others, such as the common Slugs (Fig. 87), have a rudimentary shell which is completely concealed within the mantle. Others are entirely destitute of a shell. They all agree with the typical Gasteropods in creeping about ona broad, flattened foot. Crass III. Prrropopa (Gr. pteron, wing ; podes, feet).— 186 INVERTEBRATE ANIMALS. This class is a very small one, and includes a number of minute oceanic Mollusks, which are found swimming near the sur- face in the open ocean, far from land, and often in enormous numbers. The organs of locomotion are two wing-like fins (Fig. 88) attached to the sides of the head, and formed by a Fig. 88.—Pteropoda, a Cleodora pyramidata; b Cucieria columnella. (After Woodward.) modification of a portion of the foot. The body is usually pro- tected by a symmetrical glassy shell (Fig. 88), consisting of two plates united along their edges, or in other cases forming a spiral. In some, however, there is no shell, and the body is quite naked. The head is rudimentary, and bears the mouth, which is furnished with an odontophore. The heart consists of an auricle and ventricle, and the respiratory organs are extremely rudimentary. The sexes are united in the same individual in all the Pteropoda. The Pteropoda occur, as already said, in the open ocean, and they are found in all seas from the tropics to within the arctic circle, sometimes in such numbers as to discolor the water for many miles. Minute as they are, they constitute in high latitudes one of the staple articles of diet of the whale, and they themselves in turn are probably carnivorous, feed- ing upon small Crustaceans and other diminutive creatures. Though all the living forms are small, geology leads us to be- lieve that formerly there existed comparatively gigantic forms, which appear to be truly referable to this class, CHAPTER XXII. CEPHALOPODA. Cuass IV; CepHatopopa.—The last and highest class of the Mollusca is that of the Cephalopoda, comprising the Cuttle-fishes, Calamaries, Squids, and the Pearly Nautilus, They are all inhabitants of the sea, and are all carnivorous; and they are possessed of considerable powers of locomotion. At the bottom of the sea they can walk about, head downward, by means of the arms (Fig. 89), which surround the mouth, which are usually provided with numerous suckers, and which are really produced by a splitting up of the margin of the foot. It is from the presence of these arms that the class derives its name (Gr. kephale, head; and podes, feet). The Cuttle-fishes can also swim rapid- ly, either by means of expansions of the skin constituting fins, or by the forcible expulsion of water from the cavity of the mantle, the reaction of which causes the animal to move in the opposite direction. The majority of the living Cephalo- yy4. 59 sepiota Atlantiea, one of pods are naked, possessing only an _the pute ishes ater: Hoo internal skeleton, and this oftena “*"- rudimentary one; but the Argonaut (Paper Nautilus) and the Pearly Nautilus are protected by an external shell, though the nature of this is extremely different in the two forms, 188 INVERTEBRATE ANIMALS, The body in the Cephalopoda is symmetrical, and is en closed in an integument which may be regarded as a modifica, tion of the mantle of the other Mollusca. Ordinarily there is a tolerably distinct division of the body into an anterior por- tion, carrying the head, and a posterior portion, in which the internal organs are enclosed. The head (Fig. 89) is very distinct, bearing a pair of large globular eyes, and having the mouth in its centre. The mouth is surrounded by a circle of eight, ten, or more, long muscular processes, or arms, which are generally provided with rows of suckers, Each sucker consists of a cup-shaped cavity, the muscular fibres of which converge to the centre, where there is a little muscular eminence. When the sucker is applied to any surface, the contraction of the radiating muscular fibres de- presses the central eminence so as to produce a vacuum below it, and in this way each sucker acts most efficiently as an ad- hesive organ. The whole of this complex mechanism of suckers is completely under the control of the animal, and the ir- ritability of the suckers is retained even for days after death. In most of the Cuttle-fishes (Octopoda) there are only eight arms, and these are nearly similar to one another. In others, however (Fig. 89), there are ten processes round the mouth, of which eight are like each other, and constitute the true arms, while two—called tentacles—are much longer than the others, and bear suckers only toward their extremities, which are enlarged and club-shaped. The Paper Nautilus (Fig. 90) has two of the arms webbed at their extremities and secreting a shell; and the Pearly Nautilus, alone of all living Cephalo- poda, has numerous arms, more than ten in number, and destitute of suckers. The mouth leads into a cavity containing two powerful horny or partially calcareous jaws working vertically, very like the beak of a bird, together with an “ odontophore” or “tongue,” the hinder part of which is furnished with recurved spines. This cavity leads by a gullet, furnished with salivary glands, into a stomach, from which an intestine is continued to terminate by a distinct anus, which opens on the ventral surface at the base of the so-called “funnel.” The funnel is a muscular tube placed on the under surface of the head, and communicating on the one hand with the external medium, and on the other with the cavity of the mantle. In the Vaw tilus alone it is simply formed of two muscular lobes, which are in apposition, but are not united together so as to form a tube. In many cases there is also a special gland, known as CEPHALOPODA. 189 the “ink-bag,” for the secretion of an inky fluid, which the animal discharges into the water, so as to enable it to escape when menaced or pursued. The duct of the ink-bag opens at the base of the funnel near the anus, but the Pearly Nautilus and the allied fossil forms are without this means of defence, which the presence of an external shell renders unnecessary. The respiratory organs are in the form of plume-like gills, placed on the sides of the body in a branchial chamber, which opens in front on the under surface of the body. In almost all the living Cephalopoda there are only two gills, one on each side, and hence this section is known as that of the “* Dibranchiata.” In the Pearly Nautilus alone there are four gills, two on each side, hence the name of “ Tetrabranchiata” applied to the order of which this is the only living represent- ative. In the Cuttle-fishes, at the base of each gill is a special contractile cavity, called a “branchial heart,” by which the venous blood, returned from the body, is driven through the gills. In addition to these branchial hearts there is a true arterial heart, by which the aérated blood received from the gills is driven through the body. The admission of water to the branchiz is effected by the expansion of the mantle, which allows the entrance of the outer water into the mantle-cavity. The mantle then contracts, and the water is forcibly expelled through the funnel, which is often furnished with a valve, al- lowing the passage of water outward, but preventing its en- trance inward. By a repetition of this process both respira- tion and locomotion are simultaneously effected, for the jets of water expelled from the funnel by their reaction drive the animal in the opposite direction. In this case, therefore, as in many others, the more active the animal is, the more perfectly is the respiratory process carried on, The nervous system is formed upon essentially the same plan as in the other Mollusca, but the cerebral ganglia are protected by a cartilage, which is to be regarded as arudimen- tary skull. This structure, therefore, is a decided approach to the Vertebrate type of organization. The sexes in all the Cephalopoda are in different individ- uals, and the reproductive process in the Cuttle-fishes is at- tended with some singular phenomena. The most remarkable point in this connection is the modification of one of the arms of the male Cuttle-fishes, for the purpose of conveying the male element to the female. The details of the modification vary in different species of Cuttle-fish. In some species one arm is simply so modified as to be 190 INVERTEBRATE ANIMALS. able to transmit the sperm-cells to the female, but it remains permanently attached to the animal. In the Paper Nautilus (Argonaut) the process goes still further. The female of this species (Fig. 90) attains a considerable size, and is protected by an external shell. The male is not more than an inch in: length, is devoid of a shell, and has its third left arm meta- morphosed. This arm is developed in a cyst, and is ultimately detached from the body, and deposited by the male within the mantle-cavity of the female. When first discovered in this position, it was described as a worm living parasitically on the Argonaut, under the name of “ Hectocotylus” (Gr. hekaton, a hundred ; and kotulos, a cup), from the suckers, or cups, with which it was furnished. Subsequently it was described as the entire male Argonaut; and it is only recently that it has been proved to be nothing more than one of the arms of the male, detached for the purpose of conveying the sperm-cells to the female. The shell of the Cephalopoda is sometimes external, some- times internal. The internal skeleton is seen in the various Cuttle-fishes, in which it is known as the “cuttle-bone” or “pen.” It may be either horny or calcareous, and it is some- times complicated by the addition of a chambered portion. The only living Cephalopods which are provided with an ex- ternal shell are the Paper Nautilus (Argonauta) and the Pearly Nautilus (Nautilus pompilius); but not only is the structure of the animal different in each of these, but the nature of the shell itself is entirely different. The shell of the Argonaut (Fig. 90) is coiled into a spiral, but it is not di- vided into chambers, and it is secreted by the webbed extrem- ities of two of the dorsal arms of the female. These arms are bent backward, so as to allow the animal to live in the shell; but there is no organic connection between the shell and the body of the animal, The shell of the Pearly Nautilus, on the other hand, is secreted by the mantle, and is organically connécted to the animal. It is coiled into a spiral (Fig. 91), but it differs from the shell of the Argonaut in being divided into a series of chambers by means of shelly partitions, which are connected together by a tube or “siphuncle,” the animal itself living in the last and largest chamber only of the shell. The Cephalopoda are divided into two extremely dis- tinct and natural orders, termed respectively Dibranchiata and Tetrabranchiata, according as they have two or four gills or branchiz. : The Dibranchiata comprise the Cuttle-fishes, Squids, Cala- CEPHALOPODA. 191 maries, and Paper Nautilus, and they are characterized by being almost invariably destitute of any external shell; by never having more than eight or ten arms, which are always furnished with suckers; by having only two gills, which are provided with “branchial hearts;” by the possession of an “ink-bag ;” and by the fact that the “funnel” forms a com- plete tube. They are divided into two sections— Octopoda and Decapoda—according as they have only eight arms, or eight arms with two additional longer processes or “tentacles ” (Fig. 89). Among the Octopoda are the Paper Nautilus and the Poulpes (Octopus). The Paper Nautilus is found in the warmer seas of various parts of the world, generally floating at the surface. The two sexes differ, as already said, greatly in external appearance. The female (Fig. 90) inhabits a beau- Fic. 90.—Argonauta argo, the Paper Nautilus, female. The animal is represented in its shell, but the webbed dorsal arms are separated from the shell which they secrete, and which they ordinarily embrace, tiful one-chambered shell, which is secreted by the webbed ex- tremities of two of the dorsal arms. The shell is not in any way attached to the body of the animal, but the webbed arms are turned backward, and the animal sits in the shell with the 192 INVERTEBRATE ANIMALS, funnel turned toward the keel. It swims by the jets of water emitted from the funnel, and crawls upon the sea-bottom, head downward, carrying its shell on its back. The male Argonaut is only about an inch in length, has no shell, and has all its arms alike, except the one which is metamorphosed into the “hectocotylus.” The Poulpes (Octopi) are universally dis- * tributed in the seas of both temperate and tropical regions. They are the “polypi” of Homer and Aristotle, and are yo- racious animals inhabiting rocky shores. The Decapoda are chiefly found in the open sea, often in enormous numbers, and the best known are the Calamaries and Squids. The body is elongated, and is always furnished with lateral fins, with which they swim actively. The shell is internal, and differs considerably in different members of the group. To this section of the Dibranchiata belong the sin- gular fossil forms which are known to the geologist as Belem- nites. These singular forms are known almost solely by their complicated internal skeleton, and they appear to have abound- ed in the seas of the Secondary period. The second order of the Cephalopoda—that of the Tetra- branchiata—comprises forms characterized by being creeping animals, protected by an external, many-chambered shell, the partitions between the chambers being perforated for the pas- sage of a membranous or calcareous tube, termed the “si- phuncle.” The arms are more than ten in number, and are devoid of suckers; the gills are four in number, two on each side of the body; the funnel does not form a complete tube; and there is no ink-bag. . : Though abundantly represented by many and varied fossil forms, the only living member of the Tetrabranchiata with which we are acquainted is the Pearly Nautilus, which has long been known by its beautiful chambered shell. The shell of the Pearly Nautilus (Fig. 91) is coiled into a spiral, and is many-chambered, the chambers being walled off from one an- other by curved shelly partitions or septa, perforated centrally by a foramen which transmits a membranous tube or siphuncle. The animal inhabits only the last and largest chamber of the shell, from which it can protrude its head at will. The func- tion of the chambers of the shell is not very clearly under- stood; but it appears to be that of reducing the specific grav- ity of the shell to near that of the surrounding water; since they appear to be filled with some gas apparently secreted by the animal. The siphuncle does not communicate in any way with the chambers of the shell, and its functions are also un- CEPHALOPODA. 193 known, except that it must certainly serve to maintain the vitality of the shell. Fia. 91.—The Pearly Nautilus (Nautilus pompilius). a Mantle; 6 Its dorsal fold; c Hood; o Eye; ¢ Tentacles; 7 Funnel. Of the fossil Tetrabranchiata the most important are the Orthocerata and the Ammonites. The Orthocerata (Fig. 92) played a very important part in the seas of the Palzozoic or Ancient-life period of the earth’s history, in which they ap- parently filled the place now taken by the predacious cuttle- Fig. 92.—Orthoceras explorator. 1. Side view of a fragment, showing the edges of the septa, 2. Transverse section of the same, showing the siphuncle (s). (Billings.) fishes. They agreed with the Nautilus in having a many- chambered shell, divided by curved partitions, perforated by a tube or siphuncle. The shell, however, differed from that of the Nautilus in not being curved or coiled up, but in being 194 INVERTEBRATE ANIMALS. straight. In other nearly-allied forms the shell was bent or even partially coiled up, but never so completely as in the true Nautilus. Many of the Orthocerata were of small size, but some of them were colossal, shells having been found of six or seven feet in length, and as thick as the body of a man. The Ammonites, with a number of allied forms of varied shapes and beautiful structure, appear to have taken the place of the Mautilide, to a great extent, in the seas of the Second- ary period; at which time, too, Dibranchiate Cephalopods first made their appearance. The true Ammonites resembled the Nautilus in having a many-chambered shell, which was coiled up into a spiral, but the position of the siphuncle was differ- ent, and the partitions or septa between the various chambers of the shell were wonderfully folded and lobed instead of being simply curved. The numerous beautiful shells allied to the Ammonites cannot be even mentioned here; but it is to be remembered that they are almost all characteristic of the Secondary period in geology, and that they are hardly known as occurring in the older period (Paleozoic epoch). VERTEBRATE ANIMAIS. CHAPTER XXIII. GENERAL CHARACTERS OF THE VERTEBRATA, TuE five sub-kingdoms which we have previously consid- ered, namely, the Protozoa, Coelenterata, Annuloida, Annu- losa, and Mollusca, were grouped together by Lamarck into one great division, which he termed the Invertebrata. The remaining sub-kingdom, that of the Vertebrata, is so well marked and compact a division, and its distinctive characters are so numerous and so important, that this mode of viewing the animal kingdom is, at any rate, a very convenient one. The sub-kingdom Vertebrata includes the five great classes of the Fishes (Pisces), Amphibians, Reptiles, Birds (Aves), and Mammals; and the name of the sub-kingdom is derived from the very general, though not universal, presence of the bony axis known as the “vertebral column” or backbone. One of the most fundamental of the distinctive characters of Vertebrate animals is to be found in the fact that the main masses of the nervous system (that is to say, the brain and spinal cord) are completely shut off from the general cavity of the body. In all Invertebrate animals (Fig. 93, A), the body may be regarded as a single tube, enclosing all the vis- cera; and, consequently, when a distinct nervous system and alimentary canal are present, these are in no way shut off from one another. The transverse section, however, of any Vertebrate animal (Fig. 93, B) shows two tubes, one of which contains the great nervous axis (7’) or brain and spinal cord, while the other contains the alimentary canal, the chief circu- latory organs, and certain portions of the nervous system (n), 196 VERTEBRATE ANIMALS. which are known to anatomists as the “sympathetic” system. Leaving the brain and spinal cord out of sight for a mo- ment, we see that the lower or visceral tube of a Vertebrate animal contains the digestive canal (6), the blood-vascular sys- tem (c), and a system of nervous ganglia (7). Now, this is Fig. 93.—Diagrams representing transverse sections of one of the higher Invertebrata, A, and one of the Vertebrata, B. a Wall of the body; } Alimentary canal; ce Hemal or blood-vascular system; Nervous system; 7’ Cerebro-spinal axis, or brain and spinal cord, enclosed in a separate tube; ch Notochord, or chorda dorsalis. exactly what is contained within the visceral cavity of any Invertebrate animal; and it follows from this that it is the “sympathetic” system of Vertebrate animals which is truly comparable with the nervous system of the Invertebrata. The brain and spinal cord, or “ cerebro-spinal axis,” are to be looked upon as something not represented at all in the Invertebrata. Another peculiarity which is present in all the Vertebrata is, that at an early period of life there is developed, in the low- er wall of the tube which contains the cerebro-spinal axis, a singular structure known as the “ notochord ” (Gr. notos, back ; chordé, string) (Fig. 93, B, ch). This is a semi-gelatinous rod, tapering at both ends, and extending along the floor of the cerebro-spinal tube. In some cases, the notochord remains permanently in this condition, but, in most cases, it is replaced at maturity by the bony column or backbone, from which the Vertebrata derive their name. The general structure of the vertebral column will be described shortly, and it is sufficient to state here that it consists of a series of more or less com- pletely bony segments or “ vertebra,” arranged so as to form a longitudinal axis upon which the spinal cord is supported. It is to be remembered, however, that all Vertebrate animals do not possess a vertebral column. They all possess a noto- chord, but this may remain persistent throughout life, and, in many cases, the development of the spinal column is very im- perfect. GENERAL CHARACTERS OF THE VERTEBRATA. 197 The skeleton of all Vertebrate animals is internal, and the muscles are attached to its several parts. The value of this character is in no way affected by the fact that many Verte- brates, such as the Tortoises, Crocodiles, and others, possess an external skeleton as well. The limbs of Vertebrate ani- mals are always articulated or jointed to the body, and they are always turned away from that side of the body (the “neu- ral” side) upon which the great masses of the nervous system are placed. The limbs may be altogether wanting, or partial. ly 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 distinct blood-vascular system is present in all Ver- tebrates, and in all except one—the Lancelet—there is a single contractile cavity or heart, furnished with valvular open- ings. Paki the masticatory organs of all Vertebrates are modi- fications of parts of the walls of the head, and are never modified limbs or hard structures developed in the mucous membrane of the digestive tube, as they are in the Inverte- brates. The above are the leading characters which distinguish the Vertebrata as a whole, and, before going on to consider the different classes, it may be as well to give a short and general sketch of the anatomy of the Vertebrates, commencing with their bony framework or skeleton. The skeleton of the Vertebrata may be regarded as con- sisting of the bones which go to form the trunk and head on the one hand, and of those which form the supports for the limbs on the other hand, The bones of the trunk and head may be regarded as essentially composed of a series of bony rings or segments, arranged longitudinally. Anteriorly, these segments are much expanded and also 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 in which is contained the spinal cord, and they are arranged one behind the other, forming the “ ver- tebral column.” The segments which form the vertebral column are called “vertebre,” and they have the following general structure: Each vertebra (Fig. 94, A) consists of a central portion known as the “ body,” or “centrum” (c), placed immediately below the spinal cord, and giving origin to certain “processes.” The ends of the bodies of the vertebrae are all united together in different ways, so as to give the col- 198 VERTEBRATE ANIMALS, Fic. 94.—A. Vertebra (lumbar) of the whale. ¢ Centrum or body; Neural arches; g Spinous process; @ Articular process; @ Transverse processes. 3B. Thoracic segment or vertebra. c Centrum of vertebra; 7 Neural arches, enclosing the canal for the spinal cote . 5 Spinous process; 7 Ribs; p Costal cartilages; & Breastbone or sternum. (After wen. umn great flexibility. From the back of the body of the ver- tebra proceed two bony arches which unite behind and thus form with the centrum a bony canal in which the spinal cord is contained. Yor this reason, these arches (7) are called the “neural” arches. From the point where the neural arches unite—that is to say, from the back of the neural canal—pro- ceeds a long process, sometimes cleft at its extremity, termed the “spinous process” (s). Springing also from each neural arch is a second shorter process (a) termed the “ articular pro- cess,” since by means of these, as well as by the bodies, the vertebrae are jointed or “articulated” together. Also arising from the neural arches at their junction with the body of the vertebra, there may be two lateral processes (d) which are called “transverse processes.” This is the ordinary structure of the vertebra of a Mammal, and the names here used are those applied to the parts of the vertebra in human anatomy. In philosophical anatomy, however, these parts have proper technical names which can be employed for them in all animals alike. The nature of this work, however, will not allow of the introduction of these here. In the typical vertebra the segment is completed by a second arch, which is placed in front of or beneath the body of the vertebra, and which is known as the “ hemal” arch, as it includes and protects the principal organs of the blood cir- culation (Fig. 94, B). This second arch is often only recog: GENERAL CHARACTERS OF THE VERTEBRATA. 199 nizable with great difficulty, as its parts are generally much modified; but a good example may be obtained in the human chest. Here, attached to the front of the vertebra, we find a series of bony arches, known as the ribs (r), followed by a series of cartilaginous pieces of a similar shape, termed the “costal cartilages ” (p), the whole united in front by a central bone, known as the breastbone or “sternum” (4). Fig. 95.—Skeleton of the Beaver (Castor Jiber), showing the regions of the vertebra column. ¢ Cervical region, or region of the neck; @ Dorsal region, or region of the ae 5 aad region, or region of the loins; s Sacrum ; ¢ Caudal region, or region of the tail. As a general rule, among the higher Vertebrates, the fol- lowing regions may be recognized in the vertebral column: Firstly, the cervical region (Fig. 95, ¢), comprising a variable number of vertebrae, which constitute the neck, and immedi- ately follow the head. Secondly, the cervical region is suc- ceeded by a variable number of vertebrae which usually carry ribs, and are known as the dorsal vertebrse (d), or vertebrae of the back. Thirdly, come certain vertebrae which constitute the lumbar region (6), or the region of the loins, Fourthly, there usually follows a series of vertebrae which are immova. bly united together to form a single bone, which is termed the sacrum (s). Lastly, there comes a variable series of vertebrae 200 VERTEBRATE ANIMALS. which are usually free and movable upon one another, and which constitute the caudal region, or the region of the tail (¢). The nature of the bones which enter into the composition of the limbs varies somewhat in different Vertebrates in ac- cordance with their mode of life; but in all the higher mem- bers of the sub-kingdom the limbs are built upon a general Fig. 96.—Fore-limb of the Chimpanzee. c Collar- Fic. 97.—Hind-limb of the Chimpan- bone, or clavicle; 8 Shoulder-blade, or scapu- zee, 7% Innominate bone; / Thigh- la; 6 Bone of the upper arm, or humerus; 7 pone, or femur; ¢ Tibia; s Fibula; Radius; « Ulna; @ Bones of the wrist, or car- r Bones of the ankle, or tarsus; m pus; m Bones of the root of the hand, or me- Metatarsus ; p Phalanges. tacarpus ; p Bones of the digits, or phalanges. and easily-recognizable type. The fore-limb consists generally of the following parts: 1. A series of bones uniting the limb to the trunk, the two most important being the shoulder blade (scapula) and the collar-bone (clavicle) (Fig. 96, s and c). 2. The bone which forms the upper portion of the limb proper, and which is known as the humerus (6). 3. Two bones which form the lower portion of the limb (e. g., the forearm in man), GENERAL CHARACTERS OF THE VERTEBRATA. 201 and which are known as the radius and ulna (r and u), of which the former is the bone mainly concerned in carrying the hand or fore-foot. 4. A number of small bones, which form the wrist, and are termed the carpus (d). 5. The cylindrical bones (usually five in number) which form the root of the hand, and are known as the metacarpus (m). 6. The bones which form the fingers proper, and which are known as the phalanges (p). Essentially the same parts can be traced in the hind-limb of a typical Vertebrate animal, but they are known by differ- ent names. The bones which unite the limb to the trunk are usually more or less completely united together, constituting a single mass, known as the innominate bone (Fig. 97, 7). This is followed by a long, cylindrical bone, which forms the upper portion of the hind-limb, and is known as the “ thigh- bone,” or femur (f). Following this are the two bones of the shank, corresponding to the radius and ulna of the fore- limb, and known as the tibia and fibula (¢ and s). Of these, the tibia (¢) corresponds to the radius, and is mainly con- cerned in carrying the foot. Next comes a series of small bones, which form the ankle, and are known as the tarsus (r). This is succeeded by a series of cylindrical bones (usually five in number), which form the root of the foot, and which are termed the metatarsus (m). Finally, the metatarsus is succeeded by the bones of the toes, which in this case are again termed the phalanges (p). In both limbs the usual number of pha- langes to each toe or “digit” is three. The digestive system of the Vertebrata does not require a Jengthened notice. The mouth is usually furnished with teeth, which have for their chief function the reduction of the food to a condition in which it can be digested. In some animals, however, such as the snakes, the teeth are only used to hold the prey, and not for mastication; and in others, such as the turtles and birds, the jaws are not furnished with any teeth at all. The food is also usually subjected in the mouth to the action of a special fluid—the saliva—which acts chemically as well as mechanically upon the food, and which is secreted by special glands, known as the “salivary glands.” From the mouth the food passes through a muscular tube—the gullet, or esophagus (Fig. 98, g)—to the proper digestive cavity, or stomach (s). Here it is subjected to the action of a special digestive fluid—the “gastric juice”—and is converted into a thick, pasty fluid, which is called chyme. From the stomach the chyme passes into a long, convoluted, muscular tube, which 202 VERTEBRATE ANIMALS. is called the “small intestine” (sm). Here it is subjected to the action of two other digestive fluids, called the “bile” and “ pancreatic juice,” as well as to the fluids secreted by the intestine itself. The bile is secreted by a large gland, which is known as the “liver,” while the pancreatic juice is produced by another, termed the “ pancreas,” both pouring their secre- tion into the upper part of the small intestine. By the combined action of these digestive fluids the chyme is ultimately converted into a milky fluid, which is called chyle, when it is fit to be taken up into the blood- vessels. The small intestine finally opens into a tube of larger diameter, which is called the “ large intestine” (m), and this opens on the surface of the body by an anal aperture. In the large intestine the last remain- ing portions of the food which can be rendered useful are absorbed into the blood, the indigestible portions being ultimately got rid of as use- less. The fluid products of diges- tion (chyle) are chiefly absorbed from the intestinal canal by a set of special vessels, which are present in all Vertebrates, and which are called the lacteals (Lat. lac, milk) from the milky fluid they contain. These hacks ; ; lacteals combine to form a large oPromal eestive .oystem of a trunk, by which their contents are gus Stomach; 6m Smal Sn ultimately added to the circulating Large iitestitie terainating tills blood. Part of the products of di- fnal portion, called the “ree- gestion are absorbed by the veins . which ramify on the intestinal canal, and which ultimately unite to form a great vessel, called the “vena porte,” which goes to the liver. The materials, how- ever, which are taken up in this way also ultimately reach the circulating blood. In this way, therefore, fresh’ matter is being constantly added to the blood to replace the waste caused by the performance of the vital functions. The blood is thus formed out of the materials which are taken into the alimentary canal as food; and in all the Verte- brata (with one exception) it is of a red color, when viewed in GENERAL CHARACTERS OF THE VERTEBRATA. 203 mass. This is due to the presence in it of numerous micro- scopical particles, which are known as the “ blood-corpuscles,” the fluid itself being colorless. In Fig. 99 are represented Fic. 99.—Blood-corpuscles, magnified. a@ Man; 4 Goose; ¢ Crocodile; d Frog; ¢ Skate. some of the forms of blood-corpuscles which are found in dif- ferent divisions of the Vertebrata. The blood is always distributed through the body by means of a system of closed tubes, which constitute the ‘“‘blood- vessels,” and, with the single exception of the Lancelet, it is always propelled by means of a contractile muscular cavity or “heart.” The heart and other circulatory arrangements differ considerably in different classes of the Vertebrata, but these differences will be best considered at a later period. Respira- tion in all the Vertebrata is effected by means of distinct breathing-organs, assisted in many cases by the skin. In the water-breathing Vertebrates, such as fishes, the respiratory organs are in the form of gills or branchise, which are richly supplied with blood, and are exposed to the influence of water holding oxygen in solution. In the air-breathing Vertebrates, the breathing organs are in the form of lungs. These essen- tially consist of cellular or spongy organs, placed in the cavity of the chest, richly furnished with blood-vessels, and receiving constant supplies of fresh air by means of a tube which opens in the throat and is known as the “ windpipe,” or trachea. In the higher Vertebrates the heart becomes a double organ, one side being concerned wholly with driving the impure (oanous) blood to the lungs, while the other side propels the pure oxy- genated (arterial) blood to all parts of the body. The waste substances of the body—of which the most im- portant are water, carbonic acid, and the peculiar substance called wrea—are got rid of by the skin and lungs, but prin- cipally by two glands which are called the kidneys. The ex- cretion of urea from the body, as a general rule, is wholly effected by means of the kidneys alone; and this is their most important function, as the retention of this substance within the body rapidly causes death. The secretion of the kidneys is sometimes got rid of by means of special canals appropriated 204 VERTEBRATE ANIMALS. to this alone; but in the lower Vertebrata it is discharged in- to the hinder extremity of the alimentary canal, and is evacu- ated along with the undigested portions of the food. The nervous system varies greatly in its development in the Vertebrata. In the little fish called the Lancelet, the main mass of the nervous system consists of a cord of nervous mat- ter, representing the spinal marrow, but not having in front any enlargement which represents the brain. In all the other Vertebrata the central masses of the nervous system (termed the cerebro-spinal axis) consist of a nervous cord (the spinal cord) contained in the canal formed by the neural arches of the vertebrze, and of an anterior mass of nervous matter, which is protected by the skull, and is termed the encephalon or brain. The size and development, however, of the brain vary enormously in different Vertebrates; and in the lower forms the brain is little more than an aggregation or collection of nervous masses or “ ganglia,” which are connected with the special senses, sight, hearing, taste, and smell, special organs for which are present in almost all the Vertebrata. Reproduction in the Vertebrata is always truly sexual, the sexes are always in different individuals, and in no case are compound organisms produced by a process of budding or fis- sion. Most are oviparous, producing eggs from which the young are developed. Some retain the eggs within the body till the young are ready to be hatched, and these are some- times said to be ovo-viviparous, The higher Vertebrates, however, bring forth their young alive, and are said to be viviparous (Latin, vivus, living; and pario, I bring forth), Primary Divisions oF THE VERTEBRATA. — The Verte- brata are variously divided into great primary sections by dif- ferent writers, and all of these divisions have more or less merit. Here, however, the classification proposed by Prof. Huxley will be followed, and it is not necessary to enter into any consideration of the others. It has also been thought ad- visable to give in this place a brief account of the leading characters which separate these divisions from one another, though it is not to be expected that the learner will be able to appreciate the full value of these characters till he has com- pleted his study of the Vertebrata as a whole. The Vertebrata are divided by Prof. Huxley into the fol- lowing great divisions: I. Icururopsipa (Gr. ichthus, a fish; and opsis, appear- ance).—In this section are included the fishes (Class Pisces), GENERAL CHARACTERS OF THE VERTEBRATA. 205 and the frogs, newts, and their allies (Class Amphibia). They are all characterized by the fact that they possess gills or branchiz, either throughout life or during the earlier stages of their existence; that they possess nucleated red blood- corpuscles (i. e., blood-corpuscles with a central particle or nucleus, Fig. 99, d, e), and by certain embryonic characters as well. From the temporary or permanent possession of gills, they are often spoken of as the Branchiate Vertebrates. II. Savrorsmpa (Gr. saura, a lizard; and opsis, appear- ance).—In this division are the birds (Class Aves), and the true reptiles (Class Reptilia), They are characterized by the fact that at no time of their life are they ever provided with gills; that the skull is jointed to the vertebral column by a single articulating surface (or condyle); that the lower jaw is composed of several pieces, and is united to the skull by means of a special bone (called the os guadratum) ; that they possess nucleated red blood-eorpuscles (Fig. 99, 6, c), and by certain embryonic characters as well.* Ti. Mamata (Lat. mamma, the breast).—In this di- vision are all the ordinary quadrupeds; characterized by the constant absence of gills; by the skull being jointed to the vertebral column by two articulating surfaces (or condyles) ; by the fact that the lower jaw is composed of only two pieces, and is not united to the skull by means of a special bone (the quadrate bone) ; by having non-nucleated red blood-corpuscles (Fig. 99, a); and by having special glands — the mammary glands—which secrete a special fluid—the milk—by which ae ae are nourished for a longer or shorter period after irth. These three primary divisions comprise the five great classes into which the Vertebrata are divided: 1. Fishes (Pisces). 2. Amphibia (Frogs, Newts, etc.). 3. Reptilia (True Reptiles). 4, Aves (Birds). 5. Mammalia. * Recent researches have led to the belief that the appearance of nuclei in the red blood- corpuscles of the Oviparous Vertebrates is due to changes taking place after death, and that these structures are not present during life. 10 ICHTHYOPSIDA. CHAPTER XXIV. CLASS I. PISCES. Tue fishes form the lowest class of the Vertebrata, and they may be broadly defined as being Vertebrate animals pro- vided with gills, whereby they are enabled to breathe air dis- solved in water; the heart, when present, consists of a single auricle and ventricle (with the exception of the mud-fishes) ; and the limbs, when present, are in the form of fins, or expan- sions of the integument. In their external form, fishes are in most cases adapted for rapid locomotion in water, the shape of the body being such as to cause the least possible friction in swimming. To this end, as well as for purposes of defence, the body is generally enveloped in a species of chain-mail formed by overlapping scales, to which bony plates, tubercles, and spines, are some- times added. Valuable characters can sometimes be drawn from the nature of the scales, and with a view to this the integumentary appendages of fishes have been divided by Agassiz as follows (Fig. 100): 1. Cycloid scales (a), consisting of thin, flexible, horny scales, which are circular or elliptical in shape, and have a smooth outline. These scales occur in most of our common fishes (e. g., the pike). 2. Ctenoid scales (6). These resemble the cycloid scales in being thin, flexible, horny scales, but they are distinguished by having their hinder margins cut into comb-like projections, or fringed with spines. The common perch supplies a good example of these scales, 3. Placoid scales (c). These are detached bony grains, PISCES. 207 tubercles, or plates, scattered through the skin, and sometimes armed with projecting spines. 4, Ganoid scales (d,) composed of a layer of true bone, covered by a layer of hard polished enamel. These scales are usually much thicker and larger than the ordinary scales; they are often oblong or rhomboidal in shape; they are often con- nected together by little processes ; and they generally are in contact by their edges, but rarely overlap one another. 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 of this line is perforated by a minute tube, which leads into a longitudinal canal, believed to secrete the mucus with which the general surface is lubricated, or to have some sensory function. As regards the true internal skeleton, fishes differ very widely from ene Bu other, but the skeleton Fig. 100.—Scales of different Fishes. iP so complicated that only a few . g Coole te ee b Ctenoid the most important points can be = Gio eis C cideuale, Pan mentioned Heke, i one fish—the ieee” ene Lancelet—there can hardly be said to be any true skeleton, the vertebral column being repre- sented permanently by the semi-gelatinous notochord (Fig. 105). In others, such as the Lampreys, Sturgeons, and Rays, the skeleton remains permanently in the condition of gristle (cartilage); in others itis partially cartilaginous and partially ossified; and, lastly, in most modern fishes it is completely converted into bone. The vertebral column in a bony fish consists of a number of vertebree which are hollow or cup- shaped at both ends (bi-concave or “ amphiccelous”’), the cup- like margins being united together by ligaments, The cavities formed by the apposition of the vertebree are filled with the gelatinous remains of the notochord. This gelatinous elastic substance acts as a ball-and-socket joint between the vertebre, thus giving the whole spine the extreme flexibility which is essential to animals living in a watery medium. The entire spinal column is divisible into no more than two distinct regions, an abdominal and a caudal. The ribs are attached to the transverse processes or to the bodies of the abdominal 208 VERTEBRATE ANIMALS. vertebree (Fig. 101, *) ; and they do not enclose any thoracic cavity, or protect the organs which are usually contained in the chest—namely, the heart and breathing-organs. The anterior or lower ends of the ribs of fishes are free, or are rarely united to hard productions of the integument; but there is never any breastbone or sternum properly so called. SSSREERAANASIIUEZY Yj, | ZZipRW GY Fig. 101.—Skeleton of the common Perch (Perca fluviatilis). p Pectoral fin; 7 One of the ventral fins; @ Anal fin, supported upon interspinous bones (7); ¢ Caudal fin; d First dorsal fin; @’ Second dorsal fin, both supported upon interspinous bones; 7¢ Interspinous bones; 7 Ribs; s Spinous processes of vertebrae; 2 Hemal processes of vertebra. The only remaining bones of the trunk proper are the so- called “interspinous bones” (Fig. 101, 77). These are a series of pointed, dagger-like bones, imbedded in the middle line of the body, between the great lateral muscles which form the greater part of the body of a fish. The inner ends or points of the interspinous bones are attached by ligament to the spinous processes of the vertebrae, and at their outer ends they support the framework (rays) of the so-called “median” fins, As arule there is only one interspinous bone to each vertebra, but in the flat-fishes (Sole, Turbot, etc.) there are two. The limbs of fishes may be wholly wanting, or one pair may be ab- sent, but in no case is the number greater than the regular vertebrate type—namely, two pairs. When developed, how- ever, the limbs of fishes are very different from those of other Vertebrates, consisting of expansions of the integument, furnished with bony or gristly supports or rays, and thus con- stituting what are called “fins” (Fig. 102). The pair of limbs which correspond to the arms of man and to the fore-limbs of other Vertebrates are termed the pectoral fins, and they are PISCES. 209 attached to a bony arch which is attached either to the back of the skull or to the spinal column (Fig. 101, p, and 102, p). The hind-limbs in fishes are known as the ventral fins (Figs. 101, 102, v), and are not only often wanting altogether, but when present are less developed than the pectorals and less fixed in their position. They are united to an imperfect bony Fig. 102.—Outline of a Fish dee granulata), showing the “paired” and “median” fins. p Pectoral fin; v Ventral fin; @ First dorsal fin; d’ Second dorsal fin; ¢ Caudal fin; @ Anal fin. - arch, which represents the innominate bones, or pelvic arch, of the higher Vertebrates, but which is never joined to the spinal column. In some fishes the ventral fins are placed far back, and in these the bony arch which supports them is freely suspended in the muscles, In others the ventral fins are alto- gether out of position, and are placed beneath, or even in front of the pectoral fins; and in these cases the pelvic arch is attached to part of the pectoral arch. The pectoral and ven- tral fins represent, as just said, the fore and hind limbs, and consequently there are always two of each, when they are present at all. They are, therefore, spoken of as the “paired” fins. Besides these, however, or in the absence of one or other of these, there is also a series of what are called “ me- dian” fins; that is to say, fins which are placed in the middle line of the body, and which are unpaired, having no fellows. These median fins agree with the paired fins in being expan- sions of the integument, supported by bony or gristly supports or “rays,” and they are carried by the heads of the “inter- spinous” bones, already described (Fig. 101,77). They are 210 VERTEBRATE ANIMALS. variable in number, and in some cases there is only a single fringe running round the hinder extremity of the body. Common- ly, however, the median fins con- sist of one or two expansions of the dorsal integument, called the “dorsal” fins (Fig. 101, dd’); one or two on the ventral or lower surface near the vent, called the “anal” fins (a); and a broad fin at the extremity of the vertebral column, constituting the “caudal” fin or tail (c). The tail in all fishes is placed vertically—that is to say, it strikes the water laterally, or from side to side, and it is the chief organ of Fig. 103.—Tails of different Fishes. progression in the fish. Two very Hletorvocreal tall (Serseny” distinct types of tail are found among the fishes. In one of these, found in most living forms, the tail is composed of two nearly equal lobes which spring from the end of the spine (Fig. 103, a). This form of tail is said to be “homocercal.” In the other type of tail, found in the dog-fishes, sharks, and other living fishes, as well as in many extinct forms, the tail is un- equally lobed, and is said to be “heterocercal” (Fig. 103, 8). In these forms the vertebral column is prolonged into the upper lobe of the tail, and the greater portion of the tail is found below the spine. In both the paired and the median fins the integument is supported by a series of spine-like bones, which are called “rays.” These rays are sometimes simple undivided rays or spines, when they are called “spinous rays” (Fig. 101, d); but in other cases they are both divided by transverse joints, and split up into numerous longitudinal branches toward their ex- tremities, when they are spoken of as “soft rays” (Fig. 101, d'), The soft rays occur in many fishes in different fins, but they are invariably present in the caudal fin or tail. As regards the digestive system in fishes, the mouth is usually furnished with a complicated system of teeth, de- veloped not only upon the jaws, but upon any or every bone which enters into the composition of the oral cavity. The gullet opens into a stomach, usually of large size, and its hin- der aperture (the pylorus) is usually furnished with a valve. PISCES. 211 Immediately behind the pyloric opening of the stomach there is usually a variable number of blind tubes (called the “ py- loric ceca”) which open into the intestine, and which are be- lieved to represent the pancreas. In some fishes, however, there is a well-developed pancreas, and in others even these tubes are wanting. The intestinal canal is a longer or shorter, more or less convoluted tube, and its absorbing surface is sometimes largely increased by a spiral folding of the mucous membrane, which winds like a screw in close turns from the pylorus to the anus. The liver is usually of large size, and - saturated with oil, but in the Lancelet it is doubtfully rep- resented by a hollow, sac-like organ. The kidneys in fishes are of great comparative size, forming two elongated organs, situated beneath the spine, and extending along the whole length of the abdomen. Respiration in all fishes is aquatic, and is effected by means of gills or branchie, in all except the Lancelet, in which res- piration is effected by branchial filaments placed round the pharynx, and also by a greatly-developed pharynx perforated hy ciliated apertures (Fig. 105). The arrangement and struct- te of the gills in fishes vary a good deal in different orders, and the leading modifications will be noticed hereafter. In the mean while it will be sufficient to give a short description of the branchial apparatus in one of the bony fishes. In such a fish the gills consist of a single or double series of flat carti- laginous leaflets, covered by mucous membrane, richly supplied with blood, and arranged on bony or cartilaginous arches which are connected with the tongue-bone (Ayoid bone) below and with the under surface of the head above. The branchial arches and branchie are suspended in cavities placed on the side of the neck, and in the ordinary bony fishes there is only one such cavity on each side. The water is taken in at the mouth by a process analogous to swallowing, and it gains ad- mission to the branchial chamber by means of a series of clefts or slits which perforate the sides of the pharynx. Having passed over the gills and lost its oxygen, the effete water makes its escape behind by an aperture called the “ gill-slit,” which is placed on the side of the neck. The opening of the gil-slit is closed in front by a chain of flat bones which con- stitute the “gill-cover,” and by a membrane which is sup- ported upon a variable number of slender bony spines. This is the general mechanism of respiration in one of the bony fishes, but different arrangements are found in other cases, which will be subsequently noticed. ~ 212 VERTEBRATE ANIMALS, The heart in fishes may be regarded as essentially a branchial or respiratory driving the venous and Fic. 104.—Diagram of the Circula- tion ina Fish. The arterial sys- tem is represented black; the venous system is left light. @ Au- ricle, receiving the venous blood from the body; » Ventricle; m Bulbus arteriosus; Branchial artery, carrying the venous blood to the gills (0); ¢ Great systemic vessel, carrying the pure blood to the tissues. heart, being concerned chiefly with impure blood to the gills. It con- sists in almost all cases of two cavities, an auricle and a ventricle (Fig. 104). The auricle (@) receives the venous blocd which has passed through all the various parts of the body, and propels it into the ven- tricle (v). From the ventricle pro- ceeds a single great vessel (the “branchial artery’), the base of which is usually developed into a muscular cavity, the “ bulbus arte- riosus” (7m), which acts as a kind of additional ventricle. By the ventri- cle and bulbus arteriosus the venous blood is driven to the gills, where it is subjected to the action of the wa- ter. The aérated blood is not re- turned to the heart, but is driven from the gills through all parts of the body, the propulsive force neces- sary for this being derived partly from the heart, and partly from the contractions of the muscles between which the blood-vessels pass. The essential peculiarity of the circulation of fishes consists in this, that the ar- terialized blood returned from the gills is propelled through the gen- eral vessels of the body (systemic vessels) without being sent back to the heart. In the Lancelet, alone of all fishes, there is no single heart, and the circulation is effected by means of contractile dila- tations situated upon several of the vessels. In the Mud- fish (Lepidosiren) the heart consists of two auricles and a ventricle. In all cases the blood is cold, or, in other words, has « temperature very little, or not at all, higher than that of the surrounding medium. The blood-corpuscles (Fig. 99, e) are always nucleated, and, except in the Lancelet, are most of them red. While the respiration of all fishes is truly aquatic, most PISCES, 213 are, nevertheless, furnished with an organ which doubtless corresponds to (or is homologous with) the lungs of the higher Vertebrata. 'This is known as the “air” or “swim bladder,” and is a sac filled with gas and situated between the alimen- tary canal and the kidneys. In most cases, the sac contains ‘only a single cavity, but, in many instances, it is variously divided by partitions. In most fresh-water fishes, the gases in the swim-bladder are mainly composed of nitrogen, but, in the sea fishes, it is chiefly filled with oxygen. The sac of the swim-bladder is often closed, but, in other cases, it opens into the gullet by means of a duct which corresponds to the wind- pipe. In the great majority of fishes, the functions of the air-bladder are mainly hydrostatic, that is to say, it serves to maintain the necessary agreement between the specific gravity of the fish and that of the surrounding water. In the singu- lar Mud-fish (Lepidosiren), the air-bladder is composed of two distinct sacs, divided into a number of cellular compartments, and opening into the gullet by a tube. In this fish it acts as a respiratory organ, and is, therefore, not only in structure, but also in function, the representative of the lungs of the other Vertebrates. The nervous system of fishes is of an inferior type of or- ganization, the brain being of comparatively small size, and consisting mainly of a collection of ganglia. As regards the or- gans of the senses, two peculiarities deserve notice. In the first place, though fishes possess the essential parts of the organ of hearing, they possess no external ears, and in no case is there any direct communication between the ear and the outer world. In the second place, the organs of smell consist of a double cavity lined by a mucous membrane folded into numer- ous plaits, into which water is admitted, usually by two dis- tinct apertures or nostrils. Behind, however, the nasal sacs are closed, and they do not communicate by any aperture with the throat, as they do in all the higher Vertebrates. The only exceptions to this rule are the Hag-fishes and their allies (Myzxinoids) and the Mud-fish (Lepidosiren). As regards their reproductive system, most fishes are truly oviparous, and the ovaries are familiarly known as the “roe,” Some fishes are ovo-viviparous, retaining their eggs within the body till the young are hatched. The male organs of repro- duction are commonly spoken of as the “milt” or “ soft roe.” CHAPTER XXV. ORDERS OF FISHES. Tue number of different kinds of fishes is so enormous that nothing further will be attempted than merely to give an out- line of the leading peculiarities which distinguish the different orders. The classification here adopted is the one proposed by Prof. Huxley, who divides the class Pisces into the follow- ing six orders: 1. Pharyngobranchii. 2. Marsipobranchii. 3. TZeleostet. 4, Ganoidei. 5. Elasmobranchii. 6. Dipnoi. Orper I. Poaryrncosrancanm (Gr. pharugs, the upper part of the gullet, and bragchia, gills)—This order of fishes in- cludes only a single animal, the anomalous Amphiozxus, or Lancelet, the organization of which differs in almost all its important points from that of all the other members of the class. In fact, the Lancelet presents us with the lowest type of organization as yet known in the Vertebrata. The Lance- let is an extraordinary little fish, from one and a half to two inches long, which burrows in sand-banks in various seas, but is especially abundant in the Mediterranean. The body is lanceolate in shape, and is provided with a narrow membra- nous border, of the nature of a median fin, which runs along the whole of the dorsal and a portion of the ventral surface, ais expands ay the tail ea form a lancet-shaped caudal fin. Aere are no true “ paired” fins, representin hind limbs. The one isa lonitudtaal ees Sheu ates front of the head, and completely destitute of jaws, but sur- ORDERS OF FISHES. 215 rounded by a number of cartilaginous filaments. The throat is provided with several leaf-like filaments, which are richly supplied with blood, and are believed to discharge in part the function of gills. The mouth (Fig. 105, m) opens into a dilated chamber, which is believed to represent the pharynx, and is termed the pharyngeal or “branchial” sac. The walls of this chamber (p) are strengthened by numerous cartilagi- Fic. 105.—Diagram of the Lancelet (Amphioxwus lanceolatus). m Mouth with cartilagi- nous filaments ; p Greatly-developed pharynx, or branchial sac, perforated by ciliated apertures; ¢ Intestine; @ Anus; 2 Blood-vessels, with pulsating dilatations in place of a heart; ch Notochord ; 7 Spinal cord. nous filaments, between which are a series of transverse slits or clefts, and the whole is covered with a richly-ciliated mu- cous membrane. The function of this sac is clearly respiratory, the water from without being admitted through the mouth, passing through the branchial clefts into the abdominal cavity, and finally escaping by means of an aperture placed on the _ventral surface a little in front of the anus. From the hinder end of the branchial sac proceeds the alimentary canal, which has appended to it a sac-like organ, believed to represent the liver, and which terminates behind in a distinct anal aperture. There is no heart, and the circulation is entirely effected by means of several contractile dilatations, developed upon the great blood-vessels (i). The blood itself is colorless. No kidneys have hitherto been discovered, and the reproductive elements are emitted into the abdominal cavity, from which they escape by the pore placed upon the lower surface. There is no skeleton properly so called. The notochord (ch) remains throughout life as a semi-gelatinous rod, enclosed in a membranous sheath, and supporting the spinal cord. There is no skull, and the spinal cord (mn) does not expand in front to form a distinct brain. The brain, however, may be said to be represented, as the front portion of the nervous axis gives off nerves to a pair of eyes, and another branch to 216 VERTEBRATE ANIMALS. a ciliated pit, which is believed to be a rudimentary organ of smell, Orper II. Marstroprancun (Gr. marsipos, a pouch; brag- chia, gills)—This order includes the Hag-fishes (Myxinide) and the Lampreys (Petromyzonide), and it is defined by the following characters: The body is cylindrical and worm-like, and is destitute of limbs. The skull is cartilaginous, there is no lower jaw, and the notochord remains through life, so that there is no vertebral column. The heart is composed of an auricle and a ventricle, but there is no bulbus arteriosus. { The gills are pouch-like, communicating with the throat on the one hand, and opening externally on the other by means of apertures placed on the sides of the neck. The Hag-fish (Mysine) is an eel-like fish, which agrees with the Lampreys in having neither pectoral nor ventral fins, the representatives of the fore and hind limbs. The mouth is of a very remarkable character, and enables the Hag-fish to lead a very peculiar existence. It is generally found imbedded in the interior of some large fish, into which it has penetrated by means of a single serrated and recurved fang attached to the centre of the palate. The mouth itself is destitute of jaws, and forms a sucking disk or cup. Another remarkable peculiarity of the Hag-fishes is found in the structure of the nose. In all fishes, namely, except these and the Mud-fish (Lepidosiren), the nasal chambers are closed behind, and do not communicate with the cavity of the mouth, as they do in the higher Vertebrates. In the Myxinoids, however, such a communication does exist. The nasal sacs are placed in com- munication with the throat (pharynx) by means of a canal which perforates the palate. A second canal leads from the nasal’ cavities in front to open by an external aperture (the nostril or “spiracle”) on the top of the head behind the mouth, Another peculiarity, which is best considered in the Lam- preys, is to be found in the structure of the respiratory or- gans, from which the name of the order is derived. When viewed externally, instead of the single great “ gill-slit,” cov- ered bya “ gill-cover,” as seen in the ordinary bony-fishes, the side of the neck presents seven round holes placed far back in a line on each side. These holes are the external apertures of the gills (Fig. 106, A), which in these fishes are in the form of sacs or pouches, the lining membrane of which is thrown into numerous folds or plaits, over which the branchial ORDERS OF FISHES. 217 vessels ramify (Fig. 106, B). Internally the sacs communi- cate with the cavity of the pharynx, by means of a common respiratory tube into which they all open. It follows from this arrangement that the gill-pouches on the two sides of the neck communicate freely with one another through the phar- ynx. The object of this arrangement is to obviate the ne- cessity for admitting the water to the gills through the mouth, Fig. 106.—A, Lamprey (Petromyzon), showing the sucking-mouth and the apertures of the gill-sacs. B, Diagram to illustrate the structure of the gills in the Lampreys. @ Pharynx; 6 Tube leading from the pharynx into one of the gill-sacs; c One of the gill- sacs, showing the lining membrane thrown into folds; d External opening of the gill- sac. (In reality the gill-sacs do not open directly into the pharynx, but into a common respiratory tube which communicates with the pharynx; but this is omitted for the sake of clearness.) as ordinary fishes do. These fishes are in the habit of fixing themselves to foreign objects by means of the suctorial mouth ; and, when in this position, it is, of course, impossible that they can obtain the necessary water of respiration through the mouth, As the gill-sacs, however, on the two sides of the neck communicate freely with one another through the phar- ynx, water can readily pass in and out. The gills are not provided with cilia, but the circulation of water is assisted by a kind of elastic cartilaginous framework upon which the whole respiratory apparatus is supported, and which acts some- what like the ribs of the higher Vertebrates. The nasal cavities of the Lampreys, unlike those of the Myxinoids, are closed behind, and do not communicate with the throat. Some of the Lampreys are permanently inhabit- ants of rivers, but the great sea-lamprey (Petromyzon mari- nus) only quits the salt water and betakes itself to fresh in order to deposit its eggs. ; Orver III. Tereosrer (Gr. teleios, perfect; and osteon, bone).—The fishes comprised in this order, as implied in their name, have a well-ossified or bony skeleton, and they are com- 218 VERTEBRATE AN TMALS. monly known as the “ bony » fishes. In all the Teleostei, the skeleton is bony, the skull is composed of distinct bones, and there is a lower jaw. The vertebral column always consists of more or less completely ossified vertebrae; and the two pairs of limbs, when present, are in the form of fins, supported by rays. The gills are free, comb-like or tufted in shape, and always protected by a bony gill-cover. The bulbus arteriosus is not capable of regular contractions, and is separated from the ventricle by only a single valve. The order Zeleostet comprises almost all the most familiar fishes, and it will be unnecessary to dilate here upon their structure, as they were taken as the type of the class inde- | scribing the fishes generally. It may be as well, however, to recapitulate some of the leading points in the anatomy of the bony fishes. 1. The skeleton is always more or less complete- ly ossified, and does not remain cartilaginous throughout life. The notochord is not permanent, and the vertebral column consists of a number of distinct vertebree. The vertebrae, however, are “ amphiccelous,” or hollow at both ends, so that there is left between each pair a doubly-conical cavity, which is filled with the cartilaginous or semi-gelatinous remains of the notochord. In this way an extraordinary amount of flexi- bility is given to the entire vertebral column. In no fish (ex- cept the Bony Pike, which belongs to another order) is the conversion of the bodies of the vertebrae into bone carried further than this. 2. The integument usually develops scales, and these in the great majority of cases are of the forms known as “cy- cloid”’ and “ctenoid,” the former being circular or elliptical horny plates, with plain margins; while the latter have their hinder margins cut into comb-like projections, or fringed with spines (Fig. 100, a, 5). 3. The anterior and posterior limbs are usually, but not always, present, and when developed they are always in the form of fins. These fins may be supported by “ spinous rays” or “soft rays,” or by both. The spinous rays are simple un- divided bony spines which taper to a point. The soft rays are doubly divided, splitting up toward their extremities into a number of secondary rays, and being also divided by trans- verse joints into numerous short pieces. 4. Besides the “paired” fins which represent the limbs, ao also a series be unpaired or “ median” fins, the rays which are supported upon a series of d TH : deeply plunged in the flesh in the saiddle Line of ike body ORDERS OF FISHES. 219 and known as the “interspinous” bones (Fig. 101). The me- dian fins are variable in number, but when fully developed they consist of one or two 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, or tail, Fig. 102). In all the Zeleoste, the caudal fin has the shape called “ homocercal ” —that is to say, it consists of two equal lobes—and the vertebral column is not prolonged into the upper lobe (Fig. 103, «). 5. The heart consists of two cavities, an auricle and a ven- tricle, but the bulbus arteriosus is not rhythmically contractile, and is separated from the ventricle by only a single pair of valves. 6. The respiratory organs are in the form of free, comb- like, or tufted gills, enclosed in two cavities placed on the sides of the neck. Each of these branchial chambers opens externally by a single aperture, the “ gill-slit,” which is pro- tected by a chain of bones, forming the “ gill-cover,” and by a membrane supported by bony rays. Internally the branchial chambers communicate with the throat by a series of clefts or fissures, and the water required in respiration is taken in at the mouth by a process analogous to swallowing. %. The nasal sacs never communicate behind with the throat (pharynx). TaBuLaR VIEW oF THE Marn Divisions oF THE TELEOSTEI. Sus-orper I, Matacopreri.—Usually a complete series 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 is always connected with the gullet by a duct. The skin is rarely naked, and is mostly furnished with cycloid scales, but sometimes ganoid scales are present. Among the more important families in this sub-order are the Eels (fu- renide), Herrings (Clupeide), Pikes (Hsocide), Carps (Cyprinide), Salmon and Trout (Selmonide), and Sheat-fishes (Siluride). Sus-orver IJ. ANacanTHINI.—Fins entirely supported by soft rays, and never by spinous rays. Ventral fins either wanting, or placed under the throat, beneath or in advance of the pectorals. The two leading families in this sub-order are the Cod, Ling, and Haddock family (Gadide), and the Flat-fishes (Plewronectide), comprising the Sole, Turbot, Flounder, and others. Sus-orper III. Acanruorrert.—Fins with one or more of the first rays in the form of undivided, inflexible, spinous rays. Scales mostly ctenoid. Swim- bladder without a duct. The leading families in this order are the Wrasses (COyclo-labride), the Perches (Percide), the Mackerels (Scomberide), the Mullets (Mugilide), and the Gobies ( Gobiide). 220 VERTEBRATE ANIMALS. Sus-orper IV. Precrognatsi.—Certain of the bones of the mouth (the maxillary and pre-maxillary bones) immovably connected on each side of the jaw. Integumentary skeleton in the form of ganoid plates, scales, or spines. ‘ The chief families in this sub-order are the File-fishes (Balistide), and the Trunk-fishes ( Ostraciontide). Sus-orper V. Lopnosrancai.—Gills arranged in little tufts on the branchial arches. Integumentary skeleton in the form of ganoid scales. The two families contained in this division are the Sea-horses (Hippocam- pide), and the Pipe-fishes (Syngnathide). Orver IV. Ganorpe! (Gr. ganos, splendor, or brightness). —The fourth order of fishes is that of the Ganoidet, including few living forms, but having a great and varied development in past geological epochs. The Ganoid fishes are dis- tinguished by the imperfect development of the skeleton, which is mostly cartilaginous throughout life, and by having an integumentary skeleton composed of ganoid scales, plates, or spiues (Fig. 100, d). The skull is composed of distinct bones, and there is always a lower jaw. ‘There are usually two pairs of fins (pectoral and ventral), supported by many series of cartilages, and the ventral fins are placed very far back. The first rays in the fins are usually in the form of strong spines. The caudal fin or tail is mostly heterocercal or unsymmetrical (Fig. 103, 6). The swim-bladder is always present, is often cellular, and is provided with an air-duct. The gills and gill-covers are essentially the same as in the bony fishes. The heart has one auricle and a ventricle; and the bulbus arteriosus is rhythmically contractile, is furnished with a distinct coat of muscular fibres, and is furnished with several transverse rows of valves. The best known of the living Ganoids are the Bony Pike (Zepidosteus), the Sturgeon (Sturio), and the Polypterus. Of these, the Bony Pike is found in the rivers and lakes of North America. It is a large fish, attaining a length of several feet, and it has the body entirely covered with an armor of ganoid scales arranged in obliquely transverse rows. The jaws form a long, narrow snout, armed with a double series of teeth, and the tail is heterocercal. ‘The vertebral column is more perfect- ly ossified than in any other fish, the bodies of the vertebree being convex in front and concave behind ( “ opisthoccelous”’). The Polypterus (Fig. 107, A) inhabits the rivers Nile and Senegal, and is remarkable for the peculiar structure of the dorsal fin, which is broken up into a series of small, detached portions, each composed of a single spine in front, with a soft fin attached to it behind. Some of the species of Polypterus ORDERS OF FISHES. 221 ed Ee es B ¢ : a Fig. 107—Ganoid Fishes. A, Polypterus, a living Ganoid. B, Osteolepis, a fossil Ganoid (restored): @ Pectoral fin; b Ventral fin; ¢ Anal fin; d d@’ Dorsal fins. are stated to possess external gills when young, which they lose when grown up, thus making an approach to the Am- phibia. Many of the fossil Ganoids are more or less closely allied to the living Lepidosteus and Polypterus. Another great group of the Ganoid fishes is represented by the Sturgeons (Sturioniae), in which the skeleton is always very imperfectly ossified, and the head, with more or less of the body, is protected by large ganoid plates, which are often united together at their edges by sutures. The true Sturgeons are chiefly found in the North Sea, the Caspian, and the Black Sea, and they are captured when ascending the great rivers for the purpose of spawning. The swim-bladder of the Stur- geons is one of the chief sources from which ésinglass is pre- pared, and the roe is sold as a delicacy under the name of caviare. The place of the Sturgeons in North America is taken by the Paddle-fishes (Spatularia). The group of Ganoids represented at the present day by the Sturgeons and Paddle-fishes was formerly represented by numerous remarkable fishes, which are most abundant in the system of rocks known to geologists as the “ Old Red Sand- stoue.” The graphic descriptions of Hugh Miller have placed many of these fishes before us as living pictures, but space will not allow of any further notice of them here. One, how- ever, of the more striking forms is figured hereafter (Fig. 108). Orvrr V, Exasmosrancat (Gr. elasma,a thin plate; and bragchia, gills)—This order includes the Sharks and Rays, 222 VERTEBRATE ANIMALS. «< dictinouished by the following characters: The skull oe eee ne ‘well developed, but the skull is not com- Fic. 108.—Cephalaspis Lyelii, from the Old Red Sandstone of Scotland, posed of distinct bones, and simply forms a kind of cartila- ginous box. The vertebral column is sometimes cartilaginous, sometimes composed of distinct vertebra. The integument- ary skeleton is in the form of placoid scales (Fig. 100, c)— Fra. 109, ——~Elasmobranchii. A, White Shark z i De frharian, B. King of the Herrings ORDERS OF FISHES. ; 223 that is to say, of detached grains, tubercles, or plates. There are two pairs of fins, corresponding to the fore and hind limbs, and the ventral fins are placed far back, close to the anus. The heart consists of an auricle and ventricle; and the bulbus arteriosus is rhythmically contractile, is provided with a dis- tinct coat of muscular fibres, and is furnished with several transverse rows of valves. The gills are fixed, and form a number of pouches, which open internally into the pharynx, and communicate with the outer world by a series of aper- tures placed on the side of the neck (Fig. 109). The intestine is very short, but, to compensate for this, the mucous mem- brane is thrown into a fold, which winds round the intestine in close turns from the pyloric orifice of the stomach to the anus, and which thus greatly increases its absorbing surface. The best-known members of this order are the Sharks and Rays, but numerous extinct forms testify to its great abun- dance in past geological epochs. TaBuLarR VIEW OF THE DIVISIONS oF THE ELASMOBRANCHII. Sos-orper I. Horocer#atr.—The mouth placed at the end of the head, and the external opening of the gills in the form of a single gill-slit, The best-known member of this sub-order is the Chimera monstrosa, sometimes called the “ King of the Herrings.” Sus-orver IT. PLaciostom1.—Mouth transverse, placed on the under sur- face of the head ; external opening of the gills in the form of several slits on each side of the neck, not protected by a gill-cover. Fam. a, Cestraphori.— Ex, Port-Jackson Shark. Fam. b. Selachii.— Ez, Sharks and Dog-fishes. Fam, ¢. Batides,—Ex. Rays. Orver VI. Dienor (Gr. di, double; pnoé, breath).—This order is a very small one, and includes only the very singular Mud-fishes (Lepidosiren),* which are of great interest from the many points of affinity which they exhibit to the Am- phibia, The body of the Mud-fish (Fig. 110) is completely fish-like, and is protected by a covering of small, horny, over- lapping scales, which have the cycloid characters. There are two pairs of limbs, but these are in the form of awl-shaped organs, each supported by a single jointed cartilaginous rod. The pectoral limbs have a membranous fringe inferiorly, and the ventrals are placed very far back. There is also a median * Recently a singular fish has been discovered in the rivers of Queensland (Australia), which will probably have to be referred to the order Dipnoi; but our knowledge about it is still imperfect. VERTEBRATE ANIMALS. 224 fin behind, forming @ cont: tail, and supp? inuous fringe round the compressed rted by cartilaginous rays. Fra. 110.—Lepidosiren annectens, the Mud-fish. p Pectoral limbs; o Ventral limbs. The skull is composed of distinct bones, and there is a lower jaw, but the notochord is persistent, and there are no bodies of vertebrae developed. The respiratory organs are twofold, consisting, firstly, of free filamentous branchiz or gills, contained ina branchial chamber, which opens externally by a single vertical gill-slit; and, secondly, of true lungs, in the form of a double cellular air-bladder communicating with the gullet by means of an air-duct or windpipe. Sometimes, if not always, there are rudimentary eaternal gills as well, placed on the side of the neck. The heart consists of a ven- tricle, and of two auricles, divided from one another by an incomplete partition. Lastly, the nasal sacs open behind into the throat, and do not form closed chambers opening only by the nostrils, as they do in all other fishes, except the Myxi- noids. The two best-known species are the Lepidosiren paradoxa from the Amazons, and the Z. annectens from the Gambia. They both inhabit marshy tracts, and both appear to be able in the dry season to bury themselves in the mud, and to form a kind of chamber, in which they remain dormant till the rains of the wet season set them free- ICHTHYOPSIDA. CHAPTER XXVI. CLASS II. AMPHIBIA. Tats class of Vertebrata comprises the Frogs and Toads, the Newts and Land-salamanders, the Ceciliew, and some ex- tinct forms, and it may be briefly defined as follows: In al’ cases gills or branchise adapted for aquatic respiration are pres- ent during a part or the whole of life; but, in all cases, true lungs adapted for breathing air are ultimately developed, even when the gills are retained through life. All pass through some sort of a metamorphosis after being set free from the egg. The limbs may be absent or there may be only one pair, but in no case are they ever converted into fins, When median fins are present, as is sometimes the case, these are never furnished with fin-rays or interspinous bones, as in the fishes. The skull always articulates with, or is jointed to, the spinal column by two articular surfaces or condyles. The heart consists of two auricles and a single ventricle. The na- sal sacs always open behind into the mouth; and there is'a common cavity or “cloaca” which receives not only the ter- mination of the intestine (rectum), but also the ducts of the kidneys and of the reproductive organs. The great and distinguishing character of the Amphibia (Gr. amphi, both ; bios, life) is, that they invariably undergo some kind of metamorphosis after birth, though, in some rare cases, the eggs are retained so long within the body of the parent that there is little or no obvious change. In the great majority of cases, however, the Amphibians commence life as water-breathing larve, provided with gills; but, in their adult state, they possess true air-breathing lungs, the gills sometimes disappearing when the lungs are developed, but being some- 226 2 VERTEBRATE ANIMALS. times retained throughout life. Most Amphibians, therefore, are to a greater or less extent amphibious, that is to say, more or less capable of living indifferently either on land or in the water. In the majority of cases, the gills are external, placed on the sides of the neck, and not contained in a.special cavity, thus differing altogether from the gills of fishes. In the Frogs and Toads, and in some others, there are two sets of gills, one external and the other internal, of which the for- mer is soonest lost. The lungs of the Amphibians never attain a very high state of development, and, in those forms in which the gills are retained throughout life, the chief business of respiration appears to be carried on by the gills. In accord- ance with the changes in the respiratory process, correspond- ing alterations take place in the blood-vessels. With the development of the lungs, the vessels which carry blood to them (the pulmonary arteries) increase in size, while the branchial vessels which carry the blood to the gills undergo a proportionate diminution. At first, the condition of the circu- lation is very much the same as it is in fishes, but ultimately it becomes nearly the same as in the true reptiles. The Amphibia are divided into three living and one ex- tinct order, as follow: 1. Ophiomorpha. 2. Urodela. 3. Anoura. 4, Labyrinthodontia. Orpen I. Orniomorrua (Gr. ophis, a serpent ; and morphe, form).—This order is an extremely small one, and, as its name implies, it comprises certain snake-like Amphibians. The order includes only the curious animals known as Cecilie@, which are found in Java, Ceylon, South America, and Guinea. The body is entirely destitute of limbs, and is enclosed in an integument which is thrown into numerous transverse wrinkles, and some- times has numerous horny scales imbedded in it. The eyes are concealed by the skin, and are rudimentary. There is no tail, and the anal aperture is placed almost at the extreme end of the body. When adult, respiration is carried on by means of lungs, but gills are present in the young, and there can, there- fore, be no doubt as to their being genuine Amphibians. The Cecilie are found burrowing in marshy ground, and they are not unlike large earth-worms in appearance, but they sometimes attain a length of several feet. AMPHIBIA, 227 Fic. 111.—a Siphonops annulatus, one of the Cacilians, much reduced ; 6 Head of the same; ¢ Mouth, showing the tongue, teeth, and internal openings of the nostrils; @ Tail of the same. (After Dumeril and Bibron.) Orver II. Uropreta or IcutuyomorpHa (Gr. ichthus, a fish, and morphe, shape).—In this order are a number of fish- like Amphibians, of which the Newts and Land-salamanders are the most familiar examples. In all the members of this section, the skin is naked, and never develops any hard struct- ures, and in all there is a well-developed, fish-like tail, which is retained throughout life. The vertebrae are sometimes hol- low at both ends (amphiccelous), sometimes hollow behind and convex or rounded in front (opisthoccelous). The ribs are rudimentary and the bones of the forearm (radius and ulna), and of the shank (tibia and fibula), are separate, and are not combined so as to form single bones. The Zchthyomorpha are not unfrequently spoken of as the “Tailed” Amphibians (Urodela), and they fall into two natu- ral sections, according as the gills are permanently retained throughout life, or are cast off before maturity is attained. The animals belonging to the first section are often called “perennibranchiate,” while those belonging to the second are said to be “ caducibranchiate.” Among the Perennibranchiate forms, in which the gills are permanently retained after the lungs make their appearance, the best-known examples are Axolotl (Fig. 112), the curious Proteus anguinus, and the Mud-eel (Siren). The Axolotls 228 VERTEBRATE ANIMALS, inhabit various of the lakes of the American Continent, the best- known species being the Siredon pisciforme of the Mexican lakes (Fig. 112). It attains a length of a foot or more, and Fig. 112,—The Axolotl (Siredon pisciforme). (After Tegetmeier.) possesses both pairs of limbs, the fore-feet having four toes, the hind-feet five toes. The branchie are in the form of three long ramified processes on each side of the head; and the tail is compressed, and fringed by a fin which is prolonged on the back between the shoulders. In a state of nature, the Axolotl is certainly perennibranchiate, and it breeds freely in this condition. It has been shown, however, by Prof. Marsh, of New Haven, that some species, when kept in confinement, lose their gills, and undergo certain other changes, becoming ul- timately converted into a Salamandroid, apparently belonging to the genus Amblystoma. The Proteus is an extraordinary Amphibian which is found inhabiting the waters of caves in Illyria and Dalmatia. It attains a length of about a foot, and is of a pale flesh-color or nearly white. The gills, which are retained throughout life, are of a bright scarlet. Both pairs of limbs are developed, but they are only short and weak, the fore-limbs having three toes each, and the hind-limbs only two. The eyes are extremely small, the animal spending its existence in darkness; and swimming is effected mainly by means of the tail. The Stren, or Mud-eel, is a large lizard-like Amphibian, which is found abundantly in the swamps of South Carolina, and attains the great length of three feet. The ex- ternal branchie are retained throughout life, and they are the main organs of respiration. The fore-limbs are present, but the hinder pair of limbs is never developed. dete. . G AMPHIBIA. 229 The “caducibranchiate”’ section of this order is charac- lerized by the fact that both pairs of limbs are always de- veloped, and the branchiw are never retained throughout life. The most familiar examples are the Water-salamanders or Newts (Zriton), and the Land-salamanders. The Newts (Fig. 113) are well known as inhabiting pools in many countries, ee * SS OS », ——y oe SO Fia. 118.—The great Water-Newt (Triton cristatus), male. (After Bell.) and the young lead a strictly aquatic life. When the lungs are developed the external gills wholly disappear, and the respiration becomes strictly aérial, though the animals still spend a great part of their time in the water. The larva or oung form is at first destitute of limbs, and the fore-limbs are the first to be developed, the reverse of this taking place in the Frogs. In accordance with their mode of life, the tail is compressed and flattened, so as to form an efficient swimming apparatus. The Water-salamanders are all oviparous, and the young are like the tadpoles of the common frog. The Land-salamanders, in both their adult and young state, live upon land, and the tail is rounded and cylindrical. The young are not developed in water, but are retained with- in the body of the parent for a longer or shorter period, so that the reproduction becomes ovo-viviparous, or even vivip- arous. The best-known Salamanders occur upon the Con- tinent of Europe, and one species is singular in the fact that it inhabits high mountains. It is important to remember in connection with all these “tailed” Amphibians, that they are wholly distinct from the true Lizards, with which they are often confounded. Many of them are completely lizard-like in form, having a long tail and two pairs of legs; all, however, at some time or other in their life, respire by means of gills, and this is never the case with any true ees It must be confessed, however, that a 230 VERTEBRATE ANIMALS. near approach to the Lizards is made by the Land-salamanders, the young of which have sometimes lost their gills before birth, Orver III. Anovra or TaErtomorpna (Gr. ther, a beast; and morphe, shape).—This order is the highest of the Am- phibia, and comprises the Frogs and Toads, It is sometimes known by the name of Batrachia (Gr. batrachos, a frog), or Anoura (Gr. a, without; oura, a tail), the. latter name being derived from the fact that the adults are “ tailless.” : The tailless Amphibia or Theriomorpha are characterized by the fact that while the larva possesses a tail, and is fur- nished with gills, the adult has no tail, and breathes wholly by lungs. Both pairs of limbs are always developed in the full-grown animal, and the hind-limbs are usually considerably longer than the fore-limbs, and generally have the toes webbed, while those of the fore-limbs are free. The skin is Fie. 114.—Anoura. Tree-frog (Hyla leucotenia). (After Ginther.) soft, and there are rarely any traces of any integumentary skeleton. The spinal column (Fig. 114) is short; the dorsal vertebre are very long; and the ribs are quite rudimentary, their place being taken by greatly-developed transverse pro- cesses. The bodies of the vertebre are hollow in front and convex behind (procelous). The bones of the forearm (radius and wna), and those of the shank (¢éb¢a and fibula), are united together to form single bones. The upper jaw is usually fur- AMPHIBIA. 231 nished with teeth, and the lower jaw sometimes, but there are no teeth in the Toads. The lungs are well developed, comparatively speaking; and, as there are no ribs by which the cavity of the chest can be expanded, the air is taken into the lungs by a process nearly akin to that of swallowing. There can be no doubt, also, that the skin plays a very im- portant part in the aération of the blood, and that the frogs, especially, can carry on their respiration by means of the skin without the assistance of the lungs for a very lengthened period. This, however, should not lead to any credence being given to the often-repeated stories of frogs and toads being found in closed cavities in solid rock, no authenticated instance of such an occurrence being known to science. The ova of the frogs and toads are deposited, in masses or strings, in water, and the young or larve are familiar to every one as tadpoles. Upon its escape from the egg, the young frog (Fig. Fic. 115.—Development of the common Frog. @ Tadpole, viewed from above, showing the external branchia (g); b Side view of a somewhat older specimen, showing the fish-like tail; ¢ Older specimen, in which the hind-legs have made their appearance; d@ Specimen in which all the limbs are present, but the tail has not been wholly absorbed. (After Beil.) 115) presents itself as a little fish-like creature with a broad head, a sac-like belly, and a long, compressed tail with which it swims actively. It breathes by means of gills or branchia, of which there are two sets, one external, and the other in- ternal; at first there are no limbs; but, as development pro- ceeds, the limbs make their appearance—the hind-legs first, and then the fore-legs. The tail, however (Fig. 115), is still retained as an instrument of progression. Ultimately, when 232 VERTEBRATE ANIMALS. the limbs are fully developed, and the gills have given place to lungs, the tail disappears, and the animal now takes to the land as a perfect frog. The development of the Frog is a good illustration of the general zoological law, that the transitory embryonic stages of the higher members of any division of the animal kingdom are often represented by the permanent condition of the lower members of the same division. Thus the transitory condition of the young Frog, in which it breathes by external branchiz, is toa certain extent permanently represented by the perma- nent condition of a perennibranchiate Amphibian, such as the Proteus. The stage at which the external branchiz have dis- appeared, but the tail is still present, and the limbs are de- veloped, is permanently represented in the common tailed Amphibians, such as the Newts. The order Anoura comprises the three families of the Frogs, Toads, and Surinam Toads. The Frogs (Ranide) are distinguished by having a tongue which is fixed to the front of the mouth, and can be protruded at will, while the upper jaw is always armed with teeth. The typical Frogs have enormously-developed hind legs, the toes of which are united by membrane, or are “webbed.” They swim very power- fully, and can take extensive leaps. The Tree-frogs (Fig. 114), on the other hand, are adapted for a wholly different life, inhabiting trees, among which they climb with great ease by the help of suckers developed upon the ends of the toes. They are mostly found in warm countries, especially in Amer- ica, but one species is European. In the equally familiar Toads (Bufonide) the structure of the tongue is the same as in the Frogs, but the jaws are not furnished with teeth. In the Surinam Toads (Pipide) there is no tongue at all, and usually no teeth. Orper IV. Lanyrivraopont1a.—This, the last order of the Amphibia, is not represented by any living forms, and re- quires to be little more than mentioned. The Labyrinthodonts were Amphibia which were mostly of large size, and of which some must have obtained absolutely gigantic dimensions, the skull of one species being three feet in length and two in breadth. They were first known to science simply by their footprints, which were found in certain Secondary sandstones (Trias). These footprints consisted of a series of alternately placed pairs of hand-shaped impressions, the hinder print of each pair being much larger than the fore one. So like were AMPHIBIA. 233 these prints to the shape of the human hand that the unknown animal which had produced them was christened the “ Cheiro- therium” (Gr. cheir, hand; ther, beast). Further researches, however, showed that these footprints were produced by various species of large Amphibians, to which the name of Labyrinthodontia was applied, in consequence of the compli- cated microscopic structure of the teeth. These extinct Am- phibians are known to have existed at the time of the Coal, but they are most characteristic of the period known to geolo- gists as the Trias, SAUROPSIDA. CHAPTER XXVII. CLASS III. REPTILIA. ‘WE commence now the second great primary division of the Vertebrata, namely, that of the Sauropsida, comprising the Reptiles and the Birds. These two classes, though very unlike in external appearance, are united by the following characters: There are never at any period of life gills or bran- chie adapted for aquatic respiration; the red corpuscles of the blood are nucleated (Fig. 99, 0, c); the skull articulates with the vertebral column by means of a single articulating surface or condyle; each half of the lower jaw is composed of several pieces, and is jointed to the skull, not directly, but by the intervention of a special bone (the so-called “ quadrate bone”). Thee being the characters by which, among others, Rep- tiles and Birds are collectively distinguished from other Ver- tebrates, it remains to see what are the characters by which the Reptiles are distinguished, as a class, from Birds. In all Reptiles the blood is cold—that is to say, very slightly warm- er than the temperature of the external medium in which they live. The integument secretes scales, with or without bony plates, but in no case do the integumentary appendages take the form of feathers. The heart consists of two auricles, and a ventricle, which in most is partially divided into two cham- bers by an incomplete partition, and in a few is completely divided. In any case, however, more or less of the impure venous blood is mixed with the pure arterial blood which cir- culates over the body. There is no division between the cavi- ties of the thorax and abdomen, and the lungs are not con- nected with air-sacs placed in various parts of the body. The limbs may be wanting, or rudimentary, but in no case are the REPTILIA, 235 fore-limbs constructed upon the type of the “ wing” of birds, and in no living Reptile is there the bone which is known in Birds as the “ tarso-metatarsus.” The class Reptilia includes the Tortoises and Turtles ( Che- lonia), the Snakes ( Ophidia), the Lizards (Lacertilia), and the Crocodiles ( Crocodilia). With the exception of the Tortoises and Turtles, they are mostly of an elongated cylindrical form, furnished behind with a long tail. The limbs may be alto- gether absent or quite rudimentary, as in the Snakes, but in almost all the higher members of the class there are two pairs of limbs, which may be either adapted for walking or swim- ming, and which in some extinct forms support a flying mem- brane. The internal skeleton is always bony, never cartila- ginous or semi-cartilaginous as in many of the fishes. The skull is joined to the spine by a single articulating surface (or condyle). The lower jaw is complex, each half being com- posed of several pieces united by sutures. In Tortoises and Turtles, however, these separate pieces are amalgamated to- gether, and the two halves are also united, so that the whole lower jaw appears to form a single piece. In most Reptiles, on the other hand, the two halves of the lower jaw (Fig. 116) are only loosely united; in the Snakes by ligaments and mus- cles, in the Lizards by gristle, and in the Crocodiles by suture. ) my: TV Fia. 116.—Skull of a Serpent (Eyton). @ Quadrate bone; 6 Lower jaw, articulating with he movable quadrate bone. In all, the lower jaw is jointed to the skull by means of a special bone, called the “quadrate bone;” and as this often projects backward, the opening of the mouth is often very extensive, and may even extend backward beyond the base of the skull (Fig. 116, a). Teeth are generally present, but these are used chiefly to hold the prey, and not in biting or chewing 236 VERTEBRATE ANIMALS. the food. Except in the Crocodiles, the teeth are not sunk into distinct sockets, and they are usually replaced as fast as shed, They likewise do not differ. from one another sufficient- ly in form or function as to allow of their being divided into different sets, as they can be in the Mammals. Usually the teeth are confined to the jaws proper, but in some cases they are carried by other bones of the mouth. In the Tortoises and Turtles there are no teeth, and the jaws are ‘simply sheathed in horn, so as to constitute a kind of beak, like that of a bird. The integumentary skeleton is in the form of scales, sometimes combined with bony plates, In the Tor- toises and Turtles the integumentary skeleton is so united with the true skeleton as to form a kind of bony case or box, in which the body is enclosed. The digestive system presents little worthy of special no- tice, except that the termination of the intestine (rectum) opens into a cavity called the “cloaca,” which receives also the ducts of the urinary and generative organs. Itis, however, in the structure of the circulatory and respir- atory organs that the most important characters of the Reptiles are to be looked for. The heart in all Reptiles may be regarded as being, in function, three-chambered, being composed of two auricles and a single ventricle, imperfectly divided by an in- complete partition. In the Crocodiles alone the heart is, séruct- urally, four-chambered, the ventricle being divided into two by a complete partition. Here, however, the same results are brought about as in the other Reptiles, by means of a commu- nication which subsists between the great vessels which spring from the ventricles thus formed. In the ordinary Reptiles the course of the circulation is as follows (Fig. 117): The impure or venous blood that has circulated through the body is poured by the great veins into the right auricle (a). The pure or arterial blood that has been submitted to the action of the lungs is poured by the pulmonary veins into the left auricle (a'). Both auricles empty their contents into the rentricle, and, as the partition which divides the ventricle is an incom- plete one, it follows that the venous and arterial streams must mix to a greater or less extent in the ventricle. From the ventricle arise the great vessels which carry the blood to the lungs and to all parts of the body, and it follows, as a matter of necessity, that all these parts are supplied with a mixed fluid, consisting partly of impure or venous blood, and partly of pure or arterial blood. In the Crocodiles, in which there are two ventricles completely separated from each other, the REPTILIA. 237 same result is brought about by means of a communication which takes place between the great vessels which spring from the ventricles, in the imme- diate neighborhood of the heart. From this brief description it will be seen that the peculiarity of the circulation in Reptiles con- sists in the fact, that the lungs and all parts of the body are sup- plied with mixed blood; whereas in the higher Vertebrates the lungs are supplied with pure venous blood, and the various tis- sues of the body with pure arte- rial blood. As regards the structure of the lungs, it is merely to be notcu that there is no partition (dia- phragm or midriff) separating the two cavities of the thorax and abdomen, and that the lungs, therefore, often attain a great pro- portionate size, sometimes ex- tending through almost the whole length of the cavity of the trunk. ‘There are also no air-sacs commu- nicating with the lungs, as in the Birds. Lastly, all Reptiles are essen- tially oviparous, some being ovo- viviparous. The egg-shell is usu- ally parchment-like, but in other tases contains more or less cal- careous matter. Fic. 117.—Diagram of the circulation of a Reptile. a Right auricle, receivin, venous blood from the body; .a’ Le: auricle, receiving arterial blood from the lungs; v Arterio-venous ventri- ele, containing mixed blood, which is driven by (p) the pulmonary artery to the lungs, and by (0) the aorta to the body. (The venous system is left light, the arterial system is black, and the vessels containing mixed blood are cross-shaded.) The class Reptilia is divided into four living and five ex- tinct orders, as follows, but the latter require but brief notice: Ichthyopterygia . Sauropterygia . Pterosauria Anomodontia . Deinosauria OMIA IPw;WPE . Chelonia (Tortoises and Turtles). . Ophidia (Snakes). . Lacertilia (Lizards). . Crocodilia (Crocodiles). Extinct. CHAPTER XXVIII. DIVISIONS OF REPTILIA. Orper I. Cuetonia (Gr. chelone, a tortoise).—In this order are included the various Tortoises and Turtles, charac- terized by having the body enclosed in a bony case or box, and by the fact that the jaws are not provided with teeth, but are encased in horn, so as to form a kind of beak. The case in which the body of a Cheloniau is protected is composed partly of integumentary plates, and partly of flattened bones belonging to the true skeleton, and it is composed essentially of two pieces, one placed on the back and the other on the lower surface of the body, firmly united together at their edges, The dorsal shield is more or less convex and rounded, and is called the carapace (Fig. 118, ea) ; while the ventral shield is more or less completely flat or concave, and is called the plas- tron. The carapace and plastron, as just said, are united by their edges, but they leave two openings, one in front for the head, and one behind for the tail. The carapace is essentially composed of the flattened and expanded spinous processes of the vertebrae and the greatly-developed ribs, covered by a series of horny plates. These are growths of the integument, and in some cases they constitute the “ tortoise-shell” of com- merce. The plastron is also composed partly of bony and — partly of horny plates, but opinions differ as to whether the bony plates are to be looked upon as formed by an expanded breastbone, or whether they are merely integumentary, the probabilities being in favor of the latter view. The remaining peculiarities with regard to the skeleton which deserve special mention are: Firstly, that the dorsal vertebra are immovably connected together, so that this region of the spine is quite inflexible; secondly, that the heads of the ribs are articulated directly to the bodies of the vertebree ; and, DIVISIONS OF REPTILIA. 239 thirdly, that the scapular and pelvic arches, supporting respec- tively the fore and hind limbs, are situated within the carapace (Fig. 118, s and p), so that the shoulder-blade is placed inside the ribs instead of outside, as is usually the case. Fie. 118,—Skeleton of a Tortoise (Zmys Huropea), seen from below, the plastron_ having been removed. ca Carapace, showing the flattened and expanded ribs; s Scapular arch, carrying the fore-limbs, and placed in the interior of the carapace; p Pelvic arch, carrying the hind-limbs; 7 Ribs. The Chelonia are conveniently divided into groups, accord- ing as the limbs are adapted for swimming (natatory), or for progression on land (terrestrial); or, again, enable the animal to lead an amphibious life, sometimes on land and sometimes in the water. Of the strictly aquatic forms the best known are the edible Green Turtle (Chelonia midas) and the Hawk’s- bill Turtle (Chelonia imbricata), The former is found abun- dantly in many of the seas of warm climates, and is largely imported into Europe as a delicacy. The latter (Fig. 119) is truly a native of warm seas, though an occasional straggler has reached the shores of Britain. It is of comparatively small size—not more than about three feet in length—but is 240 VERTEBRATE ANIMALS. of considerable commercial importance, as it furnishes the “ tortoise-shell” of trade, so largely used in various kinds of ornamental work, cS Fig. 119—The Hawk-billed Turtle (Chelonia imbricata). (After Bell.) The Sea-tortoises or Turtles have the carapace much flat- tened, the legs of unequal length, in the form of solid fins or oars, the toes being conjoined, and hardly distinct from one another. The Marsh, Pond, and River Tortoises are generally fur- nished with webbed feet, and lead an amphibious, semi-aquatic existence. The so-called “ Soft Tortoises” (Zrionycide) be- long here, and are distinguished by the imperfect condition of the carapace, which is simply covered with a leathery skin. A good example is the Soft-shelled Turtle (Zi ferow) of the Southern States. Here also belong the Snapping-turtles, so well known in the person of the common American species (Chelydra serpentina), and the Terrapins (Emydide), of which many forms are found in all parts of the United States. In the curious little Box-tortoise (Cistuwdo Virginea) the plas- tron is composed of two movable portions which can be brought into accurate apposition with the carapace, thus com- pletely protecting the animal within. The Land Tortoises have short legs of nearly equal length, the toes little distinct, and united into a sort of stump, with indistinct, horny claws. Good examples of this group are the YW MS ree ve DIVISIONS OF REPTILIA. 241 common European Tortoise (Testudo Greca) and the Indian Tortoise (Z. Indica), the last attaining a length of over three feet. Orver JI. Oparpia (Gr. ophis, a serpent).—This order in- cludes most of the animals which would commonly be called snakes or serpents, and is characterized by the following pecu- liarities: The body is always more or less elongated, worm- like or cylindrical, and the skin develops horny scales, but never bony plates. There is never any breastbone (sternum), nor pectoral arch, nor fore-limbs; nor, as a rule, are there any traces of hind-limbs. In a few cases, however, rudimentary hind-limbs can be detected. The ribs are always very numer- ous. The two halves of the lower jaw are composed of several pieces each, and they are united to one another in front only by ligaments and muscles (Fig. 120). Hooked, conical teeth Fig. 120.—The Waja Haje, » poisonous Snake of Egypt. are always present, but they are never lodged in distinct sockets, and are only used to hold the prey, and not in masti- cation. The lungs and other paired organs are often not sym- metrical, one of each pair being usually smaller than the other, or altogether absent. 242 VERTEBRATE ANIMALS. The most striking of these characters of the snakes is to be found in the nature of the organs of locomotion. The fore-limbs are invariably altogether wanting, and there is no pectoral arch nor breastbone; and the hind-limbs are either totally absent or are at best rudimentary and never exhibit any outward evidence of their existence, beyond the occasion- al presence of short, horny claws or spurs. In the entire ab- sence, then, or rudimentary condition of the limbs, the snakes progress by means of the ribs, which are always excessively numerous, and, in the absence of a breastbone, are also ex- tremely movable. Their free ends, in fact, are simply attached by muscular fibres to the scales or “scutes,” which cover the lower or abdominal surface of the animal. The number of ribs varies from 50 up to 320 pairs, and, by means of this arrangement, the snakes are able to progress rapidly, walking, as it were, upon the ends of the ribs. Their movements are also much assisted by the extreme flexibility of the whole spine, caused by the cup-and-ball articulation of the bodies of the vertebree, each of which is concave in front and convex behind (procclous). Of the other characters of the snakes, a few words may be said as to the tongue, the eye, and the teeth—all important structures in this order. The tongue, in serpents, is probably more an organ of touch than of taste, and consists of two muscular cylinders, which are united toward their bases. The forked organ thus formed can be protruded and retracted at will, being in constant vibration when protruded, and being in great part concealed by a sheath when retracted. The eye of serpents (Fig. 121, A) is not protected by any eyelids, and hence the peculiar stony and unwinking stare for which these reptiles are celebrated. In place of eyelids, the outer layer of the skin is prolonged over the eye as a continuous and transparent film, behind which is a chamber formed by the mucous covering of the eye, into which the tears are dis- charged. -The outer membrane is periodically shed along with the rest of the external or epidermic layer of the integument, and is again renewed. The pupil is round in most serpents, but it forms a vertical slit or fissure in the venomous snakes and in the Boas. As regards the teeth, it is to be noticed that the snakes are not in the habit of chewing their prey, but of swallowing it whole, and the construction of their dental apparatus is in accordance with this peculiarity. The lower jaw, as before said, articulates with the skull by means of a quadrate bone DIVISIONS OF REPTILIA. 243 (Fig. 117), and this in turn is movably jointed to the cranium. The two halves of the lower jaw are also merely united loosely in front by ligaments and muscles. In consequence of this peculiar arrangement of parts, the serpents have the power of opening the mouth to an extraordinary width, and they can perform the most astonishing feats in the way of’ swallowing. The teeth are simply fitted for seizing and hold- ing the prey, but not in any way for chewing or dividing it. In the harmless snakes, the teeth are in the form of solid cones, which are arranged in rows round the whole of the upper and lower jaws, a double row existing on the palate as well. In the venomous snakes, on the other hand, the ordinary teeth are usually wanting upon the upper jaws, and these bones are themselves much reduced in size. In place of the ordinary teeth, however, the upper jaws carry the so- called “ poison-fangs” (Fig 121,B). These are a pair of long, Fie. 121.—A, Diagrammatic Section of the Eye of a Viper (after Cloquet). @ Eyeball; } Optic nerve ; ¢ Chamber into which the tears are poured; @ Epidermic layer covering the eye. B, Head of the common Viper (after Bell), showing the poison-fangs. curved fangs, one on each maxilla or upper jawbone, which, when not in use, are pointed backward, and concealed in a fold of the gum, but can be raised at will by special muscles. Each tooth is perforated by a fine canal or tube, which opens by a distinct aperture at the point of the fang, and is connect- ed with the duct of the “poison-gland.” This is a gland, situated under and behind the eye, secreting the poisonous fluid which renders the bites of these snakes dangerous or fatal. When the serpent strikes at any animal, the poison is forced through the poison-fang into the wound, partly by the contractions of the muscular walls of the gland, and partly by the compressive action of the muscles of the jaws. In some other snakes, several of which are not certainly known to be 244 VERTEBRATE ANIMALS. venomous, there are large, grooved fangs placed far back in the mouth upon the upper jaw. Of the non-venomous, harmless snakes, we have an excel- lent instance in the common Ringed Snake (Coluber natriz), which is of frequent occurrence in most parts of Europe. Like all the snakes, it is strictly carnivorous, having a special liking for frogs, which it swallows whole. It often takes to the water, and can swim rapidly and gracefully, though, in this respect, it is excelled by the true venomous water-snakes (Hydrophide), which are adapted to an aquatic life by having a compressed swimming-tail. A well-known American exam- ple of this group is the common Black Snake (Bascanion constrictor). It attains a length of from three to five feet, but is perfectly harmless so far as man is concerned, Other non- venomous snakes, such as the Boas and Pythons, though des- titute of poison-fangs, are, nevertheless, highly dangerous and destructive animals, Their bite is harmless, and they seize their prey by coiling themselves round it in numerous folds. By gradually tightening these folds, they reduce their victim to the condition of a shapeless bolus, which they finally pro- ceed to swallow whole. In this way, a large Python or Boa will certainly succeed in disposing of an animal as large asa sheep or calf, and it has been asserted that human beings, and even oxen, can also be swallowed by unusually large specimens of this family. The Boas and Pythons have a horny spur on each side of the vent, and the tail is prehensile. Their dental apparatus is extremely powerful, giving them a firm hold for the constric- tion of their prey. They are the largest of all the serpents, attaining a length of thirty to forty feet. The true Boas and Anacondas belong to the New World, but the Pythons are confined to India, Africa, and the Indian Archipelago. The poisonous snakes are represented by the Crotalide of the New World and the Viperidw of the Old World. The common Rattlesnake (Crotalus horridus) of the United States has the extremity of the tail furnished with a “rattle” or horny appendage composed of several membranous cells of a pyramidal shape articulated one within the other. Before striking its prey, it throws itself into a coil, and shakes its rattle. Another highly-dangerous species is the Copperhead ee ee contortriz), The common European viper Pelias berus) is hardly fatal to adults, but its bite causes serious inflammation, Highly deadly, however, is the Cobra di Capello or Spectacled Snake (Naja tripudians) of India, as DIVISIONS OF REPTILIA. 245 also is the nearly-allied Waja haje (Fig. 120) of Africa. Oth- er venomous snakes of evil notoriety are the Death-adder (Acanthophis tortor) of Australia, the Puff-adder ( Vipera in- fiata) of South Africa, the Horned Viper (Cerastes cornutus) of Egypt, and the Harlequin-snakes (Z/aps), but many others are equally dangerous. Orver IIT. Lacerrimia (Lat. lacerta, a lizard).—The third order of reptiles is that of the Lacertilia, comprising all the ani- mals which are properly known as Lizards, together with some snake-like creatures, such as the Blind-worm. They are distin- guished by the following characters : Usually there are two pairs of well-developed limbs, but there may be only one pair, or all the limbs may be rudimentary. In all cases, however, a scapular arch is present. The vertebre are usually hollow in front (proccelous), rarely hollow at both ends (amphiceelous). In no living Lacertilian are the teeth lodged in distinct sockets. The eyes are mostly furnished with movable eyelids. As a general rule, the animals included under this head have four well-developed legs, and would, therefore, be popu- larly called “ Lizards.” Some of them, however, such as the common Blind-worm (Anguis fragilis) of Europe, exhibit no external indications of limbs, and would, therefore, be generally regarded as Snakes. These snake-like Lizards, however, can be distinguished from the true Ophidians by the consolidation of the bones of the head and jaws, and by the fact that the eyes are generally provided with movable eyelids. Dissection also shows that the shoulder-girdle (or scapular arch) is always present in a rudimentary condition. Of the snake-like Lizards, a good example is to be found in the common Blind-worm or Slow-worm of Europe. It is completely serpentiform, without any external indications of limbs (Fig. 122), and it is quite harmless. It is remarkable for the fact that, when alarmed, it stiffens its muscles to such an extent that the tail can readily be broken off, as if it were brittle. This same brittleness exists in the Glass-snake ( Ophi- saurus ventralis) of the Southern States, in which also there are no limbs. In other allied genera, there may be fore-feet alone, or hind-feet may be present, or all four limbs exist in a more or less rudimentary condition. In the true Lizards (Lacerta), all four limbs are present in a well-developed form; as seen in the common Green Lizard (L. viridis) of Europe. The genus Lacerta is represented in America by the Ameiva, of which the Striped Lizard (Ameiva sex-lineata) of the Southern 246 VERTEBRATE ANIMALS. States may be taken as a good example. Of all living Lizards, the largest are the Monitors ( Varanide,) which are exclusively confined to the Old World, and attain sometimes a length of from six to eight feet. Very large, too, are some of the Fic. 122,—Blind-worm (Anguis fragilis). (After Bell.) Iguanas which occur in warm regions in various parts of the world, but especially in South America, where they are often eaten. Related to the Iguanas are the singular Lizards known as the Flying Dragons (Draco volans), various species of which inhabit the Indian Archipelago and the East Indies, They are all of small size, living in trees and feeding on in- sects ; and their great peculiarity consists in the fact that cer- tain of the ribs are straightened out, and support a wing-like fold of the skin on each side of the body, by means of which the animal can take very extensive leaps from tree to tree. The Scincoid Lizards form a very large family, represented by numerous species in all parts of the world. The species figured below is a common form in Egypt and Arabia, and was formerly used as a remedy in various diseases. A nearly- allied species is the Blue-tailed Lizard (Scincus fasciatus) of the United States. The Geckos (Geckotide) form a large group of night-lov- ing Lizards, which are found in most parts of the world, and DIVISIONS OF REPTILIA. 247 chiefly deserve notice from the fact that their eyes are not pro- vided with movable eyelids. The Chameleons, also, cannot be said to possess movable eyelids, for the eye is covered with Fic. 123.—The Skink (Setnous officinalis) a single lid, leaving only a central aperture for the pupil. The common species (Chameleo Africanus) occurs abundantly in the north of Africa, and has long been known for the changes of color which it has the power of exhibiting. It isa sluggish animal, and catches insects by darting out its long and pro- trusible tongue with extreme rapidity. Orvrr IV. Crocopriia.—The last and highest order of the living Reptiles is that of the Crocodilia, comprising the Crocodiles, Alligators, and Gavials, and characterized by the following peculiarities: The outer or integumentary skeleton consists partly of horny scales developed by the outer layer of the skin, and partly of large bony plates produced by the inner layer of the skin. The bones of the skull and face are firmly united, and the two halves of the lower jaw are joined by a distinct suture. The teeth form a single row in both jaws, and are implanted in distinct and separate sockets. The front ribs of the trunk are double-headed, and there are no collar-bones. The heart consists of four distinct chambers, two auricles and two ventricles, all completely separated from 248 VERTEBRATE ANIMALS. one another. The mixture of arterial and venous blood, how- ever, which is so characteristic of Reptiles, is provided for by a communication between the great vessels which spring from the two ventricles in the immediate neighborhood of the heart, The eyes are protected by movable eyelids, and the ear by a movable earlid. The tongue is large and fleshy, and is im- movably attached to the bottom of the mouth (hence the be- lief of the ancients that the Crocodile had no tongue). Lastly, the Crocodilia agree with the typical Lizards, and differ from the Snakes in having four well-developed limbs. Fic. 124—Ifead and fore-part of the body of the common Crocodile (Crocodilus vulgaris). The Crocodilia abound in the fresh waters of hot climates, and are the largest of all living Reptiles, not uncommonly at- taining a length of sixteen feet or upward. The best known of the Crocodilia is the Nilotic Crocodile, which occurs abun- dantly in Egypt, and was described by both Herodotus and Aristotle. The true Crocodiles have the feet completely webbed, the hind-legs bordered by a fringe, and the fourth tooth in the lower jaw received in a notch on the side of the upper jaw. They belong mainly to Africa and Asia, but they are also rep- resented in the West Indies and in South America. The Alligators have the hind-legs simply rounded, and the toes not completely webbed; while the fourth tooth in the lower jaw fits into a cavity in the palate, and is concealed from view when the mouth is shut. Like the Crocodiles they are essentially aquatic in their habits, and lie dormant during the winter in cold climates and the hot season in warm coun- tries. They are extremely voracious, and live upon fish and small Mammals. The best-known species are the common Alligator (A. Mississippiensis) of the Southern States, the Caiman (A. palpebrosus) of Surinam and Guiana, and the “Jacaré” (A. sclerops) of South America. The Gavial or Gangetic Crocodile occurs in India, and is DIVISIONS OF REPTILIA. 249 distinguished by its narrow, elongated jaws, forming a kind of beak, It attains a length of more than ten feet. Oxprr V. Icutuyvorreryera (Gr. ichthus, fish; pterua, wing).—In this order are included a number of gigantic, fish- like Reptiles, which are all extinct, and are characteristic of the Secondary period of geology, and especially of the forma- tion known as the Lias. The chief characters by which they are distinguished have reference to their purely aquatic life, for there can be no doubt that they were inhabitants of the sea, Thus the body was fish-like, without any distinct neck. The vertebrae were hollow at both ends (amphicclous), and the spine thus possessed the flexibility and power of motion so characteristic of the true fishes. The limbs also consti- tuted powerful swimming-paddles (Fig. 125), and it is proba- ble that there was a vertical tail-fin. Much has been gathered from various sources as to the habits of the Ichthyosaurt, and their history is one of the most interesting chapters in the geological record. That they chiefly kept to open seas may be inferred from their strong and well-developed swimming apparatus; but the presence of a powerful bony arch supporting the forelimbs proves that Fig. 125.—Ichthyosaurus communis. they must have occasionally betaken themselves to the land. That they were tenants of stormy waters, or were in the habit of diving in search of prey, has been inferred from the fact that the eyeball is protected from pressure by a ring of bony plates. That they possessed great powers of vision, espe- cially in the dusk, seems to be rendered certain from the size of the pupil and the enormous width of the bony cavities (orbits) which contained the eyes. Lastly, that they were carnivorous and predacious in the highest degree is shown by their wide mouths, long jaws, and numerous powerful and pointed teeth. This is also proved by an examination of their petrified droppings, which are known as “coprolites,” and which contain in abundance undigested fragments of fishes and other marine animals. 250 VERTEBRATE ANIMALS. Orver VI. Savropreryera (Gr. saura, lizard; pteruz, wing).—The Reptiles belonging to this order agree with the last in being all extinct, and in being confined to the Sedond- ary period of geology. The best known are the Plesiosauri, which resembled the Jchthyosauri in having all the limbs con- verted into swimming-paddles, but differed in several respects, of which the most obvious is the great elongation of the neck (Fig. 126). The Plesiosauri were gigantic marine Reptiles, Fie. 126.—Plesiosaurus dolichodeirus, chiefly characteristic of the formations known as the Lias and Oolites. As regards the habits of the Plesiosaurus, Dr. Cony- beare concludes: “That it was aquatic is evident from the form of its paddles ; that it was marine is almost equally so from the remains with which it is universally associated; that it may have occasionally visited the shore, the resemblance of its ex- tremities to those of the Turtle may lead us to conjecture; its movements, however, must have been very awkward on land; and its long neck must have impeded its progress through the water, presenting a striking contrast to the organization which so admirably fits the Ichthyosaurus tv cut through the waves.” As its breathing-organs are such that it must of ne- cessity have required to obtain air frequently, it may be in- ferred “that it swam upon or near the surface, arching back its long neck like a swan, and occasionally darting it down at the fish which happened to float within its reach. It may per- haps have lurked in shoal-water along the coast, concealed among the sea-weed, and, raising its nostrils to a level with the surface from a considerable depth, may have found a se- cure retreat from the assaults of powerful enemies; while the length and flexibility of its neck may have compensated for the want of strength in its jaws and its incapacity for swift motion through the water.” _ Orver VII. Prerosavria (Gr. pteron, wing; saura, lizard).—The Reptiles of this order are all extinct, and, like those of the preceding orders, are exclusively confined to the DIVISIONS OF REPTILIA. 251 Secondary period of geology. The most familiar examples are the so-called Pterodactyles, and the distinguishing charac- ters of the order have reference to the fact that they were all adapted for an aérial life, They present, in fact, an extraor- dinary combination of the characters of birds and reptiles, and they make also some approach to the Mammalian order of the Bats. In the presence of teeth in distinct sockets, and, as we shall see hereafter, in the structure of the fore-limbs, the Pterodactyles differ altogether from all known birds; and there can be little doubt as to their being genuine Reptiles. The only living Reptile which has any power of sustaining itself in'the air is the little Draco volans, which has been pre- viously mentioned. In this case, however, the animal has no power of true flight, but is simply enabled to take extensive leaps by means of a membranous expansion on each side of the body. In the Bats, again, the power of genuine flight is present; and this is given by means of a leathery membrane which is supported chiefly by certain of the fingers—which are greatly lengthened—and is attached to the sides of the body and hind-limbs. In the Pterodactyles the power of true flight was present, and this was also conditioned by means of a leathery expand- ed membrane, attached to the hind-limbs, the sides of the body, and the fore-limbs. In this case, however, the chief support of the flying membrane was derived from the outer- most finger of the fore-limb, which was enormously elongated (Fig. 127). That the Pterodactyles passed their existence Fig. 127.—Pterodactylus brevirostris, the skeleton and the animal restored. chiefly in the air, and did not simply leap from tree to tree, is shown by two characters in which they agree with the flying 252 VERTEBRATE ANIMALS. birds. Many of the bones, namely, were “ pneumatic ”—that, is to say, were hollow and were filled with air, thus giving the animal the degree of lightness necessary for flight.. Secondly. while the shoulder-girdle has many of the characters of birds, the breastbone (sternum) is furnished with a prominent ridge or keel, serving for the attachment of the great muscles which work the wings. There can be no doubt, therefore, as to the Pterodactyles having enjoyed the power of genuine flight, ' Many of them attained no great size, but some of them must have been gigantic, the expanse of wing in one species having been calculated at probably about twenty-seven feet from tip to tip. Orper VIII. Anomopontia (Gr. anomos, irregular; odous, tooth).—This order comprises a few Reptiles which be- long to the Triassic period of geology, and are distinguished by the fact that the jaws were sheathed in horn, so as to form a kind of beak very like that of the Turtles. In some species there appear to have been no teeth at all; but in one genus there were two long tusks, one on each side of the upper jaw. The limbs were fitted for walking and not for swimming, and these singular Reptiles must, therefore, have been terrestrial in their habits. Orver IX. Derosauria (Gr. deinos, terrible; saura, lizard).—In this order are included a number of extinct Rep- tiles, most of which were of gigantic size, and which are con- fined to the Secondary period of geology. They possessed teeth, sunk in distinct sockets, and the limbs were extremely strong, and adapted for progression on land. In some cases the fore-limbs were very much smaller than the hind-limbs, and there is reason to suppose that some of these extraordi- nary animals, though of enormous size, walked habitually upon their hind-legs, like Birds. It is also interesting to note that the gigantic footprints of the Sandstones of the Connecti- cut Valley, formerly regarded as formed by Birds, are now with great probability looked upon as truly the tracks of Dei- nosaurian Reptiles. CHAPTER XXIX. CLASS IV.—AVES. Tus fourth class of the Vertebrates is that of the Birds or Aves, which may be shortly defined as being “ oviparous Ver- tebrates, with warm blood, a double circulation, and a cover- ing of feathers” (Owen). The other leading characters which separate the Birds from the other Vertebrata are that the red blood-corpuscles are nucleated, the skull articulates with the spine by a single articulating surface (or condyle), the breath- ing-organs are in the form of lungs, which communicate with a variable number of air-sacs scattered through the body, and the fore-limbs are never terminated (in existing birds) by more than two fingers, ending in claws, and are generally modified so as to form “ wings” or organs of flight. The feathers, which form such a distinctive character of birds, are formed by a modification of the outer layer of the skin (epidermis), and from their non-conducting nature they serve to maintain the high temperature of the body which is so characteristic of the class. A typical feather, such as one of the long feathers of the tail or wing, consists of the follow- ing parts: 1. A horny cylindrical tube, which forms the lowest portion of the feather, and is termed the “quill.” 2. The “ shaft,” which forms the central axis of the feather, and which is simply the continuation of the “quill.” The under surface of the shaft is always marked by a strong longitudinal groove, and it consists of a horny sheath, filled with a white spongy material, not unlike the pith of a plant. 3. The “webs,” which form the lateral expansions of the feather, and are attached to the sides of the shaft. Each web is composed of a number of small branches, called the “barbs,” and each barb, in turn, is furnished with a series of smaller fibres called the “ bar- bules.” Asa ale, the barbs are all kept in connection with 254 VERTEBRATE ANIMALS. one another by means of the barbules, the ends of which are hooked. Toward the base of the shaft, however, the barbs are usually more or less separate and placed at a distance from one another, constituting what is known as the “down.” In the Ostriches and the birds allied to them, all the barbs are disunited and placed at a distance, and they are often not at all unlike hairs in appearance. The feathers of birds not onl greatly conduce to the high temperature of the body, but also serve to keep out moisture, to which end there is a peculiar oil-gland at the base of the tail, with the secretion of which the bird anoints its plumage. The skeleton of birds exhibits many points of peculiar interest, mostly in adaptation to an aérial mode of life; but only some of the more important of these can be noticed here, The entire skeleton is at the same time peculiarly compact and singularly light, the compactness being due to the pres- ence of an unusual quantity of phosphate of lime, and the lightness to the fact that many of the bones are filled with air in place of marrow. The cervical region (neck) of the verte- bral column is unusually long and flexible, since the fore-limbs are useless as organs of prehension, and all these functions have to be performed by the beak. In all birds the neck is, at any rate, sufficiently long to allow of the application of the beak to the tail, so as to permit of the cleaning and oiling of the whole plumage. The vertebrae which form the back or dorsal region of the spine are generally more or less immov- ably connected together, so as to give a base of resistance to the wings. In the Ostrich, however, and in other birds in which the power of flight is either very limited or is absent, the dorsal vertebrae are more or less movable one upon the other. The vertebrae which follow the dorsal region of the spine are all amalgamated together to form a single bony mass, which is termed the “sacrum,” and this, in turn, is united on both sides with the bones which form the pelvic arch, which carries the hind-limbs. The vertebra of the tail are more or less movable upon one another; and in almost all living birds, when fully grown, the last joint of the tail (Fig. 129, B, s) is a long, slender, ploughshare-shaped bone, which is really composed of several vertebree united together. It is usually set on at an angle nearly perpendicular to the axis of the body, and it serves to support the great tail-feathers, which act as a rudder during flight. It also serves to support the oil-gland, which supplies the secretion with which the feathers are lubricated. The skull in birds has its several AVES. 255 bones generally so amalgamated in the adult, that it forms a bony case of a single piece, the lower jaw alone remaining movable. The head is jointed to the spine by no more than a single articulating surface or condyle. The beak, which forms such a conspicuous feature in birds, is composed of two halves, an upper half or “upper mandible,” and a “lower mandible.” The lower mandible, like the lower jaw of all the Sauropsida, is at first composed of several pieces, but these are all undistinguishably united in the adult, and the two halves of the jaw are also amalgamated together. In no adult bird are teeth ever developed in either mandible; but both mandibles are sheathed in horn, constituting the “beak,” and the margins of this sheath are sometimes serrated. The most characteristic points, however, in the skeleton of the birds, are to be found in the structure of the limbs. The cavity of the chest or thorax is bounded behind by the dorsal vertebree, on the sides by the ribs, and in front by the breast- bone or sternum. The ribs vary in number from seven to eleven pairs, and in most birds each rib gives off a peculiar process (Fig. 128, B), which passes over the rib next in suc- cession behind. In front the ribs are jointed to a series of straight bones, which are called the “sternal ribs,” and these, in turn, are movably articulated to the breastbone in front, According to Owen, these sternal ribs are “the centres upon which the respiratory movements hinge.” In front the cavity of the chest is completed by an enormously-expanded breast- bone or sternum (Fig. 128, A), which, in most birds of any powers of flight, extends more or less over the abdominal cavity as well. The sternum of all birds which possess the power of flight is characterized by the presence of a prominent ridge or “keel” (Fig. 128, A, 5), to which are attached the great muscles (pectoral muscles) which move the wings. As a general rule, the size of this crest or keel gives a tolerably just estimate of the flying powers of the bird to which it be- longed. The keel is, of course, most largely developed in those birds which possess the power of flight in its greatest perfection ; and in those which do not fly, such as the Ostrich, there is no sternal keel at all. The pectoral arch or shoulder- girdle of birds consists of the shoulder-blades (scapulc), the clavicles or collar-bones, and of two bones, which are distinct in birds, and are called the “coracoid bones.” The shoulder- blades (ss) are usually long and narrow bones. The coracoid bones (4) correspond with the part of the shoulder-blade which is known in most of the Mammals as the “coracoid 256 VERTEBRATE ANIMALS. Tic. 128.—A, Breastbone, shoulder-girdle, and fore-limb of Penguin (after Owen); } Breast- bone (sternum), with its prominent ridge or keel; ss Shoulder-blades (scapula); kk Coracoid bones; ¢ Furculum or Merry-thought, composed of the united collar-bones (clavicles); h Bone of the upper arm or humerus, r Radius; uv Ulna, formi nee the forearm; g Bones of the wrist or carpus; t Thumb; m Metacarpus; p ges Pa ee ae B, Ribs of the Golden Eagle; aa Ribs giving off processes (00); ce ternal ribs. process ;” and in birds they are not only separate bones, but they are the strongest bones of the pectoral arch. They are more or less nearly vertical, and they form fixed points for the downward stroke of the wing. The collar-bones or clavi- cles (c) in the great majority of birds are united together in front, so as to form a somewhat V-shaped bone, which is tech- nically called the “furculum,” but is familiarly called the “merry-thought.” The function of this clavicular arch is to keep the wings asunder during their downward stroke, and the strength of the furculum varies, therefore, with the powers of flight enjoyed by each bird. The bones which form the limb proper, or “ wing,” are considerably modified to suit the special function of flight, but essentially the same parts are present as in the fore-limb of the Mammals. The upper arm is constituted by a single bone, the humerus (h), which is gen- erally short and stout, The forearm is composed of two bones, the radius (r) and the ulna (u), of which the ulna is the bigger. These are followed by the small bones, which AVES. 257 form the wrist or carpus (g), but these are reduced to two in number. ‘The carpus is followed by the bones which con- stitute the root of the hand or metacarpus (m), but these are also reduced to two, instead of being five in number, as they are in most Mammals, The two metacarpal bones are also amalgamated together at both ends, so as to form a single piece, at the base of which, on its outer side, is a rudimentary digit, the “thumb” (é), which carries a tuft of feathers, known as the “bastard wing.” The metacarpal bones, finally, sup- port each a single finger (p), of which one is never composed of more than one bone or phalanx, while the other is com- posed of two or three phalanges. (To understand thoroughly the leading modifications of the limbs of birds, the student will do well to refer to the general description of the limbs of Vertebrates, p. 200, Figs. 96, 917.) As regards the composition of the hind-limb in birds, the two halves of the pelvic arch (i.¢., the innominate bones) al- Fia. 129.—A, Pelvis and bones of the Leg of the Loon or Diver (after Owen): i Innominate bone; f Thigh-bone (femur); ¢ Tibia, 7 fibula, together forming the shank; m Tarso- metatarsus; p Phalanges of the toes. B, Tail of the Golden Eagle; s Ploughshare- shaped bone, carrying the great tail-feathers. 258 VERTEBRATE ANIMALS. ways form a single piece each, and they are always firmly united with the sacral region of the spine. With the single exception, however, of the Ostrich, they do not unite below but remain separate. As in the higher Vertebrates, the lower limb consists of a thigh-bone (femur), a shank, composed of two bones (¢ibéa and jibula), a tarsus, a metatarsus, and pha- langes, but some of these parts are obscured by coalescence, The thigh-bone or femur (Fig. 129, 7) is generally very short. comparatively speaking; and the chief bone of the leg is the tibia (t), to which a thin and tapering fibula (r) is attached, In the regular typical limb of a Vertebrate animal the tibia and fibula would be followed by a series of small bones, called the éarsus, constituting the ankle-joint (Fig. 97); and the tar- sus would in turn be followed by a series of bones constituting the root of the foot, or metatarsus. In Birds, however, the tibia and fibula are followed by a single cylindrical bone, which is called the “tarsc-metatarsus” (m), and which is formed by the amalgamation of the entire metatarsus with the whole or a portion of the tarsus. The most probable view is that only the dower portion of the tarsus is present in the tarso-metatarsus, and that the upper portion of the tarsus is fused with the lower end of the tibia. In this case the ankle- joint is placed in the middle of the tarsus. The tarso-meta- tarsus is followed below by the foot, which consists in most birds of four toes, of which three are directed forward and one backward. In no wild birds are there more than four toes; but some domesticated varieties possess a fifth. In most birds with four toes, the toe which is directed backward consists of two phalanges; the innermost of the three forward toes has three phalanges, the next has four, and the outer- most toe is composed of five. In many birds, such as the Parrots, the outermost toe is turned backward, so that there are two toes in front and two behind. In the Swifts, again, all the four toes are turned forward. In many of the swim- ming-birds (Vatatores) the hinder toe is wanting or rudimen- tary; and in the Ostrich both this and the next toe are ab- sent, so that the foot consists of no more than two toes. The digestive system in Birds consists of the beak, tongue, gullet, stomach, intestine, and cloaca, with certain accessory glands. There are no teeth, and the beak is employed, in dif ferent birds, for holding and tearing the prey, for prehension, for climbing, and in some cases as an organ of touch, being in these last instances more or less soft, and supplied with nervous filaments. In many birds, too, the base of the bill is AVES. 259 surrounded by a circle of naked skin, constituting what is called the “cere,” and this, too, serves as an organ of touch. The tongue of birds can rarely be looked upon as an organ of taste, since it is generally cased in horn, like the mandibles, It is principally employed as an organ of prehension, but it is soft and fleshy in the Parrots, and in them, doubtless, acts as an organ of taste. Salivary glands are always present, but they are rarely of large size, and are often of extremely simple structure. In accordance with the length of the neck, the gullet is usually very long in birds, and is generally very di- latable. In the flesh-eating and grain-eating birds the gullet is dilated (Fig. 130, c) into a pouch which is called the Fig. 130.—Digestive System of the common Fowl (after Owen). o Guillet; ¢ Crop; p Pro- ees g Gizzard; sm Small intestine; & Intestinal ceea; 2 Large Taezotine: aca. “crop,” and is situated in the lower part of the neck, just in front of the merry-thought. This may be simply a dilatation of the tube of the gullet, or it may be a single or double pouch. The function of the crop is to detain the food, for a longer or shorter period, according to its nature, before it is submitted to the action of the proper digestive organs. In the Pigeons, the food which has been previously softened in the 260 VERTEBRATE ANIMALS, crop is returned to the mouth, and supplied to the young in a state suitable for digestion. The gullet, after leaving the crop, shortly opens into a second cavity, called the “ proven- triculus,” which is the true digesting stomach, and is richly supplied with glands which secrete the digestive fluid or gas- tric juice (py). This, in turn, opens into a muscular cavity which is called the “ gizzard” (g), and which leads into the commencement of the small intestine. The characters of the gizzard vary with the nature of the food. In the birds of prey, which live on a easily-digested animal diet, the walls of the gizzard are thin and membranous. In the grain-eating birds, such as the fowls, whose hard food requires to be crushed before it can be properly digested, the walls of the gizzard are extremely thick and muscular, and the inner lin- ing is hard and horny. In these birds the gizzard constitutes a kind of grinding apparatus, like the stones of a mill; while the “crop” may be compared to the “hopper” of the mill, since it supplies to the gizzard “small successive quantities of food as it is wanted (Owen). The grinding action of the gizzard is further assisted by the small pebbles and gravel which, as is well known, so many birds are in the habit of swallowing. These pebbles take the place of teeth, and there can be no doubt that they are in many cases essential to health, the bird being otherwise unable to triturate its food properly. The intestinal canal extends from the gizzard to the cloaca (cl), and is comparatively short. The secretions of the liver and pancreas are poured into the commencement of the small intestine. The commencement of the large intestine is furnished in most birds with two blind tubes or ceca (f). These vary considerably in length in different birds, and are sometimes wanting; while their exact function is still ques- tionable. The large intestine is seldom more than a tenth part of the length of the body, and is generally conducted straight from the ceca to the cloaca. The cloaca is a com- mon cavity which in birds, as in Reptiles, receives the termi- nation of the intestine and the ducts of the generative and urinary organs (cl). Respiration is effected in Birds more completely, exten- sively, and actively, than in any other class of the Vertebrata, and, as the result of this, their average temperature is higher than in any other Vertebrates. This extensive development of the respiratory process is due to the fact that air is admit- ted in Birds not only to the lungs, but also to the interior of a greater or less number of the bones, and to a series of air- AVES. 261 receptacles which are scattered through various parts of the body. The lungs are two in number, of a bright-red color, and spongy texture, and they are confined to the back part of the chest. They differ from the lungs of Mammals in not being freely suspended in a membranous bag (pleura), but in being fixed to the back wall of the chest. The thoracic and abdominal cavities are not separated from one another by a complete partition (midriff or diaphragm) as the Mammals, but the common thoracico-abdominal cavity is subdivided by means of membranous partitions into a series of cavities or sacs, which are termed the “air-receptacles.” These air-sacs are filled with air from the lungs, and vary considerably in number and size in different birds. They not only serve greatly to reduce the specific gravity of the body, but also assist largely in the aération of the blood. Connected with the air-receptacles, and supplementing their action in both of these respects, is a series of cavities occupying the interior of a greater or less number of the bones, and also containing air. In young birds these air-cavities in the bones do not exist, and the bones are simply filled with marrow, as in the Mammals. In the Pen- guin, which does not fly, none of the bones contain air-cavities or are “pneumatic;” and in the Ostrich only a few of the bones contain air. In the Pelican and Gannet all the bones of the skeleton, except the phalanges of the toes, are per- meated by air; and in the Hornbill even these are pneu- matic. ; The heart in all birds consists of four chambers, and the two sides of the heart are completely separated from one another. In all essential details, as regards the structure of the heart and great vessels, and the course of the circulating fluid, Birds agree with Mammals. The impure venous blood which has traversed the body is returned by the great veins to the right auricle. From the right auricle it passes into the right ventricle, from which it is driven by the pulmonary artery to the lungs. Having been submitted to the action of the air contained in the lungs, and having been thereby changed into arterial blood, the blood is sent back to the left auricle by means of the pulmonary veins. Thence it passes into the left ventricle, by which it is again propelled throughout the whole body, to return again as venous blood to the right side of the heart. The heart, therefore, of birds, differs from that of reptiles in consisting of two sides, each composed of an auricle and ventricle, the right side being wholly concerned with sending the venous blood to the lungs, and the left side 262 VERTEBRATE ANIMALS. being entirely occupied with sending the arterial blood to the body. The right side of the heart is therefore venous, the left side arterial. In all Reptiles, on the other hand, the two cir- culations—namely, that through the lungs and that through the body—communicate with one another, either in the heart itself or in its immediate neighborhood ; so that both the lungs and the body are supplied with a mixture of venous with arte- rial blood. Though the heart of Birds resembles that of Mam- mals in general structure, its cavities are “ relatively stronger, their valvular mechanism is more perfect, and the contractions of this organ are more forcible and frequent in Birds, in ac- cordance with their more extended respiration and their more energetic muscular actions” (Owen). The urinary organs of birds consists of two elongated kidneys, which open by means of their ducts (the ureters) into the cloaca, along with the ter- mination of the intestine and the ducts of the reproductive organs. Asa general rule, the female bird is provided with only a single ovary—that of the left side—and all birds, with- out exception, are oviparous, The egg is always enclosed in a calcareous shell, and is developed after expulsion from the body, by the process of “incubation” or “ brooding ”—a pro- cess for which birds are especially adapted, in consequence of their very high average temperature. The young bird, when ready for an independent existence, perforates the shell, often by means of a temporary calcareous excrescence developed upon the point of the upper mandible of the bill. In some birds, mostly in the case of those which live upon the ground, the young are able to run about and look for food directly after they come out of the egg, as is seen in the common Fowl. In most birds, however, the young are liberated from the egg in a perfectly helpless and naked condition, aud re- quire to be fed by their parents for a longer or shorter time, before they are able to take care of themselves. Most of these birds, such as our common song-birds, reside in trees, and build more or less elaborate nests. As regards their nervous system, the brain of Birds is rela- tively larger than the brain of Reptiles, but it is destitute of those folds or convolutions which form so marked a feature in the brain of most Mammals. The organs of sense, with the exception of touch and taste, are well developed in Birds, vision especially being generally extremely acute. The eyes are always well developed, and in no bird are they ever want- ing or rudimentary. The chief peculiarity of the eye of Birds is, that its anterior portion (cornea) forms the segment of a AVES. 263 much smaller circle than does the eyeball proper; so that the whole eye assumes a conical shape. Another peculiarity is that the form of the eye is maintained by means of a circle of from thirteen to twenty bony plates, which are placed in the front portion of the fibrous coat of the eye (sclerotic). Hye- lashes are almost universally absent; but, in addition to the ordinary upper and lower eyelids, Birds possess a third mem- branous eyelid—the membrana nictitans—which is placed on the inner side of the eye. This nictitating membrane is some- times transparent, sometimes pearly white, and it can be drawn over the front of the eye like a curtain, moderating the too great intensity of the light. As regards the organ of hearing, the chief point to remark is that Birds have mostly no external ear, by means of which the undulations of sound can be col- lected and transmitted to the internal ear. In some birds, however, as the Ostrich, the external opening af the organ of hearing is provided with a circle of feathers, which can be raised and depressed at will. In the nocturnal Birds, also, (such as Owls), the external opening of the ear is protected by a musculo-membranous valve, foreshadowing the gristly external ear of Mammals. The sense of smell is apparently seldom very acute in Birds, and even the Birds of Prey appear to seek their food mainly by the sight. The external nostrils are usually placed on the sides of the upper mandible, near its base, and form simple perforations which sometimes communi- cate from side to side. In the curious Apteryx of New Zea- land, the nostrils are placed at the extreme end of the elon- gated beak. Sometimes the nostrils are defended by bristles, and sometimes by a cartilaginous scale. Before passing on to a consideration of the divisions of Birds, a few words may be said on the migrations of Birds. In temperate and cold climates, few birds remain constantly in the same region in which they were originally hatched. Those which do so are called “permanent birds.” Other birds, such as the Woodpeckers, migrate from place to place without fol- lowing any very definite course. These are called “ wander- ing birds,” and their movements are chiefly conditioned by the scarcity or abundance of food in any particular locality. Other birds, however, at certain seasons of the year, undertake long journeys, usually uniting for this purpose into larger or smaller flocks. Such birds—of which the Swallows are a familiar in- stance—are properly called “migratory birds,” and their move- ments are conditioned by the necessity of having a certain average temperature, without which they cannot live. Thus 264 VERTEBRATE ANIMALS. the migratory birds of cold climates, when the cold season comes on, travel to warmer countries ; but when the hot sea- son of these regions approaches, they migrate back again to temperate zones. CHAPTER XXX. DIVISIONS OF BIRDS. Brrps may be variously divided, but for our present pur- pose it is most convenient to regard them as divided into the following eight orders: I. Natatores or Swimming Birds, characterized by having the feet webbed, and the legs short and placed far back, while the body is closely covered with feathers and with a thick coating of down next the skin. (Aa. Ducks, Geese, Pelicans.) IL Grallatores or Wading Birds, characterized by having very long legs, which are destitute of feathers from the lower end of the tibia downward. The toes are usually long and straight, and are never connected to one another by membrane. (Zx. Curlews, Snipes, Herons, Storks.) Ill. Cursores or Running Birds, characterized by having very short wings, which are not used in flight; the breast- bone is without a ridge or keel ; the legs are very robust; and the ial is wanting or rudimentary. (Zz. Ostriches and Emeus. IV. Rasores or Scratching Birds, characterized by usually having strong feet, with powerful blunt claws, used for scratch- ing. The upper mandible of the bill is strongly curved and vaulted, and the nostrils are pierced in a membranous space at its base, and are covered by a cartilaginous scale. (Hx, Fowls, Pheasants, Pigeons.) V. Scansores or Climbing Birds, characterized by having a climbing foot, in which two toes are turned backward and two forward. (x. Woodpeckers, Parrots, Cuckoos.) VI. Insessores or Perching Birds, characterized by having short and slender legs, with three toes in front and one be- hind, the whole foot being adapted for perching. (2x. Larks, Linnets, Swallows, Crows, Humming-birds.) 266 VERTEBRATE ANIMALS. VIL. Raptores or Birds of Prey, characterized by having a strong, sharp-edged, and sharp-pointed beak, adapted for tearing animal food, and by their robust legs, armed with four toes, three in front and one behind, all of which are furnished with long, strong, crooked claws or talons. (Hx. Eagles, Hawks, Owls.) VIL Saurure or Lizard-tailed Birds, characterized by having a tail longer than the body, composed of numerous distinct and movable vertebra, each of which carries a single pair of quill-feathers. (This order includes only the remark- able fossil bird, the Archceopteryz.) Orper I, Nararores (Lat. natator, a swimmer),—The order of the Swimming Birds comprises birds which are as much at home in the water as upon land, or even more so. In accordance with their aquatic mode of life, the Watatores have a boat-shaped body, generally elongated, and usually having a long neck. The legs are short, and are placed behind the cen- CP ae MA Fie. 181.—Natatores. Penguin (Spheniscus demersua). DIVISIONS OF BIRDS. 267 tre of gravity of the body; this position enabling them to act admirably as swimming-paddles, at the same time that it ren- ders the gait upon dry land comparatively awkward and shuf- fling. The toes in all the Watatores are webbed toa greater or less extent, or, in other words, are united by a membrane (Fig. 131). In many the web or membrane between the toes is stretched completely from toe to toe, but in others the mem- brane is divided between the toes, so that the feet are only imperfectly webbed. As their aquatic mode of life exposes them to great reductions of temperature, the body in the Na- tatorial birds is closely covered with feathers, with a thick covering of down next the skin. They are further protected against becoming wet while in the water by the great develop- ment of the oil-gland at the tail, by means of which the dense plumage is kept constantly oiled. As a rule, the Natatorial birds are polygamous, each male having several females; and the young are hatched in a condition not requiring assistance from their parents, being able to swim about and procure food for themselves the instant they are liberated ficm the egg. Among the more important families of the Natatores may be enumerated the Penguins (Spheniscide), the Auks (Al cide), the Gulls and Terns (Laridc), the Petrels (Procedla- vida the Pelicans (Pelicanus), the Cormorants (Phalacro- corax), the Gannets (Sula), the Ducks (Anatidc), the Geese (Anserine), and the Swans ( Cygnide). The Penguins and Auks, with their allies the Divers, Guil- lemots, and Grebes, have rudimentary, or at any rate small, wings, and are all more at home in the water than upon land. The Gulls, Terns, and Petrels, on the contrary, are all birds of powerful flight, and some of them, such as the Albatross, are habitually found hundreds of miles from the nearest land. The Pelicans, with their allies the Cormorants, Frigate-birds, and Darters, are excellent flyers, and also not uncommonly perch on trees, which few Natatorial birds do. They are dis- tinguished by having the hinder toe directed inward, and united to the innermost of the front toes by a continuous membrane. The Gannets, Ducks, Geese, and Swans, have the bill very much flattened and covered by a soft skin. The edges of the bill are also furnished with a series of transverse plates, which form a kind of fringe or “strainer,” by means of which these birds sift the mud in which they habitually seek their food. Orper II. Grattarores (Lat. graile, stilts) —The Wading Birds for the most part frequent moist situations, such as 268 VERTEBRATE ANIMALS, marshes and shallow ponds, the shore of the sea, or the banks of rivers or lakes, though some of them keep entirely, or al- most entirely, to the dry land. In accordance with their semi- aquatic, amphibious habits, the Waders are distinguished by the great length of their legs—the increase in length being chiefly due to the elongation of the tarso-metatarsus, The legs (Fig. 132) are also unfeathered or naked, as far as the 4 a, 2 a —_— j == a we. UME OERER a a — ee Fie. 182.—Grallatores. Common Heron (Ardea cinerea). lower end of the tibia, at any rate. There are three anterior toes, and usually a short hind-toe; but the toes are never com- pletely webbed, though they are sometimes partially palmate. The wings are long, and the power of flight is usually consid- erable ; but the tail is very short, and its function as a rudder is chiefly transferred to the long legs, which are stretched out behind in flight. The beak is almost always of great length, generally longer than the head (Fig. 132), and usually more or less pointed, though it is sometimes flattened. In the Avocet the bill is curved upward, instead of being straight, or bent downward, as is generally the case. The typical Waders, as before said, spend most of their time wading about in shallow DIVISIONS OF BIRDS. 269 water, feeding upon small fishes, shell-fish, worms, and insects. Others, such as the Storks, live mostly upon the land, and are more or less exclusively vegetable-feeders. Among the more important Grallatorial birds are the Rails Rallide), Water-hens ( Gallinulc), Cranes ( Gruidw), Herons RN Storks (Ciconine), Snipes (Scolopacide), Sand- pipers (Zringide), Curlews (Numenius), Plovers ( Charadrii- de), and Bustards ( Otide). The Rails are more or less terrestrial in their habits, but inhabit marshes and fens. Good examples are the Marsh Hen (Radllus elegans) and the Virginia Rail (R. Virginianus) of North America, and the Corn Crake (Crex pratensis) of Europe. The Water-hens (Gallinula) and Coots (fulica) are aquatic or semi-aquatic, swimming and diving with the great- est ease. The Cranes are in the main vegetable-feeders, and inhabit dry plains. The Herons, Egrets, Bitterns, and Night Herons, form a beautiful family of wading birds, represented in almost every portion of the known world. Nearly allied to these are the brilliantly-colored Ibises (Zantaline), which inhabit all warm countries. The Ciconine are all large birds, and comprise the Storks and Adjutant, while the Spoon- bills are mainly separated from them by their flattened, spoon- shaped bill. The Scolopacide, comprising the Snipes and Woodcocks, the Zringide (or Sandpipers), the Curlews (Wu- menius), and various other allied birds, are distinguished from the preceding by the possession of a long, soft, slender bill, which is used in probing the ground for food. In the Chara- driide are comprised the Oyster-catchers, Turnstones, Lap- wings, Plovers, Thick-knee, and many other familiar birds. Lastly, the Otidc comprise only the Bustards, which are ex- clusively confined to the Old World, and make a decided ap- proach to the Cursorial Birds. Orper III. Cursors (Lat. curro, I run).—The Running or Cursorial Birds, comprising the Ostrich, Cassowary, Emeu, Rhea, and Apteryx, are characterized by the rudimentary con- dition of the wings, which are useless as organs of flight, and by the compensating length and strength of the legs. In ac- cordance with this condition of the limbs, the bones have few air-cells, and the breast-bone is destitute of the prominent ridge or keel to which the great muscles of the wings are at- tached. The two sides of the pelvis are united together below in the Ostrich, and in all the pelvic arch has great strength and stability. The legs are extremely powerful, and the hinder 270 VERTEBRATE ANIMALS. toe is wanting in all except the Apteryz, in which it is present in a rudimentary condition, The front toes (Fig, 183) are either two or three in number, and are furnished with strong blunt claws or nails, The feathers present the remarkabie peculiarity, that the barbs, instead of being connected by means of the barbules, are disconnected and separate from one another, thus coming to resemble hairs in appearance, The African Ostrich (Struthio camelus), which is one of the best-known members of this order, inhabits the desert plains of Africa and Arabia, and is the largest of living birds, attaining a height of from six to eight feet. The head and neck are nearly naked, and the quill-feathers of the wings and tail have their barbs wholly separate, constituting the ostrich- plumes of commerce. The legs are extremely strong, and the feet have only two toes each. The Ostriches run with extraor- dinary speed, and can outstrip the fastest horse. They are polygamous, each male having several females, and they keep together in larger or smaller flocks, 'The American Ostriches or Rheas are much smaller than the African Ostrich, and have the head feathered, while the feet are furnished with three toes each. They inhabit the great plains of South America, and are polygamous. The Emeu (Dromatus) is exclusively confined to New Holland. In size it nearly equals the African DIVISIONS OF BIRDS. 271 Ostrich, standing from five to seven feet in height, and it is not uncommonly kept as a domestic pet. The Cassowary (Caswarius galeatus) 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 the head. Another species of Cassowary in- habits Australia, and other species are known to exist in the Indian Archipelago. The last of the living Cursorial birds is the curious bird, the Apteryx (Fig. 183) of New Zealand. In this remarkable bird the beak is extremely long and slender, and the nostrils are placed at the extremity of the upper man- dible. The legs are comparatively short, and there is a rudi- mentary hind-toe, provided with a claw. The feathers of the general plumage are long and hair-like, and the wings are altogether rudimentary. Orper IV. Rasorss (Lat. rado, I scratch).—The Scratch- ing Birds—or, as they are often called, the Gallinaceous Birds —are characterized by the fact that the upper mandible of the bill is convex and vaulted (Fig. 134), and has a membranous space at its base, in which the nostrils are pierced. The nos- trils are also covered by a cartilaginous scale. The legs are strong and muscular, and are often covered with feathers as far as the ankle-joint. There are four toes (Fig. 134), three in front, and a short hind-toe placed on a higher level than the others, All the toes, in the typical members of the order, are provided with strong, blunt claws, suitable for scratching. The food of the Masores consists chiefly of hard grains and seeds, and, in accordance with this, they have a large crop, and an extremely strong and muscular gizzard. They gener- ally lay their eggs upon the ground, and they are mostly polygamous, each male having several mates. The Doves, however, pair for life. The males take no part in building the nest or in hatching the eggs; and the young are generally precocious, being able to run about and provide themselves with food from the moment they quit the egg. The wings are usually weak, and the flight feeble, and accompanied with whirring sound; but many of the Pigeons are powerful lyers. The order Rasores is divided into two very well marked sections or sub-orders, called respectively the Gallinacei and Columbacei, In the Gallinacei are all the typical forms of the order, and the characters of this section are therefore the same as those of the order itself. They are distinguished from 272 VERTEBRATE ANIMALS. 3 the Columbacei mainly by being less fully adapted for flight, their bodies being much heavier, comparatively speaking, their legs and feet stronger, and their wings shorter. ‘They are also generally polygamous, and the males usually possess “ spurs,” and are more brilliantly colored than the females. Fig. 184.—Rasores. Rock-pigeon (Colwmba livia), The leading families of the Gallinaceous birds are: 1. The Tetraonide or Grouse family, comprising the true Grouse and Black Game (Zetrao), the Ptarmigans (Zagopus), the Ruffed Grouse (Bonasa), etc. 2. The Perdicide or Partridge family, comprising the Partridges (Perdix), Quails (Coturnia), Vir- ginian and Mountain Quails ( Ortyx), Crested Quails (Zophor- tyz), etc. 3. The Phasianide, or Pheasant family, comprising the various Pheasants (Phasianus), the Domestic and Jungle fowls (Gallus), the Turkeys (Meleagris), the Guinea-fowls (Numida), and the Pea-fowl (Pavo). 4. The Megapodide, or Mound-builders, comprising only some singular Australian and Indian birds, which build enormous mounds, in which they deposit their eggs. 5. The Cracide, or Curassow family, DIVISIONS OF BIRDS. 278 comprising the large South and Central American birds known as Curassows and Guans. The Columbacet comprise the Pigeons and Doves (Fig. 184), and they are separated from the typical Rasores by being much more fully adapted for flight. They are furnished with strong wings and are good flyers ; and, in place of being ground- birds, their habits are to a great extent arboreal, in accordance with which the feet are slender and are adapted for perching. They are also not polygamous, and their voice is of a much more gentle, soft, and melancholy character. (Hence the name of Gemitores applied to this section, while the Gallinacei are called the Clamatores.) Besides the true Pigeons and Doves, this sub-order includes also the remarkable extinct bird, the Dodo, which was of gigantic size, comparatively speaking, and inhabited the island of Mauritius up to the commencement of the seventeenth century. Orprer V. Scansorzs (Lat. scando, I climb).—The order of Scansores or Climbing Birds is very shortly and easily de- fined, having no other distinctive and exclusive peculiarity except the fact that the feet have four toes, of which two are turned backward and two forward (Fig. 135). Of the two toes which are turned backward, one is the proper hind-toe, and the other is the outermost toe. This arrangement of the toes enables the Scansorial birds to climb with great ease and readiness. Their powers of flight are usually very moderate, and below the general average, and their food con- sists of insects and fruits of various kinds. Their nests are usually made in the hollows of old trees, but some (Cuckoos) have the remarkable habit of depositing their eggs in the nests of other birds. They are never polygamous, and the young are born in a naked and helpless condition. The following families have been established in the Sean- sores: 1. The Cuculide or Cuckoo family, comprising the true Cuckoos and some allied birds. They are remarkable for the fact that many of them are “ parasitic,” that is to say, they lay their eggs in the nests of other birds. The Yellow-billed Cuckoo (C. Americanus), however, of the United States, builds a nest for itself and brings up its own young. 2. The Picide or Woodpecker family, comprising many familiar birds, all of which climb and run up trees with the greatest facility. They live mostly on insects, which they catch by darting out their long, worm-like, barbed tongue. 3. The Psittacide or Parrot family, comprising the true Parrots, the 274 VERTEBRATE ANIMALS. Cockatoos, the Lories, the Parrakeets, and the Macaws. They are all natives of hot climates, and are most remarkable for their brilliant plumage, and loud, harsh, and grating voices. Fic. 185.—Scansores. Purple-capped Lory (Lorius domicella). The beak (Fig. 135) is hooked, and is used as a kind of third foot in climbing, but some move about actively on the ground. 4. The Rhamphastide or Toucans, distinguished by their enormously large and cellular bills, the sides of which are ser- rated. They live in deep forests, in small flocks, and are con- fined to tropical America. 5. The Zrogonidce or Trogons, which inhabit the most retired recesses of the forests of the intertropical regions of both hemispheres, and are distin- guished by their resplendent plumage. Orper VI. Insxssorss (Lat. énsedeo, I sit upon, or perch). —The sixth order of Birds is that of the Znsessores or Perchers, often spoken of as the Passerine Birds (Lat. passer, a sparrow). DIVISIONS OF BIRDS. 275 They are defined 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. 136, A, B). “The Perchers form by far the most numerous order of birds, but are the least easily recognizable by distinctive char- acters common to the whole group. Their feet, being more especially adapted to the delicate labors of nidification a (building the nest), “have neither the webbed structure of those of the Swimmers, nor the robust strength and destruc- tive talons which characterize 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 plants; but the toes are slender, flexible, and moder- ately elongated, with long, pointed, and slightly-curved claws. Fic. 186.—Insessores. A, Foot of Yellow Wagtail; B, Foot of Water Ouzel; C, Conirostral beak (Hawfinch); D, Dentirostral beak (Shrike); I, Tenuirostral beak (Humming-bird) : F, Fissirostral beak (Swift), “The Perchers, in general, have the females smaller and less brilliant in their plumage 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 are wholly dependent for subsistence 276 VERTEBRATE ANIMALS, 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 utmost complexity; and all the charac- teristics 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, then, of the feet 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 na- ture of the food, which may be “small or young birds, carrion, insects, fruit, seeds, vegetable juices, or of a mixed kind.” In accordance with this character, the Jnsessores have been di- vided into four great sections, as follows: 1. Conirostres—in which the bill is strong and on the whole conical, broad at the base and tapering with consider. able rapidity to the point (Fig. 136, C). The upper mandible is not markedly toothed at its lower margin. Good exam. ples of the Conirostral beak are to be found in the commen Sparrow, Bullfinch, Crow, or Hawfinch (C). The greater part of the Conirostres are omnivorous, eating any thing which may come in their way; but some are granivorous, subsisting upon grains and seeds. To this section belong the Hornbills (Buceride), the Starlings (Sturnide), the Crows, Jays, and Magpies (Corvide), the Cross-bills (Loxiade), and the nu- merous Finches, Buntings, Grosbeaks, Tanagers, and Larks (Fringillide). 2. Dentirostres.—The birds of this section are characterized by the fact that the upper mandible of the beak is notched or toothed on its lower margin near the tip (Fig. 136, D). They all feed upon animal food, especially upon insects. In this section are the Shrikes (Laniide@), the Fly-catchers (Muscica- pide), the Thrushes (Merulide), the Tits (Paride), and the Warblers (Sylviade). 3. Tenwirostres—In this section the beak is long and slender, gradually tapering to a point (Fig. 136, E). The toes are generally very long and slender, especially the hinder toe. Many live to a great extent upon vegetable juices, and among these are some of the most fragile and brightly-colored of all the birds. A great many, however, live upon insects, either partially or entirely, and some of these approach nearly to the Dentirostres in many of their characters. Among the more important groups included in this section are the Creepers and Wrens ( Certhide), the Honey-eaters (Meliphagide), the Hum- ming-birds (Ziochélide), and the Hoopoes ( Upupine). DIVISIONS OF BIRDS. 277 4, Fissirostres—The beak in the Fissirostral birds (Fig. 136, F) is generally short, and remarkably wide in its gape, and the opening of the bill is protected by a number of bristles, This arrangement is in accordance with the habits of the Fissirostres, the typical forms of which live upon in- sects and take their prey upon the wing. The most typical Fissirostres, in fact, such as the Swallows and Goat-suckers, fly about with their mouths open, and the insects which they catch in this way are prevented from escaping, partly by the bristles which border the gape, and partly by a sticky secretion within the mouth. The most typical Fissirostral birds are the Swallows and Martens (Hirundinide), the Goat-suckers (Ca- primulgide), and the Swifts (Cypselide); but to these the Bee-eaters (Meropide) and the King-fishers (Alcedinida) are usually added. Orper VII. Rarrorrs (Lat. rapto, I plunder).—The Birds of Prey are characterized by the form of the beak, which is adapted for tearing animal food (Fig. 137, B). The upper mandible is the longest, hooked at its point, “strong, curved, sharp-edged, and sharp-pointed, often armed with a lateral tooth” (Owen). The body is extremely muscular; the Fic. 187.—Raptores. A, Foot of Peregrine Falcon; B, Head of Buzzard. legs are robust, short, with three toes in front and one behind; all the toes armed with strong, curved, crooked claws or talons (Fig. 137, A). They all feed upon the flesh of other animals, which they either kill for themselves or find dead, and their flight is generally extremely rapid and powerful. They are not polygamous, and the female is larger than the male. They usually build their nest in lofty and inaccessible situations, and seldom lay more than four eggs. The young are hatched in a naked and Felpless condition. 278 VERTEBRATE ANIMALS. The Rapiores are divided into two sections—the Nocturnal Birds of Prey, which hunt at night, and the Diurnal Birds of Prey, which hunt by day. In the former section is only the single family of the Owls (Strigida), in which the eyes are large, and are directed forward; while the plumage is exceed- ingly soft and loose, so as to render their flight almost noise- less. The Owls (Fig. 138) hunt their prey in the twilight or on moonlight nights, and they live mostly upon field-mice and small birds, but they will also eat insects and frogs, In the Fig. 188.—A, Foot of Tawny Owl; B, Head of White Owl. section of the diurnal Raptores are the Falcons and Hawks, the Eagles and the Vultures. In all these the eyes are smaller than in the Owls, and are placed laterally, and the plumage is “not soft. They usually possess extraordinary powers of flight. The wings are long and pointed, the sternal keel is greatly developed, the pectoral muscles are of large size, and many of them exhibit powers of locomotion more rapid than those en- joyed by any other members of the animal kingdom. Of the diurnal Raptores, America has many examples, and some of these are among the most celebrated members of the entire order. Besides many Hawks, Buzzards, and Kites, may be especially mentioned the Bald Eagle, the Californian Vul- ture, and the Condor. The Bald or White-headed Eagle (Halietus leucocephalus) is well known as the national emblem of the United States. It is a fine and courageous bird, and lives toa great extent upon fish, which it either catches for itself, or, more commonly, wrests forcibly from the American Osprey. The Californian Vulture (Cathartes Californianus) is the largest of the Birds of Prey, with the single exception DIVISIONS OF BIRDS. 279 of the Condor. It is entirely confined to the Pacific coast. The Condor (Sarcorhampus gryphus) has a stretch of wing of from 12 to 14 feet, and is usually seen soaring in majestic cir- cles at great elevations, rising, it is said, to a height of over 20,000 feet. It inhabits the lofty mountain-ranges of the Andes, and lays its eggs at a height of from 10,000 to 15,000 feet. Orver VII. Savrurs (Gr. savra, lizard; owra, tail).— This order includes only the single extinct bird, the Archwop- teryx, which has been found in the Oolitic rocks of Germany. The Archeopteryx was about as big as a common Rook, and shows many singular points of resemblance to the true Rep- tiles. It differs from all living birds in having two free claws to the wing, and in possessing a long, lizard-like tail. Instead of the ploughshare-shaped bone which terminates the tail in Fic. 139.—Archeopteryx. Tail and detached bones. living birds (Fig. 129, B), the tail in the Archwopteryx is very long, and consists of about twenty distinct and separate ver- tebree, each of which supports a pair of quill-feathers. The tail, therefore, except for the presence of feathers, must have been very like that of a Lizard. MAMMALIA, CHAPTER XXXI. CLASS V.—MAMMALIA. Tae Mammalia include all the ordinary quadrupeds, and may be shortly defined as comprising Vertebrate Animals in which some part or other of the skin is always provided with hairs, 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 peculiarities are of themselves sufficient to separate the Mammals from all other classes of the Vertebrate sub-kingdom. In addition, however, to these two leading characteristics, the following points are of scarcely less importance : 1. The skull is united with the spinal column by means of two articulating surfaces or condyles, instead of one, as in the Reptiles and Birds. 2. The lower jaw consists of two halves, each composed of a single piece, and united in front. The lower jaw, also, is always jointed directly with the skull, and there is no quad- rate bone. 3. The heart consists—as in Birds—of four distinct cham- bers, two auricles and two ventricles. The right and left sides of the heart are completely separated from one another, and there is never any direct communication between the blood sent to the lungs and that sent to the body. The red corpuscles of the blood (Fig. 99, a) are, in the great majority of cases, in the form of circular disks, and they never contain any inter- nal solid particle or nucleus. 4, The cavities of the chest (thorax) and abdomen are separated from one another by a muscular partition, which is called the midriff or diaphragm, and is the chief agent in res- piration. MAMMALIA, 281 5. The respiratory organs are in the form of two lungs, placed in the chest, and never communicating with air-recep- tacles situated in different parts of the body. In no case and at no period of life are gills or branchiz present. As regards the skeleton of the Mammalia it is not neces- sary to add much to what was said in speaking of the Verte- brata generally. With few exceptions, the spinal column is divisible into the same regions as in man—namely, the neck or cervical region, the back or dorsal region, the loins or lum- bar region, the sacral region, and the tail or caudal region (see Fig. 95). In spite of the great differences observable in the length of the neck in different Mammals, the number of ver- tebrae which form the cervical region is extraordinarily con- stant, being almost invariably seven. In this respect the Giraffe, which is the longest-necked of Mammals, agrees with the Whale, which can hardly be said to have a neck at all. The vertebree of the back or dorsal region are mostly thirteen in number, but are often more. In man there are only twelve; and in some cases there are only eleven or ten. The lumbar vertebr are usually six or seven in number; five in man; rarely less than four. The sacral vertebrae are usually amalga- mated to form asingle bone—the sacrwm—but this is wanting in the Whales. The number of vertebrae in the tail or caudal region varies from four to as many as five-and-forty, and they are usually freely movable upon one another. The thoracic cavity or chest in Mammals is always enclosed by a series of ribs; the number of which varies with the number of the dor- sal vertebrae. As a rule, the ribs are united to the breastbone or sternum in front, not by bony pieces, as in birds, but by cartilages. Only the front ribs reach the sternum, and these are called the “true” ribs; the hinder ribs fall short of the breastbone, and are called the “false” ribs. The sternum is composed of several pieces, placed one behind the other, but usually amalgamated to form a single bone. It is usually long and narrow in shape, and is only rarely furnished with any ridge or keel, as it is in birds. The regular number of limbs in the Mammals is four, two anterior and two posterior; and for this reason the Mammals are often-spoken of as Quadru- peds. Some Mammals, however, such as the Whales and Dolphins, have only the anterior limbs, and many of the Am- phibia and Reptiles walk upon four legs. As regards the structure of the fore-limbs (Fig. 96), the general plan of con- formation is the same as described in treating of the Verte- 282 VERTEBRATE ANIMALS. brata generally (p. 202). The shoulder-blade or scapula is never absent; and the coracoid bone, which is so marked a feature in the Birds, is with hardly an exception amalgamated with the scapula. The clavicles or collar-bones are often want- ing or rudimentary, but in no Mammal are they ever united together in front so as to form a merry-thought or “ furculum.” The regular number of fingers is five, but they vary from one to five, the middle finger being the longest and most persist- ent of all, and being the only finger left in the Horse. Prop- erly each finger consists of three short bones or phalanges, except the thumb, which has two; but this rule is occasionally departed from. While the fore-limbs are never wanting, the hind-limbs are sometimes absent, as in the Whales. Generally speaking, however, the posterior limbs are present, and the pelvic arch has much the same structure as in man. The foot —like the hand—consists regularly of five digits, but it is sub- ject to the same abortion of parts, as we shall see hereafter. The great majority of Mammals possess teeth, but these are only present in the embryo of the whalebone Whales, and are altogether wanting in the scaly and great Ant-eaters. The teeth are also almost invariably implanted in distinct sockets in the jaw. Some Mammals have only a single set of teeth; but in most cases the young Mammal possesses a set of what are called the milk-teeth or deciduous teeth, which is ultimate- ly replaced by a second set, constituting the permanent teeth. No Mammal has ever more than two sets.of teeth. In man, and in many other Mammals, the teeth are divisible into four groups, which differ from one another in position, appearance, and function. These are termed respectively the incisors, ca- nines, premolars, and molars. It is impossible to describe fully which teeth come under each of these heads without en- tering into unnecessary details as to the structure of the jaws. It must be sufficient here to point out the general characters and position of these groups ina good illustrative example, such as one of the higher Apes (Fig. 140). The incisors (2) vary greatly in size and number, but they are always placed in the front of the mouth, and are the teeth which are used in simply biting or dividing the food. The canine or eye-tooth (c) is generally larger or more pointed than the other teeth. The canines are sometimes wanting, or are sometimes present in one jaw and not in the other; but there are never more than four altogether—that is to say, one in each jaw on each side, The premolars and molars (jm and m) are the so-called “back-teeth,” and they vary a good deal in number and function, MAMMALIA. 288 being sometimes adapted for cutting the food, but more usual- ly for chewing and grinding it down. Fic. 140.—Teeth of the right side of the lower jaw of the Chimpanzee (after Owen). ¢ In- cisors; ¢ Canine tooth; pm Premolars; m Molars. All these kinds of teeth are not necessarily present, and the teeth constitute most important characters for separating the various orders of Mammals from one another. For this reason it is usual to express the number of the teeth in any particular animal by an arithmetical formula, called the dental jormula. For example, the formula for the portion of the jaw of the Chimpanzee figured above (Fig. 140) would be as follows: 423; 61; pm2; m3. But this is only one half of the lower jaw, and the dental for- mula must include both sides, so that it would be: 422; ¢1—1; pm 2—2; m 3—3. That this would be the formula is at once evident, when it is remembered that the two sides of the jaw of course contain exactly the same teeth. Still, the formula as given above only includes the lower jaw, and to render it perfect it must take in the teeth of the upper jaw as well. This is effected by placing the figures in two rows separated by short lines, all the figures in the upper row referring to the upper jaw, and those in the lower row to the lower jaw; the short dashes be- tween the figures of each row still indicating the teeth on the two sides of the mouth. The complete formula would there- fore run as follows: 284 VERTEBRATE ANIMALS. .2—2 1-1, 2-2 388 32 eg a ae In this way the dentition—that is to say, the number and ar- rangement of the teeth—can be presented in a manner which can be instantly recognized by the eye. It must be remem- bered, however, that the formula seldom exhibits the regular- ity of the one of the Chimpanzee given above. The teeth are not necessarily the same in both jaws, and in many cases some may be altogether wanting. To show this there is sub- joined the dental formula of a typical Ruminant animal, such as a sheep: 0—0, 0—0, 3-3, 388 39 ea 3 From this formula it will be seen that the sheep has 82 teeth in both jaws taken together. The upper incisors and canines are wanting, and there are three premolars and three molars on each side of the upper jaw. In the lower jaw there are six incisors, two canines, and the same number of premolars and molars as in the upper jaw. As regards the digestive system of Mammals, the alimen- tary canal and digestive glands have on the whole the same general structure and arrangement as in man (pp. 203, 204). Some very remarkable modifications, however, in the structure of the stomach and in the termination of the intestine occur in certain Mammals; but these will be noticed in speaking of the orders in which they occur. The cavity of the abdomen in Mammals is always separated from that of the thorax by a complete muscular partition—the diaphragm. The abdomen contains the greater part of the alimentary canal, the liver, pancreas, kidneys, and other or- gans. The thorax contains chiefly the heart and lungs. The heart is contained in a membranous sac—the pericardium, and consists of two auricles and two ventricles. The heart con- sists functionally of two sides, each having an auricle and a ventricle, which communicate with one another by apertures, so guarded by valves that the blood can pass from the auricle into the ventricle, but not, under ordinary circumstances, from the ventricle to the auricle. There is in the adult no direct communication between the two sides of the heart. The course of the circulation is indicated in the subjoined diagram, and is shortly as follows: The venous blood, which has become impure by passing through the tissues, is returned by the great veins to the right auricle, from which it passes into the MAMMALIA. 285 right ventricle. From here it is driven through a great vessel, called the pulmonary artery, to the lungs, where it is submitted to the action of the air, and becomes arterial blood. It is then returned to the heart by a series of vessels, called the pulmo- nary veins, and is poured into the /eft auricle, from which it passes into the left ventricle. From the left ventricle it is propelled to all parts of the body by a great systemic vessel, which is called the aorta (Fig. 141). The dungs of Mammals are two in number, and differ from those of Birds in being freely suspended in membranous bags. They are spongy and cellular throughout, and they never communicate by apertures on their surface with air-sacs placed in different parts of the body. The nervous system of Mammals is chiefly remarkable for the great proportionate development of the brain, as compared with the spinal cord. In the higher Mammals, also, the two halves (hemispheres) of the brain proper (cerebrum) are con- Fre. 141—Diagram of the circulation nected together by a great band or ina Mammal. (The cavities con- bridge of nervous tissue, constitut- ing what is known as the corpus taining venous blood are marked black, those containing arterial blood are left white.) a Right auricle; v Right ventricle; p Pul- monary artery carrying venous callosum. This structure is nota = © a é Z ood to the lungs; pv Pulmonary conspicuous feature in the two low- _veins carrying arterial blood from est orders of the Mammalia. The ear ie a ee senses, as a rule, attain great per- Aas fection in the Mammals; and the pi a Sea yee only sense which can ever be said to be entirely wanting is that of sight. Eyes, however, are always present, though they may be rudimentary; and in those Mammals which are said to be “blind,” it is not generally that the eyes are want- ing, but that the skin passes unbrokenly over the eyeball, or the optic nerve is degenerated. Even in these cases, however, it is not impossible that there may be some perception of light through the skin. An external ear for collecting sounds is usually present; but it is wanting in the Whales and Dol- phins, and in some of the Seals. 286 VERTEBRATE ANIMALS. The skin is invariably furnished over a greater or less part of its surface with the epidermic appendages known as hairs, which differ from feathers chiefly in not splitting up as they are produced. In the scaly Ant-eater (Manis), the hairs are aggregated together so as to form horny scales; and in the Hedge-hog, Porcupine, and other animals, many of the hairs are developed into long spines or prickles. In other cases, again, as in the Armadillos, the skin is more or less covered by an armor of bony plates. The only apparent exception to the universal presence of hair on some part or other of the in- tegument of all Mammals is constituted by the true Cetaceans (Whales and Dolphins), many of which are without hair when grown up. Some, however, such as the Whales, have a few bristles in the neighborhood of the mouth, even when adult, And the Dolphins, which are totally hairless when grown up, exhibit tufts of hair upon the muzzle before they are born. The young Mammal is always born in a helpless condition, and is nourished for a longer or shorter time by means of the milk of the mother. The milk is secreted by special organs, called the mammary glands, which are present in both sexes, but are normally undeveloped in the male. The number and position of the mammze vary a good deal in different cases, but they are always placed on the lower surface of the body, and their ducts almost always open upon a special eminence, called the teat or nipple. In one or two cases, however, the mammary glands open by simple slits in the skin of the abdo- men, and not by distinct nipples. In ordinary Mammals the milk is obtained by voluntary suction on the part of the young, but in the Marsupials (Kangaroos, Opossums, etc.) the milk is forced into the mouth of the young animal by the action of a special muscle. __ So much difference of opinion obtains as to the best foun- dation upon which to establish a division of the Mammalia into great primary sections, that it has been thought advisable to leave this subject wholly out of consideration. For our present purpose it is enough to adopt the old classification of Mammals into the two great divisions of the Placental and Non-placental forms. In the Placental Mammals the young is nourished within the body of the mother by means of a structure called the placenta, or “ after-birth,” through which the nutrient materials of the mother’s blood reach the young. In consequence of this, the young of the Placental Mammals can be retained within the body for a considerable period, and, MAMMALIA. 284 when born, they are able to obtain their natural food—the milk—by their own exertions. In the Non-placental Mam- mals, on the other hand, the young are born at an extremely early period of their development, before there is any necessity that a placenta should be formed for the nourishment of the foetus. In these cases, therefore, the young when born are much more immature and helpless than in the case of the Placental Mammals. So helpless are they, that they are even unable to suck, and have in most cases to be fixed by the mother herself upon the teats, while the milk is forced into their mouths by a muscle which is spread over the mammary gland. Adopting these primary sections as practically suf- ficient in an elementary work, the whole class of the Mammalia may be divided into the following fourteen orders : Division A.—APLACENTAL MAMMALS. Order 1.—WNMonotremata. Order 2.—Marsupialia, Division B.—PuiacentaL MamMatzs, Order 8.—Edentata. Order 4.—Sirenia. Order 5.—Cetacea. Order 6.—Ungulata, Order 1%.—Hyracoidea. Order 8.—Proboscidea. Order 9.—Carnivora. Order 10.—Rodentia. Order 11.—Cheiroptera. Order 12.—Insectivora, Order 13.—Quadrumana, Order 14.—Bimana, CHAPTER XXXII. ORDERS OF MAMMALIA. Orver {. Monorremata (Gr. monos, single; trema, aper- ture).—The first and lowest order of the Mammals—that of the Monotremata—comprises only two very remarkable ani- mals, both of which are exclusively confined to New Holland. These are the Duck-mole ( Ornithorhynchus) and the Porcupine Ant-eater (Hchidna). The Monotremata are essentially charac- terized by the fact that, as in Birds, the termination of the in- testine opens into acommon chamber or cloaca, which receives also the ducts of the urinary and reproductive organs. The jaws are destitute of true teeth; but the Ornithorhynchus has a kind of beak, like the bill of a duck, furnished with small horny plates, which act as teeth. The pectoral arch, which supports the fore-limbs, resembles that of Birds in several respects, but especially in the fact that the coracoid bones are distinct, and are not amalgamated with the shoulder- blade. There is no pouch developed on the abdomen of the females, but there are the so-called “ marsupial bones.” These are two small bones which arise from the front of the pelvis. They are really to be regarded as formed by a conversion into bone of the tendons of one of the muscles of the abdomen. There are no external ears, The mammary glands have no nipples, and the young are said to be devoid of a placenta. The Duck-mole (Fig. 142) is one of the most extraordinary of Mammals, and is found inhabiting the rivers and lakes of Australia and Tasmania. The body resembles that of a small otter, and is covered with a short brown fur. The tail is broad and flattened, and the jaws are sheathed with horn, so as to form a flattened beak, very like the bill of a duck. The legs are short, furnished with five toes each, and webbed, so that the animal swims with great facility. Their food consists ORDERS OF MAMMALIA. 289 chiefly of aquatic insects and mollusks, and they make very extensive burrows in the banks of streams. Fic. 142.—Monotremata. Duck-mole (Ornithorhynchus paradoxus). (After Waterhouse.) The other member of the Monotremata is the Porcupine Ant-eater or Echidna, which is not unlike a large hedgehog in appearance. The snout is very long, and is enclosed in a continuous skin till close upon its extremity, where there is a small aperture for the protrusion of a long and flexible tongue. There are no teeth, nor any organs to act as teeth. The feet have five toes each, and are furnished with strong digging- claws, but the toes are not webbed. The skin is covered with strong prickly spines interspersed with bristly hair. The Echidna measures from fifteen to eighteen inches in length, and is a nocturnal animal. It lives in burrows, and feeds upon insects, which it captures by protruding its long, sticky tongue. Orver II. Marsuprat1a.—The name of Marsupials is de- rived from the fact that the females of this order are mostly furnished with an abdominal pouch or marsupium, within which the nipples are situated. When born, the young are placed by the mother within this pouch, where they adhere to the teats, and can be carried about without injury. Even when further advanced in their development, the young often petake themselves to the shelter of the marsupium. The so- called “marsupial bones” are present, and as they spring from the front of the pelvis they no doubt serve to support the pouch ; but this cannot be their sole use, as they exist in the males, and also in the Monotremes, in whom there is no pouch. All Marsupials possess teeth, and the pectoral arch has now the same form as in the higher Mammals, the coracoid bones 290 VERTEBRATE ANIMALS, being now amalgamated with the shoulder-blade. The intes- tine does not terminate in a cloaca. Though the Marsupialia form an extremely natural order. sharply separated from the other Mammals, they include a large number of varied forms. In fact, this order, from its being the almost exclusive possessor of a continent so large as Australia, has to discharge, in the general economy of nature functions which are elsewhere performed by several orders, As regards their geographical distribution, with the single Ze 74 Y VA 1 LS Fie. 143.—Marsupialia. The Koala or Kangaroo-bear (Phascolarctos cinereus). After Gould.) exception of the family Déidelphide (the true Opossums), the whole order of the Marsupials is exclusively confined to Aus- tralia, Van Diemen’s Land, New Guinea, and the adjacent islands. The Marsupials may be primarily divided into the vege- table-eating and rapacious or carnivorous forms—the former characterized by the absence or rudimentary condition of the canine teeth, the molars having broad, grinding crowns; while in the latter there are well-developed canines, and the molars are not adapted for grinding. Of the vegetable-eating forms, the best known are the Kangaroos (Macropodide), distinguished by the remarkable disproportion between the ORDERS OF MAMMALIA, 291 hind and fore limbs, the former being by far the longest and strongest, By their long hind-legs, assisted by a powerful tail, the Kangaroos can perform astonishing jumps, and, in fact, leaping is their mode of progression when pursued. — The typical Kangaroos live on the great grassy plains of Australia; but the Tree Kangaroos spend a great part of their time in trees, and the Rock Kangaroos affect mountainous districts, The Kangaroo-bear or Native Sloth (Phascolare. tos cinereus, Fig. 143) has no tail, and has the body covered with a short, dense fur, while the ears are tufted. The fore- feet can be used as hands, and the toes are all furnished with strong, curved claws. It is a harmless, nocturnal animal, and spends most of its existence in trees. The typical group, however, of the vegetable-eating Marsupials is that of the Phalangers, comprising a large number of small animals which live in trees, and generally possess a prehensile tail. The most familiar example is the Australian “Opossum” (Phalan- gista vulpina), which is largely hunted by the natives. In the so-called “flying” Phalangers, again, the tail is not pre- hensile, and the animal takes extensive leaps from tree to tree, by means of a fold of skin which stretches between the body and the fore and hind limbs. Of the carnivorous Marsupials, the Bandicoots (Perameles), the Native Devil (Dasyurus), the Native Tiger (Zhylacinus), and the American Opossums (Didelphide), may be mentioned. The Bandicoots are little, rabbit-like Australian animals, which live upon insects, and seem to fill the place held in the Old World by the Hedgehogs and Shrew-mice. The Native Devil _ and Thylacine, though both of comparatively small size, are extremely ferocious, and do much mischief to the flocks of the Tasmanian colonists, About twenty species of Didelphide are known, and they are all exclusively confined to the Ameri- can Continent. They are all of small size, have prehensile tails, and mostly live among trees. The best-known species is the Virginian Opossum (Didelphys Virginiana). Orver III. Epenrara (Lat. ¢, without; dens, tooth).— This order of Placental Mammals comprises the Ant-eaters, Armadillos, and Sloths, and is characterized by the fact that the teeth are not covered with enamel, have no complete roots, and are never replaced by a second set. Further, in none of the Edentates are there any central incisor teeth, and in all but one there are no incisors at all. In two genera only are there no teeth; so that the name Hdentata is not a very 292 VERTEBRATE ANIMALS. appropriate one. In all, the toes are furnished with long and powerful claws. The Adentata admit of division into two sections, accord- ing as they live upon a vegetable diet and live in trees, or are carnivorous and live upon or below the ground. In the first section are only the Sloths (Bradypodide), which are exclu- sively confined to South America, inhabiting the vast primeval forests of this continent. They are in every way adapted for an arboreal life, and are “ destined to be produced, to live, and to die on trees.” They are excessively awkward when upon the ground; but the feet are furnished with extremely long, curved claws, so that the animal is enabled to move about freely, suspended back downward from the branches of the és. ee N Sy ae x SS NS BT NAN 2 ANS “INN, can Fie. 144.—Edentata. (Chlamyphorus truncatus.) trees. The Armadillos (Dasypodidw) are also exclusively confined to South America; but they are carnivorous, burrow- ing animals, and are furnished with strong digging-claws. The upper surface of the body is covered with a kind of armor, formed of hard, bony plates or shields, which are united at their edges (Fig. 144). Most of them can roll themselves up into a ball, and they can all bury themselves in the ground when pursued. The remaining South American Edentates are the hairy Ant-eaters, of which the best known is the great Ant-eater (Myrmecophaga jubata). The body in this family is covered with hair, the tail is long, and the teeth are altogether want- ing. They feed chiefly upon ants and termites, which they ORDERS OF MAMMALIA. 293 catch by protruding their long and sticky tongues, having previously broken into the nests by means of their strong, curved claws. The Hdentata are represented in the Old World by only two genera. One of these is the genus Manis, comprising the scaly Ant-eaters or Pangolins, which are exclusively con- fined to Asia and Africa. In these singular animals the body and tail are covered by a flexible armor, composed of horny plates or scales overlapping like the tiles ef a roof. The other genus is Orycteropus, comprising only the so-called Ground-hog of South Africa; which also lives upon insects, and burrows by means of its strong digging-claws. As regards the geographical distribution of the Hdentata, it is to be remembered that the order has a very limited range at the present day. The true Ant-eaters, the Armadillos, and the Sloths, are exclusively confined to South America, in which country a group of gigantic extinct Edentates existed in the later portion of the Tertiary epoch. The scaly Ant- eater is common to Asia and Africa; and the Ground-hog is confined to South Africa. Orper IV. Srrenza (Gr. seiren, a Mermaid).—This order comprises only certain large marine Mammals, known as Du- gongs and Manatees, which were long classed with the Whales and Dolphins (Cetacea). They agree with the Whales in the adaptation of the body to an aquatic life, especially in the facts that the anterior limbs are converted into swimming- paddles, the hind-limbs are wholly wanting, and the hinder end of the body forms a powerful caudal fin, which is placed so as to strike the water horizontally, and not vertically as in Fishes. They differ from the Cetacea in having the nostrils placed at the anterior part of the head, and in having molar teeth with Hat crowns, adapted for a vegetable diet. Fleshy lips are present, the upper one usually with a mustache, and the skin is covered with scanty bristles, The head is not dis- proportionately large as compared with the body, and there is a tolerably distinct neck. They are vegetable-eaters, feeding chiefly upon sea-weeds, and haunting the mouths of rivers and estuaries, The only existing Sirenia are the Manatee (Manatus) and the Dugong (Halicore), often called “Sea-cows.” The Man- atees are found on the east coast of America, and on the west coast of Africa. They are large, awkward animals, attaining a length of from eight to ten or fifteen feet, and their flesh is 294 VERTEBRATE ANIMALS. said to be very palatable and wholesome. The Dugongs (Fig. 145) differ little in appearance and habits from the Manatees, They are found on the coasts of the Indian Ocean and the north coast of Australia, and are often killed and eaten, They attain a length of from eighteen to twenty feet. The bones of the skeleton are remarkable for their extreme hardness and density. Fig. 145.—Sirenia. The Dugong (Halicore Indicus). Besides these living forms, the Sirenia were represented by a gigantic species which formerly inhabited Behring Island on the coast of Kamtchatka. This animal was described by a M. Steller who accompanied Behring on his second expedition, and he named it Rhytina. This enormous animal attained a length of twenty-five feet, and a circumference of twenty feet, and it appears to have been completely exterminated, no spe- cimen having been seen for two centuries. OrpEr V. Creracra (Gr. Aetos, a Whale).—This order comprises the Whales, Dolphins, and Porpoises, and it is characterized by the complete adaptation of its members to a watery life. The body is completely fish-like in form, the fore- limbs are converted ‘into swimming-paddles, and the hind- limbs are completely wanting; while the hinder end of the — body forms an extremely powerful, horizontal caudal fin. Sometimes there is a dorsal fin as well. The nostrils may be single or double, but always are placed on the top of the head, constituting the “blow-hole.” The body is very sparingly furnished with hairs, or is wholly without them in the adult. The head is generally of disproportionately large size as com- pared with the body, and is rarely separable from the trunk by any distinct constriction or neck. There is no sacrum, and the pelvis is only represented in a rudimentary form. Lastly, the adult is either wholly destitute of teeth, or possesses only ORDERS OF MAMMALIA. 295 a single set, which are always conical in shape, and are never divisible into distinct groups. All the true Cetacea are car- nivorous, living upon animal food. Chief among the Cetaceans in importance and zoological interest are the Whalebone Whales (Balenide), in which the adult is destitute of teeth, though the young whale pos- sesses teeth which never cut the gum. The place of teeth is taken by a series of transverse plates of whalebone or baleen, which are used as a kind of screening apparatus or filter to separate from the sea-water the minute Mollusks and Jelly- fishes upon which these enormous animals live. The most important member of this family, from a commercial point of - view, is the Greenland Whale (Balena mysticetus), which yields most of the whale-oil and whalebone of commerce. The Greenland Whale attains a length of from forty to sixty feet, and of this enormous length about a third is taken up by the head alone. The oil is derived from a thick layer of fat or “blubber,” which is situated under the skin, and serves to pro- tect the animal from cold. Though an inhabitant of the sea, the whale is obliged to come to the surface to breathe, and in so doing it ejects from the blow-holes what looks like a column of water, the whole operation being known to the whalers as “blowing.” The true nature of this act is still somewhat questionable, but it appears certain that the apparent jet of water is in reality, mainly if not entirely, due to the condensa- tion of the moisture which is contained in the air expelled from the lungs. The old view was that “blowing” consisted in the whale ejecting through the nose the water which had pre- viously been filtered through the baleen-plates of the mouth ; but it appears to be quite certain that this view, at any rate, is not the correct one. The Rorquals or Finner Whales re- semble the Greenland Whale in most respects, but the skin is furrowed with deep plaits or folds, and there is a dorsal fin, placed on the back. Some of these attain a gigantic size (eighty feet or more), but they are seldom captured, as their commercial value is small. The Toothed Whales (Odontoceti) are best known by the Sperm Whale, an animal as large as, or larger than, the Green- land Whale, but distinguished by having numerous conical teeth, a single blow-hole, and a curiously-truncated head. They yield an excellent oil, and the singular fatty substance which is known as “spermaceti.” They also yield the sub- stance called “ambergris,” which is used as a perfume; but this is probably a product of disease. 296 VERTEBRATE ANIMALS. The last family of the Cetacea is that of the Delphinida, comprising the Dolphins (Fig. 146) and Porpoises. They have numerous conical teeth in both jaws, and the nostrils open by a single aperture on the top of the head. The Dolphins are Fig. 146.—Cetacea, The Common Dolphin (Delphinus delphis). inhabitants of the sea, but two species live in rivers—one in India, and the other in America. The Porpoises are also marine, and occur in all seas. The most remarkable of the Delphinide is the Narwhal or Sea-Unicorn, which is found in the Arctic seas, and which attains a length of as much as fif- teen feet in the body alone. The chief peculiarity of the Nar- whal is in the dentition. The females, as a rule, have no teeth, the upper jaw alone having two rudimentary incisors which never cut the gum. In the males, however, while the lower jaw is without teeth, one of the two central incisors of the upper juw is enormously developed, and grows throughout the life of the animal, It forms a tusk of from eight to ten feet in length, the whole surface of which is spirally twisted. The fucction of this extraordinary tooth is doubtless offensive. Orver VI. Uneurata (Lat. ungula, a hoof).—This order is often spoken of as that of the Hoofed Quadrupeds, and is one of the largest and most important of the orders of Mam- malia. The order is characterized by having all the four limbs and by having that portion of the toe which touches the ground encased in a greatly-expanded nail or hoof. There are never more than four full-sized toes to each leg, and owing to the presence of hoofs the limbs are useless for grasping, and are only of use in locomotion and in supporting the weight of the body. There are always two sets of teeth, and the molars have broad crowns adapted for grinding vegetable sub- stances, The Ungulata are divided into two great primary sections, according as the toes are even or odd in number: ORDERS OF MAMMALIA. 297 A. Perissodactyla, or Odd-toed Ungulates, in which the toes are odd in number—either one or three.* If horns are present, they are not in pairs. B. Artiodactyla, or Even-toed Ungulates, in which the toes are even in number—either two or four; and, if horns are present, they are in pairs. The living Perissodactyle Ungulates are the Rhinoceroses, the Tapirs, and the Horse and its allies. The 2Rhinoceroses are extremely large and bulky brutes, having a very thick and nearly hairless skin, usually thrown into deep folds. The feet (Fig. 147, D) are furnished with three toes each, all en- Fig. 147.—Ungulata. A, Perissodactyle foot of Zebra. B, Artiodactyle foot of Llama. C, Artiodactyle foot of Antelope. D, Perissodactyle foot of Rhinoceros. cased in hoofs. The nose is furnished with one or two horns, composed of longitudinal fibres compacted together, and not having any central core of bone. When there is only one horn, it is, of course, unsymmetrical ; and, when there are two, these are not paired, but one is always placed behind the other in the middle line of the head, and the hinder one is much the shorter. The various species of Rhinoceros are found in India, Java, Sumatra, and Africa, inhabiting marshy places and feeding chiefly on the foliage of trees. The Zapirs have four toes to each of the fore-legs, but only three toes on the hind-legs, so that they are properly odd-toed. ‘The nose forms a short, movable proboscis, used in stripping off the leaves of trees. They are large, clumsy animals, which inhabit South * The fore-feet of the Tapirs are even-toed, but the hind-feet are perissodactyle. 298 VERTEBRATE ANIMALS, America, Sumaira, and Malacca, The third and last family of the Perissodactyla is that of the Hguide, comprising the Horse, Ass, Zebra, and Quagga, In this family the toes are reduced to one to each foot, enclosed in a single broad hoof, Fic. 148.—Head of Two-horned Rhinoceros (22. bicornis). without any supplementary hoofs. There is a continuous series of incisor teeth in both jaws, and in the males canines are present. The dental formula is: . 3—3 1—1 3—3 38—3 to—33 Ci (or none) ; pm z—33 Mz—3 = 40 All the varieties of Horses appear to be descended from the single species Equus caballus, which seems to have been primitively a native of Central Asia. When the American Continent was discovered it certainly possessed no living horse, but the horse has now become completely naturalized there, and we know that America formerly possessed about twenty species of horses, all of which are now extinct. In the genus Asinus are the Asses, Zebras, and Quaggas. The Wild Ass is a native of Asia, and the domestic Ass is probably descended from it. The Zebras and Quaggas are exclusively African, and ae distinguished by their beautifully-striped and banded bodies. The Artiodactyles or Hven-toed Ungulates are divided into two groups: 1. Omnivora, as the Pig and Hippopotamus. 2. Ruminantia, which chew the cud, such as Oxen, Deer, Camels, etc. Of the Omnivorous forms the Hippopotamus or River- ORDERS OF MAMMALIA. 299 horse is characterized by its massive heavy body, short blunt muzzle, and feet with four hoofed toes each. The Hippopota- mus is found in the rivers of Abyssinia, and throughout the whole of Africa to the south of this, It reaches a length of from eleven to twelve feet, is nocturnal in its habits, and swims and dives with great facility. It lives upon vegetable food, and is tolerably harmless unless attacked or irritated. The Pigs, Peccaries, and Wart-hogs, constitute the family Suida, and have usually four toes to each foot, though sometimes the hind-feet have only three toes. All the toes are hoofed, but it is only two which support the weight of the body, the remain- ing toe or toes being placed at some elevation on the back of the foot. The snout is truncated and cylindrical, and is ca- pable of extensive movement. The tail is very.short, or is represented only by a tubercle. Of the Swine the most important and best known is the Wild Boar (Sus scrofa), from which it is probable that all our domestic varieties of swine have sprung. Another form is the Babyroussa or Hog-deer (Sus babyrussa), which inhabits the Indian Archipelago, and is remarkable for the great size and backward curvature of the upper canine teeth. The Wart- hogs (Phacocheerus) are African, and derive their name from the possession of a fleshy wart under eacheye. The Peccaries are exclusively American, the best-known species being the Collared Peccary (Dicotyles torquatus). They are not at all unlike small pigs both in appearance and habits, and they are generally found in small flocks. The Ruminantia form a most natural group of the Ungu- lata, characterized by the structure of the foot, the dentition, and the structure of the stomach, The foot is “ cloven,” consisting of a symmetrical pair of toes, encased in hoofs, and looking as if produced by the cleav- age of a single hoof. In most cases there are also two small supplementary hoofed toes placed on the back of the foot. As regards the dentition, the typical state of things is that there should be no incisor nor canine teeth in the upper jaw, but that the lower jaw should have six incisors and two canines, which are all similar in size and form, and constitute a con- tinuous and uninterrupted series of eight teeth placed in the front of the lower jaw. There are six molar teeth on each side of each jaw, and these have grinding surfaces. The typi- cal dental formula, therefore, for a Ruminant is: 0—0 0—0 6—6 a 33) c 7? pm and m a 32 300 VERTEBRATE ANIMALS. In the absence of incisor teeth in the upper jaw, the lower incisors bite against a callous pad of hardened gum. The Camel tribe differs in its dentition from the above typical formula, and certain exceptions likewise occur in the males of some other forms, and in one or two other less important instances. The stomach in the Ruminants is complex, and is divided into several compartments, this being in accordance with their mode of eating. They all, namely, “ ruminate” or “ chew the cud; ” that is to say, they first swallow their food unmasti- cated, and then bring it up again after a longer or shorter period in order to chew it. This is effected as follows (Fig. 149): The gullet opens at a point between the first two com- Fie. 149.—Stomach of a Sheep. o Gullet; » Rumen or Paunch: h Honeycomb bag or Reticulum ; p Many-plies or Psalterium ; a Abomasum or Fourth Stomach. partments or stomachs, of which the largest lies to the left and is called the “ paunch,” while the smaller right cavity is called the “honeycomb bag” (reticulum). The paunch (rumen) is the cavity into which the food is first received, and here it is moistened and allowed to soak for some time. After the food has lain sufficiently long in the paunch, it passes into the “honeycomb bag,” where it is made up into little balls or pellets, which are then returned to the mouth by a reversed action of the muscles of the gullet. After having been thor- oughly chewed, and prepared for digestion, the food is now swallowed a second time. On this occasion, however, instead of passing into the paunch, the masticated food is conveyed into the third stomach. This is known as the “ many-plies or “psalterium,” because its lining membrane is thrown into a number of longitudinal folds, like the leaves of a book, The ORDERS OF MAMMALIA. 301 psalterium opens by a wide aperture into the fourth and last stomach, known as the “abomasum.” This is a cavity of considerable size, which secretes the true digestive fluid (gas- tric juice), and it is here that the food is really digested. ‘The abomasum terminates, of course, in the commencement of the small intestine. The Ruminantia include a number of families, of which it is only possible to notice the leading characters of the more important ones—namely, the Camelide, Cervide, Giraffes, and Cavicornia. The family Camelide comprises the Camel and Dromedary of the Old World and the Llamas of the New, and is charac- terized by having no horns, by having two incisors in the upper jaw, and a pair of canines in both jaws; while the foot consists of only two toes, covered with imperfect nail-like hoofs, and destitute of the two supplementary toes. The soles of the feet are covered with a callous horny integument upon which the animal walks. In the Camels the toes are conjoined below by a callous pad, and the back is furnished with one or two fleshy humps. The Arabian Camel or Dromedary has but one hump, and its structure admirably adapts it for a beast of burden in the sandy deserts of Arabia and Africa. One special provision toward this end is the possession of large cells in the paunch, in which a large quantity of water can be stored up, thus enabling the animal to travel for days without drink- ing. The Bactrian Camel resembles the Dromedary in most respects, but it possesses two humps. The place of the Camels of the Old World is filled in South America by the Llamas and Alpacas (Auchenia), which have separate toes, and have no hump. The Llama is extensively used as a beast of burden, but the Alpaca is chiefly of value for its long wool, which is largely manufactured. The family Cervide includes the true Deer, and is charac- terized by the fact that the forehead carries two solid bony antlers, which are not hollow, and are usually much branched. With the single exception of the Reindeer, these appendages are exclusively confined to the males, and they are deciduous; that is to say, they are only produced at certain seasons (an- nually, at the breeding-season), and, when they have fulfilled their purpose, they are shed. They increase in size and in the number of branches-every time they are reproduced, till in the old males they may attain an enormous size. Among the more familiar of the Deer may be mentioned the Elk, or Moose (Alees epee es of Scandinavia and North America, the 302 VERTEBRATE ANIMALS. Reindeer and Caribou (Cervus tarandus) of Northern Europe, Asia, and North America; the Red Deer ( Cervus elaphus, Fig. 150) of Europe; the Wapiti (C. Canadensis) of Canada; and the Roebuck ( Capreolus caproea) of Northern Europe. Of the Giraffes or Camelopardalide there is only a single living species, exclusively confined to the African Continent. Both sexes have two pairs of short horns, carried on the fore- head; but these are persistent, and are covered with a hairy skin, The neck is extremely long, and the fore-legs much longer than the hind-legs. Itis the largest of living Ruminants, and measures as much as from fifteen to eighteen feet in height. The Cavicornia or Hollow-horned Ruminants comprise the Oxen, Sheep, Goats, and Antelopes, and are characterized by having horns, which may be present in one or both sexes, and consist of a horny sheath surrounding a central bony axis, or “horn-core.” The horns are persistent, and are not peri- odically shed, and there is usually only a single pair, though sometimes there are two pairs. In their dentition, and in ORDERS OF MAMMALIA, 303 other respects, the Cavicornia are to be regarded as being the most typical examples of the Ruminantia, and they in- clude a number of animals which are of the highest utility to man. ‘The Antelopes form a very extensive group, closely re- sembling the true Deer, but distinguished by the possession of hollow horns, in place of solid antlers. Most of the Ante- lopes are African, and there are only two European forms (the Chamois being one), while America possesses only the Prong- buck (Antilope furcifer). Among the more familiar African species may be mentioned the Gazelle, the Koodoo (Fig. 151), = Fic. 151.—Antelopida. Head of the Koodoo (Strepsiceros Koodoo). the Gnu, the Gemsbok, and the Springhok. The Sheep and the Goats (Ovide) are closely allied to one another, and are well known by their domestic varieties. All the Sheep appear to be natives of the Old World, with the exception of the “Bighorn” (Ovis montana) of the Rocky Mountains. Among the true Oxen (Bovidee) the most important species is the domestic Ox (Bos taurus) with its innumerable varieties. The true Buffalos (Bubalus) are natives of Asia and Africa, and are characterized by their wide horns united at the base. The American Buffalo, or Bison, as it is properly called (Bison Americanus), is distinguished by its enormous head, shaggy mane, and conical hump between the shoulders. America also possesses another singular Ox in the person of the Musk Ox (Ovibos moschatus), which is found north of the 60th parallel, and is remarkable for its small size and long, woolly coat. Orver VII. Hrracomra (Gr. hurax, a shrew; eidos, form).—This order includes only a single small genus (Hyrar), 304 VERTEBRATE ANIMALS. of which only a few species are known. They are all gregarious little animals, living in holes of the rocks, and capable of do- mestication. One species (Hyrax Capensis) occurs commonly in South Africa, and is known to the Dutch colonists as the “Badger.” Another species (Hyrax Syriacus) occurs in the rocky parts of Arabia and Palestine, and is believed to be the “cony” of Scripture. They present many curious points of resemblance to the gigantic Rhinoceros, and are often placed in the same order, the similarity being especially great as re- gards the form of the molar teeth. The incisor teeth of the upper jaw are long and curved, with sharp cutting edges, and they grow from a permanent pulp, thus resembling the teeth of the genuine Rodents (such as the Rabbit or Beaver). Orper VIII. Proposcmza (Lat. proboscis, the snout).— This order is only represented at the present day by the Ele- phant, of which there are only two species living. One of these is the African Elephant, which is distinguished by its convex forehead and great flapping ears; the other is the In- dian Elephant, which has a concave forehead and small ears. The Proboscidea are characterized by having the nose pro- longed into a cylindrical trunk or proboscis, at the extremity of which the nostrils are placed (Fig. 152, 2). The trunk is extremely flexible and highly sensitive, and terminates in a finger-like prehensile lobe. There are no canine teeth; the molars are few in number, large, and transversely ridged, or furnished with tubercles. In the living forms there are no lower incisors, but the upper incisors are two in number, grow from a permanent pulp, and constitute enormous tusks (Fig. 152, 7). In some of the extinct forms there are two tusk-like lower incisors, and sometimes both the lower and upper in- cisors are developed into tusks. The feet are furnished with five toes each, but these are only partially indicated externally by the divisions of the hoof. The animal walks upon thick pads of integument, which constitute the soles of the feet. The Indian Elephant inhabits India and the Indian Archi- pelago and has five hoofs on the fore-feet, but only four on the hind-feet. Like the Ceylon Elephant, which is a mere variety, the males alone possess well-developed tusks. The- African Elephant has four hoofs on the fore-feet, and only three on the hind feet, while it is smaller and darker in color than the Indian species. Both sexes also possess tusks, though those of the males are largest. All the Elephants feed upon vege- table matter. ORDERS OF MAMMALIA, 305 Fig. 152.—Skull of the Indian Elephant (Zlephas Indicus). < Tusk-like upper incisors; m Lower jaw, with grinding molars, but without incisors; 2 Nostrils, placed at the ex- tremity of the proboscis. Though there are now but two living species of Elephant, there is no doubt but that some of the fossil forms have died out since the appearance of man upon the globe. Of these, the best known is the Mammoth, frozen carcases of which have been found in the icy wilds of Siberia. OrpErR IX. Carnrvora (Lat. caro, flesh; voro, 1 devour).— The ninth order of Mammals is that of the Carnivora or Beasts of Prey, comprising the Lions, Tigers, Wolves, Dogs, Cats, Hyzenas, Seals, Walruses, etc. The Carnivora are distin- guished by possessing two sets of teeth, which are simply enamelled, and are always of three kinds, incisors, canines, and molars, differing from one another in size and shape. The in- cisor teeth are generally six in each jaw; the canines are al- ways two in each jaw, and are much longer and larger than the other teeth. The molars are mostly cutting-teeth, fur- nished with sharp, uneven edges, but one or more of the hinder teeth have tuberculate crowns. The molars, too, graduate 806 VERTEBRATE ANIMALS. from a cutting to a tuberculate form as the diet is strictly car- nivorous or becomes more or less miscellaneous. The dental formula differs considerably in different mem- bers of the order, but subjoined is the dental formula of the Cats (Felide), which are the most typical examples of the Carnivora— — 1—1 ae a a Besides the strictly flesh-eating dentition of the Carnivo- ra, the order is distinguished by always having the feet pro- vided with strong, curved claws, and the collar-bones (clavi- cles) are either quite rudimentary, or are altogether absent. The Carnivora are divided into the following three sections, founded upon the nature of the limbs : i Fic. 153.—Feet of Carnivora (after Owen). A, Plantigrada, Foot of Bear; B, Pinna grada, Hind-teet of Seal; C, Digitigrada, Foot of Lion. 1. Pinnigrada (Fig. 153, B), in which both the fore and hind legs are short, and the feet form broad, webbed, swim- ming-paddles. The hind-feet are placed very far back, nearly in a line with the axis of the body, and they form with the hinder end of the body a powerful caudal fin. In this section are the Seals and Walruses. ' 2. Plantigrada (Fig. 153, A), comprising the Bears, 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. 3. Digitigrada (Fig. 153, C), comprising the Cats, Lions, ORDERS OF MAMMALIA. 307 Tigers, Dogs, etc., in which the heel is raised from the ground, and the animal walks upon tiptoe. The Seals and Walruses, forming the family Pinnigrada, are distinguished from the other Carnivora by their adapta- tion to an aquatic mode of life. In this respect they agree with the thoroughly aquatic Whales and Dolphins, but they differ from both the Cetacea and the Sirenia, not only in their dentition, but also in always having well-developed hind-limbs. The Seals (Fig. 154) are characterized by having incisor teeth in both jaws, at the same time that the canine teeth are not immoderately developed. They form a very numerous family, of which species are found in most seas out of the limits of Fic. 154.—Greenland Seal (Phoca Groenlandica). the tropics. They abound, however, especially in the seas of the Arctic and Antarctic regions. They are largely captured both for their oil and for their fur. The Walrus or Morse (Trichecus) is distinguished from the true Seals by the fact that in the adult only two of the upper incisors are present ; while the upper canines are enormously developed, and form two pointed tusks—fifteen inches or more in length—which are directed downward between the small lower canines, and pro- ject considerably below the chin. The Walrus is a large, heavy animal, from ten to fifteen feet in length, which is found in flocks in the Arctic seas, and is hunted both for its blubber and for the ivory of the tusks. The Plantigrade Carnivora apply the whole or the great- er part of the sole of the foot to the ground in walking; and 308 VERTEBRATE ANIMALS. this portion of the foot is nearly or altogether destitute of hairs, except in the White Bear. The most typical members of the Plantigrada are the Bears (Urside), of which the common Brown Bear and the White or Polar Bear are familiar examples. The Bears are much less purely carnivorous than the majority of the order, and, in accordance with their om- nivorous habits, the teeth do not exhibit the typical carnivo- rous characters. The incisors and canines have their usual car- nivorous form, but the premolars and molars are furnished with broad tubercular crowns. The claws are large, curved, and strong, but are not retractile. The tongue is smooth, the ears small and erect, the tail short, the nose mobile, and the pupil circular. Most of the Bears are only carnivorous, in so far that they eat flesh when they can get it; but a great part of their food consists of roots, acorns, honey, and even insects. Nearly related to the true Bears are the familiar Raccoons (Procyon) of America, the Coatis (Vasua) of South America, and the Wah (Azturus) of India. The only remaining Plantigrades of importance are the Badgers (Meles) of Europe, Asia, and America, the Gluttons or Wolverines ( G‘ulo) of the same continents, and the Honey- badgers (Mellivora) of Africa, Forming a kind of transition between the Plantigrada and the Digitigrada is a group of Carnivora which comprises nu- merous forms, such as the Weasels, Otters, and Civets, which apply part, but not the whole, of the sole of the foot to the ground, The Weasels (Mustelidw) have short legs and elongated, worm-like bodies, with a stealthy, gliding mode of progression. Good examples are the Pole-cat, the Mink, the Ermine, and the Sable. The two latter furnish the beautiful and valuable furs known by their names. Here also belongs the Skunk (Mephitis), celebrated for its intensely disagreeable odor when alarmed or irritated. The Otters are nearly allied to the Weasels, but have webbed feet adapted for swimming. The great Sea-otter yields a very valuable fur. The Civets and Genettes (Viverride) all belong to the Old World. The true Civet-cat inhabits North Africa, and is furnished with a pouch which secretes the peculiar fatty substance which is used as a perfume under the name of “ civet.” The typical group of the Carnivora is that of the Digiti- grada, comprising the three tribes of the Dogs (Canide), the Hyzenas (Hywnide), and the Cats (Felide). The family anide comprises the true Dogs, the Wolves, the Foxes, and ORDERS OF MAMMALIA, 309 the Jackals, all characterized by their pointed muzzles, smooth tongues, and non-retractile claws, and by the fact that the fore-feet have five toes, while the hind-feet have only four. In the Hycenide, comprising the Hyznas, there are only four toes to all the feet, the muzzle is rounded, the tongue is rough, and the hind-legs are shorter than the forelegs. The Hyznas are ill-conditioned, ferocious animals, which occur in Africa, Asia Minor, Arabia, and Persia. The most highly carnivorous, and therefore the most typi- cal, group of the Carnivora is that of the Cats or Felidae, comprising the Lions, Tigers, Leopards, Panthers, Cats, and others. In all these the animal walks lightly upon the tips of the toes, and the soles of the feet are hairy. The jaws are short, and, owing to this and to the great size of the muscles which move the lower jaw, the head assumes a rounded form, with a short muzzle. The molars and premolars are fewer in number than in any other of the Carnivora—hence the short- ness of the jaws; and they are all furnished with cutting- edges, except the last molar in the upper jaw, which is tuber- culate. The legs are nearly of equal length, and the hind-feet ‘have only four toes, while the fore-feet have five toes each. 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. The tongue is armed with horny eininences, which render it rough and prickly, and adapt it for the office of licking flesh from the bones of the prey. They are all extremely light upon their feet, and excessively muscu- lar; and all have the habit of seizing their prey by suddenly springing upon it. In this section are the Lion (Felis ar the Tiger (Helis Tigris), the Jaguar (Felis onca), the Puma (Felis concolor), the Leopard (Félis leopardus), the Lynxes, and the true Cats. The Lions are entirely confined to the Old World, inhabit- ing Southern Asia and Africa. The males are maned, and the tail is tufted. The Royal Tiger is exclusively Asiatic, as are most of the Tiger-cats, but some of the latter are American. The Spotted Cats or Leopards are represented, among others, by the Leopard and Cheetah of the Old World, and the well- known Jaguar of the American Continent. The Puma is also American, but its color is uniform. The Lynxes are distin- guished by their tufted ears, and are found both in the Eastern and Western hemispheres. Orprer X. Ropentia (Lat. rodo, I gnaw).—In this order 310 VERTEBRATE ANIMALS. are a number of small animals, characterized by the absence of canine teeth, and the possession of two long curved incisor teeth in both jaws, which are separated by a wide interval from the molars (Fig. 155). There are seldom more than two Fra. 155.—A, Skull of the Beaver (after Owen); B, Diagram of one of the incisor teeth ti ir ae showing the chisel-shaped point. a@ Enamel; d Soft tooth-substance entine). incisors in the upper jaw (sometimes four), but there are never more than two in the lower jaw. The molar teeth are few in number (rarely more than four on each side of each jaw). The feet are usually furnished with five toes each. The most characteristic point about the Rodents is to be found in the structure of the incisor teeth, which are adapted for continuous gnawing. They grow from persistent pulps. and consequently continue growing as long as the animal lives. Fig. 156.—Hamster (Cricetus vulgaris). They are large, long, and curved, and are covered in front with a layer of hard enamel, so that the softer parts of the tooth ORDERS OF MAMMALIA. 311 are placed behind (Fig. 155, B). The result of this is, that as the tooth is used in gnawing, the softer parts behind wear away more rapidly than the hard enamel in front, and thus the crown of the tooth acquires by use a chisel shape, bevelled away behind, and the enamel forms a persistent cutting-edge. . The Rodents are almost all of small size, and are very prolific. They subsist principally, if not entirely, on vegetable matters, especially the harder parts of plants, such as the bark and roots. Many possess the power of building very elaborate nests, and most of them hybernate (7. e., remain torpid through- out the winter). They are very generally distributed over the whole world. ‘ The order Rodentia comprises a large number of families, of which little more than the names can be mentioned. The most important families of Rodents are the following: 1. Le- poride, comprising the Hares and Rabbits. The Hares gen- erally occur in temperate regions, but some are African, and one species occurs in the Arctic regions, while the common American Hare (Lepus Americanus) extends from Canada to Mexico. 2. Cavidw, comprising the Capybaras, Guinea-pigs, etc. The Capybara is the largest of living Rodents, and is not unlike a small pig. It is a native of South America, and leads an amphibious life. Here also belong the Agoutis (Dasyprocta) of South America and the West Indies, and the Pacas of South America. 3. Hystricide, comprising the Por- cupines, and characterized by the fact that the body is covered with longer or shorter spines or quills mixed with bristly hairs. Most of the Porcupines live in burrows, and are much like the Rabbits in their habits, but some are furnished with prehen- sile tails, and live in trees. 4. Castoridw or Beaver family, comprising the Beaver, Musquash, and Coypu. The Beaver has webbed feet and a scaly tail, and the fur is an article of considerable value. It inhabits both North America and Europe. The Musquash resembles the Beaver in many re- spects, and is also a native of Northern America; but the Coypu is South American. 5. Muride, comprising the Mice, Rats, Hamster (Fig. 156), Lemmings, etc. The Rats and Mice are too well known to require more than merely to be mentioned. 6. Dipodidw, comprising the Jerboas of the Old World, and the Jumping Mice of America. 1%. Myowidc, com- prising the Dormice, which must not be confounded with the true Mice on the one hand, or with the Shrew-mice on the other hand. 8. Sciuridw, comprising the Squirrels, Flying Squirrels, and Marmots. The Flying Squirrels do not really 312 VERTEBRATE ANIMALS. fly, but, like the “ flying” Phalangers, they take long leaps from tree to tree by means of laterally-extended folds of skin. The Marmots, unlike the typical Squirrels, are ground-animals, and live in burrows. An excellent example is afforded by the Prairie-dog (Arctomys Ludovicianus) of North America. Orprr XI. Currroprera (Gr. cheir, hand; pteron, wing). —This order is undoubtedly one of the most natural and dis- Fie, 157,—Skeleton of a Bat (Pteropus.) (After Owen.) tinctly circumscribed orders in the whole class of the Man- malia, comprising only the Bats. In many respects, however, it might be well to regard the order as merely a modified branch of the Jnsectivora, just as the Pinnigrada are regard- ed as a modified offshoot of the Carnivora. The Cheiroptera or Bats are essentially characterized by the fact that the fore- limbs are much longer than the hind-limbs, and have several of the fingers enormously elongated. These enormously length- ened digits are united by an expanded leathery membrane or “patagium,” which not only stretches between the fingers, but is also extended between the fore and hind limbs, and is attached to the sides of the body (Fig. 157). The patagium ORDERS OF MAMMALIA. 313 thus formed often includes the tail, and is nearly or quite ° naked or destitute of hairs on both sides. It is used as an organ of true flight, and, in accordance with this, there are well-developed collar-bones (clavicles), and the breastbone is furnished with a ridge for the attachment of the pectoral mus- cles. Of the fingers of the hand at least three are destitute of nails. The mammary glands are placed upon the chest. Teeth of three kinds are always present, and the canines are always well developed. The Bats are all twilight-loving or nocturnal animals, and they are the only Mammals which pussess the power of true flight, though several others can make extended leaps from tree to tree. 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 in rocks, where they suspend them- selves by the short thumbs, which are provided with claws. In their flight, though they can turn with great ease, they are by no means as rapid and active as the true Birds. The tail is sometimes very short, sometimes moderately long, and is usually included in a continuation of the “ patagium,” which extends between the hind-legs. The body is covered with hair, but the patagium is usually nearly or quite hairless. Most of the Bats hybernate. The Cheiroptera are conveniently divided into the two sections of the Insectivorous and Frugivorous Bats. In the first section are all the bats of temperate climates, most of which are of very small size, and all of which live upon in- sects. Here also belong the great Vampire-bats (Phyllosto- mide) of South America. In the second, or fruit-eating sec- tion of the Cheiroptera, are only the Fox-bats (Pteropide), which are especially characteristic of the Pacific Archipelago, inhabiting Australia, Java, Sumatra, Borneo, etc., but occur- ring also in Asia and Africa. They are among the largest of the Bats, one species—the Pteropus edulis or Kalong—at- taining a length of from four to five feet from the tip of one wing to the tip of the other. OxpeR XII. Inszctrvora (Lat. insectum, an insect ; voro, I devour),—The twelfth order of Mammals is that of the In- sectivora, which comprises a number of small animals, very similar in many respects to the Rodents, but wanting the peculiar incisors of that order, and also being provided with clavicles. All the three kinds of teeth are present, but the dentition is very various, and the only common character is 314 VERTEBRATE ANIMALS, that the crowns of the molar teeth are furnished with small pointed eminences or cusps, adapted for crushing insects. All the toes have claws, there are usually five toes to each foot, and most of the Jnsectivora are plantigrade, that is to say, walk upon the soles of the feet. They are all small, and they exist over the whole world, except in Australia and South America, where their place is taken by Marsupials, such as the Opossums. The Jnsectivora are divided into the three families of the Moles (Zalpide), the Shrews (Soricide), and the Hedgehogs (Erinaceide). The Moles (Fig. 158) are distinguished by Fig. 158.—Insectivora. Mole (Zalpa Europea). having the body covered with hair, the feet short and formed for digging, and the toes furnished with strong, curved claws. There is no external ear, and the eyes are either extremely small, or are completely concealed beneath the fur. They are all nocturnal burrowing animals, The Star-nosed Moles ( Con- dylura) are American, but their habits are like those of the European Mole (Zalpa Europea, Fig. 158). The Golden Moles ( Chrysochloris) are African, and are remarkable for the iridescence of their fur. The Shrews are very like the true Mice in external appearance, but they are really widely dif- ferent. The body is covered with hair, the feet are not adapted for digging, and there are mostly external ears, while the eyes are well developed. No division of the Jnsectivora is more abundant or more widely distributed than the Sortcide, and one of the Shrews is probably the smallest of existing Mam- mals, not exceeding two and a half inches in length, counting in the tail. Besides the true Shrews (Sorex), this family in- cludes also the Elephant Shrews (Macroscelides) of Africa, and the common Water-mole (Sealops aquaticus) of North ORDERS OF MAMMALIA, 315 America. The third family includes only the well-known Hedgehogs, which have the power of rolling themselves into a ball at the approach of danger, and which have the upper surface of the body covered with short prickly spines, forming a protective armor. The common European Hedgehog (Zii- naceus Huropeeus) is the type of the family, but other species occur in Africa and India. The “Tenrecs” (Centetes) of Madagascar are closely allied to the Hedgehogs, but have no power of rolling themselves up. The “ Banxrings” (Zupaia) of the Indian Archipelago have a long, compressed tail, and live mostly in trees. Before passing on to the next order, a few words must be said about a curious transitional form, which has been alter- nately placed in the Chetroptera, the Insectivora, or the Quadrumana, or has been regarded as the type of a separate order, The animal alluded to is the so-called Flying Lemur ( Galeopithecus volitans), of which more than one species is known as inhabiting the Indian Archipelago. The leading characteristic in this singular animal is the possession of a fly- ing-membrane, which extends 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. The fingers are not elon- gated, and do not support a “patagium,” so that the animal has no power of true flight, but can simply take extended leaps from tree to tree. The G‘aleopithecus lives chiefly upon small insects and birds, and it should, probably, be regarded as an aberrant form of the Jnsectivora. Orprr XIII. Quaprumana (Lat. guatuer, four; manus, hand).—The thirteenth order of Mammals is that of the Quad- rumana, comprising the Apes, Monkeys, Baboons, and Le- murs. The characteristic of this order is that the innermost toe (great-toe) of the hind-limbs can be opposed to the other toes, so that the hind-feet become prehensile hands. The term “opposed” simply implies that the toe can be so adjusted, as regards the extremities of the other toes, that any object can be grasped between them, just as the thumb of the human hand can be “ opposed” to any of the fingers. The fore-feet may be destitute of a thumb, but, when this is present, it too is generally opposable to the other digits, so that the animal becomes truly four-handed or “ quadrumanous.” The Quadrumana are divided into three very natural sec- tions, separated from one another both by their anatomical characters and their geographical distribution. 316 VERTEBRATE ANIMALS. Section A. Strepsirhina.—Characterized by having the nostrils twisted or curved, and placed at the end of the nose, while the second toe of the hind-feet is furnished with a claw. The Quadrumana of this section are chiefly referable to Mada- gascar as their geographical centre, but they spread from Madagascar westward into Africa, and eastward to the Indian Archipelago. In this family are the Aye-Aye (Cheiromys), the Loris and Slow Lemurs (Nycticebidw), and the Lemurs (Lemuride). The Aye-Aye is confined to Madagascar, and is not unlike a large squirrel in appearance, having a long bushy tail, The incisors grow from permanent pulps, like those of Rodents, and there are no canines. The Loris and Slow Le- murs have either no tail or a rudimentary one, and they are confined to Southern Asia, and the great islands of the Indian Archipelago. The true Lemurs are natives of Madagascar, and are often spoken of as “Madagascar cats.” They have a soft, woolly fur, and a long tail, which is prehensile. The sec- ond toe of the hind-foot has a long and pointed claw. Section B. Platyrhina.—This section includes those mon- keys in which the nostrils are simple, and are placed far apart ; the thumbs of the fore-feet are wanting, or, if present, are not opposable; and the tail is generally prehensile. The Platy- rhine Monkeys are exclusively confined to South America, oc- curring especially in Brazil, and they are all adapted for a more or less purely arboreal life. The best-known members of this section are the Marmosets (Hapalide), and the great family of the Cebide, comprising the Spider-monkeys, the Howlers, and others. The Howlers (Mycetes) are remarkable for having a bony drum at the summit of the windpipe, by which the voice is rendered extraordinarily resonant, and peculiarly weird and terrifying to those who hear it. Section é Catarhina.—In this, the highest section of the Quadrumana, the nostrils are oblique and placed close to- gether, and the thumbs of all the feet are opposable, so that they are truly “quadrumanous.” The dental formula agrees with that of man: pe, 1—1, o 2—2 | po = 39 po PTs Pe gg eg The incisor teeth, however, are prominent and projecting, and the canines, especially in the males, are large and pointed, while the teeth form an uneven series. The tail is never pre- hensile, and is sometimes absent. Cheek-pouches are often ORDERS OF MAMMALIA, 317 present. In one single instance (Colobus) the thumbs of the fore-limbs are wanting. Fig. 159.—Quadrumana. Green Monkey (Cercocebus sabecus). (After Cuvier.) With the single exception of a Monkey which occurs on the Rock of Gibraltar, all the Catarhine Monkeys are confined to Africa and Asia. The most typical forms of the section are the Semnopithect and Macaques of Asia. Less typical are the Baboons, which inhabit Africa, and are among the most re- pulsive of all the Quadrumana. In these the tail is always short, and often quite rudimentary. The head is large, and the muzzle greatly prolonged, having the nostrils at its ex- tremity. More than any other of the Monkeys they employ the fore-limbs in terrestrial progression, running upon all fours with the greatest ease. The third family of the Catarhine Monkeys is that of the Anthropoid Apes, so called from their making a nearer ap- proach to man in anatomical structure than is the case with any other Mammal. The Anthropoid Apes are distinguished by having no tail, nor cheek-pouches. The hind-limbs are short—shorter than the fore-limbs—and the animal can pro- gress in an erect or semi-erect posture. Atthe same time the hind-feet are strictly prehensile, since the thumbs are oppos- 318 VERTEBRATE ANIMALS, able to the other toes. The canine teeth of the males are very long, strong, and pointed, but this is not the case in the females. In this tribe are the Gibbons, the Chimpanzee, the Orang- outang, and the Gorilla. The Gibbons form the genus Hylo- bates, and they belong to Asia, India, and the Indian Archi- pelago. The anterior limbs in these monkeys are extremely long, and the hands nearly or quite touch the ground when the animal stands erect. The Orang-outang (Simia) has no cheek-pouches, and the hips are covered with hair. The arms are of excessive length, and the hind-legs very short. When young; the head of the Orang-outang is not very different from that of a child, but, as the animal grows, the bones of the face gradually lengthen, while the skull remains much about the same; great bony ridges are developed for the attachment of the muscles which act upon the jaws; the incisors project; the canine teeth of the males become long and pointed, till ultimately the muzzle becomes as pronounced and well marked as in the Carnivorous animals (Fig. 160, A). The best-known Fra. 160.—A, Skull of the Orang-outang; B, Skull of a European adult. species of Orang is the Simia Satyrus, which inhabits Suma- tra, Borneo, and the other larger islands of the Indian Archi- pelago; but there are probably other species or varieties. The Chimpanzee and Gorilla both belong to Africa, and form the genus Zroglodytes. The Chimpanzee is a native of West- ern Africa, and has the arms much shorter proportionately than in the Gibbons and Orangs. Still they are much longer ORDERS OF MAMMALIA, 319 than the hind-limbs, and reach below the knees. The hands are naked to the wrist, and the face is also naked and much wrinkled. The Gorilla is in most respects like the Chimpan- zee, but is much larger, attaining a height of fully five feet. It is a native of Lower Guinea and Equatorial Africa, and is enormously strong and very ferocious. It is now generally looked upon as the highest of the Anthropoid Apes. Orper XIV. Biwana (Lat. bis, twice; manus, hand).— In this order stands Man alone, and little, therefore, needs to be said on this head. Man is distinguished zoologically from all other Mammals by his habitually erect posture and’ pro- gression upon two legs. The lower limbs are exclusively de- voted to progression and to supporting the weight of the body. The fore-limbs are shorter than the legs, and have nothing to do with progression. The thumb can be opposed to the other fingers, and the hands are therefore prehensile. The fingers and toes are furnished with nails; but the innermost digit of the foot (the great-toe) is not capable of being opposed to the other toes, so that the foot is useless as a grasping organ. The foot is broad and plantigrade, the whole sole being ap- plied to the ground in walking. The teeth are thirty-two in number, and they form a nearly even and uninterrupted series, without any gap or interval. The dental formula is: 8. Tost 5% 38 "gg? Vg oy? gag a The brain is more largely developed, and more richly furnished with large and deep foldings or convolutions, than is the case in any other Mammal. Lastly, Man is the only terrestrial Mammal in which the body is not furnished with a general covering of hair. The purely anatomical distinctions between Man and the other Mammals are thus seen to be not very striking, and of themselves they would hardly entitle Man to the position of more than a distinct order in the class Mammalia. When, however, we take into account the vast and unsurmountable mental differences, both intellectual and moral, between Man and the highest of the brutes, and when we reflect that this mental difference must have some physical correspondence, it becomes a question whether the group Bimana should not have the value of a distinct sub-kingdom, while there 320 VERTEBRATE ANIMALS. can be little hesitation in giving Man at least a class to himself. In the words of Dr. Pritchard, “the sentiments, feelings, sympathies, internal consciousness, and mind, and the habi- tudes of mind and action thence resulting, are the real and essential characteristics of humanity.” GLOSSARY. As-po'mEN (Lat. abdo, I conceal). The posterior cavity of the body, contain- ing the intestines and others of the viscera. In many Invertebrates there is no separation of the body-cavity into thorax and abdomen, and it is only in the higher Annulosa that a distinct abdomen can be said to exist. Ax-er'RANT (Lat. aberro, I wander away). Departing from the regular type. Az-nor’maL (Lat. ab, from; norma,arule). Irregular; deviating from the ordinary standard. Az-o-ma'sum. The fourth cavity of the complex stomach of the Ruminants. A-BRANOH'I-ATE (Gr. @, without; bragchia, gills). Destitute of gills or bran- chie. A-ca-te'pua (Gr. akaléphe, 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 microscepic cells, called ‘‘ thread- cells,” in the integument. A-oaN-rHO-cEPH'A-LA (Gr. akantha, a thorn; kephale, head). A class of para- sitic worms in which the head is armed with spines. A-oan-THo-mz-rri'na (Gr. akantha ; and metra, the womb). A family of Pro- tozoa, characterized by having radiating siliceous spines. A-oAN-THO-PTER-¥@'-1-1 (Gr. akantha, spine ; beg wing). A group of bony fishes with spinous rays in the front part of the dorsal fin, A-car't-na (Gr. akuri, a mite). A division of the Arachnida, of which the Cheese-mite is the type. Ao-oRE'TION. eo aid (Gr. a, without; kephale, head). Not possessing a distinct ead. A-oz-Tan'u-La (Lat. acetabulum, acup). The suckers with which the cephalic processes of many Cephalopoda Cuttle-fishes) are provided. A-or-Tas'v-LuM. The cup-shaped socket of the hip-joint in Vertebrates. Ao'ri-ta (Gr. a&ritos, confused). A term sometimes employed as synony- mous with Protozoa or the lowest division of the animal kingdom. Ao-t1-nom’ERES (Gr. aktin, a ray; meros, a part). The lobes which are mapped out on the surface of the body of the Ctenophora, by the cteno- phores, or comb-like rows of cilia. Ao-rrw-o-so'ma (Gr. aktin ; and soma, body). Employed to designate the entire body of any Actinozoén, whether this be simple (as in the Sea- anemones), or composed of several zodids (as in most Corals). Ao-rin-o-zo'a (Gr. aktin ; and zoén, an animal). That division of the Calen- terata of which the Sea-anemones may be taken as the type. Ap-5L-AR-THRO-s0’mMA-TA (Gr. adelos, hidden; arthros, joint; soma, body). An order of the Arachnida. Ap-pvo'TOR. A-i'RI-AL. A-cax'ro (Gr. a, without; gamos, marriage). Applied to all forms of repro- duction in which the sexes are not directly concerne 322 GLOSSARY. AL-tan-Torw's-A. The group of Vertebrata in which the fetus is furnished with an allantois, comprising the Reptiles, Birds, and Mammals, AL-Lan-tots’ (Gr. allas, a sausage). One of the “membranes” of the fetus in certain Vertebrates. Au-vez'o-11 (Lat. dim. ot alvus, nelly} Applied to the sockets of the teeth. Am-su-La’ora (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 Lchinodermata. Am'gu-La-To-Ry (Lat. ambulo, I walk). Formed for walking. Applied to a single limb, or to an entire animal. a A-MET-A-BoL'lo (Gr. @, without; metabole, change). Applied to those insects which do not possess wings when perfect, and which do not, therefore, pass through any marked metamorphosis. Am'n1-on (Gr. amnos, a lamb). One of the foetal membranes of the higher Vertebrates. Ax-nt-o'ra, The group of Vertebrata in which the fetus is furnished with an amnion, comprising the Reptiles, Birds, and Mammals. A-uc'BA (Gr. amoibos, changing). A species of Rhizopod, so called from the numerous changes of form which it undergoes. A-ua'si-rorm. Kesembling an Ameba in form. A-MOR-PHO-20'A Moe a, without ; morphe, shape ; 20m, animal). A name some- times used to designate the Sponges. A-MoR'PHOUS. Am-pup't-a (Gr. amphi, both ; bios, life). The Frogs, Newts, and the like, which have gills when young, but can always breathe air directly when adult. Am-pui-ca’tovus (Gr. amphi, at both ends; foilos, hollow). Applied to ver- tebre which are concave at both ends. Am'pur-piscs (Gr. amphi, at both ends ; diskos, a quoit, or round plate). The spicula which surround the aaa of Spongilla, and resemble two toothed wheels united by an axle. Au-pui-ox'us (Gr. amphi, at both ends; oxus, sharp). The Lancelet, a little fish, which alone constitutes the order Pharyngobranchit. Am-pHI-pyEus'ta (Gr. amphi, both ; pneo, I breathe). apie to the “ pe- rennibranchiate ” Amphibians which retain their gills through life, Am-puir’o-pa (Gr. amphi; and pous, a foot). An order of Crustacea. A'nax (Lat. anus, the vent). Connected with the anus, or situated near the anus. AN-AL-LAN-Tow’E-a. The group of Vertebrata in which the embryo is not furnished with an allantois. A-nat'o-cous. Applied to parts which perform the same function. AN-AM-NI-O'TA, e group of Vertebrata in which the embryo is destitute of an amnion. AN-ARTH-ROP’0-DA (Gr. @, without; arthros, a joint; pous, foot). That divi- sion of Annulose animals in which there are no articulated appendages. Ancu-y-Lo’sis or Ank-Y-Lo'sis (Gr. ankulos, crooked). The union of two bones by osseous matter, so that they become one bone, or are immovably joined together. An-proe'y-novus (Gr. anér, aman; gune, a woman). Synonymous with her- ah eas and implying that the two sexes are united in the same indi- vidual. An'‘pro-pPHorts (Gr. anér, a man ; and eS Tcarry). Applied to medusiform onophores of the Hydrozoa, which carry the spermatozoa, and differ in ‘orm from those in which the ova are developed. , An-nEL'I-pa (a Gallicised form of Annulata). The Ringed Worms, which form one of the divisions of the Anarthropoda. An'nu-La-tep. Composed of a succession of rings. An-nv-Lor'pa (Lat. annulus, a ring; Gr. edos, pues The sub-kingdom comprising the Echinodermata and the Scolecida (= Echinozoa). An-nu-1o’sa (Lat. annulus). The sub-kingdom comprising the Anarthropoda and the Arthropoda or Articulata, in all of which the body is more or less evidently composed of a succession of rings. GLOSSARY. 323 AN-o-Mo-Don'TI-a (Gr. anomos, irregular; odous, tooth). An extinct order of Reptiles, often called Dicynodontza, Ay-o-mo'ra (Gr. anomos, irregular ; oura, tail). A tribe of Decapod Crusta- cea, of which the Hermit-crab is the type. An-o-PLu'Ra (Gr. anoplos, unarmed ; oura, tail). An order of Apterous Insects. A-nou'rA (Gr. a, without ; oura, tail), The order of Amphibia comprisin the Frogs and Toads, in which the adult is destitute of a tail. Often calle Batrachia. An-ren'n= (Lat. antenna, a yard-arm). The jointed horns or feelers pos- sessed by the majority of the Articulata. An-TEN'NULES (dim. of antennw). Applied to the smaller pair of antenne in the Crustacea. An'THRO-POID. An-v1-Bra'cuI-um (Gr. anti, in front of; brachion, the arm). The fore-arm of the higher Vertebrates, composed of the radius and ulna. Anrt'Lers, Properly the branches of the horns of the Deer tribe (Cervida), but generally applied to the entire horns. An'tii-a (Lat. antlia,a pump). The spiral trunk or proboscis with which Butterflies and other Lepidopterous Insects suck up the juices of flowers. Apu-a-nip'TE-RA (Gr. aphanos, inconspicuous ; pteron, a wing). An order of Insects comprisin the Fleas. Ap-a-cen-Ta'Li-a. The section of the Mammalia, comprising the two divisions of the Didelphia and Monodelphia, in which the young is not furnished with a placenta. Apr’o-pa (Gr. a, without; podes, feet). aoe to those fishes which have no ventral fins. Also to the footless Cacilie among the Amphibia. Apr'o-paL. Devoid of feet. Ap-o-pEM's-Ta (Gr. apodaio, I portion off). Applied to certain chitinous septa which divide the tissues in Crustacea. Ap'rE-Ra (Gr. a, without; pteron, a wing). A division of Insects, which is characterized by the absence of wings in the adult condition. Ap’ter-ous. Devoid of wings. Ap’rer-yx (Gr. a, without ; pee awing). A wingless bird of New Zea- land, belonging to the order Cursores. A-quar'lo. A-QUIF’E-ROUS. A-naon'ni-pa (Gr. arachne, a spider). A class of the Articulata, comprising Spiders, Scorpions, and allied animals. AR-A-NE'I-DA. An-zo-rEs'ceNT. Branched like a tree. Ar-onz-op’TE-ryx (Gr. archaios, ancient; pterux, wing’. The singular fossil bird which alone constitutes the order of the Sawrur. AnrcH-EN-cEPH’A-LA (Gr. archo, I overrule; egkephalos, brain). The name applied by Owen to his fourth and highest group of Mammalia, compris- ing Man alone. Ar-k-na’oE-ous. Sandy, or composed of grains of sand. AR-THROP'0-Ds. Ar-i0-u-LA'TA (Lat. articulus, a joint). A ‘division of the animal kingdom, comprising Insects, Centipedes, Spiders, and Crustaceans, characterized by the possession of jointed bodies or jointed limbs. The term Arthropoda is now more usually employed. Ar-ti-o-pao'Ty-La (Gr. artios, even; daktulos, a finger or toe). A division of the hoofed quadrupeds (Ungulata) in which each foot has an even num- ber of toes (two or four). As-or-1-or'pa (Gr. askos, a bottle; eddos,a form). Asynonym of Tunicata,a class of Molluscous animals, which have the shape, in many cases, of a two- necked bottle. . A-sex'u-at. Applied to modes of reproduction in which the sexes are not concerned. A-stpn’o-waTE. Not porsessing a respiratory tube or siphon. (Applied to a division of the Lamellibranchiate Molluscs.) 824 GLOSSARY. As'tER-orp (Gr. aster, a star; and eédos, form). Star-shaped, or possessing radiating lobes or rays like a star-fish. As-re-Rorp’e-a. An order of Echinodermata, comprising the Star-fishes, characterized by their rayed form. A-stom’s-Tous (Gr. @, without; stoma, mouth). Not possessing a mouth. Ar’zas (Gr. the god who holds up the heavens). The first vertebra of the neck, which articulates with and supports the skull. A’rri-um (Lat. fora hall). Applied to the great chamber or “ cloa’ca,’’ into which the intestine opens in the Tunzcata. Av-rzt'ia (Lat. aurum, gold), Applied to the chrysalides of some Leptdop- tera, on account of their exhibiting a golden lustre. Av’rI-cLE (Lat. dim. of auris, ear). Applied to one of the cavities of the heart, by which blood is driven into the ventricle. Av-ropH'a-GI (Gr. autos, selt'; phago,I eat). Applied to birds whose young ae run about and obtain food for themselves as soon as they escape from the egg. A'vEs Cate avis, a bird). The class of the Birds. Av-1-ou-La’RI-uM (Lat. avicula, dim. of avis,abird). A singular appendage, often shaped like the head ofa bird, found in many of the Polyzoa. Axis (er axon, a pivot). The second vertebra of the neck, upon which the skull and atlas usually rotate. Az'y-gos (Gr. a, without; eugon, yoke). Single; without a fellow. Bao-re’ri-um (Gr. bakterion, a staff). A kind of staff-shaped filament which appears in organic infusions after they have been exposed to the air. BaL’an-cErs. Ba-Lan'I-p& (Gr. balanos, an acorn). A family of sessile Cirripedes, com- monly called ‘“ ‘Acorn-shells.” Ba-tzeEn’ (Lat. balena, a whale). The horny plates which occupy the palate of the true or ‘‘ whale-bone’’? Whales. Bar't-pEes (Gr. batos, a bramble). The family of the Z£lasmobranchit, com- prising the Rays. Ba-rra‘onr-a (Gr. batrachos, a frog). Often loosely applied to any of the Amphibia, but sometimes restricted to the Amphibians as a class, or to the single order of the Anoura. Br'Fiw (Lat. bis, twice; jindo, I cleave). Cleft into two parts; forked. Br-Lat’ER-AL (Lat. bis, twice ; latus, a side). Having two symmetrical sides. Br-ma'na (Lat. b2s, twice ; manus, a hand). The order of Mammalia compris- ing Man alone. Bre'e-pau (Lat. bés, twice ; pes, foot). "Walking upon two legs. Br-ra'movs (Lat. bs, twice; ramus, a branch). Applied to a limb which is divided into two branches Ss g., the limbs of Cirripedes). Br'vauveE (Lat. bis, twice; valve, tolding-doors). Composed of two plates or valves; applied to the shell of the Lamellibranchiata and Brachiopoda, and of the carapace of certain Crustacea. Bras-rorw’E-a (Gr. blastos, a bud; and e¢dos, form). An extinct order of Zchi- nodermata, often called Pentremites. Bracu-1-op’o-pa (Gr. brachion, an arm; pous, the foot). A class of the Mol- luscoida, often called ‘‘ Lamp-shells,” characterized by possessing two fleshy arms continued from the sides of the mouth. ee (Gr. brachkion, arm). Applied to the upper arm of Verte- rates, Braou-x-v'ra (Gr. brachus, short; owra, tail), A tribe of the Decapod Crus- taceans with short tails (2. e., the Crabs). Bractrs. (See Hydrophyliia.) Brap-x-pop'l-p& (Gr. dradus, slow; podes, feet). The family of Zdentata comprising the Sloths. Branon't-a (Gr. bragchia, the gills of fishes). A respiratory organ adapted to breathe air dissolved in water. Branon't-ate. Possessing gills or branchix. Bran-outr's-ra (Gr. bragchia, gills; and phero, I carry). A division of Gas GLOSSARY. 325 teropodous Molluscs, in which the respiration is aquatic, and the respi- ratory organs are mostly in the form of distinct gills. BRANOH-I-0-GAS-TE-ROP'O-DA (= Branchifera). Bran-cul-or’o-pa (Gr. bragchia; and pous, foot). A legion of Crustacea, in which the gills are Boner’ by the feet, Bran-cul-os TE-Ga (Gr. bragchia, gills; stego, I cover). Applied to a mem- brane and rays by which the gills are protected in many fishes. ae ut (Lat. brevis, short ; dingua, tongue). A division of the Za- certilia. Brev-1-Pen-na'tz (Lat. brevis, short; penna,a wing). A group of the Na- tatorial Birds. Bronou't (Gr. brogchos, the windpipe). The branches of the windpipe (trachea), by which the air is conveyed to the vesicles of the lung. Bru’ta (Lat. brutus, heavy, stupid). Often used to designate the Mamma- lian order of the Zdentata. Bry-o-zo'a oe bruon, moss; zodn, animal). A synonym of Polyzoa, a class of the Molluscoida. Buo'oat (Lat. bucca, mouth or cheeks). Connected with the mouth. er nega (Lat. bursa, a purse; forma, shape). Shaped like a purse; sub- spherical. Bys-srr’E-rovus. Producing a byssus. Bys’sus (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. Ca-pU-cl-BRANOH'I-ATE (Lat. caducus, falling off; Gr. bragchia, gills). Applied to those Amphibians in which the gills fall off before maturity is reached. CARD OG0R. pplied to parts which fall off or are shed during the life of the animal. Cz'oax (Lat. cecus, blind). Terminating biodly or in a closed extremity. Cz'oum (Lat. cecus). A tube which terminates lindly. Cas'PI-TosE (Lat. cos aturf). Tufted. Cat-no-zo'1o. (See Kainozoic. ) Caz'oar (Lat. fora spur). Applied to the “spurs” of Rasorial Birds; and also to the rudiments of the hind limbs in certain Snakes. Cat-oa'RE-ovs (Lat. cal, lime). Composed of carbonate of lime. Cau'tcr. The little cup in which the polype of a coralligenous Zoophyte ( Actinozoén) is contained. Cau-y-co-pHor'I-pz (Gr. kalux, a cup; and phero, I carry). An order of the oceanic Hydrozoa, so called trom their possessing bell-shaped swimming organs (nechocalyces). 5 Ca'tyx (Lat. calyx, a cup). Applied to the cup-shaped body of Vorticella (Protozoa), or of a Crinoid ( Lchinodermata). Pees eras (Lat. campanula, a little bell). An order of Hydroid Zod- phytes. Ca-nine’ (Lat. canis, a dog). The eye-tooth of Mammals, or the tooth which is placed at or close to the premaxillary suture in the upper jaw, and the corresponding tooth in the lower jaw, Ca-pir'u-LUM nt dim. of caput, head). Applied to the body of a Barnacle (Lepadide), from its being supported upon a stalk or peduncle. Car’a-pacr. A protective shield. Applied to the upper shells of Crabs, Lobsters, and many other Crustacea; also to the case with which certain of the Jnfusoria are provided, Also the upper half of the immovable case in which the body of a Chelonian is protected, arte Can-1-na'ta (Lat. carina, a keel). Applied by Husley to all those birds in which the sternum is furnished with a median ridge or keel. . Car-niv'o-ra (Lat, caro, flesh; varo, I devour). An order of the Mammalia, Can-niv'o-Rovs (Lat. caro, flesh; voro, 1 devour), Feeding upon flesh, Car’nosx (Lat. caro). Fleshy. — : Can-porn’a-ca (Gr. karpos, fruit; phago, I eat). A section of the Marsu- pralig, 15 326 GLOSSARY. Car'pus (Gr. karpos, the wrist). The small bones which intervene between the fore-arm and the metacarpus. Ca-Tar’RuIn-a (Gr. kata, downward; rhines, nostrils). A group of the Quadrumana. Cav'pat (Lat. cauda, the tail). Belonging to the tail. Cav-i-cor'n1-a (Lat. cavus, hollow; cornu, ahorn). The ‘hollow-hormned” Ruminants, in which the horn consists of a central bony “ horn-core”’ sur- rounded by a horny sheath. = Crn’trum (Gr. kentron, the point round which a circle is described by a pair of compasses). The central portion or ‘‘ body” of a vertebra. Cr-pHat'to (Gr. kephale, head). Belonging to the head. CEPH-A-LO-BRANCH I-aTE (Gr. kephale ¢ aud bragehia, gills), Carrying gills upon the head. Applied to a section of the Annelida, which, like the Serpula, have tufts of external gills placed upon the head. Crpu-a-LopH’o-ra (Gr. kephale; and Dr, I carry). Used synonymously with Encephala, to designate those Mollusca which possess a distinct head. Crpu-a-Lop’o-pa (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. CEpH-a-LO-THO'RAX (Gr. kephale; and thorax, chest). The anterior division of the body in many Crustacea and Arachnida, which is composed of the coalesced head and chest. Crre. The naked space found at the base of the bill of some birds, CER'E-BRAL. CrR’E-BRUM. Czr’vi-cat (Gr. cerviz, neck), Connected with the region of the neck. Ces-torp'E-a (Gr. sestos, a girdle). An old name for the Zeniada, a class of intestinal worms with flat bodies like tape (hence the name Tapeworms). Crs-TrapH’o-RI (Gr. kestra, a weapon; phero, I carry). The group of £lasmo- branchit represented at the present day by the Port Jackson Shark. Ce-ta'ce-a (Gr. étos, a whale). The order of Mammals comprising the Whales and Dolphins. - Cu2z-rToe'na-THA (Gr. chaife, bristle; gnothos, jaw). An order of the Anar- thropoda, comprising only the oceanic genus Sagitia. CHEI-ROP’TER-A Gr. cheir, hand; pteron, a wing). The order of Mammals comprising the Bats. Cue'L& (Gr. chele,a claw). The prehensile claws with which some of the limbs are terminated in certain Crustacea, such as the Crab, Lobster, etc. Cur’tatTr. Possessing chele; applied to a limb. CuE-tic'E-Rz (Gr. dhale, a claw; and keras, a horn). The prehensile claws of the Scorpion, supposed to be homologous with antenne. Geen Gn shane, a tortoise). The order of Reptiles comprising the Tortoises and Turtles. Cux-Lo-no-BA-TRA'cHI-A (Gr. chelone, a tortoise; batrachos, a ie . Some- times applied to the Amphibian order of the Anouwra (Frogs and Toads). err as (Gr. cheilos, a lip; and gnathos, a jaw). Anorder of the My- riapoda. Gers owk (Gr. cheilos ; and podes, feet). An order of the Myriapoda. Cur'trnz (Gr. chiton, a coat). “The peculiar chemical principle, nearly allied to horn, which forms the exoskeleton in many Invertebrate animals, espe- cially in the Arthropoda (Crustacea, Insecta, etc.). Cuto'RO-PHYLL (Gr. chloros, green; and phullon, aleaf), The green coloring matter of plants. Curo-mat'o-pHorEs (Gr. chroma, complexion, or color; and phero, I carry). Little sacs which contain pigment-granules, and are found in the integu- ment of Cuttle-fishes. Curys'a-1is (Gr. chrusos, gold). The motionless ae of butterflies and moths, so called because sometimes ae a g°. den lustre. Cuy-xa'qux-ous FLUID. A fluid consisting partly of water derived from the exterior, and partly of the products of digestion (chyle), occupying the body-cavity or perivisceral space in many Invertebrates (Annelides, Echino- GLOSSARY. 327 derms, etc.), and sometimes having a special canal-system for its conduction (chylaqueous canals). Cay ez (Gr. chulos, juice). The milky fluid which is the result of the action of the various digestive fluids upon the food. Cuy-ur'to (Gr. chulos, juice [chyle]; and Lat. facto, I make). Producing chyle. Applied to one of the stomachs, when more than one is present. The word is of mongrel origin; and “‘ chylopoétic”’ is more correct. Cuyme (Gr. chumos, juice). The acid, pasty fluid produced by the action of the gastric juice upon the food. Cuyme-mass, The central, semi-fluid sarcode in the interior of an Jnfusorian. Cru'1-a (Lat. ciliwm, an eyelash). Microscopic, hair-like filaments, which have the power of lashing backward and forward, thus creating currents in the surrounding or contiguous fluid, or subserving locomotion in the animal which possesses them. Cu-1-0-eRra'Da (Lat. ciliwm and gradior, I walk). Synonymous with Cteno- phora, an order of Actinozoa. Cin’oxi-pes (Gr. kigklis, a lattice). Special ap sronites in the column-walls of some Sea-anemones (Actinie), which probably serve for the emission of the cord-like ‘ craspeda.”” ; Crr’rt (Lat. cirrus, a curl). Tendril-like appendages, such as the feet of Barnacles and Acorn-shells ( Cirripedes), the lateral processes on the arms of Brachiopoda, ete. Crr-R1r’ER-ovs or Cir-rIc’ER-ouvs. Carrying cirri. Crr-rI-Pe'DIA, Cir-RHI-PE'DI-A, or C1R-RHOP 0-DA (Lat. cirrus, a curl; and pes, a foot). A sub-class of Crustacea with curled jointed feet. Crr-Ros'To-m1 (Lat. cirrus, a tendril; Gr. stoma, mouth). Sometimes used to designate the Pha: mgobranchit. Cua-poo'r-Ra (Gr. klados, a branch; keras,a horn). An order of Crustacea with branched antenne. Cra'vate (Lat. elavus, a club), Club-shaped. Crav't-ciE (Lat. clavicula, a little ke + The “collar-bone,” forming one of the elements of the pectoral arch off ertebrates. Cxo-a'ca (Lat. fora sink). The cavity into which the intestinal canal and the ducts of the generative and urinary organs open in common, in some Invertebrates (e. g., in Insects), and also in many Vertebrate animals. Ciyp'E-1-rorm (Lat. clypeus, a shield ; a On shape). Shield-shaped ; applied, for example, to the carapace of the abears't. Ont'pz (Gr. knide, a nettle). The urticating cells, or “ thread-cells,” where- by many Calenterate animals obtain their power of stinging. Coo'co-tiTHs (Gr. kokkos, a berry; Uthos, stone). Minute oval or rounded rae which are found either free or attached to the surface of cocco- spheres. Coo’co-sPHERES sea kokkos ; and sphaira, a sphere). Spherical masses of sar- code, enclosed in a delicate udleareots envelope, and bearing coccoliths upon their external surface. Both coccospheres and coccoliths are em- bedded in a diffused plasmodium of sarcode, the whole constituting a low Rhizopodic organism. Coo-cye’E-aL, Connected with the coccyx. Coo'crx (Gr. kokkux, a cuckoo). The terminal portion of the spinal column in man, so called from its resemblance to a cuckoo’s beak. Co-coon’ (French coton, the cocoon of the silk-worm; connected with Fr. oe shell, which is derived from the Lat. concha). The outer coverin, 0. silky hairs with which the ups or chrysalis of many insects is protected. Co-po-nos’ro-ma (Gr. kodon, a bel ; stoma, mouth). The ned ee or mouth of the dise (nechocalyx) of a Medusa, or of the bell (gonocalyx) of a medusi- form gonophore. : (@-LEN-TE-Ra’TA (Gr. Zoilos, hollow ; enéeron, the bowel). The sub-kingdom which comprises the Hydrozoa and Actinozoa. Proposed by Frey and con in place of the old term Radiata, which included other animals as we Ce-nen'ony-ma (Gr. Loinos, common; egchuma, tissue). The common cal- 328 GLOSSARY. careous tissue which unites together the various corallites of a compound coralluin. Ca-nae'ci-um (Gr. koinos, common ; ozkos, house). The entire dermal system of any Polyzoén ; employed in place of the terms polyzoary or polypidom. Ca@n'o-sarc (Gr. koinos, common; sarz, flesh). The common organized me- dium by which the separate polypites of a compound Hydrozoén are con- nected together. Cox-z-or'reR-a (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. Cox-v-zrI'na (Lat. coluber, asnake). A division of the OpAzdia. Cou-vum-Ba'cE-1 (Lat. columba, a dove). The division of Rasorial Birds com- prising the Doves and Pigeons. Cot-u-mEL'La (Lat. dim. of columna, a solu 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 thece of many corals. Cox'uMn. ave ied to the cylindrical body of a Sea-anemone (Actinia) ; also to the jointed stem or peduncle of the stalked Crinoids. CoM-MIs’SU-RAL Pe committo, I solder together). Connecting together ; usually applied to the nerve-fibres which unite different ganglia. Con’oua (Lat. for a shell). The external ear by which sounds are collected and transmitted to the internal ear. Con-curr’s-ra (Lat. concha, a shell; fero, I carry). Shell-fish. Appliedina restricted sense to the bivalve Molluses, and used as a synonym for Lamelli- branchiata. Con'pytz (Gr. kondulos, a knuckle). The surface by which one bone articu- lates with another. Applied especially to the articular surface or sur- faces by which the skull articulates with the vertebral column, Con-1-Ros'TRES (Lat. conus, a cone; rostrum, a beak). The division of Perch- ing Birds with conical beaks. Co-pxp’o-pa (Gr. kope, an oar; podes, feet). An order of Crustacea. Cor'a-cor (Gr. korax, a crow; eidos, form). One of the bones which enters into the composition of the pectoral arch in Birds, Reptiles, 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. Cor-aL-tie’nn-ovs. Producing a corallum. Cor'at-uits. The corallum secreted by an Actinozodn which consists of a single polype; or the portion of a composite corallum which belongs to, and is secreted by, an individual pelyte Cor-at'tum (from the Latin for red coral), The hard structures deposited in, or by, the tissues of an Actinozoin—commonly called a “ coral.” Co-r1-a'ceous (Lat. corium, hide). Leathery. Cor'pus Cat-Lo’sum (Lat. for the “firm body’’). The great band of nervous matter which unites the two hemispheres of the cerebrum in the Mammals, Cor-pvs'cu-LA-TED (Lat. conpusculum, a little body or particle). Applied to fluids which, like the blood, contain floating solid particles or ‘‘ corpuscles.” Cor'rI-oAL Lay'eR. The layer of consistent sarcode, which in the Jnfusoria encloses the chyme mass, and is surrounded by the cuticle. Sometimes called the ‘‘ parenchyma of the body.” Co-RYN'I-DA. Cos'rz (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). Among the Corals the ‘ cost’ are vertical ra es which occur on the outer surface of the theca, and mark the position of the septa within. Cos'tat (Lat. costa, a rib). Connected with the ribs. Ora'ni-um (Gr. kranion, the skull). The bony or cartilaginous case in which the brain is contained. Cras'PE-pa (Gr. draspedon, a margin or fringe). The long, convo.uted cords, containing thread-cells, which are attached to the free margins of the mesenteries of a Sea-anemone. GLOSSARY. 329 Cre-pvs'ou-Lar (Lut. crepusculum, dusk), Applied to animals which are active in the dusk or irs Cri-nor'pE-a (Gr. krinon, a lily; eidos, form), An order of Echinodermata, appt lates orms which are usually stalked, and sometimes resemble lilies in shape. Croc-o-pit'ta (Gr. krokodeilos, a crocodile). An order of Reptiles. Crop. A partial dilatation of the gullet, technically called ‘‘ ingluvies.” Crus-ta'ce-a (Lat. crusta, a crust). A class of articulate animals, comprising Crabs, Lobsters, etc., characterized by the possession of a hard shell or crust, which they cast periodically. Cren‘o-cyst (Gr. Ateis,a comb ; kustis, a bag or cyst), The sense-organ (prob- ably auditory) which occurs in the Ctenophora. Crz'nor (Gr. #teis, a comb; eidos, form). Applied to those scales of fishes, the hinder margins of which are fringed with spines or comb-like pro- ections. issn onk (Gr. kteis,acomb; and phero, I carry). An order of Actinozoa, comprising oceanic creatures, which swim by means of ‘‘ ctenophores,” or bands of cilia arranged in comb-like plates. Cur-so’rEs (Lat. curro, run). An order of Aves, comprising birds destitute of the power of flight, but formed for running vigorously (¢.g., the Ostrich and Emeu). Cus'pi-patz. Furnished with small pointed eminences or ‘‘ cusps.” Co’rl-oLE (Lat. cuticula,’dim. of cutis, skin). The pellicle which forms the outer layer of the body among the Jnfusoria. The outer layer of the in- tegument generally. Cu't1s (Lat. for skin). The inferior vascular layer of the integument, often called the cutis vera, the corium, or the derma. Cr'citom (Gr. kuklos, a circle ; eidos, form). Applied to those scales of fishes which have a regularly circular or elliptical outline with an even margin. Cy-cros’ro-m1. Sometimes used to designate the Hag-fishes and Lampreys, forming the order Marsipobranchit. Cyst (Gr. kustis, a bladder or bag). A sac or vesicle. Cys'tIc. Cys't1-ca. The embryonic forms (scolices) of certain intestinal worms (Tape- worms), which were described as a distinct order, until their true nature was discovered. Cys-tor'pr-a. (Gr. £ustis, a bladder; and eidos, form). An extinct order of Behinodermata. Der-oap’o-pa (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. Dez-crp'v-ovs (Lat. decido, I fall off). Applied to parts which fall off or are shed during the life of the animal. De-cot'La-Tep (Lat. decol/o, I behead). Zpetse to univalve shells, the apex of which falls off in the course of growth. Dzt-no-sau'ri-a (Gr. deénos, terrible; saura, lizard), An extinct order of Reptiles. Diar ser goat, Den-prir'ic, Den’prorp (Gr. dendron, a tree). Branched like a tree, arborescent. Den’rat. - Den-r1-Ros'rrxs (Lat. dens, a tooth; rostrum,a beak). The group of Perchin; Birds in which the upper mandible of the beak has its lower margin toothe Dera. (See Cutis.) : Der'mat (Gr. derma, skin). Belonging to the integument. ; : Der-mo-scre’RiTEs (Gr. derma, skin ; skleros, hard), Masses of spicules which occur in the tissues of some of the Aleyonida (Actinozoa). | Lf Des-snp'l-2. Minute fresh-water plwts, of agreen color, without a siliceous epidermis. 7 : . Dzv-rer-o-zo'dms (Gr. deuteros, second; zoin, animal; eddos, form). The zodids which are produced by gemmation from zodids. 830 GLOSSARY. Dex'trat (Lat. dextra, the right hand). Right-handed ; spyhed to the direc- tion of the spiral in the greater number of univalve shells. Dr'a-ruraem (Gr. diaphragma, a partition). The “midriff,” or the muscle which in Mammalia forms a partition between the cavities of the thorax and abdomen. Dr-a-ste'ma (Gr. dia, apart; histemi, to place). A gap or interval, especially between teeth. Dr-as'T0-LE (Gr. diastello, I separate or eapand), The expansion of a contrace tile cavity such as the heart, which follows its contraction or ‘systole.’ Di-a-To-ma'cE-& (Gr. diatemno, I sever). An order of minute plants, which are provided with siliceous envelopes. Di-sranou-1-a'ra (Gr. dis, twice; bragchia, gills). The order of Cephalopoda (comprising the Cuttle-fishes, etc.), in which only two gills are present. Di-orn-o-pon’'t1-a (Gr. dis, twice ; kuon, dog ; odows, tooth). An extinct order of Reptiles. Di-per'pat-a (Gr. dis, twice; delphus, womb). The subdivision of Mammals comprising the Marsupials. Die'rr (Lat, digitus, a finger). A finger or toe. Dic-1-11-era'pa (Lat. digitus; gradior, I walk). A subdivision of the Car nivora, Die't-r1-crape. Walking upon the tips of the toes, and not upon the soles of the feet. Din-z-Ro-so'ma-Ta (Gr, diss meros, part; soma, body). Anorder 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-a-ry (Gr. dis, twice ; mus, muscle). Applied to those bivalve Molluscs (Lamellibranchiata) in which the shell is closed by two adductor muscles. D1-a'cious (Gr. dis, twice ; oikos, house). Having the sexes distinct ; applied to species which consist of male and female individuals. Dipu'y-o-ponr (Gr. dis, twice; phuo, I generate; odous, tooth). Applied to those Mammals which have two sets of teeth. Diru-y-o-zo'o1ps. Detached reproductive portions of adult Calycophoride, an order of oceanic Hydrozoa. Dir'no1 (Gr. dis, twice; pnoé, breath). The order of Fishes represented by the Lepidosiren. Dir'rer-a (Gr. dis, twice; pteron, wing). An order of Insects characterized by the possession of two wings. Disc'or (Gr. diskos, a quoit ; etdos, form). Shaped like a round plate or quoit. Dis-copn'o-ra (Gr. diskos, a quoit; phero, I carry). This term is applied to the Meduse, 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. : Dis-szp't-ments (Lat. dessepio, I partition off). Partitions, Used in a restricted sense to designate certain imperfect transverse partitions, which grow from the septa of many corals. Dis'tat. Applied to the quickly-growing end of the hydrosoma. of a Hydro- zoin,y the opposite, or ‘‘proximal,’”? extremity growing less rapidly, and being the end by which the organism is fixed, when attached at all. DE UNNaE: (Lat. dees, day). Applied to animals which are active during the ay. Di-ver-tio'u-Lum (Lat. déverticulum, a by-road). A lateral tube with a blind extremity springing from the side of another tube. Dor’sax (Lat. dorsum, back}. Connected with the back. Don-si-BRANCH'I-ATE (Lat, dorsum, the back; Gr. bragchia, gills). Having ex- ternal gills attached to the back; applied to certain Annelides and Molluscs, The term is of mongrel composition, and ‘‘notobranchiate’ is more cor- rectly employed. Eo'pz-Row (Gr, e%, out; deros, ie The outer plane of growth of the ex- ternal integumentary layer (viz., the ectoderm, or epidermis), : GLOSSARY, 331 Eo'py-sts (Gr. ekdusis, a stripping off). A shedding or moulting of the skin. E-out-no-coc'cr (Gr. echinos, a he gehog 5 kokkos, a berry). The larval forms scolices) of the tapeworm of the dog (Twnia echinococcus), commonly nown as ‘‘ hydatids.”’ E-cHt-No-pER'mA-Ta (Gr. echinos ; and derma, skin). A class of animals com- Bretng the Sea-urchins, Star-fishes, and others, most of which have spiny skins. E-out-vor'pE-a (Gr. echinos ; and eidos, form). An order of Echinodermata, comprising the Sea-urchins. E-cuin'v-Late. Possessing spines. Ec'ro-crst (Gr. ektos, outside; £ustis, a bladder). The external investment of the ceencecium of a Polyzoin. Eo'ro-perm (Gr. ektos ; and derma, skin), The external integumentary layer of the Celenterata. Ec'ro-saro (Gr. ektos ; sarz, flesh). The outer transparent sarcode-layer of certain jaepees, such as the Ameba, E-pew-ra'ra (Lat. e, without; dens, tooth), An order of Mammalia often called Bruta. E-pen’tu-Lovus. Toothless; without any dental apparatus. Applied to the mouth of any animal, or to the hinge of’ the bivalve Molluscs. E-prI-oPH-THAL'MA-Ta (Gr. hedraios, sitting ; ophthalmos, eye). The division of eka in which the eyes are sessile, and are not supported upon stalks. E-as-mo-BRANCH'I-I (Gr. elasma, a plate; bragchia, gills), An order of Fishes, including the Sharks and Rays. Ex'y-tra (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). En'Bry-o (Gr. en, in; bruo, I swell). The earliest stage at which the young animal is recognizable in the impregnated ovum. En-cern'a-Lon (Gr. egkephalos, brain). The portion of the cerebro-spinal nervous axis contained within the cranium. En-cern’a-Lous (Gr. en, in; kephale, the head). Possessing a distinct head. Usually applied to all the Mollusca proper, except the Lamellibranchiata, En-ors-ta'Tion (Gr. en, in; kustis, a bag). The transformation undergone by certain of the Protozoa, when they become motionless, and pauanne them- selves by a thick coating or cyst. En'pr-ron (Gr. en, in; deros, skin). The inner plane of growth of the outer integumentary layer (viz., the ectoderm, or epidermis). En'po-orst (Gr. endon, within ; kustis, a bag). The inner membrane or in- tegumentary layer of a Polyzoin. In Cristatella, where there is no “ ecto- cyst,” the endocyst constitutes the entire integument. En'po-pErM (Gr. endon ; and derma, skin). The inner integumentary layer of the Calenterata. En-por’o-pitE (Gr. endon ; and pous, foot). The inner of the two secondary joints into which the typical limb of a Crustacean is divided. En'po-sarc (Gr. endon ; and sare, flesh). The inner molecular layer of sarcode in the Ameba and other allied Rhizopods. Ey-po-skEL'E-Ton (Gr. endon,; and skeletos, dry). The internal hard struc- tures, such as bones, which serve for the attachment of muscles, or the pro- tection of organs, and which are not a mere hardening of the integument. En’sI-FORM (Lat. ensis, a sword; forma, shape). Sword-shaped. En-ro-moru’A-ca (Gr. entoma, insects; phago, leat). A section of the Mar- supialia. Ben ae nn eik (Gx, entoma, insects; ostrakon, a shell). Literally, shelled insects—applied to a division of Crustacea. En-t0-z0'a tc r. entos, within ; zodn, animal). Animals which are parasitic in the interior of other animals. F’o-cznx (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 represented. 332 GLOSSARY. Ep-1-pDEr'mis (Gr. epz, upon; derma, the true skin). The outer non-vascular layer of the skin, often called the scarf-skin or cuticle, Ep-1-mz’Ra (Gr. ep2, upon; méron, thigh). The lateral pieces of the dorsal - arc of the somite of a Crustacean. Ep-1-po'p1-a (Gr. epi, upon; pous, the foot). Muscular lobes developed from the lateral and upper surfaces of the “‘foot”’ of some Molluscs. E-rrr'o-pirz (Gr. ep2, upon; pous, foot). A process Bevel upon the basal joint, or ‘‘ protopodite,” of some of the limbs of certain Crustacea. Ep-1-ster'Na (Gr. epz, upon; sternon, the breast-bone). The lateral pieces of the inferior or ventral are of the somite of a Crustacean. Ep't-sromm (Gr. epi, and stoma, mouth). A valve-like organ which arches over the mouth in certain of the Polyzoa. Ep-1-rne'oa (Gr. epi, and theke, a sheath). A continuous layer surrounding the thec in some Corals, and being the external indications of tabule. Ep-t-zo'a (Gr. epi, upon; zodn, animal). Animals which are parasitic upon other animals. In a restricted sense, a division of Crustacea which are parasitic upon fishes. E-QUI-LAT'ER-AL ne equus, equal; datus, side). Having its sides equal. Usually applied to the shells of the Brachiopoda. When applied to the spiral shells of the Foramin¢fera, it means that all the convolutions of the shell lie in the same plane. E’qui-vaLvE (Lat. eguus, equal; valve, folding-doors), Applied to shells which are composed of two equal pieces or valves. Er-ran’t1-a (Lat. erro, | wander). An order of Annelida, often called Nereidea, distinguished b7 their great locomotive powers. Ev-ryp-TER I-pa (Gr, ewrus, broad; pteron, wing). An extinct sub-order of Crustacea. Ex-op’o-pire (Gr. exo, autside; pous, foot). The outer of the two secondary joints into which the typical limb of a Crustacean is divided. Ex-0-sKEL'E-ron (Gr. exo, outside; skeletos, dry). The external skeleton. which is constituted by a hardening of the integument, and is often ealled a“ dermoskeleton.”” Fas-cic'v-La-TED (Lat. fasciculus, a Sandie). Arranged in bundles. Fav'na (Lat. Fawni, the rural deities of the Romans). The general assem- blage of the animals of any region or district. Fr'mur. The thigh-bone, intervening between the pelvis and the bones of the leg proper (#dia and fibula), ; Fre‘v-1a (Lat. a brooch). The outermost of the two bones of the leg in the higher Vertebrata ; corresponding to the wna of the fore-arm. Fiz't-rorm (Lat. jilum, a thread; forma, shape). Thread-shaped. Fis-si-Lrn'eur-a (Lat. jindo, I cleave; Lingua, tongue). A division of Lacer- tilia, with bifid tongues. ieee Fis'ston (Lat, jindo, 1 cleave). Multiplication by means of a process of self- division. Fis-stp'a-rous (Lat. jindo; and pario, I produce). Giving origin to fresh structures by a process of fission. Fis-si-ros'trREs (Lat. jindo, I cleave; rostrum, beak). A sub-order of the Perching Birds. fae Fra-cex'Lum (Lat. for whip). The lash-like appendage exhibited by many Infusoria, which are therefore said to be “ flagellate.” Fro’ra (Lat. Flora, the goddess of flowers). e general assemblage of the plants of any region or district. Foor. * Foor-saws. The limbs of Crustacea, which are modified to subserve mastica- tion. Foor-ss-crr'tion. The term applied by Mr. Dana to the sclerobasic corallum of certain Actinozoa. Foor-ru'ser-ctes. The unarticulated appendages of the Annelida, often called parapodia. Fo-pam-I-nir E-RA (Lat. foramen, an aperture; fero,I carry). An order of GLOSSARY. 333 Protozoa, usually characterized by the possession of a shell perforated by numerous pseudopodial apertures. Fru-erv'o-Rrovs (Lat. frux, fruit; voro; I devour). Living upon fruits. Fon'ne.. oe Fur'ou-Lum (Lat. dim. of furca, a fork). The ‘‘ merry-thought”’ of birds, or the veheped bone formed by the united clavicles. Fo'st-rorm (Lat. fusus, a spindle; and forma, shape). Spindle-shaped, or pointed at both ends. : Gat-1i-wa'cr-1 (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. Gan’cui-on (Gr. gagglion, a knot). A mass of nervous matter containing nerve-cells, giving origin to nerve-fibres, Ga'nor (Gr. ganos, splendor, 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. Ga-nor'pE-a. An order of Fishes. Gas-re-Rop’0-pa (Gr. gaster, stomach ; pous, foot). The class of the Mollusca comprising the ordinary univalves, in which locomotion is ricapay effected by a muscular expansion of the under surtace of the body (the ‘“ foot’). Gem'mz (Lat. gemma,a bud). The buds produced by any animal, whether detached or not. Gem-ma’tion, The process of producing new structures by budding. Gem-urp’ar-ous (Lat. gemma, a bud; pario,I produce). Giving origin to. new structures by a process of budding. Gen’ muxes (Lat. dim. of gemma). The ciliated embryos of many Celenterata y also the seed-like Le egy bodies or “ spores” of Spongilla. Gu-puyr's-a (Gr. gephura, a bridge). A class of the Anarthropoda, com- prising the Spoon-worms (Sipunculus) and their allies. Giz'zarp. A muscular division of the stomach in Birds, Insects, ete. Gua'pi-us (Lat. for a sword). Applied to the horny endoskeleton or ‘* pen” of certain Cuttle-fishes. Guz'norp (Gr. glenz, a cavity; eddos, 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. Gwata'tres (Gr. gnathos, a jaw). The masticatory organs of Crustacea. Gon-o-BLas-TID'I-a (Gr. gonos, offspring ; blastidion, dim. of blastos, a bud). The processes which carry the reproductive receptacles, or ‘‘ gonophores,”’ in many of the Hydrozoa. Gon-o-ca'Lyx (Gr. gonos ; and kalux, cup). The swimming-bell in a medusi- form gonophore, or the same structure ina geugphor which is not detached. Gon'o-pHorE (Gr. gonos ; and phero,I carry). The generative buds, or recep- tacles of the reproductive elements, in the Hydrozoa, whether these become detached or not. Goy’o-some (Gr. gonos, and soma, body). Applied as a collective term to the reproductive zodids of a Hydrozoin. ae Gon-o-rHE’oa (Gr. gonos ; and theke, a nee The chitinous receptacle within which the gonophores of certain of the Hydrozoa are produced. : a alae (hat gralle, stilts). The order of the long-legged Wading- ‘Birds. Gra-ntv’o-rovs (Lat. granum, a grain or seed; voro,I devour). Living upon grains or other seeds. . . Grap-to-Lir'1-p#& (Gr. grapho, I write; lithos, stone). An extinct sub-class of the Hydrozoa. et: Grec-a-RIW’I-Da (Lat. gregarius, occurring in numbers together). A class of the Protozoa. Guarp. The cylindrical fibrous sheath with which the internal chambered shell (phragmacone) of a Belemuite is protected. Gou’Lzr. 7 Gyu-no-Lz'mMa-tTa (Gr. gumnos, naked ; Jaimos, the throat). An order of the 334 GLOSSARY. Polyzoa in which the mouth is devoid of the valvular structure known as the ‘ epistome.” Gym-no-PHi'o-na (Gr. gumnos, naked; ophis, a snake). The order of the Amphibia comprising the snake-like Cacilia. Gym-nopo-THAL'Ma-Ta (Gr. gumnos; and ophthalmos, the eye). Applied by Edward Forbes to those Meduse in which the eye-specks at the margin of the disc are unprotected. The division is now abandoned. Gyn-no-so'sa-ra (Gr. gumnos ; and soma, the body). The order of Pteropoda in which the body is not protected by a shell. Gyn'o-PHORES (Gr. gune, Woman; phero,I carry). The generative buds, or gonophores, of Hydrozoa, which contain ova alone, and differ in form from those which contain spermatozoa. Gy-nEn-cEepH'a-La (Gr. guroo, I wind about ; egkephalos, brain). aves by Owen to a section of the Mammalia in which the cerebral hemispheres are abundantly convoluted. Ha'mat (Gr. haima, blood). Connected with the blood-vessels, or with the circulatory system. Ha-ma-too ry-a (Gr. haima, blood; kruos, cold). Applied by Owen to the “cold-blooded”? Vertebrates—viz., the Fishes, Am Etbia, and Reptiles. H2-ma-to-THEr'Ma (Gr. haima, blood ; thermos, warm). Applied by Owen to the ‘“‘warm-blooded” Vertebrates—viz., Birds and Mammals. Hat/Lux (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. : Hat-re'res (Gr. haltzres, weights used by athletes to steady themselves in leaping). The rudimentary filaments or “‘ balancers’’ which represent the posterior pair of wings in the Diptera, an order of Insects. Havs'tEL-LaTe (Lat, Aaurio, I drink). Adapted for sucking or pumping up fluids ; applied to the mouth of certain Crustacea and Insecta. HeEc-ro-cor'y-Lus (Gr. hekaton, a hundred ; kotulos, a ae The metamor- phosed reproductive arm of certain of the male Cuttle-fishes. In the Argonaut the arm becomes detached, and was originally described as a parasitic worm. HeE.'sun-THow (Gr. Aelmins, an intestinal worm). Worm-shaped, vermiform. HE-MEL’y-tTra (Gr. hemi, half ; elutron, a sheath). The wings of certain In- sects, in which the apex of the wing is membranous, while the inner por- tion is chitinous, and resembles the elytron of a beetle. Hen-t-xcet-a-Bou'io (Gr. hemi, half; metabole, change). Applied to those insects which undergo an incomplete metamorphosis. He-mip’Te-Ra (Gr. hemi, and pteron, wing). An order of insects in which the anterior wings are sometimes ‘“ hemelytra.” Her-mapu’Ro-piTe (Gr. Hermes, Mercury; Aphrodite, Venus). Possessing the characters of both sexes combined. Het-£-ro-cER’caL (Gr. heteros, diverse; kerkos, tail). Applied to the tail of Fishes when it is unsymmetrical, or composed of two unequal lobes. HET-E-RO-GE/NE-OvS, Her-z-R0-GANn GL1-aTE (Gr. heteros, diverse; gagglion, a knot). Possessing a nervous system in which the ganglia are scattered and unsymmetrical (as in the Mollusca, for example). Her-£-R0o-Mor’Puic (Gr. heteros ; morphe, form). Differing in form or shape. Het-g-ropu’a-a (Gr. heteros, other; phago, I eat). Applied to Birds the young of which are born in a helpless condition, ard require to be fed by the parents for a longer or shorter period. HeEt-r-Rop’o Da. He ree (Gr. hexa, six; pous, foot). Possessing six legs; applied to the msecta. Hr’tum (Lat. Azlum, a little thing). A small aperture (as in the gemmules of sponges), or a small depression (as in Woctiluca). Hir-v-pm'n-a (Lat. Aérwdo, a horse-leech). The order of Annelida com: prising the Leeches. GLOSSARY. 335 His-ror’o-ey (Gr. histos, a web ; Jogos, a discourse). The study of the tissues; more especially of the minuter elements of the body. Hot-o-cepa’a-11 (Gr. holos, whole; kephaie, head). A sub-order of the Elasmobranchii, comprising the Chimera. Hot-o-mer-a-Bor'to (Gr. holos, whole; metabole, change). Applied to insects which undergo a complete metamorphosis. Hot-o-sto'’ma-Ta (Gr. holos, whole; stoma, mouth). A division of Gasteropo- dous Molluscs, in which the aperture of the shell is rounded, or “entire. Hox-o-rnv-ror'pE-a (Gr. holos; thura, door; and eidos, form), An order of Echinodermata comprising the Trepangs. Hom-o-cEr’cat (Gr. homos, same ; kerkos, tail). Applied to the tail of Fishes -when it is symmetrical, or composed of two ahaal obes. Ho-Mo -Gz’NE-ovs. Ho-mo-¢an'GLi-aTE (Gr. homos, same; gagglion, a knot). Having a nervous system in which the ganglia are symmetrically arranged (as in the Annu- losa, for example). Ho-mor’o-cous (Gr. homos ; and logos, a discourse). Applied to parts which are constructed upon the same fundamental plan. Ho-mo-mor’pHovs (Gr. homos ; and morphe, form). Having a similar external appearance or form. Hu’me-rvus. The bone of the upper arm (brachium) in the Vertebrates. Hy'a-.uve (Gr. Aualos, crystal). Crystalline or glassy. Hyn'-a-rT1ps (Gr. hudatis, a vesicle). The vesicle containing the larval forms (Zehinococet) of the tapeworm of the sy Pe pero Resembling the common fresh-water polype (Aydra) in form. Y'DRA, Hy-pro-cav'ius (Gr. hudra, a water-serpent; and kawlos,astem). The main stem of the ecenosare of a Hydrozoin. Hy'-pro-cysts (Gr. hudra; and kustis, a cyst). Curious processes attached to the ccenosarc of the Physophoride, and termed ‘ feelers” (Fihler and Taster of the Germans). Hy-prq@'ci-um (Gr. Audra ; and oikos, a house). The chamber into which the ccoenosare in many of the Calycophoride can be retracted. Hy-pror'pa (Gr. hudra; and pre form). The sub-class of the Hydrozoa, which epmprises the animals most nearly allied to the Hydra. Hy-pro-puru't1-a (Gr. hudra; and phullon, a leat). Overlapping append- ages or plates which protect the polypites in some of the oceanic Hydrozoa (Calycophoride and Physophoride). They are often termed ‘ bracts,’”’ and are the Decksticke of the Germans. Hy-pro-rat'za (Gr. hudra; and rhiza, root). The adherent base or proximal extremity of any Hydrozoin. . Hy-pro-so'ma (Gr. hudra; and soma, body). The entire organism of any Hydrozoin, Hy-pro-tur’ca (Gr. Audra ; and theke, a case). The little chitinous cups in ihre the polypites of the Sertularida and Campanularida are pro- tected. Hy-pro-zo’a (Gr. hudra ; and zoin, animal), The class of the Celenterata, which comprises animals constructed after the type of the Hydra. Hy-men-or'tEr-a (Gr. huwmen, a membrane; pteron, a wing). An order of Insects (comprising Bees, Ants, etc.) characterized by the possession of four membranous wings. 2 Ily’or (Gr. x ; e¢dos, form). The bone which ianae the tongue in Ver- tebrates, and derives its name from its resemblance in man to the Greek letter y. Hy'ro-stome (Gr. hupo, under; stoma, mouth). The upper lip, or “ Jabrum,” of certain Crustacea (¢. 9., Trilobites). Hy-ra-corp'n-a (Gr. hurax, a shrew; eidos, form), An order of the Mam- malia constituted for the reception of the single genus Hyrax. Jou-tuy-o-por’y-uite (Gr. ichthus, fish; dorw, spear; Lithos, stone). The fossil fin-spines of Fishes. 336 GLOSSARY. Icu-ray-o-mor'pHa (Gr. ichthus ; morphe wees An order of Amphibians, often called Urodela cop yoe the fish-like Newts, etc. ToH-ray-opHu-THl' RA (Gr, ichthus ; phtheir, a louse). An order of Crustacea comprising animals which are parasitic upon Fishes. Icu-ruy-or'si-pa (Gr. ichthus ; opsis, appearance). The primary division of Vertebrata, comprising the Fishes an Amphibia. Often spoken of as the Branchiate Vertebrata. Icu-THY-OP-TER-¥G'I-A (Gr. ichthus,; pterux, wing). An extinct order of Reptiles. Ton-ray-o-sav'R1-a (Gr. ichthus,; sawra, lizard). Synonymous with Ichthy- opterygia. In't-um. The haunch-bone, one of the bones of the p2lvic arch in the higher Vertebrates. I-ma'co (Lat. for an image or apparition). The perfect insect, after it has undergone its metamorphoses. ee eae Applied to scales or plates which overlap one another like tiles. In-cr'sor (Lat. éncido, I cut). The cutting teeth fixed in the intermaxillary bones of the Mammalia, and the corresponding teeth in the lower jaw. In-E-QUI-LAT'ER-aL. Having the two sides unequal, as in the case of the shells of the ordinary bivalves (Lamellibranchiata). When eypied. 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. In-z'Qui-vaLvE. Composed of two unequal pieces or valves. In-Fun-p1s'v-Lum (Lat. for funnel). The tube formed by the coalescence or apposition of the epipodia in the Cephalopoda—commonly termed the “funnel,” or ‘‘ siphon.” In-ru-so'ri-a (Lat. infusum, an infusion). A class of Protozoa, so called be- cause they are often developed in organic infusions. In'aumy-au (Lat. énguen, groin). Connected with, or situated upon, the groin. In-o-pER-cu-La'ra (Lat. 2, 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. In-sec'ra (Lat. énseco, I cut into). The class of Articulate animals commonly known as Insects. : In-sko-T1v'o-Ra (Lat. insectum, an insect; voro, I devour). An order of Mammals. In-sEc-trv'o-Rovs, Living upon Insects. In-sEs-so'REs (Lat. insideo, I sit upon). The order of the Perching Birds, often called Passeres, Iy-TER-AM-BU-La'oRA (Lat. inter, between; ambulacrum, that which serves for walking). The rows of plates in an Echinoderm which are not per- forated for the emission of the ‘ tube-feet.”’ In-TeR-MAx-IL'L#, or Pra-max-1'Le (Lat. inter, between; pra, before; maxilla, the Her: The two bones which are situated between the two superior maxilla in Vertebrata. In man, and some monkeys, the premax- illee anchylose with the maxille, so as to be irrecognizable in the adult. Ly-rus-sus-cep'tion (Lat. intus, within; suscipéo, I take up). The act of taking foreign matter into a living being. IN-vVER-TE-BRA'TA (Lat. Zn, without ; vertebra, a bone of the back). Animals without a spinal column or backbone. ‘ I hal (Gr. zschion, the hip). One of the bones of the pelvic arch in Ver- tebrates. I-sop’o-pa (Gr. ésos, equal; podes, feet). An order of Crustacea in which tho feet are like one another and equal. Ju'ev-Lar (Lat. yugulum, the throat). Connected with, or placed upon, the throat. Applied to the ventral fins of fishes when they are pincer beneath or in advance of the pectorals. Kar-no-zo'1o (Gr. kainos, recent; 20é, life). The Tertiary period in Geology, GLOSSARY. 337 comprising those formations in which the organic remains approximate more or less closely to the existing fauna and flora. Ker’a-rope (Gr. keras, horn; eidos, form). The horny substance of which the skeleton of many sponges is made up. Ker-a-to'sa. The division of Sponges in which the skeleton is composed of keratode. La’si-um (Lat. for lip). Restricted to the lower lip of Articulate animals.: La'srum (Lat. for lip). Restricted to the upper lip of Articulate animals. Las-y-runtH-o-pon'Ti-a (Gr. laburinthos, a labyrinth; odous, tooth). An extinct order of Amphibia, so called from the complex microscopic structure of the teeth. Lac-er-m11't-a (Lat. lacerta, alizard). An order of Reptilia comprising the Lizards and Slow-worms. Lz-mo-pir'o-pa (Gr. laimos, throat; dis, twice; podes, feet). An order of Crustacea, so called because they have two feet placed far forward, as it were under the throat. : La-MeL-Li-Branon-i-a'ta (Lat. lamella, a plate; Gr. bragchia, gills). The class of Mollusca, comprising the ordinary bivalves, characterized by the possession of lamellar gills. LA-mEL-L1-Ros'tRES (Lat. lamella, a plate; rostrum, beak). The flat-billed Swimming Birds (eraeoree, such as Ducks, Geese, Swans, etc. Lar’va (Lat. fora mask). The insect in its first Panes after its emergence from the egg, when it is usually very different from the adult. Lar'ywx. e 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. Len-r10'v-Lar (Lat. Jens, a bean). Shaped like a biconvex lens. Lep-1-por’rn-ra (Gr. lepis, a scale; pteron, a wing An order of Insects, comprising Butterflies and Moths, characterized by possessing four wings which are usually covered with minute scales. Ler-1-po'ra (Gr. lonidalon, covered with scales). Formerly applied to the order Dipnoi, containing the Mud-fishes (Lepidosiren). Lep-ro-car'p1-a (Gr. leptos, slender, small; “ardia, heart). The name given by Miller to the order of Fishes comprising the Lancelet, now called Pha- ryngobranchit. Lig-a-MEn’ruM Nu'oH# (Fr. nugue, the nape of the neck). The bandof elastic fibres by which the weight of the head in Mammadia is supported. Lin’evat (Lat. lingua, the tongue). Connected with the tongue. Luy'ev-La (Lat. dinguia, a little tongue). The upper flexible portion of the labium or lower lip in Insects. ; Lis-sen-cEPu'A-LA (Gr. lissos, smooth ; egkephalos, brain). A pouty division of Mammalia, according to Owen, in which the cerebral hemispheres are smooth or have few convolutions. Lira’o-cysrs (Gr. lithos, a stone ; bustis, a cyst). The sense-organs or ‘ mar- ginal bodies” of the Lucernarzda or Steganophthalmate Medusa. Lon-i-pen-na'tz (Lat. longus, long; penna, wing). A group of the Nata- torial Birds. . ; Lon-ai-ros'TREs (Lat. longus ; rostrum, beak). A group of the Wading Birds. Lopn’-o-raore (Gr. lophos, a crest; and phero,I carry). The disc or stage upon which the tentacles of the Polyzoa are borne. Lopa-u-rop’o-pA (Gr. lophouros, having stiff hairs; and podes, feet). An order of Crustacea. i ; y Lo-rr'ca (Lat. for a igen neg Applied to the protective case with which certain Jnfusoria are provided. A ; “es Lor-1-ca'ra (Lat. orica, a cuirass). The division of Reptiles comprising the Chelonia and Crocodilia, in which bony plates are developed in the skin derma). asic en (Lat. Zucerna, alamp). An order of the Hydrozoa. Lum'BaRr eb lumbus, loin). Connected with the loins. Lu‘wats (Lat. wna, moon). Crescentic in shape. 838 GLOSSARY. Ly-rn-crrn’a-1a (Gr. lwo, I loose; egkephalos, brain). A primary division of Mammals, according to Owen. ’ aa , : = Mao-no-pac’ry-11 (Gr. makros, long; daktulos, a finger), A group of the Wading Birds. Ma-crv'ra (Gr. makros, long; owra, tail). A tribe of Decapod Crustaceans with long tails (¢.9., the Lobster, Shrimp, etc.). Manv-RE-Por'I-rorM. Perforated with small holes, like a coral; applied to the tubercle by which the ambulacral system of the Zchinoderms mostly com- municates with the exterior. Mat-a-co-DERM'A-TA, Mat-a-cos’tra-ca (Gr. malakos, soft; ostrakon, shell). A division of Crus- tacea. Originally applied by Aristotle to the entire class Crustacea, because their shells were softer than those of the Mollusca. Mat-Lopn’s-ea (Gr. maiios, a fleece; phago, I eat), An order of Insects which are mostly parasitic upon birds. Man-ma'L1a etd mamma, the breast). The class of Vertebrate animals which suckle their young. Man'pI-BLE ee mandibulum, a jaw). The upper pair of jaws in Insects; also applied to one of the pairs of sens in Crustacea and Spiders, to the beak of Cep. mlopedss the lower jaw of Vertebrates, etc. Man’tte. The external integument of most of the Mollusca, which is largely developed, and forms a cloak in which the viscera are protected. Technt- eally called the “ pallium.” Ma-nv'sri-um (Lat. for a handle). Phe poles which is suspended from the roof of the swimming-bell of a Medusa, or from the gonocalyx of a medusiform gonophore among the Hydrozoa. Ma'‘nus (Lat. for the hand). The hand of the higher Vertebrates. Mar-stp-o-Brancu'I-1 (Gr. marsipos, a pouch; bragchia, gills), The order of Fishes comprising the Hag-fishes and Lampreys, with pouch-like gills. Mar-su-pPiea'Li-a (Lat. marsupium, a pouch). An order of Mammals in which the females mostly have an abdominal pouch in which the young are carried, Mas’rax (Gr. for mouth). The muscular pharynx or ‘ buccal funnel” into which the mouth opens in most of the Rotifera. Mas-ri-ca'To-Ry (Lat. mastico, 1chew). Applied to parts adapted for chewing. Max-ir'La (Lat. for jaws). The inferior pair or pairs of jaws in the Arthro- oda (Insects, Crustacea, ete. ). The upper jaw-bones of Vertebrates. X-IL'LI-PEDES (Lat. maxille, jaws; pes, the foot). The limbs in Crustacea and Myriapoda which are converted into masticatory organs, and are com- monly called ‘‘ foot-jaws.” Me-put'ta (Lat. for marrow). Sponed to the marrow of bones, or to the spinal cord, with or without the adjective ‘ spinadis.” Mz-pv'sz. An order of Hydrozoa, commonly known as Jelly-fishes (Disco- phora, or Acalephe), so called because of the resemblance of their tentacles to the snaky hair of the Medusa. Many Meduse are now known to be merely the gonophores of Hydrozoa. Mer-pv'st-rorm. Resembling a Medusa in shape. Meg-pv’sor. Like a Medusa ; used substantively to designate the medusiform gonophores of the Hydrozoa. __ : Mem-sra'wa Nio'TI-Tans (Lat. nécto, I wink). The third eyeng of Birds, etc. Men'tum (Lat. for the chin), The basal portion of the labium or lower lip in Insects. Me-ro-stom'a-Ta (Gr. méron, thigh; stoma, mouth). An order of Crustacea in which the oe. which are placed round the mouth, and which officiate as jaws, have their free extremities developed into walking or pre- hensile organs. Mas-rn-re'rI-Es (Gr. mesos, intermediate; enteron, intestine). In a restricted sense, the vertical plates which divide the somatic cavity of a Sea-anemone (Actinia) into chambers. Mes-o-Po'DI-UM {Gr mesos, middle; pous, foot). The middle portion of the “foot”? of Molluscs. GLOSSARY. 339 Mzs-o-stzr'num (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). Mzs-o-rno’Rax (Gr. mesos; and thorax, the peat), The middle ring of the thorax in Insects. Mzs-o-z0'1o (Gr. mesos » 208, life). The Secondary period in Geology. Mer-a-car’Pus (Gr. meta, after; harpos, the wrist). The bones which form the ‘root of the hand,” and intervene between the wrist and the fingers. MeEt-s-mor'puo-sis (Gr, meta, implying change ; morphe, shape). The changes of form which certain animals undergo in passing from their younger to their fully-grown condition. Mert-a-po'pi-um (Gr. meta, after; pous, the foot). The posterior lobe of the foot in Mollusca ; often called the operculigerous lobe,” because it de- velops the operculum when this structure is present. Mz-ras’ro-ma (Gr. meta, atter; stoma, mouth). The plate which closes the mouth posteriorly in the Crustacea. Mer-a-rar'sus (Gr. mda, atter; tarsos, the aston) The bones which inter- vene between the bones of the ankle (¢arsws) and the digits in the hind-foot of the higher Vertebrates. MET-A-THO'RAX re mea, after; thorax, the chest). The posterior ring of the thorax in Insects. Mi-mer'io (Gr. mimetikos, imitative). Applied to organs or animals which resemble each other in external appearance, but not in essential structure. Mo’'zars (Lat. mola, amill). The ‘ grinders” in man, or the teeth in diphyo- dont Mammals which are not preceded by milk-teeth. | Mot-tus'oa (Lat. molizs, 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. Mot-tus-oor'pa (Mollusca ; Gr. etdos, form). The lower division of the Mol- lusea, comprising the Polyzoa, Tunicata, and Brachiopoda. Mon’aps (Gr. monas, unity). Microscopical organisms of an extremely simple character, developed in organic infusions. Mo-noc'u-Lous (Gr. monos, single ; Lat. oculus, eye). Possessed of only one eye. Mon-o-pEtrH't-a (Gr. monos, single ; delphus, womb). The division of Mam- malia in which the uterus is single. Mo-nae’ct-ous (Gr. monos, single ; oikos, house). Applied to individuals in which the sexes are united. Mon-o-my'a-RY monos, single; mus, muscle). Applied to those bivalves (Lamellibranchiata) in which the shell is closed by a single adductor muscle. Mon-o-puy'o-pont (Gr. monos ; phuo, I generate ; odous, tooth). a to those Mammals in which only a single set of teeth is ever developed. Mon-o-rTHat'a-mous (Gr. monos ; and thalamos, chamber). Possessing only a single chamber. Applied to the shells of Foraminifera and Mollusca. Mon-o-trem'a-Ta (Gr. monos , tréma, aperture). The order of Mammals com- rising the Duck-mole and Zchidna, in which the intestinal canal opens into a * cloaca’? common to the ducts of the urinary and generative organs, Mot-ri-Loo'u-Lar (Lat. multi, many; oculus, a little purse). Divided into many chambers. : Mut'ti-vatve. Applied to shells which are composed of many pieces. _ : Mot-roun’ev-xa (Lat. multi, many; ungula, hoof). The division of Perisso- dactyle Ungulates, in which each foot has more than a single hoof. My’'E-ton (Gr. muelos, marrow). The spinal cord of Vertebrates. Myr-r-ap’o-pa (Gr. murioi, ten thousand ; podes, feet). A class of Arthropoda Sets the Centipedes and their allies, characterized by their numerous eet. Na’orz-ovs (Fr. nacre, mother-of-pearl, originally Oriental). Pearly; of the texture of mother-of-pearl. eruet : Nat-a-To/RES (ae nare, to swim). The order of the Swimming Birds. Na'ta-to-ry (Lat. nave, to swim). Formed for swimming. 340 GLOSSARY. Nav’t1-tom. Resembling the shell of the Wautdlus in shape. ECH-O-CAL'Y-CES, ‘ Necu-o-oa'tyx (Gr. necho, I swim; kalux, cup). The swimming-bell ox “ dise”’ of a Medusa or Jelly-fish. : ’ Nen-a-TEt'ui-a (Gr. néma, thread; helmins,a worm). The division of Scole- cida comprising the Round-worms, Thread-worms, etc. NeE-mar'0-oysts (hr. nema, thread; kustis,a bag). The thread-cells of the Calenterata, (See Cnide.) : NeEw-a-to'pa. Nem-a-rorp'E-a (Gr. n2ma, thread; eédos, form). An order of Scolecida com- prising the Thread-worms, Vinegar-eels, etc. Ne-mar'0-PHOREs (Gr. néma, thiead ; phero, I carry). Czcal processes found on the ceenosare of certain of the Sértularida, containing numerous thread- cells at their extremities. Nu-wer'ri-pa (Gr. Wemertes, proper name). A division of the Turbellarian Worms, commonly called RP bon-worms.” Nerv’ores (Lat. nervus, a sinew). The ribs which support the membranous wings of insects. Nezvu'rar (Gr. neuron, anerve). Connected with the nervous system. Nerv-ra-ropu'y-sis (Gr. neuron, & nerve ; apophusis, a projecting part). The “ spinous process’? of a vertebra, or the process formed at the point cf junction of the neural arches. NeEvr-o-ro'pi-um (Gr. neuron, a nerve; pous, the foot). The ventral or in- ferior division of the ‘‘foot tubercle” of an Annelide, often called the “ventral oar.” Nev-ror’/Te-ra (Gr. neuron ; and pteron, a wing). An order of Insects charac- terized by four membranous wings with numerous reticulated nervures (¢. g., Dragon-fiies). Nev'rer (Lat. for neither the one nor the other). Having no fully-developed sex. Nip-1-r1-ca'tion (Lat. nidus, a nest; facio, I make). The building of a nest. Noo-tur’/nat (Lat. now, night). Applied to animals which are active by night. Nor’mat (Lat. norma, a rule). Conforming to the ordinary standard. No-ro-Brancu-1-a'Ta (Gr. notos, the back; and bragchia, gills). Carrying the gills upon the back; applied to a division of the Annelda. No’ro-cuorp (Gr. notos, back ; chorde, string), A cellular rod which is devel- oped 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 ‘‘ chorda dorsalis.” No-ro-po'p1-um (Gr. notos, the back; and pous, the foot). The dorsal divis- ion of one of the foot-tubercles or parapodia of an Annedide ; often called the “ dorsal oar.” Nv'otz-a-Tzp. Possessing a nucleus or central particle. No-crz’o-Lus. 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 “ i or ovary, of certain Tap ieoria, performing the functions of a testicle. Nov’cxe-vs ae 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 anovary. 8. 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. Nv-pi-sranou-1-a'Ta (Lat. nudus, naked; and Gr. bragchia, gills). An order of the Gasteropoda in which the gills are naked. Nymens. The active pups of certain Insects. Oc-or'l-rau. Connected with the occiput, or the back part of the head. QO-cz-an’1o, Applied to animals which inhabit the open ocean (= pelagic). O-cgx't1 (Lat. diminutive of oculus, eye). The siaph u e eyes of many Echino- derms, Spiders, Crustaceans, Molluscs, ete. GLOSSARY. 341 Oo-ror’o-pa (Gr. octo, eight; pous, foot). The tribe of Cuttle-fishes with eight arms attached to the head. O-pon-To-cx’T1 (Gr. odous, tooth ; kétos, whale). The ‘toothed’? Whales, in contradistinction to the ‘‘ whalebone’? Whales. O-vow'torp (Gr. odous ; eidos, form). The ‘ odontoid process”’ is the centrum or body of the first cervical vertebra (atZas). 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, Q-pon'’T0-PHORE (Gr. odous, tooth; phero, I carry), The so-called “‘ tongue” or masticatory apparatus of Gasteropoda, Pteropoda, and Cephalopoda. Gi-sorn’a-aus. The gullet or tube leading from the mouth to the stomach. Ot-1-co-cnz'Ta (Gr. oligot, few ; chaite, hair). An order of Annelida, com- prising the Earth-worms, in which there are few bristles. O-ma'sum (Lat. for bullock’s tripe). The third stomach of Ruminants, com- monly called the psalterium, or many-plies. Om-niv'o-rous (Lat. omnia, everything; vore, 1 devour). Feeding indis- criminately upon all sorts of food. O-per-ou-La'ra (Lat. operculum, a lid). characters 0: . Rail, 269." £3 INDEX. 871 Rattlesnake, 244. Sheep, 303. Red Coral, 92. Shell, of Foraminifera, 84; of Mollusca, Red Deer, 302. 166, of Brachiopoda, 174; of Lamelli- Regnum Protisticum, 4. branchiata, 178; of Gasteropoda, 182; of Reindeer, 301. Heteropoda, 185; of Pteropoda, 186; of Reprenston, general features of, 53, 54; in ydroid Zoophytes, 62-66, ces 205; characters of, 234; jaw of, 5; teeth of, 235; circulation of, 236; res- piration of, 287; orders of, 237. Respiratory tree, of Holothurians, 107. Respiratory tubes, of Rotifera, 117. Rhea, 269, 270. Lhinoceros, 297, 298. Rhizocephala, 138. Rhizocrinus, 104, 105. apes a 27; characters of, 29; divisions of, 29. Rhizostoma, 82. Rhizostomide, 82. Rhytina, 294. Ribbon-worms, 113. Rodentia, 287; characters of, 309, 310. Roe-buck, 302. Rorqual, 295. Rotifera, 109; characters of, 115. Round-worms, 114. Ruffed Grouse, 272. Rugosa, 92. Ruminantia, 298, 299; dentition of, 299; stomach of, 800; families of, 801. Sable, 808. Sagitta, 119. Salmonida, 219. Sandpipers, 269. Sanguisuga, 122. Sarcode, 26. Sarcoids, of Sponges, 41. Sarcorhampus, 279. Sauropsida, 205. Sauropterygia, 237; characters of, 250. Saurure, 266, 280. Saw-flies, 160. ters of, 273. Sclerobasica (Zoantharia), 90. Sclerobasic Corals, 88, 91, 92. Sclerodermata (Zoantharia), 87. Sclerodermic Corals, 88, 91, 92. Scolecida, 95; characters of, 108, Scolopacida, 269, Scolopendra, 145. Scomberide, 219. Scorpion, 141, 142. Sea-anemones, 86. Sea-cucumbers, 106. - Seals, 806, 307. Sea-mosses, 167, 168. Sea-mouse, 124, 125. Sea-slugs, 184. Sea-spiders, 140. Sea-squirts, 165, 171. are organs of Annelides, 121. Selachizi, 223, elle eee 816. Serpula, 128, 124. Sertularida, 57, 61; characters of, 66; poly- pites of, 66; reproduction of, 67. the Argonaut, 190,191; of Pearly Nautilus, 190, 192. Shrew-mice, 314. Silk-moth, 160. Silurida, 219. Simia, 318. Siphonophora, 51; characters of, 70. Siphons, of Lamellibranchiuta, 174, 179. Stipunculus, 120. Siren, 227, 228 Sirenia, 28T; characters of, 293, Skink, 246, 247. Skunk, 308. Sloths, 292. Slow-worm, 245. Snakes, 201, 285. Snapping-turtle, 240. Snipes, 269. Soft-tortoises, 240. Solaster, 101. Stien, 180. Somatic cavity, of Calenterata, 51, 84. Sorex, 314. Soricida, 314. Spatularia, 221. Sperm-whale, 295. Spheniscida, 267. Spider-monkeys, 316. Spiders, 189, 140, 142. Spinneret, of Spiders, 148; of Caterpillars, 159. Spirorbis, 124. Spongida, 29; characters of, 86; aquiferous system of, 41; reproduction of, 43; dis- tribution of, in space, 43. Spongilla, 42; reproduction of, 43. Spoon-bill, 269. Spoon-worm, 120. Spring-bok, 303. Spring-tails, 153. Squids, 187, 190, 192. Squilla, 138. Squirrel, 311. Star-nosed Mole, 314. Stentor, 5, 48, 49. Stephanoceros, 116. Stomapoda, 188. Storks, 269. Strepsirhina, 816. Strepsiptera, 162. Strigida, 278. Struthio, 270. Sturgeon, 220, 221. Sturio, 220. Sturionida, 221, Sub-kingdoms, 11, 15. Suctoria (Infusoria), 49. Sula, 267. Surinam Toad, 232. 299. Swallows, 277. Swifts, 258, 277. Swim-bladder, of Fishes, 218. Swimming-bells, 70, 71 Syngnathida, 220. Syring, 120. 872 INDEX. Tabanida, 159. Turkey, 272. Tenia, 109, 111. Tuwn-stone, 269. of, 219, 220. Tenree, 815. Tenthredinida, 160. Termites, 156, 157. Terrapin, 240. Test, of Foraminifera, 34; of Echinoidea, 97; of Tunicata, 172. Testudo, 241. Tetrabranchiata, 189, 192, 193. Tetranychus, 141. Tetrao, 272. Tetraonida, 272. Thalassicolla, 89, 40. Thalassicoliida, 39. Theriomorpha, 230. Thick-knee, 269. Thread-cells, 52. Thread-worms, 114. Thylacinus, 291. Thysanura, 153. Ticks, 140, 141. Tiger, 309. Tipula, 158. ‘Sits, 276. ‘Toads, 230-282. Tongue, of Gasteropods, 181; of Cuttle-fish- es, 188; of Snakes, 242; of Birds, 259. Tortoises, 235, 286, 238, 240, ‘Trachez, 140, 149, Tree-frog, 280, 282. Tr toda, 108; Trichecus, 307. Trichina, 115. Trigonocephalus, 244, Trilobita, 135. Tringida, 269. Trionycida, 240. Triton, 229, Trochilida, 276. Troglodytes, 318. Trogonida, 274. Trophosome, 63. haracters of, 112. Tubularida (see Corynida). Tumicata, 165, 167; characters of, 171, 172. Tupaia, 315. Turbellaria, 108; characters of, 113. Turritella, 183. Turtles, 285, 286, 238, 239. Umbo, 178. Umbrella, of Zucernarida, 78, 80-82. Univalve Shells, 167, 180, 182. oe oa characters of, 296. ine, 276, Teaser Jot. Urodela, 226, 227. Orsida, 308. Vagnolee, of Ameba, 81; of Paramecium, Vaginicola, 48, 49. Valkeria, 170. Vampire-bats, 313, Varanida, 246. Veil, of gonophores, 64, 68; of nectocalyces, 71; of naked-eyed Medusa, 76. Velella, 72, 78. Venus’s Flower-basket, 42. Venus's Girdle, 94. Vermes, 119. Vertebra, structure of, 197, 198. Vertebrata, 195; general characters of, 195; skeleton of, 197-201; digestive system of, 201; blood of, 202; respiration of, 203; nervous system of, 204; reproduction of, 204; divisions of, 204, 205. Vesicle, contractile, of Protozoa, 26. Vespida, 160. Viperide, 244. Virgularia, 90. Viverrida, 308. Vorticella, 48, 49. 7 Vulture, 278. Wasps, 160. Water-hens, 269. Water-vascular system, 95, 96. Weasel, 308. Wolf, 308. Wolverine, 308. Woodcock, 269. Woodpeckers, 278. Wren, 276. Xiphosura, 188. Zebra, 298. Zoantharia, 86; Malacodermata, 86; Scle- robasica. 90; sclerodermata, 87. Zoanthus, 87. Zobid, 55. Zoology, definition of, 3. THE END.